What's hot today:
Current papers in developmental biology and gene function
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| ARCHIVE | Monday, July 31st, 2017 |
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What's hot today
February 2020 January 2020 December 2019 November 2019 October 2019 September 2019 August 2019 July 2019 June 2019 May 2019 April 2019 March 2019 February 2019 January 2019 December 2018 November 2018 October 2018 September 2018 August 2018 July 2018 June 2018 August 2017 June 2017 | Renda, F., Pellacani, C., Strunov, A., Bucciarelli, E., Naim, V., Bosso, G., Kiseleva, E., Bonaccorsi, S., Sharp, D. J., Khodjakov, A., Gatti, M. and Somma, M. P. (2017). The Drosophila orthologue of the INT6 onco-protein regulates mitotic microtubule growth and kinetochore structure. PLoS Genet 13(5): e1006784. PubMed ID: 28505193
Summary: INT6/eIF3e is a highly conserved component of the translation initiation complex that interacts with both the 26S proteasome and the COP9 signalosome, two complexes implicated in ubiquitin-mediated protein degradation. The INT6 gene was originally identified as the insertion site of the mouse mammary tumor virus (MMTV), and later shown to be involved in human tumorigenesis. Here we show that depletion of the Drosophila orthologue of INT6 (Int6) results in short mitotic spindles and deformed centromeres and kinetochores with low intra-kinetochore distance. Poleward flux of microtubule subunits during metaphase is reduced, although fluorescence recovery after photobleaching (FRAP) demonstrates that microtubules remain dynamic both near the kinetochores and at spindle poles. Mitotic progression is delayed during metaphase due to the activity of the spindle assembly checkpoint (SAC). Interestingly, a deubiquitinated form of the kinesin Klp67A (a putative orthologue of human Kif18A) accumulates near the kinetochores in Int6-depleted cells. Consistent with this finding, Klp67A overexpression mimics the Int6 RNAi phenotype. Furthermore, simultaneous depletion of Int6 and Klp67A results in a phenotype identical to RNAi of just Klp67A, which indicates that Klp67A deficiency is epistatic over Int6 deficiency. It is proposed that Int6-mediated ubiquitination is required to control the activity of Klp67A. In the absence of this control, excess of Klp67A at the kinetochore suppresses microtubule plus-end polymerization, which in turn results in reduced microtubule flux, spindle shortening, and centromere/kinetochore deformation. | Rattani, A., Ballesteros Mejia, R., Roberts, K., Roig, M. B., Godwin, J., Hopkins, M., Eguren, M., Sanchez-Pulido, L., Okaz, E., Ogushi, S., Wolna, M., Metson, J., Pendas, A. M., Malumbres, M., Novak, B., Herbert, M. and Nasmyth, K. (2017). APC/CCdh1 enables removal of Shugoshin-2 from the arms of bivalent chromosomes by moderating Cyclin-dependent kinase activity. Curr Biol 27(10): 1462-1476 e1465. PubMed ID: 28502659
Evolutionary Homolog Study In mammalian females, germ cells remain arrested as primordial follicles. Resumption of meiosis is heralded by germinal vesicle breakdown, condensation of chromosomes, and their eventual alignment on metaphase plates. At the first meiotic division, anaphase-promoting complex/cyclosome associated with Cdc20 (APC/CCdc20; see Drosophila Cdc20) activates separase (see Drosophila Separase) and thereby destroys cohesion along chromosome arms. Because cohesion around centromeres is protected by shugoshin-2 (see Drosophila mei-S332), sister chromatids remain attached through centromeric/pericentromeric cohesin. This study shows that, by promoting proteolysis of cyclins and Cdc25B (see Drosophila String) at the germinal vesicle (GV) stage, APC/C associated with the Cdh1 protein (APC/CCdh1; see Drosophila Fizzy-related) delays the increase in Cdk1 (see Drosophila Cdk2) activity, leading to germinal vesicle breakdown (GVBD). More surprisingly, by moderating the rate at which Cdk1 is activated following GVBD, APC/CCdh1 creates conditions necessary for the removal of shugoshin-2 from chromosome arms by the Aurora B/C kinase (see Drosophila Aurora B), an event crucial for the efficient resolution of chiasmata. |
| Yamada, T., Tahara, E., Kanke, M., Kuwata, K. and Nishiyama, T. (2017). Drosophila Dalmatian combines sororin and shugoshin roles in establishment and protection of cohesion. EMBO J [Epub ahead of print]. PubMed ID: 28483815
Summary: Sister chromatid cohesion is crucial to ensure chromosome bi-orientation and equal chromosome segregation. Cohesin removal via mitotic kinases and Wapl has to be prevented in pericentromeric regions in order to protect cohesion until metaphase, but the mechanisms of mitotic cohesion protection remain elusive in Drosophila This study shows that dalmatian (Dmt), an ortholog of the vertebrate cohesin-associated protein sororin, is required for protection of mitotic cohesion in flies. Dmt is essential for cohesion establishment during interphase and is enriched on pericentromeric heterochromatin. Dmt is recruited through direct association with heterochromatin protein-1 (HP1), and this interaction is required for cohesion. During mitosis, Dmt interdependently recruits protein phosphatase 2A (PP2A) to pericentromeric regions, and PP2A binding is required for Dmt to protect cohesion. Intriguingly, Dmt is sufficient to protect cohesion upon heterologous expression in human cells. These findings of a hybrid system, in which Dmt exerts both sororin-like establishment functions and shugoshin-like (see mei-S332) heterochromatin-based protection roles, provide clues to the evolutionary modulation of eukaryotic cohesion regulation systems. | Moura, M., Osswald, M., Leca, N., Barbosa, J., Pereira, A. J., Maiato, H., Sunkel, C. E. and Conde, C. (2017). Protein Phosphatase 1 inactivates Mps1 to ensure efficient Spindle Assembly Checkpoint silencing. Elife 6 [Epub ahead of print]. PubMed ID: 28463114
Summary: Faithfull genome partitioning during cell division relies on the Spindle Assembly Checkpoint (SAC), a conserved signaling pathway that delays anaphase onset until all chromosomes are attached to spindle microtubules. Mps1 kinase is an upstream SAC regulator that promotes the assembly of an anaphase inhibitor through a sequential multi-target phosphorylation cascade. Thus, the SAC is highly responsive to Mps1, whose activity peaks in early mitosis as a result of its T-loop autophosphorylation. However, the mechanism controlling Mps1 inactivation once kinetochores attach to microtubules and the SAC is satisfied remains unknown. This study shows in vitro and in Drosophila that Protein Phosphatase 1 (PP1) inactivates Mps1 by dephosphorylating its T-loop. PP1-mediated dephosphorylation of Mps1 occurs at kinetochores and in the cytosol, and inactivation of both pools of Mps1 during metaphase is essential to ensure prompt and efficient SAC silencing. Overall, these findings uncover a mechanism of SAC inactivation required for timely mitotic exit. |
Sunday, July 30th |
| Cerro-Herreros, E., Chakraborty, M., Perez-Alonso, M., Artero, R. and Llamusi, B. (2017). Expanded CCUG repeat RNA expression in Drosophila heart and muscle trigger Myotonic Dystrophy type 1-like phenotypes and activate autophagocytosis genes. Sci Rep 7(1): 2843. PubMed ID: 28588248
Summary: Myotonic dystrophies (DM1-2) are neuromuscular genetic disorders caused by the pathological expansion of untranslated microsatellites. DM1 and DM2, are caused by expanded CTG repeats in the 3'UTR of the DMPK gene and CCTG repeats in the first intron of the CNBP gene, respectively. Mutant RNAs containing expanded repeats are retained in the cell nucleus, where they sequester nuclear factors and cause alterations in RNA metabolism. However, for unknown reasons, DM1 is more severe than DM2. To study the differences and similarities in the pathogenesis of DM1 and DM2, model flies were generated by expressing pure expanded CUG ([250]x) or CCUG ([1100]x) repeats, respectively, and compared them with control flies expressing either 20 repeat units or GFP. Surprisingly, severe muscle reduction and cardiac dysfunction were observed in CCUG-expressing model flies. The muscle and cardiac tissue of both DM1 and DM2 model flies showed DM1-like phenotypes including overexpression of autophagy-related genes, RNA mis-splicing and repeat RNA aggregation in ribonuclear foci along with the Muscleblind protein. These data reveal, for the first time, that expanded non-coding CCUG repeat-RNA has similar in vivo toxicity potential as expanded CUG RNA in muscle and heart tissues and suggests that specific, as yet unknown factors, quench CCUG-repeat toxicity in DM2 patients. | Chang, J. C. and Morton, D. B. (2017). Drosophila lines with mutant and wild type human TDP-43 replacing the endogenous gene reveals phosphorylation and ubiquitination in mutant lines in the absence of viability or lifespan defects. PLoS One 12(7): e0180828. PubMed ID: 28686708
Summary: Mutations in TDP-43 (see Drosophila TDPH) are associated with proteinaceous inclusions in neurons and are believed to be causative in neurodegenerative diseases such as frontotemporal dementia or amyotrophic lateral sclerosis. This study describes a Drosophila system where the genome was engineered to replace the endogenous TDP-43 orthologue with wild type or mutant human TDP-43(hTDP-43). In contrast to other models, these flies express both mutant and wild type hTDP-43 at similar levels to those of the endogenous gene and importantly, no age-related TDP-43 accumulation was observed among all the transgenic fly lines. Immunoprecipitation of TDP-43 showed that flies with hTDP-43 mutations had increased levels of ubiquitination and phosphorylation of the hTDP-43 protein. Furthermore, histologically, flies expressing hTDP-43 M337V showed global, robust neuronal staining for phospho-TDP. All three lines: wild type hTDP-43, -G294A and -M337V were homozygous viable, with no defects in development, life span or behaviors observed. The primary behavioral defect was that flies expressing either hTDP-43 G294A or M337V showed a faster decline with age in negative geotaxis. Together, these observations implied that neurons could handle these TDP-43 mutations by phosphorylation- and ubiquitin-dependent proteasome systems, even in a background without the wild type TDP-43. These findings suggest that these two specific TDP-43 mutations are not inherently toxic, but may require additional environmental or genetic factors to affect longevity or survival. |
| Eom, H. J., Liu, Y., Kwak, G. S., Heo, M., Song, K. S., Chung, Y. D., Chon, T. S. and Choi, J. (2017). Inhalation toxicity of indoor air pollutants in Drosophila melanogaster using integrated transcriptomics and computational behavior analyses. Sci Rep 7: 46473. PubMed ID: 28621308
Summary: This study conducted an inhalation toxicity test on the alternative animal model, Drosophila melanogaster, to investigate potential hazards of indoor air pollution. The inhalation toxicity of toluene and formaldehyde was investigated using comprehensive transcriptomics and computational behavior analyses. The ingenuity pathway analysis (IPA) based on microarray data suggests the involvement of pathways related to immune response, stress response, and metabolism in formaldehyde and toluene exposure based on hub molecules. A toxicity test was conducted using mutants of the representative genes in these pathways to explore the toxicological consequences of alterations of these pathways. Furthermore, extensive computational behavior analysis showed that exposure to either toluene or formaldehyde reduced most of the behavioral parameters of both wild-type and mutants. Interestingly, behavioral alteration caused by toluene or formaldehyde exposure was most severe in the p38b mutant, suggesting that the defects in the p38 pathway underlie behavioral alteration. Overall, the results indicate that exposure to toluene and formaldehyde via inhalation causes severe toxicity in Drosophila, by inducing significant alterations in gene expression and behavior, suggesting that Drosophila can be used as a potential alternative model in inhalation toxicity screening. | Feng, G., Pang, J., Yi, X., Song, Q., Zhang, J., Li, C., He, G. and Ping, Y. (2017). Down-regulation of KV4 channel in Drosophila mushroom body neurons contributes to Abeta42-induced courtship memory deficits. Neuroscience [Epub ahead of print]. PubMed ID: 28627422
Summary: Accumulation of amyloid-β (Aβ) is widely believed to be an early event in the pathogenesis of Alzheimer's disease (AD). Kv4 is an A-type K+ channel, and previous work has shown that degradation of Kv4, induced by the β42 accumulation, may be a critical contributor to the hyperexcitability of neurons in a Drosophila AD model. This study used well-established courtship memory assay to investigate the contribution of the Kv4 channel to short-term memory (STM) deficits in the Aβ42-expressing AD model. Aβ42 over-expression in Drosophila leads to age-dependent courtship STM loss, which can be also induced by driving acute Aβ42 expression post-developmentally. Interestingly, mutants with eliminated Kv4-mediated A-type K+ currents (IA) by transgenically expressing dominant-negative subunit (DNKv4) phenocopied Aβ42 flies in defective courtship STM. Kv4 channels in mushroom body (MB) and projection neurons (PNs) were found to be required for courtship STM. Furthermore, the STM phenotypes can be rescued, at least partially, by restoration of Kv4 expression in Aβ42 flies, indicating the STM deficits could be partially caused by Kv4 degradation. In addition, IA is significantly decreased in MB neurons (MBNs) but not in PNs, suggesting Kv4 degradation in MBNs, in particular, plays a critical role in courtship STM loss in Aβ42 flies. These data highlight causal relationship between region-specific Kv4 degradation and age-dependent learning decline in the AD model, and provide a mechanism for the disturbed cognitive function in AD. |
| Fernius, J., Starkenberg, A. and Thor, S. (2017). Bar-coding neurodegeneration: Identifying sub-cellular effects of human neurodegenerative disease proteins using Drosophila leg neurons. Dis Model Mech [Epub ahead of print]. PubMed ID: 28615189
Summary: Genetic, biochemical and histological studies have identified a number of different proteins as key drivers of human neurodegenerative diseases. Whereas different proteins are typically involved in different disease, there is also considerable overlap. Addressing disease protein dysfunction in an in vivo neuronal context is often time-consuming and requires labor-intensive analysis of transgenic models. To facilitate the rapid, cellular analysis of disease protein dysfunction, a fruit fly (Drosophila melanogaster) adult leg neuron assay was developed. The robustness of 41 transgenic fluorescent reporters was tested, and a number were identified that were readily detected in the legs, and could report on different cellular events. To test these reporters, a number of human proteins involved in neurodegenerative disease were expressed, both in their mutated and wild type versions, to address the effects on reporter expression and localization. Strikingly different effects were found of the different disease proteins upon the various reporters, with for example: Aβ1-42 being highly neuro-toxic, Tau, Parkin and Htt128Q affecting mitochondrial distribution/integrity, and Aβ1-42, Tau, Htt128Q and ATX182Q affecting the F-actin network. This study provides proof-of-concept for using the Drosophila adult leg for inexpensive and rapid analysis of cellular effects of neurodegenerative disease proteins in mature neurons. | Garschall, K., Dellago, H., Galikova, M., Schosserer, M., Flatt, T. and Grillari, J. (2017). Ubiquitous overexpression of the DNA repair factor dPrp19 reduces DNA damage and extends Drosophila life span. NPJ Aging Mech Dis 3: 5. PubMed ID: 28649423
Summary: Mechanisms that ensure and maintain the stability of genetic information are fundamentally important for organismal function and can have a large impact on disease, aging, and life span. While a multi-layered cellular apparatus exists to detect and respond to DNA damage, various insults from environmental and endogenous sources continuously affect DNA integrity. Over time this can lead to the accumulation of somatic mutations, which is thought to be one of the major causes of aging. Previous work has found that overexpression of the essential human DNA repair and splicing factor SNEV, also called PRP19 or hPso4, extends replicative life span of cultured human endothelial cells and impedes accumulation of DNA damage. This study show that adult-specific overexpression of dPrp19, the D. melanogaster ortholog of human SNEV/PRP19/hPso4, robustly extends life span in female fruit flies. This increase in life span is accompanied by reduced levels of DNA damage and improved resistance to oxidative and genotoxic stress. These findings suggest that dPrp19 plays an evolutionarily conserved role in aging, life span modulation and stress resistance, and support the notion that superior DNA maintenance is key to longevity. |
Saturday, July 29th |
| Elliott, K. H., Betini, G. S. and Norris, D. R. (2017). Fear creates an Allee effect: experimental evidence from seasonal populations. Proc Biol Sci 284(1857). PubMed ID: 28659452
Summary: Allee effects, a decline in individual fitness at low population size or density, driven by predation can play a strong role in the decline of small populations but are conventionally thought to occur when generalist predators target specific prey (i.e. type II functional response). However, aside from direct consumption, fear of predators could also increase vigilance and reduce time spent foraging as population size decreases, as has been observed in wild mammals living in social groups. To investigate the role of fear on fitness in relation to population density in a species with limited sociality, varying densities of Drosophila melanogaster were exposed to mantid predators either during an experimental breeding season or non-breeding season. The presence of mantids in either season decreased the reproductive performance of individuals but only at low breeding densities, providing evidence for an Allee effect. The experimental results were used to parametrize a mathematical model to examine the population consequences of fear at low densities. Fear tended to destabilize population dynamics and increase the risk of extinction up to sevenfold. The study provides unique experimental evidence that the indirect effects of the presence of predators can cause an Allee effect and has important consequences for understanding of the dynamics of small populations. | Fuchikawa, T., Beer, K., Linke-Winnebeck, C., Ben-David, R., Kotowoy, A., Tsang, V. W. K., Warman, G. R., Winnebeck, E. C., Helfrich-Forster, C. and Bloch, G. (2017). Neuronal circadian clock protein oscillations are similar in behaviourally rhythmic forager honeybees and in arrhythmic nurses. Open Biol 7(6). PubMed ID: 28615472
Summary: Internal clocks driving rhythms of about a day (circadian) are ubiquitous in animals, allowing them to anticipate environmental changes. Genetic or environmental disturbances to circadian clocks or the rhythms they produce are commonly associated with illness, compromised performance or reduced survival. Nevertheless, some animals including Arctic mammals, open sea fish and social insects such as honeybees are active around-the-clock with no apparent ill effects. The mechanisms allowing this remarkable natural plasticity are unknown. This study generated and validated a new and specific antibody against the clock protein Period of the honeybee Apis mellifera (amPER) and used it to characterize the circadian network in the honeybee brain. Many similarities to Drosophila melanogaster and other insects were found, suggesting common anatomical organization principles in the insect clock that have not been appreciated before. Time course analyses revealed strong daily oscillations in amPER levels in foragers, which show circadian rhythms, and also in nurses that do not, although the latter have attenuated oscillations in brain mRNA clock gene levels. The oscillations in nurses show that activity can be uncoupled from the circadian network and support the hypothesis that a ticking circadian clock is essential even in around-the-clock active animals in a constant physical environment. |
| Bath, E., Bowden, S., Peters, C., Reddy, A., Tobias, J. A., Easton-Calabria, E., Seddon, N., Goodwin, S. F. and Wigby, S. (2017). Sperm and sex peptide stimulate aggression in female Drosophila. Nat Ecol Evol 1(6): 0154. PubMed ID: 28580431
Summary: Female aggression towards other females is associated with reproduction in many taxa, and traditionally thought to be related to the protection or provisioning of offspring, such as through increased resource acquisition. However, the underlying reproductive factors causing aggressive behaviour in females remain unknown. This study shows that female aggression in the fruit fly Drosophila melanogaster is strongly stimulated by the receipt of sperm at mating, and in part by an associated seminal fluid protein, the Sex peptide. It was further shown that the post-mating increase in female aggression is decoupled from the costs of egg production and from post-mating decreases in sexual receptivity. The results suggest that male ejaculates can have a surprisingly direct influence on aggression in recipient females. Male ejaculate traits thus influence the female social competitive environment with potentially far-reaching ecological and evolutionary consequences. | Chung, B. Y., Ro, J., Hutter, S. A., Miller, K. M., Guduguntla, L. S., Kondo, S. and Pletcher, S. D. (2017). Drosophila Neuropeptide F signaling independently regulates feeding and sleep-wake behavior. Cell Rep 19(12): 2441-2450. PubMed ID: 28636933
Summary: Proper regulation of sleep-wake behavior and feeding is essential for organismal health and survival. While previous studies have isolated discrete neural loci and substrates important for either sleep or feeding, how the brain is organized to coordinate both processes with respect to one another remains poorly understood. This study provides evidence that the Drosophila Neuropeptide F (NPF) network forms a critical component of both adult sleep and feeding regulation. Activation of NPF signaling in the brain promotes wakefulness and adult feeding, likely through its cognate receptor NPFR. Flies carrying a loss-of-function NPF allele do not suppress sleep following prolonged starvation conditions, suggesting that NPF acts as a hunger signal to keep the animal awake. NPF-expressing cells, specifically those expressing the circadian photoreceptor cryptochrome, are largely responsible for changes to sleep behavior caused by NPF neuron activation, but not feeding, demonstrating that different NPF neurons separately drive wakefulness and hunger. |
Friday, July 28th |
| Cao, C., Cogni, R., Barbier, V. and Jiggins, F. M. (2017). Complex coding and regulatory polymorphisms in a restriction factor determine the susceptibility of Drosophila to viral infection. Genetics [Epub ahead of print]. PubMed ID: 28630113
Summary: It is common to find that major-effect genes are an important cause of variation in susceptibility to infection. This study characterised natural variation in a gene called pastrel that explains over half of the genetic variance in susceptibility to the virus DCV in populations of Drosophila melanogaster. Extensive allelic heterogeneity was found, with a sample of seven alleles of pastrel from around the world conferring four phenotypically distinct levels of resistance. By modifying candidate SNPs in transgenic flies, this study showed that the largest effect is caused by an amino acid polymorphism that arose when an ancestral threonine was mutated to alanine, greatly increasing resistance to DCV. Overexpression of the ancestral susceptible allele provides strong protection against DCV, indicating that this mutation acted to improve an existing restriction factor. The pastrel locus also contains complex structural variation and cis-regulatory polymorphisms altering gene expression. Higher expression of pastrel was associated with increased survival after DCV infection. To understand why this variation is maintained in populations, genetic variation was investigated surrounding the amino acid variant that is causing flies to be resistant. No evidence was found of natural selection causing either recent changes in allele frequency or geographical variation in frequency, suggesting that this is an old polymorphism that has been maintained at a stable frequency. Overall, these data demonstrate how complex genetic variation at a single locus can control susceptibility to a virulent natural pathogen. | Shokal, U., Kopydlowski, H, and Eleftherianos I. (2017). The distinct function of Tep2 and Tep6 in the immune defense of Drosophila melanogaster against the pathogen Photorhabdus. Virulence [Epub ahead of print]. PubMed ID: 28498729
Summary: Previous and recent investigations on the innate immune response of Drosophila have identified certain mechanisms that promote pathogen elimination. However, the function of Thioester-containing proteins (TEPs) in the fly still remains elusive. Recent work has shown the contribution of TEP4 in the antibacterial immune defense of Drosophila against non-pathogenic E. coli, and the pathogens Photorhabdus luminescens and P. asymbiotica. This study examined the function of Tep genes in both humoral and cellular immunity upon E. coli and Photorhabdus infection. While Tep2 is induced after Photorhabdus and E. coli infection; Tep6 is induced by P. asymbiotica only. Moreover, functional ablation of hemocytes results in significantly low transcript levels of Tep2 and Tep6 in response to Photorhabdus. This study shows that tep2 and tep6 loss-of-function mutants have prolonged survival against P. asymbiotica, tep6 mutants survive better the infection of P. luminescens, and both tep mutants are resistant to E. coli and Photorhabdus. A distinct pattern of immune signaling pathway induction was found in E. coli or Photorhabdus infected tep2 and tep6 mutants. Tep2 and Tep6 were shown to participate in the activation of hemocytes in Drosophila responding to Photorhabdus. Finally, inactivation of Tep2 or Tep6 affects phagocytosis and melanization in flies infected with Photorhabdus. These results indicate that distinct Tep genes might be involved in different yet crucial functions in the Drosophila antibacterial immune response. |
| Daisley, B. A., Trinder, M., McDowell, T. W., Welle, H., Dube, J. S., Ali, S. N., Leong, H. S., Sumarah, M. W. and Reid, G. (2017). Neonicotinoid-induced pathogen susceptibility is mitigated by Lactobacillus plantarum immune stimulation in a Drosophila melanogaster model. Sci Rep 7(1): 2703. PubMed ID: 28578396
Summary: Pesticides are used extensively in food production to maximize crop yields. However, neonicotinoid insecticides exert unintentional toxicity to honey bees (Apis mellifera) that may partially be associated with massive population declines referred to as colony collapse disorder. It was hypothesized that imidacloprid (common neonicotinoid; IMI) exposure would make Drosophila melanogaster (an insect model for the honey bee) more susceptible to bacterial pathogens, heat stress, and intestinal dysbiosis. The results suggested that the immune deficiency (Imd) pathway is necessary for D. melanogaster survival in response to IMI toxicity. IMI exposure induced alterations in the host-microbiota as noted by increased indigenous Acetobacter and Lactobacillus spp. Furthermore, sub-lethal exposure to IMI resulted in decreased D. melanogaster survival when simultaneously exposed to bacterial infection and heat stress (37 degrees C). This coincided with exacerbated increases in TotA and Dpt (Imd downstream pro-survival and antimicrobial genes, respectively) expression compared to controls. Supplementation of IMI-exposed D. melanogaster with Lactobacillus plantarum ATCC 14917 mitigated survival deficits following Serratia marcescens (bacterial pathogen) septic infection. These findings support the insidious toxicity of neonicotinoid pesticides and potential for probiotic lactobacilli to reduce IMI-induced susceptibility to infection. | Wu, S. C., Cao, Z. S., Chang, K. M. and Juang, J. L. (2017). Intestinal microbial dysbiosis aggravates the progression of Alzheimer's disease in Drosophila. Nat Commun 8(1): 24. PubMed ID: 28634323
Summary: Neuroinflammation caused by local deposits of Abeta42 in the brain is key for the pathogenesis and progression of Alzheimer's disease. However, inflammation in the brain is not always a response to local primary insults. Gut microbiota dysbiosis, which is recently emerging as a risk factor for psychiatric disorders, can also initiate a brain inflammatory response. It still remains unclear however, whether enteric dysbiosis also contributes to Alzheimer's disease. This study shows that in a Drosophila Alzheimer's disease model, enterobacteria infection exacerbated progression of Alzheimer's disease by promoting immune hemocyte recruitment to the brain, thereby provoking TNF-JNK mediated neurodegeneration. Genetic depletion of hemocytes attenuates neuroinflammation and alleviated neurodegeneration. It was further found that enteric infection increases the motility of the hemocytes, making them more readily attracted to the brain with an elevated oxidative stress status. This work highlights the importance of gut-brain crosstalk as a fundamental regulatory system in modulating Alzheimer's disease neurodegeneration. Emerging evidence suggests that gut microbiota influences immune function in the brain and may play a role in neurological diseases. This study offers in vivo evidence from a Drosophila model that supports a role for gut microbiota in modulating the progression of Alzheimer's disease. |
Thursday, July 27th |
| Coates, K. E., Majot, A. T., Zhang, X., Michael, C. T., Spitzer, S. L., Gaudry, Q. and Dacks, A. M. (2017). Identified serotonergic modulatory neurons have heterogeneous synaptic connectivity within the olfactory system of Drosophila. J Neurosci [Epub ahead of print]. PubMed ID: 28659283
Summary: Modulatory neurons project widely throughout the brain, dynamically altering network processing based on an animal's physiological state. The connectivity of individual modulatory neurons can be complex, as they often receive input from a variety of sources and are diverse in their physiology, structure, and gene expression profiles. To establish basic principles about the connectivity of individual modulatory neurons, a pair of identified neurons was examined, the 'contralaterally projecting, serotonin-immunoreactive deutocerebral neurons' (CSDns), within the olfactory system of Drosophila. Specifically, the neuronal classes were determined providing synaptic input to the CSDns within the antennal lobe (AL), an olfactory network targeted by the CSDns, along with the degree to which CSDn active zones are uniformly distributed across the AL. Using anatomical techniques, the CSDns were found to receive glomerulus-specific input from olfactory receptor neurons (ORNs) and projection neurons (PNs), and network-wide input from local interneurons (LNs). Furthermore, the number of CSDn active zones was quantified in each glomerulus; CSDn output was fount to be not uniform, but rather heterogeneous across glomeruli and stereotyped from animal to animal. Finally, it was demonstrated that the CSDns synapse broadly onto LNs and PNs throughout the AL, but do not synapse upon ORNs. These results demonstrate that modulatory neurons do not necessarily provide purely top-down input, but rather receive neuron class-specific input from the networks that they target, and that even a two cell modulatory network has highly heterogeneous, yet stereotyped pattern of connectivity. | Jang, A. I., Wittig, J. H., Jr., Inati, S. K. and Zaghloul, K. A. (2017). Human cortical neurons in the anterior temporal lobe reinstate spiking activity during verbal memory retrieval. Curr Biol 27(11): 1700-1705 e1705. PubMed ID: 28552361
Evolutionary Homolog Study When we recall an experience, we rely upon the associations that we formed during the experience, such as those among objects, time, and place. These associations are better remembered when they are familiar and draw upon generalized knowledge, suggesting that we use semantic memory in the service of episodic memory. Moreover, converging evidence suggests that episodic memory retrieval involves the reinstatement of neural activity that was present when we first experienced the event. Therefore, it was hypothesized that retrieving associations should also reinstate the neural activity responsible for semantic processing. Indeed, previous studies have suggested that verbal memory retrieval leads to the reinstatement of activity across regions of the brain that include the distributed semantic processing network, but it is unknown whether and how individual neurons in the human cortex participate in the reinstatement of semantic representations. Recent advances using high-density microelectrode arrays (MEAs) have allowed clinicians to record from populations of neurons in the human cortex. This study used MEAs to record neuronal spiking activity in the human middle temporal gyrus (MTG), a cortical region supporting the semantic representation of words, as participants performed a verbal paired-associates task. Novel evidence is provided that population spiking activity in the MTG forms distinct representations of semantic concepts and that these representations are reinstated during the retrieval of those words. |
| Dylla, K. V., Raiser, G., Galizia, C. G. and Szyszka, P. (2017). Trace conditioning in Drosophila induces associative plasticity in mushroom body kenyon cells and dopaminergic neurons. Front Neural Circuits 11: 42. PubMed ID: 28676744
Summary: Dopaminergic neurons (DANs) signal punishment and reward during associative learning. In mammals, DANs show associative plasticity that correlates with the discrepancy between predicted and actual reinforcement (prediction error) during classical conditioning. Also in insects, such as Drosophila, DANs show associative plasticity that is, however, less understood. This study examined ssociative plasticity in DANs and their synaptic partners, the Kenyon cells (KCs) in the mushroom bodies (MBs), while training Drosophila to associate an odorant with a temporally separated electric shock (trace conditioning). In most MB compartments DANs strengthened their responses to the conditioned odorant relative to untrained animals. This response plasticity preserved the initial degree of similarity between the odorant- and the shock-induced spatial response patterns, which decreased in untrained animals. Contrary to DANs, KCs (α'/β'-type) decreased their responses to the conditioned odorant relative to untrained animals. No evidence was found for prediction error coding by DANs during conditioning. Rather, the data supports the hypothesis that DAN plasticity encodes conditioning-induced changes in the odorant's predictive power. | Damulewicz, M., Mazzotta, G. M., Sartori, E., Rosato, E., Costa, R. and Pyza, E. M. (2017). Cryptochrome is a regulator of synaptic plasticity in the visual system of Drosophila melanogaster. Front Mol Neurosci 10: 165. PubMed ID: 28611590
Summary: Drosophila Cryptochrome (Cry) is a blue light sensitive protein with a key role in circadian photoreception. A main feature of Cry is that light promotes an interaction with the circadian protein Timeless (Tim) resulting in their ubiquitination and degradation, a mechanism that contributes to the synchronization of the circadian clock to the environment. Moreover, Cry participates in non-circadian functions such as magnetoreception, modulation of neuronal firing, phototransduction and regulation of synaptic plasticity. This study used co-immunoprecipitation, yeast 2 hybrid (Y2H) and in situ proximity ligation assay (PLA) to show that Cry can physically associate with the presynaptic protein Bruchpilot (Brp) and that Cry-Brp complexes are located mainly in the visual system. Additionally, evidence is presented that light-activated Cry may decrease Brp levels in photoreceptor termini in the distal lamina, probably targeting Brp for degradation. |
Wednesday, July 26th |
| Chen, P., Zhou, Z., Yao, X., Pang, S., Liu, M., Jiang, W., Jiang, J. and Zhang, Q. (2017). Capping enzyme mRNA-cap/RNGTT regulates Hedgehog pathway activity by antagonizing Protein kinase A. Sci Rep 7(1): 2891. PubMed ID: 28588207
Summary: Hedgehog (Hh) signaling plays a pivotal role in animal development and its deregulation in humans causes birth defects and several types of cancer. Protein Kinase A (PKA) modulates Hh signaling activity through phosphorylating the transcription factor Cubitus interruptus (Ci) and G protein coupled receptor (GPCR) family protein Smoothened (Smo) in Drosophila, but how PKA activity is regulated remains elusive. This study identified a novel regulator of the Hh pathway, the capping-enzyme mRNA-cap, which positively regulates Hh signaling activity through modulating PKA activity. Genetic and biochemical evidence is provided that mRNA-cap inhibits PKA kinase activity to promote Hh signaling. Interestingly, regulation of Hh signaling by mRNA-cap depends on its cytoplasmic capping-enzyme activity. In addition, the mammalian homolog of mRNA-cap, RNGTT, can replace mRNA-cap to play the same function in the Drosophila Hh pathway, and knockdown of Rngtt in cultured mammalian cells compromised Shh pathway activity, suggesting that RNGTT is functionally conserved. This study makes an unexpected link between the mRNA capping machinery and the Hh signaling pathway, unveils a new facet of Hh signaling regulation, and reveals a potential drug target for modulating Hh signaling activity. | Bollepalli, M. K., Kuipers, M. E., Liu, C. H., Asteriti, S. and Hardie, R. C. (2017). Phototransduction in Drosophila is compromised by Gal4 expression but not by InsP3 receptor knockdown or mutation. eNeuro 4(3). PubMed ID: 28660247
Summary: Drosophila phototransduction is mediated by phospholipase C, leading to activation of transient receptor potential (TRP) and TRP-like (TRPL) channels by mechanisms that are unresolved. A role for InsP3 receptors (IP3Rs) had been excluded because IP3R mutants (itpr) appeared to have normal light responses; however, this was recently challenged by Kohn et al. ("Functional cooperation between the IP3 receptor and phospholipase C secures the high sensitivity to light of Drosophila photoreceptors in vivo," Journal of Neuroscience 35:2530), who reported defects in phototransduction after IP3R-RNAi knockdown. They concluded that InsP3-induced Ca2+ release plays a critical role in facilitating channel activation, and that previous failure to detect IP3R phenotypes resulted from trace Ca2+ in electrodes substituting for InsP3-induced Ca2+ release. In an attempt to confirm this, electroretinograms, whole-cell recordings, and GCaMP6f Ca2+ imaging were performed from both IP3R-RNAi flies and itpr-null mutants. Like Kohn et al., this study used GMRGal4 to drive expression of UAS-IP3R-RNAi, but controls expressing GMRGal4 alone were also used. Several GMRGal4 phenotypes are described suggestive of compromised development, including reductions in sensitivity, dark noise, potassium currents, and cell size and capacitance, as well as extreme variations in sensitivity between cells. However, no effect of IP3R RNAi or mutation was found on photoreceptor responses or Ca2+ signals, indicating that the IP3R plays little or no role in Drosophila phototransduction. |
| Choubey, P. K. and Roy, J. K. (2017). Rab11 is required for tubulogenesis of Malpighian tubules in Drosophila melanogaster. Genesis [Epub ahead of print]. PubMed ID: 28653473
Summary: Intracellular vesicular trafficking is one of the important tools in maintaining polarity, adhesion, and shape of epithelial cells. Rab11, a subfamily of the Ypt/Rab gene family of ubiquitously expressed GTPases and a molecular marker of recycling endosomes, transports different components of plasma membrane. This study reports that Rab11 affects tubulogenesis of Malpighian tubules (MTs). MTs are simple polarized epithelial tubular structures, considered as functional analogue of human Kidney. Rab11 has pleiotropic effects on MTs development as down-regulation of Rab11 in principal cells of MTs from embryonic stages of development, results in reduced endoreplication, clustering of cells, disorganized cytoskeleton and disruption of polarity leading to shortening of MTs in third instar larvae. Rab11 is also required for proper localization of different transporters in PCs, essential for physiological activity of MTs. Collectively these data suggest that Rab11 plays a key role in the process of tubulogenesis of MTs in Drosophila. | Dogliotti, G., Kullmann, L., Dhumale, P., Thiele, C., Panichkina, O., Mendl, G., Houben, R., Haferkamp, S., Puschel, A. W. and Krahn, M. P. (2017). Membrane-binding and activation of LKB1 by phosphatidic acid is essential for development and tumour suppression. Nat Commun 8: 15747. PubMed ID: 28649994
Summary: The serine/threonine kinase LKB1 regulates various cellular processes such as cell proliferation, energy homeostasis and cell polarity and is frequently downregulated in various tumours. Many downstream pathways controlled by LKB1 have been described but little is known about the upstream regulatory mechanisms. This study shows that targeting of the kinase to the membrane by a direct binding of LKB1 to phosphatidic acid is essential to fully activate its kinase activity. Consequently, LKB1 mutants that are deficient for membrane binding fail to activate the downstream target AMPK to control mTOR signalling. Furthermore, the in vivo function of LKB1 during development of Drosophila depends on its capacity to associate with membranes. Strikingly, LKB1 found to be downregulated in malignant melanoma, which exhibit aberrant activation of Akt and overexpress phosphatidic acid generating Phospholipase D. These results provide evidence for a fundamental mechanism of LKB1 activation and its implication in vivo and during carcinogenesis. |
Tuesday, July 25th |
| Banisch, T. U., Maimon, I., Dadosh, T. and Gilboa, L. (2017). Escort cells generate a dynamic compartment for germline stem cell differentiation via combined Stat and Erk signalling. Development 144(11): 1937-1947. PubMed ID: 28559239
Summary: Two different compartments support germline stem cell (GSC) self-renewal and their timely differentiation: the classical niche provides maintenance cues, while a differentiation compartment, formed by somatic escort cells (ECs), is required for proper GSC differentiation. ECs extend long protrusions that invade between tightly packed germ cells, and alternate between encapsulating and releasing them. How ECs achieve this dynamic balance has not been resolved. By combining live imaging and genetic analyses in Drosophila, this study has characterised EC shapes and their dynamic changes. Germ cell encapsulation by ECs is shown to be a communal phenomenon, whereby EC-EC contacts stabilise an extensive meshwork of protrusions. It was further shown that Signal Transducer and Activator of Transcription (Stat) and Epidermal Growth Factor Receptor (Egfr) signalling sustain EC protrusiveness and flexibility by combinatorially affecting the activity of different RhoGTPases. The results reveal how a complex signalling network can determine the shape of a cell and its dynamic behaviour. It also explains how the differentiation compartment can establish extensive contacts with germ cells, while allowing a continual posterior movement of differentiating GSC daughters. | Lobell, A. S., Kaspari, R. R., Serrano Negron, Y. L. and Harbison, S. T. (2017). The genetic architecture of ovariole number in Drosophila melanogaster: Genes with major, quantitative, and pleiotropic effects. G3 (Bethesda) [Epub ahead of print]. PubMed ID: 28550012
Summary: Ovariole number has a direct role in the number of eggs produced by an insect, suggesting that it is a key morphological fitness trait. Many studies have documented the variability of ovariole number and its relationship to other fitness and life-history traits in natural populations of Drosophila. However, the genes contributing to this variability are largely unknown. A genome-wide association study of ovariole number was conducted in a natural population of flies. Using mutations and RNAi-mediated knockdown, the effects of twenty-four candidate genes on ovariole number was confirmed, including a novel gene, anneboleyn (formerly CG32000), that impacts both ovariole morphology and numbers of offspring produced. Pleiotropic genes were identified that regulated ovariole number traits and sleep and activity behavior. While few polymorphisms overlapped between sleep parameters and ovariole number, thirty-nine candidate genes were nevertheless in common. The effects of seven genes on both ovariole number and sleep were verified: bin3, blot, CG42389, kirre, slim, VAChT, and zfh1. Linkage disequilibrium among the polymorphisms in these common genes was low, suggesting that these polymorphisms may evolve independently. |
| Crest, J., Diz-Munoz, A., Chen, D. Y., Fletcher, D. A. and Bilder, D. (2017). Organ sculpting by patterned extracellular matrix stiffness. Elife 6. PubMed ID: 28653906
Summary: How organ-shaping mechanical imbalances are generated is a central question of morphogenesis, with existing paradigms focusing on asymmetric force generation within cells. This study shows that organs can be sculpted instead by patterning anisotropic resistance within their extracellular matrix (ECM). Using direct biophysical measurements of elongating Drosophila egg chambers, this study documents robust mechanical anisotropy in the ECM-based basement membrane (BM) but not the underlying epithelium. Atomic force microscopy (AFM) on wild-type BM in vivo reveals an A-P symmetric stiffness gradient, which fails to develop in elongation-defective mutants. Genetic manipulation of ECM components Collagen IV, Laminin, and Perlecan showed that the BM is instructive for tissue elongation and the determinant is relative rather than absolute stiffness, creating differential resistance to isotropic tissue expansion. The stiffness gradient requires morphogen-like signaling to regulate BM incorporation, as well as planar-polarized organization to homogenize it circumferentially. These results demonstrate how fine mechanical patterning in the ECM can guide cells to shape an organ. | Diaz de la Loza, M. C., Diaz-Torres, A., Zurita, F., Rosales-Nieves, A. E., Moeendarbary, E., Franze, K., Martin-Bermudo, M. D. and Gonzalez-Reyes, A. (2017). Laminin levels regulate tissue migration and anterior-posterior polarity during egg morphogenesis in Drosophila. Cell Rep 20(1): 211-223. PubMed ID: 28683315 Summary: Basement membranes (BMs) are specialized extracellular matrices required for tissue organization and organ formation. The role of laminin and its integrin receptor were studied in the regulation of tissue migration during Drosophila oogenesis. Egg production in Drosophila involves the collective migration of follicle cells (FCs) over the BM to shape the mature egg. Laminin content in the BM was shown to increase with time, whereas integrin amounts in FCs do not vary significantly. Manipulation of integrin and laminin levels reveals that a dynamic balance of integrin-laminin amounts determines the onset and speed of FC migration. Thus, the interplay of ligand-receptor levels regulates tissue migration in vivo. Laminin depletion also affects the ultrastructure and biophysical properties of the BM and results in anterior-posterior misorientation of developing follicles. Laminin emerges as a key player in the regulation of collective cell migration, tissue stiffness, and the organization of anterior-posterior polarity in Drosophila. |
Monday, July 24th |
| Avila, F. W. and Wolfner, M. F. (2017). Cleavage of the Drosophila seminal protein Acp36DE in mated females enhances its sperm storage activity. J Insect Physiol. PubMed ID: 28676322 Summary: Sperm storage in the mated female reproductive tract (RT) is required for optimal fertility in numerous species with internal fertilization. In Drosophila melanogaster, sperm storage is dependent on female receipt of seminal fluid proteins (SFPs) during mating. The seminal fluid protein Acp36DE is necessary for the accumulation of sperm into storage. In the female RT, Acp36DE localizes to the anterior mating plug and also to a site in the common oviduct, potentially "corralling" sperm near the entry sites into the storage organs. Genetic studies showed that Acp36DE is also required for a series of conformational changes of the uterus that begin at the onset of mating and are hypothesized to move sperm towards the entry sites of the sperm storage organs. After Acp36DE is transferred to the female RT, the protein is cleaved by the astacin-metalloprotease Semp1. However, the effect of this cleavage on Acp36DE's function in sperm accumulation into storage is unknown. This study used mass spectrometry to identify the single cleavage site in Acp36DE. This site was then mutated and the effects on sperm storage were tested. Mutations of Acp36DE's cleavage site that slowed or prevented cleavage of the protein slowed the accumulation of sperm into storage, although they did not affect uterine conformational changes in mated females. Moreover, the N-terminal cleavage product of Acp36DE was sufficient to mediate sperm accumulation in storage, and it did so faster than versions of Acp36DE that could not be cleaved or were only cleaved slowly. These results suggest that cleavage of Acp36E may increase the number of bioactive molecules within the female RT, a mechanism similar to that hypothesized for Semp1's other substrate, the seminal fluid protein ovulin. | Zhao, X. and Karpac, J. (2017). Muscle directs diurnal energy homeostasis through a Myokine-dependent hormone module in Drosophila. Curr Biol 27(13): 1941-1955 e1946. PubMed ID: 28669758
Summary: Inter-tissue communication is critical to control organismal energy homeostasis in response to temporal changes in feeding and activity or external challenges. Muscle is emerging as a key mediator of this homeostatic control through consumption of lipids, carbohydrates, and amino acids, as well as governing systemic signaling networks. However, it remains less clear how energy substrate usage tissues, such as muscle, communicate with energy substrate storage tissues in order to adapt with diurnal changes in energy supply and demand. Using Drosophila, this study shows that muscle plays a crucial physiological role in promoting systemic synthesis and accumulation of lipids in fat storage tissues, which subsequently impacts diurnal changes in circulating lipid levels. The data reveal that the metabolic transcription factor Foxo governs expression of the cytokine unpaired 2 (Upd2) in skeletal muscle, which acts as a myokine to control glucagon-like adipokinetic hormone (AKH) secretion from specialized neuroendocrine cells. Circulating AKH levels in turn regulate lipid homeostasis in fat body/adipose and the intestine. The data also reveal that this novel myokine-dependent hormone module is critical to maintain diurnal rhythms in circulating lipids. This tissue crosstalk provides a putative mechanism that allows muscle to integrate autonomous energy demand with systemic energy storage and turnover. Together, these findings reveal a diurnal inter-tissue signaling network between muscle and fat storage tissues that constitutes an ancestral mechanism governing systemic energy homeostasis. |
| Bayliak, M. M., Lylyk, M. P., Maniukh, O. V., Storey, J. M., Storey, K. B. and Lushchak, V. I. (2017). Dietary L-arginine accelerates pupation and promotes high protein levels but induces oxidative stress and reduces fecundity and life span in Drosophila melanogaster. J Comp Physiol B. PubMed ID: 28668996 Summary: L-Arginine, a precursor of many amino acids and of nitric oxide, plays multiple important roles in nutrient metabolism and regulation of physiological functions. In this study, the effects of L-arginine-enriched diets on selected physiological responses and metabolic processes were assessed in Drosophila melanogaster. Dietary L-arginine at concentrations 5-20 mM accelerated larval development and increased body mass, and total protein concentrations in third instar larvae, but did not affect these parameters when diets contained 100 mM arginine. Young (2 days old) adult flies of both sexes reared on food supplemented with 20 and 100 mM L-arginine possessed higher total protein concentrations and lower glucose and triacylglycerol concentrations than controls. Additionally, flies fed 20 mM L-arginine had higher proline and uric acid concentrations. L-Arginine concentration in the diet also affected oxidative stress intensity in adult flies. Food with 20 mM L-arginine promoted lower protein thiol concentrations and higher catalase activity in flies of both sexes and higher concentrations of low molecular mass thiols in males. When flies were fed on a diet with 100 mM L-arginine, lower catalase activities and concentrations of protein thiols were found in both sexes as well as lower low molecular mass thiols in females. L-Arginine-fed males demonstrated higher climbing activity, whereas females showed higher cold tolerance and lower fecundity, compared with controls. Food containing 20 mM L-arginine shortened life span in both males and females. The results suggest that dietary L-arginine shows certain beneficial effects at the larval stage and in young adults. However, the long-term consumption of L-arginine-enriched food had unfavorable effects on D. melanogaster due to decreasing fecundity and life span. | Malloy, C., Sifers, J., Mikos, A., Samadi, A., Omar, A., Hermanns, C. and Cooper, R. L. (2017). Using optogenetics to assess neuroendocrine modulation of heart rate in Drosophila melanogaster larvae. J Comp Physiol A Neuroethol Sens Neural Behav Physiol [Epub ahead of print]. PubMed ID: 28612236
Summary: The Drosophila melanogaster heart has become a principal model in which to study cardiac physiology and development. While the morphology of the heart in Drosophila and mammals is different, many of the molecular mechanisms that underlie heart development and function are similar and function can be assessed by similar physiological measurements, such as cardiac output, rate, and time in systole or diastole. This study utilized an intact, optogenetic approach to assess the neural influence on heart rate in the third instar larvae. To simulate the release of modulators from the nervous system in response to environmental influences, expression of channel-rhodopsin variants were directed to targeted neuronal populations to assess the role of these neural ensembles in directing release of modulators that may affect heart rate in vivo. The observations show that the activation of targeted neurons, including cholinergic, dopaminergic, and serotonergic neurons, stimulate the release of cardioactive substances that increase heart rate after the initial activation at both room temperature and in a cold environment. This parallels previous studies suggesting these modulators play a crucial role in altering heart rate when applied to exposed hearts and adds to understanding of chemical modulation of heart rate in intact Drosophila larvae. |
Sunday, July 23rd |
| Paiardi, C., Mirzoyan, Z., Zola, S., Parisi, F., Vingiani, A., Pasini, M. E. and Bellosta, P. (2017). The Stearoyl-CoA Desaturase-1 (Desat1) in Drosophila cooperated with Myc to induce autophagy and growth, a potential new link to tumor survival. Genes (Basel) 8(5). PubMed ID: 28452935
Summary: Lipids are an important energy supply in our cells and can be stored or used to produce macromolecules during lipogenesis when cells experience nutrient starvation. Proteomic analysis reveals that the Drosophila homologue of human Stearoyl-CoA desaturase-1 Desat1) is an indirect target of Myc in fat cells. Stearoyl-CoA desaturases are key enzymes in the synthesis of monounsaturated fatty acids critical for the formation of complex lipids such as triglycerides and phospholipids. Their function is fundamental for cellular physiology, however in tumors, overexpression of SCD-1 and SCD-5 has been found frequently associated with a poor prognosis. Another gene that is often upregulated in tumors is the proto-oncogene c-myc, where its overexpression or increased protein stability, favor cellular growth. This study reports a potential link between Myc and Desat1 to control autophagy and growth. Using Drosophila, it was found that expression of Desat1, in metabolic tissues like the fat body, in the gut and in epithelial cells, is necessary for Myc function to induce autophagy a cell eating mechanism important for energy production. In addition, it was observed that reduction of Desat1 affects Myc ability to induce growth in epithelial cells. These data also identify, in prostatic tumor cells, a significant correlation between the expression of Myc and SCD-1 proteins, suggesting the existence of a potential functional relationship between the activities of these proteins in sustaining tumor progression. | Jo, J., Im, S. H., Babcock, D. T., Iyer, S. C., Gunawan, F., Cox, D. N. and Galko, M. J. (2017). Drosophila caspase activity is required independently of apoptosis to produce active TNF/Eiger during nociceptive sensitization. Cell Death Dis 8(5): e2786. PubMed ID: 28492538
Summary: Tumor necrosis factor (TNF) signaling is required for inflammatory nociceptive (pain) sensitization in Drosophila and vertebrates. Nociceptive sensitization in Drosophila larvae following UV-induced tissue damage is accompanied by epidermal apoptosis and requires epidermal-derived TNF/Eiger and the initiator caspase, Dronc. In this study, apoptotic cell death and thermal nociceptive sensitization are genetically and procedurally separable in a Drosophila model of UV-induced nociceptive sensitization. Activation of epidermal Dronc induces TNF-dependent but effector caspase-independent nociceptive sensitization in the absence of UV. In addition, knockdown of Dronc attenuated nociceptive sensitization induced by full-length TNF/Eiger but not by a constitutively soluble form. UV irradiation induced TNF production in both in vitro and in vivo, but TNF secretion into hemolymph was not sufficient to induce thermal nociceptive sensitization. Downstream mediators of TNF-induced sensitization included two TNF receptor-associated factors, a p38 kinase, and the transcription factor nuclear factor kappa B. Finally, sensory neuron-specific microarray analysis revealed downstream TNF target genes induced during thermal nociceptive sensitization. One of these, enhancer of zeste (E(z)), functions downstream of TNF during thermal nociceptive sensitization. These findings suggest that an initiator caspase is involved in TNF processing/secretion during nociceptive sensitization, and that TNF activation leads to a specific downstream signaling cascade and gene transcription required for sensitization. These findings have implications for both the evolution of inflammatory caspase function following tissue damage signals and the action of TNF during sensitization in vertebrates. |
| Choi, J. Y., Qiao, Q., Hong, S. H., Kim, C. M., Jeong, J. H., Kim, Y. G., Jung, Y. K., Wu, H. and Park, H. H. (2017). CIDE domains form functionally important higher-order assemblies for DNA fragmentation. Proc Natl Acad Sci U S A. PubMed ID: 28652364
Summary: Cell death-inducing DFF45-like effector (CIDE) domains, initially identified in apoptotic nucleases, form a family with diverse functions ranging from cell death to lipid homeostasis. This study shows that the CIDE domains of Drosophila and human apoptotic nucleases Drep2, Drep4, and DFF40 all form head-to-tail helical filaments. Opposing positively and negatively charged interfaces mediate the helical structures, and mutations on these surfaces abolish nuclease activation for apoptotic DNA fragmentation. Conserved filamentous structures are observed in CIDE family members involved in lipid homeostasis, and mutations on the charged interfaces compromise lipid droplet fusion, suggesting that CIDE domains represent a scaffold for higher-order assembly in DNA fragmentation and other biological processes such as lipid homeostasis. | Reynolds-Peterson, C. E., Zhao, N., Xu, J., Serman, T. M., Xu, J. and Selleck, S. B. (2017). Heparan sulfate proteoglycans regulate autophagy in Drosophila. Autophagy: 12:1-18. PubMed ID: 28402693
Summary: Heparan sulfate-modified proteoglycans (HSPGs) are important regulators of signaling and molecular recognition at the cell surface and in the extracellular space. The Drosophila NMJ provides a tractable model for understanding the activities of HSPGs at a synapse that displays developmental and activity-dependent plasticity. Muscle cell-specific knockdown of HS biosynthesis disrupted the organization of a specialized postsynaptic membrane, the subsynaptic reticulum (SSR), and affected the number and morphology of mitochondria. Evidence is provided that these changes result from a dysregulation of macroautophagy (hereafter referred to as autophagy). Cellular and molecular markers of autophagy are all consistent with an increase in the levels of autophagy in the absence of normal HS-chain biosynthesis and modification. Genetic mosaic analysis indicates that HS-dependent regulation of autophagy occurs non-cell autonomously, consistent with HSPGs influencing this cellular process via signaling in the extracellular space. These findings demonstrate that HS biosynthesis has important regulatory effects on autophagy and that autophagy is critical for normal assembly of postsynaptic membrane specializations. |
Saturday, July 22nd |
| Charlton-Perkins, M. A., Sendler, E. D., Buschbeck, E. K. and Cook, T. A. (2017). Multifunctional glial support by Semper cells in the Drosophila retina. PLoS Genet 13(5): e1006782. PubMed ID: 28562601
Summary: Glial cells play structural and functional roles central to the formation, activity and integrity of neurons throughout the nervous system. In the retina of vertebrates, the high energetic demand of photoreceptors is sustained in part by Muller glia, an intrinsic, atypical radial glia with features common to many glial subtypes. Accessory and support glial cells also exist in invertebrates, but which cells play this function in the insect retina is largely undefined. Using cell-restricted transcriptome analysis, this study shows that the ommatidial cone cells (aka Semper cells) in the Drosophila compound eye are enriched for glial regulators and effectors, including signature characteristics of the vertebrate visual system. In addition, cone cell-targeted gene knockdowns demonstrate that such glia-associated factors are required to support the structural and functional integrity of neighboring photoreceptors. Specifically, this study shows that distinct support functions (neuronal activity, structural integrity and sustained neurotransmission) can be genetically separated in cone cells by down-regulating transcription factors associated with vertebrate gliogenesis (pros/Prox1, Pax2/5/8, and Oli/Olig1,2, respectively). Further, specific factors critical for glial function in other species are also critical in cone cells to support Drosophila photoreceptor activity. These include ion-transport proteins (Na/K+-ATPase, Eaat1, and Kir4.1-related channels) and metabolic homeostatic factors (dLDH and Glut1). These data define genetically distinct glial signatures in cone/Semper cells that regulate their structural, functional and homeostatic interactions with photoreceptor neurons in the compound eye of Drosophila. In addition to providing a new high-throughput model to study neuron-glia interactions, the fly eye will further help elucidate glial conserved "support networks" between invertebrates and vertebrates. | Hu, J., Ferguson, L., Adler, K., Farah, C. A., Hastings, M. H., Sossin, W. S. and Schacher, S. (2017). Selective erasure of distinct forms of long-term synaptic plasticity underlying different forms of memory in the same postsynaptic neuron. Curr Biol 27(13): 1888-1899 e1884. PubMed ID: 28648820
Evolutionary Homolog Study Generalization of fear responses to non-threatening stimuli is a feature of anxiety disorders. It has been challenging to target maladaptive generalized memories without affecting adaptive memories. Synapse-specific long-term plasticity underlying memory involves the targeting of plasticity-related proteins (PRPs) to activated synapses. If distinct tags and PRPs are used for different forms of plasticity, one could selectively remove distinct forms of memory. Using a stimulation paradigm in which associative long-term facilitation (LTF) occurs at one input and non-associative LTF at another input to the same postsynaptic neuron in an Aplysia sensorimotor preparation, this study found that each form of LTF is reversed by inhibiting distinct isoforms of protein kinase M (PKM), putative PRPs, in the postsynaptic neuron. A dominant-negative (dn) atypical PKM selectively reversed associative LTF, while a dn classical PKM selectively reversed non-associative LTF. Although both PKMs are formed from calpain-mediated cleavage of protein kinase C (PKC; see Drosophila PKC) isoforms, each form of LTF is sensitive to a distinct dn calpain expressed in the postsynaptic neuron. Associative LTF is blocked by dn classical calpain, whereas non-associative LTF is blocked by dn small optic lobe (SOL) calpain. Interfering with a putative synaptic tag, the adaptor protein KIBRA (see Drosophila Kibra), which protects the atypical PKM from degradation, selectively erases associative LTF. Thus, the activity of distinct PRPs and tags in a postsynaptic neuron contribute to the maintenance of different forms of synaptic plasticity at separate inputs, allowing for selective reversal of synaptic plasticity and providing a cellular basis for developing therapeutic strategies for selectively reversing maladaptive memories. |
| King, A. N., Barber, A. F., Smith, A. E., Dreyer, A. P., Sitaraman, D., Nitabach, M. N., Cavanaugh, D. J. and Sehgal, A. (2017). A peptidergic circuit links the circadian clock to locomotor activity. Curr Biol 27(13): 1915-1927 e1915. PubMed ID: 28669757
Summary: The mechanisms by which clock neurons in the Drosophila brain confer an approximately 24-hr rhythm onto locomotor activity are unclear, but involve the neuropeptide diuretic hormone 44 (DH44), an ortholog of corticotropin-releasing factor. This study identified DH44 receptor 1 as the relevant receptor for rest:activity rhythms and its site of action was mapped to hugin-expressing neurons in the subesophageal zone (SEZ). A circuit was traced that extends from Dh44-expressing neurons in the pars intercerebralis (PI) through hugin+ SEZ neurons to the ventral nerve cord. Hugin neuropeptide, a neuromedin U ortholog, also regulates behavioral rhythms. The DH44 PI-Hugin SEZ circuit controls circadian locomotor activity in a daily cycle but has minimal effect on feeding rhythms, suggesting that the circadian drive to feed can be separated from circadian locomotion. These findings define a linear peptidergic circuit that links the clock to motor outputs to modulate circadian control of locomotor activity. | Boulanger-Weill, J., Candat, V., Jouary, A., Romano, S. A., Perez-Schuster, V. and Sumbre, G. (2017). Functional interactions between newborn and mature neurons leading to integration into established neuronal circuits. Curr Biol 27(12): 1707-1720 e1705. PubMed ID: 28578928
Evolutionary Homolog Study From development up to adulthood, the vertebrate brain is continuously supplied with newborn neurons that integrate into established mature circuits. This study monitored spontaneous and induced activity of large neuronal populations containing newborn and functionally mature neurons. The maturation of newborn neurons was observed to be a 4-day process. Initially, newborn neurons showed undeveloped dendritic arbors, no neurotransmitter identity, and were unresponsive to visual stimulation, although they displayed spontaneous calcium transients. Later on, newborn-labeled neurons began to respond to visual stimuli but in a very variable manner. At the end of the maturation period, newborn-labeled neurons exhibited visual tuning curves (spatial receptive fields and direction selectivity) and spontaneous correlated activity with neighboring functionally mature neurons. At this developmental stage, newborn-labeled neurons presented complex dendritic arbors and neurotransmitter identity (excitatory or inhibitory). Removal of retinal inputs significantly perturbed the integration of newborn neurons into the functionally mature tectal network. These results provide a comprehensive description of the maturation of newborn neurons during development and shed light on potential mechanisms underlying their integration into a functionally mature neuronal circuit. |
Friday, July 21st |
| Willoughby, L. F., Manent, J., Allan, K., Lee, H., Portela, M., Wiede, F., Warr, C., Meng, T. C., Tiganis, T. and Richardson, H. E. (2017). Differential regulation of protein tyrosine kinase signaling by Dock and the PTP61F variants. FEBS J. 284(14):2231-2250. PubMed ID: 28544778
Summary: Tyrosine phosphorylation-dependent signalling is coordinated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). There is a growing list of adaptor proteins that interact with PTPs and facilitate the dephosphorylation of substrates. The extent to which any given adaptor confers selectivity for any given substrate in vivo remains unclear. This study took advantage of Drosophila as a model organism to explore the influence of the SH3/SH2 adaptor protein Dock on the abilities of the membrane (PTP61Fm)- and nuclear (PTP61Fn)-targeted variants of PTP61F (the Drosophila orthologue of the mammalian enzymes PTP1B and TCPTP respectively) to repress PTK signaling pathways in vivo. PTP61Fn effectively repressed the eye overgrowth associated with activation of the epidermal growth factor receptor (EGFR) PTK, or the expression of the platelet derived growth factor/vascular endothelial growth factor receptor (PVR) or insulin receptor (InR) PTKs. PTP61Fn repressed EGFR and PVR-induced mitogen-activated protein kinase signaling and attenuated PVR-induced STAT92E signaling. By contrast, PTP61Fm effectively repressed EGFR- and PVR-, but not InR-induced tissue overgrowth. Importantly, co-expression of Dock with PTP61F allowed for the efficient repression of the InR-induced eye overgrowth, but did not enhance the PTP61Fm-mediated inhibition of EGFR and PVR-induced signaling. Instead, Dock expression increased, and PTP61Fm co-expression further exacerbated the PVR-induced eye overgrowth. These results demonstrate that Dock selectively enhances the PTP61Fm attenuation of InR signaling and underscores the specificity of PTPs and the importance of adaptor proteins in regulating PTP function in vivo. | Anderson, A. M., Bailetti, A. A., Rodkin, E., De, A. and Bach, E. A. (2017). A genetic screen reveals an unexpected role for Yorkie signaling in JAK/STAT-dependent hematopoietic malignancies in Drosophila melanogaster. G3 (Bethesda) [Epub ahead of print]. PubMed ID: 28620086
Summary: A gain-of-function mutation in the tyrosine kinase JAK2 (JAK2V617F) causes human myeloproliferative neoplasms (MPNs). These patients present with high numbers of myeloid lineage cells and have numerous complications. Since current MPN therapies are not curative, there is a need to find new regulators and targets of JAK/STAT signaling that may represent additional clinical interventions. Drosophila melanogaster offers a low complexity model to study MPNs as JAK/STAT signaling is simplified with only one JAK (Hopscotch (Hop)) and one STAT (Stat92E). hopTumorous-lethal (Tum-l) is a gain-of-function mutation that causes dramatic expansion of myeloid cells, which then form lethal melanotic tumors. Through an F1 deficiency (Df) screen, this study identified 11 suppressors and 35 enhancers of melanotic tumors in hopTum-l animals. Dfs that uncover the Hippo (Hpo) pathway genes expanded (ex) and warts (wts) strongly enhanced the hopTum-l tumor burden, as did mutations in expanded, wts and other Hpo pathway genes. Target genes of the Hpo pathway effector Yorkie (Yki) were significantly upregulated in hopTum-l blood cells, indicating that Yki signaling was increased. Ectopic hematopoietic activation of Yki in otherwise wild-type animals increased hemocyte proliferation but did not induce melanotic tumors. However, hematopoietic depletion of Yki significantly reduced the hopTum-l tumor burden, demonstrating that Yki is required for melanotic tumors in this background. These results support a model in which elevated Yki signaling increases the number of hemocytes, which become melanotic tumors as a result of elevated JAK/STAT signaling. |
| Banerjee, J. J., Aerne, B. L., Holder, M. V., Hauri, S., Gstaiger, M. and Tapon, N. (2017). Meru couples planar cell polarity with apical-basal polarity during asymmetric cell division. Elife 6. PubMed ID: 28665270
Summary: Polarity is a shared feature of most cells. In epithelia, apical-basal polarity often coexists, and sometimes intersects with planar cell polarity (PCP), which orients cells in the epithelial plane. From a limited set of core building blocks (e.g. the Par complexes for apical-basal polarity and the Frizzled/Dishevelled complex for PCP), a diverse array of polarized cells and tissues are generated. This suggests the existence of little-studied tissue-specific factors that rewire the core polarity modules to the appropriate conformation. In Drosophila sensory organ precursors (SOPs), the core PCP components initiate the planar polarization of apical-basal determinants, ensuring asymmetric division into daughter cells of different fates. This study shows that Meru, a RASSF9/RASSF10 homologue, is expressed specifically in SOPs, recruited to the posterior cortex by Frizzled/Dishevelled, and in turn polarizes the apical-basal polarity factor Bazooka (Par3). Thus, Meru belongs to a class of proteins that act cell/tissue-specifically to remodel the core polarity machinery. | Wang, X., Sun, Y., Han, S., Wu, C., Ma, Y., Zhao, Y., Shao, Y., Chen, Y., Kong, L., Li, W., Zhang, F. and Xue, L. (2017). Amyloid precursor like protein-1 promotes JNK-mediated cell migration in Drosophila. Oncotarget [Epub ahead of print]. PubMed ID: 28537903
Summary: The amyloid precursor like protein-1 (APLP1) is a member of the amyloid precursor protein (APP) family in mammals. While many studies have been focused on the pathologic role of APP in Alzheimer's disease, the physiological functions of APLP1 have remained largely elusive. This study reports that ectopic expression of APLP1 in Drosophila induces cell migration, which is suppressed by the loss of JNK signaling and enhanced by the gain of JNK signaling. APLP1 activates JNK signaling through phosphorylation of JNK, which up-regulates the expression of matrix metalloproteinase MMP1 required for basement membrane degradation and promotes actin remodeling essential for cell migration. These data thus provide the first in vivo evidence for a cell-autonomous role of APLP1 protein in migration. |
Thursday, July 20th |
| Salazar-Jaramillo, L., Jalvingh, K. M., de Haan, A., Kraaijeveld, K., Buermans, H. and Wertheim, B. (2017). Inter- and intra-species variation in genome-wide gene expression of Drosophila in response to parasitoid wasp attack. BMC Genomics 18(1): 331. PubMed ID: 28449654
Summary: A study of inter- and intra-species variation in resistance to parasitoid attack used RNA-seq after parasitization in lines experimentally selected for increased resistance. A core set of genes was found that are consistently up-regulated after parasitoid attack. Another set showed no up-regulation or expression in D. sechellia, the species unable to raise an immune response against parasitoids. This set consists largely of genes that are lineage-restricted to the melanogaster subgroup. Artificially selected lines did not show significant differences in gene expression with respect to non-selected lines, but several genes showed differential exon usage. This study has shown substantial similarities, but also notable differences, in the transcriptional responses to parasitoid attack among four closely related Drosophila species. In contrast, within D. melanogaster, the responses were remarkably similar. It was confirmed that in the short-term, selection does not act on a pre-activation of the immune response. Instead it may target alternative mechanisms such as differential exon usage. In the long-term, support was found for the hypothesis that the ability to immunologically resist parasitoid attack is contingent on new genes that are restricted to the melanogaster subgroup. | Castro Vargas, C., Richmond, M. P., Ramirez Loustalot Laclette, M. and Markow, T. A. (2017). Early events in speciation: Cryptic species of Drosophila aldrichi. Ecol Evol 7(12): 4220-4228. PubMed ID: 28649335
Summary: Understanding the earliest events in speciation remains a major challenge in evolutionary biology. Thus identifying species whose populations are beginning to diverge can provide useful systems to study the process of speciation. Drosophila aldrichi, a cactophilic fruit fly species with a broad distribution in North America, has long been assumed to be a single species owing to its morphological uniformity. While previous reports either of genetic divergence or reproductive isolation among different D. aldrichi strains have hinted at the existence of cryptic species, the evolutionary relationships of this species across its range have not been thoroughly investigated. This study shows that D. aldrichi actually is paraphyletic with respect to its closest relative, Drosophila wheeleri, and that divergent D. aldrichi lineages show complete hybrid male sterility when crossed. The data support the interpretation that there are at least two species of D. aldrichi, making these flies particularly attractive for studies of speciation in an ecological and geographical context. |
| Wang, X. R., Ling, L. B., Huang, H. H., Lin, J. J., Fugmann, S. D. and Yang, S. Y. (2017). Evidence for parallel evolution of a gene involved in the regulation of spermatogenesis. Proc Biol Sci 284(1855). PubMed ID: 28539513
Summary: PHD finger protein 7 (Phf7) is a male germline specific gene in Drosophila melanogaster that can trigger the male germline sexual fate and regulate spermatogenesis, and its human homologue can rescue fecundity defects in male flies lacking this gene. These findings prompted an investigation of conservation of reproductive strategies through studying the evolutionary origin of this gene. Phf7 was found to be present only in select species including mammals and some insects, whereas the closely related G2/M-phase specific E3 ubiquitin protein ligase (G2e3) is in the genome of most metazoans. Interestingly, phylogenetic analyses showed that vertebrate and insect Phf7 genes did not evolve from a common Phf7 ancestor but rather through independent duplication events from an ancestral G2e3. This is an example of parallel evolution in which a male germline factor evolved at least twice from a pre-existing template to develop new regulatory mechanisms of spermatogenesis. | Rostant, W. G., Bowyer, J., Coupland, J., Facey, J., Hosken, D. J. and Wedell, N. (2017). Pleiotropic effects of DDT resistance on male size and behaviour. Behav Genet. PubMed ID: 28466236
Summary: Understanding the evolution and spread of insecticide resistance requires knowing the relative fitness of resistant organisms. In the absence of insecticides, resistance is predicted to be costly. The Drosophila melanogaster DDT resistance allele (DDT-R) is associated with a male mating cost. This could be because resistant males are generally smaller, but DDT-R may also alter courtship behaviours. This study tested for body size and courtship effects of DDT-R on mating success in competitive and non-competitive mating trials respectively. Relative aggression was assessed in resistant and susceptible males because aggression can also influence mating success. While the effect of DDT-R on male size partly contributed to reduced mating success, resistant males also had lower rates of courtship and were less aggressive than susceptible males. These differences contribute to the observed DDT-R mating costs. Additionally, these pleiotropic effects of DDT-R are consistent with the history and spread of resistance alleles in nature. |
Wednesday, July 19th |
| Olesnicky, E. C., Bono, J. M., Bell, L., Schachtner, L. T. and Lybecker, M. C. (2017). The RNA-binding protein Caper is required for sensory neuron development in Drosophila melanogaster. Dev Dyn [Epub ahead of print]. PubMed ID: 28543982
Summary: Alternative splicing mediated by RNA-binding proteins (RBPs) is emerging as a fundamental mechanism for the regulation of gene expression. Alternative splicing has been shown to be a widespread phenomenon that facilitates the diversification of gene products in a tissue specific manner. Although defects in alternative splicing are rooted in many neurological disorders, only a small fraction of splicing factors have been investigated in detail. This study finds that the splicing factor Caper is required for the development of multiple different mechanosensory neuron subtypes at multiple life stages in Drosophila melanogaster. Disruption of Caper function causes defects in dendrite morphogenesis of larval dendrite arborization neurons, neuronal positioning of embryonic proprioceptors, as well as the development and maintenance of adult mechanosensory bristles. Additionally, Caper dysfunction was found to result in aberrant locomotor behavior in adult flies. Transcriptome-wide analyses further support a role for Caper in alternative isoform regulation of genes that function in neurogenesis. This results provide the first evidence for a fundamental and broad requirement for the highly conserved splicing factor Caper in the development and maintenance of the nervous system and provide a framework for future studies on the detailed mechanism of Caper mediated RNA regulation. | Howell, K. and Hobert, O. (2017). Morphological diversity of C. elegans sensory cilia instructed by the differential expression of an immunoglobulin domain protein. Curr Biol 27(12): 1782-1790 e1785. PubMed ID: 28578929
Evolutionary Homolog Study Cilia on dendritic endings of sensory neurons organize distinct types of sensory machinery. Ciliated endings display neuron-type-specific patterns of membrane elaborations, but it is not well understood how such neuron-type-specific morphologies are generated and whether they are coupled to the specification of other identity aspects of a terminally differentiated sensory neuron. In the course of a genome-wide analysis of members of a small family of immunoglobulin domain proteins, this study found that OIG-8, a previously uncharacterized transmembrane protein with a single immunoglobulin (Ig) domain, instructs the distinct, neuron-type-specific elaboration of ciliated endings of different olfactory neuron types in the nematode C. elegans. OIG-8 protein localizes to ciliated endings of these sensory neurons, and is transcribed at different levels in distinct olfactory neuron types. oig-8 expression levels correlate with the extent of sensory cilia growth and branching patterns. Loss of oig-8 leads to a reduction in the branching patterns of cilia, whereas raising the levels of oig-8 results in an increase in elaborations. Levels of OIG-8 expression are controlled by the specific combination of a terminal selector type of transcription factors that also specify other identity features of distinct olfactory neuron types. |
| Ramat, A., Hannaford, M. and Januschke, J. (2017). Maintenance of Miranda Localization in Drosophila Neuroblasts Involves Interaction with the Cognate mRNA. Curr Biol. PubMed ID: 28690114
Summary: How cells position their proteins is a key problem in cell biology. Targeting mRNAs to distinct regions of the cytoplasm contributes to protein localization by providing local control over translation. This study reveals that an interdependence of a protein and cognate mRNA maintains asymmetric protein distribution in mitotic Drosophila neural stem cells. Endogenous mRNA or protein products of the gene miranda that is required for fate determination were tagged with GFP. The mRNA was found to localize like the protein it encodes in a basal crescent in mitosis. GFP-specific nanobodies fused to localization domains were used to alter the subcellular distribution of the GFP-tagged mRNA or protein. Altering the localization of the mRNA resulted in mislocalization of the protein and vice versa. Protein localization defects caused by mislocalization of the cognate mRNA were rescued by introducing untagged mRNA coding for mutant non-localizable protein. Therefore, by combining the MS2 system and subcellular nanobody expression, it was uncovered that maintenance of Mira asymmetric localization requires interaction with the cognate mRNA. | Stratmann, J. and Thor, S. (2017). Neuronal cell fate specification by the molecular convergence of different spatio-temporal cues on a common initiator terminal selector gene. PLoS Genet 13(4): e1006729. PubMed ID: 28414802
Summary: The extensive genetic regulatory flows underlying specification of different neuronal subtypes are not well understood at the molecular level. The Nplp1 neuropeptide neurons in the developing Drosophila nerve cord belong to two sub-classes; Tv1 and dAp neurons, generated by two distinct progenitors. Nplp1 neurons are specified by spatial cues; the Hox homeotic network and GATA factor grn, and temporal cues; the hb -> Kr -> Pdm -> cas -> grh temporal cascade. These spatio-temporal cues combine into two distinct codes; one for Tv1 and one for dAp neurons that activate a common terminal selector feedforward cascade of col -> ap/eya -> dimm -> Nplp1. This study molecularly decodes the specification of Nplp1 neurons, and finds that the cis-regulatory organization of col functions as an integratory node for the different spatio-temporal combinatorial codes. These findings may provide a logical framework for addressing spatio-temporal control of neuronal sub-type specification in other systems. |
Tuesday, July 18th |
| Portz, B., Lu, F., Gibbs, E. B., Mayfield, J. E., Rachel Mehaffey, M., Zhang, Y. J., Brodbelt, J. S., Showalter, S. A. and Gilmour, D. S. (2017). Structural heterogeneity in the intrinsically disordered RNA polymerase II C-terminal domain. Nat Commun 8: 15231. PubMed ID: 28497792
Summary: RNA polymerase II contains a repetitive, intrinsically disordered, C-terminal domain (CTD) composed of heptads of the consensus sequence YSPTSPS. The CTD is heavily phosphorylated and serves as a scaffold, interacting with factors involved in transcription initiation, elongation and termination, RNA processing and chromatin modification. Despite being a nexus of eukaryotic gene regulation, the structure of the CTD and the structural implications of phosphorylation are poorly understood. This study presents a biophysical and biochemical interrogation of the structure of the full length CTD of Drosophila melanogaster, which is concluded to be a compact random coil. Surprisingly, it was found that the repetitive CTD is structurally heterogeneous. Phosphorylation causes increases in radius, protein accessibility and stiffness, without disrupting local structural heterogeneity. Additionally, the human CTD was also shown to be structurally heterogeneous and able to substitute for the D. melanogaster CTD in supporting fly development to adulthood. This finding implicates conserved structural organization, not a precise array of heptad motifs, as important to CTD function. | Appocher, C., Mohagheghi, F., Cappelli, S., Stuani, C., Romano, M., Feiguin, F. and Buratti, E. (2017). Major hnRNP proteins act as general TDP-43 functional modifiers both in Drosophila and human neuronal cells. Nucleic Acids Res [Epub ahead of print]. PubMed ID: 28575377
Summary: Nuclear factor TDP-43 is known to play an important role in several neurodegenerative pathologies. In general, TDP-43 is an abundant protein within the eukaryotic nucleus that binds to many coding and non-coding RNAs and influence their processing. Using Drosophila, a functional screening was performed to establish the ability of major hnRNP proteins to affect TDP-43 overexpression/depletion phenotypes. Interestingly, lowering hnRNP and TDP-43 expression has a generally harmful effect on flies locomotor abilities. In parallel, this study has also identified a distinct set of hnRNPs that is capable of powerfully rescuing TDP-43 toxicity in the fly eye (Hrb27c, CG42458, Glo and Syp). Most importantly, removing the human orthologs of Hrb27c (DAZAP1) in human neuronal cell lines can correct several pre-mRNA splicing events altered by TDP-43 depletion. Moreover, using RNA sequencing analysis, DAZAP1 and TDP-43 were shown too co-regulate an extensive number of biological processes and molecular functions potentially important for the neuron/motor neuron pathophysiology. These results suggest that changes in hnRNP expression levels can significantly modulate TDP-43 functions and affect pathological outcomes. |
| Aw, S. S., Lim, I. K. H., Tang, M. X. M. and Cohen, S. M. (2017). A glio-protective role of mir-263a by tuning sensitivity to Glutamate. Cell Rep 19(9): 1783-1793. PubMed ID: 28564598
Summary: Glutamate is a ubiquitous neurotransmitter, mediating information flow between neurons. Defects in the regulation of glutamatergic transmission can result in glutamate toxicity, which is associated with neurodegeneration. Interestingly, glutamate receptors are expressed in glia, but little is known about their function, and the effects of their misregulation, in these non-neuronal cells. This study reports a glio-protective role for Drosophila mir-263a mediated by its regulation of glutamate receptor levels in glia. mir-263a mutants exhibit a pronounced movement defect due to aberrant overexpression of glutamate receptor CG5621/Grik, Nmdar1, and Nmdar2. mir-263a mutants exhibit excitotoxic death of a subset of astrocyte-like and ensheathing glia in the CNS. Glial-specific normalization of glutamate receptor levels restores cell numbers and suppresses the movement defect. Therefore, microRNA-mediated regulation of glutamate receptor levels protects glia from excitotoxicity, ensuring CNS health. Chronic low-level glutamate receptor overexpression due to mutations affecting microRNA (miRNA) regulation might contribute to glial dysfunction and CNS impairment. | Alexiadis, A., Delidakis, C. and Kalantidis, K. (2017). Snipper, an Eri1 homologue, affects histone mRNA abundance and is crucial for normal Drosophila melanogaster development. FEBS Lett [Epub ahead of print]. PubMed ID: 28626879
Summary: The conserved 3'-5' RNA exonuclease ERI1 is implicated in RNA interference inhibition, 5.8S rRNA maturation and histone mRNA maturation and turnover. The single ERI1 homologue in Drosophila melanogaster Snipper (Snp) is a 3'-5' exonuclease, but its in vivo function remains elusive. This study reports a Snp requirement for normal Drosophila development, since its perturbation leads to larval arrest and tissue-specific downregulation results in abnormal tissue development. Additionally, Snp directly interacts with histone mRNA, and its depletion results in drastic reduction in histone transcript levels. It is proposed that Snp protects the 3'-ends of histone mRNAs and upon its absence, histone transcripts are readily degraded. This in turn may lead to cell cycle delay or arrest, causing growth arrest and developmental perturbations. |
Monday, July 17th |
| Turner-Evans, D., Wegener, S., Rouault, H., Franconville, R., Wolff, T., Seelig, J. D., Druckmann, S. and Jayaraman, V. (2017). Angular velocity integration in a fly heading circuit. Elife 6. PubMed ID: 28530551
Summary: Many animals maintain an internal representation of their heading as they move through their surroundings. Such a compass representation was recently discovered in a neural population in the Drosophila melanogaster central complex (see Anatomy suggests a potential circuit mechanism to update a compass representation), a brain region implicated in spatial navigation. This study used two-photon calcium imaging and electrophysiology in head-fixed walking flies to identify a different neural population that conjunctively encodes heading and angular velocity, and is excited selectively by turns in either the clockwise or counterclockwise direction. These mirror-symmetric turn responses combine with the neurons' connectivity to the compass neurons to create an elegant mechanism for updating the fly's heading representation when the animal turns in darkness. This mechanism, which employs recurrent loops with an angular shift, bears a resemblance to those proposed in theoretical models for rodent head direction cells. These results provide a striking example of structure matching function for a broadly relevant computation. | Wreden, C. C., Meng, J. L., Feng, W., Chi, W., Marshall, Z. D. and Heckscher, E. S. (2017). Temporal cohorts of lineage-related neurons perform analogous functions in distinct sensorimotor circuits. Curr Biol 27(10): 1521-1528.e1524. PubMed ID: 28502656
Summary: An important, but unaddressed question is whether temporal information that diversifies neuronal progeny within a single lineage also impacts circuit assembly. Circuits in the sensorimotor system (e.g., spinal cord) are thought to be assembled sequentially, making this an ideal brain region for investigating the circuit-level impact of temporal patterning within a lineage. This study used intersectional genetics, optogenetics, high-throughput behavioral analysis, single-neuron labeling, connectomics, and calcium imaging to determine how a set of bona fide lineage-related interneurons in the ventral cord contribute to sensorimotor circuitry in the Drosophila larva. Even-skipped lateral interneurons (ELs) are sensory processing interneurons. Late-born ELs contribute to a proprioceptive body posture circuit, whereas early-born ELs contribute to a mechanosensitive escape circuit. These data support a model in which a single neuronal stem cell can produce a large number of interneurons with similar functional capacity that are distributed into different circuits based on birth timing. In summary, these data establish a link between temporal specification of neuronal identity and circuit assembly at the single-cell level. |
| Tobin, W. F., Wilson, R. I. and Lee, W. A. (2017). Wiring variations that enable and constrain neural computation in a sensory microcircuit. Elife 6 [Epub ahead of print]. PubMed ID: 28530904
Summary: Neural network function can be shaped by varying the strength of synaptic connections. One way to achieve this is to vary connection structure. To investigate how structural variation among synaptic connections might affect neural computation, primary afferent connections were examined in the Drosophila olfactory system. Large-scale serial section electron microscopy was used to reconstruct all the olfactory receptor neuron (ORN) axons that target a left-right pair of glomeruli, as well as all the projection neurons (PNs) postsynaptic to these ORNs. Three variations were found in ORN-->PN connectivity. First, a systematic co-variation was found in synapse number and PN dendrite size, suggesting total synaptic conductance is tuned to postsynaptic excitability. Second, PNs were found to receive more synapses from ipsilateral than contralateral ORNs, providing a structural basis for odor lateralization behavior. Finally, evidence was found of imprecision in ORN-->PN connections that can diminish network performance. | Anzo, M., Sekine, S., Makihara, S., Chao, K., Miura, M. and Chihara, T. (2017). Dendritic Eph organizes dendrodendritic segregation in discrete olfactory map formation in Drosophila. Genes Dev 31(10): 1054-1065. PubMed ID: 28637694
Summary: Proper function of the neural network results from the precise connections between axons and dendrites of presynaptic and postsynaptic neurons, respectively. In the Drosophila olfactory system, the dendrites of projection neurons (PNs) stereotypically target one of approximately 50 glomeruli in the antennal lobe (AL), the primary olfactory center in the brain, and form synapses with the axons of olfactory receptor neurons (ORNs). This study shows that Eph and Ephrin, the well-known axon guidance molecules, instruct the dendrodendritic segregation during the discrete olfactory map formation. The Eph receptor tyrosine kinase is highly expressed and localized in the glomeruli related to reproductive behavior in the developing AL. In one of the pheromone-sensing glomeruli (DA1), the Eph cell-autonomously regulates its dendrites to reside in a single glomerulus by interacting with Ephrins expressed in adjacent PN dendrites. These data demonstrate that the trans interaction between dendritic Eph and Ephrin is essential for the PN dendritic boundary formation in the DA1 olfactory circuit, potentially enabling strict segregation of odor detection between pheromones and the other odors. |
Sunday, July 16th |
| Wang, S. and Sokolowski, M. B. (2017). Aggressive behaviours, food deprivation and the foraging gene. R Soc Open Sci 4(4): 170042. PubMed ID: 28484630
Summary: A pleiotropic gene governs multiple traits, which might constrain the evolution of complexity due to conflicting selection on these traits. However, if the pleiotropic effect is modular, then this can facilitate synergistic responses to selection on functionally related traits, thereby leveraging the evolution of complexity. To understand the evolutionary consequence of pleiotropy, the relation among functionally different traits governed by the same gene is key. This study examined a pleiotropic function of the foraging (for) gene with its rover and sitter allelic variants in fruit fly, Drosophila melanogaster. for's effect on adult male aggressive behaviours was measured and whether this effect was shaped by for's known role in food-related traits. Rover exhibited higher levels of offensive behaviour than sitters and by s2, a sitter-like mutant on rover genetic background. With a Markov chain model, w the rate of aggression escalation was measure, and the rover pattern of aggressive escalation was found to more rapidly intensify fights. Subsequent analysis revealed that this was not caused by for's effect on food-related traits, suggesting that for might directly regulate aggressive behaviours. Food deprivation did not elevate aggression, but reduced intermediate-level aggressive behaviours. Aggression and other foraging-related behaviour might comprise a synergistic trait module underlaid by this pleiotropic gene. | Almeida-Carvalho, M. J., et al. (2017). The Ol1mpiad: concordance of behavioural faculties of stage 1 and stage 3 Drosophila larvae. J Exp Biol 220(Pt 13): 2452-2475. PubMed ID: 28679796
Summary: Mapping brain function to brain structure is a fundamental task for neuroscience. For such an endeavour, the Drosophila larva is simple enough to be tractable, yet complex enough to be interesting. It features about 10,000 neurons and is capable of various taxes, kineses and Pavlovian conditioning. All its neurons are currently being mapped into a light-microscopical atlas, and Gal4 strains are being generated to experimentally access neurons one at a time. In addition, an electron microscopic reconstruction of its nervous system seems within reach. Notably, this electron microscope-based connectome is being drafted for a stage 1 larva. This study undertook a survey the behaviour of stage 1 larvae. In a community-based approach called the Ol1mpiad, stage 1 Drosophila larvae were probed for free locomotion, feeding, responsiveness to substrate vibration, gentle and nociceptive touch, burrowing, olfactory preference and thermotaxis, light avoidance, gustatory choice of various tastants plus odour-taste associative learning, as well as light/dark-electric shock associative learning (see Artificial Intelligence Helps Build Brain Atlas of Fly Behavior). Quantitatively, stage 1 larvae show lower scores in most tasks, arguably because of their smaller size and lower speed. Qualitatively, however, stage 1 larvae perform strikingly similar to stage 3 larvae in almost all cases. These results bolster confidence in mapping brain structure and behaviour across developmental stages. |
| Rohde, P. D., Gaertner, B., Wards, K., Sorensen, P. and Mackay, T. F. C. (2017). Genomic analysis of genotype by social environment interaction for Drosophila aggressive behavior. Genetics [Epub ahead of print]. PubMed ID: 28550016
Summary: Human psychiatric disorders such as schizophrenia, bipolar disorder and attention-deficit/hyper-activity disorder often include adverse behaviors including increased aggressiveness. Individuals with psychiatric disorders often exhibit social withdrawal, which can further increase the probability of conducting a violent act. This study used the inbred, sequenced lines of the Drosophila Genetic Reference Panel (DGRP) to investigate the genetic basis of variation in male aggressive behavior for flies reared in a socialized and socially isolated environment. Genetic variation was identified for aggressive behavior, as well as significant genotype by social environmental interaction (GSEI); i.e., variation among DGRP genotypes in the degree to which social isolation affected aggression. Genome-wide association (GWA) analyses was performed to identify genetic variants associated with aggression within each environment. Genomic prediction was used to partition genetic variants into gene ontology (GO) terms and constituent genes, and GO terms and genes were identified with high prediction accuracies in both social environments and for GSEI. The top predictive GO terms significantly increased the proportion of variance explained, compared to prediction models based on all segregating variants. Genomic prediction was performed across environments, and genes in common were identified between the social environments which turned to be enriched for genome-wide associated variants. A large proportion of the associated genes have previously been associated with aggressive behavior in Drosophila and mice. Further, many of these genes have human orthologs that have been associated with neurological disorders, indicating partially shared genetic mechanisms underlying aggression in animal models and human psychiatric disorders. | Shpigler, H. Y., Saul, M. C., Murdoch, E. E., Cash-Ahmed, A. C., Seward, C. H., Sloofman, L., Chandrasekaran, S., Sinha, S., Stubbs, L. J. and Robinson, G. E. (2017). Behavioral, transcriptomic and epigenetic responses to social challenge in honey bees. Genes Brain Behav 16(6): 579-591. PubMed ID: 28328153
Summary: Understanding how social experiences are represented in the brain and shape future responses is a major challenge in the study of behavior. This problem was addressed by studying behavioral, transcriptomic and epigenetic responses to intrusion in honey bees. Previous research showed that initial exposure to an intruder provokes an immediate attack; this study now shows that this also leads to longer-term changes in behavior in the response to a second intruder, with increases in the probability of responding aggressively and the intensity of aggression lasting 2 and 1 h, respectively. Previous research also documented the whole-brain transcriptomic response; it is now shown that in the mushroom bodies (MBs) there are 2 waves of gene expression, the first highlighted by genes related to cytoskeleton remodeling, and the second highlighted by genes related to hormones, stress response and transcription factors (TFs). Overall, 16 of 37 (43%) of the TFs whose cis-motifs were enriched in the promoters of the differentially expressed genes (DEGs) were also predicted from transcriptional regulatory network analysis to regulate the MB transcriptional response, highlighting the strong role played by a relatively small subset of TFs in the MB's transcriptomic response to social challenge. Whole brain histone profiling showed few changes in chromatin accessibility in response to social challenge; most DEGs were 'ready' to be activated. These results show how biological embedding of a social challenge involves temporally dynamic changes in the neurogenomic state of a prominent region of the insect brain that are likely to influence future behavior. |
| Signor, S. A., Abbasi, M., Marjoram, P. and Nuzhdin, S. V. (2017). Social effects for locomotion vary between environments in Drosophila melanogaster females. Evolution [Epub ahead of print]. PubMed ID: 28489252
Summary: Despite strong purifying or directional selection, variation is ubiquitous in populations. One mechanism for the maintenance of variation is indirect genetic effects (IGEs), as the fitness of a given genotype will depend somewhat on the genes of its social partners. IGEs describe the effect of genes in social partners on the expression of the phenotype of a focal individual. Here, it is asked what effect IGEs, and variation in IGEs between abiotic environments, has on locomotion in Drosophila. This trait is known to be subject to intralocus sexually antagonistic selection. The coefficient of interaction, Psi, was estimated using six inbred lines of Drosophila. It was found that Psi varied between abiotic environments, and that it may vary across among male genotypes in an abiotic environment specific manner. Evidence was found that social effects of males alter the value of a sexually dimorphic trait in females, highlighting an interesting avenue for future research into sexual antagonism. It is concluded that IGEs are an important component of social and sexual interactions and that they vary between individuals and abiotic environments in complex ways, with the potential to promote the maintenance of phenotypic variation. | Bazalova, O. and Dolezel, D. (2017). Daily activity of the housefly, Musca domestica, is influenced by temperature independence of 3' UTR period gene splicing. G3 (Bethesda). PubMed ID: 28620087
Summary: Circadian clocks orchestrate daily activity patterns and free running periods of locomotor activity under constant conditions. While the first often depends on temperature, the latter is temperature-compensated over a physiologically relevant range. This study explored the locomotor activity of the temperate housefly, Musca domestica Under low temperatures, activity was centered round a major and broad afternoon peak, while high temperatures resulted in activity throughout the photophase with a mild mid-day depression, which was especially pronounced in males exposed to long photoperiods. While period (per) mRNA peaked earlier under low temperatures, no temperature-dependent splicing of the last per 3' end intron was identified. The expression of timeless, vrille, and Par domain protein 1 was also influenced by temperature, each in a different manner. These data indicated that comparable behavioral trends in daily activity distribution have evolved in Drosophila melanogaster and Musca domestica, yet the behaviors of these two species are orchestrated by different molecular mechanisms. |
Saturday, July 15th |
| Shiba-Fukushima, K., Ishikawa, K. I., Inoshita, T., Izawa, N., Takanashi, M., Sato, S., Onodera, O., Akamatsu, W., Okano, H., Imai, Y. and Hattori, N. (2017). Evidence that phosphorylated ubiquitin signaling is involved in the etiology of Parkinson's disease. Hum Mol Genet [Epub ahead of print]. PubMed ID: 28541509
Summary: The ubiquitin (Ub) kinase PINK1 and the E3 Ub ligase Parkin, two gene products associated with young-onset Parkinson's disease (PD), participate in mitochondrial quality control. The phosphorylation of mitochondrial polyUb by PINK1, which is activated in a mitochondrial membrane potential (DeltaPsim)-dependent manner, facilitates the mitochondrial translocation and concomitant enzymatic activation of Parkin, leading to the clearance of phospho-polyUb-tagged mitochondria via mitophagy. Thus, Ub phosphorylation is a key event in PINK1-Parkin-mediated mitophagy. This study examined the role of phospho-Ub signaling in the pathogenesis of PD using fly PD models, human brain tissue and dopaminergic neurons derived from induced pluripotent stem cells (iPSCs) containing Parkin or PINK1 mutations, as well as normal controls. Phospho-Ub signaling was shown to be highly conserved between humans and Drosophila, and phospho-Ub signaling and the relocation of axonal mitochondria upon DeltaPsim reduction are indeed compromised in human dopaminergic neurons containing Parkin or PINK1 mutations. Moreover, phospho-Ub signaling is prominent in tyrosine hydroxylase-positive neurons compared with tyrosine hydroxylase-negative neurons, suggesting that PINK1-Parkin signaling is more required for dopaminergic neurons. These results shed light on the particular vulnerability of dopaminergic neurons to mitochondrial stress. | McLay, L. K., Green, M. P. and Jones, T. M. (2017). Chronic exposure to dim artificial light at night decreases fecundity and adult survival in Drosophila melanogaster. J Insect Physiol 100: 15-20. PubMed ID: 28499591
Summary: eas research moves into an increasing brightly lit future. |
| Shao, L., Lu, B., Wen, Z., Teng, S., Wang, L., Zhao, Y., Wang, L., Ishizuka, K., Xu, X., Sawa, A., Song, H., Ming, G. and Zhong, Y. (2017). Disrupted-in-Schizophrenia-1 (DISC1) protein disturbs neural function in multiple disease-risk pathways. Hum Mol Genet [Epub ahead of print]. PubMed ID: 28472294
Summary: Although the genetic contribution is under debate, biological studies in multiple mouse models have suggested that the Disrupted-in-Schizophrenia-1 (DISC1) protein may contribute to susceptibility to psychiatric disorders. Thus study took the advantage of the Drosophila model to dissect molecular pathways that can be affected by DISC1 in the context of pathology-related phenotypes. Three pathways that include the homologs of Drosophila Dystrophin, Trio, and Shot were found to be downregulated by introducing a C-terminal truncated mutant DISC1. Consistently, these three molecules were downregulated in the induced pluripotent stem cell-derived forebrain neurons from the subjects carrying a frameshift deletion in DISC1 C-terminus. Importantly, the three pathways were underscored in the pathophysiology of psychiatric disorders in bioinformatics analysis. Taken together, these findings are in line with the polygenic theory of psychiatric disorders. | Sealey, M. A., Vourkou, E., Cowan, C. M., Bossing, T., Quraishe, S., Grammenoudi, S., Skoulakis, E. M. C. and Mudher, A. (2017). Distinct phenotypes of three-repeat and four-repeat human tau in a transgenic model of tauopathy. Neurobiol Dis [Epub ahead of print]. PubMed ID: 28502805
Summary: Tau (see Drosophila tau) exists as six closely related protein isoforms in the adult human brain. These are generated from alternative splicing of a single mRNA transcript and they differ in the absence or presence of two N-terminal and three or four microtubule binding domains. Typically all six isoforms have been considered functionally similar. However, their differential involvement in particular tauopathies raises the possibility that there may be isoform-specific differences in physiological function and pathological role. This study has compared the phenotypes induced by the 0N3R and 0N4R isoforms in Drosophila. Expression of the 3R isoform causes more profound axonal transport defects and locomotor impairments, culminating in a shorter lifespan than the 4R isoform. In contrast, the 4R isoform leads to greater neurodegeneration and impairments in learning and memory. Furthermore, the phosphorylation patterns of the two isoforms are distinct, as is their ability to induce oxidative stress. These differences are not consequent to different expression levels and are suggestive of bona fide physiological differences in isoform biology and pathological potential. They may therefore explain isoform-specific mechanisms of tau-toxicity and the differential susceptibility of brain regions to different tauopathies. |
Friday, July 14th |
| Al Khatib, A., Siomava, N., Iannini, A., Posnien, N. and Casares, F. (2017). Specific expression and function of the Six3 optix in Drosophila serially homologous organs. Biol Open. PubMed ID: 28642242
Summary: Organ size and pattern results from the integration of two positional information systems. One global, encoded by the Hox genes, links organ type with position along the main body axis. Within specific organs, local information is conveyed by signaling molecules that regulate organ growth and pattern. The mesothoracic (T2) wing and the metathoracic (T3) haltere of Drosophila represent a paradigmatic example of this coordination. The Hox gene Ultrabithorax (Ubx), expressed in the developing T3, selects haltere identity by, among other processes, modulating the production and signaling efficiency of Dpp, a BMP2-like molecule that acts as a major regulator of size and pattern. Still, the mechanisms of the Hox-signal integration even in this well-studied system are incomplete. This study has investigated this issue by studying the expression and function of the Six3 transcription factor optix during the development of the Drosophila wing and haltere development. In both organs Dpp defines the expression domain of optix through repression, and that the specific position of this domain in wing and haltere seems to reflect the differential signaling profile among these organs. optix expression in wing and haltere primordia is conserved beyond Drosophila in other higher diptera. In Drosophila, optix is necessary for the growth of wing and haltere: In the wing, optix is required for the growth of the most anterior/proximal region (the "marginal cell") and for the correct formation of sensory structures along the proximal anterior wing margin, and the halteres of optix mutants are also significantly reduced. In addition, in the haltere optix is necessary for the suppression of sensory bristles. | Sharma, V., Pandey, A. K., Kumar, A., Misra, S., Gupta, H. P. K., Gupta, S., Singh, A., Buehner, N. A. and Ravi Ram, K. (2017). Functional male accessory glands and fertility in Drosophila require novel ecdysone receptor. PLoS Genet 13(5): e1006788. PubMed ID: 28493870
Summary: In many insects, the accessory gland, a secretory tissue of the male reproductive system, is essential for male fertility. Male accessory gland is the major source of proteinaceous secretions, collectively called as seminal proteins (or accessory gland proteins), which upon transfer, manipulate the physiology and behavior of mated females. Insect hormones such as ecdysteroids and juvenoids play a key role in accessory gland development and protein synthesis but little is known about underlying molecular players and their mechanism of action. This study examined the roles of hormone-dependent transcription factors (Nuclear Receptors), in accessory gland development, function and male fertility of a genetically tractable insect model, Drosophila melanogaster. First, an RNAi screen was carried out involving 19 hormone receptors, individually and specifically, in a male reproductive tissue (accessory gland) for their requirement in Drosophila male fertility. Subsequently, by using independent RNAi/ dominant negative forms, it was shown that Ecdysone Receptor (EcR) is essential for male fertility due to its requirement in the normal development of accessory glands in Drosophila: EcR depleted glands fail to make seminal proteins and have dying cells. Further, the data point to a novel ecdysone receptor that does not include Ultraspiracle but is probably comprised of EcR isoforms in Drosophila male accessory glands. The data suggest that this novel ecdysone receptor might act downstream of homeodomain transcription factor paired (prd) in the male accessory gland. Overall, the study suggests novel ecdysone receptor as an important player in the hormonal regulation of seminal protein production and insect male fertility. |
| Stahl, A. L., Charlton-Perkins, M., Buschbeck, E. K. and Cook, T. A. (2017). The cuticular nature of corneal lenses in Drosophila melanogaster. Dev Genes Evol [Epub ahead of print]. PubMed ID: 28477155
Summary: The dioptric visual system relies on precisely focusing lenses that project light onto a neural retina. While the proteins that constitute the lenses of many vertebrates are relatively well characterized, less is known about the proteins that constitute invertebrate lenses, especially the lens facets in insect compound eyes. To address this question, this study used mass spectrophotometry to define the major proteins that comprise the corneal lenses from the adult Drosophila melanogaster compound eye. This led to the identification of four cuticular proteins: two previously identified lens proteins, drosocrystallin and retinin, and two newly identified proteins, Cpr66D and Cpr72Ec. To determine which ommatidial cells contribute each of these proteins to the lens, in situ hybridization was conducted at 50% pupal development, a key age for lens secretion. The results confirm previous reports that drosocrystallin and retinin are expressed in the two primary corneagenous cells-cone cells and primary pigment cells. Cpr72Ec and Cpr66D, on the other hand, are more highly expressed in higher order interommatidial pigment cells. These data suggest that the complementary expression of cuticular proteins give rise to the center vs periphery of the corneal lens facet, possibly facilitating a refractive gradient that is known to reduce spherical aberration. Moreover, these studies provide a framework for future studies aimed at understanding the cuticular basis of corneal lens function in holometabolous insect eyes. | Uyehara, C. M., Nystrom, S. L., Niederhuber, M. J., Leatham-Jensen, M., Ma, Y., Buttitta, L. A. and McKay, D. J. (2017). Hormone-dependent control of developmental timing through regulation of chromatin accessibility. Genes Dev [Epub ahead of print]. PubMed ID: 28536147
Summary: Specification of tissue identity during development requires precise coordination of gene expression in both space and time. Spatially, master regulatory transcription factors are required to control tissue-specific gene expression programs. However, the mechanisms controlling how tissue-specific gene expression changes over time are less well understood. This study shows that hormone-induced transcription factors control temporal gene expression by regulating the accessibility of DNA regulatory elements. Using the Drosophila wing, it was demonstrated that temporal changes in gene expression are accompanied by genome-wide changes in chromatin accessibility at temporal-specific enhancers. A temporal cascade of transcription factors was uncovered following a pulse of the steroid hormone ecdysone such that different times in wing development can be defined by distinct combinations of hormone-induced transcription factors. Finally, the ecdysone-induced transcription factor E93 was shown to control temporal identity by directly regulating chromatin accessibility across the genome. Notably, it was found that E93 controls enhancer activity through three different modalities, including promoting accessibility of late-acting enhancers and decreasing accessibility of early-acting enhancers. Together, this work supports a model in which an extrinsic signal triggers an intrinsic transcription factor cascade that drives development forward in time through regulation of chromatin accessibility. |
Thursday, July 13th |
| Yasugi, T., Yamada, T. and Nishimura, T. (2017). Adaptation to dietary conditions by trehalose metabolism in Drosophila. Sci Rep 7(1): 1619. PubMed ID: 28487555
Summary: Trehalose is a non-reducing disaccharide that serves as the main sugar component of haemolymph in insects. Trehalose hydrolysis enzyme, called trehalase, is highly conserved from bacteria to humans. However, understanding of the physiological role of trehalase remains incomplete. This study analyzed the phenotypes of several Trehalase (Treh) loss-of-function alleles in a comparative manner in Drosophila. The previously reported mutant phenotype of Treh affecting neuroepithelial stem cell maintenance and differentiation in the optic lobe is caused by second-site alleles in addition to Treh. It is further reported that the survival rate of Treh null mutants is significantly influenced by dietary conditions. Treh mutant larvae are lethal not only on a low-sugar diet but also under low-protein diet conditions. A reduction in adaptation ability under poor food conditions in Treh mutants is mainly caused by the overaccumulation of trehalose rather than the loss of Treh, because the additional loss of Trehalose-6-phosphate synthase 1 mitigates the lethal effect of Treh mutants. These results demonstrate that proper trehalose metabolism plays a critical role in adaptation under various environmental conditions. | Stahl, B. A., Slocumb, M. E., Chaitin, H., Diangelo, J. R. and Keene, A. C. (2017). Sleep-dependent modulation of metabolic rate in Drosophila. Sleep [Epub ahead of print]. PubMed ID: 28541527
Summary: This study developed a system to simultaneously measure sleep and metabolic rate in individual Drosophila, allowing for interrogation of neural systems governing interactions between sleep and metabolic rate. Like mammals, metabolic rate in flies is reduced during sleep and increased during sleep deprivation suggesting sleep-dependent regulation of metabolic rate is conserved across phyla. The reduction of metabolic rate during sleep is not simply a consequence of inactivity because metabolic rate is reduced ~30 minutes following the onset of sleep, raising the possibility that CO2 production provides a metric to distinguish different sleep states in the fruit fly. It was determined that basal and sleep-dependent changes in metabolic rate are reduced in starved flies, suggesting that starvation inhibits normal sleep-associated effects on metabolic rate. Further, translin mutant flies that fail to suppress sleep during starvation demonstrate a lower basal metabolic rate, but this rate was further reduced in response to starvation, revealing that regulation of starvation-induced changes in metabolic rate and sleep duration are genetically distinct. Therefore, this system provides the unique ability to simultaneously measure sleep and oxidative metabolism, providing novel insight into the physiological changes associated with sleep and wakefulness in the fruit fly. |
| Zhang, X., Jin, Q. and Jin, L. H. (2017). High sugar diet disrupts gut homeostasis though JNK and STAT pathways in Drosophila. Biochem Biophys Res Commun 487(4): 910-916. PubMed ID: 28476621
Summary: The incidence of diseases associated with a high sugar diet has increased in the past years, and numerous studies have focused on the effect of high sugar intake on obesity and metabolic syndrome. However, how a high sugar diet influences gut homeostasis is still poorly understood. This study used Drosophila melanogaster as a model organism and supplemented a culture medium with 1 M sucrose to create a high sugar condition. The results indicate that a high sugar diet promoted differentiation of intestinal stem cells through upregulation of the JNK pathway and downregulation of the JAK/STAT pathway. Moreover, the number of commensal bacteria decreased in the high sugar group. These data suggests that the high caloric diet disrupts gut homeostasis and highlights Drosophila as an ideal model system to explore gastrointestinal disease. | Whon, T. W., Shin, N. R., Jung, M. J., Hyun, D. W., Kim, H. S., Kim, P. S. and Bae, J. W. (2017). Conditionally pathogenic gut microbes promote larval growth by increasing redox-dependent fat storage in high-sugar diet-fed Drosophila. Antioxid Redox Signal [Epub ahead of print]. PubMed ID: 28462587
Summary: Changes in the composition of the gut microbiota contribute to the development of obesity and subsequent complications that are associated with metabolic syndrome. This study demonstrate the inter-relationship between Drosophila and their resident gut microbiota under chronic high-sugar diet (HSD) conditions. Chronic feeding of an HSD to Drosophila resulted in a predominance of resident uracil-secreting bacteria in the gut. Axenic insects mono-associated with uracil-secreting bacteria or supplemented with uracil under HSD conditions promoted larval development. Redox signaling induced by bacterial uracil promoted larval growth by regulating sugar and lipid metabolism via activation of p38a mitogen-activated protein kinase. This study has identified a new redox-dependent mechanism by which uracil-secreting bacteria protect the host from metabolic perturbation under chronic HSD conditions. The results illustrate how Drosophila and gut microbes form a symbiotic relationship under stress conditions. |
Wednesday, July 12th |
| Praxenthaler, H., Nagel, A. C., Schulz, A., Zimmermann, M., Meier, M., Schmid, H., Preiss, A. and Maier, D. (2017). Hairless-binding deficient Suppressor of Hairless alleles reveal Su(H) protein levels are dependent on complex formation with Hairless. PLoS Genet 13(5): e1006774. PubMed ID: 28475577
Summary: Cell fate choices during metazoan development are driven by the highly conserved Notch signalling pathway. Notch receptor activation results in release of the Notch intracellular domain (NICD) that acts as transcriptional co-activator of the DNA-binding protein CSL. In the absence of signal, a repressor complex consisting of CSL bound to co-repressors silences Notch target genes. The Drosophila repressor complex contains the fly CSL orthologue Suppressor of Hairless [Su(H)] and Hairless (H). The Su(H)-H crystal structure revealed a large conformational change within Su(H) upon H binding, precluding interactions with NICD. Based on the structure, several sites in Su(H) and H were determined to specifically engage in complex formation. In particular, three mutations in Su(H) were identified that affect interactions with the repressor H but not the activator NICD. To analyse the effects these mutants have on normal fly development, these mutations were introduced into the native Su(H) locus by genome engineering. The three H-binding deficient Su(H) alleles were shown to behave similarly. As these mutants lack the ability to form the repressor complex, Notch signalling activity is strongly increased in homozygotes, comparable to a complete loss of H activity. Unexpectedly, it was found that the abundance of the three mutant Su(H) protein variants is altered, as is that of wild type Su(H) protein in the absence of H protein. In the presence of NICD, however, Su(H) mutant protein persists. Apparently, Su(H) protein levels depend on the interactions with H as well as with NICD. Based on these results, it is proposed that in vivo levels of Su(H) protein are stabilised by interactions with transcription-regulator complexes. | Yang, H., Basquin, D., Pauli, D. and Oliver, B. (2017). Drosophila melanogaster positive transcriptional elongation factors regulate metabolic and sex-biased expression in adults. BMC Genomics 18(1): 384. PubMed ID: 28521739
Summary: Transcriptional elongation is a generic function, but is also regulated to allow rapid transcription responses. Following relatively long initiation and promoter clearance, RNA polymerase II can pause and then rapidly elongate following recruitment of positive elongation factors. Multiple elongation complexes exist, but the role of specific components in adult Drosophila is underexplored. RNA-seq experiments were carried out to analyze the effect of RNAi knockdown of Suppressor of Triplolethal and lilliputian. Similarly the effect of expressing a dominant negative Cyclin-dependent kinase 9 allele was analyzed. Almost half of the genes expressed in adults showed reduced expression, supporting a broad role for the three tested genes in steady-state transcript abundance. Expression profiles following lilliputian and Suppressor of Triplolethal RNAi were nearly identical raising the possibility that they are obligatory co-factors. Genes showing reduced expression due to these RNAi treatments were short and enriched for genes encoding metabolic or enzymatic functions. The dominant-negative Cyclin-dependent kinase 9 profiles showed both overlapping and specific differential expression, suggesting involvement in multiple complexes. Hundreds of genes were observed with sex-biased differential expression following treatment. Thus, transcriptional profiles suggest that Lilliputian and Suppressor of Triplolethal are obligatory cofactors in the adult and that they can also function with Cyclin-dependent kinase 9 at a subset of loci. These results suggest that transcriptional elongation control is especially important for rapidly expressed genes to support digestion and metabolism, many of which have sex-biased function. |
| Holloway, D. M. and Spirov, A. V. (2017). Transcriptional bursting in Drosophila development: Stochastic dynamics of eve stripe 2 expression. PLoS One 12(4): e0176228. PubMed ID: 28437444
Summary: Anterior-posterior (AP) body segmentation in Drosophila is first seen in the 7-stripe spatial expression patterns of the pair-rule genes, which regulate downstream genes determining specific segment identities. This study developed a stochastic model of the spatial and temporal expression of eve stripe 2 -- binding by transcriptional activators (Bicoid and Hunchback proteins) and repressors (Giant and Kruppel proteins) with all rate parameters constrained by features of the experimental data) -- in order to analyze the noisy experimental time series and test hypotheses for how eve transcription is regulated. Short-time (minute-to-minute) statistics of the data is indicative of eve being transcribed with at least two distinct ON rates, consistent with data on the joint activation of eve by Bicoid and Hunchback. Distinct statistical signatures were predicted for cases in which eve is repressed (e.g. along the edges of the stripe) vs. cases in which activation is reduced (e.g. by mutagenesis of transcription factor binding sites). This approach presents a new way to quantify and analyze time series data during developmental patterning in order to understand regulatory mechanisms and how they propagate noise and impact embryonic robustness. | Kim, J., Lu, C., Srinivasan, S., Awe, S., Brehm, A. and Fuller, M. T. (2017). Blocking promiscuous activation at cryptic promoters directs cell type-specific gene expression. Science 356(6339): 717-721. PubMed ID: 28522526
Summary: To selectively express cell type-specific transcripts during development, it is critical to maintain genes required for other lineages in a silent state. This study shows in the Drosophila male germline stem cell lineage that a spermatocyte-specific zinc finger protein, Kumgang (Kmg; CG5204), working with the chromatin remodeler dMi-2 prevents transcription of genes normally expressed only in somatic lineages. By blocking transcription from normally cryptic promoters, Kmg restricts activation by Aly, a component of the testis-meiotic arrest complex, to transcripts for male germ cell differentiation. These results suggest that as new regions of the genome become open for transcription during terminal differentiation, blocking the action of a promiscuous activator on cryptic promoters is a critical mechanism for specifying precise gene activation. |
Tuesday, July 11th |
| Johnson, T. K., Moore, K. A., Whisstock, J. C. and Warr, C. G. (2017). Maternal Torso-like coordinates tissue folding during Drosophila gastrulation. Genetics 206(3):1459-1468. PubMed ID: 28495958
Summary: The rapid and orderly folding of epithelial tissue during developmental processes such as gastrulation requires the precise coordination of changes in cell shape. This study reports that the perforin-like protein Torso-like (Tsl), the key extracellular determinant for Drosophila embryonic terminal patterning, also functions to control epithelial morphogenesis. tsl null mutants were found display a ventral cuticular hole phenotype that is independent of the loss of terminal structures, and arises as a consequence of mesoderm invagination defects. The holes are caused by uncoordinated constriction of ventral cell apices, resulting in the formation of an incomplete ventral furrow. Consistent with these data, it was found that loss of tsl is sensitive to gene dosage of RhoGEF2, a critical mediator of Rho1-dependent ventral cell shape changes during furrow formation, suggesting that Tsl may act in this pathway. In addition, loss of tsl strongly suppressed the effects of ectopic expression of Fog, a secreted protein that promotes apical constriction. Taken together, these data suggests that Tsl controls Rho1-mediated apical constriction via Fog. It is therefore proposed that Tsl regulates extracellular Fog activity in order to synchronise cell shape changes and coordinate ventral morphogenesis in Drosophila. Identifying the Tsl-mediated event that is common to both terminal patterning and morphogenesis will be valuable for understanding of the extracellular control of developmental signalling by perforin-like proteins. | Hunding, A. and Baumgartner, S. (2017). Ancient role of ten-m/odz in segmentation and the transition from sequential to syncytial segmentation. Hereditas 154: 8. PubMed ID: 28461810
Summary: Until recently, mechanisms of segmentation established for Drosophila served as a paradigm for arthropod segmentation. However, with the discovery of gene expression waves in vertebrate segmentation, another paradigm based on oscillations linked to axial growth was established. The Notch pathway and hairy delay oscillator are basic components of this mechanism, as is the wnt pathway. With the establishment of oscillations during segmentation of the beetle Tribolium, a common segmentation mechanism may have been present in the last common ancestor of vertebrates and arthropods. However, the Notch pathway is not involved in segmentation of the initial Drosophila embryo. In arthropods, the engrailed, wingless pair has a much more conserved function in segmentation than most of the hierarchy established for Drosophila. This study worked backwards from this conserved pair by discussing possible mechanisms which could have taken over the role of the Notch pathway. A pivotal role is proposed for the large transmembrane protein Ten-m/Odz. Ten-m/Odz may have had an ancient role in cell-cell communication, parallel to the Notch and wnt pathways. The Ten-m protein binds to the membrane with properties which resemble other membrane-based biochemical oscillators. It is proposed that such a simple transition could have formed the initial scaffold, on top of which the hierarchy, observed in the syncytium of dipterans, could have evolved. |
| Winkler, F., Kriebel, M., Clever, M., Groning, S. and Grosshans, J. (2017). Essential function of the serine hydroxymethyl transferase (SHMT) gene during rapid syncytial cell cycles in Drosophila. G3 (Bethesda) 7(7):2305-2314. PubMed ID: 28515048
Summary: Many metabolic enzymes are evolutionary highly conserved and serve a central function for catabolism and anabolism of cells. The serine hydroxymethyl transferase (SHMT) catalysing the conversion of serine and glycine and vice versa feeds into the tetrahydrofolate mediated C1 metabolism. This study identified a Drosophila mutation in SHMT (CG3011) in a screen for blastoderm mutants. Embryos from SHMT mutant germline clones specifically arrest the cell cycle in interphase 13 at the time of the mid blastula transition (MBT) and prior to cellularisation. The phenotype is due to a loss of enzymatic activity as it cannot be rescued by an allele with a point mutation in the catalytic center but by an allele based on the SHMT coding sequence from E. coli. Onset of zygotic gene expression and degradation of maternal RNAs in SHMT mutant embryos are largely similar to wild type embryos. The specific timing of the defects in SHMT mutants indicates that at least one of the SHMT-dependent metabolites becomes limiting in interphase 13, if it is not produced by the embryo. These data suggest that mutant eggs contain maternally provided and SHMT-dependent metabolites in amounts which suffice for early development until interphase 13. | Arredondo, J. J., Vivar, J., Laine-Menendez, S., Martinez-Morentin, L. and Cervera, M. (2017). CF2 transcription factor is involved in the regulation of Mef2 RNA levels, nuclei number and muscle fiber size. PLoS One 12(6): e0179194. PubMed ID: 28617826
Summary: CF2 and Mef2 influence a variety of developmental muscle processes at distinct stages of development. Nevertheless, the exact nature of the CF2-Mef2 relationship and its effects on muscle building remain yet to be resolved. This study explored the regulatory role of CF2 in the Drosophila embryo muscle formation. To address this question and not having proper null CF2 mutants, loss or gain of function strategies were employed to study the contribution of CF2 to Mef2 transcription regulation and to muscle formation. The data point to CF2 as a factor involved in the regulation of muscle final size and/or the number of nuclei present in each muscle. This function is independent of its role as a Mef2 collaborative factor in the transcriptional regulation of muscle-structural genes. Although Mef2 expression patterns do not change, reductions or increases in parallel in CF2 and Mef2 transcript abundance were observed in interfered and overexpressed CF2 embryos. Since CF2 expression variations yield altered Mef2 expression levels but with correct spatio-temporal Mef2 expression patterns, it can be concluded that only the mechanism controlling expression levels is de-regulated. It is proposed that CF2 regulates Mef2 expression through a Feedforward Loop circuit. |
Monday, July 10th |
| Vonhoff, F. and Keshishian, H. (2017). In vivo calcium signaling during synaptic refinement at the Drosophila neuromuscular junction. J Neurosci [Epub ahead of print]. PubMed ID: 28476946
Summary: Neural activity plays a key role in pruning aberrant synapses in various neural systems, including the mammalian cortex, where low frequency (0.01 Hz) calcium oscillations refine topographic maps. However, the activity-dependent molecular mechanisms remain incompletely understood. Activity-dependent pruning also occurs at embryonic Drosophila neuromuscular junctions (NMJs), where low frequency Ca2+ oscillations are required for synaptic refinement and the response to the muscle-derived chemorepellant Sema2a. This study examined embryonic growth-cone filopodia in vivo to directly observe their exploration and to analyze the episodic Ca2+ oscillations involved in refinement. Motoneuron filopodia repeatedly contacted off-target muscle fibers over several hours during late embryogenesis, with episodic Ca2+ signals present in both motile filopodia as well as in later-stabilized synaptic boutons. The Ca2+ transients matured over several hours into regular low frequency (0.03Hz) oscillations. In vivo imaging of intact embryos of both sexes revealed that the formation of ectopic filopodia is increased in Sema2a heterozygotes. Genetic evidence is provided suggesting a complex presynaptic Ca2+-dependent signaling network underlying refinement that involves the phosphatases Calcineurin and PP1, as well the serine/threonine kinases CaMKII and PKA. Significantly, this network influenced the neuron's response to the muscle's Sema2a chemorepellant, critical for the removal of off-target contacts. | Shibata, T., Hadano, J., Kawasaki, D., Dong, X. and Kawabata, S. I. (2017). Drosophila TG-A transglutaminase is secreted via an unconventional Golgi-independent mechanism involving exosomes and two types of fatty acylations. J Biol Chem [Epub ahead of print]. PubMed ID: 28476891
Summary: Transglutaminases (TGs) play essential intracellular and extracellular roles by covalently cross-linking many proteins. Drosophila TG is encoded by one gene and has two alternative splicing-derived isoforms, TG-A and TG-B, which contain distinct N-terminal 46- and 38-amino acid sequences, respectively. Immunocytochemistry revealed that TG-A localizes to multivesicular-like structures, whereas TG-B localizes to the cytosol. TG-A, but not TG-B, was found to be modified concomitantly by N-myristoylation and S-palmitoylation. Moreover, TG-A, but not TG-B, was secreted in response to calcium signaling induced by Ca2+ ionophores and uracil, a pathogenic bacteria-derived substance. Brefeldin A and monensin, inhibitors of the ER/Golgi-mediated conventional pathway, did not suppress TG-A secretion, whereas inhibition of S-palmitoylation by 2-bromopalmitate blocked TG-A secretion. TG-A was shown to be secreted via exosomes together with co-transfected mammalian CD63, an exosomal marker, and the secreted TG-A was taken up by other cells. The 8-residue N-terminal fragment of TG-A containing the fatty acylation sites was both necessary and sufficient for the exosome-dependent secretion of TG-A. In conclusion, TG-A is secreted through an unconventional ER/Golgi-independent pathway involving two types of fatty acylations and exosomes. |
| Wang, C. H., Huang, Y. C., Chen, P. Y., Cheng, Y. J., Kao, H. H., Pi, H. and Chien, C. T. (2017). USP5/Leon deubiquitinase confines postsynaptic growth by maintaining ubiquitin homeostasis through Ubiquilin. Elife 6. PubMed ID: 28489002
Summary: Synapse formation and growth are tightly controlled processes. How synaptic growth is terminated after reaching proper size remains unclear. This study shows that Leon, the Drosophila USP5 deubiquitinase, controls postsynaptic growth. In leon mutants, postsynaptic specializations of neuromuscular junctions are dramatically expanded, including the subsynaptic reticulum, the postsynaptic density, and the glutamate receptor cluster. Expansion of these postsynaptic features is caused by a disruption of ubiquitin homeostasis with accumulation of free ubiquitin chains and ubiquitinated substrates in the leon mutant. Accumulation of Ubiquilin (Ubqn), the ubiquitin receptor whose human homolog ubiquilin 2 is associated with familial amyotrophic lateral sclerosis, also contributes to defects in postsynaptic growth and ubiquitin homeostasis. Importantly, accumulations of postsynaptic proteins cause different aspects of postsynaptic overgrowth in leon mutants. Thus, the deubiquitinase Leon maintains ubiquitin homeostasis and proper Ubqn levels, preventing postsynaptic proteins from accumulation to confine postsynaptic growth. | Lorincz, P., Toth, S., Benko, P., Lakatos, Z., Boda, A., Glatz, G., Zobel, M., Bisi, S., Hegedus, K., Takats, S., Scita, G. and Juhasz, G. (2017). Rab2 promotes autophagic and endocytic lysosomal degradation. J Cell Biol. PubMed ID: 28483915
Summary: Rab7 promotes fusion of autophagosomes and late endosomes with lysosomes in yeast and metazoan cells, acting together with its effector, the tethering complex HOPS. This study shows that another small GTPase, Rab2, is also required for autophagosome and endosome maturation and proper lysosome function in Drosophila melanogaster. This study demonstrates that Rab2 binds to HOPS, and that its active, GTP-locked form associates with autolysosomes. Importantly, expression of active Rab2 promotes autolysosomal fusions unlike that of GTP-locked Rab7, suggesting that its amount is normally rate limiting. It was also demonstrated that RAB2A is required for autophagosome clearance in human breast cancer cells. In conclusion, this study identified Rab2 as a key factor for autophagic and endocytic cargo delivery to and degradation in lysosomes. |
Sunday, July 9th |
| Torres, A. Y., Malartre, M., Pret, A. M. and Agnes, F. (2017). JAK/STAT signaling is necessary for cell monosis prior to epithelial cell apoptotic extrusion. Cell Death Dis 8(5): e2814. PubMed ID: 28542149
Summary: Epithelial cell extrusion is crucial for proper development and tissue homeostasis. Highly-sterotyped morphogenetic events are controlled by JAK/STAT signaling in a developmentally-programmed case of epithelial cell extrusion. Specialized somatic cells, Polar Cells (PCs), are produced in excess and then undergo apoptotic elimination from the follicular epithelium in the Drosophila ovary. This study shows that supernumerary PCs are systematically enveloped by PC neighbors on all sides in conjunction with highly-reinforced adherens junctions. The PC to be removed thus loses all contact with follicle cells, germline cells and the basement membrane in a process called cell 'monosis', for 'isolation' in Greek. PC monosis takes several hours, and always precedes, and is independent of, activation of apoptosis. JAK/STAT signaling is necessary within the surrounding follicular epithelium for PC monosis. Minutes after monosis is complete, PC apoptotic corpses are formed and extruded laterally within the epithelium. These apoptotic corpses are engulfed and eliminated by surrounding follicle cells, which are thus acting as non-professional phagocytes. This study therefore shows the non cell-autonomous impact of an epithelium, via JAK/STAT signaling activation, on cell morphogenesis events leading to apoptotic extrusion. It is likely that cell monosis and lateral extrusion within an epithelium are pertinent for other cases of epithelial cell extrusion as well. | Tsai, C. R., Anderson, A. E., Burra, S., Jo, J. and Galko, M. J. (2017). Yorkie regulates epidermal wound healing in Drosophila larvae independently of cell proliferation and apoptosis. Dev Biol 427(1):61-71. PubMed ID: 28514643 Summary: Yorkie (Yki), the transcriptional co-activator of the Hippo signaling pathway, has well-characterized roles in balancing apoptosis and cell division during organ growth control. Yki is also required in diverse tissue regenerative contexts. In most cases this requirement reflects its well-characterized roles in balancing apoptosis and cell division. Whether Yki has repair functions outside of the control of cell proliferation, death, and growth is not clear. This study shows that Yki and Scalloped (Sd) are required for epidermal wound closure in the Drosophila larval epidermis. Using a GFP-tagged Yki transgene, Yki was shown to transiently translocate to some epidermal nuclei upon wounding. Genetic analysis strongly suggests that Yki interacts with the known wound healing pathway, Jun N-terminal kinase (JNK), but not with Platelet Derived Growth Factor/Vascular-Endothelial Growth Factor receptor (Pvr). Yki likely acts downstream of or parallel to JNK signaling and does not appear to regulate either proliferation or apoptosis in the larval epidermis during wound repair. Analysis of actin structures after wounding suggests that Yki and Sd promote wound closure through actin regulation. In sum, this study found that Yki regulates an epithelial tissue repair process independently of its previously documented roles in balancing proliferation and apoptosis. |
| Tu, R., Qian, J., Rui, M., Tao, N., Sun, M., Zhuang, Y., Lv, H., Han, J., Li, M. and Xie, W. (2017). Proteolytic cleavage is required for functional Neuroligin 2 maturation and trafficking in Drosophila. J Mol Cell Biol 9(3):231-242. PubMed ID: 28498949
Summary: Neuroligins are transmembrane cell adhesion molecules playing essential roles in synapse development and function. Genetic mutations in neuroligin genes have been linked with some neurodevelopmental disorders such as autism. These mutated Neuroligins are mostly retained in the endoplasmic reticulum (ER). However, the mechanisms underlying normal Neuroligin maturation and trafficking have remained largely unknown. This study found that Drosophila Neuroligin 2 (DNlg2) undergoes proteolytic cleavage in the ER in a variety of Drosophila tissues throughout developmental stages. A region encompassing Y642-T698 is required for this process. The immature non-cleavable DNlg2 is retained in the ER and is non-functional. The C-terminal fragment (CTF) of DNlg2 instead of the full-length or non-cleavable DNlg2 is able to rescue neuromuscular junction defects and GluRIIB reduction induced by dnlg2 deletion. Intriguingly, the autism-associated R598C mutation in DNlg2 leads to similar marked defects in DNlg2 proteolytic process and ER export, revealing a potential role of the improper Neuroligin cleavage in autism pathogenesis. Collectively, these findings uncover a specific mechanism that controls DNlg2 maturation and trafficking via proteolytic cleavage in the ER, suggesting that the perturbed proteolytic cleavage of Neuroligins likely contributes to autism disorder. | Xiang, J., Bandura, J., Zhang, P., Jin, Y., Reuter, H. and Edgar, B. A. (2017). EGFR-dependent TOR-independent endocycles support Drosophila gut epithelial regeneration. Nat Commun 8: 15125. PubMed ID: 28485389
Summary: Following gut epithelial damage, epidermal growth factor receptor/mitogen-activated protein kinase (EGFR/MAPK) signalling triggers Drosophila intestinal stem cells to produce enteroblasts (EBs) and enterocytes (ECs) that regenerate the gut. As EBs differentiate into ECs, they become postmitotic, but undergo extensive growth and DNA endoreplication. This study reports that EGFR/RAS/MAPK signalling is required and sufficient to drive damage-induced EB/EC growth. Endoreplication occurs exclusively in EBs and newborn ECs that inherit EGFR and active MAPK from fast-dividing progenitors. Mature ECs lack EGF receptors and are refractory to growth signalling. Genetic tests indicated that stress-dependent EGFR/MAPK promotes gut regeneration via a novel mechanism that operates independently of Insulin/Pi3K/TOR signalling, which is nevertheless required in nonstressed conditions. The E2f1 transcription factor is required for and sufficient to drive EC endoreplication, and Ras/Raf signalling upregulates E2f1 levels posttranscriptionally. This study illustrates how distinct signalling mechanisms direct stress-dependent versus homeostatic regeneration, and highlight the importance of postmitotic cell growth in gut epithelial repair. |
Saturday, June 8th |
| Ni, J. D., Baik, L. S., Holmes, T. C. and Montell, C. (2017). A rhodopsin in the brain functions in circadian photoentrainment in Drosophila. Nature 545(7654): 340-344. PubMed ID: 28489826
Summary: Animals partition their daily activity rhythms through their internal circadian clocks, which are synchronized by oscillating day-night cycles of light. The fruitfly Drosophila melanogaster senses day-night cycles in part through rhodopsin-dependent light reception in the compound eye and photoreceptor cells in the Hofbauer-Buchner eyelet. A more noteworthy light entrainment pathway is mediated by central pacemaker neurons in the brain. The Drosophila circadian clock is extremely sensitive to light. However, the only known light sensor in pacemaker neurons, the flavoprotein Cryptochrome (Cry), responds only to high levels of light in vitro. These observations indicate that there is an additional light-sensing pathway in fly pacemaker neurons. This study describes a previously uncharacterized rhodopsin, Rh7, which contributes to circadian light entrainment by circadian pacemaker neurons in the brain. The pacemaker neurons respond to violet light, and this response depends on Rh7. Loss of either cry or rh7 caused minor defects in photoentrainment, whereas loss of both caused profound impairment. The circadian photoresponse to constant light was impaired in rh7 mutant flies, especially under dim light. The demonstration that Rh7 functions in circadian pacemaker neurons represents the first role for an opsin in the central brain. | Shimizu, K. and Stopfer, M. (2017). A population of projection neurons that inhibits the lateral horn but excites the antennal lobe through chemical synapses in Drosophila. Front Neural Circuits 11: 30. PubMed ID: 28515683
Summary: In the insect olfactory system, odor information is transferred from the antennal lobe (AL) to higher brain areas by projection neurons (PNs) in multiple AL tracts (ALTs). In several species, one of the ALTs, the mediolateral ALT (mlALT), contains some GABAergic PNs; in the Drosophila brain, the great majority of ventral PNs (vPNs) are GABAergic and project through this tract to the lateral horn (LH). Most excitatory PNs (ePNs), project through the medial ALT (mALT) to the mushroom body (MB) and the LH. Recent studies have shown that GABAergic vPNs play inhibitory roles at their axon terminals in the LH. However, little is known about the properties and functions of vPNs at their dendritic branches in the AL. This study used optogenetic and patch clamp techniques to investigate the functional roles of vPNs in the AL. Surprisingly, the results show that specific activation of vPNs reliably elicits strong excitatory postsynaptic potentials (EPSPs) in ePNs. Moreover, the connections between vPNs and ePNs are mediated by direct chemical synapses. Neither pulses of GABA, nor pharmagological, or genetic blockade of GABAergic transmission gave results consistent with the involvement of GABA in vPN-ePN excitatory transmission. These unexpected results suggest new roles for the vPN population in olfactory information processing. |
| Shyu, W. H., Chiu, T. H., Chiang, M. H., Cheng, Y. C., Tsai, Y. L., Fu, T. F., Wu, T. and Wu, C. L. (2017). Neural circuits for long-term water-reward memory processing in thirsty Drosophila. Nat Commun 8: 15230. PubMed ID: 28504254
Summary: The intake of water is important for the survival of all animals and drinking water can be used as a reward in thirsty animals. This study found that thirsty Drosophila melanogaster can associate drinking water with an odour to form a protein-synthesis-dependent water-reward long-term memory (LTM). Furthermore, the reinforcement of LTM requires water-responsive dopaminergic neurons projecting to the restricted region of mushroom body (MB) β' lobe, which are different from the neurons required for the reinforcement of learning and short-term memory (STM). Synaptic output from α'β' neurons is required for consolidation, whereas the output from γ and αβ neurons is required for the retrieval of LTM. Finally, two types of MB efferent neurons retrieve LTM from γ and αβ neurons by releasing glutamate and acetylcholine, respectively. These results therefore cast light on the cellular and molecular mechanisms responsible for processing water-reward LTM in Drosophila. | Takemura, S. Y., Nern, A., Chklovskii, D. B., Scheffer, L. K., Rubin, G. M. and Meinertzhagen, I. A. (2017). The comprehensive connectome of a neural substrate for 'ON' motion detection in Drosophila. Elife 6 [Epub ahead of print]. PubMed ID: 28432786
Summary: Analysing computations in neural circuits often uses simplified models because the actual neuronal implementation is not known. For example, a problem in vision, how the eye detects image motion, has long been analysed using Hassenstein-Reichardt (HR) detector or Barlow-Levick (BL) models. These both simulate motion detection well, but the exact neuronal circuits undertaking these tasks remain elusive. This study reconstructed a comprehensive connectome of the circuits of Drosophila's motion-sensing T4 cells using a novel EM technique. Complex T4 inputs were uncovered, and putative excitatory inputs cluster were revealed at T4's dendrite shafts, while inhibitory inputs localize to the bases. Consistent with a previous study, this. study revealed that Mi1 and Tm3 cells provide most synaptic contacts onto T4. It was not possible, however, to reproduce the spatial offset between these cells reported previously. This comprehensive connectome reveals complex circuits that include candidate anatomical substrates for both HR and BL types of motion detectors. |
Friday, July 7th |
| Liao, S., Broughton, S. and Nassel, D. R. (2017). Behavioral senescence and aging-related changes in motor neurons and brain neuromodulator levels are ameliorated by lifespan-extending reproductive dormancy in Drosophila. Front Cell Neurosci 11: 111. PubMed ID: 28503133
Summary: The lifespan of Drosophila can be extended substantially by inducing reproductive dormancy (also known as diapause) by lowered temperature and short days. This increase of longevity is accompanied by lowered metabolism and increased stress tolerance. This study asked whether behavioral senescence is ameliorated during adult dormancy. To study this flies were kept for seven or more weeks in normal rearing conditions or in diapause conditions and compared to 1-week-old flies in different behavioral assays of sleep, negative geotaxis and exploratory walking. The senescence of geotaxis and locomotor behavior seen under normal rearing conditions was negligible in flies kept in dormancy. The normal senescence of rhythmic activity and sleep patterns during the daytime was also reduced by adult dormancy. To monitor age-associated changes in neuronal circuits regulating activity rhythms, sleep and walking behavior antisera were applied to tyrosine hydroxylase (TH), serotonin and several neuropeptides to examine changes in expression levels and neuron morphology. In most neuron types the levels of stored neuromodulators decreased during normal aging, but not in diapause treated flies. No signs of neurodegeneration were seen in either condition. These data suggest that age-related changes in motor neurons could be the cause of part of the behavioral senescence and that this is ameliorated by reproductive diapause. Thus, it is likely that the retained levels of neuromodulators in dormant flies alleviate behavioral senescence. | Qiang, W., Huang, Y., Wan, Z. and Zhou, B. (2017). Metal-metal interaction mediates the iron induction of Drosophila MtnB. Biochem Biophys Res Commun 487(3): 646-652. PubMed ID: 28435068
Summary: Metallothionein (MT) protein families are a class of small and universal proteins rich in cysteine residues. They are synthesized in response to heavy metal stresses to sequester the toxic ions by metal-thiolate bridges. Five MT family members, namely MtnA, MtnB, MtnC, MtnD and MtnE, have been discovered and identified in Drosophila. These five isoforms of MTs are regulated by metal responsive transcription factor dMTF-1 and play differentiated but overlapping roles in detoxification of metal ions. Previous researches have shown that Drosophila MtnB responds to copper (Cu), cadmium (Cd) and zinc (Zn). Interestingly this study found that Drosophila MtnB expression also responds to elevated iron levels in the diet. Further investigations revealed that MtnB plays limited roles in iron detoxification, and the direct binding of MtnB to ferrous iron in vitro is also weak. The induction of MtnB by iron turns out to be mediated by iron interference of other metals, because EDTA at even a partial concentration of that of iron can suppress this induction. Indeed, in the presence of iron, zinc homeostasis is altered, as reflected by expression changes of zinc transporters dZIP1 and dZnT1. Thus, iron-mediated MtnB induction appears resulting from interrupted homeostasis of other metals such as zinc, which in turns induced MtnB expression. Metal-metal interaction may more widely exist than has been expected. |
| Shiehzadegan, S., Le Vinh Thuy, J., Szabla, N., Angilletta, M. J., Jr. and VandenBrooks, J. M. (2017). More oxygen during development enhanced flight performance but not thermal tolerance of Drosophila melanogaster. PLoS One 12(5): e0177827. PubMed ID: 28542380
Summary: High temperatures can stress animals by raising the oxygen demand above the oxygen supply. Consequently, animals under hypoxia could be more sensitive to heating than those exposed to normoxia. Although support for this model has been limited to aquatic animals, oxygen supply might limit the heat tolerance of terrestrial animals during energetically demanding activities. This model was evaluated by studying the flight performance and heat tolerance of flies (Drosophila melanogaster) acclimated and tested at different concentrations of oxygen (12%, 21%, and 31%). It was expected that flies raised at hypoxia would develop into adults that were more likely to fly under hypoxia than would flies raised at normoxia or hyperoxia. Flies were also expected to benefit from greater oxygen supply during testing. These effects should have been most pronounced at high temperatures, which impair locomotor performance. Contrary to expectations, little evidence was found that flies raised at hypoxia flew better when tested at hypoxia or tolerated extreme heat better than did flies raised at normoxia or hyperoxia. Instead, flies raised at higher oxygen levels performed better at all body temperatures and oxygen concentrations. Moreover, oxygen supply during testing had the greatest effect on flight performance at low temperature, rather than high temperature. These results poorly support the hypothesis that oxygen supply limits performance at high temperatures, but do support the idea that hyperoxia during development improves performance of flies later in life. | Tower, J., Landis, G. N., Shen, J., Choi, R., Fan, Y., Lee, D. and Song, J. (2017). Mifepristone/RU486 acts in Drosophila melanogaster females to counteract the life span-shortening and pro-inflammatory effects of male Sex Peptide. Biogerontology 18(3): 413-427. PubMed ID: 28451923
Summary: Males with null mutation of Sex Peptide (SP) gene were compared to wild-type males for the ability to cause physiological changes in females that could be reversed by mifepristone (RU-486). Males from wild-type strains decreased median female life span by average -51%. Feeding mifepristone increased life span of these females by average +106%. In contrast, SP-null males did not decrease female life span, and mifepristone increased median life span of these females by average +14%, which was equivalent to the effect of mifepristone in virgin females (average +16%). Expression of innate immune response transgenic reporter (Drosocin-GFP) was increased in females mated to wild-type males, and this expression was reduced by mifepristone. In contrast, SP-null males did not increase Drosocin-GFP reporter expression in the female. Similarly, mating increased endogenous microbial load, and this effect was reduced or absent in females fed mifepristone and in females mated to SP-null males; no loss of intestinal barrier integrity was detected using dye-leakage assay. Reduction of microbial load by treating adult flies with doxycycline reduced the effects of both mating and mifepristone on life span. Finally, mifepristone blocked the negative effect on life span caused by transgenic expression of SP in virgin females. The data support the conclusion that the majority of the life span-shortening, immune-suppressive and pro-inflammatory effects of mating are due to male SP, and demonstrate that mifepristone acts in females to counteract these effects of male SP. |
Thursday, July 6th |
| Schunter, S., Villa, R., Flynn, V., Heidelberger, J. B., Classen, A. K., Beli, P. and Becker, P. B. (2017). Ubiquitylation of the acetyltransferase MOF in Drosophila melanogaster. PLoS One 12(5): e0177408. PubMed ID: 28510597
Summary: The nuclear acetyltransferase MOF (KAT8 in mammals) is a subunit of at least two multi-component complexes involved in transcription regulation. In the context of complexes of the 'Non-Specific-Lethal' (NSL) type it controls transcription initiation of many nuclear housekeeping genes and of mitochondrial genes. While this function is conserved in metazoans, MOF has an additional, specific function in Drosophila in the context of dosage compensation. As a subunit of the male-specific-lethal dosage compensation complex (MSL-DCC) it contributes to the doubling of transcription output from the single male X chromosome by acetylating histone H4. Proper dosage compensation requires finely tuned levels of MSL-DCC and an appropriate distribution of MOF between the regulatory complexes. The amounts of DCC formed depends directly on the levels of the male-specific MSL2, which orchestrates the assembly of the DCC, including MOF recruitment. Earlier studies found that MSL2 is an E3 ligase that ubiquitylates most MSL proteins, including MOF, suggesting that ubiquitylation may contribute to a quality control of MOF's overall levels and folding state as well as its partitioning between the complex entities. This study used mass spectrometry to map the lysines in MOF that are ubiquitylated by MSL2 in vitro and identified in vivo ubiquitylation sites of MOF in male and female cells. MSL2-specific ubiquitylation in vivo could not be traced due to the dominance of other, sex-independent ubiquitylation events and conceivably may be rare or transient. Expressing appropriately mutated MOF derivatives, the importance of the ubiquitylated lysines for dosage compensation was assessed by monitoring DCC formation and X chromosome targeting in cultured cells, and by genetic complementation of the male-specific-lethal mof2 allele in flies. This study provides a comprehensive analysis of MOF ubiquitylation as a reference for future studies. | Joshi, S. S. and Meller, V. H. (2017). Satellite repeats identify X chromatin for dosage compensation in Drosophila melanogaster males. Curr Biol 27(10): 1393-1402.e1392. PubMed ID: 28457869
Summary: A common feature of sex chromosomes is coordinated regulation of X-linked genes in one sex. Drosophila melanogaster males have one X chromosome, whereas females have two. The resulting imbalance in gene dosage is corrected by increased expression from the single X chromosome of males, a process known as dosage compensation. In flies, compensation involves recruitment of the male-specific lethal (MSL) complex to X-linked genes and modification of chromatin to increase expression. The extraordinary selectivity of the MSL complex for the X chromosome has never been explained. Previously work has demonstrated that the small interfering RNA (siRNA) pathway and siRNA from a family of X-linked satellite repeats (1.688X repeats) promote X recognition. This study now tests the ability of 1.688X DNA to attract compensation to genes nearby; autosomal integration of 1.688X repeats is shown to increase MSL recruitment and gene expression in surrounding regions. Placement of 1.688X repeats opposite a lethal autosomal deletion achieves partial rescue of males, demonstrating functional compensation of autosomal chromatin. Females block formation of the MSL complex and are not rescued. The 1.688X repeats are therefore cis-acting elements that guide dosage compensation. Furthermore, 1.688X siRNA enhances rescue of males with a lethal deletion but only when repeat DNA is present on the intact homolog. It is proposed that the siRNA pathway promotes X recognition by enhancing the ability of 1.688X DNA to attract compensation in cis. The dense and near-exclusive distribution of 1.688X sequences along the X chromosome suggests that they play a primary role in determining X identity during dosage compensation. |
| Mourad, R., Li, L. and Cuvier, O. (2017). Uncovering direct and indirect molecular determinants of chromatin loops using a computational integrative approach. PLoS Comput Biol 13(5): e1005538. PubMed ID: 28542178
Summary: Chromosomal organization in 3D plays a central role in regulating cell-type specific transcriptional and DNA replication timing programs. Yet it remains unclear to what extent the resulting long-range contacts depend on specific molecular drivers. This study proposes a model that comprehensively assesses the influence on contacts of DNA-binding proteins, cis-regulatory elements and DNA consensus motifs. Using real data, a large number of predictions for long-range contacts involving known architectural proteins and DNA motifs is validated. The model outperforms existing approaches including enrichment test, random forests and correlation, and it uncovers numerous novel long-range contacts in Drosophila and human. The model uncovers the orientation-dependent specificity for long-range contacts between CTCF motifs in Drosophila, highlighting its conserved property in 3D organization of metazoan genomes. The model further unravels long-range contacts depending on co-factors recruited to DNA indirectly, as illustrated by the influence of cohesin in stabilizing long-range contacts between CTCF sites. It also reveals asymmetric contacts such as enhancer-promoter contacts that highlight opposite influences of the transcription factors EBF1, EGR1 or MEF2C depending on RNA Polymerase II pausing. | Pasquier, C., Agnel, S. and Robichon, A. (2017). The mapping of predicted triplex DNA:RNA in the Drosophila genome reveals a prominent location in development- and morphogenesis-related genes. G3 (Bethesda) [Epub ahead of print]. PubMed ID: 28515050
Summary: Double-stranded DNA is able to form triple-helical structures by accommodating a third nucleotide strand. A nucleic acid triplex occurs according to Hoogsteen rules that predict the stability and affinity of the third strand bound to the Watson-Crick duplex. The "triplex-forming oligonucleotide" (TFO) can be a short sequence of RNA that binds to the major groove of the targeted duplex only when this duplex presents a sequence of purine or pyrimidine bases in one of the DNA strands. This study identified sequences that are capable of engaging as the "triplex-forming oligonucleotide" in both the pre-lncRNA and pre-mRNA collections of Drosophila melanogaster. These motifs were matched against the Drosophila genome in order to identify putative sequences of triplex formation in intergenic regions, promoters and introns/exons. Most of the identified TFOs appear to be located in the intronic region of the analyzed genes. Computational prediction of the most targeted genes by TFOs originating from pre-lncRNAs and pre-mRNAs revealed that they are restrictively associated with development- and morphogenesis-related gene networks. The refined analysis by Gene Ontology enrichment demonstrates that some individual TFOs present genome-wide scale matches that are located in numerous genes and regulatory sequences. The triplex DNA:RNA computational mapping at the genome-wide scale suggests broad interference in the regulatory process of the gene networks orchestrated by TFO RNAs acting in association simultaneously at multiple sites. |
Wednesday July 5th |
| He, L., Huang, J. and Perrimon, N. (2017). Development of an optimized synthetic Notch receptor as an in vivo cell-cell contact sensor. Proc Natl Acad Sci U S A 114(21): 5467-5472. PubMed ID: 28490499
Summary: Detection and manipulation of direct cell-cell contact in complex tissues is a fundamental and challenging problem in many biological studies. This study reports an optimized Notch-based synthetic receptor (synNQ) useful to study direct cell-cell interactions in Drosophila. With the synNQ system, cells expressing a synthetic receptor, which contains Notch activation machinery and a downstream transcriptional activator, QF, are activated by a synthetic GFP ligand expressed by contacting neighbor cells. To avoid cis-inhibition, mutually exclusive expression of the synthetic ligand and receptor is achieved using the "flippase-out" system. Expression of the synthetic GFP ligand is controlled by the Gal4/UAS system for easy and broad applications. Using synNQ, cell-cell interactions within and between most fly tissues were successfully visualized, revealing previously undocumented cell-cell contacts. Importantly, in addition to detection of cells in contact with one another, synNQ allows for genetic manipulation in all cells in contact with a targeted cell population, which is demonstrated in the context of cell competition in developing wing disks. Altogether, the synNQ genetic system will enable a broad range of studies of cell contact in developmental biology. | Raut, S., Mallik, B., Parichha, A., V, A., Sahi, C. and Kumar, V. (2017). RNAi-mediated reverse genetic screen identified Drosophila chaperones regulating eye and neuromuscular junction morphology. G3 (Bethesda). PubMed ID: 28500055
Summary: Accumulation of toxic proteins in neurons have been linked with the onset of neurodegenerative diseases, which in many cases, are characterized by altered neuronal function and synapse loss. Molecular chaperones help protein folding and resolubilization of unfolded proteins thereby reducing the protein aggregation stress. While most of the chaperones are expressed in neurons, their functional relevance largely remains unknown. Using bioinformatics analysis, this study identified 95 Drosophila chaperones and classified them into seven different classes. Ubiquitous actin5C-Gal4 mediated RNAi knockdown revealed that about 50% of the chaperones are essential in Drosophila. Knocking down these genes in eyes revealed that about 30% of the essential chaperones are crucial for eye development. Using neuron-specific knockdown, immunocytochemistry and robust behavioural assays, a new set of chaperones were identified that play critical roles in the regulation of Drosophila NMJ structural organization. Together, these data presents the first classification and comprehensive analysis of Drosophila chaperones. The screen identified new set of chaperones that regulate eye and NMJ morphogenesis. Outcome of the screen reported here provides a useful resource for further elucidating the role of individual chaperones in Drosophila eye morphogenesis and synaptic development. |
| Meiselman, M., Lee, S. S., Tran, R. T., Dai, H., Ding, Y., Rivera-Perez, C., Wijesekera, T. P., Dauwalder, B., Noriega, F. G. and Adams, M. E. (2017). Endocrine network essential for reproductive success in Drosophila melanogaster. Proc Natl Acad Sci U S A 114(19): E3849-e3858. PubMed ID: 28439025
Summary: Ecdysis-triggering hormone (ETH) was originally discovered and characterized as a molt termination signal in insects through its regulation of the ecdysis sequence. This study reports that ETH persists in adult Drosophila melanogaster, where it functions as an obligatory allatotropin to promote juvenile hormone (JH) production and reproduction. ETH signaling deficits lead to sharply reduced JH levels and consequent reductions of ovary size, egg production, and yolk deposition in mature oocytes. Expression of ETH and ETH receptor genes is in turn dependent on ecdysone (20E). Furthermore, 20E receptor knockdown specifically in Inka cells reduces fecundity. These findings indicate that the canonical developmental roles of 20E, ETH, and JH during juvenile stages are repurposed to function as an endocrine network essential for reproductive success. | Salle, J., Gervais, L., Boumard, B., Stefanutti, M., Siudeja, K. and Bardin, A. J. (2017). Intrinsic regulation of enteroendocrine fate by Numb. EMBO J [Epub ahead of print]. PubMed ID: 28533229
Summary: How terminal cell fates are specified in dynamically renewing adult tissues is not well understood. This study explored terminal cell fate establishment during homeostasis using the enteroendocrine cells (EEs) of the adult Drosophila midgut as a paradigm. The data argue against the existence of local feedback signals, and Numb was identified as an intrinsic regulator of EE fate. The data further indicate that Numb, with alpha-adaptin, acts upstream or in parallel of known regulators of EE fate to limit Notch signaling, thereby facilitating EE fate acquisition. It was found that Numb is regulated in part through its asymmetric and symmetric distribution during stem cell divisions; however, its de novo synthesis is also required during the differentiation of the EE cell. Thus, this work identifies Numb as a crucial factor for cell fate choice in the adult Drosophila intestine. Furthermore, the findings demonstrate that cell-intrinsic control mechanisms of terminal cell fate acquisition can result in a balanced tissue-wide production of terminally differentiated cell types. |
Tuesday July 4th |
| Khare, S., et al. (2017). A KCNC3 mutation causes a neurodevelopmental, non-progressive SCA13 subtype associated with dominant negative effects and aberrant EGFR trafficking. PLoS One 12(5): e0173565. PubMed ID: 28467418
Summary: The autosomal dominant spinocerebellar ataxias (SCAs) are a diverse group of neurological disorders anchored by the phenotypes of motor incoordination and cerebellar atrophy. This study study focused on SCA13, which is caused by several allelic variants in the voltage-gated potassium channel KCNC3 (Kv3.3). The clinical phenotype of four SCA13 kindreds are detailed that confirm causation of the KCNC3R423H allele. The heralding features demonstrate congenital onset with non-progressive, neurodevelopmental cerebellar hypoplasia and lifetime improvement in motor and cognitive function that implicate compensatory neural mechanisms. Targeted expression of human KCNC3R423H in Drosophila triggers aberrant wing veins, maldeveloped eyes, and fused ommatidia consistent with the neurodevelopmental presentation of patients. Furthermore, human KCNC3R423H expression in mammalian cells results in altered glycosylation and aberrant retention of the channel in anterograde and/or endosomal vesicles. Confirmation of the absence of plasma membrane targeting was based on the loss of current conductance in cells expressing the mutant channel. Mechanistically, genetic studies in Drosophila, along with cellular and biophysical studies in mammalian systems, demonstrate the dominant negative effect exerted by the mutant on the wild-type (WT) protein, which explains dominant inheritance. Ocular co-expression of KCNC3R423H with Drosophila epidermal growth factor receptor (dEgfr) results in striking rescue of the eye phenotype, whereas KCNC3R423H expression in mammalian cells results in aberrant intracellular retention of human epidermal growth factor receptor (EGFR). Together, these results indicate that the neurodevelopmental consequences of KCNC3R423H may be mediated through indirect effects on EGFR signaling in the developing cerebellum. These results therefore confirm the KCNC3R423H allele as causative for SCA13, through a dominant negative effect on KCNC3WT and links with EGFR that account for dominant inheritance, congenital onset, and disease pathology. | Sanz, F. J., Solana-Manrique, C., Munoz-Soriano, V., Calap-Quintana, P., Molto, M. D. and Paricio, N. (2017). Identification of potential therapeutic compounds for Parkinson's disease using Drosophila and human cell models. Free Radic Biol Med 108: 683-691. PubMed ID: 28455141
Summary: Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. It is caused by a loss of dopaminergic neurons in the substantia nigra pars compacta, leading to a decrease in dopamine levels in the striatum and thus producing movement impairment. Major physiological causes of neurodegeneration in PD are oxidative stress (OS) and mitochondrial dysfunction; these pathophysiological changes can be caused by both genetic and environmental factors. Although most PD cases are sporadic, it has been shown that 5-10% of them are familial forms caused by mutations in certain genes. One of these genes is the DJ-1 oncogene (PARK7), which is involved in an early-onset recessive PD form. Currently, PD is an incurable disease for which existing therapies are not sufficiently effective to counteract or delay the progression of the disease. Therefore, the discovery of alternative drugs for the treatment of PD is essential. This study used a Drosophila PD model to identify candidate compounds with therapeutic potential for this disease. These flies carry a loss-of-function mutation in the DJ-1β gene, the Drosophila ortholog of human DJ-1, and show locomotor defects reflected by a reduced climbing ability. A pilot modifier chemical screen was performed, and several candidate compounds were identified based on their ability to improve locomotor activity of PD model flies. Some of them were also able to reduce OS levels in these flies. To validate the compounds identified in the Drosophila screen, a human cell PD model was generated by knocking down DJ-1 function in SH-SY5Y neuroblastoma cells. The results showed that some of the compounds were also able to increase the viability of the DJ-1-deficient cells subjected to OS, thus supporting the use of Drosophila for PD drug discovery. Interestingly, some of them have been previously proposed as alternative therapies for PD or tested in clinical trials and others are first suggested in this study as potential drugs for the treatment of this disease. |
| Ocorr, K., Zambon, A., Nudell, Y., Pineda, S., Diop, S., Tang, M., Akasaka, T. and Taylor, E. (2017). Age-dependent electrical and morphological remodeling of the Drosophila heart caused by hERG/seizure mutations. PLoS Genet 13(5): e1006786. PubMed ID: 28542428
Summary: One of the primary targets for therapeutic intervention into human heart disease has been the human ether a go-go (hERG; see Drosophila Eag) K+ channel that, together with the KCNQ channel, controls the rate and efficiency of repolarization in human myocardial cells. Neither of these channels plays a major role in adult mouse heart function; however, this study shows that the hERG homolog seizure (sei), along with KCNQ, both contribute significantly to adult heart function in Drosophila as they do in humans. In Drosophila, mutations in or cardiac knockdown of sei channels cause arrhythmias that become progressively more severe with age. Intracellular recordings of semi-intact heart preparations revealed that these perturbations also cause electrical remodeling that is reminiscent of the early afterdepolarizations seen in human myocardial cells defective in these channels. In contrast to KCNQ, however, mutations in sei also cause extensive structural remodeling of the myofibrillar organization, which suggests that hERG channel function has a novel link to sarcomeric and myofibrillar integrity. It is concluded that deficiency of ion channels with similar electrical functions in cardiomyocytes can lead to different types or extents of electrical and/or structural remodeling impacting cardiac output. | Pellikka, M. and Tepass, U. (2017). Unique cell biological profiles of retinal disease-causing missense mutations in the polarity protein Crumbs. J Cell Sci [Epub ahead of print]. PubMed ID: 28515229
Summary: Mutations in human Crumbs homolog CRB1 are a major cause of retinal disease that lead to blindness. CRB1 is a transmembrane protein found in the inner segment of photoreceptor cells (PRCs) and the apical membrane of Muller glia. The function of the extracellular region of CRB1 is poorly understood although more than 80 disease-causing missense mutations have been mapped to it. This study recreated four mutations in Drosophila Crumbs (Crb) that affect different extracellular domains. Crb regulates epithelial polarity and growth, and contributes to PRC differentiation and survival. The mutant Crb isoforms showed a remarkable diversity in protein abundance, subcellular distribution, and ability to rescue the lack of endogenous Crb, elicit a gain-of-function phenotype, or promote PRC degeneration. Interestingly, although expression of mutant isoforms rescued developmental defects of crb mutants substantially, they accelerated PRC degeneration compared to retinas that lack Crb, indicating that Crb function in cellular differentiation and cell survival depends on distinct molecular pathways. Several Crb mutant proteins accumulated abnormally in the rhabdomere and affected rhodopsin trafficking, suggesting that abnormal rhodopsin physiology contributes to Crb/CRB1-dependent retinal degeneration. |
Monday, July 3rd |
| Picao-Osorio, J., Lago-Baldaia, I., Patraquim, P. and Alonso, C. R. (2017). Pervasive behavioural effects of microRNA regulation in Drosophila. Genetics [Epub ahead of print]. PubMed ID: 28468905
Summary: The effects of microRNA (miRNA) regulation on the genetic programs underlying behaviour remain largely unexplored. Despite this, recent work in Drosophila shows that mutation of a single miRNA locus (miR-iab4/iab8) affects the capacity of the larva to correct its orientation if turned upside-down (self-righting, SR) suggesting that other miRNAs might also be involved in behavioural control. This study explores this possibility studying early larval SR behaviour in a collection of eighty-one Drosophila miRNA mutants covering almost the entire miRNA complement of the late embryo. Unexpectedly, it was observed that more than 40% of all miRNAs tested significantly affect SR time revealing pervasive behavioural effects of miRNA regulation in the early larva. Detailed analyses of those miRNAs affecting SR behaviour (SR-miRNAs) show that individual miRNAs can affect movement in different ways suggesting that the workings of distinct molecular and cellular elements are affected by miRNA ablation. Furthermore, gene expression analysis shows that the Hox gene Abdominal-B (Abd-B) represents one of the targets de-regulated by several SR-miRNAs. This work thus reveals pervasive effects of miRNA regulation on a complex innate behaviour in Drosophila and suggests that miRNAs may be core components of the genetic programs underlying behavioural control in other animals too. | Ilyin, A. A., Ryazansky, S. S., Doronin, S. A., Olenkina, O. M., Mikhaleva, E. A., Yakushev, E. Y., Abramov, Y. A., Belyakin, S. N., Ivankin, A. V., Pindyurin, A. V., Gvozdev, V. A., Klenov, M. S. and Shevelyov, Y. Y. (2017). Piwi interacts with chromatin at nuclear pores and promiscuously binds nuclear transcripts in Drosophila ovarian somatic cells. Nucleic Acids Res [Epub ahead of print]. PubMed ID: 28472469
Summary: Piwi in a complex with Piwi-interacting RNAs (piRNAs) triggers transcriptional silencing of transposable elements (TEs) in Drosophila ovaries, thus ensuring genome stability. To do this, Piwi must scan the nascent transcripts of genes and TEs for complementarity to piRNAs. The mechanism of this scanning is currently unknown. This study reports the DamID-seq mapping of multiple Piwi-interacting chromosomal domains in somatic cells of Drosophila ovaries. These domains significantly overlap with genomic regions tethered to Nuclear Pore Complexes (NPCs). Accordingly, Piwi was coimmunoprecipitated with the component of NPCs Elys and with the Xmas-2 subunit of RNA transcription and export complex, known to interact with NPCs. However, only a small Piwi fraction has transient access to DNA at nuclear pores. Importantly, although 36% of the protein-coding genes overlap with Piwi-interacting domains and RNA-immunoprecipitation results demonstrate promiscuous Piwi binding to numerous genic and TE nuclear transcripts, according to available data Piwi does not silence these genes, likely due to the absence of perfect base-pairing between piRNAs and their transcripts. |
| Ishizu, H., Sumiyoshi, T. and Siomi, M. C. (2017). Use of the CRISPR-Cas9 system for genome editing in cultured Drosophila ovarian somatic cells. Methods [Epub ahead of print]. PubMed ID: 28552546
Summary: The CRISPR-Cas9 system can be used for genome engineering in many organisms. PIWI-interacting RNAs (piRNAs) play a crucial role in repressing transposons to maintain genome integrity in Drosophila ovaries, and cultured ovarian somatic cells (OSCs) are widely used to elucidate the molecular mechanisms underlying the piRNA pathway. However, the germline-specific piRNA amplification system known as the ping-pong machinery does not occur in OSCs, making them unsuitable for elucidating the underlying mechanisms. Mutations in the lethal (3) malignant brain tumor gene (l(3)mbt) have been shown to cause ectopic expression of germline genes, including ping-pong factors. Genome editing of Drosophila OSCs were therefore performed using the CRISPR-Cas9 system to achieve l(3)mbt knockout, resulting in successful induction of the piRNA amplification machinery. This study describes the detailed procedures for generating knockout and knockin OSC cells. | Jeske, M., Muller, C. W. and Ephrussi, A. (2017). The LOTUS domain is a conserved DEAD-box RNA helicase regulator essential for the recruitment of Vasa to the germ plasm and nuage. Genes Dev [Epub ahead of print]. PubMed ID: 28536148 Summary: DEAD-box RNA helicases play important roles in a wide range of metabolic processes. Regulatory proteins can stimulate or block the activity of DEAD-box helicases. This study shows that LOTUS (Limkain, Oskar, and Tudor containing proteins 5 and 7) domains present in the germline proteins Oskar, TDRD5 (Tudor domain-containing 5), and TDRD7 bind and stimulate the germline-specific DEAD-box RNA helicase Vasa. Crystal structure of the LOTUS domain of Oskar in complex with the C-terminal RecA-like domain of Vasa reveals that the LOTUS domain occupies a surface on a DEAD-box helicase not implicated previously in the regulation of the enzyme's activity. In vivo, the localization of Drosophila Vasa to the nuage and germ plasm depends on its interaction with LOTUS domain proteins. The binding and stimulation of Vasa DEAD-box helicases by LOTUS domains are widely conserved. |
Sunday, July 2nd |
| Minocha, S., Boll, W. and Noll, M. (2017). Crucial roles of Pox neuro in the developing ellipsoid body and antennal lobes of the Drosophila brain. PLoS One 12(4): e0176002. PubMed ID: 28441464
Summary: The paired box gene Pox neuro (Poxn) is expressed in two bilaterally symmetric neuronal clusters of the developing adult Drosophila brain, a protocerebral dorsal cluster (DC) and a deutocerebral ventral cluster (VC). This study shows that all cells that express Poxn in the developing brain are postmitotic neurons. During embryogenesis, the DC and VC consist of only 20 and 12 neurons that express Poxn, designated embryonic Poxn-neurons. The number of Poxn-neurons increases only during the third larval instar, when the DC and VC increase dramatically to about 242 and 109 Poxn-neurons, respectively, virtually all of which survive to the adult stage, while no new Poxn-neurons are added during metamorphosis. Although the vast majority of Poxn-neurons express Poxn only during third instar, about half of them are born by the end of embryogenesis, as demonstrated by the absence of BrdU incorporation during larval stages. At late third instar, embryonic Poxn-neurons, which begin to express Poxn during embryogenesis, can be easily distinguished from embryonic-born and larval-born Poxn-neurons, which begin to express Poxn only during third instar, (1) by the absence of Pros, (ii) their overt differentiation of axons and neurites, and (iii) the strikingly larger diameter of their cell bodies still apparent in the adult brain. The embryonic Poxn-neurons are primary neurons that lay out the pioneering tracts for the secondary Poxn-neurons, which differentiate projections and axons that follow those of the primary neurons during metamorphosis. The DC and the VC participate only in two neuropils of the adult brain. The DC forms most, if not all, of the neurons that connect the bulb (lateral triangle) with the ellipsoid body, a prominent neuropil of the central complex, while the VC forms most of the ventral projection neurons of the antennal lobe, which connect it ipsilaterally to the lateral horn, bypassing the mushroom bodies. In addition, Poxn-neurons of the VC are ventral local interneurons of the antennal lobe. In the absence of Poxn protein in the developing brain, embryonic Poxn-neurons stall their projections and cannot find their proper target neuropils, the bulb and ellipsoid body in the case of the DC, or the antennal lobe and lateral horn in the case of the VC, whereby the absence of the ellipsoid body neuropil is particularly striking. Poxn is thus crucial for pathfinding both in the DC and VC. Additional implications of these results are discussed. | Ngo, K. T., Andrade, I. and Hartenstein, V. (2017). Spatio-temporal pattern of neuronal differentiation in the Drosophila visual system: A user's guide to the dynamic morphology of the developing optic lobe. Dev Biol [Epub ahead of print]. PubMed ID: 28533086
Summary: Visual information processing in animals with large image forming eyes is carried out in highly structured retinotopically ordered neuropils. Visual neuropils in Drosophila form the optic lobe, which consists of four serially arranged major subdivisions; the lamina, medulla, lobula and lobula plate; the latter three of these are further subdivided into multiple layers. The visual neuropils are formed by more than 100 different cell types, distributed and interconnected in an invariant highly regular pattern. This pattern relies on a protracted sequence of developmental steps, whereby different cell types are born at specific time points and nerve connections are formed in a tightly controlled sequence that has to be coordinated among the different visual neuropils. The developing fly visual system has become a highly regarded and widely studied paradigm to investigate the genetic mechanisms that control the formation of neural circuits. However, these studies are often made difficult by the complex and shifting patterns in which different types of neurons and their connections are distributed throughout development. This study has reconstructed the three-dimensional architecture of the Drosophila optic lobe from the early larva to the adult. Based on specific markers, it was possible to distinguish the populations of progenitors of the four optic neuropils and map the neurons and their connections. This paper presents sets of annotated confocal z-projections and animated 3D digital models of these structures for representative stages. The data reveal the temporally coordinated growth of the optic neuropils, and clarify how the position and orientation of the neuropils and interconnecting tracts (inner and outer optic chiasm) changes over time. Finally, the emergence of the discrete layers of the medulla and lobula complex were analyzed using the same markers (DN-cadherin, Brp) employed to systematically explore the structure and development of the central brain neuropil. This work will facilitate experimental studies of the molecular mechanisms regulating neuronal fate and connectivity in the fly visual system, which bears many fundamental similarities with the retina of vertebrates. |
| Liu, Q., Tabuchi, M., Liu, S., Kodama, L., Horiuchi, W., Daniels, J., Chiu, L., Baldoni, D. and Wu, M. N. (2017). Branch-specific plasticity of a bifunctional dopamine circuit encodes protein hunger. Science 356(6337): 534-539. PubMed ID: 28473588
Summary: Free-living animals must not only regulate the amount of food they consume but also choose which types of food to ingest. The shifting of food preference driven by nutrient-specific hunger can be essential for survival, yet little is known about the underlying mechanisms. This study identified a dopamine circuit that encodes protein-specific hunger in Drosophila. The activity of these neurons increased after substantial protein deprivation. Activation of this circuit simultaneously promoted protein intake and restricted sugar consumption, via signaling to distinct downstream neurons. Protein starvation triggered branch-specific plastic changes in these dopaminergic neurons, thus enabling sustained protein consumption. These studies reveal a crucial circuit mechanism by which animals adjust their dietary strategy to maintain protein homeostasis (Liu, 2017). | Nakamura, A., Tanaka, R., Morishita, K., Yoshida, H., Higuchi, Y., Takashima, H. and Yamaguchi, M. (2017). Neuron-specific knockdown of the Drosophila fat induces reduction of life span, deficient locomotive ability, shortening of motoneuron terminal branches and defects in axonal targeting. Genes Cells [Epub ahead of print]. PubMed ID: 28488382
Summary: Mutations in FAT4 gene, one of the human FAT family genes, have been identified in Van Maldergem syndrome (VMS) and Hennekam lymphangiectasia-lymphedema syndrome (HS). The FAT4 gene encodes a large protein with extracellular cadherin repeats, EGF-like domains and Laminin G-like domains. FAT4 plays a role in tumor suppression and planar cell polarity. This study knocked down Drosophila fat in the nervous system, resulting in shortened life span and a defect in locomotion. Defects in synapse structure at neuromuscular junction and aberrations in a axonal targeting of photoreceptor neurons were also observed. The results indicate that Drosophila fat plays an essential role in formation and/or maintenance of neurons. Both VMS and HS show mental retardation and neuronal defects. It is therefore considered that these two rare human diseases could possibly be caused by the defect in FAT4 function in neuronal cells. |
Saturday, July 1st |
| Moeller, M. E., Nagy, S., Gerlach, S. U., Soegaard, K. C., Danielsen, E. T., Texada, M. J. and Rewitz, K. F. (2017). Warts signaling controls organ and body Growth through regulation of ecdysone. Curr Biol. PubMed ID: 28528906
Summary: In Drosophila, Hippo/Warts signaling functions intrinsically to regulate tissue growth and organ size, whereas systemic growth is controlled via antagonistic interactions of the steroid hormone ecdysone and nutrient-dependent insulin/insulin-like growth factor (IGF) (insulin) signaling. This study shows that Warts (Wts; LATS1/2) signaling regulates systemic growth in Drosophila by activating basal ecdysone production, which negatively regulates body growth. Further, evidence is provided that Wts mediates effects of insulin and the neuropeptide prothoracicotropic hormone (PTTH) on regulation of ecdysone production through Yorkie (Yki; YAP/TAZ) and the microRNA bantam (ban). Thus, Wts couples insulin signaling with ecdysone production to adjust systemic growth in response to nutritional conditions during development. Inhibition of Wts activity in the ecdysone-producing cells non-autonomously slows the growth of the developing imaginal-disc tissues while simultaneously leading to overgrowth of the animal. This indicates that ecdysone, while restricting overall body growth, is limiting for growth of certain organs. The data show that, in addition to its well-known intrinsic role in restricting organ growth, Wts/Yki/ban signaling also controls growth systemically by regulating ecdysone production, a mechanism that is proposed to control growth between tissues and organismal size in response to nutrient availability. | Luciano, A. K., Santana, J. M., Velazquez, H. and Sessa, W. C. (2017). Akt1 controls the timing and amplitude of vascular circadian gene expression. J Biol Rhythms: 748730417704534. PubMed ID: 28452287d
Evolutionary Homolog Study The AKT signaling pathway is important for circadian rhythms in mammals and flies (Drosophila). However, AKT signaling in mammals is more complicated since there are 3 isoforms of AKT, each performing slightly different functions. This study dealt with the most ubiquitous AKT isoform, Akt1, and its role at the organismal level in the central and vascular peripheral clocks. Akt1-/- mice exhibit relatively normal behavioral rhythms with only minor differences in circadian gene expression in the liver and heart. However, circadian gene expression in the Akt1-/- aorta, compared with control aorta, follows a distinct pattern. In the Akt1-/- aorta, positive regulators of circadian transcription have lower amplitude rhythms and peak earlier in the day, and negative circadian regulators are expressed at higher amplitudes and peak later in the day. In endothelial cells, negative circadian regulators exhibit an increased amplitude of expression, while the positive circadian regulators are arrhythmic with a decreased amplitude of expression. This indicates that Akt1 conditions the normal circadian rhythm in the vasculature more so than in other peripheral tissues where other AKT isoforms or kinases might be important for daily rhythms. |
| Lv, F., Yang, X., Cui, C. and Su, C. (2017). Exogenous expression of Drp1 plays neuroprotective roles in the Alzheimer's disease in the Abeta42 transgenic Drosophila model. PLoS One 12(5): e0176183. PubMed ID: 28531191
Summary: Alzheimer's disease (AD) is one of the most common neurodegenerative disorders. Recent studies have shown that mitochondrial dysfunction is a causative factor of AD. Drp1 (Dynamin-related protein 1; see Drosophila Drp1), a regulator of mitochondrial fission, shows neuroprotective effects on Parkinson's disease. This study investigated the effect and mechanism of Drp1 on Aβ42 transgenic Drosophila. Elav-gal4/UAS>Abeta42 transgenic Drosophila model was constructed using Elav-gal4 promoter. The effects of Drp1 on the lifespan, motor ability and neuronal degeneration of the transgenic Drosophila were explored by over-expressing Drp1 in the Aβ42 transgenic Drosophila. ATP levels in the brain tissues of Aβ42 transgenic Drosophila were detected using high performance liquid chromatography (HPLC). Exogenous expression of Drp1 was shown to promote crawling ability, reduced the levels of ATP in Drosophila brain and suppressed the neuronal degeneration. It is concluded that the protective effect of Drp1 on the Aβ42 transgenic Drosophila was achieved by protecting the mitochondrial function, suggesting that Drp1 may be a potential therapeutic strategies for AD. | Moutaoufik, M. T., Morrow, G., Finet, S. and Tanguay, R. M. (2017). Effect of N-terminal region of nuclear Drosophila melanogaster small heat shock protein DmHsp27 on function and quaternary structure. PLoS One 12(5): e0177821. PubMed ID: 28520783
Summary: The importance of the N-terminal region (NTR) in the oligomerization and chaperone-like activity of the Drosophila melanogaster small nuclear heat shock protein DmHsp27 was investigated by mutagenesis using size exclusion chromatography and native gel electrophoresis. Mutation of two sites of phosphorylation in the N-terminal region, S58 and S75, did not affect the oligomerization equilibrium or the intracellular localization of DmHsp27 when transfected into mammalian cells. Deletion or mutation of specific residues within the NTR region delineated a motif (FGFG) important for the oligomeric structure and chaperone-like activity of this sHsp. While deletion of the full N-terminal region, resulted in total loss of chaperone-like activity, removal of the (FGFG) at position 29 to 32 or single mutation of F29A/Y, G30R and G32R enhanced oligomerization and chaperoning capacity under non-heat shock conditions in the insulin assay suggesting the importance of this site for chaperone activity. Unlike mammalian sHsps DmHsp27 heat activation leads to enhanced association of oligomers to form large structures of approximately 1100 kDa. A new mechanism of thermal activation for DmHsp27 is presented. |
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