What's hot today:
Current papers in developmental biology and gene function
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What's hot today
October 2024 September 2024 August 2024 July 2024 June 2024 May 2024 April 2024 March 2024 February 2024 January 2024 December 2023 November 2023 October 2023 September 2023 August 2023 July 2023 June 2023 May 2023 April 2023 February 2023 January 2023 December 2022 November 2022 October 2022 September 2022 August 2022 July 2022 June 2022 May 2022 April 2022 March 2022 February 2022 January 2022 December 2021 December 2020 April 2019 | Yu, L., Shen, H. and Lyu, X. (2022). Roles of Polycomb Complexes in the Reconstruction of 3D Genome Architecture during Preimplantation Embryonic Development. Genes (Basel) 13(12). PubMed ID: 36553649
Summary: The appropriate deployment of developmental programs depends on complex genetic information encoded by genomic DNA sequences and their positioning and contacts in the three-dimensional (3D) space within the nucleus. Current studies using novel techniques including, but not limited to, Hi-C, ChIA-PET, and Hi-ChIP reveal that regulatory elements (Res), such as enhancers and promoters, may participate in the precise regulation of expression of tissue-specific genes important for both embryogenesis and organogenesis by recruiting Polycomb Group (PcG) complexes. PcG complexes usually poise the transcription of developmental genes by forming Polycomb bodies to compact poised enhancers and promoters marked by H3K27me3 in the 3D space. Additionally, recent studies have also uncovered their roles in transcriptional activation. To better understand the full complexities in the mechanisms of how PcG complexes regulate transcription and long-range 3D contacts of enhancers and promoters during developmental programs, this paper has outline novel insights regarding PcG-associated dramatic changes in the 3D chromatin conformation in developmental programs of early embryos and naive-ground-state transitions of pluripotent embryonic stem cells (ESCs), and highlight the distinct roles of unique and common subunits of canonical and non-canonical PcG complexes in shaping genome architectures and transcriptional programs. | Koury, S. A. (2023). Predicting recombination suppression outside chromosomal inversions in Drosophila melanogaster using crossover interference theory. Heredity (Edinb). PubMed ID: 36721031
Summary: The interference hypothesis of recombination suppression proposes heterozygous inversion breakpoints possess chiasma-like properties such that recombination suppression extends from these breakpoints in a process analogous to crossover interference. This hypothesis is qualitatively consistent with chromosome-wide patterns of recombination suppression extending to both inverted and uninverted regions of the chromosome. The present study generated quantitative predictions for this hypothesis using a probabilistic model of crossover interference with gamma-distributed inter-event distances. These predictions were then tested with experimental genetic data (>40,000 meioses) on crossing-over in intervals that are external and adjacent to four common inversions of Drosophila melanogaster. The crossover interference model accurately predicted the partially suppressed recombination rates in euchromatic intervals outside inverted regions. Furthermore, assuming interference does not extend across centromeres dramatically improved model fit and partially accounted for excess recombination observed in pericentromeric intervals. Finally, inversions with breakpoints closest to the centromere had the greatest excess of recombination in pericentromeric intervals, an observation that is consistent with negative crossover interference previously documented near Drosophila melanogaster centromeres. In conclusion, the experimental data support the interference hypothesis of recombination suppression, validate a mathematical framework for integrating distance-dependent effects of structural heterozygosity on crossover distribution, and highlight the need for improved modeling of crossover interference in pericentromeric regions. |
| Aughey, G. N., Forsberg, E., Grimes, K., Zhang, S. and Southall, T. D. (2023). NuRD-independent Mi-2 activity represses ectopic gene expression during neuronal maturation. EMBO Rep: e55362. PubMed ID: 36722816
Summary: During neuronal development, extensive changes to chromatin states occur to regulate lineage-specific gene expression. The molecular factors underlying the repression of non-neuronal genes in differentiated neurons are poorly characterised. The Mi2/NuRD complex is a multiprotein complex with nucleosome remodelling and histone deacetylase activity. Whilst NuRD has previously been implicated in the development of nervous system tissues, the precise nature of the gene expression programmes that it coordinates is ill-defined. Furthermore, evidence from several species suggests that Mi-2 may be incorporated into multiple complexes that may not possess histone deacetylase activity. This study shows that Mi-2 activity is required for suppressing ectopic expression of germline genes in neurons independently of HDAC1/NuRD, whilst components of NuRD, including Mi-2, regulate neural gene expression to ensure proper development of the larval nervous system. Mi-2 binding in the genome was found to be dynamic during neuronal maturation, and Mi-2-mediated repression of ectopic gene expression is restricted to the early stages of neuronal development, indicating that Mi-2/NuRD is required for establishing stable neuronal transcriptomes during the early stages of neuronal differentiation. | Cavalheiro, G. R., Girardot, C., Viales, R. R., Pollex, T., Cao, T. B. N., Lacour, P., Feng, S., Rabinowitz, A. and Furlong, E. E. M. (2023). CTCF, BEAF-32, and CP190 are not required for the establishment of TADs in early Drosophila embryos but have locus-specific roles. Sci Adv 9(5): eade1085. PubMed ID: 36735786
Summary: The boundaries of topologically associating domains (TADs) are delimited by insulators and/or active promoters; however, how they are initially established during embryogenesis remains unclear. This was examined during the first hours of Drosophila embryogenesis. DNA-FISH confirms that intra-TAD pairwise proximity is established during zygotic genome activation (ZGA) but with extensive cell-to-cell heterogeneity. Most newly formed boundaries are occupied by combinations of CTCF, BEAF-32, and/or CP190. Depleting each insulator individually from chromatin revealed that TADs can still establish, although with lower insulation, with a subset of boundaries (~10%) being more dependent on specific insulators. Some weakened boundaries have aberrant gene expression due to unconstrained enhancer activity. However, the majority of misexpressed genes have no obvious direct relationship to changes in domain-boundary insulation. Deletion of an active promoter (thereby blocking transcription) at one boundary had a greater impact than deleting the insulator-bound region itself. This suggests that cross-talk between insulators and active promoters and/or transcription might reinforce domain boundary insulation during embryogenesis. |
| Kahn, T. G., Savitsky, M., Kuong, C., Jacquer, C., Cavalli, G., Chang, J. M. and Schwartz, Y. B. (2023). Topological screen identifies hundreds of Cp190- and CTCF-dependent Drosophila chromatin insulator elements. Sci Adv 9(5): eade0090. PubMed ID: 36735780
Summary: Drosophila insulators were the first DNA elements found to regulate gene expression by delimiting chromatin contacts. It is still not known how many of them exist and what impact they have on the Drosophila genome folding. Contrary to vertebrates, there is no evidence that fly insulators block cohesin-mediated chromatin loop extrusion. Therefore, their mechanism of action remains uncertain. To bridge these gaps, this study mapped chromatin contacts in Drosophila cells lacking the key insulator proteins CTCF and Cp190. With this approach, hundreds of insulator elements were found. Their study indicates that Drosophila insulators play a minor role in the overall genome folding but affect chromatin contacts locally at many loci. These observations argue that Cp190 promotes cobinding of other insulator proteins and that the model, where Drosophila insulators block chromatin contacts by forming loops, needs revision. This insulator catalog provides an important resource to study mechanisms of genome folding. | Moniot-Perron, L., Moindrot, B., Manceau, L., Edouard, J., Jaszczyszyn, Y., Gilardi-Hebenstreit, P., Hernandez, C., Bloyer, S. and Noordermeer, D. (2023). The Drosophila Fab-7 boundary modulates Abd-B gene activity by guiding an inversion of collinear chromatin organization and alternate promoter use. Cell Rep 42(1): 111967. PubMed ID: 36640345
Summary: Hox genes encode transcription factors that specify segmental identities along the anteroposterior body axis. These genes are organized in clusters, where their order corresponds to their activity along the body axis, a feature known as collinearity. In Drosophila, the BX-C cluster contains the three most posterior Hox genes, where their collinear activation incorporates progressive changes in histone modifications, chromatin architecture, and use of boundary elements and cis-regulatory regions. To dissect functional hierarchies, this study compareed chromatin organization in cell lines and larvae, with a focus on the Abd-B gene. This work establishes the importance of the Fab-7 boundary for insulation between 3D domains carrying different histone modifications. Interestingly, a non-canonical inversion of collinear chromatin dynamics was detected at Abd-B, with the domain of active histone modifications progressively decreasing in size. This dynamic chromatin organization differentially activates the alternative promoters of the Abd-B gene, thereby expanding the possibilities for fine-tuning of transcriptional output. |
Thursday March 30th - Disease Models |
| Kim, Y. A., Siddiqui, T., Blaze, J., Cosacak, M. I., Winters, T., Kumar, A., Tein, E., Sproul, A. A., Teich, A. F., Bartolini, F., Akbarian, S., Kizil, C., Hargus, G. and Santa-Maria, I. (2023). RNA methyltransferase NSun2 deficiency promotes neurodegeneration through epitranscriptomic regulation of tau phosphorylation. Acta Neuropathol 145(1): 29-48. PubMed ID: 36357715
Summary: Epitranscriptomic regulation adds a layer of post-transcriptional control to brain function during development and adulthood. The identification of RNA-modifying enzymes has opened the possibility of investigating the role epitranscriptomic changes play in the disease process. NOP2/Sun RNA methyltransferase 2 (NSun2) is one of the few known brain-enriched methyltransferases able to methylate mammalian non-coding RNAs. NSun2 loss of function due to autosomal-recessive mutations has been associated with neurological abnormalities in humans. This study shows NSun2 is expressed in adult human neurons in the hippocampal formation and prefrontal cortex. Strikingly, this study unraveled decreased NSun2 protein expression and an increased ratio of pTau/NSun2 in the brains of patients with Alzheimer's disease (AD) as demonstrated by Western blotting and immunostaining, respectively. In a well-established Drosophila melanogaster model of tau-induced toxicity, reduction of NSun2 exacerbated tau toxicity, while overexpression of NSun2 partially abrogated the toxic effects. Conditional ablation of NSun2 in the mouse brain promoted a decrease in the miR-125b m6A levels and tau hyperphosphorylation. Utilizing human induced pluripotent stem cell (iPSC)-derived neuronal cultures, it was confirmed that NSun2 deficiency results in tau hyperphosphorylation. This study also found that neuronal NSun2 levels decrease in response to amyloid-beta oligomers (AβO). Notably, AβO-induced tau phosphorylation and cell toxicity in human neurons could be rescued by overexpression of NSun2. Altogether, these results indicate that neuronal NSun2 deficiency promotes dysregulation of miR-125b and tau phosphorylation in AD and highlights a novel avenue for therapeutic targeting. | Katzenberger, R. J., Ganetzky, B. and Wassarman, D. A. (2023). Lissencephaly-1 mutations enhance traumatic brain injury outcomes in Drosophila. Genetics. PubMed ID: 36683334
Summary: Traumatic brain injury (TBI) outcomes vary greatly among individuals, but most of the variation remains unexplained. Using a Drosophila melanogaster TBI model and 178 genetically diverse lines from the Drosophila Genetic Reference Panel (DGRP), this study investigated the role that genetic variation plays in determining TBI outcomes. Following injury at 20-27 days old, DGRP lines varied considerably in mortality within 24 hours ('early mortality'). Additionally, the disparity in early mortality resulting from injury at 20-27 versus 0-7 days old differed among DGRP lines. These data support a polygenic basis for differences in TBI outcomes, where some gene variants elicit their effects by acting on aging-related processes. The genome-wide association study of DGRP lines identified associations between single nucleotide polymorphisms in Lissencephaly-1 (Lis-1) and Patronin and early mortality following injury at 20-27 days old. Lis-1 regulates dynein, a microtubule motor required for retrograde transport of many cargoes, and Patronin protects microtubule minus ends against depolymerization. While Patronin mutants did not affect early mortality, Lis-1 compound heterozygotes (Lis-1x/Lis-1y) had increased early mortality following injury at 20-27 or 0-7 days old compared with Lis-1 heterozygotes (Lis-1x/+), and flies that survived 24 hours after injury had increased neurodegeneration but an unaltered lifespan, indicating that Lis-1 affects TBI outcomes independently of effects on aging. These data suggest that Lis-1 activity is required in the brain to ameliorate TBI outcomes through effects on axonal transport, microtubule stability, and other microtubule proteins such as tau, implicated in chronic traumatic encephalopathy, a TBI-associated neurodegenerative disease in humans. |
| Maor, G., Dubreuil, R. R. and Feany, M. B. (2023). alpha-synuclein promotes neuronal dysfunction and death by disrupting the binding of ankyrin to ß-spectrin. J Neurosci. PubMed ID: 36653193
Summary: α-synuclein plays a key role in the pathogenesis of Parkinson's disease and related disorders, but critical interacting partners and molecular mechanisms mediating neurotoxicity are incompletely understood. This study shows that α-synuclein binds directly to β-spectrin. Using males and females in a Drosophila model of α-synuclein-related disorders this study demonstrated that β-spectrin is critical for α-synuclein neurotoxicity. Further, the ankyrin binding domain of β-spectrin is required for α-synuclein binding and neurotoxicity. A key plasma membrane target of ankyrin, Na(+)/K(+) ATPase, is mislocalized when human α-synuclein is expressed in Drosophila. Accordingly, membrane potential is depolarized in α-synuclein transgenic fly brains. The same pathway was examined in human neurons and it was found that Parkinson's disease patient-derived neurons with a triplication of the α-synuclein locus show disruption of the spectrin cytoskeleton, mislocalization of ankyrin and Na(+)/K(+) ATPase, and membrane potential depolarization. These findings define a specific molecular mechanism by which elevated levels of α-synuclein in Parkinson's disease and related α-synucleinopathies leads to neuronal dysfunction and death. | Li, J., Amoh, B. K., McCormick, E., Tarkunde, A., Zhu, K. F., Perez, A., Mair, M., Moore, J., Shulman, J. M., Al-Ramahi, I. and Botas, J. (2023). Integration of transcriptome-wide association study with neuronal dysfunction assays provides functional genomics evidence for Parkinson's disease genes. Hum Mol Genet 32(4): 685-695. PubMed ID: 36173927
Summary: Genome-wide association studies (GWAS) have markedly advanced understanding of the genetics of Parkinson's disease (PD), but they currently do not account for the full heritability of PD. This study presents an integrative approach that combines transcriptome-wide association study (TWAS) with high-throughput neuronal dysfunction analyses in Drosophila to discover and validate candidate PD genes. 160 candidate genes were identified whose misexpression is associated with PD risk via TWAS. Candidates were validated using orthogonal in silico methods and found to be functionally related to PD-associated pathways (i.e. endolysosome). These TWAS-predicted transcriptomic alterations were mimicked in a Drosophila PD model, and it was discovered that 50 candidates can modulate α-Synuclein (α-Syn)-induced neurodegeneration, allowing new genes to be nominated in previously known PD loci. This study also uncovered additional novel PD candidate genes within GWAS suggestive loci (e.g. TTC19, ADORA2B, LZTS3, NRBP1, HN1L), which are also supported by clinical and functional evidence. These findings deepen understanding of PD, and support applying the integrative approach to other complex trait disorders. |
| Lin, G., Tepe, B., McGrane, G., Tipon, R. C., Croft, G., Panwala, L., Hope, A., Liang, A. J. H., Zuo, Z., Byeon, S. K., Wang, L., Pandey, A. and Bellen, H. J. (2023). Exploring therapeutic strategies for infantile neuronal axonal dystrophy (INAD/PARK14) . Elife 12. PubMed ID: 36645408
Summary: Infantile neuroaxonal dystrophy (INAD) is caused by recessive variants in PLA2G6 and is a lethal pediatric neurodegenerative disorder. Loss of the Drosophila homolog of PLA2G6, leads to ceramide accumulation, lysosome expansion, and mitochondrial defects. This study reports that retromer function, ceramide metabolism, the endolysosomal pathway, and mitochondrial morphology are affected in INAD patient-derived neurons. In INAD mouse models, the same features are affected in Purkinje cells, arguing that the neuropathological mechanisms are evolutionary conserved and that these features can be used as biomarkers. 20 drugs that target these pathways were tested and Ambroxol, Desipramine, Azoramide, and Genistein were found to alleviate neurodegenerative phenotypes in INAD flies and INAD patient-derived neural progenitor cells. This study also developed an AAV-based gene therapy approach that delays neurodegeneration and prolongs lifespan in an INAD mouse model. | Lushchak, O., Strilbytska, O. and Storey, K. B. (2023). Gender-specific effects of pro-longevity interventions in Drosophila. Mech Ageing Dev 209: 111754. PubMed ID: 36375654
Summary: Sex differences in lifespan are well recognized in the majority of animal species. For example, in male versus female Drosophila melanogaster there are significant differences in behavior and physiology. However, little is known about the underlying mechanisms of gender differences in responses to pro-longevity interventions in this model organism. This study summarized the existing data on the effects of nutritional and pharmacological anti-aging interventions such as nutrition regimens, diet and dietary supplementation on the lifespan of male and female Drosophila. It was demonstrated that males and females have different sensitivities to interventions and that the effects are highly dependent on genetic background, mating, dose and exposure duration. This work highlights the importance of understanding the mechanisms that underlie the gender-specific effect of anti-aging manipulations. This will provide insight into how these benefits may be valuable for elucidating the primary physiological and molecular targets involved in aging and lifespan determination. |
Wednesday March 29th - Signaling |
| Maier, D., Bauer, M., Boger, M., Sanchez Jimenez, A., Yuan, Z., Fechner, J., Scharpf, J., Kovall, R. A., Preiss, A. and Nagel, A. C. (2023). Genetic and Molecular Interactions between H(ΔCT), a Novel Allele of the Notch Antagonist Hairless, and the Histone Chaperone Asf1 in Drosophila melanogaster. Genes (Basel) 14(1). PubMed ID: 36672946
Summary: Cellular differentiation relies on the highly conserved Notch signaling pathway. Notch activity induces gene expression changes that are highly sensitive to chromatin landscape. This study addressed Notch gene regulation using Drosophila as a model, focusing on the genetic and molecular interactions between the Notch antagonist Hairless and the histone chaperone Asf1. Earlier work implied that Asf1 promotes the silencing of Notch target genes via Hairless (H). A novel ΔCT) allele was generated by genome engineering. Phenotypically, ΔCT behaves as a Hairless gain of function allele in several developmental contexts, indicating that the conserved CT domain of H has an attenuator role under native biological contexts. Using several independent methods to assay protein-protein interactions, this study defined the sequences of the CT domain that are involved in Hairless-Asf1 binding. Based on previous models, where Asf1 promotes Notch repression via Hairless, a loss of Asf1 binding should reduce Hairless repressive activity. However, tissue-specific Asf1 overexpression phenotypes are increased, not rescued, in the HΔCT background. Counterintuitively, Hairless protein binding mitigates the repressive activity of Asf1 in the context of eye development. These findings highlight the complex connections of Notch repressors and chromatin modulators during Notch target-gene regulation and open the avenue for further investigations. | Hudson, J., Paul, S., Veraksa, A., Ghabrial, A., Harvey, K. F. and Poon, C. (2023). NDR kinase Tricornered genetically interacts with Ccm3 and metabolic enzymes in Drosophila melanogaster tracheal development. G3 (Bethesda). PubMed ID: 36653023
Summary: The Germinal Center Kinase III (GckIII) pathway is a Hippo-like kinase module defined by sequential activation of Ste20 kinases Thousand and One (Tao) and GckIII, followed by nuclear dbf2-related (NDR) kinase Tricornered (Trc). Previous work uncovered a role for the GckIII pathway in Drosophila melanogaster tracheal (respiratory) tube morphology. The trachea form a network of branched epithelial tubes essential for oxygen transport, and are structurally analogous to branched tubular organs in vertebrates, such as the vascular system. In the absence of GckIII pathway function, aberrant dilations form in tracheal tubes characterised by mislocalized junctional and apical proteins, suggesting that the pathway is important in maintaining tube integrity in development. This study observed a genetic interaction between trc and Cerebral cavernous malformations 3 (Ccm3), the Drosophila ortholog of a human vascular disease gene, supporting the hypothesis that the GckIII pathway functions downstream of Ccm3 in trachea, and potentially in the vertebrate cerebral vasculature. However, how GckIII pathway signalling is regulated and the mechanisms that underpin its function in tracheal development are unknown. This study undertook biochemical and genetic approaches to identify proteins that interact with Trc, the most downstream GckIII pathway kinase. Known GckIII and NDR scaffold proteins are likely to control GckIII pathway signalling in tracheal development, consistent with their conserved roles in Hippo-like modules. Furthermore, this study showed genetic interactions between trc and multiple enzymes in glycolysis and oxidative phosphorylation, suggesting a potential function of the GckIII pathway in integrating cellular energy requirements with maintenance of tube integrity. |
| Merino, M. M. (2023). Azot expression in the Drosophila gut modulates organismal lifespan. Commun Integr Biol 16(1): 2156735. PubMed ID: 36606245
Summary: Cell Competition emerged in Drosophila as an unexpected phenomenon, when confronted clones of fit vs unfit cells genetically induced. During the last decade, it has been shown that this mechanism is physiologically active in Drosophila and higher organisms. In Drosophila, Flower (Fwe) eliminates unfit cells during development, regeneration and disease states. Furthermore, studies suggest that Fwe signaling is required to eliminate accumulated unfit cells during adulthood extending Drosophila lifespan. Indeed, ahuizotl (azot) mutants accumulate unfit cells during adulthood and after physical insults in the brain and other epithelial tissues, showing a decrease in organismal lifespan. On the contrary, flies carrying three functional copies of the gene, unfit cell culling seems to be more efficient and show an increase in lifespan. During aging, Azot is required for the elimination of unfit cells, however, the specific organs modulating organismal lifespan by Azot remain unknown. This study found a potential connection between gut-specific Azot expression and lifespan which may uncover a more widespread organ-specific mechanism modulating organismal survival. | Liu, S., Baeg, G. H., Yang, Y., Goh, F. G., Bao, H., Wagner, E. J., Yang, X. and Cai, Y. (2023). The Integrator complex desensitizes cellular response to TGF-β/BMP signaling. Cell Rep 42(1): 112007. PubMed ID: 36641752
Summary: Maintenance of stem cells requires the concerted actions of niche-derived signals and stem cell-intrinsic factors. Although Decapentaplegic (Dpp), a Drosophila bone morphogenetic protein (BMP) molecule, can act as a long-range morphogen, its function is spatially limited to the germline stem cell niche in the germarium. This study shows that Integrator, a complex known to be involved in RNA polymerase II (RNAPII)-mediated transcriptional regulation in the nucleus, promotes germline differentiation by restricting niche-derived Dpp/BMP activity in the cytoplasm. Further results show that Integrator works in various developmental contexts to desensitize the cellular response to Dpp/BMP signaling during Drosophila development. Mechanistically, these results show that Integrator forms a multi-subunit complex with the type I receptor Thickveins (Tkv) and other Dpp/BMP signaling components and acts in a negative feedback loop to promote Tkv turnover independent of its transcriptional activity. Similarly, human Integrator subunits bind transforming growth factor β (TGF-β)/BMP signaling components and antagonize their activity, suggesting a conserved role of Integrator across metazoans. |
| Lei, F., Xu, X., Huang, J., Su, D. and Wan, P. (2023). Drosophila RhoGAP18B regulates actin cytoskeleton during border cell migration. PLoS One 18(1): e0280652. PubMed ID: 36662713
Summary: Drosophila RhoGAP18B was identified as a negative regulator of small GTPase in the behavioral response to ethanol. However, the effect of RhoGAP18B on cell migration is unknown. This study reports that RhoGAP18B regulates the migration of border cells in Drosophila ovary. The RhoGAP18B gene produces four transcripts and encodes three translation isoforms. Different RNAi lines were used to knockdown each RhoGAP18B isoform, and find that knockdown of RhoGAP18B-PA, but not PC or PD isoform, blocks border cell migration. Knockdown of RhoGAP18B-PA disrupts the asymmetric distribution of F-actin in border cell cluster and increases F-actin level. Furthermore, RhoGAP18B-PA may act on Rac to regulate F-actin organization. These data indicate that RhoGAP18B shows isoform-specific regulation of border cell migration. | Kim, J., Choi, N. and Kim-Ha, J. (2023). Secreted Decoy of Insulin Receptor is Required for Blood-Brain and Blood-Retina Barrier Integrity in Drosophila. BMB Rep. PubMed ID: 36593109
Summary: Glial cells play important roles during neurogenesis and in maintaining complex functions of the nervous system. This study reports the characterization of a gene, Sdr, which contains a putative insulin-like growth factor receptor domain and is required to maintain critical nervous system functions in Drosophila. Sdr is expressed in glial cells during embryonic and larval stages of development, but its role in adult flies is poorly understood. As insulin signaling is important throughout the lifespan in human, this study investigated the Sdr's role in adult flies. Ther results demonstrate that Sdr is expressed on surface glial cells that surround the nervous system. Mutation of Sdr did not affect development but caused defects in locomotion and lifespan. Sdr mutants also showed increasingly severe defects in the blood-brain- and blood-retina-barriers as they aged. Therefore, a novel role of Sdr in maintaining the integrity of the blood-brain- and blood-retina-barriers in adult flies is suggested. |
Tuesday March 28th - Adult Neural Development and Function |
| Kobayashi, R., Yamashita, Y., Suzuki, H., Hatori, S., Tomita, J. and Kume, K. (2023). rdgB knockdown in neurons reduced nocturnal sleep in Drosophila melanogaster. Biochem Biophys Res Commun 643: 24-29. PubMed ID: 36586155
Summary: Recent studies revealed behaviorally defined sleep is conserved across broad species from insect to human. For evolutional analysis, it is critical to determine how homologous genes regulate the homologous function among species. Drosophila melanogaster shares numerous sleep related genes with mammals including Sik3, salt-inducible kinase 3, whose mutation caused long sleep both in mouse and fruit fly. The Drosophila rdgB (retinal degeneration B) encodes a membrane-associated phosphatidylinositol transfer protein and its mutation caused light-induced degeneration of photoreceptor cells. rdgB mutation also impaired phototransduction and olfactory behavior, indicating rdgB is involved in the normal neural transmission. Mammalian rdgB homologue, Pitpnm2 (phosphatidylinositol transfer protein membrane-associated 2) was discovered as one of SNIPPs (sleep-need index phosphoproteins), suggesting its role in sleep. This study shows that rdgB is involved in sleep regulation in Drosophila. Pan-neuronal and mushroom body (MB) specific rdgB knockdown decreased nocturnal sleep. MB neurons play a dominant role, since the rescue of rdgB expression only in MB neurons in pan-neuronal knockdown reversed the sleep reducing effect of rdgB knockdown. These results revealed the sleep-related function of rdgB in Drosophila which may be conserved across species. | Liang, X., Holy, T. E. and Taghert, P. H. (2023). Polyphasic circadian neural circuits drive differential activities in multiple downstream rhythmic centers. Curr Biol 33(2): 351-363. PubMed ID: 36610393
Summary: Circadian clocks align various behaviors such as locomotor activity, sleep/wake, feeding, and mating to times of day that are most adaptive. How rhythmic information in pacemaker circuits is translated to neuronal outputs is not well understood. This study used brain-wide, 24-h in vivo calcium imaging in the Drosophila brain and searched for circadian rhythmic activity among identified clusters of dopaminergic (DA) and peptidergic neurosecretory (NS) neurons. Such rhythms were widespread and imposed by the PERIOD-dependent clock activity within the ∼150-cell circadian pacemaker network. The rhythms displayed either a morning (M), evening (E), or mid-day (MD) phase. Different subgroups of circadian pacemakers imposed neural activity rhythms onto different downstream non-clock neurons. Outputs from the canonical M and E pacemakers converged to regulate DA-PPM3 and DA-PAL neurons. E pacemakers regulate the evening-active DA-PPL1 neurons. In addition to these canonical M and E oscillators, evidence is for a third dedicated phase occurring at mid-day: the l-LNv pacemakers present the MD activity peak, and they regulate the MD-active DA-PPM1/2 neurons and three distinct NS cell types. Thus, the Drosophila circadian pacemaker network is a polyphasic rhythm generator. It presents dedicated M, E, and MD phases that are functionally transduced as neuronal outputs to organize diverse daily activity patterns in downstream circuits. |
| Kramer, R., Wolterhoff, N., Galic, M. and Rumpf, S. (2023). Developmental pruning of sensory neurites by mechanical tearing in Drosophila. J Cell Biol 222(3). PubMed ID: 36648440
Summary: Mechanical forces actively shape cells during development, but little is known about their roles during neuronal morphogenesis. Developmental neurite pruning, a critical circuit specification mechanism, often involves neurite abscission at predetermined sites by unknown mechanisms. Pruning of Drosophila sensory neuron dendrites during metamorphosis is triggered by the hormone ecdysone, which induces local disassembly of the dendritic cytoskeleton. Subsequently, dendrites are severed at positions close to the soma by an unknown mechanism. This study found that ecdysone signaling causes the dendrites to become mechanically fragile. Severing occurs during periods of increased pupal morphogenetic tissue movements, which exert mechanical forces on the destabilized dendrites. Tissue movements and dendrite severing peak during pupal ecdysis, a period of strong abdominal contractions, and abolishing ecdysis causes non-cell autonomous dendrite pruning defects. Thus, these data establish mechanical tearing as a novel mechanism during neurite pruning. | Kim, H., Park, H., Lee, J. and Kim, A. J. (2023). A visuomotor circuit for evasive flight turns in Drosophila. Curr Biol 33(2): 321-335. PubMed ID: 36603587
Summary: Visual systems extract multiple features from a scene using parallel neural circuits. Ultimately, the separate neural signals must come together to coherently influence action. This study characterized a circuit in Drosophila that integrates multiple visual features related to imminent threats to drive evasive locomotor turns. Using genetic perturbation methods, a pair of visual projection neurons (LPLC2) and descending neurons (DNp06) were identified that underlie evasive flight turns in response to laterally moving or approaching visual objects. Using two-photon calcium imaging or whole-cell patch clamping, these cells were shown to indeed respond to both translating and approaching visual patterns. Furthermore, by measuring visual responses of LPLC2 neurons after genetically silencing presynaptic motion-sensing neurons, it was shown that their visual properties emerge by integrating multiple visual features across two early visual structures: the lobula and the lobula plate. This study highlights a clear example of how distinct visual signals converge on a single class of visual neurons and then activate premotor neurons to drive action, revealing a concise visuomotor pathway for evasive flight maneuvers in Drosophila. |
| Lee, H., Kostal, L., Kanzaki, R. and Kobayashi, R. (2023). Spike frequency adaptation facilitates the encoding of input gradient in insect olfactory projection neurons. Biosystems 223: 104802. PubMed ID: 36375712
Summary: The olfactory system in insects has evolved to process the dynamic changes in the concentration of food odors or sex pheromones to localize the nutrients or conspecific mating partners. Experimental studies have suggested that projection neurons (PNs) in insects encode not only the stimulus intensity but also its rate-of-change (input gradient). This study aimed to develop a simple computational model for a PN to understand the mechanism underlying the coding of the rate-of-change information. The spike frequency adaptation is shown to be a potential key mechanism for reproducing the phasic response pattern of the PN in Drosophila. It was also demonstrated that this adaptation mechanism enables the PN to encode the rate-of-change of the input firing rate. Finally, the model predicts that the PN exhibits the intensity-invariant response for the pulse and ramp odor stimulus. These results suggest that the developed model is useful for investigating the coding principle underlying olfactory information processing in insects. | Lassetter, A. P., Corty, M. M., Barria, R., Sheehan, A. E., Hill, J. Q., Aicher, S. A., Fox, A. N. and Freeman, M. R. (2023). Glial TGFβ activity promotes neuron survival in peripheral nerves. J Cell Biol 222(1). PubMed ID: 36399182
Summary: Maintaining long, energetically demanding axons throughout the life of an animal is a major challenge for the nervous system. Specialized glia ensheathe axons and support their function and integrity throughout life, but glial support mechanisms remain poorly defined. This study identified a collection of secreted and transmembrane molecules required in glia for long-term axon survival in vivo. The majority of components of the TGFβ superfamily are required in glia for sensory neuron maintenance but not glial ensheathment of axons. In the absence of glial TGFβ signaling, neurons undergo age-dependent degeneration that can be rescued either by genetic blockade of Wallerian degeneration or caspase-dependent death. Blockade of glial TGFβ signaling results in increased ATP in glia that can be mimicked by enhancing glial mitochondrial biogenesis or suppressing glial monocarboxylate transporter function. It is proposed that glial TGFβ signaling supports axon survival and suppresses neurodegeneration through promoting glial metabolic support of neurons. |
Monday, March 27th - Evolution |
| Bath, E., Rostant, W., Ostridge, H. J., Smith, S., Mason, J. S., Rafaluk-Mohr, T., Mank, J. E., Chapman, T. and Perry, J. C. (2023). Sexual selection and the evolution of condition-dependence: an experimental test at two resource levels. Evolution. PubMed ID: 36648108
Summary: Stronger condition-dependence in sexually-selected traits is well-documented, but how this relationship is established remains unknown. Moreover, resource availability can shape responses to sexual selection, but resource effects on the relationship between sexual selection and condition-dependence are also unknown. This study directly tested the hypotheses that sexual selection drives the evolution of stronger-condition-dependence and that resource availability affects the ouƒtcome, by evolving fruit flies (Drosophila melanogaster) under relatively strong or weak sexual selection (through varied sex ratios) and at resource-poor or resource-rich adult diets. Then condition was experimentally manipulated via developmental diet, and condition-dependence in adult morphology, behaviour and reproduction was assed. Stronger condition-dependence in female size was observed in male-biased populations and in female ovariole production in resource-limited populations. However, no evidence was found that male condition-dependence increased in response to sexual selection, or that responses depended on resource levels. These results offer no support for the hypotheses that sexual selection increases male condition-dependence or that sexual selection's influence on condition-dependence is influenced by resource availability. This study is the first experimental test of these hypotheses. If the results that are reported are general, then sexual selection's influence on the evolution of condition-dependence may be less important than predicted. | Church, S. H., Munro, C., Dunn, C. W. and Extavour, C. G. (2023). The evolution of ovary-biased gene expression in Hawaiian Drosophila. PLoS Genet 19(1): e1010607. PubMed ID: 36689550
Summary: With detailed data on gene expression accessible from an increasingly broad array of species, it is possible test the extent to which developmental genetic knowledge from model organisms predicts expression patterns and variation across species. But to know when differences in gene expression across species are significant, it is necessary to first necessary to know how much evolutionary variation in gene expression is expected. This study provides an answer by analyzing RNAseq data across twelve species of Hawaiian Drosophilidae flies, focusing on gene expression differences between the ovary and other tissues. It was shown that over evolutionary time, there exists a cohort of ovary specific genes that is stable and that largely corresponds to described expression patterns from laboratory model Drosophila species. The results also provide a demonstration of the prediction that, as phylogenetic distance increases, variation between species overwhelms variation between tissue types. Using ancestral state reconstruction of expression, the distribution of evolutionary changes in tissue-biased expression are described, and this was used to identify gains and losses of ovary-biased expression across these twelve species. This distribution was used to calculate the evolutionary correlation in expression changes between genes, and to demonstrate that genes with known interactions in D. melanogaster are significantly more correlated in their evolution than genes with no or unknown interactions. Finally, this correlation matrix was used to infer new networks of genes that share evolutionary trajectories, and these results are presented as a dataset of new testable hypotheses about genetic roles and interactions in the function and evolution of the Drosophila ovary. |
| Harris, M. and Garud, N. R. (2023). Enrichment of Hard Sweeps on the X Chromosome in Drosophila melanogaster. Mol Biol Evol 40(1). PubMed ID: 36546413
Summary: The characteristic properties of the X chromosome, such as male hemizygosity and its unique inheritance pattern, expose it to natural selection in a way that can be different from the autosomes. This study investigated the differences in the tempo and mode of adaptation on the X chromosome and autosomes in a population of Drosophila melanogaster. Specifically, the hypothesis was tested that due to hemizygosity and a lower effective population size on the X, the relative proportion of hard sweeps, which are expected when adaptation is gradual, compared with soft sweeps, which are expected when adaptation is rapid, is greater on the X than on the autosomes. The incidence of hard versus soft sweeps was quantified in North American D. melanogaster population genomic data with haplotype homozygosity statistics and found an enrichment of the proportion of hard versus soft sweeps on the X chromosome compared with the autosomes, confirming predictions was made from simulations. Understanding these differences may enable a deeper understanding of how important phenotypes arise as well as the impact of fundamental evolutionary parameters on adaptation, such as dominance, sex-specific selection, and sex-biased demography. | Li, M., Kasan, K., Saha, Z., Yoon, Y. and Schmidt-Ott, U. (2023). Twenty-seven ZAD-ZNF genes of Drosophila melanogaster are orthologous to the embryo polarity determining mosquito gene cucoid. PLoS One 18(1): e0274716. PubMed ID: 36595500
Summary: The C2H2 zinc finger gene cucoid establishes anterior-posterior (AP) polarity in the early embryo of culicine mosquitoes. This gene is unrelated to genes that establish embryo polarity in other fly species (Diptera), such as the homeobox gene bicoid, which serves this function in the traditional model organism Drosophila melanogaster. The cucoid gene is a conserved single copy gene across lower dipterans but nothing is known about its function in other species, and its evolution in higher dipterans, including Drosophila, is unresolved. This study found that cucoid is a member of the ZAD-containing C2H2 zinc finger (ZAD-ZNF) gene family and is orthologous to 27 of the 91 members of this family in D. melanogaster, including M1BP, ranshi, ouib, nom, zaf1, odj, Nnk, trem, Zif, and eighteen uncharacterized genes. Available knowledge of the functions of cucoid orthologs in Drosophila melanogaster suggest that the progenitor of this lineage specific expansion may have played a role in regulating chromatin. Many aspects of the gene duplication history of cucoid in the brachyceran lineage of D. melanogaster are descri ed, thereby providing a framework for predicting potential redundancies among these genes in D. melanogaster. |
| De Lisle, S. P. (2023). Rapid evolution of ecological sexual dimorphism driven by resource competition. Ecol Lett 26(1): 124-131. PubMed ID: 36366784
Summary: Sex differences in ecologically important traits are common in animals and plants, and prompted Darwin to first propose an ecological cause of sexual dimorphism. Despite theoretical plausibility and Darwin's original notion, a role for ecological resource competition in the evolution of sexual dimorphism has never been directly demonstrated and remains controversial. This study used experimental evolution in Drosophila melanogaster to test the hypothesis that resource competition can drive the evolution of sex differences in diet. Following just three generations of adaptation, offspring from flies evolved in low-resource, high-competition environments show elevated sexual dimorphism in diet preference compared to both the ancestor and populations evolved on high-resource availability. This increased sexual dimorphism was the result of divergence in male sucrose intake and female yeast intake consistent with the differential nutritional requirements of the sexes. These results provide the first real-time direct evidence for evolution of sexual dimorphism driven by resource competition. | Deppisch, P., Kirsch, V., Helfrich-Forster, C. and Senthilan, P. R. (2023). Contribution of cryptochromes and photolyases for insect life under sunlight. J Comp Physiol A Neuroethol Sens Neural Behav Physiol. PubMed ID: 36609567
Summary: The cryptochrome/photolyase (CRY/PL) family is essential for life under sunlight because photolyases repair UV-damaged DNA and cryptochromes are normally part of the circadian clock that controls the activity-sleep cycle within the 24-h day. This study aimed to understand how the lineage and habitat of an insect affects its CRY/PL composition. To this end, the large number of annotated protein sequences of 340 insect species already available in databases was searched for CRY/PLs. Using phylogenetic tree and motif analyses, four frequent CRY/PLs in insects: the photolyases 6-4 PL and CPDII PL were identified, as well as the mammalian-type cryptochrome (MCRY) and Drosophila-type cryptochrome (DCRY). Assignment of CRY/PLs to the corresponding insects confirmed that light-exposed insects tend to have more CRY/PLs than insects with little light exposure. Nevertheless, even insects with greatly reduced CRY/PLs still possess MCRY, which can be regarded as the major insect cryptochrome. Only flies of the genus Schizophora, which includes Drosophila melanogaster, lost MCRY. Moreover, MCRY and CPDII PL as well as DCRY and 6-4 PL were fount to occur very frequently together, suggesting an interaction between the two pairs. |
Thursday March 23rd - Adult Nervous System Development and Function |
| Hou, X., Hayashi, R., Itoh, M. and Tonoki, A. (2023). Small-molecule screening in aged Drosophila identifies mGluR as a regulator of age-related sleep impairment. Sleep. PubMed ID: 36721967
Summary: As a normal physiological phenomenon, aging has a significant impact on sleep. Aging leads to sleep impairment, including sleep loss, fragmented sleep, and a lower arousal threshold, leading to various diseases. Because sleep regulates memory consolidation, age-dependent sleep impairment also affects memory. However, the mechanisms underlying age-related sleep dysregulation and its impact on memory remain unclear. Using male and female Drosophila, which possesses sleep characteristics similar to those of mammals and exhibits age-dependent sleep impairment as a model, small-molecule screening was performed to identify novel regulators of age-dependent decline in sleep. The screening identified 3,3´-difluorobenzaldazine (DFB), a positive allosteric modulator of the metabotropic glutamate receptor (mGluR) 5, as a novel sleep-promoting compound in aged flies. The study found that mutant flies of mGluR, a single mGluR gene in Drosophila, and decreased mGluR expression had significant impairment in sleep and memory due to olfactory conditioning. The decreased sleep phenotype in the mGluR mutants was not promoted by DFB, suggesting that the effects of DFB on age-dependent sleep impairment are dependent on mGluR. Although aging decreases the expression of mGluR and the binding scaffold proteins Homer and Shank, the transient overexpression of mGluR in neurons improves sleep in both young and aged flies. Overall, these findings indicate that age-dependent decreased expression or function of mGluR impairs sleep and memory in flies, which could lead to age-related sleep and memory impairment. | Huang, Z. (2023). A Function of Amyloid-β in Mediating Activity-Dependent Axon/Synapse Competition May Unify Its Roles in Brain Physiology and Pathology. J Alzheimers Dis. PubMed ID: 36710681
Summary: Amyloid-β protein precursor (AβPP) gives rise to amyloid-β (Aβ), a peptide at the center of Alzheimer's disease (AD). AβPP, however, is also an ancient molecule dating back in evolution to some of the earliest forms of metazoans. This suggests a possible ancestral function that may have been obscured by those that evolve later. Based on literature from the functions of Aβ/AβPP in nervous system development, plasticity, and disease, to those of anti-microbial peptides (AMPs) in bacterial competition as well as mechanisms of cell competition uncovered first by Drosophila genetics, this paper proposes that Aβ/AβPP may be part of an ancient mechanism employed in cell competition, which is subsequently co-opted during evolution for the regulation of activity-dependent neural circuit development and plasticity. This hypothesis is supported by foremost the high similarities of Aβ to AMPs, both of which possess unique, opposite (i.e., trophic versus toxic) activities as monomers and oligomers. A large body of data further suggests that the different Aβ oligomeric isoforms may serve as the protective and punishment signals long predicted to mediate activity-dependent axonal/synaptic competition in the developing nervous system and that the imbalance in their opposite regulation of innate immune and glial cells in the brain may ultimately underpin AD pathogenesis. This hypothesis can not only explain the diverse roles observed of Aβ and AβPP family molecules, but also provide a conceptual framework that can unify current hypotheses on AD. Furthermore, it may explain major clinical observations not accounted for and identify approaches for overcoming shortfalls in AD animal modeling. |
| Kanaoka, Y., Onodera, K., Watanabe, K., Hayashi, Y., Usui, T., Uemura, T. and Hattori, Y. (2023). Inter-organ Wingless/Ror/Akt signaling regulates nutrient-dependent hyperarborization of somatosensory neurons. Elife 12. PubMed ID: 36647607
Summary: Nutrition in early life has profound effects on an organism, altering processes such as organogenesis. However, little is known about how specific nutrients affect neuronal development. Dendrites of class IV dendritic arborization neurons in Drosophila larvae become more complex when the larvae are reared on a low-yeast diet compared to a high-yeast diet. A systematic search for key nutrients revealed that the neurons increase their dendritic terminal densities in response to a combined deficiency in vitamins, metal ions, and cholesterol. The deficiency of these nutrients upregulates Wingless in a closely located tissue, body wall muscle. Muscle-derived Wingless activates Akt in the neurons through the receptor tyrosine kinase Ror, which promotes the dendrite branching. In larval muscles, the expression of wingless is regulated not only in this key nutrient-dependent manner, but also by the JAK/STAT signaling pathway. Additionally, the low-yeast diet blunts neuronal light responsiveness and light avoidance behavior, which may help larvae optimize their survival strategies under low-nutritional conditions. Together, these studies illustrate how the availability of specific nutrients affects neuronal development through inter-organ signaling. | Himmel, N. J., Sakurai, A., Patel, A. A., Bhattacharjee, S., Letcher, J. M., Benson, M. N., Gray, T. R., Cymbalyuk, G. S. and Cox, D. N. (2023). Chloride-dependent mechanisms of multimodal sensory discrimination and nociceptive sensitization in Drosophila. Elife 12. PubMed ID: 36688373
Summary: Individual sensory neurons can be tuned to many stimuli, each driving unique, stimulus-relevant behaviors, and the ability of multimodal nociceptor neurons to discriminate between potentially harmful and innocuous stimuli is broadly important for organismal survival. Moreover, disruptions in the capacity to differentiate between noxious and innocuous stimuli can result in neuropathic pain. Drosophila larval Class III (CIII) neurons are peripheral noxious cold nociceptors and innocuous touch mechanosensors; high levels of activation drive cold-evoked contraction (CT) behavior, while low levels of activation result in a suite of touch-associated behaviors. However, it is unknown what molecular factors underlie CIII multimodality. This study showed that the TMEM16/anoctamins subdued and |
| Gowda, S. B. M., Banu, A., Salim, S., Peker, K. A. and Mohammad, F. (2023). Serotonin distinctly controls behavioral states in restrained and freely moving Drosophila. iScience 26(1): 105886. PubMed ID: 36654863
Summary: When trapped in a physical restraint, animals must select an escape strategy to increase their chances of survival. After falling into an inescapable trap, they react with stereotypical behaviors that differ from those displayed in escapable situations. Such behaviors involve either a wriggling response to unlock the trap or feigning death to fend off a predator attack. The neural mechanisms that regulate animal behaviors have been well characterized for escapable situations but not for inescapable traps. This study reports that restrained vinegar flies exhibit alternating flailing and immobility to free themselves from the trap. Optogenetics and intersectional genetic approaches were used to show that, while broader serotonin activation promotes immobility, serotonergic cells in the ventral nerve cord (VNC) regulate immobility states majorly via 5-HT7 receptors. Restrained and freely moving locomotor states are controlled by distinct mechanisms. Taken together, this study has identified serotonergic switches of the VNC that promote environment-specific adaptive behaviors. | Hernandez, K., Godoy, L., Newquist, G., Kellermeyer, R., Alavi, M., Mathew, D. and Kidd, T. (2023). Dscam1 overexpression impairs the function of the gut nervous system in Drosophila. Dev Dyn 252(1): 156-171. PubMed ID: 36454543
Summary: Down syndrome (DS) patients have a 100-fold increase in the risk of Hirschsprung syndrome of the colon and rectum (HSCR), a lack of enteric neurons in the colon. The leading DS candidate gene is trisomy of the Down syndrome cell adhesion molecule (DSCAM). This study found that Dscam1 protein is expressed in the Drosophila enteric/stomatogastric nervous system (SNS). Axonal Dscam1 phenotypes can be rescued equally by diverse isoforms. Overexpression of Dscam1 resulted in frontal and hindgut nerve overgrowth. Expression of dominant negative Dscam1-ΔC led to a truncated frontal nerve and increased branching of the hindgut nerve. Larval locomotion is influenced by feeding state, and it was found that the average speed of larvae with Dscam1 SNS expression was reduced, whereas overexpression of Dscam1-ΔC significantly increased the speed. Dscam1 overexpression reduced the efficiency of food clearance from the larval gut. This work demonstrates that overexpression of Dscam1 can perturb gut function in a model system. |
Wednesday, March 22nd - Disease Models |
| Dumitrescu, E., Copeland, J. M. and Venton, B. J. (2023). Parkin Knockdown Modulates Dopamine Release in the Central Complex, but Not the Mushroom Body Heel, of Aging Drosophila. ACS Chem Neurosci 14(2): 198-208. PubMed ID: 36576890
Summary: Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic neurons leading to reduced locomotion. Mutations of parkin gene in Drosophila produce the same phenotypes as vertebrate models, but the effect of parkin knockdown on dopamine release is not known. This study reports age-dependent, spatial variation of dopamine release in the brain of parkin-RNAi adult Drosophila. Dopamine was repetitively stimulated by local application of acetylcholine and quantified by fast-scan cyclic voltammetry in the central complex or mushroom body heel. In the central complex, the main area controlling locomotor function, dopamine release is maintained for repeated stimulations in aged control flies, but lower concentrations of dopamine are released in the central complex of aged parkin-RNAi flies. In the mushroom body heel, the dopamine release decrease in older parkin-RNAi flies is similar to controls. There is not significant dopaminergic neuronal loss even in older parkin knockdown flies, which indicates that the changes in stimulated dopamine release are due to alterations of neuronal function. In young parkin-RNAi flies, locomotion is inhibited by 30%, while in older parkin-RNAi flies it is inhibited by 85%. Overall, stimulated dopamine release is modulated by Parkin in an age and brain region dependent manner. Correlating the functional state of the dopaminergic system with behavioral phenotypes provides unique insights into the PD mechanism. Drosophila can be used to study dopamine functionality in PD, elucidate how genetics influence dopamine, and test potential therapies to maintain dopamine release. | Jin, J. H., Wen, D. T., Chen, Y. L. and Hou, W. Q. (2023). Muscle FOXO-Specific Overexpression and Endurance Exercise Protect Skeletal Muscle and Heart from Defects Caused by a High-Fat Diet in Young Drosophila. Front Biosci (Landmark Ed) 28(1): 16. PubMed ID: 36722272
Summary: Obesity appears to significantly reduce physical activity, but it remains unclear whether this is related to obesity-induced damage to skeletal muscle (SM) and heart muscle (HM). Endurance exercise (EE) reduces obesity-induced defects in SM and HM, but its molecular mechanism is poorly understood. The UAS/GAL4 system was used to construct the regulation of SM-specific FOXO gene expression in Drosophila, and the transgenic Drosophila was subjected to EE and high-fat diet (HFD) intervention. The structure and function of SM and HM were impaired by a HFD and muscle-FOXO-specific RNAi (MFSR), including reduced climbing speed and climbing endurance, reduced fractional shortening of the heart, damaged myofibrils, and reduced mitochondria in HM. Besides, a HFD and MFSR increased triglyceride level and malondialdehyde level, decreased the Sirt1 and FOXO protein level, and reduced carnitine palmityl transferase I, superoxide dismutase, and catalase activity level. They down-regulated FOXO and bmm expression level in SM and HM. On the contrary, both muscle FOXO-specific overexpression (MFSO) and EE prevented abnormal changes of SM and HM in function, structure, or physiology caused by HFD and MFSR. Besides, EE also prevented defects of SM and HM induced by MFSR. Current findings confirmed MFSO and EE protected SM and heart from defects caused by a HFD via enhancing FOXO-realated antioxidant pathways and lipid catabolism. FOXO played a vital role in regulating HFD-induced defects in SM and HM, but FOXO was not a key regulatory gene of EE against damages in SM and HM. The mechanism was related to activity of Sirt1/FOXO/SOD (superoxide dismutase), CAT (catalase) pathways and lipid catabolism in SM and HM. |
| Dhanushkodi, N. R., Abul Khair, S. B., Ardah, M. T. and Haque, M. E. (2023). ATP13A2 Gene Silencing in Drosophila Affects Autophagic Degradation of A53T Mutant α-Synuclein. Int J Mol Sci 24(2). PubMed ID: 36675288
Summary: Mutations in ATP13A2 (PARK9), an autophagy-related protein, cause Kufor-Rakeb syndrome, an autosomal recessive, juvenile-onset form of parkinsonism. α-Synuclein (α-syn) is a presynaptic neuronal protein that forms toxic aggregates in Parkinson's disease (PD). α-syn aggregation and autophagic flux in ATP13A2-knockdown occurs Drosophila expressing either wild-type (WT) or mutant α-syn. Dopaminergic (DA) neuron loss was studied by confocal microscopy. Sleep and circadian activity were evaluated in young and old flies using a Drosophila activity monitor. Thirty-day-old ATP13A2-RNAi A53T-α-syn flies had increased Triton-insoluble α-syn levels, compared to control A53T-α-syn flies without ATP13A2-RNAi. Whole-brain staining revealed significantly fewer dopaminergic (DA) neurons in the PPL2 cluster of 30-day-old ATP13A2-RNAi flies expressing WT-, A30P-, and A53T-α-syn than in that of controls. In ATP13A2-RNAi A53T-α-syn flies, autophagic flux was decreased, as indicated by increased accumulation of Ref(2)P, the Drosophila p62 homologue. ATP13A2 silencing decreased total locomotor activity in young, and enhanced sleep features, similar to PD (decreasing bout length), in old flies expressing A53T-α-syn. ATP13A2 silencing also altered the circadian locomotor activity of A30P- and A53T-α-syn flies. Thus, ATP13A2 may play a role in the autophagic degradation of A53T-α-syn. | Gupta, H. P., Pandey, R. and Ravi Ram, K. (2023). Altered sperm fate in the reproductive tract milieu due to oxidative stress leads to sub-fertility in type 1 diabetes females: A Drosophila-based study. Life Sci 313: 121306. PubMed ID: 36543282
Summary: Female sub-fertility, a prominent complication due to Type 1 diabetes (T1D), is generally attributed to disturbances in menstrual cycles and/or ovarian defects/disorders. T1D women, however, are high in oxidative stress, although the impact of the same on their reproduction and associated events remains unknown. Therefore, the repercussions of elevated oxidative stress on the sperm fate (storage/utilization) in the reproductive tract milieu of T1D females and their fertility using the Drosophila T1D model (Df[dilp1-5]), which lacks insulin-like peptides and displays reduced female fertility. Df[dilp1-5] females were mated to normal males and thereafter sperm storage and/or utilization were examined in conjunction with oxidative stress parameters in mated Df[dilp1-5] females at different time points. Also, the impact of antioxidant (Amla or Vitamin C) supplementation on the above oxidative stress parameters in Df[dilp1-5] females and the consequences on their sperm and fertility levels were examined. Df[dilp1-5] females showed elevated oxidative stress parameters and a few of their reproductive tract proteins are oxidatively modified. Also, these females stored significantly fewer sperm and also did not utilize sperm as efficiently as their controls. Surprisingly, amelioration of the oxidative stress in Df[dilp1-5] females' milieu through antioxidant (Amla or vitamin C) supplementation enhanced sperm storage and improved fertility. Hyperglycemia coupled with elevated oxidative stress within the female reproductive tract environment affects the sperm fate, thereby reducing female fertility in T1D. In addition, these findings suggest that antioxidant supplementation may substantially aid in the mitigation of sub-fertility in T1D females |
| Johnson, J. C., Munneke, A. S., Richardson, H. M., Gendron, C. M. and Pletcher, S. D. (2023). Light modulates Drosophila lifespan via perceptual systems independent of circadian rhythms. Aging (Albany NY) 15. PubMed ID: 36622279
Summary: Across taxa, sensory perception modulates aging in response to important ecological cues, including food, sex, and danger. The range of sensory cues involved, and their mechanism of action, are largely unknown. This study therefore sought to better understand how one potential cue, that of light, impacts aging in Drosophila melanogaster. In accordance with recently published data, it was found that flies lived significantly longer in constant darkness. Extended lifespan was not accompanied by behavioral changes that might indirectly slow aging such as activity, feeding, or fecundity, nor were circadian rhythms necessary for the effect. The lifespans of flies lacking eyes or photoreceptor neurons were unaffected by light kept at normal housing conditions, and transgenic activation of these same neurons was sufficient to phenocopy the effects of environmental light on lifespan. The relationship between light and lifespan was not correlated with its intensity, duration, nor the frequency of light-dark transitions. Furthermore, high-intensity light reduced lifespan in eyeless flies, indicating that the effects observed were largely independent of the known, non-specific damaging effects associated with light. These results suggest that much like other environmental cues, light may act as a sensory stimulus to modulate aging. | Jiao, J., Curley, M., Graca, F. A., Robles-Murguia, M., Shirinifard, A., Finkelstein, D., Xu, B., Fan, Y. and Demontis, F. (2023). Modulation of protease expression by the transcription factor Ptx1/PITX regulates protein quality control during aging. Cell Rep 42(1): 111970. PubMed ID: 36640359
Summary: Protein quality control is important for healthy aging and is dysregulated in age-related diseases. The autophagy-lysosome and ubiquitin-proteasome are key for proteostasis, but it remains largely unknown whether other proteolytic systems also contribute to maintain proteostasis during aging. This study finds that expression of proteolytic enzymes (proteases/peptidases) distinct from the autophagy-lysosome and ubiquitin-proteasome systems declines during skeletal muscle aging in Drosophila. Age-dependent protease downregulation undermines proteostasis, as demonstrated by the increase in detergent-insoluble poly-ubiquitinated proteins and pathogenic huntingtin-polyQ levels in response to protease knockdown. Computational analyses identify the transcription factor Ptx1 (homologous to human PITX1/2/3) as a regulator of protease expression. Consistent with this model, Ptx1 protein levels increase with aging, and Ptx1 RNAi counteracts the age-associated downregulation of protease expression. Moreover, Ptx1 RNAi improves muscle protein quality control in a protease-dependent manner and extends lifespan. These findings indicate that proteases and their transcriptional modulator Ptx1 ensure proteostasis during aging. |
Tuesday March 21st - Signaling |
| Hidalgo, S., Anguiano, M., Tabuloc, C. A. and Chiu, J. C. (2023). Seasonal cues act through the circadian clock and pigment-dispersing factor to control EYES ABSENT and downstream physiological changes. Curr Biol. PubMed ID: 36708710
Summary: Organisms adapt to seasonal changes in photoperiod and temperature to survive; however, the mechanisms by which these signals are integrated in the brain to alter seasonal biology are poorly understood. It has been reported previously that EYES ABSENT (EYA) shows higher levels in cold temperature or short photoperiod and promotes winter physiology in Drosophila. Nevertheless, how EYA senses seasonal cues is unclear. Pigment-dispersing factor (PDF) is a neuropeptide important for regulating circadian output rhythms. Interestingly, PDF has also been shown to regulate seasonality, suggesting that it may mediate the function of the circadian clock in modulating seasonal physiology. This study investigated the role of EYA in mediating the function of PDF on seasonal biology. It was observed that PDF abundance is lower on cold and short days as compared with warm and long days, contrary to what was previously observed for EYA. Manipulating PDF signaling in eya+ fly brain neurons, where EYA and PDF receptor are co-expressed, modulates seasonal adaptations in daily activity rhythm and ovary development via EYA-dependent and EYA-independent mechanisms. At the molecular level, altering PDF signaling impacted EYA protein abundance. Specifically, it was shown that protein kinase A (PKA), an effector of PDF signaling, phosphorylates EYA promoting its degradation, thus explaining the opposite responses of PDF and EYA abundance to changes in seasonal cues. In summary, these results support a model in which PDF signaling negatively modulates EYA levels to regulate seasonal physiology, linking the circadian clock to the modulation of seasonal adaptations. | Collins, Q. P., Grunsted, M. J., Arcila, D., Xiong, Y. and Barmchi, M. P. (2023). Transcriptomic analysis provides insight into the mechanism of IKKbeta-mediated suppression of HPV18E6-induced cellular abnormalities. G3 (Bethesda). PubMed ID: 36722216
Summary: High-risk Human Papillomaviruses (HPV) 16 and 18 are responsible for more than 70% of cervical cancers and majority of other HPV-associated cancers world-wide. Recently, a Drosophila model of HPV18E6 plus human E3 ubiquitin ligase (hUBE3A; see Drosophila Ubiquitin protein ligase E3A) was developed, and it was demonstrated that the E6-induced cellular abnormalities are conserved between humans and flies. Subsequently, it was demonstrated that reduced level and activity of IKKβ, a regulator of NF-κB, suppresses the cellular abnormalities induced by E6 oncoprotein and that the interaction of IKKβ and E6 is conserved in human cells. In this study, transcriptomic analysis was performed to identify differentially expressed genes that play a role in IKKβ-mediated suppression of E6-induced defects. Transcriptome analysis identified 215 genes whose expression were altered due to reduced levels of IKKβ. Out of these 215 genes 151 genes showed annotations. These analyses were followed by functional genetic interaction screen using RNAi, overexpression, and mutant fly strains for identified genes. The screen identified several genes including genes involved in Hippo and Toll pathways as well as junctional complexes whose downregulation or upregulation resulted in alterations of E6-induced defects. Subsequently, RT-PCR analysis was performed for validation of altered gene expression level for a few representative genes. These results indicate an involvement for Hippo and Toll pathways in IKKβ-mediated suppression of E6 + hUBE3A-induced cellular abnormalities. Therefore, this study enhances understanding of the mechanisms underlying HPV-induced cancer and can potentially lead to identification of novel drug targets for cancers associated with HPV. |
| Banzai, K. and Nishimura, T. (2023). Isolation of a novel missense mutation in insulin receptor as a spontaneous revertant in ImpL2 mutants in Drosophila. Development 150(1). PubMed ID: 36504086
Summary: Evolutionarily conserved insulin/insulin-like growth factor (IGF) signaling (IIS) correlates nutrient levels to metabolism and growth, thereby playing crucial roles in development and adult fitness. In the fruit fly Drosophila, ImpL2, an ortholog of IGFBP7, binds to and inhibits the function of Drosophila insulin-like peptides. In this study, a temperature-sensitive mutation was isolated in the insulin receptor (InR) gene as a spontaneous revertant in ImpL2 null mutants. The p.Y902C missense mutation is located at the functionally conserved amino acid residue of the first fibronectin type III domain of InR. The hypomorphic InR mutant animals showed a temperature-dependent reduction in IIS and body size. The mutant animals also exhibited metabolic defects, such as increased triglyceride and carbohydrate levels. Metabolomic analysis further revealed that defects in InR caused dysregulation of amino acid and ribonucleotide metabolism. It was also observed that InR mutant females produced tiny irregular-shaped embryos with reduced fecundity. In summary, this novel allele of InR is a valuable tool for the Drosophila genetic model of insulin resistance and type 2 diabetes. | Anand, A. S., Verma, K., Amitabh, Prasad, D. N. and Kohli, E. (2023). The interplay of calponin, wnt signaling, and cytoskeleton protein governs transgenerational phenotypic abnormalities in drosophila exposed to zinc oxide nanoparticles. Chem Biol Interact 369: 110284. PubMed ID: 36462549
Summary: ZnO nanoparticles (ZnO NPs) are widely used engineered nanomaterials. Due to induced genotoxicity, increased oxidative stress, and teratogenicity, these NPs have been reported to be toxic. To understand how protein expression regulates this particular phenotype on ZnO NPs exposure, toxicoproteomics profile of control and abnormal phenotype flies was generated using LC/MS/MS. Gene ontology enrichment studies of proteomics data were carried out using CLUEGO and STRAP software. The bioinformatics tool STRING was used to generate a protein-protein interaction map of key proteins of enrichment analysis. Following ZnO NP exposure, the differential expression of key proteins of the Wnt pathway was prominent. Altered expression of various proteins of the Wnt pathway (CaMKII), cytoskeleton (Actin), and calponin resulted in developmental defects in Drosophila progeny. In addition, immunohistology studies showed a significant deviation in the expression of Wingless protein of ZnO NPs treated larvae in comparison to control. According to these findings, the interaction of the wnt pathway and cytoskeletal proteins with ZnO NPs caused developmental abnormalities in the subsequent generation of Drosophila, highlighting the transgenerational toxic effects of these nanoparticles. |
| Zang, Y., Chaudhari, K. and Bashaw, G. J. (2022). Tace/ADAM17 is a bi-directional regulator of axon guidance that coordinates distinct Frazzled and Dcc receptor signaling outputs. Cell Rep 41(10): 111785. PubMed ID: 36476876
Summary: Frazzled (Fra) and deleted in colorectal cancer (Dcc) are homologous receptors that promote axon attraction in response to netrin. In Drosophila, Fra also acts independently of netrin by releasing an intracellular domain (ICD) that activates gene transcription. How neurons coordinate these pathways to make accurate guidance decisions is unclear. This study shows that the ADAM metalloprotease Tace cleaves Fra, and this instructs the switch between the two pathways. Genetic manipulations that either increase or decrease Tace levels disrupt midline crossing of commissural axons. These conflicting phenotypes reflect Tace's function as a bi-directional regulator of axon guidance, a function conserved in its vertebrate homolog ADAM17: while Tace induces the formation of the Fra ICD to activate transcription, excessive Tace cleavage of Fra and Dcc suppresses the response to netrin. It is proposed that Tace and ADAM17 are key regulators of midline axon guidance by establishing the balance between netrin-dependent and netrin-independent signaling. | Zhao, Y., Khallaf, M. A., Johansson, E., Dzaki, N., Bhat, S., Alfredsson, J., Duan, J., Hansson, B. S., Knaden, M. and Alenius, M. (2022). Hedgehog-mediated gut-taste neuron axis controls sweet perception in Drosophila. Nat Commun 13(1): 7810. PubMed ID: 36535958
Summary: Dietary composition affects food preference in animals. High sugar intake suppresses sweet sensation from insects to humans, but the molecular basis of this suppression is largely unknown. This study revealed that sugar intake in Drosophila induces the gut to express and secrete Hedgehog (Hh) into the circulation. The midgut secreted Hh localized to taste sensilla and suppresses sweet sensation, perception, and preference. It was further found that the midgut Hh inhibits Hh signalling in the sweet taste neurons. Electrophysiology studies demonstrate that the midgut Hh signal also suppresses bitter taste and some odour responses, affecting overall food perception and preference. It was further shown that the level of sugar intake during a critical window early in life, sets the adult gut Hh expression and sugar perception. These results together reveal a bottom-up feedback mechanism involving a "gut-taste neuron axis" that regulates food sensation and preference. |
Monday, March 20 - Enhancers and Transcriptional Regulation |
| Fisher, W. W., Hammonds, A. S., Weiszmann, R., Booth, B. W., Gevirtzman, L., Patton, J., Kubo, C., Waterston, R. H. and Celniker, S. E. (2023). A modERN Resource: Identification of Drosophila Transcription Factor candidate target genes using RNAi. Genetics. PubMed ID: 36652461
Summary: Transcription factors (TFs) play a key role in development and in cellular responses to the environment by activating or repressing the transcription of target genes in precise spatial and temporal patterns. In order to develop a catalog of target genes of D. melanogaster transcription factors, the modERN consortium systematically knocked down expression of transcription factors (TFs) using RNAi in whole embryos followed by RNA-seq. Data was generated for 45 TFs which have 18 different DNA-binding domains and are expressed in 15 of the 16 organ systems. The range of inactivation of the targeted TFs by RNAi ranged from log2fold change -3.52 to +0.49. The TFs also showed remarkable heterogeneity in the numbers of candidate target genes identified, with some generating thousands of candidates and others only tens. Detailed analysis is presented from five experiments, including those for three TFs that have been the focus of previous functional studies (ERR, sens, and zfh2) and two previously uncharacterized TFs (sens-2 and CG32006), as well as short vignettes for selected additional experiments to illustrate the utility of this resource. The RNA-seq datasets are available through the ENCODE DCC and the Sequence Read Archive (SRA). Transcription Factor and target gene expression patterns can be found here: https://insitu.fruitfly.org. These studies provide data that facilitate scientific inquiries into the functions of individual TFs in key developmental, metabolic, defensive, and homeostatic regulatory pathways, as well as provide a broader perspective on how individual TFs work together in local networks during embryogenesis. | Rzezniczak, T. Z., Rzezniczak, M. T., Reed, B. H., Dworkin, I. and Merritt, T. J. S. (2022). Regulation at Drosophila's Malic Enzyme highlights the complexity of transvection and its sensitivity to genetic background. Genetics. PubMed ID: 36482767
Summary: Transvection, a type of trans-regulation of gene expression in which regulatory elements on one chromosome influence elements on a paired homologous chromosome, is itself a complex biological phenotype subject to modification by genetic background effects. With the emergence of the "hub" model of transvection and a series of studies showing variation in transvection effects, it is becoming clear that genetic background plays an important role in how transvection influences gene transcription. This study explored the effects of genetic background on transvection by performing two independent Genome Wide Association Studies (GWAS) using the Drosophila Genetic Reference (DGRP) and a suite of Malic enzyme (Men) excision alleles. Substantial variation was found sin the amount of transvection in the 149 DGRP lines used, with broad sense heritability of 0.89 and 0.84, depending on the excision allele used. The specific genetic variation identified was dependent on the excision allele used, highlighting the complex genetic interactions influencing transvection. This study focussed primarily on genes identified as significant using a relaxed P-value cut-off in both GWASs. The most strongly associated genetic variant mapped to an intergenic SNP located upstream of Tiggrin (Tig), a gene that codes for an extracellular matrix protein. Variants in other genes, such transcription factors (CG7368, Sima), RNA binding proteins (CG10418, Rbp6, Rig), enzymes (AdamTS-A, CG9743, Pgant8), proteins influencing cell cycle progression (Dally, Eip63E) and signalling proteins (Atg-1, Axo, Egfr, Path). Although not intuitively obvious how many of these genes may influence transvection, some have been previously identified as promoting or antagonizing somatic homolog pairing. These results identify several candidate genes to further explore in the understanding of transvection at Men and in other genes regulated by transvection. |
| Kim, Y. J., Rhee, K., Liu, J., Jeammet, S., Turner, M. A., Small, S. J. and Garcia, H. G. (2022). Predictive modeling reveals that higher-order cooperativity drives transcriptional repression in a synthetic developmental enhancer. Elife 11. PubMed ID: 36503705
Summary: A challenge in quantitative biology is to predict output patterns of gene expression from knowledge of input transcription factor patterns and from the arrangement of binding sites for these transcription factors on regulatory DNA. This study tested whether widespread thermodynamic models could be used to infer parameters describing simple regulatory architectures that inform parameter-free predictions of more complex enhancers in the context of transcriptional repression by Runt in the early fruit fly embryo. By modulating the number and placement of Runt binding sites within an enhancer, and quantifying the resulting transcriptional activity using live imaging, it was discovered that thermodynamic models call for higher-order cooperativity between multiple molecular players. This higher-order cooperativity captures the combinatorial complexity underlying eukaryotic transcriptional regulation and cannot be determined from simpler regulatory architectures, highlighting the challenges in reaching a predictive understanding of transcriptional regulation in eukaryotes and calling for approaches that quantitatively dissect their molecular nature. | Hajirnis, N., Pandey, S. and Mishra, R. K. (2023). CRISPR/Cas9 and FLP-FRT mediated regulatory dissection of the BX-C of Drosophila melanogaster. Chromosome Res 31(1): 7. PubMed ID: 36719476
Summary: The homeotic genes or Hox define the anterior-posterior (AP) body axis formation in bilaterians and are often present on the chromosome in an order collinear to their function across the AP axis. However, there are many cases wherein the Hox are not collinear, but their expression pattern is conserved across the AP axis. The expression pattern of Hox is attributed to the cis-regulatory modules (CRMs) consisting of enhancers, initiators, or repressor elements that regulate the genes in a segment-specific manner. In the Drosophila melanogaster Hox complex, the bithorax complex (BX-C) and even the CRMs are organized in an order that is collinear to their function in the thoracic and abdominal segments. In the present study, the regulatorily inert regions were targeted using CRISPR/Cas9 to generate a series of transgenic lines with the insertion of FRT sequences. These FRT lines are repurposed to shuffle the CRMs associated with Abd-B to generate modular deletion, duplication, or inversion of multiple CRMs. The rearrangements yielded entirely novel phenotypes in the fly suggesting the requirement of such complex manipulations to address the significance of higher order arrangement of the CRMs. The functional map and the transgenic flies generated in this study are important resources to decipher the collective ability of multiple regulatory elements in the eukaryotic genome to function as complex modules. |
| Alamos, S., Reimer, A., Westrum, C., Turner, M. A., Talledo, P., Zhao, J., Luu, E. and Garcia, H. G. (2023). Minimal synthetic enhancers reveal control of the probability of transcriptional engagement and its timing by a morphogen gradient. Cell Syst. PubMed ID: 36696901
Summary: How enhancers interpret morphogen gradients to generate gene expression patterns is a central question in developmental biology. Recent studies have proposed that enhancers can dictate whether, when, and at what rate promoters engage in transcription, but the complexity of endogenous enhancers calls for theoretical models with too many free parameters to quantitatively dissect these regulatory strategies. To overcome this limitation, this study established a minimal promoter-proximal synthetic enhancer in embryos of Drosophila melanogaster. Here, a gradient of the Dorsal activator is read by a single Dorsal DNA binding site. Using live imaging to quantify transcriptional activity, it was found that a single binding site can regulate whether promoters engage in transcription in a concentration-dependent manner. By modulating the binding-site affinity, it was determined that a gene's decision to transcribe and its transcriptional onset time can be explained by a simple model where the promoter traverses multiple kinetic barriers before transcription can ensue. | Galupa, R., Alvarez-Canales, G., Borst, N. O., Fuqua, T., Gandara, L., Misunou, N., Richter, K., Alves, M. R. P., Karumbi, E., Perkins, M. L., Kocijan, T., Rushlow, C. A. and Crocker, J. (2023). Enhancer architecture and chromatin accessibility constrain phenotypic space during Drosophila development. Dev Cell 58(1): 51-62. PubMed ID: 36626871
Summary: Developmental enhancers bind transcription factors and dictate patterns of gene expression during development. Their molecular evolution can underlie phenotypical evolution, but the contributions of the evolutionary pathways involved remain little understood. Using mutation libraries in Drosophila melanogaster embryos, this study observed that most point mutations in developmental enhancers led to changes in gene expression levels but rarely resulted in novel expression outside of the native pattern. In contrast, random sequences, often acting as developmental enhancers, drove expression across a range of cell types; random sequences including motifs for transcription factors with pioneer activity acted as enhancers even more frequently. These findings suggest that the phenotypic landscapes of developmental enhancers are constrained by enhancer architecture and chromatin accessibility. It is proposed that the evolution of existing enhancers is limited in its capacity to generate novel phenotypes, whereas the activity of de novo elements is a primary source of phenotypic novelty. |
Friday March 17th - Adult Neural Development and Function |
| Dutta, S. B., Linneweber, G. A., Andriatsilavo, M., Hiesinger, P. R. and Hassan, B. A. (2023). EGFR-dependent suppression of synaptic autophagy is required for neuronal circuit development. Curr Biol. PubMed ID: 36640763
Summary: The development of neuronal connectivity requires stabilization of dynamic axonal branches at sites of synapse formation. Models that explain how axonal branching is coupled to synaptogenesis postulate molecular regulators acting in a spatiotemporally restricted fashion to ensure branching toward future synaptic partners while also stabilizing the emerging synaptic contacts between such partners. This study investigated this question using neuronal circuit development in the Drosophila brain as a model system. Epidermal growth factor receptor (EGFR) activity is required in presynaptic axonal branches during two distinct temporal intervals to regulate circuit wiring in the developing Drosophila visual system. EGFR is required early to regulate primary axonal branching. EGFR activity is then independently required at a later stage to prevent degradation of the synaptic active zone protein Bruchpilot (Brp). Inactivation of EGFR results in a local increase of autophagy in presynaptic branches and the translocation of active zone proteins into autophagic vesicles. The protection of synaptic material during this later interval of wiring ensures the stabilization of terminal branches, circuit connectivity, and appropriate visual behavior. Phenotypes of EGFR inactivation can be rescued by increasing Brp levels or downregulating autophagy. In summary, this study identified a temporally restricted molecular mechanism required for coupling axonal branching and synaptic stabilization that contributes to the emergence of neuronal wiring specificity. | Giesecke, A., Johnstone, P. S., Lamaze, A., Landskron, J., Atay, E., Chen, K. F., Wolf, E., Top, D. and Stanewsky, R. (2023). A novel period mutation implicating nuclear export in temperature compensation of the Drosophila circadian clock. Curr Biol 33(2): 336-350.e335. PubMed ID: 36584676
Summary: Circadian clocks are self-sustained molecular oscillators controlling daily changes of behavioral activity and physiology. For functional reliability and precision, the frequency of these molecular oscillations must be stable at different environmental temperatures, known as "temperature compensation." Despite being an intrinsic property of all circadian clocks, this phenomenon is not well understood at the molecular level. This study used behavioral and molecular approaches to characterize a novel mutation in the period (per) clock gene of Drosophila melanogaster, which alters a predicted nuclear export signal (NES) of the PER protein and affects temperature compensation. This new perI530A allele leads to progressively longer behavioral periods and clock oscillations with increasing temperature in both clock neurons and peripheral clock cells. While the mutant PERI530A protein shows normal circadian fluctuations and post-translational modifications at cool temperatures, increasing temperatures lead to both severe amplitude dampening and hypophosphorylation of PERI530A. It was further shown that PERI530A displays reduced repressor activity at warmer temperatures, presumably because it cannot inactivate the transcription factor CLOCK (CLK), indicated by temperature-dependent altered CLK post-translational modification in per(I530A) flies. With increasing temperatures, nuclear accumulation of PER(I530A) within clock neurons is increased, suggesting that wild-type PER is exported out of the nucleus at warm temperatures. Downregulating the nuclear export factor CRM1 also leads to temperature-dependent changes of behavioral rhythms, suggesting that the PER NES and the nuclear export of clock proteins play an important role in temperature compensation of the Drosophila circadian clock. |
| Sabandal, P. R., Saldes, E. B. and Han, K. A. (2022). Acetylcholine deficit causes dysfunctional inhibitory control in an aging-dependent manner. Sci Rep 12(1): 20903. PubMed ID: 36463374
Summary: Inhibitory control is a key executive function that limits unnecessary thoughts and actions, enabling an organism to appropriately execute goal-driven behaviors. The efficiency of this inhibitory capacity declines with normal aging or in neurodegenerative dementias similar to memory or other cognitive functions. Acetylcholine signaling is crucial for executive function and also diminishes with aging. Acetylcholine's contribution to the aging- or dementia-related decline in inhibitory control, however, remains elusive. This was addressed in Drosophila using a Go/No-Go task that measures inhibition capacity. This study reports that inhibition capacity declines with aging in wild-type flies, which is mitigated by lessening acetylcholine breakdown and augmented by reducing acetylcholine biosynthesis. The mushroom body (MB) γ neurons were identified as a chief neural site for acetylcholine's contribution to the aging-associated inhibitory control deficit. In addition, it was found that the MB output neurons MBON-γ2α'1 having dendrites at the MB γ2 and α'1 lobes and axons projecting to the superior medial protocerebrum and the crepine is critical for sustained movement suppression per se. This study reveals, for the first time, the central role of acetylcholine in the aging-associated loss of inhibitory control and provides a framework for further mechanistic studies. | Dombrovski, M., Peek, M. Y., Park, J. Y., Vaccari, A., Sumathipala, M., Morrow, C., Breads, P., Zhao, A., Kurmangaliyev, Y. Z., Sanfilippo, P., Rehan, A., Polsky, J., Alghailani, S., Tenshaw, E., Namiki, S., Zipursky, S. L. and Card, G. M. (2023). Synaptic gradients transform object location to action. Nature 613(7944): 534-542. PubMed ID: 36599984
Summary: To survive, animals must convert sensory information into appropriate behaviours. Vision is a common sense for locating ethologically relevant stimuli and guiding motor responses. How circuitry converts object location in retinal coordinates to movement direction in body coordinates remains largely unknown. This study shows through behaviour, physiology, anatomy and connectomics in Drosophila that visuomotor transformation occurs by conversion of topographic maps formed by the dendrites of feature-detecting visual projection neurons (VPNs) into synaptic weight gradients of VPN outputs onto central brain neurons. This gradient motif transforms the anteroposterior location of a visual looming stimulus into the fly's directional escape. Specifically, it was discovered that two neurons postsynaptic to a looming-responsive VPN type promote opposite takeoff directions. Opposite synaptic weight gradients onto these neurons from looming VPNs in different visual field regions convert localized looming threats into correctly oriented escapes. For a second looming-responsive VPN type, graded responses along the dorsoventral axis were demonstrated. This synaptic gradient motif generalizes across all 20 primary VPN cell types and most often arises without VPN axon topography. Synaptic gradients may thus be a general mechanism for conveying spatial features of sensory information into directed motor outputs. |
| Calvin-Cejudo, L., Martin, F., Mendez, L. R., Coya, R., Castaneda-Sampedro, A., Gomez-Diaz, C. and Alcorta, E. (2023). Neuron-glia interaction at the receptor level affects olfactory perception in adult Drosophila. iScience 26(1): 105837. PubMed ID: 36624835
Summary: Some types of glia play an active role in neuronal signaling by modifying their activity although little is known about their role in sensory information signaling at the receptor level. This research reports a functional role for the glia that surround the soma of the olfactory receptor neurons (OSNs) in adult Drosophila. Specific genetic modifications have been targeted to this cell type to obtain live individuals who are tested for olfactory preference and display changes both increasing and reducing sensitivity. A closer look at the antenna by Ca(2+) imaging shows that odor activates the OSNs, which subsequently produce an opposite and smaller effect in the glia that partially counterbalances neuronal activation. Therefore, these glia may play a dual role in preventing excessive activation of the OSNs at high odorant concentrations and tuning the chemosensory window for the individual according to the network structure in the receptor organ. | Clark, J. T., Ganguly, A., Ejercito, J., Luy, M., Dahanukar, A. and Ray, A. (2023). Chemosensory detection of aversive concentrations of ammonia and basic volatile amines in insects. iScience 26(1): 105777. PubMed ID: 36594011
Summary: Basic volatiles like ammonia are found in insect environments, and at high concentrations cause an atypical action potential burst, followed by inhibition in multiple classes of olfactory receptor neurons (ORNs) in Drosophila melanogaster. During the period of inhibition, ORNs are unable to fire action potentials to their ligands but continue to display receptor potentials. An increase in calcium is also observed in antennal cells of Drosophila and Aedes aegypti. In the gustatory system, ammonia inhibits sugar and salt responses in a dose-dependent manner. Other amines show similar effects in both gustatory and olfactory neurons, correlated with basicity. The concentrations that inhibit neurons reduce proboscis extension to sucrose in Drosophila. In Aedes, a brief exposure to volatile ammonia abolishes attraction to human skin odor for several minutes. These findings reveal an effect that prevents detection of attractive ligands in the olfactory and gustatory systems and has potential in insect control. |
Thursday March 16th - Adult Physiology and Metabolism |
| Zhou, X., Gan, G., Sun, Y., Ou, M., Geng, J., Wang, J., Yang, X., Huang, S., Jia, D., Xie, W. and He, H. (2022). GTPase-activating protein TBC1D5 coordinates with retromer to constrain synaptic growth by inhibiting Bone Morphogenetic Protein signaling. J Genet Genomics. PubMed ID: 36473687
Summary: Formation and plasticity of neural circuits rely on precise regulation of synaptic growth. At Drosophila neuromuscular junction (NMJ) Bone Morphogenetic Protein (BMP) signaling is critical for many aspects of synapse formation and function. The evolutionarily-conserved retromer complex and its associated GTPase-activating protein TBC1D5 are critical regulators of membrane trafficking and cellular signaling. However, their functions in regulating the formation of NMJ are less understood. This study reports that TBC1D5 is required for inhibition of synaptic growth, and loss of TBC1D5 leads to abnormal presynaptic terminal development, including excessive satellite boutons and branch formation. Ultrastructure analysis reveals that the size of synaptic vesicles and the density of subsynaptic reticulum are increased in TBC1D5 mutant boutons. Disruption of interactions of TBC1D5 with Rab7 and retromer phenocopies the loss of TBC1D5. Unexpectedly, this study found that TBC1D5 is functionally linked to Rab6, in addition to Rab7, to regulate synaptic growth. Mechanistically, this study showed that loss of TBC1D5 leads to upregulated BMP signaling by increasing the protein level of BMP type II receptor Wit at NMJ. Overall, these data establish that TBC1D5 in coordination with retromer constrains synaptic growth by regulating Rab7 activity, which negatively regulates BMP signaling through inhibiting Wit level. | Aimino, M. A., DePew, A. T., Restrepo, L. and Mosca, T. J. (2023). Synaptic Development in Diverse Olfactory Neuron Classes Uses Distinct Temporal and Activity-Related Programs. J Neurosci 43(1): 28-55. PubMed ID: 36446587
Summary: In order to study synaptic development, this study took advantage of the Drosophila antennal lobe (AL), a model olfactory circuit with remarkable genetic access and synapse-level resolution. Using tissue-specific genetic labeling of active zones, a quantitative analysis was performed of synapse formation in multiple classes of neurons of both sexes throughout development and adulthood. Olfactory receptor neurons (ORNs), projection neurons (PNs), and local interneurons (LNs) were found to each have unique time courses of synaptic development, addition, and refinement, demonstrating that each class follows a distinct developmental program. This raised the possibility that these classes may also have distinct molecular requirements for synapse formation. Neuronal activity was genetically altered in each neuronal subtype, and differing effects on synapse number were observed based on the neuronal class examined. Silencing neuronal activity in ORNs, PNs, and LNs impaired synaptic development but only in ORNs did enhancing neuronal activity influence synapse formation. ORNs and LNs demonstrated similar impairment of synaptic development with enhanced activity of a master kinase, GSK-3β, suggesting that neuronal activity and GSK-3β kinase activity function in a common pathway. ORNs also, however, demonstrated impaired synaptic development with GSK-3β loss-of-function, suggesting additional activity-independent roles in development. Ultimately, these results suggest that the requirements for synaptic development are not uniform across all neuronal classes with considerable diversity existing in both their developmental time frames and molecular requirements. These findings provide novel insights into the mechanisms of synaptic development and lay the foundation for future work determining their underlying etiologies. |
| Araujo, M., Tavares, A., Vieira, D. V., Telley, I. A. and Oliveira, R. A. (2023). Endoplasmic reticulum membranes are continuously required to maintain mitotic spindle size and forces. Life Sci Alliance 6(1). PubMed ID: 36379670
Summary: Membrane organelle function, localization, and proper partitioning upon cell division depend on interactions with the cytoskeleton. Whether membrane organelles also impact the function of cytoskeletal elements remains less clear. This study shows that acute disruption of the ER around spindle poles affects mitotic spindle size and function in Drosophila syncytial embryos. Acute ER disruption was achieved through the inhibition of ER membrane fusion by the dominant-negative cytoplasmic domain of atlastin. When centrosome-proximal ER membranes are disrupted, specifically at metaphase, mitotic spindles become smaller, despite no significant changes in microtubule dynamics. These smaller spindles are still able to mediate sister chromatid separation, yet with decreased velocity. Furthermore, by inducing mitotic exit, this study found that nuclear separation and distribution are affected by ER disruption. These results suggest that ER integrity around spindle poles is crucial for the maintenance of mitotic spindle shape and pulling forces. In addition, ER integrity also ensures nuclear spacing during syncytial divisions. | Functions of neuronal Synaptobrevin in the post-Golgi transport of Rhodopsin in Drosophila photoreceptors. Yamashita, H., Ochi, Y., Yamada, Y., Sasaki, S., Tago, T., Satoh, T. and Satoh, A. K. (2022). J Cell Sci 135(24). PubMed ID: 36444566
Summary: Polarized transport is essential for constructing multiple plasma membrane domains in the cell. Drosophila photoreceptors are an excellent model system to study the mechanisms of polarized transport. Rab11 is the key factor regulating the post-Golgi transport of rhodopsin 1 (Rh1; also known as NinaE), a photoreceptive protein, to the rhabdomere, a photoreceptive plasma membrane. This study found that neuronal Synaptobrevin (nSyb) colocalizes with Rab11 on the trans-side of Golgi stacks and post-Golgi vesicles at the rhabdomere base, and nSyb deficiency impairs rhabdomeric transport and induces accumulation of Rh1 and vesicles in the cytoplasm; this is similar to the effects of Rab11 loss. These results indicate that nSyb acts as a post-Golgi SNARE toward rhabdomeres. Surprisingly, in Rab11-, Rip11- and nSyb-deficient photoreceptors, illumination enhances cytoplasmic accumulation of Rh1, which colocalizes with Rab11, Rabenosyn5, nSyb and Arrestin 1 (Arr1). Arr1 loss, but not Rab5 dominant negative (Rab5DN) protein expression, inhibits the light-enhanced cytoplasmic Rh1 accumulation. Rab5DN inhibits the generation of Rh1-containing multivesicular bodies rather than Rh1 internalization. Overall, these results indicate that exocytic Rh1 mingles with endocytosed Rh1 and is then transported together to rhabdomeres. |
| Boda, A., Varga, L. P., Nagy, A., Szenci, G., Csizmadia, T., Lorincz, P. and Juhasz, G. (2023). Rab26 controls secretory granule maturation and breakdown in Drosophila. Cell Mol Life Sci 80(1): 24. PubMed ID: 36600084
Summary: At the onset of Drosophila metamorphosis, plenty of secretory glue granules are released from salivary gland cells and the glue is deposited on the ventral side of the forming (pre)pupa to attach it to a dry surface. Prior to this, a poorly understood maturation process takes place during which secretory granules gradually grow via homotypic fusions, and their contents are reorganized. This study shows that the small GTPase Rab26 localizes to immature (smaller, non-acidic) glue granules and its presence prevents vesicle acidification. Rab26 mutation accelerates the maturation, acidification and release of these secretory vesicles as well as the lysosomal breakdown (crinophagy) of residual, non-released glue granules. Strikingly, loss of Mon1, an activator of the late endosomal and lysosomal fusion factor Rab7, results in Rab26 remaining associated even with the large glue granules and a concomitant defect in glue release, similar to the effects of Rab26 overexpression. These data thus identify Rab26 as a key regulator of secretory vesicle maturation that promotes early steps (vesicle growth) and inhibits later steps (lysosomal transport, acidification, content reorganization, release, and breakdown), which is counteracted by Mon1. | Garrett, E. C., Bielawski, A. M., Ruchti, E., Sherer, L. M., Waghmare, I., Hess-Homeier, D., McCabe, B. D., Stowers, R. S. and Certel, S. J. (2023). The matricellular protein Drosophila CCN is required for synaptic transmission and female fertility. Genetics. PubMed ID: 36602539
Summary: Within the extracellular matrix, matricellular proteins (MCPs) are dynamically expressed non-structural proteins that interact with cell surface receptors, growth factors, and proteases, as well as with structural matrix proteins. The CCN (Cellular Communication Network Factors) family of MCPs serve regulatory roles to regulate cell function and are defined by their conserved multi-modular organization. This study characterize the expression and neuronal requirement for the Drosophila CCN family member. Drosophila CCN (dCCN) is expressed in the nervous system throughout development including in subsets of monoamine-expressing neurons. dCCN-expressing abdominal ganglion neurons innervate the ovaries and uterus and the loss of dCCN results in reduced female fertility. In addition, dCCN accumulates at the synaptic cleft and is required for neurotransmission at the larval neuromuscular junction. Analyzing the function of the single Drosophila CCN family member will enhance the ability to understand how the microenvironment impacts neurotransmitter release in distinct cellular contexts and in response to activity. |
Wednesday March 15th - Adult Physiology and Metabolism |
| Chen, M. Y., Duan, X., Wang, Q., Ran, M. J., Ai, H., Zheng, Y. and Wang, Y. F. (2023). Cytochrome c1-like is required for mitochondrial morphogenesis and individualization during spermatogenesis in Drosophila melanogaster. J Exp Biol 226(3). PubMed ID: 36645102
Summary: The Drosophila testis is an excellent system for studying the process from germ stem cells to motile sperm, including the proliferation of male germ cells, meiosis of primary spermatocytes, mitochondrial morphogenesis, and spermatid individualization. Previous work has demonstrated that ocnus (ocn) plays an essential role in male germ cell development. Among those genes and proteins whose expression levels were changed as a result of ocn knockdown, cytochrome c1-like (cyt-c1L) was downregulated significantly. This study shows that cyt-c1L is highly expressed in the testis of D. melanogaster. Knockdown or mutation of cyt-c1L in early germ cells of flies resulted in male sterility. Immunofluorescence staining showed that cyt-c1L knockdown testes had no defects in early spermatogenesis; however, in late stages, in contrast to many individualization complexes (ICs) composed of F-actin cones that appeared at different positions in control testes, no actin cones or ICs were observed in cyt-c1L knockdown testes. Furthermore, no mature sperm were found in the seminal vesicle of cyt-c1L knockdown testes whereas the control seminal vesicle was full of mature sperm with needle-like nuclei. cyt-c1L knockdown also caused abnormal mitochondrial morphogenesis during spermatid elongation. Excessive apoptotic signals accumulated in the base of cyt-c1L knockdown fly testes. These results suggest that cyt-c1L may play an important role in spermatogenesis by affecting the mitochondrial morphogenesis and individualization of sperm in D. melanogaster. | Fedorova, S., Dorogova, N. V., Karagodin, D. A., Oshchepkov, D. Y., Brusentsov, II, Klimova, N. V. and Baricheva, E. M. (2023). The complex role of transcription factor GAGA in germline death during Drosophila spermatogenesis: transcriptomic and bioinformatic analyses. PeerJ 11: e14063. PubMed ID: 36643636
Summary: The GAGA protein (also known as GAF) is a transcription factor encoded by the Trl gene in D. melanogaster. GAGA is involved in the regulation of transcription of many genes at all stages of fly development and life. Recently, the participation of GAGA in spermatogenesis was studied and it was discovered that Trl mutants experience massive degradation of germline cells in the testes. Trl underexpression induces autophagic death of spermatocytes, thereby leading to reduced testis size. This study aimed to determine the role of the transcription factor GAGA in the regulation of ectopic germline cell death. How Trl underexpression affects gene expression in the testes was examined. 15,993 genes were identified in three biological replicates of an RNA-seq analysis, and transcript levels were compared between hypomorphic Trl (R85)/Trl (362) and Oregon testes. A total of 2,437 differentially expressed genes were found, including 1,686 upregulated and 751 downregulated genes. At the transcriptional level, the development of cellular stress was detected in the Trl-mutant testes: downregulation of the genes normally expressed in the testes (indicating slowed or abrogated spermatocyte differentiation) and increased expression of metabolic and proteolysis-related genes, including stress response long noncoding RNAs. Nonetheless, in the Flybase Gene Ontology lists of genes related to cell death, autophagy, or stress, there was no enrichment with GAGA-binding sites. Furthermore, no specific GAGA-dependent cell death pathway was identified that could regulate spermatocyte death. Thus, these data suggest that GAGA deficiency in male germline cells leads to an imbalance of metabolic processes, impaired mitochondrial function, and cell death due to cellular stress. |
| Dou, W., Sun, B., Miao, Y., Huang, D. and Xiao, J. (2023). Single-cell transcriptome sequencing reveals Wolbachia-mediated modification in early stages of Drosophila spermatogenesis. Proc Biol Sci 290(1990): 20221963. PubMed ID: 36629101
Summary: Wolbachia are the most widely distributed intracellular bacteria, and their most common effect on host phenotype is cytoplasmic incompatibility (CI). A variety of models have been proposed to decipher the molecular mechanism of CI, among which the host modification (HM) model predicts that Wolbachia effectors play an important role in sperm modification. However, owing to the complexity of spermatogenesis and testicular cell-type heterogeneity, whether Wolbachia have different effects on cells at different stages of spermatogenesis or whether these effects are linked with CI remains unknown. Therefore, this study used single-cell RNA sequencing to analyse gene expression profiles in adult male Drosophila testes that were infected or uninfected by Wolbachia. Wolbachia was found to be significantly affected the proportion of different types of germ cells and affected multiple metabolic pathways in germ cells. Most importantly, Wolbachia had the greatest impact on germline stem cells, resulting in dysregulated expression of genes related to DNA compaction, and Wolbachia infection also influenced the histone-to-protamine transition in the late stage of sperm development. These results support the HM model and suggest that future studies on Wolbachia-induced CI should focus on cells in the early stages of spermatogenesis. | Beachum, A. N., Hinnant, T. D., Williams, A. E., Powell, A. M. and Ables, E. T. (2023). Beta-importin Tnpo-SR promotes germline stem cell maintenance and oocyte differentiation in female Drosophila. Dev Biol 494: 1-12. PubMed ID: 36450333
Summary: Germ cell development requires interplay between factors that balance cell fate and division. Early in their development, germ cells in many organisms divide mitotically with incomplete cytokinesis. Key regulatory events then lead to the specification of mature gametes, marked by the switch to a meiotic cell cycle program. Though the regulation of germ cell proliferation and meiosis are well understood, how these events are coordinated during development remains incompletely described. Originally characterized in their role as nucleo-cytoplasmic shuttling proteins, β-importins exhibit diverse functions during male and female gametogenesis. This study describes novel, distinct roles for the β-importin, Transportin-Serine/Arginine rich (Tnpo-SR), as a regulator of the mitosis to meiosis transition in the Drosophila ovary. Tnpo-SR was found to be necessary for germline stem cell (GSC) establishment and self-renewal, likely by controlling the response of GSCs to bone morphogenetic proteins. Depletion of Tnpo-SR results in germ cell counting defects and loss of oocyte identity. In the absence of Tnpo-SR, proteins typically suppressed in germ cells when they exit mitosis fail to be down-regulated, and oocyte-specific factors fail to accumulate. Together, these findings provide new insight into the balance between germ cell division and differentiation and identify novel roles for β-importins in germ cell development. |
| Cai, Q., Yan, J., Duan, R., Zhu, Y., Hua, Y., Liao, Y., Li, Q., Li, W. and Ji, S. (2023). E3 ligase Cul2 mediates Drosophila early germ cell differentiation through targeting Bam. Dev Biol 493: 103-108. PubMed ID: 36423673
Summary: Drosophila ovary has been one of the most mature and excellent systems for studying the in vivo regulatory mechanisms of stem cell fate determination. It has been well-known that the bone morphogenetic protein (BMP) signaling released by the niche cells promotes the maintenance of germline stem cells (GSCs) through inhibiting the transcription of the bag-of-marbles (bam) gene, which encodes a key factor for GSC differentiation. However, whether Bam is regulated at the post-translational level remains largely unknown. This study shows that the E3 ligase Cullin-2 (Cul2) is involved in modulating Bam ubiquitination, which occurs probably at multiple lysine residues of Bam's C-terminal region. Genetic evidence further supports the notion that Cul2-mediated Bam ubiquitination and turnover are essential for GSC maintenance and proper germline development. Collectively, these data not only uncover a novel regulatory mechanism by which Bam is controlled at the post-translational level, but also provides new insights into how Cullin family protein determines the differentiation fate of early germ cells. | Gao, J., Gao, Y. and Xiao, G. (2023). The expression of Catsup in escort cells affects Drosophila ovarian stem cell niche establishment and germline stem cells self-renewal via Notch signaling. Biochem Biophys Res Commun 641: 1-9. PubMed ID: 36516479
Summary: Stem cell niche provides extrinsic signals to maintain stem cell renewal or initiate cell differentiation. Drosophila ovarian stem cell niche is composed of somatic terminal filament cells, cap cells and escort cells. However, the underlying mechanism for the development of stem cell niche remains largely unclear. This study found that the expression of a zinc transporter Catsup is essential for ovary morphogenesis. Catsup knockdown in escort cells results in defects of niche establishment and germline stem cells self-renewal. These defects could be modified by altered expression of genes involved in zinc metabolism or intervention of dietary zinc levels. Further studies indicated that Catsup RNAi affected adult ovary morphogenesis by suppressing Notch signaling. Lastly, this study demonstrated that the defects of Catsup RNAi could be restored by overexpression of heat shock cognate protein 70 (Hsc70). These findings expand understanding of the mechanisms controlling adult oogenesis and niche establishment in Drosophila. |
Tuesday March 14th - Adult Physiology and Metabolism |
| Chakraborty, A., Walter, G. M., Monro, K., Alves, A. N., Mirth, C. K. and Sgro, C. M. (2023). Within-population variation in body size plasticity in response to combined nutritional and thermal stress is partially independent from variation in development time. J Evol Biol 36(1): 264-279. PubMed ID: 36208146
Summary: Ongoing climate change has forced animals to face changing thermal and nutritional environments. Animals can adjust to such combinations of stressors via plasticity. Body size is a key trait influencing organismal fitness, and plasticity in this trait in response to nutritional and thermal conditions varies among genetically diverse, locally adapted populations. The standing genetic variation within a population can also influence the extent of body size plasticity. This study generated near-isogenic lines from a newly collected population of Drosophila melanogaster at the mid-point of east coast Australia and assayed body size for all lines in combinations of thermal and nutritional stress. Isogenic lines showed distinct underlying patterns of body size plasticity in response to temperature and nutrition that were often different from the overall population response. Whether plasticity in development time could explain, and therefore regulate, variation in body size to these combinations of environmental conditions was tested. Five genotypes that showed the greatest variation in response to combined thermal and nutritional stress were selected, and the correlation between response of developmental time and body size was assessed. While significant genetic variation was found in development time plasticity, it was a poor predictor of body size among genotypes. The results therefore suggest that multiple developmental pathways could generate genetic variation in body size plasticity. This study emphasizes the need to better understand genetic variation in plasticity within a population, which will help determine the potential for populations to adapt to ongoing environmental change. | De Lazzari, F., Agostini, F., Plotegher, N., Sandre, M., Greggio, E., Megighian, A., Bubacco, L., Sandrelli, F., Whitworth, A. J. and Bisaglia, M. (2023). DJ-1 promotes energy balance by regulating both mitochondrial and autophagic homeostasis. Neurobiol Dis 176: 105941. PubMed ID: 36473592
Summary: The protein DJ-1 is mutated in rare familial forms of recessive Parkinson's disease and in parkinsonism accompanied by amyotrophic lateral sclerosis symptoms and dementia. DJ-1 is considered a multitasking protein able to confer protection under various conditions of stress. However, the precise cellular function still remains elusive. In the present work, fruit flies lacking the expression of the DJ-1 homolog dj-1β were assessed as compared to control aged-matched individuals. Behavioral evaluations included lifespan, locomotion in an open field arena, sensitivity to oxidative insults, and resistance to starvation. Molecular analyses were carried out by analyzing the mitochondrial morphology and functionality, and the autophagic response. It was demonstrated that dj-1β null mutant flies are hypoactive and display higher sensitivity to oxidative insults and food deprivation. Analysis of mitochondrial homeostasis revealed that loss of dj-1β leads to larger and more circular mitochondria, characterized by impaired complex-I-linked respiration while preserving ATP production capacity. Additionally, dj-1β null mutant flies present an impaired autophagic response, which is suppressed by treatment with the antioxidant molecule N-Acetyl-L-Cysteine. Overall, these data point to a mechanism whereby DJ-1 plays a critical role in the maintenance of energy homeostasis, by sustaining mitochondrial homeostasis and affecting the autophagic flux through the maintenance of the cellular redox state. In light of the involvement of DJ-1 in neurodegenerative diseases and considering that neurons are highly energy-demanding cells, particularly sensitive to redox stress, this study sheds light on a key role of DJ-1 in the maintenance of cellular homeostasis. |
| Carney, T. D., Hebalkar, R. Y., Edeleva, E., Cicek, I. and Shcherbata, H. R. (2023). Signaling through the dystrophin glycoprotein complex affects the stress-dependent transcriptome in Drosophila. Dis Model Mech 16(1). PubMed ID: 36594281
Summary: Deficiencies in the human dystrophin glycoprotein complex (DGC), which links the extracellular matrix with the intracellular cytoskeleton, cause muscular dystrophies, a group of incurable disorders associated with heterogeneous muscle, brain and eye abnormalities. Stresses such as nutrient deprivation and aging cause muscle wasting, which can be exacerbated by reduced levels of the DGC in membranes, the integrity of which is vital for muscle health and function. Moreover, the DGC operates in multiple signaling pathways, demonstrating an important function in gene expression regulation. To advance disease diagnostics and treatment strategies, this study strived to understand the genetic pathways that are perturbed by DGC mutations. A Drosophila model was used to investigate the transcriptomic changes in mutants of four DGC components under temperature and metabolic stress. DGC-dependent genes, stress-dependent genes and genes dependent on the DGC for a proper stress response were identified, confirming a novel function of the DGC in stress-response signaling. This perspective yields new insights into the etiology of muscular dystrophy symptoms, possible treatment directions and a better understanding of DGC signaling and regulation under normal and stress conditions. | Cao, Y., He, S., Ding, M., Gu, W., Wang, T., Zhang, S., Feng, J., Li, Q. and Zheng, L. (2023). Regular Exercise in Drosophila Prevents Age-Related Cardiac Dysfunction Caused by High Fat and Heart-Specific Knockdown of skd. Int J Mol Sci 24(2). PubMed ID: 36674733
Summary: Skuld (skd) is a subunit of the Mediator complex subunit complex. In the heart, skd controls systemic obesity, is involved in systemic energy metabolism, and is closely linked to cardiac function and aging. However, it is unclear whether the effect of cardiac skd on cardiac energy metabolism affects cardiac function. This study found that cardiac-specific knockdown of skd showed impaired cardiac function, metabolic impairment, and premature aging. Drosophila was subjected to an exercise and high-fat diet (HFD) intervention to explore the effects of exercise on cardiac skd expression and cardiac function in HFD Drosophila. Hand-Gal(4)>skd RNAi (KC) Drosophila had impaired cardiac function, metabolic impairment, and premature aging. Regular exercise significantly improved cardiac function and metabolism and delayed aging in HFD KC Drosophila. Thus, this study found that the effect of skd on cardiac energy metabolism in the heart affected cardiac function. Exercise may counteract age-related cardiac dysfunction and metabolic disturbances caused by HFD and heart-specific knockdown of skd. Skd may be a potential therapeutic target for heart disease. |
| Delbare, S. Y. N., Venkatraman, S., Scuderi, K., Wells, M. T., Wolfner, M. F., Basu, S. and Clark, A. G. (2023). Time series transcriptome analysis implicates the circadian clock in the Drosophila melanogaster female's response to sex peptide. Proc Natl Acad Sci U S A 120(5): e2214883120. PubMed ID: 36706221
Summary: Sex peptide (SP), a seminal fluid protein of Drosophila melanogaster males, has been described as driving a virgin-to-mated switch in females, through eliciting an array of responses including increased egg laying, activity, and food intake and a decreased remating rate. While it is known that SP achieves this, at least in part, by altering neuronal signaling in females, the genetic architecture and temporal dynamics of the female's response to SP remain elusive. This study used a high-resolution time series RNA-sequencing dataset of female heads at 10 time points within the first 24 h after mating to learn about the genetic architecture, at the gene and exon levels, of the female's response to SP. SP was found to be noessential to trigger early aspects of a virgin-to-mated transcriptional switch, which includes changes in a metabolic gene regulatory network. However, SP is needed to maintain and diversify metabolic changes and to trigger changes in a neuronal gene regulatory network. It was further found that SP alters rhythmic gene expression in females and suggests that SP's disruption of the female's circadian rhythm might be key to its widespread effects. | Cormier, R. J., Doiron, J. A., Touaibia, M., Surette, M. E. and Pichaud, N. (2023). Time-dependent metabolome and fatty acid profile changes following a high-fat diet exposure in Drosophila melanogaster. Insect Biochem Mol Biol 152: 103892. PubMed ID: 36493963
Summary: High-fat diets (HFDs) are often used to study metabolic disorders using different animal models. However, the underlying cellular mechanisms pertaining to the concurrent loss of metabolic homeostasis characteristics of these disorders are still unclear mainly because the effects of such diets are also dependent on the time frame of the experiments. This study used the fruit fly, Drosophila melanogaster, to investigate the metabolic dynamic effects following 0, 2, 4, 7 and 9 days of an exposure to a HFD (standard diet supplemented with 20% w/v coconut oil, rich in 12:0 and 14:0) by combining NMR metabolomics and GC-FID fatty acid profiling. The results show that after 2 days, the ingested 12:0 and 14:0 fatty acids are used for both lipogenesis and fatty acid oxidation. After 4 days, metabolites from several different pathways are highly modulated in response to the HFD, and an accumulation of 12:0 is also observed, suggesting that the balance of lipid, amino acid and carbohydrate metabolism is profoundly perturbed at this specific time point. Following a longer exposure to the HFD (and notably after 9 days), an accumulation of many metabolites is observed indicating a clear dysfunction of the metabolic system. Overall, this study highlights the relevance of the Drosophila model to study metabolic disorders and the importance of the duration of the exposure to a HFD to study the dynamics of the fundamental mechanisms that control metabolism following exposure to dietary fats. This knowledge is crucial to understand the development and progression of metabolic diseases. |
Monday March 13th - Behavior |
| Riva, S., Ispizua, J. I., Breide, M. T., Polcownuk, S., Lobera, J. R., Ceriani, M. F., Risau-Gusman, S. and Franco, D. L. (2022). Mating disrupts morning anticipation in Drosophila melanogaster females. PLoS Genet 18(12): e1010258. PubMed ID: 36548223
Summary: After mating, the physiology of Drosophila females undergo several important changes, some of which are reflected in their rest-activity cycles. To explore the hypothesis that mating modifies the temporal organization of locomotor activity patterns, this study recorded fly activity by a video tracking method. Monitoring rest-activity patterns under light/dark (LD) cycles indicated that mated females lose their ability to anticipate the night-day transition, in stark contrast to males and virgins. This postmating response is mediated by the activation of the sex peptide receptor (SPR) mainly on pickpocket (ppk) expressing neurons, since reducing expression of this receptor in these neurons restores the ability to anticipate the LD transition in mated females. Furthermore, evidence is provided of connectivity between ppk+ neurons and the pigment-dispersing factor (PDF)-positive ventral lateral neurons (sLNv), which play a central role in the temporal organization of daily activity. Since PDF has been associated to the generation of the morning activity peak, it is hypothesized that the mating signal could modulate PDF levels. Indeed, it was confirmed that mated females have reduced PDF levels at the dorsal protocerebrum; moreover, SPR downregulation in ppk+ neurons mimics PDF levels observed in males. In sum, these results are consistent with a model whereby mating-triggered signals reach clock neurons in the fly central nervous system to modulate the temporal organization of circadian behavior according to the needs of the new status. | Fanara, J. J., Beti, M. I. L., Gandini, L. and Hasson, E. (2023). Oviposition behaviour in Drosophila melanogaster: Genetic and behavioural decoupling between oviposition acceptance and preference for natural fruits. J Evol Biol 36(1): 251-263. PubMed ID: 36357966
Summary: In phytophagous insects, oviposition behaviour is an important component of habitat selection and, given the multiplicity of genetic and environmental factors affecting its expression, is defined as a complex character resulting from the sum of interdependent traits. Two components of egg-laying behaviour were examined in this study: oviposition acceptance (OA) and oviposition preference (OP) in Drosophila melanogaster using three natural fruits as resources (grape, tomato and orange) by means of no-choice and two-choice experiments, respectively. This experimental design demonstrated that the results obtained in two-choice assays (OP) cannot be accounted for by those resulting from no-choice assays (OA). Since the genomes of all lines used are completely sequenced, a genome-wide association study was performed to identify and characterize the genetic underpinnings of these oviposition behaviour traits. The analyses revealed different candidate genes affecting natural genetic variation of both OA and OP traits. Moreover, the results suggest behavioural and genetic decoupling between OA and OP and that egg-laying behaviour is plastic and context-dependent. Such independence in the genetic architectures of OA and OP variation may influence different aspects of oviposition behaviour, including plasticity, canalization, host shift and maintenance of genetic variability, which contributes to the adoption of adaptive strategies during habitat selection. |
| Lee, H. and Lim, C. (2022). Circadian gating of light-induced arousal in Drosophila sleep. J Neurogenet: 1-11. PubMed ID: 36457164
Summary: Circadian rhythms and sleep homeostasis constitute the two-process model for daily sleep regulation. However, evidence for circadian control of sleep-wake cycles has been relatively short since clock-less animals often show sleep behaviors quantitatively comparable to wild-type. This study examined Drosophila sleep behaviors under different light-dark regimes and demonstrates that circadian clocks gate light-induced arousal. Genetic excitation of tyrosine decarboxylase 2 (TDC2)-expressing neurons suppressed sleep more evidently at night, causing nocturnal activity. The arousal effects were likely mediated in part by glutamate transmission from the octopaminergic neurons and substantially masked by light. Application of T12 cycles (6-h light: 6-h dark) further showed that the light-sensitive effects of TDC2 neurons depended on the time of the day. In particular, light-sensing via visual input pathway led to strong sleep suppression at subjective night, and such an effect disappeared in clock-less mutants. Transgenic mapping revealed that light-induced arousal and free-running behavioral rhythms require distinct groups of circadian pacemaker neurons. These results provide convincing evidence that circadian control of sleep is mediated by the dedicated clock neurons for light-induced arousal. | Raouf Issa, A., J, A. C. M., Padmanabhan, A. and Alonso, C. R. (2022). A novel post-developmental role of the Hox genes underlies normal adult behavior. Proc Natl Acad Sci U S A 119(49): e2209531119. PubMed ID: 36454751
Summary: The molecular mechanisms underlying the stability of mature neurons and neural circuits are poorly understood. This problem was explored and it was discovered that the Hox genes are a component of the genetic program that maintains normal neural function in adult Drosophila. Post-developmental downregulation of the Hox gene Ultrabithorax (Ubx) in adult neurons leads to substantial anomalies in flight. Mapping the cellular basis of these effects reveals that Ubx is required within a subset of dopaminergic neurons, and cell circuitry analyses in combination with optogenetics allow linking of these dopaminergic neurons to flight control. Functional imaging experiments show that Ubx is necessary for normal dopaminergic activity, and neuron-specific RNA-sequencing defines two previously uncharacterized ion channel-encoding genes as potential mediators of Ubx behavioral roles. This study thus reveals a novel role of the Hox system in controlling adult behavior and neural function. Based on the broad evolutionary conservation of the Hox system across distantly related animal phyla, it is predicedt that the Hox genes might play neurophysiological roles in adult forms of other species, including humans. |
| Whitehead, S. C., Leone, S., Lindsay, T., Meiselman, M. R., Cowan, N. J., Dickinson, M. H., Yapici, N., Stern, D. L., Shirangi, T. and Cohen, I. (2022). Neuromuscular embodiment of feedback control elements in Drosophila flight. Sci Adv 8(50): eabo7461. PubMed ID: 36516241
Summary: While insects such as Drosophila are flying, aerodynamic instabilities require that they make millisecond time scale adjustments to their wing motion to stay aloft and on course. These stabilization reflexes can be modeled as a proportional-integral (PI) controller; however, it is unclear how such control might be instantiated in insects at the level of muscles and neurons. This study shows that the b1 and b2 motor units-prominent components of the fly's steering muscle system-modulate specific elements of the PI controller: the angular displacement (integral) and angular velocity (proportional), respectively. Moreover, these effects are observed only during the stabilization of pitch. These results provide evidence for an organizational principle in which each muscle contributes to a specific functional role in flight control, a finding that highlights the power of using top-down behavioral modeling to guide bottom-up cellular manipulation studies. | Wosniack, M. E., Festa, D., Hu, N., Gjorgjieva, J. and Berni, J. (2022). Adaptation of Drosophila larva foraging in response to changes in food resources. Elife 11. PubMed ID: 36458693
Summary: All animals face the challenge of finding nutritious resources in a changing environment. To maximize lifetime fitness, the exploratory behavior has to be flexible, but which behavioral elements adapt and what triggers those changes remain elusive. Using experiments and modeling, this study characterized extensively how Drosophila larvae foraging adapts to different food quality and distribution and how the foraging genetic background influences this adaptation. This work shows that different food properties modulated specific motor programs. Food quality controls the traveled distance by modulating crawling speed and frequency of pauses and turns. Food distribution, and in particular the food-no food interface, controls turning behavior, stimulating turns toward the food when reaching the patch border and increasing the proportion of time spent within patches of food. Finally, the polymorphism in the foraging gene (rover-sitter) of the larvae adjusts the magnitude of the behavioral response to different food conditions. This study defines several levels of control of foraging and provides the basis for the systematic identification of the neuronal circuits and mechanisms controlling each behavioral response. |
Friday March 10th - Disease Models |
| Prifti, M. V., Libohova, K., Harris, A. L., Tsou, W. L. and Todi, S. V. (2022). Ubiquitin-binding site 1 of pathogenic ataxin-3 regulates its toxicity in Drosophila models of Spinocerebellar Ataxia Type 3. Front Neurosci 16: 1112688. PubMed ID: 36733922
Summary: Spinocerebellar Ataxia Type 3 (SCA3) is a member of the family of polyglutamine (polyQ) diseases that are caused by anomalous CAG triplet repeat expansions in several genes. SCA3 results from abnormal polyQ expansion in the deubiquitinase (DUB), ataxin-3 (Atxn3). To understand the role of the different domains of mutant Atxn3 on its pathogenicity, with the hope that they can be explored for therapeutic interventions, their individual and collective effects on its toxicity was systematically studied. One such domain is ubiquitin-binding site 1 (UbS1) on the catalytic domain of Atxn3; UbS1 is necessary for the enzymatic activity of Atxn3. This study investigated the importance of UbS1 on the toxicity of pathogenic Atxn3 was investigated. Transgenic Drosophila melanogaster lines that express polyQ-expanded Atxn3 were investigated with and without a functional UbS1. Mutating UbS1 markedly exacerbates the toxicity of pathogenic Atxn3. Additional studies indicated that UbS1 regulates the toxicity of Atxn3 not by affecting its aggregation or sub-cellular localization, but by impacting its role in ubiquitin processing. These findings provide additional insights into the role of Atxn3's domains in the pathogenicity of SCA3. | Huang, S., Piao, C., Beuschel, C. B., Zhao, Z. and Sigrist, S. J. (2022). A brain-wide form of presynaptic active zone plasticity orchestrates resilience to brain aging in Drosophila. PLoS Biol 20(12): e3001730. PubMed ID: 36469518
Summary: The brain as a central regulator of stress integration determines what is threatening, stores memories, and regulates physiological adaptations across the aging trajectory. While sleep homeostasis seems to be linked to brain resilience, how age-associated changes intersect to adapt brain resilience to life history remains enigmatic. This study provides evidence that a brain-wide form of presynaptic active zone plasticity ("PreScale"), characterized by increases of active zone scaffold proteins and synaptic vesicle release factors, integrates resilience by coupling sleep, longevity, and memory during early aging of Drosophila. PreScale increased over the brain until mid-age, to then decreased again, and promoted the age-typical adaption of sleep patterns as well as extended longevity, while at the same time it reduced the ability of forming new memories. Genetic induction of PreScale also mimicked early aging-associated adaption of sleep patterns and the neuronal activity/excitability of sleep control neurons. Spermidine supplementation, previously shown to suppress early aging-associated PreScale, also attenuated the age-typical sleep pattern changes. Pharmacological induction of sleep for 2 days in mid-age flies also reset PreScale, restored memory formation, and rejuvenated sleep patterns. The data suggest that early along the aging trajectory, PreScale acts as an acute, brain-wide form of presynaptic plasticity to steer trade-offs between longevity, sleep, and memory formation in a still plastic phase of early brain aging. |
| Munneke, A. S., Chakraborty, T. S., Porter, S. S., Gendron, C. M. and Pletcher, S. D. (2022). The serotonin receptor 5-HT2A modulates lifespan and protein feeding in Drosophila melanogaster. Front Aging 3: 1068455. PubMed ID: 36531741
Summary: The conserved neurotransmitter serotonin has been shown to be an important modulator of lifespan in specific nutritional contexts; however, it remained unclear how serotonin signaling influences lifespan under normal conditions. This study shows that serotonin signaling through the 5-HT2A receptor influences lifespan, behavior, and physiology in Drosophila. Loss of the 5-HT2A receptor extends lifespan and induces a resistance to changes in dietary protein that are normally detrimental to lifespan. 5-HT2A-/- null mutant flies also display decreased protein feeding and protein content in the body. Therefore, serotonin signaling through receptor 5-HT2A is likely recruited to promote motivation for protein intake, and chronic reduction of protein-drive through loss of 5-HT2A signaling leads to a lower protein set-point adaptation, which influences physiology, decreases feeding, and increases lifespan. These findings reveal insights into the mechanisms by which organisms physiologically adapt in response to perceived inability to satisfy demand. | Chen, Y., Liu, T. T., Niu, M., Li, X., Wang, X., Liu, T. and Li, Y. (2023). Epilepsy gene prickle ensures neuropil glial ensheathment through regulating cell adhesion molecules. iScience 26(1): 105731. PubMed ID: 36582832
Summary: Human PRICKLE1 gene has been associated with epilepsy. However, the underlying pathogenetic mechanisms remain elusive. A Drosophila prickle mutant pk IG1-1 exhibiting strong epileptic seizures and, intriguingly, abnormal glial wrapping. pk was found to be required in both neurons and glia, particularly neuropil ensheathing glia (EGN), the fly analog of oligodendrocyte, for protecting the animal from seizures. It was further revealed that Pk directly binds to the membrane skeleton binding protein Ankyrin 2 (Ank2), thereby regulating the cell adhesion molecule Neuroglian (Nrg). Such protein interactions also apply to their human homologues. Moreover, nrg and ank2 mutant flies also display seizure phenotypes, and expression of either Nrg or Ank2 rescues the seizures of pk IG1-1) flies. Therefore, these findings indicate that Prickle ensures neuron-glial interaction within neuropils through regulating cell adhesion between neurons and ensheathing glia. Dysregulation of this process may represent a conserved pathogenic mechanism underlying PRICKLE1-associated epilepsy. |
| Martinez, P., Patel, H., You, Y., Jury, N., Perkins, A., Lee-Gosselin, A., Taylor, X., You, Y., Viana Di Prisco, G., Huang, X., Dutta, S., Wijeratne, A. B., Redding-Ochoa, J., Shahid, S. S., Codocedo, J. F., Min, S., Landreth, G. E., Mosley, A. L., Wu, Y. C., McKinzie, D. L., Rochet, J. C., Zhang, J., Atwood, B. K., Troncoso, J. and Lasagna-Reeves, C. A. (2022). Bassoon contributes to tau-seed propagation and neurotoxicity. Nat Neurosci 25(12): 1597-1607. PubMed ID: 36344699
Summary: Tau aggregation is a defining histopathological feature of Alzheimer's disease and other tauopathies. However, the cellular mechanisms involved in tau propagation remain unclear. In this study an unbiased quantitative proteomic study was performed to identify proteins that specifically interact with this tau seed. Bassoon (BSN), a presynaptic scaffolding protein, was identified as an interactor of the tau seed isolated from a mouse model of tauopathy, and from Alzheimer's disease and progressive supranuclear palsy postmortem samples. BSN was shown to exacerbate tau seeding and toxicity in both mouse and Drosophila models for tauopathy, and that BSN downregulation decreases tau spreading and overall disease pathology, rescuing synaptic and behavioral impairments and reducing brain atrophy. These findings improve the understanding of how tau seeds can be stabilized by interactors such as BSN. Inhibiting tau-seed interactions is a potential new therapeutic approach for neurodegenerative tauopathies. | Ren, M., Yang, Y., Heng, K. H. Y., Ng, L. Y., Chong, C. Y., Ng, Y. T., Gorur-Shandilya, S., Lee, R. M. Q., Lim, K. L., Zhang, J. and Koh, T. W. (2022). MED13 and glycolysis are conserved modifiers of alpha-synuclein-associated neurodegeneration. Cell Rep 41(12): 111852. PubMed ID: 36543134
Summary: alpha-Synuclein (α-syn) is important in synucleinopathies such as Parkinson's disease (PD). While genome-wide association studies (GWASs) of synucleinopathies have identified many risk loci, the underlying genes have not been shown for most loci. Using Drosophila, 3,471 mutant chromosomes were screened for genetic modifiers of α-synuclein and 12 genes were identified. Eleven modifiers have human orthologs associated with diseases, including MED13 and CDC27, which lie within PD GWAS loci. Drosophila Skd/Med13 and glycolytic enzymes are co-upregulated by α-syn-associated neurodegeneration. While elevated α-syn compromises mitochondrial function, co-expressing skd/Med13 RNAi and α-syn synergistically increase the ratio of oxidized-to-reduced glutathione. The resulting neurodegeneration can be suppressed by overexpressing a glycolytic enzyme or treatment with deferoxamine, suggesting that compensatory glycolysis is neuroprotective. In addition, the functional relationship between α-synuclein, MED13, and glycolytic enzymes is conserved between flies and mice. It is proposed that hypoxia-inducible factor and MED13 are part of a druggable pathway for PD. |
Thursday March 9th - Cytoskeleton and Junctions |
| Planelles-Herrero, V. J., Bittleston, A., Seum, C., Gaitan, M. G. and Derivery, E. (2022). Elongator stabilizes microtubules to control central spindle asymmetry and polarized trafficking of cell fate determinants. Nat Cell Biol 24(11): 1606-1616. PubMed ID: 36302967
Summary: Asymmetric cell division gives rise to two daughter cells that inherit different determinants, thereby acquiring different fates. Polarized trafficking of endosomes containing fate determinants recently emerged as an evolutionarily conserved feature of asymmetric cell division to enhance the robustness of asymmetric cell fate determination in flies, fish and mammals. In particular, polarized sorting of signalling endosomes by an asymmetric central spindle contributes to asymmetric cell division in Drosophila melanogaster. However, how central spindle asymmetry arises remains elusive. This study identified a moonlighting function of the Elongator complex-an established protein acetylase and tRNA methylase involved in the fidelity of protein translation-as a key factor for central spindle asymmetry. Elongator controls spindle asymmetry by stabilizing microtubules differentially on the anterior side of the central spindle. Accordingly, lowering the activity of Elongator on the anterior side using nanobodies mistargets endosomes to the wrong cell. Molecularly, Elongator regulates microtubule dynamics independently of its acetylation and methylation enzymatic activities. Instead, Elongator directly binds to microtubules and increases their polymerization speed while decreasing their catastrophe frequency. These data establish a non-canonical role of Elongator at the core of cytoskeleton polarity and asymmetric signalling. | Jakobs, M. A. H., Zemel, A. and Franze, K. (2022). Unrestrained growth of correctly oriented microtubules instructs axonal microtubule orientation. Elife 11. PubMed ID: 36214669
Summary: In many eukaryotic cells, directed molecular transport occurs along microtubules. Within neuronal axons, transport over vast distances particularly relies on uniformly oriented microtubules, whose plus-ends point towards the distal axon tip (anterogradely polymerizing, or plus-end-out). However, axonal microtubules initially have mixed orientations, and how they orient during development is not yet fully understood. Using live imaging of primary Drosophila melanogaster neurons, this study found that, in the distal part of the axon, catastrophe rates of plus-end-out microtubules were significantly reduced compared to those of minus-end-out microtubules. Physical modelling revealed that plus-end-out microtubules should therefore exhibit persistent long-term growth, while growth of minus-end-out microtubules should be limited, leading to a bias in overall axonal microtubule orientation. Using chemical and physical perturbations of microtubule growth and genetic perturbations of the anti-catastrophe factor p150, which was enriched in the distal axon tip, it was confirmed that the enhanced growth of plus-end-out microtubules is critical for achieving uniform microtubule orientation. Computer simulations of axon development integrating the enhanced plus-end-out microtubule growth identified in this studya with previously suggested mechanisms, that is, dynein-based microtubule sliding and augmin-mediated templating, correctly predicted the long-term evolution of axonal microtubule orientation as found in the experiments. This study thus leads to a holistic explanation of how axonal microtubules orient uniformly, a prerequisite for efficient long-range transport essential for neuronal functioning. |
| Gustafson, H. J., Claussen, N., De Renzis, S. and Streichan, S. J. (2022). Patterned mechanical feedback establishes a global myosin gradient. Nat Commun 13(1): 7050. PubMed ID: 36396633
Summary: Morphogenesis, the coordinated execution of developmental programs that shape embryos, raises many fundamental questions at the interface between physics and biology. In particular, how the dynamics of active cytoskeletal processes are coordinated across the surface of entire embryos to generate global cell flows is poorly understood. Two distinct regulatory principles have been identified: genetic programs and dynamic response to mechanical stimuli. Despite progress, disentangling these two contributions remains challenging. This study combined in toto light sheet microscopy with genetic and optogenetic perturbations of tissue mechanics to examine theoretically predicted dynamic recruitment of non-muscle myosin II to cell junctions during Drosophila embryogenesis. Dynamic recruitment was found to have a long-range impact on global myosin configuration, and the rate of junction deformation sets the rate of myosin recruitment. Mathematical modeling and high frequency analysis reveal myosin fluctuations on junctions around a mean value set by mechanical feedback. The model accounts for the early establishment of the global myosin pattern at 80% fidelity. Taken together these results indicate spatially modulated mechanical feedback as a key regulatory input in the establishment of long-range gradients of cytoskeletal configurations and global tissue flow patterns. | Antel, M., Simao, T., Bener, M. B. and Inaba, M. (2022). Drosophila CG17003/leaky (lky) is required for microtubule acetylation in early germ cells in Drosophila ovary. PLoS One 17(11): e0276704. PubMed ID: 36342916
Summary: Microtubule acetylation is found in populations of stable, long-lived microtubules, occurring on the conserved lysine 40 (K40) residue of α-tubulin by α-tubulin acetyltransferases (αTATs). α-tubulin K40 acetylation has been shown to stabilize microtubules via enhancing microtubule resilience against mechanical stress. This study shows that a previously uncharacterized αTAT, Drosophila CG17003/leaky (lky), is required for α-tubulin K40 acetylation in early germ cells in Drosophila ovary. Loss of lky resulted in a progressive egg chamber fusion phenotype accompanied with mislocalization of germline-specific Vasa protein in somatic follicle cells. The same phenotype was observed upon replacement of endogenous α-tubulin84B with non-acetylatable α-tubulin84BK40A, suggesting α-tubulin K40 acetylation is responsible for the phenotype. Chemical disturbance of microtubules by Colcemid treatment resulted in a mislocalization of Vasa in follicle cells within a short period of time (~30 min), suggesting that the observed mislocalization is likely caused by direct leakage of cellular contents between germline and follicle cells. Taken together, this study provides a new function of α-tubulin acetylation in maintaining the cellular identity possibly by preventing the leakage of tissue-specific gene products between juxtaposing distinct cell types. |
| Qi, Y., Liu, H., Zhang, K., Wu, Y., Shen, C. and Lin, X. (2022). Ihog proteins contribute to integrin-mediated focal adhesions. Sci China Life Sci. PubMed ID: 36103028
Summary: Integrin expression forms focal adhesions, but how this process is physiologically regulated is unclear. Ihog proteins are evolutionarily conserved, playing roles in Hedgehog signaling and serving as trans-homophilic adhesion molecules to mediate cell-cell interactions. Whether these proteins are also engaged in other cell adhesion processes remains unknown. This study reports that Drosophila Ihog proteins function in the integrin-mediated adhesions. Removal of Ihog proteins causes blister and spheroidal muscle in wings and embryos, respectively. Ihog proteins interact with integrin via the extracellular portion and that their removal perturbs integrin distribution. Finally, it was shown that Boc, a mammalian Ihog protein, rescues the embryonic defects caused by removing its Drosophila homologs. It is thus proposed that Ihog proteins contribute to integrin-mediated focal adhesions. | Chandran, L., Backer, W., Schleutker, R., Kong, D., Beati, S. A. H., Luschnig, S. and Muller, H. J. (2023). Src42A is required for E-cadherin dynamics at cell junctions during Drosophila axis elongation. Development 150(2). PubMed ID: 36628974
Summary: Src kinases are important regulators of cell adhesion. This study has explored the function of Src42A in junction remodelling during Drosophila gastrulation. Src42A is required for tyrosine phosphorylation at bicellular (bAJ) and tricellular (tAJ) junctions in germband cells, and localizes to hotspots of mechanical tension. The role of Src42A was investigated using maternal RNAi and CRISPR-Cas9-induced germline mosaics. During cell intercalations, Src42A was shown to be required for the contraction of junctions at anterior-posterior cell interfaces. The planar polarity of E-cadherin is compromised and E-cadherin accumulates at tricellular junctions after Src42A knockdown. Furthermore, Src42A was shown to act in concert with Abl kinase, which has also been implicated in cell intercalations. These data suggest that Src42A is involved in two related processes: in addition to establishing tension generated by the planar polarity of MyoII, it may also act as a signalling factor at tAJs to control E-cadherin residence time. |
Wednesday, March 8th - Larval and Adult Physiology and Metabolism |
| Wang, Z., Receveur, J. P., Pu, J., Cong, H., Richards, C., Liang, M. and Chung, H. (2022). Desiccation resistance differences in Drosophila species can be largely explained by variations in cuticular hydrocarbons. Elife 11. PubMed ID: 36473178
Summary: Maintaining water balance is a universal challenge for organisms living in terrestrial environments, especially for insects, which have essential roles in the ecosystem. Although the high surface area to volume ratio in insects makes them vulnerable to water loss, insects have evolved different levels of desiccation resistance to adapt to diverse environments. To withstand desiccation, insects use a lipid layer called cuticular hydrocarbons (CHCs) to reduce water evaporation from the body surface. It has long been hypothesized that the water-proofing capability of this CHC layer, which can confer different levels of desiccation resistance, depends on its chemical composition. However, it is unknown which CHC components are important contributors to desiccation resistance and how these components can determine differences in desiccation resistance. In this study, machine-learning algorithms, correlation analyses, and synthetic CHCs were used to investigate how different CHC components affect desiccation resistance in 50 Drosophila and related species. Desiccation resistance differences across these species were shown to be largely explained by variation in CHC composition. In particular, length variation in a subset of CHCs, the methyl-branched CHCs (mbCHCs), is a key determinant of desiccation resistance. There is also a significant correlation between the evolution of longer mbCHCs and higher desiccation resistance in these species. Given that CHCs are almost ubiquitous in insects, it is suggested that evolutionary changes in insect CHC components can be a general mechanism for the evolution of desiccation resistance and adaptation to diverse and changing environments. | Aboufares El Alaoui, A., Buhl, E., Galizia, S., Hodge, J. J. L., de Vivo, L. and Bellesi, M. (2023). Increased interaction between endoplasmic reticulum and mitochondria following sleep deprivation. BMC Biol 21(1): 1. PubMed ID: 36600217
Summary: Prolonged cellular activity may overload cell function, leading to high rates of protein synthesis and accumulation of misfolded or unassembled proteins, which cause endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR) to re-establish normal protein homeostasis. Previous molecular work has demonstrated that sleep deprivation (SD) leads to ER stress in neurons, with a number of ER-specific proteins being upregulated to maintain optimal cellular proteostasis. This study investigated the transcriptional and ultrastructural ER and mitochondrial modifications induced by sleep loss. Gene expression analysis in mouse forebrains was used to show that SD was associated with significant transcriptional modifications of genes involved in ER stress but also in ER-mitochondria interaction, calcium homeostasis, and mitochondrial respiratory activity. Using electron microscopy, it was also shown that SD was associated with a general increase in the density of ER cisternae in pyramidal neurons of the motor cortex. Moreover, ER cisternae established new contact sites with mitochondria, the so-called mitochondria associated membranes (MAMs), important hubs for molecule shuttling, such as calcium and lipids, and for the modulation of ATP production and redox state. Finally, it was demonstrated that Drosophila male mutant flies (elav > linker), in which the number of MAMs had been genetically increased, showed a reduction in the amount and consolidation of sleep without alterations in the homeostatic sleep response to SD. This study has provided evidence that sleep loss induces ER stress characterized by increased crosstalk between ER and mitochondria. MAMs formation associated with SD could represent a key phenomenon for the modulation of multiple cellular processes that ensure appropriate responses to increased cell metabolism. In addition, MAMs establishment may play a role in the regulation of sleep under baseline conditions. |
| Zeender, V., Sbilordo, S. H., Roy, J. and Lupold, S. (2022). Paternal condition affects offspring reproduction and life history in a sex-specific manner in Drosophila melanogaster. Evolution. PubMed ID: 36626809
Summary: Nongenetic parental effects can contribute to the adaptation of species to changing environments by circumventing some of the limitations of genetic inheritance. A clearer understanding of the influence of nongenetic inheritance and its potentially sex-specific responses in daughters and sons is needed to better predict the evolutionary trajectories of species. However, whereas nongenetic maternal effects have long been recognized and widely studied, comparatively little is known about corresponding paternal effects. This study followed 30 isogenic lines of Drosophila melanogaster across two generations, each reared under two dietary regimes in each generation, and examined how protein restriction during larval development of the fathers affects the fitness and health of their daughters and sons. Then genetic and non-genetic paternal, and direct environmental, effects were quantified across multiple axes of offspring fitness. Daughters and sons responded differently to their father's developmental history. While isolines differed in mean trait values, their specific responses to protein restriction generally varied little. The sex- and trait-specific responses to paternal effects emphasize the complexity of inter-generational parental effects, which raise important questions about their mode of transmission and adaptive value, including the potential for conflict between the sexes. | Barron, A. J., Lesperance, D. N. A., Doucette, J., Calle, S. and Broderick, N. A. (2023). Microbiome derived acidity protects against microbial invasion in Drosophila. bioRxiv. PubMed ID: 36711873
Summary: Microbial invasions underlie host-microbe interactions that result in microbial pathogenesis and probiotic colonization. While these processes are of broad interest, there are still gaps in understanding of the barriers to entry and how some microbes overcome them. This study explored the effects of the microbiome on invasions of foreign microbes in Drosophila melanogaster. Gut microbes Lactiplantibacillus plantarum and Acetobacter tropicalis improve survival during invasion of a lethal gut pathogen and lead to a reduction in microbial burden. Using a novel multi-organism interactions assay, it is reported that L. plantarum inhibits the growth of three invasive Gram-negative bacteria, while A. tropicalis prevents this inhibition. A series of in vitro and in vivo experiments revealed that inhibition by L. plantarum is linked to its ability to acidify both internal and external environments, including culture media, fly food, and the gut itself, while A. tropicalis diminishes the inhibition by quenching acids. It is proposed that acid produced by the microbiome serves as an important gatekeeper to microbial invasions, as only microbes capable of tolerating acidic environments can colonize the host. The methods described in this study will add to the growing breadth of tools to study microbe-microbe interactions in broad contexts. |
| Zhang, R. X., Li, S. S., Li, A. Q., Liu, Z. Y., Neely, G. G. and Wang, Q. P. (2022). dSec16 Acting in Insulin-like Peptide Producing Cells Controls Energy Homeostasis in Drosophila. Life (Basel) 13(1). PubMed ID: 36676030
Summary: Many studies show that genetics play a major contribution to the onset of obesity. Human genome-wide association studies (GWASs) have identified hundreds of genes that are associated with obesity. However, the majority of them have not been functionally validated. SEC16B has been identified in multiple obesity GWASs but its physiological role in energy homeostasis remains unknown. This study used Drosophila to determine the physiological functions of dSec16 in energy metabolism. These results showed that global RNAi of dSec16 increased food intake and triglyceride (TAG) levels. Furthermore, this TAG increase was observed in flies with a specific RNAi of dSec16 in insulin-like peptide producing cells (IPCs) with an alteration of endocrine peptides. Together, this study demonstrates that dSec16 acting in IPCs controls energy balance and advances the molecular understanding of obesity. | Tremblay, S., Zeng, Y., Yue, A., Chabot, K., Mynahan, A., Desrochers, S., Bridges, S. and Ahmad, S. T. (2022). Caffeine Delays Ethanol-Induced Sedation in Drosophila. Biology (Basel) 12(1). PubMed ID: 36671755
Summary: Caffeine and ethanol are among the most widely available and commonly consumed psychoactive substances. Both interact with adenosine receptor-mediated signaling which regulates numerous neurological processes including sleep and waking behaviors. In mammals, caffeine is an adenosine receptor antagonist and thus acts as a stimulant. Conversely, ethanol is a sedative because it promotes GABAergic neurotransmission, inhibits glutamatergic neurotransmission, and increases the amount of adenosine in the brain. Despite seemingly overlapping interactions, not much is known about the effect of caffeine on ethanol-induced sedation in Drosophila. In this study, using Drosophila melanogaster as a model, it was shown that caffeine supplementation in food delays the onset of ethanol-induced sedation in males and females of different strains. The resistance to sedation reverses upon caffeine withdrawal. Heterozygous adenosine receptor mutant flies are resistant to sedation. These findings suggest that caffeine and adenosine receptors modulate the sedative effects of ethanol in Drosophila. |
Tuesday March 7th - Protein expression, evolution, structure, and function |
| Mokashi, S. S., Shankar, V., Johnstun, J. A., Mackay, T. F. C. and Anholt, R. R. H. (2022). Pleiotropic Fitness Effects of a Drosophila Odorant-binding Protein. G3 (Bethesda). PubMed ID: 36454098
Summary: Insect odorant-binding proteins (OBPs) are members of a rapidly evolving multigene family traditionally thought to facilitate chemosensation. However, studies on Drosophila have shown that members of this family have evolved functions beyond chemosensation, as evident from their expression in reproductive tissues and the brain. Previous studies implicated diverse functions of Obp56h, a member of the largest gene cluster of the D. melanogaster Obp repertoire. This study examined the effect of CRISPR/Cas9-mediated deletion of Obp56h on two fitness phenotypes, resistance to starvation stress and heat stress, and on locomotion and sleep phenotypes. Obp56h-/- mutants show a strong sexually dimorphic effect on starvation stress survival, with females being more resistant to starvation stress than the control. In contrast, Obp56h-/- females, but not males, are highly sensitive to heat stress. Both sexes show changes in locomotion and sleep patterns. Transcriptional profiling of RNA from heads of Obp56h-/- flies and the wildtype control reveal differentially expressed genes, including gene products associated with antimicrobial immune responses and members of the Turandot family of stress-induced secreted peptides. In addition, differentially expressed genes of unknown function were identified in both sexes. Genes encoding components of the mitochondrial electron transport chain, cuticular proteins, gene products associated with regulation of feeding behavior (Lst and CCHa2), ribosomal proteins, lncRNAs, snoRNAs, tRNAs, and snRNAs show changes in transcript abundances in Obp56h-/- females. These differentially expressed genes are likely to contribute to Obp56h-mediated effects on the diverse phenotypes that arise upon deletion of this odorant binding protein. | Thakkar, N., Giesecke, A., Bazalova, O., Martinek, J., Smykal, V., Stanewsky, R. and Dolezel, D. (2022). Evolution of casein kinase 1 and functional analysis of new doubletime mutants in Drosophila. Front Physiol 13: 1062632. PubMed ID: 36589447
Summary: Circadian clocks are timing devices that rhythmically adjust organism's behavior, physiology, and metabolism to the 24-h day-night cycle. Eukaryotic circadian clocks rely on several interlocked transcription-translation feedback loops, where protein stability is the key part of the delay between transcription and the appearance of the mature proteins within the feedback loops. In bilaterian animals, including mammals and insects, the circadian clock depends on a homologous set of proteins. Despite mostly conserved clock components among the fruit fly Drosophila and mammals, several lineage-specific differences exist. This study has systematically explored the evolution and sequence variability of insect DBT proteins and their vertebrate homologs casein kinase 1 delta (CKIδ) and epsilon (CKIε), dated the origin and separation of CKIδ from CKIε, and identified at least three additional independent duplications of the CKIδ/ε gene in Petromyzon, Danio, and Xenopus. Conserved regions were identified in DBT specific to Diptera, and a subset of those were functionally tested in D. melanogaster. Replacement of Lysine K224 with acidic residues strongly impacts the free-running period even in heterozygous flies, whereas homozygous mutants are not viable. K224D mutants have a temperature compensation defect with longer free-running periods at higher temperatures, which is exactly the opposite trend of what was reported for corresponding mammalian mutants. All DBTs of dipteran insects contain the NKRQK motif at positions 220-224. The occurrence of this motif perfectly correlates with the presence of BRIDE OF DOUBLETIME, BDBT, in Diptera. BDBT is a non-canonical FK506-binding protein that physically interacts with Drosophila DBT. The phylogeny of FK506-binding proteins suggests that BDBT is either absent or highly modified in non-dipteran insects. In addition to in silico analysis of DBT/CKIδ/ε evolution and diversity, four novel casein kinase 1 genes specific to the Drosophila genus were identified. |
| Sustar, A. E., Strand, L. G., Zimmerman, S. G. and Berg, C. A. (2022). Imaginal disc growth factors are Drosophila Chitinase-like Proteins with roles in morphogenesis and CO2 response. Genetics. PubMed ID: 36576887
Summary: Chitinase-like proteins (CLPs) are members of the family 18 glycosyl hydrolases, which include chitinases and the enzymatically inactive CLPs. A mutation in the enzyme's catalytic site, conserved in vertebrates and invertebrates, allowed CLPs to evolve independently with functions that do not require chitinase activity. CLPs normally function during inflammatory responses, wound healing, and host defense, but when they persist at excessive levels at sites of chronic inflammation and in tissue-remodeling disorders, they correlate positively with disease progression and poor prognosis. Little is known, however, about their physiological function. Drosophila melanogaster has six CLPS, termed Imaginal disc growth factors (Idgfs), encoded by Idgf1, Idgf2, Idgf3, Idgf4, Idgf5, and Idgf6. This study developed tools to facilitate characterization of the physiological roles of the Idgfs by deleting each of the Idgf genes using the CRISPR/Cas9 system and assessing loss-of-function phenotypes. Using null lines, it was shown that loss-of-function for all six Idgf proteins significantly lowers viability and fertility. It was also found that Idgfs play roles in epithelial morphogenesis, maintaining proper epithelial architecture and cell shape, regulating E-cadherin and cortical Actin, and remarkably, protecting these tissues against CO2 exposure. Defining the normal molecular mechanisms of CLPS is key to understanding how deviations tip the balance from a physiological to a pathological state. | Molano-Fernandez, M., Hickson, I. D. and Herranz, H. (2022). Cyclin E overexpression in the Drosophila accessory gland induces tissue dysplasia. Front Cell Dev Biol 10: 992253. PubMed ID: 36704199
Summary: The regulation of the cell division cycle is governed by a complex network of factors that together ensure that growing or proliferating cells maintain a stable genome. Defects in this system can lead to genomic instability that can affect tissue homeostasis and thus compromise human health. Variations in ploidy and cell heterogeneity are observed frequently in human cancers. This study examined the consequences of upregulating the cell cycle regulator Cyclin E in the Drosophila melanogaster male accessory gland. The accessory gland is the functional analog of the human prostate. This organ is composed of a postmitotic epithelium that is emerging as a powerful in vivo system for modelling different aspects of tumor initiation and progression. Cyclin E upregulation in this model was shown to be sufficient to drive tissue dysplasia. Cyclin E overexpression drives endoreplication and affects DNA integrity, which results in heterogeneous nuclear and cellular composition and variable degrees of DNA damage. Evidence is presented showing that, despite the presence of genotoxic stress, those cells are resistant to apoptosis and thus defective cells are not eliminated from the tissue. It was also shown that Cyclin E-expressing cells in the accessory gland display mitochondrial DNA aggregates that colocalize with Cyclin E protein. Together, these findings show that Cyclin E upregulation in postmitotic cells of the accessory gland organ causes cellular defects such as genomic instability and mitochondrial defects, eventually leading to tissue dysplasia. This study highlights novel mechanisms by which Cyclin E might contribute to disease initiation and progression. |
| Yang, S. and Johnson, A. N. (2022). The serine/threonine kinase Back seat driver prevents cell fusion to maintain cell identity. Dev Biol 495: 35-41. PubMed ID: 36528051
Summary: Cell fate specification is essential for every major event of embryogenesis, and subsequent cell maturation ensures individual cell types acquire specialized functions. The mechanisms that regulate cell fate specification have been studied exhaustively, and each technological advance in developmental biology ushers in a new era of studies aimed at uncovering the most fundamental processes by which cells acquire unique identities. What is less appreciated is that mechanisms are in place to ensure cell identity is maintained throughout the life of the organism. The body wall musculature in the Drosophila embryo is a well-established model to study cell fate specification, as each hemisegment in the embryo generates and maintains thirty muscles with distinct identities. Once specified, the thirty body wall muscles fuse with mononucleate muscle precursors that lack a specific identity to form multinucleate striated muscles. Multinucleate body wall muscles do not fuse with each other, which maintains a diversification of muscle cell identities. This study shows the serine/threonine kinase Back seat driver (Bsd) prevents inappropriate muscle fusion to maintain cell identity. Thus, the regulation of cell fusion is one mechanism that maintains cell identity. | Agip, A. A., Chung, I., Sanchez-Martinez, A., Whitworth, A. J. and Hirst, J. (2023). Cryo-EM structures of mitochondrial respiratory complex I from Drosophila melanogaster. Elife 12. PubMed ID: 36622099
Summary: Respiratory complex I powers ATP synthesis by oxidative phosphorylation, exploiting the energy from NADH oxidation by ubiquinone to drive protons across an energy-transducing membrane. Drosophila melanogaster is a candidate model organism for complex I due to its high evolutionary conservation with the mammalian enzyme, well-developed genetic toolkit, and complex physiology for studies in specific cell types and tissues. Complex I was isolated from Drosophila, and its structure was determined, revealing a 43-subunit assembly with high structural homology to its 45-subunit mammalian counterpart, including a hitherto unknown homologue to subunit NDUFA3. The major conformational state of the Drosophila enzyme is the mammalian-type 'ready-to-go' active resting state, with a fully ordered and enclosed ubiquinone-binding site, but a subtly altered global conformation related to changes in subunit ND6. The mammalian-type 'deactive' pronounced resting state is not observed: in two minor states the ubiquinone-binding site is unchanged, but a deactive-type p-bulge is present in ND6-TMH3. This detailed structural knowledge of Drosophila complex I provides a foundation for new approaches to disentangle mechanisms of complex I catalysis and regulation in bioenergetics and physiology. |
Friday March 3rd - Signaling |
| Fulton, T. L., Mirth, C. K. and Piper, M. D. W. (2022). Restricting a single amino acid cross-protects Drosophila melanogaster from nicotine poisoning through mTORC1 and GCN2 signalling. Open Biol 12(12): 220319. PubMed ID: 36514979
Summary: Dietary interventions that restrict protein intake have repeatedly been shown to offer beneficial health outcomes to the consumer. Benefits such as increased stress tolerance can be observed when individual amino acids are restricted, thus mimicking dietary protein restriction. This study sought to further understand the relationship between dietary amino acids and stress tolerance using Drosophila melanogaster. Using a chemically defined medium for Drosophila, this study found that transiently restricting adult flies of a single essential amino acid generally protects against a lethal dose of the naturally occurring insecticide, nicotine. This protection varied with the identity of the focal amino acid and depended on the duration and intensity of its restriction. To understand the molecular basis of these effects, the signalling of two cellular sensors of amino acids, GCN2 and mTORC1 were modified, in combination with amino acid restriction. GCN2 was necessary for diets to protect against nicotine, whereas the suppression of mTORC1 was sufficient to induce nicotine resistance. This finding implies that amino acid restriction acts via amino acid signalling to cross-protect against seemingly unrelated stressors. Altogether, this study offers new insights into the physiological responses to restriction of individual amino acids that confer stress tolerance. | Shapiro-Kulnane, L., Selengut, M. and Salz, H. K. (2022). Safeguarding Drosophila female germ cell identity depends on an H3K9me3 mini domain guided by a ZAD zinc finger protein. PLoS Genet 18(12): e1010568. PubMed ID: 36548300
Summary: H3K9me3-based gene silencing is a conserved strategy for securing cell fate, but the mechanisms controlling lineage-specific installation of this epigenetic mark remain unclear. In Drosophila, H3K9 methylation plays an essential role in securing female germ cell fate by silencing lineage inappropriate phf7 transcription. Thus, phf7 regulation in the female germline provides a powerful system to dissect the molecular mechanism underlying H3K9me3 deposition onto protein coding genes. Genetic studies were used to identify the essential cis-regulatory elements, finding that the sequences required for H3K9me3 deposition are conserved across Drosophila species. Transposable elements are also silenced by an H3K9me3-mediated mechanism. But the finding that phf7 regulation does not require the dedicated piRNA pathway components, piwi, aub, rhino, panx, and nxf2, indicates that the mechanisms of H3K9me3 recruitment are distinct. Lastly, it was discovered that an uncharacterized member of the zinc finger associated domain (ZAD) containing C2H2 zinc finger protein family, IDENTITY CRISIS (IDC; CG4936), is necessary for H3K9me3 deposition onto phf7. Loss of idc in germ cells interferes with phf7 transcriptional regulation and H3K9me3 deposition, resulting in ectopic PHF7 protein expression. IDC's role is likely to be direct, as it localizes to a conserved domain within the phf7 gene. Collectively, these findings support a model in which IDC guides sequence-specific establishment of an H3K9me3 mini domain, thereby preventing accidental female-to-male programming. |
| Serizier, S. B., Peterson, J. S. and McCall, K. (2022). Non-autonomous cell death induced by the Draper phagocytosis receptor requires signaling through the JNK and SRC pathways. J Cell Sci 135(20). PubMed ID: 36177600
Summary: The last step of cell death is cell clearance, a process critical for tissue homeostasis. For efficient cell clearance to occur, phagocytes and dead cells need to reciprocally signal to each other. One important phenomenon that is under-investigated, however, is that phagocytes not only engulf corpses but contribute to cell death progression. The aims of this study were to determine how the phagocytic receptor Draper non-autonomously induces cell death, using the Drosophila ovary as a model system. Draper, expressed in epithelial follicle cells, was shown to require its intracellular signaling domain to kill the adjacent nurse cell population. Kinases Src42A, Shark and JNK (Bsk) were required for Draper-induced nurse cell death. Signs of nurse cell death occurred prior to apparent engulfment and required the caspase Dcp-1, indicating that it uses a similar apoptotic pathway to starvation-induced cell death. These findings indicate that active signaling by Draper is required to kill nurse cells via the caspase Dcp-1, providing novel insights into mechanisms of phagoptosis driven by non-professional phagocytes. | Sokabe, T., Bradshaw, H. B., Tominaga, M., Leishman, E., Chandel, A. and Montell, C. (2022). Endocannabinoids produced in photoreceptor cells in response to light activate Drosophila TRP channels. Sci Signal 15(755): eabl6179. PubMed ID: 36219683
Summary: Drosophila phototransduction is a model for signaling cascades that culminate in the activation of transient receptor potential (TRP) cation channels. TRP and TRPL are the canonical TRP (TRPC) channels that are regulated by light stimulation of rhodopsin and engagement of Gα(q) and phospholipase Cβ. Lipid metabolite(s) generated downstream of PLC are essential for the activation of the TRPC channels in photoreceptor cells. Attempts were made to identify the key lipids produced subsequent to PLC stimulation that contribute to channel activation. Using genetics, lipid analysis, and Ca(2+) imaging, this study found that light increased the amount of an abundant endocannabinoid, 2-linoleoyl glycerol (2-LG), in vivo. The increase in 2-LG amounts depended on the PLC and diacylglycerol lipase encoded by norpA and inaE, respectively. This endocannabinoid facilitated TRPC-dependent Ca(2+) influx in a heterologous expression system and in dissociated ommatidia from compound eyes. Moreover, 2-LG and mechanical stimulation cooperatively activated TRPC channels in ommatidia. It is proposed that 2-LG is a physiologically relevant endocannabinoid that activates TRPC channels in photoreceptor cells. |
| Fernandez Lahore, R. G., Pampaloni, N. P., Peter, E., Heim, M. M., Tillert, L., Vierock, J., Oppermann, J., Walther, J., Schmitz, D., Owald, D., Plested, A. J. R., Rost, B. R. and Hegemann, P. (2022). Calcium-permeable channelrhodopsins for the photocontrol of calcium signalling. Nat Commun 13(1): 7844. PubMed ID: 36543773
Summary: Channelrhodopsins are light-gated ion channels used to control excitability of designated cells in large networks with high spatiotemporal resolution. While ChRs selective for H(+), Na(+), K(+) and anions have been discovered or engineered, Ca(2+)-selective ChRs have not been reported to date. This study analysed ChRs and mutant derivatives with regard to their Ca(2+) permeability and improve their Ca(2+) affinity by targeted mutagenesis at the central selectivity filter. The engineered channels, termed CapChR1 and CapChR2 for calcium-permeable channelrhodopsins, exhibit reduced sodium and proton conductance in connection with strongly improved Ca(2+) permeation at negative voltage and low extracellular Ca(2+) concentrations. In cultured cells and neurons, CapChR2 reliably increases intracellular Ca(2+) concentrations. Moreover, CapChR2 can robustly trigger Ca(2+) signalling in hippocampal neurons. When expressed together with genetically encoded Ca(2+) indicators in Drosophila melanogaster mushroom body output neurons, CapChRs mediate light-evoked Ca(2+) entry in brain explants. | Koca, Y., Vuong, L. T., Singh, J., Giniger, E. and Mlodzik, M. (2022). Notch-dependent Abl signaling regulates cell motility during ommatidial rotation in Drosophila. Cell Rep 41(10): 111788. PubMed ID: 36476875
Summary: A collective cell motility event that occurs during Drosophila eye development, ommatidial rotation (OR), serves as a paradigm for signaling-pathway-regulated directed movement of cell clusters. OR is instructed by the EGFR and Notch pathways and Frizzled/planar cell polarity (Fz/PCP) signaling, all of which are associated with photoreceptor R3 and R4 specification. This study shows that Abl kinase negatively regulates OR through its activity in the R3/R4 pair. Abl is localized to apical junctional regions in R4, but not in R3, during OR, and this apical localization requires Notch signaling. Abl and Notch interact genetically during OR, and Abl co-immunoprecipitates in complexes with Notch in eye discs. Perturbations of Abl interfere with adherens junctional organization of ommatidial preclusters, which mediate the OR process. Together, these data suggest that Abl kinase acts directly downstream of Notch in R4 to fine-tune OR via its effect on adherens junctions. |
Thursday, March 2nd - Gonads |
| Keramidioti, A., Golegou, E., Psarra, E., Paschalidis, N., Kalodimou, K., Yamamoto, S., Delidakis, C., Vakaloglou, K. M. and Zervas, C. G. (2022). Epithelial morphogenesis in the Drosophila egg chamber requires Parvin and ILK. Front Cell Dev Biol 10: 951082. PubMed ID: 36531940
Summary: Integrins are the major family of transmembrane proteins that mediate cell-matrix adhesion and have a critical role in epithelial morphogenesis. Integrin function largely depends on the indirect connection of the integrin cytoplasmic tail to the actin cytoskeleton through an intracellular protein network, the integrin adhesome. What is currently unknown is the role of individual integrin adhesome components in epithelia dynamic reorganization. Drosophila egg chamber consists of the oocyte encircled by a monolayer of somatic follicle epithelial cells that undergo specific cell shape changes. Egg chamber morphogenesis depends on a developmental array of cell-cell and cell-matrix signalling events. Recent elegant work on the role of integrins in the Drosophila egg chamber has indicated their essential role in the early stages of oogenesis when the pre-follicle cells assemble into the follicle epithelium. This study has focused on the functional requirement of two key integrin adhesome components, Parvin and Integrin-Linked Kinase (ILK). Both proteins are expressed in the developing ovary from pupae to the adult stage and display enriched expression in terminal filament and stalk cells, while their genetic removal from early germaria results in severe disruption of the subsequent oogenesis, leading to female sterility. Combining genetic mosaic analysis of available null alleles for both Parvin and Ilk with conditional rescue utilizing the UAS/Gal4 system, this study found that Parvin and ILK are required in pre-follicle cells for germline cyst encapsulation and stalk cell morphogenesis. Collectively, this study has uncovered novel developmental functions for both Parvin and ILK, which closely synergize with integrins in epithelia. | Misra, S., Buehner, N. A., Singh, A. and Wolfner, M. F. (2022). Female factors modulate Sex Peptide's association with sperm in Drosophila melanogaster. BMC Biol 20(1): 279. PubMed ID: 36514080
Summary: Male-derived seminal fluid proteins (SFPs) that enter female fruitflies during mating induce a myriad of physiological and behavioral changes, optimizing fertility of the mating pair. Some post-mating changes in female Drosophila melanogaster persist for ~10-14 days. Their long-term persistence is because the seminal protein that induces these particular changes, the Sex Peptide (SP), is retained long term in females by binding to sperm, with gradual release of its active domain from sperm. Several other "long-term response SFPs" (LTR-SFPs) "prime" the binding of SP to sperm. Whether female factors play a role in this process is unknown, though it is important to study both sexes for a comprehensive physiological understanding of SFP/sperm interactions and for consideration in models of sexual conflict. This study reports that sperm in male ejaculates bind SP more weakly than sperm that have entered females. Moreover, it was shown that the amount of SP, and other SFPs, bound to sperm increases with time and transit of individual seminal proteins within the female reproductive tract (FRT). Thus, female contributions are needed for maximal and appropriate binding of SP, and other SFPs, to sperm. Towards understanding the source of female molecular contributions spermathecal secretory cells (SSCs) and/or parovaria (female accessory glands), which contribute secretory proteins to the FRT, were ablated. No dramatic change was found in the initial levels of SP bound to sperm stored in mated females with ablated or defective SSCs and/or parovaria, indicating that female molecules that facilitate the binding of SP to sperm are not uniquely derived from SSCs and parovaria. However, higher levels of SP (and sperm) retention long term in females whose SSCs and parovaria had been ablated, indicating secretions from these female tissues are necessary for the gradual release of Sex Peptide's active region from stored sperm. This study reveals that the SP-sperm binding pathway is not entirely male-derived and that female contributions are needed to regulate the levels of SP associated with sperm stored in their storage sites. |
| Weichselberger, V., Dondl, P. and Classen, A. K. (2022). Eya-controlled affinity between cell lineages drives tissue self-organization during Drosophila oogenesis. Nat Commun 13(1): 6377. PubMed ID: 36289235
Summary: Cooperative morphogenesis of cell lineages underlies the development of functional units and organs. To study mechanisms driving the coordination of lineages, this study investigated soma-germline interactions during oogenesis. From invertebrates to vertebrates, oocytes develop as part of a germline cyst that consists of the oocyte itself and so-called nurse cells, which feed the oocyte and are eventually removed. The enveloping somatic cells specialize to facilitate either oocyte maturation or nurse cell removal, which makes it essential to establish the right match between germline and somatic cells. This study uncovered that the transcriptional regulator Eya, expressed in the somatic lineage, controls bilateral cell-cell affinity between germline and somatic cells in Drosophila oogenesis. Employing functional studies and mathematical modelling, this study shows that differential affinity and the resulting forces drive somatic cell redistribution over the germline surface and control oocyte growth to match oocyte and nurse cells with their respective somatic cells. Thus, these data demonstrate that differential affinity between cell lineages is sufficient to drive the complex assembly of inter-lineage functional units and underlies tissue self-organization during Drosophila oogenesis. | Zhou, S., Li, P., Liu, J., Liao, J., Li, H., Chen, L., Li, Z., Guo, Q., Belguise, K., Yi, B. and Wang, X. (2022). Two Rac1 pools integrate the direction and coordination of collective cell migration. Nat Commun 13(1): 6014. PubMed ID: 36224221
Summary: Integration of collective cell direction and coordination is believed to ensure collective guidance for efficient movement. Previous studies demonstrated that chemokine receptors PVR and EGFR govern a gradient of Rac1 activity essential for collective guidance of Drosophila border cells, whose mechanistic insight is unknown. By monitoring and manipulating subcellular Rac1 activity, this study reveal two switchable Rac1 pools at border cell protrusions and supracellular cables, two important structures responsible for direction and coordination. Rac1 and Rho1 form a positive feedback loop that guides mechanical coupling at cables to achieve migration coordination. Rac1 cooperates with Cdc42 to control protrusion growth for migration direction, as well as to regulate the protrusion-cable exchange, linking direction and coordination. PVR and EGFR guide correct Rac1 activity distribution at protrusions and cables. Therefore, these studies emphasize the existence of a balance between two Rac1 pools, rather than a Rac1 activity gradient, as an integrator for the direction and coordination of collective cell migration. |
| Wang, Q. Q., You, D. D. and Liu, J. L. (2022). Cytoophidia Maintain the Integrity of Drosophila Follicle Epithelium. Int J Mol Sci 23(23). PubMed ID: 36499609
Summary: ">CTP synthase (CTPS) forms a filamentous structure termed the cytoophidium in all three domains of life. The female reproductive system of Drosophila is an excellent model for studying the physiological function of cytoophidia. This study used CTPS(H355A), a point mutation that destroys the cytoophidium-forming ability of CTPS, to explore the in vivo function of cytoophidia. In CTPS(H355A) egg chambers, the ingression and increased heterogeneity of follicle cells was observed. In addition, it was found that the cytoophidium-forming ability of CTPS, rather than the protein level, is the cause of the defects observed in CTPS(H355A) mutants. To sum up, these data indicate that cytoophidia play an important role in maintaining the integrity of follicle epithelium. | Tixtha, E. J., Super, M. K., Titus, M. B., Bono, J. M. and Olesnicky, E. C. (2022). Roles for the RNA-Binding Protein Caper in Reproductive Output in Drosophila melanogaster. J Dev Biol 11(1). PubMed ID: 36648904
Summary: RNA binding proteins (RBPs) play a fundamental role in the post-transcriptional regulation of gene expression within the germline and nervous system. This is underscored by the prevalence of mutations within RBP-encoding genes being implicated in infertility and neurological disease. Previous work described roles for the highly conserved RBP Caper in neurite morphogenesis in the Drosophila larval peripheral system and in locomotor behavior. However, caper function has not been investigated outside the nervous system, although it is widely expressed in many different tissue types during embryogenesis. This study describes novel roles for Caper in fertility and mating behavior.Caper is expressed in ovarian follicles throughout oogenesis but is dispensable for proper patterning of the egg chamber. Additionally, reduced caper function, through either a genetic lesion or RNA interference-mediated knockdown of caper in the female germline, results in females laying significantly fewer eggs than their control counterparts. Moreover, this phenotype is exacerbated with age. caper dysfunction also results in partial embryonic and larval lethality. Given that caper is highly conserved across metazoa, these findings may also be relevant to vertebrates. |
Wednesday, March 1st - RNAs and Transposons |
| Solorzano, J., Carrillo-de Santa Pau, E., Laguna, T. and Busturia, A. (2022). A genome-wide computational approach to define microRNA-Polycomb/trithorax gene regulatory circuits in Drosophila. Dev Biol 495: 63-75. PubMed ID: 36596335
Summary: Characterization of gene regulatory networks is fundamental to understanding homeostatic development. This process can be simplified by analyzing relatively simple genomes such as the genome of Drosophila melanogaster. In this work a computational framework in Drosophila was developed to explore for the presence of gene regulatory circuits between two large groups of transcriptional regulators: the epigenetic group of the Polycomb/trithorax (PcG/trxG) proteins and the microRNAs (miRNAs). This study searched genome-wide for miRNA targets in PcG/trxG transcripts as well as for Polycomb Response Elements (PREs) in miRNA genes. The results show that 10% of the analyzed miRNAs could be controlling PcG/trxG gene expression, while 40% of those miRNAs are putatively controlled by the selected set of PcG/trxG proteins. The integration of these analyses has resulted in the predicted existence of 3 classes of miRNA-PcG/trxG crosstalk interactions that define potential regulatory circuits. In the first class, miRNA-PcG circuits are defined by miRNAs that reciprocally crosstalk with PcG. In the second, miRNA-trxG circuits are defined by miRNAs that reciprocally crosstalk with trxG. In the third class, miRNA-PcG/trxG shared circuits are defined by miRNAs that crosstalk with both PcG and trxG regulators. These putative regulatory circuits may uncover a novel mechanism in Drosophila for the control of PcG/trxG and miRNAs levels of expression. The computational framework developed in this study for Drosophila melanogaster can serve as a model case for similar analyses in other species. Moreover, this work provides, for the first time, a new and useful resource for the Drosophila community to consult prior to experimental studies investigating the epigenetic regulatory networks of miRNA-PcG/trxG mediated gene expression. | Ruggieri, A. A., Livraghi, L., Lewis, J. J., Evans, E., Cicconardi, F., Hebberecht, L., Ortiz-Ruiz, Y., Montgomery, S. H., Ghezzi, A., Rodriguez-Martinez, J. A., Jiggins, C. D., McMillan, W. O., Counterman, B. A., Papa, R. and Van Belleghem, S. M. (2022). A butterfly pan-genome reveals that a large amount of structural variation underlies the evolution of chromatin accessibility. Genome Res 32(10): 1862-1875. PubMed ID: 36109150
Summary: Despite insertions and deletions being the most common structural variants (SVs) found across genomes, not much is known about how much these SVs vary within populations and between closely related species, nor their significance in evolution. To address these questions, this study characterized the evolution of indel SVs using genome assemblies of three closely related Heliconius butterfly species. Over the relatively short evolutionary timescales investigated, up to 18.0% of the genome was composed of indels between two haplotypes of an individual Heliconius charithonia butterfly and up to 62.7% included lineage-specific SVs between the genomes of the most distant species (11 Mya). Lineage-specific sequences were mostly characterized as transposable elements (TEs) inserted at random throughout the genome and their overall distribution was similarly affected by linked selection as single nucleotide substitutions. Using chromatin accessibility profiles (i.e., ATAC-seq) of head tissue in caterpillars to identify sequences with potential cis-regulatory function, this study found that out of the 31,066 identified differences in chromatin accessibility between species, 30.4% were within lineage-specific SVs and 9.4% were characterized as TE insertions. These TE insertions were localized closer to gene transcription start sites than expected at random and were enriched for sites with significant resemblance to several transcription factor binding sites with known function in neuron development in Drosophila 24 TE insertions were identified with head-specific chromatin accessibility. These results show high rates of structural genome evolution that were previously overlooked in comparative genomic studies and suggest a high potential for structural variation to serve as raw material for adaptive evolution. |
| Sami, J. D., Spitale, R. C. and Cleary, M. D. (2022). mRNAs encoding neurodevelopmental regulators have equal N6-methyladenosine stoichiometry in Drosophila neuroblasts and neurons. Neural Dev 17(1): 9. PubMed ID: 36243726
Summary: >N(6)-methyladenosine (m6A) is the most prevalent internal mRNA modification in metazoans and is particularly abundant in the central nervous system. The extent to which m6A is dynamically regulated and whether m6A contributes to cell type-specific mRNA metabolism in the nervous system, however, is largely unknown. To address these knowledge gaps, m6A was mapped and mRNA decay was measured in neural progenitors (neuroblasts) and neurons of the Drosophila melanogaster larval brain. W867 m6A targets were identified; 233 of these are novel and preferentially encode regulators of neuroblast proliferation, cell fate-specification and synaptogenesis. Comparison of the neuroblast and neuron m6A transcriptomes revealed that m6A stoichiometry is largely uniform; no evidence was found of neuroblast-specific or neuron-specific m6A modification. While m6A stoichiometry is constant, m6A targets are significantly less stable in neuroblasts than in neurons, potentially due to m6A-independent stabilization in neurons. In vivo quantitative imaging of m6A target proteins was used in Mettl3 methyltransferase null brains and Ythdf m6A reader overexpressing brains to assay metabolic effects of m6A. Target protein levels decreased in Mettl3 null brains and increased in Ythdf overexpressing brains, supporting a previously proposed model in which m6A enhances translation of target mRNAs. It is concluded that m6A does not directly regulate mRNA stability during Drosophila neurogenesis but is rather deposited on neurodevelopmental transcripts that have intrinsic low stability in order to augment protein output. | Cappucci, U., Casale, A. M., Proietti, M., Marinelli, F., Giuliani, L. and Piacentini, L. (2022). WiFi Related Radiofrequency Electromagnetic Fields Promote Transposable Element Dysregulation and Genomic Instability in Drosophila melanogaster. Cells 11(24). PubMed ID: 36552798
Summary: Exposure to artificial radio frequency electromagnetic fields (RF-EMFs) has greatly increased in recent years, thus promoting a growing scientific and social interest in deepening the biological impact of EMFs on living organisms. The current legislation governing the exposure to RF-EMFs is based exclusively on their thermal effects, without considering the possible non-thermal adverse health effects from long term exposure to EMFs. This study investigated the biological non-thermal effects of low-level indoor exposure to RF-EMFs produced by WiFi wireless technologies, using Drosophila melanogaster as the model system. Flies were exposed to 2.4 GHz radiofrequency in a Transverse Electromagnetic (TEM) cell device to ensure homogenous controlled fields. Signals were continuously monitored during the experiments and regulated at non thermal levels. The results of this study demonstrate that WiFi electromagnetic radiation causes extensive heterochromatin decondensation and thus a general loss of transposable elements epigenetic silencing in both germinal and neural tissues. Moreover, the findings provide evidence that WiFi related radiofrequency electromagnetic fields can induce reactive oxygen species (ROS) accumulation, genomic instability, and behavioural abnormalities. Finally, this study demonstrated that WiFi radiation can synergize with Ras(V12) to drive tumor progression and invasion. All together, these data indicate that radiofrequency radiation emitted from WiFi devices could exert genotoxic effects in Drosophila and set the stage to further explore the biological effects of WiFi electromagnetic radiation on living organisms. |
| Mukherjee, S., Calvi, B. R., Hundley, H. A. and Sokol, N. S. (2022). MicroRNA mediated regulation of the onset of enteroblast differentiation in the Drosophila adult intestine. Cell Rep 41(3): 111495. PubMed ID: 36261011
Summary: Somatic adult stem cell lineages in high-turnover tissues are under tight gene regulatory control. Like its mammalian counterpart, the Drosophila intestine precisely adjusts the rate of stem cell division with the onset of differentiation based on physiological demand. Although Notch signaling is indispensable for these decisions, the regulation of Notch activity that drives the differentiation of stem cell progenies into functional, mature cells is not well understood. This study reports that commitment to the terminally differentiated enterocyte (EC) cell fate is under microRNA control. An intestinally enriched microRNA, miR-956, fine-tunes Notch signaling activity specifically in intermediate, enteroblast (EB) progenitor cells to control EC differentiation. This study further identified insensitive mRNA as a target of miR-956 that regulates EB/EC ratios by repressing Notch activity in EBs. In summary, this study highlights a post-transcriptional gene-regulatory mechanism for controlling differentiation in an adult intestinal stem cell lineage. | Chan, S. N. and Pek, J. W. (2022). Distinct biogenesis pathways may have led to functional divergence of the human and Drosophila Arglu1 sisRNA. EMBO Rep: e54350. PubMed ID: 36533631
Summary: Stable intronic sequence RNAs (sisRNAs) are stable, long noncoding RNAs containing intronic sequences. While sisRNAs have been found across diverse species, their level of conservation remains poorly understood. This study reports that the biogenesis and functions of a sisRNA transcribed from the highly conserved Arglu1 locus are distinct in human and Drosophila melanogaster. The Arglu1 genes in both species show similar exon-intron structures where the intron 2 is orthologous and positionally conserved. In humans, Arglu1 sisRNA retains the entire intron 2 and promotes host gene splicing. Mechanistically, Arglu1 sisRNA represses the splicing-inhibitory activity of ARGLU1 protein by binding to ARGLU1 protein and promoting its localization to nuclear speckles, away from the Arglu1 gene locus. In contrast, Drosophila dArglu1 sisRNA forms via premature cleavage of intron 2 and represses host gene splicing. This repression occurs through a local accumulation of dARGLU1 protein and inhibition of telescripting by U1 snRNPs at the dArglu1 locus. It is proposed that distinct biogenesis of positionally conserved Arglu1 sisRNAs in both species may have led to functional divergence. |
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