InteractiveFly: GeneBrief

WD repeat domain 62: Biological Overview | References

The second most commonly mutated gene in primary (MCPH) patients is wd40-repeat protein 62 (wdr62), but the relative contribution of WDR62 function to the growth of major brain lineages is unknown. This study used Drosophila models to dissect lineage-specific WDR62 function(s). Interestingly, although neural stem cell (neuroblast)-specific depletion of WDR62 significantly decreased neuroblast number, brain size was unchanged. In contrast, glial lineage-specific WDR62 depletion significantly decreased brain volume. Moreover, loss of function in glia not only decreased the glial population but also non-autonomously caused neuroblast loss. It was further demonstrated that WDR62 controls brain growth through lineage-specific interactions with master mitotic signaling kinase, AURKA (Aurora A). Depletion of AURKA in neuroblasts drives brain overgrowth, which was suppressed by WDR62 co-depletion. In contrast, glial-specific depletion of AURKA significantly decreased brain volume, which was further decreased by WDR62 co-depletion. Thus, dissecting relative contributions of MCPH factors to individual neural lineages will be critical for understanding complex diseases such as microcephaly (Lim, 2017).

Genome-wide exome sequencing of microcephaly (MCPH) patients identified wd40-repeat protein 62 (wdr62) as the second most commonly mutated gene. WDR62 is a ubiquitously expressed cytoplasmic protein in interphase and localizes to the spindle pole in mitosis. A feature of many WDR62 MCPH-associated alleles is an inability to localize to the mitotic spindle pole, and wdr62 depletion is also associated with defects in spindle and centrosomal integrity, mitotic delay, and reduced brain growth in rodents. The neural stem cell (NSC) population gives rise to all neuronal cells in the adult brain. NSC behavior is governed by both cell intrinsic factors and extrinsic factors from the supporting stem cell niche, including the glial lineage, which acts non-autonomously to control stem cell renewal and differentiation of daughters (Lim, 2017).

The connection between NSCs and their niche, and the importance of spindle integrity to asymmetric division, has been best defined for Drosophila NSCs/neuroblasts (NB). WDR62 scaffolds kinases that are important mitotic regulators including c-Jun N-terminal kinase (JNK) members of the mitogen-activated protein kinase superfamily and Aurora kinase A (AURKA). In flies, AURKA regulates NB proliferation and is required for the localization of mitotic NB polarity complex protein Bazooka (mammalian Par3) to the apical Par complex (comprising the Par anchor, Inscuteable [Insc] adaptor protein, and Gαi/Pins/Mud complex). This establishes the apical-basal NB axis essential for self-renewal and differentiation. As a consequence, mutant aurka causes NB overproliferation and tissue overgrowth. The WDR62 ortholog in Drosophila (dWDR62) is required for brain growth (Nair, 2016), but whether signaling between WDR62 and AURKA modulates brain development has not been reported (Lim, 2017).

In addition to the NB lineage, Drosophila studies suggest that the glial lineage governs overall brain volume through regulation of cell-cycle re-entry and neuroepithelial expansion of NBs. However, potential contribution(s) of individual brain lineage(s) (NB or glia) to the defective brain growth associated with global depletion of wdr62 or aurka is currently unclear. This study confirmed that WDR62 is required for spindle orientation in NBs (Nair, 2016), however, wdr62 depletion specifically in NBs does not significantly retard brain growth. Rather, control of brain growth predominantly depends upon glial lineage function, as depletion of either aurka or wdr62 specifically in the glial lineage significantly reduces brain volume. Moreover, although wdr62 depletion suppressed brain overgrowth associated with aurka depletion in NBs, wdr62 knockdown specifically in the glial lineage enhanced the small brain phenotype associated with aurka depletion. Collectively, these data suggest that WDR62 function is negatively regulated by AURKA in NBs but positively regulated by AURKA in glia, and thus demonstrates that lineage-specific signaling functions of AURKA-WDR62 in Drosophila orchestrate larval brain growth and development (Lim, 2017).

In the mammalian brain, radial glia behave as NSCs that are supported by outer radial glia through cell-cell contact and secretion of growth factors required for maintenance of a stem cell niche. Another class of glial cells, the microglia population, regulates neural precursor cell numbers to govern final neuronal numbers residing in the cortex. However, whether MCPH genes such as wdr62 are important for glial cell fate is unclear. This study dissected the lineage-specific contribution of WDR62 to brain development and revealed that loss of WDR62 function specifically in the glial, but not the NB lineage, profoundly altered brain growth. Moreover, wdr62 depletion in glia likely impairs brain growth autonomously (i.e., through depletion of glia), and also results in NSC loss, suggesting that a focus on WDR62 function in glia will be integral to elucidating how wdr62 loss of function contributes to MCPH. That depletion of wdr62 in the NB lineage was not associated with reduced brain volume, despite reducing NB number, also provides a likely explanation for the recent observation that NB defects associated with global wdr62 depletion fail to account for reduced brain size (Lim, 2017).

Hypomorphic wdr62 mutant mice have reduced brain size, with associated mitotic defects and an overall decrease in neural progenitor cells. In Drosophila, spindle orientation defects following wdr62 loss of function likely underlie the G2 delay and increased mitotic figures in NBs. This phenotype is also reminiscent of the cleavage plane misorientation observed in NSCs in wdr62-depleted rat brains. In Drosophila NBs, WDR62 regulates the interphase localization of Centrosomin (CNN, mammalian CDK5RAP2) to the apical centrosome, and thus centrosomal maturation and positioning. Interestingly, CNN is also an AURKA target that governs spindle orientation independently from cortical polarity establishment during mitosis. Similar to the phenotype observed for wdr62 depletion in NBs, cnn loss of function is associated with spindle orientation defects and reduced NB number. Thus, it is tempting to speculate that WDR62 and CNN function in the same AURKA-dependent signaling complex during mitosis (Lim, 2017).

Ex vivo studies have demonstrated that AURKA phosphorylation of WDR62 promotes spindle pole localization during mitosis (Lim, 2015, Lim, 2016). Mouse models suggest AURKA and WDR62 interact in vivo to control brain growth (Chen, 2014). Compound heterozygous wdr62+/-;aurka+/- mice have a much smaller body size than single heterozygotes but, although the mitotic index of the cerebral cortex was significantly increased and NSCs were reduced, consistent with a mitotic delay radial glia, potential changes to brain volume were not measured (Chen, 2014). This study, demonstrates that the brain overgrowth associated with aurka depletion specifically in NBs was suppressed by co-depletion of wdr62, bringing brain volume to within the control range. In contrast, the small brain phenotypes, due to glial-specific depletion of either aurka or wdr62, were further reduced by co-knockdown. Thus, in the context of normal brain development, AURKA likely acts to promote WDR62-dependent glial proliferation, but antagonizes WDR62 function in the NB lineage (Lim, 2017).

These findings indicate that WDR62 likely functions in AURKA-mediated regulation of spindle orientation but not in the establishment of cortical polarity. One reason for the differential output of AURKA regulation of WDR62 (between NB and glia) could stem from the symmetrical nature of glial division, where there is no evidence for cortical polarization. In contrast to the in vivo mammalian studies and previous Drosophila studies, which employed global depletion strategies for wdr62, these studies have enabled dissection of the relative contribution of wdr62 loss-of-function from each of the major brain lineages. In particular, the observation that depletion in either the NB or glial lineage is associated with reduced cell number, but an overall reduction in brain size was only observed when wdr62 was reduced in glia, places great interest in examining the relative contribution of glial-specific depletion of wdr62 in mice to brain size. Moreover, future studies of the pathogenic wdr62 mutations, and identified AURKA phosphorylation sites on WDR62, in the glial lineage are likely to inform on the contribution of this lineage to impaired brain growth in microcephaly (Lim, 2017).

Micro-computed tomography as a platform for exploring Drosophila development

Understanding how events at the molecular and cellular scales contribute to tissue form and function is key to uncovering mechanisms driving animal development, physiology, and disease. Elucidating these mechanisms has been enhanced through the study of model organisms and use of sophisticated genetic, biochemical, and imaging tools. This paper presents an accessible method for non-invasive imaging of Drosophila melanogaster at high resolution using micro-computed tomography (micro-CT). Rapid processing of intact animals at any developmental stage, provides precise quantitative assessment of tissue size and morphology, and permits analysis of inter-organ relationships. Micro-CT imaging was used to study growth defects in the Drosophila brain through the characterization of Abnormal spindle (asp) and WD Repeat Domain 62 (wdr62), orthologs of the two most commonly mutated genes in human microcephaly patients. This work demonstrates the power of combining micro-CT with traditional genetic, cellular, and developmental biology tools available in model organisms to address novel biological mechanisms that control animal development and disease (Schoborg, 2019).

To demonstrate the utility of μ-CT when combined with the genetic power of Drosophila, the technique to investigate brain defects in two models of human microcephaly, which is characterized by reduced brain size, cognitive function, and lifespan. Previous work has shown that mutations in abnormal spindle (asp), the fly ortholog of abnormal spindle-like microcephaly-associated (ASPM), leads to adult flies displaying a reduction in head and brain size (Schoborg, 2015). This study used μ-CT to explore heterozygous adult control (asp^t25/+) and asp mutant (asp^t25/Df) animals. Morphological examination revealed that optic lobe neuropils (medulla, lobula and lobula plate) in asp mutants were extremely disorganized whereas the central brain neuropils appeared only mildly affected compared with wild-type tissue, a finding supported by confocal imaging (Schoborg, 2019).

μ-CT was used to perform volume analysis on asp^- brains. 3D tomograms revealed a ~12% reduction in entire brain volume in asp^- animals. Further analysis of entire brain sub-regions (optic lobes and central brain) revealed a ~30% reduction in optic lobe size; central brain volume was not affected. Other asp alleles (asp^E3 and asp^L1) showed nearly an identical volume decrease in the optic lobe, but also a significant decrease in the central brain. This discrepancy could be due to either allele-specific effects or genetic background differences between strains, which can influence the phenotype of a given allele. For example, significant differences were observed in entire brain and sub-region (optic lobe and central brain) size when comparing two independent heterozygous control animals, asp^t25/+ and asp^t25/TM6B. These data suggest that the genetic background should be carefully considered for any μ-CT investigation, because it is sensitive enough to detect small differences in volume for structures (e.g. tissues) that are larger than the effective resolution of the technique (10-50 μm) (Schoborg, 2019).

asp has previously been shown to interact genetically with another microcephaly gene, Wdr62, to promote proper brain size in vertebrates (Jayaraman, 2016). The current analysis found no detectable reduction in the central brain or the optic lobes in Wdr62^Δ3-9/Df animals compared with controls (Wdr62^Δ3-9/+), suggesting that the smaller brains reported for larval Wdr62 brains do not lead to microcephaly in adults. However, no genetic interaction was detected between Wdr62 and asp;double mutant (Wdr62^Δ3-9/Df; asp^t25/Df) optic lobes showed a further ~25% reduction in volume compared with controls and also a significant decrease in central brain volume (Schoborg, 2019).

Finally, to understand better the domains of Asp required for its ability to promote brain size, asp mutants expressing various truncated N-terminal constructs tagged with GFP were imaged. This revealed that the first 573 amino acids of Asp were sufficient to rescue both brain morphology and size; this fragment was termed AspMF ('minimal fragment'). Shorter truncations, including AspASH (ASH domain) and AspPhos (predicted CDK1 phosphorylation region), could not rescue optic lobe size even when co-expressed in the same animal (AspASH/AspPhos). To test the necessity of the ASH domain or the phosphorylation region, transgenic animals were generated expressing full-length Asp carrying either a mutation of a highly conserved asparagine residue (AspFL-N57A), or a deletion of the phosphorylation region (AspFLΔPhos). Both failed to restore optic lobe size to the level of the AspFL control, demonstrating that the ASH domain and the phosphorylation region are necessary, but not sufficient, for Asp's function in specifying brain size. Although the precise functions of these two regions remain unknown, an equivalent deletion of the AspMF region in the human ASPM gene has been identified in an individual with MCPH, further highlighting conserved mechanisms of brain development (Schoborg, 2019).

As a final highlight of the capabilities of μ-CT, the asp dataset was used to perform phenotyping analysis to identify additional tissue defects and provide a more complete description of asp function. In addition to the well-characterized small brain phenotype, this analysis revealed severe defects in the visual circuit. The size and morphology of the lamina and the retina were severely compromised, and the ocelli were reduced in size, extremely disorganized or completely absent in asp mutant animals. This suggests that Asp is essential for proper development of the entire visual circuit and that the reduction in head size of asp mutant animals results from multiple tissue defects, rather than just a small brain per se (Schoborg, 2019).

Novel defects were also found in the gut of asp^t25 animals. The cardia, which functions as a sphincter to regulate the passage of food from the foregut to the midgut, was significantly reduced in volume. The epithelium of the midgut was thinner in asp mutants and the morphology of the villi-like structures was also altered. Egg chambers within the ovary were also defective, consisting of only a few early-stage oocytes and likely explaining the sterility defects observed in asp mutant females. These tissue defects are not pleiotropic, as no defects were found in the heart, flight muscles, hindgut or other tissues (Schoborg, 2019).

Together, these data suggest that Asp has tissue-specific functions, and demonstrates how whole-animal phenotyping with μ-CT can direct new investigations at the cellular and molecular level (e.g. the retina or gut) to achieve a complete understanding of gene function (Schoborg, 2019).

Control of intestinal cell fate by dynamic mitotic spindle repositioning influences epithelial homeostasis and longevity

Tissue homeostasis depends on precise yet plastic regulation of stem cell daughter fates. During growth, Drosophila intestinal stem cells (ISCs) adjust fates by switching from asymmetric to symmetric lineages to scale the size of the ISC population. Using a combination of long-term live imaging, lineage tracing, and genetic perturbations, this study demonstrates that this switch is executed through the control of mitotic spindle orientation by Jun-N-terminal kinase (JNK) signaling. JNK interacts with the WD40-repeat protein Wdr62 at the spindle and transcriptionally represses the kinesin Kif1a to promote planar spindle orientation. In stress conditions, this function becomes deleterious, resulting in overabundance of symmetric fates and contributing to the loss of tissue homeostasis in the aging animal. Restoring normal ISC spindle orientation by perturbing the JNK/Wdr62/Kif1a axis is sufficient to improve intestinal physiology and extend lifespan. These findings reveal a critical role for the dynamic control of SC spindle orientation in epithelial maintenance (Hu, 2019).

This study directly demonstrates that cell fate and spindle orientation are tightly linked and identifies a function for JNK signaling in promoting symmetric lineages through the realignment of the mitotic spindle. The data support a model in which the mutual recruitment of phosphorylated JNK (pJNK) and Wdr62 to the spindle, as well as the JNK-dependent transcriptional repression of Kif1a, is required for spindle positioning toward a planar orientation. Because the activation of JNK also prevents cortical localization of Mud, it is proposed that JNK activity disrupts engagement of the spindle with cortical determinants of spindle orientation and limits the force exerted on astral microtubules by repressing Kif1a expression (Hu, 2019).

Live long-term lineage tracing results reveal that planar spindles result in symmetric division outcomes, whereas oblique spindles precede asymmetric outcomes. As such, changes in spindle orientation (after paraquat, short-term refeeding, and age) reflect changes in division modes. Although live imaging is a powerful tool to directly visualize spindle orientation and fate outcomes, the lower resolution compared with fixed imaging could potentially cause a wider error range in spindle angle measurements. Nonetheless, the ability to clearly visualize the vector bisecting the segregation of the two cell bodies during telophase and the vector lining the basal region of neighboring stem cells helps alleviate this issue. Another potential caveat in this analysis is that fates of ISC daughter cells may have been mis-scored because of a delay in Su(H) activation. However, an asymmetric outcome was never observed to derive from planar spindles, and division outcomes were scored as symmetric only if Su(H) activity was not observed at the end of the time-lapse recording, which was ~4 h after Su(H) activation was first observed in divisions with outcomes scored as asymmetric. In paraquat-exposed animals that overexpressed Kif1a in ISCs, Su(H) expression was detected in outcomes scored as asymmetric at roughly the same time frame as in control conditions, suggesting that stress conditions like paraquat exposure do not grossly perturb regulation of Su(H) expression (Hu, 2019).

The spindle angle that separates symmetric and asymmetric divisions is ~15°, and it is unclear whether cell fate specification during divisions with spindle orientation around that angle is deterministic or stochastic. A small subset of spindle orientations above 20° (2 of 22 examples) resulted in 2 YFP+ cells rather than 1 YFP+ cell and 1 YFP+/mCherry+ cell. It is possible that these divisions still result in an asymmetric outcome but may have generated an mCherry- EE cell rather than an mCherry+ EB cell. The rare occurrence of these events is consistent with the smaller population of EEs compared with EB/ECs in the intestine, and spindle orientation during EE fate specification may be important to segregate prospero (Hu, 2019).

Although the results are thus compatible with a deterministic model for cell fate specification, they do not rule out a role for neutral drift. In a neutral drift model, the stem cell pool is maintained by a balance of ISC loss (by generating two differentiated cells) and duplication. It is unknown how regulation of spindle orientation affects neutral drift and whether spindle orientation differs between divisions leading to two ISCs or two EBs. Addressing these issues will be important for comprehensive understanding of cell fate determination in this system (Hu, 2019).

The disparity between spindle behaviors after paraquat treatment and those after Ecc15 infection shows that the nature of the environmental trigger is critical. Although both stresses induce strong proliferative responses, their effects on spindle orientation and the corresponding cell fate outcome are different. Based on the data in this study, this disparity is likely caused by differing levels of JNK activity. JNK is activated by oxidative stress and is thus strongly induced by paraquat exposure. Ecc15 infection, in turn, promotes ISC proliferation by predominantly stimulating JAK/signal transducer and activator of transcription (STAT) activation in ISCs and only transiently activating JNK. JNK was shown to be activated immediately after Ecc15 infection (30 min post-infection), but the genes encoding components of the JNK pathway were no longer upregulated as early as 4 h post-infection. These observations are consistent with analysis 16-20 h post-infection, particularly the absence of phosphorylated JNK at the mitotic spindle in Ecc15-infected animals. However, a possible role of JNK on spindle orientation at earlier time points after infection cannot be ruled out (Hu, 2019).

Previous studies have reported that similar to the current observations with Ecc15, infection of another strain of bacteria, Pseudomonas entomophila, largely promoted asymmetric fate outcomes. However, JNK activity was still detected in the entire gut 2 days post-infection, although the specific cell type (stem cells versus differentiated cells) in which JNK was activated was not examined. The possibility that JNK is activated in ISCs after P. entomophila infection was not ruled out. The difference in pathology of P. entomophila-which is lethal, unlike Ecc15-may contribute to a different response in JNK activation. One hypothesis is that although JNK may be activated after P. entomophila infection in ISCs, it is not recruited to the mitotic spindle and therefore would not affect spindle orientation. Future studies are needed to test this hypothesis and explore possible mechanisms of a pathogen-specific difference (Hu, 2019).

In recruitment to the spindle, pJNK and Wdr62 depend mutually on each other. Although JNK clearly plays a critical role in this process, the data do not rule out a role for other kinases that have been reported to recruit Wdr62 to the centrosome, including Aurora A and Polo-like kinase. Unlike other reports in neural stem cells, this study did not find an obvious role for Wdr62 in maintaining bipolar spindles. Reports have also identified roles for Wdr62 in stabilizing microtubules and centrosomes in interphase neural stem cells, and although the effects of Wdr62 depletion during interphase was not tested in this study, the absence of gross mitotic defects suggests that in Drosophila ISCs, Wdr62 may function selectively in spindle orientation. However, somewhat smaller clone sizes were observed of ISC lineages deficient for Wdr62, and therefore a function for interphase Wdr62 cannot be ruled out. Disruption of Wdr62 activity during interphase may also contribute to the inconsistent effect on lifespan observed after Wdr62 depletion, despite the restoration of oblique spindles in ISCs of old flies (Hu, 2019).

The consequences of the loss of Pins and Mud seem to vary depending on the tissue: disrupting Pins and Mud in Drosophila neuroblasts randomizes the mitotic spindle, but in the mammalian skin, basal stem cells with depleted LGN favor planar spindles, similar to observations in Drosophila ISCs. A loss of cortical Mud was observed after JNK activation, supporting the notion that JNK regulates the interaction between the astral microtubules and the cell cortex to promote planar spindles. The extent to which JNK or Wdr62 interacts directly with Mud is an important question for further study (Hu, 2019).

The mechanism by which Kif1a promotes oblique spindle orientation in ISCs is unclear. Khc-73, a kinesin in the same Kinesin-3 family, is believed to interact with Pins or Disc Large in Drosophila S2 cells and neuroblasts to orient astral microtubules to the cell cortex, and Kif1a may play similar roles in ISCs. Although the data suggest that JNK regulates Kif1a levels transcriptionally, it is possible that JNK also regulates Kif1a at the protein level and may direct its possible interaction with the spindle recruitment machinery (Hu, 2019).

The data reveal how a physiological role for JNK signaling in regulating spindle positioning during periods of tissue resizing becomes hijacked under stress and age, limiting tissue homeostasis and shortening lifespan. It remains unclear how JNK is activated in ISCs during starvation-refeeding, but insulin signaling has been implicated in promoting symmetric outcomes during adaptive resizing of the Drosophila intestine. It will be interesting to test whether insulin signaling and JNK interact to regulate spindle positioning in ISCs, because elevated insulin signaling activity may also contribute to the age-related chronic activation of JNK. The age-related bias toward planar spindle orientations is reminiscent of the changes in spindle orientation of germline stem cells in old male flies, and restoring oblique spindle orientation in aged ISCs by increasing Kif1a expression is sufficient to improve intestinal physiology and extend lifespan. Understanding the exact mechanisms and consequences of ISC spindle positioning will be critical to identifying new intervention strategies to allay age-related dysfunction in barrier epithelia (Hu, 2019).

Such interventions are likely to have significant clinical relevance, because barrier epithelia in mammals regenerate and age through mechanisms that are similar to the Drosophila intestinal epithelium. However, although SC fate determination by changes in spindle orientation is observed in multiple mammalian tissues during development, the extent to which similar mechanisms determine cell fate in adult mammalian tissues is unclear. Mouse ISCs within the adult intestine use different mechanisms to establish cell fate, because spindle orientation is largely planar, and extrinsic cues preferentially differentiate one of the daughter cells. In the mouse trachea, however, it has been reported that spindle orientation fluctuates in basal stem cells in response to injury and may affect cell fate specification. Given the variation in lineage, cell composition, and organization in different adult tissues, it is likely that the importance of spindle orientation in cell specification differs among tissues. Determining the tissues in which spindle orientation is linked with cell fate, and testing whether the role of JNK in the regulation of spindle orientation in these SCs is conserved, will provide important insight into regenerative biology (Hu, 2019).

The microcephaly-associated protein Wdr62/CG7337 is required to maintain centrosome asymmetry in Drosophila neuroblasts

Centrosome asymmetry has been implicated in stem cell fate maintenance in both flies and vertebrates, but the underlying molecular mechanisms are incompletely understood. This paper reports that loss of CG7337, the fly ortholog of WDR62, compromises interphase centrosome asymmetry in fly neural stem cells (neuroblasts). Wdr62 maintains an active interphase microtubule-organizing center (MTOC) by stabilizing microtubules (MTs), which are necessary for sustained recruitment of Polo/Plk1 to the pericentriolar matrix (PCM) and downregulation of Pericentrin-like protein (Plp). The loss of an active MTOC in wdr62 mutants compromises centrosome positioning, spindle orientation, and biased centrosome segregation. wdr62 mutant flies also have an approximately 40% reduction in brain size as a result of cell-cycle delays. It is proposed that CG7337/Wdr62, a microtubule-associated protein, is required for the maintenance of interphase microtubules, thereby regulating centrosomal Polo and Plp levels. Independent of this function, Wdr62 is also required for the timely mitotic entry of neural stem cells (Nair, 2016).

Centrosomes, microtubule (MT)-organizing centers (MTOCs) of metazoan cells, segregate asymmetrically in both fly and vertebrate neural stem cells and have been implicated in stem cell fate maintenance. The building blocks of centrosomes are centrioles, cylindrical MT-based structures ensheathed by pericentriolar matrix (PCM) proteins. Centrosomes are intrinsically asymmetric since centrioles replicate semi-conservatively, generating an older mother centriole and a younger daughter centriole. Centrosome asymmetry is also manifested in the localization of daughter or mother centriole-specific centrosome markers and differential MTOC activity. However, the molecular mechanisms underlying centrosome asymmetry and its function are incompletely understood (Nair, 2016).

An ideal system for studying centrosome asymmetry in vivo are Drosophila neuroblasts, the neural stem cells of the fly. Neuroblasts establish and maintain centrosome asymmetry during interphase. For instance, their centrosomes separate during early interphase into two centrosomes, containing only one centriole each. These centrioles differ in age and molecular composition; the homolog of the human daughter centriole-specific protein Centrobin (Cnb) localizes to the younger daughter centriole but is absent from the older mother centriole. Cnb is phosphorylated by Polo kinase (Plk1 in vertebrates), a requirement to maintain an active MTOC, tethering the daughter centriole-containing centrosome to the apical interphase cortex. The mother centriole downregulates Polo and MTOC activity, mediated by Pericentrin (PCNT)-like protein (PLP) and Bld10 (Cep135 in vertebrates). As a consequence of MTOC downregulation, the mother centriole subsequently moves away from the apical cortex and randomly migrates through the cytoplasm. This centrosome asymmetry is maintained until early prophase, when centrosome maturation starts with the reaccumulation of PCM and the formation of a second MTOC on the basal cortex (Nair, 2016).

Previous work has shown that Bld10/Cep135 is implicated in the establishment of centrosome asymmetry in Drosophila neuroblasts. Mutations in Cep135 have been linked to primary microcephaly, an autosomal recessive neurodevelopmental disorder, manifested in small brains and mental retardation. Several loci (MCPH1-12) have been implicated in primary microcephaly, most of which encode for centrosomal proteins. To test whether a causal relationship between centrosome asymmetry and microcephaly exists, this study examined CG7337, an uncharacterized fly gene corresponding to WD40 repeat protein 62 (WDR62/MCPH2) in vertebrates. Mutations in wdr62 are the second most prevalent cause for microcephaly, but its role in this neurodevelopmental disorder is incompletely understood. WDR62 localizes to the nucleus but also to the spindle poles, and it has been implicated in spindle formation and neuronal progenitor cell (NPC) proliferation. WDR62 is a c-Jun N-terminal kinase (JNK) scaffold protein, reported to regulate rat neurogenesis through JNK1 by controlling symmetric and asymmetric NPC divisions in the rat neocortex. In mice, WDR62 interacts with Aurora A kinase, necessary to regulate spindle formation, mitotic progression, and brain size. However, whether WDR62 is implicated in other important cellular processes is currently unclear (Nair, 2016).

This study reports that CG7337/Wdr62 is required to maintain centrosome asymmetry in Drosophila neuroblasts by directly or indirectly stabilizing the interphase MTs necessary to accumulate and maintain PCM-associated Polo. Failure to maintain centrosome asymmetry in wdr62 mutants perturbs centrosome positioning and segregation as well as spindle orientation. Additionally, and independent of this function, this study found that wdr62 mutant neuroblasts show cell-cycle defects, resulting in a developmental delay and a dramatic reduction in fly brains. It is concluded that Wdr62 controls at least two distinct but important aspects of fly neurogenesis (Nair, 2016).

This study shows that CG7337, the fly ortholog of the microcephaly protein MCPH2/WDR62, is required to maintain centrosome asymmetry in Drosophila neural stem cells. Wdr62 is shown to be a spindle-associated protein, localizing to the active interphase MTOC and subsequently also decorating the entire mitotic spindle. In agreement with this localization, it was demonstrated that Wdr62 is required to directly or indirectly stabilize MTs and to maintain MTOC activity on the apical interphase centrosome. In wdr62 mutants, Polo, Cnn, and γ-Tub are downregulated, causing a loss in apical MTOC activity. These findings are consistent with previous reports, showing that maintenance of apical MTOC activity in interphase neuroblasts depends on the mitotic kinase Polo/Plk1. Polo has been shown to phosphorylate PCM components such as Cnn but also the daughter centriole-specific protein Cnb, which is necessary to maintain MTOC activity. How Polo's localization is controlled is unclear, but in Drosophila neuroblasts, it was reported that Polo levels are partially regulated through Plp. Plp is asymmetrically localized in wild-type neuroblasts, containing higher Plp on the mother centriole-containing basal centrosome. This asymmetric localization could be controlled through a direct molecular interaction between Cnb and Plp, since ectopically localizing Cnb to both centrosomes decreases Plp levels, and the yeast-two hybrid data indicate that Cnb directly interacts with Plp. Cnb localization does not change in wdr62 mutants, but Plp levels increase on the apical centrosome with the consequence that both centrosomes contain similar levels of Plp (Nair, 2016).

Plp and Polo could also be regulated through other mechanisms. For instance, using 3D-SIM, this study discovered that apical interphase neuroblast centrosomes contain a centriolar and a PCM-associated pool of Polo protein. PCM-associated Polo has recently been seen in metaphase centrosomes of Drosophila S2 cells and embryonic interphase centrosomes. wdr62 specifically perturbed the localization of Polo associated with PCM, whereas Cnb is required to maintain both PCM and centriolar Polo (Nair, 2016).

Based on these results and previously published data, the following model is proposed: neuroblasts exit mitosis with a robust array of MTs, which originates from the preceding centrosome maturation cycle. This array is used to increase the amount of Polo protein on the apical Cnb+ centrosome through new recruitment as the neuroblast exits mitosis. Indeed, live imaging and 3D SIM data show that interphase MTs are decorated with Polo and that colcemid treatment decreases PCM Polo levels. Furthermore, Polo levels are usually lowest at metaphase, increase after mitosis, and stay high throughout interphase. Polo recruitment to the centrosome occurs via astral MTs, which is supported by photoconversion experiments. To allow for sustained Polo recruitment, it is proposed that Wdr62 stabilizes interphase MTs, which is consistent with Wdr62's localization, live imaging, and cold assay data. To maintain this cycle, Polo needs to phosphorylate not only PCM proteins (e.g., Cnn) but also Cnb. This is consistent with previous data, showing that increasing levels of Polo on the basal centrosome transforms the basal centrosome into an active MTOC, failing to shed the Polo target Cnn. Furthermore, cnb phosphomutants are unable to rescue cnb's loss-of-function phenotype. The model further proposes that phosphorylated Cnb is necessary to prevent Plp protein levels from increasing on the apical interphase centrosome. Indeed, it was found that Cnb directly interacts with Plp. The basal centrosome, however, also recruits Polo through MTs, but due to the lack of Cnb, Plp is upregulated, inducing the shedding of Polo and PCM and preventing the maintenance of MTs and, thus, the new recruitment of Polo (Nair, 2016).

This model predicts that loss of Wdr62 and depletion of MTs should have the same phenotype. In support of this, it was found that loss of MTs mimics the phenotype of wdr62 mutants; in colcemid-treated neuroblasts, Polo and Cnn are downregulated on the apical centrosome with a concomitant increase in Plp, reaching levels similar to that of the basal centrosome. Furthermore, PCM-associated Polo is lost. Taken together, it is proposed that maintenance of the apical, daughter centriole-containing centrosome's MTOC activity-and, thus, neuroblast centrosome asymmetry-can be established and maintained by balancing Plp-mediated shedding of Polo and MT-dependent Polo recruitment and maintenance. Wdr62 plays a key role in this process by stabilizing MTs (Nair, 2016).

Similar to wdr62, pins mutant neuroblasts also show loss in interphase MTOC activity. However, since Pins does not co-localize with Wdr62 and Cnb during the neuroblast cell cycle, it is currently unclear how this protein affects interphase MTOC activity. Pins could compromise Polo localization in interphase in a Cnb- and Wdr62-independent manner. Alternatively, since Pins has been reported to affect spindle asymmetry, it could also influence centrosome architecture in mitotic neuroblasts, preventing the apical centrosome from maintaining MTOC activity in interphase. Recently, Bld10 was implicated in Polo and PCM shedding, but additional work is needed to fit Bld10 and Pins into the proposed model (Nair, 2016).

MTOC asymmetry is important for proper centrosome positioning and spindle orientation. Whereas wild-type neuroblasts always retain the daughter centriole-containing centrosome, wdr62 mutants show centrosome segregation defects with low frequency. Similarly, spindle orientation defects occur but are corrected in wdr62 mutants, suggesting that backup mechanisms are in place to detect and correct spindle misalignment if centrosome mispositioning occurs. Phenotypic analysis also revealed that Wdr62 is involved in normal brain development, in agreement with previously published vertebrate model systems. Wdr62 mutant brains are ~40% smaller compared to wild-type brains, showing only a minor decrease of neural stem cells. Based on cell-cycle measurements, the simplest interpretation is that cell-cycle delays cause a reduction in brain size. In embryonic neural stem cells, Wdr62 controls mitotic progression through interactions with Aurora A kinase (Chen, 2014), and it is hypothesized that the same mechanism could control neuroblast cell-cycle progression, which is consistent with the aurA mutant neuroblast phenotype. Inactivation of the apical MTOC does not seem to compromise normal brain development, since cnb RNAi-treated animals show normal cell-cycle length and normal brain size. However, the aforementioned backup mechanisms, correcting centrosome mispositioning and spindle misorientation, could prevent more severe developmental perturbations. This hypothesis is consistent with a recent report showing that centrosome cycle misregulation compromises spindle orientation in mouse neural progenitors, biasing the progenitor division mode toward asymmetric divisions (Nair, 2016).

Although this study failed to find a causal relationship between centrosome asymmetry and microcephaly, perturbed centrosome segregation could affect brain development in ways that have escaped attention. For instance, recent reports suggest that biased sister chromatid and midbody segregation could be connected with centrosome asymmetry. Thus, the finding that centrosome positioning and biased centrosome segregation is highly stereotypic would argue for an important function of this process. However, more refined assays will be necessary to determine the consequence of compromised centrosome asymmetry. Taken together, this study discovered that Wdr62 is required to stabilize MTs, ensuring MTOC activity and centrosome asymmetry, a requirement for spindle orientation and biased centrosome segregation (Nair, 2016).

A genetic mosaic screen identifies genes modulating Notch signaling in Drosophila

Notch signaling is conserved in most multicellular organisms and plays critical roles during animal development. The core components and major signal transduction mechanism of Notch signaling have been extensively studied. However, understanding of how Notch signaling activity is regulated in diverse developmental processes still remains incomplete. This study reports a genetic mosaic screen in Drosophila melanogaster that leads to identification of Notch signaling modulators during wing development. A group of genes was discovered required for the formation of the fly wing margin, a developmental process that is strictly dependent on the balanced Notch signaling activity. These genes encode transcription factors, protein phosphatases, vacuolar ATPases and factors required for RNA transport, stability, and translation. These data support the view that Notch signaling is controlled through a wide range of molecular processes. These results also provide foundations for further study by showing that Me31B and Wdr62 function as two novel modulators of Notch signaling activity (Ren, 2018).

Glial-specific functions of microcephaly protein WDR62 and interaction with the mitotic kinase AURKA are essential for Drosophila brain growth

The second most commonly mutated gene in primary microcephaly (MCPH) patients is wd40-repeat protein 62 (wdr62), but the relative contribution of WDR62 function to the growth of major brain lineages is unknown. This study used Drosophila models to dissect lineage-specific WDR62 function(s). Interestingly, although neural stem cell (neuroblast)-specific depletion of WDR62 significantly decreased neuroblast number, brain size was unchanged. In contrast, glial lineage-specific WDR62 depletion significantly decreased brain volume. Moreover, loss of function in glia not only decreased the glial population but also non-autonomously caused neuroblast loss. It was further demonstrated that WDR62 controls brain growth through lineage-specific interactions with master mitotic signaling kinase, AURKA. Depletion of AURKA in neuroblasts drives brain overgrowth, which was suppressed by WDR62 co-depletion. In contrast, glial-specific depletion of AURKA significantly decreased brain volume, which was further decreased by WDR62 co-depletion. Thus, dissecting relative contributions of MCPH factors to individual neural lineages will be critical for understanding complex diseases such as microcephaly (Lim, 2017).

The association of microcephaly protein WDR62 with CPAP/IFT88 is required for cilia formation and neocortical development

WDR62 mutations that result in protein loss, truncation or single amino-acid substitutions are causative for human microcephaly, indicating critical roles in cell expansion required for brain development. WDR62 missense mutations that retain protein expression loss-of-function mutants that may therefore provide specific insights into radial glial cell processes critical for brain growth. This study utilized CRISPR/Cas9 approaches to generate three strains of WDR62 mutant mice; WDR62 V66M/V66M and WDR62R439H/R439H mice recapitulate conserved missense mutations found in humans with microcephaly, with the third strain being a null allele (WDR62stop/stop). Each of these mutations resulted in embryonic lethality to varying degrees and gross morphological defects consistent with ciliopathies (dwarfism, anophthalmia and microcephaly). WDR62 mutant proteins (V66M and R439H) localize to the basal body but fail to recruit CPAP. As a consequence, deficient recruitment was observed of IFT88, a protein that is required for cilia formation. This underpins the maintenance of radial glia as WDR62 mutations caused premature differentiation of radial glia resulting in reduced generation of neurons and cortical thinning. These findings highlight the important role of the primary cilium in neocortical expansion and implicate ciliary dysfunction as underlying the pathology of MCPH2 patients (Shohayeb, 2020).

Microcephaly proteins Wdr62 and Aspm define a mother centriole complex regulating centriole biogenesis, apical complex, and cell fate

Mutations in several genes encoding centrosomal proteins dramatically decrease the size of the human brain. This study shows that Aspm (abnormal spindle-like, microcephaly-associated) and Wdr62 (WD repeat-containing protein 62) interact genetically to control brain size, with mice lacking Wdr62, Aspm, or both showing gene dose-related centriole duplication defects that parallel the severity of the microcephaly and increased ectopic basal progenitors, suggesting premature delamination from the ventricular zone. Wdr62 and Aspm localize to the proximal end of the mother centriole and interact physically, with Wdr62 required for Aspm localization, and both proteins, as well as microcephaly protein Cep63, required to localize CENPJ/CPAP/Sas-4, a final common target. Unexpectedly, Aspm and Wdr62 are required for normal apical complex localization and apical epithelial structure, providing a plausible unifying mechanism for the premature delamination and precocious differentiation of progenitors. Together, these results reveal links among centrioles, apical proteins, and cell fate, and illuminate how alterations in these interactions can dynamically regulate brain size (Jayaraman, 2016).

Aurora A phosphorylation of WD40-repeat protein 62 in mitotic spindle regulation

Mitotic spindle organization is regulated by centrosomal kinases that potentiate recruitment of spindle-associated proteins required for normal mitotic progress including the microcephaly protein WD40-repeat protein 62 (WDR62). WDR62 functions underlie normal brain development as autosomal recessive mutations and wdr62 loss cause microcephaly. This study investigated the signaling interactions between WDR62 and the mitotic kinase Aurora A (AURKA) that has been recently shown to cooperate to control brain size in mice. The spindle recruitment of WDR62 is closely correlated with increased levels of AURKA following mitotic entry. Depletion of TPX2 attenuated WDR62 localization at spindle poles indicating that TPX2 co-activation of AURKA is required to recruit WDR62 to the spindle. AURKA activity contributed to the mitotic phosphorylation of WDR62 residues Ser49 and Thr50 and phosphorylation of WDR62 N-terminal residues was required for spindle organization and metaphase chromosome alignment. This analysis of several MCPH-associated WDR62 mutants (V65M, R438H and V1314RfsX18) that are mislocalized in mitosis revealed that their interactions and phosphorylation by AURKA was substantially reduced consistent with the notion that AURKA is a key determinant of WDR62 spindle recruitment. Thus, this study highlights the role of AURKA signaling in the spatiotemporal control of WDR62 at spindle poles where it maintains spindle organization (Lim, 2016).

Microcephaly disease gene Wdr62 regulates mitotic progression of embryonic neural stem cells and brain size

Human genetic studies have established a link between a class of centrosome proteins and microcephaly. Current studies of microcephaly focus on defective centrosome/spindle orientation. Mutations in WDR62 are associated with microcephaly and other cortical abnormalities in humans. This study created a mouse model of Wdr62 deficiency and found that the mice exhibit reduced brain size due to decreased neural progenitor cells (NPCs). Wdr62 depleted cells show spindle instability, spindle assembly checkpoint (SAC) activation, mitotic arrest and cell death. Mechanistically, Wdr62 associates and genetically interacts with Aurora A to regulate spindle formation, mitotic progression and brain size. These results suggest that Wdr62 interacts with Aurora A to control mitotic progression, and loss of these interactions leads to mitotic delay and cell death of NPCs, which could be a potential cause of human microcephaly (Chen, 2014).

Microcephaly-associated protein WDR62 regulates neurogenesis through JNK1 in the developing neocortex

Xu, D., Zhang, F., Wang, Y., Sun, Y. and Xu, Z. (2014). Microcephaly-associated protein WDR62 regulates neurogenesis through JNK1 in the developing neocortex. Cell Rep 6(1): 104-116. PubMed ID: 24388750

Mutations of WD40-repeat protein 62 (WDR62) have been identified recently to cause human MCPH (autosomal-recessive primary microcephaly), a neurodevelopmental disorder characterized by decreased brain size. However, the underlying mechanism is unclear. This study investigate the function of WDR62 in brain development and the pathological role of WDR62 mutations. WDR62 knockdown was found to lead to premature differentiation of neural progenitor cells (NPCs). The defect can be rescued by wild-type human WDR62, but not by the five MCPH-associated WDR62 mutants. WDR62 acts upstream of JNK signaling in the control of neurogenesis. Depletion of JNK1 and WDR62 incurs very similar defects including abnormal spindle formation and mitotic division of NPCs as well as premature NPC differentiation during cortical development. Thus, these findings indicate that WDR62 is required for proper neurogenesis via JNK1 and provide an insight into the molecular mechanisms underlying MCPH pathogenesis (Xu, 2014).

Opposing roles for JNK and Aurora A in regulating the association of WDR62 with spindle microtubules

WD40-repeat protein 62 (WDR62) is a spindle pole protein required for normal cell division and neuroprogenitor differentiation during brain development. Microcephaly-associated mutations in WDR62 lead to mitotic mislocalization, highlighting a crucial requirement for precise WDR62 spatiotemporal distribution, although the regulatory mechanisms are unknown. This study demonstrates that the WD40-repeat region of WDR62 is required for microtubule association, whereas the disordered C-terminal region regulates cell-cycle-dependent compartmentalization. In agreement with a functional requirement for the WDR62-JNK1 complex during neurogenesis, WDR62 specifically recruits JNK1 (also known as MAPK8), but not JNK2 (also known as MAPK9), to the spindle pole. However, JNK-mediated phosphorylation of WDR62 T1053 negatively regulated microtubule association, and loss of JNK signaling resulted in constitutive WDR62 localization to microtubules irrespective of cell cycle stage. In contrast, this study identified that Aurora A kinase (AURKA) and WDR62 were in complex and that AURKA-mediated phosphorylation was required for the spindle localization of WDR62 during mitosis. These studies highlight complex regulation of WDR62 localization, with opposing roles for JNK and AURKA in determining its spindle association (Lim, 2015).

Docking interactions of the JNK scaffold protein WDR62

JNK (c-Jun N-terminal kinase) is part of a MAPK (mitogen-activated protein kinase) signalling cascade. Scaffold proteins simultaneously associate with various components of the MAPK signalling pathway and play a crucial role in signal transmission and MAPK regulation. WDR62 (WD repeat domain 62) is a JNK scaffold protein. Recessive mutations within WDR62 result in severe cerebral cortical malformation. The present study demonstrates the association of WDR62 with endogenous and overexpressed proteins of both JNK2 and the JNK2-activating kinase MKK7 (MAPK kinase 7). Association of WDR62 with JNK2 and MKK7 occurs via direct protein-protein interactions. The docking domain of WDR62 responsible for the association with JNK was mapped. WDR62 interacts with all JNK isoforms through a D domain motif located at the C-terminus. A WDR62 mutant lacking the putative JNK-binding domain fails to activate and recruit JNK to cellular granules. Furthermore, a synthetic peptide composed of the WDR62 docking domain inhibits JNK2 activity in vitro. WDR62 association with JNK2 requires both the JNK CD and ED domains, and the binding requisite is distinct from that of the previously described JNK2 association with JIP1 (JNK-interacting protein 1). Next, the association was characterized between WDR62 and MKK7. WDR62 associates directly with the MKK7beta1 isoform independently of JNK binding, but fails to interact with MKK7alpha1. Furthermore, MKK7beta1 recruits a protein phosphatase that dephosphorylates WDR62. Interestingly, a premature termination mutation in WDR62 that results in severe brain developmental defects does not abrogate WDR62 association with either JNK or MKK7. Therefore such mutations represent a loss of WDR62 function independent of JNK signalling (Cohen-Katsenelson, 2011).

A novel c-Jun N-terminal kinase (JNK)-binding protein WDR62 is recruited to stress granules and mediates a nonclassical JNK activation

The c-Jun N-terminal kinase (JNK) is part of a mitogen-activated protein kinase (MAPK) signaling cascade. Scaffold proteins simultaneously associate with various components of the MAPK signaling pathway and play a role in signal transmission and regulation. This study describes the identification of a novel scaffold JNK-binding protein, WDR62, with no sequence homology to any of the known scaffold proteins. WDR62 is a ubiquitously expressed heat-sensitive 175-kDa protein that specifically associates with JNK but not with ERK and p38. Association between WDR62 and JNKs occurs in the absence and after either transient or persistent stimuli. WDR62 potentiates JNK kinase activity; however it inhibits AP-1 transcription through recruitment of JNK to a nonnuclear compartment. HEK-293T cells transfected with WDR62 display cytoplasmic granular localization. Overexpression of stress granule (SG) resident proteins results in the recruitment of endogenous WDR62 and activated JNK to SG. In addition, cell treatment with arsenite results in recruitment of WDR62 to SG and activated JNK to processing bodies (PB). JNK inhibition results in reduced number and size of SG and reduced size of PB. Collectively, it is proposed that JNK and WDR62 may regulate the dynamic interplay between polysomes SG and PB, thereby mediating mRNA fate after stress (Wasserman, 2010).

Search PubMed for articles about Drosophila Wdr62

Chen, J. F., Zhang, Y., Wilde, J., Hansen, K. C., Lai, F. and Niswander, L. (2014). Microcephaly disease gene Wdr62 regulates mitotic progression of embryonic neural stem cells and brain size. Nat Commun 5: 3885. PubMed ID: 24875059

Cohen-Katsenelson, K., Wasserman, T., Khateb, S., Whitmarsh, A. J. and Aronheim, A. (2011). Docking interactions of the JNK scaffold protein WDR62. Biochem J 439(3): 381-390. PubMed ID: 21749326

Hu, D. J. and Jasper, H. (2019). Control of intestinal cell fate by dynamic mitotic spindle repositioning influences epithelial homeostasis and longevity. Cell Rep 28(11): 2807-2823. PubMed ID: 31509744

Jayaraman, D., Kodani, A., Gonzalez, D. M., Mancias, J. D., Mochida, G. H., Vagnoni, C., Johnson, J., Krogan, N., Harper, J. W., Reiter, J. F., Yu, T. W., Bae, B. I. and Walsh, C. A. (2016). Microcephaly proteins Wdr62 and Aspm define a mother centriole complex regulating centriole biogenesis, apical complex, and cell fate. Neuron 92(4): 813-828. PubMed ID: 27974163

Lim, N. R., Yeap, Y. Y., Zhao, T. T., Yip, Y. Y., Wong, S. C., Xu, D., Ang, C. S., Williamson, N. A., Xu, Z., Bogoyevitch, M. A. and Ng, D. C. (2015). Opposing roles for JNK and Aurora A in regulating the association of WDR62 with spindle microtubules. J Cell Sci 128(3): 527-540. PubMed ID: 25501809

Lim, N. R., Yeap, Y. Y., Ang, C. S., Williamson, N. A., Bogoyevitch, M. A., Quinn, L. M. and Ng, D. C. (2016). Aurora A phosphorylation of WD40-repeat protein 62 in mitotic spindle regulation. Cell Cycle 15(3): 413-424. PubMed ID: 26713495

Lim, N. R., Shohayeb, B., Zaytseva, O., Mitchell, N., Millard, S. S., Ng, D. C. H. and Quinn, L. M. (2017). Glial-specific functions of microcephaly protein WDR62 and interaction with the mitotic kinase AURKA are essential for Drosophila brain growth. Stem Cell Reports 9(1): 32-41. PubMed ID: 28625535

Nair, A. R., Singh, P., Salvador Garcia, D., Rodriguez-Crespo, D., Egger, B. and Cabernard, C. (2016). The microcephaly-associated protein Wdr62/CG7337 is required to maintain centrosome asymmetry in Drosophila neuroblasts. Cell Rep 14(5): 1100-1113. PubMed ID: 26804909

Ren, L., Mo, D., Li, Y., Liu, T., Yin, H., Jiang, N. and Zhang, J. (2018). A genetic mosaic screen identifies genes modulating Notch signaling in Drosophila. PLoS One 13(9): e0203781. PubMed ID: 30235233

Schoborg, T., Zajac, A. L., Fagerstrom, C. J., Guillen, R. X. and Rusan, N. M. (2015). An Asp-CaM complex is required for centrosome-pole cohesion and centrosome inheritance in neural stem cells. J Cell Biol 211(5): 987-998. PubMed ID: 26620907

Schoborg, T. A., Smith, S. L., Smith, L. N., Morris, H. D. and Rusan, N. M. (2019). Micro-computed tomography as a platform for exploring Drosophila development. Development. PubMed ID: 31722883

Shohayeb, B., Ho, U., Yeap, Y. Y., Parton, R. G., Millard, S. S., Xu, Z., Piper, M. and Ng, D. C. H. (2020). The association of microcephaly protein WDR62 with CPAP/IFT88 is required for cilia formation and neocortical development. Hum Mol Genet 29(2): 248-263. PubMed ID: 31816041

Wasserman, T., Katsenelson, K., Daniliuc, S., Hasin, T., Choder, M. and Aronheim, A. (2010). A novel c-Jun N-terminal kinase (JNK)-binding protein WDR62 is recruited to stress granules and mediates a nonclassical JNK activation. Mol Biol Cell 21(1): 117-130. PubMed ID: 19910486

Xu, D., Zhang, F., Wang, Y., Sun, Y. and Xu, Z. (2014). Microcephaly-associated protein WDR62 regulates neurogenesis through JNK1 in the developing neocortex. Cell Rep 6: 104-116. PubMed ID: 24388750

date revised: 15 October 2020

Home page: The Interactive Fly © 2011 Thomas Brody, Ph.D.