Biology subjects

Allen, B. L.

Publications and source records attributed to Allen, B. L..

9 recordsLinked to original sources

bioRxiv2024

KIF3C Regulates Bergmann Glia Density and Patterning during Cerebellar Development

Kinesin-2 motors have been demonstrated to regulate Hedgehog (HH) signaling, particularly within the developing cerebellum (Spassky et al., 2008; Waas et al., 2024). KIF3A/KIF3B are required for ciliogenesis in mice, and loss of this motor complex results in cerebellar hypoplasia due to lack of mitogenic response of HH-responsive cerebellar granule neural progenitors (CGNPs). Homodimeric KIF17 regulates HH-dependent CGNP proliferation through regulating levels of SHH and GLI3 but is not required for ciliogenesis in the developing cerebellum. Germline deletion of Kif3c has previously been reported to have no effect on embryonic development or gross cerebellar morphology in adult mice (Yang et al., 2001). Examination of these mice during neonatal development reveal cerebellar hypoplasia due to reduced CGNP proliferation in Kif3c mutant mice. While decreased CGNP proliferation is often associated with reduced Hedgehog (HH) signaling, we did not detect a change in the levels of HH signaling in Kif3c-/- cerebella. However, we observed Bergmann glia density and localization is altered in Kif3c mutants, a phenotype consistent with disrupted Notch signaling. Further, we detected reduced expression of Hes1 in Kif3c-/- cerebella. Altogether, these data demonstrate KIF3C is required for proper cerebellar development but in a HH-independent manner. HighlightsO_LIKif3c is widely expressed in developing cerebellum C_LIO_LIKIF3C regulates cerebellar size, but in a HH-independent manner C_LIO_LIKif3c-/- mice have increased BG density and abnormal spatial patterning C_LI

developmental biology↗

bioRxiv2024

Semaphorin Receptors Antagonize Wnt Signaling Through Beta-Catenin Degradation

Precise control of morphogen signaling levels is essential for proper development. An outstanding question is: what mechanisms ensure proper morphogen activity and correct cellular responses? Previous work has identified Semaphorin (SEMA) receptors, Neuropilins (NRPs) and Plexins (PLXNs), as positive regulators of the Hedgehog (HH) signaling pathway. Here, we provide evidence that NRPs and PLXNs antagonize Wnt signaling in both fibroblasts and epithelial cells. Further, Nrp1/2 deletion in fibroblasts results in elevated baseline Wnt pathway activity and increased maximal responses to Wnt stimulation. Notably, and in contrast to HH signaling, SEMA receptor-mediated Wnt antagonism is independent of primary cilia. Mechanistically, PLXNs and NRPs act downstream of Dishevelled (DVL) to destabilize {beta}-catenin (CTNNB1) in a proteosome-dependent manner. Further, NRPs, but not PLXNs, act in a GSK3b/CK1-dependent fashion to antagonize Wnt signaling, suggesting distinct repressive mechanisms for these SEMA receptors. Overall, this study identifies SEMA receptors as novel Wnt pathway antagonists that may also play larger roles integrating signals from multiple inputs.

developmental biology↗

bioRxiv2024

Hedgehog-dependent and Hedgehog-independent roles for Growth Arrest Specific 1 in mammalian kidney morphogenesis

Growth arrest specific 1 (GAS1) is a key regulator of mammalian embryogenesis, best known for its role in Hedgehog (HH) signaling, but with additional described roles in the FGF, RET, and NOTCH pathways. Previous work indicated a later role for GAS1 in kidney development through FGF pathway modulation. Here, we demonstrate that GAS1 is essential for both mesonephrogenesis and metanephrogenesis- most notably, Gas1 deletion in mice results in renal agenesis in a genetic background-dependent fashion. Mechanistically, GAS1 promotes mesonephrogenesis in a HH-dependent fashion, performing a unique co-receptor function, while promoting metanephrogenesis in a HH-independent fashion, acting as a putative secreted RET co-receptor. Our data indicate that Gas1 deletion leads to renal agenesis through a transient reduction in metanephric mesenchyme proliferation- a phenotype that can be rescued by exogenous RET pathway stimulation. Overall, this study indicates that GAS1 contributes to early kidney development through the integration of multiple different signaling pathways.

developmental biology↗

bioRxiv2022

Gli2 and Gli3 Regulate Horizontal Basal Cell-Mediated Regeneration of the Olfactory Epithelium

The olfactory epithelium (OE) is a specialized neuroepithelium that is replenished by two stem cell populations: globose basal cells (GBCs) and horizontal basal cells (HBCs). Previous work indicated that HBCs contain primary cilia, organelles that mediate Hedgehog (HH) pathway activity. However, a role for HH signaling in HBCs has not been investigated. We find that GLI2 and GLI3, transcriptional effectors of the HH pathway, are expressed in HBCs in the adult OE and that their expression expands following injury. Further, Gli2-expressing descendants contribute to all major OE cell types during OE regeneration. HBC-specific expression of constitutively active GLI2 drives inappropriate HBC proliferation, alters HBC identity, and culminates in a failure of HBCs to differentiate into olfactory sensory neurons (OSNs) following injury. HBC- specific deletion of endogenous Gli2 and Gli3 results in decreased HBCs and OSNs following OE injury. These data identify GLI2 and GLI3 as key regulators of HBC-mediated OE regeneration.

cell biology↗

bioRxiv2022

Dual and Opposing Roles for the Kinesin-2 Motor, KIF17, in Hedgehog-dependent Cerebellar Development

While the kinesin-2 motors KIF3A and KIF3B have essential roles in ciliogenesis and Hedgehog (HH) signal transduction, potential role(s) for another kinesin-2 motor, KIF17, in HH signaling have yet to be explored. Here, we investigated the contribution of KIF17 to HH-dependent cerebellar development, where Kif17 is expressed in both HH-producing Purkinje cells and HH-responding cerebellar granule neuron progenitors (CGNPs). Germline Kif17 deletion in mice results in cerebellar hypoplasia due to reduced CGNP proliferation, a consequence of decreased HH pathway activity mediated through decreased Sonic HH (SHH) protein. Notably, Purkinje cell-specific Kif17 deletion phenocopies Kif17 germline mutants. Surprisingly, CGNP-specific Kif17 deletion results in the opposite phenotype- increased CGNP proliferation and HH target gene expression due to altered GLI transcription factor processing. Together these data identify KIF17 as a key regulator of HH-dependent cerebellar development, with dual and opposing roles in HH-producing Purkinje cells and HH-responding CGNPS. TeaserDuring cerebellar development, the KIF17 microtubule motor performs opposing roles in HH-producing and HH-responding cells.

developmental biology↗

bioRxiv2021

Plexins Promote Hedgehog Signaling Through Their Cytoplasmic GAP Activity

Hedgehog signaling controls tissue patterning during embryonic and postnatal development and continues to play important roles throughout life. Characterizing the full complement of Hedgehog pathway components is essential to understanding its wide- ranging functions. Previous work has identified Neuropilins, established Semaphorin receptors, as positive regulators of Hedgehog signaling. Neuropilins require Plexin co- receptors to mediate Semaphorin signaling, but a role for Plexins in Hedgehog signaling has not yet been explored. Here, we provide evidence that multiple Plexins promote Hedgehog signaling in NIH/3T3 fibroblasts and that Plexin loss-of-function in these cells results in significantly reduced Hedgehog pathway activity. Catalytic activity of the Plexin GTPase activating protein (GAP) domain is required for Hedgehog signal promotion, and constitutive activation of the GAP domain further amplifies Hedgehog signaling. Additionally, we demonstrate that Plexins promote Hedgehog signaling at the level of GLI transcription factors and that this promotion requires intact primary cilia. Finally, we find that Plexin loss-of-function significantly reduces the response to Hedgehog pathway activation in the mouse dentate gyrus. Together, these data identify Plexins as novel components of the Hedgehog pathway and provide insight into their mechanism of action.

developmental biology↗

bioRxiv2019

Suppression of p53 response by targeting p53-Mediator binding with a stapled peptide

DNA-binding transcription factors (TFs) remain challenging to target with molecular probes. Many TFs function in part through interaction with Mediator; we sought to block p53 function by disrupting the p53-Mediator interaction. Through rational design and activity-based screening, we characterized a stapled peptide, with functional mimics of both p53 activation domains, that selectively inhibited p53- and Mediator-dependent transcription in vitro. This \"bivalent peptide\" also suppressed p53 transcriptional response in human cancer cells. Our strategy circumvents the TF and instead targets the TF-Mediator interface, with desired transcriptional outcomes. Different TFs target Mediator through different subunits, suggesting this strategy could be broadly applied.

molecular biology↗

bioRxiv2018

Developing Future Biologists: creating and assessing a portable short course to engage underrepresented undergraduate students in developmental biology

Many barriers discourage underrepresented students from pursuing science careers. To access graduate education, undergraduate students must first gain exposure to a particular subject and subsequently accumulate related coursework and research experience. Many underrepresented students lack exposure to developmental biology due to limited undergraduate course offerings and finite resources at smaller institutions. To address this disparity, a group of University of Michigan graduate students and postdoctoral fellows created a portable short course focusing on developmental biology, titled \"Developing Future Biologists\" (DFB). This weeklong educational initiative provides hands-on laboratory sessions, interactive lectures, and professional development workshops to teach students about developmental biology and increase awareness of scientific career options. To evaluate course effectiveness, we developed a pre-post assessment, incorporating main ideas from the BioCore Guide. Student understanding of basic concepts and perceived experience in developmental biology increased in DFB participants, despite the abbreviated nature of the course. Here, we provide all course materials and an in-depth analysis of the assessment we created. The DFB portable short course model is an easily adaptable tool that connects undergraduate students with opportunities for advanced study and lowers barriers for underrepresented students in science, technology, engineering, and mathematics.

scientific communication and education↗

bioRxiv2018

Acute inhibition of heterotrimeric kinesin-2 function reveals mechanisms of intraflagellar transport in mammalian cilia

The trafficking of components within cilia, called intraflagellar transport (IFT), is powered by kinesin-2 and dynein-2 motors. Loss of function in any subunit of the heterotrimeric KIF3A/KIF3B/KAP kinesin-2 motor prevents ciliogenesis in mammalian cells and has hindered an understanding of how kinesin-2 motors function in IFT. We used a chemical-genetic approach to engineer an inhibitable KIF3A/KIF3B (i3A/i3B) kinesin-2 motor that is capable of rescuing WT motor function in Kif3a/Kif3b double-knockout cells. Inhibitor addition blocks ciliogenesis or, if added to ciliated cells, blocks IFT within two minutes, which leads to a complete loss of primary cilia within six hours. The kinesin-2 family members KIF3A/KIF3C and KIF17 cannot rescue ciliogenesis in Kif3a/Kif3b double-knockout cells nor delay the disassembly of full-formed cilia upon i3A/i3B inhibition. These data suggest that KIF3A/KIF3B/KAP is the sole and essential motor for cilia assembly and function in mammalian cells, indicating a species-specific adaptation of kinesin-2 motors for IFT function.

cell biology↗