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PhD Exit Seminar – Morley Willoughby (Bruce Lab)

August 13, 2021 @ 1:10 pm - 2:00 pm

The recycling endosome protein Rab25 coordinates collective cell movements in the zebrafish surface epithelium during epiboly



The surface epithelium of the zebrafish gastrula spreads to completely enclose an underlying yolk cell in a process known as epiboly. Epithelial epiboly is coordinated by oriented cell division and intercalation events, as well as the transmission and modulation of global tissue tensions. Currently, the molecular mechanisms underpinning zebrafish epithelial epiboly movements are unknown. Here I present the findings of a poorly characterized Rab protein, Rab25, during zebrafish epithelial tissue spreading and show that Rab25 is a recycling endosome protein that coordinates collective cell movements through endomembrane trafficking. Spatiotemporal analysis showed rab25a and rab25b transcripts were restricted to the outer epithelium upon epiboly initiation. Rab25 fluorescent fusion proteins distributed near cytokinetic midbodies and cell vertices during cytokinesis and cell intercalations, respectively. In maternal-zygotic Rab25a and Rab25b embryos, cytokinetic abscission and vertex remodelling was impaired, leading to anisotropic shaped multinucleate cells and uncoordinated cell rearrangements. At the tissue scale, global reductions in contractile actomyosin networks were associated with altered viscoelastic responses of the tissue. Taken together the slow cell rearrangements and defective tissue material properties likely contribute to delayed epiboly. I present a model in which Rab25 vesicle transport coordinates timely epiboly movements by regulating local cell behaviours and tissue scale forces via cytokinetic bridge abscission, cell intercalation and junctional actomyosin maintenance.


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Meeting ID: 817 4154 1128

Host: Ashley Bruce (ashley.bruce@utoronto.ca)



August 13, 2021
1:10 pm - 2:00 pm
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