76 Oral - Cell Biology II
Friday April 08, 11:30 AM - 11:45 AM

Authors:
Lisa Calvary; Piere Pouchin; Graziella Richard; Vincent Mirouse

Affiliation: iGReD, Université Clermont Auvergne - CNRS UMR 6293- INSERM U1103 - Clermont-Ferrand, France

Keywords:
a. cytoskeleton; t. cell junctions and adhesion

How cells change their respective position to allow a tissue acquiring a specific shape is a major question in development. Drosophila follicle elongates through its antero-posterior axis and this elongation depends on the follicular epithelium. We recently described that this elongation relies on two steps, the first one occurring from stage 3 to 7 and involving, among other mechanisms, cell intercalations (Alégot et al., eLife, 2018). However, in these cells there is no junctional planar polarization of Myosin II as it is the case in some other epithelia undergoing cell intercalations. In this context, we got interested in the role of F-Actin in cell rearrangements.
By performing a reverse genetic screen of F-Actin regulators, we identified the WAVE regulatory complex (WRC), a complex involved in the generation of branched F-Actin, as required for follicle early elongation. In follicular cells, WRC is localized at tri-cellular junctions and colocalized with an intense spot of F-Actin. Tricellular junctions are important hotspots for tissue dynamics thought their function is not yet fully understood. In mutant cells for WRC subunits, this spot of F-Actin is absent suggesting that it reflects the protrusive activity of this complex. Accordingly, high-resolution analysis reveals that these spots correspond to protrusions from one cell between the bicellular junction of the two others. In addition, mutants cells for WRC exhibit a strong packing defect, leading to the conclusion that WRC is involved in cell rearrangements. We therefore propose that the protrusive activity of WRC at tri-cellular junctions promotes cell intercalations, allowing follicle elongation. Data of our current analyze on living samples of the relationship between F-Actin protrusions induced by WRC and cell junction dynamics will be presented.