Systematic characterization ofDrosophilaRhoGEF/GAP localizations uncovers regulators of mechanosensing and junction formation during epithelial cell division

Abstract

Cell proliferation is central to epithelial tissue development, repair and homeostasis. During cell division, small RhoGTPases control both actomyosin dynamics and cell-cell junction remodelling to faithfully segregate the duplicated genome while maintaining tissue polarity and integrity. To decipher the mechanisms of RhoGTPases spatiotemporal regulation during epithelial cell division, we generated a transgenic fluorescently tagged library for Drosophila Rho Guanine exchange factors (GEF) and GTPase activating proteins (GAP), and systematically characterized their endogenous distributions by time-lapse microscopy. Thereby, we unveiled candidate regulators of the interplay between actomyosin and junctional dynamics during epithelial cell division. Building on these findings, we uncovered that during cytokinesis, Cysts and RhoGEF4 play sequential roles in mechanosensing and de novo junction formation, respectively. We foresee that the RhoGEF/GAP library will be a key resource to understand the broad range of biological processes regulated by RhoGTPases.

Kinesin-1 patterns Par-1 and Rho signaling at the cortex of syncytial embryos of Drosophila

“…Rho1 is activated by guanyl nucleotide exchange factors (RhoGEFs) and inhibited by GTPase-activating proteins (RhoGAPs). Following screening a library of tagged RhoGEFs/GAPs ( di Pietro et al, 2022 , Preprint ), we decided to focus on the RhoGEF Pebble (Pbl). Pebble is best known for its function in cytokinesis, where it positions the cytokinetic furrow in response to a signal from microtubules ( Somers and Saint, 2003 ; Zavortink et al, 2005 ; Lehner, 1992 , Hime and Saint, 1992 ; Propopenko et al, 1999 ).…”

“…We find it more likely, however, that additional RhoGEFs or RhoGAPs beside Pebble are involved in activation of Rho signaling in intercaps. Systematic screening for such Rho GEF/GAP regulators is feasible now, given the genome-wide library of endogenously tagged RhoGEFs and RhoGAPs ( di Pietro et al, 2022 Preprint ). We expect RhoGEFs are restricted to the intercap region to promote Rho activation in intercap; RhoGAPs are restricted to the cap region.…”