When migrating cells with a leading edge come together and form a cadherin contact a number of actin cytoskeletal rearrangement occur that regulates a robust transition called mesenchymal-to-epithelial-like transitions. Christopher Toret in André Le Bivic’s team, in collaboration with Pierre François Lenne’s team, used genetic interaction studies in Drosophila dorsal closure models to probe Rho family of GTPases (Rho1 and Rac) activities during these transitions in the epidermis. They defined precisely in time and space Rac and Rho activities during dorsal closure at the epidermal leading edge and newly formed cadherin contacts. They also identified roles for the atypical Rac GEF complex made of Engulfment and Cell Motility (ELMO) and Myoblast city (MBC) and the RhoGAP19d to coordinate Rho GTPase cycles for F-actin remodeling required to transmit forces during mesenchymal-to-epithelial-like transitions. These studies should advance our understanding of the role of mechanosensing actin-regulatory proteins in the control of spatiotemporal actin dynamics in developmental processes.
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