CRB3 and ARP2/3 regulate cell biomechanical properties to set epithelial monolayers for collective movement

Several cellular processes during morphogenesis, tissue healing or cancer progression involve collective cell migration. To set the cells for motion, there is an initial breaking of organization of the epithelial tissue that modifies the epithelial phenotype and axis of polarity. During this process, the actin cytoskeleton and cellular junctions are extensively remodeled correlating with the buildup of mechanical forces. As the collective migration proceeds, mechanical forces generated by the actin cytoskeleton align with the direction of migration ensuring an organized and efficient collective cell behavior, but how forces are regulated during the breaking of symmetry at the onset of collective motion remains an unaddressed question. It is known that the polarity complex CRB3/PALS1/PATJ, and in particular, CRB3 regulates the organization of the actin cytoskeleton associated to the apical domain thus pointing at a potential role of CRB3 in controlling mechanical forces. Whether and how CRB3 influences epithelial biomechanics during collective cell motion remains, however, largely unexplored. Here, we systematically combine mechanical and molecular analyses to show that CRB3 regulates the biomechanical properties of collective epithelial cells during the initial breaking of epithelial tissue organization. CRB3 interacts with ARP2/3 and controls the remodeling of actin via the modulation of the Rho-/Rac-GTPase balance, and more precisely by acting upstream of the activation of Rac1. Taken together, our results identified CRB3, a polarity protein, as a regulator of epithelial monolayer mechanics during collective cell motion.