Rap1 coordinates cell-cell adhesion and cytoskeletal reorganization to drive collective cell migration in vivo.

Collective cell movements contribute to tissue development and repair and spread metastatic disease. In epithelia, cohesive cell movements require reorganization of adherens junctions and the actomyosin cytoskeleton. However, the mechanisms that coordinate cell-cell adhesion and cytoskeletal remodeling during collective cell migration in vivo are unclear. We investigated the mechanisms of collective cell migration during epidermal wound healing in Drosophila embryos. Upon wounding, the cells adjacent to the wound internalize cell-cell adhesion molecules and polarize actin and the motor protein non-muscle myosin II to form a supracellular cable around the wound that coordinates cell movements. The cable anchors at former tricellular junctions (TCJs) along the wound edge, and TCJs are reinforced during wound closure. We found that the small GTPase Rap1 was necessary and sufficient for rapid wound repair. Rap1 promoted myosin polarization to the wound edge and E-cadherin accumulation at TCJs. Using embryos expressing a mutant form of the Rap1 effector Canoe/Afadin that cannot bind Rap1, we found that Rap1 signals through Canoe for adherens junction remodeling, but not for actomyosin cable assembly. Instead, Rap1 was necessary and sufficient for RhoA/Rho1 activation at the wound edge. The RhoGEF Ephexin localized to the wound edge in a Rap1-dependent manner, and Ephexin was necessary for myosin polarization and rapid wound repair, but not for E-cadherin redistribution. Together, our data show that Rap1 coordinates the molecular rearrangements that drive embryonic wound healing, promoting actomyosin cable assembly through Ephexin-Rho1, and E-cadherin redistribution through Canoe, thus enabling rapid collective cell migration in vivo. • The small GTPase Rap1 directs collective cell migration for rapid wound healing • Rap1 acts through Canoe/Afadin to reinforce tricellular adherens junctions • Rap1 promotes Rho1/RhoA signaling to recruit myosin to the wound edge • Adhesion and cytoskeletal remodeling generate forces to coordinate cell migration Rothenberg et al. demonstrate the role of the Rap1 GTPase in embryonic wound healing. Rap1 signals through Canoe/Afadin to reinforce adherens junctions around the wound and through the RhoGEF Ephexin to activate Rho1/RhoA and polarize myosin at the wound edge. Cell adhesion and cytoskeletal remodeling coordinate cell movements for rapid wound repair. [ABSTRACT FROM AUTHOR]