E-cadherin clustering as a regulator of morphogenesis

Cell adhesion enables animal multicellular development. E-cadherin and the cadherin-catenin adhesion complex at adherens junctions are engaged in dynamic interactions with actomyosin generated contractile forces to drive epithelial morphogenesis. However, our understanding of how adhesion is regulated and how the tuning of adhesion contributes to morphogenesis remains incomplete. One key determinant of E-cadherin adhesion strength is clustering of the cadherin-catenin adhesion complex, a property studied extensively in vitro. Here, we use optogenetics to enhance E-cadherin cluster formation in the Drosophila embryo. Enlarged clusters were associated with increased E-cadherin surface abundance, assembled a normal cadherin-catenin complex, and showed reduced membrane mobility and turnover consistent with an increase in cell adhesion strength. Drosophila embryos with enhanced E-cadherin clustering displayed a severe reduction in cell intercalation and convergent extension of the anterior-posterior axis. To account for these observations, we modified existing vertex models to include junction-specific viscous forces representing E-cadherin-mediated friction between cells. This dissipative adhesion model predicts that enhanced adhesion increases resistance to cell rearrangements, thereby reducing cell neighbor exchanges and impairing convergent extension. To test model predictions, we analyzed two types of morphogenetic movements in embryos with enhanced E-cadherin clustering. Neuroblast ingression, which requires both apical constriction and cell rearrangement, was severely slowed. In contrast, mesoderm invagination, which requires apical constriction without neighbor exchanges, proceeded normally. Our findings suggest that optogenetic clustering, in contrast to overexpression of E-cadherin, is a valuable tool to examine the consequences of enhancing adhesion strength in tissue morphogenesis. Moreover, we propose that regulating E-cadherin clustering is essential for movements that require cell-cell contact changes.