αE-catenin regulates cell-cell adhesion and membrane blebbing during zebrafish epiboly

alpha E-catenin is an actin-binding protein associated with the E-cadherin-based adherens junction that regulates cell-cell adhesion. Recent studies identified additional E-cadherin-independent roles of alpha E-catenin in regulating plasma membrane dynamics and cell migration. However, little is known about the roles of alpha E-catenin in these different cellular processes in vivo during early vertebrate development. Here, we examined the functions of alpha E-catenin in cell-cell adhesion, cell migration and plasma membrane dynamics during morphogenetic processes that drive epiboly in early Danio rerio (zebrafish) development. We show that depletion of alpha E-catenin caused a defect in radial intercalation that was associated with decreased cell-cell adhesion, in a similar manner to E-cadherin depletion. Depletion of alpha E-catenin also caused deep cells to have protracted plasma membrane blebbing, and a defect in plasma membrane recruitment of ERM proteins that are involved in controlling membrane-to-cortex attachment and membrane blebbing. Significantly, depletion of both E-cadherin and alpha E-catenin suppressed plasma membrane blebbing. We suggest that during radial intercalation the activities of E-cadherin and alpha E-catenin in the maintenance of membrane-to-cortex attachment are balanced, resulting in stabilization of cell-cell adhesion and suppression of membrane blebbing, thereby enabling proper radial intercalation.