The Ajuba family protein Wtip regulates actomyosin contractility during vertebrate neural tube closure

Abstract

Ajuba family proteins are implicated in the assembly of cell junctions and have been reported to antagonize Hippo signaling in response to cytoskeletal tension. To assess the role of these proteins in actomyosin contractility, we examined the localization and function of Wtip, a member of the Ajuba family, in Xenopus early embryos. Targeted in vivo depletion of Wtip inhibited apical constriction in neuroepithelial cells and elicited neural tube defects. Fluorescent protein-taggedWtip showed predominant punctate localization along the cell junctions in the epidermis and a linear junctional pattern in the neuroectoderm. In cells undergoing Shroom3-induced apical constriction, the punctate distribution was reorganized into a linear pattern.Conversely, the linear junctional pattern of Wtip in neuroectoderm changed to a more punctate distribution in cells with reduced myosin II activity. The Cterminal fragment of Wtip physically associated with Shroom3 and interfered with Shroom3 activity and neural fold formation.We therefore propose that Wtip is a tension-sensitive cytoskeletal adaptor that regulates apical constriction during vertebrate neurulation.