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

Abstract

Ajuba LIM proteins are implicated in the assembly of cell junctions and have been reported to antagonize Hippo signaling in response to cytoskeletal tension. To assess a 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-tagged Wtip 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 linear. Conversely, the linear junctional pattern of Wtip in neuroectoderm changed to puncta in cells with reduced myosin II activity. Suggestive of a potential mechanism, the C-terminal fragment of Wtip physically associated with Shroom3 and interfered with Shroom3 activity and neural fold formation. We propose that Wtip is a tension-sensitive cytoskeletal adaptor that regulates apical constriction during vertebrate neurulation.