Claudins are essential for cell shape changes and convergent extension movements during neural tube closure

Amanda I Baumholtz,Annie Simard,Evanthia Nikolopoulou,Marcus Oosenbrug,Michelle M Collins,Anna Piontek,Gerd Krause,Jörg Piontek,Nicholas D.E Greene,Aimee K Ryan

doi:10.1016/j.ydbio.2017.05.013

Abstract

During neural tube closure, regulated changes at the level of individual cells are translated into large-scale morphogenetic movements to facilitate conversion of the flat neural plate into a closed tube. Throughout this process, the integrity of the neural epithelium is maintained via cell interactions through intercellular junctions, including apical tight junctions. Members of the claudin family of tight junction proteins regulate paracellular permeability, apical-basal cell polarity and link the tight junction to the actin cytoskeleton. Here, we show that claudins are essential for neural tube closure: the simultaneous removal of Cldn3, −4 and −8 from tight junctions caused folate-resistant open neural tube defects. Their removal did not affect cell type differentiation, neural ectoderm patterning nor overall apical-basal polarity. However, apical accumulation of Vangl2, RhoA, and pMLC were reduced, and Par3 and Cdc42 were mislocalized at the apical cell surface. Our data showed that claudins act upstream of planar cell polarity and RhoA/ROCK signaling to regulate cell intercalation and actin-myosin contraction, which are required for convergent extension and apical constriction during neural tube closure, respectively.

Highlights

The molecular interactions that regulate many of the morphogenetic changes required for neural tube closure occur at the apical cell surface (Colas and Schoenwolf, 2001; Lawson et al, 2001)
We showed by whole mount in situ hybridization that Cldn3, −4, −8 and −14 are the only C-CPE-sensitive claudins expressed during neural tube closure in chick embryos
We tested the ability of C-CPE to effectively remove these claudins from tight junctions as compared to effects on Cldn1, which does not interact with C-CPE (Fig. 1A and B)

Summary

Introduction

The molecular interactions that regulate many of the morphogenetic changes required for neural tube closure occur at the apical cell surface (Colas and Schoenwolf, 2001; Lawson et al, 2001). Apical constriction of cells at the midline to form the median hinge point depends upon the actin-myosin contractile force driven by localized myosin light chain phosphorylation downstream of RhoA-ROCK signaling (Suzuki et al, 2012; Kinoshita et al, 2008). This allows the neural plate to bend and the neural folds to elevate. Apical tight junctions are a hallmark of vertebrate epithelial cell layers They maintain apical-basal polarity by preventing the mixing of apical and basolateral membrane proteins and regulate the paracellular movement of ions, solutes and water (Gunzel and Yu, 2013; Suzuki et al, 2015).

Methods

Results

Conclusion