Fig. 4

Loss of Claudin5a does not affect neuroepithelial tissue integrity. (A) Shown are apical views of immunohistochemical stainings onto the hindbrain ventricular zone of cell polarity mutants, Cldn5a- or Atp1a1-deficient embryos, or ouabain-treated embryos at 30 hpf. The neuroepithelial localization of Zonula occludens-1 (ZO-1) or aPKC is only affected in the cell polarity mutants nok^m520/mpp5a and ome^m289/crb2. (Scale bar: 20 μm.) (B) Loss of Cldn5a does not affect the neuroepithelial localization of Na⁺,K⁺-ATPase which is labeled with the a6F antibody. Shown are confocal microscopic images of sections of immunohistochemical stainings of the hindbrain and ventricle. (Scale bar: 20 μm.) (C) Schematic diagram of developmental/cellular processes contributing to brain ventricle expansion. Our study suggests that the cell polarity regulators Crb2 and Mpp5a are essential for neuroepithelial integrity and maintenance of the TJ. Moreover, Crumbs complex proteins may be directly required for lumen formation (Results and Discussion). Tightness of the TJ is, at least in part, regulated by Cldn5a, which seals the neuroepithelial layer to maintain the fluid pressure, which may depend on the ion pump activity of Atp1a1. Ventricular fluid accumulation drives expansion of brain ventricles and tissue morphogenesis. crumbs2 (crb2); heart and mind (had); membrane protein, palmitoylated 5a (mpp5a); nagie oko (nok); oko meduzy (ome); Ventricle (V).