The occluding junction protein Neurexin-IV is required for tissue integrity in the Drosophila wing disc epithelium

Abstract

Epithelia are essential tissues in all multicellular organisms to establish a barrier against the external environment. To exert this vital function, epithelial cells need to be tightly connected to each other while at the same time they allow for complex tissue and cell shapes to arise. Occluding Junctions (OJs) have evolved to become epithelia’s gatekeepersthey seal intercellular spaces but also provide selective permeability. Recent studies have also proposed that OJs regulate epithelial morphogenesis and polarity, but themechanisms are still poorly understood. Herewe explored novel functions of OJs by investigating the function of Neurexin-IV (Nrx-IV), a conserved transmembrane protein of the Neurexin/Contactin family localized at invertebrate OJs, using theDrosophila melanogaster larval epithelium as a model system. By knocking down the expression of this protein in a specific subset of epithelial cells and in a time-controlled manner, we show that Nrx-IV is required for proper epithelial tissue organization and survival. This suggests that OJs play a more important role in epithelial morphogenesis than previously anticipated. As Nrx-IV is also present in invertebrate glial OJs and in vertebrate axo-glial junctions this work not only increases our knowledge about epithelia but can also have implications in nervous system biology.