Distinct Non-occluding Functions of Septate Junction Components in Signaling Pathway Regulation and Cell Polarity During Epithelial Development

Abstract

Occluding junctions are essential for epithelial tissue integrity and barrier function but also exert non-occluding roles. Here we identify a several crucial function of the invertebrate occluding junction components Coracle, Nervana 2, Neurexin-IV, and Kune-kune in regulating cell polarity during follicle epithelium development. We show that the morphogenesis of the follicular stalk is an actin-driven process that requires intact apical-basal cell polarity, which is controlled by septate junction components. Occluding junction components further regulate signaling pathways in a cell-type specific manner. In undifferentiated stem cells and immediate daughters, septate junction components promote effective Wnt signaling to control proliferation, while they limit Jak-STAT signaling activity induced by polar cells. Together, our data emphasize the multiple roles of occluding junction components independent of their classical role in forming the paracellular barrier.