C. elegansAfadin is required for epidermal morphogenesis and functionally interfaces with the cadherin-catenin complex and RhoGAP PAC-1/ARHGAP21

Abstract

AbstractDuring epithelial morphogenesis, the apical junctions connecting cells must remodel as cells change shape and make new connections with their neighbors. In theC. elegansembryo, new apical junctions form when epidermal cells migrate and seal with one another to encase the embryo in skin (‘ventral enclosure’), and junctions remodel when epidermal cells change shape to squeeze the embryo into a worm shape (‘elongation’). The junctional cadherin-catenin complex (CCC), which links epithelial cells to each other and to cortical actomyosin, is essential forC. elegansepidermal morphogenesis. RNAi genetic enhancement screens have identified several proteins that interact with the CCC to promote epidermal morphogenesis, including the scaffolding protein Afadin (AFD-1), whose depletion alone results in only minor morphogenesis defects. Here, by creating a null mutation inafd-1, we show thatafd-1provides a significant contribution to ventral enclosure and elongation on its own. Unexpectedly, we find thatafd-1mutant phenotypes are strongly modified by diet, revealing a previously unappreciated maternal nutritional input to morphogenesis. We identify functional interactions between AFD-1 and the CCC by demonstrating that E-cadherin is required for the polarized distribution of AFD-1 to cell contact sites in early embryos. Finally, we show thatafd-1promotes the enrichment of polarity regulator and CCC-interacting protein PAC-1/ARHGAP21 to cell contact sites, and identify genetic interactions suggesting thatafd-1andpac-1regulate epidermal morphogenesis at least in part through parallel mechanisms. Our findings reveal thatC. elegansAFD-1 makes a significant contribution to epidermal morphogenesis and functionally interfaces with core and associated CCC proteins.