RT Journal Article SR Electronic T1 Germ layer specific regulation of cell polarity and adhesion: insight into the evolution of mesoderm JF bioRxiv FD Cold Spring Harbor Laboratory SP 235267 DO 10.1101/235267 A1 Miguel Salinas-Saavedra A1 Amber Q. Rock A1 Mark Q Martindale YR 2017 UL http://biorxiv.org/content/early/2017/12/15/235267.abstract AB In triploblastic animals, Par proteins regulate cell-polarity and adherens junctions of both ectodermal and endodermal epithelia. But, in embryos of the diploblastic cnidarian Nematostella vectensis, Par proteins are eliminated altogether in the bifunctional endomesodermal epithelia. Using immunohistochemistry, CRISPR/Cas9, and overexpression of specific mRNAs, we describe the functional association between Par proteins, ß-catenin, and snail genes in N. vectensis embryos. We demonstrate that the aPKC/Par complex regulates the localization of ß-catenin in the ectoderm by directing its role in cell adhesion, and that endomesodermal epithelia are organized by a different cell adhesion system. We also show that snail genes, which are mesodermal markers in bilaterians, are sufficient to downregulate Par proteins and translocate ß-catenin from the junctions to the cytoplasm in N. vectensis. These data provide insight into the evolution of epithelial structure and the evolution of mesoderm in metazoan embryos.