Meeting Abstract
Epithelial cells of bilaterian animals are polarized along the apico-basal axis by the stabilization of adherens and septate junctions, respectively. Previous studies obtained in the lab, using embryos of the cnidarian Nematostella vectensis, suggest that this mechanism of polarization could have already been present in the most common ancestor of Bilateria and Cnidaria: While adherens junctions stabilizes the localization of the aPKC/Par complex at the apical cortex of the cells, septate junctions stabilizes Lgl and Par-1 at the basolateral cortex of the cells. Interestingly, even though cadherins (a component of adherens junctions) are present in the genome of the ctenophore Mnemiopsis leidyi, the latter does not possess the components necessaries to assemble the septate junctions that are present in bilaterian animals. Concordantly, in M. leidyi embryos Par-6 localizes to the apical cortex but Par-1 remains cytoplasmic, different from what we have described for N. vectensis embryos. This data suggest that the absence of septate junctions may be related to this localization pattern. To test this hypothesis we disassembled the formation of septate junctions by using CRISPR/Cas9 to knock down Contactin (a component of septate junctions) in N. vectensis embryos, and analyzed the localization of Par-1 and Lgl by immunofluorescence. In addition, using a ctenophore-specific ß-catenin antibody and a GFP-labeled mRNA reporter as markers for adherens junctions, for the first time we describe its localization during the M. leidyi embryogenesis, and compared it to N. vectensis and bilaterians embryos.
