Meeting Abstract
Par proteins are conserved components of cellular polarization during early embryogenesis and their role in establishing embryonic asymmetry have been widely studied in bilaterianS. In embryos of the cnidarian Nematostella vectensis the components of the Par system (NvPar-1, NvPar-3, NvPar-6, NvaPKC, and NvLgl) distribute throughout the microtubule cytoskeleton of pre-blastula stages without any clear polarization along any embryonic axis. However, they become asymmetrically localized at later stages, when the embryo forms an ectodermal epithelial layer in a manner seen in bilaterian animals: NvLgl and NvPar-1 localize in the basolateral cortex, and NvaPKC, NvPar-6, and NvPar-3 at the apical zone of the cell. Interestingly, N. vectensis shows a “random” cleavage pattern and it undergoes gastrulation at the animal (not vegetal) pole of the egg. In contrast, Ctenophores (which also gastrulate at the animal pole) develop under a highly stereotyped embryogenesis; begging the question of whether Par genes regulate the cleavage program and help specify the site of gastrulation. By immunohistochemistry and in vivo imaging of cytoskeletal components we characterized the cytology of blastomeres and epithelial cells during the early embryogenesis of the ctenophore Mnemiopsis leidyi. In addition, mRNA over expression of the components of the ctenophore Par system shows that these proteins distribute differently compared to what we have described for N. vectensis embryos. These observation were confirmed using cross reactive antibody staining. These data will provide a glimpse into the evolution of cell polarity in metazoan embryos.
