WIKRAMANAYAKE, A.H. ; HONG, M.; LEE, P.N.*; PANG, K.; BYRUM, C.A.; BINCE, J.M.; XU, R.; MARTINDALE, M.Q.; University of Hawai�i at Manoa; University of Hawai�i at Manoa; Kewalo Marine Lab/Pacific Biomedical Research Center; Kewalo Marine Lab/Pacific Biomedical Research Center; University of Hawai�i at Manoa; University of Hawai�i at Manoa; University of Hawai�i at Manoa; Kewalo Marine Lab/Pacific Biomedical Research Center: Axial polarity and germ layer segregation in the basal cnidarian Nematostella vectensis: an ancient role for &beta-catenin
The bifunctional protein, &beta-catenin, is involved in both cadherin-mediated cell adhesion and Wnt-directed cell signaling. The role of Wnt/&beta-catenin signaling in a variety of diverse developmental processes, including embryonic polarity determination, germ layer formation, gap junction communication, and neural patterning, obscures the ancestral function of &beta-catenin. However, in many different bilaterian embryos, activation of &beta-catenin signaling, through translocation of &beta-catenin to the nucleus, occurs in cells at the site of gastrulation and endomesodmerm formation. The conservation of this mechanism between diverse phyla suggests that a spatially asymmetric activation of &beta-catenin in embryos was involved in determination of axial polarity and segregation of the germ layers in the bilaterian ancestor. To test if the nuclear translocation of &beta-catenin protein is involved in axial specification and germ layer formation in a “prebilaterian”, we examined the distribution, stability, and function of &beta-catenin protein in embryos of the starlet sea anemone Nematostella vectensis (Anthozoa, Cnidaria). Using an N. vectensis &beta-catenin-GFP fusion protein and loss-of-function assays, we show that N. vectensis &beta-catenin is differentially stabilized along the oral-aboral axis, translocated to nuclei in blastomeres at the site of gastrulation, and used to specify germ layers, indicating an evolutionarily ancient role for this protein in early pattern formation.
