The cnidarian and the canon: the role of Wnt/beta-catenin signaling in the evolution of metazoan embryos

Bioessays. 2004 May;26(5):474-8. doi: 10.1002/bies.20031.

Abstract

In a recent publication, Wikramanayake and colleagues have implicated the canonical Wnt/beta-catenin signaling pathway as a mediator of axial polarity and germ-layer specification in embryos of the cnidarian Nematostella. In this anthozoan, beta-catenin is localized in nuclei of blastomeres in one region of the 16- to 32-cell embryo whose descendants subsequently form the entoderm of the embryo. They claim that the pattern of nuclear localization is significant for two reasons: (1) when nuclear localization of beta-catenin was inhibited, gastrulation does not occur, and (2) when localization of beta-catenin took place in all cells of the pregastrula embryo, the number of entodermal cells increases. Since the Wnt/beta-catenin signaling pathway also plays a role in establishing axial polarity and specifying endoderm and mesoderm in a number of bilaterians, Wikramanayake et al. imply that this developmental mechanism is an evolutionary inheritance from a radially symmetrical ancestor. Some of the gaps in the current evidence, which must be filled to evaluate their interpretation, are discussed.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biological Evolution*
  • Body Patterning
  • Cnidaria / anatomy & histology
  • Cnidaria / embryology*
  • Cnidaria / metabolism*
  • Cytoskeletal Proteins / metabolism*
  • Morphogenesis
  • Proto-Oncogene Proteins / metabolism*
  • Signal Transduction*
  • Trans-Activators / metabolism*
  • Wnt Proteins
  • beta Catenin

Substances

  • Cytoskeletal Proteins
  • Proto-Oncogene Proteins
  • Trans-Activators
  • Wnt Proteins
  • beta Catenin