Identification of homologues to beta-catenin/plakoglobin/armadillo in two invertebrates, Urechis caupo and Tripneustes gratilla.

beta-Catenin and plakoglobin are intracellular proteins that participate in cell-cell adhesion, probably through interaction with the cadherin family of transmembrane adhesion proteins. They are also homologous to the segment polarity gene, armadillo, from Drosophila. I have cloned and sequenced armadillo/beta-catenin/plakoglobin homologues from two other invertebrates, Urechis caupo and Tripneustes gratilla, and shown that the mRNA is present in oocytes, eggs and early embryos. In Urechis, the mRNA is particularly abundant in oocytes, but is not translated until after fertilization. These results provide further indications that cell adhesion proteins play a key role during embryogenesis.