beta-catenin is a major tyrosine-phosphorylated protein during mouse oocyte maturation and preimplantation development

During mouse preimplantation development, the components of the E-cadherin- catenin complex are derived from both maternal and zygotic gene activity an d the adhesion complex is increasingly accumulated and stored in a nonfunct ional form, ready to be used for compaction and the formation of the trophe ctoderm cell layer (Ohsugi et al,, Dev, Dyn. 206:391-102, 1996), Here, we s how that beta-catenin is a major tyrosine-phosphorylated protein in oocytes and early cleavage-stage embryos and that the relative amount of phosphory lated beta-catenin is greatly reduced during the morula-blastocyst transiti on, Peptide-specific antibodies indicate that beta-catenin undergoes confor mational changes and/or that the carboxy-terminal region of beta-catenin is blocked during preimplantation development. Moreover, the availability of a carboxy-terminal epitope seems to depend on the tyrosine phosphorylation state of beta-catenin and becomes unmasked when oocytes are treated with th e tyrosine kinase inhibitor genistein, Our results suggest that tyrosine ph osphorylation of beta-catenin represents a molecular mechanism to keep the accumulating E-cadherin adhesion complex in a nonfunctional form. Dev Dyn 1 999;216: 168-176, (C) 1999 Wiley-Liss, Inc.