A transphyletic study of metazoan β-catenin protein complexes

β-catenin plays a vital role in various biological processes, such as body axis determination and cell differentiation, during embryonic development in metazoans. These β-catenin functions are thought to be exerted through complexes formed with various types of proteins. Although β-catenin complex proteins have been identified in several bilaterian models, little is known about the structural and functional properties of β-catenin complexes in the early metazoan evolutionary phases. In this study, we performed a comparative analysis of β-catenin sequences in nonbilaterian lineages that branched off early in metazoan evolution. We aslo carried out a transphyletic function experiments of β-catenin from non-bilaterian metazoans using developing Xenopus embryos, which included secondary axis induction in embryos and proteomic analysis of the β-catenin protein complex. Comparative functional analysis of nonbilaterian β-catenins also demonstrated sequence characteristics important for β-catenin function, and the deep origin and evolutionary conservation of the cadherin-catenin complex. Proteins coimmunoprecipitated with β-catenin included several proteins conserved across metazoans. These data provide a new insight into the conserved repertoire of β-catenin complexes.