β-catenin localization in the ctenophore Mnemiopsis leidyi suggests an ancestral role in cell adhesion and nuclear function

Abstract

The emergence of multicellularity in animals marks a pivotal evolutionary event which was likely enabled by molecular innovations in the way cells adhere and communicate with one another. {beta}-catenin is significant to this transition due to its dual role as both a structural component in the cadherin-catenin complex and as a transcriptional coactivator involved in the Wnt/{beta}-catenin signaling pathway. However, our knowledge of how this protein functions in ctenophores, one of the earliest diverging metazoans, is limited. To study {beta}-catenin function in the ctenophore Mnemiopsis leidyi, we generated affinity-purified polyclonal antibodies targeting Ml{beta}-catenin. We then used this tool to observe {beta}-catenin protein localization in developing Mnemiopsis embryos. In this article we provide evidence of consistent {beta}-catenin protein enrichment at cell-cell interfaces in Mnemiopsis embryos, suggesting that Ml{beta}-catenin had an ancestral role in cell adhesion. Additionally, we found {beta}-catenin enrichment in some nuclei, particularly restricted to the oral pole around the time of gastrulation, suggesting Ml{beta}-catenin may have a nuclear function in Mnemiopsis embryos. The Ml{beta}-catenin affinity-purified antibodies now provide us with a powerful reagent to study the ancestral functions of {beta}-catenin in cell adhesion and transcriptional regulation.