β-catenin localization in the ctenophoreMnemiopsis leidyisuggests an ancestral role in cell adhesion and nuclear function

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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. β-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/β-catenin signaling pathway. However, our knowledge of how this protein functions in ctenophores, one of the earliest diverging metazoans, is limited. To study β-catenin function in the ctenophore Mnemiopsis leidyi , we generated affinity-purified polyclonal antibodies targeting Ml β-catenin. We then used this tool to observe β-catenin protein localization in developing Mnemiopsis embryos. In this article we provide evidence of consistent β-catenin protein enrichment at cell-cell interfaces in Mnemiopsis embryos, suggesting that Ml β-catenin has an ancestral role in cell adhesion. Additionally, we found β-catenin enrichment in some nuclei, particularly restricted to the oral pole around the time of gastrulation, suggesting Ml β-catenin may have nuclear function in Mnemiopsis embryos. The Ml β-catenin affinity-purified antibodies now provide us with a powerful reagent to study the ancestral functions of β-catenin in cell adhesion and transcriptional regulation.