Loss of Cell-Cell Contact Inhibits Cellular Differentiation of α-Catenin Knock Out P19 Embryonal Carcinoma Cells and Their Colonization into the Developing Mouse Embryos

Cadherin-catenin cell-cell adhesion complexes, composed of cadherin, β-catenin or plakoglobin, and α-catenin (α-cat) molecules, are crucial for maintaining cell-cell contact and are commonly referred to as "adherens junctions (AJs)." Inactivating this system leads to loss of cell-cell contact and developmental arrest in early embryos. However, it remains unclear whether the loss of cell-cell contact affects the differentiation of embryonic cells. In this study, we explored the use of a murine embryonal carcinoma cell line, P19, as an in vitro model for early embryogenesis. P19 cells easily form embryoid bodies (EBs) and are susceptible to cellular differentiation in response to retinoic acid (RA) and teratoma formation. Using CRISPR/Cas9 technology to disrupt the endogenous <i>α-cat</i> gene in P19 cells, we generated <i>α-cat</i> knockout (KO) cells that exhibited a loss of cell-cell contact. When cultivated on non-coated dishes, these <i>α-cat</i> KO cells formed EBs, but their structures were labile. In the RA-containing medium, the <i>α-cat</i> KO EBs failed to produce differentiated cells on their outer layer and continued to express SSEA-1, an antigen specific to pluripotent cells. Teratoma formation assays revealed an absence of overt differentiated cells in tumors derived from <i>α-cat</i> KO P19 cells. Aggregation assays revealed the inability of the KO cells to colonize into the zona pellucida-denuded 8-cell embryos. These findings suggest that the AJs are essential for promoting the early stages of cellular differentiation and for the colonization of early-developing embryos.