Cell adhesion in the preimplantation mammalian embryo and its role in trophectoderm differentiation and blastocyst morphogenesis.

Cell adhesion plays a critical role in the differentiation of the trophectoderm epithelium and the morphogenesis of the blastocyst. In the mouse embryo, E-cadherin mediated adhesion initiates at compaction at the 8-cell stage, regulated post-translationally via protein kinase C and other signalling molecules. E-cadherin adhesion organises epithelial polarisation of blastomeres at compaction. Subsequently, the proteins of the epithelial tight junction are expressed and assemble at the apicolateral contact region between outer blastomeres in three phases, culminating at the 32-cell stage when blastocoel cavitation begins. Cell adhesion events also coordinate the cellular allocation and spatial segregation of the inner cell mass (ICM) of the blastocyst, and the maintenance of epithelial (trophectoderm) and non-epithelial (ICM) phenotypes during early morphogenesis.