Extracellular matrix 5: adhesive interactions in early mammalian embryogenesis, implantation, and placentation.

Normal morphogenesis and differentiation depend heavily on the coordination of cell-cell and cell-extracellular matrix interactions. During early mammalian development, the first cell lineages to be established are extraembryonic (trophoblast and extraembryonic endoderm), which are essential for satisfying the nutritional requirements of the developing embryo. This review emphasizes the importance of the cadherin family of cell-cell adhesion molecules and the integrin family of extracellular matrix receptors in mediating interactions between cells and their environment during early development. The review first discusses the critical role of cell-cell interactions in fertilization and early lineage decisions that occur during pre- and peri-implantation development in the mouse, using the calcium-dependent cell adhesion molecule E-cadherin as the primary example. The remainder of the review discusses the importance of cell-ECM interactions in the further morphogenesis and differentiation of the newly segregated lineages. The critical roles of integrins in differentiation, migration, and invasion of trophoblast in both mouse and human are emphasized.