E-CADHERIN NULL MUTANT EMBRYOS FAIL TO FORM A TROPHECTODERM EPITHELIUM

The cell adhesion molecule E-cadherin mediates the compaction process of mouse preimplantation embryos and is important for the maintenance and function of epithelial cell layers. To determine precisely the rol e of E-cadherin in epithelial biogenesis we monitored the developmenta l potential of embryos homozygously negative for E-cadherin that were derived from E-cadherin heterozygous transgenic mice. The homozygous n egative embryos died around the time of implantation, although they di d undergo compaction like their littermate controls, largely due to th e presence of residual maternal E-cadherin. At the blastocyst stage, E -cadherin-negative embryos failed to form a trophectodermal epithelium or a blastocyst cavity. These results demonstrate the pivotal role of E-cadherin in one of the most basic morphogenetic events in the devel opment of multicellular organisms, the biogenesis of an epithelium.