Junctional complexes in the early mammalian embryo

Preimplantation embryos generate intercellular junctions during differentia tion of the trophectoderm epithelium and the formation of the blastocyst. T hese membrane complexes comprise gap junctions, adherens junctions, tight j unctions, and desmosomes, each performing fundamental roles in cellular com munication, adhesion, and differentiation. The mouse embryo has been used a s a model for the biogenesis of cell junctions. Their construction is achie ved by temporally regulated gene expression programs. Mechanisms of junctio n membrane assembly include the timing of transcription, translation, and p osttranslational modifications of specific junctional proteins. Human embry os exhibit similar expression programs, and defects in these programs may c ontribute to reduced embryo viability.