Cell-to-cell coupling in early-stage bovine embryos: A preliminary report

Gap junction communication has been implicated in providing positional information within an embryo. This positional information is then used to direct the differentiation of the early embryo. To begin to gain an assessment of the cell-to-cell communication observed in the early bovine embryo, fluorescein (5%) was microinjected into single blastomeres of freshly collected embryos. Dye communication was not observed in any of the 8-to 16-cell stage embryos. Very limited dye coupling was observed in compact morula (18%) and expanded blastocysts (25%). Interestingly, none of the expanded blastocysts resulting from in vitro maturation and in vitro fertilization showed any dye coupling. The degree of coupling observed in the bovine embryo was less than that observed in compact morula mouse embryos, where almost all (95%) embryos showed dye coupling. This experimental data is discussed in context with previous electron microscopy data.