Abstract
The formation of junctional complexes and the location of actin and cytokeratin were morphologically examined in parthenogenetic mouse embryos during the course of blastocyst formation. Although there was no junctional complex in untransformed 8- and 16-cell embryos, zonula occludens, predesmosomes and gap junctions appeared between each pair of flattened blastomeres of transformed 8- and 16-cell embryos. In these transformed embryos, gap junctions were observed between every two round blastomeres as well as between a flattened blastomere and a round one. Desmosomes also appeared between some pairs of blastomeres in morulae. In blastocysts, zonula occludens, zonula adherens, desmosomes, predesmosomes and gap junctions existed between each pair of trophoblast cells, and predesmosomes and gap junctions existed between every two inner-cell-mass cells and between a trophoblast cell and an inner-cell-mass cell. The kinds and locations of junctional complexes observed in parthenogenetic embryos and the developmental stages of their appearance did not differ from those of fertilized embryos. The location of actin and cytokeratin in parthenogenetic embryos was also similar to that in fertilized embryos, whereas in parthenogenetic embryos at the morula and blastocyst stages, there existed a small number of blastomeres or cells devoid of these proteins. From these results, it was inferred that the cell-binding in parthenogenetic embryos is comparable to that of fertilized embryos.
