Protein synthesis in microsurgically produced androgenetic and gynogenetic mouse embryos.

In order to compare paternal and maternal gene activity at the protein synthesis level during early development, androgenetic and gynogenetic mouse embryos were experimentally produced by microsurgically removing either the female or the male pronucleus from fertilized mouse eggs. The resulting haploid eggs were diploidized in a medium containing cytochalasin B and then cultured under normal conditions to the blastocyst stage. Protein synthesis was analyzed at different stages of preimplantation development using 2-dimensional polyacrylamide gel electrophoresis. Both types of uniparental embryos synthesized a similar set of proteins independent of whether the paternal or the maternal genome was present. The isodiploid embryos expressed a protein pattern that corresponded remarkably to normal embryos at the subsequent cleavage stage. This temporal change is probably due to the fact that the operated haploid eggs were kept overnight in cytochalasin B in order to allow chromosomal replication to occur without cell division, and the resulting eggs therefore corresponded to normal 2-cell embryos with respect to karyokinesis but differed as far as cytokinesis was concerned. Several 2-cell specific proteins appeared in these isodiploid eggs and, similarly, following their first cleavage some 4-cell specific proteins were detected in 2-cell androgenetic and gynogenetic embryos. The discordance between nuclear and cellular division, which was retained through the 4-cell stage, however disappeared during subsequent cleavage divisions. At the blastocyst stage, both kinds of uniparental embryos showed a similar protein pattern compared to normal embryos. Our data suggest that some stage-specific proteins are synthesized during preimplantation development and correspond to nuclear rather than cellular divisions.