Developmental ability of trophoblast stem cells in uniparental mouse embryos

Neither parthenogenetic (PG) nor androgenetic (AG) mouse embryos survive after day 9.5 of pregnancy, owing to the inadequate growth of extraembryonic tissues, including the placenta. At day 9.5 of pregnancy, the placental structures are poorly developed in PG embryos, while trophoblast giant cells are abundant at the implantation site in AG embryos. These findings suggest that both parental genomes are required for placental development. To gain further insight into the trophoblast lineage in PG and AG embryos, we attempted to derive trophoblast stem (TS)-like cell lines from uniparental embryos. Furthermore, we sought to assess their ability to differentiate into cells of the trophoblast lineage by using gene expression analysis. Three cell lines that expressed marker genes for undifferentiated TS cells (Cdx2 and Errbeta) were derived from AG embryos. Under differentiation conditions, these cells expressed the trophoblast giant cell-specific genes, but did not express the spongiotrophoblast-specific genes. In contrast, none of the four cell lines from PG embryos expressed marker genes for undifferentiated TS cells, but they expressed Oct3/4, a marker gene for embryonic stem cells. Immunohistochemical analysis indicated that PG blastocysts expressed Oct3/4 and Cdx2 specifically in inner cell mass and the trophectoderm respectively. These results suggest that PG embryos do not possess TS cells, because of the lack of the developmental ability of trophoblast cells.