Pre- and post-implantation development of parthenogenetic embryos induced by progesterone, and birth of aggregation chimeras with diploids in mice

We have previously demonstrated that parthenogenetic activation of mouse oocytes can be induced by exposure to 100 micro M progesterone for 6 h, and activated eggs developed to the blastocyst stage. Here we examined the pre- and post-implantation development of these parthenogenones in mice, and whether they could be rescued and develop to term by forming aggregation chimeras with in vivo-derived embryos or triploids. When these parthenogenetic embryos were diploidized by 5 micro g/ml cytochalasin B, 23% of them developed to the blastocyst stage, and the implantation rate was 51% after transfer to recipients, live parthenogenetic fetuses were also found on day 10.5 of gestation, but parthenogenones could not survive beyond day 10.5 of gestation. To rescue these lethal parthenogenetic embryos, aggregation chimeras of parthenogenones and in vivo-derived embryos were made at the 4-cell stage. Sixty six percent of chimeric embryos which developed to single blastocysts were transferred to 8 recipients. Two of them delivered a total of nine live pups, and one of them was chimeric. In the present study we confirmed that parthenogenetic mouse embryos, even when activated by progesterone, developed to the mid-gestation stage, and could be rescued by forming chimeras consisted of parthenogenetic and diploid embryos. On the other hand, aggregation chimeras derived from parthenogenetic and triploid embryos were lethal after implantation.