DEVELOPMENTAL ARREST OF FERTILIZED-EGGS FROM THE B6.Y-DOM SEX-REVERSED FEMALE MOUSE

When the Y chromosome of a Mus musculus domesticus mouse strain is pla ced onto the C57BL/6J (B6) inbred background, the XY progeny develop o varies or ovotestes but never normal testes during fetal life. While s ome oi: the hermaphroditic males become fertile, none of the XY female s produces litters. Here, we examined the fertility and development of oocytes derived from the XY female mouse. With or without preceding i njection of gonadotropins, female mice were mated with normal B6 males , and their embryos were recovered at various developmental stages. In vitro fertilization was performed with the eggs recovered from the ov iduct after treatment with gonadotropins. Development of embryos was e xamined by both light and electron microscopy. The results indicate th at the oocytes released from the B6.y(DOM) ovary were efficiently fert ilized and often initiated the first cell cleavage, but all embryos di ed during early preimplantation periods. Even when oocytes were fertil ized in vitro, minimizing their exposure to the XY oviduct/uterus envi ronment, most embryos died at the 1- or 2-cell stage. A few exceptiona l embryos reached the 4- or 8-cell stage, but abnormalities were evide nt in both nuclear and cytoplasmic structures of all embryos. After cl eavage, neighbouring blastomeres were only loosely associated, and mic rovilli were abundant at the intercellular interfaces. We postulate th at oocytes of the B6.y(DOM) female mouse become defective during XY ov arian differentiation, and, hence, fail to proceed through normal embr yonic development. (C) 1994 Wiley-Liss, Inc.