Sexing of in vitro-fertilized preimplantation mouse embryos by the PCR method.

The applicability of the dual PCR method to embryo sexing was examined with the aim of establishing a noninvasive method of preimplantation diagnosis for human genetic disorders. Mouse pre-embryos obtained by in vitro fertilization were studied. The Sry gene sequence and the myogenin sequence were amplified as the Y-specific and internal control sequences, respectively. Amplification of as little as 10 pg of mouse genomic DNA was possible with the dual PCR method, the sensitivity being 10-fold greater than that of the single PCR method. The sex was identified in 100% (24/24) and 96% (23/24) of the pre-embryos tested at the 16- and 4-cell stages, respectively. In addition, the sex of all four single blastomeres dissociated from 4-cell pre-embryos agreed in 76% (16/21) of the specimens tested and 94% (79/84) of dissociated blastomeres could be sexed. The sex of single blastomeres biopsied from pre-embryos at the 8-cell stage could be identified. After transfer of 13 male and 25 female sexed pre-embryos, six viable fetuses were obtained. Histological examination showed that all these fetuses were of the predicted sex. Sexing of biopsied single blastomeres by the dual PCR method was rapid and reliable, suggesting its feasibility for preimplantation diagnosis of in vitro fertilized human pre-embryos.