BRCA1 expression on bovine pre-implantation embryos produced by in vitro fertilization

Abstract: The present study was conducted to examine the expression and localization of BRCA1 on pre-implantation bovine embryos, at the 2-cell embryo, 8-cell embryo, morula, blastocyst, and hatched blastocyst stages, that were produced by in vitro fertilization of Japanese Black cattle. Expression levels on the embryos of BRCA1 mRNA were assayed by real-time RT-PCR and did not significantly differ among the stages. BRCA1 protein expression by immunohistochemical analysis was found across the entire surface of the blastomeres except at the points of contact between adjacent blastomeres at the 2-cell, 8-cell, and morula stages. In addition, the percentage of embryos in which BRCA1 protein was localized in the nucleus increased as embryonic development progressed from the 2-cell to morula stages. No expression was observed in the inner cell mass of any blastocyst or hatched blastocyst, but BRCA1 protein was expressed in the nucleus or cytoplasm of trophectoderm cells. These results suggest that bovine BRCA1 may play a role in the regulation of the cell cycle and DNA repair in the early embryo.