Characterization of porcine growth differentiation factor-9 and its expression in oocyte maturation.

During follicular development, the importance of the interaction between oocytes and somatic cells is well-known for maturation oocyte. Growth differentiation factor-9 (gdf-9) is thought to play an important role in such process. In this study, we characterized porcine gdf-9 gene and investigate its expression during development. Also we determined its expression by different hormones during in vitro oocyte maturation. Overall length of pig gdf-9 cDNA was cloned and its presumptive protein sequence of isolated cDNA has high homology to human or mouse GDF-9 sequences. The gdf-9 transcript was expressed in all stage of preimplantation embryos and fetuses, and was also expressed in the heart, brain, cumulus cells, spleen, ovary, and testis. Porcine GDF-9 protein was specifically localized in in vitro matured oocyte and oocytes from adult ovary. In order to investigate the potential regulator of gdf-9 gene expression, expression level of gdf-9 gene was determined using serum-free in vitro maturation (IVM) system. Supplementing with human chorionic gonadotrophin (hCG), pregnant mare serum gonadotrophin (PMSG), gonadotropin-releasing hormone (GnRH), follicular stimulating hormone, luteinizing hormone (LH), or epidermal growth factor (EGF) did not affect level of gdf-9 gene expression during ooycte maturation. In conclusion, porcine gdf-9 gene is expressed in the porcine reproductive organ, especially in oocytes and embryos, and its expression is decreased during IVM.