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

Abstract

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. Mol. Reprod. Dev. 75: 707–714, 2008.