Growth differentiation factor 8 (GDF8) is a member of the transforming growth factor-β that has been identified as a strong physiological regulator. The purpose of this study is to investigate the effects of GDF8 on porcine oocytes during in vitro maturation (IVM). We investigated a specific gene transcription levels in oocytes and cumulus cells (CC) after IVM, and protein kinase B (PKB) expression and activation levels in matured CCs by western blotting. Each concentration (0, 1, 10, and 100 ng/ml) of GDF8 was treated in maturation medium (TCM199) while process of IVM. Data were analyzed by ANOVA followed by Duncan using SPSS (Statistical Package for Social Science). Data are presented as the mean and differences were considered significant at P < 0.05. After 44 h of IVM, oocytes are mechanically denuded from CCs with 0.1% of hyaluronidase, and then the separated each group of oocytes and CCs were sampled. To assess the effect of GDF8 on specific gene transcription level changes as a dose response during IVM, the realtime PCR was performed. In CCs, all of GDF8 treatment groups showed significantly higher CREB transcription regulator cbp mRNA and the 1- and 10 ng/ml treatment groups observed significantly increased cumulus expansion related genes areg, cox-2, has2, ptx3 and tnfaip6 transcription levels after IVM. In matured oocytes, the maternal factors jmjd3 and zar1, transcriptional regulator foxo1 and sirt1, mitochondrial activity factor sirt3 and acadl, and anti-apoptosis gene bcl-2 mRNA transcription levels were significantly increased in 1- and10 ng/mL of GDF8 treatment groups compared with control. To determine effect of GDF8 treatment during IVM, translation regulator PKB protein expression and phosphorylation levels were analyzed in CCs by western blotting. The 10 ng/ml treatment group showed significantly increased phosphorylated PKB (1.4 times higher than control) protein levels (P < 0.05). In conclusion, treatment 10 ng/ml of GDF8 during IVM activates CREB related transcription and induced cumulus cells expansion via activation of PKB signaling in CCs. The transcriptional landscape changes in CCs result maternal factors accumulation and mitochondrial activation in oocytes during IVM.

• Junchul David Yoon(Laboratory of Veterinary Embryology and Biotechnology (VETEMBIO), College of Veterinary Medicine, Chungbuk National University, Cheongju 361-763, Republic of Korea)
• Eunsong Lee(Laboratory of Theriogenology, College of Veterinary Medicine, Kangwon National University, Kangwon, Republic of Korea)
• Sang-Hwan Hyun(Laboratory of Veterinary Embryology and Biotechnology (VETEMBIO), College of Veterinary Medicine, Chungbuk National University, Cheongju 361-763, Republic of Korea)