Effects of E2 binding enzyme UBC9 on porcine oocyte maturation, apoptosis and embryo development

SUMOylation is a dynamic post-translational modification process. However, the function of small ubiquitin-like modifiers (SUMOs) in the maturation of porcine oocytes and embryo growth is not well known. Therefore, the aim of this study was to investigate the effect of E2 binding enzyme UBC9 on the expression of SUMO-1 protein during the in vitro maturation of porcine oocytes and embryo development after in vitro fertilization. Four groups were used: 0 (Control), 5, 10 and 15 µg/ml UBC9. Western blotting, flow cytometry and RT-qPCR were used to detect the in vitro maturation of porcine oocytes, SUMO-1 content, viability and the expression of apoptotic genes. Compared to those in the control treatment, the maturation rate (p < .05) and viability (p < .01) of oocytes in the 5 μg/ml treatment group decreased significantly. SUMO-1 protein markers appeared at 59 and 71 kDa and the content of SUMO-1 protein in the 10 µg/ml treatment group decreased significantly (p < .05). In the expression of apoptosis-related genes, Bcl-2 gene expression was significantly downregulated in the 10 μg/ml treatment group (p < .05). However, Bax and Caspase-3 were significantly upregulated in the 5 μg/ml treatment group (p < .05). During embryonic development, the cleavage rate of oocytes in the 10 µg/ml treatment group was significantly reduced (p < .05), whereas blastocyst formation rate in the 5 µg/ml treatment group was significantly reduced. UBC9 regulates SUMO-1 content in mature pig oocytes in vitro, which affects oocyte maturation rate, viability, apoptotic genes expression and embryo development after fertilization.