Effects of Heat Stress on Epigenetic Modifications and Developmental Competence of Bovine Oocytes and Their Embryos
The aim of this study was to investigate the effects of heat stress on epigenetic modifi-cations and developmental capacity of bovine oocytes and their embryos.In this study,oocytes were cultured under in vitro heat stress conditions(41 ℃ for 12 h+38.5 ℃ for 12 h)for in vitro maturation(IVM)and in vitro fertilization(IVF).The developmental ability of oocytes and embryos and the modification levels of epigenetic modifications histone H1,histone H2,histone H4,and DNA methylation were examined in control(38.5 ℃ for 24 h)and heat-stressed cattle.In this study,we also examined oocyte reactive oxygen species(ROS)levels,mitochondrial membrane potential(△Ψm)levels,and expression levels of genes associated with epigenetic modifications and developmental competence.The results showed that the maturation rate((59.21±4.29)％),oocyte cleavage rate((57.78±4.58)％)and blastocyst rate((22.31±1.67)％)of the heat stress treatment group were significantly lower than those of the control group((85.10±6.75)％,(78.64±2.46)％,and(42.64±1.38)％,P＜0.05);The levels of epigenetic modifications histone H1,histone H2,histone H4,and DNA methylation of bovine oocytes and embryos at all stages in the heat stress group were significantly lower than those of the control group(P＜0.05);the level of △Ψm of bovine oocytes in the heat stress group was significantly lower than that of the control group(P＜0.05);the level of ROS in bovine oocytes of heat stress group was significantly higher than that of the control group(P＜0.05);the mRNA expression levels of genes related to epigenetic modification of bovine oocytes DNMT1,DNMT3A,DNMT3B,Histone H2A,SMYD3,and IGF-2R were significantly lower in the heat stress group than in the control group(P＜0.05);the mRNA expression levels of the genes C-MOS,GDF-9 and POU5F1 related to oocyte developmental competence were significantly lower in the heat stress group than in the control group(P＜0.05).The results showed that heat stress significantly reduced the levels of epigenetic modifications histone H1,histone H2,histone H4,and DNA methylation,significantly decreased the levels of △Ψm and mRNA expression of genes related to epigenetic modifications and developmental competence,and significantly increased the levels of ROS and reduced the quality of bovine oocytes and embryos.
万方数据
维普
