Key Laboratory of Animal Reproductive Physiology & Embryo Technology, Institution of biotechnology, College of Veterinary Medicine, Northwest A & F University, Yangling 712100, China.
J Genet Genomics. 2010 May;37(5):297-304. doi: 10.1016/S1673-8527(09)60047-3.
In order to investigate DNA methylation profiles of five pluripotency-related genes (Oct4, Sox2, Nanog, Rex1 and Fgf4) during bovine maternal to zygotic transition (MZT) in both in vitro fertilized (IVF) and nuclear transfer (NT) embryos, sodium bisulfite sequencing method was used to detect DNA methylation levels, accompanied by the statistical analysis of embryo developmental rates. The results showed that Oct4, Nanog, Rex1 and Fgf4 were respectively demethylated by 25.22% (P < 0.01), 3.84% (P > 0.05), 31.82% (P < 0.01) and 10% (P > 0.05) while Sox2 retained unmethylation during MZT in IVF embryos. By contrast, Oct4 and Rex1 respectively underwent demethylation by 23.04% (P < 0.01) and 6.02% (P > 0.05), and, reversely, Sox2, Nanog and Fgf4 respectively experienced remethylation by 0.84% (P > 0.05), 5.39% (P > 0.05) and 5.46% (P > 0.05) during MZT in NT embryos. Interestingly, the CpG 14 site of Sox2 was specifically methylated in both 8-cell and morula NT embryos. In addition, the development of blastocysts between IVF and NT embryos showed no significant difference. DNA methylation analysis showed that only Oct4 and Sox2 underwent the correct methylation reprogramming process, which may be responsible for the development of blastocysts of NT embryos to a certain extent. In conclusion, the five genes respectively experienced demethylation to different extents and incomplete DNA methylation reprogramming during bovine MZT in both IVF and NT embryos, suggesting that they may be used as indicators for bovine embryo developmental competence.
为了研究体外受精（IVF）和核移植（NT）胚胎中牛母-合子过渡（MZT）期间五个多能性相关基因（Oct4、Sox2、Nanog、Rex1 和 Fgf4）的 DNA 甲基化谱，采用亚硫酸氢盐测序法检测 DNA 甲基化水平，并对胚胎发育率进行了统计分析。结果表明，在 IVF 胚胎中，Oct4、Nanog、Rex1 和 Fgf4 分别去甲基化 25.22%（P<0.01）、3.84%（P>0.05）、31.82%（P<0.01）和 10%（P>0.05），而 Sox2 在 MZT 期间保持未甲基化。相比之下，Oct4 和 Rex1 分别经历了 23.04%（P<0.01）和 6.02%（P>0.05）的去甲基化，而 Sox2、Nanog 和 Fgf4 分别经历了 0.84%（P>0.05）、5.39%（P>0.05）和 5.46%（P>0.05）的重新甲基化，在 NT 胚胎中 MZT。有趣的是，Sox2 的 CpG14 位点在 8 细胞和桑椹胚 NT 胚胎中均被特异性甲基化。此外，IVF 和 NT 胚胎的囊胚发育无显著差异。DNA 甲基化分析表明，只有 Oct4 和 Sox2 经历了正确的甲基化重编程过程，这可能在一定程度上负责 NT 胚胎囊胚的发育。总之，在 IVF 和 NT 胚胎的牛 MZT 期间，五个基因分别经历了不同程度和不完全的 DNA 甲基化重编程，表明它们可能被用作牛胚胎发育能力的指标。
