INSERM U846, Institut Cellule Souche et Cerveau, 18 Av Doyen Lépine, Bron 69500, France.
Hum Reprod. 2012 Oct;27(10):2948-54. doi: 10.1093/humrep/des284. Epub 2012 Aug 21.
What is the methylation status of the Nanog and Oct4 promoters in human gametes and ICSI embryos and is abnormal reprogramming of their methylation associated with developmental failure of ICSI embryos?
Developmental failure of human ICSI embryos is associated with high methylation of the Oct4 promoter.
Nanog and Oct4 genes play critical roles in the establishment and maintenance of pluripotency during normal early embryonic development, and both are negatively regulated through the methylation of their promoters.
STUDY DESIGN, SIZE AND DURATION: We analysed the methylation profile of Nanog and Oct4 promoters in 5 control sperm from normally fertile men, 70 metaphase II oocytes, 21 4-cell control ICSI embryos, 7 control blastocysts and 45 ICSI embryos arrested at 2- to 8-cell stage following prolonged culture.
PARTICIPANTS, MATERIALS, SETTING AND METHODS: Embryos and gametes were donated for research by patients from the Department of Reproductive Medicine at the Hôpital Femme Mère Enfant (Bron, France) and the Clinique du Tonkin (Villeurbanne, France) after giving their informed consent.
For both promoters, high methylation was observed in sperm cells. Although, in general, the promoters were unmethylated in oocytes, the methylation of some alleles was observed, particularly in oocytes from women with known infertility. Both gene promoters were hypomethylated in control blastocyst ICM (inner cell mass) and in control 2-8-cells embryos obtained from 6 out of 8 couples. However, they appeared highly methylated in embryos obtained from the other two couples. In most arrested ICSI embryos, the Nanog promoter was unmethylated while the Oct4 promoter was highly methylated. High methylation of the Oct4 promoter was significantly more pronounced in embryos from couples where a male factor was the only known cause of infertility. When the embryos were heterozygous for a G/A single nucleotide polymorphism, both alleles could be methylated, each likely representing a paternally inherited or a maternally inherited copy.
The study was done on a limited number of oocytes and embryos and the gametes of the couples were not available.
These results provide new insight regarding the roles of epigenetic abnormalities in early developmental failure in humans.
STUDY FUNDING/COMPETING INTEREST(S): No external funding was obtained for this study. There was no competing interest.
人类配子和 ICSI 胚胎中 Nanog 和 Oct4 启动子的甲基化状态如何？异常的甲基化重编程是否与 ICSI 胚胎发育失败有关？
人类 ICSI 胚胎的发育失败与 Oct4 启动子的高甲基化有关。
Nanog 和 Oct4 基因在正常早期胚胎发育过程中对多能性的建立和维持起着关键作用，它们都通过启动子的甲基化受到负调控。
研究设计、大小和持续时间：我们分析了来自 5 名正常生育男性的 5 个精子、70 个中期 II 卵母细胞、21 个 4 细胞对照 ICSI 胚胎、7 个对照囊胚和 45 个在延长培养后停留在 2-8 细胞阶段的 ICSI 胚胎中 Nanog 和 Oct4 启动子的甲基化谱。
参与者、材料、地点和方法：胚胎和配子是由法国 Bron 的 Hôpital Femme Mère Enfant （HFE）和法国 Villeurbanne 的 Clinique du Tonkin 的患者自愿捐献的，他们在知情同意的情况下同意进行研究。
两个启动子在精子细胞中都表现出高甲基化。尽管在一般情况下，卵母细胞中的启动子未被甲基化，但也观察到了一些等位基因的甲基化，特别是在不孕妇女的卵母细胞中。在 6 对夫妇中，两个基因的启动子在对照囊胚 ICM（内细胞团）和对照 2-8 细胞胚胎中都呈低甲基化。然而，在来自另外两对夫妇的胚胎中，它们的甲基化程度很高。在大多数停滞的 ICSI 胚胎中，Nanog 启动子未被甲基化，而 Oct4 启动子则高度甲基化。在男性因素是唯一已知不孕原因的胚胎中，Oct4 启动子的高甲基化更为明显。当胚胎存在 G/A 单核苷酸多态性杂合子时，两个等位基因都可以被甲基化，每个等位基因可能代表父系或母系遗传的拷贝。
这项研究只在有限数量的卵母细胞和胚胎上进行，而且夫妇的配子不可用。
这些结果为人类早期发育失败中表观遗传异常的作用提供了新的见解。
研究资金/竞争利益：本研究无外部资金支持。没有竞争利益。
