Institute of Human Genetics, Department of Pediatric Pathology, Johannes Gutenberg University, Mainz, Germany.
Am J Pathol. 2010 Mar;176(3):1084-90. doi: 10.2353/ajpath.2010.090764. Epub 2010 Jan 21.
Imprinted genes play an important role in fetal and placental development. Using quantitative bisulfite pyrosequencing assays, we determined the DNA methylation levels at two paternally methylated (H19 and MEG3) and four maternally methylated (LIT1, NESP55, PEG3, and SNRPN) imprinted regions in fetal muscle samples from abortions and stillbirths. Two of 55 (4%) spontaneous abortions and 10 of 57 (18%) stillbirths displayed hypermethylation in multiple genes. Interestingly, none of 34 induced abortions had extreme methylation values in multiple genes. All but two abortions/stillbirths with multiple methylation abnormalities were male, indicating that the male embryo may be more susceptible to excess methylation. Hypermethylation of multiple imprinted genes is consistent with stochastic failures of the mechanism, which normally protects the hypomethylated allele from de novo methylation after fertilization. Two of six informative abortions/stillbirths with H19 hypermethylation revealed significant biallelic expression of the autocrine growth factor IGF2. In two other cases hypermethylation of MEG3 was associated with transcriptional down-regulation. We propose that primary epimutations resulting in inappropriate methylation and expression patterns of imprinted genes may contribute to both normal human variation and disease, in particular spontaneous pregnancy loss.
印迹基因在胎儿和胎盘发育中发挥重要作用。我们使用定量亚硫酸氢盐焦磷酸测序检测了来自流产和死胎的胎儿肌肉样本中两个父源甲基化（H19 和 MEG3）和四个母源甲基化（LIT1、NESP55、PEG3 和 SNRPN）印迹区域的 DNA 甲基化水平。在 55 例自发流产中，有 2 例（4%）和在 57 例死胎中，有 10 例（18%）存在多个基因的过度甲基化。有趣的是，在 34 例人工流产中，没有一个基因出现多个基因的极端甲基化值。除了两个具有多个甲基化异常的流产/死胎外，所有其他的都是男性，这表明男性胚胎可能更容易受到过度甲基化的影响。多个印迹基因的过度甲基化与随机机制失效一致，该机制通常可以防止受精后去甲基化等位基因的从头甲基化。在 6 例有 H19 过度甲基化的可分析流产/死胎中，有 2 例存在自分泌生长因子 IGF2 的显著双等位基因表达。在另外两个病例中，MEG3 的过度甲基化与转录下调有关。我们提出，导致印迹基因异常甲基化和表达模式的原发性表观突变可能导致正常的人类变异和疾病，特别是自发性妊娠丢失。
