부산대학교 도서관

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 (H19and 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 novomethylation after fertilization. Two of six informative abortions/stillbirths with H19hypermethylation revealed significant biallelic expression of the autocrine growth factor IGF2. In two other cases hypermethylation of MEG3was 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.