Epigenetic status of imprinted genes in placenta during recurrent pregnancy loss

An analysis of differential methylation of 47 imprinted genes in placenta tissues of spontaneous abortions at the first trimester of pregnancy from women with recurrent pregnancy loss or with one sporadic abortion was performed using the DNA-microarray approach. We showed that epimutations of the imprinted genes were registered significantly more often in abortions from women with recurrent miscarriage in contrast to the embryos from women with sporadic pregnancy loss with frequency of 6.2 and 3.7% per locus, respectively (p < 0.01). The predominant type of epimutation appeared to be a postzygotic hypomethylation of the imprinted genes on chromosomes of maternal origin, which was observed in the examined samples in 5.1 and 2.89% of cases, respectively. Replicative study of the methylation status of seven imprinted genes (DLK1, PEG10, PLAGL1, KCNQ1OT1, PEG3, GRB10, and PEG1/MEST) in the enlarged embryo samples supported the results of microarray analysis in respect to both epimutation frequency and predominance of somatic hypomethylation of maternal alleles. It was also demonstrated that pregnancy loss was associated with multilocus methylation defects of imprinted genes, the frequency of which was also significantly increased in the placental tissues of spontaneous abortions in women with recurrent miscarriage.