Two common SNPs in pri-miR-125a alter the mature miRNA expression and associate with recurrent pregnancy loss in a Han-Chinese population

Although there are plenty of evidence that single-nucleotide polymorphisms (SNPs) that fall within coding sequences of genes are involved in recurrent pregnancy loss (RPL), it is still unknown whether the polymorphisms in microRNAs (miRNAs) are related with RPL. In this study, we established this kind of association by confirming significant differences in genotype distribution of rs41275794 (p = 0.0005) and rs12976445 (p = 0.001) within the pri-miR-125a in 217 Han Chinese patients of RPL compared with 431 controls. Based on this observation, two-locus haplotypes were constructed and the A-T haplotype was found to be associated with an increased risk of RPL (OR = 2.84, 95% C. I. 1.98-4.07, p = 0.0000000057). Further analysis showed that the levels of pre- and mature-miR-125a were downregulated in the cells transfected with the A-T haplotype, which was consistent with in vivo detection that the level of mature miR-125a was lower in 30 pregnant women with A-T haplotype than that with G-C haplotype. During in vitro RNA processing assays, we found a similar decrease in the amount of pre-miR-125a and increase in binding capacity of nuclear factors to pri-miR-125a with A-T haplotype. More importantly, the reduction in miR-125a, as a consequence of A-T haplotype, further led to less efficient inhibition of target genes, LIFR and ERBB2, which play important roles in the embryo implantation and decidualization. Thus, our data collectively suggest that two common polymorphisms in pre-miR-125a might contribute to the genetic predisposition to RPL by disrupting the production of miR-125a, which consequently interfered in the expression and function of target genes of miR-125a.