Array-based DNA methylation profiling in peripheral blood leukocytes of 30 infertile men with impaired spermatogenesis as compared to 10 fertile men using the Illumina Infinium HumanMethylation 450k Bead Chip reveald 471 CpG sites (287 genes) to be differentially methylated between both groups. These CpG loci were significantly enriched for the gene ontology functions MHC class II receptor activity and piRNA binding. The latter was associated with two methylation-sensitive SNPs in the genes PIWIL1 and PIWIL2, respectivly, which showed significant allele distribution skewing in the infertile cohort. 445/471 differentially methylated CpGs were associated with SNPs, but 26 (15 genes) were not genomically templated and included the ENO1, MTA2, BRSK2 and LBX2 genes previously associated with fertility and spermatogenesis. The study identifies surrogate DNA methylation markers for idiopathic infertility in peripheral blood and suggests allele-specific DNA methylation differences at regulatory sites of genes involved in piRNA regulation to be associated with disturbed spermatogenesis.
Bisulfite converted DNA of peripheral blood leukocytes from 30 infertile men and 10 fertile men as controls were hybridized to the Illumina Infinium HumanMethylation 450k Bead Chip.