ABSTRACT
OBJECTIVE: To identify CpG sites differentially methylated in peripheral blood of men with idiopathic infertility due to impaired spermatogenesis as compared with fertile controls. DESIGN: DNA methylation profiling on peripheral blood samples using the HumanMethylation450 BeadChip (Illumina) in patients and controls, single-nucleotide polymorphism (SNP) typing by Sanger sequencing. SETTING: University institute in cooperation with genetic and infertility clinics. PATIENT(S): 30 infertile men with normal CFTR and AZF tests and karyotype, and 10 fertile male controls. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): DNA methylation levels at CpG sites. RESULT(S): We identified 471 CpGs (287 genes) as differentially methylated between patients and controls. These were significantly enriched for the gene ontology functions MHC class II receptor activity and piwi-interacting (piRNA) binding. The latter was associated with two methylation-sensitive SNPs in the genes PIWIL1 and PIWIL2, respectively, which showed significant allele distribution skewing in the infertile cohort. We found that 445 (94.5%) of 471 differentially methylated CpGs were associated with SNPs, but 26 (15 genes) were not genomically templated, including the ENO1, MTA2, BRSK2, and LBX2 genes previously associated with fertility and spermatogenesis. CONCLUSION(S): Our study identifies surrogate DNA methylation markers for idiopathic infertility in peripheral blood and suggests that allele-specific DNA methylation differences at regulatory sites of genes involved in piRNA regulation are associated with disturbed spermatogenesis.
