Methylenetetrahydrofolate reductase gene promoter hypermethylation in semen samples of infertile couples correlates with recurrent spontaneous abortion.

STUDY QUESTION: Is the methylation status of the methylenetetrahydrofolate reductase (MTHFR) promoter region in semen samples associated with 'recurrent spontaneous abortion' (RSA)? SUMMARY ANSWER: MTHFR promoter hypermethylation is more frequent in semen samples from RSA couples than in semen samples from infertile couples with no history of RSA (NRSA) and affects the whole sperm population significantly more often. WHAT IS KNOWN ALREADY: Modifications to the MTHFR gene such as polymorphisms and promoter methylations are associated with male infertility. STUDY DESIGN, SIZE AND DURATION: Retrospective cohort study of semen samples from 20 RSA couples, 147 NRSA couples and 20 fertile men between 2011 and 2012. MATERIALS, SETTING AND METHODS: DNA from the semen samples of RSA, NRSA and fertile men were analyzed by methylation-specific PCR amplification using primers which anneal to the methylated or unmethylated cytosine-phosphodiester bond guanine (CpG) islands within the promoter region of MTHFR. The specificity of the PCR products was assessed by DNA sequencing. MAIN RESULTS AND THE ROLE OF CHANCE: The methylated MTHFR epigenotype (including samples where it co-existed with unmethylated MTHFR epigenotypes) was detected in 75% of RSA men, 54% of NRSA men and 15% of fertile men. MTHFR methylation was observed in the whole sperm population in semen samples from 55% of RSA men compared with 8% in NRSA men (P < 0.05) and 0% in fertile men (P < 0.05). DNA sequencing analysis was fully concordant with the PCR results and revealed that when MTHFR methylation occurred, CpG islands within the promoter region were 100% methylated (hypermethylation of MTHFR promoter). LIMITATIONS, REASONS FOR CAUTION: The relatively small sample size of RSA infertile couples. WIDER IMPLICATIONS OF THE FINDINGS: The hypermethylation of the MTHFR gene promoter should be taken into consideration as a novel putative risk factor in RSA etiology. STUDY FUNDING/COMPETING INTEREST(S): Our institution has received an FAR research grant from the University of Ferrara, Ferrara, Italy. No competing interests declared.