Methylation pattern of methylene tetrahydrofolate reductase and small nuclear ribonucleoprotein polypeptide N promoters in oligoasthenospermia: a case-control study.

Alterations in DNA methylation patterns in several genes may lead to abnormal male sexual development and infertility. This study investigated the promoter methylation status of MTHFR and SNRPN in infertile men from Romania by quantitative methylation-specific PCR in order to investigate possible correlations with sperm abnormalities. The study groups included patients (n=27) with a median age of 31 years (range 26-41 years) as well as controls (n=11) with a median age of 30 years (range 24-37 years) recruited from couples seeking advice for infertility. DNA was isolated from sperm samples and promoter methylation was assessed using direct. Significant trends were detected for both genes that indicate a tendency towards promoter hypermethylation in spermatozoa with low motility (MTHFR P=0.0032, r=0.23; SNRPN P=0.0003, r=0.32) and poor morphology (MTHFR P=0.0012, r=0.27; SNRPN P=0.0003, r=0.33) but no trend was found in cases of low sperm count (MTHFR r=0.007; SNRPN r=0.06). The data indicate that the methylation patterns of the promoters of MTHFR and SNRPN are associated with changes in sperm motility and morphology, which could lead to male infertility. A large number of studies are now focused on the causes of male infertility. Among these are epigenetic modifications, which are important contributors to reproductive pathology in the male by providing dynamic changes of the phenotype according to the environmental and metabolic factors. The most known epigenetic modification is DNA methylation and alterations in this pattern in several genes could induce male infertility. The present study aims to investigate the promoter methylation status of the genes for methylene tetrahydrofolate reductase (MTHFR) and small nuclear ribonucleoprotein polypeptide N (SNRPN) in infertile males from Romania, in order to establish a correlation with sperm parameters. MTHFR is an enzyme involved in the folate pathway and in de novo nucleotide biosynthesis but also a good example for gene-environment interaction in phenotype development. SNRPN is involved in both somatic cell expression and inheritance of the imprint and the methylation pattern of its gene seems to correlate not only with imprinted disorders but also with infertility. Our study includes patients (n=27, median age 31 years, range 26-41 years) recruited from men seeking advice for couple infertility and control group (n=11, median age 30.5 years, range 24-37 years). The data we obtained indicated significant correlations between hypermethylation of the investigated genes and sperm motility and morphology. No significant correlation between DNA methylation and sperm number was found. Our data suggest that methylation pattern of MTHFR and SNRPN is linked with sperm anomalies of motility and morphology and therefore male infertility.