Evaluation of DNA methylation at imprinted DMRs in the spermatozoa of oligozoospermic men in association withMTHFRC677T genotype

Abstract

SUMMARYAltered DNA methylation has been previously identified in the spermatozoa of infertile men; however, the origins of these errors are poorly understood. DNA methylation is an epigenetic modification which is thought to play a fundamental role in male germline development. DNA methylation reactions rely on the cellular availability of methyl donors, which are primarily products of folate metabolism, where a key enzyme is methylenetetrahydrofolate reductase (MTHFR). The MTHFR C677T single nucleotide polymorphism (SNP) reduces enzyme activity and may potentially alter DNA methylation processes during germline development. The objective of this study was to determine whether altered DNA methylation in spermatozoa is associated with the MTHFR C677T SNP. DNA methylation was evaluated at the H19, IG-GTL2, and MEST imprinted differentially methylated regions in the spermatozoa of 53 men -44 oligozoospermic men and nine fertile men with normal sperm parameters via bisulfite sequencing of sperm clones. The 44 infertile men were stratified by severity of oligozoospermia -three normal (>15 million spermatozoa/mL), eight moderate (5-15 million spermatozoa/mL), 23 severe (1-5 million spermatozoa/mL), and 10 very severe (<1 million spermatozoa/mL). MTHFR C677T SNP genotyping was conducted in a subset of 44 peripheral blood samples via restriction fragment length polymorphism. A total of three men -severe oligozoospermic and CT genotype -were found to be altered, which is defined as having ≥50% of their clones altered, where an altered clone was in turn defined as ≥50% of CpGs with incorrect DNA methylation patterns. The incidence of three altered men within the CT subgroup, however, was not significantly higher than the incidence in the CC subgroup. Taken together, altered DNA methylation in spermatozoa was not significantly associated with the MTHFR C677T SNP; however, there was a trend for higher incidence of alterations among severe oligozoospermic infertile men with CT genotypes.

Methylenetetrahydrofolate reductase and psychiatric diseases

“…Those reports suggested a MTHFR polymorphism independent mechanism in aging and cell-type specific global DNA methylation. Furthermore, a similar results were reported in a study of individuals with or without oligozoospermic which showed no significant association between DNA methylation in spermatozoa and the MTHFR C677T genotypes although a trend for higher incidence of methylation alterations in severe oligozoospermic infertile men with CT genotypes were observed 34 , suggesting that a much more complicated or indirect interactions between MTHFR polymorphism and methylation are involved.…”

Epigenetics of Male Infertility: The Role of DNA Methylation

“…Contrariwise, no correlation was found between methylation errors at H19 and MEST genes and inactivating MTHFR C677T single-nucleotide polymorphism (SNP) [a cytosine (C) to a thymine (T) substitution at position 677] in sperm DNA from infertile patients with defective semen parameters. However, a higher incidence trend of aberrant DNA methylation among severe oligozoospermic infertile males carrying C677T genotype was observed (Louie et al, 2016).…”

Sperm miR‐15a and miR‐29b are associated with bull fertility

“…Methylated regions of imprinted genes are established during spermatogenesis and maintained in mature spermatozoa by DNMT1 (Tang et al, ). Recently, a study demonstrated that abnormal DNA methylation‐mediated genomic imprinting is associated with oligozoospermia in men (Louie et al, ). In addition, DNA methylation levels in human spermatozoa from patients with unexplained infertility had different methylation patterns when compared to those of fertile men (Urdinguio et al, ).…”