Abstract
BackgroundMale infertility is a complex disease caused by a combination of genetic, environmental, and lifestyle factors. Abnormal epigenetic programming has been proposed as a possible mechanism compromising male fertility. Recent studies suggest that aberrant imprinting in spermatozoa in a subset of infertile men is a risk factor for congenital diseases in children conceived via assisted reproduction techniques. In this study, we examined the DNA methylation status of CpG sites within the differentially methylated regions (DMRs) of three imprinted genes, H19, GNAS, and DIRAS3, using combined bisulfite PCR restriction analysis and bisulfite sequencing in sperm obtained from 135 men with idiopathic male infertility, including normozoospermia (n = 39), moderate oligozoospermia (n = 45), and severe oligozoospermia (n = 51), and fertile controls (n = 59). The percentage of global methylation was compared between fertile controls and infertile patients displaying abnormal DNA methylation status of imprinted loci. Moreover, we also analyzed whether the DNA methyltransferases (DNMTs) polymorphisms impact upon the methylation patterns of imprinted genes in idiopathic infertile males.ResultsAberrant methylation patterns of imprinted genes were more prevalent in idiopathic infertile males, especially in patients with oligozoospermia. Infertile males with aberrant methylation patterns of imprinted genes displayed a tendency of lower global methylation levels, although not reaching statistical significance (P = 0.13). In the genotype-epigenotype correlation analysis, no significant association was observed between aberrant methylation patterns of the three imprinted genes and genotypes of the four DNA methyltransferase (DNMT) genes.ConclusionWe conclude that abnormalities of DMR within imprinted genes may be associated with idiopathic male infertility. Disruption in methylation pattern of the three imprinted genes does not occur in high-risk genotypes of DNMTs.
Highlights
Male infertility is a multifactorial disorder which affects approximately 15% of couples at reproductive age globally with substantial clinical and social impact [1]
Each group of cases and controls were well matched for age, body mass index (BMI), smoking status, and alcohol drinking (P > 0.05)
As the analyzed genes were chosen as indicators of paternal and maternal imprinting, > 90% methylation was expected for the paternally imprinted H19 and < 10% for the maternally imprinted DIRAS3 and GNAS in sperm DNA [20]
Summary
Male infertility is a multifactorial disorder which affects approximately 15% of couples at reproductive age globally with substantial clinical and social impact [1]. DNA methylation at differentially methylated regions (DMRs) is one of the regulatory mechanisms controlling the allele-specific expression of imprinted genes. Because imprinted genes escape epigenetic reprogramming after fertilization and maintain their parent-specific germline patterns, aberrant methylation imprints can be transmitted directly from the father’s sperm into the developing embryo [12]. We examined the DNA methylation status of CpG sites within the differentially methylated regions (DMRs) of three imprinted genes, H19, GNAS, and DIRAS3, using combined bisulfite PCR restriction analysis and bisulfite sequencing in sperm obtained from 135 men with idiopathic male infertility, including normozoospermia (n = 39), moderate oligozoospermia (n = 45), and severe oligozoospermia (n = 51), and fertile controls (n = 59). We analyzed whether the DNA methyltransferases (DNMTs) polymorphisms impact upon the methylation patterns of imprinted genes in idiopathic infertile males
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