Investigation of the effects of epigenetic factors DNMT3A and DNMT3B gene expressions on male infertility

Infertility, recognized as a global public health issue, is defined as the failure to achieve clinical pregnancy after 12 months of regular, unprotected intercourse. Male infertility refers to a man's inability to cause pregnancy in a fertile woman after at least one year of unprotected intercourse. Among the causes of male infertility such as cryptorchidism, varicocele, endocrinological disorders, obstruction/absence of seminal ducts and infections, genetic alterations also stand out as important factors. Recent studies have increasingly focused on the role of epigenetics in spermatogenesis and male infertility. Epigenetic changes are regional and reversible modifications that influence gene expression without altering the DNA sequence. DNA methylation, the most common epigenetic mechanism, occurs at CpG islands in gene promoters often leading to decreased gene expression. DNA methyltransferases (DNMTs) are a family of enzymes that catalyze the transfer of methyl groups to DNA. Among them, DNMT3A and DNMT3B play a crucial role in development and are indispensable for spermatogenesis. Our study aimed to investigate changes in DNMT3A and DNMT3B gene expressions at both RNA and protein levels in infertile males diagnosed with normozoospermia and oligozoospermia. The study included 53 men (30 normozoospermic, 12 oligozoospermic, and 11 severely oligozoospermic) whose semen samples were analyzed by spermiogram. Following RNA isolation from sperm cells separated from the ejaculate plasma, DNMT3A and DNMT3B gene expression levels were analyzed using qPCR after cDNA conversion. While a notable reduction in DNMT3A expression and in both DNMT3A and DNMT3B expression levels was observed in oligozoospermia and severe oligozoospermia, this reduction was not statistically significant. However, DNMT3A expression was correlated with infertility (p<0.05). Consistent with our findings, in experimental DNMT knockout mice no association was found with DNMT3B and infertility, but DNMT3A knockout resulted in spermatogenic arrest and azoospermia. Further studies with larger sample sizes are required to validate our findings.