Altered Methyltransferase Gene Expression, Mitochondrial Copy Number, and 4977-bp Common Deletion in Subfertile Men with Variable Sperm Parameters

Background: Semen parameters have been found to poorly predict reproductive success yet are the most prevalent diagnostic tool for male infertility. There are few but conflicting reports regarding the correlation of DNA methyltransferase (DNMT) genes expression, mitochondrial DNA copy number (mtDNAcn), and deletion (mtDNAdel) with different sperm parameters. This study performed to investigate DNMT mRNA level, mtDNAcn, and deletion in infertile men with different sperm parameters compared with fertile men. Methods: Semen samples from 30 men with unknown male infertility and normal sperm parameters (experimental group I), 30 infertile patients with at least two abnormal sperm parameters (experimental group II), and 30 fertile normozoospermic men (control group) were collected. After semen analysis, total RNA and DNA were extracted. Isolated DNA was used for assessing the respective mtDNAcn and the presence of 4977-bp common deletion in mtDNA by applying real-time quantitative polymerase chain reaction (PCR) and multiplex PCR, respectively. Synthesized cDNA from total RNAs was used to quantify DNMT1, DNMT3A, and DNMT3B transcripts in the study groups using real-time quantitative reverse-transcription PCR. Results: Significantly higher proportions of mtDNAcn were found in experimental group II. DNMT1 was significantly down-regulated in both experimental groups. 4977-bp deletion was not detected. Progressive motility and normal morphology were significantly and negatively correlated with mtDNAcn. A significant positive correlation was detected between sperm parameters and DNMT1 mRNA levels. Conclusion: Infertile men with different sperm parameter qualities showed elevated mtDNA content. mtDNAcn could serve as a non-invasive biomarker in male infertility namely in unknown cases. Abnormal sperm parameters are associated with DNMT1 gene expression, indicating the possibility of changes in some epigenetic aspects of spermatogenesis in subfertile men with different sperm parameters. Keywords * Spermatozoa * Methyltransferases * Infertility * Gene expression