Influence of variation in global sperm DNA methylation level on the expression level of protamine genes and human semen parameters.

An infertility problem is a complex issue that affects 15% approximately of couples worldwide. The current study was designed to evaluate if there is a variation in the status of global DNA methylation among the study groups and to assess their impact on the protamine expression level and human semen parameters. Totalling 200 semen samples were collected from men (50 proved fertile, 60 normospermia and 90 oligospermia) with an average age of 34.9 ± 4.3 years. The DNA and RNA were isolated from purified spermatozoa; then, ELISA and qPCR were applied to estimate the status of global sperm DNA methylation and protamine expression level respectively. Besides that, the sperm chromatin decondensation and sperm DNA fragmentation were assessed. A significant variation was found in the global sperm DNA methylation and the protamine 1 and protamine 2 expression level among the study groups (p ≤ .001). Down-regulation has been found in the protamine 1 and protamine 2 expression levels in the oligospermia group compared to the proved fertile group with fold change (0.001 and 0.0002 respectively). In conclusion, this study proposes that the alteration in global DNA methylation may influence the protamine expression level and may be lead to abnormalities in human semen parameters.