[Methylation level of MEG3 and semen quality]

To study the relationship between semen quality and the methylation level of maternally expressed gene 3 (MEG3) in sperm.

We collected the general demographic data, semen samples and results of clinical semen analysis from 403 married men undergoing pre-conception examinations in March and April 2015 and March and April 2016. Using pyrosequencing, we quantitatively detected the methylation level at 8 CpG sites in the differentially methylated region of MEG3, and subjected the data obtained to variance analysis, Pearson correlation analysis, two-sample t-test and multivariate linear regression analysis.

Both the individual and mean methylation levels at CpG sites 1－8 of MEG3 were correlated highly negatively with sperm concentration (P < 0.05), but not with the semen volume, sperm motility, or the percentage of morphologically normal sperm (P > 0.05). The men with an abnormal sperm concentration exhibited significantly higher individual and mean methylation levels at the 8 CpG sites than those with a normal one (P < 0.05). After adjusting for age as a confounding factor, multivariate linear regression analysis showed a decrease of 1.684 × 106/mL in sperm concentration for every 1% increase in the average methylation of MEG3 (P < 0.05).

The imprinting gene MEG3 is involved in spermatogenesis and its methylation level may influence sperm concentration.