DNA methylation level of spermatozoa from subfertile and proven fertile and its relation to standard sperm parameters.

The epigenetic mechanism plays an important role in spermatogenesis such as DNA methylation where this episode is represented by either switching genes on or off. Twenty-eight samples (14 case and 14 controls) were subjected to Infinium 450K BeadChip arrays to identify genomic regions that differ in sperm DNA methylation patterns in the subfertile compared to the proven fertile group. Then two CpGs were validated by deep bisulphite sequencing on 82 sperm samples. The results screening study revealed eight CpGs were significantly different in their sperm DNA methylation levels between cases and control group. The results of the validation study for the two CpGs (cg19779893 and cg19406113) showed that a significant variation in the methylation level at 2 CpGs of 3 CpGs related to cg19779893 site amplicon in cases compared to the controls. Moreover, six CpGs related to the cg19406113 site amplicon showed significant differences in sperm DNA methylation between the cases and the control group. Furthermore, there was a significant decrease in the sperm parameters in the cases compared to the control group. This study found two CpGs altered in their sperm DNA methylation levels. In addition, a strong association was found between changes in the sperm DNA methylation levels in these CpGs sites and sperm parameters.

Relationship between nuclear DNA fragmentation, mitochondrial DNA damage and standard sperm parameters in spermatozoa of fertile and sub-fertile men before and after freeze-thawing procedure.

The aim of this study was to assess the stability of nuclear and mitochondrial DNA (n-DNA and mt-DNA) of spermatozoa under freeze-thawing and to find out the correlation between them and their association with standard sperm parameters. Forty-three semen samples were collected from fertile (G.1; n = 29) and sub-fertile (G.2; n = 14). N-DNA fragmentation was determined by TUNEL assay and mt-DNA using caspase 3 staining. Each semen sample was frozen at -196°C by the programmed freezer. Freeze-thawing decrease vitality, total motility and membrane integrity from (43.02 ± 22.74%; 31.63 ± 18.15%; 51.5 ± 24.82%) to (22.71 ± 17.3%; 9.21 ± 6.61%; 34.64 ± 19.92% respectively [p < .001]). G.1 native spermatozoa stained positive with TUNEL and caspase 3 were (14.85 ± 17.6% and 5.8 ± 11.59%) and increased after freeze-thawing to 27.54 ± 19.74% (p = .004) and 7.3 ± 6.13% (p = .01) respectively. In G.2, TUNEL and caspase 3 were (19.84 ± 17.52% and 7.53 ± 8.56%) and increased to (29.48 ± 16.97% [p = .03] and 10.21 ± 11.73%). In conclusion, freeze-thawing process affects not only semen parameters but also n-DNA and mt-DNA. Therefore, n-DNA and mt-DNA could be used as sensitive parameters for assessment of the cryodamage of human spermatozoa.

Impact of cigarette-smoking on sperm DNA methylation and its effect on sperm parameters.

DNA methylation is an epigenetic modification of the genome. The purpose of this study was to determine the influence of cigarette-smoking on sperm DNA methylation from a genomewide survey of sperm samples and to ascertain its effect on sperm parameters. Twenty-eight sperm DNA samples (from 14 fertile smokers as a case study and 14 proven fertile nonsmokers as controls) were subjected to Infinium 450K BeadChip arrays to identify the changes in the DNA methylation level between the two groups. Then, deep bisulphite sequencing was used to validate five CpGs on 78 samples. The results from the Infinium 450K found that only 11 CpGs showed a significant difference in DNA methylation between the case and the control groups. Five CpGs of the eleven (cg00648582, cg0932376, cg19169023, cg23841288 and cg27391564) underwent deep bisulphite sequencing where cg00648582, related to the PGAM5 gene, and the cg23841288 CpGs, related to the PTPRN2 gene amplicons, showed a significant increase in their DNA methylation level in more than one CpG in the case group. In contrast, a significant decrease was found at cg19169023 and at its various neighbouring CpGs in the TYRO3 gene-related amplicons. Furthermore, this study demonstrated a significant correlation between the variation in sperm DNA methylation level and standard sperm parameters in the case group.

Aberrant DNA methylation patterns of human spermatozoa in current smoker males.

The purpose of this study was to investigate the impact of current cigarette smoking on sperm DNA methylation patterns. A total of 108 males (51 current smokers and 57 never smoked males) were included in the study. Using 450 BeadChip Arrays, the differentially methylated CpGs between current smokers (n=15) and never smoked males (n=15) were identified. Out of significantly 11 CpGs identified, 2 CpGs namely cg07869343 and cg19169023, which are located in the MAPK8IP3 and TKR genes were selected for further analysis. Using deep bisulfite sequencing in an independent cohort of current smokers (n=36) and never smoked males (n=42), 6 and 1 CpGs showed a significant difference in the MAPK8IP (CpG3, CpG5, CpG6, CpG7, CpG8, and CpG21) and in the TKR (CpG4) were identified, respectively (P≤0.05). Our results indicate that cigarette smoking causes biochemical changes in the sperm DNA methylation in many regions and could adversely affect semen parameters.

Spermatozoa from males with reduced fecundity exhibit differential DNA methylation patterns.

Infertility affects 10-15% of couples, and approximately 50% of cases are linked to male factor infertility. The purpose of this study was to evaluate the DNA methylation patterns in spermatozoa from males who are suffering from a reduction in fecundity. Thirty samples were subjected to 450K arrays as a screening study to evaluate the variation in sperm DNA methylation levels between cases and controls groups, and then four CpG sites (cg05799088, cg07227024, cg16338278, and cg08408433) underwent to deep bisulfite sequencing to validate the observed methylation differences in 111 samples (56 proven fertile males as 'controls' and 55 males suffering from a reduction in fecundity as 'cases'). A significant difference in the mean methylation level was found between cases and controls in the CpGs of PRICKLE2 gene-related amplicon (CpG1, p ≤ 0.002, and CpG2, p ≤ 0.004) and CpG of ALS2CR12 gene-related amplicon (CpG1, p ≤ 0.015, and CpG2, p ≤ 0.009). Besides, a significant difference was found at seven from thirteen CpGs tested in the ALDH3B2 gene amplicon CpG2, CpG6, CpG9, CpG10, CpG11, CpG12, and CpG13 (p ≤ 0.005, p ≤ 0.004, p ≤ 0.012, p ≤ 0.028, p ≤ 0.012, p ≤ 0.009, and p ≤ 0.001, respectively). In addition, the results showed that nine CpGs out of the twenty-six within the PTGIR gene-related amplicon (CpG4, CpG6, CpG8, CpG9, CpG11, CpG15, CpG19, CpG23, and CpG26) had a significant difference in their mean methylation level (p ≤ 0.006, p ≤ 0.009, p ≤ 0.003, p ≤ 0.003, p ≤ 0.007, p ≤ 0.002, p ≤ 0.018, p ≤ 0.018, and p ≤ 0.040, respectively) in the case vs. CONTROL GROUP: In conclusion, an alteration in the methylation levels of sperm DNA from males with reduced fecundity was observed. In addition, an association between changes in the methylation level for these CpGs and different semen parameters has been found.