Sperm global DNA methylation level: association with semen parameters and genome integrity

Abstract

SUMMARYSperm DNA methylation abnormalities have been detected in oligozoospermic men. However, the association between sperm DNA methylation defects, sperm parameters and sperm DNA, and chromatin integrity remains poorly understood. This study was designed to clarify this issue. We recruited a cohort of 92 men (62 normozoospermic and 30 oligoasthenozoospermic) presenting for infertility evaluation during a 1-year period. Sperm global DNA methylation was evaluated by an ELISA-like method, DNA fragmentation was evaluated by flow cytometry-based terminal transferase dUTP nick end-labeling (TUNEL) assay (reported as DNA fragmentation index or DFI), and sperm denaturation was evaluated by aniline blue staining (reported as sperm denaturation index or SDI, a marker of chromatin compaction). We found a significant positive association between sperm global DNA methylation level and conventional sperm parameters (sperm concentration and motility), supported by the results of methylation analysis on H19-DMR. We also identified significant inverse relationships between sperm global DNA methylation, and, both DFI and SDI. However, sperm global DNA methylation level was not related to sperm vitality or morphology. Our findings suggest that global sperm DNA methylation levels are related to conventional sperm parameters, as well as, sperm chromatin and DNA integrity.

Guidance and Self‐Sorting of Active Swimmers: 3D Periodic Arrays Increase Persistence Length of Human Sperm Selecting for the Fittest

“…Chromatin Condensation Analysis : Sperm sorted using SPARTAN were subjected to chromatin condensation analysis using the aniline dye blue test (a dye that selectively stains lysine‐rich histone proteins) and compared with sperm sorted by swim‐up and unprocessed semen as previously described 17. Briefly, sperm were washed twice in phosphate‐buffered saline (PBS), treated with 1% sodium dodecyl sulfate in sodium citrate, spread onto a glass slide and allowed to dry.…”

“…With ICSI, individual sperm are then selected visually based on motility and morphology by a trained embryologist for injection to an egg 7, 8. However, other important sperm attributes that can affect ART outcomes, including sperm DNA–chromatin or chromosomal integrity, mutational, or methylome composition, and the presence of reactive oxygen species (ROS)9, 10, 11, 12, 13, 14, 15, 16, 17 are typically not considered. In particular, long periods of incubation, as well as shear stresses due to centrifugation, increase ROS accumulation.…”

Male fertility: Genome integrity and sperm DNA methylation

“…Rodent models showed that exposure to these molecules triggers DNA hypomethylation in sperm along with a dose-dependent drop in sperm counts, impaired testicular histology, reduced sperm production and infertility [29,30] . Interestingly, preliminary observations made in rodents were confirmed in humans since methylation changes in sperm DNA have also been identified in men showing disruptive spermatogenesis and more recently in idiopathic infertility cases [31][32][33][34][35][36][37][38][39][40] . As analyses of DNA methylation pattern in Differentially Methylated Regions (DMRs) of H19 and PEG1/MEST in men with disruptive spermatogenesis clearly showed a link between reduced sperm counts and abnormal methylation [31] , several studies broaden DMRs analysis, including a larger number of genes: IGF2, PEG3, ZAC, LIT1, SNRPN as well as non-imprinted repetitive elements, such as long interspersed nucleotide elements (LINE1) and Alu elements, as surrogates for genomewide DNA methylation changes [33,35] .…”

Epigenetic: A new approach to etiology of infertility

“…In addition, the research of Montjean et al 22 showed that global DNA methylation in sperm was associated with sperm concentration. Oligozoospermic men had global DNA methylation level which were significantly lower compared to normozoospermic men.…”