Genome-wide 5-hydroxymethylcytosine patterns in human spermatogenesis are associated with semen quality

Abstract

We performed immunofluorescent analysis of DNA hydroxymethylation and methylation in human testicular spermatogenic cells from azoospermic patients and ejaculated spermatozoa from sperm donors and patients from infertile couples. In contrast to methylation which was present throughout spermatogenesis, hydroxymethylation was either high or almost undetectable in both spermatogenic cells and ejaculated spermatozoa. On testicular cytogenetic preparations, 5-hydroxymethylcytosine was undetectable in mitotic and meiotic chromosomes, and was present exclusively in interphase spermatogonia Ad and in a minor spermatid population. The proportions of hydroxymethylated and non-hydroxymethylated diploid and haploid nuclei were similar among samples, suggesting that the observed alterations of 5-hydroxymethylcytosine patterns in differentiating spermatogenic cells are programmed. In ejaculates, a few spermatozoa had high 5-hydroxymethylcytosine level, while in the other ones hydroxymethylation was almost undetectable. The percentage of highly hydroxymethylated (5-hydroxymethylcytosine-positive) spermatozoa varied strongly among individuals. In patients from infertile couples, it was higher than in sperm donors (P<0.0001) and varied in a wider range: 0.12-21.24% versus 0.02-0.46%. The percentage of highly hydroxymethylated spermatozoa correlated strongly negatively with the indicators of good semen quality – normal morphology (r=-0.567, P<0.0001) and normal head morphology (r=-0.609, P<0.0001) – and strongly positively with the indicator of poor semen quality: sperm DNA fragmentation (r=0.46, P=0.001). Thus, the immunocytochemically detected increase of 5hmC in individual spermatozoa is associated with infertility in a couple and with deterioration of sperm parameters. We hypothesize that this increase is not programmed, but represents an induced abnormality and, therefore, it can be potentially used as a novel indicator of semen quality.

Inter-Cell and Inter-Chromosome Variability of 5-Hydroxymethylcytosine Patterns in Noncultured Human Embryonic and Extraembryonic Cells

“…In neither chromosome did we observe DNA hemimethylation, partial methylation, or absence of 5mC. Overall, this 5mC pattern was very similar to that reported previously in human chorion, lymphocytes, and spermatogonia [Kokalj-Vokac et al, 1998;Pfarr et al, 2005;Pendina et al, 2005;Efimova et al, 2017].…”

A Decade of Exploring the Mammalian Sperm Epigenome: Paternal Epigenetic and Transgenerational Inheritance

“…low sperm concentration (Marques et al, 2008 ; Poplinski et al, 2010 ). More recently, it was also reported that modification in 5hmC pattern in sperm is associated with male infertility (Wang et al, 2015 ; Efimova et al, 2017 ). In these reports, infertile males were shown to contain higher rate of 5 hmC than fertile males and infertility correlated with defects in sperm morphology and a high sperm DNA fragmentation rate (Efimova et al, 2017 ).…”

“…More recently, it was also reported that modification in 5hmC pattern in sperm is associated with male infertility (Wang et al, 2015 ; Efimova et al, 2017 ). In these reports, infertile males were shown to contain higher rate of 5 hmC than fertile males and infertility correlated with defects in sperm morphology and a high sperm DNA fragmentation rate (Efimova et al, 2017 ). Several studies have also reported that a link exists between assisted reproductive technologies (ART) and loss of imprinting resulting in an increased incidence of genomic imprinting disorders in children conceived via ART (for review, see Ventura-Juncá et al, 2015 ).…”

DNA hydroxymethylation rate in the AChE and HoxC4 promoter associated with human sperm quality

“…Interestingly, the 5hmC levels on the gene bodies and proximal promoters of highly expressed genes were markedly higher than those of genes expressed at lower levels in different stages of mouse spermatogenesis, indicating that 5hmC plays an important role in active gene transcription in spermatogenesis (Gan et al., ). Alteration in 5hmc has been found to exist widely in globozoospermia spermatozoa (Wang et al., ) and the spermatozoa from infertile men (Efimova et al., ). We recently reported the presence of genome‐wide alteration of 5hmc in the spermatozoa from the men exposed to bisphenol A (BPA; Zheng et al., ), a widely studied endocrine‐disrupting chemical (EDC) which has a power to reduce human sperm quality, according to the human epidemiologic studies (Li et al., ).…”