Genome-Scale Assessment of Age-Related DNA Methylation Changes in Mouse Spermatozoa

PLoS One. 2016 Nov 23;11(11):e0167127. doi: 10.1371/journal.pone.0167127. eCollection 2016.

Abstract

DNA methylation plays important roles in the production and functioning of spermatozoa. Recent studies have suggested that DNA methylation patterns in spermatozoa can change with age, but the regions susceptible to age-related methylation changes remain to be fully elucidated. In this study, we conducted genome-scale DNA methylation profiling of spermatozoa obtained from C57BL/6N mice at 8 weeks (8w), 18 weeks (18w) and 17 months of age (17m). There was no substantial difference in the global DNA methylation patterns between 18w and 17m samples except for a slight increase of methylation levels in long interspersed nuclear elements in the 17m samples. We found that maternally methylated imprinting control regions (mICRs) and spermatogenesis-related gene promoters had 5-10% higher methylation levels in 8w samples than in 18w or 17m samples. Analysis of individual sequence reads suggested that these regions were fully methylated (80-100%) in a subset of 8w spermatozoa. These regions are also known to be highly methylated in a subset of postnatal spermatogonia, which might be the source of the increased DNA methylation in 8w spermatozoa. Another possible source was contamination by somatic cells. Although we carefully purified the spermatozoa, it was difficult to completely exclude the possibility of somatic cell contamination. Further studies are needed to clarify the source of the small increase in DNA methylation in the 8w samples. Overall, our findings suggest that DNA methylation patterns in mouse spermatozoa are relatively stable throughout reproductive life.

MeSH terms

  • Aging / physiology*
  • Animals
  • DNA Methylation / physiology*
  • Genomic Imprinting / physiology*
  • Male
  • Mice
  • Spermatozoa / cytology
  • Spermatozoa / metabolism*

Grant support

This work was supported by Grants-in-Aids for Scientific Research (KAKENHI) (15K15592), Health and Labour Sciences Research Grant (H25-Jisedai-Ippan-001) and the Takeda Science Foundation (TA) and by Grant-in-Aid of Tohoku University, Division for Interdisciplinary Advanced Research and Education (NK). The work was also supported by the Core Research for Evolutional Science and Technology (CREST) from the Japan Agency for Medical Research and Development (AMED) (TA). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.