What the human sperm methylome tells us

Abstract

Aim: To characterize the sperm methylome in semen samples from 19 donors with proven fertility. Materials & methods: Bisulfite-converted sperm DNA was hybridized on the HumanMethylation450 Infinium BeadChip platform. CpG fluorescence intensities were extracted and converted to β-values. Results: The sperm methylome is highly homogeneous and hypomethylated. Genes with hypomethylated promoters are ontologically associated to biological functions related to spermatogenesis and embryogenesis. Sex chromosomes are the most hypomethylated chromosomes, supporting data that indicated their essential role in spermatogenesis. A total of 94 genes are resistant to demethylation, being strong candidates for transgenerational inheritance. Conclusion: Spermatozoa carry a homogeneous methylation profile that is a footprint of past events (spermatogenesis), is designed to facilitate future events (embryogenesis) and has a possible influence in the adult life (transgenerational effects).