What the human sperm methylome tells us. Homo sapiens

Aim: To characterize the sperm methylome in semen samples from 19 donors with proven fertility. Material and 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. Ninety-four 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). Overall design: 19 samples from fertile patients.