Repressive and active histone methylation mark distinct promoters in human and mouse spermatozoa (Illumina)

In higher eukaryotes, histone methylation is involved in the maintenance of cellular identity during somatic development. During spermatogenesis, Since most nucleosomes are replaced by protamines during spermatogenesis . Iit is therefore unclear whether if histone modifications function in paternal transmission of epigenetic information. Here we show that H3K4 di-methylation (H3K4me2) and H3K27 tri-methylation (H3K27me3), two modifications important for Trithorax and Polycomb-mediated gene regulation, display methylation-specific distributions at regulatory regions in human spermatozoa. H3K4 dimethylation H3K4me2-marksed promoters of genes relevant control gene functions in spermatogenesis and cellular homeostasis suggesting that this mark reflects germline transcription. In contrast, H3K27 trimethylation (H3K27me3) marks promoters of key developmental regulators in sperm like in somatic cells. Promoters of orthologous genes are similarly modified in mouse spermatozoa. Further, particularly genes with extensive H3K27me3 coverage around transcriptional start sites are never expressed during male and female gametogenesis, nor in pre-implantation embryos. These data are compatible with a function for Polycomb in repressing somatic determinants across generations. Importantly, however, we observe only modest selective retention of nucleosomes at regulatory regions in human sperm suggesting that paternal transmission of H3K27me3-encoded epigenetic information may be subjected to variegation.