Epigenetic landscape of murine testicular histone variants TH2A and TH2B in sperm

In this study, chromatin immunoprecipitated sequencing was done for testis specific histone variants of H2B and H2A, TH2B and TH2A to understand the epigenomics of these retained histones, using murine caudal sperm.Our in silico analysis has attributed a myriad of novel functions to sperm retained TH2B with respect to embryo development and spermatogenesis.Also, based on genomic regions, TH2B was observed to be associated with spindle assembly and various meiosis-specific genes, which is an important finding as TH2A/TH2B DKO mice have been reported to have defective cohesin release.We also observed a degree of evolutionary conservation between the TH2B-DNA linkage across human and mouse.This overlap included genes important for embryogenesis. Most importantly, heterogeneity in the epigenetic landscape of TH2A and TH2B was seen which is intriguing as TH2B and TH2A are well reported to be present in the same nucleosomes to promote open chromatin. Additionally, unlike TH2B, TH2A was enriched on the mitochondrial chromosome. We presume that TH2A is associated with mitochondrial DNA inserted in the nuclear DNA and this observation needs further validation.. A comprehensive analysis of these observations indicates novel functions for the sperm retained TH2B and TH2A. Overall design: Native-ChIP of sperm histones TH2A and TH2B in murine caudal sperm using 8-12 weeks old BALB/c-129-E mice