Dynamic expression patterns of H3K9 methylation and acetylation modifications during mouse testicular development

To address the ambiguous spatiotemporal dynamics of histone H3 lysine 9 （H3K9） methylation modifications in murine testicular tissue， the expression patterns of H3K9me1， H3K9me2， H3K9me3 and H3K9ac across various developmental stages of mouse germ cells were systematically analyzed by Western blot and paraffin section immunofluorescence techniques. The findings indicated that H3K9me1 and H3K9me3 shared similar distribution patterns， characterized by elevated expression in leptotene， zygotene spermatocytes and elongated spermatids， with a marked reduction in spermatogonia， pachytene， diplotene cells and round spermatids. Notably， no expression was observed in mature spermatozoa. In contrast， H3K9me2 was expressed across all spermatogenic cell types， with significantly higher levels in early elongated spermatids and pre-meiotic cells compared to other stages. H3K9ac demonstrated specific enrichment in leptotene， pachytene spermatocytes and the heads of elongated spermatids. Importantly， H3K9me3 was silenced during the initiation of meiosis， whereas H3K9ac was specifically activated during chromatin remodeling. The observed dynamic variations in H3K9 modification formed during critical stages of spermatogenesis implied a potential role in germ cell differentiation via distinct epigenetic regulatory mechanisms. The first time， a comprehensive expression profile of H3K9 modifications was offered throughout the mouse spermatogenic epithelial cycle.