Deciphering the role of Hat1 in spermatogenesis: Chromatin organization and beyond.

Spermatogenesis, a core process for male fertility, relies heavily on chromatin organization regulated by histone acetyltransferases (HATs). However, the spatiotemporal expression pattern of histone acetyltransferase 1 (Hat1) in mouse testes and its specific role in spermatogenesis via chromatin organization remain unclear. This study employed RT-qPCR, Western blot, immunofluorescence localization, and bioinformatics to explore Hat1's dynamic expression and regulatory mechanisms during mouse spermatogenesis. Results showed that both Hat1 mRNA and protein were significantly upregulated in the testes of 8-week-old (mature) mice compared to 3-week-old (immature) mice. Immunofluorescence revealed Hat1 was predominantly localized in the nuclei of male germ cells, with stage-specific expression: highest in spermatogonia and sperm, intermediate in primary spermatocytes, and lowest in secondary spermatocytes. Bioinformatics analysis (based on single-cell sequencing data GSE214315) identified 246 differentially expressed genes (DEGs) related to chromatin organization-these DEGs were screened between adjacent stages of male germ cell development during spermatogenesis, including comparisons of leptotene-zygotene vs. pachytene-diplotene cells, pachytene-diplotene vs. round spermatids, round spermatids vs. early elongating spermatids, and early elongating vs. late elongating spermatids (screening criteria: FDR < 0.05, |log2(FC)| ≥ 1). Additionally, 41 Hat1-interacting proteins encoded by these DEGs were identified. Functional enrichment indicated stage-specific roles of Hat1: in the leptotene-zygotene phase, it participated in transcription regulation to initiate meiosis; in round spermatids, it shifted to refined epigenetic regulation and chromatin assembly for subsequent spermiogenesis; in late spermiogenesis and sperm, it was involved in DNA repair and ATP-dependent chromatin remodeling to protect sperm genetic material. In summary, the stage-specific expression patterns of Hat1 and its interactors highlighted the importance of precise control of gene expression and chromatin remodeling, as well as DNA repair in protection of sperm genetic material, in the development of male germ cells. However, future research should conduct functional assays. Overall, this research provides valuable insights into the epigenetic regulatory mechanisms of spermatogenesis and a foundation for male fertility research.