Male Reproductive Tract
Session: Poster Session C
Yiyun Zhang
Visiting scholar
University of Pennsylvania
Philadelphia, Pennsylvania, United States
The divergent roles of the DOT1L histone methyltransferase activity in spermatogonial stem cell renewal and histone-to-protamine exchange
Yiyun Zhang1,2, Patrick E. Fields3, Xin Wu2, P. Jeremy Wang1
1.Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, USA.
2.State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, Jiangsu, China.
3.Department of Pathology and Laboratory medicine, University of Kansas Medical Center, Kansas City, KS, United States
Abstract Text:
Histone modifications are key regulators of chromatin remodeling and gene expression, playing essential roles in both development and disease. During spermatogenesis, these modifications are critical for orchestrating chromatin dynamics. DOT1L, the sole histone H3K79 methyltransferase, is vital for spermatogonial stem cell (SSC) self-renewal and has been implicated in the histone-to-protamine transition during sperm maturation. In the testis, DOT1L functions synergistically with MLLT10, and the loss of either protein results in smaller testes, reduced sperm counts, and male subfertility. Both proteins are indispensable for H3K79 methylation, a modification that promotes histone replacement during spermatogenesis.
Despite these established roles, whether DOT1L’s methyltransferase activity is required for these processes remains unclear. Here, we demonstrate that DOT1L’s catalytic activity is essential for SSC self-renewal but is dispensable for the histone-to-protamine transition in mice. Utilizing a point mutant mouse that eliminates DOT1L’s enzymatic function but maintains its protein abundance, we find that the absence of H3K79 methylation leads to progressive SSC depletion and impaired spermatogenesis. Mechanistically, transcriptomic analysis reveals that DOT1L regulates SSC maintenance via the RET/GFRA1 signaling pathway, a GDNF-driven SSC self-renewal mechanism.
Surprisingly, despite its critical role in SSCs, DOT1L’s methyltransferase activity is dispensable for histone eviction during spermiogenesis. Mutant spermatozoa successfully complete the histone-to-protamine transition, suggesting that DOT1L regulates the histone replacement via a methyltransferase activity-independent mechanism. Collectively, our findings reveal a stage-specific requirement for DOT1L enzymatic activity in male germ cell development, identifying its essential role in SSC self-renewal while uncovering its non-enzymatic function in histone-to-protamine replacement during spermiogenesis.