Researchers deployed a liquid chromatography-tandem mass spectrometry platform to measure the abundance of 27 different RNA modifications simultaneously. They examined total RNA, tRNA-enriched RNA, and small RNA populations isolated from developing mouse testes, from purified spermatogenic cells at specific stages, and from sperm collected sequentially from the caput, corpus, and cauda segments of the epididymis. This approach captured modifications ranging from the well-known N6-methyladenosine to a host of lesser-studied marks on transfer RNA, allowing a system-wide view of how the epitranscriptome is remodelled.

The analysis revealed that tRNA-enriched RNA carries the most pronounced stage-specific signatures. As germ cells progressed through the complex choreography of meiosis and spermiogenesis, the modification profiles on tRNA species shifted dramatically, suggesting that the translational machinery itself is being epigenetically tuned for the specialized demands of sperm development. Modifications such as 5-methylcytosine and various wobble uridine derivatives rose and fell in patterns that aligned with known developmental transitions, hinting at a layer of regulation that operates beyond transcription.

Surprisingly, the reprogramming of RNA marks did not end when sperm left the testis. During transit through the epididymis—where sperm acquire forward motility and the ability to fertilize an egg—the RNA modification landscape underwent further extensive remodelling. Sperm taken from the early caput epididymis already displayed a distinct modification signature, but this profile was markedly different in cells from the middle corpus and further altered in mature sperm stored in the cauda. The data demonstrate that the epitranscriptomic code of sperm continues to be rewritten during the final functional maturation steps, potentially reflecting the addition of epididymosome-delivered small RNAs and the action of extracellular modification enzymes.

This elaborate programme appears to be vulnerable to physiological stress. In a mouse model of type 2 diabetes, the study found that epididymal maturation was accompanied by widespread alterations in sperm RNA modification profiles. Not only were the absolute levels of individual marks changed, but the correlation networks connecting different modifications were disrupted. For instance, certain modifications that normally co-vary in a tightly coordinated manner became uncoupled, implying that the regulatory logic of the epitranscriptome is eroded by metabolic disease. These findings raise the possibility that a father’s metabolic health could imprint durable epigenetic changes on sperm that influence the next generation.

The technical breadth of the study—profiling 27 modifications across multiple RNA fractions and cell types—provides a foundational resource for the field. The authors note, however, that the mass spectrometry approach measures overall modification abundance in a pool of RNA, rather than pinpointing which exact nucleotide sites are modified on specific transcripts. Knowing that a particular tRNA modification is globally elevated in the cauda epididymis, for example, does not reveal which tRNAs carry the mark or how it affects codon decoding. Future work combining transcriptome-wide sequencing with site-specific modification detection will be needed to map these marks at single-nucleotide resolution and unravel their functional consequences.

Nevertheless, the study reveals a strikingly coordinated reshaping of RNA modifications that parallels the well-known epigenetic reprogramming of DNA methylation and histone modifications during germ cell development. The sperm epitranscriptome emerges as a highly dynamic layer of information that is refined stepwise from the testis to the epididymis. Disruption of this process by diabetes suggests that environmental and metabolic insults can leave a molecular scar on sperm RNA, potentially linking paternal health to embryonic development and offspring phenotype.

The work establishes a framework for exploring how RNA modifications in sperm contribute to male fertility and intergenerational inheritance. By cataloguing the changing landscape of over two dozen chemical marks, the study opens the door to mechanistic investigations into how specific tRNA and small RNA modifications regulate the translational and silencing functions of sperm-borne RNA. It also underscores that the male gamete is far from a passive carrier of DNA; instead, it carries a rich and malleable epigenetic history that is still being written in the final hours before fertilization.

Subject of Research: Dynamics of RNA modifications during mammalian spermatogenesis and epididymal maturation
Article Title: RNA modification dynamics during mammalian spermatogenesis and maturation
News Publication Date: Not provided
Web References: 10.1007/s11427-025-3134-1
References: DOI: 10.1007/s11427-025-3134-1
Image Credits: ©Science China Press
Keywords: RNA modifications, spermatogenesis, epididymal maturation, tRNA, epitranscriptome, sperm, diabetes, LC-MS/MS, epigenetic inheritance