Epididymal dynamics and preimplantation roles of a sperm-enriched 5' fragment of tRNA-valine.

Sperm small RNAs are implicated in non-genetic transmission of paternal environmental effects; however, their biogenesis and functions remain poorly understood. We previously identified a 5' fragment of tRNA-valine-CAC-2 (tRFValCAC) as one of the most abundant tRNA fragments (tRFs) in mature mouse sperm. tRFValCAC is enriched in sperm during epididymal maturation, and extracellular vesicles (EVs) secreted by epididymal epithelial cells can deliver tRFValCAC to sperm. Here, we investigate the mechanistic basis of tRFValCAC delivery to sperm and its potential functions in the preimplantation embryo. We demonstrate that heterogeneous nuclear ribonucleoprotein A/B (hnRNPAB) binds tRFValCAC in the epididymis and regulates its abundance in EVs, thereby modulating its levels in sperm. Inhibition of tRFValCAC in preimplantation embryos alters the transcript abundance of genes involved in RNA splicing and mRNA processing and dysregulates alternative splicing. Phenotypically, tRFValCAC inhibition results in fewer embryos reaching the blastocyst stage. These findings illuminate the mechanism underlying sperm tRF-mediated intergenerational inheritance.