RIP-sequencing of cKIT positive cells in male mice

The regulatory network and key factors ensuring the precise transition from mitosis to meiosis in mammalian germ cells remain elusive. Herein, we identify heterogeneous nuclear ribonucleoprotein U (hnRNPU) as a pivotal integrator of dual-layer regulation essential for this fate transition. Conditional knockout of hnRNPU in differentiating spermatogonia led to complete male infertility, accompanied by defects in spermatogonial differentiation and meiotic arrest at the leptotene stage. Integrated multi-omics and mechanistic studies revealed that hnRNPU orchestrates both transcriptional and post-transcriptional programs. On the chromatin level, hnRNPU interacts with the histone variant H2A.Z and directs its incorporation into transcriptional start sites (TSS) of critical meiotic genes, such as Meiosin and its targets Meioc, Sycp2, and Dmc1 etc. Concurrently, on the RNA level, hnRNPU cooperates with the m6A readers YTHDC1 and YTHDC2 to modulate the alternative splicing of meiosis-critical genes (e.g., Sycp1, Tex14), likely in an m6A-dependent manner. Our study establishes a novel paradigm in which hnRNPU serves as a central node coupling chromatin-based and RNA-based mechanisms to ensure the robust initiation of meiosis, providing profound insights into male reproductive biology.