PCID2 is essential for spermatogonial differentiation by regulating alternative splicing

The progression of spermatogenesis is under dynamic transcriptional regulation. As a subunit of the transcription-export complex 2 (TREX-2), PCI domain-containing protein 2 (PCID2), participates in RNA processing. However, the physiological functions of PCID2 in spermatogenesis remain poorly understood. Here, we generate germline conditional knockout (Pcid2-SKO) mice using Stra8-Cre, and it is found that Pcid2-SKO mice are infertile, exhibit extensive germ cell apoptosis, impaired spermatogonial differentiation, and failure of meiosis initiation. Single-cell transcriptome analysis reveals developmental arrest at the transition from type A to type B spermatogonia in Pcid2-SKO mice. Gene Set Enrichment Analysis (GSEA) demonstrates a significant decrease in the enrichment of mRNA splicing pathway in Pcid2-SKO germ cells. IP-MS results indicate candidate proteins interacting with PCID2 are significantly enriched in RNA splicing pathway. Co-IP results indicate that PCID2 interacts with SNRPG, hnRNPH1 and SF3B1 to modulate alternative splicing in germ cells. Combining RNA sequencing and PCR identifies four key genes (Prpf3, Nek3, Dvl2, and Slc30a9) as splicing targets of PCID2. Collectively, PCID2 is essential for normal spermatogenesis and male fertility by regulating the alternative splicing (AS) of genes critical for cell cycle progression, spliceosome assembly, and mitochondrial homeostasis. This study provides novel insights into the molecular mechanisms underlying spermatogenesis and highlights the importance of AS in germ cell development.