Prpf4 Sequentially Regulates the Expansion and Maturation of Erythrocyte through Distinct Mechanisms

The proliferation of early erythrocyte and the subsequent erythrocyte maturation are critical events during erythropoiesis, how these two independent but interconnected processes are efficiently orchestrated during erythropoiesis was largely unknown. Prpf4 expression is enriched from Pre-Colony Forming Unit-Erythroid (PreCFU-E) to Nucleated Erythrocytes, especially in the CFU-E cells, implying Prpf4 plays a critical role in erythropoiesis. Here, we demonstrate that prpf4 sequentially regulates erythrocyte proliferation and maturation during zebrafish definitive hematopoiesis. The data show that prpf4 mutation results in severe defects in erythropoiesis, characterized by a substantial reduction in erythroid cell numbers and impaired erythrocyte maturation. Further analysis indicates that prpf4 mutation leads to cell cycle arrest of erythrocytes at the S and G2/M phases, as well as a significant increase in erythrocyte apoptosis. Mechanistically, prpf4 mutation leads to DNA damage and the subsequent activation of DNA damage response, triggering the ATM/CHK2-p53 signaling pathway. This process inhibits the proliferation of early erythrocyte and induces erythrocyte apoptosis. On the other hand, the data reveal that prpf4 mutation causes significant defect in skipped-exon during pre-mRNA splicing, accompanying severe splicing defect in slc25a39 pre-mRNA. This results in a significant downregulation of slc25a39 mRNA, ultimately impairing erythrocyte maturation in late erythropoiesis. In conclusion, we identify that prpf4 sequentially regulates early erythrocyte proliferation and the sequential erythrocyte maturation, the dual function of prpf4 partially explaining how early erythrocyte proliferation and late erythrocyte maturation are efficiently coordinated during erythropoiesis.