Prdm15 deficiency perturbs hematopoietic stem and progenitor cell homeostasis.

The maintenance of homeostasis in hematopoietic stem and progenitor cells (HSPCs) is essential for the proper development of the entire hematopoietic system. However, the mechanisms underlying this regulatory equilibrium remain elusive. Here, we report that Prdm15 deficiency in HSPCs induces the accumulation of immature hematopoietic stem cells in mice. A series of transplantation assays shows that these cells display impaired reconstitution capacity and competitive fitness, which are associated with abnormal differentiation trajectories and transcriptional alterations identified by single-cell RNA sequencing. Mechanistically, integrated multi-omics analyses including ATAC-seq and CUT&Tag sequencing of HSPCs indicate that Prdm15 deficiency induces significant transcriptional and epigenetic alterations, particularly affecting the methyltransferase KMT2C and altering H3K4me1 and H3K27ac modifications at the promoters of hematopoietic developmental genes. Collectively, our findings establish PRDM15 as a critical epigenetic regulator of HSPCs, offering valuable insights into the molecular mechanisms underlying hematopoietic homeostasis.