show Abstracthide AbstractHematopoietic stem and progenitor cell (HSPC) formation and lineage differentiation involve gene expression programs orchestrated by transcription factors and epigenetic regulators. Knockdown of the chromatin remodeler chromodomain-helicase-DNA-binding protein 7 (CHD7) expanded phenotypic HSPCs, erythroid, and myeloid lineages in zebrafish and mouse embryos. CHD7 acts to suppress hematopoietic differentiation in a cell autonomous manner in the embryo and adult. CHD7 chromatin immunoprecipitation in human CD34+ and mouse HSPCs revealed enrichment of binding motifs for hematopoietic transcription factors including Runx1 and GATA factors, and decreased Runx1 occupancy correlated with loss of CHD7 occupancy. CHD7 physically interacts with Runx1 and suppresses Runx1-induced expansion of HSPCs during development, providing both physical and genetic evidence for the Runx1-CHD7 interaction. CHD7 modulates Runx1 activity to provide proper timing and function of HSPCs as they emerge during hematopoietic development or mature in adults, representing a distinct and evolutionarily conserved control mechanism to ensure accurate hematopoietic lineage differentiation. Overall design: ChIP sequencing of GATA2, RUNX1 and PolII-phospho-serineII in G1ER cells.