H3-K27M mutation alters the dynamics of human hematopoietic stem cells and delays erythroid differentiation

Acute myeloid leukemia (AML) is an aggressive blood cancer driven by genetic and epigenetic alterations that disrupt normal hematopoiesis. Among these, the histone H3-K27M mutation, originally identified in pediatric high-grade gliomas, reshapes gene repression programs by reducing global H3-K27 trimethylation. Although rare, H3-K27M mutations have been detected in preleukemic hematopoietic stem cells (HSCs) of AML patients, suggesting its role in early leukemogenesis and identifying it as a promising therapeutic target. Here, we investigated how H3-K27M alters hematopoiesis using a longitudinal xenotransplantation mouse model of human hematopoietic stem and progenitor cells carrying either wild-type H3 or H3-K27M. To quantify hematopoietic dynamics, we developed a collection of mathematical models representing alternative lineage hierarchies and fit them to our longitudinal experimental data. Using information criteria, we identified the model that best depicts blood dynamics in each condition. Our results show that H3-K27M promotes HSC proliferation and differentiation and erythroid commitment while reducing multipotent progenitor self-renewal potential and lymphoid commitment, ultimately increasing blood cell numbers despite impairing erythroid maturation. Mathematical modelling inferred the progenitor-level alterations, which were not readily evident from the blood cell count alone. H3-K27M also induced distinct kinetics in human HSC1 and HSC2 subpopulations that were not observed in wild-type H3 controls. Together, our results provide the first quantitative framework to reveal how H3-K27M influences the hematopoietic hierarchy roadmap and alters blood cell dynamics in preleukemia.