Importantly, this implicates a previously unrecognized HSC-intrinsic role for Flt3 and Flt3-ITD in governing the dynamics of the HSC compartment and potentially radically revises our understanding of the role of Flt3 in normal hematopoiesis and the impact of FLT3-ITDs on HSCs in hematologic malignancies. The gene discussed is FLT3; the disease is hematologic disorder.