KMT2A and leukemia: The FLT3 receptor is for instance expressed in the most primitive human long-term HSCs, but not in murine LT-HSCs [45–47], and it is possible the FLT3 signaling is less important in the GMP-driven MLL-AF9 leukemia models in the mouse compared to more HSC-driven MLL-AF9 leukemia in human CB model systems [22].