KMT2A and leukemia: Generally, in different types of leukemia, chromosomal rearrangements lead to MLL oncogenic fusion proteins (i.e., MLL-AF9 and MLL-ENL), which lack the catalytic domain but are able to reprogram committed cells (both hematopoietic SCs and myeloid progenitors) towards LSCs and initiate tumorigenesis [84–86].