Regarding the human system, as mentioned above, the study of Barabé et al. [41] represented a highly significant step forward, in that it provided the first conclusive evidence that AML-associated oncogenes derived from MLL rearrangements; in this case, MLL-ENL and MLL-AF9-could transform human primitive hematopoietic cells as a single hit and confer on them leukemogenic properties. Here, KMT2A is linked to acute myeloid leukemia.