Rearrangements of the mixed-lineage leukemia 1 (MLL1) gene (now renamed Lysine [K]-specific methyl transferase 2A or KMT2A) on chromosome 11q23 to over 80 different partner genes define a subtype of leukemia with lymphoid and myeloid features and poor prognosis [12,56]. Here, KMT2A is linked to leukemia.