KMT2A and acute leukemia: In ~10% of acute leukemias in which KMT2A is fused to one of >80 fusion partners [20, 24], KMT2A fusion breakpoints are located primarily within exons 8–14 (the so-called “breakpoint cluster region”) [20, 22, 25], preserving both the CxxC-binding domain in exons 5–6 and the adjacent repression domain 2 (RD2) largely encoded by exons 7–8.