We performed a CRISPR-tiling screen targeting known H3K4 methylation modifiers in mouse MLL-AF9/FLT3-ITD/Cas9 AML cells to identify the H3K4 methylation modifiers implicated in MLL-r/FLT3-ITD AML (Fig. 1A). Here, MLLT3 is linked to acute myeloid leukemia.