RUNX1 and leukemia: Relative to well-defined AML splicing-factor mutations and oncofusions in Leucegene, this intron-retention exclusion profile was most dominant in MLL-rearranged leukemias and to a lesser extent in core binding factor rearrangements (RUNX1, CBFB-MYH11) (Supplementary Fig. 5A) Visual inspection of AS events in MBNL1 knockdown using IGV readily confirmed these bioinformatics predictions (Fig. 6c).