KMT2A and acute myeloid leukemia: We then delivered this library into the Cas9-expressing murine MLL-AF9 leukemia cells (a well-established AML model driven by a t(9;11) oncogenic fusion protein) (22) using the lentiviral transduction and compared the change of frequency of each integrated sgRNA construct in early (day 0) and late (day 12) time points.