KMT2C and infection: After scrutinizing normalized read counts and sample clustering to confirm dropout versus baseline at the final state (Supplemental Figure 2A), the enrichment of sgRNAs in live cells after 15 and 21 days of selection was compared with cells harvested after 3 days of infection without selection to identify genes for which Cas9 KO caused negative selection of MLL3/4 KO relative to WT cells (Figure 1A).