Although representation of a nontargeting control sgRNA did not change significantly in vivo, 5 of 5 sgRNAs targeting the positive control Hoxa9, essential for MLL-AF9 leukemia cells (Faber et al., 2009), showed a median depletion of more than 2-fold, demonstrating that the screen was robust (Figure 1C). The gene discussed is HOXA9; the disease is leukemia.