BCR and cancer: When we compared the phenotypes of CRISPRi sgRNAs to CRISPR nuclease at the BCR amplicon, with all phenotypes standardized to the distribution of negative controls to facilitate comparison, we found that sgRNAs targeting BCR were strongly depleted in both screens, as expected based on the critical role of the BCR-ABL fusion in this cancer cell line (Naumann et al., 2001), but few other CRISPRi sgRNAs in the region elicited growth defects (Figure 3E).