Validation of hit genes from the primary screen. (A) Heat map representation of knockdown phenotype scores from CRISPRi validation screens in a panel of MM cell lines for cell surface levels of BCMA and CD38. Both genes and screens were hierarchically clustered based on Pearson correlation. AMO1 and RPMI8226 cells treated with indicated concentrations of the γ-secretase inhibitor RO4929097 or DMSO for 48 hours were analyzed by using flow cytometry (B) and immunoblotting (C) for changes in BCMA levels. Fold changes in BCMA cell surface levels as shown in panel B were determined by normalizing to DMSO-treated cells. Data points are means of three biological replicates, and error bars denote standard deviations. Western blot of endogenous BCMA is shown in panel C. GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was used as a loading control.