iSCREAM of ERBB4. Scatter plot demonstrates the enrichment of specific ERBB4 mutations in Ba/F3 cells engineered to express 7,396 different missense and nonsense mutations of ERBB4. The cells were cultured for 8 days in the presence of 10 ng/mL of the ERBB4 ligand NRG-1 in the absence of IL3. The x-axis shows the position of the mutated residue on the ERBB4 primary sequence. The y-axis indicates the observed fold change in the variant frequency of a mutation in the surviving cell pool when compared with the variant frequency of that mutation in the cDNA mutation library. The dashed horizontal line indicates a cutoff at 50-fold enrichment (q < 0.00001) for the mutation in the surviving cell pool as compared with the mutation library. The size of the dot as well as the intensity of its red color indicate the variant frequency of the mutation in the surviving cell pool. The gap in the x-axis (at residues 1046–1061) represents the 16 amino acids (aa) that are absent in the ERBB4 splice variant JM-a CYT-2 which was used for generating the mutation library.