Genome editing of the α-globin locus ameliorates globin balance in thalassemic HSPCs. InDels (A), HBA2 copies (B), and β^AS3 integrated copies (C) quantification in edited thalassemic HSPCs in erythroid liquid culture (●) or in BFU-E (■). Black lines represent mean. HSPCs from 1 patient of each genotype were used. (D) α/β-like globin mRNA ratios in edited thalassemic erythroblasts at day 12. Black lines indicate mean; gray line shows the range of α/β-like globin ratio in healthy donor MPB and UCB HSPCs (n = 5). (E) Relative abundance of endogenous β and integrated β^AS3 mRNA at day 12 of erythroid liquid culture. Black lines represent mean. (F) α/β-like globin mRNA ratios in edited thalassemic BFU-E. β⁰/β⁺colonies (n = 71) are plotted on the left axis, β⁰/β⁰ (n = 63) on the right axis. Each dot represents a single colony. Black lines indicate mean ± SD (***P < .001; **P < .01; ANOVA, Tukey test). HSPCs derived from 1 patient of each genotype were used for this figure.