Evaluation of the effect of ALS20αI transduction on HbH and α-globin mRNA levels in mutant cells. (A) The percentage of total HbH relative to VCN measured by cation-exchange HPLC in erythroblasts differentiated from HUDEP-αKO clones, α-globin–KO CD34⁺ cells, and cells from patients with HbH. Each symbol represents 1 biological replicate: Patients 1 (n = 12), 3 (n = 3), 4 (n = 5), and 5 (n = 5). Genotypes are summarized in Table 2. In HUDEP-αKO clone 9, n = 7, in clone 7, n = 2, and in clone 62, n = 2. In α-globin–KO CD34⁺, n = 2. (B) The HBA:(HBB + HBG + HBD) mRNA relative to VCN in a patient with the –α^3.7/− −^SEA deletion (n = 8, patient 1 in Table 2), in a patient with homozygous Agrinio (427 T>A) mutation (n = 5, patient 5 in Table 2), and in α-globin–KO CD34⁺–derived erythroid cells. These analyses also suggested that 1 copy of ALS20αI produced as many human α-globin chains as those of a single endogenous α-globin gene.