Gene Replacement Of Alpha-Globin With Beta-Globin Restores Hemoglobin Balance In Beta-Thalassemia-Derived Hematopoietic Stem And Progenitor Cells

beta-Thalassemia pathology is due not only to loss of beta-globin (HBB), but also to erythrotoxic accumulation and aggregation of the beta-globin-binding partner, alpha-globin (HBA1/2). Here we describe a Cas9/AAV6-mediated genome editing strategy that can replace the entire HBA1 gene with a full-length HBB transgene in beta-thalassemia-derived hematopoietic stem and progenitor cells (HSPCs), which is sufficient to normalize beta-globin:alpha-globin messenger RNA and protein ratios and restore functional adult hemoglobin tetramers in patient-derived red blood cells. Edited HSPCs were capable of long-term and bilineage hematopoietic reconstitution in mice, establishing proof of concept for replacement of HBA1 with HBB as a novel therapeutic strategy for curing beta-thalassemia.A new genome editing strategy can normalize the beta-globin:alpha-globin balance in human hematopoietic stem cells from patients with beta-thalassemia and restore functional adult hemoglobin tetramers in patient-derived red blood cells.