Wu Y, Zeng J, Roscoe B P, et al. Highly efficient therapeutic gene editing of human hematopoietic stem cells[J]. Nature Medicine, 2019.
Re-expression of the paralogous γ-globin genes (HBG1/2 could be a universal strategy to ameliorate the severe β-globin disorders sickle cell disease (SCD) and β-thalassemia by induction of fetal hemoglobin (HbF, α2γ2)1. Previously, we and others have shown that core sequences at the BCL11A erythroid enhancer are required for repression of HbF in adultstage erythroid cells but are dispensable in non-erythroid cells2-6. CRISPR-Cas9-mediated gene modification has demonstrated variable efficiency, specificity, and persistence in hematopoietic stem cells (HSCs). Here, we demonstrate that Cas9: sgRNA ribonucleoprotein(RNP)-mediated cleavage within a GATAL binding site at the +58 BCLTLA erythroid enhancer results in highly penetrant disruption of this motif, reduction of BCLTLA expression, and induction of fetal γ-globin. We optimize conditions for selection-free on-target editing in patient-derived HSCs as a nearly complete reaction lacking detectable genotoxicity or deleterious impact on stem cell function. HSCs preferentially undergo non-homologous compared with microhomology-mediated end joining repair. Erythroid progeny of edited engrafting SCD HSCs express herapeutic levels of HbF and resist sickling, while those from patients with β-thalassemia show restored globin chain balance. Non-homologous end joining repair-based BCL11A enhancer editing approaching complete allelic disruption in HSCs is a practicable therapeutic strategy to produce durable HBF induction.