CD34 and sickle cell disease: Cas9-dependent disruption of this enhancer element in isolated CD34+ hematopoietic stem cells causes marked downregulation of the BCL11A repressor and concomitant upregulation of its target genes, which include those encoding the γ-globin subunits, allowing for stable resumption of HbF production that is protective against sickle cell disease and β-thalassemia.