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Disorders resulting from mutations in the hemoglobin subunit beta gene (HBB; which encodes β-globin), mainly sickle cell disease (SCD) and β-thalassemia, become symptomatic postnatally as fetal γ-globin expression from two paralogous genes, hemoglobin subunit gamma 1 (HBG1) and HBG2, decreases and adult β-globin expression increases, thereby shifting red blood cell (RBC) hemoglobin from the fetal (referred to as HbF or α2γ2) to adult (referred to as HbA or α2β2) form. These disorders are alleviated when postnatal expression of fetal γ-globin is maintained. For example, in hereditary persistence of fetal hemoglobin (HPFH), a benign genetic condition, mutations attenuate γ-globin-to-β-globin switching, causing high-level HbF expression throughout life. Co-inheritance of HPFH with β-thalassemia- or SCD-associated gene mutations alleviates their clinical manifestations. Here we performed CRISPR-Cas9-mediated genome editing of human blood progenitors to mutate a 13-nt sequence that is present in the promoters of the HBG1 and HBG2 genes, thereby recapitulating a naturally occurring HPFH-associated mutation. Edited progenitors produced RBCs with increased HbF levels that were sufficient to inhibit the pathological hypoxia-induced RBC morphology found in SCD. Our findings identify a potential DNA target for genome-editing-mediated therapy of β-hemoglobinopathies.

Original publication

DOI

10.1038/nm.4170

Type

Journal article

Journal

Nat Med

Publication Date

09/2016

Volume

22

Pages

987 - 990

Keywords

Anemia, Sickle Cell, CRISPR-Cas Systems, Erythroid Precursor Cells, Fetal Hemoglobin, Gene Editing, Hemoglobin A, Humans, In Situ Hybridization, Fluorescence, Mutagenesis, Site-Directed, Mutation, Promoter Regions, Genetic, RNA, Messenger, Reverse Transcriptase Polymerase Chain Reaction, beta-Globins, beta-Thalassemia, gamma-Globins