Editing an α-globin enhancer in primary human hematopoietic stem cells as a treatment for β-thalassemia

Abstract

β-Thalassemia is one of the most common inherited anemias, with no effective cure for most patients. The pathophysiology reflects an imbalance between α- and β-globin chains with an excess of free α-globin chains causing ineffective erythropoiesis and hemolysis. When α-thalassemia is co-inherited with β-thalassemia, excess free α-globin chains are reduced significantly ameliorating the clinical severity. Here we demonstrate the use of CRISPR/Cas9 genome editing of primary human hematopoietic stem/progenitor (CD34+) cells to emulate a natural mutation, which deletes the MCS-R2 α-globin enhancer and causes α-thalassemia. When edited CD34+ cells are differentiated into erythroid cells, we observe the expected reduction in α-globin expression and a correction of the pathologic globin chain imbalance in cells from patients with β-thalassemia. Xenograft assays show that a proportion of the edited CD34+ cells are long-term repopulating hematopoietic stem cells, demonstrating the potential of this approach for translation into a therapy for β-thalassemia.

Mutations in the zebrafishhmgcs1gene reveal a novel function for isoprenoids during red blood cell development

“…Here we show that cholesterol and isoprenoids regulate erythropoiesis using a zebrafish harboring mutations in the hmgcs1 gene (Vu57 allele). Mutations in human HMGCS1 have not been associated with disease, but there are 8 congenital anomalies that occur as a consequence of mutations within other enzymes of the CSP [5][6][7][8][9][10][11]13,48 . These congenital anomalies are characterized by diverse phenotypes 7,21,[48][49][50] and mutations in the zebrafish hmgcs1 gene mimics these disorders resulting in a multiple congenital anomaly syndrome.…”

“…Diamond-Blackfan anemia and sickle cell anemia are two examples of rare congenital anomalies that arise from defects in the production of RBCs 3 , and polycythemia occurs as a consequence of too many RBCs [4][5][6] . Genetic disorders of RBCs have revealed critical mediators of erythropoiesis [7][8][9][10][11] , many of which include transcription factors. For example, Diamond-Blackfan anemia can result from mutations in the transcription factor GATA1 [12][13][14] .…”

Adenovirus vectors in hematopoietic stem cell genome editing

“…The 12 kb transgene with regulatory elements was flanked by two FRT-IR/DRs sequences at each side. As an alternative target locus, one of the a-globin loci can be considered because an excess amount of a-globin production in b-thalassemia and SCD patients causes ineffective erythropoiesis and hemolysis [206]. The percentage of c-globin-positive erythrocytes increased to nearly 100% after selection.…”

“…It remains to be investigated whether further extension of the homology regions is beneficial. As an alternative target locus, one of the a-globin loci can be considered because an excess amount of a-globin production in b-thalassemia and SCD patients causes ineffective erythropoiesis and hemolysis [206].…”

A combination of the (αα)GZ and ‐‐SEA deletions causing a severe form of hemoglobin H disease

“…Research shows that HS-40 deletions strongly reduce expression of α-globin and thereby can cause α-thalassemia. 3,4 Deletion of α-globin genes combined with HS-40 deletions causing Hb H diseases is rare and helps us understand HS-40 features. 5,6 Here, we describe a novel deletion located in the HS-40 region in the α-globin gene cluster in a 3-year-old girl from Ganzhou City, Jiangxi Province of southern China, who showed severe anemia symptoms at 3 months and needed a blood transfusion every 45-50 days to maintain normal life activities.…”