Targeted deletion of BCL11A gene by CRISPR-Cas9 system for fetal hemoglobin reactivation: A promising approach for gene therapy of beta thalassemia disease.

Hemoglobinopathies， such as β-thalassemia， and sickle cell disease (SCD) are caused by abnormal structure or reduced production of β-chains and affect millions of people worldwide. Hereditary persistence of fetal hemoglobin (HPFH) is a condition which is naturally occurring and characterized by a considerable elevation of fetal hemoglobin (HbF) in adult red blood cells. Individuals with compound heterozygous β-thalassemia or SCD and HPFH have milder clinical symptoms. So， HbF reactivation has long been sought as an approach to mitigate the clinical symptoms of β-thalassemia and SCD. Using CRISPR-Cas9 genome-editing strategy， we deleted a 200bp genomic region within the human erythroid-specific BCL11A (B-cell lymphoma/leukemia 11A) enhancer in KU-812， KG-1， and K562?cell lines. In our study， deletion of 200bp of BCL11A erythroid enhancer including GATAA motif leads to strong induction of γ-hemoglobin expression in K562?cells， but not in KU-812 and KG-1?cells. Altogether， our findings highlight the therapeutic potential of CRISPR-Cas9 as a precision genome editing tool for treating β-thalassemia. In addition， our data indicate that KU-812 and KG-1?cell lines are not good models for studying HbF reactivation through inactivation of BCL11A silencing pathway.