CRISPR/Cas9-based multiplex genome editing of BCL11A and HBG efficiently induces fetal hemoglobin expression.

Beta-hemoglobinopathies are caused by mutations in the β-globin gene. One strategy to cure this disease relies on re-activating the γ-globin expression. BCL11A is an important transcription factor that suppresses the γ-globin expression, which makes it one of the most promising therapeutic targets in β-hemoglobinopathies. Here, we performed single-gene editing and multiplex gene editing via CRISPR/Cas9 technology to edit BCL11A erythroid-specific enhancer and BCL11A binding site on γ-globin gene promoter in HUDEP-2 cells and adult human CD34+ cells. Multiplex gene editing led to higher γ-globin expression than single-gene editing without inhibiting erythroid differentiation. By further optimizing the on-target DNA editing efficiency of multiplex gene editing, the percentage of F-cells exceeded 50% in HUDEP-2 cells. Amplicon deep sequencing and whole genome sequencing were used to detect the editing frequency of on- and potential off-target sites in CD34+ cells. No off-target mutations were detected, suggesting its accuracy in HSPCs. In summary, our study provides a new approach which can be used for the treatment of β-hemoglobinopathies in the future.