Potent and uniform fetal hemoglobin induction via base editing

Area of Science:

• Hematology
• Gene Editing
• Molecular Biology

Background:

• Inducing fetal hemoglobin (HbF) is a therapeutic strategy for β-thalassemia and sickle cell disease.
• Hematopoietic stem and progenitor cells (HSPCs) are targets for gene therapy to increase HbF production.

Purpose of the Study:

• To compare the efficacy of different gene editing strategies for inducing fetal hemoglobin (HbF).
• To evaluate the use of adenine base editors versus Cas9 nuclease in HSPCs for HbF induction.

Main Methods:

• Comparison of five distinct gene editing strategies in CD34+ HSPCs.
• Utilizing adenine base editors and Cas9 nuclease for targeted gene modification.
• Assessing HbF levels in edited erythroid colonies and in vivo after mouse transplantation.

Main Results:

• Adenine base editor generation of γ-globin -175A>G resulted in significantly higher HbF levels (81% ± 7%) compared to unedited controls (17% ± 11%).
• Cas9 strategies targeting BCL11A regulatory elements showed lower and more variable HbF induction.
• The -175A>G base edit demonstrated superior potency in inducing HbF compared to Cas9 in a mouse transplantation model.

Conclusions:

• Adenine base editing at the γ-globin -175 locus is a potent and uniform strategy for HbF induction.
• Base editing circumvents the phenotypic variability associated with Cas9-induced indels.
• This approach offers insights into γ-globin gene regulation and a potential therapeutic avenue for hemoglobinopathies.