Abstract
Recent advances in base editing have created an exciting opportunity to precisely correct disease-causing mutations. However, the large size of base editors and their inherited off-target activities pose challenges for in vivo base editing. Moreover, the requirement of a protospacer adjacent motif (PAM) nearby the mutation site further limits the targeting feasibility. Here we modify the NG-targeting adenine base editor (iABE-NGA) to overcome these challenges and demonstrate the high efficiency to precisely edit a Duchenne muscular dystrophy (DMD) mutation in adult mice. Systemic delivery of AAV9-iABE-NGA results in dystrophin restoration and functional improvement. At 10 months after AAV9-iABE-NGA treatment, a near complete rescue of dystrophin is measured in mdx4cv mouse hearts with up to 15% rescue in skeletal muscle fibers. The off-target activities remains low and no obvious toxicity is detected. This study highlights the promise of permanent base editing using iABE-NGA for the treatment of monogenic diseases.
Highlights
Recent advances in base editing have created an exciting opportunity to precisely correct disease-causing mutations
174 out of 508 pathogenic point mutations for Duchenne muscular dystrophy (DMD) are due to G:C to A:T conversion (Supplementary Table S1), which could potentially be targeted by adenine base editors (ABEs) editing
The mdx4cv mouse carries a premature stop codon (CAA-to-TAA) in the exon 53 of the Dmd gene[38], which disrupts the expression of dystrophin and leads to the development of muscular dystrophy
Summary
Recent advances in base editing have created an exciting opportunity to precisely correct disease-causing mutations. Previous studies showed that exon deletion through clustered regularly interspaced short palindromic repeats (CRISPR) genome editing can restore dystrophin expression and function in dystrophic animals and cells[6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] Promising, this strategy raises potential safety concerns as it relies on the repair of the double-strand DNA break (DSB) created by CRISPR/Cas[921–23], which may cause unwanted large deletion and even DNA rearrangement[24,25,26]. We explore the feasibility and long-term efficacy of correcting a commonly used mouse model of DMD, mdx4cv mice[38], using NG-targeting base editors
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