Optimized genomic editing of a common Duchenne muscular dystrophy mutation in patient-derived muscle cells and a new humanized mouse model.

Duchenne muscular dystrophy (DMD) is a fatal X-linked, recessive disease caused by mutations in the DMD gene encoding dystrophin, a membrane-associated protein necessary for maintaining muscle structure and function. One of the common DMD mutations is the deletion of exon 52 (Δ52), which introduces a premature stop codon in exon 53, preventing the expression of functional dystrophin protein. Patients with this mutation could benefit from skipping or reframing exon 53 to restore the dystrophin open reading frame. In this study, we investigated the efficacy of single-cut CRISPR gene editing with Staphylococcus pyogenes Cas9 (SpCas9)-LRVQR to restore dystrophin expression in patient-derived induced pluripotent stem cells (iPSCs) and a newly generated humanized DMD mouse model. We compared two injection routes for adeno-associated virus (AAV) serotype 9 to deliver gene-editing components to neonatal mice: intraperitoneal (IP) and facial vein (FV) injection. We observed efficient restoration of dystrophin protein expression across multiple skeletal muscle groups and the heart. The AAV9-mediated CRISPR single-cut approach ameliorated key DMD hallmarks, including histopathological phenotypes, impaired grip strength, and elevated serum creatine kinase levels. Our optimized strategies for dystrophin restoration in humanized DMD mice with exon 52 deletion represent a promising treatment for DMD.