Researchers in France have demonstrated the successful use of CRISPR-Cas9 gene editing to correct dystrophin duplications in patient-derived cells from individuals with Duchenne muscular dystrophy (DMD). The study, published in Scientific Reports, offers a potential therapeutic strategy for patients with duplications in exons 2-9 of the DMD gene, a subgroup for whom no targeted treatments are currently available.
DMD is a rare, X-linked muscle disease affecting approximately 1 in 3,500 to 5,000 live male births worldwide. It is characterized by progressive muscle wasting, inflammation, and loss of mobility, leading to premature death typically between the second and fourth decades of life. Mutations in the DMD gene, which encodes the dystrophin protein crucial for muscle function, are the underlying cause. Exonic duplications within the DMD gene are frequently observed in DMD patients.
The research team employed CRISPR-Cas9 to target intronic regions within the DMD gene in immortalized myogenic cells from DMD patients. Their objective was to delete specific duplicated regions, including duplications of exon 2, exons 2-9, or exons 8-9, which are known mutation hotspots in DMD. Following CRISPR-based deletion of the target duplications, the researchers confirmed restoration of the DMD open reading frame and rescued dystrophin expression. This was evidenced through western blotting and immunostaining of myotubes. RNA sequencing further suggested the rescue of genes within dystrophin-related pathways.
Importantly, off-target analysis, focusing on predicted close-match off-target sites, revealed no significant unintended gene editing at these locations. This finding supports the specificity and safety of the CRISPR-Cas9 approach in this context.
While DMD remains incurable, existing treatments such as eteplirsen, golodirsen, viltolarsen, and casimersen (all from Sarepta Therapeutics) induce exon skipping to address mutations in exons 45, 51, or 53, covering approximately 30% of DMD cases. However, no approved therapies directly address duplications in exons 2-9, making this CRISPR-based approach a potentially significant advancement for this patient subgroup.
