Prevention of early-onset cardiomyopathy in Dmd exon 52-54 deletion mice by CRISPR-Cas9-mediated exon skipping.

Duchenne muscular dystrophy (DMD) is a disease with a life-threatening trajectory resulting from mutations in the dystrophin gene, leading to degeneration of skeletal muscle and fibrosis of cardiac muscle. The overwhelming majority of mutations are multiexonic deletions. We previously established a dystrophic mouse model with deletion of exons 52-54 in Dmd that develops an early-onset cardiac phenotype similar to DMD patients. Here we employed CRISPR-Cas9 delivered intravenously by adeno-associated virus (AAV) vectors to restore functional dystrophin expression via excision or skipping of exon 55. Exon skipping with a solitary guide significantly improved editing outcomes and dystrophin recovery over dual guide excision. Some improvements to genomic and transcript editing levels were observed when the guide dose was enhanced, but dystrophin restoration did not improve considerably. Editing and dystrophin recovery were restricted primarily to cardiac tissue. Remarkably, our exon skipping approach completely prevented onset of the cardiac phenotype in treated mice up to 12 weeks. Thus, our results demonstrate that intravenous delivery of a single-cut CRISPR-Cas9-mediated exon skipping therapy can prevent heart dysfunction in DMD in vivo.

Advances in CRISPR/Cas9 Genome Editing for the Treatment of Muscular Dystrophies.

Muscular dystrophies (MDs) comprise a diverse group of inherited disorders characterized by progressive muscle loss and weakness. Given the genetic etiology underlying MDs, researchers have explored the potential of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) genome editing as a therapeutic intervention, resulting in significant advances. Here, we review recent progress on the use of CRISPR/Cas9 genome editing as a potential therapy for MDs. Significant strides have been made in this realm, made possible through innovative techniques such as precision genetic editing by modified forms of CRISPR/Cas9. These approaches have shown varying degrees of success in animal models of MD, including Duchenne MD, congenital muscular dystrophy type 1A, and myotonic dystrophy type 1. Even so, there are several challenges facing the development of CRISPR/Cas9-based MD therapies, including the targeting of satellite cells, improved editing efficiency in skeletal and cardiac muscle tissue, delivery vehicle enhancements, and the host immunogenic response. Although more work is needed to advance CRISPR/Cas9 genome editing past the preclinical stages, its therapeutic potential for MD is extremely promising and justifies concentrated efforts to move into clinical trials.