Duchenne muscular dystrophy (DMD) is an inherited X-linked disease caused by mutations in the gene encoding dystrophin, a protein required for muscle fiber integrity. The dystrophin gene is one of the largest human genes and consists of 79 exons. Although there are thousands of individual DMD mutations that have been identified in humans, these mutations are concentrated in hot spot regions of the dystrophin gene. DMD affects approximately 1 in 5,000 boys and is characterized by progressive severe muscle weakness and a shortened lifespan. Despite intense efforts to find cures for DMD through a variety of approaches, including myoblast transfer, viral delivery of dystrophin, and oligonucleotide-mediated exon skipping, there remains no cure for this disease. Our approach is to use CRISPR/Cas9 genomic editing to permanently correct DMD by skipping or reframing the mutant dystrophin exons in postnatal muscle tissue in vivo. We refer to this strategy as Myoediting. This genome editing approach removes the genetic mutation responsible for the disease, allowing for permanent correction of muscle structure and function. We deliver the CRISPR/Cas9 components using an adeno-associated virus-9 (AAV9) delivery system which has been shown to provide robust expression in skeletal muscle, heart and brain, the major tissues affected in DMD patients. To date, we have successfully corrected the dystrophin gene mutation in several DMD animal models having mutations in key hot spot regions of the dystrophin gene. In the previous funding period, we generated several other DMD animals models covering the remaining human hot spot regions and propose to correct these mutations using CRISPR/Cas genomic editing. Although we have made much progress using CRISPR/Cas genomic editing to correct DMD, there remains more work to be done to translate this gene editing therapy to the clinic. The efficiency of delivering the CRISPR/Cas9 components needs to be optimized and questions remain as to the durability of dystrophin expression after correction. Furthermore, since muscle fibers have hundreds of nuclei, we need to understand the occurrence of CRISPR/Cas9 genomic editing at the individual nuclear level. The long-term goal of this project remains to optimize and adapt CRISPR/Cas9-mediated genome editing to postnatal muscle and ultimately to leverage this approach to correct DMD mutations in humans. This project continues to represent a close collaboration between clinicians and basic scientists sharing the common goal of advancing a new therapeutic strategy to permanently cure DMD.
There is no cure available for Duchenne muscular dystrophy. We are using CRISPR/Cas9-mediated genomic editing (we call ?Myoediting) to correct the mutation causing Duchenne muscular dystrophy in human cells and animal models. This project represents a close collaboration between clinicians and basic scientists sharing the common goal of advancing Myoediting, an new therapeutic strategy to permanently cure Duchenne muscular dystrophy in humans.
