Duchenne muscular dystrophy (DMD), the most common and severe form of muscular dystrophy among boys, is characterized by progressive muscle degeneration and weakness. It is caused by mutations in the X-linked DMD gene that encodes the protein dystrophin. The disease affects one in 3,500 to 5,000 boys, according to the Centers for Disease Control and Prevention and other estimates, and often leads to premature death by the early 30s.
Although the genetic cause of DMD has been known for nearly 30 years, no effective treatments exist. The disease breaks down muscle fibers and replaces them with fibrous or fatty tissue, causing the muscle to gradually weaken. This condition often results in heart muscle disease, or cardiomyopathy, the leading cause of death in these patients.
In the study published in Science, researchers used a gene-editing approach to permanently correct the DMD mutation that causes the disease in young mice.
Previously the research team first used this technique - called CRISPR/Cas9-mediated genome editing - to correct the mutation in the germ line of mice and prevent muscular dystrophy. This paved the way for novel genome editing-based therapeutics in DMD. It also raised several challenges for clinical applications of gene editing. Since germ line editing is not feasible in humans, strategies would need to be developed to deliver gene-editing components to postnatal tissues.
To test this out, researchers delivered gene-editing components to the mice via adeno-associated virus 9 (AAV9). DMD mice treated with this technique produced dystrophin protein and progressively showed improved structure and function of skeletal muscle and heart.
Now, the research team is working to apply this gene-editing technique to cells from DMD patients and in larger preclinical animal models.