By Dina Fine Maron
Duchenne muscular dystrophy is a life-threatening muscle-wasting illness. Occurring mostly in males, it is the most common type of muscular dystrophy, striking about one in 3,500 boys and causing their muscles to start breaking down in early childhood. It often confines patients to wheelchairs by the time they are teenagers and usually leads to an early death from heart or respiratory failure. There is no cure—but a genetic fix tested in dogs may offer new hope.
The disease is caused by gene mutations that make patients’ muscle cells unable to produce enough dystrophin, a protein that helps muscles absorb shocks and protects them against degradation over time. In a recent study, scientists used a gene-editing technique called CRISPR/Cas9 to pump up muscle protein levels in four dogs suffering from Duchenne. The advance may hasten clinical trials for similar treatments in humans.
The research team, led by the University of Texas Southwestern Medical Center, worked with young beagles bred to have Duchenne. The scientists edited the dogs’ muscle cells to remove a key barrier to higher protein production—a short, problematic segment of protein-coding DNA that occurs in both canines and humans with the illness. Within about two months the dogs were producing greater amounts of dystrophin; levels in skeletal muscle ranged up to 90 percent of normal, depending on the muscle type and dosage used. (Some dogs produced significantly less.) In cardiac muscle, a crucial target for treatment, levels climbed to as high as 92 percent of normal. The U.T. Southwestern researchers, who published their findings in August in Science, report that they did not detect any unintended changes to other regions of the genome—a common concern with gene-editing technology—and there was no evidence the technique made the dogs ill.
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