CRISPR helps heal mice with muscular dystrophy

The red-hot genome editing tool known as CRISPR has scored another achievement: Researchers have used it to treat a severe form of muscular dystrophy in mice. Three groups report today in Science that they wielded CRISPR to snip out part of a defective gene in mice with Duchenne muscular dystrophy (DMD), allowing the animals to make an essential muscle protein. The approach is the first time CRISPR has been successfully delivered throughout the body to treat grown animals with a genetic disease.

DMD, which mainly affects boys, stems from defects in the gene coding for dystrophin, a protein that helps strengthen and protect muscle fibers. Without dystrophin, skeletal and heart muscles degenerate; people with DMD typically end up in a wheelchair, then on a respirator, and die around age 25. The rare disease usually results from missing DNA or other defects in the 79 exons, or stretches of protein-coding DNA, that make up the long dystrophin gene.

Researchers haven’t yet found an effective treatment for the disorder. It has proven difficult to deliver enough muscle-building stem cells into...