Scientists have for the first time used gene-editing to treat Duchenne muscular dystrophy in a large mammal, a significant step towards effective treatment for people with the disorder.
The condition, which has no cure, leads to loss of muscle function and strength and ultimately an early death.
But in a study on dogs, scientists were able to partially restore the key protein people with DMD cannot make.
They hope in the future to test the technique in people.
Duchenne muscular dystrophy (DMD) is the most common fatal genetic disease in children and almost entirely affects boys and young men - about 2,500 of them in the UK have the condition.
Children born with the degenerative disease have a genetic mutation that stops them producing dystrophin, a protein that is vital for muscle strength and function.
The same disorder also occurs in many dog breeds.
Using the Crispr gene-editing tool, scientists were able to restore dystrophin in four dogs that had the most common genetic mutation seen in DMD patients, by making a single strategic cut in the faulty DNA.
This was done by injecting the dogs, who were one month old, with two harmless viruses that edited the genome of the dog in the cells of the muscles and heart, reports BBC.
Gene-editing technique could transform future
Within several weeks of the edit made in the dogs, the missing protein was restored in muscle tissue throughout the body, including a 92 per cent correction in the heart and 58 per cent in the diaphragm, the main muscle needed for breathing, according to the study in the journal Science.
Scientists have estimated that a 15 per cent or greater improvement is needed to significantly help patients.
The study was a collaboration between the Royal Veterinary College, in London, and the UT Southwestern Medical Center, in the US.
Dr Eric Olson, one of the authors, from UT Southwestern, said: "Children with DMD often die either because their heart loses the strength to pump or their diaphragm becomes too weak to breathe.
"This encouraging level of dystrophin expression would hopefully prevent that from happening."
Richard Piercy, professor of comparative neuromuscular disease at the Royal Veterinary College, said: "The ambition is to show that this is safe and effective in dogs and then move into humans trials.