About 10 years ago, researchers at the Royal Veterinary College found a family of King Charles Spaniels that had a canine version of Duchenne Muscular Dystrophy (DMD). With this, they began research in the hopes of one day finding a cure. Now in a new study, scientists have halted the progression of the disease in some of the dog descendants from the King Charles Spaniel family using the gene editing tool CRISPR.
DMD is the most fatal genetic disease in children, and mostly affects boys and young men, around 2,500 people in the UK have the condition. Those born with the disease have a genetic mutation that stops them producing dystrophin, a protein that is vital for muscle strength and function. It has a high fatality rate in children as their heart loses the strength to pump blood to the body, or their diaphragm becomes too weak to breathe.
This new study was a collaboration between the Royal Veterinary College in London, and the University of Texas Southwestern Medical Centre in the US. They wanted to test gene editing in dogs as DMD also occurs in many dog breeds, which means a positive result could lead to better treatment for both dogs and humans. The researchers wanted to show that CRISPR was safe and effective in dogs and then move on to human trials.
The team did not know what to expect from the study, as using CRISPR body-wide in a large mammal had never been done before. They prepared for the worst – inflammatory immune response, liver toxicity, anaphylaxis – but all they saw was puppies who could play again.
The study consisted of injecting one-month-old dogs with two harmless viruses that edited the genome in cells of the muscles and heart. Within weeks of the gene edit in the dogs, the missing dystrophin was restored in muscle tissue around the body, including up to 92% the heart and 58% in the diaphragm. Scientists previously have estimated that a 15% or greater improvement is needed to significantly help patients, so the statistics from the study are very encouraging.
This new strategy edits the mutation that causes the disease, but the technique used in the study was only for a genetic fault that affects around 13% of DMD sufferers. However, experts are hopeful it could be applied to the many other mutations those with the condition have.
This was a small study, but the researchers are optimistic that it will be regarded as a ground-breaking study that led the way to effective treatment. The next step will be to conduct larger and longer studies to see if gene editing does help to slow the progression of DMD and improve muscle strength. It won’t be a cure but will certainly be a beneficial treatment for those suffering with DMD.