CRISPR gene-editing successfully stops muscle-eating disease in young dogs

The gene-editing tool CRISPR has been used to halt muscle dystrophy in a breed of beagle puppies. This brings gene editing one step closer to use in treating human genetic disorders.In a study published in Science, researchers have reported that using CRISPR, they were able to successfully correct a common genetic disease called Duchenne Muscular Dystrophy (DMD) in young dogs.DMD results from mutation of a gene that makes a protein called dystrophin.In puppies, insufficient amounts of dystrophin lead to muscle weakness, clumsy movements and even choking on their tongues – all as early as months after they are born.The disease also affects humans similarly. People born with the disease are confined to wheelchairs as the muscle degeneration gets progressively worse. In terminal cases, it can even cause vital organs like the lungs and heart failure to stop working.The four one-month-old beagles that were treated for DMD in the study had their mutant dystrophin gene ‘fixed’ using CRISPR. The researchers cut out a small part of the gene – its mutated section – at a precise location. They then used CRISPR to insert a properly functioning copy of dystrophin wherever it was otherwise mutated and faulty.Just removing this small section allowed the dogs’ cells to produce enough of the normal protein for healthy muscle function.[caption id="attachment_5094121" align="alignnone" width="1280"]

Representational image. Pixnio[/caption]Researchers used a virus to pack and deliver the gene editing components into the muscle cells of these dogs. They picked a virus with a particular affinity for muscle cells.Millions of virus copies containing the corrected DNA were injected in one of two possible places in the four pups. Two of the pups received the shot in their legs, and the other two directly into their bloodstream through by intravenous (IV) infusion.Dogs that received the IV injections showed a marked improvement in muscle function all over the body – lungs, heart, limbs – and their cells began to produce anywhere between three percent to 90 percent of normal dystrophin levels eight weeks post-injection, the study reports.The other pups that received a muscle injection of the CRISPR sequence also showed similarly improved levels of dystrophin production, but only in that localised area around the muscle.Either way, just recovering 15 percent of normal dystrophin activity, can significantly improve the quality of life of a DMD patient, according to the study.The researchers are moving towards treatments in humans but is yet to study the long-term effects of the treatment in these pups that clinical trials and commercial treatments require.The study concludes by disclosing that these safety tests will likely be completed by the end of 2019.