Muscle-gene edit creates buff beagles

Bully whippets may have competition in doggy body-building contests. Two beagles in China have been genetically engineered to be extra buff. The small hounds are the latest addition to a menagerie of gene-edited animals that also includes pigs and monkeys.

Researchers in China decided to mutate a muscle gene in beagles to test whether a powerful gene-editing technology called CRISPR/Cas9 will work in dogs. Mutations in the gene, called myostatin, give bully whippets and Belgian Blue cattle their bulky muscles, but are not known to cause health problems.

Liangxue Lai of the South China Institute for Stem Cell Biology and Regenerative Medicine in Guangzhou, China, and colleagues injected the gene editor into 35 beagle embryos. Of 27 puppies born, two had edited genes, the team reports October 12 in the Journal of Molecular Cell Biology.

A female puppy named Tiangou has both copies of the myostatin gene mutated in all of her cells. At 4 months, Tiangou had more muscular thighs than her unedited sister. A male puppy, Hercules, who carries double mutations in most, but not all, of his cells, wasn’t more muscular than other 4-month-old puppies. Both dogs have packed on more muscle as they’ve matured, and Lai says their fur may be concealing how ripped they are.

The low number of puppies born with edited myostatin genes indicate that the editor is not very efficient in dogs, but Lai says the process just needs to be optimized.

Next, Lai and colleagues hope to make mutations in beagles that mimic genetic changes implicated in Parkinson’s disease and hearing loss in humans to study those diseases and potential therapies. The researchers have no plans to make designer pets, Lai says.