This Dog Breed Has More Harmful Genetic Mutations Than Others

Breeding practices have led to more disease-causing genetic variants in dogs. In a new study, a team of researchers has found that a particular breed has so far incurred more harmful mutations than others.

Selective breeding for "desirable traits" over the course of 200 to 300 years has led to "extraordinary diversity" in dogs as well as their behavior, the researchers of a new study, published in PLOS Genetics Thursday, said. However, it has also caused certain disease-causing mutations to be more common in some dog breeds.

In many breeds, the creatures have become more inbred and more likely to inherit genetic diseases, PLOS noted in a news release.

For their study, the researchers took a closer look at the number of disease-causing mutations in 20 individual dogs from eight common dog breeds. These included cavalier King Charles spaniel, West Highland white terrier, beagle, German shepherd, golden retriever, Labrador retriever, rottweiler and standard poodles. Apart from the two labrador breeds, each of them was "approximately equally distantly related" and represented a separate European breed clade, the researchers noted.

Through whole-genome sequencing, the researchers found that cavalier King Charles spaniels, which experienced the "most intense breeding," had more harmful genetic variants compared to the other breeds. According to the researchers, this suggests that "past breeding practices may have increased the overall levels of harmful genetic variation in dogs."

The researchers also looked at the genetic mutations that are common in cavalier King Charles spaniels but are "rare" in other breeds. It was to possibly identify variants that are linked to a condition known as myxomatous mitral valve disease (MMVD), a heart condition in which the mitral valve in the heart degenerates, according to PLOS. It accounts for 75% of all cardiac disease cases in the general dog population and is the most common disease in cavalier King Charles spaniels, the researchers noted.

They were able to identify two specific genetic variants linked to the disease, possibly providing an explanation for why it is particularly prevalent in the breed.

"We find that recent breeding may have led to an accelerated accumulation of harmful mutations in certain dog breeds," study co-author Erik Azelsson of Uppsala University said in the PLOS news release. "In the Cavalier King Charles spaniel specifically, one or several of these mutations affect heart muscle protein NEBL and may predispose this breed to devastating heart disease."