In the last three hundred years, the breeding and selection of purebred dogs has intensified, a process that also carries a risk: many of these breeds have become more inbred, with little genetic diversity and therefore more likely to inherit certain diseases . A team of researchers from the University of Uppsala (Sweden) has carried out a study to analyze whether these breeding practices have increased the number of variants that cause diseases in dogs. To do this, they sequenced the complete genomes of twenty dogs of eight very common breeds such as Beagles, German Shepherds and Golden Retrievers.
The results revealed that the Cavalier King Charles Spaniel, which has undergone more intense breeding, is a breed that carries more damaging genetic variants. Some of these mutations, in particular, are related to myxomatous mitral valve disease (MMVD). In this heart condition, the mitral valve of the heart degenerates, allowing blood to leak from the left ventricle into the left atrium. The researchers identified two genetic variants related to the disease, which appear to regulate a gene that codes for a common protein in heart muscle. The findings offer a possible explanation for why the arrogant King Charles spaniel is more predisposed to developing the disease.
Why does this breed have more mutations?
This is most likely due to their breeding history – records suggest that small spaniel-type dogs have been around for at least a thousand years and were very popular in the royal courts of Asia and Europe. These spaniels experienced several “bottlenecks” in which only a small percentage of the population passed their genes on to the next generation. Bottlenecks may have made harmful genes more common in the King Charles spaniel genome before the dog achieved breed recognition in 1945.
“ Recent breeding may have led to an accelerated accumulation of harmful mutations in certain breeds of dogs. In the cavalier King Charles spaniel specifically, one or more of these mutations affect the NEBL protein of the heart muscle and can predispose this breed to devastating heart disease ”, explained Erik Axelsson, one of the authors of this work that has been published in PLOS Genetics magazine.
