The arrogant King Charles Spaniel is the dog breed that carries the most disease-causing genetic mutations, a new study reveals.
The small but cute breed has been negatively impacted by years of inbreeding, putting it at greater risk for heart disease, the study warns.
In particular, it has genetic variants linked to myxomatous mitral valve disease (MMVD), a common and deadly heart condition.
The past 300 years of dog breeding has created an incredible diversity of breeds with different sizes, shapes and abilities, the authors say.
But unfortunately this has also made many breeds more inbred and more likely to inherit genetic diseases.
Both King Charles I and his son Charles II were followers of the breed. The particularly large number of potentially harmful genes in the genome of Cavalier King Charles Spaniels, compared to other dogs, was probably the result of breeding history
Erik Axelsson of Uppsala University in Sweden and colleagues published the new findings today in the journal PLOS Genetics.
“We find that individuals belonging to the breed affected by the most intense breeding – Cavalier King Charles Spaniel (cKCs) – carry more harmful variants than other breeds,” they say in their paper.
[This indicates] that previous breeding practices may have increased the overall levels of harmful genetic variation in dogs.”
THE EIGHT BREEDS
1. Cavalier King Charles Spaniel
3. German Shepherd
4. Golden Retriever
5. Labrador Retriever
6. Standard Poodle
8. West Highland White Terrier
(Note: The breeds are not listed in order of genetic mutations, although the Cavalier King Charles Spaniel was most affected.)
The study’s researchers wanted to know whether recent breeding practices had increased the number of disease-causing variants in dogs.
They sequenced the entire genome of 20 dogs from eight common breeds, including the Beagle, German Shepherd, Golden Retriever and Standard Poodle.
They found that the arrogant King Charles Spaniel, who experienced the most intense breeding, carried more harmful genetic variants than the others.
Standard Poodles were also found to carry more harmful mutations than several of the other breeds, but not as many as the arrogant King Charles Spaniel.
Comparisons of Dachshunds with and without signs of heart disease were used to help identify mutations that may predispose Cavalier King Charles Spaniels to develop MMVD.
In this condition, the mitral valve in the heart degenerates, causing blood to leak from the left ventricle back into the left atrium.
Researchers identified two genetic variants linked to the disease, which appear to regulate a gene encoding a common protein in heart muscle called NEBL.
“We find that recent breeding may have led to an accelerated accumulation of deleterious mutations in certain dog breeds,” says Axelsson.
Comparisons of Dachshunds (right) with and without signs of heart disease were used to help identify mutations that may predispose Cavalier King Charles Spaniels to developing MMVD
“Particularly in the Cavalier King Charles Spaniel, one or more of these mutations affect the heart muscle protein NEBL and can predispose this breed to devastating heart disease.”
While the breed’s predisposition to the disease is already known compared to other dogs, the new findings offer a possible explanation as to why this is so.
Portrait of King Charles II, a follower of the breed
Axelsson told MailOnline that because of the low number of breeds looked at — just eight — it’s likely there are several other races that carry similar amounts of potentially harmful mutations as cavaliers.
“Future research is likely to answer this question and possibly provide a more accurate answer as to why we see these differences,” he said.
The particularly large number of potentially harmful genes in the genome of Cavalier King Charles Spaniels, compared to other dogs, was probably the result of breeding history.
Data suggests that small spaniel-like dogs have been around for at least 1,000 years and were popular at royal courts in Asia and Europe for hundreds of years, including the court of King Charles II (1630-1685).
These spaniels experienced several bottlenecks with only a small percentage of the population passing on their genes to the next generation.
These bottlenecks made the deleterious genes more prevalent in the Cavalier King Charles Spaniel genome before the dog was recognized as a breed in 1945.
Both King Charles I and his son Charles II were supporters of the breed, as the American Kennel Club (AKC) explains.
“Charles II was so attached to his spaniels that they went everywhere with him,” the AKC says on its website.
He issued a royal decree that the dogs should be allowed in all public areas, including parliament. The breed is even named after the monarch.’
MEET THE CAVALIER KING CHARLES SPANIEL
The Cavalier King Charles Spaniel is a small spaniel with a short, but distinct muzzle, large brown eyes, and a silky coat.
The colors are black and brown, ruby, red and white (Blenheim) and tricolor (chestnut markings on a pearly white background).
Adults measure 11.8 to 13 inches (30-33 cm) and weigh 5.5-8 kg.
The original Cavalier King Charles Spaniel dog breed was developed from the toy spaniels depicted in the work of 16th-, 17th- and 18th-century painters such as Titian and Gainsborough.
They were common as pets for ladies and used to heat laps.
King Charles II was so fond of his spaniels that he could not be separated from them.
By 1800, the snub-nosed variety had taken over in popularity and the original spaniel was all but lost.
Only the Duke of Marlborough kept a line alive and bred them at Blenheim Castle.
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