Dog breeding has produced canines in a variety of shapes and sizes, but has also led to a build-up of harmful mutations in certain breeds. A new study suggests that cavalier King Charles spaniels carry a particularly high level of mutations, including variants linked to a heart condition called myxomatous mitral valve disease.
at Uppsala University in Sweden and his colleagues compared the sequenced genomes of 20 individual dogs from eight popular dog breeds, such as German shepherds and golden retrievers, and found that cavalier King Charles spaniels had the highest number of potentially harmful variants of genetic mutations.
The team also looked for genetic variants that might explain why cavalier King Charles spaniels are particularly likely to develop a heart valve condition called myxomatous mitral valve disease, which affects nearly 100 per cent of 11-year-old cavalier King Charles spaniels. They found six variants in the heart-specific NEBL gene that seemed to be correlated with the condition in the spaniels 鈥� and three of the variants were also associated with early onset of the heart condition in a second dog breed, dachshunds.
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In what way these variants might be harmful is unknown. While they may cause disease, it could also be that they don鈥檛 really have much of an effect on dogs today because we are more able to take care of their health than we were in the past, says Axelsson.
The finding may be related to the fact that dog breeds often begin when humans selectively breed dogs taken from a small group with a desired set of traits, he says. It could be that the negative variants were unintentionally selected along with the genes responsible for the desired qualities.
鈥淚f populations 鈥� whether in the wild or domestic animals 鈥� are too small, you actually run the risk of accumulating these harmful variants,鈥� says Axelsson. 鈥淲hen a population is small, it鈥檚 harder for natural selection to filter out harmful variants.鈥�
鈥淲hen we think about bad variation, we always [ask] why it鈥檚 in the genome,鈥� says at the National Institutes of 午夜福利1000集合 in Maryland. 鈥淚f we select very strongly on a gene for, say, purple coats because we want a purple-coated dog, are there other variants that are in the same area [of the genome] that aren鈥檛 good for the health of the dog that get swept up and selected as well?鈥�
PLoS Genetics
