Cavalier Health: Study looks at genetic consequences of dog breed formation

A study reported on ​CavalierHealth.org states that ​Cavaliers have higher levels of deleterious genetic variations, compared to seven other breeds. This is a pilot study and the researchers do air caution saying, "... although cKCs have accumulated deleterious alleles that are likely to have large phenotypic effects, the total number of added mutations may be relatively low and it may hence be premature to use our results as an argument to discourage further breeding of cKCs."
The interesting bit for me is the bit about gene NEBL in papillary muscles, where they say, "The most common disease in cKCs is myxomatous mitral valve disease (MMVD). To identify variants linked to this disease we next characterize mutations that are common in cKCs, but rare in other breeds, and then investigate if these mutations can predict MMVD in dachshunds. We find that variants that regulate the expression of the gene NEBL in papillary muscles may increase the risk of the disease, indicating that loss of papillary muscle integrity could contribute to the development of MMVD."
PLOS have published the whole study and you can read the study HERE