Myostatin deficiency (whippet type) is an inherited muscular disorder affecting dogs. Dogs that inherit two copies of the Mutation associated with myostatin deficiency (whippet type) have broad chests and overly developed muscles especially of the neck and legs as well as an overbite. These dogs are easily discernible from unaffected littermates. Dogs that inherit one copy of the mutation have more muscling than dogs without the mutation but less muscling than dogs with two copies of the mutation. Dogs with one copy of the mutation tend to perform better when racing. Dogs with two copies of the mutation typically live normal lives but may be prone to muscle cramping of the shoulder and thigh muscles.
Genetic testing of the MSTN gene will reliably determine whether a dog is a genetic Carrier of myostatin deficiency (whippet type). Myostatin deficiency (whippet type) is inherited in an autosomal incomplete dominant manner in dogs meaning that dogs only need to inherit one copy of the mutated gene to have increased muscling, though, dogs with two copies of the Mutation have more muscling and are prone to muscle cramping. When a carrier of this mutation is bred with another dog that also is a carrier of the same mutation, there is risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance that the puppy will inherit two copies of the mutation and a 50% chance that the puppy will inherit one copy of the mutation and, in either case, will have increased muscling. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Dogs that do not have the mutation have no increased risk of having affected pups when bred to a dog that is also clear for this mutation.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Mosher DS, Quignon P, Bustamante CD, Sutter NB, Mellersh CS, Parker HG, Ostrander EA. A mutation in the myostatin gene increases muscle mass and enhances racing performance in heterozygote dogs. PLoS Genet. 2007 May 25;3(5):e79.
Shelton GD, Engvall E. Gross muscle hypertrophy in whippet dogs is caused by a mutation in the myostatin gene. Neuromuscul Disord. 2007 Oct;17(9-10):721-2.