Canine mutation creates strong tail wind
(June 13th 2007) Faster, higher, stronger - the Olympic motto incites athletes to train hard to achieve top performances. However, a driving ambition does not necessarily make a winner; this needs, above all, natural skill and talent. This can be conferred by genes and mutations. US-scientists found a new gene that controls speed and muscle mass of racing dogs, the middle-distance runners amongst animal athletes. After all, pace isn't achieved by magic, reports Susanne Dorn.
Racing dogs are perceived to be naturally sporty, as they are bred to run. One well-known breed in this field is the whippet, the small, thin brother to the greyhound. They are recorded as being the fastest mammals on earth relative to their size, sprinting to top speeds of about 65 km/h. Well, the best of them at least! As in every line of sport, hence also in dog racing, there are the fast and the faster! What is it that makes some guys faster than their fellows?
A team of scientists at the National Institutes of Health (NIH) led by Elaine A. Ostrander recently came a step closer to the answer (
PLoS Genetics, May 1, 2007). Studying the genetic profiles of whippets, the researchers found that the gene coding for the muscle protein myostatin (
MTSN) plays a pivotal role in achieving best performance. Usually, this gene limits muscle cell division, however, a mutation within
MTSN leads to an increase in muscle mass development. So it's reasonable to assume that carriers of the mutation would run faster, "More muscles, more speed!"
But this is only half the truth. Some whippets are not slim but extremely beefy. The muscle structure of these so called "bully" whippets resembles the double-muscled phenotype known from "mighty mice", cattle, sheep and from a young boy. The double-muscled phenotype has previously been shown to be linked to a mutation in the
MTSN gene. Bearing that finding in mind, Ostrander and colleagues sequenced the
MTSN gene in 22 different whippets, namely: bully whippets, those that had given birth to or sired bully whippets, and "normal" dogs with no known relation to a bully phenotype. It turned out that bully individuals had a homozygous mutation in the
MTSN gene, a two-base-pair deletion leading to an abnormally shortened myostatin protein. With their gross excess of muscle mass they are subsequently too bulky to race; they are prone to cramping in the shoulder and/or thigh and are therefore rarely found among competitive runners.
The advantage of a
MTSN gene mutation is seen in whippets carrying the mutation in only one allele. Those were also found to be more muscular than wild-type dogs but not as excessive. They are significantly faster than homozygous
MTSN wild-type runners. Additional gene status analysis of the breeders' fastest racers showed a significant association between a dog's genetic profile and its speed. Many of the top racers carried the mutation. That's not really surprising, since breeders selecting for speed inadvertently boosted persistence and inheritance of the mutation. However, the researchers did not see this association in other species of dogs, which are also bred for speed, including greyhounds.
The results linking increased athletic performance to a
MSTN mutation could, for the first time, implicate competitive sports in dogs, horses and possibly even humans, write Ostrander and colleagues. Of course, in the era of increasing doping abuse, it might be alluring to utilise the findings for gene doping via disruption of
MSTN but the scientists warn imploringly: Given the poorly understood consequences for overall health and well-being, extreme caution should be exercised when acting upon these results.
The article is available online in
PLoS Genetics
