The Genetics of Being Swole

No, the dog in the picture above is not on steroids, though it is easy to understand why many might jump to that conclusion. In comparison, this muscular dog dwarfs the regular one beside it and is nearly double its size. The reason for this? Basic Genetics.

One single mutation in the MSTN gene leads to a loss in myostatin function (an inhibitor of muscle growth). The effect of this mutation is quite clear: increased muscle size and strength. Given the fundamental qualities of this gene, the function of MSTN is highly conserved in many mammals and the mutation also occurs naturally in a few of them; dogs, cattle, mice, and even humans. While studies have been conducted upon the majority of these species, the canine test subjects have provided the most recent and interesting results.

These studies focus on whippets, the breed depicted in the picture. Bred as racing dogs, whippets have always been focused on athletic performance so it is not difficult to see why mutations in athletic genes would occur here. Known as bully whippets, these dogs have something known as the Double-Muscling phenotype. Studies have shown that this phenotype seems to follow Mendelian Genetics, appearing to be autosomal recessive. Interestingly, the actual athletic performance attributed to the mutation is observed in heterozygous and homozygous individuals. Experiments indicated that the majority of top performing dogs were animals with at least one mutated allele. The Double-Muscling phenotype had already been studied in great depth in mice and cattle, however this new insight into the actual implications the mutation has on activity and performance is a recent development in the research of the MSTN gene. It is the first time the gene has been linked to actual athletic performance and ability, showing that the extra muscle growth actually leads to functional muscle.

The most important implication of this finding is the potential contribution to human disease and clinical applications. Research as already begun on the gene’s relevance to muscular dystrophy. While work with MSTN certainly has a lot of clinical potential and will be beneficial to therapeutic treatments of diseases involving muscle loss, the rising field of athletic genetics is not without controversy. The fact that this gene confers athletic advantage will undoubtedly cause it to receive some unwanted attention. There are many ways to use this gene for medical purposes, however there are just as many ways to abuse it for athletic gain as well. Research in this area is still young, though it will be very interesting to see where the conversation of ethical genetic application will lead. Like all technology, it is something that can be used for positive, selfless purpose just as easily as it can be used for selfish gain. The MSTN gene could play a huge role in treating many debilitating muscular diseases, and hopefully the discussion of genetic potential will result in a prioritization of these medical benefits instead of trying to constantly push the bounds of what is ethically and athletically accepted.


Harris Jackson (Week 1)


Citation: Lee, S. J. (2007). Sprinting without myostatin: a genetic determinant of athletic prowess. Trends in genetics, 23(10), 475-477.