Where does an Appaloosa get its spots? What makes one horse more naturally suited for Western pleasure than dressage? Why do some horses get laminitis, and others don't? The short answer we all know is, "It's in the genes." Accurate, but abstract.
The Horse Genome Project is finally able to answer some of these mystifying questions. For the past four years, the participants in this multinational project have been unraveling the equine genetic code. Led by Claire Wade, BSc, PhD, a senior research scientist at the Broad Institute, a part of the Massachusetts Institute of Technology and Harvard University, this research team has been bringing that age-old term "in the genes" down to an exact science.
--Dr. Claire Wade
True, DNA identification tests have been allowing breeders to confirm parental ties between horses for years. But that's just one small step of DNA recognition, evaluating less than 5% of the horse's DNA, according to Wade. Genome mapping is an entirely different arena, requiring millions of dollars of computer-aided research to identify each and every one of the 2.7 billion bases of the equine genome.
"We can now develop [new] tests for genetic diseases and better understand the biology of diseases, and that will lead to new treatments," Wade said.
The genome is the entire set of genetic information available in the chromosomes. Chromosomes are like single-file rows of apples--in varying orders of red, green, yellow, and brown--that go on for miles. It's the order of the "colors" that creates the genetic code for everything from coat pattern to basic disposition.
Wade's team meticulously analyzed the DNA sequences in all 32 chromosomes of Twilight, a Thoroughbred mare from the equine research facility at Cornell University's College of Veterinary Medicine in Ithaca, N.Y., documenting the mare's physiology down to the very last base pair. Smaller sections of DNA sequences from seven other horses representing six different breeds were also analyzed to provide contrast.
With that information, researchers have been able to create a map--a true, physical map that will lead scientists right to the precise areas on the genome where specific information about diseases, physical characteristics, and other hereditary traits can be found on every horse's genome. With these "signposts," scientists can pinpoint DNA testing for certain illnesses to an exact location, yielding results that are not only accurate, but also cost-efficient.
"Using these newly discovered signposts, we've been able to create a tool that lets us instantly read 60,000 markers (specific sites on the genome) from individual horses for only $500," she said, adding that the costs will continue to drop over time. Previously, if an individual began a project on a particular DNA region, he or she first would have to obtain a DNA sequence for that region. The preliminary work would take six to eight months and cost up to $80,000.
Other benefits of this research include an improved understanding of coat coloring, as well as enhanced knowledge of equine origins and the evolution of various breeds, she said.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
