Health

Genetics: The New Frontier

The equine genome map is as important to the future of horses as the development of antibiotics was 45 years ago.

More than 45 years ago, the introduction of antibiotics for use in animals greatly improved animal health and productivity. Today, genetic testing, gene therapy and the identification of genetic markers for certain diseases offer an even bigger opportunity for advancement in the equine industry.

The completion of the equine genome map is “a $20 to $30 million contribution to the horse, the likes of which have never occurred before,” says Ernest Bailey, Ph.D., coordinator of the equine genome project, a collaborative effort based at the University of Kentucky that began in 1995 with 70 scientists from 20 countries. “It’s amazing. Its applications are comparable to the development of antibiotics. Antibiotics benefited the health of everything; this is going to benefit the health of horses to the same extent in the next 50 years because of the things we can find out.”

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In 2007, after 12 years of diligent work, researchers and other interested in equine genetics were given free access to the horse genome map and database. The resulting findings included the development of a diagnostic tool that identifies genes and the diseases to which they are linked; genetic tests for diseases and heritable traits like coat color; and deeper digging into the causes of certain diseases.

Breeders especially can benefit from the development of the equine genome map because they now are able to select matings or reject breeding stock based on genetic traits in the horses’ DNA.

Gene Expression

Dr. Alicia Bertone, professor of surgery in the Department of Veterinary Clinical Sciences at Ohio State University, collaborated with Affymetrix Inc., based in Santa Clara, California, to develop the first equine gene chip, a diagnostic tool that looks at gene expression, which occurs when certain genes react to a specific disease by expressing proteins. Identifying those active genes and how they interact, then linking them to the specific disease that causes them is called a diagnostic signature.

The computer chip contains an array of most known horse genes. By comparing the genetic material in an individual horse’s sample to the baseline array for a normal horse of that age and gender, it is possible to determine a pattern of genetic activity that would indicate early stages of disease.

Dr. Bertone gave the example of comparing blood or synovial fluid of an arthritic horse to that of a normal horse, using the gene chip.

“You may find genes that are always abnormal in the arthritic horse or horse with osteochondrosis, a developmental joint disease, and are not abnormal in the normal horse,” she says. “Not only could you use those signatures then to identify horses with impending disease problems – meaning early in the process, when you might be able to intervene with medication – but also, you can monitor the progression of the disease.”

Using the gene chip, Dr. Bertone was able to develop a diagnostic signature for osteoarthritis by studying the gene expression of cartilage in horses with the disease, and she was able to differentiate between he early and end stages of osteroarthritis.

“That hasn’t been done in any species,” Dr. Bertone says. “We were able to show that the gene chip could essentially define a profile that represented these different states of the cartilage. It allowed us to understand that the end-stage cells are undergoing a death pathway. In the earlier process they are not; they are potentially recoverable. It also helps you determines what kind of drugs you would need to get these cells to kick back in. So it does help to determine therapeutics.”

Stay tuned next week for the second part of this story.

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