Etalon Diagnostics
Kids and horse
Genetic testing will change the horse industry’s future by providing data to prevent disease, improve breeding and make more informed decisions about purchasing, training, and managing horses. With data constantly evolving, genetic testing for horses is fast becoming not only affordable, but a mainstay tool for veterinarians, breeders and trainers alike.
Thanks to “23andMe” and similar human genetic testing companies, the field of genomics has gained huge attention lately. However, we have a group of equine geneticists and clinicians to thank from the “Horse Genome Project” for 15 years of research in 22 labs in 12 countries that worked together to develop various linkage, physical and comparative gene maps of the horse increasing the level of detail as data was added. In 2006, the horse was added to the list of mammalian species to have full genome sequencing under the National Institutes of Health (NIH) and the National Human Genome Research Institute (NHGRI).
Today, there are several companies focusing on equine genetic testing, some were labs who evolved out of blood testing for breeders, while others such as Etalon Diagnostics specifically evolved to bring the state-of-the-art technology of gene sequencing and information technology together for equestrians.
“Equine genetic testing will help both the lives of humans and horses as we collaborate with horse groups and horse people around the world,” says Christa Lafayette, equestrian, founder and chief executive officer of Etalon Diagnostics. She calls her company jokingly “32 and You,” as horses have 32 pairs of chromosomes while humans have 23.
As more horses are tested, the open database continues to grow providing information on everything from disease to behavior. With at least 11 known mutations causing more than 10 clinical syndromes in horses, the database grows monthly. Now, you may find all of your horse’s relatives, identify your wild horse’s lineage, know if your horse is predisposed to certain diseases, help determine your horse’s athletic potential, understand why it can’t do lead changes or learn why your horse is spooky or quiet. The more data acquired, the more associations are made, providing more useful information.
Value of Genetic Tests
Geneticists, researchers and clinicians are excited to confirm such relationships between sensorineural deafness and coat color pattern which has long been researched in various mammals. More recently they have found in both Waardenburg and Tietz syndromes that mutations in various genes are responsible for melanocyte development and migration reportedly inherited as autosomal recessive or dominant traits. This is true in humans and horses alike (1,2). Likewise[MSP1] the gene TRMP1 mutation associated with leopard coloring in Appaloosas is also associated with night blindness (3).
Breeders and Genetic Tests
While breeders have had the most interest in genetic testing for years, it is now coming into mainstream as a tool for better understanding your horse’s behavior as well as its physical capabilities (or lack thereof ) for a specific discipline. Since many conditions are breed specific, it is clear what conditions each breed may be at risk to have based on inherited genes (4).
The American Quarter Horse Association (AQHA) and the American Paint Horse Association (APHA) now require a five panel test for all registered breeding stallions for those conditions known to affect their breeds. This panel includes:
1.Glycogen Branching Enzyme Deficiency ( GBED) - a fatal condition of the
body to properly store glycogen leading to organ failure and overall weakness.
2. Hereditary Equine Regional Dermal Asthenia ( HERDA) - a connective tissue
condition does not allow the skin to heal and causes it to tear easily.
3. Malignant Hyperthermia (MH) - a disorder that causes muscle rigidity, fever and excessive sweating as well as shallow breathing and irregular heart under
stress.
4. Polysaccharide Storage Myopathy - Type 1 (PSSM1) -Not limited to Quarter Horse, this is found in more than 20 breeds, including Warmbloods.
The disorder may also be related to diet, but it causes an abnormal amount of sugars to be stored in the muscles causing, cramping, tremors, and muscle damage.
5. Hyperkalemic Periodic Paralysis (HYPP) - Caused by a mutation in the sodium
channel gene, it causes dysfunction of the electrical impulses necessary for
muscle contraction and can cause muscle tremors and paralysis.
Behavior and Training
Possibly the most interesting breakthroughs in horse genetics are coming from the integration and contribution of horse owners, trainers and veterinarians.
“We work with the people who know the horses best - horse owners and riders. By just listening to someone talk about their horse you'll find they know much more than anyone else, including all of the secrets that make that horse unique, capable or incapable, easy or difficult, etcetera. We firmly believe that the key to discovery lies within the horse community and that's why we collaborate so closely,” says Lafayette.
One fascinating discovery is that one of Etalon’s experimental tests for "temperament" (Curiosity vs. Vigilance) has proven to be valid.
In 2005, based on research that combined gene sequencing with a questionnaire to horse caretakers conducted on Thoroughbreds, Japanese researchers discovered an association between equine temperament and polymorphism in the dopamine D4 receptor gene (4). They identified this as “Curiosity and Vigilance.” It showed horses without the A allele had significantly higher Curiosity and lower Vigilance scores than those with the A allele. Etalon is finding similar results with a broad group of horses and questionnaires to horse owners including links to coat color and sensitivity. Hence, genetics may be the reason people think “chestnut mares” may be more difficult.
“The ‘discovery/experimental’ tests show a strong correlation with the owner/trainer opinion of the horse's temperament type. There are always exceptions of course, and we are aware that personality certainly doesn't entail only one gene, but the predictive power of this test has been startling. The same region is associated with aggression in dogs and thrill seeking behavior in humans,” says Lafayette.
Another recent discovery has shown a single mutation common to all horses that can pace called DMRT3 – “the gait gene.” Both copies of the gene in pacing horses were mutated. While it is a benefit to “pacers” and gaited horses, it is a disorder for dressage horses and jumpers. It displays has a neurological disconnect between the front end and hind end limiting the horse’s ability to canter correctly, perform lead changes or tempi changes. The “four-beat” canter which may be fine in western pleasure horses, is not an advantage in dressage or jumping. Hence identifying the gene before engaging in a specific discipline would certainly help the horse that may endure hours of training trying to learn a movement it cannot perform.
Soundness and Discipline
Two alleles (different forms of a gene at one chromosome location) on the MSTN gene have been identified as T-allele for distance and the C-allele for sprinting, and may help you determine what your horse is best suited for if you are interested in endurance or racing. While Quarter Horses most often have more C-allele, Thoroughbreds have a mix.
Determining whether your horse may be a “roarer” recurrent laryngeal neuropathy (RLN) or develop Equine Metabolic Syndrome (EMS) can also be identified in a DNA test. There is nothing more frustrating than having the perfect “hunter” with a beautiful jump, only to find out your horse is now a roarer, or your lovely young Warmblood is getting sore muscles from developing EMS. Identifying “risk factors” using genetics can help you develop the correct programs and actions to help mitigate genetic predisposition to specific conditions.
More Affordable Tests
What was once expensive with limited information, genetic testing is now affordable to every horse owner. Requiring just a handful of hair (30-40 mane hairs with roots), testing laboratories are now available and growing rapidly. Here are some examples:
- Texas A & M University’s Animal Genetics Laboratory offers a basic “ancestry test” for $45 which gives you an overview of your horse’s DNA profile.
- The UC Davis Veterinary Genetics Laboratory offers individual tests for specific breed related disorders, costing $40 per test per horse.
- Etalon’s Comprehensive Equine DNA testing starts at $99 for more than 55 genetic tests including coat color and patterns, various health and disease risks, and abilities and performance genetics. A more comprehensive test costs $149 to test for more complex diseases and syndromes.
Future Possibilities
Predicting disease risks, identifying health issues, understanding your horse’s temperament, and knowing its limitations are now realities with genetic tests, allowing people to develop training, feed programs, and overall management best suited for their horse. Genetic tests will also assist in horse marketing/sales, veterinary diagnostics, and pre-purchase exams.
The future of genomics is rapidly evolving giving researchers, clinicians and equestrians an opportunity to work together sharing information for the betterment of the horse.
Mary Ann Simonds, MA, BS, an international author, clinician, speaker, researcher and educator, has consulted for over 40 years as an equine psychology/behavioral expert working with equestrian professionals and veterinarians around the globe. For more information go to www.maryannsimonds.com, www.heartmindspeak.com, www.mystichorse.com, or email: [email protected]. She lives in Wellington, FL and continues to learn something new from every horse.
References
- V, Ente D, stot-Le MF, et al. Review and update of mutations causing Waardenburg syndrome. Hum Mutat. 2010;31:391–406.
- Smith SD, Kelley PM, Kenyon JB, Hoover D. Tietz syndrome (hypopigmentation/deafness) caused by mutation of MITF. J Med Genet. 2000;37:446–448.
3 Bellone RR, Forsyth G, Leeb T, et al. Fine-mapping and mutation analysis of TRPM1: A candidate gene for leopard complex (LP) spotting and congenital stationary night blindness in horses. Brief Funct Genomic Proteomic. 2010.
4. Momozawa Y, Takeuchi Y, Kusunose R, et al. Association between equine temperament and polymorphisms in dopamine D4 receptor gene in Mammalian Genome 16(7) 538-44 · August 2005.
5. Anderson S Lisa, Larhammar M, Memic F, Andersson Leif, et al. Mutations in DMRT3 affect locomotion in horses and spinal circuit function in mice. Nature. 2012 Aug 30; 488(7413): 642–646. doi: 10.1038/nature11399