A truly American horse breed, the American Quarter Horse first came to being in the early colonial era in America. And in a study recently reported in the journal, BMC Genomics, researchers at Texas A&M University’s College of Veterinary Medicine & Biomedical Sciences (CVM), working with collaborators in the Texas A&M College of Agriculture and Life Sciences and the AgriLife Genomics and Bioinformatics Center, have sequenced the first Quarter Horse genome – unlocking the secrets of what makes this breed so unique.

Genome sequencing is not a new science, but advances in sequencing technology, often referred to as next-generation sequencing, have made it easier and cheaper to sequence the genome of an individual, which can then be analyzed for clues causing genetic disorders and distinctive traits. The Texas A&M Quarter Horse is the first horse to be sequenced using next-generation sequencing technology.

“Genome sequencing aids our study of normal and abnormal genetic variation,” said Dr. Scott Dindot, Assistant Professor in the Department of Veterinary Pathobiology at the CVM. “This project is important because it is a start towards understanding what genetic factors make breeds unique, and what mutations may play a role in presenting or diagnosing disease.”

Dr. Noah Cohen, Professor in the Department of Large Animal Clinical Sciences in the CVM and collaborator in the study, underscored the importance of the role genetic variation plays in the disease process.

“This study represents a valuable contribution to our understanding of genetic variation in horses,” said Cohen, “including efforts to study the relationship between genetic variation and susceptibility to important diseases in Quarter Horses and other breeds.”

The first horse genome to be sequenced and assembled, a Thoroughbred mare, was completed by a large international consortium. This reference assembly was used to map the Quarter Horse genome and to identify differences in genetic information between the two horses. The sequence data from the project has been made available publicly for researchers interested in equine genetics.

“The horse used in the study, a mare named Sugar, is the descendant of key foundation sires in the Quarter Horse breed,” added Dindot. “We were able to identify several genetic variants in this mare, both good and bad, known to be common among Quarter Horses. Results from this study have increased our knowledge of genetic variation in horses three- to four-fold, and proved that through collaborations such as this, we can one day apply this state-of-the-art technology to identify and possibly to manage genetic disorders not only in horses, but also in other species.”

The genome sequence of a Quarter Horse has a the potential to have a tremendous impact on the equine industry, as the American Quarter Horse Association represents the largest breed registry in the United States. The information from this study may lead to improvements in performance in horses, and facilitate the management of health of horses everywhere.

“Many diseases and ‘syndromes’ are the result of genetic variation,” said Dr. Jason Sawyer, Texas AgriLife Research scientist and Associate Professor of animal science. “Perhaps more importantly, the ability to combat infectious diseases may be greatly impacted by the underlying genome and the variation that arises during recombination. This study has identified areas of variation that may play a role in the health and disease resistance of horses. While more research must be done to specifically identify desirable and beneficial variants, this study has set the stage to enable those future studies.”

Funding for the study was provided by the G. Willard and Ginger Pool Equine Teaching and Research Endowment, the Link Equine Research Endowment, Texas A&M AgriLife Research, Texas A&M Department of Animal Science, and the Department of Veterinary Pathobiology at the CVM.