Commentary on the Equine Genome

We no longer listen to music on records or tapes. When we write, we “keyboard,” using some form of word processor. Our lives have changed profoundly as a consequence of technology. Therefore, it should be no surprise that changes of comparable or even greater magnitude are occurring in the realm of biology.

Before 2000, the two most significant contributions of veterinary genetics to horses were the discovery of the cause of hemolytic disease of newborn foals (neonatal isoerythrolysis) and the invention of parentage testing. Beyond that, genetic principles simply provided a basis for understanding hereditary diseases. From a practical standpoint, genetics was a black box.

The Human Genome Project changed that.

This $3-billion project led to invention of methods and tools that allowed us to inexpensively sequence genomes of other animals, including horses. The horse genome sequence was completed in 2006 and is routinely used to discover the genetic basis for many hereditary diseases, performance traits and coat color patterns.

However, molecular genetics is not just about hereditary diseases. Today, the DNA sequence of every economically important animal has been determined. Scientists studying muscle biology, reproduction, infectious diseases, immunology and pharmacology routinely use DNA sequences to investigate targets for treatment and responses to intervention. Furthermore, the genome sequence is a financial boon to research. Scientists studying horses used to spend months, and tens of thousands of dollars, cloning and sequencing genes. Now an undergraduate student can identify the DNA sequence of any gene in 15 minutes on the computer, for free.

Unfortunately, the horse genome sequence by itself is inadequate to address many important questions. However it is a great foundation for new tools. We can use the horse genome sequence as a basis to investigate gene expression. We can determine what train of events is initiated when we vaccinate a horse, when a horse eats a particular diet, or when a horse experiences an infection. Each of these activities triggers changes in gene expression. If we could identify the set of genes expressed in each tissue under different consequences, we would have a powerful way to design therapeutic treatments. This is the kind of information that will help us understand complex metabolic diseases and difficulties in engendering protective immunity to infectious diseases. Scientists are already trying to determine this kind of information, but the magnitude of the problem and the paucity of resources combine to thwart real progress.

A central repository is needed for gene expression information for the horse. The United States Department of Agriculture is encouraging scientists to collaborate in developing these resources for all agriculturally important species. ENCODE is the name of a similar resource developed for human medical research. Consequently, the effort for animals has been called AG-ENCODE. The potential to benefit equine veterinary medicine is huge. We tend to fund research to solve specific problems and poorly support development of research infrastructure. However, developing Equine-ENCODE would not be an answer to a single, specific question but could be key in solving many problems.

Dr. Ernie Bailey can be contacted at 859-218-1105,

Information provided by the University of Kentucky Gluck Equine Research Center’s Lloyd’s Equine Disease Quarterly.

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