Horse added to Broad's genome stable

By Nicole Davis, Communications, July 20th, 2006

Long prized for its physical prowess, the horse has filled diverse and instrumental roles in human civilization, ranging from warfare and transportation to sport and agriculture. Now another chapter in its rich history has opened with a scientific collaboration aimed at decoding and analyzing the horse's DNA.

A research team led by scientists at the Broad Institute is working to create a high-quality genome sequence of the domestic horse, Equus caballus, together with a compendium of genetic differences among seven different horse breeds. This analysis may help to define the key genetic features that have been preserved across various mammalian species, including humans, and also lays the foundation for revealing the genetic roots of equine diseases, some of which also afflict humans.

"We can gain insight into the most valuable parts of the human genome by reconstructing their genetic history in other mammals," said Kerstin Lindblad-Toh, the co-director of the Genome Sequencing and Analysis Program at the Broad Institute and one of the project's principal investigators. "A thorough analysis of the horse genome will give us an important piece in this evolutionary puzzle and will also provide us with the tools needed to reveal the genetic underpinnings of disease — both in horse and in human."

The horse genome project has emerged from an ongoing effort, funded by the National Human Genome Research Institute, to highlight the most evolutionarily conserved, and therefore important, elements of the human genome by decoding the genomes of several different mammals and identifying their genetic similarities to humans. Toward this goal, the scientists have completed a preliminary analysis of the ~ 2.7 billion DNA bases that make up the horse genome. This “low coverage" sequence will now be revised into an accurate and high-quality version. A female thoroughbred named "Twilight" has been selected as the representative horse for genome sequencing.

The scientists will also examine DNA from a variety of modern and ancestral breeds, including the Akelteke, Andalusian, Arabian, Icelandic horse, Quarter horse, Standardbred, and Thoroughbred, to create a map of ~1 million DNA sequence differences, know as single nucleotide polymorphisms ("SNPs"). This catalogue of SNPs will provide scientists with a genome-wide view of genetic variability in horses, which will help them to identify the genetic contributions to physical and behavioral differences, as well as to disease.

To date, there are more than 80 known genetic conditions in horses that have a similar genetic basis in humans. Because of these similarities and presumably many others, genome analyses of horses will shed light on the genetic factors that influence diseases in both species. As horses have been selectively bred for hundreds of years, particularly for features that augment athletic performance, these genomic tools will foster an understanding of the genetic aspects of exercise physiology as well as a host of musculoskeletal, neuromuscular, cardiovascular and respiratory diseases that affect equines and humans, too.