(Photo : Summerhill Stud)
HORSE DNA CODE CRACKED
For three hundred years, the welfare of the thoroughbred and the shaping of the breed has rested in the hands of the British aristocracy. In more recent times, it’s been hijacked by venture capitalists, and while that has catapulted breeding from what was originally a sporting preoccupation into an international business, it hasn’t necessarily been good for the advancement of the thoroughbred as an animal.
Commercial imperatives have witnessed an emphasis on the sales ring in the selection process, instead of the racecourse. We are in the business of “running”, and unless our focus is on the production of a runner, we’re going to fall short on the real purpose of our business and that is producing better athletes.
One of the marvellous imponderables in producing a racehorse, is the unknown of the outcome, given that we’re dealing with a hybrid, comprising strains of animals whose histories have been forged in different places, from different forebears in different eras. When breeders make their plans for a mating season, they dip their hands into the well of genetic imponderables, and unless they’re intimately connected with their horses (or have someone at their disposal who is), the outcome is often less certain than the spin of a wheel. Until now, this has left the instinctively talented horseman who knows his stock and its anecdotal history, with a distinct advantage.
In recent decades, scientists have been hard at work trying to track the genome of the racehorse, with implications for human health as well as horse breeding. At last, it seems progress has been made, and while this will not detract from the role of the artist, nor provide certainty in the outcome, what it will do is aid us in identifying the course and origins of beneficial and non- beneficial genes.
At around the same time that parallel progress has been made in the sphere of seed technology, scientists in America have advanced the cause of the horse. Alan Harmon reports…
The genome of the domestic horse has been completely sequenced. This has important Implications for better horse breeding and for studies of human health. The International Horse Genome Project’s work was done by the genomesequencing centre of the Broad Instituteof the MassachusettsInstitute of Technology (MIT) and Harvard University, in collaboration with an international team of researchers that included scientists at the University of California, Davis. “This gives us specific sequence information, which we can apply to identify the genes for specific traits in the horse,” geneticist Dr Cecilia Penedo of UC Davis told the journal Science. Dr Penedo supplied DNA from Arabian horses and Quarter Horses and worked on a horse linkage map, which identified genetic markers for various traits across the horse chromosomes.
UC Davis professor of animal science James Murray, who has worked with the Horse Genome Project since its inception in 1995, says having access to multiple genome sequences makes it easier to understand all genomes. “By looking at the horse genome, we can better understand human biology and human diseases,” he explains. The researchers noted that over 90 hereditary conditions affect both humans and horses, including infertility, inflammatory diseases and muscle disorders. Therefore the horse is an important model for improving the understanding of human diseases. The project found that the horse genome is somewhat larger than the dog genome and smaller than the human and cow genomes. They also discovered evidence that fewer chromosome rearrangements separate humans from horses than from dogs. The researchers were suprised to find the existence of an evolutionary new centromere on horse chromosome 11. Centromeres are key structural features of chromosomes that are necessary for the movement of chromosomes when cells divide, a function that ensures normal distribution of all genetic material to each daughter cell. This functional, but evolutionary immature, centomere may provide a model to study the functioning of centromeres.
Eliminating genetic conditions
Dr Penedo notes researchers can use the specific gene sequences to map traits in horses. She and graduate student Leah Brault are using this information to identify the cause of equine cerebellar abiotrophy, a genetic, neurological condition found almost exclusively in Arabian horses. Studies show that a horse can carry the gene for equine cerebellar abiotrophy and not be affected by it. However, if two horses carrying the gene are bred, there is a 25% likelihood the foal will manifest the condition, which causes serious nearological problems including head tremors and poor equilibrium.