A thoroughbred warming up before a race
The beautiful and powerful horse, critical to human exploration and farming, is the latest animal to join the genome party. The genome of a female Thoroughbred was sequenced by the Broad Institute and was reported in last week’s issue of Science.
Horses were first domesticated ~5000 years ago in Central Asia in the region now known as Khazakhstan. Evidence from the horse genome bolsters the idea that the founding gene pool of the domestic horse consisted of many, many mares and just a few busy stallions. Researchers can tell this, in part, by looking at the sequence variation in the horse’s Y chromosome.
The genome of the horse, like the genomes of all of our animal cousins, can teach us about human disease. Horses and humans both suffer from muscle disorders and inflammatory diseases and these diseases may have similar genetic causes. About 15,000 of the 20,000 genes in the horse genome have a close counterpart in the human genome.
There are also many extended stretches of genes in the horse genome that are in the same chromosomal order as found in humans. This property of shared order, called synteny, can tell us many interesting things about the history of a genome. For example, the number of places in which the order of genes differs between species can tell you how closely related they are– genomes that share more syntenic regions are typically more closely related to one another than genomes that do not share as much synteny.
A leopard-spotted Appaloosa
In order to explore the genetic basis of the differences in shape, strength and speed of the world’s many horse breeds, The Horse Genome Project partially sequenced the genomes of several other breeds and identified which places in the genome differ from breed to breed. Because certain breeds are more prone to certain diseases, this research will aid in the identification of the genetic basis of some of these maladies. The enchanting spots of the Appaloosa, for example, are likely caused by an alteration of a gene that produces a protein found in both skin cells as well as eyes called melastatin 1. If a horse has two copies of the spotty version of melastatin 1, it will suffer from a form of night blindness. The study’s authors have narrowed down the source of this genetic alteration to just two candidate single-letter (i.e. A, T, G, or C) changes in the melastatin 1 gene.
