FROM Nicholas Silver to Desert Orchid, they have enchanted generations of racegoers. Now scientists have identified the genetic mutation that turns horses grey.
Grey horses are typically descended from Arabian ancestors, including the famous Lipizzaner stallions that are trained for classical dressage.
Born with dark hair, greys gradually lose pigmentation. As their hair becomes white they take on a gr
ey appearance due to their black skin underneath.
Dr Leif Andersson and colleagues at Uppsala University, Sweden, found mutated genes in more than eight hundred grey horses from eight different breeds.
Through further DNA mapping the phenomenon was nailed down to the over-expression of two neighbouring genes known as STX17 and NR4A3.
It is not yet known if one, or both, of the genes, is responsible for the loss of hair pigmentation, according to the study published online in Nature Genetics.
Dr Andersson's team also point out between 70 and 80 per cent of grey horses older than 15 have melanomas, a form of skin cancer that reduces their lifespan.
They believe the genes trigger both the disease and the loss of hair colour through reducing protective pigment-containing cells.
Dr Andersson said: "Since the first description of melanomas in grey horses in 1903, researchers have questioned how a mutation causing loss of hair pigmentation can also cause melanomas. Our results suggest a possible explanation."
