PARIS: Scientists said on Wednesday they had identified a genetic variant that influences gait in horses, a potential boon for breeders but also for the quest to fix human spine injuries.

A patented DNA test will become available from Thursday, enabling horse buyers to spot an animal with a higher genetic chance of success at harness racing, they said.

Reporting in the journal Nature, researchers in Sweden said the telltale gene had been unearthed in the Icelandic Horse, a breed that famously likes to “pace.”Pacing is a peculiar kind of equine gait, in which the legs on one side of the animal move forward at the same time.

It is particularly prominent among Icelandic horses, descendants of horses introduced to Iceland by the Vikings and recognised as a purebred strain that gives a smooth, sure-footed ride.

Building on earlier work on lab mice, a team led by Leif Andersson at Uppsala University and the Swedish University of Agricultural Sciences compared the genetic code of 70 horses, 40 that could pace and 30 that could not.

What emerged starkly was that in the 40 pacing horses, there was a tiny change, of just one letter in the code, in a key gene known as DMRT3.

DMRT3 controls a protein in nerve cells in the spinal cord that, Andersson believes, is crucial in the coordination of leg movements in vertebrates.

Just as surprising, said Andersson, was to find that the mutation also occurs strongly among trotters, or breeds that are used for harness racing, in which the horse pulls a two-wheeled buggy called a sulky.

Trotters have a gait that is diagonal, meaning that the rear leg and foreleg that are diagonally opposite to each other move at the same time.

In trotting races, a horse is not allowed to gallop, otherwise it is disqualified.

“What we think this mutation is doing is that it inhibits the transition to the gallop,” Andersson said in a phone interview.

“That has some obvious applications in horse breeding.”The genetic variant is widely spread among a breed called the American Trotter, but is found far less frequently among a rival called the French Trotter, he said.

“French Trotters are famous for being often very strong, but they are also famous for sometimes having problems in keeping the trot. They don't keep a clean trot as much as American Trotters do, and we think the reason is that the breed does not have as high a frequency of the mutation.”

The team have patented the discovery and, from Thursday, licensed laboratories will be able carry out a test to scan a trotter's genome for the DMRT3 variant.

Andersson said it was likely that further work would turn up other variants that influence horses' gait, but for pacing and trotting horses, the DMRT3 mutation was clearly of enormous importance.

“It's an important discovery also for human medicine,” Andersson said, referring to fundamental research into paralysis.

“It is a really critical discovery because we have found new basic knowledge about how the spinal cord controls the movement of the legs.”