Scientists Find Gene Can Explain Horses" Ability to Pace Eadweard Muybridge, an English photographer, settled a bet in 1872 by showing, with a single photographic negative, that a horse has four feet off the ground at the trot. This evidence was groundbreaking for photography, and now, 140 years later, trotting horses have yielded another breakthrough, this time in the field of genetics. Scientists at Sweden's 535-year-old Uppsala University recently discovered that a single gene, which they have called DMRT3, largely explained why some horses could trot or pace and why some could not. Leif Andersson, the lead researcher and a professor of functional genomics at Uppsala, called it a "sensational finding." The discovery could greatly affect harness racing, which traces its American roots to the mid-18th century. The findings are so new that almost nobody in the sport has heard about them yet. But Jimmy Takter has. Takter is a Hall of Fame trainer who has twice won the Hambletonian Stakes, the top event in harness racing. One of his owners, Bengt Agerup, a Swedish scientist and entrepreneur who won the 2010 Hambletonian with the Takter-trained Muscle Massive, financed the study. Agerup, who last year sold his company Q-Med to the German pharmaceutical company Galderma for about $1.2 billion, lives in Uppsala, Sweden. "It's very new but it's actually quite interesting," the Swedish-born Takter said. If you can see the DNA, which makes a horse more likely to have the right coordination, and you can eliminate for your training the ones who don't, it's a big plus. Especially for me, who buys expensive horses. The three naturally occurring gaits in horses, in increasing speed, are the walk, the trot and the canter/gallop. Some have a fourth, an ambling gait, or a fifth, a pace. Standardbreds, which are the breed of horses in harness racing, either trot, in which a horse's legs move in diagonal pairs, or pace, where the foreleg and hind leg move in unison. Trotters must be trained not to break their gait at high speeds and gallop, which is a disqualification during a race. Andersson said researchers began their investigation in January 2011 with Icelandic horses. These horses have an ambling gait called tolt, a gait so calm for the rider that it is "like sitting on a sofa," Andersson explained. But only some horses can pace, and they wanted to find out why. They found that a single gene differentiated pacers and nonpacers. They searched for this genetic mutation in other gaited horses, like the Paso Fino in South America and the Tennessee walking horse, and discovered the same gene. Its genesis must have happened more than 1,000 years ago, Andersson said. The horses with this gene would have had a smoother ride and thus been kept and bred. Next came trotters in Sweden. The researchers found the genetic mutation at a high frequency, which told them that its presence must inhibit a horse's transition from trot to gallop at high speeds. But was there a link to performance? In June 2011, Andersson and his team went to Agerup's Uppsala stable to conduct a blind test on his 61 horses. Agerup's trainer, Daniel Reden, told the scientists that a few horses had trouble keeping their trot despite several years of training. They were not informed of the exact number (it was two) or the identities of the horses. The researchers collected hair samples, ran a DNA test, and in a few days selected the two horses in question. With this genetic evidence, Reden decided those two, ages 4 and 5, could never become racehorses and donated them to nonracing careers. "We knew that we had made an important discovery," Andersson said. But we were amazed to see such a strong effect on racing performance. By experimenting on mice, the Swedish researchers next determined that these genes were held in neurons in the spinal cord, which controls locomotion. That makes sense; trotting demands diagonal and coordinated movements. Andersson said he believed their discovery could affect the racing and breeding of standardbreds. Of course, it would not predict the outcome of a race. But an owner could test the DNA of a foal soon after birth and immediately conclude whether it has the correct gene. The same goes for checking the DNA of a broodmare before deciding to breed her. "Training a horse for two years is a costly practice," Andersson said. If a horse doesn't have the best constitution, it's a waste of your money. Andersson's team did more than test Swedish trotters. Ninety-seven American standardbreds were tested, of which 57 were trotters, and every horse examined had the proper genetic mutation, evidence of the breed's nearly 300-year history in the United States. The researchers found that 95 percent of Swedish horses fit the category, yet half of French-bred trotters imported to Sweden did not. Although known for sturdiness, French trotters have a reputation for breaking their gait. For purposes of breeding, Andersson said that breeding select French trotters with American ones could be a dynamic pairing. Sweden rivals the United States in trotting's popularity, so it makes sense that the study originated there. For Andersson, his motivation was focused more on science than on sport. He said his father once owned trotters, although he never became that interested. "Come to think of it, his first horse was probably heterozygous," Andersson said, meaning that the horse lacked the proper DMRT3 mutation. He was a good horse, but he had a tendency to break his gait and go into a gallop.