Most horse breeds have 4 natural gaits that happen at different speeds of motion. Some breeds have unique natural gaits.
This confirms what breeders have long known. It's in the genes.
Researchers have discovered a single genetic mutation that affects the way horses move, specifically, their ability to alternate gaits.
Since the mutation endows them with a wider repertoire, the findings will likely have a huge effect on racing performance and the diversity of domestic horses, and it could even shed light on the genes behind movement disorders in humans.
Horses use a variety of gaits with different footfall patterns: walk, trot and gallop. The trot, for example, involves the diagonal front and hind legs moving together. But certain breeds can perform extra gaits — such as pacing, where the two legs on the same side of the body move together (pictured). And all these limb movements are coordinated by neural circuits in the spine.
A team led by Leif Andersson at Uppsala University in Sweden studied the genomes of 70 horses that could perform extra gaits — 40 could pace, and 30 could perform other alternate gaits.
The analysis revealed a single mutation common to all the horses that could pace, in a gene called DMRT3.
Horses without this mutation can’t move their right hindleg and right foreleg forward at the same time, Andersson says. But with the mutation, “the regulation of the movement isn’t so strict anymore, and becomes more flexible,” he adds.
Then using mice experiments to verify the gene’s link to locomotion, they found that mice with no functional copy of the gene had trouble coordinating their limbs. And, the gene was expressed in cells in the mouse spinal cord that connected to motor neurons.
The work could provide a basis for studies of human disorders. Nature News explains:
Genes linked to specific physical characteristics or behaviors can provide clues to the genetic basis of human syndromes. The relationship between a mutation and the resulting phenotype may not be as simple in humans as in gaited horses, but walking difficulty is a common symptom of many neuromuscular disorders.
The work was published in Nature today.
[Via Nature News]
Image: Freyja Imsland
