April Flowers for redOrbit.com Your Universe Online

An international consortium of researchers from Uppsala University, Swedish University of Agricultural Sciences and Texas A&M University have discovered a mutation in a single gene in horses that is critical for the ability to perform ambling gaits and pacing that has a major effect on performance in harness racing. The study, published in Nature, is a breakthrough for understanding spinal cord neuronal circuitry and locomotion in vertebrates.

A complex coordination of muscle contractions carried out by neuronal circuits in our spinal cords allow us to walk and run, but how does this work at the level of nerve cells and molecules?

There is a great variability in the pattern of locomotion for horses, including the three naturally occurring gaits: walk, trot and canter/gallop. Some horses, however, have additional gaits such as ambling gaits or pace. For instance, Icelandic Horses can tolt (ambling gait) and flying pace. The team decided to investigate the genetic basis for these locomotive differences.

Gus Cothran, a professor in the Animal Genetic Lab of the College of Veterinary Medicine & Biomedical Sciences at Texas A&M, and the team used a process called whole genome SNP analysis to study the genes of 70 Icelandic horses that had either four gaits or five, with the pace being the fifth gait.

The team sequenced the DMRT3 gene of the test horses and found that in almost every case of gaited horses, there was mutation in the DMRT3 that caused a premature stop codon which causes the protein product of the gene to be terminated before the whole protein is completed. This alters the function of the protein, which leads to the differences associated with the gait.

We suspected a strong genetic component, but were almost shocked when we discovered that a single gene, DMRT3, largely explained the genetic difference between pacers and non-pacers, explains Lisa Andersson one of the PhD students involved in the project.

A separate group of researchers from Uppsala University, led by Klas Kullander, found that this particular gene, DMRT3, is expressed in a previously unknown type of neuron in the spinal cord of mice. The characteristics of these neurons, including their location, suggested that these neurons could take part in the neuronal circuitry that coordinates movement.

When the two groups of scientists compared their data, they realized an important biological finding was imminent.

At that moment, we realized that our discovery did not only extend our understanding of spinal neuronal circuits in mice, but that we had discovered a tangible population of nerve cells that also seemed to be critical for the control of gaits in horses. The new type of nerve cell is dependent on DMRT3, and is tentatively named after this gene, said Kullander.

Read more here:
Single Gene Has Impact On Gait Of Horses And Mice

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