Study of the doublesex and Mab-3 related transcription factor 3 gene in Italian trotters

Horses show a large variability in their pattern of locomotion. The three natural gaits are walk, trot and canter/gallop. Most breeds are called “non-gaited”, including horses that are able to perform just the natural gaits. But some breeds, called “gaited”, can also use alternative gaits. Some authors showed that the doublesex and mab-3 related transcription factor 3 (DMRT3) gene plays a key role in this attitude. They demonstrated that a single nucleotide substitution (C>A) in this gene, causing a premature stop codon, is essential for the ability to perform alternate gaits and has a favorable effect on harness racing performance. Trotters are used for harness racing thanks to their ability to trot at high speed without falling into gallop. In fact, the “gaited” pattern of locomotion is under selection in trotter breeds. The DMRT3 gene has never been studied in the Italian Trotter, even though this breed includes horses that are among the best trotters in the world. Given the importance of this gene, our aim was to analyze some of the best Italian Trotters by a sequencing analysis. We analyzed 32 Italian Trotter horses from five stud farms well known in Italy for this breed. In addition, we analyzed 8 horses belonging to different “non-gaited” breeds, two samples per breed, as a control. The latter included two cosmopolite breeds, Arabian horse and Thoroughbred, and two Italian native breeds, Maremmano and Murgese. DNA was extracted from whole blood and the last exon of DMRT3 gene was sequenced. Sequences were aligned, confirming the SNP at position chr23:22999655. No other polymorphisms were found in this region. The SNP was then genotyped on the sample of 32 Italian Trotters. The wild CC genotype seems to be fixed, as expected, in all the breeds other than the Italian Trotter. But all the Italian Trotter horses analyzed were homozygous for the mutant allele A, except for two heterozygous animals. The genotype of these two horses at the analyzed locus confirmed what expected. In fact, they were signaled by the breeders for genealogy and attitude. Our results confirm the importance of the polymorphism in DMRT3 gene also for the Italian Trotter population. The analysis of further samples of this breed, including animals with low performance, may be useful.