To pace or not to pace: a pilot study of four- and five-gaited Icelandic horses homozygous for the DMRT3 ‘Gait Keeper’ mutation.

The research involved a detailed genetic analysis of four- and five-gaited Icelandic horses with a specific gene mutation, recognized for its influence on a horse’s ability to display different gaits. The findings suggested that the capability to perform the pace gait was not solely determined by that one gene variant.

Introduction to the Research

The study focuses on Icelandic horses, known especially for their capacity to perform certain unique gaits – the ‘tölt’ and the lateral two-beat gait known as the ‘pace’. Both gaits are largely desired by breeders. Earlier research showed that a nonsense mutation (C>A) in the DMRT3 gene — often referred to as the ‘Gait Keeper’ mutation — is the key genetic factor possessing the gait alternatives besides the standard walk, trot, and canter.

• The DMRT3 gene mutation is recognized as the principal genetic factor enabling horses to produce additional gaits.
• Certain Icelandic horses can perform a specific ambling four-beat gait called ‘tölt’ and a lateral two-beat gait known as ‘pace’.

Purpose of the Study

The research pursued a dual purpose:

• The main objective was to perform a genetic comparison between four and five-gaited Icelandic horses who were homozygous for the DMRT3 mutation, meaning they had two identical forms of this particular gene.
• The secondary objective was to ascertain why, despite having the mutation, only about 70% of these horses could carry out the pace gait.

Methodology

A total of 55 horses were genotyped using the 670K Axiom Equine Genotyping Array. Following this, a genome-wide association (GWA) analysis was conducted utilizing the GenABEL package in R — a programming language used for statistical computing.

• A genome-wide association (GWA) analysis is a method used in genetics to find variants in the genome associated with traits such as diseases or phenotypes.
• The horses were split into two categories, ones that could perform four gaits, and ones that could perform five (including the pace gait).

Results and Conclusion

There was no single nucleotide polymorphism (SNP) of genome-wide significance. An SNP refers to variation at a single position in a DNA sequence among individuals.

• Therefore, it was concluded that the ability to perform the ‘pace’ gait is not determined solely by the DMRT3 mutation, indicating the presence of other genetic factors.
• Although this study had certain limits, it has augmented the understanding of the genetic complexity surrounding the pacing ability in horses.
• To gain a more thorough comprehension of the genetic differences between four- and five-gaited Icelandic horses, further research involving larger samples and consistent phenotyping is necessary.