Gene or Region: LCORL / NCAPG
Reference Variant: T
Mutant Variant: C
Affected Breeds: Many
Research Confidence: Moderate - Findings reproduced in multiple studies
Explanation of Results: H1/H1 = homozygous for Height/Size, likely taller/larger than like-bred siblings or breeds H1/n = heterozygous for Height/Size, likely taller/larger than like-bred siblings or breeds n/n = no variant detected
The domestic horse displays a wide range of size variation, from the tiny Miniature Horses to the towering draft breeds. While height is a complex trait involving a variety of genetic and environmental factors, the breeding systems of domestic animals has led to a small number of genes being responsible for large amounts of variation in several species. One study in the horse has shown four loci can explain up to 83.5% of body size variation. This SNP in particular explained 68.5% of the measured variation in height, with the T allele being associated with small body size, and the C allele with large size (T/C animals displaying an intermediate size).
T/T - Typical/Average risk; no contribution to height from this variant T/C - Likely taller/larger than like-bred siblings or breeds (formerly LCORL/n) C/C - Likely taller/larger than like bred siblings or breeds (average of 2.9 inches taller than "T/T" horses) (formerly LCORL/LCORL)
LCORL is a transcription factor that has been associated with body size in a variety of species. One study in the horse has suggested that the C allele removes a binding site for TFIID (which is involved with skeletal development), which is further associated with decreased expression of LCORL. This alteration of gene expression could be the molecular basis for the association with body size.
Signer-Hasler H et al., “A genome-wide association study reveals loci influencing height and other conformation traits in horses.” (2012) PLoS One. 7: e37282. PMID: 22615965
Makvandi-Nejad S et al., “Four loci explain 83% of size variation in the horse.” (2012) PLoS One. 7: e39929. PMID: 22808074
Metzger J et al., “Expression levels of LCORL are associated with body size in horses.” (2013) PLoS One. 8: e56497. PMID: 23418579
Tetens J et al., “A genome-wide association study indicates LCORL/NCAPG as a candidate locus for withers height in German Warmblood horses.” (2013) Anim Genet. 44: 467-71. PMID: 23418885
Boyko AR et al., “Genomic analysis establishes correlation between growth and laryngeal neuropathy in Thoroughbreds.” (2014) BMC Genomics. 15: 259. PMID: 24707981
"Gaited" (DMRT3) horses display a wide variation in locomotion, with breeds displaying a range of unique footfall patterns at intermediate speeds. Even amongst the non-gaited (trotting) breeds, some individuals are capable of lateral movements. Also, while most horses will shift into the three beat canter at higher speeds, some horses are able to remain in their intermediate gaits (for example, harness racing breeds).
Temperament is a complex trait influenced by multiple genetic and environmental factors. Individual components of temperament are potentially under different controls. Curiosity in the horse has been defined as an interest in novel objects and a willingness to approach them. Vigilance refers to the tendency of a horse to examine its surroundings.
The domestic horse displays a wide range of size variation, from the tiny Miniature Horses to the towering draft breeds. While height is a complex trait involving a variety of genetic and environmental factors, the breeding systems of domestic animals has led to a small number of genes being responsible for large amounts of variation in several species.
Thoroughbred races are held at a variety of distances, with individual racehorses usually displaying a preference for a range. There is some suggestion that sprint horses (which compete at distances less than 6 furlongs, or 2/3rds of a mile) are more compact and muscular than horses that run at longer distances. This insertion has been associated with racing distance for winning Thoroughbreds at the top level of competition, with A/A horses excelling at distances of 8 furlongs or less and T/T horses found more in races of 9 furlongs or more. Horses with one copy of each allele won at all distances. Research Confidence: High confidence, findings reproduced in multiple studies