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German scientists investigating the genetic basis for different body sizes of horses have discovered a gene that greatly influences height.
Researchers at the Institute of Animal Breeding and Genetics of the University of Veterinary Medicine in Hannover compared thousands of genetic variants between ponies and horses to find out if there was a mutation for the size differences in horses.
These so-called point mutations, or single nucleotide polymorphisms (single nucleotide polymorphisms, SNPs), are the most common genetic variants.
Using gene expression analysis, the scientists identified the key gene for the development of size in horses.
Their findings have been published in the international open-access scientific journal, PLoS One.
The gene in question is known as LCORL.
“We conclude that LCORL limited the growth in size of horses,” said Professor Ottmar Distl, director of the Institute for Animal Breeding and Genetics at the university.
“The stronger LCORL is expressed, the smaller the horse.”
The researchers conducted across-breed analysis in 1851 horses, of 42 different breeds
All original Przewalski wild horses carried the mutation, they found.
Warmblood horses showed a large range in height at the withers and wide genetic variation.
For almost half of this variation, the regulatory mutation of the LCORL gene was responsible. Smaller Warmblood horses were homozygous for the mutation. Warmblood horses of medium size carried two genetic variants and were therefore heterozygous. Large warmblood horses were homozygous for the mutation.
For large draft horse breeds such as the Rhenish-German Cold Blood, Saxon-Thuringian, Noric and Süddeutsche, there were no animals with the homozygous mutation, and only isolated cases occurred in heterozygous animals.
Distl said the distribution of mutations in the different pony breeds suggests that, for large horses, the mutation first arose during the domestication of horses in Western Europe.
In humans, the LCORL gene affected torso and hip length. It was not a major regulator of size.
But in horses, the scientists found that LCORL was a decisive influence in horse height.
However, height is a complex trait and other genes are involved. The scientists are looking to conduct further work.
The researchers say horse breeders can use the new insights for their breeding decisions. The university can provide a genetic test for expression of the gene.