Gene analysis aids racing Quarter horse selection

27 Feb 2015

Take home message: Analysing the complete genetic sequence of Quarter Horses has identified which genes are positively selected for during the breeding of racing line horses compared to cutting line horses. The Quarter Horse breed is renowned for its functional versatility and the selection of these horses for different purposes has led to the formation of lines. The cutting line is used in functional tests, exploring abilities such as agility, obedience and cow sense, which are important for the management of cattle ranches. The racing line explores the sprinting ability of the animals over short distances. Through domestication and breed formation the animals have gone through natural and artificial selection. Identifying which regions of the genome (the complete set of genes in a particular organism) are undergoing selection can now be can be carried out by analysing patterns in the genome without the need for observational (phenotypical) information. Once identified and mapped, it is possible to annotate the biological function of these genomic regions and, consequently, to better understand how selection acts on complex traits of interest. The recent search for signatures of selection in the racing Quarter Horse has allowed the identification of genes and single changes in a given genetic sequence, known as SNPs (single nucleotide polymorphisms) These SNPs might be useful as markers associated to racing performance. The objective of this study carried out by researchers from Brazil’s Sao Paulo State University, was to identify genomic regions which are different in the racing line of Quarter Horses in relation to the cutting line. 188 Quarter Horses (120 racing line and 68 cutting line) of both sexes, born between 1985 and 2009, were genotyped using SNP analysis. Genes involved in muscle growth (n = 8), skeletal growth (n = 10), muscle energy metabolism (n =15), cardiovascular system (n = 14) and nervous system (n = 23) were identified. The use of SNP genotype analysis allowed the identification of regions in the horse genome that were divergently selected in racing Quarter Horses in relation to cutting. Gene annotation in these regions was used to identify genes that could have been important during formation of the racing line and that are related to racing performance. Lead author Dr Meira cautions that association and validation studies will be required to confirm the relation of these markers with racing performance, however, these genes should be used in the future in association studies on Quarter Horse racing, for the development of tools to increase selection efficiency. Mota, M. D. S. (2014). Prospection of genomic regions divergently selected in racing line of Quarter Horses in relation to cutting line, 1754–1764. doi:10.1017/S175173111400176 By Joanne Stocks, University of Nottingham.