02 June 2009

Dr Emmeline Hill identifies the groups of genes that characterise the Thoroughbred

Rachel Pagones, Racing Post, 02 June 2009

A TEAM of scientists based in Ireland have reported for the first time that they have identified genes which they believe contribute to athletic performance in thoroughbreds. The findings will reignite industry debate - simmering on a deliberately neglected back burner - over the role genetics may play in future selection of thoroughbreds.

Genetic research in racehorses has popularly been given the shorthand term "the search for the speed gene".

But writing in a paper published today in the peer-reviewed online journal PLoS ONE, lead author Dr Emmeline Hill, of the School of Agriculture, Food Science and Veterinary Medicine at University College, Dublin, reveals the 'speed gene' is likely to be several genes.

This is something geneticists have long told the industry. What is new and surprising is that the holy grail of speed appears to be found in metabolic pathways - sequences of chemical reactions occurring within cells. The genes the researchers have pinpointed involve such things as how thoroughbreds metabolise energy and what gives them their long, lean physique compared to other breeds.

The scientists have not identified the actual genetic coding for these traits. Rather, they have identified regions of the horse genome - the entire set of genetic information of the horse - which contain genes they believe are very likely to be responsible for them, based on what is known about the function of those genes in other species.

Speaking to the Racing Post, Dr Hill said: "It's very likely that the genes contributing to performance are the genes involved in insulin signalling, fatty acid metabolism, and muscle strength. It's also very likely that these genes may contain the differences between Group race winners and non winners." Fatty acid metabolism is involved in the production of energy within the cells, while an increased sensitivity to insulin "would result in the lean phenotype that the thoroughbred is known for, because they have highly adapted the ability to metabolise sugars and remain lean under those circumstances," she said.

She added: "Most of our understanding of the functioning of these genes comes from other research done in animal models.

There is similarity in function between related species, so we can learn a lot from what's gone previously.

"The next step is to understand whether there are DNA differences between the elites and the non-elite performers. What we will be pursuing is really trying to understand the role of genes and the more refined physiology, rather than talk about the overall performance. This is the first time been we've been able to look inside and see the ingredients [that make a racehorse]." However, Hill does intend to pursue the development of testing for genetic variants that lead to high-level performance attributes.

"Knowing the biology of genes and the genes that are important to thoroughbred makeup, we can use that knowledge to devise tests based on our knowledge of gene function," she said.

"We are investigating genes that contribute to performance.

And we hope that will lead to tests that will be helpful to the breeder." How receptive the breeding industry will be to such help is an open question. The reaction at times has appeared negative; at the Thoroughbred Racing and Breeding Seminar at Cheltenham in November, a widely attended event partly sponsored by the Levy Board, Tim Morris, director of equine science and welfare for the BHA, opened his talk on genetics research by saying: "The performance gene is not the focus of British racing research, because first, it's not wanted and second, it doesn't exist." However, Hill - who shook up the breeding industry seven years ago when co-publishing, with Professor Patrick Cunningham, genetic proof of historic errors in the Stud Book - says she has received positive feedback all along.

"There is tremendous support from the industry, for new knowledge and new genetic knowledge. I can say, and I am very fortunate in this, there is a large amount of support from some of the top trainers and breeders in this country [Ireland], the UK and New Zealand, where I have done some of my work."