Equine Connection-Spring 2011 - University of Minnesota College ...

DRIVEN TO DISCOVERa nuisance to farriers, who have difficultywhen the horse snatches its limb away andslams it to the ground. However, if shiversprogresses, owners may not be able topick up the feet, and the exaggerated limbflexion will be apparent even when thehorse is standing still or walking forward,to the point that it impairs performance.Draper is collecting information on shiversthrough a Web site where owners canupload videos of their cases of shiversfor evaluation. Working with a team ofveterinarians and kinesiologists at theUniversity of Minnesota, Draper andValberg will tackle this perplexing diseaseby statistically analyzing informationon shivers cases from hundreds of horseowners to determine risk factors andpossible treatment strategies. For moreinformation, visitwww.cvm.umn.edu/umec/shivers.Equine genetics andgenomicsResearch in the Equine Genetics andGenomics (EGG) Laboratory focuses ongenetic mutations underlying simple andcomplex genetic diseases, the geneticsbehind breed differences in the domestichorse, and how these genetic mutationscause disease.Simple genetic diseases, such ashyperkalemic periodic paralysis andsevere combined immunodeficiency,are caused by a single gene. EGGresearchers have discovered thegenetic mutation responsible for type1 polysaccharide storage myopathy(PSSM), a muscle disease that results inmuscle pain, cramping, and muscle celldamage with exercise —and in someinstances, progressive muscle atrophy.Although the genetic mutation has beenidentified, ongoing research focuseson understanding muscle dysfunctionin PSSM. Research is also underwayto identify the genetic basis of anothermuscle glycogen storage disease, type 2PSSM.Most of the genetic diseases underinvestigation in the EGG laboratory arecomplex. Complex genetic diseases areA horse’s hocks are injected to treat the onset ofarthritic changes.often caused by more than one geneticmutation, and development of diseaseand disease severity are often affected byenvironmental factors. When an individualinherits a genetic mutation for a complexdisease, it is not a guarantee they willdevelop the disease, but that they are atincreased risk.Equine metabolic syndrome (EMS) is acomplex genetic disease currently underinvestigation in the EGG laboratory. EMSis a devastating disease characterizedby three main features: obesity, insulinresistance, and laminitis. Certain breedsor individual horses are predisposed toEMS, and are often referred to as “easykeepers.” These horses are very efficient atutilizing calories and often require a lowerplane of nutrition to maintain body weightthan other horses. This tendency to be aneasy keeper likely begins with a geneticpredisposition.The EGG laboratory is leading alarge-scale investigation into the roleof environment (diet and exercise)and genetics in EMS, with the goal ofidentifying the genetic mutations thatunderlie disease risk. Other complexgenetic diseases under investigationin the EGG laboratory includerecurrent exertional rhabdomyolysis,osteochondrosis dessicans, equinerecurrent uveitis, shivers, andsusceptibility to melanoma.EGG research is focused onunderstanding the genetic diversityin modern horse breeds and the genesunderlying desirable traits in differentbreeds. The EGG lab is leading aninternational collaboration, the EquineGenetic Diversity Consortium, whichconsists of more than 30 scientistsfrom over 25 institutions worldwide.The consortium is studying the geneticdifferences and relationships between40 different horse breeds from acrossthe globe.This project represents the largestand most comprehensive data set ongenetic diversity in the modern horse,which will allow insight into the overalleffect of current breeding practices.For the first time, researchers will havesystematically identified the regions ofthe genome that have been influencedby selective breeding during the historyof the domestic horse, which will enablethem to start untangling the genetic basisof enhanced performance in certainpopulations and disciplines.This horse is part of a research project beingconducted by Dr. Molly McCue, who is investigatingequine metabolic syndrome, a complex geneticdisease characterized by obesity, insulinresistance, and laminitis.9