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  Discussion on Research Summary: GYS1 Mutation predominant form of PSSM in Draft and QH breeds
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Moderator:
DrO

Posted on Tuesday, Sep 23, 2008 - 10:12 am:

Recently one cause of PSSM has been identified as a genetic defect in horses that results in abnormal glycogen synthesis within the muscle cells. Genetic testing on over 800 horses with PSSM it has been found that 84% of the drafts and 72% of the QH's with PSSM have this defect. 24% of other light breeds with PSSM also have this defect. It is time we identify these individuals and weed out this problem through selective breeding. For more on this see the article on PSSM.
DrO


J Vet Intern Med. 2008 Aug 6;
Glycogen Synthase 1 (GYS1) Mutation in Diverse Breeds with Polysaccharide Storage Myopathy.

McCue ME, Valberg SJ, Lucio M, Mickelson JR.

Department of Veterinary Population Medicine, University of Minnesota College of Veterinary Medicine, St Paul, MN, USA.

Background: A missense mutation in the GYS1 gene was recently described in horses with polysaccharide storage myopathy (PSSM). Objectives: The first objective was to determine the prevalence of the GYS1 mutation in horses with PSSM from diverse breeds. The second objective was to determine if the prevalence of the GYS1 mutation differed between horses diagnosed with PSSM based on grade 1 (typically amylase-sensitive) or grade 2 (typically amylase-resistant) polysaccharide. Animals: Eight hundred and thirty-one PSSM horses from 36 breeds. Procedures: Horses with PSSM diagnosed by histopathology of skeletal muscle biopsy samples were identified from the Neuromuscular Disease Laboratory database. Eight hundred and thirty-one cases had blood or tissue that was available for DNA isolation; these 831 cases were genotyped for the GYS1 mutation by restriction fragment length polymorphism. Results: The PSSM mutation was identified in horses from 17 different breeds. The prevalence of the GYS1 mutation in PSSM horses was high in Draft- (87%) and Quarter Horse-related breeds (72%) and lower in Warmbloods (18%) and other light horse breeds (24%), when diagnosis was based on grade 2 diagnostic criteria. Overall, the PSSM mutation was present in 16% of grade 1 and 70% of grade 2 PSSM horses. Conclusions and Clinical Importance: GYS1 mutation causes PSSM in diverse breeds and is the predominant form of PSSM in Draft- and Quarter Horse-related breeds. False-positive diagnosis, as well as the possibility of a second glycogenosis in horses with neuromuscular disease (type 2 PSSM), might explain the absence of the GYS1 mutation in horses diagnosed with excessive glycogen accumulation in muscle.
Member:
maggienm

Posted on Tuesday, Sep 23, 2008 - 4:49 pm:

Is this a test that is readily available so anyone with a draft or draft cross can have their horse tested?
Moderator:
DrO

Posted on Tuesday, Sep 23, 2008 - 9:51 pm:

Check out the article Lori, these tests are available and explains how to get information about testing.
DrO
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