Polysaccharide storage myopathy phenotype in quarter horse-related breeds is modified by the presence of an RYR1 mutation

Molly E McCue, Stephanie J Valberg, M. Jackson, L. Borgia, M. Lucio, James R Mickelson

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38 Scopus citations

Abstract

In this study we examined a family of Quarter Horses with Polysaccharide Storage Myopathy (PSSM) with a dominant mutation in the skeletal muscle glycogen synthase (GYS1) gene. A subset of horses within this family had a more severe and occasionally fatal PSSM phenotype. The purpose of this study was to identify a modifying gene(s) for the severe clinical phenotype. A genetic association analysis was used to identify RYR1 as a candidate modifying gene. A rare, known equine RYR1 mutation, associated with malignant hyperthermia (MH), was found to segregate in this GYS1 PSSM family. Retrospective analysis of patient records (n = 179) demonstrated that horses with both the GYS1 and RYR1 mutations had a more severe clinical phenotype than horses with the GYS1 mutation alone. A treadmill trial (n = 8) showed that serum creatine kinase activity was higher and exercise intolerance greater in horses with both mutations compared to the GYS1 mutation alone.

Original languageEnglish (US)
Pages (from-to)37-43
Number of pages7
JournalNeuromuscular Disorders
Volume19
Issue number1
DOIs
StatePublished - Jan 2009

Bibliographical note

Funding Information:
Funding provided by the Morris Animal Foundation grants D07EQ-041 and D07EQ-402 (ME McCue, salary support) and the American Quarter Horse Association grant “Genetic Analysis of Glycogen Storage Disorders in Quarter Horses”.

Keywords

  • GYS1
  • Glycogen synthase
  • Glycogenosis
  • Malignant hyperthermia
  • RYR1

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