The mild myopathy in heterozygous mutant mice (Ryr1I4895T/+) is associated with progressive ER stress and UPR and increased levels of the mediators CHOP (CAATT enhancer-binding protein homologous protein) and ERO1-alpha (Endoplasmic reticulum oxidoreductin 1-alpha, henceforth ERO1). This evidence concerns the gene DDIT3 and myopathy.