A GYS1 gene mutation is highly associated with polysaccharide storage myopathy in Cob Normand draught horses.

The research investigates how a mutation in the GYS1 gene is largely linked to a disease known as polysaccharide storage myopathy (PSSM) in Cob Normand draught horses. The study aims to examine the potential associations between genetic differences in four potential genes of the glycogen pathway, including the GYS1 mutation, in horses diagnosed with PSSM.

Introduction

• Glycogen storage diseases, or glycogenoses, are inherited diseases caused by irregularities in enzymes that control the synthesis or degradation of glycogen, a form of sugar stored in the body for energy.
• These can occur from harmful mutations in multiple genes in the glycolytic or glycogenesis pathways. At present, mutations in fourteen different genes are known of that cause animal or human glycogenoses.
• The diseases often result in myopathies, which are diseases of the muscle tissue, and/or disorders of the liver.

Glycogenosis in Horses

• In horses, two forms of glycogenosis are presently identified.
• A fatal form known as type IV glycogenosis affects neonatal Quarter Horse foals. This form is inherited recessively, meaning both parents must carry the gene to transmit the disorder. This disease is due to a mutation in the glycogen branching enzyme gene (GBE1).
• Another form of glycogenosis, polysaccharide storage myopathy (PSSM), is observed more commonly in adult Quarter Horses and other breeds. PSSM is said to be severe in draught horses.

Research Aims and Methodology

• The research aims to explore the link between the GYS1 gene mutation and the case of PSSM in Cob Normand draught horses specifically.
• The mutation in the GYS1 gene appears to result in an overactive enzyme which leads to the buildup of a less-branched polysaccharide, similar to glycogen, in skeletal muscle. This is inherited as a dominant trait.
• The study tests for potential associations between genetic variations in four possible genes of the glycogen pathway or the GYS1 mutation in Cob Normand draught horses identified with PSSM through muscle biopsy.