GM1 Gangliosidosis (GLB1 gene, Portuguese Water Dog)

Gangliosidoses in dogs are a group of rare lysosomal storage diseases that result in the abnormal accumulation of a fatty substance called ganglioside in the brain and other body organs such as the liver. There are two main forms of gangliosidosis in dogs: the GM1 form and the GM2 form, caused by deficiency in the enzymes acid galactosidase and β-hexosaminidase, respectively.

Symptoms

Symptoms of gangliosidosis usually appear during the first two years of life and may include weight loss, muscle weakness and blindness. When ganglioside accumulation is severe, the dog's coordination is affected and cerebellar ataxia often occurs. The dog may appear lethargic or depressed. Head jerking is often observed, especially when eating. Seizures may occur in some cases. Symptoms worsen with time and euthanasia is often resorted to.

Disease Management

Currently, there is no cure for gangliosidosis in dogs. Treatment focuses on alleviating symptoms and improving the animal's quality of life. If you suspect that your dog may be affected by this disease, it is important that you take your dog to a veterinarian specializing in veterinary neurology for proper diagnosis and treatment.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

GM1 gangliosidosis is a disease that affects the brain and other tissues and is caused by alterations in the enzyme acid beta-galactosidase which is encoded by the GLB1 gene and plays a vital role in the breakdown and recycling of complex molecules within cell lysosomes. When there is deficiency in beta-galactosidase activity, accumulation of glycoconjugates in lysosomes occurs, especially in cells of the central nervous system triggering GM1. The variant analyzed here, c.179G>A of the GLB1 gene, is specific to Portuguese water dogs. Dogs with two copies of c.179G>A may develop GM1 gangliosidosis. Other mutations in the GLB1 gene that could cause the disease have been identified in other breeds such as shiba inu and Alaskan husky.

Most affected breeds

  • Alaskan Husky
  • Beagle
  • English Springer Spaniel
  • Portugese water dog
  • Shiba Inu

Bibliography

Wang ZH, Zeng B, Shibuya H,et al. Isolation and characterization of the normal canine beta-galactosidase gene and its mutation in a dog model of GM1-gangliosidosis. J Inherit Metab Dis. 2000 Sep;23(6):593-606.

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