Gangliosidoses are degenerative, fatal neurological diseases caused by abnormal accumulation of lipids known as gangliosides in central and peripheral nervous systems, and nerve cells in particular. Cats affected with gangliosidosis have progressive neurologic dysfunction and premature death. Two forms of gangliosidosis affect Korat cats – GM1 and GM2. Both have a genetic basis and a recessive mode of inheritance. Two copies of the defective gene are needed to cause the disease. Both diseases cause similar progressive neurologic dysfunction, including tremors, ataxia and dysmetria. Disease progression is more rapid in GM2.
Korat GM1 is caused by a mutation in exon 14 of the Beta-Galactosidase gene (GLB1). Disease onset begins around 3 months of age and reaches terminal stage around 9-10 months, at which point blindness and epileptiform seizures are also observed. The mutation has been found in the Siamese breed which was used in the development of the Korat breed.
Korat GM2 is caused by a mutation in the feline Hexoaminidase β-subunit (HEXB) gene. Disease onset is observed as early as 4 weeks of age, beginning with fine head tremors, followed rapidly by ataxia, and progresses to death before 8 months of age.
The VGL offers DNA tests for GM1 and GM2 in Korat cats to assist owners and breeders in identifying affected and carrier cats. The tests are done with DNA collected from buccal swabs thus avoiding invasive blood collection. Breeders can use these tests as a tool to avoid breeding carriers together which would produce 25% affected offspring.
Results reported as:
|Test Result||GM1 Gangliosidosis Status|
|N/N||Normal, cat does not have GM1 Korat mutation*|
|N/GM1k||Carrier, cat has one copy of GM1 Korat mutation. Breedings between carriers will is expected to produce 25% affected kittens.|
|Test Result||GM2 Gangliosidosis Status|
|N/N||Normal, cat does not have GM2 Korat mutation**|
|N/GM2k||Carrier, cat has one copy of GM2 Korat mutation. Breedings between carriers will be expected to produce 25% affected kittens.|
Martin D.R., B.A. Rigat, P. Foureman et al. Molecular consequences of the pathogenic mutation in feline GM1 gangliosidosis. Molecular Genetics and Metabolism 94: 212-221, 2008.
Muldoon L.L., E.A. Neuwelt, M.A. Pagel, D.L. Weiss. Characterization of the molecular defect in a feline model for type II GM2-gangliosidosis (Sandhoff Disease). American Journal of Pathology 144:1109-1118, 1994.
Baker H.J., B.F. Smith, D.R. Martin & P. Foureman. Molecular Diagnosis of Gangliosidoses: A Model for Elimination of Inherited Diseases in Pure Breeds. In Consultations in Feline Internal Medicine 4, J.R. August (ed.). W.B. Saunders, Philadelphia, 2001, pp 615-620.
* This test is specific for the single base substitution in the GLB1 gene that causes GM1 in Korat and Siamese cats. It will not detect other gangliosidosis mutations known to exist in other breeds of cats.
* * This test is specific for the 1 base deletion in the HEXB gene that causes GM2 in Korat cats. It will not detect other HEXB mutations known to exist in other breeds of cats.