Testing of dogs: Spinocerebellar Ataxia
Related tests
- Combination Alpine Dachsbracke SCN8A + NCL8 + HUU
- Spinocerebellar Ataxia + NCL8 double test for Alpine Dachsbracke
Spinocerebellar ataxia in Alpine Dachsbracke
Spinocerebellar ataxia is an umbrella term for clinically and neuropathologically heterogeneous hereditary neurodegenerative diseases that is usually associated with cerebellum degeneration. The disease manifests itself in movement coordination disorder and affects several dog breeds.
In Alpine Dachsbrake the disease is caused by mutation in SCN8A gene that encodes a voltage-gated sodium channel, which is important for the transport of sodium ions to neurons in the central and peripheral nervous system. It is most abundant in the maturing nodes of Ranvier in myelinated axons of the central nervous system, in which it contributes to nerve conduction velocity. It was also found at the axon initial segment of excitatory and inhibitory neurons, where it regulates the formation of action potential, which is essential for membrane depolarization. Due to the missense variant of the mutation SCN8A: c.4898G> T the amino acid is incorrectly linked and on that account the function of sodium channels changes as well. Altering of the sodium channels leads to abnormally, either increased or decreased, neuronal signalling resulting in progressive neuronal degeneration. There are obvious structural changes in brain – axonal degeneration, astrogliosis or vacuolation of white and grey matter indicating myelin splitting in the entire brain. These changes are most severe in the vestibulocochlear nucleus, cerebellar nuclei, thalamus and brainstem.
The clinical symptoms appear at the age of three weeks when the puppies are behind their healthy littermates in walking and maintaining balance. Older puppies show remarkable gait abnormalities – cerebellar ataxia (movement coordination ataxia), tremor, balance loss and associated movement abnormalities, such as eye movement disorder, loss of vision or behavioural disorders.
Spinocerebellar Ataxia is inherited as an autosomal recessive trait. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive /negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.
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Publication:
Letko, A., Dietschi, E., Nieburg, M., Jagannathan, V., Gurtner, C., Oevermann, A., Drögemüller, C. : A Missense Variant in SCN8A in Alpine Dachsbracke Dogs Affected by Spinocerebellar Ataxia. Genes (Basel) 10:, 2019. Pubmed reference: 31083464. DOI: 10.3390/genes10050362.