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SDCA2- Spongy degeneration with cerebellar ataxia
| Acronym: | SDCA2 |
| Gene: | ATP1B2 |
| Mutation: | c.130_131ins[227] |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
SDCA2 is a form of spongy degeneration with cerebellar ataxia, an inherited disorder that affects the Belgian Shepherd Dog. It is part of a wider group of disorders known as inherited cerebellar ataxia which represents a wide group of heterogeneous neurodegenerative disorders characterized by progressive degeneration of the cerebellum and extracerebellar structures. In humans, inherited ataxia shows various modes of inheritance, with autosomal dominant inheritance as the most prevalent. In dogs, a genetic basis of cerebellar ataxias has been described for only some autosomal recessive inherited disorders.
Affected puppies start to show symptoms around 4 weeks of age. Symptoms include generalized ataxic gait, seizures, and pacing as well as circling and central blindness. These clinical signs showed very rapid progression. Affected puppies may die during a seizure. Histopathological examination revealed vacuolation of the neuropil, and neuronal necrosis, and severe gliosis in the spinal cord. In the hippocampus, neuronal necrosis and the presence of hypertrophic astrocytes with vesicular nuclei are present, similar to in Alzheimer type II cells.
SDCA2, Spongy degeneration with cerebellar ataxia in Belgian Shepherd dog is caused by a mutation in exon 2 of the ATP1B2 gene, which encodes a subunit of Na+/K+-ATPase, an enzyme crucial for signal transduction. The disorder is inherited in an autosomal recessive pattern. A dog can be clear, carrier, or affected. Carriers of the gene are heterozygous and do not develop the disease’s symptoms. When mating two carrier dogs, each future cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Mauri, N., Kleiter, M., Dietschi, E., Leschnik, M., Högler, S., Wiedmer, M., … Leeb, T. (2017). A SINE Insertion in ATP1B2 in Belgian Shepherd Dogs Affected by Spongy Degeneration with Cerebellar Ataxia (SDCA2). G3: Genes|Genomes|Genetics, 7(8), 2729–2737. http://doi.org/10.1534/g3.117.043018