Cerebellar abiotrophy in Beagles

Cerebellar abiotrophy (NCCD) is a neurodegenerative disease described in several canine breeds including the Beagle.
NCCD is a disease characterised with a number of clinical signs causing the dysfunction of the cerebellum, such as dissymmetrical ataxia, wide-based stance, loss of balance and body tremor. In Beagles, the neurological signs are first noticed at around three weeks of age. The affected puppies exhibit abnormal wide-based stance, loss of balance, dissymmetric gait with inability to regulate rate and the range of movement. The majority of puppies affected with NCCD are euthanized shortly after diagnosing the first signs of this disease.
The main histopathological lesions of the cerebellum characterising the NCDD-disease in Beagles are extensive degenerations leading to the loss of Purkinje cells and secondary lesions in the granular layer.
The NCCD in Beagles is caused by the mutation c.5855_5862del SPTBN2 (Forman et al., 2012).
The clinical signs of cerebellar abiotrophy are also known in other canine breeds - Rhodesian Ridgeback, Samoyed and Irish Setter. In these breeds, the casual mutation has not been found yet. The described mutation in GRM1 gene is associated with neonatal cerebellar ataxia (BNAt) in Coton de Tulear dogs.

Mutation that causes NCCD in Beagles 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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Reference:

Forman et al.: Genome-wide mRNA sequencing of a single canine cerebellar cortical degeneration case leads to the identification of a disease associated SPTBN2 mutation. BMC Genetics 2012