Polyneuropathy in Leonbergers and Saint Bernards

Polyneuropathy is characterized by non-traumatic involvement of peripheral nerves. The hereditary variant of this disease is severe, chronic, and progressive. Clinical signs, which appear at a young age, are typically more severe and progress more rapidly. They include gait abnormalities, muscle atrophy, particularly of the pelvic limbs, and general weakness. In affected dogs, problems with breathing such as whistling, or inspiratory stridor (due to laryngeal paralysis) and dyspnoea are also common.

The disease is caused by mutation c.1955_1958+6del in the ARHGEF10 gene. The mutation results in a shift of the reading frame and generates a premature stop codon, which results in a by half truncated protein.

The mode of inheritance of the mutation is probably autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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References:

Ekenstedt, K.J., Becker, D., Minor, K.M., Shelton, G.D., Patterson, E.E., Bley, T., Oevermann, A., Bilzer, T., Leeb, T., Drögemüller, C., Mickelson, J.R. : An ARHGEF10 deletion is highly associated with a juvenile-onset inherited polyneuropathy in Leonberger and Saint Bernard dogs. PLoS Genet 10:e1004635, 2014. Pubmed reference: 25275565