Polyneuropathy LPN2 in Leonbergers

Polyneuropathy is characterized by non-traumatic involvement of peripheral nerves. The hereditary variant of this disease is severe, chronic, and progressive. Clinical symptoms, 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. Whistling or wheezing during inspiration (due to laryngeal paralysis) and dyspnoea are also common.

In Leonbergers, the disease is caused by mutation c.1107_1108delAG in the GJA9 gene, which encodes the alpha9 subunit of the gap junction that ensures cellular connection. The mutation leads to a shift in the reading frame, premature insertion of the stop codon, and truncation of the resulting protein by almost half.

The inheritance of this mutation is incompletely autosomal dominant. This means that only one copy of the mutated gene inherited from either parent is needed to cause symptoms of the disease. However, the affected homozygote will differ from the heterozygote in the severity of the symptoms. The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to avoid unintentional breeding of puppies with this disease.

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References:

Granger, N.: Canine inherited motor and sensory neuropathies: an updated classification in 22 breeds and comparison to Charcot-Marie-Tooth disease. Vet J 188:274-85, 2011. Pubmed reference: 20638305