Sensory Neuropathy (SN) in border collies

Senzory neuropathy is a severe neurologic disease caused by degeneration of sensory and, to a lesser extent, motor nerve cells.

Affected dogs start to show symptoms from 2 to 7 months of age and signs include progressive loss of coordination, joint laxity and extreme stretching of limb muscles. The affected dogs are not able to feel the stretching of individual muscles and ligaments (loss of proprioception). That means that the affected dogs are not able to perceive its position and consequently the motor abilities are markedly worsened. Moreover, the affected dogs loose sensation of pain (loss of pain receptor, nociceptors) which lead to self-mutilation of paws. Pelvic limbs are usually more affected than thoracic limbs.  In some case, autonomous symptoms such as urinary incontinence and regurgitation (backflow of body fluids, e.g. swallowed food coming up into the throat or mouth or blood flow in the opposite direction) can also occur.  As the quality of life is severely affected, the dogs are after some time euthanized.

The disorder is caused by mutation (inversion) in FAM134B-gene, which encodes a cis-Golgi transmembrane protein that is necessary for the long-time survival of nociceptive neurons and autonomic ganglion neurons. In case of its dysfunction axon degeneration, connective tissue fibrosis near the peripheral nerves and extensive loss of peripheral nervous fibres occur.

SN is autosomal recessive inherited disease. 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.

The genetic tests can reveal the genotype of the animal and can help prevent the unintentional spread of this disease.

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Reference:

Forman, O.P., Hitti, R.J., Pettitt, L., Jenkins, C.A., O'Brien, D.P., Shelton, G.D., De Risio, L., Gutierrez Quintana, R., Beltran, E., Mellersh, C.: An Inversion Disrupting FAM134B Is Associated with Sensory Neuropathy in the Border Collie Dog Breed. G3 (Bethesda) :, 2016. Pubmed reference: 27527794. DOI: 10.1534/g3.116.027896.