Hereditary ataxia in Gordon Setters and Old English Sheepdogs

Hereditary Ataxia (HA) is described as a disorder of coordination in the movements of different muscles and represents a relatively non-specific clinical symptom. In dogs, it can be caused by mutations in more than eight different genes. In Gordon Setters and Bobtails, the disorder has the same molecular basis. It is caused by the c.113A>C mutation in the RAB24 gene. The onset of cerebellar ataxia symptoms is observed in young dogs or young adults between 6 months and 4 years of age. The affected dogs develop hypermetria (excessive movement), truncal sway and tremor of the limbs during purposeful movement, and the signs gradually progress to a severe gait disturbance. It leads to cerebellar atrophy with dramatic loss of Purkinje cells.

The mode of inheritance of the mutation is 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:

Agler, C., Nielsen, D.M., Urkasemsin, G., Singleton, A., Tonomura, N., Sigurdsson, S., Tang, R., Linder, K., Arepalli, S., Hernandez, D., Lindblad-Toh, K., van de Leemput, J., Motsinger-Reif, A., O'Brien, D.P., Bell, J., Harris, T., Steinberg, S., Olby, N.J. :  Canine hereditary ataxia in Old English Sheepdogs and Gordon Setters is associated with a defect in the autophagy gene encoding RAB24. PLoS Genet 10:e1003991, 2014. Pubmed reference: 24516392