Testing of dogs: Cystinuria in Labrador Retrievers

Cystinuria type I-A in Labrador Retrievers

Cystinuria is an inherited metabolic disorder of amino acid transport (cystine, ornithine, lysine, arginine) in the kidneys. This disease occurs in various animal species including humans. There is a clinical diversity among dog breeds suffering from cystinuria. The degree of involvement is related to age.

In individuals affected by cystinuria, cystine accumulates in the urine, cystine crystals and eventually urinary stones are formed, which can lead to unpleasant health complications such as: irritation of the urinary tract, stagnation of urine, susceptibility to more frequent urinary tract infections or even complete closure of the urinary tract, which can cause kidney failure. The disease affects males more because they have a longer urinary tract than females.

In Labradors, the disease is caused by the c.350del mutation in the SLC3A1 gene.

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:

Brons, A.K., Henthorn, P.S., Raj, K., Fitzgerald, C.A., Liu, J., Sewell, A.C., Giger, U. : SLC3A1 and SLC7A9 mutations in autosomal recessive or dominant canine cystinuria: a new classification system. J Vet Intern Med 27:1400-8, 2013. Pubmed reference: 24001348