Cystinuria type 3 is an inherited disease affecting kidney function in dogs. Dogs with cystinuria are deficient of a specific protein the kidneys use to transport cystine. Normal kidneys reabsorb cystine so that only small amounts pass into the urine. Dogs with cystinuria fail to reabsorb cystine, allowing large amounts to pass into the urine. Excessive cystine can form crystals and/or stones in the urinary tract, which can block the ureters or Urethra and stop the normal flow of urine. Symptoms of disease include straining to urinate, blood in the urine, frequent urination of small volumes or inability to urinate. Dogs with cystinuria often have recurrent inflammation of the urinary tract and if not treated, urinary stones can cause urinary tract infections, kidney failure and even death. Affected males are also at increased risk for urinary obstruction due to anatomical differences.
This test examines the genome for a genetic Mutation in the SLC3A1 gene associated with cystinuria type 3 (Variant 2). This mutation is not the actual mutation responsible for the disorder. It is considered a “linked marker” for cystinuria type 3. Linked markers are present in close proximity to the disease-causing mutation and are predictably inherited along with it. Making a test for the genetic mutation in the SLC3A1 gene a useful tool to assess cystinuria risk. Dogs that inherit one copy of the SLC3A1 mutation are considered carriers of the disease and will not show clinical signs of cystinuria. Cystinuria type 3 is an androgen-dependent form of the disease. Therefore, only intact males (and not females) are at an increased risk. Male dogs which inherit two copies of the SLC3A1 mutation are considered affected with cystinuria type 3 and may develop clinical signs. Although, female dogs with the SLC3A1 mutations should not develop clinical signs, they can produce at-risk/affected male offspring if bred with a dog that has also inherited these mutations.
This test also examines the genome for a genetic mutation in the SLC7A9 gene speculatively associated with cystinuria type 3 (Variant 3). This mutation is not believed to be the actual mutation responsible for the disorder. However, it may be a “linked marker” for cystinuria type 3, meaning that this marker may be present in close proximity in the genome to the mutation responsible for cystinuria type 3 and may be inherited along with the mutation which causes this disease. However, it is unconfirmed at this time if one or two copies of the SLC7A9 mutation alone is associated with cystinuria type 3.