Cystinuria type I-A is a kidney disorder in which the kidneys are unable to reabsorb cystine, leading to the formation of crystals in the urinary tract, which can cause urinary obstruction, difficulty in passing urine, and presence of blood in the urine.
Phenotype: Dogs with this disease fail to reabsorb cystine in their kidneys, thus leading to the formation of crystals in the urinary tract, which result in urinary obstruction, stranguria (difficulty in passing urine) and hematuria (presence of blood in the urine). Affected male dogs typically show signs between 6 and 14 months of age but female dogs tend to develop signs later. Dogs with cystinuria often have frequent episodes of urinary tract inflammation that can lead to kidney failure and death, if not treated.
Mode of Inheritance:Autosomal recessive
Alleles: N = Normal, C = Cystinuria type I-A
Breeds appropriate for testing: Labrador Retriever
Explanation of Results:
Dogs with N/N genotype will not have cystinuria type I-A and cannot transmit this cystinuria type I-A variant to their offspring.
Dogs with N/C genotype will not be affected by cystinuria type I-A, but are carriers. They will transmit this cystinuria type I-A variant to 50% their offspring. Matings between two carriers are predicted to produce 25% cystinuria type I-A-affected puppies.
Dogs with C/C genotype will have cystinuria type I-A and will transmit this cystinuria type I-A variant to all of their offspring.
At least 15 business days; may be delayed beyond 15 business days if sample requires additional testing, or a new sample is requested.
Cystinuria Type I-A is an inherited metabolic disorder that affects kidney function. Affected dogs fail to reabsorb cystine in their kidneys, which leads to the formation of cystine crystals and uroliths in the urinary tract. Signs of this disease include urinary obstruction, stranguria (difficulty in passing urine), and hematuria (presence of blood in the urine). Obstruction of urine flow is more common and occurs earlier in males because of their urinary tract anatomy. Affected male dogs typically show signs between 6 and 14 months of age while female dogs tend to present these later. Dogs with cystinuria often have frequent episodes of urinary tract inflammation that can lead to kidney failure and death, if not treated.
Cystinuria Type I-A in Labrador Retrievers is caused by a single nucleotide deletion (c.350delG) in exon 1 of the solute carrier family 3, member 1 (SLC3A1) gene. The mode of inheritance for this disease is autosomal recessive, which means that males and females are equally affected and that two copies of the deletion are needed to cause cystinuria type I-A. Screening of a random set of Labradors Retrievers at the VGL determined that the cystinuria type I-A disease allele is rare in this breed, with a frequency less than 1%.
Testing for cystinuria type I-A can assist clinicians, owners, and breeders in identifying affected and carrier dogs. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected dogs.
Note: This test is specific for cystinuria type I-A in Labrador Retrievers and does not detect cystinuria in other breeds.
No copies of the cystinuria type I-A mutation detected. Dog is normal.
1 copy of the cystinuria type I-A mutation detected. Dog is a carrier. If bred to another carrier, 25% of offspring are predicted to be affected.
2 copies of the cystinuria type I-A mutation detected. Dog is affected and will develop cystinuria.
Brons, A. K., Henthorn, P., Raj, K., Fitzgerald, C. A., Liu, J., Sewell, A. C., & Giger, U. (2014). SLC3A1 and SLC7A9 mutations in autosomal recessive or dominant canine cystinuria: a new classification system. Journal of Veterinary Internal Medicine, 27(6), 1400-1408. doi: 10.1111/jvim.12176