Canine cystinuria: polymorphism in the canine<Emphasis Type="Italic"> SLC3A1</Emphasis> gene and identification of a nonsense mutation in cystinuric Newfoundland dogs

Cystinuria is an inherited renal and intestinal disease characterized by defective amino acid reabsorption and cystine urolithiasis. Different forms of the disease, designated type I and non-type I in cystinuric humans, can be distinguished clinically and biochemically, and have been associated with mutations in the SLC3A1 (rBAT) and SLC7A9 genes, respectively. Type I cystinuria is the most common form and is inherited as an autosomal recessive trait in humans. Cystinuria has been recognized in more than 60 breeds of dogs and a severe form, resembling type I cystinuria, has been characterized in the Newfoundland breed. Here we report the cloning and sequencing of the canine SLC3A1 cDNA and gene, and the identification of a nonsense mutation in exon 2 of the gene in cystinuric Newfoundland dogs. A mutation-specific test was developed for the diagnosis and control of cystinuria in Newfoundland dogs. In cystinuric dogs of six other breeds, either heterozygosity at the SLC3A1 locus or lack of mutations in the coding region of the SLC3A1 gene were observed, indicating that cystinuria is genetically heterogeneous in dogs, as it is in humans. The canine homologue of human type I cystinuria provides the opportunity to use a large animal model to investigate molecular approaches for the treatment of cystinuria and other renal tubular diseases.