Affected genes: SLC3A1
Transmission: Autosomal recessive
Mutation: CanFam3.1 chr10:46706001: C>T

Appropriate breeds for testing: Landseer Newfoundland, Newfoundland

Symptoms
Type I A cystinuria causes a defect in cystine reabsorption in the proximal renal tubule, leading to cystine precipitation in the urine.
The formation of crystals and stones leads to urolithiasis and urinary tract obstruction. Stones can lodge in the bladder, urethra or kidney, causing partial or complete urinary blockage, potentially leading to renal failure (Brons et al., 2013). The age of onset of the disease is relatively early in Newfoundlands compared with other breeds that develop cystinuria.

References:
Brons AK, Henthorn PS, Raj K, et al. (2013) SLC3A1 and SLC7A9 mutations in autosomal recessive or dominant canine cystinuria: a new classification system. J Vet Intern Med 27:1400-8. [pubmed/24001348]
Casal ML, Giger U, Bovee KC, Patterson DF. Inheritance of cystinuria and renal defect in newfoundlands. J Am Vet Med Assoc. 1995 Dec 15;207(12):1585-9.
Henthorn PS, Liu J, Gidalevich T, Fang J, Casal ML, Patterson DF, Giger U. Canine cystinuria: polymorphism in the canine SLC3A1 gene and identification of a nonsense mutation in cystinuric Newfoundland dogs. Hum Genet. 2000 Oct; 107(4):295-303.