Testing of dogs: Cystinuria

Cystinuria in Newfoundlands and Landseer

Cystinuria is a hereditary autosomal recessive metabolic disorder. Cystinuria is based on disorder of kidney aminoacid transport (cystine, ornithine, lysine, arginine). Cystinuria appears in many animals and in humans.

Cystine does not dissolve in acid surroundings very well. Insoluble cystine accumulates in urine of individuals suffering with cystinuria (because urine is acid). Than, accumulated cystine forms crystals and stones – concrements (Segal a Thier 1995). Concrements lead to unpleasant health problems like often urinary system infections, urine stagnation, even urinary system obstruction. Seriousness of disease depends on gender, urine pH and urine density. Males are more often cystinuria affected than females (because males have longer urinary system). Urine flowage is reduced mostly at positions where urethra changes its direction. The more acid urine is, the more crystals are formed. Dense urine contains more cystine so that more sand or stones are created.

Cystinuria has been found in more than 60 dog breeds. It was proved cystinuria in Newfoundlands as an autosomal recessive disease (Casal et al. 1995). Clinical symptoms manifestate from 4 to 6 months – cystine, lysine, ornithine and arginine levels rapidly increase in homozygous affected dogs and stay normal in heterozygous dogs. A nonsence mutation was found in SLC31 gene, exon 2 of Newfoundlands and specific genetic test was designed.

Many other dog breeds were examined but no mutation in SLC31 gene was found (Henthorn S. P. et. al. 2000). Anyway cystinuria was identified in other carnivorous animals included minks, wolfs (Bovee et al. 1981), cats (DiBartola et al. 1991) and dogs (Brand a Cahill 1936).

With respect to kinship of Newfoundlands and Landseers the same mutation in SLC31 gene can be expected in Landseers.

In a study (Urs Giger, ACVIM & ECVIM University of Pennsylvania), there were 1400 Newfoundlands examined – 1 % of the dogs were cystinuria affected, 20 % of the dogs were carriers of the mutated gene. In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

Thanks to Urs Giger, University of Pennsylvania School of Veterinary Medicine.

References:

Bovee KC, Bush M, Dietz J, Jezyk P, Segal S: Cystinuria in the maned wolf of South America. Science (1981) 212:919-920
Brand E, Cahill GF: Canine cystinuria. III. J Biol Chem (1936) 114:XV
Casal ML, Giger U, Bovee KC, Patterson DF: Inheritance of cystinuria and renal defect in Newfoundlands. J Am Vet Med Assoc (1995) 207:1585-1589
DiBartola SP, Chew DJ, Horton ML: Cystinuria in a cat. J Am Vet Med Assoc (1991) 198:102-104
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) 107:295-303
Segal S, Thier SO.: Cystinuria. In: Scriver C (ed) Metabolic and molecular bases of inherited disease, 7th edn. McGraw-Hill, New York, (1995) pp 3581-3601
Tichá V. Cystinurie - dědičně podmíněná metabolická porucha psů, [online], [citováno 1. června 2008], dostupné z WWW: http://www.veterina-info.cz/
Diseases of the Kidneys [online], [citováno 1. června 2008], dostupné z WWW: http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2002&PID=2621