Cystinuria type I-A / cystine stones (SLC3A1 c.586C>T) - Newfoundland

What does this test analyse?

This genetic test analyses the SLC3A1 variant c.586C>T for cystinuria in Newfoundland dogs. Cystinuria is also described as cystine urolithiasis, cystine stones, cystine calculi, bladder stones or kidney stones. The test determines whether the dog is clear, heterozygous positive/carrier or homozygous positive/affected for this specific variant.

What does cystinuria mean for the dog?

Cystinuria is an inherited metabolic disorder in which the kidneys fail to reabsorb cystine and related amino acids efficiently. As a result, too much cystine remains in the urine. Cystine is poorly soluble and can form crystals or stones in the bladder, urethra or kidneys.

The condition is also known as cystine urolithiasis, cystine stones, cystine calculi, bladder stones or kidney stones. Signs may include straining to urinate, frequent small urinations, blood in the urine, recurrent bladder inflammation and urinary obstruction. In male dogs, obstruction can become serious quickly because of the narrower urethra.

Practical value of this test

• Gives breeders clear information about clear, carrier and genetically affected dogs before mating decisions are made.
• Helps avoid risk combinations while allowing valuable carriers to be managed responsibly in a breeding programme.
• Supports targeted selection in breeds where cystine stones are known, so puppies are not unexpectedly born with two copies of the variant.
• Gives owners and veterinarians genetic context when cystine crystals, cystine stones or recurrent urinary signs occur.

Inheritance and result

The trait is inherited as autosomal recessive. A dog with two normal alleles is clear. A dog with one copy is a carrier and can pass the variant on. A dog with two copies is genetically affected for this tested form of cystinuria.

Other causes can also produce urinary signs. This test therefore gives targeted genetic information about the variant for which the analysis was designed.