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IN DOGS, only 3 per cent of urolithiasis is represented by a cystine ( Ling and others 1998 , Osborne and others 1999 ); according to Bartges and others (1994) , English bulldogs are characterised by a cystine urolith frequency 32 times higher than any other dog. In 1977 , Brown and others examined 438 uroliths. Among these, 95 were made of a cystine and were mainly found in English bulldogs, Newfoundlands and dachshunds. Later, Chew and others (2011) published research listing the same breeds as the most affected by cystinuria. In English bulldogs, four mutations have been identified at the homozygous level in the SLC3A1 gene, whereas two mutations have been described in the SLC7A9 gene ( Harnevik and others 2006 ). In a recent study, Brons and others (2013) suggested a new classification for cystinuria, which seems to have different characters and involve different genes depending on the breed. In labrador retrievers and mixed breeds, cystinuria is described as an autosomic-recessive disease involving the SLC3A1 gene; in Australian cattle dogs, the disease seems to be autosomic dominant.
The aim of this study was to investigate the association between cystine uroliths in some English bulldogs and the genetic mutations in the SLC3A1 and SLC7A9 genes.
Specimen collections and analyses were carried out at the Faculty of Veterinary Medicine, University of Milan.
A total of 24 client-owned English bulldogs (19 healthy and 5 with symptoms related to a urinary tract obstruction or presence of urolithiasis) were genetically analysed for a cystinuria mutation. One millilitre of whole blood was collected in EDTA tubes, then immediately frozen and stored (-20°C) for 2-14 days. The standard procedure for DNA extraction was performed; the extracted DNA was amplified by PCR. Studied genes are reported in Table 1 .
Clinical status | Gene | Genetic alteration (SNP) | Involved amino acid |
Unaffected | SLC3A1 | 574 A (EX2) | I192V |
Affected | SLC3A1 | 574 A->G (EX2) | I192V |
Unaffected | SLC3A1 | 2092 A (EX10) | S698G |
Affected | SLC3A1 | 2092 A->G (EX10) | S698G |
Unaffected | SLC7A9 | 649 G (EX4) | A217T |
Affected | SLC7A9 | 649 G->A (EX4) | A217T |
A, adenine; A->G, adenine-to-guanine nucleotide change; EX, exon; G, guanine; G->A, guanine-to-adenine nucleotide change
Clinically affected dogs underwent a clinical examination, haematological test (CBC and biochemical panel-Sysmex XT-2000iV, Cobas Mira), urinalysis (physical, chemical, microscopic evaluation and...