SLC7A9 cDNA cloning and mutational analysis of SLC3A1 and SLC7A9 in canine cystinuria

Epidemiological Evaluation of Neuter Status, Sex, and Breed in Dogs With Cystine Uroliths

BACKGROUND

The majority of cystine uroliths occur in intact male dogs. Androgen-dependent (Type III) cystinuria is considered the most common cause.

OBJECTIVES

Identify dog breeds in which castration is likely to decrease the risk of cystine uroliths, the potential effect of delaying castration on cystine urolith formation, and urolith recurrence frequency.

ANIMALS

Records of 5477 dogs with cystine uroliths and comparison groups without cystine uroliths (263 938 dogs with non-cystine uroliths and 44 491 dogs from a hospital population).

METHODS

In this case-control study, odds ratios and 95% confidence intervals (CIs) were calculated to identify breeds where the proportion of intact males with cystine uroliths was higher than that of intact males without cystine uroliths. The proportions of intact males forming cystine uroliths before 12, 24, and 36 months of age were calculated. Cystine urolith recurrence rates were assessed by breed in male dogs.

RESULTS

Dogs with cystine uroliths were 99% male. Across 60 breeds, the median proportion of male cystine urolith formers that were intact was 98% (range, 40%-100%). When compared with dogs without cystine uroliths, intact males were overrepresented in cystine urolith formers in all breeds except 8 (Akita, Belgian Malinois, Brussels Griffon, Cane Corso, Coonhound, Newfoundland, Scottish Terrier, and Silky Terrier). Diagnosis occurred before 36 months of age in 28% (n = 1328) of intact male cystine urolith formers. Cystine uroliths recurred in 5.0% (n = 255) of males; 81% (n = 207) were intact males.

CONCLUSIONS AND CLINICAL IMPORTANCE

Androgens likely play a role in the development of cystine uroliths across many dog breeds.

Urinary Calculi of Small Ruminants

Urolithiasis is a multifactorial disease of male ruminants causing significant economic loss and compromise of animal welfare. Known risk factors include anatomic factors, urine pH, water intake, dietary composition, and genetic factors. Clinical cases of obstructive urolithiasis may be treated using a variety of medical and surgical interventions, including tube cystostomy, perineal urethrostomy, urinary bladder marsupialization, and modifications of these procedures designed to optimize patient outcome.

Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs

Hundreds of genetic variants implicated in Mendelian disease have been characterized in dogs and commercial screening is being offered for most of them worldwide. There is typically limited information available regarding the broader population frequency of variants and uncertainty regarding their functional and clinical impact in ancestry backgrounds beyond the discovery breed. Genetic panel screening of disease-associated variants, commercially offered directly to the consumer or via a veterinary clinician, provides an opportunity to establish large-scale cohorts with phenotype data available to address open questions related to variant prevalence and relevance. We screened the largest canine cohort examined in a single study to date (1,054,293 representative dogs from our existing cohort of 3.5 million; a total of 811,628 mixed breed dogs and 242,665 purebreds from more than 150 countries) to examine the prevalence and distribution of a total of 250 genetic disease-associated variants in the general population. Electronic medical records from veterinary clinics were available for 43.5% of the genotyped dogs, enabling the clinical impact of variants to be investigated. We provide detailed frequencies for all tested variants across breeds and find that 57% of dogs carry at least one copy of a studied Mendelian disease-associated variant. Focusing on a subset of variants, we provide evidence of full penetrance for 10 variants, and plausible evidence for clinical significance of 22 variants, on diverse breed backgrounds. Specifically, we report that inherited hypocatalasia is a notable oral health condition, confirm that factor VII deficiency presents as subclinical bleeding propensity and verify two genetic causes of reduced leg length. We further assess genome-wide heterozygosity levels in over 100 breeds, and show that a reduction in genome-wide heterozygosity is associated with an increased Mendelian disease variant load. The accumulated knowledge represents a resource to guide discussions on genetic test relevance by breed.

Cystinuria in Dogs and Cats: What Do We Know after Almost 200 Years?

The purpose of this review is to summarize current knowledge on canine and feline cystinuria from available scientific reports. Cystinuria is an inherited metabolic defect characterized by abnormal intestinal and renal amino acid transport in which cystine and the dibasic amino acids ornithine, lysine, and arginine are involved (COLA). At a normal urine pH, ornithine, lysine, and arginine are soluble, but cysteine forms a dimer, cystine, which is relatively insoluble, resulting in crystal precipitation. Mutations in genes coding COLA transporter and the mode of inheritance were identified only in some canine breeds. Cystinuric dogs may form uroliths (mostly in lower urinary tract) which are associated with typical clinical symptoms. The prevalence of cystine urolithiasis is much higher in European countries (up to 14% according to the recent reports) when compared to North America (United States and Canada) where it is approximately 1-3%. Cystinuria may be diagnosed by the detection of cystine urolithiasis, cystine crystalluria, assessment of amino aciduria, or using genetic tests. The management of cystinuria is aimed at urolith removal or dissolution which may be reached by dietary changes or medical treatment. In dogs with androgen-dependent cystinuria, castration will help. In cats, cystinuria occurs less frequently in comparison with dogs.

Cystine Urolithiasis in Ferrets

Urolithiasis in captive domestic ferrets has previously been predominantly struvite uroliths, although more recent laboratory submissions show a shift to predominantly cystine uroliths. Genetic mutations for cystinuria have been identified in dogs, and it is suspected that underlying genetic mutations are partly responsible for this disease in ferrets. Currently, surgery remains the only definitive treatment of cystine urolithiasis in ferrets, since dietary dissolution protocols have not been thoroughly explored. Despite this, medical management with dietary and urinary manipulation should be considered for use in ferrets postoperatively based on principles of cystine urolithiasis management in dogs adapted for ferrets.

An experimental model for calcium carbonate urolithiasis in goats

BACKGROUND

Calcium carbonate is a common urolith type in small ruminants with no high-yield experimental model to evaluate animal susceptibility or preventative measure response.

HYPOTHESIS

That novel plastic winged implants would allow accumulation and quantification of calcium carbonate calculus formation in goats on a high-calcium diet and identify individual variation between goats in the mass of calculi produced.

ANIMALS

Eight nonpregnant 3- and 4-year-old Boer-cross does, weighing 22.3-39.5 kg, determined to be healthy based on physical examination, were used in these experiments.

METHODS

Prospective cohort study for in vivo experimental model development. Implants were placed into the urinary bladder lumen in 8 goats over 2 evaluation periods. The alfalfa-based ration had a total ration Ca : P of 3.29 and 3.84 : 1, respectively. Urine was collected at 0, 28, 56, and 84 days in the 1st experiment; blood and urine at those timepoints in the 2nd experiment. For each evaluation period, the implants were removed 84 days after implantation and weighed. Accumulated calculi mass was calculated and compared between goats and was analyzed for composition.

RESULTS

Implant retention was 100% and 86% in the 2 studies. All goats with retained implants accumulated calcium carbonate at a mean implant gain per day across studies ranging from 0.44 to 57.45 mg. Two goats accumulated (0.44-7.65 mg/day and 33.64 & 57.45 mg/day) significantly more urolith material than the cohort across both studies (P = .047). No routine analytes on blood or urine were found to be explanatory for the difference observed.

CONCLUSIONS AND CLINICAL IMPORTANCE

These findings form a basis for implant and diet selection for use in future studies of urolithiasis development and for studies regarding individual susceptibility to urolithiasis.

Association between cystine urolithiasis and neuter status of dogs within the UK

OBJECTIVES

The objectives of the study were to examine the association between diagnosis of cystine urolithiasis and entire versus neutered status in male dogs and whether the strength of association varies among breeds.

MATERIALS AND METHODS

A previously reported canine urolithiasis database was used, documenting all urolith submissions to Hill's Pet Nutrition UK over a 10-year period. Uroliths were classified as cystine or non-cystine, and only male dogs with known neuter status were included in the analysis. Breeds of dog (and an additional crossbreed group), for which there was a minimum of 10 cystine urolith submissions, were analysed individually, with all other breeds combined together to form a reference group. Results were analysed using chi-squared and Fisher's exact tests. Logistic regression was used to assess associations between breed and neuter status and formation of cystine calculi.

RESULTS

In multiple breeds, dogs with cystine uroliths were significantly more likely to be entire than dogs forming other types of urolith. Being an entire male, regardless of breed, was associated with an increased risk of cystine urolithiasis (odds ratio=4·5; 95% confidence interval: 3·22 to 6·37; P<0·001).

CLINICAL SIGNIFICANCE

Increased odds of cystine formation in entire dogs supports further investigation of castration as a method to prevent cystine urolithiasis.

SLC3A1 and SLC7A9 mutations in autosomal recessive or dominant canine cystinuria: a new classification system

BACKGROUND

Cystinuria, one of the first recognized inborn errors of metabolism, has been reported in many dog breeds.

HYPOTHESIS/OBJECTIVES

To determine urinary cystine concentrations, inheritance, and mutations in the SLC3A1 and SLC7A9 genes associated with cystinuria in 3 breeds.

ANIMALS

Mixed and purebred Labrador Retrievers (n = 6), Australian Cattle Dogs (6), Miniature Pinschers (4), and 1 mixed breed dog with cystine urolithiasis, relatives and control dogs.

METHODS

Urinary cystinuria and aminoaciduria was assessed and exons of the SLC3A1 and SLC7A9 genes were sequenced from genomic DNA.

RESULTS

In each breed, male and female dogs, independent of neuter status, were found to form calculi. A frameshift mutation in SLC3A1 (c.350delG) resulting in a premature stop codon was identified in autosomal-recessive (AR) cystinuria in Labrador Retrievers and mixed breed dogs. A 6 bp deletion (c.1095_1100del) removing 2 threonines in SLC3A1 was found in autosomal-dominant (AD) cystinuria with a more severe phenotype in homozygous than in heterozygous Australian Cattle Dogs. A missense mutation in SLC7A9 (c.964G>A) was discovered in AD cystinuria in Miniature Pinschers with only heterozygous affected dogs observed to date. Breed-specific DNA tests were developed, but the prevalence of each mutation remains unknown.

CONCLUSIONS AND CLINICAL IMPORTANCE

These studies describe the first AD inheritance and the first putative SLC7A9 mutation to cause cystinuria in dogs and expand our understanding of this phenotypically and genetically heterogeneous disease, leading to a new classification system for canine cystinuria and better therapeutic management and genetic control in these breeds.

Stones in cats and dogs: What can be learnt from them?

Objective

To review the clinical features of stone disease in dogs and cats for a non-veterinary audience.

Methods

Relevant peer-reviewed scientific reports were reviewed.

Results

Lower urinary tract stones are more common in dogs and cats than they are in humans. In addition to struvite stones, calcium oxalate, urate and cystine stones are all commonly found in the bladder and the urethra. The genetic basis for stone disease in some breeds of dog has been elucidated. The small size of cats creates technical challenges when managing ureterolithiasis.

Conclusions

Naturally occurring stone disease in companion animals is a valuable area for further study. The structure of the canine genome might facilitate the identification of novel disease loci in breeds of dog predisposed to stone formation.

Metabonomics and population studies: age-related amino acids excretion and inferring networks through the study of urine samples in two Italian isolated populations

The study of two different Italian isolated populations was combined with a metabonomic approach to better understand tubular handling of amino acids. Levels of amino acids and metabolites have been analyzed by Nucleic Magnetic Resonance and expressed as ratio vs urinary creatinine concentration (mmol/mol). For most of the amino acids there is an age-related U shape pattern of excretion, with the peaks during childhood and old age, and a significant reduction in the adult age. Hierarchical cluster analysis has clearly identified three groups clustering the same amino acids: His, Thr and Ala (group one); Gly and Phe (group two) and a third larger one. Results have been further confirmed by factor and regression analysis, and used to confirm and, in some cases, infer new amino acids networks. As a matter of facts, the identification of strong evidences for clustering of urine excretion of several neutral amino acids suggests the predominant impact of relevant and common transporters.