Canine Copper Toxicosis Research Articles

The canine copper toxicosis locus is not syntenic with ATP7B or ATX1 and maps to a region showing homology to human 2p21.

The canine copper toxicosis locus is not syntenic with ATP7B or ATX1 and maps to a region showing homology to human 2p21.

Wilson disease and canine copper toxicosis

In this article we review the current clinical and research status of Wilson disease and canine copper toxicosis. One of the main clinical challenges in Wilson disease is for clinicians to recognize the possibility of Wilson disease when young patients present with liver disease, psychiatric disease, or a movement-disorder type of neurologic disease. Once the possibility of the disease is recognized, many copper-related tests are available that are quite accurate in making the diagnosis or ruling it out. It is important to remember that this is an inherited disease and that family members at risk should be screened, particularly siblings. The cloning of the Wilson disease gene opened up the possibility that a direct DNA test could be developed, allowing convenient screening of certain patients and family members. However, the large number of mutations already found, with no small set of mutations dominating the picture, have thwarted this approach. Once the diagnosis has been made, a variety of treatments are available. For maintenance therapy, therapy of presymptomatic patients, and therapy of pregnant patients, we use zinc. For initial therapy of patients with liver disease, we use a combination of zinc and trientine. For initial therapy of patients with neurologic disease we use tetrathiomolybdate. Canine copper toxicosis in Bedlington terriers is due to a gene different from the gene for Wilson disease. However, the disease is treatable with the same array of anticopper therapies that work in humans. Recently, we established linkage of the copper toxicosis gene to a microsatellite marker, which has made available a linkage test to breeders of Bedlington terriers.

Linkage of a microsatellite marker to the canine copper toxicosis locus in Bedlington Terriers

Abstract Objective To identify a DNA marker for the copper toxicosis (CT) locus in Bedlington Terriers (BT). Animals 77 BT, of which 25 were affected. Diagnosis of affected or unaffected with CT was made in all cases by quantitative copper determinations on liver biopsy samples by use of established criteria. Procedure BT pedigrees segregating for CT were identified. Linkage studies were carried out using polymorphic microsatellite markers developed for the canine genome in these pedigrees. DNA was isolated from blood samples of pedigree members. Polymerase chain reaction was used to amplify and type alleles at 213 microsatellite loci in each dog, and findings were subjected to linkage analysis. Results One microsatellite marker was identified to be closely linked to CT with logarithm of odds score of 5.96 at a recombination fraction of zero. Conclusions Using the linked marker, it has become possible to distinguish affected, homozygous normal, and carrier dogs in some BT pedigrees. Clinical Relevance In informative pedigrees where the marker is variable in the parents, it is possible to identify which dogs will require anticopper therapy and provide breeders with sound scientific advice about breeding strategies. (Am J Vet Res 1997;58:23–27)

Linkage Studies of the Esterase D and Retinoblastoma Genes to Canine Copper Toxicosis: A Model for Wilson Disease

Canine copper toxicosis, an autosomal recessive disorder, is prevalent among certain dog breeds. It results in liver disease from copper accumulation and toxicity similar to the human autosomal recessive disorder, Wilson disease. The Wilson disease locus has been mapped to 13q and is closely linked to the esterase D and retinoblastoma genes. We developed informative polymorphic systems in the dog using the human cDNA clones of the esterase D and retinoblastoma loci as probes. We investigated the linkage relationship of these two loci to the copper toxicosis locus, and to each other in the dog. Our results indicate that none of the loci are closely linked in the dog. Linkage of copper toxicosis to the retinoblastoma locus can be excluded up to 13% recombination, and to esterase D up to 5% recombination. Furthermore, esterase D and retinoblastoma, tightly linked in the mouse and human genomes, are not found to be closely linked in the canine genome.

Use of 64copper measurements to diagnose canine copper toxicosis.

Inherited canine copper toxicosis is a serious problem in Bedlington terriers and West Highland White terriers, and may also be a problem in other less-studied breeds. Affected dogs become ill at midlife with progressive and ultimately fatal liver disease. Treatments for removal of copper and prevention of copper accumulation are available, but are most effective if begun before the dog becomes ill. Until recently diagnosis has not been available until the dog is 1 year of age, and then only by an invasive liver biopsy with determination of liver copper concentration. The authors studied the use of 64copper for early diagnosis of canine copper toxicosis. Two procedures were evaluated. The first involved measuring the concentration of 64copper in blood 24 hours after oral administration of the radioisotope. At this time, 64copper was associated primarily with ceruloplasmin secreted into the blood by the liver. This procedure is useful in the diagnosis of the human counterpart, Wilson's disease. However, the authors found it to be nondiscriminatory between affected and unaffected dogs. In contrast, the second procedure, which involved measuring 64copper excreted in stool during 48 hours after an intravenous dose of radioisotope, yielded results that differentiated most affected and unaffected dogs.

Variations in the intralobular distribution of copper in the livers of copper-loaded rats in relation to the pathogenesis of copper storage diseases

There are differences in the hepatic intralobular distribution of copper in copper storage related diseases which may be of pathogenetic significance. Male rats fed a high copper diet (1500 ppm) for 16 weeks were killed at intervals in an attempt to compare copper distribution in their livers with those in human, canine and ovine copper toxicosis. Copper was found to accumulate almost exclusively in the periportal and mid-zones of the rat liver lobules and was associated with progressive pathological changes which included focal and periportal degeneration and necrosis. This pattern of copper distribution contrasts markedly with the centrilobular retention reported in familial canine copper toxicosis and chronic copper poisoning in sheep which suggests that, in these conditions, a secretory deficiency may be less important than a metabolic zonal defect of intracellular copper metabolism. The pathological changes observed in copper-loaded rats have a different micro-anatomical localization from those in dogs and sheep, but show similarities to the early changes reported in the latter species and indicate the possibility of a similar cellular lesion.