Bedlington Terriers Research Articles

Untangling the genetic traits underlying the development of copper toxicosis in Bedlington terriers.

Untangling the genetic traits underlying the development of copper toxicosis in Bedlington terriers.

Copper toxicosis in Bedlington terriers is associated with multiple independent genetic variants.

Bedlington terrier copper toxicosis (CT) is due to a homozygous exon deletion in COMMD1. CT also occurs in Bedlingtons lacking this deletion. An association with two ABCA12 single nuceotide polymorphism (SNP) splice variants was reported. Labrador retriever CT is associated with a missense mutation in ATP7B, and with a protective mutation in ATP7A. Liver and DNA samples from 24 affected and 10 unaffected Bedlingtons were assessed for copper and genetic variants. Allelic frequencies were compared. The ATP7B mutation frequency was investigated in 144 dogs of other breeds. The ABCA12 SNPs showed no differences between groups. The COMMD1 deletion was less frequent in unaffected than in affected dogs and in affected dogs post-2001 than pre-2001. The ATP7B mutation was more frequent in affected than unaffected Bedlingtons. Thirty-five of 144 dogs of other breeds were homo- or heterozygous for the ATP7B mutation. The ATP7A mutation was absent from Bedlingtons. Clinical information and qualitative copper measurements were unavailable for most dogs. The COMMD1 deletion remains present in Bedlington terriers but is no longer the primary cause of CT. ABCA12 SNPs were not associated with CT. The ATP7B:c.4358G>A mutation was significantly associated with Bedlington CT and was more common in dogs of this breed than in the 144 dogs of other breeds.

COMMD1 Exemplifies the Power of Inbred Dogs to Dissect Genetic Causes of Rare Copper-Related Disorders.

Simple SummaryResearch on rare diseases has specific problems, such as low or small patient groups, limited public awareness, and limited financial support. By definition, a rare disease affects not more than 50 per 100,000 individuals, but with over 6000 unique, rare diseases, more than 300 million people are affected worldwide. Especially, genetic screens are difficult to perform for rare diseases. Due to selective inbreeding in dogs, often these rare diseases present at high frequency in specific dog breeds. This paper in the special issue on “(epi) genetic disorders in companion animals” describes an example of how a novel gene was found that regulates copper accumulation in the liver in a specific dog breed, the Bedlington terriers, and describes an example of how gene products titrate each other’s function on the liver copper accumulation in Labrador retrievers. These two examples clearly show the power in dog genetics for both veterinary and human medicine. Although inbreeding is under great societal scrutiny due to its consequential large number of inherited diseases, dog genetics will directly positively influence animal welfare, in addition to basic knowledge of biochemical regulation systems, and lastly, it will be beneficial for people suffering from rare diseases.Wilson’s Disease is a rare autosomal recessive disorder in humans, often presenting with hepatic copper overload. Finding the genetic cause of a rare disease, especially if it is related to food constituents like the trace element copper, is a Herculean task. This review describes examples of how the unique population structure of in-bred dog strains led to the discovery of a novel gene and two modifier genes involved in inherited copper toxicosis. COMMD1, after the discovery in 2002, was shown to be a highly promiscuous protein involved in copper transport, protein trafficking/degradation, regulation of virus replication, and inflammation. Mutations in the ATP7A and ATP7B proteins in Labrador retrievers and Dobermann dogs resulted in a wide variation in hepatic copper levels in these breeds. To our knowledge, numerous dog breeds with inherited copper toxicosis of unknown genetic origin exist. Therefore, the possibility that men’s best friend will provide new leads in rare copper storage diseases seems realistic.

Copper-associated hepatitis in a young Dalmatian dog in Japan.

A male 25-month-old Dalmatian dog attended our veterinary hospital because of anorexia and high circulating liver enzyme activities. Abdominal computed tomography showed a slightly small liver with rounded edges, and laparoscopic examination showed that the liver was yellowish. Histopathological examination revealed multifocal necrosis of hepatocytes and severe chronic hepatitis. Rhodanine staining showed severe copper accumulation in hepatocytes and a quantitative analysis of the copper content of the liver showed substantial accumulation (10.3 mg/g dry mass), suggesting a diagnosis of copper-associated hepatitis. Previously reported canine mutation in the COMMD1, the gene responsible for the copper-associated hepatitis in the Bedlington terrier, was not identified. To our knowledge, this is the first report of copper-associated hepatitis in a Dalmatian in Japan.

Evaluation of COMMD1 in copper toxicosis in Labrador retrievers and Dobermans

Copper toxicosis is a major cause of hepatitis in dogs. We have shown that variants in ATP7A and ATP7B modulate hepatic copper levels in Labrador retrievers and Dobermans. However, these variants cannot fully explain the observed variation in hepatic copper levels in these dog breeds. Homozygous deletion of exon 2 of COMMD1 causes copper toxicosis in Bedlington terriers. We investigated the possible involvement of COMMD1 in the multifactorial aetiology of copper toxicosis in Labrador retrievers and Dobermans. Thirty dogs of each breed with known hepatic copper status were selected for DNA sequence analysis of the three exons and flanking intronic regions of COMMD1. The observed variants were tested for association with hepatic copper levels by linear model analysis. Several variants were observed in the DNA sequence of COMMD1 in both Labrador retrievers (nine variants) and Dobermans (11 variants) but none of these was associated with variations of hepatic copper concentrations. We conclude that COMMD1 did not play a major role in the aetiology of copper associated hepatitis in Labrador retrievers and Dobermans.

Reduced FXR Target Gene Expression in Copper-Laden Livers of COMMD1-Deficient Dogs.

Wilson’s disease (WD), an autosomal recessive disorder, results in copper accumulation in the liver as a consequence of mutations in the gene ATPase copper transporting beta (ATP7B). The disease is characterized by chronic hepatitis, eventually resulting in liver cirrhosis. Recent studies have shown that dysregulation of nuclear receptors (NR) by high hepatic copper levels is an important event in the pathogenesis of liver disease in WD. Intracellular trafficking of ATP7B is mediated by COMMD1 and, in Bedlington terriers, a mutation in the COMMD1 gene results in high hepatic copper levels. Here, we demonstrate a reduced Farnesoid X nuclear receptor (FXR)-activity in liver biopsies of COMMD1-deficient dogs with copper toxicosis, a unique large animal model of WD. FXR-induced target genes, small heterodimer partner (SHP), and apolipoprotein E (ApoE) were down-regulated in liver samples from COMMD1-deficient dogs with hepatic copper accumulation. In contrast, the relative mRNA levels of the two CYP-enzymes (reduced by FXR activity) was similar in both groups. These data are in line with the previously observed reduced FXR activity in livers of ATP7B−/− mice and WD patients. Therefore, these data further corroborate on the importance of the COMMD1-deficient dogs as a large animal model for WD.

Preclinical models of Wilson's disease, why dogs are catchy alternatives.

Copper toxicosis is frequently encountered in various dog breeds. A number of differences and similarities occur between Wilson disease and copper toxicosis in Bedlington terriers, caused by a mutation in the COMMD1 gene, and copper toxicosis in Labrador retrievers, caused by mutations in both ATP7A and ATP7B gene. First the specific population structure of dog breeds is explained with reference to its applicability for genetic investigations. The relatively large body size (variable from less than 1 kg to over 50 kg) and life-span (over 10 years) of dogs facilitates preclinical studies on safety on long-term effects of novel procedures. Then copper toxicosis in the two dog breeds is described in detail with an emphasis on the functions of the causative proteins. Some of the advantages of this species for preclinical studies are described with an example of liver stem cell transplantations in COMMD1 deficient dogs. Since the genetic background of copper toxicosis in other dogs' breeds has not yet been elucidated, it is conceivable that novel copper-related gene products or modifier genes will be discovered. About a century after the Novel prize was awarded to the research on dogs (Pavlov), dogs are in spotlight again as important preclinical model animals.

Supravalvular Pulmonic Stenosis with Pulmonary Hypertension in a Bedlington Terrier Dog

Supravalvular Pulmonic Stenosis with Pulmonary Hypertension in a Bedlington Terrier Dog

Prevalence and Clinical Relevance of Exon 2 Deletion of COMMD1 in Bedlington Terriers in Korea.

BackgroundDeletion of exon 2 of copper metabolism domain containing 1 (COMMD1) results in copper toxicosis in Bedlington terriers (CT‐BT).ObjectivesThis study was conducted to identify the prevalence and clinical relevance of the COMMD1 mutation in Bedlington terriers in Korea.AnimalsA total of 105 purebred Bedlington terriers (50 males, 55 females) from the kennels and pet dog clubs in Korea were examined during the period 2008–2013.MethodsA multiplex PCR was carried out to detect exon 2 deletion of COMMD1. Clinical analysis was performed on each genetic group, and clinical status of the dogs was followed up to estimate survival probability.ResultsOf the 105 samples, 52 (49%) were wild‐type homozygote, 47 (45%) were heterozygote, and 6 (6%) were mutant‐type homozygote. Plasma alanine aminotransferase (ALT) activity was increased in the mutant‐type homozygous group >2 years of age (P < .0001). The survival probability of 6 mutant‐type homozygotes surviving 2.5 years was 0.67, and 4 years was 0.5.Conclusions and Clinical ImportanceResults show the prevalence and clinical relevance of exon 2 deletion of COMMD1 and could help establish a structured selective breeding program to prevent CT‐BT in Korea.

The Roll of COMMD1 in Membrane Protein Trafficking

Copper is essential for all life due to its role as a catalyst in redox reactions. However, it must be tightly regulated as excess copper can cause oxidative damage to the cell. One example of copper dyshomeostasis is the autosomal recessive condition is known as Wilson disease which can result in liver disease and neurological problems. To maintain copper homeostasis, cells rely on a system of chaperone proteins as well as three copper transporters; CRT1, ATP7A, and ATP7B. ATP7B is a large multidomain membrane‐spanning protein that exports copper from the cytosol and is highly expressed in liver, brain, and kidney cells. ATP7B has a dual role in maintaining copper homeostasis. In the liver, ATP7B functions in the trans‐Golgi network where it pumps copper into the lumen for biosynthesis of secreted cuproproteins. When cellular copper levels are elevated, ATP7B traffics in vesicles towards the apical membrane to move excess copper into bile for excretion from the body. This proves to be a complex decision for the cell as it must retain some ATP7B at the trans‐Golgi for continued biosynthesis of cuproproteins while simultaneously removing the excess. When copper levels are low, ATP7B returns to the Golgi, though it is likely that some is degraded. Although maintaining proper copper homeostasis is important, the mechanism that influences ATP7B distribution is poorly understood. Since being identified as mutated in Bedlington Terriers exhibiting canine copper toxicosis, the protein COMMD1 has been of particular interest as a regulator of cellular copper levels. COMMD1 exhibits both Phosphatidylinositol (PdtIns) effector and Ubiquitin ligase adaptor activity. COMMD1 interacts with a number of membrane proteins including ATP7B. Importantly, COMMD1 downregulation affects cellular copper levels. To investigate the relationship between COMMD1 and ATP7B we used quantitative immunofluorescence microscopy in HepG2 hepatoma cells to analyze the subcellular locations of ATP7B in response to misexpression of COMMD1. The overexpression of the COMMD1 T174M mutant, which was first identified in an atypical Wilson disease patient, significantly decreased the Golgi‐associated fraction of ATP7B and colocalization between ATP7B and lysosomes was also reduced during retrograde trafficking. The T174M mutation may affect PtdIns(4,5)P2 binding by COMMD1, thus we believe that PtdIns(4,5)P2 recruits and facilitates a functional interaction between COMMD1 and ATP7B.Support or Funding InformationNational Science Foundation (MCB‐1411890), NIH 8P20GM103395‐12 (JLB Sub‐Project)

Copper toxicosis in non-COMMD1 Bedlington terriers is associated with metal transport gene ABCA12

Wilson’s disease, caused by a mutation in the ATP-ase 7B gene, is the only genetically characterised human disease with inhibition of biliary copper excretion and toxic copper accumulation in liver and occasionally brain. A similar copper toxicosis occurs in Bedlington terriers (CT) with liver damage only. Although CT has been associated with a defect in the COMMD1 gene (COMMD1 del/del), Bedlington terriers with CT and lacking this mutation are also recognised (non-COMMD1 del/del).A study was designed to identify any other gene polymorphisms associated with copper toxicity in Bedlington terriers employing genome wide association studies (GWAS) followed by deep sequencing of the candidate region. Blood for DNA analysis and liver for confirmation of the diagnosis was obtained from 30 non-COMMD1 del/del Bedlington terriers comprising equal numbers of CT-affected dogs and controls. DNA was initially subjected to GWAS screening and then further sequencing to target the putative mutant gene.The study has identified a significant disease association with a region on chromosome 37 containing identified SNP’s which are highly significantly associated with non-COMMD1 del/del Bedlington terrier CT. This region contains the ABCA12 gene which bears a close functional relationship to ATP-ase 7B responsible for Wilson’s disease in man.

Inherited disease in boxer dogs: a cautionary tale for molecular geneticists

IN a study summarised on p 492 of this issue of Veterinary Record , Bruce Cattanach and collaborators from four institutions remind us of the importance of old-fashioned pedigree analysis...

The Exon 2 Deletion of the COMMD1 Causing Copper Toxicosis in Bedlington Terriers in Korea

This study was performed to survey prevalence of Copper metabolism domain containing 1 (COMMD1) mutation using molecular diagnostic method in a population of Bedlington terriers in Korea. COMMD1 gene (formerly MURR1) functions as a regulator of sodium transport and copper metabolism. The deletion of exon 2 of the COMMD1 gene causes copper toxicosis in Bedlington terriers. Bedlington terriers with this autosomal recessive disorder were shown to have the elevated liver copper levels due to genetic derangement in the biliary copper excretion pathway. DNA samples were extracted from whole blood collected from 257 Bedlington terriers (109 males, 148 females) of pet dog clubs in Korea. A multiplex PCR was carried out to detect of exon 2 deletion of COMMD1 gene. In this study, it was possible to know the existence and prevalence of exon 2 deletion of COMMD1 in Bedlington terriers in Korea. Of the 257 samples, 131 (51%) were wild type homozygous for the normal COMMD1 gene, 108 (42%) were heterozygous, having both normal and mutated copy of the COMMD1 gene. The eighteen (7%) were mutant type homozygous. The results of genetic analysis could help establish proper management strategy and selective breeding program to prevent COMMD1 mutation in Bedlington terriers in Korea.

New canine models of copper toxicosis: diagnosis, treatment, and genetics.

The One Health principle recognizes that human health, animal health, and environmental health are inextricably linked. An excellent example is the study of naturally occurring copper toxicosis in dogs to help understand human disorders of copper metabolism. Besides the Bedlington terrier, where copper toxicosis is caused by a mutation in the COMMD1 gene, more complex hereditary forms of copper-associated hepatitis were recognized recently in other dog breeds. The Labrador retriever is one such breed, where an interplay between genetic susceptibility and exposure to copper lead to clinical copper toxicosis. Purebred dog populations are ideal for gene mapping studies, and because genes involved in copper metabolism are highly conserved across species, newly identified gene mutations in the dog may help unravel the genetic complexity of different human forms of copper toxicosis. Furthermore, increasing knowledge with respect to diagnosis and treatment strategies will benefit both species.

Bedlington terrier의 다발성 안기형 1례

Bedlington terrier의 다발성 안기형 1례

D-penicillamine treatment of copper-associated hepatitis in Labrador retrievers

d-penicillamine is effectively used in the lifelong treatment of copper toxicosis in Bedlington terriers and Wilson’s disease in humans. A complex form of copper-associated hepatitis has recently been characterized in the Labrador retriever. The aims of this study were to evaluate the effectiveness of d-penicillamine treatment for copper-associated hepatitis in this breed, to study the effects on hepatic copper, iron and zinc concentrations, and to evaluate parameters to predict optimal duration of treatment. Forty-three client owned Labrador retrievers that were diagnosed with increased hepatic copper were treated with d-penicillamine and underwent at least one follow-up examination including a liver biopsy for histopathological scoring of inflammatory lesions. Hepatic copper, iron and zinc concentrations were determined in the initial and follow-up biopsies by instrumental neutron activation analysis. The influence of initial hepatic copper concentration, sex, age, d-penicillamine formulation and the occurrence of side effects were investigated for their influence on hepatic copper concentration after a certain period of treatment by generalized mixed modelling.d-penicillamine proved to be effective in reducing hepatic copper concentration and associated inflammatory lesions. Parameters derived from the model can be used to estimate the necessary duration of d-penicillamine treatment for Labrador retrievers with increased hepatic copper concentration. Continuous, lifelong d-penicillamine treatment is not recommended in this breed, as there may be a risk for hepatic copper and zinc deficiency.

Liver-Specific Commd1 Knockout Mice Are Susceptible to Hepatic Copper Accumulation

Canine copper toxicosis is an autosomal recessive disorder characterized by hepatic copper accumulation resulting in liver fibrosis and eventually cirrhosis. We have identified COMMD1 as the gene underlying copper toxicosis in Bedlington terriers. Although recent studies suggest that COMMD1 regulates hepatic copper export via an interaction with the Wilson disease protein ATP7B, its importance in hepatic copper homeostasis is ill-defined. In this study, we aimed to assess the effect of Commd1 deficiency on hepatic copper metabolism in mice. Liver-specific Commd1 knockout mice (Commd1 Δhep) were generated and fed either a standard or a copper-enriched diet. Copper homeostasis and liver function were determined in Commd1 Δhep mice by biochemical and histological analyses, and compared to wild-type littermates. Commd1 Δhep mice were viable and did not develop an overt phenotype. At six weeks, the liver copper contents was increased up to a 3-fold upon Commd1 deficiency, but declined with age to concentrations similar to those seen in controls. Interestingly, Commd1 Δhep mice fed a copper-enriched diet progressively accumulated copper in the liver up to a 20-fold increase compared to controls. These copper levels did not result in significant induction of the copper-responsive genes metallothionein I and II, neither was there evidence of biochemical liver injury nor overt liver pathology. The biosynthesis of ceruloplasmin was clearly augmented with age in Commd1 Δhep mice. Although COMMD1 expression is associated with changes in ATP7B protein stability, no clear correlation between Atp7b levels and copper accumulation in Commd1 Δhep mice could be detected. Despite the absence of hepatocellular toxicity in Commd1 Δhep mice, the changes in liver copper displayed several parallels with copper toxicosis in Bedlington terriers. Thus, these results provide the first genetic evidence for COMMD1 to play an essential role in hepatic copper homeostasis and present a valuable mouse model for further understanding of the molecular mechanisms underlying hepatic copper homeostasis.

Canine models of copper toxicosis for understanding mammalian copper metabolism.

Hereditary forms of copper toxicosis exist in man and dogs. In man, Wilson’s disease is the best studied disorder of copper overload, resulting from mutations in the gene coding for the copper transporter ATP7B. Forms of copper toxicosis for which no causal gene is known yet are recognized as well, often in young children. Although advances have been made in unraveling the genetic background of disorders of copper metabolism in man, many questions regarding disease mechanisms and copper homeostasis remain unanswered. Genetic studies in the Bedlington terrier, a dog breed affected with copper toxicosis, identified COMMD1, a gene that was previously unknown to be involved in copper metabolism. Besides the Bedlington terrier, a number of other dog breeds suffer from hereditary copper toxicosis and show similar phenotypes to humans with copper storage disorders. Unlike the heterogeneity of most human populations, the genetic structure within a purebred dog population is homogeneous, which is advantageous for unraveling the molecular genetics of complex diseases. This article reviews the work that has been done on the Bedlington terrier, summarizes what was learned from studies into COMMD1 function, describes hereditary copper toxicosis phenotypes in other dog breeds, and discusses the opportunities for genome-wide association studies on copper toxicosis in the dog to contribute to the understanding of mammalian copper metabolism and copper metabolism disorders in man.

The puzzle posed by COMMD1, a newly discovered protein binding Cu(ii)

Copper is critically important for cellular metabolism. It plays essential roles in developmental processes, including angiogenesis. The liver is central to mammalian copper homeostasis: biliary excretion is the major route of excretion for ingested copper and serves to regulate the total amount of copper in the organism. An extensive network of proteins manipulates copper disposition in hepatocytes, but comparatively little is known about this protein system. Copper exists in two oxidation states: most extracellular copper is Cu(II) and most, if not all, intracellular copper is Cu(I). Typical intracellular copper-binding proteins, such as the Cu-transporting P-type ATPases ATP7B (Wilson ATPase) and ATP7A (Menkes ATPase), bind copper as Cu(I). Accordingly, the recent discovery that the ubiquitous protein COMMD1 binds Cu(II) exclusively raises the question as to what role Cu(II) may play in intracellular processes. This issue is particularly important in the liver and brain. In humans, Wilson’s disease, due to mutations in ATP7B, exhibits progressive liver damage from copper accumulation; in some Bedlington terriers, mutations in COMMD1 are associated with chronic copper-overloaded liver disease, clinically distinct from Wilson’s disease. It seems unlikely that Cu(II), which generates reactive oxygen species through the Fenton reaction, has a physiological role intracellularly; however, Cu(II) might be the preferred state of copper for elimination from the cell, such as by biliary excretion. We argue that COMMD1 participates in the normal disposition of copper within the hepatocyte and we speculate about that role. COMMD1 may contribute to the mechanism of biliary excretion of copper by virtue of binding Cu(II). Additionally, or alternatively, COMMD1 may be an important component of an intracellular system for utilizing Cu(II), or for detecting and detoxifying it.

Molecular pathology of Wilson’s disease: A brief

Department of Cell Biology and Immunology, Centro de Biologia Molecular Severo Ochoa and Centro de Enfermedades Hepaticas y Digestivas (CIBEREHD), Universidad Autonoma de Madrid, 28049 Madrid, Spain; INSERM Unite 757, Orsay F-91400, France; Universite Paris-Sud, UMR-S 757, Orsay F-91405, France; AP-HP Hopital Paul Brousse, Centre Hepato-Biliaire, Villejuif F-94800, France; Universite Paris-Sud, UMR-S 785, Villejuif F-94800, France; Inserm, Unite 785, Villejuif F-94800, France; Centre de Reference de la maladie de Wilson Centre Hepato-Biliaire Hopital Paul Brousse, Villejuif, France