Analysis of most common mutations R778G, R778L, R778W, I1102T and H1069Q in Indian Wilson disease patients: correlation between genotype/phenotype/copper ATPase activity

Navigating the CRISPR/Cas Landscape for Enhanced Diagnosis and Treatment of Wilson's Disease

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system continues to evolve, thereby enabling more precise detection and repair of mutagenesis. The development of CRISPR/Cas-based diagnosis holds promise for high-throughput, cost-effective, and portable nucleic acid screening and genetic disease diagnosis. In addition, advancements in transportation strategies such as adeno-associated virus (AAV), lentiviral vectors, nanoparticles, and virus-like vectors (VLPs) offer synergistic insights for gene therapeutics in vivo. Wilson's disease (WD), a copper metabolism disorder, is primarily caused by mutations in the ATPase copper transporting beta (ATP7B) gene. The condition is associated with the accumulation of copper in the body, leading to irreversible damage to various organs, including the liver, nervous system, kidneys, and eyes. However, the heterogeneous nature and individualized presentation of physical and neurological symptoms in WD patients pose significant challenges to accurate diagnosis. Furthermore, patients must consume copper-chelating medication throughout their lifetime. Herein, we provide a detailed description of WD and review the application of novel CRISPR-based strategies for its diagnosis and treatment, along with the challenges that need to be overcome.

Monitoring of Copper in Wilson Disease

(1) Introduction: Wilson's disease (WND) is an autosomal recessive disorder of copper (Cu) metabolism. Many tools are available to diagnose and monitor the clinical course of WND. Laboratory tests to determine disorders of Cu metabolism are of significant diagnostic importance. (2) Methods: A systematic review of the literature in the PubMed, Science Direct, and Wiley Online Library databases was conducted. (Results): For many years, Cu metabolism in WND was assessed with serum ceruloplasmin (CP) concentration, radioactive Cu test, total serum Cu concentration, urinary copper excretion, and Cu content in the liver. The results of these studies are not always unambiguous and easy to interpret. New methods have been developed to calculate non-CP Cu (NCC) directly. New parameters, such as relative Cu exchange (REC), reflecting the ratio of CuEXC to total serum Cu, as well as relative Cu exchange (REC), reflecting the ratio of CuEXC to total serum Cu, have been shown to be an accurate tool for the diagnosis of WND. Recently, a direct and fast LC-ICP-MS method for the study of CuEXC was presented. A new method to assess Cu metabolism during treatment with ALXN1840 (bis-choline tetrathiomolybdate [TTM]) has been developed. The assay enables the bioanalysis of CP and different types of Cu, including CP-Cu, direct NCC (dNCC), and labile bound copper (LBC) in human plasma. Conclusions: A few diagnostic and monitoring tools are available for patients with WND. While many patients are diagnosed and adequately assessed with currently available methods, diagnosis and monitoring is a real challenge in a group of patients who are stuck with borderline results, ambiguous genetic findings, and unclear clinical phenotypes. Technological progress and the characterization of new diagnostic parameters, including those related to Cu metabolism, may provide confidence in the more accurate diagnosis of WND in the future.

Genomic Variations in ATP7B Gene in Indian Patients with Wilson Disease

OBJECTIVE

To report genotype data of the patients with Wilson disease (WD) hailing from across several parts of India to add to the available spectrum of causative variants in ATP7B gene (ATPase copper transporting beta polypeptide gene) and associated phenotypes in the Indian population.

METHODS

The entire ATP7B gene was sequenced in 58 patients with WD and additional testing was also done by MLPA to look for intragenic deletions duplications and exome sequencing to rule out genetic variations with similar phenotypic overlap.

RESULTS

Of all patients, 37 patients had a total of 33 distinct pathogenic variations, including 29 in the exonic regions and 4 at intronic splice sites. Of the variations identified, six were novel. The underlying genomic variations could be identified in nearly two-thirds of the patients by sequencing the entire gene.

CONCLUSIONS

This study reports the genotype-phenotype data to add to the available spectrum of causative variants in ATP7B gene. The inability to detect a pathogenic variation in some patients and the existence of phenotypic variations in individuals with the same variation suggest that additional factors or genes may play a role in causation of the disease. Further, a marked genetic heterogeneity was found in the study patients, indicating ethnic diversity of the Indian population.

Mutation analysis of the ATP7B gene and genotype-phenotype correlation in Chinese patients with Wilson disease

AIM

To discover the novel ATP7B mutations in 103 southern Chinese patients with Wilson disease (WD), and to determine the spectrum and frequency of mutations in the ATP7B gene and genotype-phenotype correlation in a large-scale sample of Chinese WD patients.

METHODS

One hundred three WD patients from 101 unrelated families in southern China were enrolled in this study. Genomic DNA was extracted from the peripheral blood. Direct sequencing of all 21 exons within ATP7B was performed. Subsequently, an extensive study of the overall spectrum and frequency of ATP7B mutations and genotype-phenotype correlation was performed in all Chinese patients eligible from the literature, combined with the current southern group.

RESULTS

In 103 patients with WD, we identified 48 different mutations (42 missense mutations, 4 nonsense mutations and 2 frameshifts). Of these, 3 mutations had not been previously reported: c.1510_1511insA, c.2233C>A (p.Leu745Met) and c.3824T>C (p.Leu1275Ser). The c.2333G>T (p.Arg778 Leu) at exon 8, was the most common mutation with an allelic frequency of 18.8%, followed by c.2975C>T (p.Pro992Leu) at exon 13, with an allelic frequency of 13.4%. In the comprehensive study, 233 distinct mutations were identified, including 154 missense mutations, 23 nonsense mutations and 56 frameshifts. Eighty-five variants were identified as novel mutations. The c.2333G>T (p.Arg778 Leu) and c.2975C>T (p.Pro992Leu) were the most common mutations, with allelic frequencies of 28.6% and 13.0%, respectively. Exons 8, 12, 13, 16 and 18 were recognised as hotspot exons. Phenotype-genotype correlation analysis suggested that c.2333G>T (p.Arg778 Leu) was significantly associated with lower levels of serum ceruloplasmin (P = 0.034). c.2975C>T (p.Pro992Leu) was correlated with earlier age of disease onset (P = 0.002). Additionally, we found that the c.3809A>G (p.Asn1270Ser) mutation significantly indicated younger onset age (P = 0.012), and the c.3884C>T (p.Ala1295Val) mutation at exon 18 was significantly associated with hepatic presentation (P = 0.048). Moreover, the patients with mixed presentation displayed the initial WD features at an older onset age than the groups with either liver disease or neurological presentation (P = 0.039, P = 0.015, respectively). No significant difference was observed in the presence of KF rings among the three groups with different clinical manifestations.

CONCLUSION

In this study, we identified three novel mutations in 103 WD patients from the southern part of China, which could enrich the previously established mutational spectrum of the ATP7B gene. Moreover, we tapped into a large-scale study of a Chinese WD cohort to characterise the overall phenotypic and genotypic spectra and assess the association between genotype and phenotype, which enhances the current knowledge about the population genetics of WD in China.

Difference in iron metabolism may partly explain sex-related variability in the manifestation of Wilson's disease

BACKGROUND/AIM

Wilson's disease (WD) is a hereditary disorder characterized by abnormal metabolism of copper. For unknown reasons, the clinical picture of this disease appears to be sex-dependent. Because the metabolism of copper and iron is interrelated, we aimed to evaluate whether the variability in the clinical picture of WD could be explained by the sex difference in iron metabolism.

METHODS

A total of 138 WD patients were examined in this study: 39 newly diagnosed, treatment naive patients and 99 individuals already treated with decoppering drugs. The serum concentration of ceruloplasmin (Cp) and copper were measured using an enzymatic colorimetric assay and by atomic absorption spectroscopy, respectively. The parameters of iron metabolism were determined by using standard laboratory methods and enzyme immunoassays.

RESULTS

In the treatment naive group men had a higher median serum concentration of ferritin (290.5 vs. 81.0 ng/mL, p < 10^-4), and hepcidin (Hepc) (55.4 vs. 22.8 ng/mL, p < 10^-3) compared to women, and tended to have higher concentration of iron, hemoglobin (HGB) and number of red blood cells (RBC). In the treated group men had higher median ferritin (122.0 vs. 46.0 ng/mL, p < 10^-4), Hepc (23.5 vs. 10.8 ng/mL, p < 10^-4), iron (102.5 vs. 68.0 μg/dL, p < 10^-4), HGB (15.0 vs. 13.2 g/dL, p < 10^-4), and RBC (5.0 vs. 4.5 M/L, p < 10^-4) than women.

CONCLUSION

Iron metabolism differs between men and women with WD, which may partly explain the sex difference noted in the disease manifestation.

Effect of homeostatic iron regulator protein gene mutation on Wilson's disease clinical manifestation: original data and literature review

OBJECTIVE

Wilson's disease (WD) is a hereditary disorder of copper metabolism. The metabolic pathways of copper and iron are interrelated. Our goal was to determine the frequency of the two most common mutations in the coding region of the human iron homeostatic protein gene (HFE) in Europe: C282Y (rs1800562) and H63D (rs1799945) in WD patients, as well as to analyze their relation with WD phenotypic traits.

MATERIAL AND METHODS

HFE mutations were studied by PCR RFLP method in 445 WD patients and 102 controls. All patients met the diagnostic criteria of WD 8^th International Conference on Wilson Disease and Menkes Disease.

RESULTS

HFE C282Y heterozygotes, both women and men, showed WD symptoms earlier than patients with wild-type HFE genotype. HFE 63HD heterozygous men presented symptoms later than HFE 63HH homozygotes, but HFE 63HD women manifested symptoms later than those with HFE 63HH genotype.

CONCLUSIONS

HFE genotype seems to be one of the factors modifying Wilson's disease phenotype.

Characterization of mutation spectrum and identification of novel mutations in ATP7B gene from a cohort of Wilson disease patients: Functional and therapeutic implications

Wilson disease (WD), a copper metabolism disorder, occurs due to the presence of mutations in the gene encoding ATP7B, a protein that primarily facilitates hepatic copper excretion. A better understanding of spectrum and functional significance of ATP7B variants is critical to formulating targeted and personalized therapies. Henceforth, we screened and sequenced 21 exons of ATP7B gene from 50 WD patients and 60 healthy subjects. We identified 28 variants comprising, seven novels in 20% alleles, while eight variations affecting 23% alleles were first time reported in Indian cohort. The c.813C>A, p.(Cys271*) (10%) was the most frequent mutation. Bioinformatics analysis revealed five of seven novel variants viz. c.1600C>A, p.(Pro534Thr); c.1616C>A, p.(Pro539His); c.1924G>T, p.(Asp642Tyr); c.2168G>C, p.(Arg723Thr); c.2174G>C, p.(Arg725Thr) resulted in protein misfolding. Sequence conservation analysis of ATP7B regions containing novel variants documented an evolutionarily conserved nature. Functional analysis of these novel variants in five different cell lines lacking inherent ATP7B expression demonstrated sensitivity to CuCl₂ -treatment, experiencing augmented cellular copper retention and decreased copper excretion as well as ceruloplasmin secretion to that of wildtype-ATP7B expressing cells. Interestingly, pharmacological chaperone 4-phenylbutyrate, a clinically approved compound, partially restored protein function of ATP7B mutants. These findings might enable novel treatment strategies in WD by clinically enhancing the protein expression of mutant ATP7B with residual copper export activity.

Abundance of active ingredients in sea-buckthorn oil

Vegetable oils are obtained by mechanical extraction or cold pressing of various parts of plants, most often: seeds, fruits, and drupels. Chemically, these oils are compounds of the ester-linked glycerol and higher fatty acids with long aliphatic chain hydrocarbons (min. C14:0). Vegetable oils have a variety of properties, depending on their percentage of saturation. This article describes sea-buckthorn oil, which is extracted from the well characterized fruit and seeds of sea buckthorn. The plant has a large number of active ingredients the properties of which are successfully used in the cosmetic industry and in medicine. Valuable substances contained in sea-buckthorn oil play an important role in the proper functioning of the human body and give skin a beautiful and healthy appearance. A balanced composition of fatty acids give the number of vitamins or their range in this oil and explains its frequent use in cosmetic products for the care of dry, flaky or rapidly aging skin. Moreover, its unique unsaturated fatty acids, such as palmitooleic acid (omega-7) and gamma-linolenic acid (omega-6), give sea-buckthorn oil skin regeneration and repair properties. Sea-buckthorn oil also improves blood circulation, facilitates oxygenation of the skin, removes excess toxins from the body and easily penetrates through the epidermis. Because inside the skin the gamma-linolenic acid is converted to prostaglandins, sea-buckthorn oil protects against infections, prevents allergies, eliminates inflammation and inhibits the aging process. With close to 200 properties, sea-buckthorn oil is a valuable addition to health and beauty products.

Geographic distribution of ATP7B mutations in Wilson disease

CONTEXT

Geographic distribution of ATP7B mutations in different populations.

OBJECTIVE

To summarise common mutations in the ATP7B gene and graphically illustrate their prevalence in different populations.

METHODS

A literature search was done using PubMed and the Wilson Disease Mutation Database (http://www.wilsondisease.med.ualberta.ca/database).

RESULTS

p.His1069Gln is the most prevalent mutation seen in Europe. In the Mediterranean countries, the array of prevalent mutations is different from the rest of Europe. In Far East Asian countries, the mutation p.Arg778Leu is the most common. In India, no single mutation seems to be dominant, owing to the vast ethnic diversity of the country. The p.Cys271* mutation is dominant in the east, west and south, but not reported in the north. In the Middle East, data from Saudi Arabia shows the p.Gln1399Arg mutation as the most prevalent. In the US, the p.His1069Gln is dominant, whereas in Brazil the mutation c.3402delC dominates.

CONCLUSION

Clinical features in WD patients can be misleading and often absent. Genetic testing is used to confirm the diagnosis. However, owing to the large gene size and vast diversity in the mutations, genetic testing can be time-consuming and tedious. This study reviews ATP7B mutations seen in different populations and can help develop time-saving methods and expediate the process of genetic analysis of WD.

Spectrum of mutations in the ATP binding domain of ATP7B gene of Wilson Disease in a regional Indian cohort

Wilson disease is an autosomal recessive disorder of abnormal copper accumulation in the liver, brain, kidney and cornea, resulting in hepatic and neurological abnormalities, which results from impaired ATP7B protein function due to mutations in candidate ATP7B gene, till date more than 500 disease causing mutations were found. In India most disease causing mutations were identified in ATP-BD. DNA samples of the 101 WD cases and 100 control population were analyzed for mutations. 11 mutations were identified in 57 chromosomes. Three novel mutations, c.3310T>A (p.Cys1104Ser), c.3337C>A (p.Leu1113Met) on exon 15 and c.3877G>A (p.Glu1293Lys) on exon 18 were identified for the first time in the ATP7B gene. Two mutations, c.3121C>T (p.Arg1041Trp) and c.3128T>C (p.Leu1043Pro) on exon 14 were discovered for the first time in Indian Wilson disease patients. Four previously reported mutations c.3008C>T, c.3029A>G on exon 13, c.3182G>A on exon 14 and c.3809A>G on exon 18 from South India were also found in this study. Our research has enriched the spectrum of mutations of the ATP7B gene in the south Indian population. The detection of new mutations in the ATP7B gene can aid in genetic counseling and clinical or/prenatal diagnosis.

Laser ablation inductively coupled plasma mass spectrometry imaging of metals in experimental and clinical Wilson's disease

Wilson's disease is an autosomal recessive disorder in which the liver does not properly release copper into bile, resulting in prominent copper accumulation in various tissues. Affected patients suffer from hepatic disorders and severe neurological defects. Experimental studies in mutant mice in which the copper-transporting ATPase gene (Atp7b) is disrupted revealed a drastic, time-dependent accumulation of hepatic copper that is accompanied by formation of regenerative nodes resembling cirrhosis. Therefore, these mice represent an excellent exploratory model for Wilson's disease. However, the precise time course in hepatic copper accumulation and its impact on other trace metals within the liver is yet poorly understood. We have recently established novel laser ablation inductively coupled plasma mass spectrometry protocols allowing quantitative metal imaging in human and murine liver tissue with high sensitivity, spatial resolution, specificity and quantification ability. By use of these techniques, we here aimed to comparatively analyse hepatic metal content in wild-type and Atp7b deficient mice during ageing. We demonstrate that the age-dependent accumulation of hepatic copper is strictly associated with a simultaneous increase in iron and zinc, while the intrahepatic concentration and distribution of other metals or metalloids is not affected. The same findings were obtained in well-defined human liver samples that were obtained from patients suffering from Wilson's disease. We conclude that in Wilson's disease the imbalances of hepatic copper during ageing are closely correlated with alterations in intrahepatic iron and zinc content.

Gene variants encoding proteins involved in antioxidant defense system and the clinical expression of Wilson disease

BACKGROUND & AIMS

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism resulting from pathogenic mutations of the ATP7B gene. The basis of phenotypic variability of the disease is not understood. The main mechanism of copper toxicity is probably related to generation of intracellular oxidative stress. To evaluate whether interindividual variability within genes encoding proteins involved in antioxidant defense system may modulate phenotypic expressions of WD.

METHODS

Variability within genes encoding the cytosolic enzymes: glutathione peroxidase (GPX1 rs1050450) and manganese superoxide dismutase (SOD2 rs4880), and peroxisomal enzyme: catalase (CAT rs1001179) were analysed in 435 patients. Individual genotypes were tested for their relationship with phenotypic features of WD.

RESULTS

GPX1 genotypes were not related to phenotypic manifestations of WD. Among males homozygocity for the SOD2 rs4880 T allele was related to earlier onset of WD. Patients homozygous for the CAT rs1001179 T allele characterized with later onset of WD [median (interquartile range) age: 29.0 (14.0) years vs. 22.0 (12.0) years, respectively, P < 0.004], later manifestation of hepatic symptoms [34.5 (14.0) years vs. 22.0 (12.0) years, P < 0.0009], and later presentation of neurological symptoms [37.0 (16.0) years vs. 28.0 (13.0) years, P < 0.03] than those having one or two C alleles.

CONCLUSION

Variability within the CAT gene may be an important modifier of the clinical course of WD. SOD2 genotype may influence WD phenotype among males. These observations indirectly confirm a role of oxidative stress in the pathogenesis of WD, as well as indirectly suggest that peroxisomes impairment may be involved in WD pathophysiology.

Wilson disease mutation pattern with genotype-phenotype correlations from Western India: confirmation of p.C271* as a common Indian mutation and identification of 14 novel mutations

Wilson disease (WD) is an autosomal recessive disorder resulting from mutations in the ATP7B gene, with over 600 mutations described. Identification of mutations has made genetic diagnosis of WD feasible in many countries. The heterogeneity of ATP7B mutants is, however, yet to be identified in the Indian population. We analyzed the mutational pattern of WD in a large region of Western India. We studied patients (n = 52) for ATP7B gene mutations in a cohort of families with WD and also in first-degree relatives (n = 126). All 21 exon-intron boundaries of the WD gene were amplified and directly sequenced. We identified 36 different disease-causing mutations (31 exonic and five intronic splice site variants). Fourteen novel mutations were identified. Exons 2, 8, 13, 14, and 18 accounted for the majority of mutations (86.4%). A previously recognized mutation, p.C271*, and the novel mutation p.E122fs, were the most common mutations with allelic frequencies of 20.2% and 10.6%, respectively. Frequent homozygous mutations (58.9%) and disease severity assessments allowed analysis of genotype-phenotype correlations. Our study significantly adds to the emerging data from other parts of India suggesting that p.C271* may be the most frequent mutation across India, and may harbor a moderate to severely disabling phenotype with limited variability.

Mutation analysis of ATP7B gene in Turkish Wilson disease patients: identification of five novel mutations

Wilson disease is an autosomal recessive disorder of copper metabolism caused by mutations in the ATP7B gene that encodes a P-type copper transporting ATPase. The aim of this study was to screen and detect mutations of the ATP7B gene in unrelated Turkish Wilson disease patients (n = 46) and control group (n = 52). Mutations were screened and detected by DNA sequencing. 30 out of 46 patients had mutations. 24 different Wilson disease related mutations were identified in those patients. The distribution of mutations in ATP7B gene was as follow: 17 missense, 3 nonsense, 1 silent, 3 frameshift (1 insertion, 2 deletion). None of them were not found in the control group. Five out of 24 mutations were found to be novel. Four of them were missense (c.2363C > T, c.3106G > A, c.3451C > T, c.3733C > A). The last one was deletion (c.3111delC). 10 single nucleotide polymorphisms (SNPs) given in the literature were found in both control and patients groups. Moreover one new polymorphism in exon 18 (c.3727G > A) not reported previously was discovered in both groups. It was striking that most of the mutations were found in exons 8, 12-14. This is the first study covering Turkish Wilson disease patients and control groups for mutation screening in all the coding regions of ATP7B gene by DNA sequencing method and adding five new mutations and one polymorphism into the HUGO Wilson disease mutation database.

Mutational analysis of ATP7B in north Chinese patients with Wilson disease

Wilson disease (WD) is an autosomal recessive inherited disease caused by abnormalities of the copper-transporting protein encoding gene ATP7B. In this study, we examined ATP7B for mutations in 114 individuals of Chinese Han population living in north China who were diagnosed as WD. Totally, we identified 36 mutations and 11 single-nucleotide polymorphisms (SNPs), of which 14 mutations have never been reported previously and 5 were firstly described in Chinese. Among these, p.R778L (21.5%), p.A874V (7.5%) and p.P992L (6.1%) were the most frequent mutations. A genotype of p.L770L+p.R778L+p.P992L was the most frequent triple mutations and two pairs of mutations, p.L770L/p.R778L and p.A874V/p.I929V, were closely related. In addition, a database was established to summarize all ATP7B mutations, including those reported previously and those identified in this study. Popular algorithms were used to predict the functional effects of these mutations, and finally, by comparative genomics approaches, we predicted a group of mutation hot spots for ATP7B. Our study will broaden our knowledge about ATP7B mutations in WD patients in north China, and be helpful for clinical genetic testing.

Genetic variability in the methylenetetrahydrofolate reductase gene (MTHFR) affects clinical expression of Wilson's disease

BACKGROUND & AIMS

Wilson's disease (WND) is an autosomal recessive disorder of copper (Cu) transport, resulting from pathogenic mutations in the ATP7B gene. The reason for the high variability in phenotypic expressions of WND is unknown. Hepatotoxic and neurotoxic effects of homocysteine (Hcy), as well as interrelationships between Hcy and Cu toxicity, were documented.

METHODS

We genotyped the two 5,10-methylenetetrahydrofolate reductase (one of the key folate/Hcy pathway enzymes) gene (MTHFR) polymorphisms: C677T and A1298C in 245 WND patients. Next, we tested the modulation of WND phenotypes by genotypes of MTHFR.

RESULTS

MTHFR C677T genotype distribution deviated from that expected from a population in Hardy-Weinberg equilibrium (C677T, χ(2) = 12.14, p = 0.0005). Patients with the MTHFR 1298C allele were younger at symptoms' onset than those without this allele (median (IQR) age, 24.9 (14.0) years vs. 28.5 (12.0) years, p = 0.006). Carriers of MTHFR "high activity" diplotype (double wild-type homozygotes 677CC/1298AA) manifested WND at older age, than non-carriers (median (IQR) age, 33.5 (9.0) years vs. 25.0 (13.0) years, p = 0.0009). Patients with the MTHFR 677T allele less frequently exhibited the neurological WND phenotype (31 (29.5%) vs. 36 (48.0%)), and more frequently presented with hepatic WND (44 (41.9%) vs. 22 (29.3%)), compared with subjects MTHFR 677T(-).

CONCLUSIONS

We postulate that MTHFR polymorphism contributes to the phenotypic variability of WND.

Wilson's disease

In the almost 100 years since Wilson's description of the illness that now bears his name, tremendous advances have been made in our understanding of this disorder. The genetic basis for Wilson's disease - mutation within the ATP7B gene - has been identified. The pathophysiologic basis for the damage resulting from the inability to excrete copper via the biliary system with its consequent gradual accumulation, first in the liver and ultimately in the brain and other organs and tissues, is now known. This has led to the development of effective diagnostic and treatment modalities that, although they may not eliminate the disorder, do provide the means for efficient diagnosis and effective amelioration if carried out in a dedicated and persistent fashion. Nevertheless, Wilson's disease remains both a diagnostic and treatment challenge for physician and patient. Its protean clinical manifestations make diagnosis difficult. Appropriate diagnostic evaluations to confirm the diagnosis and institute treatment can be confusing. In this chapter, the clinical manifestations, diagnostic evaluation, and treatment approaches for Wilson's disease are discussed.

Reduced expression of ATP7B affected by Wilson disease-causing mutations is rescued by pharmacological folding chaperones 4-phenylbutyrate and curcumin

Wilson disease (WD) is an autosomal recessive copper overload disorder of the liver and basal ganglia. WD is caused by mutations in the gene encoding ATP7B, a protein localized to the trans-Golgi network that primarily facilitates hepatic copper excretion. Current treatment comprises reduction of circulating copper by zinc supplementation or copper chelation. Despite treatment, a significant number of patients have neurological deterioration. The aim of this study was to investigate the possibility that defects arising from some WD mutations are ameliorated by drug treatment aimed at improvement of protein folding and restoration of protein function. This necessitated systematic characterization of the molecular consequences of distinct ATP7B missense mutations associated with WD. With the exception of p.S1363F, all mutations tested (p.G85V, p.R778L, p.H1069Q, p.C1104F, p.V1262F, p.G1343V, and p.S1363F) resulted in reduced ATP7B protein expression, whereas messenger RNA abundance was unaffected. Retention of mutant ATP7B in the endoplasmic reticulum, increased protein expression, and normalization of localization after culturing cells at 30 degrees C, and homology modeling suggested that these proteins were misfolded. Four distinct mutations exhibited residual copper export capacity, whereas other mutations resulted in complete disruption of copper export by ATP7B. Treatment with pharmacological chaperones 4-phenylbutyrate (4-PBA) and curcumin, a clinically approved compound, partially restored protein expression of most ATP7B mutants.

CONCLUSION

These findings might enable novel treatment strategies in WD by directly enhancing the protein expression of mutant ATP7B with residual copper export activity. 1795.).

Atp7b-/- mice as a model for studies of Wilson's disease

Wilson's disease is a severe human disorder of copper homoeostasis. The disease is associated with various mutations in the ATP7B gene that encodes a copper-transporting ATPase, and a massive accumulation of copper in the liver and several other tissues. The most frequent disease manifestations include a wide spectrum of liver pathologies as well as neurological and psychiatric abnormalities. A combination of copper chelators and zinc therapy has been used to prevent disease progression; however, accurate and timely diagnosis of the disease remains challenging. Similarly, side effects of treatments are common. To understand better the biochemical and cellular basis of Wilson's disease, several animal models have been developed. This review focuses on genetically engineered Atp7b(-/-) mice and describes the properties of these knockout animals, insights into the disease progression generated using Atp7b(-/-) mice, as well as advantages and limitations of Atp7b(-/-) mice as an experimental model for Wilson's disease.

Diagnosis of Wilson's disease: a comprehensive review

Wilson's disease is an autosomal recessive disorder of copper metabolism. The culprit gene is ATP7B. The worldwide prevalence is about 1 in 30,000, which may vary by population. Higher prevalence rates were reported using more sensitive screening techniques and pilot population screening. Typical presentations include neuropsychiatric and hepatic dysfunction, whereas atypical presentations are protean. Diagnosis relies on a high clinical suspicion, typical neurological symptoms, presence of Kayser-Fleischer rings, and reduced serum ceruloplasmin concentration. The conventional value of < 0.20 g/l is not a universal diagnostic value. Age of the subjects and analytical variations should be considered when interpreting these levels. Patients with inconclusive findings require further investigations such as 24 h urinary free-copper excretion, penicillamine challenge test, liver copper measurement, and detection of gene mutations. Direct molecular diagnosis remains the most decisive tool. Other tests such as non-ceruloplasmin-bound copper are unreliable. Potential pitfalls and limitations of these diagnostic markers are critically reviewed in this paper. The mainstays of therapy are trientine, penicillamine, and/or zinc. Liver transplantation is lifesaving for those with advanced disease. Ceruloplasmin oxidase activity and serum free-copper concentration should be monitored in patients on long-term de-coppering therapy to prevent iatrogenic copper deficiency.

Diagnostic accuracy of serum ceruloplasmin in Wilson disease: determination of sensitivity and specificity by ROC curve analysis among ATP7B-genotyped subjects

BACKGROUND

A serum ceruloplasmin concentration below 0.20 g/L is conventionally considered as one of the major diagnostic criteria for Wilson disease. This decision threshold has not been fully validated for its diagnostic characteristics, however. In this study, we evaluated various decision thresholds of serum ceruloplasmin concentration in the diagnosis of Wilson disease based on genotype-verified Wilson disease patients, carriers, and normal individuals.

METHODS

Serum ceruloplasmin concentration was measured by a nephelometric method in 57 Wilson disease patients and 71 family members (49 heterozygotes and 22 wild-type homozygotes), a validation group of 25 subjects clinically suspected of Wilson disease, and 690 normal individuals. We performed ROC analysis using Analyze-it software and confirmed the genotypes by direct DNA sequencing of ATP7B.

RESULTS

Serum ceruloplasmin concentrations <0.20, 0.14, and 0.10 g/L showed positive predictive values of 48.3%, 100%, and 100%, respectively, and negative predictive values of 98.7%, 97.1%, and 91.9%. In the validation group, a serum ceruloplasmin threshold of 0.14 g/L rendered 100% sensitivity and specificity. Forty of 690 healthy subjects had serum ceruloplasmin concentrations <0.20 g/L; however, these 40 individuals had normal genotypes by DNA sequencing, and none of the 40 had ceruloplasmin concentrations <0.14 g/L.

CONCLUSIONS

The diagnostic accuracy for Wilson disease using a serum ceruloplasmin concentration of 0.14 g/L as the local decision threshold was better than that using a threshold of 0.20 g/L. We suggest that laboratories providing ceruloplasmin assays determine decision thresholds based on local populations.

Molecular pathogenesis of Wilson disease among Indians: a perspective on mutation spectrum in ATP7B gene, prevalent defects, clinical heterogeneity and implication towards diagnosis

AIMS

We aim to identify the molecular defects in the ATP7B, the causal gene for Wilson disease (WD), in eastern Indian patients and attempt to assess the overall mutation spectrum in India for detection of mutant allele for diagnostic purposes.

METHODS

Patients from 109 unrelated families and their first-degree relatives comprising 400 individuals were enrolled in this study as part of an ongoing project. Genomic DNA was prepared from the peripheral blood of Indian WD patients. PCR was done to amplify the exons and flanking regions of the WD gene followed by sequencing, to identify the nucleotide variants.

RESULTS

In addition to previous reports, we recently identified eight mutations including three novel (c.3412 + 1G > A, c.1771 G > A, c.3091 A > G) variants, and identified patients with variable phenotype despite similar mutation background suggesting potential role of modifier locus.

CONCLUSIONS

So far we have identified 17 mutations in eastern India including five common mutations that account for 44% of patients. Comparative study on WD mutations between different regions of India suggests high genetic heterogeneity and the absence of a single or a limited number of common founder mutations. Genotype-phenotype correlation revealed that no particular phenotype could be assigned to a particular mutation and even same set of mutations in different patients showed different phenotypes.

Genotyping microarray as a novel approach for the detection of ATP7B gene mutations in patients with Wilson disease

Wilson disease (WD) is an autosomal recessive inherited disorder of copper metabolism that is caused by mutations in the ATP7B gene. To date, more than 300 mutations have been described in this gene. Molecular diagnostics of WD utilizes restriction enzyme digestion, multiplex ligation-dependent probe amplification or a direct sequencing of the whole gene. To simplify and speed up the screening of ATP7B mutations, we have developed a genotyping microarray for the simultaneous detection of 87 mutations and 17 polymorphisms in the ATP7B gene based on the arrayed primer extension reaction. The patient's DNA is amplified in four multiplex polymerase chain reactions, fragmented products are annealed to arrayed primers spotted on a chip, which enables DNA polymerase extension reactions with fluorescently labeled dideoxynucleotides. The Wilson microarray was validated by screening 97 previously genetically confirmed WD patients. In total, we detected 43 mutations and 15 polymorphisms that represent a majority of the common mutations occurring in the Czech and Slovak populations. All screened sequence variants were detected with 100% accuracy. The Wilson chip appears to be a rapid, sensitive and cost-effective tool, representing the prototype of a disease chip that facilitates and speeds up the screening of potential WD patients.