Novel mutations of the ATP7B gene in Han Chinese families with pre-symptomatic Wilson's disease

Wilson's Disease with Acute Hepatic Onset: How to Diagnose and Treat It

Wilson's disease (WD) with acute onset poses a diagnostic challenge because it is clinically indistinguishable from other acute liver diseases. In addition, serum ceruloplasmin and urinary copper excretion, the first-line diagnostic tools for WD, can show false positive results in the case of acute liver failure, and the diagnostic role of genetic analysis is limited by the time required to perform it. In the case of fulminant onset, there is a clear indication of liver transplantation. "New Wilson Index" is frequently used to discriminate between patients who need liver transplantation versus those who can be successfully managed by medical treatment, but its reliability remains controversial. Timely referral of patients with acute liver failure due to WD may be a key factor in improving patient survival. Although liver transplant very often represents the only chance for such patients, maximum effort should be made to promote survival with a native liver. The management of these aspects of WD is still a matter of debate and will be the subject of this review.

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.

Genetic studies discover novel coding and non-coding mutations in patients with Wilson's disease in China

OBJECTIVES

Wilson disease (WD) is a rare autosomal recessive genetic disorder associated with various mutations in the ATP7B gene and leads to significant disability or death if untreated. Early diagnosis and proper therapy usually predict a good prognosis, especially in pre-symptomatic WD. Genetic testing provides an accurate and effective diagnostic method for the early diagnosis of WD.

METHODS

We recruited 18 clinically diagnosed WD patients from 16 unrelated families and two independent individuals. The next-generation sequencing of the ATP7B gene was performed. The 293T cell lines were divided into wild-type (WT) ATP7B and mutated ATP7B groups. Cell proliferation was determined by Cell Counting Kit-8 (CCK-8) assay and apoptosis was detected by Annexin V/propidium iodide (PI) assays.

RESULTS

Pedigree analysis showed that compound heterozygous variants (17/18, 94.44%) were present in the majority of WD patients. A total of 33 ATP7B gene variants were identified, including three variants with uncertain significance (VUS) [two splice mutations (c.51+2T>G, c.1543+40G>A) and one frameshift mutation (c.3532_3535del)]. The CCK-8 and apoptosis assays demonstrated that the VUS of ATP7B could significantly affect the transportation of copper.

CONCLUSIONS

The study revealed genetic defects of 16 Chinese families and two independent individuals with WD, which enriched the mutation spectrum of the ATP7B gene worldwide and provided valuable information for studying the mutation types of ATP7B in the Chinese populations. Genetic testing in WD patients is necessary to shorten the time to initiate therapy, reduce damage to the liver and improve the prognosis.

ATP7B variant penetrance explains differences between genetic and clinical prevalence estimates for Wilson disease

Wilson disease (WD) is a genetic disorder of copper metabolism caused by variants in the copper transporting P-type ATPase gene ATP7B. Estimates for WD population prevalence vary with 1 in 30,000 generally quoted. However, some genetic studies have reported much higher prevalence rates. The aim of this study was to estimate the population prevalence of WD and the pathogenicity/penetrance of WD variants by determining the frequency of ATP7B variants in a genomic sequence database. A catalogue of WD-associated ATP7B variants was constructed, and then, frequency information for these was extracted from the gnomAD data set. Pathogenicity of variants was assessed by (a) comparing gnomAD allele frequencies against the number of reports for variants in the WD literature and (b) using variant effect prediction algorithms. 231 WD-associated ATP7B variants were identified in the gnomAD data set, giving an initial estimated population prevalence of around 1 in 2400. After exclusion of WD-associated ATP7B variants with predicted low penetrance, the revised estimate showed a prevalence of around 1 in 20,000, with higher rates in the Asian and Ashkenazi Jewish populations. Reanalysis of other recent genetic studies using our penetrance criteria also predicted lower population prevalences for WD in the UK and France than had been reported. Our results suggest that differences in variant penetrance can explain the discrepancy between reported epidemiological and genetic prevalences of WD. They also highlight the challenge in defining penetrance when assigning causality to some ATP7B variants.

GENETIC DIAGNOSTICS AND CLINICAL FEATURES OF WILSON’S DISEASE IN CHILDREN

A disorder of copper metabolism at Wilson’s disease (WD), conditioned by a mutation of adenosine thriphospate P-type gene (ATP7B), results in irreversible changes in the liver and in the nervous system. Mortality is high at WD, but it is one of hereditary diseases, well subjected to the therapy. The disease is manifested in the early age, but its clinical course in children is symptomless that essentially complicates diagnostics. A single reliable method is genetic analysis for revealing mutations in ATP7B gene. The aim of the work was to analyze clinical manifestations and course of Wilson’s disease cases, genetically verified in children by detecting mutations of ATP7B gene. The research group included children of 6-17 years old with different injury degrees of the hepatobiliary system. According to results of the molecular-genetic analysis, the most spread allele variant of ATP7B gene (H1069Q) in Europe was confirmed in 10 patients of child age, including 4 cases of homozygosity. In 10 cases of the confirmed diagnosis of Wilson’s disease in child age in 100% (in all 10) of persons, a clinical manifestation was characterized by disorders from the hepatobiliary system, and only in 1 (10 %) – changes from the nervous system. At raising the level of transaminase in children, even at the normal bilirubin level and negative tests for viral hepatitis, it is recommended to carry out genetic testing for Wilson’s disease

Alanine Aminotransferase as the First Test Parameter for Wilson's Disease

Background and Aims: The liver is the first organ affected by toxic copper in the classical and severe hepatic forms of Wilson's disease (WD). Because their associated chronic liver damage is mostly asymptomatic, an intervention using a special test including serum alanine aminotransferase (ALT) activity is needed for detecting WD. Methods: Using the modified international criteria for the diagnosis of WD, 45 patients were selected from the collective databases of our institutions, and 7 infants were reviewed from the literature. Two patients had the severe hepatic form, with normoceruloplasminemia and no mutations in ATP7B. The rapid ALT change during hemolytic anemia was adjusted for a baseline. The diagnostic potential of the ALT test was assessed from the age-dependent natural course of the liver damage of WD. Results: The natural course had three stages. ALTs were still low in some infants younger than 4 years-old. They were high in all children between the ages of 4 and 8 years-old; then, they reduced to low levels in some patients over 9 years of age. The high ALT stage represents chronic active hepatitis, and the subsequent low ALT stage is due to silent cirrhosis. The hepatic copper content is a reliable but invasive test, while urinary copper secretion is an alternative, non-invasive test for copper toxicosis of WD. The serum ceruloplasmin and ATP7B analyses are subtype tests of WD. The response to anti-copper regimens is the final test result. Conclusions: ALT could be the first parameter to test to detect WD in children between the ages of 4 and 8 years.

Complex ATP7B mutation patterns in Wilson disease and evaluation of a yeast model for functional analysis of variants

Wilson disease (WD) is a rare autosomal recessive genetic disorder that is associated with various mutations in the ATP7B gene. Although ATP7B variants are frequently identified, the exact mutation patterns remain unknown because of the absence of pedigree studies, and the functional consequences of individual ATP7B variants remain to be clarified. In this study, we recruited 65 clinically diagnosed WD patients from 60 unrelated families. Pedigree analysis showed that besides several ATP7B homozygous variants (8/65, 12.3%), compound heterozygous variants (43/65, 66.2%) were present in the majority of WD patients. There were 20% of the patients had one (12/65, 18.5%) or multiple (1/65, 1.5%) variants in only a single allele, characterized by a high ratio of splicing or frameshift variants. Nine ATP7B variants were cloned into the pAG426GPD yeast expression vector to evaluate their functional consequences, and the results suggested different degrees of functional disruption from mild or uncertain to severe, consistent with the corresponding phenotypes. Our study revealed the complex ATP7B mutation patterns in WD patients and the applicability of a yeast model system to the evaluation of the functional consequences of ATP7B variants, which is essential for WD cases that are difficult to interpret.

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.

High genetic carrier frequency of Wilson's disease in France: discrepancies with clinical prevalence

Background

Wilson’s disease (WD) is a rare autosomal recessive metabolic disease caused by ATP7B gene mutations tat cause excessively high copper levels, particularly in the liver and brain. The WD phenotype varies in terms of its clinical presentation and intensity. Diagnosing this metabolic disorder is important as a lifelong treatment, based on the use of copper chelating agents or zinc salts, is more effective if it’s started early. Worldwide prevalence of WD is variable, with an average of 1/30,000. In France, a recent study based on French health insurance data estimated the clinical prevalence of the disease to be around 3/200,000.

Methods

To estimate the genetic prevalence of WD in France, we analysed the ATP7B gene by Next Generation Sequencing from a large French cohort of indiscriminate subjects.

Results

We observed a high heterozygous carrier frequency of ATP7B in France. Among the 697 subjects studied, 18 variants classified as pathogenic or probably pathogenic were found at heterozygous level in 22 subjects (22 alleles/1394 alleles), yielding a prevalence of 0.032 or 1/31 subjects.

Conclusions

This considerable and unexplained discrepancy between the heterozygous carrier frequency and the clinical prevalence of WD may be explained by the clinical variability, the incomplete penetrance and the existence of modifiers genes. It suggests that the molecular analysis of ATP7B should be interpreted with caution, always alongside copper assays (ceruloplasmin, relative exchangeable copper, 24 h-urinary copper excretion) with particular respect to exome sequencing.

Familial screening of children with Wilson disease: Necessity of screening in previous generation and screening methods

Wilson disease (WD) is an autosomal recessive genetic disorder associated with copper metabolism. Early diagnosis and therapy can result in good prognosis of WD. Thus, it is highly recommended to perform familial screening. In this study, we aimed to investigate the range of familial screening of children with WD and determine the appropriate screening methods.We enrolled 20 children with WD and 50 family members of each of these patients (40 parents and 10 siblings). All the subjects underwent a physical examination, Kayser-Fleischer (K-F) rings in the cornea, abdominal ultrasonography (Abdl Ur), cranial magnetic resonance imaging (MRI), serum ceruloplasmin, serum copper, 24-hour urine copper, blood alanine transaminase (ALT) and aspartate transaminase (AST), and ATP7B gene.Two new patients with presymptomatic WD (1 mother and 1 brother) in 2 families were found by screening. They had no clinical symptoms and K-F rings in corneal. Biochemical examination indicated decreased serum ceruloplasmin and serum copper in the mother and decreased serum ceruloplasmin in the brother. Gene sequencing revealed compound heterozygous mutations in them. In addition, 48 heterozygous carriers of Wilson disease (WHDzc) were found in this study. The levels of ceruloplasmin and serum copper in patients of WD were significantly less than WHDzc and 24-hour urinary copper were significantly higher than WHDzc (P = .000). The biochemical profiles of WD and WDHzc overlapped in range of 0.8 to 1.5 g/L in ceruloplasmin, above 9 μmol/L in serum copper and below 100 μg/24 h in urinary copper. Gene sequencing showed 2 pathological mutations in all patients with WD and 1 pathological mutation in all WDHzc.Not only siblings but also the previous generation of children probands with WD should be screened. Genetic testing should be conducted for the diagnosis of presymptomatic patients with WD.

Identification of two novel mutations in the ATP7B gene that cause Wilson's disease

BACKGROUND

Wilson's disease is an autosomal recessive disorder characterized by liver disease and/or neurologic deficits due to copper accumulation and is caused by pathogenic mutations in the ATP7B gene.

DATA SOURCES

Two unrelated Chinese patients born to nonconsanguineous parents who were diagnosed with earlyonset Wilson's disease. DNA sequencing and bioinformation analysis were conducted.

RESULTS

We have identified four mutations in two family trios, of which two were novel, namely, c. 3028A>G (p. K1010E) and c.3992T>G (p.Y1331X), in each patient.

CONCLUSIONS

Gene testing is playing an important role in diagnosis of Wilson's disease. The early-onset of Wilson's disease is apparently not associated with P-ATPase domain in the ATP7B protein. Our findings further widen the spectrum of mutations involving the ATP7B gene.