Carrier frequency of the R778L, A874V, and N1270S mutations in the ATP7B gene in a Korean population

Investigating common mutations in ATP7B gene and the prevalence of Wilson's disease in the Thai population using population-based genome-wide datasets

Wilson's disease (WD) is a rare metabolic disorder caused by variations in the ATP7B gene. It usually manifests hepatic, neurologic, and psychiatric symptoms due to excessive copper accumulation. The prevalence of WD and its common variants differ across populations. This study aimed to examine these aspects of WD within the Thai population, where information has been limited. We reviewed ClinVar and the Wilson Disease Mutation Database, organizing variants classified as pathogenic or likely pathogenic in one or both databases as "relaxed" and "strict" lists. Allele frequencies were estimated from genotyping array data (Asian Screening Array: ASA; Illumina Corp, CA) of 6291 Thai subjects, which also underwent genotype imputation. The prevalence of WD in the Thai population was estimated assuming Hardy-Weinberg Equilibrium. The strict list yielded a prevalence of 1/24,128 (carrier frequency=1/78), while the relaxed list yielded a prevalence of 1/9971 (carrier frequency=1/50). The most common WD variants in Thai subjects were c.2333 G > T, c.3443 T > C, and c.813 C > A from the strict list, and c.3316 G > A and c.2605 G > A from the relaxed list. The ASA chip covered approximately 59 and 24% of WD variants from the strict and relaxed lists, respectively. Based on the estimated prevalence, a carrier screening program for WD is not currently required in Thailand. However, as genotyping services become more affordable and accessible, such a program would facilitate early identification, treatment, and prevention of WD.

Prevalence, Incidence, and Treatment Pattern of Wilson's Disease Using National Health Insurance Data From 2010-2020, Korea

BACKGROUND

Wilson's disease (WD) is an autosomal recessive disorder in which copper (Cu) accumulates in organs, particularly in the liver and central nervous system. This study aimed to investigate the prevalence, incidence, and treatment patterns of WD patients in Korea.

METHODS

National Health Insurance System (NHIS) claims data from 2010 to 2020 were analyzed. patients with WD as a primary or additional diagnosis at least once were identified using the International Classification of Diseases (ICD)-10 disease code E83.0 and a record for a registration program for rare intractable diseases in Korea.

RESULTS

The average age- and sex-adjusted prevalence and incidence of WD between 2010 and 2020 were 3.06/100,000 and 0.11/100,000, respectively. The mean age of the patients with newly diagnosed WD was 21.0 ± 15.9 years. Among the 622 WD incident cases during the study period, 19.3% of the patients had liver cirrhosis and 9.2% had received liver transplantation. Psychological and neurological diseases were present in 40.7% and 48.1% of the patients, respectively. Regarding the diagnosis of WD, liver biopsy was performed in only 51.6% of new cases. D-penicillamine, trientine, or zinc were prescribed in 81.5% of the incident cases, and the treatment uptake rates decreased with increasing age.

CONCLUSION

The prevalence of WD in Korea is 3.06/100,000 and approximately 1,800 patients use medical services annually. A significant proportion of patients are diagnosed at the cirrhotic stage and not treated with Cu-chelating therapeutics, suggesting the need for early diagnosis and adequate treatment to improve prognosis.

Actionable secondary findings in the 73 ACMG-recommended genes in 1559 Thai exomes

High-throughput DNA sequencing provides not only primary diagnosis but also makes available other genetic variants with potential health implications. the American College of Medical Genetics and Genomics (ACMG) has recommended a list of medically actionable genes since 2013 and very recently released an updated ACMG SF v3.0 list comprising 73 genes. Here, we analyzed exome data of 1559 unrelated Thai individuals to determine the frequency and spectrum of pathogenic (P) or likely pathogenic (LP) variants in the 73 genes. Based on the ACMG guidelines for the interpretation of sequence variants, 68 different P/LP variants in 26 genes associated with 18 diseases inherited in an autosomal-dominant manner of 186 individuals (11.9%; 186/1559) were identified. Of these, 22 P/LP variants in 15 genes associated with 13 diseases of 85 individuals (5.5%; 85/1559) were also reported as P/LP in the ClinVar archive. The majority harbored variants in genes related to cardiovascular diseases (4.7%; 74/1559), followed by cancer phenotypes (0.5%; 8/1559). None of the individuals in our cohort harbored biallelic variants in genes responsible for diseases inherited in an autosomal recessive manner. The results would serve as a basis for precision medicine practice at individual and population levels.

Management Perspective of Wilson's Disease: Early Diagnosis and Individualized Therapy

Wilson's disease (WD) is an inherited disease caused by mutations in ATP7B and is characterized by the pathological accumulation of copper in the liver and brain. Common clinical manifestations of WD include a wide range of liver disease and neurological symptoms. In some patients, psychiatric symptoms may be the only manifestation at the time of diagnosis. The clinical features of WD are highly variable and can mimic any disease of internal medicine. Therefore, for unexplained medical diseases, the possibility of WD should not be ignored. Early diagnosis and treatment can improve the prognosis of WD patients and reduce disability and early death. Gene sequencing is becoming a valuable method to diagnose WD, and if possible, all WD patients and their siblings should be genetically sequenced. Copper chelators including D-penicillamine, trientine, and dimercaptosuccinic acid can significantly improve the liver injury and symptoms of WD patients but may have a limited effect on neurological symptoms. Zinc salts may be more appropriate for the treatment of asymptomatic patients or for the maintenance treatment of symptomatic patients. High-quality clinical trials for the drug treatment of WD are still lacking, therefore, individualized treatment options for patients are recommended. Individualized treatment can be determined based on the clinical features of the WD patients, efficacy and adverse effects of the drugs, and the experience of the physician. Liver transplantation is the only effective method to save patients with acute liver failure or with severe liver disease who fail drug treatment.

Frequency and spectrum of actionable pathogenic secondary findings in Taiwanese exomes

Background

Exome sequencing has recently become more readily available, and more information about incidental findings has been disclosed. However, data from East Asia are scarce. We studied the application of exome sequencing to the identification of pathogenic/likely pathogenic variants in the ACMG 59 gene list and the frequency of these variants in the Taiwanese population.

Methods

This study screened 161 Taiwanese exomes for variants from the ACMG 59 gene list. The identified variants were reviewed based on information from different databases and the available literature and classified according to the ACMG standard guidelines.

Results

We identified seven pathogenic/likely pathogenic variants in eight individuals, with five participants with autosomal recessive variants in one allele and three participants with autosomal dominant variants. Approximately 1.86% (3/161) of the Taiwanese individuals had a reportable pathogenic/likely pathogenic variant as determined by whole‐exome sequencing (WES), which was comparable to the proportions published previously in other countries. We further investigated the high carrier rate of rare variants in the ATP7B gene, which might indicate a founder effect in our population.

Conclusion

This study was the first to provide Taiwanese population data of incidental findings and emphasized a high carrier rate of candidate pathogenic/likely pathogenic variants in the ATP7B gene.

The Prevalence of Wilson's Disease: An Update

BACKGROUND AND AIMS

In 1984, Scheinberg and Sternlieb estimated the prevalence of Wilson's disease to be 1:30,000 based on the limited available data. This suggested a large number of overlooked cases with potentially fatal consequences. The "Scheinberg-Sternlieb Estimate" is still widely used, although more recent clinical and genetic studies of higher quality are now available. In the present study, we included these data to update the prevalence estimate.

APPROACH AND RESULTS

A MEDLINE Ovid, Science Citation Index Expanded, and PubMed systematic search for all relevant studies on the prevalence of Wilson's disease was conducted. In total, 59 studies (50 clinical and 9 population-based genetic) were included in the final analysis. We identified 4 recent clinical studies based on nationwide databases of high quality, providing prevalence estimates from 1:29,000 to 1:40,000. Higher frequency populations do exist because of frequent first-cousin marriages and/or a higher mutation frequency. When calculating prevalence from the incidence related to number of births, estimates were 1:40,000-1:50,000. Clinical screening studies, including examination for Kayser-Fleischer rings or ceruloplasmin, did not improve these estimates because of insufficient sample size or selection biases. Population-based genetic studies in US and UK populations were not in disagreement with the clinically based estimates. At the same time, studies from France and Sardinia suggested that the genetic prevalence may be 3-4 times higher than the clinical disease prevalence. This raises the question whether the penetrance is indeed 100% as generally assumed.

CONCLUSIONS

The original prevalence estimate from 1984 of 1:30,000-1:50,000 still appears valid, at least for the United States, Europe, and Asia. In some population-based studies, the genetic prevalence was 3-4 times higher than clinically based estimates. The question of penetrance needs further evaluation.

The rate of hepatic artery complications is higher in pediatric liver transplant recipients with metabolic liver diseases than with biliary atresia

BACKGROUND

Liver transplantation (LT) is an excellent treatment option for patients with biliary atresia (BA) who fail portoenterostomy surgery. LT is also increasingly performed in patients with metabolic liver diseases. This study compared the outcomes in pediatric patients who underwent LT for metabolic liver diseases and BA.

BASIC PROCEDURES

Data from 237 pediatric patients who underwent primary LT at Seoul National University Hospital from 1988 to 2015, including 33 with metabolic liver diseases and 135 with BA, were retrospectively analyzed.

MAIN FINDINGS

Compared with children with BA, children with metabolic liver diseases were significantly older at the time of LT (121.3 vs. 37.3 months; P < 0.001), and had lower Child-Pugh (7.1 vs. 8.4; P = 0.010) and Pediatric End-stage Liver Disease (6.5 vs. 12.8; P = 0.042) scores. Overall survival rates were similar (87.8% vs. 90.8%; P = 0.402), but hepatic artery (HA) complications were significantly more frequent in children with metabolic liver diseases (12.1% vs. 1.5%; P = 0.014).

PRINCIPAL CONCLUSION

Despite similar overall survival, children with metabolic liver diseases had a higher rate of HA complications.

TYPE OF SUBMISSION

Original article, Case control study, Retrospective.

EVIDENCE LEVEL

III.

Biochemical and molecular characterisation of neurological Wilson disease

Background

To identify biochemical and genetic features that characterise neurological Wilson disease as a distinct disease subgroup.

Methods

Detailed biochemical profiles and genotypic characteristics of neurological (86 patients) and hepatic subgroups (233 patients) from 368 unrelated Korean families were analysed.

Results

Compared with patients in the hepatic subgroup, patients in the neurological subgroup had a later age at onset, a higher proportion with Kayser-Fleischer rings and higher serum creatinine levels, and a lower proportion with favourable outcome (62% vs 80%, P<0.016). At diagnosis, the neurological subgroup had lower serum ceruloplasmin (3.1±2.1 mg/dL vs 4.2±3.2 mg/dL, P<0.001), total copper (26.4±13.8 µg/dL vs 35.8±42.4 µg/dL, P=0.005), free copper (17.2±12.5 µg/dL vs 23.5±38.2 µg/dL, P=0.038) and urinary copper (280.9±162.9 µg/day vs 611.1±1124.2 µg/day, P<0.001) levels. Serum aspartate aminotransferase, alanine aminotransferase, gamma glutamyltransferase and total bilirubin levels, as well as prothrombin time, were also lower in the neurological subgroup. Liver cirrhosis was more common but mostly compensated in the neurological subgroup. Frameshift, nonsense or splice-site ATP7B mutations and mutations in transduction or ATP hinge domains (2.4% vs 23.1%, P=0.006) were less common in the neurological subgroup.

Conclusion

The neurological subgroup had distinct clinical, biochemical and genetic profiles. Further studies are required to identify the factors, with or without association with copper metabolism, underlying the neurological presentation for which treatment needs to be targeted to improve the clinical outcome of this subgroup.

Epidemiology, diagnosis, and treatment of Wilson's disease

Wilson's disease (WD) is an autosomal recessive disease caused by a mutation of the ATP7B gene, resulting in abnormal copper metabolism. The major clinical features of WD include liver disease, neurological disorders, K-F rings, and osteoporosis. The prevalence of WD in China is higher than that in Western countries. Early diagnosis and lifelong treatment will lead to better outcomes. Drugs such as sodium dimercaptosuccinate (Na-DMPS), Zn, and Gandou Decoction can be used to treat WD. Some studies have shown that the combination of traditional Chinese medicine and Western medicine is the best approach to treating WD. In order to identify better treatments, this article describes the specific clinical symptoms of Wilson's disease, its diagnosis, and treatment options.

Wilson's Disease in China

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism. Its incidence is higher in China than in western countries. ATP7B is the causative gene and encodes a P-type ATPase, which participates in the synthesis of holoceruloplasmin and copper excretion. Disease-causing variants of ATP7B disrupt the normal structure or function of the enzyme and cause copper deposition in multiple organs, leading to diverse clinical manifestations. Given the variety of presentations, misdiagnosis is not rare. Genetic diagnosis plays an important role and has gradually become a routine test in China. The first Chinese spectrum of disease-causing mutations of ATP7B has been established. As a remediable hereditary disorder, most WD patients have a good prognosis with an early diagnosis and chelation treatment. However, clinical trials are relatively few in China, and most treatments are based on the experience of experts and evidences from other countries. It is necessary to study and develop appropriate regimens specific for Chinese WD patients.

Carrier frequency of Wilson's disease in the Korean population: a DNA-based approach

Wilson's disease (WD) is an autosomal recessive disorder caused by ATP7B gene mutation. The frequency of WD is about 1 in 30 000 worldwide. In the present study, we screened 14 835 dried blood spots (DBSs) from asymptomatic Korean neonates and retrospectively reviewed massively parallel sequencing of 1090 control individuals to estimate carrier frequency. TaqMan real-time PCR assays were conducted to detect six mutations that account for 58.3% of mutations in Korean WD patients: c.2333G>T (p.Arg778Leu), c.2621C>T (p.Ala874Val), c.3086C>T (p.Thr1029Ile), c.3247C>T (p.Leu1083Phe), c.3556G>A (p.Gly1186Ser) and c.3809A>G (p.Asn1270Ser). We also retrospectively reviewed data from 1090 individuals with various indications other than WD for whom whole-exome or panel sequencing data were available. Mutant allele frequency based on the six most common mutations was 0.0067 among the total of 14 835 DBSs screened. Given that these six mutations account for 58.3% of mutations in Korean WD patients, the corrected mutant allele frequency is 0.0115 (95% confidence interval (CI): 0.0103-0.0128). Corresponding incidence (q²) and carrier frequency (2pq) were estimated to be 1:7561 and 1:44, respectively. In retrospective data analysis of 1090 control individuals, allele frequency of pathogenic or likely pathogenic variants was 0.0096 (95% CI: 0.0063-0.0146). Corresponding carrier frequency was estimated to be 1:53. Estimated allele and carrier frequencies based on DNA screening were relatively higher than those reported previously based on clinical ascertainment.

Spectrum of ATP7B mutations and genotype-phenotype correlation in large-scale Chinese patients with Wilson Disease

Wilson disease (WD), an inherited disorder associated with ATP7B gene, has a wide spectrum of genotypes and phenotypes. In this study, we developed a rapid multiplex PCR-MassArray method for detecting 110 mutant alleles of interest, and used it to examine genomic DNA from 1222 patients and 110 healthy controls. In patients not found to have any mutation in the 110 selected alleles, PCR-Sanger sequencing was used to examine the ATP7B gene. We identified 88 mutations, including 9 novel mutations. Our analyses revealed p.Arg778Leu, p.Arg919Gly and p.Thr935Met showed some correlations to phenotype. The p.Arg778Leu was related to younger onset age and lower levels of ceruloplasmin (Cp) and serum copper, while p.Arg919Gly and p.Thr935Met both indicated higher Cp levels. Besides, the p.Arg919Gly was related to neurological subtype, and p.Thr935Met showed significant difference in the percentage of combined neurological and visceral subtype. Moreover, for ATP7B mutations, the more severe impact on ATP7B protein was, the younger onset age and lower Cp level presented. The feasibility of presymptomatic DNA diagnosis and predicting clinical manifestation or severity of WD would be facilitated with identified mutations and genotype-phenotype correlation precisely revealed in the study.

Spectrum and Classification of ATP7B Variants in a Large Cohort of Chinese Patients with Wilson's Disease Guides Genetic Diagnosis

BACKGROUND

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism caused by ATP7B pathogenic mutations. The symptoms of WD can be effectively prevented if the affected individuals are identified and intervened early. However, clinical utility of this molecular analysis is challenging due to hundreds of variants with various clinical effects in the gene. Here, we aim to describe the spectrum of ATP7B variants and assess their clinical effects in the Han Chinese population.

METHODS

The ATP7B gene was directly sequenced in 632 unrelated WD patients and 503 unrelated healthy individuals. The effects of identified variants were classified according to the American College of Medical Genetics and Genomics (ACMG) standards and guidelines. Different frequency of variants observed in both cases and controls were tested using Chi-square or Fisher's exact tests.

RESULTS

We detected 161 non-synonymous variants in these 632 WD patients, 58 of which were novel. Among these variants, 78, 64, 8, 4, and 7 were classified as 'pathogenic variants', 'likely pathogenic variants', 'variants with uncertain significance', 'likely benign variants', and 'benign variants', respectively. Ninety percent (569/632) of these WD patients can be genetically diagnosed with two or more 'pathogenic' or 'likely pathogenic' variants. The 14 most common disease-causing variants were found at least once in 94% (537/569) of genetically diagnosed patients.

CONCLUSIONS

These data expand the spectrum of ATP7B variants and facilitate effective screening for ATP7B variants for early diagnosis of WD and development of individualized treatment regimens.

Estimation of carrier frequencies of six autosomal-recessive Mendelian disorders in the Korean population

Although many studies have been performed to identify mutations in Korean patients with various autosomal-recessive Mendelian disorders (AR-MDs), little is known about the carrier frequencies of AR-MDs in the Korean population. Twenty common mutations from six AR-MDs, including Wilson disease (WD), non-syndromic hearing loss (NSHL), glycogen storage disease type Ia (GSD Ia), phenylketonuria (PKU), congenital hypothyroidism (CH), and congenital lipoid adrenal hyperplasia (CLAH) were selected to screen for based on previous studies. A total of 3057 Koreans were genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry followed by confirmation using the Sanger sequencing. We found 201 and 8 carriers with either one or two mutations in different genes, respectively, yielding a total carrier frequency of 1 in 15 (6.7%). Of the six AR-MDs, NSHL has the highest carrier frequency followed by WD, CH, CLAH, GSD Ia, and PKU. As carrier screening tests are becoming prevalent and the number of mutations known and tested is rising, a priori data on the carrier frequencies in different ethnic groups is mandatory to plan a population screening program and to estimate its efficiency. In light of this, the present results can be used as a basis to establish a screening policy for common AR-MRs in the Korean population.

Systems biology approach to Wilson's disease

Wilson's disease (WD) is a severe disorder of copper misbalance, which manifests with a wide spectrum of liver pathology and/or neurologic and psychiatric symptoms. WD is caused by mutations in a gene encoding a copper-transporting ATPase ATP7B and is accompanied by accumulation of copper in tissues, especially in the liver. Copper-chelation therapy is available for treatment of WD symptoms and is often successful, however, significant challenges remain with respect to timely diagnostics and treatment of the disease. The lack of genotype-phenotype correlation remains unexplained, the causes of fulminant liver failure are not known, and the treatment of neurologic symptoms is only partially successful, underscoring the need for better understanding of WD mechanisms and factors that influence disease manifestations. Recent gene and protein profiling studies in animal models of WD began to uncover cellular processes that are primarily affected by copper accumulation in the liver. The results of such studies, summarized in this review, revealed new molecular players and pathways (cell cycle and cholesterol metabolism, mRNA splicing and nuclear receptor signaling) linked to copper misbalance. A systems biology approach promises to generate a comprehensive view of WD onset and progression, thus helping with a more fine-tune treatment and monitoring of the disorder.