High prevalence of the H1069Q mutation in East German patients with Wilson disease: rapid detection of mutations by limited sequencing and phenotype–genotype analysis
Introduction
Wilson disease (WD) is an autosomal recessive disorder of copper metabolism, characterized by decreased biliary copper excretion. Progressive accumulation of copper in various organs, primarily in the liver and brain, results in chronic liver disease and/or neurological impairment [1]. Age of onset and clinical presentation of the disorder vary greatly. In most populations, WD has a prevalence of approximately 1:30 000 and a corresponding carrier frequency of 1:90 [2], [3]. Since biochemical markers of impaired copper metabolism can be misleading, diagnosis may be difficult in the absence of typical symptoms and in asymptomatic siblings [1]. However, early diagnosis is critical, since treatment prevents lifelong neurological disability and/or liver cirrhosis.
The gene defective in WD (ATP7B), (MIM277900) (locus 13q14.3), encodes a copper-transporting P-type ATPase [4], [5], which is highly homologous to the Menkes disease gene (ATP7A). ATP7B is predominantly expressed in the liver, while reduced expression is observed in the kidney, brain and placenta [6]. ATP7B has 21 expressed exons (22 in kidney), spanning a DNA region of approximately 100 kb, and encoding a protein of 1465 amino acids [6], [7]. Alternative splice variants of exons 6–8 and 12–13 in brain tissue may have an alternative function [7].
More than 200 mutations in the ATP7B gene, covering nearly the entire coding region, have been reported so far, thus making genetic testing a difficult task. Most mutations are rare and found only in single patients. H1069Q, the most common mutation, is found predominantly in Eastern and northern European populations [4], [7], [8], [9], [10] but not Asian WD patients [11], [12], [13]. The second most common mutations of the WD gene are located within exon 8, suggesting a mutational hotspot [7], [14]. Two point mutations in codon 778 (R778L, R778G) were frequently observed in Taiwanese WD patients [15], and a similar one (R778W) is found in European populations [8], [16]. The 2299insC mutation is present in many populations.
The precise mechanisms of protein dysfunction for particular mutations of ATP7B are largely unknown. Conflicting results on genotype–phenotype correlations of the most common mutations have been reported. No correlations were found in studies in mixed population of WD patients [7], [8], [17], [18], while investigations in patients from a well defined region found that H1069Q homozygosity is associated with late onset neurologic disease [9], [19]. The state of Saxonia offers a unique opportunity to study this issue further. In the former German Democratic Republic all WD patients were referred to a single center – the Department of Neurology of the University of Leipzig. Between 1950 and 1989 data of more than 400 patients were collected [3], [20], [21]. The aim of this study was to analyze the spectrum of mutations of theATP7B gene in these patients and possible genotype–phenotype correlations. In addition, this study should allow to address the feasibility of mutation screening in a defined area.
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Patients
Eighty-four WD patients from 82 families residing in the state of Saxonia or its immediate surroundings were examined, representing all known patients with WD in this area. Fifty-eight patients were diagnosed and followed up at the University Leipzig (Departments of Neurology, Pediatrics, and Gastroenterology), and 26 at the University of Dresden (Departments of Neurology and Pediatrics). In the absence of neurologic symptoms and Kayser–Fleischer Rings diagnosis of WD was based on the presence
H1069Q, exons 8 and 15 mutation screen
Eighty-four WD patients from 82 independent families were screened for the H1069Q mutation, exon 8 and exon 15 mutations. 72 WD patients were index patients. The remaining 10 patients were asymptomatic siblings of index patients who were not available for genetic testing. Thirty-two (39%) of 82 WD patients (independent families) were homozygous for the H1069Q mutation and 39 (48%) were H1069Q compound heterozygous (allele frequency 63%). Eleven (13%) patients had mutations in both alleles that
Discussion
Genetic testing of WD is hampered by considerable mutational heterogeneity. While the large number of the ATP7B mutations limit the worldwide use of DNA-testing in WD, the results of this study indicate that only very few mutations are present in this geographic area with a homogeneous population, making genetic testing feasible. The H1069Q mutation was found in 87% of WD patients in Saxonia. By adding sequence analysis of exons 8 and 15, 65% of WD patients (53 of 82 patients tested) could
Acknowledgements
The authors thank Antje Löchel and Annett Raßmann, University of Leipzig, for their excellent technical assistance. This study was partially supported by a grant (BE 890/5-3) from the Deutsche Forschungsgemeinschaft.
References (35)
- et al.
Identification and analysis of mutations in the Wilson disease gene (ATP7B): population frequencies, genotype–phenotype correlation, and functional analyses
Am J Hum Genet
(1997) - et al.
Haplotype and mutation analysis in Japanese patients with Wilson disease
Am J Hum Genet
(1997) - et al.
Efficient detection of mutations in Wilson disease by manifold sequencing
Genomics
(1996) - et al.
Improved method for investigation of copper metabolism in patients with Wilson's disease using Cu-64
Clin Chim Acta
(1972) - et al.
Analysis of functional domains of Wilson disease protein (ATP7B) in Saccharomyces cerevisiae
FEBS Lett
(1998) - et al.
Functional characterization of missense mutations in ATP7B: Wilson disease mutation or normal variant?
Am J Hum Genet
(1998) Perspectives on Wilson's disease
Hepatology
(1990)- et al.
Wilson's disease
- et al.
Wilson's disease in East Germany: in retrospect and perspectives – an evaluation
Psychiatr Neurol Med Psychol
(1990) - et al.
The Wilson disease gene is a copper transporting ATPase with homology to the Menkes disease gene
Nat Genet
(1993)
The Wilson disease gene is a putative copper transporting P-type ATPase similar to the Menkes gene
Nat Genet
Characterization of the Wilson disease gene encoding a P-type copper transporting ATPase: genomic organization, alternative splicing, and structure/function predictions
Hum Mol Genet
The Wilson disease gene: spectrum of mutations and their consequences
Nat Genet
Detection of the His1069Gln mutation in Wilson disease by rapid polymerase chain reaction
Ann Intern Med
The His1069Gln mutation in the ATP7B gene in Russian patients with Wilson disease
J Med Genet
Molecular analysis and diagnosis in Japanese patients with Wilson's disease
Pediatr Int
Identification of three novel mutations and a high frequency of the Arg778Leu mutation in Korean patients with Wilson disease
Hum Mutat
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