Very high frequency of the His1069Gln mutation in Polish Wilson disease patients

Whole-exome sequencing identifies novel pathogenic variants across the ATP7B gene and some modifiers of Wilson's disease phenotype

BACKGROUND & AIMS

Wilson's disease (WD) is an autosomal recessive disorder associated with disease-causing alterations across the ATP7B gene, with highly variable symptoms and age of onset. We aimed to assess whether the clinical variability of WD relates to modifier genes.

METHODS

A total of 248 WD patients were included, of whom 148 were diagnosed after age of 17. Human exome libraries were constructed using AmpliSeq technology and sequenced using the IonProton platform.

RESULTS

ATP7B p.His1069Gln mutation was present in 215 patients, with 112 homozygotes and 103 heterozygotes. Three other mutations: p.Gln1351Ter, p.Trp779Ter and c.3402delC were identified in >10 patients. Among patients, 117 had a homozygous mutation, 101 were compound heterozygotes, 27 had one heterozygous mutation, and 3 other patients had no identifiable pathogenic variant of ATP7B. Sixteen mutations were novel, found as part of a compound mutation or as a sole, homozygous mutation. For disease phenotype prediction, age at diagnosis was a deciding factor, while frameshift allelic variants of ATP7B and being male increased the odds of developing a neurological phenotype. Rare allelic variants in ESD and INO80 increased and decreased chances for the neurological phenotype, respectively, while rare variants in APOE and MBD6 decreased the chances of WD early manifestation. Compound mutations contributed to earlier age of onset.

CONCLUSIONS

In a Polish population, genetic screening for WD may help genotype for four variants (p.His1069Gln, p.Gln1351Ter, p.Trp779Ter and c.3402delC), with direct sequencing of all ATP7B amplicons as a second diagnostic step. We also identified some allelic variants that may modify a WD phenotype.

Apolipoprotein E deletion has no effect on copper-induced oxidative stress in the mice brain

The current study was designed to investigate effect of copper administration on oxidative damage to the brain in ApoE^−/− mice and to explore the putative neuroprotective effects rendered by apolipoprotein E (ApoE). Male C57BL/6 ApoE^−/− and wild-type mice were randomly assigned into four groups, ApoE^−/− mice wild-type mice treated with either copper or saline. Copper sulphate pentahydrate or saline (200 µl) were administered intragastrically daily for 12 weeks. Expression of malondialdehyde, superoxide dismutase (SOD), hemeoxygenase 1 (HO-1), and NAD(P)H: quinone oxidoreductase 1 (NQO1) were determined by a combination of biochemical assays. The concentration of copper in the brain of C57BL/6 mice and ApoE^−/− mice treated by copper significantly increased compared with mice treated by saline (P=0.0099 and P=0.0443). Compared with the C57BL/6 mice treated by copper, the level of the ApoE⁻/⁻ mice treated by copper was higher (P=0.018). TBARS and SOD activities or the expressions of NQO1 and HO-1 in the brain were not significantly different amongst the four experimental groups of mice. The relative value of NQO1/β-actin expression in the brain of the ApoE^−/− mice was similar in both saline and copper administration experimental groups. However, Western blot analysis showed that NQO1 expression was significantly higher in the ApoE^−/− mice brain treated with saline compared with saline treated wild-type mice (P=0.0449). ApoE does not function in protecting the brain from oxidative damage resulting from copper build-up in Wilson’s disease, but may play a role in regulating copper accumulation in the brain.

Chemosensitivity of U251 Cells to the Co-treatment of D-Penicillamine and Copper: Possible Implications on Wilson Disease Patients

D-Penicillamine (PA), a copper chelator, and one of the recommended drugs for treatment of Wilson disease (WD) has been reported to worsen the symptoms of patients with neurologic presentations. However, the cause of this paradoxical response has not been fully elucidated and requires further investigations. Accordingly, we have studied the in vitro effect of Copper (Cu) and/or PA treatment on human glioblastoma U251 cells as an in vitro model of Cu cytotoxicity. Treatment of U251 cells with either Cu or PA exerted no significant effect on their morphology, viability or ROS level. In contrast, co-treatment with Cu-PA caused a decrease in viability, altered glutathione and ceruloplasmin expression coupled with marked increase in ROS; depolarization of mitochondrial membrane potential; and an increase in Sub G0 phase; along with alpha-Fodrin proteolysis. These findings along with the absence of LDH release in these assays, suggest that combined Cu-PA exposure induced apoptosis in U251 cells. In addition, pre-/or co-treatment with antioxidants showed a protective effect, with catalase being more effective than N-acetyl cysteine or trolox in restoring viability and reducing generated ROS levels. By comparison, a similar analysis using other cell lines showed that rat PC12 cells were resistant to Cu and/or PA treatment, while the neuroblastoma cell line SH-SY5Y was sensitive to either compound alone, resulting in decreased viability and increased ROS level. Taken together, this study shows that glioblastoma U251 cells provide a model for Cu-PA cytotoxicity mediated by H₂O₂. We postulate that PA oxidation in presence of Cu yields H₂O₂ which in turn permeates the plasma membrane and induced apoptosis. However, other cell lines exhibited different responses to these treatments, potentially providing a model for cell type- specific cytotoxic responses in the nervous system. The sensitivity of different neural and glial cell types to Cu-PA treatment may therefore underlie the neurologic worsening occurring in some PA-treated WD patients. Our results also raise the possibility that the side effects of PA treatment might be reduced or prevented by administering antioxidants.

Genetic variants in diseases of the extrapyramidal system

Knowledge on the genetics of movement disorders has advanced significantly in recent years. It is now recognized that disorders of the basal ganglia have genetic basis and it is suggested that molecular genetic data will provide clues to the pathophysiology of normal and abnormal motor control. Progress in molecular genetic studies, leading to the detection of genetic mutations and loci, has contributed to the understanding of mechanisms of neurodegeneration and has helped clarify the pathogenesis of some neurodegenerative diseases. Molecular studies have also found application in the diagnosis of neurodegenerative diseases, increasing the range of genetic counseling and enabling a more accurate diagno-sis. It seems that understanding pathogenic processes and the significant role of genetics has led to many experiments that may in the future will result in more effective treatment of such diseases as Parkinson’s or Huntington’s. Currently used molecular diagnostics based on DNA analysis can identify 9 neurodegenerative diseases, including spinal cerebellar ataxia inherited in an autosomal dominant manner, dentate-rubro-pallido-luysian atrophy, Friedreich’s disease, ataxia with ocu-lomotorapraxia, Huntington's disease, dystonia type 1, Wilson’s disease, and some cases of Parkinson's disease.

Diagnosis of Wilson disease in young children: molecular genetic testing and a paradigm shift from the laboratory diagnosis

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism that results in accumulation of copper primarily in the liver, brain and cornea. Mutations in the WD gene, ATP7B, cause failure of copper excretion from hepatocyte into bile and a defective synthesis of ceruloplasmin. More than 500 mutations are now recognized, scattered throughout the ATP7B gene. Since WD has protean clinical presentations, awareness of WD in clinical practice is important for the early diagnosis and prevention of accumulated copper toxicity. Molecular genetic testing is playing an increasingly important role in the diagnosis of WD in uncertain cases and family screening. Siblings should be screened for WD once an index case has been diagnosed. Discrimination of heterozygotes from asymptomatic patients is essential to avoid inappropriate lifelong therapy for heterozygotes. Genetic testing, either by haplotype analysis or by mutation analysis, is the only definite solution for differentiating heterozygote carriers from affected asymptomatic patients. Routine genetic testing, because of the multitude of documented mutations, has been thought to be impractical until recently. However, genetic testing is now being more actively applied to the diagnosis of WD, particularly in young children in whom conventional biochemical diagnosis has much limitation and only genetic testing is able to confirm WD. Because advancement of modern biochemical technology now allows more rapid, easier, and less expensive mutation detection, direct DNA sequencing could be actively considered as the primary mode of diagnostic investigation rather than a supplementary test to the conventional biochemical tests. This review will focus on the recent advancement of molecular genetics and genetic diagnosis of WD in very young children on the basis of research data of the Seoul National University Children's Hospital and recent literature.

Fine motor skills disorders in the course of Wilson's disease

Objectives

Fine motor skills disorders belong to the neurological manifestation of Wilson's disease. The aim of this study is to investigate if fine motor performance changes during the course of the disease and with therapy.

Methods:

In 15 neurological patients with Wilson's disease, severity of neurological symptoms was assessed with a neurology score. A test battery consisting of the hand writing of a test sentence, lines of “double-I” and retracing a circle was carried out for analysis. By means of a computer-aided analysis of the patient's handwriting, 10 kinematic parameters of the writing trace were calculated. These parameters were determined once at the very beginning of the study and then again after 7 years.

Results:

Improvement of clinical symptoms was observed after onset of therapy only within the first 2 years. In contrast to the standard population, a reduced degree of automation could be detected both at the beginning and at the end of the 7-year interval. There was no significant change in 8 out of the 10 kinematic parameters during the observation period, 2 deteriorated.

Discussion:

The absence of a significant increase in fine motor disturbances proves, on the one hand, the efficacy of the therapy regime applied. On the other hand, the end point of a possible reversibility had been reached. A computer-aided analysis of the patient's handwriting allows for a sensitive detection of the “functional scar” in the extrapyramidal control and can subsequently prompt a timely correction of therapy in case of progression.

[Haplotype analysis and possible founder effect at the R778L mutation of the ATP7B gene in Korean patients with Wilson's disease]

BACKGROUND/AIMS

Wilson's disease (WD) is an inherited disorder of copper metabolism caused by alteration of the P-type adenosine triphosphatase (ATP) 7B gene. In this study, we analyzed the frequency of well-known mutations and constructed the first haplotypes for Koreans. In addition, we evaluated whether a founder effect existed in Korean patients with WD.

METHODS

We obtained DNA samples from 21 patients with WD and their parents (total cohort n=63). ATP7B gene mutations were identified by direct sequencing methods, and microsatellite typing was performed at D13S315, D13S1325, and D13S316 with fluorescent dye-labeled primers. Any founder effect was identified by using 42 normal alleles from parents with a normal phenotype as a control group. The chi square test and Fisher's exact test were used for statistical analysis.

RESULTS

Three common mutations were found in 23 chromosomes obtained from 21 patients: the R778L mutation at exon 8 (15/23, 65.2%), the A874V mutation at exon 11 (6/23, 26.1%), and the N1270S mutation at exon 18 (2/23, 8.7%). D13S315 and D13S316 showed linkage disequilibrium at alleles 5 and 4, respectively, in patients with the R778L mutation (P=0.0157 and 0.0001, respectively). The haplotype made up of these two alleles occurred significantly more frequently in patients with the R778L mutation (5-R778L-4, D13S315-mutation-D13S316) than in the controls (P=0.0018).

CONCLUSIONS

The arche haplotype of the ATP7B gene in Korean patients with WD may be 5-R778L-4 (D13S315.mutation.D13S316), and it might illustrate a founder effect.

Genotype-phenotype correlation in Italian children with Wilson's disease

BACKGROUND/AIMS

Wilson's disease phenotype is very variable for clinical and laboratory features. Our aim was to assess the role of the type of ATP7B disease causing mutations on Wilson's disease phenotype.

METHODS

We retrospectively evaluated the data of children with Wilson's disease from eight pediatric departments.

RESULT

Fifty-eight patients (34 male, median age at diagnosis 7.4 years) from 47 unrelated families were studied, carrying 34 different mutations. The most common mutations were the missense p.H1069Q and p.M769V, the nonsense p.R1319X, the frameshift c.2299delC, c.2298_2299insC and c.2530delA, and the splice site mutation c.2447+5G>A. Serum ceruloplasmin and copper were lower among the patients' homozygotes for nonsense and frameshift mutations than in patients with missense mutations. A normalization of serum alanine aminotransferase after therapy was not achieved in 23.6% of patients with missense mutations versus 45.5% of patients with nonsense/frameshift mutations. A direct linear correlation was found between age at diagnosis and urinary copper excretion at diagnosis.

CONCLUSIONS

The type of mutation explains at least a part of Wilson's disease phenotype, and mutation analysis should be considered as an integrative tool for such a challenging diagnosis. Urinary copper excretion appears to be correlated to the age at diagnosis rather than genotype.

Molecular pathogenesis of Wilson and Menkes disease: correlation of mutations with molecular defects and disease phenotypes

The trace metal copper is essential for a variety of biological processes, but extremely toxic when present in excessive amounts. Therefore, concentrations of this metal in the body are kept under tight control. Central regulators of cellular copper metabolism are the copper-transporting P-type ATPases ATP7A and ATP7B. Mutations in ATP7A or ATP7B disrupt the homeostatic copper balance, resulting in copper deficiency (Menkes disease) or copper overload (Wilson disease), respectively. ATP7A and ATP7B exert their functions in copper transport through a variety of interdependent mechanisms and regulatory events, including their catalytic ATPase activity, copper-induced trafficking, post-translational modifications and protein-protein interactions. This paper reviews the extensive efforts that have been undertaken over the past few years to dissect and characterise these mechanisms, and how these are affected in Menkes and Wilson disease. As both disorders are characterised by an extensive clinical heterogeneity, we will discus how the underlying genetic defects correlate with the molecular functions of ATP7A and ATP7B and with the clinical expression of these disorders.

Novel mutations of the ATP7B gene among 109 Hungarian patients with Wilson's disease

BACKGROUND/AIMS

Diagnosis of Wilson's disease may be difficult in patients presenting with liver disease and in asymptomatic siblings. The aim of the present study was to assess the impact of genetic testing for diagnosis of the disease in a large cohort (n=109) from Hungary.

PATIENTS/METHODS

One hundred and nine patients with Wilson's disease were studied (65 men and 44 women; mean age at onset of symptoms: 20+/-9 years). Diagnosis of the disease was based on typical clinical and laboratory features (all had a Wilson's disease score of >or=4). H1069Q was assessed by the semi-nested polymerase chain reaction-based restriction fragment length polymorphism assay. H1069Q heterozygotes and H1069Q negative samples were then screened for mutations (on exons 6 to 20) by denaturating high-performance liquid chromatography and than sequenced on a genetic analyser.

RESULTS

Twenty-three different mutations were found. H1069Q was the most frequent mutation in Hungary, detected in 77 patients (71%). Fourteen further known mutations were found by sequencing. We identified eight new mis-sense mutations not described before: N676I, S693Y, Y715H, M769L, W939C, P1273S, G1281D and G1341V. In 36/109 patients (33%) the diagnosis of Wilson's disease was established by adding mutational analysis. The Kayser-Fleischer ring was more frequent in H1069Q homozygous patients and their mean age at the time of diagnosis was higher than in patients heterozygous or negative for H1069Q.

CONCLUSION

Eight novel mutations in addition to the 15 that are already known were found in Hungarian patients with Wilson's disease. Our results underline the importance and usefulness of genetic testing for patients presenting with liver disease and for family screening.

Clinical and molecular characterization of Wilson disease in Spanish patients

Wilson disease (WD) results when specific mutations occur at the ATP7B gene. The presence of mutations in the ATP7B gene was studied in the coding region and the intron-exon boundaries in 15 WD Spanish patients, and their first-degree relatives when possible. A total of 20 nucleotide sequence changes were detected, 18 missense and two splicing mutations. Six of these variants were classified as disease-causing mutations, five missense, and one splicing; four of them have been previously described (M645R, A1065P, H1069Q, and 3060 + 5G > T), whereas two were novel (P768L and A990P). No mutation was clearly prevalent, although the H1069Q mutation predominated, nor did a good phenotype-genotype correlation exist. The two new mutations described were manifested as an asymptomatic increase in serum transaminases. The remaining 14 changes were classified as polymorphisms and their potential effects on protein function are discussed. The identification of mutations in the ATP7B gene has allowed a conclusive diagnosis to be made of WD in patients presenting neurological phenotype or neurological of hepatic phenotype, who would otherwise not have been diagnosed using classical criteria. WD patients could start chelating treatment earlier on and possibly modify the natural progression of the disease.

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

The present study was intended to estimate the frequencies of the most common mutations (R778L, R778W, R778G, I1102T and H1069Q) of ATP7B in Indian Wilson disease (WD) population and to explore the correlation between genotype/phenotype and copper ATPase activity. A total of 33 WD patients and their family members from North West states of India were examined. The H1069Q, R778W and R778L mutations were absent in these WD patients. R778W and I1102T mutations were present in 36% of WD patients. Family analysis for these mutations using PCR-RFLP documented 5 carriers and 2 asymptomatic WD patients. The copper ATPase activity in WD patients was significantly reduced (50%) than that of control individuals. No significant difference was observed in copper stimulated ATPase activity between homozygous (R778W/R778W, I1102T/I1102T) and compound heterozygous (R778W/unknown mutation, I1102T/unknown mutation) WD patients. Serum ceruloplasmin, serum copper levels were significantly lower in homozygous WD patients than that of compound heterozygous. However, no significant difference was observed in liver copper contents between heterozygous and homozygous patients. In conclusion, the data suggest that R778W and I1102T are most common mutations and provide the basis of genetic (PCR-RFLP) diagnostic tool for Indian WD patients as well as in siblings/parents where biochemical parameters are ambiguous.

The H1069Q mutation in ATP7B is associated with late and neurologic presentation in Wilson disease: results of a meta-analysis

BACKGROUND AND AIMS

Wilson disease is an hereditary disorder of copper metabolism, caused by mutations in the ATP7B gene, and leading to hepatic or neurologic disease. We examined whether H1069Q, the most common ATP7B mutation, is associated with a specific phenotype.

METHODS

Genotyping results in 70 Dutch patients were related to clinical presentation. Subsequently a meta-analysis for genotype-phenotype correlation was performed on all patients available from literature, combined with the current Dutch group, a total of 577 patients.

RESULTS

The Dutch patients homozygous or heterozygous for the H1069Q mutation presented more frequently with neurologic disease (63% and 43% vs. 15%), and at a later age (20.9 and 15.9 vs. 12.6 years) than patients without the H1069Q mutation. In the meta-analysis the odds-ratio for neurologic presentation in homozygous or heterozygous H1069Q vs. non-H1069Q patients was 3.50 (95% CI 2.01-6.09) and 2.13 (95% CI 1.18-3.83), respectively. Age at presentation was 21.1, 19.2 and 16.5 years, respectively, corresponding to a weighted mean difference (WMD) of 4.41 (95% CI 1.56-7.26) for homozygous H1069Q vs. heterozygous patients and 6.68 (95% CI 4.33-9.38) for homozygous H1069Q vs. non-H1069Q patients.

CONCLUSIONS

Our results indicate that the H1069Q mutation is associated with a late and neurologic presentation.

New mutation (T1232P) of the ATP-7B gene associated with neurologic and neuropsychiatric dominance onset of Wilson’s disease in three unrelated Colombian kindred

Wilson's disease is an autosomal recessive disorder of hepatic copper metabolism caused by mutations in a gene encoding a copper-transporting P-type ATPase. We report the clinical and molecular characterization of six members from three unrelated Colombian kindred. Completed sequence DNA analysis linked to the gene ATP-7B from patient wd-1 revealed a novel A to C transversion in exon 17 at position 3856 (A3856C) of the ATP-7B mRNA resulting in a threonine for proline substitution at position 1232 of the ATP-7B protein (T1232P). Additionally, two novel polymorphisms were detected (2785G:Gly875 in exon 11; and intron at +38 a > c:tgcgcccga in exon 19). All affected individuals were homozygous for the T1232P mutation and displayed neurologic and neuropsychiatric dominant onset. This work expands the knowledge about the number, type, and implication of mutations in WD.

Wilson disease

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism. Since daily copper intake exceeds the body's requirements, effective means of excreting excess copper are essential. These are accomplished by ATP7B, a new member of the cation-transporting p-type ATPase family, which is mainly expressed in the liver and mediates both copper secretion into plasma (coupled with ceruloplasmin synthesis) and its excretion into bile. Thus far, more than 200 mutations of the WD gene have been detected, causing impairment of ATP7B function and, ultimately, copper accumulation. Excess copper, however, induces free-radical reactions and lipid peroxidation. Resultant liver damage leads to steatosis, inflammation, cirrhosis, and, occasionally, fulminant liver failure. The diagnosis of WD is commonly made on the basis of typical clinical and laboratory findings, including low serum ceruloplasmin, increased urinary copper excretion, and increased hepatic copper content. Since liver morphology is non-specific, and copper histochemistry may lead to both false-negative and false-positive results, the pathologist usually only suspects the disease or assists in its confirmation. Although the value of molecular genetic testing is limited due to the high number of possible gene mutations, polymerase chain reaction may be useful for the evaluation of family members of homozygous index patients.

Characterization of the molecular defect in the ATP7B gene in Wilson disease patients from Yugoslavia

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism resulting from the absence or dysfunction of a copper transporting P-type ATPase (ATP7B). Approximately 150 mutations of the ATP7B have been identified to date. In this paper, we report the results of molecular characterization and genotype-phenotype analysis, which we have carried out on 35 patients from Yugoslavia affected by WD. Using single-strand conformational polymorphism (SSCP) followed by direct sequencing, we characterized the molecular defect in 80% of WD chromosomes and found 11 different mutations, three of which are novel. The most common mutations that accounted for the molecular defect in 71.3% of WD chromosomes were H1069Q (48.9%), 2304-2305insC (11.4%), R616Q (5.7%), and A1003T (5.7%). The results produced in this paper indicate that the best strategy for mutation detection in Yugoslavian patients with WD is an SSCP analysis of exons 14, 8, 5, and 13, where most of the defects (73.1%) lie, followed by mutation analysis of the remaining exons in ATP7B in patients in whom the mutation was not detected by the finitial screening. These data can be used to develop straightforward genetic testing in this population or in other countries composed of a genetically mixed population like the United States, where a significant number of immigrants came from Central and Eastern Europe.

Correlation of ATP7B genotype with phenotype in Chinese patients with Wilson disease

AIM: To determine the mutational characterization of P-type ATP7B gene and to explore the correlation of ATP7B genotype to phenotype in Chinese patients with Wilson disease (WD).

METHODS: Seventy-five patients with WD from 72 no-kinship families, 44 males and 31 females, were enrolled in this study. The age of onset ranged from 4 to 39 years, ≤ 18 years in 72 patients. Some exons of ATP7B gene mutations were analyzed in patients with WD by using biochemical methods, polymerase chain reaction-single strand configuration polymorphism (PCR-SSCP) and DNA sequence analysis. A total of 778 coding regions were identified with restriction enzyme Msp I. The activity of Cu-ATPase was assessed by measuring inorganic phosphorus.

RESULTS: Sixty-six of 75 patients (88%) had with hepatic manifestations, 39 of them had only hepatic manifestations, 27 patients had hepatic and neurological manifestations or other symptoms at the same time (16 patients had associated neurological manifestation, 3 patients had osteopathy, 8 patients had other symptoms). Eight of the 75 patients (10.7%) had only neurological symptoms, one patient (5 years old) had no symptom. Twelve changing patterns were detected in ATP7B gene by DNA sequencing, including seven mutations (R778L, C656X, G943D, V1140A, V1106I V1216M and 1384del17), six polymorphisms (IVS4-5t/c, A2495G, C2310G, IVS18 + 6c/t and IVS20 + 5a/g). R778L occurred in 49/66 patients (74%) with hepatic manifestations, homozygosis of R778L in 16 patients, heterozygosity of R778L in 33 patients. V1106I mutation of ATP7B gene occurred in 2 patients with delaying onset of clinical symptoms. Cu-ATPase activity of three patients with known mutations (R778L/ V1106I/A2495G, R778L/V1216M and R778L/R778L) were determined, and the activity of Cu-ATPase was decreased by 44.55%, 88.23% and 69.49% respectively.

CONCLUSION: 1384del17bp is a novel mutation found in WD patients. R778L is the most common mutation of ATP7B gene. There is a correlation between R778L and hepatic manifestations in WD patient.

Common mutations of ATP7B in Wilson disease patients from Hungary

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism. The H1069Q mutation in exon 14 of ATP7B is far the most frequent in Wilson patients of European origin. Mutations in exon 8 and 15 are also common among the over 150 described mutations in the WD gene. The aim was to investigate the frequency of these common WD gene mutations in Hungarian patients. A total of 42 patients with WD from 39 Hungarian families were examined. The H1069Q mutation was assessed by a seminested polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) assay, while mutations in exons 8, 13, 15, and 18 of WD gene were identified by sequencing. In addition, haplotype analysis was performed using three common microsatellite markers (D13S314, D13S301, D13S316). The H1069Q mutation was found in 27 patients (64.3%). Nine patients were H1069Q homozygous. Eighteen patients were H1069Q compound heterozygous, two of them had H1069Q/P969Q and one patient H1069Q/3400delC genotype. In two of the 15 H1069Q-negative patients a novel mutation in exon 13 (T977M) was detected. One H1069Q-negative patient had a mutation in exon 8 (G710S). None of the studied mutations was detected in 12 WD patients. H1069Q-positive patients from various European countries had the same haplotype pattern. The H1069Q point mutation is frequent in Hungarian patients with WD and appears to have originated from a single founder in Eastern Europe. In contrast, mutations in exons 8, 13, 15, and 18 are uncommon in Hungarian WD patients.

Hepatic transport systems

The identification of the genes responsible for various genetic liver disorders lead to a better understanding of basic physiology of hepatic transport systems. In this review we focus on transport systems involved in the generation of bile and in the maintenance of copper homeostasis. Abnormal function of these transporters results in diseases like Wilson's disease, progressive familial cholestasis syndromes, Dubin-Johnson syndrome and cystic fibrosis. Beyond these well defined diseases, functional impairments of transport proteins may predispose to non-genetic diseases ranging from intrahepatic cholestasis of pregnancy to neurodegenerative disorders including Alzheimer's disease.

High prevalence of the H1069Q mutation in East German patients with Wilson disease: rapid detection of mutations by limited sequencing and phenotype-genotype analysis

BACKGROUND/AIMS

Wilson disease is caused by a large number of different mutations in the ATP7B gene. Wilson disease patients from a homogeneous ethnical background (Saxonia) were studied for distribution and phenotypes of ATP7B mutations.

METHODS

Eighty-two patients were analyzed. The H1069Q mutation was assayed by a polymerase chain reaction-based restriction fragment length polymorphism test. Exons 8 and 15 were sequenced in all, and the entire gene in 30, non-H1069Q-homozygotes.

RESULTS

Four novel and 12 known mutations were found. Thirty-two (39%) Wilson disease patients were homozygous and 39 (48%) heterozygous for the H1069Q mutation (allele frequency 63%). Together with sequence analysis of exons 8 and 15 mutations in both alleles were identified in 65% of patients. Only one patient had both mutations at other locations. In H1069Q homozygotes symptoms started later (21.3+/-7.2 years) than in H1069Q compound heterozygotes (14.6+/-5.8, P<0.001) or H1069Q negatives (10+/-4.4, P<0.001), and they had more frequently neurologic symptoms (93 vs. 47%, P<0.001) and Kayser-Fleischer rings (82 vs. 51%, P<0.001). Mutation status did not correlate with liver biopsy findings, serum ceruloplasmin levels or (64)Cu-assay results.

CONCLUSIONS

In spite of many known ATP7B mutations, only few occur in this homogeneous population. Limited genetic testing is useful to confirm Wilson disease in this population.

Molecular diagnosis of Wilson disease

Wilson disease (WD) is caused by mutations in the ATP7B gene. The diagnosis is based on clinical and biochemical criteria but these are increasingly recognized to have low sensitivity. Genetic diagnosis is considered impractical due to the large coding region of the ATP7B gene and extreme diversity of mutations. We assessed the feasibility and utility of genetic diagnosis in WD. The coding region of the ATP7B gene was scanned by single-stranded conformation polymorphism (SSCP) analysis in 6 cases in whom the diagnosis of WD was uncertain. In addition, we attempted molecular diagnosis in 26 WD patients of similar ethnicity but variable disease manifestations. In 6 individuals in whom the biochemical/clinical diagnosis was uncertain, DNA analyses were useful for assigning their status with respect to WD. Molecular diagnosis identified presymptomatic individuals in families affected by WD and assigned heterozygote carrier or wild-type status to individuals previously diagnosed as affected. In 26 WD patients, 92% of disease alleles were identified. The most common mutations were H1069Q, L936X, and 2532delA representing 48, 10, and 8% of disease alleles, respectively. Three novel mutations were identified: Q898R, 3061(-1)g --> a, and 3972insC. Genetic diagnosis is feasible for WD. Greater application of molecular diagnosis should enable an appreciation of the full spectrum of WD phenotype that is not possible with currently available diagnostic criteria.

Frequency of His1069Gln and Gly1267Lys mutations in Polish Wilson's disease population

Wilson's disease is an autosomal recessive disorder. More than 60 mutations of the Wilson's disease gene have been described so far. We have analysed 148 Polish Wilson's disease patients from 95 families for His1069Gln and Gly1267Lys mutations and correlated this finding with age and clinical form of the disease at presentation. To identify these mutations, single strand conformation polymorphism analysis was performed. In our group there were 94 patients with neurological presentation, 28 with hepatic presentation, whilst 26 were in a pre-clinical stage of the disease. His1069Gln mutation was present on 171 (57%) of the 296 studied chromosomes, and Gly1267Lys mutation was present on 27 chromosomes (9.1%). Most of our patients were homozygous or heterozygous for His1069Gln mutation (39.9% and 30.4%, respectively); 4% of the patients were homozygous for Gly1267Lys mutation and 5.4% had both of these described mutations on their chromosomes. His1069Gln and Gly1267Lys mutations occurred often in our Wilson's disease patient population but we did not find any relationship between investigated mutations and the clinical form of Wilson's disease or age of first symptoms.

Mutation spectrum of ATP7A, the gene defective in Menkes disease

Our knowledge about Menkes disease (MD) has expanded greatly since its description in 1962 as a new X-linked recessive neurodegenerative disorder of early infancy. Ten years later a defect in copper metabolism was established as the underlying biochemical deficiency. In the beginning of 1990s efforts were concentrated on the molecular genetic aspects. The disease locus was mapped to Xq13.3 and the gene has been isolated by means of positional cloning. This was the beginning of a series of new findings which have greatly enhanced our understanding of copper metabolism not only in human, but also in other species. This review will focus on the molecular genetic aspects of Menkes disease and its allelic form occipital horn syndrome. The mutations will be compared briefly with those described in the animal model mottled mouse, and in Wilson disease, the autosomal recessive disorder of copper metabolism.