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PubMed2004

Spectrum of hemojuvelin gene mutations in 1q-linked juvenile hemochromatosis.

Juvenile or type 2 hemochromatosis (JH) is transmitted as a recessive trait that leads to severe iron overload and organ damage typically before age 30 years. Linkage to a locus on chromosome 1q has been found in most patients with JH. The recently identified causal gene encodes hemojuvelin, a protein with a proposed crucial role in iron metabolism. A second, rare type of JH, with clinical expression identical to the 1q-linked form, is due to inactivation of hepcidin, the key regulator of iron homeostasis. Here we report the spectrum of mutations of the hemojuvelin gene (HJV) in 34 patients who did not show hepcidin mutations. This represents the largest cohort of patients with JH collected worldwide. We identified 17 different (16 novel) mutations of HJV, both at the homozygous and at the compound heterozygous state. Mutations either generate premature termination codons or were missense substitutions, affecting highly conserved residues, relevant to the protein structure and/or function.

Adolescent↗
PubMed2004

The hereditary hemochromatosis protein, HFE, lowers intracellular iron levels independently of transferrin receptor 1 in TRVb cells.

Hereditary hemochromatosis (HH) is an autosomal recessive disease that leads to parenchymal iron accumulation. The most common form of HH is caused by a single amino acid substitution in the HH protein, HFE, but the mechanism by which HFE regulates iron homeostasis is not known. In the absence of transferrin (Tf), HFE interacts with transferrin receptor 1 (TfR1) and the 2 proteins co-internalize, and in vitro studies have shown that HFE and Tf compete for TfR1 binding. Using a cell line lacking endogenous transferrin receptors (TRVb cells) transfected with different forms of HFE and TfR1, we demonstrate that even at low concentrations Tf competes effectively with HFE for binding to TfR1 on living cells. Transfection of TRVb cells or the derivative line TRVb1 (which stably expresses human TfR1) with HFE resulted in lower ferritin levels and decreased Fe2+ uptake. These data indicate that HFE can regulate intracellular iron storage independently of its interaction with TfR1. Earlier studies found that in HeLa cells, HFE expression lowers Tf-mediated iron uptake; here we show that HFE lowers non-Tf-bound iron in TRVb cells and add to a growing body of evidence that HFE may play different roles in different cell types.

Antigens, CD↗
PubMed2004

Haptoglobin modifies the hemochromatosis phenotype in mice.

Classic hereditary hemochromatosis (HH) is a common genetic disorder of iron metabolism caused by a mutation in the HFE gene. Whereas the prevalence of the mutation is very high, the clinical penetrance of the disease is low, suggesting that the HFE mutation is a necessary but not sufficient cause of clinical HH. Several candidate modifier genes have been proposed in mice and humans, including haptoglobin. Haptoglobin is the plasma protein with the highest binding affinity for hemoglobin. It delivers free plasma hemoglobin to the reticuloendothelial system, thus reducing loss of hemoglobin through the glomeruli and allowing heme-iron recycling. To gain insight into the role of haptoglobin as a modifier gene in HH, we used Hfe and haptoglobin double-null mice. Here, we show that Hfe and haptoglobin compound mutant mice accumulate significantly less hepatic iron than Hfe-null mice, thus demonstrating that haptoglobin-mediated heme-iron recovery may contribute significantly to iron loading in HH.

Animals↗
PubMed2001

Tumor necrosis factor alpha promoter polymorphisms influence the phenotypic expression of hereditary hemochromatosis.

Severe iron overload usually develops in patients with hereditary hemochromatosis (HHC), but variability in the phenotypic expression of the disease has been reported. This study assessed whether tumor necrosis factor alpha (TNF-alpha) plays a role in phenotypic expression of HHC. Sixty-four patients with HHC and 172 healthy volunteers (controls) were studied. Release of TNF-alpha from stimulated peripheral blood monocytes was measured by enzyme-linked immunosorbent assay, and 308 and 238 TNF-alpha polymorphisms were detected with polymerase chain reaction and restriction fragment-length polymorphism analysis. The relation between TNF-alpha polymorphisms and clinical expression of HHC was evaluated. Patients with HHC released less TNF-alpha than controls, but the difference was significant only in homozygotes for the C282Y mutation. The prevalence of the 308 TNF-alpha polymorphism was similar in patients and controls, whereas the prevalence of the 238 polymorphic allele was significantly lower in patients (3% versus 16%; P =.002). A lower prevalence of cirrhosis was observed in patients with TNF-alpha polymorphism than in those without it (4 of 15 [27%] versus 28 of 49 [57%]), but the difference was not significant (P =.07). In nonhomozygotes for the C282Y mutation, severe liver siderosis was less prevalent in patients with the 308 polymorphism than in those without it (P =.05). Alanine aminotransferase (ALT) values were significantly lower in patients with TNF-alpha polymorphism (P =.006), even when patients with other hepatotoxic factors were excluded. Multivariate analysis showed that TNF-alpha polymorphism was independently associated with ALT values (P =.0008 and P =.045, respectively, in homozygotes and nonhomozygotes for the C282Y mutation) and siderosis in nonhomozygotes (P =.047). Thus, TNF-alpha appears to play a role in HHC by modulating the severity of liver damage. (Blood. 2001;97:3707-3712)

Adult↗
PubMed2005

Impact of HFE genetic testing on clinical presentation of hereditary hemochromatosis: new epidemiological data.

BACKGROUND: Hereditary hemochromatosis (HH) is a common inherited disorder of iron metabolism in Northern European populations. The discovery of a candidate gene in 1996 (HFE), and of its main mutation (C282Y), has radically altered the way to diagnose this disease. The aim of this study was to assess the impact of the HFE gene discovery on the clinical presentation and epidemiology of HH. METHODS: We studied our cohort of 415 patients homozygous for the C282Y allele and included in a phlebotomy program in a blood centre in western Brittany, France. RESULTS: In this cohort, 56.9% of the patients were male and 21.9% began their phlebotomy program before the implementation of the genetic test. A significant decrease in the sex ratio was noticed following implementation of this DNA test, from 3.79 to 1.03 (p < 10(-5)), meaning that the proportion of diagnosed females relatives to males greatly increased. The profile of HH patients at diagnosis changed after the DNA test became available. Serum ferritin and iron values were lower and there was a reduced frequency of clinical signs displayed at diagnosis, particularly skin pigmentation (20.1 vs. 40.4%, OR = 0.37, p < 0.001) and hepatomegaly (11.0 vs. 22.7%, OR = 0.42, p = 0.006). In contrast, fatigue became a more common symptom at diagnosis (68.0 vs. 51.2%, OR = 2.03, p = 0.004). CONCLUSION: This study highlights the importance of the HFE gene discovery, which has simplified the diagnosis of HH and modified its clinical presentation and epidemiology. This study precisely measures these changes. Enhanced diagnosis of HFE-related HH at an early stage and implementation of phlebotomy treatment are anticipated to maintain normal life expectancy for these patients.

Adolescent↗
PubMed2002

Genotyping of hemochromatosis-associated mutations in the HFE gene by PCR-RFLP and a novel reverse hybridization method.

Comparative analysis of the hemochromatosis-associated mutations C282Y, H63D and S65C in the HFE gene in 51 patients using three different methods is reported. One PCR-RFLP method was based on general primers, whereas another employed mutation-specific mismatched primers. The third method was a new PCR-based reverse hybridisation line probe assay (LiPA), comprising DNA amplification by general primers followed by a single step reverse hybridization to specific probes, immobilized on a nitrocellulose strip. Forty-eight (94%) of the 51 samples yielded identical results by all three methods. Three discrepant results were obtained, caused by polymorphisms in the primer binding region, resulting in no amplification at all or selective amplification, leading to misinterpretation of the HFE genotype by PCR-RFLP. The design of the assay and the stringency of the reaction conditions used are crucial to obtain a correct HFE genotype. PCR-LiPA offers an easy and reliable alternative to currently used conventional methods.

Base Sequence↗
PubMed2006

Possible roles of the hereditary hemochromatosis protein, HFE, in regulating cellular iron homeostasis.

Hereditary hemochromatosis (HH) is the most common inherited disorder in people of Northern European descent. Over 83% of the cases of HH result from a single mutation of a Cys to Tyr in the HH protein. HFE. This mutation causes a recessive disease resulting in an accumulation of iron in selected tissues. Iron overload damages these organs leading to cirrhosis of the liver, diabetes, cardiomyopathy, and arthritis. The mechanism by which HFE influences iron homeostasis in cells and in the body remains elusive. Lack of functional HFE in humans produces the opposite effects in different cell types in the body. In the early stages of the disease. Kupffer cells in the liver and enterocytes in the intestine cells are iron depleted and have low intracellular ferritin levels, whereas hepatocytes in the liver are iron overloaded and have high intracellular iron levels. This review gives the background and a model as to possible mechanisms of how HFE could exert different effects on iron homeostasis in different cell types.

Animals↗
PubMed2002

Clinical relevance of hemochromatosis-related HFE C282Y/H63D gene mutations in patients on chronic dialysis.

BACKGROUND: The actual prevalence and the clinical relevance of gene mutations of HFE (which are linked to hemochromatosis) have not yet been established in patients on chronic dialysis. On the basis of theoretical premises, it could be hypothesized that these genetic determinants might influence the response to iron intake and the susceptibility for iron overload in patients in parenteral iron therapy. Furthermore, carriers for these mutations might be prone to develop sporadic porphyria cutanea tarda and cardiovascular events. METHODS: C282Y/H63D mutations of HFE gene were evaluated in 132 patients (34 in peritoneal dialysis, 98 in HD) and correlated with biochemical parameters of iron status (ferritin (FER) concentration and transferrin saturation (TSAT)), red cell parameters (red cell size and hemoglobin content), erythropoietin (EPO) dosage, major cardiovascular events and C-reactive protein as marker of chronic inflammation, in patients without iron therapy and after i.v. iron supplementation (< or = 60 mg/week) and with the presence of biopsy-proven porphyria. RESULTS: C282Y heterozygous mutation was found in 8/132 (6.6%); H63D homozygous and heterozygous mutations were found in 3/132 (2.3%) and 22/132 (16%) patients, respectively. Two patients (1.5%) showed double heterozygosis. No differences in baseline serum FER and TSAT and the other biochemical and clinical parameters were found in patients bearing mutations alleles nor after continuous iron therapy at low dosages. However, the prevalence of patients capable of maintaining normal hemoglobin (Hb) level without EPO therapy is increased in the C282Y-mutated patients. Only 1 patient out of the 4 with biopsy-proven porphyria cutanea tarda was bearing gene mutations (H63D heterozygosis). CONCLUSION: C282Y/H63D HFE gene mutations do not seem to be related to major abnormalities in biochemical parameters of iron status in dialysis patients without iron therapy or after i.v. iron supplementation, granted that low dosages are employed. Obviously, as our patients were exposed to a relatively uniform iron regimen in our clinical center (< or = 60 mg/week), it is unclear if other dosing regimens will unmask clinically significant differences between the heterozygotes and normals. The fact that the C282Y-mutated patients more frequently maintain high Hb values without EPO is interesting as could suggest a better use of available iron for erythopoiesis, but needs to be confirmed in larger samples. No clear association is demonstrated with porphyria cutanea tarda and major cardiovascular events.

Aged↗
PubMed2003

Bioelectronic sensor technology for detection of cystic fibrosis and hereditary hemochromatosis mutations.

CONTEXT: Bioelectronic sensors, which combine microchip and biological components, are an emerging technology in clinical diagnostic testing. An electronic detection platform using DNA biochip technology (eSensor) is under development for molecular diagnostic applications. Owing to the novelty of these devices, demonstrations of their successful use in practical diagnostic applications are limited. OBJECTIVE: To assess the performance of the eSensor bioelectronic method in the validation of 6 Epstein-Barr virus-transformed blood lymphocyte cell lines with clinically important mutations for use as sources of genetic material for positive controls in clinical molecular genetic testing. Two cell lines carry mutations in the CFTR gene (cystic fibrosis), and 4 carry mutations in the HFE gene (hereditary hemochromatosis). DESIGN: Samples from each cell line were sent for genotype determination to 6 different molecular genetic testing facilities, including the laboratory developing the DNA biochips. In addition to the bioelectronic method, at least 3 different molecular diagnostic methods were used in the analysis of each cell line. Detailed data were collected from the DNA biochip output, and the genetic results were compared with those obtained using the more established methods. RESULTS: We report the successful use of 2 applications of the bioelectronic platform, one for detection of CFTR mutations and the other for detection of HFE mutations. In all cases, the results obtained with the DNA biochip were in concordance with those reported for the other methods. Electronic signal output from the DNA biochips clearly differentiated between mutated and wild-type alleles. This is the first report of the use of the cystic fibrosis detection platform. CONCLUSIONS: Bioelectronic sensors for the detection of disease-causing mutations performed well when used in a "real-life" situation, in this case, a validation study of positive control blood lymphocyte cell lines with mutations of public health importance. This study illustrates the practical potential of emerging bioelectronic DNA detection technologies for use in current molecular diagnostic applications.

Base Sequence↗
PubMed1999

The influence of hemochromatosis mutations on iron overload of thalassemia major.

BACKGROUND AND OBJECTIVE: Hemochromatosis is a genetic form of iron overload due to a defective HFE gene. Secondary iron overload is the main complication in transfusion-dependent thalassemia patients. In this work we have examined the prevalence of HFE mutations in thalassemia major and evaluated the degree of iron overload of patients with and without HFE mutations. DESIGN AND METHODS: HFE mutations were studied in 71 Italian thalassemic patients and in 189 normal controls, using PCR and restriction enzyme analysis. The degree of iron overload, assessed by serum ferritin and liver iron concentration (LIC), was compared in 17 patients with mutations in the HFE gene, and in 17 subjects with wild type HFE genotype. The two groups of patients had comparable globin gene mutations, were matched for age and were homogeneous for transfusion and chelation history. In all cases the iron balance calculated on the basis of transfusion regimen and iron excreted by chelation was available. RESULTS: The allele frequencies of C282Y and H63D were respectively 1.4% and 12.7% in patients and 1.1% and 11.4% in controls. No case of C282Y homozygosity was recorded among patients. No significant difference was found in terms of serum ferritin, LIC, or the age at chelation start between patients with and without HFE mutations. The single patient with H63D homozygosity was severely iron-loaded. INTERPRETATION AND CONCLUSIONS: Our data suggest that the presence of a single mutation in the HFE gene does not influence the severity of iron loading in thalassemia patients following a regular transfusion and chelation program.

Adolescent↗
PubMed2000

Use of HFE mutation analysis for hereditary hemochromatosis: the need for physician education in the translation of basic science to clinical practice.

BACKGROUND: Hereditary hemochromatosis (HH) is a common hereditary disorder of iron metabolism causing iron overload, organ failure, and malignancy. Preclinical diagnosis using HFE gene analysis followed by prophylactic phlebotomy can completely prevent the disease. METHODS: We conducted a mail survey of all registered primary care physicians, gastroenterologists, and hematologists in Arkansas (n = 860) to determine utilization of HFE mutation analysis in clinical medicine a year after the new molecular test first became available. RESULTS: Of 346 responding physicians (40%), 71 (21%) were aware of the test, 36 (10%) knew that the test was available in Arkansas, and 10 (3%) had used the test. One physician had used the test to screen first-degree relatives of a homozygous HH proband. CONCLUSIONS: Because of poor utilization of the test, the discovery of the role of HFE mutations in HH has had minimal impact on clinical care in Arkansas.

Arkansas↗
PubMed2000

Wild-type HFE protein normalizes transferrin iron accumulation in macrophages from subjects with hereditary hemochromatosis.

Hereditary hemochromatosis (HC) is one of the most common single-gene hereditary diseases. A phenotypic hallmark of HC is low iron in reticuloendothelial cells in spite of body iron overload. Most patients with HC have the same mutation, a change of cysteine at position 282 to tyrosine (C282Y) in the HFE protein. The role of HFE in iron metabolism and the basis for the phenotypic abnormalities of HC are not understood. To clarify the role of HFE in the phenotypic expression of HC, we studied monocytes-macrophages from subjects carrying the C282Y mutation in the HFE protein and clinically expressing HC and transfected them with wild-type HFE by using an attenuated Salmonella typhimurium strain as a gene carrier. The Salmonella system allowed us to deliver genes of interest specifically to monocytes-macrophages with high transduction efficiency. The accumulation of (55)Fe delivered by (55)Fe-Tf was significantly lower in macrophages from patients with HC than from controls expressing wild-type HFE. Transfection of HC macrophages with the HFE gene resulted in a high level of expression of HFE protein at the cell surface. The accumulation of (55)Fe delivered by (55)Fe-Tf was raised by 40% to 60%, and this was reflected by an increase in the (55)Fe-ferritin pool within the HFE-transfected cells. These results suggest that the iron-deficient phenotype of HC macrophages is a direct effect of the HFE mutation, and they demonstrate a role for HFE in the accumulation of iron in these cells.

Cells, Cultured↗
PubMed2000

Rapid single-tube screening of the C282Y hemochromatosis mutation by real-time multiplex allele-specific PCR without fluorescent probes.

BACKGROUND: An accurate determination of the major HFE mutation (C282Y), which is associated with hereditary hemochromatosis, is important in diagnosis and risk assessment for this disease. We report a single-tube high-throughput PCR method for the detection of C282Y. METHODS: We combined three previously described principles: allele-specific PCR, mutagenically separated PCR, and amplicon identification by specific dissociation curves. PCR amplification was performed with fluorescence detection or conventional thermocycler using the same primers, reactant constituents, and cycling protocol. Primer cross-reactions were prevented by deliberate primer:primer and primer:template mismatches. RESULTS: PCR products were identified by their characteristic melting temperatures based on SYBR Green I fluorescence. For each of the 256 random and 17 known HFE C282Y samples, mutant homozygous, wild-type, and heterozygous samples were unequivocally distinguished. CONCLUSIONS: This homogeneous assay is rapid, reproducible, does not require fluorescent oligonucleotide probes, and correctly identifies HFE genotypes.

Alleles↗
PubMed2000

Asymptomatic hemochromatosis subjects: genotypic and phenotypic profiles.

Screening for hereditary hemochromatosis (HHC) by means of transferrin saturation (TS) levels has been advocated and will identify many patients who are asymptomatic. The purposes of this study were (1) to determine HFE genotypes among asymptomatic HHC patients and correlate this profile with the degree of iron overload and (2) to evaluate the relationship between mobilized iron (mob Fe), age, serum ferritin (SF), and quantitative hepatic iron (QHI) in this population. One hundred twenty-three asymptomatic HHC patients were evaluated; all had quantitative phlebotomy to determine mob Fe and genotyping for C282Y and H63D mutations. Liver biopsies with QHI determinations were performed on 72 of the 123 patients. Of the entire group, 60% were homozygous for C282Y, and 13% were compound heterozygotes (C282Y/H63D). Among asymptomatic patients, the prevalence of homozygous C282Y is lower compared with previous studies that include clinically affected patients. Of those patients with more than 4 g mob Fe, 77% were homozygous C282Y. Asymptomatic patients with lower iron burdens frequently had genotypes other than homozygous C282Y. There was no correlation between age and mob Fe in these patients; however, there was a correlation between mob Fe and both SF (r = 0.68) and QHI (r = 0.75). In conclusion, asymptomatic patients with moderate iron overload had a different genotypic profile than was seen in advanced iron overload. The significance of identifying patients with modest degrees of iron loading, who may not be homozygous for C282Y, must be addressed if routine TS screening is to be implemented. (Blood. 2000;96:3707-3711)

Adult↗
PubMed2001

Solid-phase amplification for detection of C282y and H63D hemochromatosis (HFE) gene mutations.

BACKGROUND: There is a need for simple, rapid, and inexpensive methods for the detection of single-nucleotide polymorphisms. Our aim was to develop a single-tube ELISA-like PCR assay and evaluate it by detecting the common C282Y and H63D mutations found in the hemochromatosis gene (HFE) by use of clinical samples. METHODS: The method, termed solid-phase amplification (SPA), involves dual liquid- and solid-phase amplification of a target sequence by the use of two PCR primers, one of which is in two forms: the first is covalently immobilized to the wall of a microwell, and the second is free in solution. During allele-specific amplification, both the free and solid-phase amplicons are labeled by incorporation of digoxigenin (DIG)-dUTP. The amount of surface-bound amplicon is determined colorimetrically by the use of an alkaline phosphatase-anti-DIG-Fab conjugate and p-nitrophenyl phosphate. RESULTS: Two different amplicon-labeling methods were evaluated. Analysis of 173 clinical samples for the C282Y and H63D HFE point mutations with SPA revealed that only one sample was incorrectly diagnosed, apparently because of operator error, when compared with conventional restriction fragment length polymorphism assay results. CONCLUSIONS: The SPA assay has potential for medium-scale mutation detection, having the advantage of being manipulatively simple and immediately adaptable for use in clinical laboratories with existing ELISA instrumentation.

Electrophoresis, Agar Gel↗
PubMed2001

Complete scanning of the hereditary hemochromatosis gene (HFE) by use of denaturing HPLC.

BACKGROUND: Between 4% and 35% of hereditary hemochromatosis (HC) probands are C282Y or H63D heterozygotes or lack both of these two common HFE mutations, and 15 novel HFE mutations have been described recently. We evaluated denaturing HPLC (DHPLC) for screening of the whole HFE coding region and further defined whether HC probands with an incomplete HFE genotype carry uncommon mutations. METHODS: Analytical conditions for each coding exon were determined by a combination of computer melting profile predictions and experimental melting curves. To test accuracy for scanning the complete HFE coding region and optimize DHPLC running conditions, each melting domain was investigated with at least one mutation or one polymorphism as reference. We tested 100 DNA samples harboring the C282Y, H63D, or S65C mutations and 17 artificially created positive controls that carried either 1 of the 14 other known HFE mutations or 3 selected polymorphisms. RESULTS: Investigations on each of the coding exons 1, 2, 4, 5, and 6 could be performed at one analysis temperature. Coding exon 3 displayed a more complex melting profile and required two analysis temperatures. DHPLC detected all known HFE mutations as well as the three selected polymorphisms. CONCLUSIONS: DHPLC can be used to scan the HFE gene in HC probands in whom at least one chromosome lacks an assigned mutation.

Chromatography, High Pressure Liquid↗
PubMed2002

Pathogenesis of hereditary hemochromatosis: genetics and beyond.

Hereditary hemochromatosis (HH) comprises several inherited disorders of iron homeostasis characterized by increased gastrointestinal iron absorption and secondary tissue iron deposition. The most common form of this disorder is called HFE-related HH and is caused by homozygosity for the C282Y mutation in the HFE gene. Recently, other less common hereditary forms of iron overload have been recognized and are designated as non-HFE-related HH. The identification and cloning of HFE and other genes involved in iron metabolism has greatly expanded our understanding of many aspects of HH. The introduction of a commercially available genetic test for the C282Y and H63D mutations of HFE allows presymptomatic diagnosis, and adds precision to studies of the population genetics of HFE-related HH. It is now recognized that a substantial proportion of C282Y homozygotes does not develop clinically significant iron overload, and modifier genes may be involved in this phenomenon. Mouse models of HH and cell culture studies have increased our understanding of the normal physiology and pathophysiology of iron homeostasis. Future investigations will refine our knowledge of the mechanisms of action of HFE protein, the phenotypic variability observed in persons homozygous for the C282Y mutation, and the mechanisms responsible for non-HFE-related HH.

Animals↗