Hereditary hemochromatosis in Spain

The C282Y mutation of the HFE gene has been reported as the main cause of hereditary hemochromatosis (HH). Another missense mutation (H63D) has also been detected at an increased frequency in a compound heterozygote state with the C282Y mutation in HH patients. However, these two mutations are not present in all of the HH patients, indicating that other mutations in the HFE gene, or in other loci, should exist. The present study reports the frequencies of the C282Y and H63D mutations in 74 Spanish HH patients and the results of the sequencing analysis of the HFE exons, intron-exon boundaries, and 588 bp of the 5' region in 5 patients negative for the C282Y mutation. We have detected a high frequency of the C282Y mutation (85.1%) in Spanish HH patients, indicating that this mutation is the most common defect associated with the disease in Spain. The screening of the HFE regions in our patients without the C282Y mutation has revealed the presence of five polymorphisms. However, no other pathological mutations have been found. Therefore, further efforts to characterize the unscreened part of the HFE gene or other loci should be taken to identify the potential genetic factors causing HH in the C282Y-negative patients.     

Frequency of HFE H63D, S65C, and C282Y mutations in patients with iron overload and controls from Toledo, Spain

Hereditary hemochromatosis (HH) is an autosomal recessive disease caused by a defective iron absorption. C282Y is the most frequent HFE gene mutation causing HH in Northern European populations and their descendants. However, two other mutations, H63D and S65C, have been described as pathogenic changes. In this study, we have tried to evaluate the frequency of these three mutations in our community. Eighty-three patients with clinical and/or biochemical features of hemochromatosis and 150 controls were screened for H63D, S65C, and C282Y mutations using a PCR-restriction fragment length polymorphism (RFLP)-based strategy. In contrast to previous studies, 7% of the patients were homozygous for C282Y mutation. The remaining patients were 20% H63D homozygous, 10% H63D/C282Y compound heterozygous, 1% H63D/S65C compound heterozygous, 22% H63D heterozygous, 2% C282Y heterozygous, 2% S65C heterozygous, and 36% of patients lacked any of the three mutations studied, despite the fact that they showed clinical/biochemical features of hemochromatosis. We observed a high frequency of the H63D mutation in both the control group and patients, whereas the main genotypes implicated in HH in our series were H63D homozygous and H63D/C282Y compound heterozygous. We propose that the H63D mutation be analyzed in HH patients from our geographic area. Moreover, further studies are needed to elucidate the role of this mutation in the development of HH and the genetic, environmental or other factors that affect the genotype-phenotype correlation between H63D and hemochromatosis.     

Genetic hemochromatosis, a Celtic disease: is it now time for population screening?

In populations of northern European ancestry, hereditary hemochromatosis (HH) is tightly linked to mutations within the hemochromatosis gene (HFE gene). Over 93% of Irish HH patients are homozygous for the HFE gene C282Y mutation, providing a reliable diagnostic marker of the disease in this population. However, the prevalence of the C282Y mutation and that of the second HFE gene mutation, H63D, have yet to be determined within the Irish population. The objective of this study was to identify the true prevalence of the genetic form of HH in the Irish population. DNA was extracted from 1002 randomly selected newborn screening cards and analyzed for the C282Y and H63D mutations within the HFE gene. Complete results were obtained from 800 cards. Mutations were identified in 364 (46%) neonates. Eight (1%) neonates were homozygous for C282Y and 8 (1%) were homozygous for H63D. One hundred and fifty-five (19%) neonates were C282Y heterozygous and 226 (28%) were H63D heterozygous. Of these, 33 (4%) carried one copy of both C282Y and H63D mutations, i.e., compound heterozygous. Allele frequencies for C282Y and H63D were 11% and 15%, respectively. The high C282Y allele frequency in the Irish population together with its close linkage to HH indicate that C282Y genotyping is the preferred screening strategy for this disease in Ireland.     

Hereditary hemochromatosis in a Brazilian university hospital in São Paulo State (1990-2000)

Hereditary hemochromatosis (HH) is the most common genetic disease among individuals of European descent. Two mutations (845G-->A, C282Y and 187C-->G, H63D) in the hemochromatosis gene (HFE gene) are associated with HH. About 85-90% of patients of northern European descent with HH are C282Y homozygous. The prevalence of HH in the Brazilian population, which has a very high level of racial admixture, is unknown. The aims of the present study were to identify individuals with diagnostic criteria for HH among patients with a body iron overload attended at the university hospital of the Faculty of Medicine of Ribeirao Preto from 1990 to 2000, and to evaluate the prevalence of HFE mutations. We screened first-degree relatives for HFE mutations. Four of 72 patients (three men and one woman, mean age 47 years) fulfilled the criteria for HH. HFE mutations were studied in three patients [two C282Y homozygotes (patients 1 and 2) and one H63D heterozygote]. Patient 1 had four children (all C282Y heterozygotes with no iron overload) and seven brothers and sisters: two sisters (66 and 76 years old) were C282Y homozygotes and both had an iron overload (a liver biopsy in one showed severe iron deposits), one sister (79 years old) was a compound heterozygote with no iron overload, one brother (78 years old) was a C282Y heterozygote with no iron overload, two individuals were H63D heterozygotes (one brother, 49 years old, obese, with a body iron overload and abnormal liver enzymes - a biopsy showed non-alcoholic steatohepatitis, and one 70-year-old sister with no iron overload). Patient 2 had two children (22 and 24 years old who were C282Y heterozygotes with no iron overload) but no brothers or sisters. These results showed that HH was uncommon among individuals attended at our hospital, although HFE mutations were found in all patients. Familial screening is valuable for the early diagnosis of individuals at risk since it allows treatment to be initiated before the onset of the clinical manifestations of organ damage associated with HH.     

Hereditary hemochromatosis: the clinical significance of the S65C mutation

Hereditary hemochromatosis (HH) is a common genetic disease with iron overload in certain organs, especially the liver. Most cases are homozygous for the C282Y mutation in the HFE gene; a few are C282Y heterozygous, compound C282Y/H63D heterozygous, or have no known mutation. A third mutation, S65C, has been associated with HH, but this finding is disputed. We have studied the clinical significance of various genotypes with the S65C mutation. In a population-based screening for HH in 65,238 persons, 613 had high serum transferrin saturation in two blood samples and were invited for HFE genotyping. In 556 persons with complete data sets, we studied the serum ferritin concentration and the risk of being diagnosed with phenotypic HH in the various genotypic groups. The phenotypic diagnosis was given without knowing the genotypic result. Except for the C282Y homozygotes, no differences in median serum ferritin concentrations were found between the various genotypic groups. However, the C282Y/S65C compound heterozygous group had a higher risk of being diagnosed with phenotypic HH than the wild-type group, as did the C282Y homozygous and the C282Y/H63D compound heterozygous groups. When combined with the C282Y mutation, the S65C mutation is associated with an increased risk of being diagnosed with phenotypic HH.     

Hereditary haemochromatosis: only 1% of adult HFEC282Y homozygotes in South Wales have a clinical diagnosis of iron overload

In northern Europe, about 90% of patients with hereditary haemochromatosis (HH) are homozygous for a single mutation (C282Y) of the HFEgene and approximately 1 in 150 people in the general population carries this genotype. However, the clinical significance of HFE mutations remains uncertain, as is the proportion of people homozygous for C282Y who will develop clinical symptoms leading to a diagnosis of HH. A systematic review of patients with HH over a 2-year period within a defined UK region has revealed that only 1.2% of adult C282Y homozygotes have been diagnosed with iron overload and received treatment. In those in whom body iron load could be estimated, only 51% has more than 4 g iron (the diagnostic threshold for iron overload).     

Geography of HFE C282Y and H63D mutations

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder causing inappropriate dietary iron absorption that affects North Europeans. HH is associated with the C282Y mutation of the HFE gene, and the H63D mutation to a lesser degree. Both mutations are abundant in Europe, with H63D also appearing in North Africa, the Middle East, and Asia. Emigration from Europe over the past 500 years has introduced C282Y and H63D to America, Australia, New Zealand, and South Africa in an essentially predictable fashion. The distinctive characteristics of the population genetics of HH are the confined racial distribution and high frequency in North European peoples. C282Y frequencies in North Europeans are typically between 5% and 10%, with homozygotes accounting for between 1/100 and 1/400 of these populations. The scarcity of the C282Y mutation in other populations accounts for the lack of HH in non-Europeans.     

Protective role of calreticulin in HFE hemochromatosis

HFE gene mutations are associated with over 80% of cases of hereditary hemochromatosis (HH), an iron-overload disease in which the liver is the most frequently affected organ. Research on HFE has traditionally focused on its interaction with the transferrin receptor. More recent studies have suggested a more complex function for this nonclassical MHC-I protein. The aim of this study was to examine how HFE and its two most common mutations affect the expression of selected genes in a hepatocyte-like cell line. Gene expression was analyzed in HepG2 cells overexpressing wild-type and mutant HFE. The effect of HFE in iron import and oxidative stress levels was assessed. Unfolded protein response (UPR)-activated gene expression was analyzed in peripheral blood mononuclear cells from characterized HH patients. C282Y HFE down-regulated hepcidin and enhanced calreticulin mRNA expression. Calreticulin levels correlated with intracellular iron increase and were associated with protection from oxidative stress. In C282Y(+/+) patients calreticulin levels correlated with the expression of the UPR marker BiP and showed a negative association with the number of hereditary hemochromatosis clinical manifestations. The data show that expression of C282Y HFE triggers a stress-protective response in HepG2 cells and suggest a role for calreticulin as a modifier of the clinical expression of HH.     

Frequency of HFE gene mutations C282Y and H63D in Bosnia and Herzegovina

Genetic epidemiology studies of hereditary hemochromatosis (HHC) have shown a high prevalence of the C282Y mutation in individuals of the North Western European origin, whereas lower prevalence of HFE gene mutations was detected in the populations from southern European countries. However, no HFE mutation prevalence data have been provided for the population of Bosnia-Herzegovina so far. Therefore, the aim of this study was to determine the frequency of the C282Y and H63D HFE gene mutations in the population of Bosnia-Herzegovina. Among 200 analysed subjects 8 (4%) were C282Y heterozygotes; no C282Y homozygotes were found. The frequency of the H63D allele was 11.5%. There were 33 (16.5%) heterozygotes and 6 (3%) homozygotes for the H63D mutation. One (0.5%) compound heterozygote C282Y/H63D was identified. The observed C282Y and H63D allele frequency was 2.25% (95% confidence interval: 1.2-4.2) and 11.5% (95% confidence interval: 8.7-14.9), respectively. The prevalence of the C282Y and H63D mutations was estimated in Bosnia-Herzegovina, which fit well in the European northwest-to-southeast gradient of the C282Y mutation distribution. In addition, these results have an important implication for clinical evaluation of HHC in Bosnia-Herzegovina.     

Major histocompatibility complex class I associations in iron overload: evidence for a new link between the HFE H63D mutation, HLA-A29, and non-classical forms of hemochromatosis

 The present study is an analysis of the frequencies of HFE mutations in patients with different forms of iron overload compared with the frequencies found in healthy subjects from the same region. The frequencies of HLA-A and -B antigens and HLA haplotypes were also analyzed in the same subjects. The study population included: 71 healthy individuals; 39 genetically and clinically well-characterized patients with genetic hemochromatosis (HH); and 25 patients with non-classical forms of iron overload (NCH), excluding secondary hemochromatosis. All subjects were HLA-typed and HFE-genotyped by the oligonucleotide ligation assay (OLA). The gene frequencies found for the C282Y and H63D mutations of HFE were respectively: 0.03 and 0.23 in healthy individuals, 0.86 and 0.04 in HH patients, and 0.08 and 0.48 in NCH patients. An expected significant association between HH and HLA-A3 was observed, which was found to be in linkage disequilibrium with the C282Y mutation. A new association was seen, however, between HLA-A29 and NCH, in linkage disequilibrium with the H63D mutation. Again as expected, the HLA-B antigen B7 was associated with HH in linkage disequilibrium with HLA-A3. In addition, the HLA-B antigen B44 was found to be associated with NCH but not in linkage disequilibrium with either A29 or the H63D mutation. In conclusion, a new association of the HFE H63D mutation with forms of hemochromatosis other than HH and a new association between the HLA phenotype A29 and the HFE H63D mutation were found in the same patients. These findings reinforce evidence for the involvement of the major histocompatibility class I in iron metabolism, supporting the notion of a physiological role for the immunological system in the regulation of iron load. Received: 11 June 1997 / Revised: 29 October 1997     

Uncommon mutations and polymorphisms in the hemochromatosis gene

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder of iron metabolism. Iron absorption from the gut is inappropriately high, resulting in increasing iron overload. The hemochromatosis gene (HFE) was identified in 1996 by extensive positional cloning by many groups over a period of about 20 years. Two missense mutations were identified. Homozygosity for one of these, a substitution of a tyrosine for a conserved cysteine (C282Y), has now clearly been shown to be associated with HH in 60-100% of patients. The role of the second mutation, the substitution of an aspartic acid for a histidine (H63D), is not so clear but compound heterozygotes for both these mutations have a significant risk of developing HH. Here we review other putative mutations in the HFE gene and document a number of diallelic polymorphisms in HFE introns.     

Unique frequencies of HFE gene variants in Roma/Gypsies

The aim of this study was to assess the frequencies of three hemochromatosis gene (HFE) mutations in ethnic Roma/Gypsies in Slovakia. A cohort of 367 individuals representing general population and not preselected for health status was genotyped by TaqMan real-time PCR assay for C282Y, H63D and S65C mutations in HFE gene. A unique genetic profile was revealed: C282Y is found in the highest frequency of all Central European countries (4.90%), while the frequency of H63D mutation (4.09%) is lower than any reported in Europe so far. S65C mutation was not present in the cohort. These mutation frequencies can be explained rather by gene influx and genetic isolation than by genetic inheritance from a former Roma/Gypsy homeland.     

Frequency of hemochromatosis C282Y and H63D mutations in Sardinia

Hereditary hemochromatosis (HH) is one of the most common autosomal recessive disorders of iron metabolism among Caucasians, and it is associated with C282Y mutation of the HFE gene in populations of Celtic origins. A second mutation, H63D, shows a very high widespread frequency, although its role in iron metabolism is still inconclusive. There are no data on the frequencies of these two mutations in Sardinia, an island in the Mediterranean sea that has not been invaded by Celtic peoples. We examined 836 chromosomes from Sardinian subjects and tested for the mutation by restriction enzyme digestion of PCR products. Among the 836 analyzed chromosomes, we found a C282Y allele frequency of 0.0036 and an H63D allele frequency of 0.173. These data could explain the observed rarity of HH in Sardinia. The high allele frequency of H63D and the rarity of HH in Sardinia is suggestive that this mutation is not a major contributor to this disease.     

Chemical chaperones reduce endoplasmic reticulum stress and prevent mutant HFE aggregate formation

HFE C282Y, the mutant protein associated with hereditary hemochromatosis (HH), fails to acquire the correct conformation in the endoplasmic reticulum (ER) and is targeted for degradation. We have recently shown that an active unfolded protein response (UPR) is present in the cells of patients with HH. Now, by using HEK 293T cells, we demonstrate that the stability of HFE C282Y is influenced by the UPR signaling pathway that promotes its degradation. Treatment of HFE C282Y-expressing cells with tauroursodeoxycholic acid (TUDCA), a bile acid derivative with chaperone properties, or with the chemical chaperone sodium 4-phenylbutyrate (4PBA) impeded the UPR activation. However, although TUDCA led to an increased stability of the mutant protein, 4PBA contributed to a more efficient disposal of HFE C282Y to the degradation route. Fluorescence microscopy and biochemical analysis of the subcellular localization of HFE revealed that a major portion of the C282Y mutant protein forms intracellular aggregates. Although neither TUDCA nor 4PBA restored the correct folding and intracellular trafficking of HFE C282Y, 4PBA prevented its aggregation. These data suggest that TUDCA hampers the UPR activation by acting directly on its signal transduction pathway, whereas 4PBA suppresses ER stress by chemically enhancing the ER capacity to cope with the expression of misfolded HFE, facilitating its degradation. Together, these data shed light on the molecular mechanisms involved in HFE C282Y-related HH and open new perspectives on the use of orally active chemical chaperones as a therapeutic approach for HH.     

Hemochromatosis: As a conformational disorder

Hereditary hemochroamtosis (HH) refers to a unique clinicopathologic subset of iron overload syndromes that includes the disorder related to C282Y homozygous mutation of the hemochromatosis protein (HFE), the most common form of hereditary hemochromatosis. Recent reports have highlighted analogies with the class of disorders, known as the conformational diseases whereby HFE C282Y mutant protein forms aggregates and is subsequently retained in the endoplasmic reticulum (ER). In conformational disorders, accumulation of unfolded or misfolded proteins in the ER can activate a complex cascade linked to the regulation of diverse physiologic processes, disease onset and progression. To-date, reviews on HFE C282Y HH have largely dealt with the end-stage consequence of this disorder (iron overload). However, our review focuses on upstream molecular events resulting from the mislocalization of the aggregation-prone HFE C282Y protein leading to potential advances in treatment and diagnosis.     

Effect of C282Y Genotype on Self-Reported Musculoskeletal Complications in Hereditary Hemochromatosis

Objective

Arthropathy that mimics osteoarthritis (OA) and osteoporosis (OP) is considered a complication of hereditary hemochromatosis (HH). We have limited data comparing OA and OP prevalence among HH patients with different hemochromatosis type 1 (HFE) genotypes. We investigated the prevalence of OA and OP in patients with HH by C282Y homozygosity and compound heterozygosity (C282Y/H63D) genotype.

Methods

A total of 306 patients with HH completed a questionnaire. Clinical and demographic characteristics and presence of OA, OP and related complications were compared by genotype, adjusting for age, sex, body mass index (BMI), current smoking and menopausal status.

Results

In total, 266 of the 306 patients (87%) were homozygous for C282Y, and 40 (13%) were compound heterozygous. The 2 groups did not differ by median age [60 (interquartile range [IQR] 53 to 68) vs. 61 (55 to 67) years, P=0.8], sex (female: 48.8% vs. 37.5%, P=0.18) or current smoking habits (12.4% vs. 10%, P=0.3). As compared with compound heterozygous patients, C282Y homozygous patients had higher median serum ferritin concentration at diagnosis [1090 (IQR 610 to 2210) vs. 603 (362 to 950) µg/L, P<0.001], higher median transferrin saturation [80% (IQR 66 to 91%) vs. 63% (55 to 72%), P<0.001]) and lower median BMI [24.8 (22.1 to 26.9) vs. 26.2 (23.5 to 30.3) kg/m2, P<0.003]. The overall prevalence of self-reported OA was significantly higher with C282Y homozygosity than compound heterozygosity (53.4% vs. 32.5%; adjusted odds ratio [aOR] 2.4 [95% confidence interval 1.2–5.0]), as was self-reported OP (25.6% vs. 7.5%; aOR 3.5 [1.1–12.1]).

Conclusion

Patients with C282Y homozygosity may be at increased risk of musculoskeletal complications of HH.     

Expression of hereditary hemochromatosis C282Y HFE protein in HEK293 cells activates specific endoplasmic reticulum stress responses

Background  

Hereditary Hemochromatosis (HH) is a genetic disease associated with iron overload, in which individuals homozygous for the mutant C282Y HFE associated allele are at risk for the development of a range of disorders particularly liver disease. Conformational diseases are a class of disorders associated with the expression of misfolded protein. HFE C282Y is a mutant protein that does not fold correctly and consequently is retained in the Endoplasmic Reticulum (ER). In this context, we sought to identify ER stress signals associated with mutant C282Y HFE protein expression, which may have a role in the molecular pathogenesis of HH.     

A candidate gene for hemochromatosis: frequency of the C282Y and H63D mutations

The gene whose alteration causes hereditary hemochromatosis (HFE according to the international nomenclature) was, more than 20 years ago, shown to map to 6p21.3. It has since escaped all efforts to identify it by positional cloning strategies. Quite recently, a gene named HLA-H was reported as being responsible for the disease. Two missense mutations, Cys282Tyr (C282Y) and His63Asp (H63D), were observed, but no proof was produced that the gene described is the hemochromatosis gene. To validate this gene as the actual site of the alteration causing hemochromatosis, we decided to look for the two mutations in 132 unrelated patients from Brittany. Our results indicate that more than 92% of these patients are homozygous for the C282Y mutation, and that all 264 chromosomes but 5 carry either mutation. These findings confirm the direct implication of HLA-H in hemochromatosis. Received: 16 December 1996 / Accepted: 13 May 1997     

Prevalence of C282Y and H63D mutations in the haemochromatosis (HFE) gene in Tunisian population

The studies of the HFE mutations: H63D and C282Y in North African populations have revealed the extreme rarity or even the absence of the C282Y mutation. We have examined 1140 chromosomes (570 Tunisian people) for the presence of the two HFE mutations by PCR-RFLP analysis. We have found that the allele frequencies are, respectively, 15.17% (+/-2.1%) for the H63D and 0.09% (+/-0.17%) for the C282Y. These results are consistent with the worldwide spread of the H63D mutation and the north European restriction of the C282Y. This study will be completed by determining whether homozygote trait for H63D and associated risk factors (beta thalassémia) can lead to iron overload in Tunisia.     

Multicentric origin of hemochromatosis gene (HFE) mutations

Genetic hemochromatosis (GH) is believed to be a disease restricted to those of European ancestry. In northwestern Europe, >80% of GH patients are homozygous for one mutation, the substitution of tyrosine for cysteine at position 282 (C282Y) in the unprocessed protein. In a proportion of GH patients, two mutations are present, C282Y and H63D. The clinical significance of this second mutation is such that it appears to predispose 1%-2% of compound heterozygotes to expression of the disease. The distribution of the two mutations differ, C282Y being limited to those of northwestern European ancestry and H63D being found at allele frequencies>5%, in Europe, in countries bordering the Mediterranean, in the Middle East, and in the Indian subcontinent. The C282Y mutation occurs on a haplotype that extends 相似文献