Celtic origin of the C282Y mutation of hemochromatosis

The main hereditary hemochromatosis mutation C282Y in the HFE gene was recently described, and the C282Y frequencies were reported for various European populations. The aim of this synthesis is to compile the Y allele frequencies of the C282Y mutation for 40 European populations. The most elevated values are observed in residual Celtic populations in Ireland, the United Kingdom, and France, in accordance with the hypothesis of Simon et al. (1980) concerning a Celtic origin of the hereditary hemochromatosis mutation.     

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     

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.     

A rapid automated SSCP multiplex capillary electrophoresis protocol that detects the two common mutations implicated in hereditary hemochromatosis (HH)

Currently two mutations in the HFE gene are known to be associated with the manifestation of the autosomal recessive disorder hereditary hemochromatosis (HH). A single-base mutation resulting in Cys282Tyr appears to have a causative role in the development of the disease, and a point mutation resulting in His63Asp may also be involved. Recent observations with a fully automated capillary electrophoresis (CE) system (ABI Prism 310) suggested that this instrument could be used for the precise identification of known mutations based on single-strand conformation polymorphism (SSCP). Two DNA fragments, each specific for one of the HFE mutation sites and labeled with a different fluorophor, were coamplified and without further manipulation simultaneously analyzed by CE-SSCP. Wild-type samples showed a mobility pattern that was clearly distinguishable from homozygous Cys282Tyr, homozygous His63Asp, or a compound heterozygous sample. To evaluate the reliability of this system for the detection of both mutations, 20 samples were analyzed blind. All genotypes, which were called automatically, were in concordance with those obtained by a previously validated restriction fragment length polymorphism method. Thus, SSCP in combination with CE provides a fast and precise research tool for the simultaneous identification of the two common mutations implicated in HH. Received: 9 September 1998 / Accepted: 5 November 1998     

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.     

Congenital hypogonadotropic hypogonadism due to GnRH receptor mutations in three brothers reveal sites affecting conformation and coupling

Congenital hypogonadotropic hypogonadism (CHH) is characterized by low gonadotropins and failure to progress normally through puberty. Mutations in the gene encoding the GnRH receptor (GNRHR1) result in CHH when present as compound heterozygous or homozygous inactivating mutations. This study identifies and characterizes the properties of two novel GNRHR1 mutations in a family in which three brothers display normosmic CHH while their sister was unaffected. Molecular analysis in the proband and the affected brothers revealed two novel non-synonymous missense GNRHR1 mutations, present in a compound heterozygous state, whereas their unaffected parents possessed only one inactivating mutation, demonstrating the autosomal recessive transmission in this kindred and excluding X-linked inheritance equivocally suggested by the initial pedigree analysis. The first mutation at c.845 C>G introduces an Arg substitution for the conserved Pro 282 in transmembrane domain (TMD) 6. The Pro282Arg mutant is unable to bind radiolabeled GnRH analogue. As this conserved residue is important in receptor conformation, it is likely that the mutation perturbs the binding pocket and affects trafficking to the cell surface. The second mutation at c.968 A>G introduces a Cys substitution for Tyr 323 in the functionally crucial N/DPxxY motif in TMD 7. The Tyr323Cys mutant has an increased GnRH binding affinity but reduced receptor expression at the plasma membrane and impaired G protein-coupling. Inositol phosphate accumulation assays demonstrated absent and impaired Gα(q/11) signal transduction by Pro282Arg and Tyr323Cys mutants, respectively. Pretreatment with the membrane permeant GnRHR antagonist NBI-42902, which rescues cell surface expression of many GNRHR1 mutants, significantly increased the levels of radioligand binding and intracellular signaling of the Tyr323Cys mutant but not Pro282Arg. Immunocytochemistry confirmed that both mutants are present on the cell membrane albeit at low levels. Together these molecular deficiencies of the two novel GNRHR1 mutations lead to the CHH phenotype when present as a compound heterozygote.     

Hemochromatosis gene variants in three different ethnic populations: effects of admixture for screening programs

Genetic testing for hemochromatosis may have important implications for diagnosis and screening of the disease. However, the relative importance of mutations in the gene for hereditary hemochromatosis, HFE, may vary among populations, when the mutant allele frequencies and their penetrance in a particular genetic and environmental background are taken into account. We present data on the allele and genotype frequencies and population structure of two HFE genetic variants in three different ethnic groups from a highly mixed urban population (S?o Paulo, Brazil). Allele frequencies for both the C282Y and H63D HFE mutations showed significant differences among the studied populations (for the C282Y mutation, Euro-Brazilian 3.7%, admixed 0.7%, Afro-Brazilian 0.5%; and for the H63D mutation, Euro-Brazilian 20.3%, admixed 13.0%, Afro-Brazilian 6.4). The data substantiate a European origin for these mutations. Furthermore, they provide a basis for a more rational strategic planning of population screening programs for the disease.     

Penetrance of Hemochromatosis in HFE Genotypes Resulting in p.Cys282Tyr and p.[Cys282Tyr];[His63Asp] in the eMERGE Network

Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder associated with pathogenic HFE variants, most commonly those resulting in p.Cys282Tyr and p.His63Asp. Recommendations on returning incidental findings of HFE variants in individuals undergoing genome-scale sequencing should be informed by penetrance estimates of HH in unselected samples. We used the eMERGE Network, a multicenter cohort with genotype data linked to electronic medical records, to estimate the diagnostic rate and clinical penetrance of HH in 98 individuals homozygous for the variant coding for HFE p.Cys282Tyr and 397 compound heterozygotes with variants resulting in p.[His63Asp];[Cys282Tyr]. The diagnostic rate of HH in males was 24.4% for p.Cys282Tyr homozygotes and 3.5% for compound heterozygotes (p < 0.001); in females, it was 14.0% for p.Cys282Tyr homozygotes and 2.3% for compound heterozygotes (p < 0.001). Only males showed differences across genotypes in transferrin saturation levels (100% of homozygotes versus 37.5% of compound heterozygotes with transferrin saturation > 50%; p = 0.003), serum ferritin levels (77.8% versus 33.3% with serum ferritin > 300 ng/ml; p = 0.006), and diabetes (44.7% versus 28.0%; p = 0.03). No differences were found in the prevalence of heart disease, arthritis, or liver disease, except for the rate of liver biopsy (10.9% versus 1.8% [p = 0.013] in males; 9.1% versus 2% [p = 0.035] in females). Given the higher rate of HH diagnosis than in prior studies, the high penetrance of iron overload, and the frequency of at-risk genotypes, in addition to other suggested actionable adult-onset genetic conditions, opportunistic screening should be considered for p.[Cys282Tyr];[Cys282Tyr] individuals with existing genomic data.     

The hemochromatosis 845 G-->A and 187 C-->G mutations: prevalence in non-Caucasian populations.

Hemochromatosis, the inherited disorder of iron metabolism, leads, if untreated, to progressive iron overload and premature death. The hemochromatosis gene, HFE, recently has been identified, and characterization of this gene has shown that it contains two mutations that result in amino acid substitutions-cDNA nucleotides 845 G-->A (C282Y) and 187 C-->G (H63D). Although hemochromatosis is common in Caucasians, affecting >=1/300 individuals of northern European origin, it has not been recognized in other populations. The present study used PCR and restriction-enzyme digestion to analyze the frequency of the 845 G-->A and 187 C-->G mutations in HLA-typed samples from non-Caucasian populations, comprising Australian Aboriginal, Chinese, and Pacific Islanders. Results showed that the 845 G-->A mutation was present in these populations (allele frequency 0.32%), and, furthermore, it was always seen in conjunction with HLA haplotypes common in Caucasians, suggesting that 845 G-->A may have been introduced into these populations by Caucasian admixture. 187 C-->G was present at an allele frequency of 2.68% in the two populations analyzed (Australian Aboriginal and Chinese). In the Australian Aboriginal samples, 187 C-->G was found to be associated with HLA haplotypes common in Caucasians, suggesting that it was introduced by recent admixture. In the Chinese samples analyzed, 187 C-->G was present in association with a wide variety of HLA haplotypes, showing this mutation to be widespread and likely to predate the more genetically restricted 845 G-->A mutation.     

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   

Ancestral association between HLA and HFE H63D and C282Y gene mutations from northwest Colombia

A significant association between HFE gene mutations and the HLA-A*03-B*07 and HLA-A*29-B*44 haplotypes has been reported in the Spanish population. It has been proposed that these mutations are probably connected with Celtic and North African ancestry, respectively. We aimed to find the possible ancestral association between HLA alleles and haplotypes associated with the HFE gene (C282Y and H63D) mutations in 214 subjects from Antioquia, Colombia. These were 18 individuals with presumed hereditary hemochromatosis (“HH”) and 196 controls. The HLA-B*07 allele was in linkage disequilibrium (LD) with C282Y, while HLA-A*23, A*29, HLA-B*44, and B*49 were in LD with H63D. Altogether, our results show that, although the H63D mutation is more common in the Antioquia population, it is not associated with any particular HLA haplotype, whereas the C282Y mutation is associated with HLA-A*03-B*07, this supporting a northern Spaniard ancestry.     

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.     

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.     

Common variants in the BMP2, BMP4, and HJV genes of the hepcidin regulation pathway modulate HFE hemochromatosis penetrance

Most cases of genetic hemochromatosis (GH) are associated with the HFE C282Y/C282Y (p.Cys282Tyr/p.Cys282Tyr) genotype in white populations. The symptoms expressed by C282Y homozygotes are extremely variable. Only a few suffer from an overt disease. Several studies have suggested that, in addition to environmental factors, a genetic component could explain a substantial part of this phenotypic variation, although very few genetic factors have been identified so far. In the present study, we tested the association between common variants in candidate genes and hemochromatosis penetrance, in a large sample of C282Y homozygotes, using pretherapeutic serum ferritin level as marker of hemochromatosis penetrance. We focused on two biologically relevant gene categories: genes involved in non-HFE GH (TFR2, HAMP, and SLC40A1) and genes involved in the regulation of hepcidin expression, including genes from the bone morphogenetic protein (BMP) regulatory pathway (BMP2, BMP4, HJV, SMAD1, SMAD4, and SMAD5) and the IL6 gene from the inflammation-mediated regulation pathway. A significant association was detected between serum ferritin level and rs235756, a common single-nucleotide polymorphism (SNP) in the BMP2 genic region (P=4.42x10-5). Mean ferritin level, adjusted for age and sex, is 655 ng/ml among TT genotypes, 516 ng/ml in TC genotypes, and 349 ng/ml in CC genotypes. Our results further suggest an interactive effect on serum ferritin level of rs235756 in BMP2 and a SNP in HJV, with a small additive effect of a SNP in BMP4. This first reported association between common variants in the BMP pathway and iron burden suggests that full expression of HFE hemochromatosis is linked to abnormal liver expression of hepcidin, not only through impairment in the HFE function but also through functional modulation in the BMP pathway. Our results also highlight the BMP regulation pathway as a good candidate for identification of new modifier genes.     

Genetic hematology of french basques: recent data about this peculiar pyrenean people

The Basques demonstrate marked specificities regarding language, genetics and culture among all European populations. They live at the Western end of the Pyrenees along the Atlantic Ocean and are thought to represent the descendants of the Upper-Palaeolithic men. We have investigated French Basques for several genetic hematology markers including hemotypology (ABO and Rhesus groups) and inherited diseases such as genetic hemochromatosis (iron overload mainly related to the C282Y mutation), factor V Leiden (the most important inherited prothrombotic risk factor among Europeans) and coagulation factors deficiency. We found that this population has vonserved its peculiar hemotypology profile described many decades ago but with interprovince heterogeneity. The C282Y mutation was less prevalent than in European neighbouring populations and we noted a quasi-absence of factor V Leiden. In contrast, an unusual high frequency of factor XI deficiency (a rare coagulation condition worldwide) was evidenced and associated with the still unpublished Cys38Arg mutation, this finding being suggestive of a founder effect. Our results, interpreted in the view of population genetics, could contribute to a better understanding of the history of the Basque people.     

Hemochromatosis gene sequence deviations in German patients with porphyria cutanea tarda

Patients with porphyria cutanea tarda (PCT) reveal a susceptibility to reversible inactivation of hepatic uroporphyrinogen decarboxylase, which might be triggered by alcohol, hepatitis C virus infection, and iron overload. Inherited factors that may predispose to clinically overt PCT also include sequence deviations in the HFE gene that is mutated in classical hemochromatosis. Here, we studied the prevalence of both common and rare hemochromatosis gene variations in 51 PCT patients and 54 healthy controls of German origin. The frequency of the common HFE gene mutation C282Y was 15.7 % in PCT patients and 2.8 % in healthy control individuals (P < 0.001). By contrast, the frequencies of the common H63D mutation did not differ, and the allele frequencies of the less frequently observed sequence deviations as substitution S65C in the HFE gene and mutation Y250X in the TFR2 gene underlying hemochromatosis type 3 (HFE3) were < 0.02 both in PCT patients and controls. Our results comprise the first molecular studies of both common and rare hemochromatosis gene variants in German PCT patients, indicating a significant role of the C282Y mutation in the pathogenesis of PCT.     

HLA-H and associated proteins in patients with hemochromatosis.

BACKGROUND: The 845A(C282Y) mutation in the HLA-H gene accounts for most cases of hereditary hemochromatosis in patients who are of European origin. Some lack this mutation, however, and it is not present in Asian patients. Thus, other mutations either in HLA-H or associated proteins may be present in such patients. HLA-H associates with beta-2-microglobulin. Calreticulin associates with class 1 HLA proteins and appears to be identical with mobilferrin, a putative iron transport protein. These two proteins are therefore candidates for mutations in patients with hemochromatosis. MATERIALS AND METHODS: We have sequenced the coding region and parts of introns of the HLA-H gene, the beta-2-microglobulin gene, and the calreticulin (mobilferrin) gene of 10, 7, and 5 hemochromatosis patients, respectively, selecting those who were not homozygous for the 845A(C282Y) mutation. The number of chromosomes at risk studied were 18 for HLA-H, 14 for beta-2-microglobulin and 10 for calreticulin. RESULTS: We detected 3 new intronic polymorphisms in the HLA-H gene, each a point mutation. Some differences from published sequences of beta-2-microglobulin and calreticulin were documented, but these were uniformly present in all samples. CONCLUSIONS: The lack of additional mutations in the HLA-H gene is remarkable, and we speculate that the C282Y mutation may be a gain-of-function change.     

Porphyria cutanea tarda: the etiological importance of mutations in the HFE gene and viral infection is population-dependent.

A number of factors, including increased iron stores and alcohol consumption, are known to be associated with the development of porphyria cutanea tarda (PCT) in susceptible individuals. Recent reports have described a significant association between inheritance of the C282Y and H63D mutations in the HFE gene, associated with genetic hemochromatosis (GH) and PCT. A strong association between hepatitis C virus infection and PCT has also been demonstrated, while case reports record a link between human immunodeficiency virus (HIV) and PCT. We have investigated the frequency of these factors in a racially-mixed population of patients with PCT in Cape Town, South Africa. 57 patients with PCT drawn from three ethnic groups were screened for the presence of the C282Y and H63D mutations linked to GH, and the prevalences were compared with corresponding healthy control populations. The seroprevalence of markers for HCV, hepatitis B (HBV) and HIV infection were examined in 28 of these. In the control populations, we found that both the C282Y and H63D mutations are highly prevalent in South Africans of European origin. In a population of mixed or Asian origin, the C282Y mutation is very rare whereas the H63D mutation is common. Neither mutation was encountered in any African subject. Both mutations are associated with PCT, but the association is dependent on the ethnic origins of the population to which the patient belongs. In contrast to other studies, HCV infection is numerically unimportant in PCT in our patients. HIV infection is increasingly encountered in our patients with PCT, but the strength of the association cannot be determined in view of the high background prevalence of HIV infection in some sectors of the South African population. The contribution of specific risk factors may be heavily dependent on the population from which patients are drawn, and care should be taken in extrapolating from observations in one racial or geographic population to any other.     

Linkage disequilibrium between the four most common cystic fibrosis mutations and microsatellite haplotypes in the Celtic population of Brittany

Microsatellite haplotypes were determined for 117 chromosomes carrying the four most frequent mutations in the cystic fibrosis (CF) gene identified in the Breton population of Celtic origin, as well as for 83 normal chromosomes (noncarriers of a CF mutation). Each of the three non-ΔF508 mutations was associated with a single haplotype: 1078delT with 16-31-13, G551D with 16-7-17, and W846X with 16-32-13. Although these results suggest identity-by-descent for each mutation, recurrent mutations, although unlikely, could not be completely ruled out. The four most frequent haplotypes on normal chromosomes and the three most frequent haplotypes on ΔF508 chromosomes are the same as those found in Ireland, Spain, and Italy. This suggests that some haplotypes, associated or not with the ΔF508 mutation, were present in an ancestral population from which all four populations descended. Received: 27 November 1995 / Revised: 1 February 1996     

Haemochromatosis gene mutations in Finns, Swedes and Swedish Saamis

Frequencies of three different mutant haemochromatosis (HFE) alleles (282Tyr, 63Asp and 65Cys) were studied in three northern European populations, i.e. Finns, Swedes and Swedish Saamis. In Finns and Swedes the allele frequencies were within the range found in other populations from northern and western Europe. The Saamis differed from the Swedes with respect to all mutant alleles. Lower frequencies compared to Swedes were found for the 282Tyr (p = 0.0046) and 63Asp (p = 0.034) alleles, whereas the frequency of the 65Cys allele was higher (p = 0.046) in the Saamis. The total distribution of HFE alleles in Saamis showed a highly significant difference from that in Swedes (chi2 = 16.7, 3 d.f., p = 0.0008). These results further underline the genetic uniqueness of the Saamis.