HFE codon 63/282 (H63D/C282Y) dimorphism in German patients with genetic hemochromatosis

Quantification of liver iron overload disease with laser ablation inductively coupled plasma mass spectrometry

BACKGROUND

Hereditary hemochromatosis is the most frequent, identified, genetic disorder in Caucasians affecting about 1 in 1000 people of Northern European ancestry, where the associated genetic defect (homozygosity for the p.Cys282Tyr polymorphism in the HFE gene) has a prevalence of approximately 1:200. The disorder is characterized by excess iron stores in the body. Due to the incomplete disease penetrance of disease-associated genotype, genetic testing and accurate quantification of hepatic iron content by histological grading of stainable iron, quantitative chemical determination of iron, or imaging procedures are important in the evaluation and staging of hereditary hemochromatosis.

METHODS

We here established novel laser ablation inductively coupled plasma mass spectrometry protocols for hepatic metal bio-imaging for diagnosis of iron overload.

RESULTS

We demonstrate that these protocols are a significant asset in the diagnosis of iron overload allowing iron measurements and simultaneous determination of various other metals and metalloids with high sensitivity, spatial resolution, and quantification ability.

CONCLUSIONS

The simultaneous measurement of various metals and metalloids offers unique opportunities for deeper understanding of metal imbalances. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a highly powerful and sensitive technique for the analysis of a variety of solid samples with high spatial resolution. We conclude that this method is an important add-on to routine diagnosis of iron overload and associated hepatic metal dysbalances resulting thereof.

Prevalence of 845G>A HFE mutation in Slavic populations: an east-west linear gradient in South Slavs

AIM

To compare A allele frequencies of the 845G>A mutation of 10 Slavic populations in central, eastern, and southern Europe between each other and with other European populations.

METHODS

The 845G>A mutation from the DNA of 400 Polish neonates collected in 2005-2006 was analyzed by polymerase chain reaction-restriction fragment length polymorphism. The data were compared with reports from other countries.

RESULTS

We identified 381 GG homozygotes, 18 GA heterozygotes, and 1 AA homozygote. The 845A allele frequency was 2.5%, which makes the summary figure for Poland from this and previous studies 3.5%. The average prevalence for Poland and other West Slavic countries was 3.6%, similar to Russia (inhabited by the East Slavs, 3.5%). The average prevalence in South Slavic countries was 2.2%, gradually decreasing from 3.6% in Slovenia to 0% in Bulgaria, with a longitudinal linear gradient (adjusted R(2)=0.976, P<0.001).

CONCLUSIONS

The West and East Slavs, together with Finland, Estonia, Germany, Austria, Hungary, Slovenia, and Croatia, form a group with 845A allele frequencies between 3% and 4%. In the South Slavs, there is a gradual decline in the prevalence of 845A allele from northwest to southeast, with a surprisingly exact east-west linear gradient.

Hemochromatosis genotypes and risk of iron overload--a meta-analysis

PURPOSE

The incomplete phenotypic penetrance of high iron Fe genotypes in relation to hemochromatosis poses a practical problem in the interpretation of the genotyping results by clinicians. We carried out meta-analyses of the associations between hemochromatosis genotypes C282Y/C282Y, C282Y/H63D, C282Y/wild-type, H63D/H63D, H63D/wild-type, versus wild-type/wild-type and iron overload, both provisional (elevated serum iron markers) and documented (elevated serum iron markers associated with evidence of iron excess based on liver biopsy and/or quantitative phlebotomy).

METHODS

After reviewing 3572 article titles and evaluating 92 articles in detail, odds ratios were pooled from 43 study populations (9986 cases and 25,492 controls) using a random-effects model.

RESULTS

Homozygosity for either variant or compound heterozygosity was associated with both provisional and documented iron overload. Single heterozygosity conferred no risk for elevated hepatic iron index and/or mobilizable iron by quantitative phlebotomy. In patients with clinical hereditary hemochromatosis, no evidence of provisional and documented iron overload with transferrin saturation (TS) values greater than 55% was evidenced for C282Y and H63D single heterozygotes whereas documented iron overload including TS of 45% to 50% was weakly associated with C282Y/wild-type genotype; H63D/H63D genotype was not associated with documented iron overload in patients with TS values of 45% to 50%.

CONCLUSIONS

The results, mainly from case-control studies, cannot necessarily be extrapolated to the general population.

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.

HFE C282Y heterozygosity in hepatocellular carcinoma: evidence for an increased prevalence

BACKGROUND & AIMS

Iron overload is observed frequently in chronic liver disease, and some studies have suggested that chronic iron overload may contribute to the pathogenesis of hepatocellular carcinoma (HCC). Heterozygosity for hereditary hemochromatosis (HH) is associated with increased body iron stores. The discovery of the HH gene HFE has enabled identification of the heterozygote status. The aim of this study was to evaluate if heterozygosity for HH is a risk factor for HCC.

METHODS

The C282Y and the H63D mutation of the HFE gene were analyzed in 137 patients with HCC and no history of HH, 107 patients with cirrhosis without HCC and 126 healthy controls. Hepatic iron content was measured by using a semiquantitative histologic score.

RESULTS

Seventeen of 137 HCC patients (12.4%) were C282Y heterozygote, compared with only 4 of 107 (3.7%) cirrhotic patients without HCC and 6 of 126 (4.8%) healthy controls (P < 0.05). The frequency of the H63D mutation showed no significant differences. C282Y heterozygote HCC patients had significantly higher levels of serum ferritin and transferrin saturation than C282Y wild-type patients (793 +/- 122 vs. 355 +/- 23 ng/mL, and 42.3% +/- 7.3% vs. 29.2% +/- 1.7%, respectively), and significantly higher iron deposition in HCC as well as in nontumorous liver tissue.

CONCLUSIONS

The C282Y heterozygous genotype is significantly more common in HCC patients and is associated with significantly increased intrahepatic iron deposition and systemic iron stores. These results suggest that C282Y heterozygosity plays a role in liver iron deposition and could contribute to hepatocarcinogenesis via the accumulation of potentially carcinogenic iron. These findings may have implications for HCC screening and prevention strategies.

Non-invasive liver iron quantification by SQUID-biosusceptometry and serum ferritin iron as new diagnostic parameters in hereditary hemochromatosis

In the HFE-gene era, precise diagnostic parameters remain important to characterize individual iron stores, because the indication for therapy and prognosis are mainly related to the extent of iron loading. The frequently used serum ferritin interferes with non-iron related factors such as inflammation and may produce falsely positive values. We used a SQUID-biosusceptometer in a large series of patients (n = 679) to measure liver iron concentration in the differential diagnosis and therapy control of hereditary hemochromatosis (SQUID = superconducting quantum interference device). This truly non-invasive technique is sensitive, reliable, fast (online results), and also cost-effective when compared to invasive liver biopsy. Recently, ferritin iron content was propagated as a better parameter than ferritin protein. However, we found a poor correlation between ferritin iron and individual liver iron concentrations in patients with iron overload. Ferritin iron saturation varied in a range between 3 and 10%, independent from liver iron concentration. No differences were found between patients with hemochromatosis and secondary iron overload disease. Only patients with liver cell damage had increased ferritin iron saturations. In conclusion the diagnostic values of serum ferritin protein and iron to assess iron overload are limited.

HLA-A and -B alleles and haplotypes in hemochromatosis probands with HFE C282Y homozygosity in central Alabama

BACKGROUND

We wanted to quantify HLA-A and -B allele and haplotype frequencies in Alabama hemochromatosis probands with HFE C282Y homozygosity and controls, and to compare results to those in other populations.

METHODS

Alleles were detected using DNA-based typing (probands) and microlymphocytotoxicity (controls).

RESULTS

Alleles were determined in 139 probands (1,321 controls) and haplotypes in 118 probands (605 controls). In probands, A*03 positivity was 0.7482 (0.2739 controls; p = or < 0.0001; odds ratio (OR) 7.9); positivity for B*07, B*14, and B*56 was also increased. In probands, haplotypes A*03-B*07 and A*03-B*14 were more frequent (p < 0.0001, respectively; OR = 12.3 and 11.1, respectively). The haplotypes A*01-B*60, A*02-B*39, A*02-B*62, A*03-B*13, A*03-B*15, A*03-B*27, A*03-B*35, A*03-B*44, A*03-B*47, and A*03-B*57 were also significantly more frequent in probands. 37.3% of probands were HLA-haploidentical with other proband(s).

CONCLUSIONS

A*03 and A*03-B*07 frequencies are increased in Alabama probands, as in other hemochromatosis cohorts. Increased absolute frequencies of A*03-B*35 have been reported only in the present Alabama probands and in hemochromatosis patients in Italy. Increased absolute frequencies of A*01-B*60, A*02-B*39, A*02-B*62, A*03-B*13, A*03-B*15, A*03-B*27, A*03-B*44, A*03-B*47, and A*03-B*57 in hemochromatosis cohorts have not been reported previously.

A homozygous HFE gene splice site mutation (IVS5+1 G/A) in a hereditary hemochromatosis patient of Vietnamese origin

The vast majority of Caucasian patients presenting with hereditary hemochromatosis demonstrate a single homozygous missense mutation in the HFE gene (C282Y). The underlying genetic defects in hemochromatosis patients of non-Caucasian origin are largely unknown. A 48-year-old man of Vietnamese origin presented with insulin-dependent diabetes mellitus, tertiary adrenocortical insufficiency, and laboratory results highly indicative of hereditary hemochromatosis. Because the patient was negative for the known HFE gene mutations C282Y, H63D, and S65C HFE, the entire coding region and intron/exon boundaries of the HFE gene was investigated. Sequencing studies identified a homozygous G-to-A transition at position +1 of intron 5 (IVS5+1 G/A). This newly described mutation alters the invariant G at position +1 of the 5' splice site causing altered mRNA splicing and exon skipping with exon 4 being spliced to exon 6. Both heterozygously affected children (age 19 and 20 years) had moderately increased ferritin levels with normal serum iron concentration and transferrin saturation. The newly described mutation was not detected in a control group consisting of 220 Caucasian individuals as verified by allele-specific polymerase chain reaction. We describe for the first time a homozygous HFE splice site mutation (IVS5+1 G/A) in a non-Caucasian patient with hereditary hemochromatosis. Although the absence of this novel HFE gene mutation in Caucasian subjects suggests that the mutation is exclusive to this family, mutation screening in populations of different ethnic background is recommended to precisely define its contribution to hereditary hemochromatosis in non-Caucasian patients.

Detection of an unusual combination of mutations in the HFE gene for hemochromatosis

In the present paper, we describe an individual, found as part of a screening study, being homozygous for the C282Y mutation and at the same time heterozygous for the H63D mutation in the HFE gene. Identical results were obtained by three different methods, i.e., by PCR-RFLP, by sequencing, and by melting curve analysis. Thus, the common conception that the C282Y and the H63D mutations are mutually exclusive is not valid. Clinical symptoms and laboratory data on the individual were similar to hemochromatosis patients homozygous for the C282Y mutation. The implications of our finding for diagnostic analytical laboratory procedures are briefly discussed.

Frequency analysis and allele map in favor of the celtic origin of the C282Y mutation of hemochromatosis

After the main hereditary hemochromatosis mutation C282Y in the HFE gene was described, we report here the C282Y frequencies for various European populations. The aim of this meta-analysis is to compile the Y allele frequencies of the C282Y mutation for 53 European populations, representing a total of 9265 unrelated people representing control samples. The most elevated values are observed in residual Celtic populations in Ireland, in the United Kingdom, and in France, in accordance with the initial hypothesis of Simon et al. (Prog. Med. Genet. 4, 135-168, 1980) concerning a Celtic origin of the hereditary hemochromatosis mutation.

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.

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.

Large-scale screening for HFE mutations: methodology and cost

Large-scale detection of mutations at the DNA level requires the development of cost-effective methods for the screening of thousands of samples. Hemochromatosis is an appropriate testing ground for the development of such technologies, and we report the methods that we have developed to screen large numbers of samples using equipment available in most laboratories. We are able to examine DNA samples for two mutations in the HFE gene at a cost of only slightly over $8 per sample, a cost that includes overhead and the approximately 40 hr per week of technician time required to perform the studies. The technologies involved in mutation analysis are evolving rapidly and ultimately more highly automated, lower-cost technologies may become available. At present, however, we find the methodology described to be very suitable for large-scale, low-cost mutation screening.

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.

Detection of C282Y and H63D in the HFE gene

The gene for hemochromatosis was identified in 1996 and two mutations were found. Homozygosity for one of these, C282Y, is associated with hemochromatosis in a high percentage of patients. Genetic analysis of patient DNA is, therefore, a very useful tool to aid and confirm diagnosis and to screen asymptomatic relatives of patients to identify those at risk of developing this common, easily treated disease.

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.

Iron-overload and genotypic expression of HFE mutations H63D/C282Y and transferrin receptor Hin6I and BanI polymorphism in german patients with hereditary haemochromatosis

Gene variations of HFE, a HLA-class I like molecule, are highly associated with hereditary haemochromatosis (HH). Functional as well as molecular studies of the HFE protein have indicated that the molecule is involved in iron metabolism and that the HFE gene variations observed among HH patients affect its interaction with the transferrin receptor (TfR). In the present study, we have therefore analysed the relationship between the HFE gene variants, C282Y and H63D, and body iron status among 85 German HH patients. In addition, two TfR gene polymorphism, TfR-Hin6I and TfR-BanI, were typed that have been reported to define ethnically distinct haplotypes. As controls we used 251/159 healthy German blood donors. Seventy-eight (92%) patients were C292Y homozygous, the H63D mutation was present in five (6%) patients with none of the patients being H63D homozygous. Serum transferrin, transferrin saturation and liver iron content were determined prior to therapeutic intervention. Among C282Y homozygous patients serum ferritin levels (2294 +/- 3174 vs. 463 +/- 224 microg L-1, P < 0.0001) and transferrin saturation (86 +/- 18% vs. 62 +/- 25%, P = 0.048) were elevated significantly compared with C282Y and/or H63D heterozygous patients. In addition, the liver iron content (291 +/- 165 vs. 138 +/- 95 micromol g-1, P = 0.028) and liver iron index (6.4 +/- 2.8 vs. 3.2 +/- 2.3, P = 0.019) were increased among C282Y homozygotes compared with C282Y heterozygotes. In contrast, no difference was observed between patients and controls regarding the distribution of TfR-Hin6I and TfR-BanI alleles. These data indicate that the iron intake is higher among C282Y homozygous patients compared with C282Y heterozygous or C282Y/H63D compound heterozygous individuals and supports the functional role of the HFE protein in iron metabolism whereas the TfR gene variants seem to have no influence on iron uptake.

HFE genotypes and haemochromatosis: quantifying the risks of disease

Hereditary haemochromatosis (HH) is an autosomal recessive disease involving mutations in the recently characterised HFE gene linked to HLA-A in the major histocompatibility complex. The known HFE polymorphisms include the wild-type allele, a G-->A substitution at base 845 (845A) and a C-->G substitution at position 187 (187G). Although most cases of HH are accountable by homozygosity of the 845A allele the exact risk of other HFE genotypes, especially those involving the 187G allele has not been determined. We have compiled estimates of disease risk for all known HFE genotypes by re-analyzing published studies. The data show a hierarchical risk calculated as odds ratio (OR) for each genotype 845A/ 845A (OR=2101); 845A/187G (OR=24); 187G/187G (OR=9); 845A/Wt (OR=5); 187G/Wt (OR=2). Interestingly, the disease risk of 187G-genotypes suggests that subtle functional changes in the HFE product can interact with other genetic factors (e.g. trans allele, gender) and environmental factors (e.g. diet) to manifest either as clinical disease, altered iron stores or a normal phenotype. This paradigm is potentially useful in understanding the contribution of HLA alleles to risk of various disorders especially autoimmunity.

Prevalence of the C282Y and H63D mutations in the HFE gene in patients with hereditary haemochromatosis and in control subjects from Northern Germany

Mutation analysis was performed for two HFE mutations (C282Y, H63D) in unrelated patients with hereditary haemochromatosis (n = 92), family members of patients (n = 34), and unrelated controls (n = 157) from Northern Germany, 87/92 patients (94.6%) revealed the C282Y mutation in homozygous form, five were heterozygous. No H63D mutation was found in 174 chromosomes of patients homozygous for C282Y, whereas four of the heterozygote patients also carried the H63D mutation. Among the control group, 9.6% were heterozygotes for C282Y. 2/157 subjects were homozygous, 37/157 were heterozygous for the H63D mutation, but showed no signs of iron overload.

Celtic origin of the C282Y mutation of hemochromatosis

The C282Y mutation in the HFE gene is the main mutation causing hemochromatosis, and C282Y frequencies have been reported for various European populations. The aim of this review is to compile the Y allele frequencies of the C282Y mutation for twenty European populations. The most elevated value (6.88%) is observed in residual Celtic populations in UK and France, in accordance to the hypothesis of Simon et al. concerning a Celtic origin of the hereditary hemochromatosis mutation.

Determination of gene frequencies for two common haemochromatosis mutations in the Danish population by a novel polymerase chain reaction with sequence-specific primers

Hereditary haemochromatosis (HH), a condition of abnormal iron metabolism which leads to iron overload and organ damage, previously known as bronze diabetes or idiopathic haemochromatosis, is the most common disease-producing genetic disorder among Europeans. Two mutations, C282Y and H63D, are described for the candidate gene, HFE, reported as being responsible for the disease. Since molecular testing of these mutations will be of value in early diagnosis of haemochromatosis, the aim of this study was to develop a simple, fast and inexpensive technique for the determination of the polymorphism in the HFE gene on a large scale. We designed sequence-specific primers for polymerase chain reaction (PCR-SSP) and tested 200 randomly selected healthy Danes and found the result completely comparable to results obtained by a previously described method, PCR-RFLP. The gene frequencies in the Danish population are similar to reported results for the White population, with a frequency of 0.068 for the C282Y mutation and a frequency of 0.128 for the H63D mutation.