Cys282Tyr Mutation Research Articles

Osteoporosis in an elderly man as interplay of multiple diseases

Osteoporosis continues to be overlooked in men. In this population, osteoporosis is often related to corticosteroid use, alcohol abuse and hypogonadism. Osteoporosis-related fractures often result in long-term hospitalization with a consequent decline in quality of life. Bone mass density (BMD) in the aging male population is positively associated with endogenous androgen and estrogen levels, and testosterone treatment improves bone mineralization in hypogonadal men. Type 1 hereditary hemochromatosis (HH), is an autosomal recessive disorder associated with a mutation of the HFE (high iron Fe, hemochromatosis) gene, leading to a progressive iron overload which impairs the function of many organs. HH is an unusual cause of hypogonadotropic hypogonadism. In addition, hemochromatosis per se causes significant bone loss that cannot be solely explained by hypogonadism. A 71-year-old man was referred to our endocrinology unit from the Center of Metabolic Bone Diseases of our hospital for the finding of undetectable testosterone levels during screening for osteoporosis 1 year earlier. His family history was unremarkable; by contrast, the patient’s anamnesis was remarkable for type 2 diabetes mellitus, which had been satisfactorily treated with insulin therapy during the last 10 years, and longstanding (~50 years) epilepsy, treated with phenobarbital 150 mg/day. In addition, the patient reported phlebotomies and chelation therapies for “high iron levels” 20 years earlier, which had been withdrawn for poor compliance and tolerance. Over the last 2 years, the patient had been complaining of asthenia and worsening back pain; the latter was treated with analgesics. Targeted anamnesis ascertained no libido or erections and absence of sexual intercourses dating back many years. Previous examinations included computed tomography (CT) of the spine which showed osteoarthritis and thinning of the lumbar vertebrae secondary to osteoporosis, and dual-energy X-ray absorptiometry (DXA) scan which evidenced markedly reduced BMD both in the lumbar spine (0.8 g/cm, T-score -3.6) and in the proximal femur neck (0.57 g/cm, T-score -4). Secondary hyperparathyroidism characterized by increased parathyroid hormone levels, normal calcium levels (corrected for albumin) of 9.3 mg/dL (normal range 8.5–10.5) and 25-OH vitamin D deficiency (Table 1), and undetectable testosterone levels had been ascertained. Current therapy included alendronate 70 mg/week, colecalciferol 7500 IU/week and analgesics. On physical evaluation, the patient looked pale, had no axillary or pubic hair, and markedly decreased testis volume. Further laboratory evaluations were undertaken and abnormal values are shown in Table 1. Severe hypogonadotropic hypogonadism, normochromic normocytic anemia and increased iron levels were found. No testosterone response was observed after human chorionic gonadotropin (hCG; 2000 IU i.m.) testing. Dual-energy X-ray absorptiometry scan showed an improvement in BMD only in the lumbar spine (0.84 g/cm, T-score -3.3, +3.4% vs baseline). Contrast-enhanced magnetic resonance imaging (MRI) of the pituitary gland was unremarkable. Testosterone gel 50 mg/day was started; this normalized testosterone levels (5–6 ng/mL) over months, improved libido and sexual capability, and reduced asthenia. Lipids and liver function did not change over time and anemia reversed. DXA scan performed 1 year later (during which time also bisphosphonate and vitamin D therapy were continued) showed a significant BMD increase at both lumbar (+11.4% increase vs baseline) and femur (+5.9% increase vs baseline) levels. Owing to the clinical history, the patient was referred to the Center for Iron Overload Diseases of our hospital. Markedly increased ferritin and increased percent of transferrin saturation levels were found (Table 1). Genetic testing of the HFE gene showed the homozygous p.C282Y (Cys282Tyr) mutation. The final diagnosis was type 1 HH. Measurement of liver Geriatr Gerontol Int 2011; 11: 123–126

A Phase 1/2, Dose-Escalation Trial of Deferasirox for the Treatment of Iron Overload in HFE -Related Hereditary Hemochromatosis

Hereditary hemochromatosis (HH) is characterized by increased intestinal iron absorption that may result in iron overload. Although phlebotomy is widely practiced, it is poorly tolerated or contraindicated in patients with anemias, severe heart disease, or poor venous access, and compliance can vary. The once-daily, oral iron chelator, deferasirox (Exjade) may provide an alternative treatment option. Patients with HH carrying the HFE gene who were homozygous for the Cys282Tyr mutation, serum ferritin levels of 300-2000 ng/mL, transferrin saturation ≥45%, and no known history of cirrhosis were enrolled in this dose-escalation study to characterize the safety and efficacy of deferasirox, comprising a core and an extension phase (each 24 weeks). Forty-nine patients were enrolled and received starting deferasirox doses of 5 (n = 11), 10 (n = 15), or 15 (n = 23) mg/kg/day. Adverse events were generally dose-dependent, the most common being diarrhea, headache, and nausea (n = 18, n = 10, and n = 8 in the core and n = 1, n = 1, and n = 0 in the extension, respectively). More patients in the 15 mg/kg/day than in the 5 or 10 mg/kg/day cohorts experienced increases in alanine aminotransferase and serum creatinine levels during the 48-week treatment period; six patients had alanine aminotransferase >3× baseline and greater than the upper limit of normal range, and eight patients had serum creatinine >33% above baseline and greater than upper limit of normal on two consecutive occasions. After receiving deferasirox for 48 weeks, median serum ferritin levels decreased by 63.5%, 74.8%, and 74.1% in the 5, 10, and 15 mg/kg/day cohorts, respectively. In all cohorts, median serum ferritin decreased to <250 ng/mL. Conclusion: Deferasirox doses of 5, 10, and 15 mg/kg/day can reduce iron burden in patients with HH. Based on the safety and efficacy results, starting deferasirox at 10 mg/kg/day appears to be most appropriate for further study in this patient population. (Hepatology 2010)

Defective Bone Morphogenic Protein Signaling Underlies Hepcidin Deficiency in HFE Hereditary Hemochromatosis

Hereditary hemochromatosis (HH) is a common inherited iron overload disorder. The vast majority of patients carry the missense Cys282Tyr mutation of the HFE gene. Hepcidin, the central regulator of iron homeostasis, is deficient in HH, leading to unchecked iron absorption and subsequent iron overload. The bone morphogenic protein (BMP)/small mothers against decapentaplegic (Smad) signaling cascade is central to the regulation of hepcidin. Recent data from HH mice models indicate that this pathway may be defective in the absence of the HFE protein. Hepatic BMP/Smad signaling has not been characterized in a human HFE-HH cohort to date. Hepatic expression of BMP/Smad-related genes was examined in 20 HFE-HH males with significant iron overload, and compared to seven male HFE wild-type controls using quantitative real-time reverse transcription polymerase chain reaction. Hepatic expression of BMP6 was appropriately elevated in HFE-HH compared to controls (P = 0.02), likely related to iron overload. Despite this, no increased expression of the BMP target genes hepcidin and Id1 was observed, and diminished phosphorylation of Smad1/Smad5/Smad8 protein relative to iron burden was found upon immunohistochemical analysis, suggesting that impaired BMP signaling occurs in HFE-HH. Furthermore, Smad6 and Smad7, inhibitors of BMP signaling, were up-regulated in HFE-HH compared to controls (P = 0.001 and P = 0.018, respectively). New data arising from this study suggest that impaired BMP signaling underlies the hepcidin deficiency of HFE-HH. Moreover, the inhibitory Smads, Smad6, and Smad7 are identified as potential disruptors of this signal and, hence, contributors to the pathogenesis of this disease.

THE EFFECT OF COLCHICINE ON MEIOSIS IN ALLIUM

We described in the paper a new high-throughput screening method for Cys282Tyr mutation in hereditary haemochromatosis with double-stranded probe using synchronous fluorometry. The probe for wild type was labeled with Fam, the probe for mutant type was labeled with Joe. After PCR, reaction tubes were transferred to a spectrofluorometer, where synchronous spectra were scanned in a constant-wavelength mode. The genotype could be obtained through the appearance of the fluorescence peaks corresponding to each probe. The results were totally in agreement with restriction endonuclease analysis. Considering the simplicity,low cost and specificity, this approach could be generally applied to detect varieties of gene mutations.

HFE Cys282Tyr homozygotes with serum ferritin concentrations below 1000 microg/L are at low risk of hemochromatosis.

Hemochromatosis gene (HFE)-associated hereditary hemochromatosis (HH) is a genetic predisposition to iron overload and subsequent signs and symptoms of disease that potentially affects approximately 80,000 persons in Australia and almost 1 million persons in the United States. Most clinical cases are homozygous for the Cys282Tyr (C282Y) mutation in the HFE gene, with serum ferritin (SF) concentration >1000 microg/L as the strongest predictor of cirrhosis. The optimal treatment regimen for those with SF concentrations above the normal range but <1000 microg/L is unknown. We assessed HFE mutations in a prospective cohort of 31,192 participants of northern European descent, aged 40-69 years. An HFE-stratified random sample of 1438 participants including all C282Y homozygotes with iron studies 12 years apart were examined by physicians blinded to participants' HFE genotype. All previously undiagnosed C282Y homozygotes (35 male, 67 female) and all HFE wild-types (131 male, 160 female) with baseline and follow-up SF concentrations <1000 microg/L were assessed for HH-associated signs and symptoms including abnormal second/third metacarpophalangeal joints (MCP2/3), raised liver enzymes, hepatomegaly, and self-reported liver disease, fatigue, diabetes mellitus, and use of arthritis medication. The prevalence of HH-associated signs and symptoms was similar for C282Y homozygotes and HFE wild-types for both normal and moderately elevated SF concentrations. The maximum prevalence difference between HFE genotype groups with moderately elevated SF was 11% (MCP2/3, 95% confidence interval = -6%, 29%; P = 0.22) and for normal SF was 6% (arthritis medicine use, 95% confidence interval = -3%, 16%; P = 0.11). Previously undiagnosed C282Y homozygotes with SF concentrations that remain below 1000 microg/L are at low risk of developing HH-associated signs and symptoms at an age when disease would be expected to have developed. These observations have implications for the management of C282Y homozygotes.

Hereditary hemochromatosis and diabetes mellitus: implications for clinical practice

Hereditary hemochromatosis (HH) is a genetic condition that can lead to unregulated absorption of iron from the gut with resultant iron overload. The most common form of HH is caused by mutations in the HFE gene, with most cases of HH presenting in patients who are homozygous for the Cys282Tyr mutation. The prevalence of HFE gene mutations in persons of Northern European ancestry is fairly high (0.3-0.7% homozygous and 9-14% heterozygous for the Cys282Tyr mutation), but the penetrance of the disease is considered fairly low and is quite variable. While routine screening of the general population is not recommended, a targeted approach to screening in symptomatic patients and in those with a family member with iron overload is warranted. Untreated, iron overload can lead to considerable morbidity including liver cirrhosis, arthritis and diabetes mellitus, and increased mortality. The pathophysiology of diabetes mellitus in HH is thought to be due primarily to defects in the early insulin response to glucose. An Hfe(-/-) mouse model of HH has demonstrated defects in beta-cell function and beta-cell apoptosis that may be mediated by increased oxidative stress. Fortunately, these defects seem to be reversible if phlebotomy treatment is initiated before the development of cirrhosis or diabetes mellitus in patients. Further research into the long-term effects of treatment on prevention of diabetes mellitus in HH is needed.

Body Iron Stores and Glucose Intolerance in Premenopausal Women

OBJECTIVEIncreased serum ferritin levels and iron stores may be involved in the development of abnormal glucose tolerance in women presenting with obesity and/or polycystic ovary syndrome (PCOS). We aimed to study the determinants of serum ferritin levels in premenopausal women among indexes of insulin resistance, adiposity, hyperandrogenism, and genotypes pertaining to inflammation, oxidative stress, and iron metabolism.RESEARCH DESIGN AND METHODSA total of 257 premenopausal women, classified depending on the presence or absence of PCOS, obesity, and/or abnormal glucose tolerance, underwent a complete metabolic evaluation, serum ferritin, haptoglobin, and C-reactive protein (CRP) measurements, and genotyping for proinflammatory and prooxidant variants and mutations in the HFE gene.RESULTSSerum ferritin concentrations were increased in women presenting with PCOS and/or abnormal glucose tolerance, independent of obesity. A stepwise multivariate linear regression analysis (R2 = 0.18, P < 0.0001) retained menstrual dysfunction (β = 0.14, P = 0.035), free testosterone (β = 0.14, P = 0.052), insulin sensitivity index (β = −0.12, P = 0.012), the His63Asp variant in HFE (β = 0.16, P = 0.008), and abnormal glucose tolerance (β = 0.15, P = 0.015) as significant predictors of the logarithm of ferritin levels, whereas CRP, haptoglobin, waist-to-hip ratio, or variants in the TNFα, TNFRSF1B, IL6, IL6ST, IL6Rα, PON1, and HFE Cys282Tyr mutation exerted no influence.CONCLUSIONSAndrogen excess (partly because of hyperandrogenemia and partly because of menstrual dysfunction), insulin resistance, abnormal glucose tolerance, and the HFE His63Asp variant correlate with ferritin levels in premenopausal women.

A novel (Leu183Pro-)mutation in the HFE-gene co-inherited with the Cys282Tyr mutation in two unrelated Dutch hemochromatosis patients

We describe a novel heterozygous mutation in exon 3 of the HFE-gene that was co-inherited with Cys282Tyr in two unrelated Dutch men both presenting a classical form of hereditary hemochromatosis. Heterozygosity for this mutation was also found in one out of 100 healthy controls of Dutch descent. This c.548T>C mutation converts a leucine to a proline residue at position 183 in the α2-helix of the HFE-protein (Leu183Pro). Standard bioinformatics analysis shows that the mutation is likely to disturb the HFE interaction with TfR1. This disrupting role of the mutation in the iron regulatory pathway is further corroborated by the familial co-occurrence of the observed compound heterozygosity with increased serum iron parameters. Haplotype analysis strongly suggests that this novel mutation arose from a common ancestor in the distant past. These findings may have implications for HFE-testing of iron overloaded heterozygous Cys282Tyr-patients of Northern European origin and their relatives.

Hepatocellular Carcinoma Associated with Hereditary Hemochromatosis Occurring in Non-Cirrhotic Liver

The occurrence of primary hepatocellular carcinoma (HCC) in patients with hereditary hemochromatosis (HH) is well known. Thereby, the development of liver cirrhosis seems to be a prerequisite. Whether or not a hepatic iron overload in the context of hereditary hemochromatosis is an independent risk factor for HCC remains unclear. To date there are only a few reports about HCC arising in non-cirrhotic livers in the presence of HH. We report the case of a 64-year-old man who presented to our outpatient clinic with HCC. Liver cirrhosis could be excluded. Detailed exploration of the patient's history revealed that he had been treated by venesection for about 10 years up to 15 years ago. Subsequent investigations showed an elevated serum ferritin and transferrin saturation. The diagnosis of HH was confirmed by genetic testing, with homozygosity for the Cys282Tyr mutation. The patient received palliative chemotherapy and finally died 15 months after initial diagnosis of HCC.

Reverse cascade screening of newborns for hereditary haemochromatosis: a model for other late onset diseases?

Background: Genetic testing can determine those at risk for hereditary haemochromatosis (HH) caused by HFE mutations before the onset of symptoms. However, there is no optimum screening strategy, mainly owing...

Use of community genetic screening to prevent HFE-associated hereditary haemochromatosis

HFE-associated hereditary haemochromatosis is a recessive, iron-overload disorder that affects about one in 200 north Europeans and that can be easily prevented. However, genetic screening for this disease is controversial, and so we assessed whether such screening was suitable for communities. Cheek-brush screening for the Cys282Tyr HFE mutation was offered to individuals in the workplace. Outcomes were assessed by questionnaires before and after testing. 11,307 individuals were screened. We recorded no increase in anxiety in individuals who were homozygous for the Cys282Tyr mutation or non-homozygous. Self-reported tiredness before testing was significantly higher in homozygous participants than in non-homozygous participants (chi2 test, p=0.029). Of the 47 homozygous individuals identified, 46 have taken steps to treat or prevent iron accumulation. Population genetic screening for HFE-associated hereditary haemochromatosis can be practicable and acceptable.

Evidence that the Cys282Tyr mutation of the HFE gene originated from a population in Southern Scandinavia and spread with the Vikings.

Hereditary hemochromatosis has been recognized as a clinical disorder for more than 100 years. The common form of the disorder is caused by the Cys282Tyr mutation (C282Y) of the HFE gene. Hereditary hemochromatosis affects predominantly people of Northern European origin. The C282Y mutation probably occurred on a single chromosome carrying the ancestral hemochromatosis haplotype, which subsequently was spread by emigration and the founder effect. It has been estimated that the C282Y mutation appeared 60-70 generations ago. It was initially suggested that the ancestral C282Y mutation occurred within the Celtic group of peoples. However, we hypothesize that the distribution of the C282Y mutation in Europe is more consistent with an origin among the Germanic Iron Age population in Southern Scandinavia. From this area, the mutation could later be spread by the migratory activities of the Vikings. The aim of the present study was to evaluate the validity of these two hypotheses. Several arguments are in favor of the 'Viking hypothesis': first, the highest frequencies (5.1-9.7%) of the C282Y mutation are observed in populations in the Northern part of Europe, i.e. Denmark, Norway, Sweden, Faeroe Islands, Iceland, Eastern part of England (Danelaw) and the Dublin area, all Viking homelands and settlements. Second, the highest allele frequencies are reported among populations living along the coastlines. Third, the frequencies of the C282Y mutation decline from Northern to Southern Europe. Intermediate allele frequencies (3.1-4.8%) are seen in the populations in Central Europe, which is the original Celtic homeland. Low allele frequencies (0-3.1%) are recognized in populations in Southern Europe and the Mediterranean.

Heterozygosity for the Cys282Tyr mutation in the HFE gene and the risk of colorectal cancer (Netherlands).

Heterozygosity for the Cys282Tyr transition in the HFE-gene is associated with slightly increased iron levels and may therefore be a potential risk factor for colorectal cancer. We studied the relationship between Cys282Tyr-heterozygosity and colorectal cancer using a case-control design. The 240 colorectal cancer cases and 635 controls in our study were derived from a prospective cohort study of 12,242 postmenopausal women, who were invited for an experimental breast cancer screening program in Utrecht, The Netherlands. The women were age 51-69 at time of inclusion and were followed for a period of 20 years. HFE genotyping was performed by PCR and allele-specific oligonucleotide (ASO) hybridization. The risk of colorectal cancer was higher for women who were heterozygous for the Cys282Tyr mutation, than for those who were Cys282Tyr-wildtypes, although this was not statistically significant (Age-adjusted OR = 1.2, 95% CI: 0.6-2.2). Cys282Tyr-heterozygotes who smoked seemed to be at higher risk of colorectal cancer, although the p-value for interaction was not significant (p-value 0.42). The Cys282Tyr mutation is not associated with an increased risk for colorectal cancer in postmenopausal women, although in combination with smoking a slightly increased risk cannot be excluded.

Importancia del polimorfismo 5569G/A del intrón 4 del gen HFE en el diagnóstico de la hemocromatosis hereditaria

The presence of the 5569A polymorphism may lead to misdiagnosis of patients susceptible of hereditary hemochromatosis (HH). For that reason, samples containing the Cys282Tyr mutation were revised and the frequency of this polymorphism in our environment was assessed. Twenty samples were retested and 56 controls were included. The study was performed by PCR-RFLP. The diagnosis was confirmed in 8 cases susceptible of error. However, an amplification deficiency of normal alleles was detected in 2 heterozygous (17%). The allelic frequency of the 5569A polymorphism in the control population was 14.3%. Although misdiagnosis was not committed, we recommend changing to any primer that does not include the 5569G/A polymorphism in the study of HH.

The pituitary gland and hereditary haemochromatosis

A 38-year-old man presented with a 6-month history of decreased libido and erectile failure. Clinical examination revealed slate-grey skin pigmentation and facial telangiectasia. Low plasma testosterone and no gonadotropin response to gonadotropin-releasing hormone were indicative of hypogonadotropic hypogonadism. Anterior pituitary and liver function tests were otherwise normal, as was fasting blood glucose. Serum ferritin was raised: 2559 μg/L (normal 25–400 μ g/L). Genotyping confirmed homozygosity for the Cys282Tyr mutation in the HFE gene on chromosome 6, confirming the clinical and biochemical diagnosis of hereditary haemochromatosis.

Evaluation of a Nucleic Acid-based Cross-Linking Assay to Screen for Hereditary Hemochromatosis in Healthy Blood Donors

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder (frequency, 1 in 300–500 in the Northern European population) characterized by overabsorption of iron with consequent multiorgan failure secondary to iron overload (1)(2). Because early diagnosis and therapy can entirely prevent clinical complications, HH presents a model system for presymptomatic detection at the molecular level. HFE , the disease-causing gene of HH, encodes a 343-amino acid protein with high structural similarity to MHC class I molecules (3)(4). The primary disease-causing mutation is a single G-to-A transition at position 845, encoding a protein with a Cys282Tyr amino acid substitution (3). Current HH genotyping techniques include restriction fragment length polymorphism (RFLP) analysis (5) and heteroduplex analysis (6), both PCR based. We evaluated a nucleic acid-based test with cross-linkable DNA probes to screen for the Cys282Tyr mutation in a total of 101 presumably healthy blood donors. The assay uses oligonucleotide probes modified with photo-activatable cross-linker molecules (7) and has been used to detect the factor V Leiden mutation (8). Two sets of allele-specific cross-linkable DNA probes were prepared that detect either the wild-type or mutant Cys282Tyr gene sequences. Samples prepared from donor blood were assayed with each probe set, and the genotype of each individual was determined by comparison of the fluorescent signals obtained. All blood samples were also assayed by a PCR-RFLP test. Two capture probes that hybridized preferentially to the wild-type or mutant HFE gene sequence, respectively, were synthesized for the cross-linking assay: …

Hemochromatosis genes and other factors contributing to the pathogenesis of porphyria cutanea tarda

Inherited and acquired factors have been implicated in the pathogenesis of porphyria cutanea tarda (PCT), a disorder characterized by a photosensitive dermatosis and hepatic siderosis. This study, comprising 108 patients with PCT, was intended to define the role of hemochromatosis gene (HFE) mutations in the expression of PCT and to determine the contribution of acquired factors including alcohol, hepatitis C virus (HCV), and estrogen. The 2 known HFE mutations, cysteine 282 tyrosine (Cys282Tyr) and histidine 63 asparagine (His63Asp), were detected by polymerase chain reaction, and anti-HCV immunoglobulin G was detected serologically. Liver biopsies were graded for iron content, inflammation, and fibrosis. Estimates of alcohol and estrogen use were based on a questionnaire. Of the PCT patients tested, 19% were homozygous for the Cys282Tyr mutation; controls were equal to 0.5%. The compound heterozygous genotype was detected in 7% of the PCT patients; controls were less than 1%. The transferrin saturation, serum ferritin, and liver iron burden of all PCT patients were higher than those of nonporphyric controls. The highest values were found in PCT patients homozygous for the Cys282Tyr mutation. Of the patients studied, 59% were HCV positive (compared with 1.8% of the population), and 46% consumed more than 70 g of alcohol daily. Of the female patients, 63% were ingesting estrogens. Hepatic damage was most marked in patients with the Cys282Tyr/Cys282Tyr genotype who had HCV and drank heavily. Homozygosity for the Cys282Tyr mutation and HCV are the greatest risk factors for expression of PCT, and in most patients, more than 1 risk factor was identified. It was common for patients with HCV to consume alcohol. Patients with PCT should be screened for HFE mutations and for HCV. (Blood. 2000;95:1565-1571)

No evidence of increased risk of colorectal cancer in individuals heterozygous for the Cys282Tyr haemochromatosis mutation.

Previous studies have suggested that increased body iron stores and heterozygosity for haemochromatosis are associated with an increased risk of colorectal carcinoma. The aim of this study is to determine if there is an association between (i) colorectal carcinoma and heterozygosity for the Cys282Tyr mutation of the haemochromatosis gene (HFE) and (ii) this mutation and tumour site or stage. Two hundred and twenty-nine unselected patients (127 males, 102 females, mean age 68.0 years) with sporadic colorectal carcinoma and 228 controls (145 males, 83 females, mean age 69.7 years) were studied. DNA was tested for the presence of the Cys282Tyr mutation by digestion with Rsa1 and fragments separated by electrophoresis. Twenty-one patients with colorectal cancer and 23 control subjects were heterozygous for the Cys282Tyr mutation of HFE (relative risk 0.90). There was no association between heterozygosity of the Cys282Tyr mutation and tumour site or stage. Heterozygosity for the Cys282Tyr mutation of HFE does not appear to be a risk factor for colorectal carcinoma.

Rapid Genotyping of Hemochromatosis Gene Mutations on the LightCycler with Fluorescent Hybridization Probes

Two point mutations in the hemochromatosis gene (HFE) are considered responsible for the development of hereditary hemochromatosis (HH), an autosomal recessive iron overload disease. One of these mutations produces a cysteine-to-tyrosine amino acid substitution at position 282 of the HFE protein (Cys282Tyr), caused by a G-to-A transition at nucleotide position 845. A homozygous Cys282Tyr mutation is present in 80–100% of hemochromatosis patients (1)(2). This mutation prevents interaction of HFE protein with β2-microglobulin, leading to an inability to bind to the transferrin receptor, a process that is necessary for iron resorption (3)(4). A second mutation, which changes histidine at position 63 to aspartic acid (His63Asp), caused by a C187G transversion does not affect this binding but possibly blocks the interaction with other ligands (3)(5). In contrast to the Cys282Tyr mutation, the role of the His63Asp mutation in the pathogenesis of the disease is uncertain. A heterozygous His63Asp mutation is often observed in Cys282Tyr heterozygous patients. This genotype combination is called compound heterozygosity and is observed in 4–5% of HH cases. Therefore, it must be considered, like the homozygous Cys282Tyr mutation, as a genetic disposition for HH. However, it seems to play a subordinate role and seems to be important only in combination with the Cys282Tyr mutation (6). Approximately 3% of the population is homozygous for the His63Asp mutation, and thus is not considered in the risk group for HH (6)(7). In rare HH cases, none of these known HFE mutations are present. Other mutations, possibly not associated with HFE , might contribute to the development of hemochromatosis (2). There are many current methods available for genotyping the two known hemochromatosis-causing mutations, including oligonucleotide ligation assay (8), single-strand conformation polymorphism (9), allele-specific PCR (10)(11), and PCR-restriction fragment length …

Increased risk of acute myocardial infarction in carriers of the hemochromatosis gene Cys282Tyr mutation : a prospective cohort study in men in eastern Finland.

Background-Homozygosity for a relatively common Cys282Tyr mutation of the human hemochromatosis-associated (HFE) gene was recently found to account for most cases of hereditary hemochromatosis. Because excess iron has been postulated to enhance risk of vascular disease, we studied whether occurrence of this mutation was associated with increased risk of first acute myocardial infarction in healthy middle-aged men in a prospective cohort study. Methods and Results-Study subjects were the 1150 participants in the population-based Kuopio Ischemic Heart Disease Risk Factor Study (KIHD), aged 42, 48, 54, or 60 years at baseline, who had no coronary heart disease at baseline and for whom a DNA sample was available. Information about myocardial infarctions was collected prospectively by use of FINMONICA (FINnish MONItoring of trends and determinants in CArdiovascular disease study) and hospital data. Events were classified by MONICA (MONItoring of trends and determinants in CArdiovascular disease study) diagnostic criteria. The HFE Cys282Tyr mutation was assayed by a solid-phase minisequencing technique. One subject was homozygous and 76 individuals were heterozygous for the HFE Cys282Tyr mutation (6.7%). During a mean follow-up of 9 years, 8 (10.4%) of 77 carriers and 60 (5.6%) of 1073 noncarriers experienced an acute myocardial infarction. In a Cox proportional hazards model allowing for the other strongest risk factors, the carriers had a 2.3-fold (95% CI 1. 1 to 4.8; P=0.03) risk of acute myocardial infarction compared with noncarriers. Conclusions-Male carriers of the common hemochromatosis gene mutation are at 2-fold risk for first acute myocardial infarction compared with noncarriers.