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Fine AG, Steinrücken M. A novel expectation-maximization approach to infer general diploid selection from time-series genetic data. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.10.593575. [PMID: 38798346 PMCID: PMC11118272 DOI: 10.1101/2024.05.10.593575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Detecting and quantifying the strength of selection is a main objective in population genetics. Since selection acts over multiple generations, many approaches have been developed to detect and quantify selection using genetic data sampled at multiple points in time. Such time series genetic data is commonly analyzed using Hidden Markov Models, but in most cases, under the assumption of additive selection. However, many examples of genetic variation exhibiting non-additive mechanisms exist, making it critical to develop methods that can characterize selection in more general scenarios. Thus, we extend a previously introduced expectation-maximization algorithm for the inference of additive selection coefficients to the case of general diploid selection, in which heterozygote and homozygote fitnesses are parameterized independently. We furthermore introduce a framework to identify bespoke modes of diploid selection from given data, as well as a procedure for aggregating data across linked loci to increase power and robustness. Using extensive simulation studies, we find that our method accurately and efficiently estimates selection coefficients for different modes of diploid selection across a wide range of scenarios; however, power to classify the mode of selection is low unless selection is very strong. We apply our method to ancient DNA samples from Great Britain in the last 4,450 years, and detect evidence for selection in six genomic regions, including the well-characterized LCT locus. Our work is the first genome-wide scan characterizing signals of general diploid selection.
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Affiliation(s)
- Adam G Fine
- Department of Ecology and Evolution, University of Chicago
- Graduate Program in Biophysical Sciences, University of Chicago
| | - Matthias Steinrücken
- Department of Ecology and Evolution, University of Chicago
- Department of Human Genetics, University of Chicago
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2
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Girelli D, Busti F, Brissot P, Cabantchik I, Muckenthaler MU, Porto G. Hemochromatosis classification: update and recommendations by the BIOIRON Society. Blood 2022; 139:3018-3029. [PMID: 34601591 PMCID: PMC11022970 DOI: 10.1182/blood.2021011338] [Citation(s) in RCA: 48] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 09/05/2021] [Indexed: 12/15/2022] Open
Abstract
Hemochromatosis (HC) is a genetically heterogeneous disorder in which uncontrolled intestinal iron absorption may lead to progressive iron overload (IO) responsible for disabling and life-threatening complications such as arthritis, diabetes, heart failure, hepatic cirrhosis, and hepatocellular carcinoma. The recent advances in the knowledge of pathophysiology and molecular basis of iron metabolism have highlighted that HC is caused by mutations in at least 5 genes, resulting in insufficient hepcidin production or, rarely, resistance to hepcidin action. This has led to an HC classification based on different molecular subtypes, mainly reflecting successive gene discovery. This scheme was difficult to adopt in clinical practice and therefore needs revision. Here we present recommendations for unambiguous HC classification developed by a working group of the International Society for the Study of Iron in Biology and Medicine (BIOIRON Society), including both clinicians and basic scientists during a meeting in Heidelberg, Germany. We propose to deemphasize the use of the molecular subtype criteria in favor of a classification addressing both clinical issues and molecular complexity. Ferroportin disease (former type 4a) has been excluded because of its distinct phenotype. The novel classification aims to be of practical help whenever a detailed molecular characterization of HC is not readily available.
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Affiliation(s)
- Domenico Girelli
- Department of Medicine, Section of Internal Medicine, EuroBloodNet Center, University of Verona and Azienda Ospedaliera Universitaria Integrata Verona, Verona, Italy
| | - Fabiana Busti
- Department of Medicine, Section of Internal Medicine, EuroBloodNet Center, University of Verona and Azienda Ospedaliera Universitaria Integrata Verona, Verona, Italy
| | - Pierre Brissot
- INSERM, Univ-Rennes, Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1241, Institut NuMeCan, Rennes, France
| | - Ioav Cabantchik
- Alexander Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel
| | - Martina U. Muckenthaler
- Department of Pediatric Oncology, Hematology, and Immunology and Molecular Medicine Partnership Unit, University of Heidelberg, Heidelberg, Germany
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Translational Lung Research Center, German Center for Lung Research, Heidelberg, Germany
- German Centre for Cardiovascular Research, Partner Site Heidelberg, Mannheim, Germany
| | - Graça Porto
- Institute for Molecular and Cell Biology, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Clinical Hematology, Santo António Hospital, Porto University, Porto, Portugal
| | - on behalf of the Nomenclature Committee of the International Society for the Study of Iron in Biology and Medicine (BIOIRON Society)
- Department of Medicine, Section of Internal Medicine, EuroBloodNet Center, University of Verona and Azienda Ospedaliera Universitaria Integrata Verona, Verona, Italy
- INSERM, Univ-Rennes, Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1241, Institut NuMeCan, Rennes, France
- Alexander Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel
- Department of Pediatric Oncology, Hematology, and Immunology and Molecular Medicine Partnership Unit, University of Heidelberg, Heidelberg, Germany
- Molecular Medicine Partnership Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Translational Lung Research Center, German Center for Lung Research, Heidelberg, Germany
- German Centre for Cardiovascular Research, Partner Site Heidelberg, Mannheim, Germany
- Institute for Molecular and Cell Biology, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Clinical Hematology, Santo António Hospital, Porto University, Porto, Portugal
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3
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Hemochromatosis redefined. Blood 2022; 139:3001-3002. [PMID: 35587868 DOI: 10.1182/blood.2021014036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 09/23/2021] [Indexed: 11/20/2022] Open
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Kowdley DS, Kowdley KV. Appropriate Clinical Genetic Testing of Hemochromatosis Type 2-4, Including Ferroportin Disease. Appl Clin Genet 2021; 14:353-361. [PMID: 34413666 PMCID: PMC8369226 DOI: 10.2147/tacg.s269622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/18/2021] [Indexed: 11/23/2022] Open
Abstract
Hereditary hemochromatosis (HH) is an inherited iron overload disorder due to a deficiency of hepcidin, or a failure of hepcidin to degrade ferroportin. The most common form of HH, Type 1 HH, is most commonly due to a homozygous C282Y mutation in HFE and is relatively well understood in significance and action; however, other rare forms of HH (Types 2–4) exist and are more difficult to identify and diagnose in clinical practice. In this review, we describe the clinical characteristics of HH Type 2–4 and the mutation patterns that have been described in these conditions. We also review the different methods for genetic testing available in clinical practice and a pragmatic approach to the patient with suspected non-HFE HH.
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Affiliation(s)
- Devan S Kowdley
- Liver Institute Northwest and Elson S. Floyd College of Medicine, Washington State University, Seattle, WA, USA
| | - Kris V Kowdley
- Liver Institute Northwest and Elson S. Floyd College of Medicine, Washington State University, Seattle, WA, USA
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5
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Kang W, Barad A, Clark AG, Wang Y, Lin X, Gu Z, O'Brien KO. Ethnic Differences in Iron Status. Adv Nutr 2021; 12:1838-1853. [PMID: 34009254 PMCID: PMC8483971 DOI: 10.1093/advances/nmab035] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/02/2021] [Accepted: 03/05/2021] [Indexed: 02/07/2023] Open
Abstract
Iron is unique among all minerals in that humans have no regulatable excretory pathway to eliminate excess iron after it is absorbed. Iron deficiency anemia occurs when absorbed iron is not sufficient to meet body iron demands, whereas iron overload and subsequent deposition of iron in key organs occur when absorbed iron exceeds body iron demands. Over time, iron accumulation in the body can increase risk of chronic diseases, including cirrhosis, diabetes, and heart failure. To date, only ∼30% of the interindividual variability in iron absorption can be captured by iron status biomarkers or iron regulatory hormones. Much of the regulation of iron absorption may be under genetic control, but these pathways have yet to be fully elucidated. Genome-wide and candidate gene association studies have identified several genetic variants that are associated with variations in iron status, but the majority of these data were generated in European populations. The purpose of this review is to summarize genetic variants that have been associated with alterations in iron status and to highlight the influence of ethnicity on the risk of iron deficiency or overload. Using extant data in the literature, linear mixed-effects models were constructed to explore ethnic differences in iron status biomarkers. This approach found that East Asians had significantly higher concentrations of iron status indicators (serum ferritin, transferrin saturation, and hemoglobin) than Europeans, African Americans, or South Asians. African Americans exhibited significantly lower hemoglobin concentrations compared with other ethnic groups. Further studies of the genetic basis for ethnic differences in iron metabolism and on how it affects disease susceptibility among different ethnic groups are needed to inform population-specific recommendations and personalized nutrition interventions for iron-related disorders.
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Affiliation(s)
- Wanhui Kang
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
| | - Alexa Barad
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
| | - Andrew G Clark
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA,Department of Computational Biology, Cornell University, Ithaca, NY, USA
| | - Yiqin Wang
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
| | - Xu Lin
- Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, Shanghai, China
| | - Zhenglong Gu
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
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Abstract
Iron deficiency or overload poses an increasingly complex issue in cardiovascular disease, especially heart failure. The potential benefits and side effects of iron supplementation are still a matter of concern, even though current guidelines suggest therapeutic management of iron deficiency. In this review, we sought to examine the iron metabolism and to identify the rationale behind iron supplementation and iron chelation. Cardiovascular disease is increasingly linked with iron dysmetabolism, with an increased proportion of heart failure patients being affected by decreased plasma iron levels and in turn, by the decreased quality of life. Multiple studies have concluded on a benefit of iron administration, even if just for symptomatic relief. However, new studies field evidence for negative effects of dysregulated non-bound iron and its reactive oxygen species production, with concern to heart diseases. The molecular targets of iron usage, such as the mitochondria, are prone to deleterious effects of the polyvalent metal, added by the scarcely described processes of iron elimination. Iron supplementation and iron chelation show promise of therapeutic benefit in heart failure, with the extent and mechanisms of both prospects not being entirely understood. It may be that a state of decreased systemic and increased mitochondrial iron levels proves to be a useful frame for future advancements in understanding the interconnection of heart failure and iron metabolism.
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Piperno A, Pelucchi S, Mariani R. Inherited iron overload disorders. Transl Gastroenterol Hepatol 2020; 5:25. [PMID: 32258529 DOI: 10.21037/tgh.2019.11.15] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 11/12/2019] [Indexed: 12/21/2022] Open
Abstract
Hereditary iron overload includes several disorders characterized by iron accumulation in tissues, organs, or even single cells or subcellular compartments. They are determined by mutations in genes directly involved in hepcidin regulation, cellular iron uptake, management and export, iron transport and storage. Systemic forms are characterized by increased serum ferritin with or without high transferrin saturation, and with or without functional iron deficient anemia. Hemochromatosis includes five different genetic forms all characterized by high transferrin saturation and serum ferritin, but with different penetrance and expression. Mutations in HFE, HFE2, HAMP and TFR2 lead to inadequate or severely reduced hepcidin synthesis that, in turn, induces increased intestinal iron absorption and macrophage iron release leading to tissue iron overload. The severity of hepcidin down-regulation defines the severity of iron overload and clinical complications. Hemochromatosis type 4 is caused by dominant gain-of-function mutations of ferroportin preventing hepcidin-ferroportin binding and leading to hepcidin resistance. Ferroportin disease is due to loss-of-function mutation of SLC40A1 that impairs the iron export efficiency of ferroportin, causes iron retention in reticuloendothelial cell and hyperferritinemia with normal transferrin saturation. Aceruloplasminemia is caused by defective iron release from storage and lead to mild microcytic anemia, low serum iron, and iron retention in several organs including the brain, causing severe neurological manifestations. Atransferrinemia and DMT1 deficiency are characterized by iron deficient erythropoiesis, severe microcytic anemia with high transferrin saturation and parenchymal iron overload due to secondary hepcidin suppression. Diagnosis of the different forms of hereditary iron overload disorders involves a sequential strategy that combines clinical, imaging, biochemical, and genetic data. Management of iron overload relies on two main therapies: blood removal and iron chelators. Specific therapeutic options are indicated in patients with atransferrinemia, DMT1 deficiency and aceruloplasminemia.
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Affiliation(s)
- Alberto Piperno
- Department of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.,Centre for Rare Diseases, Disorder of Iron Metabolism, ASST-Monza, S. Gerardo Hospital, Monza, Italy
| | - Sara Pelucchi
- Department of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
| | - Raffaella Mariani
- Centre for Rare Diseases, Disorder of Iron Metabolism, ASST-Monza, S. Gerardo Hospital, Monza, Italy
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8
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Phenotypic analysis of hemochromatosis subtypes reveals variations in severity of iron overload and clinical disease. Blood 2018; 132:101-110. [PMID: 29743178 DOI: 10.1182/blood-2018-02-830562] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 05/03/2018] [Indexed: 12/15/2022] Open
Abstract
The clinical progression of HFE-related hereditary hemochromatosis (HH) and its phenotypic variability has been well studied. Less is known about the natural history of non-HFE HH caused by mutations in the HJV, HAMP, or TFR2 genes. The purpose of this study was to compare the phenotypic and clinical presentations of hepcidin-deficient forms of HH. A literature review of all published cases of genetically confirmed HJV, HAMP, and TFR2 HH was performed. Phenotypic and clinical data from a total of 156 patients with non-HFE HH was extracted from 53 publications and compared with data from 984 patients with HFE-p.C282Y homozygous HH from the QIMR Berghofer Hemochromatosis Database. Analyses confirmed that non-HFE forms of HH have an earlier age of onset and a more severe clinical course than HFE HH. HJV and HAMP HH are phenotypically and clinically very similar and have the most severe presentation, with cardiomyopathy and hypogonadism being particularly prevalent findings. TFR2 HH is more intermediate in its age of onset and severity. All clinical outcomes analyzed were more prevalent in the juvenile forms of HH, with the exception of arthritis and arthropathy, which were more commonly seen in HFE HH. This is the first comprehensive analysis comparing the different phenotypic and clinical aspects of the genetic forms of HH, and the results will be valuable for the differential diagnosis and management of these conditions. Importantly, our analyses indicate that factors other than iron overload may be contributing to joint pathology in patients with HFE HH.
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Abstract
Primary sclerosing cholangitis (PSC) is a chronic disease leading to fibrotic scarring of the intrahepatic and extrahepatic bile ducts, causing considerable morbidity and mortality via the development of cholestatic liver cirrhosis, concurrent IBD and a high risk of bile duct cancer. Expectations have been high that genetic studies would determine key factors in PSC pathogenesis to support the development of effective medical therapies. Through the application of genome-wide association studies, a large number of disease susceptibility genes have been identified. The overall genetic architecture of PSC shares features with both autoimmune diseases and IBD. Strong human leukocyte antigen gene associations, along with several susceptibility genes that are critically involved in T-cell function, support the involvement of adaptive immune responses in disease pathogenesis, and position PSC as an autoimmune disease. In this Review, we survey the developments that have led to these gene discoveries. We also elaborate relevant interpretations of individual gene findings in the context of established disease models in PSC, and propose relevant translational research efforts to pursue novel insights.
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Badar S, Busti F, Ferrarini A, Xumerle L, Bozzini P, Capelli P, Pozzi-Mucelli R, Campostrini N, De Matteis G, Marin Vargas S, Giorgetti A, Delledonne M, Olivieri O, Girelli D. Identification of novel mutations in hemochromatosis genes by targeted next generation sequencing in Italian patients with unexplained iron overload. Am J Hematol 2016; 91:420-5. [PMID: 26799139 DOI: 10.1002/ajh.24304] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 01/08/2016] [Accepted: 01/13/2016] [Indexed: 12/14/2022]
Abstract
Hereditary hemochromatosis, one of the commonest genetic disorder in Caucasians, is mainly associated to homozygosity for the C282Y mutation in the HFE gene, which is highly prevalent (allele frequency up to near 10% in Northern Europe) and easily detectable through a widely available "first level" molecular test. However, in certain geographical regions like the Mediterranean area, up to 30% of patients with a HH phenotype has a negative or non-diagnostic (i.e. simple heterozygosity) test, because of a known heterogeneity involving at least four other genes (HAMP, HJV, TFR2, and SLC40A1). Mutations in such genes are generally rare/private, making the diagnosis of atypical HH essentially a matter of exclusion in clinical practice (from here the term of "non-HFE" HH), unless cumbersome traditional sequencing is applied. We developed a Next Generation Sequencing (NGS)-based test targeting the five HH genes, and applied it to patients with clinically relevant iron overload (IO) and a non-diagnostic first level genetic test. We identified several mutations, some of which were novel (i.e. HFE W163X, HAMP R59X, and TFR2 D555N) and allowed molecular reclassification of "non-HFE" HH clinical diagnosis, particularly in some highly selected IO patients without concurring acquired risk factors. This NGS-based "second level" genetic test may represent a useful tool for molecular diagnosis of HH in patients in whom HH phenotype remains unexplained after the search of common HFE mutations.
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Affiliation(s)
- Sadaf Badar
- Department of Medicine; Section of Internal Medicine, University of Verona; Verona Italy
| | - Fabiana Busti
- Department of Medicine; Section of Internal Medicine, University of Verona; Verona Italy
| | | | - Luciano Xumerle
- Department of Biotechnology; University of Verona; Verona Italy
| | - Paolo Bozzini
- Department of Medicine; Section of Internal Medicine, University of Verona; Verona Italy
| | - Paola Capelli
- Unit of Pathology, Azienda Ospedaliera Universitaria Integrata Verona; Verona Italy
| | - Roberto Pozzi-Mucelli
- Department of Diagnostics and Public Health; Section of Radiology, University of Verona; Verona Italy
| | - Natascia Campostrini
- Department of Medicine; Section of Internal Medicine, University of Verona; Verona Italy
| | - Giovanna De Matteis
- Unit of Clinical Chemistry, Azienda Ospedaliera Universitaria Integrata Verona; Verona Italy
| | | | | | | | - Oliviero Olivieri
- Department of Medicine; Section of Internal Medicine, University of Verona; Verona Italy
| | - Domenico Girelli
- Department of Medicine; Section of Internal Medicine, University of Verona; Verona Italy
- Veneto Regional Referral Center for Iron Metabolism Disorders, GIMFer (Gruppo Interdisciplinare Sulle Malattie Del Ferro); Azienda Ospedaliera Uiversitaria Integrata Verona; Verona Italy
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11
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Ravasi G, Rausa M, Pelucchi S, Arosio C, Greni F, Mariani R, Pelloni I, Silvestri L, Pineda P, Camaschella C, Piperno A. Transferrin receptor 2 mutations in patients with juvenile hemochromatosis phenotype. Am J Hematol 2015; 90:E226-7. [PMID: 26408288 DOI: 10.1002/ajh.24202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 08/31/2015] [Accepted: 09/17/2015] [Indexed: 01/06/2023]
Affiliation(s)
- Giulia Ravasi
- Department of Health Sciences; University of Milano-Bicocca; Monza Italy
| | - Marco Rausa
- Division of Genetics and Cell Biology; San Raffaele Scientific Institute, Vita-Salute University; Milan Italy
| | - Sara Pelucchi
- Department of Health Sciences; University of Milano-Bicocca; Monza Italy
| | | | - Federico Greni
- Department of Health Sciences; University of Milano-Bicocca; Monza Italy
| | - Raffaella Mariani
- Unit of Internal Medicine 2, Centre for Iron Metabolism Disorders, S. Gerardo Hospital; Monza Italy
| | - Irene Pelloni
- Unit of Internal Medicine 2, Centre for Iron Metabolism Disorders, S. Gerardo Hospital; Monza Italy
| | - Laura Silvestri
- Division of Genetics and Cell Biology; San Raffaele Scientific Institute, Vita-Salute University; Milan Italy
| | - Pedro Pineda
- Seccíon Endocrinología y Diabetes; Departamento de Medicina; Hospital Clínico Universidad de Chile; Santiago Chile
| | - Clara Camaschella
- Division of Genetics and Cell Biology; San Raffaele Scientific Institute, Vita-Salute University; Milan Italy
| | - Alberto Piperno
- Department of Health Sciences; University of Milano-Bicocca; Monza Italy
- Consortium of Human Molecular Genetics; Monza Italy
- Unit of Internal Medicine 2, Centre for Iron Metabolism Disorders, S. Gerardo Hospital; Monza Italy
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Genetics of liver disease: From pathophysiology to clinical practice. J Hepatol 2015; 62:S6-S14. [PMID: 25920091 DOI: 10.1016/j.jhep.2015.02.025] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Revised: 02/14/2015] [Accepted: 02/16/2015] [Indexed: 12/24/2022]
Abstract
Paralleling the first 30 years of the Journal of Hepatology we have witnessed huge advances in our understanding of liver disease and physiology. Genetic advances have played no small part in that. Initial studies in the 1970s and 1980s identified the strong major histocompatibility complex associations in autoimmune liver diseases. During the 1990 s, developments in genomic technologies drove the identification of genes responsible for Mendelian liver diseases. Over the last decade, genome-wide association studies have allowed for the dissection of the genetic susceptibility to complex liver disorders, in which also environmental co-factors play important roles. Findings have allowed the identification and elaboration of pathophysiological processes, have indicated the need for reclassification of liver diseases and have already pointed to new disease treatments. In the immediate future genetics will allow further stratification of liver diseases and contribute to personalized medicine. Challenges exist with regard to clinical implementation of rapidly developing technologies and interpretation of the wealth of accumulating genetic data. The historical perspective of genetics in liver diseases illustrates the opportunities for future research and clinical care of our patients.
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Yun S, Vincelette ND. Update on iron metabolism and molecular perspective of common genetic and acquired disorder, hemochromatosis. Crit Rev Oncol Hematol 2015; 95:12-25. [PMID: 25737209 DOI: 10.1016/j.critrevonc.2015.02.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 01/29/2015] [Accepted: 02/11/2015] [Indexed: 12/14/2022] Open
Abstract
Iron is an essential component of erythropoiesis and its metabolism is tightly regulated by a variety of internal and external cues including iron storage, tissue hypoxia, inflammation and degree of erythropoiesis. There has been remarkable improvement in our understanding of the molecular mechanisms of iron metabolism past decades. The classical model of iron metabolism with iron response element/iron response protein (IRE/IRP) is now extended to include hepcidin model. Endogenous and exogenous signals funnel down to hepcidin via wide range of signaling pathways including Janus Kinase/Signal Transducer and Activator of Transcription 3 (JAK/STAT3), Bone Morphogenetic Protein/Hemojuvelin/Mothers Against Decapentaplegic Homolog (BMP/HJV/SMAD), and Von Hippel Lindau/Hypoxia-inducible factor/Erythropoietin (VHL/HIF/EPO), then relay to ferroportin, which directly regulates intra- and extracellular iron levels. The successful molecular delineation of iron metabolism further enhanced our understanding of common genetic and acquired disorder, hemochromatosis. The majority of the hereditary hemochromatosis (HH) patients are now shown to have mutations in the genes coding either upstream or downstream proteins of hepcidin, resulting in iron overload. The update on hepcidin centered mechanisms of iron metabolism and their clinical perspective in hemochromatosis will be discussed in this review.
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Affiliation(s)
- Seongseok Yun
- Department of Medicine, University of Arizona, Tucson, AZ 85721, USA.
| | - Nicole D Vincelette
- Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55902, USA
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Bardou-Jacquet E, Ben Ali Z, Beaumont-Epinette MP, Loreal O, Jouanolle AM, Brissot P. Non-HFE hemochromatosis: pathophysiological and diagnostic aspects. Clin Res Hepatol Gastroenterol 2014; 38:143-54. [PMID: 24321703 DOI: 10.1016/j.clinre.2013.11.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/04/2013] [Accepted: 11/13/2013] [Indexed: 02/04/2023]
Abstract
Rare genetic iron overload diseases are an evolving field due to major advances in genetics and molecular biology. Genetic iron overload has long been confined to the classical type 1 hemochromatosis related to the HFE C282Y mutation. Breakthroughs in the understanding of iron metabolism biology and molecular mechanisms led to the discovery of new genes and subsequently, new types of hemochromatosis. To date, four types of hemochromatosis have been identified: HFE-related or type1 hemochromatosis, the most frequent form in Caucasians, and four rare types, named type 2 (A and B) hemochromatosis (juvenile hemochromatosis due to hemojuvelin and hepcidin mutation), type 3 hemochromatosis (related to transferrin receptor 2 mutation), and type 4 (A and B) hemochromatosis (ferroportin disease). The diagnosis relies on the comprehension of the involved physiological defect that can now be explored by biological and imaging tools, which allow non-invasive assessment of iron metabolism. A multidisciplinary approach is essential to support the physicians in the diagnosis and management of those rare diseases.
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Affiliation(s)
- Edouard Bardou-Jacquet
- University Hospital of Rennes, French reference center for rare iron overload diseases of genetic origin, Rennes, France; University of Rennes1, Inserm UMR 991, 35000 Rennes, France; University Hospital of Rennes, Liver disease department, Rennes, France.
| | - Zeineb Ben Ali
- University Hospital of Rennes, French reference center for rare iron overload diseases of genetic origin, Rennes, France; University Hospital of Rennes, Liver disease department, Rennes, France
| | - Marie-Pascale Beaumont-Epinette
- University Hospital of Rennes, French reference center for rare iron overload diseases of genetic origin, Rennes, France; University Hospital of Rennes, Molecular Genetics Department, Rennes, France
| | - Olivier Loreal
- University Hospital of Rennes, French reference center for rare iron overload diseases of genetic origin, Rennes, France; University of Rennes1, Inserm UMR 991, 35000 Rennes, France
| | - Anne-Marie Jouanolle
- University Hospital of Rennes, French reference center for rare iron overload diseases of genetic origin, Rennes, France; University Hospital of Rennes, Molecular Genetics Department, Rennes, France
| | - Pierre Brissot
- University Hospital of Rennes, French reference center for rare iron overload diseases of genetic origin, Rennes, France; University of Rennes1, Inserm UMR 991, 35000 Rennes, France; University Hospital of Rennes, Liver disease department, Rennes, France
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15
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TFR2-related hereditary hemochromatosis as a frequent cause of primary iron overload in patients from Central-Southern Italy. Blood Cells Mol Dis 2014; 52:83-7. [DOI: 10.1016/j.bcmd.2013.08.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 07/23/2013] [Indexed: 11/21/2022]
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16
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Brissot P, Bardou-Jacquet E, Troadec MB, Mosser A, Island ML, Detivaud L, Loréal O, Jouanolle AM. Molecular diagnosis of genetic iron-overload disorders. Expert Rev Mol Diagn 2014; 10:755-63. [DOI: 10.1586/erm.10.55] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Abstract
INTRODUCTION The discovery of hemochromatosis genes and the availability of molecular-genetic tests considerably modified the knowledge of the disease relative to physiopathology, penetrance, and expression, and had major impact in the diagnostic settings. AREAS COVERED Hemochromatosis is a heterogenous disorder at both genetic and phenotypic level. The review discusses criteria to define patients' iron phenotype and to use molecular tests to diagnose HFE-related and non-HFE hemochromatosis. The material examined includes articles published in the journals covered by PubMed US National Library of Medicine. The author has been working in the field of iron overload diseases for several years and has contributed 18 of the papers cited in the references. EXPERT OPINION Hemochromatosis genotyping is inseparable from phenotype characterization. A full clinical assessment is needed and DNA test performed when data suggest a clear indication of suspicion of being at risk for HH. HFE testing for p.Cys282Tyr mutation and p.His63Asp variant is the first molecular diagnostic step. Genotyping for rare mutations can be offered to patients with negative first-level HFE testing who have iron overload with no other explanation and should be performed in referral centers for iron overload disorders that can provide genetic advice and in-house genotyping services.
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Affiliation(s)
- Alberto Piperno
- University of Milano-Bicocca, Centre for the Diagnosis and Treatment of Hemochromatosis and Iron Disorders, S.Gerardo Hospital, Department of Health Sciences, Monza, Italy.
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18
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Santos PCJDL, Dinardo CL, Cançado RD, Schettert IT, Krieger JE, Pereira AC. Non-HFE hemochromatosis. Rev Bras Hematol Hemoter 2012; 34:311-6. [PMID: 23049448 PMCID: PMC3460409 DOI: 10.5581/1516-8484.20120079] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 07/10/2012] [Indexed: 12/15/2022] Open
Abstract
Hereditary hemochromatosis (HH) is an autosomal recessive disorder classically related to HFE mutations. However, since 1996, it is known that HFE mutations explain about 80% of HH cases, with the remaining around 20% denominated non-HFE hemochromatosis. Nowadays, four main genes are implicated in the pathophysiology of clinical syndromes classified as non-HFE hemochromatosis: hemojuvelin (HJV, type 2Ajuvenile HH), hepcidin (HAMP, type 2B juvenile HH), transferrin receptor 2 (TFR2, type 3 HH) and ferroportin (SLC40A1, type 4 HH). The aim of this review is to explore molecular, clinical and management aspects of non-HFE hemochromatosis.
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Delima RD, Chua ACG, Tirnitz-Parker JEE, Gan EK, Croft KD, Graham RM, Olynyk JK, Trinder D. Disruption of hemochromatosis protein and transferrin receptor 2 causes iron-induced liver injury in mice. Hepatology 2012; 56:585-93. [PMID: 22383097 DOI: 10.1002/hep.25689] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 02/19/2012] [Indexed: 12/21/2022]
Abstract
UNLABELLED Mutations in hemochromatosis protein (HFE) or transferrin receptor 2 (TFR2) cause hereditary hemochromatosis (HH) by impeding production of the liver iron-regulatory hormone, hepcidin (HAMP). This study examined the effects of disruption of Hfe or Tfr2, either alone or together, on liver iron loading and injury in mouse models of HH. Iron status was determined in Hfe knockout (Hfe(-/-)), Tfr2 Y245X mutant (Tfr2(mut)), and double-mutant (Hfe(-/-) ×Tfr2(mut) ) mice by measuring plasma and liver iron levels. Plasma alanine transaminase (ALT) activity, liver histology, and collagen deposition were evaluated to assess liver injury. Hepatic oxidative stress was assessed by measuring superoxide dismutase (SOD) activity and F(2)-isoprostane levels. Gene expression was measured by real-time polymerase chain reaction. Hfe(-/-) ×Tfr2(mut) mice had elevated hepatic iron with a periportal distribution and increased plasma iron, transferrin saturation, and non-transferrin-bound iron, compared with Hfe(-/-), Tfr2(mut), and wild-type (WT) mice. Hamp1 expression was reduced to 40% (Hfe(-/-) and Tfr2(mut) ) and 1% (Hfe(-/-) ×Tfr2(mut)) of WT values. Hfe(-/-) ×Tfr2(mut) mice had elevated plasma ALT activity and mild hepatic inflammation with scattered aggregates of infiltrating inflammatory cluster of differentiation 45 (CD45)-positive cells. Increased hepatic hydoxyproline levels as well as Sirius red and Masson's Trichrome staining demonstrated advanced portal collagen deposition. Hfe(-/-) and Tfr2(mut) mice had less hepatic inflammation and collagen deposition. Liver F(2) -isoprostane levels were elevated, and copper/zinc and manganese SOD activities decreased in Hfe(-/-) ×Tfr2(mut), Tfr2(mut), and Hfe(-/-) mice, compared with WT mice. CONCLUSION Disruption of both Hfe and Tfr2 caused more severe hepatic iron overload with more advanced lipid peroxidation, inflammation, and portal fibrosis than was observed with the disruption of either gene alone. The Hfe(-/-) ×Tfr2(mut) mouse model of iron-induced liver injury reflects the liver injury phenotype observed in human HH.
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Affiliation(s)
- Roheeth D Delima
- School of Medicine and Pharmacology, Fremantle Hospital, University of Western Australia, Fremantle, Western Australia, Australia
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20
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Siddique A, Kowdley KV. Review article: the iron overload syndromes. Aliment Pharmacol Ther 2012; 35:876-93. [PMID: 22385471 DOI: 10.1111/j.1365-2036.2012.05051.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 06/26/2011] [Accepted: 02/08/2012] [Indexed: 12/12/2022]
Abstract
BACKGROUND Iron overload syndromes encompass a wide range of hereditary and acquired conditions. Major developments in the field of genetics and the discovery of hepcidin as a central regulator of iron homeostasis have greatly increased our understanding of the pathophysiology of iron overload syndromes. AIM To review advances in iron regulation and iron overload syndrome with special emphasis on hereditary haemochromatosis, the prototype iron overload syndrome. METHODS A PubMed search using words such as 'iron overload', 'hemochromatosis', 'HFE', 'Non-HFE', 'secondary iron overload' was undertaken. RESULTS Iron overload is associated with significant morbidity and mortality. Sensitive diagnostic tests and effective therapy are widely available and can prevent complications associated with iron accumulation in end- organs. Therapeutic phlebotomy remains the cornerstone of therapy for removal of excess body iron, but novel therapeutic agents including oral iron chelators have been developed for iron overload associated with anaemia. CONCLUSIONS Iron overload disorders are common. Inexpensive screening tests as well as confirmatory diagnostic tests are widely available. Increased awareness of the causes and importance of early diagnosis and knowledge of the appropriate use of genetic testing are encouraged. The availability of novel treatments should increase therapeutic options for patients with iron overload disorders.
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Affiliation(s)
- A Siddique
- Department of Hepatology, Virginia Mason Medical Center, Seattle, WA, USA.
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21
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Chen J, Enns CA. Hereditary hemochromatosis and transferrin receptor 2. Biochim Biophys Acta Gen Subj 2011; 1820:256-63. [PMID: 21864651 DOI: 10.1016/j.bbagen.2011.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/26/2011] [Accepted: 07/29/2011] [Indexed: 02/08/2023]
Abstract
BACKGROUND Multicellular organisms regulate the uptake of calories, trace elements, and other nutrients by complex feedback mechanisms. In the case of iron, the body senses internal iron stores, iron requirements for hematopoiesis, and inflammatory status, and regulates iron uptake by modulating the uptake of dietary iron from the intestine. Both the liver and the intestine participate in the coordination of iron uptake and distribution in the body. The liver senses inflammatory signals and iron status of the organism and secretes a peptide hormone, hepcidin. Under high iron or inflammatory conditions hepcidin levels increase. Hepcidin binds to the iron transport protein, ferroportin (FPN), promoting FPN internalization and degradation. Decreased FPN levels reduce iron efflux out of intestinal epithelial cells and macrophages into the circulation. Derangements in iron metabolism result in either the abnormal accumulation of iron in the body, or in anemias. The identification of the mutations that cause the iron overload disease, hereditary hemochromatosis (HH), or iron-refractory iron-deficiency anemia has revealed many of the proteins used to regulate iron uptake. SCOPE OF THE REVIEW In this review we discuss recent data concerning the regulation of iron homeostasis in the body by the liver and how transferrin receptor 2 (TfR2) affects this process. MAJOR CONCLUSIONS TfR2 plays a key role in regulating iron homeostasis in the body. GENERAL SIGNIFICANCE The regulation of iron homeostasis is important. One third of the people in the world are anemic. HH is the most common inherited disease in people of Northern European origin and can lead to severe health complications if left untreated. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Juxing Chen
- Department of Cell and Developmental Biology L215, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA
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22
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Speeckaert MM, Speeckaert R, Delanghe JR. Biological and clinical aspects of soluble transferrin receptor. Crit Rev Clin Lab Sci 2011; 47:213-28. [DOI: 10.3109/10408363.2010.550461] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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23
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Girelli D, Trombini P, Busti F, Campostrini N, Sandri M, Pelucchi S, Westerman M, Ganz T, Nemeth E, Piperno A, Camaschella C. A time course of hepcidin response to iron challenge in patients with HFE and TFR2 hemochromatosis. Haematologica 2010; 96:500-6. [PMID: 21173098 DOI: 10.3324/haematol.2010.033449] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Inadequate hepcidin production leads to iron overload in nearly all types of hemochromatosis. We explored the acute response of hepcidin to iron challenge in 25 patients with HFE-hemochromatosis, in two with TFR2-hemochromatosis and in 13 controls. Sixteen patients (10 C282Y/C282Y homozygotes, 6 C282Y/H63D compound heterozygotes) had increased iron stores, while nine (6 C282Y/C282Y homozygotes, 3 C282Y/H63D compound heterozygotes) were studied after phlebotomy-induced normalization of iron stores. DESIGN AND METHODS We analyzed serum iron, transferrin saturation, and serum hepcidin by both enzyme-linked immunosorbent assay and mass-spectrometry at baseline, and 4, 8, 12 and 24 hours after a single 65-mg dose of oral iron. RESULTS Serum iron and transferrin saturation significantly increased at 4 hours and returned to baseline values at 8-12 hours in all groups, except in the iron-normalized patients who showed the highest and longest increase of both parameters. The level of hepcidin increased significantly at 4 hours and returned to baseline at 24 hours in controls and in the C282Y/H63D compound heterozygotes at diagnosis. The hepcidin response was smaller in C282Y-homozygotes than in controls, barely detectable in the patients with iron-depleted HFE-hemochromatosis and absent in those with TFR2-hemochromatosis. Conclusions Our results are consistent with a scenario in which TFR2 plays a prominent and HFE a contributory role in the hepcidin response to a dose of oral iron. In iron-normalized patients with HFE hemochromatosis, both the low baseline hepcidin level and the weak response to iron contribute to hyperabsorption of iron.
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Affiliation(s)
- Domenico Girelli
- Department of Medicine, University of Verona, Policlinico GB Rossi, 37134 Verona, Italy.
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24
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Fracanzani AL, Piperno A, Valenti L, Fraquelli M, Coletti S, Maraschi A, Consonni D, Coviello E, Conte D, Fargion S. Hemochromatosis in Italy in the last 30 years: role of genetic and acquired factors. Hepatology 2010; 51:501-10. [PMID: 20101754 DOI: 10.1002/hep.23333] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
UNLABELLED The clinical presentation of hereditary hemochromatosis has changed markedly in recent years. The aim of this study was to analyze a large series of consecutive Italian patients with hemochromatosis diagnosed between 1976 and 2007 to determine whether the genetic background and the presence of acquired risk factors influenced the severity of iron overload and the natural history of the disease. A cohort of 452 Italian patients with iron overload-338 HFE-related (C282Y homozygotes or compound C82Y/H63D heterozygotes) and 114 non-HFE-related-were followed prospectively for a median of 112 months. Alcohol intake, smoking habits, and iron removed to depletion were similar in patients with and without HFE-related iron overload. Hepatitis B virus (4% and 9%; P = 0.04) and hepatitis C virus (6% and 19%; P = 0.002) infections were more frequent in patients with non-HFE-related iron overload. Seventy-three percent of patients with HFE and 61% of patients with non-HFE-related disease had no acquired risk factor. Cirrhosis was significantly more frequent in non-HFE patients independent of the presence of acquired risk factors (P = 0.02). Sex, alcohol intake, prevalence of smoking, hepatitis C virus infection, glucose, lipids, iron-related parameters, and prevalence of C282Y/H63D differed significantly over the years. At enrollment, cirrhosis was present in 145 cases and was significantly more frequent in the first decade (80%, 47%, and 13%; P = 0.001). Survival did not differ across the decades in cirrhotic patients; hepatocellular carcinoma occurred similarly in HFE and non-HFE patients. CONCLUSION Patients with HFE and non-HFE-related iron overload have comparable iron overload and similar clinical history. Patients who were diagnosed during the last 10 years and were not identified as cirrhotic at enrollment have less severe disease and lower prevalence of acquired risk factors, independent of genetic background.
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Affiliation(s)
- Anna Ludovica Fracanzani
- Department of Internal Medicine, Policlinico Mangiagalli Regina Elena Hospital Foundation IRCCS, University of Milan, Italy
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Ricerca BM, Radio FC, De Marinis L, De Bernardo C, Castori M, Sacco E, Grammatico P, Majore S. Natural history of TFR2-related hereditary hemochromatosis in a 47-yr-old Italian patient. Eur J Haematol 2009; 83:494-6. [DOI: 10.1111/j.1600-0609.2009.01297.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Castagna A, Campostrini N, Zaninotto F, Girelli D. Hepcidin assay in serum by SELDI-TOF-MS and other approaches. J Proteomics 2009; 73:527-36. [PMID: 19683083 DOI: 10.1016/j.jprot.2009.08.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 08/05/2009] [Indexed: 01/01/2023]
Abstract
Hepcidin, a liver peptide hormone, is the central regulator of iron homeostasis. Hepcidin synthesis is modulated by iron stores, so that iron repletion increases its levels to prevent pathological overload, while iron deficiency strongly inhibits hepcidin to allow an increase in iron absorption from duodenal cells. The emerging pivotal role of hepcidin in iron homeostasis, along with its important links with basic pathways like inflammation, makes the availability of an accurate hepcidin assay as a potentially powerful investigative tool to improve our understanding as well as our diagnostic/prognostic capabilities in many human diseases. There has been a great interest worldwide in developing a reliable and widely applicable assay of the hormone in biological fluids. Being optimal for low-molecular-weight biomarkers, SELDI-TOF-MS has emerged as a valid tool for hepcidin assay. Here we review recent results obtained with this technique, as well as with other Mass Spectrometry-based and immunological methods.
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Affiliation(s)
- Annalisa Castagna
- Department of Clinical and Experimental Medicine, University of Verona, Verona, Italy.
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27
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Gan EK, Trinder D, Ayonrinde OT, Olynyk JK. Genetics of hereditary hemochromatosis: a clinical perspective. Expert Rev Endocrinol Metab 2009; 4:225-239. [PMID: 30743791 DOI: 10.1586/eem.09.9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hereditary hemochromatosis due to homozygosity for the C282Y mutation in the HFE gene product is the most common autosomal recessive genetic disorder in populations of northern European descent, where it attains a maximum prevalence of approximately one in 200. Cross-sectional and longitudinal studies have revealed that clinically significant iron-overload disease develops in at least 28% of male and 1% of female HFE C282Y homozygotes. The relatively low clinical penetrance is largely unexplained. Current evidence suggests a limited role for digenic inheritance of mutations in iron homeostasis genes in modifying the penetrance of hemochromatosis. Male gender is a strong genetic factor, promoting expression of clinical disease. Dietary intake of alcohol and noncitrus fruit may also act as important environmental modifiers of penetrance. With genetic analyses becoming simpler to perform, new genetic modifiers of hepatic iron loading and liver fibrogenesis are likely to be forthcoming.
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Affiliation(s)
- Eng K Gan
- a School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
| | - Debbie Trinder
- b School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
| | - Oyekoya T Ayonrinde
- c School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
| | - John K Olynyk
- d Professor, School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
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Abstract
Following the discovery of the HFE gene in 1996 and its linkage to the iron overload disorder hereditary hemochromatosis (HH) there have been profound developments in our understanding of the pathogenesis of the biochemical and clinical manifestations of a number of iron overload disorders. This article provides an update of recent developments and key issues relating to iron homeostasis and inherited disorders of iron overload, with emphasis on HFE-related HH, and is based on the content of the American Association for the Study of Liver Diseases Single-Topic Conference entitled "Hemochromatosis: What has Happened After HFE?" which was held at the Emory Convention Center in Atlanta, September 7-9, 2007.
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Affiliation(s)
- John K Olynyk
- School of Medicine and Pharmacology, University of Western Australia, Fremantle Hospital, Fremantle, Western Australia, Australia.
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Lubitz SA, Goldbarg SH, Mehta D. Sudden cardiac death in infiltrative cardiomyopathies: sarcoidosis, scleroderma, amyloidosis, hemachromatosis. Prog Cardiovasc Dis 2008; 51:58-73. [PMID: 18634918 DOI: 10.1016/j.pcad.2007.10.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Sarcoidosis, scleroderma, amyloidosis, and hemachromatosis are systemic infiltrative disorders that commonly affect the heart. Owing to their potential for diffuse organ involvement, these diseases may present with myriad clinical manifestations. Conduction system abnormalities are common, and each of these disorders has been associated with sudden cardiac death. In this review, we summarize the epidemiology, clinical features, diagnosis, and treatment of each of these entities. We place special emphasis on existing literature as it pertains to risk stratification and therapy aimed at the prevention of sudden cardiac death in these infiltrative cardiomyopathies.
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Affiliation(s)
- Steven A Lubitz
- Zena and Michael Wiener Cardiovascular Institute, Mount Sinai School of Medicine, NY, USA
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Brissot P, Troadec MB, Bardou-Jacquet E, Le Lan C, Jouanolle AM, Deugnier Y, Loréal O. Current approach to hemochromatosis. Blood Rev 2008; 22:195-210. [PMID: 18430498 DOI: 10.1016/j.blre.2008.03.001] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Iron overload diseases of genetic origin are an ever changing world, due to major advances in genetics and molecular biology. Five major categories are now established: HFE-related or type1 hemochromatosis, frequently found in Caucasians, and four rarer diseases which are type 2 (A and B) hemochromatosis (juvenile hemochromatosis), type 3 hemochromatosis (transferrin receptor 2 hemochromatosis), type 4 (A and B) hemochromatosis (ferroportin disease), and a(hypo)ceruloplasminemia. Increased duodenal iron absorption and enhanced macrophagic iron recycling, both due to an impairment of hepcidin synthesis, account for the development of cellular excess in types 1, 2, 3, and 4B hemochromatosis whereas decreased cellular iron egress is involved in the main form of type 4A) hemochromatosis and in aceruloplasminemia. Non-transferrin bound iron plays an important role in cellular iron excess and damage. The combination of magnetic resonance imaging (for diagnosing visceral iron overload) and of genetic testing has drastically reduced the need for liver biopsy. Phlebotomies remain an essential therapeutic tool but the improved understanding of the intimate mechanisms underlying these diseases paves the road for innovative therapeutic approaches.
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Affiliation(s)
- Pierre Brissot
- Liver Disease Unit, Liver Research Unit Inserm U-522, IFR 140, University of Rennes1, Hemochromatosis Reference Center, Laboratory of Molecular Genetics, University Hospital Pontchaillou, Rennes, France.
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Nelson JE, Kowdley KV. Non-HFE hemochromatosis: genetics, pathogenesis, and clinical management. Curr Gastroenterol Rep 2008; 7:71-80. [PMID: 15701302 DOI: 10.1007/s11894-005-0069-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Recent advances in our understanding of iron metabolism and the epidemiology of iron overload disorders have shown that hereditary forms of hemochromatosis can result from mutations in several iron metabolism genes other than HFE, including Hamp, HJV, TFR2, and SCL40A. These "non-HFE" forms of hemochromatosis are much rarer than HFE-related hemochromatosis but exhibit a similar phenotype, and with the exception of ferroportin disease, a similar pattern of inheritance and parenchymal iron accumulation. Therefore, these diseases can be thought of as variant forms of a primary hepatic iron overload syndrome; thus, a unified approach can be used for evaluation and diagnosis. Management generally consists of periodic phlebotomies until iron is depleted.
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Affiliation(s)
- James E Nelson
- Department of Medicine, Division of Gastroenterology, University of Washington Medical Center, 1959 NE Pacific Street, Box 356424, Seattle, WA 98195, USA
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Wallace DF, Summerville L, Crampton EM, Subramaniam VN. Defective trafficking and localization of mutated transferrin receptor 2: implications for type 3 hereditary hemochromatosis. Am J Physiol Cell Physiol 2008; 294:C383-90. [DOI: 10.1152/ajpcell.00492.2007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transferrin receptor 2 (TfR2), a homologue of transferrin receptor 1 (TfR1), is a key molecule involved in the regulation of iron homeostasis. Mutations in TfR2 result in iron overload with similar features to HFE-associated hereditary hemochromatosis. The precise role of TfR2 in iron metabolism and the functional consequences of disease-causing mutations have not been fully determined. We have expressed wild-type and various mutant forms of TfR2 that are associated with human disease in a mouse liver cell line. Intracellular and surface analysis shows that all the TfR2 mutations analyzed cause the intracellular retention of the protein in the endoplasmic reticulum, whereas the wild-type protein is expressed in endocytic structures and at the cell surface. Our results indicate that the majority of mutations that cause type 3 hereditary hemochromatosis are a consequence of the defective localization of the protein.
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Ayonrinde OT, Milward EA, Chua ACG, Trinder D, Olynyk JK. Clinical Perspectives on Hereditary Hemochromatosis. Crit Rev Clin Lab Sci 2008; 45:451-84. [DOI: 10.1080/10408360802335716] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Lim FL, Dooley JS, Roques AW, Grellier L, Dhillon AP, Walker AP. Hepatic iron concentration, fibrosis and response to venesection associated with the A77D and V162del "loss of function" mutations in ferroportin disease. Blood Cells Mol Dis 2007; 40:328-33. [PMID: 18160317 DOI: 10.1016/j.bcmd.2007.11.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 11/13/2007] [Accepted: 11/16/2007] [Indexed: 12/13/2022]
Abstract
Ferroportin disease is an autosomal dominant form of hemochromatosis associated with siderosis in cells of the mononuclear phagocyte system and, to varying degrees, in hepatocytes. Ferroportin was investigated as a candidate gene in two pedigrees with hyperferritinaemia and siderosis in mononuclear phagocytes. The entire ferroportin coding region was sequenced and hepatic iron concentration, histology and response to treatment were determined. The results were compared with previously reported cases. The A77D mutation was detected in patient 1, his father (patient 2) and his brother (patient 3), who had portal fibrosis. The V162del mutation was detected in patient 4, who developed anemia after the third weekly venesection. While the disease is rare, A77D and V162del are the most common ferroportin mutations in Caucasians. The spectrum of clinical expression of these two mutations was reviewed in all cases described to date. These mutations were associated with fibrosis in about a third of cases. For A77D and V162del, this analysis confirms that the threshold hepatic iron concentration for development of fibrosis may be higher than for classical hemochromatosis. These two mutations, which both decreased iron export in cell culture studies, give rise to similar patterns of clinical expression and morbidity, although the highest hepatic iron concentrations have been observed with A77D. It is important for clinicians to consider ferroportin disease in cases where there are features of iron overload unrelated to HFE, autosomal dominant inheritance and/or iron deposition in mononuclear phagocytes.
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Affiliation(s)
- Francesca L Lim
- Centre for Molecular Medicine, Department of Medicine, The Rayne Institute, University College London, 5 University Street, London, WC1E 6JF, UK
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Abstract
The human body requires about 1-2 mg of iron per day for its normal functioning, and dietary iron is the only source for this essential metal. Since humans do not possess a mechanism for the active excretion of iron, the amount of iron in the body is determined by the amount absorbed across the proximal small intestine and, consequently, intestinal iron absorption is a highly regulated process. In recent years, the liver has emerged as a central regulator of both iron absorption and iron release from other tissues. It achieves this by secreting a peptide hormone called hepcidin that acts on the small intestinal epithelium and other cells to limit iron delivery to the plasma. Hepcidin itself is regulated in response to various systemic stimuli including variations in body iron stores, the rate of erythropoiesis, inflammation and hypoxia, the same stimuli that have been known for many years to modulate iron absorption. This review will summarize recent findings on the role played by the liver and hepcidin in the regulation of body iron absorption.
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Affiliation(s)
- Deepak Darshan
- Iron Metabolism Laboratory, Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane Queensland 4029, Australia
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36
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Abstract
Non-HFE hereditary haemochromatosis (HH) refers to a genetically heterogeneous group of iron overload disorders that are unlinked to mutations in the HFE gene. The four main types of non-HFE HH are caused by mutations in the hemojuvelin, hepcidin, transferrin receptor 2 and ferroportin genes. Juvenile haemochromatosis is an autosomal recessive disorder and can be caused by mutations in either hemojuvelin or hepcidin. An adult onset form of HH similar to HFE-HH is caused by homozygosity for mutations in transferrin receptor 2. The autosomal dominant iron overload disorder ferroportin disease is caused by mutations in the iron exporter ferroportin. The clinical characteristics and molecular basis of the various types of non-HFE haemochromatosis are reviewed. The study of these disorders and the molecules involved has been invaluable in improving our understanding of the mechanisms involved in the regulation of iron metabolism.
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Affiliation(s)
- Daniel-F Wallace
- Membrane Transport Laboratory, The Queensland Institute of Medical Research, 300 Herston Road, Herston, Brisbane, QLD 4006 Australia
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37
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Abstract
Fe homeostasis is maintained by regulation of Fe absorption to balance largely unregulated body Fe losses. The majority of human subjects maintain relatively constant Fe stores; however, Fe deficiency and Fe overload are common conditions. Fe overload is frequently associated with mutations in genes of Fe metabolism. The present paper summarises present knowledge of these mutations as well as indicating other genes that animal studies have implicated as candidates for influencing body Fe stores.
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Affiliation(s)
- Johanne McGregor
- Division of Life Sciences, King's College London, London SE1 9NN, UK
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38
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Abstract
AbstractOur knowledge of mammalian iron metabolism has advanced dramatically over recent years. Iron is an essential element for virtually all living organisms. Its intestinal absorption and accurate cellular regulation is strictly required to ensure the coordinated synthesis of the numerous iron-containing proteins involved in key metabolic processes, while avoiding the uptake of excess iron that can lead to organ damage. A range of different proteins exist to ensure this fine control within the various tissues of the body. Among these proteins, transferrin receptor (TFR2) seems to play a key role in the regulation of iron homeostasis. Disabling mutations in TFR2 are responsible for type 3 hereditary hemochromatosis (Type 3 HH). This review describes the biological properties of this membrane receptor, with a particular emphasis paid to the structure, function and cellular localization. Although much information has been garnered on TFR2, further efforts are needed to elucidate its function in the context of the iron regulatory network.
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Drake SF, Morgan EH, Herbison CE, Delima R, Graham RM, Chua ACG, Leedman PJ, Fleming RE, Bacon BR, Olynyk JK, Trinder D. Iron absorption and hepatic iron uptake are increased in a transferrin receptor 2 (Y245X) mutant mouse model of hemochromatosis type 3. Am J Physiol Gastrointest Liver Physiol 2007; 292:G323-8. [PMID: 16935854 DOI: 10.1152/ajpgi.00278.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hereditary hemochromatosis type 3 is an iron (Fe)-overload disorder caused by mutations in transferrin receptor 2 (TfR2). TfR2 is expressed highly in the liver and regulates Fe metabolism. The aim of this study was to investigate duodenal Fe absorption and hepatic Fe uptake in a TfR2 (Y245X) mutant mouse model of hereditary hemochromatosis type 3. Duodenal Fe absorption and hepatic Fe uptake were measured in vivo by 59Fe-labeled ascorbate in TfR2 mutant mice, wild-type mice, and Fe-loaded wild-type mice (2% dietary carbonyl Fe). Gene expression was measured by real-time RT-PCR. Liver nonheme Fe concentration increased progressively with age in TfR2 mutant mice compared with wild-type mice. Fe absorption (both duodenal Fe uptake and transfer) was increased in TfR2 mutant mice compared with wild-type mice. Likewise, expression of genes participating in duodenal Fe uptake (Dcytb, DMT1) and transfer (ferroportin) were increased in TfR2 mutant mice. Nearly all of the absorbed Fe was taken up rapidly by the liver. Despite hepatic Fe loading, hepcidin expression was decreased in TfR2 mutant mice compared with wild-type mice. Even when compared with Fe-loaded wild-type mice, TfR2 mutant mice had increased Fe absorption, increased duodenal Fe transport gene expression, increased liver Fe uptake, and decreased liver hepcidin expression. In conclusion, despite systemic Fe loading, Fe absorption and liver Fe uptake were increased in TfR2 mutant mice in association with decreased expression of hepcidin. These findings support a model in which TfR2 is a sensor of Fe status and regulates duodenal Fe absorption and liver Fe uptake.
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Affiliation(s)
- S F Drake
- School of Medicine and Pharmacology, Fremantle Hospital, University of Western Australia, PO Box 480, Fremantle, 6959, WA, Australia
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40
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Lambert LA, Mitchell SL. Molecular Evolution of the Transferrin Receptor/Glutamate Carboxypeptidase II Family. J Mol Evol 2006; 64:113-28. [PMID: 17160644 DOI: 10.1007/s00239-006-0137-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Accepted: 10/03/2006] [Indexed: 02/07/2023]
Abstract
The transferrin receptor family is represented by at least seven different homologous proteins in primates. Transferrin receptor (TfR1) is a type II membrane glycoprotein that, as a cell surface homodimer, binds iron-loaded transferrin as part of the process of iron transfer and uptake. Other family members include transferrin receptor 2 (TfR2), glutamate carboxypeptidase II (GCP2 or PSMA), N-acetylated alpha-linked acidic dipeptidase-like protein (NLDL), N-acetylated alpha-linked acidic dipeptidase 2 (NAALAD2), and prostate-specific membrane antigen-like protein (PMSAL/GCPIII). We compared 86 different sequences from 24 different species, from mammals to fungi. Through this comparison, we have identified several highly conserved residues specific to each family not previously associated with clinical mutations. The evolutionary history of the TfR/GCP2 family shows repeated episodes of duplications consistent with recent theories that nondispensable, slowly evolving genes are more likely to form multiple gene families.
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Affiliation(s)
- Lisa Ann Lambert
- Department of Biology, Chatham College, Woodland Road, Pittsburgh, PA 15232, USA.
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41
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Abstract
In recent years, the number of proteins implicated in iron homeostasis has increased dramatically, and genetic causes have apparently been identified for the major disorders associated with tissue iron overload. These dramatic steps forward have transformed the way we look at iron-related disorders, particularly hemochromatosis. This review presents a concept of this disease that is based on this new knowledge and stems from the idea that, beyond their genetic diversities, all known hemochromatoses originate from the same metabolic error, the genetic disruption of human tendency for circulatory iron constancy. Hepcidin, the iron hormone, seems to hold a central pathogenic place in hemochromatosis, similar to insulin in diabetes: Genetically determined lack of hepcidin synthesis or activity may cause the disease.
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Affiliation(s)
- Antonello Pietrangelo
- Department of Internal Medicine, Center for Hemochromatosis, University of Modena and Reggio Emilia, Policlinico, 41100 Modena, Italy.
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42
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Abstract
The molecular basis of haemochromatosis has proved more complex than expected. After the 1996 identification of the main causative gene HFE and confirmation that most patients were homozygous for the founder C282Y mutation, it became clear that some families were linked to rarer conditions, first named 'non-HFE haemochromatosis'. The genetics of these less common forms was intensively studied between 2000 and 2004, leading to the recognition of haemojuvelin (HJV), hepcidin (HAMP), transferrin receptor 2 (TFR2) and ferroportin-related haemochromatosis, and opening the way for novel hypotheses such as those related to digenic modes of inheritance or the involvement of modifier genes. Molecular studies of rare haemochromatosis disorders have contributed to our understanding of iron homeostasis. In turn, recent findings from studies of knockout mice and functional studies have confirmed that HAMP plays a central role in mobilization of iron, shown that HFE, TFR2 and HJV modulate HAMP production according to the body's iron status, and demonstrated that HAMP negatively regulates cellular iron efflux by affecting the ferroportin cell surface availability. These data shed new light on the pathophysiology of all types of haemochromatosis, and offer novel opportunities to comment on phenotypic differences and distinguish mutations.
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43
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Abstract
Mutations in the hepcidin gene HAMP and the hemojuvelin gene HJV have recently been shown to result in juvenile haemochromatosis (JH). Hepcidin is an antimicrobial peptide that plays a key role in regulating intestinal iron absorption. Hepcidin levels are reduced in patients with haemochromatosis due to mutations in the HFE and HJV genes. Digenic inheritance of mutations in HFE and HAMP can result in either JH or hereditary haemochromatosis (HH) depending upon the severity of the mutation in HAMP. Here we review these findings and discuss how understanding the different types of haemochromatosis and our increasing knowledge of iron metabolism may help to elucidate the host's response to infection.
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44
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Camaschella C. Understanding iron homeostasis through genetic analysis of hemochromatosis and related disorders. Blood 2005; 106:3710-7. [PMID: 16030190 DOI: 10.1182/blood-2005-05-1857] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Genetic analysis of hemochromatosis has led to the discovery of a number of genes whose mutations disrupt iron homeostasis and lead to iron overload. The introduction of molecular tests into clinical practice has provided a tool for early diagnosis of these conditions. It has become clear that hemochromatosis includes a spectrum of disorders that range from simple biochemical abnormalities to chronic asymptomatic tissue damage in midlife to serious life-threatening diseases in young subjects. Molecular studies have identified the systemic loop that controls iron homeostasis and is centered on the hepcidin-ferroportin interaction. The complexity of this regulatory pathway accounts for the genetic heterogeneity of hemochromatosis and related disorders and raises the possibility that genes encoding components of the pathway may be modifiers of the main genotype. Molecular diagnosis has improved the classification of the genetic conditions leading to iron overload and identified novel entities, characterized by both iron loading and variable degrees of anemia. Despite the progress in the diagnosis, classification, and mechanisms of iron overload disorders, the treatment of affected patients continues to rely on regular phlebotomy. Understanding the molecular circuitry of iron control may lead to the identification of potential therapeutic targets for novel treatment strategies to be used in association with or as an alternative to phlebotomy.
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Affiliation(s)
- Clara Camaschella
- Università Vita-Salute and Istituto di Ricovero e Cura a Carratere Scientifico Ospedale San Raffaele, Via Olgettina, 60, 20132 Milano, Italy.
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45
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Abstract
Elucidation of the molecular pathways of iron transport through cells and its control is leading to an understanding of genetic iron loading conditions. The general phenotype of haemochromatosis is iron accumulation in liver parenchymal cells, a raised serum transferrin saturation and ferritin concentration. Four types have been identified: type 1 is the common form and is an autosomal recessive disorder of low penetrance strongly associated with mutations in the HFE gene on chromosome 6(p21.3); type 2 (juvenile haemochromatosis) is autosomal recessive, of high penetrance with causative mutations identified in the HFE2 gene on chromosome 1 (q21) and the HAMP gene on chromosome 19 (q13); type 3 is also autosomal recessive with mutations in the TfR2 gene on chromosome 3 (7q22); type 4 is an autosomal dominant condition with heterozygous mutations in the ferroportin 1 gene. In type 4, iron accumulates in both parenchymal and reticuloendothelial cells and the transferrin saturation may be normal. There are also inherited neurodegenerative conditions associated with iron accumulation. The current research challenges include understanding the central role of the HAMP gene (hepcidin) in controlling iron absorption and the reasons for the variable penetrance in HFE type 1.
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Affiliation(s)
- Mark Worwood
- Department of Haematology, University of Wales College of Medicine, Cardiff CF14 4XN, Wales, UK.
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46
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Cadet E, Perez AS, Capron D, Rochette J. Bases moléculaires des hémochromatoses génétiques. Rev Med Interne 2005; 26:393-402. [PMID: 15893030 DOI: 10.1016/j.revmed.2004.09.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Accepted: 09/16/2004] [Indexed: 10/26/2022]
Abstract
PURPOSE Recent discoveries in molecular mechanisms of iron metabolism have changed the classical view of hereditary iron overload conditions. We present natural mutations in newly discovered genes and related phenotypes observed in patients with different form of haemochromatosis. CURRENT KNOWLEDGE AND KEY POINTS Most haemochromatosis patients are homozygous for the C282Y mutation in the HFE gene. Ferroportin, TFR2, hemojuvelin and hepcidin mutations also cause iron overload. Recent data support the hypothesis that haemochromatosis should no longer be considered a monogenic disease but rather an oligogenic disorder. Several results suggest that haemochromatosis could result from digenic inheritance of mutations in HFE and HAMP. FUTURE PROSPECTS AND PROJECTS Other modifier genes probably influence penetrance in C282Y homozygous patients. Such genes could enhance or reduce the phenotypic expression in various iron overload conditions.
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Affiliation(s)
- E Cadet
- Service de génétique moléculaire médicale et UPRES EA 2629, CHU d'Amiens, université de Picardie-Jules-Verne, 3, rue des Louvels, 80036 Amiens cedex, France.
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Aguilar-Martinez P, Schved JF, Brissot P. The evaluation of hyperferritinemia: an updated strategy based on advances in detecting genetic abnormalities. Am J Gastroenterol 2005; 100:1185-94. [PMID: 15842597 DOI: 10.1111/j.1572-0241.2005.40998.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The number of new genes implicated in iron metabolism has dramatically increased during the last few years. Alterations of these genes may cause hyperferritinemia associated or not with iron overload. Correct assignment of the specific disorder of iron metabolism requires the identification of the causative gene mutation. Here, we propose a rational strategy that allows targeting the gene(s) to be screened for a diagnostic purpose. This strategy relies on the age of onset of the disease, the type of clinical symptoms, the biochemical profile (elevated or normal serum transferrin saturation (TfSat)), the presence or not of visceral iron excess, and the mode of inheritance (autosomal recessive or dominant). Then, two main entities can be differentiated: genetic (adult or juvenile) hemochromatosis characterized by elevated TfSat, and hereditary hyperferritinemias where TfSat is normal (or only slightly modified). Adult genetic hemochromatosis (GH) is related mainly to mutations of the HFE gene, and exceptionally to mutations of the TFR2 gene. Juvenile GH is a rare condition related principally to mutations of the HJV gene coding for hemojuvelin, and rarely to mutations of the HAMP gene coding for hepcidin. Hereditary hyperferritinemias are linked to mutations of three genes: the L-ferritin gene responsible for the hereditary hyperferritinemia cataract syndrome (without iron overload), the ferroportin gene leading to a dominant form of iron overload, and the ceruloplasmin (CP) gene corresponding to an iron overload syndrome with neurological symptoms. The proposed strategic approach may change with the identification of other genes involved in iron metabolism.
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48
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Takeo M, Kobayashi Y, Fujita N, Urawa N, Iwasa M, Horiike S, Tanaka H, Kaito M, Adachi Y. Upregulation of transferrin receptor 2 and ferroportin 1 mRNA in the liver of patients with chronic hepatitis C. J Gastroenterol Hepatol 2005; 20:562-9. [PMID: 15836704 DOI: 10.1111/j.1440-1746.2005.03770.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Iron accumulation has been reported to be associated with progression of liver injury. The mechanism of iron accumulation in the liver is not known. In the present study, hepatic messenger RNA (mRNA) expression of transferrin receptor (TfR)1, TfR2, and ferroportin (FP)1 was measured in patients with chronic hepatitis (CH). METHODS Eleven patients with CH-B and 43 patients with CH-C were enrolled. All patients underwent liver biopsy. Hepatic expression of TfR1, TfR2 and FP1 mRNA was analyzed using a real-time polymerase chain reaction. Total hepatic iron score (THIS) was evaluated by Prussian blue staining. RESULTS Serum ferritin concentration is significantly higher in CH-C than in CH-B. Values of THIS of >/=5 were observed only in CH-C patients (44% of CH-C patients). The expression level of TfR2 mRNA was 10-26-fold higher than the TfR1 mRNA expression level. The TfR2 and FP1 mRNA expression was significantly higher in CH-C than in CH-B patients. Hepatic expression of TfR2 and FP1 mRNA was well correlated with THIS. CONCLUSIONS Hepatic iron accumulation is more severe in patients with CH-C. Upregulation of hepatic iron transporters may contribute to the hepatic iron accumulation in CH-C.
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Affiliation(s)
- Masaki Takeo
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Mie University School of Medicine, Mie, Japan
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49
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Pietrangelo A, Caleffi A, Henrion J, Ferrara F, Corradini E, Kulaksiz H, Stremmel W, Andreone P, Garuti C. Juvenile hemochromatosis associated with pathogenic mutations of adult hemochromatosis genes. Gastroenterology 2005; 128:470-9. [PMID: 15685557 DOI: 10.1053/j.gastro.2004.11.057] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND AND AIMS Juvenile hemochromatosis is a severe form of hereditary iron overload that has thus far been linked to pathogenic mutations of the gene coding for hemojuvelin (HJV), on chromosome 1, or, more rarely, that coding for hepcidin ( HAMP ), on chromosome 19. A milder adult-onset form is due to pathogenic mutations of HFE or, rarely, serum transferrin receptor 2. METHODS We studied a pedigree with siblings affected by both juvenile and adult-onset hereditary hemochromatosis. Affected subjects underwent full clinical evaluation, as well as microsatellite and gene sequencing analysis. RESULTS Two siblings (male and female, aged 24 and 25 years, respectively) were hospitalized for severe endocrinopathy and cardiomyopathy. At age 18 and 17 years, they had presented with impotence and amenorrhea, respectively, and increased serum iron levels. Hypogonadotropic hypogonadism was confirmed in both, and liver biopsy showed marked hepatic iron accumulation and micronodular cirrhosis. Iron levels were normalized after 24 months (female) and 36 months (male) of weekly phlebotomies. Microsatellite analysis showed no linkage with chromosome 1 and 19, and gene sequencing showed no hemojuvelin or hepcidin gene mutations. Instead, combined mutations of HFE (C282Y/H63D compound heterozygosity) and serum transferrin receptor 2 (Q317X homozygosity) were found. A 21-year-old brother with a milder phenotype resembling classic adult-onset hereditary hemochromatosis carried only the Q317X serum transferrin receptor 2 homozygote mutation. CONCLUSIONS Juvenile hereditary hemochromatosis is not a distinct monogenic disorder invariably due to hemojuvelin or hepcidin mutations: it may be genetically linked to the adult-onset form of hereditary hemochromatosis.
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Affiliation(s)
- Antonello Pietrangelo
- Department of Internal Medicine, University of Modena and Regio Emilia, Policlinico, Modena, Italy.
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50
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Lorenz M, Kletzmayr J, Huber A, Hörl WH, Sunder-Plassmann G, Födinger M. Iron overload in kidney transplants: Prospective analysis of biochemical and genetic markers. Kidney Int 2005; 67:691-7. [PMID: 15673318 DOI: 10.1111/j.1523-1755.2005.67129.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND The prevalence of iron overload and the influence of mutations in the HFE and TRF2 gene on biochemical markers of iron overload among renal transplant patients is unknown. METHODS Serum iron, ferritin, transferrin saturation (TSAT), and liver function parameters were analyzed in a cohort of 438 renal transplants. In patients with iron overload, the time course of biochemical markers of iron status as well as the influence of iron loading mutations was investigated during a time period of 5 years. RESULTS Of 438 renal transplant patients 41 (9.4%) presented with an iron loading phenotype (TSAT above 40% and/or ferritin above 800 ng/mL). Mutations in the HFE gene were present in 12 of 33 (36.3%) patients with iron overload. Among these one patient was homozygous for HFE C282Y, and two patients were compound heterozygous for HFE C282Y/H63D. No individual tested positive for nine other mutations in HFE as well as theTRF2 Y250X mutation. Over time we observed a decrease of mean iron and ferritin levels, and of mean TSAT in our study sample. In patients with mutations in HFE this decrease was less pronounced as compared to patients without mutations. We found an independent positive association between the presence of mutations in HFE and serum alanine-aminotransferase levels at follow-up (P= 0.003). CONCLUSION Our study demonstrates that iron overload is frequently present in renal transplant patients and shows a continuous decrease over time. This decrease is possibly impaired by the HFE C282Y and HFE H63D mutations. Furthermore, mutations in HFE may influence liver function as reflected by increased alanine-aminotransferase concentrations.
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Affiliation(s)
- Matthias Lorenz
- Division of Nephrology and Dialysis, Department of Medicine III, Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University Vienna, Vienna, Austria
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