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Timoteo VJ, Chiang KM, Yang HC, Pan WH. Common and ethnic-specific genetic determinants of hemoglobin concentration between Taiwanese Han Chinese and European Whites: findings from comparative two-stage genome-wide association studies. J Nutr Biochem 2023; 111:109126. [PMID: 35964923 DOI: 10.1016/j.jnutbio.2022.109126] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 06/21/2022] [Accepted: 07/15/2022] [Indexed: 12/23/2022]
Abstract
Human iron nutrition is a result of interplays between genetic and environmental factors. However, there has been scarcity of data on the genetic variants associated with altered iron homeostasis and ethnic-specific associations are further lacking. In this study, we compared between the Taiwanese Han Chinese (HC) and European Whites the genetic determinants of hemoglobin (Hb) concentration, a biochemical parameter that in part reflects the amount of functional iron in the body. Through sex-specific two-stage genome-wide association studies (2S-GWAS), we observed the consistent Hb-association of SNPs in TMPRSS6 (chr 22), ABO (chr 9), and PRKCE (chr 2) across sexes in both ethnic groups. Specific to the Taiwanese HC, the Hb-association of AXIN1, together with other loci near the chr 16 alpha-globin gene cluster, was found novel. On the other hand, majority of the Hb-associated SNPs among Europeans were identified along the chr 6 major histocompatibility complex (MHC) region, which has established roles in immune system control. We report here strong Hb-associations of HFE and members of gene families (SLC17; H2A, H2B, H3, H4, H1; TRIM; ZSCAN, ZKSCAN, ZNF; HLA; BTN, OR), numerous SNPs in/nearby CARMIL1, PRRC2A, PSORS1C1, NOTCH4, TSBP1, C6orf15, and distinct associations with non-coding RNA genes. Our findings provide evidence for both common and ethnic-specific genetic determinants of Hb between East Asians and Caucasians. These will help to further our understanding of the iron and/or erythropoiesis physiology in humans and to identify high risk subgroups for iron imbalances - a primary requirement to meet the goal of precision nutrition for optimal health.
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Affiliation(s)
- Vanessa Joy Timoteo
- Taiwan International Graduate Program in Molecular Medicine, National Yang Ming Chiao Tung University and Academia Sinica, Taipei City, Taiwan; Institute of Biomedical Sciences, Academia Sinica, Taipei City, Taiwan
| | - Kuang-Mao Chiang
- Institute of Biomedical Sciences, Academia Sinica, Taipei City, Taiwan
| | - Hsin-Chou Yang
- Institute of Statistical Science, Academia Sinica, Taipei City, Taiwan
| | - Wen-Harn Pan
- Institute of Biomedical Sciences, Academia Sinica, Taipei City, Taiwan.
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Udomponglukkana R, Sasanakul W, Tangbubpha N, Chuansumrit A, Tim-Aroon T, Pongphitcha P, Sirachainan N. Response to Prolonged Duration of Therapeutic Dose Oral Iron Therapy in a Girl With Novel TMPRSS6 Gene Variants: A Case Report and Review Literature. J Pediatr Hematol Oncol 2023; 45:e109-18. [PMID: 36598965 DOI: 10.1097/MPH.0000000000002573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 09/18/2022] [Indexed: 01/05/2023]
Abstract
Iron-refractory iron deficiency anemia (IRIDA) is an autosomal recessive disorder caused by mutations in the TMPRSS6 gene, which impair iron homeostasis. We reported a 4-year-old girl who presented with a 1-year history of iron deficiency anemia. Her hemoglobin level increased from 6.5 g/dL to 12.6 g/dL with a prolonged duration of therapeutic dose oral iron therapy (5 mg/kg/d), and the level remained quite stable during the therapy. Genetic analysis of the TMPRSS6 gene revealed compound heterozygotes of 2 novel pathogenic variants: c.811C> T (NM_153609.3) in exon 7 (NP_705837: p.R271Ter) and c.1254C> G in exon 11 (p.Y418Ter). The results highlight the significance of genetic investigation and long-term iron therapy in iron-refractory iron deficiency anemia patients.
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Al-Jamea LH, Woodman A, M. Heiba N, Elshazly SA, Ben Khalaf N, Al-Yami FS, Bilal Waheed K, Al Mutair A, Alsedi A, Quiambao JV, Alzahrani FM, Albaqami WF, Al Qahtani FH, Mohammed Aljarah N, Fathallah DM, Halim Deifalla A. TMPRSS6 gene mutations in six Saudi families with iron refractory iron deficiency anemia. Gene 2023; 851:146977. [DOI: 10.1016/j.gene.2022.146977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 10/07/2022] [Accepted: 10/12/2022] [Indexed: 11/06/2022]
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Hoving V, Korman SE, Antonopoulos P, Donker AE, Schols SEM, Swinkels DW. IRIDA Phenotype in TMPRSS6 Monoallelic-Affected Patients: Toward a Better Understanding of the Pathophysiology. Genes (Basel) 2022; 13:genes13081309. [PMID: 35893046 PMCID: PMC9331965 DOI: 10.3390/genes13081309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/19/2022] [Accepted: 07/21/2022] [Indexed: 12/19/2022] Open
Abstract
Iron-refractory iron deficiency anemia (IRIDA) is an autosomal recessive inherited form of iron deficiency anemia characterized by discrepantly high hepcidin levels relative to body iron status. However, patients with monoallelic exonic TMPRSS6 variants have also been reported to express the IRIDA phenotype. The pathogenesis of an IRIDA phenotype in these patients is unknown and causes diagnostic uncertainty. Therefore, we retrospectively summarized the data of 16 patients (4 men, 12 women) who expressed the IRIDA phenotype in the presence of only a monoallelic TMPRSS6 variant. Eight unaffected relatives with identical exonic TMPRSS6 variants were used as controls. Haplotype analysis was performed to assess the (intra)genetic differences between patients and relatives. The expression and severity of the IRIDA phenotype were highly variable. Compared with their relatives, patients showed lower Hb, MCV, and TSAT/hepcidin ratios and inherited a different wild-type allele. We conclude that IRIDA in monoallelic TMPRSS6-affected patients is a phenotypically and genotypically heterogeneous disease that is more common in female patients. We hypothesize that allelic imbalance, polygenetic inheritance, or modulating environmental factors and their complex interplay are possible causes. This explorative study is the first step toward improved insights into the pathophysiology and improved diagnostic accuracy for patients presenting with IRIDA and a monoallelic exonic TMPRSS6 variant.
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Affiliation(s)
- Vera Hoving
- Department of Hematology, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GE Nijmegen, The Netherlands;
| | - Scott E. Korman
- Translational Metabolic Laboratory, Department of Laboratory Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GE Nijmegen, The Netherlands; (S.E.K.); (P.A.); (D.W.S.)
| | - Petros Antonopoulos
- Translational Metabolic Laboratory, Department of Laboratory Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GE Nijmegen, The Netherlands; (S.E.K.); (P.A.); (D.W.S.)
| | - Albertine E. Donker
- Department of Pediatrics, Máxima Medical Center, De Run 4600, 5504 NB Veldhoven, The Netherlands;
| | - Saskia E. M. Schols
- Department of Hematology, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GE Nijmegen, The Netherlands;
- Correspondence:
| | - Dorine W. Swinkels
- Translational Metabolic Laboratory, Department of Laboratory Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GE Nijmegen, The Netherlands; (S.E.K.); (P.A.); (D.W.S.)
- Sanquin Blood Bank, Sanquin Diagnostics BV, Plesmanlaan 125, 1066 NH Amsterdam, The Netherlands
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Pratt CA, Brown AGM, Dixit S, Farmer N, Natarajan A, Boyington J, Shi S, Lu Q, Cotton P. Perspectives: on Precision Nutrition Research in Heart, Lung, and Blood Diseases and Sleep Disorders. Adv Nutr 2022; 13:1402-1414. [PMID: 35561742 PMCID: PMC9526828 DOI: 10.1093/advances/nmac053] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 04/20/2022] [Accepted: 05/06/2022] [Indexed: 01/28/2023] Open
Abstract
The release of the 2020-2030 Strategic Plan for NIH Nutrition Research (SPNR) and its emphasis on precision nutrition has provided an opportunity to identify future nutrition research that addresses individual variability in response to diet and nutrition across the life span-including those relevant to the Strategic Vision of the National Heart, Lung, and Blood Institute (NHLBI). The SPNR and the NHLBI's Strategic Vision were developed with extensive input from the extramural research community, and both have 4 overarching strategic goals within which are embedded several objectives for research. For the SPNR, these include 1) spur discovery science and normal biological functions (e.g., role of the microbiome in health and disease), 2) population science to understand individual differences (e.g., biomarkers including 'omics that predict disease status), 3) emerging scientific areas of investigation and their application (e.g., data science, artificial intelligence), and 4) cross-cutting themes (e.g., training the scientific workforce and minority health and health disparities). These strategic goals and objectives serve as blueprints for research and training. Nutrition remains important in the prevention and treatment of heart, lung, blood, and sleep (HLBS) disorders and diseases, and the NHLBI has played a pivotal role in supporting nutrition research. In this paper, we report important gaps in the scientific literature related to precision nutrition in HLBS diseases. Research opportunities that could stimulate precision nutrition and their alignment with the SPNR and the NHLBI Strategic Vision Objectives are provided. These opportunities include 1) exploring individual differences in response to varying dietary patterns and nutrients; 2) investigating genetic/epigenetic, biological (e.g., microbiome, biomarkers), social, psychosocial, and environmental underpinnings of individual variability in diet; 3) elucidating the role of circadian rhythm and chrononutrition; and 4) applying implementation science research methods in precision nutrition interventions relevant to HLBS diseases.
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Affiliation(s)
| | - Alison G M Brown
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
| | - Shilpy Dixit
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
| | - Nicole Farmer
- National Institutes of Health, Clinical Center, Bethesda, MD, USA
| | - Aruna Natarajan
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
| | - Josephine Boyington
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
| | - Scarlet Shi
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
| | - Qing Lu
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
| | - Paul Cotton
- National Heart Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD, USA
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Al-Jamea LH, Woodman A, Heiba NM, Elshazly SA, Khalaf NB, Fathallah DM, Al-Nashmi ME, Quiambao JV, Deifalla AH. Genetic analysis of TMPRSS6 gene in Saudi female patients with iron deficiency anemia. Hematol Oncol Stem Cell Ther 2020; 14:41-50. [PMID: 32446932 DOI: 10.1016/j.hemonc.2020.04.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 04/20/2020] [Accepted: 04/24/2020] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVE/BACKGROUND Mutations in transmembrane protease serine 6 (TMPRSS6) gene induce high hepcidin level, which causes iron-refractory iron deficiency anemia (IRIDA) by preventing duodenal iron absorption. This study aims to identify the common genetic variations of the TMPRSS6 gene that affect iron levels among Saudi female patients with iron deficiency anemia (IDA). METHODS All study participants were Saudi females (12-49 years old): 32 patients with IDA, 32 patients with IRIDA, and 34 healthy individuals comprising the control group. Hematological investigations, iron profile, serum hepcidin level, and TMPRSS6 gene transcription were determined. The TMPRSS6 gene was amplified, sequenced, and analyzed among all study participants. RESULTS The mean hepcidin and TMPRSS6 RNA transcription levels in IDA and IRIDA groups were significantly lower than those in the control group. TMPRSS6 gene sequence analysis detected 41 variants: two in the 5' untranslated region (5'UTR), 17 in introns, and 22 in exons. Thirty-three variants were previously reported in the Single Nucleotide Polymorphism Database, and eight variants were novel; one novel variant was in 5'UTR (g.-2 T > G); five novel variants were detected in exons (p.W73X, p.D479N, p.E523K, p.L674L, and p.I799I). At the time of the sequence analysis of our samples, two variants-p.D479N and p.674L-were novel. However, these variants are present at a very low allele frequency in other populations (L674L, 0.00007761 and D479N, 0.000003980). CONCLUSION This is the first study to investigate the genetic variants of TMPRSS6 gene in Saudi female patients with IDA. The generated data will serve as a reference for future studies on IDA in the Arab population.
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Affiliation(s)
- Lamiaa H Al-Jamea
- Clinical Laboratory Sciences, Prince Sultan Military College of Health Sciences, Dhahran, Saudi Arabia.
| | - Alexander Woodman
- Postgraduate Studies and Research, Prince Sultan Military College of Health Sciences, Dhahran, Saudi Arabia
| | | | | | - Noureddine Ben Khalaf
- Department of Life Sciences, Health Biotechnology Program, College of Graduate Studies, Arabian Gulf University, Manama, Bahrain
| | - Dahmani M Fathallah
- Department of Life Sciences, Health Biotechnology Program, College of Graduate Studies, Arabian Gulf University, Manama, Bahrain
| | - Moudi E Al-Nashmi
- Department of Medical Laboratory Services, Ministry of Health, Kuwait
| | - Jenifer Vecina Quiambao
- Postgraduate Studies and Research, Prince Sultan Military College of Health Sciences, Dhahran, Saudi Arabia
| | - Abdel Halim Deifalla
- Anatomy Department, College of Medicine and Medical Sciences, Arabian Gulf University, Manama, Bahrain
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Li Y, Huang X, Wang J, Huang R, Wan D. Regulation of Iron Homeostasis and Related Diseases. Mediators Inflamm 2020; 2020:6062094. [PMID: 32454791 DOI: 10.1155/2020/6062094] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 03/23/2020] [Indexed: 12/18/2022] Open
Abstract
The liver is the organ for iron storage and regulation; it senses circulating iron concentrations in the body through the BMP-SMAD pathway and regulates the iron intake from food and erythrocyte recovery into the bloodstream by secreting hepcidin. Under iron deficiency, hypoxia, and hemorrhage, the liver reduces the expression of hepcidin to ensure the erythropoiesis but increases the excretion of hepcidin during infection and inflammation to reduce the usage of iron by pathogens. Excessive iron causes system iron overload; it accumulates in never system and damages neurocyte leading to neurodegenerative diseases such as Parkinson's syndrome. When some gene mutations affect the perception of iron and iron regulation ability in the liver, then they decrease the expression of hepcidin, causing hereditary diseases such as hereditary hemochromatosis. This review summarizes the source and utilization of iron in the body, the liver regulates systemic iron homeostasis by sensing the circulating iron concentration, and the expression of hepcidin regulated by various signaling pathways, thereby understanding the pathogenesis of iron-related diseases.
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Kong X, Dong X, Yang S, Qian J, Yang J, Jiang Q, Li X, Wang B, Yan D, Lu S, Zhu L, Li G, Li M, Yi S, Deng M, Sun L, Zhou X, Mao H, Gou X. Natural selection on TMPRSS6 associated with the blunted erythropoiesis and improved blood viscosity in Tibetan pigs. Comp Biochem Physiol B Biochem Mol Biol 2019; 233:11-22. [PMID: 30885835 DOI: 10.1016/j.cbpb.2019.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 03/08/2019] [Accepted: 03/08/2019] [Indexed: 02/04/2023]
Abstract
Tibetan pigs, indigenous to Tibetan plateau, are well adapted to hypoxia. So far, there have been not any definitively described genes and functional sites responsible for hypoxia adaptation for the Tibetan pig. The whole genome-wide association studies in human suggested that genetic variations in TMPRSS6 was associated with hemoglobin concentration (HGB) and red cell counts (RBC). Here we conducted resequencing of the nearly entire genomic region (40.1 kb) of the candidate gene TMPRSS6 in 40 domestic pigs and 40 wild boars along continuous altitudes and identified 708 SNPs, in addition to an indel (CGTG/----) in the intron 10. We conduct the CGTG indel in 838 domestic pigs, both the CGTG deletion frequency and the pairwise r2 linkage disequilibrium showed an increase with elevated altitudes, suggesting that TMPRSS6 has been under Darwinian positive selection. As the conserved core sequence of hypoxia-response elements (HREs), the deletion of CGTG in Tibetan pigs decreased the expression levels of TMPRSS6 mRNA and protein in the liver revealed by real-time quantitative PCR and western blot, respectively. We compared domestic pigs and Tibetan pigs living continuous altitudes, found that the blood-related traits with the increase of altitude, however, the HGB did not increase with the elevation in Tibetan pigs. Genotype association analysis results dissected a genetic effect on reducing HGB by 13.25 g/L in Gongbo'gyamda Tibetan pigs, decreasing mean corpuscular volume (MCV) by 4.79 fl in Diqing Tibetan pigs. In conclusion, the CGTG deletion of TMPRSS6 resulted in lower HGB and smaller MCV, which could reflect a blunting erythropoiesis and improving blood viscosity as well as erythrocyte deformability. It remains to be determined whether a blunting of erythropoiesis for TMPRSS6 or others genetic effects are the physiological adaptations among Tibetan pigs.
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Affiliation(s)
- Xiaoyan Kong
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Xinxing Dong
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Shuli Yang
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Jinhua Qian
- Department of Animal Science, Yuxi Agriculture Vocational-Technical College, Yuxi, Yunnan, China
| | - Jianfa Yang
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Qiang Jiang
- Dairy Cattle Research Center, Shandong Academy of Agricultural Science, Jinan, Shandong, China
| | - Xingrun Li
- Department of Animal Science, Dali Vocational and Technical College of Agriculture and Forestry, Dali, Yunnan, China
| | - Bo Wang
- Research Experimental Center, Yunnan University of Traditional Chinese Medicine, Kunming, Yunnan, China
| | - Dawei Yan
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Shaoxiong Lu
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Li Zhu
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Gen Li
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Minjuan Li
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Shengnan Yi
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Mingyue Deng
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Liyuan Sun
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Xiaoxia Zhou
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China
| | - Huaming Mao
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China.
| | - Xiao Gou
- Faculty of Animal Science and Technology, Yunnan Agricultural University, Kunming, Yunnan, China.
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Nalado AM, Dickens C, Dix-Peek T, Mahlangu JN, Olorunfemi G, Paget G, Duarte R, Naicker S. TMPRSS6 rs855791 polymorphism and susceptibility to iron deficiency anaemia in non-dialysis chronic kidney disease patients in South Africa. Int J Mol Epidemiol Genet 2019; 10:1-9. [PMID: 30911357 PMCID: PMC6420716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 01/16/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND In genome-wide studies, there is a strong association between the TMPRSS6 allele A736V (rs855791) and significantly lower levels of serum iron, transferrin saturation, haemoglobin, and mean corpuscular volumes. The influence of this genetic variant on susceptibility to iron deficiency anaemia (IDA) in chronic kidney disease (CKD) patients is unknown. METHODS In this cross-sectional study, we measured the full blood count and TMPRSS6 T>C polymorphism in black adult participants (n=260) with CKD and healthy controls (n=146) at the Charlotte Maxeke Johannesburg Academic Hospital, South Africa. RESULTS The overall prevalence of anaemia in the CKD and control population was 46.9% and 19.6% respectively. Twenty-six per cent of CKD participants were iron deficient. The prevalence of rs855791 C homozygosity was similar among iron deficient and non-iron deficient anaemia groups (86.1% vs 84.2%, P=0.723). When the analysis was confined to subjects with or without functional iron deficiency anaemia, C homozygote (88.3% vs 84.4%, P=0.425) was similar for both groups. CONCLUSIONS Our study suggests that homozygosity for TMPRSS6 rs855791 C genotype does not influence IDA in non-dialysis CKD patients in our population.
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Affiliation(s)
- Aishatu Muhammad Nalado
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of The WitwatersrandJohannesburg, South Africa
- Department of Internal Medicine, College of Health Sciences, Bayero UniversityKano, Nigeria
| | - Caroline Dickens
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of The WitwatersrandJohannesburg, South Africa
| | - Therese Dix-Peek
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of The WitwatersrandJohannesburg, South Africa
| | - Johnny N Mahlangu
- School of Pathology, Faculty of Health Sciences, University of The WitwatersrandJohannesburg, South Africa
| | - Gbenga Olorunfemi
- Division of Epidemiology and Biostatistics, School of Public Health, University of The WitwatersrandJohannesburg, South Africa
| | - Graham Paget
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of The WitwatersrandJohannesburg, South Africa
| | - Raquel Duarte
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of The WitwatersrandJohannesburg, South Africa
| | - Saraladevi Naicker
- Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Science, University of The WitwatersrandJohannesburg, South Africa
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Dion SP, Béliveau F, Morency LP, Désilets A, Najmanovich R, Leduc R. Functional diversity of TMPRSS6 isoforms and variants expressed in hepatocellular carcinoma cell lines. Sci Rep 2018; 8:12562. [PMID: 30135444 DOI: 10.1038/s41598-018-30618-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 08/02/2018] [Indexed: 02/06/2023] Open
Abstract
TMPRSS6, also known as matriptase-2, is a type II transmembrane serine protease that plays a major role in iron homeostasis by acting as a negative regulator of hepcidin production through cleavage of the BMP co-receptor haemojuvelin. Iron-refractory iron deficiency anaemia (IRIDA), an iron metabolism disorder, is associated with mutations in the TMPRSS6 gene. By analysing RNA-seq data encoding TMPRSS6 isoforms and other proteins involved in hepcidin production, we uncovered significant differences in expression levels between hepatocellular carcinoma (HCC) cell lines and normal human liver samples. Most notably, TMPRSS6 and HAMP expression was found to be much lower in HepG2 and Huh7 cells when compared to human liver samples. Furthermore, we characterized the common TMPRSS6 polymorphism V736A identified in Hep3B cells, the V795I mutation found in HepG2 cells, also associated with IRIDA, and the G603R substitution recently detected in two IRIDA patients. While variant V736A is as active as wild-type TMPRSS6, mutants V795I and G603R displayed significantly reduced proteolytic activity. Our results provide important information about commonly used liver cell models and shed light on the impact of two TMPRSS6 mutations associated with IRIDA.
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Abstract
Measurement of serum ferritin (SF) is currently the laboratory test recommended for diagnosing iron deficiency. In the absence of an associated disease, a low SF value is an early and highly specific indicator of iron deficiency. The WHO criteria proposed to define depleted storage iron are 12μg/L for children under 5 years and 15μg/L for those over 5 years. A higher threshold of 30μg/L is used in the presence of infection or inflammation. Iron deficiency anemia, with typical low mean corpuscular volume and mean corpuscular hemoglobin, is only present at the end stage of iron deficiency. Other diagnostic tests for iron deficiency including iron parameters (low serum iron, increased total iron-binding capacity, low transferrin saturation) and erythrocyte traits (low mean corpuscular volume, increased zinc protoporphyrin) provide little additional diagnostic value over SF. In children, serum soluble transferrin receptor (sTfR) has been reported to be a sensitive indicator of iron deficiency and is relatively unaffected by inflammation. On the other hand, sTfR is directly related to extent of erythroid activity and not commonly used in clinical practice. In population surveys, approaches based on combinations of markers have been explored to improve the specificity and sensitivity of diagnostic. In addition to Hb value determination, a combination of parameters (among transferrin saturation, zinc protoporphyrin, mean corpuscular volume or serum ferritin) was generally used to assess iron deficiency. More recently sTfR/ ferritin index were evaluated, sTfR in conjunction with SF allowing to better distinguishing iron deficiency from inflammatory anemia. Also, hepcidin measurements appeared an interesting marker for diagnosing iron deficiency and identifying individuals in need of iron supplementation in populations where inflammatory or infectious diseases are frequently encountered. Reticulocyte Hb content (CHr) determination is an early parameter of iron deficiency erythropoiesis. CHr can be measured with several automated hematology analyzers and so, used for individual's iron status assessment. In addition to Hb concentration determination, individual's iron status is commonly assessed in the pediatric clinical practice by the SF measurement accompanied by the determination of C-reactive protein for detection of a simultaneous acute infection and/or inflammation.
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Affiliation(s)
- I Thuret
- Service d'onco-hématologie pédíatrique, CHU Timone Enfants, centre de référence des thalassémies, 264, rue Saint-Pierre, 13005 Marseille, France.
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Abstract
Haemochromatosis is defined as systemic iron overload of genetic origin, caused by a reduction in the concentration of the iron regulatory hormone hepcidin, or a reduction in hepcidin-ferroportin binding. Hepcidin regulates the activity of ferroportin, which is the only identified cellular iron exporter. The most common form of haemochromatosis is due to homozygous mutations (specifically, the C282Y mutation) in HFE, which encodes hereditary haemochromatosis protein. Non-HFE forms of haemochromatosis due to mutations in HAMP, HJV or TFR2 are much rarer. Mutations in SLC40A1 (also known as FPN1; encoding ferroportin) that prevent hepcidin-ferroportin binding also cause haemochromatosis. Cellular iron excess in HFE and non-HFE forms of haemochromatosis is caused by increased concentrations of plasma iron, which can lead to the accumulation of iron in parenchymal cells, particularly hepatocytes, pancreatic cells and cardiomyocytes. Diagnosis is noninvasive and includes clinical examination, assessment of plasma iron parameters, imaging and genetic testing. The mainstay therapy is phlebotomy, although iron chelation can be used in some patients. Hepcidin supplementation might be an innovative future approach.
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Affiliation(s)
- Pierre Brissot
- INSERM, Univ. Rennes, INRA, Institut NUMECAN (Nutrition Metabolisms and Cancer) UMR_A 1341, UMR_S 1241, F-35000 Rennes, France
| | - Antonello Pietrangelo
- Division of Internal Medicine 2 and Center for Haemochromatosis, University Hospital of Modena, Modena, Italy
| | - Paul C. Adams
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
| | - Barbara de Graaff
- Menzies Institute for Medical Research, University of Tasmania, Tasmania, Australia
| | | | - Olivier Loréal
- INSERM, Univ. Rennes, INRA, Institut NUMECAN (Nutrition Metabolisms and Cancer) UMR_A 1341, UMR_S 1241, F-35000 Rennes, France
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Dion SP, Béliveau F, Désilets A, Ghinet MG, Leduc R. Transcriptome analysis reveals TMPRSS6 isoforms with distinct functionalities. J Cell Mol Med 2018; 22:2498-2509. [PMID: 29441715 PMCID: PMC5867103 DOI: 10.1111/jcmm.13562] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 01/10/2018] [Indexed: 11/30/2022] Open
Abstract
TMPRSS6 (matriptase-2) is a type II transmembrane serine protease involved in iron homoeostasis. At the cell surface of hepatocytes, TMPRSS6 cleaves haemojuvelin (HJV) and regulates the BMP/SMAD signalling pathway leading to production of hepcidin, a key regulator of iron absorption. Although four TMPRSS6 human isoforms and three mice Tmprss6 isoforms are annotated in databases (Ensembl and RefSeq), their relative expression or activity has not been studied. Analyses of RNA-seq data and RT-PCR from human tissues reveal that TMPRSS6 isoform 1 (TMPRSS6-1) and 3 are mostly expressed in human testis while TMPRSS6-2 and TMPRSS6-4 are the main transcripts expressed in human liver, testis and pituitary. Furthermore, we confirm the existence and analyse the relative expression of three annotated mice Tmprss6 isoforms. Using heterologous expression in HEK293 and Hep3B cells, we show that all human TMPRSS6 isoforms reach the cell surface but only TMPRSS6-1 undergoes internalization. Moreover, truncated TMPRSS6-3 or catalytically altered TMPRSS6-4 interact with HJV and prevent its cleavage by TMPRSS6-2, suggesting their potential role as dominant negative isoforms. Taken together, our results highlight the importance of understanding the precise function of each TMPRSS6 isoforms both in human and in mouse.
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Affiliation(s)
- Sébastien P. Dion
- Department of Pharmacology‐PhysiologyFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
- Institut de Pharmacologie de SherbrookeFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
| | - François Béliveau
- Department of Pharmacology‐PhysiologyFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
- Institut de Pharmacologie de SherbrookeFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
| | - Antoine Désilets
- Department of Pharmacology‐PhysiologyFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
- Institut de Pharmacologie de SherbrookeFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
| | - Mariana Gabriela Ghinet
- Department of Pharmacology‐PhysiologyFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
- Institut de Pharmacologie de SherbrookeFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
| | - Richard Leduc
- Department of Pharmacology‐PhysiologyFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
- Institut de Pharmacologie de SherbrookeFaculty of Medicine and Health SciencesUniversité de SherbrookeSherbrookeQCCanada
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15
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Bhatia P, Jain R, Singh A. A structured approach to iron refractory iron deficiency anemia (IRIDA) diagnosis (SAID): The more is “SAID” about iron, the less it is. Pediatric Hematology Oncology Journal 2017. [DOI: 10.1016/j.phoj.2017.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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16
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Cheng M, Lin L, Huang M, Lee H, Ji D, Lin C, Hsia K. Downexpression of Matriptase-2 Correlates With Tumor Progression and Clinical Prognosis in Oral Squamous-Cell Carcinoma. Appl Immunohistochem Mol Morphol 2017; 25:481-8. [DOI: 10.1097/pai.0000000000000324] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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17
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Abstract
OBJECTIVES We report a case of a 7-year-old girl with severe hypochromic microcytic anemia, who was unresponsive to classical iron supplements. We suspected IRIDA, iron-refractory iron-deficiency anemia, a genetic iron metabolism disorder, caused by TMPRSS6 variations. TMPRSS6 encodes matriptase-2, a negative regulator of hepcidin, and its pathological variants are related to normal to high levels of hepcidin. We analyzed the TMPRSS6 gene and we improved clinical management of the patient, selecting the appropriate supplementation therapy. Intervention & Technique: The parenteral iron therapy was started, but the patient was only partially responsive and the anemia persisted. To confirm the diagnosis, the TMPRSS6 gene sequence was analyzed by DNA sequencing and other relevant biochemical parameters were evaluated. RESULTS The TMPRSS6 sequence analysis showed a complex genotype with a rare heterozygous missense variant, in addition to other common polymorphisms. The serum hepcidin value was normal. We unexpectedly observed a normalization of patient's hemoglobin (Hb) levels only after liposomal iron treatment. DISCUSSION AND CONCLUSION The proband was symptomatic for IRIDA during a critical phase of growth and development, but we did not find a clearly causative genotype. A long-term result, improving stably patient's Hb levels, was obtained only after liposomal iron supplementation. Children may be at greater risk for iron deficiency and the degree of anemia as well as the response to the iron supplements varies markedly patient to patient. Here, we show the importance of comprehensive study of these patients in order to collect useful information about genotype-phenotype association of genes involved in iron metabolism.
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Affiliation(s)
- Anna Paola Capra
- a Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi' , 'Gaetano Martino' University Hospital of Messina , Messina , Italy
| | - Elisa Ferro
- a Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi' , 'Gaetano Martino' University Hospital of Messina , Messina , Italy
| | - Laura Cannavò
- a Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi' , 'Gaetano Martino' University Hospital of Messina , Messina , Italy
| | - Maria Angela La Rosa
- a Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi' , 'Gaetano Martino' University Hospital of Messina , Messina , Italy
| | - Giuseppina Zirilli
- a Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi' , 'Gaetano Martino' University Hospital of Messina , Messina , Italy
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18
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Yaish HM, Farrell CP, Christensen RD, MacQueen BC, Jackson LK, Trochez-Enciso J, Kaplan J, Ward DM, Salah WK, Phillips JD. Two novel mutations in TMPRSS6 associated with iron-refractory iron deficiency anemia in a mother and child. Blood Cells Mol Dis 2017; 65:38-40. [PMID: 28460265 DOI: 10.1016/j.bcmd.2017.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/07/2017] [Accepted: 04/08/2017] [Indexed: 01/06/2023]
Abstract
In an iron deficient child, oral iron repeatedly failed to improve the condition. Whole exome sequencing identified one previously reported plus two novel mutation in the TMPRSS6 gene, with no mutations in other iron-associated genes. We propose that these mutations result in a novel variety of iron-refractory iron deficiency anemia.
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Affiliation(s)
- Hassan M Yaish
- Division of Hematology/Oncology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA.
| | - Colin P Farrell
- Center for Iron and Heme Disorders, University of Utah, and Division of Hematology/Oncology, Department of Medicine and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Robert D Christensen
- Division of Hematology/Oncology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA; Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Brianna C MacQueen
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Laurie K Jackson
- Center for Iron and Heme Disorders, University of Utah, and Division of Hematology/Oncology, Department of Medicine and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Jesus Trochez-Enciso
- Center for Iron and Heme Disorders, University of Utah, and Division of Hematology/Oncology, Department of Medicine and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Jerry Kaplan
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Diane M Ward
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Walid K Salah
- Division of Hematology/Oncology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - John D Phillips
- Center for Iron and Heme Disorders, University of Utah, and Division of Hematology/Oncology, Department of Medicine and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA; Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA
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19
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Donker AE, Schaap CC, Novotny VMJ, Smeets R, Peters TMA, van den Heuvel BLP, Raphael MF, Rijneveld AW, Appel IM, Vlot AJ, Versluijs AB, van Gelder M, Granzen B, Janssen MC, Rennings AJ, van de Veerdonk FL, Brons PP, Bakkeren DL, Nijziel MR, Vlasveld LT, Swinkels DW. Iron refractory iron deficiency anemia: a heterogeneous disease that is not always iron refractory. Am J Hematol 2016; 91:E482-E490. [PMID: 27643674 PMCID: PMC6586001 DOI: 10.1002/ajh.24561] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 09/13/2016] [Accepted: 09/15/2016] [Indexed: 12/16/2022]
Abstract
TMPRSS6 variants that affect protein function result in impaired matriptase‐2 function and consequently uninhibited hepcidin production, leading to iron refractory iron deficiency anemia (IRIDA). This disease is characterized by microcytic, hypochromic anemia and serum hepcidin values that are inappropriately high for body iron levels. Much is still unknown about its pathophysiology, genotype–phenotype correlation, and optimal clinical management. We describe 14 different TMPRSS6 variants, of which 9 are novel, in 21 phenotypically affected IRIDA patients from 20 families living in the Netherlands; 16 out of 21 patients were female. In 7 out of 21 cases DNA sequencing and multiplex ligation dependent probe amplification demonstrated only heterozygous TMPRSS6 variants. The age at presentation, disease severity, and response to iron supplementation were highly variable, even for patients and relatives with similar TMPRSS6 genotypes. Mono‐allelic IRIDA patients had a milder phenotype with respect to hemoglobin and MCV and presented significantly later in life with anemia than bi‐allelic patients. Transferrin saturation (TSAT)/hepcidin ratios were lower in IRIDA probands than in healthy relatives. Most patients required parenteral iron. Genotype alone was not predictive for the response to oral iron. We conclude that IRIDA is a genotypically and phenotypically heterogeneous disease. The high proportion of female patients and the discrepancy between phenotypes of probands and relatives with the same genotype, suggest a complex interplay between genetic and acquired factors in the pathogenesis of IRIDA. In the absence of inflammation, the TSAT/hepcidin ratio is a promising diagnostic tool, even after iron supplementation has been given. Am. J. Hematol. 91:E482–E490, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Albertine E. Donker
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Translational Metabolic Laboratory, Department of Laboratory MedicineRadboud University Medical CenterNijmegen, The Netherlands
| | - Charlotte C.M. Schaap
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Translational Metabolic Laboratory, Department of Laboratory MedicineRadboud University Medical CenterNijmegen, The Netherlands
| | - Vera M. J. Novotny
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Department of HematologyRadboud University Medical CenterNijmegen The Netherlands
| | - Roel Smeets
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Translational Metabolic Laboratory, Department of Laboratory MedicineRadboud University Medical CenterNijmegen, The Netherlands
| | - Tessa M. A. Peters
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Translational Metabolic Laboratory, Department of Laboratory MedicineRadboud University Medical CenterNijmegen, The Netherlands
| | - Bert L. P. van den Heuvel
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Translational Metabolic Laboratory, Department of Laboratory MedicineRadboud University Medical CenterNijmegen, The Netherlands
| | - Martine F. Raphael
- Department of Pediatric HematologyUniversity Medical CenterUtrecht The Netherlands
| | | | - Inge M. Appel
- Department of Pediatric HematologyErasmus MC, Sophia Children's Hospital Rotterdam The Netherlands
| | - Andre J. Vlot
- Department of Internal MedicineRijnstate Hospital Arnhem, Arnhem The Netherlands
| | | | | | - Bernd Granzen
- Department of PediatricsMaastricht UMCMaastricht The Netherlands
| | - Mirian C.H. Janssen
- Department of Internal MedicineRadboud University Medical CenterNijmegen The Netherlands
| | - Alexander J.M. Rennings
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Department of Internal MedicineRadboud University Medical CenterNijmegen The Netherlands
| | | | - Paul P.T. Brons
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Department of Pediatric Hemato‐OncologyRadboud University Medical CenterNijmegen, The Netherlands
| | - Dirk L. Bakkeren
- Department of Laboratory MedicineMáxima Medical Center, VeldhovenEindhoven The Netherlands
| | - Marten R. Nijziel
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Department of HematologyRadboud University Medical CenterNijmegen The Netherlands
- Department of Hemato‐OncologyMáxima Medical CenterVeldhoven Eindhoven The Netherlands
| | - L. Thom Vlasveld
- Department of Internal MedicineBronovo HospitalThe Hague The Netherlands
| | - Dorine W. Swinkels
- Radboudumc Expert Center for Iron Disorders, Radboud University Medical CenterNijmegen, The Netherlands
- Translational Metabolic Laboratory, Department of Laboratory MedicineRadboud University Medical CenterNijmegen, The Netherlands
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20
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Baeza-Richer C, Arroyo-Pardo E, Blanco-Rojo R, Toxqui L, Remacha A, Vaquero MP, López-Parra AM. Genetic contribution to iron status: SNPs related to iron deficiency anaemia and fine mapping of CACNA2D3 calcium channel subunit. Blood Cells Mol Dis 2015; 55:273-80. [DOI: 10.1016/j.bcmd.2015.07.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/13/2015] [Accepted: 07/14/2015] [Indexed: 12/13/2022]
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21
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Abstract
Iron is essential for life because it is indispensable for several biological reactions, such as oxygen transport, DNA synthesis, and cell proliferation. Over the past few years, our understanding of iron metabolism and its regulation has changed dramatically. New disorders of iron metabolism have emerged, and the role of iron as a cofactor in other disorders has begun to be recognized. The study of genetic conditions such as hemochromatosis and iron-refractory iron deficiency anemia (IRIDA) has provided crucial insights into the molecular mechanisms controlling iron homeostasis. In the future, these advances may be exploited to improve treatment of both genetic and acquired iron disorders. IRIDA is caused by mutations in TMPRSS6, the gene encoding matriptase-2, which downregulates hepcidin expression under conditions of iron deficiency. The typical features of this disorder are hypochromic, microcytic anemia with a very low mean corpuscular volume of erythrocytes, low transferrin saturation, no (or inadequate) response to oral iron, and only a partial response to parenteral iron. In contrast to classic iron deficiency anemia, serum ferritin levels are usually low-normal, and serum or urinary hepcidin levels are inappropriately high for the degree of anemia. Although the number of cases reported thus far in the literature does not exceed 100, this disorder is considered the most common of the “atypical” microcytic anemias. The aim of this review is to share the current knowledge on IRIDA and increase awareness in this field.
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Affiliation(s)
- Ebru Yılmaz Keskin
- Samsun Education and Research Hospital, Clinic of Pediatric Hematology and Oncology, Samsun, Turkey. E-mail:
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22
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McLaren CE, Emond MJ, Subramaniam VN, Phatak PD, Barton JC, Adams PC, Goh JB, McDonald CJ, Powell LW, Gurrin LC, Allen KJ, Nickerson DA, Louie T, Ramm GA, Anderson GJ, McLaren GD. Exome sequencing in HFE C282Y homozygous men with extreme phenotypes identifies a GNPAT variant associated with severe iron overload. Hepatology 2015; 62:429-39. [PMID: 25605615 PMCID: PMC4508230 DOI: 10.1002/hep.27711] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 01/13/2015] [Indexed: 12/12/2022]
Abstract
UNLABELLED To identify polymorphisms associated with variability of iron overload severity in HFE-associated hemochromatosis, we performed exome sequencing of DNA from 35 male HFE C282Y homozygotes with either markedly increased iron stores (n = 22; cases) or with normal or mildly increased iron stores (n = 13; controls). The 35 participants, residents of the United States, Canada, and Australia, reported no or light alcohol consumption. Sequencing data included 82,068 single-nucleotide variants, and 10,337 genes were tested for a difference between cases and controls. A variant in the GNPAT gene showed the most significant association with severe iron overload (P = 3 × 10(-6) ; P = 0.033 by the likelihood ratio test after correction for multiple comparisons). Sixteen of twenty-two participants with severe iron overload had glyceronephosphate O-acyltransferase (GNPAT) polymorphism p.D519G (rs11558492; 15 heterozygotes, one homozygote). No control participant had this polymorphism. To examine functional consequences of GNPAT deficiency, we performed small interfering RNA-based knockdown of GNPAT in the human liver-derived cell line, HepG2/C3A. This knockdown resulted in a >17-fold decrease in expression of the messenger RNA encoding the iron-regulatory hormone, hepcidin. CONCLUSION GNPAT p.D519G is associated with a high-iron phenotype in HFE C282Y homozygotes and may participate in hepcidin regulation.
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Affiliation(s)
| | - Mary J. Emond
- Department of Biostatistics, University of Washington, Seattle, WA
| | - V. Nathan Subramaniam
- QIMR Berghofer Medical Research Institute, Brisbane, Australia,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | | | | | - Paul C. Adams
- Department of Medicine, London Health Sciences Centre, London, ON, Canada
| | - Justin B. Goh
- QIMR Berghofer Medical Research Institute, Brisbane, Australia,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | | | - Lawrie W. Powell
- QIMR Berghofer Medical Research Institute, Brisbane, Australia,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia,Royal Brisbane & Women’s Hospital, Brisbane, Australia
| | - Lyle C. Gurrin
- Centre for MEGA Epidemiology, The University of Melbourne, Melbourne, Australia
| | | | | | - Tin Louie
- Department of Biostatistics, University of Washington, Seattle, WA
| | - Grant A. Ramm
- QIMR Berghofer Medical Research Institute, Brisbane, Australia,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Gregory J. Anderson
- QIMR Berghofer Medical Research Institute, Brisbane, Australia,School of Medicine and School of Chemistry and Molecular Bioscience, University of Queensland
| | - Gordon D. McLaren
- Department of Veterans Affairs Long Beach Healthcare System, Long Beach, CA,Division of Hematology/Oncology, Department of Medicine, University of California, Irvine, CA
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23
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Poggiali E, Andreozzi F, Nava I, Consonni D, Graziadei G, Cappellini MD. The role of TMPRSS6 polymorphisms in iron deficiency anemia partially responsive to oral iron treatment. Am J Hematol 2015; 90:306-9. [PMID: 25557470 DOI: 10.1002/ajh.23929] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 12/16/2014] [Accepted: 12/22/2014] [Indexed: 12/18/2022]
Abstract
Iron refractory iron deficiency anemia (IRIDA) is a rare hereditary disease caused by mutations in TMPRSS6 gene encoding Matriptase-2, a negative regulator of hepcidin transcription. Up to now, 53 IRIDA patients from 35 families with different ethnic origins have been reported and 41 TMPRSS6 mutations have been identified. TMPRSS6 polymorphisms are more frequent than mutations, and have been associated with variation in iron and hematologic parameters. Our study evaluated their presence in 113 subjects with iron deficiency anemia (IDA) partially responsive to oral iron therapy and in 50 healthy blood donors. Thalassemic trait was diagnosed in 38 patients. Sequencing analysis of TMPRSS6 gene revealed that the frequency of several polymorphisms was markedly different between IDA subjects and controls. In particular, the V736A TMPRSS6 polymorphism was associated to moderately lower hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin levels, and in thalassemia carriers with marked anemia and microcytosis. A new variant-H448R- and two uncommon polymorphisms -A719T and V795I- were also identified. These results indicate that TMPRSS6 polymorphisms are more frequent in subjects with persistent IDA than in healthy controls, and in thalassemia carriers V736A variant may account for lower hemoglobin and MCV levels. Further studies in larger court of patients are necessary to identify potential haplotypes and polymorphisms responsible for low response to oral iron treatment and may be useful for planning a correct iron supplementation.
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Affiliation(s)
- Erika Poggiali
- Dipartimento di Medicina Interna; IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano; Italy
- Dipartimento di Scienze Cliniche e di Comunità; Università degli Studi di Milano; Italy
| | - Fabio Andreozzi
- Dipartimento di Medicina Interna; IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano; Italy
| | - Isabella Nava
- Dipartimento di Medicina Interna; IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano; Italy
| | - Dario Consonni
- Unità di Epidemiologia; Dipartimento di Medicina preventiva; IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico; Milano Italy
| | - Giovanna Graziadei
- Dipartimento di Medicina Interna; IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano; Italy
| | - Maria Domenica Cappellini
- Dipartimento di Medicina Interna; IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano; Italy
- Dipartimento di Scienze Cliniche e di Comunità; Università degli Studi di Milano; Italy
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24
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Donker AE, Brons PPT, Swinkels DW. Microcytic anaemia with low transferrin saturation, increased serum hepcidin and non-synonymous TMPRSS6 variants: not always iron-refractory iron deficiency anaemia. Br J Haematol 2014; 169:150-1. [PMID: 25312922 DOI: 10.1111/bjh.13186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Albertine E Donker
- Department of Laboratory Medicine, Laboratory of Genetic, Endocrine and Metabolic diseases, Nijmegen, The Netherlands
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25
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Kodama K, Noguchi A, Adachi H, Hebiguchi M, Yano M, Takahashi T. Novel mutation in the TMPRSS6 gene with iron-refractory iron deficiency anemia. Pediatr Int 2014; 56:e41-4. [PMID: 25252070 DOI: 10.1111/ped.12395] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 02/28/2014] [Accepted: 03/24/2014] [Indexed: 01/04/2023]
Abstract
Iron-refractory iron deficiency anemia (IRIDA) is a rare autosomal recessive disease characterized by congenital hypochromic microcytic anemia, low transferrin saturation, low serum iron, normal-high serum ferritin, and increased hepcidin. This disease is caused by loss-of-function mutations in TMPRSS6 that lead to high hepcidin and result in severe anemia. We report our experience with an 11-year-old Japanese girl with hypochromic microcytic anemia, low serum iron, and high serum ferritin, with anemia that was refractory to the oral iron that was prescribed frequently from early childhood. Presence of high hepcidin suggested a diagnosis of IRIDA, which was eventually confirmed by identification of a novel homozygous mutation, p.Pro354Leu, in the TMPRSS6 gene. This case suggests that serum hepcidin should be routinely measured for differential diagnosis when patients with IDA are unresponsive to oral iron or have unusual clinical features.
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Affiliation(s)
- Koya Kodama
- Department of Pediatrics, Akita University Graduate School of Medicine, Akita, Japan
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26
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Abstract
Iron deficiency anemia is a common global problem whose etiology is typically attributed to acquired inadequate dietary intake and/or chronic blood loss. However, in several kindreds multiple family members are affected with iron deficiency anemia that is unresponsive to oral iron supplementation and only partially responsive to parenteral iron therapy. The discovery that many of these cases harbor mutations in the TMPRSS6 gene led to the recognition that they represent a single clinical entity: iron-refractory iron deficiency anemia (IRIDA). This article reviews clinical features of IRIDA, recent genetic studies, and insights this disorder provides into the regulation of systemic iron homeostasis.
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27
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Abstract
Matriptase-2 is a hepatic membrane serine protease that regulates iron homeostasis. Defects in matriptase-2 cause iron deficiency anemia. In cells, matriptase-2 is synthesized as a zymogen. To date, how matriptase-2 expression and activation are regulated remains poorly understood. Here we expressed human matriptase-2 in HEK293 and hepatic BEL-7402, SMMC-7721, and QGY-7703 cells. By labeling cell surface proteins and Western analysis, we examined matriptase-2 cell surface expression, zymogen activation, and ectodomain shedding. Our results show that matriptase-2 was activated on the cell surface but not intracellularly. Activated matriptase-2 underwent ectodomain shedding, producing soluble fragments in the conditioned medium. By testing inactive mutants, R576A and S762A, we found that matriptase-2 activation and shedding were mediated by its own catalytic activity and that the one-chain form of matriptase-2 had little activity in ectodomain shedding. We made additional matriptase-2 mutants, N136Q, N184Q, N216Q, N338Q, N433Q, N453Q, and N518Q, in which each of the predicted N-glycosylation sites was mutated. All of these mutants were expressed on the cell surface. However, mutants N216Q, N453Q, and N518Q, but not the other mutants, had impaired zymogen activation and ectodomain shedding. Our results indicate that N-glycans at specific sites are critical for matriptase-2 activation. Together, these data provide new insights into the cell surface expression, zymogen activation, and ectodomain shedding of matriptase-2.
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Affiliation(s)
- Jiang Jiang
- From the Cyrus Tang Hematology Center and Ministry of Education Engineering Center of Hematological Disease, the Department of Clinic Laboratories, the Second Affiliated Hospital
| | - Jianfeng Yang
- From the Cyrus Tang Hematology Center and Ministry of Education Engineering Center of Hematological Disease
| | - Ping Feng
- the Department of Clinic Laboratories, the Second Affiliated Hospital
| | - Bin Zuo
- From the Cyrus Tang Hematology Center and Ministry of Education Engineering Center of Hematological Disease
| | - Ningzheng Dong
- From the Cyrus Tang Hematology Center and Ministry of Education Engineering Center of Hematological Disease, the Ministry of Health Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital, and the Collaborative Innovation Center of Hematology, Soochow University, Suzhou 215006, China and
| | - Qingyu Wu
- From the Cyrus Tang Hematology Center and Ministry of Education Engineering Center of Hematological Disease, the Collaborative Innovation Center of Hematology, Soochow University, Suzhou 215006, China and the Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Yang He
- From the Cyrus Tang Hematology Center and Ministry of Education Engineering Center of Hematological Disease, the Ministry of Health Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital, and the Collaborative Innovation Center of Hematology, Soochow University, Suzhou 215006, China and
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Nie N, Shi J, Shao Y, Li X, Ge M, Huang J, Zhang J, Huang Z, Li D, Zheng Y. A novel tri-allelic mutation of TMPRSS6 in iron-refractory iron deficiency anaemia with response to glucocorticoid. Br J Haematol 2014; 166:300-3. [PMID: 24661031 DOI: 10.1111/bjh.12843] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Neng Nie
- State Key Laboratory of Experimental Haematology, Institute of Haematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, China
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29
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Donker AE, Raymakers RA, Vlasveld LT, van Barneveld T, Terink R, Dors N, Brons PP, Knoers NV, Swinkels DW. Practice guidelines for the diagnosis and management of microcytic anemias due to genetic disorders of iron metabolism or heme synthesis. Blood 2014; 123:3873-86; quiz 4005. [PMID: 24665134 DOI: 10.1182/blood-2014-01-548776] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
During recent years, our understanding of the pathogenesis of inherited microcytic anemias has gained from the identification of several genes and proteins involved in systemic and cellular iron metabolism and heme syntheses. Numerous case reports illustrate that the implementation of these novel molecular discoveries in clinical practice has increased our understanding of the presentation, diagnosis, and management of these diseases. Integration of these insights into daily clinical practice will reduce delays in establishing a proper diagnosis, invasive and/or costly diagnostic tests, and unnecessary or even detrimental treatments. To assist the clinician, we developed evidence-based multidisciplinary guidelines on the management of rare microcytic anemias due to genetic disorders of iron metabolism and heme synthesis. These genetic disorders may present at all ages, and therefore these guidelines are relevant for pediatricians as well as clinicians who treat adults. This article summarizes these clinical practice guidelines and includes background on pathogenesis, conclusions, and recommendations and a diagnostic flowchart to facilitate using these guidelines in the clinical setting.
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Akin M, Atay E, Oztekin O, Karadeniz C, Karakus YT, Yilmaz B, Erdogan F. Responsiveness to parenteral iron therapy in children with oral iron-refractory iron-deficiency anemia. Pediatr Hematol Oncol 2014; 31:57-61. [PMID: 24087940 DOI: 10.3109/08880018.2013.829540] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
UNLABELLED Intravenous (IV) ferric iron (Fe)-carbohydrate complexes are used for treating Fe deficiency in children with iron-refractory iron-deficiency anemia (IRIDA). An optimal treatment has yet to be determined. There are relatively little publications on the responsiveness to IV iron therapy in children with IRIDA. PATIENTS AND METHOD This study analyzed responses to IV iron sucrose therapy given to 11 children, ranging in age from 2 to 13 years (mean 4.8 years), with iron-deficiency anemia who were unresponsive to oral iron therapy. RESULTS The hemoglobin and ferritin values (mean) of the 11 children with IRIDA were 7.7 g/dL and 4.8 ng/mL at diagnosis. Both hemoglobin and ferritin levels increased to 9.5 g/dL, and 24 ng/mL, respectively, at 6 weeks after the first therapy. Although the level of hemoglobin was steady at 6 months after the first, and 6 weeks after the second therapy, the ferritin levels continued to increase up to 30 ng/mL and 47 ng/mL at 6 months after the first and 6 weeks after the second therapy, respectively. CONCLUSION We recommend that IRIDA should be considered in patients presenting with iron-deficiency anemia of unknown cause that is unresponsive to oral iron therapy. Our results suggest that IV iron therapy should be administered only once in cases of IRIDA. Continued administration of IV iron would be of no benefit to increase hemoglobin levels. On the contrary, ferritin levels may continue to increase resulting in untoward effects of hyperferritinemia.
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Affiliation(s)
- Mehmet Akin
- Department of Pediatric Hematology, Denizli State Hospital , Denizli , Turkey
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31
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Cau M, Melis MA, Congiu R, Galanello R. Iron-deficiency anemia secondary to mutations in genes controlling hepcidin. Expert Rev Hematol 2014; 3:205-16. [DOI: 10.1586/ehm.10.2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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De Falco L, Sanchez M, Silvestri L, Kannengiesser C, Muckenthaler MU, Iolascon A, Gouya L, Camaschella C, Beaumont C. Iron refractory iron deficiency anemia. Haematologica 2013; 98:845-53. [PMID: 23729726 DOI: 10.3324/haematol.2012.075515] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Iron refractory iron deficiency anemia is a hereditary recessive anemia due to a defect in the TMPRSS6 gene encoding Matriptase-2. This protein is a transmembrane serine protease that plays an essential role in down-regulating hepcidin, the key regulator of iron homeostasis. Hallmarks of this disease are microcytic hypochromic anemia, low transferrin saturation and normal/high serum hepcidin values. The anemia appears in the post-natal period, although in some cases it is only diagnosed in adulthood. The disease is refractory to oral iron treatment but shows a slow response to intravenous iron injections and partial correction of the anemia. To date, 40 different Matriptase-2 mutations have been reported, affecting all the functional domains of the large ectodomain of the protein. In vitro experiments on transfected cells suggest that Matriptase-2 cleaves Hemojuvelin, a major regulator of hepcidin expression and that this function is altered in this genetic form of anemia. In contrast to the low/undetectable hepcidin levels observed in acquired iron deficiency, in patients with Matriptase-2 deficiency, serum hepcidin is inappropriately high for the low iron status and accounts for the absent/delayed response to oral iron treatment. A challenge for the clinicians and pediatricians is the recognition of the disorder among iron deficiency and other microcytic anemias commonly found in pediatric patients. The current treatment of iron refractory iron deficiency anemia is based on parenteral iron administration; in the future, manipulation of the hepcidin pathway with the aim of suppressing it might become an alternative therapeutic approach.
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33
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Steinbicker AU, Muckenthaler MU. Out of balance--systemic iron homeostasis in iron-related disorders. Nutrients 2013; 5:3034-61. [PMID: 23917168 DOI: 10.3390/nu5083034] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 07/16/2013] [Accepted: 07/19/2013] [Indexed: 02/06/2023] Open
Abstract
Iron is an essential element in our daily diet. Most iron is required for the de novo synthesis of red blood cells, where it plays a critical role in oxygen binding to hemoglobin. Thus, iron deficiency causes anemia, a major public health burden worldwide. On the other extreme, iron accumulation in critical organs such as liver, heart, and pancreas causes organ dysfunction due to the generation of oxidative stress. Therefore, systemic iron levels must be tightly balanced. Here we focus on the regulatory role of the hepcidin/ferroportin circuitry as the major regulator of systemic iron homeostasis. We discuss how regulatory cues (e.g., iron, inflammation, or hypoxia) affect the hepcidin response and how impairment of the hepcidin/ferroportin regulatory system causes disorders of iron metabolism.
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34
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Khuong-Quang DA, Schwartzentruber J, Westerman M, Lepage P, Finberg KE, Majewski J, Jabado N. Iron refractory iron deficiency anemia: presentation with hyperferritinemia and response to oral iron therapy. Pediatrics 2013; 131:e620-5. [PMID: 23319530 PMCID: PMC3675830 DOI: 10.1542/peds.2012-1303] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Iron-refractory iron-deficiency anemia (IRIDA) is an autosomal recessive disorder caused by mutations in TMPRSS6. Patients have hypochromic microcytic anemia refractory to oral iron and are only partially responsive to parenteral iron administration. We report a French-Canadian kindred in which 2 siblings presented in early childhood with severe microcytic anemia, hypoferremia, and hyperferritinemia. Both children have been successfully treated solely with low-dose oral iron since diagnosis. Clinical and biological presentation did not fit any previously described genetic iron-deficiency anemia. Whole exome sequencing identified in both patients compound heterozygous mutations of TMPRSS6 leading to p.G442R and p.E522K, 2 mutations previously reported to cause classic IRIDA, and no additional mutations in known iron-regulatory genes. Thus, the phenotype associated with the unique combination of mutations uncovered in both patients expands the spectrum of disease associated with TMPRSS6 mutations to include iron deficiency anemia that is accompanied by hyperferritinemia at initial presentation and is responsive to continued oral iron therapy. Our results have implications for genetic testing in early childhood iron deficiency anemia. Importantly, they emphasize that whole exome sequencing can be used as a diagnostic tool and greatly facilitate the elucidation of the genetic basis of unusual clinical presentations, including hypomorphic mutations or compound heterozygosity leading to different phenotypes in known Mendelian diseases.
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Affiliation(s)
| | | | | | - Pierre Lepage
- McGill University and Genome Quebec Innovation Centre, Montreal, Canada
| | - Karin E. Finberg
- Department of Pathology, Duke University School of Medicine, Durham, North Carolina
| | - Jacek Majewski
- Department of Human Genetics, and ,McGill University and Genome Quebec Innovation Centre, Montreal, Canada
| | - Nada Jabado
- Department of Human Genetics, and ,Pediatrics, McGill University, Montreal, Canada
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35
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Lehmberg K, Grosse R, Muckenthaler MU, Altamura S, Nielsen P, Schmid H, Graubner U, Oyen F, Zeller W, Schneppenheim R, Janka GE. Administration of recombinant erythropoietin alone does not improve the phenotype in iron refractory iron deficiency anemia patients. Ann Hematol 2012. [PMID: 23180434 DOI: 10.1007/s00277-012-1618-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mutations in transmembrane protease, serine 6 (TMPRSS6) cause iron refractory iron deficiency anemia (IRIDA). Parenteral iron administration may slightly improve hemoglobin level but is troublesome for patients. Optimal treatment has yet to be determined. We identified five patients from four independent families displaying the IRIDA picture with truncating biallelic mutations in TMPRSS6, one of which is novel. Liver iron determined by superconducting quantum interference device biosusceptometry ranged from 390 to 720 µg Fe/g wet weight (normal range 100-500; n = 3). Intestinal iron absorption (12 and 32 %, normal range 10-50; n = 2) and 59Fe erythrocyte incorporation after ingestion of 59Fe (57 and 38 %, normal range 70-90; n = 2) were inadequately low for iron-deficient anemic individuals. Baseline serum erythropoietin was elevated or borderline high in four patients. Administration of recombinant human erythropoietin (rhEPO) at up to 273 and 188 U/kg body weight/week alone did not improve anemia or result in a decrease of urinary hepcidin in two individuals. In conclusion, the ability of exogenous rhEPO to increase hemoglobin level appears to be impaired in IRIDA.
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Affiliation(s)
- Kai Lehmberg
- Department of Pediatric Hematology and Oncology, University Medical Center Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
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Abstract
Although the involvement of immune mechanisms in multiple sclerosis (MS) is undisputed, some argue that there is insufficient evidence to support the hypothesis that MS is an autoimmune disease, and that the difference between immune- and autoimmune disease mechanisms has yet to be clearly delineated. Uncertainties surrounding MS disease pathogenesis and the modest efficacy of currently used disease modifying treatments (DMTs) in the prevention of disability, warrant the need to explore other possibilities. It is evident from the literature that people diagnosed with MS differ widely in symptoms and clinical outcome--some patients have a benign disease course over many years without requiring any DMTs. Attempting to include all patients into a single entity is an oversimplification and may obscure important observations with therapeutic consequences. In this review we advocate an individualised approach named Pathology Supported Genetic Testing (PSGT), in which genetic tests are combined with biochemical measurements in order to identify subgroups of patients requiring different treatments. Iron dysregulation in MS is used as an example of how this approach may benefit patients. The theory that iron deposition in the brain contributes to MS pathogenesis has caused uncertainty among patients as to whether they should avoid iron. However, the fact that a subgroup of people diagnosed with MS show clinical improvement when they are on iron supplementation emphasises the importance of individualised therapy, based on genetic and biochemical determinations.
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Affiliation(s)
- Susan J van Rensburg
- Division of Chemical Pathology, National Health Laboratory Service and University of Stellenbosch, Tygerberg Hospital, PO Box 19113, 7505 Tygerberg, South Africa.
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37
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Guillem F, Kannengiesser C, Oudin C, Lenoir A, Matak P, Donadieu J, Isidor B, Méchinaud F, Aguilar-Martinez P, Beaumont C, Vaulont S, Grandchamp B, Nicolas G. Inactive matriptase-2 mutants found in IRIDA patients still repress hepcidin in a transfection assay despite having lost their serine protease activity. Hum Mutat 2012; 33:1388-96. [PMID: 22581667 DOI: 10.1002/humu.22116] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 05/02/2012] [Indexed: 12/21/2022]
Abstract
Mutations of the TMPRSS6 gene, which encodes Matriptase-2, are responsible for iron-refractory iron-deficiency anemia. Matriptase-2 is a transmembrane protease that downregulates hepcidin expression. We report one frameshift (p.Ala605ProfsX8) and four novel missense mutations (p.Glu114Lys, p.Leu235Pro, p.Tyr418Cys, p.Pro765Ala) found in IRIDA patients. These mutations lead to changes in both the catalytic and noncatalytic domains of Matriptase-2. Analyses of the mutant proteins revealed a reduction of autoactivating cleavage and the loss of N-Boc-Gln-Ala-Arg-p-nitroanilide hydrolysis. This resulted either from a direct modification of the active site or from the lack of the autocatalytic cleavage that transforms the zymogen into an active protease. In a previously described transfection assay measuring the ability of Matriptase-2 to repress the hepcidin gene (HAMP) promoter, all mutants retained some, if not all, of their transcriptional repression activity. This suggests that caution is called for in interpreting the repression assay in assessing the functional relevance of Matriptase-2 substitutions. We propose that Matriptase-2 activity should be measured directly in the cell medium of transfected cells using the chromogenic substrate. This simple test can be used to determine whether a sequence variation leading to an amino acid substitution is functionally relevant or not.
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38
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Choi HS, Yang HR, Song SH, Seo JY, Lee KO, Kim HJ. A novel mutation Gly603Arg of TMPRSS6 in a Korean female with iron-refractory iron deficiency anemia. Pediatr Blood Cancer 2012; 58:640-2. [PMID: 21618415 DOI: 10.1002/pbc.23190] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 04/11/2011] [Indexed: 12/20/2022]
Abstract
Iron-refractory iron deficiency anemia (IRIDA) is a rare hereditary form of IDA with autosomal recessive inheritance. IRIDA is characterized by hypochromic microcytic anemia unresponsive to oral iron treatment, low transferrin saturation, and a high level of iron-regulated hormone hepcidin. The genetic background of IRIDA is mutations in the TMPRSS6 gene encoding matriptase-2 (TMPRSS6) that prevent inactivation of hemojuvelin, an activator of hepcidin transcription. We herein report a Korean female with IRIDA who was compound heterozygous for two mutations in TMPRSS6: a novel missense mutation c.1807G>C (p.Gly603Arg) in the serine protease domain and a known splicing mutation c.863+1G>T (IVS6+1G>T).
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Affiliation(s)
- Hyoung Soo Choi
- Department of Pediatrics, Seoul National University Bundang Hospital, Seongnam, Korea
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39
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Golub MS, Hogrefe CE, Unger EL. Influence of prenatal iron deficiency and MAOA genotype on response to social challenge in rhesus monkey infants. Genes Brain Behav 2012; 11:278-90. [PMID: 22340208 DOI: 10.1111/j.1601-183x.2012.00772.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Social and emotional behaviors are known to be sensitive to both developmental iron deficiency (ID) and monoamine oxidase A (MAOA) gene polymorphisms. In this study, male rhesus monkey infants deprived of dietary iron in utero were compared with iron sufficient (IS) controls (n = 10/group). Half of each group had low MAOA activity genotypes and half had high MAOA activity genotypes. A series of social response tests were conducted at 3-14 months of age. MAOA genotype influenced attention to a video of aggressive behavior, emotional expression (fear, grimace and sniff) in the social intruder test, social actions (displacement, grooming) in the social dyad test, and aggressive responses to a threatening picture. Interactions between MAOA and prenatal ID were seen in response to the aggressive video, in temperament ratings, in affiliative behavior in the social dyad test, in cortisol response in the social buffering test and in response to a social intruder and to pictures with social and nonsocial themes. In general, the effects of ID were dependent on MAOA genotype in terms of both direction and size of the effect. Nutrition/genotype interactions may shed new light on behavioral consequences of nutritional deprivation during brain development.
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Affiliation(s)
- M S Golub
- Department of Environmental Toxicology California National Primate Research Center, University of California, Davis, Davis, CA, USA.
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Gan W, Guan Y, Wu Q, An P, Zhu J, Lu L, Jing L, Yu Y, Ruan S, Xie D, Makrides M, Gibson RA, Anderson GJ, Li H, Lin X, Wang F. Association of TMPRSS6 polymorphisms with ferritin, hemoglobin, and type 2 diabetes risk in a Chinese Han population. Am J Clin Nutr 2012; 95:626-32. [PMID: 22301935 DOI: 10.3945/ajcn.111.025684] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Transmembrane protease serine 6 (TMPRSS6) regulates iron homeostasis by inhibiting the expression of hepcidin. Multiple common variants in TMPRSS6 were significantly associated with serum iron in recent genome-wide association studies, but their effects in the Chinese remain to be elucidated. OBJECTIVE The objective was to determine whether the TMPRSS6 single nucleotide polymorphisms (SNPs) rs855791(V736A) and rs4820268(D521D) were associated with blood hemoglobin and plasma ferritin concentrations and risk of type 2 diabetes in Chinese individuals. DESIGN The SNPs rs855791(V736A) and rs4820268(D521D) in the TMPRSS6 gene were genotyped and tested for their associations with plasma iron and type 2 diabetes risk in 1574 unrelated Chinese Hans from Beijing. RESULTS The 2 TMPRSS6 SNPs rs855791(V736A) and rs4820268(D521D) were both significantly associated with plasma ferritin (P ≤ 0.0058), hemoglobin (P ≤ 0.0013), iron overload risk (P ≤ 0.0068), and type 2 diabetes risk (P ≤ 0.0314). None of the associations with hemoglobin or plasma ferritin remained significant (P ≥ 0.1229) when the 2 variants were both included in one linear regression model. A haplotype carrying both iron-lowering alleles from the 2 TMPRSS SNPs showed significant associations with lower hemoglobin (P = 0.0014), lower plasma ferritin (P = 0.0027), and a reduced risk of iron overload (P = 0.0017) and of type 2 diabetes (P = 0.0277). CONCLUSIONS These findings suggest that TMPRSS6 variants were significantly associated with plasma ferritin, hemoglobin, risk of iron overload, and type 2 diabetes in Chinese Hans. The type 2 diabetes risk conferred by the TMPRSS6 SNPs is possibly mediated by plasma ferritin.
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Affiliation(s)
- Wei Gan
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai, China
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Cau M, Galanello R, Giagu N, Melis MA. Responsiveness to oral iron and ascorbic acid in a patient with IRIDA. Blood Cells Mol Dis 2012; 48:121-3. [DOI: 10.1016/j.bcmd.2011.11.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 11/15/2011] [Accepted: 11/16/2011] [Indexed: 12/01/2022]
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Lee PL, Barton JC, Khaw PL, Bhattacharjee SY, Barton JC. Common TMPRSS6 mutations and iron, erythrocyte, and pica phenotypes in 48 women with iron deficiency or depletion. Blood Cells Mol Dis 2012; 48:124-7. [PMID: 22265928 DOI: 10.1016/j.bcmd.2011.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 11/29/2011] [Indexed: 01/14/2023]
Abstract
BACKGROUND TMPRSS6 A736V is associated with lower transferrin saturation (TS), hemoglobin (Hb), and mean corpuscular volume (MCV) levels in general adult populations. We sought to identify relationships of TMPRSS6 K253E, A736V, and Y739Y to iron, erythrocyte, and pica phenotypes in women with iron deficiency or depletion. METHODS We tabulated observations on 48 outpatient non-pregnant women who had iron deficiency (serum ferritin (SF) <14pmol/L and TS <10%) or iron depletion (SF<112pmol/L). We performed direct sequencing of TMPRSS6 exons 7 and 17 in each patient. We used age, TS, SF, Hb, MCV, pica, and TMPRSS6 allele positivity (dichotomous) or mutation genotypes (trichotomous) as variables for analyses. RESULTS Forty-six women were white; two were black. 58.3% had iron deficiency. 45.8% had pica (pagophagia, each case). Allele frequencies were 41.7% (K253E), 36.5% (A736V), and 39.6% (Y739Y). K253E frequency was greater in women with TS ≥10% (p=0.0001). Y739Y was more frequent in women with TS <10% (p=0.0135). Mean TS was also lower in women positive for Y739Y (6±4% vs. 13±16%, respectively; p=0.0021). In multiple regressions, neither K253E, A736V, nor Y739Y genotypes were significantly associated with other variables. CONCLUSIONS TMPRSS6 K253E frequency was greater in women with TS ≥10%. Frequency of Y739 was greater in women with TS <10%. Mean TS was lower in women with Y739Y. We observed no other significant relationship of TMPRSS6 K253E, A736V, or Y739Y with iron, erythrocyte, or pica phenotypes.
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Affiliation(s)
- Pauline L Lee
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA, USA.
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43
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Abstract
BACKGROUND The peptide hormone hepcidin plays a central role in regulating dietary iron absorption and body iron distribution. Many human diseases are associated with alterations in hepcidin concentrations. The measurement of hepcidin in biological fluids is therefore a promising tool in the diagnosis and management of medical conditions in which iron metabolism is affected. CONTENT We describe hepcidin structure, kinetics, function, and regulation. We moreover explore the therapeutic potential for modulating hepcidin expression and the diagnostic potential for hepcidin measurements in clinical practice. SUMMARY Cell-culture, animal, and human studies have shown that hepcidin is predominantly synthesized by hepatocytes, where its expression is regulated by body iron status, erythropoietic activity, oxygen tension, and inflammatory cytokines. Hepcidin lowers serum iron concentrations by counteracting the function of ferroportin, a major cellular iron exporter present in the membrane of macrophages, hepatocytes, and the basolateral site of enterocytes. Hepcidin is detected in biologic fluids as a 25 amino acid isoform, hepcidin-25, and 2 smaller forms, i.e., hepcidin-22 and -20; however, only hepcidin-25 has been shown to participate in the regulation of iron metabolism. Reliable assays to measure hepcidin in blood and urine by use of immunochemical and mass spectrometry methods have been developed. Results of proof-of-principle studies have highlighted hepcidin as a promising diagnostic tool and therapeutic target for iron disorders. However, before hepcidin measurements can be used in routine clinical practice, efforts will be required to assess the relevance of hepcidin isoform measurements, to harmonize the different assays, to define clinical decision limits, and to increase assay availability for clinical laboratories.
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Affiliation(s)
- Joyce J C Kroot
- Department of Laboratory Medicine, Laboratory of Genetic, Endocrine and Metabolic Disorders, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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44
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Wu HM, Li L, Yuan XW, Zhou YQ, Xiao QZ, Liu WY, Zhou WJ, Xu XM. Rapid, accurate detection of TMPRSS6 gene causative mutations with a high-resolution melting assay. Blood Cells Mol Dis 2011; 47:198-204. [DOI: 10.1016/j.bcmd.2011.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/31/2011] [Accepted: 06/13/2011] [Indexed: 01/23/2023]
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45
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Sato T, Iyama S, Murase K, Kamihara Y, Ono K, Kikuchi S, Takada K, Miyanishi K, Sato Y, Takimoto R, Kobune M, Kato J. Novel missense mutation in the TMPRSS6 gene in a Japanese female with iron-refractory iron deficiency anemia. Int J Hematol 2011; 94:101-103. [PMID: 21643693 DOI: 10.1007/s12185-011-0881-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 05/17/2011] [Accepted: 05/19/2011] [Indexed: 10/18/2022]
Abstract
Iron-refractory iron deficiency anemia (IRIDA) is a rare autosomal-recessive disorder hallmarked by hypochromic microcytic anemia, low transferrin saturation, and unresponsiveness to oral iron with partial recovery after parenteral iron administration. The disease is caused by mutations in TMPRSS6 (transmembrane protease serine 6) that prevent inactivation of membrane-bound hemojuvelin, an activator of hepcidin transcription. To date, 38 cases have been characterized and reported in European countries and the United States. In this paper, we describe the first case of a Japanese female with IRIDA, who carried a novel mutation (K253E) in the CUB (complement factor C1r/C1s, urchin embryonic growth factor and bone morphogenetic protein 1) domain of the TMPRSS6 gene.
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Affiliation(s)
- Tsutomu Sato
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Satoshi Iyama
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Kazuyuki Murase
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Yusuke Kamihara
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Kaoru Ono
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Shohei Kikuchi
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Kohichi Takada
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Koji Miyanishi
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Yasushi Sato
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Rishu Takimoto
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Masayoshi Kobune
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan
| | - Junji Kato
- Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan.
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Lakhal S, Schödel J, Townsend ARM, Pugh CW, Ratcliffe PJ, Mole DR. Regulation of type II transmembrane serine proteinase TMPRSS6 by hypoxia-inducible factors: new link between hypoxia signaling and iron homeostasis. J Biol Chem 2011; 286:4090-7. [PMID: 20966077 PMCID: PMC3039360 DOI: 10.1074/jbc.m110.173096] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 10/14/2010] [Indexed: 12/21/2022] Open
Abstract
Hepcidin is a liver-derived hormone with a key role in iron homeostasis. In addition to iron, it is regulated by inflammation and hypoxia, although mechanisms of hypoxic regulation remain unclear. In hepatocytes, hepcidin is induced by bone morphogenetic proteins (BMPs) through a receptor complex requiring hemojuvelin (HJV) as a co-receptor. Type II transmembrane serine proteinase (TMPRSS6) antagonizes hepcidin induction by BMPs by cleaving HJV from the cell membrane. Inactivating mutations in TMPRSS6 lead to elevated hepcidin levels and consequent iron deficiency anemia. Here we demonstrate that TMPRSS6 is up-regulated in hepatic cell lines by hypoxia and by other activators of hypoxia-inducible factor (HIF). We show that TMPRSS6 expression is regulated by both HIF-1α and HIF-2α. This HIF-dependent up-regulation of TMPRSS6 increases membrane HJV shedding and decreases hepcidin promoter responsiveness to BMP signaling in hepatocytes. Our results reveal a potential role for TMPRSS6 in hepcidin regulation by hypoxia and provide a new molecular link between oxygen sensing and iron homeostasis.
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Affiliation(s)
- Samira Lakhal
- From the Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom and
| | - Johannes Schödel
- From the Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom and
| | - Alain R. M. Townsend
- the Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX4 9DS, United Kingdom
| | - Christopher W. Pugh
- From the Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom and
| | - Peter J. Ratcliffe
- From the Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom and
| | - David R. Mole
- From the Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford OX3 7BN, United Kingdom and
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Abstract
Iron, an essential element for life, is regulated primarily at the level of uptake, storage, and transport in order to maintain sufficient availability for normal physiology. The key protein in iron homeostasis is a 25-amino-acid peptide, hepcidin, which modulates the amount of iron in the circulation by binding and promoting the degradation of the iron exporter ferroportin. Given the central importance of hepcidin, recent studies have focused on how iron is sensed and how the iron signal is transmitted to hepcidin. Mutations in a type II serine protease, matriptase-2/TMPRSS6, were recently identified to be associated with severe iron deficiency caused by inappropriately high levels of hepcidin expression. A key biologically relevant substrate for the proteolytic activity of matriptase-2/TMPRSS6 was found to be hemojuvelin, a cell surface protein that regulates hepcidin expression through a BMP/SMAD pathway. In this review, we discuss the putative role of matriptase-2/TMPRSS6 in iron homeostasis.
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Affiliation(s)
- Pauline Lee
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037, USA.
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