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Sharma A, Kumar A, Saha PK, Saha L. The role of TMPRSS6 gene polymorphism in iron resistance iron deficiency anaemia (IRIDA): a systematic review. Ann Hematol 2024; 103:1085-1102. [PMID: 38072851 DOI: 10.1007/s00277-023-05576-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 11/30/2023] [Indexed: 03/16/2024]
Abstract
Iron resistance iron deficiency anaemia is a rare autosomal recessive disorder characterized by hypochromic microcytic anaemia, low transferrin saturation and inappropriately high hepcidin levels. The aetiology of this condition is rooted in genetic variations within the transmembrane serine protease 6 (TMPRSS6) genes, responsible for encoding matriptase-2, a pivotal negative regulator of hepcidin. We conducted a systematic search across four electronic databases, yielding 538 articles in total out of which 25 were finally included and were preceded further, aiming to prognosticate prevalent single nucleotide polymorphisms (SNPs) and detrimental genetic alterations. This review aims to elucidate the effects of various SNPs and pathogenic mutations on both haematological and biochemical parameters, as well as their potential interethnic correlation. Employing bioinformatics tools, we subjected over 100 SNPs to scrutiny, discerning their potential functional ramifications. We found rs1373272804, rs1430692214 and rs855791 variants to be most frequent and were having a significant impact on haematological and biochemical profile. We found that individuals of European ancestry were more prone to have these variants compared to other ethnic groups. In conclusion, this review not only sheds light on the association of TMPRSS6 polymorphism in iron resistance iron deficiency anaemia (IRIDA), but also highlights the critical need for further investigations involving larger sample size and more diverse ethnic groups around the globe. These future studies will be vital for gaining a stronger and more reliable understanding of how these genetic differences are linked to the development of IRIDA.
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Affiliation(s)
- Antika Sharma
- Department of Pharmacology, Post Graduate Institute of Medical Education & Research (PGIMER), 4Th Floor, Research Block B, Chandigarh, India, 160012
| | - Anil Kumar
- Department of Pharmacology, Post Graduate Institute of Medical Education & Research (PGIMER), 4Th Floor, Research Block B, Chandigarh, India, 160012
| | - Pradip Kumar Saha
- Department of Obstetrics and Gynaecology, Post Graduate Institute of Medical Education & Research (PGIMER), Chandigarh, India, 160012
| | - Lekha Saha
- Department of Pharmacology, Post Graduate Institute of Medical Education & Research (PGIMER), 4Th Floor, Research Block B, Chandigarh, India, 160012.
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Pettinato M, Aghajan M, Guo S, Bavuso Volpe L, Carleo R, Nai A, Pagani A, Altamura S, Silvestri L. A functional interplay between the two BMP-SMAD pathway inhibitors TMPRSS6 and FKBP12 regulates hepcidin expression in vivo. Am J Physiol Gastrointest Liver Physiol 2024; 326:G310-G317. [PMID: 38252872 DOI: 10.1152/ajpgi.00305.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/18/2024] [Accepted: 01/18/2024] [Indexed: 01/24/2024]
Abstract
The Activin A Receptor type I (ALK2) is a critical component of BMP-SMAD signaling that, in the presence of ligands, phosphorylates cytosolic SMAD1/5/8 and modulates important biological processes, including bone formation and iron metabolism. In hepatocytes, the BMP-SMAD pathway controls the expression of hepcidin, the liver peptide hormone that regulates body iron homeostasis via the BMP receptors ALK2 and ALK3, and the hemochromatosis proteins. The main negative regulator of the pathway in the liver is transmembrane serine protease 6 (TMPRSS6), which downregulates hepcidin by cleaving the BMP coreceptor hemojuvelin. ALK2 function is inhibited also by the immunophilin FKBP12, which maintains the receptor in an inactive conformation. FKBP12 sequestration by tacrolimus or its silencing upregulates hepcidin in primary hepatocytes and in vivo in acute but not chronic settings. Interestingly, gain-of-function mutations in ALK2 that impair FKBP12 binding to the receptor and activate the pathway cause a bone phenotype in patients affected by Fibrodysplasia Ossificans Progressiva but not hepcidin and iron metabolism dysfunction. This observation suggests that additional mechanisms are active in the liver to compensate for the increased BMP-SMAD signaling. Here we demonstrate that Fkbp12 downregulation in hepatocytes by antisense oligonucleotide treatment upregulates the expression of the main hepcidin inhibitor Tmprss6, thus counteracting the ALK2-mediated activation of the pathway. Combined downregulation of both Fkbp12 and Tmprss6 blocks this compensatory mechanism. Our findings reveal a previously unrecognized functional cross talk between FKBP12 and TMPRSS6, the main BMP-SMAD pathway inhibitors, in the control of hepcidin transcription.NEW & NOTEWORTHY This study uncovers a previously unrecognized mechanism of hepcidin and BMP-SMAD pathway regulation in hepatocytes mediated by the immunophilin FKBP12 and the transmembrane serine protease TMPRSS6.
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Affiliation(s)
- Mariateresa Pettinato
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
- San Raffaele Vita-Salute University, Milan, Italy
| | - Mariam Aghajan
- Ionis Pharmaceuticals, Inc., Carlsbad, California, United States
| | - Shuling Guo
- Ionis Pharmaceuticals, Inc., Carlsbad, California, United States
| | - Letizia Bavuso Volpe
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Rossana Carleo
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Antonella Nai
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
- San Raffaele Vita-Salute University, Milan, Italy
| | - Alessia Pagani
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
- San Raffaele Vita-Salute University, Milan, Italy
| | - Sandro Altamura
- Department of Pediatric Oncology, Hematology and Immunology, University Hospital Heidelberg, Heidelberg, Germany
| | - Laura Silvestri
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy
- San Raffaele Vita-Salute University, Milan, Italy
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Arora EK, Sharma V. Iron metabolism: pathways and proteins in homeostasis. REV INORG CHEM 2022. [DOI: 10.1515/revic-2022-0031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Iron is essential to human survival. The biological role and trafficking of this trace essential inorganic element which is also a potential toxin is constantly being researched and unfolded. Vital for oxygen transport, DNA synthesis, electron transport, neurotransmitter biosynthesis and present in numerous other heme and non-heme enzymes the physiological roles are immense. Understanding the molecules and pathways that regulate this essential element at systemic and cellular levels are of importance in improving therapeutic strategies for iron related disorders. This review highlights the progress in understanding the metabolism and trafficking of iron along with the pathophysiology of iron related disorders.
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Affiliation(s)
- Ekta Kundra Arora
- Chemistry Department, St. Stephen’s College , University of Delhi , Delhi 110007 , India
| | - Vibha Sharma
- Chemistry Department, St. Stephen’s College , University of Delhi , Delhi 110007 , India
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Malherbe JAJ, Cole CH. Double trouble: A case of fraternal twins with iron-refractory iron-deficiency anemia. Clin Case Rep 2022; 10:e6401. [PMID: 36254154 PMCID: PMC9558572 DOI: 10.1002/ccr3.6401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 09/22/2022] [Indexed: 11/06/2022] Open
Abstract
Iron‐refractory iron‐deficiency anemia (IRIDA) is a rare autosomal recessive disease that presents in childhood. We report the case of fraternal twins presenting with severe hypochromic microcytic anemia and hypoferritinemia. Two missense mutations affecting the TRMPSS6 gene were identified, consistent with IRIDA. Subsequent parenteral iron therapy improved clinical and blood parameters.
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Affiliation(s)
- Jacques A. J. Malherbe
- Department of HaematologyFiona Stanley HospitalMurdochWestern AustraliaAustralia,School of Biomedical SciencesUniversity of Western AustraliaCrawleyWestern AustraliaAustralia
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Machta J, Trompeter S, Yamamoto AK, Eisen S. Iron-deficiency anaemia: the perils of excessive milk-drinking. Arch Dis Child Educ Pract Ed 2022; 107:145-149. [PMID: 34045288 DOI: 10.1136/archdischild-2020-320687] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 05/10/2021] [Indexed: 11/04/2022]
Abstract
Iron-deficiency anaemia is a widespread and largely preventable problem in the paediatric population, with numerous potential sequelae. We describe the case of a 2-year-old girl presenting with non-specific symptoms, who was found to be iron-deficient and anaemic, in the context of excessive cow's milk consumption. We explore the patient's diagnostic journey, including a neurological deterioration and the link between her iron deficiency and the final diagnosis.
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Affiliation(s)
- Joseph Machta
- Department of Paediatrics, Barnet Hospital, Royal Free London NHS Foundation Trust, London, UK
| | - Sara Trompeter
- Department of Haematology, University College London Hospitals NHS Foundation Trust, London, UK.,Haematology, NHS Blood and Transplant, Watford, Hertfordshire, UK
| | - Adam Kenji Yamamoto
- Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, UK
| | - Sarah Eisen
- Department of Paediatrics, University College London Hospitals NHS Foundation Trust, London, UK
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Cappellini MD, Russo R, Andolfo I, Iolascon A. Inherited microcytic anemias. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2020; 2020:465-470. [PMID: 33275715 PMCID: PMC7727536 DOI: 10.1182/hematology.2020000158] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Inherited microcytic anemias can be broadly classified into 3 subgroups: (1) defects in globin chains (hemoglobinopathies or thalassemias), (2) defects in heme synthesis, and (3) defects in iron availability or iron acquisition by the erythroid precursors. These conditions are characterized by a decreased availability of hemoglobin (Hb) components (globins, iron, and heme) that in turn causes a reduced Hb content in red cell precursors with subsequent delayed erythroid differentiation. Iron metabolism alterations remain central to the diagnosis of microcytic anemia, and, in general, the iron status has to be evaluated in cases of microcytosis. Besides the very common microcytic anemia due to acquired iron deficiency, a range of hereditary abnormalities that result in actual or functional iron deficiency are now being recognized. Atransferrinemia, DMT1 deficiency, ferroportin disease, and iron-refractory iron deficiency anemia are hereditary disorders due to iron metabolism abnormalities, some of which are associated with iron overload. Because causes of microcytosis other than iron deficiency should be considered, it is important to evaluate several other red blood cell and iron parameters in patients with a reduced mean corpuscular volume (MCV), including mean corpuscular hemoglobin, red blood cell distribution width, reticulocyte hemoglobin content, serum iron and serum ferritin levels, total iron-binding capacity, transferrin saturation, hemoglobin electrophoresis, and sometimes reticulocyte count. From the epidemiological perspective, hemoglobinopathies/thalassemias are the most common forms of hereditary microcytic anemia, ranging from inconsequential changes in MCV to severe anemia syndromes.
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Affiliation(s)
| | - Roberta Russo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Naples, Italy; and
- CEINGE Biotecnologie Avanzate, Naples, Italy
| | - Immacolata Andolfo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Naples, Italy; and
- CEINGE Biotecnologie Avanzate, Naples, Italy
| | - Achille Iolascon
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Naples, Italy; and
- CEINGE Biotecnologie Avanzate, Naples, Italy
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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] [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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Two Novel TMPRSS6 Variants in a Compound Heterozygous Child With Iron Refractory Iron Deficiency Anemia. J Pediatr Hematol Oncol 2020; 42:e238-e239. [PMID: 31714439 DOI: 10.1097/mph.0000000000001640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We describe a Caucasian family with asymptomatic, nonconsanguineous parents, and a daughter with unexplained microcytic anemia diagnosed on routine hemoglobin screening at her 12-month well child check. After failed response to oral and parental iron supplementation, iron refractory iron deficiency anemia was suspected. The family underwent genetic testing and the proband was found to be a compound heterozygote for 2 previously unreported TMPRSS6 variants.
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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] [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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10
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Functional diversity of TMPRSS6 isoforms and variants expressed in hepatocellular carcinoma cell lines. Sci Rep 2018; 8:12562. [PMID: 30135444 PMCID: PMC6105633 DOI: 10.1038/s41598-018-30618-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [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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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] [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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12
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Zivot A, Lipton JM, Narla A, Blanc L. Erythropoiesis: insights into pathophysiology and treatments in 2017. Mol Med 2018; 24:11. [PMID: 30134792 PMCID: PMC6016880 DOI: 10.1186/s10020-018-0011-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 03/02/2018] [Indexed: 12/20/2022] Open
Abstract
Erythropoiesis is a tightly-regulated and complex process originating in the bone marrow from a multipotent stem cell and terminating in a mature, enucleated erythrocyte.Altered red cell production can result from the direct impairment of medullary erythropoiesis, as seen in the thalassemia syndromes, inherited bone marrow failure as well as in the anemia of chronic disease. Alternatively, in disorders such as sickle cell disease (SCD) as well as enzymopathies and membrane defects, medullary erythropoiesis is not, or only minimally, directly impaired. Despite these differences in pathophysiology, therapies have traditionally been non-specific, limited to symptomatic control of anemia via packed red blood cell (pRBC) transfusion, resulting in iron overload and the eventual need for iron chelation or splenectomy to reduce defective red cell destruction. Likewise, in polycythemia vera overproduction of red cells has historically been dealt with by non-specific myelosuppression or phlebotomy. With a deeper understanding of the molecular mechanisms underlying disease pathophysiology, new therapeutic targets have been identified including induction of fetal hemoglobin, interference with aberrant signaling pathways and gene therapy for definitive cure. This review, utilizing some representative disorders of erythropoiesis, will highlight novel therapeutic modalities currently in development for treatment of red cell disorders.
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Affiliation(s)
- Andrea Zivot
- Laboratory of Developmental Erythropoiesis, Center for Autoimmune, Musculoskeletal, and Hematopoietic Diseases, The Feinstein Institute for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA
- Division of Pediatrics Hematology/Oncology and Stem Cell Transplantation, Cohen Children's Medical Center, New Hyde Park, NY, 11040, USA
| | - Jeffrey M Lipton
- Laboratory of Developmental Erythropoiesis, Center for Autoimmune, Musculoskeletal, and Hematopoietic Diseases, The Feinstein Institute for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA
- Division of Pediatrics Hematology/Oncology and Stem Cell Transplantation, Cohen Children's Medical Center, New Hyde Park, NY, 11040, USA
- Stanford University School of Medicine, Stanford, CA, USA
| | - Anupama Narla
- Department of Molecular Medicine and Pediatrics, Donald and Barbara Zucker School of Medicine at Hofstra Northwell, Hempstead, NY, 11549, USA
| | - Lionel Blanc
- Laboratory of Developmental Erythropoiesis, Center for Autoimmune, Musculoskeletal, and Hematopoietic Diseases, The Feinstein Institute for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA.
- Division of Pediatrics Hematology/Oncology and Stem Cell Transplantation, Cohen Children's Medical Center, New Hyde Park, NY, 11040, USA.
- Stanford University School of Medicine, Stanford, CA, USA.
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A new form of IRIDA due to combined heterozygous mutations of TMPRSS6 and ACVR1A encoding the BMP receptor ALK2. Blood 2017; 129:3392-3395. [PMID: 28476747 DOI: 10.1182/blood-2017-03-773481] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Capra AP, Ferro E, Cannavò L, La Rosa MA, Zirilli G. A child with severe iron-deficiency anemia and a complex TMPRSS6 genotype. ACTA ACUST UNITED AC 2017; 22:559-564. [PMID: 28447549 DOI: 10.1080/10245332.2017.1317990] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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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15
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Bhatia P, Singh A, Hegde A, Jain R, Bansal D. Systematic evaluation of paediatric cohort with iron refractory iron deficiency anaemia (IRIDA) phenotype reveals multipleTMPRSS6gene variations. Br J Haematol 2017; 177:311-318. [DOI: 10.1111/bjh.14554] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 11/23/2016] [Indexed: 02/06/2023]
Affiliation(s)
- Prateek Bhatia
- Paediatric Haematology-Oncology Unit; Department of Paediatrics; Advanced Paediatric Centre; Post Graduate Institute of Medical Education and Research; Chandigarh India
| | - Aditya Singh
- Paediatric Haematology-Oncology Unit; Department of Paediatrics; Advanced Paediatric Centre; Post Graduate Institute of Medical Education and Research; Chandigarh India
| | - Avani Hegde
- Paediatric Haematology-Oncology Unit; Department of Paediatrics; Advanced Paediatric Centre; Post Graduate Institute of Medical Education and Research; Chandigarh India
| | - Richa Jain
- Paediatric Haematology-Oncology Unit; Department of Paediatrics; Advanced Paediatric Centre; Post Graduate Institute of Medical Education and Research; Chandigarh India
| | - Deepak Bansal
- Paediatric Haematology-Oncology Unit; Department of Paediatrics; Advanced Paediatric Centre; Post Graduate Institute of Medical Education and Research; Chandigarh India
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16
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Sal E, Keskin EY, Yenicesu I, Bruno M, De Falco L. Iron-refractory iron deficiency anemia (IRIDA) cases with 2 novel TMPRSS6 mutations. Pediatr Hematol Oncol 2016; 33:226-32. [PMID: 27120435 DOI: 10.3109/08880018.2016.1157229] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Iron-refractory iron deficiency anemia (IRIDA) is a rarely diagnosed autosomal recessive disorder that presents with hypochromic, microcytic anemia due to mutations in TMPRSS6, which encodes matriptase-2. Contrary to classical iron deficiency anemia, serum hepcidin levels are found to be elevated in this disorder. Here, we report 5 cases from 4 unrelated families with inadequate response to iron therapy, who were consequently diagnosed as IRIDA. The mean age of the cases at diagnosis was 5.0 years (range: 0.7-11.3 years). All cases were either homozygous or compound heterozygous for missense or frameshift mutations in the TMPRSS6 gene, 2 of the mutations being novel (Cys410Ser and Leu689Pro). IRIDA should be considered in patients with findings of iron deficiency anemia unresponsive to oral iron therapy, whose serum ferritin levels are found normal or elevated.
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Affiliation(s)
- Ertan Sal
- a Clinic of Pediatric Hematology-Oncology, Batman State Hospital , Batman , Turkey
| | - Ebru Yılmaz Keskin
- b Clinic of Pediatric Hematology-Oncology, Samsun Education and Research Hospital , Samsun , Turkey
| | - Idil Yenicesu
- c Department of Pediatric Hematology , Gazi University Faculty of Medicine , Ankara , Turkey
| | - Mariasole Bruno
- d Department of Molecular Medicine and Medical Biotechnology , University Federico II , Naples , Italy.,e CEINGE, Advanced Biotechnologies , Naples , Italy
| | - Luigia De Falco
- d Department of Molecular Medicine and Medical Biotechnology , University Federico II , Naples , Italy.,e CEINGE, Advanced Biotechnologies , Naples , Italy
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17
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Kovac S, Böser P, Cui Y, Ferring-Appel D, Casarrubea D, Huang L, Fung E, Popp A, Mueller BK, Hentze MW. Anti-hemojuvelin antibody corrects anemia caused by inappropriately high hepcidin levels. Haematologica 2016; 101:e173-6. [PMID: 26944476 DOI: 10.3324/haematol.2015.140772] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Suzana Kovac
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | | | - Yifang Cui
- Abbvie Deutschland GmbH & Co KG, Ludwigshafen, Germany
| | | | | | - Lili Huang
- Abbvie Bioresearch Center, Worcester, USA
| | - Emma Fung
- Abbvie Bioresearch Center, Worcester, USA
| | - Andreas Popp
- Abbvie Deutschland GmbH & Co KG, Ludwigshafen, Germany
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18
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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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19
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McDonald CJ, Ostini L, Bennett N, Subramaniam N, Hooper J, Velasco G, Wallace DF, Subramaniam VN. Functional analysis of matriptase-2 mutations and domains: insights into the molecular basis of iron-refractory iron deficiency anemia. Am J Physiol Cell Physiol 2015; 308:C539-47. [DOI: 10.1152/ajpcell.00264.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 01/09/2015] [Indexed: 12/17/2022]
Abstract
Mutations in the TMPRSS6 gene are associated with severe iron-refractory iron deficiency anemia resulting from an overexpression of hepcidin, the key regulator of iron homeostasis. The matriptase (MT)-2 protein (encoded by the TMPRSS6 gene) regulates hepcidin expression by cleaving hemojuvelin [HJV/hemochromatosis type 2 (HFE2)], a bone morphogenetic protein (BMP) coreceptor in the hepcidin regulatory pathway. We investigated the functional consequences of five clinically associated TMPRSS6 variants and the role of MT-2 protein domains by generating epitope-tagged mutant and domain-swapped MT-2-MT-1 (encoded by the ST14 gene) chimeric constructs and expressing them in HepG2/C3A cells. We developed a novel cell culture immunofluorescence assay to assess the effect of MT-2 on cell surface HJV expression levels, compatible with HJV cleavage. The TMPRSS6 variants Y141C, I212T, G442R, and C510S were retained intracellularly and were unable to inhibit BMP6 induction of hepcidin. The R271Q variant, although it has been associated with iron-refractory iron deficiency anemia, appears to remain functional. Analysis of the chimeric constructs showed that replacement of sperm protein, enterokinase, and agrin (SEA), low-density-lipoprotein receptor class A (LDLRA), and protease (PROT) domains from MT-2 with those from MT-1 resulted in limited cell surface localization, while the complement C1r/C1s, Uegf, Bmp1 (CUB) domain chimera retained localization at the cell surface. The SEA domain chimera was able to reduce cell surface HJV expression, while the CUB, LDLRA, and PROT domain chimeras were not. These studies suggest that the SEA and LDLRA domains of MT-2 are important for trafficking to the cell surface and that the CUB, LDLRA, and PROT domains are required for cleavage of HJV.
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Affiliation(s)
- Cameron J. McDonald
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Lesa Ostini
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Nigel Bennett
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Nanthakumar Subramaniam
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - John Hooper
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Gloria Velasco
- Departamento de Bioquímica y Biología Molecular, Instituto Universitario de Oncología, Universidad de Oviedo, Oviedo, Spain; and
| | - Daniel F. Wallace
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - V. Nathan Subramaniam
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
- Faculty of Medicine and Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
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20
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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] [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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21
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De Falco L, Silvestri L, Kannengiesser C, Morán E, Oudin C, Rausa M, Bruno M, Aranda J, Argiles B, Yenicesu I, Falcon-Rodriguez M, Yilmaz-Keskin E, Kocak U, Beaumont C, Camaschella C, Iolascon A, Grandchamp B, Sanchez M. Functional and clinical impact of novel TMPRSS6 variants in iron-refractory iron-deficiency anemia patients and genotype-phenotype studies. Hum Mutat 2014; 35:1321-9. [PMID: 25156943 DOI: 10.1002/humu.22632] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 07/29/2014] [Indexed: 12/11/2022]
Abstract
Iron-refractory iron-deficiency anemia (IRIDA) is a rare autosomal-recessive disorder characterized by hypochromic microcytic anemia, low transferrin saturation, and inappropriate high levels of the iron hormone hepcidin. The disease is caused by variants in the transmembrane protease serine 6 (TMPRSS6) gene that encodes the type II serine protease matriptase-2, a negative regulator of hepcidin transcription. Sequencing analysis of the TMPRSS6 gene in 21 new IRIDA patients from 16 families with different ethnic origin reveal 17 novel mutations, including the most frequent mutation in Southern Italy (p.W590R). Eight missense mutations were analyzed in vitro. All but the p.T287N variant impair matriptase-2 autoproteotylic activation, decrease the ability to cleave membrane HJV and inhibit the HJV-dependent hepcidin activation. Genotype-phenotype studies in IRIDA patients have been so far limited due to the relatively low number of described patients. Our genotype-phenotype correlation analysis demonstrates that patients carrying two nonsense mutations present a more severe anemia and microcytosis and higher hepcidin levels than the other patients. We confirm that TMPRSS6 mutations are spread along the gene and that mechanistically they fully or partially abrogate hepcidin inhibition. Genotyping IRIDA patients help in predicting IRIDA severity and may be useful for predicting response to iron treatment.
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22
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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] [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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23
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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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Jiang J, Yang J, Feng P, Zuo B, Dong N, Wu Q, He Y. N-glycosylation is required for matriptase-2 autoactivation and ectodomain shedding. J Biol Chem 2014; 289:19500-7. [PMID: 24867957 DOI: 10.1074/jbc.m114.555110] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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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25
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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] [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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26
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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] [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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27
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Silvestri L, Rausa M, Pagani A, Nai A, Camaschella C. How to Assess Causality ofTMPRSS6Mutations? Hum Mutat 2013; 34:1043-5. [DOI: 10.1002/humu.22321] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 03/12/2013] [Indexed: 12/26/2022]
Affiliation(s)
- Laura Silvestri
- Vita-Salute University and San Raffaele Scientific Institute; Division of Genetic and Cell Biology; Milan Italy
| | - Marco Rausa
- Vita-Salute University and San Raffaele Scientific Institute; Division of Genetic and Cell Biology; Milan Italy
| | - Alessia Pagani
- Vita-Salute University and San Raffaele Scientific Institute; Division of Genetic and Cell Biology; Milan Italy
| | - Antonella Nai
- Vita-Salute University and San Raffaele Scientific Institute; Division of Genetic and Cell Biology; Milan Italy
| | - Clara Camaschella
- Vita-Salute University and San Raffaele Scientific Institute; Division of Genetic and Cell Biology; Milan Italy
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28
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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] [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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Bartnikas TB, Steinbicker AU, Campagna DR, Blevins S, Woodward LS, Herrera C, Bloch KD, Justice MJ, Fleming MD. Identification and characterization of a novel murine allele of Tmprss6. Haematologica 2013; 98:854-61. [PMID: 23300183 DOI: 10.3324/haematol.2012.074617] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mutagenesis screens can establish mouse models of utility for the study of critical biological processes such as iron metabolism. Such screens can produce mutations in novel genes or establish novel alleles of known genes, both of which can be useful tools for study. In order to identify genes of relevance to hematologic as well as other phenotypes, we performed N-ethyl-N-nitrosourea mutagenesis in C57BL/6J mice. An anemic mouse was identified and a putative mutation was characterized by mapping, sequencing and in vitro activity analysis. The mouse strain was backcrossed for ten generations then phenotypically characterized with respect to a previously established null mouse strain. Potential modifying loci were identified by quantitative trait locus analysis. Mapping and sequencing in an anemic mouse termed hem8 identified an I286F substitution in Tmprss6, a serine protease essential for iron metabolism; this substitution impaired in vitro protease activity. After backcrossing to C57BL6/J for ten generations, the hem8(-/-) strain exhibited a phenotype similar in some but not all aspects to that of Tmprss6(-/-) mice. The hem8 and Tmprss6-null mutations were allelic. Both hem8(-/-) and Tmprss6(-/-) mice responded similarly to pharmacological modulators of bone morphogenetic protein signaling, a key regulator of iron metabolism. Quantitative trait locus analysis in the hem8 strain identified potential modifying loci on chromosomes 2, 4, 7 and 10. In conclusion, the hem8 mouse model carries a novel allele of Tmprss6. Potential uses for this strain in the study of iron metabolism are discussed.
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Affiliation(s)
- Thomas B Bartnikas
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, USA.
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30
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Li J, Glessner JT, Zhang H, Hou C, Wei Z, Bradfield JP, Mentch FD, Guo Y, Kim C, Xia Q, Chiavacci RM, Thomas KA, Qiu H, Grant SFA, Furth SL, Hakonarson H, Sleiman PMA. GWAS of blood cell traits identifies novel associated loci and epistatic interactions in Caucasian and African-American children. Hum Mol Genet 2012; 22:1457-64. [PMID: 23263863 DOI: 10.1093/hmg/dds534] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Hematological traits are important clinical indicators, the genetic determinants of which have not been fully investigated. Common measures of hematological traits include red blood cell (RBC) count, hemoglobin concentration (HGB), hematocrit (HCT), mean corpuscular hemoglobin (MCH), MCH concentration (MCHC), mean corpuscular volume (MCV), platelet count (PLT) and white blood cell (WBC) count. We carried out a genome-wide association study of the eight common hematological traits among 7943 African-American children and 6234 Caucasian children. In African Americans, we report five novel associations of HBE1 variants with HCT and MCHC, the alpha-globin gene cluster variants with RBC and MCHC, and a variant at the ARHGEF3 locus with PLT, as well as replication of four previously reported loci at genome-wide significance. In Caucasians, we report a novel association of variants at the COPZ1 locus with PLT as well as replication of four previously reported loci at genome-wide significance. Extended analysis of an association observed between MCH and the alpha-globin gene cluster variants demonstrated independent effects and epistatic interaction at the locus, impacting the risk of iron deficiency anemia in African Americans with specific genotype states. In summary, we extend the understanding of genetic variants underlying hematological traits based on analyses in African-American children.
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Affiliation(s)
- Jin Li
- Center for Applied Genomics, Abramson Research Center and Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
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31
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Jaspers A, Caers J, Le Gac G, Ferec C, Beguin Y, Fillet G. A novel mutation in the CUB sequence of matriptase-2 (TMPRSS6) is implicated in iron-resistant iron deficiency anaemia (IRIDA). Br J Haematol 2012; 160:564-5. [DOI: 10.1111/bjh.12147] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Jo Caers
- Department of Haematology; CHU Liège; Liege; Belgium
| | - Gerald Le Gac
- INSERM 0115; Centre Hospitalier Universitaire; Brest; France
| | - Claude Ferec
- INSERM 0115; Centre Hospitalier Universitaire; Brest; France
| | - Yves Beguin
- Department of Haematology; CHU Liège; Liege; Belgium
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32
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Abstract
Iron metabolism has been intensively examined over the last decade and there are many new players in this field which are worth to be introduced. Since its discovery many studies confirmed role of liver hormone hepcidin as key regulator of iron metabolism and pointed out liver as the central organ of system iron homeostasis. Liver cells receive multiple signals related to iron balance and respond by transcriptional regulation of hepcidin expression. This liver hormone is negative regulator of iron metabolism that represses iron efflux from macrophages, hepatocytes and enterocytes by its binding to iron export protein ferroportin. Ferroportin degradation leads to cellular iron retention and decreased iron availability. At level of a cell IRE/IRP (iron responsive elements/iron responsive proteins) system allows tight regulation of iron assimilation that prevents an excess of free intracellular iron which could lead to oxidative stress and damage of DNA, proteins and lipid membranes by ROS (reactive oxygen species). At the same time IRE/IRP system provides sufficient iron in order to meet the metabolic needs. Recently a significant progress in understanding of iron metabolism has been made and new molecular participants have been characterized. Article gives an overview of the current understanding of iron metabolism: absorption, distribution, cellular uptake, release, and storage. We also discuss mechanisms underlying systemic and cellular iron regulation with emphasis on central regulatory hormone hepcidin.
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Affiliation(s)
- Leida Tandara
- Department of Medical Laboratory Diagnosis, University Hospital Center Split, Split, Croatia.
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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] [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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Camaschella C. How I manage patients with atypical microcytic anaemia. Br J Haematol 2012; 160:12-24. [PMID: 23057559 DOI: 10.1111/bjh.12081] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 09/07/2012] [Indexed: 01/19/2023]
Abstract
Microcytic hypochromic anaemias are a result of defective iron handling by erythroblasts that decrease the haemoglobin content per red cell. Recent advances in our knowledge of iron metabolism and its homeostasis have led to the discovery of novel inherited anaemias that need to be distinguished from common iron deficiency or other causes of microcytosis. These atypical microcytic anaemias can be classified as: (i) defects of intestinal iron absorption (ii) disorders of the transferrin receptor cycle that impair erythroblast iron uptake (iii) defects of mitochondrial iron utilization for haem or iron sulphur cluster synthesis and (iv) defects of iron recycling. A careful patient history and evaluation of laboratory tests may enable these rare conditions to be distinguished from the more common iron deficiency anaemia. Molecular studies allow distinction of the different types, a prerequisite for differentiated therapy.
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Affiliation(s)
- Clara Camaschella
- Vita-Salute University and San Raffaele Scientific Institute, Via Olgettina 60, Milan, Italy.
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35
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Pellegrino RM, Coutinho M, D'Ascola D, Lopes AM, Palmieri A, Carnuccio F, Costa M, Zecchina G, Saglio G, Costa E, Barbot J, Porto G, Pinto JP, Roetto A. Two novel mutations in the tmprss6 gene associated with iron-refractory iron-deficiency anaemia (irida) and partial expression in the heterozygous form. Br J Haematol 2012; 158:668-72. [PMID: 22765023 DOI: 10.1111/j.1365-2141.2012.09198.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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36
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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] [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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37
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Kloss-Brandstätter A, Erhart G, Lamina C, Meister B, Haun M, Coassin S, Seifert M, Klein-Franke A, Paulweber B, Kedenko L, Kollerits B, Swinkels DW, Vermeulen SH, Galesloot TE, Kronenberg F, Weiss G. Candidate gene sequencing of SLC11A2 and TMPRSS6 in a family with severe anaemia: common SNPs, rare haplotypes, no causative mutation. PLoS One 2012; 7:e35015. [PMID: 22509377 PMCID: PMC3324414 DOI: 10.1371/journal.pone.0035015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 03/08/2012] [Indexed: 12/26/2022] Open
Abstract
Background Iron-refractory iron deficiency anaemia (IRIDA) is a rare disorder which was linked to mutations in two genes (SLC11A2 and TMPRSS6). Common polymorphisms within these genes were associated with serum iron levels. We identified a family of Serbian origin with asymptomatic non-consanguineous parents with three of four children presenting with IRIDA not responding to oral but to intravenous iron supplementation. After excluding all known causes responsible for iron deficiency anaemia we searched for mutations in SLC11A2 and TMPRSS6 that could explain the severe anaemia in these children. Methodology/Results We sequenced the exons and exon–intron boundaries of SLC11A2 and TMPRSS6 in all six family members. Thereby, we found seven known and fairly common SNPs, but no new mutation. We then genotyped these seven SNPs in the population-based SAPHIR study (n = 1,726) and performed genetic association analysis on iron and ferritin levels. Only two SNPs, which were top-hits from recent GWAS on iron and ferritin, exhibited an effect on iron and ferritin levels in SAPHIR. Six SAPHIR participants carrying the same TMPRSS6 genotypes and haplotype-pairs as one anaemic son showed lower ferritin and iron levels than the average. One individual exhibiting the joint SLC11A2/TMPRSS6 profile of the anaemic son had iron and ferritin levels lying below the 5th percentile of the population's iron and ferritin level distribution. We then checked the genotype constellations in the Nijmegen Biomedical Study (n = 1,832), but the profile of the anaemic son did not occur in this population. Conclusions We cannot exclude a gene-gene interaction between SLC11A2 and TMPRSS6, but we can also not confirm it. As in this case candidate gene sequencing did not reveal causative rare mutations, the samples will be subjected to whole exome sequencing.
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Affiliation(s)
- Anita Kloss-Brandstätter
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - Gertraud Erhart
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - Claudia Lamina
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - Bernhard Meister
- Department of Paediatrics II, Innsbruck Medical University, Innsbruck, Austria
| | - Margot Haun
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - Stefan Coassin
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - Markus Seifert
- Department of Internal Medicine I, Clinical Immunology and Infectious Diseases, Innsbruck Medical University, Innsbruck, Austria
| | | | - Bernhard Paulweber
- First Department of Internal Medicine, Paracelsus Medical University, Salzburg, Austria
| | - Lyudmyla Kedenko
- First Department of Internal Medicine, Paracelsus Medical University, Salzburg, Austria
| | - Barbara Kollerits
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - Dorine W. Swinkels
- Department of Laboratory Medicine, Laboratory of Genetic, Endocrine and Metabolic Diseases, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Sita H. Vermeulen
- Department of Epidemiology, Biostatistics and HTA, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Tessel E. Galesloot
- Department of Epidemiology, Biostatistics and HTA, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Florian Kronenberg
- Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
- * E-mail: (FK); (GW)
| | - Günter Weiss
- Department of Internal Medicine I, Clinical Immunology and Infectious Diseases, Innsbruck Medical University, Innsbruck, Austria
- * E-mail: (FK); (GW)
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Abstract
Inappropriately low expression of the key iron regulator hepcidin (HAMP) causes iron overload in untransfused patients affected by β-thalassemia intermedia and Hamp modulation provides improvement of the thalassemic phenotype of the Hbb(th3/+) mouse. HAMP expression is activated by iron through the bone morphogenetic protein (BMP)-son of mothers against decapentaplegic signaling pathway and inhibited by ineffective erythropoiesis through an unknown "erythroid regulator." The BMP pathway is inactivated by the serine protease TMPRSS6 that cleaves the BMP coreceptor hemojuvelin. Here, we show that homozygous loss of Tmprss6 in Hbb(th3/+) mice improves anemia and reduces ineffective erythropoiesis, splenomegaly, and iron loading. All these effects are mediated by Hamp up-regulation, which inhibits iron absorption and recycling. Because Hbb(th3/+) mice lacking Tmprss6 show residual ineffective erythropoiesis, our results indicate that Tmprss6 is essential for Hamp inhibition by the erythroid regulator. We also obtained partial correction of the phenotype in Tmprss6 haploinsufficient Hbb(th3/+) male but not female mice and showed that the observed sex difference reflects an unequal balance between iron and erythropoiesis-mediated Hamp regulation. Our study indicates that preventing iron overload improves β-thalassemia and strengthens the essential role of Tmprss6 for Hamp suppression, providing a proof of concept that Tmprss6 manipulation can offer a novel therapeutic option in this condition.
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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] [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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40
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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] [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] [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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42
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Iron disorders of genetic origin: a changing world. Trends Mol Med 2011; 17:707-13. [DOI: 10.1016/j.molmed.2011.07.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 07/13/2011] [Accepted: 07/20/2011] [Indexed: 12/15/2022]
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Chen J, Enns CA. Hereditary hemochromatosis and transferrin receptor 2. Biochim Biophys Acta Gen Subj 2011; 1820:256-63. [PMID: 21864651 DOI: 10.1016/j.bbagen.2011.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/26/2011] [Accepted: 07/29/2011] [Indexed: 02/08/2023]
Abstract
BACKGROUND Multicellular organisms regulate the uptake of calories, trace elements, and other nutrients by complex feedback mechanisms. In the case of iron, the body senses internal iron stores, iron requirements for hematopoiesis, and inflammatory status, and regulates iron uptake by modulating the uptake of dietary iron from the intestine. Both the liver and the intestine participate in the coordination of iron uptake and distribution in the body. The liver senses inflammatory signals and iron status of the organism and secretes a peptide hormone, hepcidin. Under high iron or inflammatory conditions hepcidin levels increase. Hepcidin binds to the iron transport protein, ferroportin (FPN), promoting FPN internalization and degradation. Decreased FPN levels reduce iron efflux out of intestinal epithelial cells and macrophages into the circulation. Derangements in iron metabolism result in either the abnormal accumulation of iron in the body, or in anemias. The identification of the mutations that cause the iron overload disease, hereditary hemochromatosis (HH), or iron-refractory iron-deficiency anemia has revealed many of the proteins used to regulate iron uptake. SCOPE OF THE REVIEW In this review we discuss recent data concerning the regulation of iron homeostasis in the body by the liver and how transferrin receptor 2 (TfR2) affects this process. MAJOR CONCLUSIONS TfR2 plays a key role in regulating iron homeostasis in the body. GENERAL SIGNIFICANCE The regulation of iron homeostasis is important. One third of the people in the world are anemic. HH is the most common inherited disease in people of Northern European origin and can lead to severe health complications if left untreated. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Juxing Chen
- Department of Cell and Developmental Biology L215, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA
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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] [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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Chappell SL, Daly L, Lotya J, Alsaegh A, Guetta-Baranes T, Roca J, Rabinovich R, Morgan K, Millar AB, Donnelly SC, Keatings V, MacNee W, Stolk J, Hiemstra PS, Miniati M, Monti S, O'Connor CM, Kalsheker N. The role of IREB2 and transforming growth factor beta-1 genetic variants in COPD: a replication case-control study. BMC MEDICAL GENETICS 2011; 12:24. [PMID: 21320324 PMCID: PMC3047296 DOI: 10.1186/1471-2350-12-24] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 02/14/2011] [Indexed: 11/10/2022]
Abstract
Background Genetic factors are known to contribute to COPD susceptibility and these factors are not fully understood. Conflicting results have been reported for many genetic studies of candidate genes based on their role in the disease. Genome-wide association studies in combination with expression profiling have identified a number of new candidates including IREB2. A meta-analysis has implicated transforming growth factor beta-1 (TGFbeta1) as a contributor to disease susceptibility. Methods We have examined previously reported associations in both genes in a collection of 1017 white COPD patients and 912 non-diseased smoking controls. Genotype information was obtained for seven SNPs in the IREB2 gene, and for four SNPs in the TGFbeta1 gene. Allele and genotype frequencies were compared between COPD cases and controls, and odds ratios were calculated. The analysis was adjusted for age, sex, smoking and centre, including interactions of age, sex and smoking with centre. Results Our data replicate the association of IREB2 SNPs in association with COPD for SNP rs2568494, rs2656069 and rs12593229 with respective adjusted p-values of 0.0018, 0.0039 and 0.0053. No significant associations were identified for TGFbeta1. Conclusions These studies have therefore confirmed that the IREB2 locus is a contributor to COPD susceptibility and suggests a new pathway in COPD pathogenesis invoking iron homeostasis.
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Affiliation(s)
- Sally L Chappell
- The University of Nottingham, School of Molecular Medical Sciences, University Hospital, Queens Medical Centre, Nottingham, UK
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Abstract
PURPOSE OF REVIEW To discuss inherited iron disorders, their pathophysiology and clinical implications in the light of the recent advances in our knowledge of iron metabolism and its regulation. RECENT FINDINGS In previous years the molecular mechanisms of cellular iron uptake and release and the cellular and systemic iron homeostasis have been substantially clarified. New proteins (hepcidin, hemojuvelin, HFE, TFR2 and ferroportin), mutated in hereditary hemochromatosis, have been identified with a crucial role in iron regulation. These advances have modified our understanding of the pathophysiology of hemochromatosis, now considered a disorder either due to hepcidin deficiency or (rarely) due to hepcidin resistance. Novel genetic forms of iron-related microcytic anemia have been identified, due to defects of iron transport/utilization or to TMPRSS6 deficiency and hepcidin hyperproduction, as occurs in iron-refractory iron deficiency anemia (IRIDA). A role for hepcidin has been identified also in acquired conditions, as in iron-loading anemias and in anemia of chronic diseases and inflammation. SUMMARY Advances in basic research have improved the classification and diagnosis of genetic anemias and iron overload and are paving the way towards the development of drugs that target the molecular lesions.
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Affiliation(s)
- Clara Camaschella
- Vita-Salute University, San Raffaele Scientific Institute, Milan, Italy.
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Sebastiani G, Pantopoulos K. Disorders associated with systemic or local iron overload: from pathophysiology to clinical practice. Metallomics 2011; 3:971-86. [DOI: 10.1039/c1mt00082a] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Isabelle T, Marguerite NA, Photis B. Cryptic splice site usage leading to truncated TMPRSS6 is responsible for iron refractory iron deficiency anaemia in an Italian Family. Eur J Haematol 2010; 86:178-9. [DOI: 10.1111/j.1600-0609.2010.01547.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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49
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Camaschella C, Pagani A. Iron and erythropoiesis: a dual relationship. Int J Hematol 2010; 93:21-6. [PMID: 21170616 DOI: 10.1007/s12185-010-0743-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 11/30/2010] [Indexed: 01/13/2023]
Abstract
Iron is essential for cell life and especially for erythropoiesis which is the major body consumer of iron for red cell production. The study of genetic disorders of iron metabolism, the identification of iron transporters and of the role of hepcidin as the key regulator of systemic iron homeostasis have greatly contributed to our understanding of iron handling by the erythroid marrow. Spontaneous and engineered animal models of iron disorders have help to add further insights to the issue. A still incompletely understood aspect remains the regulation that erythropoiesis exerts on iron.
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Affiliation(s)
- Clara Camaschella
- Division of Genetics and Cell Biology, Università Vita-Salute e IRCCS San Raffaele, Via Olgettina 60, 20132 Milan, Italy.
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Proteolytic processing of the serine protease matriptase-2: identification of the cleavage sites required for its autocatalytic release from the cell surface. Biochem J 2010; 430:87-95. [PMID: 20518742 DOI: 10.1042/bj20091565] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Matriptase-2 is a member of the TTSPs (type II transmembrane serine proteases), an emerging class of cell surface proteases involved in tissue homoeostasis and several human disorders. Matriptase-2 exhibits a domain organization similar to other TTSPs, with a cytoplasmic N-terminus, a transmembrane domain and an extracellular C-terminus containing the non-catalytic stem region and the protease domain. To gain further insight into the biochemical functions of matriptase-2, we characterized the subcellular localization of the monomeric and multimeric form and identified cell surface shedding as a defining point in its proteolytic processing. Using HEK (human embryonic kidney)-293 cells, stably transfected with cDNA encoding human matriptase-2, we demonstrate a cell membrane localization for the inactive single-chain zymogen. Membrane-associated matriptase-2 is highly N-glycosylated and occurs in monomeric, as well as multimeric, forms covalently linked by disulfide bonds. Furthermore, matriptase-2 undergoes shedding into the conditioned medium as an activated two-chain form containing the catalytic domain, which is cleaved at the canonical activation motif, but is linked to a released portion of the stem region via a conserved disulfide bond. Cleavage sites were identified by MS, sequencing and mutational analysis. Interestingly, cell surface shedding and activation of a matriptase-2 variant bearing a mutation at the active-site serine residue is dependent on the catalytic activity of co-expressed or co-incubated wild-type matriptase-2, indicating a transactivation and trans-shedding mechanism.
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