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Duggal N, Singh N, Sachdev S, Singh AK, Hira JK, Chhabra S, Bansal D, Malhotra P, Varma N, Das R, Sharma P. A Screening Approach for Inherited Erythrocytosis due to the VHL:c.598C > T Mutation (Chuvash Polycythemia). Indian J Hematol Blood Transfus 2023:1-5. [PMID: 37362405 PMCID: PMC10183085 DOI: 10.1007/s12288-023-01668-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 05/01/2023] [Indexed: 06/28/2023] Open
Abstract
Genetic work-up of unexplained erythrocytosis that is suspected to be inherited in nature currently requires either laborious exon-by-exon gene panel testing by Sanger sequencing or expensive next-generation sequencing. A high prevalence of Chuvash polycythemia (61%) has been previously reported among north Indian erythrocytosis patients. We assessed PCR-RFLP for VHL c.598C > T mutation as a first-line test in 99 persons with JAK2 V617F-negative, unexplained erythrocytosis. We enrolled two groups: Group A (n = 38) had erythrocytosis patients (n = 33) or their first-degree relatives (n = 5), and, Group B with 61 healthy blood donation volunteers who were deferred after the discovery of unexplained high hemoglobin levels. Detailed history and clinical examination, hemogram, erythropoietin levels and PCR-RFLP for the VHL:c.598C > T;p.R200W mutation were done. In Group A, three (8%) persons aged 9, 13 and 30-years were homozygous for VHL:c.598C > T. Two were heterozygous (parents of a known case of Chuvash polycythemia). None of the Group B subjects had the Chuvash mutation. Erythropoietin levels in group A were low in 5/26 cases (19%) and normal in 18/26 (69%). In Group B, seven (11%) donors had normal values while the remaining 54 (89%) had high erythropoietin levels. Despite a lower frequency (8%) compared to literature, our results suggest that the relatively simpler PCR-RFLP for VHL:c.598C > T mutation may be considered for the initial genetic screening of unexplained, suspected congenital erythrocytosis in regions where Chuvash polycythemia comprises a large proportion of inherited erythrocytosis, after polycythemia vera and common acquired secondary causes are excluded. Supplementary Information The online version contains supplementary material available at 10.1007/s12288-023-01668-9.
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Affiliation(s)
- Nisha Duggal
- Pathology Group of Departments, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Namrata Singh
- Department of Hematology, Level 5, Research Block A, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012 India
| | - Suchet Sachdev
- Department of Transfusion Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | | | - Jasbir Kaur Hira
- Department of Hematology, Level 5, Research Block A, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012 India
| | - Sanjeev Chhabra
- Department of Hematology, Level 5, Research Block A, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012 India
| | - Deepak Bansal
- Pediatric Hematology-Oncology Unit, Department of Pediatric Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Pankaj Malhotra
- Department of Clinical Hematology and Medical Oncology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Neelam Varma
- Department of Hematology, Level 5, Research Block A, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012 India
| | - Reena Das
- Department of Hematology, Level 5, Research Block A, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012 India
| | - Prashant Sharma
- Department of Hematology, Level 5, Research Block A, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, 160012 India
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Yang Y, Yuan H, Yang T, Li Y, Gao C, Jiao T, Cai Y, Zhao S. The Expression Regulatory Network in the Lung Tissue of Tibetan Pigs Provides Insight Into Hypoxia-Sensitive Pathways in High-Altitude Hypoxia. Front Genet 2021; 12:691592. [PMID: 34691141 PMCID: PMC8529057 DOI: 10.3389/fgene.2021.691592] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 08/31/2021] [Indexed: 12/31/2022] Open
Abstract
To adapt to a low-oxygen environment, Tibetan pigs have developed a series of unique characteristics and can transport oxygen more effectively; however, the regulation of the associated processes in high-altitude animals remains elusive. We performed mRNA-seq and miRNA-seq, and we constructed coexpression regulatory networks of the lung tissues of Tibetan and Landrace pigs. HBB, AGT, COL1A2, and EPHX1 were identified as major regulators of hypoxia-induced genes that regulate blood pressure and circulation, and they were enriched in pathways related to signal transduction and angiogenesis, such as HIF-1, PI3K-Akt, mTOR, and AMPK. HBB may promote the combination of hemoglobin and oxygen as well as angiogenesis for high-altitude adaptation in Tibetan pigs. The expression of MMP2 showed a similar tendency of alveolar septum thickness among the four groups. These results indicated that MMP2 activity may lead to widening of the alveolar wall and septum, alveolar structure damage, and collapse of alveolar space with remarkable fibrosis. These findings provide a perspective on hypoxia-adaptive genes in the lungs in addition to insights into potential candidate genes in Tibetan pigs for further research in the field of high-altitude adaptation.
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Affiliation(s)
- Yanan Yang
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Haonan Yuan
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Tianliang Yang
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Yongqing Li
- Research on Quality Standard of Animal Husbandry, Xinjiang Academy of Animal Sciences, Xinjiang, China
| | - Caixia Gao
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Ting Jiao
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China.,College of Grassland Science, Gansu Agricultural University, Lanzhou, China
| | - Yuan Cai
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Shengguo Zhao
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
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Roles of HIF and 2-Oxoglutarate-Dependent Dioxygenases in Controlling Gene Expression in Hypoxia. Cancers (Basel) 2021; 13:cancers13020350. [PMID: 33477877 PMCID: PMC7832865 DOI: 10.3390/cancers13020350] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/12/2021] [Accepted: 01/15/2021] [Indexed: 02/07/2023] Open
Abstract
Simple Summary Hypoxia—reduction in oxygen availability—plays key roles in both physiological and pathological processes. Given the importance of oxygen for cell and organism viability, mechanisms to sense and respond to hypoxia are in place. A variety of enzymes utilise molecular oxygen, but of particular importance to oxygen sensing are the 2-oxoglutarate (2-OG) dependent dioxygenases (2-OGDs). Of these, Prolyl-hydroxylases have long been recognised to control the levels and function of Hypoxia Inducible Factor (HIF), a master transcriptional regulator in hypoxia, via their hydroxylase activity. However, recent studies are revealing that such dioxygenases are involved in almost all aspects of gene regulation, including chromatin organisation, transcription and translation. Abstract Hypoxia—reduction in oxygen availability—plays key roles in both physiological and pathological processes. Given the importance of oxygen for cell and organism viability, mechanisms to sense and respond to hypoxia are in place. A variety of enzymes utilise molecular oxygen, but of particular importance to oxygen sensing are the 2-oxoglutarate (2-OG) dependent dioxygenases (2-OGDs). Of these, Prolyl-hydroxylases have long been recognised to control the levels and function of Hypoxia Inducible Factor (HIF), a master transcriptional regulator in hypoxia, via their hydroxylase activity. However, recent studies are revealing that dioxygenases are involved in almost all aspects of gene regulation, including chromatin organisation, transcription and translation. We highlight the relevance of HIF and 2-OGDs in the control of gene expression in response to hypoxia and their relevance to human biology and health.
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Lappin TR, Lee FS. Update on mutations in the HIF: EPO pathway and their role in erythrocytosis. Blood Rev 2019; 37:100590. [PMID: 31350093 DOI: 10.1016/j.blre.2019.100590] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 07/02/2019] [Accepted: 07/15/2019] [Indexed: 12/20/2022]
Abstract
Identification of the underlying defects in congenital erythrocytosis has provided mechanistic insights into the regulation of erythropoiesis and oxygen homeostasis. The Hypoxia Inducible Factor (HIF) pathway plays a key role in this regard. In this pathway, an enzyme, Prolyl Hydroxylase Domain protein 2 (PHD2), constitutively prolyl hydroxylates HIF-2α, thereby targeting HIF-2α for degradation by the von Hippel Lindau (VHL) tumor suppressor protein. Under hypoxia, this modification is attenuated, resulting in the stabilization of HIF-2α and transcriptional activation of the erythropoietin (EPO) gene. Circulating EPO then binds to the EPO receptor (EPOR) on red cell progenitors in the bone marrow, leading to expansion of red cell mass. Loss of function mutations in PHD2 and VHL, as well as gain of function mutations in HIF-2α and EPOR, are well established causes of erythrocytosis. Here, we highlight recent developments that show that the study of this condition is still evolving. Specifically, novel mutations have been identified that either change amino acids in the zinc finger domain of PHD2 or alter splicing of the VHL gene. In addition, continued study of HIF-2α mutations has revealed a distinctive genotype-phenotype correlation. Finally, novel mutations have recently been identified in the EPO gene itself. Thus, the cascade of genes that at a molecular level leads to EPO action, namely PHD2 - > HIF2A - > VHL - > EPO - > EPOR, are all mutational targets in congenital erythrocytosis.
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Affiliation(s)
- Terence R Lappin
- Centre for Cancer Research and Cell Biology, Queen's University, Belfast, UK.
| | - Frank S Lee
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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Shin SY, Kim HY, Kim HJ, Kim HG. Hb Heathrow [β103(G5)Phe→Leu], a First Report in an Asian Patient with Erythrocytosis. Yonsei Med J 2017; 58:665-667. [PMID: 28332377 PMCID: PMC5368157 DOI: 10.3349/ymj.2017.58.3.665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 12/24/2015] [Indexed: 11/30/2022] Open
Abstract
Congenital erythrocytosis (CE) is a rare and heterogeneous disease. The high oxygen affinity hemoglobin (Hb) variants are the most common cause of CE. Herein, we report a Korean patient with isolated erythrocytosis. A 25-year-old man was referred to our hospital for evaluation of high Hb level (Hb 20.4 g/dL, hematocrit 58%, reticulocyte count 2.90%, white blood cell count 6.83×10⁹/L, and platelet count 195×10⁹/L). Bone marrow biopsy revealed normocellular marrow without myeloproliferative features. JAK2 (V617F, exon 12), CALR (exon 9), and MPL W515K/L mutations were not detected. P₅₀ (partial pressure at which Hb is half saturated with oxygen), which is an indicator of left-shift of oxygen dissociation curve (high oxygen affinity state), was 14.3 mm Hg (reference value 22.6-29.4 mm Hg). He was suspected to have CE. Mutation analysis of the HBB gene revealed the known Hb variant, Hb Heathrow [β103(G5)Phe→Leu]. This is the first report of Hb Heathrow in Asian.
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Affiliation(s)
- Sang Yong Shin
- Department of Laboratory Medicine, Gyeongsang National University School of Medicine, Jinju, Korea
| | - Hyun Young Kim
- Department of Laboratory Medicine & Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Hee Jin Kim
- Department of Laboratory Medicine & Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
| | - Hoon Gu Kim
- Department of Internal Medicine, Gyeongsang National University School of Medicine, Jinju, Korea.
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Camps C, Petousi N, Bento C, Cario H, Copley RR, McMullin MF, van Wijk R, Ratcliffe PJ, Robbins PA, Taylor JC. Gene panel sequencing improves the diagnostic work-up of patients with idiopathic erythrocytosis and identifies new mutations. Haematologica 2016; 101:1306-1318. [PMID: 27651169 PMCID: PMC5394871 DOI: 10.3324/haematol.2016.144063] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 07/26/2016] [Indexed: 12/31/2022] Open
Abstract
Erythrocytosis is a rare disorder characterized by increased red cell mass and elevated hemoglobin concentration and hematocrit. Several genetic variants have been identified as causes for erythrocytosis in genes belonging to different pathways including oxygen sensing, erythropoiesis and oxygen transport. However, despite clinical investigation and screening for these mutations, the cause of disease cannot be found in a considerable number of patients, who are classified as having idiopathic erythrocytosis. In this study, we developed a targeted next-generation sequencing panel encompassing the exonic regions of 21 genes from relevant pathways (~79 Kb) and sequenced 125 patients with idiopathic erythrocytosis. The panel effectively screened 97% of coding regions of these genes, with an average coverage of 450×. It identified 51 different rare variants, all leading to alterations of protein sequence, with 57 out of 125 cases (45.6%) having at least one of these variants. Ten of these were known erythrocytosis-causing variants, which had been missed following existing diagnostic algorithms. Twenty-two were novel variants in erythrocytosis-associated genes (EGLN1, EPAS1, VHL, BPGM, JAK2, SH2B3) and in novel genes included in the panel (e.g. EPO, EGLN2, HIF3A, OS9), some with a high likelihood of functionality, for which future segregation, functional and replication studies will be useful to provide further evidence for causality. The rest were classified as polymorphisms. Overall, these results demonstrate the benefits of using a gene panel rather than existing methods in which focused genetic screening is performed depending on biochemical measurements: the gene panel improves diagnostic accuracy and provides the opportunity for discovery of novel variants.
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Affiliation(s)
- Carme Camps
- National Institute for Health Research (NIHR) Comprehensive Biomedical Research Centre, Oxford, UK
- Wellcome Trust Centre for Human Genetics, University of Oxford, UK
| | - Nayia Petousi
- Nuffield Department of Medicine, University of Oxford, UK
| | - Celeste Bento
- Hematology Department, Centro Hospitalar e Universitário de Coimbra, Portugal
| | - Holger Cario
- Department of Pediatrics and Adolescent Medicine, University Medical Center, Ulm, Germany
| | - Richard R Copley
- National Institute for Health Research (NIHR) Comprehensive Biomedical Research Centre, Oxford, UK
- Wellcome Trust Centre for Human Genetics, University of Oxford, UK
| | | | | | | | - Peter A Robbins
- Department of Physiology, Anatomy and Genetics, University of Oxford, UK
| | - Jenny C Taylor
- National Institute for Health Research (NIHR) Comprehensive Biomedical Research Centre, Oxford, UK
- Wellcome Trust Centre for Human Genetics, University of Oxford, UK
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Erythrocytosis due to PHD2 Mutations: A Review of Clinical Presentation, Diagnosis, and Genetics. Case Rep Hematol 2016; 2016:6373706. [PMID: 27034858 PMCID: PMC4789426 DOI: 10.1155/2016/6373706] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Revised: 02/08/2016] [Accepted: 02/10/2016] [Indexed: 12/17/2022] Open
Abstract
The association of mutations in the PHD2 protein of the hypoxia-sensing pathway and erythrocytosis has only been established in the last decade. Here we report the case of a novel PHD2 gene mutation in a patient with erythrocytosis and summarize all reported cases to date. Case Report. A 55-year-old man presented with dyspnea and a previous diagnosis of idiopathic erythrocytosis. PHD gene sequencing revealed a mutation on exon 2. The mutation was recognized as p.(Trp334⁎) (c. 1001G>A) resulting in a truncation of a highly conserved amino acid residue in catalytic domain. A diagnosis of erythrocytosis secondary to mutant PHD2 gene was made. Conclusions. Our findings indicate that with PHD2 mutations there is moderate erythrocytosis and erythropoietin (Epo) levels are generally low to normal. Two patients with PHD2 substitution mutations were found to have paraganglioma and one of these patients had a concurrent pheochromocytoma. In addition, one mutation was associated with sagittal sinus thrombosis. Given the severity of some of the clinical features of these mutations, we conclude that clinical guidelines should include the PHD2 mutation in the idiopathic erythrocytosis workup.
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8
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Minervini G, Quaglia F, Tosatto SCE. Computational analysis of prolyl hydroxylase domain-containing protein 2 (PHD2) mutations promoting polycythemia insurgence in humans. Sci Rep 2016; 6:18716. [PMID: 26754054 PMCID: PMC4709589 DOI: 10.1038/srep18716] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/06/2015] [Indexed: 12/18/2022] Open
Abstract
Idiopathic erythrocytosis is a rare disease characterized by an increase in red blood cell mass due to mutations in proteins of the oxygen-sensing pathway, such as prolyl hydroxylase 2 (PHD2). Here, we present a bioinformatics investigation of the pathological effect of twelve PHD2 mutations related to polycythemia insurgence. We show that few mutations impair the PHD2 catalytic site, while most localize to non-enzymatic regions. We also found that most mutations do not overlap the substrate recognition site, suggesting a novel PHD2 binding interface. After a structural analysis of both binding partners, we suggest that this novel interface is responsible for PHD2 interaction with the LIMD1 tumor suppressor.
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Affiliation(s)
- Giovanni Minervini
- Department of Biomedical Sciences and CRIBI Biotechnology Center, University of Padova, Viale G. Colombo 3, 35121, Padova, Italy
| | - Federica Quaglia
- Department of Biomedical Sciences and CRIBI Biotechnology Center, University of Padova, Viale G. Colombo 3, 35121, Padova, Italy
| | - Silvio C E Tosatto
- Department of Biomedical Sciences and CRIBI Biotechnology Center, University of Padova, Viale G. Colombo 3, 35121, Padova, Italy.,CNR Institute of Neuroscience, Viale G. Colombo 3, 35121, Padova, Italy
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Collier AB, Coon LM, Monteleone P, Umaru S, Swanson KC, Hoyer JD, Oliveira JL. A Novelβ-Globin Chain Hemoglobin Variant, Hb Allentown [β137(H15)Val→Trp (GTG>TGG)HBB: c.412_413delinsTG, p.Val138Trp], Associated with Low Oxygen Saturation, Intermittent Aplastic Crises and Splenomegaly. Hemoglobin 2015; 40:130-3. [DOI: 10.3109/03630269.2015.1115766] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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10
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Choi CW, Bang SM, Jang S, Jung CW, Kim HJ, Kim HY, Kim SJ, Kim YK, Park J, Won JH. Guidelines for the management of myeloproliferative neoplasms. Korean J Intern Med 2015; 30:771-88. [PMID: 26552452 PMCID: PMC4642006 DOI: 10.3904/kjim.2015.30.6.771] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 03/30/2015] [Indexed: 01/04/2023] Open
Abstract
Polycythemia vera, essential thrombocythemia, and primary myelofibrosis are collectively known as 'Philadelphia-negative classical myeloproliferative neoplasms (MPNs).' The discovery of new genetic aberrations such as Janus kinase 2 (JAK2) have enhanced our understanding of the pathophysiology of MPNs. Currently, the JAK2 mutation is not only a standard criterion for diagnosis but is also a new target for drug development. The JAK1/2 inhibitor, ruxolitinib, was the first JAK inhibitor approved for patients with intermediate- to high-risk myelofibrosis and its effects in improving symptoms and survival benefits were demonstrated by randomized controlled trials. In 2011, the Korean Society of Hematology MPN Working Party devised diagnostic and therapeutic guidelines for Korean MPN patients. Subsequently, other genetic mutations have been discovered and many kinds of new drugs are now under clinical investigation. In view of recent developments, we have revised the guidelines for the diagnosis and management of MPN based on published evidence and the experiences of the expert panel. Here we describe the epidemiology, new genetic mutations, and novel therapeutic options as well as diagnostic criteria and standard treatment strategies for MPN patients in Korea.
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Affiliation(s)
- Chul Won Choi
- Division of Oncology-Hematology, Department of Internal Medicine, Korea University Guro Hospital, Seoul, Korea
| | - Soo-Mee Bang
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Seongsoo Jang
- Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Chul Won Jung
- Division of Hematology/Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Hee-Jin Kim
- Department of Laboratory Medicine & Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ho Young Kim
- Department of Internal Medicine, Hallym University Sacred Heart Hospital, Anyang, Korea
| | - Soo-Jeong Kim
- Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
| | - Yeo-Kyeoung Kim
- Division of Hematology-Oncology, Department of Internal Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea
| | - Jinny Park
- Division of Hematology-Oncology, Department of Internal Medicine, Gachon University Gil Medical Center, Incheon, Korea
| | - Jong-Ho Won
- Division of Hematology-Oncology, Department of Internal Medicine, Soonchunhyang University College of Medicine, Seoul, Korea
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Gardie B, Percy MJ, Hoogewijs D, Chowdhury R, Bento C, Arsenault PR, Richard S, Almeida H, Ewing J, Lambert F, McMullin MF, Schofield CJ, Lee FS. The role of PHD2 mutations in the pathogenesis of erythrocytosis. HYPOXIA 2014; 2:71-90. [PMID: 27774468 PMCID: PMC5045058 DOI: 10.2147/hp.s54455] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The transcription of the erythropoietin (EPO) gene is tightly regulated by the hypoxia response pathway to maintain oxygen homeostasis. Elevations in serum EPO level may be reflected in an augmentation in the red cell mass, thereby causing erythrocytosis. Studies on erythrocytosis have provided insights into the function of the oxygen-sensing pathway and the critical proteins involved in the regulation of EPO transcription. The α subunits of the hypoxia-inducible transcription factor are hydroxylated by three prolyl hydroxylase domain (PHD) enzymes, which belong to the iron and 2-oxoglutarate-dependent oxygenase superfamily. Sequence analysis of the genes encoding the PHDs in patients with erythrocytosis has revealed heterozygous germline mutations only occurring in Egl nine homolog 1 (EGLN1, also known as PHD2), the gene that encodes PHD2. To date, 24 different EGLN1 mutations comprising missense, frameshift, and nonsense mutations have been described. The phenotypes associated with the patients carrying these mutations are fairly homogeneous and typically limited to erythrocytosis with normal to elevated EPO. However, exceptions exist; for example, there is one case with development of concurrent paraganglioma (PHD2-H374R). Analysis of the erythrocytosis-associated PHD2 missense mutations has shown heterogeneous results. Structural studies reveal that mutations can affect different domains of PHD2. Some are close to the hypoxia-inducible transcription factor α/2-oxoglutarate or the iron binding sites for PHD2. In silico studies demonstrate that the mutations do not always affect fully conserved residues. In vitro and in cellulo studies showed varying effects of the mutations, ranging from mild effects to severe loss of function. The exact mechanism of a potential tumor-suppressor role for PHD2 still needs to be elucidated. A knockin mouse model expressing the first reported PHD2-P317R mutation recapitulates the phenotype observed in humans (erythrocytosis with inappropriately normal serum EPO levels) and demonstrates that haploinsufficiency and partial deregulation of PHD2 is sufficient to cause erythrocytosis.
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Affiliation(s)
- Betty Gardie
- Laboratoire de Génétique Oncologique de l'Ecole Pratique des Hautes Etudes, Villejuif; Unité Mixte de Recherche, Institut national de la santé et de la recherche médicale U892, Centre national de la recherche scientifique 6299, Centre de Recherche en Cancérologie Nantes/Angers, Université de Nantes, Nantes, France
| | - Melanie J Percy
- Department of Haematology, Belfast City Hospital, Belfast, UK
| | - David Hoogewijs
- Institute of Physiology and Zürich Center for Integrative Human Physiology, University of Zürich, Zürich, Switzerland
| | - Rasheduzzaman Chowdhury
- Department of Chemistry and Oxford Centre for Integrative Systems Biology, Chemistry Research Laboratory, University of Oxford, Oxford, UK
| | - Celeste Bento
- Department of Hematology, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Patrick R Arsenault
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Stéphane Richard
- Laboratoire de Génétique Oncologique de l'Ecole Pratique des Hautes Etudes, Villejuif; Institut national de la santé et de la recherche médicale U753, Institut de cancérologie Gustave Roussy (IGR), Villejuif, France; Faculté de Médecine Paris-Sud, Le Kremlin-Bicêtre, France
| | - Helena Almeida
- Department of Hematology, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | | | - Frédéric Lambert
- Center for Human Genetics, Pathology Institute, UniLab-Lg, Molecular Haemato-Oncology Unit, CHU of Liege, Liege, Belgium
| | | | - Christopher J Schofield
- Department of Chemistry and Oxford Centre for Integrative Systems Biology, Chemistry Research Laboratory, University of Oxford, Oxford, UK
| | - Frank S Lee
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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