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Dou X, Chen Z, Liu Y, Li Y, Ye J, Lu L. Zebrafish mutants in egln1 display a hypoxic response and develop polycythemia. Life Sci 2024; 344:122564. [PMID: 38492922 DOI: 10.1016/j.lfs.2024.122564] [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: 01/22/2024] [Revised: 03/10/2024] [Accepted: 03/13/2024] [Indexed: 03/18/2024]
Abstract
AIMS Prolyl hydroxylase domain 2 (PHD2), encoded by the Egln1 gene, serves as a pivotal regulator of the hypoxia-inducible factor (HIF) pathway and acts as a cellular oxygen sensor. Somatic inactivation of Phd2 in mice results in polycythemia and congestive heart failure. However, due to the embryonic lethality of Phd2 deficiency, its role in development remains elusive. Here, we investigated the function of two egln1 paralogous genes, egln1a and egln1b, in zebrafish. MAIN METHODS The egln1 null zebrafish were generated using the CRISPR/Cas9 system. Quantitative real-time PCR assays and Western blot analysis were employed to detect the effect of egln1 deficiency on the hypoxia signaling pathway. The hypoxia response of egln1 mutant zebrafish were assessed by analyzing heart rate, gill agitation frequency, and blood flow velocity. Subsequently, o-dianisidine staining and in situ hybridization were used to investigate the role of egln1 in zebrafish hematopoietic function. KEY FINDINGS Our data show that the loss of egln1a or egln1b individually has no visible effects on growth rate. However, the egln1a; egln1b double mutant displayed significant growth retardation and elevated mortality at around 2.5 months old. Both egln1a-null and egln1b-null zebrafish embryo exhibited enhanced tolerance to hypoxia, systemic hypoxic response that include hif pathway activation, increased cardiac activity, and polycythemia. SIGNIFICANCE Our research introduces zebrafish egln1 mutants as the first congenital embryonic viable systemic vertebrate animal model for PHD2, providing novel insights into hypoxic signaling and the progression of PHD2- associated disease.
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Affiliation(s)
- Xuehan Dou
- Laboratory for Marine Drugs and Bioproducts of Laoshan Laboratory, Qingdao, China; Key Laboratory of Marine Drugs, The Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China
| | - Zhongyuan Chen
- Laboratory for Marine Drugs and Bioproducts of Laoshan Laboratory, Qingdao, China; Key Laboratory of Marine Drugs, The Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China
| | - Yunzhang Liu
- Laboratory for Marine Drugs and Bioproducts of Laoshan Laboratory, Qingdao, China; Key Laboratory of Marine Drugs, The Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China
| | - Yun Li
- Laboratory for Marine Drugs and Bioproducts of Laoshan Laboratory, Qingdao, China; Key Laboratory of Marine Drugs, The Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China
| | - Junli Ye
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Ling Lu
- Laboratory for Marine Drugs and Bioproducts of Laoshan Laboratory, Qingdao, China; Key Laboratory of Marine Drugs, The Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China.
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Moore JA, Hubbi ME, Wang C, Wang Y, Luo W, Hofmann S, Rambally S. Isolated Erythrocytosis Associated With 3 Novel Missense Mutations in the EGLN1 Gene. J Investig Med High Impact Case Rep 2021; 8:2324709620947256. [PMID: 32755251 PMCID: PMC7543148 DOI: 10.1177/2324709620947256] [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] [Indexed: 11/24/2022] Open
Abstract
Hypoxia-inducible factor-1 (HIF-1) is a key regulator of erythropoiesis. In this article, we report 3 novel mutations, P378S, A385T, and G206C, on the EGLN1 gene encoding the negative HIF-1α regulator prolyl hydroxylase domain-2 (PHD2) in 3 patients with isolated erythrocytosis. These mutations impair PHD2 protein stability and partially reduce PHD2 activity, leading to increased HIF-1α protein levels in cultured cells.
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Affiliation(s)
- Joseph A Moore
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Maimon E Hubbi
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Chenliang Wang
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yingfei Wang
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Weibo Luo
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sandra Hofmann
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Siayareh Rambally
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
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3
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Tremblay D, Yacoub A, Hoffman R. Overview of Myeloproliferative Neoplasms: History, Pathogenesis, Diagnostic Criteria, and Complications. Hematol Oncol Clin North Am 2021; 35:159-176. [PMID: 33641861 PMCID: PMC8669599 DOI: 10.1016/j.hoc.2020.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Myeloproliferative disorders are a group of diseases morphologically linked by terminal myeloid cell expansion that frequently evolve from one clinical phenotype to another and eventually progress to acute myeloid leukemia. Diagnostic criteria for the Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) have been established by the World Health Organization and they are recognized as blood cancers. MPNs have a complex and incompletely understood pathogenesis that includes systemic inflammation, clonal hematopoiesis, and constitutive activation of the JAK-STAT pathway. Complications, such as thrombosis and progression to overt forms of myelofibrosis and acute leukemia, contribute significantly to morbidity and mortality of patients with MPN.
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Affiliation(s)
- Douglas Tremblay
- Division of Hematology and Medical Oncology, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Abdulraheem Yacoub
- Division of Hematologic Malignancies and Cellular Therapeutics, Department of Internal Medicine, The University of Kansas Cancer Center, 2330 Shawnee Mission Parkway, Westwood, KS 66205, USA
| | - Ronald Hoffman
- Division of Hematology and Medical Oncology, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA.
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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: 50] [Impact Index Per Article: 10.0] [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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Zhou Y, Ouyang N, Liu L, Tian J, Huang X, Lu T. An EGLN1 mutation may regulate hypoxic response in cyanotic congenital heart disease through the PHD2/HIF-1A pathway. Genes Dis 2019; 6:35-42. [PMID: 30906831 PMCID: PMC6411777 DOI: 10.1016/j.gendis.2018.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 03/06/2018] [Indexed: 12/21/2022] Open
Abstract
Cyanotic congenital heart disease (CCHD), a term describing the most severe congenital heart diseases are characterized by the anatomic malformation of a right to left shunt. Although the incidence of CCHD are far less than the that of congenital heart diseases (CHD), patients with CCHD always present severe clinical features such as hypoxia, dyspnea, and heart failure. Chronic hypoxia induces hypoxemia that significantly contributes to poor prognosis in CCHD. Current studies have demonstrated that the prolyl-4-hydroxylase2 (PHD2, encoded by EGLN1)/hypoxia-inducible factor-1A (HIF-1A) pathway is a key regulator of hypoxic response. Thus, we aim to assess the associations of single polymorphisms (SNPs) of the EGLN1 gene and hypoxic response in CCHD. A missense variant of EGLN1 c.380G>C (rs1209790) was found in 46 patients (46/126), with lower hypoxia incidence and higher rate of collateral vessel formation, compared with the wild type (P < 0.05). In vitro experiments, during hypoxia, EGLN1 mutation reduced EGLN1 expression compared with the wild type, with higher HIF-1A, VEGF and EPO expression levels in the mutant. No difference in HK1 expression was observed between the mutant and wild type. CCHD patients with c.380G>C showed improved response to hypoxia compared with the wild-type counterparts. The EGLN1 c.380G>C mutation improves hypoxic response through the PHD2/HIF-1A pathway, which may provide a molecular mechanism for hypoxic response in CCHD. The effects of the EGLN1 c.380G>C mutation on CCHD prognosis deserve further investigation.
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Affiliation(s)
- Yuanlin Zhou
- Department of Cardiology, Children's Hospital of Chongqing Medical University, Chongqing, PR China
- Key Laboratory of Developmental Disease in Childhood (Chongqing Medical University), Ministry of Education, Chongqing, PR China
- Key Laboratory of Pediatrics in Chongqing, Chongqing, PR China
- Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, PR China
| | - Na Ouyang
- Department of Cardiology, Children's Hospital of Chongqing Medical University, Chongqing, PR China
- Key Laboratory of Developmental Disease in Childhood (Chongqing Medical University), Ministry of Education, Chongqing, PR China
- Key Laboratory of Pediatrics in Chongqing, Chongqing, PR China
- Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, PR China
| | - Lingjuan Liu
- Department of Cardiology, Children's Hospital of Chongqing Medical University, Chongqing, PR China
- Key Laboratory of Developmental Disease in Childhood (Chongqing Medical University), Ministry of Education, Chongqing, PR China
- Key Laboratory of Pediatrics in Chongqing, Chongqing, PR China
- Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, PR China
| | - Jie Tian
- Department of Cardiology, Children's Hospital of Chongqing Medical University, Chongqing, PR China
- Key Laboratory of Developmental Disease in Childhood (Chongqing Medical University), Ministry of Education, Chongqing, PR China
- Key Laboratory of Pediatrics in Chongqing, Chongqing, PR China
- Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, PR China
| | - Xupei Huang
- Department of Biomedical Science, Charlie E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL, USA
| | - Tiewei Lu
- Department of Cardiology, Children's Hospital of Chongqing Medical University, Chongqing, PR China
- Key Laboratory of Developmental Disease in Childhood (Chongqing Medical University), Ministry of Education, Chongqing, PR China
- Key Laboratory of Pediatrics in Chongqing, Chongqing, PR China
- Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, PR China
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7
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Barradas J, Rodrigues CD, Ferreira G, Rocha P, Constanço C, Andrade MR, Bento C, Silva HM. Congenital erythrocytosis - discover of a new mutation in the EGLN1 gene. Clin Case Rep 2018; 6:1109-1111. [PMID: 29881576 PMCID: PMC5986049 DOI: 10.1002/ccr3.1499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 02/03/2018] [Accepted: 02/23/2018] [Indexed: 01/03/2023] Open
Abstract
Congenital erythrocytosis is a hereditary disorder due to an increase in red cell mass that can be caused by mutations in proteins involved in HIF-α pathway, as PHD2. Hereby, we describe a new familial mutation in PHD2 gene. Considering an increased thrombotic potential, patients began antiplatelet aggregation therapy and phlebotomies.
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Affiliation(s)
- João Barradas
- Centro Hospitalar de Tondela‐ViseuEPE – Serviço de Hematologia ClínicaCoimbraPortugal
| | | | - Gisela Ferreira
- Centro Hospitalar do Baixo VougaEPE – Serviço de Hematologia ClínicaViseuPortugal
| | - Paula Rocha
- Centro Hospitalar de Tondela‐ViseuEPE – Serviço de Hematologia ClínicaCoimbraPortugal
| | - Conceição Constanço
- Centro Hospitalar de Tondela‐ViseuEPE – Serviço de Hematologia ClínicaCoimbraPortugal
| | - Maria Reis Andrade
- Centro Hospitalar de Tondela‐ViseuEPE – Serviço de Hematologia ClínicaCoimbraPortugal
| | - Celeste Bento
- Centro Hospitalar e Universitário de CoimbraEPE – Serviço de Hematologia ClínicaCoimbraPortugal
| | - Helena Matos Silva
- Centro Hospitalar de Tondela‐ViseuEPE – Serviço de Hematologia ClínicaCoimbraPortugal
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Prolyl-4-hydroxylase 2 and 3 coregulate murine erythropoietin in brain pericytes. Blood 2016; 128:2550-2560. [PMID: 27683416 DOI: 10.1182/blood-2016-05-713545] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 09/22/2016] [Indexed: 12/20/2022] Open
Abstract
A classic response to systemic hypoxia is the increased production of red blood cells due to hypoxia-inducible factor (HIF)-mediated induction of erythropoietin (EPO). EPO is a glycoprotein hormone that is essential for normal erythropoiesis and is predominantly synthesized by peritubular renal interstitial fibroblast-like cells, which express cellular markers characteristic of neuronal cells and pericytes. To investigate whether the ability to synthesize EPO is a general functional feature of pericytes, we used conditional gene targeting to examine the von Hippel-Lindau/prolyl-4-hydroxylase domain (PHD)/HIF axis in cell-expressing neural glial antigen 2, a known molecular marker of pericytes in multiple organs. We found that pericytes in the brain synthesized EPO in mice with genetic HIF activation and were capable of responding to systemic hypoxia with the induction of Epo. Using high-resolution multiplex in situ hybridization, we determined that brain pericytes represent an important cellular source of Epo in the hypoxic brain (up to 70% of all Epo-expressing cells). We furthermore determined that Epo transcription in brain pericytes was HIF-2 dependent and cocontrolled by PHD2 and PHD3, oxygen- and 2-oxoglutarate-dependent prolyl-4-hydroxylases that regulate HIF activity. In summary, our studies provide experimental evidence that pericytes in the brain have the ability to function as oxygen sensors and respond to hypoxia with EPO synthesis. Our findings furthermore suggest that the ability to synthesize EPO may represent a functional feature of pericytes in the brain and kidney.
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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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10
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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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Hypoxia Signaling Cascade for Erythropoietin Production in Hepatocytes. Mol Cell Biol 2015; 35:2658-72. [PMID: 26012551 DOI: 10.1128/mcb.00161-15] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 05/22/2015] [Indexed: 01/01/2023] Open
Abstract
Erythropoietin (Epo) is produced in the kidney and liver in a hypoxia-inducible manner via the activation of hypoxia-inducible transcription factors (HIFs) to maintain oxygen homeostasis. Accelerating Epo production in hepatocytes is one plausible therapeutic strategy for treating anemia caused by kidney diseases. To elucidate the regulatory mechanisms of hepatic Epo production, we analyzed mouse lines harboring liver-specific deletions of genes encoding HIF-prolyl-hydroxylase isoforms (PHD1, PHD2, and PHD3) that mediate the inactivation of HIF1α and HIF2α under normal oxygen conditions. The loss of all PHD isoforms results in both polycythemia, which is caused by Epo overproduction, and fatty livers. We found that deleting any combination of two PHD isoforms induces polycythemia without steatosis complications, whereas the deletion of a single isoform induces no apparent phenotype. Polycythemia is prevented by the loss of either HIF2α or the hepatocyte-specific Epo gene enhancer (EpoHE). Chromatin analyses show that the histones around EpoHE dissociate from the nucleosome structure after HIF2α activation. HIF2α also induces the expression of HIF3α, which is involved in the attenuation of Epo production. These results demonstrate that the total amount of PHD activity is more important than the specific function of each isoform for hepatic Epo expression regulated by a PHD-HIF2α-EpoHE cascade in vivo.
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12
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Germ-line PHD1 and PHD2 mutations detected in patients with pheochromocytoma/paraganglioma-polycythemia. J Mol Med (Berl) 2014; 93:93-104. [PMID: 25263965 DOI: 10.1007/s00109-014-1205-7] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/27/2014] [Accepted: 09/02/2014] [Indexed: 10/24/2022]
Abstract
UNLABELLED We have investigated genetic/pathogenetic factors associated with a new clinical entity in patients presenting with pheochromocytoma/paraganglioma (PHEO/PGL) and polycythemia. Two patients without hypoxia-inducible factor 2α (HIF2A) mutations, who presented with similar clinical manifestations, were analyzed for other gene mutations, including prolyl hydroxylase (PHD) mutations. We have found for the first time a germ-line mutation in PHD1 in one patient and a novel germ-line PHD2 mutation in a second patient. Both mutants exhibited reduced protein stability with substantial quantitative protein loss and thus compromised catalytic activities. Due to the unique association of patients' polycythemia with borderline or mildly elevated erythropoietin (EPO) levels, we also performed an in vitro sensitivity assay of erythroid progenitors to EPO and for EPO receptor (EPOR) expression. The results show inappropriate hypersensitivity of erythroid progenitors to EPO in these patients, indicating increased EPOR expression/activity. In addition, the present study indicates that HIF dysregulation due to PHD mutations plays an important role in the pathogenesis of these tumors and associated polycythemia. The PHD1 mutation appears to be a new member contributing to the genetic landscape of this novel clinical entity. Our results support the existence of a specific PHD1- and PHD2-associated PHEO/PGL-polycythemia disorder. KEY MESSAGE • A novel germ-l i n e PHD1 mutation causing heochromocytoma/paraganglioma and polycythemia. • Increased EPOR activity and inappropriate hypersensitivity of erythroid progenitors to EPO.
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Lorenzo FR, Huff C, Myllymäki M, Olenchock B, Swierczek S, Tashi T, Gordeuk V, Wuren T, Ri-Li G, McClain DA, Khan TM, Koul PA, Guchhait P, Salama ME, Xing J, Semenza GL, Liberzon E, Wilson A, Simonson TS, Jorde LB, Kaelin WG, Koivunen P, Prchal JT. A genetic mechanism for Tibetan high-altitude adaptation. Nat Genet 2014; 46:951-6. [PMID: 25129147 PMCID: PMC4473257 DOI: 10.1038/ng.3067] [Citation(s) in RCA: 273] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 07/24/2014] [Indexed: 11/09/2022]
Abstract
Tibetans do not exhibit increased hemoglobin concentration at high altitude. We describe a high-frequency missense mutation in the EGLN1 gene, which encodes prolyl hydroxylase 2 (PHD2), that contributes to this adaptive response. We show that a variant in EGLN1, c.[12C>G; 380G>C], contributes functionally to the Tibetan high-altitude phenotype. PHD2 triggers the degradation of hypoxia-inducible factors (HIFs), which mediate many physiological responses to hypoxia, including erythropoiesis. The PHD2 p.[Asp4Glu; Cys127Ser] variant exhibits a lower K(m) value for oxygen, suggesting that it promotes increased HIF degradation under hypoxic conditions. Whereas hypoxia stimulates the proliferation of wild-type erythroid progenitors, the proliferation of progenitors with the c.[12C>G; 380G>C] mutation in EGLN1 is significantly impaired under hypoxic culture conditions. We show that the c.[12C>G; 380G>C] mutation originated ∼8,000 years ago on the same haplotype previously associated with adaptation to high altitude. The c.[12C>G; 380G>C] mutation abrogates hypoxia-induced and HIF-mediated augmentation of erythropoiesis, which provides a molecular mechanism for the observed protection of Tibetans from polycythemia at high altitude.
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Affiliation(s)
- Felipe R Lorenzo
- 1] Department of Medicine, University of Utah School of Medicine and George E. Wahlin Veterans Administration Medical Center, Salt Lake City, Utah, USA. [2]
| | - Chad Huff
- 1] Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, USA. [2] Department of Epidemiology, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA. [3]
| | - Mikko Myllymäki
- 1] Biocenter Oulu, Faculty of Biochemistry and Molecular Medicine, Oulu Center for Cell-Matrix Research, University of Oulu, Oulu, Finland. [2]
| | - Benjamin Olenchock
- Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Sabina Swierczek
- Department of Medicine, University of Utah School of Medicine and George E. Wahlin Veterans Administration Medical Center, Salt Lake City, Utah, USA
| | - Tsewang Tashi
- Department of Medicine, University of Utah School of Medicine and George E. Wahlin Veterans Administration Medical Center, Salt Lake City, Utah, USA
| | - Victor Gordeuk
- Sickle Cell Center, University of Illinois, Chicago, Illinois, USA
| | - Tana Wuren
- Research Center for High-Altitude Medicine, Qinghai University, Xining, People's Republic of China
| | - Ge Ri-Li
- Research Center for High-Altitude Medicine, Qinghai University, Xining, People's Republic of China
| | - Donald A McClain
- Department of Medicine, University of Utah School of Medicine and George E. Wahlin Veterans Administration Medical Center, Salt Lake City, Utah, USA
| | - Tahsin M Khan
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Parvaiz A Koul
- Sher-i-Kashmir Institute of Medical Sciences, Srinagar, India
| | | | - Mohamed E Salama
- 1] Department of Pathology, University of Utah, Salt Lake City, Utah, USA. [2] ARUP Laboratories, Hematopathology, Salt Lake City, Utah, USA
| | - Jinchuan Xing
- 1] Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, USA. [2] Department of Genetics, Rutgers, State University of New Jersey, Piscataway, New Jersey, USA
| | - Gregg L Semenza
- Vascular Program, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Ella Liberzon
- 1] Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA. [2] Howard Hughes Medical Institute, Chevy Chase, Maryland, USA
| | - Andrew Wilson
- Departmant of Family and Preventive Medicine, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Tatum S Simonson
- 1] Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, USA. [2] Division of Physiology, University of California San Diego School of Medicine, La Jolla, California, USA
| | - Lynn B Jorde
- Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - William G Kaelin
- 1] Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA. [2] Howard Hughes Medical Institute, Chevy Chase, Maryland, USA
| | - Peppi Koivunen
- 1] Biocenter Oulu, Faculty of Biochemistry and Molecular Medicine, Oulu Center for Cell-Matrix Research, University of Oulu, Oulu, Finland. [2]
| | - Josef T Prchal
- 1] Department of Medicine, University of Utah School of Medicine and George E. Wahlin Veterans Administration Medical Center, Salt Lake City, Utah, USA. [2] Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, USA. [3]
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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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15
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Hong WJ, Gotlib J. Hereditary erythrocytosis, thrombocytosis and neutrophilia. Best Pract Res Clin Haematol 2014; 27:95-106. [DOI: 10.1016/j.beha.2014.07.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 07/11/2014] [Indexed: 10/25/2022]
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16
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Jang JH, Seo JY, Jang J, Jung CW, Lee KO, Kim SH, Kim HJ. Hereditary gene mutations in Korean patients with isolated erythrocytosis. Ann Hematol 2014; 93:931-5. [PMID: 24482100 DOI: 10.1007/s00277-014-2006-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 01/03/2014] [Indexed: 02/02/2023]
Abstract
Most cases of erythrocytosis occur secondary to chronic tissue hypoxia or as a clonal disease such as polycythemia vera with somatic mutations in the Janus kinase 2 (JAK2) gene. Rarely, erythrocytosis is caused by hereditary gene mutations. This study investigated hereditary gene mutations in 38 unrelated Korean patients with isolated erythrocytosis without (1) JAK2 mutation and (2) secondary causes of erythrocytosis other than smoking history. Direct sequencing analyses were performed on six genes associated with hereditary erythrocytosis [HBB, exon 2 and exon 3 of HBA2, VHL, EGLN1 (previously PHD2), exon 12 of EPAS1 (previously HIF2A), and exons 5-8 of EPOR]. As a result, mutations were detected in five patients (three never smokers and two current smokers) out of 38 patients (13.2 %). The mutations detected in those five patients were EPOR:p.W439*, EPOR:p.G212C, HBB:p.H98Q (or conventionally H97Q, Hb Malmö [β 97(FG4) His > Gln]), HBB:p.V138M (V137M), and EGLN1:p.L279Tfs43*, all in heterozygous state. No patient had mutations in HBA2, VHL, or in EPAS1. This study indicates that workup for hereditary gene mutations is needed for isolated erythrocytosis with or without smoking history.
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Affiliation(s)
- Ja-Hyun Jang
- Department of Laboratory Medicine & Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul, South Korea, 135-710
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17
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Bento C, Percy MJ, Gardie B, Maia TM, van Wijk R, Perrotta S, Della Ragione F, Almeida H, Rossi C, Girodon F, Aström M, Neumann D, Schnittger S, Landin B, Minkov M, Randi ML, Richard S, Casadevall N, Vainchenker W, Rives S, Hermouet S, Ribeiro ML, McMullin MF, Cario H, Chauveau A, Gimenez-Roqueplo AP, Bressac-de-Paillerets B, Altindirek D, Lorenzo F, Lambert F, Dan H, Gad-Lapiteau S, Catarina Oliveira A, Rossi C, Fraga C, Taradin G, Martin-Nuñez G, Vitória H, Diaz Aguado H, Palmblad J, Vidán J, Relvas L, Ribeiro ML, Luigi Larocca M, Luigia Randi M, Pedro Silveira M, Percy M, Gross M, Marques da Costa R, Beshara S, Ben-Ami T, Ugo V. Genetic basis of congenital erythrocytosis: mutation update and online databases. Hum Mutat 2013; 35:15-26. [PMID: 24115288 DOI: 10.1002/humu.22448] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 09/13/2013] [Indexed: 12/15/2022]
Abstract
Congenital erythrocytosis (CE), or congenital polycythemia, represents a rare and heterogeneous clinical entity. It is caused by deregulated red blood cell production where erythrocyte overproduction results in elevated hemoglobin and hematocrit levels. Primary congenital familial erythrocytosis is associated with low erythropoietin (Epo) levels and results from mutations in the Epo receptor gene (EPOR). Secondary CE arises from conditions causing tissue hypoxia and results in increased Epo production. These include hemoglobin variants with increased affinity for oxygen (HBB, HBA mutations), decreased production of 2,3-bisphosphoglycerate due to BPGM mutations, or mutations in the genes involved in the hypoxia sensing pathway (VHL, EPAS1, and EGLN1). Depending on the affected gene, CE can be inherited either in an autosomal dominant or recessive mode, with sporadic cases arising de novo. Despite recent important discoveries in the molecular pathogenesis of CE, the molecular causes remain to be identified in about 70% of the patients. With the objective of collecting all the published and unpublished cases of CE the COST action MPN&MPNr-Euronet developed a comprehensive Internet-based database focusing on the registration of clinical history, hematological, biochemical, and molecular data (http://www.erythrocytosis.org/). In addition, unreported mutations are also curated in the corresponding Leiden Open Variation Database.
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Affiliation(s)
- Celeste Bento
- Department of Hematology, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
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18
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Bento C, Almeida H, Maia TM, Relvas L, Oliveira AC, Rossi C, Girodon F, Fernandez-Lago C, Aguado-Diaz A, Fraga C, Costa RM, Araújo AL, Silva J, Vitória H, Miguel N, Silveira MP, Martin-Nuñez G, Ribeiro ML. Molecular study of congenital erythrocytosis in 70 unrelated patients revealed a potential causal mutation in less than half of the cases (Where is/are the missing gene(s)?). Eur J Haematol 2013; 91:361-8. [PMID: 23859443 DOI: 10.1111/ejh.12170] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/14/2013] [Indexed: 01/28/2023]
Abstract
INTRODUCTION Congenital erythrocytosis can be classified as primary, when the defect is intrinsic to the RBC progenitors and independent of the serum erythropoietin (Epo) concentration, or secondary, when the erythrocytosis is the result of an upregulation of Epo production. Primary erythrocytosis is associated with mutations in the EPOR gene, secondary CE can de due to mutations that stabilize the hemoglobin in the oxygenated form or to mutations in the genes that control the transcriptional activation of the EPO gene - VHL, EGLN1, EPAS1. Chuvash polycythemia, caused by mutations in VHL gene, shares features of both primary and secondary erythrocytosis, with increased Epo production but also hypersensitivity of progenitors to Epo. MATERIAL AND METHODS With the main objective of describing the etiology and molecular basis of CE, we have studied 70 consecutive unrelated patients presenting with idiopathic erythrocytosis from our hematology clinic or referred from other centers. According to a study algorithm, we have sequenced all the genes described as associated with CE. RESULTS AND DISCUSSION Erythrocytosis molecular etiology was identify in 25 (36%) of the 70 subjects. High-affinity Hb variants were the most common cause, present in 20% of the cases. New mutations were identified in the JAK2, EPOR, VHL, and EGLN1 genes. CONCLUSIONS High-affinity hemoglobin variants are a very rare cause of secondary CE, but it seems likely that their incidence may be underestimated. Our experience shows that in erythrocytosis with a dominant inheritance and normal or inappropriate high Epo levels, the HBB and HBA genes should be the first to be studied. In spite of the seven genes known to be involved in CE, the majority of the cases have unknown etiology.
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Affiliation(s)
- Celeste Bento
- Serviço de Hematologia, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
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Abstract
Myeloproliferative neoplasms (MPNs) are haematological disorders characterized by an overproduction of mature myeloid cells with a tendency to transform to acute myeloid leukaemia. Clonal proliferation of myeloid progenitor cells is driven by somatically acquired mutations, most notably JAK2 V617F, but there are important features relating to pathogenesis and phenotypic diversity that cannot be explained by acquired mutations alone. In this review we consider what is currently known about the role that inherited factors play in the development and biology of both sporadic and familial forms of MPN. Although most MPN cases appear to be sporadic, familial predisposition has been recognized for many years in a subset of cases and epidemiological studies have indicated the presence of common susceptibility alleles. Currently the JAK2 46/1 haplotype (also referred to as 'GGCC') is the strongest known predisposition factor for sporadic MPNs carrying a JAK2 V617F mutation, explaining a large proportion of the heritability of this disorder. Less is known about what genetic variants predispose to MPNs that lack JAK2 V617F, but there have been recent reports of interesting associations in biologically plausible candidates, and more loci are set to emerge with the application of systematic genome-wide association methodologies. Several highly penetrant predisposition variants that affect erythropoietin signalling, thrombopoietin signalling or oxygen sensing have been characterized in families with nonclonal hereditary erythrocytosis or thrombocytosis, but much less is known about familial predisposition to true clonal MPN. The heterogeneous pattern of inheritance and presumed genetic heterogeneity in these families makes analysis difficult, but whole exome or genome sequencing should provide novel insights into these elusive disorders.
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Affiliation(s)
- Amy V Jones
- Wessex Regional Genetics Laboratory, Salisbury, UK, Faculty of Medicine, University of Southampton, Southampton, UK
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Abstract
Organisms living under aerobic conditions need oxygen for the metabolic conversion of nutrition into energy. With the appearance of increasingly complex animals, a specialized transport system (erythrocytes) arose during evolution to provide oxygen to virtually every single cell in the body. Moreover, in case of low environmental partial pressure of oxygen, the number of erythrocytes automatically increases to preserve sustained oxygen delivery. This process relies predominantly on the cytokine erythropoietin (Epo) and its transcription factor hypoxia inducible factor (HIF), whereas the von Hippel-Lindau (VHL) ubiquitin ligase as well as the oxygen-sensitive prolyl hydroxylases (PHDs) represent essential regulators of this oxygen-sensing system. Deregulation of particular members of this pathway (eg, PHD2, HIF2α, VHL) lead to disorders in blood homeostasis as a result of insufficient (anemia) or excessive (erythrocytosis) red blood cell production.
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Myllyharju J. Prolyl 4-hydroxylases, master regulators of the hypoxia response. Acta Physiol (Oxf) 2013; 208:148-65. [PMID: 23489300 DOI: 10.1111/apha.12096] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 11/07/2012] [Accepted: 03/08/2013] [Indexed: 12/13/2022]
Abstract
A decrease in oxygenation is a life-threatening situation for most organisms. An evolutionarily conserved efficient and rapid hypoxia response mechanism activated by a hypoxia-inducible transcription factor (HIF) is present in animals ranging from the simplest multicellular phylum Placozoa to humans. In humans, HIF induces the expression of more than 100 genes that are required to increase oxygen delivery and to reduce oxygen consumption. As its name indicates HIF is found at protein level only in hypoxic cells, whereas in normoxia, it is degraded by the proteasome pathway. Prolyl 4-hydroxylases, enzymes that require oxygen in their reaction, are the cellular oxygen sensors regulating the stability of HIF. In normoxia, 4-hydroxyproline residues formed in the α-subunit of HIF by these enzymes lead to its ubiquitination by the von Hippel-Lindau E3 ubiquitin ligase and immediate destruction in proteasomes thus preventing the formation of a functional HIF αβ dimer. Prolyl 4-hydroxylation is inhibited in hypoxia, facilitating the formation of the HIF dimer and activation of its target genes, such as those for erythropoietin and vascular endothelial growth factor. This review starts with a summary of the molecular and catalytic properties and individual functions of the four HIF prolyl 4-hydroxylase isoenzymes. Induction of the hypoxia response via inhibition of the HIF prolyl 4-hydroxylases may provide a novel therapeutic target in the treatment of hypoxia-associated diseases. The current status of studies aiming at such therapeutic approaches is introduced in the final part of this review.
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Affiliation(s)
- J. Myllyharju
- Oulu Center for Cell-Matrix Research; Biocenter Oulu and Department of Medical Biochemistry and Molecular Biology; University of Oulu; Oulu; Finland
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22
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Abstract
A classic physiologic response to systemic hypoxia is the increase in red blood cell production. Hypoxia-inducible factors (HIFs) orchestrate this response by inducing cell-type specific gene expression changes that result in increased erythropoietin (EPO) production in kidney and liver, in enhanced iron uptake and utilization and in adjustments of the bone marrow microenvironment that facilitate erythroid progenitor maturation and proliferation. In particular HIF-2 has emerged as the transcription factor that regulates EPO synthesis in the kidney and liver and plays a critical role in the regulation of intestinal iron uptake. Its key function in the hypoxic regulation of erythropoiesis is underscored by genetic studies in human populations that live at high-altitude and by mutational analysis of patients with familial erythrocytosis. This review provides a perspective on recent insights into HIF-controlled erythropoiesis and iron metabolism, and examines cell types that have EPO-producing capability. Furthermore, the review summarizes clinical syndromes associated with mutations in the O(2)-sensing pathway and the genetic changes that occur in high altitude natives. The therapeutic potential of pharmacologic HIF activation for the treatment of anemia is discussed.
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Affiliation(s)
- Volker H Haase
- Department of Medicine, Vanderbilt School of Medicine, Nashville, TN, USA.
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Transmembrane prolyl 4-hydroxylase is a fourth prolyl 4-hydroxylase regulating EPO production and erythropoiesis. Blood 2012; 120:3336-44. [DOI: 10.1182/blood-2012-07-441824] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
AbstractAn endoplasmic reticulum transmembrane prolyl 4-hydroxylase (P4H-TM) is able to hydroxylate the α subunit of the hypoxia-inducible factor (HIF) in vitro and in cultured cells, but nothing is known about its roles in mammalian erythropoiesis. We studied such roles here by administering a HIF-P4H inhibitor, FG-4497, to P4h-tm−/− mice. This caused larger increases in serum Epo concentration and kidney but not liver Hif-1α and Hif-2α protein and Epo mRNA levels than in wild-type mice, while the liver Hepcidin mRNA level was lower in the P4h-tm−/− mice than in the wild-type. Similar, but not identical, differences were also seen between FG-4497–treated Hif-p4h-2 hypomorphic (Hif-p4h-2gt/gt) and Hif-p4h-3−/− mice versus wild-type mice. FG-4497 administration increased hemoglobin and hematocrit values similarly in the P4h-tm−/− and wild-type mice, but caused higher increases in both values in the Hif-p4h-2gt/gt mice and in hematocrit value in the Hif-p4h-3−/− mice than in the wild-type. Hif-p4h-2gt/gt/P4h-tm−/− double gene-modified mice nevertheless had increased hemoglobin and hematocrit values without any FG-4497 administration, although no such abnormalities were seen in the Hif-p4h-2gt/gt or P4h-tm−/− mice. Our data thus indicate that P4H-TM plays a role in the regulation of EPO production, hepcidin expression, and erythropoiesis.
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Magnussen K, Hasselbalch HC, Ullum H, Bjerrum OW. Characterization of blood donors with high haemoglobin concentration. Vox Sang 2012; 104:110-4. [DOI: 10.1111/j.1423-0410.2012.01644.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Kremyanskaya M, Mascarenhas J, Hoffman R. Why Does My Patient Have Erythrocytosis? Hematol Oncol Clin North Am 2012; 26:267-83, vii-viii. [DOI: 10.1016/j.hoc.2012.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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