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Williamson G, Bizior A, Harris T, Pritchard L, Hoskisson P, Javelle A. Biological ammonium transporters from the Amt/Mep/Rh superfamily: mechanism, energetics, and technical limitations. Biosci Rep 2024; 44:BSR20211209. [PMID: 38131184 PMCID: PMC10794816 DOI: 10.1042/bsr20211209] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/12/2023] [Accepted: 12/21/2023] [Indexed: 12/23/2023] Open
Abstract
The exchange of ammonium across cellular membranes is a fundamental process in all domains of life and is facilitated by the ubiquitous Amt/Mep/Rh transporter superfamily. Remarkably, despite a high structural conservation in all domains of life, these proteins have gained various biological functions during evolution. It is tempting to hypothesise that the physiological functions gained by these proteins may be explained at least in part by differences in the energetics of their translocation mechanisms. Therefore, in this review, we will explore our current knowledge of energetics of the Amt/Mep/Rh family, discuss variations in observations between different organisms, and highlight some technical drawbacks which have hampered effects at mechanistic characterisation. Through the review, we aim to provide a comprehensive overview of current understanding of the mechanism of transport of this unique and extraordinary Amt/Mep/Rh superfamily of ammonium transporters.
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Affiliation(s)
- Gordon Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Adriana Bizior
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Thomas Harris
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Leighton Pritchard
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Paul A. Hoskisson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
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Williamson G, Harris T, Bizior A, Hoskisson PA, Pritchard L, Javelle A. Biological ammonium transporters: evolution and diversification. FEBS J 2024. [PMID: 38265636 DOI: 10.1111/febs.17059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/14/2023] [Accepted: 01/09/2024] [Indexed: 01/25/2024]
Abstract
Although ammonium is the preferred nitrogen source for microbes and plants, in animal cells it is a toxic product of nitrogen metabolism that needs to be excreted. Thus, ammonium movement across biological membranes, whether for uptake or excretion, is a fundamental and ubiquitous biological process catalysed by the superfamily of the Amt/Mep/Rh transporters. A remarkable feature of the Amt/Mep/Rh family is that they are ubiquitous and, despite sharing low amino acid sequence identity, are highly structurally conserved. Despite sharing a common structure, these proteins have become involved in a diverse range of physiological process spanning all domains of life, with reports describing their involvement in diverse biological processes being published regularly. In this context, we exhaustively present their range of biological roles across the domains of life and after explore current hypotheses concerning their evolution to help to understand how and why the conserved structure fulfils diverse physiological functions.
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Affiliation(s)
- Gordon Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Thomas Harris
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Adriana Bizior
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Paul Alan Hoskisson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Leighton Pritchard
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
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3
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Stewart GW, Gibson JS, Rees DC. The cation-leaky hereditary stomatocytosis syndromes: A tale of six proteins. Br J Haematol 2023; 203:509-522. [PMID: 37679660 DOI: 10.1111/bjh.19093] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 08/13/2023] [Accepted: 08/22/2023] [Indexed: 09/09/2023]
Abstract
This review concerns a series of dominantly inherited haemolytic anaemias in which the membrane of the erythrocyte 'leaks' the univalent cations, compromising the osmotic stability of the cell. The majority of the conditions are explained by mutations in one of six genes, coding for multispanning membrane proteins of different structure and function. These are: RhAG, coding for an ammonium carrier; SLC4A1, coding for the band 3 anion exchanger; PIEZO1, coding for a mechanosensitive cation channel; GLUT1, coding for a glucose transporter; KCNN4, coding for an internal-calcium-activated potassium channel; and ABCB6, coding for a porphyrin transporter. This review describes the five clinical syndromes associated with genetic defects in these genes and their variable genotype/phenotype relationships.
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Affiliation(s)
- Gordon W Stewart
- Division of Medicine, Faculty of Medical Sciences, University College London, London, UK
| | - John S Gibson
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - David C Rees
- Haematological Medicine, Kings College London, London, UK
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4
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von Lindern M, Egée S, Bianchi P, Kaestner L. The Function of Ion Channels and Membrane Potential in Red Blood Cells: Toward a Systematic Analysis of the Erythroid Channelome. Front Physiol 2022; 13:824478. [PMID: 35177994 PMCID: PMC8844196 DOI: 10.3389/fphys.2022.824478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/04/2022] [Indexed: 01/14/2023] Open
Abstract
Erythrocytes represent at least 60% of all cells in the human body. During circulation, they experience a huge variety of physical and chemical stimulations, such as pressure, shear stress, hormones or osmolarity changes. These signals are translated into cellular responses through ion channels that modulate erythrocyte function. Ion channels in erythrocytes are only recently recognized as utmost important players in physiology and pathophysiology. Despite this awareness, their signaling, interactions and concerted regulation, such as the generation and effects of “pseudo action potentials”, remain elusive. We propose a systematic, conjoined approach using molecular biology, in vitro erythropoiesis, state-of-the-art electrophysiological techniques, and channelopathy patient samples to decipher the role of ion channel functions in health and disease. We need to overcome challenges such as the heterogeneity of the cell population (120 days lifespan without protein renewal) or the access to large cohorts of patients. Thereto we will use genetic manipulation of progenitors, cell differentiation into erythrocytes, and statistically efficient electrophysiological recordings of ion channel activity.
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Affiliation(s)
- Marieke von Lindern
- Sanquin Research and Landsteiner Laboratory, Department of Hematopoiesis, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Cell Biology and Genetics, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Stéphane Egée
- Integrative Biology of Marine Models, Station Biologique de Roscoff, CNRS, UMR 8227, Sorbonne Université, Roscoff Cedex, France
- Laboratoire d’Excellence GR-Ex, Paris, France
| | - Paola Bianchi
- Pathophysiology of Anemia Unit, Hematology Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico of Milan, Milan, Italy
| | - Lars Kaestner
- Theoretical Medicine and Biosciences, Medical Faculty, Saarland University, Homburg, Germany
- Dynamics of Fluids, Experimental Physics, Saarland University, Saarbrücken, Germany
- *Correspondence: Lars Kaestner,
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5
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Abstract
Heterogeneous red blood cell (RBC) membrane disorders and hydration defects often present with the common clinical findings of hemolytic anemia, but they may require substantially different management, based on their pathophysiology. An accurate and timely diagnosis is essential to avoid inappropriate interventions and prevent complications. Advances in genetic testing availability within the last decade, combined with extensive foundational knowledge on RBC membrane structure and function, now facilitate the correct diagnosis in patients with a variety of hereditary hemolytic anemias (HHAs). Studies in patient cohorts with well-defined genetic diagnoses have revealed complications such as iron overload in hereditary xerocytosis, which is amenable to monitoring, prevention, and treatment, and demonstrated that splenectomy is not always an effective or safe treatment for any patient with HHA. However, a multitude of variants of unknown clinical significance have been discovered by genetic evaluation, requiring interpretation by thorough phenotypic assessment in clinical and/or research laboratories. Here we discuss genotype-phenotype correlations and corresponding clinical management in patients with RBC membranopathies and propose an algorithm for the laboratory workup of patients presenting with symptoms and signs of hemolytic anemia, with a clinical case that exemplifies such a workup.
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MESH Headings
- Anemia, Hemolytic, Congenital/diagnosis
- Anemia, Hemolytic, Congenital/genetics
- Anemia, Hemolytic, Congenital/pathology
- Anemia, Hemolytic, Congenital/therapy
- Disease Management
- Elliptocytosis, Hereditary/diagnosis
- Elliptocytosis, Hereditary/genetics
- Elliptocytosis, Hereditary/pathology
- Elliptocytosis, Hereditary/therapy
- Erythrocyte Membrane/pathology
- Genetic Testing
- Humans
- Hydrops Fetalis/diagnosis
- Hydrops Fetalis/genetics
- Hydrops Fetalis/pathology
- Hydrops Fetalis/therapy
- Infant
- Male
- Mutation
- Spherocytosis, Hereditary/diagnosis
- Spherocytosis, Hereditary/genetics
- Spherocytosis, Hereditary/pathology
- Spherocytosis, Hereditary/therapy
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Affiliation(s)
- Theodosia A. Kalfa
- Correspondence Theodosia A. Kalfa, Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, MLC 7015, Cincinnati, OH 45229-3039; e-mail:
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Wu Z, Wen Y, Fan G, He H, Zhou S, Chen L. HEMGN and SLC2A1 might be potential diagnostic biomarkers of steroid-induced osteonecrosis of femoral head: study based on WGCNA and DEGs screening. BMC Musculoskelet Disord 2021; 22:85. [PMID: 33451334 PMCID: PMC7811219 DOI: 10.1186/s12891-021-03958-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Accepted: 01/05/2021] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Steroid-induced osteonecrosis of the femoral head (SONFH) is a chronic and crippling bone disease. This study aims to reveal novel diagnostic biomarkers of SONFH. METHODS The GSE123568 dataset based on peripheral blood samples from 10 healthy individuals and 30 SONFH patients was used for weighted gene co-expression network analysis (WGCNA) and differentially expressed genes (DEGs) screening. The genes in the module related to SONFH and the DEGs were extracted for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Genes with |gene significance| > 0.7 and |module membership| > 0.8 were selected as hub genes in modules. The DEGs with the degree of connectivity ≥5 were chosen as hub genes in DEGs. Subsequently, the overlapping genes of hub genes in modules and hub genes in DEGs were selected as key genes for SONFH. And then, the key genes were verified in another dataset, and the diagnostic value of key genes was evaluated by receiver operating characteristic (ROC) curve. RESULTS Nine gene co-expression modules were constructed via WGCNA. The brown module with 1258 genes was most significantly correlated with SONFH and was identified as the key module for SONFH. The results of functional enrichment analysis showed that the genes in the key module were mainly enriched in the inflammatory response, apoptotic process and osteoclast differentiation. A total of 91 genes were identified as hub genes in the key module. Besides, 145 DEGs were identified by DEGs screening and 26 genes were identified as hub genes of DEGs. Overlapping genes of hub genes in the key module and hub genes in DEGs, including RHAG, RNF14, HEMGN, and SLC2A1, were further selected as key genes for SONFH. The diagnostic value of these key genes for SONFH was confirmed by ROC curve. The validation results of these key genes in GSE26316 dataset showed that only HEMGN and SLC2A1 were downregulated in the SONFH group, suggesting that they were more likely to be diagnostic biomarkers of SOFNH than RHAG and RNF14. CONCLUSIONS Our study identified that two key genes, HEMGN and SLC2A1, might be potential diagnostic biomarkers of SONFH.
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Affiliation(s)
- Zhixin Wu
- Department of Orthopedic Surgery, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan City, 430071, Hubei Province, China
| | - Yinxian Wen
- Department of Orthopedic Surgery, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan City, 430071, Hubei Province, China.
| | - Guanlan Fan
- Department of Obstetrics and Gynecology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China
| | - Hangyuan He
- Department of Orthopedic Surgery, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan City, 430071, Hubei Province, China
| | - Siqi Zhou
- Department of Orthopedic Surgery, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan City, 430071, Hubei Province, China
| | - Liaobin Chen
- Department of Orthopedic Surgery, Zhongnan Hospital of Wuhan University, 169 Donghu Road, Wuhan City, 430071, Hubei Province, China.
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7
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Grishin D, Kasap E, Izotov A, Lisitsa A. Multifaceted ammonia transporters. All Life 2020. [DOI: 10.1080/26895293.2020.1812443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Affiliation(s)
- D.V. Grishin
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - E.Y. Kasap
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - A.A. Izotov
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - A.V. Lisitsa
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
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8
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Abstract
Erythrocytes are among the most abundant cells in mammals and are perfectly adapted to their main functions, i.e., the transport of O2 to peripheral tissues and the contribution to CO2 transport to the lungs. In contrast to other cells, they are fully devoid of organelles. Similar to apoptosis of nucleated cells erythrocytes may enter suicidal death, eryptosis, which is characterized by the presentation of membrane phosphatidylserine on the cell surface and cell shrinkage, hallmarks that are also typical of apoptosis. Eryptosis may be triggered by an increase in the cytosolic Ca2+ concentration, which may be due to Ca2+ influx via non-selective cation channels of the TRPC family. Eryptosis is further induced by ceramide, which sensitizes erythrocytes to the eryptotic effect of Ca2+. Signaling regulating eryptosis further involves a variety of kinases including AMPK, PAK2, cGKI, JAK3, CK1α, CDK4, MSK1/2 and casein kinase. Eryptosis-dependent shrinkage is induced by K+ efflux through Ca2+-activated K+ channel KCa3.1, the Gardos channel. Eryptotic cells are phagocytosed and may adhere to endothelial cells. Eryptosis may help prevent hemolysis since defective erythrocytes usually undergo eryptosis followed by rapid clearance from circulating blood. Excessive eryptosis stimulated by various diseases and xenobiotics may result in anemia and/or impaired microcirculation. This review focuses on the significance and mechanisms of eryptosis as well as on the ion fluxes involved. Moreover, a short summary of further ion transport mechanisms of the erythrocyte membrane is provided.
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Affiliation(s)
- Michael Föller
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Florian Lang
- Department of Physiology Institute of Physiology, University of Tübingen, Tübingen, Germany
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9
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Abstract
Hereditary erythrocyte membrane disorders are caused by mutations in genes encoding various transmembrane or cytoskeletal proteins of red blood cells. The main consequences of these genetic alterations are decreased cell deformability and shortened erythrocyte survival. Red blood cell membrane defects encompass a heterogeneous group of haemolytic anaemias caused by either (i) altered membrane structural organisation (hereditary spherocytosis, hereditary elliptocytosis, hereditary pyropoikilocytosis and Southeast Asian ovalocytosis) or (ii) altered membrane transport function (overhydrated hereditary stomatocytosis, dehydrated hereditary stomatocytosis or xerocytosis, familial pseudohyperkalaemia and cryohydrocytosis). Herein we provide a comprehensive review of the recent literature on the molecular genetics of erythrocyte membrane defects and their reported clinical consequences. We also describe the effect of low-expression genetic variants on the high inter- and intra-familial phenotype variability of erythrocyte structural defects.
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Affiliation(s)
- Achille Iolascon
- Department of Molecular Medicine and Medical Biotechnologies, Federico II" University of Naples, Naples, Italy.,CEINGE - Biotecnologie Avanzate, Naples, Italy
| | - Immacolata Andolfo
- Department of Molecular Medicine and Medical Biotechnologies, Federico II" University of Naples, Naples, Italy.,CEINGE - Biotecnologie Avanzate, Naples, Italy
| | - Roberta Russo
- Department of Molecular Medicine and Medical Biotechnologies, Federico II" University of Naples, Naples, Italy.,CEINGE - Biotecnologie Avanzate, Naples, Italy
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10
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Andolfo I, Russo R, Gambale A, Iolascon A. Hereditary stomatocytosis: An underdiagnosed condition. Am J Hematol 2018; 93:107-121. [PMID: 28971506 DOI: 10.1002/ajh.24929] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 09/26/2017] [Accepted: 09/27/2017] [Indexed: 12/11/2022]
Abstract
Hereditary stomatocytoses are a wide class of hemolytic anemias characterized by alterations of ionic flux with increased cation permeability that results in inappropriate shrinkage or swelling of the erythrocytes, and water lost or gained osmotically. The last few years have been crucial for new acquisitions in this field in terms of identifying new causative genes and of studying their pathogenetic mechanisms. This review summarizes the main features of erythrocyte membrane transport diseases, dividing them into forms with either isolated erythroid phenotype (nonsyndromic) or extra-hematological manifestations (syndromic), and focusing particularly on the most recent advances regarding dehydrated forms of hereditary stomatocytosis and familial pseudohyperkalemia.
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Affiliation(s)
- Immacolata Andolfo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II; Napoli Italy
- CEINGE Biotecnologie Avanzate; Napoli Italy
| | - Roberta Russo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II; Napoli Italy
- CEINGE Biotecnologie Avanzate; Napoli Italy
| | - Antonella Gambale
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II; Napoli Italy
- CEINGE Biotecnologie Avanzate; Napoli Italy
| | - Achille Iolascon
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II; Napoli Italy
- CEINGE Biotecnologie Avanzate; Napoli Italy
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11
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Abstract
The erythrocyte contains a network of pathways that regulate salt and water content in the face of extracellular and intracellular osmotic perturbations. This allows the erythrocyte to maintain a narrow range of cell hemoglobin concentration, a process critical for normal red blood cell function and survival. Primary disorders that perturb volume homeostasis jeopardize the erythrocyte and may lead to its premature destruction. These disorders are marked by clinical, laboratory, and physiologic heterogeneity. Recent studies have revealed that these disorders are also marked by genetic heterogeneity. They have implicated roles for several proteins, PIEZO1, a mammalian mechanosensory protein; GLUT1, the glucose transporter; SLC4A1, the anion transporter; RhAG, the Rh-associated glycoprotein; KCNN4, the Gardos channel; and ABCB6, an adenosine triphosphate-binding cassette family member, in the maintenance of erythrocyte volume homeostasis. Secondary disorders of erythrocyte hydration include sickle cell disease, thalassemia, hemoglobin CC, and hereditary spherocytosis, where cellular dehydration may be a significant contributor to disease pathology and clinical complications. Understanding the pathways regulating erythrocyte water and solute content may reveal innovative strategies to maintain normal volume in disorders associated with primary or secondary cellular dehydration. These mechanisms will serve as a paradigm for other cells and may reveal new therapeutic targets for disease prevention and treatment beyond the erythrocyte.
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12
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Chen XL, Zhang B, Chng YR, Ong JLY, Chew SF, Wong WP, Lam SH, Nakada T, Ip YK. Ammonia exposure affects the mRNA and protein expression levels of certain Rhesus glycoproteins in the gills of climbing perch. ACTA ACUST UNITED AC 2017; 220:2916-2931. [PMID: 28576822 DOI: 10.1242/jeb.157123] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 05/30/2017] [Indexed: 01/08/2023]
Abstract
The freshwater climbing perch, Anabas testudineus, is an obligate air-breathing and euryhaline teleost capable of active ammonia excretion and tolerant of high concentrations of environmental ammonia. As Rhesus glycoproteins (RhGP/Rhgp) are known to transport ammonia, this study aimed to obtain the complete cDNA coding sequences of various rhgp isoforms from the gills of A. testudineus, and to determine their mRNA and protein expression levels during 6 days of exposure to 100 mmol l-1 NH4Cl. The subcellular localization of Rhgp isoforms in the branchial epithelium was also examined in order to elucidate the type of ionocyte involved in active ammonia excretion. Four rhgp (rhag, rhbg, rhcg1 and rhcg2) had been identified from the gills of A. testudineus They had conserved amino acid residues for NH4+ binding, NH4+ deprotonation, channel gating and lining of the vestibules. Despite inwardly directed NH3 and NH4+ gradients, there were significant increases in the mRNA expression levels of the four branchial rhgp in A. testudineus at certain time points during 6 days of ammonia exposure, with significant increases in the protein abundances of Rhag and Rhcg2 on day 6. Immunofluorescence microscopy revealed a type of ammonia-inducible Na+/K+-ATPase α1c-immunoreactive ionocyte with apical Rhag and basolateral Rhcg2 in the gills of fish exposed to ammonia for 6 days. Hence, active ammonia excretion may involve NH4+ entering the ionocyte through the basolateral Rhcg2 and being excreted through the apical Rhag, driven by a transapical membrane electrical potential generated by the apical cystic fibrosis transmembrane conductance regulator Cl- channel, as suggested previously.
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Affiliation(s)
- Xiu L Chen
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Biyan Zhang
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - You R Chng
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Jasmine L Y Ong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Shit F Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Republic of Singapore
| | - Wai P Wong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Siew H Lam
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore.,NUS Environmental Research Institute, National University of Singapore, Kent Ridge, Singapore 117411, Republic of Singapore
| | - Tsutomu Nakada
- Department of Molecular Pharmacology, Shinshu University School of Medicine, Matsumoto, Nagano 390-8621, Japan
| | - Yuen K Ip
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
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13
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Zhang P, Zawadzki RJ, Goswami M, Nguyen PT, Yarov-Yarovoy V, Burns ME, Pugh EN Jr. In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors. Proc Natl Acad Sci U S A 2017; 114:E2937-46. [PMID: 28320964 DOI: 10.1073/pnas.1620572114] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The light responses of rod and cone photoreceptors have been studied electrophysiologically for decades, largely with ex vivo approaches that disrupt the photoreceptors' subretinal microenvironment. Here we report the use of optical coherence tomography (OCT) to measure light-driven signals of rod photoreceptors in vivo. Visible light stimulation over a 200-fold intensity range caused correlated rod outer segment (OS) elongation and increased light scattering in wild-type mice, but not in mice lacking the rod G-protein alpha subunit, transducin (Gαt), revealing these responses to be triggered by phototransduction. For stimuli that photoactivated one rhodopsin per Gαt the rod OS swelling response reached a saturated elongation of 10.0 ± 2.1%, at a maximum rate of 0.11% s-1 Analyzing swelling as osmotically driven water influx, we find the H2O membrane permeability of the rod OS to be (2.6 ± 0.4) × 10-5 cm⋅s-1, comparable to that of other cells lacking aquaporin expression. Application of Van't Hoff's law reveals that complete activation of phototransduction generates a potentially harmful 20% increase in OS osmotic pressure. The increased backscattering from the base of the OS is explained by a model combining cytoplasmic swelling, translocation of dissociated G-protein subunits from the disc membranes into the cytoplasm, and a relatively higher H2O permeability of nascent discs in the basal rod OS. Translocation of phototransduction components out of the OS may protect rods from osmotic stress, which could be especially harmful in disease conditions that affect rod OS structural integrity.
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14
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Igbokwe NA, Igbokwe IO. Phenotypic homogeneity with minor deviance in osmotic fragility of Sahel goat erythrocytes in non-ionic sucrose media during various physiologic states. J Basic Clin Physiol Pharmacol 2016; 27:633-641. [PMID: 27428847 DOI: 10.1515/jbcpp-2016-0004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 06/04/2016] [Indexed: 11/15/2022]
Abstract
BACKGROUND Erythrocyte swelling in non-ionic sucrose media and the subsequent osmotic lysis are influenced by mechanisms of regulatory volume adjustment and osmotic water permeability. Kinetics of transmembrane water and ion fluxes in varied physiologic states may determine the phenotype of erythrocyte osmotic fragility (EOF) and affect estimates of EOF. METHODS Effects of sex, age, late pregnancy (third trimester) and lactation on the haemolysis of Sahel goat erythrocytes incubated in a series of hyposmotic non-ionic sucrose media were investigated. RESULTS The fragiligram was sigmoidal in 72 (97%) out of 74 goats. Two male (3%) goats with low and high extreme median erythrocyte fragilities (MEF), had non-sigmoidal curves. The mean fragilities at osmolarities of 30-300 mosmol/L of sucrose and the mean osmolarities responsible for 10%-90% haemolysis (CH10-CH90) were not significantly different between males and non-pregnant dry (NPD) females, amongst the age groups and between pregnant or lactating and NPD female goats. The MEF (CH50) of the goats were at osmolarities of 126-252 mosmol/L (median of data: 171 mosmol/L) with a mean of 175.24±16.20 mosmol/L. Therefore, phenotypic homogeneity of EOF occurred with minor deviance, since EOF variables were not differentiated by sex, age, late pregnancy or lactation. CONCLUSIONS Physiologic states of the goat did not affect EOF phenotype in non-ionic sucrose media. Sigmoidal fragility phenotype seemed to be homogeneously conserved by osmoregulatory mechanisms not partitioned by sex, age, late pregnancy or lactation, but a minor non-sigmoidal curve might have occurred due to altered erythrocyte osmotic behaviour that would require further investigation.
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15
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Abstract
Genetic defects of erythrocyte transport proteins cause disorders of red blood cell volume that are characterized by abnormal permeability to the cations Na(+) and K(+) and, consequently, by changes in red cell hydration. Clinically, these disorders are associated with chronic haemolytic anaemia of variable severity and significant co-morbidities, such as iron overload. This review provides an overview of recent insights into the molecular basis of this group of rare anaemias involving cation channels and transporters dysfunction. To date, a total of 5 different membrane proteins have been reported to be responsible for volume homeostasis alteration when mutated, 3 of them leading to overhydrated cells (AE1 [also termed SLC4A1], RHAG and GLUT1 [also termed SCL2A1) and 2 others to dehydrated cells (PIEZO1 and the Gardos Channel). These findings are not only of basic scientific interest, but also of direct clinical significance for improving diagnostic procedures and identify potential approaches for novel therapeutic strategies.
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Affiliation(s)
- Catherine Badens
- APHM Department of Medical Genetics, Hôpital de la Timone, Aix Marseille Univ, INSERM, GMGF, Marseille, France
| | - Hélène Guizouarn
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
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16
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Andolfo I, Russo R, Manna F, Shmukler BE, Gambale A, Vitiello G, De Rosa G, Brugnara C, Alper SL, Snyder LM, Iolascon A. Novel Gardos channel mutations linked to dehydrated hereditary stomatocytosis (xerocytosis). Am J Hematol 2015; 90:921-6. [PMID: 26178367 DOI: 10.1002/ajh.24117] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 07/08/2015] [Indexed: 02/06/2023]
Abstract
Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca(2+) -sensitive K(+) channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development.
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Affiliation(s)
- Immacolata Andolfo
- Department Of Molecular Medicine And Medical Biotechnologies; “Federico II” University Of Naples; Naples Italy
- Biotecnologie Avanzate; CEINGE; Naples Italy
| | - Roberta Russo
- Department Of Molecular Medicine And Medical Biotechnologies; “Federico II” University Of Naples; Naples Italy
- Biotecnologie Avanzate; CEINGE; Naples Italy
| | - Francesco Manna
- Department Of Molecular Medicine And Medical Biotechnologies; “Federico II” University Of Naples; Naples Italy
- Biotecnologie Avanzate; CEINGE; Naples Italy
| | - Boris E. Shmukler
- Renal Division And Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Harvard Medical School; Boston Massachusetts
- Department Of Medicine, Harvard Medical School; Boston Massachusetts
| | - Antonella Gambale
- Department Of Molecular Medicine And Medical Biotechnologies; “Federico II” University Of Naples; Naples Italy
- Biotecnologie Avanzate; CEINGE; Naples Italy
| | - Giuseppina Vitiello
- Biotecnologie Avanzate; CEINGE; Naples Italy
- Medical Genetics Unit; Policlinico Tor Vergata University Hospital; Viale Oxford Rome Italy
| | - Gianluca De Rosa
- Department Of Molecular Medicine And Medical Biotechnologies; “Federico II” University Of Naples; Naples Italy
- Biotecnologie Avanzate; CEINGE; Naples Italy
| | - Carlo Brugnara
- Department Of Laboratory Medicine, Boston Children's Hospital And Department Of Pathology; Harvard Medical School; Boston Massachusetts
| | - Seth L. Alper
- Renal Division And Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Harvard Medical School; Boston Massachusetts
| | - L. Michael Snyder
- Dept Of Hospital Laboratories; University Of Massachusetts Medical Center; Worcester MA
- Quest Diagnositics, LLC MA; Marlborough Massachusetts
| | - Achille Iolascon
- Department Of Molecular Medicine And Medical Biotechnologies; “Federico II” University Of Naples; Naples Italy
- Biotecnologie Avanzate; CEINGE; Naples Italy
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17
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Abstract
Cell mechanics plays a role in stem cell reprogramming and differentiation. To understand this process better, we created a genetically encoded optical probe, named actin-cpstFRET-actin (AcpA), to report forces in actin in living cells in real time. We showed that stemness was associated with increased force in actin. We reprogrammed HEK-293 cells into stem-like cells using no transcription factors but simply by softening the substrate. However, Madin-Darby canine kidney (MDCK) cell reprogramming required, in addition to a soft substrate, Harvey rat sarcoma viral oncogene homolog expression. Replating the stem-like cells on glass led to redifferentiation and reduced force in actin. The actin force probe was a FRET sensor, called cpstFRET (circularly permuted stretch sensitive FRET), flanked by g-actin subunits. The labeled actin expressed efficiently in HEK, MDCK, 3T3, and bovine aortic endothelial cells and in multiple stable cell lines created from those cells. The viability of the cell lines demonstrated that labeled actin did not significantly affect cell physiology. The labeled actin distribution was similar to that observed with GFP-tagged actin. We also examined the stress in the actin cross-linker actinin. Actinin force was not always correlated with actin force, emphasizing the need for addressing protein specificity when discussing forces. Because actin is a primary structural protein in animal cells, understanding its force distribution is central to understanding animal cell physiology and the many linked reactions such as stress-induced gene expression. This new probe permits measuring actin forces in a wide range of experiments on preparations ranging from isolated proteins to transgenic animals.
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18
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Affiliation(s)
- Nazih L. Nakhoul
- Department of Physiology; Tulane University Medical School; New Orleans LA USA
- Department of Medicine, Section of Nephrology; Tulane University Medical School; New Orleans LA USA
| | - L. Lee Hamm
- Department of Medicine, Section of Nephrology; Tulane University Medical School; New Orleans LA USA
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Abstract
PURPOSE OF REVIEW Regulation of erythrocyte volume homeostasis is critical for survival of the erythrocyte. Inherited or acquired disorders that perturb this homeostasis jeopardize the erythrocyte, leading to its premature destruction. This report reviews recent insights into pathways that influence cellular water and solute homeostasis and cell volume. RECENT FINDINGS The molecular and genetic bases of primary disorders of erythrocyte hydration are beginning to be revealed. Recent studies have implicated roles for a new protein PIEZO1, a long sought after mammalian mechanosensory protein; GLUT1, the glucose transporter; SLC4A1, the anion transporter; RhAG, the Rh-associated glycoprotein; and ABCB6, an ATP-binding cassette family member. Secondary disorders associated with perturbed cellular volume and volume regulation include sickle cell disease, thalassemia, and hereditary spherocytosis, in which dehydration contributes to disease pathology and clinical complications. Advances in understanding the mechanisms regulating erythrocyte solute and water content, particularly associated with mechanotransduction pathways, have revealed novel mechanisms controlling erythrocyte hydration. Understanding these processes may provide innovative strategies to maintain normal erythrocyte volume in disorders associated with primary or secondary cellular dehydration. SUMMARY Understanding the mechanisms controlling erythrocyte volume regulation will serve as a paradigm for other cells and may reveal new therapeutic targets for disease prevention and treatment.
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20
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Nakhoul NL, Lee Hamm L. Characteristics of mammalian Rh glycoproteins (SLC42 transporters) and their role in acid-base transport. Mol Aspects Med 2013; 34:629-37. [PMID: 23506896 DOI: 10.1016/j.mam.2012.05.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 04/16/2012] [Indexed: 01/06/2023]
Abstract
The mammalian Rh glycoproteins belong to the solute transporter family SLC42 and include RhAG, present in red blood cells, and two non-erythroid members RhBG and RhCG that are expressed in various tissues, including kidney, liver, skin and the GI tract. The Rh proteins in the red blood cell form an "Rh complex" made up of one D-subunit, one CE-subunit and two RhAG subunits. The Rh complex has a well-known antigenic effect but also contributes to the stability of the red cell membrane. RhBG and RhCG are related to the NH4(+) transporters of the yeast and bacteria but their exact function is yet to be determined. This review describes the expression and molecular properties of these membrane proteins and their potential role as NH3/NH4(+) and CO2 transporters. The likelihood that these proteins transport gases such as CO2 or NH3 is novel and significant. The review also describes the physiological importance of these proteins and their relevance to human disease.
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21
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Deschuyteneer A, Boeckstaens M, De Mees C, Van Vooren P, Wintjens R, Marini AM. SNPs altering ammonium transport activity of human Rhesus factors characterized by a yeast-based functional assay. PLoS One 2013; 8:e71092. [PMID: 23967154 PMCID: PMC3742762 DOI: 10.1371/journal.pone.0071092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 06/24/2013] [Indexed: 01/23/2023] Open
Abstract
Proteins of the conserved Mep-Amt-Rh family, including mammalian Rhesus factors, mediate transmembrane ammonium transport. Ammonium is an important nitrogen source for the biosynthesis of amino acids but is also a metabolic waste product. Its disposal in urine plays a critical role in the regulation of the acid/base homeostasis, especially with an acid diet, a trait of Western countries. Ammonium accumulation above a certain concentration is however pathologic, the cytotoxicity causing fatal cerebral paralysis in acute cases. Alteration in ammonium transport via human Rh proteins could have clinical outcomes. We used a yeast-based expression assay to characterize human Rh variants resulting from non synonymous single nucleotide polymorphisms (nsSNPs) with known or unknown clinical phenotypes and assessed their ammonium transport efficiency, protein level, localization and potential trans-dominant impact. The HsRhAG variants (I61R, F65S) associated to overhydrated hereditary stomatocytosis (OHSt), a disease affecting erythrocytes, proved affected in intrinsic bidirectional ammonium transport. Moreover, this study reveals that the R202C variant of HsRhCG, the orthologue of mouse MmRhcg required for optimal urinary ammonium excretion and blood pH control, shows an impaired inherent ammonium transport activity. Urinary ammonium excretion was RHcg gene-dose dependent in mouse, highlighting MmRhcg as a limiting factor. HsRhCG(R202C) may confer susceptibility to disorders leading to metabolic acidosis for instance. Finally, the analogous R211C mutation in the yeast ScMep2 homologue also impaired intrinsic activity consistent with a conserved functional role of the preserved arginine residue. The yeast expression assay used here constitutes an inexpensive, fast and easy tool to screen nsSNPs reported by high throughput sequencing or individual cases for functional alterations in Rh factors revealing potential causal variants.
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Affiliation(s)
- Aude Deschuyteneer
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - Mélanie Boeckstaens
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - Christelle De Mees
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - Pascale Van Vooren
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - René Wintjens
- Laboratoire des Biopolymères et des nanomatériaux supramoléculaires, Université Libre de Bruxelles, Brussels, Belgium
| | - Anna Maria Marini
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail:
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Shmukler BE, Mukodzi S, Andres O, Eber S, Alper SL. Autosomal dominant overhydrated stomatocytosis associated with the heterozygous RhAG mutation F65S: a case of missed heterozygosity due to allelic dropout. Br J Haematol 2013; 161:602-4. [DOI: 10.1111/bjh.12261] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Boris E. Shmukler
- Renal Division and Molecular and Vascular Medicine Division; Beth Israel Deaconess Medical Center; Boston MA USA
- Department of Medicine; Harvard Medical School; Boston MA USA
| | - Sally Mukodzi
- Paediatric Clinic; Klinikum-Wolfsburg; Wolfsburg Germany
| | - Oliver Andres
- Department of Paediatrics; Children's Hospital; University of Wuerzburg; Wuerzburg Germany
| | - Stefan Eber
- Department of Paediatrics; Children's Hospital; University of Wuerzburg; Wuerzburg Germany
- Practice for Paediatric Haematology and Children's Hospital; Technical University of Munich; Munich Germany
| | - Seth L. Alper
- Renal Division and Molecular and Vascular Medicine Division; Beth Israel Deaconess Medical Center; Boston MA USA
- Department of Medicine; Harvard Medical School; Boston MA USA
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23
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Shmukler BE, Rivera A, Vandorpe DH, Alves J, Bonfanti U, Paltrinieri S, Alper SL. Cation-leak stomatocytosis in standard schnauzers does not cosegregate with coding mutations in the RhAG, SLC4A1, or GLUT1 genes associated with human disease. Blood Cells Mol Dis 2012; 48:219-25. [PMID: 22406315 DOI: 10.1016/j.bcmd.2012.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Autosomal dominant overhydrated cation-leak stomatocytosis in humans has been associated with missense mutations in the erythroid membrane transport genes AE1, RhAG, and GLUT1. Syndromic stomatocytosis has been reported in three dog breeds, but stomatocytosis in Standard Schnauzers is usually asymptomatic, and is accompanied by minimal if any anemia. We have extended the evaluation of a cohort of schnauzers. We found that low-level stomatocytosis was accompanied by increased MCV and increased red cell Na content, and minimal or no reticulocytosis. Red cells from two affected dogs exhibited increased currents in on-cell patches measured in symmetrical NaCl solutions, but Na,K-ATPase and NKCC-mediated cation flux was minimal. Three novel coding polymorphisms found in canine RhAG cDNA and three novel polymorphisms found in canine SLC4A1 cDNA did not cosegregate with MCV or Na content. The GLUT1 cDNA sequence was normal. We conclude that unlike human overhydrated cation-leak stomatocytosis, stomatocytosis in this cohort of Standard Schnauzers is not caused by mutations in the genes encoding RhAG, SLC4A1, or GLUT1.
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Affiliation(s)
- Boris E Shmukler
- Dept. of Medicine, Beth Israel Deaconess Med. Ctr, Boston, MA 02215, United States
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