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Morrison AR. Magnesium Homeostasis: Lessons from Human Genetics. Clin J Am Soc Nephrol 2023; 18:01277230-990000000-00067. [PMID: 36723340 PMCID: PMC10356123 DOI: 10.2215/cjn.0000000000000103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 01/20/2023] [Indexed: 02/02/2023]
Abstract
Mg2+, the fourth most abundant cation in the body, serves as a co-factor for about 600 cellular enzymes. One third of ingested Mg2+ is absorbed from the gut through a saturable transcellular process and a concentration-dependent paracellular process. Absorbed Mg2+ is excreted by the kidney and maintains serum Mg2+ within a narrow range of 0.7 to 1.25 mmol/L. The reabsorption of Mg2+ by the nephron is characterized by paracellular transport in the proximal tubule and thick ascending limb. The nature of the transport pathways in the gut epithelia and thick ascending limb has emerged from an understanding of the molecular mechanisms responsible for rare monogenetic disorders presenting with clinical hypomagnesemia. These human disorders due to loss-of function mutations, in concert with mouse models have led to a deeper understanding of Mg2+ transport in the gut and renal tubule. This review focuses on the nature of the transporters and channels revealed by human and mouse genetics and how they are integrated into an understanding of human Mg2+ physiology.
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Affiliation(s)
- Aubrey R Morrison
- Division of Nephrology Department of Medicine and Developmental Biology Washington University School of Medicine, St Louis MO, 63110 USA
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van der Wijst J, Belge H, Bindels RJM, Devuyst O. Learning Physiology From Inherited Kidney Disorders. Physiol Rev 2019; 99:1575-1653. [PMID: 31215303 DOI: 10.1152/physrev.00008.2018] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.
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Affiliation(s)
- Jenny van der Wijst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Hendrica Belge
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Olivier Devuyst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
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Abu-Amer N, Priel E, Karlish S, Farfel Z, Mayan H. Hypermagnesuria in Humans Following Acute Intravenous Administration of Digoxin. Nephron Clin Pract 2017; 138:113-118. [DOI: 10.1159/000481468] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 09/12/2017] [Indexed: 12/19/2022] Open
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Li H, Sun S, Chen J, Xu G, Wang H, Qian Q. Genetics of Magnesium Disorders. KIDNEY DISEASES 2017; 3:85-97. [PMID: 29344503 DOI: 10.1159/000477730] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 05/23/2017] [Indexed: 12/30/2022]
Abstract
Background Magnesium (Mg2+), the second most abundant cation in the cell, is woven into a multitude of cellular functions. Dysmagnesemia is associated with multiple diseases and, when severe, can be life-threatening. Summary This review discusses Mg2+ homeostasis and function with specific focus on renal Mg2+ handling. Intrarenal channels and transporters related to Mg2+ absorption are discussed. Unraveling the rare genetic diseases with manifestations of dysmagnesemia has greatly increased our understanding of the complex and intricate regulatory network in the kidney, specifically, functions of tight junction proteins including claudin-14, -16, -19, and -10; apical ion channels including: TRPM6, Kv1.1, and ROMK; small regulatory proteins including AC3 and ANK3; and basolateral proteins including EGF receptor, γ-subunit (FXYD2) of Na-K-ATPase, Kir4.1, CaSR, CNNM2, and SLC41A. Although our understanding of Mg2+ handling of the kidney has expanded considerably in the last two decades, many questions remain. Future studies are needed to elucidate a multitude of unknown aspects of Mg2+ handling in the kidney. Key Message Understanding rare and genetic diseases of Mg2+ dysregulation has expanded our knowledge and furthers the development of strategies for preventing and managing dysmagnesemia.
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Affiliation(s)
- Heng Li
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.,Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Shiren Sun
- Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xian, China
| | - Jianghua Chen
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Goushuang Xu
- Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xian, China
| | - Hanmin Wang
- Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xian, China
| | - Qi Qian
- Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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de Baaij JHF, Dorresteijn EM, Hennekam EAM, Kamsteeg EJ, Meijer R, Dahan K, Muller M, van den Dorpel MA, Bindels RJM, Hoenderop JGJ, Devuyst O, Knoers NVAM. Recurrent FXYD2 p.Gly41Arg mutation in patients with isolated dominant hypomagnesaemia. Nephrol Dial Transplant 2015; 30:952-7. [PMID: 25765846 DOI: 10.1093/ndt/gfv014] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 12/15/2014] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Magnesium (Mg(2+)) is an essential ion for cell growth, neuroplasticity and muscle contraction. Blood Mg(2+) levels <0.7 mmol/L may cause a heterogeneous clinical phenotype, including muscle cramps and epilepsy and disturbances in K(+) and Ca(2+) homeostasis. Over the last decade, the genetic origin of several familial forms of hypomagnesaemia has been found. In 2000, mutations in FXYD2, encoding the γ-subunit of the Na(+)-K(+)-ATPase, were identified to cause isolated dominant hypomagnesaemia (IDH) in a large Dutch family suffering from hypomagnesaemia, hypocalciuria and chondrocalcinosis. However, no additional patients have been identified since then. METHODS Here, two families with hypomagnesaemia and hypocalciuria were screened for mutations in the FXYD2 gene. Moreover, the patients were clinically and genetically characterized. RESULTS We report a p.Gly41Arg FXYD2 mutation in two families with hypomagnesaemia and hypocalciuria. Interestingly, this is the same mutation as was described in the original study. As in the initial family, several patients suffered from muscle cramps, chondrocalcinosis and epilepsy. Haplotype analysis revealed an overlapping haplotype in all families, suggesting a founder effect. CONCLUSIONS The recurrent p.Gly41Arg FXYD2 mutation in two new families with IDH confirms that FXYD2 mutation causes hypomagnesaemia. Until now, no other FXYD2 mutations have been reported which could indicate that other FXYD2 mutations will not cause hypomagnesaemia or are embryonically lethal.
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Affiliation(s)
- Jeroen H F de Baaij
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Eiske M Dorresteijn
- Pediatric Nephrology, Erasmus MC, Sophia Childrens Hospital, Rotterdam, The Netherlands
| | - Eric A M Hennekam
- Department of Medical Genetics, University Medical Centre Utrecht, Utrecht 3508 AB, The Netherlands
| | - Erik-Jan Kamsteeg
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rowdy Meijer
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Karin Dahan
- Institut de Génétique et de Pathologie, IPG, Gosselies, Belgium
| | | | | | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost G J Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Olivier Devuyst
- Institute of Physiology, ZIHP, University of Zurich, Zürich, Switzerland
| | - Nine V A M Knoers
- Department of Medical Genetics, University Medical Centre Utrecht, Utrecht 3508 AB, The Netherlands
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Abstract
Magnesium (Mg2+) balance is tightly regulated by the concerted actions of the intestine, bone and kidneys. This balance can be disturbed by a broad variety of drugs. Diuretics, modulators of the EGFR (epidermal growth factor receptor), proton pump inhibitors, antimicrobials, calcineurin inhibitors and cytostatics may all cause hypomagnesaemia, potentially leading to tetany, seizures and cardiac arrhythmias. Conversely, high doses of Mg2+ salts, frequently administered as an antacid or a laxative, may lead to hypermagnesaemia causing various cardiovascular and neuromuscular abnormalities. A better understanding of the molecular mechanisms underlying the adverse effects of these medications on Mg2+ balance will indicate ways of prevention and treatment of these adverse effects and could potentially provide more insight into Mg2+ homoeostasis.
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Stuiver M, Lainez S, Will C, Terryn S, Günzel D, Debaix H, Sommer K, Kopplin K, Thumfart J, Kampik N, Querfeld U, Willnow T, Němec V, Wagner C, Hoenderop J, Devuyst O, Knoers N, Bindels R, Meij I, Müller D. CNNM2, encoding a basolateral protein required for renal Mg2+ handling, is mutated in dominant hypomagnesemia. Am J Hum Genet 2011; 88:333-43. [PMID: 21397062 DOI: 10.1016/j.ajhg.2011.02.005] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 02/14/2011] [Accepted: 02/17/2011] [Indexed: 01/13/2023] Open
Abstract
Familial hypomagnesemia is a rare human disorder caused by renal or intestinal magnesium (Mg(2+)) wasting, which may lead to symptoms of Mg(2+) depletion such as tetany, seizures, and cardiac arrhythmias. Our knowledge of the physiology of Mg(2+) (re)absorption, particularly the luminal uptake of Mg(2+) along the nephron, has benefitted from positional cloning approaches in families with Mg(2+) reabsorption disorders; however, basolateral Mg(2+) transport and its regulation are still poorly understood. Here, by using a candidate screening approach, we identified CNNM2 as a gene involved in renal Mg(2+) handling in patients of two unrelated families with unexplained dominant hypomagnesemia. In the kidney, CNNM2 was predominantly found along the basolateral membrane of distal tubular segments involved in Mg(2+) reabsorption. The basolateral localization of endogenous and recombinant CNNM2 was confirmed in epithelial kidney cell lines. Electrophysiological analysis showed that CNNM2 mediated Mg(2+)-sensitive Na(+) currents that were significantly diminished in mutant protein and were blocked by increased extracellular Mg(2+) concentrations. Our data support the findings of a recent genome-wide association study showing the CNNM2 locus to be associated with serum Mg(2+) concentrations. The mutations found in CNNM2, its observed sensitivity to extracellular Mg(2+), and its basolateral localization signify a critical role for CNNM2 in epithelial Mg(2+) transport.
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Garcia-Lopez R, Perea-Milla E, Garcia CR, Rivas-Ruiz F, Romero-Gonzalez J, Moreno JL, Faus V, Aguas GDC, Diaz JCR. New therapeutic approach to Tourette Syndrome in children based on a randomized placebo-controlled double-blind phase IV study of the effectiveness and safety of magnesium and vitamin B6. Trials 2009; 10:16. [PMID: 19284553 PMCID: PMC2660319 DOI: 10.1186/1745-6215-10-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 03/10/2009] [Indexed: 11/26/2022] Open
Abstract
Background Tourette Syndrome (TS) is a neurological condition presenting chronic motor and phonic tics, and important degree of comorbidity. Considered an uncommon illness, it first becomes apparent during childhood. Current standard treatment only achieves partial control of the condition, and provokes frequent, and sometimes severe, side effects. Methods and design Main aim: To show that, with respect to placebo treatment, the combination of 0.5 mEq/Kg magnesium and 2 mg/Kg vitamin B6 reduces motor and phonic tics and incapacity in cases of exacerbated TS among children aged 7–14 years, as measured on the Yale Global Tic Severity Scale (YGTSS). Secondary aims: Assess the safety of the treatment. Describe metabolic changes revealed by PET. Measure the impact of the experimental treatment on family life. Methodology Randomized, blinded clinical trials. Phase IV study (new proposal for treatment with magnesium and vitamin B6). Scope: children in the geographic area of the study group. Recruitment of subjects: to include patients diagnosed with TS, in accordance with DSM-IV criteria (307.23), during a period of exacerbation, and provided none of the exclusion criteria are met. Instrumentation: clinical data and the YGTSS score will be obtained at the outset of a period of exacerbation (t0). The examinations will be made after 15 (t1), 30 (t2), 60 (t3) and 90 days (t4). PET will be performed at the t0 and t4. We evaluated decrease in the overall score (t0, t1, t2, t3, t4), PET variations, and impact made by the treatment on the patient's life (Psychological General Well-Being Index). Discussion Few clinical trials have been carried out on children with TS, but they are necessary, as current treatment possibilities are insufficient and often provoke side effects. The difficulty of dealing with an uncommon illness makes designing such a study all the more complicated. The present study seeks to overcome possible methodological problems by implementing a prior, phase II study, in order to calculate the relevant statistical parameters and to determine the safety of the proposed treatment. Providing a collateral treatment with magnesium and vitamin B6 could improve control of the illness and help reduce side effects. This protocol was approved by the Andalusian Government Committee for Clinical Trials (Spain). This study was funded by the Health Department of the Andalusian Regional Government and by the Healthcare Research Fund of the Carlos III Healthcare Institute (Spanish Ministry of Health). Trial Registration Current Controlled Trials ISRCTN41082378
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Affiliation(s)
- Rafael Garcia-Lopez
- Department of Anaesthesia and Reanimation, Hospital Costa del Sol, Ctra Nacional 340, km 187, 29603 Marbella, Spain.
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10
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Naderi ASA, Reilly RF. Hereditary etiologies of hypomagnesemia. ACTA ACUST UNITED AC 2008; 4:80-9. [PMID: 18227801 DOI: 10.1038/ncpneph0680] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2007] [Accepted: 09/20/2007] [Indexed: 12/15/2022]
Abstract
Magnesium ions are essential to all living cells. As the second most abundant intracellular cation, magnesium has a crucial role in fundamental metabolic processes such as DNA and protein synthesis, oxidative phosphorylation, enzyme function, ion channel regulation, and neuromuscular excitability. After presenting an overview of magnesium homeostasis, we review the etiologies of hypomagnesemia, with an emphasis on hereditary causes.
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Affiliation(s)
- Amir Said Alizadeh Naderi
- Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-8837, USA.
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van de Graaf SFJ, Bindels RJM, Hoenderop JGJ. Physiology of epithelial Ca2+ and Mg2+ transport. Rev Physiol Biochem Pharmacol 2007; 158:77-160. [PMID: 17729442 DOI: 10.1007/112_2006_0607] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ca2+ and Mg2+ are essential ions in a wide variety of cellular processes and form a major constituent of bone. It is, therefore, essential that the balance of these ions is strictly maintained. In the last decade, major breakthrough discoveries have vastly expanded our knowledge of the mechanisms underlying epithelial Ca2+ and Mg2+ transport. The genetic defects underlying various disorders with altered Ca2+ and/or Mg2+ handling have been determined. Recently, this yielded the molecular identification of TRPM6 as the gatekeeper of epithelial Mg2+ transport. Furthermore, expression cloning strategies have elucidated two novel members of the transient receptor potential family, TRPV5 and TRPV6, as pivotal ion channels determining transcellular Ca2+ transport. These two channels are regulated by a variety of factors, some historically strongly linked to Ca2+ homeostasis, others identified in a more serendipitous manner. Herein we review the processes of epithelial Ca2+ and Mg2+ transport, the molecular mechanisms involved, and the various forms of regulation.
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Affiliation(s)
- S F J van de Graaf
- Radboud University Nijmegen Medical Centre, 286 Cell Physiology, PO Box 9101, 6500 HB Nijmegen, The Netherlands
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Dharnidharka VR, Carney PR. Isolated idiopathic hypomagnesemia presenting as aphasia and seizures. Pediatr Neurol 2005; 33:61-5. [PMID: 15876516 DOI: 10.1016/j.pediatrneurol.2005.02.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2004] [Revised: 03/09/2004] [Accepted: 02/07/2005] [Indexed: 11/26/2022]
Abstract
Isolated hypomagnesemia of the idiopathic form is a rare condition that is known to present as generalized motor seizures in children. This report describes a 4-year-old African-American male who presented with a predominant symptom of sudden onset aphasia and no clear initial motor seizure activity. An evaluation revealed an isolated and severe hypomagnesemia (initial serum magnesium levels <1.0 mg/dL) and inappropriate renal handling of magnesium (fractional excretion of magnesium >40% under conditions of hypomagnesemia). The child had subsequent generalized tonic-clonic seizures that were brought under control with valproic acid therapy and magnesium supplementation. Six months after the diagnosis, he had regained 50-60% of his speech and had no further staring spells or motor seizure activity after the initial episode. Isolated and idiopathic hypomagnesemia caused by defective renal reabsorption of magnesium is a rare familial condition with variable inheritance. Aphasia as the solitary presenting symptom has not been described before. The exact pathophysiology of hypomagnesemic aphasia and seizures is not known but may relate to disinhibition of specific types of glutamate receptors. In the present case, neuronal depolarization may have been localized to language areas in the temporal lobes.
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Affiliation(s)
- Vikas R Dharnidharka
- Division of Pediatric Nephrology, University of Florida College of Medicine, Gainesville, FL 32610-0296, USA
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Abstract
MORE PRECISE IDENTIFICATION: The progress in molecular genetics has led to better understanding of primitive magnesium deficiency. Transporters of this cation have been identified in the intestines and kidneys. The majority of congential hypomanesemia phenotypes have been correlated with a defect in magnesium transport. The primary deficiency of intestinal absorption of magnesium is responsible for hypomagnesemia and subsequent hypocalcemia. DEPENDING ON THE MECHANISM: Magnesium absorption defects in Henle's loop induce hypomagnesemia with hypercalciuria and nephrocalcinosis, autosomal dominant hypocalcemia or Bartter syndrome. In isolated dominant hypomagnesemia and Gitelman syndrome, an abnormality in the distal convoluted tubule explains the primitive hypomagnesemia, through renal leaking. Conversely, the mechanisms of recessive isolated hypomagnesemia remains unknown. ORIENTING GENETIC DIAGNOSIS: In a context of primitive hypomagnesemia, the clinical and biological presentation will orient genetic research leading to correct diagnosis. However, there are many border-line phenotypes and the pheno-genotype correlation is still imperfect.
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Affiliation(s)
- David Montaigne
- Service d'endocrinologie et métabolisme, Centre hospitalo-universitaire, Lille (59)
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Schlingmann KP, Konrad M, Seyberth HW. Genetics of hereditary disorders of magnesium homeostasis. Pediatr Nephrol 2004; 19:13-25. [PMID: 14634861 DOI: 10.1007/s00467-003-1293-z] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2003] [Revised: 07/25/2003] [Accepted: 07/28/2003] [Indexed: 10/26/2022]
Abstract
Magnesium plays an essential role in many biochemical and physiological processes. Homeostasis of magnesium is tightly regulated and depends on the balance between intestinal absorption and renal excretion. During the last decades, various hereditary disorders of magnesium handling have been clinically characterized and genetic studies in affected individuals have led to the identification of some molecular components of cellular magnesium transport. In addition to these hereditary forms of magnesium deficiency, recent studies have revealed a high prevalence of latent hypomagnesemia in the general population. This finding is of special interest in view of the association between hypomagnesemia and common chronic diseases such as diabetes, coronary heart disease, hypertension, and asthma. However, valuable methods for the diagnosis of body and tissue magnesium deficiency are still lacking. This review focuses on clinical and genetic aspects of hereditary disorders of magnesium homeostasis. We will review primary defects of epithelial magnesium transport, disorders associated with defects in Ca(2+)/ Mg(2+) sensing, as well as diseases characterized by renal salt wasting and hypokalemic alkalosis, with special emphasis on disturbed magnesium homeostasis.
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Affiliation(s)
- Karl P Schlingmann
- Department of Pediatrics, Philipps University, Deutschhausstrasse 12, 35037 Marburg, Germany
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Meij IC, Koenderink JB, De Jong JC, De Pont JJHHM, Monnens LAH, Van Den Heuvel LPWJ, Knoers NVAM. Dominant isolated renal magnesium loss is caused by misrouting of the Na+,K+-ATPase gamma-subunit. Ann N Y Acad Sci 2003; 986:437-43. [PMID: 12763862 DOI: 10.1111/j.1749-6632.2003.tb07226.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Hereditary primary hypomagnesemia comprises a clinically and genetically heterogeneous group of disorders in which hypomagnesemia is due to either renal or intestinal Mg(2+) wasting. These disorders share the general symptoms of hypomagnesemia, tetany and epileptiformic convulsions, and often include secondary or associated disturbances in calcium excretion. In a large Dutch family with autosomal dominant renal hypomagnesemia, associated with hypocalciuria, we mapped the disease locus to a 5.6-cM region on chromosome 11q23. After candidate screening, we identified a heterozygous mutation in the FXYD2 gene, encoding the Na(+),K(+)-ATPase gamma-subunit, cosegregating with the patients of this family, which was not found in 132 control chromosomes. The mutation leads to a G41R substitution, introducing a charged amino acid residue in the predicted transmembrane region of the gamma-subunit protein. Expression studies in insect Sf9 and COS-1 cells showed that the mutant gamma-subunit protein was incorrectly routed and accumulated in perinuclear structures. In addition to disturbed routing of the G41R mutant, Western blot analysis of Xenopus oocytes expressing wild-type or mutant gamma-subunit showed mutant gamma-subunit lacking a posttranslational modification. Finally, we investigated two individuals lacking one copy of the FXYD2 gene and found their serum Mg(2+) levels to be within the normal range. We conclude that the arrest of mutant gamma-subunit in distinct intracellular structures is associated with aberrant posttranslational processing and that the G41R mutation causes dominant renal hypomagnesemia associated with hypocalciuria through a dominant negative mechanism.
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Affiliation(s)
- Iwan C Meij
- Department of Human Genetics, Institute of Cellular Signaling, University Medical Center Nijmegen, the Netherlands
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Crambert G, Geering K. FXYD Proteins: New Tissue-Specific Regulators of the Ubiquitous Na,K-ATPase. Sci Signal 2003. [DOI: 10.1126/scisignal.1662003re1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Crambert G, Geering K. FXYD proteins: new tissue-specific regulators of the ubiquitous Na,K-ATPase. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2003; 2003:RE1. [PMID: 12538882 DOI: 10.1126/stke.2003.166.re1] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Maintenance of the Na+ and K+ gradients between the intracellular and extracellular milieus of animal cells is a prerequisite for basic cellular homeostasis and for functions of specialized tissues. The Na,K-ATPase, an oligomeric P-type adenosine triphosphatase (ATPase), is composed of a catalytic alpha subunit and a regulatory beta subunit and is the main player that fulfils these tasks. A variety of regulatory mechanisms are necessary to guarantee appropriate Na,K-ATPase expression and activity adapted to changing physiological demands. Recently, a regulatory mechanism was defined that is mediated by interaction of Na,K-ATPase with small proteins of the FXYD family, which possess a single transmembrane domain and so far have been considered as channels or regulators of ion channels. The mammalian FXYD proteins FXYD1 through FXYD7 exhibit tissue-specific distribution. Phospholemman (FXYD1) in heart and skeletal muscle, the gamma subunit of Na,K-ATPase (FXYD2) and corticosteroid hormone-induced factor (FXYD4, also known as CHIF) in the kidney, and FXYD7 in the brain associate preferentially with the widely expressed Na,K-ATPase alpha1-beta1 isozyme and modulate its transport activity in a way that conforms to tissue-specific requirements. Thus, tissue- and isozyme-specific interaction of Na,K-ATPase with FXYD proteins contributes to proper handling of Na+ and K+ by the Na,K-ATPase, and ensures correct function in such processes as renal Na+-reabsorption, muscle contraction, and neuronal excitability.
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Affiliation(s)
- Gilles Crambert
- Institute of Pharmacology and Toxicology, University of Lausanne, rue du Bugnon 27, CH-Lausanne, Switzerland
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Konrad M, Weber S. Recent advances in molecular genetics of hereditary magnesium-losing disorders. J Am Soc Nephrol 2003; 14:249-60. [PMID: 12506158 DOI: 10.1097/01.asn.0000049161.60740.ce] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Recent advances in molecular genetics in hereditary hypomagnesemia substantiated the role of a variety of genes and their encoded proteins in human magnesium transport mechanisms. This knowledge on underlying genetic defects helps to distinguish different clinical subtypes and gives first insight into molecular components involved in magnesium transport. By mutation analysis and functional protein studies, novel pathophysiologic aspects were elucidated. For some of these disorders, transgenic animal models were generated to study genotype-phenotype relations and disease pathology. This review will discuss genetic and clinical aspects of familial disorders associated with magnesium wasting and focuses on the recent progress that has been made in molecular genetics. Besides isolated renal forms of hereditary hypomagnesemia, the following disorders will also be presented: familial hypomagnesemia with hypercalciuria and nephrocalcinosis, hypomagnesemia with secondary hypocalcemia, Ca2+/Mg2+-sensing receptor-associated disorders, and disorders associated with renal salt-wasting and hypokalemic metabolic alkalosis, comprising the Gitelman syndrome and the Bartter-like syndromes.
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Grimaldi BL. The central role of magnesium deficiency in Tourette's syndrome: causal relationships between magnesium deficiency, altered biochemical pathways and symptoms relating to Tourette's syndrome and several reported comorbid conditions. Med Hypotheses 2002; 58:47-60. [PMID: 11863398 DOI: 10.1054/mehy.2001.1447] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Prior studies have suggested a common etiology involved in Tourette's syndrome and several comorbid conditions and symptomatology. Reportedly, current medications used in Tourette's syndrome have intolerable side-effects or are ineffective for many patients. After thoroughly researching the literature, I hypothesize that magnesium deficiency may be the central precipitating event and common pathway for the subsequent biochemical effects on substance P, kynurenine, NMDA receptors, and vitamin B6 that may result in the symptomatology of Tourette's syndrome and several reported comorbid conditions. These comorbid conditions and symptomatology include allergy, asthma, autism, attention deficit hyperactivity disorder, obsessive compulsive disorder, coprolalia, copropraxia, anxiety, depression, restless leg syndrome, migraine, self-injurious behavior, autoimmunity, rage, bruxism, seizure, heart arrhythmia, heightened sensitivity to sensory stimuli, and an exaggerated startle response. Common possible environmental and genetic factors are discussed, as well as biochemical mechanisms. Clinical studies to determine the medical efficacy for a comprehensive magnesium treatment option for Tourette's syndrome need to be conducted to make this relatively safe, low side-effect treatment option available to doctors and their patients.
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Bastani B, Pandurangan G. Intraperitoneal route of magnesium sulphate supplementation in a patient with severe renal magnesium wasting. Nephrol Dial Transplant 2001; 16:2086-9. [PMID: 11572903 DOI: 10.1093/ndt/16.10.2086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- B Bastani
- Division of Nephrology, Department of Internal Medicine, Saint Louis University School of Medicine, St Louis, MO 63110, USA.
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Wetzel RK, Sweadner KJ. Immunocytochemical localization of Na-K-ATPase alpha- and gamma-subunits in rat kidney. Am J Physiol Renal Physiol 2001; 281:F531-45. [PMID: 11502602 DOI: 10.1152/ajprenal.2001.281.3.f531] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The gamma-subunit of the Na-K-ATPase is a single-span membrane protein that alters the kinetic properties of the enzyme. It is expressed in the kidney, but our initial observations indicated that it is not present in all nephron segments (Arystarkhova E, Wetzel RK, Asinovski NK, and Sweadner KJ. J Biol Chem 274: 33183-33185, 1999). Here we used triple-label confocal immunofluorescence microscopy in rat kidney with antibodies to Na-K-ATPase alpha1- and gamma-subunits and nephron segment-specific markers. Na-K-ATPase alpha1-subunit stain was low but unambiguous in proximal segments, moderate in macula densa, connecting tubules, and cortical collecting ducts, high in thick ascending limb and distal convoluted tubules, and nearly undetectable in glomeruli, descending and ascending thin limb, and medullary collecting ducts. The gamma-subunit colocalized at staining levels similar to alpha1-subunit in basolateral membranes in all segments except cortical thick ascending limb and cortical collecting ducts, which had alpha1-subunit but no detectable gamma-subunit stain. Selective gamma-subunit expression may contribute to the variations in Na-K-ATPase properties in different renal segments.
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Affiliation(s)
- R K Wetzel
- Laboratory of Membrane Biology, Neuroscience Center, Massachusetts General Hospital, 149 13th St., Charlestown, MA 02129, USA
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Dai LJ, Ritchie G, Kerstan D, Kang HS, Cole DE, Quamme GA. Magnesium transport in the renal distal convoluted tubule. Physiol Rev 2001; 81:51-84. [PMID: 11152754 DOI: 10.1152/physrev.2001.81.1.51] [Citation(s) in RCA: 250] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The distal tubule reabsorbs approximately 10% of the filtered Mg(2+), but this is 70-80% of that delivered from the loop of Henle. Because there is little Mg(2+) reabsorption beyond the distal tubule, this segment plays an important role in determining the final urinary excretion. The distal convoluted segment (DCT) is characterized by a negative luminal voltage and high intercellular resistance so that Mg(2+) reabsorption is transcellular and active. This review discusses recent evidence for selective and sensitive control of Mg(2+) transport in the DCT and emphasizes the importance of this control in normal and abnormal renal Mg(2+) conservation. Normally, Mg(2+) absorption is load dependent in the distal tubule, whether delivery is altered by increasing luminal Mg(2+) concentration or increasing the flow rate into the DCT. With the use of microfluorescent studies with an established mouse distal convoluted tubule (MDCT) cell line, it was shown that Mg(2+) uptake was concentration and voltage dependent. Peptide hormones such as parathyroid hormone, calcitonin, glucagon, and arginine vasopressin enhance Mg(2+) absorption in the distal tubule and stimulate Mg(2+) uptake into MDCT cells. Prostaglandin E(2) and isoproterenol increase Mg(2+) entry into MDCT cells. The current evidence indicates that cAMP-dependent protein kinase A, phospholipase C, and protein kinase C signaling pathways are involved in these responses. Steroid hormones have significant effects on distal Mg(2+) transport. Aldosterone does not alter basal Mg(2+) uptake but potentiates hormone-stimulated Mg(2+) entry in MDCT cells by increasing hormone-mediated cAMP formation. 1,25-Dihydroxyvitamin D(3), on the other hand, stimulates basal Mg(2+) uptake. Elevation of plasma Mg(2+) or Ca(2+) inhibits hormone-stimulated cAMP accumulation and Mg(2+) uptake in MDCT cells through activation of extracellular Ca(2+)/Mg(2+)-sensing mechanisms. Mg(2+) restriction selectively increases Mg(2+) uptake with no effect on Ca(2+) absorption. This intrinsic cellular adaptation provides the sensitive and selective control of distal Mg(2+) transport. The distally acting diuretics amiloride and chlorothiazide stimulate Mg(2+) uptake in MDCT cells acting through changes in membrane voltage. A number of familial and acquired disorders have been described that emphasize the diversity of cellular controls affecting renal Mg(2+) balance. Although it is clear that many influences affect Mg(2+) transport within the DCT, the transport processes have not been identified.
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Affiliation(s)
- L J Dai
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Sweadner KJ, Wetzel RK, Arystarkhova E. Genomic organization of the human FXYD2 gene encoding the gamma subunit of the Na,K-ATPase. Biochem Biophys Res Commun 2000; 279:196-201. [PMID: 11112438 DOI: 10.1006/bbrc.2000.3907] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although the gamma subunit of the Na,K-ATPase has only 66 or 68 amino acids, its human gene (FXYD2) was found to span 9.2 kb and have seven exons, including two alternatively spliced exons encoding different N-termini. Two candidate promoters with consensus sites for transcription factors Sp1, AP-1, and AP-2 are present, consistent with independent transcription of the splice variants. Multiple ESTs support the transcriptional competence of the identified gene elements. In the FXYD2 gene, there are two closely spaced polyadenylation signals, and both are used. A proposed third splice variant encoding a 31-residue N-terminal extension was not found in the gene, nor was the predicted larger protein found in human kidney Na,K-ATPase. Instead, evidence was found for the origin of the larger cDNA clone in homologous recombination with unrelated DNA from chromosome 2. FXYD2 is on chromosome 11q23 close to a site of tumorigenic chromosomal translocations, and has a number of repeat elements.
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Affiliation(s)
- K J Sweadner
- Neuroscience Center, Massachusetts General Hospital, 149 13th Street, Charlestown, Massachusetts 02129, USA.
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Chollet D, Franken P, Raffin Y, Malafosse A, Widmer J, Tafti M. Blood and brain magnesium in inbred mice and their correlation with sleep quality. Am J Physiol Regul Integr Comp Physiol 2000; 279:R2173-8. [PMID: 11080083 DOI: 10.1152/ajpregu.2000.279.6.r2173] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A strong genetic component in the regulation of blood magnesium (Mg) levels has been demonstrated. The regulation and distribution of brain Mg levels, however, have never been assessed. Herein we report on the genetic variation of peripheral and central Mg levels in six inbred strains of mice. In addition, the possible involvement of Mg in sleep regulation was assessed by establishing correlations between Mg and sleep parameters obtained before and after a 6-h sleep deprivation. Although genotype strongly determined blood Mg levels, it did not affect brain Mg, suggesting that central and peripheral Mg are regulated differently. Central Mg displayed a highly structure-specific distribution with frontal cortex having the highest and brain stem the lowest values. Whereas for the amount and distribution of baseline sleep only marginal correlations with Mg were found, Mg contents in four of nine brain structures were highly positively correlated with the length of slow-wave sleep episodes during recovery. This relationship suggests that higher levels of Mg in specific brain sites promote sleep quality as part of a recovery process.
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Affiliation(s)
- D Chollet
- Biochemistry and Neurophysiology Unit, Department of Psychiatry, University of Geneva, 1225 Geneva, Switzerland
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Meij IC, Koenderink JB, van Bokhoven H, Assink KF, Groenestege WT, de Pont JJ, Bindels RJ, Monnens LA, van den Heuvel LP, Knoers NV. Dominant isolated renal magnesium loss is caused by misrouting of the Na(+),K(+)-ATPase gamma-subunit. Nat Genet 2000; 26:265-6. [PMID: 11062458 DOI: 10.1038/81543] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Primary hypomagnesaemia is composed of a heterogeneous group of disorders characterized by renal or intestinal Mg(2+) wasting, often associated with disturbances in Ca(2+) excretion. We identified a putative dominant-negative mutation in the gene encoding the Na(+), K(+)-ATPase gamma-subunit (FXYD2), leading to defective routing of the protein in a family with dominant renal hypomagnesaemia.
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Affiliation(s)
- I C Meij
- Department of Pediatrics, Institute of Cellular Signaling, University Medical Centre Nijmegen, Nijmegen, The Netherlands
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Abstract
The genetic basis and cellular defects of a number of primary magnesium wasting diseases have been elucidated over the past decade. This review correlates the clinical pathophysiology with the primary defect and secondary changes in cellular electrolyte transport. The described disorders include (1) hypomagnesemia with secondary hypocalcemia, an earlyonset, autosomal-recessive disease segregating with chromosome 9q12-22.2; (2) autosomal-dominant hypomagnesemia caused by isolated renal magnesium wasting, mapped to chromosome 11q23; (3) hypomagnesemia with hypercalciuria and nephrocalcinosis, a recessive condition caused by a mutation of the claudin 16 gene (3q27) coding for a tight junctional protein that regulates paracellular Mg(2+) transport in the loop of Henle; (4) autosomal-dominant hypoparathyroidism, a variably hypomagnesemic disorder caused by inactivating mutations of the extracellular Ca(2+)/Mg(2+)-sensing receptor, CASR: gene, at 3q13.3-21 (a significant association between common polymorphisms of the CASR: and extracellular Mg(2+) concentration has been demonstrated in a healthy adult population); and (5) Gitelman syndrome, a recessive form of hypomagnesemia caused by mutations in the distal tubular NaCl cotransporter gene, SLC12A3, at 16q13. The basis for renal magnesium wasting in this disease is not known. These inherited conditions affect different nephron segments and different cell types and lead to variable but increasingly distinguishable phenotypic presentations. No doubt, there are in the general population other disorders that have not yet been identified or characterized. The continued use of molecular techniques to probe the constitutive and congenital disturbances of magnesium metabolism will increase the understanding of cellular magnesium transport and provide new insights into the way these diseases are diagnosed and managed.
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Affiliation(s)
- David E C Cole
- Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, and Department of Medicine, University of British Columbia, Koerner Pavilion, University Hospital, Vancouver, British Columbia, Canada
| | - Gary A Quamme
- Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, and Department of Medicine, University of British Columbia, Koerner Pavilion, University Hospital, Vancouver, British Columbia, Canada
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Benigno V, Canonica CS, Bettinelli A, von Vigier RO, Truttmann AC, Bianchetti MG. Hypomagnesaemia-hypercalciuria-nephrocalcinosis: a report of nine cases and a review. Nephrol Dial Transplant 2000; 15:605-10. [PMID: 10809799 DOI: 10.1093/ndt/15.5.605] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The cardinal characteristics of primary hypomagnesaemia-hypercalciuria-nephrocalcinosis include renal magnesium wasting, marked hypercalciuria, renal stones, nephrocalcinosis, a tendency towards chronic renal insufficiency and sometimes even ocular abnormalities or hearing impairment. METHODS As very few patients with this syndrome have been described, we provide information on nine patients on follow-up at our institutions and review the 42 cases reported in the literature (33 females and 18 males). RESULTS Urinary tract infections, polyuria-polydipsia, renal stones and tetanic convulsions were the main clinical findings at diagnosis. The clinical course was highly variable; renal failure was often reported. The concomitant occurrence of ocular involvement or hearing impairment was reported in a large subset of patients. Parental consanguinity was noted in some families. CONCLUSIONS The results indicate an autosomal recessive inheritance. The diagnosis of primary hypomagnesaemia-hypercalciuria-nephrocalcinosis deserves consideration in any patient with nephrocalcinosis and hypercalciuria.
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Affiliation(s)
- V Benigno
- Department of Pediatrics, University of Bern, Switzerland
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Niemann S, Becker-Follmann J, N�rnberg G, R�schendorf F, Sieweke N, H�gens-Penzel M, Traupe H, Wienker TF, Reis A, M�ller U. Assignment of PGL3 to chromosome 1 (q21-q23) in a family with autosomal dominant non-chromaffin paraganglioma. ACTA ACUST UNITED AC 2000. [DOI: 10.1002/1096-8628(20010101)98:1<32::aid-ajmg1004>3.0.co;2-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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29
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Simon DB, Lu Y, Choate KA, Velazquez H, Al-Sabban E, Praga M, Casari G, Bettinelli A, Colussi G, Rodriguez-Soriano J, McCredie D, Milford D, Sanjad S, Lifton RP. Paracellin-1, a renal tight junction protein required for paracellular Mg2+ resorption. Science 1999; 285:103-6. [PMID: 10390358 DOI: 10.1126/science.285.5424.103] [Citation(s) in RCA: 722] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Epithelia permit selective and regulated flux from apical to basolateral surfaces by transcellular passage through cells or paracellular flux between cells. Tight junctions constitute the barrier to paracellular conductance; however, little is known about the specific molecules that mediate paracellular permeabilities. Renal magnesium ion (Mg2+) resorption occurs predominantly through a paracellular conductance in the thick ascending limb of Henle (TAL). Here, positional cloning has identified a human gene, paracellin-1 (PCLN-1), mutations in which cause renal Mg2+ wasting. PCLN-1 is located in tight junctions of the TAL and is related to the claudin family of tight junction proteins. These findings provide insight into Mg2+ homeostasis, demonstrate the role of a tight junction protein in human disease, and identify an essential component of a selective paracellular conductance.
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Affiliation(s)
- D B Simon
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA
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30
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Affiliation(s)
- Z S Agus
- University of Pennsylvania School of Medicine, Philadelphia, USA.
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