1
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Yang G, Mack H, Harraka P, Colville D, Savige J. Ocular manifestations of the genetic renal tubulopathies. Ophthalmic Genet 2023; 44:515-529. [PMID: 37702059 DOI: 10.1080/13816810.2023.2253901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 08/26/2023] [Indexed: 09/14/2023]
Abstract
BACKGROUND The genetic tubulopathies are rare and heterogenous disorders that are often difficult to identify. This study examined the tubulopathy-causing genes for ocular associations that suggested their genetic basis and, in some cases, the affected gene. METHODS Sixty-seven genes from the Genomics England renal tubulopathy panel were reviewed for ocular features, and for retinal expression in the Human Protein Atlas and an ocular phenotype in mouse models in the Mouse Genome Informatics database. The genes resulted in disease affecting the proximal tubules (n = 24); the thick ascending limb of the loop of Henle (n = 10); the distal convoluted tubule (n = 15); or the collecting duct (n = 18). RESULTS Twenty-five of the tubulopathy-associated genes (37%) had ocular features reported in human disease, 49 (73%) were expressed in the retina, although often at low levels, and 16 (24%) of the corresponding mouse models had an ocular phenotype. Ocular abnormalities were more common in genes affected in the proximal tubulopathies (17/24, 71%) than elsewhere (7/43, 16%). They included structural features (coloboma, microphthalmia); refractive errors (myopia, astigmatism); crystal deposition (in oxalosis, cystinosis) and sclerochoroidal calcification (in Bartter, Gitelman syndromes). Retinal atrophy was common in the mitochondrial-associated tubulopathies. Structural abnormalities and crystal deposition were present from childhood, but sclerochoroidal calcification typically occurred after middle age. CONCLUSIONS Ocular abnormalities are uncommon in the genetic tubulopathies but may be helpful in recognizing the underlying genetic disease. The retinal expression and mouse phenotype data suggest that further ocular associations may become apparent with additional reports. Early identification may be necessary to monitor and treat visual complications.
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Affiliation(s)
- GeFei Yang
- Department of Medicine (Melbourne Health and Northern Health), The University of Melbourne, Royal Melbourne Hospital, Parkville, Australia
| | - Heather Mack
- Department of Surgery (Ophthalmology), The University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Philip Harraka
- Department of Medicine (Melbourne Health and Northern Health), The University of Melbourne, Royal Melbourne Hospital, Parkville, Australia
| | - Deb Colville
- Department of Surgery (Ophthalmology), The University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Judy Savige
- Department of Medicine (Melbourne Health and Northern Health), The University of Melbourne, Royal Melbourne Hospital, Parkville, Australia
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2
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Staruschenko A, Hodges MR, Palygin O. Kir5.1 channels: potential role in epilepsy and seizure disorders. Am J Physiol Cell Physiol 2022; 323:C706-C717. [PMID: 35848616 PMCID: PMC9448276 DOI: 10.1152/ajpcell.00235.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/06/2022] [Accepted: 07/08/2022] [Indexed: 11/22/2022]
Abstract
Inwardly rectifying potassium (Kir) channels are broadly expressed in many mammalian organ systems, where they contribute to critical physiological functions. However, the importance and function of the Kir5.1 channel (encoded by the KCNJ16 gene) have not been fully recognized. This review focuses on the recent advances in understanding the expression patterns and functional roles of Kir5.1 channels in fundamental physiological systems vital to potassium homeostasis and neurological disorders. Recent studies have described the role of Kir5.1-forming Kir channels in mouse and rat lines with mutations in the Kcnj16 gene. The animal research reveals distinct renal and neurological phenotypes, including pH and electrolyte imbalances, blunted ventilatory responses to hypercapnia/hypoxia, and seizure disorders. Furthermore, it was confirmed that these phenotypes are reminiscent of those in patient cohorts in which mutations in the KCNJ16 gene have also been identified, further suggesting a critical role for Kir5.1 channels in homeostatic/neural systems health and disease. Future studies that focus on the many functional roles of these channels, expanded genetic screening in human patients, and the development of selective small-molecule inhibitors for Kir5.1 channels, will continue to increase our understanding of this unique Kir channel family member.
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Affiliation(s)
- Alexander Staruschenko
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
- Hypertension and Kidney Research Center, University of South Florida, Tampa, Florida
- James A. Haley Veterans Hospital, Tampa, Florida
| | - Matthew R Hodges
- Department of Physiology and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Oleg Palygin
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
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3
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Beverley KM, Pattnaik BR. Inward rectifier potassium (Kir) channels in the retina: living our vision. Am J Physiol Cell Physiol 2022; 323:C772-C782. [PMID: 35912989 PMCID: PMC9448332 DOI: 10.1152/ajpcell.00112.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 07/25/2022] [Accepted: 07/25/2022] [Indexed: 11/22/2022]
Abstract
Channel proteins are vital for conducting ions throughout the body and are especially relevant to retina physiology. Inward rectifier potassium (Kir) channels are a class of K+ channels responsible for maintaining membrane potential and extracellular K+ concentrations. Studies of the KCNJ gene (that encodes Kir protein) expression identified the presence of all of the subclasses (Kir 1-7) of Kir channels in the retina or retinal-pigmented epithelium (RPE). However, functional studies have established the involvement of the Kir4.1 homotetramer and Kir4.1/5.1 heterotetramer in Müller glial cells, Kir2.1 in bipolar cells, and Kir7.1 in the RPE cell physiology. Here, we propose the potential roles of Kir channels in the retina based on the physiological contributions to the brain, pancreatic, and cardiac tissue functions. There are several open questions regarding the expressed KCNJ genes in the retina and RPE. For example, why does not the Kir channel subtype gene expression correspond with protein expression? Catching up with multiomics or functional "omics" approaches might shed light on posttranscriptional changes that might influence Kir subunit mRNA translation within the retina that guides our vision.
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Affiliation(s)
- Katie M Beverley
- Endocrinology and Reproductive Physiology Graduate Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
| | - Bikash R Pattnaik
- Endocrinology and Reproductive Physiology Graduate Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
- McPherson Eye Research Institute, University of Wisconsin, Madison, Wisconsin
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
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4
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Bamgbola OF. Review of the Pathophysiologic and Clinical Aspects of Hypokalemia in Children and Young Adults: an Update. CURRENT TREATMENT OPTIONS IN PEDIATRICS 2022; 8:96-114. [PMID: 37521171 PMCID: PMC9115742 DOI: 10.1007/s40746-022-00240-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Accepted: 04/18/2022] [Indexed: 11/28/2022]
Abstract
This article examines the regulatory function of the skeletal muscle, renal, and adrenergic systems in potassium homeostasis. The pathophysiologic bases of hypokalemia, systematic approach for an early diagnosis, and therapeutic strategy to avert life-threatening complications are highlighted. By promoting skeletal muscle uptake, intense physical exercise (post), severe trauma, and several toxins produce profound hypokalemia. Hypovolemia due to renal and extra-renal fluid losses and ineffective circulation activate secondary aldosteronism causing urinary potassium wasting. In addition to hypokalemic alkalosis, primary aldosteronism causes low-renin hypertension. Non-aldosterone mineralocorticoid activation leading to low-renin and low-aldosterone hypertension occurs in Liddle's syndrome and apparent mineralocorticoid excess. Although there is enzymatic inhibition of cortisol synthesis in congenital adrenal hyperplasia, precursors of aldosterone produce low-renin hypokalemic hypertension. In addition to the glucocorticoid effect, hypercortisolism activates mineralocorticoid receptors in Cushing's syndrome. Genetic mutations involving furosemide-sensitive Na+-K+-2Cl- co-transporters and thiazide-sensitive Na+-Cl- transporters result in (non-hypertensive) salt-wasting nephropathy. Proximal and distal renal tubular acidosis is associated with hypokalemia. Eating disorders causing hypokalemia include bulimia, laxative abuse, and diuretic misuse. Low urinary potassium (<15 mmol/day) and/or low urinary chloride (<20 mol/L) suggest a gastrointestinal pathology. Co-morbidity of hypokalemia with chronic pulmonary and cardiovascular diseases may increase the fatality rate.
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Affiliation(s)
- Oluwatoyin Fatai Bamgbola
- Division of Pediatric Nephrology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203 USA
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5
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Lo J, Forst AL, Warth R, Zdebik AA. EAST/SeSAME Syndrome and Beyond: The Spectrum of Kir4.1- and Kir5.1-Associated Channelopathies. Front Physiol 2022; 13:852674. [PMID: 35370765 PMCID: PMC8965613 DOI: 10.3389/fphys.2022.852674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 02/08/2022] [Indexed: 12/13/2022] Open
Abstract
In 2009, two groups independently linked human mutations in the inwardly rectifying K+ channel Kir4.1 (gene name KCNJ10) to a syndrome affecting the central nervous system (CNS), hearing, and renal tubular salt reabsorption. The autosomal recessive syndrome has been named EAST (epilepsy, ataxia, sensorineural deafness, and renal tubulopathy) or SeSAME syndrome (seizures, sensorineural deafness, ataxia, intellectual disability, and electrolyte imbalance), accordingly. Renal dysfunction in EAST/SeSAME patients results in loss of Na+, K+, and Mg2+ with urine, activation of the renin-angiotensin-aldosterone system, and hypokalemic metabolic alkalosis. Kir4.1 is highly expressed in affected organs: the CNS, inner ear, and kidney. In the kidney, it mostly forms heteromeric channels with Kir5.1 (KCNJ16). Biallelic loss-of-function mutations of Kir5.1 can also have disease significance, but the clinical symptoms differ substantially from those of EAST/SeSAME syndrome: although sensorineural hearing loss and hypokalemia are replicated, there is no alkalosis, but rather acidosis of variable severity; in contrast to EAST/SeSAME syndrome, the CNS is unaffected. This review provides a framework for understanding some of these differences and will guide the reader through the growing literature on Kir4.1 and Kir5.1, discussing the complex disease mechanisms and the variable expression of disease symptoms from a molecular and systems physiology perspective. Knowledge of the pathophysiology of these diseases and their multifaceted clinical spectrum is an important prerequisite for making the correct diagnosis and forms the basis for personalized therapies.
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Affiliation(s)
- Jacky Lo
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Anna-Lena Forst
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Richard Warth
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Anselm A. Zdebik
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
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6
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Akyuz E, Koklu B, Uner A, Angelopoulou E, Paudel YN. Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy. J Neurosci Res 2021; 100:413-443. [PMID: 34713909 DOI: 10.1002/jnr.24985] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 09/23/2021] [Accepted: 10/01/2021] [Indexed: 01/29/2023]
Abstract
Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.
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Affiliation(s)
- Enes Akyuz
- Faculty of International Medicine, Department of Biophysics, University of Health Sciences, Istanbul, Turkey
| | - Betul Koklu
- Faculty of Medicine, Namık Kemal University, Tekirdağ, Turkey
| | - Arda Uner
- Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey
| | - Efthalia Angelopoulou
- Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Yam Nath Paudel
- Neuropharmacology Research Strength, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
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7
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Taukulis IA, Olszewski RT, Korrapati S, Fernandez KA, Boger ET, Fitzgerald TS, Morell RJ, Cunningham LL, Hoa M. Single-Cell RNA-Seq of Cisplatin-Treated Adult Stria Vascularis Identifies Cell Type-Specific Regulatory Networks and Novel Therapeutic Gene Targets. Front Mol Neurosci 2021; 14:718241. [PMID: 34566577 PMCID: PMC8458580 DOI: 10.3389/fnmol.2021.718241] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/17/2021] [Indexed: 11/21/2022] Open
Abstract
The endocochlear potential (EP) generated by the stria vascularis (SV) is necessary for hair cell mechanotransduction in the mammalian cochlea. We sought to create a model of EP dysfunction for the purposes of transcriptional analysis and treatment testing. By administering a single dose of cisplatin, a commonly prescribed cancer treatment drug with ototoxic side effects, to the adult mouse, we acutely disrupt EP generation. By combining these data with single cell RNA-sequencing findings, we identify transcriptional changes induced by cisplatin exposure, and by extension transcriptional changes accompanying EP reduction, in the major cell types of the SV. We use these data to identify gene regulatory networks unique to cisplatin treated SV, as well as the differentially expressed and druggable gene targets within those networks. Our results reconstruct transcriptional responses that occur in gene expression on the cellular level while identifying possible targets for interventions not only in cisplatin ototoxicity but also in EP dysfunction.
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Affiliation(s)
- Ian A. Taukulis
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Rafal T. Olszewski
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Soumya Korrapati
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Katharine A. Fernandez
- Laboratory of Hearing Biology and Therapeutics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Erich T. Boger
- Genomics and Computational Biology Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Tracy S. Fitzgerald
- Mouse Auditory Testing Core Facility, National Institutes of Health, Bethesda, MD, United States
| | - Robert J. Morell
- Genomics and Computational Biology Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Lisa L. Cunningham
- Laboratory of Hearing Biology and Therapeutics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Michael Hoa
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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8
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Suzumoto Y, Columbano V, Gervasi L, Giunta R, Mattina T, Trimarchi G, Capolongo G, Simeoni M, Perna AF, Zacchia M, Toriello G, Pollastro RM, Rapisarda F, Capasso G, Trepiccione F. A case series of adult patients affected by EAST/SeSAME syndrome suggests more severe disease in subjects bearing KCNJ10 truncating mutations. Intractable Rare Dis Res 2021; 10:95-101. [PMID: 33996354 PMCID: PMC8122315 DOI: 10.5582/irdr.2020.03158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
EAST/SeSAME syndrome is a rare disease affecting the Central Nervous System (CNS), inner ear, and kidney. The syndrome is due to loss-of-function mutations in the KCNJ10 gene encoding the inward-rectifying potassium channel Kir4.1. EAST/SeSAME syndrome is mainly diagnosed during childhood with a tonic-clonic seizure being the usual first symptom. Due to a limited number of patients and recent identification of the disease, few data are available on the clinical progress of this disease in adulthood. In particular, neurologic and nephrological outcomes have not been reported. We present a case series of 4 adult patients harbouring homozygous missense mutation p.Ala167Val and homozygous frameshift mutations p.Asn232Glnfs*14 and p.Gly275Valfs*7. Effects of these mutations were predicted by in silico modelling and bioinformatic tools. Patients with truncating mutations were associated with more severe outcomes, both in tubulopathy severity and neurological symptomatology. Conversely, either missense or truncating mutations were correlated with similar severity of epilepsy, with a long free-of-event period up to 20 years old. No eGFR decline was documented. Modelling predicted that truncating mutations lead to complete Kir4.1 dysfunction. Finally, all patients had a mild increase in urinary protein excretion. Our study indicates that the prognosis of patients suffering from EAST/SeSAME syndrome is related to the severity of the mutation causing the disease. As predicted by in silico modelling, truncating mutations of KCNJ10 are associated with more severe disease, with recurrence of symptomatic hypokalemia and more severe neurological phenotype. The type of mutation should be considered for the therapy tailored to patients' phenotype.
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Affiliation(s)
| | - Valeria Columbano
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Luciano Gervasi
- School of Nephrology, Department of Clinical and Experimental Medicine, University of Catania, Italy
| | - Rosa Giunta
- School of Nephrology, Department of Clinical and Experimental Medicine, University of Catania, Italy
| | - Teresa Mattina
- Department of Biomedical and Biotechnological Sciences, University of Catania, Italy
| | - Gabriele Trimarchi
- Department of Biomedical and Biotechnological Sciences, University of Catania, Italy
| | - Giovanna Capolongo
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Mariadelina Simeoni
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Alessandra F. Perna
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Miriam Zacchia
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | | | - Rosa M. Pollastro
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Francesco Rapisarda
- School of Nephrology, Department of Clinical and Experimental Medicine, University of Catania, Italy
| | - Giovambattista Capasso
- Biogem Research Institute, Ariano Irpino, Italy
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Francesco Trepiccione
- Biogem Research Institute, Ariano Irpino, Italy
- Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
- Address correspondence to:Francesco Trepiccione, Department of Translational Medical Sciences University of Campania "L.Vanvitelli", Via Pansini n5, 80131 Naples, Italy. E-mail:
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9
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Kinboshi M, Ikeda A, Ohno Y. Role of Astrocytic Inwardly Rectifying Potassium (Kir) 4.1 Channels in Epileptogenesis. Front Neurol 2020; 11:626658. [PMID: 33424762 PMCID: PMC7786246 DOI: 10.3389/fneur.2020.626658] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/08/2020] [Indexed: 12/25/2022] Open
Abstract
Astrocytes regulate potassium and glutamate homeostasis via inwardly rectifying potassium (Kir) 4.1 channels in synapses, maintaining normal neural excitability. Numerous studies have shown that dysfunction of astrocytic Kir4.1 channels is involved in epileptogenesis in humans and animal models of epilepsy. Specifically, Kir4.1 channel inhibition by KCNJ10 gene mutation or expressional down-regulation increases the extracellular levels of potassium ions and glutamate in synapses and causes hyperexcitation of neurons. Moreover, recent investigations demonstrated that inhibition of Kir4.1 channels facilitates the expression of brain-derived neurotrophic factor (BDNF), an important modulator of epileptogenesis, in astrocytes. In this review, we summarize the current understanding on the role of astrocytic Kir4.1 channels in epileptogenesis, with a focus on functional and expressional changes in Kir4.1 channels and their regulation of BDNF secretion. We also discuss the potential of Kir4.1 channels as a therapeutic target for the prevention of epilepsy.
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Affiliation(s)
- Masato Kinboshi
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan.,Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Yukihiro Ohno
- Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Takatsuki, Japan
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10
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Bamgbola OF, Ahmed Y. Differential diagnosis of perinatal Bartter, Bartter and Gitelman syndromes. Clin Kidney J 2020; 14:36-48. [PMID: 33564404 PMCID: PMC7857843 DOI: 10.1093/ckj/sfaa172] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 06/29/2020] [Indexed: 12/20/2022] Open
Abstract
The common finding of hypokalemic alkalosis in several unrelated disorders may confound the early diagnosis of salt-losing tubulopathy (SLT). Antenatal Bartter syndrome (BS) must be considered in idiopathic early-onset polyhydramnios. Fetal megabladder in BS may allow its distinction from third-trimester polyhydramnios that occurs in congenital chloride diarrhea (CCD). Fetal megacolon occurs in CCD while fecal chloride >90 mEq/L in infants is diagnostic. Failure-to-thrive, polydipsia and polyuria in early childhood are the hallmarks of classic BS. Unlike BS, there is low urinary chloride in hypokalemic alkalosis of intractable emesis and cystic fibrosis. Rarely, renal salt wasting may result from cystinosis, Dent disease, disorders of paracellular claudin-10b and Kir4.1 potassium-channel deficiency. Acquired BS may result from calcimimetic up-regulation of a calcium-sensing receptor or autoantibody inactivation of sodium chloride co-transporters in Sjögren syndrome. A relatively common event of heterozygous gene mutations for Gitelman syndrome increases the likelihood of its random occurrence in certain diseases of adult onset. Finally, diuretic abuse is the most common differential diagnosis of SLT. Unlike the persistent elevation in BS, urinary chloride concentration losses waxes and wanes on day-to-day assessment in patients with diuretic misuse.
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Affiliation(s)
- Oluwatoyin Fatai Bamgbola
- Department of Pediatrics, Division of Pediatric Nephrology, SUNY Downstate Medical Center, Brooklyn, NY, USA
| | - Youssef Ahmed
- Department of Pediatrics, Kings County Hospital, Brooklyn, NY, USA
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11
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Bhowmick SS, Lang AE. Movement Disorders and Renal Diseases. Mov Disord Clin Pract 2020; 7:763-779. [PMID: 33043074 DOI: 10.1002/mdc3.13005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 02/06/2023] Open
Abstract
Movement disorders often emerge from the interplay of complex pathophysiological processes involving the kidneys and the nervous system. Tremor, myoclonus, ataxia, chorea, and parkinsonism can occur in the context of renal dysfunction (azotemia and electrolyte abnormalities) or they can be part of complications of its management (dialysis and renal transplantation). On the other hand, myoglobinuria from rhabdomyolysis in status dystonicus and certain drugs used in the management of movement disorders can cause nephrotoxicity. Distinct from these well-recognized associations, it is important to appreciate that there are several inherited and acquired disorders in which movement abnormalities do not occur as a consequence of renal dysfunction or vice versa but are manifestations of common pathophysiological processes affecting the nervous system and the kidneys. These disorders are the emphasis of this review. Increasing awareness of these conditions among neurologists may help them to identify renal involvement earlier, take timely intervention by anticipating complications and focus on therapies targeting common mechanisms in addition to symptomatic management of movement disorders. Recognition of renal impairment in a patient with complex neurological presentation may narrow down the differentials and aid in reaching a definite diagnosis.
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Affiliation(s)
- Suvorit S Bhowmick
- Division of Neurology, Department of Medicine, Morton and Gloria Shulman Movement Disorders Clinic and the Edmond J. Safra Program in Parkinson's Disease, Toronto Western Hospital University Health Network Toronto Ontario Canada
| | - Anthony E Lang
- Division of Neurology, Department of Medicine, Morton and Gloria Shulman Movement Disorders Clinic and the Edmond J. Safra Program in Parkinson's Disease, Toronto Western Hospital University Health Network Toronto Ontario Canada
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12
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Morán-Zendejas R, Delgado-Ramírez M, Xu J, Valdés-Abadía B, Aréchiga-Figueroa IA, Cui M, Rodríguez-Menchaca AA. In vitro and in silico characterization of the inhibition of Kir4.1 channels by aminoglycoside antibiotics. Br J Pharmacol 2020; 177:4548-4560. [PMID: 32726456 DOI: 10.1111/bph.15214] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 06/11/2020] [Accepted: 07/15/2020] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Aminoglycoside antibiotics are positively charged molecules that are known to inhibit several ion channels. In this study, we have shown that aminoglycosides also inhibit the activity of Kir4.1 channels. Aminoglycosides inhibit Kir4.1 channels by a pore-blocking mechanism, plugging the central vestibule of the channel. EXPERIMENTAL APPROACH Patch-clamp recordings were made in HEK-293 cells transiently expressing Kir4.1 channels to analyse the effects of gentamicin, neomycin and kanamycin. In silico modelling followed by mutagenesis were realized to identify the residues critical for aminoglycosides binding to Kir4.1. KEY RESULTS Aminoglycoside antibiotics block Kir4.1 channels in a concentration- and voltage-dependent manner, getting access to the protein from the intracellular side of the plasma membrane. Aminoglycosides block Ki4.1 with a rank order of potency as follows: gentamicin ˃ neomycin ˃ kanamycin. The residues T128 and principally E158, facing the central cavity of Kir4.1, are important structural determinants for aminoglycosides binding to the channel, as determined by our in silico modelling and confirmed by mutagenesis experiments. CONCLUSION AND IMPLICATIONS Kir4.1 channels are also target of aminoglycoside antibiotics, which could affect potassium transport in several tissues.
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Affiliation(s)
- Rita Morán-Zendejas
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | - Mayra Delgado-Ramírez
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | - Jie Xu
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, China.,Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Belkis Valdés-Abadía
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | | | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Aldo A Rodríguez-Menchaca
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
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13
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Beckner ME. A roadmap for potassium buffering/dispersion via the glial network of the CNS. Neurochem Int 2020; 136:104727. [PMID: 32194142 DOI: 10.1016/j.neuint.2020.104727] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 03/08/2020] [Accepted: 03/09/2020] [Indexed: 12/19/2022]
Abstract
Glia use multiple mechanisms to mediate potassium fluxes that support neuronal function. In addition to changes in potassium levels within synapses, these ions are dynamically dispersed through the interstitial parenchyma, perivascular spaces, leptomeninges, cerebrospinal fluid, choroid plexus, blood, vitreous, and endolymph. Neural circuits drive diversity in the glia that buffer potassium and this is reciprocal. Glia mediate buffering of potassium locally at glial-neuronal interfaces and via widespread networked connections. Control of potassium levels in the central nervous system is mediated by mechanisms operating at various loci with complexity that is difficult to model. However, major components of networked glial buffering are known. The role that potassium buffering plays in homeostasis of the CNS underlies some pathologic phenomena. An overview of potassium fluxes in the CNS is relevant for understanding consequences of pathogenic sequence variants in genes that encode potassium buffering proteins. Potassium flows in the CNS are described as follows: K1, the coordinated potassium fluxes within the astrocytic cradle around the synapse; K2, temporary storage of potassium within astrocytic processes in proposed microdomains; K3, potassium fluxes between oligodendrocytes and astrocytes; K4, potassium fluxes between astrocytes; K5, astrocytic potassium flux mediation of neurovasular coupling; K6, CSF delivery of potassium to perivascular spaces with dispersion to interstitial fluid between astrocytic endfeet; K7, astrocytic delivery of potassium to CSF and K8, choroid plexus (modified glia) regulation of potassium at the blood-CSF barrier. Components, mainly potassium channels, transporters, connexins and modulators, and the pathogenic sequence variants of their genes with the associated diseases are described.
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Affiliation(s)
- Marie E Beckner
- School of Biomedical Sciences, Kent State University, Kent, OH, USA.
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14
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Morin M, Forst AL, Pérez-Torre P, Jiménez-Escrig A, Barca-Tierno V, García-Galloway E, Warth R, Lopez-Sendón Moreno JL, Moreno-Pelayo MA. Novel mutations in the KCNJ10 gene associated to a distinctive ataxia, sensorineural hearing loss and spasticity clinical phenotype. Neurogenetics 2020; 21:135-143. [PMID: 32062759 DOI: 10.1007/s10048-020-00605-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 02/01/2020] [Indexed: 12/31/2022]
Abstract
KCNJ10 encodes the inward-rectifying potassium channel (Kir4.1) that is expressed in the brain, inner ear, and kidney. Loss-of-function mutations in KCNJ10 gene cause a complex syndrome consisting of epilepsy, ataxia, intellectual disability, sensorineural deafness, and tubulopathy (EAST/SeSAME syndrome). Patients with EAST/SeSAME syndrome display renal salt wasting and electrolyte imbalance that resemble the clinical features of impaired distal tubular salt transport in Gitelman's syndrome. A key distinguishing feature between these two conditions is the additional neurological (extrarenal) manifestations found in EAST/SeSAME syndrome. Recent reports have further expanded the clinical and mutational spectrum of KCNJ10-related disorders including non-syndromic early-onset cerebellar ataxia. Here, we describe a kindred of three affected siblings with early-onset ataxia, deafness, and progressive spasticity without other prominent clinical features. By using targeted next-generation sequencing, we have identified two novel missense variants, c.488G>A (p.G163D) and c.512G>A (p.R171Q), in the KCNJ10 gene that, in compound heterozygosis, cause this distinctive EAST/SeSAME phenotype in our family. Electrophysiological characterization of these two variants confirmed their pathogenicity. When expressed in CHO cells, the R171Q mutation resulted in 50% reduction of currents compared to wild-type KCNJ10 and G163D showed a complete loss of function. Co-expression of G163D and R171Q had a more pronounced effect on currents and membrane potential than R171Q alone but less severe than single expression of G163D. Moreover, the effect of the mutations seemed less pronounced in the presence of Kir5.1 (encoded by KCNJ16), with whom the renal Kir4.1 channels form heteromers. This partial functional rescue by co-expression with Kir5.1 might explain the lack of renal symptoms in the patients. This report illustrates that a spectrum of disorders with distinct clinical symptoms may result from mutations in different parts of KCNJ10, a gene initially associated only with the EAST/SeSAME syndrome.
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Affiliation(s)
- Matias Morin
- Servicio de Genética, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) and Hospital Universitario Ramón y Cajal, CIBERER, 28034, Madrid, Spain
| | - Anna-Lena Forst
- Medical Cell Biology, University of Regensburg, 93053, Regensburg, Germany
| | - Paula Pérez-Torre
- Servicio de Neurología, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain
| | | | - Verónica Barca-Tierno
- Servicio de Genética, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) and Hospital Universitario Ramón y Cajal, CIBERER, 28034, Madrid, Spain
| | - Eva García-Galloway
- Servicio de Genética, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) and Hospital Universitario Ramón y Cajal, CIBERER, 28034, Madrid, Spain
| | - Richard Warth
- Medical Cell Biology, University of Regensburg, 93053, Regensburg, Germany
| | | | - Miguel Angel Moreno-Pelayo
- Servicio de Genética, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) and Hospital Universitario Ramón y Cajal, CIBERER, 28034, Madrid, Spain.
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15
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Zhang H, Zhu L, Wang F, Wang R, Hong Y, Chen Y, Zhu B, Gao Y, Luo H, Zhang X, Sun H, Zhou Y, Yao Y, Wang X. Novel KCNJ10 Compound Heterozygous Mutations Causing EAST/SeSAME-Like Syndrome Compromise Potassium Channel Function. Front Genet 2019; 10:912. [PMID: 31781151 PMCID: PMC6856220 DOI: 10.3389/fgene.2019.00912] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 08/29/2019] [Indexed: 11/13/2022] Open
Abstract
Inwardly rectifying K+ channel 4.1 (Kir4.1), encoded by KCNJ10, is a member of the inwardly rectifying potassium channel family. In the brain, Kir4.1 is predominant in astrocytic glia and accounts for the spatial buffering of K+ released by neurons during action potential propagation. A number of studies have shown that mutations in KCNJ10 are associated with SeSAME/EAST syndrome, which is characterized by seizures, ataxia, sensorineural deafness, and electrolyte imbalance. Herein, we identified two siblings presenting with seizures and motor delays in one outbred kindred. Customized targeted-exome sequencing showed that both affected siblings are compound heterozygous for two KCNJ10 missense mutations (NM_002241.4: c.601G > A: p.A201T and c.626T > C: p.I209T). Prediction tools suggested that both amino acid substitutions were deleterious or disease causing. Further functional studies showed that Chinese hamster ovary (CHO) cells expressing either A201T and/or I209T Kir4.1 channels exhibited lower K+ currents, indicating compromised Kir4.1 biological function. Intriguingly, the A201T but not I209T mutation decreased total and cell surface Kir4.1 levels. Kir4.1 channels with the A201T mutation were unstable and degraded through lysosomal pathway. In conclusion, these data indicated that both A201T and I209T mutations disrupt Kir4.1 activity and are the cause of SeSAME/EAST-like syndrome in the siblings.
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Affiliation(s)
- Hongfeng Zhang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Lin Zhu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Fengpeng Wang
- Department of Functional Neurosurgery, Xiamen Humanity Hospital, Xiamen, China
| | - Ruimin Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Yujuan Hong
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Yangqin Chen
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Bin Zhu
- Departments of Neurosurgery, Dongfang Affliated Hospital of Xiamen University, Xiamen, China
| | - Yue Gao
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Hong Luo
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Xian Zhang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Hao Sun
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
| | - Ying Zhou
- National Institute for Data Science in Health and Medicine, School of Medicine, Xiamen University, Xiamen, China
| | - Yi Yao
- Department of Functional Neurosurgery, Xiamen Humanity Hospital, Xiamen, China.,Department of Neurosurgery, Shenzhen Children's Hospital, Shenzhen, China
| | - Xin Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, School of Medicine, Xiamen University, Xiamen, China
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16
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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: 56] [Impact Index Per Article: 11.2] [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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17
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Mir A, Chaudhary M, Alkhaldi H, Alhazmi R, Albaradie R, Housawi Y. Epilepsy in patients with EAST syndrome caused by mutation in the KCNJ10. Brain Dev 2019; 41:706-715. [PMID: 30952461 DOI: 10.1016/j.braindev.2019.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 03/03/2019] [Accepted: 03/19/2019] [Indexed: 11/20/2022]
Abstract
OBJECTIVE EAST syndrome comprises of epilepsy, ataxia, sensorineural deafness, and tubulopathy. It is caused by a mutation in KCNJ10 gene. Less than thirty cases have been reported in the literature with emphasis on genetic mutation and renal tubulopathy. In this article, our goal is to present a comprehensive description of epilepsy and its management. A literature review is also presented to consolidate and compare our findings with the previously reported cases. METHODS Retrospective chart review was done to collect patient data. Research clinic was organized to obtain missing data. Molecular genetic testing was done at the CGC Genetics Laboratory. Electroencephalogram (EEG) was done for all patients and interpreted by a pediatric epileptologist and brain MRI was reviewed by a pediatric neuroradiologist. Developmental assessment was done by a developmental pediatrician using Griffiths Mental Developmental Scale. RESULTS In patients with EAST syndrome, seizure is the first symptom occurring around 3-4 months of age. Most common seizure type was generalized tonic clonic (GTC). Usually, the seizures were brief lasting <3 min but few patients also presented with status epilepticus especially when the medication was weaned. Carbamazepine (CBZ) was found to be effective in most cases. Lamotrigine (LTG), valproic acid (VPA), and topiramate (TPM) were also found to be helpful. Routine EEGs were usually normal or showed non-specific findings. In few patients, EEG showed background slowing. Brain MRI revealed hyperintensity in the dentate nuclei in some patients, and quantitative volumetric analysis studies showed volume loss in different regions of the brain especially the cerebellum. All our five patients have the same homozygous c.170C>T (p.Thr57Ile) missense mutation in KCNJ10 gene. CONCLUSION This article provides the readers with an understanding of the natural history of epilepsy in this syndrome to help in early recognition, avoid unnecessary investigations, and provide the best treatment for seizures. It also helps the physicians to share the prognosis of this rare syndrome with the parents.
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Affiliation(s)
- Ali Mir
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia.
| | - Mohammed Chaudhary
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Hani Alkhaldi
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Rami Alhazmi
- Medical Imaging Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Raidah Albaradie
- Pediatric Neurology Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
| | - Yousef Housawi
- Genetic and Metabolic Department, King Fahad Specialist Hospital, Dammam, Saudi Arabia
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18
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Hussain T, Kil H, Hattiangady B, Lee J, Kodali M, Shuai B, Attaluri S, Takata Y, Shen J, Abba MC, Shetty AK, Aldaz CM. Wwox deletion leads to reduced GABA-ergic inhibitory interneuron numbers and activation of microglia and astrocytes in mouse hippocampus. Neurobiol Dis 2018; 121:163-176. [PMID: 30290271 DOI: 10.1016/j.nbd.2018.09.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 09/18/2018] [Accepted: 09/30/2018] [Indexed: 02/07/2023] Open
Abstract
The association of WW domain-containing oxidoreductase WWOX gene loss of function with central nervous system (CNS) related pathologies is well documented. These include spinocerebellar ataxia, epilepsy and mental retardation (SCAR12, OMIM: 614322) and early infantile epileptic encephalopathy (EIEE28, OMIM: 616211) syndromes. However, there is complete lack of understanding of the pathophysiological mechanisms at play. In this study, using a Wwox knockout (Wwox KO) mouse model (2 weeks old, both sexes) and stereological studies we observe that Wwox deletion leads to a significant reduction in the number of hippocampal GABA-ergic (γ-aminobutyric acid) interneurons. Wwox KO mice displayed significantly reduced numbers of calcium-binding protein parvalbumin (PV) and neuropeptide Y (NPY) expressing interneurons in different subfields of the hippocampus in comparison to Wwox wild-type (WT) mice. We also detected decreased levels of Glutamic Acid Decarboxylase protein isoforms GAD65/67 expression in Wwox null hippocampi suggesting lower levels of GABA synthesis. In addition, Wwox deficiency was associated with signs of neuroinflammation such as evidence of activated microglia, astrogliosis, and overexpression of inflammatory cytokines Tnf-a and Il6. We also performed comparative transcriptome-wide expression analyses of neural stem cells grown as neurospheres from hippocampi of Wwox KO and WT mice thus identifying 283 genes significantly dysregulated in their expression. Functional annotation of transcriptome profiling differences identified 'neurological disease' and 'CNS development related functions' to be significantly enriched. Several epilepsy-related genes were found differentially expressed in Wwox KO neurospheres. This study provides the first genotype-phenotype observations as well as potential mechanistic clues associated with Wwox loss of function in the brain.
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Affiliation(s)
- Tabish Hussain
- Department of Epigenetics and Molecular Carcinogenesis, Science Park, The University of Texas MD Anderson Cancer Center, Smithville, TX, United States
| | - Hyunsuk Kil
- Department of Epigenetics and Molecular Carcinogenesis, Science Park, The University of Texas MD Anderson Cancer Center, Smithville, TX, United States
| | - Bharathi Hattiangady
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, Temple and College Station, TX, United States; Research Service, Olin E. Teague Veterans' Medical Center, CTVHCS, Temple, TX, United States
| | - Jaeho Lee
- Department of Epigenetics and Molecular Carcinogenesis, Science Park, The University of Texas MD Anderson Cancer Center, Smithville, TX, United States
| | - Maheedhar Kodali
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, Temple and College Station, TX, United States; Research Service, Olin E. Teague Veterans' Medical Center, CTVHCS, Temple, TX, United States
| | - Bing Shuai
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, Temple and College Station, TX, United States; Research Service, Olin E. Teague Veterans' Medical Center, CTVHCS, Temple, TX, United States
| | - Sahithi Attaluri
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, Temple and College Station, TX, United States; Research Service, Olin E. Teague Veterans' Medical Center, CTVHCS, Temple, TX, United States
| | - Yoko Takata
- Department of Epigenetics and Molecular Carcinogenesis, Science Park, The University of Texas MD Anderson Cancer Center, Smithville, TX, United States
| | - Jianjun Shen
- Department of Epigenetics and Molecular Carcinogenesis, Science Park, The University of Texas MD Anderson Cancer Center, Smithville, TX, United States
| | - Martin C Abba
- CINIBA, School of Medicine, UNLP, La Plata, Argentina
| | - Ashok K Shetty
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, Temple and College Station, TX, United States; Research Service, Olin E. Teague Veterans' Medical Center, CTVHCS, Temple, TX, United States
| | - C Marcelo Aldaz
- Department of Epigenetics and Molecular Carcinogenesis, Science Park, The University of Texas MD Anderson Cancer Center, Smithville, TX, United States.
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19
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Dadas A, Janigro D. Breakdown of blood brain barrier as a mechanism of post-traumatic epilepsy. Neurobiol Dis 2018; 123:20-26. [PMID: 30030025 DOI: 10.1016/j.nbd.2018.06.022] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 06/15/2018] [Accepted: 06/28/2018] [Indexed: 12/31/2022] Open
Abstract
Traumatic brain injury (TBI) accounts for approximately 16% of acute symptomatic seizures which usually occur in the first week after trauma. Children are at higher risk for post-traumatic seizures than adults. Post-traumatic seizures are a risk factor for delayed development of epilepsy. Delayed, chronic post-traumatic epilepsy is preceded by a silent period during which therapeutic interventions may arrest, revert or prevent epileptogenesis. A number of recent review articles summarize the most important features of post-traumatic seizures and epilepsy; this review will instead focus on the link between cerebrovascular permeability, epileptogenesis and ictal events after TBI. The possibility of acting on the blood-brain barrier (BBB) and the neurovascular unit to prevent, disrupt or treat post-traumatic epilepsy is also discussed. Finally, we describe the latest quest for biomarkers of epileptogenesis which may allow for a more targeted intervention.
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Affiliation(s)
- Aaron Dadas
- Department of Physiology, Case Western Reserve University, Cleveland, OH, United States
| | - Damir Janigro
- Department of Physiology, Case Western Reserve University, Cleveland, OH, United States; FloTBI Inc., 4415 Euclid Ave., Cleveland, OH, United States.
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20
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Celmina M, Micule I, Inashkina I, Audere M, Kuske S, Pereca J, Stavusis J, Pelnena D, Strautmanis J. EAST/SeSAME syndrome: Review of the literature and introduction of four new Latvian patients. Clin Genet 2018; 95:63-78. [PMID: 29722015 DOI: 10.1111/cge.13374] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/12/2018] [Accepted: 04/23/2018] [Indexed: 11/28/2022]
Abstract
EAST (Epilepsy, Ataxia, Sensorineural deafness, Tubulopathy) or SeSAME (Seizures, Sensorineural deafness, Ataxia, Mental retardation, and Electrolyte imbalance) syndrome is a rare autosomal recessive syndrome first described in 2009 independently by Bockenhauer and Scholl. It is caused by mutations in KCNJ10, which encodes Kir4.1, an inwardly rectifying K+ channel found in the brain, inner ear, kidney and eye. To date, 16 mutations and at least 28 patients have been reported. In this paper, we review mutations causing EAST/SeSAME syndrome, clinical manifestations in detail, and efficacy of treatment in previously reported patients. We also report a new Latvian kindred with 4 patients. In contrast to the majority of previous reports, we found a progressive course of the disorder in terms of hearing impairment and neurologic deficit. The treatment is based on antiepileptic drugs, electrolyte replacement, hearing aids and mobility devices. Future research should concentrate on recognizing the lesions in the central nervous system to evaluate new potential diagnostic criteria and on formally evaluating intellectual disability.
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Affiliation(s)
- M Celmina
- Clinic for Pediatrics, Children's Clinical University Hospital, Riga, Latvia.,Faculty of Continuing Education, University of Latvia, Riga, Latvia
| | - I Micule
- Clinic for Medical Genetics and Prenatal Diagnostics, Children's Clinical University Hospital, Riga, Latvia
| | - I Inashkina
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - M Audere
- ENT Department, Children's Clinical University Hospital, Riga, Latvia
| | - S Kuske
- Latvian Children's Hearing Center, Riga, Latvia
| | - J Pereca
- Emergency Department, Royal Infirmary of Edinburg, Edinburgh, United Kingdom
| | - J Stavusis
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - D Pelnena
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - J Strautmanis
- Clinic for Pediatric Neurology and Neurosurgery, Children's Clinical University Hospital, Riga, Latvia
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21
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Unusual white matter involvement in EAST syndrome associated with novel KCNJ10 mutations. J Neurol 2018; 265:1419-1425. [PMID: 29666984 DOI: 10.1007/s00415-018-8826-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/05/2018] [Accepted: 03/08/2018] [Indexed: 01/06/2023]
Abstract
BACKGROUND Epilepsy, ataxia, sensorineural deafness, and tubulopathy (EAST syndrome) is a rare channelopathy due to KCNJ10 mutations. So far, only mild cerebellar hypoplasia and/or dentate nuclei abnormalities have been reported as major neuroimaging findings in these patients. METHODS We analyzed the clinical and brain MRI features of two unrelated patients (aged 27 and 23 years) with EAST syndrome carrying novel homozygous frameshift mutations (p.Asn232Glnfs*14and p.Gly275Valfs*7) in KCNJ10, detected by whole exome sequencing. RESULTS Brain MRI examinations at 8 years in Patient 1 and at 13 years in Patient 2 revealed a peculiar brain and spinal cord involvement characterized by restricted diffusion of globi pallidi, thalami, brainstem, dentate nuclei, and cervical spinal cord in keeping with intramyelinic edema. The follow-up studies, performed, respectively, after 19 and 10 years, showed mild cerebellar atrophy and slight progression of the brain and spinal cord T2 signal abnormalities with increase of the restricted diffusion in the affected regions. CONCLUSION The present cases harboring novel homozygous frameshift mutations in KCNJ10 expand the spectrum of brain abnormalities in EAST syndrome, including mild cerebellar atrophy and intramyelinic edema, resulting from abnormal function of the Kir4.1 inwardly rectifying potassium channel at the astrocyte endfeet, with disruption of water-ion homeostasis.
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22
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Nicita F, Tasca G, Nardella M, Bellacchio E, Camponeschi I, Vasco G, Schirinzi T, Bertini E, Zanni G. Novel Homozygous KCNJ10 Mutation in a Patient with Non-syndromic Early-Onset Cerebellar Ataxia. THE CEREBELLUM 2018; 17:499-503. [DOI: 10.1007/s12311-018-0924-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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23
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Bertini E, Zanni G, Boltshauser E. Nonprogressive congenital ataxias. HANDBOOK OF CLINICAL NEUROLOGY 2018; 155:91-103. [PMID: 29891079 DOI: 10.1016/b978-0-444-64189-2.00006-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The terminology of nonprogressive congenital ataxia (NPCA) refers to a clinically and genetically heterogeneous group of disorders characterized by congenital or early-onset ataxia, but no progression or even improvement on follow-up. Ataxia is preceded by muscular hypotonia and delayed motor (and usually language) milestones. We exclude children with prenatal, perinatal, and postnatal acquired diseases, malformations other than cerebellar hypoplasia, and defined syndromic disorders. Patients with NPCA have a high prevalence of cognitive and language impairments, in addition to increased occurrence of seizures, ocular signs (nystagmus, strabismus), behavior changes, and microcephaly. Neuroimaging is variable, ranging from normal cerebellar anatomy to reduced cerebellar volume (hypoplasia in the proper sense), and enlarged interfolial spaces, potentially mimicking atrophy. The latter appearance is often called "hypoplasia" as well, in view of the static clinical course. Some patients had progressive enlargement of cerebellar fissures, but a nonprogressive course. There is no imaging-clinical-genetic correlation. Dominant, recessive, and X-linked inheritance is documented for NPCA. Here, we focus on the still rather short list of dominant and recessive genes associated with NPCA, identified in the last few years. With future advances in genetics, we expect a rapid expansion of knowledge in this field.
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Affiliation(s)
- Enrico Bertini
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesu' Children's Research Hospital, Rome, Italy.
| | - Ginevra Zanni
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesu' Children's Research Hospital, Rome, Italy
| | - Eugen Boltshauser
- Department of Pediatric Neurology, University Children's Hospital, University of Zurich, Zurich, Switzerland
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Kinboshi M, Mukai T, Nagao Y, Matsuba Y, Tsuji Y, Tanaka S, Tokudome K, Shimizu S, Ito H, Ikeda A, Inanobe A, Kurachi Y, Inoue S, Ohno Y. Inhibition of Inwardly Rectifying Potassium (Kir) 4.1 Channels Facilitates Brain-Derived Neurotrophic Factor (BDNF) Expression in Astrocytes. Front Mol Neurosci 2017; 10:408. [PMID: 29358904 PMCID: PMC5768989 DOI: 10.3389/fnmol.2017.00408] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/24/2017] [Indexed: 11/16/2022] Open
Abstract
Inwardly rectifying potassium (Kir) 4.1 channels in astrocytes regulate neuronal excitability by mediating spatial potassium buffering. Although dysfunction of astrocytic Kir4.1 channels is implicated in the development of epileptic seizures, the functional mechanisms of Kir4.1 channels in modulating epileptogenesis remain unknown. We herein evaluated the effects of Kir4.1 inhibition (blockade and knockdown) on expression of brain-derived neurotrophic factor (BDNF), a key modulator of epileptogenesis, in the primary cultures of mouse astrocytes. For blockade of Kir4.1 channels, we tested several antidepressant agents which reportedly bound to and blocked Kir4.1 channels in a subunit-specific manner. Treatment of astrocytes with fluoxetine enhanced BDNF mRNA expression in a concentration-dependent manner and increased the BDNF protein level. Other antidepressants (e.g., sertraline and imipramine) also increased the expression of BDNF mRNA with relative potencies similar to those for inhibition of Kir4.1 channels. In addition, suppression of Kir4.1 expression by the transfection of small interfering RNA (siRNA) targeting Kir4.1 significantly increased the mRNA and protein levels of BDNF. The BDNF induction by Kir4.1 siRNA transfection was suppressed by the MEK1/2 inhibitor U0126, but not by the p38 MAPK inhibitor SB202190 or the JNK inhibitor SP600125. The present results demonstrated that inhibition of Kir4.1 channels facilitates BDNF expression in astrocytes primarily by activating the Ras/Raf/MEK/ERK pathway, which may be linked to the development of epilepsy and other neuropsychiatric disorders.
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Affiliation(s)
- Masato Kinboshi
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan.,Department of Neurology, Wakayama Medical University, Wakayama, Japan.,Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takahiro Mukai
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yuki Nagao
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yusuke Matsuba
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yoshimi Tsuji
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Shiho Tanaka
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Kentaro Tokudome
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan.,Department of Molecular and Cellular Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Saki Shimizu
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Hidefumi Ito
- Department of Neurology, Wakayama Medical University, Wakayama, Japan
| | - Akio Ikeda
- Department of Epilepsy, Movement Disorders and Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Atsushi Inanobe
- Department of Molecular and Cellular Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Yoshihisa Kurachi
- Department of Molecular and Cellular Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Seiji Inoue
- Education and Research Center for Fundamental Pharmaceutical Sciences, Osaka University of Pharmaceutical Sciences, Osaka, Japan
| | - Yukihiro Ohno
- Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan
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26
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Al Dhaibani MA, El-Hattab AW, Holroyd KB, Orthmann-Murphy J, Larson VA, Siddiqui KA, Szolics M, Schiess N. Novel mutation in the KCNJ10 gene in three siblings with seizures, ataxia and no electrolyte abnormalities. J Neurogenet 2017; 32:1-5. [PMID: 29191078 DOI: 10.1080/01677063.2017.1404057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We report a consanguineous family with three affected siblings with novel mutation in the KCNJ10 gene. All three presented with central nervous system symptoms in the form of infantile focal seizures, ataxia, slurred speech with early developmental delay and intellectual disability in two siblings. None had any associated electrolyte abnormalities and no symptomatic hearing deficits were observed.
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Affiliation(s)
- Muna A Al Dhaibani
- a Department of Pediatrics , Tawam Hospital , Al Ain , United Arab Emirates
| | - Ayman W El-Hattab
- b Division of Clinical Genetics and Metabolic Disorders Pediatrics Department , Tawam Hospital , Al Ain , United Arab Emirates
| | | | | | - Valerie A Larson
- d Johns Hopkins Hospital and Health System , Baltimore , MD , USA
| | | | - Miklos Szolics
- f Department of Neurology , Al Tawam Hospital , Al Ain , United Arab Emirates
| | - Nicoline Schiess
- g Department of Neurology , Johns Hopkins University , Baltimore , MD , USA
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27
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Kesselheim A, Ashton E, Bockenhauer D. Potential and pitfalls in the genetic diagnosis of kidney diseases. Clin Kidney J 2017; 10:581-585. [PMID: 28980668 PMCID: PMC5622903 DOI: 10.1093/ckj/sfx075] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 06/13/2017] [Indexed: 12/14/2022] Open
Abstract
Next-generation sequencing has dramatically decreased the cost of gene sequencing, facilitating the simultaneous analysis of multiple genes at the same time; obtaining a genetic result for an individual patient has become much easier. The article by Ars and Torra in this issue of the Clinical Kidney Journal provides examples of the ever-increasing ability to understand a given patient's disease on the molecular level, so that in some cases not only the causative variants in a disease gene are identified, but also potential modifiers in other genes. Yet, with increased sequencing, a large number of variants are discovered that are difficult to interpret. These so-called 'variants of uncertain significance' raise important questions: when and how can pathogenicity be clearly attributed? This is of critical importance, as there are potentially serious consequences attached: decisions about various forms of treatment and even about life and death, such as termination of pregnancy, may hinge on the answer to these questions. Geneticists, thus, need to use the utmost care in the interpretation of identified variants and clinicians must be aware of this problem. We here discuss the potential of genetics to facilitate personalized treatment, but also the pitfalls and how to deal with them.
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Affiliation(s)
- Anne Kesselheim
- Centre for Nephrology, University College London, London, UK
| | - Emma Ashton
- Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
- North East Thames Regional Genetics Service, Molecular Genetics, London, UK
| | - Detlef Bockenhauer
- Centre for Nephrology, University College London, London, UK
- Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
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28
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Papavasiliou A, Foska K, Ioannou J, Nagel M. Epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome in a European child with KCNJ10 mutations: A case report. SAGE Open Med Case Rep 2017; 5:2050313X17723549. [PMID: 28835827 PMCID: PMC5536383 DOI: 10.1177/2050313x17723549] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 07/07/2017] [Indexed: 11/23/2022] Open
Abstract
Background: Epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome is a multi-organ disorder that links to autosomal recessive mutations in the KCNJ10 gene, which encodes for the Kir4.1 potassium channel. It is mostly described in consanguineous, non-European families. Case Report: A European male of non-consanguineous birth, with early-onset, static ataxic motor disorder, intellectual disability and epilepsy, imitating cerebral palsy, presented with additional findings of renal tubulopathy, sensorineural deafness and normal neuroimaging leading to the diagnosis of epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome. The patient was heterozygous for two KCNJ10 mutations: a missense mutation (p.R65C) that is already published and a not yet published duplication (p.F119GfsX25) that creates a premature truncation of the protein. Both mutations are likely damaging. Parental testing has not been performed, and therefore, we do not know for certain whether the mutations are on different alleles. This young man presents some clinical and laboratory features that differ from previously reported patients with epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome. Conclusion: The necessity of accurate diagnosis through genetic testing in patients with static motor disorders resembling cerebral palsy phenotypes, atypical clinical features and noncontributory neuroimaging is emphasized.
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Affiliation(s)
| | - Katerina Foska
- Department of Pediatric Neurology, Pendeli Children's Hospital, Athens, Greece
| | - John Ioannou
- Department of Pediatric Neurology, Pendeli Children's Hospital, Athens, Greece
| | - Mato Nagel
- Laboratory for Molecular Diagnostics, Weisswasser, Germany
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29
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Hasan S, Balobaid A, Grottesi A, Dabbagh O, Cenciarini M, Rawashdeh R, Al-Sagheir A, Bove C, Macchioni L, Pessia M, Al-Owain M, D'Adamo MC. Lethal digenic mutations in the K + channels Kir4.1 ( KCNJ10) and SLACK ( KCNT1) associated with severe-disabling seizures and neurodevelopmental delay. J Neurophysiol 2017; 118:2402-2411. [PMID: 28747464 DOI: 10.1152/jn.00284.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 07/05/2017] [Accepted: 07/21/2017] [Indexed: 01/14/2023] Open
Abstract
A 2-yr-old boy presented profound developmental delay, failure to thrive, ataxia, hypotonia, and tonic-clonic seizures that caused the death of the patient. Targeted and whole exome sequencing revealed two heterozygous missense variants: a novel mutation in the KCNJ10 gene that encodes for the inward-rectifying K+ channel Kir4.1 and another previously characterized mutation in KCNT1 that encodes for the Na+-activated K+ channel known as Slo2.2 or SLACK. The objectives of this study were to perform the clinical and genetic characterization of the proband and his family and to examine the functional consequence of the Kir4.1 mutation. The mutant and wild-type KCNJ10 constructs were generated and heterologously expressed in Xenopus laevis oocytes, and whole cell K+ currents were measured using the two-electrode voltage-clamp technique. The KCNJ10 mutation c.652C>T resulted in a p.L218F substitution at a highly conserved residue site. Wild-type KCNJ10 expression yielded robust Kir current, whereas currents from oocytes expressing the mutation were reduced, remarkably. Western Blot analysis revealed reduced protein expression by the mutation. Kir5.1 subunits display selective heteromultimerization with Kir4.1 constituting channels with unique kinetics. The effect of the mutation on Kir4.1/5.1 channel activity was twofold: a reduction in current amplitudes and an increase in the pH-dependent inhibition. We thus report a novel loss-of-function mutation in Kir4.1 found in a patient with a coexisting mutation in SLACK channels that results in a fatal disease.NEW & NOTEWORTHY We present and characterize a novel mutation in KCNJ10 Unlike previously reported EAST/SeSAME patients, our patient was heterozygous, and contrary to previous studies, mimicking the heterozygous state by coexpression resulted in loss of channel function. We report in the same patient co-occurrence of a KCNT1 mutation resulting in a more severe phenotype. This study provides new insights into the phenotypic spectrum and to the genotype-phenotype correlations associated with EAST/SeSAME and MMFSI.
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Affiliation(s)
- Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Ameera Balobaid
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | | | - Omar Dabbagh
- Department of Neurosciences, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Marta Cenciarini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Rifaat Rawashdeh
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Afaf Al-Sagheir
- Department of Pediatrics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
| | - Cecilia Bove
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Lara Macchioni
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy.,Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
| | - Mohammed Al-Owain
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.,College of Medicine, AlFaisal University, Riyadh, Saudi Arabia; and
| | - Maria Cristina D'Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta; .,Fondazione Santa Lucia, IRCCS, Rome, Italy
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30
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Abstract
Many mutations of genes for ion channels result in some epilepsies. Their electrophysiological studies reveal pathophysiological mechanisms underlining epilepsy and also mechanism of action of several antiepileptic drugs. In this review, We briefly summarize pathophysiology of epilepsy and the mechanisms of antiepileptic drugs.
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Affiliation(s)
- Yoshihiro Sugiura
- Department of Neurology, Fukushima Medical University School of Medicine
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31
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Palygin O, Pochynyuk O, Staruschenko A. Role and mechanisms of regulation of the basolateral K ir 4.1/K ir 5.1K + channels in the distal tubules. Acta Physiol (Oxf) 2017; 219:260-273. [PMID: 27129733 PMCID: PMC5086442 DOI: 10.1111/apha.12703] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 01/28/2016] [Accepted: 04/28/2016] [Indexed: 12/11/2022]
Abstract
Epithelial K+ channels are essential for maintaining electrolyte and fluid homeostasis in the kidney. It is recognized that basolateral inward-rectifying K+ (Kir ) channels play an important role in the control of resting membrane potential and transepithelial voltage, thereby modulating water and electrolyte transport in the distal part of nephron and collecting duct. Monomeric Kir 4.1 (encoded by Kcnj10 gene) and heteromeric Kir 4.1/Kir 5.1 (Kir 4.1 together with Kir 5.1 (Kcnj16)) channels are abundantly expressed at the basolateral membranes of the distal convoluted tubule and the cortical collecting duct cells. Loss-of-function mutations in KCNJ10 cause EAST/SeSAME tubulopathy in humans associated with salt wasting, hypomagnesaemia, metabolic alkalosis and hypokalaemia. In contrast, mice lacking Kir 5.1 have severe renal phenotype that, apart from hypokalaemia, is the opposite of the phenotype seen in EAST/SeSAME syndrome. Experimental advances using genetic animal models provided critical insights into the physiological role of these channels in electrolyte homeostasis and the control of kidney function. Here, we discuss current knowledge about K+ channels at the basolateral membrane of the distal tubules with specific focus on the homomeric Kir 4.1 and heteromeric Kir 4.1/Kir 5.1 channels. Recently identified molecular mechanisms regulating expression and activity of these channels, such as cell acidification, dopamine, insulin and insulin-like growth factor-1, Src family protein tyrosine kinases, as well as the role of these channels in NCC-mediated transport in the distal convoluted tubules, are also described.
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Affiliation(s)
- Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
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32
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Abdelhadi O, Iancu D, Tekman M, Stanescu H, Bockenhauer D, Kleta R. Founder mutation in KCNJ10 in Pakistani patients with EAST syndrome. Mol Genet Genomic Med 2016; 4:521-6. [PMID: 27652280 PMCID: PMC5023937 DOI: 10.1002/mgg3.227] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 11/11/2022] Open
Abstract
Background EAST syndrome is an autosomal recessive disorder caused by loss‐of‐function mutations in the gene KCNJ10. Among the 14 pathogenic mutations described so far, the p.R65P mutation stands out as the most frequent one and is particularly associated with patients of Pakistani origin. As a result we aimed to establish the existence of a potential founder effect in the Pakistani population. Methods To this end, we genotyped 12 patients from seven families and we compared disease haplotypes with ethnically matched control chromosomes. This haplotype was used together with demographic data for Pakistan to estimate the age of this founder mutation. Results We identified a small homozygous 0.694 Mb region around the KCNJ10 p.R65P mutation that had identical haplotypes in all of the patients which were completely absent in the control sample. Based on current demographic data and knowledge about disease frequency, we estimate that this particular p.R65P mutation arose 20 generations (about 500 years) ago. Conclusion By knowing the prevalent mutation in a given population more efficient diagnostics can be performed and the families can benefit from specific counseling.
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Affiliation(s)
- Ola Abdelhadi
- Centre for Nephrology University College London London UK
| | - Daniela Iancu
- Centre for Nephrology University College London London UK
| | - Mehmet Tekman
- Centre for Nephrology University College London London UK
| | - Horia Stanescu
- Centre for Nephrology University College London London UK
| | | | - Robert Kleta
- Centre for Nephrology University College London London UK
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33
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Abdelhadi O, Iancu D, Stanescu H, Kleta R, Bockenhauer D. EAST syndrome: Clinical, pathophysiological, and genetic aspects of mutations in KCNJ10. Rare Dis 2016; 4:e1195043. [PMID: 27500072 PMCID: PMC4961265 DOI: 10.1080/21675511.2016.1195043] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/02/2016] [Accepted: 05/24/2016] [Indexed: 11/04/2022] Open
Abstract
EAST syndrome is a recently described autosomal recessive disorder secondary to mutations in KCNJ10 (Kir4.1), a gene encoding a potassium channel expressed in the brain, eye, ear and kidney. This condition is characterized by 4 cardinal features; Epilepsy, Ataxia, Sensorineural deafness, and (a renal salt-wasting) Tubulopathy, hence the acronym EAST syndrome. Here we review reported clinical manifestations, in particular the neurological signs and symptoms which typically have the most impact on the quality of life of patients. In addition we review the pathophysiology and genetic aspects of the disease. So far 14 different KCNJ10 mutations have been published which either directly affect channel function or may lead to mislocalisation. Investigations of the pathophysiology may provide clues to potential treatments.
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Affiliation(s)
- Ola Abdelhadi
- Center for Nephrology, University College London, London, UK
| | - Daniela Iancu
- Center for Nephrology, University College London, London, UK
| | - Horia Stanescu
- Center for Nephrology, University College London, London, UK
| | - Robert Kleta
- Center for Nephrology, University College London, London, UK
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34
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Villa C, Combi R. Potassium Channels and Human Epileptic Phenotypes: An Updated Overview. Front Cell Neurosci 2016; 10:81. [PMID: 27064559 PMCID: PMC4811893 DOI: 10.3389/fncel.2016.00081] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 03/15/2016] [Indexed: 12/03/2022] Open
Abstract
Potassium (K+) channels are expressed in almost every cells and are ubiquitous in neuronal and glial cell membranes. These channels have been implicated in different disorders, in particular in epilepsy. K+ channel diversity depends on the presence in the human genome of a large number of genes either encoding pore-forming or accessory subunits. More than 80 genes encoding the K+ channels were cloned and they represent the largest group of ion channels regulating the electrical activity of cells in different tissues, including the brain. It is therefore not surprising that mutations in these genes lead to K+ channels dysfunctions linked to inherited epilepsy in humans and non-human model animals. This article reviews genetic and molecular progresses in exploring the pathogenesis of different human epilepsies, with special emphasis on the role of K+ channels in monogenic forms.
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Affiliation(s)
- Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Romina Combi
- School of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
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35
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Humphries ESA, Dart C. Neuronal and Cardiovascular Potassium Channels as Therapeutic Drug Targets: Promise and Pitfalls. JOURNAL OF BIOMOLECULAR SCREENING 2015; 20:1055-73. [PMID: 26303307 PMCID: PMC4576507 DOI: 10.1177/1087057115601677] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 07/26/2015] [Accepted: 07/28/2015] [Indexed: 12/21/2022]
Abstract
Potassium (K(+)) channels, with their diversity, often tissue-defined distribution, and critical role in controlling cellular excitability, have long held promise of being important drug targets for the treatment of dysrhythmias in the heart and abnormal neuronal activity within the brain. With the exception of drugs that target one particular class, ATP-sensitive K(+) (KATP) channels, very few selective K(+) channel activators or inhibitors are currently licensed for clinical use in cardiovascular and neurological disease. Here we review what a range of human genetic disorders have told us about the role of specific K(+) channel subunits, explore the potential of activators and inhibitors of specific channel populations as a therapeutic strategy, and discuss possible reasons for the difficulty in designing clinically relevant K(+) channel modulators.
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Affiliation(s)
| | - Caroline Dart
- Institute of Integrative Biology, University of Liverpool, UK
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36
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Mutational Consequences of Aberrant Ion Channels in Neurological Disorders. J Membr Biol 2014; 247:1083-127. [DOI: 10.1007/s00232-014-9716-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Accepted: 07/25/2014] [Indexed: 12/25/2022]
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37
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Gitelman Syndrome in a School Boy Who Presented with Generalized Convulsion and Had a R642H/R642W Mutation in the SLC12A3 Gene. Case Rep Pediatr 2014; 2014:279389. [PMID: 25140267 PMCID: PMC4124700 DOI: 10.1155/2014/279389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 06/06/2014] [Accepted: 06/12/2014] [Indexed: 12/15/2022] Open
Abstract
An 8-year-old Japanese boy presented with a generalized convulsion. He had hypokalemia (serum K 2.4 mEq/L), hypomagnesemia, and metabolic alkalosis (BE 5.7 mmol/L). In addition, his plasma renin activity was elevated. He was tentatively diagnosed with epilepsy on the basis of the electroencephalogram findings and was treated by potassium L-aspartate and carbamazepine to control the hypokalemia and seizure, respectively. However, a year later, the patient continued to have similar abnormal laboratory data. A presumptive diagnosis of Gitelman syndrome (GS) was then made and the patient's peripheral blood mononuclear cells were subjected to sequence analysis of the SLC12A3 gene, which encodes a thiazide-sensitive sodium-chloride cotransporter. The patient was found to have compound heterozygous mutations, namely, R642H inherited from his father and R642W inherited from his mother. Thus, if a patient shows persistent hypokalemia and metabolic alkalosis, GS must be considered, even if the patient exhibits atypical clinical symptoms.
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38
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Reid CA, Mullen S, Kim TH, Petrou S. Epilepsy, energy deficiency and new therapeutic approaches including diet. Pharmacol Ther 2014; 144:192-201. [PMID: 24924701 DOI: 10.1016/j.pharmthera.2014.06.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 05/28/2014] [Indexed: 02/08/2023]
Abstract
Metabolic dysfunction leading to epilepsy is well recognised. Dietary therapy, in particular the ketogenic diet, is now considered an effective option. Recent genetic studies have highlighted the central role that metabolism can play in setting seizure susceptibility. Here we discuss various metabolic disorders implicated in epilepsy focusing on energy deficiency due to genetic and environmental causes. We argue that low, uncompensated brain glucose levels can precipitate seizures. We will also explore mechanisms of disease and therapy in an attempt to identify common metabolic pathways involved in modulating seizure susceptibility. Finally, newer therapeutic approaches based on diet manipulation in the context of energy deficiency are discussed.
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Affiliation(s)
- Christopher A Reid
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia.
| | - Saul Mullen
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
| | - Tae Hwan Kim
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
| | - Steven Petrou
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia; Centre for Neural Engineering, The University of Melbourne, Parkville, Melbourne, Australia; Department of Electrical Engineering, The University of Melbourne, Parkville, Melbourne, Australia
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39
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Chen J, Zhao HB. The role of an inwardly rectifying K(+) channel (Kir4.1) in the inner ear and hearing loss. Neuroscience 2014; 265:137-46. [PMID: 24480364 DOI: 10.1016/j.neuroscience.2014.01.036] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 01/16/2014] [Accepted: 01/18/2014] [Indexed: 11/18/2022]
Abstract
The KCNJ10 gene which encodes an inwardly rectifying K(+) channel Kir4.1 subunit plays an essential role in the inner ear and hearing. Mutations or deficiency of KCNJ10 can cause hearing loss with EAST or SeSAME syndromes. This review mainly focuses on the expression and function of Kir4.1 potassium channels in the inner ear and hearing. We first introduce general information about inwardly rectifying potassium (Kir) channels. Then, we review the expression and function of Kir4.1 channels in the inner ear, especially in endocochlear potential (EP) generation. Finally, we review KCNJ10 mutation-induced hearing loss and functional impairments. Kir4.1 is strongly expressed on the apical membrane of intermediate cells in the stria vascularis and in the satellite cells of cochlear ganglia. Functionally, Kir4.1 has critical roles in cochlear development and hearing through two distinct aspects of extracellular K(+) homeostasis: First, it participates in the generation and maintenance of EP and high K(+) concentration in the endolymph inside the scala media. Second, Kir4.1 is the major K(+) channel in satellite glial cells surrounding spiral ganglion neurons to sink K(+) ions expelled by the ganglion neurons during excitation. Kir4.1 deficiency leads to hearing loss with the absence of EP and spiral ganglion neuron degeneration. Deafness mutants show loss-of-function and reduced channel membrane-targeting and currents, which can be rescued upon by co-expression with wild-type Kir4.1. This review provides insights for further understanding Kir potassium channel function in the inner ear and the pathogenesis of deafness due to KCNJ10 deficiency, and also provides insights for developing therapeutic strategies targeting this deafness.
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Affiliation(s)
- J Chen
- Department of Morphology, Medical College of China Three Gorges University, Yichang, Hubei 443002, PR China; Department of Otolaryngology, University of Kentucky Medical Center, Lexington, KY 40536-0293, USA
| | - H-B Zhao
- Department of Otolaryngology, University of Kentucky Medical Center, Lexington, KY 40536-0293, USA.
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Schmidt K, Ripper M, Tegtmeier I, Humberg E, Sterner C, Reichold M, Warth R, Bandulik S. Dynamics of Renal Electrolyte Excretion in Growing Mice. ACTA ACUST UNITED AC 2013; 124:7-13. [DOI: 10.1159/000356816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 10/25/2013] [Indexed: 11/19/2022]
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Zdebik AA, Mahmood F, Stanescu HC, Kleta R, Bockenhauer D, Russell C. Epilepsy in kcnj10 morphant zebrafish assessed with a novel method for long-term EEG recordings. PLoS One 2013; 8:e79765. [PMID: 24244558 PMCID: PMC3828195 DOI: 10.1371/journal.pone.0079765] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 09/30/2013] [Indexed: 11/18/2022] Open
Abstract
We aimed to develop and validate a reliable method for stable long-term recordings of EEG activity in zebrafish, which is less prone to artifacts than current invasive techniques. EEG activity was recorded with a blunt electrolyte-filled glass pipette placed on the zebrafish head mimicking surface EEG technology in man. In addition, paralysis of agarose-embedded fish using D-tubocurarine excluded movement artifacts associated with epileptic activity. This non-invasive recording technique allowed recordings for up to one hour and produced less artifacts than impaling the zebrafish optic tectum with a patch pipette. Paralyzed fish survived, and normal heartbeat could be monitored for over 1h. Our technique allowed the demonstration of specific epileptic activity in kcnj10a morphant fish (a model for EAST syndrome) closely resembling epileptic activity induced by pentylenetetrazol. This new method documented that seizures in the zebrafish EAST model were ameliorated by pentobarbitone, but not diazepam, validating its usefulness. In conclusion, non-invasive recordings in paralyzed EAST syndrome zebrafish proved stable, reliable and robust, showing qualitatively similar frequency spectra to those obtained from pentylenetetrazol-treated fish. This technique may prove particularly useful in zebrafish epilepsy models that show infrequent or conditional seizure activity.
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Affiliation(s)
- Anselm A. Zdebik
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
- * E-mail:
| | - Fahad Mahmood
- Department of Comparative Biological Sciences, Royal Veterinary College, London, United Kingdom
| | - Horia C. Stanescu
- Centre for Nephrology, University College London, London, United Kingdom
| | - Robert Kleta
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
- Institute of Child Health, University College London, London, United Kingdom
| | - Detlef Bockenhauer
- Centre for Nephrology, University College London, London, United Kingdom
- Institute of Child Health, University College London, London, United Kingdom
| | - Claire Russell
- Department of Comparative Biological Sciences, Royal Veterinary College, London, United Kingdom
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Parrock S, Hussain S, Issler N, Differ AM, Lench N, Guarino S, Oosterveld MJS, Keijzer-Veen M, Brilstra E, van Wieringen H, Konijnenberg AY, Amin-Rasip S, Dumitriu S, Klootwijk E, Knoers N, Bockenhauer D, Kleta R, Zdebik AA. KCNJ10 mutations display differential sensitivity to heteromerisation with KCNJ16. Nephron Clin Pract 2013; 123:7-14. [PMID: 24193250 DOI: 10.1159/000356353] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 10/16/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Mutations in the inwardly-rectifying K(+)-channel KCNJ10/Kir4.1 cause autosomal recessive EAST syndrome (epilepsy, ataxia, sensorineural deafness and tubulopathy). KCNJ10 is expressed in the distal convoluted tubule of the kidney, stria vascularis of the inner ear and brain glial cells. Patients diagnosed clinically with EAST syndrome were genotyped and mutations in KCNJ10 were studied functionally. METHODS Patient DNA was amplified and sequenced, and new mutations were identified. Mutant and wild-type KCNJ10 constructs were cloned and heterologously expressed in Xenopus oocytes. Whole-cell K(+) currents were measured by 2-electrode voltage clamping and channel expression was analysed by Western blotting. RESULTS We identified 3 homozygous mutations in KCNJ10 (p.F75C, p.A167V and p.V91fs197X), with mutation p.A167V previously reported in a compound heterozygous state. Oocytes expressing wild-type human KCNJ10 showed inwardly rectified currents, which were significantly reduced in all of the mutants (p < 0.001). Specific inhibition of KCNJ10 currents by Ba(2+) demonstrated a large residual function in p.A167V only, which was not compatible with causing disease. However, co-expression with KCNJ16 abolished function in these heteromeric channels almost completely. CONCLUSION This study provides an explanation for the pathophysiology of the p.A167V KCNJ10 mutation, which had previously not been considered pathogenic on its own. These findings provide evidence for the functional cooperation of KCNJ10 and KCNJ16. Thus, in vitro ascertainment of KCNJ10 function may necessitate co-expression with KCNJ16.
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Affiliation(s)
- Sophie Parrock
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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Cross JH, Arora R, Heckemann RA, Gunny R, Chong K, Carr L, Baldeweg T, Differ AM, Lench N, Varadkar S, Sirimanna T, Wassmer E, Hulton SA, Ognjanovic M, Ramesh V, Feather S, Kleta R, Hammers A, Bockenhauer D. Neurological features of epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome. Dev Med Child Neurol 2013; 55:846-56. [PMID: 23924083 PMCID: PMC4298033 DOI: 10.1111/dmcn.12171] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/14/2013] [Indexed: 01/30/2023]
Abstract
AIM Recently, we reported a previously unrecognized symptom constellation comprising epilepsy, ataxia, sensorineural deafness, and tubulopathy (EAST syndrome) associated with recessive mutations in the KCNJ10 gene. Here, we provide a detailed characterization of the clinical features of the syndrome to aid patient management with respect to diagnosis, prognostic counselling, and identification of best treatment modalities. METHOD We conducted a retrospective review of the detailed neurological and neuroradiological features of nine children (four females, five males; age range at last examination 6-20y) with genetically proven EAST syndrome. RESULTS All children presented with tonic-clonic seizures in infancy. Later, non-progressive, cerebellar ataxia and hearing loss were noted. Whilst seizures mostly responded well to treatment, ataxia proved to be the most debilitating feature, with three patients non-ambulant. All available magnetic resonance imaging (MRI) revealed subtle symmetrical signal changes in the cerebellar dentate nuclei. Moreover, four patients had a small corpus callosum and brainstem hypoplasia, and three had a small spinal cord. Regional quantitative volumetric analysis of the images confirmed the corpus callosum and brainstem hypoplasia and showed further patterns of variation from the norm. INTERPRETATION The neurological features of EAST syndrome appear to be non-progressive, which is important for prognostic counselling. The spectrum of EAST syndrome includes consistent abnormalities on brain MRI, which may aid diagnosis. Further longitudinal documentation is required to determine the true natural history of the disorder.
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Affiliation(s)
- J Helen Cross
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child Health, London, UK.
| | - Ruchi Arora
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | | | - Roxana Gunny
- Department of Radiology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Kling Chong
- Department of Radiology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Lucinda Carr
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Torsten Baldeweg
- Developmental Cognitive Neuroscience Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Ann-Marie Differ
- Department of Molecular Genetics, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Nicholas Lench
- Department of Molecular Genetics, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Sophie Varadkar
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Tony Sirimanna
- Department of Audiology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | | | | | | | | | - Sally Feather
- Leeds Teaching Hospitals/University of LeedsLeeds, UK
| | - Robert Kleta
- Department of Nephrology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Alexander Hammers
- The Neurodis FoundationLyon, France,Division of Experimental Medicine, Imperial College LondonLondon, UK
| | - Detlef Bockenhauer
- Department of Nephrology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
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Scholl UI, Dave HB, Lu M, Farhi A, Nelson-Williams C, Listman JA, Lifton RP. SeSAME/EAST syndrome--phenotypic variability and delayed activity of the distal convoluted tubule. Pediatr Nephrol 2012; 27:2081-2090. [PMID: 22907601 DOI: 10.1007/s00467-012-2219-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 05/09/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND Mutations in the K(+) channel KCNJ10 (Kir4.1) cause an autosomal recessive syndrome featuring seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance (SeSAME). Kir4.1 localizes to the basolateral membrane of the renal distal convoluted tubule, and its loss of function mimics renal features of Gitelman syndrome, with hypokalemic alkalosis, hypomagnesemia, and hypocalciuria. Presentation early in life due to seizures provides an opportunity to investigate the development of the electrolyte defect with age. METHODS We used DNA sequencing, electrophysiology, confocal imaging, and biochemistry to identify a new KCNJ10 mutation in a previously unreported family and determine its impact on channel function. We examined medical records to follow the development of electrolyte disorders with age. RESULTS The four affected members were all homozygous for a novel T57I mutation that confers biochemical loss-of-function. Electrolytes in affected children were normal in the first years of life but showed significant worsening with age, resulting in clinically significant defects at age 5-8 years. Similar findings were seen in other SeSAME patients. CONCLUSIONS These findings provide evidence for a delayed activity of salt reabsorption by the distal convoluted tubule and suggest an explanation for the delayed clinical presentation of subjects with Gitelman syndrome.
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Affiliation(s)
- Ute I Scholl
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - Haatal B Dave
- Department of Pediatrics, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Ming Lu
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - Anita Farhi
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - Carol Nelson-Williams
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - James A Listman
- Department of Pediatrics, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Richard P Lifton
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA. .,Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 333 Cedar St., SHM I308, New Haven, CT, 06510, USA.
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Affiliation(s)
- Ivana Y Kuo
- Departments of †Pharmacology and ‡Cellular and Molecular Physiology School of Medicine, Yale University , 333 Cedar Street, New Haven, Connecticut 06520
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Hamilton KL, Devor DC. Basolateral membrane K+ channels in renal epithelial cells. Am J Physiol Renal Physiol 2012; 302:F1069-81. [PMID: 22338089 DOI: 10.1152/ajprenal.00646.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The major function of epithelial tissues is to maintain proper ion, solute, and water homeostasis. The tubule of the renal nephron has an amazingly simple structure, lined by epithelial cells, yet the segments (i.e., proximal tubule vs. collecting duct) of the nephron have unique transport functions. The functional differences are because epithelial cells are polarized and thus possess different patterns (distributions) of membrane transport proteins in the apical and basolateral membranes of the cell. K(+) channels play critical roles in normal physiology. Over 90 different genes for K(+) channels have been identified in the human genome. Epithelial K(+) channels can be located within either or both the apical and basolateral membranes of the cell. One of the primary functions of basolateral K(+) channels is to recycle K(+) across the basolateral membrane for proper function of the Na(+)-K(+)-ATPase, among other functions. Mutations of these channels can cause significant disease. The focus of this review is to provide an overview of the basolateral K(+) channels of the nephron, providing potential physiological functions and pathophysiology of these channels, where appropriate. We have taken a "K(+) channel gene family" approach in presenting the representative basolateral K(+) channels of the nephron. The basolateral K(+) channels of the renal epithelia are represented by members of the KCNK, KCNJ, KCNQ, KCNE, and SLO gene families.
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Affiliation(s)
- Kirk L Hamilton
- Department of Physiology, Otago School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
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