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Soufi M, Ruppert V, Rinné S, Mueller T, Kurt B, Pilz G, Maieron A, Dodel R, Decher N, Schaefer JR. Increased KCNJ18 promoter activity as a mechanism in atypical normokalemic periodic paralysis. NEUROLOGY-GENETICS 2018; 4:e274. [PMID: 30338294 PMCID: PMC6186026 DOI: 10.1212/nxg.0000000000000274] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/02/2018] [Indexed: 11/21/2022]
Abstract
Objective To identify the genetic basis of a patient with symptoms of normokalemic sporadic periodic paralysis (PP) and to study the effect of KCNJ18 mutations. Methods A candidate gene approach was used to identify causative gene mutations, using Sanger sequencing. KCNJ18 promoter activity was analyzed in transfected HEK293 cells with a luciferase assay, and functional analysis of Kir2.6 channels was performed with the two-electrode voltage-clamp technique. Results Although we did not identify harmful mutations in SCN4A, CACNA1S, KCNJ2 and KCNE3, we detected a monoallelic four-fold variant in KCNJ18 (R39Q/R40H/A56E/I249V), together with a variant in the respective promoter of this channel (c.-542T/A). The exonic variants in Kir2.6 did not alter the channel function; however, luciferase assays revealed a 10-fold higher promoter activity of the c.-542A promoter construct, which is likely to cause a gain-of-function by increased expression of Kir2.6. We found that reducing extracellular K+ levels causes a paradoxical reduction in outward currents, similar to that described for other inward rectifying K+ channels. Thus, reducing the extracellular K+ levels might be a therapeutic strategy to antagonize the transcriptionally increased KCNJ18 currents. Consistently, treatment of the patient with K+ reducing drugs dramatically improved the health situation and prevented PP attacks. Conclusions We show that a promoter defect in the KCNJ18 gene is likely to cause periodic paralysis, as the observed transcriptional upregulation will be linked to increased Kir2.6 function. This concept is further supported by our observation that most of the PP attacks in our patient disappeared on medical treatment with K+ reducing drugs.
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Affiliation(s)
- Muhidien Soufi
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Volker Ruppert
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Susanne Rinné
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Tobias Mueller
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Bilgen Kurt
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Guenter Pilz
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Andreas Maieron
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Richard Dodel
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Niels Decher
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
| | - Juergen R Schaefer
- Center for Undiagnosed and Rare Diseases (ZusE) (M.S., T.M., B.K., J.R.S.); Department of Cardiology (V.R.) and Department of Neurology (R.D.), University Hospital Giessen and Marburg; Vegetative Physiology (S.R., N.D.), Philipps-University Marburg, Institute of Physiology and Pathophysiology, & Marburg Center for Mind, Brain and Behavior, Marburg, Germany; Institute for Algebra (G.P.), Johannes Kepler University Linz; and Department of Gastroenterology (A.M.), Hospital Elisabethinen, Linz, Austria
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Hasdemir C, Juang JJM, Kose S, Kocabas U, Orman MN, Payzin S, Sahin H, Celen C, Ozcan EE, Chen CYJ, Gunduz R, Turan OE, Senol O, Burashnikov E, Antzelevitch C. Coexistence of atrioventricular accessory pathways and drug-induced type 1 Brugada pattern. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2018; 41:1078-1092. [PMID: 29953624 DOI: 10.1111/pace.13414] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/30/2018] [Accepted: 05/13/2018] [Indexed: 11/30/2022]
Abstract
BACKGROUND Atrial arrhythmias, particularly atrioventricular nodal reentrant tachycardia, can coexist with drug-induced type 1 Brugada electrocardiogram (ECG) pattern (DI-Type1-BrP). The present study was designed to determine the prevalence of DI-Type1-BrP in patients with atrioventricular accessory pathways (AV-APs) and to investigate the clinical, electrocardiographic, electrophysiologic, and genetic characteristics of these patients. METHODS One-hundred twenty-four consecutive cases of AV-APs and 84 controls underwent an ajmaline challenge test to unmask DI-Type1-BrP. Genetic screening and analysis was performed in 55 of the cases (19 with and 36 without DI-Type1-BrP). RESULTS Patients with AV-APs were significantly more likely than controls to have a Type1-BrP unmasked (16.1 vs 4.8%, P = 0.012). At baseline, patients with DI-Type1-BrP had higher prevalence of chest pain, QR/rSr' pattern in V1 and QRS notching/slurring in V2 and aVL during preexcitation, rSr' pattern in V1 -V2 , and QRS notching/slurring in aVL during orthodromic atrioventricular reentrant tachycardia (AVRT) compared to patients without DI-Type1-BrP. Abnormal QRS configuration (QRS notching/slurring and/or fragmentation) in V2 during preexcitation was present in all patients with DI-Type1 BrP. The prevalence of spontaneous preexcited atrial fibrillation (AF) and history of AF were similar (15% vs 18.3%, P = 0.726) in patients with and without DI-Type1-BrP, respectively. The prevalence of mutations in Brugada-susceptibility genes was higher (36.8% vs 8.3%, P = 0.02) in patients with DI-Type1-BrP compared to patients without DI-Type1-BrP. CONCLUSIONS DI-Type1-BrP is relatively common in patients with AV-APs. We identify 12-lead ECG characteristics during preexcitation and orthodromic AVRT that point to an underlying type1-BrP, portending an increased probability for development of malignant arrhythmias.
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Affiliation(s)
- Can Hasdemir
- Department of Cardiology, Ege University School of Medicine, Izmir, Turkey
| | | | | | - Umut Kocabas
- Department of Cardiology, Ege University School of Medicine, Izmir, Turkey
| | - Mehmet N Orman
- Department of Biostatistics and Medical Informatics, Ege University School of Medicine, Izmir, Turkey
| | - Serdar Payzin
- Department of Cardiology, Ege University School of Medicine, Izmir, Turkey
| | - Hatice Sahin
- Department of Cardiology, Ege University School of Medicine, Izmir, Turkey
| | - Candan Celen
- Department of Cardiology, Ege University School of Medicine, Izmir, Turkey
| | - Emin E Ozcan
- Department of Cardiology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Ching-Yu Julius Chen
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | | | | | | | | | - Charles Antzelevitch
- Lankenau Institute for Medical Research, Wynnewood, PA, USA.,Lankenau Heart Institute, Wynnewood, PA, USA.,Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
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4
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Abou Ziki MD, Seidelmann SB, Smith E, Atteya G, Jiang Y, Fernandes RG, Marieb MA, Akar JG, Mani A. Deleterious protein-altering mutations in the SCN10A voltage-gated sodium channel gene are associated with prolonged QT. Clin Genet 2018; 93:741-751. [PMID: 28407228 PMCID: PMC5640462 DOI: 10.1111/cge.13036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 03/27/2017] [Accepted: 04/09/2017] [Indexed: 12/19/2022]
Abstract
BACKGROUND Long QT syndrome (LQT) is a pro-arrhythmogenic condition with life-threatening complications. Fifteen genes have been associated with congenital LQT, however, the genetic causes remain unknown in more than 20% of cases. MATERIALS AND METHODS Eighteen patients with history of palpitations, pre-syncope, syncope and prolonged QT were referred to the Yale Cardiovascular Genetics Program. All subjects underwent whole-exome sequencing (WES) followed by confirmatory Sanger sequencing. Mutation burden analysis was carried out using WES data from 16 subjects with no identifiable cause of LQT. RESULTS Deleterious and novel SCN10A mutations were identified in 3 of the 16 patients (19%) with idiopathic LQT. These included 2 frameshifts and 1 missense variants (p.G810fs, p.R1259Q, and p.P1877fs). Further analysis identified 2 damaging SCN10A mutations with allele frequencies of approximately 0.2% (p.R14L and p.R1268Q) in 2 independent cases. None of the SCN10A mutation carriers had mutations in known arrhythmia genes. Damaging SCN10A mutations (p.R209H and p.R485C) were also identified in the 2 subjects on QT prolonging medications. CONCLUSION Our findings implicate SCN10A in LQT. The presence of frameshift mutations suggests loss-of-function as the underlying disease mechanism. The common association with atrial fibrillation suggests a unique mechanism of disease for this LQT gene.
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Affiliation(s)
- Maen D. Abou Ziki
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Sara B. Seidelmann
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 02115
| | - Emily Smith
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Gourg Atteya
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Yuexin Jiang
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Rodolfo Gil Fernandes
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Mark A. Marieb
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Joseph G. Akar
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
| | - Arya Mani
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, 06510
- Deparetment of Genetics, Yale University School of Medicine, New Haven, CT, 06510
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Savio-Galimberti E, Argenziano M, Antzelevitch C. Cardiac Arrhythmias Related to Sodium Channel Dysfunction. Handb Exp Pharmacol 2018; 246:331-354. [PMID: 28965168 DOI: 10.1007/164_2017_43] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The voltage-gated cardiac sodium channel (Nav1.5) is a mega-complex comprised of a pore-forming α subunit and 4 ancillary β-subunits together with numerous protein partners. Genetic defects in the form of rare variants in one or more sodium channel-related genes can cause a loss- or gain-of-function of sodium channel current (INa) leading to the manifestation of various disease phenotypes, including Brugada syndrome, long QT syndrome, progressive cardiac conduction disease, sick sinus syndrome, multifocal ectopic Purkinje-related premature contractions, and atrial fibrillation. Some sodium channelopathies have also been shown to be responsible for sudden infant death syndrome (SIDS). Although these genetic defects often present as pure electrical diseases, recent studies point to a contribution of structural abnormalities to the electrocardiographic and arrhythmic manifestation in some cases, such as dilated cardiomyopathy. The same rare variants in SCN5A or related genes may present with different clinical phenotypes in different individuals and sometimes in members of the same family. Genetic background and epigenetic and environmental factors contribute to the expression of these overlap syndromes. Our goal in this chapter is to review and discuss what is known about the clinical phenotype and genotype of each cardiac sodium channelopathy, and to briefly discuss the underlying mechanisms.
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Affiliation(s)
| | - Mariana Argenziano
- Lankenau Institute for Medical Research, 100 E. Lancaster Avenue, Wynnewood, PA, 19096, USA
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, 100 E. Lancaster Avenue, Wynnewood, PA, 19096, USA.
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9
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Visser M, Palstra RJ, Kayser M. Human skin color is influenced by an intergenic DNA polymorphism regulating transcription of the nearby BNC2 pigmentation gene. Hum Mol Genet 2014; 23:5750-62. [PMID: 24916375 DOI: 10.1093/hmg/ddu289] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Single nucleotide polymorphisms (SNPs) found to be statistically significant when associated with human diseases, and other phenotypes are most often located in non-coding regions of the genome. One example is rs10765819 located in the first intron of the BNC2 gene previously associated with (saturation of) human skin color. Here, we demonstrate that a nearby intergenic SNP (rs12350739) in high linkage disequilibrium with rs10756819 is likely the causal DNA variant for the observed BNC2 skin color association. The highly conserved region surrounding rs12350739 functions as an enhancer element regulating BNC2 transcription in human melanocytes, while the activity of this enhancer element depends on the allelic status of rs12350739. When the rs12350739-AA allele is present, the chromatin at the region surrounding rs12350739 is inaccessible and the enhancer element is only slightly active, resulting in low expression of BNC2, corresponding with light skin pigmentation. When the rs12350739-GG allele is present however, the chromatin at the region surrounding rs12350739 is more accessible and the enhancer is active, resulting in a higher expression of BNC2, corresponding with dark skin pigmentation. Overall, we demonstrate the identification of the functional DNA variant that explains the BNC2 skin color association signal, providing another important step towards further understanding human pigmentation genetics beyond statistical association. We thus deliver a clear example of how an intergenic non-coding DNA variant modulates the regulatory potential of the enhancer element it is located within, which in turn results in allele-dependent differential gene expression affecting variation in common human traits.
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Affiliation(s)
- Mijke Visser
- Department of Forensic Molecular Biology, Erasmus MC University Medical Centre Rotterdam, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Robert-Jan Palstra
- Department of Forensic Molecular Biology, Erasmus MC University Medical Centre Rotterdam, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Manfred Kayser
- Department of Forensic Molecular Biology, Erasmus MC University Medical Centre Rotterdam, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
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