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Copier JS, Bootsma M, Ng CA, Wilde AAM, Bertels RA, Bikker H, Christiaans I, van der Crabben SN, Hol JA, Koopmann TT, Knijnenburg J, Lommerse AAJ, van der Smagt JJ, Bezzina CR, Vandenberg JI, Verkerk AO, Barge-Schaapveld DQCM, Lodder EM. Reclassification of a likely pathogenic Dutch founder variant in KCNH2; implications of reduced penetrance. Hum Mol Genet 2023; 32:1072-1082. [PMID: 36269083 PMCID: PMC10026256 DOI: 10.1093/hmg/ddac261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 10/03/2022] [Accepted: 10/14/2022] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Variants in KCNH2, encoding the human ether a-go-go (hERG) channel that is responsible for the rapid component of the cardiac delayed rectifier K+ current (IKr), are causal to long QT syndrome type 2 (LQTS2). We identified eight index patients with a new variant of unknown significance (VUS), KCNH2:c.2717C > T:p.(Ser906Leu). We aimed to elucidate the biophysiological effect of this variant, to enable reclassification and consequent clinical decision-making. METHODS A genotype-phenotype overview of the patients and relatives was created. The biophysiological effects were assessed independently by manual-, and automated calibrated patch clamp. HEK293a cells expressing (i) wild-type (WT) KCNH2, (ii) KCNH2-p.S906L alone (homozygous, Hm) or (iii) KCNH2-p.S906L in combination with WT (1:1) (heterozygous, Hz) were used for manual patching. Automated patch clamp measured the variants function against known benign and pathogenic variants, using Flp-In T-rex HEK293 KCNH2-variant cell lines. RESULTS Incomplete penetrance of LQTS2 in KCNH2:p.(Ser906Leu) carriers was observed. In addition, some patients were heterozygous for other VUSs in CACNA1C, PKP2, RYR2 or AKAP9. The phenotype of carriers of KCNH2:p.(Ser906Leu) ranged from asymptomatic to life-threatening arrhythmic events. Manual patch clamp showed a reduced current density by 69.8 and 60.4% in KCNH2-p.S906L-Hm and KCNH2-p.S906L-Hz, respectively. The time constant of activation was significantly increased with 80.1% in KCNH2-p.S906L-Hm compared with KCNH2-WT. Assessment of KCNH2-p.S906L-Hz by calibrated automatic patch clamp assay showed a reduction in current density by 35.6%. CONCLUSION The reduced current density in the KCNH2-p.S906L-Hz indicates a moderate loss-of-function. Combined with the reduced penetrance and variable phenotype, we conclude that KCNH2:p.(Ser906Leu) is a low penetrant likely pathogenic variant for LQTS2.
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Affiliation(s)
- Jaël S Copier
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
| | - Marianne Bootsma
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2300 Leiden, The Netherlands
| | - Chai A Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Arthur A M Wilde
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
| | - Robin A Bertels
- Department of Paediatric Cardiology, Leiden University Medical Center, Willem-Alexander Children's Hospital, Albinusdreef 2, 2333 Leiden, Netherlands
| | - Hennie Bikker
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
- Human Genetics, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | - Imke Christiaans
- Department of Clinical Genetics, University Medical Centre Groningen, 9713GZ Groningen, The Netherlands
| | - Saskia N van der Crabben
- Human Genetics, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | - Janna A Hol
- Erasmus MC, Clinical Genetics, Doctor Molewaterplein 40, 3015 Rotterdam, The Netherlands
| | - Tamara T Koopmann
- Clinical Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 Leiden, The Netherlands
| | - Jeroen Knijnenburg
- Clinical Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 Leiden, The Netherlands
| | - Aafke A J Lommerse
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2300 Leiden, The Netherlands
| | - Jasper J van der Smagt
- Clinical Genetics, University Medical Center Utrecht, Lundlaan 6, Utrecht, The Netherlands
| | - Connie R Bezzina
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Arie O Verkerk
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
- Medical Biology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | | | - Elisabeth M Lodder
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
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Huynh MT, Proust A, Bouligand J, Popescu E. AKAP9-Related Channelopathy: Novel Pathogenic Variant and Review of the Literature. Genes (Basel) 2022; 13:2167. [PMID: 36421840 PMCID: PMC9690169 DOI: 10.3390/genes13112167] [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: 10/18/2022] [Revised: 11/16/2022] [Accepted: 11/18/2022] [Indexed: 08/30/2023] Open
Abstract
Disease-associated pathogenic variants in the A-Kinase Anchor Protein 9 (AKAP9) (MIM *604001) have been recently identified in patients with autosomal dominant long QT syndrome 11 (MIM #611820), lethal arrhythmia (ventricular fibrillation, polymorphic ventricular tachycardia), Brugada syndrome, and sudden unexpected death. However, AKAP9 sequence variations were rarely reported and AKAP9 was classified as a "disputed evidence" gene to support disease causation due to the insufficient genetic evidence and a limited number of reported AKAP9-mutated patients. Here, we describe a 47-year-old male carrying a novel frameshift AKAP9 pathogenic variant who presented recurrent syncopal attacks and sudden cardiac arrest that required a semi-automatic external defibrillator implant and an electric shock treatment of ventricular arrhythmia. This study provides insight into the mechanism underlying cardiac arrest and confirms that AKAP9 loss-of-function variants predispose to serious, life-threatening ventricular arrhythmias.
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Affiliation(s)
- Minh-Tuan Huynh
- Centre Hospitalier du Havre, Unité de Génétique Clinique, 29 Avenue Pierre Mendès-France, 76290 Montivilliers, France
- Laboratoire de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Hôpital Bicêtre, APHP Université Paris Saclay, 94270 Le Kremlin-Bicêtre, France; Inserm UMR_S 1185, Faculté de Médecine Paris Saclay, Université Paris Saclay, 94270 Le Kremlin-Bicêtre, France
| | - Alexis Proust
- Laboratoire de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Hôpital Bicêtre, APHP Université Paris Saclay, 94270 Le Kremlin-Bicêtre, France; Inserm UMR_S 1185, Faculté de Médecine Paris Saclay, Université Paris Saclay, 94270 Le Kremlin-Bicêtre, France
| | - Jérôme Bouligand
- Laboratoire de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Hôpital Bicêtre, APHP Université Paris Saclay, 94270 Le Kremlin-Bicêtre, France; Inserm UMR_S 1185, Faculté de Médecine Paris Saclay, Université Paris Saclay, 94270 Le Kremlin-Bicêtre, France
| | - Elena Popescu
- Centre Hospitalier du Havre, Service de Cardiologie, 29 Avenue Pierre Mendès-France, 76290 Montivilliers, France
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