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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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Dong J, Williams N, Cerrone M, Borck C, Wang D, Zhou B, Eng LS, Subbotina E, Um SY, Lin Y, Ruiter K, Rojas L, Coetzee WA, Sampson BA, Tang Y. Molecular autopsy: using the discovery of a novel de novo pathogenic variant in the KCNH2 gene to inform healthcare of surviving family. Heliyon 2018; 4:e01015. [PMID: 30582040 PMCID: PMC6288419 DOI: 10.1016/j.heliyon.2018.e01015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 10/24/2018] [Accepted: 12/04/2018] [Indexed: 01/23/2023] Open
Abstract
Background Molecular testing of the deceased (Molecular Autopsy) is an overlooked area in the United States healthcare system and is not covered by medical insurance, leading to ineffective care for surviving families of thousands of sudden unexpected natural deaths each year. We demonstrated the precision management of surviving family members through the discovery of a novel de novo pathogenic variant in a decedent. Methods Forensic investigation and molecular autopsy were performed on an 18-year-old female who died suddenly and unexpectedly. Co-segregation family study of the first-degree relatives and functional characterization of the variant were conducted. Findings We identified a novel nonsense variant, NP_000229.1:p.Gln1068Ter, in the long QT syndrome type II gene KCNH2 in the decedent. This finding correlated with her ante-mortem electrocardiograms. Patch clamp functional studies using transfected COS-7 cells show that hERG-ΔQ1068 has a mixed phenotype, with both gain- (negative voltage shift of steady-state activation curve, the positive shift of the steady-state inactivation curve, and accelerated activation) and loss-of function (reduced current density, reduced surface expression and accelerated deactivation) hallmarks. Loss of cumulative activation during rapid pacing demonstrates that the loss-of-function phenotype predominates. The wild-type channel did not rescue the hERG-ΔQ1068 defects, demonstrating haploinsufficiency of the heterozygous state. Targeted variant testing in the family showed that the variant in KCNH2 arose de novo, which eliminated the need for exhaustive genome testing and annual cardiac follow-up for the parents and four siblings. Interpretation Molecular testing enables accurate determination of natural causes of death and precision care of the surviving family members in a time and cost-saving manner. We advocate for molecular autopsy being included under the healthcare coverage in US.
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Affiliation(s)
- Jingyun Dong
- Department of Pediatrics, NYU School of Medicine, USA.,Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, USA.,Department of Physiology and Neurosciences, NYU School of Medicine, USA
| | - Nori Williams
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Marina Cerrone
- Cardiovascular Genetics Program, Leon H Charney Division of Cardiology, NYU School of Medicine, NY, USA
| | - Christopher Borck
- Department of Pathology, New York City Office of Chief Medical Examiner, USA
| | - Dawei Wang
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Bo Zhou
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Lucy S Eng
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Ekaterina Subbotina
- Department of Pediatrics, NYU School of Medicine, USA.,Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, USA.,Department of Physiology and Neurosciences, NYU School of Medicine, USA
| | - Sung Yon Um
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Ying Lin
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Kevin Ruiter
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - Lisa Rojas
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
| | - William A Coetzee
- Department of Pediatrics, NYU School of Medicine, USA.,Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, USA.,Department of Physiology and Neurosciences, NYU School of Medicine, USA
| | - Barbara A Sampson
- Department of Pathology, New York City Office of Chief Medical Examiner, USA
| | - Yingying Tang
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, USA
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Large-scale mutational analysis of Kv11.1 reveals molecular insights into type 2 long QT syndrome. Nat Commun 2014; 5:5535. [PMID: 25417810 PMCID: PMC4243539 DOI: 10.1038/ncomms6535] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 10/09/2014] [Indexed: 12/23/2022] Open
Abstract
It has been suggested that deficient protein trafficking to the cell membrane is the dominant mechanism associated with type 2 Long QT syndrome (LQT2) caused by Kv11.1 potassium channel missense mutations, and that for many mutations the trafficking defect can be corrected pharmacologically. However, this inference was based on expression of a small number of Kv11.1 mutations. We performed a comprehensive analysis of 167 LQT2-linked missense mutations in four Kv11.1 structural domains and found that deficient protein trafficking is the dominant mechanism for all domains except for the distal carboxy-terminus. Also, most pore mutations--in contrast to intracellular domain mutations--were found to have severe dominant-negative effects when co-expressed with wild-type subunits. Finally, pharmacological correction of the trafficking defect in homomeric mutant channels was possible for mutations within all structural domains. However, pharmacological correction is dramatically improved for pore mutants when co-expressed with wild-type subunits to form heteromeric channels.
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He FZ, McLeod HL, Zhang W. Current pharmacogenomic studies on hERG potassium channels. Trends Mol Med 2013; 19:227-38. [PMID: 23369369 DOI: 10.1016/j.molmed.2012.12.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 12/18/2012] [Accepted: 12/27/2012] [Indexed: 11/25/2022]
Abstract
Genetic polymorphisms in human ether-a-go-go-related gene (hERG) potassium channels are associated with many complex diseases and sensitivity to channel-related drugs. Genotypes may underlie different sensitivities to the same drug, and different drugs selectively repair the functional deficits caused by individual mutations. In fact, not all drugs that block hERG function have adverse effects as previously thought. This suggests that the severe adverse reactions observed clinically may only occur in subjects with a particular genotype, but to others may be safe. Similarly, a drug that is ineffective in one population may be both safe and effective in another. Therefore, detecting polymorphisms in KCNH2 encoding hERG1 is of great significance in guiding the prevention and treatment of related diseases, re-evaluating drug safety, and individualizing treatment. This article reviews current pharmacogenomic studies on hERG potassium channels to provide a reference for developing individualized treatments and evaluating their safety.
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Affiliation(s)
- Fa-Zhong He
- Pharmacogenetics Research Institute, Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha, Hunan 410078, PR China
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Liu L, Hayashi K, Kaneda T, Ino H, Fujino N, Uchiyama K, Konno T, Tsuda T, Kawashiri MA, Ueda K, Higashikata T, Shuai W, Kupershmidt S, Higashida H, Yamagishi M. A novel mutation in the transmembrane nonpore region of the KCNH2 gene causes severe clinical manifestations of long QT syndrome. Heart Rhythm 2012; 10:61-7. [PMID: 23010577 DOI: 10.1016/j.hrthm.2012.09.053] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Long QT syndrome (LQTS) is characterized by prolonged ventricular repolarization and variable clinical course with arrhythmia-related syncope and sudden death. Mutations in the nonpore region of the LQTS-associated KCNH2 gene (also known as hERG) are mostly associated with coassembly or trafficking abnormalities, resulting in haplotype insufficiency and milder clinical phenotypes compared with mutations in the pore domain. OBJECTIVE To investigate the effect of a nonpore mutation on the channel current, which was identified from an LQTS family with severe clinical phenotypes. METHODS Two members of a Japanese family with LQTS were searched for mutations in KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, and KCNJ2 genes by using automated DNA sequencing. We characterized the electrophysiological properties and glycosylation pattern of the mutant channels by using patch clamp recording and Western blot analysis. RESULTS In the LQTS patient with torsades de pointes and cardiopulmonary arrest, we identified the novel T473P mutation in the transmembrane nonpore region of KCNH2. The proband's father carried the same mutation and showed prolonged corrected QT interval and frequent torsades de pointes in the presence of hypokalemia following the administration of garenoxacin. Patch clamp analysis in heterologous cells showed that hERG T473P channels generated no current and exhibited a dominant negative effect when coexpressed with wild-type protein. Only incompletely glycosylated hERG T473P channels were observed by using Western blot analysis, suggesting impaired trafficking. CONCLUSIONS These results demonstrated that a trafficking-deficient mutation in the transmembrane nonpore region of KCNH2 causes a dominant negative effect and a severe clinical course in affected patients.
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Affiliation(s)
- Li Liu
- Department of Biophysical Genetics, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
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