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Thomson KL, Jiang C, Richardson E, Westphal DS, Burkard T, Wolf CM, Vatta M, Harrison SM, Ingles J, Bezzina CR, Kroncke BM, Vandenberg JI, Ng CA. Clinical interpretation of KCNH2 variants using a robust PS3/BS3 functional patch-clamp assay. HGG Adv 2024; 5:100270. [PMID: 38219013 PMCID: PMC10840334 DOI: 10.1016/j.xhgg.2024.100270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 01/07/2024] [Accepted: 01/08/2024] [Indexed: 01/15/2024] Open
Abstract
Long QT syndrome (LQTS), caused by the dysfunction of cardiac ion channels, increases the risk of sudden death in otherwise healthy young people. For many variants in LQTS genes, there is insufficient evidence to make a definitive genetic diagnosis. We have established a robust functional patch-clamp assay to facilitate classification of missense variants in KCNH2, one of the key LQTS genes. A curated set of 30 benign and 30 pathogenic missense variants were used to establish the range of normal and abnormal function. The extent to which variants reduced protein function was quantified using Z scores, the number of standard deviations from the mean of the normalized current density of the set of benign variant controls. A Z score of -2 defined the threshold for abnormal loss of function, which corresponds to 55% wild-type function. More extreme Z scores were observed for variants with a greater loss-of-function effect. We propose that the Z score for each variant can be used to inform the application and weighting of abnormal and normal functional evidence criteria (PS3 and BS3) within the American College of Medical Genetics and Genomics variant classification framework. The validity of this approach was demonstrated using a series of 18 KCNH2 missense variants detected in a childhood onset LQTS cohort, where the level of function assessed using our assay correlated to the Schwartz score (a scoring system used to quantify the probability of a clinical diagnosis of LQTS) and the length of the corrected QT (QTc) interval.
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Affiliation(s)
- Kate L Thomson
- Oxford Genetics Laboratories, Churchill Hospital, Oxford, UK
| | - Connie Jiang
- Faculty of Medicine and Health, UNSW Sydney, Kensington, NSW, Australia; Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Ebony Richardson
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, NSW, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, VIC, Australia
| | - Dominik S Westphal
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine and Health, Technical University of Munich, Munich, Germany; Department of Internal Medicine I, Klinikum Rechts der Isar, School of Medicine and Health, Technical University of Munich, Munich, Germany; European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart
| | - Tobias Burkard
- Department of Congenital Heart Disease and Pediatric Cardiology, German Heart Center Munich, Technical University of Munich, School of Medicine and Health, Munich, Germany
| | - Cordula M Wolf
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart; Department of Congenital Heart Disease and Pediatric Cardiology, German Heart Center Munich, Technical University of Munich, School of Medicine and Health, Munich, Germany; DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, Munich, Germany
| | | | | | - Jodie Ingles
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, NSW, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, VIC, Australia
| | - Connie R Bezzina
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart; Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC, Amsterdam, the Netherlands
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
| | - Chai-Ann Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
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Wang T, Chen X, Yu J, Du Q, Zhu J, Yang M, Wu H, Wang M, Zhu Y. High-Throughput Electrophysiology Screen Revealed Cardiotoxicity of Strychnine by Selectively Targeting hERG Channel. Am J Chin Med 2018; 46:1825-1840. [PMID: 30545237 DOI: 10.1142/s0192415x1850091x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Although the efficacy and the health care advantages of Chinese herbal medicine (CHM) have become increasingly recognized worldwide, the potential side effects and toxicity still restrict its broader application. This study established and applied an integrated platform anchored on automatic patch clamp system to screen and evaluate a collection of CHM extracts, compositions and monomeric compounds for in vitro cardiac toxicity. Of 1036 CHM samples screened, 2.79% significantly inhibited hERG channel activity. Among them, Strychnine was identified for the first time as a potent hERG inhibitor with an IC 50 of 6.65±1.04μ M in comparison to that of Dofetilide at 1.80±0.24μ M and Quinidine at 7.42±0.54μ M. Langendorff-perfusion experiments confirmed that strychnine increased QT interphase from 71.69±5.34 ms to 98.61±5.54 ms and decreased heart rates from 227.65±5.40 bmp to 162.91±14.70 bmp in isolated rat hearts. The cardiac toxicity effect of strychnine appears to be specific to hERG channel since an in vitro multiplex imaging analysis showed that it did not affect cellular phenotypes such as cell vitality, nucleus area, mitochondria mass and function, nor intracellular calcium in rat primary myocytes. This integrated high-throughput hERG patch clamp and high-content multi-parameter imaging cardiac toxicity screen approach should be useful for large-scale preclinical evaluation of complex Chinese herbal medicine.
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Affiliation(s)
- Taiyi Wang
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Xiaonan Chen
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Jiahui Yu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Qunqun Du
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Jie Zhu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Mingzhu Yang
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Honghua Wu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Meng Wang
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
| | - Yan Zhu
- 1 Tianjin State Key Laboratory of Modern, Chinese Medicine, Tianjin University of Traditional, Chinese Medicine, Tianjin 300193, P. R. China.,2 Research and Development Center of TCM, Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, P. R. China
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