A Functional Assay for Sick Sinus Syndrome Genetic Variants

• Published in: Cellular physiology and biochemistry Vol. 42; no. 5; pp. 2021 - 2029
• Main Authors: Jou, Chuanchau J., Arrington, Cammon B., Barnett, Spencer, Shen, Jiaxiang, Cho, Scott, Sheng, Xiaoming, McCullagh, Patrick C., Bowles, Neil E., Pribble, Chase M., Saarel, Elizabeth V., Pilcher, Thomas A., Etheridge, Susan P., Tristani-Firouzi, Martin
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland S. Karger AG 01-01-2017; Cell Physiol Biochem Press GmbH & Co KG
• Subjects: Amino acids; Animals; Animals, Genetically Modified; Arrhythmia; Bradycardia - etiology; Cardiac arrhythmia; Cardiology; Deoxyribonucleic acid; DNA; Embryo, Nonmammalian - drug effects; Embryo, Nonmammalian - metabolism; Embryos; Genetic testing; Genetic Variation; Genetics; Genomes; Genotype; Heart - drug effects; Heart - physiology; Heart rate; Heart Rate - drug effects; Humans; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels - antagonists & inhibitors; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels - genetics; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels - metabolism; In Situ Hybridization; Long QT syndrome; Morpholinos - metabolism; Muscle Proteins - antagonists & inhibitors; Muscle Proteins - genetics; Muscle Proteins - metabolism; Mutagenesis; Mutation; Neurosciences; Original Paper; Patch-Clamp Techniques; Pediatrics; Phenotype; Potassium Channels - genetics; Potassium Channels - metabolism; Pyrimidines - pharmacology; Sick sinus syndrome; Sick Sinus Syndrome - genetics; Sick Sinus Syndrome - pathology; Sinuses; Sudden cardiac death; Zebrafish; Zebrafish - metabolism; Cleveland Ohio; United States > US; Utah; Genetics; Zebrafish; Arrhythmia; Sudden cardiac death; Sick sinus syndrome
• ISSN: 1015-8987; 1421-9778
• DOI: 10.1159/000479897

Background/Aims: Congenital Sick Sinus Syndrome (SSS) is a disorder associated with sudden cardiac death due to severe bradycardia and prolonged pauses. Mutations in HCN4, the gene encoding inward Na + /K + current (I f ), have been described as a cause of congenital SSS. The objective of this study is to develop an SSS model in embryonic zebrafish, and use zebrafish as a moderate-throughput assay to functionally characterize HCN4 variants. Methods: To determine the function of hcn4 in zebrafish, embryos were either bathed in the I f -specific blocker (ZD-7288), or endogenous hcn4 expression was knocked down using splice-blocking morpholinos. To assess whether the zebrafish model discriminates benign from pathogenic variants, we tested four HCN4 mutations known to cause human SSS and four variants of unknown significance (VUS). Results: Pharmacological blockade and knockdown of hcn4 in zebrafish phenocopied human SSS, displaying bradycardia and cardiac pauses in intact embryos and explanted hearts. The zebrafish assay correctly identified all disease-causing variants. Of the VUS, the assay predicted 2 as benign and 2 as hypomorphic variants. Conclusions: We conclude that our embryonic zebrafish assay is a novel and effective tool to functionally characterize human HCN4 variants, which can be translated into important clinical prognostic information.