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Shi J, Pan X, Wang Z, Yi M, Xie S, Zhang X, Tao D, Yang Y, Liu Y. SCN5A-L256del and L1621F exhibit loss-of-function properties related to autosomal recessive congenital cardiac disorders presenting as sick sinus syndrome, dilated cardiomyopathy, and sudden cardiac death. Gene 2024; 898:148093. [PMID: 38123004 DOI: 10.1016/j.gene.2023.148093] [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: 10/20/2023] [Revised: 11/30/2023] [Accepted: 12/17/2023] [Indexed: 12/23/2023]
Abstract
Pathogenic mutations in SCN5A could result in dysfunctions of Nav1.5 and consequently lead to a wide range of inherited cardiac diseases. However, the presence of numerous SCN5A-related variants with unknown significance (VUS) and the comprehensive genotype-phenotype relationship pose challenges to precise diagnosis and genetic counseling for affected families. Here, we functionally identified two novel compound heterozygous variants (L256del and L1621F) in SCN5A in a Chinese family exhibiting complex congenital cardiac phenotypes from sudden cardiac death to overlapping syndromes including sick sinus syndrome and dilated cardiomyopathy in an autosomal recessive pattern. In silico tools predicted decreased stability and hydrophobicity of the two mutated proteins due to conformational changes. Patch-clamp electrophysiology revealed slightly decreased sodium currents, accelerated inactivation, and reduced sodium window current in the Nav1.5-L1621F channels as well as no sodium currents in the Nav1.5-L256del channels. Western blotting analysis demonstrated decreased expression levels of mutated Nav1.5 on the plasma membrane, despite enhanced compensatory expression of the total Nav1.5 expression levels. Immunofluorescence imaging showed abnormal condensed spots of the mutated channels within the cytoplasm instead of normal membrane distribution, indicating impaired trafficking. Overall, we identified the loss-of-function characteristics exhibited by the two variants, thereby providing further evidence for their pathogenic nature. Our findings not only extended the variation and phenotype spectrums of SCN5A, but also shed light on the crucial role of patch-clamp electrophysiology in the functional analysis of VUS in SCN5A, which have significant implications for the clinical diagnosis, management, and genetic counseling in affected individuals with complex cardiac phenotypes.
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Affiliation(s)
- Jiaying Shi
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Xueqi Pan
- School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China
| | - Zhaokun Wang
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Ming Yi
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Shengyu Xie
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Xinyue Zhang
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Dachang Tao
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Yuan Yang
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
| | - Yunqiang Liu
- Department of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
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