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Published on: January 16, 2019
Identification of a Kir3.4 mutation in congenital long QT syndrome
Yanzong Yang1, Yiqing Yang, Bo Liang
1Key Laboratory of Arrhythmias, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
Insights
A novel mutation in the KCNJ5 gene, Kir3.4-Gly387Arg, is linked to congenital long QT syndrome (LQTS) in a Chinese family. This discovery sheds light on the genetic causes of LQTS and sudden cardiac death.
Area of Science:
- Genetics
- Cardiology
- Molecular Biology
Background:
- Congenital long QT syndrome (LQTS) is an inherited disorder causing fatal cardiac arrhythmias and sudden cardiac death.
- The genetic basis for 30-40% of LQTS cases remains unidentified.
- Autosomal-dominant LQTS families present a critical opportunity to uncover novel genetic etiologies.
Observation:
- A large Chinese family with autosomal-dominant LQTS underwent clinical evaluation and genome-wide linkage analysis.
- Linkage analysis mapped the LQTS-associated gene to chromosome 11q23.3-24.3.
- A heterozygous mutation, Kir3.4-Gly387Arg, was identified in the KCNJ5 gene, encoding the Kir3.4 potassium channel subunit.
Findings:
- The Kir3.4-Gly387Arg mutation was exclusively found in affected family members and absent in 528 controls.
- Western blotting confirmed significant Kir3.4 expression in human cardiac ventricles.
- Functional studies revealed a loss-of-function phenotype for Kir3.4-Gly387Arg due to reduced membrane expression.
Implications:
- This study identifies a novel role for the Kir3.4 potassium channel subunit in the pathogenesis of LQTS.
- The findings expand our understanding of the genetic landscape of LQTS.
- This research may contribute to improved genetic diagnostics and therapeutic strategies for LQTS patients.
Abstract:
Congenital long QT syndrome (LQTS) is a hereditary disorder that leads to sudden cardiac death secondary to fatal cardiac arrhythmias. Although many genes for LQTS have been described, the etiology remains unknown in 30%-40% of cases. In the present study, a large Chinese family (four generations, 49 individuals) with autosomal-dominant LQTS was clinically evaluated. Genome-wide linkage analysis was performed by using polymorphic microsatellite markers to map the genetic locus, and positional candidate genes were screened by sequencing for mutations. The expression pattern and functional characteristics of the mutated protein were investigated by western blotting and patch-clamp electrophysiology. The genetic locus of the LQTS-associated gene was mapped to chromosome 11q23.3-24.3. A heterozygous mutation (Kir3.4-Gly387Arg) was identified in the G protein-coupled, inwardly rectifying potassium channel subunit Kir3.4, encoded by the KCNJ5 gene. The Kir3.4-Gly387Arg mutation was present in all nine affected family members and absent in 528 ethnically matched controls. Western blotting of human cardiac tissue demonstrated significant Kir3.4 expression levels in the cardiac ventricles. Heterologous expression studies with Kir3.4-Gly387Arg revealed a loss-of-function electrophysiological phenotype resulting from reduced plasma membrane expression. Our findings suggest a role for Kir3.4 in the etiology of LQTS.
