Gain-of-function mutation in TASK-4 channels and severe cardiac conduction disorder

Area of Science:

• Cardiovascular Genetics
• Molecular Cardiology
• Ion Channel Physiology

Background:

• Cardiac conduction disorders and idiopathic ventricular fibrillation (IVF) pose significant clinical challenges.
• Genetic factors play a crucial role in the pathogenesis of severe cardiac arrhythmias.
• The interplay between different ion channel mutations can lead to complex phenotypes.

Purpose of the Study:

• To investigate the genetic basis of severe cardiac conduction disorder and IVF in a patient.
• To identify novel genes and mutations associated with complex cardiac arrhythmias.
• To elucidate the functional consequences of identified mutations on ion channel activity and cardiac function.

Main Methods:

• Whole-exome sequencing (WES) to identify genetic variants.
• Site-directed mutagenesis to create the KCNK17 p.Gly88Arg (G88R) mutation.
• Electrophysiological studies (e.g., patch-clamp) to assess channel function.
• Expression analysis in HL-1 cells to evaluate effects on cardiac cell electrophysiology.

Main Results:

• A splice site mutation in SCN5A and a heterozygous gain-of-function mutation (p.Gly88Arg) in KCNK17 (encoding TASK-4 potassium channel) were identified.
• Mutant TASK-4 channels exhibited threefold increased currents with unchanged surface expression, indicating enhanced conductivity.
• KCNK17 is expressed in human Purkinje cells; G88R overexpression caused hyperpolarization and slowed upstroke velocity in HL-1 cells.

Conclusions:

• Gain-of-function of TASK-4 potassium channels may exacerbate cardiac conduction slowing, potentially acting as a second hit alongside SCN5A mutations.
• KCNK17 is identified as a novel gene associated with cardiac arrhythmias.
• WES is a valuable tool for uncovering genetic underpinnings of complex inherited arrhythmia syndromes.