Functional Characterization of the SCN5A p.D372H Variant Associated with Brugada Syndrome

Area of Science:

• Cardiology
• Molecular Biology
• Genetics

Background:

• Brugada syndrome (BrS) is an inherited cardiac arrhythmia linked to SCN5A gene variants.
• It increases the risk of ventricular arrhythmias and sudden cardiac death (SCD).
• SCN5A variants often cause loss-of-function in the cardiac sodium channel Nav1.5.

Purpose of the Study:

• To investigate the functional impact of the SCN5A D372H variant on Nav1.5 channel function.
• To elucidate the molecular mechanisms underlying the D372H variant's contribution to Brugada syndrome.

Main Methods:

• Constructed SCN5A D372H variant using PCR and site-directed mutagenesis.
• Utilized HEK293 cells for transfection and assessed sodium currents via patch-clamp.
• Analyzed channel expression and localization using confocal microscopy, Western blot, and RT-qPCR.

Main Results:

• The D372H variant caused a near-complete loss of sodium currents in HEK293 cells.
• Co-expression with wild-type (WT) SCN5A significantly reduced current density without altering kinetics.
• Reduced channel expression was confirmed at both protein and mRNA levels.

Conclusions:

• The D372H variant impairs Nav1.5 function through reduced current density and decreased channel expression.
• This defect diminishes inward sodium current crucial for cardiac depolarization.
• Findings provide mechanistic insights into the D372H variant's role in Brugada syndrome pathogenesis.