A novel KCNH2 mutation as a modifier for short QT interval

Area of Science:

• Cardiology
• Molecular Biology
• Genetics

Background:

• Short QT syndrome is a rare inherited disorder characterized by a shortened QT interval on electrocardiogram.
• It is associated with an increased risk of ventricular arrhythmias and sudden cardiac death.
• The KCNH2 gene encodes the hERG protein, a subunit of the rapidly activating delayed rectifier potassium current (IKr), crucial for cardiac repolarization.

Observation:

• A novel C-terminal KCNH2 mutation, R1135H, was identified in a 34-year-old male patient presenting with a short QT interval (QTc 329 ms).
• The patient's clinical presentation indicated a potential genetic basis for his cardiac condition.

Findings:

• Heterologous expression of the mutant KCNH2 channels in CHO cells revealed significantly slowed deactivation kinetics.
• This altered channel function resulted in a gain-of-function for the reconstituted 'IKr' currents.
• The R1135H mutation directly impacts the function of the hERG potassium channel.

Implications:

• The identified KCNH2 mutation, R1135H, provides a potential molecular explanation for the patient's short QT syndrome.
• Understanding the functional consequences of this mutation can aid in predicting and managing the patient's clinical phenotype.
• This finding contributes to the growing knowledge of genetic variants associated with cardiac channelopathies and short QT syndrome.