A Type 2 Ryanodine Receptor Variant in the Helical Domain 2 Associated with an Impairment of the Adrenergic Response

Area of Science:

• Cardiovascular Genetics
• Molecular Cardiology
• Arrhythmology

Background:

• Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a life-threatening arrhythmia triggered by adrenergic stress.
• The RYR2 gene, encoding the cardiac ryanodine receptor (RyR2), is the primary genetic cause of CPVT.
• Existing CPVT genetic research has focused on specific mutation hotspots within the RYR2 gene.

Purpose of the Study:

• To identify and characterize a novel RYR2 gene variant associated with CPVT.
• To investigate the functional consequences of the identified RYR2 variant on RyR2 channel function.
• To elucidate the mechanism by which this variant contributes to CPVT pathogenesis.

Main Methods:

• Genetic analysis of three CPVT families with a history of sudden cardiac death.
• Identification and segregation analysis of a novel RYR2 variant (p.Asp3291Val).
• In vitro functional studies using transfected HEK293 and HL-1 cells to assess RyR2 channel activity and response to adrenergic stimulation.

Main Results:

• A novel RYR2 missense variant, p.Asp3291Val, was identified in three CPVT families, including homozygous cases.
• The D3291V-RyR2 variant exhibited normal cytosolic Ca2+ response but reduced luminal Ca2+ sensitivity.
• Crucially, the D3291V-RyR2 channels showed a complete lack of response to 8-bromo-cAMP and forskolin stimulation.

Conclusions:

• The p.Asp3291Val variant in the RYR2 gene represents a novel cause of an atypical form of CPVT.
• This loss-of-function variant leads to impaired RyR2 channel function, particularly its response to adrenergic stimulation.
• The unresponsiveness of D3291V-RyR2 channels to adrenergic signals explains the predisposition to fatal cardiac events in affected individuals.