Na Channel Mutation That Causes Both Brugada Syndrome and Long-QT Syndrome Phenotypes: A Simulation Study of Mechanism (INa1795insD Mutant Endocardial Cell)

Na Channel Mutation That Causes Both Brugada Syndrome and Long-QT Syndrome Phenotypes: A Simulation Study of Mechanism

Model Status

This CellML model represents the INa1795insD endocardial cell. For more details on the curation status of this model please see this separate notes document.

Model Structure

ABSTRACT: BACKGROUND: Complex physiological interactions determine the functional consequences of gene abnormalities and make mechanistic interpretation of phenotypes extremely difficult. A recent example is a single mutation in the C terminus of the cardiac Na(+) channel, 1795insD. The mutation causes two distinct clinical syndromes, long QT (LQT) and Brugada, leading to life-threatening cardiac arrhythmias. Coexistence of these syndromes is seemingly paradoxical; LQT is associated with enhanced Na(+) channel function, and Brugada with reduced function. METHODS AND RESULTS: Using a computational approach, we demonstrate that the 1795insD mutation exerts variable effects depending on the myocardial substrate. We develop Markov models of the wild-type and 1795insD cardiac Na(+) channels. By incorporating the models into a virtual transgenic cell, we elucidate the mechanism by which 1795insD differentially disrupts cellular electrical behavior in epicardial and midmyocardial cell types. We provide a cellular mechanistic basis for the ECG abnormalities observed in patients carrying the 1795insD gene mutation. CONCLUSIONS: We demonstrate that the 1795insD mutation can cause both LQT and Brugada syndromes through interaction with the heterogeneous myocardium in a rate-dependent manner. The results highlight the complexity and multiplicity of genotype-phenotype relationships, and the usefulness of computational approaches in establishing a mechanistic link between genetic defects and functional abnormalities.

The original paper reference is cited below:

Na⁺ Channel Mutation That Causes Both Brugada and Long-QT Syndrome Phenotypes: A Simulation Study of Mechanism, Colleen E. Clancy and Yoram Rudy, 2002, Circulation , 105, 1208-1213. PubMed ID: 11889015

A Markovian model for the wild-type cardiac Na⁺ channel, embedded within an updated version of the Luo-Rudy dynamic model. C, indicates a closed channel state; IC, a closed-inactivation state; IF, a fast inactivation state; IM, an intermediate inactivation state, and O, an open state.

A Markovian model for the mutant 1795insD cardiac Na⁺ channel, embedded within an updated version of the Luo-Rudy dynamic model. U (upper) indicates background mode of gating; L (lower), represents a small population of bursting channels which fail to inactivate.