Key result
ZASP S196L mutation in mice leads to hemodynamic dysfunction, conduction defects, and altered ion currents.
Why the study?
The molecular pathways linking dilated cardiomyopathy to arrhythmias and sudden cardiac death are unknown, motivating investigation of the ZASP S196L mutation's role in cardiac abnormalities.
The ZASP S196L mutation causes both cytoskeletal and electrical abnormalities in a mouse model, linking structural protein mutations to arrhythmias in dilated cardiomyopathy.
Animal models link ZASP mutation to DCM conduction defects; leaves open human arrhythmia mechanisms and risk stratification.
BACKGROUND: Dilated cardiomyopathy (DCM) is a primary disease of the heart muscle associated with sudden cardiac death secondary to ventricular tachyarrhythmias and asystole. However, the molecular pathways linking DCM to arrhythmias and sudden cardiac death are unknown. We previously identified a S196L mutation in exon 4 of LBD3-encoded ZASP in a family with DCM and sudden cardiac death. These findings led us to hypothesize that this mutation may precipitate both cytoskeletal and conduction abnormalities in vivo. Therefore, we investigated the role of the ZASP4 mutation S196L in cardiac cytoarchitecture and ion channel biology. METHODS AND RESULTS: We generated and analyzed transgenic mice with cardiac-restricted expression of the S196L mutation. We also performed cellular electrophysiological analysis on isolated S196L cardiomyocytes and protein-protein interaction studies. Ten month-old S196L mice developed hemodynamic dysfunction consistent with DCM, whereas 3-month-old S196L mice presented with cardiac conduction defects and atrioventricular block. Electrophysiological analysis on isolated S196L cardiomyocytes demonstrated that the L-type Ca(2+) currents and Na(+) currents were altered. The pull-down assay demonstrated that ZASP4 complexes with both calcium (Ca(v)1.2) and sodium (Na(v)1.5) channels. CONCLUSIONS: Our findings provide new insight into the mechanisms by which mutations of a structural/cytoskeletal protein, such as ZASP, lead to cardiac functional and electric abnormalities. This work represents a novel framework to understand the development of conduction defects and arrhythmias in subjects with cardiomyopathies, including DCM.
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Li et al. (2010) studied Dilated cardiomyopathy and arrhythmias. ZASP4 mutation S196L was evaluated on Hemodynamic dysfunction, cardiac conduction defects, and altered ion currents. Expression of the ZASP S196L mutation in mice led to hemodynamic dysfunction, conduction defects, and altered L-type Ca2+ and Na+ currents.
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