A ZASP Missense Mutation, S196L, Leads to Cytoskeletal and Electrical Abnormalities in a Mouse Model of Cardiomyopathy

Abstract

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 proteinprotein 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 2ϩ currents and Na ϩ 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. (Circ Arrhythm Electrophysiol. 2010;3:646-656.)

A Novel Disease Gene for Brugada Syndrome

“…Recently, it was reported that a Z-disc protein, ZASP, formed a macromolecular complex with hNav1.5, but there was no direct interaction between ZASP and hNav1.5, and a ZASP mutation disturbed the hNav1.5 function without affecting the localization of hNav1.5. 37 The function of hNav1.5 in cardiomyocytes may be regulated by a fine-tuning mechanism in which many proteins are directly or indirectly involved. Finally, although the loss of hNav1.5 function is often associated with prolongation of PR and QRS, no conduction delay was observed in ECGs from both patients carrying the SLMAP mutations.…”

Phenotype and Functional Analyses in a Transgenic Mouse Model of Left Ventricular Noncompaction Caused by a <i>DTNA</i> Mutation

“…In some previous studies focusing on the establishment of genetically modified mice associated with LVNC candidate genes, 9,[20][21][22][23] the notch signaling pathway has been found to play a vital role in the development of LVNC. Cardiac-specific inactive Mib1 (an E3 ubiquitin ligase of NOTCH ligands) in mice could cause LVNC by disrupting the Notch pathway.…”

“…5) Nevertheless, neither cardiac-specific Cypher knockout mice nor the transgenic mice with cardiacspecific expression of the ZASP-p.S196L mutation showed the expected phenotype of LVNC. 22,23) Therefore, only various parts of mouse models can effectively reproduce the LVNC phenotype. These results suggest that the different genetic background between mice and humans may affect the development of LVNC.…”

Heart Failure

“…This work represents a novel framework to understand the development of conduction defects and arrhythmias in subjects with cardiomyopathies, including DCM. 30 …”