A ZASP missense mutation, S196L, leads to cytoskeletal and electrical abnormalities in a mouse model of cardiomyopathy.
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.


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.
Li
Zhaohui
Z
Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, Tex, USA.
Ai
Tomohiko
T
Samani
Kaveh
K
Xi
Yutao
Y
Tzeng
Huei-Ping
HP
Xie
Mingxing
M
Wu
Shan
S
Ge
Shuping
S
Taylor
Michael D
MD
Dong
Jian-Wen
JW
Cheng
Jie
J
Ackerman
Michael J
MJ
Kimura
Akinori
A
Sinagra
Gianfranco
G
Brunelli
Luca
L
Faulkner
Georgine
G
Vatta
Matteo
M
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D003599:Cytoskeleton / Q000648:ultrastructure*; D004247:DNA / Q000235:genetics*; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D005091:Exons; D005260:Female; D005786:Gene Expression Regulation; D006329:Heart Conduction System / Q000503:physiopathology* / Q000648:ultrastructure; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics*; D007150:Immunohistochemistry; D060588:LIM Domain Proteins; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D046529:Microscopy, Electron, Transmission; D009124:Muscle Proteins; D020125:Mutation, Missense; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000648:ultrastructure*; D016133:Polymerase Chain Reaction
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; C485639:Ldb3 protein, mouse; D009124:Muscle Proteins; D004247:DNA