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.)

Vohwinkel syndrome (VS) is a rare autosomal dominant condition, also known as mutilating palmoplantar keratoderma accompanied by sensorineural deafness. The LOR and GJB2 genes are reported to be responsible for VS. The GJB2 gene encodes connexin 26, a component of intercellular gap junctions expressed in various tissues. We report the case of a 31‐year‐old Chinese woman with classic VS characterized by sensorineural deafness and mutilating palmoplantar keratoderma. Further genetic studies demonstrated a nucleotide change (c.175G>A) in the GJB2 gene, leading to an amino acid alteration (G59S). This identical missense mutation (G59S) has also been reported in a patient with Bart–Pumphrey syndrome. Together with our findings and previous studies, we conclude that the identical mutation (G59S) in the GJB2 gene contributes to various manifestations.