Cardiac-Myocyte-Specific Excision of the Vinculin Gene Disrupts Cellular Junctions, Causing Sudden Death or Dilated Cardiomyopathy

Abstract

Vinculin is a ubiquitously expressed multiliganded protein that links the actin cytoskeleton to the cell membrane. In myocytes, it is localized in protein complexes which anchor the contractile apparatus to the sarcolemma. Its function in the myocardium remains poorly understood. Therefore, we developed a mouse model with cardiac-myocyte-specific inactivation of the vinculin (Vcl) gene by using Cre-loxP technology. Sudden death was found in 49% of the knockout (cVclKO) mice younger than 3 months of age despite preservation of contractile function. Conscious telemetry documented ventricular tachycardia as the cause of sudden death, while defective myocardial conduction was detected by optical mapping. cVclKO mice that survived through the vulnerable period of sudden death developed dilated cardiomyopathy and died before 6 months of age. Prior to the onset of cardiac dysfunction, ultrastructural analysis of cVclKO heart tissue showed abnormal adherens junctions with dissolution of the intercalated disc structure, expression of the junctional proteins cadherin and β1D integrin were reduced, and the gap junction protein connexin 43 was mislocalized to the lateral myocyte border. This is the first report of tissue-specific inactivation of the Vcl gene and shows that it is required for preservation of normal cell-cell and cell-matrix adhesive structures.

We thank Ju Chen and Kirk Knowlton as well as members of the Ross, Chen, and Knowlton laboratories for helpful criticisms and Steve Padilla for expert technical assistance. Jon Seidman and Paul Clopton provided useful discussion on statistical analyses.

This work was supported by NIH grants HL57872 and HL73393 and a Veterans Administration Merit Award to R.S.R. A.D.M. was supported by NIH grant HL46345 and NSF grant BES-0506252. A portion of the work was performed in UCSD's NCMIR, supported by P41-R004050 from NIH.