Obstructive hypertrophic cardiomyopathy is associated with reduced expression of vinculin in the intercalated disc

Mutations in the cardiac-specific insert of vinculin, metavinculin, rarely cause hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Subsequently, a missense mutation in the ubiquitously expressed vinculin was discovered in a patient with obstructive HCM. Microscopic examination of both myectomy specimens from patients bearing genetic defects in metavinculin and vinculin showed a marked reduction of vinculin/metavinculin expression in the intercalated disc, but normal expression in the Z-disc. Given that distinct functional domains were altered by the metavinculin and vinculin mutations, we hypothesized that the intercalated disc-specific reduction of vinculin may stem from left ventricular tract obstruction in general rather than rarely observed perturbations in VCL-encoded vinculin. To test this hypothesis, we examined the localization of vinculin/metavinculin in hypertrophied human heart tissue from patients with cardiovascular conditions associated with obstruction and hemodynamic overload using an immunohistochemistry approach. Tissue specimens derived from patients with obstructive HCM and aortic stenosis (AS) showed a universal defect of vinculin/metavinculin expression in the intercalated disc but preserved expression in the cardiac Z-disc, whereas tissue specimens derived from patients with either DCM, hypertensive heart disease (HTN), or pulmonary hypertension (PHTN) exhibited normal expression of vinculin/metavinculin in both the Z- and the intercalated disc despite being associated with hypertrophy. Results of this study suggest that cardiac hypertrophy may be associated with different expression of the marker vinculin/metavinculin depending on the underlying pathophysiology; hemodynamic overload may not affect the localization whereas obstructive disease substantially reduces the expression of vinculin preferentially in the intercalated disc.