Background

The small GTP binding protein is a key regulator of cell growth in eukaryotic cells and has been implicated in the hypertrophic response of cardiomyocytes both in vitro and in vivo (Thorburn et al., 1993; Hunter et al., 1995; Sadoshima & Izumo, 1996; Abdellatif et al., 1998). Previous studies have shown that mice with ventricular-specific overexpression of constitutively active display morphological, physiological, and genetic markers of marked concentric hypertrophy, qualitatively similar to those seen in hypertrophy due to pressure overload (Hunter et al., 1995).

In order to determine the cardiac-specific "loss of function" phenotype, we generated transgenic mice overexpressing the dominant-negative (dn) form of (H-rasN17). Transgenic mice show severe cardiac dilation with decreased contractility, which is associated with lethality within 10 weeks of age (mean 69 4 days). Histopathological analysis did not reveal any signs of myocyte disarray, necrosis or interstitial fibrosis (not shown). Examination of ECG by a novel noninvasive technique showed a slower heart rate. On echocardiography, the left ventricular diastolic diameter was increased (5.5 0.4 vs 3.4 0.1 mm, p<0.001) and fractional shortening was decreased (25 3 vs 65 6, p<0.001) (Shioi et al., unpublished). Low frequency of TUNEL positive cells were detected, most of which were non-myocytes. Dn- mice provide a model of severe cardiac dilation and an opportunity to study the cellular mechanisms regulating cardiac contractility.

Experimental Design

Mice heterozygous for dn- and non-transgenic littermates were sacrificed at 10 weeks of age. Ventricles were isolated and snap-frozen in liquid nitrogen as described.

Back to top^

Page last modified: 08-Jan-2003