Prabhakar R, Boivin GP, Grupp IL, Hoit B, Arteaga G, Solaro RJ, Wieczorek DF. A familial hypertrophic cardiomyopathy alpha-tropomyosin mutation causes severe cardiac hypertrophy and death in mice.
J Mol Cell Cardiol 2001;
33:1815-28. [PMID:
11603924 DOI:
10.1006/jmcc.2001.1445]
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Abstract
Tropomyosin, an essential component of the sarcomere, regulates muscle contraction through Ca(2+)-mediated activation. Familial hypertrophic cardiomyopathy (FHC) is caused by mutations in numerous cardiac sarcomeric proteins, including myosin heavy and light chains, actin, troponin T and I, myosin binding protein C, and alpha-tropomyosin. This study developed transgenic mouse lines that encode an FHC mutation in alpha-tropomyosin; this mutation is an amino acid substitution at codon 180 (Glu180Gly) which occurs in a troponin T binding region. Non-transgenic and control mice expressing wild-type alpha-tropomyosin demonstrate no morphological or physiological changes. Expression of exogenous mutant tropomyosin leads to a concomitant decrease in endogenous alpha-tropomyosin without altering the expression of other contractile proteins. Histological analysis shows that initial pathological changes, which include ventricular concentric hypertrophy, fibrosis and atrial enlargement, are detected within 1 month. The disease-associated changes progressively increase and result in death between 4 and 5 months. Physiological analyses of the FHC mice using echocardiography, work-performing heart analyses, and force measurements of cardiac myofibers, demonstrate dramatic functional differences in diastolic performance and increased sensitivity to calcium. This report demonstrates that mutations in alpha-tropomyosin can be severely disruptive of sarcomeric function, which consequently triggers a dramatic hypertrophic response that culminates in lethality.
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