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Isolation, Culture, and Functional Characterization of Adult Mouse Cardiomyoctyes
Published on: September 24, 2013
Cardiac troponin T mutations result in allele-specific phenotypes in a mouse model for hypertrophic cardiomyopathy
J C Tardiff1, T E Hewett, B M Palmer
1Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA.
The Journal of Clinical Investigation
|August 17, 1999
Summary
Familial hypertrophic cardiomyopathy (FHC) linked to cardiac troponin T (cTnT) mutations causes sudden death. New R92Q cTnT mouse models reveal hypercontractility and diastolic dysfunction, offering insights into FHC pathogenesis.
Area of Science:
- Cardiovascular Biology
- Molecular Cardiology
- Genetics of Heart Disease
Background:
- Familial hypertrophic cardiomyopathy (FHC) is often caused by mutations in cardiac troponin T (cTnT).
- Patients with cTnT mutations typically show minimal ventricular hypertrophy but a high risk of sudden cardiac death.
- Understanding the cellular mechanisms underlying FHC phenotypes is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the functional consequences of a specific missense cTnT mutation (R92Q) associated with FHC.
- To develop and characterize novel transgenic mouse models expressing varying levels of the R92Q cTnT allele.
- To elucidate the cellular and molecular basis for the distinct clinical presentations of FHC.
Main Methods:
- Generation of transgenic mouse lines expressing different percentages (30%, 67%, 92%) of the R92Q cTnT missense mutation.
- Analysis of cardiac structure and function, including ventricular dimensions, gene expression (atrial natriuretic factor, beta-myosin heavy chain), and histopathology (fibrosis, mitochondrial pathology).
- Assessment of isolated cardiac myocyte function (sarcomeric activation, relaxation, sarcomere length) and ex vivo working heart performance (contractility, diastolic function).
Main Results:
- R92Q cTnT mouse hearts exhibited smaller left ventricles compared to wild-type, unlike truncation models.
- Significant induction of atrial natriuretic factor and beta-myosin heavy chain transcripts, interstitial fibrosis, and mitochondrial abnormalities were observed.
- Isolated R92Q myocytes showed increased basal sarcomeric activation, impaired relaxation, and shorter sarcomere lengths.
- Working hearts displayed hypercontractility and diastolic dysfunction, mirroring FHC patient phenotypes.
Conclusions:
- The R92Q cTnT mouse models are the first to exhibit hypercontractility and provide a valuable system for studying FHC cellular pathogenesis.
- Distinct phenotypes observed in mice with different cTnT alleles suggest that allele-specific mechanisms contribute to the clinical heterogeneity of FHC.
- These findings highlight the importance of specific cTnT mutations in driving FHC pathophysiology, including hypercontractility and diastolic dysfunction.
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