Transgenic rabbit model for human troponin I-based hypertrophic cardiomyopathy.

Abstract

BACKGROUND:

Transgenic and gene-targeted models have focused on the mouse. Fundamental differences between the mouse and human exist in Ca2+ handling during contraction/relaxation and in alterations in Ca2+ flux during heart failure, with the rabbit more accurately reflecting the human system.

METHODS AND RESULTS:

Cardiac troponin I (cTnI) mutations can cause familial hypertrophic cardiomyopathy. An inhibitory domain mutation, arginine146-->glycine (cTnI(146Gly)), was modeled with the use of transgenic expression in the rabbit ventricle. cTnI(146Gly) levels >40% of total cTnI were perinatally lethal, whereas replacement levels of 15% to 25% were well tolerated. cTnI(146Gly) expression led to a leftward shift in the force-pCa2+ curves with cardiomyocyte disarray, fibrosis, and altered connexin43 organization. In isolated cTnI(146Gly) myocytes, twitch relaxation amplitudes were smaller than in normal cells, but [Ca]i transients and sarcoplasmic reticulum Ca2+ load were not different. Detrended fluctuation analysis of the QT(max) intervals was used to evaluate the cardiac repolarization phase and showed a significantly higher scaling exponent in the transgenic animals.

CONCLUSIONS:

Expression of modest amounts of cTnI(146Gly) led to subtle defects without severely affecting cardiac function. Aberrant connexin organization, subtle morphological deficits, and an altered fractal pattern of the repolarization phase of transgenic rabbits, in the absence of entropy or other ECG abnormalities, may indicate an early developing pathology before the onset of more obvious repolarization abnormalities or major alterations in cardiac mechanics.

• Authors: Atsushi Sanbe, Jeanne James, Volkan Tuzcu, Selman Nas, Lisa Martin, James Gulick, Hanna Osinska, Sadayappan Sakthivel, Raisa Klevitsky, Kenneth S Ginsburg, Donald M Bers, Bruce Zinman, Edward G Lakatta, Jeffrey Robbins
• Journal: Circulation (Circulation) Vol. 111 Issue 18 Pg. 2330-8 (May 10 2005) ISSN: 1524-4539 [Electronic] United States
• PMID: 15867176 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Connexin 43
• Troponin I
• Calcium

Topics

• Animals
• Animals, Genetically Modified
• Calcium (metabolism)
• Cardiomegaly
• Cardiomyopathy, Hypertrophic, Familial (genetics, pathology, physiopathology)
• Connexin 43 (metabolism)
• Disease Models, Animal
• Electrocardiography
• Fibrosis
• Heart Function Tests
• Heart Ventricles (metabolism)
• Humans
• Mutation, Missense
• Myocytes, Cardiac (pathology)
• Phenotype
• Rabbits
• Transgenes
• Troponin I (genetics)