Inotropic Stimulation Induces Cardiac Dysfunction in Transgenic Mice Expressing a Troponin T (I79N) Mutation Linked to Familial Hypertrophic Cardiomyopathy

Björn C. Knollmann, Stephen A. Blatt, Kenneth Horton, Fatima De Freitas, Todd Miller, Michael Bell, Philippe R. Housmans, Neil J. Weissman, Martin Morad, James D. Potter

Research output: Contribution to journalArticle

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Abstract

The cardiac troponin T (TnT) I79N mutation has been linked to familial hypertrophic cardiomyopathy and a high incidence of sudden death, despite causing little or no cardiac hypertrophy. In skinned fibers, I79N increased myofilamental calcium sensitivity (Miller, T., Szczesna, D., Housmans, P. R., Zhao, J., deFreitas, F., Gomes, A. V., Culbreath, L., McCue, J., Wang, Y., Xu, Y., Kerrick, W. G., and Potter, J. D. (2001) J. Biol. Chem. 276, 3743-3755). To further study the functional consequences of this mutation, we compared the cardiac performance of transgenic mice expressing either human TnT-I79N or human wild-type TnT. In isolated hearts, cardiac function was different depending on the Ca2+ concentration of the perfusate; systolic function was significantly increased in Tg-I79N hearts at 0.5 and 1 mmol/liter. At higher Ca2+ concentrations, systolic function was not different, but diastolic dysfunction became manifest as increased end-diastolic pressure and time to 90% relaxation. In vivo measurements by echocardiography and Doppler confirmed that base-line systolic function was significantly higher in Tg-I79N mice without evidence for diastolic dysfunction. Inotropic stimulation with isoproterenol resulted only in a modest contractile response but caused significant mortality in Tg-I79N mice. Doppler studies ruled out aortic outflow obstruction and were consistent with increased chamber stiffness. We conclude that in vivo, the increased myofilament Ca2+ sensitivity due to the I79N mutation enhances base-line contractility but leads to cardiac dysfunction during inotropic stimulation.

Original languageEnglish
Pages (from-to)10039-10048
Number of pages10
JournalJournal of Biological Chemistry
Volume276
Issue number13
DOIs
StatePublished - Mar 30 2001
Externally publishedYes

Fingerprint

Familial Hypertrophic Cardiomyopathy
Troponin T
Transgenic Mice
Mutation
Doppler Echocardiography
Myofibrils
Cardiomegaly
Sudden Death
Isoproterenol
Echocardiography
Blood Pressure
Calcium
Mortality
Incidence
Stiffness
Fibers

ASJC Scopus subject areas

  • Biochemistry

Cite this

Inotropic Stimulation Induces Cardiac Dysfunction in Transgenic Mice Expressing a Troponin T (I79N) Mutation Linked to Familial Hypertrophic Cardiomyopathy. / Knollmann, Björn C.; Blatt, Stephen A.; Horton, Kenneth; De Freitas, Fatima; Miller, Todd; Bell, Michael; Housmans, Philippe R.; Weissman, Neil J.; Morad, Martin; Potter, James D.

In: Journal of Biological Chemistry, Vol. 276, No. 13, 30.03.2001, p. 10039-10048.

Research output: Contribution to journalArticle

Knollmann, BC, Blatt, SA, Horton, K, De Freitas, F, Miller, T, Bell, M, Housmans, PR, Weissman, NJ, Morad, M & Potter, JD 2001, 'Inotropic Stimulation Induces Cardiac Dysfunction in Transgenic Mice Expressing a Troponin T (I79N) Mutation Linked to Familial Hypertrophic Cardiomyopathy', Journal of Biological Chemistry, vol. 276, no. 13, pp. 10039-10048. https://doi.org/10.1074/jbc.M006745200
Knollmann, Björn C. ; Blatt, Stephen A. ; Horton, Kenneth ; De Freitas, Fatima ; Miller, Todd ; Bell, Michael ; Housmans, Philippe R. ; Weissman, Neil J. ; Morad, Martin ; Potter, James D. / Inotropic Stimulation Induces Cardiac Dysfunction in Transgenic Mice Expressing a Troponin T (I79N) Mutation Linked to Familial Hypertrophic Cardiomyopathy. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 13. pp. 10039-10048.
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abstract = "The cardiac troponin T (TnT) I79N mutation has been linked to familial hypertrophic cardiomyopathy and a high incidence of sudden death, despite causing little or no cardiac hypertrophy. In skinned fibers, I79N increased myofilamental calcium sensitivity (Miller, T., Szczesna, D., Housmans, P. R., Zhao, J., deFreitas, F., Gomes, A. V., Culbreath, L., McCue, J., Wang, Y., Xu, Y., Kerrick, W. G., and Potter, J. D. (2001) J. Biol. Chem. 276, 3743-3755). To further study the functional consequences of this mutation, we compared the cardiac performance of transgenic mice expressing either human TnT-I79N or human wild-type TnT. In isolated hearts, cardiac function was different depending on the Ca2+ concentration of the perfusate; systolic function was significantly increased in Tg-I79N hearts at 0.5 and 1 mmol/liter. At higher Ca2+ concentrations, systolic function was not different, but diastolic dysfunction became manifest as increased end-diastolic pressure and time to 90{\%} relaxation. In vivo measurements by echocardiography and Doppler confirmed that base-line systolic function was significantly higher in Tg-I79N mice without evidence for diastolic dysfunction. Inotropic stimulation with isoproterenol resulted only in a modest contractile response but caused significant mortality in Tg-I79N mice. Doppler studies ruled out aortic outflow obstruction and were consistent with increased chamber stiffness. We conclude that in vivo, the increased myofilament Ca2+ sensitivity due to the I79N mutation enhances base-line contractility but leads to cardiac dysfunction during inotropic stimulation.",
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AU - Knollmann, Björn C.

AU - Blatt, Stephen A.

AU - Horton, Kenneth

AU - De Freitas, Fatima

AU - Miller, Todd

AU - Bell, Michael

AU - Housmans, Philippe R.

AU - Weissman, Neil J.

AU - Morad, Martin

AU - Potter, James D.

PY - 2001/3/30

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N2 - The cardiac troponin T (TnT) I79N mutation has been linked to familial hypertrophic cardiomyopathy and a high incidence of sudden death, despite causing little or no cardiac hypertrophy. In skinned fibers, I79N increased myofilamental calcium sensitivity (Miller, T., Szczesna, D., Housmans, P. R., Zhao, J., deFreitas, F., Gomes, A. V., Culbreath, L., McCue, J., Wang, Y., Xu, Y., Kerrick, W. G., and Potter, J. D. (2001) J. Biol. Chem. 276, 3743-3755). To further study the functional consequences of this mutation, we compared the cardiac performance of transgenic mice expressing either human TnT-I79N or human wild-type TnT. In isolated hearts, cardiac function was different depending on the Ca2+ concentration of the perfusate; systolic function was significantly increased in Tg-I79N hearts at 0.5 and 1 mmol/liter. At higher Ca2+ concentrations, systolic function was not different, but diastolic dysfunction became manifest as increased end-diastolic pressure and time to 90% relaxation. In vivo measurements by echocardiography and Doppler confirmed that base-line systolic function was significantly higher in Tg-I79N mice without evidence for diastolic dysfunction. Inotropic stimulation with isoproterenol resulted only in a modest contractile response but caused significant mortality in Tg-I79N mice. Doppler studies ruled out aortic outflow obstruction and were consistent with increased chamber stiffness. We conclude that in vivo, the increased myofilament Ca2+ sensitivity due to the I79N mutation enhances base-line contractility but leads to cardiac dysfunction during inotropic stimulation.

AB - The cardiac troponin T (TnT) I79N mutation has been linked to familial hypertrophic cardiomyopathy and a high incidence of sudden death, despite causing little or no cardiac hypertrophy. In skinned fibers, I79N increased myofilamental calcium sensitivity (Miller, T., Szczesna, D., Housmans, P. R., Zhao, J., deFreitas, F., Gomes, A. V., Culbreath, L., McCue, J., Wang, Y., Xu, Y., Kerrick, W. G., and Potter, J. D. (2001) J. Biol. Chem. 276, 3743-3755). To further study the functional consequences of this mutation, we compared the cardiac performance of transgenic mice expressing either human TnT-I79N or human wild-type TnT. In isolated hearts, cardiac function was different depending on the Ca2+ concentration of the perfusate; systolic function was significantly increased in Tg-I79N hearts at 0.5 and 1 mmol/liter. At higher Ca2+ concentrations, systolic function was not different, but diastolic dysfunction became manifest as increased end-diastolic pressure and time to 90% relaxation. In vivo measurements by echocardiography and Doppler confirmed that base-line systolic function was significantly higher in Tg-I79N mice without evidence for diastolic dysfunction. Inotropic stimulation with isoproterenol resulted only in a modest contractile response but caused significant mortality in Tg-I79N mice. Doppler studies ruled out aortic outflow obstruction and were consistent with increased chamber stiffness. We conclude that in vivo, the increased myofilament Ca2+ sensitivity due to the I79N mutation enhances base-line contractility but leads to cardiac dysfunction during inotropic stimulation.

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