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<jats:p> To study the mechanisms by which missense mutations in α-tropomyosin cause familial hypertrophic cardiomyopathy, we generated transgenic rats overexpressing α-tropomyosin with one of two disease-causing mutations, Asp<jats:sup>175</jats:sup>Asn or Glu<jats:sup>180</jats:sup>Gly, and analyzed phenotypic changes at molecular, morphological, and physiological levels. The transgenic proteins were stably integrated into the sarcomere, as shown by immunohistochemistry using a human-specific anti-α-tropomyosin antibody, ARG1. In transgenic rats with either α-tropomyosin mutation, molecular markers of cardiac hypertrophy were induced. Ca<jats:sup>2+</jats:sup> sensitivity of cardiac skinned-fiber preparations from animals with mutation Asp<jats:sup>175</jats:sup>Asn, but not Glu<jats:sup>180</jats:sup>Gly, was decreased. Furthermore, elevated frequency and amplitude of spontaneous Ca<jats:sup>2+</jats:sup> waves were detected only in cardiomyocytes from animals with mutation Asp<jats:sup>175</jats:sup>Asn, suggesting an increase in intracellular Ca<jats:sup>2+</jats:sup> concentration compensating for the reduced Ca<jats:sup>2+</jats:sup> sensitivity of isometric force generation. Accordingly, in Langendorff-perfused heart preparations, myocardial contraction and relaxation were accelerated in animals with mutation Asp<jats:sup>175</jats:sup>Asn. The results allow us to propose a hypothesis of the pathogenetic changes caused by α-tropomyosin mutation Asp<jats:sup>175</jats:sup>Asn in familial hypertrophic cardiomyopathy on the basis of changes in Ca<jats:sup>2+</jats:sup> handling as a sensitive mechanism to compensate for alterations in sarcomeric structure. </jats:p>

Original publication

DOI

10.1152/ajpregu.00620.2003

Type

Journal article

Journal

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

Publisher

American Physiological Society

Publication Date

09/2004

Volume

287

Pages

R685 - R695