alpha-Tropomyosin mutations Asp(175)Asn and Glu(180)Gly affect cardiac function in transgenic rats in different ways.
To study the mechanisms by which missense mutations in alpha-tropomyosin cause familial hypertrophic cardiomyopathy, we generated transgenic rats overexpressing alpha-tropomyosin with one of two disease-causing mutations, Asp(175)Asn or Glu(180)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-alpha-tropomyosin antibody, ARG1. In transgenic rats with either alpha-tropomyosin mutation, molecular markers of cardiac hypertrophy were induced. Ca(2+) sensitivity of cardiac skinned-fiber preparations from animals with mutation Asp(175)Asn, but not Glu(180)Gly, was decreased. Furthermore, elevated frequency and amplitude of spontaneous Ca(2+) waves were detected only in cardiomyocytes from animals with mutation Asp(175)Asn, suggesting an increase in intracellular Ca(2+) concentration compensating for the reduced Ca(2+) sensitivity of isometric force generation. Accordingly, in Langendorff-perfused heart preparations, myocardial contraction and relaxation were accelerated in animals with mutation Asp(175)Asn. The results allow us to propose a hypothesis of the pathogenetic changes caused by alpha-tropomyosin mutation Asp(175)Asn in familial hypertrophic cardiomyopathy on the basis of changes in Ca(2+) handling as a sensitive mechanism to compensate for alterations in sarcomeric structure.
Wernicke
Dirk
D
Max-Delbrück Center for Molecular Medicine, Robert-Roessle-Str. 10, Berlin 13092, Germany. dwernic@mdc-berlin.de
Thiel
Corinna
C
Duja-Isac
Corina M
CM
Essin
Kirill V
KV
Spindler
Matthias
M
Nunez
Derek J R
DJ
Plehm
Ralph
R
Wessel
Niels
N
Hammes
Annette
A
Edwards
Robert-J
RJ
Lippoldt
Andrea
A
Zacharias
Ute
U
Strömer
Hinrik
H
Neubauer
Stefan
S
Davies
Michael J
MJ
Morano
Ingo
I
Thierfelder
Ludwig
L
D000818:Animals; D030801:Animals, Genetically Modified; D001216:Asparagine; D001224:Aspartic Acid; D015415:Biomarkers / Q000032:analysis; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D024741:Cardiomyopathy, Hypertrophic, Familial / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D015870:Gene Expression; D018698:Glutamic Acid; D005998:Glycine; D006321:Heart / Q000503:physiopathology*; D006352:Heart Ventricles; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D018485:Muscle Fibers, Skeletal / Q000187:drug effects; D020125:Mutation, Missense; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism; D051381:Rats; D012518:Sarcomeres / Q000378:metabolism; D019076:Transgenes; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism
D015415:Biomarkers; D014335:Tropomyosin; D001224:Aspartic Acid; D018698:Glutamic Acid; D001216:Asparagine; D002118:Calcium; D005998:Glycine