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A cytoskeletal tropomyosin can compromise the structural integrity of skeletal muscle

Anthony J Kee1, Peter W Gunning, Edna C Hardeman

  • 1Department of Anatomy, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.

Cell Motility and the Cytoskeleton
|June 17, 2009
PubMed

Insights

Introducing tropomyosin (Tm) isoforms, this study reveals that expressing an abnormal cytoskeletal Tm3 in mice leads to muscular dystrophy. This condition increases susceptibility to muscle damage during exercise and contraction.

Area of Science:

  • Muscle physiology
  • Molecular biology
  • Genetics

Background:

  • Extra-sarcomeric actin filaments are defined by cytoskeletal tropomyosin (Tm) isoforms.
  • Expression of non-native cytoskeletal Tm isoforms in skeletal muscle can induce muscular dystrophy.

Purpose of the Study:

  • To investigate the impact of expressing a non-native cytoskeletal tropomyosin (Tm3) isoform in skeletal muscle.
  • To characterize the onset, affected muscles, and functional consequences of Tm3-induced muscular dystrophy in a transgenic mouse model.

Main Methods:

  • Generation of transgenic mice expressing Tm3 in skeletal muscle.
  • Assessment of muscle pathology onset and localization.
  • Measurement of Evans blue dye uptake and serum creatine kinase levels post-exercise.
  • Evaluation of muscle force drop following lengthening contractions in isolated extensor digitorum longus muscles.

Main Results:

  • Muscle pathology in Tm3 mice is late-onset (2-6 months) and predominantly affects back and paraspinal muscles.
  • Tm3 mice exhibited significantly increased Evans blue dye uptake and serum creatine kinase levels after downhill exercise.
  • Isolated muscles from Tm3 mice showed a significantly greater force drop after repeated lengthening contractions.

Conclusions:

  • Expression of inappropriate tropomyosin isoforms in skeletal muscle leads to increased susceptibility to contraction-induced damage.
  • The extra-sarcomeric actin cytoskeleton plays a crucial role in protecting muscles against contractile stress.
  • This study highlights the importance of specific Tm isoform expression for maintaining skeletal muscle integrity and function.

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