Differential susceptibility of muscles to myotonia and force impairment in a mouse model of myotonic dystrophy

Muscle Nerve. 2011 Jun;43(6):818-27. doi: 10.1002/mus.21988. Epub 2011 Mar 14.

Abstract

Introduction: Myotonic dystrophy, or dystrophia myotonica (DM), is characterized by prominent muscle wasting and weakness as well as delayed muscle relaxation resulting from persistent electrical discharges.

Methods: We hypothesized heterogeneity among muscles in degree of weakness and myotonia in an expanded [(CUG)(250)] repeats transgenic (HSA(LR)) mouse DM model. Muscle contraction was compared among diaphragm, extensor digitorum longus (EDL), and soleus muscles.

Results: Myotonia was found only in EDL, as manifested by longer late-relaxation time and elevated myotonic index. EDL, but not the other two muscles, had impaired force over a wide range of stimulation frequencies. During fatigue-inducing stimulation, DM EDL muscle force per cross-sectional area was significantly impaired during 25-Hz stimulation, whereas there were no differences in fatigue response for DM diaphragm or soleus.

Conclusion: In an expanded repeats model of DM the EDL is more susceptible to myotonia and force impairment than muscles with lower proportions of fast-twitch fibers.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Disease Models, Animal
  • Electric Stimulation / methods
  • Electromyography / methods
  • Genetic Predisposition to Disease / genetics*
  • Mice
  • Mice, Transgenic
  • Muscle Contraction / genetics
  • Muscle Strength* / genetics
  • Muscle Weakness / diagnosis
  • Muscle Weakness / genetics*
  • Muscle Weakness / physiopathology*
  • Muscle, Skeletal / physiopathology*
  • Myotonic Dystrophy / diagnosis
  • Myotonic Dystrophy / genetics*
  • Myotonic Dystrophy / physiopathology*
  • Trinucleotide Repeat Expansion / genetics