Alterations at the Cross-Bridge Level Are Associated with a Paradoxical Gain of Muscle Function In Vivo in a Mouse Model of Nemaline Myopathy

Charlotte Gineste (1) , Coen Ottenheijm (2) , Yann Le Fur (1) , Sébastien Banzet (3) , Emilie Pecchi (1) , Christophe Vilmen (1) , Patrick J. Cozzone (1) , Nathalie Koulmann (3) , Edna C Hardeman (4) , David Bendahan (1) , Julien Gondin (1)

1 CRMBM - Centre de résonance magnétique biologique et médicale
2 Department of Physiology
3 CRSSA - Centre de Recherches du Service de Santé des Armées
4 UNSW - University of New South Wales [Sydney]

Nemaline myopathy is the most common disease entity among non-dystrophic skeletal muscle congenital diseases. The first disease causing mutation (Met9Arg) was identified in the gene encoding a-tropomyosin slow gene (TPM3). Considering the conflicting findings of the previous studies on the transgenic (Tg) mice carrying the TPM3 Met9Arg mutation, we investigated carefully the effect of the Met9Arg mutation in 8–9 month-old Tg(TPM3) Met9Arg mice on muscle function using a multiscale methodological approach including skinned muscle fibers analysis and in vivo investigations by magnetic resonance imaging and 31-phosphorus magnetic resonance spectroscopy. While in vitro maximal force production was reduced in Tg(TPM3) Met9Arg mice as compared to controls, in vivo measurements revealed an improved mechanical performance in the transgenic mice as compared to the former. The reduced in vitro muscle force might be related to alterations occuring at the cross-bridges level with muscle-specific underlying mechanisms. In vivo muscle improvement was not associated with any changes in either muscle volume or energy metabolism. Our findings indicate that TPM3(Met9Arg) mutation leads to a mild muscle weakness in vitro related to an alteration at the cross-bridges level and a paradoxical gain of muscle function in vivo. These results clearly point out that in vitro alterations are muscle-dependent and do not necessarily translate into similar changes in vivo.

Keywords: Mouse models; Muscle functions; Muscle fibers; Muscle analysis; Muscle proteins; Skeletal muscles; Myosins; Muscle contraction

Domains: Life Sciences [q-bio]; Human health and pathology; Life Sciences [q-bio]; Genetics; Engineering Sciences [physics]; Mechanics [physics.med-ph]; Biomechanics [physics.med-ph]

Charlotte Gineste, Coen Ottenheijm, Yann Le Fur, Sébastien Banzet, Emilie Pecchi, et al.. Alterations at the Cross-Bridge Level Are Associated with a Paradoxical Gain of Muscle Function In Vivo in a Mouse Model of Nemaline Myopathy. PLoS ONE, 2014, 9 (9), pp.e109066. ⟨10.1371/journal.pone.0109066⟩. ⟨hal-01772506⟩