title: Expression of the dystrophin isoform Dp116 preserves functional muscle mass and extends lifespan without preventing dystrophy in severely dystrophic mice.
abstract: Dp116 is a non-muscle isoform of dystrophin that assembles the dystrophin-glycoprotein complex (DGC), but lacks actin-binding domains. To examine the functional role of the DGC, we expressed the Dp116 transgene in mice lacking both dystrophin and utrophin (mdx:utrn(-/-)). Unexpectedly, expression of Dp116 prevented the most severe aspects of the mdx:utrn(-/-) phenotype. Dp116:mdx:utrn(-/-) transgenic mice had dramatic improvements in growth, mobility and lifespan compared with controls. This was associated with increased muscle mass and force generating capacity of limb muscles, although myofiber size and specific force were unchanged. Conversely, Dp116 had no effect on dystrophic injury as determined by muscle histopathology and serum creatine kinase levels. Dp116 also failed to restore normal fiber-type distribution or the post-synaptic architecture of the neuromuscular junction. These data demonstrate that the DGC is critical for growth and maintenance of muscle mass, a function that is independent of the ability to prevent dystrophic pathophysiology. Likewise, this is the first demonstration in skeletal muscle of a positive functional role for a dystrophin protein that lacks actin-binding domains. We conclude that both mechanical and non-mechanical functions of dystrophin are important for its role in skeletal muscle.
authors.affiliation: Department of Neurology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195-7720, USA.
authors.forename: Luke M
authors.initials: LM
authors.lastname: Judge
authors.forename: Andrea L H
authors.initials: AL
authors.lastname: Arnett
authors.forename: Glen B
authors.initials: GB
authors.lastname: Banks
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Chamberlain
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003402:Creatine Kinase / Q000097:blood; D016189:Dystrophin / Q000737:chemistry / Q000378:metabolism*; D004947:Esophagus / Q000473:pathology; D005260:Female; D008136:Longevity; D008297:Male; D051379:Mice; D018101:Mice, Inbred mdx; D008822:Mice, Transgenic; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology* / Q000648:ultrastructure; D009137:Muscular Dystrophy, Animal / Q000097:blood / Q000473:pathology* / Q000503:physiopathology / Q000517:prevention & control*; D009469:Neuromuscular Junction / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D009929:Organ Size; D020033:Protein Isoforms / Q000378:metabolism; D016019:Survival Analysis; D049411:Utrophin / Q000172:deficiency / Q000378:metabolism
chemical_list: D016189:Dystrophin; D020033:Protein Isoforms; D049411:Utrophin; D003402:Creatine Kinase