title: Four-week rapamycin treatment improves muscular dystrophy in a fukutin-deficient mouse model of dystroglycanopathy.
abstract: BACKGROUND
  Secondary dystroglycanopathies are a subset of muscular dystrophy caused by abnormal glycosylation of α-dystroglycan (αDG). Loss of αDG functional glycosylation prevents it from binding to laminin and other extracellular matrix receptors, causing muscular dystrophy. Mutations in a number of genes, including FKTN (fukutin), disrupt αDG glycosylation.
  
  
  METHODS
  We analyzed conditional Fktn knockout (Fktn KO) muscle for levels of mTOR signaling pathway proteins by Western blot. Two cohorts of Myf5-cre/Fktn KO mice were treated with the mammalian target of rapamycin (mTOR) inhibitor rapamycin (RAPA) for 4 weeks and evaluated for changes in functional and histopathological features.
  
  
  RESULTS
  Muscle from 17- to 25-week-old fukutin-deficient mice has activated mTOR signaling. However, in tamoxifen-inducible Fktn KO mice, factors related to Akt/mTOR signaling were unchanged before the onset of dystrophic pathology, suggesting that Akt/mTOR signaling pathway abnormalities occur after the onset of disease pathology and are not causative in early dystroglycanopathy development. To determine any pharmacological benefit of targeting mTOR signaling, we administered RAPA daily for 4 weeks to Myf5/Fktn KO mice to inhibit mTORC1. RAPA treatment reduced fibrosis, inflammation, activity-induced damage, and central nucleation, and increased muscle fiber size in Myf5/Fktn KO mice compared to controls. RAPA-treated KO mice also produced significantly higher torque at the conclusion of dosing.
  
  
  CONCLUSIONS
  These findings validate a misregulation of mTOR signaling in dystrophic dystroglycanopathy skeletal muscle and suggest that such signaling molecules may be relevant targets to delay and/or reduce disease burden in dystrophic patients.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 240 W. Green St., Athens, GA 30602 USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Foltz
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 240 W. Green St., Athens, GA 30602 USA.
authors.forename: Junna
authors.initials: J
authors.lastname: Luan
authors.affiliation: Department of Kinesiology, University of Georgia, Athens, GA 30602 USA ; Regenerative Bioscience Center, University of Georgia, Athens, GA 30602 USA.
authors.forename: Jarrod A
authors.initials: JA
authors.lastname: Call
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 240 W. Green St., Athens, GA 30602 USA.
authors.forename: Ankit
authors.initials: A
authors.lastname: Patel
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 240 W. Green St., Athens, GA 30602 USA.
authors.forename: Kristen B
authors.initials: KB
authors.lastname: Peissig
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 240 W. Green St., Athens, GA 30602 USA.
authors.forename: Marisa J
authors.initials: MJ
authors.lastname: Fortunato
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 240 W. Green St., Athens, GA 30602 USA.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Beedle
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D015536:Down-Regulation; D049030:Dystroglycans / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D020022:Genetic Predisposition to Disease; D006031:Glycosylation; D008297:Male; D018345:Mice, Knockout; D009119:Muscle Contraction; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009137:Muscular Dystrophy, Animal / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D051787:Myogenic Regulatory Factor 5 / Q000172:deficiency / Q000235:genetics; D010641:Phenotype; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors; D019415:Torque; D014166:Transferases
chemical_list: C497418:Myf5 protein, mouse; D051787:Myogenic Regulatory Factor 5; D047428:Protein Kinase Inhibitors; D011506:Proteins; D049030:Dystroglycans; C491879:Fcmd protein, mouse; D014166:Transferases; C546843:mTOR protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
keywords: Dystroglycan; Fukutin; Mammalian target of rapamycin (mTOR); Muscular dystrophy; Rapamycin; Skeletal muscle