title: Phospholamban overexpression in mice causes a centronuclear myopathy-like phenotype.
abstract: Centronuclear myopathy (CNM) is a congenital myopathy that is histopathologically characterized by centrally located nuclei, central aggregation of oxidative activity, and type I fiber predominance and hypotrophy. Here, we obtained commercially available mice overexpressing phospholamban (Pln(OE)), a well-known inhibitor of sarco(endo)plasmic reticulum Ca(2+)-ATPases (SERCAs), in their slow-twitch type I skeletal muscle fibers to determine the effects on SERCA function. As expected with a 6- to 7-fold overexpression of phospholamban, SERCA dysfunction was evident in Pln(OE) muscles, with marked reductions in rates of Ca(2+) uptake, maximal ATPase activity and the apparent affinity of SERCA for Ca(2+). However, our most significant discovery was that the soleus and gluteus minimus muscles from the Pln(OE) mice displayed overt signs of myopathy: they histopathologically resembled human CNM, with centrally located nuclei, central aggregation of oxidative activity, type I fiber predominance and hypotrophy, progressive fibrosis and muscle weakness. This phenotype is associated with significant upregulation of muscle sarcolipin and dynamin 2, increased Ca(2+)-activated proteolysis, oxidative stress and protein nitrosylation. Moreover, in our assessment of muscle biopsies from three human CNM patients, we found a significant 53% reduction in SERCA activity and increases in both total and monomeric PLN content compared with five healthy subjects, thereby justifying future studies with more CNM patients. Altogether, our results suggest that the commercially available Pln(OE) mouse phenotypically resembles human CNM and could be used as a model to test potential mechanisms and therapeutic strategies. To date, there is no cure for CNM and our results suggest that targeting SERCA function, which has already been shown to be an effective therapeutic target for murine muscular dystrophy and human cardiomyopathy, might represent a novel therapeutic strategy to combat CNM.
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Val A
authors.initials: VA
authors.lastname: Fajardo
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Bombardier
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Elliott
authors.initials: E
authors.lastname: McMillan
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Khanh
authors.initials: K
authors.lastname: Tran
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Brennan J
authors.initials: BJ
authors.lastname: Wadsworth
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gamu
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hopf
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Chris
authors.initials: C
authors.lastname: Vigna
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Smith
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Catherine
authors.initials: C
authors.lastname: Bellissimo
authors.affiliation: Department of Exercise Science, Concordia University, Montreal, Quebec H4B 1R6, Canada.
authors.forename: Robin N
authors.initials: RN
authors.lastname: Michel
authors.affiliation: Departement of Kinesiology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada Department of Pediatrics, McMaster University, Hamilton, Ontario L8N 3Z5, Canada Department of Medicine, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Tarnopolsky
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Joe
authors.initials: J
authors.lastname: Quadrilatero
authors.affiliation: Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada rtupling@uwaterloo.ca.
authors.forename: A Russell
authors.initials: AR
authors.lastname: Tupling
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D034285:Dynamin II / Q000378:metabolism; D005355:Fibrosis; D006801:Humans; D008297:Male; D051379:Mice; D009132:Muscles / Q000201:enzymology / Q000473:pathology; D009133:Muscular Atrophy / Q000378:metabolism / Q000473:pathology; D009137:Muscular Dystrophy, Animal / Q000473:pathology; D020914:Myopathies, Structural, Congenital / Q000378:metabolism* / Q000473:pathology*; D018384:Oxidative Stress / Q000187:drug effects; D010641:Phenotype; D059748:Proteolysis / Q000187:drug effects; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D000099211:Phospholamban
chemical_list: D002118:Calcium; D002135:Calcium-Binding Proteins; D034285:Dynamin II; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban
keywords: Calcium regulation; Congenital myopathy; Dynamin 2; SERCA; Skeletal muscle