AAV-mediated intramuscular delivery of myotubularin corrects the myotubular myopathy phenotype in targeted murine muscle and suggests a function in plasma membrane homeostasis.
Myotubular myopathy (XLMTM, OMIM 310400) is a severe congenital muscular disease due to mutations in the myotubularin gene (MTM1) and characterized by the presence of small myofibers with frequent occurrence of central nuclei. Myotubularin is a ubiquitously expressed phosphoinositide phosphatase with a muscle-specific role in man and mouse that is poorly understood. No specific treatment exists to date for patients with myotubular myopathy. We have constructed an adeno-associated virus (AAV) vector expressing myotubularin in order to test its therapeutic potential in a XLMTM mouse model. We show that a single intramuscular injection of this vector in symptomatic Mtm1-deficient mice ameliorates the pathological phenotype in the targeted muscle. Myotubularin replacement in mice largely corrects nuclei and mitochondria positioning in myofibers and leads to a strong increase in muscle volume and recovery of the contractile force. In addition, we used this AAV vector to overexpress myotubularin in wild-type skeletal muscle and get insight into its localization and function. We show that a substantial proportion of myotubularin associates with the sarcolemma and I band, including triads. Myotubularin overexpression in muscle induces the accumulation of packed membrane saccules and presence of vacuoles that contain markers of sarcolemma and T-tubules, suggesting that myotubularin is involved in plasma membrane homeostasis of myofibers. This study provides a proof-of-principle that local delivery of an AAV vector expressing myotubularin can improve the motor capacities of XLMTM muscle and represents a novel approach to study myotubularin function in skeletal muscle.
Buj-Bello
Anna
A
Department of Neurobiology and Genetics, , INSERM U596, CNRS UMR 7104, Université Louis Pasteur de Strasbourg, Collège de France, 67404 Illkirch, France. mtm@igbmc.u-strasbg.fr
Fougerousse
Françoise
F
Schwab
Yannick
Y
Messaddeq
Nadia
N
Spehner
Danièle
D
Pierson
Christopher R
CR
Durand
Muriel
M
Kretz
Christine
C
Danos
Olivier
O
Douar
Anne-Marie
AM
Beggs
Alan H
AH
Schultz
Patrick
P
Montus
Marie
M
Denèfle
Patrice
P
Mandel
Jean-Louis
JL
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000229:Dependovirus / Q000235:genetics / Q000378:metabolism; D005260:Female; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D006706:Homeostasis; D007273:Injections, Intramuscular; D008297:Male; D051379:Mice; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020914:Myopathies, Structural, Congenital / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D010641:Phenotype; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000008:administration & dosage / Q000032:analysis / Q000235:genetics* / Q000378:metabolism
D054558:Protein Tyrosine Phosphatases, Non-Receptor; C099588:myotubularin