Human Molecular Genetics Advance Access first published online on April 22, 2008
This version published online on April 28, 2008
Human Molecular Genetics, doi:10.1093/hmg/ddn112
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AAV-mediated intramuscular delivery of myotubularin corrects the myotubular myopathy phenotype in targeted murine muscle and suggests a function in plasma membrane homeostasis
1 Department of Neurobiology and Genetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U596, CNRS UMR 7104, Université Louis Pasteur Collège de France, 67404 Illkirch, France 2 Généthon, R&D Department, 1 rue de l'Internationale, 91000 Evry 3 Imaging Center – Electron Microscopy, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U596, CNRS UMR 7104, Université Louis Pasteur 4 Department of Structural Biology and Genomics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U596, CNRS UMR 7104, Université Louis Pasteur 5 Children's Hospital, Harvard Medical School, Boston, USA
* To whom correspondence should be adressed: 1, rue Laurent Fries, BP. 10142, 67404 Illkirch, France. Telephone: +33 3 88653244. Fax: +33 3 88653246. Email: mtm{at}igbmc.u-strasbg.fr
Received December 10, 2007; Revised April 5, 2008; Accepted April 8, 2008
Myotubular myopathy (XLMTM, OMIM 310400 [OMIM] ) is a severe congenital muscular disease due to mutations in the myotubularin gene (MTM1) and characterized by the presence of small myofibres with frequent occurence 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 myofibres 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 insights into its localisation and function. We show that a substantial proportion of myotubularin associates to 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 myofibres. 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.
6 Present address: Research Institute at Nationwide Children's Hospital, Columbus, USA
7 Present address: INSERM U781, Hôpital Necker-Enfants Malades, Paris, France