title: Dynamin-2 mutations associated with centronuclear myopathy are hypermorphic and lead to T-tubule fragmentation.
abstract: Skeletal muscle requires adequate membrane trafficking and remodeling to maintain its normal structure and functions. Consequently, many human myopathies are caused by mutations in membrane trafficking machinery. The large GTPase dynamin-2 (Dyn2) is best known for catalyzing membrane fission during clathrin-mediated endocytosis (CME), which is critical for cell signaling and survival. Despite its ubiquitous expression, mutations of Dyn2 are associated with two tissue-specific congenital disorders: centronuclear myopathy (CNM) and Charcot-Marie-Tooth (CMT) neuropathy. Several disease models for CNM-Dyn2 have been established to study its pathogenic mechanism; yet the cellular and biochemical effects of these mutations are still not fully understood. Here we comprehensively compared the biochemical activities of disease-associated Dyn2 mutations and found that CNM-Dyn2 mutants are hypermorphic with enhanced membrane fission activity, whereas CMT-Dyn2 is hypomorphic. More importantly, we found that the expression of CNM-Dyn2 mutants does not impair CME in myoblast, but leads to T-tubule fragmentation in both C2C12-derived myotubes and Drosophila body wall muscle. Our results demonstrate that CNM-Dyn2 mutants are gain-of-function mutations, and their primary effect in muscle is T-tubule disorganization, which explains the susceptibility of muscle to Dyn2 hyperactivity.
authors.affiliation: Institute of Molecular Medicine, College of Medicine.
authors.forename: Yu-Han
authors.initials: YH
authors.lastname: Chin
authors.affiliation: Department of Chemistry, College of Science and.
authors.forename: Albert
authors.initials: A
authors.lastname: Lee
authors.affiliation: Graduate Institute of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: Hung-Wei
authors.initials: HW
authors.lastname: Kan
authors.affiliation: Institute of Molecular Medicine, College of Medicine.
authors.forename: Jessica
authors.initials: J
authors.lastname: Laiman
authors.affiliation: Institute of Molecular Medicine, College of Medicine.
authors.forename: Mei-Chun
authors.initials: MC
authors.lastname: Chuang
authors.affiliation: Graduate Institute of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: Sung-Tsang
authors.initials: ST
authors.lastname: Hsieh
authors.affiliation: Institute of Molecular Medicine, College of Medicine, yawenliu@ntu.edu.tw.
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Liu
mesh_terms: D000818:Animals; D002460:Cell Line; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002966:Clathrin / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D034285:Dynamin II / Q000235:genetics* / Q000378:metabolism; D004705:Endocytosis; D006801:Humans; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism; D009154:Mutation; D020914:Myopathies, Structural, Congenital / Q000235:genetics / Q000378:metabolism / Q000473:pathology*
chemical_list: D002966:Clathrin; D029721:Drosophila Proteins; C000608793:DNM2 protein, Drosophila; C000608792:DNM2 protein, mouse; D034285:Dynamin II