title: Microtubule-dependent transport and organization of sarcomeric myosin during skeletal muscle differentiation.
abstract: It has been proposed that microtubules (MTs) participate in skeletal muscle cell differentiation. However, it is still unclear how this happens. To examine whether MTs could participate directly in the organization of thick and thin filaments into sarcomeres, we observed the concomitant reorganization and dynamics of MTs with the behavior of sarcomeric actin and myosin by time-lapse confocal microscopy. Using green fluorescent protein (GFP)-EB1 protein to label MT plus ends, we determined that MTs become organized into antiparallel arrays along fusing myotubes. Their dynamics and orientation was found to be different across the thickness of the myotubes. We observed fast movements of Dsred-myosin along GFP-MTs. Comparison of GFP-EB1 and Dsred-myosin dynamics revealed that myosin moved toward MT plus ends. Immuno-electron microscopy experiments confirmed that myosin was actually associated with MTs in myotubes. Finally, we confirmed that MTs were required for the stabilization of myosin-containing elements prior to incorporation into mature sarcomeres. Collectively, our results strongly suggest that MTs become organized into a scaffold that provides directional cues for the positioning and organization of myosin filaments during sarcomere formation.
authors.affiliation: Institut Jacques Monod, Paris, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Pizon
authors.forename: Fabien
authors.initials: F
authors.lastname: Gerbal
authors.forename: Carmen Cifuentes
authors.initials: CC
authors.lastname: Diaz
authors.forename: Eric
authors.initials: E
authors.lastname: Karsenti
mesh_terms: D000199:Actins / Q000378:metabolism / Q000648:ultrastructure; D002454:Cell Differentiation; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D008954:Models, Biological; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D009218:Myosins / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport; D012518:Sarcomeres / Q000648:ultrastructure*; D014404:Tubulin / Q000032:analysis
chemical_list: D000199:Actins; D014404:Tubulin; D049452:Green Fluorescent Proteins; D009218:Myosins