title: Nap1-mediated actin remodeling is essential for mammalian myoblast fusion.
abstract: Myoblast fusion is crucial for the formation, growth, maintenance and regeneration of healthy skeletal muscle. Unfortunately, the molecular machinery, cell behaviors, and membrane and cytoskeletal remodeling events that govern fusion and myofiber formation remain poorly understood. Using time-lapse imaging approaches on mouse C2C12 myoblasts, we identify discrete and specific molecular events at myoblast membranes during fusion and myotube formation. These events include rearrangement of cell shape from fibroblast to spindle-like morphologies, changes in lamellipodial and filopodial extensions during different periods of differentiation, and changes in membrane alignment and organization during fusion. We find that actin-cytoskeleton remodeling is crucial for these events: pharmacological inhibition of F-actin polymerization leads to decreased lamellipodial and filopodial extensions and to reduced myoblast fusion. Additionally, shRNA-mediated inhibition of Nap1, a member of the WAVE actin-remodeling complex, results in accumulations of F-actin structures at the plasma membrane that are concomitant with a decrease in myoblast fusion. Our data highlight distinct and essential roles for actin cytoskeleton remodeling during mammalian myoblast fusion, provide a platform for cellular and molecular dissection of the fusion process, and suggest a functional conservation of Nap1-regulated actin-cytoskeleton remodeling during myoblast fusion between mammals and Drosophila.
authors.affiliation: Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Nowak
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Nahirney
authors.forename: Anna-Katerina
authors.initials: AK
authors.lastname: Hadjantonakis
authors.forename: Mary K
authors.initials: MK
authors.lastname: Baylies
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002450:Cell Communication; D002454:Cell Differentiation; D002459:Cell Fusion; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002465:Cell Movement; D048430:Cell Shape; D002470:Cell Survival; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000648:ultrastructure; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D034741:RNA, Small Interfering / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000199:Actins; D008565:Membrane Proteins; C502089:Nckap1 protein, mouse; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins
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