Cytoskeletons of Cultured Rat Fetal Muscle Cells

Uhm, Chang Sub; Lee, Dong Ho; Kim, Hyun; Suh, Young Suk

Abstract

Myoblasts fuse together to form multinucleated myotubes. However, only a few studies have been reported on the cytoskeletal changes during the fusion process. To understand the change of cytoskeleton during the fusion process, isolated myoblasts from embryonic day 21 Sprague-Dawley rats were cultured on formvar-, carbon-, and gelatin-coated gold grids for electron microscopy. The cells were fixed and plasma membrane and cytoplasm were extracted with triton X-100 and observed directly with Hitachi H-600 transmission electron microscope without staining. Fusiform myoblasts have complex cytoskeletal networks at the center of the cells, which were too dense to be resolved, however the margins of myoblasts and myotubes have bundles of cytoskeletons running in the longitudinal direction with reticulated cytoskeletal networks in between. Lamellipodial ruffles at both ends of myoblasts were characterized by a cytoskeletal lattice at the base and a few radiating strands into the filopodia-like processes. Radiating cytoskeletons originated either from the longitudinally oriented cytoskeletal bundles or reticular lattice continuous to them. The fusion areas were characterized by thin filaments connecting adjacent cells and the connection of longitudinal filament bundles from the fusing cells. These results suggest the modification of cytoskeletons during myoblast fusion.