Immunoelectron microscopic and freeze etch studies of muscle plasma membrane and extracelular matrix in normal and diseased skeletal myofiber

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Immunogold electron microscopic investigation was carried out in human skeletal muscles by using anti beta-dystroglycan antibodies and anti merosin monoclonal antibody. We also intended to perform the study by using anti alpha-dystroglycan antibodies. Anti alpha-dystroglycan antibodies were generated against three synthetic peptides deduced on the published alpha-dystroglycan cDNA sequence (Nature 355 : 696-702,1992). However, our alpha-dystroglycan antibodies are now under analysis for their characterization. The anti beta-dystroglycan was ultrastructurally localized in the subsarcolemmal area of skeletal myofibers (J Electron Microsc 43 : 327-331,1994 ; Am J Pathol 146 : 189-196,1995). In contrast, the ultrastructural localization of merosin in human skeletal myofiber was present just outside of muscle plasma membrane and just inside area of basal lamina components. In addition, electron microscopy of basal lamina of freeze etched replica showed that the short cytoskeleton was standing perpendicular to the surface of muscle plasma membrane and it was connected to the network formation of this small fibrillar structures of basal lamina which also contained more thick collagen type IV fibrills. The signal of merosin was localized at the inside part of the complicated basal lamina of huma skeletal myofibers. The merosin was turned out to be the alpha-dystroglycan receptor (Sunada Y.et al.J Biol Chem 269 : 13729-13732,1994), so the cytoskeletal element associated with the gold labelled merosin molecules is thought to be the alpha-dystroglycan which is connected with dystrophin vir beta-dystroglycan.