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F. Pedrosa Domellof, L.–E. Thornell; Cytoskeletal Proteins in Human Extraocular Muscles . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4678. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To characterize the muscle fibers of the human extraocular muscles (EOMs) with respect to their cytoskeletal protein composition. The cytoskeletal proteins are of crucial importance for the maintenance of muscle cell integrity. Their major function is to link and anchor structural components inside the cell. Methods: Eight EOMs and one levator palpebrae (LP) samples were obtained from 3 individuals at autopsy. Sections were processed for immunocytochemistry, with monoclonal antibodies (mAb) against intermediate filament and intermediate filament associated proteins desmin, nestin, synemin, plectin, alpha–B crystallin.; and against subsarcolemmal cytoskeletal proteins dystrophin, vinculin, and spectrin. Results: Desmin was present in all fibers of EOMs and LP, but there was some heterogeneity in staining intensity among the fibers in the LP and one EOM. Nestin was present in all fibers, generally with stronger staining in the orbital layer (OL) and in a population of very small fibers distributed among both layers which were also more positive for desmin and synemin. Synemin mAb labeled the majority of the fibers moderately but somewhat more intensely in the OL. Dystrophin was strikingly absent from the rim of some of the fibers in the EOMs. Vinculin was also very weak/absent in some of the fibers, whereas plectin and alpha–B crystallin were found in all fibers. The staining for spectrin also revealed heterogeneity among the fibers. Conclusions: The human EOMs showed important fiber heterogeneity in cytoskeletal protein composition and additionally differed from limb muscles by the presence of nestin in all fibers. Studies are under way to extend these results to a larger sample collection and to correlate the heterogeneity in cytoskeletal protein content with the fiber types based on the myosin heavy chain content. A different cytoskeletal organization is likely to be of importance for the particular responses of the EOMs to neuromuscular disease.
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