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Adrihan H. Janbaz, Fatima Pedrosa-Domellöf; Cytolinker Organization in the Human Extraocular Muscles. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2223.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the distribution of the cytolinker protein plectin, and its relation to other cell components in human extraocular muscles [EOMs].
Nine EOM samples obtained from six donors, with ethical approval, were serially cross-sectioned and processed for immunohistochemistry, with a battery of four specific antibodies (pAbs: #46 and GP20; mAbs 5B3 and 10F6) against the cytolinker protein plectin and other cytoskeletal proteins desmin (the major intermediate filament protein in muscle fibers that has plectin as a linker protein), myotilin (a Z-disc component) and different myosin heavy chain (MyHC) isoforms. The mitochondrial activity rate was estimated by using NADH labeling.
Plectin was detected in practically all muscle fibers. Throughout the muscle length the staining intensity with #46 was more homogeneous in the orbital layer [OL], whereas a more variable pattern was revealed in the global layer [GL]. Muscle fibers containing MyHC slow or slow-tonic in both OL and GL were generally more intensely stained with #46 than were fibers containing MyHC fast. In addition these fibers had a more intense staining for myotilin.In contrast 10F6 strongly labeled fibers lacking MyHC slow or slow tonic, and these fibers were consistently faintly stained with both desmin and myotilin.Stronger staining intensity with 5B3 correlated with high NADH activity and generally stronger myotilin labeling in both OL and GL. However, there were muscle fibers with high NADH activity in GL that did not stain strongly with 5B3.
Plectin is a ubiquitous linker cytoskeletal protein necessary for maintenance of myofibrillar architecture. Plectin exists in several isoforms. The C-terminal attaches to desmin and the N-terminal binds to the nucleus, the mitochondria, the Z-discs and the sarcolemmal dystroglycan-complex.The present data indicate that a subset of human EOM fibers containing MyHC slow and/or slow-tonic has stronger staining pattern for plectin. In particular there seems to be variation in the organization of the cytoskeleton among fibers containing MyHC slow and/or slow-tonic.Additional experiments are under way in order to further clarify the organization of the cytoskeleton in the different fiber population.
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