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K. Park, S. Oh; Myosin Isoform Expression in Human Extraocular Muscle: Longitudinal Variations and Patterns in Global and Orbital Layers. Invest. Ophthalmol. Vis. Sci. 2010;51(13):23.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the distribution of myosin heavy chain (MyHC) isoforms along the length of global and orbital layers of human extraocular muscles (EOM), and between EOM.
Human EOMs were assessed via SDS-PAGE, immunoblotting, and immunocytochemistry, using antibodies against MyHC isoforms. Serial samples of orbital and global layers of extraocular muscles were processed for gel electrophoresis, and relative amounts of each MyHC isoform in each sample were determined via scanning densitometry.
Four prominent MyHC isoforms, and two additional MyHC isoforms at very low levels, were expressed. Four prominent MyHC isoforms, MyHCemb/IIx, MyHCIIa, MyHCeom, and MyHCI, were expressed along the entire length of the global and orbital layers of all six extraocular muscles with marked gradients in the levels along the length of both layers. In the rectus muscles and inferior oblique muscle, MyHC eom was enriched in the central region, where it accounts for ~50% of the total; however, the levels of MyHCeom were reduced in proximal and distal ends of the muscle to ~20% and ~10%, respectively. In those regions, IIa isoforms predominates. In the superior oblique muscle, the relative level of MyHCeom was slightly greater in the central region than in the peripheral regions, however, the changes of relative levels of other MyHC isoforms including MyHCIia, MyHCI and MyHCemb/IIx along the length of EOMs were subtle and no characteristic patterns were noted.
The present study entailed a quantitative analysis of MyHC isoform expression along the entire length of both layers in human extraocular muscles and between extraocular muscles. Further studies, will be required in order to correlate the expression of myosin with fiber physiology.
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