Distribution of Myosin Heavy Chain Isoform in Human Extraocular Muscles

Kyung-Ah Park; Sei Yeul Oh

doi:10.3341/jkos.2009.50.2.285

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Park and Oh: Distribution of Myosin Heavy Chain Isoform in Human Extraocular Muscles

Original Article

J Korean Ophthalmol Soc 2009;50(2):285-289.

Published online: 3 January 2009

DOI: https://doi.org/10.3341/jkos.2009.50.2.285

Distribution of Myosin Heavy Chain Isoform in Human Extraocular Muscles

Kyung-Ah Park, MD, Sei Yeul Oh, MD

Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

Address reprint requests to Sei Yeul Oh, MD Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine #50 Ilwon‐dong, Gangnam‐gu, Seoul 135-710, Korea. Tel: 82‐2‐3410‐3568, Fax: 82‐2‐3410‐0074, E-mail: syoh@skku.edu

Received 29 September 2008 Accepted 25 November 2008

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To provide quantitative data on the distribution of MyHCeom and compare the proportion of myosin heavy chain (MyHC) isoforms between the central and peripheral regions of human extraocular muscles (EOMs).

Methods

Medial rectus, lateral rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique muscle samples were taken from three men with brain death. To examine the longitudinal distribution of myosin isoforms, the muscles were divided into central and peripheral portions of equal length. Electrophoresis and densitometry were used to quantify the distribution of MyHC isoforms.

Results

Electrophoresis of whole‐ muscle extracts of sampled EOMs revealed four MyHC bands that were identified as MyHCI, MyHCeom, MyHCIIa, and MyHCIIx. The proportion of MyHCeom was higher in the central region, whereas the proportion of MyHCIIa was higher in the peripheral region. The relative proportions of MyHCI, MyHCeom, and MyHCIIa were not significantly different among the EOMs. There was a tendency for higher levels of MyHCIIx in the inferior rectus muscle.

Conclusions

The proportion of MyHCeom was higher in the central region of human EOMs. Further studies are needed to investigate the consequences of this distributional difference on the function of EOMs.

Keywords: Electrophoresis, Human extraocualr muscle, Myosin heavy chain isoform

References

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Figure 1.

SDS-PAGE of the human superior, medial, lateral and inferior rectus muscles and inferior oblique muscle (MyHCI, MyHCeom, MyHCIIa, and MyHCIIx).

Figure 2.

Longitudinal variation in myosin heavy chain (MyHC) expression detected by high resolution SDS-PAGE. (A) Superior rectus muscle was cut into two parts as shown. (B) Myofibrils prepared from each region identified in A were analyzed by SDS-PAGE and stained with silver. The bands were identified by comparison with the migration positions in muscles of known myosin composition,⁵ and as described in Materials and methods. (C) Relative amounts of each MyHC were determined by scanning with visible light and densitometer.

Figure 3.

Relative proportions of myosin heavy chain (MyHC) isoforms of extraocular muscles.

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