Extraocular muscles (EOMs) are categorized as skeletal muscles; however, emerging evidence indicates that their gene expression profile, metabolic characteristics and functional properties are significantly different from the prototypical members of this muscle class. Gene expression profiling of developing and adult EOM suggest that many myofilament and cytoskeletal proteins have unique expression patterns in EOMs, including the maintained expression of embryonic and fetal isoforms of myosin heavy chains (MyHC), the presence of a unique EOM specific MyHC and mixtures of both cardiac and skeletal muscle isoforms of thick and thin filament accessory proteins. We demonstrate that nonmuscle myosin IIB (nmMyH IIB) is a sarcomeric component in ?. 20% of the global layer fibers in adult rat EOMs. Comparisons of the myofibrillar distribution of nmMyHC IIB with sarcomeric MyHCs indicate that nmMyH IIB co-exists with slow MyHC isoforms. In longitudinal sections of adult rat EOM, nmMyHC IIB appears to be restricted to the A-bands. Although nmMyHC IIB has been previously identified as a component of skeletal and cardiac sarcomeres at the level of the Z-line, the novel distribution of this protein within the A band in EOMs is further evidence of both the EOMs complexity and unconventional phenotype.
|Number of pages||8|
|Journal||Experimental Cell Research|
|State||Published - Jul 2010|
Bibliographical noteFunding Information:
The authors would like to thank Dr. Robert Adelstein for helpful suggestions on this work. We are also indebted to the members of the Center for Muscle Biology at UK for their insightful comments. This work was supported by grants from the National Eye Institute (NEI, part of NIH) to CLM ( R21 EY018112 ) and FHA ( R01 EY012998 ).
- Thick filament
- Tonic fibers
ASJC Scopus subject areas
- Cell Biology