Article  |   April 2012
Myosin Heavy Chain Composition of the Human Genioglossus Muscle
Author Affiliations & Notes
  • Megan Daugherty
    Emory University, Atlanta, GA
  • Qingwei Luo
    Emory University, Atlanta, GA
  • Alan J. Sokoloff
    Emory University, Atlanta, GA
  • Correspondence to Alan J. Sokoloff: asokolo@emory.edu
  • Editor: Anne Smith
    Editor: Anne Smith×
  • Associate Editor: Jack Jiang
    Associate Editor: Jack Jiang×
Article Information
Special Populations / Genetic & Congenital Disorders / Speech
Article   |   April 2012
Myosin Heavy Chain Composition of the Human Genioglossus Muscle
Journal of Speech, Language, and Hearing Research, April 2012, Vol. 55, 609-625. doi:10.1044/1092-4388(2011/10-0287)
History: Received October 15, 2010 , Revised April 19, 2011 , Accepted August 11, 2011
Journal of Speech, Language, and Hearing Research, April 2012, Vol. 55, 609-625. doi:10.1044/1092-4388(2011/10-0287)
History: Received October 15, 2010; Revised April 19, 2011; Accepted August 11, 2011
Web of Science® Times Cited: 3

Background: The human tongue muscle genioglossus (GG) is active in speech, swallowing, respiration, and oral transport, behaviors encompassing a wide range of tongue shapes and movement speeds. Studies demonstrate substantial diversity in patterns of human GG motor unit activation, but whether this is accompanied by complex expression of muscle contractile proteins is not known.

Purpose: The authors tested for conventional myosin heavy chain (MHC) MHCI, MHCIIA, MHCIIX, developmental MHCembryonic and MHCneonatal and unconventional MHCαcardiac, MHCextraocular, and MHCslow tonic in antero-superior (GG-A) and posterior (GG-P) adult human GG.

Method: SDS-PAGE, Western blot, and immunohistochemistry were used to describe MHC composition of GG-A and GG-P and the prevalence of muscle fiber MHC phenotypes in GG-A.

Results: By SDS-PAGE, only conventional MHC are present with ranking from most to least prevalent MHCIIA > MHCI > MHCIIX in GG-A and MHCI > MHCIIA > MHCIIX in GG-P. By immunohistochemistry, many muscle fibers contain MHCI, MHCIIA, and MHCIIX, but few contain developmental or unconventional MHC. GG-A is composed of 5 phenotypes (MHCIIA > MHCI-IIX > MHCI > MHCI-IIA > MHCIIX). Phenotypes MHCI, MHCIIA, and MHCI-IIX account for 96% of muscle fibers.

Conclusions: Despite activation of GG during kinematically diverse behaviors and complex patterns of GG motor unit activity, the human GG is composed of conventional MHC isoforms and 3 primary MHC phenotypes.

Acknowledgments
This work was supported by the National Institute on Deafness and Other Communication Disorders Grant DC005017, awarded to the third author. We would also like to thank Kirk Easley for help with statistical analyses. Human tissue was kindly provided by the Emory University School of Medicine Body Donor Program or purchased from the National Disease Research Interchange.
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