Myosin heavy chain isoform composition of human masseter muscle from subjects with different mandibular plane angles.
OBJECTIVE
To investigate the presence of myosin heavy chain isoforms in human masseter muscle and to describe any differences in orthognathic surgery patients with different mandibular plane angles.


METHODS
Biopsies were obtained from the anterior border of the superficial masseter muscle in 18 patients undergoing various orthognathic procedures. Myosin heavy chain isoforms were isolated and analysed by SDS-PAGE gel electrophoresis. Steiner's mandibular plane angles were measured from pretreatment lateral cephalometric radiographs and used to classify the vertical dimension of each subject.


RESULTS
Despite the fact that there was wide individual variation, there appeared to be no direct association between the presence of myosin heavy chain isoforms and specific vertical facial patterns. Type I myosin heavy chain isoform was the most common isoform found in all subjects. More Type IIA myosin heavy chain isoforms were observed in dolichofacial subjects. There were no differences between genders in myosin heavy chain expression.


CONCLUSIONS
A wide variation of myosin heavy chain isoforms exists in the masseter muscle of individuals with different mandibular plane angles. Further investigations involving larger sample sizes and the incorporation of bite-force measurements may help to clarify the relationship between mandibular muscle characteristics and the vertical facial dimension.
Lim
Donna
D
School of Dental Science, The University of Melbourne, Melbourne, Australia.
Beitzel
Felice
F
Lynch
Gordon
G
Woods
Michael G
MG
D000293:Adolescent; D000328:Adult; D002508:Cephalometry; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000145:classification* / Q000601:surgery; D008334:Mandible / Q000473:pathology* / Q000601:surgery; D008406:Masseter Muscle / Q000737:chemistry*; D018995:Myosin Heavy Chains / Q000032:analysis*; D024461:Myosin Type I / Q000032:analysis; D024462:Myosin Type II / Q000032:analysis; D024507:Nonmuscle Myosin Type IIA / Q000032:analysis; D024501:Nonmuscle Myosin Type IIB / Q000032:analysis; D020033:Protein Isoforms / Q000032:analysis*; D012737:Sex Factors; D014716:Vertical Dimension
D020033:Protein Isoforms; D024461:Myosin Type I; D024462:Myosin Type II; D024507:Nonmuscle Myosin Type IIA; D024501:Nonmuscle Myosin Type IIB; D018995:Myosin Heavy Chains