title: Grouping patients for masseter muscle genotype-phenotype studies.
abstract: OBJECTIVE
  To use various facial classifications, including either/both vertical and horizontal facial criteria, to assess their effects on the interpretation of masseter muscle (MM) gene expression.
  
  
  METHODS
  Fresh MM biopsies were obtained from 29 patients (age, 16-36 years) with various facial phenotypes. Based on clinical and cephalometric analysis, patients were grouped using three different classifications: (1) basic vertical, (2) basic horizontal, and (3) combined vertical and horizontal. Gene expression levels of the myosin heavy chain genes MYH1, MYH2, MYH3, MYH6, MYH7, and MYH8 were recorded using quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and were related to the various classifications. The significance level for statistical analysis was set at P ≤ .05.
  
  
  RESULTS
  Using classification 1, none of the MYH genes were found to be significantly different between long face (LF) patients and the average vertical group. Using classification 2, MYH3, MYH6, and MYH7 genes were found to be significantly upregulated in retrognathic patients compared with prognathic and average horizontal groups. Using classification 3, only the MYH7 gene was found to be significantly upregulated in retrognathic LF compared with prognathic LF, prognathic average vertical faces, and average vertical and horizontal groups.
  
  
  CONCLUSIONS
  The use of basic vertical or basic horizontal facial classifications may not be sufficient for genetics-based studies of facial phenotypes. Prognathic and retrognathic facial phenotypes have different MM gene expressions; therefore, it is not recommended to combine them into one single group, even though they may have a similar vertical facial phenotype.
authors.affiliation: Riyadh Military Hospital, Riyadh, Kingdom of Saudi Arabia.
authors.forename: Hadwah Abdelmatloub
authors.initials: HA
authors.lastname: Moawad
authors.forename: Andrea C M
authors.initials: AC
authors.lastname: Sinanan
authors.forename: Mark P
authors.initials: MP
authors.lastname: Lewis
authors.forename: Nigel P
authors.initials: NP
authors.lastname: Hunt
mesh_terms: D000293:Adolescent; D000328:Adult; D001706:Biopsy; D024722:Cardiac Myosins / Q000235:genetics; D002508:Cephalometry; D005260:Female; D015870:Gene Expression; D005838:Genotype; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000473:pathology*; D018995:Myosin Heavy Chains / Q000235:genetics; D010641:Phenotype; D011378:Prognathism / Q000235:genetics; D063173:Retrognathia / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D014716:Vertical Dimension; D055815:Young Adult
chemical_list: C094239:MYH6 protein, human; C501641:MYH7 protein, human; C488292:MYH8 protein, human; D024722:Cardiac Myosins; D018995:Myosin Heavy Chains