Masseter muscle gene expression in relation to various craniofacial deformities: a genotype-phenotype study

Craniofacial form is defined by a number of factors. A major contributor is the jaw musculature especially of the masseter muscle, as differences in transcription and translation of various genes have been documented from this tissue. Up to this point however, no reliable biological predictors of form have been identified. The aims of this study were therefore, to describe the transcriptome of the masseter muscle using microarray technology and to establish and correlate the expression levels of potential candidate and known “informative” genes in masseter muscle with selected clinical, radiographic and dental features of subjects with a variety of craniofacial morphologies. A total of 29 patients (18 deformity and 11 control) were selected from the orthodontic/orthognathic clinics at the Eastman Dental and Whipps Cross Hospitals, London, and Riyadh Military Hospital, Saudi Arabia. Microarray results indicated five “novel” genes not previously reported in relation to the masseter muscles of subjects with variable craniofacial morphologies. Two genes (KIAA1671 and DGCR6) were down-regulated in long face patients, one (SERGEF) was down-regulated in Class III patients and one (LOC730245) was up-regulated in Class II long faces and in all Class III subjects, compared to controls. Another gene (NDRG2) was down-regulated in Class II compared to Class III individuals. Subsequent quantitative Reverse Transcriptase PCR results strongly confirmed that the “novel” gene SERGEF was down-regulated in relation to the clinical, dental and radiographic features of subjects with Class III appearance. SERGEF gene had a positive relationship to the number of dental occlusal contacts and ANB angle. The “informative” gene MHC7 was strongly related to both vertical and horizontal facial deformities. These data suggest that the expression profiles of a number of genes can be analysed and used to make assessments as to their role in the primary aetiology and successful or unsuccessful treatment of patients with specific craniofacial morphologies.