Differential Expression of miRNA328 in Malocclusion Subjects with Facial Asymmetry

Objectives: MicroRNAs regulate posttranscriptional expression of target genes leading to inhibition or degradation of mRNA therefore inhibiting synthesis of protein coding genes. We reported that miRNA genes associated with response to ion-channel/transporter functions are differentially expressed in masseter of subjects with facial asymmetry. We have selected one species, miRNA328, to test whether its expression associates with malocclusion types, asymmetry and TMD among orthognathic surgery patients.
Methods: RNA was isolated from muscle of patients undergoing mandibular sagittal-split surgical procedures for non-syndromic skeletal discrepancies. Subjects were diagnosed with one of the following types of malocclusion, with or without TMD and facial asymmetry: Class-II or Class-III with vertical normal, open or deep bite. A two-step process was used for quantification of miRNAs. RNA was reverse transcribed and assayed using specific TaqMan ^TM primers and probe for miR328. Standard curve experiments were used for assay analysis.
Results: miR328 expression values were low, ranging from 1-80pg throughout. Quantifiable differences were detected in comparisons between parameter groups, but analyses by a series of unpaired t-tests did not find statistically significant associations. Nevertheless, interesting differences were identified among asymmetry and sagittal malocclusion groups with p<0.20 found for both sets of comparisons. Power analyses were done to determine the sample sizes needed for each group to attain significance.
Conclusions: miR328 is differentially expressed in masseter of subjects with Class-II/Class-III malocclusion and in facial asymmetry. Larger sample sizes are needed to verify whether miR328 expression acts in both disorders. By power analysis, to reach p<0.05 with a power =0.8, 27 samples are needed in both symmetry and asymmetry groups. Likewise, for sagittal dimension malocclusion, sample size of 36 per group is needed to reach significance. Differential expression miR328 seen here suggests that it may have a regulatory effect on muscle target genes and contribute to variations in craniofacial development.