Investigation of a genetic association of a class III skeletal pattern

Abstract Background The present study investigated the association between the human growth hormone receptor (GHR) and collagen type II alpha 1 chain (COL2A1) gene polymorphism of malocclusions in patients presenting with a maxillary retrognathic-related Class III skeletal pattern and a mandibular prognathic-related Class III skeletal pattern. Subjects The study was comprised of 255 subjects which included 85 patients who had a skeletal Class I (control group) and 170 patients who presented with a skeletal Class III pattern (study group). Of the 170 patients with a skeletal Class III identified by cephalometric analysis, 85 had maxillary retrognathism and 85 had mandibular prognathism. Methods Extracted blood samples were assayed to identify genomic DNA which was subsequently followed by PCR and pyro-sequencing steps to determine single nucleotide polymorphisms (SNPs) in the GHR and COL2A1 genes of the skeletal Class III patients. One-way analysis of variance (ANOVA) and two-sample t tests were performed to measure the quantitative variables in the intergroup comparisons. Pyro-sequencing described the allele frequencies and genotypes of the COL2A1 gene SNP rs1793953, and the GHR gene SNPs rs6182 and rs6184 of each individual. Results A relationship between the polymorphism of the GHR gene SNPs rs6182 and rs6184 and ramus height was determined in the mandibular prognathic group. No correlation was found between craniofacial properties and COL2A1 polymorphism. Conclusions The present study supports GHR as a candidate gene associated with a Class III skeletal pattern in the Turkish population. The COL2A1 gene SNP rs1793953 was found to have no association with the sub-types of a Class III malocclusion.