Title: EDAR Gene Variants and Mandibular Morphology in a Japanese Sample
Benjamin Salameh (Presenter)
University of Illinois at Chicago College of Dentistry
Christina Nicholas, University of Illinois at Chicago College of Dentistry
Steven Miller, Midwestern University
Tetsutaro Yamaguchi, Showa University
Objectives: Recent advances in both genetics and 3D shape analysis are driving new insights into the specific genetic variation underlying facial form. Previous research has shown that a derived allele for EDAR (G; rs3827760) that is common in East Asian populations is associated with mandibular shape in both a mouse model and a large Latino sample. The same gene variants may produce differing effects in different populations, and thus it is important to run population-specific analyses investigating purported genotype-phenotype relationships. To date, the EDAR results have yet to be replicated in a Japanese sample. Furthermore, the Latino sample was based upon facial photographs, not CBCT (i.e., not skeletal) data, leaving open the possibility that detected differences represent soft tissue variation.
Methods: Using 3D geometric morphometrics, we examine the relationship between our target SNP and mandibular morphology in a healthy Japanese population. We used a combination of 20 landmarks and 17 sliding semi-landmarks placed on the mandible to analyze shape from CBCT scans (n=70). The EDAR SNP of interest (rs3827760) was compared with the 3D shape data using multiple regression and a discriminant function analysis (DFA).
Results: The DFA revealed statistically significant (p<0.001) differences in mandibular shape across the three allele combinations for rs3827760 (AA, AG, GG). Individuals with two copies of the ancestral allele (AA) showed a relatively more projecting chin, a relatively narrower distance between the mandibular angles, and a mandibular body that was less broad antero-posteriorly than that seen in the derived allele (GG) individuals. Those individuals who were heterozygous for the minor allele were most similar in their mandibular morphology to the ancestral allele.
Conclusions: These results confirm recently published data in a Latin American sample, further elaborating on the role of EDAR in facial development in individuals of East Asian descent.