Have you ever been told you have your mom’s nose or your dad’s mouth? Resemblances between parents and their children have been recognized for centuries, but genetic studies have confirmed that physical characteristics tend to be more strongly influenced by genetic factors than environmental factors. The formation of a face is an evolutionarily conserved and precisely orchestrated process involving the cellular migration, interaction, proliferation, and differentiation of diverse tissue cells, all of which are functions of genes. But what exact genetic tidbits are responsible for our looks? New research attempts to shed some light on this question.
Face morphology is not only a matter of appearance but also an important feature for the study of skull and facial malformations (craniofacial deformities) as well as a valuable tool in forensic sciences. Several GWAS have shown that genetic variants were related to facial traits, including width, depth, and nose shape. Despite these studies, current data on face morphology is not yet sufficient to identify the etiology of human craniofacial malformations and externally visible characteristics. In order to uncover more genetic details related to facial traits, for the first time researchers have conducted a large scale GWAS in a Korean study population.
In the first phase of this study, 5,643 Koreans were recruited from the Korean Genome and Epidemiology Study (KoGES) for discovery GWAS. Traits were delineated by data such as distance, distance ratio, angle, area, and curvature (eyelid) from 23 frontal and seven lateral facial points, which were automatically extracted from each picture using software developed by the researchers. They perform a GWAS for 85 facial traits, of which, 7 traits (two eye-related and five nose-related) demonstrated significant genetic associations. In the second research phase, an additional cohort of 1,926 Korean participants, 128 SNPs in 65 traits which had suggestive associations in the GWAS were validated. Additionally, a meta-analysis of the two cohorts found five loci with significant relationships. One of these loci, the HOXD-MTX2 (rs970797) gene, was highly associated with the curvature of the upper eyelid, impacting overall eye shape. Though not statistically significant, researchers also found that participants with an A allele of this gene may have been more likely to have longer eye tail lengths when compared to participants with CC homozygous genotype. Of note, rs970797 is the only SNP found in the GWAS catalogue and the UK Biobank, where evidence suggests it is associated with likelihood of having a monobrow and earlobe attachment.
A major limitation of this study is that the facial measurements were derived from two-dimensional images rather than three-dimensional images, which is the gold standard in this type of research. Also, the study populations were Korean, limiting the generalizability of these results. Despite these limits, there is no doubt that this study may contribute to a better understanding of craniofacial deformities and provide useful genetic information for externally visible characteristics in forensic sciences. Read more about the study here: https://www.ncbi.nlm.nih.gov/pubmed/29921221
Are you interested in learning more about your genetic tendency for eye tail length? You can login to your Genomelink dashboard to see this new genetic trait.