How is "Distance between Eyeballs" encoded by the genome?
The variation in face shape and structure is one of the most noticeable characteristics of humans. Facial appearance has a strong genetic component—for example, just look at identical twins vs fraternal twins, genetics account for the differences in looks. Some externally visible human characteristics, such as eye and hair color, can already be inferred from a DNA sample with practically useful accuracy. While other face traits like height and position and lower jaw also seem to be more hereditary. Yet, there is still many facial traits that scientists are still discovering the heritability.
A candidate gene study was carried out in two independent European population samples more recently. A potential association between risk alleles for non-syndromic cleft lip with or without cleft palate and nose width and facial width in the normal population has been investigated. However, facial landmarks derived from 3-Dimensional (3D) magnetic resonance images (MRI) in one population and 2-Dimensional (2D) portrait images in the other population were not completely comparable, posing a challenge for combining phenotype data. In this study, researchers focus on the MRI-based approach for capturing facial morphology since previous facial imaging studies by some of us have demonstrated that MRI-derived soft tissue landmarks represent a reliable data source.
Using this same data from three dimensional images (MRIs), researchers conducted a genome-wide association study for facial shape phenotypes in multiple discovery and replication cohorts, considering almost ten thousand individuals of European descent from several countries. All SNPs which showed significant association in the discovery phase GWAS were sought for replication in SYS, TwinsUK, and BLTS. They identified five independent genetic loci associated with different facial phenotypes, suggesting the involvement of five candidate genes, including the Tumor Protein P63 (TP63) gene. An intronic SNP of TP63 on chromosome 3q28, rs17447439, showed an association with the distance between eyeballs. Participants having at least one G allele for rs17447439 showed a significant tendency to have a decreased distance between eyeballs in the discovery cohort (N=5,388) and the replication cohort (BLTS+TwinSUK, N=3,867). The TP63 gene has been reported to encode a transcription factor belonging to the p53 family and plays an important role in tissue development.
Overall, this study provides novel and confirmatory links between common DNA variants and normal variations in facial structure. The results also suggest that the high heritability of facial phenotypes seems to be explained by a large number of DNA variants with relatively small individual effect size, a phenomenon well known for other complex human traits, such as adult body height. Read more about the study here: https://pubmed.ncbi.nlm.nih.gov/23028347/
Are you interested in learning more about your genetic tendency for the distance between eyeballs? You can login to your Genomelink YOUR TRAITS to see this new genetic trait.
