Admixture Analysis of Human Eye Color

• Activity Number: 683
• Type: Contributed
• Date/Time: Thursday, August 8, 2013 : 10:30 AM to 12:20 PM
• Sponsor: Biometrics Section
• Author(s): Kaustubh Adhikari*+ and Andres Ruiz-Linares
• Companies: University College London and University College London
• Keywords: association study ; Eye colour ; admixture analysis

Abstract

Human eye colour is among the most noticeable phenotypes. Initially thought to be a binary Mendelian trait, it has now been established as a complex polygenic trait with several known genes. Eye colour variation is seen mostly in Europeans, and thus genetic association studies have mostly been restricted to European subjects only. In our population-based study across several Latin American countries, we consider the effect of Native American and African admixture onto European ancestry. We develop a system for semi-automatic quantitative iris colour extraction from volunteers' frontal facial photographs, and demonstrate how its distribution in the colour space relates to the variability in ancestry. The HSL colourspace reflects the natural variation more realistically than RGB, but it also throws unique challenges. In the process, we show that a multi-ring system is necessary for properly classifying green eyes. After showing that the data can be reduced to fewer dimensions of variation, we observe that lightness correlates the best with Ancestry, and perform genome-wide association studies as well as admixture mapping to identify and replicate interesting genes.