title: Iris pigmentation as a quantitative trait: variation in populations of European, East Asian and South Asian ancestry and association with candidate gene polymorphisms.
abstract: In this study, we present a new quantitative method to measure iris colour based on high-resolution photographs. We applied this method to analyse iris colour variation in a sample of individuals of East Asian, European and South Asian ancestry. We show that measuring iris colour using the coordinates of the CIELAB colour space uncovers a significant amount of variation that is not captured using conventional categorical classifications, such as 'brown', 'blue' or 'green'. We tested the association of a selected panel of polymorphisms with iris colour in each population group. Six markers showed significant associations with iris colour in the European sample, three in the South Asian sample and two in the East Asian sample. We also observed that the marker HERC2 rs12913832, which is the main determinant of 'blue' versus 'brown' iris colour in European populations, is also significantly associated with central heterochromia in the European sample.
authors.affiliation: Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, Canada.
authors.forename: Melissa
authors.initials: M
authors.lastname: Edwards
authors.affiliation: Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Cha
authors.affiliation: Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Krithika
authors.affiliation: Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, Canada.
authors.forename: Monique
authors.initials: M
authors.lastname: Johnson
authors.affiliation: Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, Canada.
authors.forename: Gillian
authors.initials: G
authors.lastname: Cook
authors.affiliation: Department of Anthropology, University of Toronto Mississauga, Mississauga, ON, Canada.
authors.forename: Esteban J
authors.initials: EJ
authors.lastname: Parra
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People / Q000235:genetics*; D005127:Eye Color / Q000235:genetics*; D005260:Female; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics*; D006801:Humans; D007498:Iris; D007499:Iris Diseases / Q000235:genetics; D008297:Male; D010859:Pigmentation Disorders / Q000235:genetics; D011110:Polymorphism, Genetic; D019655:Quantitative Trait, Heritable; D044767:Ubiquitin-Protein Ligases; D044465:White People / Q000235:genetics*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; C118566:HERC2 protein, human; D044767:Ubiquitin-Protein Ligases
keywords: Iris colour; ancestry; association; central heterochromia; high-resolution photographs; single-nucleotide polymorphisms