Molecular parallelisms between pigmentation in the avian iris and the integument of ectothermic vertebrates

• Published in: PLoS genetics Vol. 17; no. 2; p. e1009404
• Main Authors: Andrade, Pedro, Gazda, Małgorzata A, Araújo, Pedro M, Afonso, Sandra, Rasmussen, Jacob A, Marques, Cristiana I, Lopes, Ricardo J, Gilbert, M Thomas P, Carneiro, Miguel
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-02-2021; Public Library of Science (PLoS)
• Subjects: Animals; Biology and Life Sciences; Birds; Blood vessels; Chromatophores; Chromatophores - metabolism; Color; Coloration; Columbidae - genetics; Columbidae - metabolism; Domestication; Electron microscopy; Eye Color - genetics; Gene expression; Gene Expression Profiling - methods; Genetic analysis; Genetic diversity; Genome-Wide Association Study - methods; Genomes; Genomics - methods; Genotype & phenotype; Glucose Transport Proteins, Facilitative - genetics; Haplotypes; Hypotheses; Integument; Iris; Iris - metabolism; Medicine and Health Sciences; Mutation; Phenotypes; Physical Sciences; Pigmentation; Pigmentation - genetics; Pigments; Polymorphism; RNA Stability - genetics; Skin Pigmentation - genetics; Vertebrates - genetics; Vertebrates - metabolism; Whole Genome Sequencing - methods
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1009404

Birds exhibit striking variation in eye color that arises from interactions between specialized pigment cells named chromatophores. The types of chromatophores present in the avian iris are lacking from the integument of birds or mammals, but are remarkably similar to those found in the skin of ectothermic vertebrates. To investigate molecular mechanisms associated with eye coloration in birds, we took advantage of a Mendelian mutation found in domestic pigeons that alters the deposition of yellow pterin pigments in the iris. Using a combination of genome-wide association analysis and linkage information in pedigrees, we mapped variation in eye coloration in pigeons to a small genomic region of ~8.5kb. This interval contained a single gene, SLC2A11B, which has been previously implicated in skin pigmentation and chromatophore differentiation in fish. Loss of yellow pigmentation is likely caused by a point mutation that introduces a premature STOP codon and leads to lower expression of SLC2A11B through nonsense-mediated mRNA decay. There were no substantial changes in overall gene expression profiles between both iris types as well as in genes directly associated with pterin metabolism and/or chromatophore differentiation. Our findings demonstrate that SLC2A11B is required for the expression of pterin-based pigmentation in the avian iris. They further highlight common molecular mechanisms underlying the production of coloration in the iris of birds and skin of ectothermic vertebrates.