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Identification of the yellow skin gene reveals a hybrid origin of the domestic chicken
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
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2008 (English)In: PLoS Genetics, ISSN 1553-7390, Vol. 4, no 2, e1000010- p.Article in journal (Refereed) Published
Abstract [en]

Yellow skin is an abundant phenotype among domestic chickens and is caused by a recessive allele (W*Y) that allows deposition of yellow carotenoids in the skin. Here we show that yellow skin is caused by one or more cis-acting and tissue-specific regulatory mutation(s) that inhibit expression of BCDO2 (beta-carotene dioxygenase 2) in skin. Our data imply that carotenoids are taken up from the circulation in both genotypes but are degraded by BCDO2 in skin from animals carrying the white skin allele (W*W). Surprisingly, our results demonstrate that yellow skin does not originate from the red junglefowl (Gallus gallus), the presumed sole wild ancestor of the domestic chicken, but most likely from the closely related grey junglefowl (Gallus sonneratii). This is the first conclusive evidence for a hybrid origin of the domestic chicken, and it has important implications for our views of the domestication process.

Place, publisher, year, edition, pages
2008. Vol. 4, no 2, e1000010- p.
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-98252DOI: 10.1371/journal.pgen.1000010ISI: 000255386100011PubMedID: 18454198OAI: oai:DiVA.org:uu-98252DiVA: diva2:173954
Available from: 2009-02-18 Created: 2009-02-18 Last updated: 2012-01-16Bibliographically approved
In thesis
1. Genetic Studies of Pigmentation in Chicken
Open this publication in new window or tab >>Genetic Studies of Pigmentation in Chicken
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Domestic animals have been selected by humans for thousands of years, which have drastically altered their genetic constitution and phenotypes. In this thesis, several of the most important genes causing pigmentation differences between the wild red junglefowl (Gallus gallus) and domestic chickens have been identified. Pigmentation phenotypes are easily scored, and the genes underlying these phenotypes are valuable models to study gene function and gene interaction.

Dominant white colour is widespread among domestic chickens. The Dominant white allele specifically inhibits the expression of black (eumelanin) pigment and we identified several insertion/deletion mutations in the PMEL17 gene causing the different phenotypes controlled by this locus. The Silver allele on the other hand inhibits the expression of red (pheomelanin) colour and is a genetic variant of the SLC45A2 gene. Silver is the first pheomelanin-specific mutation(s) reported for this gene. An 8 kb deletion, including a conserved enhancer element, 14 kb upstream of the transcription factor SOX10 is causing the Dark brown phenotype. This phenotype restricts the expression of eumelanin and enhances red pheomelanin in specific parts of the plumage. These three gene identifications have extended the knowledge about genes affecting melanocyte function.

Carotenoid-based pigmentation is of utmost importance in birds and other animals. The yellow skin allele in chicken allows deposition of carotenoids in skin and explains why most domestic chickens have yellow legs. We demonstrated that the yellow skin phenotype is caused by a tissue specific regulatory mutation in the gene for the enzyme beta-caroten dioxygenase 2 (BCDO2). This was the first identification of a specific gene underlying carotenoid-based pigmentation. Interestingly, the yellow skin haplotype was shown to originate from the grey junglefowl (Gallus sonneratii) and not the red junglefowl as expected, thus presenting the first conclusive evidence for a hybrid origin of the domestic chicken.

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 44 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 428
Series
Identifiers
urn:nbn:se:uu:diva-98426 (URN)978-91-554-7439-3 (ISBN)
Public defence
2009-04-03, B42, BMC, Husargatan 3 , Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-03-12 Created: 2009-02-22 Last updated: 2009-05-28Bibliographically approved
2. Genetic and Genomic Studies in Chicken: Assigning Function to Vertebrate Genes
Open this publication in new window or tab >>Genetic and Genomic Studies in Chicken: Assigning Function to Vertebrate Genes
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A major challenge in the post-genomic era is to understand how genome sequence variants (genotype) give rise to the enormous diversity observed in terms of morphology, physiology and behavior (phenotype) among living organisms. Domestic animals—with their tremendous phenotypic variation—are excellent model organisms for determining the relationships between genotype and phenotype. In this thesis, I describe the utilization of the chicken, in combination with modern genetic and genomic approaches, in developing our understanding of the genetic mechanisms underlying phenotypic variation. These studies provide novel information on the genetics behind variation in carotenoid- and melanin-based pigmentation—observed in many organisms—and also cast light on the genetic basis of chicken domestication.

In paper I, we report that the yellow skin phenotype—observed in most commercial chickens—is caused by one or several tissue-specific mutations altering the expression of beta-carotene oxygenase 2 (BCO2 or BCDO2) in skin. In addition, we present the first conclusive evidence of a hybrid origin of the domestic chicken, since the allele causing yellow skin most likely originates from the grey jungle fowl (Gallus sonneratii) and not from the previously described sole ancestor, the red jungle fowl (Gallus gallus).

In paper II, we detect a number of loci that were likely important during the domestication process of chicken and the later specialization into meat (broiler) and egg (layer) producing lines. One of the major findings was that worldwide, almost all domestic chickens carry a missense mutation in TSHR (thyroid stimulating hormone receptor) in a position that is completely conserved amongst vertebrates. We speculate that this “domestication-mutation” has played an important role in the transformation of the wild red jungle fowl ancestor into the modern domestic chicken.

In paper III, we demonstrate that the dilution of red (pheomelanin) pigmentation—observed in the plumage of the Inhibitor of Gold chicken—is caused by a frame-shift mutation in the catechol-O-methyltransferase domain containing 1 (COMTD1) gene. The production and regulation of pheomelanin is poorly understood and this discovery advances our current knowledge of this pathway.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 732
Keyword
Chicken, BCO2, TSHR, COMTD1, Phenotypic variation, Domestication, Selective sweeps, Pigmentation
National Category
Medical and Health Sciences
Research subject
Molecular Genetics
Identifiers
urn:nbn:se:uu:diva-162597 (URN)978-91-554-8246-6 (ISBN)
Public defence
2012-02-03, B42, BMC, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2012-01-13 Created: 2011-12-01 Last updated: 2012-01-16Bibliographically approved

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