title: The evolution of Sex-linked barring alleles in chickens involves both regulatory and coding changes in CDKN2A.
abstract: Sex-linked barring is a fascinating plumage pattern in chickens recently shown to be associated with two non-coding and two missense mutations affecting the ARF transcript at the CDKN2A tumor suppressor locus. It however remained a mystery whether all four mutations are indeed causative and how they contribute to the barring phenotype. Here, we show that Sex-linked barring is genetically heterogeneous, and that the mutations form three functionally different variant alleles. The B0 allele carries only the two non-coding changes and is associated with the most dilute barring pattern, whereas the B1 and B2 alleles carry both the two non-coding changes and one each of the two missense mutations causing the Sex-linked barring and Sex-linked dilution phenotypes, respectively. The data are consistent with evolution of alleles where the non-coding changes occurred first followed by the two missense mutations that resulted in a phenotype more appealing to humans. We show that one or both of the non-coding changes are cis-regulatory mutations causing a higher CDKN2A expression, whereas the missense mutations reduce the ability of ARF to interact with MDM2. Caspase assays for all genotypes revealed no apoptotic events and our results are consistent with a recent study indicating that the loss of melanocyte progenitors in Sex-linked barring in chicken is caused by premature differentiation and not apoptosis. Our results show that CDKN2A is a major locus driving the differentiation of avian melanocytes in a temporal and spatial manner.
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.|GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Doreen
authors.identifier: 0000-0002-0090-4355
authors.initials: D
authors.lastname: Schwochow Thalmann
authors.affiliation: Department of Neuroscience, Uppsala University, Uppsala, Sweden.
authors.forename: Henrik
authors.identifier: 0000-0002-7659-9043
authors.initials: H
authors.lastname: Ring
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Elisabeth
authors.identifier: 0000-0003-0938-4023
authors.initials: E
authors.lastname: Sundström
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Cao
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Mårten
authors.initials: M
authors.lastname: Larsson
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Susanne
authors.initials: S
authors.lastname: Kerje
authors.affiliation: Linköping University, IFM Biologi, AVIAN Behavioural Genomics and Physiology group, Linköping, Sweden.
authors.forename: Andrey
authors.initials: A
authors.lastname: Höglund
authors.affiliation: Linköping University, IFM Biologi, AVIAN Behavioural Genomics and Physiology group, Linköping, Sweden.
authors.forename: Jesper
authors.identifier: 0000-0002-0868-8722
authors.initials: J
authors.lastname: Fogelholm
authors.affiliation: Linköping University, IFM Biologi, AVIAN Behavioural Genomics and Physiology group, Linköping, Sweden.
authors.forename: Dominic
authors.initials: D
authors.lastname: Wright
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Jemth
authors.affiliation: Department of Neuroscience, Uppsala University, Uppsala, Sweden.
authors.forename: Finn
authors.identifier: 0000-0001-7552-187X
authors.initials: F
authors.lastname: Hallböök
authors.affiliation: GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Bed'Hom
authors.affiliation: Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, United States of America.
authors.forename: Ben
authors.initials: B
authors.lastname: Dorshorst
authors.affiliation: GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors.forename: Michèle
authors.initials: M
authors.lastname: Tixier-Boichard
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.|Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.|Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Leif
authors.identifier: 0000-0002-4085-6968
authors.initials: L
authors.lastname: Andersson
mesh_terms: D000483:Alleles; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002645:Chickens; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D019143:Evolution, Molecular; D005241:Feathers / Q000254:growth & development / Q000378:metabolism; D005260:Female; D008040:Genetic Linkage; D005838:Genotype; D009154:Mutation; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics*
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16