title: A genomic duplication is associated with ectopic eomesodermin expression in the embryonic chicken comb and two duplex-comb phenotypes.
abstract: Duplex-comb (D) is one of three major loci affecting comb morphology in the domestic chicken. Here we show that the two Duplex-comb alleles, V-shaped (D*V) and Buttercup (D*C), are both associated with a 20 Kb tandem duplication containing several conserved putative regulatory elements located 200 Kb upstream of the eomesodermin gene (EOMES). EOMES is a T-box transcription factor that is involved in mesoderm specification during gastrulation. In D*V and D*C chicken embryos we find that EOMES is ectopically expressed in the ectoderm of the comb-developing region as compared to wild-type embryos. The confinement of the ectopic expression of EOMES to the ectoderm is in stark contrast to the causal mechanisms underlying the two other major comb loci in the chicken (Rose-comb and Pea-comb) in which the transcription factors MNR2 and SOX5 are ectopically expressed strictly in the mesenchyme. Interestingly, the causal mutations of all three major comb loci in the chicken are now known to be composed of large-scale structural genomic variants that each result in ectopic expression of transcription factors. The Duplex-comb locus also illustrates the evolution of alleles in domestic animals, which means that alleles evolve by the accumulation of two or more consecutive mutations affecting the phenotype. We do not yet know whether the V-shaped or Buttercup allele correspond to the second mutation that occurred on the haplotype of the original duplication event.
authors: Science for Life Laboratory, Dept. of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden; Dept. of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, United States of America.
authors: Ben
authors: B
authors: Dorshorst
authors: Dept. of Neuroscience, Uppsala University, Uppsala, Sweden.
authors: Mohammad
authors: M
authors: Harun-Or-Rashid
authors: Dept. of Neuroscience, Uppsala University, Uppsala, Sweden.
authors: Alireza Jian
authors: AJ
authors: Bagherpoor
authors: Science for Life Laboratory, Dept. of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors: Carl-Johan
authors: CJ
authors: Rubin
authors: Prestage Dept. of Poultry Science, North Carolina State University, Raleigh, North Carolina, United States of America.
authors: Chris
authors: C
authors: Ashwell
authors: INRA, UE 1295 PEAT Pôle d'Expérimentation Avicole de Tours, Nouzilly, France.
authors: David
authors: D
authors: Gourichon
authors: INRA, AgroParisTech, UMR1313 Animal Genetics and Integrative Biology, Jouy-en-Josas, France.
authors: Michèle
authors: M
authors: Tixier-Boichard
authors: Dept. of Neuroscience, Uppsala University, Uppsala, Sweden.
authors: Finn
authors: F
authors: Hallböök
authors: Science for Life Laboratory, Dept. of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden; Science for Life Laboratory, Dept. of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors: Leif
authors: L
authors: Andersson
mesh_terms: D000818:Animals; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics / Q000254:growth & development; D004475:Ectoderm / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D047108:Embryonic Development / Q000235:genetics*; D054262:Gastrulation / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D020131:Genes, Duplicate; D016678:Genome; D023281:Genomics; D006239:Haplotypes; D009154:Mutation; D020825:T-Box Domain Proteins / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D020825:T-Box Domain Proteins