title: Molecular characterization and developmental expression of the aryl hydrocarbon receptor from the chick embryo.
abstract: The aryl hydrocarbon receptor (AhR) was cloned from the chick embryo and its function and developmental expression characterized. Chicken AhR cDNA coded for 858 amino acid protein and 396 bp of 3' UTR. The basic helix loop helix domain exhibited 87-100% amino acid identity to avian, mammalian, and amphibian AhR, and 69-74% to piscine AhR. The PAS (Per-ARNT-Sim) region was slightly less well conserved with (a) 97% identity to other avian sequences, (b) 81-86% to amphibian and mammalian AhR, and (c) 64-69% with piscine AhR. The carboxy terminus diverged the most among species with less than 53% amino acid identity between chicken and any available mammalian and piscine AhR sequences. The chicken AhR RNA and protein were 6.1 kb and 103 kDa, respectively. Chicken AhR dimerized with human AhR nuclear translocator and bound the mammalian dioxin-response element in a ligand-dependent manner. AhR protein was detected in neural ganglia; smooth, cardiac, and skeletal muscle; and epithelium involved in epithelial-to-mesenchymal transformations, such as pituitary, gastrointestinal tract, limb apical-ectodermal ridge, and kidney collecting ducts. AhR mRNA was detected in all tissues expressing protein, except myocardium. Cytochrome P4501A4 mRNA was highly induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in a subset of tissues expressing AhR, including small intestine, liver, kidney, blood vessels, and outflow tract myocardium. In conclusion, the AhR sequence and function is highly conserved between birds and mammals, and although many tissues express AhR during chick embryo development, only a subset are responsive to TCDD induction of CYP1A4.
authors.affiliation: College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque 87131, USA. mkwalker@unm.edu
authors.forename: M K
authors.initials: MK
authors.lastname: Walker
authors.forename: S E
authors.initials: SE
authors.lastname: Heid
authors.forename: S M
authors.initials: SM
authors.lastname: Smith
authors.forename: H I
authors.initials: HI
authors.lastname: Swanson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D030161:Avian Proteins; D015152:Blotting, Northern; D015153:Blotting, Western; D002642:Chick Embryo; D002645:Chickens; D003001:Cloning, Molecular; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins; D004586:Electrophoresis; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000502:physiology*; D004790:Enzyme Induction / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000096:biosynthesis / Q000235:genetics; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013723:Teratogens / Q000633:toxicity; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C497396:ARNT protein, human; C497397:Arnt protein, mouse; D030161:Avian Proteins; D004268:DNA-Binding Proteins; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D013723:Teratogens; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D001189:Aryl Hydrocarbon Hydroxylases; C416342:CYP1A4 protein, Gallus gallus; D019363:Cytochrome P-450 CYP1A1