title: Cloning and expression of a DAX1 homologue in the chicken embryo.
abstract: DAX1 is an unusual member of the orphan nuclear receptor family of transcription factors. Mutations in human DAX1 cause X-linked adrenal hypoplasia congenita, while abnormal duplication of the gene is responsible for male-to-female dosage-sensitive sex reversal. Based on these and other observations, DAX1 is thought to play a role in adrenal and gonadal development in mammals. As DAX1 has not previously been described in any other vertebrate, a putative avian DAX1 clone was isolated from an embryonic chicken (Gallus domesticus) urogenital ridge cDNA library. The expression profile of this cDNA was then examined during gonadogenesis. The clone included the conserved 3' ligand-binding motif identified in humans and mice but the 5' region lacked the repeat motif thought to specify a DNA-binding domain in mammals. Southern blot analysis and fluorescence in situ hybridisation mapping showed that the gene is autosomal, located on chromosome 1q. Sequence comparisons showed that the putative chicken DAX1 protein has 63 and 60% identity with the human and mouse proteins respectively over the region of the conserved ligand-binding domain. However, stronger identity (74%) exists with a putative alligator DAX1 sequence over the same region. Northern blotting detected a single 1.4 kb transcript in late embryonic chicken gonads, while RNase protection assays revealed expression in the embryonic gonads of both sexes during the period of sexual differentiation. Expression increased in both sexes during gonadogenesis, but was higher in females than in males. This is the first description of a DAX1 homologue in a non-mammalian vertebrate.
authors.affiliation: Department of Paediatrics and Centre for Hormone Research, The University of Melbourne, Royal Children's Hospital, Melbourne, Victoria 3052, Australia. smithc@cryptic.rch.unimelb.edu.au
authors.forename: C A
authors.initials: CA
authors.lastname: Smith
authors.forename: V
authors.initials: V
authors.lastname: Clifford
authors.forename: P S
authors.initials: PS
authors.lastname: Western
authors.forename: S A
authors.initials: SA
authors.lastname: Wilcox
authors.forename: K S
authors.initials: KS
authors.lastname: Bell
authors.forename: A H
authors.initials: AH
authors.lastname: Sinclair
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002642:Chick Embryo; D003001:Cloning, Molecular; D057137:DAX-1 Orphan Nuclear Receptor; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008969:Molecular Sequence Data; D018168:Receptors, Retinoic Acid / Q000235:genetics*; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D019849:Sex Determination Processes; D014157:Transcription Factors / Q000235:genetics*; D014566:Urogenital System / Q000378:metabolism
chemical_list: D057137:DAX-1 Orphan Nuclear Receptor; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C539965:NR0B1 protein, human; C539966:Nr0b1 protein, mouse; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D014157:Transcription Factors