title: Ras-dva is a novel Pit-1- and glucocorticoid-regulated gene in the embryonic anterior pituitary gland.
abstract: Glucocorticoids play a role in functional differentiation of pituitary somatotrophs and lactotrophs during embryogenesis. Ras-dva was identified as a gene regulated by anterior neural fold protein-1/homeobox expressed in embryonic stem cells-1, a transcription factor known to be critical in pituitary development, and has an expression profile in the chicken embryonic pituitary gland that is consistent with in vivo regulation by glucocorticoids. The objective of this study was to characterize expression and regulation of ras-dva mRNA in the developing chicken anterior pituitary. Pituitary ras-dva mRNA levels increased during embryogenesis to a maximum on embryonic day (e) 18 and then decreased and remained low or undetectable after hatch. Ras-dva expression was highly enriched in the pituitary gland on e18 relative to other tissues examined. Glucocorticoid treatment of pituitary cells from mid- and late-stage embryos rapidly increased ras-dva mRNA, suggesting it may be a direct transcriptional target of glucocorticoids. A reporter construct driven by 4 kb of the chicken ras-dva 5'-flanking region, containing six putative pituitary-specific transcription factor-1 (Pit-1) binding sites and two potential glucocorticoid receptor (GR) binding sites, was highly activated in embryonic pituitary cells and up-regulated by corticosterone. Mutagenesis of the most proximal Pit-1 site decreased promoter activity in chicken e11 pituitary cells, indicating regulation of ras-dva by Pit-1. However, mutating putative GR binding sites did not substantially reduce induction of ras-dva promoter activity by corticosterone, suggesting additional DNA elements within the 5'-flanking region are responsible for glucocorticoid regulation. We have identified ras-dva as a glucocorticoid-regulated gene that is likely expressed in cells of the Pit-1 lineage within the developing anterior pituitary gland.
authors.affiliation: Molecular and Cell Biology Program and Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Ellestad
authors.forename: Tom E
authors.initials: TE
authors.lastname: Porter
mesh_terms: D000818:Animals; D001665:Binding Sites; D002642:Chick Embryo; D002645:Chickens; D005434:Flow Cytometry; D005938:Glucocorticoids / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050817:Transcription Factor Pit-1 / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D050817:Transcription Factor Pit-1; D020559:Monomeric GTP-Binding Proteins