title: Gizzard formation and the role of Bapx1.
abstract: The anterior-posterior gut pattern is formed from three broad domains: fore-, mid-, and hindgut that have distinct functional, morphological, and molecular boundaries. The stomach demarcates the posterior boundary of the foregut. Avian stomachs are composed of two chambers: the anterior chamber (proventriculus) and the thick muscular posterior chamber (gizzard). Expression of candidate pattern formation control factors are restricted in the chick stomach regions such that Bmp4 and Wnt5a are not expressed in the gizzard. We previously implicated Bmp4 as controlling growth and differentiation of the gut musculature. Bmp4 is not expressed in the developing gizzard but is expressed in the rest of the gut including the adjacent proventriculus and midgut. Bapx1 (Nkx3.2) is expressed in the gizzard musculature but not in the proventriculus or midgut. We show ectopic expression of Bapx1 in the proventriculus results in a gizzard-like morphology and inhibits the normal proventricular expression of Bmp4 and Wnt5a. Overexpression of a reverse-function Bapx1 construct can result in a small stomach and ectopic extension of Bmp4 and Wnt5a expression into the gizzard. We suggest the role of Bapx1 is to regulate the expression of Bmp4 and Wnt5a to pattern the avian stomach.
authors.affiliation: Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
authors.forename: C
authors.initials: C
authors.lastname: Nielsen
authors.forename: L C
authors.initials: LC
authors.lastname: Murtaugh
authors.forename: J C
authors.initials: JC
authors.lastname: Chyung
authors.forename: A
authors.initials: A
authors.lastname: Lassar
authors.forename: D J
authors.initials: DJ
authors.lastname: Roberts
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000502:physiology; D002642:Chick Embryo; D005895:Gizzard, Avian / Q000196:embryology*; D018398:Homeodomain Proteins / Q000502:physiology*; D009687:Nuclear Proteins; D051761:Paired Box Transcription Factors; D014157:Transcription Factors / Q000502:physiology; D000097577:Homeobox Protein PITX2
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C101485:homeobox protein PITX1; C433629:homeobox protein PITX3