title: Wnt3 signaling in the epiblast is required for proper orientation of the anteroposterior axis.
abstract: The establishment of anteroposterior (AP) polarity in the early mouse epiblast is crucial for the initiation of gastrulation and the subsequent formation of the embryonic (head to tail) axis. The localization of anterior and posterior determining genes to the appropriate region of the embryo is a dynamic process that underlies this early polarity. Several studies indicate that morphological and molecular markers which define the early AP axis are first aligned along the short axis of the elliptical egg cylinder. Subsequently, just prior to the time of primitive streak formation, a conformational change in the embryo realigns these markers with the long axis. We demonstrate that embryos lacking the signaling factor Wnt3 exhibit defects in this axial realignment. In addition, chimeric analyses and conditional removal of Wnt3 activity reveal that Wnt3 expression in the epiblast is required for induction of the primitive streak and mesoderm whereas activity in the posterior visceral endoderm is dispensable.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA. jeff_barrow@byu.edu
authors.forename: Jeffery R
authors.initials: JR
authors.lastname: Barrow
authors.forename: William D
authors.initials: WD
authors.lastname: Howell
authors.forename: Michael
authors.initials: M
authors.lastname: Rule
authors.forename: Shigemi
authors.initials: S
authors.lastname: Hayashi
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Thomas
authors.forename: Mario R
authors.initials: MR
authors.lastname: Capecchi
authors.forename: Andrew P
authors.initials: AP
authors.lastname: McMahon
mesh_terms: D000483:Alleles; D000818:Animals; D019521:Body Patterning; D002678:Chimera; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D047108:Embryonic Development; D005775:Gastrula / Q000378:metabolism; D005855:Germ Layers / Q000196:embryology* / Q000378:metabolism*; D019426:Integrases / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism*; D060508:Wnt3 Protein
chemical_list: D051153:Wnt Proteins; D060508:Wnt3 Protein; C555508:Wnt3 protein, mouse; C045073:Cre recombinase; D019426:Integrases