Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract??? Siamois is the transcriptional mediator of the dorsal Wnt signaling pathway and is necessary for formation of the Spemann organizer and dorsoanterior development in Xenopus. We have determined that XIC, a Xenopus I-mfa domain protein that regulates Tcf3 binding, is required for dorsoaxial development and specifically for Siamois activity in establishing the dorsal organizer. In loss-of-function studies, we found that embryos injected with a morpholino to XIC mRNA (XIC morphpolino) are missing head structures, neural tube, notochord, and paraxial mesoderm as well as NCAM and XMyoD expression. Although Siamois, Twin, and Xnr3 expression is normal in morpholino-injected embryos, levels of downstream organizer factors, including goosecoid, Xnot, Cerberus, and chordin, are severely reduced. Ectopic axis formation induced by Siamois is repressed by injection of the XIC morpholino and further repressed by coinjection of beta-catenin or a constitutively active Tcf3/HMG/G4A fusion. Activation of reporters driven by the Siamois-responsive proximal element of the goosecoid promoter is inhibited in the presence of the morpholino and can be rescued by murine I-mfa and by a dominant-negative Tcf3. The data indicate a role for XIC in limiting Tcf3-dependent repression of Siamois activities that are required for goosecoid transcription and for dorsal organizer formation.
Blitz,
Anterior neurectoderm is progressively induced during gastrulation: the role of the Xenopus homeobox gene orthodenticle.
1995, Pubmed,
Xenbase
Blitz,
Anterior neurectoderm is progressively induced during gastrulation: the role of the Xenopus homeobox gene orthodenticle.
1995,
Pubmed
,
Xenbase
Bouwmeester,
Cerberus is a head-inducing secreted factor expressed in the anterior endoderm of Spemann's organizer.
1996,
Pubmed
,
Xenbase
Bradley,
The structure and expression of the Xenopus Krox-20 gene: conserved and divergent patterns of expression in rhombomeres and neural crest.
1993,
Pubmed
,
Xenbase
Brannon,
A beta-catenin/XTcf-3 complex binds to the siamois promoter to regulate dorsal axis specification in Xenopus.
1997,
Pubmed
,
Xenbase
Carnac,
The homeobox gene Siamois is a target of the Wnt dorsalisation pathway and triggers organiser activity in the absence of mesoderm.
1996,
Pubmed
,
Xenbase
Chen,
I-mf, a novel myogenic repressor, interacts with members of the MyoD family.
1996,
Pubmed
Christian,
Interactions between Xwnt-8 and Spemann organizer signaling pathways generate dorsoventral pattern in the embryonic mesoderm of Xenopus.
1993,
Pubmed
,
Xenbase
Christian,
Isolation of cDNAs partially encoding four Xenopus Wnt-1/int-1-related proteins and characterization of their transient expression during embryonic development.
1991,
Pubmed
,
Xenbase
Cui,
Xwnt-8b: a maternally expressed Xenopus Wnt gene with a potential role in establishing the dorsoventral axis.
1995,
Pubmed
,
Xenbase
Darken,
Axis induction by wnt signaling: Target promoter responsiveness regulates competence.
2001,
Pubmed
,
Xenbase
Darras,
Animal and vegetal pole cells of early Xenopus embryos respond differently to maternal dorsal determinants: implications for the patterning of the organiser.
1997,
Pubmed
,
Xenbase
De Robertis,
The establishment of Spemann's organizer and patterning of the vertebrate embryo.
2000,
Pubmed
,
Xenbase
Engleka,
Siamois cooperates with TGFbeta signals to induce the complete function of the Spemann-Mangold organizer.
2001,
Pubmed
,
Xenbase
Fan,
A role for Siamois in Spemann organizer formation.
1997,
Pubmed
,
Xenbase
Gawantka,
Antagonizing the Spemann organizer: role of the homeobox gene Xvent-1.
1995,
Pubmed
,
Xenbase
Hamilton,
Difference in XTcf-3 dependency accounts for change in response to beta-catenin-mediated Wnt signalling in Xenopus blastula.
2001,
Pubmed
,
Xenbase
Harland,
Formation and function of Spemann's organizer.
1997,
Pubmed
Heasman,
Beta-catenin signaling activity dissected in the early Xenopus embryo: a novel antisense approach.
2000,
Pubmed
,
Xenbase
Hemmati-Brivanlou,
Cephalic expression and molecular characterization of Xenopus En-2.
1991,
Pubmed
,
Xenbase
Hensey,
Programmed cell death during Xenopus development: a spatio-temporal analysis.
1998,
Pubmed
,
Xenbase
Hopwood,
MyoD expression in the forming somites is an early response to mesoderm induction in Xenopus embryos.
1989,
Pubmed
,
Xenbase
Houston,
Repression of organizer genes in dorsal and ventral Xenopus cells mediated by maternal XTcf3.
2002,
Pubmed
,
Xenbase
Hurlstone,
T-cell factors: turn-ons and turn-offs.
2002,
Pubmed
Jones,
Development of the ectoderm in Xenopus: tissue specification and the role of cell association and division.
1986,
Pubmed
,
Xenbase
Kelly,
Histological preparation of Xenopus laevis oocytes and embryos.
1991,
Pubmed
,
Xenbase
Kessler,
Siamois is required for formation of Spemann's organizer.
1997,
Pubmed
,
Xenbase
Kintner,
Expression of Xenopus N-CAM RNA in ectoderm is an early response to neural induction.
1987,
Pubmed
,
Xenbase
Kodjabachian,
Siamois functions in the early blastula to induce Spemann's organiser.
2001,
Pubmed
,
Xenbase
Laurent,
The Xenopus homeobox gene twin mediates Wnt induction of goosecoid in establishment of Spemann's organizer.
1997,
Pubmed
,
Xenbase
Lemaire,
Expression cloning of Siamois, a Xenopus homeobox gene expressed in dorsal-vegetal cells of blastulae and able to induce a complete secondary axis.
1995,
Pubmed
,
Xenbase
McGrew,
Direct regulation of the Xenopus engrailed-2 promoter by the Wnt signaling pathway, and a molecular screen for Wnt-responsive genes, confirm a role for Wnt signaling during neural patterning in Xenopus.
1999,
Pubmed
,
Xenbase
McKendry,
LEF-1/TCF proteins mediate wnt-inducible transcription from the Xenopus nodal-related 3 promoter.
1997,
Pubmed
,
Xenbase
Molenaar,
XTcf-3 transcription factor mediates beta-catenin-induced axis formation in Xenopus embryos.
1996,
Pubmed
,
Xenbase
Moon,
From cortical rotation to organizer gene expression: toward a molecular explanation of axis specification in Xenopus.
1998,
Pubmed
,
Xenbase
Niehrs,
Regionally specific induction by the Spemann-Mangold organizer.
2004,
Pubmed
Piccolo,
The head inducer Cerberus is a multifunctional antagonist of Nodal, BMP and Wnt signals.
1999,
Pubmed
,
Xenbase
Rupp,
Xenopus embryos regulate the nuclear localization of XMyoD.
1994,
Pubmed
,
Xenbase
Sadowski,
A vector for expressing GAL4(1-147) fusions in mammalian cells.
1989,
Pubmed
Sasai,
Xenopus chordin: a novel dorsalizing factor activated by organizer-specific homeobox genes.
1994,
Pubmed
,
Xenbase
Smith,
A nodal-related gene defines a physical and functional domain within the Spemann organizer.
1995,
Pubmed
,
Xenbase
Smith,
Expression of a Xenopus homolog of Brachyury (T) is an immediate-early response to mesoderm induction.
1991,
Pubmed
,
Xenbase
Snider,
Inhibition of Tcf3 binding by I-mfa domain proteins.
2001,
Pubmed
,
Xenbase
Sokol,
Wnt signaling and dorso-ventral axis specification in vertebrates.
1999,
Pubmed
Stewart,
The anterior extent of dorsal development of the Xenopus embryonic axis depends on the quantity of organizer in the late blastula.
1990,
Pubmed
,
Xenbase
Watabe,
Molecular mechanisms of Spemann's organizer formation: conserved growth factor synergy between Xenopus and mouse.
1995,
Pubmed
,
Xenbase
Wessely,
Analysis of Spemann organizer formation in Xenopus embryos by cDNA macroarrays.
2004,
Pubmed
,
Xenbase
Yamamoto,
Molecular link in the sequential induction of the Spemann organizer: direct activation of the cerberus gene by Xlim-1, Xotx2, Mix.1, and Siamois, immediately downstream from Nodal and Wnt signaling.
2003,
Pubmed
,
Xenbase
Yang,
Beta-catenin/Tcf-regulated transcription prior to the midblastula transition.
2002,
Pubmed
,
Xenbase
Yost,
The axis-inducing activity, stability, and subcellular distribution of beta-catenin is regulated in Xenopus embryos by glycogen synthase kinase 3.
1996,
Pubmed
,
Xenbase
Zaraisky,
The homeobox-containing gene XANF-1 may control development of the Spemann organizer.
1995,
Pubmed
,
Xenbase
Zhang,
The role of maternal VegT in establishing the primary germ layers in Xenopus embryos.
1998,
Pubmed
,
Xenbase
von Dassow,
Induction of the Xenopus organizer: expression and regulation of Xnot, a novel FGF and activin-regulated homeo box gene.
1993,
Pubmed
,
Xenbase
