Endodermal Nodal-related signals and mesoderm induction in Xenopus

Development ◽  
2000 ◽  
Vol 127 (6) ◽  
pp. 1173-1183 ◽  
Author(s):  
E. Agius ◽  
M. Oelgeschlager ◽  
O. Wessely ◽  
C. Kemp ◽  
E.M. De Robertis
Keyword(s):  
Dose Response ◽  
Mesoderm Induction ◽  
Beta Catenin ◽  
Blastula Stage ◽  
Modified Model ◽  
Terminal Fragment ◽  
Endogenous Activity ◽  
Carboxy Terminal ◽  
Endodermal Cells ◽  
Molecular Nature

In Xenopus, mesoderm induction by endoderm at the blastula stage is well documented, but the molecular nature of the endogenous inductive signals remains unknown. The carboxy-terminal fragment of Cerberus, designated Cer-S, provides a specific secreted antagonist of mesoderm-inducing Xenopus Nodal-Related (Xnr) factors. Cer-S does not inhibit signalling by other mesoderm inducers such as Activin, Derriere, Vg1 and BMP4, nor by the neural inducer Xnr3. In the present study we show that Cer-S blocks the induction of both dorsal and ventral mesoderm in animal-vegetal Nieuwkoop-type recombinants. During blastula stages Xnr1, Xnr2 and Xnr4 are expressed in a dorsal to ventral gradient in endodermal cells. Dose-response experiments using cer-S mRNA injections support the existence of an endogenous activity gradient of Xnrs. Xnr expression at blastula can be activated by the vegetal determinants VegT and Vg1 acting in synergy with dorsal (beta)-catenin. The data support a modified model for mesoderm induction in Xenopus, in which mesoderm induction is mediated by a gradient of multiple Nodal-related signals released by endoderm at the blastula stage.

Expression of a novel FGF in the Xenopus embryo. A new candidate inducing factor for mesoderm formation and anteroposterior specification

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 711-720 ◽  
Author(s):  
H.V. Isaacs ◽  
D. Tannahill ◽  
J.M. Slack
Keyword(s):  
Specific Activity ◽  
Biological Properties ◽  
The Body ◽  
Mesoderm Induction ◽  
Gastrula Stage ◽  
Blastula Stage ◽  
Mesoderm Formation ◽  
Low Levels

We have cloned and sequenced a new member of the fibroblast growth factor family from Xenopus laevis embryo cDNA. It is most closely related to both mammalian kFGF (FGF-4) and FGF-6 but as it is not clear whether it is a true homologue of either of these genes we provisionally refer to it as XeFGF (Xenopus embryonic FGF). Two sequences were obtained, differing by 11% in derived amino acid sequence, which probably represent pseudotetraploid variants. Both the sequence and the behaviour of in vitro translated protein indicates that, unlike bFGF (FGF-2), XeFGF is a secreted molecule. Recombinant XeFGF protein has mesoderm-inducing activity with a specific activity similar to bFGF. XeFGF mRNA is expressed maternally and zygotically with a peak during the gastrula stage. Both probe protection and in situ hybridization showed that the zygotic expression is concentrated in the posterior of the body axis and later in the tailbud. Later domains of expression were found near the midbrain/hindbrain boundary and at low levels in the myotomes. Because of its biological properties and expression pattern, XeFGF is a good candidate for an inducing factor with possible roles both in mesoderm induction at the blastula stage and in the formation of the anteroposterior axis at the gastrula stage.

bozozok and squint act in parallel to specify dorsal mesoderm and anterior neuroectoderm in zebrafish

Development ◽  
2000 ◽  
Vol 127 (12) ◽  
pp. 2583-2592 ◽  
Author(s):  
H.I. Sirotkin ◽  
S.T. Dougan ◽  
A.F. Schier ◽  
W.S. Talbot
Keyword(s):  
Neural Development ◽  
Mutational Analysis ◽  
Homeobox Gene ◽  
Beta Catenin ◽  
Neural Patterning ◽  
Blastula Stage ◽  
Mesoderm Development ◽  
Dorsal Mesoderm ◽  
Family Gene ◽  
Bmp Antagonists

In vertebrate embryos, maternal (beta)-catenin protein activates the expression of zygotic genes that establish the dorsal axial structures. Among the zygotically acting genes with key roles in the specification of dorsal axial structures are the homeobox gene bozozok (boz) and the nodal-related (TGF-(beta) family) gene squint (sqt). Both genes are expressed in the dorsal yolk syncytial layer, a source of dorsal mesoderm inducing signals, and mutational analysis has indicated that boz and sqt are required for dorsal mesoderm development. Here we examine the regulatory interactions among boz, sqt and a second nodal-related gene, cyclops (cyc). Three lines of evidence indicate that boz and sqt act in parallel to specify dorsal mesoderm and anterior neuroectoderm. First, boz requires sqt function to induce high levels of ectopic dorsal mesoderm, consistent with sqt acting either downstream or in parallel to boz. Second, sqt mRNA is expressed in blastula stage boz mutants, indicating that boz is not essential for activation of sqt transcription, and conversely, boz mRNA is expressed in blastula stage sqt mutants. Third, boz;sqt double mutants have a much more severe phenotype than boz and sqt single mutants. Double mutants consistently lack the anterior neural tube and axial mesoderm, and ventral fates are markedly expanded. Expression of chordin and noggin1 is greatly reduced in boz;sqt mutants, indicating that the boz and sqt pathways have overlapping roles in activating secreted BMP antagonists. In striking contrast to boz;sqt double mutants, anterior neural fates are specified in boz;sqt;cyc triple mutants. This indicates that cyc represses anterior neural development, and that boz and sqt counteract this repressive function. Our results support a model in which boz and sqt act in parallel to induce dorsalizing BMP-antagonists and to counteract the repressive function of cyc in neural patterning.

A Major Role of p95/611-CTF, a Carboxy-Terminal Fragment of HER2, in the Down-modulation of the Estrogen Receptor in HER2-Positive Breast Cancers

2010 ◽  
Vol 70 (21) ◽  
pp. 8537-8546 ◽  
Author(s):  
Josep Lluís Parra-Palau ◽  
Kim Pedersen ◽  
Vicente Peg ◽  
Maurizio Scaltriti ◽  
Pier Davide Angelini ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Breast Cancers ◽  
Her2 Positive ◽  
Terminal Fragment ◽  
Carboxy Terminal

XCtBP is a XTcf-3 co-repressor with roles throughout Xenopus development

Development ◽  
1999 ◽  
Vol 126 (14) ◽  
pp. 3159-3170 ◽  
Author(s):  
M. Brannon ◽  
J.D. Brown ◽  
R. Bates ◽  
D. Kimelman ◽  
R.T. Moon
Keyword(s):  
Binding Sites ◽  
Transcriptional Repression ◽  
Wnt Pathway ◽  
Ectopic Expression ◽  
Axis Formation ◽  
Beta Catenin ◽  
Carboxy Terminus ◽  
Xenopus Development ◽  
Carboxy Terminal Domain ◽  
Carboxy Terminal

XTcf-3 is an HMG box transcription factor that mediates Xenopus dorsal-ventral axis formation. As a Wnt pathway effector, XTcf-3 interacts with beta-catenin and activates the expression of the dorsal organizing gene siamois, while in the absence of beta-catenin, XTcf-3 functions as a transcriptional repressor. We show that XTcf-3 contains amino- and carboxy-terminal repressor domains and have identified a Xenopus member of the C-terminal Binding Protein family of transcriptional co-repressors (XCtBP) as the C-terminal co-repressor. We show that two XCtBP binding sites near the XTcf-3 carboxy-terminus are required for the interaction of XTcf-3 and XCtBP and for the transcriptional repression mediated by the XTcf-3 carboxy-terminal domain. By fusing the GAL4 activation domain to XCtBP we have generated an antimorphic protein, XCtBP/G4A, that activates siamois transcription through an interaction with endogenous XTcf-3. Ectopic expression of XCtBP/G4A demonstrates that XCtBP functions in the regulation of head and notochord development. Our data support a role for XCtBP as a co-repressor throughout Xenopus development and indicate that XCtBP/G4A will be a useful tool in determining how XCtBP functions in various developmental processes.

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