Graded interference with FGF signalling reveals its dorsoventral asymmetry at the mid-hindbrain boundary

Development ◽  
1999 ◽  
Vol 126 (24) ◽  
pp. 5659-5667 ◽  
Author(s):  
M. Carl ◽  
J. Wittbrodt
Keyword(s):  
Target Gene ◽  
Fibroblast Growth Factors ◽  
Dominant Negative ◽  
Signalling Pathways ◽  
Neural Patterning ◽  
Central Importance ◽  
Fgf Receptor ◽  
Anteroposterior Patterning ◽  
Dorsoventral Axis ◽  
Fgf Signalling

Signalling by fibroblast growth factors (FGFs) at the mid-hindbrain boundary (MHB) is of central importance for anteroposterior neural patterning from the isthmic organiser. Graded suppression of FGF signalling by increasing amounts of a dominant negative FGF receptor provides evidence that in addition to anteroposterior patterning, FGF signalling is also involved in patterning along the dorsoventral axis at the MHB. FGF signalling at the MHB is required for the activation of the HH target gene spalt at the MHB. Our results indicate that FGF signalling mediates the competence of the MHB to activate spalt in response to SHH. This interdependence of the two signalling pathways is also found in the outbudding optic vesicle where HH requires functional FGF signalling to activate spalt in the proximal eye region.

eFGF, Xcad3 and Hox genes form a molecular pathway that establishes the anteroposterior axis in Xenopus

Development ◽  
1996 ◽  
Vol 122 (12) ◽  
pp. 3881-3892 ◽  
Author(s):  
M.E. Pownall ◽  
A.S. Tucker ◽  
J.M. Slack ◽  
H.V. Isaacs
Keyword(s):  
Hox Genes ◽  
Dominant Negative ◽  
Transformation Model ◽  
Neural Patterning ◽  
Fgf Receptor ◽  
Anteroposterior Patterning ◽  
Anteroposterior Axis ◽  
Ectopic Activation ◽  
Transforming Activity ◽  
Fgf Signalling

Classical embryological experiments suggest that a posterior signal is required for patterning the developing anteroposterior axis. In this paper, we investigate a potential role for FGF signalling in this process. During normal development, embryonic fibroblast growth factor (eFGF) is expressed in the posterior of the Xenopus embryo. We have previously shown that overexpression of eFGF from the start of gastrulation results in a posteriorised phenotype of reduced head and enlarged proctodaeum. We have now determined the molecular basis of this phenotype and we propose a role for eFGF in normal anteroposterior patterning. In this study, we show that the overexpression of eFGF causes the up-regulation of a number of posteriorly expressed genes, and prominent among these are Xcad3, a caudal homologue, and the Hox genes, in particular HoxA7. There is both an increase of expression within the normal domains and an extension of expression towards the anterior. Application of eFGF-loaded beads to specific regions of gastrulae reveals that anterior truncations arise from an effect on the developing dorsal axis. Similar anterior truncations are caused by the dorsal overexpression of Xcad3 or HoxA7. This suggests that this aspect of the eFGF overexpression phenotype is caused by the ectopic activation of posterior genes in anterior regions. Further results using the dominant negative FGF receptor show that the normal expression of posterior Hox genes is dependent on FGF signalling and that this regulation is likely mediated by the activation of Xcad3. The biological activity of eFGF, together with its expression in the posterior of the embryo, make it a good candidate to fulfil the role of the ‘transforming’ activity proposed by Nieuwkoop in his ‘activation and transformation’ model for neural patterning.

FGF signalling in the early specification of mesoderm in Xenopus

Development ◽  
1993 ◽  
Vol 118 (2) ◽  
pp. 477-487 ◽  
Author(s):  
E. Amaya ◽  
P.A. Stein ◽  
T.J. Musci ◽  
M.W. Kirschner
Keyword(s):  
Dorsal Side ◽  
Dominant Negative ◽  
Early Gene ◽  
Immediate Early ◽  
Mesoderm Induction ◽  
Fgf Receptor ◽  
Muscle Formation ◽  
Fgf Signalling ◽  
Lateral Mesoderm

We have examined the role of FGF signalling in the development of muscle and notochord and in the expression of early mesodermal markers in Xenopus embryos. Disruption of the FGF signalling pathway by expression of a dominant negative construct of the FGF receptor (XFD) generally results in gastrulation defects that are later evident in the formation of the trunk and tail, though head structures are formed nearly normally. These defects are reflected in the loss of notochord and muscle. Even in embryos that show mild defects and gastrulate properly, muscle formation is impaired, suggesting that morphogenesis and tissue differentiation each depend on FGF. The XFD protein inhibits the expression of the immediate early gene brachyury throughout the marginal zone, including the dorsal side; it does not, however, inhibit the dorsal lip marker goosecoid, which is expressed in the first involuting mesoderm at the dorsal side that will underlie the head. The XFD protein also inhibits Xpo expression, an immediate early marker of ventral and lateral mesoderm. These results suggest that FGF is involved in the earliest events of most mesoderm induction that occur before gastrulation and that the early dorsal mesoderm is already composed of two cell populations that differ in their requirements for FGF.

Induction of the mesendoderm in the zebrafish germ ring by yolk cell-derived TGF-beta family signals and discrimination of mesoderm and endoderm by FGF

Development ◽  
1999 ◽  
Vol 126 (14) ◽  
pp. 3067-3078 ◽  
Author(s):  
A. Rodaway ◽  
H. Takeda ◽  
S. Koshida ◽  
J. Broadbent ◽  
B. Price ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Dominant Negative ◽  
Fibroblast Growth ◽  
Tgf Beta ◽  
Fgf Receptor ◽  
Activin Receptor ◽  
Yolk Cell ◽  
Endogenous Expression ◽  
Vertebrate Embryo ◽  
Fgf Signalling

The endoderm forms the gut and associated organs, and develops from a layer of cells which emerges during gastrula stages in the vertebrate embryo. In comparison to mesoderm and ectoderm, little is known about the signals which induce the endoderm. The origin of the endoderm is intimately linked with that of mesoderm, both by their position in the embryo, and by the molecules that can induce them. We characterised a gene, zebrafish gata5, which is expressed in the endoderm from blastula stages and show that its transcription is induced by signals originating from the yolk cell. These signals also induce the mesoderm-expressed transcription factor no tail (ntl), whose initial expression coincides with gata5 in the cells closest to the blastoderm margin, then spreads to encompass the germ ring. We have characterised the induction of these genes and show that ectopic expression of activin induces gata5 and ntl in a pattern which mimics the endogenous expression, while expression of a dominant negative activin receptor abolishes ntl and gata5 expression. Injection of RNA encoding a constitutively active activin receptor leads to ectopic expression of gata5 and ntl. gata5 is activated cell-autonomously, whereas ntl is induced in cells distant from those which have received the RNA, showing that although expression of both genes is induced by a TGF-beta signal, expression of ntl then spreads by a relay mechanism. Expression of a fibroblast growth factor (eFGF) or a dominant negatively acting FGF receptor shows that ntl but not gata5 is regulated by FGF signalling, implying that this may be the relay signal leading to the spread of ntl expression. In embryos lacking both squint and cyclops, members of the nodal group of TGF-beta related molecules, gata5 expression in the blastoderm is abolished, making these factors primary candidates for the endogenous TGF-beta signal inducing gata5.

scholarly journals Spatial response to fibroblast growth factor signalling in Xenopus embryos

Development ◽  
1999 ◽  
Vol 126 (1) ◽  
pp. 119-125 ◽  
Author(s):  
B. Christen ◽  
J.M. Slack
Keyword(s):  
Growth Factors ◽  
Source Region ◽  
Dominant Negative ◽  
Fibroblast Growth ◽  
Fgf Receptor ◽  
Erk Activation ◽  
Activation Domains ◽  
Stage Of Development ◽  
Fgf Signalling

We have examined the spatial pattern of activation of the extracellular signal-regulated protein kinase (ERK) during Xenopus development, and show that it closely resembles the expression of various fibroblast growth factors (FGFs). Until the tailbud stage of development, all ERK activation domains are sensitive to the dominant negative FGF receptor, showing that activation is generated by endogenous FGF signalling. ERK is not activated by application of other growth factors like BMP4 or activin, nor is endogenous activation blocked by the respective dominant negative receptors. This shows that various domains of FGF expression, including the periblastoporal region and the midbrain-hindbrain boundary, are also sites of FGF signalling in vivo. Wounding induces a transient (<60 minutes) activation of ERK which is not significantly reduced by the dominant negative FGF receptor. An artificial FGF source, created by injection of eFGF mRNA into cleavage stage embryos, provokes ERK activation outside of its injection site over a range of several cell diameters. The range and extent of ERK activation outside the source region is unchanged by co-injection of a dominant negative form of Ras, which blocks ERK-activation within the source. This suggests that FGF protein can diffuse over several cell diameters.

Fgf signalling through MAPK cascade is required for development of the subpallial telencephalon in zebrafish embryos

Development ◽  
2001 ◽  
Vol 128 (21) ◽  
pp. 4153-4164 ◽  
Author(s):  
Minori Shinya ◽  
Sumito Koshida ◽  
Atsushi Sawada ◽  
Atsushi Kuroiwa ◽  
Hiroyuki Takeda
Keyword(s):  
Anterior Part ◽  
Immunohistochemical Analysis ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Zebrafish Embryos ◽  
Fgf Receptor ◽  
Erk Activation ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Fgf Signalling

The telencephalon is formed in the most anterior part of the central nervous system (CNS) and is organised into ventral subpallial and dorsal pallial domains. In mice, it has been demonstrated that Fgf signalling has an important role in induction and patterning of the telencephalon. However, the precise role of Fgf signalling is still unclear, owing to overlapping functions of Fgf family genes. To address this, we have examined, in zebrafish embryos, the activation of Ras/mitogen-activated protein kinase (MAPK), one of the major downstream targets of Fgf signalling. Immunohistochemical analysis reveals that an extracellular signal-regulated kinase (ERK), a vertebrate MAPK is activated in the anterior neural boundary (ANB) of the developing CNS at early segmentation stages. Experiments with Fgf inhibitors reveal that ERK activation at this stage is totally dependent on Fgf signalling. Interestingly, a substantial amount of ERK activation is observed in ace mutants in which fgf8 gene is mutated. We then examine the function of Fgf signalling in telencephalic development by use of several inhibitors to Fgf signalling cascade, including dominant-negative forms of Ras (RasN17) and the Fgf receptor (Fgfr), and a chemical inhibitor of Fgfr, SU5402. In treated embryos, the induction of telencephalic territory normally proceeded but the development of the subpallial telencephalon was suppressed, indicating that Fgf signalling is required for the regionalisation within the telencephalon. Finally, antisense experiments with morpholino-modified oligonucleotides suggest that zebrafish fgf3, which is also expressed in the ANB, co-operates with fgf8 in subpallial development.

A truncated FGF receptor blocks neural induction by endogenous Xenopus inducers

Development ◽  
1996 ◽  
Vol 122 (3) ◽  
pp. 869-880 ◽  
Author(s):  
C. Launay ◽  
V. Fromentoux ◽  
D.L. Shi ◽  
J.C. Boucaut
Keyword(s):  
Neural Induction ◽  
Cement Gland ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Fgf Receptor ◽  
Dorsal Mesoderm ◽  
Poorly Differentiated ◽  
Neural Marker ◽  
Fgf Signalling

We have examined the role of fibroblast growth factor (FGF) signalling in neural induction. The approach takes advantage of the fact that both noggin and the dominant negative mutant activin receptor (delta1XAR1) directly induce neural tissues in the absence of dorsal mesoderm. A truncated FGF receptor (XFD) is co-expressed with noggin or delta1XAR1 in both whole embryos and isolated animal caps. We demonstrate that inhibition of FGF signalling prevents neural induction by both factors. Furthermore, neural induction by organizers (the dorsal lip of blastopore and Hensen's node) is also blocked by inhibiting FGF signalling in ectoderm. It has been proposed that the specification of anterior neuroectoderm, including the cement gland, occurs in a sequential manner as gastrulation proceeds. We show that the specification of the most anterior neuroectoderm by noggin may occur before gastrulation and does not require FGF signalling, since both the cement gland marker XCG-1 and the anterior neural marker Otx-2 are normally expressed in ectodermal explants co-injected with noggin and XFD RNAs, but the cement gland cells are poorly differentiated. In contrast, the expression of both genes induced by CSKA.noggin, which is expressed after the mid-blastula transition, is strongly inhibited by the presence of XFD. Therefore the noggin-mediated neural induction that takes place at gastrula stages is abolished in the absence of FGF signalling. Since inhibition of FGF signalling blocks the neuralizing effect of different neural inducers that function through independent mechanisms, we propose that FGF receptor-related-signalling is required for the response to inducing signals of ectodermal cells from gastrula.

scholarly journals Fibroblast Growth Factors Regulate Prolactin Transcription via an Atypical Rac-Dependent Signaling Pathway

2003 ◽  
Vol 17 (10) ◽  
pp. 1921-1930 ◽  
Author(s):  
Twila A. Jackson ◽  
David M. Koterwas ◽  
Melissa A. Morgan ◽  
Andrew P. Bradford
Keyword(s):  
Gene Expression ◽  
Growth Factors ◽  
Signaling Pathway ◽  
Promoter Activity ◽  
Fibroblast Growth Factors ◽  
Dominant Negative ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Fibroblast Growth ◽  
Prl Gene

Abstract Fibroblast growth factors (FGFs) play a critical role in pituitary development and in pituitary tumor formation and progression. We have previously characterized FGF signal transduction and regulation of the tissue-specific rat prolactin (rPRL) promoter in GH4 pituitary cells. FGF induction of rPRL transcription is independent of Ras, but mediated by a protein kinase C-δ (PKCδ)-dependent activation of MAPK (ERK). Here we demonstrate a functional role for the Rho family monomeric G protein, Rac1, in FGF regulation of PRL gene expression via an atypical signaling pathway. Expression of dominant negative Rac, but not RhoA or Cdc42, selectively inhibited FGF-induced rPRL promoter activity. Moreover, expression of dominant negative Rac also attenuated FGF-2 and FGF-4 stimulation of MAPK (ERK). However, in contrast to other Rac-dependent signaling pathways, FGF activation of rPRL promoter activity was independent of the c-Jun N-terminal kinase (JNK) and phosphoinositide 3-kinase/Akt cascades. FGFs failed to activate JNK1 or JNK2, and expression of dominant negative JNK or Akt constructs did not block FGF-induced PRL transcription. Consistent with the role of PKCδ in FGF regulation of PRL gene expression, activation of the rPRL promoter was blocked by an inhibitor of phospholipase Cγ (PLCγ) activity. FGF treatment also induced rapid tyrosine phosphorylation of PLCγ in a Rac-dependent manner. These results suggest that FGF-2 and FGF-4 activate PRL gene expression via a novel Rac1, PLCγ, PKCδ, and ERK cascade, independent of phosphoinositol-3-kinase and JNK.

scholarly journals Role of FGF signalling in neural crest cell migration during early chick embryo development

Zygote ◽  
2018 ◽  
Vol 26 (6) ◽  
pp. 457-464 ◽  
Author(s):  
Xiao-tan Zhang ◽  
Guang Wang ◽  
Yan Li ◽  
Manli Chuai ◽  
Kenneth Ka Ho Lee ◽  
...  
Keyword(s):  
Neural Crest ◽  
Neural Tube ◽  
Neural Crest Cell ◽  
Dominant Negative ◽  
Neural Tubes ◽  
Dorsal Neural Tube ◽  
Neural Crest Cell Migration ◽  
Fgf Signalling ◽  
Crest Cell

SummaryFibroblast growth factor (FGF) signalling acts as one of modulators that control neural crest cell (NCC) migration, but how this is achieved is still unclear. In this study, we investigated the effects of FGF signalling on NCC migration by blocking this process. Constructs that were capable of inducing Sprouty2 (Spry2) or dominant-negative FGFR1 (Dn-FGFR1) expression were transfected into the cells making up the neural tubes. Our results revealed that blocking FGF signalling at stage HH10 (neurulation stage) could enhance NCC migration at both the cranial and trunk levels in the developing embryos. It was established that FGF-mediated NCC migration was not due to altering the expression of N-cadherin in the neural tube. Instead, we determined that cyclin D1 was overexpressed in the cranial and trunk levels when Sprouty2 was upregulated in the dorsal neural tube. These results imply that the cell cycle was a target of FGF signalling through which it regulates NCC migration at the neurulation stage.

Integration of FGF and TWIST in calvarial bone and suture development

Development ◽  
2000 ◽  
Vol 127 (9) ◽  
pp. 1845-1855 ◽  
Author(s):  
D.P. Rice ◽  
T. Aberg ◽  
Y. Chan ◽  
Z. Tang ◽  
P.J. Kettunen ◽  
...  
Keyword(s):  
Expression Analysis ◽  
Splice Variants ◽  
Bone Development ◽  
Dominant Negative ◽  
Calvarial Bone ◽  
Fgf Receptor ◽  
Helix Loop Helix ◽  
Suture Closure ◽  
Potential Ligand

Mutations in the FGFR1-FGFR3 and TWIST genes are known to cause craniosynostosis, the former by constitutive activation and the latter by haploinsufficiency. Although clinically achieving the same end result, the premature fusion of the calvarial bones, it is not known whether these genes lie in the same or independent pathways during calvarial bone development and later in suture closure. We have previously shown that Fgfr2c is expressed at the osteogenic fronts of the developing calvarial bones and that, when FGF is applied via beads to the osteogenic fronts, suture closure is accelerated (Kim, H.-J., Rice, D. P. C., Kettunen, P. J. and Thesleff, I. (1998) Development 125, 1241–1251). In order to investigate further the role of FGF signalling during mouse calvarial bone and suture development, we have performed detailed expression analysis of the splicing variants of Fgfr1-Fgfr3 and Fgfr4, as well as their potential ligand Fgf2. The IIIc splice variants of Fgfr1-Fgfr3 as well as the IIIb variant of Fgfr2 being expressed by differentiating osteoblasts at the osteogenic fronts (E15). In comparison to Fgf9, Fgf2 showed a more restricted expression pattern being primarily expressed in the sutural mesenchyme between the osteogenic fronts. We also carried out a detailed expression analysis of the helix-loop-helix factors (HLH) Twist and Id1 during calvaria and suture development (E10-P6). Twist and Id1 were expressed by early preosteoblasts, in patterns that overlapped those of the FGF ligands, but as these cells differentiated their expression dramatically decreased. Signalling pathways were further studied in vitro, in E15 mouse calvarial explants. Beads soaked in FGF2 induced Twist and inhibited Bsp, a marker of functioning osteoblasts. Meanwhile, BMP2 upregulated Id1. Id1 is a dominant negative HLH thought to inhibit basic HLH such as Twist. In Drosophila, the FGF receptor FR1 is known to be downstream of Twist. We demonstrated that in Twist(+/)(−) mice, FGFR2 protein expression was altered. We propose a model of osteoblast differentiation integrating Twist and FGF in the same pathway, in which FGF acts both at early and late stages. Disruption of this pathway may lead to craniosynostosis.

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