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 Activin-mediated mesoderm induction requires FGF

Development ◽  
1994 ◽  
Vol 120 (2) ◽  
pp. 453-462 ◽  
Author(s):  
R.A. Cornell ◽  
D. Kimelman
Keyword(s):  
Dominant Negative ◽  
Mesoderm Induction ◽  
Fibroblast Growth ◽  
Fgf Signaling ◽  
Tgf Beta ◽  
Fgf Receptor ◽  
Basic Fgf ◽  
Dominant Negative Form ◽  
Negative Form

The early patterning of mesoderm in the Xenopus embryo requires signals from several intercellular factors, including mesoderm-inducing agents that belong to the fibroblast growth factor (FGF) and TGF-beta families. In animal hemisphere explants (animal caps), basic FGF and the TGF-beta family member activin are capable of converting pre-ectodermal cells to a mesodermal fate, although activin is much more effective at inducing dorsal and anterior mesoderm than is basic FGF. Using a dominant-negative form of the Xenopus type 1 FGF receptor, we show that an FGF signal is required for the full induction of mesoderm by activin. Animal caps isolated from embryos that have been injected with the truncated FGF receptor and cultured with activin do not extend and the induction of some genes, including cardiac actin and Xbra, is greatly diminished, while the induction of other genes, including the head organizer-specific genes gsc and Xlim-1, is less sensitive. These results are consistent with the phenotype of the truncated FGF receptor-injected embryo and imply that the activin induction of mesoderm depends on FGF, with some genes requiring a higher level of FGF signaling than others.

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 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.

scholarly journals Zebrafish Mesp family genes, mesp-a and mesp-b are segmentally expressed in the presomitic mesoderm, and Mesp-b confers the anterior identity to the developing somites

Development ◽  
2000 ◽  
Vol 127 (8) ◽  
pp. 1691-1702 ◽  
Author(s):  
A. Sawada ◽  
A. Fritz ◽  
Y. Jiang ◽  
A. Yamamoto ◽  
K. Yamasu ◽  
...  
Keyword(s):  
Fibroblast Growth Factor Receptor ◽  
Ectopic Expression ◽  
Growth Factor Receptor ◽  
Paraxial Mesoderm ◽  
Signalling Pathways ◽  
Fibroblast Growth ◽  
Presomitic Mesoderm ◽  
Receptor Signalling ◽  
Vertebrate Embryo ◽  
Bhlh Transcription Factors

Segmentation of a vertebrate embryo begins with the subdivision of the paraxial mesoderm into somites through a not-well-understood process. Recent studies provided evidence that the Notch-Delta and the FGFR (fibroblast growth factor receptor) signalling pathways are required for segmentation. In addition, the Mesp family of bHLH transcription factors have been implicated in establishing a segmental prepattern in the presomitic mesoderm. In this study, we have characterized zebrafish mesp-a and mesp-b genes that are closely related to Mesp family genes in other vertebrates. During gastrulation, only mesp-a is expressed in the paraxial mesoderm at the blastoderm margin. During the segmentation period, both genes are segmentally expressed in one to three stripes in the anterior parts of somite primordia. In fused somites (fss) embryos, in which all early somite boundary formation is blocked, initial mesp-a expression at the gastrula stage remains intact, but the expression of mesp-a and mesp-b is not detected during the segmentation period. This suggests that these genes are downstream targets of fss at the segmentation stage. Comparison with her1 expression (Muller, M., von Weizsacker, E. and Campos-Ortega, J. A. (1996) Development 122, 2071–2078) suggests that, like her1, mesp genes are not expressed in primordia of the first several somites. Furthermore, we found that zebrafish her1 expression oscillates in the presomitic mesoderm. The her1 stripe, which first appears in the tailbud region, moves in a caudal to rostral direction, and it finally overlaps the most rostral mesp stripe. Thus, in the trunk region, both her1 and mesp transcripts are detected in every somite primordium posterior to the forming somites. Ectopic expression of Mesp-b in embryos causes a loss of the posterior identity within the somite primordium, leading to a segmentation defect. These embryos show a reduction in expression of the posterior genes, myoD and notch5, with uniform expression of the anterior genes, FGFR1, papc and notch6. These observations suggest that zebrafish mesp genes are involved in anteroposterior specification within the presumptive somites, by regulating the essential signalling pathways mediated by Notch-Delta and FGFR.

Retention in the Golgi apparatus and expression on the cell surface of Cfr/Esl-1/Glg-1/MG-160 are regulated by two distinct mechanisms

2011 ◽  
Vol 440 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Yuichiro Miyaoka ◽  
Hidenori Kato ◽  
Kazuki Ebato ◽  
Shigeru Saito ◽  
Naoko Miyata ◽  
...  
Keyword(s):  
Growth Factor ◽  
Golgi Apparatus ◽  
Cell Surface ◽  
Fibroblast Growth Factor ◽  
Fibroblast Growth Factor Receptor ◽  
Growth Factor Receptor ◽  
Fibroblast Growth ◽  
Fgf Receptor ◽  
Juxtamembrane Region ◽  
Fgf Signalling

Cfr (cysteine-rich fibroblast growth factor receptor) is an Fgf (fibroblast growth factor)-binding protein without a tyrosine kinase. We have shown previously that Cfr is involved in Fgf18 signalling via Fgf receptor 3c. However, as Cfr is also known as Glg (Golgi apparatus protein)-1 or MG-160 and occurs in the Golgi apparatus, it remains unknown how the distribution of Cfr is regulated. In the present study, we performed a mutagenic analysis of Cfr to show that two distinct regions contribute to its distribution and stability. First, the C-terminal region retains Cfr in the Golgi apparatus. Secondly, the Cfr repeats in the extracellular juxtamembrane region destabilizes Cfr passed through the Golgi apparatus. This destabilization does not depend on the cleavage and secretion of the extracellular domain of Cfr. Furthermore, we found that Cfr with a GPI (glycosylphosphatidylinositol) anchor was predominantly expressed on the cell surface in Ba/F3 cells and affected Fgf18 signalling in a similar manner to the full-length Cfr, indicating that the interaction of Cfr with Fgfs on the cell surface is important for its function in Fgf signalling. These results suggest that the expression of Cfr in the Golgi apparatus and on the plasma membrane is finely tuned through two distinct mechanisms for exhibiting different functions.

Initial anteroposterior pattern of the zebrafish central nervous system is determined by differential competence of the epiblast

Development ◽  
1998 ◽  
Vol 125 (10) ◽  
pp. 1957-1966 ◽  
Author(s):  
S. Koshida ◽  
M. Shinya ◽  
T. Mizuno ◽  
A. Kuroiwa ◽  
H. Takeda
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Ectopic Expression ◽  
Neural Tissue ◽  
Ventral Side ◽  
Expression Domain ◽  
Anteroposterior Patterning ◽  
Endogenous Expression ◽  
Neural Marker ◽  
Fgf Signalling

Analyses using amphibian embryos proposed that induction and anteroposterior patterning of the central nervous system is initiated by signals that are produced by the organizer and organizer-derived axial mesoderm. However, we show here that the initial anteroposterior pattern of the zebrafish central nervous system depends on the differential competence of the epiblast and is not imposed by organizer-derived signals. This anteroposterior information is present throughout the epiblast in ectodermal cells that normally give rise both to neural and non-neural derivatives. Because of this information, organizer tissues transplanted to the ventral side of the embryo induce neural tissue but the anteroposterior identity of the induced neural tissue is dependent upon the position of the induced tissue within the epiblast. Thus, otx2, an anterior neural marker, was only ever induced in anterior regions of the embryo, irrespective of the position of the grafts. Similarly, hoxa-1, a posterior neural marker was induced only in the posterior regions. Furthermore, the boundary of each ectopic expression domain on the ventral side was always at an equivalent latitude to that of the endogenous expression of the dorsal side of the embryo. The anteroposterior specification of the epiblast is independent of the dorsoventral specification of the embryo because neural tissues induced in the ventralized embryos also showed anteroposterior polarity. Cell transplantation and RNA injection experiments showed that non-axial marginal mesoderm and FGF signalling is required for anteroposterior specification of the epiblast. However, the requirement for FGF signalling is indirect in that cells with compromised ability to respond to FGF can still respond to anteroposterior positional information.

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.

Insights into the role of heparan sulphate in fibroblast growth factor signalling

2006 ◽  
Vol 34 (3) ◽  
pp. 442-445 ◽  
Author(s):  
N.J. Harmer
Keyword(s):  
Growth Factor ◽  
Heparan Sulphate ◽  
Fibroblast Growth ◽  
Fgf Receptor ◽  
Signalling System ◽  
Wide Range ◽  
Growth Factor Signalling ◽  
Heparin Complexes ◽  
Fgf Signalling ◽  
Receptor Clusters

Signalling from the FGFs (fibroblast growth factors) is crucial for the correct development and homoeostasis of a wide range of cells and tissues. The FGF/FGFR (FGF receptor) signalling system forms an important paradigm for HS (heparan sulphate)-binding proteins, as both the growth factor and receptor bind to HS, and HS or heparin is an absolute requirement for full signalling. The FGF signalling system has been extremely well structurally characterized, and details of each interaction involved in forming a ternary complex of FGF–FGFR–heparin have been elucidated. Recent work has focused on a more thorough understanding of the nature of the FGF–heparin complex in particular, demonstrating that FGFs preferentially bind to similar sites on the co-receptor, and that FGF–FGFR pairs show greater specificity for heparin sulphation patterns than individual FGFs. Further work has suggested that FGF–FGFR–heparin signalling complexes contain one molecule of heparin only, and that when longer fragments of heparin are used to form FGF–FGFR–heparin complexes, multiple complexes form upon the saccharide. These observations form the basis of a model where the range of interactions that FGFs and FGFRs can form with one another and with HS may lead to the formation of complexes with more than two FGFR units. Therefore HS will be crucial to FGF signalling from the initial signalling event to the formation of large receptor clusters.

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.

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