scholarly journals Mesoderm induction and mesoderm-inducing factors in early amphibian development

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 665-677 ◽  
Author(s):  
J. C. SMITH
Keyword(s):  
Mesoderm Induction ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

scholarly journals The Xenopus MyoD gene: an unlocalised maternal mRNA predates lineage-restricted expression in the early embryo

Development ◽  
1990 ◽  
Vol 108 (4) ◽  
pp. 669-680 ◽  
Author(s):  
R.P. Harvey
Keyword(s):  
Gene Expression ◽  
Cultured Cells ◽  
Early Response ◽  
Early Embryo ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Early Expression ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors ◽  
Myod Gene

Expression of the mouse MyoD gene appears to represent a critical point in the commitment of cultured cells to muscle. In Xenopus, myogenic commitment begins during mesoderm induction which is initiated early in development by endogenous growth factors. To study MyoD gene expression during induction, a Xenopus MyoD gene and homologous cDNAs were selected from Xenopus libraries and analysed. Two different cDNAs have been sequenced. They code for proteins closely related to each other and to mouse MyoD and are likely to be expressed from duplicated Xenopus MyoD genes. Surprisingly, MyoD mRNA is first detected during oogenesis and the maternal species is not localized exclusively to the region of the blastula fated to muscle. Zygotic MyoD mRNA accumulates slowly above maternal levels beginning at the MBT and new transcripts are localized to the somitic mesoderm. Expression outside of somites has been detected in developing heads of tailbud embryos and can be induced in blastula animal pole explants treated with mesoderm-inducing factors. The early expression of MyoD in Xenopus development suggests that it may play a part in the induction of muscle mesoderm and generally strengthens the evidence that MyoD is determinative in muscle commitment. In addition, the initiation of MyoD transcription at the MBT and its stimulation by mesoderm-inducing factors implies that MyoD gene expression is an immediate early response to mesoderm induction.

Xwnt-8, a Xenopus Wnt-1/int-1-related gene responsive to mesoderm-inducing growth factors, may play a role in ventral mesodermal patterning during embryogenesis

Development ◽  
1991 ◽  
Vol 111 (4) ◽  
pp. 1045-1055 ◽  
Author(s):  
J.L. Christian ◽  
J.A. McMahon ◽  
A.P. McMahon ◽  
R.T. Moon
Keyword(s):  
Growth Factors ◽  
Cell Fate ◽  
Ectopic Expression ◽  
Mesoderm Induction ◽  
Related Gene ◽  
Mesodermal Cell ◽  
Peptide Growth Factors ◽  
Basic Body ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

In amphibian embryos, formation of the basic body plan depends on positional differences in the mesoderm. Although peptide growth factors involved in mesoderm induction have tentatively been identified, additional signals are required to generate pattern in this tissue. We have isolated a Xenopus cDNA for a Wnt-1 related gene, designated Xwnt-8, which is activated in response to mesoderm-inducing growth factors. Xwnt-8 transcripts are transiently expressed, being most abundant during gastrulation at which time expression is confined primarily to ventral mesodermal cells. Embryos dorsoanteriorized by exposure to lithium exhibit greatly reduced levels of Xwnt-8 mRNA, supporting a correlation between Xwnt-8 expression and a ventral mesodermal cell fate. Surprisingly, ectopic expression of Xwnt-8 in embryos causes a dorsoanterior-enhanced phenotype. These findings suggest that Xwnt-8 may be a secondary signalling agent which is produced in response to mesoderm-inducing factors and is involved in the early steps of mesodermal patterning.

FGF is a prospective competence factor for early activin-type signals in Xenopus mesoderm induction

Development ◽  
1995 ◽  
Vol 121 (8) ◽  
pp. 2429-2437 ◽  
Author(s):  
R.A. Cornell ◽  
T.J. Musci ◽  
D. Kimelman
Keyword(s):  
Ectopic Expression ◽  
Equatorial Region ◽  
Mesoderm Induction ◽  
Normal Pattern ◽  
Fgf Receptor ◽  
Competence Factor ◽  
Low Levels ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors ◽  
Cellular Competence

Normal pattern formation during embryonic development requires the regulation of cellular competence to respond to inductive signals. In the Xenopus blastula, vegetal cells release mesoderm-inducing factors but themselves become endoderm, suggesting that vegetal cells may be prevented from expressing mesodermal genes in response to the signals that they secrete. We show here that addition of low levels of basic fibroblast growth factor (bFGF) induces the ectopic expression of the mesodermal markers Xbra, MyoD and muscle actin in vegetal explants, even though vegetal cells express low levels of the FGF receptor. Activin, a potent mesoderm-inducing agent in explanted ectoderm (animal explants), does not induce ectopic expression of these markers in vegetal explants. However, activin-type signaling is present in vegetal cells, since the vegetal expression of Mix.1 and goosecoid is inhibited by the truncated activin receptor. These results, together with the observation that FGF is required for mesoderm induction by activin, support our proposal that a maternal FGF acts at the equator as a competence factor, permitting equatorial cells to express mesoderm in response to an activin-type signal. The overlap of FGF and activin-type signaling is proposed to restrict mesoderm to the equatorial region.

scholarly journals Quantitative comparison of mesoderm inducing factors in xenopus

1989 ◽  
Vol 27 ◽  
pp. 53
Author(s):  
J.B.A. Green ◽  
G. Howes ◽  
M. Yaqoob ◽  
J. Cooke ◽  
J.C. Smith
Keyword(s):  
Quantitative Comparison ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

Mechanism of anteroposterior axis specification in vertebrates. Lessons from the amphibians

Development ◽  
1992 ◽  
Vol 114 (2) ◽  
pp. 285-302 ◽  
Author(s):  
J.M. Slack ◽  
D. Tannahill
Keyword(s):  
Molecular Markers ◽  
Expression Patterns ◽  
Signal Transduction Pathway ◽  
Homeobox Gene ◽  
Neural Induction ◽  
High Sensitivity ◽  
Neural Plate ◽  
Mesoderm Induction ◽  
Inducing Factors ◽  
Almost All

Interest in the problem of anteroposterior specification has quickened because of our near understanding of the mechanism in Drosophila and because of the homology of Antennapedia-like homeobox gene expression patterns in Drosophila and vertebrates. But vertebrates differ from Drosophila because of morphogenetic movements and interactions between tissue layers, both intimately associated with anteroposterior specification. The purpose of this article is to review classical findings and to enquire how far these have been confirmed, refuted or extended by modern work. The “pre-molecular” work suggests that there are several steps to the process: (i) Formation of anteroposterior pattern in mesoderm during gastrulation with posterior dominance. (ii) Regional specific induction of ectoderm to form neural plate. (iii) Reciprocal interactions from neural plate to mesoderm. (iv) Interactions within neural plate with posterior dominance. Unfortunately, almost all the observable markers are in the CNS rather than in the mesoderm where the initial specification is thought to occur. This has meant that the specification of the mesoderm has been assayed indirectly by transplantation methods such as the Einsteckung. New molecular markers now supplement morphological ones but they are still mainly in the CNS and not the mesoderm. A particular interest attaches to the genes of the Antp-like HOX clusters since these may not only be markers but actual coding factors for anteroposterior levels. We have a new understanding of mesoderm induction based on the discovery of activins and fibroblast growth factors (FGFs) as candidate inducing factors. These factors have later consequences for anteroposterior pattern with activin tending to induce anterior, and FGF posterior structures. Recent work on neural induction has implicated cAMP and protein kinase C (PKC) as elements of the signal transduction pathway and has provided new evidence for the importance of tangential neural induction. The regional specificity of neural induction has been reinvestigated using molecular markers and provides conclusions rather similar to the classical work. Defects in the axial pattern may be produced by retinoic acid but it remains unclear whether its effects are truly coordinate ones or are concentrated in certain regions of high sensitivity. In general the molecular studies have supported and reinforced the “pre-molecular ones”. Important questions still remain: (i) How much pattern is there in the mesoderm (how many states?) (ii) How is this pattern generated by the invaginating organizer? (iii) Is there one-to-one transmission of codings to the neural plate? (iv) What is the nature of the interactions within the neural plate? (v) Are the HOX cluster genes really the anteroposterior codings?

Mesoderm-inducing factors and Spemann's organiser phenomenon in amphibian development

Development ◽  
1989 ◽  
Vol 107 (2) ◽  
pp. 229-241 ◽  
Author(s):  
J. Cooke
Keyword(s):  
Growth Factor ◽  
Pattern Formation ◽  
Marginal Zone ◽  
Natural Control ◽  
Graft Size ◽  
Two Factors ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors ◽  
Host Embryo ◽  
Factor Concentration

Certain proteins from ‘growth factor’ families can initiate mesodermal development in animal cap cells of the amphibian blastula. Cells that are in early stages of their response to one such factor, XTC-MIF (Smith et al. 1988), initiate the formation of a new axial body plan when grafted to the ventral marginal zone of a similarly aged host embryo (Cooke et al. 1987). This replicates the natural control of this phase of development by the dorsal blastoporal lip when similarly grafted; the classical ‘organiser’ phenomenon. I have explored systematically the effect, upon the outcome of this pattern formation using defined inducing factors, of varying graft size, XTC-MIF concentration to which graft cells were exposed, length of exposure before grafting, and host age. The ‘mesodermal organiser’ status, evoked by the factor, appears to be stable, and the variables most influencing the degree of completeness and orderliness of second patterns are graft size and factor concentration. Inappropriately large grafts are not effective. A Xenopus basic fibroblast growth factor homologue, present in the embryo and known to be a strong inducer but of mesoderm with a different character from that induced by XTC-MIF, produced no episode of pattern formation at all when tested in the procedure described in this paper. Organiser status of grafts that have been exposed to mixtures of the two factors is set entirely by the supplied XTC-MIF concentration. Lineage labelling of these grafts, and of classical dorsal lip grafts, reveals closely similar though not identical patterns of contribution to the new structure within the host. Implications of the results for the normal mechanism of body pattern formation are discussed.

scholarly journals Regulation of the zebrafish goosecoid promoter by mesoderm inducing factors and Xwnt1

1996 ◽  
Vol 55 (1) ◽  
pp. 3-18 ◽  
Author(s):  
Jos Joore ◽  
Claudia Fasciana ◽  
Johanna E. Speksnijder ◽  
Wiebe Kruijer ◽  
Olivier H.J. Destrée ◽  
...  
Keyword(s):  
Inducing Factors ◽  
Mesoderm Inducing Factors

Analysis of competence and of Brachyury autoinduction by use of hormone-inducible Xbra

Development ◽  
1997 ◽  
Vol 124 (11) ◽  
pp. 2225-2234 ◽  
Author(s):  
M. Tada ◽  
M.A. O'Reilly ◽  
J.C. Smith
Keyword(s):  
Glucocorticoid Receptor ◽  
Target Genes ◽  
Early Embryo ◽  
Fate Map ◽  
Animal Pole ◽  
Reading Frame ◽  
Xenopus Development ◽  
Series Of Experiments ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

Analysis of gene function in Xenopus development frequently involves over-expression experiments, in which RNA encoding the protein of interest is microinjected into the early embryo. By taking advantage of the fate map of Xenopus, it is possible to direct expression of the protein to particular regions of the embryo, but it has not been possible to exert control over the timing of expression; the protein is translated immediately after injection. To overcome this problem in our analysis of the role of Brachyury in Xenopus development, we have, like Kolm and Sive (1995; Dev. Biol. 171, 267–272), explored the use of hormone-inducible constructs. Animal pole regions derived from embryos expressing a fusion protein (Xbra-GR) in which the Xbra open reading frame is fused to the ligand-binding domain of the human glucocorticoid receptor develop as atypical epidermis, presumably because Xbra is sequestered by the heat-shock apparatus of the cell. Addition of dexamethasone, which binds to the glucocorticoid receptor and releases Xbra, causes formation of mesoderm. We have used this approach to investigate the competence of animal pole explants to respond to Xbra-GR, and have found that competence persists until late gastrula stages, even though by this time animal caps have lost the ability to respond to mesoderm-inducing factors such as activin and FGF. In a second series of experiments, we demonstrate that Xbra is capable of inducing its own expression, but that this auto-induction requires intercellular signals and FGF signalling. Finally, we suggest that the use of inducible constructs may assist in the search for target genes of Brachyury.

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