Mesoderm induction in Xenopus laevis: responding cells must be in contact for mesoderm formation but suppression of epidermal differentiation can occur in single cells

Development ◽  
1988 ◽  
Vol 104 (4) ◽  
pp. 609-618 ◽  
Author(s):  
K. Symes ◽  
M. Yaqoob ◽  
J.C. Smith
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Early Stage ◽  
Divalent Cations ◽  
Single Cells ◽  
Epidermal Differentiation ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Mesodermal Cell

When Xenopus embryos are cultured in calcium- and magnesium-free medium (CMFM), the blastomeres lose adhesion but continue dividing to form a loose heap of cells. If divalent cations are restored at the early gastrula stage the cells re-adhere and eventually form muscle (a mesodermal cell type) as well as epidermis. If, however, the cells are dispersed during culture in CMFM, muscle does not form following reaggregation although epidermis does. This suggests that culturing blastomeres in a heap allows the transmission of mesoderm-induction signals from cell to cell while dispersion effectively dilutes the signal. In this paper, we have attempted to substitute for cell proximity by culturing dispersed blastomeres in XTC mesoderm-inducing factor (MIF). We find that dispersed cells do not respond to XTC-MIF by forming mesodermal cell types after reaggregation, but the factor does inhibit epidermal differentiation. One interpretation of this observation is that an early stage in mesoderm induction is the suppression of epidermal differentiation and that formation of mesoderm may require contact-mediated signals that are produced in response to XTC-MIF. We have gone on to study the suppression of epidermal differentiation in more detail. We find that this is a dose-dependent phenomenon that can occur in single cells in the absence of cell division. Animal pole blastomeres become more difficult to divert from epidermal differentiation at later stages of development and by stage 12 they are ‘determined’ to this fate. Fibroblast growth factor (FGF) also suppresses epidermal differentiation in isolated animal pole blastomeres and transforming growth factor-beta 1 acts synergistically with FGF in doing so.

The biological effects of XTC-MIF: quantitative comparison with Xenopus bFGF

Development ◽  
1990 ◽  
Vol 108 (1) ◽  
pp. 173-183 ◽  
Author(s):  
J.B. Green ◽  
G. Howes ◽  
K. Symes ◽  
J. Cooke ◽  
J.C. Smith
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Biological Effects ◽  
Tissue Type ◽  
Mesoderm Induction ◽  
Tgf Beta ◽  
Signal Molecule ◽  
Animal Pole

Mesoderm in Xenopus and other amphibian embryos is induced by signals from the vegetal hemisphere acting on equatorial or animal hemisphere cells. These signals are diffusible and two classes of candidate signal molecule have been identified: the fibroblast growth factor (FGF) and transforming growth factor beta (TGF-beta) types. In this paper, we compare the effects of cloned Xenopus basic FGF (XbFGF) and electophoretically homogeneous XTC-MIF (a TGF-beta-like factor obtained from a Xenopus cell line) on animal pole explants. We find that they have a similar minimum active concentration (0.1-0.2 ng ml-1) but that, nonetheless, XTC-MIF is at least 40 times more active in inducing muscle. In general, we find that the two factors cause inductions of significantly different characters in terms of tissue type, morphology, gene expression and timing. At low concentrations (0.1-1.0 ng ml-1) both factors induce the differentiation of ‘mesenchyme’ and ‘mesothelium’ as well as blood-like cells. These latter cells do not, however, react with an antibody to Xenopus globin. This raised the possibility that the identification of red blood cells in other studies on mesoderm induction might have been mistaken, but combinations of animal pole regions with ventral vegetal pole regions confirmed that genuine erythrocytes are formed. The identity of the blood-like cells formed in response to the inducing factors remains unknown. At higher concentrations XTC-MIF induces neural tissue, notochord, pronephros and substantial and often segmented muscle. By contrast, XbFGF only induces significant amounts of muscle above 24 ng ml-1 and even then this is much less than that induced by XTC-MIF. For both factors an exposure of less than 30 min is effective. Competence of animal pole cells to respond to XbFGF is completely lost by the beginning of gastrulation (stage 10) while competence to XTC-MIF is detectable until somewhat later (stage 11). Since animal pole tissue is known to be able to respond to the natural inducer at least until stage 10, and perhaps until stage 10.5, this suggests that bFGF cannot be the sole inducer of mesoderm in vivo. Taken together, these results are consistent with XTC-MIF being a dorsoanterior inducer and XbFGF a ventroposterior inducer, suggesting that body pattern is established by the interaction of two types of inducing signal. This model is discussed in view of the qualitative and quantitative differences between the factors.

Induction of dorsal mesoderm by soluble, mature Vg1 protein

Development ◽  
1995 ◽  
Vol 121 (7) ◽  
pp. 2155-2164 ◽  
Author(s):  
D.S. Kessler ◽  
D.A. Melton
Keyword(s):  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Specific Inhibitor ◽  
Mesoderm Induction ◽  
Binding Assays ◽  
Animal Pole ◽  
Xenopus Development ◽  
Mechanism Of Inhibition ◽  
Dorsal Mesoderm ◽  
High Doses

Mesoderm induction during Xenopus development has been extensively studied, and two members of the transforming growth factor-beta family, activin beta B and Vg1, have emerged as candidates for a natural inducer of dorsal mesoderm. Heretofore, analysis of Vg1 activity has relied on injection of hybrid Vg1 mRNAs, which have not been shown to direct efficient secretion of ligand and, therefore, the mechanism of mesoderm induction by processed Vg1 protein is unclear. This report describes injection of Xenopus oocytes with a chimeric activin-Vg1 mRNA, encoding the pro-region of activin beta B fused to the mature region of Vg1, resulting in the processing and secretion of mature Vg1. Treatment of animal pole explants with mature Vg1 protein resulted in differentiation of dorsal, but not ventral, mesodermal tissues and dose-dependent activation of both dorsal and ventrolateral mesodermal markers. At high doses, mature Vg1 induced formation of ‘embryoids’ with a rudimentary axial pattern, head structures including eyes and a functional neuromuscular system. Furthermore, truncated forms of the activin and FGF receptors, which block mesoderm induction in the intact embryo, fully inhibited mature Vg1 activity. To examine the mechanism of inhibition, we have performed receptor-binding assays with radiolabeled Vg1. Finally, follistatin, a specific inhibitor of activin beta B which is shown not to block endogenous dorsal mesoderm induction, failed to inhibit Vg1. The results support a role for endogenous Vg1 in dorsal mesoderm induction during Xenopus development.

The transforming growth factor beta type II receptor can replace the activin type II receptor in inducing mesoderm

1994 ◽  
Vol 14 (6) ◽  
pp. 4280-4285
Author(s):  
A Bhushan ◽  
H Y Lin ◽  
H F Lodish ◽  
C R Kintner
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Full Range ◽  
Type Ii ◽  
Tgf Beta ◽  
Mesodermal Cell ◽  
Xenopus Embryos ◽  
Growth Factor Beta

The type II receptors for the polypeptide growth factors transforming growth factor beta (TGF-beta) and activin belong to a new family of predicted serine/threonine protein kinases. In Xenopus embryos, the biological effects of activin and TGF-beta 1 are strikingly different; activin induces a full range of mesodermal cell types in the animal cap assay, while TGF-beta 1 has no effects, presumably because of the lack of functional TGF-beta receptors. In order to assess the biological activities of exogenously added TGF-beta 1, RNA encoding the TGF-beta type II receptor was introduced into Xenopus embryos. In animal caps from these embryos, TGF-beta 1 and activin show similar potencies for induction of mesoderm-specific mRNAs, and both elicit the same types of mesodermal tissues. In addition, the response of animal caps to TGF-beta 1, as well as to activin, is blocked by a dominant inhibitory ras mutant, p21(Asn-17)Ha-ras. These results indicate that the activin and TGF-beta type II receptors can couple to similar signalling pathways and that the biological specificities of these growth factors lie in their different ligand-binding domains and in different competences of the responding cells.

scholarly journals Differential Expression of Interleukin-4 (IL-4) and IL-4δ2 mRNA, but Not Transforming Growth Factor Beta (TGF-β), TGF-βRII, Foxp3, Gamma Interferon, T-bet, or GATA-3 mRNA, in Patients with Fast and Slow Responses to Antituberculosis Treatment

2008 ◽  
Vol 15 (8) ◽  
pp. 1165-1170 ◽  
Author(s):  
Joel Fleury Djoba Siawaya ◽  
Nchinya Bennedict Bapela ◽  
Katharina Ronacher ◽  
Nulda Beyers ◽  
Paul van Helden ◽  
...  
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Early Stage ◽  
Gamma Interferon ◽  
Sputum Culture ◽  
Interleukin 4 ◽  
Antituberculosis Treatment ◽  
Ifn Γ ◽  
Growth Factor Beta

ABSTRACT This study investigated interleukin-4 (IL-4), IL-4δ2, transforming growth factor beta (TGF-β), TGF-βRII, Foxp3, GATA-3, T-bet, and gamma interferon (IFN-γ) transcription in peripheral blood samples of adult pulmonary tuberculosis patients prior to and after 1 week of therapy. Twenty patients with positive results for sputum culture for Mycobacterium tuberculosis were enrolled and treated with directly observed short-course antituberculosis chemotherapy. Early treatment response was assessed. At the end of the intensive phase of treatment (month 2), 12 patients remained sputum culture positive (slow responders) and 8 converted to a negative culture (fast responders). Only the expression levels of IL-4 (4-fold decrease) and IL-4δ2 (32-fold increase) changed significantly during the first week of therapy in the 20 patients. No baseline differences were present between the responder groups, but fast responders had significantly higher IL-4 transcripts than slow responders at week 1. Fast responders showed a 19-fold upregulation and slow responders a 47-fold upregulation of IL-4δ2 at week 1. Only slow responders also showed a significant decrease in IL-4 expression at week 1. There were no significant differences in expression of TGF-β, TGF-βRII, Foxp3, IFN-γ, and GATA-3 between the groups. These data show that differential IL-4-related gene expression in the early stage of antituberculosis treatment accompanies differential treatment responses and may hold promise as a marker for treatment effect.

scholarly journals The transforming growth factor beta type II receptor can replace the activin type II receptor in inducing mesoderm.

1994 ◽  
Vol 14 (6) ◽  
pp. 4280-4285 ◽  
Author(s):  
A Bhushan ◽  
H Y Lin ◽  
H F Lodish ◽  
C R Kintner
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Full Range ◽  
Type Ii ◽  
Tgf Beta ◽  
Mesodermal Cell ◽  
Xenopus Embryos ◽  
Growth Factor Beta

The type II receptors for the polypeptide growth factors transforming growth factor beta (TGF-beta) and activin belong to a new family of predicted serine/threonine protein kinases. In Xenopus embryos, the biological effects of activin and TGF-beta 1 are strikingly different; activin induces a full range of mesodermal cell types in the animal cap assay, while TGF-beta 1 has no effects, presumably because of the lack of functional TGF-beta receptors. In order to assess the biological activities of exogenously added TGF-beta 1, RNA encoding the TGF-beta type II receptor was introduced into Xenopus embryos. In animal caps from these embryos, TGF-beta 1 and activin show similar potencies for induction of mesoderm-specific mRNAs, and both elicit the same types of mesodermal tissues. In addition, the response of animal caps to TGF-beta 1, as well as to activin, is blocked by a dominant inhibitory ras mutant, p21(Asn-17)Ha-ras. These results indicate that the activin and TGF-beta type II receptors can couple to similar signalling pathways and that the biological specificities of these growth factors lie in their different ligand-binding domains and in different competences of the responding cells.

scholarly journals Elevation of cell cycle control proteins during spontaneous immortalization of human keratinocytes.

1993 ◽  
Vol 4 (2) ◽  
pp. 185-194 ◽  
Author(s):  
R H Rice ◽  
K E Steinmann ◽  
L A deGraffenried ◽  
Q Qin ◽  
N Taylor ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Early Stage ◽  
Cell Cycle Control ◽  
Normal Karyotype ◽  
Microscopic Appearance ◽  
Colony Forming Efficiency ◽  
Forming Efficiency

A human line of spontaneously immortalized keratinocytes (SIK cells) has been derived from ostensibly normal epidermis and has proven useful in dissecting molecular changes associated with immortalization. The original cultures had a normal karyotype and a colony forming efficiency of approximately 3% through 10 passages. At passage 15, after which normal strains ordinarily senesce, these cells continued vigorous growth and gradually increased in colony forming efficiency, stabilizing at approximately 30% by passage 40. During the early stage of increasing colony forming efficiency, the cells acquired a single i(6p) chromosomal aberration and 5- to 10-fold increases in expression of the cell-cycle control proteins cyclin A, cyclin B, and p34cdc2. Additional chromosomal aberrations accumulated at later passages (i(8q) and +7), but the i(6p) and the increased expression of cell-cycle proteins were maintained, raising the possibility that these features were important for immortalization. Regulation of cell growth and differentiation in the cultures appeared minimally altered compared with normal keratinocytes as judged by their microscopic appearance and generation of abortive colonies, sensitivity to growth suppression by transforming growth factor-beta and tetradecanoylphorbol acetate, and dependence upon epidermal growth factor for progressive growth.

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