Specific modulation of ectodermal cell fates in Xenopus embryos by glycogen synthase kinase

Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 3979-3988 ◽  
Author(s):  
K. Itoh ◽  
T.L. Tang ◽  
B.G. Neel ◽  
S.Y. Sokol
Keyword(s):  
Signaling Pathways ◽  
Glycogen Synthase ◽  
Neural Tissue ◽  
Lineage Tracing ◽  
Glycogen Synthase Kinase ◽  
Cell Fates ◽  
Cell Stage ◽  
Xenopus Embryos ◽  
Mammalian Homologue ◽  
Molecular Marker Analysis

Shaggy is a downstream component of the wingless and Notch signaling pathways which operate during Drosophila development. To address the role of glycogen synthase kinase 3 beta (GSK3 beta), a mammalian homologue of Shaggy, in vertebrate embryogenesis, it was overexpressed in Xenopus embryos. Microinjection of rat GSK3 beta mRNA into animal ventral blastomeres of 8-cell-stage embryos triggered development of ectopic cement glands with an adjacent anterior neural tissue as evidenced by in situ hybridization with Xotx2, a fore/midbrain marker, and NCAM, a pan-neural marker. In contrast, animal dorsal injection of the same dose of GSK3 beta mRNA caused eye deficiencies, whereas vegetal injections had no pronounced effects on normal development. Using several mutated forms of rat GSK3 beta, we demonstrate that the observed phenotypes are dose-dependent and tightly correlate with GSK3 beta enzymatic activity. Lineage tracing experiments showed that the effects of GSK3 beta are cell autonomous and that ectopic cement glands and eye deficiencies arose directly from cells containing GSK3 beta mRNA. Molecular marker analysis of ectodermal explants overexpressing GSK3 beta has revealed activation of Xotx2 and of cement gland marker XAG-1, but expression of NCAM and XIF-3 was not detected. Phenotypic effects of mRNA encoding a Xenopus homologue of GSK3 beta were identical to those of rat GSK3 beta mRNA. We hypothesize that GSK3 beta mediates the initial steps of neural tissue specification and modulates anteroposterior ectodermal patterning via activation of Otx2 transcription. Our observations implicate GSK3 beta in signaling pathways operating during neural tissue development and during specification of anterior ectodermal cell fates.

Maternal beta-catenin establishes a ‘dorsal signal’ in early Xenopus embryos

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 2987-2996 ◽  
Author(s):  
C. Wylie ◽  
M. Kofron ◽  
C. Payne ◽  
R. Anderson ◽  
M. Hosobuchi ◽  
...  
Keyword(s):  
Glycogen Synthase ◽  
Axis Formation ◽  
Beta Catenin ◽  
Cell Stage ◽  
Midblastula Transition ◽  
Xenopus Embryos ◽  
Ability To Act ◽  
Zygotic Transcription ◽  
Spatial Terms ◽  
Marginal Zones

In previous work, we demonstrated that maternally encoded beta-catenin, the vertebrate homolog of armadillo, is required for formation of dorsal axial structures in early Xenopus embryos (Heasman, J., Crawford, A., Goldstone, K., Garner-Hamrick, P., Gumbiner, B., Kintner, C., Yoshida-Noro, C. and Wylie, C. (1994). Cell 79, 791–803). Here we investigated, firstly, the role(s) of beta-catenin in spatial terms, in different regions of the embryo, by injecting beta-catenin mRNA into individual blastomeres of beta-catenin-depleted embryos at the 32 cell stage. The results indicate that beta-catenin can rescue the dorsal axial structures in a non-cell-autonomous way and without changing the fates of the injected cells. This suggests that cells overexpressing beta-catenin send a ‘dorsal signal’ to other cells. This was confirmed by showing that beta-catenin overexpressing animal caps did not cause wild-type caps to form mesoderm, but did cause isolated beta-catenin-deficient marginal zones to form dorsal mesoderm. Furthermore beta-catenin-deficient vegetal masses treated with overexpressing caps regained their ability to act as Nieuwkoop Centers. Secondly, we studied the temporal activity of beta-catenin. We showed that zygotic transcription of beta-catenin starts after the midblastula transition (MBT), but does not rescue dorsal axial structures. We further demonstrated that the vegetal mass does not release a dorsal signal until after the onset of transcription, at the midblastula stage, suggesting that maternal beta-catenin protein is required at or before this time. Thirdly we investigated where, in relationship to other gene products known to be active in axis formation, beta-catenin is placed. We find that BVg1, bFGF, tBR (the truncated form of BMP2/4R), siamois and noggin activities are all downstream of beta-catenin, as shown by the fact that injection of their mRNAs rescues the effect of depleting maternally encoded beta-catenin. Interference with the action of glycogen synthase kinase (GSK), a vertebrate homolog of the Drosophila gene product, zeste white 3 kinase, does not rescue the effect, suggesting that it is upstream.

scholarly journals Glycogen Synthase Kinase-3 Is Required for EfficientDictyosteliumChemotaxis

2010 ◽  
Vol 21 (15) ◽  
pp. 2788-2796 ◽  
Author(s):  
Regina Teo ◽  
Kimberley J. Lewis ◽  
Josephine E. Forde ◽  
W. Jonathan Ryves ◽  
Jonathan V. Reddy ◽  
...  
Keyword(s):  
Cell Signaling ◽  
Signaling Pathways ◽  
Cell Fate ◽  
Glycogen Synthase ◽  
Cell Aggregation ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Cell Fate Determination ◽  
Cell Signaling Pathways

Glycogen synthase kinase-3 (GSK3) is a highly conserved protein kinase that is involved in several important cell signaling pathways and is associated with a range of medical conditions. Previous studies indicated a major role of the Dictyostelium homologue of GSK3 (gskA) in cell fate determination during morphogenesis of the fruiting body; however, transcriptomic and proteomic studies have suggested that GSK3 regulates gene expression much earlier during Dictyostelium development. To investigate a potential earlier role of GskA, we examined the effects of loss of gskA on cell aggregation. We find that cells lacking gskA exhibit poor chemotaxis toward cAMP and folate. Mutants fail to activate two important regulatory signaling pathways, mediated by phosphatidylinositol 3,4,5-trisphosphate (PIP3) and target of rapamycin complex 2 (TORC2), which in combination are required for chemotaxis and cAMP signaling. These results indicate that GskA is required during early stages of Dictyostelium development, in which it is necessary for both chemotaxis and cell signaling.

scholarly journals Differential perturbations in the morphogenesis of anterior structures induced by overexpression of truncated XB- and N-cadherins in Xenopus embryos.

1994 ◽  
Vol 127 (2) ◽  
pp. 521-535 ◽  
Author(s):  
S Dufour ◽  
J P Saint-Jeannet ◽  
F Broders ◽  
D Wedlich ◽  
J P Thiery
Keyword(s):  
Xenopus Laevis ◽  
Neural Development ◽  
Neural Tissue ◽  
Cell Stage ◽  
Crucial Step ◽  
Tissue Integrity ◽  
Xenopus Embryos ◽  
Additive Perturbation ◽  
Early Neurogenesis ◽  
Anchor Structure

Cadherins, a family of Ca-dependent adhesion molecules, have been proposed to act as regulators of morphogenetic processes and to be major effectors in the maintenance of tissue integrity. In this study, we have compared the effects of the expression of two truncated cadherins during early neurogenesis in Xenopus laevis. mRNA encoding deleted forms of XB- and N-cadherin lacking most of the extracellular domain were injected into the four animal dorsal blastomeres of 32-cell stage Xenopus embryos. These truncated cadherins altered the cohesion of cells derived from the injected blastomeres and induced morphogenetic defects in the anterior neural tissue to which they chiefly contributed. Truncated XB-cadherin was more efficient than N-cadherin in inducing these perturbations. Moreover, the coexpression of both truncated cadherins had additive perturbation effects on neural development. The two truncated cadherins can interact with the three known catenins, but with distinct affinities. These results suggest that the adhesive signal mediated by cadherins can be perturbed by overexpressing their cytoplasmic domains by competing with different affinity with catenins and/or a common anchor structure. Therefore, the correct regulation of cadherin function through the cytoplasmic domain appears to be a crucial step in the formation of the neural tissue.

scholarly journals Glycogen Synthase Kinase-3β Is a Negative Regulator of Cardiomyocyte Hypertrophy

2000 ◽  
Vol 151 (1) ◽  
pp. 117-130 ◽  
Author(s):  
Syed Haq ◽  
Gabriel Choukroun ◽  
Zhao Bin Kang ◽  
Hardeep Ranu ◽  
Takashi Matsui ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Signaling Pathways ◽  
Cellular Response ◽  
Glycogen Synthase ◽  
Negative Regulator ◽  
Glycogen Synthase Kinase ◽  
Cardiomyocyte Hypertrophy ◽  
Glycogen Synthase Kinase 3Β ◽  
Activated T Cells ◽  
Gsk 3Β

Hypertrophy is a basic cellular response to a variety of stressors and growth factors, and has been best characterized in myocytes. Pathologic hypertrophy of cardiac myocytes leads to heart failure, a major cause of death and disability in the developed world. Several cytosolic signaling pathways have been identified that transduce prohypertrophic signals, but to date, little work has focused on signaling pathways that might negatively regulate hypertrophy. Herein, we report that glycogen synthase kinase-3β (GSK-3β), a protein kinase previously implicated in processes as diverse as development and tumorigenesis, is inactivated by hypertrophic stimuli via a phosphoinositide 3-kinase–dependent protein kinase that phosphorylates GSK-3β on ser 9. Using adenovirus-mediated gene transfer of GSK-3β containing a ser 9 to alanine mutation, which prevents inactivation by hypertrophic stimuli, we demonstrate that inactivation of GSK-3β is required for cardiomyocytes to undergo hypertrophy. Furthermore, our data suggest that GSK-3β regulates the hypertrophic response, at least in part, by modulating the nuclear/cytoplasmic partitioning of a member of the nuclear factor of activated T cells family of transcription factors. The identification of GSK-3β as a transducer of antihypertrophic signals suggests that novel therapeutic strategies to treat hypertrophic diseases of the heart could be designed that target components of the GSK-3 pathway.

scholarly journals Analysis of the Signaling Activities of Localization Mutants of β-Catenin during Axis Specification in Xenopus

1997 ◽  
Vol 139 (1) ◽  
pp. 229-243 ◽  
Author(s):  
Jeffrey R. Miller ◽  
Randall T. Moon
Keyword(s):  
Cell Fate ◽  
Protein Interactions ◽  
Glycogen Synthase ◽  
Regulation Of Gene Expression ◽  
Unexpected Result ◽  
Protein Protein Interactions ◽  
Cell Fates ◽  
Xenopus Embryos ◽  
Axis Specification ◽  
Dorsal Cell Fate

In Xenopus embryos, β-catenin has been shown to be both necessary and sufficient for the establishment of dorsal cell fates. This signaling activity is thought to depend on the binding of β-catenin to members of the Lef/Tcf family of transcription factors and the regulation of gene expression by this complex. To test whether β-catenin must accumulate in nuclei to establish dorsal cell fate, we constructed various localization mutants that restrict β-catenin to either the plasma membrane, the cytosol, or the nucleus. When overexpressed in Xenopus embryos, the proteins localize as predicted, but surprisingly all forms induce an ectopic axis, indicative of inducing dorsal cell fates. Given this unexpected result, we focused on the membrane-tethered form of β-catenin to resolve the apparent discrepancy between its membrane localization and the hypothesized role of nuclear β-catenin in establishing dorsal cell fate. We demonstrate that overexpression of membrane-tethered β-catenin elevates the level of free endogenous β-catenin, which subsequently accumulates in nuclei. Consistent with the hypothesis that it is this pool of non–membrane-associated β-catenin that signals in the presence of membrane-tethered β-catenin, overexpression of cadherin, which binds free β-catenin, blocks the axis-inducing activity of membrane- tethered β-catenin. The mechanism by which ectopic membrane-tethered β-catenin increases the level of endogenous β-catenin likely involves competition for the adenomatous polyposis coli (APC) protein, which in other systems has been shown to play a role in degradation of β-catenin. Consistent with this hypothesis, membrane-tethered β-catenin coimmunoprecipitates with APC and relocalizes APC to the membrane in cells. Similar results are observed with ectopic plakoglobin, casting doubt on a normal role for plakoglobin in axis specification and indicating that ectopic proteins that interact with APC can artifactually elevate the level of endogenous β-catenin, likely by interfering with its degradation. These results highlight the difficulty in interpreting the activity of an ectopic protein when it is assayed in a background containing the endogenous protein. We next investigated whether the ability of β-catenin to interact with potential protein partners in the cell may normally be regulated by phosphorylation. Compared with nonphosphorylated β-catenin, β-catenin phosphorylated by glycogen synthase kinase-3 preferentially associates with microsomal fractions expressing the cytoplasmic region of N-cadherin. These results suggest that protein–protein interactions of β-catenin can be influenced by its state of phosphorylation, in addition to prior evidence that this phosphorylation modulates the stability of β-catenin.

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