scholarly journals Using 32-Cell Stage Xenopus Embryos to Probe PCP Signaling

2011 ◽  
pp. 91-104 ◽  
Author(s):  
Hyun-Shik Lee ◽  
Sergei Y. Sokol ◽  
Sally A. Moody ◽  
Ira O. Daar
Keyword(s):  
Cell Stage ◽  
Xenopus Embryos ◽  
Pcp Signaling

The origins of primitive blood in Xenopus: implications for axial patterning

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 423-434 ◽  
Author(s):  
M.C. Lane ◽  
W.C. Smith
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Cell Stage ◽  
Axial Patterning ◽  
Xenopus Embryos ◽  
Spemann's Organizer ◽  
Dorsal Mesoderm

The marginal zone in Xenopus laevis is proposed to be patterned with dorsal mesoderm situated near the upper blastoporal lip and ventral mesoderm near the lower blastoporal lip. We determined the origins of the ventralmost mesoderm, primitive blood, and show it arises from all vegetal blastomeres at the 32-cell stage, including blastomere C1, a progenitor of Spemann's organizer. This demonstrates that cells located at the upper blastoporal lip become ventral mesoderm, not solely dorsal mesoderm as previously believed. Reassessment of extant fate maps shows dorsal mesoderm and dorsal endoderm descend from the animal region of the marginal zone, whereas ventral mesoderm descends from the vegetal region of the marginal zone, and ventral endoderm descends from cells located vegetal of the bottle cells. Thus, the orientation of the dorsal-ventral axis of the mesoderm and endoderm is rotated 90(degrees) from its current portrayal in fate maps. This reassessment leads us to propose revisions in the nomenclature of the marginal zone and the orientation of the axes in pre-gastrula Xenopus embryos.

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.

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.

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 ARHGEF3.2 modulates Wnt‐PCP signaling in dorsal marginal zone of Xenopus embryos during early development

2013 ◽  
Vol 27 (S1) ◽  
Author(s):  
Jaeho Yoon ◽  
Jee‐In Heo ◽  
Sung Chan Kim ◽  
Jae‐Bong Park ◽  
Jae‐Yong Lee ◽  
...  
Keyword(s):  
Early Development ◽  
Marginal Zone ◽  
Xenopus Embryos ◽  
Pcp Signaling

Relocation and reorganization of germ plasm in Xenopus embryos after fertilization

Development ◽  
1988 ◽  
Vol 103 (3) ◽  
pp. 507-518 ◽  
Author(s):  
R.E. Ressom ◽  
K.E. Dixon
Keyword(s):  
Mitotic Spindle ◽  
Germ Plasm ◽  
Normal Development ◽  
Second Phase ◽  
Cell Stage ◽  
The Third ◽  
Xenopus Embryos ◽  
Third Phase ◽  
Vegetal Pole ◽  
Artificial Activation

In the unfertilized egg, germ plasm is widely distributed throughout the vegetal subcortex in small islets. Following fertilization or artificial activation, the location and organization changes, and by the 4- to 8-cell stage the germ plasm forms a small number of large patches overlying the vegetal pole. We distinguish three processes that produce these changes. The first of these is aggregation which involves the islets moving towards the vegetal pole to form large patches by coalescence. This phase requires microtubules but does not depend on cleavage or dynamic microfilaments. The second phase is ingression during which the patches of germ plasm move to the interior of the egg. The movement is due to a flow of cytoplasm from the vegetal pole internally and the cytoplasmic current does not require either microtubules or dynamic microfilaments. In the third phase, the germ plasm is trapped in the vegetal hemisphere by microtubular arrays—in normal development, the mitotic spindle.

Pattern regulation in isolated halves and blastomeres of early Xenopus laevis

Development ◽  
1983 ◽  
Vol 74 (1) ◽  
pp. 221-234
Author(s):  
H. Kageura ◽  
K. Yamana
Keyword(s):  
Xenopus Laevis ◽  
Calf Serum ◽  
The Other ◽  
Foetal Calf Serum ◽  
Cell Stage ◽  
Macroscopic Appearance ◽  
Xenopus Embryos ◽  
Early Embryos ◽  
Tailbud Stage ◽  
Pattern Regulation

Xenopus embryos at the 2-cell stage were cut into right and left halves, those at the 4-cell stage into dorsal and ventral halves or individual blastomeres, and those at the 8-cell stage into lateral, animal and vegetal halves. Defect embryos, that is, 8-cell embryos from which a particular pair of blastomeres had been removed, were also prepared. These halves, blastomeres and defect embryos were cultured in 50% Leibovitz (L-15) medium supplemented with 10% foetal calf serum and then in 10% Steinberg solution. Their development was determined from their macroscopic appearance when controls reached stage 26 (early tailbud stage) or later. The only halves that could develop into normal larvae or frogs were lateral ones of 2- and 8-cell embryos. An interesting finding was that these halves of 2-cell embryos developed into only half-embryos when cultured in the above Leibovitz medium beyond the beginning of gastrulation. On the other hand, most or all the dorsal and ventral halves at the 4-cell stage and the animal and vegetal quartets at the 8-cell stage did not form normally proportioned embryos. Defect embryos lacking any two blastomeres of the animal half gave rise to nearly normal embryos, whereas those lacking two dorsal or two ventral blastomeres of the vegetal half did not. From the present results and those of studies now in progress, it is concluded that development of blastomeres and halves from these early embryos, except lateral halves from 2- and 8-cell embryos, is not regulative as expected earlier, and that a certain combination of blastomeres is essential for complete pattern regulation.

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