The cleavage stage origin of Spemann's Organizer: analysis of the movements of blastomere clones before and during gastrulation in Xenopus

Development ◽  
1994 ◽  
Vol 120 (5) ◽  
pp. 1179-1189 ◽  
Author(s):  
D.V. Bauer ◽  
S. Huang ◽  
S.A. Moody
Keyword(s):  
Neural Induction ◽  
Axis Formation ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Genetic Manipulations ◽  
Spemann's Organizer ◽  
History Of ◽  
Clonal Origin ◽  
The Relationship ◽  
Early Gastrula

Recent investigations into the roles of early regulatory genes, especially those resulting from mesoderm induction or first expressed in the gastrula, reveal a need to elucidate the developmental history of the cells in which their transcripts are expressed. Although fates both of the early blastomeres and of regions of the gastrula have been mapped, the relationship between the two sets of fate maps is not clear and the clonal origin of the regions of the stage 10 embryo are not known. We mapped the positions of each blastomere clone during several late blastula and early gastrula stages to show where and when these clones move. We found that the dorsal animal clone (A1) begins to move away from the animal pole at stage 8, and the dorsal animal marginal clone (B1) leaves the animal cap by stage 9. The ventral animal clones (A4 and B4) spread into the dorsal animal cap region as the dorsal clones recede. At stage 10, the ventral animal clones extend across the entire dorsal animal cap. These changes in the blastomere constituents of the animal cap during epiboly may contribute to the changing capacity of the cap to respond to inductive growth factors. Pregastrulation movements of clones also result in the B1 clone occupying the vegetal marginal zone to become the primary progenitor of the dorsal lip of the blastopore (Spemann's Organizer). This report provides the fundamental descriptions of clone locations during the important periods of axis formation, mesoderm induction and neural induction. These will be useful for the correct targeting of genetic manipulations of early regulatory events.

XIPOU 2, a noggin-inducible gene, has direct neuralizing activity

Development ◽  
1995 ◽  
Vol 121 (3) ◽  
pp. 721-730 ◽  
Author(s):  
S.E. Witta ◽  
V.R. Agarwal ◽  
S.M. Sato
Keyword(s):  
Cell Fate ◽  
Neural Induction ◽  
Mesoderm Induction ◽  
Class Iii ◽  
Cell Stage ◽  
Neuronal Phenotype ◽  
Pou Domain ◽  
Spemann's Organizer ◽  
Stage Embryo ◽  
Synthetic Mrna

XIPOU 2, a member of the class III POU domain family, is expressed initially in Spemann's organizer, and later, in discrete regions of the developing nervous system in Xenopus laevis. XIPOU 2 may act downstream from initial neural induction events, since it is activated by the neural inducer, noggin. To determine if XIPOU 2 participates in the early events of neurogenesis, synthetic mRNA was microinjected into specific blastomeres of the 32-cell stage embryo. Misexpression of XIPOU 2 in the epidermis causes a direct switch in cell fate from an epidermal to a neuronal phenotype. In the absence of mesoderm induction, XIPOU 2 has the ability to induce a neuronal phenotype in uncommitted ectoderm. These data demonstrate the potential of XIPOU 2 to act as a master regulator of neurogenesis.

Fibroblast growth factor is a direct neural inducer, which combined with noggin generates anterior-posterior neural pattern

Development ◽  
1995 ◽  
Vol 121 (11) ◽  
pp. 3627-3636 ◽  
Author(s):  
T.M. Lamb ◽  
R.M. Harland
Keyword(s):  
Neural Induction ◽  
Neural Tissue ◽  
Mesoderm Induction ◽  
Gastrula Stage ◽  
Neural Patterning ◽  
The Third ◽  
Dorsal Mesoderm ◽  
Early Gastrula ◽  
Anterior Posterior ◽  
Mesodermal Tissue

Neural tissue in developing Xenopus embryos is induced by signals from the dorsal mesoderm. Induction of anterior neural tissue could be mediated by noggin, a secreted polypeptide found in dorsal mesoderm. We show that bFGF, a known mesoderm inducer of blastula staged ectoderm, induces neural tissue from gastrula stage ectoderm. The type of neural tissue induced by bFGF from stage 10.25 ectoderm is posterior, as marked by Hox B9 expression. When bFGF and noggin are combined on early gastrula stage ectoderm, a more complete neural pattern is generated and no mesodermal tissue is detected. Explants treated with noggin and bFGF elongate and display distinct anterior and posterior ends marked by otx2 and Hox B9 expression, respectively. Furthermore, treatment of early gastrula ectoderm with noggin and bFGF results in the induction of En-2, a marker of the midbrain-hindbrain junction and Krox 20, a marker of the third and fifth rhombomeres of the hindbrain. Neither of these genes is induced by noggin alone or bFGF alone at this stage, suggesting a synergy in anterior-posterior neural patterning. The response of later gastrula (stage 11–12) ectoderm to bFGF changes so that Krox 20 and En-2 are induced by bFGF alone, while induction of more posterior tissue marked by Hox B9 is eliminated. The dose of bFGF affects the amount of neural tissue induced, but has little effect on the anterior-posterior character, rather the age of the ectoderm treated is the determinant of the response. Thus, an FGF signal may account for posterior neural induction, and anterior-posterior neural patterning could be partly explained by the actions of noggin and FGF, together with the changing response of the ectoderm to these factors.

Developmental expression of the Xenopus int-2 (FGF-3) gene: activation by mesodermal and neural induction

Development ◽  
1992 ◽  
Vol 115 (3) ◽  
pp. 695-702 ◽  
Author(s):  
D. Tannahill ◽  
H.V. Isaacs ◽  
M.J. Close ◽  
G. Peters ◽  
J.M. Slack
Keyword(s):  
Gene Activation ◽  
Neural Induction ◽  
Developmental Expression ◽  
Mesoderm Induction ◽  
Junction Region ◽  
Expression Domain ◽  
Optic Vesicles ◽  
Cranial Ganglia ◽  
Temporal And Spatial ◽  
Early Gastrula

We have used a probe specific for the Xenopus homologue of the mammalian proto-oncogene int-2 (FGF-3) to examine the temporal and spatial expression pattern of the gene during Xenopus development. int-2 is expressed from just before the onset of gastrulation through to prelarval stages. In the early gastrula, it is expressed around the blastopore lip. This is maintained in the posterior third of the prospective mesoderm and neuroectoderm in the neurula. A second expression domain in the anterior third of the neuroectoderm alone appears in the late gastrula, which later resolves into the optic vesicles, hypothalamus and midbrain-hindbrain junction region. Further domains of expression arise in tailbud to prelarval embryos, including the stomodeal mesenchyme, the endoderm of the pharyngeal pouches and the cranial ganglia flanking the otocyst. It is shown, by treatment of blastula ectoderm with bFGF and activin, that int-2 can be expressed in response to mesoderm induction. By heterotypic grafting of gastrula ectoderm into axolotl neural plate, we have also demonstrated that int-2 can be expressed in response to neural induction. These results suggest that int-2 has multiple functions in development, including an early role in patterning of the anteroposterior body axis and a later role in the development of the tail, brain-derived structures and other epithelia.

scholarly journals Establishing embryonic territories in the context of Wnt signaling

2020 ◽  
Vol 52 ◽  
Author(s):  
Ian Velloso ◽  
Lorena A. Maia ◽  
Nathalia G. Amado ◽  
Alice H. Reis ◽  
Xi He ◽  
...  
Keyword(s):  
Wnt Pathway ◽  
Neural Induction ◽  
Neural Tissue ◽  
Research Groups ◽  
Major Player ◽  
History Of ◽  
Neural Ectoderm ◽  
Trunk Organizer ◽  
Early Gastrula ◽  
Developmental Windows

This review highlights the work that my research group has been developing, together with international collaborators, during the last decade. Since we were able to establish Xenopus laevis experimental model in Brazil we have been focused on understanding early embryonic patterns regarding neural induction and axes establishment. In this context, Wnt pathway appears as a major player and has been much explored by us and other research groups. Here we chose to review three published works that we consider landmarks within the history of our research on the developmental biology field and the neural induction and patterning modern findings. We intend to show how our series of discoveries, when painted together, tells a story that covers crucial developmental windows of early differentiation paths of anterior neural tissue. Being those: 1. Establishing Head organizer in contrast to trunk organizer at early gastrula; 2. deciding between neural ectoderm and epidermis ectoderm at the blastula/gastrula stages, and 3. the gathering of prechordal unique properties at late gastrula/early neurula.

Direct neural induction and selective inhibition of mesoderm and epidermis inducers by Xnr3

Development ◽  
1997 ◽  
Vol 124 (2) ◽  
pp. 483-492 ◽  
Author(s):  
C.S. Hansen ◽  
C.D. Marion ◽  
K. Steele ◽  
S. George ◽  
W.C. Smith
Keyword(s):  
Family Members ◽  
Neural Induction ◽  
Structural Features ◽  
Site Directed Mutagenesis ◽  
Structural Basis ◽  
Mesoderm Induction ◽  
Related Factors ◽  
Spemann's Organizer ◽  
Secreted Factors ◽  
C Terminus

During gastrulation in amphibians, secreted factors from Spemann's organizer act on dorsal ectoderm to induce the central nervous system. A number of secreted factors produced by Spemann's organizer have recently been identified. The TGFbeta family member Xnr3 is similar in amino acid sequence to the mouse factor nodal and is expressed in a restricted group of cells in the superficial layer of Spemann's organizer. Xnr3, unlike the related factors nodal, Xnr1 and Xnr2, lacks mesoderm-inducing activity. We report here that Xnr3 can directly induce neural tissue in Xenopus ectoderm explants (animal caps). Injection of animal caps with either Xnr3 RNA or plasmids induces the expression of the pan-neural genes NCAM and nrp1, as well as the anterior neural marker Cpl1. A growing body of evidence suggests that neural induction in Xenopus proceeds as the default in the absence of epidermis inducers. The best candidates for the endogenous epidermis inducers are BMP-4 and BMP-7. The neural inducing activity of Xnr3 can be inhibited by overexpression of BMP-4, as has been observed with the neural inducers noggin, chordin and follistatin. Furthermore, Xnr3 can block mesoderm induction by BMP-4 and activin, but not by Xnr2. The structural basis underlying the divergent activities of Xnr2 and Xnr3 was analyzed using site-directed mutagenesis. Mutations introduced to the conserved cysteine residues characteristic of the TGFbeta family were found to inactivate Xnr2, but not Xnr3. The most unique feature of Xnr3 is the absence of a conserved cysteine at the C terminus of the protein. This feature distinguishes Xnr3 from other TGFbeta family members, including Xnr2. However, we observed that changing the C terminus of Xnr3 to more closely resemble other TGFbeta family members did not significantly alter its activity, suggesting that other structural features of Xnr3 distinguish its biological activity from Xnr2.

scholarly journals A dual function of FGF signaling in Xenopus left-right axis formation

2018 ◽  
Author(s):  
Isabelle Schneider ◽  
Jennifer Kreis ◽  
Axel Schweickert ◽  
Martin Blum ◽  
Philipp Vick
Keyword(s):  
Model Organisms ◽  
Dual Function ◽  
Axis Formation ◽  
Mesoderm Induction ◽  
Nodal Signaling ◽  
Fgf Signaling ◽  
Mesoderm Development ◽  
Flow Sensing ◽  
Early Gastrula

AbstractOrgan left-right (LR) asymmetry is a conserved vertebrate feature, which is regulated by left-sided activation of Nodal signaling. Nodal asymmetry is established by a leftward fluid-flow generated at the ciliated LR organizer (LRO). While the role of fibroblast growth factor (FGF) signaling pathways during mesoderm development are conserved, diverging results from different model organisms suggested a non-conserved function in LR asymmetry. Here, we demonstrate that FGF is required during gastrulation in a dual function at consecutive stages of Xenopus embryonic development. In the early gastrula, FGF is necessary for LRO precursor induction, acting in parallel to FGF-mediated mesoderm induction. During late gastrulation, the FGF/Ca2+-branch is required for specification of the flow sensing lateral LRO cells, a function related to FGF-mediated mesoderm morphogenesis. This second function in addition requires input from the calcium channel Polycystin-2. Thus, analogous to mesoderm development, FGF activity is required in a dual role for laterality specification, namely for generating and sensing of leftward flow. Moreover, our data show that FGF functions in LR asymmetric development are conserved across vertebrate species, from fish to mammals.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Investigating the Relationship Between Self-Esteem and Stigma Among Young Adults With History of Suicide Attempts

Crisis ◽  
2016 ◽  
Vol 37 (4) ◽  
pp. 265-270 ◽  
Author(s):  
Meshan Lehmann ◽  
Matthew R. Hilimire ◽  
Lawrence H. Yang ◽  
Bruce G. Link ◽  
Jordan E. DeVylder
Keyword(s):  
Young Adults ◽  
Suicide Attempts ◽  
Self Esteem ◽  
High Risk Population ◽  
High Functioning ◽  
People With Mental Illness ◽  
History Of ◽  
The Individual ◽  
The Impact ◽  
The Relationship

Abstract. Background: Self-esteem is a major contributor to risk for repeated suicide attempts. Prior research has shown that awareness of stigma is associated with reduced self-esteem among people with mental illness. No prior studies have examined the association between self-esteem and stereotype awareness among individuals with past suicide attempts. Aims: To understand the relationship between stereotype awareness and self-esteem among young adults who have and have not attempted suicide. Method: Computerized surveys were administered to college students (N = 637). Linear regression analyses were used to test associations between self-esteem and stereotype awareness, attempt history, and their interaction. Results: There was a significant stereotype awareness by attempt interaction (β = –.74, p = .006) in the regression analysis. The interaction was explained by a stronger negative association between stereotype awareness and self-esteem among individuals with past suicide attempts (β = –.50, p = .013) compared with those without attempts (β = –.09, p = .037). Conclusion: Stigma is associated with lower self-esteem within this high-functioning sample of young adults with histories of suicide attempts. Alleviating the impact of stigma at the individual (clinical) or community (public health) levels may improve self-esteem among this high-risk population, which could potentially influence subsequent suicide risk.

Misreading Egypt

2018 ◽  
Author(s):  
Jesse Schotter
Keyword(s):  
New Media ◽  
Narrative Form ◽  
Experimental Film ◽  
Tower Of Babel ◽  
Avant Garde ◽  
Sergei Eisenstein ◽  
History Of ◽  
The One ◽  
The Relationship ◽  
Modern Technologies

The first chapter of Hieroglyphic Modernisms exposes the complex history of Western misconceptions of Egyptian writing from antiquity to the present. Hieroglyphs bridge the gap between modern technologies and the ancient past, looking forward to the rise of new media and backward to the dispersal of languages in the mythical moment of the Tower of Babel. The contradictory ways in which hieroglyphs were interpreted in the West come to shape the differing ways that modernist writers and filmmakers understood the relationship between writing, film, and other new media. On the one hand, poets like Ezra Pound and film theorists like Vachel Lindsay and Sergei Eisenstein use the visual languages of China and of Egypt as a more primal or direct alternative to written words. But Freud, Proust, and the later Eisenstein conversely emphasize the phonetic qualities of Egyptian writing, its similarity to alphabetical scripts. The chapter concludes by arguing that even avant-garde invocations of hieroglyphics depend on narrative form through an examination of Hollis Frampton’s experimental film Zorns Lemma.

Meat without Animals: Outcast Objects and the Improvement of London

2018 ◽  
Author(s):  
Ted Geier
Keyword(s):  
Animal Rights ◽  
Legal Reform ◽  
Meat Production ◽  
History Of ◽  
Relationship Of ◽  
The Relationship

Covers the long history of the Smithfield animal market and legal reform in London. Shows the relationship of civic improvement tropes, including animal rights, to animal erasure in the form of new foodstuffs from distant meat production sites. The reduction of lives to commodities also informed public abasement of the butchers.

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