scholarly journals Characterizing the zebrafish organizer: microsurgical analysis at the early-shield stage

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1313-1322 ◽  
Author(s):  
J. Shih ◽  
S.E. Fraser
Keyword(s):  
Neural Development ◽  
Neural Induction ◽  
Leading Edge ◽  
Axis Formation ◽  
Embryonic Patterning ◽  
Fish Embryo ◽  
Embryo Patterning ◽  
Embryonic Shield ◽  
Microsurgical Techniques ◽  
Notochord Cells

The appearance of the embryonic shield, a slight thickening at the leading edge of the blastoderm during the formation of the germ ring, is one of the first signs of dorsoventral polarity in the zebrafish embryo. It has been proposed that the shield plays a role in fish embryo patterning similar to that attributed to the amphibian dorsal lip. In a recent study, we fate mapped many of the cells in the region of the forming embryonic shield, and found that neural and mesodermal progenitors are intermingled (Shih, J. and Fraser, S.E. (1995) Development 121, 2755–2765), in contrast to the coherent region of mesodermal progenitors found at the amphibian dorsal lip. Here, we examine the fate and the inductive potential of the embryonic shield to determine if the intermingling reflects a different mode of embryonic patterning than that found in amphibians. Using the microsurgical techniques commonly used in amphibian and avian experimental embryology, we either grafted or deleted the region of the embryonic shield. Homotopic grafting experiments confirmed the fates of cells within the embryonic shield region, showing descendants in the hatching gland, head mesoderm, notochord, somitic mesoderm, endoderm and ventral aspect of the neuraxis. Heterotopic grafting experiments demonstrated that the embryonic shield can organize a second embryonic axis; however, contrary to our expectations based on amphibian research, the graft contributes extensively to the ectopic neuraxis. Microsurgical deletion of the embryonic shield region at the onset of germ ring formation has little effect on neural development: embryos with a well-formed and well-patterned neuraxis develop in the complete absence of notochord cells. While these results show that the embryonic shield is sufficient for ectopic axis formation, they also raise questions concerning the necessity of the shield region for neural induction and embryonic patterning after the formation of the germ ring.

Anteroposterior patterning in the zebrafish, Danio rerio: an explant assay reveals inductive and suppressive cell interactions

Development ◽  
1996 ◽  
Vol 122 (6) ◽  
pp. 1873-1883 ◽  
Author(s):  
C.G. Sagerstrom ◽  
Y. Grinblat ◽  
H. Sive
Keyword(s):  
Danio Rerio ◽  
Neural Induction ◽  
Active Role ◽  
Cell Number ◽  
Type I ◽  
Animal Pole ◽  
Anteroposterior Patterning ◽  
Embryonic Shield ◽  
Low Levels ◽  
Neural Markers

We report the first extended culture system for analysing zebrafish (Danio rerio) embryogenesis with which we demonstrate neural induction and anteroposterior patterning. Explants from the animal pole region of blastula embryos ('animal caps') survived for at least two days and increased in cell number. Mesodermal and neural-specific genes were not expressed in cultured animal caps, although low levels of the dorsoanterior marker otx2 were seen. In contrast, we observed strong expression of gta3, a ventral marker and cyt1, a novel type I cytokeratin expressed in the outer enveloping layer. Isolated ‘embryonic shield’, that corresponds to the amphibian organizer and amniote node, went on to express the mesodermal genes gsc and ntl, otx2, the anterior neural marker pax6, and posterior neural markers eng3 and krx20. The expression of these genes defined a precise anteroposterior axis in shield explants. When conjugated to animal caps, the shield frequently induced expression of anterior neural markers. More posterior markers were rarely induced, suggesting that anterior and posterior neural induction are separable events. Mesodermal genes were also seldom activated in animal caps by the shield, demonstrating that neural induction did not require co-induction of mesoderm in the caps. Strikingly, ventral marginal zone explants suppressed the low levels of otx2 in animal caps, indicating that ventral tissues may play an active role in axial patterning. These data suggest that anteroposterior patterning in the zebrafish is a multi-step process.

scholarly journals Neural Induction, Neural Fate Stabilization, and Neural Stem Cells

2002 ◽  
Vol 2 ◽  
pp. 1147-1166 ◽  
Author(s):  
Sally A. Moody ◽  
Hyun-Soo Je
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Neural Stem Cells ◽  
Neural Development ◽  
Current Knowledge ◽  
Embryonic Stem ◽  
Neural Induction ◽  
Neural Plate ◽  
Natural Rate ◽  
Neural Fate

The promise of stem cell therapy is expected to greatly benefit the treatment of neurodegenerative diseases. An underlying biological reason for the progressive functional losses associated with these diseases is the extremely low natural rate of self-repair in the nervous system. Although the mature CNS harbors a limited number of self-renewing stem cells, these make a significant contribution to only a few areas of brain. Therefore, it is particularly important to understand how to manipulate embryonic stem cells and adult neural stem cells so their descendants can repopulate and functionally repair damaged brain regions. A large knowledge base has been gathered about the normal processes of neural development. The time has come for this information to be applied to the problems of obtaining sufficient, neurally committed stem cells for clinical use. In this article we review the process of neural induction, by which the embryonic ectodermal cells are directed to form the neural plate, and the process of neural�fate stabilization, by which neural plate cells expand in number and consolidate their neural fate. We will present the current knowledge of the transcription factors and signaling molecules that are known to be involved in these processes. We will discuss how these factors may be relevant to manipulating embryonic stem cells to express a neural fate and to produce large numbers of neurally committed, yet undifferentiated, stem cells for transplantation therapies.

scholarly journals Xenopus laevisMacrophage Migration Inhibitory Factor Is Essential for Axis Formation and Neural Development

2004 ◽  
Vol 279 (20) ◽  
pp. 21406-21414 ◽  
Author(s):  
Masaki Suzuki ◽  
Yumi Takamura ◽  
Mitsugu Maéno ◽  
Shin Tochinai ◽  
Daisuke Iyaguchi ◽  
...  
Keyword(s):  
Neural Development ◽  
Migration Inhibitory Factor ◽  
Inhibitory Factor ◽  
Axis Formation

scholarly journals Extracellular vesicles from neuronal cells promote neural induction of mESCs through cyclinD1

2021 ◽  
Author(s):  
Lu Song ◽  
Xinran Tian ◽  
Randy Schekman
Keyword(s):  
Cyclin D1 ◽  
Extracellular Vesicles ◽  
Neural Development ◽  
Neuronal Cells ◽  
Buoyant Density ◽  
Embryonic Stem ◽  
Neural Induction ◽  
Induction Effect ◽  
Differentiated Cells

Extracellular vesicles (EVs) that are thought to mediate the transport of proteins and RNAs involved in intercellular communication. Here, we show dynamic changes in the buoyant density and abundance of extracellular vesicles that are secreted by PC12 cells stimulated with nerve growth factor (NGF), N2A cells treated with retinoic acid to induce neural differentiation and mESCs differentiated into neuronal cells. EVs secreted from in vitro differentiated cells promote neural induction of mouse embryonic stem cells (mESCs). Cyclin D1 enriched within the EVs derived from differentiated neuronal cells contributes to this induction. EVs purified from cells overexpressing cyclin D1 are more potent in neural induction of mESC cells. Depletion of cyclin D1 from the EVs reduced the neural induction effect. Our results suggest that extracellular vesicles regulate neural development through sorting of cyclin D1.

scholarly journals The mlpt/Ubr3/Svb module comprises an ancient developmental switch for embryonic patterning

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Suparna Ray ◽  
Miriam I Rosenberg ◽  
Hélène Chanut-Delalande ◽  
Amélie Decaras ◽  
Barbara Schwertner ◽  
...  
Keyword(s):  
Molecular Complexes ◽  
Open Reading Frames ◽  
Epidermal Differentiation ◽  
Editorial Note ◽  
Embryonic Patterning ◽  
Embryo Patterning ◽  
Polished Rice ◽  
Developmental Switch ◽  
Small Open Reading Frames ◽  
Drosophila Embryos

Small open reading frames (smORFs) encoding ‘micropeptides’ exhibit remarkable evolutionary complexity. Conserved peptides encoded by mille-pattes (mlpt)/polished rice (pri)/tarsal less (tal) are essential for embryo segmentation in Tribolium but, in Drosophila, function in terminal epidermal differentiation and patterning of adult legs. Here, we show that a molecular complex identified in Drosophila epidermal differentiation, comprising Mlpt peptides, ubiquitin-ligase Ubr3 and transcription factor Shavenbaby (Svb), represents an ancient developmental module required for early insect embryo patterning. We find that loss of segmentation function for this module in flies evolved concomitantly with restriction of Svb expression in early Drosophila embryos. Consistent with this observation, artificially restoring early Svb expression in flies causes segmentation defects that depend on mlpt function, demonstrating enduring potency of an ancestral developmental switch despite evolving embryonic patterning modes. These results highlight the evolutionary plasticity of conserved molecular complexes under the constraints of essential genetic networks.Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (<xref ref-type="decision-letter" rid="SA1">see decision letter</xref>).

A forkhead gene related to HNF-3beta is required for gastrulation and axis formation in the ascidian embryo

Development ◽  
1997 ◽  
Vol 124 (18) ◽  
pp. 3609-3619 ◽  
Author(s):  
C.L. Olsen ◽  
W.R. Jeffery
Keyword(s):  
Muscle Cells ◽  
Single Copy ◽  
The Body ◽  
Axis Formation ◽  
Vegetal Pole ◽  
Tailbud Stage ◽  
Notochord Cells ◽  
Mesenchyme Cells ◽  
Forkhead Gene

We have isolated a member of the HNF-3/forkhead gene family in ascidians as a means to determine the role of winged-helix genes in chordate development. The MocuFH1 gene, isolated from a Molgula oculata cDNA library, exhibits a forkhead DNA-binding domain most similar to zebrafish axial and rodent HNF-3beta. MocuFH1 is a single copy gene but there is at least one other related forkhead gene in the M. oculata genome. The MocuFH1 gene is expressed in the presumptive endoderm, mesenchyme and notochord cells beginning during the late cleavage stages. During gastrulation, MocuFH1 expression occurs in the prospective endoderm cells, which invaginate at the vegetal pole, and in the presumptive notochord and mesenchyme cells, which involute over the anterior and lateral lips of the blastopore, respectively. However, this gene is not expressed in the presumptive muscle cells, which involute over the posterior lip of the blastopore. MocuFH1 expression continues in the same cell lineages during neurulation and axis formation, however, during the tailbud stage, MocuFH1 is also expressed in ventral cells of the brain and spinal cord. The functional role of the MocuFH1 gene was studied using antisense oligodeoxynucleotides (ODNs), which transiently reduce MocuFH1 transcript levels during gastrulation. Embryos treated with antisense ODNs cleave normally and initiate gastrulation. However, gastrulation is incomplete, some of the endoderm and notochord cells do not enter the embryo and undergo subsequent movements, and axis formation is abnormal. In contrast, the prospective muscle cells, which do not express MocuFH1, undergo involution and later express muscle actin and acetylcholinesterase, markers of muscle cell differentiation. The results suggest that MocuFH1 is required for morphogenetic movements of the endoderm and notochord precursor cells during gastrulation and axis formation. The effects of inhibiting MocuFH1 expression on embryonic axis formation in ascidians are similar to those reported for knockout mutations of HNF-3beta in the mouse, suggesting that HNF-3/forkhead genes have an ancient and fundamental role in organizing the body plan in chordates.

Expression of Xenopus N-CAM RNA in ectoderm is an early response to neural induction

Development ◽  
1987 ◽  
Vol 99 (3) ◽  
pp. 311-325 ◽  
Author(s):  
C.R. Kintner ◽  
D.A. Melton
Keyword(s):  
Neural Development ◽  
Transcriptional Activation ◽  
Neural Induction ◽  
Early Response ◽  
Neural Plate ◽  
Cdna Clones ◽  
Epidermal Tissue ◽  
Early Expression ◽  
Neural Ectoderm

We have isolated Xenopus laevis N-CAM cDNA clones and used these to study the expression of N-CAM RNA during neural induction. The results show that the first marked increase in N-CAM RNA levels occurs during gastrulation when mesoderm comes in contact with ectoderm and induces neural development. In situ hybridization results show that the early expression of N-CAM RNA is localized to the neural plate and its later expression is confined to the neural tube. Induction experiments with explanted germ layers show that N-CAM RNA is not expressed in ectoderm unless there is contact with inducing tissue. Together these results suggest an approach to studying how ectoderm is committed to form neural rather than epidermal tissue. Specifically, the data suggest that neural commitment is marked and perhaps mediated by the transcriptional activation of genes, like N-CAM, in the neural ectoderm.

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.

Grasshopper hunchback expression reveals conserved and novel aspects of axis formation and segmentation

Development ◽  
2001 ◽  
Vol 128 (18) ◽  
pp. 3459-3472 ◽  
Author(s):  
Nipam H. Patel ◽  
David C. Hayward ◽  
Sabbi Lall ◽  
Nicole R. Pirkl ◽  
Daniel DiPietro ◽  
...  
Keyword(s):  
Expression Patterns ◽  
Axis Formation ◽  
Embryonic Cells ◽  
Embryonic Patterning ◽  
Axial Patterning ◽  
Gap Gene ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Set Up ◽  
Pair Rule

While the expression patterns of segment polarity genes such as engrailed have been shown to be similar in Drosophila melanogaster and Schistocerca americana (grasshopper), the expression patterns of pair-rule genes such as even-skipped are not conserved between these species. This might suggest that the factors upstream of pair-rule gene expression are not conserved across insect species. We find that, despite this, many aspects of the expression of the Drosophila gap gene hunchback are shared with its orthologs in the grasshoppers S. americana and L. migratoria. We have analyzed both mRNA and protein expression during development, and find that the grasshopper hunchback orthologs appear to have a conserved role in early axial patterning of the germ anlagen and in the specification of gnathal and thoracic primordia. In addition, distinct stepped expression levels of hunchback in the gnathal/thoracic domains suggest that grasshopper hunchback may act in a concentration-dependent fashion (as in Drosophila), although morphogenetic activity is not set up by diffusion to form a smooth gradient. Axial patterning functions appear to be performed entirely by zygotic hunchback, a fundamental difference from Drosophila in which maternal and zygotic hunchback play redundant roles. In grasshoppers, maternal hunchback activity is provided uniformly to the embryo as protein and, we suggest, serves a distinct role in distinguishing embryonic from extra-embryonic cells along the anteroposterior axis from the outset of development – a distinction made in Drosophila along the dorsoventral axis later in development. Later hunchback expression in the abdominal segments is conserved, as are patterns in the nervous system, and in both Drosophila and grasshopper, hunchback is expressed in a subset of extra-embryonic cells. Thus, while the expected domains of hunchback expression are conserved in Schistocerca, we have found surprising and fundamental differences in axial patterning, and have identified a previously unreported domain of expression in Drosophila that suggests conservation of a function in extra-embryonic patterning.

Dorsalizing and neuralizing properties of Xdsh, a maternally expressed Xenopus homolog of dishevelled

Development ◽  
1995 ◽  
Vol 121 (6) ◽  
pp. 1637-1647 ◽  
Author(s):  
S.Y. Sokol ◽  
J. Klingensmith ◽  
N. Perrimon ◽  
K. Itoh
Keyword(s):  
Signal Transduction ◽  
Signal Transduction Pathway ◽  
Neural Induction ◽  
Neural Tissue ◽  
Lineage Tracing ◽  
Axis Formation ◽  
Transduction Pathway ◽  
Vertebrate Development ◽  
Dorsal Axis ◽  
Wnt Signal

Signaling factors of the Wnt proto-oncogene family are implicated in dorsal axis formation during vertebrate development, but the molecular mechanism of this process is not known. Studies in Drosophila have indicated that the dishevelled gene product is required for wingless (Wnt1 homolog) signal transduction. We demonstrate that injection of mRNA encoding a Xenopus homolog of dishevelled (Xdsh) into prospective ventral mesodermal cells triggers a complete dorsal axis formation in Xenopus embryos. Lineage tracing experiments show that cells derived from the injected blastomere contribute to anterior and dorsal structures of the induced axis. In contrast to its effect on mesoderm, overexpression of Xdsh mRNA in prospective ectodermal cells triggers anterior neural tissue differentiation. These studies suggest that Wnt signal transduction pathway is conserved between Drosophila and vertebrates and point to a role for maternal Xdsh product in dorsal axis formation and in neural induction.

Sign in / Sign up

Export Citation Format

Share Document