Frizzled-8 is expressed in the Spemann organizer and plays a role in early morphogenesis

Development ◽  
1998 ◽  
Vol 125 (14) ◽  
pp. 2687-2700 ◽  
Author(s):  
M.A. Deardorff ◽  
C. Tan ◽  
L.J. Conrad ◽  
P.S. Klein
Keyword(s):  
Ectopic Expression ◽  
Axis Formation ◽  
Vertebrate Development ◽  
Spemann Organizer ◽  
Secondary Axis ◽  
Wnt Ligands ◽  
Endogenous Role ◽  
Dorsal Cells ◽  
Wnt Signal

Wnts are secreted signaling molecules implicated in a large number of developmental processes. Frizzled proteins have been identified as likely receptors for Wnt ligands in vertebrates and invertebrates, but a functional role for vertebrate frizzleds has not yet been defined. To assess the endogenous role of frizzled proteins during vertebrate development, we have identified and characterized a Xenopus frizzled gene (xfz8). It is highly expressed in the deep cells of the Spemann organizer prior to dorsal lip formation and in the early involuting marginal zone. Ectopic expression of xfz8 in ventral cells leads to complete secondary axis formation and can synergize with Xwnt-8 while an inhibitory form of xfz8 (Nxfz8) blocks axis duplication by Xwnt-8, consistent with a role for xfz8 in Wnt signal transduction. Expression of Nxfz8 in dorsal cells has profound effects on morphogenesis during gastrulation and neurulation that result in dramatic shortening of the anterior-posterior axis. Our results suggest a role for xfz8 in morphogenesis during the gastrula stage of embryogenesis.

Regulation of Spemann organizer formation by the intracellular kinase Xgsk-3

Development ◽  
1995 ◽  
Vol 121 (3) ◽  
pp. 755-765 ◽  
Author(s):  
S.B. Pierce ◽  
D. Kimelman
Keyword(s):  
Ectopic Expression ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Axis Formation ◽  
Serine Threonine Kinase ◽  
Spemann Organizer ◽  
Isolation And Characterization ◽  
Secondary Axis ◽  
Dorsal Axis ◽  
Negative Effect

Dorsal axis formation in the Xenopus embryo can be induced by the ectopic expression of several Wnt family members. In Drosophila, the protein encoded by the Wnt family gene, wingless, signals through a pathway that antagonizes the effects of the serine/threonine kinase zeste-white 3/shaggy. We describe the isolation and characterization of a Xenopus homolog of zeste-white 3/shaggy, Xgsk-3. A kinase-dead mutant of Xgsk-3, Xgsk-3K-->R, has a dominant negative effect and mimics the ability of Wnt to induce a secondary axis by induction of an ectopic Spemann organizer. Xgsk-3K-->R, like Wnt, induces dorsal axis formation when expressed in the deep vegetal cells, which do not contribute to the axis. These results indicate that the dorsal fate is actively repressed by Xgsk-3, which must be inactivated for dorsal axis formation to occur. Furthermore, our work suggests that the effects of Xgsk-3K-->R are mediated by an additional intercellular signal.

A cytoplasmic determinant for dorsal axis formation in an early embryo of Xenopus laevis

Development ◽  
1990 ◽  
Vol 110 (4) ◽  
pp. 1051-1056 ◽  
Author(s):  
M. Yuge ◽  
Y. Kobayakawa ◽  
M. Fujisue ◽  
K. Yamana
Keyword(s):  
Xenopus Laevis ◽  
Direct Evidence ◽  
Early Embryo ◽  
Dorsal Side ◽  
Axis Formation ◽  
Secondary Axis ◽  
Dorsal Axis ◽  
Cell Embryo ◽  
Dorsal Cells ◽  
Cytoplasmic Determinant

In Xenopus laevis, dorsal cells that arise at the future dorsal side of an early cleaving embryo have already acquired the ability to cause axis formation. Since the distribution of cytoplasmic components is markedly heterogeneous in an egg and embryo, it has been supposed that the dorsal cells are endowed with the activity to form axial structures by inheriting a unique cytoplasmic component or components localized in the dorsal region of an egg or embryo. However, there has been no direct evidence for this. To examine the activity of the cytoplasm of dorsal cells, we injected cytoplasm (dorsal cytoplasm) from dorsal vegetal cells of a Xenopus 16-cell embryo into ventral vegetal cells of a simultaneous recipient. The cytoplasm caused secondary axis formation in 42% of recipients. Histological examination revealed that well-developed secondary axes included notochord, as well as a neural tube and somites. However, injection of cytoplasm of ventral vegetal cells never caused secondary axis and most recipients became normal tailbud embryos. Furthermore, about two-thirds of ventral isolated halves injected with dorsal cytoplasm formed axial structures. These results show that dorsal, but not ventral, cytoplasm contains the component or components responsible for axis formation. This can be the first step towards identifying the molecular basis of dorsal axis formation.

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.

scholarly journals Wnt/β-catenin signaling is an evolutionarily conserved determinant of chordate dorsal organizer

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Iryna Kozmikova ◽  
Zbynek Kozmik
Keyword(s):  
Cell Fate ◽  
Current View ◽  
Specific Gene ◽  
Axis Formation ◽  
Dependent Manner ◽  
Evolutionarily Conserved ◽  
Dorsal Axis ◽  
Dorsal Cells ◽  
Dorsal Cell Fate

Deciphering the mechanisms of axis formation in amphioxus is a key step to understanding the evolution of chordate body plan. The current view is that Nodal signaling is the only factor promoting the dorsal axis specification in the amphioxus, whereas Wnt/β-catenin signaling plays no role in this process. Here, we re-examined the role of Wnt/βcatenin signaling in the dorsal/ventral patterning of amphioxus embryo. We demonstrated that the spatial activity of Wnt/β-catenin signaling is located in presumptive dorsal cells from cleavage to gastrula stage, and provided functional evidence that Wnt/β-catenin signaling is necessary for the specification of dorsal cell fate in a stage-dependent manner. Microinjection of Wnt8 and Wnt11 mRNA induced ectopic dorsal axis in neurulae and larvae. Finally, we demonstrated that Nodal and Wnt/β-catenin signaling cooperate to promote the dorsal-specific gene expression in amphioxus gastrula. Our study reveals high evolutionary conservation of dorsal organizer formation in the chordate lineage.

FAST-1 is a key maternal effector of mesoderm inducers in the early Xenopus embryo

Development ◽  
1999 ◽  
Vol 126 (24) ◽  
pp. 5621-5634 ◽  
Author(s):  
M. Watanabe ◽  
M. Whitman
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Ectopic Expression ◽  
Axis Formation ◽  
Mesoderm Induction ◽  
Transcriptional Program ◽  
Blocking Antibody ◽  
Responsive Element ◽  
Axial Development

We have examined the role of the maternally encoded transcription factor FAST-1 in the establishment of the mesodermal transcriptional program in Xenopus embryos. FAST-1 has been shown to associate with Smad2 and Smad4, transducers of TGFbeta superfamily signals, in response to stimulation by several TGFbeta superfamily ligands. The FAST-1/Smad2/Smad4 complex binds and activates a 50 bp activin responsive element identified in the promoter of the meso-endodermal marker Mix.2. We have now used three complementary approaches to demonstrate that FAST-1 is a central regulator of mesoderm induction by ectopic TGFbeta superfamily ligands and during endogenous patterning: ectopic expression of mutationally activated FAST-1, ectopic expression of dominant inhibitory FAST-1, and injection of a blocking antibody specific for FAST-1. Expression of constitutively transcriptionally active FAST-1 fusion protein (FAST-VP16(A)) in prospective ectoderm can directly induce the same set of general and dorsal mesodermal genes, as well as some endodermal genes, as are induced by activin or Vg1. In intact embryos, this construct can induce secondary axes similar to those induced by activin or Vg1. Conversely, expression of a FAST-1-repressor fusion (FAST-En(R)) in prospective ectoderm blocks induction of mesodermal genes by activin, while expression of FAST-En(R) in intact embryos prevents general/dorsal mesodermal gene expression and axial development. Injection of a blocking antibody specific for FAST-1 prevents induction of mesodermal response genes by activin or Vg1, but not by FGF. In intact embryos, this antibody can prevent the expression of early mesodermal markers and inhibit axis formation, demonstrating that FAST-1 is a necessary component of the first steps in the specification of mesoderm.

scholarly journals A novel role for Ets4 in axis specification and cell migration in the spider Parasteatoda tepidariorum

2017 ◽  
Author(s):  
Matthias Pechmann ◽  
Matthew A. Benton ◽  
Nathan J. Kenny ◽  
Nico Posnien ◽  
Siegfried Roth
Keyword(s):  
Embryonic Development ◽  
Cell Fate ◽  
Ectopic Expression ◽  
Specific Gene ◽  
Dorsoventral Patterning ◽  
Embryonic Axes ◽  
Parasteatoda Tepidariorum ◽  
Spemann Organizer ◽  
Secondary Axis ◽  
And Migration

AbstractOrganizers play important roles during the embryonic development of many animals. The most famous example is the Spemann organizer that sets up embryonic axes in amphibian embryos.In spiders, a group of BMP secreting mesenchymal cells (the cumulus) functions as an organizer of the dorsoventral axis. Similar to experiments performed with the Spemann organizer, transplantation of the cumulus is able to induce a secondary axis in spiders.Despite the importance of this structure, it is unknown which factors are needed to activate cumulus specific gene expression.To address this question, we performed a transcriptomic analysis of early embryonic development in the spider Parasteatoda tepidariorum. Through this work, we found that the transcription factor Pt-Ets4 is needed for cumulus integrity, dorsoventral patterning and for the activation of Pt-hunchback and Pt-twist expression. Furthermore, ectopic expression of Pt-Ets4 is sufficient to induce cell delamination and migration by inducing a mesoderm-like cell fate.

scholarly journals The role of apterous in the control of dorsoventral compartmentalization and PS integrin gene expression in the developing wing of Drosophila

Development ◽  
1994 ◽  
Vol 120 (7) ◽  
pp. 1805-1815 ◽  
Author(s):  
S.S. Blair ◽  
D.L. Brower ◽  
J.B. Thomas ◽  
M. Zavortink
Keyword(s):  
Gene Expression ◽  
Ectopic Expression ◽  
Cell Lineage ◽  
Wing Disc ◽  
Specific Gene ◽  
Dividing Cells ◽  
Integrin Gene ◽  
Dorsal Cells ◽  
Anterior Posterior

During the development of Drosophila appendages from imaginal discs lineage restrictions appear that prevent dividing cells from crossing between regionally distinct compartments. These compartments correspond not only to regions of cell lineage restrictions but also to regions of specific gene expression. When compartments were first discovered, it was proposed that their formation relied on compartment-specific ‘selector’ gene activity; engrailed is thought to play such a role for the early-arising anterior-posterior restriction. Recent results suggest that the dorsally expressed transcription factor encoded by apterous may control dorsoventral identity in the wing. In this study we use mosaic analysis to show that apterous maintains the late-arising dorsoventral lineage restriction in a manner that strongly supports the selector gene hypothesis: loss of apterous function from dorsal cells after the formation of the boundary causes them to cross into the ventral compartment. Moreover, we show that apterous plays a role controlling patterns of gene expression in the developing wing disc. The PS1 and PS2 integrins are normally expressed in primarily dorsal-specific and ventral-specific patterns, respectively. We show that ectopic expression of apterous induces ectopic ventral expression of PS1 integrin and alpha PS1 mRNA, while loss of apterous can induce the ectopic dorsal expression of PS2 integrin. Thus, apterous plays a selector-like role both in terms of the control of lineage restrictions and the regulation of downstream gene expression.

scholarly journals A novel role for Ets4 in axis specification and cell migration in the spider Parasteatoda tepidariorum

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Matthias Pechmann ◽  
Matthew A Benton ◽  
Nathan J Kenny ◽  
Nico Posnien ◽  
Siegfried Roth
Keyword(s):  
Embryonic Development ◽  
Cell Fate ◽  
Ectopic Expression ◽  
Specific Gene ◽  
Embryonic Axes ◽  
Parasteatoda Tepidariorum ◽  
Spemann Organizer ◽  
Secondary Axis ◽  
Twist Expression ◽  
And Migration

Organizers play important roles during the embryonic development of many animals. The most famous example is the Spemann organizer that sets up embryonic axes in amphibian embryos. In spiders, a group of BMP secreting mesenchymal cells (the cumulus) functions as an organizer of the dorsoventral axis. Similar to experiments performed with the Spemann organizer, transplantation of the cumulus is able to induce a secondary axis in spiders. Despite the importance of this structure, it is unknown which factors are needed to activate cumulus specific gene expression. To address this question, we performed a transcriptomic analysis of early embryonic development in the spider Parasteatoda tepidariorum. Through this work, we found that the transcription factor Pt-Ets4 is needed for cumulus integrity, dorsoventral patterning and for the activation of Pt-hunchback and Pt-twist expression. Furthermore, ectopic expression of Pt-Ets4 is sufficient to induce cell delamination and migration by inducing a mesoderm-like cell fate.

Centrosome Aurora A gradient ensures single polarity axis in C. elegans embryos

2020 ◽  
Vol 48 (3) ◽  
pp. 1243-1253 ◽  
Author(s):  
Sukriti Kapoor ◽  
Sachin Kotak
Keyword(s):  
Symmetry Breaking ◽  
Cell Fate ◽  
Cell Cortex ◽  
Axis Formation ◽  
Aurora A Kinase ◽  
Aurora A ◽  
C Elegans ◽  
Cell Embryo ◽  
Polarity Establishment

Cellular asymmetries are vital for generating cell fate diversity during development and in stem cells. In the newly fertilized Caenorhabditis elegans embryo, centrosomes are responsible for polarity establishment, i.e. anterior–posterior body axis formation. The signal for polarity originates from the centrosomes and is transmitted to the cell cortex, where it disassembles the actomyosin network. This event leads to symmetry breaking and the establishment of distinct domains of evolutionarily conserved PAR proteins. However, the identity of an essential component that localizes to the centrosomes and promotes symmetry breaking was unknown. Recent work has uncovered that the loss of Aurora A kinase (AIR-1 in C. elegans and hereafter referred to as Aurora A) in the one-cell embryo disrupts stereotypical actomyosin-based cortical flows that occur at the time of polarity establishment. This misregulation of actomyosin flow dynamics results in the occurrence of two polarity axes. Notably, the role of Aurora A in ensuring a single polarity axis is independent of its well-established function in centrosome maturation. The mechanism by which Aurora A directs symmetry breaking is likely through direct regulation of Rho-dependent contractility. In this mini-review, we will discuss the unconventional role of Aurora A kinase in polarity establishment in C. elegans embryos and propose a refined model of centrosome-dependent symmetry breaking.

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