scholarly journals Vegetally localized Vrtn functions as a novel repressor to modulate bmp2b transcription during dorsoventral patterning in zebrafish

2017 ◽  
Author(s):  
Ming Shao ◽  
Min Wang ◽  
Yi-Wen Ge ◽  
Yan-Jun Zhang ◽  
De-Li Shi
Keyword(s):  
Bone Morphogenetic Proteins ◽  
Early Embryo ◽  
Upstream Sequence ◽  
Loss Of Function ◽  
Dorsoventral Patterning ◽  
Dorsoventral Axis ◽  
Spemann Organizer ◽  
Vegetal Pole ◽  
Bmp Signalling ◽  
Maternal Regulation

ABSTRACTThe vegetal pole cytoplasm represents a critical source of maternal signals for patterning the primary dorsoventral axis of the early embryo. Vegetally localized dorsal determinants are essential for the formation of the Spemann organizer, which expresses both bone morphogenetic proteins and their antagonists. The extracellular regulation of BMP signalling activity has been well characterized, however, transcriptional regulation of bmp genes along the dorsoventral axis remains largely unknown. Here, we report a novel mode of maternal regulation of BMP signalling in the lateral and ventral regions by analyzing the unexpected dorsalizing effect following vegetal yolk ablation experiment. We identified Vrtn as a novel vegetally localized maternal factor displaying dorsalizing activity. It functions as a novel transcriptional repressor to regulate bmp2b expression in the marginal region. Mechanistically, Vrtn binds bmp2b upstream sequence and inhibits its transcription independently of maternal Wnt/ß-catenin signalling. By creating vrtn loss-of-function mutation and analyzing maternal-zygotic mutant embryos, we further showed that Vrtn is required for the formation of dorsoventral axis. Our work thus unveils a novel maternal mechanism regulating BMP gradient during dorsoventral specification.

Endogenous bone morphogenetic proteins regulate outgrowth and epithelial survival during avian lip fusion

Development ◽  
2002 ◽  
Vol 129 (19) ◽  
pp. 4647-4660 ◽  
Author(s):  
Amir M. Ashique ◽  
Katherine Fu ◽  
Joy M. Richman
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Bone Morphogenetic Proteins ◽  
Loss Of Function ◽  
Rapid Induction ◽  
Similar Phenotype ◽  
Primary Palate ◽  
Bmp Signalling ◽  
Frontonasal Mass

Our expression studies of bone morphogenetic proteins (BMPs) and Noggin (a BMP antagonist) in the embryonic chicken face suggested that BMP signals were important for closure of the upper lip or primary palate. We noted that Noggin expression was restricted to the frontonasal mass epithelium but was reduced at the corners of the frontonasal mass (globular processes) just prior to fusion with the adjacent maxillary prominences. We therefore performed gain- and loss-of-function experiments to determine the role of BMPs in lip formation. Noggin treatment led to reduced proliferation and outgrowth of the frontonasal mass and maxillary prominences and ultimately to the deletion of the maxillary and palatine bones. The temporary block in BMP signalling in the mesenchyme also promoted epithelial survival. Noggin treatment also upregulated expression of endogenous BMPs, therefore we investigated whether increasing BMP levels would lead to the same phenotype. A BMP2 bead was implanted into the globular process and a similar phenotype to that produced by Noggin resulted. However, instead of a decrease in proliferation, defects were caused by increased programmed cell death, first in the epithelium and then in the mesenchyme. Programmed cell death was induced primarily in the lateral frontonasal mass with very little cell death medial to the bead. The asymmetric cell death pattern was correlated with a rapid induction of Noggin in the same embryos, with transcripts complementary to the regions with increased cell death. We have demonstrated a requirement for endogenous BMP in the proliferation of facial mesenchyme and that mesenchymal signals promote either survival or thinning of the epithelium. We furthermore demonstrated in vivo that BMP homeostasis is regulated by increasing expression of ligand or antagonist and that such mechanisms may help to protect the embryo from changes in growth factor levels during development or after exposure to teratogens.

The homeobox genesvoxandventare redundant repressors of dorsal fates in zebrafish

Development ◽  
2001 ◽  
Vol 128 (12) ◽  
pp. 2407-2420 ◽  
Author(s):  
Yoshiyuki Imai ◽  
Michael A. Gates ◽  
Anna E. Melby ◽  
David Kimelman ◽  
Alexander F. Schier ◽  
...  
Keyword(s):  
Early Embryo ◽  
Dorsal Side ◽  
Bmp Signaling ◽  
Loss Of Function ◽  
Dorsoventral Patterning ◽  
Patterning Defect ◽  
Morpholino Oligonucleotides ◽  
Redundant Functions ◽  
Antisense Morpholino Oligonucleotides ◽  
Antisense Morpholino

Ventralizing transcriptional repressors in the Vox/Vent family have been proposed to be important regulators of dorsoventral patterning in the early embryo. While the zebrafish genes vox (vega1) and vent (vega2) both have ventralizing activity in overexpression assays, loss-of-function studies are needed to determine whether these genes have distinct or redundant functions in dorsoventral patterning and to provide critical tests of the proposed regulatory interactions among vox, vent and other genes that act to establish the dorsoventral axis. We show that vox and vent are redundant repressors of dorsal fates in zebrafish. Mutants that lack vox function have little or no dorsoventral patterning defect, and inactivation of either vox or vent by injection of antisense morpholino oligonucleotides has little or no effect on the embryo. In contrast, embryos that lack both vox and vent function have a dorsalized phenotype. Expression of dorsal mesodermal genes, including chordin, goosecoid and bozozok, is strongly expanded in embryos that lack vox and vent function, indicating that the redundant action of vox and vent is required to restrict dorsal genes to their appropriate territories. Our genetic analysis indicates that the dorsalizing transcription factor Bozozok promotes dorsal fates indirectly, by antagonizing the expression of vox and vent. In turn, vox and vent repress chordin expression, restricting its function as an antagonist of ventral fates to the dorsal side of the embryo. Our results support a model in which BMP signaling induces the expression of ventral genes, while vox and vent act redundantly to prevent the expression of chordin, goosecoid and other dorsal genes in the lateral and ventral mesendoderm.

Independent regulation of Dlx2 expression in the epithelium and mesenchyme of the first branchial arch

Development ◽  
2000 ◽  
Vol 127 (2) ◽  
pp. 217-224 ◽  
Author(s):  
B.L. Thomas ◽  
J.K. Liu ◽  
J.L. Rubenstein ◽  
P.T. Sharpe
Keyword(s):  
Tooth Development ◽  
Branchial Arch ◽  
Oral Epithelium ◽  
Upstream Sequence ◽  
Loss Of Function ◽  
Signalling Molecules ◽  
Molar Teeth ◽  
Overlapping Domains ◽  
Upper Molar

Dlx2, a member of the distal-less gene family, is expressed in the first branchial arch, prior to the initiation of tooth development, in distinct, non-overlapping domains in the mesenchyme and the epithelium. In the mesenchyme Dlx2 is expressed proximally, whereas in oral epithelium it is expressed distally. Dlx2 has been shown to be involved in the patterning of the murine dentition, since loss of function of Dlx1 and Dlx2 results in early failure of development of upper molar teeth. We have investigated the regulation of Dlx2 expression to determine how the early epithelial and mesenchymal expression boundaries are maintained, to help to understand the role of these distinct expression domains in patterning of the dentition. Transgenic mice produced with a lacZ reporter construct, containing 3.8 kb upstream sequence of Dlx2, led to the mapping of regulatory regions driving epithelial but not mesenchymal expression in the first branchial arch. We show that the epithelial expression of Dlx2 is regulated by planar signalling by BMP4, which is coexpressed in distal oral epithelium. Mesenchymal expression is regulated by a different mechanism involving FGF8, which is expressed in the overlying epithelium. FGF8 also inhibits expression of Dlx2 in the epithelium by a signalling pathway that requires the mesenchyme. Thus, the signalling molecules BMP4 and FGF8 provide the mechanism for maintaining the strict epithelial and mesenchymal expression domains of Dlx2 in the first arch.

scholarly journals Spemann organizer transcriptome induction by early beta-catenin, Wnt, Nodal, and Siamois signals in Xenopus laevis

2017 ◽  
Vol 114 (15) ◽  
pp. E3081-E3090 ◽  
Author(s):  
Yi Ding ◽  
Diego Ploper ◽  
Eric A. Sosa ◽  
Gabriele Colozza ◽  
Yuki Moriyama ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Gene Signature ◽  
Dorsal Side ◽  
Beta Catenin ◽  
Loss Of Function ◽  
Spemann Organizer ◽  
Signature Genes ◽  
A Genome ◽  
Vertebrate Model ◽  
Chloride Treatment

The earliest event in Xenopus development is the dorsal accumulation of nuclear β-catenin under the influence of cytoplasmic determinants displaced by fertilization. In this study, a genome-wide approach was used to examine transcription of the 43,673 genes annotated in the Xenopus laevis genome under a variety of conditions that inhibit or promote formation of the Spemann organizer signaling center. Loss of function of β-catenin with antisense morpholinos reproducibly reduced the expression of 247 mRNAs at gastrula stage. Interestingly, only 123 β-catenin targets were enriched on the dorsal side and defined an early dorsal β-catenin gene signature. These genes included several previously unrecognized Spemann organizer components. Surprisingly, only 3 of these 123 genes overlapped with the late Wnt signature recently defined by two other groups using inhibition by Dkk1 mRNA or Wnt8 morpholinos, which indicates that the effects of β-catenin/Wnt signaling in early development are exquisitely regulated by stage-dependent mechanisms. We analyzed transcriptome responses to a number of treatments in a total of 46 RNA-seq libraries. These treatments included, in addition to β-catenin depletion, regenerating dorsal and ventral half-embryos, lithium chloride treatment, and the overexpression of Wnt8, Siamois, and Cerberus mRNAs. Only some of the early dorsal β-catenin signature genes were activated at blastula whereas others required the induction of endomesoderm, as indicated by their inhibition by Cerberus overexpression. These comprehensive data provide a rich resource for analyzing how the dorsal and ventral regions of the embryo communicate with each other in a self-organizing vertebrate model embryo.

The relationship between ovarian and embryonic dorsoventral patterning in Drosophila

Development ◽  
1994 ◽  
Vol 120 (8) ◽  
pp. 2245-2257 ◽  
Author(s):  
S. Roth ◽  
T. Schupbach
Keyword(s):  
Egf Receptor ◽  
Germ Line ◽  
Early Embryo ◽  
Follicular Epithelium ◽  
Forming Process ◽  
Cell Fates ◽  
Dorsoventral Axis ◽  
Potential Ligand ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

In Drosophila, the dorsoventral asymmetry of the egg chamber depends on a dorsalizing signal that emanates from the oocyte. This signal is supplied by the TGF alpha-like gurken protein whose RNA is localized to the dorsal-anterior corner of the oocyte, gurken protein is the potential ligand of the Drosophila EGF receptor homolog (torpedo), which is expressed in the follicular epithelium surrounding the oocyte. Here, we describe how changes in the dorsalizing germ-line signal affect the embryonic dorsoventral pattern. A reduction in strength of the germ-line signal as produced by mutations in gurken or torpedo does not change the slope of the embryonic dorsoventral morphogen gradient, but causes a splitting of the gradient ventrally. This leads to embryos with two partial dorsoventral axes. A change in distribution of the germ-line signal as caused by fs(1)K10, squid and orb mutations leads to a shift in the orientation of the embryonic dorsoventral axis relative to the anterior-posterior axis. In extreme cases, this results in embryos with a dorsoventral axis almost parallel to the anterior-posterior axis. These results imply that gurken, unlike other localized cytoplasmic determinants, is not directly responsible for the establishment of cell fates along a body axis, but that it restricts and orients an active axis-forming process which occurs later in the follicular epithelium or in the early embryo.

Homeostatic balance between dorsal and cactus proteins in the Drosophila embryo

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 135-148 ◽  
Author(s):  
S. Govind ◽  
L. Brennan ◽  
R. Steward
Keyword(s):  
Direct Interaction ◽  
Drosophila Embryo ◽  
Loss Of Function ◽  
Wild Type ◽  
Wild Type Embryo ◽  
Cleavage Stage ◽  
Dorsoventral Axis ◽  
Maternal Effect Gene ◽  
Early Embryos ◽  
Effect Gene

The maternal-effect gene dorsal encodes the ventral morphogen that is essential for elaboration of ventral and ventrolateral fates in the Drosophila embryo. Dorsal belongs to the rel family of transcription factors and controls asymmetric expression of zygotic genes along the dorsoventral axis. The dorsal protein is cytoplasmic in early embryos, possibly because of a direct interaction with cactus. In response to a ventral signal, dorsal protein becomes partitioned into nuclei of cleavage-stage syncytial blastoderms such that the ventral nuclei have the maximum amount of dorsal protein, and the lateral and dorsal nuclei have progressively less protein. Here we show that transgenic flies containing the dorsal cDNA, which is driven by the constitutively active hsp83 promoter, exhibits rescue of the dorsal- phenotype. Transformed lines were used to increase the level of dorsal protein. Females with dorsal levels roughly twice that of wild-type produced normal embryos, while a higher level of dorsal protein resulted in phenotypes similar to those observed for loss-of-function cactus mutations. By manipulating the cactus gene dose, we found that in contrast to a dorsal/cactus ratio of 2.5 which resulted in fully penetrant weak ventralization, a cactus/dorsal ratio of 3.0 was acceptable by the system. By manipulating dorsal levels in different cactus and dorsal group mutant backgrounds, we found that the relative amounts of ventral signal to that of the dorsal-cactus complex is important for the elaboration of the normal dorsoventral pattern. We propose that in a wild-type embryo, the activities of dorsal and cactus are not independently regulated; excess cactus activity is deployed only if a higher level of dorsal protein is available. Based on these results we discuss how the ventral signal interacts with the dorsal-cactus complex, thus forming a gradient of nuclear dorsal protein.

The role of bone morphogenetic proteins in the differentiation of the ventral optic cup

Development ◽  
2002 ◽  
Vol 129 (13) ◽  
pp. 3161-3171 ◽  
Author(s):  
Ruben Adler ◽  
Teri L. Belecky-Adams
Keyword(s):  
Bone Morphogenetic Proteins ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Ectopic Expression ◽  
Neural Retina ◽  
Optic Disk ◽  
Loss Of Function ◽  
In Ovo ◽  
Optic Stalk ◽  
Optic Cup

The ventral region of the chick embryo optic cup undergoes a complex process of differentiation leading to the formation of four different structures: the neural retina, the retinal pigment epithelium (RPE), the optic disk/optic stalk, and the pecten oculi. Signaling molecules such as retinoic acid and sonic hedgehog have been implicated in the regulation of these phenomena. We have now investigated whether the bone morphogenetic proteins (BMPs) also regulate ventral optic cup development. Loss-of-function experiments were carried out in chick embryos in ovo, by intraocular overexpression of noggin, a protein that binds several BMPs and prevents their interactions with their cognate cell surface receptors. At optic vesicle stages of development, this treatment resulted in microphthalmia with concomitant disruption of the developing neural retina, RPE and lens. At optic cup stages, however, noggin overexpression caused colobomas, pecten agenesis, replacement of the ventral RPE by neuroepithelium-like tissue, and ectopic expression of optic stalk markers in the region of the ventral retina and RPE. This was frequently accompanied by abnormal growth of ganglion cell axons, which failed to enter the optic nerve. The data suggest that endogenous BMPs have significant effects on the development of ventral optic cup structures.

Suppression of GATA factor activity causes axis duplication in Xenopus

Development ◽  
1998 ◽  
Vol 125 (23) ◽  
pp. 4595-4605 ◽  
Author(s):  
T.G. Sykes ◽  
A.R. Rodaway ◽  
M.E. Walmsley ◽  
R.K. Patient
Keyword(s):  
Cell Fate ◽  
Homeobox Gene ◽  
Dominant Negative ◽  
Gata Factor ◽  
Dorsoventral Axis ◽  
Morphogenetic Protein ◽  
Head Formation ◽  
Bmp Signalling ◽  
Bmp Antagonist

In Xenopus, the dorsoventral axis is patterned by the interplay between active signalling in ventral territories, and secreted antagonists from Spemann's organiser. Two signals are important in ventral cells, bone morphogenetic protein-4 (BMP-4) and Wnt-8. BMP-4 plays a conserved role in patterning the vertebrate dorsoventral axis, whilst the precise role of Wnt-8 and its relationship with BMP-4, are still unclear. Here we have investigated the role played by the GATA family of transcription factors, which are expressed in ventral mesendoderm during gastrulation and are required for the differentiation of blood and endodermal tissues. Injection ventrally of a dominant-interfering GATA factor (called G2en) induced the formation of secondary axes that phenocopy those induced by the dominant-negative BMP receptor. However, unlike inhibiting BMP signalling, inhibiting GATA activity in the ectoderm does not lead to neuralisation. In addition, analysis of gene expression in G2en injected embryos reveals that at least one known target gene for BMP-4, the homeobox gene Vent-2, is unaffected. In contrast, the expression of Wnt-8 and the homeobox gene Vent-1 is suppressed by G2en, whilst the organiser-secreted BMP antagonist chordin becomes ectopically expressed. These data therefore suggest that GATA activity is essential for ventral cell fate and that subsets of ventralising and dorsalising genes require GATA activity for their expression and suppression, respectively. Finally, using G2en, we show that suppression of Wnt-8 expression, in conjunction with blocked BMP signalling, does not lead to head formation, suggesting that the head-suppressing Wnt signal may not be Wnt-8.

The role of Xenopus dickkopf1 in prechordal plate specification and neural patterning

Development ◽  
2000 ◽  
Vol 127 (22) ◽  
pp. 4981-4992 ◽  
Author(s):  
O. Kazanskaya ◽  
A. Glinka ◽  
C. Niehrs
Keyword(s):  
Target Genes ◽  
Loss Of Function ◽  
Dorsoventral Patterning ◽  
Gastrula Stage ◽  
Neural Patterning ◽  
Prechordal Plate ◽  
Wnt Inhibitor ◽  
The Central Nervous System ◽  
Wnt Inhibitors

Dickkopf1 (dkk1) encodes a secreted WNT inhibitor expressed in Spemann's organizer, which has been implicated in head induction in Xenopus. Here we have analyzed the role of dkk1 in endomesoderm specification and neural patterning by gain- and loss-of-function approaches. We find that dkk1, unlike other WNT inhibitors, is able to induce functional prechordal plate, which explains its ability to induce secondary heads with bilateral eyes. This may be due to differential WNT inhibition since dkk1, unlike frzb, inhibits Wnt3a signalling. Injection of inhibitory antiDkk1 antibodies reveals that dkk1 is not only sufficient but also required for prechordal plate formation but not for notochord formation. In the neural plate dkk1 is required for anteroposterior and dorsoventral patterning between mes- and telencephalon, where dkk1 promotes anterior and ventral fates. Both the requirement of anterior explants for dkk1 function and their ability to respond to dkk1 terminate at late gastrula stage. Xenopus embryos posteriorized with bFGF, BMP4 and Smads are rescued by dkk1. dkk1 does not interfere with the ability of bFGF to induce its immediate early target gene Xbra, indicating that its effect is indirect. In contrast, there is cross-talk between BMP and WNT signalling, since induction of BMP target genes is sensitive to WNT inhibitors until the early gastrula stage. Embryos treated with retinoic acid (RA) are not rescued by dkk1 and RA affects the central nervous system (CNS) more posterior than dkk1, suggesting that WNTs and retinoids may act to pattern anterior and posterior CNS, respectively, during gastrulation.

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