Misexpression of chick Vg1 in the marginal zone induces primitive streak formation

Development ◽  
1997 ◽  
Vol 124 (24) ◽  
pp. 5127-5138 ◽  
Author(s):  
S.B. Shah ◽  
I. Skromne ◽  
C.R. Hume ◽  
D.S. Kessler ◽  
K.J. Lee ◽  
...  
Keyword(s):  
Marginal Zone ◽  
Ectopic Expression ◽  
Primitive Streak ◽  
Axis Formation ◽  
Mesoderm Induction ◽  
Cell Fates ◽  
Signalling Molecules ◽  
Posterior Area ◽  
Area Pellucida

In the chick embryo, the primitive streak is the first axial structure to develop. The initiation of primitive streak formation in the posterior area pellucida is influenced by the adjacent posterior marginal zone (PMZ). We show here that chick Vg1 (cVg1), a member of the TGFbeta family of signalling molecules whose homolog in Xenopus is implicated in mesoderm induction, is expressed in the PMZ of prestreak embryos. Ectopic expression of cVg1 protein in the marginal zone chick blastoderms directs the formation of a secondary primitive streak, which subsequently develops into an ectopic embryo. We have used cell marking techniques to show that cells that contribute to the ectopic primitive streak change fate, acquiring two distinct properties of primitive streak cells, defined by gene expression and cell movements. Furthermore, naive epiblast explants exposed to cVg1 protein in vitro acquire axial mesodermal properties. Together, these results show that cVg1 can mediate ectopic axis formation in the chick by inducing new cell fates and they permit the analysis of distinct events that occur during primitive streak formation.

Cwnt-8C: a novel Wnt gene with a potential role in primitive streak formation and hindbrain organization

Development ◽  
1993 ◽  
Vol 119 (4) ◽  
pp. 1147-1160 ◽  
Author(s):  
C.R. Hume ◽  
J. Dodd
Keyword(s):  
Gene Family ◽  
Potential Role ◽  
Marginal Zone ◽  
Cell Signalling ◽  
Primitive Streak ◽  
Axis Formation ◽  
Restricted Domain ◽  
Signalling Molecules ◽  
Wnt Proteins ◽  
Chick Embryogenesis

To begin to examine the possibility that Wnt proteins act as cell signalling molecules during chick embryogenesis, PCR was used to identify Wnt genes expressed in Hensen's node. We have identified a novel member of the Wnt gene family, Cwnt-8C, which is expressed prior to gastrulation in the posterior marginal zone, the primitive streak and Hensen's node. Injection of Cwnt-8C mRNA into Xenopus embryos caused axis duplication and dorsalization of mesodermal tissues. During neurulation, Cwnt-8C is expressed transiently in a restricted domain of the prospective hindbrain neurectoderm that will give rise to rhombomere 4. This domain is defined prior to the formation of rhombomere boundaries and also precedes the up-regulation and restriction of expression of Hox B1 in the same region. Thus, Cwnt-8C is potentially involved in the regulation of axis formation and hindbrain patterning.

Interactions between Wnt and Vg1 signalling pathways initiate primitive streak formation in the chick embryo

Development ◽  
2001 ◽  
Vol 128 (15) ◽  
pp. 2915-2927 ◽  
Author(s):  
Isaac Skromne ◽  
Claudio D. Stern
Keyword(s):  
Chick Embryo ◽  
Marginal Zone ◽  
Primitive Streak ◽  
Embryonic Axis ◽  
Normal Embryo ◽  
Signalling Pathways ◽  
Axis Formation ◽  
Distinct Region ◽  
Wnt Pathways ◽  
Area Pellucida

The posterior marginal zone (PMZ) of the chick embryo has Nieuwkoop centre-like properties: when transplanted to another part of the marginal zone, it induces a complete embryonic axis, without making a cellular contribution to the induced structures. However, when the PMZ is removed, the embryo can initiate axis formation from another part of the remaining marginal zone. Chick Vg1 can mimic the axis-inducing ability of the PMZ, but only when misexpressed somewhere within the marginal zone. We have investigated the properties that define the marginal zone as a distinct region. We show that the competence of the marginal zone to initiate ectopic primitive streak formation in response to cVg1 is dependent on Wnt activity. First, within the Wnt family, only Wnt8C is expressed in the marginal zone, in a gradient decreasing from posterior to anterior. Second, misexpression of Wnt1 in the area pellucida enables this region to form a primitive streak in response to cVg1. Third, the Wnt antagonists Crescent and Dkk-1 block the primitive streak-inducing ability of cVg1 in the marginal zone. These findings suggest that Wnt activity defines the marginal zone and allows cVg1 to induce an axis. We also present data suggesting some additional complexity: first, the Vg1 and Wnt pathways appear to regulate the expression of downstream components of each other’s pathway; and second, misexpression of different Wnt antagonists suggests that different classes of Wnts may cooperate with each other to regulate axis formation in the normal embryo.

Xrel3/XrelA attenuates β-catenin-mediated transcription during mesoderm formation in Xenopus embryos

2011 ◽  
Vol 435 (1) ◽  
pp. 247-257 ◽  
Author(s):  
Mark W. L. Kennedy ◽  
Kenneth R. Kao
Keyword(s):  
Cell Fate ◽  
Target Genes ◽  
Marginal Zone ◽  
Ectopic Expression ◽  
Nuclear Factor Κb ◽  
Mesoderm Induction ◽  
Mesoderm Cell ◽  
Mesoderm Formation

In Xenopus laevis embryonic development, activation of the Wnt/β-catenin pathway promotes mesoderm cell fate determination via Xnr (Xenopus nodal-related) expression. We have demonstrated previously that Rel/NF-κB (nuclear factor κB) proteins expressed in presumptive ectoderm limit the activity of Xnrs to the marginal zone of embryos during mesoderm induction, which assists to distinguish mesoderm from ectoderm. The mechanism of this regulation, however, is unknown. In the present study, we investigated whether Rel/NF-κB proteins are able to modulate mesoderm formation by mediating Wnt/β-catenin signalling. We determined that ectopic expression of XrelA or Xrel3 in the dorsal marginal zone perturbed dorsal mesoderm formation by down-regulating multiple Wnt/β-catenin target genes including Xnr3, Xnr5 and Xnr6. Ventral co-expression of XrelA or Xrel3 with either wild-type β-catenin or constitutively active β-cateninS37A abrogated β-catenin-induced axis duplication and attenuated β-catenin-stimulated reporter transcription. Lastly, we provide evidence that Xrel3, but not XrelA, can interact with β-catenin without affecting the association of β-catenin with other transcriptional co-activators in vitro. Both Xrel3 and XrelA, however, prevented the accumulation, in nuclei, of exogenously expressed and endogenous β-catenin in vivo. These results suggest that Rel proteins are able to bind β-catenin and attenuate β-catenin-mediated transcription by nuclear exclusion.

The posterior section of the chick's area pellucida and its involvement in hypoblast and primitive streak formation

Development ◽  
1992 ◽  
Vol 116 (3) ◽  
pp. 819-830 ◽  
Author(s):  
H. Eyal-Giladi ◽  
A. Debby ◽  
N. Harel
Keyword(s):  
Distribution Pattern ◽  
Marginal Zone ◽  
Primitive Streak ◽  
Fluorescent Dye ◽  
Narrow Strip ◽  
Posterior Section ◽  
Area Pellucida

Posterior marginal zone sections with or without Koller's sickle were cut out of stage X, XI and XII E.G&K blastoderms, labelled with the fluorescent dye rhodamine-dextran-lysine (RDL) and returned to their original location. In control experiments, a similar lateral section of the marginal zone was identically treated. Different blastoderms were incubated at 37°C for different periods and were fixed after reaching stages from XII E.G&K to 4 H&H. The conclusions drawn from the analysis of the distribution pattern of the labelled cells in the serially sectioned blastoderms concern the cellular contributions to both the forming hypoblast and the forming primitive streak. Koller's sickle and the marginal zone behind it were found to contribute all the centrally located cells of the growing hypoblast. The lengthening pregastrulation PS (until stage 3+ H&H) was found to be entirely composed of epiblastic cells that at stage X were located in a narrow strip anterior to Koller's sickle. A model is proposed to integrate the results spatially and temporally.

scholarly journals Avian marginal zone cells function as primitive streak inducers only after their migration into the hypoblast

Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2501-2509 ◽  
Author(s):  
H. Eyal-Giladi ◽  
T. Lotan ◽  
T. Levin ◽  
O. Avner ◽  
J. Hochman
Keyword(s):  
Incubation Medium ◽  
Marginal Zone ◽  
Electrophoretic Pattern ◽  
Primitive Streak ◽  
Electrophoretic Analysis ◽  
Avian Embryo ◽  
Central Disc ◽  
Induction Process ◽  
Marginal Zones

Hypoblast cells of posterior marginal zone origin have been shown previously to be the inducers of primitive streak in the avian embryo. Here we checked: (1) whether the above cells acquire their inductivity while still whithin the marginal zone; (2) can inductivity be found in supernatants of defined blastodermic regions; (3) can differences in the electrophoretic pattern be shown between inducing and non-inducing tissue fragments and their conditioned media, which might give a clue as to what the inductive substance is. The following observations were made: 1. (a) Stage X chick posterior marginal zone cells prior to their migration into the hypoblast do not induce a primitive streak, when applied to a stage XIII competent epiblast central disc. (b) A posterior marginal zone fragment, when applied to an epiblast central disc, even after being preincubated for up to 9 hours in vitro, is still non-inductive. (c) Mechanically fragmented stage X posterior marginal zones when applied as a layer to epiblast central discs are non-inductive. (d) Hypoblastic tissue in strip form induces a primitive streak. 2. Competent stage XIII epiblast central discs (chick) were incubated for 2 hours in supernatants of stage XIII epiblasts or hypoblasts. Whereas no inductive effect was exerted by the epiblast supernatant, primitive streaks developed in about 50% of the epiblast central discs incubated in the hypoblast supernatant. 3. Electrophoretic analysis (quails) reveals a protein of 28x10-3 Mr that is enriched in both hypoblastic tissue and its incubation medium and not in the epiblast + marginal zone + area opaca and their incubation medium. These findings suggest a possible correlation between this protein and the induction process.

scholarly journals Molecular mechanism of symmetry breaking in a 3D model of a human epiblast

2018 ◽  
Author(s):  
Mijo Simunovic ◽  
Jakob J. Metzger ◽  
Fred Etoc ◽  
Anna Yoney ◽  
Albert Ruzo ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Axial Symmetry ◽  
3D Model ◽  
Epithelial To Mesenchymal Transition ◽  
Embryonic Stem ◽  
Primitive Streak ◽  
Molecular Evidence ◽  
Axis Formation ◽  
Mesenchymal Transition

ABSTRACTBreaking the anterior-posterior (AP) symmetry in mammals takes place at gastrulation. Much of the signaling network underlying this process has been elucidated in the mouse, however there is no direct molecular evidence of events driving axis formation in humans. Here, we use human embryonic stem cells to generate an in vitro 3D model of a human epiblast whose size, cell polarity, and gene expression are similar to a 10-day human epiblast. A defined dose of bone mor-phogenetic protein 4 (BMP4) spontaneously breaks axial symmetry, and induces markers of the primitive streak and epithelial to mesenchymal transition. By gene knockouts and live-cell imaging we show that, downstream of BMP4, WNT3 and its inhibitor DKK1 play key roles in this process. Our work demonstrates that a model human epiblast can break axial symmetry despite no asymmetry in the initial signal and in the absence of extraembryonic tissues or maternal cues. Our 3D model opens routes to capturing molecular events underlying axial symmetry breaking phenomena, which have largely been unexplored in model human systems.

scholarly journals Xenopus embryonic cell adhesion to fibronectin: position-specific activation of RGD/synergy site-dependent migratory behavior at gastrulation.

1996 ◽  
Vol 134 (1) ◽  
pp. 227-240 ◽  
Author(s):  
J W Ramos ◽  
D W DeSimone
Keyword(s):  
Cell Adhesion ◽  
Matrix Protein ◽  
Marginal Zone ◽  
Cell Attachment ◽  
Extracellular Matrix Protein ◽  
Mesoderm Induction ◽  
Type Iii ◽  
Basic Body ◽  
And Migration

During Xenopus laevis gastrulation, the basic body plan of the embryo is generated by movement of the marginal zone cells of the blastula into the blastocoel cavity. This morphogenetic process involves cell adhesion to the extracellular matrix protein fibronectin (FN). Regions of FN required for the attachment and migration of involuting marginal zone (IMZ) cells were analyzed in vitro using FN fusion protein substrates. IMZ cell attachment to FN is mediated by the Arg-Gly-Asp (RGD) sequence located in the type III-10 repeat and by the Pro-Pro-Arg-Arg-Ala-Arg (PPRRAR) sequence in the type III-13 repeat of the Hep II domain. IMZ cells spread and migrate persistently on fusion proteins containing both the RGD and synergy site sequence Pro-Pro-Ser-Arg-Asn (PPSRN) located in the type III-9 repeat. Cell recognition of the synergy site is positionally regulated in the early embryo. During gastrulation, IMZ cells will spread and migrate on FN whereas presumptive pre-involuting mesoderm, vegetal pole endoderm, and animal cap ectoderm will not. However, animal cap ectoderm cells acquire the ability to spread and migrate on the RGD/synergy region when treated with the mesoderm inducing factor activin-A. These data suggest that mesoderm induction activates the position-specific recognition of the synergy site of FN in vivo. Moreover, we demonstrate the functional importance of this site using a monoclonal antibody that blocks synergy region-dependent cell spreading and migration on FN. Normal IMZ movement is perturbed when this antibody is injected into the blastocoel cavity indicating that IMZ cell interaction with the synergy region is required for normal gastrulation.

Regional specification within the mesoderm of early embryos of Xenopus laevis

Development ◽  
1987 ◽  
Vol 100 (2) ◽  
pp. 279-295 ◽  
Author(s):  
L. Dale ◽  
J.M. Slack
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Mesoderm Induction ◽  
Intermediate Type ◽  
Cell Stage ◽  
Early Embryos ◽  
Significant Difference ◽  
Cell Embryo ◽  
Single Blastomeres

We have further analysed the roles of mesoderm induction and dorsalization in the formation of a regionally specified mesoderm in early embryos of Xenopus laevis. First, we have examined the regional specificity of mesoderm induction by isolating single blastomeres from the vegetalmost tier of the 32-cell embryo and combining each with a lineage-labelled (FDA) animal blastomere tier. Whereas dorsovegetal (D1) blastomeres induce ‘dorsal-type’ mesoderm (notochord and muscle), laterovegetal and ventrovegetal blastomeres (D2–4) induce either ‘intermediate-type’ (muscle, mesothelium, mesenchyme and blood) or ‘ventral-type’ (mesothelium, mesenchyme and blood) mesoderm. No significant difference in inductive specificity between blastomeres D2, 3 and 4 could be detected. We also show that laterovegetal and ventrovegetal blastomeres from early cleavage stages can have a dorsal inductive potency partially activated by operative procedures, resulting in the induction of intermediate-type mesoderm. Second, we have determined the state of specification of ventral blastomeres by isolating and culturing them in vitro between the 4-cell stage and the early gastrula stage. The majority of isolates from the ventral half of the embryo gave extreme ventral types of differentiation at all stages tested. Although a minority of cases formed intermediate-type and dorsal-type mesoderms we believe these to result from either errors in our assessment of the prospective DV axis or from an enhancement, provoked by microsurgery, of some dorsal inductive specificity. The results of induction and isolation experiments suggest that only two states of specification exist in the mesoderm of the pregastrula embryo, a dorsal type and a ventral type. Finally we have made a comprehensive series of combinations between different regions of the marginal zone using FDA to distinguish the components. We show that, in combination with dorsal-type mesoderm, ventral-type mesoderm becomes dorsalized to the level of intermediate-type mesoderm. Dorsal-type mesoderm is not ventralized in these combinations. Dorsalizing activity is confined to a restricted sector of the dorsal marginal zone, it is wider than the prospective notochord and seems to be graded from a high point at the dorsal midline. The results of these experiments strengthen the case for the three-signal model proposed previously, i.e. dorsal and ventral mesoderm inductions followed by dorsalization, as the simplest explanation capable of accounting for regional specification within the mesoderm of early Xenopus embryos.

scholarly journals A novel role for the extraembryonic area opaca in positioning the primitive streak of the early chick embryo

2021 ◽  
Author(s):  
Hyung Chul Lee ◽  
Claudio D Stern
Keyword(s):  
Chick Embryo ◽  
Early Development ◽  
Marginal Zone ◽  
Outer Region ◽  
Primitive Streak ◽  
Support Functions ◽  
Anterior Half ◽  
Embryonic Polarity ◽  
Classical Studies ◽  
Area Pellucida

Classical studies have established that the marginal zone, a ring of extraembryonic epiblast immediately surrounding the embryonic epiblast (area pellucida) of the chick embryo is important in setting embryonic polarity by positioning the primitive streak, the site of gastrulation. The more external extraembryonic region (area opaca) was only thought to have nutritive and support functions. Using experimental embryology approaches, this study reveals three separable functions for this outer region: first, juxtaposition of the area opaca directly onto the area pellucida induces a new marginal zone from the latter; this induced domain is entirely posterior in character. Second, ablation and grafting experiments using an isolated anterior half of the blastoderm and pieces of area opaca suggest that the area opaca can influence the polarity of the adjacent marginal zone. Finally, we show that the loss of the ability of such isolated anterior half-embryos to regulate (re-establish polarity spontaneously) at the early primitive streak stage can be rescued by replacing the area opaca by one from a younger stage. These results uncover new roles of chick extraembryonic tissues in early development.

Exosomes derived miR-454-3P to promote the progression of colorectal cancer via MIER1-mediated Notch signaling activation.

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. e15108-e15108
Author(s):  
Dawei Li ◽  
Senglin Zhao ◽  
Ye Xu ◽  
Xinxiang Li ◽  
Sanjun Cai
Keyword(s):  
Epithelial To Mesenchymal Transition ◽  
Ectopic Expression ◽  
Notch Pathway ◽  
Early Response ◽  
Mesoderm Induction ◽  
Cancer Proliferation ◽  
Mesenchymal Transition ◽  
Mechanistic Investigation

e15108 Background: Mesoderm induction early response 1 (MIER1) was downregulated and predicted poor prognosis in CRC patients. However, the mechanisms of the down regulation of MIER1 in CRC remained unclear. Increasing evidence indicates that dysregulation of microRNAs promotes the progression of cancer through the repression of tumour suppressors.Here, we identified exosomes derived miR-454-3p as a novel regulator of MIER1 in CRC. Methods: The effect of miR-454-3p expression on cancer proliferation and metastasis was assessed in cells by altering the expression of miR-454-3p in vitro and in vivo. Mechanistic investigation was carried out by using cell and molecular biology approaches. Results: Functionally, ectopic expression or silencing of exosomes derived miR-454-3P, respectively, promoted or inhibited CRC cell proliferation, colony formation and cell cycle transition, as well as enhanced or prevented the invasion, metastasis of CRC cells and epithelial to mesenchymal transition of CRC cells in vitro and in vivo. Molecularly, exosomes derived miR-454-3P functioned as an onco-miRNA by activating the MIER1-regulated NOTCH pathway. Overexpression or silencing of MIER1 could partially reverse the effects of the overexpression or repression of exosomes derived miR-454-3P on CRC progress caused by activation of the NOTCH pathway in vitro and in vivo. Clinically, high miR-454-3P expression predicted poor survival in CRC patients, especially combined with low MIER1 expression. Conclusions: Collectively, we identified exosomes derived miR- 454-3p as an onco-miRNA, which acts by directly repressing MIER1 in CRC.

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