Distinct roles for Fgf, Wnt and retinoic acid in posteriorizing the neural ectoderm

Early neural patterning in vertebrates involves signals that inhibit anterior (A) and promote posterior (P) positional values within the nascent neural plate. In this study, we have investigated the contributions of, and interactions between, retinoic acid (RA), Fgf and Wnt signals in the promotion of posterior fates in the ectoderm. We analyze expression and function of cyp26/P450RAI, a gene that encodes retinoic acid 4-hydroxylase, as a tool for investigating these events. Cyp26 is first expressed in the presumptive anterior neural ectoderm and the blastoderm margin at the late blastula. When the posterior neural gene hoxb1b is expressed during gastrulation, it shows a strikingly complementary pattern to cyp26. Using these two genes, as well as otx2 and meis3 as anterior and posterior markers, we show that Fgf and Wnt signals suppress expression of anterior genes, including cyp26. Overexpression of cyp26 suppresses posterior genes, suggesting that the anterior expression of cyp26 is important for restricting the expression of posterior genes. Consistent with this, knock-down of cyp26 by morpholino oligonucleotides leads to the anterior expansion of posterior genes. We further show that Fgf- and Wnt-dependent activation of posterior genes is mediated by RA, whereas suppression of anterior genes does not depend on RA signaling. Fgf and Wnt signals suppress cyp26 expression, while Cyp26 suppresses the RA signal. Thus, cyp26 has an important role in linking the Fgf, Wnt and RA signals to regulate AP patterning of the neural ectoderm in the late blastula to gastrula embryo in zebrafish.

Download Full-text

Functional association of retinoic acid and hedgehog signaling in Xenopus primary neurogenesis

Development ◽

10.1242/dev.126.19.4257 ◽

1999 ◽

Vol 126 (19) ◽

pp. 4257-4265 ◽

Cited By ~ 10

Author(s):

P.G. Franco ◽

A.R. Paganelli ◽

S.L. Lopez ◽

A.E. Carrasco

Keyword(s):

Retinoic Acid ◽

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Inhibitory Effect ◽

Neural Plate ◽

Neural Ectoderm ◽

Differentiation And Proliferation ◽

Primary Neurogenesis ◽

Xenopus Laevis Embryos

Previous work has shown that the posteriorising agent retinoic acid can accelerate anterior neuronal differentiation in Xenopus laevis embryos (Papalopulu, N. and Kintner, C. (1996) Development 122, 3409–3418). To elucidate the role of retinoic acid in the primary neurogenesis cascade, we investigated whether retinoic acid treatment of whole embryos could change the spatial expression of a set of genes known to be involved in neurogenesis. We show that retinoic acid expands the N-tubulin, X-ngnr-1, X-MyT1, X-Δ-1 and Gli3 domains and inhibits the expression of Zic2 and sonic hedgehog in the neural ectoderm, whereas a retinoid antagonist produces opposite changes. In contrast, sonic and banded hedgehog overexpression reduced the N-tubulin stripes, enlarged the neural plate at the expense of the neural crest, downregulated Gli3 and upregulated Zic2. Thus, retinoic acid and hedgehog signaling have opposite effects on the prepattern genes Gli3 and Zic2 and on other genes acting downstream in the neurogenesis cascade. In addition, retinoic acid cannot rescue the inhibitory effect of Notch(ICD), Zic2 or sonic hedgehog on primary neurogenesis. Our results suggest that retinoic acid acts very early, upstream of sonic hedgehog, and we propose a model for regulation of differentiation and proliferation in the neural plate, showing that retinoic acid might be activating primary neurogenesis by repressing sonic hedgehog expression.

Download Full-text

NFATc3 regulates the transcription of genes involved in T-cell activation and angiogenesis

Blood ◽

10.1182/blood-2010-12-322701 ◽

2011 ◽

Vol 118 (3) ◽

pp. 795-803 ◽

Cited By ~ 31

Author(s):

Katia Urso ◽

Arantzazu Alfranca ◽

Sara Martínez-Martínez ◽

Amelia Escolano ◽

Inmaculada Ortega ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Cell Activation ◽

Target Genes ◽

Gene Knockout ◽

Activated T Cells ◽

Knock Down ◽

And Function

Abstract The nuclear factor of activated T cells (NFAT) family of transcription factors plays important roles in many biologic processes, including the development and function of the immune and vascular systems. Cells usually express more than one NFAT member, raising the question of whether NFATs play overlapping roles or if each member has selective functions. Using mRNA knock-down, we show that NFATc3 is specifically required for IL2 and cyclooxygenase-2 (COX2) gene expression in transformed and primary T cells and for T-cell proliferation. We also show that NFATc3 regulates COX2 in endothelial cells, where it is required for COX2, dependent migration and angiogenesis in vivo. These results indicate that individual NFAT members mediate specific functions through the differential regulation of the transcription of target genes. These effects, observed on short-term suppression by mRNA knock-down, are likely to have been masked by compensatory effects in gene-knockout studies.

Download Full-text

Abstract 3: Il-10 Regulated Mir-375 Enhances Endothelial Progenitor Cell Mediated Myocardial Repair And Survival After Myocardial Infarction.

Circulation Research ◽

10.1161/res.115.suppl_1.3 ◽

2014 ◽

Vol 115 (suppl_1) ◽

Author(s):

Venkata N Garikipati ◽

Prasanna Krishnamurthy ◽

Suresh K Verma ◽

Alexandra R Mackie ◽

Erin E Vaughan ◽

...

Keyword(s):

Capillary Density ◽

Tube Formation ◽

Lv Function ◽

Myocardial Repair ◽

Knock Down ◽

Cardiac Functions ◽

Dependent Protein ◽

And Function ◽

Deficient Mice

We hypothesized that IL-10 regulates miR-375 signaling in EPCs to enhance their survival and function in ischemic myocardium after MI. miR-375 knock down EPC were transplanted intramyocardially after induction of MI. Mice receiving EPC treated with miR-375 inhibitor showed increased number of GFP+EPCs retention that was associated with reduced EPC apoptosis in the myocardium. The engraftment of EPC into the vascular structures and the associated capillary density was significantly higher in miR-375-treated mice. The above findings further correlated with reduced infarct size, fibrosis and enhanced LV function (echocardiography) in miR-375 knock down EPC group as compared to scrambled EPC. Our in vitro studies revealed that the knockdown of miR-375 enhanced EPC proliferation, migration; tube formation ability and inhibited cell apoptosis, while the up-regulation of miR-375 with the mimic had the opposite effects. In addition, we found that miR-375 negatively regulates the expression of 3-phosphoinositide-dependent protein kinase 1 (PDK1) by directly targeting the 3'UTR of the PDK1 transcript. Interestingly, EPC isolated from IL-10-deficient mice has elevated basal levels of miR-375 and exhibited poor proliferation and tube formation ability where as miR-375 knock down in EPC isolated from IL-10 deficient mice attenuated these effects. Furthermore, transplantation of miR-375 knock down IL-10 deficient EPC after MI resulted in attenuated cardiac functions compared to scramble IL-10 deficient EPCs. Taken together, our studies suggest that IL-10 regulated miR-375 enhances EPC survival and function, associated with efficient myocardial repair via activation of PDK-1/AKT signaling cascades.

Download Full-text

Is there a ventral neural ridge in chick embryos? Implications for the origin of adenohypophyseal and other APUD cells

Development ◽

10.1242/dev.57.1.71 ◽

1980 ◽

Vol 57 (1) ◽

pp. 71-78

Author(s):

N. B. Levy ◽

Ann Andrew ◽

B. B. Rawdon ◽

Beverley Kramer

Keyword(s):

Neural Crest ◽

Endocrine Cells ◽

Ventral Surface ◽

Neural Plate ◽

Chick Embryos ◽

Serial Sections ◽

Apud Cells ◽

Surface Ectoderm ◽

Neural Ectoderm ◽

Thickened Surface

Two- to ten-somite chick embryos were studied in order to ascertain whether, as has been proposed, there exists a ‘ventral neural ridge’ which gives rise to the hypophyseal (Rathke's) pouch. Serial sections and stereo-microscopy were used. The neural ridges arch around the rostral end of the embryo onto the ventral surface of the head, but no evidence was found for their extension to form a ‘ventral neural ridge’ reaching the stomodaeum: in fact a considerable expanse of non-thickened surface ectoderm was seen to separate the ventral portions of the neural ridges from the stomodaeum. The thickening of neural ectoderm which does appear on the ventral surface of the head results from apposition and fusion of the opposite neural ridges flanking the neural plate and thus the tip of the anterior neuropore - the classically accepted mode of closure of the neuropore. These findings are in accord with the generally accepted concept of the origin of thehypophyseal pouch rather than with its derivation from a ‘ventral neural ridge’. No sign of neural crest formation was encountered ventrally; this observation excludes the possibility that endocrine cells of the APUD series could originate from neural crest in this region.

Download Full-text

Origins of the avian neural crest: the role of neural plate-epidermal interactions

Development ◽

10.1242/dev.121.2.525 ◽

1995 ◽

Vol 121 (2) ◽

pp. 525-538 ◽

Cited By ~ 39

Author(s):

M.A. Selleck ◽

M. Bronner-Fraser

Keyword(s):

Neural Crest ◽

Neural Crest Cell ◽

Neural Crest Cells ◽

Neural Plate ◽

Neural Tube Closure ◽

Whole Embryo Culture ◽

Early Stages ◽

Tissue Interactions ◽

Neural Ectoderm

We have investigated the lineage and tissue interactions that result in avian neural crest cell formation from the ectoderm. Presumptive neural plate was grafted adjacent to non-neural ectoderm in whole embryo culture to examine the role of tissue interactions in ontogeny of the neural crest. Our results show that juxtaposition of non-neural ectoderm and presumptive neural plate induces the formation of neural crest cells. Quail/chick recombinations demonstrate that both the prospective neural plate and the prospective epidermis can contribute to the neural crest. When similar neural plate/epidermal confrontations are performed in tissue culture to look at the formation of neural crest derivatives, juxtaposition of epidermis with either early (stages 4–5) or later (stages 6–10) neural plate results in the generation of both melanocytes and sympathoadrenal cells. Interestingly, neural plates isolated from early stages form no neural crest cells, whereas those isolated later give rise to melanocytes but not crest-derived sympathoadrenal cells. Single cell lineage analysis was performed to determine the time at which the neural crest lineage diverges from the epidermal lineage and to elucidate the timing of neural plate/epidermis interactions during normal development. Our results from stage 8 to 10+ embryos show that the neural plate/neural crest lineage segregates from the epidermis around the time of neural tube closure, suggesting that neural induction is still underway at open neural plate stages.

Download Full-text

Retinoic Acid Signaling and Neural Patterning☆

Reference Module in Biomedical Sciences ◽

10.1016/b978-0-12-801238-3.04752-8 ◽

2014 ◽

Author(s):

G. Duester

Keyword(s):

Retinoic Acid ◽

Retinoic Acid Signaling ◽

Neural Patterning

Download Full-text

Expression of an engrailed-related protein is induced in the anterior neural ectoderm of early Xenopus embryos

Development ◽

10.1242/dev.106.3.611 ◽

1989 ◽

Vol 106 (3) ◽

pp. 611-617 ◽

Cited By ~ 35

Author(s):

A.H. Brivanlou ◽

R.M. Harland

Keyword(s):

Nuclear Protein ◽

Neural Plate ◽

Brain Cells ◽

Related Protein ◽

Anterior Portion ◽

Head Mesoderm ◽

C Terminus ◽

Licl Treatment ◽

Neural Ectoderm ◽

Xenopus Laevis Embryos

We have used a monoclonal antibody directed against the C-terminus of the Drosophila invected homeodomain to detect a nuclear protein in brain cells of Xenopus laevis embryos. We refer to this antigen as the Xenopus EN protein. The EN protein is localized at midneurula stage to a band of cells in the anterior portion of the neural plate, on each side of the neural groove. Later in development, the expression coincides with the boundary of the midbrain and hindbrain, and persists at least to the swimming tadpole stage. These properties make the EN protein an excellent molecular marker for anterior neural structures. In embryos where inductive interactions between mesodermal and ectodermal tissues have been perturbed, the expression of the EN protein is altered; in embryos that have been anterodorsalized by LiCl treatment, the region that expresses the EN protein is expanded, but still well organized. In ventralized UV-irradiated embryos, the absence of the protein is correlated with the absence of anterior neural structures. In extreme exogastrulae, where the contacts between head mesoderm and prospective neurectoderm are lost, the EN protein is not expressed.

Download Full-text