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Borday C, Parain K, Thi Tran H, Vleminckx K, Perron M, Monsoro-Burq AH. An atlas of Wnt activity during embryogenesis in Xenopus tropicalis. PLoS One 2018; 13:e0193606. [PMID: 29672592 PMCID: PMC5908154 DOI: 10.1371/journal.pone.0193606] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 02/14/2018] [Indexed: 12/22/2022] Open
Abstract
Wnt proteins form a family of highly conserved secreted molecules that are critical mediators of cell-cell signaling during embryogenesis. Partial data on Wnt activity in different tissues and at different stages have been reported in frog embryos. Our objective here is to provide a coherent and detailed description of Wnt activity throughout embryo development. Using a transgenic Xenopus tropicalis line carrying a Wnt-responsive reporter sequence, we depict the spatial and temporal dynamics of canonical Wnt activity during embryogenesis. We provide a comprehensive series of in situ hybridization in whole-mount embryos and in cross-sections, from gastrula to tadpole stages, with special focus on neural tube, retina and neural crest cell development. This collection of patterns will thus constitute a valuable resource for developmental biologists to picture the dynamics of Wnt activity during development.
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Affiliation(s)
- Caroline Borday
- CNRS UMR 3347, INSERM U1021, Univ. Paris Sud, Université Paris Saclay, Centre Universitaire, Orsay, France
- Institut Curie Research Division, PSL Research University, CNRS UMR 3347, INSERM U1021, Orsay, France
| | - Karine Parain
- Paris-Saclay Institute of Neuroscience, CNRS, Univ Paris Sud, Université Paris-Saclay, Orsay, France
| | - Hong Thi Tran
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Kris Vleminckx
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Muriel Perron
- Paris-Saclay Institute of Neuroscience, CNRS, Univ Paris Sud, Université Paris-Saclay, Orsay, France
- * E-mail: (MP); (AHMB)
| | - Anne H. Monsoro-Burq
- CNRS UMR 3347, INSERM U1021, Univ. Paris Sud, Université Paris Saclay, Centre Universitaire, Orsay, France
- Institut Curie Research Division, PSL Research University, CNRS UMR 3347, INSERM U1021, Orsay, France
- Institut Universitaire de France, Paris, France
- * E-mail: (MP); (AHMB)
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2
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Bipartite recognition of DNA by TCF/Pangolin is remarkably flexible and contributes to transcriptional responsiveness and tissue specificity of wingless signaling. PLoS Genet 2014; 10:e1004591. [PMID: 25188465 PMCID: PMC4154663 DOI: 10.1371/journal.pgen.1004591] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 07/08/2014] [Indexed: 11/19/2022] Open
Abstract
The T-cell factor (TCF) family of transcription factors are major mediators of Wnt/β-catenin signaling in metazoans. All TCFs contain a High Mobility Group (HMG) domain that possesses specific DNA binding activity. In addition, many TCFs contain a second DNA binding domain, the C-clamp, which binds to DNA motifs referred to as Helper sites. While HMG and Helper sites are both important for the activation of several Wnt dependent cis-regulatory modules (W-CRMs), the rules of what constitutes a functional HMG-Helper site pair are unknown. In this report, we employed a combination of in vitro binding, reporter gene analysis and bioinformatics to address this question, using the Drosophila family member TCF/Pangolin (TCF/Pan) as a model. We found that while there were constraints for the orientation and spacing of HMG-Helper pairs, the presence of a Helper site near a HMG site in any orientation increased binding and transcriptional response, with some orientations displaying tissue-specific patterns. We found that altering an HMG-Helper site pair from a sub-optimal to optimal orientation/spacing dramatically increased the responsiveness of a W-CRM in several fly tissues. In addition, we used the knowledge gained to bioinformatically identify two novel W-CRMs, one that was activated by Wnt/β-catenin signaling in the prothoracic gland, a tissue not previously connected to this pathway. In sum, this work extends the importance of Helper sites in fly W-CRMs and suggests that the type of HMG-Helper pair is a major factor in setting the threshold for Wnt activation and tissue-responsiveness. Regulation of gene expression is controlled in large part by proteins known as transcription factors, which bind to specific DNA sequences in the genome. The DNA binding domains of transcription factors recognize short stretches (5–11 base pairs) of DNA with considerable sequence degeneracy. This means that a single DNA binding domain, on its own, cannot find its targets in the vast excess of genomic sequence. We are studying this question using TCF/Pangolin, a Drosophila transcription factor that mediates Wnt/β-catenin signaling, an important developmental cell-cell communication pathway. TCF/Pangolin contains two DNA binding domains that bind to a pair of DNA motifs known as HMG and Helper sites. We used a combination of biochemistry, genetics and bioinformatics to elucidate the spacing and orientation constraints of HMG-Helper site pairs. We found that HMG-Helper site spacing/orientation influenced the sensitivity of a target to Wnt signaling, as well as its tissue-responsiveness. We used this information to improve our ability to search the Drosophila genome for Wnt targets, one of which was activated by the pathway in the fly ring gland, the major endocrine organ in insects. Our work is relevant to related mammalian TCF family members, which are implicated in development, stem cell biology and the progression of cancer.
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Tiwari SK, Agarwal S, Seth B, Yadav A, Nair S, Bhatnagar P, Karmakar M, Kumari M, Chauhan LKS, Patel DK, Srivastava V, Singh D, Gupta SK, Tripathi A, Chaturvedi RK, Gupta KC. Curcumin-loaded nanoparticles potently induce adult neurogenesis and reverse cognitive deficits in Alzheimer's disease model via canonical Wnt/β-catenin pathway. ACS NANO 2014; 8:76-103. [PMID: 24467380 DOI: 10.1021/nn405077y] [Citation(s) in RCA: 368] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Neurogenesis, a process of generation of new neurons, is reported to be reduced in several neurodegenerative disorders including Alzheimer's disease (AD). Induction of neurogenesis by targeting endogenous neural stem cells (NSC) could be a promising therapeutic approach to such diseases by influencing the brain self-regenerative capacity. Curcumin, a neuroprotective agent, has poor brain bioavailability. Herein, we report that curcumin-encapsulated PLGA nanoparticles (Cur-PLGA-NPs) potently induce NSC proliferation and neuronal differentiation in vitro and in the hippocampus and subventricular zone of adult rats, as compared to uncoated bulk curcumin. Cur-PLGA-NPs induce neurogenesis by internalization into the hippocampal NSC. Cur-PLGA-NPs significantly increase expression of genes involved in cell proliferation (reelin, nestin, and Pax6) and neuronal differentiation (neurogenin, neuroD1, neuregulin, neuroligin, and Stat3). Curcumin nanoparticles increase neuronal differentiation by activating the Wnt/β-catenin pathway, involved in regulation of neurogenesis. These nanoparticles caused enhanced nuclear translocation of β-catenin, decreased GSK-3β levels, and increased promoter activity of the TCF/LEF and cyclin-D1. Pharmacological and siRNA-mediated genetic inhibition of the Wnt pathway blocked neurogenesis-stimulating effects of curcumin. These nanoparticles reverse learning and memory impairments in an amyloid beta induced rat model of AD-like phenotypes, by inducing neurogenesis. In silico molecular docking studies suggest that curcumin interacts with Wif-1, Dkk, and GSK-3β. These results suggest that curcumin nanoparticles induce adult neurogenesis through activation of the canonical Wnt/β-catenin pathway and may offer a therapeutic approach to treating neurodegenerative diseases such as AD, by enhancing a brain self-repair mechanism.
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Affiliation(s)
- Shashi Kant Tiwari
- CSIR-Indian Institute of Toxicology Research (CSIR-IITR), 80 MG Marg, Lucknow 226001, India
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4
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Tran HT, Vleminckx K. Design and use of transgenic reporter strains for detecting activity of signaling pathways in Xenopus. Methods 2013; 66:422-32. [PMID: 23816788 DOI: 10.1016/j.ymeth.2013.06.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 06/02/2013] [Accepted: 06/21/2013] [Indexed: 12/19/2022] Open
Abstract
Embryos and larvae of vertebrate species with external development are ideal subjects for investigating the dynamic spatiotemporal activity of developmental signaling pathways. The availability of efficient transgene technologies in Xenopus and zebrafish and the translucency and/or transparency of their embryos and larvae make these two species attractive for direct in vivo imaging of reporter gene expression. In this article we describe the design of efficient signaling reporters, using the Wnt/β-catenin pathway as a representative example. We define methods for validating the reporter constructs and describe how they can be used to generate stable transgenic lines in Xenopus. We provide efficient methods used in our laboratory for raising the tadpoles and froglets rapidly to sexual maturity. We further discuss how the reporter lines can be used for delineating the dynamic activity of a signaling pathway and how modulators of the pathway can be scrutinized via chemical intervention and the micro-injection of synthetic RNAs or morpholinos. The strategic outline discussed in this paper provides a template for studying other developmental signaling pathways in Xenopus.
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Affiliation(s)
- Hong Thi Tran
- Department of Molecular Biomedical Research, VIB, Technologiepark 927, B-9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
| | - Kris Vleminckx
- Department of Molecular Biomedical Research, VIB, Technologiepark 927, B-9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
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5
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Shimizu N, Kawakami K, Ishitani T. Visualization and exploration of Tcf/Lef function using a highly responsive Wnt/β-catenin signaling-reporter transgenic zebrafish. Dev Biol 2012; 370:71-85. [PMID: 22842099 DOI: 10.1016/j.ydbio.2012.07.016] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 07/03/2012] [Accepted: 07/10/2012] [Indexed: 01/09/2023]
Abstract
Evolutionarily conserved Tcf/Lef transcription factors (Lef1, Tcf7, Tcf7l1, and Tcf7l2) mediate gene expression regulated by Wnt/β-catenin signaling, which has multiple roles in early embryogenesis, organogenesis, adult tissue homeostasis, and tissue regeneration. However, the spatiotemporal dynamics of Tcf/Lef activity during these events remain poorly understood. We generated stable transgenic zebrafish lines carrying a new Wnt/β-catenin signaling reporter, Tcf/Lef-miniP:dGFP. The reporter revealed the transcriptional activities of four Tcf/Lef members controlled by Wnt/β-catenin signaling, which were expressed in known Wnt/β-catenin signaling-active sites during embryogenesis, organ development and growth, and tissue regeneration. We used the transgenic lines to demonstrate the contribution of Tcf/Lef-mediated Wnt/β-catenin signaling to the development of the anterior lateral line, dorsal and secondary posterior lateral lines, and gill filaments. Thus, these reporter lines are highly useful tools for studying Tcf/Lef-mediated Wnt/β-catenin signaling-dependent processes.
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Affiliation(s)
- Nobuyuki Shimizu
- Division of Cell Regulation Systems, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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6
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Abstract
Cystic kidney diseases have been linked to defective WNT signal transduction. Perturbations of cystic disease genes cause activation of canonical WNT/β-catenin/TCF/Lef1 signaling in model organisms and cultured cells. Inappropriate levels of WNT/β-catenin signaling cause renal cyst formation in mice. These observations have prompted the idea that an activation of WNT/β-catenin signaling may constitute a common causative event in cyst formation. Now this view is challenged by key genetic mouse models of cystic kidney disease that do not display WNT/β-catenin activity in cyst-lining epithelia.
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Affiliation(s)
- Anne Wuebken
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
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7
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Chai R, Xia A, Wang T, Jan TA, Hayashi T, Bermingham-McDonogh O, Cheng AGL. Dynamic expression of Lgr5, a Wnt target gene, in the developing and mature mouse cochlea. J Assoc Res Otolaryngol 2011; 12:455-69. [PMID: 21472479 DOI: 10.1007/s10162-011-0267-2] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 03/17/2011] [Indexed: 12/11/2022] Open
Abstract
The Wnt signaling pathway is a recurring theme in tissue development and homeostasis. Its specific roles during inner ear development are just emerging, but few studies have characterized Wnt target genes. Lgr5, a member of the G protein-coupled receptor family, is a Wnt target in the gastrointestinal and integumentary systems. Although its function is unknown, its deficiency leads to perinatal lethality due to gastrointestinal distension. In this study, we used a knock-in reporter mouse to examine the spatiotemporal expression of Lgr5 in the cochlear duct during embryonic and postnatal periods. In the embryonic day 15.5 (E15.5) cochlear duct, Lgr5-EGFP is expressed in the floor epithelium and overlapped with the prosensory markers Sox2, Jagged1, and p27(Kip1). Nascent hair cells and supporting cells in the apical turn of the E18.5 cochlear duct express Lgr5-EGFP, which becomes downregulated in hair cells and subsets of supporting cells in more mature stages. In situ hybridization experiments validated the reporter expression, which gradually decreases until the second postnatal week. Only the third row of Deiters' cells expresses Lgr5-EGFP in the mature organ of Corti. Normal cochlear development was observed in Lgr5(EGFP/EGFP) and Lgr5(EGFP/+) mice, which exhibited normal auditory thresholds. The expression pattern of Lgr5 contrasts with another Wnt target gene, Axin2, a feedback inhibitor of the Wnt pathway. Robust Axin2 expression was found in cells surrounding the embryonic cochlear duct and becomes restricted to tympanic border cells below the basilar membrane in the postnatal cochlea. Both Lgr5 and Axin2 act as Wnt targets in the cochlea because purified Wnt3a promoted and Wnt antagonist suppressed their expression. Their differential expression among cell populations highlights the dynamic but complex distribution of Wnt-activated cells in and around the embryonic and postnatal cochlea.
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Affiliation(s)
- Renjie Chai
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, CA 94305, USA
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Koenig SF, Brentle S, Hamdi K, Fichtner D, Wedlich D, Gradl D. En2, Pax2/5 and Tcf-4 transcription factors cooperate in patterning the Xenopus brain. Dev Biol 2010; 340:318-28. [DOI: 10.1016/j.ydbio.2010.02.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Revised: 02/01/2010] [Accepted: 02/10/2010] [Indexed: 11/25/2022]
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9
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Denayer T, Tran HT, Vleminckx K. Transgenic reporter tools tracing endogenous canonical Wnt signaling in Xenopus. Methods Mol Biol 2009; 469:381-400. [PMID: 19109721 DOI: 10.1007/978-1-60327-469-2_24] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Activation of the canonical Wnt pathway leads to the transcriptional activation of a particular subset of downstream Wnt target genes. To track this localized cellular output in a living organism, reporter constructs can be designed containing multimerized consensus lymphoid enhancer binding factor (LEF)-1/T cell factor (TCF) transcription factor binding sites, generally referred to as TCF optimal promoter (TOP) sites. In Xenopus, several Wnt-responsive reporter systems have been designed containing a number of these TOP sites that, in combination with a minimal promoter, drive the expression of a reporter gene. Following transgenic integration in Xenopus embryos, a Wnt reporter tool reveals the spatiotemporal delineation of endogenous Wnt pathway activities throughout development. Assumed to be a general readout of the Wnt pathway, such reporters can assist in elucidating unknown functional implications in developing Xenopus embryos.
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Affiliation(s)
- Tinneke Denayer
- Department for Molecular Biomedical Research, VIB and Molecular Biology, Ghent University, Ghent, Belgium
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10
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Li S, Lou X, Wang J, Liu B, Ma L, Su Z, Ding X. Retinoid signaling can repress blastula Wnt signaling and impair dorsal development in Xenopus embryo. Differentiation 2008; 76:897-907. [PMID: 18452549 DOI: 10.1111/j.1432-0436.2008.00269.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Vitamin A derivatives (retinoids) are actively involved during vertebrate embryogenesis. However, exogenous retinoids have also long been known as potent teratogens. The defects caused by retinoid treatment are complex. Here, we provided evidence that RAR-mediated retinoid signaling can repress Xenopus blastula Wnt signaling and impair dorsal development. Exogenous retinoic acid (RA) could antagonize the dorsalizing effects of lithium chloride-mediated Wnt activation in blastula embryos. The Wnt-responsive reporter gene transgenesis and luciferase assay showed that excess RA can repress the Wnt signaling in blastula embryos. In addition, the downstream target genes of the Wnt signaling that direct embryonic dorsal development, were also down-regulated in the RA-treated embryos. Mechanically, RA did not interfere with the stability of beta-catenin, but promoted its nuclear accumulation. The inverse agonist of retinoic acid receptors (RAR) rescued the Wnt signaling repression by RA and relieved the RA-induced nuclear accumulation of beta-catenin. Our results explain one of the reasons for the complicated teratogenic effects of retinoids and shed light on the endogenous way of interactions between two developmentally important signaling pathways.
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Affiliation(s)
- Shuangwei Li
- Key Laboratory of Stem Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai
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11
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Chesneau A, Sachs LM, Chai N, Chen Y, Pasquier LD, Loeber J, Pollet N, Reilly M, Weeks DL, Bronchain OJ. Transgenesis procedures in Xenopus. Biol Cell 2008; 100:503-21. [PMID: 18699776 PMCID: PMC2967756 DOI: 10.1042/bc20070148] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Stable integration of foreign DNA into the frog genome has been the purpose of several studies aimed at generating transgenic animals or producing mutations of endogenous genes. Inserting DNA into a host genome can be achieved in a number of ways. In Xenopus, different strategies have been developed which exhibit specific molecular and technical features. Although several of these technologies were also applied in various model organizms, the attributes of each method have rarely been experimentally compared. Investigators are thus confronted with a difficult choice to discriminate which method would be best suited for their applications. To gain better understanding, a transgenesis workshop was organized by the X-omics consortium. Three procedures were assessed side-by-side, and the results obtained are used to illustrate this review. In addition, a number of reagents and tools have been set up for the purpose of gene expression and functional gene analyses. This not only improves the status of Xenopus as a powerful model for developmental studies, but also renders it suitable for sophisticated genetic approaches. Twenty years after the first reported transgenic Xenopus, we review the state of the art of transgenic research, focusing on the new perspectives in performing genetic studies in this species.
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Affiliation(s)
- Albert Chesneau
- Laboratoire Evolution et Développement, Université Paris Sud, F-91405 Orsay cedex, France
- CNRS UMR 8080, F-91405 Orsay, France
| | - Laurent M. Sachs
- Département Régulation, Développement et Diversité Moléculaire, MNHN USM 501, CNRS UMR 5166, CP32, 7 rue Cuvier, 75231 Paris cedex 05, France
| | - Norin Chai
- Muséum National d’Histoire Naturelle, Ménagerie du Jardin des Plantes, 57 rue Cuvier, 75005 Paris, France
| | - Yonglong Chen
- Georg-August-Universitat Gottingen, Zentrum Biochemie und Molekular Zellbiologie, Abteilung Entwicklungsbiochemie, 37077 Gottingen, Germany
- Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou Science City, 510663 Guangzhou, People’s Republic of China
| | - Louis Du Pasquier
- Institute of Zoology and Evolutionary Biology, University of Basel, Vesalgasse 1, CH-4051 Basel, Switzerland
| | - Jana Loeber
- Georg-August-Universitat Gottingen, Zentrum Biochemie und Molekular Zellbiologie, Abteilung Entwicklungsbiochemie, 37077 Gottingen, Germany
| | - Nicolas Pollet
- Laboratoire Evolution et Développement, Université Paris Sud, F-91405 Orsay cedex, France
- CNRS UMR 8080, F-91405 Orsay, France
| | - Michael Reilly
- Division of Developmental Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, U.K
| | - Daniel L. Weeks
- Department of Biochemistry, Bowen Science Building, University of Iowa, Iowa City, IA 52242, U.S.A
| | - Odile J. Bronchain
- Laboratoire Evolution et Développement, Université Paris Sud, F-91405 Orsay cedex, France
- CNRS UMR 8080, F-91405 Orsay, France
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12
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Lou X, Fang P, Li S, Hu RY, Kuerner KM, Steinbeisser H, Ding X. Xenopus Tbx6 mediates posterior patterning via activation of Wnt and FGF signalling. Cell Res 2008; 16:771-9. [PMID: 16953215 DOI: 10.1038/sj.cr.7310093] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In vertebrates, the patterning of anterior-posterior (AP) axis is a fundamental process during embryogenesis. Wnt and FGF signalling pathways play important roles in regulating the patterning of embryo AP axis. Mouse Tbx6 encodes a transcription factor that has been demonstrated to be involved in the specification of the posterior tissue in mouse embryonic body. Here, we prove that morpholino-induced knockdown of XTbx6 impairs posterior development, indicating the requirement of XTbx6 in this process. Meanwhile, gain of XTbx6 function is sufficient to induce ectopic posterior structures in Xenopus embryos. Furthermore, XTbx6 activates the expression of Xwnt8 and FGF8, which are two mediators of posterior development, suggesting a mechanism by which XTbx6 modulates posterior patterning via Wnt and FGF signalling pathway activation.
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Affiliation(s)
- Xin Lou
- Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai, China
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13
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Abstract
Xenopus is an established and powerful model system for the study of Wnt signaling in vertebrates. Above all, the relatively large size of the embryos enables microinjection experiments, which have led to key discoveries not only about the functional role of Wnt signaling in vertebrate embryos, but also about the molecular mechanisms of Wnt signaling in vertebrate cells. A major advantage of the Xenopus model is the ability to obtain large numbers of embryos, which develop relatively rapidly and which can be studied in natural separation from sentient adult parental animals. In order to obtain Xenopus embryos, ovulation in females is induced with a simple hormone injection, the eggs collected and fertilized with sperm from males. The Xenopus model system has been further strengthened by recent advances such as morpholino technology and efficient transgenic methods, as well as the development of Xenopus tropicalis as a diploid genetic model system with a shorter generation time and a genome similar to higher vertebrates.
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Affiliation(s)
- Stefan Hoppler
- School of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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14
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Affiliation(s)
- Shoko Ishibashi
- The Healing Foundation Centre, Michael Smith Building, Faculty of Life Sciences, University of Manchester, Manchester, UK
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15
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Wang J, Li S, Chen Y, Ding X. Wnt/β-catenin signaling controls Mespo expression to regulate segmentation during Xenopus somitogenesis. Dev Biol 2007; 304:836-47. [PMID: 17266950 DOI: 10.1016/j.ydbio.2006.12.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 11/17/2006] [Accepted: 12/14/2006] [Indexed: 10/23/2022]
Abstract
The vertebral column is derived from somites, which are transient segments of the paraxial mesoderm that are present in developing vertebrates. The strict spatial and temporal regulation of somitogenesis is of crucial developmental importance. Signals such as Wnt and FGF play roles in somitogenesis, but details regarding how Wnt signaling functions in this process remain unclear. In this study, we report that Wnt/beta-catenin signaling regulates the expression of Mespo, a basic-helix-loop-helix (bHLH) gene critical for segmental patterning in Xenopus somitogenesis. Transgenic analysis of the Mespo promoter identifies Mespo as a direct downstream target of Wnt/beta-catenin signaling pathway. We also demonstrate that activity of Wnt/beta-catenin signaling in somitogenesis can be enhanced by the PI3-K/AKT pathway. Our results illustrate that Wnt/beta-catenin signaling in conjunction with PI3-K/AKT pathway plays a key role in controlling development of the paraxial mesoderm.
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Affiliation(s)
- Jinhu Wang
- Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, and Graduate School of Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
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16
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Abstract
The Wnt signaling pathway controls a large and diverse set of cell fate decisions in embryonic development, adult organ maintenance and disease. At the transcriptional level, Wnt/beta-catenin signaling is primarily mediated by the T-cell factor (TCF)/Lef-1 family of transcription factors, referred to here as TCFs. In order to track Wnt pathway activity during animal development, several laboratories have built transgenic reporter constructs containing multimerized TCF binding sites. Most of these reporters are active at multiple known sites of Wnt signaling, and several act as faithful reporters of pathway activity in specific contexts. However, multimerized TCF reporters should not be assumed to give a complete or definitive readout of Wnt signaling in vivo. Direct comparisons reveal discrepancies among reporters; in addition, there is good reason to expect that some important types of pathway activity, including target gene de-repression and TCF-independent Wnt or beta-catenin signaling, will not be accurately reported by such constructs. This review will discuss various transgenic Wnt/beta-catenin/TCF reporters, address the fidelity and completeness of their Wnt responsiveness, and contrast their in vivo transcriptional responses with those of natural Wnt target genes. Finally, three caveats to the interpretation of multimerized TCF reporter expression patterns will be proposed.
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Affiliation(s)
- S Barolo
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA.
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17
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Denayer T, Van Roy F, Vleminckx K. In vivo tracing of canonical Wnt signaling inXenopustadpoles by means of an inducible transgenic reporter tool. FEBS Lett 2005; 580:393-8. [PMID: 16376877 DOI: 10.1016/j.febslet.2005.11.084] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Revised: 11/24/2005] [Accepted: 11/30/2005] [Indexed: 10/25/2022]
Abstract
The canonical Wnt pathway is recurrently used during embryogenesis and adult life. To track the cellular output of Wnt signaling in a living organism, we designed a hormone-inducible Wnt responsive system, capable to dynamically and specifically report Wnt pathway activities through eGFP expression. In contrast to previous in vivo reporters, our system essentially avoids interference of consecutive signals by remaining dormant until addition of hormone, which makes it a valuable tool to map canonical Wnt signaling in post-embryonic stages. Transgenic Xenopus laevis embryos were analyzed revealing at tadpole stage in specific tissues and organs cell populations with high Wnt pathway activity.
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Affiliation(s)
- Tinneke Denayer
- Developmental Biology Unit, Department for Molecular Biomedical Research, VIB-Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
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