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van Boxtel AL, Chesebro JE, Heliot C, Ramel MC, Stone RK, Hill CS. A Temporal Window for Signal Activation Dictates the Dimensions of a Nodal Signaling Domain. Dev Cell 2015; 35:175-85. [PMID: 26506307 PMCID: PMC4640439 DOI: 10.1016/j.devcel.2015.09.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 08/11/2015] [Accepted: 09/23/2015] [Indexed: 11/22/2022]
Abstract
Morphogen signaling is critical for the growth and patterning of tissues in embryos and adults, but how morphogen signaling gradients are generated in tissues remains controversial. The morphogen Nodal was proposed to form a long-range signaling gradient via a reaction-diffusion system, on the basis of differential diffusion rates of Nodal and its antagonist Lefty. Here we use a specific zebrafish Nodal biosensor combined with immunofluorescence for phosphorylated Smad2 to demonstrate that endogenous Nodal is unlikely to diffuse over a long range. Instead, short-range Nodal signaling activation in a temporal window is sufficient to determine the dimensions of the Nodal signaling domain. The size of this temporal window is set by the differentially timed production of Nodal and Lefty, which arises mainly from repression of Lefty translation by the microRNA miR-430. Thus, temporal information is transformed into spatial information to define the dimensions of the Nodal signaling domain and, consequently, to specify mesendoderm.
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Affiliation(s)
- Antonius L van Boxtel
- Developmental Signalling, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - John E Chesebro
- Developmental Signalling, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Claire Heliot
- Developmental Signalling, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Marie-Christine Ramel
- Developmental Signalling, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Richard K Stone
- Experimental Histopathology, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Caroline S Hill
- Developmental Signalling, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
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Ma P, Swartz MR, Kindt LM, Kangas AM, Liang JO. Temperature Sensitivity of Neural Tube Defects in Zoep Mutants. Zebrafish 2015; 12:448-56. [PMID: 26366681 DOI: 10.1089/zeb.2015.1113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Neural tube defects (NTD) occur when the flat neural plate epithelium fails to fold into the neural tube, the precursor to the brain and spinal cord. Squint (Sqt/Ndr1), a Nodal ligand, and One-eyed pinhead (Oep), a component of the Nodal receptor, are required for anterior neural tube closure in zebrafish. The NTD in sqt and Zoep mutants are incompletely penetrant. The penetrance of several defects in sqt mutants increases upon heat or cold shock. In this project, undergraduate students tested whether temperature influences the Zoep open neural tube phenotype. Single pairs of adults were spawned at 28.5°C, the normal temperature for zebrafish, and one half of the resulting embryos were moved to 34°C at different developmental time points. Analysis of variance indicated temperature and clutch/genetic background significantly contributed to the penetrance of the open neural tube phenotype. Heat shock affected the embryos only at or before the midblastula stage. Many factors, including temperature changes in the mother, nutrition, and genetic background, contribute to NTD in humans. Thus, sqt and Zoep mutants may serve as valuable models for studying the interactions between genetics and the environment during neurulation.
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Affiliation(s)
- Phyo Ma
- 1 Department of Biology, University of Minnesota Duluth , Duluth, Minnesota
| | - Morgan R Swartz
- 1 Department of Biology, University of Minnesota Duluth , Duluth, Minnesota
| | - Lexy M Kindt
- 1 Department of Biology, University of Minnesota Duluth , Duluth, Minnesota.,2 Integrated Biosciences Graduate Program, University of Minnesota , Duluth, Minnesota
| | - Ashley M Kangas
- 1 Department of Biology, University of Minnesota Duluth , Duluth, Minnesota
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Dubrulle J, Jordan BM, Akhmetova L, Farrell JA, Kim SH, Solnica-Krezel L, Schier AF. Response to Nodal morphogen gradient is determined by the kinetics of target gene induction. eLife 2015; 4. [PMID: 25869585 PMCID: PMC4395910 DOI: 10.7554/elife.05042] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Accepted: 03/02/2015] [Indexed: 12/24/2022] Open
Abstract
Morphogen gradients expose cells to different signal concentrations and induce target genes with different ranges of expression. To determine how the Nodal morphogen gradient induces distinct gene expression patterns during zebrafish embryogenesis, we measured the activation dynamics of the signal transducer Smad2 and the expression kinetics of long- and short-range target genes. We found that threshold models based on ligand concentration are insufficient to predict the response of target genes. Instead, morphogen interpretation is shaped by the kinetics of target gene induction: the higher the rate of transcription and the earlier the onset of induction, the greater the spatial range of expression. Thus, the timing and magnitude of target gene expression can be used to modulate the range of expression and diversify the response to morphogen gradients. DOI:http://dx.doi.org/10.7554/eLife.05042.001 How a cell can tell where it is in a developing embryo has fascinated scientists for decades. The pioneering computer scientist and mathematical biologist Alan Turing was the first person to coin the term ‘morphogen’ to describe a protein that provides information about locations in the body. A morphogen is released from a group of cells (called the ‘source’) and as it moves away its activity (called the ‘signal’) declines gradually. Cells sense this signal gradient and use it to detect their position with respect to the source. Nodal is an important morphogen and is required to establish the correct identity of cells in the embryo; for example, it helps determine which cells should become a brain or heart or gut cell and so on. The zebrafish is a widely used model to study animal development, in part because its embryos are transparent; this allows cells and proteins to be easily observed under a microscope. When Nodal acts on cells, another protein called Smad2 becomes activated, moves into the cell's nucleus, and then binds to specific genes. This triggers the expression of these genes, which are first copied into mRNA molecules via a process known as transcription and are then translated into proteins. The protein products of these targeted genes control cell identity and movement. Several models have been proposed to explain how different concentrations of Nodal switch on the expression of different target genes; that is to say, to explain how a cell interprets the Nodal gradient. Dubrulle et al. have now measured factors that underlie how this gradient is interpreted. Individual cells in zebrafish embryos were tracked under a microscope, and Smad2 activation and gene expression were assessed. Dubrulle et al. found that, in contradiction to previous models, the amount of Nodal present on its own was insufficient to predict the target gene response. Instead, their analysis suggests that the size of each target gene's response depends on its rate of transcription and how quickly it is first expressed in response to Nodal. These findings of Dubrulle et al. suggest that timing and transcription rate are important in determining the appropriate response to Nodal. Further work will be now needed to find out whether similar mechanisms regulate other processes that rely on the activity of morphogens. DOI:http://dx.doi.org/10.7554/eLife.05042.002
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Affiliation(s)
- Julien Dubrulle
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Benjamin M Jordan
- Department of Mathematics, College of Science and Engineering, University of Minnesota, Minneapolis, United States
| | - Laila Akhmetova
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Jeffrey A Farrell
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Seok-Hyung Kim
- Division of Medicine, Medical University of South Carolina, Charleston, United States
| | - Lilianna Solnica-Krezel
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, United States
| | - Alexander F Schier
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
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Ghaedi M, Niklason LE, Williams J. Development of Lung Epithelium from Induced Pluripotent Stem Cells. CURRENT TRANSPLANTATION REPORTS 2015; 2:81-89. [PMID: 26052480 PMCID: PMC4452199 DOI: 10.1007/s40472-014-0039-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Considerable progress has been made in the field of in vitro development of alveolar epithelium from induced pluripotent stem cells. Patient specific derived alveolar cells could potentially populate tissue engineered lungs, provide a cell source for drug testing or function as a model for research into lung diseases. Induced to pluripotency through a variety of techniques, stem cells can be differentiated to alveolar epithelium through exposure to a variety of different culture conditions and growth media. The ultimate success of differentiated cells for translational medicine applications will depend on further advances in the understanding of the human lung developmental pathway, and successful application to in vitro culture. In this review will focus the major signaling pathways and molecules in lung development and the existing protocol for directed different ion of iPSC and hESC to cells resembling respiratory epithelium in vitro.
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Affiliation(s)
- Mahboobe Ghaedi
- Departments of Anesthesia and Biomedical Engineering, Yale University, New Haven, Connecticut, 06520, USA
| | - Laura E. Niklason
- Departments of Anesthesia and Biomedical Engineering, Yale University, New Haven, Connecticut, 06520, USA
| | - Jordana Williams
- Departments of Anesthesia and Biomedical Engineering, Yale University, New Haven, Connecticut, 06520, USA
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Abstract
Activin/Nodal growth factors control a broad range of biological processes, including early cell fate decisions, organogenesis and adult tissue homeostasis. Here, we provide an overview of the mechanisms by which the Activin/Nodal signalling pathway governs stem cell function in these different stages of development. We describe recent findings that associate Activin/Nodal signalling to pathological conditions, focusing on cancer stem cells in tumorigenesis and its potential as a target for therapies. Moreover, we will discuss future directions and questions that currently remain unanswered on the role of Activin/Nodal signalling in stem cell self-renewal, differentiation and proliferation.
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Affiliation(s)
- Siim Pauklin
- Anne McLaren Laboratory For Regenerative Medicine, Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, West Forvie Building, Robinson Way, University of Cambridge, Cambridge CB2 0SZ, UK
| | - Ludovic Vallier
- Anne McLaren Laboratory For Regenerative Medicine, Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, West Forvie Building, Robinson Way, University of Cambridge, Cambridge CB2 0SZ, UK
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Terashima AV, Mudumana SP, Drummond IA. Odd skipped related 1 is a negative feedback regulator of nodal-induced endoderm development. Dev Dyn 2014; 243:1571-80. [PMID: 25233796 DOI: 10.1002/dvdy.24191] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 09/03/2014] [Accepted: 09/10/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Early embryo patterning is orchestrated by tightly regulated morphogen gradients. The Nodal morphogen patterns the mesendoderm, giving rise to all endoderm and head and trunk mesoderm. High Nodal concentrations favor endoderm differentiation while lower promote mesoderm differentiation. Nodal signaling is controlled by both positive and negative feedback regulation to ensure robust developmental patterning. RESULTS Here we identify odd skipped related 1 (osr1), a zinc finger transcription factor, as a new element in Nodal feedback regulation affecting endoderm development. We show that osr1 expression in zebrafish germ ring mesendoderm requires Nodal signaling; osr1 expression was lost in embryos lacking Nodal signaling. Conversely, osr1 expression was ectopically induced by the activation of Nodal signaling. Furthermore we demonstrate that osr1 responds directly to Nodal signaling. Additionally, osr1 knockdown generated excess endoderm cells marked by sox32 expression while expression of osr1 mRNA was not affected in sox32-deficient embryos. CONCLUSIONS Our findings identify osr1 as a Nodal-induced, negative feedback regulator of Nodal signaling that acts at the earliest stages of endoderm differentiation to limit the number of endoderm progenitors. As such, we propose that osr1 represents a novel network motif controlling the output of Nodal signaling to regulate mesendoderm patterning.
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Nelson AC, Cutty SJ, Niini M, Stemple DL, Flicek P, Houart C, Bruce AEE, Wardle FC. Global identification of Smad2 and Eomesodermin targets in zebrafish identifies a conserved transcriptional network in mesendoderm and a novel role for Eomesodermin in repression of ectodermal gene expression. BMC Biol 2014; 12:81. [PMID: 25277163 PMCID: PMC4206766 DOI: 10.1186/s12915-014-0081-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Indexed: 12/27/2022] Open
Abstract
Background Nodal signalling is an absolute requirement for normal mesoderm and endoderm formation in vertebrate embryos, yet the transcriptional networks acting directly downstream of Nodal and the extent to which they are conserved is largely unexplored, particularly in vivo. Eomesodermin also plays a role in patterning mesoderm and endoderm in vertebrates, but its mechanisms of action and how it interacts with the Nodal signalling pathway are still unclear. Results Using a combination of expression analysis and chromatin immunoprecipitation with deep sequencing (ChIP-seq) we identify direct targets of Smad2, the effector of Nodal signalling in blastula stage zebrafish embryos, including many novel target genes. Through comparison of these data with published ChIP-seq data in human, mouse and Xenopus we show that the transcriptional network driven by Smad2 in mesoderm and endoderm is conserved in these vertebrate species. We also show that Smad2 and zebrafish Eomesodermin a (Eomesa) bind common genomic regions proximal to genes involved in mesoderm and endoderm formation, suggesting Eomesa forms a general component of the Smad2 signalling complex in zebrafish. Combinatorial perturbation of Eomesa and Smad2-interacting factor Foxh1 results in loss of both mesoderm and endoderm markers, confirming the role of Eomesa in endoderm formation and its functional interaction with Foxh1 for correct Nodal signalling. Finally, we uncover a novel role for Eomesa in repressing ectodermal genes in the early blastula. Conclusions Our data demonstrate that evolutionarily conserved developmental functions of Nodal signalling occur through maintenance of the transcriptional network directed by Smad2. This network is modulated by Eomesa in zebrafish which acts to promote mesoderm and endoderm formation in combination with Nodal signalling, whilst Eomesa also opposes ectoderm gene expression. Eomesa, therefore, regulates the formation of all three germ layers in the early zebrafish embryo. Electronic supplementary material The online version of this article (doi:10.1186/s12915-014-0081-5) contains supplementary material, which is available to authorized users.
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58
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Evolutionary conservation of early mesoderm specification by mechanotransduction in Bilateria. Nat Commun 2014; 4:2821. [PMID: 24281726 PMCID: PMC3868206 DOI: 10.1038/ncomms3821] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 10/24/2013] [Indexed: 02/08/2023] Open
Abstract
The modulation of developmental biochemical pathways by mechanical cues is an emerging feature of animal development, but its evolutionary origins have not been explored. Here we show that a common mechanosensitive pathway involving β-catenin specifies early mesodermal identity at gastrulation in zebrafish and Drosophila. Mechanical strains developed by zebrafish epiboly and Drosophila mesoderm invagination trigger the phosphorylation of β-catenin–tyrosine-667. This leads to the release of β-catenin into the cytoplasm and nucleus, where it triggers and maintains, respectively, the expression of zebrafish brachyury orthologue notail and of Drosophila Twist, both crucial transcription factors for early mesoderm identity. The role of the β-catenin mechanosensitive pathway in mesoderm identity has been conserved over the large evolutionary distance separating zebrafish and Drosophila. This suggests mesoderm mechanical induction dating back to at least the last bilaterian common ancestor more than 570 million years ago, the period during which mesoderm is thought to have emerged. Mechanical cues can induce morphogenetic processes during development. Here the authors show that mechanical changes during embryonic development in both zebrafish and Drosophila lead to nuclear localization of β-catenin, which regulates genes required for early mesoderm development in both species.
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59
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Lush ME, Piotrowski T. ErbB expressing Schwann cells control lateral line progenitor cells via non-cell-autonomous regulation of Wnt/β-catenin. eLife 2014; 3:e01832. [PMID: 24642408 PMCID: PMC3957165 DOI: 10.7554/elife.01832] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Proper orchestration of quiescence and activation of progenitor cells is crucial during embryonic development and adult homeostasis. We took advantage of the zebrafish sensory lateral line to define niche-progenitor interactions to understand how integration of diverse signaling pathways spatially and temporally regulates the coordination of these processes. Our previous studies demonstrated that Schwann cells play a crucial role in negatively regulating lateral line progenitor proliferation. Here we demonstrate that ErbB/Neuregulin signaling is not only required for Schwann cell migration but that it plays a continued role in postmigratory Schwann cells. ErbB expressing Schwann cells inhibit lateral line progenitor proliferation and differentiation through non-cell-autonomous inhibition of Wnt/β-catenin signaling. Subsequent activation of Fgf signaling controls sensory organ differentiation, but not progenitor proliferation. In addition to the lateral line, these findings have important implications for understanding how niche-progenitor cells segregate interactions during development, and how they may go wrong in disease states. DOI: http://dx.doi.org/10.7554/eLife.01832.001.
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Affiliation(s)
- Mark E Lush
- Stowers Institute for Medical Research, Kansas City, United States
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60
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Fontenille L, Rouquier S, Lutfalla G, Giorgi D. Microtubule-associated protein 9 (Map9/Asap) is required for the early steps of zebrafish development. Cell Cycle 2014; 13:1101-14. [PMID: 24553125 PMCID: PMC4013161 DOI: 10.4161/cc.27944] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Microtubules are structural components of the cell cytoskeleton and key factors for mitosis and ciliogenesis in eukaryotes. The regulation of MT dynamics requires non-motor MAPs. We previously showed that, in human cells in culture, MAP9 (also named ASAP) is involved in MT dynamics and is essential for mitotic spindle formation and mitosis progression. Indeed, misexpression of MAP9 leads to severe mitotic defects and cell death. Here, we investigated the in vivo role of map9 during zebrafish development. Map9 is expressed mainly as a maternal gene. Within cells, Map9 is associated with the MT network of the mitotic spindle and with centrosomes. Morpholino-mediated depletion of map9 leads to early development arrest before completion of epiboly. Map9 localizes to the MT array of the YSL. This MT network is destroyed in Map9-depleted embryos, and injection of anti-map9 morpholinos directly in the nascent YSL leads to arrest of epiboly/gastrulation. Finally, map9 knockdown deregulates the expression of genes involved in endodermal differentiation, dorso-ventral and left-right patterning, and other MT-based functions. At low morpholino doses, the surviving embryos show dramatic developmental defects, spindle and mitotic defects, and increased apoptosis. Our findings suggest that map9 is a crucial factor in early zebrafish development by regulating different MT-based processes.
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Affiliation(s)
- Laura Fontenille
- Institute of Human Genetics; UPR 1142; CNRS; Montpellier, France; Université de Montpellier 1; Montpellier, France
| | - Sylvie Rouquier
- Institute of Human Genetics; UPR 1142; CNRS; Montpellier, France
| | - Georges Lutfalla
- Dynamique des Interactions Membranaires Normales et Pathologiques; UMR 5235; CNRS; Universités de Montpellier 1&2; Montpellier, France
| | - Dominique Giorgi
- Institute of Human Genetics; UPR 1142; CNRS; Montpellier, France
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Kumari P, Gilligan PC, Lim S, Tran LD, Winkler S, Philp R, Sampath K. An essential role for maternal control of Nodal signaling. eLife 2013; 2:e00683. [PMID: 24040511 PMCID: PMC3771576 DOI: 10.7554/elife.00683] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 08/06/2013] [Indexed: 12/26/2022] Open
Abstract
Growth factor signaling is essential for pattern formation, growth, differentiation, and maintenance of stem cell pluripotency. Nodal-related signaling factors are required for axis formation and germ layer specification from sea urchins to mammals. Maternal transcripts of the zebrafish Nodal factor, Squint (Sqt), are localized to future embryonic dorsal. The mechanisms by which maternal sqt/nodal RNA is localized and regulated have been unclear. Here, we show that maternal control of Nodal signaling via the conserved Y box-binding protein 1 (Ybx1) is essential. We identified Ybx1 via a proteomic screen. Ybx1 recognizes the 3’ untranslated region (UTR) of sqt RNA and prevents premature translation and Sqt/Nodal signaling. Maternal-effect mutations in zebrafish ybx1 lead to deregulated Nodal signaling, gastrulation failure, and embryonic lethality. Implanted Nodal-coated beads phenocopy ybx1 mutant defects. Thus, Ybx1 prevents ectopic Nodal activity, revealing a new paradigm in the regulation of Nodal signaling, which is likely to be conserved. DOI:http://dx.doi.org/10.7554/eLife.00683.001 In many organisms, embryonic development is controlled in part by RNAs that are deposited into the egg as it forms inside the mother. These ‘maternal RNAs’ may localize to particular regions of the egg or embryo, where they are then exclusively translated into protein and carry out their specific function. This helps to establish asymmetry in the developing organism—that is, to produce tissues that will eventually become the top or bottom, front or back, and left or right of the organism. One such maternal RNA encodes Nodal, a key signaling molecule that is conserved across vertebrate and some invertebrate organisms. In zebrafish, the equivalent RNA is called squint, and plays an important role in embryonic development. The squint RNA deposited by the mother localizes to the dorsal region—the embryo’s back—and signals that region to make dorsal tissues, but how squint is regulated is not well understood. Now, Kumari et al. identify a protein that controls the positioning of squint RNA, and find that it can also prevent this RNA from being translated into protein. The squint RNA contains a ‘dorsal localization element’ that recruits it to the dorsal cells of the embryo by the 4-cell stage (i.e., within two cell divisions after the egg is fertilized). Kumari et al. identified a protein called Ybx1 that could bind to this element: this protein may help to correctly position RNAs in many other organisms, including fruit flies and mammals. Strikingly, embryos formed abnormally when their maternally derived Ybx1 protein was mutant, and these mutations also prevented the squint RNA from localizing properly. This suggests that maternally derived Ybx1 protein directly regulates the squint RNA. As well as positioning the squint RNA correctly, the embryo must translate this RNA into protein at the right time. In embryos with mutant maternal Ybx1 protein, the Squint protein could be detected at the 16-cell stage, whereas in wild-type embryos this protein is not translated until the 256-cell stage; this indicates that Ybx1 protein might normally repress the translation of the squint RNA. Indeed, Kumari et al. found that Ybx1 binds to another protein—eIF4E—that recruits mRNAs to the ribosome (the cell’s translational machinery). Ybx1 might therefore prevent eIF4E from associating with other components of the ribosomal complex, and initiating the translation of the squint RNA, until additional signals have been received. It will be interesting to determine how widespread this regulatory mechanism is in other organisms. DOI:http://dx.doi.org/10.7554/eLife.00683.002
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Affiliation(s)
- Pooja Kumari
- Temasek Life Sciences Laboratory , National University of Singapore , Singapore , Singapore ; Department of Biological Sciences , National University of Singapore , Singapore , Singapore
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Fleming BM, Yelin R, James RG, Schultheiss TM. A role for Vg1/Nodal signaling in specification of the intermediate mesoderm. Development 2013; 140:1819-29. [PMID: 23533180 PMCID: PMC3621495 DOI: 10.1242/dev.093740] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/14/2013] [Indexed: 11/20/2022]
Abstract
The intermediate mesoderm (IM) is the embryonic source of all kidney tissue in vertebrates. The factors that regulate the formation of the IM are not yet well understood. Through investigations in the chick embryo, the current study identifies and characterizes Vg1/Nodal signaling (henceforth referred to as 'Nodal-like signaling') as a novel regulator of IM formation. Excess Nodal-like signaling at gastrulation stages resulted in expansion of the IM at the expense of the adjacent paraxial mesoderm, whereas inhibition of Nodal-like signaling caused repression of IM gene expression. IM formation was sensitive to levels of the Nodal-like pathway co-receptor Cripto and was inhibited by a truncated form of the secreted molecule cerberus, which specifically blocks Nodal, indicating that the observed effects are specific to the Nodal-like branch of the TGFβ signaling pathway. The IM-promoting effects of Nodal-like signaling were distinct from the known effects of this pathway on mesoderm formation and left-right patterning, a finding that can be attributed to specific time windows for the activities of these Nodal-like functions. Finally, a link was observed between Nodal-like and BMP signaling in the induction of IM. Activation of IM genes by Nodal-like signaling required an active BMP signaling pathway, and Nodal-like signals induced phosphorylation of Smad1/5/8, which is normally associated with activation of BMP signaling pathways. We postulate that Nodal-like signaling regulates IM formation by modulating the IM-inducing effects of BMP signaling.
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Affiliation(s)
- Britannia M. Fleming
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Ronit Yelin
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Richard G. James
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, USA
| | - Thomas M. Schultheiss
- Department of Anatomy and Cell Biology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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63
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Woo S, Housley MP, Weiner OD, Stainier DYR. Nodal signaling regulates endodermal cell motility and actin dynamics via Rac1 and Prex1. ACTA ACUST UNITED AC 2013; 198:941-52. [PMID: 22945937 PMCID: PMC3432772 DOI: 10.1083/jcb.201203012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nodal, acting through Prex1 and Rac1, promotes dynamic actin and random motility in endodermal cells during early gastrulation. Embryo morphogenesis is driven by dynamic cell behaviors, including migration, that are coordinated with fate specification and differentiation, but how such coordination is achieved remains poorly understood. During zebrafish gastrulation, endodermal cells sequentially exhibit first random, nonpersistent migration followed by oriented, persistent migration and finally collective migration. Using a novel transgenic line that labels the endodermal actin cytoskeleton, we found that these stage-dependent changes in migratory behavior correlated with changes in actin dynamics. The dynamic actin and random motility exhibited during early gastrulation were dependent on both Nodal and Rac1 signaling. We further identified the Rac-specific guanine nucleotide exchange factor Prex1 as a Nodal target and showed that it mediated Nodal-dependent random motility. Reducing Rac1 activity in endodermal cells caused them to bypass the random migration phase and aberrantly contribute to mesodermal tissues. Together, our results reveal a novel role for Nodal signaling in regulating actin dynamics and migration behavior, which are crucial for endodermal morphogenesis and cell fate decisions.
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Affiliation(s)
- Stephanie Woo
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
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64
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Mercier S, David V, Ratié L, Gicquel I, Odent S, Dupé V. NODAL and SHH dose-dependent double inhibition promotes an HPE-like phenotype in chick embryos. Dis Model Mech 2012; 6:537-43. [PMID: 23264560 PMCID: PMC3597036 DOI: 10.1242/dmm.010132] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Holoprosencephaly (HPE) is a common congenital defect that results from failed or incomplete forebrain cleavage. HPE is characterized by a wide clinical spectrum, with inter- and intrafamilial variability. This heterogeneity is not well understood and it has been suggested that HPE involves a combination of multiple gene mutations. In this model, several mutated alleles or modifying factors are presumed to act in synergy to cause and determine the severity of HPE. This could explain the various clinical phenotypes. Screening for HPE-associated genes in humans suggests the involvement of NODAL or SHH signaling, or both. To test this multigenic hypothesis, we investigated the effects of chemical inhibition of these two main HPE signaling pathways in a chick embryo model. SB-505124, a selective inhibitor of transforming growth factor-B type I receptors was used to inhibit the NODAL pathway. Cyclopamine was used to inhibit the SHH pathway. We report that both inhibitors caused HPE-like defects that were dependent on the drug concentration and on the developmental stage at the time of treatment. We also investigated double inhibition of NODAL and SHH pathways from the onset of gastrulation by using subthreshold inhibitor concentrations. The inhibitors of the NODAL and SHH pathways, even at low concentration, acted synergistically to promote an HPE-like phenotype. These findings support the view that genetic heterogeneity is important in the etiology of HPE and may contribute to the phenotypic variability.
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Affiliation(s)
- Sandra Mercier
- Institut de Génétique et Développement, CNRS UMR6290, Université de Rennes 1, IFR140 GFAS, Faculté de Médecine, 35043 Rennes, France
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65
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Roussigne M, Blader P, Wilson SW. Breaking symmetry: the zebrafish as a model for understanding left-right asymmetry in the developing brain. Dev Neurobiol 2012; 72:269-81. [PMID: 22553774 DOI: 10.1002/dneu.20885] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
How does left-right asymmetry develop in the brain and how does the resultant asymmetric circuitry impact on brain function and lateralized behaviors? By enabling scientists to address these questions at the levels of genes, neurons, circuitry and behavior,the zebrafish model system provides a route to resolve the complexity of brain lateralization. In this review, we present the progress made towards characterizing the nature of the gene networks and the sequence of morphogenetic events involved in the asymmetric development of zebrafish epithalamus. In an attempt to integrate the recent extensive knowledge into a working model and to identify the future challenges,we discuss how insights gained at a cellular/developmental level can be linked to the data obtained at a molecular/genetic level. Finally, we present some evolutionary thoughts and discuss how significant discoveries made in zebrafish should provide entry points to better understand the evolutionary origins of brain lateralization.
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Affiliation(s)
- Myriam Roussigne
- Universite Paul Sabatier, Centre de Biologie du Developpement,Toulouse, France.
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66
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Wang A, Sander M. Generating cells of the gastrointestinal system: current approaches and applications for the differentiation of human pluripotent stem cells. J Mol Med (Berl) 2012; 90:763-71. [DOI: 10.1007/s00109-012-0923-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/07/2012] [Accepted: 05/24/2012] [Indexed: 12/19/2022]
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67
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Howell JC, Wells JM. Generating intestinal tissue from stem cells: potential for research and therapy. Regen Med 2012; 6:743-55. [PMID: 22050526 DOI: 10.2217/rme.11.90] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Intestinal resection and malformations in adult and pediatric patients result in devastating consequences. Unfortunately, allogeneic transplantation of intestinal tissue into patients has not been met with the same measure of success as the transplantation of other organs. Attempts to engineer intestinal tissue in vitro include disaggregation of adult rat intestine into subunits called organoids, harvesting native adult stem cells from mouse intestine and spontaneous generation of intestinal tissue from embryoid bodies. Recently, by utilizing principles gained from the study of developmental biology, human pluripotent stem cells have been demonstrated to be capable of directed differentiation into intestinal tissue in vitro. Pluripotent stem cells offer a unique and promising means to generate intestinal tissue for the purposes of modeling intestinal disease, understanding embryonic development and providing a source of material for therapeutic transplantation.
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Affiliation(s)
- Jonathan C Howell
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA
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68
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Kimelman D, Martin BL. Anterior-posterior patterning in early development: three strategies. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2011; 1:253-66. [PMID: 23801439 DOI: 10.1002/wdev.25] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The anterior-posterior (AP) axis is the most ancient of the embryonic axes and exists in most metazoans. Different animals use a wide variety of mechanisms to create this axis in the early embryo. In this study, we focus on three animals, including two insects (Drosophila and Tribolium) and a vertebrate (zebrafish) to examine different strategies used to form the AP axis. While Drosophila forms the entire axis within a syncytial blastoderm using transcription factors as morphogens, zebrafish uses signaling factors in a cellularized embryo, progressively forming the AP axis over the course of a day. Tribolium uses an intermediate strategy that has commonalities with both Drosophila and zebrafish. We discuss the specific molecular mechanisms used to create the AP axis and identify conserved features.
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Affiliation(s)
- David Kimelman
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
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69
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Mesnard D, Donnison M, Fuerer C, Pfeffer PL, Constam DB. The microenvironment patterns the pluripotent mouse epiblast through paracrine Furin and Pace4 proteolytic activities. Genes Dev 2011; 25:1871-80. [PMID: 21896659 DOI: 10.1101/gad.16738711] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The fate of pluripotent cells in early mouse embryos is controlled by graded Nodal signals that are activated by the endoproteases Furin and Pace4. Soluble forms of Furin and Pace4 cleave proNodal in vitro and after secretion in transfected cells, but direct evidence for paracrine activity in vivo is elusive. Here, we show that Furin and Pace4 are released by the extraembryonic microenvironment, and that they cleave a membrane-bound reporter substrate in adjacent epiblast cells and activate Nodal to maintain pluripotency. Secreted Pace4 and Furin also stimulated mesoderm formation, whereas endoderm was only induced by Pace4, correlating with a difference in the spatiotemporal distribution of these proteolytic activities. Our analysis of paracrine Furin and Pace4 activities and their in vivo functions significantly advances our understanding of how the epiblast is patterned by its microenvironment. Adding cell-cell communication to the pleiotropic portfolio of these proteases provides a new framework to study proprotein processing also in other relevant contexts.
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Affiliation(s)
- Daniel Mesnard
- Ecole Polytechnique Fédérale de Lausanne (EPFL) SV ISREC, CH-1015 Lausanne, Switzerland
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70
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Lou X, Deshwar AR, Crump JG, Scott IC. Smarcd3b and Gata5 promote a cardiac progenitor fate in the zebrafish embryo. Development 2011; 138:3113-23. [DOI: 10.1242/dev.064279] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Development of the heart requires recruitment of cardiovascular progenitor cells (CPCs) to the future heart-forming region. CPCs are the building blocks of the heart, and have the potential to form all the major cardiac lineages. However, little is known regarding what regulates CPC fate and behavior. Activity of GATA4, SMARCD3 and TBX5 – the `cardiac BAF' (cBAF) complex, can promote myocardial differentiation in embryonic mouse mesoderm. Here, we exploit the advantages of the zebrafish embryo to gain mechanistic understanding of cBAF activity. Overexpression of smarcd3b and gata5 in zebrafish results in an enlarged heart, whereas combinatorial loss of cBAF components inhibits cardiac differentiation. In transplantation experiments, cBAF acts cell autonomously to promote cardiac fate. Remarkably, cells overexpressing cBAF migrate to the developing heart and differentiate as cardiomyocytes, endocardium and smooth muscle. This is observed even in host embryos that lack endoderm or cardiac mesoderm. Our results reveal an evolutionarily conserved role for cBAF activity in cardiac differentiation. Importantly, they demonstrate that Smarcd3b and Gata5 can induce a primitive, CPC-like state.
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Affiliation(s)
- Xin Lou
- Program in Development and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 1L7, Canada
| | - Ashish R. Deshwar
- Program in Development and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 1L7, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - J. Gage Crump
- Broad CIRM Center, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
| | - Ian C. Scott
- Program in Development and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 1L7, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
- Heart and Stroke/Richard Lewar Centre of Excellence, University of Toronto, Toronto, ON M5S 3E2, Canada
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71
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Abstract
Morphogens are long-range signaling molecules that pattern developing tissues in a concentration-dependent manner. The graded activity of morphogens within tissues exposes cells to different signal levels and leads to region-specific transcriptional responses and cell fates. In its simplest incarnation, a morphogen signal forms a gradient by diffusion from a local source and clearance in surrounding tissues. Responding cells often transduce morphogen levels in a linear fashion, which results in the graded activation of transcriptional effectors. The concentration-dependent expression of morphogen target genes is achieved by their different binding affinities for transcriptional effectors as well as inputs from other transcriptional regulators. Morphogen distribution and interpretation are the result of complex interactions between the morphogen and responding tissues. The response to a morphogen is dependent not simply on morphogen concentration but also on the duration of morphogen exposure and the state of the target cells. In this review, we describe the morphogen concept and discuss the mechanisms that underlie the generation, modulation, and interpretation of morphogen gradients.
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Affiliation(s)
- Katherine W Rogers
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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72
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Liu W, Foley AC. Signaling pathways in early cardiac development. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2011; 3:191-205. [PMID: 20830688 DOI: 10.1002/wsbm.112] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Cardiomyocyte differentiation is a complex multistep process requiring the proper temporal and spatial integration of multiple signaling pathways. Previous embryological and genetic studies have identified a number of signaling pathways that are critical to mediate the initial formation of the mesoderm and its allocation to the cardiomyocyte lineage. It has become clear that some of these signaling networks work autonomously, in differentiating myocardial cells whereas others work non-autonomously, in neighboring tissues, to regulate cardiac differentiation indirectly. Here, we provide an overview of three signaling networks that mediate cardiomyocyte specification and review recent insights into their specific roles in heart development. In addition, we demonstrate how systems level, 'omic approaches' and other high-throughput techniques such as small molecules screens are beginning to impact our understanding of cardiomyocyte specification and, to identify novel signaling pathways involved in this process. In particular, it now seems clear that at least one chemokine receptor CXCR4 is an important marker for cardiomyocyte progenitors and may play a functional role in their differentiation. Finally, we discuss some gaps in our current understanding of early lineage selection that could be addressed by various types of omic analysis.
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Affiliation(s)
- Wenrui Liu
- Greenberg Division of Cardiology, Department of Medicine, Weill Medical College of Cornell University, New York, NY, USA
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73
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Spence JR, Lauf R, Shroyer NF. Vertebrate intestinal endoderm development. Dev Dyn 2011; 240:501-20. [PMID: 21246663 DOI: 10.1002/dvdy.22540] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2010] [Indexed: 12/12/2022] Open
Abstract
The endoderm gives rise to the lining of the esophagus, stomach and intestines, as well as associated organs. To generate a functional intestine, a series of highly orchestrated developmental processes must occur. In this review, we attempt to cover major events during intestinal development from gastrulation to birth, including endoderm formation, gut tube growth and patterning, intestinal morphogenesis, epithelial reorganization, villus emergence, as well as proliferation and cytodifferentiation. Our discussion includes morphological and anatomical changes during intestinal development as well as molecular mechanisms regulating these processes.
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74
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Abstract
Due to the powerful combination of genetic and embryological techniques, the teleost fish Danio rerio has emerged in the last decade as an important model organism for the study of embryonic development. It is relatively easy to inject material such as mRNA or synthetic oligonucleotides to reduce or increase the expression of a gene product. Changes in gene expression can be analyzed at the level of mRNA, by whole-mount in situ hybridization, or at the level of protein, by immunofluorescence. It is also possible to quantitatively analyze protein levels by Western and immunoprecipitation. Cell behavior can be analyzed in detail by cell transplantation and by fate mapping. Because a large number of mutations have been identified in recent years, these methods can be applied in a variety of contexts to provide a deep understanding of gene function that is often more difficult to achieve in other vertebrate model systems.
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Affiliation(s)
- Yuhua Sun
- Department of Cellular Biology, The University of Georgia, Athens, GA, USA.
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75
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Smith JC. Forming and interpreting gradients in the early Xenopus embryo. Cold Spring Harb Perspect Biol 2010; 1:a002477. [PMID: 20066079 DOI: 10.1101/cshperspect.a002477] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The amphibian embryo provides a powerful model system to study morphogen gradients because of the ease with which it is possible to manipulate the early embryo. In particular, it is possible to introduce exogenous sources of morphogen, to follow the progression of the signal, to monitor the cellular response to induction, and to up- or down-regulate molecules that are involved in all aspects of long-range signaling. In this article, I discuss the evidence that gradients exist in the early amphibian embryo, the way in which morphogens might traverse a field of cells, and the way in which different concentrations of morphogens might be interpreted to activate the expression of different genes.
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Affiliation(s)
- James C Smith
- National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA.
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76
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Abstract
Nodal signals belong to the TGF-beta superfamily and are essential for the induction of mesoderm and endoderm and the determination of the left-right axis. Nodal signals can act as morphogens-they have concentration-dependent effects and can act at a distance from their source of production. Nodal and its feedback inhibitor Lefty form an activator/inhibitor pair that behaves similarly to postulated reaction-diffusion models of tissue patterning. Nodal morphogen activity is also regulated by microRNAs, convertases, TGF-beta signals, coreceptors, and trafficking factors. This article describes how Nodal morphogens pattern embryonic fields and discusses how Nodal morphogen signaling is modulated.
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77
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Swanhart LM, Takahashi N, Jackson RL, Gibson GA, Watkins SC, Dawid IB, Hukriede NA. Characterization of an lhx1a transgenic reporter in zebrafish. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2010; 54:731-6. [PMID: 20209443 DOI: 10.1387/ijdb.092969ls] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The LIM-domain containing transcription factor, Lhx1, is involved in the regulation of early gastrulation cell movements, kidney organogenesis and other processes in vertebrate model organisms. To follow the expression of this gene in live embryos, we created transgenic zebrafish expressing enhanced green fluorescent protein (EGFP) under the control of lhx1a regulatory regions. Tg(lhx1a:EGFP)(pt303) recapitulates the expression of endogenous lhx1a beginning at early gastrula stages through 72 hours of development with only few exceptions. In addition, over-expression of the Nodal ligand, ndr1, results in the concomitant expansion of the transgene and endogenous lhx1a expression. Treatment of Tg(lhx1a:EGFP)(pt303) embryos with the small molecule SB-431542, an inhibitor of Nodal signaling, results in the loss of both transgene and endogenous lhx1a expression. These experiments suggest that Tg(lhx1a:EGFP)(pt303) is regulated in a manner similar to endogenous lhx1a. Therefore, this reporter can be utilized not only for monitoring lhx1a expression, but also for numerous applications, including chemical genetics screening.
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Affiliation(s)
- Lisa M Swanhart
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
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78
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Ribes V, Balaskas N, Sasai N, Cruz C, Dessaud E, Cayuso J, Tozer S, Yang LL, Novitch B, Marti E, Briscoe J. Distinct Sonic Hedgehog signaling dynamics specify floor plate and ventral neuronal progenitors in the vertebrate neural tube. Genes Dev 2010; 24:1186-200. [PMID: 20516201 PMCID: PMC2878655 DOI: 10.1101/gad.559910] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Accepted: 04/07/2010] [Indexed: 12/14/2022]
Abstract
The secreted ligand Sonic Hedgehog (Shh) organizes the pattern of cellular differentiation in the ventral neural tube. For the five neuronal subtypes, increasing levels and durations of Shh signaling direct progenitors to progressively more ventral identities. Here we demonstrate that this mode of action is not applicable to the generation of the most ventral cell type, the nonneuronal floor plate (FP). In chick and mouse embryos, FP specification involves a biphasic response to Shh signaling that controls the dynamic expression of key transcription factors. During gastrulation and early somitogenesis, FP induction depends on high levels of Shh signaling. Subsequently, however, prospective FP cells become refractory to Shh signaling, and this is a prerequisite for the elaboration of their identity. This prompts a revision to the model of graded Shh signaling in the neural tube, and provides insight into how the dynamics of morphogen signaling are deployed to extend the patterning capacity of a single ligand. In addition, we provide evidence supporting a common scheme for FP specification by Shh signaling that reconciles mechanisms of FP development in teleosts and amniotes.
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Affiliation(s)
- Vanessa Ribes
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
| | - Nikolaos Balaskas
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
| | - Noriaki Sasai
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
| | - Catarina Cruz
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
| | - Eric Dessaud
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
| | - Jordi Cayuso
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain
| | - Samuel Tozer
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
| | - Lin Lin Yang
- Department of Neurobiology, Broad Center of Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Ben Novitch
- Department of Neurobiology, Broad Center of Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Elisa Marti
- Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain
| | - James Briscoe
- Developmental Neurobiology, Medical Research Council-National Institute for Medical Research, London NW7 1AA, United Kingdom
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79
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Dessaud E, Ribes V, Balaskas N, Yang LL, Pierani A, Kicheva A, Novitch BG, Briscoe J, Sasai N. Dynamic assignment and maintenance of positional identity in the ventral neural tube by the morphogen sonic hedgehog. PLoS Biol 2010; 8:e1000382. [PMID: 20532235 PMCID: PMC2879390 DOI: 10.1371/journal.pbio.1000382] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Accepted: 04/20/2010] [Indexed: 12/31/2022] Open
Abstract
Morphogens are secreted signalling molecules that act in a graded manner to control the pattern of cellular differentiation in developing tissues. An example is Sonic hedgehog (Shh), which acts in several developing vertebrate tissues, including the central nervous system, to provide positional information during embryonic patterning. Here we address how Shh signalling assigns the positional identities of distinct neuronal subtype progenitors throughout the ventral neural tube. Assays of intracellular signal transduction and gene expression indicate that the duration as well as level of signalling is critical for morphogen interpretation. Progenitors of the ventral neuronal subtypes are established sequentially, with progressively more ventral identities requiring correspondingly higher levels and longer periods of Shh signalling. Moreover, cells remain sensitive to changes in Shh signalling for an extended time, reverting to antecedent identities if signalling levels fall below a threshold. Thus, the duration of signalling is important not only for the assignment but also for the refinement and maintenance of positional identity. Together the data suggest a dynamic model for ventral neural tube patterning in which positional information corresponds to the time integral of Shh signalling. This suggests an alternative to conventional models of morphogen action that rely solely on the level of signalling.
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Affiliation(s)
- Eric Dessaud
- Developmental Neurobiology, MRC-National Institute for Medical Research, London, United Kingdom
| | - Vanessa Ribes
- Developmental Neurobiology, MRC-National Institute for Medical Research, London, United Kingdom
| | - Nikolaos Balaskas
- Developmental Neurobiology, MRC-National Institute for Medical Research, London, United Kingdom
| | - Lin Lin Yang
- Department of Neurobiology, Broad Center of Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Alessandra Pierani
- Institut Jacques Monod, Université Paris Diderot, Program of Development and Neurobiology, Paris, France
| | - Anna Kicheva
- Developmental Neurobiology, MRC-National Institute for Medical Research, London, United Kingdom
| | - Bennett G. Novitch
- Department of Neurobiology, Broad Center of Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - James Briscoe
- Developmental Neurobiology, MRC-National Institute for Medical Research, London, United Kingdom
| | - Noriaki Sasai
- Developmental Neurobiology, MRC-National Institute for Medical Research, London, United Kingdom
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80
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Nojima H, Rothhämel S, Shimizu T, Kim CH, Yonemura S, Marlow FL, Hibi M. Syntabulin, a motor protein linker, controls dorsal determination. Development 2010; 137:923-33. [PMID: 20150281 DOI: 10.1242/dev.046425] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In amphibian and teleost embryos, the dorsal determinants (DDs) are believed to be initially localized to the vegetal pole and then transported to the prospective dorsal side of the embryo along a microtubule array. The DDs are known to activate the canonical Wnt pathway and thereby promote the expression of genes that induce the dorsal organizer. Here, by identifying the locus of the maternal-effect ventralized mutant tokkaebi, we show that Syntabulin, a linker of the kinesin I motor protein, is essential for dorsal determination in zebrafish. We found that syntabulin mRNA is transported to the vegetal pole during oogenesis through the Bucky ball (Buc)-mediated Balbiani body-dependent pathway, which is necessary for establishment of animal-vegetal (AV) oocyte polarity. We demonstrate that Syntabulin is translocated from the vegetal pole in a microtubule-dependent manner. Our findings suggest that Syntabulin regulates the microtubule-dependent transport of the DDs, and provide evidence for the link between AV and dorsoventral axis formation.
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Affiliation(s)
- Hideaki Nojima
- Laboratory for Vertebrate Axis Formation, RIKEN Center for Developmental Biology, Hyogo 650-0047, Japan
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81
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Luxardi G, Marchal L, Thomé V, Kodjabachian L. Distinct Xenopus Nodal ligands sequentially induce mesendoderm and control gastrulation movements in parallel to the Wnt/PCP pathway. Development 2010; 137:417-26. [PMID: 20056679 DOI: 10.1242/dev.039735] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The vertebrate body plan is established in two major steps. First, mesendoderm induction singles out prospective endoderm, mesoderm and ectoderm progenitors. Second, these progenitors are spatially rearranged during gastrulation through numerous and complex movements to give rise to an embryo comprising three concentric germ layers, polarised along dorsoventral, anteroposterior and left-right axes. Although much is known about the molecular mechanisms of mesendoderm induction, signals controlling gastrulation movements are only starting to be revealed. In vertebrates, Nodal signalling is required to induce the mesendoderm, which has precluded an analysis of its potential role during the later process of gastrulation. Using time-dependent inhibition, we show that in Xenopus, Nodal signalling plays sequential roles in mesendoderm induction and gastrulation movements. Nodal activity is necessary for convergent extension in axial mesoderm and for head mesoderm migration. Using morpholino-mediated knockdown, we found that the Nodal ligands Xnr5 and Xnr6 are together required for mesendoderm induction, whereas Xnr1 and Xnr2 act later to control gastrulation movements. This control is operated via the direct regulation of key movement-effector genes, such as papc, has2 and pdgfralpha. Interestingly, however, Nodal does not appear to mobilise the Wnt/PCP pathway, which is known to control cell and tissue polarity. This study opens the way to the analysis of the genetic programme and cell behaviours that are controlled by Nodal signalling during vertebrate gastrulation. It also provides a good example of the sub-functionalisation that results from the expansion of gene families in evolution.
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Affiliation(s)
- Guillaume Luxardi
- Institut de Biologie du Développement de Marseille Luminy, UMR 6216, CNRS-Université de la Méditerranée, Case 907, 13288 Marseille Cedex 09, France
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82
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Abstract
The endoderm germ layer contributes to the respiratory and gastrointestinal tracts and to all of their associated organs. Over the past decade, studies in vertebrate model organisms, including frog, fish, chick, and mouse, have greatly enhanced our understanding of the molecular basis of endoderm organ development. We review this progress with a focus on early stages of endoderm organogenesis including endoderm formation, gut tube morphogenesis and patterning, and organ specification. Lastly, we discuss how developmental mechanisms that regulate endoderm organogenesis are used to direct differentiation of embryonic stem cells into specific adult cell types, which function to alleviate disease symptoms in animal models.
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Affiliation(s)
- Aaron M Zorn
- Division of Developmental Biology, Cincinnati Children's Research Foundation and Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45229, USA.
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83
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Saunders T, Howard M. When it pays to rush: interpreting morphogen gradients prior to steady-state. Phys Biol 2009; 6:046020. [PMID: 19940351 DOI: 10.1088/1478-3975/6/4/046020] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
During development, morphogen gradients precisely determine the position of gene expression boundaries despite the inevitable presence of fluctuations. Recent experiments suggest that some morphogen gradients may be interpreted prior to reaching steady-state. Theoretical work has predicted that such systems will be more robust to embryo-to-embryo fluctuations. By analyzing two experimentally motivated models of morphogen gradient formation, we investigate the positional precision of gene expression boundaries determined by pre-steady-state morphogen gradients in the presence of embryo-to-embryo fluctuations, internal biochemical noise and variations in the timing of morphogen measurement. Morphogens that are direct transcription factors are found to be particularly sensitive to internal noise when interpreted prior to steady-state, disadvantaging early measurement, even in the presence of large embryo-to-embryo fluctuations. Morphogens interpreted by cell-surface receptors can be measured prior to steady-state without significant decrease in positional precision provided fluctuations in the timing of measurement are small. Applying our results to experiment, we predict that Bicoid, a transcription factor morphogen in Drosophila, is unlikely to be interpreted prior to reaching steady-state. We also predict that Activin in Xenopus and Nodal in zebrafish, morphogens interpreted by cell-surface receptors, can be decoded in pre-steady-state.
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Affiliation(s)
- Timothy Saunders
- Department of Computational and Systems Biology, John Innes Centre, Norwich, UK
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84
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Roessler E, Pei W, Ouspenskaia MV, Karkera JD, Veléz JI, Banerjee-Basu S, Gibney G, Lupo PJ, Mitchell LE, Towbin JA, Bowers P, Belmont JW, Goldmuntz E, Baxevanis AD, Feldman B, Muenke M. Cumulative ligand activity of NODAL mutations and modifiers are linked to human heart defects and holoprosencephaly. Mol Genet Metab 2009; 98:225-34. [PMID: 19553149 PMCID: PMC2774839 DOI: 10.1016/j.ymgme.2009.05.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Accepted: 05/19/2009] [Indexed: 11/25/2022]
Abstract
The cyclopic and laterality phenotypes in model organisms linked to disturbances in the generation or propagation of Nodal-like signals are potential examples of similar impairments resulting in birth defects in humans. However, the types of gene mutation(s) and their pathogenetic combinations in humans are poorly understood. Here we describe a mutational analysis of the human NODAL gene in a large panel of patients with phenotypes compatible with diminished NODAL ligand function. Significant reductions in the biological activity of NODAL alleles are detected among patients with congenital heart defects (CHD), laterality anomalies (e.g. left-right mis-specification phenotypes), and only rarely holoprosencephaly (HPE). While many of these NODAL variants are typical for family-specific mutations, we also report the presence of alleles with significantly reduced activity among common population variants. We propose that some of these common variants act as modifiers and contribute to the ultimate phenotypic outcome in these patients; furthermore, we draw parallels with strain-specific modifiers in model organisms to bolster this interpretation.
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Affiliation(s)
- Erich Roessler
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Wuhong Pei
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Maia V. Ouspenskaia
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Jayaprakash D. Karkera
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Jorge Ivan Veléz
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Sharmilla Banerjee-Basu
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Gretchen Gibney
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Philip J. Lupo
- Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas, USA
| | - Laura E. Mitchell
- Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas, USA
| | - Jeffrey A. Towbin
- Division of Cardiology, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
| | - Peter Bowers
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - John W. Belmont
- Division of Cardiology, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
| | - Elizabeth Goldmuntz
- Division of Cardiology, The Children’s Hospital of Philadelphia, Philadelphia, USA
| | - Andreas D. Baxevanis
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Benjamin Feldman
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Maximilian Muenke
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
- Corresponding author: Maximilian Muenke, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, 35 Convent Drive, MSC 3717, Building 35, Room 1B-203, Bethesda, MD 20892-3717, Tel.: (301) 402-8167, Fax.: (301) 480-7876,
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85
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Abstract
How morphogen gradients are formed in target tissues is a key question for understanding the mechanisms of morphological patterning. Here, we review different mechanisms of morphogen gradient formation from theoretical and experimental points of view. First, a simple, comprehensive overview of the underlying biophysical principles of several mechanisms of gradient formation is provided. We then discuss the advantages and limitations of different experimental approaches to gradient formation analysis.
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86
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Running the gauntlet: an overview of the modalities of travel employed by the putative morphogen Nodal. Curr Opin Genet Dev 2009; 19:302-7. [DOI: 10.1016/j.gde.2009.06.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 06/09/2009] [Accepted: 06/10/2009] [Indexed: 11/15/2022]
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87
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Temporal dynamics of patterning by morphogen gradients. Curr Opin Genet Dev 2009; 19:315-22. [DOI: 10.1016/j.gde.2009.05.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Accepted: 05/18/2009] [Indexed: 12/21/2022]
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88
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Wloga D, Webster DM, Rogowski K, Bré MH, Levilliers N, Jerka-Dziadosz M, Janke C, Dougan ST, Gaertig J. TTLL3 Is a tubulin glycine ligase that regulates the assembly of cilia. Dev Cell 2009; 16:867-76. [PMID: 19531357 DOI: 10.1016/j.devcel.2009.04.008] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 03/09/2009] [Accepted: 04/17/2009] [Indexed: 10/20/2022]
Abstract
In most ciliated cell types, tubulin is modified by glycylation, a posttranslational modification of unknown function. We show that the TTLL3 proteins act as tubulin glycine ligases with chain-initiating activity. In Tetrahymena, deletion of TTLL3 shortened axonemes and increased their resistance to paclitaxel-mediated microtubule stabilization. In zebrafish, depletion of TTLL3 led to either shortening or loss of cilia in several organs, including the Kupffer's vesicle and olfactory placode. We also show that, in vivo, glutamic acid and glycine ligases oppose each other, likely by competing for shared modification sites on tubulin. We propose that tubulin glycylation regulates the assembly and dynamics of axonemal microtubules and acts either directly or indirectly by inhibiting tubulin glutamylation.
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Affiliation(s)
- Dorota Wloga
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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89
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Kwon HJ, Riley BB. Mesendodermal signals required for otic induction: Bmp-antagonists cooperate with Fgf and can facilitate formation of ectopic otic tissue. Dev Dyn 2009; 238:1582-94. [PMID: 19418450 PMCID: PMC2835543 DOI: 10.1002/dvdy.21955] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Induction of otic placodes requires Fgf from surrounding tissues. We tested the hypothesis that mesendodermally derived Bmp-antagonists Chordin, Follistatin-a, and Crossveinless-2 cooperate in this process. Injecting morpholinos for all three genes, or treatment with the Nodal inhibitor SB431542 to block mesoderm-formation, reduces otic induction and strongly enhances the effects of disrupting fgf3 or fgf8. In contrast, using a lower dose of SB431542, combined with partial loss of Fgf, causes a dramatic medial expansion of otic tissue and formation of a single, large otic vesicle spanning the width of the hindbrain. Under these conditions, paraxial cephalic mesoderm forms ectopically at the midline, migrates into the head, and later transfates to form otic tissue beneath the hindbrain. Blocking expression of Bmp-antagonists blocks formation of medial otic tissue. These data show the importance of mesendodermal Bmp-antagonists for otic induction and that paraxial cephalic mesendoderm can facilitate its own otic differentiation under certain circumstances. Developmental Dynamics 238:1582-1594, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Hye-Joo Kwon
- Biology Department, Texas A&M University, College Station, Texas, USA
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90
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Harvey SA, Smith JC. Visualisation and quantification of morphogen gradient formation in the zebrafish. PLoS Biol 2009; 7:e1000101. [PMID: 19419239 PMCID: PMC2675906 DOI: 10.1371/journal.pbio.1000101] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Accepted: 03/18/2009] [Indexed: 11/18/2022] Open
Abstract
During embryonic development, signalling molecules known as morphogens act in a concentration-dependent manner to provide positional information to responding tissues. In the early zebrafish embryo, graded signalling by members of the nodal family induces the formation of mesoderm and endoderm, thereby patterning the embryo into three germ layers. Nodal signalling has also been implicated in the establishment of the dorso-ventral axis of the embryo. Although one can infer the existence of nodal gradients by comparing gene expression patterns in wild-type embryos and embryos in which nodal signalling is diminished or augmented, real understanding can only come from directly observing the gradients. One approach is to determine local ligand concentrations in the embryo, but this is technically challenging, and the presence of inhibitors might cause the effective concentration of a ligand to differ from its actual concentration. We have therefore taken two approaches to visualise a direct response to nodal signalling. In the first, we have used transgenic embryos to study the nuclear accumulation of a Smad2-Venus fusion protein, and in the second we have used bimolecular fluorescence complementation to visualise the formation of a complex between Smad2 and Smad4. This has allowed us to visualise, in living embryos, the formation of a graded distribution of nodal signalling activity. We have quantified the formation of the gradient in time and space, and our results not only confirm that nodal signalling patterns the embryo into three germ layers, but also shed light on its role in patterning the dorso-ventral axis and highlight unexpected complexities of mesodermal patterning. One of the earliest events in vertebrate embryonic development is the patterning of the embryo into three germ layers: the ectoderm, mesoderm, and endoderm. Morphogens are signalling molecules that act in a concentration-dependent manner to induce the formation of different cell types. Members of the nodal family are thought to form a morphogen gradient in the developing zebrafish embryo and to be essential for pattern formation. Mesoderm and endoderm are believed to develop due to high levels of nodal signalling, while cells experiencing the lowest concentrations of nodal signalling become ectoderm. Although this idea is widely accepted, the formation of a nodal morphogen gradient has never been observed directly, and we have therefore used two different approaches to visualise the intensity of nodal signalling within individual cells. Our approaches have allowed us to visualise a gradient of nodal signalling activity in the developing zebrafish embryo. Quantification of the levels of nodal signalling experienced by individual cells confirms that nodal signalling patterns the animal-vegetal axis of the zebrafish embryo and, in contrast to previous studies, also suggests that it plays a role in patterning the dorso-ventral axis of the zebrafish embryo. Gradients of nodal signalling in developing zebrafish embryos are visualized using a novel biofluorescence complementation reporter and quantified, demonstrating a role for nodal signalling in dorso-ventral patterning in addition to specifying the animal-vegetal axis.
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Affiliation(s)
- Steven A Harvey
- Wellcome Trust/CR-UK Gurdon Institute and Department of Zoology, The University of Cambridge, Cambridge, United Kingdom
| | - James C Smith
- Wellcome Trust/CR-UK Gurdon Institute and Department of Zoology, The University of Cambridge, Cambridge, United Kingdom
- MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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91
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O-GlcNAc modifications regulate cell survival and epiboly during zebrafish development. BMC DEVELOPMENTAL BIOLOGY 2009; 9:28. [PMID: 19383152 PMCID: PMC2680843 DOI: 10.1186/1471-213x-9-28] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2008] [Accepted: 04/21/2009] [Indexed: 12/27/2022]
Abstract
Background The post-translational addition of the monosaccharide O-linked β-N-acetylglucosamine (O-GlcNAc) regulates the activity of a wide variety of nuclear and cytoplasmic proteins. The enzymes O-GlcNAc Transferase (Ogt) and O-GlcNAcase (Oga) catalyze, respectively, the attachment and removal of O-GlcNAc to target proteins. In adult mice, Ogt and Oga attenuate the response to insulin by modifying several components of the signal transduction pathway. Complete loss of ogt function, however, is lethal to mouse embryonic stem cells, suggesting that the enzyme has additional, unstudied roles in development. We have utilized zebrafish as a model to determine role of O-GlcNAc modifications in development. Zebrafish has two ogt genes, encoding six different enzymatic isoforms that are expressed maternally and zygotically. Results We manipulated O-GlcNAc levels in zebrafish embryos by overexpressing zebrafish ogt, human oga or by injecting morpholinos against ogt transcripts. Each of these treatments results in embryos with shortened body axes and reduced brains at 24 hpf. The embryos had 23% fewer cells than controls, and displayed increased rates of cell death as early as the mid-gastrula stages. An extensive marker analysis indicates that derivatives of three germ layers are reduced to variable extents, and the embryos are severely disorganized after gastrulation. Overexpression of Ogt and Oga delayed epiboly and caused a severe disorganization of the microtubule and actin based cytoskeleton in the extra-embryonic yolk syncytial layer (YSL). The cytoskeletal defects resemble those previously reported for embryos lacking function of the Pou5f1/Oct4 transcription factor spiel ohne grenzen. Consistent with this, Pou5f1/Oct4 is modified by O-GlcNAc in human embryonic stem cells. Conclusion We conclude that O-GlcNAc modifications control the activity of proteins that regulate apoptosis and epiboly movements, but do not seem to regulate germ layer specification. O-GlcNAc modifies the transcription factor Spiel ohne grenzen/Pou5f1 and may regulate its activity.
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92
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Constam DB. Riding Shotgun: A Dual Role for the Epidermal Growth Factor-Cripto/FRL-1/Cryptic Protein Cripto in Nodal Trafficking. Traffic 2009; 10:783-91. [DOI: 10.1111/j.1600-0854.2009.00874.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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93
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Blanchet MH, Le Good JA, Oorschot V, Baflast S, Minchiotti G, Klumperman J, Constam DB. Cripto Localizes Nodal at the Limiting Membrane of Early Endosomes. Sci Signal 2008; 1:ra13. [DOI: 10.1126/scisignal.1165027] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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94
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Esterberg R, Delalande JM, Fritz A. Tailbud-derived Bmp4 drives proliferation and inhibits maturation of zebrafish chordamesoderm. Development 2008; 135:3891-901. [PMID: 18948415 DOI: 10.1242/dev.029264] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In zebrafish, BMP signaling establishes cell identity along the dorsoventral (DV) axis during gastrulation. Owing to the early requirements of BMP activity in DV patterning, it has been difficult to assign later roles in cell fate specification to specific BMP ligands. In this study, we have taken advantage of two follistatin-like genes (fstl1 and fstl2), as well as a transgenic zebrafish line carrying an inducible truncated form of the BMP-type 1 receptor to study the role of Bmp4 outside of the context of DV specification. Characterization of fstl1/2 suggests that they exert a redundant role as BMP antagonists during late gastrulation, regulating BMP activity in axial mesoderm. Maintenance of appropriate levels of BMP signaling is crucial for the proper development of chordamesoderm, a subset of axial mesoderm that gives rise to the notochord, but not prechordal mesoderm, which gives rise to the prechordal plate. Bmp4 activity in particular is required during a crucial window beginning at late gastrulation and lasting through early somitogenesis to promote chordamesoderm proliferation. In the absence of Bmp4, the notochord precursor pool is depleted, and the notochord differentiates prematurely. Our results illustrate a role for Bmp4 in the proliferation and timely differentiation of axial tissue after DV axis specification.
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95
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Hawkins TA, Cavodeassi F, Erdélyi F, Szabó G, Lele Z. The small molecule Mek1/2 inhibitor U0126 disrupts the chordamesoderm to notochord transition in zebrafish. BMC DEVELOPMENTAL BIOLOGY 2008; 8:42. [PMID: 18419805 PMCID: PMC2359734 DOI: 10.1186/1471-213x-8-42] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Accepted: 04/17/2008] [Indexed: 11/10/2022]
Abstract
Background Key molecules involved in notochord differentiation and function have been identified through genetic analysis in zebrafish and mice, but MEK1 and 2 have so far not been implicated in this process due to early lethality (Mek1-/-) and functional redundancy (Mek2-/-) in the knockout animals. Results Here, we reveal a potential role for Mek1/2 during notochord development by using the small molecule Mek1/2 inhibitor U0126 which blocks phosphorylation of the Mek1/2 target gene Erk1/2 in vivo. Applying the inhibitor from early gastrulation until the 18-somite stage produces a specific and consistent phenotype with lack of dark pigmentation, shorter tail and an abnormal, undulated notochord. Using morphological analysis, in situ hybridization, immunhistochemistry, TUNEL staining and electron microscopy, we demonstrate that in treated embryos the chordamesoderm to notochord transition is disrupted and identify disorganization in the medial layer of the perinotochordal basement mebrane as the probable cause of the undulations and bulges in the notochord. We also examined and excluded FGF as the upstream signal during this process. Conclusion Using the small chemical U0126, we have established a novel link between MAPK-signaling and notochord differentiation. Our phenotypic analysis suggests a potential connection between the MAPK-pathway, the COPI-mediated intracellular transport and/or the copper-dependent posttranslational regulatory processes during notochord differentiation.
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Affiliation(s)
- Thomas A Hawkins
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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96
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Xiang F, Hagos EG, Xu B, Sias C, Kawakami K, Burdine RD, Dougan ST. Nodal signals mediate interactions between the extra-embryonic and embryonic tissues in zebrafish. Dev Biol 2007; 310:363-78. [PMID: 17850782 PMCID: PMC2044568 DOI: 10.1016/j.ydbio.2007.08.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 07/18/2007] [Accepted: 08/03/2007] [Indexed: 10/23/2022]
Abstract
In many vertebrates, extra-embryonic tissues are important signaling centers that induce and pattern the germ layers. In teleosts, the mechanism by which the extra-embryonic yolk syncytial layer (YSL) patterns the embryo is not understood. Although the Nodal-related protein Squint is expressed in the YSL, its role in this tissue is not known. We generated a series of stable transgenic lines with GFP under the control of squint genomic sequences. In all species, nodal-related genes induce their own expression through a positive feedback loop. We show that two tissue specific enhancers in the zebrafish squint gene mediate the response to Nodal signals. Expression in the blastomeres depends upon a conserved Nodal response element (NRE) in the squint first intron, while expression in the extra-embryonic enveloping layer (EVL) is mediated by an element upstream of the transcription start site. Targeted depletion experiments demonstrate that the zebrafish Nodal-related proteins Squint and Cyclops are required in the YSL for endoderm and head mesoderm formation. Thus, Nodal signals mediate interactions between embryonic and extra-embryonic tissues in zebrafish that maintain nodal-related gene expression in the margin. Our results demonstrate a high degree of functional conservation between the extra-embryonic tissues of mouse and zebrafish.
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Affiliation(s)
- Fan Xiang
- Department of Cellular Biology, The University of Georgia, Athens, GA 30602
| | - Engda G. Hagos
- Department of Cellular Biology, The University of Georgia, Athens, GA 30602
| | - Bo Xu
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Christina Sias
- Department of Cellular Biology, The University of Georgia, Athens, GA 30602
| | - Koichi Kawakami
- Division of Molecular and Developmental Biology, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Rebecca D. Burdine
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Scott T. Dougan
- Department of Cellular Biology, The University of Georgia, Athens, GA 30602
- *Corresponding author Paul D. Coverdell Center for Biomedical and Health Sciences, 500 DW Brooks Dr., The University of Georgia, Athens, GA 30602, (706) 583-8194 (voice), (706) 542-4271 (fax),
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97
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Recent Papers on Zebrafish and Other Aquarium Fish Models. Zebrafish 2007. [DOI: 10.1089/zeb.2007.9987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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98
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Hagos EG, Fan X, Dougan ST. The role of maternal Activin-like signals in zebrafish embryos. Dev Biol 2007; 309:245-58. [PMID: 17692308 DOI: 10.1016/j.ydbio.2007.07.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2007] [Revised: 06/24/2007] [Accepted: 07/12/2007] [Indexed: 12/15/2022]
Abstract
Maternal Activin-like proteins, a subgroup of the TGF-beta superfamily, play a key role in establishing the body axes in many vertebrates, but their role in teleosts is unclear. At least two maternal Activin-like proteins are expressed in zebrafish, including the Vg1 orthologue, zDVR-1, and the nodal-related gene, Squint. Our analysis of embryos lacking both maternal and zygotic squint function revealed that maternal squint is required in some genetic backgrounds for the formation of dorsal and anterior tissues. Conditional inactivation of the ALK4, 5 and 7 receptors by SB-505124 treatment during the cleavage stages ruled out a role for maternal Squint, zDVR-1, or other Activin-like ligands before the mid-blastula transition, when the dorsal axis is established. Furthermore, we show that maternal Squint and zDVR-1 are not required during the cleavage stages to induce zygotic nodal-related gene expression. nodal-related gene expression decreases when receptor inhibition continues past the mid-blastula transition, resulting in a progressive loss of mesoderm and endoderm. We conclude that maternally expressed Activin-like signals do not act before the mid-blastula transition in zebrafish, but do have a variably penetrant role in the later stages of axis formation. This contrasts with the early role for these signals during Xenopus development.
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Affiliation(s)
- Engda G Hagos
- Department of Cellular Biology, The University of Georgia, Athens, GA 30602, USA
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