1
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Lange M, Ohnesorge N, Hoffmann D, Rocha SF, Benedito R, Siekmann AF. Zebrafish mutants in vegfab can affect endothelial cell proliferation without altering ERK phosphorylation and are phenocopied by loss of PI3K signaling. Dev Biol 2022; 486:26-43. [PMID: 35337795 PMCID: PMC11238767 DOI: 10.1016/j.ydbio.2022.03.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 12/23/2022]
Abstract
The formation of appropriately patterned blood vessel networks requires endothelial cell migration and proliferation. Signaling through the Vascular Endothelial Growth Factor A (VEGFA) pathway is instrumental in coordinating these processes. mRNA splicing generates short (diffusible) and long (extracellular matrix bound) Vegfa isoforms. The differences between these isoforms in controlling cellular functions are not understood. In zebrafish, vegfaa generates short and long isoforms, while vegfab only generates long isoforms. We found that mutations in vegfaa had an impact on endothelial cell (EC) migration and proliferation. Surprisingly, mutations in vegfab more strongly affected EC proliferation in distinct blood vessels, such as intersegmental blood vessels in the zebrafish trunk and central arteries in the head. Analysis of downstream signaling pathways revealed no change in MAPK (ERK) activation, while inhibiting PI3 kinase signaling phenocopied vegfab mutant phenotypes in affected blood vessels. Together, these results suggest that extracellular matrix bound Vegfa might act through PI3K signaling to control EC proliferation in a distinct set of blood vessels during angiogenesis.
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Affiliation(s)
- Martin Lange
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, D-48149, Muenster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Muenster, Muenster, Germany
| | - Nils Ohnesorge
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, D-48149, Muenster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Muenster, Muenster, Germany
| | - Dennis Hoffmann
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, D-48149, Muenster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Muenster, Muenster, Germany
| | - Susana F Rocha
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, E28029, Spain
| | - Rui Benedito
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, E28029, Spain
| | - Arndt F Siekmann
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, D-48149, Muenster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Muenster, Muenster, Germany; Department of Cell and Developmental Biology and Cardiovascular Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
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2
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Willsey HR, Guille M, Grainger RM. Modeling Human Genetic Disorders with CRISPR Technologies in Xenopus. Cold Spring Harb Protoc 2022; 2022:pdb.prot106997. [PMID: 34531330 DOI: 10.1101/pdb.prot106997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Combining the power of Xenopus developmental biology with CRISPR-based technologies promises great discoveries in understanding and treating human genetic disorders. Here we provide a practical pipeline for how to go from known disease gene(s) or risk gene(s) of interest to methods for gaining functional insight into the contribution of these genes to disorder etiology in humans.
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Affiliation(s)
- Helen Rankin Willsey
- Department of Psychiatry and Behavioral Sciences, Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, California 94143, USA;
| | - Matthew Guille
- European Xenopus Resource Centre, School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2UP, United Kingdom
| | - Robert M Grainger
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904, USA
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3
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Solini GE, Pownall ME, Hillenbrand MJ, Tocheny CE, Paudel S, Halleran AD, Bianchi CH, Huyck RW, Saha MS. Xenopus embryos show a compensatory response following perturbation of the Notch signaling pathway. Dev Biol 2020; 460:99-107. [PMID: 31899211 PMCID: PMC7263880 DOI: 10.1016/j.ydbio.2019.12.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 12/03/2019] [Accepted: 12/24/2019] [Indexed: 11/09/2022]
Abstract
As an essential feature of development, robustness ensures that embryos attain a consistent phenotype despite genetic and environmental variation. The growing number of examples demonstrating that embryos can mount a compensatory response to germline mutations in key developmental genes has heightened interest in the phenomenon of embryonic robustness. While considerable progress has been made in elucidating genetic compensation in response to germline mutations, the diversity, mechanisms, and limitations of embryonic robustness remain unclear. In this work, we have examined whether Xenopus laevis embryos are able to compensate for perturbations of the Notch signaling pathway induced by RNA injection constructs that either upregulate or inhibit this signaling pathway. Consistent with earlier studies, we found that at neurula stages, hyperactivation of the Notch pathway inhibited neural differentiation while inhibition of Notch signaling increases premature differentiation as assayed by neural beta tubulin expression. However, surprisingly, by hatching stages, embryos begin to compensate for these perturbations, and by swimming tadpole stages most embryos exhibited normal neuronal gene expression. Using cell proliferation and TUNEL assays, we show that the compensatory response is, in part, mediated by modulating levels of cell proliferation and apoptosis. This work provides an additional model for addressing the mechanisms of embryonic robustness and of genetic compensation.
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Affiliation(s)
- Grace E Solini
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Mark E Pownall
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Molly J Hillenbrand
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Claire E Tocheny
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Sudip Paudel
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Andrew D Halleran
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Catherine H Bianchi
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Ryan W Huyck
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA
| | - Margaret S Saha
- Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
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4
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Tu F, Sedzinski J, Ma Y, Marcotte EM, Wallingford JB. Protein localization screening in vivo reveals novel regulators of multiciliated cell development and function. J Cell Sci 2018; 131:jcs.206565. [PMID: 29180514 DOI: 10.1242/jcs.206565] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 11/20/2017] [Indexed: 12/23/2022] Open
Abstract
Multiciliated cells (MCCs) drive fluid flow in diverse tubular organs and are essential for the development and homeostasis of the vertebrate central nervous system, airway and reproductive tracts. These cells are characterized by dozens or hundreds of motile cilia that beat in a coordinated and polarized manner. In recent years, genomic studies have not only elucidated the transcriptional hierarchy for MCC specification but also identified myriad new proteins that govern MCC ciliogenesis, cilia beating and cilia polarization. Interestingly, this burst of genomic data has also highlighted that proteins with no obvious role in cilia do, in fact, have important ciliary functions. Understanding the function of proteins with little prior history of study presents a special challenge, especially when faced with large numbers of such proteins. Here, we define the subcellular localization in MCCs of ∼200 proteins not previously implicated in cilia biology. Functional analyses arising from the screen provide novel links between actin cytoskeleton and MCC ciliogenesis.
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Affiliation(s)
- Fan Tu
- Dept. of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Jakub Sedzinski
- Dept. of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.,The Danish Stem Cell Centre (DanStem), University of Copenhagen, 2200 Copenhagen, Denmark
| | - Yun Ma
- Dept. of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.,The Otorhinolaryngology Hospital, First Affiliated Hospital of Sun Yat-sen University, SunYat-sen University, Guangzhou, P.R. China
| | - Edward M Marcotte
- Dept. of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - John B Wallingford
- Dept. of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
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5
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Abstract
Electroporation allows targeting of genetic materials (e.g., DNA, RNA, antisense morpholinos) to the tissue of interest with high spatial and temporal specificity. Here, we describe a highly efficient and reproducible electroporation strategy for targeting the central nervous system in Xenopus. This versatile approach can be combined with live imaging or other existing experimental procedures to aid the investigation of different research questions.
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Affiliation(s)
- Hovy Ho-Wai Wong
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Christine E Holt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
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6
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Abstract
The amphibian Xenopus laevis has long been used as a model for studying vertebrate cell and developmental biology largely due to the easiness to manipulate this system in vivo and in vitro. While most of the developmental studies have been on Xenopus embryogenesis, considerable efforts have been made to understand its metamorphosis, a process mimicking postembryonic development in mammals when many organs mature into their adult forms in the presence of high levels of thyroid hormone (T3). Amphibian metamorphosis is totally dependent on T3 and offers a number of advantages for experimental analyses compared to the late stage, uterus-enclosed mammalian embryos. Earlier studies on metamorphosis in Xenopus laevis have revealed dual functions of T3 receptors (TR) during premetamorphic development and metamorphosis as well as important roles of TR-interacting corepressors and coactivators during these two periods, respectively. The development of gene-editing technologies that functions in amphibians in recent years has made possible for the first time to study function of endogenous TRs, especially in the highly related diploid anuran species Xenopus tropicalis. Here, we first review the current mechanistic understanding of the regulation of metamorphosis by T3 and TR, and then describe a detailed method to use TALEN to knock out TRα for studying its role in gene regulation by T3 in vivo and Xenopus development.
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Affiliation(s)
- Liezhen Fu
- Section on Molecular Morphogenesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Luan Wen
- Section on Molecular Morphogenesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Yun-Bo Shi
- Section on Molecular Morphogenesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA.
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7
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Abstract
Cilia are key organelles in development and homeostasis. The ever-expanding complement of cilia associated proteins necessitates rapid and tractable models for in vivo functional investigation. Xenopus laevis provides an attractive model for such studies, having multiple ciliated populations, including primary and multiciliated tissues. The rapid external development of Xenopus and the large cells make it an especially excellent platform for imaging studies. Here we present embryological and cell biological methods for the investigation of cilia structure and function in X. laevis, with a focus on quantitative live and fixed imaging.
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8
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Abstract
Antibody-based detection of protein distribution patterns both in wholemount and on sections revolutionized Xenopus research and ushered in the visual-based era of Xenopus data presentation. The ability to view the distribution of a gene product throughout an embryo makes it possible to rapidly map normal expression profiles and profiles that have been altered by an experimental intervention. The main limiting element in Xenopus immunostaining techniques has always been the availability of antibodies that work well on fixed whole embryos, a problem that persists. However, new antibodies are constantly being generated and improvements in detection systems allow antibodies that were once below the limits of detection to be utilized in multichannel immunofluorescence using tyramide amplification.
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9
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Colas AR, McKeithan WL, Cunningham TJ, Bushway PJ, Garmire LX, Duester G, Subramaniam S, Mercola M. Whole-genome microRNA screening identifies let-7 and mir-18 as regulators of germ layer formation during early embryogenesis. Genes Dev 2012; 26:2567-79. [PMID: 23152446 DOI: 10.1101/gad.200758.112] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Tight control over the segregation of endoderm, mesoderm, and ectoderm is essential for normal embryonic development of all species, yet how neighboring embryonic blastomeres can contribute to different germ layers has never been fully explained. We postulated that microRNAs, which fine-tune many biological processes, might modulate the response of embryonic blastomeres to growth factors and other signals that govern germ layer fate. A systematic screen of a whole-genome microRNA library revealed that the let-7 and miR-18 families increase mesoderm at the expense of endoderm in mouse embryonic stem cells. Both families are expressed in ectoderm and mesoderm, but not endoderm, as these tissues become distinct during mouse and frog embryogenesis. Blocking let-7 function in vivo dramatically affected cell fate, diverting presumptive mesoderm and ectoderm into endoderm. siRNA knockdown of computationally predicted targets followed by mutational analyses revealed that let-7 and miR-18 down-regulate Acvr1b and Smad2, respectively, to attenuate Nodal responsiveness and bias blastomeres to ectoderm and mesoderm fates. These findings suggest a crucial role for the let-7 and miR-18 families in germ layer specification and reveal a remarkable conservation of function from amphibians to mammals.
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10
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Liu Y, Szaro BG. hnRNP K post-transcriptionally co-regulates multiple cytoskeletal genes needed for axonogenesis. Development 2011; 138:3079-90. [PMID: 21693523 DOI: 10.1242/dev.066993] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The RNA-binding protein, hnRNP K, is essential for axonogenesis. Suppressing its expression in Xenopus embryos yields terminally specified neurons with severely disorganized microtubules, microfilaments and neurofilaments, raising the hypothesis that hnRNP K post-transcriptionally regulates multiple transcripts of proteins that organize the axonal cytoskeleton. To identify downstream candidates for this regulation, RNAs that co-immunoprecipitated from juvenile brain with hnRNP K were identified on microarrays. A substantial number of these transcripts were linked to the cytoskeleton and to intracellular localization, trafficking and transport. Injection into embryos of a non-coding RNA bearing multiple copies of an hnRNP K RNA-binding consensus sequence found within these transcripts largely phenocopied hnRNP K knockdown, further supporting the idea that it regulates axonogenesis through its binding to downstream target RNAs. For further study of regulation by hnRNP K of the cytoskeleton during axon outgrowth, we focused on three validated RNAs representing elements associated with all three polymers - Arp2, tau and an α-internexin-like neurofilament. All three were co-regulated post-transcriptionally by hnRNP K, as hnRNP K knockdown yielded comparable defects in their nuclear export and translation but not transcription. Directly knocking down expression of all three together, but not each one individually, substantially reproduced the axonless phenotype, providing further evidence that regulation of axonogenesis by hnRNP K occurs largely through pleiotropic effects on cytoskeletal-associated targets. These experiments provide evidence that hnRNP K is the nexus of a novel post-transcriptional regulatory module controlling the synthesis of proteins that integrate all three cytoskeletal polymers to form the axon.
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Affiliation(s)
- Yuanyuan Liu
- Department of Biological Sciences and the Center for Neuroscience Research, University at Albany, State University of New York, Albany, NY 12222, USA
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11
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McCoy KE, Zhou X, Vize PD. Non-canonical wnt signals antagonize and canonical wnt signals promote cell proliferation in early kidney development. Dev Dyn 2011; 240:1558-66. [PMID: 21465621 DOI: 10.1002/dvdy.22626] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2011] [Indexed: 11/11/2022] Open
Abstract
Canonical and non-canonical wnt signals often have opposed roles. In this report, we use developing Xenopus embryos to demonstrate a novel anti-proliferative role for non-canonical wnt signals in the very earliest stages of kidney development. Non-canonical wnt signals were down-regulated using PDZ domain mutants of dishevelled 2 and up-regulated using wild-type vang-like 2, while canonical signals were manipulated using dominant-negative forms of lef1 or treatment with lithium. When non-canonical signals are down-regulated in the developing Xenopus pronephros, cell proliferation rates increased and when canonical signals were shutdown the opposite occurred. Treatment with lithium chloride has a powerful pro-proliferative effect on the forming nephric primordium. Together these data show that in addition to previously documented antagonisms between these distinct wnt signaling pathways, they also have opposing effects on cell division.
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Affiliation(s)
- Kyle E McCoy
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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12
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Rosa A, Brivanlou AH. Synthetic mRNAs: powerful tools for reprogramming and differentiation of human cells. Cell Stem Cell 2011; 7:549-50. [PMID: 21040893 DOI: 10.1016/j.stem.2010.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this issue of Cell Stem Cell, Warren et al. (2010) describe a new methodology, using synthetic mRNA, for efficiently generating iPSCs without compromising genomic integrity. This powerful approach can also be used for directed differentiation of iPSCs, or even for trans-differentiation to generate clinically relevant differentiated cell types.
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Affiliation(s)
- Alessandro Rosa
- Laboratory of Molecular Vertebrate Embryology, The Rockefeller University, New York, NY 10065, USA
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13
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Abstract
Xenopus laevis embryos are particularly well suited to address questions requiring either knockdown or overexpression of genes in a tissue-specific fashion during vertebrate embryonic development. These manipulations are achieved by targeted injection of either antisense morpholino oligonucleotides or synthetic mRNAs, respectively, into the early embryo. Herein we offer detailed protocols describing how to design and perform these experiments successfully, as well as a brief discussion of considerations for performing a microarray analysis in this organism.
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Affiliation(s)
- Mizuho S Mimoto
- Department of Cell and Developmental Biology, Oregon Health and Science University, School of Medicine, Portland, OR, USA
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14
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Aw S, Koster J, Pearson W, Nichols C, Shi NQ, Carneiro K, Levin M. The ATP-sensitive K(+)-channel (K(ATP)) controls early left-right patterning in Xenopus and chick embryos. Dev Biol 2010; 346:39-53. [PMID: 20643119 PMCID: PMC2937067 DOI: 10.1016/j.ydbio.2010.07.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 06/21/2010] [Accepted: 07/08/2010] [Indexed: 11/17/2022]
Abstract
Consistent left-right asymmetry requires specific ion currents. We characterize a novel laterality determinant in Xenopus laevis: the ATP-sensitive K(+)-channel (K(ATP)). Expression of specific dominant-negative mutants of the Xenopus Kir6.1 pore subunit of the K(ATP) channel induced randomization of asymmetric organ positioning. Spatio-temporally controlled loss-of-function experiments revealed that the K(ATP) channel functions asymmetrically in LR patterning during very early cleavage stages, and also symmetrically during the early blastula stages, a period when heretofore largely unknown events transmit LR patterning cues. Blocking K(ATP) channel activity randomizes the expression of the left-sided transcription of Nodal. Immunofluorescence analysis revealed that XKir6.1 is localized to basal membranes on the blastocoel roof and cell-cell junctions. A tight junction integrity assay showed that K(ATP) channels are required for proper tight junction function in early Xenopus embryos. We also present evidence that this function may be conserved to the chick, as inhibition of K(ATP) in the primitive streak of chick embryos randomizes the expression of the left-sided gene Sonic hedgehog. We propose a model by which K(ATP) channels control LR patterning via regulation of tight junctions.
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Affiliation(s)
- Sherry Aw
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
- Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Joseph Koster
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Wade Pearson
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Colin Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Nian-Qing Shi
- Department of Medicine, University of Wisconsin, Madison, WI 53706, USA
| | - Katia Carneiro
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
| | - Michael Levin
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
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15
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Kieserman EK, Lee C, Gray RS, Park TJ, Wallingford JB. High-magnification in vivo imaging of Xenopus embryos for cell and developmental biology. Cold Spring Harb Protoc 2010; 2010:pdb.prot5427. [PMID: 20439414 DOI: 10.1101/pdb.prot5427] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Embryos of the frog Xenopus laevis are an ideal model system for in vivo imaging of dynamic biological processes, from the inner workings of individual cells to the reshaping of tissues during embryogenesis. Their externally developing embryos are more amenable to in vivo analysis than internally developing mammalian embryos, and the large size of the embryos make them particularly suitable for time-lapse analysis of tissue-level morphogenetic events. In addition, individual cells in Xenopus embryos are larger than those in other vertebrate models, making them ideal for imaging cell behavior and subcellular processes (e.g., following the dynamics of fluorescent fusion proteins in living or fixed cells and tissues). Xenopus embryos are amenable to simple manipulations of gene function, including knockdown and misexpression, and the large number of embryos available allows even an inexperienced researcher to perform hundreds of such manipulations per day. Transgenesis is quite effective as well. Finally, because the fate map of Xenopus embryos is stereotypical, simple targeted microinjections can reliably deliver reagents into specific tissues and cell types for gene manipulation or for imaging. Although yolk opacity can hinder deep imaging in intact embryos, almost any cell in the early embryo can be placed into organotypic culture, such that the cells of interest are directly apposed to the cover glass. Furthermore, live imaging techniques can be complemented with immunostaining and in situ hybridization approaches in fixed tissues. This protocol describes methods for labeling and high-magnification time-lapse imaging of cell biological and developmental processes in Xenopus embryos by confocal microscopy.
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Affiliation(s)
- Esther K Kieserman
- Howard Hughes Medical Institute and Section of Molecular Cell and Developmental Biology, University of Texas, Austin, TX 78712, USA
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16
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Sheets MD, Fritz B, Hartley RS, Zhang Y. Polyribosome analysis for investigating mRNA translation in Xenopus oocytes, eggs and embryos. Methods 2010; 51:152-6. [PMID: 20096782 DOI: 10.1016/j.ymeth.2010.01.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 01/16/2010] [Accepted: 01/19/2010] [Indexed: 10/19/2022] Open
Abstract
The earliest stages of animal development occur without the benefit of zygotic transcription. The absence of transcription necessitates that all changes in the levels of specific proteins must be controlled by post-transcriptional mechanisms, such as the regulated translation of stored maternal mRNAs. One of the major challenges to investigating translational mechanisms is the availability of reliable methods for assaying the translational state of specific mRNAs. The most definitive assay of an mRNA's translational state is polyribosome association; mRNAs actively translated are engaged with polyribosomes while mRNAs translationally repressed are not. While linear gradient centrifugation is commonly used to purify polyribosomes from a wide variety of cell types in different organisms, the isolation of polyribosomes from Xenopus oocytes, eggs and embryos presents some unique challenges. Here we detail the methodology for the isolation and analysis of polyribosomes from Xenopus oocytes, eggs and embryos using step gradient centrifugation. We present detailed protocols, describe the critical controls and provide several examples to guide the interpretation of experimental results regarding the translational state of specific mRNAs.
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Affiliation(s)
- M D Sheets
- University of Wisconsin School of Medicine and Public Health, Department of Biomolecular Chemistry, Madison, WI 53706, USA.
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17
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Smith EM, Mitsi M, Nugent MA, Symes K. PDGF-A interactions with fibronectin reveal a critical role for heparan sulfate in directed cell migration during Xenopus gastrulation. Proc Natl Acad Sci U S A 2009; 106:21683-8. [PMID: 19966216 PMCID: PMC2799789 DOI: 10.1073/pnas.0902510106] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Indexed: 12/18/2022] Open
Abstract
Platelet-derived growth factor (PDGF) signaling is essential for processes involving cell motility and differentiation during embryonic development in a wide variety of organisms including the mouse, frog, zebrafish, and sea urchin. In early Xenopus laevis embryos, PDGF-AA provides guidance cues for the migration of anterior mesendoderm cells as they move across a fibronectin-rich extracellular matrix. The long form of PDGF-A includes a positively charged carboxyl-terminal retention motif that can interact with the extracellular matrix and heparan sulfate proteoglycans (HSPGs). In this study we demonstrate that PDGF-AA binds directly to fibronectin and that this association is greatly enhanced by heparin. The PDGF-AA-fibronectin binding occurs across a broad range of pHs (5.5-9), which is significant because the PDGF-guided migration of Xenopus mesendoderm cells occurs under basic extracellular conditions (pH 8.4). We further demonstrate that endogenous HSPG's are required for the PDGF-AA-guided mesendoderm movement, suggesting an in vivo role for HSPGs in mediating the interaction between PDGF-AA and fibronectin.
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Affiliation(s)
- Erin M. Smith
- Department of Biochemistry, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118; and
| | - Maria Mitsi
- Department of Biochemistry, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118; and
- Institute of Biologically Oriented Materials, Eidgenössische Technische Hochschule Zürich, Wolfgang-Pauli-Strasse 10, HCI F443 (Hönggerberg), CH-8093 Zürich, Switzerland
| | - Matthew A. Nugent
- Department of Biochemistry, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118; and
| | - Karen Symes
- Department of Biochemistry, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118; and
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18
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Abstract
Despite intense study, the role of the immune system in detecting (immunosurveillance), controlling and remodeling (immunoediting) neoplasia remains elusive. We present here a comparative view of the complex interactions between neoplasia and the host immune system. We provide evidence, in the amphibian Xenopus laevis, consistent with an evolutionarily conserved and crucial role of the immune system in controlling neoplasia, which involves a striking variety of anti-tumoral immune effectors including conventional CTLs, classical MHC class Ia unrestricted CTLs (CCU-CTLs) that interact with nonclassical MHC class Ib molecules, CD8 NKT-like cells and NK cells. We also review the tumors found in X. laevis with an emphasis on thymic lymphoid tumors and a rare ovarian dysgerminoma. Finally, we consider the use of X. laevis for in vivo study of tumorigenesis. Given our current knowledge, the experimental systems already established in X. laevis, and the rapid accumulation of genetic resources for the sister species Silurana (Xenopus) tropicalis, it is our conviction that these species provide an ideal alternative to the murine system for studying tumorigenesis and tumor immunity.
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Affiliation(s)
- Ana Goyos
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
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19
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Involvement of Mos-MEK-MAPK pathway in cytostatic factor (CSF) arrest in eggs of the parthenogenetic insect, Athalia rosae. Mech Dev 2008; 125:996-1008. [PMID: 18793721 DOI: 10.1016/j.mod.2008.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 07/17/2008] [Accepted: 08/26/2008] [Indexed: 01/23/2023]
Abstract
Extensive survey of meiotic metaphase II arrest during oocyte maturation in vertebrates revealed that the mitogen-activated protein kinase (MAPK) pathway regulated by the c-mos proto-oncogene product, Mos, has an essential role in cytostatic activity, termed cytostatic factor (CSF). In contrast, little is known in invertebrates in which meiotic arrest occurs in most cases at metaphase I (MI arrest). A parthenogenetic insect, the sawfly Athalia rosae, in which artificial egg activation is practicable, has advantages to investigate the mechanisms of MI arrest. Both the MAPK/extracellular signal-regulated protein kinase kinase (MEK) and MAPK were phosphorylated and maintained active in MI-arrested sawfly eggs, whereas they were dephosphorylated soon after egg activation. Treatment of MI-arrested eggs with U0126, an inhibitor of MEK, resulted in dephosphorylation of MAPK and MI arrest was resumed. The sawfly c-mos gene orthologue encoding a serine/threonine kinase was cloned and analyzed. It was expressed in nurse cells in the ovaries. To examine CSF activity of the sawfly Mos, synthesized glutathione S-transferase (GST)-fusion sawfly Mos protein was injected into MI-resumed eggs in which MEK and MAPK were dephosphorylated. Both MEK and MAPK were phosphorylated again upon injection. In these GST-fusion sawfly Mos-injected eggs subsequent mitotic (syncytial) divisions were blocked and embryonic development was ceased. These results demonstrated that the MEK-MAPK pathway was involved in maintaining CSF arrest in sawfly eggs and Mos functioned as its upstream regulatory molecule.
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Colas A, Cartry J, Buisson I, Umbhauer M, Smith JC, Riou JF. Mix.1/2-dependent control of FGF availability during gastrulation is essential for pronephros development in Xenopus. Dev Biol 2008; 320:351-65. [DOI: 10.1016/j.ydbio.2008.05.547] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 04/30/2008] [Accepted: 05/20/2008] [Indexed: 10/22/2022]
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21
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Developmental regulation of central spindle assembly and cytokinesis during vertebrate embryogenesis. Curr Biol 2008; 18:116-23. [PMID: 18207743 DOI: 10.1016/j.cub.2007.12.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Revised: 12/10/2007] [Accepted: 12/12/2007] [Indexed: 11/24/2022]
Abstract
Mitosis and cytokinesis not only ensure the proper segregation of genetic information but also contribute importantly to morphogenesis in embryos. Cytokinesis is controlled by the central spindle, a microtubule-based structure containing numerous microtubule motors and microtubule-binding proteins, including PRC1. We show here that central spindle assembly and function differ dramatically between two related populations of epithelial cells in developing vertebrate embryos examined in vivo. Compared to epidermal cells, early neural epithelial cells undergo exaggerated anaphase chromosome separation, rapid furrowing, and a marked reduction of microtubule density in the spindle midzone. Cytokinesis in normal early neural epithelial cells thus resembles that in cultured vertebrate cells experimentally depleted of PRC1. We find that PRC1 mRNA and protein expression is surprisingly dynamic in early vertebrate embryos and that neural-plate cells contain less PRC1 than do epidermal cells. Expression of excess PRC1 ameliorates both the exaggerated anaphase and reduced midzone microtubule density observed in early neural epithelial cells. These PRC1-mediated modifications to the cytokinetic mechanism may be related to the specialization of the midbody in neural cells. These data suggest that PRC1 is a dose-dependent regulator of the central spindle in vertebrate embryos and demonstrate unexpected plasticity to fundamental mechanisms of cell division.
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22
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Morokuma J, Blackiston D, Levin M. KCNQ1 and KCNE1 K+ channel components are involved in early left-right patterning in Xenopus laevis embryos. Cell Physiol Biochem 2008; 21:357-72. [PMID: 18453744 PMCID: PMC3632048 DOI: 10.1159/000129628] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2008] [Indexed: 01/12/2023] Open
Abstract
Several ion transporters have been implicated in left-right (LR) patterning. Here, we characterize a new component of the early bioelectrical circuit: the potassium channel KCNQ1 and its accessory subunit KCNE1. Having cloned the native Xenopus versions of both genes, we show that both are asymmetrically localized as maternal proteins during the first few cleavages of frog embryo development in a process dependent on microtubule and actin organization. Molecular loss-of-function using dominant negative constructs demonstrates that both gene products are required for normal LR asymmetry. We propose a model whereby these channels provide an exit path for K(+) ions brought in by the H(+),K(+)-ATPase. This physiological module thus allows the obligate but electroneutral H(+),K(+)-ATPase to generate an asymmetric voltage gradient on the left and right sides. Our data reveal a new, bioelectrical component of the mechanisms patterning a large-scale axis in vertebrate embryogenesis.
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Affiliation(s)
- Junji Morokuma
- Center for Regenerative and Developmental Biology, Forsyth Institute, Developmental Biology Department, Harvard School of Dental Medicine, Boston, MA 02115, USA
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23
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Aw S, Adams DS, Qiu D, Levin M. H,K-ATPase protein localization and Kir4.1 function reveal concordance of three axes during early determination of left-right asymmetry. Mech Dev 2008; 125:353-72. [PMID: 18160269 PMCID: PMC2346612 DOI: 10.1016/j.mod.2007.10.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 10/05/2007] [Accepted: 10/24/2007] [Indexed: 12/23/2022]
Abstract
Consistent laterality is a fascinating problem, and study of the Xenopus embryo has led to molecular characterization of extremely early steps in left-right patterning: bioelectrical signals produced by ion pumps functioning upstream of asymmetric gene expression. Here, we reveal a number of novel aspects of the H+/K+-ATPase module in chick and frog embryos. Maternal H+/K+-ATPase subunits are asymmetrically localized along the left-right, dorso-ventral, and animal-vegetal axes during the first cleavage stages, in a process dependent on cytoskeletal organization. Using a reporter domain fused to molecular motors, we show that the cytoskeleton of the early frog embryo can provide asymmetric, directional information for subcellular transport along all three axes. Moreover, we show that the Kir4.1 potassium channel, while symmetrically expressed in a dynamic fashion during early cleavages, is required for normal LR asymmetry of frog embryos. Thus, Kir4.1 is an ideal candidate for the K+ ion exit path needed to allow the electroneutral H+/K+-ATPase to generate voltage gradients. In the chick embryo, we show that H+/K+-ATPase and Kir4.1 are expressed in the primitive streak, and that the known requirement for H+/K+-ATPase function in chick asymmetry does not function through effects on the circumferential expression pattern of Connexin43. These data provide details crucial for the mechanistic modeling of the physiological events linking subcellular processes to large-scale patterning and suggest a model where the early cytoskeleton sets up asymmetric ion flux along the left-right axis as a system of planar polarity functioning orthogonal to the apical-basal polarity of the early blastomeres.
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Affiliation(s)
- Sherry Aw
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dany S. Adams
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dayong Qiu
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Michael Levin
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
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Leung KM, Holt CE. Live visualization of protein synthesis in axonal growth cones by microinjection of photoconvertible Kaede into Xenopus embryos. Nat Protoc 2008; 3:1318-27. [PMID: 18714300 PMCID: PMC3687492 DOI: 10.1038/nprot.2008.113] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Photoconvertible fluorescent proteins, such as Kaede, can be switched irreversibly from their native color to a new one. This property can be exploited to visualize de novo mRNA translation, because newly synthesized proteins can be distinguished from preexisting ones by their color. In this protocol, Kaede cDNA linked to the 3' untranslated region (UTR) of beta-actin is delivered into cells fated to become the retina by injection into Xenopus blastomeres. Brief exposure (6-10 s) to UV light (350-410 nm) of Kaede-positive retinal axons/growth cones efficiently converts Kaede from its native green fluorescence to red. The reappearance of the green signal reports the synthesis of new Kaede protein. This approach can be used to investigate the spatiotemporal control of translation of specific mRNAs in response to external stimuli and to test the efficiency of full-length versus mutant UTRs. The 3-d protocol can be adapted for broad use with other photoactivatable fluorescent proteins.
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Affiliation(s)
- Kin-Mei Leung
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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25
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Ogino H, McConnell WB, Grainger RM. High-throughput transgenesis in Xenopus using I-SceI meganuclease. Nat Protoc 2007; 1:1703-10. [PMID: 17487153 DOI: 10.1038/nprot.2006.208] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this report we describe an easy, highly efficient transgenesis method for Xenopus. The method is very simple; a commercially available meganuclease, I-SceI, is incubated with a transgene construct carrying its recognition sites, and is subsequently microinjected into fertilized eggs. Approximately 30% (in Xenopus tropicalis) or 20% (in Xenopus laevis) of injected embryos exhibit non-mosaic, promoter-dependent transgene expression, and transgenes from the founder animals are transmitted to offspring. The method is compatible with mRNA or antisense morpholino oligonucleotide injection, and these secondary reagents can be introduced simultaneously or sequentially with a transgene to test their interaction. This high-throughput transgenic technique will be a powerful tool for studying the complex wiring of regulatory networks at the genome-wide level, as well as for facilitating genetic studies in the rapidly breeding diploid frog, X. tropicalis.
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Affiliation(s)
- Hajime Ogino
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904, USA
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26
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Falk J, Drinjakovic J, Leung KM, Dwivedy A, Regan AG, Piper M, Holt CE. Electroporation of cDNA/Morpholinos to targeted areas of embryonic CNS in Xenopus. BMC DEVELOPMENTAL BIOLOGY 2007; 7:107. [PMID: 17900342 PMCID: PMC2147031 DOI: 10.1186/1471-213x-7-107] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Accepted: 09/27/2007] [Indexed: 02/07/2023]
Abstract
Background Blastomere injection of mRNA or antisense oligonucleotides has proven effective in analyzing early gene function in Xenopus. However, functional analysis of genes involved in neuronal differentiation and axon pathfinding by this method is often hampered by earlier function of these genes during development. Therefore, fine spatio-temporal control of over-expression or knock-down approaches is required to specifically address the role of a given gene in these processes. Results We describe here an electroporation procedure that can be used with high efficiency and low toxicity for targeting DNA and antisense morpholino oligonucleotides (MOs) into spatially restricted regions of the Xenopus CNS at a critical time-window of development (22–50 hour post-fertilization) when axonal tracts are first forming. The approach relies on the design of "electroporation chambers" that enable reproducible positioning of fixed-spaced electrodes coupled with accurate DNA/MO injection. Simple adjustments can be made to the electroporation chamber to suit the shape of different aged embryos and to alter the size and location of the targeted region. This procedure can be used to electroporate separate regions of the CNS in the same embryo allowing separate manipulation of growing axons and their intermediate and final targets in the brain. Conclusion Our study demonstrates that electroporation can be used as a versatile tool to investigate molecular pathways involved in axon extension during Xenopus embryogenesis. Electroporation enables gain or loss of function studies to be performed with easy monitoring of electroporated cells. Double-targeted transfection provides a unique opportunity to monitor axon-target interaction in vivo. Finally, electroporated embryos represent a valuable source of MO-loaded or DNA transfected cells for in vitro analysis. The technique has broad applications as it can be tailored easily to other developing organ systems and to other organisms by making simple adjustments to the electroporation chamber.
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Affiliation(s)
- Julien Falk
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Jovana Drinjakovic
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Kin Mei Leung
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Asha Dwivedy
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Aoife G Regan
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Michael Piper
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
- The Queensland Brain Institute, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Christine E Holt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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27
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Fink M, Flekna G, Ludwig A, Heimbucher T, Czerny T. Improved translation efficiency of injected mRNA during early embryonic development. Dev Dyn 2007; 235:3370-8. [PMID: 17068769 DOI: 10.1002/dvdy.20995] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Injection techniques are a powerful approach to study gene function in fish and frog model systems. In particular, in vitro transcribed mRNA is broadly used for such misexpression experiments. Sequence elements flanking the coding region, such as untranslated repeats and polyadenylation sequences, are known to affect the stability and the translation efficiency of mRNA. Here we show that in early embryos, poly(A) signals strongly contribute to the activity of the injected mRNA. Of interest, they only marginally affect mRNA stability, whereas the translation efficiency is dramatically enhanced. Combination of a poly(A) tail and an SV40 late poly(A) signal leads to highly synergistic effects of the two elements for injected mRNA. Compared with established vector systems, we detected a 20-fold improvement for mRNA derived from the novel transcription vector pMC.
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Affiliation(s)
- Maria Fink
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine, Vienna, Austria
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28
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Lee C, Scherr HM, Wallingford JB. Shroom family proteins regulate gamma-tubulin distribution and microtubule architecture during epithelial cell shape change. Development 2007; 134:1431-41. [PMID: 17329357 DOI: 10.1242/dev.02828] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cell shape changes require the coordination of actin and microtubule cytoskeletons. The molecular mechanisms by which such coordination is achieved remain obscure, particularly in the context of epithelial cells within developing vertebrate embryos. We have identified a novel role for the actin-binding protein Shroom3 as a regulator of the microtubule cytoskeleton during epithelial morphogenesis. We show that Shroom3 is sufficient and also necessary to induce a redistribution of the microtubule regulator gamma-tubulin. Moreover, this change in gamma-tubulin distribution underlies the assembly of aligned arrays of microtubules that drive apicobasal cell elongation. Finally, experiments with the related protein, Shroom1, demonstrate that gamma-tubulin regulation is a conserved feature of this protein family. Together, the data demonstrate that Shroom family proteins govern epithelial cell behaviors by coordinating the assembly of both microtubule and actin cytoskeletons.
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Affiliation(s)
- Chanjae Lee
- Department of Molecular Cell and Developmental Biology, and Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA
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29
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Cartry J, Nichane M, Ribes V, Colas A, Riou JF, Pieler T, Dollé P, Bellefroid EJ, Umbhauer M. Retinoic acid signalling is required for specification of pronephric cell fate. Dev Biol 2006; 299:35-51. [PMID: 16979153 DOI: 10.1016/j.ydbio.2006.06.047] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 06/20/2006] [Accepted: 06/27/2006] [Indexed: 10/24/2022]
Abstract
The mechanisms by which a subset of mesodermal cells are committed to a nephrogenic fate are largely unknown. In this study, we have investigated the role of retinoic acid (RA) signalling in this process using Xenopus laevis as a model system and Raldh2 knockout mice. Pronephros formation in Xenopus embryo is severely impaired when RA signalling is inhibited either through expression of a dominant-negative RA receptor, or by expressing the RA-catabolizing enzyme XCyp26 or through treatment with chemical inhibitors. Conversely, ectopic RA signalling expands the size of the pronephros. Using a transplantation assay that inhibits RA signalling specifically in pronephric precursors, we demonstrate that this signalling is required within this cell population. Timed antagonist treatments show that RA signalling is required during gastrulation for expression of Xlim-1 and XPax-8 in pronephric precursors. Moreover, experiments conducted with a protein synthesis inhibitor indicate that RA may directly regulate Xlim-1. Raldh2 knockout mouse embryos fail to initiate the expression of early kidney-specific genes, suggesting that implication of RA signalling in the early steps of kidney formation is evolutionary conserved in vertebrates.
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Affiliation(s)
- Jérôme Cartry
- Laboratoire de Biologie du Développement, équipe Signalisation et Morphogenèse, UMR CNRS 7622, Université Paris VI, 9 quai Saint-Bernard, 75005 Paris, France
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30
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Li WM, Webb SE, Lee KW, Miller AL. Recruitment and SNARE-mediated fusion of vesicles in furrow membrane remodeling during cytokinesis in zebrafish embryos. Exp Cell Res 2006; 312:3260-75. [PMID: 16876784 DOI: 10.1016/j.yexcr.2006.06.028] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 06/14/2006] [Accepted: 06/19/2006] [Indexed: 11/21/2022]
Abstract
Cytokinesis is the final stage in cell division that serves to partition cytoplasm and daughter nuclei into separate cells. Membrane remodeling at the cleavage plane is a required feature of cytokinesis in many species. In animal cells, however, the precise mechanisms and molecular interactions that mediate this process are not yet fully understood. Using real-time imaging in live, early stage zebrafish embryos, we demonstrate that vesicles labeled with the v-SNARE, VAMP-2, are recruited to the cleavage furrow during deepening in a microtubule-dependent manner. These vesicles then fuse with, and transfer their VAMP-2 fluorescent label to, the plasma membrane during both furrow deepening and subsequent apposition. This observation indicates that new membrane is being inserted during these stages of cytokinesis. Inhibition of SNAP-25 (a cognate t-SNARE of VAMP-2), using a monoclonal antibody, blocked VAMP-2 vesicle fusion and furrow apposition. Transient expression of mutant forms of SNAP-25 also produced defects in furrow apposition. SNAP-25 inhibition by either method, however, did not have any significant effect on furrow deepening. Thus, our data clearly indicate that VAMP-2 and SNAP-25 play an essential role in daughter blastomere apposition, possibly via the delivery of components that promote the cell-to-cell adhesion required for the successful completion of cytokinesis. Our results also support the idea that new membrane addition, which occurs during late stage cytokinesis, is not required for furrow deepening that results from contractile band constriction.
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Affiliation(s)
- Wai Ming Li
- Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, PRC
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31
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Urban AE, Zhou X, Ungos JM, Raible DW, Altmann CR, Vize PD. FGF is essential for both condensation and mesenchymal-epithelial transition stages of pronephric kidney tubule development. Dev Biol 2006; 297:103-17. [PMID: 16872594 DOI: 10.1016/j.ydbio.2006.04.469] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 04/10/2006] [Accepted: 04/28/2006] [Indexed: 11/25/2022]
Abstract
The pronephros is a transient embryonic kidney that is essential for the survival of aquatic larvae. It is also absolutely critical for adult kidney development, as the pronephric derivative the wolffian duct forms the ductal system of the adult kidney and also triggers the condensation of metanephric mesenchyme into the adult nephrons. While exploring Xenopus pronephric patterning, we observed that epidermally delivered hedgehog completely suppresses pronephric kidney tubule development but does not effect development of the pronephric glomus, the equivalent of the mammalian glomerulus or corpuscle. This effect is not mediated by apoptosis. Microarray analysis of microdissected primordia identified FGF8 as one of the potential mediators of hedgehog action. Further investigation demonstrated that SU5402-sensitive FGF signaling plays a critical role in the very earliest stages of pronephric tubule development. Modulation of FGF8 activity using a morpholino has a later effect that blocks condensation of pronephric mesenchyme into the pronephric tubule. Together, these data show that FGF signaling plays a critical role at two stages of embryonic kidney development, one in the condensation of the pronephric primordium from the intermediate mesoderm and a second in the later epithelialization of this mesenchyme into the pronephric nephron. The data also show that in Xenopus, development of the glomus/glomerulus can be uncoupled from nephron formation via ectopic hedgehog expression and provides an experimental avenue for investigating glomerulogenesis in the complete absence of tubules.
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Affiliation(s)
- Anna E Urban
- Department of Biological Science, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
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32
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Adams DS, Robinson KR, Fukumoto T, Yuan S, Albertson RC, Yelick P, Kuo L, McSweeney M, Levin M. Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates. Development 2006; 133:1657-71. [PMID: 16554361 PMCID: PMC3136117 DOI: 10.1242/dev.02341] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Biased left-right asymmetry is a fascinating and medically important phenomenon. We provide molecular genetic and physiological characterization of a novel, conserved, early, biophysical event that is crucial for correct asymmetry: H+ flux. A pharmacological screen implicated the H+-pump H+-V-ATPase in Xenopus asymmetry, where it acts upstream of early asymmetric markers. Immunohistochemistry revealed an actin-dependent asymmetry of H+-V-ATPase subunits during the first three cleavages. H+-flux across plasma membranes is also asymmetric at the four- and eight-cell stages, and this asymmetry requires H+-V-ATPase activity. Abolishing the asymmetry in H+ flux, using a dominant-negative subunit of the H+-V-ATPase or an ectopic H+ pump, randomized embryonic situs without causing any other defects. To understand the mechanism of action of H+-V-ATPase, we isolated its two physiological functions, cytoplasmic pH and membrane voltage (Vmem) regulation. Varying either pH or Vmem, independently of direct manipulation of H+-V-ATPase, caused disruptions of normal asymmetry, suggesting roles for both functions. V-ATPase inhibition also abolished the normal early localization of serotonin, functionally linking these two early asymmetry pathways. The involvement of H+-V-ATPase in asymmetry is conserved to chick and zebrafish. Inhibition of the H+-V-ATPase induces heterotaxia in both species; in chick, H+-V-ATPase activity is upstream of Shh; in fish, it is upstream of Kupffer's vesicle and Spaw expression. Our data implicate H+-V-ATPase activity in patterning the LR axis of vertebrates and reveal mechanisms upstream and downstream of its activity. We propose a pH- and Vmem-dependent model of the early physiology of LR patterning.
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Affiliation(s)
- Dany S. Adams
- The Forsyth Center for Regenerative and Developmental Biology, and Department of Developmental Biology, Harvard School of Dental Medicine, 140 The Fenway, Boston, MA 02115, USA
| | - Kenneth R. Robinson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47906, USA
| | - Takahiro Fukumoto
- Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA
| | - Shipeng Yuan
- Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - R. Craig Albertson
- Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA
| | - Pamela Yelick
- Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA
| | - Lindsay Kuo
- Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA
| | - Megan McSweeney
- Department of Cytokine Biology, The Forsyth Institute, 140 The Fenway, Boston, MA 02115, USA
| | - Michael Levin
- The Forsyth Center for Regenerative and Developmental Biology, and Department of Developmental Biology, Harvard School of Dental Medicine, 140 The Fenway, Boston, MA 02115, USA
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33
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Ogino H, McConnell WB, Grainger RM. Highly efficient transgenesis in Xenopus tropicalis using I-SceI meganuclease. Mech Dev 2006; 123:103-13. [PMID: 16413175 DOI: 10.1016/j.mod.2005.11.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Revised: 11/23/2005] [Accepted: 11/23/2005] [Indexed: 02/07/2023]
Abstract
In this study, we report a highly efficient transgenesis technique for Xenopus tropicalis based on a method described first for Medaka. This simple procedure entails co-injection of meganuclease I-SceI and a transgene construct flanked by two I-SceI sites into fertilized eggs. Approximately 30% of injected embryos express transgenes in a promoter-dependent manner. About 1/3 of such embryos show incorporation of the transgene at the one-cell stage and the remainder are 'half-transgenics' suggesting incorporation at the two-cell stage. Transgenes from both classes of embryos are shown to be transmitted and expressed in offspring. The procedure also works efficiently in Xenopus laevis. Because the needle injection procedure does not significantly damage embryos, a high fraction develop normally and can, as well, be injected with a second reagent, for example an mRNA or antisense morpholino oligonucleotide, thus allowing one to perform several genetic manipulations on embryos at one time. This simple and efficient technique will be a powerful tool for high-throughput transgenesis assays in founder animals, and for facilitating genetic studies in the fast-breeding diploid frog, X. tropicalis.
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Affiliation(s)
- Hajime Ogino
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
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34
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Allen BG, Weeks DL. Transgenic Xenopus laevis embryos can be generated using phiC31 integrase. Nat Methods 2006; 2:975-9. [PMID: 16299484 PMCID: PMC3552317 DOI: 10.1038/nmeth814] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 10/17/2005] [Indexed: 01/15/2023]
Abstract
Bacteriophage phiC31 encodes an integrase that can mediate the insertion of extrachromosomal DNA into genomic DNA. Here we show that the coinjection of mRNA encoding phiC31 integrase with plasmid DNA encoding the green fluorescent protein (GFP) can be used to generate transgenic X. laevis embryos. Despite integration into the genome, appropriate promoter expression required modification of the reporter plasmid by bracketing the GFP reporter gene with tandem copies of the chicken beta-globin 5' HS4 insulator to relieve silencing owing to chromatin position effects. These experiments demonstrate that the integration of insulated gene sequences using phiC31 integrase can be used to efficiently create transgenic embryos in X. laevis and may increase the practical use of phiC31 integrase in other systems as well.
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Affiliation(s)
- Bryan G Allen
- Department of Biochemistry, Bowen Science Building, University of Iowa, Iowa City, Iowa 52242, USA
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35
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Pickard B, Damjanovski S. Overexpression of the tissue inhibitor of metalloproteinase-3 during Xenopus embryogenesis affects head and axial tissue formation. Cell Res 2005; 14:389-99. [PMID: 15538971 DOI: 10.1038/sj.cr.7290239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Tissue inhibitors of metalloproteinases (TIMPs) modulate extracellular matrix remodeling during embryonic development and disease. TIMP-3 expression was examined during Xenopus laevis embryogenesis: TIMP-3 transcripts detected in the maternal pool of RNA increased at the mid-blastula transition, decreased dramatically during gastrulation and increased again during neurulation and axis elongation. Interestingly, the decrease during gastrulation was not seen in LiCl treated (dorsalized) embryos. Whole mount in situ hybridization of TIMP-3 using DIG-labeled RNA probes demonstrated that the transcripts were present in all dorsal tissues during embryogenesis, but were prominent only in head structures starting at stage 35. Overexpression of TIMP-3 through transgenesis and RNA injections led to developmental abnormalities and death. Both overexpression strategies resulted in post-gastrulation perturbation including those to neural and head structures, as well as truncated axes. However, RNA injections resulted in more severe early defects such as failure of neural tube closure, and transgenesis caused truncated axes and head abnormalities. No transgenic embryo expressing TIMP-3 survived past stage 40.
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Affiliation(s)
- Bryce Pickard
- Department of Biology, University of Western Ontario, London, Ontario, Canada
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36
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Ataliotis P, Ivins S, Mohun TJ, Scambler PJ. XTbx1 is a transcriptional activator involved in head and pharyngeal arch development inXenopus laevis. Dev Dyn 2005; 232:979-91. [PMID: 15736267 DOI: 10.1002/dvdy.20276] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The development of pharyngeal arch derivatives in mouse and zebrafish embryos depends on the activity of the transcription factor Tbx1. We cloned the Xenopus laevis orthologue of Tbx1 (XTbx1) and show that the pattern of expression is similar to that in other vertebrate species. Zygotic transcripts are first detected shortly after the mid-blastula transition and are localized to the presumptive mesoderm at mid-gastrula stages. XTbx1 expression persists in the lateral plate mesoderm at neurula stages and is found in the pharyngeal arches and otic vesicles from early tail bud stages onward. We demonstrate that XTbx1 is a transcriptional activator and that this trans-activation requires the C-terminal region of the protein. A dominant interfering mutant of XTbx1 disrupts the development of Xenopus head structures and pharyngeal arch derivatives. Lineage labeling reveals a requirement for XTbx1 function in cells that contribute to the pharyngeal mesoderm and for fgf8 expression.
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Affiliation(s)
- Paris Ataliotis
- Molecular Medicine Unit, Institute of Child Health, London WC1N 1EH, United Kingdom.
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37
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Bunney TD, De Boer AH, Levin M. Fusicoccin signaling reveals 14-3-3 protein function as a novel step in left-right patterning during amphibian embryogenesis. Development 2003; 130:4847-58. [PMID: 12930777 DOI: 10.1242/dev.00698] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
To gain insight into the molecular mechanisms underlying the control of morphogenetic signals by H+ flux during embryogenesis, we tested Fusicoccin-A (FC), a compound produced by the fungus Fusicoccum amygdali Del. In plant cells, FC complexes with 14-3-3 proteins to activate H+ pumping across the plasma membrane. It has long been thought that FC acts on higher plants only; here, we show that exposing frog embryos to FC during early development specifically results in randomization of the asymmetry of the left-right (LR) axis (heterotaxia). Biochemical and molecular-genetic evidence is presented that 14-3-3-family proteins are an obligate component of Xenopus FC receptors and that perturbation of 14-3-3 protein function results in heterotaxia. The subcellular localization of 14-3-3 mRNAs and proteins reveals novel cytoplasmic destinations, and a left-right asymmetry at the first cell division. Using gain-of-function and loss-of-function experiments, we show that 14-3-3E protein is likely to be an endogenous and extremely early aspect of LR patterning. These data highlight a striking conservation of signaling pathways across kingdoms, suggest common mechanisms of polarity establishment between C. elegans and vertebrate embryos, and uncover a novel entry point into the pathway of left-right asymmetry determination.
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Affiliation(s)
- Tom D Bunney
- Vrije Universiteit, Faculty of Earth and Life Sciences, Department of Developmental Genetics, Section Molecular Plant Physiology and Biophysics, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
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38
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Penzo-Mendèz A, Umbhauer M, Djiane A, Boucaut JC, Riou JF. Activation of Gbetagamma signaling downstream of Wnt-11/Xfz7 regulates Cdc42 activity during Xenopus gastrulation. Dev Biol 2003; 257:302-14. [PMID: 12729560 DOI: 10.1016/s0012-1606(03)00067-8] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Wnt-11/Xfz7 signaling plays a major role in the regulation of convergent extension movements affecting the dorsal marginal zone (DMZ) of gastrulating Xenopus embryos. In order to provide data concerning the molecular targets of Wnt-11/Xfz7 signals, we have analyzed the regulation of the Rho GTPase Cdc42 by Wnt-11. In animal cap ectoderm, Cdc42 activity increases as a response to Wnt-11 expression. This increase is inhibited by pertussis toxin, or sequestration of free Gbetagamma subunits by exogenous Galphai2 or Galphat. Activation of Cdc42 is also produced by the expression of bovine Gbeta1 and Ggamma2. This process is abolished by a PKC inhibitor, while phorbol esther treatment of ectodermal explants activates Cdc42 in a PKC-dependent way, implicating PKC downstream of Gbetagamma. In activin-treated animal caps and in the embryo, interference with Gbetagamma signaling rescues morphogenetic movements inhibited by Wnt-11 hyperactivation, thus phenocopying the dominant negative version of Cdc42 (N(17)Cdc42). Conversely, expression of Gbeta1gamma2 blocks animal cap elongation. This effect is reversed by N(17)Cdc42. Together, our results strongly argue for a role of Gbetagamma signaling in the regulation of Cdc42 activity downstream of Wnt-11/Xfz7 in mesodermal cells undergoing convergent extension. This idea is further supported by the observation that expression of Galphat in the DMZ causes severe gastrulation defects.
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Affiliation(s)
- Alfredo Penzo-Mendèz
- Laboratoire de Biologie du Dévelopment, groupe Biologie Expérimentale, UMR CNRS 7622, Université Paris VI, 9 quai Saint-Bernard, 75005 Paris, France
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39
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Abler LL, Sheets MD. Expression of scFv antibodies in Xenopus embryos to disrupt protein function: implications for large-scale evaluation of the embryonic proteome. Genesis 2003; 35:107-13. [PMID: 12533793 DOI: 10.1002/gene.10171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SUMMARY We evaluated the use of single-chain antibody (scFv) expression as a tool to disrupt the function of specific proteins in embryos of the frog, Xenopus laevis. The expression of scFvs that recognize the bone morphogenetic protein receptor (ALK3) or the fibroblast growth factor receptor1 (FGFR1) as endoplasmic reticulum-anchored proteins caused distinct developmental defects that were virtually indistinguishable from the defects caused by expression of the dominant negative forms of each receptor. These results demonstrate that scFvs from phage-display libraries can be readily fashioned into effective and specific inhibitors of signaling pathways in developing embryos. In addition, as several effective scFvs against a specific target can be isolated rapidly, this approach represents a valuable new tool for large-scale functional analysis of the embryonic proteome.
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MESH Headings
- Activin Receptors, Type I/metabolism
- Activin Receptors, Type I/physiology
- Animals
- Antibodies/metabolism
- Bone Morphogenetic Protein Receptors, Type I
- Endoplasmic Reticulum/metabolism
- Enzyme-Linked Immunosorbent Assay
- Immunoglobulin Variable Region/immunology
- Immunohistochemistry
- In Situ Hybridization
- Peptide Library
- Protein Binding
- Protein Serine-Threonine Kinases
- Protein Structure, Tertiary
- Proteome/analysis
- RNA, Messenger/metabolism
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptor Protein-Tyrosine Kinases/physiology
- Receptor, Fibroblast Growth Factor, Type 1
- Receptors, Fibroblast Growth Factor/metabolism
- Receptors, Fibroblast Growth Factor/physiology
- Receptors, Growth Factor
- Signal Transduction
- Time Factors
- Xenopus laevis/embryology
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Affiliation(s)
- Lisa L Abler
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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40
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Lim W, Furlow JD. Ribozyme suppression of endogenous thyroid hormone receptor activity in Xenopus laevis cells. Nucleic Acids Res 2002; 30:3490-6. [PMID: 12140335 PMCID: PMC137085 DOI: 10.1093/nar/gkf461] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Xenopus laevis is an excellent model for thyroid hormone (T3)-regulated gene expression. T3 initiates two drastically different pathways during metamorphosis: death of larval tissues and growth of adult tissues. The role that each T3 receptor (TR) isotype, alpha and beta, plays in metamorphosis is uncertain. The X.laevis tetraploid genome limits experiments to overexpression, misexpression and dominant negative studies. Ribozymes offer an alternative by suppressing gene activity through specific mRNA reduction. It has been suggested that ribozymes will not work in X.laevis because of the organism's intracellular environment and body temperature. In this study, we show that hammerhead ribozymes are active in vitro against transcribed TRbeta message and in vivo against a TRbeta-luciferase fusion protein. We next show that TRbeta-targeted ribozymes can inhibit T3-induced transcription of a reporter gene in cultured X.laevis cells, using T3 response elements from two T3-responsive transcription factor genes. One has early expression kinetics in response to T3 and is proposed to be TRalpha regulated whereas the other has intermediate induction kinetics and thus may be partially TRbeta regulated. Therefore, ribozymes are a potentially valuable tool for overcoming the limitations in this system for examining gene function in X.laevis.
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Affiliation(s)
- Wayland Lim
- Section of Neurobiology, Physiology and Behavior, Division of Biological Sciences, University of California, Davis, CA 95616, USA
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41
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Kitaguchi T, Mizugishi K, Hatayama M, Aruga J, Mikoshiba K. Xenopus Brachyury regulates mesodermal expression of Zic3, a gene controlling left-right asymmetry. Dev Growth Differ 2002; 44:55-61. [PMID: 11869292 DOI: 10.1046/j.1440-169x.2002.00624.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Brachyury gene has a critical role in the formation of posterior mesoderm and notochord in vertebrate development. A recent study showed that Brachyury is also responsible for the formation of the left-right (L-R) axis in mouse and zebrafish. However, the role of Brachyury in L-R axis specification is still elusive. Here, it is demonstrated that Brachyury is involved in L-R specification of the Xenopus laevis embryo and regulates expression of Zic3, which controls the L-R specification process. Overexpression of Xenopus Brachyury (Xbra) and dominant-negative type Xbra (Xbra-EnR) altered the orientation of heart and gut looping, concomitant with disturbed laterality of nodal-related 1 (Xnr1) and Pitx2 expression, both of which are normally expressed in the left lateral plate mesoderm. Furthermore, activation of inducible type Xbra (Xbra-GR) induces Zic3 expression within 20 min. These results suggest that a role of Brachyury in L-R specification may be the direct regulation of Zic3 expression.
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Affiliation(s)
- Tetsuya Kitaguchi
- Laboratory for Developmental Neurobiology, Riken Brain Science Institute, Wako-shi, Saitama 351-0198, Japan
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42
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Saito R, Fujita N, Nagata S. Overexpression of Fyn tyrosine kinase causes abnormal development of primary sensory neurons in Xenopus laevis embryos. Dev Growth Differ 2001; 43:229-38. [PMID: 11422288 DOI: 10.1046/j.1440-169x.2001.00568.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The expression and function of the Src family protein tyrosine kinase Fyn in Xenopus laevis embryos have been examined. In situ hybridization analysis demonstrated nervous system-specific expression of Fyn mRNA in tail-bud embryos. However, a class of primary sensory neurons; that is, Rohon-Beard (RB) neurons, which is positive for immunoglobulin superfamily cell adhesion molecules (CAM), neural cell adhesion molecule (N-CAM) and contactin, is devoid of Fyn expression. Injection of Fyn mRNA into one of the blastomeres at the 2-cell stage led to overexpression of Fyn in the injected half of the tail-bud embryos. Immunolabeling of the embryos with anti-HNK-1 antibody revealed that the peripheral axons of RB neurons were partially misguided and bound to each other to form abnormal subcutaneous fascicles. Similar abnormality was induced by injection of the Fyn overexpression vector. The incidence of abnormality appeared dose-dependent, being 68-92% of the injected embryos at 50-400 pg of mRNA. Co-injection of the contactin antisense vector depleted contactin mRNA accumulation without affecting Fyn overexpression and reduced the incidence of the abnormal RB-cell phenotype. However, the N-CAM antisense was ineffective in reducing this abnormality. These results suggest that Fyn can modify signals regulating axonal guidance or fasciculation in the developing X. laevis nervous system and that contactin may affect this action of Fyn.
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Affiliation(s)
- R Saito
- Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Tokyo 112-8681, Japan
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43
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Kil SH, Collazo A. Origins of inner ear sensory organs revealed by fate map and time-lapse analyses. Dev Biol 2001; 233:365-79. [PMID: 11336501 DOI: 10.1006/dbio.2001.0211] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The inner ear develops from a simple ectodermal thickening called the otic placode into a labyrinth of chambers which house sensory organs that sense sound and are used to maintain balance. Although the morphology and function of the sensory organs are well characterized, their origins and lineage relationships are virtually unknown. In this study, we generated a fate map of Xenopus laevis inner ear at otic placode and otocyst stages to determine the developmental origins of the sensory organs. Our lineage analysis shows that all regions of the otic placode and otocyst can give rise to the sensory organs of the inner ear, though there were differences between labeled quadrants in the range of derivatives formed. A given region often gives rise to cells in multiple sensory organs, including cells that apparently dispersed from anterior to posterior poles and vice versa. These results suggest that a single sensory organ arises from cells in different parts of the placode or otocyst and that cell mixing plays a large role in ear development. Time-lapse videomicroscopy provides further evidence that cells from opposite regions of the inner ear mix during the development of the inner ear, and this mixing begins at placode stages. Lastly, bone morphogenetic protein 4 (BMP-4), a member of the transforming growth factor beta (TGF-beta) family, is expressed in all sensory organs of the frog inner ear, as it is in the developing chicken ear. Inner ear fate maps provide a context for interpreting gene expression patterns and embryological manipulations.
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Affiliation(s)
- S H Kil
- Leslie and Susan Gonda (Goldschmied) Department of Cell and Molecular Biology, House Ear Institute, 2100 West Third Street, Los Angeles, California 90057, USA
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44
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Quivy JP, Grandi P, Almouzni G. Dimerization of the largest subunit of chromatin assembly factor 1: importance in vitro and during Xenopus early development. EMBO J 2001; 20:2015-27. [PMID: 11296234 PMCID: PMC125230 DOI: 10.1093/emboj/20.8.2015] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2000] [Revised: 02/01/2001] [Accepted: 02/20/2001] [Indexed: 11/14/2022] Open
Abstract
To date, the in vivo importance of chromatin assembly factors during development in vertebrates is unknown. Chromatin assembly factor 1 (CAF-1) represents the best biochemically characterized factor promoting chromatin assembly during DNA replication or repair in human cell-free systems. Here, we identify a Xenopus homologue of the largest subunit of CAF-1 (p150). Novel dimerization properties are found conserved in both Xenopus and human p150. A region of 36 amino acids required for p150 dimerization was identified. Deletion of this domain abolishes the ability of p150 to promote chromatin assembly in vitro. A dominant-negative interference based on these dimerization properties occurs both in vitro and in vivo. In the embryo, nuclear organization was severely affected and cell cycle progression was impaired during the rapid early cleaving stages of Xenopus development. We propose that the rapid proliferation at early developmental stages necessitates the unique properties of an assembly factor that can ensure a tight coupling between DNA replication or repair and chromatin assembly.
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Affiliation(s)
| | - Paola Grandi
- Laboratoire de Dynamique Nucléaire et Plasticité du Génome (UMR 218 du CNRS), Institut Curie/Section de Recherche, 26 rue d’Ulm, 75231 Paris Cedex 05, France
Present address; CellZome, Meyerhofstrasse 1, D-69117 Heidelberg, Germany Corresponding author e-mail: J.-P.Quivy and P.Grandi contributed equally to this work
| | - Geneviève Almouzni
- Laboratoire de Dynamique Nucléaire et Plasticité du Génome (UMR 218 du CNRS), Institut Curie/Section de Recherche, 26 rue d’Ulm, 75231 Paris Cedex 05, France
Present address; CellZome, Meyerhofstrasse 1, D-69117 Heidelberg, Germany Corresponding author e-mail: J.-P.Quivy and P.Grandi contributed equally to this work
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45
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Standley HJ, Zorn AM, Gurdon JB. eFGF and its mode of action in the community effect during Xenopus myogenesis. Development 2001; 128:1347-57. [PMID: 11262235 DOI: 10.1242/dev.128.8.1347] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The community effect is an interaction among a group of many nearby precursor cells, necessary for them to maintain tissue-specific gene expression and differentiate co-ordinately. During Xenopus myogenesis, the muscle precursor cells must be in group contact throughout gastrulation in order to develop into terminally differentiated muscle. The molecular basis of this community interaction has not to date been elucidated. We have developed an assay for testing potential community factors, in which isolated muscle precursor cells are treated with a candidate protein and cultured in dispersion. We have tested a number of candidate factors and we find that only eFGF protein is able to mediate a community effect, stimulating stable muscle-specific gene expression in demonstrably single muscle precursor cells. In contrast, Xwnt8, bFGF, BMP4 and TGF(β)2 do not show this capacity. We show that eFGF is expressed in the muscle precursor cells at the right time to mediate the community effect. Moreover, the time when the muscle precursor cells are sensitive to eFGF corresponds to the period of the endogenous community effect. Finally, we demonstrate that FGF signalling is essential for endogenous community interactions. We conclude that eFGF is likely to mediate the community effect in Xenopus myogenesis.
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Affiliation(s)
- H J Standley
- Wellcome/CRC Institute, Tennis Court Road, Cambridge, CB2 1QR and Department of Zoology, University of Cambridge, UK
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46
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Yamashita A, Katsube T, Hashimoto N, Tomita K, Takahisa M, Ueda R, Togashi S. Identification of Xenopus Cortactin: Two Isoforms of the Transcript and Multiple Forms of the Protein. Zoolog Sci 2001. [DOI: 10.2108/zsj.18.331] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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47
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Takahashi T, Koshimizu U, Abe H, Obinata T, Nakamura T. Functional involvement of Xenopus LIM kinases in progression of oocyte maturation. Dev Biol 2001; 229:554-67. [PMID: 11150247 DOI: 10.1006/dbio.2000.9999] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
LIM kinases (LIMK), including LIMK1 and LIMK2, are unique LIM-family proteins containing a catalytic (kinase) domain. These kinases phosphorylate an actin-depolymerizing factor, cofilin, involved in the regulation of actin-filament dynamics. An unanswered question is the in vivo function of LIMK and how they contribute to development. When we cloned Xenopus homologues of mammalian LIMK, Xlimk1 and Xlimk2, we found that their mRNA and products were abundantly expressed in oocytes. In addition, we obtained evidence for the functional involvement of Xlimk1/2 during oocyte maturation. The microinjection of Xlimk1/2 mRNA into progesterone-treated oocytes significantly inhibited the appearance of a white maturation spot (WMS), an indicator of entry into meiosis. In oocytes lacking a WMS, the organization and/or migration of the microtubule-derived precursor of the meiotic spindle was predominantly affected. We also found that the ectopic expression of Xlimk1/2 clearly prevented dephosphorylation (activation) of Xenopus cofilin (XAC) during oocyte maturation. Furthermore, co-injection of Xlimk1/2 with the constitutively active type of XAC overcame the inhibitory effects by Xlimk1/2, suggesting that XLIMK-induced abnormality in oocyte maturation was mediated by XAC inactivation. Based on these findings, we propose that XLIMK is a putative regulator of cytoskeletal rearrangements during oocyte maturation, and the interaction between XLIMK activity and microtubule dynamics seems highly likely.
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Affiliation(s)
- T Takahashi
- Division of Biochemistry, Department of Oncology, Biomedical Research Center B7, Osaka University Medical School, Suita, Osaka, 565-0871, Japan
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48
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Wang W, Mariani FV, Harland RM, Luo K. Ski represses bone morphogenic protein signaling in Xenopus and mammalian cells. Proc Natl Acad Sci U S A 2000; 97:14394-9. [PMID: 11121043 PMCID: PMC18929 DOI: 10.1073/pnas.97.26.14394] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The bone morphogenic proteins (BMPs) play important roles in vertebrate development. In Xenopus, BMPs act as epidermal inducers and also as negative regulators of neurogenesis. Antagonism of BMP signaling results in neuralization. BMPs signal through the cell-surface receptors and downstream Smad molecules. Upon stimulation with BMP, Smad1, Smad5, and Smad8 are phosphorylated by the activated BMP receptors, form a complex with Smad4, and translocate into the nucleus, where they regulate the expression of BMP target genes. Here, we show that the Ski oncoprotein can block BMP signaling and the expression of BMP-responsive genes in both Xenopus and mammalian cells by directly interacting with and repressing the activity of BMP-specific Smad complexes. This ability to antagonize BMP signaling results in neuralization by Ski in the Xenopus embryo and blocking of osteoblast differentiation of murine W-20-17 cells. Thus, Ski is able to repress the activity of all receptor-associated Smads and may regulate vertebrate development by modulating the signaling activity of transforming growth factor-beta family members.
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Affiliation(s)
- W Wang
- Life Sciences Division, Lawrence Berkeley National Laboratory, and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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49
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Kitaguchi T, Nagai T, Nakata K, Aruga J, Mikoshiba K. Zic3 is involved in the left-right specification of the Xenopus embryo. Development 2000; 127:4787-95. [PMID: 11044394 DOI: 10.1242/dev.127.22.4787] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Establishment of left-right (L-R) asymmetry is fundamental to vertebrate development. Several genes involved in L-R asymmetry have been described. In the Xenopus embryo, Vg1/activin signals are implicated upstream of asymmetric nodal related 1 (Xnr1) and Pitx2 expression in L-R patterning. We report here that Zic3 carries the left-sided signal from the initial activin-like signal to determinative factors such as Pitx2. Overexpression of Zic3 on the right side of the embryo altered the orientation of heart and gut looping, concomitant with disturbed laterality of expression of Xnr1 and Pitx2, both of which are normally expressed in the left lateral plate mesoderm. The results indicate that Zic3 participates in the left-sided signaling upstream of Xnr1 and Pitx2. At early gastrula, Zic3 was expressed not only in presumptive neuroectoderm but also in mesoderm. Correspondingly, overexpression of Zic3 was effective in the L-R specification at the early gastrula stage, as revealed by a hormone-inducible Zic3 construct. The Zic3 expression in the mesoderm is induced by activin (beta) or Vg1, which are also involved in the left-sided signal in L-R specification. These findings suggest that an activin-like signal is a potent upstream activator of Zic3 that establishes the L-R axis. Furthermore, overexpression of the zinc-finger domain of Zic3 on the right side is sufficient to disturb the L-R axis, while overexpression of the N-terminal domain on the left side affects the laterality. These results suggest that Zic3 has at least two functionally important domains that play different roles and provide a molecular basis for human heterotaxy, which is an L-R pattern anomaly caused by a mutation in human ZIC3.
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Affiliation(s)
- T Kitaguchi
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan. jp
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50
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Abstract
The photoreceptor layer in the retina of Xenopus laevis harbors a circadian clock. Many molecular components known to drive the molecular clock in other organisms have been identified in Xenopus, such as XClock, Xper2, and Xcrys, demonstrating phylogenetic conservation. This model system displays a wide array of rhythms, including melatonin release, ERG rhythms, and retinomotor movements, suggesting that the ocular clock is important for proper retinal function. A flow-through culture system allows measurements of retinal rhythms such as melatonin release in vitro over time from a single eyecup. This system is suited for pharmacological perturbations of the clock, and has led to important observations regarding the circadian control of melatonin release, the roles of light and dopamine as entraining agents, and the circadian mechanisms regulating retinomotor movements. The development of a transgenic technique in Xenopus allows precise and reliable molecular perturbations. Since it is possible to follow rhythms in eyecups obtained from adults or tadpoles, the combination of the flow-through culture system and the transgenic technique leads to the fast generation of transgenic tadpoles to monitor the effects of molecular perturbations on the clock.
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Affiliation(s)
- F E Anderson
- Department of Biology, NSF Center for Biological Timing, University of Virginia, Charlottesville, Virginia 22903, USA
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