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Pera EM, Nilsson-De Moura J, Pomeshchik Y, Roybon L, Milas I. Inhibition of the serine protease HtrA1 by SerpinE2 suggests an extracellular proteolytic pathway in the control of neural crest migration. eLife 2024; 12:RP91864. [PMID: 38634469 PMCID: PMC11026092 DOI: 10.7554/elife.91864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2024] Open
Abstract
We previously showed that SerpinE2 and the serine protease HtrA1 modulate fibroblast growth factor (FGF) signaling in germ layer specification and head-to-tail development of Xenopus embryos. Here, we present an extracellular proteolytic mechanism involving this serpin-protease system in the developing neural crest (NC). Knockdown of SerpinE2 by injected antisense morpholino oligonucleotides did not affect the specification of NC progenitors but instead inhibited the migration of NC cells, causing defects in dorsal fin, melanocyte, and craniofacial cartilage formation. Similarly, overexpression of the HtrA1 protease impaired NC cell migration and the formation of NC-derived structures. The phenotype of SerpinE2 knockdown was overcome by concomitant downregulation of HtrA1, indicating that SerpinE2 stimulates NC migration by inhibiting endogenous HtrA1 activity. SerpinE2 binds to HtrA1, and the HtrA1 protease triggers degradation of the cell surface proteoglycan Syndecan-4 (Sdc4). Microinjection of Sdc4 mRNA partially rescued NC migration defects induced by both HtrA1 upregulation and SerpinE2 downregulation. These epistatic experiments suggest a proteolytic pathway by a double inhibition mechanism. SerpinE2 ┤HtrA1 protease ┤Syndecan-4 → NC cell migration.
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Affiliation(s)
- Edgar M Pera
- Vertebrate Developmental Biology Laboratory, Department of Laboratory Medicine, Lund Stem Cell Center, University of LundLundSweden
| | - Josefine Nilsson-De Moura
- Vertebrate Developmental Biology Laboratory, Department of Laboratory Medicine, Lund Stem Cell Center, University of LundLundSweden
| | - Yuriy Pomeshchik
- iPSC Laboratory for CNS Disease Modeling, Department of Experimental Medical Science, Lund Stem Cell Center, Strategic Research Area MultiPark, Lund UniversityLundSweden
| | - Laurent Roybon
- iPSC Laboratory for CNS Disease Modeling, Department of Experimental Medical Science, Lund Stem Cell Center, Strategic Research Area MultiPark, Lund UniversityLundSweden
| | - Ivana Milas
- Vertebrate Developmental Biology Laboratory, Department of Laboratory Medicine, Lund Stem Cell Center, University of LundLundSweden
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2
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Tokarz J, Schmitt SM, Möller G, Brändli AW, Adamski J. Functional characterization of two 20β-hydroxysteroid dehydrogenase type 2 homeologs from Xenopus laevis reveals multispecificity. J Steroid Biochem Mol Biol 2021; 210:105874. [PMID: 33722706 DOI: 10.1016/j.jsbmb.2021.105874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 02/25/2021] [Accepted: 03/09/2021] [Indexed: 11/23/2022]
Abstract
The African clawed frog, Xenopus laevis, is a versatile model for biomedical research and is largely similar to mammals in terms of organ development, anatomy, physiology, and hormonal signaling mechanisms. Steroid hormones control a variety of processes and their levels are regulated by hydroxysteroid dehydrogenases (HSDs). The subfamily of 20β-HSD type 2 enzymes currently comprises eight members from teleost fish and mammals. Here, we report the identification of three 20β-HSD type 2 genes in X. tropicalis and X. laevis and the functional characterization of the two homeologs from X. laevis. X. laevis Hsd20b2.L and Hsd20b2.S showed high sequence identity with known 20β-HSD type 2 enzymes and mapped to the two subgenomes of the allotetraploid frog genome. Both homeologs are expressed during embryonic development and in adult tissues, with strongest signals in liver, kidney, intestine, and skin. After recombinant expression in human cell lines, both enzymes co-localized with the endoplasmic reticulum and catalyzed the conversion of cortisone to 20β-dihydrocortisone. Both Hsd20b2.L and Hsd20b2.S catalyzed the 20β-reduction of further C21 steroids (17α-hydroxyprogesterone, progesterone, 11-deoxycortisol, 11-deoxycorticosterone), while only Hsd20b2.S was able to convert corticosterone and cortisol to their 20β-reduced metabolites. Estrone was only a poor and androstenedione no substrate for both enzymes. Our results demonstrate multispecificity of 20β-HSD type 2 enzymes from X. laevis similar to other teleost 20β-HSD type 2 enzymes. X. laevis 20β-HSD type 2 enzymes are probably involved in steroid catabolism and in the generation of pheromones for intraspecies communication. A role in oocyte maturation is unlikely.
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Affiliation(s)
- Janina Tokarz
- Helmholtz Zentrum München, German Research Center for Environmental Health, Research Unit Molecular Endocrinology and Metabolism, Neuherberg, Germany.
| | - Stefan M Schmitt
- Walter Brendel Centre of Experimental Medicine, University Hospital and Ludwig-Maximilians-University Munich, Munich, Germany
| | - Gabriele Möller
- Helmholtz Zentrum München, German Research Center for Environmental Health, Research Unit Molecular Endocrinology and Metabolism, Neuherberg, Germany
| | - André W Brändli
- Walter Brendel Centre of Experimental Medicine, University Hospital and Ludwig-Maximilians-University Munich, Munich, Germany
| | - Jerzy Adamski
- Helmholtz Zentrum München, German Research Center for Environmental Health, Research Unit Molecular Endocrinology and Metabolism, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Lehrstuhl für Experimentelle Genetik, Technische Universität München, Freising-Weihenstephan, Germany; Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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3
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Abdul-Wajid S, Morales-Diaz H, Khairallah SM, Smith WC. T-type Calcium Channel Regulation of Neural Tube Closure and EphrinA/EPHA Expression. Cell Rep 2015; 13:829-839. [PMID: 26489462 DOI: 10.1016/j.celrep.2015.09.035] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 08/06/2015] [Accepted: 09/11/2015] [Indexed: 10/22/2022] Open
Abstract
A major class of human birth defects arise from aberrations during neural tube closure (NTC). We report on a NTC signaling pathway requiring T-type calcium channels (TTCCs) that is conserved between primitive chordates (Ciona) and Xenopus. With loss of TTCCs, there is a failure to seal the anterior neural folds. Accompanying loss of TTCCs is an upregulation of EphrinA effectors. Ephrin signaling is known to be important in NTC, and ephrins can affect both cell adhesion and repulsion. In Ciona, ephrinA-d expression is downregulated at the end of neurulation, whereas, with loss of TTCC, ephrinA-d remains elevated. Accordingly, overexpression of ephrinA-d phenocopied TTCC loss of function, while overexpression of a dominant-negative Ephrin receptor was able to rescue NTC in a Ciona TTCC mutant. We hypothesize that signaling through TTCCs is necessary for proper anterior NTC through downregulation of ephrins, and possibly elimination of a repulsive signal.
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Affiliation(s)
- Sarah Abdul-Wajid
- Department of Molecular, Cell and Developmental Biology, and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Heidi Morales-Diaz
- Department of Molecular, Cell and Developmental Biology, and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Stephanie M Khairallah
- Department of Molecular, Cell and Developmental Biology, and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - William C Smith
- Department of Molecular, Cell and Developmental Biology, and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
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Kaufmann LT, Niehrs C. Gadd45a and Gadd45g regulate neural development and exit from pluripotency in Xenopus. Mech Dev 2011; 128:401-11. [PMID: 21854844 DOI: 10.1016/j.mod.2011.08.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 08/01/2011] [Accepted: 08/03/2011] [Indexed: 01/07/2023]
Abstract
Gadd45 genes encode a small family of multifunctional stress response proteins, mediating cell proliferation, apoptosis, DNA repair and DNA demethylation. Their role during embryonic development is incompletely understood. Here we identified Xenopus Gadd45b, compared Gadd45a, Gadd45b and Gadd45g expression during Xenopus embryogenesis, and characterized their gain and loss of function phenotypes. Gadd45a and Gadd45g act redundantly and double Morpholino knock down leads to pleiotropic phenotypes, including shortened axes, head defects and misgastrulation. In contrast, Gadd45b, which is expressed at very low levels, shows little effect upon knock down or overexpression. Gadd45ag double Morphants show reduced neural cell proliferation and downregulation of pan-neural and neural crest markers. In contrast, Gadd45ag Morphants display increased expression of multipotency marker genes including Xenopus oct4 homologs as well as gastrula markers, while mesodermal markers are downregulated. The results indicate that Gadd45ag are required for early embryonic cells to exit pluripotency and enter differentiation.
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Affiliation(s)
- Lilian T Kaufmann
- Division of Molecular Embryology, DKFZ-ZMBH Alliance, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 581, Heidelberg, Germany
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5
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Marino D, Dabouras V, Brändli AW, Detmar M. A role for all-trans-retinoic acid in the early steps of lymphatic vasculature development. J Vasc Res 2010; 48:236-51. [PMID: 21099229 PMCID: PMC2997449 DOI: 10.1159/000320620] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 08/13/2010] [Indexed: 12/11/2022] Open
Abstract
The molecular mechanisms that regulate the earliest steps of lymphatic vascular system development are unknown. To identify regulators of lymphatic competence and commitment, we used an in vitro vascular assay with mouse embryonic stem cell-derived embryoid bodies (EBs). We found that incubation with retinoic acid (RA) and, more potently, with RA in combination with cAMP, induced the expression of the lymphatic competence marker LYVE-1 in the vascular structures of the EBs. This effect was dependent on RA receptor (RAR)-α and protein kinase A signaling. RA-cAMP incubation also promoted the development of CD31+/LYVE-1+/Prox1+ cell clusters. In situ studies revealed that RAR-α is expressed by endothelial cells of the cardinal vein in ED 9.5-11.5 mouse embryos. Timed exposure of mouse and Xenopus embryos to excess of RA upregulated LYVE-1 and VEGFR-3 on embryonic veins and increased formation of Prox1-positive lymphatic progenitors. These findings indicate that RA signaling mediates the earliest steps of lymphatic vasculature development.
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Affiliation(s)
- Daniela Marino
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich, Switzerland
| | - Vasilios Dabouras
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich, Switzerland
| | - André W. Brändli
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich, Switzerland
- Walter-Brendel-Centre of Experimental Medicine, Ludwig-Maximilians-University, Munich, Germany
| | - Michael Detmar
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich, Switzerland
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6
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Steinberg F, Zhuang L, Beyeler M, Kälin RE, Mullis PE, Brändli AW, Trueb B. The FGFRL1 receptor is shed from cell membranes, binds fibroblast growth factors (FGFs), and antagonizes FGF signaling in Xenopus embryos. J Biol Chem 2009; 285:2193-202. [PMID: 19920134 DOI: 10.1074/jbc.m109.058248] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
FGFRL1 (fibroblast growth factor receptor like 1) is the fifth and most recently discovered member of the fibroblast growth factor receptor (FGFR) family. With up to 50% amino acid similarity, its extracellular domain closely resembles that of the four conventional FGFRs. Its intracellular domain, however, lacks the split tyrosine kinase domain needed for FGF-mediated signal transduction. During embryogenesis of the mouse, FGFRL1 is essential for the development of parts of the skeleton, the diaphragm muscle, the heart, and the metanephric kidney. Since its discovery, it has been hypothesized that FGFRL1 might act as a decoy receptor for FGF ligands. Here we present several lines of evidence that support this notion. We demonstrate that the FGFRL1 ectodomain is shed from the cell membrane of differentiating C2C12 myoblasts and from HEK293 cells by an as yet unidentified protease, which cuts the receptor in the membrane-proximal region. As determined by ligand dot blot analysis, cell-based binding assays, and surface plasmon resonance analysis, the soluble FGFRL1 ectodomain as well as the membrane-bound receptor are capable of binding to some FGF ligands with high affinity, including FGF2, FGF3, FGF4, FGF8, FGF10, and FGF22. We furthermore show that ectopic expression of FGFRL1 in Xenopus embryos antagonizes FGFR signaling during early development. Taken together, our data provide strong evidence that FGFRL1 is indeed a decoy receptor for FGFs.
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7
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Winklbauer R. Cell adhesion in amphibian gastrulation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:215-75. [PMID: 19815180 DOI: 10.1016/s1937-6448(09)78005-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The amphibian gastrula can be regarded as a single coherent tissue which folds and distorts itself in a reproducible pattern to establish the embryonic germ layers. It is held together by cadherins which provide the flexible adhesion required for the massive cell rearrangements that accompany gastrulation. Cadherin expression and adhesiveness increase as one goes from the vegetal cell mass through the anterior mesendoderm to the chordamesoderm, and then decrease again slightly in the ectoderm. Together with a basic random component of cell motility, this flexible, differentially expressed adhesiveness generates surface and interfacial tension effects which, in principle, can exert strong forces. However, conclusive evidence for an in vivo role of differential adhesion-related effects in gastrula morphogenesis is still lacking. The most important morphogenetic process in the amphibian gastrula seems to be intercellular migration, where cells crawl actively across each other's surface. The crucial aspect of this process is that cell motility is globally oriented, leading for example to mediolateral intercalation of bipolar cells during convergent extension of the chordamesoderm or to the directional migration of unipolar cells during translocation of the anterior mesendoderm on the ectodermal blastocoel roof. During these movements, the boundary between ectoderm and mesoderm is maintained by a tissue separation process.
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Affiliation(s)
- Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada
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8
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Gene expression analysis defines the proximal tubule as the compartment for endocytic receptor-mediated uptake in the Xenopus pronephric kidney. Pflugers Arch 2008; 456:1163-76. [DOI: 10.1007/s00424-008-0488-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 02/28/2008] [Indexed: 12/22/2022]
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9
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Raciti D, Reggiani L, Geffers L, Jiang Q, Bacchion F, Subrizi AE, Clements D, Tindal C, Davidson DR, Kaissling B, Brändli AW. Organization of the pronephric kidney revealed by large-scale gene expression mapping. Genome Biol 2008; 9:R84. [PMID: 18492243 PMCID: PMC2441470 DOI: 10.1186/gb-2008-9-5-r84] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 03/19/2008] [Accepted: 05/20/2008] [Indexed: 11/28/2022] Open
Abstract
Gene expression mapping reveals 8 functionally distinct domains in the Xenopus pronephros. Interestingly, no structure equivalent to the mammalian collecting duct is identified. Background The pronephros, the simplest form of a vertebrate excretory organ, has recently become an important model of vertebrate kidney organogenesis. Here, we elucidated the nephron organization of the Xenopus pronephros and determined the similarities in segmentation with the metanephros, the adult kidney of mammals. Results We performed large-scale gene expression mapping of terminal differentiation markers to identify gene expression patterns that define distinct domains of the pronephric kidney. We analyzed the expression of over 240 genes, which included members of the solute carrier, claudin, and aquaporin gene families, as well as selected ion channels. The obtained expression patterns were deposited in the searchable European Renal Genome Project Xenopus Gene Expression Database. We found that 112 genes exhibited highly regionalized expression patterns that were adequate to define the segmental organization of the pronephric nephron. Eight functionally distinct domains were discovered that shared significant analogies in gene expression with the mammalian metanephric nephron. We therefore propose a new nomenclature, which is in line with the mammalian one. The Xenopus pronephric nephron is composed of four basic domains: proximal tubule, intermediate tubule, distal tubule, and connecting tubule. Each tubule may be further subdivided into distinct segments. Finally, we also provide compelling evidence that the expression of key genes underlying inherited renal diseases in humans has been evolutionarily conserved down to the level of the pronephric kidney. Conclusion The present study validates the Xenopus pronephros as a genuine model that may be used to elucidate the molecular basis of nephron segmentation and human renal disease.
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Affiliation(s)
- Daniela Raciti
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
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10
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Reggiani L, Raciti D, Airik R, Kispert A, Brändli AW. The prepattern transcription factor Irx3 directs nephron segment identity. Genes Dev 2007; 21:2358-70. [PMID: 17875669 PMCID: PMC1973149 DOI: 10.1101/gad.450707] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The nephron, the basic structural and functional unit of the vertebrate kidney, is organized into discrete segments, which are composed of distinct renal epithelial cell types. Each cell type carries out highly specific physiological functions to regulate fluid balance, osmolarity, and metabolic waste excretion. To date, the genetic basis of regionalization of the nephron has remained largely unknown. Here we show that Irx3, a member of the Iroquois (Irx) gene family, acts as a master regulator of intermediate tubule fate. Comparative studies in Xenopus and mouse have identified Irx1, Irx2, and Irx3 as an evolutionary conserved subset of Irx genes, whose expression represents the earliest manifestation of intermediate compartment patterning in the developing vertebrate nephron discovered to date. Intermediate tubule progenitors will give rise to epithelia of Henle's loop in mammals. Loss-of-function studies indicate that irx1 and irx2 are dispensable, whereas irx3 is necessary for intermediate tubule formation in Xenopus. Furthermore, we demonstrate that misexpression of irx3 is sufficient to direct ectopic development of intermediate tubules in the Xenopus mesoderm. Taken together, irx3 is the first gene known to be necessary and sufficient to specify nephron segment fate in vivo.
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Affiliation(s)
- Luca Reggiani
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Daniela Raciti
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Rannar Airik
- Institute of Molecular Biology, Hannover Medical School, D-30625 Hannover, Germany
| | - Andreas Kispert
- Institute of Molecular Biology, Hannover Medical School, D-30625 Hannover, Germany
| | - André W. Brändli
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, CH-8093 Zurich, Switzerland
- Corresponding author.E-MAIL ; FAX 41-44-633-1358
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11
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Kälin RE, Kretz MP, Meyer AM, Kispert A, Heppner FL, Brändli AW. Paracrine and autocrine mechanisms of apelin signaling govern embryonic and tumor angiogenesis. Dev Biol 2007; 305:599-614. [PMID: 17412318 DOI: 10.1016/j.ydbio.2007.03.004] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 03/02/2007] [Accepted: 03/06/2007] [Indexed: 01/13/2023]
Abstract
Apelin and its G protein-coupled receptor APJ play important roles in blood pressure regulation, body fluid homeostasis, and possibly the modulation of immune responses. Here, we report that apelin-APJ signaling is essential for embryonic angiogenesis and upregulated during tumor angiogenesis. A detailed expression analysis demonstrates that both paracrine and autocrine mechanisms mark areas of embryonic and tumor angiogenesis. Knockdown studies in Xenopus reveal that apelin-APJ signaling is required for intersomitic vessel angiogenesis. Moreover, ectopic expression of apelin but not vascular endothelial growth factor A (VEGFA) is sufficient to trigger premature angiogenesis. In vitro, apelin is non-mitogenic for primary human endothelial cells but promotes chemotaxis. Epistasis studies in Xenopus embryos suggest that apelin-APJ signaling functions downstream of VEGFA. Finally, we show that apelin and APJ expression is highly upregulated in microvascular proliferations of brain tumors such as malignant gliomas. Thus, our results define apelin and APJ as genes of potential diagnostic value and promising targets for the development of a new generation of anti-tumor angiogenic drugs.
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Affiliation(s)
- Roland E Kälin
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland
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12
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Nelson BR, Sadhu M, Kasemeier JC, Anderson LW, Lefcort F. Identification of genes regulating sensory neuron genesis and differentiation in the avian dorsal root ganglia. Dev Dyn 2004; 229:618-29. [PMID: 14991717 DOI: 10.1002/dvdy.20030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The dorsal root ganglia (DRG) derive from a population of migrating neural crest cells that coalesce laterally to the neural tube. As the DRG matures, discrete cell types emerge from a pool of differentiating progenitor cells. To identify genes that regulate sensory genesis and differentiation, we have designed screens to identify members from families of known regulatory molecules such as receptor tyrosine kinases, and generated full-length and subtractive cDNA libraries between immature and mature DRG for identifying novel genes not previously implicated in DRG development. Several genes were identified in these analyses that belong to important regulatory gene families. Quantitative PCR confirmed differential expression of candidate cDNAs identified from the subtraction/differential screening. In situ hybridization further validated dynamic expression of several cDNAs identified in our screens. Our results demonstrate the utility of combining specific and general screening approaches for isolating key regulatory genes involved in the genesis and differentiation of discrete cell types and tissues within the classic embryonic chick model system.
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Affiliation(s)
- Branden R Nelson
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
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13
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Saulnier DME, Ghanbari H, Brändli AW. Essential function of Wnt-4 for tubulogenesis in the Xenopus pronephric kidney. Dev Biol 2002; 248:13-28. [PMID: 12142017 DOI: 10.1006/dbio.2002.0712] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the vertebrate embryo, development of the excretory system is characterized by the successive formation of three distinct kidneys: the pronephros, mesonephros, and metanephros. While tubulogenesis in the metanephric kidney is critically dependent on the signaling molecule Wnt-4, it is unknown whether Wnt signaling is equally required for the formation of renal epithelia in the other embryonic kidney forms. We therefore investigated the expression of Wnt genes during the pronephric kidney development in Xenopus. Wnt4 was found to be associated with developing pronephric tubules, but was absent from the pronephric duct. Onset of pronephric Wnt-4 expression coincided with mesenchyme-to-epithelium transformation. To investigate Wnt-4 gene function, we performed gain- and loss-of-function experiments. Misexpression of Wnt4 in the intermediate and lateral mesoderm caused abnormal morphogenesis of the pronephric tubules, but was not sufficient to initiate ectopic tubule formation. We used a morpholino antisense oligonucleotide-based gene knockdown strategy to disrupt Wnt-4 gene function. Xenopus embryos injected with antisense Wnt-4 morpholinos developed normally, but marker gene and morphological analysis revealed a complete absence of pronephric tubules. Pronephric duct development was largely unaffected, indicating that ductogenesis may occur normally in the absence of pronephric tubules. Our results show that, as in the metanephric kidney, Wnt-4 is critically required for tubulogenesis in the pronephric kidney, indicating that a common, evolutionary conserved gene regulatory network may control tubulogenesis in different vertebrate excretory organs.
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Affiliation(s)
- Didier M E Saulnier
- Department of Applied Biosciences, Swiss Federal Institute of Technology (ETHZ), CH-8057 Zürich, Switzerland
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14
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Mann F, Ray S, Harris W, Holt C. Topographic mapping in dorsoventral axis of the Xenopus retinotectal system depends on signaling through ephrin-B ligands. Neuron 2002; 35:461-73. [PMID: 12165469 DOI: 10.1016/s0896-6273(02)00786-9] [Citation(s) in RCA: 179] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Ephrin-B and EphB are distributed in matching dorsoventral gradients in the embryonic Xenopus visual system with retinal axons bearing high levels of ligand (dorsal) projecting to tectal regions with high receptor expression (ventral). In vitro stripe assays show that dorsal retinal axons prefer to grow on EphB receptor stripes supporting an attractive guidance mechanism. In vivo disruption of EphB/ephrin-B function by application of exogenous EphB or expression of dominant-negative ephrin-B ligand in dorsal retinal axons causes these axons to shift dorsally in the tectum, while misexpression of wild-type ephrin-B in ventral axons causes them to shift ventrally. These dorsoventral targeting errors are consistent with the hypothesis that an attractive mechanism that requires ephrin-B cytoplasmic domain is critical for retinotectal mapping in this axis.
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Affiliation(s)
- Fanny Mann
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge CB2 3DY, United Kingdom.
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15
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Hutson LD, Bothwell M. Expression and function of Xenopus laevis p75(NTR) suggest evolution of developmental regulatory mechanisms. JOURNAL OF NEUROBIOLOGY 2001; 49:79-98. [PMID: 11598917 DOI: 10.1002/neu.1067] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Neurotrophins signal through two different classes of receptors, members of the trk family of receptor tyrosine kinases, and p75 neurotrophin receptor (p75(NTR)), a member of the tumor necrosis factor receptor family. While neurotrophin binding to trks results in, among other things, increased cell survival, p75(NTR) has enigmatically been implicated in promoting both survival and cell death. Which of these two signals p75(NTR) imparts depends on the specific cellular context. Xenopus laevis is an excellent system in which to study p75(NTR) function in vivo because of its amenability to experimental manipulation. We therefore cloned partial cDNAs of two p75(NTR) genes from Xenopus, which we have termed p75(NTR)a and p75(NTR)b. We then cloned two different cDNAs, both of which encompass the full coding region of p75(NTR)a. Early in development both p75(NTR)a and p75(NTR)b are expressed in developing cranial ganglia and presumptive spinal sensory neurons, similar to what is observed in other species. Later, p75(NTR)a expression largely continues to parallel p75(NTR) expression in other species. However, Xenopus p75(NTR)a is additionally expressed in the neuroepithelium of the anterior telencephalon, all layers of the retina including the photoreceptor layer, and functioning axial skeletal muscle. Finally, misexpression of full length p75(NTR) and each of two truncated mutants in developing retina reveal that p75(NTR) probably signals for cell survival in this system. This result contrasts with the reported role of p75(NTR) in developing retinae of other species, and the possible implications of this difference are discussed.
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MESH Headings
- Amino Acid Sequence
- Animals
- Apoptosis
- Central Nervous System/embryology
- Central Nervous System/growth & development
- Central Nervous System/metabolism
- Chickens
- Consensus Sequence
- Cranial Nerves/embryology
- Cranial Nerves/growth & development
- Cranial Nerves/metabolism
- DNA, Complementary/genetics
- Embryo, Nonmammalian/metabolism
- Evolution, Molecular
- Eye Proteins/biosynthesis
- Eye Proteins/genetics
- Eye Proteins/physiology
- Gene Expression Regulation, Developmental
- Genes
- Genes, Synthetic
- Humans
- In Situ Hybridization
- In Situ Nick-End Labeling
- Larva
- Molecular Sequence Data
- Muscle Proteins/biosynthesis
- Muscle Proteins/genetics
- Muscle Proteins/physiology
- Muscle, Skeletal/embryology
- Muscle, Skeletal/metabolism
- Nerve Tissue Proteins/biosynthesis
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Neurons, Afferent/metabolism
- Organ Specificity
- RNA, Messenger/genetics
- Rats
- Receptor, Nerve Growth Factor
- Receptors, Nerve Growth Factor/biosynthesis
- Receptors, Nerve Growth Factor/genetics
- Receptors, Nerve Growth Factor/physiology
- Recombinant Fusion Proteins/physiology
- Retina/embryology
- Retina/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Alignment
- Sequence Homology, Amino Acid
- Species Specificity
- Transfection
- Tumor Necrosis Factor-alpha/pharmacology
- Xenopus laevis/embryology
- Xenopus laevis/genetics
- Xenopus laevis/growth & development
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Affiliation(s)
- L D Hutson
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
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16
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Bermingham-McDonogh O, Stone JS, Reh TA, Rubel EW. FGFR3 expression during development and regeneration of the chick inner ear sensory epithelia. Dev Biol 2001; 238:247-59. [PMID: 11784008 DOI: 10.1006/dbio.2001.0412] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Several studies suggest fibroblast growth factor receptor 3 (FGFR3) plays a role in the development of the auditory epithelium in mammals. We undertook a study of FGFR3 in the developing and mature chicken inner ear and during regeneration of this epithelium to determine whether FGFR3 shows a similar pattern of expression in birds. FGFR3 mRNA is highly expressed in most support cells in the mature chick basilar papilla but not in vestibular organs of the chick. The gene is expressed early in the development of the basilar papilla. Gentamicin treatment sufficient to destroy hair cells in the basilar papilla causes a rapid, transient downregulation of FGFR3 mRNA in the region of damage. In the initial stages of hair cell regeneration, the support cells that reenter the mitotic cycle in the basilar papilla do not express detectable levels of FGFR3 mRNA. However, once the hair cells have regenerated in this region, the levels of FGFR3 mRNA and protein expression rapidly return to approximate those in the undamaged epithelium. These results indicate that FGFR3 expression changes after drug-induced hair cell damage to the basilar papilla in an opposite way to that found in the mammalian cochlea and may be involved in regulating the proliferation of support cells.
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Affiliation(s)
- O Bermingham-McDonogh
- Virginia Merrill Bloedel Hearing Research Center, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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17
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Eid SR, Brändli AW. Xenopus Na,K-ATPase: primary sequence of the beta2 subunit and in situ localization of alpha1, beta1, and gamma expression during pronephric kidney development. Differentiation 2001; 68:115-25. [PMID: 11686233 DOI: 10.1046/j.1432-0436.2001.680205.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The osmoregulatory function of the pronephric kidney, the first excretory organ of the vertebrate embryo, is essential for embryonic survival. The transport systems engaged in pronephric osmotic regulation are however poorly understood. The Na,K-ATPase is the key component in renal solute transport and water homeostasis. In the present study, we characterized the alpha, beta, and gamma subunits of the Na,K-ATPase of the developing Xenopus embryo. In addition to the known alpha1, beta1, beta3 and gamma subunits, we report here the identification of a novel cDNA encoding the Xenopus beta2 subunit. We demonstrate by in situ hybridization that each Xenopus Na,K-ATPase subunit exhibits a distinct tissue-specific and developmentally regulated expression pattern. We found that the developing pronephric kidney expresses alpha1, beta1, and gamma subunits uniformly along the entire length of the nephron. Onset of pronephric Na,K-ATPase subunit expression occurred in a coordinated fashion indicating that a common regulatory mechanism may initiate pronephric transcription of these genes. The ability to engage in active Na+ reabsorption appears to be established early in pronephric development, since Na,K-ATPase expression was detected well before the completion of pronephric organogenesis. Furthermore, Na,K-ATPase expression defines at the molecular level the onset of maturation phase during pronephric kidney organogenesis. Taken together, our studies reveal a striking conservation of Na,K-ATPase subunit expression between pronephric and metanephric kidneys. The pronephric kidney may therefore represent a simplified model to dissect the regulatory mechanisms underlying renal Na,K-ATPase subunit expression.
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Affiliation(s)
- S R Eid
- Department of Applied Biosciences, Swiss Federal Institute of Technology (ETHZ), Zürich
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18
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Ghanbari H, Seo HC, Fjose A, Brändli AW. Molecular cloning and embryonic expression of Xenopus Six homeobox genes. Mech Dev 2001; 101:271-7. [PMID: 11231090 DOI: 10.1016/s0925-4773(00)00572-4] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Six genes are vertebrate homologues of the homeobox-containing gene sine oculis, which plays an essential role in controlling Drosophila compound eye development. Here we report the identification and expression patterns of all three subfamilies of Xenopus Six genes. Two Six2 subfamily genes (Six1, Six2) showed very similar expression patterns in cranial ganglia, otic placodes and the eyes. Non-neural expression of Six1 and Six2 was observed with mesodermal head mesenchyme, somites and their derivatives, the muscle anlagen of the embryonic trunk. In addition, Six2 expression was also found with mesenchyme associated with the developing stomach and pronephros. Expression of Six3 subfamily genes (Six3.1, Six3.2, Six6.1, and Six6.2) was restricted to the developing head, where expression was especially observed in derivatives of the forebrain (eyes, optic stalks, the hypothalamus and pituitary gland). Interestingly, expression of all Six3 subfamily members but Six6.2 was also found with the pineal gland primordium and the tegmentum. Expression of Six4 subfamily genes (Six4.1, Six4.2) was present in the developing visceral arches, placodal derivatives (otic vesicle, olfactory system), head mesenchyme and the eye. The observed dynamic expression patterns are largely conserved between lower and higher vertebrates and imply important roles of Six family genes not only in eye formation and myogenesis, but also in the development of the gut, the kidney and of placode-derived structures.
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Affiliation(s)
- H Ghanbari
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, CH-8093, Zürich, Switzerland
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19
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Holder N, Durbin L, Cooke J. Eph receptors and ephrins are key regulators of morphogenesis. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2000:123-47. [PMID: 10943308 DOI: 10.1007/978-3-662-04264-9_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- N Holder
- Department of Anatomy and Developmental Biology, University College, London, UK
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20
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Heller N, Brändli AW. Xenopus Pax-2/5/8 orthologues: novel insights into Pax gene evolution and identification of Pax-8 as the earliest marker for otic and pronephric cell lineages. DEVELOPMENTAL GENETICS 2000; 24:208-19. [PMID: 10322629 DOI: 10.1002/(sici)1520-6408(1999)24:3/4<208::aid-dvg4>3.0.co;2-j] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Pax genes are a family of transcription factors playing fundamental roles during organogenesis. We have recently demonstrated the expression of Pax-2 during Xenopus embryogenesis [Heller N, Brändli AW (1997): Mech Dev 69: 83-104]. Here we report the cloning and characterization of Xenopus Pax-5 and Pax-8, two orthologues of the Pax-2/5/8 gene family. Molecular phylogenetic analysis indicates that the amphibian Pax-2/5/8 genes are close relatives of their mammalian counterparts and that all vertebrate Pax-2/5/8 genes are derived from a single ancestral gene. Xenopus Pax-2/5/8 genes are expressed in spatially and temporally overlapping patterns during development of at least seven distinct tissues. Most strikingly, Xenopus Pax-8 was identified as the earliest marker of the prospective otic placode and of the intermediate mesoderm, indicating that Pax-8 may play a central role in auditory and excretory system development. Comparison of the expression patterns of fish, amphibian, and mammalian Pax-2/5/8 genes revealed that the tissue specificity of Pax-2/5/8 gene family expression is overall evolutionarily conserved. The expression domains of individual orthologues can however vary in a species-specific manner. For example, the thyroid glands of mammals express Pax-8, while in Xenopus Pax-2 is expressed instead. Our findings indicate that differential silencing of Pax-2/5/8 gene expression may have occurred after the different classes of vertebrates began to evolve separately.
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Affiliation(s)
- N Heller
- Institute of Cell Biology, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland
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21
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Sato K, Tokmakov AA, Fukami Y. Fertilization signalling and protein-tyrosine kinases. Comp Biochem Physiol B Biochem Mol Biol 2000; 126:129-48. [PMID: 10874161 DOI: 10.1016/s0305-0491(00)00192-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Fertilization is initiated by species-specific gamete cell recognition, i.e. sperm-egg interaction, followed by a rapid and sustained activation of multiple cellular and biochemical events, collectively called 'egg activation', which is indispensable for successful formation of zygotic nucleus and later embryogenesis. It is well known that sperm-induced egg activation is mediated by a transient release of calcium ions that originates from the sperm entry point and propagates through the entire egg cytoplasm. It is unclear, however, what kind of upstream events prelude to the calcium transient after sperm-egg interaction. Recently, much attention has been paid to the role of protein-tyrosine phosphorylation in egg activation process by a number of studies on some well-established model organisms. These includes marine invertebrates, frogs, and mammals. In this review, we will summarize the recent findings that begin to uncover a 'missing link' between sperm-egg interaction and egg activation with emphasis on the role of egg protein-tyrosine kinases (PTKs) in Xenopus egg fertilization.
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Affiliation(s)
- K Sato
- Laboratory of Molecular Biology, Biosignal Research Center, Kobe University, Nada, Japan.
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22
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Wilkinson DG. Eph receptors and ephrins: regulators of guidance and assembly. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 196:177-244. [PMID: 10730216 DOI: 10.1016/s0074-7696(00)96005-4] [Citation(s) in RCA: 162] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent advances have started to elucidate the developmental functions and biochemistry of Eph receptor tyrosine kinases and their membrane-bound ligands, ephrins. Interactions between these molecules are promiscuous, but they largely fall into two groups: EphA receptors bind to GPI-anchored ephrin-A ligands, while EphB receptors bind to ephrin-B proteins that have a transmembrane and cytoplasmic domain. Remarkably, ephrin-B proteins transduce signals, such that bidirectional signaling can occur upon interaction with Eph receptor. In many tissues, specific Eph receptors and ephrins have complementary domains, whereas other family members may overlap in their expression. An important role of Eph receptors and ephrins is to mediate cell-contact-dependent repulsion. Complementary and overlapping gradients of expression underlie establishment of a topographic map of neuronal projections in the retinotectal system. Eph receptors and ephrins also act at boundaries to channel neuronal growth cones along specific pathways, restrict the migration of neural crest cells, and via bidirectional signaling prevent intermingling between hindbrain segments. Intriguingly, Eph receptors and ephrins can also trigger an adhesive response of endothelial cells and are required for the remodeling of blood vessels. Biochemical studies suggest that the extent of multimerization of Eph receptors modulates the cellular response and that the actin cytoskeleton is one major target of the intracellular pathways activated by Eph receptors. Eph receptors and ephrins have thus emerged as key regulators of the repulsion and adhesion of cells that underlie the establishment, maintenance, and remodeling of patterns of cellular organization.
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Affiliation(s)
- D G Wilkinson
- Division of Developmental Neurobiology, National Institute for Medical Research, London, United Kingdom
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23
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Helbling PM, Saulnier DM, Brändli AW. The receptor tyrosine kinase EphB4 and ephrin-B ligands restrict angiogenic growth of embryonic veins in Xenopus laevis. Development 2000; 127:269-78. [PMID: 10603345 DOI: 10.1242/dev.127.2.269] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cues and signaling systems that guide the formation of embryonic blood vessels in tissues and organs are poorly understood. Members of the Eph family of receptor tyrosine kinases and their cell membrane-anchored ligands, the ephrins, have been assigned important roles in the control of cell migration during embryogenesis, particularly in axon guidance and neural crest migration. Here we investigated the role of EphB receptors and their ligands during embryonic blood vessel development in Xenopus laevis. In a survey of tadpole-stage Xenopus embryos for EphB receptor expression, we detected expression of EphB4 receptors in the posterior cardinal veins and their derivatives, the intersomitic veins. Vascular expression of other EphB receptors, including EphB1, EphB2 or EphB3, could however not be observed, suggesting that EphB4 is the principal EphB receptor of the early embryonic vasculature of Xenopus. Furthermore, we found that ephrin-B ligands are expressed complementary to EphB4 in the somites adjacent to the migratory pathways taken by intersomitic veins during angiogenic growth. We performed RNA injection experiments to study the function of EphB4 and its ligands in intersomitic vein development. Disruption of EphB4 signaling by dominant negative EphB4 receptors or misexpression of ephrin-B ligands in Xenopus embryos resulted in intersomitic veins growing abnormally into the adjacent somitic tissue. Our findings demonstrate that EphB4 and B-class ephrins act as regulators of angiogenesis possibly by mediating repulsive guidance cues to migrating endothelial cells.
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Affiliation(s)
- P M Helbling
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, CH-8093 Zürich, Switzerland
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24
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Helbling PM, Saulnier DM, Robinson V, Christiansen JH, Wilkinson DG, Brändli AW. Comparative analysis of embryonic gene expression defines potential interaction sites for Xenopus EphB4 receptors with ephrin-B ligands. Dev Dyn 1999; 216:361-73. [PMID: 10633856 DOI: 10.1002/(sici)1097-0177(199912)216:4/5<361::aid-dvdy5>3.0.co;2-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Eph family of receptor tyrosine kinases and their ligands, the ephrins, act as signaling molecules regulating the migratory behavior of neurons and neural crest cells, and are implicated in tissue patterning, blood vessel formation, and tumorigenesis. On the basis of structural similarities and overlapping binding specificities, Eph receptors as well as their ligands can be divided into A and B subfamilies with orthologues found in all vertebrates. We describe here the isolation of cDNAs encoding Xenopus EphB4 receptors and show that embryonic expression is prominently associated with the developing vasculature, newly forming somites, the visceral arches, and non-neuronal tissues of the embryonic head. In a screen to identify potential ligands for EphB4 in Xenopus embryos, we isolated cDNAs for the Xenopus ephrin-B2 and -B3, which demonstrates that the Xenopus genome harbors genes encoding orthologues to all three currently known mammalian ephrin-B genes. We next performed in situ hybridizations to identify tissues and organs where EphB4 receptors may encounter ephrin-B ligands during embryonic development. Our analysis revealed distinct, but overlapping patterns of ephrin-B gene expression. Interestingly, each ephrin-B ligand displayed expression domains either adjacent to or within EphB4-expressing tissues. These findings indicate that EphB4 receptors may interact in vivo with multiple B-class ephrins. The expression patterns also suggest that EphB4 receptors and their ligands may be involved in visceral arch formation, somitogenesis, and blood vessel development.
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Affiliation(s)
- P M Helbling
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, Zürich, Switzerland
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25
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Abstract
Eph receptor tyrosine kinases and their ligands, the ephrins, appear to lie functionally at the interface between pattern formation and morphogenesis. We review the role of Eph and ephrin signalling in the formation of segmented structures, in the control of axon guidance and cell migration and in the development of the vasculature. We address the question of how the specificity of response is achieved and discuss the specificity of ephrin-Eph interactions and the significance of structural domains in Eph receptors.
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Affiliation(s)
- N Holder
- Department of Anatomy and Developmental Biology, University College, Gower Street, London, WC1 6BT, UK.
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26
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Helbling PM, Tran CT, Brändli AW. Requirement for EphA receptor signaling in the segregation of Xenopus third and fourth arch neural crest cells. Mech Dev 1998; 78:63-79. [PMID: 9858686 DOI: 10.1016/s0925-4773(98)00148-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We describe here the isolation of a full-length cDNA encoding a Xenopus orthologue of the mammalian EphA2 receptor tyrosine kinase and investigate its role in cranial neural crest migration. We show that the primary sites of Xenopus EphA2 expression are rhombomere 4 of the developing hindbrain, migratory cranial neural crest cells and mesoderm of the visceral arches. To interfere with EphA2 and related receptors during cranial neural crest migration, we took a dominant negative approach. Overexpression of kinase-deficient EphA2 receptor variants led to abnormal migration of cranial neural crest cells. Neural crest cells of the third arch were found to mismigrate posteriorly, resulting in the failure of third and fourth arch neural crest to separate into distinct streams. These defects could be rescued by expression of full-length EphA2 receptors. A comparison of the expression domains of EphA2-binding proteins mapped by receptor affinity probe (RAP) in situ staining with those for EphA2 receptors revealed co-expression of ligands and receptors in the visceral arch mesenchyme. Taken together, these results suggest that EphA receptors may mediate attractive or adhesive signals during migration of cranial neural crest cells.
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Affiliation(s)
- P M Helbling
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, CH-8093, Zürich, Switzerland
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27
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Abstract
To begin to determine the role of receptor-like tyrosine phosphatases during Xenopus development, we have isolated a cDNA predicted to encode receptor-like tyrosine phosphatase with significant amino acid sequence identity to mouse and human protein tyrosine phosphatase alpha (PTPalpha). Xenopus PTPalpha (XPTPalpha) exists as a maternally expressed mRNA that decreases in expression during gastrulation and then maintains a constant lower level of expression through early tadpole stages. In situ hybridization reveals that XPTPalpha mRNA is expressed throughout the gastrula stage embryo. During subsequent development, XPTPalpha mRNA becomes restricted in its expression to various regions of the brain and the visceral arches. XPTPalpha mRNA is also expressed in several adult tissues and in Xenopus XTC cells. Immunoblot analysis demonstrates that XPTPalpha protein is expressed at relatively uniform levels throughout development. Expression of XPTPalpha protein in insect cells with a recombinant baculovirus results in a glycosylated polypeptide of 110-130 kDa with intrinsic phosphotyrosine phosphatase activity. The spatial and temporal patterns of expression of XPTPalpha indicate that it may play multiple roles during early development including development of the brain.
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Affiliation(s)
- C Q Yang
- Department of Molecular Biology, Holland Laboratory, American Red Cross, Rockville, Maryland, USA
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28
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Abstract
The Eph receptors are the largest known family of receptor tyrosine kinases. Initially all of them were identified as orphan receptors without known ligands, and their specific functions were not well understood. During the past few years, a corresponding family of ligands has been identified, called the ephrins, and specific functions have now been identified in neural development. The ephrins and Eph receptors are implicated as positional labels that may guide the development of neural topographic maps. They have also been implicated in pathway selection by axons, the guidance of cell migration, and the establishment of regional pattern in the nervous system. The ligands are anchored to cell surfaces, and most of the functions so far identified can be interpreted as precise guidance of cell or axon movement. This large family of ligands and receptors may make a major contribution to the accurate spatial patterning of connections and cell position in the nervous system.
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Affiliation(s)
- J G Flanagan
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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29
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George SE, Simokat K, Hardin J, Chisholm AD. The VAB-1 Eph receptor tyrosine kinase functions in neural and epithelial morphogenesis in C. elegans. Cell 1998; 92:633-43. [PMID: 9506518 DOI: 10.1016/s0092-8674(00)81131-9] [Citation(s) in RCA: 186] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mutations in the C. elegans vab-1 gene disrupt the coordinated movements of cells during two periods of embryogenesis. vab-1 mutants are defective in the movement of neuroblasts during closure of the ventral gastrulation cleft and in the movements of epidermal cells during ventral enclosure of the embryo by the epidermis. We show that vab-1 encodes a receptor tyrosine kinase of the Eph family. Disruption of the kinase domain of VAB-1 causes weak mutant phenotypes, indicating that VAB-1 may have both kinase-dependent and kinase-independent activities. VAB-1 is expressed in neurons during epidermal enclosure and is required in these cells for normal epidermal morphogenesis, demonstrating that cell-cell interactions are required between neurons and epidermal cells for epidermal morphogenesis.
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Affiliation(s)
- S E George
- Department of Biology, Sinsheimer Laboratories, University of California, Santa Cruz 95064, USA
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30
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Heller N, Brändli AW. Xenopus Pax-2 displays multiple splice forms during embryogenesis and pronephric kidney development. Mech Dev 1997; 69:83-104. [PMID: 9486533 DOI: 10.1016/s0925-4773(97)00158-5] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Kidney organogenesis is initiated with the formation of the pronephric kidney and requires Pax-2 gene function. We report here the cloning and characterization of Pax-2 cDNAs from the frog Xenopus laevis, a model system suitable for the study of early kidney organogenesis. We show that expression of Xenopus Pax-2 (XPax-2) genes was confined to the nervous system, sensory organs, the visceral arches, and the developing excretory system. DNA sequencing of XPax-2 cDNAs isolated from head and pronephric kidney libraries revealed seven novel alternatively spliced Pax-2 isoforms. They all retain DNA-binding domains, but can differ significantly in their C termini with some isoforms containing a novel Pax-2 exon. We investigated the spectrum of XPax-2 splice events in pronephric kidneys, animal cap cultures and in whole embryos. Splicing of XPax-2 transcripts was found to be extensive and temporally regulated during Xenopus embryogenesis. Since all investigated tissues expressed essentially the full spectrum of XPax-2 splice variants, we conclude that splicing of XPax-2 transcripts does not occur in a tissue-specific manner.
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Affiliation(s)
- N Heller
- Institute of Cell Biology, Swiss Federal Institute of Technology, Zürich
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31
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Takahashi T, Aoki S, Nakamura T, Koshimizu U, Matsumoto K, Nakamura T. Xenopus LIM motif-containing protein kinase, Xlimk1, is expressed in the developing head structure of the embryo. Dev Dyn 1997; 209:196-205. [PMID: 9186054 DOI: 10.1002/(sici)1097-0177(199706)209:2<196::aid-aja5>3.0.co;2-d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The LIM double zinc finger motif locates in several developmentally functioning and cytoskeletal proteins, and is considered to act as a specific motif for protein-protein interactions. LIM kinase (LIMK) is a novel protein kinase containing two LIM motifs at the N-terminal, the function of which has yet to be clearly defined. In this study, we cloned a cDNA encoding Xenopus counterpart of human LIMK1 gene by RT-PCR mediated cloning, and designated in Xlimk1. Xlimk1 is highly homologous to mammalian LIMK1 in each structural domain, particularly in LIM and protein kinase domains. In Northern blot analysis, two distinct Xlimk1 transcripts of 9.0 Kb and 3.7 Kb were present in early cleavage stages of the embryo. Both mRNA species were subsequently decreased at the gastrula stages. The 9.0 Kb of Xlimk1 mRNA again appeared in late neurula stage, then the expression level gradually increased in later stages of the embryo. Whole-mount in situ hybridization analysis showed the localization of Xlimk1 transcripts in the animal half of the blastula embryo. In post-neurula stages, specific signals for Xlimk1 were predominant in the anterior (head) region of the embryo, including developing brain, hyoid and branchial arches, and anlagen of sensory organs. These results indicate that Xlimk1 may play an important role in neural development and formation of anterior (head) structures in the Xenopus embryo.
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Affiliation(s)
- T Takahashi
- Department of Oncology, Osaka University Medical School, Japan
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32
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Weinstein DC, Rahman SM, Ruiz JC, Hemmati-Brivanlou A. Embryonic expression of eph signalling factors in Xenopus. Mech Dev 1996; 57:133-44. [PMID: 8843391 DOI: 10.1016/0925-4773(96)00536-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cellular communication in the developing embryo is mediated by receptor-ligand interactions at the cell surface. Receptor protein tyrosine kinases (RTKs) have been shown to play a critical role in the development of the vertebrate embryo. The eph receptors are a large subclass of RTKs for which a corresponding ligand family has only recently been described. The restricted expression patterns of several eph receptors imply roles for these molecules in early vertebrate development. We have isolated both a ligand of the eph ligand family (ELF), that we have named XELF-a, and an eph-related receptor, XE10, the likely homolog of the murine eck/Sek-2 receptor. At least two forms of the XELF-a transcript are present in the developing embryo. A truncated form of the XELF-a ligand, XELF-á, is the first ELF ligand isolated that lacks both the membrane-spanning and membrane-anchoring motifs conserved among this family, suggesting that ELF ligands can function as fully soluble molecules in vivo. XELF-a and XE10 are expressed maternally and throughout early embryogenesis, while XELF-á is only expressed zygotically. The dynamic expression patterns of these signalling molecules, in both mesoderm and neurectoderm, suggest that they may play a role in the patterning of the early vertebrate embryo.
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33
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Kinoshita N, Minshull J, Kirschner MW. The identification of two novel ligands of the FGF receptor by a yeast screening method and their activity in Xenopus development. Cell 1995; 83:621-30. [PMID: 7585965 DOI: 10.1016/0092-8674(95)90102-7] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have developed a functional screen in yeast to identify ligands for receptor tyrosine kinases. Using this method, we cloned two Xenopus genes that activate the fibroblast growth factor (FGF) receptor. These encode novel secreted proteins, designated FRL1 and FRL2, distantly related to the epidermal growth factor and angiogenin/ribonuclease families, respectively. Both genes activate the FGF receptor in Xenopus oocytes as well as in yeast. Overexpression induces mesoderm and neural-specific genes in Xenopus explants; induction is blocked by a dominant negative inhibitor of the FGF receptor. FRL1 is broadly expressed during gastrulation and neurulation, while FRL2 is expressed principally in the axial mesoderm and brain at later stages. Our results indicate that despite their lack of similarity with FGF, FRL1 and FRL2 are ligands for the FGF receptor that play distinct roles in development.
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Affiliation(s)
- N Kinoshita
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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