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Bolognesi R, Beermann A, Farzana L, Wittkopp N, Lutz R, Balavoine G, Brown SJ, Schröder R. Tribolium Wnts: evidence for a larger repertoire in insects with overlapping expression patterns that suggest multiple redundant functions in embryogenesis. Dev Genes Evol 2008; 218:193-202. [PMID: 18392880 DOI: 10.1007/s00427-007-0170-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 06/18/2007] [Indexed: 01/26/2023]
Abstract
Wingless (wg)/Wnt family genes encode secreted glycoproteins that function as signalling molecules in the development of vertebrates as well as invertebrates. In a survey of Wnt family genes in the newly sequenced Tribolium genome, we found a total of nine Wnt genes. In addition to wg or Wnt1, Tribolium contains orthologs of the vertebrate Wnt5-7 and Wnt9-11 genes. As in Drosophila, Wnt1, Wnt6 and Wnt10 are clustered in the genome. Comparative genomics indicates that Wnt9 is also a conserved member of this cluster in several insects for which genome sequence is available. One of the Tribolium Wnt genes appears to be a member of the WntA family, members of which have been identified in Anopheles and other invertebrates but not in Drosophila or vertebrates. Careful phylogenetic examination suggests an Apis Wnt gene, previously identified as a Wnt4 homolog, is also a member of the WntA family. The ninth Tribolium Wnt gene is related to the diverged Drosophila WntD gene, both of which phylogenetically group with Wnt8 genes. Some of the Tribolium Wnt genes display multiple overlapping expression patterns, suggesting that they may be functionally redundant in segmentation, brain, appendage and hindgut development. In contrast, the unique expression patterns of Wnt5, Wnt7 and Wnt11 in developing appendages likely indicate novel functions.
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Affiliation(s)
- Renata Bolognesi
- Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66502, USA
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Abstract
Signaling by the wingless pathway has been shown to govern numerous developmental processes. Much of our current understanding of wingless signaling mechanisms comes from studies conducted in Drosophila melanogaster, which offers superior experimental tractability for genetic and developmental studies. Wingless signaling is highly consequential during normal development and patterning of Drosophila. Its earliest identifiable role during development of Drosophila is in the embryonic segmentation cascade, wherein wingless functions as a segment polarity gene and serves to pattern each individual segment along the antero-posterior axis of the developing embryo. Subsequent developmental roles fulfilled by wingless include patterning the developing wings, legs, eyes, CNS, heart, and muscles. Each of these developmental contexts offers excellent systems to query mechanisms regulating different aspects of wingless signal transduction such as synthesis, secretion, reception, and transcription. This chapter presents a brief overview on the functions of wingless signaling during development of Drosophila melanogaster.
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Affiliation(s)
- Foster C Gonsalves
- Department of Pharmacology, New York University School of Medicine/Cancer Institute, New York, NY, USA
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Abstract
The fly immune response is actively turned down, and if it is not, pathology results.
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Affiliation(s)
- David S Schneider
- Department of Microbiology and Immunology, Stanford University, Stanford, California, United States of America.
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54
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The Drosophila systemic immune response: sensing and signalling during bacterial and fungal infections. Nat Rev Immunol 2007; 7:862-74. [DOI: 10.1038/nri2194] [Citation(s) in RCA: 640] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Copley RR, Totrov M, Linnell J, Field S, Ragoussis J, Udalova IA. Functional conservation of Rel binding sites in drosophilid genomes. Genome Res 2007; 17:1327-35. [PMID: 17785540 PMCID: PMC1950901 DOI: 10.1101/gr.6490707] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Evolutionary constraints on gene regulatory elements are poorly understood: Little is known about how the strength of transcription factor binding correlates with DNA sequence conservation, and whether transcription factor binding sites can evolve rapidly while retaining their function. Here we use the model of the NFKB/Rel-dependent gene regulation in divergent Drosophila species to examine the hypothesis that the functional properties of authentic transcription factor binding sites are under stronger evolutionary constraints than the genomic background. Using molecular modeling we compare tertiary structures of the Drosophila Rel family proteins Dorsal, Dif, and Relish and demonstrate that their DNA-binding and protein dimerization domains undergo distinct rates of evolution. The accumulated amino acid changes, however, are unlikely to affect DNA sequence recognition and affinity. We employ our recently developed microarray-based experimental platform and principal coordinates statistical analysis to quantitatively and systematically profile DNA binding affinities of three Drosophila Rel proteins to 10,368 variants of the NFKB recognition sequences. We then correlate the evolutionary divergence of gene regulatory regions with differences in DNA binding affinities. Genome-wide analyses reveal a significant increase in the number of conserved Rel binding sites in promoters of developmental and immune genes. Significantly, the affinity of Rel proteins to these sites was higher than to less conserved sites and was maintained by the conservation of the DNA binding site sequence (static conservation) or in some cases despite significantly diverged sequences (dynamic conservation). We discuss how two types of conservation may contribute to the stabilization and optimization of a functional gene regulatory code in evolution.
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Affiliation(s)
- Richard R. Copley
- Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom
- Corresponding authors.E-mail ; fax 44-208-3834499.E-mail ; fax 44-1865-287664
| | | | - Jane Linnell
- Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom
| | - Simon Field
- Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom
| | - Jiannis Ragoussis
- Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom
| | - Irina A. Udalova
- Wellcome Trust Centre for Human Genetics, Oxford University, Oxford OX3 7BN, United Kingdom
- Kennedy Institute of Rheumatology, Imperial College, London W6 8LH, United Kingdom
- Corresponding authors.E-mail ; fax 44-208-3834499.E-mail ; fax 44-1865-287664
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56
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Sandmann T, Girardot C, Brehme M, Tongprasit W, Stolc V, Furlong EE. A core transcriptional network for early mesoderm development in Drosophila melanogaster. Genes Dev 2007; 21:436-49. [PMID: 17322403 PMCID: PMC1804332 DOI: 10.1101/gad.1509007] [Citation(s) in RCA: 255] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Embryogenesis is controlled by large gene-regulatory networks, which generate spatially and temporally refined patterns of gene expression. Here, we report the characteristics of the regulatory network orchestrating early mesodermal development in the fruitfly Drosophila, where the transcription factor Twist is both necessary and sufficient to drive development. Through the integration of chromatin immunoprecipitation followed by microarray analysis (ChIP-on-chip) experiments during discrete time periods with computational approaches, we identified >2000 Twist-bound cis-regulatory modules (CRMs) and almost 500 direct target genes. Unexpectedly, Twist regulates an almost complete cassette of genes required for cell proliferation in addition to genes essential for morophogenesis and cell migration. Twist targets almost 25% of all annotated Drosophila transcription factors, which may represent the entire set of regulators necessary for the early development of this system. By combining in vivo binding data from Twist, Mef2, Tinman, and Dorsal we have constructed an initial transcriptional network of early mesoderm development. The network topology reveals extensive combinatorial binding, feed-forward regulation, and complex logical outputs as prevalent features. In addition to binary activation and repression, we suggest that Twist binds to almost all mesodermal CRMs to provide the competence to integrate inputs from more specialized transcription factors.
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Affiliation(s)
- Thomas Sandmann
- European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
| | - Charles Girardot
- European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
| | - Marc Brehme
- European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
| | - Waraporn Tongprasit
- Genome Research Facility, NASA Ames Research Center, Moffet Field, California 94035, USA
| | - Viktor Stolc
- Genome Research Facility, NASA Ames Research Center, Moffet Field, California 94035, USA
| | - Eileen E.M. Furlong
- European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
- Corresponding author.E-MAIL ; FAX 49-6221-387166
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57
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Zeitlinger J, Zinzen RP, Stark A, Kellis M, Zhang H, Young RA, Levine M. Whole-genome ChIP-chip analysis of Dorsal, Twist, and Snail suggests integration of diverse patterning processes in the Drosophila embryo. Genes Dev 2007; 21:385-90. [PMID: 17322397 PMCID: PMC1804326 DOI: 10.1101/gad.1509607] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Genetic studies have identified numerous sequence-specific transcription factors that control development, yet little is known about their in vivo distribution across animal genomes. We determined the genome-wide occupancy of the dorsoventral (DV) determinants Dorsal, Twist, and Snail in the Drosophila embryo using chromatin immunoprecipitation coupled with microarray analysis (ChIP-chip). The in vivo binding of these proteins correlate tightly with the limits of known enhancers. Our analysis predicts substantially more target genes than previous estimates, and includes Dpp signaling components and anteroposterior (AP) segmentation determinants. Thus, the ChIP-chip data uncover a much larger than expected regulatory network, which integrates diverse patterning processes during development.
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Affiliation(s)
- Julia Zeitlinger
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA
| | - Robert P. Zinzen
- Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, California 94720, USA
| | - Alexander Stark
- Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts 02141, USA
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Manolis Kellis
- Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts 02141, USA
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Hailan Zhang
- Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA
| | - Richard A. Young
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Michael Levine
- Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, California 94720, USA
- Corresponding author.E-MAIL ; FAX (510) 643-5785
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58
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Zhang C, Carl TF, Trudeau ED, Simmet T, Klymkowsky MW. An NF-kappaB and slug regulatory loop active in early vertebrate mesoderm. PLoS One 2006; 1:e106. [PMID: 17205110 PMCID: PMC1762408 DOI: 10.1371/journal.pone.0000106] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 11/23/2006] [Indexed: 01/11/2023] Open
Abstract
Background In both Drosophila and the mouse, the zinc finger transcription factor Snail is required for mesoderm formation; its vertebrate paralog Slug (Snai2) appears to be required for neural crest formation in the chick and the clawed frog Xenopus laevis. Both Slug and Snail act to induce epithelial to mesenchymal transition (EMT) and to suppress apoptosis. Methodology & Principle Findings Morpholino-based loss of function studies indicate that Slug is required for the normal expression of both mesodermal and neural crest markers in X. laevis. Both phenotypes are rescued by injection of RNA encoding the anti-apoptotic protein Bcl-xL; Bcl-xL's effects are dependent upon IκB kinase-mediated activation of the bipartite transcription factor NF-κB. NF-κB, in turn, directly up-regulates levels of Slug and Snail RNAs. Slug indirectly up-regulates levels of RNAs encoding the NF-κB subunit proteins RelA, Rel2, and Rel3, and directly down-regulates levels of the pro-apopotic Caspase-9 RNA. Conclusions/Significance These studies reveal a Slug/Snail–NF-κB regulatory circuit, analogous to that present in the early Drosophila embryo, active during mesodermal formation in Xenopus. This is a regulatory interaction of significance both in development and in the course of inflammatory and metastatic disease.
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Affiliation(s)
- Chi Zhang
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Timothy F. Carl
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Evan D. Trudeau
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Thomas Simmet
- Institute of Pharmacology of Natural Products and Clinical Pharmacology, University of Ulm, Ulm, Germany
| | - Michael W. Klymkowsky
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
- * To whom correspondence should be addressed. E-mail:
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59
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Biemar F, Nix DA, Piel J, Peterson B, Ronshaugen M, Sementchenko V, Bell I, Manak JR, Levine MS. Comprehensive identification of Drosophila dorsal-ventral patterning genes using a whole-genome tiling array. Proc Natl Acad Sci U S A 2006; 103:12763-8. [PMID: 16908844 PMCID: PMC1636694 DOI: 10.1073/pnas.0604484103] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Dorsal-ventral (DV) patterning of the Drosophila embryo is initiated by Dorsal, a sequence-specific transcription factor distributed in a broad nuclear gradient in the precellular embryo. Previous studies have identified as many as 70 protein-coding genes and one microRNA (miRNA) gene that are directly or indirectly regulated by this gradient. A gene regulation network, or circuit diagram, including the functional interconnections among 40 Dorsal target genes and 20 associated tissue-specific enhancers, has been determined for the initial stages of gastrulation. Here, we attempt to extend this analysis by identifying additional DV patterning genes using a recently developed whole-genome tiling array. This analysis led to the identification of another 30 protein-coding genes, including the Drosophila homolog of Idax, an inhibitor of Wnt signaling. In addition, remote 5' exons were identified for at least 10 of the approximately 100 protein-coding genes that were missed in earlier annotations. As many as nine intergenic uncharacterized transcription units were identified, including two that contain known microRNAs, miR-1 and -9a. We discuss the potential functions of these recently identified genes and suggest that intronic enhancers are a common feature of the DV gene network.
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Affiliation(s)
- Frédéric Biemar
- *Division of Genetics and Development, Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, CA 94720; and
| | | | - Jessica Piel
- *Division of Genetics and Development, Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, CA 94720; and
| | - Brant Peterson
- *Division of Genetics and Development, Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, CA 94720; and
| | - Matthew Ronshaugen
- *Division of Genetics and Development, Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, CA 94720; and
| | | | - Ian Bell
- Affymetrix, Inc., Santa Clara, CA 95951
| | | | - Michael S. Levine
- *Division of Genetics and Development, Department of Molecular Cell Biology, Center for Integrative Genomics, University of California, Berkeley, CA 94720; and
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60
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Moussian B, Roth S. Dorsoventral axis formation in the Drosophila embryo--shaping and transducing a morphogen gradient. Curr Biol 2006; 15:R887-99. [PMID: 16271864 DOI: 10.1016/j.cub.2005.10.026] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The graded nuclear location of the transcription factor Dorsal along the dorsoventral axis of the early Drosophila embryo provides positional information for the determination of different cell fates. Nuclear uptake of Dorsal depends on a complex signalling pathway comprising two parts: an extracellular proteolytic cascade transmits the dorsoventral polarity of the egg chamber to the early embryo and generates a gradient of active Spätzle protein, the ligand of the receptor Toll; an intracellular cascade downstream of Toll relays this graded signal to embryonic nuclei. The slope of the Dorsal gradient is not determined by diffusion of extracellular or intracellular components from a local source, but results from self-organised patterning, in which positive and negative feedback is essential to create and maintain the ratio of key factors at different levels, thereby establishing and stabilising the graded spatial information for Dorsal nuclear uptake.
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Affiliation(s)
- Bernard Moussian
- Department of Genetics, Max-Planck Institute for Developmental Biology, Spemannstr. 35, 72076 Tübingen, Germany
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61
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Carneiro K, Fontenele M, Negreiros E, Lopes E, Bier E, Araujo H. Graded maternal short gastrulation protein contributes to embryonic dorsal-ventral patterning by delayed induction. Dev Biol 2006; 296:203-18. [PMID: 16781701 DOI: 10.1016/j.ydbio.2006.04.453] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 04/04/2006] [Accepted: 04/19/2006] [Indexed: 10/24/2022]
Abstract
Establishment of the dorsal-ventral (DV) axis of the Drosophila embryo depends on ventral activation of the maternal Toll pathway, which creates a gradient of the NFkB/c-rel-related transcription factor dorsal. Signaling through the maternal BMP pathway also alters the dorsal gradient, probably by regulating degradation of the IkB homologue Cactus. The BMP4 homologue decapentaplegic (dpp) and the BMP antagonist short gastrulation (sog) are expressed by follicle cells during mid-oogenesis, but it is unknown how they affect embryonic patterning following fertilization. Here, we provide evidence that maternal Sog and Dpp proteins are secreted into the perivitelline space where they remain until early embryogenesis to modulate Cactus degradation, enabling their dual function in patterning the eggshell and embryo. We find that metalloproteases encoded by tolloid (tld) and tolkin (tok), which cleave Sog, are expressed by follicle cells and are required to generate DV asymmetry in the Dpp signal. Expression of tld and tok is ventrally restricted by the TGF-alpha ligand encoded by gurken, suggesting that signaling via the EGF receptor pathway may regulate embryonic patterning through two independent mechanisms: by restricting the expression of pipe and thereby activation of Toll signaling and by spatially regulating BMP activity.
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Affiliation(s)
- K Carneiro
- Department of Histology and Embryology, Universidade Federal do Rio de Janeiro, CCS, Bl. F, Sala F2-031, Av. Brig. Trompowski, s/n, 21949-900 Rio de Janeiro, RJ, Brazil
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62
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Seaver EC, Kaneshige LM. Expression of 'segmentation' genes during larval and juvenile development in the polychaetes Capitella sp. I and H. elegans. Dev Biol 2005; 289:179-94. [PMID: 16330020 DOI: 10.1016/j.ydbio.2005.10.025] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 10/14/2005] [Accepted: 10/18/2005] [Indexed: 11/16/2022]
Abstract
Polychaete annelids and arthropods are both segmented protostome invertebrates. To investigate whether the segmented body plan of these two phyla share a common molecular ground pattern, we report the developmental expression of orthologues of the arthropod segment polarity genes engrailed (en), hedgehog (hh), and wingless (wg/Wnt1) in larval and juvenile stages of the polychaete annelid Capitella sp. I and en in a second polychaete, Hydroides elegans. Temporally, neither Wnt1 nor hh are detected in the segmented region of the larval body until after morphological segmentation is apparent. Expression of CapI-Wnt1 is limited to a ring of ectoderm marking the future anus during larval segmentation. CapI-hh is expressed in a ring of the hindgut internal to that of CapI-Wnt1, as well as in a subset of ventral nerve cord neurons, anterior gut tissue, and mesoderm. In both H. elegans and Capitella sp. I, en is expressed in a spatially and temporally dynamic manner in segmentally iterated structures as well as a population of cells that migrate internally from ectoderm to mesoderm, possibly representing a population of ecto-mesodermal precursors. Significantly, the expression patterns we report for wg, en, and hh orthologues in Capitella sp. I and for en in larval development of H. elegans are not comparable to the highly conserved ectodermal segment polarity pattern observed in arthropods at any life history stage, consistent with distinct origins of segmentation between annelids and arthropods.
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Affiliation(s)
- Elaine C Seaver
- Kewalo Marine Lab, PBRC/University of Hawaii, Honolulu, 96813, USA.
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63
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Povelones M, Nusse R. The role of the cysteine-rich domain of Frizzled in Wingless-Armadillo signaling. EMBO J 2005; 24:3493-503. [PMID: 16163385 PMCID: PMC1276175 DOI: 10.1038/sj.emboj.7600817] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 08/05/2005] [Indexed: 01/06/2023] Open
Abstract
The Frizzled (Fz) receptors contain seven transmembrane helices and an amino-terminal cysteine-rich domain (CRD) that is sufficient and necessary for binding of the ligands, the Wnts. Recent genetic experiments have suggested, however, that the CRD is dispensable for signaling. We engineered fz CRD mutant transgenes and tested them for Wg signaling activity. None of the mutants was functional in cell culture or could fully replace fz in vivo. We also show that replacing the CRD with a structurally distinct Wnt-binding domain, the Wnt inhibitory factor, reconstitutes a functional Wg receptor. We therefore hypothesized that the function of the CRD is to bring Wg in close proximity with the membrane portion of the receptor. We tested this model by substituting Wg itself for the CRD, a manipulation that results in a constitutively active receptor. We propose that Fz activates signaling in two steps: Fz uses its CRD to capture Wg, and once bound Wg interacts with the membrane portion of the receptor to initiate signaling.
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Affiliation(s)
- Michael Povelones
- Department of Developmental Biology, Beckman Center, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Roel Nusse
- Department of Developmental Biology, Beckman Center, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA
- Department of Developmental Biology, Beckman Center, Howard Hughes Medical Institute, Beckman Center, Stanford University Medical School, Stanford, CA 94305-5428, USA. Tel.: +1 650 723 7769; Fax: +1 650 723 1399; E-mail:
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64
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Gordon MD, Dionne MS, Schneider DS, Nusse R. WntD is a feedback inhibitor of Dorsal/NF-kappaB in Drosophila development and immunity. Nature 2005; 437:746-9. [PMID: 16107793 PMCID: PMC1256032 DOI: 10.1038/nature04073] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2005] [Accepted: 07/20/2005] [Indexed: 11/10/2022]
Abstract
Regulating the nuclear factor-kappaB (NF-kappaB) family of transcription factors is of critical importance to animals, with consequences of misregulation that include cancer, chronic inflammatory diseases and developmental defects. Studies in Drosophila melanogaster have proved fruitful in determining the signals used to control NF-kappaB proteins, beginning with the discovery that the Toll/NF-kappaB pathway, in addition to patterning the dorsal-ventral axis of the fly embryo, defines a major component of the innate immune response in both Drosophila and mammals. Here, we characterize the Drosophila wntD (Wnt inhibitor of Dorsal) gene. We show that WntD acts as a feedback inhibitor of the NF-kappaB homologue Dorsal during both embryonic patterning and the innate immune response to infection. wntD expression is under the control of Toll/Dorsal signalling, and increased levels of WntD block Dorsal nuclear accumulation, even in the absence of the IkappaB homologue Cactus. The WntD signal is independent of the common Wnt signalling component Armadillo (beta-catenin). By engineering a gene knockout, we show that wntD loss-of-function mutants have immune defects and exhibit increased levels of Toll/Dorsal signalling. Furthermore, the wntD mutant phenotype is suppressed by loss of zygotic dorsal. These results describe the first secreted feedback antagonist of Toll signalling, and demonstrate a novel Wnt activity in the fly.
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Affiliation(s)
- Michael D Gordon
- Department of Developmental Biology, Howard Hughes Medical Institute, Beckman Center and
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