1
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Abstract
The Drosophila melanogaster pair-rule gene odz (odd Oz, or Ten-m) is expressed in distinct patterns in the larval eye imaginal disc. Its earliest eye expression occurs in ommatidial precursors starting from the posterior edge of the morphogenetic furrow. Loss of function of odz activity leads to visible light photoreceptor loss; R7 photoreceptor loss; ommatidial size, shape, and rotation defects; ommatidial disorder and fusions; interommatidial bristle defects; and ommatidial lens defects. The same effects are seen in odz eye mitotic clones, in odz-Ten-a transheterozygous combinations, and in eyes expressing an Odz-Dominant Negative transgene (Odz-DN). Effects of the same strength are also seen when the Odz-DN transgene is driven only in regions of scabrous expression, which overlaps the four columns of Odz expression clusters behind the furrow. Small odz mitotic clones suggest an odz role in cell proliferation or survival. Senseless is expressed in odz mutant clones, in a fairly ordered manner, indicating that Odz acts downstream of R8 specification. Disorder within each ommatidium in odz clones is accompanied by some loss of R7 precursors and visible photoreceptor precursor order.
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Affiliation(s)
- Yael Kinel-Tahan
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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2
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Mindorff EN, O'Keefe DD, Labbé A, Yang JP, Ou Y, Yoshikawa S, van Meyel DJ. A gain-of-function screen for genes that influence axon guidance identifies the NF-kappaB protein dorsal and reveals a requirement for the kinase Pelle in Drosophila photoreceptor axon targeting. Genetics 2007; 176:2247-63. [PMID: 17603113 PMCID: PMC1950629 DOI: 10.1534/genetics.107.072819] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
To identify novel regulators of nervous system development, we used the GAL4-UAS misexpression system in Drosophila to screen for genes that influence axon guidance in developing embryos. We mobilized the Gene Search (GS) P element and identified 42 lines with insertions in unique loci, including leak/roundabout2, which encodes an axon guidance receptor and confirms the utility of our screen. The genes we identified encode proteins of diverse classes, some acting near the cell surface and others in the cytoplasm or nucleus. We found that one GS line drove misexpression of the NF-kappaB transcription factor Dorsal, causing motor axons to bypass their correct termination sites. In the developing visual system, Dorsal misexpression also caused photoreceptor axons to reach incorrect positions within the optic lobe. This mistargeting occurred without observable changes of cell fate and correlated with localization of ectopic Dorsal in distal axons. We found that Dorsal and its inhibitor Cactus are expressed in photoreceptors, though neither was required for axon targeting. However, mutation analyses of genes known to act upstream of Dorsal revealed a requirement for the interleukin receptor-associated kinase family kinase Pelle for layer-specific targeting of photoreceptor axons, validating our screen as a means to identify new molecular determinants of nervous system development in vivo.
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Affiliation(s)
- Elizabeth N Mindorff
- Graduate Program in Neurological Sciences, McGill University, Montreal, Quebec, Canada
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3
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Tsai YC, Yao JG, Chen PH, Posakony JW, Barolo S, Kim J, Sun YH. Upd/Jak/STAT signaling represses wg transcription to allow initiation of morphogenetic furrow in Drosophila eye development. Dev Biol 2007; 306:760-71. [PMID: 17498684 DOI: 10.1016/j.ydbio.2007.04.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Revised: 04/08/2007] [Accepted: 04/11/2007] [Indexed: 12/23/2022]
Abstract
The initiation of retinal development in Drosophila begins at the posterior center (PC) of the eye disc margin. The front of the differentiation wave, recognized as a morphogenetic furrow (MF), moves from posterior to anterior. What determines MF initiates from the specific PC site is still unclear. The unpaired (upd) gene is expressed at PC at early third instar, just before the time of MF initiation. Therefore, upd is expressed at the appropriate time and location for a specific role in defining the site of MF initiation. upd encodes a ligand for the Jak/STAT signaling pathway. In this report, we showed that the Upd/Jak/STAT signaling is required and sufficient to determine MF initiation. This is primarily achieved by repressing the transcription of wingless (wg), which is known to block MF initiation.
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Affiliation(s)
- Yu-Chen Tsai
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China
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4
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Nam SC, Mukhopadhyay B, Choi KW. Antagonistic functions of Par-1 kinase and protein phosphatase 2A are required for localization of Bazooka and photoreceptor morphogenesis in Drosophila. Dev Biol 2007; 306:624-35. [PMID: 17475233 PMCID: PMC1975814 DOI: 10.1016/j.ydbio.2007.03.522] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 03/27/2007] [Accepted: 03/28/2007] [Indexed: 12/23/2022]
Abstract
Establishment and maintenance of apical basal cell polarity are essential for epithelial morphogenesis and have been studied extensively using the Drosophila eye as a model system. Bazooka (Baz), a component of the Par-6 complex, plays important roles in cell polarity in diverse cell types including the photoreceptor cells. In ovarian follicle cells, localization of Baz at the apical region is regulated by Par-1 protein kinase. In contrast, Baz in photoreceptor cells is targeted to adherens junctions (AJs). To examine the regulatory pathways responsible for Baz localization in photoreceptor cells, we studied the effects of Par-1 on Baz localization in the pupal retina. Loss of Par-1 impairs the maintenance of AJ markers including Baz and apical polarity proteins of photoreceptor cells but not the establishment of cell polarity. In contrast, overexpression of Par-1 or Baz causes severe mislocalization of junctional and apical markers, resulting in abnormal cell polarity. However, flies with similar overexpression of kinase-inactive mutant Par-1 or unphosphorylatable mutant Baz protein show relatively normal photoreceptor development. These results suggest that dephosphorylation of Baz at the Par-1 phosphorylation sites is essential for proper Baz localization. We also show that the inhibition of protein phosphatase 2A (PP2A) mimics the polarity defects caused by Par-1 overexpression. Furthermore, Par-1 gain-of-function phenotypes are strongly enhanced by reduced PP2A function. Thus, we propose that antagonism between PP2A and Par-1 plays a key role in Baz localization at AJ in photoreceptor morphogenesis.
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Affiliation(s)
- Sang-Chul Nam
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030
| | - Bibhash Mukhopadhyay
- Department of Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030
| | - Kwang-Wook Choi
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030
- Department of Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030
- *Corresponding author Tel: 713-798-8649, Fax: 713-798-4266,
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5
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Abstract
Fly visual circuits are organized into lattice-like arrays and layers. Recent genetic studies have provided insights into how these reiterated structures are assembled through stepwise processes and how precise connections are established during development. Afferent-derived morphogens, such as Hedgehog, play a key role in organizing the overall structure by inducing and recruiting target neurons and glia. In turn, the target-derived ligand DWnt4 guides Frizzled2-expressing photoreceptor afferents to their proper destination. Photoreceptor afferents select specific synaptic targets by forming adhesive interactions and regulating actin cytoskeleton in growth cones. Target specificity is probably achieved by restricting the expression of adhesive molecules, such as Capricious, to appropriate presynaptic and postsynaptic partners, and by differentially regulating the function of broadly expressed adhesive molecules such as N-cadherin.
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Affiliation(s)
- Chun-Yuan Ting
- Unit on Neuronal Connectivity, Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20817, USA
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6
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Bicker G. Pharmacological approaches to nitric oxide signalling during neural development of locusts and other model insects. Arch Insect Biochem Physiol 2007; 64:43-58. [PMID: 17167749 DOI: 10.1002/arch.20161] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
A novel aspect of cellular signalling during the formation of the nervous system is the involvement of the messenger molecule nitric oxide (NO), which has been discovered in the mammalian vascular system as mediator of smooth muscle relaxation. NO is a membrane-permeant molecule, which activates soluble guanylyl cyclase (sGC) and leads to the formation of cyclic GMP (cGMP) in target cells. The analysis of specific cell types in model insects such as Locusta, Schistocerca, Acheta, Manduca, and Drosophila shows that the NO/cGMP pathway is required for the stabilization of photoreceptor growth cones at the start of synaptic assembly in the optic lobe, for regulation of cell proliferation, and for correct outgrowth of pioneer neurons. Inhibition of the NOS and sGC enzymes combined with rescue experiments show that NO, and potentially also another atypical messenger, carbon monoxide (CO), orchestrate cell migration of enteric neurons. Cultured insect embryos are accessible model systems in which the molecular pathways linking cytoskeletal rearrangement to directed cell movements can be analyzed in natural settings. Based on the results obtained from the insect models, I discuss current evidence for NO and cGMP as essential signalling molecules for the development of vertebrate brains.
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Affiliation(s)
- Gerd Bicker
- University of Veterinary Medicine Hannover, Cell Biology, Institute of Physiology, Hannover, Germany.
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7
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Zhang T, Ranade S, Cai CQ, Clouser C, Pignoni F. Direct control of neurogenesis by selector factors in the fly eye: regulation of atonal by Ey and So. Development 2006; 133:4881-9. [PMID: 17108002 DOI: 10.1242/dev.02669] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During eye development, the selector factors of the Eyeless/Pax6 or Retinal Determination (RD) network control specification of organ-type whereas the bHLH-type proneural factor Atonal drives neurogenesis. Although significant progress has been made in dissecting the acquisition of ;eye identity' at the transcriptional level, the molecular mechanisms underlying the progression from neuronal progenitor to differentiating neuron remain unclear. A recently proposed model for the integration of organ specification and neurogenesis hypothesizes that atonal expression in the eye is RD-network-independent and that Eyeless works in parallel or downstream of atonal to modify the neurogenetic program. We show here that distinct cis-regulatory elements control atonal expression specifically in the eye and that the RD factors Eyeless and Sine oculis function as direct regulators. We find that these transcription factors interact in vitro and provide indirect evidence that this interaction may be required in vivo. The subordination of neurogenesis to the RD pathway in the eye provides a direct mechanism for the coordination of neurogenesis and tissue specification during sensory organ formation.
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Affiliation(s)
- Tianyi Zhang
- Ophthalmology Department, Harvard Medical School/MEEI, Boston, MA 02114, USA
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8
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Singh A. Eye development at the Houston "Fly Meeting". Int J Dev Biol 2006; 50:659-63. [PMID: 17051475 DOI: 10.1387/ijdb.062186as] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The 47th Annual Drosophila Research Conference or "Fly Meeting" took place at Houston, Texas, USA from March 29th- April 2nd, 2006, under the aegis of the Genetics Society of America. The Fly Meeting provides an excellent opportunity for fly researchers to present their work and to get a snapshot of recent developments and upcoming trends in their research field. The fruit fly, Drosophila melanogaster is a very versatile model to study growth, patterning, neural development, evolution, systemetics and various other facets of biomedical science. The topics presented in the meeting covered a very broad spectrum of fly research. In this commentary, I have focused mainly on the presentations related to two fields: 1) research in various fields that use the Drosophila eye as a model system, and 2) the community resources available to all fly researchers.
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Affiliation(s)
- Amit Singh
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
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9
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Abstract
Although many of the factors responsible for conferring identity to the eye field in Drosophila have been identified, much less is known about how the expression of the retinal ;trigger', the signaling molecule Hedgehog, is controlled. Here, we show that the co-expression of the conserved odd-skipped family genes at the posterior margin of the eye field is required to activate hedgehog expression and thereby the onset of retinogenesis. The fly Wnt1 homologue wingless represses the odd-skipped genes drm and odd along the anterior margin and, in this manner, spatially restricts the extent of retinal differentiation within the eye field.
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10
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Phuong Thao DT, Ida H, Yoshida H, Yamaguchi M. Identification of the Drosophila skpA gene as a novel target of the transcription factor DREF. Exp Cell Res 2006; 312:3641-50. [PMID: 16962096 DOI: 10.1016/j.yexcr.2006.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 08/09/2006] [Accepted: 08/09/2006] [Indexed: 10/24/2022]
Abstract
SKPa is component of a Drosophila SCF complex that functions in combination with the ubiquitin-conjugating enzyme UbcD1. skpA null mutation results in centrosome overduplication, unusual chromatin condensation, defective endoreduplication and cell-cycle progression. While the molecular mechanisms that regulate expression of the skpA gene are poorly understood, the DNA replication-related element (DRE) and the DRE-binding factor (DREF) play important roles in regulating proliferation-related genes in Drosophila and DRE (5'-TATCGATA) and DRE-like (5'-CATCGATT) sequences were here found to be involved in skpA promoter activity. Thus both luciferase transient expression assays in cultured Drosophila S2 cells using skpA promoter-luciferase fusion plasmids and anti-lacZ immunostaining of various tissues from transgenic third instar larvae carrying the skpA promoter-lacZ fusion genes provided supportive evidence. Furthermore, anti-SKPa immunostaining of eye imaginal discs from flies overexpressing DREF showed ectopic expression of protein in the region posterior to the morphogenetic furrow where DREF is overexpressed. Knockdown of DREF in some tissues where SKPa distribution is well known almost completely abrogated the skpA gene expression. These findings, taken together, indicate that the Drosophila skpA gene is a novel target of the transcription factor DREF.
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Affiliation(s)
- Dang Thi Phuong Thao
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
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11
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Hofmeyer K, Maurel-Zaffran C, Sink H, Treisman JE. Liprin-alpha has LAR-independent functions in R7 photoreceptor axon targeting. Proc Natl Acad Sci U S A 2006; 103:11595-600. [PMID: 16864797 PMCID: PMC1544215 DOI: 10.1073/pnas.0604766103] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the Drosophila visual system, the color-sensing photoreceptors R7 and R8 project their axons to two distinct layers in the medulla. Loss of the receptor tyrosine phosphatase LAR from R7 photoreceptors causes their axons to terminate prematurely in the R8 layer. Here we identify a null mutation in the Liprin-alpha gene based on a similar R7 projection defect. Liprin-alpha physically interacts with the inactive D2 phosphatase domain of LAR, and this domain is also essential for R7 targeting. However, another LAR-dependent function, egg elongation, requires neither Liprin-alpha nor the LAR D2 domain. Although human and Caenorhabditis elegans Liprin-alpha proteins have been reported to control the localization of LAR, we find that LAR localizes to focal adhesions in Drosophila S2R+ cells and to photoreceptor growth cones in vivo independently of Liprin-alpha. In addition, Liprin-alpha overexpression or loss of function can affect R7 targeting in the complete absence of LAR. We conclude that Liprin-alpha does not simply act by regulating LAR localization but also has LAR-independent functions.
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Affiliation(s)
- Kerstin Hofmeyer
- Skirball Institute for Biomolecular Medicine and Departments of *Cell Biology and
| | | | - Helen Sink
- Pharmacology, New York University School of Medicine, 540 First Avenue, New York, NY 10016
| | - Jessica E. Treisman
- Skirball Institute for Biomolecular Medicine and Departments of *Cell Biology and
- To whom correspondence should be addressed. E-mail:
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12
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Hagedorn EJ, Bayraktar JL, Kandachar VR, Bai T, Englert DM, Chang HC. Drosophila melanogaster auxilin regulates the internalization of Delta to control activity of the Notch signaling pathway. ACTA ACUST UNITED AC 2006; 173:443-52. [PMID: 16682530 PMCID: PMC2063844 DOI: 10.1083/jcb.200602054] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have isolated mutations in the Drosophila melanogaster homologue of auxilin, a J-domain-containing protein known to cooperate with Hsc70 in the disassembly of clathrin coats from clathrin-coated vesicles in vitro. Consistent with this biochemical role, animals with reduced auxilin function exhibit genetic interactions with Hsc70 and clathrin. Interestingly, the auxilin mutations interact specifically with Notch and disrupt several Notch-mediated processes. Genetic evidence places auxilin function in the signal-sending cells, upstream of Notch receptor activation, suggesting that the relevant cargo for this auxilin-mediated endocytosis is the Notch ligand Delta. Indeed, the localization of Delta protein is disrupted in auxilin mutant tissues. Thus, our data suggest that auxilin is an integral component of the Notch signaling pathway, participating in the ubiquitin-dependent endocytosis of Delta. Furthermore, the fact that auxilin is required for Notch signaling suggests that ligand endocytosis in the signal-sending cells needs to proceed past coat disassembly to activate Notch.
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MESH Headings
- Animals
- Auxilins/genetics
- Auxilins/physiology
- Body Patterning/genetics
- Body Patterning/physiology
- Clathrin/genetics
- Clathrin/metabolism
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/physiology
- Endocytosis/genetics
- Endocytosis/physiology
- ErbB Receptors/genetics
- ErbB Receptors/physiology
- Eye Abnormalities/genetics
- Eye Abnormalities/ultrastructure
- Gene Expression Regulation, Developmental
- Genotype
- HSC70 Heat-Shock Proteins/genetics
- HSC70 Heat-Shock Proteins/metabolism
- Intracellular Signaling Peptides and Proteins
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Microscopy, Electron, Scanning
- Mutation/genetics
- Nervous System/embryology
- Nervous System/metabolism
- Phenotype
- Photoreceptor Cells, Invertebrate/embryology
- Photoreceptor Cells, Invertebrate/metabolism
- RNA, Small Interfering/genetics
- Receptors, Notch/genetics
- Receptors, Notch/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Wings, Animal/embryology
- Wings, Animal/metabolism
- Wings, Animal/ultrastructure
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Affiliation(s)
- Elliott J Hagedorn
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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13
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Anderson J, Salzer CL, Kumar JP. Regulation of the retinal determination gene dachshund in the embryonic head and developing eye of Drosophila. Dev Biol 2006; 297:536-49. [PMID: 16780828 PMCID: PMC2717003 DOI: 10.1016/j.ydbio.2006.05.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 04/13/2006] [Accepted: 05/03/2006] [Indexed: 11/29/2022]
Abstract
The retinal determination gene dachshund is distantly related to the family of Ski/Sno proto-oncogenes and influences the development of a wide range of tissues including the embryonic head, optic lobes, brain, central nervous system as well as the post-embryonic leg, wing, genital and eye-antennal discs. We were interested in the regulatory mechanisms that control the dynamic expression pattern of dachshund and in this report we set out to ascertain how the transcription of dachshund is modulated in the embryonic head and developing eye-antennal imaginal disc. We demonstrate that the TGFbeta signaling cascade, the transcription factor zerknullt and several other patterning genes prevent dachshund from being expressed inappropriately within the embryonic head. Additionally, we show that several members of the eye specification cascade influence the transcription of dachshund during normal and ectopic eye development. Our results suggest that dachshund is regulated by a complex combinatorial code of transcription factors and signaling pathways. Unraveling this code may lead to an understanding of how dachshund regulates the development of many diverse tissue types including the eye.
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14
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Yang L, Baker NE. Notch activity opposes Ras-induced differentiation during the Second Mitotic Wave of the developing Drosophila eye. BMC Dev Biol 2006; 6:8. [PMID: 16504047 PMCID: PMC1420272 DOI: 10.1186/1471-213x-6-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 02/21/2006] [Indexed: 12/03/2022]
Abstract
Background EGF receptor acts through Ras and the MAPK cascade to trigger differentiation and maintain survival of most of cell types in the Drosophila retina. Cell types are specified sequentially by separate episodes of EGFR activity. All the cell types differentiate in G1 phase of the cell cycle. Before differentiating, many cells pass through the cell cycle in the "Second Mitotic Wave" in response to Notch activity, but no cell fates are specified during the Second Mitotic Wave. It is not known how fate specification is limited to G1-arrested cells. Results Competence to differentiate in response to activated RasV12 was diminished during the Second Mitotic Wave accounting for the failure to recruit cell fates from cycling cells. Competence was not restored by blocking cell cycle progression, but was restored by reduced Notch activity. Conclusion Competence to differentiate does not depend on cell cycle progression per se, but on the same receptor activity that also induces cell cycle entry. Dual effects of Notch on the cell cycle and on differentiation help ensure that only G1 phase cells undergo fate specification.
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Affiliation(s)
- Lihui Yang
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Nicholas E Baker
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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15
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Abstract
Glial cells have diverse functions that are necessary for the proper development and function of complex nervous systems. Various insects, primarily the fruit fly Drosophila melanogaster and the moth Manduca sexta, have provided useful models of glial function during development. The present review will outline evidence of glial contributions to embryonic, visual, olfactory and wing development. We will also outline evidence for non-developmental functions of insect glia including blood-brain-barrier formation, homeostatic functions and potential contributions to synaptic function. Where relevant, we will also point out similarities between the functions of insect glia and their vertebrate counterparts.
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Affiliation(s)
- Robert J Parker
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC, Canada V6T 1Z4
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16
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Richard M, Grawe F, Knust E. DPATJ plays a role in retinal morphogenesis and protects against light-dependent degeneration of photoreceptor cells in theDrosophila eye. Dev Dyn 2006; 235:895-907. [PMID: 16245332 DOI: 10.1002/dvdy.20595] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The establishment of apicobasal polarity in epithelial cells is a prerequisite for their function. Drosophila photoreceptor cells derive from epithelial cells, and their apical membranes undergo elaborate differentiation during pupal development, forming photosensitive rhabdomeres and associated stalk membranes. Crumbs (Crb), a transmembrane protein involved in the maintenance of epithelial polarity in the embryo, defines the stalk as a subdomain of the apical membrane. Crb organizes a complex composed of several PDZ domain-containing proteins, including DPATJ (formerly known as Discs lost). Taking advantage of a DPATJ mutant line in which only a truncated form of the protein is synthesized, we demonstrate that DPATJ is necessary for the stability of the Crb complex at the stalk membrane and is crucial for stalk membrane development and rhabdomere maintenance during late pupal stages. Moreover, DPATJ protects against light-induced photoreceptor degeneration.
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Affiliation(s)
- Mélisande Richard
- Institut für Genetik, Heinrich Heine Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
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17
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Abstract
Structural synapses are key regulators of information flow in neuronal networks. To understand the function and formation of neuronal circuits, the development and function of synapses have therefore been intensely studied in both vertebrate and invertebrate species. Precise descriptions of synapses and their amenability to genetic analysis in the model organism Drosophila provide an efficient platform from which to explore mechanisms and principles of synapse formation, which find many counterparts in other animals. Here we summarise our knowledge of the structure of Drosophila synapses. Focussing on neuromuscular junctions and photoreceptor synapses, we provide an overview of mechanisms underlying the development of synaptic structure in Drosophila.
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Affiliation(s)
- Andreas Prokop
- The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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18
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Abstract
The retina provides an example of a fundamental property of developing cells: cell fate decisions are stable. A recent paper reports a double negative feedback loop that leads to bistable fate decisions in the colour-detecting photoreceptors of Drosophila.
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19
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Fan Y, Soller M, Flister S, Hollmann M, Müller M, Bello B, Egger B, White K, Schäfer MA, Reichert H. The egghead gene is required for compartmentalization in Drosophila optic lobe development. Dev Biol 2005; 287:61-73. [PMID: 16182276 DOI: 10.1016/j.ydbio.2005.08.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2005] [Revised: 08/15/2005] [Accepted: 08/16/2005] [Indexed: 11/18/2022]
Abstract
The correct targeting of photoreceptor neurons (R-cells) in the developing Drosophila visual system requires multiple guidance systems in the eye-brain complex as well as the precise organization of the target area. Here, we report that the egghead (egh) gene, encoding a glycosyltransferase, is required for a compartment boundary between lamina glia and lobula cortex, which is necessary for appropriate R1-R6 innervation of the lamina. In the absence of egh, R1-R6 axons form a disorganized lamina plexus and some R1-R6 axons project abnormally to the medulla instead of the lamina. Mosaic analysis demonstrates that this is not due to a loss of egh function in the eye or in the neurons and glia of the lamina. Rather, as indicated by clonal analysis and cell-specific genetic rescue experiments, egh is required in cells of the lobula complex primordium which transiently abuts the lamina and medulla in the developing larval brain. In the absence of egh, perturbation of sheath-like glial processes occurs at the boundary region delimiting lamina glia and lobula cortex, and inappropriate invasion of lobula cortex cells across this boundary region disrupts the pattern of lamina glia resulting in inappropriate R1-R6 innervation. This finding underscores the importance of the lamina/lobula compartment boundary in R1-R6 axon targeting.
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Affiliation(s)
- Yun Fan
- Biozentrum/Pharmazentrum, University of Basel, Klingelbergstrasse 50, CH-4056 Basel, Switzerland.
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20
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Abstract
Global changes in gene expression and exit from the cell cycle underlie differentiation. Therefore, understanding chromatin behavior in differentiating nuclei and late G1 is key to understanding this developmental event. A nuclear event that has been shown to specifically occur in late G1 is the association of two heterochromatic blocks in Drosophila. The brown(Dominant) (bw(D)) chromosome of Drosophila melanogaster contains a large block of heterochromatin near the end of 2R. This distal block associates with centric heterochromatin (2Rh), but not until at least 5 hours into G1. We used the bw(D) allele as a model for nuclear organization to determine whether its association with the heterochromatic compartment of the second chromosomes (2Rh) strictly requires differentiation or if this change is a stochastic event, its occurrence being proportional to time spent in G1/G0 phase of the cell cycle. Fluorescence in situ hybridization on eye imaginal discs showed increased association between the bw locus and 2Rh in differentiated cells. Interestingly, an increase in the number of nuclei showing bw(D)-2Rh association in the brains of developmentally delayed larvae that were compromised for differentiation was also observed. Live fluorescence imaging showed that the kinetics of chromatin movement remains unchanged in the developmentally arrested nuclei. These observations suggest that nuclear reorganization is not directly controlled by specific inductive signals during differentiation and that this nuclear reorganization can happen in a cell, regardless of differentiation state, that is arrested in the appropriate cell cycle stage. However, we did see changes that appear to be more directly correlated with differentiation. Dynamic imaging in eye imaginal discs showed that the movement of chromatin is more constrained in differentiated cells, implying that confinement of loci to a smaller nuclear space may help to maintain the changed organization and the transcription profile that accompanies differentiation.
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Affiliation(s)
- Rajika Thakar
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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21
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Anderson J, Bhandari R, Kumar JP. A genetic screen identifies putative targets and binding partners of CREB-binding protein in the developing Drosophila eye. Genetics 2005; 171:1655-72. [PMID: 15998717 PMCID: PMC1456093 DOI: 10.1534/genetics.105.045450] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Drosophila CREB-binding protein (dCBP) is a very large multidomain protein, which belongs to the CBP/p300 family of proteins that were first identified by their ability to bind the CREB transcription factor and the adenoviral protein E1. Since then CBP has been shown to bind to >100 additional proteins and functions in a multitude of different developmental contexts. Among other activities, CBP is known to influence development by remodeling chromatin, by serving as a transcriptional coactivator, and by interacting with terminal members of several signaling transduction cascades. Reductions in CBP activity are the underlying cause of Rubinstein-Taybi syndrome, which is, in part, characterized by several eye defects, including strabismus, cataracts, juvenile glaucoma, and coloboma of the eyelid, iris, and lens. Development of the Drosophila melanogaster compound eye is also inhibited in flies that are mutant for CBP. However, the vast array of putative protein interactions and the wide-ranging roles played by CBP within a single tissue such as the retina can often complicate the analysis of CBP loss-of-function mutants. Through a series of genetic screens we have identified several genes that could either serve as downstream transcriptional targets or encode for potential CBP-binding partners and whose association with eye development has hitherto been unknown. The identification of these new components may provide new insight into the roles that CBP plays in retinal development. Of particular interest is the identification that the CREB transcription factor appears to function with CBP at multiple stages of retinal development.
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Affiliation(s)
- Jason Anderson
- Department of Biology, Indiana University, 1001 E. 3rd Street, Jordan Hall A318, Bloomington, IN 47401, USA
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22
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Djiane A, Yogev S, Mlodzik M. The apical determinants aPKC and dPatj regulate Frizzled-dependent planar cell polarity in the Drosophila eye. Cell 2005; 121:621-631. [PMID: 15907474 DOI: 10.1016/j.cell.2005.03.014] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2004] [Revised: 01/26/2005] [Accepted: 03/11/2005] [Indexed: 12/18/2022]
Abstract
Planar cell polarity (PCP) is a common feature of many vertebrate and invertebrate epithelia and is perpendicular to their apical/basal (A/B) polarity axis. While apical localization of PCP determinants such as Frizzled (Fz1) is critical for their function, the link between A/B polarity and PCP is poorly understood. Here, we describe a direct molecular link between A/B determinants and Fz1-mediated PCP establishment in the Drosophila eye. We demonstrate that dPatj binds the cytoplasmic tail of Fz1 and propose that it recruits aPKC, which in turn phosphorylates and inhibits Fz1. Accordingly, components of the aPKC complex and dPatj produce PCP defects in the eye. We also show that during PCP signaling, aPKC and dPatj are downregulated, while Bazooka is upregulated, suggesting an antagonistic effect of Bazooka on dPatj/aPKC. We propose a model whereby the dPatj/aPKC complex regulates PCP by inhibiting Fz1 in cells where it should not be active.
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Affiliation(s)
- Alexandre Djiane
- Brookdale Department of Molecular, Cell and Developmental Biology, Mount Sinai School of Medicine, New York, New York 10029
| | - Shaul Yogev
- Brookdale Department of Molecular, Cell and Developmental Biology, Mount Sinai School of Medicine, New York, New York 10029
| | - Marek Mlodzik
- Brookdale Department of Molecular, Cell and Developmental Biology, Mount Sinai School of Medicine, New York, New York 10029.
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23
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Abstract
The development and evolution of eyes is an "old problem" in biology, which required a special treatment in Charles Darwin's "Origin of the species" (1882) under the heading of "Difficulties of the theory". Darwin postulated a simple and imperfect eye, as a prototype, which can vary and evolve under natural selection into more complex and perfect eyes. Based upon morphological criteria and the different modes of development of the different kinds of eyes, neodarwinists have postulated that the various eye-types are polyphyletic in origin and that the eyes have evolved independently in the various animal phyla. Recent developmental genetic experiments and molecular phylogenetic analyses cast serious doubts on this interpretation and argue strongly for a monophyletic origin of the eyes from a Darwinian prototype and subsequent divergent, parallel and convergent evolution leading to the various eye-types.
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Affiliation(s)
- Walter J Gehring
- Dept. Cell Biology, Biozentrum, University of Basel, Switzerland.
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24
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Abstract
The paired-like homeobox-containing gene Rx has a critical role in the eye development of several vertebrate species including Xenopus, mouse, chicken, medaka, zebrafish and human. Rx is initially expressed in the anterior neural region of developing embryos, and later in the retina and ventral hypothalamus. Abnormal regulation or function of Rx results in severe abnormalities of eye formation. Overexpression of Rx in Xenopus and zebrafish embryos leads to overproliferation of retinal cells. A targeted elimination of Rx in mice results in a lack of eye formation. Mutations in Rx genes are the cause of the mouse mutation eyeless (ey1), the medaka temperature sensitive mutation eyeless (el) and the zebrafish mutation chokh. In humans, mutations in Rx lead to anophthalmia. All of these studies indicate that Rx genes are key factors in vertebrate eye formation. Because these results cannot be easily reconciled with the most popular dogmas of the field, we offer our interpretation of eye development and evolution.
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Affiliation(s)
- Travis J Bailey
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
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25
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Abstract
We show that reducing the activity of the Drosophila Runx protein Lozenge (Lz) during pupal development causes a decrease in cell death in the eye. We identified Lz-binding sites in introns of argos (aos) and klumpfuss (klu) and demonstrate that these genes are directly activated targets of Lz. Loss of either aos or klu reduces cell death, suggesting that Lz promotes apoptosis at least in part by regulating aos and klu. These results provide novel insights into the control of programmed cell death (PCD) by Lz during Drosophila eye development.
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Affiliation(s)
- Jill Wildonger
- Center for Neurobiology and Behavior, Howard Hughes Medical Institute, Columbia University Medical School, New York, NY 10032, USA
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26
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Abstract
Signaling pathways generally contain multiple negative regulators that are induced by the signal they repress, constructing negative feedback loops. Although such negative regulators are often expressed in a tissue- or cell-type specific manner during development, little is known about the significance of their differential expression patterns and possible interactions. We show the role and interplay of two cell-type specific negative feedback loops during specification of photoreceptor neurons in the Drosophila compound eye, a process that occurs via epidermal growth factor (EGF)-mediated sequential induction through the activation of the Ras/MAPK signaling pathway. Inducing cells secreting EGF express a negative regulator Sprouty (SPRY) that lowers Ras/MAPK signaling activity, and as a consequence reduces the signal-dependent expression of a secreted EGF inhibitor, Argos (AOS). Induced cells in turn express an orphan nuclear receptor Seven-up (SVP), which represses SPRY expression thereby allowing expression and secretion of AOS, preventing further induction. When this intricate system fails, as in spry mutants, sequential induction is no longer constant and the number of photoreceptor neurons becomes variable. Thus, cell-type specific utilization of multiple negative feedback loops not only confers developmental robustness through functional redundancy, but is a key component in generating consistent patterning.
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Affiliation(s)
- Masaki Iwanami
- Division of Developmental Genetics, National Institute of Genetics, Mishima, Shizuoka, 411-8540, Japan
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27
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Jenny A, Reynolds-Kenneally J, Das G, Burnett M, Mlodzik M. Diego and Prickle regulate Frizzled planar cell polarity signalling by competing for Dishevelled binding. Nat Cell Biol 2005; 7:691-7. [PMID: 15937478 DOI: 10.1038/ncb1271] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Accepted: 05/05/2005] [Indexed: 11/08/2022]
Abstract
Epithelial planar cell polarity (PCP) is evident in the cellular organization of many tissues in vertebrates and invertebrates. In mammals, PCP signalling governs convergent extension during gastrulation and the organization of a wide variety of structures, including the orientation of body hair and sensory hair cells of the inner ear. In Drosophila melanogaster, PCP is manifest in adult tissues, including ommatidial arrangement in the compound eye and hair orientation in wing cells. PCP establishment requires the conserved Frizzled/Dishevelled PCP pathway. Mutations in PCP-pathway-associated genes cause aberrant orientation of body hair or inner-ear sensory cells in mice, or misorientation of ommatidia and wing hair in D. melanogaster. Here we provide mechanistic insight into Frizzled/Dishevelled signalling regulation. We show that the ankyrin-repeat protein Diego binds directly to Dishevelled and promotes Frizzled signalling. Dishevelled can also be bound by the Frizzled PCP antagonist Prickle. Strikingly, Diego and Prickle compete with one another for Dishevelled binding, thereby modulating Frizzled/Dishevelled activity and ensuring tight control over Frizzled PCP signalling.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Animals
- Binding Sites/genetics
- Binding, Competitive
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Carrier Proteins/physiology
- Cell Polarity/genetics
- Cell Polarity/physiology
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- DNA-Binding Proteins/physiology
- Dishevelled Proteins
- Drosophila Proteins/genetics
- Drosophila Proteins/metabolism
- Drosophila Proteins/physiology
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/physiology
- Eye/cytology
- Eye/embryology
- Eye/metabolism
- Eye Proteins/genetics
- Eye Proteins/metabolism
- Frizzled Receptors
- Gene Expression Regulation, Developmental
- Immunoprecipitation
- LIM Domain Proteins
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Membrane Proteins/physiology
- Models, Biological
- Mutation
- Phenotype
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Phosphoproteins/physiology
- Phosphorylation
- Photoreceptor Cells, Invertebrate/cytology
- Photoreceptor Cells, Invertebrate/embryology
- Photoreceptor Cells, Invertebrate/metabolism
- Protein Binding
- Receptor Protein-Tyrosine Kinases/genetics
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptors, G-Protein-Coupled
- Signal Transduction/genetics
- Signal Transduction/physiology
- Two-Hybrid System Techniques
- Wings, Animal/cytology
- Wings, Animal/embryology
- Wings, Animal/metabolism
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Affiliation(s)
- Andreas Jenny
- Mount Sinai School of Medicine, Brookdale Department of Molecular, Cellular and Developmental Biology, 1 Gustave L. Levy Place, New York, NY 10029, USA
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28
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Abstract
The misexpression of an activated form of the FGF receptor (FGFR) Breathless in conjunction with downstream-of-FGF-receptor (Dof), an essential signaling molecule of the FGF pathway, in the Drosophila eye imaginal discs impairs eye development and results in a rough eye phenotype. We used this phenotype in a gain-of-function screen to search for modifiers of FGF signaling. We identified 50 EP stocks with insertions defining at least 35 genes that affect the rough eye phenotype. Among these genes, 4 appear to be specific for FGFR signaling, but most of the genes also influence other signaling pathways, as assessed by their effects on rough eyes induced by other activated receptor tyrosine kinases (RTKs). Analysis of loss-of-function alleles of a number of these genes in embryos indicates that in many cases the products are provided maternally and are involved in germ cell development. At least two of the genes, sar1 and robo2, show a genetic interaction with a hypomorphic dof allele, suggesting that they participate in FGF-mediated morphogenetic events during embryogenesis.
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Affiliation(s)
- Min Yan Zhu
- Institut für Genetik, Universität zu Köln, Germany
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29
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Abstract
The human translocation (t8;21) is associated with approximately 12% of the cases of acute myelogenous leukemia. Two genes, AML1 and ETO, are fused together at the translocation breakpoint, resulting in the expression of a chimeric protein called AML1-ETO. AML1-ETO is thought to interfere with normal AML1 function, although the mechanism by which it does so is unclear. Here, we have used Drosophila genetics to investigate two models of AML1-ETO function. In the first model, AML1-ETO is a constitutive transcriptional repressor of AML1 target genes, regardless of whether they are normally activated or repressed by AML1. In the second model, AML1-ETO dominantly interferes with AML1 activity by, for example, competing for a common co-factor. To discriminate between these models, the effects of expressing AML1-ETO were characterized and compared with loss-of-function phenotypes of lozenge (lz), an AML1 homolog expressed during Drosophila eye development. We also present results of genetic interaction experiments with AML1 co-factors that are not consistent with AML1-ETO behaving as a dominant-negative factor. Instead, our data suggest that AML1-ETO acts as a constitutive transcriptional repressor.
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Affiliation(s)
- Jill Wildonger
- Center for Neurobiology and Behavior, Columbia University Medical School, New York, NY 10032, USA
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30
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Inoue Y, Miyawaki K, Terasawa T, Matsushima K, Shinmyo Y, Niwa N, Mito T, Ohuchi H, Noji S. Expression patterns of dachshund during head development of Gryllus bimaculatus (cricket). Gene Expr Patterns 2005; 4:725-31. [PMID: 15465496 DOI: 10.1016/j.modgep.2004.03.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 03/24/2004] [Accepted: 03/25/2004] [Indexed: 11/17/2022]
Abstract
We report that Gryllus bimaculatus dachshund (Gbdac), a cricket homologue of Drosophila dachshund (Dmdac), is expressed in the developing eye and brain. During brain development, Gbdac was first expressed in the medial head region, corresponding to a part of developing protocephalic region, and expressed in the primordial and adult Kenyon cells. During eye development, Gbdac was first expressed in the lateral head region, becoming to the eye primordium and a part of the deutocerebrum. Then, Gbdac was expressed in the posterior region of the eye primordium, prior to the formation of compound eyes. The expression domain shifted to the anterior domain concomitantly with the movement of morphogenetic furrows. Gbdac was also expressed in the developing optic lobes during differentiation of the retina. These expression patterns were compared with those of Dmdac. We found that although developmental processes of the Gryllus eye and brain differ from those of the Drosophila ones, the expression patterns of Gbdac are essentially similar to those of the Dmdac.
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Affiliation(s)
- Yoshiko Inoue
- Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, 2-1 Minami-jyosanjima-cho, Tokushima 770-8506, Japan
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31
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Abstract
Context-specific integration of information received from the Notch, Transforming growth factor beta, Wingless/Wnt, Hedgehog and Epidermal growth factor receptor signaling pathways sets the stage for deployment of the retinal determination gene network (RDGN), a group of transcription factors that collectively directs the formation of the eye and other tissues. Recent investigations have revealed how these transcription factors are regulated by their interactions with each other and with effectors of the above signaling pathways. Further study of the RDGN may provide insights into how common cues can generate context-specific responses, a key aspect of developmental regulation that remains poorly understood.
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Affiliation(s)
- Serena J Silver
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
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32
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Abstract
The NURD and Sin3 histone deacetylase complexes are involved in transcriptional repression through global deacetylation of chromatin. Both complexes contain many different components that may control how histone deacetylase complexes are regulated and interact with other transcription factors. In a genetic screen for modifiers of wingless signaling in the Drosophila eye, we isolated mutations in the Drosophila homolog of p66, a protein previously purified as part of the Xenopus NURD/Mi-2 complex. p66 encodes a highly conserved nuclear zinc-finger protein that is required for development and we propose that the p66 protein acts as a regulatory component of the NURD complex. Animals homozygous mutant for p66 display defects during metamorphosis possibly caused by misregulation of ecdysone-regulated expression. Although heterozygosity for p66 enhances a wingless phenotype in the eye, loss-of-function clones in the wing and the eye discs do not have any detectable phenotype, possibly due to redundancy with the Sin3 complex. Overexpression of p66, on the other hand, can repress wingless-dependent phenotypes. Furthermore, p66 expression can repress multiple reporters in a cell culture assay, including a Wnt-responsive TCF reporter construct, implicating the NURD complex in repression of Wnt target genes. By co-immunoprecipitation, p66 associates with dMi-2, a known NURD complex member.
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MESH Headings
- Alleles
- Amino Acid Sequence
- Animals
- Cell Nucleus/metabolism
- Cells, Cultured
- Cloning, Molecular
- Crosses, Genetic
- Drosophila Proteins/metabolism
- Ecdysone/metabolism
- Gene Expression Regulation
- Gene Expression Regulation, Developmental
- Genes, Reporter
- Genetic Techniques
- Green Fluorescent Proteins/metabolism
- Heterozygote
- Histone Deacetylases/biosynthesis
- Histone Deacetylases/metabolism
- Homozygote
- Humans
- Immunoprecipitation
- In Situ Hybridization
- Luciferases/metabolism
- Metamorphosis, Biological
- Mi-2 Nucleosome Remodeling and Deacetylase Complex
- Microscopy, Electron, Scanning
- Models, Genetic
- Molecular Sequence Data
- Mutation
- Phenotype
- Photoreceptor Cells, Invertebrate/embryology
- Plasmids/metabolism
- Protein Binding
- Proto-Oncogene Proteins/metabolism
- Receptors, Antigen, T-Cell/metabolism
- Signal Transduction
- Sin3 Histone Deacetylase and Corepressor Complex
- Time Factors
- Transcription, Genetic
- Wnt1 Protein
- Zinc Fingers
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Affiliation(s)
- Charlene Kon
- Department of Developmental Biology, Howard Hughes Medical Institute, Beckman Center, Stanford University School of Medicine, California 94305-5329, USA
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33
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Ting CY, Yonekura S, Chung P, Hsu SN, Robertson HM, Chiba A, Lee CH. Drosophila N-cadherin functions in the first stage of the two-stage layer-selection process of R7 photoreceptor afferents. Development 2005; 132:953-63. [PMID: 15673571 DOI: 10.1242/dev.01661] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Visual information received from the three types of photoreceptor neurons (R1-R6, R7 and R8) in the fly compound eyes converges to the external part of the medulla neuropil (M1-M6 layers) in a layer-specific fashion: R7 and R8 axons terminate at the M6 and M3 layers, respectively, whereas lamina neurons (L1-L5) relay R1-R6 to multiple medulla layers (M1-M5). Here, we show that during development, R7 and R8 neurons establish layer-specific projections in two separate stages: during the first stage, R7 and R8 axons sequentially target to the R7- and R8-temporary layers, respectively; and at the second stage, R7 and R8 growth cones progress synchronously to their destined layers. Using a set of mutations that delete different afferent subsets or alter R7 connectivity, we defined the mechanism of layer selection. We observed that R8, R7 and L1-L5 afferents target to their temporary layers independently, suggesting that afferent-target, but not afferent-afferent, interactions dictate the targeting specificity. N-cadherin is required in the first stage for R7 growth cones to reach and remain in the R7-temporary layer. The Ncad gene contains three pairs of alternatively spliced exons and encodes 12 isoforms. However, expressing a single Ncad isoform in Ncad mutant R7s is sufficient to rescue mistargeting phenotypes. Furthermore, Ncad isoforms mediate promiscuous heterophilic interactions in an in vitro cell-aggregation assay. We propose that Ncad isoforms do not form an adhesion code; rather, they provide permissive adhesion between R7 growth cones and their temporary targets.
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Affiliation(s)
- Chun-Yuan Ting
- Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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34
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Kristiansen LV, Velasquez E, Romani S, Baars S, Berezin V, Bock E, Hortsch M, Garcia-Alonso L. Genetic analysis of an overlapping functional requirement for L1- and NCAM-type proteins during sensory axon guidance in Drosophila. Mol Cell Neurosci 2005; 28:141-52. [PMID: 15607949 DOI: 10.1016/j.mcn.2004.09.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 08/30/2004] [Accepted: 09/02/2004] [Indexed: 10/26/2022] Open
Abstract
L1- and NCAM-type cell adhesion molecules represent distinct protein families that function as specific receptors for different axon guidance cues. However, both L1 and NCAM proteins promote axonal growth by inducing neuronal tyrosine kinase activity and are coexpressed in subsets of axon tracts in arthropods and vertebrates. We have studied the functional requirements for the Drosophila L1- and NCAM-type proteins, Neuroglian (Nrg) and Fasciclin II (FasII), during postembryonic sensory axon guidance. The rescue of the Neuroglian loss-of-function (LOF) phenotype by transgenically expressed L1- and NCAM-type proteins demonstrates a functional interchangeability between these proteins in Drosophila photoreceptor pioneer axons, where both proteins are normally coexpressed. In contrast, the ectopic expression of Fasciclin II in mechanosensory neurons causes a strong enhancement of the axonal misguidance phenotype. Moreover, our findings demonstrate that this functionally redundant specificity to mediate axon guidance has been conserved in their vertebrate homologs, L1-CAM and NCAM.
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MESH Headings
- Animals
- Cell Adhesion Molecules, Neuronal/genetics
- Cell Adhesion Molecules, Neuronal/metabolism
- Cell Communication/genetics
- Drosophila/embryology
- Drosophila/genetics
- Drosophila/metabolism
- Drosophila Proteins
- Eye/cytology
- Eye/embryology
- Eye/metabolism
- Gene Expression Regulation, Developmental/genetics
- Growth Cones/metabolism
- Growth Cones/ultrastructure
- Mechanoreceptors/cytology
- Mechanoreceptors/embryology
- Mechanoreceptors/metabolism
- Nervous System/cytology
- Nervous System/embryology
- Nervous System/metabolism
- Neural Cell Adhesion Molecule L1/genetics
- Neural Cell Adhesion Molecule L1/metabolism
- Neural Cell Adhesion Molecules/genetics
- Neural Cell Adhesion Molecules/metabolism
- Neurons, Afferent/cytology
- Neurons, Afferent/metabolism
- Phenotype
- Photoreceptor Cells, Invertebrate/cytology
- Photoreceptor Cells, Invertebrate/embryology
- Photoreceptor Cells, Invertebrate/metabolism
- Transgenes/genetics
- Wings, Animal/cytology
- Wings, Animal/embryology
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Affiliation(s)
- Lars V Kristiansen
- Instituto de Neurociencias CSIC-UMH, Universidad Miguel Hernandez, Sant Joan d'Alacant, 03550 Spain
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35
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Namciu SJ, Fournier REK. Human matrix attachment regions are necessary for the establishment but not the maintenance of transgene insulation in Drosophila melanogaster. Mol Cell Biol 2004; 24:10236-45. [PMID: 15542833 PMCID: PMC529032 DOI: 10.1128/mcb.24.23.10236-10245.2004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 07/06/2004] [Accepted: 09/01/2004] [Indexed: 11/20/2022] Open
Abstract
Human matrix attachment regions (MARs) can insulate transgene expression from chromosomal position effects in Drosophila melanogaster. To gain insight into the mechanism(s) by which chromosomal insulation occurs, we studied the expression phenotypes of Drosophila transformants expressing mini-white transgenes in which MAR sequences from the human apoB gene were arranged in a variety of ways. In agreement with previous reports, we found that a single copy of the insulating element was not sufficient for position-independent transgene expression; rather, two copies were required. However, the arrangement of the two elements within the transgene was unimportant, since chromosomal insulation was equally apparent when both copies of the insulator were upstream of the mini-white reporter as when the transcription unit was flanked by insulator elements. Moreover, experiments in which apoB 3' MAR sequences were removed from integrated transgenes in vivo by site-specific recombination demonstrated that MAR sequences were required for the establishment but not for the maintenance of chromosomal insulation. These observations are not compatible with the chromosomal loop model in its simplest form. Alternate mechanisms for MAR function in this system are proposed.
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Affiliation(s)
- Stephanie J Namciu
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Seattle, WA 98109, USA
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36
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Abstract
Brain morphogenesis depends on the maintenance of boundaries between populations of non-intermingling cells. We used molecular markers to characterize a boundary within the optic lobe of the Drosophila brain and found that Slit and the Robo family of receptors, well-known regulators of axon guidance and neuronal migration, inhibit the mixing of adjacent cell populations in the developing optic lobe. Our data suggest that Slit is needed in the lamina to prevent inappropriate invasion of Robo-expressing neurons from the lobula cortex. We show that Slit protein surrounds lamina glia, while the distal cell neurons in the lobula cortex express all three Drosophila Robos. We examine the function of these proteins in the visual system by isolating a novel allele of slit that preferentially disrupts visual system expression of Slit and by creating transgenic RNA interference flies to inhibit the function of each Drosophila Robo in a tissue-specific fashion. We find that loss of Slit or simultaneous knockdown of Robo, Robo2 and Robo3 causes distal cell neurons to invade the lamina, resulting in cell mixing across the lamina/lobula cortex boundary. This boundary disruption appears to lead to alterations in patterns of axon navigation in the visual system. We propose that Slit and Robo-family proteins act to maintain the distinct cellular composition of the lamina and the lobula cortex.
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Affiliation(s)
| | | | - Paul A. Garrity
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue 68-230B, Cambridge, MA 02139, USA
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37
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Abstract
Animal eyes have long served as a classical example of independent origin followed by convergence of structures onto a few different solutions. During the past decade this view has been challenged by the discovery of shared developmental regulatory genes. The Pax6 gene in particular is almost universally employed for eye formation in bilaterian animals, despite widely different embryological origins. The resulting controversy on the multiple or single origins of animal eyes has gradually been sharpened by continuing discoveries of further general similarities in the genetic regulatory circuits of eye development. Recent work on gene expression in specified cell types, together with comparative studies of developmental genes in cnidarians, now show some promise to a solution of the controversy.
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Affiliation(s)
- Dan-E Nilsson
- Department of Cell and Organism Biology, Lund University, Zoology building, Helgonavägen 3, 22362 Lund, Sweden.
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38
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Abstract
The sensory tasks performed by the eye are diverse and complex. In Drosophila, the eye performs motion detection for navigation as well as detection of the quality of light (color and polarized light). Both types of inputs are processed separately, as different photoreceptors are specialized in these tasks and contact different target cell layers in the optic lobe. However, their respective outputs are likely to be integrated in higher brain centers. Here, we discuss the cell diversity and potential role of the several ganglia that form the fly optic lobe. We also discuss the power of modern genetic tools to provide the potential to trace the visual neural networks.
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Affiliation(s)
- Javier Morante
- Department of Biology, New York University, 1009 Silver Building, 100 Washington Square East, New York, NY 10003, USA
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39
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Abstract
The ontogeny of photosensitivity has been studied in a holometabolous insect, the midge Chironomus ramosus. The life cycle of midges shifts from an aquatic environment to a non-aquatic environment. Extracellular electrical activity of photoreceptor organs was recorded at larval and adult stages. We found an increase in photosensitivity as the larva metamorphosed to the adult stage. This is the first report of changes in photosensitivity during the development of any insect described in an ecological context.
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Affiliation(s)
- A A Babrekar
- Department of Zoology, University of Pune, 411 007, India
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40
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Hernández G, Vázquez-Pianzola P, Zurbriggen A, Altmann M, Sierra JM, Rivera-Pomar R. Two functionally redundant isoforms of Drosophila melanogaster eukaryotic initiation factor 4B are involved in cap-dependent translation, cell survival, and proliferation. ACTA ACUST UNITED AC 2004; 271:2923-36. [PMID: 15233788 DOI: 10.1111/j.1432-1033.2004.04217.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Eukaryotic initiation factor (eIF) 4B is part of the protein complex involved in the recognition and binding of mRNA to the ribosome. DrosophilaeIF4B is a single-copy gene that encodes two isoforms, termed eIF4B-L (52.2 kDa) and eIF4B-S (44.2 kDa), generated as a result of the alternative recognition of two polyadeynlation signals during transcription termination and subsequent alternative splicing of the two pre-mRNAs. Both eIF4B mRNAs and proteins are expressed during the entire embryogenesis and life cycle. The proteins are cytoplasmic with polarized distribution. The two isoforms bind RNA with the same affinity. eIF4B-L and eIF4B-S preferentially enhance cap-dependent over IRES-dependent translation initiation in a Drosophila cell-free translation system. RNA interference experiments suggest that eIF4B is required for cell survival, although only a modest reduction in rate of protein synthesis is observed. Overexpression of eIF4B in Drosophila cells in culture and in developing eye imaginal discs promotes cell proliferation.
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Affiliation(s)
- Greco Hernández
- Max-Planck-Institute für biophysikalische Chemie, Göttingen, Germany
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41
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Abstract
This report shows that the Wingless signaling pathway regulates the expression of epidermal growth factor receptor (EGFR) in Drosophila. This pathway specifies cell fate during head development. Blocking wingless signaling upregulates Drosophila epidermal growth factor receptor (DER) activity and expands its expression domains in the eye primordium. Moreover, ectopic expression of wingless inhibits DER signaling and dramatically restricts its expression domain. This study suggests a novel role of wingless in specifying the Drosophila dorsal head via blocking vein expression in this region.
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Affiliation(s)
- Amr Amin
- Biology Department, UAE University, Al-Ain, UAE.
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Pi H, Huang SK, Tang CY, Sun YH, Chien CT. phyllopod is a target gene of proneural proteins in Drosophila external sensory organ development. Proc Natl Acad Sci U S A 2004; 101:8378-83. [PMID: 15148389 PMCID: PMC420402 DOI: 10.1073/pnas.0306010101] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proneural basic helix-loop-helix (bHLH) proteins initiate neurogenesis in both vertebrates and invertebrates. The Drosophila Achaete (Ac) and Scute (Sc) proteins are among the first identified members of the large bHLH proneural protein family. phyllopod (phyl), encoding an ubiquitin ligase adaptor, is required for ac- and sc-dependent external sensory (ES) organ development. Expression of phyl is directly activated by Ac and Sc. Forced expression of phyl rescues ES organ formation in ac and sc double mutants. phyl and senseless, encoding a Zn-finger transcriptional factor, depend on each other in ES organ development. Our results provide the first example that bHLH proneural proteins promote neurogenesis through regulation of protein degradation.
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Affiliation(s)
- Haiwei Pi
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
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43
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Abstract
The identification of Drosophila genes that inhibit proliferation while simultaneously promoting apoptosis--decreasing cell number--or that promote proliferation while simultaneously inhibiting apoptosis--increasing cell number--has revealed new ways that cell birth and death may be coupled to meet the needs of development.
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Affiliation(s)
- Burnley Jaklevic
- Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309-0347, USA
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44
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Abstract
Ezrin-Radixin-Moesin (ERM) family proteins organize heterogeneous sub-plasma membrane protein scaffolds that shape membranes and their physiology. In Drosophila oocytes and imaginal discs, epithelial organization, fundamental to development and physiology, is devastated by the loss of Moesin. Here, we show that Moesin is crucial for Drosophila photoreceptor morphogenesis. Beyond its requirement for retinal epithelium integrity, Moesin is essential for the proper assembly of the apical membrane skeleton that builds the photosensitive membrane, the rhabdomere. Moesin localizes to the rhabdomere base, a dynamic locus of cytoskeletal reorganization and membrane traffic. Downregulation of Moesin through RNAi or genetic loss of function profoundly disrupts the membrane cytoskeleton and apical membrane organization. We find normal levels and distribution of Moesin in photoreceptors of a Moesin mutant previously regarded as protein null, suggesting alternative interpretations for studies using this allele. Our results show an essential structural role for Moesin in photoreceptor morphology.
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Affiliation(s)
- Sue A Karagiosis
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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45
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Abstract
The Drosophila compound eye has long served as an outstanding model system to study many processes, including cell fate specification, cell division, cell growth and cell death. In addition, exploring the molecular basis of eye specification in Drosophila has identified a set of nuclear factors that trigger the conversion of a group of multipotent epithelial cells into eye primordia. These nuclear factors act in complex networks to regulate retinal specification and appear to be conserved throughout phylogeny. Finally, evidence suggests that these nuclear networks have been co-opted to specify cell fates in other tissues. We review the latest developments in the field of retinal specification in Drosophila and discuss several future directions that remain open for investigation.
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Affiliation(s)
- Kartik S Pappu
- Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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46
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Abstract
In this review we highlight two genetic pathways important for eye morphogenesis that are partially conserved between flies and vertebrates. Initially we focus on the ey paradigm and establish which aspects of this genetic hierarchy are conserved in vertebrates. We discuss experiments that evaluate the non-linear relationship amongst the genes of the hierarchy with a concentration on vertebrate functional genetics. We specifically consider the Six genes and their relationship to sine oculis, as tremendous amounts of new data have emerged on this topic. Finally, we highlight similarities between Shh/Hh directed morphogenesis mediated by basic Helix-Loop-Helix factors in vertebrate retinal cell specification and in specification of fly photoreceptors.
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Affiliation(s)
- Amy L Donner
- Division of Genetics, Department of Medicine, BWH and HMS, Boston, MA, USA
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47
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Abstract
Drosophila eye development provides an excellent model system to study the role of inter-cellular signaling in the specification of unique cell fates. Behavioral screens by Benzer and his colleagues led to the identification of a gene, Sevenless, a receptor tyrosine kinase (RTK) receptor, required for the specification of the UV sensitive R7 cell. Genetic analysis further showed that the Ras/Raf/MAPK pathway function downstream of Sevenless in the specification of R7 fate. Signaling mediated by another RTK, EGFR and Notch have also been shown to function in either an antagonistic or a synergistic manner in the specification of cell fate during eye development. In some instances, these pathways are linked in a sequential manner by the regulation of the expression of Notch ligand, Delta by EGFR, while in others, these pathways function in a combinatorial fashion on enhancer elements to control target gene expression. In this review, we highlight the elegant genetic strategies used by several laboratories in early elucidation of the Sevenless pathway which helped link the RTK receptor to the Ras/Raf/MAPK cascade and discuss how EGFR and Notch signaling pathways are used in a reiterative manner and by combining in different modes, generate sufficient diversity required for the specification of unique cell fates.
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Affiliation(s)
- Raghavendra Nagaraj
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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Lim J, Choi KW. Bar homeodomain proteins are anti-proneural in the Drosophila eye: transcriptional repression of atonal by Bar prevents ectopic retinal neurogenesis. Development 2003; 130:5965-74. [PMID: 14573515 DOI: 10.1242/dev.00818] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Atonal (Ato)/Math (Mammalian atonal homolog) family proneural proteins are key regulators of neurogenesis in both vertebrates and invertebrates. In the Drosophila eye, Ato is essential for the generation of photoreceptor neurons. Ato expression is initiated at the anterior ridge of the morphogenetic furrow but is repressed in the retinal precursor cells behind the furrow to prevent ectopic neurogenesis. We show that Ato repression is mediated by the conserved homeobox proteins BarH1 and BarH2. Loss of Bar causes cell-autonomous ectopic Ato expression, resulting in excess photoreceptor clusters. The initial ommatidial spacing at the furrow occurs normally in the absence of Bar, suggesting that the ectopic neurogenesis within Bar mutant clones is not due to the lack of Notch (N)-dependent lateral inhibition. Targeted misexpression of Bar is sufficient to repress ato expression. Furthermore, we provide evidence that Bar represses ato expression at the level of transcription without affecting the expression of an ato activator, Cubitus interruptus (Ci). Thus, we propose that Bar is essential for transcriptional repression of ato and the prevention of ectopic neurogenesis behind the furrow.
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Affiliation(s)
- Janghoo Lim
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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49
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Abstract
The coordinated polarization of cells within an epithelium is required for the development and function of some tissues. Recent work has shown that the EGF receptor signaling pathway plays a key role in establishing epithelial polarity in the compound eye of Drosophila.
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Affiliation(s)
- Tanya Wolff
- Washington University School of Medicine, Department of Genetics, Box 8232, St. Louis, Missouri 63110, USA
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50
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Abstract
ERK MAP kinase plays a key role in relaying extracellular signals to transcriptional regulation. As different activity levels or the different duration of ERK activity can elicit distinct responses in one and the same cell, ERK has to be under strict positive and negative control. Although numerous genes acting positively in the ERK signaling pathway have been recovered in genetic screens, mutations in genes encoding negative ERK regulators appear underrepresented. We therefore sought to genetically characterize the dual-specificity phosphatase DMKP3. First, we established a novel assay to elucidate the substrate preferences of eukaryotic phosphatases in vivo and thereby confirmed the specificity of DMKP3 as an ERK phosphatase. The Dmkp3 overexpression phenotype characterized in this assay permitted us to isolate Dmkp3 null mutations. By genetic analysis we show that DMKP3 and the tyrosine phosphatase PTP-ER perform partially redundant functions on the same substrate, ERK. DMKP3 functions autonomously in a subset of photoreceptor progenitor cells in eye imaginal discs. In addition, DMKP3 function appears to be required in surrounding non-neuronal cells for ommatidial patterning and photoreceptor differentiation.
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Affiliation(s)
- Felix Rintelen
- Zoologisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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