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Leiss F, Koper E, Hein I, Fouquet W, Lindner J, Sigrist S, Tavosanis G. Characterization of dendritic spines in the Drosophila central nervous system. Dev Neurobiol 2009; 69:221-34. [PMID: 19160442 DOI: 10.1002/dneu.20699] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Dendritic spines are a characteristic feature of a number of neurons in the vertebrate nervous system and have been implicated in processes that include learning and memory. In spite of this, there has been no comprehensive analysis of the presence of spines in a classical genetic system, such as Drosophila, so far. Here, we demonstrate that a subset of processes along the dendrites of visual system interneurons in the adult fly central nervous system, called LPTCs, closely resemble vertebrate spines, based on a number of criteria. First, the morphology, size, and density of these processes are very similar to those of vertebrate spines. Second, they are enriched in actin and devoid of tubulin. Third, they are sites of synaptic connections based on confocal and electron microscopy. Importantly, they represent a preferential site of localization of an acetylcholine receptor subunit, suggesting that they are sites of excitatory synaptic input. Finally, their number is modulated by the level of the small GTPase dRac1. Our results provide a basis to dissect the genetics of dendritic spine formation and maintenance and the functional role of spines.
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Affiliation(s)
- Florian Leiss
- Dendrite Differentiation Group, Department of Molecular Neurobiology, Max Planck Institute of Neurobiology, Munich-Martinsried 82152, Germany
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52
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Abstract
Cell motility is a widely researched and clinically relevant process that has primarily been investigated using cell culture models. While these in vitro assays are useful in allowing for high-resolution analysis of cell movement, there will always be questions surrounding the physiological relevance of studying cell migration on artificial 2-dimensional substrates. Therefore, a number of groups in recent years have started developing alternative systems, either ex vivo or in vivo, to begin extrapolating our knowledge surrounding cell motility to actual developmental and disease processes. One such example exploits the translucence of Drosophila embryos, and the genetic tractability of this well-characterized model organism, to understand the cellular and molecular events surrounding inflammation and wound healing. Laser ablation of a small patch of embryonic epithelium in the Drosophila embryo results in a repair process that can be timelapse imaged in its entirety as the epithelial hole is sealed shut. Additionally, Drosophila macrophages can be imaged as they rapidly respond and chemotax to these sites of damage in a process reminiscent of the vertebrate inflammatory response. In both cases the imaging is of a spatial and temporal resolution approaching that which can be obtained from in vitro systems, making the Drosophila embryo an ideal model to begin dissecting the genetic control of cell migration during wound healing and inflammation in an in vivo setting.
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Affiliation(s)
- Brian Stramer
- Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
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53
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A two-tiered mechanism for stabilization and immobilization of E-cadherin. Nature 2008; 453:751-6. [PMID: 18480755 DOI: 10.1038/nature06953] [Citation(s) in RCA: 314] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Accepted: 03/31/2008] [Indexed: 12/17/2022]
Abstract
Epithelial tissues maintain a robust architecture which is important for their barrier function, but they are also remodelled through the reorganization of cell-cell contacts. Tissue stability requires intercellular adhesion mediated by E-cadherin, in particular its trans-association in homophilic complexes supported by actin filaments through beta- and alpha-catenin. How alpha-catenin dynamic interactions between E-cadherin/beta-catenin and cortical actin control both stability and remodelling of adhesion is unclear. Here we focus on Drosophila homophilic E-cadherin complexes rather than total E-cadherin, including diffusing 'free' E-cadherin, because these complexes are a better proxy for adhesion. We find that E-cadherin complexes partition in very stable microdomains (that is, bona fide adhesive foci which are more stable than remodelling contacts). Furthermore, we find that stability and mobility of these microdomains depend on two actin populations: small, stable actin patches concentrate at homophilic E-cadherin clusters, whereas a rapidly turning over, contractile network constrains their lateral movement by a tethering mechanism. alpha-Catenin controls epithelial architecture mainly through regulation of the mobility of homophilic clusters and it is largely dispensable for their stability. Uncoupling stability and mobility of E-cadherin complexes suggests that stable epithelia may remodel through the regulated mobility of very stable adhesive foci.
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54
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Knot/Collier and cut control different aspects of dendrite cytoskeleton and synergize to define final arbor shape. Neuron 2008; 56:963-78. [PMID: 18093520 DOI: 10.1016/j.neuron.2007.10.031] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 09/10/2007] [Accepted: 10/19/2007] [Indexed: 11/21/2022]
Abstract
In a complex nervous system, neuronal functional diversity is reflected in the wide variety of dendritic arbor shapes. Different neuronal classes are defined by class-specific transcription factor combinatorial codes. We show that the combination of the transcription factors Knot and Cut is particular to Drosophila class IV dendritic arborization (da) neurons. Knot and Cut control different aspects of the dendrite cytoskeleton, promoting microtubule- and actin-based dendritic arbors, respectively. Knot delineates class IV arbor morphology by simultaneously synergizing with Cut to promote complexity and repressing Cut-mediated promotion of dendritic filopodia/spikes. Knot increases dendritic arbor outgrowth through promoting the expression of Spastin, a microtubule-severing protein disrupted in autosomal dominant hereditary spastic paraplegia (AD-HSP). Knot and Cut may modulate cellular mechanisms that are conserved between Drosophila and vertebrates. Hence, this study gives significant general insight into how multiple transcription factors combine to control class-specific dendritic arbor morphology through controlling different aspects of the cytoskeleton.
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55
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Eppinga RD, Peng IF, Lin JLC, Wu CF, Lin JJC. Opposite effects of overexpressed myosin Va or heavy meromyosin Va on vesicle distribution, cytoskeleton organization, and cell motility in nonmuscle cells. ACTA ACUST UNITED AC 2008; 65:197-215. [DOI: 10.1002/cm.20255] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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56
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Abstract
Myoblast fusion requires a number of cellular behaviors, including cell migration, recognition, and adhesion, as well as a series of subcellular behaviors, such as cytoskeletal rearrangements, vesicle trafficking, and membrane dynamics, leading to two cells becoming one. With the discovery of fluorescent proteins that can be introduced and studied within living cells, the possibility of monitoring these complex processes within the living embryo is now a reality. Live imaging, unlike imaging techniques for fixed embryos, allows the opportunity to visualize and measure the dynamics of these processes in vivo. This chapter describes the development and use of live imaging techniques to study myoblast fusion in Drosophila.
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Affiliation(s)
- Brian E. Richardson
- Program in Developmental Biology, Sloan Kettering Institute, New York, New York 10021,Weill Graduate School at Cornell Medical School, New York, New York 10021
| | - Karen Beckett
- Program in Developmental Biology, Sloan Kettering Institute, New York, New York 10021
| | - Mary K. Baylies
- Program in Developmental Biology, Sloan Kettering Institute, New York, New York 10021,Weill Graduate School at Cornell Medical School, New York, New York 10021
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57
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Besse F, Mertel S, Kittel RJ, Wichmann C, Rasse TM, Sigrist SJ, Ephrussi A. The Ig cell adhesion molecule Basigin controls compartmentalization and vesicle release at Drosophila melanogaster synapses. ACTA ACUST UNITED AC 2007; 177:843-55. [PMID: 17548512 PMCID: PMC2064284 DOI: 10.1083/jcb.200701111] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Synapses can undergo rapid changes in size as well as in their vesicle release function during both plasticity processes and development. This fundamental property of neuronal cells requires the coordinated rearrangement of synaptic membranes and their associated cytoskeleton, yet remarkably little is known of how this coupling is achieved. In a GFP exon-trap screen, we identified Drosophila melanogaster Basigin (Bsg) as an immunoglobulin domain-containing transmembrane protein accumulating at periactive zones of neuromuscular junctions. Bsg is required pre- and postsynaptically to restrict synaptic bouton size, its juxtamembrane cytoplasmic residues being important for that function. Bsg controls different aspects of synaptic structure, including distribution of synaptic vesicles and organization of the presynaptic cortical actin cytoskeleton. Strikingly, bsg function is also required specifically within the presynaptic terminal to inhibit nonsynchronized evoked vesicle release. We thus propose that Bsg is part of a transsynaptic complex regulating synaptic compartmentalization and strength, and coordinating plasma membrane and cortical organization.
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Affiliation(s)
- Florence Besse
- Developmental Biology Unit, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
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58
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Prasad M, Montell DJ. Cellular and Molecular Mechanisms of Border Cell Migration Analyzed Using Time-Lapse Live-Cell Imaging. Dev Cell 2007; 12:997-1005. [PMID: 17543870 DOI: 10.1016/j.devcel.2007.03.021] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 03/13/2007] [Accepted: 03/30/2007] [Indexed: 10/23/2022]
Abstract
Border cells in the Drosophila ovary originate within an epithelium, detach from it, invade neighboring nurse cells, and migrate as a coherent cluster. This migration has served as a useful genetic model for understanding epithelial cell motility. The prevailing model of growth factor-mediated chemotaxis in general, and of border cells in particular, posits that receptor activation promotes cellular protrusion at the leading edge. Here we report the time-lapse video imaging of border cell migration, allowing us to test this model. Reducing the activities of the guidance receptors EGFR and PVR did not result in the expected inhibition of protrusion, but instead resulted in protrusion in all directions. In contrast, reduction in Notch activity resulted in failure of the cells to detach from the epithelium without affecting direction sensing. These observations provide new insight into the cellular dynamics and molecular mechanisms of cell migration in vivo.
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Affiliation(s)
- Mohit Prasad
- Department of Biological Chemistry, Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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59
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Massarwa R, Carmon S, Shilo BZ, Schejter ED. WIP/WASp-based actin-polymerization machinery is essential for myoblast fusion in Drosophila. Dev Cell 2007; 12:557-69. [PMID: 17419994 DOI: 10.1016/j.devcel.2007.01.016] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 01/16/2007] [Accepted: 01/25/2007] [Indexed: 11/19/2022]
Abstract
Formation of syncytial muscle fibers involves repeated rounds of cell fusion between growing myotubes and neighboring myoblasts. We have established that Wsp, the Drosophila homolog of the WASp family of microfilament nucleation-promoting factors, is an essential facilitator of myoblast fusion in Drosophila embryos. D-WIP, a homolog of the conserved Verprolin/WASp Interacting Protein family of WASp-binding proteins, performs a key mediating role in this context. D-WIP, which is expressed specifically in myoblasts, associates with both the WASp-Arp2/3 system and with the myoblast adhesion molecules Dumbfounded and Sticks and Stones, thereby recruiting the actin-polymerization machinery to sites of myoblast attachment and fusion. Our analysis demonstrates that this recruitment is normally required late in the fusion process, for enlargement of nascent fusion pores and breakdown of the apposed cell membranes. These observations identify cellular and developmental roles for the WASp-Arp2/3 pathway, and provide a link between force-generating actin polymerization and cell fusion.
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Affiliation(s)
- R'ada Massarwa
- Department of Molecular Genetics, Weizmann Institute of Science, 76100 Rehovot, Israel
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60
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Wasser M, Bte Osman Z, Chia W. EAST and Chromator control the destruction and remodeling of muscles during Drosophila metamorphosis. Dev Biol 2007; 307:380-93. [PMID: 17540360 DOI: 10.1016/j.ydbio.2007.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 04/30/2007] [Accepted: 05/01/2007] [Indexed: 11/26/2022]
Abstract
Metamorphosis involves the destruction of larval, the formation of adult and the transformation of larval into adult tissues. In this study, we demonstrate the role of the Drosophila nuclear proteins EAST and Chromator in tissue destruction and remodeling. To better understand the function of east, we performed a yeast two-hybrid screen and identified the euchromatin associated protein Chromator as a candidate interactor. To analyze the functional significance of our two-hybrid data, we generated a set of novel pupal lethal Chro alleles by P-element excision. The pupal lethal Chro mutants resemble lethal east alleles as homozygous mutants develop into pharates with normal looking body parts, but fail to eclose. The eclosion defect of the Chro alleles is rescued in an east heterozygous background, indicating antagonistic genetic interactions between the two genes. Live cell imaging was applied to study muscle development during metamorphosis. Consistent with the eclosion defects, mutant pharates of both genes show loss and abnormal differentiation of adult eclosion muscles. The two genes have opposite effects on the destruction of larval muscles in metamorphosis. While Chro mutants show incomplete histolysis, muscles degenerate prematurely in east mutants. Moreover east mutants affect the remodeling of abdominal larval muscles into adult eclosion muscles. During this process, loss of east interferes with the spatial coordination of thinning of the larval muscles. Overexpression of EAST-GFP can prevent the disintegration of polytene chromosomes during programmed cell death. We propose that Chro activates and east inhibits processes and genes involved in tissue destruction and remodeling.
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Affiliation(s)
- Martin Wasser
- Bioinformatics Institute, Department of Imaging Informatics, Republic of Singapore.
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61
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Brown S, Zeidler MP, Hombría JECG. JAK/STAT signalling in Drosophila controls cell motility during germ cell migration. Dev Dyn 2006; 235:958-66. [PMID: 16477645 DOI: 10.1002/dvdy.20709] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The gonad is formed from two populations of cells originating at different locations: the primordial germ cells (PGCs), giving rise to either sperm or oocytes, and the somatic gonadal mesoderm precursors (SGPs), which support development of the gametes. Following the PGCs' migration during gastrulation, these two populations meet, forming the immature gonad. We present evidence that during embryonic development, the PGCs require the canonical JAK/STAT signalling cascade to migrate efficiently towards the SGPs. Loss of function for any element of the JAK/STAT pathway causes frequent germ cell mislocalisation. We have found that wild-type germ cells produce filopodia while they migrate through the mesoderm towards the gonad. Our observations suggest that PGCs use filopodia to migrate and to keep contact with each other. Interestingly, activation of the JAK/STAT pathway is required for these filopodia to form, and ectopic JAK/STAT activation enhances their formation.
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Affiliation(s)
- Stephen Brown
- Faculty of Life Sciences, University of Manchester, C.1247 Michael Smith Building, Oxford Road, Manchester M13 9PT, U.K.
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62
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Andersen R, Li Y, Resseguie M, Brenman JE. Calcium/calmodulin-dependent protein kinase II alters structural plasticity and cytoskeletal dynamics in Drosophila. J Neurosci 2006; 25:8878-88. [PMID: 16192377 PMCID: PMC6725600 DOI: 10.1523/jneurosci.2005-05.2005] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Drosophila dendritic arborization (da) neurons contain subclasses of neurons with distinct dendritic morphologies. We investigated calcium/calmodulin-dependent protein kinase II (CaMKII) regulation of dendritic structure and dynamics in vivo using optically transparent Drosophila larvae. CaMKII increases the dynamic nature and formation of dendritic filopodia throughout larval development but only affects neurons that normally contain dendritic filopodia. In parallel, we examined the effects of Rac1 activity on dendritic structure to explore signaling specificity. In contrast to CaMKII activity, Rac1 does not alter filopodia stability but instead causes de novo filopodia formation on all da neurons. Although both mediators increase cytoskeletal turnover, measured by fluorescence recovery after photobleaching experiments, only CaMKII increases the dynamic nature of dendritic filopodia. CaMKII signaling thus appears to use mechanisms and machinery distinct from Rac1 signaling. This study illustrates a molecular means of uncoupling cytoskeletal regulation from morphological regulation. Our results suggest that Drosophila dendritic filopodia may share some cytoskeletal regulatory mechanisms with mammalian dendritic filopodia. Furthermore, general dendrite cytoskeletal compartmentalization is conserved in multipolar neurons.
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Affiliation(s)
- Ryan Andersen
- Department of Cell and Developmental Biology, Neuroscience Center, University of North Carolina Chapel Hill, North Carolina 27599, USA
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63
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Medina PMB, Swick LL, Andersen R, Blalock Z, Brenman JE. A novel forward genetic screen for identifying mutations affecting larval neuronal dendrite development in Drosophila melanogaster. Genetics 2006; 172:2325-35. [PMID: 16415365 PMCID: PMC1456372 DOI: 10.1534/genetics.105.051276] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vertebrate and invertebrate dendrites are information-processing compartments that can be found on both central and peripheral neurons. Elucidating the molecular underpinnings of information processing in the nervous system ultimately requires an understanding of the genetic pathways that regulate dendrite formation and maintenance. Despite the importance of dendrite development, few forward genetic approaches have been used to analyze the latest stages of dendrite development, including the formation of F-actin-rich dendritic filopodia or dendritic spines. We developed a forward genetic screen utilizing transgenic Drosophila second instar larvae expressing an actin, green fluorescent protein (GFP) fusion protein (actin::GFP) in subsets of sensory neurons. Utilizing this fluorescent transgenic reporter, we conducted a forward genetic screen of >4000 mutagenized chromosomes bearing lethal mutations that affected multiple aspects of larval dendrite development. We isolated 13 mutations on the X and second chromosomes composing 11 complementation groups affecting dendrite outgrowth/branching, dendritic filopodia formation, or actin::GFP localization within dendrites in vivo. In a fortuitous observation, we observed that the structure of dendritic arborization (da) neuron dendritic filopodia changes in response to a changing environment.
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Affiliation(s)
- Paul Mark B Medina
- Department of Cell and Developmental Biology and Neuroscience Center, University of North Carolina-Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599-7250, USA
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64
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Sano H, Renault AD, Lehmann R. Control of lateral migration and germ cell elimination by the Drosophila melanogaster lipid phosphate phosphatases Wunen and Wunen 2. ACTA ACUST UNITED AC 2006; 171:675-83. [PMID: 16301333 PMCID: PMC2171572 DOI: 10.1083/jcb.200506038] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
In most organisms, primordial germ cells (PGCs) arise far from the region where somatic gonadal precursors (SGPs) are specified. Although PGCs in general originate as a single cluster of cells, the somatic parts of the gonad form on each site of the embryo. Thus, to reach the gonad, PGCs not only migrate from their site of origin but also split into two groups. Taking advantage of high-resolution real-time imaging, we show that in Drosophila melanogaster PGCs are polarized and migrate directionally toward the SGPs, avoiding the midline. Unexpectedly, neither PGC attractants synthesized in the SGPs nor known midline repellents for axon guidance were required to sort PGCs bilaterally. Repellent activity provided by wunen (wun) and wunen-2 (wun-2) expressed in the central nervous system, however, is essential in this migration process and controls PGC survival. Our results suggest that expression of wun/wun-2 repellents along the migratory paths provides faithful control over the sorting of PGCs into two gonads and eliminates PGCs left in the middle of the embryo.
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Affiliation(s)
- Hiroko Sano
- Department of Cell Biology, Developmental Genetics Program, Skirball Institute of Biomolecular Medicine and Howard Hughes Medical Institute, New York University Medical Center, New York, NY 10016
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65
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Denholm B, Brown S, Ray RP, Ruiz-Gómez M, Skaer H, Hombría JCG. crossveinless-c is a RhoGAP required for actin reorganisation during morphogenesis. Development 2005; 132:2389-400. [PMID: 15843408 DOI: 10.1242/dev.01829] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Members of the Rho family of small GTPases are required for many of the morphogenetic processes required to shape the animal body. The activity of this family is regulated in part by a class of proteins known as RhoGTPase Activating Proteins (RhoGAPs) that catalyse the conversion of RhoGTPases to their inactive state. In our search for genes that regulate Drosophila morphogenesis, we have isolated several lethal alleles of crossveinless-c (cv-c). Molecular characterisation reveals that cv-c encodes the RhoGAP protein RhoGAP88C. During embryonic development, cv-c is expressed in tissues undergoing morphogenetic movements; phenotypic analysis of the mutants reveals defects in the morphogenesis of these tissues. Genetic interactions between cv-c and RhoGTPase mutants indicate that Rho1, Rac1 and Rac2 are substrates for Cv-c, and suggest that the substrate specificity might be regulated in a tissue-dependent manner. In the absence of cv-c activity, tubulogenesis in the renal or Malpighian tubules fails and they collapse into a cyst-like sack. Further analysis of the role of cv-c in the Malpighian tubules demonstrates that its activity is required to regulate the reorganisation of the actin cytoskeleton during the process of convergent extension. In addition, overexpression of cv-c in the developing tubules gives rise to actin-associated membrane extensions. Thus, Cv-c function is required in tissues actively undergoing morphogenesis, and we propose that its role is to regulate RhoGTPase activity to promote the coordinated organisation of the actin cytoskeleton, possibly by stabilising plasma membrane/actin cytoskeleton interactions.
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Affiliation(s)
- Barry Denholm
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
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66
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Abstract
Wound healing involves a coordinated series of tissue movements that bears a striking resemblance to various embryonic morphogenetic episodes. There are several ways in which repair recapitulates morphogenesis. We describe how almost identical cytoskeletal machinery is used to repair an embryonic epithelial wound as is involved during the morphogenetic episodes of dorsal closure in Drosophila and eyelid fusion in the mouse foetus. For both naturally occurring and wound-activated tissue movements, JNK signalling appears to be crucial, as does the tight regulation of associated cell divisions and adhesions. In the embryo, both morphogenesis and repair are achieved with a perfect end result, whereas repair of adult tissues leads to scarring. We discuss whether this may be due to the adult inflammatory response, which is absent in the embryo.
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Affiliation(s)
- Paul Martin
- Department of Physiology, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
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67
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Dorman JB, James KE, Fraser SE, Kiehart DP, Berg CA. bullwinkle is required for epithelial morphogenesis during Drosophila oogenesis. Dev Biol 2004; 267:320-41. [PMID: 15013797 DOI: 10.1016/j.ydbio.2003.10.020] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2003] [Revised: 10/04/2003] [Accepted: 10/07/2003] [Indexed: 11/29/2022]
Abstract
Many organs, such as the liver, neural tube, and lung, form by the precise remodeling of flat epithelial sheets into tubes. Here we investigate epithelial tubulogenesis in Drosophila melanogaster by examining the development of the dorsal respiratory appendages of the eggshell. We employ a culture system that permits confocal analysis of stage 10-14 egg chambers. Time-lapse imaging of GFP-Moesin-expressing egg chambers reveals three phases of morphogenesis: tube formation, anterior extension, and paddle maturation. The dorsal-appendage-forming cells, previously thought to represent a single cell fate, consist of two subpopulations, those forming the tube roof and those forming the tube floor. These two cell types exhibit distinct morphological and molecular features. Roof-forming cells constrict apically and express high levels of Broad protein. Floor cells lack Broad, express the rhomboid-lacZ marker, and form the floor by directed cell elongation. We examine the morphogenetic phenotype of the bullwinkle (bwk) mutant and identify defects in both roof and floor formation. Dorsal appendage formation is an excellent system in which cell biological, molecular, and genetic tools facilitate the study of epithelial morphogenesis.
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Affiliation(s)
- Jennie B Dorman
- Department of Genome Sciences, University of Washington, Seattle, WA 98195-7730, USA
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68
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Iioka H, Ueno N, Kinoshita N. Essential role of MARCKS in cortical actin dynamics during gastrulation movements. ACTA ACUST UNITED AC 2004; 164:169-74. [PMID: 14718521 PMCID: PMC2172330 DOI: 10.1083/jcb.200310027] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Myristoylated alanine-rich C kinase substrate (MARCKS) is an actin-binding, membrane-associated protein expressed during Xenopus embryogenesis. We analyzed its function in cytoskeletal regulation during gastrulation. Here, we show that blockade of its function impaired morphogenetic movements, including convergent extension. MARCKS was required for control of cell morphology, motility, adhesion, protrusive activity, and cortical actin formation in embryonic cells. We also demonstrate that the noncanonical Wnt pathway promotes the formation of lamellipodia- and filopodia-like protrusions and that MARCKS is necessary for this activity. These findings show that MARCKS regulates the cortical actin formation that is requisite for dynamic morphogenetic movements.
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Affiliation(s)
- Hidekazu Iioka
- Dept. of Developmental Biology, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji Okazaki, Aichi 444-8585, Japan
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