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Casal J, Lawrence PA, Struhl G. Two separate molecular systems, Dachsous/Fat and Starry night/Frizzled, act independently to confer planar cell polarity. Development 2006; 133:4561-72. [PMID: 17075008 PMCID: PMC2747022 DOI: 10.1242/dev.02641] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Planar polarity is a fundamental property of epithelia in animals and plants. In Drosophila it depends on at least two sets of genes: one set, the Ds system, encodes the cadherins Dachsous (Ds) and Fat (Ft), as well as the Golgi protein Four-jointed. The other set, the Stan system, encodes Starry night (Stan or Flamingo) and Frizzled. The prevailing view is that the Ds system acts via the Stan system to orient cells. However, using the Drosophila abdomen, we find instead that the two systems operate independently: each confers and propagates polarity, and can do so in the absence of the other. We ask how the Ds system acts; we find that either Ds or Ft is required in cells that send information and we show that both Ds and Ft are required in the responding cells. We consider how polarity may be propagated by Ds-Ft heterodimers acting as bridges between cells.
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Affiliation(s)
- José Casal
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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102
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Cho E, Feng Y, Rauskolb C, Maitra S, Fehon R, Irvine KD. Delineation of a Fat tumor suppressor pathway. Nat Genet 2006; 38:1142-50. [PMID: 16980976 DOI: 10.1038/ng1887] [Citation(s) in RCA: 356] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 08/18/2006] [Indexed: 11/09/2022]
Abstract
Recent studies in Drosophila melanogaster of the protocadherins Dachsous and Fat suggest that they act as ligand and receptor, respectively, for an intercellular signaling pathway that influences tissue polarity, growth and gene expression, but the basis for signaling downstream of Fat has remained unclear. Here, we characterize functional relationships among D. melanogaster tumor suppressors and identify the kinases Discs overgrown and Warts as components of a Fat signaling pathway. fat, discs overgrown and warts regulate a common set of downstream genes in multiple tissues. Genetic experiments position the action of discs overgrown upstream of the Fat pathway component dachs, whereas warts acts downstream of dachs. Warts protein coprecipitates with Dachs, and Warts protein levels are influenced by fat, dachs and discs overgrown in vivo, consistent with its placement as a downstream component of the pathway. The tumor suppressors Merlin, expanded, hippo, salvador and mob as tumor suppressor also share multiple Fat pathway phenotypes but regulate Warts activity independently. Our results functionally link what had been four disparate groups of D. melanogaster tumor suppressors, establish a basic framework for Fat signaling from receptor to transcription factor and implicate Warts as an integrator of multiple growth control signals.
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Affiliation(s)
- Eunjoo Cho
- Howard Hughes Medical Institute and Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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103
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Matakatsu H, Blair SS. Separating the adhesive and signaling functions of the Fat and Dachsous protocadherins. Development 2006; 133:2315-24. [PMID: 16687445 DOI: 10.1242/dev.02401] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The protocadherins Fat (Ft) and Dachsous (Ds) are required for several processes in the development of Drosophila, including controlling growth of imaginal discs, planar cell polarity (PCP) and the proximodistal patterning of appendages. Ft and Ds bind in a preferentially heterophilic fashion, and Ds is expressed in distinct patterns along the axes of polarity. It has thus been suggested that Ft and Ds serve not as adhesion molecules, but as receptor and ligand in a poorly understood signaling pathway. To test this hypothesis, we performed a structure-function analysis of Ft and Ds, separating their adhesive and signaling functions. We found that the extracellular domain of Ft is not required for its activity in growth, PCP and proximodistal patterning. Thus, ligand binding is not necessary for Ft activity. By contrast, the extracellular domain of Ds is necessary and sufficient to mediate its effects on PCP, consistent with the model that Ds acts as a ligand during PCP. However, we also provide evidence that Ds can regulate growth independently of Ft, and that the intracellular domain of Ds can affect proximodistal patterning, both suggestive of functions independent of binding Ft. Finally, we show that ft mutants or a dominant-negative Ft construct can affect disc growth without changes in the expression of wingless and Wingless target genes.
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Affiliation(s)
- Hitoshi Matakatsu
- Department of Zoology, University of Wisconsin, 250 North Mills Street, Madison, WI 53706, USA
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104
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Price MH, Roberts DM, McCartney BM, Jezuit E, Peifer M. Cytoskeletal dynamics and cell signaling during planar polarity establishment in theDrosophilaembryonic denticle. J Cell Sci 2006; 119:403-15. [PMID: 16418222 DOI: 10.1242/jcs.02761] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many epithelial cells are polarized along the plane of the epithelium, a property termed planar cell polarity. The Drosophila wing and eye imaginal discs are the premier models of this process. Many proteins required for polarity establishment and its translation into cytoskeletal polarity were identified from studies of those tissues. More recently, several vertebrate tissues have been shown to exhibit planar cell polarity. Striking similarities and differences have been observed when different tissues exhibiting planar cell polarity are compared. Here we describe a new tissue exhibiting planar cell polarity – the denticles, hair-like projections of the Drosophila embryonic epidermis. We describe in real time the changes in the actin cytoskeleton that underlie denticle development, and compare this with the localization of microtubules, revealing new aspects of cytoskeletal dynamics that may have more general applicability. We present an initial characterization of the localization of several actin regulators during denticle development. We find that several core planar cell polarity proteins are asymmetrically localized during the process. Finally, we define roles for the canonical Wingless and Hedgehog pathways and for core planar cell polarity proteins in denticle polarity.
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Affiliation(s)
- Meredith H Price
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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105
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Shimada Y, Yonemura S, Ohkura H, Strutt D, Uemura T. Polarized Transport of Frizzled along the Planar Microtubule Arrays in Drosophila Wing Epithelium. Dev Cell 2006; 10:209-22. [PMID: 16459300 DOI: 10.1016/j.devcel.2005.11.016] [Citation(s) in RCA: 242] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 11/05/2005] [Accepted: 11/21/2005] [Indexed: 02/03/2023]
Abstract
Cells in a variety of developmental contexts sense extracellular cues that are given locally on their surfaces, and subsequently amplify the initial signal to achieve cell polarization. Drosophila wing cells acquire planar polarity along the proximal-distal (P-D) axis, in which the amplification of the presumptive cue involves assembly of a multiprotein complex that spans distal and proximal boundaries of adjacent cells. Here we pursue the mechanisms that place one of the components, Frizzled (Fz), at the distal side. Intracellular particles of GFP-tagged Fz moved preferentially toward distal boundaries before Fz::GFP and other components were tightly localized at the P/D cortex. Arrays of microtubules (MTs) were approximately oriented along the P-D axis and these MTs contributed to the formation of the cortical complex. Furthermore, there appeared to be a bias in the P-D MTs, with slightly more plus ends oriented distally. The hypothesis of polarized vesicular trafficking of Fz is discussed.
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Affiliation(s)
- Yuko Shimada
- Laboratory of Cell Recognition and Pattern Formation, Graduate School of Biostudies, South Campus Research Building (Building G), Room 118, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
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106
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Le Garrec JF, Lopez P, Kerszberg M. Establishment and maintenance of planar epithelial cell polarity by asymmetric cadherin bridges: A computer model. Dev Dyn 2006; 235:235-46. [PMID: 16258926 DOI: 10.1002/dvdy.20617] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Animal scales, hairs, feathers, and cilia are oriented due to cell polarization in the epithelial plane. Genes involved have been identified, but the signal and mechanism remain unknown. In Drosophila wing polarization, the action of a gradient of Frizzled activity is widely assumed; and cell-cell signalling by cadherins such as Flamingo surely plays a major role. We present a computer model where reading the Frizzled gradient occurs through biased, feedback-reinforced formation of Flamingo-based asymmetric intercellular complexes. Through these complexes neighboring cells are able to compare their Frizzled activity levels. Our computations are highly noise-resistant and reproduce both wild-type and all known mutant wing phenotypes; other phenotypes are predicted. The model puts stringent limits on a Frizzled activation signal, which should exhibit unusual properties: (1) the extracellular Frizzled signalling gradient should be counterdirectional--decreasing from proximal (P) to distal (D), whereas during polarization, the intracellular Frizzled gradient builds up from P to D; (2) the external gradient should be relatively weak and short-lived, lest it prevent inversion of intracellular Frizzled. These features, largely independent of model details, may provide useful clues for future experimental efforts.
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Affiliation(s)
- Jean-François Le Garrec
- Modélisation Dynamique des Systèmes Biologiques Intégrés, CNRS UMR 7138 Systématique, Adaptation, Evolution, Université Pierre et Marie Curie, Paris, France
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107
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Abstract
Polarization is a feature common to many cell types. Epithelial cells, for example, exhibit a characteristic apical-basolateral polarity that is critical for their function. In addition to this ubiquitous form of polarity, whole fields of cells are often polarized in a plane perpendicular to the apical-basal axis. This form of polarity, referred to as planar cell polarity (PCP), exists in all adult Drosophila cuticular tissues, as well as in numerous vertebrate tissues, including the mammalian skin and inner ear epithelia. Recent advances in the study of PCP establishment are beginning to unravel the molecular mechanisms underlying this cellular process. This review discusses new developments in the molecular understanding of PCP in Drosophila and vertebrates and integrates the current data in a model to illustrate how interactions between PCP factors might function to generate planar polarity.
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Affiliation(s)
- Thomas J Klein
- Mount Sinai School of Medicine, Brookdale Department of Molecular, Cell and Developmental Biology, New York, NY 10029, USA.
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108
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Saburi S, McNeill H. Organising cells into tissues: new roles for cell adhesion molecules in planar cell polarity. Curr Opin Cell Biol 2005; 17:482-8. [PMID: 16099635 DOI: 10.1016/j.ceb.2005.08.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 08/03/2005] [Indexed: 01/09/2023]
Abstract
Planar cell polarity (PCP) is the coordinated organization of cells within the plane of the epithelium, first described in Drosophila. A Frizzled signalling pathway dedicated to PCP (the non-canonical Frizzled pathway) acts through Dishevelled and small G proteins, as does the classical Wnt pathway, but then diverges downstream of Dishevelled. Recent studies have demonstrated a crucial role for several atypical cadherin molecules (Fat, Dachsous and Flamingo) in controlling PCP signalling. Recent work has also indicated that the first sign of PCP during development is the polarized localization of PCP proteins (Frizzled, Flamingo, Dishevelled, etc). Exciting new data reveal that this PCP pathway is conserved to man.
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Affiliation(s)
- Sakura Saburi
- Samuel Lunenfeld Research Institute, Toronto, Ontario M5G 1X, Canada
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109
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Abstract
Epithelial cells are patterned not only along their apical-basolateral axis, but also along the plane of the epithelial sheet; the latter event is regulated by the planar cell polarity (PCP) pathway. PCP regulates diverse outputs, such as the distal placement of a hair in all cells of the Drosophila wing, and convergent extension movements during gastrulation in the vertebrate embryo. This primer describes the molecular mechanisms that initiate and establish PCP, as well as biochemical pathways that translate PCP signaling to cell type-specific patterning events. The primer concludes with a discussion of current topics in the field with two PCP researchers, Matt Kelley, Ph.D., and Helen McNeill, Ph.D.
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Affiliation(s)
- Julie C Kiefer
- Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112, USA.
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110
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Abstract
The formation of properly differentiated organs often requires the planar coordination of cell polarization within the tissues. Such planar cell polarization (PCP) events are best studied in Drosophila, where many of the key players, known as PCP genes, have already been identified. Genetic analysis of the PCP genes suggests that the establishment of polarity consists of three major steps. The first step involves the generation of a global polarity cue; this in turn promotes the second step, the redistribution of the core PCP proteins, leading to the formation of asymmetrically localized signaling centers. During the third step, these complexes control tissue-specific cellular responses through the activation of cell type specific effector genes. Here we discuss some of the most recent advances that have provided valuable new insight into each of the three major steps of planar cell polarization.
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Affiliation(s)
- József Mihály
- Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary.
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111
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Povelones M, Howes R, Fish M, Nusse R. Genetic evidence that Drosophila frizzled controls planar cell polarity and Armadillo signaling by a common mechanism. Genetics 2005; 171:1643-54. [PMID: 16085697 PMCID: PMC1456092 DOI: 10.1534/genetics.105.045245] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The frizzled (fz) gene in Drosophila controls two distinct signaling pathways: it directs the planar cell polarization (PCP) of epithelia and it regulates cell fate decisions through Armadillo (Arm) by acting as a receptor for the Wnt protein Wingless (Wg). With the exception of dishevelled (dsh), the genes functioning in these two pathways are distinct. We have taken a genetic approach, based on a series of new and existing fz alleles, for identifying individual amino acids required for PCP or Arm signaling. For each allele, we have attempted to quantify the strength of signaling by phenotypic measurements. For PCP signaling, the defect was measured by counting the number of cells secreting multiple hairs in the wing. We then examined each allele for its ability to participate in Arm signaling by the rescue of fz mutant embryos with maternally provided fz function. For both PCP and Arm signaling we observed a broad range of phenotypes, but for every allele there is a strong correlation between its phenotypic strength in each pathway. Therefore, even though the PCP and Arm signaling pathways are genetically distinct, the set of signaling-defective fz alleles affected both pathways to a similar extent. This suggests that fz controls these two different signaling activities by a common mechanism. In addition, this screen yielded a set of missense mutations that identify amino acids specifically required for fz signaling function.
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Affiliation(s)
- Michael Povelones
- Howard Hughes Medical Institute, Department of Developmental Biology, Beckman Center, Stanford University School of Medicine, Stanford, CA 94305, USA
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112
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113
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Abstract
The mechanisms by which cells become polarised in the plane of an epithelium have been studied in Drosophila for many years. Work has focussed on two key questions: firstly, how individual cells adopt a defined polarity, and secondly how the polarity of each cell within a tissue is aligned with its neighbours. It has been established that asymmetric subcellular localisation of a number of polarity proteins is an essential mechanism underlying polarisation of single cells. The process by which this polarity is coordinated between cells however is less well understood, but is thought to involve gradients of activity of the atypical cadherins Dachsous and Fat. Subsequently, this long-range polarity signal is refined by local cell-cell interactions involving the transmembrane molecules Frizzled, Strabismus and Flamingo. The role of these factors in coordinating polarity will be discussed.
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Affiliation(s)
- Helen Strutt
- Centre for Developmental and Biomedical Genetics, Department of Biomedical Science, University of Sheffield, Sheffield, UK.
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