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Lloyd VJ, Burg SL, Harizanova J, Garcia E, Hill O, Enciso-Romero J, Cooper RL, Flenner S, Longo E, Greving I, Nadeau NJ, Parnell AJ. The actin cytoskeleton plays multiple roles in structural colour formation in butterfly wing scales. Nat Commun 2024; 15:4073. [PMID: 38769302 PMCID: PMC11106069 DOI: 10.1038/s41467-024-48060-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 04/19/2024] [Indexed: 05/22/2024] Open
Abstract
Vivid structural colours in butterflies are caused by photonic nanostructures scattering light. Structural colours evolved for numerous biological signalling functions and have important technological applications. Optically, such structures are well understood, however insight into their development in vivo remains scarce. We show that actin is intimately involved in structural colour formation in butterfly wing scales. Using comparisons between iridescent (structurally coloured) and non-iridescent scales in adult and developing H. sara, we show that iridescent scales have more densely packed actin bundles leading to an increased density of reflective ridges. Super-resolution microscopy across three distantly related butterfly species reveals that actin is repeatedly re-arranged during scale development and crucially when the optical nanostructures are forming. Furthermore, actin perturbation experiments at these later developmental stages resulted in near total loss of structural colour in H. sara. Overall, this shows that actin plays a vital and direct templating role during structural colour formation in butterfly scales, providing ridge patterning mechanisms that are likely universal across lepidoptera.
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Affiliation(s)
- Victoria J Lloyd
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Alfred Denny Building, Western bank, Sheffield, S10 2TN, UK.
| | - Stephanie L Burg
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK
| | - Jana Harizanova
- Central Laser Facility-Science & Technology Facility Council, The Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0FA, UK
- Core Facility for Integrated Microscopy, Department of Biomedical Sciences, University of Copenhagen, 2200N, Copenhagen, Denmark
| | - Esther Garcia
- Central Laser Facility-Science & Technology Facility Council, The Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0FA, UK
| | - Olivia Hill
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK
| | - Juan Enciso-Romero
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Alfred Denny Building, Western bank, Sheffield, S10 2TN, UK
- Department of Biological Sciences, University of Lethbridge, 4401 University Drive, Lethbridge, AB, T1K 3M4, Canada
| | - Rory L Cooper
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Alfred Denny Building, Western bank, Sheffield, S10 2TN, UK
- Department of Genetics and Evolution, University of Geneva, Sciences III, Geneva, 1205, Switzerland
| | - Silja Flenner
- Helmholtz-Zentrum Hereon, Max-Planck-Strasse 1, 21502, Geesthacht, Germany
| | - Elena Longo
- Elettra-Sincrotrone Trieste S.C.p.A., 34149, Basovizza, Trieste, Italy
| | - Imke Greving
- Helmholtz-Zentrum Hereon, Max-Planck-Strasse 1, 21502, Geesthacht, Germany
| | - Nicola J Nadeau
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Alfred Denny Building, Western bank, Sheffield, S10 2TN, UK.
| | - Andrew J Parnell
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK.
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Zhang Y, Tan Q, Lin M, Shen C, Jin L, Li G. Dusky-like Is Critical for Morphogenesis of the Cellular Protuberances and Formation of the Cuticle in Henosepilachna vigintioctopunctata. BIOLOGY 2023; 12:866. [PMID: 37372150 DOI: 10.3390/biology12060866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 06/12/2023] [Accepted: 06/13/2023] [Indexed: 06/29/2023]
Abstract
Dusky-like (Dyl) is a transmembrane protein containing a zona pellucida domain. Its physiological roles during metamorphosis have been well explored in Drosophila melanogaster and have also been documented in Tribolium castaneum. However, Dyl has undergone a functional shift between Diptera and Coleoptera insects. Further investigation of Dyl in other insects will be helpful to further clarify its function in insect growth and development. Henosepilachna vigintioctopunctata is an important Coleoptera that causes enormous economic losses in agriculture in China. In this study, we found that the expression of Hvdyl was detectable in embryos, larvae, prepupae, pupae, and adults. We knocked down Hvdyl in third- and fourth-instar larvae and pupae with RNA interference (RNAi). RNAi of Hvdyl mainly caused two phenotypic defects. Firstly, the growth of epidermal cellular protuberances was suppressed. Injection of dsdyl (double-stranded dusky-like RNA) at the third-instar larval stage truncated the scoli throughout the thorax and abdomen and shortened the setae on the head capsules and mouthparts of the fourth-instar larvae. Introduction of dsdyl at the third- and fourth-instar stages led to misshapen pupal setae. The setae were shortened or became black nodules. Treatment with dsdyl at the larval and pupal stages resulted in deformed adults with completely suppressed wing hairs. Moreover, the knockdown of Hvdyl at the third-instar stage caused deformed larval mouthparts at the fourth-instar period. As a result, foliage consumption was inhibited, and larval growth was slowed. The results indicate that Dyl is associated with the growth of cellular protuberances throughout development and with the formation of the cuticle in H. vigintioctopunctata.
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Affiliation(s)
- Yuxing Zhang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Qiao Tan
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Mengjiao Lin
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Chenhui Shen
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Lin Jin
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Guoqing Li
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
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3
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Djokic S, Bakhrat A, Li M, Akbari OS, Abdu U. Scale-type-specific requirement for the mosquito Aedes aegypti Spindle-F homologue by regulating microtubule organization. INSECT MOLECULAR BIOLOGY 2022; 31:216-224. [PMID: 34919304 PMCID: PMC10537241 DOI: 10.1111/imb.12752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/11/2021] [Accepted: 12/12/2021] [Indexed: 06/14/2023]
Abstract
Insect epithelial cells contain unique cellular extensions such as bristles, hairs, and scales. In contrast to bristle and hair, which are not divergent in their shape, scale morphology shows high diversity. In our attempt to characterize the role of the insect-specific gene, Spindle-F (spn-F), in mosquito development, we revealed a scale-type specific requirement for the mosquito Aedes aegypti spn-F homologue. Using CRISPR-Cas9, we generated Ae-spn-F mutants and found that Ae-spn-F is an essential gene, but we were able to recover a few adult escapers. These escapers could not fly nor move, and died after 3 to 4 days. We found that in Ae-spn-F mutants, only the tip part of the bristle was affected with bulbous with misoriented ribs. We also show that in Ae-spn-F mutants, only in falcate scales, which are curved with a sharp or narrowly rounded apex, and not in other scale types, the tip region is strongly affected. Our analysis also revealed that in contrast to Drosophila spn-F, which show strong defects in both the actin and microtubule (MT) network in the bristle, the Ae-spn-F gene is required only for MT organization in scales and bristles. In summary, our results reveal that Ae-spn-F is required for shaping tapered epithelial cellular extension structures, namely, the bristle and falcate scales by affecting MT organization.
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Affiliation(s)
- Sanja Djokic
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Anna Bakhrat
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Ming Li
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, San Diego, CA, USA
| | - Omar S. Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, San Diego, CA, USA
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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4
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Krishnan RK, Halachmi N, Baskar R, Bakhrat A, Zarivach R, Salzberg A, Abdu U. Revisiting the Role of ß-Tubulin in Drosophila Development: β-tubulin60D is not an Essential Gene, and its Novel Pin1 Allele has a Tissue-Specific Dominant-Negative Impact. Front Cell Dev Biol 2022; 9:787976. [PMID: 35111755 PMCID: PMC8802551 DOI: 10.3389/fcell.2021.787976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/09/2021] [Indexed: 11/19/2022] Open
Abstract
Diversity in cytoskeleton organization and function may be achieved through alternative tubulin isotypes and by a variety of post-translational modifications. The Drosophila genome contains five different β-tubulin paralogs, which may play an isotype tissue-specific function in vivo. One of these genes, the β-tubulin60D gene, which is expressed in a tissue-specific manner, was found to be essential for fly viability and fertility. To further understand the role of the β-tubulin60D gene, we generated new β-tubulin60D null alleles (β-tubulin60DM) using the CRISPR/Cas9 system and found that the homozygous flies were viable and fertile. Moreover, using a combination of genetic complementation tests, rescue experiments, and cell biology analyses, we identified Pin1, an unknown dominant mutant with bristle developmental defects, as a dominant-negative allele of β-tubulin60D. We also found a missense mutation in the Pin1 mutant that results in an amino acid replacement from the highly conserved glutamate at position 75 to lysine (E75K). Analyzing the ß-tubulin structure suggests that this E75K alteration destabilizes the alpha-helix structure and may also alter the GTP-Mg2+ complex binding capabilities. Our results revisited the credence that β-tubulin60D is required for fly viability and revealed for the first time in Drosophila, a novel dominant-negative function of missense β-tubulin60D mutation in bristle morphogenesis.
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Affiliation(s)
| | - Naomi Halachmi
- Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Raju Baskar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer’Sheva, Israel
| | - Anna Bakhrat
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer’Sheva, Israel
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer’Sheva, Israel
- National Institute for Biotechnology in the Negev and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Adi Salzberg
- Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer’Sheva, Israel
- *Correspondence: Uri Abdu,
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5
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Pomerantz AF, Siddique RH, Cash EI, Kishi Y, Pinna C, Hammar K, Gomez D, Elias M, Patel NH. Developmental, cellular and biochemical basis of transparency in clearwing butterflies. J Exp Biol 2021; 224:268372. [PMID: 34047337 PMCID: PMC8340268 DOI: 10.1242/jeb.237917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 04/16/2021] [Indexed: 12/16/2022]
Abstract
The wings of butterflies and moths (Lepidoptera) are typically covered with thousands of flat, overlapping scales that endow the wings with colorful patterns. Yet, numerous species of Lepidoptera have evolved highly transparent wings, which often possess scales of altered morphology and reduced size, and the presence of membrane surface nanostructures that dramatically reduce reflection. Optical properties and anti-reflective nanostructures have been characterized for several ‘clearwing’ Lepidoptera, but the developmental processes underlying wing transparency are unknown. Here, we applied confocal and electron microscopy to create a developmental time series in the glasswing butterfly, Greta oto, comparing transparent and non-transparent wing regions. We found that during early wing development, scale precursor cell density was reduced in transparent regions, and cytoskeletal organization during scale growth differed between thin, bristle-like scale morphologies within transparent regions and flat, round scale morphologies within opaque regions. We also show that nanostructures on the wing membrane surface are composed of two layers: a lower layer of regularly arranged nipple-like nanostructures, and an upper layer of irregularly arranged wax-based nanopillars composed predominantly of long-chain n-alkanes. By chemically removing wax-based nanopillars, along with optical spectroscopy and analytical simulations, we demonstrate their role in generating anti-reflective properties. These findings provide insight into morphogenesis and composition of naturally organized microstructures and nanostructures, and may provide bioinspiration for new anti-reflective materials. Summary: Transparency is a fascinating, yet poorly studied, optical property in living organisms. We elucidated the developmental processes underlying scale and nanostructure formation in glasswing butterflies, and their roles in generating anti-reflective properties.
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Affiliation(s)
- Aaron F Pomerantz
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Radwanul H Siddique
- Image Sensor Lab, Samsung Semiconductor, Inc., 2 N Lake Ave. Ste. 240, Pasadena, CA 91101, USA.,Department of Medical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Elizabeth I Cash
- Department of Environmental Science, Policy, & Management, University of California Berkeley, Berkeley, CA 94720, USA
| | - Yuriko Kishi
- Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Charline Pinna
- ISYEB, 45 rue Buffon, CP50, 75005, Paris, CNRS, MNHN, Sorbonne Université, EPHE, Université des Antilles, France
| | - Kasia Hammar
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Doris Gomez
- CEFE, 1919 route de Mende, 34090, Montpellier, CNRS, Université Montpellier, Université Paul Valéry Montpellier 3, EPHE, IRD, France
| | - Marianne Elias
- ISYEB, 45 rue Buffon, CP50, 75005, Paris, CNRS, MNHN, Sorbonne Université, EPHE, Université des Antilles, France
| | - Nipam H Patel
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,Marine Biological Laboratory, Woods Hole, MA 02543, USA.,Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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6
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Krishnan RK, Baskar R, Anna B, Elia N, Boermel M, Bausch AR, Abdu U. Recapitulating Actin Module Organization in the Drosophila Oocyte Reveals New Roles for Bristle-Actin-Modulating Proteins. Int J Mol Sci 2021; 22:ijms22084006. [PMID: 33924532 PMCID: PMC8070096 DOI: 10.3390/ijms22084006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 04/05/2021] [Accepted: 04/06/2021] [Indexed: 11/16/2022] Open
Abstract
The generation of F-actin bundles is controlled by the action of actin-binding proteins. In Drosophila bristle development, two major actin-bundling proteins—Forked and Fascin—were identified, but still the molecular mechanism by which these actin-bundling proteins and other proteins generate bristle actin bundles is unknown. In this study, we developed a technique that allows recapitulation of bristle actin module organization using the Drosophila ovary by a combination of confocal microscopy, super-resolution structured illumination microscopy, and correlative light and electron microscope analysis. Since Forked generated a distinct ectopic network of actin bundles in the oocyte, the additive effect of two other actin-associated proteins, namely, Fascin and Javelin (Jv), was studied. We found that co-expression of Fascin and Forked demonstrated that the number of actin filaments within the actin bundles dramatically increased, and in their geometric organization, they resembled bristle-like actin bundles. On the other hand, co-expression of Jv with Forked increased the length and density of the actin bundles. When all three proteins co-expressed, the actin bundles were longer and denser, and contained a high number of actin filaments in the bundle. Thus, our results demonstrate that the Drosophila oocyte could serve as a test tube for actin bundle analysis.
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Affiliation(s)
- Ramesh Kumar Krishnan
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; (R.K.K.); (R.B.); (B.A.); (N.E.)
| | - Raju Baskar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; (R.K.K.); (R.B.); (B.A.); (N.E.)
| | - Bakhrat Anna
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; (R.K.K.); (R.B.); (B.A.); (N.E.)
| | - Natalie Elia
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; (R.K.K.); (R.B.); (B.A.); (N.E.)
- National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Mandy Boermel
- Electron Microscopy Core Facility, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany;
| | - Andreas R. Bausch
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany;
- Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747 Garching, Germany
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel; (R.K.K.); (R.B.); (B.A.); (N.E.)
- Correspondence:
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7
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Sallee JL, Crawford JM, Singh V, Kiehart DP. Mutations in Drosophila crinkled/Myosin VIIA disrupt denticle morphogenesis. Dev Biol 2021; 470:121-135. [PMID: 33248112 PMCID: PMC7855556 DOI: 10.1016/j.ydbio.2020.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 10/22/2022]
Abstract
Actin filament crosslinking, bundling and molecular motor proteins are necessary for the assembly of epithelial projections such as microvilli, stereocilia, hairs, and bristles. Mutations in such proteins cause defects in the shape, structure, and function of these actin - based protrusions. One protein necessary for stereocilia formation, Myosin VIIA, is an actin - based motor protein conserved throughout phylogeny. In Drosophila melanogaster, severe mutations in the MyoVIIA homolog crinkled (ck) are "semi - lethal" with only a very small percentage of flies surviving to adulthood. Such survivors show morphological defects related to actin bundling in hairs and bristles. To better understand ck/MyoVIIA's function in bundled - actin structures, we used dominant female sterile approaches to analyze the loss of maternal and zygotic (M/Z) ck/MyoVIIA in the morphogenesis of denticles, small actin - based projections on the ventral epidermis of Drosophila embryos. M/Z ck mutants displayed severe defects in denticle morphology - actin filaments initiated in the correct location, but failed to elongate and bundle to form normal projections. Using deletion mutant constructs, we demonstrated that both of the C - terminal MyTH4 and FERM domains are necessary for proper denticle formation. Furthermore, we show that ck/MyoVIIA interacts genetically with dusky - like (dyl), a member of the ZPD family of proteins that links the extracellular matrix to the plasma membrane, and when mutated also disrupts normal denticle formation. Loss of either protein alone does not alter the localization of the other; however, loss of the two proteins together dramatically enhances the defects in denticle shape observed when either protein alone was absent. Our data indicate that ck/MyoVIIA plays a key role in the formation and/or organization of actin filament bundles, which drive proper shape of cellular projections.
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Affiliation(s)
- Jennifer L Sallee
- Department of Biology, Duke University, Durham, NC, 27708, USA; Department of Biology, North Central College, Naperville, IL, 60540, USA.
| | | | - Vinay Singh
- Department of Biology, Duke University, Durham, NC, 27708, USA
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8
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Actin bundles play a different role in shaping scales compared to bristles in the mosquito Aedes aegypti. Sci Rep 2020; 10:14885. [PMID: 32913276 PMCID: PMC7483531 DOI: 10.1038/s41598-020-71911-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 08/21/2020] [Indexed: 11/25/2022] Open
Abstract
Insect epithelial cells contain cellular extensions such as bristles, hairs, and scales. These cellular extensions are homologous structures that differ in morphology and function. They contain actin bundles that dictate their cellular morphology. While the organization, function, and identity of the major actin-bundling proteins in bristles and hairs are known, this information on scales is unknown. In this study, we characterized the development of scales and the role of actin bundles in the mosquito, Aedes aegypti. We show that scales undergo drastic morphological changes during development, from a cylindrical to flat shape with longer membrane invagination. Scale actin-bundle distribution changes from the symmetrical organization of actin bundles located throughout the bristle membrane to an asymmetrical organization. By chemically inhibiting actin polymerization and by knocking out the forked gene in the mosquito (Ae-Forked; a known actin-bundling protein) by CRISPR-Cas9 gene editing, we showed that actin bundles are required for shaping bristle, hair, and scale morphology. We demonstrated that actin bundles and Ae-Forked are required for bristle elongation, but not for that of scales. In scales, actin bundles are required for width formation. In summary, our results reveal, for the first time, the developmental process of mosquito scale formation and also the role of actin bundles and actin-bundle proteins in scale morphogenesis. Moreover, our results reveal that although scale and bristle are thought to be homologous structures, actin bundles have a differential requirement in shaping mosquito scales compared to bristles.
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9
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Baskar R, Bahkrat A, Otani T, Wada H, Davidov G, Pandey H, Gheber L, Zarivach R, Hayashi S, Abdu U. The plus-tip tracking and microtubule stabilizing activities of Javelin-like regulate microtubule organization and cell polarity. FEBS J 2019; 286:3811-3830. [PMID: 31152621 DOI: 10.1111/febs.14944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 05/03/2019] [Accepted: 05/30/2019] [Indexed: 11/29/2022]
Abstract
Cell polarity is essential for building cell asymmetry in all eukaryotic cells. Drosophila oocyte and bristle development require the newly characterized Spn-F protein complex, which includes Spn-F, IKKε, and Javelin-like (Jvl), to establish polarity. Jvl is a novel microtubule (MT)-associated protein; however, the mechanism by which it regulates MT organization is still unknown. We found that overexpression of Jvl stabilizes MTs and that jvl is needed for stable MT arrangement at the bristle tip and organization of the dynamic MT throughout the bristle shaft. At low levels of expression in cultured cells, Jvl behaved as a microtubule plus-end tracking protein. We demonstrated that Jvl physically interacts with the highly conserved MT end-binding protein 1 (EB1) using yeast two-hybrid and GST pull-down assays. This interaction is, however, dispensable for Jvl function in oocyte and bristle development. In addition, using a MT-binding assay, we saw that Jvl-C terminus directly binds to MTs. We also revealed that oocyte developmental arrest caused by Jvl overexpression in the germline can be rescued by mutations in its partners, spn-F and ikkε, suggesting that complex formation with Spn-F and IKKε is required for Jvl function in vivo. In summary, our results show that the microtubule plus-end tracking and stabilizing activities of Jvl are central for controlling cell polarity of oocytes and bristles.
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Affiliation(s)
- Raju Baskar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Anna Bahkrat
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Tetsuhisa Otani
- Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics, Kobe, Japan
| | - Housei Wada
- Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics, Kobe, Japan
| | - Geula Davidov
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,National Institute for Biotechnology in the Negev and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Himanshu Pandey
- Department of Chemistry and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Larisa Gheber
- Department of Chemistry and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.,National Institute for Biotechnology in the Negev and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Shigeo Hayashi
- Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics, Kobe, Japan
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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10
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Melkov A, Baskar R, Alcalay Y, Abdu U. A new mode of mitochondrial transport and polarized sorting regulated by Dynein, Milton and Miro. Development 2016; 143:4203-4213. [PMID: 27707795 DOI: 10.1242/dev.138289] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 09/23/2016] [Indexed: 11/20/2022]
Abstract
Intrinsic cell microtubule (MT) polarity, together with molecular motors and adaptor proteins, determines mitochondrial polarized targeting and MT-dependent transport. In polarized cells, such as neurons, mitochondrial mobility and transport require the regulation of kinesin and dynein by two adaptor proteins, Milton and Miro. Recently, we found that dynein heavy chain 64C (Dhc64C) is the primary motor protein for both anterograde and retrograde transport of mitochondria in the Drosophila bristle. In this study, we show that a molecular lesion in the Dhc64C allele that reduced bristle mitochondrial velocity generated a variant that acts as a 'slow' dynein in an MT-gliding assay, indicating that dynein directly regulates mitochondrial transport. We also showed that in milton-RNAi flies, mitochondrial flux into the bristle shaft, but not velocity, was significantly reduced. Surprisingly, mitochondria retrograde flux, but not net velocity, was significantly decreased in miro-RNAi flies. We thus reveal a new mode of mitochondrial sorting in polarized cell growth, whereby bi-directional mitochondrial transport undertaken exclusively by dynein is regulated by Milton in the anterograde direction and by a Miro-dependent switch to the retrograde direction.
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Affiliation(s)
- Anna Melkov
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 8410500, Israel
| | - Raju Baskar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 8410500, Israel
| | - Yehonatan Alcalay
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 8410500, Israel
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 8410500, Israel
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11
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Atypical mechanoreceptors in larvae of biting midges Forcipomyia nigra (Diptera: Ceratopogonidae). Micron 2016; 88:68-76. [PMID: 27428285 DOI: 10.1016/j.micron.2016.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/13/2016] [Accepted: 06/27/2016] [Indexed: 11/23/2022]
Abstract
The dorsolateral setae of Forcipomyia nigra have been investigated. They are mechanoreceptors, sensilla trichoidea, innerved by a single neuron. The tubular body is located at the base of the hair shaft. Although the fine structure of the dorsolateral setae is similar to dorsal setae that perform a double function: secretion of a hygroscopic viscous substance through the pores and mechanoreception dorsolateral setae, they do not secrete any fluid. In both types of setae, trichogen cells (hair forming cells) produce the hair shafts and thereafter do not retract from the cavity of the setae. They contain a large polyploid nucleus and expanded bundles of microtubules. In dorsolateral mechanoreceptors, the microtubules form a network around the nucleus of the trichogen cell and are especially numerous in the cytoplasm invading the interior of the seta, which is evidenced by immunofluorescence light microscopy. No tormogen cell, responsible for the production of the setal socket, was found. Our observations indicate that the dorsolateral setae are solely mechanoreceptors but their trichogen cells reveal some glandular activity.
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12
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Melkov A, Simchoni Y, Alcalay Y, Abdu U. Dynamic microtubule organization and mitochondrial transport are regulated by distinct Kinesin-1 pathways. Biol Open 2015; 4:1696-706. [PMID: 26581590 PMCID: PMC4736040 DOI: 10.1242/bio.015206] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The microtubule (MT) plus-end motor kinesin heavy chain (Khc) is well known for its role in long distance cargo transport. Recent evidence showed that Khc is also required for the organization of the cellular MT network by mediating MT sliding. We found that mutations in Khc and the gene of its adaptor protein, kinesin light chain (Klc) resulted in identical bristle morphology defects, with the upper part of the bristle being thinner and flatter than normal and failing to taper towards the bristle tip. We demonstrate that bristle mitochondria transport requires Khc but not Klc as a competing force to dynein heavy chain (Dhc). Surprisingly, we demonstrate for the first time that Dhc is the primary motor for both anterograde and retrograde fast mitochondria transport. We found that the upper part of Khc and Klc mutant bristles lacked stable MTs. When following dynamic MT polymerization via the use of GFP-tagged end-binding protein 1 (EB1), it was noted that at Khc and Klc mutant bristle tips, dynamic MTs significantly deviated from the bristle parallel growth axis, relative to wild-type bristles. We also observed that GFP-EB1 failed to concentrate as a focus at the tip of Khc and Klc mutant bristles. We propose that the failure of bristle tapering is due to defects in directing dynamic MTs at the growing tip. Thus, we reveal a new function for Khc and Klc in directing dynamic MTs during polarized cell growth. Moreover, we also demonstrate a novel mode of coordination in mitochondrial transport between Khc and Dhc. Summary: Highly polarized Drosophila bristle cells reveal that dynamic microtubule organization and mitochondrial transport are regulated by distinct Kinesin-1 pathways, and a novel mode of coordination between Khc and Dhc in mitochondrial transport.
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Affiliation(s)
- Anna Melkov
- Department of Life Sciences, Ben-Gurion University, Beer-Sheva 8410500, Israel
| | - Yasmin Simchoni
- Department of Life Sciences, Ben-Gurion University, Beer-Sheva 8410500, Israel
| | - Yehonatan Alcalay
- Department of Life Sciences, Ben-Gurion University, Beer-Sheva 8410500, Israel
| | - Uri Abdu
- Department of Life Sciences, Ben-Gurion University, Beer-Sheva 8410500, Israel
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13
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Dinwiddie A, Null R, Pizzano M, Chuong L, Leigh Krup A, Ee Tan H, Patel NH. Dynamics of F-actin prefigure the structure of butterfly wing scales. Dev Biol 2014; 392:404-18. [PMID: 24930704 DOI: 10.1016/j.ydbio.2014.06.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Revised: 06/02/2014] [Accepted: 06/04/2014] [Indexed: 11/24/2022]
Abstract
The wings of butterflies and moths consist of dorsal and ventral epidermal surfaces that give rise to overlapping layers of scales and hairs (Lepidoptera, "scale wing"). Wing scales (average length ~200 µm) are homologous to insect bristles (macrochaetes), and their colors create the patterns that characterize lepidopteran wings. The topology and surface sculpture of wing scales vary widely, and this architectural complexity arises from variations in the developmental program of the individual scale cells of the wing epithelium. One of the more striking features of lepidopteran wing scales are the longitudinal ridges that run the length of the mature (dead) cell, gathering the cuticularized scale cell surface into pleats on the sides of each scale. While also present around the periphery of other insect bristles and hairs, longitudinal ridges in lepidopteran wing scales gain new significance for their creation of iridescent color through microribs and lamellae. Here we show the dynamics of the highly organized F-actin filaments during scale cell development, and present experimental manipulations of actin polymerization that reveal the essential role of this cytoskeletal component in wing scale elongation and the positioning of longitudinal ribs.
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Affiliation(s)
- April Dinwiddie
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA.
| | - Ryan Null
- Department of Molecular and Cell Biology & Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720-3200, USA
| | - Maria Pizzano
- Department of Molecular and Cell Biology & Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720-3200, USA
| | - Lisa Chuong
- Department of Molecular and Cell Biology & Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720-3200, USA
| | - Alexis Leigh Krup
- Department of Molecular and Cell Biology & Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720-3200, USA
| | - Hwei Ee Tan
- Department of Molecular and Cell Biology & Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720-3200, USA
| | - Nipam H Patel
- Department of Molecular and Cell Biology & Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720-3200, USA.
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14
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Adler PN, Sobala LF, Thom D, Nagaraj R. dusky-like is required to maintain the integrity and planar cell polarity of hairs during the development of the Drosophila wing. Dev Biol 2013; 379:76-91. [PMID: 23623898 DOI: 10.1016/j.ydbio.2013.04.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 02/11/2013] [Accepted: 04/04/2013] [Indexed: 11/17/2022]
Abstract
The cuticular hairs and sensory bristles that decorate the adult Drosophila epidermis and the denticles found on the embryo have been used in studies on planar cell polarity and as models for the cytoskeletal mediated morphogenesis of cellular extensions. ZP domain proteins have recently been found to be important for the morphogenesis of both denticles and bristles. Here we show that the ZP domain protein Dusky-like is a key player in hair morphogenesis. As is the case in bristles, in hairs dyl mutants display a dramatic phenotype that is the consequence of a failure to maintain the integrity of the extension after outgrowth. Hairs lacking dyl function are split, thinned, multipled and often very short. dyl is required for normal chitin deposition in hairs, but chitin is not required for the normal accumulation of Dyl, hence dyl acts upstream of chitin. A lack of chitin however, does not mimic the dyl hair phenotype, thus Dyl must have other targets in hair morphogenesis. One of these appears to be the actin cytoskeleton. Interestingly, dyl mutants also display a unique planar cell polarity phenotype that is distinct from that seen with mutations in the frizzled/starry night or dachsous/fat pathway genes. Rab11 was previously found to be essential for Dyl plasma membrane localization in bristles. Here we found that the expression of a dominant negative Rab11 can mimic the dyl hair morphology phenotype consistent with Rab11 also being required for Dyl function in hairs. We carried out a small directed screen to identify genes that might function with dyl and identified Chitinase 6 (Cht6) as a strong candidate, as knocking down Cht6 function led to weak versions of all of the dyl hair phenotypes.
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Affiliation(s)
- Paul N Adler
- Biology Department, Institute for Morphogenesis and Regenerative Medicine, University of Virginia, Charlottesville, VA 22903, USA.
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15
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Abstract
Abstract Chitin is the second most abundant polysaccharide on earth. It is produced at the apical side of epidermal, tracheal, fore-, and hindgut epithelial cells in insects as a central component of the protective and supporting extracellular cuticle. Chitin is also an important constituent of the midgut peritrophic matrix that encases the food supporting its digestion and protects the epithelium against invasion by possibly ingested pathogens. The enzyme producing chitin is a glycosyltransferase that resides in the apical plasma membrane forming a pore to extrude the chains of chitin into the extracellular space. The apical plasma membrane is not only a platform for chitin synthases but, probably through its shape and equipment with distinct factors, also plays an important role in orienting and organizing chitin fibers. Here, I review findings on the cellular and molecular constitution of the apical plasma membrane of chitin-producing epithelia mainly focusing on work done in the fruit fly Drosophila melanogaster.
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Affiliation(s)
- Bernard Moussian
- Animal Genetics, Interfaculty Institute for Cell Biology, University of Tübingen, 72076 Tübingen, Germany.
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16
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Bitan A, Rosenbaum I, Abdu U. Stable and dynamic microtubules coordinately determine and maintain Drosophila bristle shape. Development 2012; 139:1987-96. [PMID: 22513371 DOI: 10.1242/dev.076893] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Within interphase cells, microtubules (MTs) are organized in a cell-specific manner to support cell shape and function. Here, we report that coordination between stable and dynamic MTs determines and maintains the highly elongated bristle cell shape. By following MT-decorating hooks and by tracking EB1 we identified two MT populations within bristles: a stable MT population polarized with their minus ends distal to the cell body, and a dynamic MT population that exhibits mixed polarity. Manipulating MT dynamics by Klp10A downregulation demonstrates that MTs can initiate new shaft extensions and thus possess the ability to determine growth direction. Actin filament bundling subsequently supports the newly formed shaft extensions. Analysis of ik2 mutant bristles, established by elongation defects in the Drosophila ikkε homolog, led to the observation that stable and dynamic MT orientation and polarized organization are important for proper bristle elongation. Thus, we demonstrate for the first time that coordination between stable and dynamic MT sets that are axially organized yet differently polarized drives cell elongation.
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Affiliation(s)
- Amir Bitan
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva 84105, Israel
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17
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Nagaraj R, Adler PN. Dusky-like functions as a Rab11 effector for the deposition of cuticle during Drosophila bristle development. Development 2012; 139:906-16. [PMID: 22278919 DOI: 10.1242/dev.074252] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The morphogenesis of Drosophila sensory bristles is dependent on the function of their actin and microtubule cytoskeleton. Actin filaments are important for bristle shape and elongation, while microtubules are thought to mediate protein and membrane trafficking to promote growth. We have identified an essential role for the bristle cuticle in the maintenance of bristle structure and shape at late stages of bristle development. We show that the small GTPase Rab11 mediates the organized deposition of chitin, a major cuticle component in bristles, and disrupting Rab11 function leads to phenotypes that result from bristle collapse rather than a failure to elongate. We further establish that Rab11 is required for the plasma membrane localization of the ZP domain-containing Dusky-like (Dyl) protein and that Dyl is also required for cuticle formation in bristles. Our data argue that Dyl functions as a Rab11 effector for mediating the attachment of the bristle cell membrane to chitin to establish a stable cuticle. Our studies also implicate the exocyst as a Rab11 effector in this process and that Rab11 trafficking along the bristle shaft is mediated by microtubules.
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Affiliation(s)
- Ranganayaki Nagaraj
- Biology Department, Cell Biology Department, Institute for Morphogenesis and Regenerative Medicine, University of Virginia, Charlottesville, VA 22903, USA
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18
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The Drosophila javelin gene encodes a novel actin-associated protein required for actin assembly in the bristle. Mol Cell Biol 2011; 31:4582-92. [PMID: 21930794 DOI: 10.1128/mcb.05730-11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Drosophila melanogaster bristle is a highly polarized cell that builds specialized cytoskeletal structures. Whereas actin is required for increasing bristle length, microtubules are essential for bristle axial growth. To identify new proteins involved in cytoskeleton organization during bristle development, we focused on identifying and characterizing the javelin (jv) locus. We found that in a jv mutant, the bristle tip is swollen and abnormal organization of bristle grooves is seen over the entire bristle. Using confocal and electron microscopy, we found that in jv mutant bristles, actin bundles do not form properly due to a loss of actin filaments within the bundle. We show that jv is an allele of the predicted CG32397 gene that encodes a protein with no homologs outside insects. Expression of the Jv protein fused to a green fluorescent protein (GFP) shows that the protein is colocalized with actin bundles in the bristle. Moreover, expression of Jv-GFP within the germ line led to the formation of ectopic actin bundles that surround the nucleus of nurse cells. Thus, we report that Jv is a novel actin-associated protein required for actin assembly during Drosophila bristle development.
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19
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Hung RJ, Yazdani U, Yoon J, Wu H, Yang T, Gupta N, Huang Z, van Berkel WJH, Terman JR. Mical links semaphorins to F-actin disassembly. Nature 2010; 463:823-7. [PMID: 20148037 DOI: 10.1038/nature08724] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 11/26/2009] [Indexed: 12/22/2022]
Abstract
How instructive cues present on the cell surface have their precise effects on the actin cytoskeleton is poorly understood. Semaphorins are one of the largest families of these instructive cues and are widely studied for their effects on cell movement, navigation, angiogenesis, immunology and cancer. Semaphorins/collapsins were characterized in part on the basis of their ability to drastically alter actin cytoskeletal dynamics in neuronal processes, but despite considerable progress in the identification of semaphorin receptors and their signalling pathways, the molecules linking them to the precise control of cytoskeletal elements remain unknown. Recently, highly unusual proteins of the Mical family of enzymes have been found to associate with the cytoplasmic portion of plexins, which are large cell-surface semaphorin receptors, and to mediate axon guidance, synaptogenesis, dendritic pruning and other cell morphological changes. Mical enzymes perform reduction-oxidation (redox) enzymatic reactions and also contain domains found in proteins that regulate cell morphology. However, nothing is known of the role of Mical or its redox activity in mediating morphological changes. Here we report that Mical directly links semaphorins and their plexin receptors to the precise control of actin filament (F-actin) dynamics. We found that Mical is both necessary and sufficient for semaphorin-plexin-mediated F-actin reorganization in vivo. Likewise, we purified Mical protein and found that it directly binds F-actin and disassembles both individual and bundled actin filaments. We also found that Mical utilizes its redox activity to alter F-actin dynamics in vivo and in vitro, indicating a previously unknown role for specific redox signalling events in actin cytoskeletal regulation. Mical therefore is a novel F-actin-disassembly factor that provides a molecular conduit through which actin reorganization-a hallmark of cell morphological changes including axon navigation-can be precisely achieved spatiotemporally in response to semaphorins.
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Affiliation(s)
- Ruei-Jiun Hung
- Department of Neuroscience, Neuroscience Graduate Program, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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20
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Bitan A, Guild GM, Bar-Dubin D, Abdu U. Asymmetric microtubule function is an essential requirement for polarized organization of the Drosophila bristle. Mol Cell Biol 2010; 30:496-507. [PMID: 19917727 PMCID: PMC2798467 DOI: 10.1128/mcb.00861-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/14/2009] [Accepted: 11/06/2009] [Indexed: 01/21/2023] Open
Abstract
While previous studies have shown that microtubules (MTs) are essential for maintaining the highly biased axial growth of the Drosophila bristle, the mechanism for this process has remained vague. We report that the MT minus-end marker, Nod-KHC, accumulates at the bristle tip, suggesting that the MT network in the bristle is organized minus end out. Potential markers for studying the importance of properly polarized MTs to bristle axial growth are Ik2 and Spindle-F (Spn-F), since mutations in spn-F and ik2 affect bristle development. We demonstrate that Spn-F and Ik2 are localized to the bristle tip and that mutations in ik2 and spn-F affect bristle MT and actin organization. Specifically, mutation in ik2 affects polarized bristle MT function. It was previously found that the hook mutant exhibited defects in bristle polarity and that hook is involved in endocytic trafficking. We found that Hook is localized at the bristle tip and that this localization is affected in ik2 mutants, suggesting that the contribution of MTs within the bristle shaft is important for correct endocytic trafficking. Thus, our results show that MTs are organized in a polarized manner within the highly elongated bristle and that this organization is essential for biased bristle axial growth.
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Affiliation(s)
- Amir Bitan
- Department of Life Sciences and National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva, Israel, Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Gregory M. Guild
- Department of Life Sciences and National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva, Israel, Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Dikla Bar-Dubin
- Department of Life Sciences and National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva, Israel, Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Uri Abdu
- Department of Life Sciences and National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva, Israel, Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
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21
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Shalaby NA, Parks AL, Morreale EJ, Osswalt MC, Pfau KM, Pierce EL, Muskavitch MAT. A screen for modifiers of notch signaling uncovers Amun, a protein with a critical role in sensory organ development. Genetics 2009; 182:1061-76. [PMID: 19448274 PMCID: PMC2728848 DOI: 10.1534/genetics.108.099986] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 05/11/2009] [Indexed: 12/14/2022] Open
Abstract
Notch signaling is an evolutionarily conserved pathway essential for many cell fate specification events during metazoan development. We conducted a large-scale transposon-based screen in the developing Drosophila eye to identify genes involved in Notch signaling. We screened 10,447 transposon lines from the Exelixis collection for modifiers of cell fate alterations caused by overexpression of the Notch ligand Delta and identified 170 distinct modifier lines that may affect up to 274 genes. These include genes known to function in Notch signaling, as well as a large group of characterized and uncharacterized genes that have not been implicated in Notch pathway function. We further analyze a gene that we have named Amun and show that it encodes a protein that localizes to the nucleus and contains a putative DNA glycosylase domain. Genetic and molecular analyses of Amun show that altered levels of Amun function interfere with cell fate specification during eye and sensory organ development. Overexpression of Amun decreases expression of the proneural transcription factor Achaete, and sensory organ loss caused by Amun overexpression can be rescued by coexpression of Achaete. Taken together, our data suggest that Amun acts as a transcriptional regulator that can affect cell fate specification by controlling Achaete levels.
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Affiliation(s)
- Nevine A Shalaby
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA
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22
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Ren N, Charlton J, Adler PN. The flare gene, which encodes the AIP1 protein of Drosophila, functions to regulate F-actin disassembly in pupal epidermal cells. Genetics 2007; 176:2223-34. [PMID: 17565945 PMCID: PMC1950627 DOI: 10.1534/genetics.107.072959] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Adult Drosophila are decorated with several types of polarized cuticular structures, such as hairs and bristles. The morphogenesis of these takes place in pupal cells and is mediated by the actin and microtubule cytoskeletons. Mutations in flare (flr) result in grossly abnormal epidermal hairs. We report here that flr encodes the Drosophila actin interacting protein 1 (AIP1). In other systems this protein has been found to promote cofilin-mediated F-actin disassembly. In Drosophila cofilin is encoded by twinstar (tsr). We show that flr mutations result in increased levels of F-actin accumulation and increased F-actin stability in vivo. Further, flr is essential for cell proliferation and viability and for the function of the frizzled planar cell polarity system. All of these phenotypes are similar to those seen for tsr mutations. This differs from the situation in yeast where cofilin is essential while aip1 mutations result in only subtle defects in the actin cytoskeleton. Surprisingly, we found that mutations in flr and tsr also result in greatly increased tubulin staining, suggesting a tight linkage between the actin and microtubule cytoskeleton in these cells.
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Affiliation(s)
- Nan Ren
- Biology Department, Institute for Morphogenesis and Regenerative Medicine and Cancer Center, University of Virginia, Charlottesville, VA 22903, USA
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23
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Disanza A, Mantoani S, Hertzog M, Gerboth S, Frittoli E, Steffen A, Berhoerster K, Kreienkamp HJ, Milanesi F, Di Fiore PP, Ciliberto A, Stradal TEB, Scita G. Regulation of cell shape by Cdc42 is mediated by the synergic actin-bundling activity of the Eps8–IRSp53 complex. Nat Cell Biol 2006; 8:1337-47. [PMID: 17115031 DOI: 10.1038/ncb1502] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Accepted: 08/04/2006] [Indexed: 11/09/2022]
Abstract
Actin-crosslinking proteins organize actin into highly dynamic and architecturally diverse subcellular scaffolds that orchestrate a variety of mechanical processes, including lamellipodial and filopodial protrusions in motile cells. How signalling pathways control and coordinate the activity of these crosslinkers is poorly defined. IRSp53, a multi-domain protein that can associate with the Rho-GTPases Rac and Cdc42, participates in these processes mainly through its amino-terminal IMD (IRSp53 and MIM domain). The isolated IMD has actin-bundling activity in vitro and is sufficient to induce filopodia in vivo. However, the manner of regulation of this activity in the full-length protein remains largely unknown. Eps8 is involved in actin dynamics through its actin barbed-ends capping activity and its ability to modulate Rac activity. Moreover, Eps8 binds to IRSp53. Here, we describe a novel actin crosslinking activity of Eps8. Additionally, Eps8 activates and synergizes with IRSp53 in mediating actin bundling in vitro, enhancing IRSp53-dependent membrane extensions in vivo. Cdc42 binds to and controls the cellular distribution of the IRSp53-Eps8 complex, supporting the existence of a Cdc42-IRSp53-Eps8 signalling pathway. Consistently, Cdc42-induced filopodia are inhibited following individual removal of either IRSp53 or Eps8. Collectively, these results support a model whereby the synergic bundling activity of the IRSp53-Eps8 complex, regulated by Cdc42, contributes to the generation of actin bundles, thus promoting filopodial protrusions.
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Affiliation(s)
- Andrea Disanza
- Istituto FIRC di Oncologia Molecolare (IFOM), Via Adamello 16, 20139, Milan, Italy
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24
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Frank DJ, Hopmann R, Lenartowska M, Miller KG. Capping protein and the Arp2/3 complex regulate nonbundle actin filament assembly to indirectly control actin bundle positioning during Drosophila melanogaster bristle development. Mol Biol Cell 2006; 17:3930-9. [PMID: 16822838 PMCID: PMC1593168 DOI: 10.1091/mbc.e06-06-0500] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Drosophila melanogaster bristle development is dependent on actin assembly, and prominent actin bundles form against the elongating cell membrane, giving the adult bristle its characteristic grooved pattern. Previous work has demonstrated that several actin-regulating proteins are required to generate normal actin bundles. Here we have addressed how two actin regulators, capping protein, a barbed end binding protein, and the Arp2/3 complex, a potent actin assembly nucleator, function to generate properly organized bundles. As predicted from studies in motile cells, we find that capping protein and the Arp2/3 complex act antagonistically to one another during bristle development. However, these proteins do not primarily act directly on bundles, but rather on a dynamic population of actin filaments that are not part of the bundles. These nonbundle filaments, termed snarls, play an important role in determining the number and spacing of the actin bundles. Reduction of capping protein leads to an increase in snarls, which prevents actin bundles from properly attaching to the membrane. Conversely, loss of an Arp2/3 complex component leads to a loss of snarls and accumulation of excess membrane-attached bundles. These results indicate that in nonmotile cells dynamic actin filaments can function to regulate the positioning of stable actin structures. In addition, our results suggest that the Arpc1 subunit may have an additional function, independent of the rest of the Arp2/3 complex.
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Affiliation(s)
- Deborah J. Frank
- *Department of Biology, Washington University, St. Louis, MO 63130; and
| | - Roberta Hopmann
- *Department of Biology, Washington University, St. Louis, MO 63130; and
| | - Marta Lenartowska
- *Department of Biology, Washington University, St. Louis, MO 63130; and
- Laboratory of Developmental Biology, Institute of General and Molecular Biology, Nicolaus Copernicus University, 87-100 Torun, Poland
| | - Kathryn G. Miller
- *Department of Biology, Washington University, St. Louis, MO 63130; and
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Shapiro RS, Anderson KV. DrosophilaIk2, a member of the IκB kinase family, is required for mRNA localization during oogenesis. Development 2006; 133:1467-75. [PMID: 16540511 DOI: 10.1242/dev.02318] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In both Drosophila and mammals, IκB kinases (IKKs) regulate the activity of Rel/NF-κB transcription factors by targeting their inhibitory partner proteins, IκBs, for degradation. We identified mutations in ik2, the gene that encodes one of two Drosophila IKKs, and found that the gene is essential for viability. During oogenesis, ik2 is required in an NF-κB-independent process that is essential for the localization of oskar and gurken mRNAs; as a result, females that lack ik2 in the germline produce embryos that are both bicaudal and ventralized. The abnormal RNA localization in ik2 mutant oocytes can be attributed to defects in the organization of microtubule minus-ends. In addition, both mutant oocytes and mutant escaper adults have abnormalities in the organization of the actin cytoskeleton. These data suggest that this IκB kinase has an NF-κB-independent role in mRNA localization and helps to link microtubule minus-ends to the oocyte cortex, a novel function of the IKK family.
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Affiliation(s)
- Risa S Shapiro
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10021, USA
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26
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Abdu U, Bar D, Schüpbach T. spn-F encodes a novel protein that affects oocyte patterning and bristle morphology in Drosophila. Development 2006; 133:1477-84. [PMID: 16540510 DOI: 10.1242/dev.02319] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The anteroposterior and dorsoventral axes of the Drosophila embryo are established during oogenesis through the activities of Gurken (Grk), a Tgfalpha-like protein, and the Epidermal growth factor receptor (Egfr). spn-F mutant females produce ventralized eggs similar to the phenotype produced by mutations in the grk-Egfr pathway. We found that the ventralization of the eggshell in spn-F mutants is due to defects in the localization and translation of grk mRNA during mid-oogenesis. Analysis of the microtubule network revealed defects in the organization of the microtubules around the oocyte nucleus. In addition, spn-F mutants have defective bristles. We cloned spn-F and found that it encodes a novel coiled-coil protein that localizes to the minus end of microtubules in the oocyte, and this localization requires the microtubule network and a Dynein heavy chain gene. We also show that Spn-F interacts directly with the Dynein light chain Ddlc-1. Our results show that we have identified a novel protein that affects oocyte axis determination and the organization of microtubules during Drosophila oogenesis.
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Affiliation(s)
- Uri Abdu
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva 84105, Israel.
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27
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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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28
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Tilney LG, DeRosier DJ. How to make a curved Drosophila bristle using straight actin bundles. Proc Natl Acad Sci U S A 2005; 102:18785-92. [PMID: 16357198 PMCID: PMC1323189 DOI: 10.1073/pnas.0509437102] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This, our Inaugural Article as Academy Members, is ironically our swan song from the field of the actin cytoskeleton. By reviewing what we have learned and what we think is going on during development, we hope to lure you, the reader, into applying your skills to the bristle cell. The processes of the assembly and disassembly of actin bundles is laid out in time and space in an organism that lends itself to genetic manipulation. The cell provides every process you could want: filament nucleation, growth of microvilli, joining of microvillar bundles into modules, assembly of modules into bundles, time-dependent use of at least two crossbridging proteins, filament turnover, treadmilling, disassembly, and filament translocation.
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Affiliation(s)
- Lewis G Tilney
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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29
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Hammonds AS, Fristrom JW. Mutational analysis of Stubble-stubbloid gene structure and function in Drosophila leg and bristle morphogenesis. Genetics 2005; 172:1577-93. [PMID: 16322506 PMCID: PMC1456279 DOI: 10.1534/genetics.105.047100] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The Stubble-stubbloid (Sb-sbd) gene is required for ecdysone-regulated epithelial morphogenesis of imaginal tissues during Drosophila metamorphosis. Mutations in Sb-sbd are associated with defects in apical cell shape changes critical for the evagination of the leg imaginal disc and with defects in assembly and extension of parallel actin bundles in growing mechanosensory bristles. The Sb-sbd gene encodes a type II transmembrane serine protease (TTSP). Here we use a Sb-sbd transgenic construct to rescue both bristle and leg morphogenesis defects in Sb-sbd mutations. Molecular characterization of Sb-sbd mutations and rescue experiments with wild-type and modified Sb-sbd transgenic constructs show that the protease domain is required for both leg and bristle functions. Truncated proteins that express the noncatalytic domains without the protease have dominant effects in bristles but not in legs. Leg morphogenesis, but not bristle growth, is sensitive to Sb-sbd overexpression. Antibody localization of the Sb-sbd protein shows apical expression in elongating legs. Sb-sbd protein is found in the base and shaft in budding bristles and then concentrates at the growing tip when bristles are elongating rapidly. We propose a model whereby Sb-sbd helps coordinate proteolytic modification of extracellular matrix attachments with cytoskeletal changes in both legs and bristles.
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Affiliation(s)
- Ann S Hammonds
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
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30
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He Y, Emoto K, Fang X, Ren N, Tian X, Jan YN, Adler PN. Drosophila Mob family proteins interact with the related tricornered (Trc) and warts (Wts) kinases. Mol Biol Cell 2005; 16:4139-52. [PMID: 15975907 PMCID: PMC1196325 DOI: 10.1091/mbc.e05-01-0018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The function of Tricornered (Trc), the Drosophila Ndr (Nuclear Dbf2-related) serine/threonine protein kinase, is required for the normal morphogenesis of a variety of polarized outgrowths including epidermal hairs, bristles, arista laterals, and dendrites. In yeast the Trc homolog Cbk1 needs to bind Mob2 to activate the RAM pathway. In this report, we provide genetic and biochemical data that Drosophila Trc also interacts with and is activated by Drosophila Dmob proteins. In addition, Drosophila Mob proteins appear to interact with the related Warts/Lats kinase, which functions as a tumor suppressor in flies and mammals. Interestingly, the overgrowth tumor phenotype that results from mutations in Dmob1 (mats) was only seen in genetic mosaics and not when the entire animal was mutant. We conclude that unlike in yeast, in Drosophila individual Mob proteins interact with multiple kinases and that individual NDR family kinases interact with multiple Mob proteins. We further provide evidence that Mo25, the Drosophila homolog of the RAM pathway hym1 gene does not function along with Trc.
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Affiliation(s)
- Ying He
- Department of Biology, Center for Morphogenesis and Regenerative Medicine and Cancer Center, University of Virginia, Charlottesville, VA 22903, USA
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31
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Criel GRJ, Van Oostveldt P, MacRae TH. Spatial organization and isotubulin composition of microtubules in epidermal tendon cells of Artemia franciscana. J Morphol 2005; 263:203-15. [PMID: 15593343 DOI: 10.1002/jmor.10298] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Epidermally derived tendon cells attach the exoskeleton (cuticle) of the Branchiopod crustacean, Artemia franciscana, to underlying muscle in the hindgut, while the structurally similar transalar tendon (epithelial) cells, which also arise from the epidermis and are polarized, connect dorsal and ventral exopodite surfaces. To establish these latter attachments the transalar tendon cells interact with cuticles on opposite sides of the exopodite by way of their apical surfaces and with one another via basal regions, or the cuticle attachments may be mediated through linkages with phagocytic storage cells found in the hemolymph. In some cases, phyllopod tendon cells attach directly to muscle cells. Tendon cells in the hindgut of Artemia possess microtubule bundles, as do the transalar cells, and they extend from the basal myotendinal junction to the apical domain located near the cuticle. The bundled microtubules intermingle with thin filaments reminiscent of microfilaments, but intermediate filament-like structures are absent. Microtubule bundles converging at apical cell surfaces contact structures termed apical invaginations, composed of cytoplasmic membrane infoldings associated with electron-dense material. Intracuticular rods protrude from apical invaginations, either into the cuticle during intermolt or the molting fluid in premolt. Confocal microscopy of immunofluorescently stained samples revealed tyrosinated, detyrosinated, and acetylated tubulins, the first time posttranslationally modified isoforms of this protein have been demonstrated in crustacean tendon cells. Microfilaments, as shown by staining with phalloidin, coincided spatially with microtubule bundles. Artemia tendon cells clearly represent an interesting system for study of cytoskeleton organization within the context of cytoplasmic polarity and the results in this article indicate functional cooperation of microtubules and microfilaments. These cytoskeletal elements, either acting independently or in concert, may transmit tension from muscle to cuticle in the hindgut and resist compression when connecting exopodite cuticular surfaces.
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Affiliation(s)
- Godelieve R J Criel
- Department of Anatomy, Embryology and Histology, University of Gent, Gent, Belgium
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32
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Guild GM, Connelly PS, Ruggiero L, Vranich KA, Tilney LG. Actin filament bundles in Drosophila wing hairs: hairs and bristles use different strategies for assembly. Mol Biol Cell 2005; 16:3620-31. [PMID: 15917291 PMCID: PMC1182302 DOI: 10.1091/mbc.e05-03-0185] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Actin filament bundles can shape cellular extensions into dramatically different forms. We examined cytoskeleton formation during wing hair morphogenesis using both confocal and electron microscopy. Hairs elongate with linear kinetics (approximately 1 microm/h) over the course of approximately 18 h. The resulting structure is vividly asymmetric and shaped like a rose thorn--elongated in the distal direction, curved in two dimensions with an oval base and a round tip. High-resolution analysis shows that the cytoskeleton forms from microvilli-like pimples that project actin filaments into the cytoplasm. These filaments become cross-linked into bundles by the sequential use of three cross-bridges: villin, forked and fascin. Genetic loss of each cross-bridge affects cell shape. Filament bundles associate together, with no lateral membrane attachments, into a cone of overlapping bundles that matures into an oval base by the asymmetric addition of bundles on the distal side. In contrast, the long bristle cell extension is supported by equally long (up to 400 microm) filament bundles assembled together by end-to-end grafting of shorter modules. Thus, bristle and hair cells use microvilli and cross-bridges to generate the common raw material of actin filament bundles but employ different strategies to assemble these into vastly different shapes.
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Affiliation(s)
- Gregory M Guild
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
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33
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Tilney LG, Connelly PS, Ruggiero L, Vranich KA, Guild GM, Derosier D. The role actin filaments play in providing the characteristic curved form of Drosophila bristles. Mol Biol Cell 2004; 15:5481-91. [PMID: 15371540 PMCID: PMC532027 DOI: 10.1091/mbc.e04-06-0472] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Drosophila bristles display a precise orientation and curvature. An asymmetric extension of the socket cell overlies the newly emerging bristle rudiment to provide direction for bristle elongation, a process thought to be orchestrated by the nerve dendrite lying between these cells. Scanning electron microscopic analysis of individual bristles showed that curvature is planar and far greater near the bristle base. Correlated with this, as development proceeds the pupa gradually recedes from the inner pupal case (an extracellular layer that encloses the pupa) leading to less bristle curvature along the shaft. We propose that the inner pupal case induces elongating bristles to bend when they contact this barrier. During elongation the actin cytoskeleton locks in this curvature by grafting together the overlapping modules that comprise the long filament bundles. Because the bristle is curved, the actin bundles on the superior side must be longer than those on the inferior side. This is accomplished during grafting by greater elongation of superior side modules. Poor actin cross-bridging in mutant bristles results in altered curvature. Thus, the pattern of bristle curvature is a product of both extrinsic factors-the socket cell and the inner pupal case--and intrinsic factors--actin cytoskeleton assembly.
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Affiliation(s)
- Lewis G Tilney
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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34
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Tilney LG, Connelly PS, Guild GM. Microvilli appear to represent the first step in actin bundle formation in Drosophila bristles. J Cell Sci 2004; 117:3531-8. [PMID: 15226373 DOI: 10.1242/jcs.01215] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During bristle development the emerging bristle shaft, socket cell, and the apical surface of thoracic epithelial cells form tiny protuberances or pimples that contain electron-dense material located on the cytoplasmic surface of the pimple tip. In a few cases short actin filaments extend from this material into the cortical cytoplasm. When cultured in the presence of jasplakinolide, an agent that prevents filament disassembly, pimples elongate to form microvilli containing a core of crosslinked filaments. Emerging-bristle mutants delay cortical bundle formation and are aggregated by forked protein crossbridges. Using these mutants and enhancing core bundle formation with jasplakinolide we found that microvillar formation represents the first stage in the morphogenesis of much larger actin bundles in Drosophila bristle shaft cells. Evidence is presented showing that socket cells do not contain forked protein crossbridges, a fact that may explain why cortical bundles only appear in bristle shaft cells. Furthermore, as pimples and microvilli form in the absence of both forked and fascin crossbridges, we also conclude that neither of these crossbridges account for core bundle formation in microvilli, but there must exist a third, as yet unidentified crossbridge in this system. Immunocytochemisty suggested that this new crossbridge is not Drosophila villin. Finally, ultrastructural comparisons suggest that microspikes and microvilli form very differently.
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Affiliation(s)
- Lewis G Tilney
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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35
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Affiliation(s)
- Antonio Jacinto
- Instituto Gulbenkian de Ciencia, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal
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36
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Guild GM, Connelly PS, Ruggiero L, Vranich KA, Tilney LG. Long continuous actin bundles in Drosophila bristles are constructed by overlapping short filaments. J Cell Biol 2003; 162:1069-77. [PMID: 12975350 PMCID: PMC2172841 DOI: 10.1083/jcb.200305143] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The actin bundles essential for Drosophila bristle elongation are hundreds of microns long and composed of cross-linked unipolar filaments. These long bundles are built from much shorter modules that graft together. Using both confocal and electron microscopy, we demonstrate that newly synthesized modules are short (1-2 microm in length); modules elongate to approximately 3 microm by growing over the surface of longitudinally adjacent modules to form a graft; the grafted regions are initially secured by the forked protein cross-bridge and later by the fascin cross-bridge; actin bundles are smoothed by filament addition and appear continuous and without swellings; and in the absence of grafting, dramatic alterations in cell shape occur that substitutes cell width expansion for elongation. Thus, bundle morphogenesis has several components: module formation, elongation, grafting, and bundle smoothing. These actin bundles are much like a rope or cable, made by overlapping elements that run a small fraction of the overall length, and stiffened by cross-linking.
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Affiliation(s)
- Gregory M Guild
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
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37
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Szuplewski S, Kottler B, Terracol R. The Drosophila bZIP transcription factor Vrille is involved in hair and cell growth. Development 2003; 130:3651-62. [PMID: 12835382 DOI: 10.1242/dev.00588] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Vri is closely related to bZIP transcription factors involved in growth or cell death. vri clonal and overexpression analyses revealed defects at the cellular level. vri clones in the adult cuticle contain smaller cells with atrophic bristles. The phenotypes are strictly cell autonomous. Clones induced in the eye precursor cells lead to individuals with smaller eyes and reduced number of ommatidia with an abnormal morphology and shorter photoreceptor cell stalks. Overexpression of vri is anti-proliferative in embryonic dorsal epidermis and in imaginal discs, and induces apoptosis. On the wing surface, larger cells with multiple trichomes are observed, suggesting cytoskeletal defects. In salivary glands, vri overexpression leads to smaller cells and organs. We also show that vri is involved in locomotion and flight and interacts genetically with genes encoding actin-binding proteins. The phenotypes observed are consistent with the hypothesis that vri is required for normal cell growth and proliferation via the regulation of the actin cytoskeleton.
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Affiliation(s)
- Sébastien Szuplewski
- Laboratoire de Génétique du Développement et Evolution, Institut Jacques Monod, 2 Place Jussieu Tour 43, 75251 Paris Cedex 05, France
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38
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Tilney LG, Connelly PS, Ruggiero L, Vranich KA, Guild GM. Actin filament turnover regulated by cross-linking accounts for the size, shape, location, and number of actin bundles in Drosophila bristles. Mol Biol Cell 2003; 14:3953-66. [PMID: 14517310 PMCID: PMC206991 DOI: 10.1091/mbc.e03-03-0158] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Drosophila bristle cells are shaped during growth by longitudinal bundles of cross-linked actin filaments attached to the plasma membrane. We used confocal and electron microscopy to examine actin bundle structure and found that during bristle elongation, snarls of uncross-linked actin filaments and small internal bundles also form in the shaft cytoplasm only to disappear within 4 min. Thus, formation and later removal of actin filaments are prominent features of growing bristles. These transient snarls and internal bundles can be stabilized by culturing elongating bristles with jasplakinolide, a membrane-permeant inhibitor of actin filament depolymerization, resulting in enormous numbers of internal bundles and uncross-linked filaments. Examination of bundle disassembly in mutant bristles shows that plasma membrane association and cross-bridging adjacent actin filaments together inhibits depolymerization. Thus, highly cross-bridged and membrane-bound actin filaments turn over slowly and persist, whereas poorly cross-linked filaments turnover more rapidly. We argue that the selection of stable bundles relative to poorly cross-bridged filaments can account for the size, shape, number, and location of the longitudinal actin bundles in bristles. As a result, filament turnover plays an important role in regulating cytoskeleton assembly and consequently cell shape.
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Affiliation(s)
- Lewis G Tilney
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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39
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Noguchi T, Miller KG. A role for actin dynamics in individualization during spermatogenesis in Drosophila melanogaster. Development 2003; 130:1805-16. [PMID: 12642486 DOI: 10.1242/dev.00406] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In order to better understand the mechanism of sperm individualization during spermatogenesis in Drosophila melanogaster, we have developed an in vitro culture system in which we can perform live observation of individualization in isolated cysts. The whole process of individualization, during which a bundle of 64 syncytial spermatids is separated into individual sperm, takes place in these cultures. Individualization complexes, which consist of 64 cones of actin that assemble around the sperm nuclei, move to the basal end of the tails, forming a characteristic "cystic bulge" that contains an accumulation of cytoplasm, syncytial membrane and vesicles. The cystic bulge is the site of membrane remodeling and its movement was used to follow the progress of individualization. The speed of cystic bulge movement is fairly constant along the length of the cyst. Actin drugs, but not microtubule drugs inhibit cystic bulge movement, suggesting that the movement requires proper actin dynamics but not microtubules. GFP-tagged actin was expressed in the cyst and fluorescence recovery after photobleaching was monitored using confocal microscopy to analyze actin dynamics in cones. Actin turns over throughout the cone, with that at the leading edge of the cones turning over with slightly faster kinetics. Actin does not treadmill from the front to the back of the cone. Actin in moving actin cones turns over in about 12 minutes, although prior to onset of movement, turnover is much slower. Visualization of membrane using FM1-43 reveals that the cystic bulge has an extremely complicated series of membrane invaginations and the transition from syncytial to individualized spermatids occurs at the front of the actin cones. We also suggest that endocytosis and exocytosis might not be important for membrane remodeling. This system should be suitable for analysis of defects in male sterile mutants and for investigating other steps of spermatogenesis.
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Affiliation(s)
- Tatsuhiko Noguchi
- Department of Biology, Washington University in St Louis, Campus Box 1229, 1 Brookings Drive, St Louis, MO 63130, USA.
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40
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Hopmann R, Miller KG. A balance of capping protein and profilin functions is required to regulate actin polymerization in Drosophila bristle. Mol Biol Cell 2003; 14:118-28. [PMID: 12529431 PMCID: PMC140232 DOI: 10.1091/mbc.e02-05-0300] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Profilin is a well-characterized protein known to be important for regulating actin filament assembly. Relatively few studies have addressed how profilin interacts with other actin-binding proteins in vivo to regulate assembly of complex actin structures. To investigate the function of profilin in the context of a differentiating cell, we have studied an instructive genetic interaction between mutations in profilin (chickadee) and capping protein (cpb). Capping protein is the principal protein in cells that caps actin filament barbed ends. When its function is reduced in the Drosophila bristle, F-actin levels increase and the actin cytoskeleton becomes disorganized, causing abnormal bristle morphology. chickadee mutations suppress the abnormal bristle phenotype and associated abnormalities of the actin cytoskeleton seen in cpb mutants. Furthermore, overexpression of profilin in the bristle mimics many features of the cpb loss-of-function phenotype. The interaction between cpb and chickadee suggests that profilin promotes actin assembly in the bristle and that a balance between capping protein and profilin activities is important for the proper regulation of F-actin levels. Furthermore, this balance of activities affects the association of actin structures with the membrane, suggesting a link between actin filament dynamics and localization of actin structures within the cell.
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Affiliation(s)
- Roberta Hopmann
- Department of Biology, Washington University, St Louis, Missouri 63130, USA
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41
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Gilliland LU, Kandasamy MK, Pawloski LC, Meagher RB. Both vegetative and reproductive actin isovariants complement the stunted root hair phenotype of the Arabidopsis act2-1 mutation. PLANT PHYSIOLOGY 2002; 130:2199-209. [PMID: 12481103 PMCID: PMC166731 DOI: 10.1104/pp.014068] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2001] [Revised: 09/18/2002] [Accepted: 09/18/2002] [Indexed: 05/17/2023]
Abstract
The ACT2 gene, encoding one of eight actin isovariants in Arabidopsis, is the most strongly expressed actin gene in vegetative tissues. A search was conducted for physical defects in act2-1 mutant plants to account for their reduced fitness compared with wild type in population studies. The act2-1 insertion fully disrupted expression of ACT2 RNA and significantly lowered the level of total actin protein in vegetative organs. The root hairs of the act2-1 mutants were 10% to 70% the length of wild-type root hairs, and they bulged severely at the base. The length of the mutant root hairs and degree of bulging at the base were affected by adjusting the osmolarity and gelling agent of the growth medium. The act2-1 mutant phenotypes were fully rescued by an ACT2 genomic transgene. When the act2-1 mutation was combined with another vegetative actin mutation, act7-1, the resulting double mutant exhibited extensive synergistic phenotypes ranging from developmental lethality to severe dwarfism. Transgenic overexpression of the ACT7 vegetative isovariant and ectopic expression of the ACT1 reproductive actin isovariant also rescued the root hair elongation defects of the act2-1 mutant. These results suggest normal ACT2 gene regulation is essential to proper root hair elongation and that even minor differences may cause root defects. However, differences in the actin protein isovariant are not significant to root hair elongation, in sharp contrast to recent reports on the functional nonequivalency of plant actin isovariants. Impairment of root hair functions such as nutrient mining, water uptake, and physical anchoring are the likely cause of the reduced fitness seen for act2-1 mutants in multigenerational studies.
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Affiliation(s)
- Laura U Gilliland
- Department of Genetics, University of Georgia, Athens, Georgia 30602-7223, USA
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42
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Fei X, He B, Adler PN. The growth of Drosophila bristles and laterals is not restricted to the tip or base. J Cell Sci 2002; 115:3797-806. [PMID: 12235290 DOI: 10.1242/jcs.00065] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The highly elongated bristles of Drosophila have proven to be a valuable model system for studying cellular morphogenesis. Extending bristles contain a series of large bundles of actin filaments juxtaposed to the plasma membrane and centrally located microtubules. Models to explain the extension of the bristle have principally focused on the assembly of actin filaments at the distal tip of the bristle. We have used time-lapse observations of wild-type and mutant bristles and the related arista laterals and come to the conclusion that growth takes place throughout the growing cellular extension. This distributed growth can explain the behavior of split laterals and the shape changes seen at the tip during bristle and lateral outgrowth. Inhibitor studies suggest that the microtubule cytoskeleton is essential for maintaining the highly biased axial growth of these structures. We have used fluorescence recovery after photo-bleaching to study the dynamics of the cytoskeleton during bristle growth. Our experiments show that actin bundles in growing bristles are quite stable and move in a retrograde fashion. The bristle microtubules are less stable. The retrograde movement of the peripheral actin appears to be counterbalanced by the distally directed movement of cytoplasm in the center of the bristle.
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Affiliation(s)
- Xiaoyin Fei
- Biology Department and Cancer Center, University of Virginia, Charlottesville, VA 22903, USA
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Zhou X, Riddiford LM. Broad specifies pupal development and mediates the ‘status quo’ action of juvenile hormone on the pupal-adult transformation inDrosophilaandManduca. Development 2002; 129:2259-69. [PMID: 11959833 DOI: 10.1242/dev.129.9.2259] [Citation(s) in RCA: 199] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The understanding of the molecular basis of the endocrine control of insect metamorphosis has been hampered by the profound differences in responses of the Lepidoptera and the Diptera to juvenile hormone (JH). In both Manduca and Drosophila, the broad (br) gene is expressed in the epidermis during the formation of the pupa, but not during adult differentiation. Misexpression of BR-Z1 during either a larval or an adult molt of Drosophila suppressed stage-specific cuticle genes and activated pupal cuticle genes, showing that br is a major specifier of the pupal stage. Treatment with a JH mimic at the onset of the adult molt causes br re-expression and the formation of a second pupal cuticle in Manduca, but only in the abdomen of Drosophila. Expression of the BR isoforms during adult development of Drosophila suppressed bristle and hair formation when induced early or redirected cuticle production toward the pupal program when induced late. Expression of BR-Z1 at both of these times mimicked the effect of JH application but, unlike JH, it caused production of a new pupal cuticle on the head and thorax as well as on the abdomen. Consequently, the ‘status quo’ action of JH on the pupal-adult transformation is mediated by the JH-induced re-expression of BR.
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Affiliation(s)
- Xiaofeng Zhou
- Department of Zoology, University of Washington, Box 351800, Seattle, WA 98195-1800, USA
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Palmgren S, Vartiainen M, Lappalainen P. Twinfilin, a molecular mailman for actin monomers. J Cell Sci 2002; 115:881-6. [PMID: 11870207 DOI: 10.1242/jcs.115.5.881] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Twinfilin is a ubiquitous actin-monomer-binding protein that is composed of two ADF-homology domains. It forms a 1:1 complex with ADP-actin-monomers,inhibits nucleotide exchange on actin monomers and prevents assembly of the monomer into filaments. The two ADF-H domains in twinfilin probably have 3D structures similar to those of the ADF/cofilin proteins and overlapping actin-binding sites. Twinfilin also interacts with PtdIns(4,5)P2, which inhibits its actin-monomer-sequestering activity in vitro. Mutations in the twinfilin gene result in defects in the bipolar budding pattern in S. cerevisiae and in a rough eye phenotype and aberrant bristle morphology in Drosophila melanogaster. These phenotypes are caused by the uncontrolled polymerization of actin filaments in the absence of twinfilin. Studies on budding yeast suggest that twinfilin contributes to actin filament turnover by localizing actin monomers, in their `inactive'ADP-form, to the sites of rapid filament assembly. This is mediated through direct interactions between twinfilin and capping protein. Therefore,twinfilin might serve as a link between rapid actin filament depolymerization and assembly in cells.
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Affiliation(s)
- Sandra Palmgren
- Program in Cellular Biotechnology, Institute of Biotechnology, PO Box 56, 00014 University of Helsinki, Finland
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Guild GM, Connelly PS, Vranich KA, Shaw MK, Tilney LG. Actin filament turnover removes bundles fromDrosophilabristle cells. J Cell Sci 2002; 115:641-53. [PMID: 11861770 DOI: 10.1242/jcs.115.3.641] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Drosophila bristle cells form enormous extensions that are supported by equally impressive scaffolds of modular, polarized and crosslinked actin filament bundles. As the cell matures and support is taken over by the secreted cuticle, the actin scaffold is completely removed. This removal begins during cell elongation and proceeds via an orderly series of steps that operate on each module. Using confocal and electron microscopy, we found that the ∼500-filament modules are fractured longitudinally into 25-50-filament subbundles, indicating that module breakdown is the reverse of assembly. Time-lapse confocal analysis of GFP-decorated bundles in live cells showed that modules were shortened by subunit removal from filament barbed ends, again indicating that module breakdown is the reverse of assembly. Module shortening takes place at a fairly slow rate of ∼1μm/hour,implying that maximally crosslinked modules are not rapidly depolymerized. Barbed-end depolymerization was prevented with jasplakinolide and accelerated with cycloheximide, indicating that barbed-end maintenance requires continuous protein synthesis. Subbundle adhesion was lost in the presence of cytochalasin, indicating that continuous actin polymerization is required. Thus, these polarized actin filament bundles are dynamic structures that require continuous maintenance owing to protein and actin filament turnover. We propose that after cell elongation, maintenance falls behind turnover,resulting in the removal of this modular cytoskeleton.
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Affiliation(s)
- Gregory M Guild
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
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Niwa R, Nagata-Ohashi K, Takeichi M, Mizuno K, Uemura T. Control of actin reorganization by Slingshot, a family of phosphatases that dephosphorylate ADF/cofilin. Cell 2002; 108:233-46. [PMID: 11832213 DOI: 10.1016/s0092-8674(01)00638-9] [Citation(s) in RCA: 523] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The ADF (actin-depolymerizing factor)/cofilin family is a stimulus-responsive mediator of actin dynamics. In contrast to the mechanisms of inactivation of ADF/cofilin by kinases such as LIM-kinase 1 (LIMK1), much less is known about its reactivation through dephosphorylation. Here we report Slingshot (SSH), a family of phosphatases that have the property of F actin binding. In Drosophila, loss of ssh function dramatically increased levels of both F actin and phospho-cofilin (P cofilin) and disorganized epidermal cell morphogenesis. In mammalian cells, human SSH homologs (hSSHs) suppressed LIMK1-induced actin reorganization. Furthermore, SSH and the hSSHs dephosphorylated P cofilin in cultured cells and in cell-free assays. Our results strongly suggest that the SSH family plays a pivotal role in actin dynamics by reactivating ADF/cofilin in vivo.
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Affiliation(s)
- Ryusuke Niwa
- Department of Molecular Genetics, The Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
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Wahlström G, Vartiainen M, Yamamoto L, Mattila PK, Lappalainen P, Heino TI. Twinfilin is required for actin-dependent developmental processes in Drosophila. J Cell Biol 2001; 155:787-96. [PMID: 11724820 PMCID: PMC2150880 DOI: 10.1083/jcb.200108022] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The actin cytoskeleton is essential for cellular remodeling and many developmental and morphological processes. Twinfilin is a ubiquitous actin monomer-binding protein whose biological function has remained unclear. We discovered and cloned the Drosophila twinfilin homologue, and show that this protein is ubiquitously expressed in different tissues and developmental stages. A mutation in the twf gene leads to a number of developmental defects, including aberrant bristle morphology. This results from uncontrolled polymerization of actin filaments and misorientation of actin bundles in developing bristles. In wild-type bristles, twinfilin localizes diffusively to cytoplasm and to the ends of actin bundles, and may therefore be involved in localization of actin monomers in cells. We also show that twinfilin and the ADF/cofilin encoding gene twinstar interact genetically in bristle morphogenesis. These results demonstrate that the accurate regulation of size and dynamics of the actin monomer pool by twinfilin is essential for a number of actin-dependent developmental processes in multicellular eukaryotes.
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Affiliation(s)
- G Wahlström
- Developmental Biology Program, Institute of Biotechnology, Viikki Biocenter, FIN-00014 University of Helsinki, Finland
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Cong J, Geng W, He B, Liu J, Charlton J, Adler PN. Thefurrygene ofDrosophilais important for maintaining the integrity of cellular extensions during morphogenesis. Development 2001; 128:2793-802. [PMID: 11526084 DOI: 10.1242/dev.128.14.2793] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Drosophila imaginal cells that produce epidermal hairs, the shafts of sensory bristles and the lateral extensions of the arista are attractive model systems for studying the morphogenesis of polarized cell extensions. We now report the identification and characterization of furry, an essential Drosophila gene that is involved in maintaining the integrity of these cellular extensions during morphogenesis. Mutations in furry result in the formation of branched arista laterals, branched bristles and a strong multiple hair cell phenotype that consists of clusters of epidermal hairs and branched hairs. By following the morphogenesis of arista laterals in pupae, we have determined that the branched laterals are due to the splitting of individual laterals during elongation. In genetic mosaics furry was found to act cell autonomously in the wing. The phenotypes of double mutant cells argue that furry functions independently of the frizzled planar polarity pathway and that it probably functions in the same pathway as the tricornered gene. We used a P-element insertion allele as a tag to clone the furry gene and found it to be a large and complicated gene that encodes a pair of large conserved proteins of unknown biochemical function.
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Affiliation(s)
- J Cong
- Biology Department and Cancer Center, University of Virginia, Charlottesville, VA 22903, USA
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Abstract
Epidermal cells of Drosophila form a variety of polarized structures during their differentiation. These polarized structures include epidermal hairs, the shafts of sensory bristles, larval denticles and the arista laterals. The arista is the terminal segment of the antenna and consists of a central core and a series of lateral extensions. Here we describe the cellular mechanisms involved in the development of the arista and the morphogenesis of the laterals. We found that the development of the arista is a complex process that involves coordinated cell shape changes, elongation of the central core, apoptosis, nuclear migration, the formation of polyploid cells and the outgrowth of the laterals. This developmental program is highly conserved in the development of the arista in the housefly (Musca domestica). Altering arista cell number in Drosophila by stimulating or inhibiting apoptosis results in an altered number of laterals. Interestingly, the increased number of laterals that result from the inhibition of apoptosis in Drosophila results in an arista whose morphology is reminiscent of the Musca arista. Previous experiments have shown that both the actin and microtubule cytoskeletons have important functions in the cellular morphogenesis of hairs and bristles. Inhibitor studies reported here show that this is also the case for the formation of the arista laterals, arguing that the actin and microtubule cytoskeletons have similar functions in the morphogenesis of all of these cell types. We conclude that the arista laterals are a valuable complementary cell type system for studying the morphogenesis of polarized cellular extensions in Drosophila.
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Affiliation(s)
- B He
- Biology Department and Cancer Center, University of Virginia, Charlottesville, VA 22903, USA
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Geng W, He B, Wang M, Adler PN. The tricornered gene, which is required for the integrity of epidermal cell extensions, encodes the Drosophila nuclear DBF2-related kinase. Genetics 2000; 156:1817-28. [PMID: 11102376 PMCID: PMC1461384 DOI: 10.1093/genetics/156.4.1817] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
During their differentiation epidermal cells of Drosophila form a rich variety of polarized structures. These include the epidermal hairs that decorate much of the adult cuticular surface, the shafts of the bristle sense organs, the lateral extensions of the arista, and the larval denticles. These cuticular structures are produced by cytoskeletal-mediated outgrowths of epidermal cells. Mutations in the tricornered gene result in the splitting or branching of all of these structures. Thus, tricornered function appears to be important for maintaining the integrity of the outgrowths. tricornered mutations however do not have major effects on the growth or shape of these cellular extensions. Inhibiting actin polymerization in differentiating cells by cytochalasin D or latrunculin A treatment also induces the splitting of hairs and bristles, suggesting that the actin cytoskeleton might be a target of tricornered. However, the drugs also result in short, fat, and occasionally malformed hairs and bristles. The data suggest that the function of the actin cytoskeleton is important for maintaining the integrity of cellular extensions as well as their growth and shape. Thus, if tricornered causes the splitting of cellular extensions by interacting with the actin cytoskeleton it likely does so in a subtle way. Consistent with this possibility we found that a weak tricornered mutant is hypersensitive to cytochalasin D. We have cloned the tricornered gene and found that it encodes the Drosophila NDR kinase. This is a conserved ser/thr protein kinase found in Caenorhabditis elegans and humans that is related to a number of kinases that have been found to be important in controlling cell structure and proliferation.
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Affiliation(s)
- W Geng
- Biology Department and Cancer Center, University of Virginia, Charlottesville, Virginia 22903, USA
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