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  • Guild, Gregory M.  (11)
  • 1
    Online Resource
    Online Resource
    Microvilli appear to represent the first step in actin bundle formation in Drosophila bristles
    The Company of Biologists ; 2004
    In:  Journal of Cell Science Vol. 117, No. 16 ( 2004-07-15), p. 3531-3538
    Details
    In: Journal of Cell Science, The Company of Biologists, Vol. 117, No. 16 ( 2004-07-15), p. 3531-3538
    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.
    Type of Medium: Online Resource
    ISSN: 1477-9137 , 0021-9533
    URL: Article
    DOI: 10.1242/jcs.01215
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2004
    detail.hit.zdb_id: 219171-4
    detail.hit.zdb_id: 1483099-1
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  • 2
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    Regulation of Actin Filament Cross-linking and Bundle Shape in Drosophila Bristles
    Rockefeller University Press ; 2000
    In:  The Journal of Cell Biology Vol. 148, No. 1 ( 2000-01-10), p. 87-99
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 148, No. 1 ( 2000-01-10), p. 87-99
    Abstract: Previous studies demonstrate that in developing Drosophila bristles, two cross-linking proteins are required sequentially to bundle the actin filaments that support elongating bristle cells. The forked protein initiates the process and facilitates subsequent cross-linking by fascin. Using cross-linker–specific antibodies, mutants, and drugs we show that fascin and actin are present in excessive amounts throughout bundle elongation. In contrast, the forked cross-linker is limited throughout bundle formation, and accordingly, regulates bundle size and shape. We also show that regulation of cross-linking by phosphorylation can affect bundle size. Specifically, inhibition of phosphorylation by staurosporine results in a failure to form large bundles if added during bundle formation, and leads to a loss of cross-linking by fascin if added after the bundles form. Interestingly, inhibition of dephosphorylation by okadaic acid results in the separation of the actin bundles from the plasma membrane. We further show by thin section electron microscopy analysis of mutant and wild-type bristles that the amount of material that connects the actin bundles to the plasma membrane is also limited throughout bristle elongation. Therefore, overall bundle shape is determined by the number of actin filaments assembled onto the limited area provided by the connector material. We conclude that assembly of actin bundles in Drosophila bristles is controlled in part by the controlled availability of a single cross-linking protein, forked, and in part by controlled phosphorylation of cross-links and membrane actin connector proteins.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    URL: Article
    DOI: 10.1083/jcb.148.1.87
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 2000
    detail.hit.zdb_id: 1421310-2
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  • 3
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    Long continuous actin bundles in Drosophila bristles are constructed by overlapping short filaments
    Rockefeller University Press ; 2003
    In:  The Journal of Cell Biology Vol. 162, No. 6 ( 2003-09-15), p. 1069-1077
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 162, No. 6 ( 2003-09-15), p. 1069-1077
    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 μm in length); modules elongate to ∼3 μm 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.
    Type of Medium: Online Resource
    ISSN: 1540-8140 , 0021-9525
    URL: Article
    DOI: 10.1083/jcb.200305143
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 2003
    detail.hit.zdb_id: 1421310-2
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  • 4
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    The Role Actin Filaments Play in Providing the Characteristic Curved Form of Drosophila Bristles
    American Society for Cell Biology (ASCB) ; 2004
    In:  Molecular Biology of the Cell Vol. 15, No. 12 ( 2004-12), p. 5481-5491
    Details
    In: Molecular Biology of the Cell, American Society for Cell Biology (ASCB), Vol. 15, No. 12 ( 2004-12), p. 5481-5491
    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.
    Type of Medium: Online Resource
    ISSN: 1059-1524 , 1939-4586
    URL: Article
    DOI: 10.1091/mbc.e04-06-0472
    Language: English
    Publisher: American Society for Cell Biology (ASCB)
    Publication Date: 2004
    detail.hit.zdb_id: 1474922-1
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  • 5
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    Online Resource
    Actin Filament Bundles in Drosophila Wing Hairs: Hairs and Bristles Use Different Strategies for Assembly
    American Society for Cell Biology (ASCB) ; 2005
    In:  Molecular Biology of the Cell Vol. 16, No. 8 ( 2005-08), p. 3620-3631
    Details
    In: Molecular Biology of the Cell, American Society for Cell Biology (ASCB), Vol. 16, No. 8 ( 2005-08), p. 3620-3631
    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 (∼1 μm/h) over the course of ∼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 μm) 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.
    Type of Medium: Online Resource
    ISSN: 1059-1524 , 1939-4586
    URL: Article
    DOI: 10.1091/mbc.e05-03-0185
    Language: English
    Publisher: American Society for Cell Biology (ASCB)
    Publication Date: 2005
    detail.hit.zdb_id: 1474922-1
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  • 6
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    Actin Filament Turnover Regulated by Cross-linking Accounts for the Size, Shape, Location, and Number of Actin Bundles in Drosophila Bristles
    American Society for Cell Biology (ASCB) ; 2003
    In:  Molecular Biology of the Cell Vol. 14, No. 10 ( 2003-10), p. 3953-3966
    Details
    In: Molecular Biology of the Cell, American Society for Cell Biology (ASCB), Vol. 14, No. 10 ( 2003-10), p. 3953-3966
    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.
    Type of Medium: Online Resource
    ISSN: 1059-1524 , 1939-4586
    URL: Article
    DOI: 10.1091/mbc.e03-03-0158
    Language: English
    Publisher: American Society for Cell Biology (ASCB)
    Publication Date: 2003
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  • 7
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    Actin filament turnover removes bundles from Drosophila bristle cells
    The Company of Biologists ; 2002
    In:  Journal of Cell Science Vol. 115, No. 3 ( 2002-02-01), p. 641-653
    Details
    In: Journal of Cell Science, The Company of Biologists, Vol. 115, No. 3 ( 2002-02-01), p. 641-653
    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.
    Type of Medium: Online Resource
    ISSN: 1477-9137 , 0021-9533
    URL: Article
    DOI: 10.1242/jcs.115.3.641
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2002
    detail.hit.zdb_id: 219171-4
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  • 8
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    Actin filaments and microtubules play different roles during bristle elongation in Drosophila
    The Company of Biologists ; 2000
    In:  Journal of Cell Science Vol. 113, No. 7 ( 2000-04-01), p. 1255-1265
    Details
    In: Journal of Cell Science, The Company of Biologists, Vol. 113, No. 7 ( 2000-04-01), p. 1255-1265
    Abstract: Developing bristles in Drosophilapupae contain 7-11 bundles of crosslinked actin filaments and a large population of microtubules. During bristle growth the rate of cell elongation increases with bristle length. Thin section EM shows that bundle size is correlated with the amount of cytoplasm at all points along the bristle. Thus, as the bristle elongates and tapers, fewer actin filaments are used. To ensure penetration of inhibitors we isolated thoraces and cultured them in vitro; bristles elongate at rates identical to bristles growing in situ. Interestingly, inhibitors of actin filament assembly (cytochalasin D and latrunculin A) dramatically curtailed bristle elongation while a filament stabilizer (jasplakinolide) accelerated elongation. In contrast, inhibitors of microtubule dynamics (nocodazole, vinblastine, colchicine and taxol) did not affect bristle elongation. Surprisingly, the bristle microtubules are stable and do not turn over. Furthermore, the density of microtubules decreases as the bristle elongates. These two facts coupled with calculations and kinetics of elongation and the fact that the microtubules are short indicate that the microtubules are assembled early in development and then transported distally as the bristle grows. We conclude that actin assembly is crucial for bristle cell elongation and that microtubules must furnish other functions such as to provide bulk to the bristle cytoplasm as well as playing a role in vesicle transport.
    Type of Medium: Online Resource
    ISSN: 0021-9533 , 1477-9137
    URL: Article
    DOI: 10.1242/jcs.113.7.1255
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2000
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  • 9
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    Adaptation of a nematode parasite to living within the mammalian epithelium
    Wiley ; 2005
    In:  Journal of Experimental Zoology Part A: Comparative Experimental Biology Vol. 303A, No. 11 ( 2005-11-01), p. 927-945
    Details
    In: Journal of Experimental Zoology Part A: Comparative Experimental Biology, Wiley, Vol. 303A, No. 11 ( 2005-11-01), p. 927-945
    Type of Medium: Online Resource
    ISSN: 1548-8969 , 1552-499X
    URL: Issue
    URL: Journal
    URL: Article
    DOI: 10.1002/jez.a.v303a:11
    DOI: 10.1002/(ISSN)1552-499X
    DOI: 10.1002/jez.a.214
    Language: English
    Publisher: Wiley
    Publication Date: 2005
    detail.hit.zdb_id: 1474896-4
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  • 10
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    Actin Filament Cables in Drosophila Nurse Cells Are Composed of Modules That Slide Passively Past One Another during Dumping
    Rockefeller University Press ; 1997
    In:  The Journal of Cell Biology Vol. 138, No. 4 ( 1997-08-25), p. 783-797
    Details
    In: The Journal of Cell Biology, Rockefeller University Press, Vol. 138, No. 4 ( 1997-08-25), p. 783-797
    Abstract: At a late stage in Drosophila oogenesis, nurse cells rapidly expel their cytoplasm into the oocyte via intracellular bridges by a process called nurse cell dumping. Before dumping, numerous cables composed of actin filaments appear in the cytoplasm and extend inward from the plasma membrane toward the nucleus. This actin cage prevents the nucleus, which becomes highly lobed, from physically blocking the intracellular bridges during dumping. Each cable is composed of a linear series of modules composed of ∼25 cross-linked actin filaments. Adjacent modules overlap in the cable like the units of an extension ladder. During cable formation, individual modules are nucleated from the cell surface as microvilli, released, and then cross-linked to an adjacent forming module. The filaments in all the modules in a cable are unidirectionally polarized. During dumping as the volume of the cytoplasm decreases, the nucleus to plasma membrane distance decreases, compressing the actin cables that shorten as adjacent modules slide passively past one another just as the elements of an extension ladder slide past one another for storage. In Drosophila, the modular construction of actin cytoskeletons seems to be a generalized strategy. The behavior of modular actin cytoskeletons has implications for other actin-based cytoskeletal systems, e.g., those involved in Listeria movement, in cell spreading, and in retrograde flow in growth cones and fibroblasts.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    URL: Article
    DOI: 10.1083/jcb.138.4.783
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1997
    detail.hit.zdb_id: 1421310-2
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