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Friesen S, Hariharan IK. Coordinated growth of linked epithelia is mediated by the Hippo pathway. bioRxiv 2023:2023.02.26.530099. [PMID: 36993542 PMCID: PMC10054945 DOI: 10.1101/2023.02.26.530099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
An epithelium in a living organism seldom develops in isolation. Rather, most epithelia are tethered to other epithelial or non-epithelial tissues, necessitating growth coordination between layers. We investigated how two tethered epithelial layers of the Drosophila larval wing imaginal disc, the disc proper (DP) and the peripodial epithelium (PE), coordinate their growth. DP growth is driven by the morphogens Hedgehog (Hh) and Dpp, but regulation of PE growth is poorly understood. We find that the PE adapts to changes in growth rates of the DP, but not vice versa, suggesting a "leader and follower" mechanism. Moreover, PE growth can occur by cell shape changes, even when proliferation is inhibited. While Hh and Dpp pattern gene expression in both layers, growth of the DP is exquisitely sensitive to Dpp levels, while growth of the PE is not; the PE can achieve an appropriate size even when Dpp signaling is inhibited. Instead, both the growth of the PE and its accompanying cell shape changes require the activity of two components of the mechanosensitive Hippo pathway, the DNA-binding protein Scalloped (Sd) and its co-activator (Yki), which could allow the PE to sense and respond to forces generated by DP growth. Thus, an increased reliance on mechanically-dependent growth mediated by the Hippo pathway, at the expense of morphogen-dependent growth, enables the PE to evade layer-intrinsic growth control mechanisms and coordinate its growth with the DP. This provides a potential paradigm for growth coordination between different components of a developing organ.
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Affiliation(s)
- Sophia Friesen
- Department of Molecular and Cell Biology, University of California, Berkeley
| | - Iswar K. Hariharan
- Department of Molecular and Cell Biology, University of California, Berkeley
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Bonche R, Smolen P, Chessel A, Boisivon S, Pisano S, Voigt A, Schaub S, Thérond P, Pizette S. Regulation of the collagen IV network by the basement membrane protein perlecan is crucial for squamous epithelial cell morphogenesis and organ architecture. Matrix Biol 2022; 114:35-66. [PMID: 36343860 DOI: 10.1016/j.matbio.2022.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 10/24/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022]
Abstract
All epithelia have their basal side in contact with a specialized extracellular matrix, the basement membrane (BM). During development, the BM contributes to the shaping of epithelial organs via its mechanical properties. These properties rely on two core components of the BM, collagen type IV and perlecan/HSPG2, which both interact with another core component, laminin, the initiator of BM assembly. While collagen type IV supplies the BM with rigidity to constrain the tissue, perlecan antagonizes this effect. Nevertheless, the number of organs that has been studied is still scarce, and given that epithelial tissues exhibit a wide array of shapes, their forms are bound to be regulated by distinct mechanisms. This is underscored by mounting evidence that BM composition and assembly/biogenesis is tissue-specific. Moreover, previous reports have essentially focused on the mechanical role of the BM in morphogenesis at the tissue scale, but not the cell scale. Here, we took advantage of the robust conservation of core BM proteins and the limited genetic redundancy of the Drosophila model system to address how this matrix shapes the wing imaginal disc, a complex organ comprising a squamous, a cuboidal and a columnar epithelium. With the use of a hypomorphic allele, we show that the depletion of Trol (Drosophila perlecan) affects the morphogenesis of the three epithelia, but particularly that of the squamous one. The planar surface of the squamous epithelium (SE) becomes extremely narrow, due to a function for Trol in the control of the squamous shape of its cells. Furthermore, we find that the lack of Trol impairs the biogenesis of the BM of the SE by modifying the structure of the collagen type IV lattice. Through atomic force microscopy and laser surgery, we demonstrate that Trol provides elasticity to the SE's BM, thereby regulating the mechanical properties of the SE. Moreover, we show that Trol acts via collagen type IV, since the global reduction in the trol mutant context of collagen type IV or the enzyme that cross-links its 7S -but not the enzyme that cross-links its NC1- domain substantially restores the morphogenesis of the SE. In addition, a stronger decrease in collagen type IV achieved by the overexpression of the matrix metalloprotease 2 exclusively in the BM of the SE, significantly rescues the organization of the two other epithelia. Our data thus sustain a model in which Trol counters the rigidity conveyed by collagen type IV to the BM of the SE, via the regulation of the NC1-dependant assembly of its scaffold, allowing the spreading of the squamous cells, spreading which is compulsory for the architecture of the whole organ.
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Affiliation(s)
| | - Prune Smolen
- Université Côte d'Azur, CNRS, Inserm, iBV, France
| | | | | | | | - Aaron Voigt
- Department of Neurology, University Medical Center, RWTH Aachen University, Aachen 52074, Germany
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Ma B, Ma C, Li J, Fang Y. Revealing phosphorylation regulatory networks during embryogenesis of honey bee worker and drone (Apis mellifera). Front Cell Dev Biol 2022; 10:1006964. [PMID: 36225314 PMCID: PMC9548569 DOI: 10.3389/fcell.2022.1006964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/02/2022] [Indexed: 11/13/2022] Open
Abstract
Protein phosphorylation is known to regulate a comprehensive scenario of critical cellular processes. However, phosphorylation-mediated regulatory networks in honey bee embryogenesis are mainly unknown. We identified 6342 phosphosites from 2438 phosphoproteins and predicted 168 kinases in the honey bee embryo. Generally, the worker and drone develop similar phosphoproteome architectures and major phosphorylation events during embryogenesis. In 24 h embryos, protein kinases A play vital roles in regulating cell proliferation and blastoderm formation. At 48–72 h, kinase subfamily dual-specificity tyrosine-regulated kinase, cyclin-dependent kinase (CDK), and induced pathways related to protein synthesis and morphogenesis suggest the centrality to enhance the germ layer development, organogenesis, and dorsal closure. Notably, workers and drones formulated distinct phosphoproteome signatures. For 24 h embryos, the highly phosphorylated serine/threonine-protein kinase minibrain, microtubule-associated serine/threonine-protein kinase 2 (MAST2), and phosphorylation of mitogen-activated protein kinase 3 (MAPK3) at Thr564 in workers, are likely to regulate the late onset of cell proliferation; in contrast, drone embryos enhanced the expression of CDK12, MAPK3, and MAST2 to promote the massive synthesis of proteins and cytoskeleton. In 48 h, the induced serine/threonine-protein kinase and CDK12 in worker embryos signify their roles in the construction of embryonic tissues and organs; however, the highly activated kinases CDK1, raf homolog serine/threonine-protein kinase, and MAST2 in drone embryos may drive the large-scale establishment of tissues and organs. In 72 h, the activated pathways and kinases associated with cell growth and tissue differentiation in worker embryos may promote the configuration of rudimentary organs. However, kinases implicated in cytoskeleton organization in drone embryos may drive the blastokinesis and dorsal closure. Our hitherto most comprehensive phosphoproteome offers a valuable resource for signaling research on phosphorylation dynamics in honey bee embryos.
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Affiliation(s)
| | | | - Jianke Li
- *Correspondence: Jianke Li, ; Yu Fang,
| | - Yu Fang
- *Correspondence: Jianke Li, ; Yu Fang,
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Lu J, Wang Y, Wang X, Wang D, Pflugfelder GO, Shen J. The Tbx6 Transcription Factor Dorsocross Mediates Dpp Signaling to Regulate Drosophila Thorax Closure. Int J Mol Sci 2022; 23:4543. [PMID: 35562934 DOI: 10.3390/ijms23094543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 04/08/2022] [Accepted: 04/17/2022] [Indexed: 11/23/2022] Open
Abstract
Movement and fusion of separate cell populations are critical for several developmental processes, such as neural tube closure in vertebrates or embryonic dorsal closure and pupal thorax closure in Drosophila. Fusion failure results in an opening or groove on the body surface. Drosophila pupal thorax closure is an established model to investigate the mechanism of tissue closure. Here, we report the identification of T-box transcription factor genes Dorsocross (Doc) as Decapentaplegic (Dpp) targets in the leading edge cells of the notum in the late third instar larval and early pupal stages. Reduction of Doc in the notum region results in a thorax closure defect, similar to that in dpp loss-of-function flies. Nine genes are identified as potential downstream targets of Doc in regulating thorax closure by molecular and genetic screens. Our results reveal a novel function of Doc in Drosophila development. The candidate target genes provide new clues for unravelling the mechanism of collective cell movement.
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Abstract
The Drosophila wing imaginal disc is a tissue of undifferentiated cells that are precursors of the wing and most of the notum of the adult fly. The wing disc first forms during embryogenesis from a cluster of ∼30 cells located in the second thoracic segment, which invaginate to form a sac-like structure. They undergo extensive proliferation during larval stages to form a mature larval wing disc of ∼35,000 cells. During this time, distinct cell fates are assigned to different regions, and the wing disc develops a complex morphology. Finally, during pupal stages the wing disc undergoes morphogenetic processes and then differentiates to form the adult wing and notum. While the bulk of the wing disc comprises epithelial cells, it also includes neurons and glia, and is associated with tracheal cells and muscle precursor cells. The relative simplicity and accessibility of the wing disc, combined with the wealth of genetic tools available in Drosophila, have combined to make it a premier system for identifying genes and deciphering systems that play crucial roles in animal development. Studies in wing imaginal discs have made key contributions to many areas of biology, including tissue patterning, signal transduction, growth control, regeneration, planar cell polarity, morphogenesis, and tissue mechanics.
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Affiliation(s)
- Bipin Kumar Tripathi
- Department of Molecular Biology and Biochemistry, Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA
| | - Kenneth D Irvine
- Department of Molecular Biology and Biochemistry, Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA
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Weasner BM, Kumar JP. The timing of cell fate decisions is crucial for initiating pattern formation in the Drosophila eye. Development 2022; 149:274084. [PMID: 35072208 PMCID: PMC8917411 DOI: 10.1242/dev.199634] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 12/09/2021] [Indexed: 01/26/2023]
Abstract
The eye-antennal disc of Drosophila is composed of three cell layers: a columnar epithelium called the disc proper (DP); an overlying sheet of squamous cells called the peripodial epithelium (PE); and a strip of cuboidal cells that joins the other two cellular sheets to each other and comprises the outer margin (M) of the disc. The M cells play an important role in patterning the eye because it is here that the Hedgehog (Hh), Decapentaplegic (Dpp) and JAK/STAT pathways function to initiate pattern formation. Dpp signaling is lost from the margin of eyes absent (eya) mutant discs and, as a result, the initiation of retinal patterning is blocked. Based on these observations, Eya has been proposed to control the initiation of the morphogenetic furrow via regulation of Dpp signaling within the M. We show that the failure in pattern formation surprisingly results from M cells prematurely adopting a head epidermis fate. This switch in fate normally takes place during pupal development after the eye has been patterned. Our results suggest that the timing of cell fate decisions is essential for correct eye development.
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Abstract
In the early stages of Drosophila melanogaster (Drosophila) metamorphosis, a partial epithelial-mesenchymal transition (pEMT) takes place in the peripodial epithelium of wing imaginal discs. Blocking this pEMT results in adults with internalized wings and missing thoracic tissue. Using peripodial GAL4 drivers, GAL80ts temporal control, and UAS RNAi transgenes, one can use these phenotypes to screen for genes involved in the pEMT. Dominant modifier tests can then be employed to identify genetic enhancers and suppressors. To analyze a gene's role in the pEMT, one can then visualize peripodial cells in vivo at the time of eversion within the pupal case using live markers, and by dissecting, fixing, and immunostaining the prepupae. Alternatively, one can analyze the pEMT ex vivo by dissecting out wing discs and culturing them in the presence of ecdysone to induce eversion. This can provide a clearer view of the cellular processes involved and permit drug treatments to be easily applied.
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Affiliation(s)
- Sofia Golenkina
- School of BioSciences, University of Melbourne, Parkville, VIC, Australia
| | | | - Michael J Murray
- School of BioSciences, University of Melbourne, Parkville, VIC, Australia.
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Jefferies G, Somers J, Lohrey I, Chaturvedi V, Calabria J, Marshall OJ, Southall TD, Saint R, Murray MJ. Maintenance of Cell Fate by the Polycomb Group Gene Sex Combs Extra Enables a Partial Epithelial Mesenchymal Transition in Drosophila. G3 (Bethesda) 2020; 10:4459-71. [PMID: 33051260 DOI: 10.1534/g3.120.401785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Epigenetic silencing by Polycomb group (PcG) complexes can promote epithelial-mesenchymal transition (EMT) and stemness and is associated with malignancy of solid cancers. Here we report a role for Drosophila PcG repression in a partial EMT event that occurs during wing disc eversion, an early event during metamorphosis. In a screen for genes required for eversion we identified the PcG genes Sex combs extra (Sce) and Sex combs midleg (Scm). Depletion of Sce or Scm resulted in internalized wings and thoracic clefts, and loss of Sce inhibited the EMT of the peripodial epithelium and basement membrane breakdown, ex vivo. Targeted DamID (TaDa) using Dam-Pol II showed that Sce knockdown caused a genomic transcriptional response consistent with a shift toward a more stable epithelial fate. Surprisingly only 17 genes were significantly upregulated in Sce-depleted cells, including Abd-B, abd-A, caudal, and nubbin. Each of these loci were enriched for Dam-Pc binding. Of the four genes, only Abd-B was robustly upregulated in cells lacking Sce expression. RNAi knockdown of all four genes could partly suppress the Sce RNAi eversion phenotype, though Abd-B had the strongest effect. Our results suggest that in the absence of continued PcG repression peripodial cells express genes such as Abd-B, which promote epithelial state and thereby disrupt eversion. Our results emphasize the important role that PcG suppression can play in maintaining cell states required for morphogenetic events throughout development and suggest that PcG repression of Hox genes may affect epithelial traits that could contribute to metastasis.
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Golenkina S, Chaturvedi V, Saint R, Murray MJ. Frazzled can act through distinct molecular pathways in epithelial cells to regulate motility, apical constriction, and localisation of E-Cadherin. PLoS One 2018; 13:e0194003. [PMID: 29518139 PMCID: PMC5843272 DOI: 10.1371/journal.pone.0194003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/22/2018] [Indexed: 01/11/2023] Open
Abstract
Netrin receptors of the DCC/NEO/UNC-40/Frazzled family have well established roles in cell migration and axon guidance but can also regulate epithelial features such as adhesion, polarity and adherens junction (AJ) stability. Previously, we have shown that overexpression of Drosophila Frazzled (Fra) in the peripodial epithelium (PE) inhibits wing disc eversion and also generates cellular protrusions typical of motile cells. Here, we tested whether the molecular pathways by which Fra inhibits eversion are distinct from those driving motility. We show that in disc proper (DP) epithelial cells Fra, in addition to inducing F-Actin rich protrusions, can affect localization of AJ components and columnar cell shape. We then show that these phenotypes have different requirements for the three conserved Fra cytoplasmic P-motifs and for downstream genes. The formation of protrusions required the P3 motif of Fra, as well as integrins (mys and mew), the Rac pathway (Rac1, wave and, arpc3) and myosin regulatory light chain (Sqh). In contrast, apico-basal cell shape change, which was accompanied by increased myosin phosphorylation, was critically dependent upon the P1 motif and was promoted by RhoGef2 but inhibited by Rac1. Fra also caused a loss of AJ proteins (DE-Cad and Arm) from basolateral regions of epithelial cells. This phenotype required all 3 P-motifs, and was dependent upon the polarity factor par6. par6 was not required for protrusions or cell shape change, but was required to block eversion suggesting that control of AJ components may underlie the ability of Fra to promote epithelial stability. The results imply that multiple molecular pathways act downstream of Fra in epithelial cells.
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Affiliation(s)
- Sofia Golenkina
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Vishal Chaturvedi
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Robert Saint
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Michael J. Murray
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
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Richard M, Bauer R, Tavosanis G, Hoch M. The gap junction protein Innexin3 is required for eye disc growth in Drosophila. Dev Biol 2017; 425:191-207. [PMID: 28390801 DOI: 10.1016/j.ydbio.2017.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 03/30/2017] [Accepted: 04/03/2017] [Indexed: 12/23/2022]
Abstract
The Drosophila compound eye develops from a bilayered epithelial sac composed of an upper peripodial epithelium layer and a lower disc proper, the latter giving rise to the eye itself. During larval stages, complex signalling events between the layers contribute to the control of cell proliferation and differentiation in the disc. Previous work in our lab established the gap junction protein Innexin2 (Inx2) as crucial for early larval eye disc growth. By analysing the contribution of other Innexins to eye size control, we have identified Innexin3 (Inx3) as an important growth regulator. Depleting inx3 during larval eye development reduces eye size, while elevating inx3 levels increases eye size, thus phenocopying the inx2 loss- and gain-of-function situation. As demonstrated previously for inx2, inx3 regulates disc cell proliferation and interacts genetically with the Dpp pathway, being required for the proper activation of the Dpp pathway transducer Mad at the furrow and the expression of Dpp receptor Punt in the eye disc. At the developmental timepoint corresponding to eye disc growth, Inx3 colocalises with Inx2 in disc proper and peripodial epithelium cell membranes. In addition, we show that Inx3 protein levels critically depend on inx2 throughout eye development and that inx3 modulates Inx2 protein levels in the larval eye disc. Rescue experiments demonstrate that Inx3 and Inx2 cooperate functionally to enable eye disc growth in Drosophila. Finally, we demonstrate that expression of Inx3 and Inx2 is not only needed in the disc proper but also in the peripodial epithelium to regulate growth of the eye disc. Our data provide a functional demonstration that putative Inx2/Inx3 heteromeric channels regulate organ size.
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Affiliation(s)
- Mélisande Richard
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit University of Bonn, Carl-Troll-Straße, 31 53115 Bonn, Germany
| | - Reinhard Bauer
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit University of Bonn, Carl-Troll-Straße, 31 53115 Bonn, Germany
| | - Gaia Tavosanis
- German Center for Neurodegenerative Diseases (DZNE), Dendrite Differentiation Unit, Sigmund-Freud-Str. 27, 53127 Bonn, Germany
| | - Michael Hoch
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit University of Bonn, Carl-Troll-Straße, 31 53115 Bonn, Germany.
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Tang W, Wang D, Shen J. Asymmetric distribution of Spalt in Drosophila wing squamous and columnar epithelia ensures correct cell morphogenesis. Sci Rep 2016; 6:30236. [PMID: 27452716 DOI: 10.1038/srep30236] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 07/01/2016] [Indexed: 01/01/2023] Open
Abstract
The Drosophila wing imaginal disc is a sac-like structure that is composed of two opposing cell layers: peripodial epithelium (PE, also known as squamous epithelia) and disc proper (DP, also known as pseudostratified columnar epithelia). The molecular mechanism of cell morphogenesis has been well studied in the DP but not in the PE. Although proper Dpp signalling activity is required for proper PE formation, the detailed regulation mechanism is poorly understood. Here, we found that the Dpp target gene sal is only expressed in DP cells, not in PE cells, although pMad is present in the PE. Increasing Dpp signalling activity cannot activate Sal in PE cells. The absence of Sal in the PE is essential for PE formation. The ectopic expression of sal in PE cells is sufficient to increase the PE cell height. Down-regulation of sal in the DP reduced DP cell height. We further demonstrated that the known PE cell height regulator Lines, which can convert PE into a DP cell fate, is mediated by sal mis-activation in PE because sal-RNAi and lines co-expression largely restores PE cell morphology. By revealing the microtubule distribution, we demonstrated that Lines- and Sal-heightened PE cells are morphologically similar to the intermediate cell with cuboidal morphology.
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Romani P, Papi A, Ignesti M, Soccolini G, Hsu T, Gargiulo G, Spisni E, Cavaliere V. Dynamin controls extracellular level of Awd/Nme1 metastasis suppressor protein. Naunyn Schmiedebergs Arch Pharmacol 2016; 389:1171-1182. [DOI: 10.1007/s00210-016-1268-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 06/17/2016] [Indexed: 10/21/2022]
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Prasad N, Tarikere S, Khanale D, Habib F, Shashidhara LS. A comparative genomic analysis of targets of Hox protein Ultrabithorax amongst distant insect species. Sci Rep 2016; 6:27885. [PMID: 27296678 PMCID: PMC4906271 DOI: 10.1038/srep27885] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 05/25/2016] [Indexed: 01/07/2023] Open
Abstract
In the fruitfly Drosophila melanogaster, the differential development of wing and haltere is dependent on the function of the Hox protein Ultrabithorax (Ubx). Here we compare Ubx-mediated regulation of wing patterning genes between the honeybee, Apis mellifera, the silkmoth, Bombyx mori and Drosophila. Orthologues of Ubx are expressed in the third thoracic segment of Apis and Bombyx, although they make functional hindwings. When over-expressed in transgenic Drosophila, Ubx derived from Apis or Bombyx could suppress wing development, suggesting evolutionary changes at the level of co-factors and/or targets of Ubx. To gain further insights into such events, we identified direct targets of Ubx from Apis and Bombyx by ChIP-seq and compared them with those of Drosophila. While majority of the putative targets of Ubx are species-specific, a considerable number of wing-patterning genes are retained, over the past 300 millions years, as targets in all the three species. Interestingly, many of these are differentially expressed only between wing and haltere in Drosophila but not between forewing and hindwing in Apis or Bombyx. Detailed bioinformatics and experimental validation of enhancer sequences suggest that, perhaps along with other factors, changes in the cis-regulatory sequences of earlier targets contribute to diversity in Ubx function.
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Affiliation(s)
- Naveen Prasad
- Indian Institute of Science Education and Research Pune, 411008, India
| | | | | | - Farhat Habib
- Indian Institute of Science Education and Research Pune, 411008, India
| | - L S Shashidhara
- Indian Institute of Science Education and Research Pune, 411008, India
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Singh S, Sánchez-herrero E, Shashidhara L. Critical role for Fat/Hippo and IIS/Akt pathways downstream of Ultrabithorax during haltere specification in Drosophila. Mech Dev 2015; 138:198-209. [DOI: 10.1016/j.mod.2015.07.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 07/18/2015] [Accepted: 07/20/2015] [Indexed: 11/18/2022]
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Vicidomini R, Di Giovanni A, Petrizzo A, Iannucci LF, Benvenuto G, Nagel AC, Preiss A, Furia M. Loss of Drosophila pseudouridine synthase triggers apoptosis-induced proliferation and promotes cell-nonautonomous EMT. Cell Death Dis 2015; 6:e1705. [PMID: 25811802 DOI: 10.1038/cddis.2015.68] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 02/11/2015] [Accepted: 02/12/2015] [Indexed: 01/12/2023]
Abstract
Many developing tissues display regenerative capability that allows them to compensate cell loss and preserve tissue homeostasis. Because of their remarkable regenerative capability, Drosophila wing discs are extensively used for the study of regenerative phenomena. We thus used the developing wing to investigate the role played in tissue homeostasis by the evolutionarily conserved eukaryotic H/ACA small nucleolar ribonucleoprotein pseudouridine synthase. Here we show that localized depletion of this enzyme can act as an endogenous stimulus capable of triggering apoptosis-induced proliferation, and that context-dependent effects are elicited in different sub-populations of the silenced cells. In fact, some cells undergo apoptosis, whereas those surrounding the apoptotic foci, although identically depleted, overproliferate. This overproliferation correlates with ectopic induction of the Wg and JAK-STAT (Janus kinase-signal transducer and activator of transcription) mitogenic pathways. Expression of a p35 transgene, which blocks the complete execution of the death program and generates the so-called ‘undead cells', amplifies the proliferative response. Pseudouridine synthase depletion also causes loss of apicobasal polarity, disruption of adherens cell junctions and ectopic induction of JNK (c-Jun N-terminal kinase) and Mmp1 (matrix metalloproteinase-1) activity, leading to a significant epithelial reorganization. Unexpectedly, cell-nonautonomous effects, such as epithelial mesenchymal transition in the contiguous unsilenced squamous epithelium, are also promoted. Collectively, these data point out that cell–cell communication and long-range signaling can take a relevant role in the response to pseudouridine synthase decline. Considering that all the affected pathways are highly conserved throughout evolution, it is plausible that the response to pseudouridine synthase depletion has been widely preserved. On this account, our results can add new light on the still unexplained tumor predisposition that characterizes X-linked dyskeratosis, the human disease caused by reduced pseudouridine synthase activity.
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D'Angelo G, Matusek T, Pizette S, Thérond PP. Endocytosis of Hedgehog through dispatched regulates long-range signaling. Dev Cell 2015; 32:290-303. [PMID: 25619925 DOI: 10.1016/j.devcel.2014.12.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 09/22/2014] [Accepted: 12/01/2014] [Indexed: 01/20/2023]
Abstract
The proteins of the Hedgehog (Hh) family are secreted proteins exerting short- and long-range control over various cell fates in developmental patterning. The Hh gradient in Drosophila wing imaginal discs consists of apical and basolateral secreted pools, but the mechanisms governing the overall establishment of the gradient remain unclear. We investigated the relative contributions of endocytosis and recycling to control the Hh gradient. We show that, upon its initial apical secretion, Hh is re-internalized. We examined the effect of the resistance-nodulation-division transporter Dispatched (Disp) on long-range Hh signaling and unexpectedly found that Disp is specifically required for apical endocytosis of Hh. Re-internalized Hh is then regulated in a Rab5- and Rab4-dependent manner to ensure its long-range activity. We propose that Hh-producing cells integrate endocytosis and recycling as two instrumental mechanisms contributing to regulate the long-range activity of Hh.
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Affiliation(s)
- Gisela D'Angelo
- Institut de Biologie de Valrose - iBV, Centre de Biochimie, Université Nice Sophia Antipolis, CNRS UMR7277, INSERM 1091, Parc Valrose, 06108 Nice Cedex 2, France.
| | - Tamás Matusek
- Institut de Biologie de Valrose - iBV, Centre de Biochimie, Université Nice Sophia Antipolis, CNRS UMR7277, INSERM 1091, Parc Valrose, 06108 Nice Cedex 2, France
| | - Sandrine Pizette
- Institut de Biologie de Valrose - iBV, Centre de Biochimie, Université Nice Sophia Antipolis, CNRS UMR7277, INSERM 1091, Parc Valrose, 06108 Nice Cedex 2, France
| | - Pascal P Thérond
- Institut de Biologie de Valrose - iBV, Centre de Biochimie, Université Nice Sophia Antipolis, CNRS UMR7277, INSERM 1091, Parc Valrose, 06108 Nice Cedex 2, France.
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Buchmann A, Alber M, Zartman JJ. Sizing it up: The mechanical feedback hypothesis of organ growth regulation. Semin Cell Dev Biol 2014; 35:73-81. [DOI: 10.1016/j.semcdb.2014.06.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 06/26/2014] [Indexed: 11/28/2022]
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Marty F, Rockel-Bauer C, Simigdala N, Brunner E, Basler K. Large-scale imaginal disc sorting: A protocol for "omics"-approaches. Methods 2014; 68:260-4. [PMID: 24736056 DOI: 10.1016/j.ymeth.2014.04.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 04/03/2014] [Accepted: 04/07/2014] [Indexed: 12/29/2022] Open
Abstract
Imaginal discs, especially the wing imaginal disc, are powerful model systems to study organ development. The traditional methods to analyze wing imaginal discs depend on the laborious and time-consuming dissection of larvae. "Omics"-based approaches, such as RNA-seq, ChIP-seq, proteomics and lipidomics, offer new opportunities for the systems-level investigation of organ development. However, it is impractical to manually isolate the required starting material. This is even more problematic when experiments strive for enhanced temporal and spatial resolution. The mass isolation workflow discussed in this review, solves this problem. The semi-automated sorting of 1000 wing imaginal discs in less than 3h forms the basis of a workflow that can be connected to biochemical analyses of organ patterning and growth. In addition to the mass isolation workflow we briefly describe key "omics" technologies and their applications. The combination of mass isolation and "omics"-approaches ensures that the wing imaginal disc will continue to be a key model organ for studying developmental processes, both on the genetic, but increasingly also on the biochemical level.
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Affiliation(s)
- Florian Marty
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
| | - Claudia Rockel-Bauer
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
| | - Nikiana Simigdala
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
| | - Erich Brunner
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
| | - Konrad Basler
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland.
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Molnar C, de Celis JF. Tay bridge is a negative regulator of EGFR signalling and interacts with Erk and Mkp3 in the Drosophila melanogaster wing. PLoS Genet 2013; 9:e1003982. [PMID: 24348264 PMCID: PMC3861119 DOI: 10.1371/journal.pgen.1003982] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Accepted: 10/14/2013] [Indexed: 11/18/2022] Open
Abstract
The regulation of Extracellular regulated kinase (Erk) activity is a key aspect of signalling by pathways activated by extracellular ligands acting through tyrosine kinase transmembrane receptors. In this process, participate proteins with kinase activity that phosphorylate and activate Erk, as well as different phosphatases that inactivate Erk by de-phosphorylation. The state of Erk phosphorylation affects not only its activity, but also its subcellular localization, defining the repertoire of Erk target proteins, and consequently, the cellular response to Erk. In this work, we characterise Tay bridge as a novel component of the EGFR/Erk signalling pathway. Tay bridge is a large nuclear protein with a domain of homology with human AUTS2, and was previously identified due to the neuronal phenotypes displayed by loss-of-function mutations. We show that Tay bridge antagonizes EGFR signalling in the Drosophila melanogaster wing disc and other tissues, and that the protein interacts with both Erk and Mkp3. We suggest that Tay bridge constitutes a novel element involved in the regulation of Erk activity, acting as a nuclear docking for Erk that retains this protein in an inactive form in the nucleus. Extracellular regulated kinases (Erk) mediate signalling by pathways activated by tyrosine kinase transmembrane receptors. The level of activated Erk depends on a highly regulated balance between cytoplasmic kinases and nuclear/cytoplasmic phosphatases, which determine the state of Erk phosphorylation. This affects Erk activity and its subcellular localization, defining the repertoire of Erk targets, and consequently, the cellular response to Erk. In this work, we use a genetic approach to characterise the gene tay bridge as a novel component of the EGFR/Erk signalling pathway. Tay bridge has a domain of homology with human AUTS2, and was previously identified due to the neuronal phenotypes displayed by loss-of-function mutations. We show that Tay bridge antagonizes EGFR signalling in the Drosophila melanogaster wing disc and other tissues, and that the protein interacts with both Erk and Mkp3. We suggest that Tay bridge constitutes a novel element involved in the regulation of Erk activity, acting as a nuclear docking for Erk that retains this protein in an inactive form in the nucleus. These results could provide important insights into the clinical consequences of AUTS2 mutations in humans, which are related to behavioural perturbations including autism, mental retardation, Attention Deficit Hyperactivity Disorder and alcohol drinking behaviour.
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Affiliation(s)
- Cristina Molnar
- Centro de Biología Molecular “Severo Ochoa,” CSIC and Universidad Autónoma de Madrid, Madrid, Spain
| | - Jose F. de Celis
- Centro de Biología Molecular “Severo Ochoa,” CSIC and Universidad Autónoma de Madrid, Madrid, Spain
- * E-mail:
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Manhire-heath R, Golenkina S, Saint R, Murray MJ. Netrin-dependent downregulation of Frazzled/DCC is required for the dissociation of the peripodial epithelium in Drosophila. Nat Commun 2013; 4. [DOI: 10.1038/ncomms3790] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 10/17/2013] [Indexed: 01/02/2023] Open
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22
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Hatini V, Kula-Eversole E, Nusinow D, Del Signore SJ. Essential roles for stat92E in expanding and patterning the proximodistal axis of the Drosophila wing imaginal disc. Dev Biol 2013; 378:38-50. [PMID: 23499656 DOI: 10.1016/j.ydbio.2013.02.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/17/2013] [Accepted: 02/20/2013] [Indexed: 12/26/2022]
Abstract
The Drosophila wing imaginal disc is subdivided along the proximodistal axis into the distal pouch, the hinge, the surrounding pleura, and the notum. While the genetic pathways that specify the identity of each of these domains have been well studied, the mechanisms that coordinate the relative expansion of these domains are not well understood. Here we investigated the role of the stat92E signal transducer and activator of transcription in wing proximodistal development. We find that stat92E is active ubiquitously in early wing imaginal discs, where it acts to inhibit the induction of ectopic wing fields. Subsequently, stat92E activity is down regulated in the notum and distal pouch. These dynamics coincide with and contribute to the proportional subdivision and expansion of these primordia. As development proceeds, stat92E activity becomes restricted to the hinge, where it promotes normal expansion of the hinge, and restricts expansion of the notum. We also find that stat92E is required autonomously to specify dorsal pleura identity and inhibit notum identity to properly subdivide the body wall. Our data suggest that stat92E activity is regulated along the proximodistal axis to pattern this axis and control the relative expansion of the pouch, hinge, and notum.
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Affiliation(s)
- Victor Hatini
- Tufts University School of Medicine, Department of Anatomy & Cellular Biology, Program in Cell, Molecular and Developmental Biology, 150 Harrison Avenue, Boston, MA 02111, USA.
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Abstract
Cell shape dynamics, motility, and cell proliferation all depend on the actin cytoskeleton. Malignant cancer cells hijack the actin network to grow and migrate to secondary sites. Understanding the function of actin regulators is therefore of major interest. In the present study, we identify the actin cross-linking protein Filamin/Cheerio (Cher) as a mediator of malignancy in genetically defined Drosophila tumors. We show that in invasive tumors, resulting from cooperation of activated Ras with disrupted epithelial cell polarity, Cher is upregulated in a Jun N-terminal kinase (JNK)-dependent manner. Although dispensable in normal epithelium, Cher becomes required in the tumor cells for their growth and invasiveness. When deprived of Cher, these tumor clones lose their full potential to proliferate and breach tissue boundaries. Instead, the Cher-deficient clones remain confined within the limits of their source epithelium, permitting survival of the host animal. Through interaction with the myosin II heavy chain subunit, Cher is likely to strengthen the cortical actomyosin network and reinforce mechanical tension within the invasive tumors. Accordingly, Cher is required for aberrant expression of genes downstream of the Hippo/Yorkie signaling in the tumor tissue. Our study identifies Cher as a new target of JNK signaling that links cytoskeleton dynamics to tumor progression.
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Affiliation(s)
- Eva Külshammer
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany
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Butchar JP, Cain D, Manivannan SN, McCue AD, Bonanno L, Halula S, Truesdell S, Austin CL, Jacobsen TL, Simcox A. New negative feedback regulators of Egfr signaling in Drosophila. Genetics 2012; 191:1213-26. [PMID: 22595244 PMCID: PMC3416002 DOI: 10.1534/genetics.112.141093] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 05/07/2012] [Indexed: 12/18/2022] Open
Abstract
The highly conserved epidermal growth factor receptor (Egfr) pathway is required in all animals for normal development and homeostasis; consequently, aberrant Egfr signaling is implicated in a number of diseases. Genetic analysis of Drosophila melanogaster Egfr has contributed significantly to understanding this conserved pathway and led to the discovery of new components and targets. Here we used microarray analysis of third instar wing discs, in which Egfr signaling was perturbed, to identify new Egfr-responsive genes. Upregulated transcripts included five known targets, suggesting the approach was valid. We investigated the function of 29 previously uncharacterized genes, which had pronounced responses. The Egfr pathway is important for wing-vein patterning and using reverse genetic analysis we identified five genes that showed venation defects. Three of these genes are expressed in vein primordia and all showed transcriptional changes in response to altered Egfr activity consistent with being targets of the pathway. Genetic interactions with Egfr further linked two of the genes, Sulfated (Sulf1), an endosulfatase gene, and CG4096, an A Disintegrin And Metalloproteinase with ThromboSpondin motifs (ADAMTS) gene, to the pathway. Sulf1 showed a strong genetic interaction with the neuregulin-like ligand vein (vn) and may influence binding of Vn to heparan-sulfated proteoglycans (HSPGs). How Drosophila Egfr activity is modulated by CG4096 is unknown, but interestingly vertebrate EGF ligands are regulated by a related ADAMTS protein. We suggest Sulf1 and CG4096 are negative feedback regulators of Egfr signaling that function in the extracellular space to influence ligand activity.
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Affiliation(s)
- Jonathan P. Butchar
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Donna Cain
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | | | - Andrea D. McCue
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Liana Bonanno
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Sarah Halula
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Sharon Truesdell
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Christina L. Austin
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Thomas L. Jacobsen
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
| | - Amanda Simcox
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio 43210
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Stultz BG, Park SY, Mortin MA, Kennison JA, Hursh DA. Hox proteins coordinate peripodial decapentaplegic expression to direct adult head morphogenesis in Drosophila. Dev Biol 2012; 369:362-76. [PMID: 22824425 DOI: 10.1016/j.ydbio.2012.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 06/29/2012] [Accepted: 07/12/2012] [Indexed: 02/04/2023]
Abstract
The Drosophila BMP, decapentaplegic (dpp), controls morphogenesis of the ventral adult head through expression limited to the lateral peripodial epithelium of the eye-antennal disc by a 3.5 kb enhancer in the 5' end of the gene. We recovered a 15 bp deletion mutation within this enhancer that identified a homeotic (Hox) response element that is a direct target of labial and the homeotic cofactors homothorax and extradenticle. Expression of labial and homothorax are required for dpp expression in the peripodial epithelium, while the Hox gene Deformed represses labial in this location, thus limiting its expression and indirectly that of dpp to the lateral side of the disc. The expression of these homeodomain genes is in turn regulated by the dpp pathway, as dpp signalling is required for labial expression but represses homothorax. This Hox-BMP regulatory network is limited to the peripodial epithelium of the eye-antennal disc, yet is crucial to the morphogenesis of the head, which fate maps suggest arises primarily from the disc proper, not the peripodial epithelium. Thus Hox/BMP interactions in the peripodial epithelium of the eye-antennal disc contribute inductively to the shape of the external form of the adult Drosophila head.
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Affiliation(s)
- Brian G Stultz
- Division of Cell and Gene Therapy, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA
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Wang N, Leung HT, Mazalouskas MD, Watkins GR, Gomez RJ, Wadzinski BE. Essential roles of the Tap42-regulated protein phosphatase 2A (PP2A) family in wing imaginal disc development of Drosophila melanogaster. PLoS One 2012; 7:e38569. [PMID: 22701670 PMCID: PMC3368869 DOI: 10.1371/journal.pone.0038569] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 05/07/2012] [Indexed: 11/18/2022] Open
Abstract
Protein ser/thr phosphatase 2A family members (PP2A, PP4, and PP6) are implicated in the control of numerous biological processes, but our understanding of the in vivo function and regulation of these enzymes is limited. In this study, we investigated the role of Tap42, a common regulatory subunit for all three PP2A family members, in the development of Drosophila melanogaster wing imaginal discs. RNAi-mediated silencing of Tap42 using the binary Gal4/UAS system and two disc drivers, pnr- and ap-Gal4, not only decreased survival rates but also hampered the development of wing discs, resulting in a remarkable thorax cleft and defective wings in adults. Silencing of Tap42 also altered multiple signaling pathways (HH, JNK and DPP) and triggered apoptosis in wing imaginal discs. The Tap42RNAi-induced defects were the direct result of loss of regulation of Drosophila PP2A family members (MTS, PP4, and PPV), as enforced expression of wild type Tap42, but not a phosphatase binding defective Tap42 mutant, rescued fly survivorship and defects. The experimental platform described herein identifies crucial roles for Tap42•phosphatase complexes in governing imaginal disc and fly development.
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Affiliation(s)
- Ning Wang
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Hung-Tat Leung
- Department of Biological Sciences, Grambling State University, Grambling, Louisiana, United States of America
| | - Matthew D. Mazalouskas
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Guy R. Watkins
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Rey J. Gomez
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Brian E. Wadzinski
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- * E-mail:
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Sopory S, Kwon S, Wehrli M, Christian JL. Regulation of Dpp activity by tissue-specific cleavage of an upstream site within the prodomain. Dev Biol 2010; 346:102-12. [PMID: 20659445 DOI: 10.1016/j.ydbio.2010.07.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 07/11/2010] [Accepted: 07/17/2010] [Indexed: 12/20/2022]
Abstract
BMP4 is synthesized as an inactive precursor that is cleaved at two sites during maturation: initially at a site (S1) adjacent to the ligand domain, and then at an upstream site (S2) within the prodomain. Cleavage at the second site regulates the stability of mature BMP4 and this in turn influences its signaling intensity and range of action. The Drosophila ortholog of BMP4, Dpp, functions as a long- or short-range signaling molecule in the wing disc or embryonic midgut, respectively but mechanisms that differentially regulate its bioactivity in these tissues have not been explored. In the current studies we demonstrate, by dpp mutant rescue, that cleavage at the S2 site of proDpp is required for development of the wing and leg imaginal discs, whereas cleavage at the S1 site is sufficient to rescue Dpp function in the midgut. Both the S1 and S2 sites of proDpp are cleaved in the wing disc, and S2-cleavage is essential to generate sufficient ligand to exceed the threshold for pMAD activation at both short- and long-range in most cells. By contrast, proDpp is cleaved at the S1 site alone in the embryonic mesoderm and this generates sufficient ligand to activate physiological target genes in neighboring cells. These studies provide the first biochemical and genetic evidence that selective cleavage of the S2 site of proDPP provides a tissue-specific mechanism for regulating Dpp activity, and that differential cleavage can contribute to, but is not an absolute determinant of signaling range.
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Affiliation(s)
- Shailaja Sopory
- Department of Cell and Developmental Biology, Oregon Health and Science University, School of Medicine, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA
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Abstract
The eye-antennal imaginal disc of Drosophila melanogaster has often been described as an epithelial monolayer with complex signaling events playing out in two dimensions. However, the imaginal disc actually comprises two opposing epithelia (the peripodial epithelium, or PE, and the disc proper, or DP) separated by a lumen to form a sac-like structure. Recent studies expose complex molecular interactions between the PE and the DP, and reveal dynamic communication between the two tissues. Further findings suggest the PE makes important contributions to DP development by acting as a source of signaling molecules as well as cells. Here we summarize those findings and highlight implications for further research.
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Affiliation(s)
- Mardelle Atkins
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Crickmore MA, Ranade V, Mann RS. Regulation of Ubx expression by epigenetic enhancer silencing in response to Ubx levels and genetic variation. PLoS Genet 2009; 5:e1000633. [PMID: 19730678 PMCID: PMC2726431 DOI: 10.1371/journal.pgen.1000633] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 08/05/2009] [Indexed: 11/18/2022] Open
Abstract
For gene products that must be present in cells at defined concentrations, expression levels must be tightly controlled to ensure robustness against environmental, genetic, and developmental noise. By studying the regulation of the concentration-sensitive Drosophila melanogaster Hox gene Ultrabithorax (Ubx), we found that Ubx enhancer activities respond to both increases in Ubx levels and genetic background. Large, transient increases in Ubx levels are capable of silencing all enhancer input into Ubx transcription, resulting in the complete silencing of this gene. Small increases in Ubx levels, brought about by duplications of the Ubx locus, cause sporadic silencing of subsets of Ubx enhancers. Ubx enhancer silencing can also be induced by outcrossing laboratory stocks to D. melanogaster strains established from wild flies from around the world. These results suggest that enhancer activities are not rigidly determined, but instead are sensitive to genetic background. Together, these findings suggest that enhancer silencing may be used to maintain gene product levels within the correct range in response to natural genetic variation. Gene expression is generally governed by cis-regulatory elements, also called enhancers. For genes whose expression levels must be tightly controlled, enhancer activities must be tightly regulated. In this work, we show that enhancers that control the expression of the Hox gene Ultrabithorax (Ubx) in Drosophila are regulated by a negative autoregulatory feedback mechanism. Negative autoregulation can be triggered by less than a two-fold increase in Ubx levels or by varying the genetic background. Together, these data reveal that enhancer activities are not always hardwired, but instead may be sensitive to genetic and environmental variation and, in some cases, to the amount of gene product they regulate. The finding that enhancers are sensitive to genetic background suggests that the regulation of gene expression is more plastic than previously thought and has important implications for how transcription is controlled in vivo.
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Affiliation(s)
- Michael A. Crickmore
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - Vikram Ranade
- Department of Genetics and Development, Columbia University, New York, New York, United States of America
| | - Richard S. Mann
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, United States of America
- * E-mail:
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Benítez E, Bray SJ, Rodriguez I, Guerrero I. Lines is required for normal operation of Wingless, Hedgehog and Notch pathways during wing development. Development 2009; 136:1211-21. [PMID: 19270177 DOI: 10.1242/dev.021428] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The regulatory Lines/Drumstick/Bowl gene network is implicated in the integration of patterning information at several stages during development. Here, we show that during Drosophila wing development, Lines prevents Bowl accumulation in the wing primordium, confining its expression to the peripodial epithelium. In cells that lack lines or over-expressing Drumstick, Bowl stabilization is responsible for alterations such as dramatic overgrowths and cell identity changes in the proximodistal patterning owing to aberrant responses to signaling pathways. The complex phenotypes are explained by Bowl repressing the Wingless pathway, the earliest effect seen. In addition, Bowl sequesters the general co-repressor Groucho from repressor complexes functioning in the Notch pathway and in Hedgehog expression, leading to ectopic activity of their targets. Supporting this model, elimination of the Groucho interaction domain in Bowl prevents the activation of the Notch and Hedgehog pathways, although not the repression of the Wingless pathway. Similarly, the effects of ectopic Bowl are partially rescued by co-expression of either Hairless or Master of thickveins, co-repressors that act with Groucho in the Notch and Hedgehog pathways, respectively. We conclude that by preventing Bowl accumulation in the wing, primordial Lines permits the correct balance of nuclear co-repressors that control the activity of the Wingless, Notch and Hedgehog pathways.
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Affiliation(s)
- Elvira Benítez
- Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain
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Abstract
Overexpression of epidermal growth factor receptor (EGFR) is a common phenomenon observed in most cancers. Clinical treatment of such cancer involves the use of chemotherapeutic agents such as ge ? tinib and erlotinib which are inhibitors of tyrosine kinase (TK). These small molecules bind to the ATP-binding sites of the TK domain of EGFR.Our in silico analysis suggests that the TK domains of Drosophila and human EGFR are highly conserved. We therefore employed the Drosophila system to validate the in silico observations made with two important anticancer drugs.Since a large number of mutant flies are available,it was possible to investigate the various components of the EGFR/Ras/Raf/MAPK pathways and the phosphorylation status of diphosphorylated extracellular signal-regulated kinase (dp-ERK1/2). These studies confirm the binding of the anilinoquinazolines to the Drosophila EGFR protein and modulation of its activity. Thus,Drosophila appears to be a robust and simple model system for screening newer anticancer drugs that act as TK inhibitors (TKIs).
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Affiliation(s)
- Anuradha Aritakula
- Division of Biological Sciences,Vittal Mallya Scientific Research Foundation, K R Road,P O Box 406, Bangalore 560 004, India.
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Nusinow D, Greenberg L, Hatini V. Reciprocal roles for bowl and lines in specifying the peripodial epithelium and the disc proper of the Drosophila wing primordium. Development 2008; 135:3031-41. [PMID: 18701548 DOI: 10.1242/dev.020800] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Central to embryonic development is the generation of molecular asymmetries across fields of undifferentiated cells. The Drosophila wing imaginal disc provides a powerful system with which to understand how such asymmetries are generated and how they contribute to formation of a complex structure. Early in development, the wing primordium is subdivided into a thin layer of peripodial epithelium (PE) and an apposing thickened layer of pseudostratified columnar epithelium (CE), known as the disc proper (DP). The DP gives rise to the wing blade, hinge and dorsal mesothorax, whereas the PE makes only a minor contribution to the ventral hinge and pleura. The mechanisms that generate this major asymmetry and its contribution to wing development are poorly understood. The Lines protein destabilizes the nuclear protein Bowl in ectodermal structures. Here, we show that Bowl accumulates in the PE from early stages of wing development and is absent from the DP. Broad inhibition of Bowl in the PE resulted in the replacement of the PE with a mirror image duplication of the DP. The failure to generate the PE severely compromised wing growth and the formation of the notum. Conversely, the activation of bowl in the DP (by removal or inhibition of lines function) resulted in the transformation of the DP into PE. Thus, we provide evidence that bowl and lines act as a binary switch to subdivide the wing primordium into PE and DP, and assign crucial roles for this asymmetry in wing growth and patterning.
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Affiliation(s)
- David Nusinow
- Program in Cell, Molecular and Developmental Biology, 150 Harrison Avenue, Boston, MA 02111, USA
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Abstract
Communication among cells by means of the exchange of signaling cues is important for tissue and organ development. Recent reports indicate that one way that signaling cues can be delivered is by movement along cellular protrusions interconnecting cells. Here, by using confocal laser scanning microscopy and three-dimensional rendering, we describe in Drosophila melanogaster wing imaginal discs lateral protrusions interconnecting cells of the columnar epithelium. Moreover, we identified protrusions of the apical surface of columnar cells that reached and apparently contacted cells of the overlying squamous epithelium. Both apical and lateral protrusions could be visualized by expression of Tkv-GFP, a green fluorescent protein (GFP) -tagged version of a receptor of the Dpp/BMP4 signaling molecule, and the endosome marker GFP-Rab5. Our results demonstrate a previously unexpected richness of cellular protrusions within wing imaginal discs and support the view that cellular protrusions may provide a means for exchanging signaling cues between cells.
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Affiliation(s)
- Fabio Demontis
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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Firth LC, Baker NE. Spitz from the retina regulates genes transcribed in the second mitotic wave, peripodial epithelium, glia and plasmatocytes of the Drosophila eye imaginal disc. Dev Biol 2007; 307:521-38. [PMID: 17553483 PMCID: PMC2140239 DOI: 10.1016/j.ydbio.2007.04.037] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 04/24/2007] [Accepted: 04/27/2007] [Indexed: 01/23/2023]
Abstract
Proliferation, differentiation, and other processes must be coordinated during the development of multi-cellular animals. A discrete and regulated cell division, the Second Mitotic Wave (SMW), occurs concomitantly with early cell fate decisions in the Drosophila developing retina. Signals from the Epidermal Growth Factor Receptor (EGFR) are required to promote cell cycle arrest of specified cells and antagonize S-phase entry in the SMW. Cells that do not receive any EGFR activity enter S-phase in the SMW in response to the Notch pathway. To identify genes with potential roles in the SMW, we used microarrays and genetic manipulation of the EGFR pathway to seek transcripts regulated during the SMW. RNA in situ hybridization of 126 differentially transcribed genes revealed genes that have novel expression patterns in cells closely associated with the SMW. In addition, other genes' transcripts were regulated in the differentiating photoreceptor cells, retinal basal glia, the peripodial epithelium and blood cells (plasmatocytes) associated with the developing retina. These novel targets suggest that during eye development, EGFR activity coordinates transcriptional programs in other tissues with retinal differentiation.
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Affiliation(s)
- Lucy C. Firth
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
| | - Nicholas E. Baker
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
- Corresponding Author: , Tel: 718-430-2854, Fax: 718-430-8778
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Srivastava A, Pastor-Pareja JC, Igaki T, Pagliarini R, Xu T. Basement membrane remodeling is essential for Drosophila disc eversion and tumor invasion. Proc Natl Acad Sci U S A 2007; 104:2721-6. [PMID: 17301221 PMCID: PMC1815248 DOI: 10.1073/pnas.0611666104] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Organ and tissue integrity is often maintained in animals by a specialized extracellular matrix structure called the basement membrane (BM). Accumulated evidence indicates that BM remodeling occurs during development and tumor invasion. Although the BM organizes and functions at the organ level, most past studies have explored its biochemical and in vitro properties. In this study, we monitor the BM in vivo during developmental tissue invasion for disc eversion and tumor invasion in Drosophila and modulate BM integrity with genetic alterations affecting either the whole organism or the targeted discs or tumors. We observe that the degradation of BM by the discs or the tumors is an early event during invasion processes and that preventing BM degradation completely blocks both tissue and tumor invasion, indicating that modulation of BM is essential for developmental and tumor invasion. Furthermore, elements of the invasion machinery, including JNK-induced matrix metalloproteinase (MMP) expression, are shared by both disc eversion and tumor invasion processes. Moreover, we show that although expression of MMP inhibitor, TIMP, is sufficient to halt developmental invasion, inhibition of proteases by both TIMP and RECK are required to block tumor invasion. These data suggest that tumor cells have a more robust invasion mechanism and could acquire metastatic behavior by co-opting developmental invasion programs. This type of co-option may be a general feature contributing to the progression of tumors. Finally, although past efforts using MMP inhibitors have not yielded much success, our results strongly argue that BM modulation could be a critical target for cancer therapy.
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Affiliation(s)
- Ajay Srivastava
- Department of Genetics and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Jose Carlos Pastor-Pareja
- Department of Genetics and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Tatsushi Igaki
- Department of Genetics and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Raymond Pagliarini
- Department of Genetics and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Tian Xu
- Department of Genetics and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
- To whom correspondence should be addressed. E-mail:
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Petruk S, Sedkov Y, Riley KM, Hodgson J, Schweisguth F, Hirose S, Jaynes JB, Brock HW, Mazo A. Transcription of bxd noncoding RNAs promoted by trithorax represses Ubx in cis by transcriptional interference. Cell 2007; 127:1209-21. [PMID: 17174895 PMCID: PMC1866366 DOI: 10.1016/j.cell.2006.10.039] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 08/08/2006] [Accepted: 10/27/2006] [Indexed: 10/23/2022]
Abstract
Much of the genome is transcribed into long noncoding RNAs (ncRNAs). Previous data suggested that bithoraxoid (bxd) ncRNAs of the Drosophila bithorax complex (BX-C) prevent silencing of Ultrabithorax (Ubx) and recruit activating proteins of the trithorax group (trxG) to their maintenance elements (MEs). We found that, surprisingly, Ubx and several bxd ncRNAs are expressed in nonoverlapping patterns in both embryos and imaginal discs, suggesting that transcription of these ncRNAs is associated with repression, not activation, of Ubx. Our data rule out siRNA or miRNA-based mechanisms for repression by bxd ncRNAs. Rather, ncRNA transcription itself, acting in cis, represses Ubx. The Trithorax complex TAC1 binds the Ubx coding region in nuclei expressing Ubx, and the bxd region in nuclei not expressing Ubx. We propose that TAC1 promotes the mosaic pattern of Ubx expression by facilitating transcriptional elongation of bxd ncRNAs, which represses Ubx transcription.
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Affiliation(s)
- Svetlana Petruk
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Yurii Sedkov
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Kristen M. Riley
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Jacob Hodgson
- Department of Zoology, University of British Columbia, 6270 University Boulevard, V6T 1Z4, Vancouver, BC, Canada
| | | | - Susumu Hirose
- Department of Developmental Genetics, National Institute of Genetics, and Graduate University for Advanced Studies, Mishima, Shizuoka-ken 411-8540, Japan
| | - James B. Jaynes
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Hugh W. Brock
- Department of Zoology, University of British Columbia, 6270 University Boulevard, V6T 1Z4, Vancouver, BC, Canada
| | - Alexander Mazo
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
- * Correspondence:
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de Navas L, Foronda D, Suzanne M, Sánchez-Herrero E. A simple and efficient method to identify replacements of P-lacZ by P-Gal4 lines allows obtaining Gal4 insertions in the bithorax complex of Drosophila. Mech Dev 2006; 123:860-7. [PMID: 16971094 DOI: 10.1016/j.mod.2006.07.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2006] [Revised: 07/25/2006] [Accepted: 07/26/2006] [Indexed: 01/12/2023]
Abstract
The functional replacement of one gene product by another one is a powerful method to study specificity in development and evolution. In Drosophila, the Gal4/UAS method has been used to analyze in vivo such functional substitutions. To this aim, Gal4 lines that inactivate a gene and reproduce its expression pattern are required, and they can be frequently obtained by replacing pre-existing P-lacZ lines with such characteristics. We have devised a new method to quickly identify replacements of P-lacZ lines by P-Gal4 lines, and applied it successfully to obtain Gal4 insertions in the Ultrabithorax and Abdominal-B Hox genes. We have used these lines to study the functional replacement of a Hox gene by another one. Our experiments confirm that the abdominal-A gene can replace Ultrabithorax in haltere development but that it cannot substitute for Abdominal-B in the formation of the genitalia.
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Affiliation(s)
- Luis de Navas
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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Pallavi SK, Kannan R, Shashidhara LS. Negative regulation of Egfr/Ras pathway by Ultrabithorax during haltere development in Drosophila. Dev Biol 2006; 296:340-52. [PMID: 16815386 DOI: 10.1016/j.ydbio.2006.05.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2006] [Revised: 05/21/2006] [Accepted: 05/24/2006] [Indexed: 11/30/2022]
Abstract
In Drosophila, wings and halteres are the dorsal appendages of the second and third thoracic segments, respectively. In the third thoracic segment, homeotic selector gene Ultrabithorax (Ubx) suppresses wing development to mediate haltere development (E.B. Lewis, 1978. A gene complex controlling segmentation in Drosophila. Nature 276, 565-570). Halteres lack stout sensory bristles of the wing margin and veins that reticulate the wing blade. Furthermore, wing and haltere epithelia differ in the size, shape, spacing and number of cuticular hairs. The differential development of wing and haltere, thus, constitutes a good genetic system to study cell fate determination. Here, we report that down-regulation of Egfr/Ras pathway is critical for haltere fate specification: over-expression of positive components of this pathway causes significant haltere-to-wing transformations. RNA in situ, immunohistochemistry, and epistasis genetic experiments suggest that Ubx negatively regulates the expression of the ligand vein as well as the receptor Egf-r to down-regulate the signaling pathway. Electromobility shift assays further suggest that Egf-r is a potential direct target of Ubx. These results and other recent findings suggest that homeotic genes may regulate cell fate determination by directly regulating few steps at the top of the hierarchy of selected signal transduction pathways.
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Affiliation(s)
- S K Pallavi
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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Stultz BG, Lee H, Ramon K, Hursh DA. Decapentaplegic head capsule mutations disrupt novel peripodial expression controlling the morphogenesis of the Drosophila ventral head. Dev Biol 2006; 296:329-39. [PMID: 16814276 DOI: 10.1016/j.ydbio.2006.05.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 05/24/2006] [Accepted: 05/25/2006] [Indexed: 10/24/2022]
Abstract
Drosophila adult structures derive from imaginal discs, which are sacs with apposed epithelial sheets, the disc proper (DP) and the peripodial epithelium (PE). The Drosophila TGF-beta family member decapentaplegic (dpp) contributes to the development of adult structures through expression in all imaginal discs, driven by enhancers from the 3' cis-regulatory region of the gene. In the eye/antennal disc, there is 3' directed dpp expression in both the DP and PE associated with cell proliferation and eye formation. Here, we analyze a new class of dpp cis-regulatory mutations, which specifically disrupt a previously unknown region of dpp expression, controlled by enhancers in the 5' regulatory region of the gene and limited to the PE of eye/antennal discs. These are the first described Drosophila mutations that act by solely disrupting PE gene expression. The mutants display defects in the ventral adult head and alter peripodial but not DP expression of known dpp targets. However, apoptosis is observed in the underlying DP, suggesting that this peripodial dpp signaling source supports cell survival in the DP.
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Affiliation(s)
- Brian G Stultz
- Division of Cell and Gene Therapy, Cellular and Tissue Therapy Branch, Center for Biologics Evaluation and Research, Food and Drug Administration, HFM-740, Bldg. 29B, Rm. 1E16, 8800 Rockville Pike, Bethesda, MD 20892, USA
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Callejo A, Torroja C, Quijada L, Guerrero I. Hedgehog lipid modifications are required for Hedgehog stabilization in the extracellular matrix. Development 2006; 133:471-83. [PMID: 16396909 DOI: 10.1242/dev.02217] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The Hedgehog (Hh) family of morphogenetic proteins has important instructional roles in metazoan development. Despite Hh being modified by Ct-cholesterol and Nt-palmitate adducts, Hh migrates far from its site of synthesis and programs cellular outcomes, depending on its local concentrations. We show that in the receiving cells of the Drosophila wing imaginal disc, lipid-unmodified Hh spreads across many more cell diameters than the wild type and this spreading leads to the activation of low but not high threshold responses. Unlipidated Hh forms become internalized through the apical plasma membrane, while wild-type Hh enters through the basolateral cell surface - in all cases via a dynamin-dependent mechanism. Full activation of the Hh pathway and the spread of Hh throughout the extracellular matrix depend on the ability of lipid-modified Hh to interact with heparan sulfate proteoglycans (HSPG). However, neither Hh-lipid modifications nor HSPG function are required to activate the targets that respond to low levels of Hh. All these data show that the interaction of lipid-modified Hh with HSPG is important both for precise Hh spreading through the epithelium surface and for correct Hh reception.
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Affiliation(s)
- Ainhoa Callejo
- Centro de Biología Molecular Severo Ochoa, CSIC, Universidad Autónoma de Madrid, Cantoblanco, Spain
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Abstract
Imaginal discs of Drosophila provide an excellent system with which to study morphogenesis, pattern formation and cell proliferation in an epithelium. Discs are sac-like in structure and are composed of two epithelial layers: an upper peripodial epithelium and lower disc proper. Although development of the disc proper has been studied extensively in terms of cell proliferation, cell signaling mechanisms and pattern formation, little is known about these same processes in the peripodial epithelium. We address this topic by focusing on morphogenesis, compartmental organization, proliferation and cell lineage of the PE in wing, second thoracic leg (T2) and eye discs. We show that a subset of peripodial cells in different imaginal discs undergo a cuboidal-to-squamous cell shape change at distinct larval stages. We find that this shape change requires both Hedgehog and Decapentapelagic, but not Wingless, signaling. Additionally, squamous morphogenesis shifts the anteroposterior (AP) compartment boundary in the peripodial epithelium relative to the stationary AP boundary in the disc proper. Finally, by lineage tracing cells in the PE, we surprisingly find that peripodial cells are displaced into the disc proper during larval development and this movement leads to Ubx repression.
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Abstract
Understanding the interactions between distinct epithelial cells would help us to understand the development of tissues. Drosophila imaginal discs, which are made up of two types of epithelial cells, provide good model systems for such studies. The disc proper or the columnar epithelial cells are apposed to a layer of squamous epithelial cells (the peripodial membrane). We have examined organization of peripodial and disc proper cells vis-à-vis their polarity since cell polarity plays an important role in the polarized transport of signaling molecules. With the help of polarity-specific cell markers, we have observed that apical surfaces of peripodial and disc proper cells face each other. This provides the cellular basis for the recently demonstrated signaling interactions between peripodial and disc proper cells during disc patterning. We also report significant similarities as well as differences between peripodial and disc proper cells in Engrailed-dependent wingdisc-patterning events, which make them an appropriate model system for studying the mechanism of diffusion of signal molecules, such as Hedgehog. Results with wild-type and two mutant forms of Hedgehog suggest that direct cell-cell contact is a requirement for the movement of wild-type Hedgehog signal and reconfirm that cholesterol-modification of Hedgehog makes it a short-range signaling molecule by restricting its movement.
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Affiliation(s)
- S K Pallavi
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007 India
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Bajpai R, Sambrani N, Stadelmayer B, Shashidhara LS. Identification of a novel target of D/V signaling in Drosophila wing disc: Wg-independent function of the organizer. Gene Expr Patterns 2005; 5:113-21. [PMID: 15533826 DOI: 10.1016/j.modgep.2004.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Accepted: 05/24/2004] [Indexed: 01/12/2023]
Abstract
Growth and patterning during Drosophila wing development are mediated by signaling from its dorso-ventral (D/V) organizer. Wingless is expressed in the D/V boundary and functions as a morphogen to activate target genes at a distance. Wingless pathway and thereby D/V signaling is negatively regulated by the homeotic gene Ultrabithorax (Ubx) to mediate haltere development. In an enhancer-trap screen to identify genes that show differential expression between wing and haltere discs, we identified CG32062, which codes for a RNA-binding protein. In wing discs, CG32062 is expressed only in non-D/V cells. CG32062 expression in non-D/V cells is dependent on Notch-mediated signaling from the D/V boundary. However, CG32062 expression is independent of Wingless function, thus providing evidence for a second long-range signaling mechanism of the D/V organizer. In haltere discs, CG32062 is negatively regulated by Ubx. The non-cell autonomous nature of Ubx-mediated repression of CG32062 expression suggests that the novel component of D/V signaling is also negatively regulated during haltere specification.
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Affiliation(s)
- Ruchi Bajpai
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, India 500 007
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Abstract
We report cloning and characterization of coro, which codes for the Drosophila homologue of the F-actin binding protein coronin. Viable alleles of coro produce a variety of phenotypes in leg, wing and eye development, which are similar to the phenotypes observed as a result of mutations in genes associated with the actin cytoskeleton and/or membrane trafficking. Homozygous lethal mutations in coro results in the disruption of the actin cytoskeleton in wing imaginal discs. Formation of both basolateral septate junctions and apical adherens junctions are also adversely affected in epithelial cells. Both viable and lethal alleles of coro show genetic interactions with syntaxin1A, a gene required for membrane trafficking. They also show enhanced response to over-expression of Decapentaplegic (Dpp) and its receptor Thick vein. Tracing of Dpp morphogen using a Dpp::GFP fusion construct suggested defects in the endocytic pathway, which resulted in uniform distribution of Dpp along the AP axis rather than a gradient from the AP boundary. Our results provide a genetic link between endocytosis/exocytosis events involving F actin-coated vesicles and the establishment of morphogen gradient.
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Affiliation(s)
- V Bharathi
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, India 500 007
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46
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Abstract
Protein Phosphatase 2A (PP2A) has a heterotrimeric-subunit structure,consisting of a core dimer of ∼36 kDa catalytic and ∼65 kDa scaffold subunits complexed to a third variable regulatory subunit. Several studies have implicated PP2A in Wg/Wnt signaling. However, reports on the precise nature of PP2A role in Wg/Wnt pathway in different organisms are conflicting. We show that twins (tws), which codes for the B/PR55 regulatory subunit of PP2A in Drosophila, is a positive regulator of Wg/Wnt signaling. In tws- wing discs both short- and long-range targets of Wingless morphogen are downregulated. Analyses of tws- mitotic clones suggest that requirement of Tws in Wingless pathway is cell-autonomous. Epistatic genetic studies indicate that Tws functions downstream of Dishevelled and upstream of Sgg and Armadillo. Our results suggest that Tws is required for the stabilization of Armadillo/β-catenin in response to Wg/Wnt signaling. Interestingly,overexpression of, otherwise normal, Tws protein induce dominant-negative phenotypes. The conflicting reports on the role of PP2A in Wg/Wnt signaling could be due to the dominant-negative effect caused by the overexpression of one of the subunits.
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Affiliation(s)
- Ruchi Bajpai
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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