1
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Cumming T, Levayer R. Toward a predictive understanding of epithelial cell death. Semin Cell Dev Biol 2024; 156:44-57. [PMID: 37400292 DOI: 10.1016/j.semcdb.2023.06.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 06/15/2023] [Accepted: 06/22/2023] [Indexed: 07/05/2023]
Abstract
Epithelial cell death is highly prevalent during development and tissue homeostasis. While we have a rather good understanding of the molecular regulators of programmed cell death, especially for apoptosis, we still fail to predict when, where, how many and which specific cells will die in a tissue. This likely relies on the much more complex picture of apoptosis regulation in a tissular and epithelial context, which entails cell autonomous but also non-cell autonomous factors, diverse feedback and multiple layers of regulation of the commitment to apoptosis. In this review, we illustrate this complexity of epithelial apoptosis regulation by describing these different layers of control, all demonstrating that local cell death probability is a complex emerging feature. We first focus on non-cell autonomous factors that can locally modulate the rate of cell death, including cell competition, mechanical input and geometry as well as systemic effects. We then describe the multiple feedback mechanisms generated by cell death itself. We also outline the multiple layers of regulation of epithelial cell death, including the coordination of extrusion and regulation occurring downstream of effector caspases. Eventually, we propose a roadmap to reach a more predictive understanding of cell death regulation in an epithelial context.
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Affiliation(s)
- Tom Cumming
- Department of Developmental and Stem Cell Biology, Institut Pasteur, Université de Paris Cité, CNRS UMR 3738, 25 rue du Dr. Roux, 75015 Paris, France; Sorbonne Université, Collège Doctoral, F75005 Paris, France
| | - Romain Levayer
- Department of Developmental and Stem Cell Biology, Institut Pasteur, Université de Paris Cité, CNRS UMR 3738, 25 rue du Dr. Roux, 75015 Paris, France.
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2
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Fischer F, Ernst L, Frey A, Holstein K, Prasad D, Weichselberger V, Balaji R, Classen AK. A mismatch in the expression of cell surface molecules induces tissue-intrinsic defense against aberrant cells. Curr Biol 2024; 34:980-996.e6. [PMID: 38350446 DOI: 10.1016/j.cub.2024.01.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 09/29/2023] [Accepted: 01/19/2024] [Indexed: 02/15/2024]
Abstract
Tissue-intrinsic error correction enables epithelial cells to detect abnormal neighboring cells and facilitate their removal from the tissue. One of these pathways, "interface surveillance," is triggered by cells with aberrant developmental and cell-fate-patterning pathways. It remains unknown which molecular mechanisms provide cells with the ability to compare fate between neighboring cells. We demonstrate that Drosophila imaginal discs express an array of cell surface molecules previously implicated in neuronal axon guidance processes. They include members of the Robo, Teneurin, Ephrin, Toll-like, or atypical cadherin families. Importantly, a mismatch in expression levels of these cell surface molecules between adjacent cells is sufficient to induce interface surveillance, indicating that differences in expression levels between neighboring cells, rather than their absolute expression levels, are crucial. Specifically, a mismatch in Robo2 and Robo3, but not Robo1, induces enrichment of actin, myosin II, and Ena/Vasp, as well as activation of JNK and apoptosis at clonal interfaces. Moreover, Robo2 can induce interface surveillance independently of its cytosolic domain and without the need for the Robo-ligand Slit. The expression of Robo2 and other cell surface molecules, such as Teneurins or the Ephrin receptor is regulated by fate-patterning pathways intrinsic and extrinsic to the wing disc, as well as by expression of oncogenic RasV12. Combined, we demonstrate that neighboring cells respond to a mismatch in surface code patterns mediated by specific transmembrane proteins and reveal a novel function for these cell surface proteins in cell fate recognition and removal of aberrant cells during development and homeostasis of epithelial tissues.
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Affiliation(s)
- Friedericke Fischer
- Hilde-Mangold-Haus, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; International Max Planck Research School for Immunobiology, Epigenetics, and Metabolism, 79108 Freiburg, Germany
| | - Laurin Ernst
- Hilde-Mangold-Haus, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; International Max Planck Research School for Immunobiology, Epigenetics, and Metabolism, 79108 Freiburg, Germany
| | - Anna Frey
- Hilde-Mangold-Haus, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 79104 Freiburg, Germany
| | - Katrin Holstein
- Department of Vascular Cell Biology, Max Planck Institute for Molecular Biomedicine, 48149 Münster, Germany
| | - Deepti Prasad
- Hilde-Mangold-Haus, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 79104 Freiburg, Germany
| | - Vanessa Weichselberger
- Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, 79104 Freiburg, Germany; Aix Marseille University, CNRS, UMR 7288, IBDM, 13288 Marseille, France
| | - Ramya Balaji
- Hilde-Mangold-Haus, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Anne-Kathrin Classen
- Hilde-Mangold-Haus, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
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3
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Paul PK, Umarvaish S, Bajaj S, S. RF, Mohan H, Annaert W, Chaudhary V. Maintenance of proteostasis by Drosophila Rer1 is essential for competitive cell survival and Myc-driven overgrowth. PLoS Genet 2024; 20:e1011171. [PMID: 38408084 PMCID: PMC10919865 DOI: 10.1371/journal.pgen.1011171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 03/07/2024] [Accepted: 02/05/2024] [Indexed: 02/28/2024] Open
Abstract
Defects in protein homeostasis can induce proteotoxic stress, affecting cellular fitness and, consequently, overall tissue health. In various growing tissues, cell competition based mechanisms facilitate detection and elimination of these compromised, often referred to as 'loser', cells by the healthier neighbors. The precise connection between proteotoxic stress and competitive cell survival remains largely elusive. Here, we reveal the function of an endoplasmic reticulum (ER) and Golgi localized protein Rer1 in the regulation of protein homeostasis in the developing Drosophila wing epithelium. Our results show that loss of Rer1 leads to proteotoxic stress and PERK-mediated phosphorylation of eukaryotic initiation factor 2α. Clonal analysis showed that rer1 mutant cells are identified as losers and eliminated through cell competition. Interestingly, we find that Rer1 levels are upregulated upon Myc-overexpression that causes overgrowth, albeit under high proteotoxic stress. Our results suggest that increased levels of Rer1 provide cytoprotection to Myc-overexpressing cells by alleviating the proteotoxic stress and thereby supporting Myc-driven overgrowth. In summary, these observations demonstrate that Rer1 acts as a novel regulator of proteostasis in Drosophila and reveal its role in competitive cell survival.
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Affiliation(s)
- Pranab Kumar Paul
- Cell and developmental signaling laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, India
| | - Shruti Umarvaish
- Cell and developmental signaling laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, India
| | - Shivani Bajaj
- Cell and developmental signaling laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, India
| | - Rishana Farin S.
- Cell and developmental signaling laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, India
| | - Hrudya Mohan
- Cell and developmental signaling laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, India
| | - Wim Annaert
- Laboratory for Membrane Trafficking, VIB-Center for Brain and Disease Research, KU Leuven, Leuven, Belgium, and Department of Neurosciences, KU Leuven, Gasthuisberg, Leuven, Belgium
| | - Varun Chaudhary
- Cell and developmental signaling laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, India
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4
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Milán M. Organogenesis: Cell death matters in size and shape regulation. Curr Biol 2024; 34:R62-R64. [PMID: 38262361 DOI: 10.1016/j.cub.2023.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Anisotropic growth and large-scale morphogenetic movements contribute to the final size and shape of the adult Drosophila wing. A new study unravels an unexpected contribution of cell death, which follows a spatial and temporal pattern, to the growth of the wing and the acquisition of its elongated shape.
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Affiliation(s)
- Marco Milán
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Baldiri Reixac 10, 08028 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain.
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5
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Martinez Lyons A, Boulter L. NOTCH signalling - a core regulator of bile duct disease? Dis Model Mech 2023; 16:dmm050231. [PMID: 37605966 PMCID: PMC10461466 DOI: 10.1242/dmm.050231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023] Open
Abstract
The Notch signalling pathway is an evolutionarily conserved mechanism of cell-cell communication that mediates cellular proliferation, fate determination and maintenance of stem/progenitor cell populations across tissues. Although it was originally identified as a critical regulator of embryonic liver development, NOTCH signalling activation has been associated with the pathogenesis of a number of paediatric and adult liver diseases. It remains unclear, however, what role NOTCH actually plays in these pathophysiological processes and whether NOTCH activity represents the reactivation of a conserved developmental programme that is essential for adult tissue repair. In this Review, we explore the concepts that NOTCH signalling reactivation in the biliary epithelium is a reiterative and essential response to bile duct damage and that, in disease contexts in which biliary epithelial cells need to be regenerated, NOTCH signalling supports ductular regrowth. Furthermore, we evaluate the recent literature on NOTCH signalling as a critical factor in progenitor-mediated hepatocyte regeneration, which indicates that the mitogenic role for NOTCH signalling in biliary epithelial cell proliferation has also been co-opted to support other forms of epithelial regeneration in the adult liver.
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Affiliation(s)
| | - Luke Boulter
- MRC Human Genetics Unit, Institute of Genetics and Cancer, Edinburgh EH4 2XU, UK
- CRUK Scottish Centre, Institute of Genetics and Cancer, Edinburgh EH4 2XU, UK
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6
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Li Y, Xu B, Jin M, Zhang H, Ren N, Hu J, He J. Homophilic interaction of cell adhesion molecule 3 coordinates retina neuroepithelial cell proliferation. J Cell Biol 2023; 222:e202204098. [PMID: 37022761 PMCID: PMC10082328 DOI: 10.1083/jcb.202204098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 01/07/2023] [Accepted: 03/07/2023] [Indexed: 04/07/2023] Open
Abstract
Correct cell number generation is central to tissue development. However, in vivo roles of coordinated proliferation of individual neural progenitors in regulating cell numbers of developing neural tissues and the underlying molecular mechanism remain mostly elusive. Here, we showed that wild-type (WT) donor retinal progenitor cells (RPCs) generated significantly expanded clones in host retinae with G1-lengthening by p15 (cdkn2a/b) overexpression (p15+) in zebrafish. Further analysis showed that cell adhesion molecule 3 (cadm3) was reduced in p15+ host retinae, and overexpression of either full-length or ectodomains of Cadm3 in p15+ host retinae markedly suppressed the clonal expansion of WT donor RPCs. Notably, WT donor RPCs in retinae with cadm3 disruption recapitulated expanded clones that were found in p15+ retinae. More strikingly, overexpression of Cadm3 without extracellular ig1 domain in RPCs resulted in expanded clones and increased retinal total cell number. Thus, homophilic interaction of Cadm3 provides an intercellular mechanism underlying coordinated cell proliferation to ensure cell number homeostasis of the developing neuroepithelia.
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Affiliation(s)
- Yanan Li
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Baijie Xu
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Mengmeng Jin
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Hui Zhang
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ningxin Ren
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Jinhui Hu
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Jie He
- State Key Laboratory of Neuroscience, Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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7
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Morata G. Cell competition: A historical perspective. Dev Biol 2021; 476:33-40. [PMID: 33775694 DOI: 10.1016/j.ydbio.2021.02.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 02/16/2021] [Accepted: 02/23/2021] [Indexed: 12/21/2022]
Abstract
Cell competition is a homeostatic process designed to remove from animal tissues viable cells that are unfit, abnormal or malignant and that may compromise the general fitness or the viability of the organism. Originally discovered in Drosophila in the mid-seventies of last century, there is strong evidence that it also occurs in other metazoans, where cell competition appears to play a similar surveillance role. In this review I summarize the field of cell competition, with special emphasis in the history of the phenomenon within the general frame of Developmental Biology in the second half of the XX century, pointing out the key observations and the evolution of ideas that have led to the current understanding.
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Affiliation(s)
- Ginés Morata
- Centro de Biología Molecular CSIC-UAM, Madrid, Spain.
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8
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Uppal G, Bahcecioglu G, Zorlutuna P, Vural DC. Tissue Failure Propagation as Mediated by Circulatory Flow. Biophys J 2020; 119:2573-2583. [PMID: 33189679 DOI: 10.1016/j.bpj.2020.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 10/06/2020] [Accepted: 11/05/2020] [Indexed: 01/09/2023] Open
Abstract
Aging is driven by subcellular processes that are relatively well understood. However, the qualitative mechanisms and quantitative dynamics of how these micro-level failures cascade to a macro-level catastrophe in a tissue or organs remain largely unexplored. Here, we experimentally and theoretically study how cell failure propagates in an engineered tissue in the presence of advective flow. We argue that cells secrete cooperative factors, thereby forming a network of interdependence governed by diffusion and flow, which fails with a propagating front parallel to advective circulation.
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Affiliation(s)
- Gurdip Uppal
- Department of Physics, University of Notre Dame, Notre Dame, Indiana
| | - Gokhan Bahcecioglu
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana
| | - Pinar Zorlutuna
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana.
| | - Dervis Can Vural
- Department of Physics, University of Notre Dame, Notre Dame, Indiana.
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9
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McKenna KZ, Kudla AM, Nijhout HF. Anterior–Posterior Patterning in Lepidopteran Wings. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00146] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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10
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Klipa O, Hamaratoglu F. Cell elimination strategies upon identity switch via modulation of apterous in Drosophila wing disc. PLoS Genet 2019; 15:e1008573. [PMID: 31877129 PMCID: PMC6952109 DOI: 10.1371/journal.pgen.1008573] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/09/2020] [Accepted: 12/17/2019] [Indexed: 12/04/2022] Open
Abstract
The ability to establish spatial organization is an essential feature of any developing tissue and is achieved through well-defined rules of cell-cell communication. Maintenance of this organization requires elimination of cells with inappropriate positional identity, a poorly understood phenomenon. Here we studied mechanisms regulating cell elimination in the context of a growing tissue, the Drosophila wing disc and its dorsal determinant Apterous. Systematic analysis of apterous mutant clones along with their twin spots shows that they are eliminated from the dorsal compartment via three different mechanisms: relocation to the ventral compartment, basal extrusion, and death, depending on the position of the clone in the wing disc. We find that basal extrusion is the main elimination mechanism in the hinge, whereas apoptosis dominates in the pouch and in the notum. In the absence of apoptosis, extrusion takes over to ensure clearance in all regions. Notably, clones in the hinge grow larger than those in the pouch, emphasizing spatial differences. Mechanistically, we find that limiting cell division within the clones does not prevent their extrusion. Indeed, even clones of one or two cells can be extruded basally, demonstrating that the clone size is not the main determinant of the elimination mechanism to be used. Overall, we revealed three elimination mechanisms and their spatial biases for preserving pattern in a growing organ. As development proceeds, cells become more specialized and the compartmentalization ensures spatial separation of the specialized cells. This process of pattern formation is rather well understood. How the pattern is maintained afterwards though is largely unknown. Using the Drosophila wing disc as a model organ, we examined what happens to dorsal cells if they lose their dorsal identity. Formerly, it was shown that these cells are eliminated from the dorsal compartment via apoptosis or through relocation to the ventral compartment. Here we show that a third mode of elimination, basal extrusion, also contributes to their clearing. We quantified, for the first time, contributions of each mechanism and discovered a regional bias in their operation. Importantly, if apoptosis is blocked, basal extrusion takes over to ensure clearance from all regions. Recent modeling approaches suggested that there is a lower limit to the clone size for extrusion. Therefore, we tested the hypothesis that the choice of elimination mechanism may be dictated by the clone size. We prevented cell divisions within the clones to be eliminated and found that even 1–2 cell clones readily underwent basal extrusion, demonstrating that there is no lower limit to the clone size for extrusion.
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Affiliation(s)
- Olga Klipa
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
- School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Fisun Hamaratoglu
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
- School of Biosciences, Cardiff University, Cardiff, United Kingdom
- * E-mail:
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11
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Abstract
The morphology of male genitalia evolves rapidly, probably driven by sexual selection. However, little is known about the genes underlying genitalia differences between species. Identifying these genes is key to understanding how sexual selection acts to produce rapid phenotypic change. We have found that the gene tartan underlies differences between male Drosophila mauritiana and Drosophila simulans in the size and bristle number of the claspers—genital projections that grasp the female during copulation. Moreover, since tartan encodes a protein that is involved in cell interactions, this may represent an alternative developmental mechanism for morphological change. Therefore, our study provides insights into the genetic and developmental bases for the rapid evolution of male genitalia and organ size more generally. Male genital structures are among the most rapidly evolving morphological traits and are often the only features that can distinguish closely related species. This process is thought to be driven by sexual selection and may reinforce species separation. However, while the genetic bases of many phenotypic differences have been identified, we still lack knowledge about the genes underlying evolutionary differences in male genital organs and organ size more generally. The claspers (surstyli) are periphallic structures that play an important role in copulation in insects. Here, we show that divergence in clasper size and bristle number between Drosophila mauritiana and Drosophila simulans is caused by evolutionary changes in tartan (trn), which encodes a transmembrane leucine-rich repeat domain protein that mediates cell–cell interactions and affinity. There are no fixed amino acid differences in trn between D. mauritiana and D. simulans, but differences in the expression of this gene in developing genitalia suggest that cis-regulatory changes in trn underlie the evolution of clasper morphology in these species. Finally, analyses of reciprocal hemizygotes that are genetically identical, except for the species from which the functional allele of trn originates, determined that the trn allele of D. mauritiana specifies larger claspers with more bristles than the allele of D. simulans. Therefore, we have identified a gene underlying evolutionary change in the size of a male genital organ, which will help to better understand not only the rapid diversification of these structures, but also the regulation and evolution of organ size more broadly.
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12
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Transsynaptic Fish-lips signaling prevents misconnections between nonsynaptic partner olfactory neurons. Proc Natl Acad Sci U S A 2019; 116:16068-16073. [PMID: 31341080 DOI: 10.1073/pnas.1905832116] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our understanding of the mechanisms of neural circuit assembly is far from complete. Identification of wiring molecules with novel mechanisms of action will provide insights into how complex and heterogeneous neural circuits assemble during development. In the Drosophila olfactory system, 50 classes of olfactory receptor neurons (ORNs) make precise synaptic connections with 50 classes of partner projection neurons (PNs). Here, we performed an RNA interference screen for cell surface molecules and identified the leucine-rich repeat-containing transmembrane protein known as Fish-lips (Fili) as a novel wiring molecule in the assembly of the Drosophila olfactory circuit. Fili contributes to the precise axon and dendrite targeting of a small subset of ORN and PN classes, respectively. Cell-type-specific expression and genetic analyses suggest that Fili sends a transsynaptic repulsive signal to neurites of nonpartner classes that prevents their targeting to inappropriate glomeruli in the antennal lobe.
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13
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Morata G, Calleja M. Cell competition and tumorigenesis in the imaginal discs of Drosophila. Semin Cancer Biol 2019; 63:19-26. [PMID: 31255773 DOI: 10.1016/j.semcancer.2019.06.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/14/2019] [Accepted: 06/19/2019] [Indexed: 12/20/2022]
Abstract
Cancer is a major health issue and the object of investigations in thousands of laboratories all over the world. Most of cancer research is being carried out in in vitro systems or in animal models, generally mice or rats. However, the discovery of the high degree of genetic identity among metazoans has prompted investigation in organisms like Drosophila, on the idea that the genetic basis of cancer in flies and humans may have many aspects in common. Moreover, the sophisticated genetic methodology of Drosophila offers operational advantages and allows experimental approaches inaccessible in other species. Cell competition is a cell-quality control process that aims to identifying and subsequently removing cells within animal tissues that are unfit, abnormal or aberrant, and that may compromise the fitness or the viability of the organism. It was originally described in Drosophila imaginal discs but later work has shown it occurs in mammalian tissues where it fulfils similar roles. One aspect of the surveillance role of cell competition is to eliminate oncogenic cells that may appear during development or the life of an organism. In this review we have focussed on the work on Drosophila imaginal discs relating cell competition and tumorigenic processes. We briefly discuss related work in mammalian tissues.
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Affiliation(s)
- Ginés Morata
- Centro de Biología Molecular, CSIC-UAM, Nicolas Cabrera 1, Madrid, 28049, Spain.
| | - Manuel Calleja
- Centro de Biología Molecular, CSIC-UAM, Nicolas Cabrera 1, Madrid, 28049, Spain
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14
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Levayer R. Solid stress, competition for space and cancer: The opposing roles of mechanical cell competition in tumour initiation and growth. Semin Cancer Biol 2019; 63:69-80. [PMID: 31077845 PMCID: PMC7221353 DOI: 10.1016/j.semcancer.2019.05.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 04/23/2019] [Accepted: 05/07/2019] [Indexed: 12/24/2022]
Abstract
The regulation of cell growth, cell proliferation and cell death is at the basis of the homeostasis of tissues. While they can be regulated by intrinsic and genetic factors, their response to external signals emanating from the local environment is also essential for tissue homeostasis. Tumour initiation and progression is based on the misregulation of growth, proliferation and death mostly through the accumulation of genetic mutations. Yet, there is an increasing body of evidences showing that tumour microenvironment also has a strong impact on cancer initiation and progression. This includes the mechanical constrains and the compressive forces generated by the resistance of the surrounding tissue/matrix to tumour expansion. Recently, mechanical stress has been proposed to promote competitive interactions between cells through a process called mechanical cell competition. Cell population with a high proliferative rate can compact and eliminate the neighbouring cells which are more sensitive to compaction. While this emerging concept has been recently validated in vivo, the relevance of this process during tumour progression has never been discussed extensively. In this review, I will first describe the phenomenology of mechanical cell competition focusing on the main parameters and the pathways regulating cell elimination. I will then discuss the relevance of mechanical cell competition in tumour initiation and expansion while emphasizing its potential opposing contributions to tumourogenesis.
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Affiliation(s)
- Romain Levayer
- Institut Pasteur, Department of Developmental and Stem Cell Biology, 25 rue du Dr. Roux, 75015 Paris, France.
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15
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Pei J, Kinch LN, Grishin NV. FlyXCDB—A Resource for Drosophila Cell Surface and Secreted Proteins and Their Extracellular Domains. J Mol Biol 2018; 430:3353-3411. [DOI: 10.1016/j.jmb.2018.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 05/31/2018] [Accepted: 06/02/2018] [Indexed: 02/06/2023]
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16
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Tsuboi A, Umetsu D, Kuranaga E, Fujimoto K. Inference of Cell Mechanics in Heterogeneous Epithelial Tissue Based on Multivariate Clone Shape Quantification. Front Cell Dev Biol 2017; 5:68. [PMID: 28824908 PMCID: PMC5540905 DOI: 10.3389/fcell.2017.00068] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 07/05/2017] [Indexed: 12/16/2022] Open
Abstract
Cell populations in multicellular organisms show genetic and non-genetic heterogeneity, even in undifferentiated tissues of multipotent cells during development and tumorigenesis. The heterogeneity causes difference of mechanical properties, such as, cell bond tension or adhesion, at the cell–cell interface, which determine the shape of clonal population boundaries via cell sorting or mixing. The boundary shape could alter the degree of cell–cell contacts and thus influence the physiological consequences of sorting or mixing at the boundary (e.g., tumor suppression or progression), suggesting that the cell mechanics could help clarify the physiology of heterogeneous tissues. While precise inference of mechanical tension loaded at each cell–cell contacts has been extensively developed, there has been little progress on how to distinguish the population-boundary geometry and identify the cause of geometry in heterogeneous tissues. We developed a pipeline by combining multivariate analysis of clone shape with tissue mechanical simulations. We examined clones with four different genotypes within Drosophila wing imaginal discs: wild-type, tartan (trn) overexpression, hibris (hbs) overexpression, and Eph RNAi. Although the clones were previously known to exhibit smoothed or convoluted morphologies, their mechanical properties were unknown. By applying a multivariate analysis to multiple criteria used to quantify the clone shapes based on individual cell shapes, we found the optimal criteria to distinguish not only among the four genotypes, but also non-genetic heterogeneity from genetic one. The efficient segregation of clone shape enabled us to quantitatively compare experimental data with tissue mechanical simulations. As a result, we identified the mechanical basis contributed to clone shape of distinct genotypes. The present pipeline will promote the understanding of the functions of mechanical interactions in heterogeneous tissue in a non-invasive manner.
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Affiliation(s)
- Alice Tsuboi
- Laboratory of Theoretical Biology, Department of Biological Sciences, Osaka UniversityToyonaka, Japan
| | - Daiki Umetsu
- Laboratory of Histogenetic Dynamics, Graduate School of Life Sciences, Tohoku UniversitySendai, Japan
| | - Erina Kuranaga
- Laboratory of Histogenetic Dynamics, Graduate School of Life Sciences, Tohoku UniversitySendai, Japan
| | - Koichi Fujimoto
- Laboratory of Theoretical Biology, Department of Biological Sciences, Osaka UniversityToyonaka, Japan
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Pflugfelder G, Eichinger F, Shen J. T-Box Genes in Drosophila Limb Development. Curr Top Dev Biol 2017; 122:313-354. [DOI: 10.1016/bs.ctdb.2016.08.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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18
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Affiliation(s)
- Cristina Clavería
- Cardiovascular Development Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid 28029, Spain;
| | - Miguel Torres
- Cardiovascular Development Program, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid 28029, Spain;
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Michel M, Aliee M, Rudolf K, Bialas L, Jülicher F, Dahmann C. The Selector Gene apterous and Notch Are Required to Locally Increase Mechanical Cell Bond Tension at the Drosophila Dorsoventral Compartment Boundary. PLoS One 2016; 11:e0161668. [PMID: 27552097 PMCID: PMC4995041 DOI: 10.1371/journal.pone.0161668] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 08/09/2016] [Indexed: 11/25/2022] Open
Abstract
The separation of cells with distinct fates and functions is important for tissue and organ formation during animal development. Regions of different fates within tissues are often separated from another along straight boundaries. These compartment boundaries play a crucial role in tissue patterning and growth by stably positioning organizers. In Drosophila, the wing imaginal disc is subdivided into a dorsal and a ventral compartment. Cells of the dorsal, but not ventral, compartment express the selector gene apterous. Apterous expression sets in motion a gene regulatory cascade that leads to the activation of Notch signaling in a few cell rows on either side of the dorsoventral compartment boundary. Both Notch and apterous mutant clones disturb the separation of dorsal and ventral cells. Maintenance of the straight shape of the dorsoventral boundary involves a local increase in mechanical tension at cell bonds along the boundary. The mechanisms by which cell bond tension is locally increased however remain unknown. Here we use a combination of laser ablation of cell bonds, quantitative image analysis, and genetic mutants to show that Notch and Apterous are required to increase cell bond tension along the dorsoventral compartment boundary. Moreover, clonal expression of the Apterous target gene capricious results in cell separation and increased cell bond tension at the clone borders. Finally, using a vertex model to simulate tissue growth, we find that an increase in cell bond tension at the borders of cell clones, but not throughout the cell clone, can lead to cell separation. We conclude that Apterous and Notch maintain the characteristic straight shape of the dorsoventral compartment boundary by locally increasing cell bond tension.
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Affiliation(s)
- Marcus Michel
- Institute of Genetics, Technische Universität Dresden, 01062, Dresden, Germany
| | - Maryam Aliee
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187, Dresden, Germany
| | - Katrin Rudolf
- Institute of Genetics, Technische Universität Dresden, 01062, Dresden, Germany
| | - Lisa Bialas
- Institute of Genetics, Technische Universität Dresden, 01062, Dresden, Germany
| | - Frank Jülicher
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187, Dresden, Germany
- * E-mail: (FJ); (CD)
| | - Christian Dahmann
- Institute of Genetics, Technische Universität Dresden, 01062, Dresden, Germany
- * E-mail: (FJ); (CD)
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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 PMCID: PMC4958983 DOI: 10.1038/srep30236] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [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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Affiliation(s)
- Wenqian Tang
- Department of Entomology, China Agricultural University, 100193 Beijing, China
| | - Dan Wang
- Department of Entomology, China Agricultural University, 100193 Beijing, China
| | - Jie Shen
- Department of Entomology, China Agricultural University, 100193 Beijing, China
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21
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Bielmeier C, Alt S, Weichselberger V, La Fortezza M, Harz H, Jülicher F, Salbreux G, Classen AK. Interface Contractility between Differently Fated Cells Drives Cell Elimination and Cyst Formation. Curr Biol 2016; 26:563-74. [PMID: 26853359 PMCID: PMC5282066 DOI: 10.1016/j.cub.2015.12.063] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 11/20/2015] [Accepted: 12/16/2015] [Indexed: 01/22/2023]
Abstract
Although cellular tumor-suppression mechanisms are widely studied, little is known about mechanisms that act at the level of tissues to suppress the occurrence of aberrant cells in epithelia. We find that ectopic expression of transcription factors that specify cell fates causes abnormal epithelial cysts in Drosophila imaginal discs. Cysts do not form cell autonomously but result from the juxtaposition of two cell populations with divergent fates. Juxtaposition of wild-type and aberrantly specified cells induces enrichment of actomyosin at their entire shared interface, both at adherens junctions as well as along basolateral interfaces. Experimental validation of 3D vertex model simulations demonstrates that enhanced interface contractility is sufficient to explain many morphogenetic behaviors, which depend on cell cluster size. These range from cyst formation by intermediate-sized clusters to segregation of large cell populations by formation of smooth boundaries or apical constriction in small groups of cells. In addition, we find that single cells experiencing lateral interface contractility are eliminated from tissues by apoptosis. Cysts, which disrupt epithelial continuity, form when elimination of single, aberrantly specified cells fails and cells proliferate to intermediate cell cluster sizes. Thus, increased interface contractility functions as error correction mechanism eliminating single aberrant cells from tissues, but failure leads to the formation of large, potentially disease-promoting cysts. Our results provide a novel perspective on morphogenetic mechanisms, which arise from cell-fate heterogeneities within tissues and maintain or disrupt epithelial homeostasis.
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Affiliation(s)
- Christina Bielmeier
- Ludwig-Maximilians-University Munich, Faculty of Biology, Grosshadernerstrasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Silvanus Alt
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany; The Francis Crick Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Vanessa Weichselberger
- Ludwig-Maximilians-University Munich, Faculty of Biology, Grosshadernerstrasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Marco La Fortezza
- Ludwig-Maximilians-University Munich, Faculty of Biology, Grosshadernerstrasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Hartmann Harz
- Ludwig-Maximilians-University Munich, Faculty of Biology, Grosshadernerstrasse 2-4, 82152 Planegg-Martinsried, Germany
| | - Frank Jülicher
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany
| | - Guillaume Salbreux
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany; The Francis Crick Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
| | - Anne-Kathrin Classen
- Ludwig-Maximilians-University Munich, Faculty of Biology, Grosshadernerstrasse 2-4, 82152 Planegg-Martinsried, Germany.
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22
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Leclerc C, Haeich J, Aulestia FJ, Kilhoffer MC, Miller AL, Néant I, Webb SE, Schaeffer E, Junier MP, Chneiweiss H, Moreau M. Calcium signaling orchestrates glioblastoma development: Facts and conjunctures. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1447-59. [PMID: 26826650 DOI: 10.1016/j.bbamcr.2016.01.018] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 01/18/2016] [Accepted: 01/22/2016] [Indexed: 01/06/2023]
Abstract
While it is a relatively rare disease, glioblastoma multiform (GBM) is one of the more deadly adult cancers. Following current interventions, the tumor is never eliminated whatever the treatment performed; whether it is radiotherapy, chemotherapy, or surgery. One hypothesis to explain this poor outcome is the "cancer stem cell" hypothesis. This concept proposes that a minority of cells within the tumor mass share many of the properties of adult neural stem cells and it is these that are responsible for the growth of the tumor and its resistance to existing therapies. Accumulating evidence suggests that Ca(2+) might also be an important positive regulator of tumorigenesis in GBM, in processes involving quiescence, maintenance, proliferation, or migration. Glioblastoma tumors are generally thought to develop by co-opting pathways that are involved in the formation of an organ. We propose that the cells initiating the tumor, and subsequently the cells of the tumor mass, must hijack the different checkpoints that evolution has selected in order to prevent the pathological development of an organ. In this article, two main points are discussed. (i) The first is the establishment of a so-called "cellular society," which is required to create a favorable microenvironment. (ii) The second is that GBM can be considered to be an organism, which fights to survive and develop. Since GBM evolves in a limited space, its only chance of development is to overcome the evolutionary checkpoints. For example, the deregulation of the normal Ca(2+) signaling elements contributes to the progression of the disease. Thus, by manipulating the Ca(2+) signaling, the GBM cells might not be killed, but might be reprogrammed toward a new fate that is either easy to cure or that has no aberrant functioning. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.
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Affiliation(s)
- Catherine Leclerc
- Centre de Biologie du Développement, Université Toulouse 3, 118 route de Narbonne, F31062 Toulouse, Cedex 04, France; CNRS UMR5547, Toulouse F31062, France.
| | - Jacques Haeich
- Laboratoire d'Innovation Thérapeutique, Laboratoire d'Excellence Médalis, UMR 7200 Université de Strasbourg / CNRS, 67412 Illkirch, France
| | - Francisco J Aulestia
- Centre de Biologie du Développement, Université Toulouse 3, 118 route de Narbonne, F31062 Toulouse, Cedex 04, France
| | - Marie-Claude Kilhoffer
- Laboratoire d'Innovation Thérapeutique, Laboratoire d'Excellence Médalis, UMR 7200 Université de Strasbourg / CNRS, 67412 Illkirch, France
| | - Andrew L Miller
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, HKUST, Clear Water Bay, Hong Kong, PR China
| | - Isabelle Néant
- Centre de Biologie du Développement, Université Toulouse 3, 118 route de Narbonne, F31062 Toulouse, Cedex 04, France; CNRS UMR5547, Toulouse F31062, France
| | - Sarah E Webb
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, HKUST, Clear Water Bay, Hong Kong, PR China
| | - Etienne Schaeffer
- IREBS UMR7242 ESBS, Pôle API, Parc d'Innovation d'Illkirch, 67412 Illkirch cedex, France
| | - Marie-Pierre Junier
- Sorbonne Universités, UPMC Univ Paris 06, Centre National de la Recherche Scientifique (CNRS), UMR8246, Institut National de la Santé et de la Recherche Medicale (INSERM), U1130, Institut de Biologie Paris Seine (IBPS), Neuroscience Paris Seine (NPS), Team Glial Plasticity, 7/9 Quai St Bernard, Paris, France
| | - Hervé Chneiweiss
- Sorbonne Universités, UPMC Univ Paris 06, Centre National de la Recherche Scientifique (CNRS), UMR8246, Institut National de la Santé et de la Recherche Medicale (INSERM), U1130, Institut de Biologie Paris Seine (IBPS), Neuroscience Paris Seine (NPS), Team Glial Plasticity, 7/9 Quai St Bernard, Paris, France
| | - Marc Moreau
- Centre de Biologie du Développement, Université Toulouse 3, 118 route de Narbonne, F31062 Toulouse, Cedex 04, France; CNRS UMR5547, Toulouse F31062, France
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Organista MF, Martín M, de Celis JM, Barrio R, López-Varea A, Esteban N, Casado M, de Celis JF. The Spalt Transcription Factors Generate the Transcriptional Landscape of the Drosophila melanogaster Wing Pouch Central Region. PLoS Genet 2015; 11:e1005370. [PMID: 26241320 PMCID: PMC4524721 DOI: 10.1371/journal.pgen.1005370] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 06/17/2015] [Indexed: 12/31/2022] Open
Abstract
The Drosophila genes spalt major (salm) and spalt-related (salr) encode Zn-finger transcription factors regulated by the Decapentaplegic (Dpp) signalling pathway in the wing imaginal disc. The function of these genes is required for cell survival and proliferation in the central region of the wing disc, and also for vein patterning in the lateral regions. The identification of direct Salm and Salr target genes, and the analysis of their functions, are critical steps towards understanding the genetic control of growth and patterning of the Drosophila wing imaginal disc by the Dpp pathway. To identify candidate Salm/Salr target genes, we have compared the expression profile of salm/salr knockdown wing discs with control discs in microarray experiments. We studied by in situ hybridization the expression pattern of the genes whose mRNA levels varied significantly, and uncovered a complex transcription landscape regulated by the Spalt proteins in the wing disc. Interestingly, candidate Salm/Salr targets include genes which expression is turned off and genes which expression is positively regulated by Salm/Salr. Furthermore, loss-of-function phenotypic analysis of these genes indicates, for a fraction of them, a requirement for wing growth and patterning. The identification and analysis of candidate Salm/Salr target genes opens a new avenue to reconstruct the genetic structure of the wing, linking the activity of the Dpp pathway to the development of this epithelial tissue. How signalling pathways regulate the formation of organs with a precise size and pattern of differentiation is a fundamental question in developmental genetics. One classical example of the link between signalling and organ development is the regulation of wing disc development by the Decapentaplegic/BMP (Dpp) signalling pathway in Drosophila. A key outcome of this pathway is the transcriptional activation of the spalt major (salm) and spalt related (salr) genes, both encoding transcription factors. In this manner, the identification of Salm/Salr target genes is a critical step towards the understanding of the mode of action of these proteins and the genetic logic underlying the regulation of wing development by the Dpp signalling pathway. In order to identify these target genes, we used expression microarrays, in situ hybridization and phenotypic analysis. We identified an unexpected complexity in the transcriptional landscape of the wing disc that includes genes positively and negatively regulated by Salm/Salr. These findings have major implications for the reconstruction of the genetic hierarchy initiated by the Dpp pathway and leading to the formation of a wing with a correct size and pattern, because some of the genes we identified could explain particular aspects of the sal mutant phenotype.
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Affiliation(s)
- María F. Organista
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Mercedes Martín
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Jesus M. de Celis
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Rosa Barrio
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Ana López-Varea
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Nuria Esteban
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Mar Casado
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
| | - Jose F. de Celis
- Centro de Biología Molecular Severo Ochoa, CSIC and Universidad Autónoma de Madrid, C/Nicolás Cabrera, 1. Universidad Autónoma de Madrid, Madrid, Spain
- * E-mail:
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Ou J, Deng HM, Zheng SC, Huang LH, Feng QL, Liu L. Transcriptomic analysis of developmental features of Bombyx mori wing disc during metamorphosis. BMC Genomics 2014; 15:820. [PMID: 25261999 PMCID: PMC4196006 DOI: 10.1186/1471-2164-15-820] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 09/17/2014] [Indexed: 12/27/2022] Open
Abstract
Background Wing discs of B. mori are transformed to pupal wings during the larva-to-pupa metamorphosis with dramatic morphological and structural changes. To understand these changes at a transcriptional level, RNA-seq of the wing discs from 6-day-old fifth instar larvae (L5D6), prepupae (PP) and pupae (P0) was performed. Results In total, 12,254 transcripts were obtained from the wing disc, out of which 5,287 were identified to be differentially expressed from L5D6 to PP and from PP to P0. The results of comprehensive analysis of RNA-seq data showed that during larvae-to-pupae metamorphosis, many genes of 20E signaling pathway were up-regulated and those of JH signaling pathway were down-regulated. Seventeen transcription factors were significantly up-regulated. Cuticle protein genes (especially wing cuticle protein genes), were most abundant and significantly up-regulated at P0 stage. Genes responsible for the degradation and de novo synthesis of chitin were significantly up-regulated. There were A and B two types of chitin synthases in B. mori, whereas only chitin synthase A was up-regulated. Both trehalose and D-fructose, which are precursors of chitin synthesis, were detected in the hemolymph of L5D6, PP and P0, suggesting de novo synthesis of chitin. However, most of the genes that are related to early wing disc differentiation were down-regulated. Conclusions Extensive transcriptome and DGE profiling data of wing disc during metamorphosis of silkworm have been generated, which provided comprehensive gene expression information at the transcriptional level. These results implied that during the larva-to-pupa metamorphosis, pupal wing development and transition might be mainly controlled by 20E signaling in B. mori. The 17 up-regulated transcription factors might be involved in wing development. Chitin required for pupal wing development might be generated from both degradation of componential chitin and de novo synthesis. Chitin synthase A might be responsible for the chitin synthesis in the pupal wing, while both trehalose and D-fructose might contribute to the de novo synthesis of chitin during the formation of pupal wing. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-820) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | - Qi-Li Feng
- Laboratory of Molecular and Developmental Entomology, Guangdong Provincial Key Lab of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou 510631, China.
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Hamaratoglu F, Affolter M, Pyrowolakis G. Dpp/BMP signaling in flies: from molecules to biology. Semin Cell Dev Biol 2014; 32:128-36. [PMID: 24813173 DOI: 10.1016/j.semcdb.2014.04.036] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 04/30/2014] [Indexed: 01/08/2023]
Abstract
Decapentaplegic (Dpp), the fly homolog of the secreted mammalian BMP2/4 signaling molecules, is involved in almost all aspects of fly development. Dpp has critical functions at all developmental stages, from patterning of the eggshell to the determination of adult intestinal stem cell identity. Here, we focus on recent findings regarding the transcriptional regulatory logic of the pathway, on a new feedback regulator, Pentagone, and on Dpp's roles in scaling and growth of the Drosophila wing.
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Affiliation(s)
- Fisun Hamaratoglu
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
| | - Markus Affolter
- Growth & Development, Biozentrum, University of Basel, Basel, Switzerland
| | - George Pyrowolakis
- Institute for Biology I, Albert-Ludwigs-University of Freiburg, Freiburg, Germany; Centre for Biological Signaling Studies (BIOSS), Albert-Ludwigs-University of Freiburg, Freiburg, Germany
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26
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Vincent JP. Modulating and measuring Wingless signalling. Methods 2014; 68:194-8. [PMID: 24675402 DOI: 10.1016/j.ymeth.2014.03.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2014] [Revised: 03/10/2014] [Accepted: 03/13/2014] [Indexed: 12/19/2022] Open
Abstract
The main Wnt ligand of Drosophila activates a conserved canonical signalling pathway to regulate a plethora of cellular activities during development, regeneration and nervous system function. Here I first describe experimental means of measuring and modulating Wingless signalling in Drosophila cell culture. Various reporters have been devised by placing TCF-binding sites or DNA fragments from known target genes upstream of luciferase-coding sequences. Signalling can be activated in cells by addition of Wingless conditioned medium, treatment with a chemical inhibitor of Shaggy/GSK3 or transfection with a plasmid encoding activated Armadillo (Drosophila β-catenin). Measuring Wingless signalling in intact tissue is somewhat more challenging than in cell culture. Synthetic transgenic reporters have been devised but further improvements are needed to achieve sensitive responsiveness to Wingless at all times and places. As an alternative, gene traps in frizzled3 and notum/wingful, two context-independent endogenous targets, can be used as reporters. It is hoped that further modification of these loci could lead to more versatile and sensitive means of detecting signalling. Many genetic tools are available to trigger ectopic signalling or prevent endogenous signalling. These mostly rely on RNAi-producing transgenes or the generation of mutant patches by mitotic recombination. New developments in genome engineering are opening further means of manipulating the components of Wingless signalling with exquisite temporal and spatial precision.
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Affiliation(s)
- Jean-Paul Vincent
- MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, United Kingdom.
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27
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Organista MF, De Celis JF. The Spalt transcription factors regulate cell proliferation, survival and epithelial integrity downstream of the Decapentaplegic signalling pathway. Biol Open 2012; 2:37-48. [PMID: 23336075 PMCID: PMC3545267 DOI: 10.1242/bio.20123038] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 09/19/2012] [Indexed: 01/25/2023] Open
Abstract
The expression of the spalt genes is regulated by the Decapentaplegic signalling pathway in the Drosophila wing. These genes participate in the patterning of the longitudinal wing veins by regulating the expression of vein-specific genes, and in the establishment of cellular affinities in the central region of the wing blade epithelium. The Spalt proteins act as transcription factors, most likely regulating gene expression by repression, but the identity of their target genes in the wing is still unknown. As a preliminary step to unravel the genetic hierarchy controlled by the Spalt proteins, we have analysed their requirements during wing development, and addressed to what extent they mediate all the functions of the Decapentaplegic pathway in this developmental system. We identify additional functions for Spalt in cell division, survival, and maintenance of epithelial integrity. Thus, Spalt activity is required to promote cell proliferation, acting in the G2/M transition of the cell cycle. The contribution of Spalt to cell division is limited to the central region of the wing blade, as they do not mediate the extra growth triggered by Decapentaplegic signalling in the peripheral regions of the wing disc. In addition, Spalt function is required to maintain cell viability in cells exposed to high levels of Decapentaplegic signalling. This aspect of Spalt function is related to the repression of JNK signalling in the spalt domain of expression. Finally, we further characterise the requirements of Spalt to maintain epithelial integrity by regulating cellular affinities between cells located in the central wing region. Our results indicate that Spalt function mediates most of the requirements identified for Decapentaplegic signalling, contributing to establish the cellular qualities that differentiate central versus peripheral territories in the wing blade.
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Affiliation(s)
- María F Organista
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco , Madrid 28049 , Spain
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Hafezi Y, Bosch JA, Hariharan IK. Differences in levels of the transmembrane protein Crumbs can influence cell survival at clonal boundaries. Dev Biol 2012; 368:358-69. [PMID: 22683826 DOI: 10.1016/j.ydbio.2012.06.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 06/01/2012] [Indexed: 11/19/2022]
Abstract
The survival and growth of individual cells in a tissue can be nonautonomously regulated by the properties of adjacent cells. In mosaic Drosophila imaginal discs, for example, wild-type cells induce the elimination of adjacent slow-growing Minute cells by apoptosis, while, conversely, certain types of faster-growing cells are able to eliminate adjacent wild-type cells. This process, known as cell competition, represents one example of a diverse group of phenomena in which short-range heterotypic interactions result in the selective elimination of one type of cell by another. The mechanisms that designate "winner" and "loser" genotypes in these processes are not known. Here we show that apoptosis is observed preferentially at boundaries that separate populations of cells that express different levels of the transmembrane protein Crumbs (Crb). Cells that express higher levels of Crb tend to be eliminated when they are near cells that express lower levels of Crb. We also observe distortions in the structure of epithelia on either side of boundaries between populations of cells that differ in Crb expression. Thus, while previous studies have focused mostly on the cell autonomous functions of Crb, we show that Crb can regulate cell survival and tissue morphology nonautonomously. Moreover, we find that the extracellular domain (ECD) of Crb, which seems to be dispensable for some of the other characterised functions of Crb, is required to elicit the nonautonomous effects on cell survival. The ECD can also regulate the subcellular localisation of Hippo pathway components, and possibly other proteins, in adjacent cells and may therefore directly mediate these effects. Several genetic lesions alter Crb levels, including loss-of-function mutations in hyperplastic tumour suppressors in the Hippo-Salvador-Warts pathway and in neoplastic tumour suppressor genes, such as scribble. Thus, Crb may be part of a "surveillance mechanism" that is responsible for the cell death that is observed at the boundaries of mutant clones in these cases.
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Affiliation(s)
- Yassi Hafezi
- Department of Molecular and Cell Biology, University of California, Berkeley, 361 LSA, Berkeley, CA 94720-3200, USA
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Morata G, Shlevkov E, Pérez-Garijo A. Mitogenic signaling from apoptotic cells in Drosophila. Dev Growth Differ 2011; 53:168-76. [PMID: 21338343 DOI: 10.1111/j.1440-169x.2010.01225.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Apoptotic cells of Drosophila not only activate caspases, but also are able to secrete developmental signals like Hedgehog (Hh), Decapentaplegic (Dpp) and Wingless (Wg) before dying. Since Dpp and Wg are secreted in growing tissues and behave as growth factors, it was proposed that they play a role in compensatory proliferation, the process by which a growing blastema can restore normal size after massive apoptosis. We discuss recent results showing that there is normal compensatory proliferation in the absence of Dpp/Wg signaling, thus indicating it has no significant role in the process. Furthermore, we argue that Dpp/Wg signaling is not a resident feature of apoptotic cells, but a side effect of the necessary activation of the JNK pathway. Nevertheless, the ectopic JNK/Dpp/Wg signaling may have an important role in tissue regeneration. Recent work in other organisms suggests that paracrine signaling from apoptotic cells may be of general significance in wound healing and tissue regeneration in metazoans.
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Affiliation(s)
- Ginés Morata
- Center for Molecular Biology, Council for Scientific Research-Madrid Autonomous University, Nicolás Cabrera 1, 28049, Madrid, Spain.
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Takemura M, Adachi-Yamada T. Repair responses to abnormalities in morphogen activity gradient. Dev Growth Differ 2011; 53:161-7. [PMID: 21338342 DOI: 10.1111/j.1440-169x.2011.01249.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Establishing and maintaining a morphogen gradient are important in the growth and patterning of developing organs. When a discontinuity in a morphogen signal gradient is created by somatic mutant clones with aberrant intensities of morphogen signals within the Drosophila wing disc, the clones can be removed by apoptosis to restore the morphogen signal gradient. This apoptosis is termed "morphogenetic apoptosis" and has been observed to occur in a cell autonomous or non-cell autonomous manner. This review discusses possible molecular mechanisms of both autonomous and non-cell autonomous apoptosis in addition to similar cellular events in reference to recent findings.
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Affiliation(s)
- Masahiko Takemura
- Department of Biology, Graduate School of Science, Kobe University, Kobe, 657-8501, Japan
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Dorn DC, Dorn A. Structural characterization and primary in vitro cell culture of locust male germline stem cells and their niche. Stem Cell Res 2010; 6:112-28. [PMID: 21256099 DOI: 10.1016/j.scr.2010.11.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 10/17/2010] [Accepted: 11/12/2010] [Indexed: 11/19/2022] Open
Abstract
The establishment of in vitro culture systems to expand stem cells and to elucidate the niche/stem cell interaction is among the most sought-after culture systems of our time. To further investigate niche/stem cell interactions, we evaluated in vitro cultures of isolated intact male germline-niche complexes (i.e., apical complexes), complexes with empty niche spaces, and completely empty niches (i.e., isolated apical cells) from the testes of Locusta migratoria and the interaction of these complexes with isolated germline stem cells, spermatogonia (of transit-amplifying stages), cyst progenitor cells, cyst progenitor cell-like cells, cyst cells, and follicle envelope cells. The structural characteristics of these cell types allow the identification of the different cell types in primary cultures, which we studied in detail by light and electron microscopy. In intact testes germline stem cells strongly adhere to their niche (the apical cell), but emigrate from their niche and form filopodia if the apical complex is put into culture with "standard media." The lively movements of the long filopodia of isolated germline stem cells and spermatogonia may be indicative of their search for specific signals to home to their niche. All other incubated cell types (except for follicle envelope cells) expressed rhizopodia and lobopodia. Nevertheless isolated germline stem cells in culture do not migrate to empty niche spaces of nearby apical cells. This could indicate that apical cells lose their germline stem cell attracting ability in vitro, although apical cells devoid of germline stem cells either by emigration of germline stem cells or by mechanical removal of germline stem cells are capable of surviving in vitro up to 56 days, forming many small lobopodia and performing amoeboid movements. We hypothesize that the breakdown of the apical complex in vitro with standard media interrupts the signaling between the germline stem cells and the niche (and conceivably the cyst progenitor cells) which directs the typical behavior of the male regenerative center. Previously we demonstrated the necessity of the apical cell for the survival of the germline stem cell. From these studies we are now able to culture viable isolated germline stem cells and all cells of its niche complex, although DNA synthesis stops after Day 1 in culture. This enables us to examine the effects of supplements to our standard medium on the interaction of the germline stem cell with its niche, the apical cell. The supplements we evaluated included conditioned medium, tissues, organs, and hemolymph of male locusts, insect hormones, mammalian growth factors, Ca(2+) ion, and a Ca(2+) ionophore. Although biological effects on the germline stem cell and apical cell could be detected with the additives, none of these supplements restored the in vivo behavior of the incubated cell types. We conclude that the strong adhesion between germline stem cells and apical cells in vivo is actively maintained by peripheral factors that reach the apical complex via hemolymph, since a hemolymph-testis barrier does not exist. The in vitro culture model introduced in this study provides a platform to scan for possible regulatory factors that play a key role in a feedback loop that keeps germline stem cell division and sperm disposal in equilibrium.
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Affiliation(s)
- David C Dorn
- Department of Hematology, Hemostasis, Oncology, and Stem-Cell Transplantation, Hannover Medical School, 30625 Hannover, Germany.
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Shbailat SJ, Khila A, Abouheif E. Correlations between spatiotemporal changes in gene expression and apoptosis underlie wing polyphenism in the ant Pheidole morrisi. Evol Dev 2010; 12:580-91. [DOI: 10.1111/j.1525-142x.2010.00443.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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A tumor-suppressing mechanism in Drosophila involving cell competition and the Hippo pathway. Proc Natl Acad Sci U S A 2010; 107:14651-6. [PMID: 20679206 DOI: 10.1073/pnas.1009376107] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mutant larvae for the Drosophila gene lethal giant larva (lgl) develop neoplastic tumors in imaginal discs. However, lgl mutant clones do not form tumors when surrounded by wild-type tissue, suggesting the existence of a tumor-suppressing mechanism. We have investigated the tumorigenic potential of lgl mutant cells by generating wing compartments that are entirely mutant for lgl and also inducing clones of various genetic combinations of lgl(-) cells. We find that lgl(-) compartments can grow indefinitely but lgl(-) clones are eliminated by cell competition. lgl mutant cells may form tumors if they acquire constitutive activity of the Ras pathway (lgl(-) UAS-ras(V12)), which confers proliferation advantage through inhibition of the Hippo pathway. Yet, the majority of lgl(-) UAS-ras(V12) clones are eliminated in spite of their high proliferation rate. The formation of a tumor requires in addition the formation of a microenvironment that allows mutant cells to evade cell competition.
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Shen J, Dahmann C, Pflugfelder GO. Spatial discontinuity of optomotor-blind expression in the Drosophila wing imaginal disc disrupts epithelial architecture and promotes cell sorting. BMC DEVELOPMENTAL BIOLOGY 2010; 10:23. [PMID: 20178599 PMCID: PMC2838827 DOI: 10.1186/1471-213x-10-23] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 02/23/2010] [Indexed: 12/02/2022]
Abstract
Background Decapentaplegic (Dpp) is one of the best characterized morphogens, required for dorso-ventral patterning of the Drosophila embryo and for anterior-posterior (A/P) patterning of the wing imaginal disc. In the larval wing pouch, the Dpp target gene optomotor-blind (omb) is generally assumed to be expressed in a step function above a certain threshold of Dpp signaling activity. Results We show that the transcription factor Omb forms, in fact, a symmetrical gradient on both sides of the A/P compartment boundary. Disruptions of the Omb gradient lead to a re-organization of the epithelial cytoskeleton and to a retraction of cells toward the basal membrane suggesting that the Omb gradient is required for correct epithelial morphology. Moreover, by analysing the shape of omb gain- and loss-of-function clones, we find that Omb promotes cell sorting along the A/P axis in a concentration-dependent manner. Conclusions Our findings show that Omb distribution in the wing imaginal disc is described by a gradient rather than a step function. Graded Omb expression is necessary for normal cell morphogenesis and cell affinity and sharp spatial discontinuities must be avoided to allow normal wing development.
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Affiliation(s)
- Jie Shen
- Department of Entomology, China Agricultural University, Beijing, China
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Martín FA, Herrera SC, Morata G. Cell competition, growth and size control in the Drosophila wing imaginal disc. Development 2009; 136:3747-56. [PMID: 19855017 DOI: 10.1242/dev.038406] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We report here experiments aimed at understanding the connections between cell competition and growth in the Drosophila wing disc. The principal assay has been to generate discs containing marked cells that proliferate at different rates and to study their interactions and their contribution to the final structure. It is known that single clones of fast-dividing cells within a compartment may occupy the larger part of the compartment without affecting its size. This has suggested the existence of interactions involving cell competition between fast- and slow-dividing cells directed to accommodate the contribution of each cell to the final compartment. Here we show that indeed fast-dividing cells can outcompete slow-dividing ones in their proximity. However, we argue that this elimination is of little consequence because preventing apoptosis, and therefore cell competition, in those compartments does not affect the size of the clones or the size of the compartments. Our experiments indicate that cells within a compartment proliferate autonomously at their own rate. The contribution of each cell to the compartment is exclusively determined by its division rate within the frame of a size control mechanism that stops growth once the compartment has reached the final arresting size. This is supported by a computer simulation of the contribution of individual fast clones growing within a population of slower dividing cells and without interacting with them. The values predicted by the simulation are very close to those obtained experimentally.
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Affiliation(s)
- Francisco A Martín
- Centro de Biología Molecular CSIC-UAM, Universidad Autonoma de Madrid, 28049 Madrid, Spain
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Wayburn B, Volk T. LRT, a tendon-specific leucine-rich repeat protein, promotes muscle-tendon targeting through its interaction with Robo. Development 2009; 136:3607-15. [PMID: 19793885 DOI: 10.1242/dev.040329] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Correct muscle migration towards tendon cells, and the adhesion of these two cell types, form the basis for contractile tissue assembly in the Drosophila embryo. While molecules promoting the attraction of muscles towards tendon cells have been described, signals involved in the arrest of muscle migration following the arrival of myotubes at their corresponding tendon cells have yet to be elucidated. Here, we describe a novel tendon-specific transmembrane protein, which we named LRT due to the presence of a leucine-rich repeat domain (LRR) in its extracellular region. Our analysis suggests that LRT acts non-autonomously to better target the muscle and/or arrest its migration upon arrival at its corresponding tendon cell. Muscles in embryos lacking LRT exhibited continuous formation of membrane extensions despite arrival at their corresponding tendon cells, and a partial failure of muscles to target their correct tendon cells. In addition, overexpression of LRT in tendon cells often stalled muscles located close to the tendon cells. LRT formed a protein complex with Robo, and we detected a functional genetic interaction between Robo and LRT at the level of muscle migration behavior. Taken together, our data suggest a novel mechanism by which muscles are targeted towards tendon cells as a result of LRT-Robo interactions. This mechanism may apply to the Robo-dependent migration of a wide variety of cell types.
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Affiliation(s)
- Bess Wayburn
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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Sanders PGT, Muñoz-Descalzo S, Balayo T, Wirtz-Peitz F, Hayward P, Arias AM. Ligand-independent traffic of Notch buffers activated Armadillo in Drosophila. PLoS Biol 2009; 7:e1000169. [PMID: 19668359 PMCID: PMC2716527 DOI: 10.1371/journal.pbio.1000169] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Accepted: 07/02/2009] [Indexed: 12/13/2022] Open
Abstract
Full-length Notch receptor binds to the Wnt pathway effector β-catenin and mediates its endocytosis and degradation, demonstrating a novel mechanism by which Notch may modulate Wnt pathway activity. Notch receptors act as ligand-dependent membrane-tethered transcription factors with a prominent role in binary cell fate decisions during development, which is conserved across species. In addition there is increasing evidence for other functions of Notch, particularly in connection with Wnt signalling: Notch is able to modulate the activity of Armadillo/ß-catenin, the effector of Wnt signalling, in a manner that is independent of its transcriptional activity. Here we explore the mechanism of this interaction in the epithelium of the Drosophila imaginal discs and find that it is mediated by the ligand-independent endocytosis and traffic of the Notch receptor. Our results show that Notch associates with Armadillo near the adherens junctions and that it is rapidly endocytosed promoting the traffic of an activated form of Armadillo into endosomal compartments, where it may be degraded. As Notch has the ability to interact with and downregulate activated forms of Armadillo, it is possible that in vivo Notch regulates the transcriptionally competent pool of Armadillo. These interactions reveal a previously unknown activity of Notch, which serves to buffer the function of activated Armadillo and might underlie some of its transcription-independent effects. Establishment of the correct shape and pattern of tissues within an organism requires the integration of molecular information present in signalling and transcriptional networks and demands delicate exchanges and balances of their activities. A large body of experimental work has revealed close correlations in the activities of two pathways: Notch and Wnt, which suggest the existence of multiple links between them. Notch signalling relies in part upon the activity of the Notch protein, a membrane-bound receptor with a transcription factor domain that can be released from the membrane by proteolytic cleavage. On the other hand Wnt proteins are ligands that trigger changes in the activity of ß-catenin, which is called Armadillo in the fruit fly Drosophila melanogaster. In this study we uncover a previously unknown activity for Notch: endocytosis and trafficking of full length Notch, which targets Armadillo for degradation. This activity of Notch is independent of its ligands, Delta and Serrate, and of its downstream effector, the transcription factor Suppressor of Hairless. We further show that in the absence of Notch, which has been shown to act as a tumor suppressor in mammals, expression of an activated form of Armadillo causes tissue overgrowth and changes in the polarity of cells. Our results suggest that Drosophila Notch can promote the degradation of activated forms of Armadillo and may buffer cells against fluctuations in Wnt signalling activity.
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Affiliation(s)
- Phil G. T. Sanders
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | | | - Tina Balayo
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | | | - Penelope Hayward
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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Umemori M, Habara O, Iwata T, Maeda K, Nishinoue K, Okabe A, Takemura M, Takahashi K, Saigo K, Ueda R, Adachi-Yamada T. RNAi-mediated knockdown showing impaired cell survival in Drosophila wing imaginal disc. GENE REGULATION AND SYSTEMS BIOLOGY 2009; 3:11-20. [PMID: 19838331 PMCID: PMC2758276 DOI: 10.4137/grsb.s2100] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The genetically amenable organism Drosophila melanogaster has been estimated to have 14,076 protein coding genes in the genome, according to the flybase release note R5.13 (http://flybase.bio.indiana.edu/static_pages/docs/release_notes.html). Recent application of RNA interference (RNAi) to the study of developmental biology in Drosophila has enabled us to carry out a systematic investigation of genes affecting various specific phenotypes. In order to search for genes supporting cell survival, we conducted an immunohistochemical examination in which the RNAi of 2,497 genes was independently induced within the dorsal compartment of the wing imaginal disc. Under these conditions, the activities of a stress-activated protein kinase JNK (c-Jun N-terminal kinase) and apoptosis-executing factor Caspase-3 were monitored. Approximately half of the genes displayed a strong JNK or Caspase-3 activation when their RNAi was induced. Most of the JNK activation accompanied Caspase-3 activation, while the opposite did not hold true. Interestingly, the area activating Caspase-3 was more broadly seen than that activating JNK, suggesting that JNK is crucial for induction of non-autonomous apoptosis in many cases. Furthermore, the RNAi of essential factors commonly regulating transcription and translation showed a severe and cell-autonomous apoptosis but also elicited another apoptosis at an adjacent area in a non-autonomous way. We also found that the frequency of apoptosis varies depending on the tissues.
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Affiliation(s)
- Makoto Umemori
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan
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Krejcí A, Bernard F, Housden BE, Collins S, Bray SJ. Direct response to Notch activation: signaling crosstalk and incoherent logic. Sci Signal 2009; 2:ra1. [PMID: 19176515 DOI: 10.1126/scisignal.2000140] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Notch is the receptor in one of a small group of conserved signaling pathways that are essential at multiple stages in development. Although the mechanism of transduction impinges directly on the nucleus to regulate transcription through the CSL [CBF-1/Su(H)/LAG-1] [corrected] DNA binding protein, there are few known direct target genes. Thus, relatively little is known about the immediate cellular consequences of Notch activation. We therefore set out to determine the genome-wide response to Notch activation by analyzing the changes in messenger RNA (mRNA) expression and the sites of CSL occupancy within 30 minutes of activating Notch in Drosophila cells. Through combining these data, we identify high-confidence direct targets of Notch that are implicated in the maintenance of adult muscle progenitors in vivo. These targets are enriched in cell morphogenesis genes and in components of other cell signaling pathways, especially the epidermal growth factor receptor (EGFR) pathway. Also evident are examples of incoherent network logic, where Notch stimulates the expression of both a gene and the repressor of that gene, which may result in a transient window of competence after Notch activation. Furthermore, because targets comprise both positive and negative regulators, cells become poised for both outcomes, suggesting one mechanism through which Notch activation can lead to opposite effects in different contexts.
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Affiliation(s)
- Alena Krejcí
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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40
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A permissive role of Notch in maintaining the DV affinity boundary of the Drosophila wing. Dev Biol 2008; 322:190-8. [DOI: 10.1016/j.ydbio.2008.07.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 07/22/2008] [Accepted: 07/22/2008] [Indexed: 11/21/2022]
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Mao Y, Kerr M, Freeman M. Modulation of Drosophila retinal epithelial integrity by the adhesion proteins capricious and tartan. PLoS One 2008; 3:e1827. [PMID: 18350163 PMCID: PMC2265552 DOI: 10.1371/journal.pone.0001827] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Accepted: 02/17/2008] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND The development of the Drosophila eye imaginal disc requires complex epithelial rearrangements. Cells of the morphogenetic furrow are apically constricted and this leads to a physical indentation in the epithelium. Posterior to the furrow, cells start to rearrange into distinct clusters and eventually form a precisely patterned array of ommatidia. These morphogenetic processes include regulated changes of adhesion between cells. METHODOLOGY/PRINCIPAL FINDINGS Here, we show that two transmembrane adhesion proteins, Capricious and Tartan, have dynamic and complementary expression patterns in the eye imaginal disc. We also describe novel null mutations in capricious and double null mutations in capricious and tartan. We report that they have redundant functions in regulating the architecture of the morphogenetic furrow and ommatidial spacing. CONCLUSIONS/SIGNIFICANCE We conclude that Capricious and Tartan contribute to the adhesive properties of the cells in the morphogenetic furrow and that this regulated adhesion participates in the control of spacing ommatidial clusters.
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Affiliation(s)
- Yanlan Mao
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Martin Kerr
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Matthew Freeman
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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Demontis F, Dahmann C. Apical and lateral cell protrusions interconnect epithelial cells in live Drosophila wing imaginal discs. Dev Dyn 2008; 236:3408-18. [PMID: 17854054 DOI: 10.1002/dvdy.21324] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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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Analysis of Lrrn1 expression and its relationship to neuromeric boundaries during chick neural development. Neural Dev 2007; 2:22. [PMID: 17973992 PMCID: PMC2225406 DOI: 10.1186/1749-8104-2-22] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 10/31/2007] [Indexed: 12/24/2022] Open
Abstract
Background The Drosophila leucine-rich repeat proteins Tartan (TRN) and Capricious (CAPS) mediate cell affinity differences during compartition of the wing imaginal disc. This study aims to identify and characterize the expression of a chick orthologue of TRN/CAPS and examine its potential function in relation to compartment boundaries in the vertebrate central nervous system. Results We identified a complementary DNA clone encoding Leucine-rich repeat neuronal 1 (Lrrn1), a single-pass transmembrane protein with 12 extracellular leucine-rich repeats most closely related to TRN/CAPS. Lrrn1 is dynamically expressed during chick development, being initially localized to the neural plate and tube, where it is restricted to the ventricular layer. It becomes downregulated in boundaries following their formation. In the mid-diencephalon, Lrrn1 expression prefigures the position of the anterior boundary of the zona limitans intrathalamica (ZLI). It becomes progressively downregulated from the presumptive ZLI just before the onset of expression of the signalling molecule Sonic hedgehog (Shh) within the ZLI. In the hindbrain, downregulation at rhombomere boundaries correlates with the emergence of specialized boundary cell populations, in which it is subsequently reactivated. Immunocolocalization studies confirm that Lrrn1 protein is endocytosed from the plasma membrane and is a component of the endosomal system, being concentrated within the early endosomal compartment. Conclusion Chick Lrrn1 is expressed in ventricular layer neuroepithelial cells and is downregulated at boundary regions, where neurogenesis is known to be delayed, or inhibited. The timing of Lrrn1 downregulation correlates closely with the activation of signaling molecule expression at these boundaries. This expression is consistent with the emergence of secondary organizer properties at boundaries and its endosomal localisation suggests that Lrrn1 may regulate the subcellular localisation of specific components of signalling or cell-cell recognition pathways in neuroepithelial cells.
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Sakurai KT, Kojima T, Aigaki T, Hayashi S. Differential control of cell affinity required for progression and refinement of cell boundary during Drosophila leg segmentation. Dev Biol 2007; 309:126-36. [PMID: 17655839 DOI: 10.1016/j.ydbio.2007.07.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2007] [Revised: 06/20/2007] [Accepted: 07/02/2007] [Indexed: 11/23/2022]
Abstract
Domain boundary formation in development involves sorting of different types of cells into separate spatial domains. The segment boundary between tarsus 5 (Ta5) and the pretarsus (Pre) of the Drosophila leg initially appears at the center of the leg disc and progressively sharpens and expands to its final position, accompanied by down-regulation of the cell recognition molecule Capricious and Tartan and cell displacement from Ta5 to Pre across the boundary. Capricious and Tartan are controlled by transcription factor Bar and Al, and their loss of function leads to reduction of cell affinity to wild type neighbors and cell displacement activities. In addition, although the mutant cells formed Ta5/Pre boundary, its progression and sharpening were compromised. Cells overexpressing Capricious or Tartan became invasive within Ta5 and Pre, sometimes escaping the compartmental restriction of cell movement. Dynamic spatiotemporal regulation of cell affinity mediated by Capricious and Tartan is a key property of refinement of the Ta5/Pre boundary.
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Affiliation(s)
- Kayoko T Sakurai
- Riken Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku Kobe 650-0047, Japan
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Kim S, Chung S, Yoon J, Choi KW, Yim J. Ectopic expression of Tollo/Toll-8 antagonizes Dpp signaling and induces cell sorting in the Drosophila wing. Genesis 2007; 44:541-9. [PMID: 17078066 DOI: 10.1002/dvg.20245] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The wing imaginal disc of Drosophila consists of the primordia for the adult wing and the body wall. The zinc-finger transcription factor Teashirt (Tsh) is expressed in the region proximal to the wing primordium and regulates the formation of the wing-body wall boundary. Here, we report that Tollo/Toll-8, a member of Toll family transmembrane proteins, is also expressed proximal to the wing domain. Ectopic expression of Decapentaplegic (Dpp), a morphogen for wing development, represses tollo expression in the proximal domain. Likewise, misexpression of Tollo in the presumptive wing strongly antagonizes the effects of Dpp signaling. The extracellular domain of Tollo containing the Leucine-Rich Repeats (LRR) is required for the inhibition of Dpp signaling in the wing. Furthermore, clones of cells with Tollo overexpression are sorted out from the surrounding wild-type cells, resulting in the formation of epithelial folds around the clone boundaries. Tsh is ectopically induced at the border of Tollo-expressing clones. Despite the strong effects of Tollo overexpression on Dpp signaling and cell sorting, loss-of-function tollo mutants are viable with normal external morphology. Our data suggest that Tollo function might be redundant but is sufficient to antagonize Dpp signaling and induce sorting of Tollo expressing cells from the wing cells to develop proximal cell fate.
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Affiliation(s)
- Sangjoon Kim
- School of Biological Sciences, Seoul National University, Seoul, Korea
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46
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Jaekel R, Klein T. The Drosophila Notch Inhibitor and Tumor Suppressor Gene lethal (2) giant discs Encodes a Conserved Regulator of Endosomal Trafficking. Dev Cell 2006; 11:655-69. [PMID: 17084358 DOI: 10.1016/j.devcel.2006.09.019] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 07/12/2006] [Accepted: 09/21/2006] [Indexed: 11/19/2022]
Abstract
Notch signaling is involved in many developmental and pathological processes, and its activity must be precisely controlled in order to prevent aberrant development and disease. We have previously shown that the tumor suppressor gene lethal (2) giant discs (lgd) is required to prevent ectopic activation of Notch in developmental processes in Drosophila. Here we show that lgd is required in all imaginal disc cells to suppress the activity of the Notch pathway. lgd encodes a member of a poorly characterized protein family present in all animals, which includes a member that is involved in an inheritable form of mental retardation in humans. Our analysis reveals that Lgd is required for endosomal trafficking of Notch and other proteins. In the absence of Lgd, Notch is activated in a ligand-independent manner in probably all imaginal disc cells in an endosomal compartment downstream of the block in hrs mutants.
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Affiliation(s)
- Robert Jaekel
- Institute for Genetics, University of Cologne, Zülpicherstrasse 47, 50674 Cologne, Germany
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Francis JC, Radtke F, Logan MPO. Notch1 signals through Jagged2 to regulate apoptosis in the apical ectodermal ridge of the developing limb bud. Dev Dyn 2006; 234:1006-15. [PMID: 16245338 DOI: 10.1002/dvdy.20590] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The Notch family of receptors is involved in a wide variety of developmental processes, including cell fate specification, cell proliferation, and cell survival decisions during cell differentiation and tissue morphogenesis. Notch1 and Notch ligands are expressed in the developing limbs, and Notch signalling has been implicated in the formation of a variety of tissues that comprise the limb, such as the skeleton, musculature, and vasculature. Notch signalling has also been implicated in regulating overall limb size. We have used a conditional allele of Notch1 in combination with two different Cre transgenic lines to delete Notch1 function either in the limb mesenchyme or in the apical ectodermal ridge (AER) and limb ectoderm. We demonstrate that Notch signalling, involving Notch1 and Jagged2, is required to regulate the number of Fgf8-expressing cells that comprise the AER and that regulation of the levels of fibroblast growth factor signalling is important for the freeing of the digits during normal limb formation. Regulation of the extent of the AER is achieved by Notch signalling positively regulating apoptosis in the AER. We also demonstrate that Notch1 is not required for proper formation of all the derivatives of the limb mesenchyme.
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Affiliation(s)
- Jeffrey C Francis
- Division of Developmental Biology, National Institute for Medical Research, Mill Hill, London, UK
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Yang X, Tomita T, Wines-Samuelson M, Beglopoulos V, Tansey MG, Kopan R, Shen J. Notch1 signaling influences v2 interneuron and motor neuron development in the spinal cord. Dev Neurosci 2006; 28:102-17. [PMID: 16508308 DOI: 10.1159/000090757] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Accepted: 06/21/2005] [Indexed: 12/21/2022] Open
Abstract
The Notch signaling pathway plays a variety of roles in cell fate decisions during development. Previous studies have shown that reduced Notch signaling results in premature differentiation of neural progenitor cells, while increased Notch activities promote apoptotic death of neural progenitor cells in the developing brain. Whether Notch signaling is involved in the specification of neuronal subtypes is unclear. Here we examine the role of Notch1 in the development of neuronal subtypes in the spinal cord using conditional knockout (cKO) mice lacking Notch1 specifically in neural progenitor cells. Notch1 inactivation results in accelerated neuronal differentiation in the ventral spinal cord and gradual disappearance of the ventral central canal. These changes are accompanied by reduced expression of Hes1 and Hes5 and increased expression of Mash1 and Neurogenin 1 and 2. Using markers (Nkx2.2, Nkx6.1, Olig2, Pax6 and Dbx1) for one or multiple progenitor cell types, we found reductions of all subtypes of progenitor cells in the ventral spinal cord of Notch1 cKO mice. Similarly, using markers (Islet1/2, Lim3, Sim1, Chox10, En1 and Evx1/2) specific for motor neurons and distinct classes of interneurons, we found increases in the number of V0-2 interneurons in the ventral spinal cord of Notch1 cKO mice. Specifically, the number of Lim3+/Chox10+ V2 interneurons is markedly increased while the number of Lim3+/Islet+motor neurons is decreased in the Notch1 cKO spinal cord, suggesting that V2 interneurons are generated at the expense of motor neurons in the absence of Notch1. These results provide support for a role of Notch1 in neuronal subtype specification in the ventral spinal cord.
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Affiliation(s)
- Xudong Yang
- Center for Neurologic Diseases, Brigham and Women's Hospital, Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
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Krause C, Wolf C, Hemphälä J, Samakovlis C, Schuh R. Distinct functions of the leucine-rich repeat transmembrane proteins capricious and tartan in the Drosophila tracheal morphogenesis. Dev Biol 2006; 296:253-64. [PMID: 16764850 DOI: 10.1016/j.ydbio.2006.04.462] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 04/24/2006] [Accepted: 04/25/2006] [Indexed: 10/24/2022]
Abstract
A key step in organogenesis of the Drosophila tracheal system is the integration of isolated tracheal metameres into a connected tubular network. The interaction of tracheal cells with surrounding mesodermal cells is crucial in this process. In particular, single mesodermal cells called bridge-cells are essential for the guided outgrowth of dorsal trunk branches to direct formation of the main airway, the dorsal trunk. Here, we present evidence that the two leucine-rich repeat transmembrane proteins Capricious and Tartan contribute differently to the formation of branch interconnections during tracheal development. Capricious is specifically localized on the surface of bridge-cells and facilitates the outgrowing dorsal trunk cells of adjacent metameres toward each other. We show that Capricious requires both extracellular and intracellular domains during tracheal branch outgrowth. In contrast, Tartan is expressed broadly in mesodermal cells and exerts its role in tracheal branch outgrowth through its extracellular domain. We propose that Capricious contributes to the instructive role of bridge-cells whereas Tartan provides permissive substrate for the migrating tracheal cells during the network formation.
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Affiliation(s)
- Cindy Krause
- Abteilung Molekulare Entwicklungsbiologie, Max-Planck-Institut für biophysikalische Chemie, Am Fassberg, D-37077 Göttingen, Germany
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Abstract
Cells in multicellular organisms often do not intermingle freely with each other. Differential cell affinities can contribute to organizing cells into different tissues. Drosophila limbs and the vertebrate central nervous system are subdivided into compartments. Cells in adjacent compartments do not mix. Cell interactions mediated by Notch-family receptors have been implicated in the specification of these compartment boundaries. Two recent reports analyze the role of the Notch signaling pathway in the generation of an affinity boundary in the Drosophila wing. The first report analyzes the connection between Notch and the actin cytoskeleton. The second report analyzes the differential requirements of Notch and the transcription factor Suppressor of Hairless in generating the affinity boundary.
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Affiliation(s)
- Héctor Herranz
- ICREA and Institut de Recerca Biomedica, Parc Cientific de Barcelona, Josep Samitier, Barcelona, Spain
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