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Jiang L. Cell-Mediated Branch Fusion in the Drosophila Trachea. Results Probl Cell Differ 2024; 71:91-100. [PMID: 37996674 DOI: 10.1007/978-3-031-37936-9_5] [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] [Indexed: 11/25/2023]
Abstract
The Drosophila trachea is an interconnected network of epithelial tubes, which delivers gases throughout the entire organism. It is the premier model to study the development of tubular organs, such as the human lung, kidney, and blood vessels. The Drosophila embryonic trachea derives from a series of segmentally repeated clusters. The tracheal precursor cells in each cluster migrate out in a stereotyped pattern to form primary branches. Thereafter, the neighboring branches need to fuse to form an interconnected tubular network. The connection between neighboring branches is orchestrated by specialized cells, called fusion cells. These cells fuse with their counterparts to form a tube with a contiguous lumen. Branch fusion is a multi-step process that includes cell migration, cell adhesion, cytoskeleton track formation, vesicle trafficking, membrane fusion, and lumen formation. This review summarizes the current knowledge on fusion process in the Drosophila trachea. These mechanisms will greatly contribute to our understanding of branch fusion in mammalian systems.
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Affiliation(s)
- Lan Jiang
- Department of Biological Sciences, Oakland University, Rochester, MI, USA.
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2
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Taira Y, Wada H, Hayashi S, Kageyama Y. polished rice mediates ecdysone-dependent control of Drosophila embryonic organogenesis. Genes Cells 2021; 26:269-281. [PMID: 33621395 DOI: 10.1111/gtc.12841] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 02/05/2021] [Accepted: 02/05/2021] [Indexed: 01/08/2023]
Abstract
In many animals, progression of developmental stages is temporally controlled by steroid hormones. In Drosophila, the level of ecdysone titer oscillates and developmental stage transitions, such as larval molting and metamorphosis, are induced at each of ecdysone peaks. Ecdysone titer also peaks at the stage of mid-embryogenesis and the embryonic ecdysone is necessary for morphogenesis of several organs, although the regulatory mechanisms of embryonic organogenesis dependent on ecdysone signaling are still open questions. In this study, we find that absence or interruption of embryonic ecdysone signaling caused multiple defects in the tracheal system, including decrease in luminal protein deposition, uneven dilation of the dorsal trunk and loss of terminal branches. We also reveal that an ecdysone-inducible gene polished rice (pri) is essential for tip cell fate decision in dorsal branches. As over-expression of pri can restore the defects caused by disturbance of ecdysone biosynthesis, pri functions as one of the major mediators of embryonic ecdysone signal in tracheogenesis. These results demonstrate that ecdysone and its downstream target pri play essential roles in tracheal development by modulating cell fate decision.
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Affiliation(s)
- Yuki Taira
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan
| | - Housei Wada
- Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Shigeo Hayashi
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan.,Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Yuji Kageyama
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan.,Biosignal Research Center, Kobe University, Kobe, Japan
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3
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Palmer MA, Nelson CM. Fusion of airways during avian lung development constitutes a novel mechanism for the formation of continuous lumena in multicellular epithelia. Dev Dyn 2020; 249:1318-1333. [DOI: 10.1002/dvdy.215] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/01/2020] [Accepted: 05/28/2020] [Indexed: 12/16/2022] Open
Affiliation(s)
- Michael A. Palmer
- Department of Chemical & Biological Engineering Princeton University Princeton New Jersey USA
| | - Celeste M. Nelson
- Department of Chemical & Biological Engineering Princeton University Princeton New Jersey USA
- Department of Molecular Biology Princeton University Princeton New Jersey USA
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4
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Miao G, Hayashi S. Escargot controls the sequential specification of two tracheal tip cell types by suppressing FGF signaling in Drosophila. Development 2016; 143:4261-4271. [PMID: 27742749 PMCID: PMC5117212 DOI: 10.1242/dev.133322] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 10/04/2016] [Indexed: 01/05/2023]
Abstract
Extrinsic branching factors promote the elongation and migration of tubular organs. In the Drosophila tracheal system, Branchless (Drosophila FGF) stimulates the branching program by specifying tip cells that acquire motility and lead branch migration to a specific destination. Tip cells have two alternative cell fates: the terminal cell (TC), which produces long cytoplasmic extensions with intracellular lumen, and the fusion cell (FC), which mediates branch connections to form tubular networks. How Branchless controls this specification of cells with distinct shapes and behaviors is unknown. Here we report that this cell type diversification involves the modulation of FGF signaling by the zinc-finger protein Escargot (Esg), which is expressed in the FC and is essential for its specification. The dorsal branch begins elongation with a pair of tip cells with high FGF signaling. When the branch tip reaches its final destination, one of the tip cells becomes an FC and expresses Esg. FCs and TCs differ in their response to FGF: TCs are attracted by FGF, whereas FCs are repelled. Esg suppresses ERK signaling in FCs to control this differential migratory behavior. Summary: The migratory behavior of tracheal fusion cells is controlled by the FGF-induced expression of the transcription factor Escargot, which subsequently suppresses ERK signaling.
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Affiliation(s)
- Guangxia Miao
- Laboratory for Morphogenetic Signaling, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.,Department of Biology, Kobe University Graduate School of Science, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8051, Japan
| | - Shigeo Hayashi
- Laboratory for Morphogenetic Signaling, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan .,Department of Biology, Kobe University Graduate School of Science, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8051, Japan
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5
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Abstract
Morphogenesis is the developmental process by which tissues and organs acquire the shape that is critical to their function. Here, we review recent advances in our understanding of the mechanisms that drive morphogenesis in the developing eye. These investigations have shown that regulation of the actin cytoskeleton is central to shaping the presumptive lens and retinal epithelia that are the major components of the eye. Regulation of the actin cytoskeleton is mediated by Rho family GTPases, by signaling pathways and indirectly, by transcription factors that govern the expression of critical genes. Changes in the actin cytoskeleton can shape cells through the generation of filopodia (that, in the eye, connect adjacent epithelia) or through apical constriction, a process that produces a wedge-shaped cell. We have also learned that one tissue can influence the shape of an adjacent one, probably by direct force transmission, in a process we term inductive morphogenesis. Though these mechanisms of morphogenesis have been identified using the eye as a model system, they are likely to apply broadly where epithelia influence the shape of organs during development.
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6
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Caviglia S, Luschnig S. Tube fusion: Making connections in branched tubular networks. Semin Cell Dev Biol 2014; 31:82-90. [DOI: 10.1016/j.semcdb.2014.03.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/03/2014] [Accepted: 03/14/2014] [Indexed: 11/16/2022]
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7
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Abstract
Tyrosine phosphorylation plays a significant role in a wide range of cellular processes. The Drosophila genome encodes more than 20 receptor tyrosine kinases and extensive studies in the past 20 years have illustrated their diverse roles and complex signaling mechanisms. Although some receptor tyrosine kinases have highly specific functions, others strikingly are used in rather ubiquitous manners. Receptor tyrosine kinases regulate a broad expanse of processes, ranging from cell survival and proliferation to differentiation and patterning. Remarkably, different receptor tyrosine kinases share many of the same effectors and their hierarchical organization is retained in disparate biological contexts. In this comprehensive review, we summarize what is known regarding each receptor tyrosine kinase during Drosophila development. Astonishingly, very little is known for approximately half of all Drosophila receptor tyrosine kinases.
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Affiliation(s)
- Richelle Sopko
- Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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8
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Abstract
The graded distribution of morphogens underlies many of the tissue patterns that form during development. How morphogens disperse from a localized source and how gradients in the target tissue form has been under debate for decades. Recent imaging studies and biophysical measurements have provided evidence for various morphogen transport models ranging from passive mechanisms, such as free or hindered extracellular diffusion, to cell-based dispersal by transcytosis or cytonemes. Here, we analyze these transport models using the morphogens Nodal, fibroblast growth factor and Decapentaplegic as case studies. We propose that most of the available data support the idea that morphogen gradients form by diffusion that is hindered by tortuosity and binding to extracellular molecules.
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Affiliation(s)
- Patrick Müller
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
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9
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10
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Genetic analysis of fibroblast growth factor signaling in the Drosophila eye. G3-GENES GENOMES GENETICS 2012; 2:23-8. [PMID: 22384378 PMCID: PMC3276192 DOI: 10.1534/g3.111.001495] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 11/02/2011] [Indexed: 11/18/2022]
Abstract
The development of eyes in Drosophila involves intricate epithelial reorganization events for accurate positioning of cells and proper formation and organization of ommatidial clusters. We demonstrate that Branchless (Bnl), the fibroblast growth factor ligand, regulates restructuring events in the eye disc primordium from as early as the emergence of clusters from a morphogenetic front to the cellular movements during pupal eye development. Breathless (Btl) functions as the fibroblast growth factor receptor to mediate Bnl signal, and together they regulate expression of DE-cadherin, Crumbs, and Actin. In addition, in the eye Bnl regulates the temporal onset and extent of retinal basal glial cell migration by activating Btl in the glia. We hypothesized that the Bnl functions in the eye are Hedgehog dependent and represent novel aspects of Bnl signaling not explored previously.
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11
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Abstract
Extracellular signaling molecules have crucial roles in development and homeostasis, and their incorrect deployment can lead to developmental defects and disease states. Signaling molecules are released from sending cells, travel to target cells, and act over length scales of several orders of magnitude, from morphogen-mediated patterning of small developmental fields to hormonal signaling throughout the organism. We discuss how signals are modified and assembled for transport, which routes they take to reach their targets, and how their range is affected by mobility and stability.
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Affiliation(s)
- Patrick Müller
- Department of Molecular and Cellular Biology, Harvard Stem Cell Institute, Broad Institute, Center for Brain Science, FAS Center for Systems Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
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12
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Geudens I, Gerhardt H. Coordinating cell behaviour during blood vessel formation. Development 2011; 138:4569-83. [PMID: 21965610 DOI: 10.1242/dev.062323] [Citation(s) in RCA: 274] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The correct development of blood vessels is crucial for all aspects of tissue growth and physiology in vertebrates. The formation of an elaborate hierarchically branched network of endothelial tubes, through either angiogenesis or vasculogenesis, relies on a series of coordinated morphogenic events, but how individual endothelial cells adopt specific phenotypes and how they coordinate their behaviour during vascular patterning is unclear. Recent progress in our understanding of blood vessel formation has been driven by advanced imaging techniques and detailed analyses that have used a combination of powerful in vitro, in vivo and in silico model systems. Here, we summarise these models and discuss their advantages and disadvantages. We then review the different stages of blood vessel development, highlighting the cellular mechanisms and molecular players involved at each step and focusing on cell specification and coordination within the network.
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Affiliation(s)
- Ilse Geudens
- Vascular Patterning Laboratory, Vesalius Research Center, VIB, 3000 Leuven, Belgium
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13
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14
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Affiliation(s)
- Antoine A Khalil
- Department of Dermatology, University of Würzburg, Würzburg, Germany.
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15
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McCroskery S, Chaudhry A, Lin L, Daniels MP. Transmembrane agrin regulates filopodia in rat hippocampal neurons in culture. Mol Cell Neurosci 2006; 33:15-28. [PMID: 16860570 DOI: 10.1016/j.mcn.2006.06.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Revised: 06/02/2006] [Accepted: 06/08/2006] [Indexed: 11/27/2022] Open
Abstract
Filopodia mediate axon guidance, neurite branching and synapse formation, but the membrane molecules that regulate neuronal filopodia in response to extracellular cues are largely unknown. The transmembrane isoform of the proteoglycan agrin, expressed predominantly in the CNS, may regulate neurite outgrowth, synapse formation and excitatory signaling. Here we demonstrate that agrin positively regulates neuronal filopodia. Over-expression of TM-agrin caused the formation of excess filopodia on neurites of hippocampal neurons cultured 1-6 days. Conversely, suppression of agrin expression by siRNA reduced the number of filopodia. Time lapse analysis indicated that endogenous TM-agrin regulates filopodia by increasing their stability and initiation. The N-terminal half of agrin was necessary for induction of filopodia, and over-expression of TM-agrin in a neuronal cell line increased Cdc42 activation, suggesting a role for Cdc42 downstream of agrin. By positively regulating filopodia in developing neurons, TM-agrin may influence the pattern of neurite outgrowth and synapse formation.
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Affiliation(s)
- Seumas McCroskery
- Laboratory of Cell Biology, National Heart Lung and Blood Institute, NIH, 50 South Drive, Bldg. 50, Rm 3318, Bethesda, MD 20892, USA
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16
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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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17
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Merabet S, Ebner A, Affolter M. The Drosophila Extradenticle and Homothorax selector proteins control branchless/FGF expression in mesodermal bridge-cells. EMBO Rep 2006; 6:762-8. [PMID: 16007069 PMCID: PMC1369138 DOI: 10.1038/sj.embor.7400462] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 05/16/2005] [Accepted: 05/19/2005] [Indexed: 11/09/2022] Open
Abstract
The stereotyped outgrowth of tubular branches of the Drosophila tracheal system is orchestrated by the local and highly dynamic expression profile of branchless (bnl), which encodes a secreted fibroblast growth factor (FGF)-like molecule. Despite the importance of the spatial and temporal bnl regulation, little is known about the upstream mechanisms that establish its complex expression pattern. Here, we show that the Extradenticle and Homothorax selector proteins control bnl transcription in a single cell per segment, the mesodermal bridge-cell. In addition, we observed that a key determinant of bridge-cell specification, the transcription factor Hunchback, is also required for bnl expression. Therefore, we propose that one of the functions of the bridge-cell is to synthesize and secrete the chemoattractant Bnl. These findings provide a hitherto unknown and interesting link between combinatorial inputs of transcription factors, cell-specific ligand expression and organ morphogenesis.
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Affiliation(s)
- Samir Merabet
- Biozentrum der Universität Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Andreas Ebner
- Biozentrum der Universität Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Markus Affolter
- Biozentrum der Universität Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
- Tel: +41 61 267 2077; Fax: +41 61 267 2078; E-mail:
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18
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Hsiung F, Ramirez-Weber FA, Iwaki DD, Kornberg TB. Dependence of Drosophila wing imaginal disc cytonemes on Decapentaplegic. Nature 2005; 437:560-3. [PMID: 16177792 DOI: 10.1038/nature03951] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Accepted: 06/16/2005] [Indexed: 11/09/2022]
Abstract
The anterior/posterior (A/P) and dorsal/ventral (D/V) compartment borders that subdivide the wing imaginal discs of Drosophila third instar larvae are each associated with a developmental organizer. Decapentaplegic (Dpp), a member of the transforming growth factor-beta (TGF-beta) superfamily, embodies the activity of the A/P organizer. It is produced at the A/P organizer and distributes in a gradient of decreasing concentration to regulate target genes, functioning non-autonomously to regulate growth and patterning of both the anterior and posterior compartments. Wingless (Wg) is produced at the D/V organizer and embodies its activity. The mechanisms that distribute Dpp and Wg are not known, but proposed mechanisms include extracellular diffusion, successive transfers between neighbouring cells, vesicle-mediated movement, and direct transfer via cytonemes. Cytonemes are actin-based filopodial extensions that have been found to orient towards the A/P organizer from outlying cells. Here we show that in the wing disc, cytonemes orient towards both the A/P and D/V organizers, and that their presence and orientation correlates with Dpp signalling. We also show that the Dpp receptor, Thickveins (Tkv), is present in punctae that move along cytonemes. These observations are consistent with a role for cytonemes in signal transduction.
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Affiliation(s)
- Frank Hsiung
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, USA
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19
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Abstract
We review insights in signaling pathways controlling cell polarization and cytoskeletal organization during chemotactic movement in Dictyostelium amoebae and neutrophils. We compare and contrast these insights with our current understanding of pathways controlling chemotactic movements in more-complex multicellular developmental contexts.
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Affiliation(s)
- Markus Affolter
- Department of Cell Biology, Biozentrum University of Basel, Klingelbergstr. 70, CH-4056 Basel, Switzerland
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20
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Myat MM, Lightfoot H, Wang P, Andrew DJ. A molecular link between FGF and Dpp signaling in branch-specific migration of the Drosophila trachea. Dev Biol 2005; 281:38-52. [PMID: 15848387 PMCID: PMC2827869 DOI: 10.1016/j.ydbio.2005.02.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 01/27/2005] [Accepted: 02/07/2005] [Indexed: 11/18/2022]
Abstract
The tracheal system of Drosophila embryos achieves its archetypal branching pattern through a series of cell migration events requiring the FGF, Dpp, and Wg/WNT signaling pathways. To gain insight into tracheal cell migration, we performed an F4 EMS mutagenesis screen to generate and characterize new mutations resulting in tracheal defects. From 2591 mutagenized third chromosome lines, we identified 33 mutations with defects in tracheal development, corresponding to 12 distinct complementation groups. The new mutations included novel hypomorphic alleles of the FGF receptor gene, breathless, and the ETS-domain transcription factor gene, pointed. We show that reduced function of either breathless or pointed specifically affects migration of the dorsal and ventral tracheal branches, more specific functions than previously described for these genes. Our analysis reveals that breathless and pointed control dorsal branch migration through transcriptional regulation of the Dpp pathway effectors, Knirps and Knirps-related, which are necessary for migration of this branch. We further show that expression of knirps or knirps-related rescues dorsal but not ventral branch migration in the breathless hypomorph. These studies support a model in which both the Dpp- and the FGF-signaling pathways control expression of knirps and knirps-related, thereby regulating cell migration during dorsal branch formation.
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Affiliation(s)
- Monn Monn Myat
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
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21
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Abstract
In sprouting angiogenesis, endothelial cells must orientate in the tissue environment in order to effectively invade tissues and form vascular patterns according to the local needs. Here, we review recent data indicating that sprouting angiogenesis is a guided process resembling axonal guidance and insect trachea formation. Angiogenesis requires functional specialization of endothelial cells within the sprout. Cells situated at the tip of the sprouts sense and navigate the environment using long filopodia, whereas cells in the sprout stalks proliferate and form a vascular lumen. Migration of the tip cells depends on a graded distribution of VEGF-A and activation of VEGFR2 located on the tip-cell filopodia. Proliferation in the stalk is concomitantly regulated by the local VEGF-A levels. Thus, the shape of the VEGF-A gradient controls the balance between tip cell migration and stalk cell proliferation, which in turn determines the initial vascular pattern. An imbalance between the two processes may explain why abnormal vascular patterns develop in pathological angiogenesis.
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Affiliation(s)
- Holger Gerhardt
- Vascular Biology Laboratory, Cancer Research UK, 44 Lincoln's Inn Fields, London WC 2A 3PX, UK.
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22
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Abstract
Successful cell migration depends on the careful regulation of the timing of movement, the guidance of motile cells, and cytoskeletal and adhesive changes within the cells. This review focuses on genes that act cell-autonomously to promote these aspects of cell migration in Drosophila. We discuss recent advances in understanding the migration of the ovarian border cells, embryonic blood cells, primordial germ cells, somatic gonadal precursors, and tracheal cells. Comparison of genes that regulate these processes to those that promote tumorigenesis and metastasis in mammals demonstrates that studies in fruit flies are uncovering new genes highly relevant to cancer biology.
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Affiliation(s)
- Michelle Starz-Gaiano
- Department of Biological Chemistry, Johns Hopkins Medical Institute, Wood Basic Science Building 413, 725 N Wolfe Street, Baltimore, MD 21205, USA
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23
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Behr M, Riedel D, Schuh R. The claudin-like megatrachea is essential in septate junctions for the epithelial barrier function in Drosophila. Dev Cell 2003; 5:611-20. [PMID: 14536062 DOI: 10.1016/s1534-5807(03)00275-2] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Vertebrate claudin proteins are integral components of tight junctions, which function as paracellular diffusion barriers in epithelia. We identified Megatrachea (Mega), a Drosophila transmembrane protein homologous to claudins, and show that it acts in septate junctions, the corresponding structure of invertebrates. Our analysis revealed that Mega has transepithelial barrier function similar to the claudins. Also, Mega is necessary for normal tracheal cell morphogenesis but not for apicobasal polarity or epithelial integrity. In addition, we present evidence that Mega is essential for localization of the septate junction protein complex Coracle/Neurexin. The results indicate that claudin-like proteins are functionally conserved between vertebrates and Drosophila.
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Affiliation(s)
- Matthias Behr
- Abteilung Molekulare Entwicklungsbiologie, Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg, 37077 Göttingen, Germany
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24
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Dammai V, Adryan B, Lavenburg KR, Hsu T. Drosophila awd, the homolog of human nm23, regulates FGF receptor levels and functions synergistically with shi/dynamin during tracheal development. Genes Dev 2003; 17:2812-24. [PMID: 14630942 PMCID: PMC280629 DOI: 10.1101/gad.1096903] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Human nm23 has been implicated in suppression of metastasis in various cancers, but the underlying mechanism of such activity has not been fully understood. Using Drosophila tracheal system as a genetic model, we examined the function of the Drosophila homolog of nm23, the awd gene, in cell migration. We show that loss of Drosophila awd results in dysregulated tracheal cell motility. This phenotype can be suppressed by reducing the dosage of the chemotactic FGF receptor (FGFR) homolog, breathless (btl), indicating that btl and awd are functionally antagonists. In addition, mutants of shi/dynamin show similar tracheal phenotypes as in awd and exacerbate those in awd mutant, suggesting defects in vesicle-mediated turnover of FGFR in the awd mutant. Consistent with this, Btl-GFP chimera expressed from a cognate btl promoter-driven system accumulate at high levels on tracheal cell membrane of awd mutants as well as in awd RNA duplex-treated cultured cells. Thus, we propose that awd regulates tracheal cell motility by modulating the FGFR levels, through a dynamin-mediated pathway.
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Affiliation(s)
- Vincent Dammai
- Department of Pathology and Laboratory Medicine, and Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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25
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Abstract
Many organs including the mammalian lung and vascular system consist of branched tubular networks that transport essential gases or fluids, but the genetic programs that control the development of these complex three-dimensional structures are not well understood. The Drosophila melanogaster tracheal (respiratory) system is a network of interconnected epithelial tubes that transports oxygen and other gases in the body and provides a paradigm of branching morphogenesis. It develops by sequential sprouting of primary, secondary, and terminal branches from an epithelial sac of approximately 80 cells in each body segment of the embryo. Mapping of the cell movements and shape changes during the sprouting process has revealed that distinct mechanisms of epithelial migration and tube formation are used at each stage of branching. Genetic dissection of the process has identified a general program in which a fibroblast growth factor (FGF) and fibroblast growth factor receptor (FGFR) are used repeatedly to control branch budding and outgrowth. At each stage of branching, the mechanisms controlling FGF expression and the downstream signal transduction pathway change, altering the pattern and structure of the branches that form. During terminal branching, FGF expression is regulated by hypoxia, ensuring that tracheal structure matches cellular oxygen need. A branch diversification program operates in parallel to the general budding program: Regional signals locally modify the general program, conferring specific structural features and other properties on individual branches, such as their substrate outgrowth preferences, differences in tube size and shape, and the ability to fuse to other branches to interconnect the network.
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Affiliation(s)
- Amin Ghabrial
- Howard Hughes Medical Institute, Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307, USA
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26
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Hemphälä J, Uv A, Cantera R, Bray S, Samakovlis C. Grainy head controls apical membrane growth and tube elongation in response to Branchless/FGF signalling. Development 2003; 130:249-58. [PMID: 12466193 DOI: 10.1242/dev.00218] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Epithelial organogenesis involves concerted movements and growth of distinct subcellular compartments. We show that apical membrane enlargement is critical for lumenal elongation of the Drosophila airways, and is independently controlled by the transcription factor Grainy head. Apical membrane overgrowth in grainy head mutants generates branches that are too long and tortuous without affecting epithelial integrity, whereas Grainy head overexpression limits lumenal growth. The chemoattractant Branchless/FGF induces tube outgrowth, and we find that it upregulates Grainy head activity post-translationally, thereby controlling apical membrane expansion to attain its key role in branching. We favour a two-step model for FGF in branching: first, induction of cell movement and apical membrane growth, and second, activation of Grainy head to limit lumen elongation, ensuring that branches reach and attain their characteristic lengths.
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Affiliation(s)
- Johanna Hemphälä
- Department of Developmental Biology, Wenner-Gren Institute, Stockholm University, S-10691 Stockholm, Sweden
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