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Genome-Wide Screen for New Components of the Drosophila melanogaster Torso Receptor Tyrosine Kinase Pathway. G3-GENES GENOMES GENETICS 2018; 8:761-769. [PMID: 29363515 PMCID: PMC5844297 DOI: 10.1534/g3.117.300491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Patterning of the Drosophila embryonic termini by the Torso (Tor) receptor pathway has long served as a valuable paradigm for understanding how receptor tyrosine kinase signaling is controlled. However, the mechanisms that underpin the control of Tor signaling remain to be fully understood. In particular, it is unclear how the Perforin-like protein Torso-like (Tsl) localizes Tor activity to the embryonic termini. To shed light on this, together with other aspects of Tor pathway function, we conducted a genome-wide screen to identify new pathway components that operate downstream of Tsl. Using a set of molecularly defined chromosomal deficiencies, we screened for suppressors of ligand-dependent Tor signaling induced by unrestricted Tsl expression. This approach yielded 59 genomic suppressor regions, 11 of which we mapped to the causative gene, and a further 29 that were mapped to <15 genes. Of the identified genes, six represent previously unknown regulators of embryonic Tor signaling. These include twins (tws), which encodes an integral subunit of the protein phosphatase 2A complex, and α-tubulin at 84B (αTub84B), a major constituent of the microtubule network, suggesting that these may play an important part in terminal patterning. Together, these data comprise a valuable resource for the discovery of new Tor pathway components. Many of these may also be required for other roles of Tor in development, such as in the larval prothoracic gland where Tor signaling controls the initiation of metamorphosis.
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Determination of EGFR Signaling Output by Opposing Gradients of BMP and JAK/STAT Activity. Curr Biol 2016; 26:2572-2582. [DOI: 10.1016/j.cub.2016.07.073] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 07/25/2016] [Accepted: 07/27/2016] [Indexed: 11/24/2022]
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Fan Y, Richelme S, Avazeri E, Audebert S, Helmbacher F, Dono R, Maina F. Tissue-Specific Gain of RTK Signalling Uncovers Selective Cell Vulnerability during Embryogenesis. PLoS Genet 2015; 11:e1005533. [PMID: 26393505 PMCID: PMC4579069 DOI: 10.1371/journal.pgen.1005533] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 08/25/2015] [Indexed: 12/04/2022] Open
Abstract
The successive events that cells experience throughout development shape their intrinsic capacity to respond and integrate RTK inputs. Cellular responses to RTKs rely on different mechanisms of regulation that establish proper levels of RTK activation, define duration of RTK action, and exert quantitative/qualitative signalling outcomes. The extent to which cells are competent to deal with fluctuations in RTK signalling is incompletely understood. Here, we employ a genetic system to enhance RTK signalling in a tissue-specific manner. The chosen RTK is the hepatocyte growth factor (HGF) receptor Met, an appropriate model due to its pleiotropic requirement in distinct developmental events. Ubiquitously enhanced Met in Cre/loxP-based Rosa26stopMet knock-in context (Del-R26Met) reveals that most tissues are capable of buffering enhanced Met-RTK signalling thus avoiding perturbation of developmental programs. Nevertheless, this ubiquitous increase of Met does compromise selected programs such as myoblast migration. Using cell-type specific Cre drivers, we genetically showed that altered myoblast migration results from ectopic Met expression in limb mesenchyme rather than in migrating myoblasts themselves. qRT-PCR analyses show that ectopic Met in limbs causes molecular changes such as downregulation in the expression levels of Notum and Syndecan4, two known regulators of morphogen gradients. Molecular and functional studies revealed that ectopic Met expression in limb mesenchyme does not alter HGF expression patterns and levels, but impairs HGF bioavailability. Together, our findings show that myoblasts, in which Met is endogenously expressed, are capable of buffering increased RTK levels, and identify mesenchymal cells as a cell type vulnerable to ectopic Met-RTK signalling. These results illustrate that embryonic cells are sensitive to alterations in the spatial distribution of RTK action, yet resilient to fluctuations in signalling levels of an RTK when occurring in its endogenous domain of activity. The need to achieve precise control of RTK activation is highlighted by human pathologies such as congenital malformations and cancers caused by aberrant RTK signalling. Identifying strategies to restrain RTK activity in cancer and/or to reactivate RTKs for counteracting degenerative processes is the focus of intense research efforts. We designed a genetic system to enhance RTK signalling during mouse embryogenesis in order to examine the competence of cells to deal with changes in RTK inputs. Our data reveal that most embryonic cells are capable of: 1) handling moderate perturbations in Met-RTK expression levels, 2) imposing a threshold of intracellular signalling activation despite elevated Met-RTK inputs, and/or 3) integrating variable quantitative levels of Met-RTK signalling within biological responses. Our results also establish that certain cell types, such as limb mesenchyme, are particularly vulnerable to alterations of the spatial distribution of RTK expression. The vulnerability of limb mesenchyme to enhanced Met levels is illustrated by gene expression changes, by interference with HGF chemoattractant effects, and by loss of accessibility to incoming myoblasts, leading to limb muscle defects. These findings highlight how resilience versus vulnerability to RTK fluctuation is strictly linked to cell competence and to the robustness of the developmental programs they undergo.
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Affiliation(s)
- Yannan Fan
- Aix-Marseille Université, CNRS, IBDM UMR 7288, Parc Scientifique de Luminy, Case 907, Marseille, France
| | - Sylvie Richelme
- Aix-Marseille Université, CNRS, IBDM UMR 7288, Parc Scientifique de Luminy, Case 907, Marseille, France
| | - Emilie Avazeri
- Aix-Marseille Université, CNRS, IBDM UMR 7288, Parc Scientifique de Luminy, Case 907, Marseille, France
| | - Stéphane Audebert
- Aix-Marseille Université UM 105, CNRS UMR7258, Inserm U1068, CRCM, Institut Paoli-Calmettes, Marseille, France
| | - Françoise Helmbacher
- Aix-Marseille Université, CNRS, IBDM UMR 7288, Parc Scientifique de Luminy, Case 907, Marseille, France
| | - Rosanna Dono
- Aix-Marseille Université, CNRS, IBDM UMR 7288, Parc Scientifique de Luminy, Case 907, Marseille, France
| | - Flavio Maina
- Aix-Marseille Université, CNRS, IBDM UMR 7288, Parc Scientifique de Luminy, Case 907, Marseille, France
- * E-mail:
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Gaur K, Li J, Wang D, Dutta P, Yan SJ, Tsurumi A, Land H, Wu G, Li WX. The Birt-Hogg-Dubé tumor suppressor Folliculin negatively regulates ribosomal RNA synthesis. Hum Mol Genet 2012; 22:284-99. [PMID: 23077212 DOI: 10.1093/hmg/dds428] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Birt-Hogg-Dubé syndrome (BHD) is a human cancer disorder caused by mutations in the tumor suppressor gene Folliculin (FLCN) with unknown biological functions. Here, we show that the Drosophila homolog of FLCN, dFLCN (a.k.a. dBHD) localizes to the nucleolus and physically interacts with the 19S proteasomal ATPase, Rpt4, a nucleolar resident and known regulator of rRNA transcription. Downregulation of dFLCN resulted in an increase in nucleolar volume and upregulation of rRNA synthesis, whereas dFLCN overexpression reduced rRNA transcription and counteracted the effects of Rpt4 on rRNA production by preventing the association of Rpt4 with the rDNA locus. We further show that human FLCN exhibited evolutionarily conserved function and that Rpt4 knockdown inhibits the growth of FLCN-deficient human renal cancer cells in mouse xenografts. Our study suggests that FLCN functions as a tumor suppressor by negatively regulating rRNA synthesis.
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Affiliation(s)
- Kriti Gaur
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
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Tsurumi A, Xia F, Li J, Larson K, LaFrance R, Li WX. STAT is an essential activator of the zygotic genome in the early Drosophila embryo. PLoS Genet 2011; 7:e1002086. [PMID: 21637778 PMCID: PMC3102735 DOI: 10.1371/journal.pgen.1002086] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 04/04/2011] [Indexed: 11/18/2022] Open
Abstract
In many organisms, transcription of the zygotic genome begins during the
maternal-to-zygotic transition (MZT), which is characterized by a dramatic
increase in global transcriptional activities and coincides with embryonic stem
cell differentiation. In Drosophila, it has been shown that
maternal morphogen gradients and ubiquitously distributed general transcription
factors may cooperate to upregulate zygotic genes that are essential for pattern
formation in the early embryo. Here, we show that Drosophila
STAT (STAT92E) functions as a general transcription factor that, together with
the transcription factor Zelda, induces transcription of a large number of
early-transcribed zygotic genes during the MZT. STAT92E is present in the early
embryo as a maternal product and is active around the MZT. DNA–binding
motifs for STAT and Zelda are highly enriched in promoters of early zygotic
genes but not in housekeeping genes. Loss of Stat92E in the
early embryo, similarly to loss of zelda, preferentially
down-regulates early zygotic genes important for pattern formation. We further
show that STAT92E and Zelda synergistically regulate transcription. We conclude
that STAT92E, in conjunction with Zelda, plays an important role in
transcription of the zygotic genome at the onset of embryonic development. In the initial phase of the early embryo, transcription is inactive and
development is supported by maternally derived gene products. During a time
window termed the maternal-to-zygotic transition (MZT), the maternal gene
products are degraded and the zygotically expressed genes required for
embryogenesis initiate their transcription. How the dramatic upregulation of
zygotic genes during the MZT is achieved is not completely understood, although
it has been shown that the transcription factor Zelda plays a critical role. In
this manuscript, we show that Drosophila STAT (STAT92E)
functions as a general transcription factor that, together with Zelda, induces
transcription of a large number of early-transcribed zygotic genes during the
MZT. We further show that STAT92E and Zelda synergistically regulate
transcription. Thus, multiple transcription factors, such as STAT92E and Zelda,
cooperate to control transcription of the zygotic genome at the onset of
embryonic development.
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Affiliation(s)
- Amy Tsurumi
- Department of Biomedical Genetics, University of Rochester Medical
Center, Rochester, New York, United States of America
| | - Fan Xia
- Department of Biomedical Genetics, University of Rochester Medical
Center, Rochester, New York, United States of America
| | - Jinghong Li
- Department of Biomedical Genetics, University of Rochester Medical
Center, Rochester, New York, United States of America
- Department of Medicine, University of California San Diego, La Jolla,
California, United States of America
| | - Kimberly Larson
- Department of Biomedical Genetics, University of Rochester Medical
Center, Rochester, New York, United States of America
| | - Russell LaFrance
- Department of Biomedical Genetics, University of Rochester Medical
Center, Rochester, New York, United States of America
| | - Willis X. Li
- Department of Biomedical Genetics, University of Rochester Medical
Center, Rochester, New York, United States of America
- Department of Medicine, University of California San Diego, La Jolla,
California, United States of America
- * E-mail:
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Salamanca HH, Fuda N, Shi H, Lis JT. An RNA aptamer perturbs heat shock transcription factor activity in Drosophila melanogaster. Nucleic Acids Res 2011; 39:6729-40. [PMID: 21576228 PMCID: PMC3159435 DOI: 10.1093/nar/gkr206] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Heat shock transcription factor (HSF1) is a conserved master regulator that orchestrates the protection of normal cells from stress. However, HSF1 also protects abnormal cells and is required for carcinogenesis. Here, we generate an highly specific RNA aptamer (iaRNAHSF1) that binds Drosophila HSF1 and inhibits HSF1 binding to DNA. In Drosophila animals, iaRNAHSF1 reduces normal Hsp83 levels and promotes developmental abnormalities, mimicking the spectrum of phenotypes that occur when Hsp83 activity is reduced. The HSF1 aptamer also effectively suppresses the abnormal growth phenotypes induced by constitutively active forms of the EGF receptor and Raf oncoproteins. Our results indicate that HSF1 contributes toward the morphological development of animal traits by controlling the expression of molecular chaperones under normal growth conditions. Additionally, our study demonstrates the utility of the RNA aptamer technology as a promising chemical genetic approach to investigate biological mechanisms, including cancer and for identifying effective drug targets in vivo.
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Affiliation(s)
- H Hans Salamanca
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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Avila FW, Erickson JW. Drosophila JAK/STAT pathway reveals distinct initiation and reinforcement steps in early transcription of Sxl. Curr Biol 2007; 17:643-8. [PMID: 17363251 DOI: 10.1016/j.cub.2007.02.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 01/05/2007] [Accepted: 02/07/2007] [Indexed: 10/23/2022]
Abstract
X-linked signal elements (XSEs) communicate the dose of X chromosomes to the regulatory-switch gene Sex-lethal (Sxl) during Drosophila sex determination. Unequal XSE expression in precellular XX and XY nuclei ensures that only XX embryos will activate the establishment promoter, SxlPe, to produce a pulse of the RNA-binding protein, SXL [1]. Once XSE protein concentrations have been assessed, SxlPe is inactivated and the maintenance promoter, SxlPm, is turned on in both sexes; however, only in females is SXL present to direct the SxlPm-derived transcripts to be spliced into functional mRNA [2, 3]. Thereafter, Sxl is maintained in the on state by positive autoregulatory RNA splicing [2]. Once set in the stable on (female) or off (male) state, Sxl controls somatic sexual development through control of downstream effectors of sexual differentiation and dosage compensation [1, 4]. Most XSEs encode transcription factors that bind SxlPe, but the XSE unpaired (upd) encodes a secreted ligand for the JAK/STAT pathway [5-7]. We show that although STAT directly regulates SxlPe, it is dispensable for promoter activation. Instead, JAK/STAT is needed to maintain high-level SxlPe expression in order to ensure Sxl autoregulation in XX embryos. Thus, upd is a unique XSE that augments, rather than defines, the initial sex-determination signal.
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Affiliation(s)
- Frank W Avila
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843, USA
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Pepple KL, Anderson AE, Frankfort BJ, Mardon G. A genetic screen in Drosophila for genes interacting with senseless during neuronal development identifies the importin moleskin. Genetics 2006; 175:125-41. [PMID: 17110483 PMCID: PMC1774993 DOI: 10.1534/genetics.106.065680] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Senseless (Sens) is a conserved transcription factor required for normal development of the Drosophila peripheral nervous system. In the Drosophila retina, sens is necessary and sufficient for differentiation of R8 photoreceptors and interommatidial bristles (IOBs). When Sens is expressed in undifferentiated cells posterior to the morphogenetic furrow, ectopic IOBs are formed. This phenotype was used to identify new members of the sens pathway in a dominant modifier screen. Seven suppressor and three enhancer complementation groups were isolated. Three groups from the screen are the known genes Delta, lilliputian, and moleskin/DIM-7 (msk), while the remaining seven groups represent novel genes with previously undefined functions in neural development. The nuclear import gene msk was identified as a potent suppressor of the ectopic interommatidial bristle phenotype. In addition, msk mutant adult eyes are extremely disrupted with defects in multiple cell types. Reminiscent of the sens mutant phenotype, msk eyes demonstrate reductions in the number of R8 photoreceptors due to an R8 to R2,5 fate switch, providing genetic evidence that Msk is a component of the sens pathway. Interestingly, in msk tissue, the loss of R8 fate occurs earlier than with sens and suggests a previously unidentified stage of R8 development between atonal and sens.
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Affiliation(s)
- Kathryn L Pepple
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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Li WX. Functions and mechanisms of receptor tyrosine kinase Torso signaling: lessons from Drosophila embryonic terminal development. Dev Dyn 2005; 232:656-72. [PMID: 15704136 PMCID: PMC3092428 DOI: 10.1002/dvdy.20295] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The Torso receptor tyrosine kinase (RTK) is required for cell fate specification in the terminal regions (head and tail) of the early Drosophila embryo. Torso contains a split tyrosine kinase domain and belongs to the type III subgroup of the RTK superfamily that also includes the platelet-derived growth factor receptors, stem cell or steel factor receptor c-Kit proto-oncoprotein, colony-stimulating factor-1 receptor, and vascular endothelial growth factor receptor. The Torso pathway has been a model system for studying RTK signal transduction. Genetic and biochemical studies of Torso signaling have provided valuable insights into the biological functions and mechanisms of RTK signaling during early Drosophila embryogenesis.
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Affiliation(s)
- Willis X Li
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York 14642, USA.
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Zettervall CJ, Anderl I, Williams MJ, Palmer R, Kurucz E, Ando I, Hultmark D. A directed screen for genes involved in Drosophila blood cell activation. Proc Natl Acad Sci U S A 2004; 101:14192-7. [PMID: 15381778 PMCID: PMC521135 DOI: 10.1073/pnas.0403789101] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
An attack by a parasitic wasp activates a vigorous cellular immune response in Drosophila larvae. This response is manifested by an increased number of circulating cells, the hemocytes, and by the appearance of a specialized class of hemocyte, the lamellocytes, which participate in the encapsulation and killing of the parasite. To study the molecular mechanisms of this response, we have overexpressed different genes in the hemocytes, by using the GAL4-upstream activating sequence system and a hemocyte-specific Hemese-GAL4 driver. Multiple transgenes were tested, representing several important signaling pathways. We found that the proliferation response and the activation of lamellocyte formation are independent phenomena. A drastic increase in the number of circulating hemocytes is caused by receptor tyrosine kinases, such as Egfr, Pvr, and Alk, as well as by the downstream signaling components Ras85D and pointed, supporting the notion that the Ras-mitogen-activated protein kinase pathway regulates hemocyte numbers. In the case of Pvr and Alk, this phenotype also is accompanied by lamellocyte formation. By contrast, constitutively active hopscotch and hemipterous give massive activation of lamellocyte formation with little or no increase in total hemocyte numbers. This finding indicates that both the Jak/Stat and the Jun kinase pathways affect lamellocyte formation. Still other signals, mediated by aop(ACT), Toll(10b), and Rac1 expression, cause a simultaneous increase in lamellocyte and total cell numbers, and the same effect is seen when WNT signaling is suppressed. We conclude that the activation of a cellular response is complex and affected by multiple signaling pathways.
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Affiliation(s)
- Carl-Johan Zettervall
- Umeå Centre for Molecular Pathogenesis, Byggnad 6L, Umeå University, S-901 87 Umeå, Sweden
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