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Bernasek SM, Hur SSJ, Peláez-Restrepo N, Boisclair Lachance JF, Bakker R, Navarro HT, Sanchez-Luege N, Amaral LAN, Bagheri N, Rebay I, Carthew RW. Ratiometric sensing of Pnt and Yan transcription factor levels confers ultrasensitivity to photoreceptor fate transitions in Drosophila. Development 2023; 150:dev201467. [PMID: 36942737 PMCID: PMC10163347 DOI: 10.1242/dev.201467] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 03/13/2023] [Indexed: 03/23/2023]
Abstract
Cell state transitions are often triggered by large changes in the concentrations of transcription factors and therefore large differences in their stoichiometric ratios. Whether cells can elicit transitions using modest changes in the ratios of co-expressed factors is unclear. Here, we investigate how cells in the Drosophila eye resolve state transitions by quantifying the expression dynamics of the ETS transcription factors Pnt and Yan. Eye progenitor cells maintain a relatively constant ratio of Pnt/Yan protein, despite expressing both proteins with pulsatile dynamics. A rapid and sustained twofold increase in the Pnt/Yan ratio accompanies transitions to photoreceptor fates. Genetic perturbations that modestly disrupt the Pnt/Yan ratio produce fate transition defects consistent with the hypothesis that transitions are normally driven by a twofold shift in the ratio. A biophysical model based on cooperative Yan-DNA binding coupled with non-cooperative Pnt-DNA binding illustrates how twofold ratio changes could generate ultrasensitive changes in target gene transcription to drive fate transitions. Thus, coupling cell state transitions to the Pnt/Yan ratio sensitizes the system to modest fold-changes, conferring robustness and ultrasensitivity to the developmental program.
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Affiliation(s)
- Sebastian M. Bernasek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Suzy S. J. Hur
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Nicolás Peláez-Restrepo
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Howard Hughes Medical Institute (HHMI), Hanna H. Gray Fellows Program
| | | | - Rachael Bakker
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | | | - Nicelio Sanchez-Luege
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Luís A. N. Amaral
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
- Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL 60208, USA
- Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
- NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL 60208, USA
| | - Neda Bagheri
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
- Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL 60208, USA
- NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL 60208, USA
- Chemistry of Life Processes, Northwestern University, Evanston, IL 60208, USA
| | - Ilaria Rebay
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Richard W. Carthew
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
- NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL 60208, USA
- Department of Biochemistry and Molecular Genetics, Northwestern University, Evanston, IL 60611, USA
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2
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Bonini NM. A perspective on Drosophila genetics and its insight into human neurodegenerative disease. Front Mol Biosci 2022; 9:1060796. [PMID: 36518845 PMCID: PMC9743296 DOI: 10.3389/fmolb.2022.1060796] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 10/28/2022] [Indexed: 09/07/2023] Open
Abstract
Drosophila has been long appreciated as a classic genetic system for its ability to define gene function in vivo. Within the last several decades, the fly has also emerged as a premiere system for modeling and defining mechanisms of human disease by expressing dominant human disease genes and analyzing the effects. Here I discuss key aspects of this latter approach that first intrigued me to focus my laboratory research on this idea. Differences between the loss-of-function vs. the gain-of-function approach are raised-and the insight of these approaches for appreciating mechanisms that contribute to human neurodegenerative disease. The application of modifier genetics, which is a prominent goal of models of human disease, has implications for how specific genes or pathways intersect with the dominant disease-associated mechanisms. Models of human disease will continue to reveal unanticipated insight into fundamental cellular processes-insight that might be harder to glean from classical genetic methodologies vs modifier genetics of disease.
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Affiliation(s)
- Nancy M. Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, PA, United States
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3
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Weasner BP, Kumar JP. The early history of the eye-antennal disc of Drosophila melanogaster. Genetics 2022; 221:6573236. [PMID: 35460415 PMCID: PMC9071535 DOI: 10.1093/genetics/iyac041] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 03/04/2022] [Indexed: 12/15/2022] Open
Abstract
A pair of eye-antennal imaginal discs give rise to nearly all external structures of the adult Drosophila head including the compound eyes, ocelli, antennae, maxillary palps, head epidermis, and bristles. In the earliest days of Drosophila research, investigators would examine thousands of adult flies in search of viable mutants whose appearance deviated from the norm. The compound eyes are dispensable for viability and perturbations to their structure are easy to detect. As such, the adult compound eye and the developing eye-antennal disc emerged as focal points for studies of genetics and developmental biology. Since few tools were available at the time, early researchers put an enormous amount of thought into models that would explain their experimental observations-many of these hypotheses remain to be tested. However, these "ancient" studies have been lost to time and are no longer read or incorporated into today's literature despite the abundance of field-defining discoveries that are contained therein. In this FlyBook chapter, I will bring these forgotten classics together and draw connections between them and modern studies of tissue specification and patterning. In doing so, I hope to bring a larger appreciation of the contributions that the eye-antennal disc has made to our understanding of development as well as draw the readers' attention to the earliest studies of this important imaginal disc. Armed with the today's toolkit of sophisticated genetic and molecular methods and using the old papers as a guide, we can use the eye-antennal disc to unravel the mysteries of development.
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Affiliation(s)
- Brandon P Weasner
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Justin P Kumar
- Department of Biology, Indiana University, Bloomington, IN 47405, USA,Corresponding author: Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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4
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Maywald ML, Picciotto C, Lepa C, Bertgen L, Yousaf FS, Ricker A, Klingauf J, Krahn MP, Pavenstädt H, George B. Rap1 Activity Is Essential for Focal Adhesion and Slit Diaphragm Integrity. Front Cell Dev Biol 2022; 10:790365. [PMID: 35372328 PMCID: PMC8972170 DOI: 10.3389/fcell.2022.790365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 02/24/2022] [Indexed: 11/24/2022] Open
Abstract
Glomerular podocytes build, with their intercellular junctions, part of the kidney filter. The podocyte cell adhesion protein, nephrin, is essential for developing and maintaining slit diaphragms as functional loss in humans results in heavy proteinuria. Nephrin expression and function are also altered in many adult-onset glomerulopathies. Nephrin signals from the slit diaphragm to the actin cytoskeleton and integrin β1 at focal adhesions by recruiting Crk family proteins, which can interact with the Rap guanine nucleotide exchange factor 1 C3G. As Rap1 activity affects focal adhesion formation, we hypothesize that nephrin signals via Rap1 to integrin β. To address this issue, we combined Drosophila in vivo and mammalian cell culture experiments. We find that Rap1 is necessary for correct targeting of integrin β to focal adhesions in Drosophila nephrocytes, which also form slit diaphragm-like structures. In the fly, the Rap1 activity is important for signaling of the nephrin ortholog to integrin β, as well as for nephrin-dependent slit diaphragm integrity. We show by genetic interaction experiments that Rap1 functions downstream of nephrin signaling to integrin β and downstream of nephrin signaling necessary for slit diaphragm integrity. Similarly, in human podocyte culture, nephrin activation results in increased activation of Rap1. Thus, Rap1 is necessary for downstream signal transduction of nephrin to integrin β.
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Affiliation(s)
- Mee-Ling Maywald
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Cara Picciotto
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Carolin Lepa
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Luisa Bertgen
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | | | - Andrea Ricker
- Institute of Medical Physics and Biophysics, Westfälische Wilhelms-University Münster, Münster, Germany
| | - Jürgen Klingauf
- Institute of Medical Physics and Biophysics, Westfälische Wilhelms-University Münster, Münster, Germany
| | - Michael P. Krahn
- Medizinische Klinik D, Medical Cell Biology, University Hospital Münster, Münster, Germany
| | | | - Britta George
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
- *Correspondence: Britta George,
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5
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Clark JF, Soriano PM. Pulling back the curtain: The hidden functions of receptor tyrosine kinases in development. Curr Top Dev Biol 2022; 149:123-152. [PMID: 35606055 PMCID: PMC9127239 DOI: 10.1016/bs.ctdb.2021.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Receptor tyrosine kinases (RTKs) are a conserved superfamily of transmembrane growth factor receptors that drive numerous cellular processes during development and in the adult. Upon activation, multiple adaptors and signaling effector proteins are recruited to binding site motifs located within the intracellular domain of the RTK. These RTK-effector interactions drive subsequent intracellular signaling cascades involved in canonical RTK signaling. Genetic dissection has revealed that alleles of Fibroblast Growth Factor receptors (FGFRs) that lack all canonical RTK signaling still retain some kinase-dependent biological activity. Here we examine how genetic analysis can be used to understand the mechanism by which RTKs drive multiple developmental processes via canonical signaling while revealing noncanonical activities. Recent data from both FGFRs and other RTKs highlight potential noncanonical roles in cell adhesion and nuclear signaling. The data supporting such functions are discussed as are recent technologies that have the potential to provide valuable insight into the developmental significance of these noncanonical activities.
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Affiliation(s)
- James F Clark
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Philippe M Soriano
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States.
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6
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Sawyer JK, Kabiri Z, Montague RA, Allen SR, Stewart R, Paramore SV, Cohen E, Zaribafzadeh H, Counter CM, Fox DT. Exploiting codon usage identifies intensity-specific modifiers of Ras/MAPK signaling in vivo. PLoS Genet 2020; 16:e1009228. [PMID: 33296356 PMCID: PMC7752094 DOI: 10.1371/journal.pgen.1009228] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/21/2020] [Accepted: 10/27/2020] [Indexed: 01/05/2023] Open
Abstract
Signal transduction pathways are intricately fine-tuned to accomplish diverse biological processes. An example is the conserved Ras/mitogen-activated-protein-kinase (MAPK) pathway, which exhibits context-dependent signaling output dynamics and regulation. Here, by altering codon usage as a novel platform to control signaling output, we screened the Drosophila genome for modifiers specific to either weak or strong Ras-driven eye phenotypes. Our screen enriched for regions of the genome not previously connected with Ras phenotypic modification. We mapped the underlying gene from one modifier to the ribosomal gene RpS21. In multiple contexts, we show that RpS21 preferentially influences weak Ras/MAPK signaling outputs. These data show that codon usage manipulation can identify new, output-specific signaling regulators, and identify RpS21 as an in vivo Ras/MAPK phenotypic regulator. Cellular communication is critical in controlling the growth of organs and must be carefully regulated to prevent disease. The Ras signaling pathway is frequently used for cellular communication of tissue growth regulation but can operate at different signaling strengths. Here, we used a novel strategy to identify genes that specifically tune weak or strong Ras signaling states. We find that the gene RpS21 preferentially tunes weak Ras signaling states.
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Affiliation(s)
- Jessica K. Sawyer
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Zahra Kabiri
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Ruth A. Montague
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Scott R. Allen
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Rebeccah Stewart
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Sarah V. Paramore
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Erez Cohen
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Hamed Zaribafzadeh
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Christopher M. Counter
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Duke Cancer Institute, Duke University School of Medicine, Durham, North Carolina, United States of America
- * E-mail: (CMC); (DTF)
| | - Donald T. Fox
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Duke Cancer Institute, Duke University School of Medicine, Durham, North Carolina, United States of America
- * E-mail: (CMC); (DTF)
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7
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Wu C, Boisclair Lachance JF, Ludwig MZ, Rebay I. A context-dependent bifurcation in the Pointed transcriptional effector network contributes specificity and robustness to retinal cell fate acquisition. PLoS Genet 2020; 16:e1009216. [PMID: 33253156 PMCID: PMC7728396 DOI: 10.1371/journal.pgen.1009216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 12/10/2020] [Accepted: 10/21/2020] [Indexed: 11/18/2022] Open
Abstract
Spatiotemporally precise and robust cell fate transitions, which depend on specific signaling cues, are fundamental to the development of appropriately patterned tissues. The fidelity and precision with which photoreceptor fates are recruited in the Drosophila eye exemplifies these principles. The fly eye consists of a highly ordered array of ~750 ommatidia, each of which contains eight distinct photoreceptors, R1-R8, specified sequentially in a precise spatial pattern. Recruitment of R1-R7 fates requires reiterative receptor tyrosine kinase / mitogen activated protein kinase (MAPK) signaling mediated by the transcriptional effector Pointed (Pnt). However the overall signaling levels experienced by R2-R5 cells are distinct from those experienced by R1, R6 and R7. A relay mechanism between two Pnt isoforms initiated by MAPK activation directs the universal transcriptional response. Here we ask how the generic Pnt response is tailored to these two rounds of photoreceptor fate transitions. We find that during R2-R5 specification PntP2 is coexpressed with a closely related but previously uncharacterized isoform, PntP3. Using CRISPR/Cas9-generated isoform specific null alleles we show that under otherwise wild type conditions, R2-R5 fate specification is robust to loss of either PntP2 or PntP3, and that the two activate pntP1 redundantly; however under conditions of reduced MAPK activity, both are required. Mechanistically, our data suggest that intrinsic activity differences between PntP2 and PntP3, combined with positive and unexpected negative transcriptional auto- and cross-regulation, buffer first-round fates against conditions of compromised RTK signaling. In contrast, in a mechanism that may be adaptive to the stronger signaling environment used to specify R1, R6 and R7 fates, the Pnt network resets to a simpler topology in which PntP2 uniquely activates pntP1 and auto-activates its own transcription. We propose that differences in expression patterns, transcriptional activities and regulatory interactions between Pnt isoforms together facilitate context-appropriate cell fate specification in different signaling environments.
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Affiliation(s)
- Chudong Wu
- Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, Illinois, United States of America
| | | | - Michael Z. Ludwig
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
| | - Ilaria Rebay
- Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, Illinois, United States of America
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois, United States of America
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8
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Ong T, Trivedi N, Wakefield R, Frase S, Solecki DJ. Siah2 integrates mitogenic and extracellular matrix signals linking neuronal progenitor ciliogenesis with germinal zone occupancy. Nat Commun 2020; 11:5312. [PMID: 33082319 PMCID: PMC7576183 DOI: 10.1038/s41467-020-19063-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Accepted: 09/15/2020] [Indexed: 12/12/2022] Open
Abstract
Evidence is lacking as to how developing neurons integrate mitogenic signals with microenvironment cues to control proliferation and differentiation. We determine that the Siah2 E3 ubiquitin ligase functions in a coincidence detection circuit linking responses to the Shh mitogen and the extracellular matrix to control cerebellar granule neurons (CGN) GZ occupancy. We show that Shh signaling maintains Siah2 expression in CGN progenitors (GNPs) in a Ras/Mapk-dependent manner. Siah2 supports ciliogenesis in a feed-forward fashion by restraining cilium disassembly. Efforts to identify sources of the Ras/Mapk signaling led us to discover that GNPs respond to laminin, but not vitronectin, in the GZ microenvironment via integrin β1 receptors, which engages the Ras/Mapk cascade with Shh, and that this niche interaction is essential for promoting GNP ciliogenesis. As GNPs leave the GZ, differentiation is driven by changing extracellular cues that diminish Siah2-activity leading to primary cilia shortening and attenuation of the mitogenic response. In neural development, progenitors transition from a proliferative to a differentiated state. Here, the authors show that cerebellar granule neurons retract primary cilia as they exit their proliferative niche upon decreased ECM engagement, enabling radial migration due to loss of Shh sensitivity.
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Affiliation(s)
- Taren Ong
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Niraj Trivedi
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Randall Wakefield
- Cell and Tissue Imaging Center-EM, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - Sharon Frase
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
| | - David J Solecki
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.
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9
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Van R, Cuevas-Navarro A, Castel P, McCormick F. The molecular functions of RIT1 and its contribution to human disease. Biochem J 2020; 477:2755-2770. [PMID: 32766847 PMCID: PMC7787054 DOI: 10.1042/bcj20200442] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/01/2020] [Accepted: 07/02/2020] [Indexed: 12/29/2022]
Abstract
RIT1 is a member of the Ras family of GTPases that direct broad cellular physiological responses through tightly controlled signaling networks. The canonical Ras GTPases are well-defined regulators of the RAF/MEK/ERK pathway and mutations in these are pathogenic in cancer and a class of developmental disorders termed RASopathies. Emerging clinical evidences have now demonstrated a role for RIT1 in RASopathies, namely Noonan syndrome, and various cancers including lung adenocarcinoma and myeloid malignancies. While RIT1 has been mostly described in the context of neuronal differentiation and survival, the mechanisms underlying aberrant RIT1-mediated signaling remain elusive. Here, we will review efforts undertaken to characterize the biochemical and functional properties of the RIT1 GTPase at the molecular, cellular, and organismal level, as well as provide a phenotypic overview of different human conditions caused by RIT1 mutations. Deeper understanding of RIT1 biological function and insight to its pathogenic mechanisms are imperative to developing effective therapeutic interventions for patients with RIT1-mutant Noonan syndrome and cancer.
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Affiliation(s)
- Richard Van
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| | - Antonio Cuevas-Navarro
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| | - Pau Castel
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| | - Frank McCormick
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
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10
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Dlugos CP, Picciotto C, Lepa C, Krakow M, Stöber A, Eddy ML, Weide T, Jeibmann A, P Krahn M, Van Marck V, Klingauf J, Ricker A, Wedlich-Söldner R, Pavenstädt H, Klämbt C, George B. Nephrin Signaling Results in Integrin β1 Activation. J Am Soc Nephrol 2019; 30:1006-1019. [PMID: 31097607 DOI: 10.1681/asn.2018040362] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 03/18/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Patients with certain mutations in the gene encoding the slit diaphragm protein Nephrin fail to develop functional slit diaphragms and display severe proteinuria. Many adult-onset glomerulopathies also feature alterations in Nephrin expression and function. Nephrin signals from the podocyte slit diaphragm to the Actin cytoskeleton by recruiting proteins that can interact with C3G, a guanine nucleotide exchange factor of the small GTPase Rap1. Because Rap activity affects formation of focal adhesions, we hypothesized that Nephrin transmits signals to the Integrin receptor complex, which mediates podocyte adhesion to the extracellular matrix. METHODS To investigate Nephrin's role in transmitting signals to the Integrin receptor complex, we conducted genetic studies in Drosophila nephrocytes and validated findings from Drosophila in a cultured human podocyte model. RESULTS Drosophila nephrocytes form a slit diaphragm-like filtration barrier and express the Nephrin ortholog Sticks and stones (Sns). A genetic screen identified c3g as necessary for nephrocyte function. In vivo, nephrocyte-specific gene silencing of sns or c3g compromised nephrocyte filtration and caused nephrocyte diaphragm defects. Nephrocytes with impaired Sns or C3G expression displayed an altered localization of Integrin and the Integrin-associated protein Talin. Furthermore, gene silencing of c3g partly rescued nephrocyte diaphragm defects of an sns overexpression phenotype, pointing to genetic interaction of sns and c3g in nephrocytes. We also found that activated Nephrin recruited phosphorylated C3G and resulted in activation of Integrin β1 in cultured podocytes. CONCLUSIONS Our findings suggest that Nephrin can mediate a signaling pathway that results in activation of Integrin β1 at focal adhesions, which may affect podocyte attachment to the extracellular matrix.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Christian Klämbt
- Neurobiology, Westfälische-Wilhelms University Münster, Münster, Germany
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11
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A New Strategy to Control and Eradicate "Undruggable" Oncogenic K-RAS-Driven Pancreatic Cancer: Molecular Insights and Core Principles Learned from Developmental and Evolutionary Biology. Cancers (Basel) 2018; 10:cancers10050142. [PMID: 29757973 PMCID: PMC5977115 DOI: 10.3390/cancers10050142] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 05/08/2018] [Accepted: 05/10/2018] [Indexed: 12/15/2022] Open
Abstract
Oncogenic K-RAS mutations are found in virtually all pancreatic cancers, making K-RAS one of the most targeted oncoproteins for drug development in cancer therapies. Despite intense research efforts over the past three decades, oncogenic K-RAS has remained largely “undruggable”. Rather than targeting an upstream component of the RAS signaling pathway (i.e., EGFR/HER2) and/or the midstream effector kinases (i.e., RAF/MEK/ERK/PI3K/mTOR), we propose an alternative strategy to control oncogenic K-RAS signal by targeting its most downstream signaling module, Seven-In-Absentia Homolog (SIAH). SIAH E3 ligase controls the signal output of oncogenic K-RAS hyperactivation that drives unchecked cell proliferation, uncontrolled tumor growth, and rapid cancer cell dissemination in human pancreatic cancer. Therefore, SIAH is an ideal therapeutic target as it is an extraordinarily conserved downstream signaling gatekeeper indispensable for proper RAS signaling. Guided by molecular insights and core principles obtained from developmental and evolutionary biology, we propose an anti-SIAH-centered anti-K-RAS strategy as a logical and alternative anticancer strategy to dampen uncontrolled K-RAS hyperactivation and halt tumor growth and metastasis in pancreatic cancer. The clinical utility of developing SIAH as both a tumor-specific and therapy-responsive biomarker, as well as a viable anti-K-RAS drug target, is logically simple and conceptually innovative. SIAH clearly constitutes a major tumor vulnerability and K-RAS signaling bottleneck in pancreatic ductal adenocarcinoma (PDAC). Given the high degree of evolutionary conservation in the K-RAS/SIAH signaling pathway, an anti-SIAH-based anti-PDAC therapy will synergize with covalent K-RAS inhibitors and direct K-RAS targeted initiatives to control and eradicate pancreatic cancer in the future.
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12
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Duan H, de Navas LF, Hu F, Sun K, Mavromatakis YE, Viets K, Zhou C, Kavaler J, Johnston RJ, Tomlinson A, Lai EC. The mir-279/996 cluster represses receptor tyrosine kinase signaling to determine cell fates in the Drosophila eye. Development 2018. [PMID: 29540498 DOI: 10.1242/dev.159053] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Photoreceptors in the crystalline Drosophila eye are recruited by receptor tyrosine kinase (RTK)/Ras signaling mediated by Epidermal growth factor receptor (EGFR) and the Sevenless (Sev) receptor. Analyses of an allelic deletion series of the mir-279/996 locus, along with a panel of modified genomic rescue transgenes, show that Drosophila eye patterning depends on both miRNAs. Transcriptional reporter and activity sensor transgenes reveal expression and function of miR-279/996 in non-neural cells of the developing eye. Moreover, mir-279/996 mutants exhibit substantial numbers of ectopic photoreceptors, particularly of R7, and cone cell loss. These miRNAs restrict RTK signaling in the eye, since mir-279/996 nulls are dominantly suppressed by positive components of the EGFR pathway and enhanced by heterozygosity for an EGFR repressor. miR-279/996 limit photoreceptor recruitment by targeting multiple positive RTK/Ras signaling components that promote photoreceptor/R7 specification. Strikingly, deletion of mir-279/996 sufficiently derepresses RTK/Ras signaling so as to rescue a population of R7 cells in R7-specific RTK null mutants boss and sev, which otherwise completely lack this cell fate. Altogether, we reveal a rare setting of developmental cell specification that involves substantial miRNA control.
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Affiliation(s)
- Hong Duan
- Department of Developmental Biology, Sloan-Kettering Institute, 1275 York Ave, Box 252, New York, NY 10065, USA
| | - Luis F de Navas
- Department of Developmental Biology, Sloan-Kettering Institute, 1275 York Ave, Box 252, New York, NY 10065, USA
| | - Fuqu Hu
- Department of Developmental Biology, Sloan-Kettering Institute, 1275 York Ave, Box 252, New York, NY 10065, USA
| | - Kailiang Sun
- Department of Developmental Biology, Sloan-Kettering Institute, 1275 York Ave, Box 252, New York, NY 10065, USA.,Program in Neuroscience, Weill Cornell Medical College, New York, NY 10065, USA
| | - Yannis E Mavromatakis
- Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
| | - Kayla Viets
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Cyrus Zhou
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Joshua Kavaler
- Department of Biology, Colby College, Waterville, ME 04901, USA
| | - Robert J Johnston
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Andrew Tomlinson
- Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
| | - Eric C Lai
- Department of Developmental Biology, Sloan-Kettering Institute, 1275 York Ave, Box 252, New York, NY 10065, USA
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13
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Abstract
The rapid spread of mosquito resistance to currently available insecticides, and the current lack of an efficacious malaria vaccine are among many challenges that affect large-scale efforts for malaria control. As goals of malaria elimination and eradication are put forth, new vector-control paradigms and tools and/or further optimization of current vector-control products are required to meet public health demands. Vector control remains the most effective measure to prevent malaria transmission and present gains against malaria mortality and morbidity may be maintained as long as vector-intervention strategies are sustained and adapted to underlying vector-related transmission dynamics. The following provides a brief overview of vector-control strategies and tools either in use or under development and evaluation that are intended to exploit key entomological parameters toward driving down transmission.
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Affiliation(s)
- Neil F Lobo
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - Nicole L Achee
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - John Greico
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - Frank H Collins
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
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14
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Ong T, Solecki DJ. Seven in Absentia E3 Ubiquitin Ligases: Central Regulators of Neural Cell Fate and Neuronal Polarity. Front Cell Neurosci 2017; 11:322. [PMID: 29081737 PMCID: PMC5646344 DOI: 10.3389/fncel.2017.00322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 09/26/2017] [Indexed: 12/31/2022] Open
Abstract
During neural development, neural precursors transition from a proliferative state within their germinal niches to a migratory state as they relocate to their final laminar positions. Transitions across these states are coupled with dynamic alterations in cellular polarity. This key feature can be seen throughout the developing vertebrate brain, in which neural stem cells give rise to multipolar or unpolarized transit-amplifying progenitors. These transit-amplifying progenitors then expand to give rise to mature neuronal lineages that become polarized as they initiate radial migration to their final laminar positions. The conventional understanding of the cellular polarity regulatory program has revolved around signaling cascades and transcriptional networks. In this review, we discuss recent discoveries concerning the role of the Siah2 ubiquitin ligase in initiating neuronal polarity during cerebellar development. Given the unique features of Siah ubiquitin ligases, we highlight some of the key substrates that play important roles in cellular polarity and propose a function for the Siah ubiquitin proteasome pathway in mediating a post-translational regulatory network to control the onset of polarization.
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Affiliation(s)
- Taren Ong
- Cancer and Developmental Biology Track, Integrated Biomedical Sciences Graduate Program, University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - David J Solecki
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, United States
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15
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Golden A. From phenologs to silent suppressors: Identifying potential therapeutic targets for human disease. Mol Reprod Dev 2017; 84:1118-1132. [PMID: 28834577 DOI: 10.1002/mrd.22880] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 08/04/2017] [Indexed: 12/16/2022]
Abstract
Orthologous phenotypes, or phenologs, are seemingly unrelated phenotypes generated by mutations in a conserved set of genes. Phenologs have been widely observed and accepted by those who study model organisms, and allow one to study a set of genes in a model organism to learn more about the function of those genes in other organisms, including humans. At the cellular and molecular level, these conserved genes likely function in a very similar mode, but are doing so in different tissues or cell types and can result in different phenotypic effects. For example, the RAS-RAF-MEK-MAPK pathway in animals is a highly conserved signaling pathway that animals adopted for numerous biological processes, such as vulval induction in Caenorhabditis elegans and cell proliferation in mammalian cells; but this same gene set has been co-opted to function in a variety of cellular contexts. In this review, I give a few examples of how suppressor screens in model organisms (with a emphasis on C. elegans) can identify new genes that function in a conserved pathway in many other organisms. I also demonstrate how the identification of such genes can lead to important insights into mammalian biology. From such screens, an occasional silent suppressor that does not cause a phenotype on its own is found; such suppressors thus make for good candidates as therapeutic targets.
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Affiliation(s)
- Andy Golden
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
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16
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Pepper IJ, Van Sciver RE, Tang AH. Phylogenetic analysis of the SINA/SIAH ubiquitin E3 ligase family in Metazoa. BMC Evol Biol 2017; 17:182. [PMID: 28784114 PMCID: PMC5547486 DOI: 10.1186/s12862-017-1024-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 07/26/2017] [Indexed: 12/21/2022] Open
Abstract
Background The RAS signaling pathway is a pivotal developmental pathway that controls many fundamental biological processes including cell proliferation, differentiation, movement and apoptosis. Drosophila Seven-IN-Absentia (SINA) is a ubiquitin E3 ligase that is the most downstream signaling “gatekeeper” whose biological activity is essential for proper RAS signal transduction. Vertebrate SINA homologs (SIAHs) share a high degree of amino acid identity with that of Drosophila SINA. SINA/SIAH is the most conserved signaling component in the canonical EGFR/RAS/RAF/MAPK signal transduction pathway. Results Vertebrate SIAH1, 2, and 3 are the three orthologs to invertebrate SINA protein. SINA and SIAH1 orthologs are found in all major taxa of metazoans. These proteins have four conserved functional domains, known as RING (Really Interesting New Gene), SZF (SIAH-type zinc finger), SBS (substrate binding site) and DIMER (Dimerization). In addition to the siah1 gene, most vertebrates encode two additional siah genes (siah2 and siah3) in their genomes. Vertebrate SIAH2 has a highly divergent and extended N-terminal sequence, while its RING, SZF, SBS and DIMER domains maintain high amino acid identity/similarity to that of SIAH1. But unlike vertebrate SIAH1 and SIAH2, SIAH3 lacks a functional RING domain, suggesting that SIAH3 may be an inactive E3 ligase. The SIAH3 subtree exhibits a high degree of amino acid divergence when compared to the SIAH1 and SIAH2 subtrees. We find that SIAH1 and SIAH2 are expressed in all human epithelial cell lines examined thus far, while SIAH3 is only expressed in a limited subset of cancer cell lines. Conclusion Through phylogenetic analyses of metazoan SINA and SIAH E3 ligases, we identified many invariant and divergent amino acid residues, as well as the evolutionarily conserved functional motifs in this medically relevant gene family. Our phylomedicinal study of this unique metazoan SINA/SIAH protein family has provided invaluable evolution-based support towards future effort to design logical, potent, and durable anti-SIAH-based anticancer strategies against oncogenic K-RAS-driven metastatic human cancers. Thus, this method of evolutionary study should be of interest in cancer biology. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-1024-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ian J Pepper
- Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Leroy T. Canoles Jr. Cancer Research Center, Harry T. Lester Hall, Room 454-457, 651 Colley Avenue, Norfolk, VA, 23501, USA
| | - Robert E Van Sciver
- Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Leroy T. Canoles Jr. Cancer Research Center, Harry T. Lester Hall, Room 454-457, 651 Colley Avenue, Norfolk, VA, 23501, USA
| | - Amy H Tang
- Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Leroy T. Canoles Jr. Cancer Research Center, Harry T. Lester Hall, Room 454-457, 651 Colley Avenue, Norfolk, VA, 23501, USA.
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17
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Levayer R, Dupont C, Moreno E. Tissue Crowding Induces Caspase-Dependent Competition for Space. Curr Biol 2016; 26:670-7. [PMID: 26898471 PMCID: PMC4791483 DOI: 10.1016/j.cub.2015.12.072] [Citation(s) in RCA: 140] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 11/25/2015] [Accepted: 12/31/2015] [Indexed: 01/15/2023]
Abstract
Regulation of tissue size requires fine tuning at the single-cell level of proliferation rate, cell volume, and cell death. Whereas the adjustment of proliferation and growth has been widely studied [1, 2, 3, 4, 5], the contribution of cell death and its adjustment to tissue-scale parameters have been so far much less explored. Recently, it was shown that epithelial cells could be eliminated by live-cell delamination in response to an increase of cell density [6]. Cell delamination was supposed to occur independently of caspase activation and was suggested to be based on a gradual and spontaneous disappearance of junctions in the delaminating cells [6]. Studying the elimination of cells in the midline region of the Drosophila pupal notum, we found that, contrary to what was suggested before, Caspase 3 activation precedes and is required for cell delamination. Yet, using particle image velocimetry, genetics, and laser-induced perturbations, we confirmed [6] that local tissue crowding is necessary and sufficient to drive cell elimination and that cell elimination is independent of known fitness-dependent competition pathways [7, 8, 9]. Accordingly, activation of the oncogene Ras in clones was sufficient to compress the neighboring tissue and eliminate cells up to several cell diameters away from the clones. Mechanical stress has been previously proposed to contribute to cell competition [10, 11]. These results provide the first experimental evidences that crowding-induced death could be an alternative mode of super-competition, namely mechanical super-competition, independent of known fitness markers [7, 8, 9], that could promote tumor growth. Caspase activation is necessary for cell delamination in the Drosophila pupal notum Caspase activation is driven by local tissue crowding Crowding-induced death is activated near fast-growing clones resistant for apoptosis It is a new mode of super-competition that may promote expansion of tumoral cells
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Affiliation(s)
- Romain Levayer
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Carole Dupont
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Eduardo Moreno
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland; Champalimaud Centre for the Unknown, 1400-038 Lisbon, Portugal.
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18
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Peláez N, Gavalda-Miralles A, Wang B, Navarro HT, Gudjonson H, Rebay I, Dinner AR, Katsaggelos AK, Amaral LAN, Carthew RW. Dynamics and heterogeneity of a fate determinant during transition towards cell differentiation. eLife 2015; 4. [PMID: 26583752 PMCID: PMC4720516 DOI: 10.7554/elife.08924] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 11/18/2015] [Indexed: 02/06/2023] Open
Abstract
Yan is an ETS-domain transcription factor responsible for maintaining Drosophila eye cells in a multipotent state. Yan is at the core of a regulatory network that determines the time and place in which cells transit from multipotency to one of several differentiated lineages. Using a fluorescent reporter for Yan expression, we observed a biphasic distribution of Yan in multipotent cells, with a rapid inductive phase and slow decay phase. Transitions to various differentiated states occurred over the course of this dynamic process, suggesting that Yan expression level does not strongly determine cell potential. Consistent with this conclusion, perturbing Yan expression by varying gene dosage had no effect on cell fate transitions. However, we observed that as cells transited to differentiation, Yan expression became highly heterogeneous and this heterogeneity was transient. Signals received via the EGF Receptor were necessary for the transience in Yan noise since genetic loss caused sustained noise. Since these signals are essential for eye cells to differentiate, we suggest that dynamic heterogeneity of Yan is a necessary element of the transition process, and cell states are stabilized through noise reduction.
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Affiliation(s)
- Nicolás Peláez
- Department of Molecular Biosciences, Northwestern University, Evanston, United States.,Department of Chemical and Biological Engineering, Howard Hughes Medical Institute, University Northwestern, Evanston, United States
| | - Arnau Gavalda-Miralles
- Department of Chemical and Biological Engineering, Howard Hughes Medical Institute, University Northwestern, Evanston, United States
| | - Bao Wang
- Department Electrical Engineering and Computer Science, Northwestern University, Evanston, United States
| | - Heliodoro Tejedor Navarro
- Department of Chemical and Biological Engineering, Howard Hughes Medical Institute, University Northwestern, Evanston, United States
| | - Herman Gudjonson
- James Franck Institute, University of Chicago, Chicago, United States
| | - Ilaria Rebay
- Ben May Department for Cancer Research, University of Chicago, Chicago, United States
| | - Aaron R Dinner
- James Franck Institute, University of Chicago, Chicago, United States
| | - Aggelos K Katsaggelos
- Department Electrical Engineering and Computer Science, Northwestern University, Evanston, United States
| | - Luís A N Amaral
- Department of Chemical and Biological Engineering, Howard Hughes Medical Institute, University Northwestern, Evanston, United States.,Department of Physics and Astronomy, Northwestern University, Evanston, United States
| | - Richard W Carthew
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
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19
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Sajuthi A, Carrillo-Zazueta B, Hu B, Wang A, Brodnansky L, Mayberry J, Rivera AS. Sexually dimorphic gene expression in the lateral eyes of Euphilomedes carcharodonta (Ostracoda, Pancrustacea). EvoDevo 2015; 6:34. [PMID: 26561519 PMCID: PMC4641368 DOI: 10.1186/s13227-015-0026-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 09/22/2015] [Indexed: 12/29/2022] Open
Abstract
Background The evolution and development of sexual dimorphism illuminates a central question in biology: How do similar genomes produce different phenotypes? In an XX/XO system especially the state of a sexually dimorphic trait is determined by differences in gene expression, as there are no additional genetic loci in either sex. Here, we examine the XX/XO ostracod crustacean species Euphilomedes carcharodonta. This species exhibits radical sexual dimorphism of their lateral eyes, females have only a tiny simple lateral eye while males have elaborate ommatidial eyes. Results We find that males express three of nine eye-development gene homologs at significantly higher levels during juvenile eye development, compared to females. We also find that most eye-development genes examined are pleiotropic, with high expression levels during embryonic development as well as during juvenile eye development. Later, in adults, we find that phototransduction genes are expressed at higher levels in males than in females, as we might expect when comparing ommatidial to simple eyes. Conclusions We show here that expression changes of a handful of developmental genes may underlie the radical difference in a dimorphic character. This work gives an important point of comparison for studying eye evolution and development in the Pancrustacea. Electronic supplementary material The online version of this article (doi:10.1186/s13227-015-0026-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Andrea Sajuthi
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA ; Stritch School of Medicine, Loyola University, Chicago, IL USA
| | - Brenna Carrillo-Zazueta
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA ; Dugoni School of Dentistry, University of the Pacific, San Francisco, CA USA
| | - Briana Hu
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA
| | - Anita Wang
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA ; Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA USA
| | - Logan Brodnansky
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA ; Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA USA
| | - John Mayberry
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA
| | - Ajna S Rivera
- Department of Biological Sciences, University of the Pacific, Stockton, CA USA
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20
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Wilke ABB, Marrelli MT. Paratransgenesis: a promising new strategy for mosquito vector control. Parasit Vectors 2015; 8:342. [PMID: 26104575 PMCID: PMC4489152 DOI: 10.1186/s13071-015-0959-2] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/17/2015] [Indexed: 11/23/2022] Open
Abstract
The three main mosquito genera, Anopheles, Aedes and Culex, transmit respectively malaria, dengue and lymphatic filariasis. Current mosquito control strategies have proved unsuccessful, and there still is a substantial number of morbidity and mortality from these diseases. Genetic control methods have now arisen as promising alternative strategies, based on two approaches: the replacement of a vector population by disease-refractory mosquitoes and the release of mosquitoes carrying a lethal gene to suppress target populations. However, substantial hurdles and limitations need to be overcome if these methods are to be used successfully, the most significant being that a transgenic mosquito strain is required for every target species, making genetically modified mosquito strategies inviable when there are multiple vector mosquitoes in the same area. Genetically modified bacteria capable of colonizing a wide range of mosquito species may be a solution to this problem and another option for the control of these diseases. In the paratransgenic approach, symbiotic bacteria are genetically modified and reintroduced in mosquitoes, where they express effector molecules. For this approach to be used in practice, however, requires a better understanding of mosquito microbiota and that symbiotic bacteria and effector molecules be identified. Paratransgenesis could prove very useful in mosquito species that are inherently difficult to transform or in sibling species complexes. In this approach, a genetic modified bacteria can act by: (a) causing pathogenic effects in the host; (b) interfering with the host's reproduction; (c) reducing the vector's competence; and (d) interfering with oogenesis and embryogenesis. It is a much more flexible and adaptable approach than the use of genetically modified mosquitoes because effector molecules and symbiotic bacteria can be replaced if they do not achieve the desired result. Paratransgenesis may therefore become an important integrated pest management tool for mosquito control.
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Affiliation(s)
- André Barretto Bruno Wilke
- Departamento de Epidemiologia, Faculdade de Saúde Pública, Universidade de São Paulo, Av. Dr. Arnaldo 715, São Paulo, SP, CEP-01246-904, Brazil.
| | - Mauro Toledo Marrelli
- Departamento de Epidemiologia, Faculdade de Saúde Pública, Universidade de São Paulo, Av. Dr. Arnaldo 715, São Paulo, SP, CEP-01246-904, Brazil.
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21
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Hatzihristidis T, Desai N, Hutchins AP, Meng TC, Tremblay ML, Miranda-Saavedra D. A Drosophila-centric view of protein tyrosine phosphatases. FEBS Lett 2015; 589:951-66. [PMID: 25771859 DOI: 10.1016/j.febslet.2015.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 03/02/2015] [Accepted: 03/02/2015] [Indexed: 12/30/2022]
Abstract
Most of our knowledge on protein tyrosine phosphatases (PTPs) is derived from human pathologies and mouse knockout models. These models largely correlate well with human disease phenotypes, but can be ambiguous due to compensatory mechanisms introduced by paralogous genes. Here we present the analysis of the PTP complement of the fruit fly and the complementary view that PTP studies in Drosophila will accelerate our understanding of PTPs in physiological and pathological conditions. With only 44 PTP genes, Drosophila represents a streamlined version of the human complement. Our integrated analysis places the Drosophila PTPs into evolutionary and functional contexts, thereby providing a platform for the exploitation of the fly for PTP research and the transfer of knowledge onto other model systems.
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Affiliation(s)
- Teri Hatzihristidis
- Goodman Cancer Research Centre, McGill University, 1160 Pine Avenue, Montreal, Québec H3A 1A3, Canada; Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
| | - Nikita Desai
- Goodman Cancer Research Centre, McGill University, 1160 Pine Avenue, Montreal, Québec H3A 1A3, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Andrew P Hutchins
- Key Laboratory of Regenerative Biology and Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, Guangdong 510530, China
| | - Tzu-Ching Meng
- Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan; Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Michel L Tremblay
- Goodman Cancer Research Centre, McGill University, 1160 Pine Avenue, Montreal, Québec H3A 1A3, Canada; Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
| | - Diego Miranda-Saavedra
- World Premier International (WPI) Immunology Frontier Research Center (IFReC), Osaka University, 3-1 Yamadaoka, Suita 565-0871, Osaka, Japan; Centro de Biología Molecular Severo Ochoa, CSIC/Universidad Autónoma de Madrid, 28049 Madrid, Spain; IE Business School, IE University, María de Molina 31 bis, 28006 Madrid, Spain.
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22
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Cox AD, Der CJ. Ras history: The saga continues. Small GTPases 2014; 1:2-27. [PMID: 21686117 DOI: 10.4161/sgtp.1.1.12178] [Citation(s) in RCA: 498] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/17/2010] [Accepted: 05/24/2010] [Indexed: 12/24/2022] Open
Abstract
Although the roots of Ras sprouted from the rich history of retrovirus research, it was the discovery of mutationally activated RAS genes in human cancer in 1982 that stimulated an intensive research effort to understand Ras protein structure, biochemistry and biology. While the ultimate goal has been developing anti-Ras drugs for cancer treatment, discoveries from Ras have laid the foundation for three broad areas of science. First, they focused studies on the origins of cancer to the molecular level, with the subsequent discovery of genes mutated in cancer that now number in the thousands. Second, elucidation of the biochemical mechanisms by which Ras facilitates signal transduction established many of our fundamental concepts of how a normal cell orchestrates responses to extracellular cues. Third, Ras proteins are also founding members of a large superfamily of small GTPases that regulate all key cellular processes and established the versatile role of small GTP-binding proteins in biology. We highlight some of the key findings of the last 28 years.
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Affiliation(s)
- Adrienne D Cox
- Department of Radiation Oncology; Lineberger Comprehensive Cancer Center; University of North Carolina at Chapel Hill; Chapel Hill, NC USA
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23
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Tchankouo-Nguetcheu S, Udinotti M, Durand M, Meng TC, Taouis M, Rabinow L. Negative regulation of MAP kinase signaling in Drosophila by Ptp61F/PTP1B. Mol Genet Genomics 2014; 289:795-806. [DOI: 10.1007/s00438-014-0852-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 04/01/2014] [Indexed: 01/19/2023]
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24
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Bell GP, Thompson BJ. Colorectal cancer progression: lessons from Drosophila? Semin Cell Dev Biol 2014; 28:70-7. [PMID: 24583474 DOI: 10.1016/j.semcdb.2014.02.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 02/13/2014] [Indexed: 12/31/2022]
Abstract
Human colorectal cancers arise as benign adenomas, tumours that retain their epithelial character, and then progress to malignant adenocarcinomas and carcinomas in which the epithelium becomes disrupted. Carcinomas often exhibit transcriptional downregulation of E-cadherin and other epithelial genes in an epithelial-to-mesenchymal transition (EMT), a mechanism first discovered in Drosophila to be mediated by the transcription factors Twist and Snail. In contrast, adenocarcinomas retain expression of E-cadherin and disruption of the epithelium occurs through formation of progressively smaller epithelial cysts with apical Crumbs/CRB3, Stardust/PALS1, and Bazooka/PAR3 localised to the inner lumen. Results from Drosophila show that morphologically similar cysts form upon induction of clonal heterogeneity in Wnt, Smad, or Ras signalling levels, which causes extrusion of epithelial cells at clonal boundaries. Thus, intratumour heterogeneity might also promote formation of adenocarcinomas in humans. Finally, epithelial cysts can collectively migrate, as in the case of Drosophila border cells, a potential model system for the invasive migration of adenocarcinoma cells.
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Affiliation(s)
- Graham P Bell
- Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, United Kingdom
| | - Barry J Thompson
- Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, United Kingdom.
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25
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Ashton-Beaucage D, Udell CM, Gendron P, Sahmi M, Lefrançois M, Baril C, Guenier AS, Duchaine J, Lamarre D, Lemieux S, Therrien M. A functional screen reveals an extensive layer of transcriptional and splicing control underlying RAS/MAPK signaling in Drosophila. PLoS Biol 2014; 12:e1001809. [PMID: 24643257 PMCID: PMC3958334 DOI: 10.1371/journal.pbio.1001809] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 02/05/2014] [Indexed: 12/11/2022] Open
Abstract
A global RNAi screening approach in Drosophila cells identifies a large group of transcription and splicing factors that modulate RAS/MAPK signaling by altering the expression of MAPK. The small GTPase RAS is among the most prevalent oncogenes. The evolutionarily conserved RAF-MEK-MAPK module that lies downstream of RAS is one of the main conduits through which RAS transmits proliferative signals in normal and cancer cells. Genetic and biochemical studies conducted over the last two decades uncovered a small set of factors regulating RAS/MAPK signaling. Interestingly, most of these were found to control RAF activation, thus suggesting a central regulatory role for this event. Whether additional factors are required at this level or further downstream remains an open question. To obtain a comprehensive view of the elements functionally linked to the RAS/MAPK cascade, we used a quantitative assay in Drosophila S2 cells to conduct a genome-wide RNAi screen for factors impacting RAS-mediated MAPK activation. The screen led to the identification of 101 validated hits, including most of the previously known factors associated to this pathway. Epistasis experiments were then carried out on individual candidates to determine their position relative to core pathway components. While this revealed several new factors acting at different steps along the pathway—including a new protein complex modulating RAF activation—we found that most hits unexpectedly work downstream of MEK and specifically influence MAPK expression. These hits mainly consist of constitutive splicing factors and thereby suggest that splicing plays a specific role in establishing MAPK levels. We further characterized two representative members of this group and surprisingly found that they act by regulating mapk alternative splicing. This study provides an unprecedented assessment of the factors modulating RAS/MAPK signaling in Drosophila. In addition, it suggests that pathway output does not solely rely on classical signaling events, such as those controlling RAF activation, but also on the regulation of MAPK levels. Finally, it indicates that core splicing components can also specifically impact alternative splicing. The RAS/MAPK pathway is a cornerstone of the cell proliferation signaling apparatus. It has a notable involvement in cancer as mutations in the components of the pathway are associated with aberrant proliferation. Previous work has focused predominantly on post-translational regulation of RAS/MAPK signaling such that a large and intricate network of factors is now known to act on core pathway components. However, regulation at the pre-translational level has not been examined nearly as extensively and is comparatively poorly understood. In this study, we used an unbiased and global screening approach to survey the Drosophila genome—using Drosophila cultured cells—for novel regulators of this pathway. Surprisingly, a majority of our hits were associated to either transcription or mRNA splicing. We used a series of secondary screening assays to determine which part of the RAS/MAPK pathway these candidates target. We found that these factors were not equally distributed along the pathway, but rather converged predominantly on mapk mRNA expression and processing. Our findings raise the intriguing possibility that regulation of mapk transcript production is a key step for a diverse set of regulatory inputs, and may play an important part in RAS/MAPK signaling dynamics.
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Affiliation(s)
- Dariel Ashton-Beaucage
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Christian M. Udell
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Patrick Gendron
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Malha Sahmi
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Martin Lefrançois
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Caroline Baril
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Anne-Sophie Guenier
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Jean Duchaine
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
| | - Daniel Lamarre
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
- Département de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Sébastien Lemieux
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
- Département d'informatique et de recherche opérationnelle, Université de Montréal, Montréal, Québec, Canada
| | - Marc Therrien
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, Québec, Canada
- Département de pathologie et de biologie cellulaire, Université de Montréal, Montréal, Québec, Canada
- * E-mail:
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26
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Ras. Mol Oncol 2013. [DOI: 10.1017/cbo9781139046947.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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27
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Cell competition may function either as tumour-suppressing or as tumour-stimulating factor in Drosophila. Oncogene 2013; 33:4377-84. [PMID: 24096487 DOI: 10.1038/onc.2013.407] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 08/21/2013] [Accepted: 08/23/2013] [Indexed: 01/17/2023]
Abstract
Drosophila endocytosis-defective cells develop tumour overgrowths in the imaginal discs. We have analysed the tumorigenic potential of cells mutant for Rab5, a gene involved in endocytosis. We found that while a compartment entirely made by Rab5 mutant cells can grow indefinitely, clones of Rab5 cells surrounded by normal cells are eliminated by cell competition. However, when a group of about 400 cells are simultaneously made mutant for Rab5, they form an overgrowing tumour: mutant cells in the periphery are eliminated, but those inside survive and continue proliferating because they are beyond the range of cell competition. These results identify group protection as a mechanism to evade the tumour-suppressing function of cell competition in Drosophila. Furthermore, we find that the growth of the tumour depends to a large extent on the presence of apoptosis inside the tumour: cells doubly mutant for Rab5 and the proapoptotic gene dronc do not form overgrowing tumours. These results suggest that the apoptosis caused by cell competition acts as a tumour-stimulating factor, bringing about high levels of Jun N-terminal kinase and subsequently Wg/Dpp signalling and high proliferation levels in the growing tumour. We conclude that under these circumstances cell competition facilitates the progression of the tumour, thus reversing its normal antitumour role.
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Mitrofanov VG, Chekunova AI, Proshakov PA, Barsukov MI. Universal intracellular transducer ras and its role in the development of drosophila. Russ J Dev Biol 2013. [DOI: 10.1134/s1062360413040073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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29
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Mora N, Santa Bárbara Ruiz P, Ferreira N, Serras F. Ras signal triggers β-amyloid precursor protein (APP) expression. Small GTPases 2013; 4:171-3. [PMID: 23648941 DOI: 10.4161/sgtp.24768] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
It has recently been discovered that the Drosophila β-amyloid protein precursor like (Appl) gene, the ortholog of the human β-Amyloid Precursor Protein (APP) gene, is transcriptionally activated by receptor tyrosine kinase activity that involves Ras/MAPK signaling in vivo. This regulation is specifically controlled in photoreceptor neurons of the Drosophila retina. This suggests that some cases of Alzheimer disease, those which have been associated with high expression of the APP gene, may involve Ras signal transduction.
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Affiliation(s)
- Natalia Mora
- Departament de Genètica; Facultat de Biologia; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona; Barcelona, Spain; Laboratory of Neurogenetics; Department of Molecular and Developmental Genetics; VIB; Leuven, Belgium
| | - Paula Santa Bárbara Ruiz
- Departament de Genètica; Facultat de Biologia; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona; Barcelona, Spain
| | - Nuno Ferreira
- Departament de Genètica; Facultat de Biologia; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona; Barcelona, Spain
| | - Florenci Serras
- Departament de Genètica; Facultat de Biologia; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona; Barcelona, Spain
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30
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Mavromatakis YE, Tomlinson A. Stop and go: antagonistic signals in the specification of the Drosophila R7 photoreceptor viewed from an evolutionary perspective. Fly (Austin) 2012; 6:228-33. [PMID: 22878552 DOI: 10.4161/fly.21102] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Drosophila R7 photoreceptor precursor is directed to its fate by signals from adjacent cells that activate its Receptor Tyrosine Kinase (RTK) and Notch (N) signaling pathways. Counter-intuitively, the N activity both promotes and inhibits the photoreceptor fate in the R7 precursor. We offer an evolutionary perspective for this in which earlier ommatidia had fewer photoreceptors and used N to inhibit the addition of any more. When additional photoreceptors were added by evolution, an RTK signal was used to overcome the N inhibition in these cells, and these new additions potently activated N in their neighboring cells, preventing them from also responding to the RTK signal. The R7 precursor also receives this block, and requires robust RTK activation for it to become a photoreceptor. This is achieved by N transcriptionally activating a new RTK, one that is potently activated in the R7 precursor and sufficing to overcome the N inhibition. The unusually high RTK signal in R7 requires additional transduction components not needed when the signal is mild; in R7 the small GTPases Ras and Rap are both required to transduce the signal, but in other photoreceptors Ras alone suffices.
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Abstract
Synthetic biology is an area of biological research that combines science and engineering. Here, I merge the principles of synthetic biology and regulatory evolution to create a new species with a minimal set of known elements. Using preexisting transgenes and recessive mutations of Drosophila melanogaster, a transgenic population arises with small eyes and a different venation pattern that fulfils the criteria of a new species according to Mayr's Biological Species Concept. The population described here is the first transgenic organism that cannot hybridize with the original wild type population but remains fertile when crossed with other identical transgenic animals. I therefore propose the term "synthetic species" to distinguish it from "natural species", not only because it has been created by genetic manipulation, but also because it may never be able to survive outside the laboratory environment. The use of genetic engineering to design artificial species barriers could help us understand natural speciation and may have practical applications. For instance, the transition from transgenic organisms towards synthetic species could constitute a safety mechanism to avoid the hybridization of genetically modified animals with wild type populations, preserving biodiversity.
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Affiliation(s)
- Eduardo Moreno
- Institute of Cell Biology, University of Bern, Bern, Switzerland.
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32
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Abstract
Since the discovery of a single white-eyed male in a population of red eyed flies over 100 years ago (Morgan, 1910), the compound eye of the fruit fly, Drosophila melanogaster, has been a favorite experimental system for identifying genes that regulate various aspects of development. For example, a fair amount of what we know today about enzymatic pathways and vesicular transport is due to the discovery and subsequent characterization of eye color mutants such as white. Likewise, our present day understanding of organogenesis has been aided considerably by studies of mutations, such as eyeless, that either reduce or eliminate the compound eyes. But by far the phenotype that has provided levers into the greatest number of experimental fields has been the humble "rough" eye. The fly eye is composed of several hundred unit-eyes that are also called ommatidia. These unit eyes are packed into a hexagonal array of remarkable precision. The structure of the eye is so precise that it has been compared with that of a crystal (Ready et al., 1976). Even the slightest perturbations to the structure of the ommatidium can be visually detected by light or electron microscopy. The cause for this is two-fold: (1) any defect that affects the hexagonal geometry of a single ommatidium can and will disrupt the positioning of surrounding unit eyes thereby propagating structural flaws and (2) disruptions in genes that govern the development of even a single cell within an ommatidium will affect all unit eyes. In both cases, the effect is the visual magnification of even the smallest imperfection. Studies of rough eye mutants have provided key insights into the areas of cell fate specification, lateral inhibition, signal transduction, transcription factor networks, planar cell polarity, cell proliferation, and programmed cell death just to name a few. This review will attempt to summarize the key steps that are required to assemble each ommatidium.
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Affiliation(s)
- Justin P Kumar
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
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33
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Maeng O, Son W, Chung J, Lee KS, Lee YH, Yoo OJ, Cha GH, Paik SG. The BTB/POZ-ZF transcription factor dPLZF is involved in Ras/ERK signaling during Drosophila wing development. Mol Cells 2012; 33:457-63. [PMID: 22544070 PMCID: PMC3887728 DOI: 10.1007/s10059-012-2179-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 02/29/2012] [Accepted: 03/09/2012] [Indexed: 10/28/2022] Open
Abstract
In Drosophila, broad complex, tramtrack, bric à brac (BTB)/poxvirus and zinc finger (POZ) transcription factors are essential regulators of development. We searched the Drosophila genome for BTB/POZ-ZF domains and discovered an unknown Drosophila gene, dPLZF, which encodes an orthologue of human PLZF. We then characterized the biological function of the dPLZF via genetic interaction analysis. Ectopic expression of dPLZF in the wing induced extra vein formation during wing development in Drosophila. Genetic interactions between dPLZF and Ras or extracellular signal-regulated kinase (ERK) significantly enhanced the formation of vein cells. On the other hand, loss-of-function mutations in dPLZF resulted in a dramatic suppression of the extra and ectopic vein formation induced by elevated Ras/ERK signaling. Moreover, dPLZF activity upregulated the expression of rhomboid (rho) and spitz, which perform crucial functions in vein cell formation in the developing wing. These results indicate that dPLZF is a transcription factor controlled by the Ras/ERK signaling pathway, which is a prominent regulator of vein cell formation during wing development in Drosophila.
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Affiliation(s)
- Oky Maeng
- Department of Infection Biology, College of Medicine and Brain Korea 21 Program for Medical Science, Chungnam National University, Daejeon 301-131,
Korea
| | - Wonseok Son
- Graduate School of Medical Science and Engineering, Biomedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon 305-701,
Korea
| | - Jongkyeong Chung
- School of Biological Science, Seoul National University, Seoul 151-742,
Korea
| | - Kyu-Sun Lee
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806,
Korea
| | - Young-Ha Lee
- Department of Infection Biology, College of Medicine and Brain Korea 21 Program for Medical Science, Chungnam National University, Daejeon 301-131,
Korea
| | - Ook-Joon Yoo
- Graduate School of Medical Science and Engineering, Biomedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon 305-701,
Korea
| | - Guang-Ho Cha
- Department of Infection Biology, College of Medicine and Brain Korea 21 Program for Medical Science, Chungnam National University, Daejeon 301-131,
Korea
| | - Sang-Gi Paik
- Department of Biology, Chungnam National University, Daejeon 305-764,
Korea
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34
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The role of the small GTPase Rap in Drosophila R7 photoreceptor specification. Proc Natl Acad Sci U S A 2012; 109:3844-9. [PMID: 22355117 DOI: 10.1073/pnas.1115108109] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Drosophila R7 photoreceptor provides an excellent model system with which to study how cells receive and "decode" signals that specify cell fate. R7 is specified by the combined actions of the receptor tyrosine kinase (RTK) and Notch (N) signaling pathways. These pathways interact in a complex manner that includes antagonistic effects on photoreceptor specification: RTK promotes the photoreceptor fate, whereas N inhibits. Although other photoreceptors are subject to only mild N activation, R7 experiences a high-level N signal. To counter this effect and to ensure that the cell is specified as a photoreceptor, a high RTK signal is transduced in the cell. Thus, there are two levels of RTK transduction in the photoreceptors: in R7 it is high, whereas in others it is low. Here, we address how this high-level RTK signal is transduced in R7 and find that, in addition to Ras, another small GTPase, Rap, is also engaged. Thus, when N activity is high, a robust RTK signal operates that uses both Ras and Rap, but when N activity is low, only a mild RTK signal is transduced and Ras alone suffices for the purpose.
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35
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Katanaev VL, Kryuchkov MV. The eye of Drosophila as a model system for studying intracellular signaling in ontogenesis and pathogenesis. BIOCHEMISTRY (MOSCOW) 2012; 76:1556-81. [DOI: 10.1134/s0006297911130116] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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36
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Gafuik C, Steller H. A gain-of-function germline mutation in Drosophila ras1 affects apoptosis and cell fate during development. PLoS One 2011; 6:e23535. [PMID: 21858158 PMCID: PMC3155559 DOI: 10.1371/journal.pone.0023535] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 07/19/2011] [Indexed: 12/30/2022] Open
Abstract
The RAS/MAPK signal transduction pathway is an intracellular signaling cascade that transmits environmental signals from activated receptor tyrosine kinases (RTKs) on the cell surface and other endomembranes to transcription factors in the nucleus, thereby linking extracellular stimuli to changes in gene expression. Largely as a consequence of its role in oncogenesis, RAS signaling has been the subject of intense research efforts for many years. More recently, it has been shown that milder perturbations in Ras signaling during embryogenesis also contribute to the etiology of a group of human diseases. Here we report the identification and characterization of the first gain-of-function germline mutation in Drosophila ras1 (ras85D), the Drosophila homolog of human K-ras, N-ras and H-ras. A single amino acid substitution (R68Q) in the highly conserved switch II region of Ras causes a defective protein with reduced intrinsic GTPase activity, but with normal sensitivity to GAP stimulation. The ras1R68Q mutant is homozygous viable but causes various developmental defects associated with elevated Ras signaling, including cell fate changes and ectopic survival of cells in the nervous system. These biochemical and functional properties are reminiscent of germline Ras mutants found in patients afflicted with Noonan, Costello or cardio-facio-cutaneous syndromes. Finally, we used ras1R68Q to identify novel genes that interact with Ras and suppress cell death.
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Affiliation(s)
- Christopher Gafuik
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
| | - Hermann Steller
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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37
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Pierre S, Bats AS, Coumoul X. Understanding SOS (Son of Sevenless). Biochem Pharmacol 2011; 82:1049-56. [PMID: 21787760 DOI: 10.1016/j.bcp.2011.07.072] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Revised: 07/02/2011] [Accepted: 07/05/2011] [Indexed: 10/17/2022]
Abstract
Son of Sevenless (SOS) was discovered in Drosophila melanogaster. Essential for normal eye development in Drosophila, SOS has two human homologues, SOS1 and SOS2. The SOS1 gene encodes the Son of Sevenless 1 protein, a Ras and Rac guanine nucleotide exchange factor. This protein is composed of several important domains. The CDC25 and REM domains provide the catalytic activity of SOS1 towards Ras and the histone fold DH/PH (Dbl homology and Pleckstrin homology) domains function, in tandem, to stimulate GTP/GDP exchange for Rac. In contrast to Ras, there have been few studies that implicate SOS1 in human disease and, initially, less attention was given to this gene. However, mutations in SOS1 have been reported recently in Noonan syndrome and in type 1 hereditary gingival fibromatosis. Although, there have been very few studies that focus on the regulation of this important gene by physiological or exogenous factors, we recently found that the SOS1 gene was induced by the environmental toxin, dioxin, and that this effect was mediated by the aryl hydrocarbon receptor (AhR). These recent observations raise the possibility that alterations in the expression of the SOS1 gene and, consequently, in the activity of the SOS1 protein may affect toxicological endpoints and lead to clinical disease. These possibilities, thus, have stimulated much interest in SOS1 recently. In this article, we review the functions of SOS1 and the evidence for its roles in physiology and pathology across species.
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Affiliation(s)
- Stéphane Pierre
- INSERM UMR-S 747, Toxicologie Pharmacologie et Signalisation Cellulaire, 45 rue des Saints Pères, 75006 Paris, France
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38
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Charlton-Perkins M, Whitaker SL, Fei Y, Xie B, Li-Kroeger D, Gebelein B, Cook T. Prospero and Pax2 combinatorially control neural cell fate decisions by modulating Ras- and Notch-dependent signaling. Neural Dev 2011; 6:20. [PMID: 21539742 PMCID: PMC3123624 DOI: 10.1186/1749-8104-6-20] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 05/03/2011] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The concept of an equivalence group, a cluster of cells with equal potential to adopt the same specific fate, has served as a useful paradigm to understand neural cell type specification. In the Drosophila eye, a set of five cells, called the 'R7 equivalence group', generates a single photoreceptor neuron and four lens-secreting epithelial cells. This choice between neuronal versus non-neuronal cell fates rests on differential requirements for, and cross-talk between, Notch/Delta- and Ras/mitogen-activated protein kinase (MAPK)-dependent signaling pathways. However, many questions remain unanswered related to how downstream events of these two signaling pathways mediate distinct cell fate decisions. RESULTS Here, we demonstrate that two direct downstream targets of Ras and Notch signaling, the transcription factors Prospero and dPax2, are essential regulators of neuronal versus non-neuronal cell fate decisions in the R7 equivalence group. Prospero controls high activated MAPK levels required for neuronal fate, whereas dPax2 represses Delta expression to prevent neuronal fate. Importantly, activity from both factors is required for proper cell fate decisions to occur. CONCLUSIONS These data demonstrate that Ras and Notch signaling are integrated during cell fate decisions within the R7 equivalence group through the combinatorial and opposing activities of Pros and dPax2. Our study provides one of the first examples of how the differential expression and synergistic roles of two independent transcription factors determine cell fate within an equivalence group. Since the integration of Ras and Notch signaling is associated with many developmental and cancer models, these findings should provide new insights into how cell specificity is achieved by ubiquitously used signaling pathways in diverse biological contexts.
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Affiliation(s)
- Mark Charlton-Perkins
- Department of Pediatric Ophthalmology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229, USA
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39
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Neel NF, Martin TD, Stratford JK, Zand TP, Reiner DJ, Der CJ. The RalGEF-Ral Effector Signaling Network: The Road Less Traveled for Anti-Ras Drug Discovery. Genes Cancer 2011; 2:275-87. [PMID: 21779498 PMCID: PMC3128631 DOI: 10.1177/1947601911407329] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The high frequency of RAS mutations in human cancers (33%) has stimulated intense interest in the development of anti-Ras inhibitors for cancer therapy. Currently, the major focus of these efforts is centered on inhibitors of components involved in Ras downstream effector signaling. In particular, more than 40 inhibitors of the Raf-MEK-ERK mitogen-activated protein kinase cascade and phosphoinositide 3-kinase-AKT-mTOR effector signaling networks are currently under clinical evaluation. However, these efforts are complicated by the fact that Ras can utilize at least 9 additional functionally distinct effectors, with at least 3 additional effectors with validated roles in Ras-mediated oncogenesis. Of these, the guanine nucleotide exchange factors of the Ras-like (Ral) small GTPases (RalGEFs) have emerged as important effectors of mutant Ras in pancreatic, colon, and other cancers. In this review, we summarize the evidence for the importance of this effector pathway in cancer and discuss possible directions for therapeutic inhibition of aberrant Ral activation and signaling.
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Affiliation(s)
- Nicole F Neel
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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40
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Ashton-Beaucage D, Udell CM, Lavoie H, Baril C, Lefrançois M, Chagnon P, Gendron P, Caron-Lizotte O, Bonneil É, Thibault P, Therrien M. The Exon Junction Complex Controls the Splicing of mapk and Other Long Intron-Containing Transcripts in Drosophila. Cell 2010; 143:251-62. [DOI: 10.1016/j.cell.2010.09.014] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 08/31/2010] [Accepted: 09/02/2010] [Indexed: 12/11/2022]
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41
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Graham TGW, Tabei SMA, Dinner AR, Rebay I. Modeling bistable cell-fate choices in the Drosophila eye: qualitative and quantitative perspectives. Development 2010; 137:2265-78. [PMID: 20570936 PMCID: PMC2889600 DOI: 10.1242/dev.044826] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A major goal of developmental biology is to understand the molecular mechanisms whereby genetic signaling networks establish and maintain distinct cell types within multicellular organisms. Here, we review cell-fate decisions in the developing eye of Drosophila melanogaster and the experimental results that have revealed the topology of the underlying signaling circuitries. We then propose that switch-like network motifs based on positive feedback play a central role in cell-fate choice, and discuss how mathematical modeling can be used to understand and predict the bistable or multistable behavior of such networks.
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Affiliation(s)
- Thomas G. W. Graham
- Ben May Department for Cancer Research, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - S. M. Ali Tabei
- James Franck Institute, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Aaron R. Dinner
- James Franck Institute, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Ilaria Rebay
- Ben May Department for Cancer Research, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
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42
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Haberman AS, Akbar MA, Ray S, Krämer H. Drosophila acinus encodes a novel regulator of endocytic and autophagic trafficking. Development 2010; 137:2157-66. [PMID: 20504956 DOI: 10.1242/dev.044230] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Endosomal trafficking affects many cellular pathways from cell signaling to metabolism, but little is known about how these effects are coordinated. In a genetic screen for mutants affecting endosomal trafficking, we identified Drosophila acinus (dacn; hook-like). Its mammalian homolog Acinus has been implicated in RNA processing and chromatin fragmentation during apoptosis. Loss-of-function analysis of dacn revealed two distinct functions. First, dacn is required for stabilization of early endosomes, thus modulating levels of Notch and Egfr signaling. Second, loss of dacn interferes with cellular starvation responses by inhibiting autophagosome maturation. By contrast, overexpression of dacn causes lethality due to enhanced autophagy. We show that this enhanced autophagy is independent of the Tor pathway. Taken together, our data show that dacn encodes a regulator of endosomal and autophagosomal dynamics, modulating developmental signaling and the cellular response to starvation.
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Affiliation(s)
- Adam S Haberman
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
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43
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Beam CK, Moberg K. The gang of four gene regulates growth and patterning of the developing Drosophila eye. Fly (Austin) 2010; 4:104-16. [PMID: 20473027 DOI: 10.4161/fly.4.2.11890] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We report here the identification of a novel complementation group in the fruit fly Drosophila melanogaster named gang of four (gfr). Mutations in gfr disrupt patterns of cell differentiation in the eye and increase eye size through a proliferative mechanism that can be enhanced by a block in apoptosis. gfr mutant cells show several features of deregulated Ras/MAP kinase activity, including reduced expression of the Capicua growth suppressing transcription factor and synthetically lethality with alleles of the Jun N-terminal kinase phosphatase puckered. gfr alleles also upreguate Notch activity in the eye. Thus, gfr alleles appear to elicit growth and patterning phenotypes via effects on multiple signaling pathways. Moreover, the gfr alleles behave as gain-of-function lesions and overexpress the gene, bruno-3 (bru-3), which is located at the genomic region to which gfr lesions map. Genetic reduction of bru-3 suppresses phenotypes caused by gfr alleles, and like gfr alleles, overexpression of bru-3 depresses levels of Cic protein, indicating that overexpression of bru-3 is central to gfr mutant phenotypes.
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Affiliation(s)
- Carolyn K Beam
- Emory University School of Medicine, Department of Cell Biology, Atlanta, GA, USA
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44
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Charlton-Perkins M, Cook TA. Building a fly eye: terminal differentiation events of the retina, corneal lens, and pigmented epithelia. Curr Top Dev Biol 2010; 93:129-73. [PMID: 20959165 DOI: 10.1016/b978-0-12-385044-7.00005-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In the past, vast differences in ocular structure, development, and physiology throughout the animal kingdom led to the widely accepted notion that eyes are polyphyletic, that is, they have independently arisen multiple times during evolution. Despite the dissimilarity between vertebrate and invertebrate eyes, it is becoming increasingly evident that the development of the eye in both groups shares more similarity at the genetic level than was previously assumed, forcing a reexamination of eye evolution. Understanding the molecular underpinnings of cell type specification during Drosophila eye development has been a focus of research for many labs over the past 25 years, and many of these findings are nicely reviewed in Chapters 1 and 4. A somewhat less explored area of research, however, considers how these cells, once specified, develop into functional ocular structures. This review aims to summarize the current knowledge related to the terminal differentiation events of the retina, corneal lens, and pigmented epithelia in the fly eye. In addition, we discuss emerging evidence that the different functional components of the fly eye share developmental pathways and functions with the vertebrate eye.
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Affiliation(s)
- Mark Charlton-Perkins
- Department of Pediatric Ophthalmology, Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA
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Wu Y, Zhuang Y, Han M, Xu T, Deng K. Ras promotes cell survival by antagonizing both JNK and Hid signals in the Drosophila eye. BMC DEVELOPMENTAL BIOLOGY 2009; 9:53. [PMID: 19840402 PMCID: PMC2773777 DOI: 10.1186/1471-213x-9-53] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 10/20/2009] [Indexed: 01/03/2023]
Abstract
Background Programmed cell death, or apoptosis, is a fundamental physiological process during normal development or in pathological conditions. The activation of apoptosis can be elicited by numerous signalling pathways. Ras is known to mediate anti-apoptotic signals by inhibiting Hid activity in the Drosophila eye. Here we report the isolation of a new loss-of-function ras allele, rasKP, which causes excessive apoptosis in the Drosophila eye. Results This new function is likely to be mediated through the JNK pathway since the inhibition of JNK signalling can significantly suppress rasKP-induced apoptosis, whereas the removal of hid only weakly suppresses the phenotype. Furthermore, the reduction of JNK signalling together with the expression of the baculovirus caspase inhibitor p35, which blocks Hid activity, strongly suppresses the rasKP cell death. In addition, we find a strong correlation between rasKP-induced apoptosis in the eye disc and the activation of JNK signalling. Conclusion In the Drosophila eye, Ras may protect cells from apoptosis by inhibiting both JNK and Hid activities. Surprisingly, reducing Ras activity in the wing, however, does not cause apoptosis but rather affects cell and organ size. Thus, in addition to its requirement for cell viability, Ras appears to mediate different biological roles depending on the developmental context and on the level of its expression.
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Affiliation(s)
- Yue Wu
- Institute of Developmental Biology and Molecular Medicine and School of Life Science, Fudan University, Shanghai, PR China.
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rhomboid mediates specification of blue- and green-sensitive R8 photoreceptor cells in Drosophila. J Neurosci 2009; 29:2666-75. [PMID: 19261861 DOI: 10.1523/jneurosci.5988-08.2009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Color vision is based on the differential color sensitivity of retinal photoreceptors, however the developmental programs that control photoreceptor cell differentiation and specify color sensitivity are poorly understood. In Drosophila there is growing evidence that the color sensitivity of the R8 cell within an individual ommatidium is regulated by an inductive signal from the adjacent R7 cell. We previously examined the retinal patterning defect in Scutoid mutants, which results from a disruption of rhomboid expression. Here we show that loss of rhomboid blocks the induction of Rh5 expression and misexpression of rhomboid leads to the inappropriate induction of Rh5. These effects are specific to rhomboid, because its paralogue roughoid is neither required nor sufficient for the induction of Rh5 expression. We show that rhomboid is required cell-autonomously within the R8 photoreceptor cells and nonautonomously elsewhere in the eye for Rh5 induction. Interestingly, we found that the Epidermal growth factor receptor is also required for Rh5 induction, and its activation is sufficient to rescue the loss of Rh5 induction in a rhomboid mutant. This suggests that rhomboid may function in R8 cells to activate Epidermal growth factor receptor signaling in R7 cells and promote their differentiation to a signaling competent state.
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Oishi K, Zhang H, Gault WJ, Wang CJ, Tan CC, Kim IK, Ying H, Rahman T, Pica N, Tartaglia M, Mlodzik M, Gelb BD. Phosphatase-defective LEOPARD syndrome mutations in PTPN11 gene have gain-of-function effects during Drosophila development. Hum Mol Genet 2009; 18:193-201. [PMID: 18849586 PMCID: PMC2644650 DOI: 10.1093/hmg/ddn336] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 10/08/2008] [Indexed: 02/04/2023] Open
Abstract
Missense mutations in the PTPN11 gene, which encodes the protein tyrosine phosphatase SHP-2, cause clinically similar but distinctive disorders, LEOPARD (LS) and Noonan (NS) syndromes. The LS is an autosomal dominant disorder with pleomorphic developmental abnormalities including lentigines, cardiac defects, short stature and deafness. Biochemical analyses indicated that LS alleles engender loss-of-function (LOF) effects, while NS mutations result in gain-of-function (GOF). These biochemical findings lead to an enigma that how PTPN11 mutations with opposite effects on function result in disorders that are so similar. To study the developmental effects of the commonest LS PTPN11 alleles (Y279C and T468M), we generated LS transgenic fruitflies using corkscrew (csw), the Drosophila orthologue of PTPN11. Ubiquitous expression of the LS csw mutant alleles resulted in ectopic wing veins and, for the Y279C allele, rough eyes with increased R7 photoreceptor numbers. These were GOF phenotypes mediated by increased RAS/MAPK signaling and requiring the LS mutant's residual phosphatase activity. Our findings provide the first evidence that LS mutant alleles have GOF developmental effects despite reduced phosphatase activity, providing a rationale for how PTPN11 mutations with GOF and LOF produce similar but distinctive syndromes.
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Affiliation(s)
- Kimihiko Oishi
- Department of Pediatrics and the Center for Molecular Cardiology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.
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Almudi I, Stocker H, Hafen E, Corominas M, Serras F. SOCS36E specifically interferes with Sevenless signaling during Drosophila eye development. Dev Biol 2008; 326:212-23. [PMID: 19083999 DOI: 10.1016/j.ydbio.2008.11.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Revised: 11/17/2008] [Accepted: 11/17/2008] [Indexed: 11/19/2022]
Abstract
During the development of multicellular organisms the fate of individual cells is specified with great precision and reproducibility. Although classical genetic approaches led to the identification of many of the signaling pathways contributing to cell fate specification, they have provided little insight into the mechanisms that ensure robustness and reproducibility. We have used the specification of the R7 photoreceptor cells controlled by the Sevenless receptor tyrosine kinase (Sev) pathway to screen for modulators of pathway activity and to uncover the mechanisms underlying the robustness of cell fate decisions. Here we provide genetic evidence that the Drosophila SOCS36E adaptor protein containing an SH2 domain and a SOCS box acts as an attenuator of Sev signaling. Overexpression of Socs36E strongly suppresses the specification of extra R7 photoreceptor cells in response to constitutive activation of Sev, and loss of Socs36E function suppresses the loss of R7 cells when Sev activity is impaired. In a wild-type background, however, loss and gain of Socs36E function exhibits little effect on R7 specification. We also show that SH2 domain of SOCS36E is essential for this function in inhibiting Sev action and that Socs36E expression is suppressed by high Sev pathway activity. In our model, only the cell able to activate high levels of receptor tyrosine kinase signaling will repress SOCS36E expression, reduce the negative effect on Sev signaling and allow this cell to differentiate into R7. In contrast, the remaining cells fail to receive high signaling, and thus maintain high levels of SOCS36E. This represses residual Sev activity and blocks R7 development. Therefore, Socs36E constitutes a novel partially redundant feedback mechanism that contributes to the robustness of R7 specification. The SOCS family of adaptor proteins may have evolved as modulators of specific signaling pathways that contribute to the robustness and precision of cell fate specification.
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Affiliation(s)
- Isabel Almudi
- Departament de Genètica, Facultat de Biologia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
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Miller AC, Seymour H, King C, Herman TG. Loss of seven-up from Drosophila R1/R6 photoreceptors reveals a stochastic fate choice that is normally biased by Notch. Development 2008; 135:707-15. [PMID: 18199577 DOI: 10.1242/dev.016386] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent evidence suggests that stochasticism is important for generating cell type diversity. We have identified a novel stochastic fate choice as part of the mechanism by which Delta/Notch (Dl/N) signaling specifies R7 fate in the Drosophila eye. The equivalence of R1/R6/R7 precursors is normally broken by the activation of N, which specifies the R7 fate. The orphan nuclear hormone receptor Seven-up (Svp) is necessary and sufficient to direct R1/R6/R7 precursors to adopt the R1/R6 fate. A simple model, therefore, is that N represses Svp, which otherwise prevents adoption of the R7 fate. However, we have found that R1/R6s lacking svp stochastically adopt either the R7 or the R8 fate with equal likelihood. We show that N specifies the R7 fate by a novel branched pathway: N represses Svp expression, thereby exposing an underlying stochastic choice between the R7 and R8 fates, and then tips this choice towards the R7 fate.
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Affiliation(s)
- Adam C Miller
- Institute of Molecular Biology, University of Oregon, 1370 Franklin Blvd, Eugene, OR 97403, USA
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Gaul U, Chang H, Choi T, Karim F, Rubin GM. Identification of ras targets using a genetic approach. CIBA FOUNDATION SYMPOSIUM 2007; 176:85-92; discussion 92-5. [PMID: 8299428 DOI: 10.1002/9780470514450.ch6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Sevenless receptor tyrosine kinase is required for the development of the R7 photoreceptor cell in the Drosophila eye. Several components of the Sevenless signal transduction pathway have been identified in genetic screens for enhancers/suppressors of the sevenless phenotype. These studies suggest that activation of Sevenless leads to stimulation of Ras1 activity, whereas Gap1 appears to act as a negative regulator of the pathway. Inactivation of the Gap1 locus causes transformation of non-neuronal cone cells into supernumerary R7 cells. This same mutant phenotype is observed when activated Ras1 is expressed under the control of the sevenless promoter. While studies in other organisms have demonstrated a role for ras gene products in signal transduction, the effectors of Ras activity have not yet been identified. We are carrying out genetic screens for enhancers and suppressors of the Gap1 and activated Ras1 phenotypes in the hope of identifying genes encoding some of these effectors. We are conducting chemical mutagenesis screens and have also screened existing collections of P element lines. A molecular characterization of the most promising mutations is in progress.
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Affiliation(s)
- U Gaul
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley 94720
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