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Messer CL, Fox DT. Broken chromosomes heading into mitosis: More than one way to patch a flat tire. J Cell Biol 2024; 223:e202401085. [PMID: 38477879 PMCID: PMC10937182 DOI: 10.1083/jcb.202401085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 03/14/2024] Open
Abstract
A cell dealing with a broken chromosome in mitosis is like a driver dealing with a flat tire on the highway: damage repair must occur under non-ideal circumstances. Mitotic chromosome breaks encounter problems related to structures called micronuclei. These aberrant nuclei are linked to cell death, mutagenesis, and cancer. In the last few years, a flurry of studies illuminated two mechanisms that prevent mitotic problems related to micronuclei. One mechanism prevents micronuclei from forming during mitosis and involves DNA Polymerase Theta, a DNA repair regulator that patches up broken mitotic chromosomes. A second mechanism is activated after micronuclei form and then rupture, and involves CIP2A and TOPBP1 proteins, which patch micronuclear fragments to promote their subsequent mitotic segregation. Here, we review recent progress in this field of mitotic DNA damage and discuss why multiple mechanisms exist. Future studies in this exciting area will reveal new DNA break responses and inform therapeutic strategies.
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Affiliation(s)
- C. Luke Messer
- Department of Biology, St. Bonaventure University, St. Bonaventure, NY, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Donald T. Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
- Duke Regeneration Center, Duke University Medical Center, Durham, NC, USA
- Duke Cancer Institute, Duke University Medical Center, Durham, NC, USA
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2
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Chakraborty A, Peterson NG, King JS, Gross RT, Pla MM, Thennavan A, Zhou KC, DeLuca S, Bursac N, Bowles DE, Wolf MJ, Fox DT. Conserved chamber-specific polyploidy maintains heart function in Drosophila. Development 2023; 150:dev201896. [PMID: 37526609 PMCID: PMC10482010 DOI: 10.1242/dev.201896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 07/24/2023] [Indexed: 08/02/2023]
Abstract
Developmentally programmed polyploidy (whole-genome duplication) of cardiomyocytes is common across evolution. Functions of such polyploidy are essentially unknown. Here, in both Drosophila larvae and human organ donors, we reveal distinct polyploidy levels in cardiac organ chambers. In Drosophila, differential growth and cell cycle signal sensitivity leads the heart chamber to reach a higher ploidy/cell size relative to the aorta chamber. Cardiac ploidy-reduced animals exhibit reduced heart chamber size, stroke volume and cardiac output, and acceleration of circulating hemocytes. These Drosophila phenotypes mimic human cardiomyopathies. Our results identify productive and likely conserved roles for polyploidy in cardiac chambers and suggest that precise ploidy levels sculpt many developing tissues. These findings of productive cardiomyocyte polyploidy impact efforts to block developmental polyploidy to improve heart injury recovery.
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Affiliation(s)
- Archan Chakraborty
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
- Duke Regeneration Center, Duke University School of Medicine, Durham, NC 27710, USA
| | - Nora G. Peterson
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Juliet S. King
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Ryan T. Gross
- Department of Surgery, Duke University, Durham, NC 27710, USA
| | | | - Aatish Thennavan
- Department of Systems Biology, UT MD Anderson Cancer Center, Houston, TX 77230, USA
| | - Kevin C. Zhou
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA
| | - Sophia DeLuca
- Department of Biomedical Engineering, Duke University, Durham, NC 27710, USA
| | - Nenad Bursac
- Duke Regeneration Center, Duke University School of Medicine, Durham, NC 27710, USA
- Department of Biomedical Engineering, Duke University, Durham, NC 27710, USA
| | - Dawn E. Bowles
- Department of Surgery, Duke University, Durham, NC 27710, USA
| | - Matthew J. Wolf
- Department of Medicine, University of Virginia, Charlottesville, VA 22903, USA
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22903, USA
| | - Donald T. Fox
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
- Duke Regeneration Center, Duke University School of Medicine, Durham, NC 27710, USA
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3
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Stewart RK, Nguyen P, Laederach A, Volkan PC, Sawyer JK, Fox DT. Orb2 enables rare-codon-enriched mRNA expression during Drosophila neuron differentiation. bioRxiv 2023:2023.07.26.550700. [PMID: 37546801 PMCID: PMC10402044 DOI: 10.1101/2023.07.26.550700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Regulation of codon optimality is an increasingly appreciated layer of cell- and tissue-specific protein expression control. Here, we use codon-modified reporters to show that differentiation of Drosophila neural stem cells into neurons enables protein expression from rare-codon-enriched genes. From a candidate screen, we identify the cytoplasmic polyadenylation element binding (CPEB) protein Orb2 as a positive regulator of rare-codon-dependent expression in neurons. Using RNA sequencing, we reveal that Orb2-upregulated mRNAs in the brain with abundant Orb2 binding sites have a rare-codon bias. From these Orb2-regulated mRNAs, we demonstrate that rare-codon enrichment is important for expression control and social behavior function of the metabotropic glutamate receptor (mGluR). Our findings reveal a molecular mechanism by which neural stem cell differentiation shifts genetic code regulation to enable critical mRNA and protein expression.
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4
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Chakraborty A, Peterson NG, King JS, Gross RT, Pla MM, Thennavan A, Zhou KC, DeLuca S, Bursac N, Bowles DE, Wolf MJ, Fox DT. Conserved Chamber-Specific Polyploidy Maintains Heart Function in Drosophila. bioRxiv 2023:2023.02.10.528086. [PMID: 36798187 PMCID: PMC9934670 DOI: 10.1101/2023.02.10.528086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Developmentally programmed polyploidy (whole-genome-duplication) of cardiomyocytes is common across evolution. Functions of such polyploidy are essentially unknown. Here, we reveal roles for precise polyploidy levels in cardiac tissue. We highlight a conserved asymmetry in polyploidy level between cardiac chambers in Drosophila larvae and humans. In Drosophila , differential Insulin Receptor (InR) sensitivity leads the heart chamber to reach a higher ploidy/cell size relative to the aorta chamber. Cardiac ploidy-reduced animals exhibit reduced heart chamber size, stroke volume, cardiac output, and acceleration of circulating hemocytes. These Drosophila phenotypes mimic systemic human heart failure. Using human donor hearts, we reveal asymmetry in nuclear volume (ploidy) and insulin signaling between the left ventricle and atrium. Our results identify productive and likely conserved roles for polyploidy in cardiac chambers and suggest precise ploidy levels sculpt many developing tissues. These findings of productive cardiomyocyte polyploidy impact efforts to block developmental polyploidy to improve heart injury recovery.
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5
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Abstract
Determining cellular DNA content is valuable in the study of numerous biological processes, including organ development and injury repair. While FACS analysis of dissociated cells is a widely used method for assaying ploidy in a tissue cell population, for many tissue samples, it is possible and convenient to measure ploidy in situ using light microscopy. Here, we present two protocols for measuring cellular ploidy in tissues. These protocols are based on our studies in Drosophila melanogaster, but these are applicable to other settings as well. We present example results from Drosophila hindgut, midgut, and wing imaginal disc as examples. The first protocol focuses on measuring DNA content from decondensed interphase nuclei, while the second protocol details the visualization of condensed chromosomes for ploidy determination, either from mitotic cells or from interphase cells with drug-induced chromosome condensation. These techniques can be completed in 1 day and require standard lab supplies as well as a fluorescence light microscope.
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Affiliation(s)
- Delisa E Clay
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Benjamin M Stormo
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
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6
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Bokhari RS, Beheshti A, Blutt SE, Bowles DE, Brenner D, Britton R, Bronk L, Cao X, Chatterjee A, Clay DE, Courtney C, Fox DT, Gaber MW, Gerecht S, Grabham P, Grosshans D, Guan F, Jezuit EA, Kirsch DG, Liu Z, Maletic-Savatic M, Miller KM, Montague RA, Nagpal P, Osenberg S, Parkitny L, Pierce NA, Porada C, Rosenberg SM, Sargunas P, Sharma S, Spangler J, Tavakol DN, Thomas D, Vunjak-Novakovic G, Wang C, Whitcomb L, Young DW, Donoviel D. Looking on the horizon; potential and unique approaches to developing radiation countermeasures for deep space travel. Life Sci Space Res (Amst) 2022; 35:105-112. [PMID: 36336356 DOI: 10.1016/j.lssr.2022.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 07/29/2022] [Accepted: 08/04/2022] [Indexed: 06/16/2023]
Abstract
Future lunar missions and beyond will require new and innovative approaches to radiation countermeasures. The Translational Research Institute for Space Health (TRISH) is focused on identifying and supporting unique approaches to reduce risks to human health and performance on future missions beyond low Earth orbit. This paper will describe three funded and complementary avenues for reducing the risk to humans from radiation exposure experienced in deep space. The first focus is on identifying new therapeutic targets to reduce the damaging effects of radiation by focusing on high throughput genetic screens in accessible, sometimes called lower, organism models. The second focus is to design innovative approaches for countermeasure development with special attention to nucleotide-based methodologies that may constitute a more agile way to design therapeutics. The final focus is to develop new and innovative ways to test radiation countermeasures in a human model system. While animal studies continue to be beneficial in the study of space radiation, they can have imperfect translation to humans. The use of three-dimensional (3D) complex in vitro models is a promising approach to aid the development of new countermeasures and personalized assessments of radiation risks. These three distinct and unique approaches complement traditional space radiation efforts and should provide future space explorers with more options to safeguard their short and long-term health.
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Affiliation(s)
- Rihana S Bokhari
- Agile Decision Sciences, NRESS, Arlington, VA 22202, United States of America.
| | - Afshin Beheshti
- KBR, Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, 94035, United States of America; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, United States of America
| | - Sarah E Blutt
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, United States of America; Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, United States of America
| | - Dawn E Bowles
- Division of Surgical Sciences, Department of Surgery, Duke University, Durham NC, United States of America
| | - David Brenner
- Columbia University, New York, NY, 10027, United States of America
| | - Robert Britton
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, United States of America
| | - Lawrence Bronk
- The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, United States of America
| | - Xu Cao
- Stanford University School of Medicine, Stanford, CA 94305, United States of America
| | - Anushree Chatterjee
- Sachi Bioworks, Louisville, CO 80027, United States of America; University of Colorado Boulder, Boulder, CO 80303, United States of America
| | - Delisa E Clay
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, United States of America
| | | | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, United States of America
| | - M Waleed Gaber
- Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States of America
| | - Sharon Gerecht
- Chemical and Biomolecular Engineering and Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218 United States of America; Biomedical Engineering, Duke University, Durham, NC 27708, United States of America
| | - Peter Grabham
- Center for Radiological Research, College of Physicians and Surgeons, Columbia University, New York, NY 10027 United States of America
| | - David Grosshans
- The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, United States of America
| | - Fada Guan
- The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, United States of America
| | - Erin A Jezuit
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, United States of America
| | - David G Kirsch
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, United States of America
| | - Zhandong Liu
- Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States of America; Jan and Dan Duncan Neurological Research Institute, 1250 Moursund St. Houston, TX 77030, United States of America
| | - Mirjana Maletic-Savatic
- Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States of America; Jan and Dan Duncan Neurological Research Institute, 1250 Moursund St. Houston, TX 77030, United States of America
| | - Kyle M Miller
- Department of Molecular Biosciences, The University of Texas, Austin, TX 78712, United States of America
| | - Ruth A Montague
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, United States of America
| | - Prashant Nagpal
- Sachi Bioworks, Louisville, CO 80027, United States of America
| | - Sivan Osenberg
- Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States of America; Jan and Dan Duncan Neurological Research Institute, 1250 Moursund St. Houston, TX 77030, United States of America
| | - Luke Parkitny
- Department of Pediatrics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States of America; Jan and Dan Duncan Neurological Research Institute, 1250 Moursund St. Houston, TX 77030, United States of America
| | - Niles A Pierce
- Division of Biology & Biological Engineering, California Institute of Technology, Pasadena, CA 91125, United States of America; Division of Engineering & Applied Science, California Institute of Technology, Pasadena, CA 91125, United States of America; Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Christopher Porada
- Wake Forest Institute for Regenerative Medicine, Fetal Research and Therapy Program Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America
| | - Susan M Rosenberg
- Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77303, United States of America; Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77303, United States of America; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77303, United States of America; Department of Molecular Virology and Microbiology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77303, United States of America
| | - Paul Sargunas
- Chemical and Biomolecular Engineering and Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218 United States of America
| | - Sadhana Sharma
- Sachi Bioworks, Louisville, CO 80027, United States of America
| | - Jamie Spangler
- Chemical and Biomolecular Engineering and Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218 United States of America
| | | | - Dilip Thomas
- Stanford University School of Medicine, Stanford, CA 94305, United States of America
| | | | - Chunbo Wang
- Division of Surgical Sciences, Department of Surgery, Duke University, Durham NC, United States of America
| | - Luke Whitcomb
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, United States of America
| | - Damian W Young
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, United States of America
| | - Dorit Donoviel
- Translational Research Institute for Space Health, Houston, TX 77030, United States of America; Center for Space Medicine, Baylor College of Medicine, Houston, TX 77030, United States of America.
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Clay DE, Jezuit EA, Montague RA, Fox DT. Conserved function of Drosophila Fancd2 monoubiquitination in response to double-strand DNA breaks. G3 (Bethesda) 2022; 12:6589893. [PMID: 35595243 PMCID: PMC9339327 DOI: 10.1093/g3journal/jkac129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/12/2022] [Indexed: 11/12/2022]
Abstract
Fanconi anemia genes play key roles in metazoan DNA damage responses, and human FA mutations cause numerous disease phenotypes. In human cells, activating monoubiquitination of the Fanconi anemia protein Fancd2 occurs following diverse DNA damage stimuli. Monoubiquitinated Fancd2 forms nuclear foci to recruit additional repair factors. Fancd2 animal models to date have focused on molecular nulls or whole gene knockdown, leaving the specific in vivo role of monoubiquitination unclear. Using a point mutant in a conserved residue, we recently linked Drosophila Fancd2 monoubiquitination to a mitosis-specific DNA double-strand break response. In this context, we used CRISPR/Cas9 to generate the first animal model of an endogenous mutation in the conserved monoubiquitination site (fancd2K595R). Here, we expand upon our characterization of fancd2K595R. We also introduce and characterize additional Drosophila tools to study fancd2, including new mutant alleles and GFP-tagged rescue transgenes. Using these new reagents, we show the impact of Drosophila Fancd2 on organismal and cell viability, as well as on repair protein localization, in the presence or absence of double-strand breaks. These findings expand our understanding of Fanconi anemia gene function in vivo and provide useful reagents for DNA repair research.
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Affiliation(s)
- Delisa E Clay
- Department of Pharmacology and Cancer Biology, C318 Levine Science Research Center, Duke University Medical School, Durham, NC 27710, USA
| | - Erin A Jezuit
- Department of Pharmacology and Cancer Biology, C318 Levine Science Research Center, Duke University Medical School, Durham, NC 27710, USA
| | - Ruth A Montague
- Department of Pharmacology and Cancer Biology, C318 Levine Science Research Center, Duke University Medical School, Durham, NC 27710, USA
| | - Donald T Fox
- Corresponding author: Department of Pharmacology and Cancer Biology, C318 Levine Science Research Center, DUMC Box 3813, Duke University Medical School, Durham, NC 27710, USA.
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Allen SR, Stewart RK, Rogers M, Ruiz IJ, Cohen E, Laederach A, Counter CM, Sawyer JK, Fox DT. Distinct responses to rare codons in select Drosophila tissues. eLife 2022; 11:e76893. [PMID: 35522036 PMCID: PMC9116940 DOI: 10.7554/elife.76893] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 05/05/2022] [Indexed: 11/13/2022] Open
Abstract
Codon usage bias has long been appreciated to influence protein production. Yet, relatively few studies have analyzed the impacts of codon usage on tissue-specific mRNA and protein expression. Here, we use codon-modified reporters to perform an organism-wide screen in Drosophila melanogaster for distinct tissue responses to codon usage bias. These reporters reveal a cliff-like decline of protein expression near the limit of rare codon usage in endogenously expressed Drosophila genes. Near the edge of this limit, however, we find the testis and brain are uniquely capable of expressing rare codon-enriched reporters. We define a new metric of tissue-specific codon usage, the tissue-apparent Codon Adaptation Index (taCAI), to reveal a conserved enrichment for rare codon usage in the endogenously expressed genes of both Drosophila and human testis. We further demonstrate a role for rare codons in an evolutionarily young testis-specific gene, RpL10Aa. Optimizing RpL10Aa codons disrupts female fertility. Our work highlights distinct responses to rarely used codons in select tissues, revealing a critical role for codon bias in tissue biology.
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Affiliation(s)
- Scott R Allen
- Department of Cell Biology, Duke UniversityDurhamUnited States
| | - Rebeccah K Stewart
- Department of Pharmacology and Cancer Biology, Duke UniversityDurhamUnited States
| | - Michael Rogers
- Department of Pharmacology and Cancer Biology, Duke UniversityDurhamUnited States
| | - Ivan Jimenez Ruiz
- Department of Biology, University of North Carolina at Chapel HillChapel HillUnited States
| | - Erez Cohen
- Department of Cell Biology, Duke UniversityDurhamUnited States
| | - Alain Laederach
- Department of Biology, University of North Carolina at Chapel HillChapel HillUnited States
| | | | - Jessica K Sawyer
- Department of Pharmacology and Cancer Biology, Duke UniversityDurhamUnited States
| | - Donald T Fox
- Department of Cell Biology, Duke UniversityDurhamUnited States
- Department of Pharmacology and Cancer Biology, Duke UniversityDurhamUnited States
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Clay DE, Bretscher HS, Jezuit EA, Bush KB, Fox DT. Persistent DNA damage signaling and DNA polymerase theta promote broken chromosome segregation. J Cell Biol 2021; 220:e202106116. [PMID: 34613334 PMCID: PMC8500225 DOI: 10.1083/jcb.202106116] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 08/24/2021] [Accepted: 09/14/2021] [Indexed: 01/16/2023] Open
Abstract
Cycling cells must respond to DNA double-strand breaks (DSBs) to avoid genome instability. Missegregation of chromosomes with DSBs during mitosis results in micronuclei, aberrant structures linked to disease. How cells respond to DSBs during mitosis is incompletely understood. We previously showed that Drosophilamelanogaster papillar cells lack DSB checkpoints (as observed in many cancer cells). Here, we show that papillar cells still recruit early acting repair machinery (Mre11 and RPA3) and the Fanconi anemia (FA) protein Fancd2 to DSBs. These proteins persist as foci on DSBs as cells enter mitosis. Repair foci are resolved in a stepwise manner during mitosis. DSB repair kinetics depends on both monoubiquitination of Fancd2 and the alternative end-joining protein DNA polymerase θ. Disruption of either or both of these factors causes micronuclei after DNA damage, which disrupts intestinal organogenesis. This study reveals a mechanism for how cells with inactive DSB checkpoints can respond to DNA damage that persists into mitosis.
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Affiliation(s)
- Delisa E. Clay
- Department of Cell Biology, Duke University School of Medicine, Durham, NC
| | - Heidi S. Bretscher
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC
| | - Erin A. Jezuit
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC
| | - Korie B. Bush
- University Program in Genetics and Genomics, Duke University School of Medicine, Durham, NC
| | - Donald T. Fox
- Department of Cell Biology, Duke University School of Medicine, Durham, NC
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC
- University Program in Genetics and Genomics, Duke University School of Medicine, Durham, NC
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10
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Cohen E, Peterson NG, Sawyer JK, Fox DT. Accelerated cell cycles enable organ regeneration under developmental time constraints in the Drosophila hindgut. Dev Cell 2021; 56:2059-2072.e3. [PMID: 34019841 PMCID: PMC8319103 DOI: 10.1016/j.devcel.2021.04.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/10/2021] [Accepted: 04/28/2021] [Indexed: 12/22/2022]
Abstract
Individual organ development must be temporally coordinated with development of the rest of the organism. As a result, cell division cycles in a developing organ occur on a relatively fixed timescale. Despite this, many developing organs can regenerate cells lost to injury. How organs regenerate within the time constraints of organism development remains unclear. Here, we show that the developing Drosophila hindgut regenerates by accelerating the mitotic cell cycle. This process is achieved by decreasing G1 length and requires the JAK/STAT ligand unpaired-3. Mitotic capacity is then terminated by the steroid hormone ecdysone receptor and the Sox transcription factor Dichaete. These two factors converge on regulation of a hindgut-specific enhancer of fizzy-related, a negative regulator of mitotic cyclins. Our findings reveal how the cell-cycle machinery and cytokine signaling can be adapted to accomplish developmental organ regeneration.
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Affiliation(s)
- Erez Cohen
- Department of Cell Biology, Duke University School of Medicine, Durham, USA
| | - Nora G Peterson
- Department of Cell Biology, Duke University School of Medicine, Durham, USA
| | - Jessica K Sawyer
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, USA
| | - Donald T Fox
- Department of Cell Biology, Duke University School of Medicine, Durham, USA; Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, USA; Regeneration Next Initiative, Duke University School of Medicine, Durham, USA.
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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12
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Adebambo TH, Fox DT, Otitoloju AA. Toxicological Study and Genetic Basis of BTEX Susceptibility in Drosophila melanogaster. Front Genet 2020; 11:594179. [PMID: 33193742 PMCID: PMC7593870 DOI: 10.3389/fgene.2020.594179] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 09/25/2020] [Indexed: 12/21/2022] Open
Abstract
Benzene, toluene, ethylbenzene and xylene, also known as BTEX, are released into environmental media by petroleum product exploratory and exploitative activities and are harmful to humans and animals. Testing the effects of these chemicals on a significantly large scale requires an inexpensive, rapidly developing model organism such as Drosophila melanogaster. In this study, the toxicological profile of benzene, toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene in D. melanogaster was evaluated. Adult animals were monitored for acute toxicity effects. Similarly, first instar larvae reared separately on the same compounds were monitored for the ability to develop into adult flies (eclosion). Further, the impact of fixed concentrations of benzene and xylene on apoptosis and mitosis were investigated in adult progenitor tissues found in third instar larvae. Toluene is the most toxic to adult flies with an LC50 of 0.166 mM, while a significant and dose-dependent decrease in fly eclosion was observed with benzene, p-xylene, and o-xylene. An increase in apoptosis and mitosis was also observed in animals exposed to benzene and p-xylene. Through Genome Wide Association Screening (GWAS), 38 regions of the D. melanogaster genome were identified as critical for responses to p-xylene. This study reveals the strength of D. Melanogaster genetics as an accessible approach to study BTEX compounds.
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Affiliation(s)
- Temitope H Adebambo
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, United States.,Department of Zoology, University of Lagos, Lagos, Nigeria
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, United States
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13
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Fox DT, Soltis DE, Soltis PS, Ashman TL, Van de Peer Y. Polyploidy: A Biological Force From Cells to Ecosystems. Trends Cell Biol 2020; 30:688-694. [PMID: 32646579 DOI: 10.1016/j.tcb.2020.06.006] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 12/20/2022]
Abstract
Polyploidy, resulting from the duplication of the entire genome of an organism or cell, greatly affects genes and genomes, cells and tissues, organisms, and even entire ecosystems. Despite the wide-reaching importance of polyploidy, communication across disciplinary boundaries to identify common themes at different scales has been almost nonexistent. However, a critical need remains to understand commonalities that derive from shared polyploid cellular processes across organismal diversity, levels of biological organization, and fields of inquiry - from biodiversity and biocomplexity to medicine and agriculture. Here, we review the current understanding of polyploidy at the organismal and suborganismal levels, identify shared research themes and elements, and propose new directions to integrate research on polyploidy toward confronting interdisciplinary grand challenges of the 21st century.
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Affiliation(s)
- Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27710, USA.
| | - Douglas E Soltis
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA; Department of Biology, University of Florida, Gainesville, FL 32611, USA.
| | - Pamela S Soltis
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA.
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
| | - Yves Van de Peer
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium; VIB Center for Plant Systems Biology, Ghent, Belgium; Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa; College of Horticulture, Nanjing Agricultural University, Nanjing, China.
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14
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Abstract
Drosophila melanogaster has historically been a workhorse model organism for studying developmental biology. In addition, Drosophila is an excellent model for studying how damaged tissues and organs can regenerate. Recently, new precision approaches that enable both highly targeted injury and genetic manipulation have accelerated progress in this field. Here, we highlight these techniques and review examples of recently discovered mechanisms that regulate regeneration in Drosophila larval and adult tissues. We also discuss how, by applying these powerful approaches, studies of Drosophila can continue to guide the future of regeneration research.
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Affiliation(s)
- Donald T Fox
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
- Regeneration Next, Duke University, Durham, NC 27710, USA
| | - Erez Cohen
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
- Regeneration Next, Duke University, Durham, NC 27710, USA
| | - Rachel Smith-Bolton
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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15
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Cohen E, Sawyer JK, Peterson NG, Dow JAT, Fox DT. Physiology, Development, and Disease Modeling in the Drosophila Excretory System. Genetics 2020; 214:235-264. [PMID: 32029579 PMCID: PMC7017010 DOI: 10.1534/genetics.119.302289] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 11/04/2019] [Indexed: 02/06/2023] Open
Abstract
The insect excretory system contains two organ systems acting in concert: the Malpighian tubules and the hindgut perform essential roles in excretion and ionic and osmotic homeostasis. For over 350 years, these two organs have fascinated biologists as a model of organ structure and function. As part of a recent surge in interest, research on the Malpighian tubules and hindgut of Drosophila have uncovered important paradigms of organ physiology and development. Further, many human disease processes can be modeled in these organs. Here, focusing on discoveries in the past 10 years, we provide an overview of the anatomy and physiology of the Drosophila excretory system. We describe the major developmental events that build these organs during embryogenesis, remodel them during metamorphosis, and repair them following injury. Finally, we highlight the use of the Malpighian tubules and hindgut as accessible models of human disease biology. The Malpighian tubule is a particularly excellent model to study rapid fluid transport, neuroendocrine control of renal function, and modeling of numerous human renal conditions such as kidney stones, while the hindgut provides an outstanding model for processes such as the role of cell chirality in development, nonstem cell-based injury repair, cancer-promoting processes, and communication between the intestine and nervous system.
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Affiliation(s)
| | - Jessica K Sawyer
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, and
| | | | - Julian A T Dow
- Institute of Molecular, Cell, and Systems Biology, University of Glasgow, G12 8QQ, United Kingdom
| | - Donald T Fox
- Department of Cell Biology and
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, and
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16
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Peterson NG, Stormo BM, Schoenfelder KP, King JS, Lee RRS, Fox DT. Cytoplasmic sharing through apical membrane remodeling. eLife 2020; 9:58107. [PMID: 33051002 PMCID: PMC7655102 DOI: 10.7554/elife.58107] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 10/13/2020] [Indexed: 12/12/2022] Open
Abstract
Multiple nuclei sharing a common cytoplasm are found in diverse tissues, organisms, and diseases. Yet, multinucleation remains a poorly understood biological property. Cytoplasm sharing invariably involves plasma membrane breaches. In contrast, we discovered cytoplasm sharing without membrane breaching in highly resorptive Drosophila rectal papillae. During a six-hour developmental window, 100 individual papillar cells assemble a multinucleate cytoplasm, allowing passage of proteins of at least 62 kDa throughout papillar tissue. Papillar cytoplasm sharing does not employ canonical mechanisms such as incomplete cytokinesis or muscle fusion pore regulators. Instead, sharing requires gap junction proteins (normally associated with transport of molecules < 1 kDa), which are positioned by membrane remodeling GTPases. Our work reveals a new role for apical membrane remodeling in converting a multicellular epithelium into a giant multinucleate cytoplasm.
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Affiliation(s)
- Nora G Peterson
- Department of Cell Biology, Duke University Medical CenterDurhamUnited States
| | - Benjamin M Stormo
- Department of Cell Biology, Duke University Medical CenterDurhamUnited States
| | | | - Juliet S King
- Department of Pharmacology & Cancer Biology, Duke University Medical CenterDurhamUnited States
| | | | - Donald T Fox
- Department of Cell Biology, Duke University Medical CenterDurhamUnited States,University Program in Genetics and Genomics, Duke UniversityDurhamUnited States,Department of Pharmacology & Cancer Biology, Duke University Medical CenterDurhamUnited States
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17
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Stormo BM, Fox DT. Interphase cohesin regulation ensures mitotic fidelity after genome reduplication. Mol Biol Cell 2019; 30:219-227. [PMID: 30462577 PMCID: PMC6589556 DOI: 10.1091/mbc.e17-10-0582] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 10/17/2018] [Accepted: 11/15/2018] [Indexed: 12/24/2022] Open
Abstract
To ensure faithful genome propagation, mitotic cells alternate one round of chromosome duplication with one round of chromosome separation. Chromosome separation failure thus causes genome reduplication, which alters mitotic chromosome structure. Such structural alterations are well documented to impair mitotic fidelity following aberrant genome reduplication, including in diseased states. In contrast, we recently showed that naturally occurring genome reduplication does not alter mitotic chromosome structure in Drosophila papillar cells. Our discovery raised the question of how a cell undergoing genome reduplication might regulate chromosome structure to prevent mitotic errors. Here, we show that papillar cells ensure mitotic fidelity through interphase cohesin regulation. We demonstrate a requirement for cohesins during programmed rounds of papillar genome reduplication known as endocycles. This interphase cohesin regulation relies on cohesin release but not cohesin cleavage and depends on the conserved cohesin regulator Pds5 . Our data suggest that a distinct form of interphase cohesin regulation ensures mitotic fidelity after genome reduplication.
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Affiliation(s)
- Benjamin M. Stormo
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Donald T. Fox
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710
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18
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Cohen E, Allen SR, Sawyer JK, Fox DT. Fizzy-Related dictates A cell cycle switch during organ repair and tissue growth responses in the Drosophila hindgut. eLife 2018; 7:38327. [PMID: 30117808 PMCID: PMC6130973 DOI: 10.7554/elife.38327] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 08/16/2018] [Indexed: 12/21/2022] Open
Abstract
Ploidy-increasing cell cycles drive tissue growth in many developing organs. Such cycles, including endocycles, are increasingly appreciated to drive tissue growth following injury or activated growth signaling in mature organs. In these organs, the regulation and distinct roles of different cell cycles remains unclear. Here, we uncover a programmed switch between cell cycles in the Drosophila hindgut pylorus. Using an acute injury model, we identify mitosis as the response in larval pyloric cells, whereas endocycles occur in adult pyloric cells. By developing a novel genetic method, DEMISE (Dual-Expression-Method-for-Induced-Site-specific-Eradication), we show the cell cycle regulator Fizzy-related dictates the decision between mitosis and endocycles. After injury, both cycles accurately restore tissue mass and genome content. However, in response to sustained growth signaling, only endocycles preserve epithelial architecture. Our data reveal distinct cell cycle programming in response to similar stimuli in mature vs. developmental states and reveal a tissue-protective role of endocycles.
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Affiliation(s)
- Erez Cohen
- Department of Cell BiologyDuke University School of MedicineDurhamUnited States
| | - Scott R Allen
- Department of Cell BiologyDuke University School of MedicineDurhamUnited States
| | - Jessica K Sawyer
- Department of Pharmacology & Cancer BiologyDuke University School of MedicineDurhamUnited States
| | - Donald T Fox
- Department of Cell BiologyDuke University School of MedicineDurhamUnited States,Department of Pharmacology & Cancer BiologyDuke University School of MedicineDurhamUnited States,Regeneration Next InitiativeDuke University School of MedicineDurhamUnited States
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19
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Sawyer JK, Cohen E, Fox DT. Interorgan regulation of Drosophila intestinal stem cell proliferation by a hybrid organ boundary zone. Development 2017; 144:4091-4102. [PMID: 28947534 PMCID: PMC5719245 DOI: 10.1242/dev.153114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 09/15/2017] [Indexed: 12/27/2022]
Abstract
The molecular identities and regulation of cells at interorgan boundaries are often unclear, despite the increasingly appreciated role of organ boundaries in disease. Using Drosophila as a model, we here show that a specific population of adult midgut organ-boundary intestinal stem cells (OB-ISCs) is regulated by the neighboring hindgut, a developmentally distinct organ. This distinct OB-ISC control occurs through proximity to a specialized transition zone between the endodermal midgut and ectodermal hindgut that shares molecular signatures of both organs, which we term the hybrid zone (HZ). During homeostasis, proximity to the HZ restrains OB-ISC proliferation. However, injury to the adult HZ/hindgut drives upregulation of unpaired-3 cytokine, which signals through a Signal transducer and activator of transcription (STAT) protein to promote cell division only in OB-ISCs. If HZ disruption is severe, hyperplastic OB-ISCs expand across the interorgan boundary. Our data suggest that interorgan signaling plays an important role in controlling OB-ISCs in homeostasis and injury repair, which is likely to be crucial in prevention of disease.
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Affiliation(s)
- Jessica K. Sawyer
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA,Regeneration Next, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA
| | - Erez Cohen
- Regeneration Next, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA,Department of Cell Biology, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA
| | - Donald T. Fox
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA,Regeneration Next, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA,Department of Cell Biology, Duke University Medical Center, DUMC Box 3813, Durham, NC 27710, USA,Author for correspondence ()
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20
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Abstract
In this era of high-resolution mapping of chromosome territories, topological interactions, and chromatin states, it is increasingly appreciated that the positioning of chromosomes and their interactions within the nucleus is critical for cellular function. Due to their large size and distinctive structure, polytene chromosomes have contributed a wealth of knowledge regarding chromosome regulation. In this review, we discuss the diversity of polytene chromosomes in nature and in disease, examine the recurring structural features of polytene chromosomes in terms of what they reveal about chromosome biology, and discuss recent advances regarding how polytene chromosomes are assembled and disassembled. After over 130 years of study, these giant chromosomes are still powerful tools to understand chromosome biology.
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Affiliation(s)
- Benjamin M Stormo
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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21
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Bretscher HS, Fox DT. Proliferation of Double-Strand Break-Resistant Polyploid Cells Requires Drosophila FANCD2. Dev Cell 2016; 37:444-57. [PMID: 27270041 PMCID: PMC4901310 DOI: 10.1016/j.devcel.2016.05.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 02/22/2016] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Conserved DNA-damage responses (DDRs) sense genome damage and prevent mitosis of broken chromosomes. How cells lacking DDRs cope with broken chromosomes during mitosis is poorly understood. DDRs are frequently inactivated in cells with extra genomes (polyploidy), suggesting that study of polyploidy can reveal how cells with impaired DDRs/genome damage continue dividing. Here, we show that continued division and normal organ development occurs in polyploid, DDR-impaired Drosophila papillar cells. As papillar cells become polyploid, they naturally accumulate broken acentric chromosomes but do not apoptose/arrest the cell cycle. To survive mitosis with acentric chromosomes, papillar cells require Fanconi anemia proteins FANCD2 and FANCI, as well as Blm helicase, but not canonical DDR signaling. FANCD2 acts independently of previous S phases to promote alignment and segregation of acentric DNA produced by double-strand breaks, thus avoiding micronuclei and organ malformation. Because polyploidy and impaired DDRs can promote cancer, our findings provide insight into disease-relevant DNA-damage tolerance mechanisms.
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Affiliation(s)
- Heidi S Bretscher
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, DUMC Box 3813, Durham, NC 27710, USA
| | - Donald T Fox
- Department of Pharmacology & Cancer Biology, Duke University School of Medicine, DUMC Box 3813, Durham, NC 27710, USA.
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22
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Abstract
Duplicating chromosomes once each cell cycle produces sister chromatid pairs, which separate accurately at anaphase. In contrast, reduplicating chromosomes without separation frequently produces polytene chromosomes, a barrier to accurate mitosis. Chromosome reduplication occurs in many contexts, including: polytene tissue development, polytene tumors, and following treatment with mitosis-blocking chemotherapeutics. However, mechanisms responding to or resolving polyteny during mitosis are poorly understood. Here, using Drosophila, we uncover two distinct reduplicated chromosome responses. First, when reduplicated polytene chromosomes persist into metaphase, an anaphase delay prevents tissue malformation and apoptosis. Second, reduplicated polytene chromosomes can also separate prior to metaphase through a spindle-independent mechanism termed Separation-Into-Recent-Sisters (SIRS). Both reduplication responses require the spindle assembly checkpoint protein Mad2. While Mad2 delays anaphase separation of metaphase polytene chromosomes, Mad2’s control of overall mitotic timing ensures efficient SIRS. Our results pinpoint mechanisms enabling continued proliferation after genome reduplication, a finding with implications for cancer progression and prevention. DOI:http://dx.doi.org/10.7554/eLife.15204.001 Before a cell divides, it duplicates all its genetic information, which is stored on chromosomes. Then, each chromosome evenly divides into two new cells so that each cell ends up with identical copies of the genetic information. Because the cellular machinery that evenly divides chromosomes is built to recognize chromosomes that were duplicated exactly once, it is important to maintain this pattern of alternating one round of duplication with one round of division. Cells that instead duplicate their chromosomes more than once can make mistakes during division that are associated with diseases such as cancer. Chromosomes with extra duplications are present in normal tissues such as the placenta of mammals. They can also occur in human diseases and may even result from chemotherapy treatment. However, we know almost nothing about how cells respond to these problematic chromosomes when dividing. By studying cells from the Drosophila melanogaster species of fruit fly, Stormo and Fox discovered two distinct ways in which cells respond to extra chromosome duplications. One response occurs in cells that were experimentally engineered to undergo an extra chromosome duplication. These cells delay division so that the chromosome separation machinery can somehow adapt to the challenge of separating more than two chromosome copies at once. The second response occurs in cells that naturally undergo extra chromosome duplications before division. In these cells, Stormo and Fox discovered a new type of chromosome separation, whereby the extra chromosome copies move apart from each other before cell division. In doing so the chromosomes can better interact with the chromosome separation machinery during division. Stormo and Fox also found that a protein named Mad2 is important in both responses, and gives the cell enough time to respond to extra chromosome copies. Without Mad2, the separation of chromosomes with extra duplications is too hasty, and can lead to severe cell division errors and cause organs to form incorrectly. Having uncovered two new responses that cells use to adapt to extra chromosomes, it will now be important to find other proteins like Mad2 that are important in these events. Understanding these processes and the proteins involved in more detail could help to prevent diseases that are associated with extra chromosomes. DOI:http://dx.doi.org/10.7554/eLife.15204.002
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Affiliation(s)
- Benjamin M Stormo
- Department of Cell Biology, Duke University Medical Center, Durham, United States
| | - Donald T Fox
- Department of Cell Biology, Duke University Medical Center, Durham, United States.,Department of Pharamacology and Cancer biology, Duke University Medical Center, Durham, United States
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23
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Abstract
Polyploid cells, which contain more than two genome copies, occur throughout nature. Beyond well-established roles in increasing cell size/metabolic output, polyploidy can also promote nonuniform genome, transcriptome, and metabolome alterations. Polyploidy also frequently confers resistance to environmental stresses not tolerated by diploid cells. Recent progress has begun to unravel how this fascinating phenomenon contributes to normal physiology and disease.
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Affiliation(s)
- Kevin P Schoenfelder
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710
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24
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Schoenfelder KP, Montague RA, Paramore SV, Lennox AL, Mahowald AP, Fox DT. Indispensable pre-mitotic endocycles promote aneuploidy in the Drosophila rectum. Development 2014; 141:3551-60. [PMID: 25142462 DOI: 10.1242/dev.109850] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The endocycle is a modified cell cycle that lacks M phase. Endocycles are well known for enabling continued growth of post-mitotic tissues. By contrast, we discovered pre-mitotic endocycles in precursors of Drosophila rectal papillae (papillar cells). Unlike all known proliferative Drosophila adult precursors, papillar cells endocycle before dividing. Furthermore, unlike diploid mitotic divisions, these polyploid papillar divisions are frequently error prone, suggesting papillar structures may accumulate long-term aneuploidy. Here, we demonstrate an indispensable requirement for pre-mitotic endocycles during papillar development and also demonstrate that such cycles seed papillar aneuploidy. We find blocking pre-mitotic endocycles disrupts papillar morphogenesis and causes organismal lethality under high-salt dietary stress. We further show that pre-mitotic endocycles differ from post-mitotic endocycles, as we find only the M-phase-capable polyploid cells of the papillae and female germline can retain centrioles. In papillae, this centriole retention contributes to aneuploidy, as centrioles amplify during papillar endocycles, causing multipolar anaphase. Such aneuploidy is well tolerated in papillae, as it does not significantly impair cell viability, organ formation or organ function. Together, our results demonstrate that pre-mitotic endocycles can enable specific organ construction and are a mechanism that promotes highly tolerated aneuploidy.
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Affiliation(s)
- Kevin P Schoenfelder
- Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27710, USA
| | - Ruth A Montague
- Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27710, USA
| | - Sarah V Paramore
- Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27710, USA
| | - Ashley L Lennox
- Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27710, USA
| | - Anthony P Mahowald
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Box 3813, Duke University Medical Center, Durham, NC 27710, USA
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25
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Losick VP, Fox DT, Spradling AC. Polyploidization and cell fusion contribute to wound healing in the adult Drosophila epithelium. Curr Biol 2013; 23:2224-2232. [PMID: 24184101 PMCID: PMC3898104 DOI: 10.1016/j.cub.2013.09.029] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/19/2013] [Accepted: 09/13/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Reestablishing epithelial integrity and biosynthetic capacity is critically important following tissue damage. The adult Drosophila abdominal epithelium provides an attractive new system to address how postmitotic diploid cells contribute to repair. RESULTS Puncture wounds to the adult Drosophila epidermis close initially by forming a melanized scab. We found that epithelial cells near the wound site fuse to form a giant syncytium, which sends lamellae under the scab to re-epithelialize the damaged site. Other large cells arise more peripherally by initiating endocycles and becoming polyploid, or by cell fusion. Rac GTPase activity is needed for syncytium formation, while the Hippo signaling effector Yorkie modulates both polyploidization and cell fusion. Large cell formation is functionally important because when both polyploidization and fusion are blocked, wounds do not re-epithelialize. CONCLUSIONS Our observations indicate that cell mass lost upon wounding can be replaced by polyploidization instead of mitotic proliferation. We propose that large cells generated by polyploidization or cell fusion are essential because they are better able than diploid cells to mechanically stabilize wounds, especially those containing permanent acellular structures, such as scar tissue.
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Affiliation(s)
- Vicki P Losick
- Department of Embryology, Carnegie Institution for Science, Howard Hughes Medical Institute, 3520 San Martin Drive, Baltimore, MD 21218, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology and Department of Cell Biology, Duke University Medical Center, C318 LSRC Box 3813, Durham, NC 27710, USA
| | - Allan C Spradling
- Department of Embryology, Carnegie Institution for Science, Howard Hughes Medical Institute, 3520 San Martin Drive, Baltimore, MD 21218, USA.
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26
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Abstract
Polyploid cells have genomes that contain multiples of the typical diploid chromosome number and are found in many different organisms. Studies in a variety of animal and plant developmental systems have revealed evolutionarily conserved mechanisms that control the generation of polyploidy and have recently begun to provide clues to its physiological function. These studies demonstrate that cellular polyploidy plays important roles during normal development and also contributes to human disease, particularly cancer.
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Affiliation(s)
- Donald T Fox
- Department of Pharmacology and Cancer Biology, and Department of Cell Biology, Duke University, Durham, NC 27710, USA.
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27
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Losick VP, Morris LX, Fox DT, Spradling A. Drosophila stem cell niches: a decade of discovery suggests a unified view of stem cell regulation. Dev Cell 2011; 21:159-71. [PMID: 21763616 PMCID: PMC6894370 DOI: 10.1016/j.devcel.2011.06.018] [Citation(s) in RCA: 231] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Revised: 06/03/2011] [Accepted: 06/10/2011] [Indexed: 12/28/2022]
Abstract
The past decade of research on Drosophila stem cells and niches has provided key insights. Fly stem cells do not occupy a special "state" based on novel "stem cell genes" but resemble transiently arrested tissue progenitors. Moreover, individual stem cells and downstream progenitors are highly dynamic and dispensable, not tissue bulwarks. Niches, rather than fixed cell lineages, ensure tissue health by holding stem cells and repressing cell differentiation inside, but not outside. We review the five best-understood adult Drosophila stem cells and argue that the fundamental biology of stem cells and niches is conserved between Drosophila and mice.
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Affiliation(s)
- Vicki P Losick
- Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution for Science, 3520 San Martin Drive, Baltimore, MD 21218, USA
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28
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Abstract
Endopolyploidy arises during normal development in many species when cells undergo endocycles-variant cell cycles in which DNA replicates but daughter cells do not form. Normally, polyploid cells do not divide mitotically after initiating endocycles; hence, little is known about their mitotic competence. However, polyploid cells are found in many tumors, and the enhanced chromosomal instability of polyploid cells in culture suggests that such cells contribute to tumor aneuploidy. Here, we describe a novel polyploid Drosophila cell type that undergoes normal mitotic cycles as part of a remodeling process that forms the adult rectal papillae. Similar polyploid mitotic divisions, but not depolyploidizing divisions, were observed during adult ileum development in the mosquito Culex pipiens. Extended anaphases, chromosome bridges, and lagging chromosomes were frequent during these polyploid divisions, despite normal expression of cell cycle regulators. Our results show that the switch to endocycles during development is not irreversible, but argue that the polyploid mitotic cycle is inherently error-prone, and that polyploid mitoses may help destabilize the cancer genome.
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Affiliation(s)
- Donald T Fox
- Howard Hughes Medical Institute Research Laboratories, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
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Fox DT, Spradling AC. The Drosophila hindgut lacks constitutively active adult stem cells but proliferates in response to tissue damage. Cell Stem Cell 2009; 5:290-7. [PMID: 19699165 PMCID: PMC2772661 DOI: 10.1016/j.stem.2009.06.003] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 05/15/2009] [Accepted: 06/05/2009] [Indexed: 12/01/2022]
Abstract
The adult Drosophila hindgut was recently reported to contain active, tissue-replenishing stem cells, like those of the midgut, but located within an anterior ring so as to comprise a single giant crypt. In contrast to this view, we observed no active stem cells and little cell turnover in adult hindgut tissue based on clonal marking and BrdU incorporation studies. Again contradicting the previous proposal, we showed that the adult hindgut is not generated by anterior stem cells during larval/pupal development. However, severe tissue damage within the hindgut elicits cell proliferation within a ring of putative quiescent stem cells at the anterior of the pylorus. Thus, the hindgut does not provide a model of tissue maintenance by constitutively active stem cells, but has great potential to illuminate mechanisms of stress-induced tissue repair.
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Affiliation(s)
- Donald T Fox
- Department of Embryology, Howard Hughes Medical Institute, Carnegie Institution, Baltimore, MD 21218, USA
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Stevens TL, Rogers EM, Koontz LM, Fox DT, Homem CCF, Nowotarski SH, Artabazon NB, Peifer M. Using Bcr-Abl to examine mechanisms by which abl kinase regulates morphogenesis in Drosophila. Mol Biol Cell 2007; 19:378-93. [PMID: 17959833 DOI: 10.1091/mbc.e07-01-0008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Signaling by the nonreceptor tyrosine kinase Abelson (Abl) plays key roles in normal development, whereas its inappropriate activation helps trigger the development of several forms of leukemia. Abl is best known for its roles in axon guidance, but Abl and its relatives also help regulate embryonic morphogenesis in epithelial tissues. Here, we explore the role of regulation of Abl kinase activity during development. We first compare the subcellular localization of Abl protein and of active Abl, by using a phosphospecific antibody, providing a catalog of places where Abl is activated. Next, we explore the consequences for morphogenesis of overexpressing wild-type Abl or expressing the activated form found in leukemia, Bcr-Abl. We find dose-dependent effects of elevating Abl activity on morphogenetic movements such as head involution and dorsal closure, on cell shape changes, on cell protrusive behavior, and on the organization of the actin cytoskeleton. Most of the effects of Abl activation parallel those caused by reduction in function of its target Enabled. Abl activation leads to changes in Enabled phosphorylation and localization, suggesting a mechanism of action. These data provide new insight into how regulated Abl activity helps direct normal development and into possible biological functions of Bcr-Abl.
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Affiliation(s)
- Traci L Stevens
- Department of Biology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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31
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Abstract
The catenin p120 is involved in many processes, including cell-cell adhesion and cancer. Recent work explores whether p120 independently regulates two key binding partners, RhoGTPase and cadherin.
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Affiliation(s)
- Donald T Fox
- Department of Biology and Lineberger Comprehensive Cancer Center, University of North Carolina Chapel Hill, North Carolina 27599-3280, USA
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32
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Abstract
Morphogenesis involves the interplay of different cytoskeletal regulators. Investigating how they interact during a given morphogenetic event will help us understand animal development. Studies of ventral furrow formation, a morphogenetic event during Drosophila gastrulation, have identified a signaling pathway involving the G-protein Concertina (Cta) and the Rho activator RhoGEF2. Although these regulators act to promote stable myosin accumulation and apical cell constriction, loss-of-function phenotypes for each of these pathway members is not equivalent, suggesting the existence of additional ventral furrow regulators. Here, we report the identification of Abelson kinase (Abl) as a novel ventral furrow regulator. We find that Abl acts apically to suppress the accumulation of both Enabled (Ena) and actin in mesodermal cells during ventral furrow formation. Further, RhoGEF2 also regulates ordered actin localization during ventral furrow formation, whereas its activator, Cta, does not. Taken together, our data suggest that there are two crucial preconditions for apical constriction in the ventral furrow:myosin stabilization/activation, regulated by Cta and RhoGEF2; and the organization of apical actin, regulated by Abl and RhoGEF2. These observations identify an important morphogenetic role for Abl and suggest a conserved mechanism for this kinase during apical cell constriction.
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Affiliation(s)
- Donald T Fox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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33
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Abstract
During animal development, adherens junctions (AJs) maintain epithelial cell adhesion and coordinate changes in cell shape by linking the actin cytoskeletons of adjacent cells. Identifying AJ regulators and their mechanisms of action are key to understanding the cellular basis of morphogenesis. Previous studies linked both p120catenin and the small GTPase Rho to AJ regulation and revealed that p120 may negatively regulate Rho. Here we examine the roles of these candidate AJ regulators during Drosophila development. We found that although p120 is not essential for development, it contributes to morphogenesis efficiency, clarifying its role as a redundant AJ regulator. Rho has a dynamic localization pattern throughout ovarian and embryonic development. It preferentially accumulates basally or basolaterally in several tissues, but does not preferentially accumulate in AJs. Further, Rho1 localization is not obviously altered by loss of p120 or by reduction of core AJ proteins. Genetic and cell biological tests suggest that p120 is not a major dose-sensitive regulator of Rho1. However, Rho1 itself appears to be a regulator of AJs. Loss of Rho1 results in ectopic accumulation of cytoplasmic DE-cadherin, but ectopic cadherin does not accumulate with its partner Armadillo. These data suggest Rho1 regulates AJs during morphogenesis, but this regulation is p120 independent.
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Affiliation(s)
- Donald T Fox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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34
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Abstract
The proto-oncogenic kinase Abelson (Abl) regulates actin in response to cell signaling. Drosophila Abl is required in the nervous system, and also in epithelial cells, where it regulates adherens junction stability and actin organization. Abl acts at least in part via the actin regulator Enabled (Ena), but the mechanism by which Abl regulates Ena is unknown. We describe a novel role for Abl in early Drosophila development, where it regulates the site and type of actin structures produced. In Abl's absence, excess actin is polymerized in apical microvilli, whereas too little actin is assembled into pseudocleavage and cellularization furrows. These effects involve Ena misregulation. In abl mutants, Ena accumulates ectopically at the apical cortex where excess actin is observed, suggesting that Abl regulates Ena's subcellular localization. We also examined other actin regulators. Loss of Abl leads to changes in the localization of the Arp2/3 complex and the formin Diaphanous, and mutations in diaphanous or capping protein beta enhance abl phenotypes.
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Myster SH, Cavallo R, Anderson CT, Fox DT, Peifer M. Drosophila p120catenin plays a supporting role in cell adhesion but is not an essential adherens junction component. J Cell Biol 2003; 160:433-49. [PMID: 12551951 PMCID: PMC2172674 DOI: 10.1083/jcb.200211083] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cadherin-catenin complexes, localized to adherens junctions, are essential for cell-cell adhesion. One means of regulating adhesion is through the juxtamembrane domain of the cadherin cytoplasmic tail. This region is the binding site for p120, leading to the hypothesis that p120 is a key regulator of cell adhesion. p120 has also been suggested to regulate the GTPase Rho and to regulate transcription via its binding partner Kaiso. To test these hypothesized functions, we turned to Drosophila, which has only a single p120 family member. It localizes to adherens junctions and binds the juxtamembrane region of DE-cadherin (DE-cad). We generated null alleles of p120 and found that mutants are viable and fertile and have no substantial changes in junction structure or function. However, p120 mutations strongly enhance mutations in the genes encoding DE-cadherin or Armadillo, the beta-catenin homologue. Finally, we examined the localization of p120 during embryogenesis. p120 localizes to adherens junctions, but its localization there is less universal than that of core adherens junction proteins. Together, these data suggest that p120 is an important positive modulator of adhesion but that it is not an essential core component of adherens junctions.
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Affiliation(s)
- Steven H Myster
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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36
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Bai Y, Fox DT, Lacy JA, Van Lanen SG, Iwata-Reuyl D. Hypermodification of tRNA in Thermophilic archaea. Cloning, overexpression, and characterization of tRNA-guanine transglycosylase from Methanococcus jannaschii. J Biol Chem 2000; 275:28731-8. [PMID: 10862614 DOI: 10.1074/jbc.m002174200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
tRNA is structurally unique among nucleic acids in harboring an astonishing diversity of modified nucleosides. Two structural variants of the hypermodified nucleoside 7-deazaguanosine have been identified in tRNA: queuosine, which is found at the wobble position of the anticodon in bacterial and eukaryotic tRNA, and archaeosine, which is found at position 15 of the D-loop in archaeal tRNA. From homology searching of the Methanococcus jannaschii genome, a gene coding for an enzyme in the biosynthesis of archaeosine (tgt) was identified and cloned. The tgt gene was overexpressed in an Escherichia coli expression system, and the recombinant tRNA-guanine transglycosylase enzyme was purified and characterized. The enzyme catalyzes a transglycosylation reaction in which guanine is eliminated from position 15 of the tRNA and an archaeosine precursor (preQ(0)) is inserted. The enzyme is able to utilize both guanine and the 7-deazaguanine base preQ(0) as substrates, but not other 7-deazaguanine bases, and is able to modify tRNA from all three phylogenetic domains. The enzyme shows optimal activity at high temperature and acidic pH, consistent with the optimal growth conditions of M. jannaschii. The nature of the temperature dependence is consistent with a requirement for some degree of tRNA tertiary structure in order for recognition by the enzyme to occur.
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Affiliation(s)
- Y Bai
- Department of Chemistry, Portland State University, Portland, Oregon 97201, USA
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Calalb MB, Fox DT, Hanks SK. Molecular cloning and enzymatic analysis of the rat homolog of "PhK-gamma T," an isoform of phosphorylase kinase catalytic subunit. J Biol Chem 1992; 267:1455-63. [PMID: 1370475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023] Open
Abstract
Messenger RNA encoding a protein kinase closely related to the catalytic subunit of skeletal muscle phosphorylase kinase has previously been isolated from a human HeLa cell cDNA library, and cross-species Northern hybridization analysis has shown that the rat homolog of this transcript is abundant in the adult testis (Hanks, S.K. (1989) Mol. Endocrinol. 3, 110-116). We now propose that the protein encoded by this transcript be designated as "PhK-gamma T." In this article, the primary structure of the rat homolog of PhK-gamma T is described, as deduced from nucleotide sequences of cDNA and genomic clones. RNase protection analysis reveals that PhK-gamma T transcripts are actually present in a wide variety of adult rat tissues, but at levels 20-100-fold less than what is observed in the testis. In the testis, transcription of the PhK-gamma T gene is initiated at multiple sites as shown by RNase protection and primer extension. Enzymatic activity of PhK-gamma T was demonstrated using renatured bacterially expressed protein. In the presence of Ca2+/calmodulin, PhK-gamma T is able to efficiently phosphorylate glycogen phosphorylase and convert it from an inactive to an active form. We conclude that PhK-gamma T represents a true isoform of phosphorylase kinase catalytic subunit.
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Affiliation(s)
- M B Calalb
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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38
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Abstract
A binary system for gene activation and site-specific integration, based on the conditional recombination of transfected sequences mediated by the FLP recombinase from yeast, was implemented in mammalian cells. In several cell lines, FLP rapidly and precisely recombined copies of its specific target sequence to activate an otherwise silent beta-galactosidase reporter gene. Clones of marked cells were generated by excisional recombination within a chromosomally integrated copy of the silent reporter. By the reverse reaction, integration of transfected DNA was targeted to a specific chromosomal site. The results suggest that FLP could be used to mosaically activate or inactivate transgenes for analysis of vertebrate development, and to efficiently integrate transfected DNA at predetermined chromosomal locations.
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Affiliation(s)
- S O'Gorman
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037
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