1
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Lago-Baldaia I, Fernandes VM, Ackerman SD. More Than Mortar: Glia as Architects of Nervous System Development and Disease. Front Cell Dev Biol 2020; 8:611269. [PMID: 33381506 PMCID: PMC7767919 DOI: 10.3389/fcell.2020.611269] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/17/2020] [Indexed: 12/12/2022] Open
Abstract
Glial cells are an essential component of the nervous system of vertebrates and invertebrates. In the human brain, glia are as numerous as neurons, yet the importance of glia to nearly every aspect of nervous system development has only been expounded over the last several decades. Glia are now known to regulate neural specification, synaptogenesis, synapse function, and even broad circuit function. Given their ubiquity, it is not surprising that the contribution of glia to neuronal disease pathogenesis is a growing area of research. In this review, we will summarize the accumulated evidence of glial participation in several distinct phases of nervous system development and organization-neural specification, circuit wiring, and circuit function. Finally, we will highlight how these early developmental roles of glia contribute to nervous system dysfunction in neurodevelopmental and neurodegenerative disorders.
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Affiliation(s)
- Inês Lago-Baldaia
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Vilaiwan M. Fernandes
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Sarah D. Ackerman
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, United States
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2
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Crews ST. Drosophila Embryonic CNS Development: Neurogenesis, Gliogenesis, Cell Fate, and Differentiation. Genetics 2019; 213:1111-1144. [PMID: 31796551 PMCID: PMC6893389 DOI: 10.1534/genetics.119.300974] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 09/26/2019] [Indexed: 01/04/2023] Open
Abstract
The Drosophila embryonic central nervous system (CNS) is a complex organ consisting of ∼15,000 neurons and glia that is generated in ∼1 day of development. For the past 40 years, Drosophila developmental neuroscientists have described each step of CNS development in precise molecular genetic detail. This has led to an understanding of how an intricate nervous system emerges from a single cell. These studies have also provided important, new concepts in developmental biology, and provided an essential model for understanding similar processes in other organisms. In this article, the key genes that guide Drosophila CNS development and how they function is reviewed. Features of CNS development covered in this review are neurogenesis, gliogenesis, cell fate specification, and differentiation.
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Affiliation(s)
- Stephen T Crews
- Department of Biochemistry and Biophysics, Integrative Program for Biological and Genome Sciences, School of Medicine, The University of North Carolina at Chapel Hill, North Carolina 27599
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3
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Ismail JN, Badini S, Frey F, Abou-Kheir W, Shirinian M. Drosophila Tet Is Expressed in Midline Glia and Is Required for Proper Axonal Development. Front Cell Neurosci 2019; 13:252. [PMID: 31213988 PMCID: PMC6558204 DOI: 10.3389/fncel.2019.00252] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 05/20/2019] [Indexed: 01/10/2023] Open
Abstract
Ten-Eleven Translocation (TET) proteins are important epigenetic regulators that play a key role in development and are frequently deregulated in cancer. Drosophila melanogaster has a single homologous Tet gene (dTet) that is highly expressed in the central nervous system during development. Here, we examined the expression pattern of dTet in the third instar larval CNS and discovered its presence in a specific set of glia cells: midline glia (MG). Moreover, dTet knockdown resulted in significant lethality, locomotor dysfunction, and alterations in axon patterning in the larval ventral nerve cord. Molecular analyses on dTet knockdown larvae showed a downregulation in genes involved in axon guidance and reduced expression of the axon guidance cue Slit. Our findings point toward a potential role for dTet in midline glial function, specifically the regulation of axon patterning during neurodevelopment.
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Affiliation(s)
- Joy N Ismail
- Department of Experimental Pathology and Immunology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.,Center for Infectious Diseases Research, American University of Beirut Medical Center, Beirut, Lebanon
| | - Shireen Badini
- Department of Experimental Pathology and Immunology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.,Center for Infectious Diseases Research, American University of Beirut Medical Center, Beirut, Lebanon
| | - Felice Frey
- Department of Experimental Pathology and Immunology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.,Center for Infectious Diseases Research, American University of Beirut Medical Center, Beirut, Lebanon
| | - Wassim Abou-Kheir
- Department of Anatomy, Cell Biology, and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Margret Shirinian
- Department of Experimental Pathology and Immunology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.,Center for Infectious Diseases Research, American University of Beirut Medical Center, Beirut, Lebanon
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4
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McCorkindale AL, Wahle P, Werner S, Jungreis I, Menzel P, Shukla CJ, Abreu RLP, Irizarry RA, Meyer IM, Kellis M, Zinzen RP. A gene expression atlas of embryonic neurogenesis in Drosophila reveals complex spatiotemporal regulation of lncRNAs. Development 2019; 146:dev.175265. [PMID: 30923056 PMCID: PMC6451322 DOI: 10.1242/dev.175265] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 02/05/2019] [Indexed: 01/09/2023]
Abstract
Cell type specification during early nervous system development in Drosophila melanogaster requires precise regulation of gene expression in time and space. Resolving the programs driving neurogenesis has been a major challenge owing to the complexity and rapidity with which distinct cell populations arise. To resolve the cell type-specific gene expression dynamics in early nervous system development, we have sequenced the transcriptomes of purified neurogenic cell types across consecutive time points covering crucial events in neurogenesis. The resulting gene expression atlas comprises a detailed resource of global transcriptome dynamics that permits systematic analysis of how cells in the nervous system acquire distinct fates. We resolve known gene expression dynamics and uncover novel expression signatures for hundreds of genes among diverse neurogenic cell types, most of which remain unstudied. We also identified a set of conserved long noncoding RNAs (lncRNAs) that are regulated in a tissue-specific manner and exhibit spatiotemporal expression during neurogenesis with exquisite specificity. lncRNA expression is highly dynamic and demarcates specific subpopulations within neurogenic cell types. Our spatiotemporal transcriptome atlas provides a comprehensive resource for investigating the function of coding genes and noncoding RNAs during crucial stages of early neurogenesis. Summary: DIV-MARIS, an adapted technique for examining stage- and cell type-specific gene expression, reveals a complex network of mRNAs and lncRNAs expressed in specific cell types during early Drosophila embryonic nervous system development.
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Affiliation(s)
- Alexandra L McCorkindale
- Laboratory for Systems Biology of Neural Tissue Differentiation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany .,Biofrontiers Institute, University of Colorado, Boulder, CO 80303, USA
| | - Philipp Wahle
- Laboratory for Systems Biology of Neural Tissue Differentiation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany
| | - Sascha Werner
- Laboratory for Systems Biology of Neural Tissue Differentiation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany
| | - Irwin Jungreis
- MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA 02139, USA.,Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Peter Menzel
- Laboratory for Bioinformatics of RNA Structure and Transcriptome Regulation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany
| | - Chinmay J Shukla
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA.,Dana Farber Cancer Institute, Boston, MA 02215, USA
| | - Rúben Lopes Pereira Abreu
- Laboratory for Systems Biology of Neural Tissue Differentiation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany
| | | | - Irmtraud M Meyer
- Laboratory for Bioinformatics of RNA Structure and Transcriptome Regulation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany.,Freie Universität, Institute of Biochemistry, Department of Biology, Chemistry, Pharmacy, Thielallee 63, Berlin 14195, Germany
| | - Manolis Kellis
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.,Laboratory for Bioinformatics of RNA Structure and Transcriptome Regulation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany
| | - Robert P Zinzen
- Laboratory for Systems Biology of Neural Tissue Differentiation, Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Centre for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 12, 13125 Berlin, Germany
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5
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Protein O-Mannosyltransferases Affect Sensory Axon Wiring and Dynamic Chirality of Body Posture in the Drosophila Embryo. J Neurosci 2017; 38:1850-1865. [PMID: 29167399 DOI: 10.1523/jneurosci.0346-17.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 11/01/2017] [Accepted: 11/06/2017] [Indexed: 02/06/2023] Open
Abstract
Genetic defects in protein O-mannosyltransferase 1 (POMT1) and POMT2 underlie severe muscular dystrophies. POMT genes are evolutionarily conserved in metazoan organisms. In Drosophila, both male and female POMT mutants show a clockwise rotation of adult abdominal segments, suggesting a chirality of underlying pathogenic mechanisms. Here we described and analyzed a similar phenotype in POMT mutant embryos that shows left-handed body torsion. Our experiments demonstrated that coordinated muscle contraction waves are associated with asymmetric embryo rolling, unveiling a new chirality marker in Drosophila development. Using genetic and live-imaging approaches, we revealed that the torsion phenotype results from differential rolling and aberrant patterning of peristaltic waves of muscle contractions. Our results demonstrated that peripheral sensory neurons are required for normal contractions that prevent the accumulation of torsion. We found that POMT mutants show abnormal axonal connections of sensory neurons. POMT transgenic expression limited to sensory neurons significantly rescued the torsion phenotype, axonal connectivity defects, and abnormal contractions in POMT mutant embryos. Together, our data suggested that protein O-mannosylation is required for normal sensory feedback to control coordinated muscle contractions and body posture. This mechanism may shed light on analogous functions of POMT genes in mammals and help to elucidate the etiology of neurological defects in muscular dystrophies.SIGNIFICANCE STATEMENT Protein O-mannosyltransferases (POMTs) are evolutionarily conserved in metazoans. Mutations in POMTs cause severe muscular dystrophies associated with pronounced neurological defects. However, neurological functions of POMTs remain poorly understood. We demonstrated that POMT mutations in Drosophila result in abnormal muscle contractions and cause embryo torsion. Our experiments uncovered a chirality of embryo movements and a unique POMT-dependent mechanism that maintains symmetry of a developing system affected by chiral forces. Furthermore, POMTs were found to be required for proper axon connectivity of sensory neurons, suggesting that O-mannosylation regulates the sensory feedback controlling muscle contractions. This novel POMT function in the peripheral nervous system may shed light on analogous functions in mammals and help to elucidate pathomechanisms of neurological abnormalities in muscular dystrophies.
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6
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Pearson JC, McKay DJ, Lieb JD, Crews ST. Chromatin profiling of Drosophila CNS subpopulations identifies active transcriptional enhancers. Development 2017; 143:3723-3732. [PMID: 27802137 DOI: 10.1242/dev.136895] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 08/30/2016] [Indexed: 12/25/2022]
Abstract
One of the key issues in studying transcriptional regulation during development is how to employ genome-wide assays that reveals sites of open chromatin and transcription factor binding to efficiently identify biologically relevant genes and enhancers. Analysis of Drosophila CNS midline cell development provides a useful system for studying transcriptional regulation at the genomic level due to a large, well-characterized set of midline-expressed genes and in vivo validated enhancers. In this study, FAIRE-seq on FACS-purified midline cells was performed and the midline FAIRE data were compared with whole-embryo FAIRE data. We find that regions of the genome with a strong midline FAIRE peak and weak whole-embryo FAIRE peak overlap with known midline enhancers and provide a useful predictive tool for enhancer identification. In a complementary analysis, we compared a large dataset of fragments that drive midline expression in vivo with the FAIRE data. Midline enhancer fragments with a midline FAIRE peak tend to be near midline-expressed genes, whereas midline enhancers without a midline FAIRE peak were often distant from midline-expressed genes and unlikely to drive midline transcription in vivo.
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Affiliation(s)
- Joseph C Pearson
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA.,Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
| | - Daniel J McKay
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA .,Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA.,Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
| | - Jason D Lieb
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
| | - Stephen T Crews
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA .,Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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7
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Banerjee S, Mino RE, Fisher ES, Bhat MA. A versatile genetic tool to study midline glia function in the Drosophila CNS. Dev Biol 2017; 429:35-43. [PMID: 28602954 PMCID: PMC5554714 DOI: 10.1016/j.ydbio.2017.06.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 06/01/2017] [Accepted: 06/08/2017] [Indexed: 11/30/2022]
Abstract
Neuron-glial interactions are crucial for growth, guidance and ensheathment of axons across species. In the Drosophila CNS midline, neuron-glial interactions underlie ensheathment of commissural axons by midline glial (MG) cells in a manner similar to mammalian oligodendrocytes. Although there has been some advance in the study of neuron-glial interactions and ensheathment of axons in the CNS midline, key aspects of axonal ensheathment are still not fully understood. One of the limitations has been the unavailability of MG membrane markers that could highlight the glial processes wrapping the axons. Previous studies have identified two key molecular players from the neuronal and glial cell types in the CNS midline. These are the neuronal transmembrane protein Neurexin IV (Nrx IV) and the membrane-anchored MG protein Wrapper, both of which interact in trans to mediate neuron-glial interactions and ensheathment of commissural axons. In the current study, we attempt to further our understanding of MG biology and try to overcome some of the technical difficulties posed by the lack of a robust MG driver that will specifically allow expression or knockdown of genes in MG. We report the generation of BAC transgenic flies of wrapper-GAL4 and demonstrate how these flies could be used as a genetic tool to understand MG biology. We have utilized the GAL4/UAS system to drive GFP-reporter lines (membrane-bound mCD8-GFP; microtubule-associated tau-GFP) and nuclear lacZ using wrapper-GAL4 to highlight the MG cells and/or their processes that surround and perform axonal ensheathment functions in the embryonic midline. We also describe the utility of the wrapper-GAL4 driver line to down-regulate known MG genes specifically in Wrapper-positive cells. Finally, we validate the functionality of the wrapper-GAL4 driver by rescue of wrapper mutant phenotypes and lethality. Together, these studies provide us with a versatile genetic tool to investigate MG functions and will aid in future investigations where genetic screens using wrapper-GAL4 could be designed to identify novel molecular players at the Drosophila midline and unravel key aspects of MG biology.
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Affiliation(s)
- Swati Banerjee
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
| | - Rosa E Mino
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Elizabeth S Fisher
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Manzoor A Bhat
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
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8
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Schachtner LT, Sola IE, Forand D, Antonacci S, Postovit AJ, Mortimer NT, Killian DJ, Olesnicky EC. Drosophila Shep and C. elegans SUP-26 are RNA-binding proteins that play diverse roles in nervous system development. Dev Genes Evol 2015; 225:319-30. [PMID: 26271810 DOI: 10.1007/s00427-015-0514-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 08/03/2015] [Indexed: 12/14/2022]
Abstract
The Caenorhabditis elegans gene sup-26 encodes a well-conserved RNA-recognition motif-containing RNA-binding protein (RBP) that functions in dendrite morphogenesis of the PVD sensory neuron. The Drosophila ortholog of sup-26, alan shepard (shep), is expressed throughout the nervous system and has been shown to regulate neuronal remodeling during metamorphosis. Here, we extend these studies to show that sup-26 and shep are required for the development of diverse cell types within the nematode and fly nervous systems during embryonic and larval stages. We ascribe roles for sup-26 in regulating dendrite number and the expression of genes involved in mechanosensation within the nematode peripheral nervous system. We also find that in Drosophila, shep regulates dendrite length and branch order of nociceptive neurons, regulates the organization of neuronal clusters of the peripheral nervous system and the organization of axons within the ventral nerve cord. Taken together, our results suggest that shep/sup-26 orthologs play diverse roles in neural development across animal species. Moreover, we discuss potential roles for shep/sup-26 orthologs in the human nervous system.
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Affiliation(s)
- Logan T Schachtner
- Department of Biology, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA
| | - Ismail E Sola
- Department of Biology, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA
| | - Daniel Forand
- Department of Biology, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA
| | - Simona Antonacci
- Department of Molecular Biology, Colorado College, 14 East Cache La Poudre Street, Colorado Springs, CO, 80903, USA
| | - Adam J Postovit
- Department of Biology, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA
| | - Nathan T Mortimer
- Department of Biological Sciences, University of Denver, Denver, CO, 80208, USA.,School of Biological Sciences, Illinois State University, Normal, IL, 61790, USA
| | - Darrell J Killian
- Department of Molecular Biology, Colorado College, 14 East Cache La Poudre Street, Colorado Springs, CO, 80903, USA.
| | - Eugenia C Olesnicky
- Department of Biology, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA.
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9
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Ng FS, Jackson FR. The ROP vesicle release factor is required in adult Drosophila glia for normal circadian behavior. Front Cell Neurosci 2015; 9:256. [PMID: 26190976 PMCID: PMC4490253 DOI: 10.3389/fncel.2015.00256] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 06/22/2015] [Indexed: 11/22/2022] Open
Abstract
We previously showed that endocytosis and/or vesicle recycling mechanisms are essential in adult Drosophila glial cells for the neuronal control of circadian locomotor activity. In this study, our goal was to identify specific glial vesicle trafficking, recycling, or release factors that are required for rhythmic behavior. From a glia-specific, RNAi-based genetic screen, we identified eight glial factors that are required for normally robust circadian rhythms in either a light-dark cycle or in constant dark conditions. In particular, we show that conditional knockdown of the ROP vesicle release factor in adult glial cells results in arrhythmic behavior. Immunostaining for ROP reveals reduced protein in glial cell processes and an accumulation of the Par Domain Protein 1ε (PDP1ε) clock output protein in the small lateral clock neurons. These results suggest that glia modulate rhythmic circadian behavior by secretion of factors that act on clock neurons to regulate a clock output factor.
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Affiliation(s)
- Fanny S Ng
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
| | - F Rob Jackson
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine Boston, MA, USA
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10
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Altenhein B. Glial cell progenitors in the Drosophila embryo. Glia 2015; 63:1291-302. [PMID: 25779863 DOI: 10.1002/glia.22820] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/02/2015] [Indexed: 12/31/2022]
Abstract
Development and general organization of the nervous system is comparable between insects and vertebrates. Our current knowledge on the formation of neurogenic anlagen and the generation of neural stem cells is deeply influenced by work done in invertebrate model organisms such as Drosophila and Caenorhabditis elegans. It is the aim of this review to summarize the most important steps in neurogenesis in the Drosophila embryo with a special emphasis on glial cell progenitors and the specification of glial cells. Induction of neurogenic regions during early embryogenesis and determination of neural stem cells are briefly described. Special attention is given to the formation of neural precursors called neuroblasts (NB) and their lineages. NBs divide in a stem cell mode to generate a cell clone of either neurons and/or glial cells. The latter require the activation of the transcription factor glial cells missing (gcm), thus providing a binary switch between neuronal and glial cell fates. Further aspects of glial cell specification and the resulting heterogeneity of the glial population in Drosophila are discussed.
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Affiliation(s)
- Benjamin Altenhein
- Department of Neurobiology, Neurodevelopment, Zoological Institute, University of Cologne, Cologne, Germany
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11
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Abstract
Molecular genetic approaches in small model organisms like Drosophila have helped to elucidate fundamental principles of neuronal cell biology. Much less is understood about glial cells, although interest in using invertebrate preparations to define their in vivo functions has increased significantly in recent years. This review focuses on our current understanding of the three major neuron-associated glial cell types found in the Drosophila central nervous system (CNS)-astrocytes, cortex glia, and ensheathing glia. Together, these cells act like mammalian astrocytes: they surround neuronal cell bodies and proximal neurites, are coupled to the vasculature, and associate closely with synapses. Exciting recent work has shown essential roles for these CNS glial cells in neural circuit formation, function, plasticity, and pathology. As we gain a more firm molecular and cellular understanding of how Drosophila CNS glial cells interact with neurons, it is becoming clear they share significant molecular and functional attributes with mammalian astrocytes.
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12
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Slováková J, Carmena A. Canoe functions at the CNS midline glia in a complex with Shotgun and Wrapper-Nrx-IV during neuron-glia interactions. Development 2011; 138:1563-71. [PMID: 21389054 DOI: 10.1242/dev.056192] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Vertebrates and insects alike use glial cells as intermediate targets to guide growing axons. Similar to vertebrate oligodendrocytes, Drosophila midline glia ensheath and separate axonal commissures. Neuron-glia interactions are crucial during these events, although the proteins involved remain largely unknown. Here, we show that Canoe (Cno), the Drosophila ortholog of AF-6, and the DE-cadherin Shotgun (Shg) are highly restricted to the interface between midline glia and commissural axons. cno mutant analysis, genetic interactions and co-immunoprecipitation assays unveil Cno function as a novel regulator of neuron-glia interactions, forming a complex with Shg, Wrapper and Neurexin IV, the homolog of vertebrate Caspr/paranodin. Our results also support additional functions of Cno, independent of adherens junctions, as a regulator of adhesion and signaling events in non-epithelial tissues.
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Affiliation(s)
- Jana Slováková
- Instituto de Neurociencias de Alicante, CSIC/UMH, Sant Joan d'Alacant, Alicante, Spain
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13
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Watson JD, Wheeler SR, Stagg SB, Crews ST. Drosophila hedgehog signaling and engrailed-runt mutual repression direct midline glia to alternative ensheathing and non-ensheathing fates. Development 2011; 138:1285-95. [PMID: 21350018 DOI: 10.1242/dev.056895] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Drosophila CNS contains a variety of glia, including highly specialized glia that reside at the CNS midline and functionally resemble the midline floor plate glia of the vertebrate spinal cord. Both insect and vertebrate midline glia play important roles in ensheathing axons that cross the midline and secreting signals that control a variety of developmental processes. The Drosophila midline glia consist of two spatially and functionally distinct populations. The anterior midline glia (AMG) are ensheathing glia that migrate, surround and send processes into the axon commissures. By contrast, the posterior midline glia (PMG) are non-ensheathing glia. Together, the Notch and hedgehog signaling pathways generate AMG and PMG from midline neural precursors. Notch signaling is required for midline glial formation and for transcription of a core set of midline glial-expressed genes. The Hedgehog morphogen is secreted from ectodermal cells adjacent to the CNS midline and directs a subset of midline glia to become PMG. Two transcription factor genes, runt and engrailed, play important roles in AMG and PMG development. The runt gene is expressed in AMG, represses engrailed and maintains AMG gene expression. The engrailed gene is expressed in PMG, represses runt and maintains PMG gene expression. In addition, engrailed can direct midline glia to a PMG-like non-ensheathing fate. Thus, two signaling pathways and runt-engrailed mutual repression initiate and maintain two distinct populations of midline glia that differ functionally in gene expression, glial migration, axon ensheathment, process extension and patterns of apoptosis.
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Affiliation(s)
- Joseph D Watson
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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14
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Jackson FR. Glial cell modulation of circadian rhythms. Glia 2010; 59:1341-50. [PMID: 21732426 DOI: 10.1002/glia.21097] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 09/22/2010] [Indexed: 11/09/2022]
Abstract
Studies of Drosophila and mammals have documented circadian changes in the morphology and biochemistry of glial cells. In addition, it is known that astrocytes of flies and mammals contain evolutionarily conserved circadian molecular oscillators that are similar to neuronal oscillators. In several sections of this review, I summarize the morphological and biochemical rhythms of glia that may contribute to circadian control. I also discuss the evidence suggesting that glia-neuron interactions may be critical for circadian timing in both flies and mammals. Throughout the review, I attempt to compare and contrast findings from these invertebrate and vertebrate models so as to provide a synthesis of current knowledge and indicate potential research avenues that may be useful for better understanding the roles of glial cells in the circadian system.
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Affiliation(s)
- F Rob Jackson
- Department of Neuroscience, Center for Neuroscience Research, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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Fulkerson E, Estes PA. Common motifs shared by conserved enhancers of Drosophila midline glial genes. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2010; 316:61-75. [PMID: 21154525 DOI: 10.1002/jez.b.21382] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 09/07/2010] [Accepted: 09/28/2010] [Indexed: 12/12/2022]
Abstract
Coding sequences are usually the most highly conserved sectors of DNA, but genomic regions controlling the expression pattern of certain genes can also be conserved across diverse species. In this study, we identify five enhancers capable of activating transcription in the midline glia of Drosophila melanogaster and each contains sequences conserved across at least 11 Drosophila species. In addition, the conserved sequences contain reiterated motifs for binding sites of the known midline transcriptional activators, Single-minded, Tango, Dichaete, and Pointed. To understand the molecular basis for the highly conserved genomic subregions within enhancers of the midline genes, we tested the ability of various motifs to affect midline expression, both individually and in combination, within synthetic reporter constructs. Multiple copies of the binding site for the midline regulators Single-minded and Tango can drive expression in midline cells; however, small changes to the sequences flanking this transcription factor binding site can inactivate expression in midline cells and activate expression in tracheal cells instead. For the midline genes described in this study, the highly conserved sequences appear to juxtapose positive and negative regulatory factors in a configuration that activates genes specifically in the midline glia, while maintaining them inactive in other tissues, including midline neurons and tracheal cells.
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Affiliation(s)
- Eric Fulkerson
- Department of Genetics, North Carolina State University, Raleigh, North Carolina 27695, USA
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