251
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Sahoo PK, Smith DS, Perrone-Bizzozero N, Twiss JL. Axonal mRNA transport and translation at a glance. J Cell Sci 2018; 131:jcs196808. [PMID: 29654160 PMCID: PMC6518334 DOI: 10.1242/jcs.196808] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Localization and translation of mRNAs within different subcellular domains provides an important mechanism to spatially and temporally introduce new proteins in polarized cells. Neurons make use of this localized protein synthesis during initial growth, regeneration and functional maintenance of their axons. Although the first evidence for protein synthesis in axons dates back to 1960s, improved methodologies, including the ability to isolate axons to purity, highly sensitive RNA detection methods and imaging approaches, have shed new light on the complexity of the transcriptome of the axon and how it is regulated. Moreover, these efforts are now uncovering new roles for locally synthesized proteins in neurological diseases and injury responses. In this Cell Science at a Glance article and the accompanying poster, we provide an overview of how axonal mRNA transport and translation are regulated, and discuss their emerging links to neurological disorders and neural repair.
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Affiliation(s)
- Pabitra K Sahoo
- Department of Biological Sciences, University of South Carolina, 715 Sumter St., CLS 401, Columbia, SC 29208, USA
| | - Deanna S Smith
- Department of Biological Sciences, University of South Carolina, 715 Sumter St., CLS 401, Columbia, SC 29208, USA
| | - Nora Perrone-Bizzozero
- Department of Neurosciences, University of New Mexico School of Medicine, 1 University of New Mexico, MSC08 4740, Albuquerque, NM 87131, USA
| | - Jeffery L Twiss
- Department of Biological Sciences, University of South Carolina, 715 Sumter St., CLS 401, Columbia, SC 29208, USA
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252
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Tushev G, Glock C, Heumüller M, Biever A, Jovanovic M, Schuman EM. Alternative 3' UTRs Modify the Localization, Regulatory Potential, Stability, and Plasticity of mRNAs in Neuronal Compartments. Neuron 2018; 98:495-511.e6. [PMID: 29656876 DOI: 10.1016/j.neuron.2018.03.030] [Citation(s) in RCA: 225] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 01/20/2018] [Accepted: 03/16/2018] [Indexed: 02/07/2023]
Abstract
Neurons localize mRNAs near synapses where their translation can be regulated by synaptic demand and activity. Differences in the 3' UTRs of mRNAs can change their localization, stability, and translational regulation. Using 3' end RNA sequencing of microdissected rat brain slices, we discovered a huge diversity in mRNA 3' UTRs, with many transcripts showing enrichment for a particular 3' UTR isoform in either somata or the neuropil. The 3' UTR isoforms of localized transcripts are significantly longer than the 3' UTRs of non-localized transcripts and often code for proteins associated with axons, dendrites, and synapses. Surprisingly, long 3' UTRs add not only new, but also duplicate regulatory elements. The neuropil-enriched 3' UTR isoforms have significantly longer half-lives than somata-enriched isoforms. Finally, the 3' UTR isoforms can be significantly altered by enhanced activity. Most of the 3' UTR plasticity is transcription dependent, but intriguing examples of changes that are consistent with altered stability, trafficking between compartments, or local "remodeling" remain.
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Affiliation(s)
- Georgi Tushev
- Max Planck Institute for Brain Research, Frankfurt am Main, Germany
| | - Caspar Glock
- Max Planck Institute for Brain Research, Frankfurt am Main, Germany
| | | | - Anne Biever
- Max Planck Institute for Brain Research, Frankfurt am Main, Germany
| | - Marko Jovanovic
- Max Planck Institute for Brain Research, Frankfurt am Main, Germany
| | - Erin M Schuman
- Max Planck Institute for Brain Research, Frankfurt am Main, Germany.
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253
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Synaptic Paths to Neurodegeneration: The Emerging Role of TDP-43 and FUS in Synaptic Functions. Neural Plast 2018; 2018:8413496. [PMID: 29755516 PMCID: PMC5925147 DOI: 10.1155/2018/8413496] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 02/08/2018] [Accepted: 02/27/2018] [Indexed: 12/13/2022] Open
Abstract
TAR DNA-binding protein-43 KDa (TDP-43) and fused in sarcoma (FUS) as the defining pathological hallmarks for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), coupled with ALS-FTD-causing mutations in both genes, indicate that their dysfunctions damage the motor system and cognition. On the molecular level, TDP-43 and FUS participate in the biogenesis and metabolism of coding and noncoding RNAs as well as in the transport and translation of mRNAs as part of cytoplasmic mRNA-ribonucleoprotein (mRNP) granules. Intriguingly, many of the RNA targets of TDP-43 and FUS are involved in synaptic transmission and plasticity, indicating that synaptic dysfunction could be an early event contributing to motor and cognitive deficits in ALS and FTD. Furthermore, the ability of the low-complexity prion-like domains of TDP-43 and FUS to form liquid droplets suggests a potential mechanism for mRNP assembly and conversion. This review will discuss the role of TDP-43 and FUS in RNA metabolism, with an emphasis on the involvement of this process in synaptic function and neuroprotection. This will be followed by a discussion of the potential phase separation mechanism for forming RNP granules and pathological inclusions.
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254
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Neuronal RNP granules: from physiological to pathological assemblies. Biol Chem 2018; 399:623-635. [DOI: 10.1515/hsz-2018-0141] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 03/30/2018] [Indexed: 12/11/2022]
Abstract
Abstract
Neuronal cells rely on macro- and micro-cellular compartmentalization to rapidly process information, and respond locally to external stimuli. Such a cellular organization is achieved via the assembly of neuronal ribonucleoprotein (RNP) granules, dynamic membrane-less organelles enriched in RNAs and associated regulatory proteins. In this review, we discuss how these high-order structures transport mRNAs to dendrites and axons, and how they contribute to the spatio-temporal regulation of localized mRNA translation. We also highlight how recent biophysical studies have shed light on the mechanisms underlying neuronal RNP granule dynamic assembly, remodeling and maturation, in both physiological and pathological contexts.
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255
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Chudinova EM, Nadezhdina ES. Interactions between the Translation Machinery and Microtubules. BIOCHEMISTRY (MOSCOW) 2018; 83:S176-S189. [PMID: 29544439 DOI: 10.1134/s0006297918140146] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Microtubules are components of eukaryotic cytoskeleton that are involved in the transport of various components from the nucleus to the cell periphery and back. They also act as a platform for assembly of complex molecular ensembles. Ribonucleoprotein (RNP) complexes, such as ribosomes and mRNPs, are transported over significant distances (e.g. to neuronal processes) along microtubules. The association of RNPs with microtubules and their transport along these structures are essential for compartmentalization of protein biosynthesis in cells. Microtubules greatly facilitate assembly of stress RNP granules formed by accumulation of translation machinery components during cell stress response. Microtubules are necessary for the cytoplasm-to-nucleus transport of proteins, including ribosomal proteins. At the same time, ribosomal proteins and RNA-binding proteins can influence cell mobility and cytoplasm organization by regulating microtubule dynamics. The molecular mechanisms underlying the association between the translation machinery components and microtubules have not been studied systematically; the results of such studies are mostly fragmentary. In this review, we attempt to fill this gap by summarizing and discussing the data on protein and RNA components of the translation machinery that directly interact with microtubules or microtubule motor proteins.
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Affiliation(s)
- E M Chudinova
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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256
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González C, Cornejo VH, Couve A. Golgi bypass for local delivery of axonal proteins, fact or fiction? Curr Opin Cell Biol 2018; 53:9-14. [PMID: 29631154 DOI: 10.1016/j.ceb.2018.03.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 03/26/2018] [Accepted: 03/29/2018] [Indexed: 02/07/2023]
Abstract
Although translation of cytosolic proteins is well described in axons, much less is known about the synthesis, processing and trafficking of transmembrane and secreted proteins. A canonical rough endoplasmic reticulum or a stacked Golgi apparatus has not been detected in axons, generating doubts about the functionality of a local route. However, axons contain mRNAs for membrane and secreted proteins, translation factors, ribosomal components, smooth endoplasmic reticulum and post-endoplasmic reticulum elements that may contribute to local biosynthesis and plasma membrane delivery. Here we consider the evidence supporting a local secretory system in axons. We discuss exocytic elements and examples of autonomous axonal trafficking that impact development and maintenance. We also examine whether unconventional post-endoplasmic reticulum pathways may replace the canonical Golgi apparatus.
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Affiliation(s)
- Carolina González
- Department of Neuroscience, Facultad de Medicina, Universidad de Chile, Chile; Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Chile
| | - Víctor Hugo Cornejo
- Department of Neuroscience, Facultad de Medicina, Universidad de Chile, Chile; Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Chile
| | - Andrés Couve
- Department of Neuroscience, Facultad de Medicina, Universidad de Chile, Chile; Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Chile.
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257
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Müller K, Schnatz A, Schillner M, Woertge S, Müller C, von Graevenitz I, Waisman A, van Minnen J, Vogelaar CF. A predominantly glial origin of axonal ribosomes after nerve injury. Glia 2018; 66:1591-1610. [DOI: 10.1002/glia.23327] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 02/26/2018] [Accepted: 02/27/2018] [Indexed: 01/24/2023]
Affiliation(s)
- Kerstin Müller
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
| | - Andrea Schnatz
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
- Institute of Developmental Biology and Neurobiology, Section Cellular Neurobiology, Johannes Gutenberg University Mainz; Mainz 55099 Germany
| | - Miriam Schillner
- Department of Neurology, Section Neuroimmunology; University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
| | - Simone Woertge
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
| | - Christina Müller
- Institute of Developmental Biology and Neurobiology, Section Cellular Neurobiology, Johannes Gutenberg University Mainz; Mainz 55099 Germany
| | - Ilse von Graevenitz
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
| | - Ari Waisman
- Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
| | - Jan van Minnen
- Hotchkiss Brain Institute and Cumming School of Medicine; University of Calgary, 3330 Hospital Drive NW; Calgary Alberta T2N 4N1 Canada
| | - Christina F. Vogelaar
- Institute for Microanatomy and Neurobiology, University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
- Department of Neurology, Section Neuroimmunology; University Medical Center of the Johannes Gutenberg University Mainz; Mainz 55131 Germany
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258
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Cioni JM, Koppers M, Holt CE. Molecular control of local translation in axon development and maintenance. Curr Opin Neurobiol 2018; 51:86-94. [PMID: 29549711 DOI: 10.1016/j.conb.2018.02.025] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 02/24/2018] [Accepted: 02/26/2018] [Indexed: 11/27/2022]
Abstract
The tips of axons are often far away from the cell soma where most proteins are synthesized. Recent work has revealed that axonal mRNA transport and localised translation are key regulatory mechanisms that allow these distant outposts of the cell to respond rapidly to extrinsic factors and maintain axonal homeostasis. Here, we review recent evidence pointing to an increasingly broad role for local protein synthesis in controlling axon shape, synaptogenesis and axon survival by regulating diverse cellular processes such as vesicle trafficking, cytoskeletal remodelling and mitochondrial integrity. We further highlight current research on the regulatory mechanisms that coordinate the localization and translation of functionally linked mRNAs in axons.
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Affiliation(s)
- Jean-Michel Cioni
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Max Koppers
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Christine E Holt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.
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259
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Terasaki M. Axonal endoplasmic reticulum is very narrow. J Cell Sci 2018; 131:jcs.210450. [PMID: 29361544 DOI: 10.1242/jcs.210450] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 01/02/2018] [Indexed: 12/20/2022] Open
Abstract
The endoplasmic reticulum (ER) is an interconnected network of tubules and sheets. In most tissues of the body, ER tubules have a diameter of ∼60 nm. Using new methods for serial-section electron microscopy, a distinct class of very narrow, 20- to 30-nm-diameter tubules were found in neurons of both the central and peripheral nervous system. The narrow tubules appear to be the most abundant form of ER in axons, and are also found interspersed in the cell bodies and dendrites. At the site of branch points, there is a small sheet that has a similarly narrow lumen. The narrowness of the ER is likely to be important for the as yet poorly characterized functions of the axonal ER.
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Affiliation(s)
- Mark Terasaki
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA
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260
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Monavarfeshani A, Stanton G, Van Name J, Su K, Mills WA, Swilling K, Kerr A, Huebschman NA, Su J, Fox MA. LRRTM1 underlies synaptic convergence in visual thalamus. eLife 2018; 7:e33498. [PMID: 29424692 PMCID: PMC5826289 DOI: 10.7554/elife.33498] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 02/08/2018] [Indexed: 11/13/2022] Open
Abstract
It has long been thought that the mammalian visual system is organized into parallel pathways, with incoming visual signals being parsed in the retina based on feature (e.g. color, contrast and motion) and then transmitted to the brain in unmixed, feature-specific channels. To faithfully convey feature-specific information from retina to cortex, thalamic relay cells must receive inputs from only a small number of functionally similar retinal ganglion cells. However, recent studies challenged this by revealing substantial levels of retinal convergence onto relay cells. Here, we sought to identify mechanisms responsible for the assembly of such convergence. Using an unbiased transcriptomics approach and targeted mutant mice, we discovered a critical role for the synaptic adhesion molecule Leucine Rich Repeat Transmembrane Neuronal 1 (LRRTM1) in the emergence of retinothalamic convergence. Importantly, LRRTM1 mutant mice display impairment in visual behaviors, suggesting a functional role of retinothalamic convergence in vision.
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Affiliation(s)
- Aboozar Monavarfeshani
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
- Department of Biological SciencesVirginia TechBlacksburgUnited States
| | - Gail Stanton
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
- Virginia Tech Carilion School of MedicineRoanokeUnited States
| | - Jonathan Van Name
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
| | - Kaiwen Su
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
| | - William A Mills
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
- Translational Biology, Medicine, and Health Graduate ProgramVirginia TechBlacksburgUnited States
| | - Kenya Swilling
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
| | - Alicia Kerr
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
- Translational Biology, Medicine, and Health Graduate ProgramVirginia TechBlacksburgUnited States
| | | | - Jianmin Su
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
| | - Michael A Fox
- Developmental and Translational Neurobiology CenterVirginia Tech Carilion Research InstituteRoanokeUnited States
- Department of Biological SciencesVirginia TechBlacksburgUnited States
- Virginia Tech Carilion School of MedicineRoanokeUnited States
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261
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Mathur C, Johnson KR, Tong BA, Miranda P, Srikumar D, Basilio D, Latorre R, Bezanilla F, Holmgren M. Demonstration of ion channel synthesis by isolated squid giant axon provides functional evidence for localized axonal membrane protein translation. Sci Rep 2018; 8:2207. [PMID: 29396520 PMCID: PMC5797086 DOI: 10.1038/s41598-018-20684-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/18/2018] [Indexed: 12/18/2022] Open
Abstract
Local translation of membrane proteins in neuronal subcellular domains like soma, dendrites and axon termini is well-documented. In this study, we isolated the electrical signaling unit of an axon by dissecting giant axons from mature squids (Dosidicus gigas). Axoplasm extracted from these axons was found to contain ribosomal RNAs, ~8000 messenger RNA species, many encoding the translation machinery, membrane proteins, translocon and signal recognition particle (SRP) subunits, endomembrane-associated proteins, and unprecedented proportions of SRP RNA (~68% identical to human homolog). While these components support endoplasmic reticulum-dependent protein synthesis, functional assessment of a newly synthesized membrane protein in axolemma of an isolated axon is technically challenging. Ion channels are ideal proteins for this purpose because their functional dynamics can be directly evaluated by applying voltage clamp across the axon membrane. We delivered in vitro transcribed RNA encoding native or Drosophila voltage-activated Shaker KV channel into excised squid giant axons. We found that total K+ currents increased in both cases; with added inactivation kinetics on those axons injected with RNA encoding the Shaker channel. These results provide unambiguous evidence that isolated axons can exhibit de novo synthesis, assembly and membrane incorporation of fully functional oligomeric membrane proteins.
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Affiliation(s)
- Chhavi Mathur
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Kory R Johnson
- Bioinformatics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Brian A Tong
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Pablo Miranda
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Deepa Srikumar
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Daniel Basilio
- Facultad de Ciencias, Universidad de Chile, Santiago, 7750000, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, 2366103, Chile.
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois, 60637, USA.
| | - Miguel Holmgren
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA.
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262
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Ziv NE. Maintaining the active zone: Demand, supply and disposal of core active zone proteins. Neurosci Res 2018; 127:70-77. [DOI: 10.1016/j.neures.2017.09.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/26/2017] [Indexed: 11/29/2022]
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263
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Tóth EN, Lohith A, Mondal M, Guo J, Fukamizu A, Pourmand N. Single-cell nanobiopsy reveals compartmentalization of mRNAs within neuronal cells. J Biol Chem 2018; 293:4940-4951. [PMID: 29378846 DOI: 10.1074/jbc.m117.800763] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 01/21/2018] [Indexed: 12/22/2022] Open
Abstract
In highly polarized cells such as neurons, compartmentalization of mRNA and of local protein synthesis enables remarkably fast, precise, and local responses to external stimuli. These responses are highly important for neuron growth cone guidance, synapse formation, and regeneration following injury. Because an altered spatial distribution of mRNA can result in mental retardation or neurodegenerative diseases, subcellular transcriptome analysis of neurons could be a useful tool for studying these conditions, but current techniques, such as in situ hybridization, bulk microarray, and RNA-Seq, impose tradeoffs between spatial resolution and multiplexing. To obtain a comprehensive analysis of the cell body versus neurite transcriptome from the same neuron, we have recently developed a label-free, single-cell nanobiopsy platform based on scanning ion conductance microscopy that uses electrowetting within a quartz nanopipette to extract cellular material from living cells with minimal disruption of the cellular membrane and milieu. In this study, we used this platform to collect samples from the cell bodies and neurites of human neurons and analyzed the mRNA pool with multiplex RNA sequencing. The minute volume of a nanobiopsy sample allowed us to extract samples from several locations in the same cell and to map the various mRNA species to specific subcellular locations. In addition to previously identified transcripts, we discovered new sets of mRNAs localizing to neurites, including nuclear genes such as Eomes and Hmgb3 In summary, our single-neuron nanobiopsy analysis provides opportunities to improve our understanding of intracellular mRNA transport and local protein composition in neuronal growth, connectivity, and function.
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Affiliation(s)
- Eszter N Tóth
- Ph.D. Program in Human Biology, School of Integrative and Global Majors, Ibaraki 305-8577, Japan; Life Science Center, Tsukuba Advanced Research Alliance, Department of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8577, Japan; Department of Biomolecular Engineering, Jack Baskin School of Engineering, University of California at Santa Cruz, Santa Cruz, California 95064
| | - Akshar Lohith
- Department of Biomolecular Engineering, Jack Baskin School of Engineering, University of California at Santa Cruz, Santa Cruz, California 95064
| | - Manas Mondal
- Department of Chemistry and Biochemistry & Biodesign Institute, Arizona State University, Tempe, Arizona 85287
| | - Jia Guo
- Department of Chemistry and Biochemistry & Biodesign Institute, Arizona State University, Tempe, Arizona 85287
| | - Akiyoshi Fukamizu
- Ph.D. Program in Human Biology, School of Integrative and Global Majors, Ibaraki 305-8577, Japan; Life Science Center, Tsukuba Advanced Research Alliance, Department of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8577, Japan
| | - Nader Pourmand
- Department of Biomolecular Engineering, Jack Baskin School of Engineering, University of California at Santa Cruz, Santa Cruz, California 95064.
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264
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Van Driesche SJ, Martin KC. New frontiers in RNA transport and local translation in neurons. Dev Neurobiol 2018; 78:331-339. [DOI: 10.1002/dneu.22574] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/27/2017] [Accepted: 12/27/2017] [Indexed: 12/19/2022]
Affiliation(s)
- Sarah J. Van Driesche
- Department of Biological Chemistry; University of California; Los Angeles California
| | - Kelsey C. Martin
- Department of Biological Chemistry; University of California; Los Angeles California
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265
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The Expanding Toolkit of Translating Ribosome Affinity Purification. J Neurosci 2018; 37:12079-12087. [PMID: 29237735 DOI: 10.1523/jneurosci.1929-17.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/16/2017] [Accepted: 11/03/2017] [Indexed: 01/23/2023] Open
Abstract
Translating ribosome affinity purification is a method initially developed for profiling mRNA from genetically defined cell types in complex tissues. It has been applied both to identify target molecules in cell types that are important for controlling a variety of behaviors in the brain, and to understand the molecular consequences on those cells due to experimental manipulations, ranging from drugs of abuse to disease-causing mutations. Since its inception, a variety of methodological advances are opening new avenues of investigation. These advances include a variety of new methods for targeting cells for translating ribosome affinity purification by features such as their projections or activity, additional tags and mouse reagents increasing the flexibility of the system, and new modifications of the method specifically focused on studying the regulation of translation. The latter includes methods to assess cell type-specific regulation of translation in specific subcellular compartments. Here, I provide a summary of these recent advances and resources, highlighting both new experimental opportunities and areas for future technical development.
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266
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Tréfier A, Guillou F, Crépieux P. [Investigation methods to explore G protein-coupled receptor-regulated translatome]. C R Biol 2018; 341:65-74. [PMID: 29326051 DOI: 10.1016/j.crvi.2017.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/07/2017] [Accepted: 12/08/2017] [Indexed: 12/26/2022]
Abstract
With the advent of next-generation sequencing technologies, identifying the translatome, which includes genome-wide ribosome-associated mRNAs, provides new opportunities to define faithfully the protein repertoire of a cell, as opposed to transcriptomic approaches. In addition, the role that extracellular signals such as hormonal modulations could play on the translatome remains to be deciphered. In particular, the regulation of the translatome by G protein-coupled receptors (GPCR) is still poorly described, albeit the trophic role that many receptors of this family play in their target cells. Here, we provide an overview of the current methods that are used to study the translatome, applied to the GPCR receptor family.
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Affiliation(s)
- Aurélie Tréfier
- Groupe Biologie et bioinformatique des systèmes de signalisation, Inra, UMR 85, unité Physiologie de la reproduction et des comportements, 37380 Nouzilly, France; CNRS, UMR 7247, 37380 Nouzilly, France; Université François-Rabelais, 37041 Tours, France; IFCE, 37380 Nouzilly, France
| | - Florian Guillou
- Plasticité génomique et expression phénotypique, Inra, UMR 85, unité Physiologie de la reproduction et des comportements, 37380 Nouzilly, France; CNRS, UMR 7247, 37380 Nouzilly, France; Université François-Rabelais, 37041 Tours, France; IFCE, 37380 Nouzilly, France
| | - Pascale Crépieux
- Groupe Biologie et bioinformatique des systèmes de signalisation, Inra, UMR 85, unité Physiologie de la reproduction et des comportements, 37380 Nouzilly, France; CNRS, UMR 7247, 37380 Nouzilly, France; Université François-Rabelais, 37041 Tours, France; IFCE, 37380 Nouzilly, France.
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267
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Russell SA, Bashaw GJ. Axon guidance pathways and the control of gene expression. Dev Dyn 2018; 247:571-580. [PMID: 29226467 DOI: 10.1002/dvdy.24609] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 11/15/2017] [Accepted: 11/15/2017] [Indexed: 12/20/2022] Open
Abstract
Axons need to be properly guided to their targets to form synaptic connections, and this requires interactions between highly conserved extracellular and transmembrane ligands and their cell surface receptors. The majority of studies on axon guidance signaling pathways have focused on the role of these pathways in rearranging the local cytoskeleton and plasma membrane in growth cones and axons. However, a smaller body of work has demonstrated that axon guidance signaling pathways also control gene expression via local translation and transcription. Recent studies on axon guidance ligands and receptors have begun to uncover the requirements for these alternative mechanisms in processes required for neural circuit formation: axon guidance, synaptogenesis, and cell migration. Understanding the mechanisms by which axon guidance signaling regulates local translation and transcription will create a more complete picture of neural circuit formation, and they may be applied more broadly to other tissues where axon guidance ligands and receptors are required for morphogenesis. Developmental Dynamics 247:571-580, 2018. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Samantha A Russell
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Greg J Bashaw
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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268
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Abstract
Spinal muscular atrophy (SMA) is a motor neuron disease caused by mutations/deletions within the survival of motor neuron 1 (SMN1) gene that lead to a pathological reduction of SMN protein levels. SMN is part of a multiprotein complex, functioning as a molecular chaperone that facilitates the assembly of spliceosomal small nuclear ribonucleoproteins (snRNP). In addition to its role in spliceosome formation, SMN has also been found to interact with mRNA-binding proteins (mRBPs), and facilitate their assembly into mRNP transport granules. The association of protein and RNA in RNP complexes plays an important role in an extensive and diverse set of cellular processes that regulate neuronal growth, differentiation, and the maturation and plasticity of synapses. This review discusses the role of SMN in RNP assembly and localization, focusing on molecular defects that affect mRNA processing and may contribute to SMA pathology.
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269
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Abstract
Electroporation allows targeting of genetic materials (e.g., DNA, RNA, antisense morpholinos) to the tissue of interest with high spatial and temporal specificity. Here, we describe a highly efficient and reproducible electroporation strategy for targeting the central nervous system in Xenopus. This versatile approach can be combined with live imaging or other existing experimental procedures to aid the investigation of different research questions.
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Affiliation(s)
- Hovy Ho-Wai Wong
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Christine E Holt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
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270
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Abstract
Koppel & Fainzilber review translatomics and proteomics methods for studying protein synthesis at subcellular resolution.
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Affiliation(s)
- Indrek Koppel
- Department of Biomolecular Sciences
- Weizmann Institute of Science
- 76100 Rehovot
- Israel
| | - Mike Fainzilber
- Department of Biomolecular Sciences
- Weizmann Institute of Science
- 76100 Rehovot
- Israel
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271
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Axon-TRAP-RiboTag: Affinity Purification of Translated mRNAs from Neuronal Axons in Mouse In Vivo. Methods Mol Biol 2018; 1649:85-94. [PMID: 29130191 DOI: 10.1007/978-1-4939-7213-5_5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Translating ribosome affinity purification (TRAP) is a widely used technique to analyze ribosome-bound mRNAs in particular target cells that express a tagged ribosomal protein. We developed axon-TRAP-RiboTag, a TRAP-based method that allows purification and identification of translated mRNAs from distal neuronal axons in mouse, and identified more than 2000 of translated mRNAs in retinal ganglion cell (RGC) axons in vivo. The use of Cre-negative littermate control to filter out false-positive signals allows unbiased detection, and combining TRAP with in vitro ribosome run-off enables identification of actively translated mRNAs. Here, we describe a detailed protocol to identify translated mRNAs in RGC axons in mouse in vivo. This method can be applied to any neurons whose cell bodies and distal axons are anatomically separated.
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272
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Abstract
The last past decade has witnessed a revolution in our appreciation of transcriptome complexity and regulation. This remarkable expansion in our knowledge largely originates from the advent of high-throughput methodologies, and the consecutive discovery that up to 90% of eukaryotic genomes are transcribed, thus generating an unanticipated large range of noncoding RNAs (Hangauer et al., 15(4):112, 2014). Besides leading to the identification of new noncoding RNA species, transcriptome-wide studies have uncovered novel layers of posttranscriptional regulatory mechanisms controlling RNA processing, maturation or translation, and each contributing to the precise and dynamic regulation of gene expression. Remarkably, the development of systems-level studies has been accompanied by tremendous progress in the visualization of individual RNA molecules in single cells, such that it is now possible to image RNA species with a single-molecule resolution from birth to translation or decay. Monitoring quantitatively, with unprecedented spatiotemporal resolution, the fate of individual molecules has been key to understanding the molecular mechanisms underlying the different steps of RNA regulation. This has also revealed biologically relevant, intracellular and intercellular heterogeneities in RNA distribution or regulation. More recently, the convergence of imaging and high-throughput technologies has led to the emergence of spatially resolved transcriptomic techniques that provide a means to perform large-scale analyses while preserving spatial information. By generating transcriptome-wide data on single-cell RNA content, or even subcellular RNA distribution, these methodologies are opening avenues to a wide range of network-level studies at the cell and organ-level, and promise to strongly improve disease diagnostic and treatment.In this introductory chapter, we highlight how recently developed technologies aiming at detecting and visualizing RNA molecules have contributed to the emergence of entirely new research fields, and to dramatic progress in our understanding of gene expression regulation.
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Affiliation(s)
- Caroline Medioni
- Université Côte d'Azur, CNRS, Inserm, iBV, Parc Valrose, 06100, Nice, France
| | - Florence Besse
- Université Côte d'Azur, CNRS, Inserm, iBV, Parc Valrose, 06100, Nice, France.
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273
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Guidance of retinal axons in mammals. Semin Cell Dev Biol 2017; 85:48-59. [PMID: 29174916 DOI: 10.1016/j.semcdb.2017.11.027] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Revised: 11/17/2017] [Accepted: 11/20/2017] [Indexed: 11/21/2022]
Abstract
In order to navigate through the surrounding environment many mammals, including humans, primarily rely on vision. The eye, composed of the choroid, sclera, retinal pigmented epithelium, cornea, lens, iris and retina, is the structure that receives the light and converts it into electrical impulses. The retina contains six major types of neurons involving in receiving and modifying visual information and passing it onto higher visual processing centres in the brain. Visual information is relayed to the brain via the axons of retinal ganglion cells (RGCs), a projection known as the optic pathway. The proper formation of this pathway during development is essential for normal vision in the adult individual. Along this pathway there are several points where visual axons face 'choices' in their direction of growth. Understanding how these choices are made has advanced significantly our knowledge of axon guidance mechanisms. Thus, the development of the visual pathway has served as an extremely useful model to reveal general principles of axon pathfinding throughout the nervous system. However, due to its particularities, some cellular and molecular mechanisms are specific for the visual circuit. Here we review both general and specific mechanisms involved in the guidance of mammalian RGC axons when they are traveling from the retina to the brain to establish precise and stereotyped connections that will sustain vision.
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274
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Luarte A, Cornejo VH, Bertin F, Gallardo J, Couve A. The axonal endoplasmic reticulum: One organelle-many functions in development, maintenance, and plasticity. Dev Neurobiol 2017; 78:181-208. [PMID: 29134778 DOI: 10.1002/dneu.22560] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 11/02/2017] [Accepted: 11/07/2017] [Indexed: 12/11/2022]
Abstract
The endoplasmic reticulum (ER) is highly conserved in eukaryotes and neurons. Indeed, the localization of the organelle in axons has been known for nearly half a century. However, the relevance of the axonal ER is only beginning to emerge. In this review, we discuss the structure of the ER in axons, examining the role of ER-shaping proteins and highlighting reticulons. We analyze the multiple functions of the ER and their potential contribution to axonal physiology. First, we examine the emerging roles of the axonal ER in lipid synthesis, protein translation, processing, quality control, and secretory trafficking of transmembrane proteins. We also review the impact of the ER on calcium dynamics, focusing on intracellular mechanisms and functions. We describe the interactions between the ER and endosomes, mitochondria, and synaptic vesicles. Finally, we analyze available proteomic data of axonal preparations to reveal the dynamic functionality of the ER in axons during development. We suggest that the dynamic proteome and a validated axonal interactome, together with state-of-the-art methodologies, may provide interesting research avenues in axon physiology that may extend to pathology and regeneration. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 181-208, 2018.
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Affiliation(s)
- Alejandro Luarte
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Víctor Hugo Cornejo
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Francisca Bertin
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Javiera Gallardo
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Andrés Couve
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
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275
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Costa CJ, Willis DE. To the end of the line: Axonal mRNA transport and local translation in health and neurodegenerative disease. Dev Neurobiol 2017; 78:209-220. [PMID: 29115051 DOI: 10.1002/dneu.22555] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 10/20/2017] [Accepted: 11/01/2017] [Indexed: 12/14/2022]
Abstract
Axons and growth cones, by their very nature far removed from the cell body, encounter unique environments and require distinct populations of proteins. It seems only natural, then, that they have developed mechanisms to locally synthesize a host of proteins required to perform their specialized functions. Acceptance of this ability has taken decades; however, there is now consensus that axons do indeed have the capacity for local translation, and that this capacity is even retained into adulthood. Accumulating evidence supports the role of locally synthesized proteins in the proper development, maintenance, and function of neurons, and newly emerging studies also suggest that disruption in this process has implications in a number of neurodevelopmental and neurodegenerative diseases. Here, we briefly review the long history of axonal mRNA localization and local translation, and the role that these locally synthesized proteins play in normal neuronal function. Additionally, we highlight the emerging evidence that dysregulation in these processes contributes to a wide range of pathophysiology, including neuropsychiatric disorders, Alzheimer's, and motor neuron diseases such as spinal muscular atrophy and Amyotrophic Lateral Sclerosis. © 2017 Wiley Periodicals, Inc. Develop. Neurobiol 78: 209-220, 2018.
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Affiliation(s)
| | - Dianna E Willis
- Burke Medical Research Institute, White Plains, New York, 10605.,Brain & Mind Research Institute, Weill Cornell Medicine, New York, New York
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276
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Misgeld T, Schwarz TL. Mitostasis in Neurons: Maintaining Mitochondria in an Extended Cellular Architecture. Neuron 2017; 96:651-666. [PMID: 29096078 DOI: 10.1016/j.neuron.2017.09.055] [Citation(s) in RCA: 309] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 09/25/2017] [Accepted: 09/28/2017] [Indexed: 02/06/2023]
Abstract
Neurons have more extended and complex shapes than other cells and consequently face a greater challenge in distributing and maintaining mitochondria throughout their arbors. Neurons can last a lifetime, but proteins turn over rapidly. Mitochondria, therefore, need constant rejuvenation no matter how far they are from the soma. Axonal transport of mitochondria and mitochondrial fission and fusion contribute to this rejuvenation, but local protein synthesis is also likely. Maintenance of a healthy mitochondrial population also requires the clearance of damaged proteins and organelles. This involves degradation of individual proteins, sequestration in mitochondria-derived vesicles, organelle degradation by mitophagy and macroautophagy, and in some cases transfer to glial cells. Both long-range transport and local processing are thus at work in achieving neuronal mitostasis-the maintenance of an appropriately distributed pool of healthy mitochondria for the duration of a neuron's life. Accordingly, defects in the processes that support mitostasis are significant contributors to neurodegenerative disorders.
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Affiliation(s)
- Thomas Misgeld
- Technical University of Munich, Institute of Neuronal Cell Biology, Munich, Germany; German Center for Neurodegenerative Diseases, Munich, Germany; Munich Cluster for Systems Neurology, Munich, Germany; Center of Integrated Protein Science, Munich, Germany.
| | - Thomas L Schwarz
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA; F.M. Kirby Neurobiology Center, Children's Hospital, Boston, MA, USA.
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277
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Baser A, Skabkin M, Martin-Villalba A. Neural Stem Cell Activation and the Role of Protein Synthesis. Brain Plast 2017; 3:27-41. [PMID: 29765858 PMCID: PMC5928545 DOI: 10.3233/bpl-160038] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Adult neural stem cells are generated at embryonic stages by entering a quiescent state that allows their retention into adulthood and thereby maintenance of life-long brain homeostasis. Thus, a tight balance between the quiescence and activation state is instrumental to meet the brain demands for a specific cell type at the correct numbers, at a given time and position. Protein synthesis is the most energy-consuming process within the cell and, not surprisingly, it occurs at low rates in quiescent stem cells. This way quiescent cells adjust to energy constraints and avoid their premature depletion. Stem cell activation is characterized by upregulation of protein synthesis followed by cell division and differentiation. The role of such upregulation as causative or rather a consequence of the activation remains elusive. Here we summarize recent findings connecting stem cell activation to the regulation of protein synthesis, particularly focusing on embryonic and adult neural stem cells of the ventricular zone.
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Affiliation(s)
- Avni Baser
- Molecular Neurobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Maxim Skabkin
- Molecular Neurobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Ana Martin-Villalba
- Molecular Neurobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
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278
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HuD and the Survival Motor Neuron Protein Interact in Motoneurons and Are Essential for Motoneuron Development, Function, and mRNA Regulation. J Neurosci 2017; 37:11559-11571. [PMID: 29061699 DOI: 10.1523/jneurosci.1528-17.2017] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 09/09/2017] [Indexed: 01/17/2023] Open
Abstract
Motoneurons establish a critical link between the CNS and muscles. If motoneurons do not develop correctly, they cannot form the required connections, resulting in movement defects or paralysis. Compromised development can also lead to degeneration because the motoneuron is not set up to function properly. Little is known, however, regarding the mechanisms that control vertebrate motoneuron development, particularly the later stages of axon branch and dendrite formation. The motoneuron disease spinal muscular atrophy (SMA) is caused by low levels of the survival motor neuron (SMN) protein leading to defects in vertebrate motoneuron development and synapse formation. Here we show using zebrafish as a model system that SMN interacts with the RNA binding protein (RBP) HuD in motoneurons in vivo during formation of axonal branches and dendrites. To determine the function of HuD in motoneurons, we generated zebrafish HuD mutants and found that they exhibited decreased motor axon branches, dramatically fewer dendrites, and movement defects. These same phenotypes are present in animals expressing low levels of SMN, indicating that both proteins function in motoneuron development. HuD binds and transports mRNAs and one of its target mRNAs, Gap43, is involved in axonal outgrowth. We found that Gap43 was decreased in both HuD and SMN mutants. Importantly, transgenic expression of HuD in motoneurons of SMN mutants rescued the motoneuron defects, the movement defects, and Gap43 mRNA levels. These data support that the interaction between SMN and HuD is critical for motoneuron development and point to a role for RBPs in SMA.SIGNIFICANCE STATEMENT In zebrafish models of the motoneuron disease spinal muscular atrophy (SMA), motor axons fail to form the normal extent of axonal branches and dendrites leading to decreased motor function. SMA is caused by low levels of the survival motor neuron (SMN) protein. We show in motoneurons in vivo that SMN interacts with the RNA binding protein, HuD. Novel mutants reveal that HuD is also necessary for motor axonal branch and dendrite formation. Data also revealed that both SMN and HuD affect levels of an mRNA involved in axonal growth. Moreover, expressing HuD in SMN-deficient motoneurons can rescue the motoneuron development and motor defects caused by low levels of SMN. These data support that SMN:HuD complexes are essential for normal motoneuron development and indicate that mRNA handling is a critical component of SMA.
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279
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Hilton BJ, Bradke F. Can injured adult CNS axons regenerate by recapitulating development? Development 2017; 144:3417-3429. [PMID: 28974639 DOI: 10.1242/dev.148312] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In the adult mammalian central nervous system (CNS), neurons typically fail to regenerate their axons after injury. During development, by contrast, neurons extend axons effectively. A variety of intracellular mechanisms mediate this difference, including changes in gene expression, the ability to form a growth cone, differences in mitochondrial function/axonal transport and the efficacy of synaptic transmission. In turn, these intracellular processes are linked to extracellular differences between the developing and adult CNS. During development, the extracellular environment directs axon growth and circuit formation. In adulthood, by contrast, extracellular factors, such as myelin and the extracellular matrix, restrict axon growth. Here, we discuss whether the reactivation of developmental processes can elicit axon regeneration in the injured CNS.
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Affiliation(s)
- Brett J Hilton
- Laboratory for Axon Growth and Regeneration, German Centre for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Strasse 27, 53127, Bonn, Germany
| | - Frank Bradke
- Laboratory for Axon Growth and Regeneration, German Centre for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Strasse 27, 53127, Bonn, Germany
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280
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Transcriptional regulation of endothelial cell behavior during sprouting angiogenesis. Nat Commun 2017; 8:726. [PMID: 28959057 PMCID: PMC5620061 DOI: 10.1038/s41467-017-00738-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 07/25/2017] [Indexed: 01/29/2023] Open
Abstract
Mediating the expansion of vascular beds in many physiological and pathological settings, angiogenesis requires dynamic changes in endothelial cell behavior. However, the molecular mechanisms governing endothelial cell activity during different phases of vascular growth, remodeling, maturation, and quiescence remain elusive. Here, we characterize dynamic gene expression changes during postnatal development and identify critical angiogenic factors in mouse retinal endothelial cells. Using actively translating transcriptome analysis and in silico computational analyses, we determine candidate regulators controlling endothelial cell behavior at different developmental stages. We further show that one of the identified candidates, the transcription factor MafB, controls endothelial sprouting in vitro and in vivo, and perform an integrative analysis of RNA-Seq and ChIP-Seq data to define putative direct MafB targets, which are activated or repressed by the transcriptional regulator. Together, our results identify novel cell-autonomous regulatory mechanisms controlling sprouting angiogenesis. Angiogenesis is a complex process that requires coordinated changes in endothelial cell behavior. Here the authors use Ribo-tag and RNA-Seq to determine temporal profiles of transcriptional activity during postnatal retinal angiogenesis, identifying transcriptional regulators of the process.
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281
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Akins MR, Berk-Rauch HE, Kwan KY, Mitchell ME, Shepard KA, Korsak LIT, Stackpole EE, Warner-Schmidt JL, Sestan N, Cameron HA, Fallon JR. Axonal ribosomes and mRNAs associate with fragile X granules in adult rodent and human brains. Hum Mol Genet 2017; 26:192-209. [PMID: 28082376 DOI: 10.1093/hmg/ddw381] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 11/03/2016] [Indexed: 11/14/2022] Open
Abstract
Local mRNA translation in growing axons allows for rapid and precise regulation of protein expression in response to extrinsic stimuli. However, the role of local translation in mature CNS axons is unknown. Such a mechanism requires the presence of translational machinery and associated mRNAs in circuit-integrated brain axons. Here we use a combination of genetic, quantitative imaging and super-resolution microscopy approaches to show that mature axons in the mammalian brain contain ribosomes, the translational regulator FMRP and a subset of FMRP mRNA targets. This axonal translational machinery is associated with Fragile X granules (FXGs), which are restricted to axons in a stereotyped subset of brain circuits. FXGs and associated axonal translational machinery are present in hippocampus in humans as old as 57 years. This FXG-associated axonal translational machinery is present in adult rats, even when adult neurogenesis is blocked. In contrast, in mouse this machinery is only observed in juvenile hippocampal axons. This differential developmental expression was specific to the hippocampus, as both mice and rats exhibit FXGs in mature axons in the adult olfactory system. Experiments in Fmr1 null mice show that FMRP regulates axonal protein expression but is not required for axonal transport of ribosomes or its target mRNAs. Axonal translational machinery is thus a feature of adult CNS neurons. Regulation of this machinery by FMRP could support complex behaviours in humans throughout life.
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Affiliation(s)
- Michael R Akins
- Department of Biology, Drexel University, Philadelphia, PA, USA.,Department of Neuroscience, Brown University, Providence, RI
| | | | - Kenneth Y Kwan
- Department of Neuroscience and Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, CT, USA
| | | | | | - Lulu I T Korsak
- Department of Biology, Drexel University, Philadelphia, PA, USA
| | | | | | - Nenad Sestan
- Department of Neuroscience and Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, CT, USA
| | - Heather A Cameron
- Section on Neuroplasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Justin R Fallon
- Department of Neuroscience, Brown University, Providence, RI
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282
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Chyung E, LeBlanc HF, Fallon JR, Akins MR. Fragile X granules are a family of axonal ribonucleoprotein particles with circuit-dependent protein composition and mRNA cargos. J Comp Neurol 2017; 526:96-108. [PMID: 28884477 DOI: 10.1002/cne.24321] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 08/14/2017] [Accepted: 08/25/2017] [Indexed: 11/08/2022]
Abstract
Local axonal protein synthesis plays a crucial role in the formation and function of neuronal circuits. Understanding the role of this mechanism in specific circuits requires identifying the protein composition and mRNA cargos of the ribonucleoprotein particles (RNPs) that form the substrate for axonal translation. FXGs (Fragile X granules) are axonal RNPs present in a stereotyped subset of mature axons in the intact brain that contain one or more of the Fragile X related (FXR) proteins (FMRP, FXR2P, and FXR1P) along with mRNA and ribosomes. Here we performed a systematic survey of the FXR protein composition and mRNA association of FXGs in the brain. We have identified four FXG types that can be categorized based on their FXR protein complement. All FXGs contain FXR2P, with FMRP and/or FXR1P present in circuit-selective subsets. Individual neuronal cell types predominantly express a single FXG type, with FMRP-containing FXGs the most prevalent in forebrain neurons. All FXG types associate with ribosomes and mRNA, but the specific mRNA cargos are a function of FXG type, brain region and neuron class. Transcripts for β-catenin and its regulator APC associate with a subset of forebrain FXGs. Moreover, both these transcripts can colocalize within individual FXGs, suggesting that the axonal translation of functionally related proteins may be coordinately regulated with high spatiotemporal resolution. Cell type-dependent expression of specific RNP types with distinct mRNA cargos, such as FXGs, presents a potential mechanism for regulating local translation and its output in a circuit-dependent manner.
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Affiliation(s)
- Eunice Chyung
- Department of Neuroscience, Brown University, Providence, Rhode Island, 02912
| | - Hannah F LeBlanc
- Department of Neuroscience, Brown University, Providence, Rhode Island, 02912
| | - Justin R Fallon
- Department of Neuroscience, Brown University, Providence, Rhode Island, 02912
| | - Michael R Akins
- Department of Biology, Drexel University, Philadelphia, Pennsylvania, 19104.,Department of Neurobiology & Anatomy, Drexel University, Philadelphia, Pennsylvania, 19104
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283
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Zappulo A, van den Bruck D, Ciolli Mattioli C, Franke V, Imami K, McShane E, Moreno-Estelles M, Calviello L, Filipchyk A, Peguero-Sanchez E, Müller T, Woehler A, Birchmeier C, Merino E, Rajewsky N, Ohler U, Mazzoni EO, Selbach M, Akalin A, Chekulaeva M. RNA localization is a key determinant of neurite-enriched proteome. Nat Commun 2017; 8:583. [PMID: 28928394 PMCID: PMC5605627 DOI: 10.1038/s41467-017-00690-6] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 07/19/2017] [Indexed: 11/09/2022] Open
Abstract
Protein subcellular localization is fundamental to the establishment of the body axis, cell migration, synaptic plasticity, and a vast range of other biological processes. Protein localization occurs through three mechanisms: protein transport, mRNA localization, and local translation. However, the relative contribution of each process to neuronal polarity remains unknown. Using neurons differentiated from mouse embryonic stem cells, we analyze protein and RNA expression and translation rates in isolated cell bodies and neurites genome-wide. We quantify 7323 proteins and the entire transcriptome, and identify hundreds of neurite-localized proteins and locally translated mRNAs. Our results demonstrate that mRNA localization is the primary mechanism for protein localization in neurites that may account for half of the neurite-localized proteome. Moreover, we identify multiple neurite-targeted non-coding RNAs and RNA-binding proteins with potential regulatory roles. These results provide further insight into the mechanisms underlying the establishment of neuronal polarity. Subcellular localization of RNAs and proteins is important for polarized cells such as neurons. Here the authors differentiate mouse embryonic stem cells into neurons, and analyze the local transcriptome, proteome, and translated transcriptome in their cell bodies and neurites, providing a unique resource for future studies on neuronal polarity.
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Affiliation(s)
- Alessandra Zappulo
- Non-coding RNAs and Mechanisms of Cytoplasmic Gene Regulation, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - David van den Bruck
- Non-coding RNAs and Mechanisms of Cytoplasmic Gene Regulation, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Camilla Ciolli Mattioli
- Non-coding RNAs and Mechanisms of Cytoplasmic Gene Regulation, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Vedran Franke
- BIMSB Bioinformatics Platform, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Koshi Imami
- Proteome Dynamics, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Erik McShane
- Proteome Dynamics, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | | | - Lorenzo Calviello
- Computational Regulatory Genomics, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Andrei Filipchyk
- Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Esteban Peguero-Sanchez
- Non-coding RNAs and Mechanisms of Cytoplasmic Gene Regulation, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany.,Departamento de Microbiología Molecular, Instituto de Biotecnología, UNAM, Av. Universidad 2001, Cuernavaca, Morelos, CP, 62210, Mexico
| | - Thomas Müller
- Developmental Biology/Signal Transduction, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Andrew Woehler
- BIMSB Light Microscopy Platform, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Carmen Birchmeier
- Developmental Biology/Signal Transduction, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Enrique Merino
- Departamento de Microbiología Molecular, Instituto de Biotecnología, UNAM, Av. Universidad 2001, Cuernavaca, Morelos, CP, 62210, Mexico
| | - Nikolaus Rajewsky
- Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Uwe Ohler
- Computational Regulatory Genomics, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Esteban O Mazzoni
- Department of Biology, New York University, New York, NY, 10003-6688, USA
| | - Matthias Selbach
- Proteome Dynamics, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Altuna Akalin
- BIMSB Bioinformatics Platform, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany
| | - Marina Chekulaeva
- Non-coding RNAs and Mechanisms of Cytoplasmic Gene Regulation, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, 13125, Berlin, Germany.
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284
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Gomes C, Lee SJ, Gardiner AS, Smith T, Sahoo PK, Patel P, Thames E, Rodriguez R, Taylor R, Yoo S, Heise T, Kar AN, Perrone-Bizzozero N, Twiss JL. Axonal localization of neuritin/CPG15 mRNA is limited by competition for HuD binding. J Cell Sci 2017; 130:3650-3662. [PMID: 28871047 DOI: 10.1242/jcs.201244] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 08/31/2017] [Indexed: 01/11/2023] Open
Abstract
HuD protein (also known as ELAVL4) has been shown to stabilize mRNAs with AU-rich elements (ARE) in their 3' untranslated regions (UTRs), including Gap43, which has been linked to axon growth. HuD also binds to neuritin (Nrn1) mRNA, whose 3'UTR contains ARE sequences. Although the Nrn1 3'UTR has been shown to mediate its axonal localization in embryonic hippocampal neurons, it is not active in adult dorsal root ganglion (DRG) neurons. Here, we asked why the 3'UTR is not sufficient to mediate the axonal localization of Nrn1 mRNA in DRG neurons. HuD overexpression increases the ability of the Nrn1 3'UTR to mediate axonal localizing in DRG neurons. HuD binds directly to the Nrn1 ARE with about a two-fold higher affinity than to the Gap43 ARE. Although the Nrn1 ARE can displace the Gap43 ARE from HuD binding, HuD binds to the full 3'UTR of Gap43 with higher affinity, such that higher levels of Nrn1 are needed to displace the Gap43 3'UTR. The Nrn1 3'UTR can mediate a higher level of axonal localization when endogenous Gap43 is depleted from DRG neurons. Taken together, our data indicate that endogenous Nrn1 and Gap43 mRNAs compete for binding to HuD for their axonal localization and activity of the Nrn1 3'UTR.
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Affiliation(s)
- Cynthia Gomes
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Seung Joon Lee
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Amy S Gardiner
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Terika Smith
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Pabitra K Sahoo
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Priyanka Patel
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Elizabeth Thames
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Reycel Rodriguez
- Department of Biochemistry, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Ross Taylor
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Soonmoon Yoo
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, DE 19803, USA
| | - Tilman Heise
- Department of Biochemistry, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Amar N Kar
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Nora Perrone-Bizzozero
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Jeffery L Twiss
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
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285
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Transcriptomic Analysis of Ribosome-Bound mRNA in Cortical Neurites In Vivo. J Neurosci 2017; 37:8688-8705. [PMID: 28821669 DOI: 10.1523/jneurosci.3044-16.2017] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 06/29/2017] [Accepted: 07/21/2017] [Indexed: 01/19/2023] Open
Abstract
Localized translation in neurites helps regulate synaptic strength and development. Dysregulation of local translation is associated with many neurological disorders. However, due to technical limitations, study of this phenomenon has largely been limited to brain regions with laminar organization of dendrites such as the hippocampus or cerebellum. It has not been examined in the cortex, a region of importance for most neurological disorders, where dendrites of each neuronal population are densely intermingled with cell bodies of others. Therefore, we have developed a novel method, SynapTRAP, which combines synaptoneurosomal fractionation with translating ribosome affinity purification to identify ribosome-bound mRNA in processes of genetically defined cell types. We demonstrate SynapTRAP's efficacy and report local translation in the cortex of mice, where we identify a subset of mRNAs that are translated in dendrites by neuronal ribosomes. These mRNAs have disproportionately longer lengths, enrichment for FMRP binding and G-quartets, and their genes are under greater evolutionary constraint in humans. In addition, we show that alternative splicing likely regulates this phenomenon. Overall, SynapTRAP allows for rapid isolation of cell-type-specific localized translation and is applicable to classes of previously inaccessible neuronal and non-neuronal cells in vivoSIGNIFICANCE STATEMENT Instructions for making proteins are found in the genome, housed within the nucleus of each cell. These are then copied as RNA and exported to manufacture new proteins. However, in the brain, memory is thought to be encoded by strengthening individual connections (synapses) between neurons far from the nucleus. Thus, to efficiently make new proteins specifically where they are needed, neurons can transport RNAs to sites near synapses to locally produce proteins. Importantly, several mutations that cause autism disrupt this process. It has been assumed this process occurs in all brain regions, but has never been measured in the cortex. We applied a newly developed method measure to study, for the first time, local translation in cortical neurons.
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286
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Mitochondrial health maintenance in axons. Biochem Soc Trans 2017; 45:1045-1052. [DOI: 10.1042/bst20170023] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/11/2017] [Accepted: 07/13/2017] [Indexed: 02/06/2023]
Abstract
Neurons are post-mitotic cells that must function throughout the life of an organism. The high energetic requirements and Ca2+ spikes of synaptic transmission place a burden on neuronal mitochondria. The removal of older mitochondria and the replenishment of the functional mitochondrial pool in axons with freshly synthesized components are therefore important parts of neuronal maintenance. Although the mechanism of mitochondrial protein import and dynamics is studied in great detail, the length of neurons poses additional challenges to those processes. In this mini-review, I briefly cover the basics of mitochondrial biogenesis and proceed to explain the interdependence of mitochondrial transport and mitochondrial health. I then extrapolate recent findings in yeast and mammalian cultured cells to neurons, making a case for axonal translation as a contributor to mitochondrial biogenesis in neurons.
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287
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Wong HHW, Lin JQ, Ströhl F, Roque CG, Cioni JM, Cagnetta R, Turner-Bridger B, Laine RF, Harris WA, Kaminski CF, Holt CE. RNA Docking and Local Translation Regulate Site-Specific Axon Remodeling In Vivo. Neuron 2017; 95:852-868.e8. [PMID: 28781168 PMCID: PMC5563073 DOI: 10.1016/j.neuron.2017.07.016] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 06/09/2017] [Accepted: 07/14/2017] [Indexed: 12/03/2022]
Abstract
Nascent proteins can be positioned rapidly at precise subcellular locations by local protein synthesis (LPS) to facilitate localized growth responses. Axon arbor architecture, a major determinant of synaptic connectivity, is shaped by localized growth responses, but it is unknown whether LPS influences these responses in vivo. Using high-resolution live imaging, we examined the spatiotemporal dynamics of RNA and LPS in retinal axons during arborization in vivo. Endogenous RNA tracking reveals that RNA granules dock at sites of branch emergence and invade stabilized branches. Live translation reporter analysis reveals that de novo β-actin hotspots colocalize with docked RNA granules at the bases and tips of new branches. Inhibition of axonal β-actin mRNA translation disrupts arbor dynamics primarily by reducing new branch emergence and leads to impoverished terminal arbors. The results demonstrate a requirement for LPS in building arbor complexity and suggest a key role for pre-synaptic LPS in assembling neural circuits. Tracking endogenous RNA shows that RNA docking predicts axon branch emergence in vivo Axon arbor complexity in vivo depends on local protein synthesis Axonal β-actin synthesis regulates branching by increased branch initiation Live imaging reveals de novo synthesis of β-actin hotspots during branch formation
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Affiliation(s)
- Hovy Ho-Wai Wong
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Julie Qiaojin Lin
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Florian Ströhl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - Cláudio Gouveia Roque
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Jean-Michel Cioni
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Roberta Cagnetta
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Benita Turner-Bridger
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Romain F Laine
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - William A Harris
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Clemens F Kaminski
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - Christine E Holt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.
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288
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Morales D. A new model for netrin1 in commissural axon guidance. J Neurosci Res 2017; 96:247-252. [PMID: 28742927 DOI: 10.1002/jnr.24117] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 06/20/2017] [Accepted: 06/23/2017] [Indexed: 12/21/2022]
Abstract
Now-classic experiments characterized netrin1 as a major player in commissural axon guidance in the spinal cord. The data suggest a chemotactic model in which netrin1 expression in the floor plate forms a concentration gradient that attracts commissural axons. New research published independently in Neuron and in Nature tests this model by deleting netrin1 specifically in the floor plate. Surprisingly, these conditional mutant mice have no overt commissure defects. The authors report that netrin1 decorates the pial surface of the spinal cord and hindbrain, likely deposited by radial processes of progenitor cells in the ventricular zone. They find that deletion of the cue exclusively in the ventricular zone causes commissural axons to take aberrant trajectories, suggesting a short range, haptotactic guidance mechanism as opposed to chemotaxis. This minireview aims to summarize the classic and the new findings and offer some interpretations of the data.
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Affiliation(s)
- Daniel Morales
- Institut de recherches cliniques de Montréal (IRCM), Montreal, QC, H2W 1R7, Canada.,Integrated Program in Neuroscience, McGill University, Montreal, QC, H3A 2B4, Canada
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289
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Yalçın B, Zhao L, Stofanko M, O'Sullivan NC, Kang ZH, Roost A, Thomas MR, Zaessinger S, Blard O, Patto AL, Sohail A, Baena V, Terasaki M, O'Kane CJ. Modeling of axonal endoplasmic reticulum network by spastic paraplegia proteins. eLife 2017; 6. [PMID: 28742022 PMCID: PMC5576921 DOI: 10.7554/elife.23882] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 07/24/2017] [Indexed: 01/17/2023] Open
Abstract
Axons contain a smooth tubular endoplasmic reticulum (ER) network that is thought to be continuous with ER throughout the neuron; the mechanisms that form this axonal network are unknown. Mutations affecting reticulon or REEP proteins, with intramembrane hairpin domains that model ER membranes, cause an axon degenerative disease, hereditary spastic paraplegia (HSP). We show that Drosophila axons have a dynamic axonal ER network, which these proteins help to model. Loss of HSP hairpin proteins causes ER sheet expansion, partial loss of ER from distal motor axons, and occasional discontinuities in axonal ER. Ultrastructural analysis reveals an extensive ER network in axons, which shows larger and fewer tubules in larvae that lack reticulon and REEP proteins, consistent with loss of membrane curvature. Therefore HSP hairpin-containing proteins are required for shaping and continuity of axonal ER, thus suggesting roles for ER modeling in axon maintenance and function. DOI:http://dx.doi.org/10.7554/eLife.23882.001 The way we move – from simple motions like reaching out to grab something, to playing the piano or dancing – is coordinated in our brain. These processes involve many regions and steps, in which nerve cells transport signals along projections known as axons. Axons rely on sophisticated ‘engineering’ to work properly over long distances and are vulnerable to diseases that disrupt their engineering. For example, in genetic diseases called ‘hereditary spastic paraplegias’, damages to the ‘distal’ end of axons – the end furthest from the nerve cell body – cause paralysis of the lower body. Axons have several internal structures that make sure everything works properly. One of these structures is the endoplasmic reticulum, which is a network of tubular membranes that runs lengthwise along the axon. It is known that spastic paraplegias are sometimes caused by mutations affecting proteins that help to build and shape the endoplasmic reticulum, for example, the proteins of the reticulon and REEP families. However, until now it was not known how the ER forms its network in the axons and if this is influenced by these proteins. To see whether reticulons and REEPs affect the shape of the endoplasmic reticulum, Yalçιn et al. used healthy fruit fly larvae, and genetically modified ones that lacked the proteins. The results show that in healthy flies, the tubular network runs continuously along the axons. When either reticulon or REEP proteins were removed, the distal axons contained less endoplasmic reticulum. In mutant fly larvae that lacked both protein families, the endoplasmic reticulum was more interrupted and contained more gaps than in normal larvae. Using high-magnification electron microscopy confirmed these findings, and showed that the tubules of the endoplasmic reticulum in mutant axons were larger, but fewer. A next step will be to test whether these mutations also affect how the axons work and communicate over long distances. A better knowledge of the role of the endoplasmic reticulum in axons will help us to understand how damages to it could affect hereditary spastic paraplegias and other degenerative conditions. DOI:http://dx.doi.org/10.7554/eLife.23882.002
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Affiliation(s)
- Belgin Yalçın
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Lu Zhao
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Martin Stofanko
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Niamh C O'Sullivan
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Zi Han Kang
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Annika Roost
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Matthew R Thomas
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Sophie Zaessinger
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Olivier Blard
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Alex L Patto
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Anood Sohail
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Valentina Baena
- Department of Cell Biology, University of Connecticut Health Center, Farmington, United States
| | - Mark Terasaki
- Department of Cell Biology, University of Connecticut Health Center, Farmington, United States
| | - Cahir J O'Kane
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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290
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Abstract
Although much is known about the regenerative capacity of retinal ganglion cells, very significant barriers remain in our ability to restore visual function following traumatic injury or disease-induced degeneration. Here we summarize our current understanding of the factors regulating axon guidance and target engagement in regenerating axons, and review the state of the field of neural regeneration, focusing on the visual system and highlighting studies using other model systems that can inform analysis of visual system regeneration. This overview is motivated by a Society for Neuroscience Satellite meeting, "Reconnecting Neurons in the Visual System," held in October 2015 sponsored by the National Eye Institute as part of their "Audacious Goals Initiative" and co-organized by Carol Mason (Columbia University) and Michael Crair (Yale University). The collective wisdom of the conference participants pointed to important gaps in our knowledge and barriers to progress in promoting the restoration of visual system function. This article is thus a summary of our existing understanding of visual system regeneration and provides a blueprint for future progress in the field.
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291
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Younts TJ, Monday HR, Dudok B, Klein ME, Jordan BA, Katona I, Castillo PE. Presynaptic Protein Synthesis Is Required for Long-Term Plasticity of GABA Release. Neuron 2017; 92:479-492. [PMID: 27764673 DOI: 10.1016/j.neuron.2016.09.040] [Citation(s) in RCA: 133] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 07/29/2016] [Accepted: 09/20/2016] [Indexed: 12/16/2022]
Abstract
Long-term changes of neurotransmitter release are critical for proper brain function. However, the molecular mechanisms underlying these changes are poorly understood. While protein synthesis is crucial for the consolidation of postsynaptic plasticity, whether and how protein synthesis regulates presynaptic plasticity in the mature mammalian brain remain unclear. Here, using paired whole-cell recordings in rodent hippocampal slices, we report that presynaptic protein synthesis is required for long-term, but not short-term, plasticity of GABA release from type 1 cannabinoid receptor (CB1)-expressing axons. This long-term depression of inhibitory transmission (iLTD) involves cap-dependent protein synthesis in presynaptic interneuron axons, but not somata. Translation is required during the induction, but not maintenance, of iLTD. Mechanistically, CB1 activation enhances protein synthesis via the mTOR pathway. Furthermore, using super-resolution STORM microscopy, we revealed eukaryotic ribosomes in CB1-expressing axon terminals. These findings suggest that presynaptic local protein synthesis controls neurotransmitter release during long-term plasticity in the mature mammalian brain.
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Affiliation(s)
- Thomas J Younts
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA.
| | - Hannah R Monday
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Barna Dudok
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest 1051, Hungary; School of Ph.D. Studies, Semmelweis University, Budapest 1085, Hungary
| | - Matthew E Klein
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Bryen A Jordan
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA; Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - István Katona
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest 1051, Hungary
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA.
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292
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Dysregulation of mRNA Localization and Translation in Genetic Disease. J Neurosci 2017; 36:11418-11426. [PMID: 27911744 DOI: 10.1523/jneurosci.2352-16.2016] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/01/2016] [Accepted: 09/02/2016] [Indexed: 11/21/2022] Open
Abstract
RNA-binding proteins (RBPs) acting at various steps in the post-transcriptional regulation of gene expression play crucial roles in neuronal development and synaptic plasticity. Genetic mutations affecting several RBPs and associated factors lead to diverse neurological symptoms, as characterized by neurodevelopmental and neuropsychiatric disorders, neuromuscular and neurodegenerative diseases, and can often be multisystemic diseases. We will highlight the physiological roles of a few specific proteins in molecular mechanisms of cytoplasmic mRNA regulation, and how these processes are dysregulated in genetic disease. Recent advances in computational biology and genomewide analysis, integrated with diverse experimental approaches and model systems, have provided new insights into conserved mechanisms and the shared pathobiology of mRNA dysregulation in disease. Progress has been made to understand the pathobiology of disease mechanisms for myotonic dystrophy, spinal muscular atrophy, and fragile X syndrome, with broader implications for other RBP-associated genetic neurological diseases. This gained knowledge of underlying basic mechanisms has paved the way to the development of therapeutic strategies targeting disease mechanisms.
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293
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Abstract
Cells are highly organized entities that rely on intricate addressing mechanisms to sort their constituent molecules to precise subcellular locations. These processes are crucial for cells to maintain their proper organization and carry out specialized functions in the body, consequently genetic perturbations that clog up these addressing systems can contribute to disease aetiology. The trafficking of RNA molecules represents an important layer in the control of cellular organization, a process that is both highly prevalent and for which features of the regulatory machineries have been deeply conserved evolutionarily. RNA localization is commonly driven by trans-regulatory factors, including RNA binding proteins at the core, which recognize specific cis-acting zipcode elements within the RNA transcripts. Here, we first review the functions and biological benefits of intracellular RNA trafficking, from the perspective of both coding and non-coding RNAs. Next, we discuss the molecular mechanisms that modulate this localization, emphasizing the diverse features of the cis- and trans-regulators involved, while also highlighting emerging technologies and resources that will prove instrumental in deciphering RNA targeting pathways. We then discuss recent findings that reveal how co-transcriptional regulatory mechanisms operating in the nucleus can dictate the downstream cytoplasmic localization of RNAs. Finally, we survey the growing number of human diseases in which RNA trafficking pathways are impacted, including spinal muscular atrophy, Alzheimer's disease, fragile X syndrome and myotonic dystrophy. Such examples highlight the need to further dissect RNA localization mechanisms, which could ultimately pave the way for the development of RNA-oriented diagnostic and therapeutic strategies. This article is part of a Special Issue entitled "Biochemistry of Synthetic Biology - Recent Developments" Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue.
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Affiliation(s)
- Ashley Chin
- Institut de recherches cliniques de Montréal (IRCM), 110 Avenue des Pins Ouest, Montreal, Quebec, Canada; Division of Experimental Medicine, McGill University, 1001 Decarie Boulevard, Montreal, Quebec, Canada
| | - Eric Lécuyer
- Institut de recherches cliniques de Montréal (IRCM), 110 Avenue des Pins Ouest, Montreal, Quebec, Canada; Division of Experimental Medicine, McGill University, 1001 Decarie Boulevard, Montreal, Quebec, Canada; Department of Biochemistry and Molecular Medicine, University of Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec, Canada.
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294
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Whitworth GB, Misaghi BC, Rosenthal DM, Mills EA, Heinen DJ, Watson AH, Ives CW, Ali SH, Bezold K, Marsh-Armstrong N, Watson FL. Translational profiling of retinal ganglion cell optic nerve regeneration in Xenopus laevis. Dev Biol 2017; 426:360-373. [PMID: 27471010 PMCID: PMC5897040 DOI: 10.1016/j.ydbio.2016.06.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 06/01/2016] [Accepted: 06/01/2016] [Indexed: 11/29/2022]
Abstract
Unlike adult mammals, adult frogs regrow their optic nerve following a crush injury, making Xenopus laevis a compelling model for studying the molecular mechanisms that underlie neuronal regeneration. Using Translational Ribosome Affinity Purification (TRAP), a method to isolate ribosome-associated mRNAs from a target cell population, we have generated a transcriptional profile by RNA-Seq for retinal ganglion cells (RGC) during the period of recovery following an optic nerve injury. Based on bioinformatic analysis using the Xenopus laevis 9.1 genome assembly, our results reveal a profound shift in the composition of ribosome-associated mRNAs during the early stages of RGC regeneration. As factors involved in cell signaling are rapidly down-regulated, those involved in protein biosynthesis are up-regulated alongside key initiators of axon development. Using the new genome assembly, we were also able to analyze gene expression profiles of homeologous gene pairs arising from a whole-genome duplication in the Xenopus lineage. Here we see evidence of divergence in regulatory control among a significant proportion of pairs. Our data should provide a valuable resource for identifying genes involved in the regeneration process to target for future functional studies, in both naturally regenerative and non-regenerative vertebrates.
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Affiliation(s)
- G B Whitworth
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - B C Misaghi
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - D M Rosenthal
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - E A Mills
- Johns Hopkins University School of Medicine, Solomon H. Snyder Dept. of Neuroscience and Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, United States
| | - D J Heinen
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - A H Watson
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - C W Ives
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - S H Ali
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - K Bezold
- Department of Biology, Washington and Lee University, Lexington, VA, United States
| | - N Marsh-Armstrong
- Johns Hopkins University School of Medicine, Solomon H. Snyder Dept. of Neuroscience and Hugo Moser Research Institute at Kennedy Krieger, Baltimore, MD, United States
| | - F L Watson
- Department of Biology, Washington and Lee University, Lexington, VA, United States.
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295
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Gale JR, Aschrafi A, Gioio AE, Kaplan BB. Nuclear-Encoded Mitochondrial mRNAs: A Powerful Force in Axonal Growth and Development. Neuroscientist 2017; 24:142-155. [PMID: 28614981 DOI: 10.1177/1073858417714225] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Axons, their growth cones, and synaptic nerve terminals are neuronal subcompartments that have high energetic needs. As such, they are enriched in mitochondria, which supply the ATP necessary to meet these demands. To date, a heterogeneous population of nuclear-encoded mitochondrial mRNAs has been identified in distal axons and growth cones. Accumulating evidence suggests that the local translation of these mRNAs is required for mitochondrial maintenance and axonal viability. Here, we review evidence that suggests a critical role for axonal translation of nuclear-encoded mitochondrial mRNAs in axonal growth and development. Additionally, we explore the role that site-specific translation at the mitochondria itself may play in this process. Finally, we briefly review the clinical implications of dysregulation of local translation of mitochondrial-related mRNAs in neurodevelopmental disorders.
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Affiliation(s)
- Jenna R Gale
- 1 Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Armaz Aschrafi
- 1 Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Anthony E Gioio
- 1 Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Barry B Kaplan
- 1 Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
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296
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Kar AN, Lee SJ, Twiss JL. Expanding Axonal Transcriptome Brings New Functions for Axonally Synthesized Proteins in Health and Disease. Neuroscientist 2017; 24:111-129. [PMID: 28593814 DOI: 10.1177/1073858417712668] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intra-axonal protein synthesis has been shown to play critical roles in both development and repair of axons. Axons provide long-range connectivity in the nervous system, and disruption of their function and/or structure is seen in several neurological diseases and disorders. Axonally synthesized proteins or losses in axonally synthesized proteins contribute to neurodegenerative diseases, neuropathic pain, viral transport, and survival of axons. Increasing sensitivity of RNA detection and quantitation coupled with methods to isolate axons to purity has shown that a surprisingly complex transcriptome exists in axons. This extends across different species, neuronal populations, and physiological conditions. These studies have helped define the repertoire of neuronal mRNAs that can localize into axons and imply previously unrecognized functions for local translation in neurons. Here, we review the current state of transcriptomics studies of isolated axons, contrast axonal mRNA profiles between different neuronal types and growth states, and discuss how mRNA transport into and translation within axons contribute to neurological disorders.
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Affiliation(s)
- Amar N Kar
- 1 Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Seung Joon Lee
- 1 Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Jeffery L Twiss
- 1 Department of Biological Sciences, University of South Carolina, Columbia, SC, USA.,2 Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
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297
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Spaulding EL, Burgess RW. Accumulating Evidence for Axonal Translation in Neuronal Homeostasis. Front Neurosci 2017; 11:312. [PMID: 28620277 PMCID: PMC5450000 DOI: 10.3389/fnins.2017.00312] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 05/17/2017] [Indexed: 12/12/2022] Open
Abstract
The specialized structure of the neuron requires that homeostasis is sustained over the meter or more that may separate a cell body from its axonal terminus. Given this impressive distance and an axonal volume that is many times that of the cell body, how is such a compartment grown during development, re-grown after injury, and maintained throughout adulthood? While early answers to these questions focused on the local environment or the cell soma as supplying the needs of the axon, it is now well-established that the axon has some unique needs that can only be met from within. Decades of research have revealed local translation as an indispensable mechanism of axonal homeostasis during development and regeneration in both invertebrates and vertebrates. In contrast, the extent to which the adult, mammalian axonal proteome is maintained through local translation remains unclear and controversial. This mini-review aims to highlight important experiments that have helped to shape the field of axonal translation, to discuss conceptual arguments and recent evidence that supports local translation as important to the maintenance of adult axons, and to suggest experimental approaches that have the potential to further illuminate the role of axonal translation in neuronal homeostasis.
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Affiliation(s)
- Emily L Spaulding
- The Jackson LaboratoryBar Harbor, ME, United States.,Graduate School of Biomedical Sciences and Engineering, University of MaineOrono, ME, United States
| | - Robert W Burgess
- The Jackson LaboratoryBar Harbor, ME, United States.,Graduate School of Biomedical Sciences and Engineering, University of MaineOrono, ME, United States
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298
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Monday HR, Castillo PE. Closing the gap: long-term presynaptic plasticity in brain function and disease. Curr Opin Neurobiol 2017; 45:106-112. [PMID: 28570863 DOI: 10.1016/j.conb.2017.05.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 03/10/2017] [Accepted: 05/15/2017] [Indexed: 11/28/2022]
Abstract
Synaptic plasticity is critical for experience-dependent adjustments of brain function. While most research has focused on the mechanisms that underlie postsynaptic forms of plasticity, comparatively little is known about how neurotransmitter release is altered in a long-term manner. Emerging research suggests that many of the features of canonical 'postsynaptic' plasticity, such as associativity, structural changes and bidirectionality, also characterize long-term presynaptic plasticity. Recent studies demonstrate that presynaptic plasticity is a potent regulator of circuit output and function. Moreover, aberrant presynaptic plasticity is a convergent factor of synaptopathies like schizophrenia, addiction, and Autism Spectrum Disorders, and may be a potential target for treatment.
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Affiliation(s)
- Hannah R Monday
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
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299
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Gorenberg EL, Chandra SS. The Role of Co-chaperones in Synaptic Proteostasis and Neurodegenerative Disease. Front Neurosci 2017; 11:248. [PMID: 28579939 PMCID: PMC5437171 DOI: 10.3389/fnins.2017.00248] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 04/18/2017] [Indexed: 12/14/2022] Open
Abstract
Synapses must be preserved throughout an organism's lifespan to allow for normal brain function and behavior. Synapse maintenance is challenging given the long distances between the termini and the cell body, reliance on axonal transport for delivery of newly synthesized presynaptic proteins, and high rates of synaptic vesicle exo- and endocytosis. Hence, synapses rely on efficient proteostasis mechanisms to preserve their structure and function. To this end, the synaptic compartment has specific chaperones to support its functions. Without proper synaptic chaperone activity, local proteostasis imbalances lead to neurotransmission deficits, dismantling of synapses, and neurodegeneration. In this review, we address the roles of four synaptic chaperones in the maintenance of the nerve terminal, as well as their genetic links to neurodegenerative disease. Three of these are Hsp40 co-chaperones (DNAJs): Cysteine String Protein alpha (CSPα; DNAJC5), auxilin (DNAJC6), and Receptor-Mediated Endocytosis 8 (RME-8; DNAJC13). These co-chaperones contain a conserved J domain through which they form a complex with heat shock cognate 70 (Hsc70), enhancing the chaperone's ATPase activity. CSPα is a synaptic vesicle protein known to chaperone the t-SNARE SNAP-25 and the endocytic GTPase dynamin-1, thereby regulating synaptic vesicle exocytosis and endocytosis. Auxilin binds assembled clathrin cages, and through its interactions with Hsc70 leads to the uncoating of clathrin-coated vesicles, a process necessary for the regeneration of synaptic vesicles. RME-8 is a co-chaperone on endosomes and may have a role in clathrin-coated vesicle endocytosis on this organelle. These three co-chaperones maintain client function by preserving folding and assembly to prevent client aggregation, but they do not break down aggregates that have already formed. The fourth synaptic chaperone we will discuss is Heat shock protein 110 (Hsp110), which interacts with Hsc70, DNAJAs, and DNAJBs to constitute a disaggregase. Hsp110-related disaggregase activity is present at the synapse and is known to protect against aggregation of proteins such as α-synuclein. Congruent with their importance in the nervous system, mutations of these co-chaperones lead to familial neurodegenerative disease. CSPα mutations cause adult neuronal ceroid lipofuscinosis, while auxilin mutations result in early-onset Parkinson's disease, demonstrating their significance in preservation of the nervous system.
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Affiliation(s)
- Erica L Gorenberg
- Interdepartmental Neuroscience Program, Yale UniversityNew Haven, CT, United States
| | - Sreeganga S Chandra
- Department of Neurology, Yale UniversityNew Haven, CT, United States.,Department of Neuroscience, Yale UniversityNew Haven, CT, United States
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300
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Nectow AR, Moya MV, Ekstrand MI, Mousa A, McGuire KL, Sferrazza CE, Field BC, Rabinowitz GS, Sawicka K, Liang Y, Friedman JM, Heintz N, Schmidt EF. Rapid Molecular Profiling of Defined Cell Types Using Viral TRAP. Cell Rep 2017; 19:655-667. [PMID: 28423326 DOI: 10.1016/j.celrep.2017.03.048] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 02/11/2017] [Accepted: 03/14/2017] [Indexed: 12/13/2022] Open
Abstract
Translational profiling methodologies enable the systematic characterization of cell types in complex tissues, such as the mammalian brain, where neuronal isolation is exceptionally difficult. Here, we report a versatile strategy for profiling CNS cell types in a spatiotemporally restricted fashion by engineering a Cre-dependent adeno-associated virus expressing an EGFP-tagged ribosomal protein (AAV-FLEX-EGFPL10a) to access translating mRNAs by translating ribosome affinity purification (TRAP). We demonstrate the utility of this AAV to target a variety of genetically and anatomically defined neural populations expressing Cre recombinase and illustrate the ability of this viral TRAP (vTRAP) approach to recapitulate the molecular profiles obtained by bacTRAP in corticothalamic neurons across multiple serotypes. Furthermore, spatially restricting adeno-associated virus (AAV) injections enabled the elucidation of regional differences in gene expression within this cell type. Altogether, these results establish the broad applicability of the vTRAP strategy for the molecular dissection of any CNS or peripheral cell type that can be engineered to express Cre.
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Affiliation(s)
- Alexander R Nectow
- Laboratory of Molecular Genetics, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA; Princeton Neuroscience Institute, Princeton University, Lot 20 Washington Road, Princeton, NJ 08544, USA.
| | - Maria V Moya
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Mats I Ekstrand
- Laboratory of Molecular Genetics, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Awni Mousa
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Kelly L McGuire
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Caroline E Sferrazza
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Bianca C Field
- Laboratory of Molecular Genetics, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Gabrielle S Rabinowitz
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
| | - Kirsty Sawicka
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
| | - Yupu Liang
- Hospital Informatics, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
| | - Jeffrey M Friedman
- Laboratory of Molecular Genetics, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Nathaniel Heintz
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Eric F Schmidt
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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