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Jánosi B, Liewald JF, Seidenthal M, Yu SC, Umbach S, Redzovic J, Rentsch D, Alcantara IC, Bergs ACF, Schneider MW, Shao J, Gottschalk A. RIM and RIM-Binding Protein Localize Synaptic CaV2 Channels to Differentially Regulate Transmission in Neuronal Circuits. J Neurosci 2024; 44:e0535222024. [PMID: 38951038 PMCID: PMC11293454 DOI: 10.1523/jneurosci.0535-22.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/16/2024] [Accepted: 05/05/2024] [Indexed: 07/03/2024] Open
Abstract
At chemical synapses, voltage-gated Ca2+ channels (VGCCs) translate electrical signals into a trigger for synaptic vesicle (SV) fusion. VGCCs and the Ca2+ microdomains they elicit must be located precisely to primed SVs to evoke rapid transmitter release. Localization is mediated by Rab3-interacting molecule (RIM) and RIM-binding proteins, which interact and bind to the C terminus of the CaV2 VGCC α-subunit. We studied this machinery at the mixed cholinergic/GABAergic neuromuscular junction of Caenorhabditis elegans hermaphrodites. rimb-1 mutants had mild synaptic defects, through loosening the anchoring of UNC-2/CaV2 and delaying the onset of SV fusion. UNC-10/RIM deletion much more severely affected transmission. Although postsynaptic depolarization was reduced, rimb-1 mutants had increased cholinergic (but reduced GABAergic) transmission, to compensate for the delayed release. This did not occur when the excitation-inhibition (E-I) balance was altered by removing GABA transmission. Further analyses of GABA defective mutants and GABAA or GABAB receptor deletions, as well as cholinergic rescue of RIMB-1, emphasized that GABA neurons may be more affected than cholinergic neurons. Thus, RIMB-1 function differentially affects excitation-inhibition balance in the different motor neurons, and RIMB-1 thus may differentially regulate transmission within circuits. Untethering the UNC-2/CaV2 channel by removing its C-terminal PDZ ligand exacerbated the rimb-1 defects, and similar phenotypes resulted from acute degradation of the CaV2 β-subunit CCB-1. Therefore, untethering of the CaV2 complex is as severe as its elimination, yet it does not abolish transmission, likely due to compensation by CaV1. Thus, robustness and flexibility of synaptic transmission emerge from VGCC regulation.
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Affiliation(s)
- Barbara Jánosi
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Jana F Liewald
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Marius Seidenthal
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Szi-Chieh Yu
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Simon Umbach
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Jasmina Redzovic
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Dennis Rentsch
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Ivan C Alcantara
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Amelie C F Bergs
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Martin W Schneider
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Jiajie Shao
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
| | - Alexander Gottschalk
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt D-60438, Germany
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University Frankfurt, Frankfurt D-60438, Germany
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Britz S, Luccardini C, Markert SM, Merrill SA, Bessereau JL, Stigloher C. Array tomography of in vivo labeled synaptic receptors. Methods Cell Biol 2024; 187:139-174. [PMID: 38705623 DOI: 10.1016/bs.mcb.2024.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
Array tomography (AT) allows one to localize sub-cellular components within the structural context of cells in 3D through the imaging of serial sections. Using this technique, the z-resolution can be improved physically by cutting ultra-thin sections. Nevertheless, conventional immunofluorescence staining of those sections is time consuming and requires relatively large amounts of costly antibody solutions. Moreover, epitopes are only readily accessible at the section's surface, leaving the volume of the serial sections unlabeled. Localization of receptors at neuronal synapses in 3D in their native cellular ultrastructural context is important for understanding signaling processes. Here, we present in vivo labeling of receptors via fluorophore-coupled tags in combination with super-resolution AT. We present two workflows where we label receptors at the plasma membrane: first, in vivo labeling via microinjection with a setup consisting of readily available components and self-manufactured microscope table equipment and second, live receptor labeling by using a cell-permeable tag. To take advantage of a near-to-native preservation of tissues for subsequent scanning electron microscopy (SEM), we also apply high-pressure freezing and freeze substitution. The advantages and disadvantages of our workflows are discussed.
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Affiliation(s)
- Sebastian Britz
- Imaging Core Facility, Theodor-Boveri-Institute, Biocenter of the Julius-Maximilians-Universität Würzburg (JMU), Würzburg, Germany.
| | - Camilla Luccardini
- Centre d'Imagerie Quantitative Lyon Est (CIQLE), SFR Santé Lyon-Est CNRS UAR3453-INSERM US7, Université Claude Bernard Lyon 1, Lyon, France
| | - Sebastian M Markert
- Imaging Core Facility, Theodor-Boveri-Institute, Biocenter of the Julius-Maximilians-Universität Würzburg (JMU), Würzburg, Germany
| | - Sean A Merrill
- Department of Biology, University of Utah, Salt Lake City, UT, United States
| | - Jean-Louis Bessereau
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5284, INSERM U-1314, MeLiS, Institut NeuroMyoGene, Lyon, France
| | - Christian Stigloher
- Imaging Core Facility, Theodor-Boveri-Institute, Biocenter of the Julius-Maximilians-Universität Würzburg (JMU), Würzburg, Germany.
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3
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Markert SM. Studying zebrafish nervous system structure and function in health and disease with electron microscopy. Dev Growth Differ 2023; 65:502-516. [PMID: 37740826 DOI: 10.1111/dgd.12890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 09/15/2023] [Accepted: 09/19/2023] [Indexed: 09/25/2023]
Abstract
Zebrafish (Danio rerio) is a well-established model for studying the nervous system. Findings in zebrafish often inform studies on human diseases of the nervous system and provide crucial insight into disease mechanisms. The functions of the nervous system often rely on communication between neurons. Signal transduction is achieved via release of signaling molecules in the form of neuropeptides or neurotransmitters at synapses. Snapshots of membrane dynamics of these processes are imaged by electron microscopy. Electron microscopy can reveal ultrastructure and thus synaptic processes. This is crucial both for mapping synaptic connections and for investigating synaptic functions. In addition, via volumetric electron microscopy, the overall architecture of the nervous system becomes accessible, where structure can inform function. Electron microscopy is thus of particular value for studying the nervous system. However, today a plethora of electron microscopy techniques and protocols exist. Which technique is most suitable highly depends on the research question and scope as well as on the type of tissue that is examined. This review gives an overview of the electron microcopy techniques used on the zebrafish nervous system. It aims to give researchers a guide on which techniques are suitable for their specific questions and capabilities as well as an overview of the capabilities of electron microscopy in neurobiological research in the zebrafish model.
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Xuan Z, Yang S, Clark B, Hill SE, Manning L, Colón-Ramos DA. The active zone protein Clarinet regulates synaptic sorting of ATG-9 and presynaptic autophagy. PLoS Biol 2023; 21:e3002030. [PMID: 37053235 PMCID: PMC10101500 DOI: 10.1371/journal.pbio.3002030] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 02/08/2023] [Indexed: 04/14/2023] Open
Abstract
Autophagy is essential for cellular homeostasis and function. In neurons, autophagosome biogenesis is temporally and spatially regulated to occur near presynaptic sites, in part via the trafficking of autophagy transmembrane protein ATG-9. The molecules that regulate autophagy by sorting ATG-9 at synapses remain largely unknown. Here, we conduct forward genetic screens at single synapses of C. elegans neurons and identify a role for the long isoform of the active zone protein Clarinet (CLA-1L) in regulating sorting of autophagy protein ATG-9 at synapses, and presynaptic autophagy. We determine that disrupting CLA-1L results in abnormal accumulation of ATG-9 containing vesicles enriched with clathrin. The ATG-9 phenotype in cla-1(L) mutants is not observed for other synaptic vesicle proteins, suggesting distinct mechanisms that regulate sorting of ATG-9-containing vesicles and synaptic vesicles. Through genetic analyses, we uncover the adaptor protein complexes that genetically interact with CLA-1 in ATG-9 sorting. We also determine that CLA-1L extends from the active zone to the periactive zone and genetically interacts with periactive zone proteins in ATG-9 sorting. Our findings reveal novel roles for active zone proteins in the sorting of ATG-9 and in presynaptic autophagy.
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Affiliation(s)
- Zhao Xuan
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Sisi Yang
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Benjamin Clark
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Sarah E. Hill
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Laura Manning
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Daniel A. Colón-Ramos
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and Cell Biology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Instituto de Neurobiología, Recinto de Ciencias Médicas, Universidad de Puerto Rico, San Juan,Puerto Rico
- Wu Tsai Institute, Yale University, New Haven, Connecticut, United States of America
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5
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Mizumoto K, Jin Y, Bessereau JL. Synaptogenesis: unmasking molecular mechanisms using Caenorhabditis elegans. Genetics 2023; 223:iyac176. [PMID: 36630525 PMCID: PMC9910414 DOI: 10.1093/genetics/iyac176] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/22/2022] [Indexed: 01/13/2023] Open
Abstract
The nematode Caenorhabditis elegans is a research model organism particularly suited to the mechanistic understanding of synapse genesis in the nervous system. Armed with powerful genetics, knowledge of complete connectomics, and modern genomics, studies using C. elegans have unveiled multiple key regulators in the formation of a functional synapse. Importantly, many signaling networks display remarkable conservation throughout animals, underscoring the contributions of C. elegans research to advance the understanding of our brain. In this chapter, we will review up-to-date information of the contribution of C. elegans to the understanding of chemical synapses, from structure to molecules and to synaptic remodeling.
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Affiliation(s)
- Kota Mizumoto
- Department of Zoology, University of British Columbia, Vancouver V6T 1Z3, Canada
| | - Yishi Jin
- Department of Neurobiology, University of California San Diego, La Jolla, CA 92093, USA
| | - Jean-Louis Bessereau
- Univ Lyon, University Claude Bernard Lyon 1, CNRS UMR 5284, INSERM U 1314, Melis, 69008 Lyon, France
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Yang S, Park D, Manning L, Hill SE, Cao M, Xuan Z, Gonzalez I, Dong Y, Clark B, Shao L, Okeke I, Almoril-Porras A, Bai J, De Camilli P, Colón-Ramos DA. Presynaptic autophagy is coupled to the synaptic vesicle cycle via ATG-9. Neuron 2022; 110:824-840.e10. [PMID: 35065714 PMCID: PMC9017068 DOI: 10.1016/j.neuron.2021.12.031] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 10/20/2021] [Accepted: 12/20/2021] [Indexed: 01/01/2023]
Abstract
Autophagy is a cellular degradation pathway essential for neuronal health and function. Autophagosome biogenesis occurs at synapses, is locally regulated, and increases in response to neuronal activity. The mechanisms that couple autophagosome biogenesis to synaptic activity remain unknown. In this study, we determine that trafficking of ATG-9, the only transmembrane protein in the core autophagy pathway, links the synaptic vesicle cycle with autophagy. ATG-9-positive vesicles in C. elegans are generated from the trans-Golgi network via AP-3-dependent budding and delivered to presynaptic sites. At presynaptic sites, ATG-9 undergoes exo-endocytosis in an activity-dependent manner. Mutations that disrupt endocytosis, including a lesion in synaptojanin 1 associated with Parkinson's disease, result in abnormal ATG-9 accumulation at clathrin-rich synaptic foci and defects in activity-induced presynaptic autophagy. Our findings uncover regulated key steps of ATG-9 trafficking at presynaptic sites and provide evidence that ATG-9 exo-endocytosis couples autophagosome biogenesis at presynaptic sites with the activity-dependent synaptic vesicle cycle.
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Affiliation(s)
- Sisi Yang
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Daehun Park
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Laura Manning
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Sarah E Hill
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Mian Cao
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Zhao Xuan
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Ian Gonzalez
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Yongming Dong
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Benjamin Clark
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Lin Shao
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Ifechukwu Okeke
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Agustin Almoril-Porras
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Jihong Bai
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Pietro De Camilli
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Daniel A Colón-Ramos
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Instituto de Neurobiología José del Castillo, Recinto de Ciencias Médicas, Universidad de Puerto Rico, 201 Boulevard del Valle, San Juan, PR 00901, USA; Wu Tsai Institute, Yale University, New Haven, CT 06510, USA.
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Liu H, Li L, Krout M, Sheoran S, Zhao Q, Chen J, Liu H, Richmond JE, Hu Z. Protocols for electrophysiological recordings and electron microscopy at C. elegans neuromuscular junction. STAR Protoc 2021; 2:100749. [PMID: 34430921 PMCID: PMC8371263 DOI: 10.1016/j.xpro.2021.100749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Release of neurotransmitters by synaptic vesicle exocytosis at presynaptic terminals is critical for neuronal communication within the nervous system. Electrophysiology and electron microscopy are powerful and complementary approaches used to evaluate the function of synaptic proteins in synaptic transmission. Here, we provide a protocol detailing the use of these two approaches at C. elegans neuromuscular junctions, including steps for worm picking and dissection, in vivo electrophysiological recording, and sample preparation for electron microscopy, followed by imaging and analysis. For complete details on the use and execution of this protocol, please refer to Liu et al. (2021) and Li et al. (2021).
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Affiliation(s)
- Haowen Liu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane QLD, 4072, Australia
| | - Lei Li
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane QLD, 4072, Australia
| | - Mia Krout
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Seema Sheoran
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Qihong Zhao
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane QLD, 4072, Australia
| | - Jingyi Chen
- Guangzhou Laboratory, Guangzhou, Guangdong, China
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory), Guangzhou, China
| | - Huisheng Liu
- Guangzhou Laboratory, Guangzhou, Guangdong, China
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory), Guangzhou, China
| | - Janet E. Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Zhitao Hu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane QLD, 4072, Australia
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Byrd DT, Jin Y. Wired for insight-recent advances in Caenorhabditis elegans neural circuits. Curr Opin Neurobiol 2021; 69:159-169. [PMID: 33957432 PMCID: PMC8387325 DOI: 10.1016/j.conb.2021.02.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/16/2021] [Accepted: 02/22/2021] [Indexed: 11/15/2022]
Abstract
The completion of Caenorhabditis elegans connectomics four decades ago has long guided mechanistic investigation of neuronal circuits. Recent technological advances in microscopy and computation programs have aided re-examination of this connectomics, expanding our knowledge by both uncovering previously unreported synaptic connections and also generating models for neural networks underlying behaviors. Combining molecular information from single cell transcriptomes with elegant tools for cell-specific manipulation has further enhanced the ability to precisely investigate individual neurons in behaving animals. This mini-review aims to provide an overview of new information on connectomics and progress toward a molecular atlas of C. elegans nervous system, and discuss emerging findings on neuronal circuits.
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Affiliation(s)
- Dana T Byrd
- Neurobiology Section, University of California San Diego, La Jolla, CA, 92093, USA.
| | - Yishi Jin
- Neurobiology Section, University of California San Diego, La Jolla, CA, 92093, USA; Kavli Institute of Brain and Mind, University of California San Diego, La Jolla, CA, 92093, USA.
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9
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Miller-Fleming TW, Cuentas-Condori A, Manning L, Palumbos S, Richmond JE, Miller DM. Transcriptional Control of Parallel-Acting Pathways That Remove Specific Presynaptic Proteins in Remodeling Neurons. J Neurosci 2021; 41:5849-5866. [PMID: 34045310 PMCID: PMC8265810 DOI: 10.1523/jneurosci.0893-20.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 04/29/2021] [Accepted: 05/20/2021] [Indexed: 11/21/2022] Open
Abstract
Synapses are actively dismantled to mediate circuit refinement, but the developmental pathways that regulate synaptic disassembly are largely unknown. We have previously shown that the epithelial sodium channel ENaC/UNC-8 triggers an activity-dependent mechanism that drives the removal of presynaptic proteins liprin-α/SYD-2, Synaptobrevin/SNB-1, RAB-3, and Endophilin/UNC-57 in remodeling GABAergic neurons in Caenorhabditis elegans (Miller-Fleming et al., 2016). Here, we report that the conserved transcription factor Iroquois/IRX-1 regulates UNC-8 expression as well as an additional pathway, independent of UNC-8, that functions in parallel to dismantle functional presynaptic terminals. We show that the additional IRX-1-regulated pathway is selectively required for the removal of the presynaptic proteins, Munc13/UNC-13 and ELKS, which normally mediate synaptic vesicle (SV) fusion and neurotransmitter release. Our findings are notable because they highlight the key role of transcriptional regulation in synapse elimination during development and reveal parallel-acting pathways that coordinate synaptic disassembly by removing specific active zone proteins.SIGNIFICANCE STATEMENT Synaptic pruning is a conserved feature of developing neural circuits but the mechanisms that dismantle the presynaptic apparatus are largely unknown. We have determined that synaptic disassembly is orchestrated by parallel-acting mechanisms that target distinct components of the active zone. Thus, our finding suggests that synaptic disassembly is not accomplished by en masse destruction but depends on mechanisms that dismantle the structure in an organized process.
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Affiliation(s)
| | - Andrea Cuentas-Condori
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37212
| | - Laura Manning
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois 60607
| | - Sierra Palumbos
- Neuroscience Program, Vanderbilt University, Nashville, Tennessee 37212
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois 60607
| | - David M Miller
- Neuroscience Program, Vanderbilt University, Nashville, Tennessee 37212
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37212
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Lange F, Agüi-Gonzalez P, Riedel D, Phan NTN, Jakobs S, Rizzoli SO. Correlative fluorescence microscopy, transmission electron microscopy and secondary ion mass spectrometry (CLEM-SIMS) for cellular imaging. PLoS One 2021; 16:e0240768. [PMID: 33970908 PMCID: PMC8109779 DOI: 10.1371/journal.pone.0240768] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 04/13/2021] [Indexed: 11/24/2022] Open
Abstract
Electron microscopy (EM) has been employed for decades to analyze cell structure. To also analyze the positions and functions of specific proteins, one typically relies on immuno-EM or on a correlation with fluorescence microscopy, in the form of correlated light and electron microscopy (CLEM). Nevertheless, neither of these procedures is able to also address the isotopic composition of cells. To solve this, a correlation with secondary ion mass spectrometry (SIMS) would be necessary. SIMS has been correlated in the past to EM or to fluorescence microscopy in biological samples, but not to CLEM. We achieved this here, using a protocol based on transmission EM, conventional epifluorescence microscopy and nanoSIMS. The protocol is easily applied, and enables the use of all three technologies at high performance parameters. We suggest that CLEM-SIMS will provide substantial information that is currently beyond the scope of conventional correlative approaches.
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Affiliation(s)
- Felix Lange
- Research Group Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Clinic for Neurology, University Medical Center Göttingen, Göttingen, Germany
| | - Paola Agüi-Gonzalez
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Dietmar Riedel
- Laboratory of Electron Microscopy, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Nhu T. N. Phan
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Stefan Jakobs
- Research Group Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Clinic for Neurology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- * E-mail: (SJ); (SOR)
| | - Silvio O. Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- * E-mail: (SJ); (SOR)
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11
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Zheng W, Yang Z, Ge X, Feng Y, Wang Y, Liu C, Luan Y, Cai K, Vakal S, You F, Guo W, Wang W, Feng Z, Li F. Freeze substitution Hi-C, a convenient and cost-effective method for capturing the natural 3D chromatin conformation from frozen samples. J Genet Genomics 2021; 48:237-247. [PMID: 33573880 DOI: 10.1016/j.jgg.2020.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 11/28/2022]
Abstract
Chromatin interactions functionally affect genome architecture and gene regulation, but to date, only fresh samples must be used in High-through chromosome conformation capture (Hi-C) to keep natural chromatin conformation intact. This requirement has impeded the advancement of 3D genome research by limiting sample collection and storage options for researchers and severely limiting the number of samples that can be processed in a short time. Here, we develop a freeze substitution Hi-C (FS-Hi-C) technique that overcomes the need for fresh samples. FS-Hi-C can be used with samples stored in liquid nitrogen (LN2): the water in a vitreous form in the sample cells is replaced with ethanol via automated freeze substitution. After confirming that the FS step preserves the natural chromosome conformation during sample thawing, we tested the performance of FS-Hi-C with Drosophila melanogaster and Gossypium hirsutum. Beyond allowing the use of frozen samples and confirming that FS-Hi-C delivers robust data for generating contact heat maps and delineating A/B compartments and topologically associating domains, we found that FS-Hi-C outperforms the in situ Hi-C in terms of library quality, reproducibility, and valid interactions. Thus, FS-Hi-C will probably extend the application of 3D genome structure analysis to the vast number of experimental contexts in biological and medical research for which Hi-C methods have been unfeasible to date.
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Affiliation(s)
- Wu Zheng
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou 450000, China; State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, China; Wenzhou Medical University, Wenzhou 325027, China
| | - Zhaoen Yang
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou 450000, China; State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, China
| | - Xiaoyang Ge
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou 450000, China; State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, China
| | - Yijia Feng
- Wenzhou Medical University, Wenzhou 325027, China
| | - Ye Wang
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, China
| | - Chengwei Liu
- Wenzhou Medical University, Wenzhou 325027, China
| | - Yanan Luan
- Wenzhou Medical University, Wenzhou 325027, China
| | - Kun Cai
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou 450000, China
| | - Serhii Vakal
- Structural Bioinformatics Laboratory, Biochemistry, Åbo Akademi University, Turku 20520, Finland
| | - Feng You
- Wenzhou Medical University, Wenzhou 325027, China
| | - Wei Guo
- Wenzhou Medical University, Wenzhou 325027, China
| | - Wei Wang
- Department of Otorhinolaryngology-Head and Neck Surgery, Changhai Hospital, Second Military Medical University, Shanghai 200000, China
| | - Zhenhua Feng
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou 450000, China
| | - Fuguang Li
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou 450000, China; State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, China.
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12
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Guo J, Wang G, Tang W, Song D, Wang X, Hong J, Zhang Z. An optimized approach using cryofixation for high-resolution 3D analysis by FIB-SEM. J Struct Biol 2020; 212:107600. [PMID: 32798655 DOI: 10.1016/j.jsb.2020.107600] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 08/07/2020] [Accepted: 08/09/2020] [Indexed: 01/10/2023]
Abstract
Compared with conventional two-dimensional transmission electron microscopy (TEM), focused ion beam scanning electron microscopy (FIB-SEM) can provide more comprehensive 3D information on cell substructures at the nanometer scale. Biological samples prepared by cryofixation using high-pressure freezing demonstrate optimal preservation of the morphology of cellular structures, as these are arrested instantly in their near-native states. However, samples from cryofixation often show a weak back-scatter electron signal and bad image contrast in FIB-SEM imaging. In addition, it is impossible to do large amounts of heavy metal staining. This is commonly achieved via established osmium impregnation (OTO) en bloc staining protocols. Here, we compared the FIB-SEM image quality of brain tissues prepared using several common freeze-substitution media, and we developed an approach that overcomes these limitations through a combination of osmium tetroxide, uranyl acetate, tannic acid, and potassium permanganate at proper concentrations, respectively. Using this optimized sample preparation protocol for high-pressure freezing and freeze-substitution, perfect smooth membrane morphology, even of the lipid bilayers of the cell membrane, was readily obtained using FIB-SEM. In addition, our protocol is broadly applicable and we demonstrated successful application to brain tissues, plant tissues, Caenorhabditis elegans, Candida albicans, and chlorella. This approach combines the potential of cryofixation for 3D large volume analysis of subcellular structures with the high-resolution capabilities of FIB-SEM.
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Affiliation(s)
- Jiansheng Guo
- Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 310058 Hangzhou, Zhejiang, China; Center of Cryo-Electron Microscopy, Zhejiang University School of Medicine, 310058 Hangzhou, Zhejiang, China
| | - Guan Wang
- Department of Neurobiology, Zhejiang University School of Medicine, 310058 Hangzhou, Zhejiang, China
| | - Wen Tang
- Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 310058 Hangzhou, Zhejiang, China
| | - Dandan Song
- Center of Cryo-Electron Microscopy, Zhejiang University School of Medicine, 310058 Hangzhou, Zhejiang, China
| | - Xinqiu Wang
- Institute of Insect Science, Zhejiang University, Hangzhou 310058, China
| | - Jian Hong
- Center of Analysis and Measurement, Zhejiang University, Hangzhou 310029, China
| | - Zhongkai Zhang
- Biotechnology and Genetic Germplasm Resources Research Institute, Yunnan Academy of Agricultural Sciences, Key Lab of Southwestern Crop Gene Resources and Germplasm Innovation Ministry of Agriculture and Rural Affairs, Key Lab of Agricultural Biotechnology of Yunnan Province, Kunming 650205, Yunnan, China.
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13
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Cuentas-Condori A, Mulcahy B, He S, Palumbos S, Zhen M, Miller DM. C. elegans neurons have functional dendritic spines. eLife 2019; 8:e47918. [PMID: 31584430 PMCID: PMC6802951 DOI: 10.7554/elife.47918] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 10/03/2019] [Indexed: 12/15/2022] Open
Abstract
Dendritic spines are specialized postsynaptic structures that transduce presynaptic signals, are regulated by neural activity and correlated with learning and memory. Most studies of spine function have focused on the mammalian nervous system. However, spine-like protrusions have been reported in C. elegans (Philbrook et al., 2018), suggesting that the experimental advantages of smaller model organisms could be exploited to study the biology of dendritic spines. Here, we used super-resolution microscopy, electron microscopy, live-cell imaging and genetics to show that C. elegans motor neurons have functional dendritic spines that: (1) are structurally defined by a dynamic actin cytoskeleton; (2) appose presynaptic dense projections; (3) localize ER and ribosomes; (4) display calcium transients triggered by presynaptic activity and propagated by internal Ca++ stores; (5) respond to activity-dependent signals that regulate spine density. These studies provide a solid foundation for a new experimental paradigm that exploits the power of C. elegans genetics and live-cell imaging for fundamental studies of dendritic spine morphogenesis and function.
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Affiliation(s)
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research InstituteUniversity of TorontoTorontoCanada
| | - Siwei He
- Neuroscience ProgramVanderbilt UniversityNashvilleUnited States
| | - Sierra Palumbos
- Neuroscience ProgramVanderbilt UniversityNashvilleUnited States
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research InstituteUniversity of TorontoTorontoCanada
| | - David M Miller
- Department of Cell and Developmental BiologyVanderbilt UniversityNashvilleUnited States
- Neuroscience ProgramVanderbilt UniversityNashvilleUnited States
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14
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Zuber B, Lučić V. Molecular architecture of the presynaptic terminal. Curr Opin Struct Biol 2019; 54:129-138. [PMID: 30925443 DOI: 10.1016/j.sbi.2019.01.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 01/11/2019] [Accepted: 01/26/2019] [Indexed: 10/27/2022]
Abstract
Neurotransmitter release at the presynaptic terminal is one of the fundamental processes in neuronal communication. It is a complex process comprising signaling pathways that exert a precise spatio-temporal coordination to prepare and bring synaptic vesicles to exocytosis. While many molecular components involved have been identified, their direct observation at different stages of the neurotransmitter release is lacking. Three-dimensional imaging by electron tomography provided remarkable views of the synaptic vesicles and the cytomatrix. Imaging fully hydrated, vitrified samples allowed a direct visualization, precise localization and a quantitative characterization of pleomorphic synaptic vesicle-bound complexes in situ, as well as the elucidation of their function in the neurotransmitter release.
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Affiliation(s)
- Benoît Zuber
- Institute of Anatomy, University of Bern, Bern 3012, Switzerland
| | - Vladan Lučić
- Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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15
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Yu SC, Jánosi B, Liewald JF, Wabnig S, Gottschalk A. Endophilin A and B Join Forces With Clathrin to Mediate Synaptic Vesicle Recycling in Caenorhabditis elegans. Front Mol Neurosci 2018; 11:196. [PMID: 29962934 PMCID: PMC6010539 DOI: 10.3389/fnmol.2018.00196] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/17/2018] [Indexed: 01/24/2023] Open
Abstract
Synaptic vesicle (SV) recycling enables ongoing transmitter release, even during prolonged activity. SV membrane and proteins are retrieved by ultrafast endocytosis and new SVs are formed from synaptic endosomes (large vesicles—LVs). Many proteins contribute to SV recycling, e.g., endophilin, synaptojanin, dynamin and clathrin, while the site of action of these proteins (at the plasma membrane (PM) vs. at the endosomal membrane) is only partially understood. Here, we investigated the roles of endophilin A (UNC-57), endophilin-related protein (ERP-1, homologous to human endophilin B1) and of clathrin, in SV recycling at the cholinergic neuromuscular junction (NMJ) of C. elegans. erp-1 mutants exhibited reduced transmission and a progressive reduction in optogenetically evoked muscle contraction, indicative of impaired SV recycling. This was confirmed by electrophysiology, where particularly endophilin A (UNC-57), but also endophilin B (ERP-1) mutants exhibited reduced transmission. By optogenetic and electrophysiological analysis, phenotypes in the unc-57; erp-1 double mutant are largely dominated by the unc-57 mutation, arguing for partially redundant functions of endophilins A and B, but also hinting at a back-up mechanism for neuronal endocytosis. By electron microscopy (EM), we observed that unc-57 and erp-1; unc-57 double mutants showed increased numbers of synaptic endosomes of large size, assigning a role for both proteins at the endosome, because endosomal disintegration into new SVs, but not formation of endosomes were hampered. Accordingly, only low amounts of SVs were present. Also erp-1 mutants show reduced SV numbers (but no increase in LVs), thus ERP-1 contributes to SV formation. We analyzed temperature-sensitive mutants of clathrin heavy chain (chc-1), as well as erp-1; chc-1 and unc-57; chc-1 double mutants. SV recycling phenotypes were obvious from optogenetic stimulation experiments. By EM, chc-1 mutants showed formation of numerous and large endosomes, arguing that clathrin, as shown for mammalian synapses, acts at the endosome in formation of new SVs. Without endophilins, clathrin formed endosomes at the PM, while endophilins A and B compensated for the loss of clathrin at the PM, under conditions of high SV turnover.
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Affiliation(s)
- Szi-Chieh Yu
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Barbara Jánosi
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Jana F Liewald
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Sebastian Wabnig
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany.,Cluster of Excellence Frankfurt, Macromolecular Complexes (CEF-MC), Goethe University, Frankfurt, Germany
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16
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Li X, Ji G, Chen X, Ding W, Sun L, Xu W, Han H, Sun F. Large scale three-dimensional reconstruction of an entire Caenorhabditis elegans larva using AutoCUTS-SEM. J Struct Biol 2017; 200:87-96. [PMID: 28978429 DOI: 10.1016/j.jsb.2017.09.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 09/26/2017] [Accepted: 09/28/2017] [Indexed: 12/29/2022]
Abstract
Large scale, high resolution three dimensional (3D) ultrastructural reconstruction of cells and tissues has become increasingly important to our understanding of complex biological systems. There have been a few partial 3D ultra-structures of Caenorhabditis elegans (C. elegans) reported, however 3D reconstruction of a whole nematode has never been achieved. Here, we independently developed a technique called automatic collector of ultrathin sections scanning electron microscopy and using this methodology, generated a 3D reconstruction of an entire C. elegans larva with 100 nm axial and 15 nm lateral resolution. Compared to the current available ATUM (automated tape-collecting ultramicrotome) technique, our work provides another alternative complete solution that can be applied to obtain large scale 3D ultrastructure of tissues. Our workflow includes an automated hardware system for high throughput serial section collection, a software package for automatic SEM imaging, and an image reconstruction program. These combined techniques can now be used together to rapidly provide access to understand the anatomy of the whole nematodes.
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Affiliation(s)
- Xixia Li
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Gang Ji
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China.
| | - Xi Chen
- Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Wei Ding
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Lei Sun
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Wei Xu
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Hua Han
- Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Fei Sun
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China.
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17
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Wragg RT, Parisotto DA, Li Z, Terakawa MS, Snead D, Basu I, Weinstein H, Eliezer D, Dittman JS. Evolutionary Divergence of the C-terminal Domain of Complexin Accounts for Functional Disparities between Vertebrate and Invertebrate Complexins. Front Mol Neurosci 2017; 10:146. [PMID: 28603484 PMCID: PMC5445133 DOI: 10.3389/fnmol.2017.00146] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 04/30/2017] [Indexed: 12/19/2022] Open
Abstract
Complexin is a critical presynaptic protein that regulates both spontaneous and calcium-triggered neurotransmitter release in all synapses. Although the SNARE-binding central helix of complexin is highly conserved and required for all known complexin functions, the remainder of the protein has profoundly diverged across the animal kingdom. Striking disparities in complexin inhibitory activity are observed between vertebrate and invertebrate complexins but little is known about the source of these differences or their relevance to the underlying mechanism of complexin regulation. We found that mouse complexin 1 (mCpx1) failed to inhibit neurotransmitter secretion in Caenorhabditis elegans neuromuscular junctions lacking the worm complexin 1 (CPX-1). This lack of inhibition stemmed from differences in the C-terminal domain (CTD) of mCpx1. Previous studies revealed that the CTD selectively binds to highly curved membranes and directs complexin to synaptic vesicles. Although mouse and worm complexin have similar lipid binding affinity, their last few amino acids differ in both hydrophobicity and in lipid binding conformation, and these differences strongly impacted CPX-1 inhibitory function. Moreover, function was not maintained if a critical amphipathic helix in the worm CPX-1 CTD was replaced with the corresponding mCpx1 amphipathic helix. Invertebrate complexins generally shared more C-terminal similarity with vertebrate complexin 3 and 4 isoforms, and the amphipathic region of mouse complexin 3 significantly restored inhibitory function to worm CPX-1. We hypothesize that the CTD of complexin is essential in conferring an inhibitory function to complexin, and that this inhibitory activity has been attenuated in the vertebrate complexin 1 and 2 isoforms. Thus, evolutionary changes in the complexin CTD differentially shape its synaptic role across phylogeny.
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Affiliation(s)
- Rachel T Wragg
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
| | - Daniel A Parisotto
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
| | - Zhenlong Li
- Department of Physiology and Biophysics, Weill Cornell Medical College, New YorkNY, United States
| | - Mayu S Terakawa
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
| | - David Snead
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
| | - Ishani Basu
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
| | - Harel Weinstein
- Department of Physiology and Biophysics, Weill Cornell Medical College, New YorkNY, United States.,Institute for Computational Biomedicine, Weill Cornell Medical College, New YorkNY, United States
| | - David Eliezer
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
| | - Jeremy S Dittman
- Department of Biochemistry, Weill Cornell Medical College, New YorkNY, United States
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18
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Claeys M, Yushin VV, Leunissen JL, Claeys J, Bert W. Self-Pressurised Rapid Freezing (SPRF): an easy-to-use and low-cost alternative cryo-fixation method for nematodes. NEMATOLOGY 2017. [DOI: 10.1163/15685411-00003093] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Self-Pressurised Rapid Freezing (SPRF), an easy-to-use and low-cost alternative cryo-fixation method, was evaluated based on a comparative analysis of the ultrastructure of spermatozoa of the nematodes Acrobeles complexus and Caenorhabditis elegans. Sealed copper tubes, packed with active nematodes in water, were plunged into nitrogen slush, a semi-solid form of nitrogen. The water inside the capillary copper tube expands upon cooling due to the formation of hexagonal ice, thereby generating high pressure intrinsically for cryo-fixation of the sample. For sperm cells cryo-fixed by SPRF, the preservation of the ultrastructure was comparable to that achieved with high pressure freezing. This was evidenced by the clear details in mitochondria, membranous organelles and cytoskeleton in the pseudopod. It was demonstrated that SPRF fixation did not destroy antigenicity, based on the results of the immunolocalisation of the major sperm protein in both species. In conclusion, SPRF is a low-cost alternative cryo-fixation method for nematodes.
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Affiliation(s)
- Myriam Claeys
- Nematology Research Unit, Department of Biology, Ghent University, Belgium
| | - Vladimir V. Yushin
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041, Russia
- Far Eastern Federal University, Vladivostok 690950, Russia
| | | | - Jef Claeys
- Nematology Research Unit, Department of Biology, Ghent University, Belgium
| | - Wim Bert
- Nematology Research Unit, Department of Biology, Ghent University, Belgium
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19
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Bruckner JJ, Zhan H, Gratz SJ, Rao M, Ukken F, Zilberg G, O'Connor-Giles KM. Fife organizes synaptic vesicles and calcium channels for high-probability neurotransmitter release. J Cell Biol 2016; 216:231-246. [PMID: 27998991 PMCID: PMC5223599 DOI: 10.1083/jcb.201601098] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 10/19/2016] [Accepted: 11/29/2016] [Indexed: 11/22/2022] Open
Abstract
Fife is a Piccolo-RIM–related protein that regulates neurotransmission and motor behavior through an unknown mechanism. Here, Bruckner et al. show that Fife organizes synaptic vesicle docking and coupling to calcium channels to establish and modulate synaptic strength. The strength of synaptic connections varies significantly and is a key determinant of communication within neural circuits. Mechanistic insight into presynaptic factors that establish and modulate neurotransmitter release properties is crucial to understanding synapse strength, circuit function, and neural plasticity. We previously identified Drosophila Piccolo-RIM-related Fife, which regulates neurotransmission and motor behavior through an unknown mechanism. Here, we demonstrate that Fife localizes and interacts with RIM at the active zone cytomatrix to promote neurotransmitter release. Loss of Fife results in the severe disruption of active zone cytomatrix architecture and molecular organization. Through electron tomographic and electrophysiological studies, we find a decrease in the accumulation of release-ready synaptic vesicles and their release probability caused by impaired coupling to Ca2+ channels. Finally, we find that Fife is essential for the homeostatic modulation of neurotransmission. We propose that Fife organizes active zones to create synaptic vesicle release sites within nanometer distance of Ca2+ channel clusters for reliable and modifiable neurotransmitter release.
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Affiliation(s)
- Joseph J Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Hong Zhan
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Scott J Gratz
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Monica Rao
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Fiona Ukken
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Gregory Zilberg
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Kate M O'Connor-Giles
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706 .,Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706.,Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706
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20
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Ultrastructural Characterization of Phagophores Using Electron Tomography on Cryoimmobilized and Freeze Substituted Samples. Methods Enzymol 2016; 587:331-349. [PMID: 28253964 DOI: 10.1016/bs.mie.2016.09.063] [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] [Indexed: 02/17/2023]
Abstract
Electron tomography has significantly contributed to recent findings regarding the biogenesis of the phagophore, an organelle which initiates autophagic sequestration. The information obtained from 1.9nm slices through the tomograms have revealed that during biogenesis the phagophore is in contact with the membranes of apposing organelles to form tubular connections and membrane contact sites (MCSs). The most reported and established tubular connections occur between the phagophore and the endoplasmic reticulum. However, as the phagophore continues to grow and expand, connections and MCSs have also been reported to occur between the phagophore and several other organelles in a possible attempt to utilize lipids for membrane expansion from alternative sources. Since the lifespan of the phagophore is only a few minutes and membrane connections and MCSs are very dynamic, capturing these two events requires precision during fixation. Up to date there is no quicker alternative for sample preservation in transmission electron microscopy than cryoimmobilization. In this report, we describe our protocol for cryoimmobilization using high-pressure freezing and freeze substitution, and report our first findings on phagophore morphology using this approach.
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21
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Lim MA, Chitturi J, Laskova V, Meng J, Findeis D, Wiekenberg A, Mulcahy B, Luo L, Li Y, Lu Y, Hung W, Qu Y, Ho CY, Holmyard D, Ji N, McWhirter R, Samuel AD, Miller DM, Schnabel R, Calarco JA, Zhen M. Neuroendocrine modulation sustains the C. elegans forward motor state. eLife 2016; 5:19887. [PMID: 27855782 PMCID: PMC5120884 DOI: 10.7554/elife.19887] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 11/14/2016] [Indexed: 12/12/2022] Open
Abstract
Neuromodulators shape neural circuit dynamics. Combining electron microscopy, genetics, transcriptome profiling, calcium imaging, and optogenetics, we discovered a peptidergic neuron that modulates C. elegans motor circuit dynamics. The Six/SO-family homeobox transcription factor UNC-39 governs lineage-specific neurogenesis to give rise to a neuron RID. RID bears the anatomic hallmarks of a specialized endocrine neuron: it harbors near-exclusive dense core vesicles that cluster periodically along the axon, and expresses multiple neuropeptides, including the FMRF-amide-related FLP-14. RID activity increases during forward movement. Ablating RID reduces the sustainability of forward movement, a phenotype partially recapitulated by removing FLP-14. Optogenetic depolarization of RID prolongs forward movement, an effect reduced in the absence of FLP-14. Together, these results establish the role of a neuroendocrine cell RID in sustaining a specific behavioral state in C. elegans. DOI:http://dx.doi.org/10.7554/eLife.19887.001
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Affiliation(s)
- Maria A Lim
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Jyothsna Chitturi
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada
| | - Valeriya Laskova
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - Jun Meng
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - Daniel Findeis
- Institut für Genetik, Technische Universität Braunschweig Carolo Wilhelmina, Braunschweig, Germany
| | - Anne Wiekenberg
- Institut für Genetik, Technische Universität Braunschweig Carolo Wilhelmina, Braunschweig, Germany
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Linjiao Luo
- Key Laboratory of Modern Acoustics, Ministry of Education, Department of Physics, Nanjing University, Nanjing, China
| | - Yan Li
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - Yangning Lu
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - Wesley Hung
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Yixin Qu
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Chi-Yip Ho
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Douglas Holmyard
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Ni Ji
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Physics, Harvard University, Cambridge, United States
| | - Rebecca McWhirter
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
| | - Aravinthan Dt Samuel
- Center for Brain Science, Harvard University, Cambridge, United States.,Department of Physics, Harvard University, Cambridge, United States
| | - David M Miller
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
| | - Ralf Schnabel
- Institut für Genetik, Technische Universität Braunschweig Carolo Wilhelmina, Braunschweig, Germany
| | - John A Calarco
- FAS Center for Systems Biology, Harvard University, Cambridge, United States
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
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22
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Ultrastructural immunogold localization of major sperm protein (MSP) in spermatogenic cells of the nematode Acrobeles complexus (Nematoda, Rhabditida). Micron 2016; 89:43-55. [DOI: 10.1016/j.micron.2016.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/14/2016] [Accepted: 07/14/2016] [Indexed: 01/07/2023]
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23
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Markert SM, Britz S, Proppert S, Lang M, Witvliet D, Mulcahy B, Sauer M, Zhen M, Bessereau JL, Stigloher C. Filling the gap: adding super-resolution to array tomography for correlated ultrastructural and molecular identification of electrical synapses at the C. elegans connectome. NEUROPHOTONICS 2016; 3:041802. [PMID: 27175373 PMCID: PMC4855082 DOI: 10.1117/1.nph.3.4.041802] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/08/2016] [Indexed: 06/02/2023]
Abstract
Correlating molecular labeling at the ultrastructural level with high confidence remains challenging. Array tomography (AT) allows for a combination of fluorescence and electron microscopy (EM) to visualize subcellular protein localization on serial EM sections. Here, we describe an application for AT that combines near-native tissue preservation via high-pressure freezing and freeze substitution with super-resolution light microscopy and high-resolution scanning electron microscopy (SEM) analysis on the same section. We established protocols that combine SEM with structured illumination microscopy (SIM) and direct stochastic optical reconstruction microscopy (dSTORM). We devised a method for easy, precise, and unbiased correlation of EM images and super-resolution imaging data using endogenous cellular landmarks and freely available image processing software. We demonstrate that these methods allow us to identify and label gap junctions in Caenorhabditis elegans with precision and confidence, and imaging of even smaller structures is feasible. With the emergence of connectomics, these methods will allow us to fill in the gap-acquiring the correlated ultrastructural and molecular identity of electrical synapses.
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Affiliation(s)
| | - Sebastian Britz
- University of Würzburg, Biocenter, Division of Electron Microscopy, Am Hubland, Würzburg 97074, Germany
| | - Sven Proppert
- University of Würzburg, Department of Biotechnology and Biophysics, Am Hubland, Würzburg 97074, Germany
- University of Würzburg, Department of Neurophysiology, Institute of Physiology, Röntgenring 9, Würzburg 97070, Germany
| | - Marietta Lang
- University of Würzburg, Biocenter, Division of Electron Microscopy, Am Hubland, Würzburg 97074, Germany
| | - Daniel Witvliet
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
- University of Toronto, Department of Molecular Genetics, Physiology and Institute of Medical Science, 1 King's College Cir, Toronto, Ontario M5S 1A8, Canada
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
- University of Toronto, Department of Molecular Genetics, Physiology and Institute of Medical Science, 1 King's College Cir, Toronto, Ontario M5S 1A8, Canada
| | - Markus Sauer
- University of Würzburg, Department of Biotechnology and Biophysics, Am Hubland, Würzburg 97074, Germany
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
- University of Toronto, Department of Molecular Genetics, Physiology and Institute of Medical Science, 1 King's College Cir, Toronto, Ontario M5S 1A8, Canada
| | - Jean-Louis Bessereau
- Institut NeuroMyoGene, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, 16 rue R. Dubois, Villeurbanne Cedex F-69622, France
| | - Christian Stigloher
- University of Würzburg, Biocenter, Division of Electron Microscopy, Am Hubland, Würzburg 97074, Germany
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24
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Zhan H, Bruckner J, Zhang Z, O’Connor-Giles K. Three-dimensional imaging of Drosophila motor synapses reveals ultrastructural organizational patterns. J Neurogenet 2016; 30:237-246. [PMID: 27981875 PMCID: PMC5281062 DOI: 10.1080/01677063.2016.1253693] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 10/22/2016] [Accepted: 10/24/2016] [Indexed: 01/18/2023]
Abstract
We combined cryo-preservation of intact Drosophila larvae and electron tomography with comprehensive segmentation of key features to reconstruct the complete ultrastructure of a model glutamatergic synapse in a near-to-native state. Presynaptically, we detail a complex network of filaments that connects and organizes synaptic vesicles. We link the complexity of this synaptic vesicle network to proximity to the active zone cytomatrix, consistent with the model that these protein structures function together to regulate synaptic vesicle pools. We identify a net-shaped network of electron-dense filaments spanning the synaptic cleft that suggests conserved organization of trans-synaptic adhesion complexes at excitatory synapses. Postsynaptically, we characterize a regular pattern of macromolecules that yields structural insights into the scaffolding of neurotransmitter receptors. Together, these analyses reveal an unexpected level of conservation in the nanoscale organization of diverse glutamatergic synapses and provide a structural foundation for understanding the molecular machines that regulate synaptic communication at a powerful model synapse.
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Affiliation(s)
- Hong Zhan
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Joseph Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Ziheng Zhang
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Kate O’Connor-Giles
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706
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25
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Miller-Fleming TW, Petersen SC, Manning L, Matthewman C, Gornet M, Beers A, Hori S, Mitani S, Bianchi L, Richmond J, Miller DM. The DEG/ENaC cation channel protein UNC-8 drives activity-dependent synapse removal in remodeling GABAergic neurons. eLife 2016; 5. [PMID: 27403890 PMCID: PMC4980115 DOI: 10.7554/elife.14599] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 07/11/2016] [Indexed: 12/30/2022] Open
Abstract
Genetic programming and neural activity drive synaptic remodeling in developing neural circuits, but the molecular components that link these pathways are poorly understood. Here we show that the C. elegans Degenerin/Epithelial Sodium Channel (DEG/ENaC) protein, UNC-8, is transcriptionally controlled to function as a trigger in an activity-dependent mechanism that removes synapses in remodeling GABAergic neurons. UNC-8 cation channel activity promotes disassembly of presynaptic domains in DD type GABA neurons, but not in VD class GABA neurons where unc-8 expression is blocked by the COUP/TF transcription factor, UNC-55. We propose that the depolarizing effect of UNC-8-dependent sodium import elevates intracellular calcium in a positive feedback loop involving the voltage-gated calcium channel UNC-2 and the calcium-activated phosphatase TAX-6/calcineurin to initiate a caspase-dependent mechanism that disassembles the presynaptic apparatus. Thus, UNC-8 serves as a link between genetic and activity-dependent pathways that function together to promote the elimination of GABA synapses in remodeling neurons. DOI:http://dx.doi.org/10.7554/eLife.14599.001 The brain contains billions of nerve cells, or neurons, that communicate with one another through connections called synapses. As the brain develops, these circuits are extensively modified as new synapses are created and others are removed. Neurological disorders may emerge if these processes are not regulated correctly. Identifying the biological pathways that control the addition and removal of synapses could therefore provide new insights into how to treat human brain diseases. To communicate across a synapse, the signaling neuron releases chemicals called neurotransmitters that alter the activity of the receiving neuron. Some neurotransmitters, such as GABA, inhibit the activity of the receiving neuron. The activity of a neuron – and hence how often it releases neurotransmitters – depends on different ions moving into and out of the neuron through proteins called ion channels that are embedded in the cell membrane. For example, the movement of calcium ions into the neuron can trigger the release of neurotransmitters. The roundworm Caenorhabditis elegans is often used as a model organism to study how the brain develops. During development, the worm nervous system eliminates synapses that release GABA and reassembles them at new locations. However, the nervous system does not eliminate these synapses at random. Miller-Fleming, Petersen et al. now show that a C. elegans protein called UNC-8 is responsible for this effect. UNC-8 forms part of an ion channel that allows sodium ions to enter the neuron and is selectively produced in GABA neurons that are destined for remodeling. Miller-Fleming, Petersen et al. found that inside GABA-releasing neurons, calcium ions stimulate an enzyme called calcineurin that may in turn activate UNC-8. Sodium ions then enter the neuron through UNC-8 channels. This boosts the activity of the calcium ion channels, which further increases how many calcium ions enter the cell. Ultimately, the amount of calcium inside the neuron becomes high enough to activate an additional pathway that eliminates the synapse. This downstream pathway involves components of a cell-killing (or “apoptotic”) mechanism that is repurposed in this case to remove the GABA release apparatus at the synapse. Other proteins are likely to help UNC-8 sense the activity of neurons and destroy synapses in response. Further work is required to investigate these additional components and to determine how they work with UNC-8 to remove synapses in the nervous system during development. DOI:http://dx.doi.org/10.7554/eLife.14599.002
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Affiliation(s)
| | - Sarah C Petersen
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
| | - Laura Manning
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, United States
| | - Cristina Matthewman
- Department of Physiology and Biophysics, University of Miami, Miami, United States
| | - Megan Gornet
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
| | - Allison Beers
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
| | - Sayaka Hori
- Department of Physiology, Tokyo Women's Medical University, Tokyo, Japan
| | - Shohei Mitani
- Department of Physiology, Tokyo Women's Medical University, Tokyo, Japan
| | - Laura Bianchi
- Department of Physiology and Biophysics, University of Miami, Miami, United States
| | - Janet Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, United States
| | - David M Miller
- Neuroscience Program, Vanderbilt University, Nashville, United States.,Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
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26
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Abstract
While traditional chemical fixation methods for C. elegans electron microscopy (EM) have provided invaluable anatomical and structural information, the development of high-pressure freeze (HPF) and freeze substitution (FS) protocols offers advantages for high-resolution imaging. Specimens prepared using HPF methodology exhibit fewer distortion artifacts due to fixation and dehydration, have improved antigenicity, and result in a more physiologically accurate structural representation of the worm. In the HPF technique, freely moving worms are frozen at high-pressure (2100 bar) and low temperature (-180 °C) within milliseconds. These conditions prevent the formation of ice crystals that can damage cellular structures. Samples then undergo FS, during which worms are slowly brought to room temperature while substituting amorphous ice with organic solvents to preserve tissue in its near native state and provide contrast for imaging. FS can be performed in an automatic freeze substitution (AFS) machine or in makeshift, temperature controlled chambers. Fixed worms can be embedded in plastic resin and further processed for a variety of imaging techniques. Samples then viewed using scanning (SEM) or transmission electron microscopy (TEM) will show enhanced preservation of organelles, cell morphology, and antigenicity for immunocytochemistry.
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27
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Exogenous Alpha-Synuclein Alters Pre- and Post-Synaptic Activity by Fragmenting Lipid Rafts. EBioMedicine 2016; 7:191-204. [PMID: 27322472 PMCID: PMC4909369 DOI: 10.1016/j.ebiom.2016.03.038] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 02/24/2016] [Accepted: 03/24/2016] [Indexed: 12/28/2022] Open
Abstract
Alpha-synuclein (αSyn) interferes with multiple steps of synaptic activity at pre-and post-synaptic terminals, however the mechanism/s by which αSyn alters neurotransmitter release and synaptic potentiation is unclear. By atomic force microscopy we show that human αSyn, when incubated with reconstituted membrane bilayer, induces lipid rafts' fragmentation. As a consequence, ion channels and receptors are displaced from lipid rafts with consequent changes in their activity. The enhanced calcium entry leads to acute mobilization of synaptic vesicles, and exhaustion of neurotransmission at later stages. At the post-synaptic terminal, an acute increase in glutamatergic transmission, with increased density of PSD-95 puncta, is followed by disruption of the interaction between N-methyl-d-aspartate receptor (NMDAR) and PSD-95 with ensuing decrease of long term potentiation. While cholesterol loading prevents the acute effect of αSyn at the presynapse; inhibition of casein kinase 2, which appears activated by reduction of cholesterol, restores the correct localization and clustering of NMDARs. Extracellular αSyn disrupts lipid raft platforms with consequent mislocalization of several pre- and post-synaptic proteins. αSyn-driven changes in raft-partitioning of proteins blunt neurotransmission and LTP. Cholesterol loading and inhibition of CK2 restore αSyn-induced alterations of the post-synaptic density assembly.
Alpha-synuclein (αSyn), a cytosolic protein that can be released from neurons, becomes pathogenic when expressed at high levels, as in Parkinson's disease, due to multiplication of αSyn gene. We show that the mechanism responsible for the defects in synaptic vesicles mobilization and post-synaptic activity induced by extracellular αSyn is the fragmentation of lipid rafts, cholesterol-rich microdomains of the plasma membrane. Moreover restoration of lipid raft platforms and raft-partitioning of surface proteins prevents the alteration of synaptic transmission caused by exposure of neurons to αSyn.
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28
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Bert W, Slos D, Leroux O, Claeys M. Cryo-fixation and associated developments in transmission electron microscopy: a cool future for nematology. NEMATOLOGY 2016. [DOI: 10.1163/15685411-00002943] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
At present, the importance of sample preparation equipment for electron microscopy represents the driving force behind major breakthroughs in microscopy and cell biology. In this paper we present an introduction to the most commonly used cryo-fixation techniques, with special attention paid towards high-pressure freezing followed by freeze substitution. Techniques associated with cryo-fixation, such as immunolocalisation, cryo-sectioning, and correlative light and electron microscopy, are also highlighted. For studies that do not require high resolution, high quality results, or the immediate arrest of certain processes, conventional methods will provide answers to many questions. For some applications, such as immunocytochemistry, three-dimensional reconstruction of serial sections or electron tomography, improved preservation of the ultrastructure is required. This review of nematode cryo-fixation highlights that cryo-fixation not only results in a superior preservation of fine structural details, but also underlines the fact that some observations based on results solely obtained through conventional fixation approaches were either incorrect, or otherwise had severe limitations. Although the use of cryo-fixation has hitherto been largely restricted to model organisms, the advantages of cryo-fixation are sufficiently self-evident that we must conclude that the cryo-fixation method is highly likely to become the standard for nematode fixation in the near future.
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Affiliation(s)
- Wim Bert
- Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Dieter Slos
- Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Olivier Leroux
- Pteridology Research Group, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Myriam Claeys
- Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
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29
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Pallotto M, Watkins PV, Fubara B, Singer JH, Briggman KL. Extracellular space preservation aids the connectomic analysis of neural circuits. eLife 2015; 4. [PMID: 26650352 PMCID: PMC4764589 DOI: 10.7554/elife.08206] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Accepted: 10/27/2015] [Indexed: 11/16/2022] Open
Abstract
Dense connectomic mapping of neuronal circuits is limited by the time and effort required to analyze 3D electron microscopy (EM) datasets. Algorithms designed to automate image segmentation suffer from substantial error rates and require significant manual error correction. Any improvement in segmentation error rates would therefore directly reduce the time required to analyze 3D EM data. We explored preserving extracellular space (ECS) during chemical tissue fixation to improve the ability to segment neurites and to identify synaptic contacts. ECS preserved tissue is easier to segment using machine learning algorithms, leading to significantly reduced error rates. In addition, we observed that electrical synapses are readily identified in ECS preserved tissue. Finally, we determined that antibodies penetrate deep into ECS preserved tissue with only minimal permeabilization, thereby enabling correlated light microscopy (LM) and EM studies. We conclude that preservation of ECS benefits multiple aspects of the connectomic analysis of neural circuits. DOI:http://dx.doi.org/10.7554/eLife.08206.001 The brain consists of billions of neurons that are connected into many different circuits. Mapping the connections between these neurons could help researchers to understand how the nervous system works. A method commonly used to do so is to preserve samples of brain tissue in chemical fixatives, and then image thin slices of this tissue using powerful microscopes. As each tissue sample contains many neurons, computer algorithms have been developed to analyze the microscope images and automatically identify the neurons and the connections they make. However, these algorithms often make 'segmentation errors' that researchers need to manually correct: for example, overlapping neurons may be counted as a single neuron, or a neuron may be marked into several segments. Correcting these errors is a time-consuming and tedious task that limits how much of the brain can be currently mapped. Future algorithm improvements will hopefully reduce the number of errors; Pallotto, Watkins et al. explored an alternative approach by making the images themselves easier to analyze using existing algorithms. The chemicals used to preserve brain tissue often suck out the fluids that fill the spaces between the neurons, causing these 'extracellular spaces' to shrink. Pallotto, Watkins et al. have now developed a method of preserving tissue that maintains more space between the neurons, and used this method to preserve samples of mouse brain with different amounts of extracellular space. Pallotto, Watkins et al. found that the algorithm used to analyze the images of these samples made far fewer segmentation errors on samples that contained more extracellular space. It was also easier to identify the connections between different neurons in these samples. The next challenge will be to extend these methods to preserving extracellular space across whole brains. DOI:http://dx.doi.org/10.7554/eLife.08206.002
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Affiliation(s)
- Marta Pallotto
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Paul V Watkins
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Boma Fubara
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Joshua H Singer
- Department of Biology, University of Maryland, College Park, United States
| | - Kevin L Briggman
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.,Department of Biomedical Optics, Max Planck Institute for Medical Research, Heidelberg, Germany
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30
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Abstract
Synapses of the mammalian CNS are diverse in size, structure, molecular composition, and function. Synapses in their myriad variations are fundamental to neural circuit development, homeostasis, plasticity, and memory storage. Unfortunately, quantitative analysis and mapping of the brain's heterogeneous synapse populations has been limited by the lack of adequate single-synapse measurement methods. Electron microscopy (EM) is the definitive means to recognize and measure individual synaptic contacts, but EM has only limited abilities to measure the molecular composition of synapses. This report describes conjugate array tomography (AT), a volumetric imaging method that integrates immunofluorescence and EM imaging modalities in voxel-conjugate fashion. We illustrate the use of conjugate AT to advance the proteometric measurement of EM-validated single-synapse analysis in a study of mouse cortex.
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31
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Meng L, Mulcahy B, Cook SJ, Neubauer M, Wan A, Jin Y, Yan D. The Cell Death Pathway Regulates Synapse Elimination through Cleavage of Gelsolin in Caenorhabditis elegans Neurons. Cell Rep 2015; 11:1737-48. [PMID: 26074078 DOI: 10.1016/j.celrep.2015.05.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 05/01/2015] [Accepted: 05/15/2015] [Indexed: 11/17/2022] Open
Abstract
Synapse elimination occurs in development, plasticity, and disease. Although the importance of synapse elimination has been documented in many studies, the molecular mechanisms underlying this process are unclear. Here, using the development of C. elegans RME neurons as a model, we have uncovered a function for the apoptosis pathway in synapse elimination. We find that the conserved apoptotic cell death (CED) pathway and axonal mitochondria are required for the elimination of transiently formed clusters of presynaptic components in RME neurons. This function of the CED pathway involves the activation of the actin-filament-severing protein, GSNL-1. Furthermore, we show that caspase CED-3 cleaves GSNL-1 at a conserved C-terminal region and that the cleaved active form of GSNL-1 promotes its actin-severing ability. Our data suggest that activation of the CED pathway contributes to selective elimination of synapses through disassembly of the actin filament network.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Toronto, ON M5G 1X5, Canada
| | - Steven J Cook
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Marianna Neubauer
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Airong Wan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA; Department of Neurobiology and Duke Institute for Brain Sciences, Duke University Medical Center, Research Drive, Durham, NC 27710, USA.
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32
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Coordination and fine motor control depend on Drosophila TRPγ. Nat Commun 2015; 6:7288. [PMID: 26028119 DOI: 10.1038/ncomms8288] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 04/26/2015] [Indexed: 12/31/2022] Open
Abstract
Motor coordination is broadly divided into gross and fine motor control, both of which depend on proprioceptive organs. However, the channels that function specifically in fine motor control are unknown. Here we show that mutations in trpγ disrupt fine motor control while leaving gross motor proficiency intact. The mutants are unable to coordinate precise leg movements during walking, and are ineffective in traversing large gaps due to an inability in making subtle postural adaptations that are requisite for this task. TRPγ is expressed in proprioceptive organs, and is required in both neurons and glia for gap crossing. We expressed TRPγ in vitro, and found that its activity is promoted by membrane stretch. A mutation eliminating the Na(+)/Ca(2+) exchanger suppresses the gap-crossing phenotype of trpγ flies. Our findings indicate that TRPγ contributes to fine motor control through mechanical activation in proprioceptive organs, thereby promoting Ca(2+) influx, which is required for function.
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33
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Bruckner JJ, Zhan H, O'Connor-Giles KM. Advances in imaging ultrastructure yield new insights into presynaptic biology. Front Cell Neurosci 2015; 9:196. [PMID: 26052269 PMCID: PMC4440913 DOI: 10.3389/fncel.2015.00196] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/05/2015] [Indexed: 11/13/2022] Open
Abstract
Synapses are the fundamental functional units of neural circuits, and their dysregulation has been implicated in diverse neurological disorders. At presynaptic terminals, neurotransmitter-filled synaptic vesicles are released in response to calcium influx through voltage-gated calcium channels activated by the arrival of an action potential. Decades of electrophysiological, biochemical, and genetic studies have contributed to a growing understanding of presynaptic biology. Imaging studies are yielding new insights into how synapses are organized to carry out their critical functions. The development of techniques for rapid immobilization and preservation of neuronal tissues for electron microscopy (EM) has led to a new renaissance in ultrastructural imaging that is rapidly advancing our understanding of synapse structure and function.
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Affiliation(s)
- Joseph J Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison Madison, WI, USA
| | - Hong Zhan
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison Madison, WI, USA
| | - Kate M O'Connor-Giles
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison Madison, WI, USA ; Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison Madison, WI, USA ; Laboratory of Genetics, University of Wisconsin-Madison Madison, WI, USA
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34
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Nicolle O, Burel A, Griffiths G, Michaux G, Kolotuev I. Adaptation of Cryo-Sectioning for IEM Labeling of Asymmetric Samples: A Study Using Caenorhabditis elegans. Traffic 2015; 16:893-905. [PMID: 25858477 DOI: 10.1111/tra.12289] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 04/07/2015] [Accepted: 04/08/2015] [Indexed: 01/17/2023]
Abstract
Cryo-sectioning procedures, initially developed by Tokuyasu, have been successfully improved for tissues and cultured cells, enabling efficient protein localization on the ultrastructural level. Without a standard procedure applicable to any sample, currently existing protocols must be individually modified for each model organism or asymmetric sample. Here, we describe our method that enables reproducible cryo-sectioning of Caenorhabditis elegans larvae/adults and embryos. We have established a chemical-fixation procedure in which flat embedding considerably simplifies manipulation and lateral orientation of larvae or adults. To bypass the limitations of chemical fixation, we have improved the hybrid cryo-immobilization-rehydration technique and reduced the overall time required to complete this procedure. Using our procedures, precise cryo-sectioning orientation can be combined with good ultrastructural preservation and efficient immuno-electron microscopy protein localization. Also, GFP fluorescence can be efficiently preserved, permitting a direct correlation of the fluorescent signal and its subcellular localization. Although developed for C. elegans samples, our method addresses the challenge of working with small asymmetric samples in general, and thus could be used to improve the efficiency of immuno-electron localization in other model organisms.
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Affiliation(s)
- Ophélie Nicolle
- Institut de Génétique et Développement de Rennes, Faculté de Médecine, CNRS, Université de Rennes 1, F-35043, Rennes, France
| | - Agnès Burel
- Plateforme microscopie électronique MRic, Université de Rennes 1, UEB, SFR Biosit, UMS 'BIOSIT' CNRS 3480-INSERM 018, F-35043, Rennes, France
| | - Gareth Griffiths
- Department of Biosciences, University of Oslo, Blindernveien 31, 0371 Oslo, Norway
| | - Grégoire Michaux
- Institut de Génétique et Développement de Rennes, Faculté de Médecine, CNRS, Université de Rennes 1, F-35043, Rennes, France.,Plateforme microscopie électronique MRic, Université de Rennes 1, UEB, SFR Biosit, UMS 'BIOSIT' CNRS 3480-INSERM 018, F-35043, Rennes, France
| | - Irina Kolotuev
- Institut de Génétique et Développement de Rennes, Faculté de Médecine, CNRS, Université de Rennes 1, F-35043, Rennes, France.,Plateforme microscopie électronique MRic, Université de Rennes 1, UEB, SFR Biosit, UMS 'BIOSIT' CNRS 3480-INSERM 018, F-35043, Rennes, France
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Kolotuev I. Positional correlative anatomy of invertebrate model organisms increases efficiency of TEM data production. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:1392-1403. [PMID: 25180638 DOI: 10.1017/s1431927614012999] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Transmission electron microscopy (TEM) is an important tool for studies in cell biology, and is essential to address research questions from bacteria to animals. Recent technological innovations have advanced the entire field of TEM, yet classical techniques still prevail for most present-day studies. Indeed, the majority of cell and developmental biology studies that use TEM do not require cutting-edge methodologies, but rather fast and efficient data generation. Although access to state-of-the-art equipment is frequently problematic, standard TEM microscopes are typically available, even in modest research facilities. However, a major unmet need in standard TEM is the ability to quickly prepare and orient a sample to identify a region of interest. Here, I provide a detailed step-by-step method for a positional correlative anatomy approach to flat-embedded samples. These modifications make the TEM preparation and analytic procedures faster and more straightforward, supporting a higher sampling rate. To illustrate the modified procedures, I provide numerous examples addressing research questions in Caenorhabditis elegans and Drosophila. This method can be equally applied to address questions of cell and developmental biology in other small multicellular model organisms.
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Affiliation(s)
- Irina Kolotuev
- 1Fédération de Recherche BIOSIT,Université de Rennes 1,Plateforme microscopie électronique MRic,Campus santé,2 avenue du Professeur Léon-Bernard,35043 Rennes,France
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Engelke R, Riede J, Hegermann J, Wuerch A, Eimer S, Dengjel J, Mittler G. The Quantitative Nuclear Matrix Proteome as a Biochemical Snapshot of Nuclear Organization. J Proteome Res 2014; 13:3940-56. [DOI: 10.1021/pr500218f] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rudolf Engelke
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany
| | - Julia Riede
- Freiburg
Institute for Advanced Studies, School of Life Sciences − LifeNet, University of Freiburg, Albertstrasse 19, 79104 Freiburg, Germany
- Center
for Biological Systems Analysis, University of Freiburg, Habsburgerstrasse
49, 79104 Freiburg, Germany
| | - Jan Hegermann
- European Neuroscience Institute and Center for Molecular Physiology of the Brain (CMPB), 37077 Göttingen, Germany
| | - Andreas Wuerch
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany
| | - Stefan Eimer
- European Neuroscience Institute and Center for Molecular Physiology of the Brain (CMPB), 37077 Göttingen, Germany
| | - Joern Dengjel
- Freiburg
Institute for Advanced Studies, School of Life Sciences − LifeNet, University of Freiburg, Albertstrasse 19, 79104 Freiburg, Germany
- Center
for Biological Systems Analysis, University of Freiburg, Habsburgerstrasse
49, 79104 Freiburg, Germany
| | - Gerhard Mittler
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany
- BIOSS,
Center for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18, 79104 Freiburg, Germany
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Doroquez DB, Berciu C, Anderson JR, Sengupta P, Nicastro D. A high-resolution morphological and ultrastructural map of anterior sensory cilia and glia in Caenorhabditis elegans. eLife 2014; 3:e01948. [PMID: 24668170 PMCID: PMC3965213 DOI: 10.7554/elife.01948] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 02/17/2014] [Indexed: 12/22/2022] Open
Abstract
Many primary sensory cilia exhibit unique architectures that are critical for transduction of specific sensory stimuli. Although basic ciliogenic mechanisms are well described, how complex ciliary structures are generated remains unclear. Seminal work performed several decades ago provided an initial but incomplete description of diverse sensory cilia morphologies in C. elegans. To begin to explore the mechanisms that generate these remarkably complex structures, we have taken advantage of advances in electron microscopy and tomography, and reconstructed three-dimensional structures of fifty of sixty sensory cilia in the C. elegans adult hermaphrodite at high resolution. We characterize novel axonemal microtubule organization patterns, clarify structural features at the ciliary base, describe new aspects of cilia-glia interactions, and identify structures suggesting novel mechanisms of ciliary protein trafficking. This complete ultrastructural description of diverse cilia in C. elegans provides the foundation for investigations into underlying ciliogenic pathways, as well as contributions of defined ciliary structures to specific neuronal functions. DOI: http://dx.doi.org/10.7554/eLife.01948.001.
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Affiliation(s)
- David B Doroquez
- Department of Biology, Brandeis University, Waltham, United States
- National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Cristina Berciu
- Department of Biology, Brandeis University, Waltham, United States
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
| | - James R Anderson
- Department of Ophthalmology, John A Moran Eye Center, University of Utah School of Medicine, Salt Lake City, United States
| | - Piali Sengupta
- Department of Biology, Brandeis University, Waltham, United States
- National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Daniela Nicastro
- Department of Biology, Brandeis University, Waltham, United States
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, United States
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38
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Watanabe S, Lehmann M, Hujber E, Fetter RD, Richards J, Söhl-Kielczynski B, Felies A, Rosenmund C, Schmoranzer J, Jorgensen EM. Nanometer-resolution fluorescence electron microscopy (nano-EM) in cultured cells. Methods Mol Biol 2014; 1117:503-526. [PMID: 24357377 DOI: 10.1007/978-1-62703-776-1_22] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Nano-resolution fluorescence electron microscopy (nano-fEM) pinpoints the location of individual proteins in electron micrographs. Plastic sections are first imaged using a super-resolution fluorescence microscope and then imaged on an electron microscope. The two images are superimposed to correlate the position of labeled proteins relative to subcellular structures. Here, we describe the method in detail and present five technical advancements: the use of uranyl acetate during the freeze-substitution to enhance the contrast of tissues and reduce the loss of fluorescence, the use of ground-state depletion instead of photoactivation for temporal control of fluorescence, the use of organic fluorophores instead of fluorescent proteins to obtain brighter fluorescence signals, the use of tissue culture cells to broaden the utility of the method, and the use of a transmission electron microscope to achieve sharper images of ultrastructure.
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Affiliation(s)
- Shigeki Watanabe
- Department of Biology, University of Utah, Salt Lake City, UT, USA
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Kittelmann M, Hegermann J, Goncharov A, Taru H, Ellisman MH, Richmond JE, Jin Y, Eimer S. Liprin-α/SYD-2 determines the size of dense projections in presynaptic active zones in C. elegans. J Cell Biol 2013; 203:849-63. [PMID: 24322429 PMCID: PMC3857474 DOI: 10.1083/jcb.201302022] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 11/06/2013] [Indexed: 01/23/2023] Open
Abstract
Synaptic vesicle (SV) release is spatially and temporally regulated by a network of proteins that form the presynaptic active zone (AZ). The hallmark of most AZs is an electron-dense projection (DP) surrounded by SVs. Despite their importance for our understanding of triggered SV release, high-resolution analyses of DP structures are limited. Using electron microscopy, we show that DPs at Caenorhabditis elegans neuromuscular junctions (NMJs) were highly structured, composed of building units forming bays in which SVs are docked to the AZ membrane. Furthermore, larger ribbonlike DPs that were multimers of the NMJ building unit are found at synapses between inter- and motoneurons. We also demonstrate that DP size is determined by the activity of the AZ protein SYD-2/Liprin-α. Whereas loss of syd-2 function led to smaller DPs, syd-2 gain-of-function mutants displayed larger ribbonlike DPs through increased recruitment of ELKS-1/ELKS. Therefore, our data suggest that a main role of SYD-2/Liprin-α in synaptogenesis is to regulate the polymerization of DPs.
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Affiliation(s)
- Maike Kittelmann
- European Neuroscience Institute, 37077 Göttingen, Germany
- Cellular Neurobiology, Schwann-Schleiden-Centre for Molecular Cell Biology, 37077 Göttingen, Germany
| | - Jan Hegermann
- European Neuroscience Institute, 37077 Göttingen, Germany
- Center for Molecular Physiology of the Brain, 37073 Göttingen, Germany
- Institute of Functional and Applied Anatomy, Hannover Medical School, 30625 Hannover, Germany
| | - Alexandr Goncharov
- Howard Hughes Medical Institute, Division of Biological Sciences; and Center for Research on Biological Systems, National Center for Microscopy and Imaging Research and Department of Neurosciences; University of California, San Diego, La Jolla, CA 92093
| | - Hidenori Taru
- Howard Hughes Medical Institute, Division of Biological Sciences; and Center for Research on Biological Systems, National Center for Microscopy and Imaging Research and Department of Neurosciences; University of California, San Diego, La Jolla, CA 92093
- Laboratory of Neuronal Cell Biology, Graduate School of Pharmaceutical Sciences and Creative Research Institute, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
| | - Mark H. Ellisman
- Howard Hughes Medical Institute, Division of Biological Sciences; and Center for Research on Biological Systems, National Center for Microscopy and Imaging Research and Department of Neurosciences; University of California, San Diego, La Jolla, CA 92093
| | - Janet E. Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607
| | - Yishi Jin
- Howard Hughes Medical Institute, Division of Biological Sciences; and Center for Research on Biological Systems, National Center for Microscopy and Imaging Research and Department of Neurosciences; University of California, San Diego, La Jolla, CA 92093
| | - Stefan Eimer
- European Neuroscience Institute, 37077 Göttingen, Germany
- Center for Molecular Physiology of the Brain, 37073 Göttingen, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79108 Freiburg, Germany
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An organelle gatekeeper function for Caenorhabditis elegans UNC-16 (JIP3) at the axon initial segment. Genetics 2013; 194:143-61. [PMID: 23633144 DOI: 10.1534/genetics.112.147348] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Neurons must cope with extreme membrane trafficking demands to produce axons with organelle compositions that differ dramatically from those of the cell soma and dendrites; however, the mechanism by which they accomplish this is not understood. Here we use electron microscopy and quantitative imaging of tagged organelles to show that Caenorhabditis elegans axons lacking UNC-16 (JIP3/Sunday Driver) accumulate Golgi, endosomes, and lysosomes at levels up to 10-fold higher than wild type, while ER membranes are largely unaffected. Time lapse microscopy of tagged lysosomes in living animals and an analysis of lysosome distributions in various regions of unc-16 mutant axons revealed that UNC-16 inhibits organelles from escaping the axon initial segment (AIS) and moving to the distal synaptic part of the axon. Immunostaining of native UNC-16 in C. elegans neurons revealed a localized concentration of UNC-16 at the initial segment, although UNC-16 is also sparsely distributed in distal regions of axons, including the synaptic region. Organelles that escape the AIS in unc-16 mutants show bidirectional active transport within the axon commissure that occasionally deposits them in the synaptic region, where their mobility decreases and they accumulate. These results argue against the long-standing, untested hypothesis that JIP3/Sunday Driver promotes anterograde organelle transport in axons and instead suggest an organelle gatekeeper model in which UNC-16 (JIP3/Sunday Driver) selectively inhibits the escape of Golgi and endosomal organelles from the AIS. This is the first evidence for an organelle gatekeeper function at the AIS, which could provide a regulatory node for controlling axon organelle composition.
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Abstract
Local recycling of synaptic vesicles (SVs) allows neurons to sustain transmitter release. Extreme activity (e.g., during seizure) may exhaust synaptic transmission and, in vitro, induces bulk endocytosis to recover SV membrane and proteins; how this occurs in animals is unknown. Following optogenetic hyperstimulation of Caenorhabditis elegans motoneurons, we analyzed synaptic recovery by time-resolved behavioral, electrophysiological, and ultrastructural assays. Recovery of docked SVs and of evoked-release amplitudes (indicating readily-releasable pool refilling) occurred within ∼8-20 s (τ = 9.2 s and τ = 11.9 s), whereas locomotion recovered only after ∼60 s (τ = 20 s). During ∼11-s stimulation, 50- to 200-nm noncoated vesicles ("100nm vesicles") formed, which disappeared ∼8 s poststimulation, likely representing endocytic intermediates from which SVs may regenerate. In endophilin, synaptojanin, and dynamin mutants, affecting endocytosis and vesicle scission, resolving 100nm vesicles was delayed (>20 s). In dynamin mutants, 100nm vesicles were abundant and persistent, sometimes continuous with the plasma membrane; incomplete budding of smaller vesicles from 100nm vesicles further implicates dynamin in regenerating SVs from bulk-endocytosed vesicles. Synaptic recovery after exhaustive activity is slow, and different time scales of recovery at ultrastructural, physiological, and behavioral levels indicate multiple contributing processes. Similar processes may jointly account for slow recovery from acute seizures also in higher animals.
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42
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Hung WL, Hwang C, Gao S, Liao EH, Chitturi J, Wang Y, Li H, Stigloher C, Bessereau JL, Zhen M. Attenuation of insulin signalling contributes to FSN-1-mediated regulation of synapse development. EMBO J 2013; 32:1745-60. [PMID: 23665919 DOI: 10.1038/emboj.2013.91] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Accepted: 03/27/2013] [Indexed: 01/07/2023] Open
Abstract
A neuronal F-box protein FSN-1 regulates Caenorhabditis elegans neuromuscular junction development by negatively regulating DLK-mediated MAPK signalling. In the present study, we show that attenuation of insulin/IGF signalling also contributes to FSN-1-dependent synaptic development and function. The aberrant synapse morphology and synaptic transmission in fsn-1 mutants are partially and specifically rescued by reducing insulin/IGF-signalling activity in postsynaptic muscles, as well as by reducing the activity of EGL-3, a prohormone convertase that processes agonistic insulin/IGF ligands INS-4 and INS-6, in neurons. FSN-1 interacts with, and potentiates the ubiquitination of EGL-3 in vitro, and reduces the EGL-3 level in vivo. We propose that FSN-1 may negatively regulate insulin/IGF signalling, in part, through EGL-3-dependent insulin-like ligand processing.
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Affiliation(s)
- Wesley L Hung
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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43
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Yu SC, Klosterman SM, Martin AA, Gracheva EO, Richmond JE. Differential roles for snapin and synaptotagmin in the synaptic vesicle cycle. PLoS One 2013; 8:e57842. [PMID: 23469084 PMCID: PMC3585204 DOI: 10.1371/journal.pone.0057842] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 01/29/2013] [Indexed: 11/19/2022] Open
Abstract
Evoked synaptic transmission is dependent on interactions between the calcium sensor Synaptotagmin I and the SNARE complex, comprised of Syntaxin, SNAP-25, and Synaptobrevin. Recent evidence suggests that Snapin may be an important intermediate in this process, through simultaneous interactions of Snapin dimers with SNAP-25 and Synaptotagmin. In support of this model, cultured neurons derived from embryonically lethal Snapin null mutant mice exhibit desynchronized release and a reduced readily releasable vesicle pool. Based on evidence that a dimerization-defective Snapin mutation specifically disrupts priming, Snapin is hypothesized to stabilize primed vesicles by structurally coupling Synaptotagmin and SNAP-25. To explore this model in vivo we examined synaptic transmission in viable, adult C. elegans Snapin (snpn-1) mutants. The kinetics of synaptic transmission were unaffected at snpn-1 mutant neuromuscular junctions (NMJs), but the number of docked, fusion competent vesicles was significantly reduced. However, analyses of snt-1 and snt-1;snpn-1 double mutants suggest that the docking role of SNPN-1 is independent of Synaptotagmin. Based on these results we propose that the primary role of Snapin in C. elegans is to promote vesicle priming, consistent with the stabilization of SNARE complex formation through established interactions with SNAP-25 upstream of the actions of Synaptotagmin in calcium-sensing and endocytosis.
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Affiliation(s)
- Szi-Chieh Yu
- Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Susan M. Klosterman
- Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Ashley A. Martin
- Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Elena O. Gracheva
- Biological and Biomedical Sciences, Yale University, New Haven, Connecticut, United States of America
| | - Janet E. Richmond
- Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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44
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Small heat-shock proteins protect from heat-stroke-associated neurodegeneration. Nature 2012; 490:213-8. [PMID: 22972192 DOI: 10.1038/nature11417] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 07/16/2012] [Indexed: 01/20/2023]
Abstract
Heat stroke is a life-threatening condition, characterized by catastrophic collapse of thermoregulation and extreme hyperthermia. In recent years, intensification of heat waves has caused a surge of heat-stroke fatalities. The mechanisms underlying heat-related pathology are poorly understood. Here we show that heat stroke triggers pervasive necrotic cell death and neurodegeneration in Caenorhabditis elegans. Preconditioning of animals at a mildly elevated temperature strongly protects from heat-induced necrosis. The heat-shock transcription factor HSF-1 and the small heat-shock protein HSP-16.1 mediate cytoprotection by preconditioning. HSP-16.1 localizes to the Golgi, where it functions with the Ca(2+)- and Mn(2+)-transporting ATPase PMR-1 to maintain Ca(2+) homeostasis under heat stroke. Preconditioning also suppresses cell death inflicted by diverse insults, and protects mammalian neurons from heat cytotoxicity. These findings reveal an evolutionarily conserved mechanism that defends against diverse necrotic stimuli, and may be relevant to heat stroke and other pathological conditions involving necrosis in humans.
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Olendrowitz C, Bartels M, Krenkel M, Beerlink A, Mokso R, Sprung M, Salditt T. Phase-contrast x-ray imaging and tomography of the nematode Caenorhabditis elegans. Phys Med Biol 2012; 57:5309-23. [PMID: 22853964 DOI: 10.1088/0031-9155/57/16/5309] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have analyzed the model organism Caenorhabditis elegans with the help of phase-contrast x-ray tomography. This work combines techniques from x-ray imaging studies of single biological cells by in-line holography with three-dimensional reconstruction and furthermore extends these studies to the multicellular level. To preserve the sub-cellular ultrastructure of the nematodes, we used the near-native sample preparation of high-pressure freezing as commonly used in the field of electron microscopy. For the presented samples, a standard, non-magnifying parallel-beam setting, as well as a magnifying, divergent-beam setting using nanofocusing optics is evaluated based on their tomographic reconstruction potential. In this paper, we address difficulties in sample preparation and issues of image processing. By experimental refinement and through optimized reconstruction procedures, we were able to perform x-ray imaging studies on a living specimen.
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Affiliation(s)
- C Olendrowitz
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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Ernstrom GG, Weimer R, Pawar DRL, Watanabe S, Hobson RJ, Greenstein D, Jorgensen EM. V-ATPase V1 sector is required for corpse clearance and neurotransmission in Caenorhabditis elegans. Genetics 2012; 191:461-75. [PMID: 22426883 PMCID: PMC3374311 DOI: 10.1534/genetics.112.139667] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 02/29/2012] [Indexed: 11/18/2022] Open
Abstract
The vacuolar-type ATPase (V-ATPase) is a proton pump composed of two sectors, the cytoplasmic V(1) sector that catalyzes ATP hydrolysis and the transmembrane V(o) sector responsible for proton translocation. The transmembrane V(o) complex directs the complex to different membranes, but also has been proposed to have roles independent of the V(1) sector. However, the roles of the V(1) sector have not been well characterized. In the nematode Caenorhabditis elegans there are two V(1) B-subunit genes; one of them, vha-12, is on the X chromosome, whereas spe-5 is on an autosome. vha-12 is broadly expressed in adults, and homozygotes for a weak allele in vha-12 are viable but are uncoordinated due to decreased neurotransmission. Analysis of a null mutation demonstrates that vha-12 is not required for oogenesis or spermatogenesis in the adult germ line, but it is required maternally for early embryonic development. Zygotic expression begins during embryonic morphogenesis, and homozygous null mutants arrest at the twofold stage. These mutant embryos exhibit a defect in the clearance of apoptotic cell corpses in vha-12 null mutants. These observations indicate that the V(1) sector, in addition to the V(o) sector, is required in exocytic and endocytic pathways.
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Affiliation(s)
- Glen G. Ernstrom
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
| | - Robby Weimer
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
| | - Divya R. L. Pawar
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
| | - Shigeki Watanabe
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
| | - Robert J. Hobson
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
| | - David Greenstein
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455-0465
| | - Erik M. Jorgensen
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840
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TBC-8, a putative RAB-2 GAP, regulates dense core vesicle maturation in Caenorhabditis elegans. PLoS Genet 2012; 8:e1002722. [PMID: 22654674 PMCID: PMC3359978 DOI: 10.1371/journal.pgen.1002722] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 04/04/2012] [Indexed: 02/05/2023] Open
Abstract
Dense core vesicles (DCVs) are thought to be generated at the late Golgi apparatus as immature DCVs, which subsequently undergo a maturation process through clathrin-mediated membrane remodeling events. This maturation process is required for efficient processing of neuropeptides within DCVs and for removal of factors that would otherwise interfere with DCV release. Previously, we have shown that the GTPase, RAB-2, and its effector, RIC-19, are involved in DCV maturation in Caenorhabditis elegans motoneurons. In rab-2 mutants, specific cargo is lost from maturing DCVs and missorted into the endosomal/lysosomal degradation route. Cargo loss could be prevented by blocking endosomal delivery. This suggests that RAB-2 is involved in retention of DCV components during the sorting process at the Golgi-endosomal interface. To understand how RAB-2 activity is regulated at the Golgi, we screened for RAB-2-specific GTPase activating proteins (GAPs). We identified a potential RAB-2 GAP, TBC-8, which is exclusively expressed in neurons and which, when depleted, shows similar DCV maturation defects as rab-2 mutants. We could demonstrate that RAB-2 binds to its putative GAP, TBC-8. Interestingly, TBC-8 also binds to the RAB-2 effector, RIC-19. This interaction appears to be conserved as TBC-8 also interacted with the human ortholog of RIC-19, ICA69. Therefore, we propose that a dynamic ON/OFF cycling of RAB-2 at the Golgi induced by the GAP/effector complex is required for proper DCV maturation.
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Liu KSY, Siebert M, Mertel S, Knoche E, Wegener S, Wichmann C, Matkovic T, Muhammad K, Depner H, Mettke C, Bückers J, Hell SW, Müller M, Davis GW, Schmitz D, Sigrist SJ. RIM-binding protein, a central part of the active zone, is essential for neurotransmitter release. Science 2012; 334:1565-9. [PMID: 22174254 DOI: 10.1126/science.1212991] [Citation(s) in RCA: 206] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The molecular machinery mediating the fusion of synaptic vesicles (SVs) at presynaptic active zone (AZ) membranes has been studied in detail, and several essential components have been identified. AZ-associated protein scaffolds are viewed as only modulatory for transmission. We discovered that Drosophila Rab3-interacting molecule (RIM)-binding protein (DRBP) is essential not only for the integrity of the AZ scaffold but also for exocytotic neurotransmitter release. Two-color stimulated emission depletion microscopy showed that DRBP surrounds the central Ca(2+) channel field. In drbp mutants, Ca(2+) channel clustering and Ca(2+) influx were impaired, and synaptic release probability was drastically reduced. Our data identify RBP family proteins as prime effectors of the AZ scaffold that are essential for the coupling of SVs, Ca(2+) channels, and the SV fusion machinery.
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Affiliation(s)
- Karen S Y Liu
- Department of Genetics, Institute for Biology, Free University Berlin, 14195 Berlin, Germany
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Watanabe S, Jorgensen EM. Visualizing proteins in electron micrographs at nanometer resolution. Methods Cell Biol 2012; 111:283-306. [PMID: 22857934 DOI: 10.1016/b978-0-12-416026-2.00015-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To understand protein function, we need a detailed description of the molecular topography of the cell. The subcellular localization of proteins can be revealed using genetically encoded fluorescent proteins or immunofluorescence. However, the precise localization of proteins cannot be resolved due to the diffraction limit of light. Recently, the diffraction barrier has been overcome by employing several microscopy techniques. Using super-resolution fluorescence microscopy, one can pinpoint the location of proteins at a resolution of 20 nm or even less. However, the cellular context is often absent in these images. Recently, we developed a method for visualizing the subcellular structures in super-resolution images. Here we describe the method with two technical improvements. First, we optimize the method to preserve more fluorescence without compromising the morphology. Second, we implement ground-state depletion and single-molecule return (GSDIM) imaging, which does not rely on photoactivatable fluorescent proteins. These improvements extend the utility of nano-resolution fluorescence electron microscopy (nano-fEM).
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Affiliation(s)
- Shigeki Watanabe
- Howard Hughes Medical Institute and Department of Biology, University of Utah, Salt Lake City, UT 84112-0840, USA
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