1
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Martin CG, Bent JS, Hill T, Topalidou I, Singhvi A. Epithelial UNC-23 limits mechanical stress to maintain glia-neuron architecture in C. elegans. Dev Cell 2024; 59:1668-1688.e7. [PMID: 38670103 PMCID: PMC11233253 DOI: 10.1016/j.devcel.2024.04.005] [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: 11/23/2022] [Revised: 12/23/2023] [Accepted: 04/03/2024] [Indexed: 04/28/2024]
Abstract
For an organ to maintain correct architecture and function, its diverse cellular components must coordinate their size and shape. Although cell-intrinsic mechanisms driving homotypic cell-cell coordination are known, it is unclear how cell shape is regulated across heterotypic cells. We find that epithelial cells maintain the shape of neighboring sense-organ glia-neuron units in adult Caenorhabditis elegans (C. elegans). Hsp co-chaperone UNC-23/BAG2 prevents epithelial cell shape from deforming, and its loss causes head epithelia to stretch aberrantly during animal movement. In the sense-organ glia, amphid sheath (AMsh), this causes progressive fibroblast growth factor receptor (FGFR)-dependent disruption of the glial apical cytoskeleton. Resultant glial cell shape alteration causes concomitant shape change in glia-associated neuron endings. Epithelial UNC-23 maintenance of glia-neuron shape is specific both spatially, within a defined anatomical zone, and temporally, in a developmentally critical period. As all molecular components uncovered are broadly conserved across central and peripheral nervous systems, we posit that epithelia may similarly regulate glia-neuron architecture cross-species.
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Affiliation(s)
- Cecilia G Martin
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - James S Bent
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Tyler Hill
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Irini Topalidou
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Aakanksha Singhvi
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA.
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2
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Heiman MG, Bülow HE. Dendrite morphogenesis in Caenorhabditis elegans. Genetics 2024; 227:iyae056. [PMID: 38785371 PMCID: PMC11151937 DOI: 10.1093/genetics/iyae056] [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: 12/18/2023] [Accepted: 04/02/2024] [Indexed: 05/25/2024] Open
Abstract
Since the days of Ramón y Cajal, the vast diversity of neuronal and particularly dendrite morphology has been used to catalog neurons into different classes. Dendrite morphology varies greatly and reflects the different functions performed by different types of neurons. Significant progress has been made in our understanding of how dendrites form and the molecular factors and forces that shape these often elaborately sculpted structures. Here, we review work in the nematode Caenorhabditis elegans that has shed light on the developmental mechanisms that mediate dendrite morphogenesis with a focus on studies investigating ciliated sensory neurons and the highly elaborated dendritic trees of somatosensory neurons. These studies, which combine time-lapse imaging, genetics, and biochemistry, reveal an intricate network of factors that function both intrinsically in dendrites and extrinsically from surrounding tissues. Therefore, dendrite morphogenesis is the result of multiple tissue interactions, which ultimately determine the shape of dendritic arbors.
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Affiliation(s)
- Maxwell G Heiman
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Hannes E Bülow
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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3
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Chalmers N, Masouti E, Beckervordersandforth R. Astrocytes in the adult dentate gyrus-balance between adult and developmental tasks. Mol Psychiatry 2024; 29:982-991. [PMID: 38177351 PMCID: PMC11176073 DOI: 10.1038/s41380-023-02386-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 12/12/2023] [Accepted: 12/14/2023] [Indexed: 01/06/2024]
Abstract
Astrocytes, a major glial cell type in the brain, are indispensable for the integration, maintenance and survival of neurons during development and adulthood. Both life phases make specific demands on the molecular and physiological properties of astrocytes, and most research projects traditionally focus on either developmental or adult astrocyte functions. In most brain regions, the generation of brain cells and the establishment of neural circuits ends with postnatal development. However, few neurogenic niches exist in the adult brain in which new neurons and glial cells are produced lifelong, and the integration of new cells into functional circuits represent a very special form of plasticity. Consequently, in the neurogenic niche, the astrocytes must be equipped to execute both mature and developmental tasks in order to integrate newborn neurons into the circuit and yet maintain overall homeostasis without affecting the preexisting neurons. In this review, we focus on astrocytes of the hippocampal dentate gyrus (DG), and discuss specific features of the astrocytic compartment that may allow the execution of both tasks. Firstly, astrocytes of the adult DG are molecularly, morphologically and functionally diverse, and the distinct astrocytes subtypes are characterized by their localization to DG layers. This spatial separation may lead to a functional specification of astrocytes subtypes according to the neuronal structures they are embedded in, hence a division of labor. Secondly, the astrocytic compartment is not static, but steadily increasing in numbers due to lifelong astrogenesis. Interestingly, astrogenesis can adapt to environmental and behavioral stimuli, revealing an unexpected astrocyte dynamic that allows the niche to adopt to changing demands. The diversity and dynamic of astrocytes in the adult DG implicate a vital contribution to hippocampal plasticity and represent an interesting model to uncover mechanisms how astrocytes simultaneously fulfill developmental and adult tasks.
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Affiliation(s)
- Nicholas Chalmers
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Evangelia Masouti
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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4
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Varandas KC, Hodges BM, Lubeck L, Farinas A, Liang Y, Lu Y, Shaham S. Glia detect and mount a protective response to loss of dendrite substructure integrity in C. elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.16.567404. [PMID: 38014226 PMCID: PMC10680744 DOI: 10.1101/2023.11.16.567404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Neurons have elaborate structures that determine their connectivity and functions. Changes in neuronal structure accompany learning and memory formation and are hallmarks of neurological disease. Here we show that glia monitor dendrite structure and respond to dendrite perturbation. In C. elegans mutants with defective sensory-organ dendrite cilia, adjacent glia accumulate extracellular matrix-laden vesicles, secrete excess matrix around cilia, alter gene expression, and change their secreted protein repertoire. Inducible cilia disruption reveals that this response is acute. DGS-1, a 7-transmembrane domain neuronal protein, and FIG-1, a multifunctional thrombospondin-domain glial protein, are required for glial detection of cilia integrity, and exhibit mutually-dependent localization to and around cilia, respectively. While inhibiting glial secretion disrupts dendritic cilia properties, hyperactivating the glial response protects against dendrite damage. Our studies uncover a homeostatic protective dendrite-glia interaction and suggest that similar signaling occurs at other sensory structures and at synapses, which resemble sensory organs in architecture and molecules.
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5
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Liu L, Gao H, Li J, Chen S. Probing microdomain Ca 2+ activity and synaptic transmission with a node-based tripartite synapse model. FRONTIERS IN NETWORK PHYSIOLOGY 2023; 3:1111306. [PMID: 36926546 PMCID: PMC10013067 DOI: 10.3389/fnetp.2023.1111306] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 01/27/2023] [Indexed: 06/08/2023]
Abstract
Astrocytic fine processes are the most minor structures of astrocytes but host much of the Ca2+ activity. These localized Ca2+ signals spatially restricted to microdomains are crucial for information processing and synaptic transmission. However, the mechanistic link between astrocytic nanoscale processes and microdomain Ca2+ activity remains hazily understood because of the technical difficulties in accessing this structurally unresolved region. In this study, we used computational models to disentangle the intricate relations of morphology and local Ca2+ dynamics involved in astrocytic fine processes. We aimed to answer: 1) how nano-morphology affects local Ca2+ activity and synaptic transmission, 2) and how fine processes affect Ca2+ activity of large process they connect. To address these issues, we undertook the following two computational modeling: 1) we integrated the in vivo astrocyte morphological data from a recent study performed with super-resolution microscopy that discriminates sub-compartments of various shapes, referred to as nodes and shafts to a classic IP3R-mediated Ca2+ signaling framework describing the intracellular Ca2+ dynamics, 2) we proposed a node-based tripartite synapse model linking with astrocytic morphology to predict the effect of structural deficits of astrocytes on synaptic transmission. Extensive simulations provided us with several biological insights: 1) the width of nodes and shafts could strongly influence the spatiotemporal variability of Ca2+ signals properties but what indeed determined the Ca2+ activity was the width ratio between nodes and shafts, 2) the connectivity of nodes to larger processes markedly shaped the Ca2+ signal of the parent process rather than nodes morphology itself, 3) the morphological changes of astrocytic part might potentially induce the abnormality of synaptic transmission by affecting the level of glutamate at tripartite synapses. Taken together, this comprehensive model which integrated theoretical computation and in vivo morphological data highlights the role of the nanomorphology of astrocytes in signal transmission and its possible mechanisms related to pathological conditions.
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Affiliation(s)
- Langzhou Liu
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, China
- MoE Key Laboratory for Biomedical Photonics, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, China
| | - Huayi Gao
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, China
- MoE Key Laboratory for Biomedical Photonics, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, China
| | - Jinyu Li
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, China
- MoE Key Laboratory for Biomedical Photonics, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, China
| | - Shangbin Chen
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, China
- MoE Key Laboratory for Biomedical Photonics, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, China
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6
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Ackerman SD, Singhvi A, Bianchi L. Editorial: Accessory Cells of Sensory Systems and Their Functional Roles. Front Neurosci 2022; 16:965580. [PMID: 35844212 PMCID: PMC9281577 DOI: 10.3389/fnins.2022.965580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 06/17/2022] [Indexed: 11/17/2022] Open
Affiliation(s)
- Sarah D. Ackerman
- Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO, United States
| | - Aakanksha Singhvi
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA, United States
| | - Laura Bianchi
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL, United States
- *Correspondence: Laura Bianchi
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7
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Rapti G. Open Frontiers in Neural Cell Type Investigations; Lessons From Caenorhabditis elegans and Beyond, Toward a Multimodal Integration. Front Neurosci 2022; 15:787753. [PMID: 35321480 PMCID: PMC8934944 DOI: 10.3389/fnins.2021.787753] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/30/2021] [Indexed: 11/13/2022] Open
Abstract
Nervous system cells, the building blocks of circuits, have been studied with ever-progressing resolution, yet neural circuits appear still resistant to schemes of reductionist classification. Due to their sheer numbers, complexity and diversity, their systematic study requires concrete classifications that can serve reduced dimensionality, reproducibility, and information integration. Conventional hierarchical schemes transformed through the history of neuroscience by prioritizing criteria of morphology, (electro)physiological activity, molecular content, and circuit function, influenced by prevailing methodologies of the time. Since the molecular biology revolution and the recent advents in transcriptomics, molecular profiling gains ground toward the classification of neurons and glial cell types. Yet, transcriptomics entails technical challenges and more importantly uncovers unforeseen spatiotemporal heterogeneity, in complex and simpler nervous systems. Cells change states dynamically in space and time, in response to stimuli or throughout their developmental trajectory. Mapping cell type and state heterogeneity uncovers uncharted terrains in neurons and especially in glial cell biology, that remains understudied in many aspects. Examining neurons and glial cells from the perspectives of molecular neuroscience, physiology, development and evolution highlights the advantage of multifaceted classification schemes. Among the amalgam of models contributing to neuroscience research, Caenorhabditis elegans combines nervous system anatomy, lineage, connectivity and molecular content, all mapped at single-cell resolution, and can provide valuable insights for the workflow and challenges of the multimodal integration of cell type features. This review reflects on concepts and practices of neuron and glial cells classification and how research, in C. elegans and beyond, guides nervous system experimentation through integrated multidimensional schemes. It highlights underlying principles, emerging themes, and open frontiers in the study of nervous system development, regulatory logic and evolution. It proposes unified platforms to allow integrated annotation of large-scale datasets, gene-function studies, published or unpublished findings and community feedback. Neuroscience is moving fast toward interdisciplinary, high-throughput approaches for combined mapping of the morphology, physiology, connectivity, molecular function, and the integration of information in multifaceted schemes. A closer look in mapped neural circuits and understudied terrains offers insights for the best implementation of these approaches.
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8
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Konishi H, Koizumi S, Kiyama H. Phagocytic astrocytes: Emerging from the shadows of microglia. Glia 2022; 70:1009-1026. [PMID: 35142399 PMCID: PMC9305589 DOI: 10.1002/glia.24145] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 12/18/2021] [Accepted: 01/07/2022] [Indexed: 12/12/2022]
Abstract
Elimination of dead or live cells take place in both a healthy and diseased central nervous system (CNS). Dying or dead cells are quickly cleared by phagocytosis for the maintenance of a healthy CNS or for recovery after injury. Live cells or parts thereof, such as the synapses and myelin, are appropriately eliminated by phagocytosis to maintain or refine neural networks during development and adulthood. Microglia, the specific population of resident macrophages in the CNS, are classically considered as primary phagocytes; however, astrocytes have also been highlighted as phagocytes in the last decade. Phagocytic targets and receptors are reported to be mostly common between astrocytes and microglia, which raises the question of how astrocytic phagocytosis differs from microglial phagocytosis, and how these two phagocytic systems cooperate. In this review, we address the consequences of astrocytic phagocytosis, particularly focusing on these elusive points.
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Affiliation(s)
- Hiroyuki Konishi
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, University of Yamanashi, Yamanashi, Japan.,GLIA Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Hiroshi Kiyama
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya, Japan
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9
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Katz M. Genetic Methods for Cellular Manipulation in C. elegans. Methods Mol Biol 2022; 2468:51-72. [PMID: 35320560 DOI: 10.1007/978-1-0716-2181-3_4] [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: 06/14/2023]
Abstract
Neuron manipulation in vivo by ablation, activation or inactivation, and regulation of gene expression is essential for dissecting nervous system function. Here we describe genetic means for neuron manipulation in the nematode C. elegans, and provide protocols for generating transgenic animals containing these genetic tools.
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Affiliation(s)
- Menachem Katz
- Department of Biology, Technion- Israel Institute of Technology, Haifa, Israel.
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10
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Britz S, Markert SM, Witvliet D, Steyer AM, Tröger S, Mulcahy B, Kollmannsberger P, Schwab Y, Zhen M, Stigloher C. Structural Analysis of the Caenorhabditis elegans Dauer Larval Anterior Sensilla by Focused Ion Beam-Scanning Electron Microscopy. Front Neuroanat 2021; 15:732520. [PMID: 34819841 PMCID: PMC8607169 DOI: 10.3389/fnana.2021.732520] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/24/2021] [Indexed: 11/13/2022] Open
Abstract
At the end of the first larval stage, the nematode Caenorhabditis elegans developing in harsh environmental conditions is able to choose an alternative developmental path called the dauer diapause. Dauer larvae exhibit different physiology and behaviors from non-dauer larvae. Using focused ion beam-scanning electron microscopy (FIB-SEM), we volumetrically reconstructed the anterior sensory apparatus of C. elegans dauer larvae with unprecedented precision. We provide a detailed description of some neurons, focusing on structural details that were unknown or unresolved by previously published studies. They include the following: (1) dauer-specific branches of the IL2 sensory neurons project into the periphery of anterior sensilla and motor or putative sensory neurons at the sub-lateral cords; (2) ciliated endings of URX sensory neurons are supported by both ILso and AMso socket cells near the amphid openings; (3) variability in amphid sensory dendrites among dauers; and (4) somatic RIP interneurons maintain their projection into the pharyngeal nervous system. Our results support the notion that dauer larvae structurally expand their sensory system to facilitate searching for more favorable environments.
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Affiliation(s)
- Sebastian Britz
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
| | - Sebastian Matthias Markert
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
| | - Daniel Witvliet
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Molecular Genetics, Physiology and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Anna Maria Steyer
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Sarah Tröger
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Molecular Genetics, Physiology and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Philip Kollmannsberger
- Center for Computational and Theoretical Biology, Julius-Maximilians-University, Würzburg, Germany
| | - Yannick Schwab
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Molecular Genetics, Physiology and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Christian Stigloher
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
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11
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Rapti G. A perspective on C. elegans neurodevelopment: from early visionaries to a booming neuroscience research. J Neurogenet 2021; 34:259-272. [PMID: 33446023 DOI: 10.1080/01677063.2020.1837799] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The formation of the nervous system and its striking complexity is a remarkable feat of development. C. elegans served as a unique model to dissect the molecular events in neurodevelopment, from its early visionaries to the current booming neuroscience community. Soon after being introduced as a model, C. elegans was mapped at the level of genes, cells, and synapses, providing the first metazoan with a complete cell lineage, sequenced genome, and connectome. Here, I summarize mechanisms underlying C. elegans neurodevelopment, from the generation and diversification of neural components to their navigation and connectivity. I point out recent noteworthy findings in the fields of glia biology, sex dimorphism and plasticity in neurodevelopment, highlighting how current research connects back to the pioneering studies by Brenner, Sulston and colleagues. Multifaceted investigations in model organisms, connecting genes to cell function and behavior, expand our mechanistic understanding of neurodevelopment while allowing us to formulate emerging questions for future discoveries.
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Affiliation(s)
- Georgia Rapti
- European Molecular Biology Laboratory, Unit of Developmental Biology, Heidelberg, Germany
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12
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Aghayeva U, Bhattacharya A, Sural S, Jaeger E, Churgin M, Fang-Yen C, Hobert O. DAF-16/FoxO and DAF-12/VDR control cellular plasticity both cell-autonomously and via interorgan signaling. PLoS Biol 2021; 19:e3001204. [PMID: 33891586 PMCID: PMC8099054 DOI: 10.1371/journal.pbio.3001204] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 05/05/2021] [Accepted: 03/23/2021] [Indexed: 01/08/2023] Open
Abstract
Many cell types display the remarkable ability to alter their cellular phenotype in response to specific external or internal signals. Such phenotypic plasticity is apparent in the nematode Caenorhabditis elegans when adverse environmental conditions trigger entry into the dauer diapause stage. This entry is accompanied by structural, molecular, and functional remodeling of a number of distinct tissue types of the animal, including its nervous system. The transcription factor (TF) effectors of 3 different hormonal signaling systems, the insulin-responsive DAF-16/FoxO TF, the TGFβ-responsive DAF-3/SMAD TF, and the steroid nuclear hormone receptor, DAF-12/VDR, a homolog of the vitamin D receptor (VDR), were previously shown to be required for entering the dauer arrest stage, but their cellular and temporal focus of action for the underlying cellular remodeling processes remained incompletely understood. Through the generation of conditional alleles that allowed us to spatially and temporally control gene activity, we show here that all 3 TFs are not only required to initiate tissue remodeling upon entry into the dauer stage, as shown before, but are also continuously required to maintain the remodeled state. We show that DAF-3/SMAD is required in sensory neurons to promote and then maintain animal-wide tissue remodeling events. In contrast, DAF-16/FoxO or DAF-12/VDR act cell-autonomously to control anatomical, molecular, and behavioral remodeling events in specific cell types. Intriguingly, we also uncover non-cell autonomous function of DAF-16/FoxO and DAF-12/VDR in nervous system remodeling, indicating the presence of several insulin-dependent interorgan signaling axes. Our findings provide novel perspectives into how hormonal systems control tissue remodeling.
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Affiliation(s)
- Ulkar Aghayeva
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Abhishek Bhattacharya
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Surojit Sural
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Eliza Jaeger
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
| | - Matthew Churgin
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Christopher Fang-Yen
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, New York, United States of America
- * E-mail:
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13
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Raiders S, Black EC, Bae A, MacFarlane S, Klein M, Shaham S, Singhvi A. Glia actively sculpt sensory neurons by controlled phagocytosis to tune animal behavior. eLife 2021; 10:63532. [PMID: 33759761 PMCID: PMC8079151 DOI: 10.7554/elife.63532] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 03/23/2021] [Indexed: 02/07/2023] Open
Abstract
Glia in the central nervous system engulf neuron fragments to remodel synapses and recycle photoreceptor outer segments. Whether glia passively clear shed neuronal debris or actively prune neuron fragments is unknown. How pruning of single-neuron endings impacts animal behavior is also unclear. Here, we report our discovery of glia-directed neuron pruning in Caenorhabditis elegans. Adult C. elegans AMsh glia engulf sensory endings of the AFD thermosensory neuron by repurposing components of the conserved apoptotic corpse phagocytosis machinery. The phosphatidylserine (PS) flippase TAT-1/ATP8A functions with glial PS-receptor PSR-1/PSR and PAT-2/α-integrin to initiate engulfment. This activates glial CED-10/Rac1 GTPase through the ternary GEF complex of CED-2/CrkII, CED-5/DOCK180, CED-12/ELMO. Execution of phagocytosis uses the actin-remodeler WSP-1/nWASp. This process dynamically tracks AFD activity and is regulated by temperature, the AFD sensory input. Importantly, glial CED-10 levels regulate engulfment rates downstream of neuron activity, and engulfment-defective mutants exhibit altered AFD-ending shape and thermosensory behavior. Our findings reveal a molecular pathway underlying glia-dependent engulfment in a peripheral sense-organ and demonstrate that glia actively engulf neuron fragments, with profound consequences on neuron shape and animal sensory behavior. Neurons are tree-shaped cells that receive information through endings connected to neighbouring cells or the environment. Controlling the size, number and location of these endings is necessary to ensure that circuits of neurons get precisely the right amount of input from their surroundings. Glial cells form a large portion of the nervous system, and they are tasked with supporting, cleaning and protecting neurons. In humans, part of their duties is to ‘eat’ (or prune) unnecessary neuron endings. In fact, this role is so important that defects in glial pruning are associated with conditions such as Alzheimer’s disease. Yet it is still unknown how pruning takes place, and in particular whether it is the neuron or the glial cell that initiates the process. To investigate this question, Raiders et al. enlisted the common laboratory animal Caenorhabditis elegans, a tiny worm with a simple nervous system where each neuron has been meticulously mapped out. First, the experiments showed that glial cells in C. elegans actually prune the endings of sensory neurons. Focusing on a single glia-neuron pair then revealed that the glial cell could trim the endings of a living neuron by redeploying the same molecular machinery it uses to clear dead cell debris. Compared to this debris-clearing activity, however, the glial cell takes a more nuanced approach to pruning: specifically, it can adjust the amount of trimming based on the activity load of the neuron. When Raiders et al. disrupted the glial pruning for a single temperature-sensing neuron, the worm lost its normal temperature preferences; this demonstrated how the pruning activity of a single glial cell can be linked to behavior. Taken together the experiments showcase how C. elegans can be used to study glial pruning. Further work using this model could help to understand how disease emerges when glial cells cannot perform their role, and to spot the genetic factors that put certain individuals at increased risk for neurological and sensory disorders.
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Affiliation(s)
- Stephan Raiders
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.,Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, United States
| | - Erik Calvin Black
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Andrea Bae
- Laboratory of Developmental Genetics, The Rockefeller University, New York, United States.,Cellular Imaging Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Stephen MacFarlane
- Department of Physics and Department of Biology, University of Miami, Coral Gables, United States
| | - Mason Klein
- Department of Physics and Department of Biology, University of Miami, Coral Gables, United States
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, New York, United States
| | - Aakanksha Singhvi
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.,Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, United States.,Department of Biological Structure, University of Washington School of Medicine, Seattle, United States.,Brotman Baty Institute for Precision Medicine, Seattle, United States
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14
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Zhang A, Yan D. C. elegans as a model to study glial development. FEBS J 2021; 289:1476-1485. [PMID: 33570807 DOI: 10.1111/febs.15758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 01/08/2021] [Accepted: 02/09/2021] [Indexed: 12/19/2022]
Abstract
Glia make up roughly half of all cells in the mammalian nervous system and play a major part in nervous system development, function, and disease. Although research in the past few decades has shed light on their morphological and functional diversity, there is still much to be known about key aspects of their development such as the generation of glial diversity and the factors governing proper morphogenesis. Glia of the nematode C. elegans possess many developmental and morphological similarities with their vertebrate counterparts and can potentially be used as a model to understand certain aspects of glial biology owing to advantages such as its genetic tractability and fully mapped cell lineage. In this review, we summarize recent progress in our understanding of genetic pathways that regulate glial development in C. elegans and discuss how some of these findings may be conserved.
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Affiliation(s)
- Albert Zhang
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA.,Department of Neurobiology, Regeneration Next, and Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC, USA
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15
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Luth ES, Hodul M, Rennich BJ, Riccio C, Hofer J, Markoja K, Juo P. VER/VEGF receptors regulate AMPA receptor surface levels and glutamatergic behavior. PLoS Genet 2021; 17:e1009375. [PMID: 33561120 PMCID: PMC7899335 DOI: 10.1371/journal.pgen.1009375] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 02/22/2021] [Accepted: 01/22/2021] [Indexed: 01/09/2023] Open
Abstract
Several intracellular trafficking pathways contribute to the regulation of AMPA receptor (AMPAR) levels at synapses and the control of synaptic strength. While much has been learned about these intracellular trafficking pathways, a major challenge is to understand how extracellular factors, such as growth factors, neuropeptides and hormones, impinge on specific AMPAR trafficking pathways to alter synaptic function and behavior. Here, we identify the secreted ligand PVF-1 and its cognate VEGF receptor homologs, VER-1 and VER-4, as regulators of glutamate signaling in C. elegans. Loss of function mutations in ver-1, ver-4, or pvf-1, result in decreased cell surface levels of the AMPAR GLR-1 and defects in glutamatergic behavior. Rescue experiments indicate that PVF-1 is expressed and released from muscle, whereas the VERs function in GLR-1-expressing neurons to regulate surface levels of GLR-1 and glutamatergic behavior. Additionally, ver-4 is unable to rescue glutamatergic behavior in the absence of pvf-1, suggesting that VER function requires endogenous PVF-1. Inducible expression of a pvf-1 rescuing transgene suggests that PVF-1 can function in the mature nervous system to regulate GLR-1 signaling. Genetic double mutant analysis suggests that the VERs act together with the VPS-35/retromer recycling complex to promote cell surface levels of GLR-1. Our data support a genetic model whereby PVF-1/VER signaling acts with retromer to promote recycling and cell surface levels of GLR-1 to control behavior. Sensation, behavior, and cognition all depend on the proper function of neuronal connections called synapses. Synapses that use the neurotransmitter glutamate to signal between nerve cells are the most abundant type in our brain. Presynaptic neurons release glutamate, which activates glutamate receptors on postsynaptic neurons. Dysfunction of glutamate synapses leads to several neurological disorders, and changing their strength–in part by altering glutamate receptors numbers on the surface of the postsynaptic cell—provides the cellular basis of learning and memory. Much remains to be learned about how factors released from other cell types affects synaptic communication. We took advantage of light-activated molecular switches engineered into specific sensory neurons of C. elegans worms to trigger a behavioral reflex that depends on glutamate synapses. Using this behavior, we identified proteins called VER-1 and VER-4 as important for glutamate synapse function. We found that worms missing these VER proteins or their activator PVF-1 have reduced levels of glutamate receptors at the postsynaptic surface and defects in glutamate-dependent behaviors. Our results suggest that inter-tissue cross-talk between muscle PVF-1 and neuronal VERs is important for controlling the number of glutamate receptors at the cell surface, robust neuronal communication and behavioral responses.
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Affiliation(s)
- Eric S. Luth
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Department of Biology, Simmons University, Boston, Massachusetts, United States of America
| | - Molly Hodul
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Bethany J. Rennich
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Carmino Riccio
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Julia Hofer
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Kaitlin Markoja
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Peter Juo
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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16
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Bowles SN, Johnson CM. Inferences of glia-mediated control in Caenorhabditis elegans. J Neurosci Res 2021; 99:1191-1206. [PMID: 33559247 DOI: 10.1002/jnr.24803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 01/12/2021] [Indexed: 12/22/2022]
Abstract
Astrocytes modulate synaptic transmission; yet, it remains unclear how glia influence complex behaviors. Here, we explore the effects of Caenorhabditis elegans astrocyte-like cephalic glia (CEPglia ) and the glia-specific bHLH transcription factor HLH-17 on mating behavior and the defecation motor program (DMP). In C. elegans, male mating has been explicitly described through the male tail circuit and is characterized by coordination of multiple independent behaviors to ensure that copulation is achieved. Furthermore, the sex-specific male mating circuitry shares similar components with the DMP, which is complex and rhythmic, and requires a fixed sequence of behaviors to be activated periodically. We found that loss of CEPglia reduced persistence in executing mating behaviors and hindered copulation, while males that lacked HLH-17 demonstrated repetitive prodding behavior that increased the time spent in mating but did not hinder copulation. During the DMP, we found that posterior body wall contractions (pBocs) and enteric muscle contractions (EMCs) were differentially affected by loss of HLH-17 or CEPglia in males and hermaphrodites. pBocs and EMCs required HLH-17 activity in both sexes, whereas loss of CEPglia alone did not affect DMP in males. Our data suggest that CEPglia mediate complex behaviors by signaling to the GABAergic DVB neuron, and that HLH-17 activity influences those discrete steps within those behaviors. Collectively, these data provide evidence of glia as a link in cooperative regulation of complex and rhythmic behavior that, in C. elegans links circuitry in the head and the tail.
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Affiliation(s)
| | - Casonya M Johnson
- Department of Biology, Georgia State University, Atlanta, GA, USA.,Department of Biology, James Madison University, Harrisonburg, VA, USA
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17
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Abstract
During multicellular organism development, complex structures are sculpted to form organs and tissues, which are maintained throughout adulthood. Many of these processes require cells to fuse with one another, or with themselves. These plasma membrane fusions merge endoplasmic cellular content across external, exoplasmic, space. In the nematode Caenorhabditis elegans, such cell fusions serve as a unique sculpting force, involved in the embryonic morphogenesis of the skin-like multinuclear hypodermal cells, but also in refining delicate structures, such as valve openings and the tip of the tail. During post-embryonic development, plasma membrane fusions continue to shape complex neuron structures and organs such as the vulva, while during adulthood fusion participates in cell and tissue repair. These processes rely on two fusion proteins (fusogens): EFF-1 and AFF-1, which are part of a broader family of structurally related membrane fusion proteins, encompassing sexual reproduction, viral infection, and tissue remodeling. The established capabilities of these exoplasmic fusogens are further expanded by new findings involving EFF-1 and AFF-1 in endocytic vesicle fission and phagosome sealing. Tight regulation by cell-autonomous and non-cell autonomous mechanisms orchestrates these diverse cell fusions at the correct place and time-these processes and their significance are discussed in this review.
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18
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Lee IH, Procko C, Lu Y, Shaham S. Stress-Induced Neural Plasticity Mediated by Glial GPCR REMO-1 Promotes C. elegans Adaptive Behavior. Cell Rep 2021; 34:108607. [PMID: 33440160 PMCID: PMC7845533 DOI: 10.1016/j.celrep.2020.108607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/30/2020] [Accepted: 12/15/2020] [Indexed: 01/03/2023] Open
Abstract
Animal nervous systems remodel following stress. Although global stress-dependent changes are well documented, contributions of individual neuron remodeling events to animal behavior modification are challenging to study. In response to environmental insults, C. elegans become stress-resistant dauers. Dauer entry induces amphid sensory organ remodeling in which bilateral AMsh glial cells expand and fuse, allowing embedded AWC chemosensory neurons to extend sensory receptive endings. We show that amphid remodeling correlates with accelerated dauer exit upon exposure to favorable conditions and identify a G protein-coupled receptor, REMO-1, driving AMsh glia fusion, AWC neuron remodeling, and dauer exit. REMO-1 is expressed in and localizes to AMsh glia tips, is dispensable for other remodeling events, and promotes stress-induced expression of the remodeling receptor tyrosine kinase VER-1. Our results demonstrate how single-neuron structural changes affect animal behavior, identify key glial roles in stress-induced nervous system plasticity, and demonstrate that remodeling primes animals to respond to favorable conditions.
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Affiliation(s)
- In Hae Lee
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Carl Procko
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Yun Lu
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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19
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Nagai J, Yu X, Papouin T, Cheong E, Freeman MR, Monk KR, Hastings MH, Haydon PG, Rowitch D, Shaham S, Khakh BS. Behaviorally consequential astrocytic regulation of neural circuits. Neuron 2020; 109:576-596. [PMID: 33385325 DOI: 10.1016/j.neuron.2020.12.008] [Citation(s) in RCA: 122] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/23/2020] [Accepted: 12/07/2020] [Indexed: 12/16/2022]
Abstract
Astrocytes are a large and diverse population of morphologically complex cells that exist throughout nervous systems of multiple species. Progress over the last two decades has shown that astrocytes mediate developmental, physiological, and pathological processes. However, a long-standing open question is how astrocytes regulate neural circuits in ways that are behaviorally consequential. In this regard, we summarize recent studies using Caenorhabditis elegans, Drosophila melanogaster, Danio rerio, and Mus musculus. The data reveal diverse astrocyte mechanisms operating in seconds or much longer timescales within neural circuits and shaping multiple behavioral outputs. We also refer to human diseases that have a known primary astrocytic basis. We suggest that including astrocytes in mechanistic, theoretical, and computational studies of neural circuits provides new perspectives to understand behavior, its regulation, and its disease-related manifestations.
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Affiliation(s)
- Jun Nagai
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; RIKEN Center for Brain Science, 2-1 Hirosawa Wako City, Saitama 351-0198, Japan
| | - Xinzhu Yu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, 514 Burrill Hall, 407 S. Goodwin Ave, Urbana, IL 61801, USA
| | - Thomas Papouin
- Department of Neuroscience, Washington University in St. Louis, School of Medicine, Campus Box 8108, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Eunji Cheong
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Marc R Freeman
- The Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Kelly R Monk
- The Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Michael H Hastings
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Philip G Haydon
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - David Rowitch
- Department of Paediatrics, Wellcome-MRC Cambridge Stem Cell Institute, University of Cambridge, Cambridge, UK; Departments of Pediatrics and Neurosurgery, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
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20
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Duan D, Zhang H, Yue X, Fan Y, Xue Y, Shao J, Ding G, Chen D, Li S, Cheng H, Zhang X, Zou W, Liu J, Zhao J, Wang L, Zhao B, Wang Z, Xu S, Wen Q, Liu J, Duan S, Kang L. Sensory Glia Detect Repulsive Odorants and Drive Olfactory Adaptation. Neuron 2020; 108:707-721.e8. [PMID: 32970991 DOI: 10.1016/j.neuron.2020.08.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 07/25/2020] [Accepted: 08/26/2020] [Indexed: 12/18/2022]
Abstract
Glia are typically considered as supporting cells for neural development and synaptic transmission. Here, we report an active role of a glia in olfactory transduction. As a polymodal sensory neuron in C. elegans, the ASH neuron is previously known to detect multiple aversive odorants. We reveal that the AMsh glia, a sheath for multiple sensory neurons including ASH, cell-autonomously respond to aversive odorants via G-protein-coupled receptors (GPCRs) distinct from those in ASH. Upon activation, the AMsh glia suppress aversive odorant-triggered avoidance and promote olfactory adaptation by inhibiting the ASH neuron via GABA signaling. Thus, we propose a novel two-receptor model where the glia and sensory neuron jointly mediate adaptive olfaction. Our study reveals a non-canonical function of glial cells in olfactory transduction, which may provide new insights into the glia-like supporting cells in mammalian sensory procession.
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Affiliation(s)
- Duo Duan
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310053, China; Department of Neurology of Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Hu Zhang
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310053, China
| | - Xiaomin Yue
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310053, China
| | - Yuedan Fan
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310053, China
| | - Yadan Xue
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Jiajie Shao
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Gang Ding
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Du Chen
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Shitian Li
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Hankui Cheng
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Xiaoyan Zhang
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Wenjuan Zou
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Jia Liu
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Jian Zhao
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Linmei Wang
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Bingzhen Zhao
- Chinese Academy of Sciences Key Laboratory of Brain Function and Disease, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhiping Wang
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China
| | - Suhong Xu
- Center for Stem Cell and Regenerative Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Quan Wen
- Chinese Academy of Sciences Key Laboratory of Brain Function and Disease, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jie Liu
- Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC 3800, Australia
| | - Shumin Duan
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310053, China; Department of Neurology of Second Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China.
| | - Lijun Kang
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang 310053, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310053, China.
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21
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Kazatskaya A, Yuan L, Amin-Wetzel N, Philbrook A, de Bono M, Sengupta P. The URX oxygen-sensing neurons in C. elegans are ciliated. MICROPUBLICATION BIOLOGY 2020; 2020:10.17912/micropub.biology.000303. [PMID: 33005885 PMCID: PMC7520127 DOI: 10.17912/micropub.biology.000303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/08/2020] [Accepted: 09/09/2020] [Indexed: 12/21/2022]
Affiliation(s)
| | - Lisa Yuan
- Brandeis University, Waltham, MA 02454
| | - Niko Amin-Wetzel
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | | | - Mario de Bono
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
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22
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Alicea B. Raising the Connectome: The Emergence of Neuronal Activity and Behavior in Caenorhabditis elegans. Front Cell Neurosci 2020; 14:524791. [PMID: 33100971 PMCID: PMC7522492 DOI: 10.3389/fncel.2020.524791] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 08/24/2020] [Indexed: 11/15/2022] Open
Abstract
The differentiation of neurons and formation of connections between cells is the basis of both the adult phenotype and behaviors tied to cognition, perception, reproduction, and survival. Such behaviors are associated with local (circuits) and global (connectome) brain networks. A solid understanding of how these networks emerge is critical. This opinion piece features a guided tour of early developmental events in the emerging connectome, which is crucial to a new view on the connectogenetic process. Connectogenesis includes associating cell identities with broader functional and developmental relationships. During this process, the transition from developmental cells to terminally differentiated cells is defined by an accumulation of traits that ultimately results in neuronal-driven behavior. The well-characterized developmental and cell biology of Caenorhabditis elegans will be used to build a synthesis of developmental events that result in a functioning connectome. Specifically, our view of connectogenesis enables a first-mover model of synaptic connectivity to be demonstrated using data representing larval synaptogenesis. In a first-mover model of Stackelberg competition, potential pre- and postsynaptic relationships are shown to yield various strategies for establishing various types of synaptic connections. By comparing these results to what is known regarding principles for establishing complex network connectivity, these strategies are generalizable to other species and developmental systems. In conclusion, we will discuss the broader implications of this approach, as what is presented here informs an understanding of behavioral emergence and the ability to simulate related biological phenomena.
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Affiliation(s)
- Bradly Alicea
- Orthogonal Research and Education Laboratory, Champaign, IL, United States
- OpenWorm Foundation, Boston, MA, United States
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23
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Fusogen-mediated neuron-neuron fusion disrupts neural circuit connectivity and alters animal behavior. Proc Natl Acad Sci U S A 2020; 117:23054-23065. [PMID: 32855296 PMCID: PMC7502713 DOI: 10.1073/pnas.1919063117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Ramón y Cajal’s neuron doctrine, which states that neurons are individual cells that do not share any membrane or cytoplasmic continuity between them, has underpinned our view of modern neuroscience. However, there is considerable evidence that fusogens, specialized proteins essential and sufficient for the fusion of cells in other tissues, are expressed in the nervous system of several species in response to viral infection, stress conditions, and neurological disease. By manipulating the expression of fusogens in the chemosensory neurons of Caenorhabditis elegans, our results provide conclusive evidence that deregulation of fusogen expression causes neuronal fusion and can have deleterious effects on neural circuitry and behavioral outputs, revealing a possible novel underlying cause of neurological disorders. The 100-y-old neuron doctrine from Ramón y Cajal states that neurons are individual cells, rejecting the process of cell−cell fusion in the normal development and function of the nervous system. However, fusogens—specialized molecules essential and sufficient for the fusion of cells—are expressed in the nervous system of different species under conditions of viral infection, stress, or disease. Despite these findings, whether the expression of fusogens in neurons leads to cell−cell fusion, and, if so, whether this affects neuronal fate, function, and animal behavior, has not been explored. Here, using Caenorhabditis elegans chemosensory neurons as a model system, we provide proof-of-principle that aberrant expression of fusogens in neurons results in neuron−neuron fusion and behavioral impairments. We demonstrate that fusion between chemoattractive neurons does not affect the response to odorants, whereas fusion between chemoattractive and chemorepulsive neurons compromises chemosensation. Moreover, we provide evidence that fused neurons are viable and retain their original specific neuronal fate markers. Finally, analysis of calcium transients reveals that fused neurons become electrically coupled, thereby compromising neural circuit connectivity. Thus, we propose that aberrant expression of fusogens in the nervous system disrupts neuronal individuality, which, in turn, leads to a change in neural circuit connectivity and disruption of normal behavior. Our results expose a previously uncharacterized basis of circuit malfunction, and a possible underlying cause of neurological diseases.
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24
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Androwski RJ, Asad N, Wood JG, Hofer A, Locke S, Smith CM, Rose B, Schroeder NE. Mutually exclusive dendritic arbors in C. elegans neurons share a common architecture and convergent molecular cues. PLoS Genet 2020; 16:e1009029. [PMID: 32997655 PMCID: PMC7549815 DOI: 10.1371/journal.pgen.1009029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 10/12/2020] [Accepted: 08/05/2020] [Indexed: 12/31/2022] Open
Abstract
Stress-induced changes to the dendritic architecture of neurons have been demonstrated in numerous mammalian and invertebrate systems. Remodeling of dendrites varies tremendously among neuron types. During the stress-induced dauer stage of Caenorhabditis elegans, the IL2 neurons arborize to cover the anterior body wall. In contrast, the FLP neurons arborize to cover an identical receptive field during reproductive development. Using time-course imaging, we show that branching between these two neuron types is highly coordinated. Furthermore, we find that the IL2 and FLP arbors have a similar dendritic architecture and use an identical downstream effector complex to control branching; however, regulation of this complex differs between stress-induced IL2 branching and FLP branching during reproductive development. We demonstrate that the unfolded protein response (UPR) sensor IRE-1, required for localization of the complex in FLP branching, is dispensable for IL2 branching at standard cultivation temperatures. Exposure of ire-1 mutants to elevated temperatures results in defective IL2 branching, thereby demonstrating a previously unknown genotype by environment interaction within the UPR. We find that the FOXO homolog, DAF-16, is required cell-autonomously to control arborization during stress-induced arborization. Likewise, several aspects of the dauer formation pathway are necessary for the neuron to remodel, including the phosphatase PTEN/DAF-18 and Cytochrome P450/DAF-9. Finally, we find that the TOR associated protein, RAPTOR/DAF-15 regulates mutually exclusive branching of the IL2 and FLP dendrites. DAF-15 promotes IL2 branching during dauer and inhibits precocious FLP growth. Together, our results shed light on molecular processes that regulate stress-mediated remodeling of dendrites across neuron classes.
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Affiliation(s)
- Rebecca J. Androwski
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Nadeem Asad
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Janet G. Wood
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Allison Hofer
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Steven Locke
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Cassandra M. Smith
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Becky Rose
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Nathan E. Schroeder
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
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Fung W, Wexler L, Heiman MG. Cell-type-specific promoters for C. elegans glia. J Neurogenet 2020; 34:335-346. [PMID: 32696701 PMCID: PMC7855602 DOI: 10.1080/01677063.2020.1781851] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 06/08/2020] [Indexed: 12/26/2022]
Abstract
Glia shape the development and function of the C. elegans nervous system, especially its sense organs and central neuropil (nerve ring). Cell-type-specific promoters allow investigators to label or manipulate individual glial cell types, and therefore provide a key tool for deciphering glial function. In this technical resource, we compare the specificity, brightness, and consistency of cell-type-specific promoters for C. elegans glia. We identify a set of promoters for the study of seven glial cell types (F16F9.3, amphid and phasmid sheath glia; F11C7.2, amphid sheath glia only; grl-2, amphid and phasmid socket glia; hlh-17, cephalic (CEP) sheath glia; and grl-18, inner labial (IL) socket glia) as well as a pan-glial promoter (mir-228). We compare these promoters to promoters that are expressed more variably in combinations of glial cell types (delm-1 and itx-1). We note that the expression of some promoters depends on external conditions or the internal state of the organism, such as developmental stage, suggesting glial plasticity. Finally, we demonstrate an approach for prospectively identifying cell-type-specific glial promoters using existing single-cell sequencing data, and we use this approach to identify two novel promoters specific to IL socket glia (col-53 and col-177).
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Affiliation(s)
- Wendy Fung
- These authors contributed equally to this work
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children’s Hospital, Boston MA 02115
| | - Leigh Wexler
- These authors contributed equally to this work
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children’s Hospital, Boston MA 02115
| | - Maxwell G. Heiman
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children’s Hospital, Boston MA 02115
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Johnson CK, Fernandez-Abascal J, Wang Y, Wang L, Bianchi L. The Na +-K +-ATPase is needed in glia of touch receptors for responses to touch in C. elegans. J Neurophysiol 2020; 123:2064-2074. [PMID: 32292107 DOI: 10.1152/jn.00636.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Four of the five types of mammalian mechanosensors are composed of nerve endings and accessory cells. In Caenorhabditis elegans we showed that glia support the function of nose touch neurons via the activity of glial Na+ and K+ channels. We show here that a third regulator of Na+ and K+, the Na+-K+-ATPase, is needed in glia of nose touch neurons for touch. Importantly, we show that two Na+-K+-ATPase genes are needed for the function rather than structural integrity and that their ion transport activity is crucial for touch. Finally, when glial Na+-K+-ATPase genes are knocked out, touch can be restored by activation of a third Na+-K+-ATPase. Taken together, these data show the requirement in glia of touch neurons of the function of the Na+-K+-ATPase. These data underscore the importance of the homeostasis of Na+ and K+, most likely in the space surrounding touch neurons, in touch sensation, a function that might be conserved across species.NEW & NOTEWORTHY Increasing evidence supports that accessory cells in mechanosensors regulate neuronal output; however, the glial molecular mechanisms that control this regulation are not fully understood. We show here in Caenorhabditis elegans that specific glial Na+-K+-ATPase genes are needed for nose touch-avoidance behavior. Our data support the requirement of these Na+-K+-ATPases for homeostasis of Na+ and K+ in nose touch receptors. Our data add to our understanding of glial regulation of mechanosensors.
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Affiliation(s)
- Christina K Johnson
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida
| | - Jesus Fernandez-Abascal
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida
| | - Ying Wang
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida
| | - Lei Wang
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida
| | - Laura Bianchi
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida
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27
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Long-term activity drives dendritic branch elaboration of a C. elegans sensory neuron. Dev Biol 2020; 461:66-74. [PMID: 31945343 PMCID: PMC7170766 DOI: 10.1016/j.ydbio.2020.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 01/07/2020] [Accepted: 01/08/2020] [Indexed: 12/13/2022]
Abstract
Neuronal activity often leads to alterations in gene expression and cellular architecture. The nematode Caenorhabditis elegans, owing to its compact translucent nervous system, is a powerful system in which to study conserved aspects of the development and plasticity of neuronal morphology. Here we focus on one pair of sensory neurons, termed URX, which the worm uses to sense and avoid high levels of environmental oxygen. Previous studies have reported that the URX neuron pair has variable branched endings at its dendritic sensory tip. By controlling oxygen levels and analyzing mutants, we found that these microtubule-rich branched endings grow over time as a consequence of neuronal activity in adulthood. We also find that the growth of these branches correlates with an increase in cellular sensitivity to particular ranges of oxygen that is observable in the behavior of older worms. Given the strengths of C. elegans as a model organism, URX may serve as a potent system for uncovering genes and mechanisms involved in activity-dependent morphological changes in neurons and possible adaptive changes in the aging nervous system. The dendritic tip of an oxygen-sensing neuron grows elaborate microtubule-rich processes in adult C. elegans. Dendritic tip elaboration depends on the long-term activity of the neuron and calcium. The elaboration correlates with increased sensitivity of the neuron to certain ranges of oxygen as well as higher avoidance of oxygen during bordering behavior. The dendritic tip changes may reflect adaptive changes in physiology and behavior during adulthood.
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28
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Machado-Santos AR, Alves ND, Araújo B, Correia JS, Patrício P, Mateus-Pinheiro A, Loureiro-Campos E, Bessa JM, Sousa N, Pinto L. Astrocytic plasticity at the dorsal dentate gyrus on an animal model of recurrent depression. Neuroscience 2019; 454:94-104. [PMID: 31747562 DOI: 10.1016/j.neuroscience.2019.10.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 10/15/2019] [Accepted: 10/16/2019] [Indexed: 10/25/2022]
Abstract
Astrocytes are now known to play crucial roles in the central nervous system, supporting and closely interacting with neurons and therefore able to modulate brain function. Both human postmortem studies in brain samples from patients diagnosed with Major Depressive Disorder and from animal models of depression reported numerical and morphological astrocytic changes specifically in the hippocampus. In particular, these studies revealed significant reductions in glial cell density denoted by a decreased number of S100B-positive cells and a decrease in GFAP expression in several brain regions including the hippocampus. To reveal plastic astrocytic changes in the context of recurrent depression, we longitudinally assessed dynamic astrocytic alterations (gene expression, cell densities and morphologic variations) in the hippocampal dentate gyrus under repeated exposure to unpredictable chronic mild stress (uCMS) and upon treatment with two antidepressants, fluoxetine and imipramine. Both antidepressants decreased astrocytic complexity immediately after stress exposure. Moreover, we show that astrocytic alterations, particularly an increased number of S100B-positive cells, are observed after recurrent stress exposure. Interestingly, these alterations were prevented at the long-term by either fluoxetine or imipramine treatment.
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Affiliation(s)
- Ana R Machado-Santos
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Nuno D Alves
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Bruna Araújo
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Joana S Correia
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Patrícia Patrício
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - António Mateus-Pinheiro
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Eduardo Loureiro-Campos
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - João M Bessa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Luísa Pinto
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
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29
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Hong RL, Riebesell M, Bumbarger DJ, Cook SJ, Carstensen HR, Sarpolaki T, Cochella L, Castrejon J, Moreno E, Sieriebriennikov B, Hobert O, Sommer RJ. Evolution of neuronal anatomy and circuitry in two highly divergent nematode species. eLife 2019; 8:47155. [PMID: 31526477 PMCID: PMC6748829 DOI: 10.7554/elife.47155] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 08/12/2019] [Indexed: 11/17/2022] Open
Abstract
The nematodes C. elegans and P. pacificus populate diverse habitats and display distinct patterns of behavior. To understand how their nervous systems have diverged, we undertook a detailed examination of the neuroanatomy of the chemosensory system of P. pacificus. Using independent features such as cell body position, axon projections and lipophilic dye uptake, we have assigned homologies between the amphid neurons, their first-layer interneurons, and several internal receptor neurons of P. pacificus and C. elegans. We found that neuronal number and soma position are highly conserved. However, the morphological elaborations of several amphid cilia are different between them, most notably in the absence of ‘winged’ cilia morphology in P. pacificus. We established a synaptic wiring diagram of amphid sensory neurons and amphid interneurons in P. pacificus and found striking patterns of conservation and divergence in connectivity relative to C. elegans, but very little changes in relative neighborhood of neuronal processes. These findings demonstrate the existence of several constraints in patterning the nervous system and suggest that major substrates for evolutionary novelty lie in the alterations of dendritic structures and synaptic connectivity. Nerve cells, also called neurons, are responsible both for sensing signals from the environment and for determining how organisms react. This means that the unique features of an animal’s nervous system underpin its characteristic behaviors. Comparing the anatomy of the nervous systems in different animals could therefore yield valuable insights into how structural and behavioral differences emerge over time. Behavioral variation often occurs even in similar-looking animals. One example is a group of microscopic worms, called nematodes. Although many nematode species exist, their overall body plans are the same, and the worms of each species contain a fixed number of cells. Despite these apparent similarities, different species of nematodes inhabit a variety of environments and may respond differently to the same signals. The main sensory organs in nematodes are called the amphid sensilla. They are used to detect chemicals, as well as other inputs from the environment such as temperature and pheromones from other nematodes. Although researchers have often speculated that the number of cells in these organs and their arrangement are broadly the same across species, their anatomy had not been studied in detail. Hong, Riebesell et al. compared the detailed structure and genetic features of the sensory systems in two distantly related species of nematode worms, Pristionchus pacificus and Caenorhabditis elegans. These two species behave in different ways, for example, P. pacificus is usually found in association with different species of beetles, while C. elegans is free-living and usually found on rotting fruit. By comparing the two, Hong, Riebesell et al. wanted to determine whether the diverse behaviors observed in the two species could be determined by differences between their sensory systems. Experiments using electron microscopy yielded several thousand high resolution images spanning the entire sensory organ. These images were then used to create detailed reconstructions of the sensory nervous system in each worm species, demonstrating that both species had the same number of sensory nerve cells, allowing one-to-one comparisons between them. Further analysis showed that while the overall structure of the neuronal connections remains the same between the two species, the neurons in P. pacificus made more diverse connections than those in C. elegans. Detailed studies of gene activity also revealed that neurons in each species switched on a slightly different group of genes, possibly indicating that each type of worm processes sensory signals in different ways. These results shed new light on how nervous systems in related species can change over time without any change in neuron count. In the future, a better understanding of these changes could link the evolution of the nervous system to the emergence of different behaviors, in both simple and more complex organisms.
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Affiliation(s)
- Ray L Hong
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany.,Department of Biology, California State University, Northridge, Northridge, United States
| | - Metta Riebesell
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Daniel J Bumbarger
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Steven J Cook
- Department of Biological Sciences, Columbia University, New York, United States
| | - Heather R Carstensen
- Department of Biology, California State University, Northridge, Northridge, United States
| | - Tahmineh Sarpolaki
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Luisa Cochella
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jessica Castrejon
- Department of Biology, California State University, Northridge, Northridge, United States
| | - Eduardo Moreno
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Bogdan Sieriebriennikov
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, New York, United States.,Howard Hughes Medical Institute, Chevy Chase, United States
| | - Ralf J Sommer
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
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30
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How Caenorhabditis elegans Senses Mechanical Stress, Temperature, and Other Physical Stimuli. Genetics 2019; 212:25-51. [PMID: 31053616 PMCID: PMC6499529 DOI: 10.1534/genetics.118.300241] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/04/2019] [Indexed: 12/30/2022] Open
Abstract
Caenorhabditis elegans lives in a complex habitat in which they routinely experience large fluctuations in temperature, and encounter physical obstacles that vary in size and composition. Their habitat is shared by other nematodes, by beneficial and harmful bacteria, and nematode-trapping fungi. Not surprisingly, these nematodes can detect and discriminate among diverse environmental cues, and exhibit sensory-evoked behaviors that are readily quantifiable in the laboratory at high resolution. Their ability to perform these behaviors depends on <100 sensory neurons, and this compact sensory nervous system together with powerful molecular genetic tools has allowed individual neuron types to be linked to specific sensory responses. Here, we describe the sensory neurons and molecules that enable C. elegans to sense and respond to physical stimuli. We focus primarily on the pathways that allow sensation of mechanical and thermal stimuli, and briefly consider this animal’s ability to sense magnetic and electrical fields, light, and relative humidity. As the study of sensory transduction is critically dependent upon the techniques for stimulus delivery, we also include a section on appropriate laboratory methods for such studies. This chapter summarizes current knowledge about the sensitivity and response dynamics of individual classes of C. elegans mechano- and thermosensory neurons from in vivo calcium imaging and whole-cell patch-clamp electrophysiology studies. We also describe the roles of conserved molecules and signaling pathways in mediating the remarkably sensitive responses of these nematodes to mechanical and thermal cues. These studies have shown that the protein partners that form mechanotransduction channels are drawn from multiple superfamilies of ion channel proteins, and that signal transduction pathways responsible for temperature sensing in C. elegans share many features with those responsible for phototransduction in vertebrates.
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31
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Environmental Programming of Adult Foraging Behavior in C. elegans. Curr Biol 2019; 29:2867-2879.e4. [PMID: 31422888 DOI: 10.1016/j.cub.2019.07.045] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 05/26/2019] [Accepted: 07/12/2019] [Indexed: 11/22/2022]
Abstract
Foraging strategies should be tuned to the expected distribution of resources in the environment. Tuning can occur over generations and lead to genetic differences in innate foraging behavior or over shorter timescales within an individual's lifespan. Both genetically encoded and experience-based strategies are implemented by neural circuits that respond to environmental cues and track internal states. Caenorhabditis elegans exhibit both between-strain genetic differences and within-strain plasticity in foraging. In individuals, changes in foraging are usually short term and based on recent experience. Here, we tested whether developmental experience could permanently alter foraging. We found that, in most wild strains, early-life starvation led to "cautious" foraging strategies, in which exploration is reduced, and these behavioral changes are associated with altered dynamics in a locomotory circuit. Possessing either the derived (domestication-associated) or ancestral allele of the neuroglobin glb-5 determines foraging plasticity. Overall, we show that C. elegans exhibit adaptive developmental plasticity that affects multiple aspects of foraging behavior and leads to changes in a core navigation circuit and that innate foraging traits and plasticity in those traits are genetically separable. VIDEO ABSTRACT.
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32
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Low IIC, Williams CR, Chong MK, McLachlan IG, Wierbowski BM, Kolotuev I, Heiman MG. Morphogenesis of neurons and glia within an epithelium. Development 2019; 146:dev171124. [PMID: 30683663 PMCID: PMC6398450 DOI: 10.1242/dev.171124] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Accepted: 01/15/2019] [Indexed: 12/13/2022]
Abstract
To sense the outside world, some neurons protrude across epithelia, the cellular barriers that line every surface of our bodies. To study the morphogenesis of such neurons, we examined the C. elegans amphid, in which dendrites protrude through a glial channel at the nose. During development, amphid dendrites extend by attaching to the nose via DYF-7, a type of protein typically found in epithelial apical ECM. Here, we show that amphid neurons and glia exhibit epithelial properties, including tight junctions and apical-basal polarity, and develop in a manner resembling other epithelia. We find that DYF-7 is a fibril-forming apical ECM component that promotes formation of the tube-shaped glial channel, reminiscent of roles for apical ECM in other narrow epithelial tubes. We also identify a requirement for FRM-2, a homolog of EPBL15/moe/Yurt that promotes epithelial integrity in other systems. Finally, we show that other environmentally exposed neurons share a requirement for DYF-7. Together, our results suggest that these neurons and glia can be viewed as part of an epithelium continuous with the skin, and are shaped by mechanisms shared with other epithelia.
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Affiliation(s)
- Isabel I C Low
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Claire R Williams
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Megan K Chong
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Ian G McLachlan
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Bradley M Wierbowski
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Irina Kolotuev
- Université de Rennes 1, Plateforme microscopie électronique, 35043 Rennes, France
| | - Maxwell G Heiman
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
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33
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Schiweck J, Eickholt BJ, Murk K. Important Shapeshifter: Mechanisms Allowing Astrocytes to Respond to the Changing Nervous System During Development, Injury and Disease. Front Cell Neurosci 2018; 12:261. [PMID: 30186118 PMCID: PMC6111612 DOI: 10.3389/fncel.2018.00261] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/31/2018] [Indexed: 12/30/2022] Open
Abstract
Astrocytes are the most prevalent glial cells in the brain. Historically considered as “merely supporting” neurons, recent research has shown that astrocytes actively participate in a large variety of central nervous system (CNS) functions including synaptogenesis, neuronal transmission and synaptic plasticity. During disease and injury, astrocytes efficiently protect neurons by various means, notably by sealing them off from neurotoxic factors and repairing the blood-brain barrier. Their ramified morphology allows them to perform diverse tasks by interacting with synapses, blood vessels and other glial cells. In this review article, we provide an overview of how astrocytes acquire their complex morphology during development. We then move from the developing to the mature brain, and review current research on perisynaptic astrocytic processes, with a particular focus on how astrocytes engage synapses and modulate their formation and activity. Comprehensive changes have been reported in astrocyte cell shape in many CNS pathologies. Factors influencing these morphological changes are summarized in the context of brain pathologies, such as traumatic injury and degenerative conditions. We provide insight into the molecular, cellular and cytoskeletal machinery behind these shape changes which drive the dynamic remodeling in astrocyte morphology during injury and the development of pathologies.
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Affiliation(s)
- Juliane Schiweck
- Institute for Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Britta J Eickholt
- Institute for Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Kai Murk
- Institute for Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
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34
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Nichols EL, Green LA, Smith CJ. Ensheathing cells utilize dynamic tiling of neuronal somas in development and injury as early as neuronal differentiation. Neural Dev 2018; 13:19. [PMID: 30121077 PMCID: PMC6098834 DOI: 10.1186/s13064-018-0115-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 07/27/2018] [Indexed: 12/18/2022] Open
Abstract
Background Glial cell ensheathment of specific components of neuronal circuits is essential for nervous system function. Although ensheathment of axonal segments of differentiated neurons has been investigated, ensheathment of neuronal cell somas, especially during early development when neurons are extending processes and progenitor populations are expanding, is still largely unknown. Methods To address this, we used time-lapse imaging in zebrafish during the initial formation of the dorsal root ganglia (DRG). Results Our results show that DRG neurons are ensheathed throughout their entire lifespan by a progenitor population. These ensheathing cells dynamically remodel during development to ensure axons can extend away from the neuronal cell soma into the CNS and out to the skin. As a population, ensheathing cells tile each DRG neuron to ensure neurons are tightly encased. In development and in experimental cell ablation paradigms, the oval shape of DRG neurons dynamically changes during partial unensheathment. During longer extended unensheathment neuronal soma shifting is observed. We further show the intimate relationship of these ensheathing cells with the neurons leads to immediate and choreographed responses to distal axonal damage to the neuron. Conclusion We propose that the ensheathing cells dynamically contribute to the shape and position of neurons in the DRG by their remodeling activity during development and are primed to dynamically respond to injury of the neuron. Electronic supplementary material The online version of this article (10.1186/s13064-018-0115-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Evan L Nichols
- Department of Biological Sciences, University of Notre Dame, 015 Galvin Life Sciences Building, Notre Dame, IN, 46556, USA
| | - Lauren A Green
- Department of Biological Sciences, University of Notre Dame, 015 Galvin Life Sciences Building, Notre Dame, IN, 46556, USA.,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA
| | - Cody J Smith
- Department of Biological Sciences, University of Notre Dame, 015 Galvin Life Sciences Building, Notre Dame, IN, 46556, USA. .,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA.
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35
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Early Maternal Deprivation Induces Microglial Activation, Alters Glial Fibrillary Acidic Protein Immunoreactivity and Indoleamine 2,3-Dioxygenase during the Development of Offspring Rats. Mol Neurobiol 2018; 56:1096-1108. [PMID: 29873040 DOI: 10.1007/s12035-018-1161-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 05/29/2018] [Indexed: 02/07/2023]
Abstract
Maternal deprivation (MD) induces behavioral changes and impacts brain circuits that could be associated with the pathophysiology of depression. This study investigated the markers of microglia and astrocyte activation as well as indoleamine 2,3-dioxygenase (IDO) expression in developmental programming after early life MD (on postnatal days (PNDs) 20, 30, 40, and 60). On PND 60, the rats that were subjected to MD displayed depressive-like behavior. On PND 10, it was found that there was a decrease in the level of glial fibrillary acidic protein (GFAP) immunopositive cells, a decrease in the level of IDO expression, and an increase in the level of Iba-1 (microglial marker) in the hippocampus of rats that were subjected to MD. On PND 20, levels of GFAP were also found to have decreased in the hippocampus, and there was an increase in the level of Iba-1 in the hippocampus. AIF-1 (microglial marker) expression was observed in the PFC following MD. On PND 30, the levels of Iba-1 remained elevated. On PND 40, the levels of GFAP were found to have increased in the hippocampus of rats that were subjected to MD. On PND 60, the levels of GFAP and AIF-1 remained elevated following MD. These results suggest that early life stress induces negative developmental programming in rats, as demonstrated by depressive-like behavior in adult life. Moreover, MD increases microglial activation in both early and late developmental phases. The levels of GFAP and IDO decreased in the early stages but were found to be higher in later developmental periods. These findings suggest that MD could differentially affect the expression of the IDO enzyme, astrocytes, and microglial activation depending on the neurodevelopmental period. The onset of an inflammatory state from resident brain cells could be associated with the activation of the kynurenine pathway and the development of depressive behavior in adulthood.
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36
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mGlu5-mediated signalling in developing astrocyte and the pathogenesis of autism spectrum disorders. Curr Opin Neurobiol 2018; 48:139-145. [DOI: 10.1016/j.conb.2017.12.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 12/18/2017] [Accepted: 12/22/2017] [Indexed: 11/24/2022]
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Abstract
Cell-cell fusion is essential for fertilization and organ development. Dedicated proteins known as fusogens are responsible for mediating membrane fusion. However, until recently, these proteins either remained unidentified or were poorly understood at the mechanistic level. Here, we review how fusogens surmount multiple energy barriers to mediate cell-cell fusion. We describe how early preparatory steps bring membranes to a distance of ∼10 nm, while fusogens act in the final approach between membranes. The mechanical force exerted by cell fusogens and the accompanying lipidic rearrangements constitute the hallmarks of cell-cell fusion. Finally, we discuss the relationship between viral and eukaryotic fusogens, highlight a classification scheme regrouping a superfamily of fusogens called Fusexins, and propose new questions and avenues of enquiry.
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Affiliation(s)
- Javier M Hernández
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Benjamin Podbilewicz
- Department of Biology, Technion - Israel Institute of Technology, Haifa 32000, Israel
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38
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Antagonistic regulation of trafficking to Caenorhabditis elegans sensory cilia by a Retinal Degeneration 3 homolog and retromer. Proc Natl Acad Sci U S A 2017; 115:E438-E447. [PMID: 29282322 DOI: 10.1073/pnas.1712302115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Sensory neurons often possess cilia with elaborate membrane structures that are adapted to the sensory modality of the host cell. Mechanisms that target sensory transduction proteins to these specialized membrane domains remain poorly understood. Here, we show that a homolog of the human retinal dystrophy gene Retinal Degeneration 3 (RD3) is a Golgi-associated protein required for efficient trafficking of a sensory receptor, the receptor-type guanylate cyclase GCY-9, to cilia in chemosensory neurons of the nematode Caenorhabditis elegans The trafficking defect caused by mutation of the nematode RD3 homolog is suppressed in vivo by mutation of key components of the retromer complex, which mediates recycling of cargo from endosomes to the Golgi. Our data show that there exists a critical balance in sensory neurons between the rates of anterograde and retrograde trafficking of cargo destined for the sensory cilium and this balance requires molecular specialization at an early stage of the secretory pathway.
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39
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Jin Y, Qi YB. Building stereotypic connectivity: mechanistic insights into structural plasticity from C. elegans. Curr Opin Neurobiol 2017; 48:97-105. [PMID: 29182952 DOI: 10.1016/j.conb.2017.11.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 11/07/2017] [Accepted: 11/14/2017] [Indexed: 01/10/2023]
Abstract
The ability of neurons to modify or remodel their synaptic connectivity is critical for the function of neural circuitry throughout the life of an animal. Understanding the mechanisms underlying neuronal structural changes is central to our knowledge of how the nervous system is shaped for complex behaviors and how it further adapts to developmental and environmental demands. Caenorhabditis elegans provides a powerful model for examining developmental processes and for discovering mechanisms controlling neural plasticity. Recent findings have identified conserved themes underlying neural plasticity in development and under environmental stress.
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Affiliation(s)
- Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Yingchuan B Qi
- Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 310036, China.
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40
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Cell Biology of Astrocyte-Synapse Interactions. Neuron 2017; 96:697-708. [PMID: 29096081 DOI: 10.1016/j.neuron.2017.09.056] [Citation(s) in RCA: 575] [Impact Index Per Article: 82.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 09/24/2017] [Accepted: 09/28/2017] [Indexed: 12/25/2022]
Abstract
Astrocytes, the most abundant glial cells in the mammalian brain, are critical regulators of brain development and physiology through dynamic and often bidirectional interactions with neuronal synapses. Despite the clear importance of astrocytes for the establishment and maintenance of proper synaptic connectivity, our understanding of their role in brain function is still in its infancy. We propose that this is at least in part due to large gaps in our knowledge of the cell biology of astrocytes and the mechanisms they use to interact with synapses. In this review, we summarize some of the seminal findings that yield important insight into the cellular and molecular basis of astrocyte-neuron communication, focusing on the role of astrocytes in the development and remodeling of synapses. Furthermore, we pose some pressing questions that need to be addressed to advance our mechanistic understanding of the role of astrocytes in regulating synaptic development.
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41
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Lamkin ER, Heiman MG. Coordinated morphogenesis of neurons and glia. Curr Opin Neurobiol 2017; 47:58-64. [PMID: 28988011 DOI: 10.1016/j.conb.2017.09.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 09/17/2017] [Indexed: 11/19/2022]
Abstract
Glia adopt remarkable shapes that are tightly coordinated with the morphologies of their neuronal partners. To achieve these precise shapes, glia and neurons exhibit coordinated morphological changes on the time scale of minutes and on size scales ranging from nanometers to hundreds of microns. Here, we review recent studies that reveal the highly dynamic, localized morphological changes of mammalian neuron-glia contacts. We then explore the power of Drosophila and C. elegans models to study coordinated changes at defined neuron-glia contacts, highlighting the use of innovative genetic and imaging tools to uncover the molecular mechanisms responsible for coordinated morphogenesis of neurons and glia.
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Affiliation(s)
- Elizabeth R Lamkin
- Department of Genetics, Harvard Medical School and Division of Genetics and Genomics, Boston Children's Hospital, Boston MA 02115, United States
| | - Maxwell G Heiman
- Department of Genetics, Harvard Medical School and Division of Genetics and Genomics, Boston Children's Hospital, Boston MA 02115, United States.
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42
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Androwski RJ, Flatt KM, Schroeder NE. Phenotypic plasticity and remodeling in the stress-induced Caenorhabditis elegans dauer. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2017; 6:10.1002/wdev.278. [PMID: 28544390 PMCID: PMC5626018 DOI: 10.1002/wdev.278] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Revised: 03/23/2017] [Accepted: 04/14/2017] [Indexed: 12/22/2022]
Abstract
Organisms are often capable of modifying their development to better suit their environment. Under adverse conditions, the nematode Caenorhabditis elegans develops into a stress-resistant alternative larval stage called dauer. The dauer stage is the primary survival stage for C. elegans in nature. Large-scale tissue remodeling during dauer conveys resistance to harsh environments. The environmental and genetic regulation of the decision to enter dauer has been extensively studied. However, less is known about the mechanisms regulating tissue remodeling. Changes to the cuticle and suppression of feeding in dauers lead to an increased resistance to external stressors. Meanwhile reproductive development arrests during dauer while preserving the ability to reproduce once favorable environmental conditions return. Dramatic remodeling of neurons, glia, and muscles during dauer likely facilitate dauer-specific behaviors. Dauer-specific pulsation of the excretory duct likely mediates a response to osmotic stress. The power of C. elegans genetics has uncovered some of the molecular pathways regulating dauer tissue remodeling. In addition to genes that regulate single remodeling events, several mutants result in pleiotropic defects in dauer remodeling. This review details the individual aspects of morphological changes that occur during dauer formation and discusses molecular mechanisms regulating these processes. The dauer stage provides us with an excellent model for understanding phenotypic plasticity and remodeling from the individual cell to an entire animal. WIREs Dev Biol 2017, 6:e278. doi: 10.1002/wdev.278 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Rebecca J Androwski
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, USA
| | - Kristen M Flatt
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, USA
| | - Nathan E Schroeder
- Neuroscience Program and Department of Crop Sciences, University of Illinois at Urbana-Champaign, Champaign, IL, USA
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43
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Howell K, Hobert O. Morphological Diversity of C. elegans Sensory Cilia Instructed by the Differential Expression of an Immunoglobulin Domain Protein. Curr Biol 2017; 27:1782-1790.e5. [PMID: 28578929 DOI: 10.1016/j.cub.2017.05.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 04/27/2017] [Accepted: 05/03/2017] [Indexed: 01/08/2023]
Abstract
Cilia on dendritic endings of sensory neurons organize distinct types of sensory machinery [1]. Ciliated endings display neuron-type-specific patterns of membrane elaborations [1-3], but it is not well understood how such neuron-type-specific morphologies are generated and whether they are coupled to the specification of other identity aspects of a terminally differentiated sensory neuron. In the course of a genome-wide analysis of members of a small family of immunoglobulin domain proteins, we found that OIG-8, a previously uncharacterized transmembrane protein with a single immunoglobulin (Ig) domain, instructs the distinct, neuron-type-specific elaboration of ciliated endings of different olfactory neuron types in the nematode C. elegans. OIG-8 protein localizes to ciliated endings of these sensory neurons, and is transcribed at different levels in distinct olfactory neuron types. oig-8 expression levels correlate with the extent of sensory cilia growth and branching patterns. Loss of oig-8 leads to a reduction in the branching patterns of cilia, whereas raising the levels of oig-8 results in an increase in elaborations. Levels of OIG-8 expression are controlled by the specific combination of a terminal selector type of transcription factors that also specify other identity features of distinct olfactory neuron types.
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Affiliation(s)
- Kelly Howell
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA.
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA.
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Oren-Suissa M, Gattegno T, Kravtsov V, Podbilewicz B. Extrinsic Repair of Injured Dendrites as a Paradigm for Regeneration by Fusion in Caenorhabditis elegans. Genetics 2017; 206:215-230. [PMID: 28283540 PMCID: PMC5419471 DOI: 10.1534/genetics.116.196386] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 03/07/2017] [Indexed: 11/18/2022] Open
Abstract
Injury triggers regeneration of axons and dendrites. Research has identified factors required for axonal regeneration outside the CNS, but little is known about regeneration triggered by dendrotomy. Here, we study neuronal plasticity triggered by dendrotomy and determine the fate of complex PVD arbors following laser surgery of dendrites. We find that severed primary dendrites grow toward each other and reconnect via branch fusion. Simultaneously, terminal branches lose self-avoidance and grow toward each other, meeting and fusing at the tips via an AFF-1-mediated process. Ectopic branch growth is identified as a step in the regeneration process required for bypassing the lesion site. Failure of reconnection to the severed dendrites results in degeneration of the distal end of the neuron. We discover pruning of excess branches via EFF-1 that acts to recover the original wild-type arborization pattern in a late stage of the process. In contrast, AFF-1 activity during dendritic auto-fusion is derived from the lateral seam cells and not autonomously from the PVD neuron. We propose a model in which AFF-1-vesicles derived from the epidermal seam cells fuse neuronal dendrites. Thus, EFF-1 and AFF-1 fusion proteins emerge as new players in neuronal arborization and maintenance of arbor connectivity following injury in Caenorhabditis elegans Our results demonstrate that there is a genetically determined multi-step pathway to repair broken dendrites in which EFF-1 and AFF-1 act on different steps of the pathway. EFF-1 is essential for dendritic pruning after injury and extrinsic AFF-1 mediates dendrite fusion to bypass injuries.
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Affiliation(s)
- Meital Oren-Suissa
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Tamar Gattegno
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Veronika Kravtsov
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Benjamin Podbilewicz
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
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45
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Kravtsov V, Oren-Suissa M, Podbilewicz B. AFF-1 fusogen can rejuvenate the regenerative potential of adult dendritic trees via self-fusion. Development 2017; 144:2364-2374. [DOI: 10.1242/dev.150037] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 05/27/2017] [Indexed: 12/20/2022]
Abstract
The aging brain undergoes structural changes, affecting brain homeostasis, neuronal function and consequently cognition. The complex architecture of dendritic arbors poses a challenge to understanding age-dependent morphological alterations, behavioral plasticity and remodeling following brain injury. Here, we use the PVD polymodal neurons of C. elegans as a model to study how aging affects neuronal plasticity. Using confocal live imaging of C. elegans PVD neurons, we demonstrate age-related progressive morphological alterations of intricate dendritic arbors. We show that insulin/IGF-1 receptor mutations (daf-2) fail to inhibit the progressive morphological aging of dendrites and do not prevent the minor decline in response to harsh touch during aging. We uncovered that PVD aging is characterized by a major decline in regenerative potential of dendrites following experimental laser dendrotomy. Furthermore, the remodeling of transected dendritic trees via AFF-1-mediated self-fusion can be restored in old animals by DAF-2 insulin/IGF-1 receptor mutations, and can be differentially reestablished by ectopic expression of AFF-1 fusion protein (fusogen). Thus, AFF-1 fusogen ectopically expressed in the PVD and mutations in DAF-2/IGF-1R, differentially rejuvenate some aspects of dendritic regeneration following injury.
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Affiliation(s)
- Veronika Kravtsov
- Department of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel
| | - Meital Oren-Suissa
- Department of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel
| | - Benjamin Podbilewicz
- Department of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel
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46
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Herndon LA, Wolkow CA, Driscoll M, Hall DH. Effects of Ageing on the Basic Biology and Anatomy of C. elegans. HEALTHY AGEING AND LONGEVITY 2017. [DOI: 10.1007/978-3-319-44703-2_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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47
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Bainbridge C, Rodriguez A, Schuler A, Cisneros M, Vidal-Gadea AG. Magnetic orientation in C. elegans relies on the integrity of the villi of the AFD magnetosensory neurons. ACTA ACUST UNITED AC 2016; 110:76-82. [PMID: 27940210 DOI: 10.1016/j.jphysparis.2016.12.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 11/28/2016] [Accepted: 12/01/2016] [Indexed: 01/07/2023]
Abstract
The magnetic field of the earth provides many organisms with sufficient information to successfully navigate through their environments. While evidence suggests the widespread use of this sensory modality across many taxa, it remains an understudied sensory modality. We have recently showed that the nematode C. elegans orients to earth-strength magnetic fields using the first pair of described magnetosensory neurons, AFDs. The AFD cells are a pair of ciliated sensory neurons crowned by fifty villi known to be implicated in temperature sensation. We investigated the potential importance of these subcellular structures for the performance of magnetic orientation. We show that ciliary integrity and villi number are essential for magnetic orientation. Mutants with impairments AFD cilia or villi structure failed to orient to magnetic fields. Similarly, C. elegans larvae possessing immature AFD neurons with fewer villi were also unable to orient to magnetic fields. Larvae of every stage however retained the ability to orient to thermal gradients. To our knowledge, this is the first behavioral separation of magnetic and thermal orientation in C. elegans. We conclude that magnetic orientation relies on the function of both cilia and villi in the AFD neurons. The role of villi in multiple sensory transduction pathways involved in the sensory transduction of vectorial stimuli further supports the likely role of the villi of the AFD neurons as the site for magnetic field transduction. The genetic and behavioral tractability of C. elegans make it a promising system for uncovering potentially conserved molecular mechanisms by which animals across taxa detect and orient to magnetic fields.
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Affiliation(s)
- Chance Bainbridge
- School of Biological Sciences, Illinois State University, Normal, IL, USA
| | - Anjelica Rodriguez
- School of Biological Sciences, Illinois State University, Normal, IL, USA
| | - Andrew Schuler
- School of Biological Sciences, Illinois State University, Normal, IL, USA
| | - Michael Cisneros
- School of Biological Sciences, Illinois State University, Normal, IL, USA
| | - Andrés G Vidal-Gadea
- School of Biological Sciences, Illinois State University, Normal, IL, USA. http://biology.illinoisstate.edu/avidal
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48
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Grussendorf KA, Trezza CJ, Salem AT, Al-Hashimi H, Mattingly BC, Kampmeyer DE, Khan LA, Hall DH, Göbel V, Ackley BD, Buechner M. Facilitation of Endosomal Recycling by an IRG Protein Homolog Maintains Apical Tubule Structure in Caenorhabditis elegans. Genetics 2016; 203:1789-806. [PMID: 27334269 PMCID: PMC4981278 DOI: 10.1534/genetics.116.192559] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Accepted: 06/15/2016] [Indexed: 02/08/2023] Open
Abstract
Determination of luminal diameter is critical to the function of small single-celled tubes. A series of EXC proteins, including EXC-1, prevent swelling of the tubular excretory canals in Caenorhabditis elegans In this study, cloning of exc-1 reveals it to encode a homolog of mammalian IRG proteins, which play roles in immune response and autophagy and are associated with Crohn's disease. Mutants in exc-1 accumulate early endosomes, lack recycling endosomes, and exhibit abnormal apical cytoskeletal structure in regions of enlarged tubules. EXC-1 interacts genetically with two other EXC proteins that also affect endosomal trafficking. In yeast two-hybrid assays, wild-type and putative constitutively active EXC-1 binds to the LIM-domain protein EXC-9, whose homolog, cysteine-rich intestinal protein, is enriched in mammalian intestine. These results suggest a model for IRG function in forming and maintaining apical tubule structure via regulation of endosomal recycling.
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Affiliation(s)
- Kelly A Grussendorf
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045 Department of Biological Sciences, Minnesota State University, Mankato, Minnesota 56001
| | - Christopher J Trezza
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Alexander T Salem
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Hikmat Al-Hashimi
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Brendan C Mattingly
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Drew E Kampmeyer
- Department of Biological Sciences, Minnesota State University, Mankato, Minnesota 56001
| | - Liakot A Khan
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114
| | - David H Hall
- Department of Neuroscience, Center for Caenorhabditis elegans Anatomy, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Verena Göbel
- Mucosal Immunology and Biology Research Center, Developmental Biology and Genetics Core, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114
| | - Brian D Ackley
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Matthew Buechner
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
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49
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Ow MC, Hall SE. A Method for Obtaining Large Populations of Synchronized Caenorhabditis elegans Dauer Larvae. Methods Mol Biol 2016; 1327:209-19. [PMID: 26423977 DOI: 10.1007/978-1-4939-2842-2_15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
The C. elegans dauer is an attractive model with which to investigate fundamental biological questions, such as how environmental cues are sensed and are translated into developmental decisions through a series of signaling cascades that ultimately result in a transformed animal. Here we describe a simple method of using egg white plates to obtain highly synchronized purified dauers that can be used in downstream applications requiring large quantities of dauers or postdauer animals.
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Affiliation(s)
- Maria C Ow
- Department of Biology, Syracuse University, 107 College Place, Room 110, Syracuse, NY, 13244, USA
| | - Sarah E Hall
- Department of Biology, Syracuse University, 107 College Place, Room 110, Syracuse, NY, 13244, USA.
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50
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Cell-cell fusion in the nervous system: Alternative mechanisms of development, injury, and repair. Semin Cell Dev Biol 2016; 60:146-154. [PMID: 27375226 DOI: 10.1016/j.semcdb.2016.06.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/14/2016] [Accepted: 06/28/2016] [Indexed: 12/11/2022]
Abstract
Over a century ago, the seminal work of Ramón y Cajal revealed that the nervous system is made of individual units, the neurons, which are related to each other by contiguity rather than continuity. This view overturned the idea that the nervous system was a reticulum of fibers, a rete diffusa nervosa, as proposed and defined by Camillo Golgi. Although the neuron theory has been widely confirmed in every model system studied and constitutes the basis of modern neuroscience, evidence accumulated over the years suggests that neurons, similar to other types of cells, have the potential to fuse their membranes and undergo cell-cell fusion under certain conditions. This concept adds a substantial layer to our view of the nervous system and how it functions. Here, we bring together past and more recent discoveries on multiple aspects of neuronal fusion, discussing how this cellular event is generated, and what consequences it has for our understanding of nervous system development, disease, injury, and repair.
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