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Aoki I, Jurado P, Nawa K, Kondo R, Yamashiro R, Matsuyama HJ, Ferrer I, Nakano S, Mori I. OLA-1, an Obg-like ATPase, integrates hunger with temperature information in sensory neurons in C. elegans. PLoS Genet 2022; 18:e1010219. [PMID: 35675262 PMCID: PMC9176836 DOI: 10.1371/journal.pgen.1010219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Accepted: 04/26/2022] [Indexed: 11/18/2022] Open
Abstract
Animals detect changes in both their environment and their internal state and modify their behavior accordingly. Yet, it remains largely to be clarified how information of environment and internal state is integrated and how such integrated information modifies behavior. Well-fed C. elegans migrates to past cultivation temperature on a thermal gradient, which is disrupted when animals are starved. We recently reported that the neuronal activities synchronize between a thermosensory neuron AFD and an interneuron AIY, which is directly downstream of AFD, in well-fed animals, while this synchrony is disrupted in starved animals. However, it remained to be determined whether the disruption of the synchrony is derived from modulation of the transmitter release from AFD or from the modification of reception or signal transduction in AIY. By performing forward genetics on a transition of thermotaxis behavior along starvation, we revealed that OLA-1, an Obg-like ATPase, functions in AFD to promote disruption of AFD-AIY synchrony and behavioral transition. Our results suggest that the information of hunger is delivered to the AFD thermosensory neuron and gates transmitter release from AFD to disrupt thermotaxis, thereby shedding light onto a mechanism for the integration of environmental and internal state to modulate behavior.
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Affiliation(s)
- Ichiro Aoki
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Paola Jurado
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Japan
- Cancer Area, Institut d’Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Kanji Nawa
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Rumi Kondo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Riku Yamashiro
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Hironori J. Matsuyama
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Isidre Ferrer
- Neuroscience Area, Institut d’Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Shunji Nakano
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Ikue Mori
- Group of Molecular Neurobiology, Neuroscience Institute, Graduate School of Science, Nagoya University, Nagoya, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
- * E-mail:
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2
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Handley A, Wu Q, Sherry T, Cornell R, Pocock R. Diet-responsive transcriptional regulation of insulin in a single neuron controls systemic metabolism. PLoS Biol 2022; 20:e3001655. [PMID: 35594303 PMCID: PMC9162364 DOI: 10.1371/journal.pbio.3001655] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 06/02/2022] [Accepted: 04/29/2022] [Indexed: 11/18/2022] Open
Abstract
Metabolic homeostasis is coordinated through a robust network of signaling pathways acting across all tissues. A key part of this network is insulin-like signaling, which is fundamental for surviving glucose stress. Here, we show that Caenorhabditis elegans fed excess dietary glucose reduce insulin-1 (INS-1) expression specifically in the BAG glutamatergic sensory neurons. We demonstrate that INS-1 expression in the BAG neurons is directly controlled by the transcription factor ETS-5, which is also down-regulated by glucose. We further find that INS-1 acts exclusively from the BAG neurons, and not other INS-1-expressing neurons, to systemically inhibit fat storage via the insulin-like receptor DAF-2. Together, these findings reveal an intertissue regulatory pathway where regulation of insulin expression in a specific neuron controls systemic metabolism in response to excess dietary glucose. Metabolic homeostasis is coordinated through a robust network of signaling pathways acting across all tissues. This study shows that Caenorhabditis elegans nematodes fed excess dietary glucose reduce the expression of insulin-1 specifically in the BAG glutamatergic sensory neurons, and that insulin-1 produced by these neurons systemically inhibits fat storage via the insulin-like receptor DAF-2.
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Affiliation(s)
- Ava Handley
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia
- * E-mail: (AH); (RP)
| | - Qiuli Wu
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia
- Key Laboratory of Developmental Genes and Human Diseases in Ministry of Education, Medical School of Southeast University, Nanjing, China
| | - Tessa Sherry
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia
| | - Rebecca Cornell
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia
| | - Roger Pocock
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia
- * E-mail: (AH); (RP)
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3
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Godini R, Handley A, Pocock R. Transcription Factors That Control Behavior-Lessons From C. elegans. Front Neurosci 2021; 15:745376. [PMID: 34646119 PMCID: PMC8503520 DOI: 10.3389/fnins.2021.745376] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 09/02/2021] [Indexed: 11/15/2022] Open
Abstract
Behavior encompasses the physical and chemical response to external and internal stimuli. Neurons, each with their own specific molecular identities, act in concert to perceive and relay these stimuli to drive behavior. Generating behavioral responses requires neurons that have the correct morphological, synaptic, and molecular identities. Transcription factors drive the specific gene expression patterns that define these identities, controlling almost every phenomenon in a cell from development to homeostasis. Therefore, transcription factors play an important role in generating and regulating behavior. Here, we describe the transcription factors, the pathways they regulate, and the neurons that drive chemosensation, mechanosensation, thermosensation, osmolarity sensing, complex, and sex-specific behaviors in the animal model Caenorhabditis elegans. We also discuss the current limitations in our knowledge, particularly our minimal understanding of how transcription factors contribute to the adaptive behavioral responses that are necessary for organismal survival.
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4
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Rossillo M, Ringstad N. Development of specialized sensory neurons engages a nuclear receptor required for functional plasticity. Genes Dev 2020; 34:1666-1679. [PMID: 33184226 PMCID: PMC7706712 DOI: 10.1101/gad.342212.120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 09/30/2020] [Indexed: 12/12/2022]
Abstract
In this study, Rossillo and Ringstad sought to determine mechanisms that support the physiology and plasticity of BAG neurons, which are specialized neurons that sense the respiratory gas carbon dioxide (CO2) and, in a context-dependent manner, switch from mediating avoidance of CO2 to supporting CO2 attraction in C. elegans. They used tandem ChIP-seq and cell targeted RNA-seq to identify gene targets of the transcription factor ETS-5, which is required for BAG development, and their functional screen of ETS-5 targets revealed that NHR-6, the sole C. elegans NR4A-type nuclear receptor, is required for BAG-mediated avoidance of CO2 and regulates expression of a subset of BAG-specific genes. During development, the nervous system generates neurons that serve highly specialized roles and, accordingly, possess unique functional attributes. The chemosensory BAG neurons of C. elegans are striking exemplars of this. BAGs sense the respiratory gas carbon dioxide (CO2) and, in a context-dependent manner, switch from mediating avoidance of CO2 to supporting CO2 attraction. To determine mechanisms that support the physiology and plasticity of BAG neurons, we used tandem ChIP-seq and cell targeted RNA-seq to identify gene targets of the transcription factor ETS-5, which is required for BAG development. A functional screen of ETS-5 targets revealed that NHR-6, the sole C. elegans NR4A-type nuclear receptor, is required for BAG-mediated avoidance of CO2 and regulates expression of a subset of BAG-specific genes. Unlike ets-5 mutants, which are defective for both attraction to and avoidance of CO2, nhr-6 mutants are fully competent for attraction. These data indicate that the remarkable ability of BAGs to adaptively assign positive or negative valence to a chemosensory stimulus requires a gene-regulatory program supported by an evolutionarily conserved type of nuclear receptor. We suggest that NHR-6 might be an example of a developmental mechanism for modular encoding of functional plasticity in the nervous system.
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Affiliation(s)
- Mary Rossillo
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, Neuroscience Institute, New York University School of Medicine, New York, New York 10016, USA
| | - Niels Ringstad
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, Neuroscience Institute, New York University School of Medicine, New York, New York 10016, USA
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5
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Abstract
With a nervous system that has only a few hundred neurons, Caenorhabditis elegans was initially not regarded as a model for studies on learning. However, the collective effort of the C. elegans field in the past several decades has shown that the worm displays plasticity in its behavioral response to a wide range of sensory cues in the environment. As a bacteria-feeding worm, C. elegans is highly adaptive to the bacteria enriched in its habitat, especially those that are pathogenic and pose a threat to survival. It uses several common forms of behavioral plasticity that last for different amounts of time, including imprinting and adult-stage associative learning, to modulate its interactions with pathogenic bacteria. Probing the molecular, cellular and circuit mechanisms underlying these forms of experience-dependent plasticity has identified signaling pathways and regulatory insights that are conserved in more complex animals.
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Affiliation(s)
- He Liu
- Department of Organismic and Evolutionary Biology, Center for Brain Science, Harvard University, Cambridge, MA, USA
| | - Yun Zhang
- Department of Organismic and Evolutionary Biology, Center for Brain Science, Harvard University, Cambridge, MA, USA
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6
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Abstract
Caenorhabditis elegans' behavioral states, like those of other animals, are shaped by its immediate environment, its past experiences, and by internal factors. We here review the literature on C. elegans behavioral states and their regulation. We discuss dwelling and roaming, local and global search, mate finding, sleep, and the interaction between internal metabolic states and behavior.
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Affiliation(s)
- Steven W Flavell
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - David M Raizen
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Young-Jai You
- Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602, Japan
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7
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Lorenzo R, Onizuka M, Defrance M, Laurent P. Combining single-cell RNA-sequencing with a molecular atlas unveils new markers for Caenorhabditis elegans neuron classes. Nucleic Acids Res 2020; 48:7119-7134. [PMID: 32542321 PMCID: PMC7367206 DOI: 10.1093/nar/gkaa486] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 05/11/2020] [Accepted: 05/27/2020] [Indexed: 12/11/2022] Open
Abstract
Single-cell RNA-sequencing (scRNA-seq) of the Caenorhabditis elegans nervous system offers the unique opportunity to obtain a partial expression profile for each neuron within a known connectome. Building on recent scRNA-seq data and on a molecular atlas describing the expression pattern of ∼800 genes at the single cell resolution, we designed an iterative clustering analysis aiming to match each cell-cluster to the ∼100 anatomically defined neuron classes of C. elegans. This heuristic approach successfully assigned 97 of the 118 neuron classes to a cluster. Sixty two clusters were assigned to a single neuron class and 15 clusters grouped neuron classes sharing close molecular signatures. Pseudotime analysis revealed a maturation process occurring in some neurons (e.g. PDA) during the L2 stage. Based on the molecular profiles of all identified neurons, we predicted cell fate regulators and experimentally validated unc-86 for the normal differentiation of RMG neurons. Furthermore, we observed that different classes of genes functionally diversify sensory neurons, interneurons and motorneurons. Finally, we designed 15 new neuron class-specific promoters validated in vivo. Amongst them, 10 represent the only specific promoter reported to this day, expanding the list of neurons amenable to genetic manipulations.
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Affiliation(s)
- Ramiro Lorenzo
- Laboratory of Neurophysiology, ULB Neuroscience Institute (UNI), Université Libre de Bruxelles (ULB), Brussels, Belgium
- Centro de Investigación Veterinaria de Tandil (CIVETAN), CONICET-CICPBA-UNCPBA, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro (FCV-UNCPBA), Tandil, Argentina
| | - Michiho Onizuka
- Laboratory of Neurophysiology, ULB Neuroscience Institute (UNI), Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Matthieu Defrance
- Interuniversity Institute of Bioinformatics in Brussels, Université Libre de Bruxelles, Brussels, Belgium
| | - Patrick Laurent
- Laboratory of Neurophysiology, ULB Neuroscience Institute (UNI), Université Libre de Bruxelles (ULB), Brussels, Belgium
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8
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Godini R, Langebeck-Jensen K, Pocock R. A single amino acid change in the EGL-46 transcription factor causes defects in BAG neuron specification. MICROPUBLICATION BIOLOGY 2020; 2020. [PMID: 32550488 PMCID: PMC7252269 DOI: 10.17912/micropub.biology.000224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Rasoul Godini
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
| | - Kasper Langebeck-Jensen
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, Denmark
| | - Roger Pocock
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
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9
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Horowitz LB, Brandt JP, Ringstad N. Repression of an activity-dependent autocrine insulin signal is required for sensory neuron development in C. elegans. Development 2019; 146:dev.182873. [PMID: 31628111 DOI: 10.1242/dev.182873] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 10/14/2019] [Indexed: 11/20/2022]
Abstract
Nervous system development is instructed by genetic programs and refined by distinct mechanisms that couple neural activity to gene expression. How these processes are integrated remains poorly understood. Here, we report that the regulated release of insulin-like peptides (ILPs) during development of the Caenorhabditis elegans nervous system accomplishes such an integration. We find that the p38 MAP kinase PMK-3, which is required for the differentiation of chemosensory BAG neurons, limits an ILP signal that represses expression of a BAG neuron fate. ILPs are released from BAGs themselves in an activity-dependent manner during development, indicating that ILPs constitute an autocrine signal that regulates the differentiation of BAG neurons. Expression of a specialized neuronal fate is, therefore, coordinately regulated by a genetic program that sets levels of ILP expression during development, and by neural activity, which regulates ILP release. Autocrine signals of this kind might have general and conserved functions as integrators of deterministic genetic programs with activity-dependent mechanisms during neurodevelopment.
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Affiliation(s)
- Lauren Bayer Horowitz
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Biology and Medicine, Department of Cell Biology, Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
| | - Julia P Brandt
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Biology and Medicine, Department of Cell Biology, Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
| | - Niels Ringstad
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Biology and Medicine, Department of Cell Biology, Neuroscience Institute, NYU School of Medicine, New York, NY 10016, USA
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10
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Abstract
Carbon dioxide (CO2) is an important sensory cue for many animals, including both parasitic and free-living nematodes. Many nematodes show context-dependent, experience-dependent and/or life-stage-dependent behavioural responses to CO2, suggesting that CO2 plays crucial roles throughout the nematode life cycle in multiple ethological contexts. Nematodes also show a wide range of physiological responses to CO2. Here, we review the diverse responses of parasitic and free-living nematodes to CO2. We also discuss the molecular, cellular and neural circuit mechanisms that mediate CO2 detection in nematodes, and that drive context-dependent and experience-dependent responses of nematodes to CO2.
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11
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Brandt JP, Rossillo M, Du Z, Ichikawa D, Barnes K, Chen A, Noyes M, Bao Z, Ringstad N. Lineage context switches the function of a C. elegans Pax6 homolog in determining a neuronal fate. Development 2019; 146:dev168153. [PMID: 30890567 PMCID: PMC6503985 DOI: 10.1242/dev.168153] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Accepted: 03/11/2019] [Indexed: 01/26/2023]
Abstract
The sensory nervous system of C. elegans comprises cells with varied molecular and functional characteristics, and is, therefore, a powerful model for understanding mechanisms that generate neuronal diversity. We report here that VAB-3, a C. elegans homolog of the homeodomain-containing protein Pax6, has opposing functions in regulating expression of a specific chemosensory fate. A homeodomain-only short isoform of VAB-3 is expressed in BAG chemosensory neurons, where it promotes gene expression and cell function. In other cells, a long isoform of VAB-3, comprising a Paired homology domain and a homeodomain, represses expression of ETS-5, a transcription factor required for expression of BAG fate. Repression of ets-5 requires the Eyes Absent homolog EYA-1 and the Six-class homeodomain protein CEH-32. We determined sequences that mediate high-affinity binding of ETS-5, VAB-3 and CEH-32. The ets-5 locus is enriched for ETS-5-binding sites but lacks sequences that bind VAB-3 and CEH-32, suggesting that these factors do not directly repress ets-5 expression. We propose that a promoter-selection system together with lineage-specific expression of accessory factors allows VAB-3/Pax6 to either promote or repress expression of specific cell fates in a context-dependent manner. This article has an associated 'The people behind the papers' interview.
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Affiliation(s)
- Julia P Brandt
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Biology and Medicine, and Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA
| | - Mary Rossillo
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Biology and Medicine, and Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA
| | - Zhuo Du
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - David Ichikawa
- Institute for Systems Genetics and Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY 10016, USA
| | - Kristopher Barnes
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Allison Chen
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Marcus Noyes
- Institute for Systems Genetics and Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY 10016, USA
| | - Zhirong Bao
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Niels Ringstad
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Biology and Medicine, and Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA
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12
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Rojo Romanos T, Ng L, Pocock R. Behavioral Assays to Study Oxygen and Carbon Dioxide Sensing in Caenorhabditis elegans. Bio Protoc 2018; 8:e2679. [PMID: 29335676 DOI: 10.21769/bioprotoc.2679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Animals use behavioral strategies to seek optimal environments. Population behavioral assays provide a robust means to determine the effect of genetic perturbations on the ability of animals to sense and respond to changes in the environment. Here, we describe a C. elegans population behavioral assay used to measure locomotory responses to changes in environmental oxygen (O2) and carbon dioxide (CO2) concentrations. These behavioral assays are high-throughput and enable examination of genetic, neuronal and circuit function.
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Affiliation(s)
- Teresa Rojo Romanos
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Leelee Ng
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Roger Pocock
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
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Guillermin ML, Carrillo MA, Hallem EA. A Single Set of Interneurons Drives Opposite Behaviors in C. elegans. Curr Biol 2017; 27:2630-2639.e6. [PMID: 28823678 PMCID: PMC6193758 DOI: 10.1016/j.cub.2017.07.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/06/2017] [Accepted: 07/10/2017] [Indexed: 12/21/2022]
Abstract
Many chemosensory stimuli evoke innate behavioral responses that can be either appetitive or aversive, depending on an animal's age, prior experience, nutritional status, and environment [1-9]. However, the circuit mechanisms that enable these valence changes are poorly understood. Here, we show that Caenorhabditis elegans can alternate between attractive or aversive responses to carbon dioxide (CO2), depending on its recently experienced CO2 environment. Both responses are mediated by a single pathway of interneurons. The CO2-evoked activity of these interneurons is subject to extreme experience-dependent modulation, enabling them to drive opposite behavioral responses to CO2. Other interneurons in the circuit regulate behavioral sensitivity to CO2 independent of valence. A combinatorial code of neuropeptides acts on the circuit to regulate both valence and sensitivity. Chemosensory valence-encoding interneurons exist across phyla, and valence is typically determined by whether appetitive or aversive interneuron populations are activated. Our results reveal an alternative mechanism of valence determination in which the same interneurons contribute to both attractive and aversive responses through modulation of sensory neuron to interneuron synapses. This circuit design represents a previously unrecognized mechanism for generating rapid changes in innate chemosensory valence.
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Affiliation(s)
- Manon L Guillermin
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mayra A Carrillo
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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14
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The ETS-5 transcription factor regulates activity states in Caenorhabditis elegans by controlling satiety. Proc Natl Acad Sci U S A 2017; 114:E1651-E1658. [PMID: 28193866 DOI: 10.1073/pnas.1610673114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Animal behavior is shaped through interplay among genes, the environment, and previous experience. As in mammals, satiety signals induce quiescence in Caenorhabditis elegans Here we report that the C. elegans transcription factor ETS-5, an ortholog of mammalian FEV/Pet1, controls satiety-induced quiescence. Nutritional status has a major influence on C. elegans behavior. When foraging, food availability controls behavioral state switching between active (roaming) and sedentary (dwelling) states; however, when provided with high-quality food, C. elegans become sated and enter quiescence. We show that ETS-5 acts to promote roaming and inhibit quiescence by setting the internal "satiety quotient" through fat regulation. Acting from the ASG and BAG sensory neurons, we show that ETS-5 functions in a complex network with serotonergic and neuropeptide signaling pathways to control food-regulated behavioral state switching. Taken together, our results identify a neuronal mechanism for controlling intestinal fat stores and organismal behavioral states in C. elegans, and establish a paradigm for the elucidation of obesity-relevant mechanisms.
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15
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Control of Neuropeptide Expression by Parallel Activity-dependent Pathways in Caenorhabditis elegans. Sci Rep 2017; 7:38734. [PMID: 28139692 PMCID: PMC5282578 DOI: 10.1038/srep38734] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/14/2016] [Indexed: 12/19/2022] Open
Abstract
Monitoring of neuronal activity within circuits facilitates integrated responses and rapid changes in behavior. We have identified a system in Caenorhabditis elegans where neuropeptide expression is dependent on the ability of the BAG neurons to sense carbon dioxide. In C. elegans, CO2 sensing is predominantly coordinated by the BAG-expressed receptor-type guanylate cyclase GCY-9. GCY-9 binding to CO2 causes accumulation of cyclic GMP and opening of the cGMP-gated TAX-2/TAX-4 cation channels; provoking an integrated downstream cascade that enables C. elegans to avoid high CO2. Here we show that cGMP regulation by GCY-9 and the PDE-1 phosphodiesterase controls BAG expression of a FMRFamide-related neuropeptide FLP-19 reporter (flp-19::GFP). This regulation is specific for CO2-sensing function of the BAG neurons, as loss of oxygen sensing function does not affect flp-19::GFP expression. We also found that expression of flp-19::GFP is controlled in parallel to GCY-9 by the activity-dependent transcription factor CREB (CRH-1) and the cAMP-dependent protein kinase (KIN-2) signaling pathway. We therefore show that two parallel pathways regulate neuropeptide gene expression in the BAG sensory neurons: the ability to sense changes in carbon dioxide and CREB transcription factor. Such regulation may be required in particular environmental conditions to enable sophisticated behavioral decisions to be performed.
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16
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Gang SS, Hallem EA. Mechanisms of host seeking by parasitic nematodes. Mol Biochem Parasitol 2016; 208:23-32. [PMID: 27211240 DOI: 10.1016/j.molbiopara.2016.05.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 05/13/2016] [Accepted: 05/16/2016] [Indexed: 10/21/2022]
Abstract
The phylum Nematoda comprises a diverse group of roundworms that includes parasites of vertebrates, invertebrates, and plants. Human-parasitic nematodes infect more than one billion people worldwide and cause some of the most common neglected tropical diseases, particularly in low-resource countries [1]. Parasitic nematodes of livestock and crops result in billions of dollars in losses each year [1]. Many nematode infections are treatable with low-cost anthelmintic drugs, but repeated infections are common in endemic areas and drug resistance is a growing concern with increasing therapeutic and agricultural administration [1]. Many parasitic nematodes have an environmental infective larval stage that engages in host seeking, a process whereby the infective larvae use sensory cues to search for hosts. Host seeking is a complex behavior that involves multiple sensory modalities, including olfaction, gustation, thermosensation, and humidity sensation. As the initial step of the parasite-host interaction, host seeking could be a powerful target for preventative intervention. However, host-seeking behavior remains poorly understood. Here we review what is currently known about the host-seeking behaviors of different parasitic nematodes, including insect-parasitic nematodes, mammalian-parasitic nematodes, and plant-parasitic nematodes. We also discuss the neural bases of these behaviors.
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Affiliation(s)
- Spencer S Gang
- Department of Microbiology, Immunology, and Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, United States.
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, United States.
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Hobert O. A map of terminal regulators of neuronal identity in Caenorhabditis elegans. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2016; 5:474-98. [PMID: 27136279 PMCID: PMC4911249 DOI: 10.1002/wdev.233] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2016] [Revised: 02/07/2016] [Accepted: 02/21/2016] [Indexed: 12/31/2022]
Abstract
Our present day understanding of nervous system development is an amalgam of insights gained from studying different aspects and stages of nervous system development in a variety of invertebrate and vertebrate model systems, with each model system making its own distinctive set of contributions. One aspect of nervous system development that has been among the most extensively studied in the nematode Caenorhabditis elegans is the nature of the gene regulatory programs that specify hardwired, terminal cellular identities. I first summarize a number of maps (anatomical, functional, and molecular) that describe the terminal identity of individual neurons in the C. elegans nervous system. I then provide a comprehensive summary of regulatory factors that specify terminal identities in the nervous system, synthesizing these past studies into a regulatory map of cellular identities in the C. elegans nervous system. This map shows that for three quarters of all neurons in the C. elegans nervous system, regulatory factors that control terminal identity features are known. In-depth studies of specific neuron types have revealed that regulatory factors rarely act alone, but rather act cooperatively in neuron-type specific combinations. In most cases examined so far, distinct, biochemically unlinked terminal identity features are coregulated via cooperatively acting transcription factors, termed terminal selectors, but there are also cases in which distinct identity features are controlled in a piecemeal fashion by independent regulatory inputs. The regulatory map also illustrates that identity-defining transcription factors are reemployed in distinct combinations in different neuron types. However, the same transcription factor can drive terminal differentiation in neurons that are unrelated by lineage, unrelated by function, connectivity and neurotransmitter deployment. Lastly, the regulatory map illustrates the preponderance of homeodomain transcription factors in the control of terminal identities, suggesting that these factors have ancient, phylogenetically conserved roles in controlling terminal neuronal differentiation in the nervous system. WIREs Dev Biol 2016, 5:474-498. doi: 10.1002/wdev.233 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY, USA
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Brandt JP, Ringstad N. Toll-like Receptor Signaling Promotes Development and Function of Sensory Neurons Required for a C. elegans Pathogen-Avoidance Behavior. Curr Biol 2015; 25:2228-37. [PMID: 26279230 PMCID: PMC4642686 DOI: 10.1016/j.cub.2015.07.037] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 07/03/2015] [Accepted: 07/14/2015] [Indexed: 10/25/2022]
Abstract
Toll-like receptors (TLRs) play critical roles in innate immunity in many animal species. The sole TLR of C. elegans--TOL-1--is required for a pathogen-avoidance behavior, yet how it promotes this behavior is unknown. We show that for pathogen avoidance TOL-1 signaling is required in the chemosensory BAG neurons, where it regulates gene expression and is necessary for their chemosensory function. Genetic studies revealed that TOL-1 acts together with many conserved components of TLR signaling. BAG neurons are activated by carbon dioxide (CO₂), and we found that this modality is required for pathogen avoidance. TLR signaling can therefore mediate host responses to microbes through an unexpected mechanism: by promoting the development and function of chemosensory neurons that surveil the metabolic activity of environmental microbes.
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Affiliation(s)
- Julia P Brandt
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, Molecular Neurobiology Program, and Department of Cell Biology, NYU Langone Medical Center, New York, NY 10016, USA
| | - Niels Ringstad
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, Molecular Neurobiology Program, and Department of Cell Biology, NYU Langone Medical Center, New York, NY 10016, USA.
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19
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Sharabi K, Charar C, Gruenbaum Y. Pharyngeal pumping inhibition and avoidance by acute exposure to high CO2 levels are both regulated by the BAG neurons via different molecular pathways. WORM 2015; 4:e1008898. [PMID: 26430557 DOI: 10.1080/21624054.2015.1008898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 12/23/2014] [Accepted: 01/07/2015] [Indexed: 10/23/2022]
Abstract
Carbon dioxide (CO2) is a key molecule in many biological processes. Studies in humans, mice, D. melanogaster, C. elegans, unicellular organisms and plants have shed light on the molecular pathways activated by elevated levels of CO2. However, the mechanisms that organisms use to sense and respond to high CO2 levels remain largely unknown. Previous work has shown that C. elegans quickly avoid elevated CO2 levels using mechanisms that involve the BAG, ASE and AFD neurons via cGMP- and calcium- signaling pathways. Here, we discuss our recent finding that exposure of C. elegans to high CO2 levels leads to a very rapid cessation in the contraction of the pharynx muscles. Surprisingly, none of the tested CO2 avoidance mutants affected the rapid pumping inhibition response to elevated CO2 levels. A forward genetic screen identified that the hid-1-mediated pathway of dense core vesicle maturation regulates the pumping inhibition, probably through affecting neuropeptide secretion. Genetic studies and laser ablation experiments showed that the CO2 response of the pharyngeal muscle pumping is regulated by the BAG neurons, the same neurons that mediate CO2 avoidance.
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Affiliation(s)
- Kfir Sharabi
- Department of Genetics; Institute of Life Sciences ; Hebrew University of Jerusalem ; Jerusalem, Israel
| | - Chayki Charar
- Department of Genetics; Institute of Life Sciences ; Hebrew University of Jerusalem ; Jerusalem, Israel
| | - Yosef Gruenbaum
- Department of Genetics; Institute of Life Sciences ; Hebrew University of Jerusalem ; Jerusalem, Israel
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20
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Chao YC, Chen CC, Lin YC, Breer H, Fleischer J, Yang RB. Receptor guanylyl cyclase-G is a novel thermosensory protein activated by cool temperatures. EMBO J 2014; 34:294-306. [PMID: 25452496 DOI: 10.15252/embj.201489652] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Transmembrane guanylyl cyclases (GCs), with activity regulated by peptide ligands and/or calcium-binding proteins, are essential for various physiological and sensory processes. The mode of activation of the GC subtype GC-G, which is expressed in neurons of the Grueneberg ganglion that respond to cool temperatures, has been elusive. In searching for appropriate stimuli to activate GC-G, we found that its enzymatic activity is directly stimulated by cool temperatures. In this context, it was observed that dimerization/oligomerization of GC-G, a process generally considered as critical for enzymatic activity of GCs, is strongly enhanced by coolness. Moreover, heterologous expression of GC-G in cultured cells rendered these cells responsive to coolness; thus, the protein might be a sensor for cool temperatures. This concept is supported by the observation of substantially reduced coolness-induced response of Grueneberg ganglion neurons and coolness-evoked ultrasonic vocalization in GC-G-deficient mouse pups. GC-G may be a novel thermosensory protein with functional implications for the Grueneberg ganglion, a sensory organ responding to cool temperatures.
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Affiliation(s)
- Ying-Chi Chao
- Molecular Medicine Program, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Chih-Cheng Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yuh-Charn Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Heinz Breer
- Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Joerg Fleischer
- Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Ruey-Bing Yang
- Molecular Medicine Program, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
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21
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A novel role for the zinc-finger transcription factor EGL-46 in the differentiation of gas-sensing neurons in Caenorhabditis elegans. Genetics 2014; 199:157-63. [PMID: 25395666 DOI: 10.1534/genetics.114.172049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Oxygen (O2) and carbon dioxide (CO2) provoke distinct olfactory behaviors via specialized sensory neurons across metazoa. In the nematode C. elegans, the BAG sensory neurons are specialized to sense changes in both O2 and CO2 levels in the environment. The precise functionality of these neurons is specified by the coexpression of a membrane-bound receptor-type guanylyl cyclase GCY-9 that is required for responses to CO2 upshifts and the soluble guanylyl cyclases GCY-31 and GCY-33 that mediate responses to downshifts in O2. Expression of these gas-sensing molecules in the BAG neurons is partially, although not completely, controlled by ETS-5, an ETS-domain-containing transcription factor, and EGL-13, a Sox transcription factor. We report here the identification of EGL-46, a zinc-finger transcription factor, which regulates BAG gas-sensing fate in partially parallel pathways to ETS-5 and EGL-13. Thereby, three conserved transcription factors collaborate to ensure neuron type-specific identity features of the BAG gas-sensing neurons.
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22
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Sharabi K, Charar C, Friedman N, Mizrahi I, Zaslaver A, Sznajder JI, Gruenbaum Y. The response to high CO2 levels requires the neuropeptide secretion component HID-1 to promote pumping inhibition. PLoS Genet 2014; 10:e1004529. [PMID: 25101962 PMCID: PMC4125093 DOI: 10.1371/journal.pgen.1004529] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 06/09/2014] [Indexed: 11/19/2022] Open
Abstract
Carbon dioxide (CO2) is a key molecule in many biological processes; however, mechanisms by which organisms sense and respond to high CO2 levels remain largely unknown. Here we report that acute CO2 exposure leads to a rapid cessation in the contraction of the pharynx muscles in Caenorhabditis elegans. To uncover the molecular mechanisms underlying this response, we performed a forward genetic screen and found that hid-1, a key component in neuropeptide signaling, regulates this inhibition in muscle contraction. Surprisingly, we found that this hid-1-mediated pathway is independent of any previously known pathways controlling CO2 avoidance and oxygen sensing. In addition, animals with mutations in unc-31 and egl-21 (neuropeptide secretion and maturation components) show impaired inhibition of muscle contraction following acute exposure to high CO2 levels, in further support of our findings. Interestingly, the observed response in the pharynx muscle requires the BAG neurons, which also mediate CO2 avoidance. This novel hid-1-mediated pathway sheds new light on the physiological effects of high CO2 levels on animals at the organism-wide level.
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Affiliation(s)
- Kfir Sharabi
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Chayki Charar
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nurit Friedman
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Inbar Mizrahi
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alon Zaslaver
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Jacob I. Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Yosef Gruenbaum
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
- * E-mail:
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23
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Abstract
Nearly all animals are capable of sensing changes in environmental oxygen (O2) and carbon dioxide (CO2) levels, which can signal the presence of food, pathogens, conspecifics, predators, or hosts. The free-living nematode Caenorhabditis elegans is a powerful model system for the study of gas sensing. C. elegans detects changes in O2 and CO2 levels and integrates information about ambient gas levels with other internal and external cues to generate context-appropriate behavioral responses. Due to its small nervous system and amenability to genetic and genomic analyses, the functional properties of its gas-sensing microcircuits can be dissected with single-cell resolution, and signaling molecules and natural genetic variations that modulate gas responses can be identified. Here, we discuss the neural basis of gas sensing in C. elegans, and highlight changes in gas-evoked behaviors in the context of other sensory cues and natural genetic variations. We also discuss gas sensing in other free-living nematodes and parasitic nematodes, focusing on how gas-sensing behavior has evolved to mediate species-specific behavioral requirements.
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Gramstrup Petersen J, Pocock R. Neuronal cell fate decisions: O2 and CO2 sensing neurons require egl-13/Sox5. WORM 2013; 2:e27284. [PMID: 24744985 DOI: 10.4161/worm.27284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2013] [Revised: 11/07/2013] [Accepted: 11/20/2013] [Indexed: 12/17/2022]
Abstract
We recently conducted a study that aimed to describe the differentiation mechanisms used to generate O2 and CO2 sensing neurons in C. elegans. We identified egl-13/Sox5 to be required for the differentiation of both O2 and CO2 sensing neurons. We found that egl-13 functions cell autonomously to drive O2 and CO2 sensing neuron fate and is therefore essential for O2 and CO2 sensing-induced behaviors. Through systematic dissection of the egl-13 promoter we identified upstream regulators of egl-13 and proposed a model of how differentiation of O2 and CO2 sensing neurons is regulated. In this commentary we discuss our findings and open questions we wish to address in future studies.
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Affiliation(s)
- Jakob Gramstrup Petersen
- Biotech Research and Innovation Centre; University of Copenhagen; Ole Maaløes Vej 5; Copenhagen, Denmark
| | - Roger Pocock
- Biotech Research and Innovation Centre; University of Copenhagen; Ole Maaløes Vej 5; Copenhagen, Denmark
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25
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Smith ESJ, Martinez-Velazquez L, Ringstad N. A chemoreceptor that detects molecular carbon dioxide. J Biol Chem 2013; 288:37071-81. [PMID: 24240097 DOI: 10.1074/jbc.m113.517367] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Animals from diverse phyla possess neurons that are activated by the product of aerobic respiration, CO2. It has long been thought that such neurons primarily detect the CO2 metabolites protons and bicarbonate. We have determined the chemical tuning of isolated CO2 chemosensory BAG neurons of the nematode Caenorhabditis elegans. We show that BAG neurons are principally tuned to detect molecular CO2, although they can be activated by acid stimuli. One component of the BAG transduction pathway, the receptor-type guanylate cyclase GCY-9, suffices to confer cellular sensitivity to both molecular CO2 and acid, indicating that it is a bifunctional chemoreceptor. We speculate that in other animals, receptors similarly capable of detecting molecular CO2 might mediate effects of CO2 on neural circuits and behavior.
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Affiliation(s)
- Ewan St John Smith
- From the Skirball Institute of Biomolecular Medicine, Molecular Neurobiology Program and Department of Cell Biology, New York University Medical Center, New York, New York 10016 and
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26
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Serrano-Saiz E, Poole RJ, Felton T, Zhang F, De La Cruz ED, Hobert O. Modular control of glutamatergic neuronal identity in C. elegans by distinct homeodomain proteins. Cell 2013; 155:659-73. [PMID: 24243022 DOI: 10.1016/j.cell.2013.09.052] [Citation(s) in RCA: 189] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 08/14/2013] [Accepted: 09/23/2013] [Indexed: 10/26/2022]
Abstract
The choice of using one of many possible neurotransmitter systems is a critical step in defining the identity of an individual neuron type. We show here that the key defining feature of glutamatergic neurons, the vesicular glutamate transporter EAT-4/VGLUT, is expressed in 38 of the 118 anatomically defined neuron classes of the C. elegans nervous system. We show that distinct cis-regulatory modules drive expression of eat-4/VGLUT in distinct glutamatergic neuron classes. We identify 13 different transcription factors, 11 of them homeodomain proteins, that act in distinct combinations in 25 different glutamatergic neuron classes to initiate and maintain eat-4/VGLUT expression. We show that the adoption of a glutamatergic phenotype is linked to the adoption of other terminal identity features of a neuron, including cotransmitter phenotypes. Examination of mouse orthologs of these homeodomain proteins resulted in the identification of mouse LHX1 as a regulator of glutamatergic neurons in the brainstem.
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Affiliation(s)
- Esther Serrano-Saiz
- Department of Biochemistry and Molecular Biophysics, HHMI, Columbia University Medical Center, New York, NY 10032, USA.
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27
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Smith HK, Luo L, O’Halloran D, Guo D, Huang XY, Samuel ADT, Hobert O. Defining specificity determinants of cGMP mediated gustatory sensory transduction in Caenorhabditis elegans. Genetics 2013; 194:885-901. [PMID: 23695300 PMCID: PMC3730918 DOI: 10.1534/genetics.113.152660] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 05/18/2013] [Indexed: 12/21/2022] Open
Abstract
Cyclic guanosine monophosphate (cGMP) is a key secondary messenger used in signal transduction in various types of sensory neurons. The importance of cGMP in the ASE gustatory receptor neurons of the nematode Caenorhabditis elegans was deduced by the observation that multiple receptor-type guanylyl cyclases (rGCs), encoded by the gcy genes, and two presently known cyclic nucleotide-gated ion channel subunits, encoded by the tax-2 and tax-4 genes, are essential for ASE-mediated gustatory behavior. We describe here specific mechanistic features of cGMP-mediated signal transduction in the ASE neurons. First, we assess the specificity of the sensory functions of individual rGC proteins. We have previously shown that multiple rGC proteins are expressed in a left/right asymmetric manner in the functionally lateralized ASE neurons and are required to sense distinct salt cues. Through domain swap experiments among three different rGC proteins, we show here that the specificity of individual rGC proteins lies in their extracellular domains and not in their intracellular, signal-transducing domains. Furthermore, we find that rGC proteins are also sufficient to confer salt sensory responses to other neurons. Both findings support the hypothesis that rGC proteins are salt receptor proteins. Second, we identify a novel, likely downstream effector of the rGC proteins in gustatory signal transduction, a previously uncharacterized cyclic nucleotide-gated (CNG) ion channel, encoded by the che-6 locus. che-6 mutants show defects in gustatory sensory transduction that are similar to defects observed in animals lacking the tax-2 and tax-4 CNG channels. In contrast, thermosensory signal transduction, which also requires tax-2 and tax-4, does not require che-6, but requires another CNG, cng-3. We propose that CHE-6 may form together with two other CNG subunits, TAX-2 and TAX-4, a gustatory neuron-specific heteromeric CNG channel complex.
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Affiliation(s)
- Heidi K. Smith
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York 10032
| | - Linjiao Luo
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138
| | - Damien O’Halloran
- Department of Biological Sciences and Institute for Neuroscience, George Washington University, Washington DC, 20037
| | - Dagang Guo
- Department of Physiology, Cornell University Weill Medical College, New York, New York 10065
| | - Xin-Yun Huang
- Department of Physiology, Cornell University Weill Medical College, New York, New York 10065
| | - Aravinthan D. T. Samuel
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138
| | - Oliver Hobert
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University Medical Center, New York, New York 10032
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138
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28
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Carrillo MA, Guillermin ML, Rengarajan S, Okubo RP, Hallem EA. O2-sensing neurons control CO2 response in C. elegans. J Neurosci 2013; 33:9675-83. [PMID: 23739964 PMCID: PMC3721734 DOI: 10.1523/jneurosci.4541-12.2013] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 04/21/2013] [Accepted: 04/27/2013] [Indexed: 11/21/2022] Open
Abstract
Sensory behaviors are often flexible, allowing animals to generate context-appropriate responses to changing environmental conditions. To investigate the neural basis of behavioral flexibility, we examined the regulation of carbon dioxide (CO2) response in the nematode Caenorhabditis elegans. CO2 is a critical sensory cue for many animals, mediating responses to food, conspecifics, predators, and hosts (Scott, 2011; Buehlmann et al., 2012; Chaisson and Hallem, 2012). In C. elegans, CO2 response is regulated by the polymorphic neuropeptide receptor NPR-1: animals with the N2 allele of npr-1 avoid CO2, whereas animals with the Hawaiian (HW) allele or an npr-1 loss-of-function (lf) mutation appear virtually insensitive to CO2 (Hallem and Sternberg, 2008; McGrath et al., 2009). Here we show that ablating the oxygen (O2)-sensing URX neurons in npr-1(lf) mutants restores CO2 avoidance, suggesting that NPR-1 enables CO2 avoidance by inhibiting URX neurons. URX was previously shown to be activated by increases in ambient O2 (Persson et al., 2009; Zimmer et al., 2009; Busch et al., 2012). We find that, in npr-1(lf) mutants, O2-induced activation of URX inhibits CO2 avoidance. Moreover, both HW and npr-1(lf) animals avoid CO2 under low O2 conditions, when URX is inactive. Our results demonstrate that CO2 response is determined by the activity of O2-sensing neurons and suggest that O2-dependent regulation of CO2 avoidance is likely to be an ecologically relevant mechanism by which nematodes navigate gas gradients.
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Affiliation(s)
- Mayra A. Carrillo
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095
| | - Manon L. Guillermin
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095
| | - Sophie Rengarajan
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095
| | - Ryo P. Okubo
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095
| | - Elissa A. Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095
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EGL-13/SoxD specifies distinct O2 and CO2 sensory neuron fates in Caenorhabditis elegans. PLoS Genet 2013; 9:e1003511. [PMID: 23671427 PMCID: PMC3650002 DOI: 10.1371/journal.pgen.1003511] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 04/03/2013] [Indexed: 11/19/2022] Open
Abstract
Animals harbor specialized neuronal systems that are used for sensing and coordinating responses to changes in oxygen (O2) and carbon dioxide (CO2). In Caenorhabditis elegans, the O2/CO2 sensory system comprises functionally and morphologically distinct sensory neurons that mediate rapid behavioral responses to exquisite changes in O2 or CO2 levels via different sensory receptors. How the diversification of the O2- and CO2-sensing neurons is established is poorly understood. We show here that the molecular identity of both the BAG (O2/CO2-sensing) and the URX (O2-sensing) neurons is controlled by the phylogenetically conserved SoxD transcription factor homolog EGL-13. egl-13 mutant animals fail to fully express the distinct terminal gene batteries of the BAG and URX neurons and, as such, are unable to mount behavioral responses to changes in O2 and CO2. We found that the expression of egl-13 is regulated in the BAG and URX neurons by two conserved transcription factors-ETS-5(Ets factor) in the BAG neurons and AHR-1(bHLH factor) in the URX neurons. In addition, we found that EGL-13 acts in partially parallel pathways with both ETS-5 and AHR-1 to direct BAG and URX neuronal fate respectively. Finally, we found that EGL-13 is sufficient to induce O2- and CO2-sensing cell fates in some cellular contexts. Thus, the same core regulatory factor, egl-13, is required and sufficient to specify the distinct fates of O2- and CO2-sensing neurons in C. elegans. These findings extend our understanding of mechanisms of neuronal diversification and the regulation of molecular factors that may be conserved in higher organisms.
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30
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Chaisson KE, Hallem EA. Chemosensory behaviors of parasites. Trends Parasitol 2012; 28:427-36. [PMID: 22921895 PMCID: PMC5663455 DOI: 10.1016/j.pt.2012.07.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 07/21/2012] [Accepted: 07/23/2012] [Indexed: 12/17/2022]
Abstract
Many multicellular parasites seek out hosts by following trails of host-emitted chemicals. Host seeking is a characteristic of endoparasites such as parasitic worms as well as of ectoparasites such as mosquitoes and ticks. For host location, many of these parasites use CO(2), a respiration byproduct, in combination with host-specific chemicals. Recent work has begun to elucidate the behavioral responses of parasites to CO(2) and other host chemicals, and to unravel the mechanisms of these responses. Here we discuss recent findings that have greatly advanced our understanding of the chemosensory behaviors of host-seeking parasites. We focus primarily on well-studied parasites such as nematodes and insects, but also note broadly relevant findings in a few less well studied parasites.
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Affiliation(s)
- Keely E Chaisson
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095, USA
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31
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Ma DK, Ringstad N. The neurobiology of sensing respiratory gases for the control of animal behavior. ACTA ACUST UNITED AC 2012; 7:246-253. [PMID: 22876258 DOI: 10.1007/s11515-012-1219-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Aerobic metabolism is fundamental for almost all animal life. Cellular consumption of oxygen (O(2)) and production of carbon dioxide (CO(2)) signal metabolic states and physiological stresses. These respiratory gases are also detected as environmental cues that can signal external food quality and the presence of prey, predators and mates. In both contexts, animal nervous systems are endowed with mechanisms for sensing O(2)/CO(2) to trigger appropriate behaviors and maintain homeostasis of internal O(2)/CO(2). Although different animal species show different behavioral responses to O(2)/CO(2), some underlying molecular mechanisms and pathways that function in the detection of respiratory gases are fundamentally similar and evolutionarily conserved. Studies of Caenorhabditis elegans and Drosophila melanogaster have identified roles for cyclic nucleotide signaling and the hypoxia inducible factor (HIF) transcriptional pathway in mediating behavioral responses to respiratory gases. Understanding how simple invertebrate nervous systems detect respiratory gases to control behavior might reveal general principles common to nematodes, insects and vertebrates that function in the molecular sensing of respiratory gases and the neural control of animal behaviors.
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Affiliation(s)
- Dengke K Ma
- Department of Biology, and McGovern Institute for Brain Research, MIT, Cambridge, MA 02139, USA
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