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Muirhead CS, Guerra S, Fox BW, Schroeder FC, Srinivasan J. Serotonergic signaling governs C. elegans sensory response to conflicting olfactory stimuli. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.03.19.644218. [PMID: 40166147 PMCID: PMC11957155 DOI: 10.1101/2025.03.19.644218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/02/2025]
Abstract
Neural circuits that consolidate sensory cues are essential for neurological functioning. Neural circuits that perform sensory integration can vary greatly because the sensory processing regions of the brain employ various neural motifs. Here, we investigate a neural circuit that mediates the response to conflicting olfactory stimuli in C. elegans . We concurrently expose animals to an aversive dispersal pheromone, osas#9, and an attractive bacterial extract. While worms usually avoid osas#9 alone, they suppress this avoidance behavior in the presence of a bacterial extract. Loss-of-function mutants and cell-specific rescues reveal that serotonergic signaling from the ADF neuron is essential for bacterial extract-induced osas#9 avoidance attenuation. The inhibitory serotonin receptor, MOD-1, which is widely expressed on interneurons and motor neurons, is required for this sensory integration, suggesting that serotonin acts in an inhibitory manner. By performing calcium imaging on the ADF neurons in synaptic signaling ( unc-13 ) and peptidergic ( unc-31 ) signaling mutant backgrounds, we show that the ADF neurons require input from other neurons, likely the ASK neurons, to respond to food extracts. We reveal a cue integration neural circuit in which serotonergic signaling at the sensory neuron level silences an aversive neural signal. Significance Animals use sensory cues to make behavioral choices and sometimes, these cues convey opposite information. The nervous system consolidates competing sensory cues to create a coherent response to external stimuli. The neural circuits that govern this process are important, and still largely unknown. We use C. elegans, a soil-dwelling nematode, to uncover a neural circuit governing the consolidation of competing cues by concurrently exposing worms to positive and negative stimuli . We find that the neurotransmitter serotonin can suppress aversive neural signals created by negative stimuli. These results show the important neurological role that serotonin plays in modulating neural signals.
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2
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Yan L, Claman A, Bode A, Collins KM. The C. elegans uv1 Neuroendocrine Cells Provide Mechanosensory Feedback of Vulval Opening. J Neurosci 2025; 45:e0678242024. [PMID: 39788737 PMCID: PMC11800740 DOI: 10.1523/jneurosci.0678-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 12/10/2024] [Accepted: 12/29/2024] [Indexed: 01/12/2025] Open
Abstract
Neuroendocrine cells react to physical, chemical, and synaptic signals originating from tissues and the nervous system, releasing hormones that regulate various body functions beyond the synapse. Neuroendocrine cells are often embedded in complex tissues making direct tests of their activation mechanisms and signaling effects difficult to study. In the nematode worm Caenorhabditis elegans, four uterine-vulval (uv1) neuroendocrine cells sit above the vulval canal next to the egg-laying circuit, releasing tyramine and neuropeptides that feedback to inhibit egg laying. We have previously shown uv1 cells are mechanically deformed during egg laying, driving uv1 Ca2+ transients. However, whether egg-laying circuit activity, vulval opening, and/or egg release triggered uv1 Ca2+ activity was unclear. Here, we show uv1 responds directly to mechanical activation. Optogenetic vulval muscle stimulation triggers uv1 Ca2+ activity following muscle contraction even in sterile animals. Direct mechanical prodding with a glass probe placed against the worm cuticle triggers robust uv1 Ca2+ activity similar to that seen during egg laying. Direct mechanical activation of uv1 cells does not require other cells in the egg-laying circuit, synaptic or peptidergic neurotransmission, or transient receptor potential vanilloid and Piezo channels. EGL-19 L-type Ca2+ channels, but not P/Q/N-type or ryanodine receptor Ca2+ channels, promote uv1 Ca2+ activity following mechanical activation. L-type channels also facilitate the coordinated activation of uv1 cells across the vulva, suggesting mechanical stimulation of one uv1 cell cross-activates the other. Our findings show how neuroendocrine cells like uv1 report on the mechanics of tissue deformation and muscle contraction, facilitating feedback to local circuits to coordinate behavior.
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Affiliation(s)
- Lijie Yan
- Department of Biology, University of Miami, Coral Gables, Florida 33143
| | - Alexander Claman
- Department of Biology, University of Miami, Coral Gables, Florida 33143
| | - Addys Bode
- Department of Biology, University of Miami, Coral Gables, Florida 33143
| | - Kevin M Collins
- Department of Biology, University of Miami, Coral Gables, Florida 33143
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3
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Chen L, Beets I, Schafer W. Two K2P Channels, TWK-46 and TWK-26 do not affect C. elegans Egg-Laying Behavior. MICROPUBLICATION BIOLOGY 2025; 2025:10.17912/micropub.biology.001477. [PMID: 39936042 PMCID: PMC11811770 DOI: 10.17912/micropub.biology.001477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2024] [Revised: 01/08/2025] [Accepted: 01/27/2025] [Indexed: 02/13/2025]
Abstract
Two-pore domain potassium channels, also known as K2P channels, play vital roles in maintaining the resting membrane potential in excitable cells, affecting a variety of physiological processes across species. The Caenorhabditis elegans ( C. elegans ) genome contains 46 different K2P-encoding genes, yet most of their functions remain unknown. Here, we have investigated the possible roles of two C. elegans K2P channel genes - twk-26 and twk-46 - that are expressed in the egg-laying neural circuit by characterizing the egg-laying behavior of null mutants generated by CRISPR/Cas9 gene editing. However, using a variety of assays, we did not observe significant differences in egg-laying behavior between twk-26 and twk-46 mutants and wild-type worms .
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Affiliation(s)
- Li Chen
- Biology, KU Leuven, Leuven, Flanders, Belgium
| | | | - William Schafer
- Biology, KU Leuven, Leuven, Flanders, Belgium
- Neurobiology, MRC Laboratory of Molecular Biology, Cambridge, England, United Kingdom
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4
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Watteyne J, Chudinova A, Ripoll-Sánchez L, Schafer WR, Beets I. Neuropeptide signaling network of Caenorhabditis elegans: from structure to behavior. Genetics 2024; 228:iyae141. [PMID: 39344922 PMCID: PMC11538413 DOI: 10.1093/genetics/iyae141] [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: 06/17/2024] [Accepted: 08/19/2024] [Indexed: 10/01/2024] Open
Abstract
Neuropeptides are abundant signaling molecules that control neuronal activity and behavior in all animals. Owing in part to its well-defined and compact nervous system, Caenorhabditis elegans has been one of the primary model organisms used to investigate how neuropeptide signaling networks are organized and how these neurochemicals regulate behavior. We here review recent work that has expanded our understanding of the neuropeptidergic signaling network in C. elegans by mapping the evolutionary conservation, the molecular expression, the receptor-ligand interactions, and the system-wide organization of neuropeptide pathways in the C. elegans nervous system. We also describe general insights into neuropeptidergic circuit motifs and the spatiotemporal range of peptidergic transmission that have emerged from in vivo studies on neuropeptide signaling. With efforts ongoing to chart peptide signaling networks in other organisms, the C. elegans neuropeptidergic connectome can serve as a prototype to further understand the organization and the signaling dynamics of these networks at organismal level.
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Affiliation(s)
- Jan Watteyne
- Department of Biology, University of Leuven, Leuven 3000, Belgium
| | | | - Lidia Ripoll-Sánchez
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
- Department of Psychiatry, Cambridge University, Cambridge CB2 0SZ, UK
| | - William R Schafer
- Department of Biology, University of Leuven, Leuven 3000, Belgium
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Isabel Beets
- Department of Biology, University of Leuven, Leuven 3000, Belgium
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5
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Lo JY, Adam KM, Garrison JL. Neuropeptide inactivation regulates egg-laying behavior to influence reproductive health in Caenorhabditis elegans. Curr Biol 2024; 34:4715-4728.e4. [PMID: 39395417 PMCID: PMC12009563 DOI: 10.1016/j.cub.2024.09.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 07/11/2024] [Accepted: 09/23/2024] [Indexed: 10/14/2024]
Abstract
Neural communication requires both fast-acting neurotransmitters and neuromodulators that function on slower timescales to communicate. Endogenous bioactive peptides, often called "neuropeptides," comprise the largest and most diverse class of neuromodulators that mediate crosstalk between the brain and peripheral tissues to regulate physiology and behaviors conserved across the animal kingdom. Neuropeptide signaling can be terminated through receptor binding and internalization or degradation by extracellular enzymes called neuropeptidases. Inactivation by neuropeptidases can shape the dynamics of signaling in vivo by specifying both the duration of signaling and the anatomic path neuropeptides can travel before they are degraded. For most neuropeptides, the identity of the relevant inactivating peptidase(s) is unknown. Here, we established a screening platform in C. elegans utilizing mass spectrometry-based peptidomics to discover neuropeptidases and simultaneously profile the in vivo specificity of these enzymes against each of more than 250 endogenous peptides. We identified NEP-2, a worm ortholog of the mammalian peptidase neprilysin-2, and demonstrated that it regulates specific neuropeptides, including those in the egg-laying circuit. We found that NEP-2 is required in muscle cells to regulate signals from neurons to modulate both behavior and health in the reproductive system. Taken together, our results demonstrate that peptidases, which are an important node of regulation in neuropeptide signaling, affect the dynamics of signaling to impact behavior, physiology, and aging.
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Affiliation(s)
- Jacqueline Y Lo
- Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
| | - Katelyn M Adam
- Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA; Leonard Davis School of Gerontology, University of Southern California, 3715 McClintock Avenue, Los Angeles, CA 90089, USA
| | - Jennifer L Garrison
- Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA; Leonard Davis School of Gerontology, University of Southern California, 3715 McClintock Avenue, Los Angeles, CA 90089, USA; Cellular and Molecular Pharmacology, University of California, San Francisco, 600 16th Street, San Francisco, CA 94158, USA; Center for Healthy Aging in Women, 8001 Redwood Boulevard, Novato, CA 94945, USA; Productive Health Global Consortium, 8001 Redwood Boulevard, Novato, CA 94945, USA.
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6
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Mignerot L, Gimond C, Bolelli L, Bouleau C, Sandjak A, Boulin T, Braendle C. Natural variation in the Caenorhabditis elegans egg-laying circuit modulates an intergenerational fitness trade-off. eLife 2024; 12:RP88253. [PMID: 38564369 PMCID: PMC10987095 DOI: 10.7554/elife.88253] [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] [Indexed: 04/04/2024] Open
Abstract
Evolutionary transitions from egg laying (oviparity) to live birth (viviparity) are common across various taxa. Many species also exhibit genetic variation in egg-laying mode or display an intermediate mode with laid eggs containing embryos at various stages of development. Understanding the mechanistic basis and fitness consequences of such variation remains experimentally challenging. Here, we report highly variable intra-uterine egg retention across 316 Caenorhabditis elegans wild strains, some exhibiting strong retention, followed by internal hatching. We identify multiple evolutionary origins of such phenotypic extremes and pinpoint underlying candidate loci. Behavioral analysis and genetic manipulation indicates that this variation arises from genetic differences in the neuromodulatory architecture of the egg-laying circuitry. We provide experimental evidence that while strong egg retention can decrease maternal fitness due to in utero hatching, it may enhance offspring protection and confer a competitive advantage. Therefore, natural variation in C. elegans egg-laying behaviour can alter an apparent trade-off between different fitness components across generations. Our findings highlight underappreciated diversity in C. elegans egg-laying behavior and shed light on its fitness consequences. This behavioral variation offers a promising model to elucidate the molecular changes in a simple neural circuit underlying evolutionary shifts between alternative egg-laying modes in invertebrates.
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Affiliation(s)
| | | | | | | | - Asma Sandjak
- Université Côte d’Azur, CNRS, Inserm, IBVNiceFrance
| | - Thomas Boulin
- Institut NeuroMyoGène, CNRS, Inserm, Université de LyonLyonFrance
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7
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Jose A, Collins K. NALCN Channels Are Not Major targets of Gα o or Gα q Modulation in the C. elegans Egg-Laying Behavior Circuit. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001065. [PMID: 38287929 PMCID: PMC10823792 DOI: 10.17912/micropub.biology.001065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 12/18/2023] [Accepted: 01/08/2024] [Indexed: 01/31/2024]
Abstract
Sodium leak channels (NALCN) are regulators of cell membrane potential. Previous studies in mammalian neurons and C. elegans have shown that Gα q and Gα o signaling antagonistically modulates NALCN activity to regulate neuron excitability and neurotransmitter release for behavior. Here, we test whether NALCNs mediate the effects of Gα q and/or Gα o signaling in the C. elegans egg-laying circuit. We find that while gain-of-function NALCN mutants exhibit hyperactive egg-laying behavior, NALCNs are not required for the effects of Gα q or Gα o signaling for egg laying. These results show that NALCNs are not major effectors of G-protein signaling for C. elegans egg-laying behavior.
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Affiliation(s)
- Ariana Jose
- Physiology & Biophysics, University of Miami, Coral Gables, Florida, United States
| | - Kevin Collins
- Biology, University of Miami, Coral Gables, Florida, United States
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8
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Prakash SJ, Van Auken KM, Hill DP, Sternberg PW. Semantic representation of neural circuit knowledge in Caenorhabditis elegans. Brain Inform 2023; 10:30. [PMID: 37947958 PMCID: PMC10638142 DOI: 10.1186/s40708-023-00208-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 09/22/2023] [Indexed: 11/12/2023] Open
Abstract
In modern biology, new knowledge is generated quickly, making it challenging for researchers to efficiently acquire and synthesise new information from the large volume of primary publications. To address this problem, computational approaches that generate machine-readable representations of scientific findings in the form of knowledge graphs have been developed. These representations can integrate different types of experimental data from multiple papers and biological knowledge bases in a unifying data model, providing a complementary method to manual review for interacting with published knowledge. The Gene Ontology Consortium (GOC) has created a semantic modelling framework that extends individual functional gene annotations to structured descriptions of causal networks representing biological processes (Gene Ontology-Causal Activity Modelling, or GO-CAM). In this study, we explored whether the GO-CAM framework could represent knowledge of the causal relationships between environmental inputs, neural circuits and behavior in the model nematode C. elegans [C. elegans Neural-Circuit Causal Activity Modelling (CeN-CAM)]. We found that, given extensions to several relevant ontologies, a wide variety of author statements from the literature about the neural circuit basis of egg-laying and carbon dioxide (CO2) avoidance behaviors could be faithfully represented with CeN-CAM. Through this process, we were able to generate generic data models for several categories of experimental results. We also discuss how semantic modelling may be used to functionally annotate the C. elegans connectome. Thus, Gene Ontology-based semantic modelling has the potential to support various machine-readable representations of neurobiological knowledge.
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Affiliation(s)
- Sharan J Prakash
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Kimberly M Van Auken
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - David P Hill
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA
| | - Paul W Sternberg
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
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9
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Prakash SJ, Van Auken KM, Hill DP, Sternberg PW. Semantic Representation of Neural Circuit Knowledge in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.28.538760. [PMID: 37162850 PMCID: PMC10168330 DOI: 10.1101/2023.04.28.538760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In modern biology, new knowledge is generated quickly, making it challenging for researchers to efficiently acquire and synthesise new information from the large volume of primary publications. To address this problem, computational approaches that generate machine-readable representations of scientific findings in the form of knowledge graphs have been developed. These representations can integrate different types of experimental data from multiple papers and biological knowledge bases in a unifying data model, providing a complementary method to manual review for interacting with published knowledge. The Gene Ontology Consortium (GOC) has created a semantic modelling framework that extends individual functional gene annotations to structured descriptions of causal networks representing biological processes (Gene Ontology Causal Activity Modelling, or GO-CAM). In this study, we explored whether the GO-CAM framework could represent knowledge of the causal relationships between environmental inputs, neural circuits and behavior in the model nematode C. elegans (C. elegans Neural Circuit Causal Activity Modelling (CeN-CAM)). We found that, given extensions to several relevant ontologies, a wide variety of author statements from the literature about the neural circuit basis of egg-laying and carbon dioxide (CO2) avoidance behaviors could be faithfully represented with CeN-CAM. Through this process, we were able to generate generic data models for several categories of experimental results. We also discuss how semantic modelling may be used to functionally annotate the C. elegans connectome. Thus, Gene Ontology-based semantic modelling has the potential to support various machine-readable representations of neurobiological knowledge.
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Affiliation(s)
- Sharan J Prakash
- 1. Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Kimberly M Van Auken
- 1. Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - David P Hill
- 2. The Jackson Laboratory, Bar Harbor, ME, 04609 USA
| | - Paul W Sternberg
- 1. Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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10
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Medrano E, Collins KM. Muscle-directed mechanosensory feedback activates egg-laying circuit activity and behavior in Caenorhabditis elegans. Curr Biol 2023; 33:2330-2339.e8. [PMID: 37236183 PMCID: PMC10280788 DOI: 10.1016/j.cub.2023.05.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 03/29/2023] [Accepted: 05/03/2023] [Indexed: 05/28/2023]
Abstract
Mechanosensory feedback of the internal reproductive state drives decisions about when and where to reproduce.1 For instance, stretch in the Drosophila reproductive tract produced by artificial distention or from accumulated eggs regulates the attraction to acetic acid to ensure optimal oviposition.2 How such mechanosensory feedback modulates neural circuits to coordinate reproductive behaviors is incompletely understood. We previously identified a stretch-dependent homeostat that regulates egg laying in Caenorhabditis elegans. Sterilized animals lacking eggs show reduced Ca2+ transient activity in the presynaptic HSN command motoneurons that drive egg-laying behavior, while animals forced to accumulate extra eggs show dramatically increased circuit activity that restores egg laying.3 Interestingly, genetic ablation or electrical silencing of the HSNs delays, but does not abolish, the onset of egg laying,3,4,5 with animals recovering vulval muscle Ca2+ transient activity upon egg accumulation.6 Using an acute gonad microinjection technique to mimic changes in pressure and stretch resulting from germline activity and egg accumulation, we find that injection rapidly stimulates Ca2+ activity in both neurons and muscles of the egg-laying circuit. Injection-induced vulval muscle Ca2+ activity requires L-type Ca2+ channels but is independent of presynaptic input. Conversely, injection-induced neural activity is disrupted in mutants lacking the vulval muscles, suggesting "bottom-up" feedback from muscles to neurons. Direct mechanical prodding activates the vulval muscles, suggesting that they are the proximal targets of the stretch-dependent stimulus. Our results show that egg-laying behavior in C. elegans is regulated by a stretch-dependent homeostat that scales postsynaptic muscle responses with egg accumulation in the uterus.
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Affiliation(s)
- Emmanuel Medrano
- Department of Biology, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146, USA
| | - Kevin M Collins
- Department of Biology, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146, USA.
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11
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Rosikon KD, Bone MC, Lawal HO. Regulation and modulation of biogenic amine neurotransmission in Drosophila and Caenorhabditis elegans. Front Physiol 2023; 14:970405. [PMID: 36875033 PMCID: PMC9978017 DOI: 10.3389/fphys.2023.970405] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 01/23/2023] [Indexed: 02/18/2023] Open
Abstract
Neurotransmitters are crucial for the relay of signals between neurons and their target. Monoamine neurotransmitters dopamine (DA), serotonin (5-HT), and histamine are found in both invertebrates and mammals and are known to control key physiological aspects in health and disease. Others, such as octopamine (OA) and tyramine (TA), are abundant in invertebrates. TA is expressed in both Caenorhabditis elegans and Drosophila melanogaster and plays important roles in the regulation of essential life functions in each organism. OA and TA are thought to act as the mammalian homologs of epinephrine and norepinephrine respectively, and when triggered, they act in response to the various stressors in the fight-or-flight response. 5-HT regulates a wide range of behaviors in C. elegans including egg-laying, male mating, locomotion, and pharyngeal pumping. 5-HT acts predominantly through its receptors, of which various classes have been described in both flies and worms. The adult brain of Drosophila is composed of approximately 80 serotonergic neurons, which are involved in modulation of circadian rhythm, feeding, aggression, and long-term memory formation. DA is a major monoamine neurotransmitter that mediates a variety of critical organismal functions and is essential for synaptic transmission in invertebrates as it is in mammals, in which it is also a precursor for the synthesis of adrenaline and noradrenaline. In C. elegans and Drosophila as in mammals, DA receptors play critical roles and are generally grouped into two classes, D1-like and D2-like based on their predicted coupling to downstream G proteins. Drosophila uses histamine as a neurotransmitter in photoreceptors as well as a small number of neurons in the CNS. C. elegans does not use histamine as a neurotransmitter. Here, we review the comprehensive set of known amine neurotransmitters found in invertebrates, and discuss their biological and modulatory functions using the vast literature on both Drosophila and C. elegans. We also suggest the potential interactions between aminergic neurotransmitters systems in the modulation of neurophysiological activity and behavior.
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Affiliation(s)
- Katarzyna D Rosikon
- Neuroscience Program, Department of Biological Sciences, Delaware State University, Dover, DE, United States
| | - Megan C Bone
- Neuroscience Program, Department of Biological Sciences, Delaware State University, Dover, DE, United States
| | - Hakeem O Lawal
- Neuroscience Program, Department of Biological Sciences, Delaware State University, Dover, DE, United States
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12
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Functional Insights into Protein Kinase A (PKA) Signaling from C. elegans. LIFE (BASEL, SWITZERLAND) 2022; 12:life12111878. [PMID: 36431013 PMCID: PMC9692727 DOI: 10.3390/life12111878] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/04/2022] [Accepted: 11/11/2022] [Indexed: 11/16/2022]
Abstract
Protein kinase A (PKA), which regulates a diverse set of biological functions downstream of cyclic AMP (cAMP), is a tetramer consisting of two catalytic subunits (PKA-C) and two regulatory subunits (PKA-R). When cAMP binds the PKA-R subunits, the PKA-C subunits are released and interact with downstream effectors. In Caenorhabditis elegans (C. elegans), PKA-C and PKA-R are encoded by kin-1 and kin-2, respectively. This review focuses on the contributions of work in C. elegans to our understanding of the many roles of PKA, including contractility and oocyte maturation in the reproductive system, lipid metabolism, physiology, mitochondrial function and lifespan, and a wide variety of behaviors. C. elegans provides a powerful genetic platform for understanding how this kinase can regulate an astounding variety of physiological responses.
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13
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Gubert G, Gubert P, Sandes JM, Bornhorst J, Alves LC, Quines CB, Mosca DH. The nanotoxicity assessment of cube-like iron nitride magnetic nanoparticles at the organismal level of nematode Caenorhabditis elegans. Nanotoxicology 2022; 16:472-483. [PMID: 35848961 DOI: 10.1080/17435390.2022.2099768] [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: 10/17/2022]
Abstract
Magnetic nanoparticles (NPs) are suitable candidates for various medical and biological applications, despite some concerns that they may have negative impacts on human health. In this study, the toxicity effects of magnetic NPs consisting of α"-Fe16N2 captured and bioaccumulated by the nematode Caenorhabditis elegans (C. elegans) in the early larval stage are evaluated. The choice of α"-Fe16N2 NPs is based on their good structural stability when stored in saline solution and high magnetic performance. The uptake and bioaccumulation of α"-Fe16N2 NPs in intestinal cells of C. elegans was evidenced by transmission electron microscopy. After exposure to NPs up to 40 mg mL-1, C. elegans larval development, survival, feeding behavior, defecation cycles, movement and reproduction were monitored. C. elegans survival and other monitored behavioral evolutions do not show significant changes, except for a slight statistical reduction in the reproductive profile. Therefore, the present results are promising and very encouraging for investigations of applications of α"-Fe16N2 NPs in the biomedical area.
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Affiliation(s)
- Greici Gubert
- Departamento de Física, Universidade Federal do Paraná, Curitiba, Brazil.,Instituto Federal Catarinense, Rio do Sul, Brazil
| | - Priscila Gubert
- Graduate Program in Pure and Applied Chemistry, POSQUIPA. Federal University of Western Bahia, Barreiras, Brazil.,Immunopathology Laboratory Keizo Asami, LIKA. Federal University of Pernambuco, Recife, Brazil
| | - Jana Messias Sandes
- Immunopathology Laboratory Keizo Asami, LIKA. Federal University of Pernambuco, Recife, Brazil
| | - Julia Bornhorst
- Department of Food Chemistry, Institute of Nutritional Science, University of Potsdam, Nuthetal, Germany.,Food Chemistry, Faculty of Mathematics and Natural Sciences, University of Wuppertal, Wuppertal, Germany
| | - Luiz Carlos Alves
- Oswaldo Cruz Foundation, Aggeu Magalhães Institute, Department of Virology and Experimental Therapy, Recife, Brazil
| | - Caroline Brandão Quines
- Postgraduating Program in Biochemistry, Federal University of Pampa (UNIPAMPA), Uruguaiana, Brazil
| | - Dante Homero Mosca
- Departamento de Física, Universidade Federal do Paraná, Curitiba, Brazil
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14
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Dhakal P, Chaudhry SI, Signorelli R, Collins KM. Serotonin signals through postsynaptic Gαq, Trio RhoGEF, and diacylglycerol to promote Caenorhabditis elegans egg-laying circuit activity and behavior. Genetics 2022; 221:iyac084. [PMID: 35579369 PMCID: PMC9252285 DOI: 10.1093/genetics/iyac084] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/26/2022] [Indexed: 11/12/2022] Open
Abstract
Activated Gαq signals through phospholipase-Cβ and Trio, a Rho GTPase exchange factor (RhoGEF), but how these distinct effector pathways promote cellular responses to neurotransmitters like serotonin remains poorly understood. We used the egg-laying behavior circuit of Caenorhabditis elegans to determine whether phospholipase-Cβ and Trio mediate serotonin and Gαq signaling through independent or related biochemical pathways. Our genetic rescue experiments suggest that phospholipase-Cβ functions in neurons while Trio Rho GTPase exchange factor functions in both neurons and the postsynaptic vulval muscles. While Gαq, phospholipase-Cβ, and Trio Rho GTPase exchange factor mutants fail to lay eggs in response to serotonin, optogenetic stimulation of the serotonin-releasing HSN neurons restores egg laying only in phospholipase-Cβ mutants. Phospholipase-Cβ mutants showed vulval muscle Ca2+ transients while strong Gαq and Trio Rho GTPase exchange factor mutants had little or no vulval muscle Ca2+ activity. Treatment with phorbol 12-myristate 13-acetate that mimics 1,2-diacylglycerol, a product of PIP2 hydrolysis, rescued egg-laying circuit activity and behavior defects of Gαq signaling mutants, suggesting both phospholipase-C and Rho signaling promote synaptic transmission and egg laying via modulation of 1,2-diacylglycerol levels. 1,2-Diacylglycerol activates effectors including UNC-13; however, we find that phorbol esters, but not serotonin, stimulate egg laying in unc-13 and phospholipase-Cβ mutants. These results support a model where serotonin signaling through Gαq, phospholipase-Cβ, and UNC-13 promotes neurotransmitter release, and that serotonin also signals through Gαq, Trio Rho GTPase exchange factor, and an unidentified, phorbol 12-myristate 13-acetate-responsive effector to promote postsynaptic muscle excitability. Thus, the same neuromodulator serotonin can signal in distinct cells and effector pathways to coordinate activation of a motor behavior circuit.
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Affiliation(s)
- Pravat Dhakal
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA
| | - Sana I Chaudhry
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA
| | | | - Kevin M Collins
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA
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15
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Widaad A, Zulkipli IN, Petalcorin MIR. Anthelmintic Effect of Leucaena leucocephala Extract and Its Active Compound, Mimosine, on Vital Behavioral Activities in Caenorhabditis elegans. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27061875. [PMID: 35335240 PMCID: PMC8950933 DOI: 10.3390/molecules27061875] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/22/2022] [Accepted: 03/07/2022] [Indexed: 12/03/2022]
Abstract
Helminth infections continue to be a neglected global threat in tropical regions, and there have been growing cases of anthelmintic resistance reported towards the existing anthelmintic drugs. Thus, the search for a novel anthelmintic agent has been increasing, especially those derived from plants. Leucaena leucocephala (LL) is a leguminous plant that is known to have several pharmacological activities, including anthelmintic activity. It is widely known to contain a toxic compound called mimosine, which we believed could be a potential lead candidate that could exert a potent anthelmintic effect. Hence, this study aimed to validate the presence of mimosine in LL extract and to investigate the anthelmintic effect of LL extract and mimosine on head thrashing, egg-laying, and pharyngeal pumping activities using the animal model Caenorhabditis elegans (C. elegans). Mimosine content in LL extract was confirmed through an HPLC analysis of spiking LL extract with different mimosine concentrations, whereby an increasing trend in peak heights was observed at a retention time of 0.9 min. LL extract and mimosine caused a significant dose-dependent increase in the percentage of worm mortality, which produced LC50s of 73 mg/mL and 6.39 mg/mL, respectively. Exposure of C. elegans to different concentrations of LL extract and mimosine significantly decreased the head thrashing, egg-laying, and mean pump amplitude of pharyngeal pumping activity. We speculated that these behavioral changes are due to the inhibitory effect of LL extract and mimosine on an L-type calcium channel called EGL-19. Our findings provide evidential support for the potential of LL extract and its active compound, mimosine, as novel anthelmintic candidates. However, the underlying mechanism of the anthelmintic action has yet to be elucidated.
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16
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Ravi B, Zhao J, Chaudhry I, Signorelli R, Bartole M, Kopchock RJ, Guijarro C, Kaplan JM, Kang L, Collins KM. Presynaptic Gαo (GOA-1) signals to depress command neuron excitability and allow stretch-dependent modulation of egg laying in Caenorhabditis elegans. Genetics 2021; 218:6284136. [PMID: 34037773 DOI: 10.1093/genetics/iyab080] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 05/18/2021] [Indexed: 12/29/2022] Open
Abstract
Egg laying in the nematode worm Caenorhabditis elegans is a two-state behavior modulated by internal and external sensory input. We have previously shown that homeostatic feedback of embryo accumulation in the uterus regulates bursting activity of the serotonergic HSN command neurons that sustains the egg-laying active state. How sensory feedback of egg release signals to terminate the egg-laying active state is less understood. We find that Gαo, a conserved Pertussis Toxin-sensitive G protein, signals within HSN to inhibit egg-laying circuit activity and prevent entry into the active state. Gαo signaling hyperpolarizes HSN, reducing HSN Ca2+ activity and input onto the postsynaptic vulval muscles. Loss of inhibitory Gαo signaling uncouples presynaptic HSN activity from a postsynaptic, stretch-dependent homeostat, causing precocious entry into the egg-laying active state when only a few eggs are present in the uterus. Feedback of vulval opening and egg release activates the uv1 neuroendocrine cells which release NLP-7 neuropeptides which signal to inhibit egg laying through Gαo-independent mechanisms in the HSNs and Gαo-dependent mechanisms in cells other than the HSNs. Thus, neuropeptide and inhibitory Gαo signaling maintains a bi-stable state of electrical excitability that dynamically controls circuit activity in response to both external and internal sensory input to drive a two-state behavior output.
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Affiliation(s)
- Bhavya Ravi
- Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL USA 33136.,Department of Biology, University of Miami, Coral Gables, FL USA 33146
| | - Jian Zhao
- Department of Neuroscience, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Department of Molecular Biology, Massachusetts General Hospital, Boston, MA USA 02114
| | - I Chaudhry
- Department of Biology, University of Miami, Coral Gables, FL USA 33146
| | | | - Mattingly Bartole
- Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL USA 33136.,Department of Biology, University of Miami, Coral Gables, FL USA 33146
| | | | | | - Joshua M Kaplan
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA USA 02114
| | - Lijun Kang
- Department of Neuroscience, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Kevin M Collins
- Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL USA 33136.,Department of Biology, University of Miami, Coral Gables, FL USA 33146
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17
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Durbeck J, Breton C, Suter M, Luth ES, McGehee AM. The Doublesex/Mab-3 domain transcription factor DMD-10 regulates ASH-dependent behavioral responses. PeerJ 2021; 9:e10892. [PMID: 33665029 PMCID: PMC7916532 DOI: 10.7717/peerj.10892] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 01/12/2021] [Indexed: 12/28/2022] Open
Abstract
The Doublesex/Mab-3 Domain transcription factor DMD-10 is expressed in several cell types in C. elegans, including in the nervous system. We sought to investigate whether DMD-10 is required for normal neuronal function using behavioral assays. We found that mutation of dmd-10 did not broadly affect behavior. dmd-10 mutants were normal in several behavioral assays including a body bends assay for locomotion, egg laying, chemotaxis and response to gentle touch to the body. dmd-10 mutants did have defects in nose-touch responsiveness, which requires the glutamate receptor GLR-1. However, using quantitative fluorescence microscopy to measure levels of a GLR-1::GFP fusion protein in the ventral nerve cord, we found no evidence supporting a difference in the number of GLR-1 synapses or in the amount of GLR-1 present in dmd-10 mutants. dmd-10 mutants did have decreased responsiveness to high osmolarity, which, along with nose-touch, is sensed by the polymodal sensory neuron ASH. Furthermore, mutation of dmd-10 impaired behavioral response to optogenetic activation of ASH, suggesting that dmd-10 promotes neuronal signaling in ASH downstream of sensory receptor activation. Together our results suggest that DMD-10 is important in regulating the frequency of multiple ASH-dependent behavioral responses.
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Affiliation(s)
- Julia Durbeck
- Biology Department, Suffolk University, Boston, MA, USA
| | - Celine Breton
- Department of Biology, Simmons University, Boston, MA, USA
| | - Michael Suter
- Biology Department, Suffolk University, Boston, MA, USA
| | - Eric S Luth
- Department of Biology, Simmons University, Boston, MA, USA
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18
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Chen YC, Seyedsayamdost MR, Ringstad N. A microbial metabolite synergizes with endogenous serotonin to trigger C. elegans reproductive behavior. Proc Natl Acad Sci U S A 2020; 117:30589-30598. [PMID: 33199611 PMCID: PMC7720207 DOI: 10.1073/pnas.2017918117] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Natural products are a major source of small-molecule therapeutics, including those that target the nervous system. We have used a simple serotonin-dependent behavior of the roundworm Caenorhabditis elegans, egg laying, to perform a behavior-based screen for natural products that affect serotonin signaling. Our screen yielded agonists of G protein-coupled serotonin receptors, protein kinase C agonists, and a microbial metabolite not previously known to interact with serotonin signaling pathways: the disulfide-bridged 2,5-diketopiperazine gliotoxin. Effects of gliotoxin on egg-laying behavior required the G protein-coupled serotonin receptors SER-1 and SER-7, and the Gq ortholog EGL-30. Furthermore, mutants lacking serotonergic neurons and mutants that cannot synthesize serotonin were profoundly resistant to gliotoxin. Exogenous serotonin restored their sensitivity to gliotoxin, indicating that this compound synergizes with endogenous serotonin to elicit behavior. These data show that a microbial metabolite with no structural similarity to known serotonergic agonists potentiates an endogenous serotonin signal to affect behavior. Based on this study, we suggest that microbial metabolites are a rich source of functionally novel neuroactive molecules.
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Affiliation(s)
- Yen-Chih Chen
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016
| | | | - Niels Ringstad
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016;
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016
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19
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Signal Decoding for Glutamate Modulating Egg Laying Oppositely in Caenorhabditis elegans under Varied Environmental Conditions. iScience 2020; 23:101588. [PMID: 33089099 PMCID: PMC7567941 DOI: 10.1016/j.isci.2020.101588] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 08/07/2020] [Accepted: 09/16/2020] [Indexed: 11/24/2022] Open
Abstract
Animals' ability to sense environmental cues and to integrate this information to control fecundity is vital for continuing the species lineage. In this study, we observed that the sensory neurons Amphid neuron (ASHs and ADLs) differentially regulate egg-laying behavior in Caenorhabditis elegans under varied environmental conditions via distinct neuronal circuits. Under standard culture conditions, ASHs tonically release a small amount of glutamate and inhibit Hermaphrodite specific motor neuron (HSN) activities and egg laying via a highly sensitive Glutamate receptor (GLR)-5 receptor. In contrast, under Cu2+ stimulation, ASHs and ADLs may release a large amount of glutamate and inhibit Amphid interneuron (AIA) interneurons via low-sensitivity Glutamate-gated chloride channel (GLC)-3 receptor, thus removing the inhibitory roles of AIAs on HSN activity and egg laying. However, directly measuring the amount of glutamate released by sensory neurons under different conditions and assaying the binding kinetics of receptors with the neurotransmitter are still required to support this study directly. Short-term exposure of CuSO4 evokes hyperactive egg laying ASHs inhibit HSNs and egg laying via GLR-5 receptor under no Cu2+ treatment AIA interneurons suppress HSNs and thus egg laying through ACR-14 signaling Under noxious Cu2+ treatment, ASHs and ADLs suppress AIAs and augment egg laying
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20
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Weiss AKH, Albertini E, Holzknecht M, Cappuccio E, Dorigatti I, Krahbichler A, Damisch E, Gstach H, Jansen-Dürr P. Regulation of cellular senescence by eukaryotic members of the FAH superfamily - A role in calcium homeostasis? Mech Ageing Dev 2020; 190:111284. [PMID: 32574647 PMCID: PMC7116474 DOI: 10.1016/j.mad.2020.111284] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 05/29/2020] [Accepted: 06/04/2020] [Indexed: 01/04/2023]
Abstract
Fumarylacetoacetate hydrolase (FAH) superfamily members are commonly expressed in the prokaryotic kingdom, where they take part in the committing steps of degradation pathways of complex carbon sources. Besides FAH itself, the only described FAH superfamily members in the eukaryotic kingdom are fumarylacetoacetate hydrolase domain containing proteins (FAHD) 1 and 2, that have been a focus of recent work in aging research. Here, we provide a review of current knowledge on FAHD proteins. Of those, FAHD1 has recently been described as a regulator of mitochondrial function and senescence, in the context of mitochondrial dysfunction associated senescence (MiDAS). This work further describes data based on bioinformatics analysis, 3D structure comparison and sequence alignment, that suggests a putative role of FAHD proteins as calcium binding proteins.
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Affiliation(s)
- Alexander K H Weiss
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria.
| | - Eva Albertini
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
| | - Max Holzknecht
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
| | - Elia Cappuccio
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
| | - Ilaria Dorigatti
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
| | - Anna Krahbichler
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
| | - Elisabeth Damisch
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
| | - Hubert Gstach
- University of Vienna, UZ2 E349, Department of Pharmaceutical Chemistry, Faculty of Life Sciences, Althanstrasse 14, 1090, Vienna, Austria
| | - Pidder Jansen-Dürr
- University of Innsbruck, Research Institute for Biomedical Aging Research, Rennweg 10, A-6020, Innsbruck, Austria; University of Innsbruck, Center for Molecular Biosciences Innsbruck (CMBI), Austria
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21
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Cellular Expression and Functional Roles of All 26 Neurotransmitter GPCRs in the C. elegans Egg-Laying Circuit. J Neurosci 2020; 40:7475-7488. [PMID: 32847964 DOI: 10.1523/jneurosci.1357-20.2020] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 07/28/2020] [Accepted: 08/13/2020] [Indexed: 01/06/2023] Open
Abstract
Maps of the synapses made and neurotransmitters released by all neurons in model systems, such as Caenorhabditis elegans have left still unresolved how neural circuits integrate and respond to neurotransmitter signals. Using the egg-laying circuit of C. elegans as a model, we mapped which cells express each of the 26 neurotransmitter GPCRs of this organism and also genetically analyzed the functions of all 26 GPCRs. We found that individual neurons express many distinct receptors, epithelial cells often express neurotransmitter receptors, and receptors are often positioned to receive extrasynaptic signals. Receptor knockouts reveal few egg-laying defects under standard laboratory conditions, suggesting that the receptors function redundantly or regulate egg-laying only in specific conditions; however, increasing receptor signaling through overexpression more efficiently reveals receptor functions. This map of neurotransmitter GPCR expression and function in the egg-laying circuit provides a model for understanding GPCR signaling in other neural circuits.SIGNIFICANCE STATEMENT Neurotransmitters signal through GPCRs to modulate activity of neurons, and changes in such signaling can underlie conditions such as depression and Parkinson's disease. To determine how neurotransmitter GPCRs together help regulate function of a neural circuit, we analyzed the simple egg-laying circuit in the model organism C. elegans We identified all the cells that express every neurotransmitter GPCR and genetically analyzed how each GPCR affects the behavior the circuit produces. We found that many neurotransmitter GPCRs are expressed in each neuron, that neurons also appear to use these receptors to communicate with other cell types, and that GPCRs appear to often act redundantly or only under specific conditions to regulate circuit function.
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22
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Esse R, Grishok A. Caenorhabditis elegans Deficient in DOT-1.1 Exhibit Increases in H3K9me2 at Enhancer and Certain RNAi-Regulated Regions. Cells 2020; 9:cells9081846. [PMID: 32781660 PMCID: PMC7464606 DOI: 10.3390/cells9081846] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 01/06/2023] Open
Abstract
The methylation of histone H3 at lysine 79 is a feature of open chromatin. It is deposited by the conserved histone methyltransferase DOT1. Recently, DOT1 localization and H3K79 methylation (H3K79me) have been correlated with enhancers in C. elegans and mammalian cells. Since earlier research implicated H3K79me in preventing heterochromatin formation both in yeast and leukemic cells, we sought to inquire whether a H3K79me deficiency would lead to higher levels of heterochromatic histone modifications, specifically H3K9me2, at developmental enhancers in C. elegans. Therefore, we used H3K9me2 ChIP-seq to compare its abundance in control and dot-1.1 loss-of-function mutant worms, as well as in rde-4; dot-1.1 and rde-1; dot-1.1 double mutants. The rde-1 and rde-4 genes are components of the RNAi pathway in C. elegans, and RNAi is known to initiate H3K9 methylation in many organisms, including C. elegans. We have previously shown that dot-1.1(-) lethality is rescued by rde-1 and rde-4 loss-of-function. Here we found that H3K9me2 was elevated in enhancer, but not promoter, regions bound by the DOT-1.1/ZFP-1 complex in dot-1.1(-) worms. We also found increased H3K9me2 at genes targeted by the ALG-3/4-dependent small RNAs and repeat regions. Our results suggest that ectopic H3K9me2 in dot-1.1(-) could, in some cases, be induced by small RNAs.
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23
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Castaneda PG, Cecchetelli AD, Pettit HN, Cram EJ. Gα/GSA-1 works upstream of PKA/KIN-1 to regulate calcium signaling and contractility in the Caenorhabditis elegans spermatheca. PLoS Genet 2020; 16:e1008644. [PMID: 32776941 PMCID: PMC7444582 DOI: 10.1371/journal.pgen.1008644] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 08/20/2020] [Accepted: 06/29/2020] [Indexed: 11/18/2022] Open
Abstract
Correct regulation of cell contractility is critical for the function of many biological systems. The reproductive system of the hermaphroditic nematode C. elegans contains a contractile tube of myoepithelial cells known as the spermatheca, which stores sperm and is the site of oocyte fertilization. Regulated contraction of the spermatheca pushes the embryo into the uterus. Cell contractility in the spermatheca is dependent on actin and myosin and is regulated, in part, by Ca2+ signaling through the phospholipase PLC-1, which mediates Ca2+ release from the endoplasmic reticulum. Here, we describe a novel role for GSA-1/Gαs, and protein kinase A, composed of the catalytic subunit KIN-1/PKA-C and the regulatory subunit KIN-2/PKA-R, in the regulation of Ca2+ release and contractility in the C. elegans spermatheca. Without GSA-1/Gαs or KIN-1/PKA-C, Ca2+ is not released, and oocytes become trapped in the spermatheca. Conversely, when PKA is activated through either a gain of function allele in GSA-1 (GSA-1(GF)) or by depletion of KIN-2/PKA-R, the transit times and total numbers, although not frequencies, of Ca2+ pulses are increased, and Ca2+ propagates across the spermatheca even in the absence of oocyte entry. In the spermathecal-uterine valve, loss of GSA-1/Gαs or KIN-1/PKA-C results in sustained, high levels of Ca2+ and a loss of coordination between the spermathecal bag and sp-ut valve. Additionally, we show that depleting phosphodiesterase PDE-6 levels alters contractility and Ca2+ dynamics in the spermatheca, and that the GPB-1 and GPB-2 Gβ subunits play a central role in regulating spermathecal contractility and Ca2+ signaling. This work identifies a signaling network in which Ca2+ and cAMP pathways work together to coordinate spermathecal contractions for successful ovulations.
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Affiliation(s)
- Perla G. Castaneda
- Department of Biology, Northeastern University, Boston, MA, United States
| | | | - Hannah N. Pettit
- Department of Biology, Northeastern University, Boston, MA, United States
| | - Erin J. Cram
- Department of Biology, Northeastern University, Boston, MA, United States
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24
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Bouagnon AD, Lin L, Srivastava S, Liu CC, Panda O, Schroeder FC, Srinivasan S, Ashrafi K. Intestinal peroxisomal fatty acid β-oxidation regulates neural serotonin signaling through a feedback mechanism. PLoS Biol 2019; 17:e3000242. [PMID: 31805041 PMCID: PMC6917301 DOI: 10.1371/journal.pbio.3000242] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 12/17/2019] [Accepted: 11/15/2019] [Indexed: 02/02/2023] Open
Abstract
The ability to coordinate behavioral responses with metabolic status is fundamental to the maintenance of energy homeostasis. In numerous species including Caenorhabditis elegans and mammals, neural serotonin signaling regulates a range of food-related behaviors. However, the mechanisms that integrate metabolic information with serotonergic circuits are poorly characterized. Here, we identify metabolic, molecular, and cellular components of a circuit that links peripheral metabolic state to serotonin-regulated behaviors in C. elegans. We find that blocking the entry of fatty acyl coenzyme As (CoAs) into peroxisomal β-oxidation in the intestine blunts the effects of neural serotonin signaling on feeding and egg-laying behaviors. Comparative genomics and metabolomics revealed that interfering with intestinal peroxisomal β-oxidation results in a modest global transcriptional change but significant changes to the metabolome, including a large number of changes in ascaroside and phospholipid species, some of which affect feeding behavior. We also identify body cavity neurons and an ether-a-go-go (EAG)-related potassium channel that functions in these neurons as key cellular components of the circuitry linking peripheral metabolic signals to regulation of neural serotonin signaling. These data raise the possibility that the effects of serotonin on satiety may have their origins in feedback, homeostatic metabolic responses from the periphery.
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Affiliation(s)
- Aude D. Bouagnon
- Department of Physiology, University of California San Francisco, San Francisco, California, United States of America
| | - Lin Lin
- Department of Physiology, University of California San Francisco, San Francisco, California, United States of America
| | - Shubhi Srivastava
- Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California, United States of America
| | - Chung-Chih Liu
- Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California, United States of America
| | - Oishika Panda
- Boyce Thompson Institute, Cornell University, Ithaca, New York, United States of America
| | - Frank C. Schroeder
- Boyce Thompson Institute, Cornell University, Ithaca, New York, United States of America
| | - Supriya Srinivasan
- Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California, United States of America
| | - Kaveh Ashrafi
- Department of Physiology, University of California San Francisco, San Francisco, California, United States of America
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25
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Barr MM, García LR, Portman DS. Sexual Dimorphism and Sex Differences in Caenorhabditis elegans Neuronal Development and Behavior. Genetics 2018; 208:909-935. [PMID: 29487147 PMCID: PMC5844341 DOI: 10.1534/genetics.117.300294] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 01/05/2018] [Indexed: 01/05/2023] Open
Abstract
As fundamental features of nearly all animal species, sexual dimorphisms and sex differences have particular relevance for the development and function of the nervous system. The unique advantages of the nematode Caenorhabditis elegans have allowed the neurobiology of sex to be studied at unprecedented scale, linking ultrastructure, molecular genetics, cell biology, development, neural circuit function, and behavior. Sex differences in the C. elegans nervous system encompass prominent anatomical dimorphisms as well as differences in physiology and connectivity. The influence of sex on behavior is just as diverse, with biological sex programming innate sex-specific behaviors and modifying many other aspects of neural circuit function. The study of these differences has provided important insights into mechanisms of neurogenesis, cell fate specification, and differentiation; synaptogenesis and connectivity; principles of circuit function, plasticity, and behavior; social communication; and many other areas of modern neurobiology.
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Affiliation(s)
- Maureen M Barr
- Department of Genetics, Rutgers University, Piscataway, New Jersey 08854-8082
| | - L Rene García
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258
| | - Douglas S Portman
- Department of Biomedical Genetics, University of Rochester, New York 14642
- Department of Neuroscience, University of Rochester, New York 14642
- Department of Biology, University of Rochester, New York 14642
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Ravi B, Nassar LM, Kopchock RJ, Dhakal P, Scheetz M, Collins KM. Ratiometric Calcium Imaging of Individual Neurons in Behaving Caenorhabditis Elegans. J Vis Exp 2018. [PMID: 29443112 PMCID: PMC5912386 DOI: 10.3791/56911] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
It has become increasingly clear that neural circuit activity in behaving animals differs substantially from that seen in anesthetized or immobilized animals. Highly sensitive, genetically encoded fluorescent reporters of Ca2+ have revolutionized the recording of cell and synaptic activity using non-invasive optical approaches in behaving animals. When combined with genetic and optogenetic techniques, the molecular mechanisms that modulate cell and circuit activity during different behavior states can be identified. Here we describe methods for ratiometric Ca2+ imaging of single neurons in freely behaving Caenorhabditis elegans worms. We demonstrate a simple mounting technique that gently overlays worms growing on a standard Nematode Growth Media (NGM) agar block with a glass coverslip, permitting animals to be recorded at high-resolution during unrestricted movement and behavior. With this technique, we use the sensitive Ca2+ reporter GCaMP5 to record changes in intracellular Ca2+ in the serotonergic Hermaphrodite Specific Neurons (HSNs) as they drive egg-laying behavior. By co-expressing mCherry, a Ca2+-insensitive fluorescent protein, we can track the position of the HSN within ~ 1 µm and correct for fluctuations in fluorescence caused by changes in focus or movement. Simultaneous, infrared brightfield imaging allows for behavior recording and animal tracking using a motorized stage. By integrating these microscopic techniques and data streams, we can record Ca2+ activity in the C. elegans egg-laying circuit as it progresses between inactive and active behavior states over tens of minutes.
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Affiliation(s)
- Bhavya Ravi
- Neuroscience Program, University of Miami School of Medicine
| | - Layla M Nassar
- Neuroscience Program, University of Miami School of Medicine; Department of Biology, University of Miami
| | | | | | | | - Kevin M Collins
- Neuroscience Program, University of Miami School of Medicine; Department of Biology, University of Miami;
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Hakim A, Mor Y, Toker IA, Levine A, Neuhof M, Markovitz Y, Rechavi O. WorMachine: machine learning-based phenotypic analysis tool for worms. BMC Biol 2018; 16:8. [PMID: 29338709 PMCID: PMC5769209 DOI: 10.1186/s12915-017-0477-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 12/21/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Caenorhabditis elegans nematodes are powerful model organisms, yet quantification of visible phenotypes is still often labor-intensive, biased, and error-prone. We developed WorMachine, a three-step MATLAB-based image analysis software that allows (1) automated identification of C. elegans worms, (2) extraction of morphological features and quantification of fluorescent signals, and (3) machine learning techniques for high-level analysis. RESULTS We examined the power of WorMachine using five separate representative assays: supervised classification of binary-sex phenotype, scoring continuous-sexual phenotypes, quantifying the effects of two different RNA interference treatments, and measuring intracellular protein aggregation. CONCLUSIONS WorMachine is suitable for analysis of a variety of biological questions and provides an accurate and reproducible analysis tool for measuring diverse phenotypes. It serves as a "quick and easy," convenient, high-throughput, and automated solution for nematode research.
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Affiliation(s)
- Adam Hakim
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
| | - Yael Mor
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
- Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
| | - Itai Antoine Toker
- Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Amir Levine
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada (IMRIC), School of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Moran Neuhof
- Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yishai Markovitz
- Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Oded Rechavi
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
- Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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Jackson MDB, Duran-Nebreda S, Bassel GW. Network-based approaches to quantify multicellular development. J R Soc Interface 2017; 14:20170484. [PMID: 29021161 PMCID: PMC5665831 DOI: 10.1098/rsif.2017.0484] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 09/14/2017] [Indexed: 12/26/2022] Open
Abstract
Multicellularity and cellular cooperation confer novel functions on organs following a structure-function relationship. How regulated cell migration, division and differentiation events generate cellular arrangements has been investigated, providing insight into the regulation of genetically encoded patterning processes. Much less is known about the higher-order properties of cellular organization within organs, and how their functional coordination through global spatial relations shape and constrain organ function. Key questions to be addressed include: why are cells organized in the way they are? What is the significance of the patterns of cellular organization selected for by evolution? What other configurations are possible? These may be addressed through a combination of global cellular interaction mapping and network science to uncover the relationship between organ structure and function. Using this approach, global cellular organization can be discretized and analysed, providing a quantitative framework to explore developmental processes. Each of the local and global properties of integrated multicellular systems can be analysed and compared across different tissues and models in discrete terms. Advances in high-resolution microscopy and image analysis continue to make cellular interaction mapping possible in an increasing variety of biological systems and tissues, broadening the further potential application of this approach. Understanding the higher-order properties of complex cellular assemblies provides the opportunity to explore the evolution and constraints of cell organization, establishing structure-function relationships that can guide future organ design.
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Affiliation(s)
| | | | - George W Bassel
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
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Banerjee N, Bhattacharya R, Gorczyca M, Collins KM, Francis MM. Local neuropeptide signaling modulates serotonergic transmission to shape the temporal organization of C. elegans egg-laying behavior. PLoS Genet 2017; 13:e1006697. [PMID: 28384151 PMCID: PMC5398689 DOI: 10.1371/journal.pgen.1006697] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 04/20/2017] [Accepted: 03/15/2017] [Indexed: 11/18/2022] Open
Abstract
Animal behaviors are often composed of distinct alternating behavioral states. Neuromodulatory signals are thought to be critical for establishing stable behavioral states and for orchestrating transitions between them. However, we have only a limited understanding of how neuromodulatory systems act in vivo to alter circuit performance and shape behavior. To address these questions, we have investigated neuromodulatory signaling in the context of Caenorhabditis elegans egg-laying. Egg-laying activity cycles between discrete states-short bursts of egg deposition (active phases) that alternate with prolonged quiescent periods (inactive phases). Here using genetic, pharmacological and optogenetic approaches for cell-specific activation and inhibition, we show that a group of neurosecretory cells (uv1) located in close spatial proximity to the egg-laying neuromusculature direct the temporal organization of egg-laying by prolonging the duration of inactive phases. We demonstrate that the modulatory effects of the uv1 cells are mediated by peptides encoded by the nlp-7 and flp-11 genes that act locally to inhibit circuit activity, primarily by inhibiting vesicular release of serotonin from HSN motor neurons. This peptidergic inhibition is achieved, at least in part, by reducing synaptic vesicle abundance in the HSN motor neurons. By linking the in vivo actions of specific neuropeptide signaling systems with the generation of stable behavioral outcomes, our study reveals how cycles of neuromodulation emanating from non-neuronal cells can fundamentally shape the organization of a behavioral program.
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Affiliation(s)
- Navonil Banerjee
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA United States of America
| | - Raja Bhattacharya
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA United States of America
| | - Michael Gorczyca
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA United States of America
| | - Kevin M. Collins
- Department of Biology, University of Miami, Coral Gables, FL United States of America
| | - Michael M. Francis
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA United States of America
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Ardeshiri R, Rezai P. Lab-on-chips for manipulation of small-scale organisms to facilitate imaging of neurons and organs. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:5749-5752. [PMID: 28269560 DOI: 10.1109/embc.2016.7592033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Caenorhabditis elegans (C. elegans) and Drosophila melanogaster (D. melanogaster) are widely-used model organisms for neurological and cardiac studies due to their simple neuronal (302 neurons in C. elegans) and cardiac (simple tubular organ in D. melanogaster) systems. However, their small sizes and continuous mobility impede their precise and timely manipulation, hence, limiting the assays that can be done using conventional manual methods. This has resulted in a need for technologies that allow multidirectional manipulation of model organisms to enable studies on target neurons and organs throughout the body. By integration of rotatable glass capillaries with pneumatic suction into microfluidic devices, we propose novel Lab-on-Chips for multi-directional manipulation and imaging of small organisms. These hybrid Lab-on-Chips can facilitate the processes of animal handling and stimuli control, using modules for single-organism selection, orientation, imaging and chemical stimulation. We show the applications of these hybrid microdevices in manipulating C. elegans for neuronal imaging (neuron-level assay) or D. melanogaster for heart screening (organ level assay). These devices can enhance the throughput of biological assays on whole-organisms and find their applications in drug discovery and toxicology.
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31
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Wang J, Luo J, Aryal DK, Wetsel WC, Nass R, Benovic JL. G protein-coupled receptor kinase-2 (GRK-2) regulates serotonin metabolism through the monoamine oxidase AMX-2 in Caenorhabditis elegans. J Biol Chem 2017; 292:5943-5956. [PMID: 28213524 DOI: 10.1074/jbc.m116.760850] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 02/15/2017] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors (GPCRs) regulate many animal behaviors. GPCR signaling is mediated by agonist-promoted interactions of GPCRs with heterotrimeric G proteins, GPCR kinases (GRKs), and arrestins. To further elucidate the role of GRKs in regulating GPCR-mediated behaviors, we utilized the genetic model system Caenorhabditis elegans Our studies demonstrate that grk-2 loss-of-function strains are egg laying-defective and contain low levels of serotonin (5-HT) and high levels of the 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA). The egg laying defect could be rescued by the expression of wild type but not by catalytically inactive grk-2 or by the selective expression of grk-2 in hermaphrodite-specific neurons. The addition of 5-HT or inhibition of 5-HT metabolism also rescued the egg laying defect. Furthermore, we demonstrate that AMX-2 is the primary monoamine oxidase that metabolizes 5-HT in C. elegans, and we also found that grk-2 loss-of-function strains have abnormally high levels of AMX-2 compared with wild-type nematodes. Interestingly, GRK-2 was also found to interact with and promote the phosphorylation of AMX-2. Additional studies reveal that 5-HIAA functions to inhibit egg laying in a manner dependent on the 5-HT receptor SER-1 and the G protein GOA-1. These results demonstrate that GRK-2 modulates 5-HT metabolism by regulating AMX-2 function and that 5-HIAA may function in the SER-1 signaling pathway.
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Affiliation(s)
- Jianjun Wang
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Jiansong Luo
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | | | - William C Wetsel
- Departments of Psychiatry and Behavioral Sciences.,Cell Biology, and.,Neurobiology and.,Mouse Behavioral and Neuroendocrine Analysis Core Facility, Duke University Medical Center, Durham, North Carolina 27710, and
| | - Richard Nass
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Jeffrey L Benovic
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
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32
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Zang KE, Ho E, Ringstad N. Inhibitory peptidergic modulation of C. elegans serotonin neurons is gated by T-type calcium channels. eLife 2017; 6. [PMID: 28165324 PMCID: PMC5330680 DOI: 10.7554/elife.22771] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 02/06/2017] [Indexed: 12/30/2022] Open
Abstract
Serotonin is an evolutionarily ancient molecule that functions in generating and modulating many behavioral states. Although much is known about how serotonin acts on its cellular targets, how serotonin release is regulated in vivo remains poorly understood. In the nematode C. elegans, serotonin neurons that drive female reproductive behavior are directly modulated by inhibitory neuropeptides. Here, we report the isolation of mutants in which inhibitory neuropeptides fail to properly modulate serotonin neurons and the behavior they mediate. The corresponding mutations affect the T-type calcium channel CCA-1 and symmetrically re-tune its voltage-dependencies of activation and inactivation towards more hyperpolarized potentials. This shift in voltage dependency strongly and specifically bypasses the behavioral and cell physiological effects of peptidergic inhibition on serotonin neurons. Our results indicate that T-type calcium channels are critical regulators of a C. elegans serotonergic circuit and demonstrate a mechanism in which T-type channels functionally gate inhibitory modulation in vivo.
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Affiliation(s)
- Kara E Zang
- Skirball Institute for Biomolecular Medicine, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Department of Cell Biology, NYU Langone School of Medicine, New York, United States
| | - Elver Ho
- Skirball Institute for Biomolecular Medicine, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Department of Cell Biology, NYU Langone School of Medicine, New York, United States
| | - Niels Ringstad
- Skirball Institute for Biomolecular Medicine, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Department of Cell Biology, NYU Langone School of Medicine, New York, United States
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33
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Collins KM, Bode A, Fernandez RW, Tanis JE, Brewer JC, Creamer MS, Koelle MR. Activity of the C. elegans egg-laying behavior circuit is controlled by competing activation and feedback inhibition. eLife 2016; 5. [PMID: 27849154 PMCID: PMC5142809 DOI: 10.7554/elife.21126] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/14/2016] [Indexed: 01/13/2023] Open
Abstract
Like many behaviors, Caenorhabditis elegans egg laying alternates between inactive and active states. To understand how the underlying neural circuit turns the behavior on and off, we optically recorded circuit activity in behaving animals while manipulating circuit function using mutations, optogenetics, and drugs. In the active state, the circuit shows rhythmic activity phased with the body bends of locomotion. The serotonergic HSN command neurons initiate the active state, but accumulation of unlaid eggs also promotes the active state independent of the HSNs. The cholinergic VC motor neurons slow locomotion during egg-laying muscle contraction and egg release. The uv1 neuroendocrine cells mechanically sense passage of eggs through the vulva and release tyramine to inhibit egg laying, in part via the LGC-55 tyramine-gated Cl- channel on the HSNs. Our results identify discrete signals that entrain or detach the circuit from the locomotion central pattern generator to produce active and inactive states. DOI:http://dx.doi.org/10.7554/eLife.21126.001 It has been said that if the human brain were so simple that we could understand it, we would be so simple that we couldn’t. This quote neatly captures the challenge of working out how 80 billion neurons collectively generate our thoughts and behavior. Fortunately, the nervous system is also organized into simpler units called circuits. Each consists of a relatively small number of neurons, which communicate with one another to control as little as a single behavior. These circuits should in principle be simple enough for us to understand, particularly if we study them in nervous systems less complex than our own. Despite this, there is currently not a single circuit in any organism in which we can explain how communication between individual neurons generates behavior. Collins et al. therefore set out to characterize a simple neural circuit in one of the simplest model organisms: the egg-laying circuit of the worm C. elegans. Using mutations, drugs and molecular genetic techniques, Collins et al. systematically altered the activity and signaling of each of the neurons within the egg-laying circuit. The experiments revealed that cells called command neurons trigger egg laying by producing signals that switch on the rest of the circuit. Once activated, the circuit is able to respond to waves of activity from a second circuit – called the central pattern generator – that also controls the worm’s movement. Finally, laying an egg activates a third set of neurons, which release a signal that returns the circuit to its inactive state. The use of distinct signals and neurons to activate the circuit, to coordinate its ongoing activity, and to inactivate the circuit when its task is complete also applies to many other neural circuits. Now that these signals have been identified in one circuit, it should be possible to build on these findings to better understand how others work. DOI:http://dx.doi.org/10.7554/eLife.21126.002
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Affiliation(s)
- Kevin M Collins
- Department of Biology, University of Miami, Coral Gables, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Addys Bode
- Department of Biology, University of Miami, Coral Gables, United States
| | - Robert W Fernandez
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Jessica E Tanis
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Jacob C Brewer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Matthew S Creamer
- Interdepartmental Neuroscience Program, Yale University, New Haven, United States
| | - Michael R Koelle
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Interdepartmental Neuroscience Program, Yale University, New Haven, United States
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Nagy S, Goessling M, Amit Y, Biron D. A Generative Statistical Algorithm for Automatic Detection of Complex Postures. PLoS Comput Biol 2015; 11:e1004517. [PMID: 26439258 PMCID: PMC4595081 DOI: 10.1371/journal.pcbi.1004517] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 08/25/2015] [Indexed: 02/06/2023] Open
Abstract
This paper presents a method for automated detection of complex (non-self-avoiding) postures of the nematode Caenorhabditis elegans and its application to analyses of locomotion defects. Our approach is based on progressively detailed statistical models that enable detection of the head and the body even in cases of severe coilers, where data from traditional trackers is limited. We restrict the input available to the algorithm to a single digitized frame, such that manual initialization is not required and the detection problem becomes embarrassingly parallel. Consequently, the proposed algorithm does not propagate detection errors and naturally integrates in a "big data" workflow used for large-scale analyses. Using this framework, we analyzed the dynamics of postures and locomotion of wild-type animals and mutants that exhibit severe coiling phenotypes. Our approach can readily be extended to additional automated tracking tasks such as tracking pairs of animals (e.g., for mating assays) or different species.
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Affiliation(s)
- Stanislav Nagy
- The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois, United States of America
| | - Marc Goessling
- Department of Statistics, The University of Chicago, Chicago, Illinois, United States of America
| | - Yali Amit
- Department of Statistics, The University of Chicago, Chicago, Illinois, United States of America
- Department of Computer Science, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail: (YA); (DB)
| | - David Biron
- The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois, United States of America
- Department of Physics and the James Franck Institute, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail: (YA); (DB)
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Butler VJ, Branicky R, Yemini E, Liewald JF, Gottschalk A, Kerr RA, Chklovskii DB, Schafer WR. A consistent muscle activation strategy underlies crawling and swimming in Caenorhabditis elegans. J R Soc Interface 2015; 12:20140963. [PMID: 25551155 PMCID: PMC4277086 DOI: 10.1098/rsif.2014.0963] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Although undulatory swimming is observed in many organisms, the neuromuscular basis for undulatory movement patterns is not well understood. To better understand the basis for the generation of these movement patterns, we studied muscle activity in the nematode Caenorhabditis elegans. Caenorhabditis elegans exhibits a range of locomotion patterns: in low viscosity fluids the undulation has a wavelength longer than the body and propagates rapidly, while in high viscosity fluids or on agar media the undulatory waves are shorter and slower. Theoretical treatment of observed behaviour has suggested a large change in force–posture relationships at different viscosities, but analysis of bend propagation suggests that short-range proprioceptive feedback is used to control and generate body bends. How muscles could be activated in a way consistent with both these results is unclear. We therefore combined automated worm tracking with calcium imaging to determine muscle activation strategy in a variety of external substrates. Remarkably, we observed that across locomotion patterns spanning a threefold change in wavelength, peak muscle activation occurs approximately 45° (1/8th of a cycle) ahead of peak midline curvature. Although the location of peak force is predicted to vary widely, the activation pattern is consistent with required force in a model incorporating putative length- and velocity-dependence of muscle strength. Furthermore, a linear combination of local curvature and velocity can match the pattern of activation. This suggests that proprioception can enable the worm to swim effectively while working within the limitations of muscle biomechanics and neural control.
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Affiliation(s)
- Victoria J. Butler
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
- Janelia Farm Research Campus HHMI, Ashburn, VA 20147, USA
| | - Robyn Branicky
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Eviatar Yemini
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Jana F. Liewald
- Buchmann Institute for Molecular Life Sciences and Institute of Biochemistry, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute for Molecular Life Sciences and Institute of Biochemistry, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany
| | - Rex A. Kerr
- Janelia Farm Research Campus HHMI, Ashburn, VA 20147, USA
- e-mail:
| | | | - William R. Schafer
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
- Janelia Farm Research Campus HHMI, Ashburn, VA 20147, USA
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36
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The voltage-gated anion channels encoded by clh-3 regulate egg laying in C. elegans by modulating motor neuron excitability. J Neurosci 2014; 34:764-75. [PMID: 24431435 DOI: 10.1523/jneurosci.3112-13.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
CLC-2 is a hyperpolarization-activated, inwardly rectifying chloride channel. Although the properties of the CLC-2 channel have been well characterized, its function in vivo is not well understood. We have found that channels encoded by the Caenorhabditis elegans CLC-2 homolog clh-3 regulate the activity of the spontaneously active hermaphrodite-specific neurons (HSNs), which control the egg-laying behavior. We identified a gain-of-function mutation in clh-3 that increases channel activity. This mutation inhibits egg laying and inhibits HSN activity by decreasing its excitability. Conversely, loss-of-function mutations in clh-3 lead to misregulated egg laying and an increase in HSN excitability, indicating that these channels modulate egg laying by limiting HSN excitability. clh-3-encoded channels are not required for GABAA-receptor-mediated inhibition of the HSN. However, they require low intracellular chloride for HSN inhibition, indicating that they inhibit excitability directly by mediating chloride influx. This mechanism of CLH-3-dependent modulation may be conserved in other neurons in which the driving force favors chloride influx.
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37
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Lee JI, Mukherjee S, Yoon K, Dwivedi M, Bandyopadhyay J. The multiple faces of calcineurin signaling in Caenorhabditis elegans: Development, behaviour and aging. J Biosci 2013; 38:417-31. [DOI: 10.1007/s12038-013-9319-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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38
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Postsynaptic ERG potassium channels limit muscle excitability to allow distinct egg-laying behavior states in Caenorhabditis elegans. J Neurosci 2013; 33:761-75. [PMID: 23303953 DOI: 10.1523/jneurosci.3896-12.2013] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Caenorhabditis elegans regulates egg laying by alternating between an inactive phase and a serotonin-triggered active phase. We found that the conserved ERG [ether-a-go-go (EAG) related gene] potassium channel UNC-103 enables this two-state behavior by limiting excitability of the egg-laying muscles. Using both high-speed video recording and calcium imaging of egg-laying muscles in behaving animals, we found that the muscles appear to be excited at a particular phase of each locomotor body bend. During the inactive phase, this rhythmic excitation infrequently evokes calcium transients or contraction of the egg-laying muscles. During the serotonin-triggered active phase, however, these muscles are more excitable and each body bend is accompanied by a calcium transient that drives twitching or full contraction of the egg-laying muscles. We found that ERG-null mutants lay eggs too frequently, and that ERG function is necessary and sufficient in the egg-laying muscles to limit egg laying. ERG K(+) channels localize to postsynaptic sites in the egg-laying muscle, and mutants lacking ERG have more frequent calcium transients and contractions of the egg-laying muscles even during the inactive phase. Thus ERG channels set postsynaptic excitability at a threshold so that further adjustments of excitability by serotonin generate two distinct behavioral states.
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Estevez AO, Mueller CL, Morgan KL, Szewczyk NJ, Teece L, Miranda-Vizuete A, Estevez M. Selenium induces cholinergic motor neuron degeneration in Caenorhabditis elegans. Neurotoxicology 2012; 33:1021-32. [PMID: 22560997 DOI: 10.1016/j.neuro.2012.04.019] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 04/06/2012] [Accepted: 04/18/2012] [Indexed: 10/28/2022]
Abstract
Selenium is an essential micronutrient required for cellular antioxidant systems, yet at higher doses it induces oxidative stress. Additionally, in vertebrates environmental exposures to toxic levels of selenium can cause paralysis and death. Here we show that selenium-induced oxidative stress leads to decreased cholinergic signaling and degeneration of cholinergic neurons required for movement and egg-laying in Caenorhabditis elegans. Exposure to high levels of selenium leads to proteolysis of a soluble muscle protein through mechanisms suppressible by two pharmacological agents, levamisole and aldicarb which enhance cholinergic signaling in muscle. In addition, animals with reduction-of-function mutations in genes encoding post-synaptic levamisole-sensitive acetylcholine receptor subunits or the vesicular acetylcholine transporter developed impaired forward movement faster during selenium-exposure than normal animals, again confirming that selenium reduces cholinergic signaling. Finally, the antioxidant reduced glutathione, inhibits selenium-induced reductions in egg-laying through a cellular protective mechanism dependent on the C. elegans glutaredoxin, GLRX-21. These studies provide evidence that the environmental toxicant selenium induces neurodegeneration of cholinergic neurons through depletion of glutathione, a mechanism linked to the neuropathology of Alzheimer's disease, amyotrophic lateral sclerosis, and Parkinson's disease.
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Affiliation(s)
- Annette O Estevez
- Department of Neurology, University of Arizona, Tucson, AZ 85724-5023, USA.
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Dissecting a central flip-flop circuit that integrates contradictory sensory cues in C. elegans feeding regulation. Nat Commun 2012; 3:776. [PMID: 22491324 DOI: 10.1038/ncomms1780] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 03/08/2012] [Indexed: 01/16/2023] Open
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Lee JE, Jeong PY, Joo HJ, Kim H, Lee T, Koo HS, Paik YK. STR-33, a novel G protein-coupled receptor that regulates locomotion and egg laying in Caenorhabditis elegans. J Biol Chem 2011; 286:39860-70. [PMID: 21937442 DOI: 10.1074/jbc.m111.241000] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Despite their predicted functional importance, most G protein-coupled receptors (GPCRs) in Caenorhabditis elegans have remained largely uncharacterized. Here, we focused on one GPCR, STR-33, encoded by the str-33 gene, which was discovered through a ligand-based screening procedure. To characterize STR-33 function, we performed UV-trimethylpsolaren mutagenesis and isolated an str-33-null mutant. The resulting mutant showed hypersinusoidal movement and a hyperactive egg-laying phenotype. Two types of egg laying-related mutations have been characterized: egg laying-deficient (Egl-d) and hyperactive egg laying (Egl-c). The defect responsible for the egg laying-deficient Egl-d phenotype is related to Gα(q) signaling, whereas that responsible for the opposite, hyperactive egg-laying Egl-c phenotype is related to Gα(o) signaling. We found that the hyperactive egg-laying defect of the str-33(ykp001) mutant is dependent on the G protein GOA-1/Gα(o). Endogenous acetylcholine suppressed egg laying in C. elegans via a Gα(o)-signaling pathway by inhibiting serotonin biosynthesis or release from the hermaphrodite-specific neuron. Consistent with this, in vivo expression of the serotonin biosynthetic enzyme, TPH-1, was up-regulated in the str-33(ykp001) mutant. Taken together, these results suggest that the GPCR, STR-33, may be one of the neurotransmitter receptors that regulates locomotion and egg laying in C. elegans.
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Affiliation(s)
- Jeong-Eui Lee
- Department of Biochemistry and Yonsei Proteome Research Center, Yonsei University, Seoul 120-749, Korea
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Rivard L, Srinivasan J, Stone A, Ochoa S, Sternberg PW, Loer CM. A comparison of experience-dependent locomotory behaviors and biogenic amine neurons in nematode relatives of Caenorhabditis elegans. BMC Neurosci 2010; 11:22. [PMID: 20167133 PMCID: PMC2836364 DOI: 10.1186/1471-2202-11-22] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 02/19/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Survival of an animal depends on its ability to match its responses to environmental conditions. To generate an optimal behavioral output, the nervous system must process sensory information and generate a directed motor output in response to stimuli. The nervous system should also store information about experiences to use in the future. The diverse group of free-living nematodes provides an excellent system to study macro- and microevolution of molecular, morphological and behavioral character states associated with such nervous system function. We asked whether an adaptive behavior would vary among bacterivorous nematodes and whether differences in the neurotransmitter systems known to regulate the behavior in one species would reflect differences seen in the adaptive behavior among those species. Caenorhabditis elegans worms slow in the presence of food; this 'basal' slowing is triggered by dopaminergic mechanosensory neurons that detect bacteria. Starved worms slow more dramatically; this 'enhanced' slowing is regulated by serotonin. RESULTS We examined seven nematode species with known phylogenetic relationship to C. elegans for locomotory behaviors modulated by food (E. coli), and by the worm's recent history of feeding (being well-fed or starved). We found that locomotory behavior in some species was modulated by food and recent feeding experience in a manner similar to C. elegans, but not all the species tested exhibited these food-modulated behaviors. We also found that some worms had different responses to bacteria other than E. coli. Using histochemical and immunological staining, we found that dopaminergic neurons were very similar among all species. For instance, we saw likely homologs of four bilateral pairs of dopaminergic cephalic and deirid neurons known from C. elegans in all seven species examined. In contrast, there was greater variation in the patterns of serotonergic neurons. The presence of presumptive homologs of dopaminergic and serotonergic neurons in a given species did not correlate with the observed differences in locomotory behaviors. CONCLUSIONS This study demonstrates that behaviors can differ significantly between species that appear morphologically very similar, and therefore it is important to consider factors, such as ecology of a species in the wild, when formulating hypotheses about the adaptive significance of a behavior. Our results suggest that evolutionary changes in locomotory behaviors are less likely to be caused by changes in neurotransmitter expression of neurons. Such changes could be caused either by subtle changes in neural circuitry or in the function of the signal transduction pathways mediating these behaviors.
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Affiliation(s)
- Laura Rivard
- Dept of Biology, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA
| | - Jagan Srinivasan
- Howard Hughes Medical Institute, Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena CA 91125, USA
| | - Allison Stone
- Dept of Biology, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA
| | - Stacy Ochoa
- Dept of Biology, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA
| | - Paul W Sternberg
- Howard Hughes Medical Institute, Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena CA 91125, USA
| | - Curtis M Loer
- Dept of Biology, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA
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Pozzan T, Rudolf R. Measurements of mitochondrial calcium in vivo. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1787:1317-23. [PMID: 19100709 DOI: 10.1016/j.bbabio.2008.11.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 11/20/2008] [Accepted: 11/21/2008] [Indexed: 12/21/2022]
Abstract
Mitochondria play a pivotal role in intracellular Ca(2+) signalling by taking up and releasing the ion upon specific conditions. In order to do so, mitochondria depend on a number of factors, such as the mitochondrial membrane potential and spatio-temporal constraints. Whereas most of the basic principles underlying mitochondrial Ca(2+) handling have been successfully deciphered over the last 50 years using assays based on in vitro preparations of mitochondria or cultured cells, we have only just started to understand the actual physiological relevance of these processes in the whole animal. Recent advancements in imaging and genetically encoded sensor technologies have allowed us to visualise mitochondrial Ca(2+) transients in live mice. These studies used either two-photon microscopy or bioluminescence imaging of cameleon or aequorin-GFP Ca(2+) sensors, respectively. Both methods revealed a consistent picture of Ca(2+) uptake into mitochondria under physiological conditions even during very short-lasting elevations of cytosolic Ca(2+) levels. The big future challenge is to understand the functional impact of such Ca(2+) signals on the physiology of the observed tissue as well as of the whole organism. To that end, the development of multiparametric in vivo approaches will be mandatory.
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Affiliation(s)
- Tullio Pozzan
- Department of Biomedical Sciences and CNR Institute of Neurosciences, University of Padua, Viale Giuseppe Colombo 3, Padua 35121, Italy
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Tanis JE, Bellemer A, Moresco JJ, Forbush B, Koelle MR. The potassium chloride cotransporter KCC-2 coordinates development of inhibitory neurotransmission and synapse structure in Caenorhabditis elegans. J Neurosci 2009; 29:9943-54. [PMID: 19675228 PMCID: PMC2737711 DOI: 10.1523/jneurosci.1989-09.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 06/24/2009] [Accepted: 07/01/2009] [Indexed: 02/04/2023] Open
Abstract
Chloride influx through GABA-gated chloride channels, the primary mechanism by which neural activity is inhibited in the adult mammalian brain, depends on chloride gradients established by the potassium chloride cotransporter KCC2. We used a genetic screen to identify genes important for inhibition of the hermaphrodite-specific motor neurons (HSNs) that stimulate Caenorhabditis elegans egg-laying behavior and discovered mutations in a potassium chloride cotransporter, kcc-2. Functional analysis indicates that, like mammalian KCCs, C. elegans KCC-2 transports chloride, is activated by hypotonic conditions, and is inhibited by the loop diuretic furosemide. KCC-2 appears to establish chloride gradients required for the inhibitory effects of GABA-gated and serotonin-gated chloride channels on C. elegans behavior. In the absence of KCC-2, chloride gradients appear to be altered in neurons and muscles such that normally inhibitory signals become excitatory. kcc-2 is transcriptionally upregulated in the HSN neurons during synapse development. Loss of KCC-2 produces a decrease in the synaptic vesicle population within mature HSN synapses, which apparently compensates for a lack of HSN inhibition, resulting in normal egg-laying behavior. Thus, KCC-2 coordinates the development of inhibitory neurotransmission with synapse maturation to produce mature neural circuits with appropriate activity levels.
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Affiliation(s)
- Jessica E. Tanis
- Departments of Molecular Biophysics and Biochemistry and
- Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | | | | | - Biff Forbush
- Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
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Hapiak VM, Hobson RJ, Hughes L, Smith K, Harris G, Condon C, Komuniecki P, Komuniecki RW. Dual excitatory and inhibitory serotonergic inputs modulate egg laying in Caenorhabditis elegans. Genetics 2009; 181:153-63. [PMID: 19001289 PMCID: PMC2621164 DOI: 10.1534/genetics.108.096891] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 11/05/2008] [Indexed: 01/30/2023] Open
Abstract
Serotonin (5-HT) regulates key processes in both vertebrates and invertebrates. Previously, four 5-HT receptors that contributed to the 5-HT modulation of egg laying were identified in Caenorhabditis elegans. Therefore, to assess potential receptor interactions, we generated animals containing combinations of null alleles for each receptor, especially animals expressing only individual 5-HT receptors. 5-HT-stimulated egg laying and egg retention correlated well with different combinations of predicted excitatory and inhibitory serotonergic inputs. For example, 5-HT did not stimulate egg laying in ser-1, ser-7, or ser-7 ser-1 null animals, and ser-7 ser-1 animals retained more eggs than wild-type animals. In contrast, 5-HT-stimulated egg laying in ser-4;mod-1 animals was greater than in wild-type animals, and ser-4;mod-1 animals retained fewer eggs than wild-type animals. Surprisingly, ser-4;mod-1;ser-7 ser-1 animals retained the same number of eggs as wild-type animals and exhibited significant 5-HT-stimulated egg laying that was dependent on a previously uncharacterized receptor, SER-5. 5-HT-stimulated egg laying was absent in ser-5;ser-4;mod-1;ser-7 ser-1 animals, and these animals retained more eggs than either wild-type or ser-4;mod-1;ser-7 ser-1 animals. The 5-HT sensitivity of egg laying could be restored by ser-5 muscle expression. Together, these results highlight the dual excitatory/inhibitory serotonergic inputs that combine to modulate egg laying.
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Affiliation(s)
- Vera M Hapiak
- Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606-3390, USA
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Zhang M, Chung SH, Fang-Yen C, Craig C, Kerr RA, Suzuki H, Samuel ADT, Mazur E, Schafer WR. A self-regulating feed-forward circuit controlling C. elegans egg-laying behavior. Curr Biol 2008; 18:1445-55. [PMID: 18818084 PMCID: PMC2621019 DOI: 10.1016/j.cub.2008.08.047] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 08/05/2008] [Accepted: 08/11/2008] [Indexed: 10/21/2022]
Abstract
BACKGROUND Egg laying in Caenorhabditis elegans has been well studied at the genetic and behavioral levels. However, the neural basis of egg-laying behavior is still not well understood; in particular, the roles of specific neurons and the functional nature of the synaptic connections in the egg-laying circuit remain uncharacterized. RESULTS We have used in vivo neuroimaging and laser surgery to address these questions in intact, behaving animals. We have found that the HSN neurons play a central role in driving egg-laying behavior through direct excitation of the vulval muscles and VC motor neurons. The VC neurons play a dual role in the egg-laying circuit, exciting the vulval muscles while feedback-inhibiting the HSNs. Interestingly, the HSNs are active in the absence of synaptic input, suggesting that egg laying may be controlled through modulation of autonomous HSN activity. Indeed, body touch appears to inhibit egg laying, in part by interfering with HSN calcium oscillations. CONCLUSIONS The egg-laying motor circuit comprises a simple three-component system combining feed-forward excitation and feedback inhibition. This microcircuit motif is common in the C. elegans nervous system, as well as in the mammalian cortex; thus, understanding its functional properties in C. elegans may provide insight into its computational role in more complex brains.
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Affiliation(s)
- Mi Zhang
- San Diego State University and University of California, San Diego Joint Doctoral Program, La Jolla, CA 92093, USA
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Ringstad N, Horvitz HR. FMRFamide neuropeptides and acetylcholine synergistically inhibit egg-laying by C. elegans. Nat Neurosci 2008; 11:1168-76. [PMID: 18806786 PMCID: PMC2963311 DOI: 10.1038/nn.2186] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 07/17/2008] [Indexed: 11/09/2022]
Abstract
Egg-laying behavior of the Caenorhabditis elegans hermaphrodite is regulated by G protein signaling pathways. Here we show that the egg laying-defective mutant egl-6(n592) carries an activating mutation in a G protein-coupled receptor that inhibits C. elegans egg-laying motor neurons in a G(o)-dependent manner. Ligands for EGL-6 are Phe-Met-Arg-Phe-NH(2) (FMRFamide)-related peptides encoded by the genes flp-10 and flp-17. flp-10 is expressed in both neurons and non-neuronal cells. The major source of flp-17 peptides is a pair of presumptive sensory neurons, the BAG neurons. Genetic analysis of the egl-6 pathway revealed that the EGL-6 neuropeptide signaling pathway functions redundantly with acetylcholine to inhibit egg-laying. The retention of embryos in the uterus of the C. elegans hermaphrodite is therefore under the control of a presumptive sensory system and is inhibited by the convergence of signals from neuropeptides and the small-molecule neurotransmitter acetylcholine.
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Affiliation(s)
- Niels Ringstad
- Howard Hughes Medical Institute, McGovern Institute for Brain Research, Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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48
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Regulation of serotonin biosynthesis by the G proteins Galphao and Galphaq controls serotonin signaling in Caenorhabditis elegans. Genetics 2008; 178:157-69. [PMID: 18202365 DOI: 10.1534/genetics.107.079780] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To analyze mechanisms that modulate serotonin signaling, we investigated how Caenorhabditis elegans regulates the function of serotonergic motor neurons that stimulate egg-laying behavior. Egg laying is inhibited by the G protein Galphao and activated by the G protein Galphaq. We found that Galphao and Galphaq act directly in the serotonergic HSN motor neurons to control egg laying. There, the G proteins had opposing effects on transcription of the tryptophan hydroxylase gene tph-1, which encodes the rate-limiting enzyme for serotonin biosynthesis. Antiserotonin staining confirmed that Galphao and Galphaq antagonistically affect serotonin levels. Altering tph-1 gene dosage showed that small changes in tph-1 expression were sufficient to affect egg-laying behavior. Epistasis experiments showed that signaling through the G proteins has additional tph-1-independent effects. Our results indicate that (1) serotonin signaling is regulated by modulating serotonin biosynthesis and (2) Galphao and Galphaq act in the same neurons to have opposing effects on behavior, in part, by antagonistically regulating transcription of specific genes. Galphao and Galphaq have opposing effects on many behaviors in addition to egg laying and may generally act, as they do in the egg-laying system, to integrate multiple signals and consequently set levels of transcription of genes that affect neurotransmitter release.
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Yeh E, Ng S, Zhang M, Bouhours M, Wang Y, Wang M, Hung W, Aoyagi K, Melnik-Martinez K, Li M, Liu F, Schafer WR, Zhen M. A putative cation channel, NCA-1, and a novel protein, UNC-80, transmit neuronal activity in C. elegans. PLoS Biol 2008; 6:e55. [PMID: 18336069 PMCID: PMC2265767 DOI: 10.1371/journal.pbio.0060055] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Accepted: 01/18/2008] [Indexed: 11/19/2022] Open
Abstract
Voltage-gated cation channels regulate neuronal excitability through selective ion flux. NALCN, a member of a protein family that is structurally related to the alpha1 subunits of voltage-gated sodium/calcium channels, was recently shown to regulate the resting membrane potentials by mediating sodium leak and the firing of mouse neurons. We identified a role for the Caenorhabditis elegans NALCN homologues NCA-1 and NCA-2 in the propagation of neuronal activity from cell bodies to synapses. Loss of NCA activities leads to reduced synaptic transmission at neuromuscular junctions and frequent halting in locomotion. In vivo calcium imaging experiments further indicate that while calcium influx in the cell bodies of egg-laying motorneurons is unaffected by altered NCA activity, synaptic calcium transients are significantly reduced in nca loss-of-function mutants and increased in nca gain-of-function mutants. NCA-1 localizes along axons and is enriched at nonsynaptic regions. Its localization and function depend on UNC-79, and UNC-80, a novel conserved protein that is also enriched at nonsynaptic regions. We propose that NCA-1 and UNC-80 regulate neuronal activity at least in part by transmitting depolarization signals to synapses in C. elegans neurons.
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Affiliation(s)
- Edward Yeh
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Sharon Ng
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Mi Zhang
- Division of Biology, University of California San Diego, San Diego, California, United States of America
| | - Magali Bouhours
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Ying Wang
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Min Wang
- Department of Neuroscience, Centre for Addiction and Mental Health, Clarke Division, University of Toronto, Toronto, Ontario, Canada
| | - Wesley Hung
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Kyota Aoyagi
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Katya Melnik-Martinez
- Division of Biology, University of California San Diego, San Diego, California, United States of America
| | - Michelle Li
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Fang Liu
- Department of Neuroscience, Centre for Addiction and Mental Health, Clarke Division, University of Toronto, Toronto, Ontario, Canada
| | - William R Schafer
- Division of Biology, University of California San Diego, San Diego, California, United States of America
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Mei Zhen
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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Kindt KS, Quast KB, Giles AC, De S, Hendrey D, Nicastro I, Rankin CH, Schafer WR. Dopamine mediates context-dependent modulation of sensory plasticity in C. elegans. Neuron 2007; 55:662-76. [PMID: 17698017 DOI: 10.1016/j.neuron.2007.07.023] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 05/22/2007] [Accepted: 07/16/2007] [Indexed: 02/01/2023]
Abstract
Dopamine has been implicated in the modulation of diverse forms of behavioral plasticity, including appetitive learning and addiction. An important challenge is to understand how dopamine's effects at the cellular level alter the properties of neural circuits to modify behavior. In the nematode C. elegans, dopamine modulates habituation of an escape reflex triggered by body touch. In the absence of food, animals habituate more rapidly than in the presence of food; this contextual information about food availability is provided by dopaminergic mechanosensory neurons that sense the presence of bacteria. We find that dopamine alters habituation kinetics by selectively modulating the touch responses of the anterior-body mechanoreceptors; this modulation involves a D1-like dopamine receptor, a Gq/PLC-beta signaling pathway, and calcium release within the touch neurons. Interestingly, the body touch mechanoreceptors can themselves excite the dopamine neurons, forming a positive feedback loop capable of integrating context and experience to modulate mechanosensory attention.
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Affiliation(s)
- Katie S Kindt
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla CA 92093, USA
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