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Tsai SH, Wu YC, Palomino DF, Schroeder FC, Pan CL. Peripheral peroxisomal β-oxidation engages neuronal serotonin signaling to drive stress-induced aversive memory in C. elegans. Cell Rep 2024; 43:113996. [PMID: 38520690 PMCID: PMC11087011 DOI: 10.1016/j.celrep.2024.113996] [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: 09/03/2023] [Revised: 02/06/2024] [Accepted: 03/08/2024] [Indexed: 03/25/2024] Open
Abstract
Physiological dysfunction confers negative valence to coincidental sensory cues to induce the formation of aversive associative memory. How peripheral tissue stress engages neuromodulatory mechanisms to form aversive memory is poorly understood. Here, we show that in the nematode C. elegans, mitochondrial disruption induces aversive memory through peroxisomal β-oxidation genes in non-neural tissues, including pmp-4/very-long-chain fatty acid transporter, dhs-28/3-hydroxylacyl-CoA dehydrogenase, and daf-22/3-ketoacyl-CoA thiolase. Upregulation of peroxisomal β-oxidation genes under mitochondrial stress requires the nuclear hormone receptor NHR-49. Importantly, the memory-promoting function of peroxisomal β-oxidation is independent of its canonical role in pheromone production. Peripheral signals derived from the peroxisomes target NSM, a critical neuron for memory formation under stress, to upregulate serotonin synthesis and remodel evoked responses to sensory cues. Our genetic, transcriptomic, and metabolomic approaches establish peroxisomal lipid signaling as a crucial mechanism that connects peripheral mitochondrial stress to central serotonin neuromodulation in aversive memory formation.
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Affiliation(s)
- Shang-Heng Tsai
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan; Center for Precision Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan
| | - Yu-Chun Wu
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan; Center for Precision Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan
| | - Diana Fajardo Palomino
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Frank C Schroeder
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Chun-Liang Pan
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan.
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2
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Ferkey DM, Sengupta P, L’Etoile ND. Chemosensory signal transduction in Caenorhabditis elegans. Genetics 2021; 217:iyab004. [PMID: 33693646 PMCID: PMC8045692 DOI: 10.1093/genetics/iyab004] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 01/05/2021] [Indexed: 12/16/2022] Open
Abstract
Chemosensory neurons translate perception of external chemical cues, including odorants, tastants, and pheromones, into information that drives attraction or avoidance motor programs. In the laboratory, robust behavioral assays, coupled with powerful genetic, molecular and optical tools, have made Caenorhabditis elegans an ideal experimental system in which to dissect the contributions of individual genes and neurons to ethologically relevant chemosensory behaviors. Here, we review current knowledge of the neurons, signal transduction molecules and regulatory mechanisms that underlie the response of C. elegans to chemicals, including pheromones. The majority of identified molecules and pathways share remarkable homology with sensory mechanisms in other organisms. With the development of new tools and technologies, we anticipate that continued study of chemosensory signal transduction and processing in C. elegans will yield additional new insights into the mechanisms by which this animal is able to detect and discriminate among thousands of chemical cues with a limited sensory neuron repertoire.
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Affiliation(s)
- Denise M Ferkey
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Piali Sengupta
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Noelle D L’Etoile
- Department of Cell and Tissue Biology, University of California, San Francisco, CA 94143, USA
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3
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Yang Q, Yan C, Yin C, Gong Z. Serotonin Activated Hepatic Stellate Cells Contribute to Sex Disparity in Hepatocellular Carcinoma. Cell Mol Gastroenterol Hepatol 2017; 3:484-499. [PMID: 28462385 PMCID: PMC5403976 DOI: 10.1016/j.jcmgh.2017.01.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 01/05/2017] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Hepatocellular carcinoma (HCC) occurs more frequently and aggressively in men than in women. Although sex hormones are believed to play a critical role in this disparity, the possible contribution of other factors largely is unknown. We aimed to investigate the role of serotonin on its contribution of sex discrepancy during HCC. METHODS By using an inducible zebrafish HCC model through hepatocyte-specific transgenic krasV12 expression, differential rates of HCC in male and female fish were characterized by both pharmaceutical and genetic interventions. The findings were validated further in human liver disease samples. RESULTS Accelerated HCC progression was observed in krasV12-expressing male zebrafish and male fish liver tumors were found to have higher hepatic stellate cell (HSC) density and activation. Serotonin, which is essential for HSC survival and activation, similarly were found to be synthesized and accumulated more robustly in males than in females. Serotonin-activated HSCs could promote HCC carcinogenesis and concurrently increase serotonin synthesis via transforming growth factor (Tgf)b1 expression, hence contributing to sex disparity in HCC. Analysis of liver disease patient samples showed similar male predominant serotonin accumulation and Tgfb1 expression. CONCLUSIONS In both zebrafish HCC models and human liver disease samples, a predominant serotonin synthesis and accumulation in males resulted in higher HSC density and activation as well as Tgfb1 expression, thus accelerating HCC carcinogenesis in males.
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Key Words
- EGFP, enhanced green fluorescence protein
- Gfap, glial fibrillary acidic protein
- HCC, hepatocellular carcinoma
- HSC, hepatic stellate cell
- Htr2b, 5-hydoxytryptamine receptor 2B
- IF, immunofluorescence
- IHC, immunohistochemistry
- Kras
- Liver Cancer
- P-Tph1, phosphorylated tryptophan hydroxylase 1
- PCR, polymerase chain reaction
- TGF, transforming growth factor
- TGFB1
- Tph1, tryptophan hydroxylase 1
- WT, wild type
- Zebrafish
- cDNA, complementary DNA
- dox, doxycycline
- α-SMA, α-smooth muscle actin
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Affiliation(s)
- Qiqi Yang
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Chuan Yan
- Department of Biological Sciences, National University of Singapore, Singapore
- Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore
| | - Chunyue Yin
- Division of Gastroenterology, Hepatology and Nutrition, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio
| | - Zhiyuan Gong
- Department of Biological Sciences, National University of Singapore, Singapore
- Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore
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Lee KS, Iwanir S, Kopito RB, Scholz M, Calarco JA, Biron D, Levine E. Serotonin-dependent kinetics of feeding bursts underlie a graded response to food availability in C. elegans. Nat Commun 2017; 8:14221. [PMID: 28145493 PMCID: PMC5296638 DOI: 10.1038/ncomms14221] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 12/08/2016] [Indexed: 11/16/2022] Open
Abstract
Animals integrate physiological and environmental signals to modulate their food uptake. The nematode C. elegans, whose food uptake consists of pumping bacteria from the environment into the gut, provides excellent opportunities for discovering principles of conserved regulatory mechanisms. Here we show that worms implement a graded feeding response to the concentration of environmental bacteria by modulating a commitment to bursts of fast pumping. Using long-term, high-resolution, longitudinal recordings of feeding dynamics under defined conditions, we find that the frequency and duration of pumping bursts increase and the duration of long pauses diminishes in environments richer in bacteria. The bioamine serotonin is required for food-dependent induction of bursts as well as for maintaining their high rate of pumping through two distinct mechanisms. We identify the differential roles of distinct families of serotonin receptors in this process and propose that regulation of bursts is a conserved mechanism of behaviour and motor control.
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Affiliation(s)
- Kyung Suk Lee
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Shachar Iwanir
- Department of Physics and the James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Ronen B. Kopito
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Monika Scholz
- Department of Physics and the James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - John A. Calarco
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - David Biron
- Department of Physics and the James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
- The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Erel Levine
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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5
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Pereira MDC, Morais S, Sequeiros J, Alonso I. Large-Scale Functional RNAi Screen in C. elegans Identifies TGF-β and Notch Signaling Pathways as Modifiers of CACNA1A. ASN Neuro 2016; 8:8/2/1759091416637025. [PMID: 27005779 PMCID: PMC4811018 DOI: 10.1177/1759091416637025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 01/31/2016] [Indexed: 01/02/2023] Open
Abstract
Variants in CACNA1A that encodes the pore-forming α1-subunit of human voltage-gated Cav2.1 (P/Q-type) Ca2+ channels cause several autosomal-dominant neurologic disorders, including familial hemiplegic migraine type 1, episodic ataxia type 2, and spinocerebellar ataxia type 6. To identify modifiers of incoordination in movement disorders, we performed a large-scale functional RNAi screen, using the Caenorhabditis elegans strain CB55, which carries a truncating mutation in the unc-2 gene, the worm ortholog for the human CACNA1A. The screen was carried out by the feeding method in 96-well liquid culture format, using the ORFeome v1.1 feeding library, and time-lapse imaging of worms in liquid culture was used to assess changes in thrashing behavior. We looked for genes that, when silenced, either ameliorated the slow and uncoordinated phenotype of unc-2, or interacted to produce a more severe phenotype. Of the 350 putative hits from the primary screen, 37 genes consistently showed reproducible results. At least 75% of these are specifically expressed in the C. elegans neurons. Functional network analysis and gene ontology revealed overrepresentation of genes involved in development, growth, locomotion, signal transduction, and vesicle-mediated transport. We have expanded the functional network of genes involved in neurodegeneration leading to cerebellar ataxia related to unc-2/CACNA1A, further confirming the involvement of the transforming growth factor β pathway and adding a novel signaling cascade, the Notch pathway.
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Affiliation(s)
- Maria da Conceição Pereira
- UnIGENe, Institute for Molecular and Cell Biology (IBMC), Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Portugal Abel Salazar Institute for the Biomedical Sciences (ICBAS), University of Porto, Portugal
| | - Sara Morais
- UnIGENe, Institute for Molecular and Cell Biology (IBMC), Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Portugal Abel Salazar Institute for the Biomedical Sciences (ICBAS), University of Porto, Portugal
| | - Jorge Sequeiros
- UnIGENe, Institute for Molecular and Cell Biology (IBMC), Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Portugal Abel Salazar Institute for the Biomedical Sciences (ICBAS), University of Porto, Portugal CGPP, Institute for Molecular and Cell Biology (IBMC), Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Portugal
| | - Isabel Alonso
- UnIGENe, Institute for Molecular and Cell Biology (IBMC), Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Portugal Abel Salazar Institute for the Biomedical Sciences (ICBAS), University of Porto, Portugal CGPP, Institute for Molecular and Cell Biology (IBMC), Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Portugal
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6
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Bruckner JJ, Zhan H, O'Connor-Giles KM. Advances in imaging ultrastructure yield new insights into presynaptic biology. Front Cell Neurosci 2015; 9:196. [PMID: 26052269 PMCID: PMC4440913 DOI: 10.3389/fncel.2015.00196] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/05/2015] [Indexed: 11/13/2022] Open
Abstract
Synapses are the fundamental functional units of neural circuits, and their dysregulation has been implicated in diverse neurological disorders. At presynaptic terminals, neurotransmitter-filled synaptic vesicles are released in response to calcium influx through voltage-gated calcium channels activated by the arrival of an action potential. Decades of electrophysiological, biochemical, and genetic studies have contributed to a growing understanding of presynaptic biology. Imaging studies are yielding new insights into how synapses are organized to carry out their critical functions. The development of techniques for rapid immobilization and preservation of neuronal tissues for electron microscopy (EM) has led to a new renaissance in ultrastructural imaging that is rapidly advancing our understanding of synapse structure and function.
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Affiliation(s)
- Joseph J Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison Madison, WI, USA
| | - Hong Zhan
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison Madison, WI, USA
| | - Kate M O'Connor-Giles
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison Madison, WI, USA ; Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison Madison, WI, USA ; Laboratory of Genetics, University of Wisconsin-Madison Madison, WI, USA
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7
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Anderson A, McMullan R. From head to tail it's a 2 way street for neuro-immune communication. WORM 2014; 3:e959425. [PMID: 26430547 PMCID: PMC4588538 DOI: 10.4161/21624046.2014.959425] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 06/03/2014] [Accepted: 06/25/2014] [Indexed: 12/12/2022]
Abstract
Animals need to be able to rapidly and effectively respond to changes in their external and internal environment. To achieve this the nervous and immune systems need to coordinate their responses, integrating multiple cues including presence of potential pathogens, and availability of food. In our recent study (1) we demonstrate that signaling by sensory neurons in the head using the classical neurotransmitter serotonin can negatively regulate the rectal epithelial immune response upon infection of C. elegans with the naturally occurring bacterial pathogen Microbacterium nematophilum (M. nematophilum). The complicated nature of the mammalian brain and immune system has made it difficult to identify the molecular mechanisms mediating these interactions. With its simple, well described, nervous system and a rapidly growing understanding of its immune system, C. elegans has emerged as an excellent model to study the mechanisms by which animals recognize pathogens and coordinate behavioral and cellular immune responses to infection.
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Affiliation(s)
- A Anderson
- Department of Life Sciences; Imperial College London; South Kensington Campus ; London, UK
| | - R McMullan
- Department of Life Sciences; Imperial College London; South Kensington Campus ; London, UK
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8
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Sin O, Michels H, Nollen EAA. Genetic screens in Caenorhabditis elegans models for neurodegenerative diseases. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1951-1959. [PMID: 24525026 DOI: 10.1016/j.bbadis.2014.01.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 12/23/2013] [Accepted: 01/22/2014] [Indexed: 01/17/2023]
Abstract
Caenorhabditis elegans comprises unique features that make it an attractive model organism in diverse fields of biology. Genetic screens are powerful to identify genes and C. elegans can be customized to forward or reverse genetic screens and to establish gene function. These genetic screens can be applied to "humanized" models of C. elegans for neurodegenerative diseases, enabling for example the identification of genes involved in protein aggregation, one of the hallmarks of these diseases. In this review, we will describe the genetic screens employed in C. elegans and how these can be used to understand molecular processes involved in neurodegenerative and other human diseases. This article is part of a Special Issue entitled: From Genome to Function.
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Affiliation(s)
- Olga Sin
- University of Groningen, University Medical Centre Groningen, European Research Institute for the Biology of Aging, 9700 AD Groningen, The Netherlands; Graduate Program in Areas of Basic and Applied Biology, Abel Salazar Biomedical Sciences Institute, University of Porto, 4099-003 Porto, Portugal
| | - Helen Michels
- University of Groningen, University Medical Centre Groningen, European Research Institute for the Biology of Aging, 9700 AD Groningen, The Netherlands
| | - Ellen A A Nollen
- University of Groningen, University Medical Centre Groningen, European Research Institute for the Biology of Aging, 9700 AD Groningen, The Netherlands.
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9
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Estevez AO, Morgan KL, Szewczyk NJ, Gems D, Estevez M. The neurodegenerative effects of selenium are inhibited by FOXO and PINK1/PTEN regulation of insulin/insulin-like growth factor signaling in Caenorhabditis elegans. Neurotoxicology 2014; 41:28-43. [PMID: 24406377 PMCID: PMC3979119 DOI: 10.1016/j.neuro.2013.12.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/23/2013] [Accepted: 12/27/2013] [Indexed: 12/12/2022]
Abstract
Insulin/insulin-like signaling reduction alters selenium-induced neurodegeneration. Selenium induces nuclear translocation of DAF-16/FOXO3a. DAF-16 overexpression decreases GABAergic and cholinergic motor neuron degeneration. Loss of DAF-18/PTEN increases sensitivity to selenium-induced movement deficits. Glutathione requires DAF-18/PINK-1 to improve selenium-induced movement deficits.
Exposures to high levels of environmental selenium have been associated with motor neuron disease in both animals and humans and high levels of selenite have been identified in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis (ALS). We have shown previously that exposures to high levels of sodium selenite in the environment of Caenorhabditis elegans adult animals can induce neurodegeneration and cell loss resulting in motor deficits and death and that this is at least partially caused by a reduction in cholinergic signaling across the neuromuscular junction. Here we provide evidence that reduction in insulin/insulin-like (IIS) signaling alters response to high dose levels of environmental selenium which in turn can regulate the IIS pathway. Most specifically we show that nuclear localization and thus activation of the DAF-16/forkhead box transcription factor occurs in response to selenium exposure although this was not observed in motor neurons of the ventral cord. Yet, tissue specific expression and generalized overexpression of DAF-16 can partially rescue the neurodegenerative and behavioral deficits observed with high dose selenium exposures in not only the cholinergic, but also the GABAergic motor neurons. In addition, two modifiers of IIS signaling, PTEN (phosphatase and tensin homolog, deleted on chromosome 10) and PINK1 (PTEN-induced putative kinase 1) are required for the cellular antioxidant reduced glutathione to mitigate the selenium-induced movement deficits. Studies have suggested that environmental exposures can lead to ALS or other neurological diseases and this model of selenium-induced neurodegeneration developed in a genetically tractable organism provides a tool for examining the combined roles of genetics and environment in the neuro-pathologic disease process.
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Affiliation(s)
- Annette O Estevez
- Department of Neurology, University of Arizona College of Medicine, Tucson, AZ 85724, USA.
| | - Kathleen L Morgan
- Veterans Affairs Pittsburgh Healthcare System, Research and Development (151U), University Drive C, Pittsburgh, PA 15240, USA.
| | - Nathaniel J Szewczyk
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
| | - David Gems
- Institute of Healthy Ageing, and Department of Genetics, Evolution, and Environment, University College London, The Darwin Building, Gower Street, London WC1E 6BT, UK.
| | - Miguel Estevez
- Department of Neurology, University of Arizona College of Medicine, Tucson, AZ 85724, USA; Veterans Affairs Pittsburgh Healthcare System, Research and Development (151U), University Drive C, Pittsburgh, PA 15240, USA.
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10
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Anderson A, McMullan R. From head to tail it's a two way street for neuro-immune communication. WORM 2014. [DOI: 10.4161/worm.29735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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11
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Serotonergic chemosensory neurons modify the C. elegans immune response by regulating G-protein signaling in epithelial cells. PLoS Pathog 2013; 9:e1003787. [PMID: 24348250 PMCID: PMC3861540 DOI: 10.1371/journal.ppat.1003787] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 10/09/2013] [Indexed: 01/08/2023] Open
Abstract
The nervous and immune systems influence each other, allowing animals to rapidly protect themselves from changes in their internal and external environment. However, the complex nature of these systems in mammals makes it difficult to determine how neuronal signaling influences the immune response. Here we show that serotonin, synthesized in Caenorhabditis elegans chemosensory neurons, modulates the immune response. Serotonin released from these cells acts, directly or indirectly, to regulate G-protein signaling in epithelial cells. Signaling in these cells is required for the immune response to infection by the natural pathogen Microbacterium nematophilum. Here we show that serotonin signaling suppresses the innate immune response and limits the rate of pathogen clearance. We show that C. elegans uses classical neurotransmitters to alter the immune response. Serotonin released from sensory neurons may function to modify the immune system in response to changes in the animal's external environment such as the availability, or quality, of food.
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12
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Lee H, Crane MM, Zhang Y, Lu H. Quantitative screening of genes regulating tryptophan hydroxylase transcription in Caenorhabditis elegans using microfluidics and an adaptive algorithm. Integr Biol (Camb) 2013; 5:372-80. [PMID: 23168494 DOI: 10.1039/c2ib20078c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Forward genetic screening via mutagenesis is a powerful method for identifying regulatory factors in target pathways in model organisms such as the soil-dwelling free-living nematode Caenorhabditis elegans (C. elegans). Currently manual microscopy is the standard technique for conducting such screens; however, it is labor-intensive and time-consuming because screening requires imaging thousands of animals. Recently microfluidic chips have been developed to increase the throughput of some of such experiments; nonetheless, most of these chips are multilayer devices and complicated to fabricate and therefore prone to failure during fabrication and operation. In addition, most sorting decisions are made manually and the criteria used for sorting are subjective. To overcome these limitations, we developed a simple single-layer microfluidic device and an adaptive algorithm to make sorting decisions. The one-layer device greatly improves the reliability, while quantitative analysis with the adaptive algorithm allows for the identification of mutations that generate subtle changes in expression, which would have been hard to detect by eye. The screening criterion is set based on the mutagenized population, not separate control populations measured prior to actual screening experiments, to account for stochasticity and day-to-day variations of gene expression in mutagenized worms. Moreover, during each experiment, the threshold is constantly updated to reflect the balance between maximizing sorting rate and minimizing false-positive rate. Using this system, we screened for mutants that have altered expression levels of tryptophan hydroxylase, a key enzyme for serotonin synthesis in a CaMKII gain-of-function background. We found several putative mutants in this screen. Furthermore, this microfluidic system and quantitative analysis can be easily adapted to study other pathways in C. elegans.
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Affiliation(s)
- Hyewon Lee
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Dr NW, Atlanta, Georgia 30332, USA
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13
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Abstract
Transforming Growth Factor-β (TGF-β) superfamily ligands regulate many aspects of cell identity, function, and survival in multicellular animals. Genes encoding five TGF-β family members are present in the genome of C. elegans. Two of the ligands, DBL-1 and DAF-7, signal through a canonical receptor-Smad signaling pathway; while a third ligand, UNC-129, interacts with a noncanonical signaling pathway. No function has yet been associated with the remaining two ligands. Here we summarize these signaling pathways and their biological functions.
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Affiliation(s)
- Tina L Gumienny
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College Station, TX 77843, USA
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14
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A neuronal signaling pathway of CaMKII and Gqα regulates experience-dependent transcription of tph-1. J Neurosci 2013; 33:925-35. [PMID: 23325232 DOI: 10.1523/jneurosci.2355-12.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Dynamic serotonin biosynthesis is important for serotonin function; however, the mechanisms that underlie experience-dependent transcriptional regulation of the rate-limiting serotonin biosynthetic enzyme tryptophan hydroxylase (TPH) are poorly understood. Here, we characterize the molecular and cellular mechanisms that regulate increased transcription of Caenorhabditis elegans tph-1 in a pair of serotonergic neurons ADF during an aversive experience with pathogenic bacteria, a common environmental peril for worms. Training with pathogenic bacteria induces a learned aversion to the smell of the pathogen, a behavioral plasticity that depends on the serotonin signal from ADF neurons. We demonstrate that pathogen training increases ADF neuronal activity. While activating ADF increases tph-1 transcription, inhibiting ADF activity abolishes the training effect on tph-1, demonstrating the dependence of tph-1 transcriptional regulation on ADF neural activity. At the molecular level, the C. elegans homolog of CaMKII, UNC-43, functions cell-autonomously in ADF neurons to generate training-dependent enhancement in neuronal activity and tph-1 transcription, and this cell-autonomous function of UNC-43 is required for learning. Furthermore, selective expression of an activated form of UNC-43 in ADF neurons is sufficient to increase ADF activity and tph-1 transcription, mimicking the training effect. Upstream of ADF, the Gqα protein EGL-30 facilitates training-dependent induction of tph-1 by functional regulation of olfactory sensory neurons, which underscores the importance of sensory experience. Together, our work elucidates the molecular and cellular mechanisms whereby experience modulates tph-1 transcription.
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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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UNC-73/trio RhoGEF-2 activity modulates Caenorhabditis elegans motility through changes in neurotransmitter signaling upstream of the GSA-1/Galphas pathway. Genetics 2011; 189:137-51. [PMID: 21750262 DOI: 10.1534/genetics.111.131227] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Rho-family GTPases play regulatory roles in many fundamental cellular processes. Caenorhabditis elegans UNC-73 RhoGEF isoforms function in axon guidance, cell migration, muscle arm extension, phagocytosis, and neurotransmission by activating either Rac or Rho GTPase subfamilies. Multiple differentially expressed UNC-73 isoforms contain a Rac-specific RhoGEF-1 domain, a Rho-specific RhoGEF-2 domain, or both domains. The UNC-73E RhoGEF-2 isoform is activated by the G-protein subunit Gαq and is required for normal rates of locomotion; however, mechanisms of UNC-73 and Rho pathway regulation of locomotion are not clear. To better define UNC-73 function in the regulation of motility we used cell-specific and inducible promoters to examine the temporal and spatial requirements of UNC-73 RhoGEF-2 isoform function in mutant rescue experiments. We found that UNC-73E acts within peptidergic neurons of mature animals to regulate locomotion rate. Although unc-73 RhoGEF-2 mutants have grossly normal synaptic morphology and weak resistance to the acetylcholinesterase inhibitor aldicarb, they are significantly hypersensitive to the acetylcholine receptor agonist levamisole, indicating alterations in acetylcholine neurotransmitter signaling. Consistent with peptidergic neuron function, unc-73 RhoGEF-2 mutants exhibit a decreased level of neuropeptide release from motor neuron dense core vesicles (DCVs). The unc-73 locomotory phenotype is similar to those of rab-2 and unc-31, genes with distinct roles in the DCV-mediated secretory pathway. We observed that constitutively active Gαs pathway mutations, which compensate for DCV-mediated signaling defects, rescue unc-73 RhoGEF-2 and rab-2 lethargic movement phenotypes. Together, these data suggest UNC-73 RhoGEF-2 isoforms are required for proper neurotransmitter signaling and may function in the DCV-mediated neuromodulatory regulation of locomotion rate.
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Morgan KL, Estevez AO, Mueller CL, Cacho-Valadez B, Miranda-Vizuete A, Szewczyk NJ, Estevez M. The glutaredoxin GLRX-21 functions to prevent selenium-induced oxidative stress in Caenorhabditis elegans. Toxicol Sci 2010; 118:530-43. [PMID: 20833709 PMCID: PMC2984526 DOI: 10.1093/toxsci/kfq273] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Accepted: 09/03/2010] [Indexed: 12/22/2022] Open
Abstract
Selenium is an essential micronutrient that functions as an antioxidant. Yet, at higher concentrations, selenium is pro-oxidant and toxic. In extreme cases, exposures to excess selenium can lead to death or selenosis, a syndrome characterized by teeth, hair and nail loss, and nervous system alterations. Recent interest in selenium as an anti- tumorigenic agent has reemphasized the need to understand the mechanisms underlying the cellular consequences of increased selenium exposure. We show here, that in the nematode, Caenorhabditis elegans, selenium has a concentration range in which it functions as an antioxidant, but beyond this range it exhibits a dose- and time-dependent lethality. Oxidation-induced fluorescence emitted by the dye, carboxy-H(2)DCFDA, indicative of reactive oxygen species formation was significantly higher in animals after a brief exposure to 5mM sodium selenite. Longer-term exposures lead to a progressive selenium-induced motility impairment that could be partially prevented by coincident exposure to the cellular antioxidant-reduced glutathione. The C elegans glrx-21 gene belongs to the family of glutaredoxins (glutathione-dependent oxidoreductases) and the glrx-21(tm2921) allele is a null mutation that renders animals hypersensitive for the selenium-induced motility impairment, but not lethality. In addition, the lethality of animals with the tm2921 mutation exposed to selenium was unaffected by the addition of reduced glutathione, suggesting that GLRX-21 is required for glutathione to moderate this selenium-induced lethality. Our findings provide the first description of selenium-induced toxicity in C elegans and support its use as a model for elucidating the mechanisms of selenium toxicity.
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Affiliation(s)
- Kathleen L. Morgan
- Department of Neurology, Veterans Affairs Pittsburgh Healthcare System, Research and Development (151U), University Drive C, Pittsburgh, Pennsylvania 15240
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Annette O. Estevez
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Catherine L. Mueller
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Briseida Cacho-Valadez
- Centro Andaluz de Biología del Desarrollo (CABD-CSIC)
- Departmento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - Antonio Miranda-Vizuete
- Centro Andaluz de Biología del Desarrollo (CABD-CSIC)
- Departmento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, 41013 Sevilla, Spain
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013 Sevilla, Spain
| | - Nathaniel J. Szewczyk
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Miguel Estevez
- Department of Neurology, Veterans Affairs Pittsburgh Healthcare System, Research and Development (151U), University Drive C, Pittsburgh, Pennsylvania 15240
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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Donohoe DR, Jarvis RA, Weeks K, Aamodt EJ, Dwyer DS. Behavioral adaptation in C. elegans produced by antipsychotic drugs requires serotonin and is associated with calcium signaling and calcineurin inhibition. Neurosci Res 2009; 64:280-9. [PMID: 19447297 PMCID: PMC2692945 DOI: 10.1016/j.neures.2009.03.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Revised: 03/09/2009] [Accepted: 03/26/2009] [Indexed: 11/18/2022]
Abstract
Chronic administration of antipsychotic drugs produces adaptive responses at the cellular and molecular levels that may be responsible for both the main therapeutic effects and rebound psychosis, which is often observed upon discontinuation of these drugs. Here we show that some antipsychotic drugs produce significant functional changes in serotonergic neurons that directly impact feeding behavior in the model organism, Caenorhabditis elegans. In particular, antipsychotic drugs acutely suppress pharyngeal pumping, which is regulated by serotonin from the NSM neurons. By contrast, withdrawal from food and drug is accompanied by a striking recovery and overshoot in the rate of pharyngeal pumping. This rebound response is absent or diminished in mutant strains that lack tryptophan hydroxylase (TPH-1) or the serotonin receptors SER-7 and SER-1, and is blocked by serotonin antagonists, which implicates serotonergic mechanisms in this adaptive response. Consistent with this, continuous drug exposure stimulates an increase in serotonin and the number of varicosities along the NSM processes. Cyclosporin A and calcineurin mutant strains mimic the effects of the antipsychotic drugs and reveal a potential role for the calmodulin-calcineurin signaling pathway in the response of serotonergic neurons. Similar molecular and cellular changes may contribute to the long-term adaptive response to antipsychotic drugs in patients.
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Affiliation(s)
- Dallas R. Donohoe
- Department of Pharmacology, Toxicology and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Raymond A. Jarvis
- Department of Psychiatry, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Kathrine Weeks
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Eric J. Aamodt
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Donard S. Dwyer
- Department of Pharmacology, Toxicology and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
- Department of Psychiatry, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
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Zubenko GS, Jones ML, Estevez AO, Hughes HB, Estevez M. Identification of a CREB-dependent serotonergic pathway and neuronal circuit regulating foraging behavior in Caenorhabditis elegans: a useful model for mental disorders and their treatments? Am J Med Genet B Neuropsychiatr Genet 2009; 150B:12-23. [PMID: 19035344 PMCID: PMC3234207 DOI: 10.1002/ajmg.b.30891] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The cAMP-response element binding protein (CREB)-mediated cell signaling pathway is conserved through evolution and participates in a broad range of complex behaviors of divergent species including man. This study describes the integration of genetic, pharmacologic, and anatomic methods to elucidate a serotonergic signaling pathway by which the CREB homolog CRH-1 controls foraging rate (FR) in the model organism Caenorhabditis elegans, along with the complete neuronal circuit through which this pathway operates. In the anterior afferent arm of the circuit, CRH-1 controls FR by regulating the expression of tph-1, the sole structural gene for tryptophan hydroxylase, in serotonergic sensory (ADF) neurons whose post-synaptic effects are mediated through 5HT(2)-like SER-1 receptors. The posterior afferent limb of the circuit includes an interneuron (RIH) that does not express tph-1 and whose serotonergic phenotype is dependent on the contribution of this neurotransmitter from another source, probably the ADF neurons. The postsynaptic effects of the RIH interneuron are mediated through 5HT(1)-like SER-4 receptors. This model has potential utility for the study of clinical disorders and experimental therapeutics. Furthermore, the discovery of serotonergic neurons that depend on other sources for their neurotransmitter phenotype could provide a mechanism for rapidly altering the number and distribution of serotonergic pathways in developing and adult nervous systems, providing a dimension of functional complexity that has been previously unrecognized.
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Affiliation(s)
- George S Zubenko
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pennsylvania, USA.
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20
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Marziniak M, Jung A, Guralnik V, Evers S, Prudlo J, Geisthoff UW. An Association of Migraine with Hereditary Haemorrhagic Telangiectasia Independently of Pulmonary Right-to-Left Shunts. Cephalalgia 2009; 29:76-81. [DOI: 10.1111/j.1468-2982.2008.01703.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Hereditary haemorrhagic telangiectasia (HHT) is a genetic disorder characterized by epistaxis, telangiectasia and visceral vascular manifestations. It is associated with migraine with aura due to pulmonary arteriovenous malformations (pAVMs). The aim of the study was to evaluate headache prevalence in 106 consecutive HHT patients (67 female, 39 male, age 53.5 ± 14.5 years) and age- and gender-matched controls. An extensive clinical work-up was performed and headache prevalence was determined. Lifetime prevalence of migraine was higher in HHT patients (39.6%) than in controls (19.8%) [ P < 0.001, χ2 = 12.17, odds ratio (OR) 3.0; 95% confidence interval 1.6 < OR < 5.7]. A positive association was confirmed between HHT patients with pAVMs and migraine with aura (38.5% vs. 10%). Furthermore, HHT patients without pAVMs had a higher prevalence of migraine without aura (11.5% vs. 26.3%; χ2 = 11.85; d.f. = 2; P = 0.003). We speculate that pathophysiological mechanisms, including dysfunction of the transforming growth factor-beta pathways and resulting vascular changes, contribute to the higher prevalence of migraine without aura in HHT patients without pAVMs.
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Affiliation(s)
- M Marziniak
- Department of Neurology, University of Münster, Münster, Germany
- Department of Neurology, Saarland University, Homburg/Saar, Germany
| | - A Jung
- Department of Neurology, University of Münster, Münster, Germany
- Department of Neurology, Saarland University, Homburg/Saar, Germany
| | - V Guralnik
- Department of Neurology, Saarland University, Homburg/Saar, Germany
| | - S Evers
- Department of Neurology, University of Münster, Münster, Germany
| | - J Prudlo
- Department of Neurology, Saarland University, Homburg/Saar, Germany
| | - UW Geisthoff
- Department of Otorhinolaryngology, Saarland University, Homburg/Saar, and Hospitals of the City of Cologne, Cologne, Germany
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21
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Donohoe DR, Phan T, Weeks K, Aamodt EJ, Dwyer DS. Antipsychotic drugs up-regulate tryptophan hydroxylase in ADF neurons of Caenorhabditis elegans: role of calcium-calmodulin-dependent protein kinase II and transient receptor potential vanilloid channel. J Neurosci Res 2008; 86:2553-63. [PMID: 18438926 DOI: 10.1002/jnr.21684] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Antipsychotic drugs produce acute behavioral effects through antagonism of dopamine and serotonin receptors, and long-term adaptive responses that are not well understood. The goal of the study presented here was to use Caenorhabditis elegans to investigate the molecular mechanism or mechanisms that contribute to adaptive responses produced by antipsychotic drugs. First-generation antipsychotics, trifluoperazine and fluphenazine, and second-generation drugs, clozapine and olanzapine, increased the expression of tryptophan hydroxylase-1::green fluorescent protein (TPH-1::GFP) and serotonin in the ADF neurons of C. elegans. This response was absent or diminished in mutant strains lacking the transient receptor potential vanilloid channel (TRPV; osm-9) or calcium/calmodulin-dependent protein kinase II (CaMKII; unc-43). The role of calcium signaling was further implicated by the finding that a selective antagonist of calmodulin and a calcineurin inhibitor also enhanced TPH-1::GFP expression. The ADF neurons modulate foraging behavior (turns/reversals off food) through serotonin production. We found that short-term exposure to the antipsychotic drugs altered the frequency of turns/reversals off food. This response was mediated through dopamine and serotonin receptors and was abolished in serotonin-deficient mutants (tph-1) and strains lacking the SER-1 and MOD-1 serotonin receptors. Consistent with the increase in serotonin in the ADF neurons induced by the drugs, drug withdrawal after 24-hr treatment was accompanied by a rebound in the number of turns/reversals, which demonstrates behavioral adaptation in serotonergic systems. Characterization of the cellular, molecular, and behavioral adaptations to continuous exposure to antipsychotic drugs may provide insight into the long-term clinical effects of these medications.
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Affiliation(s)
- Dallas R Donohoe
- Department of Pharmacology, Toxicology and Neuroscience, Louisiana State University Health Sciences Center-Shreveport, Shreveport, Louisiana 71130, USA
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22
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Bryden J, Cohen N. Neural control of Caenorhabditis elegans forward locomotion: the role of sensory feedback. BIOLOGICAL CYBERNETICS 2008; 98:339-351. [PMID: 18350313 DOI: 10.1007/s00422-008-0212-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Accepted: 01/25/2008] [Indexed: 05/26/2023]
Abstract
This paper presents a simple yet biologically-grounded model for the neural control of Caenorhabditis elegans forward locomotion. We identify a minimal circuit within the C. elegans ventral cord that is likely to be sufficient to generate and sustain forward locomotion in vivo. This limited subcircuit appears to contain no obvious central pattern generated control. For that subcircuit, we present a model that relies on a chain of oscillators along the body which are driven by local and proximate mechano-sensory input. Computer simulations were used to study the model under a variety of conditions and to test whether it is behaviourally plausible. Within our model, we find that a minimal circuit of AVB interneurons and B-class motoneurons is sufficient to generate and sustain fictive forward locomotion patterns that are robust to significant environmental perturbations. The model predicts speed and amplitude modulation by the AVB command interneurons. An extended model including D-class motoneurons is included for comparison.
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Affiliation(s)
- John Bryden
- School of Computing, University of Leeds, Leeds, UK
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23
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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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24
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Loer CM, Rivard L. Evolution of neuronal patterning in free-living rhabditid nematodes I: Sex-specific serotonin-containing neurons. J Comp Neurol 2007; 502:736-67. [PMID: 17436291 DOI: 10.1002/cne.21288] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
As a first step toward understanding the evolution of neuronal patterning and function in a group of simple animals, we have examined serotonin-containing neurons in 17 species of free-living rhabditid nematodes and compared them with identified neurons of Caenorhabditis elegans. We found many serotonin-immunoreactive (serotonin-IR) neurons that are likely homologs of those in C. elegans; this paper focuses on sex-specific neurons such as the egg laying hermaphrodite-specific neurons (HSNs), VCs, and male CAs, CPs, and ray sensory neurons known to function in mating. These cells vary in number and position in the species examined but are consistent with a current molecularly based phylogeny. Two groups (Oscheius and Pristionchus) appear independently to have lost a serotonin-IR HSN. Oscheius furthermore has no serotonin-IR innervation of the vulval region, in contrast to every other species we examined. We also saw variation in the location of somas of putative HSN, consistent with evolutionary changes in HSN migration. In C. elegans, the HSN soma migrates during embryogenesis from the tail to the central body, where it innervates its major postsynaptic targets, the vulval muscles. For other species, we observed putative HSN homologs along the anterior-posterior axis from the head to the tail, but typically HSNs were located near the vulva, which also varies in anterior-posterior position among the species we examined. The varying positions of the HSN somas in other species are reminiscent of phenotypes seen in various C. elegans mutants with altered HSN migration, suggesting possible mechanisms for the evolutionary differences we observed.
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Affiliation(s)
- Curtis M Loer
- Department of Biology, University of San Diego, California 92110, USA.
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25
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Chang AJ, Chronis N, Karow DS, Marletta MA, Bargmann CI. A distributed chemosensory circuit for oxygen preference in C. elegans. PLoS Biol 2007; 4:e274. [PMID: 16903785 PMCID: PMC1540710 DOI: 10.1371/journal.pbio.0040274] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Accepted: 06/16/2006] [Indexed: 11/19/2022] Open
Abstract
The nematode Caenorhabditis elegans has complex, naturally variable behavioral responses to environmental oxygen, food, and other animals. C. elegans detects oxygen through soluble guanylate cyclase homologs (sGCs) and responds to it differently depending on the activity of the neuropeptide receptor NPR-1: npr-1(lf) and naturally isolated npr-1(215F) animals avoid high oxygen and aggregate in the presence of food; npr-1(215V) animals do not. We show here that hyperoxia avoidance integrates food with npr-1 activity through neuromodulation of a distributed oxygen-sensing network. Hyperoxia avoidance is stimulated by sGC-expressing oxygen-sensing neurons, nociceptive neurons, and ADF sensory neurons. In npr-1(215V) animals, the switch from weak aerotaxis on food to strong aerotaxis in its absence requires close regulation of the neurotransmitter serotonin in the ADF neurons; high levels of ADF serotonin promote hyperoxia avoidance. In npr-1(lf) animals, food regulation is masked by increased activity of the oxygen-sensing neurons. Hyperoxia avoidance is also regulated by the neuronal TGF-beta homolog DAF-7, a secreted mediator of crowding and stress responses. DAF-7 inhibits serotonin synthesis in ADF, suggesting that ADF serotonin is a convergence point for regulation of hyperoxia avoidance. Coalitions of neurons that promote and repress hyperoxia avoidance generate a subtle and flexible response to environmental oxygen.
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Affiliation(s)
- Andy J Chang
- Howard Hughes Medical Institute and Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, New York, United States of America
| | - Nikolas Chronis
- Howard Hughes Medical Institute and Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, New York, United States of America
| | - David S Karow
- Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Departments of Chemistry and Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- Division of Physical Biosciences, Lawrence Berkeley National Lab, Berkeley, California, United States of America
| | - Michael A Marletta
- Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Departments of Chemistry and Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- Division of Physical Biosciences, Lawrence Berkeley National Lab, Berkeley, California, United States of America
| | - Cornelia I Bargmann
- Howard Hughes Medical Institute and Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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26
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Abstract
Migraine is a chronic episodic disorder that has been linked to abnormalities in serotonin signaling and abnormal function of a presynaptic voltage-gated calcium channel, CACNA1A. Although the importance of serotonin to migraine tendency suggests a link between serotonergic signaling and CACNA1A function, the nature of this connection remains unclear in vertebrate studies. This article reviews findings, based on an invertebrate model of CACNA1A dysfunction, which suggest a potential connection between serotonergic and calcium channel abnormalities in migraine. Neurons of the invertebrate species Caenorhabditis elegans express a voltage-gated calcium channel, UNC-2, which is the closest ortholog in C. elegans of human CACNA1A. Mutations in unc-2, the gene that encodes this invertebrate channel, cause the animals to be lethargic and uncoordinated. By identifying the genes that could be altered in such a way as to suppress the lethargic phenotype of unc-2, a signaling pathway has been identified through which UNC-2 calcium channel function antagonizes a transforming growth factor-beta (TGF-beta) pathway modulating locomotion. In C. elegans, serotonergic signaling can inhibit the rate of movement. The UNC-2/transforming growth factor-beta pathway identified regulates the expression of a gene encoding the rate-limiting enzyme for serotonin synthesis, tryptophan hydroxylase. The evolutionary and functional relationship between the UNC-2 channel and the migraine-associated CACNA1A channel was further confirmed through experiments showing that transgenic expression of human CACNA1A can suppress the lethargic and serotonin-deficient phenotypes of unc-2 mutant animals. The findings in this invertebrate model constitute the first direct demonstration of how CACNA1A function might affect the levels of serotonin, a neurotransmitter known to be important in migraine.
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Affiliation(s)
- Miguel Estevez
- Veterans Administration Hospital and University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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27
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McDonald PW, Jessen T, Field JR, Blakely RD. Dopamine signaling architecture in Caenorhabditis elegans. Cell Mol Neurobiol 2006; 26:593-618. [PMID: 16724276 PMCID: PMC11520601 DOI: 10.1007/s10571-006-9003-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2006] [Accepted: 02/08/2006] [Indexed: 10/24/2022]
Abstract
AIMS In this review, we highlight the identification and analysis of molecules orchestrating dopamine (DA) signaling in the nematode Caenorhabditis elegans, focusing on recent characterizations of DA transporters and receptors. METHODS We illustrate the isolation and characterization of molecules important for C. elegans DA synthesis, packaging, reuptake and signaling and examine how mutations in these proteins are being exploited through in vitro and in vivo paradigms to yield novel insights of protein structure, DA signaling pathways and DA-supported behaviors. RESULTS DA signaling in the worm, as in man, arises by synaptic and nonsynaptic release from a small number of cells that exert modulatory control over a larger network underlying C. elegans behavior. CONCLUSIONS The C. elegans model system offers unique opportunities to elucidate ill-defined pathways that support DA release, inactivation, and signaling in addition to clarifying mechanisms of DA-mediated behavioral plasticity. Further use of the model offers prospects for the identification of novel genes and proteins whose study may yield benefits for DA-supported neural disorders in man.
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Affiliation(s)
- Paul W. McDonald
- Graduate Programs in Neuroscience and Pharmacology, Departments of Pharmacology and Psychiatry, Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8548 USA
| | - Tammy Jessen
- Graduate Programs in Neuroscience and Pharmacology, Departments of Pharmacology and Psychiatry, Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8548 USA
| | - Julie R. Field
- Graduate Programs in Neuroscience and Pharmacology, Departments of Pharmacology and Psychiatry, Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8548 USA
| | - Randy D. Blakely
- Graduate Programs in Neuroscience and Pharmacology, Departments of Pharmacology and Psychiatry, Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8548 USA
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28
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Estevez AO, Cowie RH, Gardner KL, Estevez M. Both insulin and calcium channel signaling are required for developmental regulation of serotonin synthesis in the chemosensory ADF neurons of Caenorhabditis elegans. Dev Biol 2006; 298:32-44. [PMID: 16860310 DOI: 10.1016/j.ydbio.2006.06.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Revised: 06/04/2006] [Accepted: 06/05/2006] [Indexed: 11/18/2022]
Abstract
Proper calcium channel and insulin signaling are essential for normal brain development. Leaner mice with a mutation in the P/Q-type voltage-gated calcium channel, Cacna1a, develop cerebellar atrophy and mutations in the homologous human gene are associated with increased migraine and seizure tendency. Similarly, abnormalities in insulin signaling are associated with abnormal brain growth and migraine tendency. Previously, we have shown that in the ADF chemosensory neurons of Caenorhabditis elegans UNC-2/Ca(2+) channel function affects TGF-beta-dependent developmental regulation of tryptophan hydroxylase, the rate-limiting enzyme in serotonin synthesis. Here we show that developmental expression of a tryptophan hydroxylase: :GFP reporter construct is similarly decreased by reduction-of-function mutations in the daf-2/insulin receptor. This decreased expression of tryptophan hydroxylase observed in both the daf-2 and unc-2 mutant backgrounds is suppressible either genetically by reduction-of-function mutations in the daf-16/forkhead transcription factor, an effector of the DAF-2/insulin receptor, or pharmacologically by the serotonin receptor antagonist cyproheptadine. Overall, these data suggest that both UNC-2 and DAF-2 function are required in the developmental regulation of DAF-16 and serotonin-dependent inhibition of tryptophan hydroxylase expression.
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Affiliation(s)
- Annette O Estevez
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
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29
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Zhang Y, Lu H, Bargmann CI. Pathogenic bacteria induce aversive olfactory learning in Caenorhabditis elegans. Nature 2005; 438:179-84. [PMID: 16281027 DOI: 10.1038/nature04216] [Citation(s) in RCA: 574] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 09/08/2005] [Indexed: 11/09/2022]
Abstract
Food can be hazardous, either through toxicity or through bacterial infections that follow the ingestion of a tainted food source. Because learning about food quality enhances survival, one of the most robust forms of olfactory learning is conditioned avoidance of tastes associated with visceral malaise. The nematode Caenorhabditis elegans feeds on bacteria but is susceptible to infection by pathogenic bacteria in its natural environment. Here we show that C. elegans modifies its olfactory preferences after exposure to pathogenic bacteria, avoiding odours from the pathogen and increasing its attraction to odours from familiar nonpathogenic bacteria. Particular bacteria elicit specific changes in olfactory preferences that are suggestive of associative learning. Exposure to pathogenic bacteria increases serotonin in ADF chemosensory neurons by transcriptional and post-transcriptional mechanisms. Serotonin functions through MOD-1, a serotonin-gated chloride channel expressed in sensory interneurons, to promote aversive learning. An increase in serotonin may represent the negative reinforcing stimulus in pathogenic infection.
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Affiliation(s)
- Yun Zhang
- Howard Hughes Medical Institute, Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, New York 10021, USA
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