101
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Giles AC, Rose JK, Rankin CH. Investigations of learning and memory in Caenorhabditis elegans. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 69:37-71. [PMID: 16492461 DOI: 10.1016/s0074-7742(05)69002-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Andrew C Giles
- Department of Psychology and Brain Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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102
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Kimura KD, Miyawaki A, Matsumoto K, Mori I. The C. elegans thermosensory neuron AFD responds to warming. Curr Biol 2004; 14:1291-5. [PMID: 15268861 DOI: 10.1016/j.cub.2004.06.060] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Revised: 05/07/2004] [Accepted: 06/02/2004] [Indexed: 11/21/2022]
Abstract
The mechanism of temperature sensation is far less understood than the sensory response to other environmental stimuli such as light, odor, and taste. Thermotaxis behavior in C. elegans requires the ability to discriminate temperature differences as small as approximately 0.05 degrees C and to memorize the previously cultivated temperature. The AFD neuron is the only major thermosensory neuron required for the thermotaxis behavior. Genetic analyses have revealed several signal transduction molecules that are required for the sensation and/or memory of temperature information in the AFD neuron, but its physiological properties, such as its ability to sense absolute temperature or temperature change, have been unclear. We show here that the AFD neuron responds to warming. Calcium concentration in the cell body of AFD neuron is increased transiently in response to warming, but not to absolute temperature or to cooling. The transient response requires the activity of the TAX-4 cGMP-gated cation channel, which plays an essential role in the function of the AFD neuron. Interestingly, the AFD neuron further responds to step-like warming above a threshold that is set by temperature memory. We suggest that C. elegans provides an ideal model to genetically and physiologically reveal the molecular mechanism for sensation and memory of temperature information.
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Affiliation(s)
- Koutarou D Kimura
- Group of Molecular Neurobiology, Department of Molecular Biology, Graduate School of Science, Nagoya University, Japan.
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103
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Regulation of signaling genes by TGFbeta during entry into dauer diapause in C. elegans. BMC DEVELOPMENTAL BIOLOGY 2004; 4:11. [PMID: 15380030 PMCID: PMC524168 DOI: 10.1186/1471-213x-4-11] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Accepted: 09/20/2004] [Indexed: 11/18/2022]
Abstract
Background When resources are scant, C. elegans larvae arrest as long-lived dauers under the control of insulin/IGF- and TGFβ-related signaling pathways. However, critical questions remain regarding the regulation of this developmental event. How do three dozen insulin-like proteins regulate one tyrosine kinase receptor to control complex events in dauer, metabolism and aging? How are signals from the TGFβ and insulin/IGF pathways integrated? What gene expression programs do these pathways regulate, and how do they control complex downstream events? Results We have identified genes that show different levels of expression in a comparison of wild-type L2 or L3 larvae (non-dauer) to TGFβ mutants at similar developmental stages undergoing dauer formation. Many insulin/IGF pathway and other known dauer regulatory genes have changes in expression that suggest strong positive feedback by the TGFβ pathway. In addition, many insulin-like ligand and novel genes with similarity to the extracellular domain of insulin/IGF receptors have altered expression. We have identified a large group of regulated genes with putative binding sites for the FOXO transcription factor, DAF-16. Genes with DAF-16 sites upstream of the transcription start site tend to be upregulated, whereas genes with DAF-16 sites downstream of the coding region tend to be downregulated. Finally, we also see strong regulation of many novel hedgehog- and patched-related genes, hormone biosynthetic genes, cell cycle genes, and other regulatory genes. Conclusions The feedback regulation of insulin/IGF pathway and other dauer genes that we observe would be predicted to amplify signals from the TGFβ pathway; this amplification may serve to ensure a decisive choice between "dauer" and "non-dauer", even if environmental cues are ambiguous. Up and down regulation of insulin-like ligands and novel genes with similarity to the extracellular domain of insulin/IGF receptors suggests opposing roles for several members of these large gene families. Unlike in adults, most genes with putative DAF-16 binding sites are upregulated during dauer entry, suggesting that DAF-16 has different activity in dauer versus adult metabolism and aging. However, our observation that the position of putative DAF-16 binding sites is correlated with the direction of regulation suggests a novel method of achieving gene-specific regulation from a single pathway. We see evidence of TGFβ-mediated regulation of several other classes of regulatory genes, and we discuss possible functions of these genes in dauer formation.
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104
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Lipton J, Kleemann G, Ghosh R, Lints R, Emmons SW. Mate searching in Caenorhabditis elegans: a genetic model for sex drive in a simple invertebrate. J Neurosci 2004; 24:7427-34. [PMID: 15329389 PMCID: PMC6729642 DOI: 10.1523/jneurosci.1746-04.2004] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 07/12/2004] [Accepted: 07/14/2004] [Indexed: 11/21/2022] Open
Abstract
Much of animal behavior is regulated to accomplish goals necessary for survival and reproduction. Little is known about the underlying motivational or drive states that are postulated to mediate such goal-directed behaviors. Here, we describe a mate-searching behavior of the Caenorhabditis elegans male that resembles the motivated behaviors of vertebrates. Adult C. elegans males, if isolated from mating partners, will leave the area of a food source and wander about their environment in an apparent search for a mate. When mating partners are present on the food source, males do not wander but remain with them. This behavior is sexually dimorphic for C. elegans and two additional male/hermaphrodite species studied; for these species, hermaphrodites leave food significantly slower than males. In contrast, for three male-female species examined, both males and females left food, in two cases with similar frequency, suggesting coordinate evolution of behavioral dimorphism with hermaphroditism. We use a quantitative behavioral assay to show that C. elegans male mate searching is regulated by signals from hermaphrodites and by physiological signals indicating nutritional and reproductive status. We identify genes in the serotonin, insulin, and sex determination pathways that affect the rate of mate searching. These genes may contribute to physiological and reproductive regulatory mechanisms. Our results establish C. elegans as a model genetic animal with a simple nervous system in which neural pathways leading to a motivated behavior may be genetically dissected.
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Affiliation(s)
- Jonathan Lipton
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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105
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Abstract
The nematode worm Caenorhabditis elegans can learn and remember the stimuli it encounters, the environment it is in, and its own physiological state. Analyses of mutations in C. elegans that affect different aspects of experience are beginning to address the nature of learning.
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Affiliation(s)
- Catharine H Rankin
- Brain Research Centre and Department of Psychology, University of British Columbia, 2211 Wesbrook Mall, Vancouver, British Columbia, V6T 2B5, Canada.
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106
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Satterlee JS, Ryu WS, Sengupta P. The CMK-1 CaMKI and the TAX-4 Cyclic nucleotide-gated channel regulate thermosensory neuron gene expression and function in C. elegans. Curr Biol 2004; 14:62-8. [PMID: 14711416 DOI: 10.1016/j.cub.2003.12.030] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The cultivation temperature (T(c)) modulates the thermosensory responses exhibited by C. elegans on thermal gradients. The AFD sensory neurons are essential for thermosensory behaviors, but the molecular mechanisms by which temperature is sensed and the memory of the T(c) is encoded are unknown. Here, we show that the CMK-1 Ca2+/calmodulin-dependent protein kinase I (CaMKI) and the TAX-4 cyclic nucleotide-gated channel regulate gene expression, morphology, and functions of the AFD thermosensory neurons. Mutations in cmk-1 and tax-4 result in temperature-dependent defects in AFD-specific gene expression, and TAX-4 functions are required during larval stages to maintain gene expression in the adult. CMK-1 and TAX-4 act cell autonomously to regulate AFD-mediated thermosensory behaviors. The molecular requirements for CMK-1 activity in the AFD neurons appear to be distinct from those previously described. We propose that the activation of distinct programs of AFD-specific gene expression at different temperatures by CMK-1 and TAX-4 enables C. elegans to sense and/or encode a memory for the T(c).
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Affiliation(s)
- John S Satterlee
- Department of Biology and Volen Center for Complex Systems, Brandeis University, MS 008, Waltham, Massachusetts 02454, USA
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107
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Abstract
Caenorhabditis elegans has close homologs or orthologs of most mammalian (RGS) and G proteins, and mutants for all the RGS and G-protein genes of C. elegans have been generated. C. elegans RGS proteins can be matched to the specific Galpha proteins they regulate in vivo by comparing the defects in animals lacking or transgenically overexpressing an RGS protein with defects in a specific Galpha mutant. Transgenic expression of mutated RGS proteins or subdomains in C. elegans has also been used to carry out structure/function studies of RGS proteins. We propose that similar strategies can be used to understand the function of RGS proteins from other organisms by expressing them in C. elegans. This article describes general considerations regarding such experiments and provides detailed protocols for quantitatively measuring G-protein signaling phenotypes in C. elegans.
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Affiliation(s)
- Daniel L Chase
- Department of Molecular Biophysics, The University of North Carolina at Chapel Hill, 27599-7260, USA
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108
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Abstract
Temperature is one of our most important physical cues, with extremes eliciting painful sensory warnings of tissue damage. Two recent publications present findings in Drosophila that implicate different neural substrates for low- and high-temperature responses, as well as indicating that a transient receptor potential (TRP) channel family member, painless, plays a role in these responses.
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Affiliation(s)
- Troy Zars
- University of Missouri-Columbia, Division of Biological Sciences, 114 Lefevre Hall, Columbia, MO 65211, USA.
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109
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Patapoutian A, Peier AM, Story GM, Viswanath V. ThermoTRP channels and beyond: mechanisms of temperature sensation. Nat Rev Neurosci 2003; 4:529-39. [PMID: 12838328 DOI: 10.1038/nrn1141] [Citation(s) in RCA: 580] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ardem Patapoutian
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
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110
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Abstract
The human brain contains 100 billion neurons and probably one thousand times more synapses. Such a system can be analyzed at different complexity levels, from cognitive functions to molecular structure of ion channels. However, it remains extremely difficult to establish links between these different levels. An alternative strategy relies on the use of much simpler animals that can be easily manipulated. In 1974, S. Brenner introduced the nematode Caenorhabditis elegans as a model system. This worm has a simple nervous system that only contains 302 neurons and about 7,000 synapses. Forward genetic screens are powerful tools to identify genes required for specific neuron functions and behaviors. Moreover, studies of mutant phenotypes can identify the function of a protein in the nervous system. The data that have been obtained in C. elegans demonstrate a fascinating conservation of the molecular and cellular biology of the neuron between worms and mammals through more than 550 million years of evolution.
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Affiliation(s)
- Christelle Gally
- Biologie Cellulaire de la Synapse, Inserm U.497, Ecole Normale Supérieure, 46, rue d'Ulm, 75230 Paris Cedex 05, France
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111
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Abstract
The past year has seen a doubling in the number of heat-sensitive ion channels to six, and four of these channels are from the TRPV family. These channels characteristically have Q(10) values of >10 above the thermal threshold, very different from the Q(10) values of 1.5-2.0 seen in most ion channels. Cells expressing TRPV1 show similar temperature sensitivity to small capsaicin-sensitive nociceptor neurons, consistent with these neurons expressing homomers of TRPV1. A-delta fibres exhibit properties that may be explained by TRPV2 containing channels which is present in large diameter sensory neurons that do not express TRPV1. TRPV3 has a lower temperature threshold and may contribute to warm-sensitive channels together with TRPV1. Warm sensation may also be transduced by TRPV4 expressing sensory neurons and hypothalamic neurons. We can now look forward to further work defining the properties of the recombinant channels in more detail and a re-analysis of endogenous i(heat) currents in thermosensitive neurons and other cells. Data from the study of mice in which TRPV2, TRPV3 or TRPV4 have been deleted are also eagerly awaited.
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Affiliation(s)
- Christopher D Benham
- Neurology, GlaxoSmithKline Research and Development Ltd., New Frontiers Science Park (North), Third Avenue, Harlow, Essex CM19 5AW, UK.
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112
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Strange K. From genes to integrative physiology: ion channel and transporter biology in Caenorhabditis elegans. Physiol Rev 2003; 83:377-415. [PMID: 12663863 DOI: 10.1152/physrev.00025.2002] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The stunning progress in molecular biology that has occurred over the last 50 years drove a powerful reductionist approach to the study of physiology. That same progress now forms the foundation for the next revolution in physiological research. This revolution will be focused on integrative physiology, which seeks to understand multicomponent processes and the underlying pathways of information flow from an organism's "parts" to increasingly complex levels of organization. Genetically tractable and genomically defined nonmammalian model organisms such as the nematode Caenorhabditis elegans provide powerful experimental advantages for elucidating gene function and the molecular workings of complex systems. This review has two main goals. The first goal is to describe the experimental utility of C. elegans for investigating basic physiological problems. A detailed overview of C. elegans biology and the experimental tools, resources, and strategies available for its study is provided. The second goal of this review is to describe how forward and reverse genetic approaches and direct behavioral and physiological measurements in C. elegans have generated novel insights into the integrative physiology of ion channels and transporters. Where appropriate, I describe how insights from C. elegans have provided new understanding of the physiology of membrane transport processes in mammals.
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Affiliation(s)
- Kevin Strange
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
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113
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Abstract
Thermotactic behavior in Caenorhabditis elegans is sensitive to both a worm's ambient temperature (T(amb)) and its memory of the temperature of its cultivation (T(cult)). The AFD neuron is part of a neural circuit that underlies thermotactic behavior. By monitoring the fluorescence of pH-sensitive green fluorescent protein localized to synaptic vesicles, we measured the rate of the synaptic release of AFD in worms cultivated at temperatures between 15 and 25 degrees C, and subjected to fixed, ambient temperatures in the same range. We found that the rate of AFD synaptic release is high if either T(amb) > T(cult) or T(amb) < T(cult), but AFD synaptic release is low if T(amb) congruent with T(cult). This suggests that AFD encodes a direct comparison between T(amb) and T(cult).
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114
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Abstract
Susceptibility to drug addiction depends on genetic and environmental factors and their complex interactions. Studies with mammalian models have identified molecular targets, neurochemical systems, and brain regions that mediate some of the addictive properties of abused drugs. Yet, our understanding of how the primary effects of drugs lead to addiction remains incomplete. Recently, researchers have turned to the invertebrate model systems Drosophila melanogaster and Caenorhabditis elegans to dissect the mechanisms by which abused drugs modulate behavior. Due to their sophisticated genetics, relatively simple anatomy, and their remarkable molecular similarity to mammals, these invertebrate models should provide useful insights into the mechanisms of drug action. Here we review recent behavioral and genetic studies in flies and worms on the effects of ethanol, cocaine, and nicotine, three of the most widely abused drugs in the world.
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Affiliation(s)
- Fred W Wolf
- Department of Anatomy and Program in Neuroscience, University of California San Francisco, 513 Parnassus Avenue, San Francisco, California 94143-0452, USA.
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115
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Hobert O. Behavioral plasticity in C. elegans: paradigms, circuits, genes. JOURNAL OF NEUROBIOLOGY 2003; 54:203-23. [PMID: 12486705 DOI: 10.1002/neu.10168] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Life in the soil is an intellectual and practical challenge that the nematode Caenorhabditis elegans masters by utilizing 302 neurons. The nervous system assembled by these 302 neurons is capable of executing a variety of behaviors, some of respectable complexity. The simplicity of the nervous system, its thoroughly characterized structure, several sets of well-defined behaviors, and its genetic amenability combined with its isogenic background make C. elegans an attractive model organism to study the genetics of behavior. This review describes several behavioral plasticity paradigms in C. elegans and their underlying neuronal circuits and then goes on to review the forward genetic analysis that has been undertaken to identify genes involved in the execution of these behaviors. Lastly, the review outlines how reverse genetics and genomic approaches can guide the analysis of the role of genes in behavior and why and how they will complement the forward genetic analysis of behavior.
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Affiliation(s)
- Oliver Hobert
- Department of Biochemistry and Molecular Biophysics, Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
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116
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Milani N, Guarin E, Renfer E, Nef P, Andres-Barquin PJ. Functional expression of a mammalian olfactory receptor in Caenorhabditis elegans. Neuroreport 2002; 13:2515-20. [PMID: 12499859 DOI: 10.1097/00001756-200212200-00027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The olfactory system in both vertebrates and invertebrates can recognize and distinguish thousands of chemical signals. Olfactory receptors are responsible for the early molecular events in the detection of volatile compounds and the perception of smell. Recently, candidate olfactory receptor genes have been identified in several organisms, but their characterization is far from been completed due to the difficulty to functionally express them in heterologous systems. To circumvent such difficulty, we expressed a mammalian olfactory gene, rat I7, in the nematode. We generated transgenic worms expressing I7 in AWA or AWB chemosensory neurons and performed behavioural assays using different concentrations of the rat I7 receptor agonist octanal. Pure octanal was repellent for wild-type worms whereas a 1:10 dilution was attractant. Expression of I7 in AWB neurons counteracted the volatile attraction to diluted octanal observed in control wild-type worms. Furthermore, expression of I7 in AWA neurons counteracted the volatile avoidance to pure octanal observed in wild-type worms. These results indicate that it is possible to functionally express mammalian olfactory receptors in providing a research tool to efficiently search for specific olfactory receptor ligands and to extend our understanding of the molecular basis of olfaction.
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Affiliation(s)
- Nicoletta Milani
- Department of Neuroscience, Building 93/340, F. Hoffmann-La Roche, Basel 4070, Switzerland
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117
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Coates JC, de Bono M. Antagonistic pathways in neurons exposed to body fluid regulate social feeding in Caenorhabditis elegans. Nature 2002; 419:925-9. [PMID: 12410311 DOI: 10.1038/nature01170] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2002] [Accepted: 09/30/2002] [Indexed: 11/09/2022]
Abstract
Wild isolates of Caenorhabditis elegans can feed either alone or in groups. This natural variation in behaviour is associated with a single residue difference in NPR-1, a predicted G-protein-coupled neuropeptide receptor related to Neuropeptide Y receptors. Here we show that the NPR-1 isoform associated with solitary feeding acts in neurons exposed to the body fluid to inhibit social feeding. Furthermore, suppressing the activity of these neurons, called AQR, PQR and URX, using an activated K(+) channel, inhibits social feeding. NPR-1 activity in AQR, PQR and URX neurons seems to suppress social feeding by antagonizing signalling through a cyclic GMP-gated ion channel encoded by tax-2 and tax-4. We show that mutations in tax-2 or tax-4 disrupt social feeding, and that tax-4 is required in several neurons for social feeding, including one or more of AQR, PQR and URX. The AQR, PQR and URX neurons are unusual in C. elegans because they are directly exposed to the pseudocoelomic body fluid. Our data suggest a model in which these neurons integrate antagonistic signals to control the choice between social and solitary feeding behaviour.
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Affiliation(s)
- Juliet C Coates
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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118
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Abstract
In a spatial thermal gradient, Caenorhabditis elegans migrates toward and then isothermally tracks near its cultivation temperature. A current model for thermotactic behavior involves a thermophilic drive (involving the neurons AFD and AIY) and cryophilic drive (involving the neuron AIZ) that balance at the cultivation temperature. Here, we analyze the movements of individual worms responding to defined thermal gradients. We found evidence for a mechanism for migration down thermal gradients that is active at temperatures above the cultivation temperature, and a mechanism for isothermal tracking that is active near the cultivation temperature. However, we found no evidence for a mechanism for migration up thermal gradients at temperatures below the cultivation temperature that might have supported the model of opposing drives. The mechanisms for migration down gradients and isothermal tracking control the worm's movements in different manners. Migration down gradients works by shortening (lengthening) the duration of forward movement in response to positive (negative) temperature changes. Isothermal tracking works by orienting persistent forward movement to offset temperature changes. We believe preference for the cultivation temperature is not at the balance between two drives. Instead, the worm activates the mechanism for isothermal tracking near the cultivation temperature and inactivates the mechanism for migration down gradients near or below the cultivation temperature. Inactivation of the mechanism for migration down gradients near or below the cultivation temperature requires the neurons AFD and AIY.
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119
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Ishihara T, Iino Y, Mohri A, Mori I, Gengyo-Ando K, Mitani S, Katsura I. HEN-1, a secretory protein with an LDL receptor motif, regulates sensory integration and learning in Caenorhabditis elegans. Cell 2002; 109:639-49. [PMID: 12062106 DOI: 10.1016/s0092-8674(02)00748-1] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Animals sense many environmental stimuli simultaneously and integrate various sensory signals within the nervous system both to generate proper behavioral responses and also to form relevant memories. HEN-1, a secretory protein with an LDL receptor motif, regulates such processes in Caenorhabditis elegans. The hen-1 mutants show defects in the integration of two sensory signals and in behavioral plasticity by paired stimuli, although their sensation capability seems to be identical to that of the wild-type. The HEN-1 protein is expressed in two pairs of neurons, but expression in other neurons is sufficient for wild-type behavior. In addition, expression of HEN-1 at the adult stage is sufficient. Thus, HEN-1 regulates sensory processing non-cell-autonomously in the mature neuronal circuit.
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Affiliation(s)
- Takeshi Ishihara
- Structural Biology Center, National Institute of Genetics, Mishima, Japan.
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120
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Kuhara A, Inada H, Katsura I, Mori I. Negative regulation and gain control of sensory neurons by the C. elegans calcineurin TAX-6. Neuron 2002; 33:751-63. [PMID: 11879652 DOI: 10.1016/s0896-6273(02)00607-4] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Animals sense and adapt to variable environments by regulating appropriate sensory signal transduction pathways. Here, we show that calcineurin plays a key role in regulating the gain of sensory neuron responsiveness across multiple modalities. C. elegans animals bearing a loss-of-function mutation in TAX-6, a calcineurin A subunit, exhibit pleiotropic abnormalities, including many aberrant sensory behaviors. The tax-6 mutant defect in thermosensation is consistent with hyperactivation of the AFD thermosensory neurons. Conversely, constitutive activation of TAX-6 causes a behavioral phenotype consistent with inactivation of AFD neurons. In olfactory neurons, the impaired olfactory response of tax-6 mutants to an AWC-sensed odorant is caused by hyperadaptation, which is suppressible by a mutation causing defective olfactory adaptation. Taken together, our results suggest that stimulus-evoked calcium entry activates calcineurin, which in turn negatively regulates multiple aspects of sensory signaling.
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Affiliation(s)
- Atsushi Kuhara
- Division of Biological Science, Graduate School of Science, Nagoya University, 464-8602, Nagoya, Japan
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121
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Satterlee JS, Sasakura H, Kuhara A, Berkeley M, Mori I, Sengupta P. Specification of thermosensory neuron fate in C. elegans requires ttx-1, a homolog of otd/Otx. Neuron 2001; 31:943-56. [PMID: 11580895 DOI: 10.1016/s0896-6273(01)00431-7] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Temperature is a critical modulator of animal metabolism and behavior, yet the mechanisms underlying the development and function of thermosensory neurons are poorly understood. C. elegans senses temperature using the AFD thermosensory neurons. Mutations in the gene ttx-1 affect AFD neuron function. Here, we show that ttx-1 regulates all differentiated characteristics of the AFD neurons. ttx-1 mutants are defective in a thermotactic behavior and exhibit deregulated thermosensory inputs into a neuroendocrine signaling pathway. ttx-1 encodes a member of the conserved OTD/OTX homeodomain protein family and is expressed in the AFD neurons. Misexpression of ttx-1 converts other sensory neurons to an AFD-like fate. Our results extend a previously noted conservation of developmental mechanisms between the thermosensory circuit in C. elegans and the vertebrate photosensory circuit, suggesting an evolutionary link between thermosensation and phototransduction.
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MESH Headings
- Amino Acid Sequence
- Animals
- Animals, Genetically Modified
- Behavior, Animal
- Caenorhabditis elegans/cytology
- Caenorhabditis elegans/genetics
- Caenorhabditis elegans/physiology
- Caenorhabditis elegans Proteins
- Cell Differentiation
- Cell Lineage
- Cilia/ultrastructure
- Drosophila Proteins
- Evolution, Molecular
- Gene Expression Regulation, Developmental
- Genes, Helminth
- Genes, Homeobox
- Genetic Complementation Test
- Helminth Proteins/chemistry
- Helminth Proteins/genetics
- Helminth Proteins/physiology
- Homeodomain Proteins/chemistry
- Homeodomain Proteins/genetics
- Homeodomain Proteins/physiology
- Mice
- Molecular Sequence Data
- Nerve Tissue Proteins/chemistry
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Neurons, Afferent/cytology
- Neurons, Afferent/physiology
- Neuropeptides/genetics
- Neuropeptides/physiology
- Otx Transcription Factors
- Phenotype
- Photoreceptor Cells, Vertebrate/metabolism
- Rats
- Sequence Alignment
- Sequence Homology, Amino Acid
- Signal Transduction/physiology
- Species Specificity
- Thermosensing/genetics
- Thermosensing/physiology
- Vertebrates/genetics
- Vertebrates/physiology
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Affiliation(s)
- J S Satterlee
- Department of Biology, Volen Center for Complex Systems, Brandeis University, 415 South Street, Waltham, MA 02454, USA
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122
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Pujol N, Link EM, Liu LX, Kurz CL, Alloing G, Tan MW, Ray KP, Solari R, Johnson CD, Ewbank JJ. A reverse genetic analysis of components of the Toll signaling pathway in Caenorhabditis elegans. Curr Biol 2001; 11:809-21. [PMID: 11516642 DOI: 10.1016/s0960-9822(01)00241-x] [Citation(s) in RCA: 314] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Both animals and plants respond rapidly to pathogens by inducing the expression of defense-related genes. Whether such an inducible system of innate immunity is present in the model nematode Caenorhabditis elegans is currently an open question. Among conserved signaling pathways important for innate immunity, the Toll pathway is the best characterized. In Drosophila, this pathway also has an essential developmental role. C. elegans possesses structural homologs of components of this pathway, and this observation raises the possibility that a Toll pathway might also function in nematodes to trigger defense mechanisms or to control development. RESULTS We have generated and characterized deletion mutants for four genes supposed to function in a nematode Toll signaling pathway. These genes are tol-1, trf-1, pik-1, and ikb-1 and are homologous to the Drosophila melanogaster Toll, dTraf, pelle, and cactus genes, respectively. Of these four genes, only tol-1 is required for nematode development. None of them are important for the resistance of C. elegans to a number of pathogens. On the other hand, C. elegans is capable of distinguishing different bacterial species and has a tendency to avoid certain pathogens, including Serratia marcescens. The tol-1 mutants are defective in their avoidance of pathogenic S. marcescens, although other chemosensory behaviors are wild type. CONCLUSIONS In C. elegans, tol-1 is important for development and pathogen recognition, as is Toll in Drosophila, but remarkably for the latter rôle, it functions in the context of a behavioral mechanism that keeps worms away from potential danger.
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Affiliation(s)
- N Pujol
- Laboratoire de Génétique et Physiologie du Développement, Institut National de la Santé et de la Recherche Médicale/Centre National pour la Recherche Scientifique/Université de la Mediterranée, 13288, Marseille, France
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Gomez M, De Castro E, Guarin E, Sasakura H, Kuhara A, Mori I, Bartfai T, Bargmann CI, Nef P. Ca2+ signaling via the neuronal calcium sensor-1 regulates associative learning and memory in C. elegans. Neuron 2001; 30:241-8. [PMID: 11343658 DOI: 10.1016/s0896-6273(01)00276-8] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
On a radial temperature gradient, C. elegans worms migrate, after conditioning with food, toward their cultivation temperature and move along this isotherm. This experience-dependent behavior is called isothermal tracking (IT). Here we show that the neuron-specific calcium sensor-1 (NCS-1) is essential for optimal IT. ncs-1 knockout animals show major defects in IT behavior, although their chemotactic, locomotor, and thermal avoidance behaviors are normal. The knockout phenotype can be rescued by reintroducing wild-type NCS-1 into the AIY interneuron, a key component of the thermotaxis network. A loss-of-function form of NCS-1 incapable of binding calcium does not restore IT, whereas NCS-1 overexpression enhances IT performance levels, accelerates learning (faster acquisition), and produces a memory with slower extinction. Thus, proper calcium signaling via NCS-1 defines a novel pathway essential for associative learning and memory.
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Affiliation(s)
- M Gomez
- Department of Central Nervous System, F. Hoffmann-La Roche, 4070, Basel, Switzerland
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124
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Sawin ER, Ranganathan R, Horvitz HR. C. elegans locomotory rate is modulated by the environment through a dopaminergic pathway and by experience through a serotonergic pathway. Neuron 2000; 26:619-31. [PMID: 10896158 DOI: 10.1016/s0896-6273(00)81199-x] [Citation(s) in RCA: 776] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Caenorhabditis elegans modulates its locomotory rate in response to its food, bacteria, in two ways. First, well-fed wild-type animals move more slowly in the presence of bacteria than in the absence of bacteria. This basal slowing response is mediated by a dopamine-containing neural circuit that senses a mechanical attribute of bacteria and may be an adaptive mechanism that increases the amount of time animals spend in the presence of food. Second, food-deprived wild-type animals, when transferred to bacteria, display a dramatically enhanced slowing response that ensures that the animals do not leave their newly encountered source of food. This experience-dependent response is mediated by serotonergic neurotransmission and is potentiated by fluoxetine (Prozac). The basal and enhanced slowing responses are distinct and separable neuromodulatory components of a genetically tractable paradigm of behavioral plasticity.
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Affiliation(s)
- E R Sawin
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA
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