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Kwon Y, Kim J, Son YB, Lee SA, Choi SS, Cho Y. Advanced Neural Functional Imaging in C. elegans Using Lab-on-a-Chip Technology. MICROMACHINES 2024; 15:1027. [PMID: 39203678 PMCID: PMC11356251 DOI: 10.3390/mi15081027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2024] [Revised: 08/05/2024] [Accepted: 08/06/2024] [Indexed: 09/03/2024]
Abstract
The ability to perceive and adapt to environmental changes is crucial for the survival of all organisms. Neural functional imaging, particularly in model organisms, such as Caenorhabditis elegans, provides valuable insights into how animals sense and process external cues through their nervous systems. Because of its fully mapped neural anatomy, transparent body, and genetic tractability, C. elegans serves as an ideal model for these studies. This review focuses on advanced methods for neural functional imaging in C. elegans, highlighting calcium imaging techniques, lab-on-a-chip technologies, and their applications in the study of various sensory modalities, including chemosensation, mechanosensation, thermosensation, photosensation, and magnetosensation. We discuss the benefits of these methods in terms of precision, reproducibility, and ability to study dynamic neural processes in real time, ultimately advancing our understanding of the fundamental principles of neural activity and connectivity.
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Affiliation(s)
- Youngeun Kwon
- Department of Chemical Engineering, Myongji University, Yongin 17058, Republic of Korea; (Y.K.); (J.K.); (Y.B.S.)
| | - Jihye Kim
- Department of Chemical Engineering, Myongji University, Yongin 17058, Republic of Korea; (Y.K.); (J.K.); (Y.B.S.)
| | - Ye Bin Son
- Department of Chemical Engineering, Myongji University, Yongin 17058, Republic of Korea; (Y.K.); (J.K.); (Y.B.S.)
| | - Sol Ah Lee
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA;
| | - Shin Sik Choi
- Department of Bio-Pharmaceutical Sciences, Myongji University, Yongin 17058, Republic of Korea;
- The Natural Science Research Institute, Department of Food and Nutrition, Myongji University, Yongin 17058, Republic of Korea
- elegslab Inc., Seoul 06083, Republic of Korea
| | - Yongmin Cho
- Department of Chemical Engineering, Myongji University, Yongin 17058, Republic of Korea; (Y.K.); (J.K.); (Y.B.S.)
- elegslab Inc., Seoul 06083, Republic of Korea
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2
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Banerjee N, Rojas Palato EJ, Shih PY, Sternberg PW, Hallem EA. Distinct neurogenetic mechanisms establish the same chemosensory valence state at different life stages in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2024; 14:jkad271. [PMID: 38092065 PMCID: PMC10849362 DOI: 10.1093/g3journal/jkad271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 11/17/2023] [Indexed: 02/09/2024]
Abstract
An animal's preference for many chemosensory cues remains constant despite dramatic changes in the animal's internal state. The mechanisms that maintain chemosensory preference across different physiological contexts remain poorly understood. We previously showed that distinct patterns of neural activity and motor output are evoked by carbon dioxide (CO2) in starved adults vs dauers of Caenorhabditis elegans, despite the two life stages displaying the same preference (attraction) for CO2. However, how the distinct CO2-evoked neural dynamics and motor patterns contribute to CO2 attraction at the two life stages remained unclear. Here, using a CO2 chemotaxis assay, we show that different interneurons are employed to drive CO2 attraction at the two life stages. We also investigate the molecular mechanisms that mediate CO2 attraction in dauers vs adults. We show that insulin signaling promotes CO2 attraction in dauers but not starved adults and that different combinations of neurotransmitters and neuropeptides are used for CO2 attraction at the two life stages. Our findings provide new insight into the distinct molecular and cellular mechanisms used by C. elegans at two different life stages to generate attractive behavioral responses to CO2.
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Affiliation(s)
- Navonil Banerjee
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Elisa J Rojas Palato
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Pei-Yin Shih
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Department of Ecology, Evolution and Environmental Biology, Columbia University, NewYork, NY 10027, USA
- Zuckerman Mind, Brain, Behavior Institute, Columbia University, NewYork, NY 10027, USA
| | - Paul W Sternberg
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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3
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Prakash SJ, Van Auken KM, Hill DP, Sternberg PW. Semantic representation of neural circuit knowledge in Caenorhabditis elegans. Brain Inform 2023; 10:30. [PMID: 37947958 PMCID: PMC10638142 DOI: 10.1186/s40708-023-00208-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 09/22/2023] [Indexed: 11/12/2023] Open
Abstract
In modern biology, new knowledge is generated quickly, making it challenging for researchers to efficiently acquire and synthesise new information from the large volume of primary publications. To address this problem, computational approaches that generate machine-readable representations of scientific findings in the form of knowledge graphs have been developed. These representations can integrate different types of experimental data from multiple papers and biological knowledge bases in a unifying data model, providing a complementary method to manual review for interacting with published knowledge. The Gene Ontology Consortium (GOC) has created a semantic modelling framework that extends individual functional gene annotations to structured descriptions of causal networks representing biological processes (Gene Ontology-Causal Activity Modelling, or GO-CAM). In this study, we explored whether the GO-CAM framework could represent knowledge of the causal relationships between environmental inputs, neural circuits and behavior in the model nematode C. elegans [C. elegans Neural-Circuit Causal Activity Modelling (CeN-CAM)]. We found that, given extensions to several relevant ontologies, a wide variety of author statements from the literature about the neural circuit basis of egg-laying and carbon dioxide (CO2) avoidance behaviors could be faithfully represented with CeN-CAM. Through this process, we were able to generate generic data models for several categories of experimental results. We also discuss how semantic modelling may be used to functionally annotate the C. elegans connectome. Thus, Gene Ontology-based semantic modelling has the potential to support various machine-readable representations of neurobiological knowledge.
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Affiliation(s)
- Sharan J Prakash
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Kimberly M Van Auken
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - David P Hill
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA
| | - Paul W Sternberg
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
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4
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Yoon KH, Indong RA, Lee JI. Making "Sense" of Ecology from a Genetic Perspective: Caenorhabditis elegans, Microbes and Behavior. Metabolites 2022; 12:1084. [PMID: 36355167 PMCID: PMC9697003 DOI: 10.3390/metabo12111084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/02/2022] [Accepted: 11/05/2022] [Indexed: 12/31/2023] Open
Abstract
Our knowledge of animal and behavior in the natural ecology is based on over a century's worth of valuable field studies. In this post-genome era, however, we recognize that genes are the underpinning of ecological interactions between two organisms. Understanding how genes contribute to animal ecology, which is essentially the intersection of two genomes, is a tremendous challenge. The bacterivorous nematode Caenorhabditis elegans, one of the most well-known genetic animal model experimental systems, experiences a complex microbial world in its natural habitat, providing us with a window into the interplay of genes and molecules that result in an animal-microbial ecology. In this review, we will discuss C. elegans natural ecology, how the worm uses its sensory system to detect the microbes and metabolites that it encounters, and then discuss some of the fascinating ecological dances, including behaviors, that have evolved between the nematode and the microbes in its environment.
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Affiliation(s)
- Kyoung-hye Yoon
- Department of Physiology, Mitohormesis Research Center, Yonsei University Wonju College of Medicine, Wonju 26426, Korea
| | - Rocel Amor Indong
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Wonju 26493, Korea
| | - Jin I. Lee
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Wonju 26493, Korea
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5
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Riedl J, Fieseler C, Zimmer M. Tyraminergic corollary discharge filters reafferent perception in a chemosensory neuron. Curr Biol 2022; 32:3048-3058.e6. [PMID: 35690069 DOI: 10.1016/j.cub.2022.05.051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/10/2022] [Accepted: 05/18/2022] [Indexed: 12/25/2022]
Abstract
Interpreting sensory information requires its integration with the current behavior of the animal. However, how motor-related circuits influence sensory information processing is incompletely understood. Here, we report that current locomotor state directly modulates the activity of BAG CO2 sensory neurons in Caenorhabditis elegans. By recording neuronal activity in animals freely navigating CO2 landscapes, we found that during reverse crawling states, BAG activity is suppressed by tyraminergic corollary discharge signaling. We provide genetic evidence that tyramine released from the RIM reversal interneurons extrasynaptically activates the inhibitory chloride channel LGC-55 in BAG. Disrupting this pathway genetically leads to excessive behavioral responses to CO2 stimuli. Moreover, we find that LGC-55 signaling cancels out perception of self-produced CO2 and O2 stimuli when animals reverse into their own gas plume in ethologically relevant aqueous environments. Our results show that sensorimotor integration involves corollary discharge signals directly modulating chemosensory neurons.
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Affiliation(s)
- Julia Riedl
- Department of Neuroscience and Developmental Biology, Vienna BioCenter (VBC), University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria
| | - Charles Fieseler
- Department of Neuroscience and Developmental Biology, Vienna BioCenter (VBC), University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria
| | - Manuel Zimmer
- Department of Neuroscience and Developmental Biology, Vienna BioCenter (VBC), University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria; Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria.
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6
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Soil Nematodes as the Silent Sufferers of Climate-Induced Toxicity: Analysing the Outcomes of Their Interactions with Climatic Stress Factors on Land Cover and Agricultural Production. Appl Biochem Biotechnol 2022; 195:2519-2586. [PMID: 35593954 DOI: 10.1007/s12010-022-03965-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 05/10/2022] [Indexed: 11/02/2022]
Abstract
Unsustainable anthropogenic activities over the last few decades have resulted in alterations of the global climate. It can be perceived through changes in the rainfall patterns and rise in mean annual temperatures. Climatic stress factors exert their effects on soil health mainly by modifying the soil microenvironments where the soil fauna reside. Among the members of soil fauna, the soil nematodes have been found to be sensitive to these stress factors primarily because of their low tolerance limits. Additionally, because of their higher and diverse trophic positions in the soil food web they can integrate the effects of many stress factors acting together. This is important because under natural conditions the climatic stress factors do not exert their effect individually. Rather, they interact amongst themselves and other abiotic stress factors in the soil to generate their impacts. Some of these interactions may be synergistic while others may be antagonistic. As such, it becomes very difficult to assess their impacts on soil health by simply analysing the physicochemical properties of soil. This makes soil nematodes outstanding candidates for studying the effects of climatic stress factors on soil biology. The knowledge obtained therefrom can be used to design sustainable agricultural practices because most of the conventional techniques aim at short-term benefits with complete disregard of soil biology. This can partly ensure food security in the coming decades for the expanding population. Moreover, understanding soil biology can help to preserve landscapes that have developed over long periods of climatic stability and belowground soil biota interactions.
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7
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Pujol N, Ewbank JJ. C. elegans: out on an evolutionary limb. Immunogenetics 2021; 74:63-73. [PMID: 34761293 DOI: 10.1007/s00251-021-01231-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 10/22/2021] [Indexed: 12/18/2022]
Abstract
The natural environment of the free-living nematode Caenorhabditis elegans is rich in pathogenic microbes. There is now ample evidence to indicate that these pathogens exert a strong selection pressure on C. elegans, and have shaped its genome, physiology, and behaviour. In this short review, we concentrate on how C. elegans stands out from other animals in terms of its immune repertoire and innate immune signalling pathways. We discuss how C. elegans often detects pathogens because of their effects on essential cellular processes, or organelle integrity, in addition to direct microbial recognition. We illustrate the extensive molecular plasticity that is characteristic of immune defences in C. elegans and highlight some remarkable instances of lineage-specific innovation in innate immune mechanisms.
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Affiliation(s)
- Nathalie Pujol
- Aix Marseille Univ, CNRS, INSERM, CIML, Turing Centre for Living Systems, Marseille, France.
| | - Jonathan J Ewbank
- Aix Marseille Univ, CNRS, INSERM, CIML, Turing Centre for Living Systems, Marseille, France
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8
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Britz S, Markert SM, Witvliet D, Steyer AM, Tröger S, Mulcahy B, Kollmannsberger P, Schwab Y, Zhen M, Stigloher C. Structural Analysis of the Caenorhabditis elegans Dauer Larval Anterior Sensilla by Focused Ion Beam-Scanning Electron Microscopy. Front Neuroanat 2021; 15:732520. [PMID: 34819841 PMCID: PMC8607169 DOI: 10.3389/fnana.2021.732520] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/24/2021] [Indexed: 11/13/2022] Open
Abstract
At the end of the first larval stage, the nematode Caenorhabditis elegans developing in harsh environmental conditions is able to choose an alternative developmental path called the dauer diapause. Dauer larvae exhibit different physiology and behaviors from non-dauer larvae. Using focused ion beam-scanning electron microscopy (FIB-SEM), we volumetrically reconstructed the anterior sensory apparatus of C. elegans dauer larvae with unprecedented precision. We provide a detailed description of some neurons, focusing on structural details that were unknown or unresolved by previously published studies. They include the following: (1) dauer-specific branches of the IL2 sensory neurons project into the periphery of anterior sensilla and motor or putative sensory neurons at the sub-lateral cords; (2) ciliated endings of URX sensory neurons are supported by both ILso and AMso socket cells near the amphid openings; (3) variability in amphid sensory dendrites among dauers; and (4) somatic RIP interneurons maintain their projection into the pharyngeal nervous system. Our results support the notion that dauer larvae structurally expand their sensory system to facilitate searching for more favorable environments.
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Affiliation(s)
- Sebastian Britz
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
| | - Sebastian Matthias Markert
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
| | - Daniel Witvliet
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Molecular Genetics, Physiology and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Anna Maria Steyer
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Sarah Tröger
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Molecular Genetics, Physiology and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Philip Kollmannsberger
- Center for Computational and Theoretical Biology, Julius-Maximilians-University, Würzburg, Germany
| | - Yannick Schwab
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
- Department of Molecular Genetics, Physiology and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Christian Stigloher
- Imaging Core Facility of the Biocenter, Theodor-Boveri-Institute, Julius-Maximilians-University, Würzburg, Germany
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9
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Opponent vesicular transporters regulate the strength of glutamatergic neurotransmission in a C. elegans sensory circuit. Nat Commun 2021; 12:6334. [PMID: 34732711 PMCID: PMC8566550 DOI: 10.1038/s41467-021-26575-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 09/22/2021] [Indexed: 11/30/2022] Open
Abstract
At chemical synapses, neurotransmitters are packaged into synaptic vesicles that release their contents in response to depolarization. Despite its central role in synaptic function, regulation of the machinery that loads vesicles with neurotransmitters remains poorly understood. We find that synaptic glutamate signaling in a C. elegans chemosensory circuit is regulated by antagonistic interactions between the canonical vesicular glutamate transporter EAT-4/VGLUT and another vesicular transporter, VST-1. Loss of VST-1 strongly potentiates glutamate release from chemosensory BAG neurons and disrupts chemotaxis behavior. Analysis of the circuitry downstream of BAG neurons shows that excess glutamate release disrupts behavior by inappropriately recruiting RIA interneurons to the BAG-associated chemotaxis circuit. Our data indicate that in vivo the strength of glutamatergic synapses is controlled by regulation of neurotransmitter packaging into synaptic vesicles via functional coupling of VGLUT and VST-1. The authors describe a vesicular transporter, VST-1, that is required in glutamatergic chemosensory neurons for chemotactic avoidance behavior in C. elegans. VST-1 antagonizes VGLUT-dependent packaging of glutamate into synaptic vesicles and determines the strength of synaptic glutamate signaling.
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10
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Emmons SW, Yemini E, Zimmer M. Methods for analyzing neuronal structure and activity in Caenorhabditis elegans. Genetics 2021; 218:6303616. [PMID: 34151952 DOI: 10.1093/genetics/iyab072] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 04/20/2021] [Indexed: 11/12/2022] Open
Abstract
The model research animal Caenorhabditis elegans has unique properties making it particularly advantageous for studies of the nervous system. The nervous system is composed of a stereotyped complement of neurons connected in a consistent manner. Here, we describe methods for studying nervous system structure and function. The transparency of the animal makes it possible to visualize and identify neurons in living animals with fluorescent probes. These methods have been recently enhanced for the efficient use of neuron-specific reporter genes. Because of its simple structure, for a number of years, C. elegans has been at the forefront of connectomic studies defining synaptic connectivity by electron microscopy. This field is burgeoning with new, more powerful techniques, and recommended up-to-date methods are here described that encourage the possibility of new work in C. elegans. Fluorescent probes for single synapses and synaptic connections have allowed verification of the EM reconstructions and for experimental approaches to synapse formation. Advances in microscopy and in fluorescent reporters sensitive to Ca2+ levels have opened the way to observing activity within single neurons across the entire nervous system.
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Affiliation(s)
- Scott W Emmons
- Department of Genetics and Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 1041, USA
| | - Eviatar Yemini
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA
| | - Manuel Zimmer
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna 1090, Austria and.,Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna 1030, Austria
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11
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Carstensen HR, Villalon RM, Banerjee N, Hallem EA, Hong RL. Steroid hormone pathways coordinate developmental diapause and olfactory remodeling in Pristionchus pacificus. Genetics 2021; 218:6272519. [PMID: 33963848 DOI: 10.1093/genetics/iyab071] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 04/26/2021] [Indexed: 12/31/2022] Open
Abstract
Developmental and behavioral plasticity allow animals to prioritize alternative genetic programs during fluctuating environments. Behavioral remodeling may be acute in animals that interact with host organisms, since reproductive adults and the developmentally arrested larvae often have different ethological needs for chemical stimuli. To understand the genes that coordinate the development and host-seeking behavior, we used the entomophilic nematode Pristionchus pacificus to characterize dauer-constitutive mutants (Daf-c) that inappropriately enter developmental diapause to become dauer larvae. We found two Daf-c loci with dauer-constitutive and cuticle exsheathment phenotypes that can be rescued by the feeding of Δ7-dafachronic acid, and that are dependent on the conserved canonical steroid hormone receptor Ppa-DAF-12. Specifically at one locus, deletions in the sole hydroxysteroid dehydrogenase (HSD) in P. pacificus resulted in Daf-c phenotypes. Ppa-hsd-2 is expressed in the canal-associated neurons (CANs) and excretory cells whose homologous cells in Caenorhabditis elegans are not known to be involved in the dauer decision. While in wildtype only dauer larvae are attracted to host odors, hsd-2 mutant adults show enhanced attraction to the host beetle pheromone, along with ectopic activation of a marker for putative olfactory neurons, Ppa-odr-3. Surprisingly, this enhanced odor attraction acts independently of the Δ7-DA/DAF-12 module, suggesting that Ppa-HSD-2 may be responsible for several steroid hormone products involved in coordinating the dauer decision and host-seeking behavior in P. pacificus.
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Affiliation(s)
- Heather R Carstensen
- Department of Biology, California State University, Northridge, Northridge, CA 91330-8303, USA
| | - Reinard M Villalon
- Department of Biology, California State University, Northridge, Northridge, CA 91330-8303, USA
| | - Navonil Banerjee
- Department of Microbiology, Immunology & Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology & Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ray L Hong
- Department of Biology, California State University, Northridge, Northridge, CA 91330-8303, USA
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12
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Verdu S, Perez AJ, Carrascosa C, Barat JM, Talens P, Grau R. Caenorhabditis elegans to Model the Capacity of Ascorbic Acid to Reduce Acute Nitrite Toxicity under Different Feed Conditions: Multivariate Analytics on Behavioral Imaging. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:2068. [PMID: 33672539 PMCID: PMC7923789 DOI: 10.3390/ijerph18042068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 02/17/2021] [Indexed: 01/17/2023]
Abstract
Nitrocompounds are present in the environment and human diet and form part of vegetables and processed meat products as additives. These compounds are related to negative impacts on human and animal health. The protective effect of ascorbic acid has been demonstrated by some biological systems as regards several nitrocompounds. This work focused on studying the possibility of modeling this effect on nitrite toxicity with the model Caenorhabditis elegans. The three factors studied in this work were ascorbic acid concentration, nitrite exposure concentration, and presence/absence of food. The protective effect was evaluated by scoring lethality and its impact on behavior by means of multivariate statistical methods and imaging analytics. The effects of nitrite and the influence of food availability were evidenced. Apart from increasing lethality, nitrite had disruption effects on movements. All the observed symptoms reduced when ascorbic acid was administered, and it diminished lethality in all cases. Ascorbic acid maintained nematodes' postural capacities. The results suggest that nitrites' nonspecific toxicity in C. elegans can be mitigated by ascorbic acid, as previously evidenced in other biological systems. Thus, our results reveal the ability of C. elegans to reproduce the known protective effect of ascorbic acid against nitrite.
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Affiliation(s)
- Samuel Verdu
- Departamento de Tecnología de Alimentos, Universidat Politècnica de València, 46022 Valencia, Spain; (J.M.B.); (P.T.); (R.G.)
| | - Alberto J. Perez
- Departamento de Informática de Sistemas y Computadores, Universidat Politècnica de València, 46022 Valencia, Spain;
| | - Conrado Carrascosa
- Department of Animal Pathology and Production, Bromatology and Food Technology, Faculty of Veterinary, Universidad de Las Palmas de Gran Canaria, Arucas, 35413 Las Palmas, Spain;
| | - José M. Barat
- Departamento de Tecnología de Alimentos, Universidat Politècnica de València, 46022 Valencia, Spain; (J.M.B.); (P.T.); (R.G.)
| | - Pau Talens
- Departamento de Tecnología de Alimentos, Universidat Politècnica de València, 46022 Valencia, Spain; (J.M.B.); (P.T.); (R.G.)
| | - Raúl Grau
- Departamento de Tecnología de Alimentos, Universidat Politècnica de València, 46022 Valencia, Spain; (J.M.B.); (P.T.); (R.G.)
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13
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Soares MV, Charão MF, Jacques MT, Dos Santos ALA, Luchese C, Pinton S, Ávila DS. Airborne toluene exposure causes germline apoptosis and neuronal damage that promotes neurobehavioural changes in Caenorhabditis elegans. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 256:113406. [PMID: 31662251 DOI: 10.1016/j.envpol.2019.113406] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/13/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Toluene is a highly volatile organic solvent present in gasoline. Exposure mainly occurs by absorption via the pulmonary tract and easily reaches the central nervous system, which causes toxic effects. Toluene toxicity has been described but not well established. The present work aimed to evaluate the effects of airborne exposure to toluene, the in vivo model Caenorhabditis elegans was assessed to determine whether nematode could be used to evaluate the effects of exposure to toluene and the possible mechanisms of toxicity of the solvent. Worms at the first or fourth larval stages were exposed to toluene for 48 or 24 h, respectively, in a laboratory-developed vapor chamber at concentrations of 450, 850, 1250 and 1800 ppm. We observed increases in worm mortality and significant developmental delays that occurred in a concentration-dependent manner. An increased incidence of apoptotic events in treated germline cells was shown, which was consistent with observed reductions in reproductive capacity. In addition, toluene promoted significant behavioural changes affecting swimming movements and radial locomotion, which were associated with changes in the fluorescence intensity and morphology of GABAergic and cholinergic neurons. We conclude that toluene exposure was toxic to C. elegans, with effects produced by the induction of apoptosis and neuronal damage.
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Affiliation(s)
- Marcell Valandro Soares
- Programa de Pós-Graduação em Bioquímica, Grupo de pesquisa em Bioquímica e Toxicologia em Caenorhabditis elegans (GBToxCe), Universidade Federal do Pampa, Uruguaiana, RS, 97500-970, Brazil
| | - Mariele Feiffer Charão
- Laboratório de Toxicologia Analítica, Universidade Feevale, Rua Rubem Berta, nº 200, Novo Hamburgo, CEP: 93525-090, RS, Brazil
| | - Mauricio Tavares Jacques
- Programa de Pós-Graduação em Bioquímica, Grupo de pesquisa em Bioquímica e Toxicologia em Caenorhabditis elegans (GBToxCe), Universidade Federal do Pampa, Uruguaiana, RS, 97500-970, Brazil; Laboratório de Experimentação em Neuropatologia - Departamento de Bioquímica, CCB, Universidade Federal de Santa Catarina, Bloco C, Trindade, Florianópolis, SC, CEP 88040-900, Brazil
| | - Ana Laura Anibaletto Dos Santos
- Laboratório de Toxicologia Analítica, Universidade Feevale, Rua Rubem Berta, nº 200, Novo Hamburgo, CEP: 93525-090, RS, Brazil
| | - Cristiane Luchese
- Programa de Pós-Graduação em Bioquímica e Bioprospecção, Laboratório de Pesquisa em Farmacologia Bioquímica (LaFarBio), Grupo de Pesquisa em Neurobiotecnologia (GPN), Universidade Federal de Pelotas, Pelotas, RS, 96010-900, Brazil
| | - Simone Pinton
- Programa de Pós-Graduação em Bioquímica, Grupo de pesquisa em Bioquímica e Toxicologia em Caenorhabditis elegans (GBToxCe), Universidade Federal do Pampa, Uruguaiana, RS, 97500-970, Brazil
| | - Daiana Silva Ávila
- Programa de Pós-Graduação em Bioquímica, Grupo de pesquisa em Bioquímica e Toxicologia em Caenorhabditis elegans (GBToxCe), Universidade Federal do Pampa, Uruguaiana, RS, 97500-970, Brazil.
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14
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Grandchamp A, Tahir S, Monget P. Natriuretic peptides appeared after their receptors in vertebrates. BMC Evol Biol 2019; 19:215. [PMID: 31771521 PMCID: PMC6878697 DOI: 10.1186/s12862-019-1517-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 09/20/2019] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND In mammals, the natriuretic system contains three natriuretic peptides, NPPA, NPPB and NPPC, that bind to three transmembrane receptors, NPR1, NPR2 and NPR3. The natriuretic peptides are known only in vertebrates. In contrast, the receptors have orthologs in all the animal taxa and in plants. However, in non-vertebrates, these receptors do not have natriuretic properties, and most of their ligands are unknown. How was the interaction of the NP receptors and the NP established in vertebrates? Do natriuretic peptides have orthologs in non-vertebrates? If so, what was the function of the interaction? How did that function change? If not, are the NP homologous to ancestral NPR ligands? Or did the receptor's binding pocket completely change during evolution? METHODS In the present study, we tried to determine if the pairs of natriuretic receptors and their ligands come from an ancestral pair, or if the interaction only appeared in vertebrates. Alignments, modeling, docking, research of positive selection, and motif research were performed in order to answer this question. RESULTS We discovered that the binding pocket of the natriuretic peptide receptors was completely remodeled in mammals. We found several peptides in non vertebrates that could be related to human natriuretic peptides, but a set of clues, as well as modeling and docking analysis, suggest that the natriuretic peptides undoubtedly appeared later than their receptors during animal evolution. We suggest here that natriuretic peptide receptors in non vertebrates bind to other ligands. CONCLUSIONS The present study further support that vertebrate natriuretic peptides appeared after their receptors in the tree of life. We suggest the existence of peptides that resemble natriuretic peptides in non-vertebrate species, that might be the result of convergent evolution.
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Affiliation(s)
- Anna Grandchamp
- PRC, UMR85, INRA, CNRS, IFCE, Université de Tours, F-37380 Nouzilly, France
| | - Shifa Tahir
- PRC, UMR85, INRA, CNRS, IFCE, Université de Tours, F-37380 Nouzilly, France
| | - Philippe Monget
- PRC, UMR85, INRA, CNRS, IFCE, Université de Tours, F-37380 Nouzilly, France
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15
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Beets I, Zhang G, Fenk LA, Chen C, Nelson GM, Félix MA, de Bono M. Natural Variation in a Dendritic Scaffold Protein Remodels Experience-Dependent Plasticity by Altering Neuropeptide Expression. Neuron 2019; 105:106-121.e10. [PMID: 31757604 PMCID: PMC6953435 DOI: 10.1016/j.neuron.2019.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 08/18/2019] [Accepted: 09/28/2019] [Indexed: 12/13/2022]
Abstract
The extent to which behavior is shaped by experience varies between individuals. Genetic differences contribute to this variation, but the neural mechanisms are not understood. Here, we dissect natural variation in the behavioral flexibility of two Caenorhabditis elegans wild strains. In one strain, a memory of exposure to 21% O2 suppresses CO2-evoked locomotory arousal; in the other, CO2 evokes arousal regardless of previous O2 experience. We map that variation to a polymorphic dendritic scaffold protein, ARCP-1, expressed in sensory neurons. ARCP-1 binds the Ca2+-dependent phosphodiesterase PDE-1 and co-localizes PDE-1 with molecular sensors for CO2 at dendritic ends. Reducing ARCP-1 or PDE-1 activity promotes CO2 escape by altering neuropeptide expression in the BAG CO2 sensors. Variation in ARCP-1 alters behavioral plasticity in multiple paradigms. Our findings are reminiscent of genetic accommodation, an evolutionary process by which phenotypic flexibility in response to environmental variation is reset by genetic change. Behavioral flexibility varies across Caenorhabditis and C. elegans wild isolates A natural polymorphism in ARCP-1 underpins inter-individual variation in plasticity ARCP-1 is a dendritic scaffold protein localizing cGMP signaling machinery to cilia Disrupting ARCP-1 alters behavioral plasticity by changing neuropeptide expression
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Affiliation(s)
- Isabel Beets
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Gaotian Zhang
- Institut de Biologie de l'École Normale Supérieure, CNRS, Inserm, PSL Research University, Paris 75005, France
| | - Lorenz A Fenk
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Changchun Chen
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Geoffrey M Nelson
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Marie-Anne Félix
- Institut de Biologie de l'École Normale Supérieure, CNRS, Inserm, PSL Research University, Paris 75005, France.
| | - Mario de Bono
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
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16
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Activity-Dependent Regulation of the Proapoptotic BH3-Only Gene egl-1 in a Living Neuron Pair in Caenorhabditis elegans. G3-GENES GENOMES GENETICS 2019; 9:3703-3714. [PMID: 31519744 PMCID: PMC6829140 DOI: 10.1534/g3.119.400654] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The BH3-only family of proteins is key for initiating apoptosis in a variety of contexts, and may also contribute to non-apoptotic cellular processes. Historically, the nematode Caenorhabditis elegans has provided a powerful system for studying and identifying conserved regulators of BH3-only proteins. In C. elegans, the BH3-only protein egl-1 is expressed during development to cell-autonomously trigger most developmental cell deaths. Here we provide evidence that egl-1 is also transcribed after development in the sensory neuron pair URX without inducing apoptosis. We used genetic screening and epistasis analysis to determine that its transcription is regulated in URX by neuronal activity and/or in parallel by orthologs of Protein Kinase G and the Salt-Inducible Kinase family. Because several BH3-only family proteins are also expressed in the adult nervous system of mammals, we suggest that studying egl-1 expression in URX may shed light on mechanisms that regulate conserved family members in higher organisms.
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17
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Abstract
Carbon dioxide (CO2) is an important sensory cue for many animals, including both parasitic and free-living nematodes. Many nematodes show context-dependent, experience-dependent and/or life-stage-dependent behavioural responses to CO2, suggesting that CO2 plays crucial roles throughout the nematode life cycle in multiple ethological contexts. Nematodes also show a wide range of physiological responses to CO2. Here, we review the diverse responses of parasitic and free-living nematodes to CO2. We also discuss the molecular, cellular and neural circuit mechanisms that mediate CO2 detection in nematodes, and that drive context-dependent and experience-dependent responses of nematodes to CO2.
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18
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Hong RL, Riebesell M, Bumbarger DJ, Cook SJ, Carstensen HR, Sarpolaki T, Cochella L, Castrejon J, Moreno E, Sieriebriennikov B, Hobert O, Sommer RJ. Evolution of neuronal anatomy and circuitry in two highly divergent nematode species. eLife 2019; 8:47155. [PMID: 31526477 PMCID: PMC6748829 DOI: 10.7554/elife.47155] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 08/12/2019] [Indexed: 11/17/2022] Open
Abstract
The nematodes C. elegans and P. pacificus populate diverse habitats and display distinct patterns of behavior. To understand how their nervous systems have diverged, we undertook a detailed examination of the neuroanatomy of the chemosensory system of P. pacificus. Using independent features such as cell body position, axon projections and lipophilic dye uptake, we have assigned homologies between the amphid neurons, their first-layer interneurons, and several internal receptor neurons of P. pacificus and C. elegans. We found that neuronal number and soma position are highly conserved. However, the morphological elaborations of several amphid cilia are different between them, most notably in the absence of ‘winged’ cilia morphology in P. pacificus. We established a synaptic wiring diagram of amphid sensory neurons and amphid interneurons in P. pacificus and found striking patterns of conservation and divergence in connectivity relative to C. elegans, but very little changes in relative neighborhood of neuronal processes. These findings demonstrate the existence of several constraints in patterning the nervous system and suggest that major substrates for evolutionary novelty lie in the alterations of dendritic structures and synaptic connectivity. Nerve cells, also called neurons, are responsible both for sensing signals from the environment and for determining how organisms react. This means that the unique features of an animal’s nervous system underpin its characteristic behaviors. Comparing the anatomy of the nervous systems in different animals could therefore yield valuable insights into how structural and behavioral differences emerge over time. Behavioral variation often occurs even in similar-looking animals. One example is a group of microscopic worms, called nematodes. Although many nematode species exist, their overall body plans are the same, and the worms of each species contain a fixed number of cells. Despite these apparent similarities, different species of nematodes inhabit a variety of environments and may respond differently to the same signals. The main sensory organs in nematodes are called the amphid sensilla. They are used to detect chemicals, as well as other inputs from the environment such as temperature and pheromones from other nematodes. Although researchers have often speculated that the number of cells in these organs and their arrangement are broadly the same across species, their anatomy had not been studied in detail. Hong, Riebesell et al. compared the detailed structure and genetic features of the sensory systems in two distantly related species of nematode worms, Pristionchus pacificus and Caenorhabditis elegans. These two species behave in different ways, for example, P. pacificus is usually found in association with different species of beetles, while C. elegans is free-living and usually found on rotting fruit. By comparing the two, Hong, Riebesell et al. wanted to determine whether the diverse behaviors observed in the two species could be determined by differences between their sensory systems. Experiments using electron microscopy yielded several thousand high resolution images spanning the entire sensory organ. These images were then used to create detailed reconstructions of the sensory nervous system in each worm species, demonstrating that both species had the same number of sensory nerve cells, allowing one-to-one comparisons between them. Further analysis showed that while the overall structure of the neuronal connections remains the same between the two species, the neurons in P. pacificus made more diverse connections than those in C. elegans. Detailed studies of gene activity also revealed that neurons in each species switched on a slightly different group of genes, possibly indicating that each type of worm processes sensory signals in different ways. These results shed new light on how nervous systems in related species can change over time without any change in neuron count. In the future, a better understanding of these changes could link the evolution of the nervous system to the emergence of different behaviors, in both simple and more complex organisms.
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Affiliation(s)
- Ray L Hong
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany.,Department of Biology, California State University, Northridge, Northridge, United States
| | - Metta Riebesell
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Daniel J Bumbarger
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Steven J Cook
- Department of Biological Sciences, Columbia University, New York, United States
| | - Heather R Carstensen
- Department of Biology, California State University, Northridge, Northridge, United States
| | - Tahmineh Sarpolaki
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Luisa Cochella
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jessica Castrejon
- Department of Biology, California State University, Northridge, Northridge, United States
| | - Eduardo Moreno
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Bogdan Sieriebriennikov
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, New York, United States.,Howard Hughes Medical Institute, Chevy Chase, United States
| | - Ralf J Sommer
- Department for Integrative Evolutionary Biology, Max-Planck Institute for Developmental Biology, Tuebingen, Germany
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19
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Abstract
Female Aedes aegypti mosquitoes bite human hosts to obtain a blood meal and, in the process, act as vectors for many disease-causing viruses, including the dengue, chikungunya, yellow fever, and Zika viruses. After a complete meal, the female mosquitoes lose attraction to their hosts for several days. New research shows that pharmacological activation of neuropeptide Y-like receptor (NPYLR) signaling elicits host aversion in female mosquitoes. This behavior of mosquitoes shows remarkable similarities to a bacterial-aversion behavior of the nematode Caenorhabditis elegans Feeding on pathogenic bacteria causes bloating of the gut in C. elegans that leads to activation of NPYLR signaling and bacterial aversion. Several studies suggest that this newly discovered mechanism underlying foraging may be conserved across a large number of species. A better understanding of the regulation of NPYLR signaling pathways could provide molecular targets for the control of eating behaviors in different animals, including human-disease vectors.
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Affiliation(s)
- Jogender Singh
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, Oregon, USA
| | - Alejandro Aballay
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, Portland, Oregon, USA
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20
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Kim J, Leahy W, Shlizerman E. Neural Interactome: Interactive Simulation of a Neuronal System. Front Comput Neurosci 2019; 13:8. [PMID: 30930759 PMCID: PMC6425397 DOI: 10.3389/fncom.2019.00008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 01/30/2019] [Indexed: 01/14/2023] Open
Abstract
Connectivity and biophysical processes determine the functionality of neuronal networks. We, therefore, developed a real-time framework, called Neural Interactome,, to simultaneously visualize and interact with the structure and dynamics of such networks. Neural Interactome is a cross-platform framework, which combines graph visualization with the simulation of neural dynamics, or experimentally recorded multi neural time series, to allow application of stimuli to neurons to examine network responses. In addition, Neural Interactome supports structural changes, such as disconnection of neurons from the network (ablation feature). Neural dynamics can be explored on a single neuron level (using a zoom feature), back in time (using a review feature), and recorded (using presets feature). The development of the Neural Interactome was guided by generic concepts to be applicable to neuronal networks with different neural connectivity and dynamics. We implement the framework using a model of the nervous system of Caenorhabditis elegans (C. elegans) nematode, a model organism with resolved connectome and neural dynamics. We show that Neural Interactome assists in studying neural response patterns associated with locomotion and other stimuli. In particular, we demonstrate how stimulation and ablation help in identifying neurons that shape particular dynamics. We examine scenarios that were experimentally studied, such as touch response circuit, and explore new scenarios that did not undergo elaborate experimental studies.
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Affiliation(s)
- Jimin Kim
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, United States
| | - William Leahy
- Department of Applied Mathematics, University of Washington, Seattle, WA, United States
| | - Eli Shlizerman
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, United States.,Department of Applied Mathematics, University of Washington, Seattle, WA, United States
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21
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Liang LM, Zou CG, Xu J, Zhang KQ. Signal pathways involved in microbe-nematode interactions provide new insights into the biocontrol of plant-parasitic nematodes. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180317. [PMID: 30967028 PMCID: PMC6367146 DOI: 10.1098/rstb.2018.0317] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2018] [Indexed: 11/12/2022] Open
Abstract
Plant-parasitic nematodes (PPNs) cause severe damage to agricultural crops worldwide. As most chemical nematicides have negative environmental side effects, there is a pressing need for developing efficient biocontrol methods. Nematophagous microbes, the natural enemies of nematodes, are potential biocontrol agents against PPNs. These natural enemies include both bacteria and fungi and they use diverse methods to infect and kill nematodes. For instance, nematode-trapping fungi can sense host signals and produce special trapping devices to capture nematodes, whereas endo-parasitic fungi can kill nematodes by spore adhesion and invasive growth to break the nematode cuticle. By contrast, nematophagous bacteria can secrete virulence factors to kill nematodes. In addition, some bacteria can mobilize nematode-trapping fungi to kill nematodes. In response, nematodes can also sense and defend against the microbial pathogens using strategies such as producing anti-microbial peptides regulated by the innate immunity system. Recent progresses in our understanding of the signal pathways involved in microbe-nematode interactions are providing new insights in developing efficient biological control strategies against PPNs. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.
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Affiliation(s)
- Lian-Ming Liang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and The Key Laboratory for Southwest Microbial Diversity of the Ministry of Education, Yunnan University, Kunming 650091, People's Republic of China
- School of Life Science, Yunnan University, Kunming 650091, People's Republic of China
| | - Cheng-Gang Zou
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and The Key Laboratory for Southwest Microbial Diversity of the Ministry of Education, Yunnan University, Kunming 650091, People's Republic of China
- School of Life Science, Yunnan University, Kunming 650091, People's Republic of China
| | - Jianping Xu
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and The Key Laboratory for Southwest Microbial Diversity of the Ministry of Education, Yunnan University, Kunming 650091, People's Republic of China
- Department of Biology, McMaster University, Hamilton, Ontario, CanadaL8S 4K1
| | - Ke-Qin Zhang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and The Key Laboratory for Southwest Microbial Diversity of the Ministry of Education, Yunnan University, Kunming 650091, People's Republic of China
- School of Life Science, Yunnan University, Kunming 650091, People's Republic of China
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22
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Worthy SE, Rojas GL, Taylor CJ, Glater EE. Identification of Odor Blend Used by Caenorhabditis elegans for Pathogen Recognition. Chem Senses 2019; 43:169-180. [PMID: 29373666 PMCID: PMC6018680 DOI: 10.1093/chemse/bjy001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Animals have evolved specialized pathways to detect appropriate food sources and avoid harmful ones. Caenorhabditis elegans can distinguish among the odors of various species of bacteria, its major food source, but little is known about what specific chemical cue or combination of chemical cues C. elegans uses to detect and recognize different microbes. Here, we examine the strong innate attraction of C. elegans for the odor of the pathogenic bacterium, Serratia marcescens. This initial attraction likely facilitates ingestion and infection of the C. elegans host. Using solid-phase microextraction and gas chromatography coupled with mass spectrometry, we identify 5 volatile odors released by S. marcescens and identify those that are attractive to C. elegans. We use genetic methods to show that the amphid chemosensory neuron, AWCON, senses both S. marcescens-released 2-butanone and acetone and drives attraction to S. marcescens. In C. elegans, pairing a single odorant with food deprivation results in a reduced attractive response for that specific odor. We find that pairing the natural odor of S. marcescens with food deprivation results in a reduced attraction for the natural odor of S. marcescens and a similar reduced attraction for the synthetic blend of acetone and 2-butanone. This result indicates that only 2 odorants represent the more complex odor bouquet of S. marcescens. Although bacterial-released volatiles have long been known to be attractive to C. elegans, this study defines for the first time specific volatile cues that represent a particular bacterium to C. elegans.
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Affiliation(s)
| | - German L Rojas
- Department of Neuroscience, Pomona College, Claremont, CA, USA
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23
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Feeding state sculpts a circuit for sensory valence in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2019; 116:1776-1781. [PMID: 30651312 DOI: 10.1073/pnas.1807454116] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Hunger affects the behavioral choices of all animals, and many chemosensory stimuli can be either attractive or repulsive depending on an animal's hunger state. Although hunger-induced behavioral changes are well documented, the molecular and cellular mechanisms by which hunger modulates neural circuit function to generate changes in chemosensory valence are poorly understood. Here, we use the CO2 response of the free-living nematode Caenorhabditis elegans to elucidate how hunger alters valence. We show that CO2 response valence shifts from aversion to attraction during starvation, a change that is mediated by two pairs of interneurons in the CO2 circuit, AIY and RIG. The transition from aversion to attraction is regulated by biogenic amine signaling. Dopamine promotes CO2 repulsion in well-fed animals, whereas octopamine promotes CO2 attraction in starved animals. Biogenic amines also regulate the temporal dynamics of the shift from aversion to attraction such that animals lacking octopamine show a delayed shift to attraction. Biogenic amine signaling regulates CO2 response valence by modulating the CO2-evoked activity of AIY and RIG. Our results illuminate a new role for biogenic amine signaling in regulating chemosensory valence as a function of hunger state.
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24
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Bryant AS, Hallem EA. Terror in the dirt: Sensory determinants of host seeking in soil-transmitted mammalian-parasitic nematodes. Int J Parasitol Drugs Drug Resist 2018; 8:496-510. [PMID: 30396862 PMCID: PMC6287541 DOI: 10.1016/j.ijpddr.2018.10.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 10/22/2018] [Accepted: 10/24/2018] [Indexed: 12/12/2022]
Abstract
Infection with gastrointestinal parasitic nematodes is a major cause of chronic morbidity and economic burden around the world, particularly in low-resource settings. Some parasitic nematode species, including the human-parasitic threadworm Strongyloides stercoralis and human-parasitic hookworms in the genera Ancylostoma and Necator, feature a soil-dwelling infective larval stage that seeks out hosts for infection using a variety of host-emitted sensory cues. Here, we review our current understanding of the behavioral responses of soil-dwelling infective larvae to host-emitted sensory cues, and the molecular and cellular mechanisms that mediate these responses. We also discuss the development of methods for transgenesis and CRISPR/Cas9-mediated targeted mutagenesis in Strongyloides stercoralis and the closely related rat parasite Strongyloides ratti. These methods have established S. stercoralis and S. ratti as genetic model systems for gastrointestinal parasitic nematodes and are enabling more detailed investigations into the neural mechanisms that underlie the sensory-driven behaviors of this medically and economically important class of parasites.
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Affiliation(s)
- Astra S Bryant
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA.
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25
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Metaxakis A, Petratou D, Tavernarakis N. Multimodal sensory processing in Caenorhabditis elegans. Open Biol 2018; 8:180049. [PMID: 29925633 PMCID: PMC6030117 DOI: 10.1098/rsob.180049] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/22/2018] [Indexed: 12/22/2022] Open
Abstract
Multisensory integration is a mechanism that allows organisms to simultaneously sense and understand external stimuli from different modalities. These distinct signals are transduced into neuronal signals that converge into decision-making neuronal entities. Such decision-making centres receive information through neuromodulators regarding the organism's physiological state and accordingly trigger behavioural responses. Despite the importance of multisensory integration for efficient functioning of the nervous system, and also the implication of dysfunctional multisensory integration in the aetiology of neuropsychiatric disease, little is known about the relative molecular mechanisms. Caenorhabditis elegans is an appropriate model system to study such mechanisms and elucidate the molecular ways through which organisms understand external environments in an accurate and coherent fashion.
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Affiliation(s)
- Athanasios Metaxakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, Nikolaou Plastira 100, Heraklion 70013, Crete, Greece
| | - Dionysia Petratou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, Nikolaou Plastira 100, Heraklion 70013, Crete, Greece
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, Nikolaou Plastira 100, Heraklion 70013, Crete, Greece
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion 71110, Crete, Greece
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26
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Antagonistic regulation of trafficking to Caenorhabditis elegans sensory cilia by a Retinal Degeneration 3 homolog and retromer. Proc Natl Acad Sci U S A 2017; 115:E438-E447. [PMID: 29282322 DOI: 10.1073/pnas.1712302115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Sensory neurons often possess cilia with elaborate membrane structures that are adapted to the sensory modality of the host cell. Mechanisms that target sensory transduction proteins to these specialized membrane domains remain poorly understood. Here, we show that a homolog of the human retinal dystrophy gene Retinal Degeneration 3 (RD3) is a Golgi-associated protein required for efficient trafficking of a sensory receptor, the receptor-type guanylate cyclase GCY-9, to cilia in chemosensory neurons of the nematode Caenorhabditis elegans The trafficking defect caused by mutation of the nematode RD3 homolog is suppressed in vivo by mutation of key components of the retromer complex, which mediates recycling of cargo from endosomes to the Golgi. Our data show that there exists a critical balance in sensory neurons between the rates of anterograde and retrograde trafficking of cargo destined for the sensory cilium and this balance requires molecular specialization at an early stage of the secretory pathway.
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27
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Guillermin ML, Carrillo MA, Hallem EA. A Single Set of Interneurons Drives Opposite Behaviors in C. elegans. Curr Biol 2017; 27:2630-2639.e6. [PMID: 28823678 PMCID: PMC6193758 DOI: 10.1016/j.cub.2017.07.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/06/2017] [Accepted: 07/10/2017] [Indexed: 12/21/2022]
Abstract
Many chemosensory stimuli evoke innate behavioral responses that can be either appetitive or aversive, depending on an animal's age, prior experience, nutritional status, and environment [1-9]. However, the circuit mechanisms that enable these valence changes are poorly understood. Here, we show that Caenorhabditis elegans can alternate between attractive or aversive responses to carbon dioxide (CO2), depending on its recently experienced CO2 environment. Both responses are mediated by a single pathway of interneurons. The CO2-evoked activity of these interneurons is subject to extreme experience-dependent modulation, enabling them to drive opposite behavioral responses to CO2. Other interneurons in the circuit regulate behavioral sensitivity to CO2 independent of valence. A combinatorial code of neuropeptides acts on the circuit to regulate both valence and sensitivity. Chemosensory valence-encoding interneurons exist across phyla, and valence is typically determined by whether appetitive or aversive interneuron populations are activated. Our results reveal an alternative mechanism of valence determination in which the same interneurons contribute to both attractive and aversive responses through modulation of sensory neuron to interneuron synapses. This circuit design represents a previously unrecognized mechanism for generating rapid changes in innate chemosensory valence.
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Affiliation(s)
- Manon L Guillermin
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mayra A Carrillo
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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28
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Liu Y, Sun J. G protein-coupled receptors mediate neural regulation of innate immune responses in caenorhabditis elegans. RECEPTORS & CLINICAL INVESTIGATION 2017; 4:e1543. [PMID: 30386810 PMCID: PMC6206870 DOI: 10.14800/rci.1543] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
G protein-coupled receptors (GPCRs) are a large family of transmembrane proteins that perceive many extracellular signals and transduce them into cellular physiological responses. GPCRs regulate immunity in both vertebrates and invertebrates. However, the mechanisms responsible for such regulation are not fully understood. Recent research using the genetically tractable model organism Caenorhabditis elegans has led to the identification of specific GPCRs, neurotransmitters, neurons and non-neural cells in the regulation of innate immunity. Several neural circuits have been demonstrated to function in GPCR-dependent immuno-regulatory pathways. Besides being essential in neural-immune interactions, GPCRs also regulate innate immune response in non-neural tissues cell-autonomously through mechanisms independent of neural circuits. Here we review GPCR-mediated neural control of innate immunity in C. elegans and briefly discuss GPCR-dependent immune regulation via non-neural mechanisms.
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Affiliation(s)
- Yiyong Liu
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, Washington, 99202, USA
| | - Jingru Sun
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, Washington, 99202, USA
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29
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Memory of recent oxygen experience switches pheromone valence in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2017; 114:4195-4200. [PMID: 28373553 DOI: 10.1073/pnas.1618934114] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Animals adjust their behavioral priorities according to momentary needs and prior experience. We show that Caenorhabditis elegans changes how it processes sensory information according to the oxygen environment it experienced recently. C. elegans acclimated to 7% O2 are aroused by CO2 and repelled by pheromones that attract animals acclimated to 21% O2 This behavioral plasticity arises from prolonged activity differences in a circuit that continuously signals O2 levels. A sustained change in the activity of O2-sensing neurons reprograms the properties of their postsynaptic partners, the RMG hub interneurons. RMG is gap-junctionally coupled to the ASK and ADL pheromone sensors that respectively drive pheromone attraction and repulsion. Prior O2 experience has opposite effects on the pheromone responsiveness of these neurons. These circuit changes provide a physiological correlate of altered pheromone valence. Our results suggest C. elegans stores a memory of recent O2 experience in the RMG circuit and illustrate how a circuit is flexibly sculpted to guide behavioral decisions in a context-dependent manner.
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30
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Cevallos JA, Okubo RP, Perlman SJ, Hallem EA. Olfactory Preferences of the Parasitic Nematode Howardula aoronymphium and its Insect Host Drosophila falleni. J Chem Ecol 2017; 43:362-373. [PMID: 28315996 DOI: 10.1007/s10886-017-0834-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/09/2017] [Accepted: 03/06/2017] [Indexed: 10/19/2022]
Abstract
Many parasitic nematodes have an environmental infective stage that searches for hosts. Olfaction plays an important role in this process, with nematodes navigating their environment using host-emitted and environmental olfactory cues. The interactions between parasitic nematodes and their hosts are also influenced by the olfactory behaviors of the host, since host olfactory preferences drive behaviors that may facilitate or impede parasitic infection. However, how olfaction shapes parasite-host interactions is poorly understood. Here we investigated this question using the insect-parasitic nematode Howardula aoronymphium and its host, the mushroom fly Drosophila falleni. We found that both H. aoronymphium and D. falleni are attracted to mushroom odor and a subset of mushroom-derived odorants, but they have divergent olfactory preferences that are tuned to different mushroom odorants despite their shared mushroom environment. H. aoronymphium and D. falleni respond more narrowly to odorants than Caenorhabditis elegans and Drosophila melanogaster, consistent with their more specialized niches. Infection of D. falleni with H. aoronymphium alters its olfactory preferences, rendering it more narrowly tuned to mushroom odor. Our results establish H. aoronymphium-D. falleni as a model system for studying olfaction in the context of parasite-host interactions.
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Affiliation(s)
- James A Cevallos
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Ryo P Okubo
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Steve J Perlman
- Department of Biology, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada
| | - Elissa A Hallem
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.
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31
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Control of Neuropeptide Expression by Parallel Activity-dependent Pathways in Caenorhabditis elegans. Sci Rep 2017; 7:38734. [PMID: 28139692 PMCID: PMC5282578 DOI: 10.1038/srep38734] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/14/2016] [Indexed: 12/19/2022] Open
Abstract
Monitoring of neuronal activity within circuits facilitates integrated responses and rapid changes in behavior. We have identified a system in Caenorhabditis elegans where neuropeptide expression is dependent on the ability of the BAG neurons to sense carbon dioxide. In C. elegans, CO2 sensing is predominantly coordinated by the BAG-expressed receptor-type guanylate cyclase GCY-9. GCY-9 binding to CO2 causes accumulation of cyclic GMP and opening of the cGMP-gated TAX-2/TAX-4 cation channels; provoking an integrated downstream cascade that enables C. elegans to avoid high CO2. Here we show that cGMP regulation by GCY-9 and the PDE-1 phosphodiesterase controls BAG expression of a FMRFamide-related neuropeptide FLP-19 reporter (flp-19::GFP). This regulation is specific for CO2-sensing function of the BAG neurons, as loss of oxygen sensing function does not affect flp-19::GFP expression. We also found that expression of flp-19::GFP is controlled in parallel to GCY-9 by the activity-dependent transcription factor CREB (CRH-1) and the cAMP-dependent protein kinase (KIN-2) signaling pathway. We therefore show that two parallel pathways regulate neuropeptide gene expression in the BAG sensory neurons: the ability to sense changes in carbon dioxide and CREB transcription factor. Such regulation may be required in particular environmental conditions to enable sophisticated behavioral decisions to be performed.
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32
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Olfactory circuits and behaviors of nematodes. Curr Opin Neurobiol 2016; 41:136-148. [PMID: 27668755 DOI: 10.1016/j.conb.2016.09.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 08/19/2016] [Accepted: 09/05/2016] [Indexed: 12/29/2022]
Abstract
Over one billion people worldwide are infected with parasitic nematodes. Many parasitic nematodes actively search for hosts to infect using volatile chemical cues, so understanding the olfactory signals that drive host seeking may elucidate new pathways for preventing infections. The free-living nematode Caenorhabditis elegans is a powerful model for parasitic nematodes: because sensory neuroanatomy is conserved across nematode species, an understanding of the microcircuits that mediate olfaction in C. elegans may inform studies of olfaction in parasitic nematodes. Here we review circuit mechanisms that allow C. elegans to respond to odorants, gases, and pheromones. We also highlight work on the olfactory behaviors of parasitic nematodes that lays the groundwork for future studies of their olfactory microcircuits.
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33
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GPCRs in invertebrate innate immunity. Biochem Pharmacol 2016; 114:82-7. [DOI: 10.1016/j.bcp.2016.05.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 05/31/2016] [Indexed: 12/13/2022]
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34
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Gang SS, Hallem EA. Mechanisms of host seeking by parasitic nematodes. Mol Biochem Parasitol 2016; 208:23-32. [PMID: 27211240 DOI: 10.1016/j.molbiopara.2016.05.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 05/13/2016] [Accepted: 05/16/2016] [Indexed: 10/21/2022]
Abstract
The phylum Nematoda comprises a diverse group of roundworms that includes parasites of vertebrates, invertebrates, and plants. Human-parasitic nematodes infect more than one billion people worldwide and cause some of the most common neglected tropical diseases, particularly in low-resource countries [1]. Parasitic nematodes of livestock and crops result in billions of dollars in losses each year [1]. Many nematode infections are treatable with low-cost anthelmintic drugs, but repeated infections are common in endemic areas and drug resistance is a growing concern with increasing therapeutic and agricultural administration [1]. Many parasitic nematodes have an environmental infective larval stage that engages in host seeking, a process whereby the infective larvae use sensory cues to search for hosts. Host seeking is a complex behavior that involves multiple sensory modalities, including olfaction, gustation, thermosensation, and humidity sensation. As the initial step of the parasite-host interaction, host seeking could be a powerful target for preventative intervention. However, host-seeking behavior remains poorly understood. Here we review what is currently known about the host-seeking behaviors of different parasitic nematodes, including insect-parasitic nematodes, mammalian-parasitic nematodes, and plant-parasitic nematodes. We also discuss the neural bases of these behaviors.
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Affiliation(s)
- Spencer S Gang
- Department of Microbiology, Immunology, and Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, United States.
| | - Elissa A Hallem
- Department of Microbiology, Immunology, and Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, United States.
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35
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Environmental CO2 inhibits Caenorhabditis elegans egg-laying by modulating olfactory neurons and evokes widespread changes in neural activity. Proc Natl Acad Sci U S A 2015; 112:E3525-34. [PMID: 26100886 DOI: 10.1073/pnas.1423808112] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Carbon dioxide (CO2) gradients are ubiquitous and provide animals with information about their environment, such as the potential presence of prey or predators. The nematode Caenorhabditis elegans avoids elevated CO2, and previous work identified three neuron pairs called "BAG," "AFD," and "ASE" that respond to CO2 stimuli. Using in vivo Ca(2+) imaging and behavioral analysis, we show that C. elegans can detect CO2 independently of these sensory pathways. Many of the C. elegans sensory neurons we examined, including the AWC olfactory neurons, the ASJ and ASK gustatory neurons, and the ASH and ADL nociceptors, respond to a rise in CO2 with a rise in Ca(2+). In contrast, glial sheath cells harboring the sensory endings of C. elegans' major chemosensory neurons exhibit strong and sustained decreases in Ca(2+) in response to high CO2. Some of these CO2 responses appear to be cell intrinsic. Worms therefore may couple detection of CO2 to that of other cues at the earliest stages of sensory processing. We show that C. elegans persistently suppresses oviposition at high CO2. Hermaphrodite-specific neurons (HSNs), the executive neurons driving egg-laying, are tonically inhibited when CO2 is elevated. CO2 modulates the egg-laying system partly through the AWC olfactory neurons: High CO2 tonically activates AWC by a cGMP-dependent mechanism, and AWC output inhibits the HSNs. Our work shows that CO2 is a more complex sensory cue for C. elegans than previously thought, both in terms of behavior and neural circuitry.
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36
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Laurent P, Soltesz Z, Nelson GM, Chen C, Arellano-Carbajal F, Levy E, de Bono M. Decoding a neural circuit controlling global animal state in C. elegans. eLife 2015; 4. [PMID: 25760081 PMCID: PMC4440410 DOI: 10.7554/elife.04241] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 03/10/2015] [Indexed: 02/05/2023] Open
Abstract
Brains organize behavior and physiology to optimize the response to threats or opportunities. We dissect how 21% O2, an indicator of surface exposure, reprograms C. elegans' global state, inducing sustained locomotory arousal and altering expression of neuropeptides, metabolic enzymes, and other non-neural genes. The URX O2-sensing neurons drive arousal at 21% O2 by tonically activating the RMG interneurons. Stimulating RMG is sufficient to switch behavioral state. Ablating the ASH, ADL, or ASK sensory neurons connected to RMG by gap junctions does not disrupt arousal. However, disrupting cation currents in these neurons curtails RMG neurosecretion and arousal. RMG signals high O2 by peptidergic secretion. Neuropeptide reporters reveal neural circuit state, as neurosecretion stimulates neuropeptide expression. Neural imaging in unrestrained animals shows that URX and RMG encode O2 concentration rather than behavior, while the activity of downstream interneurons such as AVB and AIY reflect both O2 levels and the behavior being executed. DOI:http://dx.doi.org/10.7554/eLife.04241.001 From humans to worms, animals must respond appropriately to environmental challenges to survive. Starving animals must conserve energy while they seek food; animals that encounter a predator must fight or flee. These responses involve the animals re-programming their bodies and behavior, and, in humans, are thought to coincide with feelings or emotions such as ‘hunger’ and ‘fear’. Understanding these states in humans is difficult, but studies of simpler animals may provide some insights. The microscopic worm Caenorhabditis elegans offers a unique advantage to these studies because it has the most precisely described nervous system of any animal. The worm lives in rotting fruit, but it avoids the fruit's surface, perhaps because there is an increased risk of it drying out or being eaten by predators. Microbes that grow within the rotting fruit reduce the oxygen level below the 21% oxygen found in the surrounding air, and so one strategy that C. elegans uses to avoid surface exposure is to continuously monitor the oxygen concentration. If the worm senses that the oxygen level is approaching 21%, which suggests it is nearing the surface, it reverses and turns around. If it cannot find a lower-oxygen environment, the worm switches to continuous rapid movement until it locates such an environment, and adapts its body for surface exposure. Laurent, Soltesz et al. sought to understand the circuit of neurons that controls this switch. Monitoring gene expression in the worms revealed that specific oxygen-sensing neurons help generate the widespread changes that occur in the worm's body. These neurons also control the switch in the worm's behavior. Sensory neurons relay signals to downstream neurons that act on muscles to alter behavior. Neurons typically communicate with other neurons via specific connections; but neurons can also release signaling molecules, which act like ‘wireless’ signals and can affect many other cells. Laurent, Soltesz et al. showed that both kinds of signaling are needed to change the worm's behavior, and suggest that the release of signaling molecules may explain the widespread effects of 21% oxygen on the worm. Laurent, Soltesz et al. then monitored the activity of neurons in freely moving worms, and found that some neurons appear to encode and relay specific sensory information. Other neurons encode the behavior the animal is performing, and yet others can encode both kinds of information. To confirm which neurons control particular behavioral responses, Laurent, Soltesz et al. measured changes in the worm’s behavior after destroying or altering specific cells, or while they used light-based techniques to artificially excite or inhibit specific neurons. At a simple level the worm's response to 21% oxygen resembles the response of a mammal to a dangerous environment: both become more aroused, change how they respond to other sensory cues, and adapt both their bodies and behavior. As such, C. elegans provides a great model to explore at a small and accessible scale how changes in animals' states are generated. DOI:http://dx.doi.org/10.7554/eLife.04241.002
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Affiliation(s)
| | - Zoltan Soltesz
- Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Geoffrey M Nelson
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Changchun Chen
- Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Emmanuel Levy
- Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Mario de Bono
- Laboratory of Molecular Biology, Cambridge, United Kingdom
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37
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Sharabi K, Charar C, Gruenbaum Y. Pharyngeal pumping inhibition and avoidance by acute exposure to high CO2 levels are both regulated by the BAG neurons via different molecular pathways. WORM 2015; 4:e1008898. [PMID: 26430557 DOI: 10.1080/21624054.2015.1008898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 12/23/2014] [Accepted: 01/07/2015] [Indexed: 10/23/2022]
Abstract
Carbon dioxide (CO2) is a key molecule in many biological processes. Studies in humans, mice, D. melanogaster, C. elegans, unicellular organisms and plants have shed light on the molecular pathways activated by elevated levels of CO2. However, the mechanisms that organisms use to sense and respond to high CO2 levels remain largely unknown. Previous work has shown that C. elegans quickly avoid elevated CO2 levels using mechanisms that involve the BAG, ASE and AFD neurons via cGMP- and calcium- signaling pathways. Here, we discuss our recent finding that exposure of C. elegans to high CO2 levels leads to a very rapid cessation in the contraction of the pharynx muscles. Surprisingly, none of the tested CO2 avoidance mutants affected the rapid pumping inhibition response to elevated CO2 levels. A forward genetic screen identified that the hid-1-mediated pathway of dense core vesicle maturation regulates the pumping inhibition, probably through affecting neuropeptide secretion. Genetic studies and laser ablation experiments showed that the CO2 response of the pharyngeal muscle pumping is regulated by the BAG neurons, the same neurons that mediate CO2 avoidance.
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Affiliation(s)
- Kfir Sharabi
- Department of Genetics; Institute of Life Sciences ; Hebrew University of Jerusalem ; Jerusalem, Israel
| | - Chayki Charar
- Department of Genetics; Institute of Life Sciences ; Hebrew University of Jerusalem ; Jerusalem, Israel
| | - Yosef Gruenbaum
- Department of Genetics; Institute of Life Sciences ; Hebrew University of Jerusalem ; Jerusalem, Israel
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38
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Sharabi K, Charar C, Friedman N, Mizrahi I, Zaslaver A, Sznajder JI, Gruenbaum Y. The response to high CO2 levels requires the neuropeptide secretion component HID-1 to promote pumping inhibition. PLoS Genet 2014; 10:e1004529. [PMID: 25101962 PMCID: PMC4125093 DOI: 10.1371/journal.pgen.1004529] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 06/09/2014] [Indexed: 11/19/2022] Open
Abstract
Carbon dioxide (CO2) is a key molecule in many biological processes; however, mechanisms by which organisms sense and respond to high CO2 levels remain largely unknown. Here we report that acute CO2 exposure leads to a rapid cessation in the contraction of the pharynx muscles in Caenorhabditis elegans. To uncover the molecular mechanisms underlying this response, we performed a forward genetic screen and found that hid-1, a key component in neuropeptide signaling, regulates this inhibition in muscle contraction. Surprisingly, we found that this hid-1-mediated pathway is independent of any previously known pathways controlling CO2 avoidance and oxygen sensing. In addition, animals with mutations in unc-31 and egl-21 (neuropeptide secretion and maturation components) show impaired inhibition of muscle contraction following acute exposure to high CO2 levels, in further support of our findings. Interestingly, the observed response in the pharynx muscle requires the BAG neurons, which also mediate CO2 avoidance. This novel hid-1-mediated pathway sheds new light on the physiological effects of high CO2 levels on animals at the organism-wide level.
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Affiliation(s)
- Kfir Sharabi
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Chayki Charar
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nurit Friedman
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Inbar Mizrahi
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alon Zaslaver
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Jacob I. Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Yosef Gruenbaum
- Department of Genetics, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
- * E-mail:
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39
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Flibotte JJ, Jablonski AM, Kalb RG. Oxygen sensing neurons and neuropeptides regulate survival after anoxia in developing C. elegans. PLoS One 2014; 9:e101102. [PMID: 24967811 PMCID: PMC4072718 DOI: 10.1371/journal.pone.0101102] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 06/02/2014] [Indexed: 11/18/2022] Open
Abstract
Hypoxic brain injury remains a major source of neurodevelopmental impairment for both term and preterm infants. The perinatal period is a time of rapid transition in oxygen environments and developmental resetting of oxygen sensing. The relationship between neural oxygen sensing ability and hypoxic injury has not been studied. The oxygen sensing circuitry in the model organism C. elegans is well understood. We leveraged this information to investigate the effects of impairments in oxygen sensing on survival after anoxia. There was a significant survival advantage in developing worms specifically unable to sense oxygen shifts below their preferred physiologic range via genetic ablation of BAG neurons, which appear important for conferring sensitivity to anoxia. Oxygen sensing that is mediated through guanylate cyclases (gcy-31, 33, 35) is unlikely to be involved in conferring this sensitivity. Additionally, animals unable to process or elaborate neuropeptides displayed a survival advantage after anoxia. Based on these data, we hypothesized that elaboration of neuropeptides by BAG neurons sensitized animals to anoxia, but further experiments indicate that this is unlikely to be true. Instead, it seems that neuropeptides and signaling from oxygen sensing neurons operate through independent mechanisms, each conferring sensitivity to anoxia in wild type animals.
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Affiliation(s)
- John J. Flibotte
- Department of Pediatrics, Division of Neonatology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Angela M. Jablonski
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Robert G. Kalb
- Department of Pediatrics, Division of Neurology, Research Institute, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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40
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Abstract
Nearly all animals are capable of sensing changes in environmental oxygen (O2) and carbon dioxide (CO2) levels, which can signal the presence of food, pathogens, conspecifics, predators, or hosts. The free-living nematode Caenorhabditis elegans is a powerful model system for the study of gas sensing. C. elegans detects changes in O2 and CO2 levels and integrates information about ambient gas levels with other internal and external cues to generate context-appropriate behavioral responses. Due to its small nervous system and amenability to genetic and genomic analyses, the functional properties of its gas-sensing microcircuits can be dissected with single-cell resolution, and signaling molecules and natural genetic variations that modulate gas responses can be identified. Here, we discuss the neural basis of gas sensing in C. elegans, and highlight changes in gas-evoked behaviors in the context of other sensory cues and natural genetic variations. We also discuss gas sensing in other free-living nematodes and parasitic nematodes, focusing on how gas-sensing behavior has evolved to mediate species-specific behavioral requirements.
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41
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Peymen K, Watteyne J, Frooninckx L, Schoofs L, Beets I. The FMRFamide-Like Peptide Family in Nematodes. Front Endocrinol (Lausanne) 2014; 5:90. [PMID: 24982652 PMCID: PMC4058706 DOI: 10.3389/fendo.2014.00090] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 05/31/2014] [Indexed: 12/31/2022] Open
Abstract
In the three decades since the FMRFamide peptide was isolated from the mollusk Macrocallista nimbosa, structurally similar peptides sharing a C-terminal RFamide motif have been identified across the animal kingdom. FMRFamide-like peptides (FLPs) represent the largest known family of neuropeptides in invertebrates. In the phylum Nematoda, at least 32 flp-genes are classified, making the FLP system of nematodes unusually complex. The diversity of the nematode FLP complement is most extensively mapped in Caenorhabditis elegans, where over 70 FLPs have been predicted. FLPs have shown to be expressed in the majority of the 302 C. elegans neurons including interneurons, sensory neurons, and motor neurons. The vast expression of FLPs is reflected in the broad functional repertoire of nematode FLP signaling, including neuroendocrine and neuromodulatory effects on locomotory activity, reproduction, feeding, and behavior. In contrast to the many identified nematode FLPs, only few peptides have been assigned a receptor and there is the need to clarify the pathway components and working mechanisms of the FLP signaling network. Here, we review the diversity, distribution, and functions of FLPs in nematodes.
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Affiliation(s)
- Katleen Peymen
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven, Leuven, Belgium
| | - Jan Watteyne
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven, Leuven, Belgium
| | - Lotte Frooninckx
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven, Leuven, Belgium
| | - Liliane Schoofs
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven, Leuven, Belgium
| | - Isabel Beets
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven, Leuven, Belgium
- *Correspondence: Isabel Beets, Functional Genomics and Proteomics Group, Department of Biology, KU Leuven, Naamsestraat 59, Leuven 3000, Belgium e-mail:
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42
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Kodama-Namba E, Fenk LA, Bretscher AJ, Gross E, Busch KE, de Bono M. Cross-modulation of homeostatic responses to temperature, oxygen and carbon dioxide in C. elegans. PLoS Genet 2013; 9:e1004011. [PMID: 24385919 PMCID: PMC3868554 DOI: 10.1371/journal.pgen.1004011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 10/24/2013] [Indexed: 11/19/2022] Open
Abstract
Different interoceptive systems must be integrated to ensure that multiple homeostatic insults evoke appropriate behavioral and physiological responses. Little is known about how this is achieved. Using C. elegans, we dissect cross-modulation between systems that monitor temperature, O₂ and CO₂. CO₂ is less aversive to animals acclimated to 15°C than those grown at 22°C. This difference requires the AFD neurons, which respond to both temperature and CO₂ changes. CO₂ evokes distinct AFD Ca²⁺ responses in animals acclimated at 15°C or 22°C. Mutants defective in synaptic transmission can reprogram AFD CO₂ responses according to temperature experience, suggesting reprogramming occurs cell autonomously. AFD is exquisitely sensitive to CO₂. Surprisingly, gradients of 0.01% CO₂/second evoke very different Ca²⁺ responses from gradients of 0.04% CO₂/second. Ambient O₂ provides further contextual modulation of CO₂ avoidance. At 21% O₂ tonic signalling from the O₂-sensing neuron URX inhibits CO₂ avoidance. This inhibition can be graded according to O₂ levels. In a natural wild isolate, a switch from 21% to 19% O₂ is sufficient to convert CO₂ from a neutral to an aversive cue. This sharp tuning is conferred partly by the neuroglobin GLB-5. The modulatory effects of O₂ on CO₂ avoidance involve the RIA interneurons, which are post-synaptic to URX and exhibit CO₂-evoked Ca²⁺ responses. Ambient O₂ and acclimation temperature act combinatorially to modulate CO₂ responsiveness. Our work highlights the integrated architecture of homeostatic responses in C. elegans.
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Affiliation(s)
| | - Lorenz A. Fenk
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Einav Gross
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Mario de Bono
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
- * E-mail:
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Smith ESJ, Martinez-Velazquez L, Ringstad N. A chemoreceptor that detects molecular carbon dioxide. J Biol Chem 2013; 288:37071-81. [PMID: 24240097 DOI: 10.1074/jbc.m113.517367] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Animals from diverse phyla possess neurons that are activated by the product of aerobic respiration, CO2. It has long been thought that such neurons primarily detect the CO2 metabolites protons and bicarbonate. We have determined the chemical tuning of isolated CO2 chemosensory BAG neurons of the nematode Caenorhabditis elegans. We show that BAG neurons are principally tuned to detect molecular CO2, although they can be activated by acid stimuli. One component of the BAG transduction pathway, the receptor-type guanylate cyclase GCY-9, suffices to confer cellular sensitivity to both molecular CO2 and acid, indicating that it is a bifunctional chemoreceptor. We speculate that in other animals, receptors similarly capable of detecting molecular CO2 might mediate effects of CO2 on neural circuits and behavior.
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Affiliation(s)
- Ewan St John Smith
- From the Skirball Institute of Biomolecular Medicine, Molecular Neurobiology Program and Department of Cell Biology, New York University Medical Center, New York, New York 10016 and
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