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Boto T, Tomchik SM. Functional Imaging of Learning-Induced Plasticity in the Central Nervous System with Genetically Encoded Reporters in Drosophila. Cold Spring Harb Protoc 2024; 2024:pdb.top107799. [PMID: 37197830 DOI: 10.1101/pdb.top107799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Learning and memory allow animals to adjust their behavior based on the predictive value of their past experiences. Memories often exist in complex representations, spread across numerous cells and synapses in the brain. Studying relatively simple forms of memory provides insights into the fundamental processes that underlie multiple forms of memory. Associative learning occurs when an animal learns the relationship between two previously unrelated sensory stimuli, such as when a hungry animal learns that a particular odor is followed by a tasty reward. Drosophila is a particularly powerful model to study how this type of memory works. The fundamental principles are widely shared among animals, and there is a wide range of genetic tools available to study circuit function in flies. In addition, the olfactory structures that mediate associative learning in flies, such as the mushroom body and its associated neurons, are anatomically organized, relatively well-characterized, and readily accessible to imaging. Here, we review the olfactory anatomy and physiology of the olfactory system, describe how plasticity in the olfactory pathway mediates learning and memory, and explain the general principles underlying calcium imaging approaches.
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Affiliation(s)
- Tamara Boto
- Department of Physiology, Trinity College Dublin, Dublin 2, Ireland
- Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
| | - Seth M Tomchik
- Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
- Stead Family Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
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2
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Lu S, Qian CS, Grueber WB. Mechanisms of gas sensing by internal sensory neurons in Drosophila larvae. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.20.576342. [PMID: 38293088 PMCID: PMC10827222 DOI: 10.1101/2024.01.20.576342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Internal sensory neurons monitor the chemical and physical state of the body, providing critical information to the central nervous system for maintaining homeostasis and survival. A population of larval Drosophila sensory neurons, tracheal dendrite (td) neurons, elaborate dendrites along respiratory organs and may serve as a model for elucidating the cellular and molecular basis of chemosensation by internal neurons. We find that td neurons respond to decreases in O2 levels and increases in CO2 levels. We assessed the roles of atypical soluble guanylyl cyclases (Gycs) and a gustatory receptor (Gr) in mediating these responses. We found that Gyc88E/Gyc89Db were necessary for responses to hypoxia, and that Gr28b was necessary for responses to CO2. Targeted expression of Gr28b isoform c in td neurons rescued responses to CO2 in mutant larvae and also induced ectopic sensitivity to CO2 in the td network. Gas-sensitive td neurons were activated when larvae burrowed for a prolonged duration, demonstrating a natural-like feeding condition in which td neurons are activated. Together, our work identifies two gaseous stimuli that are detected by partially overlapping subsets of internal sensory neurons, and establishes roles for Gyc88E/Gyc89Db in the detection of hypoxia, and Gr28b in the detection of CO2.
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Affiliation(s)
- Shan Lu
- Zuckerman Mind Brain Behavior Institute, Jerome L. Greene Science Center, 3227 Broadway, L9-007, Columbia University, New York, NY 10027
- Department of Biological Sciences, Jerome L. Greene Science Center, 3227 Broadway, L9-007, Columbia University, New York, NY 10027
| | - Cheng Sam Qian
- Zuckerman Mind Brain Behavior Institute, Jerome L. Greene Science Center, 3227 Broadway, L9-007, Columbia University, New York, NY 10027
| | - Wesley B. Grueber
- Zuckerman Mind Brain Behavior Institute, Jerome L. Greene Science Center, 3227 Broadway, L9-007, Columbia University, New York, NY 10027
- Department of Physiology and Cellular Biophysics, Jerome L. Greene Science Center, 3227 Broadway, L9-007, Columbia University, New York, NY 10027
- Department of Neuroscience, Jerome L. Greene Science Center, 3227 Broadway, L9-007, Columbia University, New York, NY 10027
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Weaver KJ, Raju S, Rucker RA, Chakraborty T, Holt RA, Pletcher SD. Behavioral dissection of hunger states in Drosophila. eLife 2023; 12:RP84537. [PMID: 37326496 DOI: 10.7554/elife.84537] [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] [Indexed: 06/17/2023] Open
Abstract
Hunger is a motivational drive that promotes feeding, and it can be generated by the physiological need to consume nutrients as well as the hedonic properties of food. Brain circuits and mechanisms that regulate feeding have been described, but which of these contribute to the generation of motive forces that drive feeding is unclear. Here, we describe our first efforts at behaviorally and neuronally distinguishing hedonic from homeostatic hunger states in Drosophila melanogaster and propose that this system can be used as a model to dissect the molecular mechanisms that underlie feeding motivation. We visually identify and quantify behaviors exhibited by hungry flies and find that increased feeding duration is a behavioral signature of hedonic feeding motivation. Using a genetically encoded marker of neuronal activity, we find that the mushroom body (MB) lobes are activated by hedonic food environments, and we use optogenetic inhibition to implicate a dopaminergic neuron cluster (protocerebral anterior medial [PAM]) to α'/β' MB circuit in hedonic feeding motivation. The identification of discrete hunger states in flies and the development of behavioral assays to measure them offers a framework to begin dissecting the molecular and circuit mechanisms that generate motivational states in the brain.
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Affiliation(s)
- Kristina J Weaver
- Department of Molecular and Integrative Physiology and Geriatrics Center, Biomedical Sciences and Research Building, University of Michigan, Ann Arbor, United States
| | - Sonakshi Raju
- College of Literature, Science, and the Arts, Biomedical Sciences and Research Building, University of Michigan, Ann Arbor, United States
| | - Rachel A Rucker
- Neuroscience Graduate Program, University of Michigan, University of Michigan, Ann Arbor, United States
| | - Tuhin Chakraborty
- Department of Molecular and Integrative Physiology and Geriatrics Center, Biomedical Sciences and Research Building, University of Michigan, Ann Arbor, United States
| | - Robert A Holt
- College of Literature, Science, and the Arts, Biomedical Sciences and Research Building, University of Michigan, Ann Arbor, United States
| | - Scott D Pletcher
- Department of Molecular and Integrative Physiology and Geriatrics Center, Biomedical Sciences and Research Building, University of Michigan, Ann Arbor, United States
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Gendron CM, Chakraborty TS, Duran C, Dono T, Pletcher SD. Ring neurons in the Drosophila central complex act as a rheostat for sensory modulation of aging. PLoS Biol 2023; 21:e3002149. [PMID: 37310911 PMCID: PMC10263353 DOI: 10.1371/journal.pbio.3002149] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 05/03/2023] [Indexed: 06/15/2023] Open
Abstract
Sensory perception modulates aging, yet we know little about how. An understanding of the neuronal mechanisms through which animals orchestrate biological responses to relevant sensory inputs would provide insight into the control systems that may be important for modulating lifespan. Here, we provide new awareness into how the perception of dead conspecifics, or death perception, which elicits behavioral and physiological effects in many different species, affects lifespan in the fruit fly, Drosophila melanogaster. Previous work demonstrated that cohousing Drosophila with dead conspecifics decreases fat stores, reduces starvation resistance, and accelerates aging in a manner that requires both sight and the serotonin receptor 5-HT2A. In this manuscript, we demonstrate that a discrete, 5-HT2A-expressing neural population in the ellipsoid body (EB) of the Drosophila central complex, identified as R2/R4 neurons, acts as a rheostat and plays an important role in transducing sensory information about the presence of dead individuals to modulate lifespan. Expression of the insulin-responsive transcription factor foxo in R2/R4 neurons and insulin-like peptides dilp3 and dilp5, but not dilp2, are required, with the latter likely altered in median neurosecretory cells (MNCs) after R2/R4 neuronal activation. These data generate new insights into the neural underpinnings of how perceptive events may impact aging and physiology across taxa.
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Affiliation(s)
- Christi M. Gendron
- Department of Molecular and Integrative Physiology and Geriatrics Center, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Tuhin S. Chakraborty
- Department of Molecular and Integrative Physiology and Geriatrics Center, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Cathryn Duran
- Department of Molecular and Integrative Physiology and Geriatrics Center, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Thomas Dono
- Department of Molecular and Integrative Physiology and Geriatrics Center, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Scott D. Pletcher
- Department of Molecular and Integrative Physiology and Geriatrics Center, University of Michigan, Ann Arbor, Michigan, United States of America
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Bansal S, Lin S. Transcriptional Genetically Encoded Calcium Indicators in Drosophila. Cold Spring Harb Protoc 2023; 2023:8-18. [PMID: 36167674 DOI: 10.1101/pdb.top107797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Knowing which neurons are active during behavior is a crucial step toward understanding how nervous systems work. Neuronal activation is generally accompanied by an increase in intracellular calcium levels. Therefore, intracellular calcium levels are widely used as a proxy for neuronal activity. Many types of synthetic components and bioluminescent or fluorescent proteins that report transient and long-term changes in intracellular calcium levels have been developed over the past 60 years. Calcium indicators that enable imaging of the dynamic activity of a large ensemble of neurons in behaving animals have revolutionized the field of neuroscience. Among these, transcription-based genetically encoded calcium indicators (transcriptional GECIs) have proven easy to use and do not depend on sophisticated imaging systems, offering unique advantages over other types of calcium indicators. Here, we describe the two currently available fly transcriptional GECIs-calcium-dependent nuclear import of LexA (CaLexA) and transcriptional reporter of intracellular calcium (TRIC)-and review studies that have used them. In the accompanying protocol, we present step-by-step details for generating CaLexA- and TRIC-ready flies and for imaging CaLexA and TRIC signals in dissected brains after experimental manipulations of intact free-moving flies.
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Affiliation(s)
- Sonia Bansal
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
| | - Suewei Lin
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
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Fischer FP, Karge RA, Weber YG, Koch H, Wolking S, Voigt A. Drosophila melanogaster as a versatile model organism to study genetic epilepsies: An overview. Front Mol Neurosci 2023; 16:1116000. [PMID: 36873106 PMCID: PMC9978166 DOI: 10.3389/fnmol.2023.1116000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 01/23/2023] [Indexed: 02/18/2023] Open
Abstract
Epilepsy is one of the most prevalent neurological disorders, affecting more than 45 million people worldwide. Recent advances in genetic techniques, such as next-generation sequencing, have driven genetic discovery and increased our understanding of the molecular and cellular mechanisms behind many epilepsy syndromes. These insights prompt the development of personalized therapies tailored to the genetic characteristics of an individual patient. However, the surging number of novel genetic variants renders the interpretation of pathogenetic consequences and of potential therapeutic implications ever more challenging. Model organisms can help explore these aspects in vivo. In the last decades, rodent models have significantly contributed to our understanding of genetic epilepsies but their establishment is laborious, expensive, and time-consuming. Additional model organisms to investigate disease variants on a large scale would be desirable. The fruit fly Drosophila melanogaster has been used as a model organism in epilepsy research since the discovery of "bang-sensitive" mutants more than half a century ago. These flies respond to mechanical stimulation, such as a brief vortex, with stereotypic seizures and paralysis. Furthermore, the identification of seizure-suppressor mutations allows to pinpoint novel therapeutic targets. Gene editing techniques, such as CRISPR/Cas9, are a convenient way to generate flies carrying disease-associated variants. These flies can be screened for phenotypic and behavioral abnormalities, shifting of seizure thresholds, and response to anti-seizure medications and other substances. Moreover, modification of neuronal activity and seizure induction can be achieved using optogenetic tools. In combination with calcium and fluorescent imaging, functional alterations caused by mutations in epilepsy genes can be traced. Here, we review Drosophila as a versatile model organism to study genetic epilepsies, especially as 81% of human epilepsy genes have an orthologous gene in Drosophila. Furthermore, we discuss newly established analysis techniques that might be used to further unravel the pathophysiological aspects of genetic epilepsies.
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Affiliation(s)
- Florian P Fischer
- Department of Epileptology and Neurology, RWTH Aachen University, Aachen, Germany
| | - Robin A Karge
- Department of Epileptology and Neurology, RWTH Aachen University, Aachen, Germany
| | - Yvonne G Weber
- Department of Epileptology and Neurology, RWTH Aachen University, Aachen, Germany.,Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Henner Koch
- Department of Epileptology and Neurology, RWTH Aachen University, Aachen, Germany
| | - Stefan Wolking
- Department of Epileptology and Neurology, RWTH Aachen University, Aachen, Germany
| | - Aaron Voigt
- Department of Neurology, RWTH Aachen University, Aachen, Germany.,JARA-BRAIN Institute Molecular Neuroscience and Neuroimaging, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
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7
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Zhang F, Wu LB, Yu Q, Wang MJ, Zeng XL, Wei XT, Wu ZJ, Cai RL, Hu L. Neurotropic Viruses as a Tool for Neural Circuit-Tracing. NEUROCHEM J+ 2021. [DOI: 10.1134/s1819712421040176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Brun NR, Panlilio JM, Zhang K, Zhao Y, Ivashkin E, Stegeman JJ, Goldstone JV. Developmental exposure to non-dioxin-like polychlorinated biphenyls promotes sensory deficits and disrupts dopaminergic and GABAergic signaling in zebrafish. Commun Biol 2021; 4:1129. [PMID: 34561524 PMCID: PMC8463681 DOI: 10.1038/s42003-021-02626-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 08/25/2021] [Indexed: 11/09/2022] Open
Abstract
The most abundant polychlorinated biphenyl (PCB) congeners found in the environment and in humans are neurotoxic. This is of particular concern for early life stages because the exposure of the more vulnerable developing nervous system to neurotoxic chemicals can result in neurobehavioral disorders. In this study, we uncover currently unknown links between PCB target mechanisms and neurobehavioral deficits using zebrafish as a vertebrate model. We investigated the effects of the abundant non-dioxin-like (NDL) congener PCB153 on neuronal morphology and synaptic transmission linked to the proper execution of a sensorimotor response. Zebrafish that were exposed during development to concentrations similar to those found in human cord blood and PCB contaminated sites showed a delay in startle response. Morphological and biochemical data demonstrate that even though PCB153-induced swelling of afferent sensory neurons, the disruption of dopaminergic and GABAergic signaling appears to contribute to PCB-induced motor deficits. A similar delay was observed for other NDL congeners but not for the potent dioxin-like congener PCB126. The effects on important and broadly conserved signaling mechanisms in vertebrates suggest that NDL PCBs may contribute to neurodevelopmental abnormalities in humans and increased selection pressures in vertebrate wildlife.
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Affiliation(s)
- Nadja R Brun
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
| | - Jennifer M Panlilio
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Kun Zhang
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.,Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China
| | - Yanbin Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.,Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China
| | - Evgeny Ivashkin
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, USA.,A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia
| | - John J Stegeman
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
| | - Jared V Goldstone
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
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Bi X, Beck C, Gong Y. Genetically Encoded Fluorescent Indicators for Imaging Brain Chemistry. BIOSENSORS 2021; 11:116. [PMID: 33920418 PMCID: PMC8069469 DOI: 10.3390/bios11040116] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 12/17/2022]
Abstract
Genetically encoded fluorescent indicators, combined with optical imaging, enable the detection of physiologically or behaviorally relevant neural activity with high spatiotemporal resolution. Recent developments in protein engineering and screening strategies have improved the dynamic range, kinetics, and spectral properties of genetically encoded fluorescence indicators of brain chemistry. Such indicators have detected neurotransmitter and calcium dynamics with high signal-to-noise ratio at multiple temporal and spatial scales in vitro and in vivo. This review summarizes the current trends in these genetically encoded fluorescent indicators of neurotransmitters and calcium, focusing on their key metrics and in vivo applications.
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Affiliation(s)
| | | | - Yiyang Gong
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA; (X.B.); (C.B.)
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Heinrich R, Hussein W, Berlin S. Photo-transformable genetically-encoded optical probes for functional highlighting in vivo. J Neurosci Methods 2021; 355:109129. [PMID: 33711357 DOI: 10.1016/j.jneumeth.2021.109129] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 03/02/2021] [Accepted: 03/04/2021] [Indexed: 12/13/2022]
Abstract
Studying the brain requires knowledge about both structure (i.e., connectome) and function of its constituents (neurons and glia alike). This need has prompted the development of novel tools and techniques, in particular optical techniques to examine cells remotely. Early works (1900's) led to the development of novel cell-staining techniques that, when combined with the use of a very simple light microscope, visualized individual neurons and their subcellular compartments in fixed tissues. Today, highlighting of structure and function can be performed on live cells, notably in vivo, owing to discovery of GFP and subsequent development of genetically encoded fluorescent optical tools. In this review, we focus our attention on a subset of optical biosensors, namely probes whose emission can be modified by light. We designate them photo-transformable genetically encoded probes. The family of photo-transformable probes embraces current probes that undergo photoactivation (PA), photoconversion (PC) or photoswitching (PS). We argue that these are particularly suited for studying multiple features of neurons, such as structure, connectivity and function concomitantly, for functional highlighting of neurons in vivo.
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Affiliation(s)
- Ronit Heinrich
- Department of Neuroscience, The Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
| | - Wessal Hussein
- Department of Neuroscience, The Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
| | - Shai Berlin
- Department of Neuroscience, The Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel.
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