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Eckstein N, Bates AS, Champion A, Du M, Yin Y, Schlegel P, Lu AKY, Rymer T, Finley-May S, Paterson T, Parekh R, Dorkenwald S, Matsliah A, Yu SC, McKellar C, Sterling A, Eichler K, Costa M, Seung S, Murthy M, Hartenstein V, Jefferis GSXE, Funke J. Neurotransmitter classification from electron microscopy images at synaptic sites in Drosophila melanogaster. Cell 2024; 187:2574-2594.e23. [PMID: 38729112 PMCID: PMC11106717 DOI: 10.1016/j.cell.2024.03.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 10/04/2023] [Accepted: 03/13/2024] [Indexed: 05/12/2024]
Abstract
High-resolution electron microscopy of nervous systems has enabled the reconstruction of synaptic connectomes. However, we do not know the synaptic sign for each connection (i.e., whether a connection is excitatory or inhibitory), which is implied by the released transmitter. We demonstrate that artificial neural networks can predict transmitter types for presynapses from electron micrographs: a network trained to predict six transmitters (acetylcholine, glutamate, GABA, serotonin, dopamine, octopamine) achieves an accuracy of 87% for individual synapses, 94% for neurons, and 91% for known cell types across a D. melanogaster whole brain. We visualize the ultrastructural features used for prediction, discovering subtle but significant differences between transmitter phenotypes. We also analyze transmitter distributions across the brain and find that neurons that develop together largely express only one fast-acting transmitter (acetylcholine, glutamate, or GABA). We hope that our publicly available predictions act as an accelerant for neuroscientific hypothesis generation for the fly.
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Affiliation(s)
- Nils Eckstein
- HHMI Janelia Research Campus, Ashburn, VA, USA; Institute of Neuroinformatics UZH/ETHZ, Zurich, Switzerland
| | - Alexander Shakeel Bates
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK; Centre for Neural Circuits and Behaviour, The University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK; Department of Neurobiology and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
| | - Andrew Champion
- Drosophila Connectomics Group, Department of Zoology, University of Cambridge, Cambridge, UK
| | - Michelle Du
- HHMI Janelia Research Campus, Ashburn, VA, USA
| | - Yijie Yin
- Drosophila Connectomics Group, Department of Zoology, University of Cambridge, Cambridge, UK
| | - Philipp Schlegel
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK; Drosophila Connectomics Group, Department of Zoology, University of Cambridge, Cambridge, UK
| | | | | | | | | | | | - Sven Dorkenwald
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Arie Matsliah
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Szi-Chieh Yu
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Claire McKellar
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Amy Sterling
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Katharina Eichler
- Drosophila Connectomics Group, Department of Zoology, University of Cambridge, Cambridge, UK
| | - Marta Costa
- Drosophila Connectomics Group, Department of Zoology, University of Cambridge, Cambridge, UK
| | - Sebastian Seung
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Mala Murthy
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, USA
| | - Volker Hartenstein
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Gregory S X E Jefferis
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK; Drosophila Connectomics Group, Department of Zoology, University of Cambridge, Cambridge, UK.
| | - Jan Funke
- HHMI Janelia Research Campus, Ashburn, VA, USA.
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2
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Rouyar A, Patil AA, Leon-Noreña M, Li M, Coutinho-Abreu IV, Akbari OS, Riffell JA. Transgenic line for characterizing GABA-receptor expression to study the neural basis of olfaction in the yellow-fever mosquito. Front Physiol 2024; 15:1381164. [PMID: 38606012 PMCID: PMC11008680 DOI: 10.3389/fphys.2024.1381164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 03/14/2024] [Indexed: 04/13/2024] Open
Abstract
The mosquito Aedes aegypti is an important vector of diseases including dengue, Zika, chikungunya, and yellow fever. Olfaction is a critical modality for mosquitoes enabling them to locate hosts, sources of nectar, and sites for oviposition. GABA is an essential neurotransmitter in olfactory processing in the insect brain, including the primary olfactory center, the antennal lobe. Previous work with Ae. aegypti has suggested that antennal lobe inhibition via GABA may be involved in the processing of odors. However, little is known about GABA receptor expression in the mosquito brain, or how they may be involved in odor attraction. In this context, generating mutants that target the mosquito's olfactory responses, and particularly the GABAergic system, is essential to achieve a better understanding of these diverse processes and olfactory coding in these disease vectors. Here we demonstrate the potential of a transgenic line using the QF2 transcription factor, GABA-B1QF2-ECFP, as a new neurogenetic tool to investigate the neural basis of olfaction in Ae. aegypti. Our results show that the gene insertion has a moderate impact on mosquito fitness. Moreover, the line presented here was crossed with a QUAS reporter line expressing the green fluorescent protein and used to determine the location of the metabotropic GABA-B1 receptor expression. We find high receptor expression in the antennal lobes, especially the cell bodies surrounding the antennal lobes. In the mushroom bodies, receptor expression was high in the Kenyon cells, but had low expression in the mushroom body lobes. Behavioral experiments testing the fruit odor attractants showed that the mutants lost their behavioral attraction. Together, these results show that the GABA-B1QF2-ECFP line provides a new tool to characterize GABAergic systems in the mosquito nervous system.
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Affiliation(s)
- Angela Rouyar
- Department of Biology, University of Washington, Seattle, WA, United States
| | - Anandrao A. Patil
- Department of Biology, University of Washington, Seattle, WA, United States
| | | | - Ming Li
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States
| | - Iliano V. Coutinho-Abreu
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States
| | - Omar S. Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States
| | - Jeff A. Riffell
- Department of Biology, University of Washington, Seattle, WA, United States
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3
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Barth-Maron A, D'Alessandro I, Wilson RI. Interactions between specialized gain control mechanisms in olfactory processing. Curr Biol 2023; 33:5109-5120.e7. [PMID: 37967554 DOI: 10.1016/j.cub.2023.10.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 08/16/2023] [Accepted: 10/23/2023] [Indexed: 11/17/2023]
Abstract
Gain control is a process that adjusts a system's sensitivity when input levels change. Neural systems contain multiple mechanisms of gain control, but we do not understand why so many mechanisms are needed or how they interact. Here, we investigate these questions in the Drosophila antennal lobe, where we identify several types of inhibitory interneurons with specialized gain control functions. We find that some interneurons are nonspiking, with compartmentalized calcium signals, and they specialize in intra-glomerular gain control. Conversely, we find that other interneurons are recruited by strong and widespread network input; they specialize in global presynaptic gain control. Using computational modeling and optogenetic perturbations, we show how these mechanisms can work together to improve stimulus discrimination while also minimizing temporal distortions in network activity. Our results demonstrate how the robustness of neural network function can be increased by interactions among diverse and specialized mechanisms of gain control.
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Affiliation(s)
- Asa Barth-Maron
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Isabel D'Alessandro
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Rachel I Wilson
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
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4
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Sizemore TR, Jonaitis J, Dacks AM. Heterogeneous receptor expression underlies non-uniform peptidergic modulation of olfaction in Drosophila. Nat Commun 2023; 14:5280. [PMID: 37644052 PMCID: PMC10465596 DOI: 10.1038/s41467-023-41012-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 08/21/2023] [Indexed: 08/31/2023] Open
Abstract
Sensory systems are dynamically adjusted according to the animal's ongoing needs by neuromodulators, such as neuropeptides. Neuropeptides are often widely-distributed throughout sensory networks, but it is unclear whether such neuropeptides uniformly modulate network activity. Here, we leverage the Drosophila antennal lobe (AL) to resolve whether myoinhibitory peptide (MIP) uniformly modulates AL processing. Despite being uniformly distributed across the AL, MIP decreases olfactory input to some glomeruli, while increasing olfactory input to other glomeruli. We reveal that a heterogeneous ensemble of local interneurons (LNs) are the sole source of AL MIP, and show that differential expression of the inhibitory MIP receptor across glomeruli allows MIP to act on distinct intraglomerular substrates. Our findings demonstrate how even a seemingly simple case of modulation can have complex consequences on network processing by acting non-uniformly within different components of the overall network.
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Affiliation(s)
- Tyler R Sizemore
- Department of Biology, Life Sciences Building, West Virginia University, Morgantown, WV, 26506, USA.
- Department of Molecular, Cellular, and Developmental Biology, Yale Science Building, Yale University, New Haven, CT, 06520-8103, USA.
| | - Julius Jonaitis
- Department of Biology, Life Sciences Building, West Virginia University, Morgantown, WV, 26506, USA
| | - Andrew M Dacks
- Department of Biology, Life Sciences Building, West Virginia University, Morgantown, WV, 26506, USA.
- Department of Neuroscience, West Virginia University, Morgantown, WV, 26506, USA.
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5
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Trebels B, Dippel S, Anders J, Ernst C, Goetz B, Keyser T, Rexer KH, Wimmer EA, Schachtner J. Anatomic and neurochemical analysis of the palpal olfactory system in the red flour beetle Tribolium castaneum, HERBST. Front Cell Neurosci 2023; 17:1097462. [PMID: 36998268 PMCID: PMC10043995 DOI: 10.3389/fncel.2023.1097462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 01/30/2023] [Indexed: 02/25/2023] Open
Abstract
The paired antennal lobes were long considered the sole primary processing centers of the olfactory pathway in holometabolous insects receiving input from the olfactory sensory neurons of the antennae and mouthparts. In hemimetabolous insects, however, olfactory cues of the antennae and palps are processed separately. For the holometabolous red flour beetle Tribolium castaneum, we could show that primary processing of the palpal and antennal olfactory input also occurs separately and at distinct neuronal centers. While the antennal olfactory sensory neurons project into the antennal lobes, those of the palps project into the paired glomerular lobes and the unpaired gnathal olfactory center. Here we provide an extended analysis of the palpal olfactory pathway by combining scanning electron micrographs with confocal imaging of immunohistochemical staining and reporter expression identifying chemosensory and odorant receptor-expressing neurons in the palpal sensilla. In addition, we extended the anatomical characterization of the gnathal olfactory center by 3D reconstructions and investigated the distribution of several neuromediators. The similarities in the neuromediator repertoire between antennal lobes, glomerular lobes, and gnathal olfactory center underline the role of the latter two as additional primary olfactory processing centers.
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Affiliation(s)
- Björn Trebels
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
- *Correspondence: Joachim Schachtner Björn Trebels Ernst A. Wimmer
| | - Stefan Dippel
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Janet Anders
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Clara Ernst
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Brigitte Goetz
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Tim Keyser
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Karl Heinz Rexer
- Biodiversity of Plants, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Ernst A. Wimmer
- Department of Developmental Biology, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, Georg-August-University Göttingen, Göttingen, Germany
- *Correspondence: Joachim Schachtner Björn Trebels Ernst A. Wimmer
| | - Joachim Schachtner
- Animal Physiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
- Clausthal University of Technology, Clausthal-Zellerfeld, Germany
- *Correspondence: Joachim Schachtner Björn Trebels Ernst A. Wimmer
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6
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Fabian B, Sachse S. Experience-dependent plasticity in the olfactory system of Drosophila melanogaster and other insects. Front Cell Neurosci 2023; 17:1130091. [PMID: 36923450 PMCID: PMC10010147 DOI: 10.3389/fncel.2023.1130091] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 02/07/2023] [Indexed: 02/24/2023] Open
Abstract
It is long known that the nervous system of vertebrates can be shaped by internal and external factors. On the other hand, the nervous system of insects was long assumed to be stereotypic, although evidence for plasticity effects accumulated for several decades. To cover the topic comprehensively, this review recapitulates the establishment of the term "plasticity" in neuroscience and introduces its original meaning. We describe the basic composition of the insect olfactory system using Drosophila melanogaster as a representative example and outline experience-dependent plasticity effects observed in this part of the brain in a variety of insects, including hymenopterans, lepidopterans, locusts, and flies. In particular, we highlight recent advances in the study of experience-dependent plasticity effects in the olfactory system of D. melanogaster, as it is the most accessible olfactory system of all insect species due to the genetic tools available. The partly contradictory results demonstrate that morphological, physiological and behavioral changes in response to long-term olfactory stimulation are more complex than previously thought. Different molecular mechanisms leading to these changes were unveiled in the past and are likely responsible for this complexity. We discuss common problems in the study of experience-dependent plasticity, ways to overcome them, and future directions in this area of research. In addition, we critically examine the transferability of laboratory data to natural systems to address the topic as holistically as possible. As a mechanism that allows organisms to adapt to new environmental conditions, experience-dependent plasticity contributes to an animal's resilience and is therefore a crucial topic for future research, especially in an era of rapid environmental changes.
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Affiliation(s)
| | - Silke Sachse
- Research Group Olfactory Coding, Max Planck Institute for Chemical Ecology, Jena, Germany
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7
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Prelic S, Pal Mahadevan V, Venkateswaran V, Lavista-Llanos S, Hansson BS, Wicher D. Functional Interaction Between Drosophila Olfactory Sensory Neurons and Their Support Cells. Front Cell Neurosci 2022; 15:789086. [PMID: 35069116 PMCID: PMC8777253 DOI: 10.3389/fncel.2021.789086] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 12/15/2021] [Indexed: 01/14/2023] Open
Abstract
Insects detect volatile chemicals using antennae, which house a vast variety of olfactory sensory neurons (OSNs) that innervate hair-like structures called sensilla where odor detection takes place. In addition to OSNs, the antenna also hosts various support cell types. These include the triad of trichogen, tormogen, and thecogen support cells that lie adjacent to their respective OSNs. The arrangement of OSN supporting cells occurs stereotypically for all sensilla and is widely conserved in evolution. While insect chemosensory neurons have received considerable attention, little is known about the functional significance of the cells that support them. For instance, it remains unknown whether support cells play an active role in odor detection, or only passively contribute to homeostasis, e.g., by maintaining sensillum lymph composition. To investigate the functional interaction between OSNs and support cells, we used optical and electrophysiological approaches in Drosophila. First, we characterized the distribution of various supporting cells using genetic markers. By means of an ex vivo antennal preparation and genetically-encoded Ca2+ and K+ indicators, we then studied the activation of these auxiliary cells during odor presentation in adult flies. We observed acute responses and distinct differences in Ca2+ and K+ fluxes between support cell types. Finally, we observed alterations in OSN responses upon thecogen cell ablation in mature adults. Upon inducible ablation of thecogen cells, we notice a gain in mechanical responsiveness to mechanical stimulations during single-sensillum recording, but a lack of change to the neuronal resting activity. Taken together, these results demonstrate that support cells play a more active and responsive role during odor processing than previously thought. Our observations thus reveal that support cells functionally interact with OSNs and may be important for the extraordinary ability of insect olfactory systems to dynamically and sensitively discriminate between odors in the turbulent sensory landscape of insect flight.
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Affiliation(s)
- Sinisa Prelic
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Venkatesh Pal Mahadevan
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Vignesh Venkateswaran
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Sofia Lavista-Llanos
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
- CIFASIS-CONICET Franco-Argentine International Center for Information and Systems Sciences—National Council for Scientific and Technical Research, Rosario, Argentina
| | - Bill S. Hansson
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Dieter Wicher
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Jena, Germany
- *Correspondence: Dieter Wicher
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8
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Gregor KM, Becker SC, Hellhammer F, Baumgärtner W, Puff C. Immunohistochemical Characterization of the Nervous System of Culex pipiens (Diptera, Culicidae). BIOLOGY 2022; 11:57. [PMID: 35053056 PMCID: PMC8772823 DOI: 10.3390/biology11010057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/29/2021] [Accepted: 12/30/2021] [Indexed: 11/24/2022]
Abstract
Arthropod-borne diseases represent one of the greatest infection-related threats as a result of climate change and globalization. Repeatedly, arbovirus-infected mosquitoes show behavioral changes whose underlying mechanisms are still largely unknown, but might help to develop control strategies. However, in contrast to well-characterized insects such as fruit flies, little is known about neuroanatomy and neurotransmission in mosquitoes. To overcome this limitation, the study focuses on the immunohistochemical characterization of the nervous system of Culex pipiens biotype molestus in comparison to Drosophila melanogaster using 13 antibodies labeling nervous tissue, neurotransmitters or neurotransmitter-related enzymes. Antibodies directed against γ-aminobutyric acid, serotonin, tyrosine-hydroxylase and glutamine synthetase were suitable for investigations in Culex pipiens and Drosophila melanogaster, albeit species-specific spatial differences were observed. Likewise, similar staining results were achieved for neuronal glycoproteins, axons, dendrites and synaptic zones in both species. Interestingly, anti-phosphosynapsin and anti-gephyrin appear to represent novel markers for synapses and glial cells, respectively. In contrast, antibodies directed against acetylcholine, choline acetyltransferase, elav and repo failed to produce a signal in Culex pipiens comparable to that in Drosophila melanogaster. In summary, present results enable a detailed investigation of the nervous system of mosquitoes, facilitating further studies of behavioral mechanisms associated with arboviruses in the course of vector research.
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Affiliation(s)
- Katharina M. Gregor
- Department of Pathology, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany; (K.M.G.); (C.P.)
| | - Stefanie C. Becker
- Institute for Parasitology, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany; (S.C.B.); (F.H.)
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany
| | - Fanny Hellhammer
- Institute for Parasitology, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany; (S.C.B.); (F.H.)
- Research Center for Emerging Infections and Zoonoses, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany
| | - Wolfgang Baumgärtner
- Department of Pathology, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany; (K.M.G.); (C.P.)
| | - Christina Puff
- Department of Pathology, University of Veterinary Medicine Hannover, Bünteweg 17, Lower Saxony, 30559 Hannover, Germany; (K.M.G.); (C.P.)
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9
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Li Q, Jang H, Lim KY, Lessing A, Stavropoulos N. insomniac links the development and function of a sleep-regulatory circuit. eLife 2021; 10:65437. [PMID: 34908527 PMCID: PMC8758140 DOI: 10.7554/elife.65437] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 10/15/2021] [Indexed: 11/17/2022] Open
Abstract
Although many genes are known to influence sleep, when and how they impact sleep-regulatory circuits remain ill-defined. Here, we show that insomniac (inc), a conserved adaptor for the autism-associated Cul3 ubiquitin ligase, acts in a restricted period of neuronal development to impact sleep in adult Drosophila. The loss of inc causes structural and functional alterations within the mushroom body (MB), a center for sensory integration, associative learning, and sleep regulation. In inc mutants, MB neurons are produced in excess, develop anatomical defects that impede circuit assembly, and are unable to promote sleep when activated in adulthood. Our findings link neurogenesis and postmitotic development of sleep-regulatory neurons to their adult function and suggest that developmental perturbations of circuits that couple sensory inputs and sleep may underlie sleep dysfunction in neurodevelopmental disorders.
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Affiliation(s)
- Qiuling Li
- Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of MedicineNew YorkUnited States
| | - Hyunsoo Jang
- Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of MedicineNew YorkUnited States
| | - Kayla Y Lim
- Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of MedicineNew YorkUnited States
| | - Alexie Lessing
- Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of MedicineNew YorkUnited States
| | - Nicholas Stavropoulos
- Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of MedicineNew YorkUnited States
- Waksman Institute, Rutgers UniversityPiscatawayUnited States
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10
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Hamid R, Sant HS, Kulkarni MN. Choline Transporter regulates olfactory habituation via a neuronal triad of excitatory, inhibitory and mushroom body neurons. PLoS Genet 2021; 17:e1009938. [PMID: 34914708 PMCID: PMC8675691 DOI: 10.1371/journal.pgen.1009938] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 11/08/2021] [Indexed: 11/18/2022] Open
Abstract
Choline is an essential component of Acetylcholine (ACh) biosynthesis pathway which requires high-affinity Choline transporter (ChT) for its uptake into the presynaptic terminals of cholinergic neurons. Previously, we had reported a predominant expression of ChT in memory processing and storing region of the Drosophila brain called mushroom bodies (MBs). It is unknown how ChT contributes to the functional principles of MB operation. Here, we demonstrate the role of ChT in Habituation, a non-associative form of learning. Odour driven habituation traces are laid down in ChT dependent manner in antennal lobes (AL), projection neurons (PNs), and MBs. We observed that reduced habituation due to knock-down of ChT in MBs causes hypersensitivity towards odour, suggesting that ChT also regulates incoming stimulus suppression. Importantly, we show for the first time that ChT is not unique to cholinergic neurons but is also required in inhibitory GABAergic neurons to drive habituation behaviour. Our results support a model in which ChT regulates both habituation and incoming stimuli through multiple circuit loci via an interplay between excitatory and inhibitory neurons. Strikingly, the lack of ChT in MBs shows characteristics similar to the major reported features of Autism spectrum disorders (ASD), including attenuated habituation, sensory hypersensitivity as well as defective GABAergic signalling. Our data establish the role of ChT in habituation and suggest that its dysfunction may contribute to neuropsychiatric disorders like ASD.
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Affiliation(s)
- Runa Hamid
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research (CSIR-CCMB), Hyderabad, India
| | - Hitesh Sonaram Sant
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research (CSIR-CCMB), Hyderabad, India
| | - Mrunal Nagaraj Kulkarni
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research (CSIR-CCMB), Hyderabad, India
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11
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A Sexually Dimorphic Olfactory Neuron Mediates Fixed Action Transition during Courtship Ritual in Drosophila melanogaster. J Neurosci 2021; 41:9732-9741. [PMID: 34649953 DOI: 10.1523/jneurosci.1168-21.2021] [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: 06/04/2021] [Revised: 10/03/2021] [Accepted: 10/06/2021] [Indexed: 11/21/2022] Open
Abstract
Animals perform a series of actions in a fixed order during ritualistic innate behaviors. Although command neurons and sensory pathways responding to external stimuli that trigger these behaviors have been identified, how each action is induced in a fixed order in response to multimodal sensory stimuli remains unclear. Here, the sexually dimorphic lateral antennal lobe tract projection neuron 4 (lPN4) in male Drosophila melanogaster mediates the expression of a fixed behavioral action pattern at the beginning of the courtship ritual, in which a male taps a female body and then extends a wing unilaterally to produce a courtship song. We found that blocking the synaptic output of lPN4 caused an increase in the ratio of male flies that extended a wing unilaterally without tapping the female body, whereas excitation of lPN4 suppressed the transition from the tapping phase to the unilateral wing extension phase. Real-time calcium imaging showed that lPN4 is activated by a volatile pheromone, palmitoleic acid, whose responses were inhibited by simultaneous gustatory stimulation with female cuticular hydrocarbons, showing the existence of an "AND-gate" for multimodal sensory inputs during male courtship behaviors. These results suggest that the function of lPN4 is to suppress unilateral wing extension while responding to a female smell, which is released by appropriate contact chemosensory inputs received when tapping a female. As the female smell also promotes male courtship behaviors, the olfactory system is ready to simultaneously promote and suppress the progress of courtship actions while responding to a female smell.SIGNIFICANCE STATEMENT Although it has been 80 years since Konrad Lorenz and Niko Tinbergen introduced how multiple acts comprising separate innate behaviors are released in a fixed order according to external stimuli, the neural circuits responsible for such fixed action patterns remain largely unknown. The male courtship behavior of Drosophila melanogaster is a good model to investigate how such a fixed behavioral sequence is determined in the brain. Here, we show that lateral antennal lobe tract projection neuron 4 (lPN4) in D. melanogaster functions as an "AND-gate" for volatile and contact chemosensory inputs, mediating the expression of tapping behaviors before unilateral wing extension during male courtship rituals.
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12
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Huang QT, Sheng CW, Jones AK, Jiang J, Tang T, Han ZJ, Zhao CQ. Functional Characteristics of the Lepidopteran Ionotropic GABA Receptor 8916 Subunit Interacting with the LCCH3 or the RDL Subunit. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:11582-11591. [PMID: 34555899 DOI: 10.1021/acs.jafc.1c00385] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The ionotropic γ-aminobutyric acid (iGABA) receptor is commonly considered as a fast inhibitory channel and is an important insecticide target. Since 1990, RDL, LCCH3, and GRD have been successively isolated and found to be potential subunits of the insect iGABA receptor. More recently, one orphan gene named 8916 was found and considered to be another potential iGABA receptor subunit according to its amino acid sequence. However, little information about 8916 has been reported. Here, the 8916 subunit from Chilo suppressalis was studied to determine whether it can form part of a functional iGABA receptor by co-expressing this subunit with CsRDL1 or CsLCCH3 in the Xenopus oocyte system. Cs8916 or CsLCCH3 did not form functional ion channels when expressed alone. However, Cs8916 was able to form heteromeric ion channels when expressed with either CsLCCH3 or CsRDL1. The recombinant heteromeric Cs8916/LCCH3 channel was a cation-selective channel, which was sensitive to GABA or β-alanine. The current of the Cs8916/LCCH3 channel was inhibited by dieldrin, endosulfan, fipronil, or ethiprole. In contrast, fluralaner, broflanilide, and avermectin showed little effect on the Cs8916/LCCH3 channel (IC50s > 10 000 nM). The Cs8916/RDL1 channel was sensitive to GABA, but was significantly different in EC50 and Imax for GABA to those of homomeric CsRDL1. Fluralaner, fipronil, or dieldrin showed antagonistic actions on Cs8916/RDL1. In conclusion, Cs8916 is a potential iGABA receptor subunit, which can interact with CsLCCH3 to generate a cation-selective channel that is sensitive to several insecticides. Also, as Cs8916/RDL1 has a higher EC50 than homomeric CsRDL1, Cs8916 may affect the physiological functions of CsRDL1 and therefore play a role in fine-tuning GABAergic signaling.
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Affiliation(s)
- Qiu Tang Huang
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Cheng Wang Sheng
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Andrew K Jones
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, U.K
| | - Jie Jiang
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Tao Tang
- Institute of Plant Protection, Hunan Academy of Agricultural Sciences, Changsha 410125, P. R. China
| | - Zhao Jun Han
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Chun Qing Zhao
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
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13
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Massah A, Neupert S, Brodesser S, Homberg U, Stengl M. Distribution and daily oscillation of GABA in the circadian system of the cockroach Rhyparobia maderae. J Comp Neurol 2021; 530:770-791. [PMID: 34586642 DOI: 10.1002/cne.25244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 12/28/2022]
Abstract
Gamma-aminobutyric acid (GABA) is the prevalent inhibitory neurotransmitter in nervous systems promoting sleep in both mammals and insects. In the Madeira cockroach, sleep-wake cycles are controlled by a circadian clock network in the brain's optic lobes, centered in the accessory medulla (AME) with its innervating pigment-dispersing factor (PDF) expressing clock neurons at the anterior-ventral rim of the medulla. GABA is present in cell clusters that innervate different circuits of the cockroach's AME clock, without colocalizing in PDF clock neurons. Physiological, immunohistochemical, and behavioral assays provided evidence for a role of GABA in light entrainment, possibly via the distal tract that connects the AME's glomeruli to the medulla. Furthermore, GABA was implemented in clock outputs to multiple effector systems in optic lobe and midbrain. Here, GABAergic brain circuits were analyzed further, focusing on the circadian system in search for sleep/wake controlling brain circuits. All GABA-immunoreactive neurons of the cockroach brain were also stained with an antiserum against the GABA-synthesizing enzyme glutamic acid decarboxylase. We found strong overlap of the distribution of GABA-immunoreactive networks with PDF clock networks in optic lobes and midbrain. Neurons in five of the six soma groups that innervate the clock exhibited GABA immunoreactivity. The intensity of GABA immunoreactivity in the distal tract showed daily fluctuations with maximum staining intensity in the middle of the day and weakest staining at the end of the day. Quantification via enzyme-linked immunosorbent assay and quantitative liquid chromatography coupled to electrospray ionization tandem mass spectrometry, likewise, showed higher GABA levels in the optic lobe during the inactivity phase of the cockroach during the day and lower levels during its activity phase at dusk. Our data further support the hypothesis that light- and PDF-dependently the circadian clock network of the cockroach controls GABA levels and thereby promotes sleep during the day.
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Affiliation(s)
- Azar Massah
- Institute of Biology, Animal Physiology, University of Kassel, Kassel, Germany
| | - Susanne Neupert
- Institute of Biology, Animal Physiology, University of Kassel, Kassel, Germany
| | - Susanne Brodesser
- Cluster of Excellence Cellular Stress Responses in Aging-Associated Diseases (CECAD), Faculty of Medicine and University Hospital of Cologne, University of Cologne, Cologne, Germany
| | - Uwe Homberg
- Department of Biology, Animal Physiology, Philipps-Universität Marburg, Marburg, Germany.,Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus Liebig University Giessen, Marburg, Germany
| | - Monika Stengl
- Institute of Biology, Animal Physiology, University of Kassel, Kassel, Germany
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14
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Trebels B, Dippel S, Goetz B, Graebner M, Hofmann C, Hofmann F, Schmid FR, Uhl M, Vuong MP, Weber V, Schachtner J. Metamorphic development of the olfactory system in the red flour beetle (Tribolium castaneum, HERBST). BMC Biol 2021; 19:155. [PMID: 34330268 PMCID: PMC8323255 DOI: 10.1186/s12915-021-01055-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 05/25/2021] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Insects depend on their olfactory sense as a vital system. Olfactory cues are processed by a rather complex system and translated into various types of behavior. In holometabolous insects like the red flour beetle Tribolium castaneum, the nervous system typically undergoes considerable remodeling during metamorphosis. This process includes the integration of new neurons, as well as remodeling and elimination of larval neurons. RESULTS We find that the sensory neurons of the larval antennae are reused in the adult antennae. Further, the larval antennal lobe gets transformed into its adult version. The beetle's larval antennal lobe is already glomerularly structured, but its glomeruli dissolve in the last larval stage. However, the axons of the olfactory sensory neurons remain within the antennal lobe volume. The glomeruli of the adult antennal lobe then form from mid-metamorphosis independently of the presence of a functional OR/Orco complex but mature dependent on the latter during a postmetamorphic phase. CONCLUSIONS We provide insights into the metamorphic development of the red flour beetle's olfactory system and compared it to data on Drosophila melanogaster, Manduca sexta, and Apis mellifera. The comparison revealed that some aspects, such as the formation of the antennal lobe's adult glomeruli at mid-metamorphosis, are common, while others like the development of sensory appendages or the role of Orco seemingly differ.
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Affiliation(s)
- Björn Trebels
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Stefan Dippel
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Brigitte Goetz
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Maria Graebner
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Carolin Hofmann
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Florian Hofmann
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Freya-Rebecca Schmid
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Mara Uhl
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Minh-Phung Vuong
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Vanessa Weber
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Joachim Schachtner
- Department of Biology, Animal Physiology, Philipps-University Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
- Clausthal University of Technology, Adolph-Roemer-Str. 2a, 38678 Clausthal-Zellerfeld, Germany
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15
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Schlegel P, Bates AS, Stürner T, Jagannathan SR, Drummond N, Hsu J, Serratosa Capdevila L, Javier A, Marin EC, Barth-Maron A, Tamimi IFM, Li F, Rubin GM, Plaza SM, Costa M, Jefferis GSXE. Information flow, cell types and stereotypy in a full olfactory connectome. eLife 2021; 10:e66018. [PMID: 34032214 PMCID: PMC8298098 DOI: 10.7554/elife.66018] [Citation(s) in RCA: 69] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 05/24/2021] [Indexed: 12/19/2022] Open
Abstract
The hemibrain connectome provides large-scale connectivity and morphology information for the majority of the central brain of Drosophila melanogaster. Using this data set, we provide a complete description of the Drosophila olfactory system, covering all first, second and lateral horn-associated third-order neurons. We develop a generally applicable strategy to extract information flow and layered organisation from connectome graphs, mapping olfactory input to descending interneurons. This identifies a range of motifs including highly lateralised circuits in the antennal lobe and patterns of convergence downstream of the mushroom body and lateral horn. Leveraging a second data set we provide a first quantitative assessment of inter- versus intra-individual stereotypy. Comparing neurons across two brains (three hemispheres) reveals striking similarity in neuronal morphology across brains. Connectivity correlates with morphology and neurons of the same morphological type show similar connection variability within the same brain as across two brains.
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Affiliation(s)
- Philipp Schlegel
- Neurobiology Division, MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | | | - Tomke Stürner
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | | | - Nikolas Drummond
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Joseph Hsu
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Alexandre Javier
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Elizabeth C Marin
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Asa Barth-Maron
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Imaan FM Tamimi
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Feng Li
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Gerald M Rubin
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Stephen M Plaza
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Marta Costa
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Gregory S X E Jefferis
- Neurobiology Division, MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
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16
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Scaplen KM, Petruccelli E. Receptors and Channels Associated with Alcohol Use: Contributions from Drosophila. Neurosci Insights 2021; 16:26331055211007441. [PMID: 33870197 PMCID: PMC8020223 DOI: 10.1177/26331055211007441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 03/03/2021] [Indexed: 12/14/2022] Open
Abstract
Alcohol Use Disorder (AUD) is a debilitating disorder that manifests as problematic patterns of alcohol use. At the core of AUD's behavioral manifestations are the profound structural, physiological, cellular, and molecular effects of alcohol on the brain. While the field has made considerable progress in understanding the neuromolecular targets of alcohol we still lack a comprehensive understanding of alcohol's actions and effective treatment strategies. Drosophila melanogaster is a powerful model for investigating the neuromolecular targets of alcohol because flies model many of the core behavioral elements of AUD and offer a rich genetic toolkit to precisely reveal the in vivo molecular actions of alcohol. In this review, we focus on receptors and channels that are often targeted by alcohol within the brain. We discuss the general roles of these proteins, their role in alcohol-associated behaviors across species, and propose ways in which Drosophila models can help advance the field.
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Affiliation(s)
- Kristin M Scaplen
- Department of Psychology, Bryant University, Smithfield, RI, USA
- Center for Health and Behavioral Studies, Bryant University, Smithfield, RI, USA
- Department of Neuroscience, Brown University, Providence, RI, USA
| | - Emily Petruccelli
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL, USA
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17
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Neuron-Specific FMRP Roles in Experience-Dependent Remodeling of Olfactory Brain Innervation during an Early-Life Critical Period. J Neurosci 2021; 41:1218-1241. [PMID: 33402421 DOI: 10.1523/jneurosci.2167-20.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 12/04/2020] [Accepted: 12/08/2020] [Indexed: 01/12/2023] Open
Abstract
Critical periods are developmental windows during which neural circuits effectively adapt to the new sensory environment. Animal models of fragile X syndrome (FXS), a common monogenic autism spectrum disorder (ASD), exhibit profound impairments of sensory experience-driven critical periods. However, it is not known whether the causative fragile X mental retardation protein (FMRP) acts uniformly across neurons, or instead manifests neuron-specific functions. Here, we use the genetically-tractable Drosophila brain antennal lobe (AL) olfactory circuit of both sexes to investigate neuron-specific FMRP roles in the odorant experience-dependent remodeling of the olfactory sensory neuron (OSN) innervation during an early-life critical period. We find targeted OSN class-specific FMRP RNAi impairs innervation remodeling within AL synaptic glomeruli, whereas global dfmr1 null mutants display relatively normal odorant-driven refinement. We find both OSN cell autonomous and cell non-autonomous FMRP functions mediate odorant experience-dependent remodeling, with AL circuit FMRP imbalance causing defects in overall glomerulus innervation refinement. We find OSN class-specific FMRP levels bidirectionally regulate critical period remodeling, with odorant experience selectively controlling OSN synaptic terminals in AL glomeruli. We find OSN class-specific FMRP loss impairs critical period remodeling by disrupting responses to lateral modulation from other odorant-responsive OSNs mediating overall AL gain control. We find that silencing glutamatergic AL interneurons reduces OSN remodeling, while conversely, interfering with the OSN class-specific GABAA signaling enhances remodeling. These findings reveal control of OSN synaptic remodeling by FMRP with neuron-specific circuit functions, and indicate how neural circuitry can compensate for global FMRP loss to reinstate normal critical period brain circuit remodeling.SIGNIFICANCE STATEMENT Fragile X syndrome (FXS), the leading monogenic cause of intellectual disability and autism spectrum disorder (ASD), manifests severe neurodevelopmental delays. Likewise, FXS disease models display disrupted neurodevelopmental critical periods. In the well-mapped Drosophila olfactory circuit model, perturbing the causative fragile X mental retardation protein (FMRP) within a single olfactory sensory neuron (OSN) class impairs odorant-dependent remodeling during an early-life critical period. Importantly, this impairment requires activation of other OSNs, and the olfactory circuit can compensate when FMRP is removed from all OSNs. Understanding the neuron-specific FMRP requirements within a developing neural circuit, as well as the FMRP loss compensation mechanisms, should help us engineer FXS treatments. This work suggests FXS treatments could use homeostatic mechanisms to alleviate circuit-level deficits.
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18
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Chvilicek MM, Titos I, Rothenfluh A. The Neurotransmitters Involved in Drosophila Alcohol-Induced Behaviors. Front Behav Neurosci 2020; 14:607700. [PMID: 33384590 PMCID: PMC7770116 DOI: 10.3389/fnbeh.2020.607700] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 11/23/2020] [Indexed: 12/18/2022] Open
Abstract
Alcohol is a widely used and abused substance with numerous negative consequences for human health and safety. Historically, alcohol's widespread, non-specific neurobiological effects have made it a challenge to study in humans. Therefore, model organisms are a critical tool for unraveling the mechanisms of alcohol action and subsequent effects on behavior. Drosophila melanogaster is genetically tractable and displays a vast behavioral repertoire, making it a particularly good candidate for examining the neurobiology of alcohol responses. In addition to being experimentally amenable, Drosophila have high face and mechanistic validity: their alcohol-related behaviors are remarkably consistent with humans and other mammalian species, and they share numerous conserved neurotransmitters and signaling pathways. Flies have a long history in alcohol research, which has been enhanced in recent years by the development of tools that allow for manipulating individual Drosophila neurotransmitters. Through advancements such as the GAL4/UAS system and CRISPR/Cas9 mutagenesis, investigation of specific neurotransmitters in small subsets of neurons has become ever more achievable. In this review, we describe recent progress in understanding the contribution of seven neurotransmitters to fly behavior, focusing on their roles in alcohol response: dopamine, octopamine, tyramine, serotonin, glutamate, GABA, and acetylcholine. We chose these small-molecule neurotransmitters due to their conservation in mammals and their importance for behavior. While neurotransmitters like dopamine and octopamine have received significant research emphasis regarding their contributions to behavior, others, like glutamate, GABA, and acetylcholine, remain relatively unexplored. Here, we summarize recent genetic and behavioral findings concerning these seven neurotransmitters and their roles in the behavioral response to alcohol, highlighting the fitness of the fly as a model for human alcohol use.
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Affiliation(s)
- Maggie M. Chvilicek
- Department of Psychiatry, University of Utah, Salt Lake City, UT, United States
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, United States
- Neuroscience Graduate Program, University of Utah, Salt Lake City, UT, United States
| | - Iris Titos
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, United States
| | - Adrian Rothenfluh
- Department of Psychiatry, University of Utah, Salt Lake City, UT, United States
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, United States
- Neuroscience Graduate Program, University of Utah, Salt Lake City, UT, United States
- Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT, United States
- Department of Human Genetics, University of Utah, Salt Lake City, UT, United States
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19
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Muscarinic Modulation of Antennal Lobe GABAergic Local Neurons Shapes Odor Coding and Behavior. Cell Rep 2020; 29:3253-3265.e4. [PMID: 31801087 PMCID: PMC6900217 DOI: 10.1016/j.celrep.2019.10.125] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 09/18/2019] [Accepted: 10/29/2019] [Indexed: 11/21/2022] Open
Abstract
In the antennal lobe (AL), the first olfactory relay of Drosophila, excitatory neurons are predominantly cholinergic. Ionotropic nicotinic receptors play a vital role in the effects of acetylcholine in the AL. However, the AL also has a high expression level of metabotropic muscarinic acetylcholine receptors type A (mAChRs-A). Nevertheless, the neurons expressing them and their role in the AL are unknown. Elucidating their function may reveal principles in olfactory modulation. Here, we show that mAChRs-A shape AL output and affect behavior. We localized mAChRs-A effects to a sub-population of GABAergic local neurons (iLNs), where they play a dual role: direct excitation of iLNs and stabilization of the synapse between receptor neurons and iLNs, which undergoes strong short-term depression. Our results reveal modulatory functions of the AL main excitatory neurotransmitter. Striking similarities to the mammalian olfactory system predict that mammalian glutamatergic metabotropic receptors could be associated with similar modulations.
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20
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Bates AS, Schlegel P, Roberts RJV, Drummond N, Tamimi IFM, Turnbull R, Zhao X, Marin EC, Popovici PD, Dhawan S, Jamasb A, Javier A, Serratosa Capdevila L, Li F, Rubin GM, Waddell S, Bock DD, Costa M, Jefferis GSXE. Complete Connectomic Reconstruction of Olfactory Projection Neurons in the Fly Brain. Curr Biol 2020; 30:3183-3199.e6. [PMID: 32619485 PMCID: PMC7443706 DOI: 10.1016/j.cub.2020.06.042] [Citation(s) in RCA: 96] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 05/07/2020] [Accepted: 06/12/2020] [Indexed: 12/21/2022]
Abstract
Nervous systems contain sensory neurons, local neurons, projection neurons, and motor neurons. To understand how these building blocks form whole circuits, we must distil these broad classes into neuronal cell types and describe their network connectivity. Using an electron micrograph dataset for an entire Drosophila melanogaster brain, we reconstruct the first complete inventory of olfactory projections connecting the antennal lobe, the insect analog of the mammalian olfactory bulb, to higher-order brain regions in an adult animal brain. We then connect this inventory to extant data in the literature, providing synaptic-resolution "holotypes" both for heavily investigated and previously unknown cell types. Projection neurons are approximately twice as numerous as reported by light level studies; cell types are stereotyped, but not identical, in cell and synapse numbers between brain hemispheres. The lateral horn, the insect analog of the mammalian cortical amygdala, is the main target for this olfactory information and has been shown to guide innate behavior. Here, we find new connectivity motifs, including axo-axonic connectivity between projection neurons, feedback, and lateral inhibition of these axons by a large population of neurons, and the convergence of different inputs, including non-olfactory inputs and memory-related feedback onto third-order olfactory neurons. These features are less prominent in the mushroom body calyx, the insect analog of the mammalian piriform cortex and a center for associative memory. Our work provides a complete neuroanatomical platform for future studies of the adult Drosophila olfactory system.
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Affiliation(s)
- Alexander S Bates
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Philipp Schlegel
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK; Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | | | - Nikolas Drummond
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Imaan F M Tamimi
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Robert Turnbull
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Xincheng Zhao
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK; Department of Entomology, College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China
| | - Elizabeth C Marin
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Patricia D Popovici
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Serene Dhawan
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Arian Jamasb
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Alexandre Javier
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | | | - Feng Li
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Gerald M Rubin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Scott Waddell
- Centre for Neural Circuits and Behaviour, The University of Oxford, Oxford OX1 3SR, UK
| | - Davi D Bock
- Department of Neurological Sciences, Larner College of Medicine, University of Vermont, VT 05405, USA
| | - Marta Costa
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Gregory S X E Jefferis
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK; Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
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21
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Henry C, Cens T, Charnet P, Cohen-Solal C, Collet C, van-Dijk J, Guiramand J, de Jésus-Ferreira MC, Menard C, Mokrane N, Roussel J, Thibault JB, Vignes M, Rousset M. Heterogeneous expression of GABA receptor-like subunits LCCH3 and GRD reveals functional diversity of GABA receptors in the honeybee Apis mellifera. Br J Pharmacol 2020; 177:3924-3940. [PMID: 32436264 DOI: 10.1111/bph.15135] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 04/24/2020] [Accepted: 05/09/2020] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND AND PURPOSE Despite a growing awareness, annual losses of honeybee colonies worldwide continue to reach threatening levels for food safety and global biodiversity. Among the biotic and abiotic stresses probably responsible for these losses, pesticides, including those targeting ionotropic GABA receptors, are one of the major drivers. Most insect genomes include the ionotropic GABA receptor subunit gene, Rdl, and two GABA-like receptor subunit genes, Lcch3 and Grd. Most studies have focused on Rdl which forms homomeric GABA-gated chloride channels, and a complete analysis of all possible molecular combinations of GABA receptors is still lacking. EXPERIMENTAL APPROACH We cloned the Rdl, Grd, and Lcch3 genes of Apis mellifera and systematically characterized the resulting GABA receptors expressed in Xenopus oocytes, using electrophysiological assays, fluorescence microscopy and co-immunoprecipitation techniques. KEY RESULTS The cloned subunits interacted with each other, forming GABA-gated heteromeric channels with particular properties. Strikingly, these heteromers were always more sensitive than AmRDL homomer to all the pharmacological agents tested. In particular, when expressed together, Grd and Lcch3 form a non-selective cationic channel that opens at low concentrations of GABA and with sensitivity to insecticides similar to that of homomeric Rdl channels. CONCLUSION AND IMPLICATIONS For off-target species like the honeybee, chronic sublethal exposure to insecticides constitutes a major threat. At these concentration ranges, homomeric RDL receptors may not be the most pertinent target to study and other ionotropic GABA receptor subtypes should be considered in order to understand more fully the molecular mechanisms of sublethal toxicity to insecticides.
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Affiliation(s)
| | - Thierry Cens
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Pierre Charnet
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Claude Collet
- UR 406 Abeilles et Environnement, INRAE, Avignon Cedex 9, France
| | | | | | | | - Claudine Menard
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Nawfel Mokrane
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Julien Roussel
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Michel Vignes
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Matthieu Rousset
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
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22
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Chen HM, Yao X, Ren Q, Chang CC, Liu LY, Miyares RL, Lee T. Enhanced Golic+: highly effective CRISPR gene targeting and transgene HACKing in Drosophila. Development 2020; 147:dev181974. [PMID: 32467238 DOI: 10.1242/dev.181974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 05/04/2020] [Indexed: 11/20/2022]
Abstract
Gene targeting is an incredibly valuable technique. Sometimes, however, it can also be extremely challenging for various intrinsic reasons (e.g. low target accessibility or nature/extent of gene modification). To bypass these barriers, we designed a transgene-based system in Drosophila that increases the number of independent gene targeting events while at the same time enriching for correctly targeted progeny. Unfortunately, with particularly challenging gene targeting experiments, our original design yielded numerous false positives. Here, we deliver a much-improved technique, named Enhanced Golic+ (E-Golic+). E-Golic+ incorporates genetic modifications to tighten lethality-based selection while simultaneously boosting efficiency. With E-Golic+, we easily achieve previously unattainable gene targeting. Additionally, we built an E-Golic+-based, high-efficiency genetic pipeline for transgene swapping. We demonstrate its utility by transforming GAL4 enhancer-trap lines into tissue-specific Cas9-expressing lines. Given the superior efficiency, specificity and scalability, E-Golic+ promises to expedite development of additional sophisticated genetic/genomic tools in Drosophila.
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Affiliation(s)
- Hui-Min Chen
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Xiaohao Yao
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Qingzhong Ren
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Chuan-Chie Chang
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Ling-Yu Liu
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Rosa Linda Miyares
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
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23
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Abstract
Habituation is a form of simple memory that suppresses neural activity in response to repeated, neutral stimuli. This process is critical in helping organisms guide attention toward the most salient and novel features in the environment. Here, we follow known circuit mechanisms in the fruit fly olfactory system to derive a simple algorithm for habituation. We show, both empirically and analytically, that this algorithm is able to filter out redundant information, enhance discrimination between odors that share a similar background, and improve detection of novel components in odor mixtures. Overall, we propose an algorithmic perspective on the biological mechanism of habituation and use this perspective to understand how sensory physiology can affect odor perception. Our framework may also help toward understanding the effects of habituation in other more sophisticated neural systems.
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24
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Short term depression, presynaptic inhibition and local neuron diversity play key functional roles in the insect antennal lobe. J Comput Neurosci 2020; 48:213-227. [PMID: 32388764 DOI: 10.1007/s10827-020-00747-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 03/13/2020] [Accepted: 04/17/2020] [Indexed: 10/24/2022]
Abstract
As the oldest, but least understood sensory system in evolution, the olfactory system represents one of the most challenging research targets in sensory neurobiology. Although a large number of computational models of the olfactory system have been proposed, they do not account for the diversity in physiology, connectivity of local neurons, and several recent discoveries in the insect antennal lobe, a major olfactory organ in insects. Recent studies revealed that the response of some projection neurons were reduced by application of a GABA antagonist, and that insects are sensitive to odor pulse frequency. To account for these observations, we propose a spiking neural circuit model of the insect antennal lobe. Based on recent anatomical and physiological studies, we included three sub-types of local neurons as well as synaptic short-term depression (STD) in the model and showed that the interaction between STD and local neurons resulted in frequency-sensitive responses. We further discovered that the unexpected response of the projection neurons to the GABA antagonist is the result of complex interactions between STD and presynaptic inhibition, which is required for enhancing sensitivity to odor stimuli. Finally, we found that odor discrimination is improved if the innervation of the local neurons in the glomeruli follows a specific pattern. Our findings suggest that STD, presynaptic inhibition and diverse physiology and connectivity of local neurons are not independent properties, but they interact to play key roles in the function of antennal lobes.
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25
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Liu G, Wu Y, Gao Y, Ju X, Ozoe Y. Potential of Competitive Antagonists of Insect Ionotropic γ-Aminobutyric Acid Receptors as Insecticides. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:4760-4768. [PMID: 32243147 DOI: 10.1021/acs.jafc.9b08189] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Ionotropic γ-aminobutyric acid (GABA) receptors (GABARs) represent an important insecticide target. Currently used GABAR-targeting insecticides are non-competitive antagonists (NCAs) of these receptors. Recent studies have demonstrated that competitive antagonists (CAs) of GABARs have functions of inhibiting insect GABARs similar to NCAs and that they also exhibit insecticidal activity. CAs have different binding sites and different mechanisms of action compared to those of NCAs. Therefore, GABAR CAs should have the potential to be developed into novel insecticides, which could be used to overcome the developed resistance of insect pests to conventional NCA insecticides. Although research on insect GABAR CAs has lagged behind that on mammalian GABAR CAs, research on the CAs of insect ionotropic GABARs has made great progress in recent years, and several series of heterocyclic compounds, such as 3-isoxazolols and 6-iminopyridazines, have been identified as insect GABAR CAs. In this review, we briefly summarize the design strategies, structures, and biological activities of the novel GABAR CAs that have been found in the past decade. Updated information about GABAR CAs may benefit the design and development of novel GABAR-targeting insecticides.
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Affiliation(s)
- Genyan Liu
- Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan, Hubei 430205, People's Republic of China
| | - Yun Wu
- Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan, Hubei 430205, People's Republic of China
| | - Ya Gao
- Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan, Hubei 430205, People's Republic of China
| | - Xiulian Ju
- Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan, Hubei 430205, People's Republic of China
| | - Yoshihisa Ozoe
- Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane 690-8504, Japan
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26
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Kim JH, Ki Y, Lee H, Hur MS, Baik B, Hur JH, Nam D, Lim C. The voltage-gated potassium channel Shaker promotes sleep via thermosensitive GABA transmission. Commun Biol 2020; 3:174. [PMID: 32296133 PMCID: PMC7160125 DOI: 10.1038/s42003-020-0902-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 03/20/2020] [Indexed: 02/07/2023] Open
Abstract
Genes and neural circuits coordinately regulate animal sleep. However, it remains elusive how these endogenous factors shape sleep upon environmental changes. Here, we demonstrate that Shaker (Sh)-expressing GABAergic neurons projecting onto dorsal fan-shaped body (dFSB) regulate temperature-adaptive sleep behaviors in Drosophila. Loss of Sh function suppressed sleep at low temperature whereas light and high temperature cooperatively gated Sh effects on sleep. Sh depletion in GABAergic neurons partially phenocopied Sh mutants. Furthermore, the ionotropic GABA receptor, Resistant to dieldrin (Rdl), in dFSB neurons acted downstream of Sh and antagonized its sleep-promoting effects. In fact, Rdl inhibited the intracellular cAMP signaling of constitutively active dopaminergic synapses onto dFSB at low temperature. High temperature silenced GABAergic synapses onto dFSB, thereby potentiating the wake-promoting dopamine transmission. We propose that temperature-dependent switching between these two synaptic transmission modalities may adaptively tune the neural property of dFSB neurons to temperature shifts and reorganize sleep architecture for animal fitness. Ji-hyung Kim and Yoonhee Ki et al. show that low temperatures suppress sleep in Drosophila by increasing GABA transmission in Shaker-expressing GABAergic neurons projecting onto the dorsal fan-shaped body, while high temperatures potentiate dopamine-induced arousal by reducing GABA transmission. This study highlights a role for Shaker in sleep modulation via a temperature-dependent switch in GABA signaling.
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Affiliation(s)
- Ji-Hyung Kim
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Yoonhee Ki
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Hoyeon Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Moon Seong Hur
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Bukyung Baik
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Jin-Hoe Hur
- UNIST Optical Biomed Imaging Center, UNIST, Ulsan, 44919, Republic of Korea
| | - Dougu Nam
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Chunghun Lim
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea.
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27
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Stanhope BA, Jaggard JB, Gratton M, Brown EB, Keene AC. Sleep Regulates Glial Plasticity and Expression of the Engulfment Receptor Draper Following Neural Injury. Curr Biol 2020; 30:1092-1101.e3. [PMID: 32142708 DOI: 10.1016/j.cub.2020.02.057] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 12/09/2019] [Accepted: 02/20/2020] [Indexed: 12/27/2022]
Abstract
Chronic sleep disturbance is associated with numerous health consequences, including neurodegenerative disease and cognitive decline [1]. Neurite damage due to apoptosis, trauma, or genetic factors is a common feature of aging, and clearance of damaged neurons is essential for maintenance of brain function. In the central nervous system, damaged neurites are cleared by Wallerian degeneration, in which activated microglia and macrophages engulf damaged neurons [2]. The fruit fly Drosophila melanogaster provides a powerful model for investigating the relationship between sleep and Wallerian degeneration [3]. Several lines of evidence suggest that glia influence sleep duration, sleep-mediated neuronal homeostasis, and clearance of toxic substances during sleep, raising the possibility that glial engulfment of damaged axons is regulated by sleep [4]. To explore this possibility, we axotomized olfactory receptor neurons and measured the effects of sleep loss or gain on the clearance of damaged neurites. Mechanical and genetic sleep deprivation impaired the clearance of damaged neurites. Conversely, treatment with the sleep-promoting drug gaboxadol accelerated clearance, while genetic induction of sleep promotes Draper expression. In sleep-deprived animals, multiple markers of glial activation were delayed, including activation of the JAK-STAT pathway, upregulation of the cell corpse engulfment receptor Draper, and innervation of the antennal lobe by glial membranes. These markers were all enhanced following genetic and pharmacological sleep induction. Taken together, these findings reveal a critical association between sleep and glial activation following neural injury, providing a platform for further investigations of the molecular mechanisms underlying sleep-dependent modulation of glial function and neurite clearance.
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Affiliation(s)
- Bethany A Stanhope
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL 33458
| | - James B Jaggard
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL 33458
| | - Melanie Gratton
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL 33458
| | - Elizabeth B Brown
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL 33458
| | - Alex C Keene
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL 33458.
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28
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Evolutionarily conserved anatomical and physiological properties of olfactory pathway through fourth-order neurons in a species of grasshopper (Hieroglyphus banian). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:813-838. [DOI: 10.1007/s00359-019-01369-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 08/08/2019] [Accepted: 09/04/2019] [Indexed: 01/18/2023]
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29
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Frechter S, Bates AS, Tootoonian S, Dolan MJ, Manton J, Jamasb AR, Kohl J, Bock D, Jefferis G. Functional and anatomical specificity in a higher olfactory centre. eLife 2019; 8:44590. [PMID: 31112127 PMCID: PMC6550879 DOI: 10.7554/elife.44590] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 04/12/2019] [Indexed: 12/16/2022] Open
Abstract
Most sensory systems are organized into parallel neuronal pathways that process distinct aspects of incoming stimuli. In the insect olfactory system, second order projection neurons target both the mushroom body, required for learning, and the lateral horn (LH), proposed to mediate innate olfactory behavior. Mushroom body neurons form a sparse olfactory population code, which is not stereotyped across animals. In contrast, odor coding in the LH remains poorly understood. We combine genetic driver lines, anatomical and functional criteria to show that the Drosophila LH has ~1400 neurons and >165 cell types. Genetically labeled LHNs have stereotyped odor responses across animals and on average respond to three times more odors than single projection neurons. LHNs are better odor categorizers than projection neurons, likely due to stereotyped pooling of related inputs. Our results reveal some of the principles by which a higher processing area can extract innate behavioral significance from sensory stimuli.
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Affiliation(s)
- Shahar Frechter
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Sina Tootoonian
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.,Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.,Neurophysiology of Behaviour Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Michael-John Dolan
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.,Janelia Research Campus, Howard Hughes Medical Institute, Chevy Chase, United States
| | - James Manton
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Johannes Kohl
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Davi Bock
- Janelia Research Campus, Howard Hughes Medical Institute, Chevy Chase, United States
| | - Gregory Jefferis
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.,Department of Zoology, University of Cambridge, Cambridge, United Kingdom
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30
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Yang CJ, Tsai KT, Liou NF, Chou YH. Interneuron Diversity: Toward a Better Understanding of Interneuron Development In the Olfactory System. J Exp Neurosci 2019; 13:1179069519826056. [PMID: 31001062 PMCID: PMC6454656 DOI: 10.1177/1179069519826056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 01/03/2019] [Indexed: 11/25/2022] Open
Abstract
The Drosophila olfactory system is an attractive model for
exploring the wiring logic of complex neural circuits. Remarkably, olfactory
local interneurons exhibit high diversity and variability in their morphologies
and intrinsic properties. Although olfactory sensory and projection neurons have
been extensively studied of development and wiring; the development, mechanisms
for establishing diversity, and integration of olfactory local interneurons into
the developing circuit remain largely undescribed. In this review, we discuss
some challenges and recent advances in the study of Drosophila
olfactory interneurons.
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Affiliation(s)
| | | | | | - Ya-Hui Chou
- Ya-Hui Chou, Institute of Cellular and
Organismic Biology, Academia Sinica, 128, Section 2, Academia Road, Nankang,
Taipei, Taiwan.
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31
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Golovin RM, Vest J, Vita DJ, Broadie K. Activity-Dependent Remodeling of Drosophila Olfactory Sensory Neuron Brain Innervation during an Early-Life Critical Period. J Neurosci 2019; 39:2995-3012. [PMID: 30755492 PMCID: PMC6468095 DOI: 10.1523/jneurosci.2223-18.2019] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 01/07/2019] [Accepted: 02/03/2019] [Indexed: 12/12/2022] Open
Abstract
Critical periods are windows of development when the environment has a pronounced effect on brain circuitry. Models of neurodevelopmental disorders, including autism spectrum disorders, intellectual disabilities, and schizophrenia, are linked to disruption of critical period remodeling. Critical periods open with the onset of sensory experience; however, it remains unclear exactly how sensory input modifies brain circuits. Here, we examine olfactory sensory neuron (OSN) innervation of the Drosophila antennal lobe of both sexes as a genetic model of this question. We find that olfactory sensory experience during an early-use critical period drives loss of OSN innervation of antennal lobe glomeruli and subsequent axon retraction in a dose-dependent mechanism. This remodeling does not result from olfactory receptor loss or OSN degeneration, but rather from rapid synapse elimination and axon pruning in the target olfactory glomerulus. Removal of the odorant stimulus only during the critical period leads to OSN reinnervation, demonstrating that remodeling is transiently reversible. We find that this synaptic refinement requires the OSN-specific olfactory receptor and downstream activity. Conversely, blocking OSN synaptic output elevates glomeruli remodeling. We find that GABAergic neurotransmission has no detectable role, but that glutamatergic signaling via NMDA receptors is required for OSN synaptic refinement. Together, these results demonstrate that OSN inputs into the brain manifest robust, experience-dependent remodeling during an early-life critical period, which requires olfactory reception, OSN activity, and NMDA receptor signaling. This work reveals a pathway linking initial olfactory sensory experience to glutamatergic neurotransmission in the activity-dependent remodeling of brain neural circuitry in an early-use critical period.SIGNIFICANCE STATEMENT Neurodevelopmental disorders manifest symptoms at specific developmental milestones that suggest an intersection between early sensory experience and brain neural circuit remodeling. One classic example is Fragile X syndrome caused by loss of an RNA-binding translation regulator of activity-dependent synaptic refinement. As a model, Drosophila olfactory circuitry is well characterized, genetically tractable, and rapidly developing, and thus ideally suited to probe underlying mechanisms. Here, we find olfactory sensory neurons are dramatically remodeled by heightened sensory experience during an early-life critical period. We demonstrate removing the olfactory stimulus during the critical period can reverse the connectivity changes. We find that this remodeling requires neural activity and NMDA receptor-mediated glutamatergic transmission. This improved understanding may help us design treatments for neurodevelopmental disorders.
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Affiliation(s)
| | | | | | - Kendal Broadie
- Vanderbilt Brain Institute,
- Department of Biological Sciences, and
- Department of Cell and Developmental Biology, Vanderbilt University and Medical Center, Nashville, Tennessee 37235
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32
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Groschner LN, Miesenböck G. Mechanisms of Sensory Discrimination: Insights from Drosophila Olfaction. Annu Rev Biophys 2019; 48:209-229. [PMID: 30786228 DOI: 10.1146/annurev-biophys-052118-115655] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
All an animal can do to infer the state of its environment is to observe the sensory-evoked activity of its own neurons. These inferences about the presence, quality, or similarity of objects are probabilistic and inform behavioral decisions that are often made in close to real time. Neural systems employ several strategies to facilitate sensory discrimination: Biophysical mechanisms separate the neuronal response distributions in coding space, compress their variances, and combine information from sequential observations. We review how these strategies are implemented in the olfactory system of the fruit fly. The emerging principles of odor discrimination likely apply to other neural circuits of similar architecture.
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Affiliation(s)
- Lukas N Groschner
- Centre for Neural Circuits and Behavior, University of Oxford, Oxford OX1 3SR, United Kingdom;
| | - Gero Miesenböck
- Centre for Neural Circuits and Behavior, University of Oxford, Oxford OX1 3SR, United Kingdom;
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33
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Brown EB, Rayens E, Rollmann SM. The Gene CG6767 Affects Olfactory Behavior in Drosophila melanogaster. Behav Genet 2019; 49:317-326. [PMID: 30710192 DOI: 10.1007/s10519-019-09949-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 01/21/2019] [Indexed: 01/09/2023]
Abstract
Chemosensory systems mediate some of the most vital animal behaviors. However, our knowledge of the genetic mechanisms that underlie behavioral responses to olfactory cues remains fragmented. Genome-wide association mapping has greatly advanced our ability to identify candidate loci associated with variation in olfactory behavior, but functional validation of these candidates remain a necessary next step in understanding the mechanisms by which these genes influence chemoreception. In previous genome-wide association analyses, a genomic region that spans multiple polymorphic loci on the left arm of the third chromosome was found to be significantly associated with variation in olfactory behavioral responses to the odorant 2,3-butanedione, a volatile compound present in fermenting fruit. In this study, behavioral analysis of flies possessing either the major or minor haplotype for this region confirmed the association between polymorphisms in the region and variation in olfactory behavior. Moreover, functional dissection of the genes within this region using P-element insertional mutagenesis together with targeted RNAi experiments revealed that the gene CG6767, a gene of previously unknown function but predicted to encode an enzyme responsible for the synthesis and metabolism of nucleic acids, affects olfactory behavioral responses to 2,3-butanedione. Specifically, RNAi mediated knockdown of CG6767 expression in different neuroanatomical populations of the olfactory system suggests that this gene functions in local interneurons of the antennal lobe. These results reveal a new role for CG6767 and its importance in olfactory behavior.
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Affiliation(s)
- Elizabeth B Brown
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, 45221-0006, USA
| | - Emily Rayens
- Department of Biology, Wittenberg University, Springfield, OH, 45501, USA
| | - Stephanie M Rollmann
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, 45221-0006, USA.
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34
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Semelidou O, Acevedo SF, Skoulakis EM. Temporally specific engagement of distinct neuronal circuits regulating olfactory habituation in Drosophila. eLife 2018; 7:39569. [PMID: 30576281 PMCID: PMC6303106 DOI: 10.7554/elife.39569] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 11/29/2018] [Indexed: 11/13/2022] Open
Abstract
Habituation is the process that enables salience filtering, precipitating perceptual changes that alter the value of environmental stimuli. To discern the neuronal circuits underlying habituation to brief inconsequential stimuli, we developed a novel olfactory habituation paradigm, identifying two distinct phases of the response that engage distinct neuronal circuits. Responsiveness to the continuous odor stimulus is maintained initially, a phase we term habituation latency and requires Rutabaga Adenylyl-Cyclase-depended neurotransmission from GABAergic Antennal Lobe Interneurons and activation of excitatory Projection Neurons (PNs) and the Mushroom Bodies. In contrast, habituation depends on the inhibitory PNs of the middle Antenno-Cerebral Track, requires inner Antenno-Cerebral Track PN activation and defines a temporally distinct phase. Collectively, our data support the involvement of Lateral Horn excitatory and inhibitory stimulation in habituation. These results provide essential cellular substrates for future analyses of the molecular mechanisms that govern the duration and transition between these distinct temporal habituation phases. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Ourania Semelidou
- Division of Neuroscience, Biomedical Sciences Research Centre "Alexander Fleming", Vari, Greece.,School of Medicine, University of Crete, Heraklion, Greece
| | - Summer F Acevedo
- Division of Neuroscience, Biomedical Sciences Research Centre "Alexander Fleming", Vari, Greece
| | - Efthimios Mc Skoulakis
- Division of Neuroscience, Biomedical Sciences Research Centre "Alexander Fleming", Vari, Greece
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35
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Horne JA, Langille C, McLin S, Wiederman M, Lu Z, Xu CS, Plaza SM, Scheffer LK, Hess HF, Meinertzhagen IA. A resource for the Drosophila antennal lobe provided by the connectome of glomerulus VA1v. eLife 2018; 7:e37550. [PMID: 30382940 PMCID: PMC6234030 DOI: 10.7554/elife.37550] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 10/31/2018] [Indexed: 02/06/2023] Open
Abstract
Using FIB-SEM we report the entire synaptic connectome of glomerulus VA1v of the right antennal lobe in Drosophila melanogaster. Within the glomerulus we densely reconstructed all neurons, including hitherto elusive local interneurons. The fruitless-positive, sexually dimorphic VA1v included >11,140 presynaptic sites with ~38,050 postsynaptic dendrites. These connected input olfactory receptor neurons (ORNs, 51 ipsilateral, 56 contralateral), output projection neurons (18 PNs), and local interneurons (56 of >150 previously reported LNs). ORNs are predominantly presynaptic and PNs predominantly postsynaptic; newly reported LN circuits are largely an equal mixture and confer extensive synaptic reciprocity, except the newly reported LN2V with input from ORNs and outputs mostly to monoglomerular PNs, however. PNs were more numerous than previously reported from genetic screens, suggesting that the latter failed to reach saturation. We report a matrix of 192 bodies each having >50 connections; these form 88% of the glomerulus' pre/postsynaptic sites.
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Affiliation(s)
- Jane Anne Horne
- Department of Psychology and NeuroscienceLife Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Carlie Langille
- Department of Psychology and NeuroscienceLife Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Sari McLin
- Department of Psychology and NeuroscienceLife Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Meagan Wiederman
- Department of Psychology and NeuroscienceLife Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Zhiyuan Lu
- Department of Psychology and NeuroscienceLife Sciences Centre, Dalhousie UniversityHalifaxCanada
- Janelia Research Campus, Howard Hughes Medical InstituteVirginiaUnited States
| | - C Shan Xu
- Janelia Research Campus, Howard Hughes Medical InstituteVirginiaUnited States
| | - Stephen M Plaza
- Janelia Research Campus, Howard Hughes Medical InstituteVirginiaUnited States
| | - Louis K Scheffer
- Janelia Research Campus, Howard Hughes Medical InstituteVirginiaUnited States
| | - Harald F Hess
- Janelia Research Campus, Howard Hughes Medical InstituteVirginiaUnited States
| | - Ian A Meinertzhagen
- Department of Psychology and NeuroscienceLife Sciences Centre, Dalhousie UniversityHalifaxCanada
- Janelia Research Campus, Howard Hughes Medical InstituteVirginiaUnited States
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36
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Tsai KT, Hu CK, Li KW, Hwang WL, Chou YH. Circuit variability interacts with excitatory-inhibitory diversity of interneurons to regulate network encoding capacity. Sci Rep 2018; 8:8027. [PMID: 29795277 PMCID: PMC5966413 DOI: 10.1038/s41598-018-26286-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 05/09/2018] [Indexed: 01/15/2023] Open
Abstract
Local interneurons (LNs) in the Drosophila olfactory system exhibit neuronal diversity and variability, yet it is still unknown how these features impact information encoding capacity and reliability in a complex LN network. We employed two strategies to construct a diverse excitatory-inhibitory neural network beginning with a ring network structure and then introduced distinct types of inhibitory interneurons and circuit variability to the simulated network. The continuity of activity within the node ensemble (oscillation pattern) was used as a readout to describe the temporal dynamics of network activity. We found that inhibitory interneurons enhance the encoding capacity by protecting the network from extremely short activation periods when the network wiring complexity is very high. In addition, distinct types of interneurons have differential effects on encoding capacity and reliability. Circuit variability may enhance the encoding reliability, with or without compromising encoding capacity. Therefore, we have described how circuit variability of interneurons may interact with excitatory-inhibitory diversity to enhance the encoding capacity and distinguishability of neural networks. In this work, we evaluate the effects of different types and degrees of connection diversity on a ring model, which may simulate interneuron networks in the Drosophila olfactory system or other biological systems.
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Affiliation(s)
- Kuo-Ting Tsai
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan.,Institute of Physics, Academia Sinica, Taipei, Taiwan
| | - Chin-Kun Hu
- Institute of Physics, Academia Sinica, Taipei, Taiwan.,Neuroscience Program of Academia Sinica, Academia Sinica, Taipei, Taiwan.,National Center for Theoretical Sciences, National Tsing Hua University, Hsinchu, Taiwan.,Business School, University of Shanghai for Science and Technology, Shanghai, China
| | - Kuan-Wei Li
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Wen-Liang Hwang
- Neuroscience Program of Academia Sinica, Academia Sinica, Taipei, Taiwan.,Institute of Information Science, Academia Sinica, Taipei, Taiwan
| | - Ya-Hui Chou
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan. .,Neuroscience Program of Academia Sinica, Academia Sinica, Taipei, Taiwan.
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37
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Ly S, Pack AI, Naidoo N. The neurobiological basis of sleep: Insights from Drosophila. Neurosci Biobehav Rev 2018; 87:67-86. [PMID: 29391183 PMCID: PMC5845852 DOI: 10.1016/j.neubiorev.2018.01.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/22/2018] [Accepted: 01/24/2018] [Indexed: 12/12/2022]
Abstract
Sleep is a biological enigma that has raised numerous questions about the inner workings of the brain. The fundamental question of why our nervous systems have evolved to require sleep remains a topic of ongoing scientific deliberation. This question is largely being addressed by research using animal models of sleep. Drosophila melanogaster, also known as the common fruit fly, exhibits a sleep state that shares common features with many other species. Drosophila sleep studies have unearthed an immense wealth of knowledge about the neuroscience of sleep. Given the breadth of findings published on Drosophila sleep, it is important to consider how all of this information might come together to generate a more holistic understanding of sleep. This review provides a comprehensive summary of the neurobiology of Drosophila sleep and explores the broader insights and implications of how sleep is regulated across species and why it is necessary for the brain.
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Affiliation(s)
- Sarah Ly
- Center for Sleep and Circadian Neurobiology, 125 South 31st St., Philadelphia, PA, 19104-3403, United States.
| | - Allan I Pack
- Center for Sleep and Circadian Neurobiology, 125 South 31st St., Philadelphia, PA, 19104-3403, United States; Division of Sleep Medicine/Department of Medicine, University of Pennsylvania Perelman School of Medicine, 125 South 31st St., Philadelphia, PA, 19104-3403, United States
| | - Nirinjini Naidoo
- Center for Sleep and Circadian Neurobiology, 125 South 31st St., Philadelphia, PA, 19104-3403, United States; Division of Sleep Medicine/Department of Medicine, University of Pennsylvania Perelman School of Medicine, 125 South 31st St., Philadelphia, PA, 19104-3403, United States.
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38
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Li X, Ishimoto H, Kamikouchi A. Auditory experience controls the maturation of song discrimination and sexual response in Drosophila. eLife 2018; 7:e34348. [PMID: 29555017 PMCID: PMC5860867 DOI: 10.7554/elife.34348] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 02/19/2018] [Indexed: 11/13/2022] Open
Abstract
In birds and higher mammals, auditory experience during development is critical to discriminate sound patterns in adulthood. However, the neural and molecular nature of this acquired ability remains elusive. In fruit flies, acoustic perception has been thought to be innate. Here we report, surprisingly, that auditory experience of a species-specific courtship song in developing Drosophila shapes adult song perception and resultant sexual behavior. Preferences in the song-response behaviors of both males and females were tuned by social acoustic exposure during development. We examined the molecular and cellular determinants of this social acoustic learning and found that GABA signaling acting on the GABAA receptor Rdl in the pC1 neurons, the integration node for courtship stimuli, regulated auditory tuning and sexual behavior. These findings demonstrate that maturation of auditory perception in flies is unexpectedly plastic and is acquired socially, providing a model to investigate how song learning regulates mating preference in insects.
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Affiliation(s)
- Xiaodong Li
- Graduate School of ScienceNagoya UniversityNagoyaJapan
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39
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Tsubouchi A, Yano T, Yokoyama TK, Murtin C, Otsuna H, Ito K. Topological and modality-specific representation of somatosensory information in the fly brain. Science 2018; 358:615-623. [PMID: 29097543 DOI: 10.1126/science.aan4428] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 09/25/2017] [Indexed: 12/11/2022]
Abstract
Insects and mammals share similarities of neural organization underlying the perception of odors, taste, vision, sound, and gravity. We observed that insect somatosensation also corresponds to that of mammals. In Drosophila, the projections of all the somatosensory neuron types to the insect's equivalent of the spinal cord segregated into modality-specific layers comparable to those in mammals. Some sensory neurons innervate the ventral brain directly to form modality-specific and topological somatosensory maps. Ascending interneurons with dendrites in matching layers of the nerve cord send axons that converge to respective brain regions. Pathways arising from leg somatosensory neurons encode distinct qualities of leg movement information and play different roles in ground detection. Establishment of the ground pattern and genetic tools for neuronal manipulation should provide the basis for elucidating the mechanisms underlying somatosensation.
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Affiliation(s)
- Asako Tsubouchi
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, 113-0032 Tokyo, Japan
| | - Tomoko Yano
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, 113-0032 Tokyo, Japan.,Department of Computational Biology, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, 277-0882 Chiba, Japan
| | - Takeshi K Yokoyama
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, 113-0032 Tokyo, Japan
| | - Chloé Murtin
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, 113-0032 Tokyo, Japan.,Department of Computational Biology, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, 277-0882 Chiba, Japan
| | - Hideo Otsuna
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Kei Ito
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, 113-0032 Tokyo, Japan. .,Department of Computational Biology, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, 277-0882 Chiba, Japan.,Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA.,Institute of Zoology, University of Cologne, 50674 Cologne, Germany
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40
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Huang TH, Niesman P, Arasu D, Lee D, De La Cruz AL, Callejas A, Hong EJ, Lois C. Tracing neuronal circuits in transgenic animals by transneuronal control of transcription ( TRACT). eLife 2017; 6:32027. [PMID: 29231171 PMCID: PMC5777821 DOI: 10.7554/elife.32027] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 12/02/2017] [Indexed: 12/20/2022] Open
Abstract
Understanding the computations that take place in brain circuits requires identifying how neurons in those circuits are connected to one another. We describe a technique called TRACT (TRAnsneuronal Control of Transcription) based on ligand-induced intramembrane proteolysis to reveal monosynaptic connections arising from genetically labeled neurons of interest. In this strategy, neurons expressing an artificial ligand (‘donor’ neurons) bind to and activate a genetically-engineered artificial receptor on their synaptic partners (‘receiver’ neurons). Upon ligand-receptor binding at synapses the receptor is cleaved in its transmembrane domain and releases a protein fragment that activates transcription in the synaptic partners. Using TRACT in Drosophila we have confirmed the connectivity between olfactory receptor neurons and their postsynaptic targets, and have discovered potential new connections between neurons in the circadian circuit. Our results demonstrate that the TRACT method can be used to investigate the connectivity of neuronal circuits in the brain. One of the main obstacles to understanding how the brain works is that we know relatively little about how its nerve cells or neurons are connected to one another. These connections make up the brain’s wiring diagram. Current methods for revealing this wiring all have limitations. The most popular method – serial electron microscopy – can reveal the connections in a small region of the brain in great detail, but it cannot show connections between neurons that are far apart. Huang et al. have now created a genetic system for visualizing these connections. For neurons to communicate, one neuron must produce a signal called a ligand. This ligand can then bind to and activate its partner neuron. Huang et al. modified the DNA of neurons so that every time those cells produced a specific ligand, they also produced a red fluorescent protein. Similar modifications ensured that every time the ligand activated a partner neuron, the activated neuron produced a green fluorescent protein. Viewing the red and green neurons under a microscope enabled Huang et al. to see which cells were communicating with which others. While these experiments took place in fruit flies, the same approach should also work in other laboratory animals, including fish, mice and rats. Once we know the wiring diagram of the brain, the next step is to investigate the role of the various connections. To understand how a computer works, for example, we might change the connections between its circuit components and look at how this affects the computer’s output. With this new method, we can change how neurons communicate with one another in the brain, and then look at the effects on behavior. This should provide insights into the workings of the human brain, and clues to what goes wrong in disorders like schizophrenia and autism.
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Affiliation(s)
- Ting-Hao Huang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Peter Niesman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Deepshika Arasu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Donghyung Lee
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Aubrie L De La Cruz
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Antuca Callejas
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States.,Department of Cell Biology, School of Science, University of Extremadura, Badajoz, Spain
| | - Elizabeth J Hong
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Carlos Lois
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
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Strube-Bloss MF, Grabe V, Hansson BS, Sachse S. Calcium imaging revealed no modulatory effect on odor-evoked responses of the Drosophila antennal lobe by two populations of inhibitory local interneurons. Sci Rep 2017; 7:7854. [PMID: 28798324 PMCID: PMC5552818 DOI: 10.1038/s41598-017-08090-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/06/2017] [Indexed: 12/26/2022] Open
Abstract
Although we have considerable knowledge about how odors are represented in the antennal lobe (AL), the insects’ analogue to the olfactory bulb, we still do not fully understand how the different neurons in the AL network contribute to the olfactory code. In Drosophila melanogaster we can selectively manipulate specific neuronal populations to elucidate their function in odor processing. Here we silenced the synaptic transmission of two distinct subpopulations of multiglomerular GABAergic local interneurons (LN1 and LN2) using shibire (shits) and analyzed their impact on odor-induced glomerular activity at the AL input and output level. We verified that the employed shits construct effectively blocked synaptic transmission to the AL when expressed in olfactory sensory neurons. Notably, selective silencing of both LN populations did not significantly affect the odor-evoked activity patterns in the AL. Neither the glomerular input nor the glomerular output activity was modulated in comparison to the parental controls. We therefore conclude that these LN subpopulations, which cover one third of the total LN number, are not predominantly involved in odor identity coding per se. As suggested by their broad innervation patterns and contribution to long-term adaptation, they might contribute to AL–computation on a global and longer time scale.
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Affiliation(s)
- Martin F Strube-Bloss
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knöll-Straße 8, 07745, Jena, Germany.,Department of Behavioral Physiology & Sociobiology, Theodor-Boveri-Institute of Bioscience, Biocenter University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Veit Grabe
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knöll-Straße 8, 07745, Jena, Germany
| | - Bill S Hansson
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knöll-Straße 8, 07745, Jena, Germany
| | - Silke Sachse
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knöll-Straße 8, 07745, Jena, Germany.
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42
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Shimizu K, Stopfer M. A Population of Projection Neurons that Inhibits the Lateral Horn but Excites the Antennal Lobe through Chemical Synapses in Drosophila. Front Neural Circuits 2017; 11:30. [PMID: 28515683 PMCID: PMC5413558 DOI: 10.3389/fncir.2017.00030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 04/10/2017] [Indexed: 11/15/2022] Open
Abstract
In the insect olfactory system, odor information is transferred from the antennal lobe (AL) to higher brain areas by projection neurons (PNs) in multiple AL tracts (ALTs). In several species, one of the ALTs, the mediolateral ALT (mlALT), contains some GABAergic PNs; in the Drosophila brain, the great majority of ventral PNs (vPNs) are GABAergic and project through this tract to the lateral horn (LH). Most excitatory PNs (ePNs), project through the medial ALT (mALT) to the mushroom body (MB) and the LH. Recent studies have shown that GABAergic vPNs play inhibitory roles at their axon terminals in the LH. However, little is known about the properties and functions of vPNs at their dendritic branches in the AL. Here, we used optogenetic and patch clamp techniques to investigate the functional roles of vPNs in the AL. Surprisingly, our results show that specific activation of vPNs reliably elicits strong excitatory postsynaptic potentials (EPSPs) in ePNs. Moreover, the connections between vPNs and ePNs are mediated by direct chemical synapses. Neither pulses of GABA, nor pharmagological, or genetic blockade of GABAergic transmission gave results consistent with the involvement of GABA in vPN-ePN excitatory transmission. These unexpected results suggest new roles for the vPN population in olfactory information processing.
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Affiliation(s)
- Kazumichi Shimizu
- National Institute of Child Health and Human Development, National Institutes of HealthBethesda, MD, USA
| | - Mark Stopfer
- National Institute of Child Health and Human Development, National Institutes of HealthBethesda, MD, USA
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43
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Minocha S, Boll W, Noll M. Crucial roles of Pox neuro in the developing ellipsoid body and antennal lobes of the Drosophila brain. PLoS One 2017; 12:e0176002. [PMID: 28441464 PMCID: PMC5404782 DOI: 10.1371/journal.pone.0176002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 04/04/2017] [Indexed: 01/18/2023] Open
Abstract
The paired box gene Pox neuro (Poxn) is expressed in two bilaterally symmetric neuronal clusters of the developing adult Drosophila brain, a protocerebral dorsal cluster (DC) and a deutocerebral ventral cluster (VC). We show that all cells that express Poxn in the developing brain are postmitotic neurons. During embryogenesis, the DC and VC consist of only 20 and 12 neurons that express Poxn, designated embryonic Poxn-neurons. The number of Poxn-neurons increases only during the third larval instar, when the DC and VC increase dramatically to about 242 and 109 Poxn-neurons, respectively, virtually all of which survive to the adult stage, while no new Poxn-neurons are added during metamorphosis. Although the vast majority of Poxn-neurons express Poxn only during third instar, about half of them are born by the end of embryogenesis, as demonstrated by the absence of BrdU incorporation during larval stages. At late third instar, embryonic Poxn-neurons, which begin to express Poxn during embryogenesis, can be easily distinguished from embryonic-born and larval-born Poxn-neurons, which begin to express Poxn only during third instar, (i) by the absence of Pros, (ii) their overt differentiation of axons and neurites, and (iii) the strikingly larger diameter of their cell bodies still apparent in the adult brain. The embryonic Poxn-neurons are primary neurons that lay out the pioneering tracts for the secondary Poxn-neurons, which differentiate projections and axons that follow those of the primary neurons during metamorphosis. The DC and the VC participate only in two neuropils of the adult brain. The DC forms most, if not all, of the neurons that connect the bulb (lateral triangle) with the ellipsoid body, a prominent neuropil of the central complex, while the VC forms most of the ventral projection neurons of the antennal lobe, which connect it ipsilaterally to the lateral horn, bypassing the mushroom bodies. In addition, Poxn-neurons of the VC are ventral local interneurons of the antennal lobe. In the absence of Poxn protein in the developing brain, embryonic Poxn-neurons stall their projections and cannot find their proper target neuropils, the bulb and ellipsoid body in the case of the DC, or the antennal lobe and lateral horn in the case of the VC, whereby the absence of the ellipsoid body neuropil is particularly striking. Poxn is thus crucial for pathfinding both in the DC and VC. Additional implications of our results are discussed.
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Affiliation(s)
- Shilpi Minocha
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
| | - Werner Boll
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
| | - Markus Noll
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- * E-mail:
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44
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Schultzhaus JN, Saleem S, Iftikhar H, Carney GE. The role of the Drosophila lateral horn in olfactory information processing and behavioral response. JOURNAL OF INSECT PHYSIOLOGY 2017; 98:29-37. [PMID: 27871975 DOI: 10.1016/j.jinsphys.2016.11.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 11/16/2016] [Accepted: 11/17/2016] [Indexed: 06/06/2023]
Abstract
Animals must rapidly and accurately process environmental information to produce the correct behavioral responses. Reactions to previously encountered as well as to novel but biologically important stimuli are equally important, and one understudied region in the insect brain plays a role in processing both types of stimuli. The lateral horn is a higher order processing center that mainly processes olfactory information and is linked via olfactory projection neurons to another higher order learning center, the mushroom body. This review focuses on the lateral horn of Drosophila where most functional studies have been performed. We discuss connectivity between the primary olfactory center, the antennal lobe, and the lateral horn and mushroom body. We also present evidence for the lateral horn playing roles in innate behavioral responses by encoding biological valence to novel odor cues and in learned responses to previously encountered odors by modulating neural activity within the mushroom body. We describe how these processes contribute to acceptance or avoidance of appropriate or inappropriate mates and food, as well as the identification of predators. The lateral horn is a sexually dimorphic and plastic region of the brain that modulates other regions of the brain to ensure that insects produce rapid and effective behavioral responses to both novel and learned stimuli, yet multiple gaps exist in our knowledge of this important center. We anticipate that future studies on olfactory processing, learning, and innate behavioral responses will include the lateral horn in their examinations, leading to a more comprehensive understanding of olfactory information relay and resulting behaviors.
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Affiliation(s)
- Janna N Schultzhaus
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258, United States
| | - Sehresh Saleem
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258, United States
| | - Hina Iftikhar
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258, United States
| | - Ginger E Carney
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258, United States.
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45
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Franco LM, Okray Z, Linneweber GA, Hassan BA, Yaksi E. Reduced Lateral Inhibition Impairs Olfactory Computations and Behaviors in a Drosophila Model of Fragile X Syndrome. Curr Biol 2017; 27:1111-1123. [PMID: 28366741 PMCID: PMC5405172 DOI: 10.1016/j.cub.2017.02.065] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 02/02/2017] [Accepted: 02/28/2017] [Indexed: 01/02/2023]
Abstract
Fragile X syndrome (FXS) patients present neuronal alterations that lead to severe intellectual disability, but the underlying neuronal circuit mechanisms are poorly understood. An emerging hypothesis postulates that reduced GABAergic inhibition of excitatory neurons is a key component in the pathophysiology of FXS. Here, we directly test this idea in a FXS Drosophila model. We show that FXS flies exhibit strongly impaired olfactory behaviors. In line with this, olfactory representations are less odor specific due to broader response tuning of excitatory projection neurons. We find that impaired inhibitory interactions underlie reduced specificity in olfactory computations. Finally, we show that defective lateral inhibition across projection neurons is caused by weaker inhibition from GABAergic interneurons. We provide direct evidence that deficient inhibition impairs sensory computations and behavior in an in vivo model of FXS. Together with evidence of impaired inhibition in autism and Rett syndrome, these findings suggest a potentially general mechanism for intellectual disability. Lack of dFMRP leads to reduced olfactory attraction and aversion in fruit flies Odor selectivity of antennal lobe projection neurons is impaired in dfmr1− flies GABAergic lateral inhibition within the antennal lobe is weaker in dfmr1− flies Deficient lateral inhibition impairs sensory computations and animal behavior
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Affiliation(s)
- Luis M Franco
- Neuroelectronics Research Flanders (NERF), KU Leuven, Kapeldreef 75, 3001 Leuven, Belgium; VIB Center for the Biology of Disease, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Center for Human Genetics, KU Leuven, Herestraat 49, 3000 Leuven, Belgium
| | - Zeynep Okray
- VIB Center for the Biology of Disease, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Center for Human Genetics, KU Leuven, Herestraat 49, 3000 Leuven, Belgium
| | - Gerit A Linneweber
- VIB Center for the Biology of Disease, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Center for Human Genetics, KU Leuven, Herestraat 49, 3000 Leuven, Belgium
| | - Bassem A Hassan
- VIB Center for the Biology of Disease, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Center for Human Genetics, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Institut du Cerveau et de la Moelle Epinière (ICM) - Hôpital Pitié-Salpêtrière, UPMC, Sorbonne Universités, Inserm, CNRS, 47 Boulevard Hôpital, 75013 Paris, France.
| | - Emre Yaksi
- Neuroelectronics Research Flanders (NERF), KU Leuven, Kapeldreef 75, 3001 Leuven, Belgium; Kavli Institute for Systems Neuroscience and Centre for Neural Computation, NTNU, Olav Kyrres gate 9, 7030 Trondheim, Norway.
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46
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Kollmann M, Schmidt R, Heuer CM, Schachtner J. Variations on a Theme: Antennal Lobe Architecture across Coleoptera. PLoS One 2016; 11:e0166253. [PMID: 27973569 PMCID: PMC5156346 DOI: 10.1371/journal.pone.0166253] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 10/25/2016] [Indexed: 12/02/2022] Open
Abstract
Beetles comprise about 400,000 described species, nearly one third of all known animal species. The enormous success of the order Coleoptera is reflected by a rich diversity of lifestyles, behaviors, morphological, and physiological adaptions. All these evolutionary adaptions that have been driven by a variety of parameters over the last about 300 million years, make the Coleoptera an ideal field to study the evolution of the brain on the interface between the basic bauplan of the insect brain and the adaptions that occurred. In the current study we concentrated on the paired antennal lobes (AL), the part of the brain that is typically responsible for the first processing of olfactory information collected from olfactory sensilla on antenna and mouthparts. We analyzed 63 beetle species from 22 different families and thus provide an extensive comparison of principal neuroarchitecture of the AL. On the examined anatomical level, we found a broad diversity including AL containing a wide range of glomeruli numbers reaching from 50 to 150 glomeruli and several species with numerous small glomeruli, resembling the microglomerular design described in acridid grasshoppers and diving beetles, and substructures within the glomeruli that have to date only been described for the small hive beetle, Aethina tumida. A first comparison of the various anatomical features of the AL with available descriptions of lifestyle and behaviors did so far not reveal useful correlations. In summary, the current study provides a solid basis for further studies to unravel mechanisms that are basic to evolutionary adaptions of the insect olfactory system.
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Affiliation(s)
- Martin Kollmann
- Department of Biology—Animal Physiology, Philipps-University Marburg, Marburg, Germany
| | - Rovenna Schmidt
- Department of Biology—Animal Physiology, Philipps-University Marburg, Marburg, Germany
- Institute of Veterinary Anatomy, Histology and Embryology, Justus-Liebig University Gießen, Gießen, Germany
| | - Carsten M. Heuer
- Department of Biology—Animal Physiology, Philipps-University Marburg, Marburg, Germany
- Fraunhofer-Institut für Naturwissenschaftlich-Technische Trendanalysen INT, Euskirchen, Germany
| | - Joachim Schachtner
- Department of Biology—Animal Physiology, Philipps-University Marburg, Marburg, Germany
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47
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Sizemore TR, Dacks AM. Serotonergic Modulation Differentially Targets Distinct Network Elements within the Antennal Lobe of Drosophila melanogaster. Sci Rep 2016; 6:37119. [PMID: 27845422 PMCID: PMC5109230 DOI: 10.1038/srep37119] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/25/2016] [Indexed: 01/10/2023] Open
Abstract
Neuromodulation confers flexibility to anatomically-restricted neural networks so that animals are able to properly respond to complex internal and external demands. However, determining the mechanisms underlying neuromodulation is challenging without knowledge of the functional class and spatial organization of neurons that express individual neuromodulatory receptors. Here, we describe the number and functional identities of neurons in the antennal lobe of Drosophila melanogaster that express each of the receptors for one such neuromodulator, serotonin (5-HT). Although 5-HT enhances odor-evoked responses of antennal lobe projection neurons (PNs) and local interneurons (LNs), the receptor basis for this enhancement is unknown. We used endogenous reporters of transcription and translation for each of the five 5-HT receptors (5-HTRs) to identify neurons, based on cell class and transmitter content, that express each receptor. We find that specific receptor types are expressed by distinct combinations of functional neuronal classes. For instance, the excitatory PNs express the excitatory 5-HTRs, while distinct classes of LNs each express different 5-HTRs. This study therefore provides a detailed atlas of 5-HT receptor expression within a well-characterized neural network, and enables future dissection of the role of serotonergic modulation of olfactory processing.
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Affiliation(s)
- Tyler R Sizemore
- Department of Biology, West Virginia University, Morgantown, WV, 26505, United States of America
| | - Andrew M Dacks
- Department of Biology, West Virginia University, Morgantown, WV, 26505, United States of America
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48
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Ian E, Zhao XC, Lande A, Berg BG. Individual Neurons Confined to Distinct Antennal-Lobe Tracts in the Heliothine Moth: Morphological Characteristics and Global Projection Patterns. Front Neuroanat 2016; 10:101. [PMID: 27822181 PMCID: PMC5075568 DOI: 10.3389/fnana.2016.00101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 10/05/2016] [Indexed: 11/13/2022] Open
Abstract
To explore fundamental principles characterizing chemosensory information processing, we have identified antennal-lobe projection neurons in the heliothine moth, including several neuron types not previously described. Generally, odor information is conveyed from the primary olfactory center of the moth brain, the antennal lobe, to higher brain centers via projection neuron axons passing along several parallel pathways, of which the medial, mediolateral, and lateral antennal-lobe tract are considered the classical ones. Recent data have revealed the projections of the individual tracts more in detail demonstrating three main target regions in the protocerebrum; the calyces are innervated mainly by the medial tract, the superior intermediate protocerebrum by the lateral tract exclusively, and the lateral horn by all tracts. In the present study, we have identified, via iontophoretic intracellular staining combined with confocal microscopy, individual projection neurons confined to the tracts mentioned above, plus two additional ones. Further, using the visualization software AMIRA, we reconstructed the stained neurons and registered the models into a standard brain atlas, which allowed us to compare the termination areas of individual projection neurons both across and within distinct tracts. The data demonstrate a morphological diversity of the projection neurons within distinct tracts. Comparison of the output areas of the neurons confined to the three main tracts in the lateral horn showed overlapping terminal regions for the medial and mediolateral tracts; the lateral tract neurons, on the contrary, targeted mostly other output areas in the protocerebrum.
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Affiliation(s)
- Elena Ian
- Department of Psychology, Norwegian University of Science and Technology Trondheim, Norway
| | - Xin C Zhao
- Department of Entomology, College of Plant Protection, Henan Agricultural University Zhengzhou, China
| | - Andreas Lande
- Department of Psychology, Norwegian University of Science and Technology Trondheim, Norway
| | - Bente G Berg
- Department of Psychology, Norwegian University of Science and Technology Trondheim, Norway
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Mechanisms Underlying Population Response Dynamics in Inhibitory Interneurons of the Drosophila Antennal Lobe. J Neurosci 2016; 36:4325-38. [PMID: 27076428 DOI: 10.1523/jneurosci.3887-15.2016] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 02/02/2016] [Indexed: 01/19/2023] Open
Abstract
UNLABELLED Local inhibitory neurons control the timing of neural activity in many circuits. To understand how inhibition controls timing, it is important to understand the dynamics of activity in populations of local inhibitory interneurons, as well as the mechanisms that underlie these dynamics. Here we describe the in vivo response dynamics of a large population of inhibitory local neurons (LNs) in the Drosophila melanogaster antennal lobe, the analog of the vertebrate olfactory bulb, and we dissect the network and intrinsic mechanisms that give rise to these dynamics. Some LNs respond to odor onsets ("ON" cells) and others to offsets ("OFF" cells), whereas still others respond at both times. Moreover, different LNs signal odor concentration fluctuations on different timescales. Some respond rapidly, and can track rapid concentration fluctuations. Others respond slowly, and are best at tracking slow fluctuations. We found a continuous spectrum of preferred stimulation timescales among LNs, as well as a continuum of ON-OFF behavior. Using in vivo whole-cell recordings, we show that the timing of an LN's response (ON vs OFF) can be predicted from the interplay of excitatory and inhibitory synaptic currents that it receives. Meanwhile, the preferred timescale of an LN is related to its intrinsic properties. These results illustrate how a population of inhibitory interneurons can collectively encode bidirectional changes in stimulus intensity on multiple timescales, and how this can arise via an interaction between synaptic and intrinsic mechanisms. SIGNIFICANCE STATEMENT Most neural circuits contain diverse populations of inhibitory interneurons. The way inhibition shapes network activity will depend on the spiking dynamics of the interneuron population. Here we describe the dynamics of activity in a large population of inhibitory interneurons in the first brain relay of the fruit fly olfactory system. Because odor plumes fluctuate on multiple timescales, the drive to this circuit can vary over a range of frequencies. We show how synaptic and cellular mechanisms interact to recruit different interneurons at different times, and in response to different temporal features of odor stimuli. As a result, inhibition is recruited over a range of conditions, and there is the potential to tune the timing of inhibition as the environment changes.
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Schürmann FW. Fine structure of synaptic sites and circuits in mushroom bodies of insect brains. ARTHROPOD STRUCTURE & DEVELOPMENT 2016; 45:399-421. [PMID: 27555065 DOI: 10.1016/j.asd.2016.08.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 07/01/2016] [Accepted: 08/05/2016] [Indexed: 06/06/2023]
Abstract
In the insect brain, mushroom bodies represent a prominent central neuropil for multisensory integration and, crucially, for learning and memory. For this reason, special attention has been focused on its small chemical synapses. Early studies on synaptic types and their distribution, using conventional electron microscopy, and recent publications have resolved basic features of synaptic circuits. More recent studies, using experimental methods for resolving neurons, such as immunocytochemistry, genetic labelling, high resolution confocal microscopy and more advanced electron microscopy, have revealed many new details about the fine structure and molecular contents of identifiable neurons of mushroom bodies and has led to more refined modelling of functional organisation. Synaptic circuitries have been described in most detail for the calyces. In contrast, the mushroom bodies' columnar peduncle and lobes have been explored to a lesser degree. In dissecting local microcircuits, the scientist is confronted with complex neuronal compartmentalisation and specific synaptic arrangements. This article reviews classical and modern studies on the fine structure of synapses and their networks in mushroom bodies across several insect species.
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Affiliation(s)
- Friedrich-Wilhelm Schürmann
- Johann-Friedrich-Blumenbach Institut für Zoologie und Anthropologie, Georg-August-University Göttingen, Berlinerstrasse 28, D-37073 Göttingen, Germany.
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