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Troup M, Tainton-Heap LAL, van Swinderen B. Neural Ensemble Fragmentation in the Anesthetized Drosophila Brain. J Neurosci 2023; 43:2537-2551. [PMID: 36868857 PMCID: PMC10082453 DOI: 10.1523/jneurosci.1657-22.2023] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 02/15/2023] [Accepted: 02/22/2023] [Indexed: 03/05/2023] Open
Abstract
General anesthetics cause a profound loss of behavioral responsiveness in all animals. In mammals, general anesthesia is induced in part by the potentiation of endogenous sleep-promoting circuits, although "deep" anesthesia is understood to be more similar to coma (Brown et al., 2011). Surgically relevant concentrations of anesthetics, such as isoflurane and propofol, have been shown to impair neural connectivity across the mammalian brain (Mashour and Hudetz, 2017; Yang et al., 2021), which presents one explanation why animals become largely unresponsive when exposed to these drugs. It remains unclear whether general anesthetics affect brain dynamics similarly in all animal brains, or whether simpler animals, such as insects, even display levels of neural connectivity that could be disrupted by these drugs. Here, we used whole-brain calcium imaging in behaving female Drosophila flies to investigate whether isoflurane anesthesia induction activates sleep-promoting neurons, and then inquired how all other neurons across the fly brain behave under sustained anesthesia. We were able to track the activity of hundreds of neurons simultaneously during waking and anesthetized states, for spontaneous conditions as well as in response to visual and mechanical stimuli. We compared whole-brain dynamics and connectivity under isoflurane exposure to optogenetically induced sleep. Neurons in the Drosophila brain remain active during general anesthesia as well as induced sleep, although flies become behaviorally inert under both treatments. We identified surprisingly dynamic neural correlation patterns in the waking fly brain, suggesting ensemble-like behavior. These become more fragmented and less diverse under anesthesia but remain wake-like during induced sleep.SIGNIFICANCE STATEMENT When humans are rendered immobile and unresponsive by sleep or general anesthetics, their brains do not shut off - they just change how they operate. We tracked the activity of hundreds of neurons simultaneously in the brains of fruit flies that were anesthetized by isoflurane or genetically put to sleep, to investigate whether these behaviorally inert states shared similar brain dynamics. We uncovered dynamic patterns of neural activity in the waking fly brain, with stimulus-responsive neurons constantly changing through time. Wake-like neural dynamics persisted during induced sleep but became more fragmented under isoflurane anesthesia. This suggests that, like larger brains, the fly brain might also display ensemble-like behavior, which becomes degraded rather than silenced under general anesthesia.
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Affiliation(s)
- Michael Troup
- Queensland Brain Institute, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Lucy A L Tainton-Heap
- Queensland Brain Institute, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Bruno van Swinderen
- Queensland Brain Institute, The University of Queensland, St. Lucia, Queensland 4072, Australia
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Zuniga G, Levy S, Ramirez P, Mange JD, Gonzalez E, Gamez M, Frost B. Tau-induced deficits in nonsense-mediated mRNA decay contribute to neurodegeneration. Alzheimers Dement 2023; 19:405-420. [PMID: 35416419 PMCID: PMC9673995 DOI: 10.1002/alz.12653] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 01/26/2022] [Accepted: 02/17/2022] [Indexed: 12/12/2022]
Abstract
INTRODUCTION While brains of patients with Alzheimer's disease and related tauopathies have evidence of altered RNA processing, we lack a mechanistic understanding of how altered RNA processing arises in these disorders and if such changes are causally linked to neurodegeneration. METHODS Using Drosophila melanogaster models of tauopathy, we find that overall activity of nonsense-mediated mRNA decay (NMD), a key RNA quality-control mechanism, is reduced. Genetic manipulation of NMD machinery significantly modifies tau-induced neurotoxicity, suggesting that deficits in NMD are causally linked to neurodegeneration. Mechanistically, we find that deficits in NMD are a consequence of aberrant RNA export and RNA accumulation within nuclear envelope invaginations in tauopathy. We identify a pharmacological activator of NMD that suppresses neurodegeneration in tau transgenic Drosophila, indicating that tau-induced deficits in RNA quality control are druggable. DISCUSSION Our studies suggest that NMD activators should be explored for their potential therapeutic value to patients with tauopathies.
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Affiliation(s)
- Gabrielle Zuniga
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Simon Levy
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Paulino Ramirez
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Jasmine De Mange
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Elias Gonzalez
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Maria Gamez
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Bess Frost
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas,Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas,Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
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Vafidis P, Owald D, D'Albis T, Kempter R. Learning accurate path integration in ring attractor models of the head direction system. eLife 2022; 11:69841. [PMID: 35723252 PMCID: PMC9286743 DOI: 10.7554/elife.69841] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/17/2022] [Indexed: 11/13/2022] Open
Abstract
Ring attractor models for angular path integration have received strong experimental support. To function as integrators, head direction circuits require precisely tuned connectivity, but it is currently unknown how such tuning could be achieved. Here, we propose a network model in which a local, biologically plausible learning rule adjusts synaptic efficacies during development, guided by supervisory allothetic cues. Applied to the Drosophila head direction system, the model learns to path-integrate accurately and develops a connectivity strikingly similar to the one reported in experiments. The mature network is a quasi-continuous attractor and reproduces key experiments in which optogenetic stimulation controls the internal representation of heading, and where the network remaps to integrate with different gains in rodents. Our model predicts that path integration requires self-supervised learning during a developmental phase, and proposes a general framework to learn to path-integrate with gain-1 even in architectures that lack the physical topography of a ring.
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Affiliation(s)
- Pantelis Vafidis
- Computation and Neural Systems, California Institute of Technology, Pasadena, United States
| | - David Owald
- NeuroCure, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Tiziano D'Albis
- Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Richard Kempter
- Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
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Hsu KJ, Lin YY, Chiang AS, Chu SW. Optical properties of adult Drosophila brains in one-, two-, and three-photon microscopy. BIOMEDICAL OPTICS EXPRESS 2019; 10:1627-1637. [PMID: 31086697 PMCID: PMC6484994 DOI: 10.1364/boe.10.001627] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/23/2019] [Accepted: 02/17/2019] [Indexed: 06/09/2023]
Abstract
Drosophila is widely used in connectome studies due to its small brain size, sophisticated genetic tools, and the most complete single-neuron-based anatomical brain map. Surprisingly, even the brain thickness is only 200-μm, common Ti:sapphire-based two-photon excitation cannot penetrate, possibly due to light aberration/scattering of trachea. Here we quantitatively characterized scattering and light distortion of trachea-filled tissues, and found that trachea-induced light distortion dominates at long wavelength by comparing one-photon (488-nm), two-photon (920-nm), and three-photon (1300-nm) excitations. Whole-Drosophila-brain imaging is achieved by reducing tracheal light aberration/scattering via brain-degassing or long-wavelength excitation at 1300-nm. Our work paves the way toward constructing whole-brain connectome in a living Drosophila.
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Affiliation(s)
- Kuo-Jen Hsu
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yen-Yin Lin
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Ann-Shyn Chiang
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
- Institute of Systems Neuroscience, National Tsing Hua University, Hsinchu 30013, Taiwan
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung 80780, Taiwan
- Kavli Institute for Brain and Mind, University of California at San Diego, La Jolla, CA 92093-0526, USA
| | - Shi-Wei Chu
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Molecular Imaging Center, National Taiwan University, Taipei 10617, Taiwan
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Modeling transport of a pulse of radiolabeled organelles in a Drosophila unipolar motor neuron. J Biol Phys 2013; 39:145-58. [PMID: 23860839 DOI: 10.1007/s10867-012-9292-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Accepted: 10/15/2012] [Indexed: 10/27/2022] Open
Abstract
Based on published experimental evidence, this paper develops a model for the transport of a pulse of radiolabeled organelles in a unipolar Drosophila motor neuron. In particular, since published data indicate that no microtubules (MTs) travel from the primary neurite into the dendrite, it is investigated how organelles are transported into the dendrite. Analytical solutions describing concentrations of kinesin- and dynein-driven organelles in the primary neurite, axon, and dendrite are obtained. The effects of increasing the width of the pulse and increasing the rate of organelle transition rate from the kinesin-driven to the dynein-driven state are investigated.
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