1
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Gabrawy MM, Westbrook R, King A, Khosravian N, Ochaney N, DeCarvalho T, Wang Q, Yu Y, Huang Q, Said A, Abadir M, Zhang C, Khare P, Fairman JE, Le A, Milne GL, Vonhoff FJ, Walston JD, Abadir PM. Dual treatment with kynurenine pathway inhibitors and NAD + precursors synergistically extends life span in Drosophila. Aging Cell 2024; 23:e14102. [PMID: 38481042 PMCID: PMC11019140 DOI: 10.1111/acel.14102] [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: 11/17/2023] [Revised: 01/19/2024] [Accepted: 01/24/2024] [Indexed: 04/17/2024] Open
Abstract
Tryptophan catabolism is highly conserved and generates important bioactive metabolites, including kynurenines, and in some animals, NAD+. Aging and inflammation are associated with increased levels of kynurenine pathway (KP) metabolites and depleted NAD+, factors which are implicated as contributors to frailty and morbidity. Contrastingly, KP suppression and NAD+ supplementation are associated with increased life span in some animals. Here, we used DGRP_229 Drosophila to elucidate the effects of KP elevation, KP suppression, and NAD+ supplementation on physical performance and survivorship. Flies were chronically fed kynurenines, KP inhibitors, NAD+ precursors, or a combination of KP inhibitors with NAD+ precursors. Flies with elevated kynurenines had reduced climbing speed, endurance, and life span. Treatment with a combination of KP inhibitors and NAD+ precursors preserved physical function and synergistically increased maximum life span. We conclude that KP flux can regulate health span and life span in Drosophila and that targeting KP and NAD+ metabolism can synergistically increase life span.
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Affiliation(s)
- Mariann M. Gabrawy
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Reyhan Westbrook
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Austin King
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
- Department of Biological SciencesUniversity of Maryland, Baltimore CountyBaltimoreMarylandUSA
| | - Nick Khosravian
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
- Department of Biological SciencesUniversity of Maryland, Baltimore CountyBaltimoreMarylandUSA
| | - Neeraj Ochaney
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
- Department of Biological SciencesUniversity of Maryland, Baltimore CountyBaltimoreMarylandUSA
| | - Tagide DeCarvalho
- Department of Biological SciencesUniversity of Maryland, Baltimore CountyBaltimoreMarylandUSA
| | - Qinchuan Wang
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Yuqiong Yu
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Qiao Huang
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Adam Said
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
- Emory UniversityAtlantaGeorgiaUSA
| | - Michael Abadir
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
- University of Maryland, College ParkCollege ParkMarylandUSA
| | | | | | - Jennifer E. Fairman
- Department of Arts as Applied to MedicineJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Anne Le
- Gigantest Inc.BaltimoreMarylandUSA
| | - Ginger L. Milne
- Vanderbilt UniversityVanderbilt Brain Institute, Neurochemistry CoreNashvilleTennesseeUSA
| | - Fernando J. Vonhoff
- Department of Biological SciencesUniversity of Maryland, Baltimore CountyBaltimoreMarylandUSA
| | - Jeremy D. Walston
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Peter M. Abadir
- School of Medicine, Division of Geriatric Medicine and Gerontology, Biology of Healthy Aging ProgramJohns Hopkins UniversityBaltimoreMarylandUSA
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2
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Sanfilippo P, Kim AJ, Bhukel A, Yoo J, Mirshahidi PS, Pandey V, Bevir H, Yuen A, Mirshahidi PS, Guo P, Li HS, Wohlschlegel JA, Aso Y, Zipursky SL. Mapping of multiple neurotransmitter receptor subtypes and distinct protein complexes to the connectome. Neuron 2024; 112:942-958.e13. [PMID: 38262414 PMCID: PMC10957333 DOI: 10.1016/j.neuron.2023.12.014] [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: 08/28/2023] [Revised: 12/03/2023] [Accepted: 12/20/2023] [Indexed: 01/25/2024]
Abstract
Neurons express various combinations of neurotransmitter receptor (NR) subunits and receive inputs from multiple neuron types expressing different neurotransmitters. Localizing NR subunits to specific synaptic inputs has been challenging. Here, we use epitope-tagged endogenous NR subunits, expansion light-sheet microscopy, and electron microscopy (EM) connectomics to molecularly characterize synapses in Drosophila. We show that in directionally selective motion-sensitive neurons, different multiple NRs elaborated a highly stereotyped molecular topography with NR localized to specific domains receiving cell-type-specific inputs. Developmental studies suggested that NRs or complexes of them with other membrane proteins determine patterns of synaptic inputs. In support of this model, we identify a transmembrane protein selectively associated with a subset of spatially restricted synapses and demonstrate its requirement for synapse formation through genetic analysis. We propose that mechanisms that regulate the precise spatial distribution of NRs provide a molecular cartography specifying the patterns of synaptic connections onto dendrites.
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Affiliation(s)
- Piero Sanfilippo
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Alexander J Kim
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Anuradha Bhukel
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Juyoun Yoo
- Neuroscience Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Pegah S Mirshahidi
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Vijaya Pandey
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Harry Bevir
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ashley Yuen
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Parmis S Mirshahidi
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Peiyi Guo
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Hong-Sheng Li
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - James A Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yoshinori Aso
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - S Lawrence Zipursky
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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3
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Mancini N, Thoener J, Tafani E, Pauls D, Mayseless O, Strauch M, Eichler K, Champion A, Kobler O, Weber D, Sen E, Weiglein A, Hartenstein V, Chytoudis-Peroudis CC, Jovanic T, Thum AS, Rohwedder A, Schleyer M, Gerber B. Rewarding Capacity of Optogenetically Activating a Giant GABAergic Central-Brain Interneuron in Larval Drosophila. J Neurosci 2023; 43:7393-7428. [PMID: 37734947 PMCID: PMC10621887 DOI: 10.1523/jneurosci.2310-22.2023] [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: 12/17/2022] [Revised: 07/19/2023] [Accepted: 08/26/2023] [Indexed: 09/23/2023] Open
Abstract
Larvae of the fruit fly Drosophila melanogaster are a powerful study case for understanding the neural circuits underlying behavior. Indeed, the numerical simplicity of the larval brain has permitted the reconstruction of its synaptic connectome, and genetic tools for manipulating single, identified neurons allow neural circuit function to be investigated with relative ease and precision. We focus on one of the most complex neurons in the brain of the larva (of either sex), the GABAergic anterior paired lateral neuron (APL). Using behavioral and connectomic analyses, optogenetics, Ca2+ imaging, and pharmacology, we study how APL affects associative olfactory memory. We first provide a detailed account of the structure, regional polarity, connectivity, and metamorphic development of APL, and further confirm that optogenetic activation of APL has an inhibiting effect on its main targets, the mushroom body Kenyon cells. All these findings are consistent with the previously identified function of APL in the sparsening of sensory representations. To our surprise, however, we found that optogenetically activating APL can also have a strong rewarding effect. Specifically, APL activation together with odor presentation establishes an odor-specific, appetitive, associative short-term memory, whereas naive olfactory behavior remains unaffected. An acute, systemic inhibition of dopamine synthesis as well as an ablation of the dopaminergic pPAM neurons impair reward learning through APL activation. Our findings provide a study case of complex circuit function in a numerically simple brain, and suggest a previously unrecognized capacity of central-brain GABAergic neurons to engage in dopaminergic reinforcement.SIGNIFICANCE STATEMENT The single, identified giant anterior paired lateral (APL) neuron is one of the most complex neurons in the insect brain. It is GABAergic and contributes to the sparsening of neuronal activity in the mushroom body, the memory center of insects. We provide the most detailed account yet of the structure of APL in larval Drosophila as a neurogenetically accessible study case. We further reveal that, contrary to expectations, the experimental activation of APL can exert a rewarding effect, likely via dopaminergic reward pathways. The present study both provides an example of unexpected circuit complexity in a numerically simple brain, and reports an unexpected effect of activity in central-brain GABAergic circuits.
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Affiliation(s)
- Nino Mancini
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
| | - Juliane Thoener
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
| | - Esmeralda Tafani
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
| | - Dennis Pauls
- Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, 04103, Germany
| | - Oded Mayseless
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Martin Strauch
- Institute of Imaging and Computer Vision, RWTH Aachen University, Aachen, 52074, Germany
| | - Katharina Eichler
- Institute of Neurobiology, University of Puerto Rico Medical Science Campus, Old San Juan, Puerto Rico, 00901
| | - Andrew Champion
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge, CB2 3EL, United Kingdom
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, Virginia
| | - Oliver Kobler
- Leibniz Institute for Neurobiology, Combinatorial Neuroimaging Core Facility, Magdeburg, 39118, Germany
| | - Denise Weber
- Department of Genetics, Institute of Biology, Leipzig University, Leipzig, 04103, Germany
| | - Edanur Sen
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
| | - Aliće Weiglein
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
| | - Volker Hartenstein
- University of California, Department of Molecular, Cell and Developmental Biology, Los Angeles, California 90095-1606
| | | | - Tihana Jovanic
- Université Paris-Saclay, Centre National de la Recherche Scientifique, Institut des neurosciences Paris-Saclay, Saclay, 91400, France
| | - Andreas S Thum
- Department of Genetics, Institute of Biology, Leipzig University, Leipzig, 04103, Germany
| | - Astrid Rohwedder
- Department of Genetics, Institute of Biology, Leipzig University, Leipzig, 04103, Germany
| | - Michael Schleyer
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
| | - Bertram Gerber
- Leibniz Institute for Neurobiology, Department Genetics of Learning and Memory, Magdeburg, 39118, Germany
- Center for Behavioral Brain Sciences, Magdeburg, 39106, Germany
- Institute for Biology, Otto von Guericke University, Magdeburg, 39120, Germany
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4
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Sanfilippo P, Kim AJ, Bhukel A, Yoo J, Mirshahidi PS, Pandey V, Bevir H, Yuen A, Mirshahidi PS, Guo P, Li HS, Wohlschlegel JA, Aso Y, Zipursky SL. Mapping of multiple neurotransmitter receptor subtypes and distinct protein complexes to the connectome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.02.560011. [PMID: 37873314 PMCID: PMC10592863 DOI: 10.1101/2023.10.02.560011] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Neurons express different combinations of neurotransmitter receptor (NR) subunits and receive inputs from multiple neuron types expressing different neurotransmitters. Localizing NR subunits to specific synaptic inputs has been challenging. Here we use epitope tagged endogenous NR subunits, expansion light-sheet microscopy, and EM connectomics to molecularly characterize synapses in Drosophila. We show that in directionally selective motion sensitive neurons, different multiple NRs elaborated a highly stereotyped molecular topography with NR localized to specific domains receiving cell-type specific inputs. Developmental studies suggested that NRs or complexes of them with other membrane proteins determines patterns of synaptic inputs. In support of this model, we identify a transmembrane protein associated selectively with a subset of spatially restricted synapses and demonstrate through genetic analysis its requirement for synapse formation. We propose that mechanisms which regulate the precise spatial distribution of NRs provide a molecular cartography specifying the patterns of synaptic connections onto dendrites.
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Affiliation(s)
- Piero Sanfilippo
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
- Howard Hughes Medical Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Alexander J Kim
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Anuradha Bhukel
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Juyoun Yoo
- Neuroscience Interdepartmental Program, University of California Los Angeles, Los Angeles, CA, USA
| | - Pegah S Mirshahidi
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Vijaya Pandey
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Harry Bevir
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Ashley Yuen
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Parmis S Mirshahidi
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Peiyi Guo
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Hong-Sheng Li
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - James A Wohlschlegel
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Yoshinori Aso
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - S Lawrence Zipursky
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
- Howard Hughes Medical Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
- Lead Contact
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5
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Hürkey S, Niemeyer N, Schleimer JH, Ryglewski S, Schreiber S, Duch C. Gap junctions desynchronize a neural circuit to stabilize insect flight. Nature 2023:10.1038/s41586-023-06099-0. [PMID: 37225999 DOI: 10.1038/s41586-023-06099-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 04/18/2023] [Indexed: 05/26/2023]
Abstract
Insect asynchronous flight is one of the most prevalent forms of animal locomotion used by more than 600,000 species. Despite profound insights into the motor patterns1, biomechanics2,3 and aerodynamics underlying asynchronous flight4,5, the architecture and function of the central-pattern-generating (CPG) neural network remain unclear. Here, on the basis of an experiment-theory approach including electrophysiology, optophysiology, Drosophila genetics and mathematical modelling, we identify a miniaturized circuit solution with unexpected properties. The CPG network consists of motoneurons interconnected by electrical synapses that, in contrast to doctrine, produce network activity splayed out in time instead of synchronized across neurons. Experimental and mathematical evidence support a generic mechanism for network desynchronization that relies on weak electrical synapses and specific excitability dynamics of the coupled neurons. In small networks, electrical synapses can synchronize or desynchronize network activity, depending on the neuron-intrinsic dynamics and ion channel composition. In the asynchronous flight CPG, this mechanism translates unpatterned premotor input into stereotyped neuronal firing with fixed sequences of cell activation that ensure stable wingbeat power and, as we show, is conserved across multiple species. Our findings prove a wider functional versatility of electrical synapses in the dynamic control of neural circuits and highlight the relevance of detecting electrical synapses in connectomics.
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Affiliation(s)
- Silvan Hürkey
- Institute of Developmental Biology and Neurobiology (iDN), Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Nelson Niemeyer
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | | | - Stefanie Ryglewski
- Institute of Developmental Biology and Neurobiology (iDN), Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Susanne Schreiber
- Institute for Theoretical Biology, Humboldt-Universität zu Berlin, Berlin, Germany.
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany.
| | - Carsten Duch
- Institute of Developmental Biology and Neurobiology (iDN), Johannes Gutenberg-University Mainz, Mainz, Germany.
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6
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Hafner AS, Triesch J. Synaptic logistics: Competing over shared resources. Mol Cell Neurosci 2023; 125:103858. [PMID: 37172922 DOI: 10.1016/j.mcn.2023.103858] [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: 11/23/2022] [Revised: 05/05/2023] [Accepted: 05/05/2023] [Indexed: 05/15/2023] Open
Abstract
High turnover rates of synaptic proteins imply that synapses constantly need to replace their constituent building blocks. This requires sophisticated supply chains and potentially exposes synapses to shortages as they compete for limited resources. Interestingly, competition in neurons has been observed at different scales. Whether it is competition of receptors for binding sites inside a single synapse or synapses fighting for resources to grow. Here we review the implications of such competition for synaptic function and plasticity. We identify multiple mechanisms that synapses use to safeguard themselves against supply shortages and identify a fundamental neurologistic trade-off governing the sizes of reserve pools of essential synaptic building blocks.
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Affiliation(s)
- Anne-Sophie Hafner
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands.
| | - Jochen Triesch
- Frankfurt Institute for Advanced Studies, Frankfurt am Main, Germany; Goethe University, Frankfurt am Main, Germany
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7
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Mayseless O, Shapira G, Rachad EY, Fiala A, Schuldiner O. Neuronal excitability as a regulator of circuit remodeling. Curr Biol 2023; 33:981-989.e3. [PMID: 36758544 PMCID: PMC10017263 DOI: 10.1016/j.cub.2023.01.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 10/18/2022] [Accepted: 01/17/2023] [Indexed: 02/11/2023]
Abstract
Postnatal remodeling of neuronal connectivity shapes mature nervous systems.1,2,3 The pruning of exuberant connections involves cell-autonomous and non-cell-autonomous mechanisms, such as neuronal activity. Indeed, experience-dependent competition sculpts various excitatory neuronal circuits.4,5,6,7,8,9 Moreover, activity has been shown to regulate growth cone motility and the stability of neurites and synaptic connections.10,11,12,13,14 However, whether inhibitory activity influences the remodeling of neuronal connectivity or how activity influences remodeling in systems in which competition is not clearly apparent is not fully understood. Here, we use the Drosophila mushroom body (MB) as a model to examine the role of neuronal activity in the developmental axon pruning of γ-Kenyon cells. The MB is a neuronal structure in insects, implicated in associative learning and memory,15,16 which receives mostly olfactory input from the antennal lobe.17,18 The MB circuit includes intrinsic neurons, called Kenyon cells (KCs), which receive inhibitory input from the GABAergic anterior paired lateral (APL) neuron among other inputs. The γ-KCs undergo stereotypic, steroid-hormone-dependent remodeling19,20 that involves the pruning of larval neurites followed by regrowth to form adult connections.21 We demonstrate that silencing neuronal activity is required for γ-KC pruning. Furthermore, we show that this is mechanistically achieved by cell-autonomous expression of the inward rectifying potassium channel 1 (irk1) combined with inhibition by APL neuron activity likely via GABA-B-R1 signaling. These results support the Hebbian-like rule "use it or lose it," where inhibition can destabilize connectivity and promote pruning while excitability stabilizes existing connections.
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Affiliation(s)
- Oded Mayseless
- Department of Molecular Cell Biology, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Gal Shapira
- Department of Molecular Cell Biology, Weizmann Institute of Science, 7610001 Rehovot, Israel; Department of Molecular Neuroscience, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - El Yazid Rachad
- Department of Molecular Neurobiology of Behavior, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, 37077 Göttingen, Germany
| | - André Fiala
- Department of Molecular Neurobiology of Behavior, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, 37077 Göttingen, Germany
| | - Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Science, 7610001 Rehovot, Israel; Department of Molecular Neuroscience, Weizmann Institute of Science, 7610001 Rehovot, Israel.
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8
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Dutta SB, Linneweber GA, Andriatsilavo M, Hiesinger PR, Hassan BA. EGFR-dependent suppression of synaptic autophagy is required for neuronal circuit development. Curr Biol 2023; 33:517-532.e5. [PMID: 36640763 DOI: 10.1016/j.cub.2022.12.039] [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: 04/01/2022] [Revised: 10/31/2022] [Accepted: 12/14/2022] [Indexed: 01/15/2023]
Abstract
The development of neuronal connectivity requires stabilization of dynamic axonal branches at sites of synapse formation. Models that explain how axonal branching is coupled to synaptogenesis postulate molecular regulators acting in a spatiotemporally restricted fashion to ensure branching toward future synaptic partners while also stabilizing the emerging synaptic contacts between such partners. We investigated this question using neuronal circuit development in the Drosophila brain as a model system. We report that epidermal growth factor receptor (EGFR) activity is required in presynaptic axonal branches during two distinct temporal intervals to regulate circuit wiring in the developing Drosophila visual system. EGFR is required early to regulate primary axonal branching. EGFR activity is then independently required at a later stage to prevent degradation of the synaptic active zone protein Bruchpilot (Brp). Inactivation of EGFR results in a local increase of autophagy in presynaptic branches and the translocation of active zone proteins into autophagic vesicles. The protection of synaptic material during this later interval of wiring ensures the stabilization of terminal branches, circuit connectivity, and appropriate visual behavior. Phenotypes of EGFR inactivation can be rescued by increasing Brp levels or downregulating autophagy. In summary, we identify a temporally restricted molecular mechanism required for coupling axonal branching and synaptic stabilization that contributes to the emergence of neuronal wiring specificity.
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Affiliation(s)
- Suchetana B Dutta
- Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié Salpêtrière, 75013 Paris, France; Division of Neurobiology, Free University of Berlin, 14195 Berlin, Germany; Einstein-BIH, Charité Universitätsmedizin, 10117 Berlin, Germany
| | | | - Maheva Andriatsilavo
- Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié Salpêtrière, 75013 Paris, France; Division of Neurobiology, Free University of Berlin, 14195 Berlin, Germany; Einstein-BIH, Charité Universitätsmedizin, 10117 Berlin, Germany
| | | | - Bassem A Hassan
- Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié Salpêtrière, 75013 Paris, France; Division of Neurobiology, Free University of Berlin, 14195 Berlin, Germany; Einstein-BIH, Charité Universitätsmedizin, 10117 Berlin, Germany.
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9
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Wit CB, Hiesinger PR. Neuronal filopodia: From stochastic dynamics to robustness of brain morphogenesis. Semin Cell Dev Biol 2023; 133:10-19. [PMID: 35397971 DOI: 10.1016/j.semcdb.2022.03.038] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 03/26/2022] [Accepted: 03/29/2022] [Indexed: 12/30/2022]
Abstract
Brain development relies on dynamic morphogenesis and interactions of neurons. Filopodia are thin and highly dynamic membrane protrusions that are critically required for neuronal development and neuronal interactions with the environment. Filopodial interactions are typically characterized by non-deterministic dynamics, yet their involvement in developmental processes leads to stereotypic and robust outcomes. Here, we discuss recent advances in our understanding of how filopodial dynamics contribute to neuronal differentiation, migration, axonal and dendritic growth and synapse formation. Many of these advances are brought about by improved methods of live observation in intact developing brains. Recent findings integrate known and novel roles ranging from exploratory sensors and decision-making agents to pools for selection and mechanical functions. Different types of filopodial dynamics thereby reveal non-deterministic subcellular decision-making processes as part of genetically encoded brain development.
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Affiliation(s)
- Charlotte B Wit
- Devision of Neurobiology, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - P Robin Hiesinger
- Devision of Neurobiology, Institute of Biology, Freie Universität Berlin, Berlin, Germany.
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10
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Remy NQ, Guevarra JA, Vonhoff FJ. Food supplementation with wheat gluten leads to climbing performance decline in Drosophila melanogaster. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000642. [PMID: 36217442 PMCID: PMC9547276 DOI: 10.17912/micropub.biology.000642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 12/05/2022]
Abstract
Gluten sensitivity is associated with digestive and neurological disorders, correlating with abnormal amino acid levels, innate immune responses, gut dysbiosis and movement incoordination. However, the molecular mechanisms linking dietary gluten and brain function remain incompletely understood. We used Drosophila melanogaster to test the effects of gluten ingestion in locomotion performance. Whereas flies on control food showed decreased climbing performance after five weeks, flies exposed to food supplemented with different gluten concentrations showed a significant locomotion decline after three weeks of treatment. Future studies will determine the mechanisms underlying the observed gluten-dependent phenotypes to establish Drosophila models for gluten sensitivity.
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Affiliation(s)
| | | | - Fernando J Vonhoff
- University of Maryland Baltimore County, Baltimore, MD, United States
,
Correspondence to: Fernando J Vonhoff (
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11
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Barnes CL, Bonnéry D, Cardona A. Synaptic counts approximate synaptic contact area in Drosophila. PLoS One 2022; 17:e0266064. [PMID: 35377898 PMCID: PMC8979427 DOI: 10.1371/journal.pone.0266064] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 03/12/2022] [Indexed: 11/19/2022] Open
Abstract
The pattern of synaptic connections among neurons defines the circuit structure, which constrains the computations that a circuit can perform. The strength of synaptic connections is costly to measure yet important for accurate circuit modeling. Synaptic surface area has been shown to correlate with synaptic strength, yet in the emerging field of connectomics, most studies rely instead on the counts of synaptic contacts between two neurons. Here we quantified the relationship between synaptic count and synaptic area as measured from volume electron microscopy of the larval Drosophila central nervous system. We found that the total synaptic surface area, summed across all synaptic contacts from one presynaptic neuron to a postsynaptic one, can be accurately predicted solely from the number of synaptic contacts, for a variety of neurotransmitters. Our findings support the use of synaptic counts for approximating synaptic strength when modeling neural circuits.
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Affiliation(s)
- Christopher L. Barnes
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Daniel Bonnéry
- Epidemiology and Modelling Group, Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Albert Cardona
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
- * E-mail:
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12
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Kiral FR, Dutta SB, Linneweber GA, Hilgert S, Poppa C, Duch C, von Kleist M, Hassan BA, Hiesinger PR. Brain connectivity inversely scales with developmental temperature in Drosophila. Cell Rep 2021; 37:110145. [PMID: 34936868 DOI: 10.1016/j.celrep.2021.110145] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 10/04/2021] [Accepted: 11/29/2021] [Indexed: 11/17/2022] Open
Abstract
Variability of synapse numbers and partners despite identical genes reveals the limits of genetic determinism. Here, we use developmental temperature as a non-genetic perturbation to study variability of brain wiring and behavior in Drosophila. Unexpectedly, slower development at lower temperatures increases axo-dendritic branching, synapse numbers, and non-canonical synaptic partnerships of various neurons, while maintaining robust ratios of canonical synapses. Using R7 photoreceptors as a model, we show that changing the relative availability of synaptic partners using a DIPγ mutant that ablates R7's preferred partner leads to temperature-dependent recruitment of non-canonical partners to reach normal synapse numbers. Hence, R7 synaptic specificity is not absolute but based on the relative availability of postsynaptic partners and presynaptic control of synapse numbers. Behaviorally, movement precision is temperature robust, while movement activity is optimized for the developmentally encountered temperature. These findings suggest genetically encoded relative and scalable synapse formation to develop functional, but not identical, brains and behaviors.
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Affiliation(s)
- Ferdi Ridvan Kiral
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Suchetana B Dutta
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Gerit Arne Linneweber
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Selina Hilgert
- Institute of Developmental Biology and Neurobiology (iDN), Hanns-Dieter-Hüsch-Weg 15, 55128 Mainz, Germany
| | - Caroline Poppa
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Carsten Duch
- Institute of Developmental Biology and Neurobiology (iDN), Hanns-Dieter-Hüsch-Weg 15, 55128 Mainz, Germany
| | - Max von Kleist
- MF1 Bioinformatics, Robert Koch-Institute, 13353 Berlin, Germany
| | - Bassem A Hassan
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany; Institut du Cerveau - Paris Brain Institute - ICM, Sorbonne Université, Inserm, CNRS, Hôpital Pitié-Salpêtrière, Paris, France
| | - P Robin Hiesinger
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany.
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13
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Rosenthal JS, Yuan Q. Constructing and Tuning Excitatory Cholinergic Synapses: The Multifaceted Functions of Nicotinic Acetylcholine Receptors in Drosophila Neural Development and Physiology. Front Cell Neurosci 2021; 15:720560. [PMID: 34650404 PMCID: PMC8505678 DOI: 10.3389/fncel.2021.720560] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/20/2021] [Indexed: 11/13/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAchRs) are widely distributed within the nervous system across most animal species. Besides their well-established roles in mammalian neuromuscular junctions, studies using invertebrate models have also proven fruitful in revealing the function of nAchRs in the central nervous system. During the earlier years, both in vitro and animal studies had helped clarify the basic molecular features of the members of the Drosophila nAchR gene family and illustrated their utility as targets for insecticides. Later, increasingly sophisticated techniques have illuminated how nAchRs mediate excitatory neurotransmission in the Drosophila brain and play an integral part in neural development and synaptic plasticity, as well as cognitive processes such as learning and memory. This review is intended to provide an updated survey of Drosophila nAchR subunits, focusing on their molecular diversity and unique contributions to physiology and plasticity of the fly neural circuitry. We will also highlight promising new avenues for nAchR research that will likely contribute to better understanding of central cholinergic neurotransmission in both Drosophila and other organisms.
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Affiliation(s)
- Justin S Rosenthal
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Quan Yuan
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
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14
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Ferreira Castro A, Baltruschat L, Stürner T, Bahrami A, Jedlicka P, Tavosanis G, Cuntz H. Achieving functional neuronal dendrite structure through sequential stochastic growth and retraction. eLife 2020; 9:e60920. [PMID: 33241995 PMCID: PMC7837678 DOI: 10.7554/elife.60920] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 11/15/2020] [Indexed: 02/06/2023] Open
Abstract
Class I ventral posterior dendritic arborisation (c1vpda) proprioceptive sensory neurons respond to contractions in the Drosophila larval body wall during crawling. Their dendritic branches run along the direction of contraction, possibly a functional requirement to maximise membrane curvature during crawling contractions. Although the molecular machinery of dendritic patterning in c1vpda has been extensively studied, the process leading to the precise elaboration of their comb-like shapes remains elusive. Here, to link dendrite shape with its proprioceptive role, we performed long-term, non-invasive, in vivo time-lapse imaging of c1vpda embryonic and larval morphogenesis to reveal a sequence of differentiation stages. We combined computer models and dendritic branch dynamics tracking to propose that distinct sequential phases of stochastic growth and retraction achieve efficient dendritic trees both in terms of wire and function. Our study shows how dendrite growth balances structure-function requirements, shedding new light on general principles of self-organisation in functionally specialised dendrites.
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Affiliation(s)
- André Ferreira Castro
- Frankfurt Institute for Advanced StudiesFrankfurt am MainGermany
- Ernst Strüngmann Institute (ESI) for Neuroscience in cooperation with Max Planck SocietyFrankfurt am MainGermany
- Center for Neurodegenerative Diseases (DZNE)BonnGermany
| | | | - Tomke Stürner
- Center for Neurodegenerative Diseases (DZNE)BonnGermany
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | | | - Peter Jedlicka
- Frankfurt Institute for Advanced StudiesFrankfurt am MainGermany
- Faculty of Medicine, ICAR3R – Interdisciplinary Centre for 3Rs in Animal Research, Justus Liebig University GiessenGiessenGermany
- Neuroscience Center, Institute of Clinical Neuroanatomy, Goethe UniversityFrankfurt am MainGermany
| | - Gaia Tavosanis
- Center for Neurodegenerative Diseases (DZNE)BonnGermany
- LIMES Institute, University of BonnBonnGermany
| | - Hermann Cuntz
- Frankfurt Institute for Advanced StudiesFrankfurt am MainGermany
- Ernst Strüngmann Institute (ESI) for Neuroscience in cooperation with Max Planck SocietyFrankfurt am MainGermany
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15
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Different functions of two putative Drosophila α 2δ subunits in the same identified motoneurons. Sci Rep 2020; 10:13670. [PMID: 32792569 PMCID: PMC7426832 DOI: 10.1038/s41598-020-69748-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 07/15/2020] [Indexed: 11/24/2022] Open
Abstract
Voltage gated calcium channels (VGCCs) regulate neuronal excitability and translate activity into calcium dependent signaling. The α1 subunit of high voltage activated (HVA) VGCCs associates with α2δ accessory subunits, which may affect calcium channel biophysical properties, cell surface expression, localization and transport and are thus important players in calcium-dependent signaling. In vertebrates, the functions of the different combinations of the four α2δ and the seven HVA α1 subunits are incompletely understood, in particular with respect to partially redundant or separate functions in neurons. This study capitalizes on the relatively simpler situation in the Drosophila genetic model containing two neuronal putative α2δ subunits, straightjacket and CG4587, and one Cav1 and Cav2 homolog each, both with well-described functions in different compartments of identified motoneurons. Straightjacket is required for normal Cav1 and Cav2 current amplitudes and correct Cav2 channel function in all neuronal compartments. By contrast, CG4587 does not affect Cav1 or Cav2 current amplitudes or presynaptic function, but is required for correct Cav2 channel allocation to the axonal versus the dendritic domain. We suggest that the two different putative α2δ subunits are required in the same neurons to regulate different functions of VGCCs.
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16
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Activity Dependent and Independent Determinants of Synaptic Size Diversity. J Neurosci 2020; 40:2828-2848. [PMID: 32127494 DOI: 10.1523/jneurosci.2181-19.2020] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 02/04/2020] [Accepted: 02/13/2020] [Indexed: 11/21/2022] Open
Abstract
The extraordinary diversity of excitatory synapse sizes is commonly attributed to activity-dependent processes that drive synaptic growth and diminution. Recent studies also point to activity-independent size fluctuations, possibly driven by innate synaptic molecule dynamics, as important generators of size diversity. To examine the contributions of activity-dependent and independent processes to excitatory synapse size diversity, we studied glutamatergic synapse size dynamics and diversification in cultured rat cortical neurons (both sexes), silenced from plating. We found that in networks with no history of activity whatsoever, synaptic size diversity was no less extensive than that observed in spontaneously active networks. Synapses in silenced networks were larger, size distributions were broader, yet these were rightward-skewed and similar in shape when scaled by mean synaptic size. Silencing reduced the magnitude of size fluctuations and weakened constraints on size distributions, yet these were sufficient to explain synaptic size diversity in silenced networks. Model-based exploration followed by experimental testing indicated that silencing-associated changes in innate molecular dynamics and fluctuation characteristics might negatively impact synaptic persistence, resulting in reduced synaptic numbers. This, in turn, would increase synaptic molecule availability, promote synaptic enlargement, and ultimately alter fluctuation characteristics. These findings suggest that activity-independent size fluctuations are sufficient to fully diversify glutamatergic synaptic sizes, with activity-dependent processes primarily setting the scale rather than the shape of size distributions. Moreover, they point to reciprocal relationships between synaptic size fluctuations, size distributions, and synaptic numbers mediated by the innate dynamics of synaptic molecules as they move in, out, and between synapses.SIGNIFICANCE STATEMENT Sizes of glutamatergic synapses vary tremendously, even when formed on the same neuron. This diversity is commonly thought to reflect the outcome of activity-dependent forms of synaptic plasticity, yet activity-independent processes might also play some part. Here we show that in neurons with no history of activity whatsoever, synaptic sizes are no less diverse. We show that this diversity is the product of activity-independent size fluctuations, which are sufficient to generate a full repertoire of synaptic sizes at correct proportions. By combining modeling and experimentation we expose reciprocal relationships between size fluctuations, synaptic sizes and synaptic counts, and show how these phenomena might be connected through the dynamics of synaptic molecules as they move in, out, and between synapses.
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17
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Werner J, Arian J, Bernhardt I, Ryglewski S, Duch C. Differential localization of voltage-gated potassium channels during Drosophila metamorphosis. J Neurogenet 2020; 34:133-150. [PMID: 31997675 DOI: 10.1080/01677063.2020.1715972] [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] [Indexed: 10/25/2022]
Abstract
Neuronal excitability is determined by the combination of different ion channels and their sub-neuronal localization. This study utilizes protein trap fly strains with endogenously tagged channels to analyze the spatial expression patterns of the four Shaker-related voltage-gated potassium channels, Kv1-4, in the larval, pupal, and adult Drosophila ventral nerve cord. We find that all four channels (Shaker, Kv1; Shab, Kv2; Shaw, Kv3; and Shal, Kv4) each show different spatial expression patterns in the Drosophila ventral nerve cord and are predominantly targeted to different sub-neuronal compartments. Shaker is abundantly expressed in axons, Shab also localizes to axons but mostly in commissures, Shaw expression is restricted to distinct parts of neuropils, and Shal is found somatodendritically, but also in axons of identified motoneurons. During early pupal life expression of all four Shaker-related channels is markedly decreased with an almost complete shutdown of expression at early pupal stage 5 (∼30% through metamorphosis). Re-expression of Kv1-4 channels at pupal stage 6 starts with abundant channel localization in neuronal somata, followed by channel targeting to the respective sub-neuronal compartments until late pupal life. The developmental time course of tagged Kv1-4 channel expression corresponds with previously published data on developmental changes in single neuron physiology, thus indicating that protein trap fly strains are a useful tool to analyze developmental regulation of potassium channel expression. Finally, we take advantage of the large diameter of the giant fiber (GF) interneuron to map channel expression onto the axon and axon terminals of an identified interneuron. Shaker, Shaw, and Shal but not Shab channels localize to the non-myelinated GF axonal membrane and axon terminals. This study constitutes a first step toward systematically analyzing sub-neuronal potassium channel localization in Drosophila. Functional implications as well as similarities and differences to Kv1-4 channel localization in mammalian neurons are discussed.
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Affiliation(s)
- Jan Werner
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Jashar Arian
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Ida Bernhardt
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Stefanie Ryglewski
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Carsten Duch
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
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18
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Özel MN, Kulkarni A, Hasan A, Brummer J, Moldenhauer M, Daumann IM, Wolfenberg H, Dercksen VJ, Kiral FR, Weiser M, Prohaska S, von Kleist M, Hiesinger PR. Serial Synapse Formation through Filopodial Competition for Synaptic Seeding Factors. Dev Cell 2019; 50:447-461.e8. [PMID: 31353313 DOI: 10.1016/j.devcel.2019.06.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 05/15/2019] [Accepted: 06/21/2019] [Indexed: 11/15/2022]
Abstract
Following axon pathfinding, growth cones transition from stochastic filopodial exploration to the formation of a limited number of synapses. How the interplay of filopodia and synapse assembly ensures robust connectivity in the brain has remained a challenging problem. Here, we developed a new 4D analysis method for filopodial dynamics and a data-driven computational model of synapse formation for R7 photoreceptor axons in developing Drosophila brains. Our live data support a "serial synapse formation" model, where at any time point only 1-2 "synaptogenic" filopodia suppress the synaptic competence of other filopodia through competition for synaptic seeding factors. Loss of the synaptic seeding factors Syd-1 and Liprin-α leads to a loss of this suppression, filopodial destabilization, and reduced synapse formation. The failure to form synapses can cause the destabilization and secondary retraction of axon terminals. Our model provides a filopodial "winner-takes-all" mechanism that ensures the formation of an appropriate number of synapses.
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Affiliation(s)
- M Neset Özel
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany; Neuroscience Graduate Program, UT Southwestern Medical Center Dallas, Dallas, TX 75390, USA
| | - Abhishek Kulkarni
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Amr Hasan
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Josephine Brummer
- Department of Visual Data Analysis, Zuse Institute Berlin, 14195 Berlin, Germany
| | - Marian Moldenhauer
- Computational Medicine and Numerical Mathematics, Zuse Institute Berlin, 14195 Berlin, Germany; Department of Mathematics and Informatics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Ilsa-Maria Daumann
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Heike Wolfenberg
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Vincent J Dercksen
- Department of Visual Data Analysis, Zuse Institute Berlin, 14195 Berlin, Germany
| | - F Ridvan Kiral
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Martin Weiser
- Computational Medicine and Numerical Mathematics, Zuse Institute Berlin, 14195 Berlin, Germany
| | - Steffen Prohaska
- Department of Visual Data Analysis, Zuse Institute Berlin, 14195 Berlin, Germany
| | - Max von Kleist
- Department of Mathematics and Informatics, Freie Universität Berlin, 14195 Berlin, Germany.
| | - P Robin Hiesinger
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany.
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19
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Abstract
The Drosophila Fragile X Syndrome model has long generated insights into this devastating neurological disease state. A recent study of olfactory neural circuitry shows that decreased lateral inhibition onto projection neurons relaying sensory input into higher brain centers causes impaired behavior.
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Affiliation(s)
- Randall M Golovin
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232, USA
| | - Kendal Broadie
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA.
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20
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Tyramine action on motoneuron excitability and adaptable tyramine/octopamine ratios adjust Drosophila locomotion to nutritional state. Proc Natl Acad Sci U S A 2019; 116:3805-3810. [PMID: 30808766 DOI: 10.1073/pnas.1813554116] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Adrenergic signaling profoundly modulates animal behavior. For example, the invertebrate counterpart of norepinephrine, octopamine, and its biological precursor and functional antagonist, tyramine, adjust motor behavior to different nutritional states. In Drosophila larvae, food deprivation increases locomotor speed via octopamine-mediated structural plasticity of neuromuscular synapses, whereas tyramine reduces locomotor speed, but the underlying cellular and molecular mechanisms remain unknown. We show that tyramine is released into the CNS to reduce motoneuron intrinsic excitability and responses to excitatory cholinergic input, both by tyraminehonoka receptor activation and by downstream decrease of L-type calcium current. This central effect of tyramine on motoneurons is required for the adaptive reduction of locomotor activity after feeding. Similarly, peripheral octopamine action on motoneurons has been reported to be required for increasing locomotion upon starvation. We further show that the level of tyramine-β-hydroxylase (TBH), the enzyme that converts tyramine into octopamine in aminergic neurons, is increased by food deprivation, thus selecting between antagonistic amine actions on motoneurons. Therefore, octopamine and tyramine provide global but distinctly different mechanisms to regulate motoneuron excitability and behavioral plasticity, and their antagonistic actions are balanced within a dynamic range by nutritional effects on TBH.
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21
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Hiesinger PR, Hassan BA. The Evolution of Variability and Robustness in Neural Development. Trends Neurosci 2018; 41:577-586. [DOI: 10.1016/j.tins.2018.05.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 05/10/2018] [Accepted: 05/15/2018] [Indexed: 11/26/2022]
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22
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Dendritic and Axonal L-Type Calcium Channels Cooperate to Enhance Motoneuron Firing Output during Drosophila Larval Locomotion. J Neurosci 2017; 37:10971-10982. [PMID: 28986465 DOI: 10.1523/jneurosci.1064-17.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 09/18/2017] [Accepted: 09/26/2017] [Indexed: 11/21/2022] Open
Abstract
Behaviorally adequate neuronal firing patterns are critically dependent on the specific types of ion channel expressed and on their subcellular localization. This study combines in situ electrophysiology with genetic and pharmacological intervention in larval Drosophila melanogaster of both sexes to address localization and function of L-type like calcium channels in motoneurons. We demonstrate that Dmca1D (Cav1 homolog) L-type like calcium channels localize to both the somatodendritic and the axonal compartment of larval crawling motoneurons. In situ patch-clamp recordings in genetic mosaics reveal that Dmca1D channels increase burst duration and maximum intraburst firing frequencies during crawling-like motor patterns in semi-intact animals. Genetic and acute pharmacological manipulations suggest that prolonged burst durations are caused by dendritically localized Dmca1D channels, which activate upon cholinergic synaptic input and amplify EPSPs, thus indicating a conserved function of dendritic L-type channels from Drosophila to vertebrates. By contrast, maximum intraburst firing rates require axonal calcium influx through Dmca1D channels, likely to enhance sodium channel de-inactivation via a fast afterhyperpolarization through BK channel activation. Therefore, in unmyelinated Drosophila motoneurons different functions of axonal and dendritic L-type like calcium channels likely operate synergistically to maximize firing output during locomotion.SIGNIFICANCE STATEMENT Nervous system function depends on the specific excitabilities of different types of neurons. Excitability is largely shaped by different combinations of voltage-dependent ion channels. Despite a high degree of conservation, the huge diversity of ion channel types and their differential localization pose challenges in assigning distinct functions to specific channels across species. We find a conserved role, from fruit flies to mammals, for L-type calcium channels in augmenting motoneuron excitability. As in spinal cord, dendritic L-type channels amplify excitatory synaptic input. In contrast to spinal motoneurons, axonal L-type channels enhance firing rates in unmyelinated Drosophila motoraxons. Therefore, enhancing motoneuron excitability by L-type channels seems an old strategy, but localization and interactions with other channels are tuned to species-specific requirements.
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