1
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Alexandris AS, Koliatsos VE. NAD +, Axonal Maintenance, and Neurological Disease. Antioxid Redox Signal 2023; 39:1167-1184. [PMID: 37503611 PMCID: PMC10715442 DOI: 10.1089/ars.2023.0350] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 05/28/2023] [Indexed: 07/29/2023]
Abstract
Significance: The remarkable geometry of the axon exposes it to unique challenges for survival and maintenance. Axonal degeneration is a feature of peripheral neuropathies, glaucoma, and traumatic brain injury, and an early event in neurodegenerative diseases. Since the discovery of Wallerian degeneration (WD), a molecular program that hijacks nicotinamide adenine dinucleotide (NAD+) metabolism for axonal self-destruction, the complex roles of NAD+ in axonal viability and disease have become research priority. Recent Advances: The discoveries of the protective Wallerian degeneration slow (WldS) and of sterile alpha and TIR motif containing 1 (SARM1) activation as the main instructive signal for WD have shed new light on the regulatory role of NAD+ in axonal degeneration in a growing number of neurological diseases. SARM1 has been characterized as a NAD+ hydrolase and sensor of NAD+ metabolism. The discovery of regulators of nicotinamide mononucleotide adenylyltransferase 2 (NMNAT2) proteostasis in axons, the allosteric regulation of SARM1 by NAD+ and NMN, and the existence of clinically relevant windows of action of these signals has opened new opportunities for therapeutic interventions, including SARM1 inhibitors and modulators of NAD+ metabolism. Critical Issues: Events upstream and downstream of SARM1 remain unclear. Furthermore, manipulating NAD+ metabolism, an overdetermined process crucial in cell survival, for preventing the degeneration of the injured axon may be difficult and potentially toxic. Future Directions: There is a need for clarification of the distinct roles of NAD+ metabolism in axonal maintenance as contrasted to WD. There is also a need to better understand the role of NAD+ metabolism in axonal endangerment in neuropathies, diseases of the white matter, and the early stages of neurodegenerative diseases of the central nervous system. Antioxid. Redox Signal. 39, 1167-1184.
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Affiliation(s)
| | - Vassilis E. Koliatsos
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Neurology, and Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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2
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Perron C, Carme P, Rosell AL, Minnaert E, Ruiz-Demoulin S, Szczkowski H, Neukomm LJ, Dura JM, Boulanger A. Chemokine-like Orion is involved in the transformation of glial cells into phagocytes in different developmental neuronal remodeling paradigms. Development 2023; 150:dev201633. [PMID: 37767633 PMCID: PMC10565233 DOI: 10.1242/dev.201633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023]
Abstract
During animal development, neurons often form exuberant or inappropriate axons and dendrites at early stages, followed by the refinement of neuronal circuits at late stages. Neural circuit refinement leads to the production of neuronal debris in the form of neuronal cell corpses, fragmented axons and dendrites, and pruned synapses requiring disposal. Glial cells act as predominant phagocytes during neuronal remodeling and degeneration, and crucial signaling pathways between neurons and glia are necessary for the execution of phagocytosis. Chemokine-like mushroom body neuron-secreted Orion is essential for astrocyte infiltration into the γ axon bundle leading to γ axon pruning. Here, we show a role of Orion in debris engulfment and phagocytosis in Drosophila. Interestingly, Orion is involved in the overall transformation of astrocytes into phagocytes. In addition, analysis of several neuronal paradigms demonstrates the role of Orion in eliminating both peptidergic vCrz+ and PDF-Tri neurons via additional phagocytic glial cells like cortex and/or ensheathing glia. Our results suggest that Orion is essential for phagocytic activation of astrocytes, cortex and ensheathing glia, and point to Orion as a trigger of glial infiltration, engulfment and phagocytosis.
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Affiliation(s)
| | - Pascal Carme
- IGH, Univ Montpellier, CNRS, Montpellier, France
| | - Arnau Llobet Rosell
- Department of Fundamental Neurosciences, University of Lausanne, 1005 Lausanne, Switzerland
| | - Eva Minnaert
- IGH, Univ Montpellier, CNRS, Montpellier, France
| | | | | | - Lukas Jakob Neukomm
- Department of Fundamental Neurosciences, University of Lausanne, 1005 Lausanne, Switzerland
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3
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Townsend LN, Clarke H, Maddison D, Jones KM, Amadio L, Jefferson A, Chughtai U, Bis DM, Züchner S, Allen ND, Van der Goes van Naters W, Peters OM, Smith GA. Cdk12 maintains the integrity of adult axons by suppressing actin remodeling. Cell Death Discov 2023; 9:348. [PMID: 37730761 PMCID: PMC10511712 DOI: 10.1038/s41420-023-01642-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 08/25/2023] [Accepted: 09/07/2023] [Indexed: 09/22/2023] Open
Abstract
The role of cyclin-dependent kinases (CDKs) that are ubiquitously expressed in the adult nervous system remains unclear. Cdk12 is enriched in terminally differentiated neurons where its conical role in the cell cycle progression is redundant. We find that in adult neurons Cdk12 acts a negative regulator of actin formation, mitochondrial dynamics and neuronal physiology. Cdk12 maintains the size of the axon at sites proximal to the cell body through the transcription of homeostatic enzymes in the 1-carbon by folate pathway which utilize the amino acid homocysteine. Loss of Cdk12 leads to elevated homocysteine and in turn leads to uncontrolled F-actin formation and axonal swelling. Actin remodeling further induces Drp1-dependent fission of mitochondria and the breakdown of axon-soma filtration barrier allowing soma restricted cargos to enter the axon. We demonstrate that Cdk12 is also an essential gene for long-term neuronal survival and loss of this gene causes age-dependent neurodegeneration. Hyperhomocysteinemia, actin changes, and mitochondrial fragmentation are associated with several neurodegenerative conditions such as Alzheimer's disease and we provide a candidate molecular pathway to link together such pathological events.
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Affiliation(s)
- L N Townsend
- School of Biosciences, Cardiff University, Cardiff, CF24 4HQ, UK
| | - H Clarke
- School of Medicine, Cardiff University, Cardiff, CF24 4HQ, UK
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - D Maddison
- School of Medicine, Cardiff University, Cardiff, CF24 4HQ, UK
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - K M Jones
- School of Biosciences, Cardiff University, Cardiff, CF24 4HQ, UK
| | - L Amadio
- School of Biosciences, Cardiff University, Cardiff, CF24 4HQ, UK
- School of Medicine, Cardiff University, Cardiff, CF24 4HQ, UK
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - A Jefferson
- School of Medicine, Cardiff University, Cardiff, CF24 4HQ, UK
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - U Chughtai
- School of Biosciences, Cardiff University, Cardiff, CF24 4HQ, UK
- School of Medicine, Cardiff University, Cardiff, CF24 4HQ, UK
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - D M Bis
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - S Züchner
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - N D Allen
- School of Biosciences, Cardiff University, Cardiff, CF24 4HQ, UK
| | | | - O M Peters
- School of Biosciences, Cardiff University, Cardiff, CF24 4HQ, UK
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - G A Smith
- School of Medicine, Cardiff University, Cardiff, CF24 4HQ, UK.
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK.
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4
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Maddison DC, Malik B, Amadio L, Bis-Brewer DM, Züchner S, Peters OM, Smith GA. COPI-regulated mitochondria-ER contact site formation maintains axonal integrity. Cell Rep 2023; 42:112883. [PMID: 37498742 PMCID: PMC10840514 DOI: 10.1016/j.celrep.2023.112883] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 06/05/2023] [Accepted: 07/12/2023] [Indexed: 07/29/2023] Open
Abstract
Coat protein complex I (COPI) is best known for its role in Golgi-endoplasmic reticulum (ER) trafficking, responsible for the retrograde transport of ER-resident proteins. The ER is crucial to neuronal function, regulating Ca2+ homeostasis and the distribution and function of other organelles such as endosomes, peroxisomes, and mitochondria via functional contact sites. Here we demonstrate that disruption of COPI results in mitochondrial dysfunction in Drosophila axons and human cells. The ER network is also disrupted, and the neurons undergo rapid degeneration. We demonstrate that mitochondria-ER contact sites (MERCS) are decreased in COPI-deficient axons, leading to Ca2+ dysregulation, heightened mitophagy, and a decrease in respiratory capacity. Reintroducing MERCS is sufficient to rescue not only mitochondrial distribution and Ca2+ uptake but also ER morphology, dramatically delaying neurodegeneration. This work demonstrates an important role for COPI-mediated trafficking in MERC formation, which is an essential process for maintaining axonal integrity.
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Affiliation(s)
- Daniel C Maddison
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK
| | - Bilal Malik
- UK Dementia Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Leonardo Amadio
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK; UK Dementia Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Dana M Bis-Brewer
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - Stephan Züchner
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - Owen M Peters
- UK Dementia Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Gaynor A Smith
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK.
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5
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Bhattacharya MRC. A nerve-wracking buzz: lessons from Drosophila models of peripheral neuropathy and axon degeneration. Front Aging Neurosci 2023; 15:1166146. [PMID: 37614471 PMCID: PMC10442544 DOI: 10.3389/fnagi.2023.1166146] [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: 02/14/2023] [Accepted: 07/24/2023] [Indexed: 08/25/2023] Open
Abstract
The degeneration of axons and their terminals occurs following traumatic, toxic, or genetically-induced insults. Common molecular mechanisms unite these disparate triggers to execute a conserved nerve degeneration cascade. In this review, we will discuss how models of peripheral nerve injury and neuropathy in Drosophila have led the way in advancing molecular understanding of axon degeneration and nerve injury pathways. Both neuron-intrinsic as well as glial responses to injury will be highlighted. Finally, we will offer perspective on what additional questions should be answered to advance these discoveries toward clinical interventions for patients with neuropathy.
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6
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Szabó Á, Vincze V, Chhatre AS, Jipa A, Bognár S, Varga KE, Banik P, Harmatos-Ürmösi A, Neukomm LJ, Juhász G. LC3-associated phagocytosis promotes glial degradation of axon debris after injury in Drosophila models. Nat Commun 2023; 14:3077. [PMID: 37248218 DOI: 10.1038/s41467-023-38755-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 05/09/2023] [Indexed: 05/31/2023] Open
Abstract
Glial engulfment of neuron-derived debris after trauma, during development, and in neurodegenerative diseases supports nervous system functions. However, mechanisms governing the efficiency of debris degradation in glia have remained largely unexplored. Here we show that LC3-associated phagocytosis (LAP), an engulfment pathway assisted by certain autophagy factors, promotes glial phagosome maturation in the Drosophila wing nerve. A LAP-specific subset of autophagy-related genes is required in glia for axon debris clearance, encoding members of the Atg8a (LC3) conjugation system and the Vps34 lipid kinase complex including UVRAG and Rubicon. Phagosomal Rubicon and Atg16 WD40 domain-dependent conjugation of Atg8a mediate proper breakdown of internalized axon fragments, and Rubicon overexpression in glia accelerates debris elimination. Finally, LAP promotes survival following traumatic brain injury. Our results reveal a role of glial LAP in the clearance of neuronal debris in vivo, with potential implications for the recovery of the injured nervous system.
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Affiliation(s)
- Áron Szabó
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary.
| | - Virág Vincze
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
| | - Aishwarya Sanjay Chhatre
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
- Doctoral School of Biology, University of Szeged, Szeged, Hungary
| | - András Jipa
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
| | - Sarolta Bognár
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
| | - Katalin Eszter Varga
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
| | - Poulami Banik
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
| | - Adél Harmatos-Ürmösi
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary
| | - Lukas J Neukomm
- Department of Fundamental Neurosciences, University of Lausanne, CH-1005, Lausanne, Switzerland
| | - Gábor Juhász
- Biological Research Center, Institute of Genetics, Eötvös Loránd Research Network (ELKH), Szeged, H-6726, Hungary.
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, H-1117, Hungary.
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7
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Ye C, Behnke JA, Hardin KR, Zheng JQ. Drosophila melanogaster as a model to study age and sex differences in brain injury and neurodegeneration after mild head trauma. Front Neurosci 2023; 17:1150694. [PMID: 37077318 PMCID: PMC10106652 DOI: 10.3389/fnins.2023.1150694] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 03/09/2023] [Indexed: 04/05/2023] Open
Abstract
Repetitive physical insults to the head, including those that elicit mild traumatic brain injury (mTBI), are a known risk factor for a variety of neurodegenerative conditions including Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although most individuals who sustain mTBI typically achieve a seemingly full recovery within a few weeks, a subset experience delayed-onset symptoms later in life. As most mTBI research has focused on the acute phase of injury, there is an incomplete understanding of mechanisms related to the late-life emergence of neurodegeneration after early exposure to mild head trauma. The recent adoption of Drosophila-based brain injury models provides several unique advantages over existing preclinical animal models, including a tractable framework amenable to high-throughput assays and short relative lifespan conducive to lifelong mechanistic investigation. The use of flies also provides an opportunity to investigate important risk factors associated with neurodegenerative conditions, specifically age and sex. In this review, we survey current literature that examines age and sex as contributing factors to head trauma-mediated neurodegeneration in humans and preclinical models, including mammalian and Drosophila models. We discuss similarities and disparities between human and fly in aging, sex differences, and pathophysiology. Finally, we highlight Drosophila as an effective tool for investigating mechanisms underlying head trauma-induced neurodegeneration and for identifying therapeutic targets for treatment and recovery.
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Affiliation(s)
- Changtian Ye
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Joseph A. Behnke
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Katherine R. Hardin
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - James Q. Zheng
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, United States
- Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA, United States
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8
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Karuparti S, Yeung AT, Wang B, Guicardi PF, Han C. A toolkit for converting Gal4 into LexA and Flippase transgenes in Drosophila. G3 (BETHESDA, MD.) 2023; 13:jkad003. [PMID: 36617215 PMCID: PMC9997562 DOI: 10.1093/g3journal/jkad003] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 10/01/2022] [Accepted: 01/02/2023] [Indexed: 01/09/2023]
Abstract
Drosophila has been a powerful model system for biological studies due to the wide range of genetic tools established for it. Among these tools, Gal4 is the most abundant, offering unparalleled tissue and developmental stage specificity for gene manipulation. In comparison, other genetic reagents are far fewer in choices. Here we present a genetic toolkit for converting Gal4 strains into LexA and Flippase transgenes through simple genetic crosses and fluorescence screening. We demonstrate the proof-of-principle by converting ten Gal4 lines that exhibit diverse tissue specificities and examined the activity patterns of the converted LexA and Flippase lines. Gal4-to-LexA and Flp conversion is fast and convenient and should greatly expand the choices of LexA and Flp for binary expression and FRT-based mosaic analysis, respectively, in Drosophila.
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Affiliation(s)
- Sasidhar Karuparti
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Ann T Yeung
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Bei Wang
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Pedro F Guicardi
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Chun Han
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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9
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Maddison DC, Mattedi F, Vagnoni A, Smith GA. Clonal Imaging of Mitochondria in the Dissected Fly Wing. Cold Spring Harb Protoc 2023; 2023:100-105. [PMID: 36180212 DOI: 10.1101/pdb.prot108051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Mitochondria are essential for long-term neuronal function and survival. They are maintained in neurons, including long axonal stretches, through dynamic processes such as fission, fusion, biogenesis, and mitophagy. Here, we describe a protocol for the in-depth morphological analysis of individual mitochondria in axons in vivo. Most mitochondrial analysis of axons is currently performed in vitro with neurons in a developmental state. Therefore, an understanding of the axonal mitochondrial network during aging in fully differentiated neurons and the long-term consequence of gene knockout is often not developed. By using a clonal system paired with fluorescent genetically encoded markers in the Drosophila wing, we can visualize individual neurons (out of the whole bundle), including their long axons and the mitochondria that they contain, using confocal imaging. The clonal system also allows visualization of neurons with genetic perturbations that would otherwise be lethal if present in the whole organism, allowing investigators to bypass lethality. This protocol can further be adapted to measure the physiological and biochemical state of the mitochondria. Mitochondrial morphology and health in axons are tightly linked to aging, axon injury, and neurodegeneration; therefore, this method can be used to investigate mitochondrial dysfunction associated with novel genes or those linked to neurodegenerative disease and axonopathy.
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Affiliation(s)
- Daniel C Maddison
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, United Kingdom
| | - Francesca Mattedi
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
| | - Alessio Vagnoni
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
| | - Gaynor Ann Smith
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, United Kingdom
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10
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Maddison DC, Mattedi F, Vagnoni A, Smith GA. Analysis of Mitochondrial Dynamics in Adult Drosophila Axons. Cold Spring Harb Protoc 2023; 2023:75-83. [PMID: 36180217 DOI: 10.1101/pdb.top107819] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Neuronal survival depends on the generation of ATP from an ever-changing mitochondrial network. This requires a fine balance between the constant degradation of damaged mitochondria, biogenesis of new mitochondria, movement along microtubules, dynamic processes, and adequate functional capacity to meet firing demands. The distribution of mitochondria needs to be tightly controlled throughout the entire neuron, including its projections. Axons in particular can be enormous structures compared to the size of the cell soma, and how mitochondria are maintained in these compartments is poorly defined. Mitochondrial dysfunction in neurons is associated with aging and neurodegenerative diseases, with the axon being preferentially vulnerable to destruction. Drosophila offer a unique way to study these organelles in fully differentiated adult neurons in vivo. Here, we briefly review the regulation of neuronal mitochondria in health, aging, and disease and introduce two methodological approaches to study mitochondrial dynamics and transport in axons using the Drosophila wing system.
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Affiliation(s)
- Daniel C Maddison
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, United Kingdom
| | - Francesca Mattedi
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
| | - Alessio Vagnoni
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
| | - Gaynor Ann Smith
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, United Kingdom
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11
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Lassetter AP, Corty MM, Barria R, Sheehan AE, Hill JQ, Aicher SA, Fox AN, Freeman MR. Glial TGFβ activity promotes neuron survival in peripheral nerves. J Cell Biol 2023; 222:e202111053. [PMID: 36399182 PMCID: PMC9679965 DOI: 10.1083/jcb.202111053] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 09/06/2022] [Accepted: 10/26/2022] [Indexed: 11/19/2022] Open
Abstract
Maintaining long, energetically demanding axons throughout the life of an animal is a major challenge for the nervous system. Specialized glia ensheathe axons and support their function and integrity throughout life, but glial support mechanisms remain poorly defined. Here, we identified a collection of secreted and transmembrane molecules required in glia for long-term axon survival in vivo. We showed that the majority of components of the TGFβ superfamily are required in glia for sensory neuron maintenance but not glial ensheathment of axons. In the absence of glial TGFβ signaling, neurons undergo age-dependent degeneration that can be rescued either by genetic blockade of Wallerian degeneration or caspase-dependent death. Blockade of glial TGFβ signaling results in increased ATP in glia that can be mimicked by enhancing glial mitochondrial biogenesis or suppressing glial monocarboxylate transporter function. We propose that glial TGFβ signaling supports axon survival and suppresses neurodegeneration through promoting glial metabolic support of neurons.
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Affiliation(s)
| | - Megan M. Corty
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Romina Barria
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Amy E. Sheehan
- Vollum Institute, Oregon Health & Science University, Portland, OR
| | - Jo Q. Hill
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR
| | - Sue A. Aicher
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR
| | - A. Nicole Fox
- University of Massachusetts Medical School, Worcester, MA
| | - Marc R. Freeman
- Vollum Institute, Oregon Health & Science University, Portland, OR
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12
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Nitta Y, Sugie A. Studies of neurodegenerative diseases using Drosophila and the development of novel approaches for their analysis. Fly (Austin) 2022; 16:275-298. [PMID: 35765969 PMCID: PMC9336468 DOI: 10.1080/19336934.2022.2087484] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
The use of Drosophila in neurodegenerative disease research has contributed to the identification of modifier genes for the pathology. The basis for neurodegenerative disease occurrence in Drosophila is the conservation of genes across species and the ability to perform rapid genetic analysis using a compact brain. Genetic findings previously discovered in Drosophila can reveal molecular pathologies involved in human neurological diseases in later years. Disease models using Drosophila began to be generated during the development of genetic engineering. In recent years, results of reverse translational research using Drosophila have been reported. In this review, we discuss research on neurodegenerative diseases; moreover, we introduce various methods for quantifying neurodegeneration in Drosophila.
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Affiliation(s)
- Yohei Nitta
- Brain Research Institute, Niigata University, Niigata, Japan
| | - Atsushi Sugie
- Brain Research Institute, Niigata University, Niigata, Japan,CONTACT Atsushi Sugie Brain Research Institute, Niigata University, Niigata, Japan
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13
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Corty MM, Hulegaard AL, Hill JQ, Sheehan AE, Aicher SA, Freeman MR. Discoidin domain receptor regulates ensheathment, survival and caliber of peripheral axons. Development 2022; 149:281293. [PMID: 36355066 PMCID: PMC10112903 DOI: 10.1242/dev.200636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 10/27/2022] [Indexed: 11/12/2022]
Abstract
Most invertebrate axons and small-caliber axons in mammalian peripheral nerves are unmyelinated but still ensheathed by glia. Here, we use Drosophila wrapping glia to study the development and function of non-myelinating axon ensheathment, which is poorly understood. Selective ablation of these glia from peripheral nerves severely impaired larval locomotor behavior. In an in vivo RNA interference screen to identify glial genes required for axon ensheathment, we identified the conserved receptor tyrosine kinase Discoidin domain receptor (Ddr). In larval peripheral nerves, loss of Ddr resulted in severely reduced ensheathment of axons and reduced axon caliber, and we found a strong dominant genetic interaction between Ddr and the type XV/XVIII collagen Multiplexin (Mp), suggesting that Ddr functions as a collagen receptor to drive axon wrapping. In adult nerves, loss of Ddr decreased long-term survival of sensory neurons and significantly reduced axon caliber without overtly affecting ensheathment. Our data establish essential roles for non-myelinating glia in nerve development, maintenance and function, and identify Ddr as a key regulator of axon-glia interactions during ensheathment and establishment of axon caliber.
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Affiliation(s)
- Megan M Corty
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | | | - Jo Q Hill
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR 97239, USA
| | - Amy E Sheehan
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Sue A Aicher
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR 97239, USA
| | - Marc R Freeman
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
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14
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Herrmann KA, Liu Y, Llobet-Rosell A, McLaughlin CN, Neukomm LJ, Coutinho-Budd JC, Broihier HT. Divergent signaling requirements of dSARM in injury-induced degeneration and developmental glial phagocytosis. PLoS Genet 2022; 18:e1010257. [PMID: 35737721 PMCID: PMC9223396 DOI: 10.1371/journal.pgen.1010257] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 05/13/2022] [Indexed: 02/06/2023] Open
Abstract
Elucidating signal transduction mechanisms of innate immune pathways is essential to defining how they elicit distinct cellular responses. Toll-like receptors (TLR) signal through their cytoplasmic TIR domains which bind other TIR domain-containing adaptors. dSARM/SARM1 is one such TIR domain adaptor best known for its role as the central axon degeneration trigger after injury. In degeneration, SARM1's domains have been assigned unique functions: the ARM domain is auto-inhibitory, SAM-SAM domain interactions mediate multimerization, and the TIR domain has intrinsic NAD+ hydrolase activity that precipitates axonal demise. Whether and how these distinct functions contribute to TLR signaling is unknown. Here we show divergent signaling requirements for dSARM in injury-induced axon degeneration and TLR-mediated developmental glial phagocytosis through analysis of new knock-in domain and point mutations. We demonstrate intragenic complementation between reciprocal pairs of domain mutants during development, providing evidence for separability of dSARM functional domains in TLR signaling. Surprisingly, dSARM's NAD+ hydrolase activity is strictly required for both degenerative and developmental signaling, demonstrating that TLR signal transduction requires dSARM's enzymatic activity. In contrast, while SAM domain-mediated dSARM multimerization is important for axon degeneration, it is dispensable for TLR signaling. Finally, dSARM functions in a linear genetic pathway with the MAP3K Ask1 during development but not in degenerating axons. Thus, we propose that dSARM exists in distinct signaling states in developmental and pathological contexts.
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Affiliation(s)
- Kelsey A. Herrmann
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Yizhou Liu
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Arnau Llobet-Rosell
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Colleen N. McLaughlin
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Lukas J. Neukomm
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Jaeda C. Coutinho-Budd
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia, United States of America
| | - Heather T. Broihier
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
- * E-mail:
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15
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Boulanger A, Dura JM. Neuron-glia crosstalk in neuronal remodeling and degeneration: Neuronal signals inducing glial cell phagocytic transformation in Drosophila. Bioessays 2022; 44:e2100254. [PMID: 35315125 DOI: 10.1002/bies.202100254] [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: 10/25/2021] [Revised: 03/04/2022] [Accepted: 03/07/2022] [Indexed: 11/09/2022]
Abstract
Neuronal remodeling is a conserved mechanism that eliminates unwanted neurites and can include the loss of cell bodies. In these processes, a key role for glial cells in events from synaptic pruning to neuron elimination has been clearly identified in the last decades. Signals sent from dying neurons or neurites to be removed are received by appropriate glial cells. After receiving these signals, glial cells infiltrate degenerating sites and then, engulf and clear neuronal debris through phagocytic mechanisms. There are few identified or proposed signals and receptors involved in neuron-glia crosstalk, which induces the transformation of glial cells to phagocytes during neuronal remodeling in Drosophila. Many of these signaling pathways are conserved in mammals. Here, we particularly emphasize the role of Orion, a recently identified neuronal CX3 C chemokine-like secreted protein, which induces astrocyte infiltration and engulfment during mushroom body neuronal remodeling. Although, chemokine signaling was not described previously in insects we propose that chemokine-like involvement in neuron/glial cell interaction is an evolutionarily ancient mechanism.
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Affiliation(s)
- Ana Boulanger
- IGH, Université de Montpellier, CNRS, Montpellier, France
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16
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Mattedi F, Chennell G, Vagnoni A. Detailed Imaging of Mitochondrial Transport and Precise Manipulation of Mitochondrial Function with Genetically Encoded Photosensitizers in Adult Drosophila Neurons. Methods Mol Biol 2022; 2431:385-407. [PMID: 35412288 DOI: 10.1007/978-1-0716-1990-2_20] [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] [Indexed: 10/18/2022]
Abstract
Precise distribution of mitochondria is essential for maintaining neuronal homeostasis. Although detailed mechanisms governing the transport of mitochondria have emerged, it is still poorly understood how the regulation of transport is coordinated in space and time within the physiological context of an organism. How alteration in mitochondrial functionality may trigger changes in organellar dynamics also remains unclear in this context. Therefore, the use of genetically encoded tools to perturb mitochondrial functionality in real time would be desirable. Here we describe methods to interfere with mitochondrial function with high spatiotemporal precision with the use of photosensitizers in vivo in the intact wing nerve of adult Drosophila. We also provide details on how to visualize the transport of mitochondria and to improve the quality of the imaging to attain super-resolution in this tissue.
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Affiliation(s)
- Francesca Mattedi
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - George Chennell
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- Wohl Cellular Imaging Centre, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Alessio Vagnoni
- Department of Basic and Clinical Neurosciences, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
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17
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Llobet Rosell A, Paglione M, Gilley J, Kocia M, Perillo G, Gasparrini M, Cialabrini L, Raffaelli N, Angeletti C, Orsomando G, Wu PH, Coleman MP, Loreto A, Neukomm LJ. The NAD + precursor NMN activates dSarm to trigger axon degeneration in Drosophila. eLife 2022; 11:80245. [PMID: 36476387 PMCID: PMC9788811 DOI: 10.7554/elife.80245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 12/06/2022] [Indexed: 12/12/2022] Open
Abstract
Axon degeneration contributes to the disruption of neuronal circuit function in diseased and injured nervous systems. Severed axons degenerate following the activation of an evolutionarily conserved signaling pathway, which culminates in the activation of SARM1 in mammals to execute the pathological depletion of the metabolite NAD+. SARM1 NADase activity is activated by the NAD+ precursor nicotinamide mononucleotide (NMN). In mammals, keeping NMN levels low potently preserves axons after injury. However, it remains unclear whether NMN is also a key mediator of axon degeneration and dSarm activation in flies. Here, we demonstrate that lowering NMN levels in Drosophila through the expression of a newly generated prokaryotic NMN-Deamidase (NMN-D) preserves severed axons for months and keeps them circuit-integrated for weeks. NMN-D alters the NAD+ metabolic flux by lowering NMN, while NAD+ remains unchanged in vivo. Increased NMN synthesis by the expression of mouse nicotinamide phosphoribosyltransferase (mNAMPT) leads to faster axon degeneration after injury. We also show that NMN-induced activation of dSarm mediates axon degeneration in vivo. Finally, NMN-D delays neurodegeneration caused by loss of the sole NMN-consuming and NAD+-synthesizing enzyme dNmnat. Our results reveal a critical role for NMN in neurodegeneration in the fly, which extends beyond axonal injury. The potent neuroprotection by reducing NMN levels is similar to the interference with other essential mediators of axon degeneration in Drosophila.
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Affiliation(s)
- Arnau Llobet Rosell
- Department of Fundamental Neurosciences, University of LausanneLausanneSwitzerland
| | - Maria Paglione
- Department of Fundamental Neurosciences, University of LausanneLausanneSwitzerland
| | - Jonathan Gilley
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of CambridgeCambridgeUnited Kingdom
| | - Magdalena Kocia
- Department of Fundamental Neurosciences, University of LausanneLausanneSwitzerland
| | - Giulia Perillo
- Department of Genetic Medicine and Development, University of GenevaGenevaSwitzerland
| | - Massimiliano Gasparrini
- Department of Agricultural, Food and Environmental Sciences, Polytechnic University of MarcheAnconaItaly
| | - Lucia Cialabrini
- Department of Agricultural, Food and Environmental Sciences, Polytechnic University of MarcheAnconaItaly
| | - Nadia Raffaelli
- Department of Agricultural, Food and Environmental Sciences, Polytechnic University of MarcheAnconaItaly
| | - Carlo Angeletti
- Department of Clinical Sciences, Section of Biochemistry, Polytechnic University of MarcheAnconaItaly
| | - Giuseppe Orsomando
- Department of Clinical Sciences, Section of Biochemistry, Polytechnic University of MarcheAnconaItaly
| | - Pei-Hsuan Wu
- Department of Genetic Medicine and Development, University of GenevaGenevaSwitzerland
| | - Michael P Coleman
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of CambridgeCambridgeUnited Kingdom
| | - Andrea Loreto
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of CambridgeCambridgeUnited Kingdom
| | - Lukas Jakob Neukomm
- Department of Fundamental Neurosciences, University of LausanneLausanneSwitzerland
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18
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An ELISA-based method for rapid genetic screens in Drosophila. Proc Natl Acad Sci U S A 2021; 118:2107427118. [PMID: 34686600 DOI: 10.1073/pnas.2107427118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/08/2021] [Indexed: 11/18/2022] Open
Abstract
Drosophila is a powerful model in which to perform genetic screens, but screening assays that are both rapid and can be used to examine a wide variety of cellular and molecular pathways are limited. Drosophila offer an extensive toolbox of GFP-based transcriptional reporters, GFP-tagged proteins, and driver lines, which can be used to express GFP in numerous subpopulations of cells. Thus, a tool that can rapidly and quantitatively evaluate GFP levels in Drosophila tissue would provide a broadly applicable screening platform. We developed a GFP-based enzyme-linked immunosorbent assay (ELISA) that can detect GFP in Drosophila lysates collected from whole animals and dissected tissues across all stages of Drosophila development. We demonstrate that this assay can detect membrane-localized GFP in a variety of neuronal and glial populations and validate that it can identify genes that change the morphology of these cells, as well as changes in STAT and JNK transcriptional activity. We found that this assay can detect endogenously GFP-tagged proteins, including Draper, Cryptochrome, and the synaptic marker Brp. This approach is able to detect changes in Brp-GFP signal during developmental synaptic remodeling, and known genetic regulators of glial synaptic engulfment could be identified using this ELISA method. Finally, we used the assay to perform a small-scale screen, which identified Syntaxins as potential regulators of astrocyte-mediated synapse elimination. Together, these studies establish an ELISA as a rapid, easy, and quantitative in vivo screening method that can be used to assay a wide breadth of fundamental biological questions.
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19
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Abstract
There is a tight association between mitochondrial dysfunction and neurodegenerative diseases and axons that are particularly vulnerable to degeneration, but how mitochondria are maintained in axons to support their physiology remains poorly defined. In an in vivo forward genetic screen for mutants altering axonal mitochondria, we identified tsg101 Neurons mutant for tsg101 exhibited an increase in mitochondrial number and decrease in mitochondrial size. TSG101 is best known as a component of the endosomal sorting complexes required for transport (ESCRT) complexes; however, loss of most other ESCRT components did not affect mitochondrial numbers or size, suggesting TSG101 regulates mitochondrial biology in a noncanonical, ESCRT-independent manner. The TSG101-mutant phenotype was not caused by lack of mitophagy, and we found that autophagy blockade was detrimental only to the mitochondria in the cell bodies, arguing mitophagy and autophagy are dispensable for the regulation of mitochondria number in axons. Interestingly, TSG101 mitochondrial phenotypes were instead caused by activation of PGC-1ɑ/Nrf2-dependent mitochondrial biogenesis, which was mTOR independent and TFEB dependent and required the mitochondrial fission-fusion machinery. Our work identifies a role for TSG101 in inhibiting mitochondrial biogenesis, which is essential for the maintenance of mitochondrial numbers and sizes, in the axonal compartment.
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20
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Behnke JA, Ye C, Setty A, Moberg KH, Zheng JQ. Repetitive mild head trauma induces activity mediated lifelong brain deficits in a novel Drosophila model. Sci Rep 2021; 11:9738. [PMID: 33958652 PMCID: PMC8102574 DOI: 10.1038/s41598-021-89121-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 04/21/2021] [Indexed: 02/08/2023] Open
Abstract
Mild head trauma, including concussion, can lead to chronic brain dysfunction and degeneration but the underlying mechanisms remain poorly understood. Here, we developed a novel head impact system to investigate the long-term effects of mild head trauma on brain structure and function, as well as the underlying mechanisms in Drosophila melanogaster. We find that Drosophila subjected to repetitive head impacts develop long-term deficits, including impaired startle-induced climbing, progressive brain degeneration, and shortened lifespan, all of which are substantially exacerbated in female flies. Interestingly, head impacts elicit an elevation in neuronal activity and its acute suppression abrogates the detrimental effects in female flies. Together, our findings validate Drosophila as a suitable model system for investigating the long-term effects of mild head trauma, suggest an increased vulnerability to brain injury in female flies, and indicate that early altered neuronal excitability may be a key mechanism linking mild brain trauma to chronic degeneration.
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Affiliation(s)
- Joseph A Behnke
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Changtian Ye
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Aayush Setty
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Kenneth H Moberg
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - James Q Zheng
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
- Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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21
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Shahid SS, Kerskens CM, Burrows M, Witney AG. Elucidating the complex organization of neural micro-domains in the locust Schistocerca gregaria using dMRI. Sci Rep 2021; 11:3418. [PMID: 33564031 PMCID: PMC7873062 DOI: 10.1038/s41598-021-82187-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 01/13/2021] [Indexed: 01/30/2023] Open
Abstract
To understand brain function it is necessary to characterize both the underlying structural connectivity between neurons and the physiological integrity of these connections. Previous research exploring insect brain connectivity has typically used electron microscopy techniques, but this methodology cannot be applied to living animals and so cannot be used to understand dynamic physiological processes. The relatively large brain of the desert locust, Schistercera gregaria (Forksȧl) is ideal for exploring a novel methodology; micro diffusion magnetic resonance imaging (micro-dMRI) for the characterization of neuronal connectivity in an insect brain. The diffusion-weighted imaging (DWI) data were acquired on a preclinical system using a customised multi-shell diffusion MRI scheme optimized to image the locust brain. Endogenous imaging contrasts from the averaged DWIs and Diffusion Kurtosis Imaging (DKI) scheme were applied to classify various anatomical features and diffusion patterns in neuropils, respectively. The application of micro-dMRI modelling to the locust brain provides a novel means of identifying anatomical regions and inferring connectivity of large tracts in an insect brain. Furthermore, quantitative imaging indices derived from the kurtosis model that include fractional anisotropy (FA), mean diffusivity (MD) and kurtosis anisotropy (KA) can be extracted. These metrics could, in future, be used to quantify longitudinal structural changes in the nervous system of the locust brain that occur due to environmental stressors or ageing.
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Affiliation(s)
- Syed Salman Shahid
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Christian M Kerskens
- Trinity College Institute of Neuroscience, Trinity Centre for Biomedical Engineering, School of Medicine, Trinity College Dublin, Dublin 2, Ireland
| | - Malcolm Burrows
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Alice G Witney
- Department of Physiology, School of Medicine, Trinity Biomedical Sciences Institute, Trinity Centre for Biomedical Engineering, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland.
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22
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Hsu JM, Kang Y, Corty MM, Mathieson D, Peters OM, Freeman MR. Injury-Induced Inhibition of Bystander Neurons Requires dSarm and Signaling from Glia. Neuron 2021; 109:473-487.e5. [PMID: 33296670 PMCID: PMC7864878 DOI: 10.1016/j.neuron.2020.11.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 09/28/2020] [Accepted: 11/13/2020] [Indexed: 12/12/2022]
Abstract
Nervous system injury and disease have broad effects on the functional connectivity of the nervous system, but how injury signals are spread across neural circuits remains unclear. We explored how axotomy changes the physiology of severed axons and adjacent uninjured "bystander" neurons in a simple in vivo nerve preparation. Within hours after injury, we observed suppression of axon transport in all axons, whether injured or not, and decreased mechano- and chemosensory signal transduction in uninjured bystander neurons. Unexpectedly, we found the axon death molecule dSarm, but not its NAD+ hydrolase activity, was required cell autonomously for these early changes in neuronal cell biology in bystander neurons, as were the voltage-gated calcium channel Cacophony (Cac) and the mitogen-activated protein kinase (MAPK) signaling cascade. Bystander neurons functionally recovered at later time points, while severed axons degenerated via α/Armadillo/Toll-interleukin receptor homology domain (dSarm)/Axundead signaling, and independently of Cac/MAPK. Interestingly, suppression of bystander neuron function required Draper/MEGF10 signaling in glia, indicating glial cells spread injury signals and actively suppress bystander neuron function. Our work identifies a new role for dSarm and glia in suppression of bystander neuron function after injury and defines two genetically and temporally separable phases of dSarm signaling in the injured nervous system.
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Affiliation(s)
- Jiun-Min Hsu
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Yunsik Kang
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Megan M Corty
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Danielle Mathieson
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Owen M Peters
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Marc R Freeman
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA.
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23
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Inducing different severities of traumatic brain injury in Drosophila using a piezoelectric actuator. Nat Protoc 2020; 16:263-282. [PMID: 33277631 DOI: 10.1038/s41596-020-00415-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 09/21/2020] [Indexed: 12/14/2022]
Abstract
Drosophila models have been instrumental in providing insights into molecular mechanisms of neurodegeneration, with wide application to human disease. The brain degeneration associated with traumatic brain injury (TBI) has been modeled in Drosophila using devices that inflict trauma on multiple parts of the fly body, including the head. However, the injuries produced by these models are not specific in location and are inconsistent between individual animals. We have recently developed a device that can be used to inflict controlled head injury to flies, resulting in physiological responses that are remarkably similar to those observed in humans with TBI. This protocol describes the construction, calibration and use of the Drosophila TBI (dTBI) device, a platform that employs a piezoelectric actuator to reproducibly deliver a force in order to briefly compress the fly head against a metal surface. The extent of head compression can be controlled through an electrical circuit, allowing the operator to set different levels of injury. The entire device can be assembled and calibrated in under a week. The device components and the necessary electrical tools are readily available and cost ~$800. The dTBI device can be used to harness the power of Drosophila genetics and perform large-scale genetic or pharmacological screens, using a 7-d post-injury survival curve to identify modifiers of injury.
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24
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Axon Degeneration: Which Method to Choose? Methods Mol Biol 2020. [PMID: 32524468 DOI: 10.1007/978-1-0716-0585-1_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Axons are diverse. They have different lengths, different branching patterns, and different biological roles. Methods to study axon degeneration are also diverse. The result is a bewildering range of experimental systems in which to study mechanisms of axon degeneration, and it is difficult to extrapolate from one neuron type and one method to another. The purpose of this chapter is to help readers to do this and to choose the methods most appropriate for answering their particular research question.
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25
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Models of Axon Degeneration in Drosophila Larvae. Methods Mol Biol 2020. [PMID: 32524490 DOI: 10.1007/978-1-0716-0585-1_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
The fruit fly Drosophila melanogaster has been a powerful model to study axonal biology including axon degeneration and regeneration (Brace et al., J Neurosci 34:8398-8410, 2014; Valakh et al. J Neurosci 33:17863-17,873, 2013; Xiong and Collins J Neurosci 32:610-615, 2012; Xiong et al. 191:211-223, 2010). Both adult and larval injury models have been developed in the fruit fly. This chapter focuses on in vivo and ex vivo methods developed for studying axon degeneration in Drosophila larvae. Additional models have been developed in the adult fly including injury models of olfactory receptor neurons in the brain and a model of axonal degeneration of sensory axons in the wing (Fang and Bonini, Annu Rev. Cell Dev Biol 28:575-597, 2012; Hoopfer et al. Neuron 50:883-895, 2006; Neukomm et al. Proc Natl Acad Sci U S A 111:9965-9970, 2014).
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26
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Hill CS, Sreedharan J, Loreto A, Menon DK, Coleman MP. Loss of highwire Protects Against the Deleterious Effects of Traumatic Brain Injury in Drosophila Melanogaster. Front Neurol 2020; 11:401. [PMID: 32477254 PMCID: PMC7235382 DOI: 10.3389/fneur.2020.00401] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 04/17/2020] [Indexed: 12/22/2022] Open
Abstract
Traumatic brain injury is a major global cause of death and disability. Axonal injury is a major underlying mechanism of TBI and could represent a major therapeutic target. We provide evidence that targeting the axonal death pathway known as Wallerian degeneration improves outcome in a Drosophila Melanogaster model of high impact trauma. This cell-autonomous neurodegenerative pathway is initiated following axon injury, and in Drosophila, involves activity of the E3 ubiquitin ligase highwire. We demonstrate that a loss-of-function mutation in the highwire gene rescues deleterious effects of a traumatic injury, including-improved functional outcomes, lifespan, survival of dopaminergic neurons, and retention of synaptic proteins. This data suggests that highwire represents a potential therapeutic target in traumatic injury.
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Affiliation(s)
- Ciaran S. Hill
- John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
- The Babraham Institute, Cambridge, United Kingdom
| | - Jemeen Sreedharan
- The Babraham Institute, Cambridge, United Kingdom
- Institute of Psychiatry, King's College London, London, United Kingdom
| | - Andrea Loreto
- John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
| | - David K. Menon
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
- Department of Clinical Neurosciences, Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom
| | - Michael P. Coleman
- John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
- The Babraham Institute, Cambridge, United Kingdom
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27
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Bolus H, Crocker K, Boekhoff-Falk G, Chtarbanova S. Modeling Neurodegenerative Disorders in Drosophila melanogaster. Int J Mol Sci 2020; 21:E3055. [PMID: 32357532 PMCID: PMC7246467 DOI: 10.3390/ijms21093055] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/14/2020] [Accepted: 04/21/2020] [Indexed: 12/12/2022] Open
Abstract
Drosophila melanogaster provides a powerful genetic model system in which to investigate the molecular mechanisms underlying neurodegenerative diseases. In this review, we discuss recent progress in Drosophila modeling Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis (ALS), Huntington's Disease, Ataxia Telangiectasia, and neurodegeneration related to mitochondrial dysfunction or traumatic brain injury. We close by discussing recent progress using Drosophila models of neural regeneration and how these are likely to provide critical insights into future treatments for neurodegenerative disorders.
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Affiliation(s)
- Harris Bolus
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA;
| | - Kassi Crocker
- Genetics Graduate Training Program, School of Medicine and Public Health, University of Wisconsin–Madison, Madison, WI 53705, USA;
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin–Madison, Madison, WI 53705, USA
| | - Grace Boekhoff-Falk
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin–Madison, Madison, WI 53705, USA
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28
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Llobet Rosell A, Neukomm LJ. Axon death signalling in Wallerian degeneration among species and in disease. Open Biol 2019; 9:190118. [PMID: 31455157 PMCID: PMC6731592 DOI: 10.1098/rsob.190118] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Axon loss is a shared feature of nervous systems being challenged in neurological disease, by chemotherapy or mechanical force. Axons take up the vast majority of the neuronal volume, thus numerous axonal intrinsic and glial extrinsic support mechanisms have evolved to promote lifelong axonal survival. Impaired support leads to axon degeneration, yet underlying intrinsic signalling cascades actively promoting the disassembly of axons remain poorly understood in any context, making the development to attenuate axon degeneration challenging. Wallerian degeneration serves as a simple model to study how axons undergo injury-induced axon degeneration (axon death). Severed axons actively execute their own destruction through an evolutionarily conserved axon death signalling cascade. This pathway is also activated in the absence of injury in diseased and challenged nervous systems. Gaining insights into mechanisms underlying axon death signalling could therefore help to define targets to block axon loss. Herein, we summarize features of axon death at the molecular and subcellular level. Recently identified and characterized mediators of axon death signalling are comprehensively discussed in detail, and commonalities and differences across species highlighted. We conclude with a summary of engaged axon death signalling in humans and animal models of neurological conditions. Thus, gaining mechanistic insights into axon death signalling broadens our understanding beyond a simple injury model. It harbours the potential to define targets for therapeutic intervention in a broad range of human axonopathies.
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Affiliation(s)
- Arnau Llobet Rosell
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, VD, Switzerland
| | - Lukas J Neukomm
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, VD, Switzerland
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29
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Smith GA, Lin TH, Sheehan AE, Van der Goes van Naters W, Neukomm LJ, Graves HK, Bis-Brewer DM, Züchner S, Freeman MR. Glutathione S-Transferase Regulates Mitochondrial Populations in Axons through Increased Glutathione Oxidation. Neuron 2019; 103:52-65.e6. [PMID: 31101394 PMCID: PMC6616599 DOI: 10.1016/j.neuron.2019.04.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 12/13/2018] [Accepted: 04/10/2019] [Indexed: 01/14/2023]
Abstract
Mitochondria are essential in long axons to provide metabolic support and sustain neuron integrity. A healthy mitochondrial pool is maintained by biogenesis, transport, mitophagy, fission, and fusion, but how these events are regulated in axons is not well defined. Here, we show that the Drosophila glutathione S-transferase (GST) Gfzf prevents mitochondrial hyperfusion in axons. Gfzf loss altered redox balance between glutathione (GSH) and oxidized glutathione (GSSG) and initiated mitochondrial fusion through the coordinated action of Mfn and Opa1. Gfzf functioned epistatically with the thioredoxin peroxidase Jafrac1 and the thioredoxin reductase 1 TrxR-1 to regulate mitochondrial dynamics. Altering GSH:GSSG ratios in mouse primary neurons in vitro also induced hyperfusion. Mitochondrial changes caused deficits in trafficking, the metabolome, and neuronal physiology. Changes in GSH and oxidative state are associated with neurodegenerative diseases like Alzheimer's. Our demonstration that GSTs are key in vivo regulators of axonal mitochondrial length and number provides a potential mechanistic link.
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Affiliation(s)
- Gaynor A Smith
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK.
| | - Tzu-Huai Lin
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Amy E Sheehan
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | | | - Lukas J Neukomm
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Department of Fundamental Neurosciences, University of Lausanne, 1005 Lausanne VD, Switzerland
| | - Hillary K Graves
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Dana M Bis-Brewer
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - Stephan Züchner
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - Marc R Freeman
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
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30
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Sapar ML, Han C. Die in pieces: How Drosophila sheds light on neurite degeneration and clearance. J Genet Genomics 2019; 46:187-199. [PMID: 31080046 DOI: 10.1016/j.jgg.2019.03.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 03/24/2019] [Accepted: 03/26/2019] [Indexed: 01/08/2023]
Abstract
Dendrites and axons are delicate neuronal membrane extensions that undergo degeneration after physical injuries. In neurodegenerative diseases, they often degenerate prior to neuronal death. Understanding the mechanisms of neurite degeneration has been an intense focus of neurobiology research in the last two decades. As a result, many discoveries have been made in the molecular pathways that lead to neurite degeneration and the cell-cell interactions responsible for the subsequent clearance of neuronal debris. Drosophila melanogaster has served as a prime in vivo model system for identifying and characterizing the key molecular players in neurite degeneration, thanks to its genetic tractability and easy access to its nervous system. The knowledge learned in the fly provided targets and fuel for studies in other model systems that have further enhanced our understanding of neurodegeneration. In this review, we will introduce the experimental systems developed in Drosophila to investigate injury-induced neurite degeneration, and then discuss the biological pathways that drive degeneration. We will also cover what is known about the mechanisms of how phagocytes recognize and clear degenerating neurites, and how recent findings in this area enhance our understanding of neurodegenerative disease pathology.
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Affiliation(s)
- Maria L Sapar
- Weill Institute for Cell and Molecular Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Chun Han
- Weill Institute for Cell and Molecular Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA.
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31
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Peters OM, Lewis EA, Osterloh JM, Weiss A, Salameh JS, Metterville J, Brown RH, Freeman MR. Loss of Sarm1 does not suppress motor neuron degeneration in the SOD1G93A mouse model of amyotrophic lateral sclerosis. Hum Mol Genet 2019; 27:3761-3771. [PMID: 30010873 PMCID: PMC6196650 DOI: 10.1093/hmg/ddy260] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/09/2018] [Indexed: 12/14/2022] Open
Abstract
Axon degeneration occurs in all neurodegenerative diseases, but the molecular pathways regulating axon destruction during neurodegeneration are poorly understood. Sterile Alpha and TIR Motif Containing 1 (Sarm1) is an essential component of the prodegenerative pathway driving axon degeneration after axotomy and represents an appealing target for therapeutic intervention in neurological conditions involving axon loss. Amyotrophic lateral sclerosis (ALS) is characterized by rapid, progressive motor neuron degeneration and muscle atrophy, causing paralysis and death. Patient tissue and animal models of ALS show destruction of upper and lower motor neuron cell bodies and loss of their associated axons. Here, we investigate whether loss of Sarm1 can mitigate motor neuron degeneration in the SOD1G93A mouse model of ALS. We found no change in survival, behavioral, electrophysiogical or histopathological outcomes in SOD1G93A mice null for Sarm1. Blocking Sarm1-mediated axon destruction alone is therefore not sufficient to suppress SOD1G93A-induced neurodegeneration. Our data suggest the molecular pathways driving axon loss in ALS may be Sarm1-independent or involve genetic pathways that act in a redundant fashion with Sarm1.
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Affiliation(s)
- Owen M Peters
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Elizabeth A Lewis
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jeannette M Osterloh
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Alexandra Weiss
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Johnny S Salameh
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jake Metterville
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Robert H Brown
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Marc R Freeman
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
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32
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Deal SL, Yamamoto S. Unraveling Novel Mechanisms of Neurodegeneration Through a Large-Scale Forward Genetic Screen in Drosophila. Front Genet 2019; 9:700. [PMID: 30693015 PMCID: PMC6339878 DOI: 10.3389/fgene.2018.00700] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Accepted: 12/13/2018] [Indexed: 01/04/2023] Open
Abstract
Neurodegeneration is characterized by progressive loss of neurons. Genetic and environmental factors both contribute to demise of neurons, leading to diverse devastating cognitive and motor disorders, including Alzheimer's and Parkinson's diseases in humans. Over the past few decades, the fruit fly, Drosophila melanogaster, has become an integral tool to understand the molecular, cellular and genetic mechanisms underlying neurodegeneration. Extensive tools and sophisticated technologies allow Drosophila geneticists to identify and study evolutionarily conserved genes that are essential for neural maintenance. In this review, we will focus on a large-scale mosaic forward genetic screen on the fly X-chromosome that led to the identification of a number of essential genes that exhibit neurodegenerative phenotypes when mutated. Most genes identified from this screen are evolutionarily conserved and many have been linked to human diseases with neurological presentations. Systematic electrophysiological and ultrastructural characterization of mutant tissue in the context of the Drosophila visual system, followed by a series of experiments to understand the mechanism of neurodegeneration in each mutant led to the discovery of novel molecular pathways that are required for neuronal integrity. Defects in mitochondrial function, lipid and iron metabolism, protein trafficking and autophagy are recurrent themes, suggesting that insults that eventually lead to neurodegeneration may converge on a set of evolutionarily conserved cellular processes. Insights from these studies have contributed to our understanding of known neurodegenerative diseases such as Leigh syndrome and Friedreich's ataxia and have also led to the identification of new human diseases. By discovering new genes required for neural maintenance in flies and working with clinicians to identify patients with deleterious variants in the orthologous human genes, Drosophila biologists can play an active role in personalized medicine.
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Affiliation(s)
- Samantha L Deal
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, United States
| | - Shinya Yamamoto
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, United States
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33
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Farley JE, Burdett TC, Barria R, Neukomm LJ, Kenna KP, Landers JE, Freeman MR. Transcription factor Pebbled/RREB1 regulates injury-induced axon degeneration. Proc Natl Acad Sci U S A 2018; 115:1358-1363. [PMID: 29295933 PMCID: PMC5819420 DOI: 10.1073/pnas.1715837115] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Genetic studies of Wallerian degeneration have led to the identification of signaling molecules (e.g., dSarm/Sarm1, Axundead, and Highwire) that function locally in axons to drive degeneration. Here we identify a role for the Drosophila C2H2 zinc finger transcription factor Pebbled [Peb, Ras-responsive element binding protein 1 (RREB1) in mammals] in axon death. Loss of Peb in Drosophila glutamatergic sensory neurons results in either complete preservation of severed axons, or an axon death phenotype where axons fragment into large, continuous segments, rather than completely disintegrate. Peb is expressed in developing and mature sensory neurons, suggesting it is required to establish or maintain their competence to undergo axon death. peb mutant phenotypes can be rescued by human RREB1, and they exhibit dominant genetic interactions with dsarm mutants, linking peb/RREB1 to the axon death signaling cascade. Surprisingly, Peb is only able to fully block axon death signaling in glutamatergic, but not cholinergic sensory neurons, arguing for genetic diversity in axon death signaling programs in different neuronal subtypes. Our findings identify a transcription factor that regulates axon death signaling, and peb mutant phenotypes of partial fragmentation reveal a genetically accessible step in axon death signaling.
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Affiliation(s)
- Jonathan E Farley
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01655
| | - Thomas C Burdett
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01655
| | - Romina Barria
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01655
| | - Lukas J Neukomm
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01655
| | - Kevin P Kenna
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01655
| | - John E Landers
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01655
| | - Marc R Freeman
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01655;
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34
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Pebbled makes ripples: A transcription factor primes glutamatergic but not cholinergic neurons for degeneration. Proc Natl Acad Sci U S A 2018; 115:1140-1142. [PMID: 29363592 DOI: 10.1073/pnas.1721435115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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35
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Glial Draper Rescues Aβ Toxicity in a Drosophila Model of Alzheimer's Disease. J Neurosci 2017; 37:11881-11893. [PMID: 29109235 DOI: 10.1523/jneurosci.0862-17.2017] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 10/19/2017] [Accepted: 10/23/2017] [Indexed: 12/24/2022] Open
Abstract
Pathological hallmarks of Alzheimer's disease (AD) include amyloid-β (Aβ) plaques, neurofibrillary tangles, and reactive gliosis. Glial cells offer protection against AD by engulfing extracellular Aβ peptides, but the repertoire of molecules required for glial recognition and destruction of Aβ are still unclear. Here, we show that the highly conserved glial engulfment receptor Draper/MEGF10 provides neuroprotection in an AD model of Drosophila (both sexes). Neuronal expression of human Aβ42arc in adult flies results in robust Aβ accumulation, neurodegeneration, locomotor dysfunction, and reduced lifespan. Notably, all of these phenotypes are more severe in draper mutant animals, whereas enhanced expression of glial Draper reverses Aβ accumulation, as well as behavioral phenotypes. We also show that the signal transducer and activator of transcription (Stat92E), c-Jun N-terminal kinase (JNK)/AP-1 signaling, and expression of matrix metalloproteinase-1 (Mmp1) are activated downstream of Draper in glia in response to Aβ42arc exposure. Furthermore, Aβ42-induced upregulation of the phagolysosomal markers Atg8 and p62 was notably reduced in draper mutant flies. Based on our findings, we propose that glia clear neurotoxic Aβ peptides in the AD model Drosophila brain through a Draper/STAT92E/JNK cascade that may be coupled to protein degradation pathways such as autophagy or more traditional phagolysosomal destruction methods.SIGNIFICANCE STATEMENT Alzheimer's disease (AD) and similar dementias are common incurable neurodegenerative disorders in the aging population. As the primary immune responders in the brain, glial cells are implicated as key players in the onset and progression of AD and related disorders. Here we show that the glial engulfment receptor Draper is protective in a Drosophila model of AD, reducing levels of amyloid β (Aβ) peptides, reversing locomotor defects, and extending lifespan. We further show that protein degradation pathways are induced downstream of Draper in AD model flies, supporting a model in which glia engulf and destroy Aβ peptides to reduce amyloid-associated toxicity.
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36
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Neukomm LJ, Burdett TC, Seeds AM, Hampel S, Coutinho-Budd JC, Farley JE, Wong J, Karadeniz YB, Osterloh JM, Sheehan AE, Freeman MR. Axon Death Pathways Converge on Axundead to Promote Functional and Structural Axon Disassembly. Neuron 2017; 95:78-91.e5. [PMID: 28683272 DOI: 10.1016/j.neuron.2017.06.031] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 05/25/2017] [Accepted: 06/19/2017] [Indexed: 01/04/2023]
Abstract
Axon degeneration is a hallmark of neurodegenerative disease and neural injury. Axotomy activates an intrinsic pro-degenerative axon death signaling cascade involving loss of the NAD+ biosynthetic enzyme Nmnat/Nmnat2 in axons, activation of dSarm/Sarm1, and subsequent Sarm-dependent depletion of NAD+. Here we identify Axundead (Axed) as a mediator of axon death. axed mutants suppress axon death in several types of axons for the lifespan of the fly and block the pro-degenerative effects of activated dSarm in vivo. Neurodegeneration induced by loss of the sole fly Nmnat ortholog is also fully blocked by axed, but not dsarm, mutants. Thus, pro-degenerative pathways activated by dSarm signaling or Nmnat elimination ultimately converge on Axed. Remarkably, severed axons morphologically preserved by axon death pathway mutations remain integrated in circuits and able to elicit complex behaviors after stimulation, indicating that blockade of axon death signaling results in long-term functional preservation of axons.
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Affiliation(s)
- Lukas J Neukomm
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA.
| | - Thomas C Burdett
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Andrew M Seeds
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Stefanie Hampel
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Jaeda C Coutinho-Budd
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jonathan E Farley
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jack Wong
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Yonca B Karadeniz
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jeannette M Osterloh
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Amy E Sheehan
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Marc R Freeman
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA.
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37
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Fernius J, Starkenberg A, Thor S. Bar-coding neurodegeneration: identifying subcellular effects of human neurodegenerative disease proteins using Drosophila leg neurons. Dis Model Mech 2017; 10:1027-1038. [PMID: 28615189 PMCID: PMC5560063 DOI: 10.1242/dmm.029637] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 06/09/2017] [Indexed: 12/20/2022] Open
Abstract
Genetic, biochemical and histological studies have identified a number of different proteins as key drivers of human neurodegenerative diseases. Although different proteins are typically involved in different diseases, there is also considerable overlap. Addressing disease protein dysfunction in an in vivo neuronal context is often time consuming and requires labor-intensive analysis of transgenic models. To facilitate the rapid, cellular analysis of disease protein dysfunction, we have developed a fruit fly (Drosophila melanogaster) adult leg neuron assay. We tested the robustness of 41 transgenic fluorescent reporters and identified a number that were readily detected in the legs and could report on different cellular events. To test these reporters, we expressed a number of human proteins involved in neurodegenerative disease, in both their mutated and wild-type versions, to address the effects on reporter expression and localization. We observed strikingly different effects of the different disease proteins upon the various reporters with, for example, Aβ1-42 being highly neurotoxic, tau, parkin and HTT128Q affecting mitochondrial distribution, integrity or both, and Aβ1-42, tau, HTT128Q and ATX182Q affecting the F-actin network. This study provides proof of concept for using the Drosophila adult leg for inexpensive and rapid analysis of cellular effects of neurodegenerative disease proteins in mature neurons.
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Affiliation(s)
- Josefin Fernius
- Department of Clinical and Experimental Medicine, Linkoping University, SE-581 85 Linkoping, Sweden
| | - Annika Starkenberg
- Department of Clinical and Experimental Medicine, Linkoping University, SE-581 85 Linkoping, Sweden
| | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linkoping University, SE-581 85 Linkoping, Sweden
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38
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Axon degeneration induces glial responses through Draper-TRAF4-JNK signalling. Nat Commun 2017; 8:14355. [PMID: 28165006 PMCID: PMC5303877 DOI: 10.1038/ncomms14355] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/20/2016] [Indexed: 12/31/2022] Open
Abstract
Draper/Ced-1/MEGF-10 is an engulfment receptor that promotes clearance of cellular debris in C. elegans, Drosophila and mammals. Draper signals through an evolutionarily conserved Src family kinase cascade to drive cytoskeletal rearrangements and target engulfment through Rac1. Glia also alter gene expression patterns in response to axonal injury but pathways mediating these responses are poorly defined. We show Draper is cell autonomously required for glial activation of transcriptional reporters after axonal injury. We identify TNF receptor associated factor 4 (TRAF4) as a novel Draper binding partner that is required for reporter activation and phagocytosis of axonal debris. TRAF4 and misshapen (MSN) act downstream of Draper to activate c-Jun N-terminal kinase (JNK) signalling in glia, resulting in changes in transcriptional reporters that are dependent on Drosophila AP-1 (dAP-1) and STAT92E. Our data argue injury signals received by Draper at the membrane are important regulators of downstream transcriptional responses in reactive glia.
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39
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Brace EJ, DiAntonio A. Models of axon regeneration in Drosophila. Exp Neurol 2017; 287:310-317. [PMID: 26996133 PMCID: PMC5026866 DOI: 10.1016/j.expneurol.2016.03.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 03/11/2016] [Accepted: 03/14/2016] [Indexed: 12/14/2022]
Abstract
Maintaining neuronal connectivity in the face of injury and disease is a major challenge for the nervous system. The great length of axons makes them particularly vulnerable to insult with dire consequences for neuronal function. In the peripheral nervous system there is a program of axonal regeneration that can reestablish connectivity. In the mammalian central nervous system, however, injured axons have little or no capacity to regenerate. The molecular mechanisms that promote axon regeneration have begun to be identified and many of the implicated pathways are evolutionarily conserved. Here we discuss Drosophila models of axonal regrowth, describe insights derived from these studies, and highlight future directions in the use of the fly for dissecting the mechanisms of axonal regeneration.
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Affiliation(s)
- E J Brace
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA, 63110
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA, 63110.
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40
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Ugur B, Chen K, Bellen HJ. Drosophila tools and assays for the study of human diseases. Dis Model Mech 2016; 9:235-44. [PMID: 26935102 PMCID: PMC4833332 DOI: 10.1242/dmm.023762] [Citation(s) in RCA: 296] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Many of the internal organ systems of Drosophila melanogaster are functionally analogous to those in vertebrates, including humans. Although humans and flies differ greatly in terms of their gross morphological and cellular features, many of the molecular mechanisms that govern development and drive cellular and physiological processes are conserved between both organisms. The morphological differences are deceiving and have led researchers to undervalue the study of invertebrate organs in unraveling pathogenic mechanisms of diseases. In this review and accompanying poster, we highlight the physiological and molecular parallels between fly and human organs that validate the use of Drosophila to study the molecular pathogenesis underlying human diseases. We discuss assays that have been developed in flies to study the function of specific genes in the central nervous system, heart, liver and kidney, and provide examples of the use of these assays to address questions related to human diseases. These assays provide us with simple yet powerful tools to study the pathogenic mechanisms associated with human disease-causing genes. Editors' choice - Drosophila Collection: In this review and accompanying poster, we highlight the physiological and molecular parallels between fly and human organs that validate the use of Drosophila to study the molecular pathogenesis underlying human diseases.
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Affiliation(s)
- Berrak Ugur
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Kuchuan Chen
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Hugo J Bellen
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030, USA Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
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41
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Delayed glial clearance of degenerating axons in aged Drosophila is due to reduced PI3K/Draper activity. Nat Commun 2016; 7:12871. [PMID: 27647497 PMCID: PMC5034330 DOI: 10.1038/ncomms12871] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 08/10/2016] [Indexed: 01/09/2023] Open
Abstract
Advanced age is the greatest risk factor for neurodegenerative disorders, but the mechanisms that render the senescent brain vulnerable to disease are unclear. Glial immune responses provide neuroprotection in a variety of contexts. Thus, we explored how glial responses to neurodegeneration are altered with age. Here we show that glia–axon phagocytic interactions change dramatically in the aged Drosophila brain. Aged glia clear degenerating axons slowly due to low phosphoinositide-3-kinase (PI3K) signalling and, subsequently, reduced expression of the conserved phagocytic receptor Draper/MEGF10. Importantly, boosting PI3K/Draper activity in aged glia significantly reverses slow phagocytic responses. Moreover, several hours post axotomy, early hallmarks of Wallerian degeneration (WD) are delayed in aged flies. We propose that slow clearance of degenerating axons is mechanistically twofold, resulting from deferred initiation of axonal WD and reduced PI3K/Draper-dependent glial phagocytic function. Interventions that boost glial engulfment activity, however, can substantially reverse delayed clearance of damaged neuronal debris. Glial engulfment declines with age, but the mechanism is unclear. Here authors show that in the Drosophila olfactory system, glial phagocytosis of injury-induced degenerating axons decreases with age due to reduced PI3K/Draper activity, and restoring Draper in aged glia rescues such defects.
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42
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Vagnoni A, Bullock SL. A simple method for imaging axonal transport in aging neurons using the adult Drosophila wing. Nat Protoc 2016; 11:1711-23. [PMID: 27560175 DOI: 10.1038/nprot.2016.112] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is growing interest in the link between axonal cargo transport and age-associated neuronal dysfunction. The study of axonal transport in neurons of adult animals requires intravital or ex vivo imaging approaches, which are laborious and expensive in vertebrate models. We describe simple, noninvasive procedures for imaging cargo motility within axons using sensory neurons of the translucent Drosophila wing. A key aspect is a method for mounting the intact fly that allows detailed imaging of transport in wing neurons. Coupled with existing genetic tools in Drosophila, this is a tractable system for studying axonal transport over the life span of an animal and thus for characterization of the relationship between cargo dynamics, neuronal aging and disease. Preparation of a sample for imaging takes ∼5 min, with transport typically filmed for 2-3 min per wing. We also document procedures for the quantification of transport parameters from the acquired images and describe how the protocol can be adapted to study other cell biological processes in aging neurons.
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Affiliation(s)
- Alessio Vagnoni
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Simon L Bullock
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, UK
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43
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Vagnoni A, Hoffmann PC, Bullock SL. Reducing Lissencephaly-1 levels augments mitochondrial transport and has a protective effect in adult Drosophila neurons. J Cell Sci 2015; 129:178-90. [PMID: 26598558 PMCID: PMC4732301 DOI: 10.1242/jcs.179184] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 11/17/2015] [Indexed: 12/22/2022] Open
Abstract
Defective transport of mitochondria in axons is implicated in the pathogenesis of several age-associated neurodegenerative diseases. However, the regulation and function of axonal mitochondrial motility during normal ageing is poorly understood. Here, we use novel imaging procedures to characterise axonal transport of these organelles in the adult Drosophila wing nerve. During early adult life there is a boost and progressive decline in the proportion of mitochondria that are motile, which is not due to general changes in cargo transport. Experimental inhibition of the mitochondrial transport machinery specifically in adulthood accelerates the appearance of focal protein accumulations in ageing axons, which is suggestive of defects in protein homeostasis. Unexpectedly, lowering levels of Lissencephaly-1 (Lis1), a dynein motor co-factor, augments axonal mitochondrial transport in ageing wing neurons. Lis1 mutations suppress focal protein accumulations in ageing neurons, including those caused by interfering with the mitochondrial transport machinery. Our data provide new insights into the dynamics of mitochondrial motility in adult neurons in vivo, identify Lis1 as a negative regulator of transport of these organelles, and provide evidence of a link between mitochondrial movement and neuronal protein homeostasis. Summary: Novel imaging procedures in the adult Drosophila wing reveal that Lissencephaly-1 restrains mitochondrial motion and that reducing levels of this protein protects against an age-related decline in protein homeostasis.
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Affiliation(s)
- Alessio Vagnoni
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Patrick C Hoffmann
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Simon L Bullock
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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Lincoln BL, Alabsi SH, Frendo N, Freund R, Keller LC. Drosophila Neuronal Injury Follows a Temporal Sequence of Cellular Events Leading to Degeneration at the Neuromuscular Junction. J Exp Neurosci 2015; 9:1-9. [PMID: 26512206 PMCID: PMC4612769 DOI: 10.4137/jen.s25516] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/20/2015] [Accepted: 09/21/2015] [Indexed: 11/12/2022] Open
Abstract
Neurodegenerative diseases affect millions of people worldwide, and as the global population ages, there is a critical need to improve our understanding of the molecular and cellular mechanisms that drive neurodegeneration. At the molecular level, neurodegeneration involves the activation of complex signaling pathways that drive the active destruction of neurons and their intracellular components. Here, we use an in vivo motor neuron injury assay to acutely induce neurodegeneration in order to follow the temporal order of events that occur following injury in Drosophila melanogaster. We find that sites of injury can be rapidly identified based on structural defects to the neuronal cytoskeleton that result in disrupted axonal transport. Additionally, the neuromuscular junction accumulates ubiquitinated proteins prior to the neurodegenerative events, occurring at 24 hours post injury. Our data provide insights into the early molecular events that occur during axonal and neuromuscular degeneration in a genetically tractable model organism. Importantly, the mechanisms that mediate neurodegeneration in flies are conserved in humans. Thus, these studies have implications for our understanding of the cellular and molecular events that occur in humans and will facilitate the identification of biomedically relevant targets for future treatments.
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Affiliation(s)
- Barron L Lincoln
- Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA
| | - Sahar H Alabsi
- Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA
| | - Nicholas Frendo
- Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA
| | - Robert Freund
- Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA
| | - Lani C Keller
- Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA
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46
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Abstract
TDP-43 is a key disease protein for amyotrophic lateral sclerosis but how it drives motor neuron degeneration remains unresolved. A new study has modeled TDP-43 age-dependent axonal death in the Drosophila leg and used a powerful forward genetic screen to identify three novel suppressor genes.
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Affiliation(s)
- Matthew D Figley
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA; Stanford Neuroscience Graduate Program, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
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47
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Lewis EA, Smith GA. Using Drosophila models of Huntington's disease as a translatable tool. J Neurosci Methods 2015; 265:89-98. [PMID: 26241927 DOI: 10.1016/j.jneumeth.2015.07.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 07/10/2015] [Accepted: 07/13/2015] [Indexed: 11/17/2022]
Abstract
The Huntingtin (Htt) protein is essential for a wealth of intracellular signaling cascades and when mutated, causes multifactorial dysregulation of basic cellular processes. Understanding the contribution to each of these intracellular pathways is essential for the elucidation of mechanisms that drive pathophysiology. Using appropriate models of Huntington's disease (HD) is key to finding the molecular mechanisms that contribute to neurodegeneration. While mouse models and cell lines expressing mutant Htt have been instrumental to HD research, there has been a significant contribution to our understating of the disease from studies utilizing Drosophila melanogaster. Flies have an Htt protein, so the endogenous pathways with which it interacts are likely conserved. Transgenic flies engineered to overexpress the human mutant HTT gene display protein aggregation, neurodegeneration, behavioral deficits and a reduced lifespan. The short life span of flies, low cost of maintaining stocks and genetic tools available for in vivo manipulation make them ideal for the discovery of new genes that are involved in HD pathology. It is possible to do rapid genome wide screens for enhancers or suppressors of the mutant Htt-mediated phenotype, expressed in specific tissues or neuronal subtypes. However, there likely remain many yet unknown genes that modify disease progression, which could be found through additional screening approaches using the fly. Importantly, there have been instances where genes discovered in Drosophila have been translated to HD mouse models.
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Affiliation(s)
- Elizabeth A Lewis
- Neurobiology Department, Aaron Lazare Research Building, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Gaynor A Smith
- Neurobiology Department, Aaron Lazare Research Building, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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48
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Sreedharan J, Neukomm LJ, Brown RH, Freeman MR. Age-Dependent TDP-43-Mediated Motor Neuron Degeneration Requires GSK3, hat-trick, and xmas-2. Curr Biol 2015; 25:2130-6. [PMID: 26234214 DOI: 10.1016/j.cub.2015.06.045] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/24/2015] [Accepted: 06/18/2015] [Indexed: 12/12/2022]
Abstract
The RNA-processing protein TDP-43 is central to the pathogenesis of amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron (MN) disease. TDP-43 is conserved in Drosophila, where it has been the topic of considerable study, but how TDP-43 mutations lead to age-dependent neurodegeneration is unclear and most approaches have not directly examined changes in MN morphology with age. We used a mosaic approach to study age-dependent MN loss in the adult fly leg where it is possible to resolve single motor axons, NMJs and active zones, and perform rapid forward genetic screens. We show that expression of TDP-43(Q331K) caused dying-back of NMJs and axons, which could not be suppressed by mutations that block Wallerian degeneration. We report the identification of three genes that suppress TDP-43 toxicity, including shaggy/GSK3, a known modifier of neurodegeneration. The two additional novel suppressors, hat-trick and xmas-2, function in chromatin modeling and RNA export, two processes recently implicated in human ALS. Loss of shaggy/GSK3, hat-trick, or xmas-2 does not suppress Wallerian degeneration, arguing TDP-43(Q331K)-induced and Wallerian degeneration are genetically distinct processes. In addition to delineating genetic factors that modify TDP-43 toxicity, these results establish the Drosophila adult leg as a valuable new tool for the in vivo study of adult MN phenotypes.
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Affiliation(s)
- Jemeen Sreedharan
- Howard Hughes Medical Institute and Department of Neurobiology, LRB-740A1, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01655, USA; Department of Neurology, S5-755, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA; Signalling ISP, The Babraham Institute, Cambridge CB22 3AT, UK.
| | - Lukas J Neukomm
- Howard Hughes Medical Institute and Department of Neurobiology, LRB-740A1, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01655, USA
| | - Robert H Brown
- Department of Neurology, S5-755, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Marc R Freeman
- Howard Hughes Medical Institute and Department of Neurobiology, LRB-740A1, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01655, USA.
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49
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Fang Y, Bonini NM. Hope on the (fruit) fly: the Drosophila wing paradigm of axon injury. Neural Regen Res 2015; 10:173-5. [PMID: 25883604 PMCID: PMC4392653 DOI: 10.4103/1673-5374.152359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2014] [Indexed: 12/01/2022] Open
Affiliation(s)
- Yanshan Fang
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Nancy M Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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50
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Schuldiner O, Yaron A. Mechanisms of developmental neurite pruning. Cell Mol Life Sci 2014; 72:101-19. [PMID: 25213356 DOI: 10.1007/s00018-014-1729-6] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/02/2014] [Accepted: 09/04/2014] [Indexed: 12/19/2022]
Abstract
The precise wiring of the nervous system is a combined outcome of progressive and regressive events during development. Axon guidance and synapse formation intertwined with cell death and neurite pruning sculpt the mature circuitry. It is now well recognized that pruning of dendrites and axons as means to refine neuronal networks, is a wide spread phenomena required for the normal development of vertebrate and invertebrate nervous systems. Here we will review the arising principles of cellular and molecular mechanisms of neurite pruning. We will discuss these principles in light of studies in multiple neuronal systems, and speculate on potential explanations for the emergence of neurite pruning as a mechanism to sculpt the nervous system.
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Affiliation(s)
- Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, 7610001, Rehovot, Israel,
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