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Miyamoto T, Hedjazi S, Miyamoto C, Amrein H. Drosophila neuronal Glucose-6-Phosphatase is a modulator of neuropeptide release that regulates muscle glycogen stores via FMRFamide signaling. Proc Natl Acad Sci U S A 2024; 121:e2319958121. [PMID: 39008673 PMCID: PMC11287260 DOI: 10.1073/pnas.2319958121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 06/07/2024] [Indexed: 07/17/2024] Open
Abstract
Neuropeptides (NPs) and their cognate receptors are critical effectors of diverse physiological processes and behaviors. We recently reported of a noncanonical function of the Drosophila Glucose-6-Phosphatase (G6P) gene in a subset of neurosecretory cells in the central nervous system that governs systemic glucose homeostasis in food-deprived flies. Here, we show that G6P-expressing neurons define six groups of NP-secreting cells, four in the brain and two in the thoracic ganglion. Using the glucose homeostasis phenotype as a screening tool, we find that neurons located in the thoracic ganglion expressing FMRFamide NPs (FMRFaG6P neurons) are necessary and sufficient to maintain systemic glucose homeostasis in starved flies. We further show that G6P is essential in FMRFaG6P neurons for attaining a prominent Golgi apparatus and secreting NPs efficiently. Finally, we establish that G6P-dependent FMRFa signaling is essential for the build-up of glycogen stores in the jump muscle which expresses the receptor for FMRFamides. We propose a general model in which the main role of G6P is to counteract glycolysis in peptidergic neurons for the purpose of optimizing the intracellular environment best suited for the expansion of the Golgi apparatus, boosting release of NPs and enhancing signaling to respective target tissues expressing cognate receptors.
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Affiliation(s)
- Tetsuya Miyamoto
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M University, Bryan, TX77807
| | - Sheida Hedjazi
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M University, Bryan, TX77807
| | - Chika Miyamoto
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M University, Bryan, TX77807
| | - Hubert Amrein
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M University, Bryan, TX77807
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Pandey P, Shrestha B, Lee Y. Avoiding alkaline taste through ionotropic receptors. iScience 2024; 27:110087. [PMID: 38947501 PMCID: PMC11214294 DOI: 10.1016/j.isci.2024.110087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 02/08/2024] [Accepted: 05/20/2024] [Indexed: 07/02/2024] Open
Abstract
Taste organs contain distinct gustatory receptors that help organisms differentiate between nourishing and potentially harmful foods. The detection of high pH levels plays a crucial role in food selection, but the specific gustatory receptors responsible for perceiving elevated pH in foods have remained unknown. By using Drosophila melanogaster as a model organism, we have uncovered the involvement of ionotropic receptors (IRs) in avoiding high-pH foods. Our study involved a combination of behavioral tests and electrophysiological analyses, which led to the identification of six Irs from bitter-sensing gustatory receptor neurons essential for rejecting food items with elevated pH levels. Using the same methodology, our study reevaluated the significance of Alka and OtopLa. The findings highlight that Alka, in conjunction with IRs, is crucial for detecting alkaline substances, whereas OtopLa does not contribute to this process. Overall, our study offers valuable insights into the intricate mechanisms governing taste perception in organisms.
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Affiliation(s)
- Prakash Pandey
- Department of Bio & Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea
| | - Bhanu Shrestha
- Department of Bio & Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea
| | - Youngseok Lee
- Department of Bio & Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea
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Miyamoto T, Hedjazi S, Miyamoto C, Amrein H. Drosophila Neuronal Glucose 6 Phosphatase is a Modulator of Neuropeptide Release that Regulates Muscle Glycogen Stores via FMRFamide Signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.28.568950. [PMID: 38077084 PMCID: PMC10705280 DOI: 10.1101/2023.11.28.568950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
Neuropeptides (NPs) and their cognate receptors are critical effectors of diverse physiological processes and behaviors. We recently reported of a non-canonical function of the Drosophila Glucose-6-Phosphatase ( G6P ) gene in a subset of neurosecretory cells in the CNS that governs systemic glucose homeostasis in food deprived flies. Here, we show that G6P expressing neurons define 6 groups of neuropeptide secreting cells, 4 in the brain and 2 in the thoracic ganglion. Using the glucose homeostasis phenotype as a screening tool, we find that neurons located in the thoracic ganglion expressing FMRFamide neuropeptides ( FMRFa G6P neurons) are necessary and sufficient to maintain systemic glucose homeostasis in starved flies. We further show that G6P is essential in FMRFa G6P neurons for attaining a prominent Golgi apparatus and secreting neuropeptides efficiently. Finally, we establish that G6P dependent FMRFa signaling is essential for the build-up of glycogen stores in the jump muscle which expresses the receptor for FMRFamides. We propose a general model in which the main role of G6P is to counteract glycolysis in peptidergic neurons for the purpose of optimizing the intracellular environment best suited for the expansion of the Golgi apparatus, boosting release of neuropeptides and enhancing signaling to respective target tissues expressing cognate receptors. SIGNIFICANCE STATEMENT Glucose-6-phosphtase (G6P) is a critical enzyme in sugar synthesis and catalyzes the final step in glucose production. In Drosophila - and insects in general - where trehalose is the circulating sugar and Trehalose phosphate synthase, and not G6P, is used for sugar production, G6P has adopted a novel and unique role in peptidergic neurons in the CNS. Interestingly, flies lacking G6P show diminished Neuropeptide secretions and have a smaller Golgi apparatus in peptidergic neurons. It is hypothesized that the role of G6P is to counteract glycolysis, thereby creating a cellular environment that is more amenable to efficient neuropeptide secretion.
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Pradhan RN, Shrestha B, Lee Y. Avoiding cantharidin through ionotropic receptors. JOURNAL OF HAZARDOUS MATERIALS 2024; 466:133497. [PMID: 38278077 DOI: 10.1016/j.jhazmat.2024.133497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 01/08/2024] [Accepted: 01/09/2024] [Indexed: 01/28/2024]
Abstract
The discernment and aversion of noxious gustatory stimuli profoundly influence homeostasis maintenance and survival of fauna. Cantharidin, a purported aphrodisiac, is a monoterpenoid compound secreted by many species of blister beetle, particularly by the Spanish fly, Lytta vesicatoria. Although the various advantageous functions of cantharidin have been described, its taste analysis and toxic properties in animalshave been rarely explored. Our study using Drosophila melanogaster examines the taste properties of cantharidin along with its potential hazardous effect in the internal organs of animals. Here, we find that cantharidin activates bitter taste receptors. Our findings show that specific ionotropic receptors (IR7g, IR51b, and IR94f) in labellar bitter-sensing neurons, along with co-receptors IR25a and IR76b, are responsible for detecting cantharidin. By introducing the IR7g and IR51b in sweet and bitter neurons, naturally expressing IR76b and IR25a, we show that these genes are sufficient for cantharidin perception. Moreover, we witness the deleterious ramifications of cantharidin on survival and visceral integrities, shedding light on its hazardous effect.
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Affiliation(s)
- Roshani Nhuchhen Pradhan
- Department of Bio & Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea
| | - Bhanu Shrestha
- Department of Bio & Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea
| | - Youngseok Lee
- Department of Bio & Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea.
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Kimura KI, Kumano R, Yamamoto D. Activin is a neural inducer of a male-specific muscle in Drosophila. Sci Rep 2024; 14:3740. [PMID: 38355873 PMCID: PMC10866940 DOI: 10.1038/s41598-024-54295-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 02/11/2024] [Indexed: 02/16/2024] Open
Abstract
Drosophila melanogaster has a pair of male-specific muscles called the muscle of Lawrence (MOL) in abdominal segment 5 (A5) of adult flies. The MOL is produced only when its innervating motoneuron expresses FruitlessM (FruM) neural masculinizing proteins. We show that MOL induction is hampered by: (1) silencing electrical activities in the motoneuron, (2) blocking vesicular release from the motoneuron, and (3) knocking down Activin ß (Actß) in the motoneuron or knocking down Actß signaling pathway components in the myoblasts. Our timelapse live imaging of the developing neuromuscular system reveals that, upon contact with the presumptive MOL, the motoneuronal axon retracts concomitant with the progression of MOL degeneration resulting from neural silencing. We conclude that MOL formation depends on the bidirectional trophic interactions between pre- and postsynaptic cells, with motoneuron-derived Actß playing an inducing role in MOL formation.
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Affiliation(s)
- Ken-Ichi Kimura
- Laboratory of Biology, Sapporo Campus, Hokkaido University of Education, Sapporo, 002-8502, Japan.
| | - Rimi Kumano
- Laboratory of Biology, Sapporo Campus, Hokkaido University of Education, Sapporo, 002-8502, Japan
| | - Daisuke Yamamoto
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe, 651-2492, Japan
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Terzi F, Knabbe J, Cambridge SB. In Vivo Optical Interrogation of Neuronal Responses to Genetic, Cell Type-Specific Silencing. J Neurosci 2023; 43:8607-8620. [PMID: 37923378 PMCID: PMC10727181 DOI: 10.1523/jneurosci.2253-22.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 05/05/2023] [Accepted: 06/26/2023] [Indexed: 11/07/2023] Open
Abstract
We established a low background, Cre-dependent version of the inducible Tet-On system for fast, cell type-specific transgene expression in vivo Coexpression of a constitutive, Cre-dependent fluorescent marker selectively allowed single-cell analyses before and after inducible, Tet-dependent transgene expression. Here, we used this method for precise, acute manipulation of neuronal activity in the living brain. The goal was to study neuronal network homeostasis at cellular resolution. Single induction of the potassium channel Kir2.1 produced cell type-specific silencing within hours that lasted for at least 3 d. Longitudinal in vivo imaging of spontaneous calcium transients and neuronal morphology demonstrated that prolonged silencing did not alter spine densities or synaptic input strength. Furthermore, selective induction of Kir2.1 in parvalbumin interneurons increased the activity of surrounding neurons in a distance-dependent manner. This high-resolution, inducible interference and interval imaging of individual cells (high I5, HighFive) method thus allows visualizing temporally precise, genetic perturbations of defined cells.SIGNIFICANCE STATEMENT Gene function is studied by KO or overexpression of a specific gene followed by analyses of phenotypic changes. However, being able to predict and analyze exactly those cells in which genetic manipulation will occur is not possible. We combined two prominent transgene overexpression methods to fluorescently highlight the targeted cells appropriately before cell type-specific transgene induction. By inducing a potassium channel that decreases neuronal firing, we investigated how neuronal networks in the living mouse brain possibly compensate swift changes in cellular activities. Unlike in vitro, known compensatory homeostatic mechanisms, such as changes in synapses, were not observed in vivo Overall, we demonstrated with our method rapid genetic manipulation and analysis of neuronal activities as well as precision transgene expression.
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Affiliation(s)
- Firat Terzi
- Heidelberg University, Heidelberg, 69120, Germany
| | | | - Sidney B Cambridge
- Heidelberg University, Heidelberg, 69120, Germany
- Dr. Senckenberg Anatomy, Institute for Anatomy II, Goethe-University Frankfurt am Main, Frankfurt, 60590, Germany
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Ahn JE, Amrein H. Opposing chemosensory functions of closely related gustatory receptors. eLife 2023; 12:RP89795. [PMID: 38060294 PMCID: PMC10703443 DOI: 10.7554/elife.89795] [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: 12/08/2023] Open
Abstract
In the fruit fly Drosophila melanogaster, gustatory sensory neurons express taste receptors that are tuned to distinct groups of chemicals, thereby activating neural ensembles that elicit either feeding or avoidance behavior. Members of a family of ligand -gated receptor channels, the Gustatory receptors (Grs), play a central role in these behaviors. In general, closely related, evolutionarily conserved Gr proteins are co-expressed in the same type of taste neurons, tuned to chemically related compounds, and therefore triggering the same behavioral response. Here, we report that members of the Gr28 subfamily are expressed in largely non-overlapping sets of taste neurons in Drosophila larvae, detect chemicals of different valence, and trigger opposing feeding behaviors. We determined the intrinsic properties of Gr28 neurons by expressing the mammalian Vanilloid Receptor 1 (VR1), which is activated by capsaicin, a chemical to which wild-type Drosophila larvae do not respond. When VR1 is expressed in Gr28a neurons, larvae become attracted to capsaicin, consistent with reports showing that Gr28a itself encodes a receptor for nutritious RNA. In contrast, expression of VR1 in two pairs of Gr28b.c neurons triggers avoidance to capsaicin. Moreover, neuronal inactivation experiments show that the Gr28b.c neurons are necessary for avoidance of several bitter compounds. Lastly, behavioral experiments of Gr28 deficient larvae and live Ca2+ imaging studies of Gr28b.c neurons revealed that denatonium benzoate, a synthetic bitter compound that shares structural similarities with natural bitter chemicals, is a ligand for a receptor complex containing a Gr28b.c or Gr28b.a subunit. Thus, the Gr28 proteins, which have been evolutionarily conserved over 260 million years in insects, represent the first taste receptor subfamily in which specific members mediate behavior with opposite valence.
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Affiliation(s)
- Ji-Eun Ahn
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M UniversityBryanUnited States
| | - Hubert Amrein
- Department of Cell Biology and Genetics, School of Medicine, Texas A&M UniversityBryanUnited States
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Ahn JE, Amrein H. Opposing chemosensory functions of closely related gustatory receptors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.20.545761. [PMID: 37905057 PMCID: PMC10614748 DOI: 10.1101/2023.06.20.545761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Most animals have functionally distinct populations of taste cells, expressing receptors that are tuned to compounds of different valence. This organizational feature allows for discrimination between chemicals associated with specific taste modalities and facilitates differentiating between unadulterated foods and foods contaminated with toxic substances. In the fruit fly D. melanogaster , primary sensory neurons express taste receptors that are tuned to distinct groups of chemicals, thereby activating neural ensembles that elicit either feeding or avoidance behavior. Members of a family of ligand gated receptor channels, the Gustatory receptors (Grs), play a central role in these behaviors. In general, closely related, evolutionarily conserved Gr proteins are co-expressed in the same type of taste neurons, tuned to chemically related compounds, and therefore triggering the same behavioral response. Here, we report that members of the Gr28 subfamily are expressed in largely non-overlapping sets of taste neurons in Drosophila larvae, detect chemicals of different valence and trigger opposing feeding behaviors. We determined the intrinsic properties of Gr28 neurons by expressing the mammalian Vanilloid Receptor (VR1), which is activated by capsaicin, a chemical to which wildtype Drosophila larvae do not respond. When VR1 is expressed in Gr28a neurons, larvae become attracted to capsaicin, consistent with reports showing that Gr28a itself encodes a receptor for nutritious RNA. In contrast, expression of VR1 in two pairs of Gr28b.c neurons triggers avoidance to capsaicin. Moreover, neuronal inactivation experiments show that the Gr28b.c neurons are necessary for avoidance of several bitter compounds. Lastly, behavioral experiments of Gr28 deficient larvae and live Ca 2+ imaging studies of Gr28b.c neurons revealed that denatonium benzoate, a synthetic bitter compound that shares structural similarities with natural bitter chemicals, is a ligand for a receptor complex containing a Gr28b.c or Gr28b.a subunit. Thus, the Gr28 proteins, which have been evolutionarily conserved over 260 million years in insects, represent the first taste receptor subfamily in which specific members mediate behavior with opposite valence.
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Piatkevich KD, Boyden ES. Optogenetic control of neural activity: The biophysics of microbial rhodopsins in neuroscience. Q Rev Biophys 2023; 57:e1. [PMID: 37831008 DOI: 10.1017/s0033583523000033] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Optogenetics, the use of microbial rhodopsins to make the electrical activity of targeted neurons controllable by light, has swept through neuroscience, enabling thousands of scientists to study how specific neuron types contribute to behaviors and pathologies, and how they might serve as novel therapeutic targets. By activating a set of neurons, one can probe what functions they can initiate or sustain, and by silencing a set of neurons, one can probe the functions they are necessary for. We here review the biophysics of these molecules, asking why they became so useful in neuroscience for the study of brain circuitry. We review the history of the field, including early thinking, early experiments, applications of optogenetics, pre-optogenetics targeted neural control tools, and the history of discovering and characterizing microbial rhodopsins. We then review the biophysical attributes of rhodopsins that make them so useful to neuroscience - their classes and structure, their photocycles, their photocurrent magnitudes and kinetics, their action spectra, and their ion selectivity. Our hope is to convey to the reader how specific biophysical properties of these molecules made them especially useful to neuroscientists for a difficult problem - the control of high-speed electrical activity, with great precision and ease, in the brain.
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Affiliation(s)
- Kiryl D Piatkevich
- School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Edward S Boyden
- McGovern Institute and Koch Institute, Departments of Brain and Cognitive Sciences, Media Arts and Sciences, and Biological Engineering, K. Lisa Yang Center for Bionics and Center for Neurobiological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
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Machamer JB, Vazquez-Cintron EJ, Stenslik MJ, Pagarigan KT, Bradford AB, Ondeck CA, McNutt PM. Neuromuscular recovery from botulism involves multiple forms of compensatory plasticity. Front Cell Neurosci 2023; 17:1226194. [PMID: 37650071 PMCID: PMC10463753 DOI: 10.3389/fncel.2023.1226194] [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: 05/20/2023] [Accepted: 07/28/2023] [Indexed: 09/01/2023] Open
Abstract
Introduction Botulinum neurotoxin (BoNT) causes neuroparalytic disease and death by blocking neuromuscular transmission. There are no specific therapies for clinical botulism and the only treatment option is supportive care until neuromuscular function spontaneously recovers, which can take weeks or months after exposure. The highly specialized neuromuscular junction (NMJ) between phrenic motor neurons and diaphragm muscle fibers is the main clinical target of BoNT. Due to the difficulty in eliciting respiratory paralysis without a high mortality rate, few studies have characterized the neurophysiological mechanisms involved in diaphragm recovery from intoxication. Here, we develop a mouse model of botulism that involves partial paralysis of respiratory muscles with low mortality rates, allowing for longitudinal analysis of recovery. Methods and results Mice challenged by systemic administration of 0.7 LD50 BoNT/A developed physiological signs of botulism, such as respiratory depression and reduced voluntary running activity, that persisted for an average of 8-12 d. Studies in isolated hemidiaphragm preparations from intoxicated mice revealed profound reductions in nerve-elicited, tetanic and twitch muscle contraction strengths that recovered to baseline 21 d after intoxication. Despite apparent functional recovery, neurophysiological parameters remained depressed for 28 d, including end plate potential (EPP) amplitude, EPP success rate, quantal content (QC), and miniature EPP (mEPP) frequency. However, QC recovered more quickly than mEPP frequency, which could explain the discrepancy between muscle function studies and neurophysiological recordings. Hypothesizing that differential modulation of voltage-gated calcium channels (VGCC) contributed to the uncoupling of QC from mEPP frequency, pharmacological inhibition studies were used to study the contributions of different VGCCs to neurophysiological function. We found that N-type VGCC and P/Q-type VGCC partially restored QC but not mEPP frequency during recovery from paralysis, potentially explaining the accelerated recovery of evoked release versus spontaneous release. We identified additional changes that presumably compensate for reduced acetylcholine release during recovery, including increased depolarization of muscle fiber resting membrane potential and increased quantal size. Discussion In addition to identifying multiple forms of compensatory plasticity that occur in response to reduced NMJ function, it is expected that insights into the molecular mechanisms involved in recovery from neuromuscular paralysis will support new host-targeted treatments for multiple neuromuscular diseases.
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Affiliation(s)
- James B. Machamer
- BASF, Research Triangle Park, NC, United States
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD, United States
| | | | - Mallory J. Stenslik
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD, United States
| | - Kathleen T. Pagarigan
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD, United States
| | - Aaron B. Bradford
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD, United States
| | - Celinia A. Ondeck
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD, United States
- Wake Forest Institute for Regenerative Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, United States
| | - Patrick M. McNutt
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD, United States
- Wake Forest Institute for Regenerative Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, United States
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11
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Shrestha B, Aryal B, Lee Y. The taste of vitamin C in Drosophila. EMBO Rep 2023; 24:e56319. [PMID: 37114473 PMCID: PMC10240197 DOI: 10.15252/embr.202256319] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 04/04/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
Vitamins are essential micronutrients, but the mechanisms of vitamin chemoreception in animals are poorly understood. Here, we provide evidence that vitamin C doubles starvation resistance and induces egg laying in Drosophila melanogaster. Our behavioral analyses of genetically engineered and anatomically ablated flies show that fruit flies sense vitamin C via sweet-sensing gustatory receptor neurons (GRNs) in the labellum. Using a behavioral screen and in vivo electrophysiological analyses of ionotropic receptors (IRs) and sweet-sensing gustatory receptors (GRs), we find that two broadly tuned IRs (i.e., IR25a and IR76b) and five GRs (i.e., GR5a, GR61a, GR64b, GR64c, and GR64e) are essential for vitamin C detection. Thus, vitamin C is directly detected by the fly labellum and requires at least two distinct receptor types. Next, we expand our electrophysiological study to test attractive tastants such as sugars, carboxylic acids, and glycerol. Our analysis elucidates the molecular basis of chemoreception in sweet-sensing GRNs.
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Affiliation(s)
- Bhanu Shrestha
- Department of Bio & Fermentation Convergence TechnologyKookmin UniversitySeoulKorea
| | - Binod Aryal
- Department of Bio & Fermentation Convergence TechnologyKookmin UniversitySeoulKorea
| | - Youngseok Lee
- Department of Bio & Fermentation Convergence TechnologyKookmin UniversitySeoulKorea
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12
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Currier TA, Pang MM, Clandinin TR. Visual processing in the fly, from photoreceptors to behavior. Genetics 2023; 224:iyad064. [PMID: 37128740 PMCID: PMC10213501 DOI: 10.1093/genetics/iyad064] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 03/22/2023] [Indexed: 05/03/2023] Open
Abstract
Originally a genetic model organism, the experimental use of Drosophila melanogaster has grown to include quantitative behavioral analyses, sophisticated perturbations of neuronal function, and detailed sensory physiology. A highlight of these developments can be seen in the context of vision, where pioneering studies have uncovered fundamental and generalizable principles of sensory processing. Here we begin with an overview of vision-guided behaviors and common methods for probing visual circuits. We then outline the anatomy and physiology of brain regions involved in visual processing, beginning at the sensory periphery and ending with descending motor control. Areas of focus include contrast and motion detection in the optic lobe, circuits for visual feature selectivity, computations in support of spatial navigation, and contextual associative learning. Finally, we look to the future of fly visual neuroscience and discuss promising topics for further study.
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Affiliation(s)
- Timothy A Currier
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Michelle M Pang
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Thomas R Clandinin
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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13
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Tian T, Cai Y, Qin X, Wang J, Wang Y, Yang X. Forebrain E-I balance controlled in cognition through coordinated inhibition and inhibitory transcriptome mechanism. Front Cell Neurosci 2023; 17:1114037. [PMID: 36909282 PMCID: PMC10000298 DOI: 10.3389/fncel.2023.1114037] [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: 12/02/2022] [Accepted: 01/31/2023] [Indexed: 02/26/2023] Open
Abstract
Introduction Forebrain neural networks are vital for cognitive functioning, and their excitatory-inhibitory (E-I) balance is governed by neural homeostasis. However, the homeostatic control strategies and transcriptomic mechanisms that maintain forebrain E-I balance and optimal cognition remain unclear. Methods We used patch-clamp and RNA sequencing to investigate the patterns of neural network homeostasis with suppressing forebrain excitatory neural activity and spatial training. Results We found that inhibitory transmission and receptor transcription were reduced in tamoxifen-inducible Kir2.1 conditional knock-in mice. In contrast, spatial training increased inhibitory synaptic connections and the transcription of inhibitory receptors. Discussion Our study provides significant evidence that inhibitory systems play a critical role in the homeostatic control of the E-I balance in the forebrain during cognitive training and E-I rebalance, and we have provided insights into multiple gene candidates for cognition-related homeostasis in the forebrain.
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Affiliation(s)
- Tian Tian
- Shenzhen Key Laboratory of Translational Research for Brain Diseases, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - You Cai
- Shenzhen Key Laboratory of Translational Research for Brain Diseases, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
- Department of Neurology, Shenzhen Institute of Translational Medicine, Shenzhen Second People’s Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Xin Qin
- Department of Medicine, Djavad Mowafaghian Centre for Brain Health, The University of British Columbia, Vancouver, BC, Canada
| | - Jiangang Wang
- Henan International Joint Laboratory of Non-Invasive Neuromodulation, Department of Physiology and Pathophysiology, Xinxiang Medical University, Xinxiang, China
| | - Yali Wang
- Henan International Joint Laboratory of Non-Invasive Neuromodulation, Department of Physiology and Pathophysiology, Xinxiang Medical University, Xinxiang, China
| | - Xin Yang
- Shenzhen Key Laboratory of Translational Research for Brain Diseases, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
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14
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Yu J, Guo X, Zheng S, Zhang W. A dedicate sensorimotor circuit enables fine texture discrimination by active touch. PLoS Genet 2023; 19:e1010562. [PMID: 36649336 PMCID: PMC9882754 DOI: 10.1371/journal.pgen.1010562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 01/27/2023] [Accepted: 12/08/2022] [Indexed: 01/18/2023] Open
Abstract
Active touch facilitates environments exploration by voluntary, self-generated movements. However, the neural mechanisms underlying sensorimotor control for active touch are poorly understood. During foraging and feeding, Drosophila gather information on the properties of food (texture, hardness, taste) by constant probing with their proboscis. Here we identify a group of neurons (sd-L neurons) on the fly labellum that are mechanosensitive to labellum displacement and synapse onto the sugar-sensing neurons via axo-axonal synapses to induce preference to harder food. These neurons also feed onto the motor circuits that control proboscis extension and labellum spreading to provide on-line sensory feedback critical for controlling the probing processes, thus facilitating ingestion of less liquified food. Intriguingly, this preference was eliminated in mated female flies, reflecting an elevated need for softer food. Our results propose a sensorimotor circuit composed of mechanosensory, gustatory and motor neurons that enables the flies to select ripe yet not over-rotten food by active touch.
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Affiliation(s)
- Jie Yu
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Xuan Guo
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Shen Zheng
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
| | - Wei Zhang
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- Tsinghua-Peking Center for Life Sciences, Beijing, China
- * E-mail:
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15
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Park A, Croset V, Otto N, Agarwal D, Treiber CD, Meschi E, Sims D, Waddell S. Gliotransmission of D-serine promotes thirst-directed behaviors in Drosophila. Curr Biol 2022; 32:3952-3970.e8. [PMID: 35963239 PMCID: PMC9616736 DOI: 10.1016/j.cub.2022.07.038] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 07/04/2022] [Accepted: 07/15/2022] [Indexed: 12/13/2022]
Abstract
Thirst emerges from a range of cellular changes that ultimately motivate an animal to consume water. Although thirst-responsive neuronal signals have been reported, the full complement of brain responses is unclear. Here, we identify molecular and cellular adaptations in the brain using single-cell sequencing of water-deprived Drosophila. Water deficiency primarily altered the glial transcriptome. Screening the regulated genes revealed astrocytic expression of the astray-encoded phosphoserine phosphatase to bi-directionally regulate water consumption. Astray synthesizes the gliotransmitter D-serine, and vesicular release from astrocytes is required for drinking. Moreover, dietary D-serine rescues aay-dependent drinking deficits while facilitating water consumption and expression of water-seeking memory. D-serine action requires binding to neuronal NMDA-type glutamate receptors. Fly astrocytes contribute processes to tripartite synapses, and the proportion of astrocytes that are themselves activated by glutamate increases with water deprivation. We propose that thirst elevates astrocytic D-serine release, which awakens quiescent glutamatergic circuits to enhance water procurement.
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Affiliation(s)
- Annie Park
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK
| | - Vincent Croset
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK; Department of Biosciences, Durham University, Durham DH1 3LE, UK.
| | - Nils Otto
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK
| | - Devika Agarwal
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK; MRC Computational Genomics Analysis and Training Programme (CGAT), MRC Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
| | - Christoph D Treiber
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK
| | - Eleonora Meschi
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK
| | - David Sims
- MRC Computational Genomics Analysis and Training Programme (CGAT), MRC Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
| | - Scott Waddell
- Centre for Neural Circuits & Behaviour, University of Oxford, Oxford OX1 3TA, UK.
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16
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Losada-Pérez M, Hernández García-Moreno M, García-Ricote I, Casas-Tintó S. Synaptic components are required for glioblastoma progression in Drosophila. PLoS Genet 2022; 18:e1010329. [PMID: 35877760 PMCID: PMC9352205 DOI: 10.1371/journal.pgen.1010329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 08/04/2022] [Accepted: 07/06/2022] [Indexed: 11/18/2022] Open
Abstract
Glioblastoma (GB) is the most aggressive, lethal and frequent primary brain tumor. It originates from glial cells and is characterized by rapid expansion through infiltration. GB cells interact with the microenvironment and healthy surrounding tissues, mostly neurons and vessels. GB cells project tumor microtubes (TMs) contact with neurons, and exchange signaling molecules related to Wingless/WNT, JNK, Insulin or Neuroligin-3 pathways. This cell to cell communication promotes GB expansion and neurodegeneration. Moreover, healthy neurons form glutamatergic functional synapses with GB cells which facilitate GB expansion and premature death in mouse GB xerograph models. Targeting signaling and synaptic components of GB progression may become a suitable strategy against glioblastoma. In a Drosophila GB model, we have determined the post-synaptic nature of GB cells with respect to neurons, and the contribution of post-synaptic genes expressed in GB cells to tumor progression. In addition, we document the presence of intratumoral synapses between GB cells, and the functional contribution of pre-synaptic genes to GB calcium dependent activity and expansion. Finally, we explore the relevance of synaptic genes in GB cells to the lifespan reduction caused by GB advance. Our results indicate that both presynaptic and postsynaptic proteins play a role in GB progression and lethality. Glioblastoma (GB) is the most frequent and aggressive type of brain tumor. It is originated from glial cells that expand and proliferate very fast in the brain. GB cells infiltrate and establish cell to cell communication with healthy neurons. Currently there is no effective treatment for GB and these tumors result incurable with an average survival of 16 months after diagnosis. Here we used a Drosophila melanogaster model to search for genetic suppressors of GB progression. The results show that genes involved in the formation of synapses are required for glial cell number increase, expansion of tumoral volume and premature death. Among these synaptic genes we found that post-synaptic genes that contribute to Neuron-GB interaction which validate previous findings in human GB. Moreover, we found electro dense structures between GB cells that are compatible with synapses and that expression of pre-synaptic genes, including brp, Lip-α and syt 1, is required for GB progression and aggressiveness. These results suggest a contribution of synapses between GB cells to disease progression, named as intratumoral synapses.
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Affiliation(s)
| | | | | | - Sergio Casas-Tintó
- Instituto Cajal-CSIC, Madrid, Spain
- IIER-Instituto de Salud CarlosIII, Majadahonda, Spain
- * E-mail:
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17
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Jia Y, Li S, Guo X, Lei B, Hu J, Xu XH, Zhang W. Selfee, self-supervised features extraction of animal behaviors. eLife 2022; 11:e76218. [PMID: 35708244 PMCID: PMC9296132 DOI: 10.7554/elife.76218] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 06/15/2022] [Indexed: 11/15/2022] Open
Abstract
Fast and accurately characterizing animal behaviors is crucial for neuroscience research. Deep learning models are efficiently used in laboratories for behavior analysis. However, it has not been achieved to use an end-to-end unsupervised neural network to extract comprehensive and discriminative features directly from social behavior video frames for annotation and analysis purposes. Here, we report a self-supervised feature extraction (Selfee) convolutional neural network with multiple downstream applications to process video frames of animal behavior in an end-to-end way. Visualization and classification of the extracted features (Meta-representations) validate that Selfee processes animal behaviors in a way similar to human perception. We demonstrate that Meta-representations can be efficiently used to detect anomalous behaviors that are indiscernible to human observation and hint in-depth analysis. Furthermore, time-series analyses of Meta-representations reveal the temporal dynamics of animal behaviors. In conclusion, we present a self-supervised learning approach to extract comprehensive and discriminative features directly from raw video recordings of animal behaviors and demonstrate its potential usage for various downstream applications.
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Affiliation(s)
- Yinjun Jia
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua UniversityBeijingChina
- Tsinghua-Peking Center for Life SciencesBeijingChina
| | - Shuaishuai Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Chinese Academy of Sciences Center for Excellence in Brain Science and Intelligence TechnologyShanghaiChina
- Shanghai Center for Brain Science and Brain-Inspired Intelligence TechnologyShanghaiChina
| | - Xuan Guo
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua UniversityBeijingChina
- Tsinghua-Peking Center for Life SciencesBeijingChina
| | - Bo Lei
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua UniversityBeijingChina
- Tsinghua-Peking Center for Life SciencesBeijingChina
| | - Junqiang Hu
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua UniversityBeijingChina
| | - Xiao-Hong Xu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Chinese Academy of Sciences Center for Excellence in Brain Science and Intelligence TechnologyShanghaiChina
- Shanghai Center for Brain Science and Brain-Inspired Intelligence TechnologyShanghaiChina
| | - Wei Zhang
- School of Life Sciences, IDG/McGovern Institute for Brain Research, Tsinghua UniversityBeijingChina
- Tsinghua-Peking Center for Life SciencesBeijingChina
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18
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Wenner PA, Pekala D. Homeostatic Regulation of Motoneuron Properties in Development. ADVANCES IN NEUROBIOLOGY 2022; 28:87-107. [PMID: 36066822 DOI: 10.1007/978-3-031-07167-6_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Homeostatic plasticity represents a set of compensatory mechanisms that are engaged following a perturbation to some feature of neuronal or network function. Homeostatic mechanisms are most robustly expressed during development, a period that is replete with various perturbations such as increased cell size and the addition/removal of synaptic connections. In this review we look at numerous studies that have advanced our understanding of homeostatic plasticity by taking advantage of the accessibility of developing motoneurons. We discuss the homeostatic regulation of embryonic movements in the living chick embryo and describe the spinal compensatory mechanisms that act to recover these movements (homeostatic intrinsic plasticity) or stabilize synaptic strength (synaptic scaling). We describe the expression and triggering mechanisms of these forms of homeostatic plasticity and thereby gain an understanding of their roles in the motor system. We then illustrate how these findings can be extended to studies of developing motoneurons in other systems including the rodents, zebrafish, and fly. Furthermore, studies in developing drosophila have been critical in identifying some of the molecular signaling cascades and expression mechanisms that underlie homeostatic intrinsic membrane excitability. This powerful model organism has also been used to study a presynaptic form of homeostatic plasticity where increases or decreases in synaptic transmission are associated with compensatory changes in probability of release at the neuromuscular junction. Further, we describe studies that demonstrate homeostatic adjustments of ion channel expression following perturbations to other kinds of ion channels. Finally, we discuss work in xenopus that shows a homeostatic regulation of neurotransmitter phenotype in developing motoneurons following activity perturbations. Together, this work illustrates the importance of developing motoneurons in elucidating the mechanisms and roles of homeostatic plasticity.
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Affiliation(s)
- Peter A Wenner
- Department of Cell Biology, Whitehead Biomedical Research Building, Emory University School of Medicine, Atlanta, GA, USA.
| | - Dobromila Pekala
- Department of Cell Biology, Whitehead Biomedical Research Building, Emory University School of Medicine, Atlanta, GA, USA
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19
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Shrestha B, Lee Y. Mechanisms of Carboxylic Acid Attraction in Drosophila melanogaster. Mol Cells 2021; 44:900-910. [PMID: 34711686 PMCID: PMC8718364 DOI: 10.14348/molcells.2021.0205] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/07/2021] [Accepted: 10/15/2021] [Indexed: 11/27/2022] Open
Abstract
Sour is one of the fundamental taste modalities that enable taste perception in animals. Chemoreceptors embedded in taste organs are pivotal to discriminate between different chemicals to ensure survival. Animals generally prefer slightly acidic food and avoid highly acidic alternatives. We recently proposed that all acids are aversive at high concentrations, a response that is mediated by low pH as well as specific anions in Drosophila melanogaster. Particularly, some carboxylic acids such as glycolic acid, citric acid, and lactic acid are highly attractive to Drosophila compared with acetic acid. The present study determined that attractive carboxylic acids were mediated by broadly expressed Ir25a and Ir76b, as demonstrated by a candidate mutant library screen. The mutant deficits were completely recovered via wild-type cDNA expression in sweet-sensing gustatory receptor neurons. Furthermore, sweet gustatory receptors such as Gr5a, Gr61a, and Gr64a-f modulate attractive responses. These genetic defects were confirmed using binary food choice assays as well as electrophysiology in the labellum. Taken together, our findings demonstrate that at least two different kinds of receptors are required to discriminate attractive carboxylic acids from other acids.
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Affiliation(s)
- Bhanu Shrestha
- Department of Bio and Fermentation Convergence Technology, Kookmin University, Seoul 02707, Korea
| | - Youngseok Lee
- Department of Bio and Fermentation Convergence Technology, Kookmin University, Seoul 02707, Korea
- Interdisciplinary Program for Bio-Health Convergence, Kookmin University, Seoul 02707, Korea
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20
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Hsu CT, Choi JTY, Sehgal A. Manipulations of the olfactory circuit highlight the role of sensory stimulation in regulating sleep amount. Sleep 2021; 44:zsaa265. [PMID: 33313876 PMCID: PMC8343592 DOI: 10.1093/sleep/zsaa265] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 11/08/2020] [Indexed: 02/06/2023] Open
Abstract
STUDY OBJECTIVES While wake duration is a major sleep driver, an important question is if wake quality also contributes to controlling sleep. In particular, we sought to determine whether changes in sensory stimulation affect sleep in Drosophila. As Drosophila rely heavily on their sense of smell, we focused on manipulating olfactory input and the olfactory sensory pathway. METHODS Sensory deprivation was first performed by removing antennae or applying glue to antennae. We then measured sleep in response to neural activation, via expression of the thermally gated cation channel TRPA1, or inhibition, via expression of the inward rectifying potassium channel KIR2.1, of subpopulations of neurons in the olfactory pathway. Genetically restricting manipulations to adult animals prevented developmental effects. RESULTS We find that olfactory deprivation reduces sleep, largely independently of mushroom bodies that integrate olfactory signals for memory consolidation and have previously been implicated in sleep. However, specific neurons in the lateral horn, the other third-order target of olfactory input, affect sleep. Also, activation of inhibitory second-order projection neurons increases sleep. No single neuronal population in the olfactory processing pathway was found to bidirectionally regulate sleep, and reduced sleep in response to olfactory deprivation may be masked by temperature changes. CONCLUSIONS These findings demonstrate that Drosophila sleep is sensitive to sensory stimulation, and identify novel sleep-regulating neurons in the olfactory circuit. Scaling of signals across the circuit may explain the lack of bidirectional effects when neuronal activity is manipulated. We propose that olfactory inputs act through specific circuit components to modulate sleep in flies.
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Affiliation(s)
- Cynthia T Hsu
- Howard Hughes Medical Institute, Chronobiology and Sleep Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Juliana Tsz Yan Choi
- Howard Hughes Medical Institute, Chronobiology and Sleep Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Amita Sehgal
- Howard Hughes Medical Institute, Chronobiology and Sleep Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
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21
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Formicola N, Heim M, Dufourt J, Lancelot AS, Nakamura A, Lagha M, Besse F. Tyramine induces dynamic RNP granule remodeling and translation activation in the Drosophila brain. eLife 2021; 10:65742. [PMID: 33890854 PMCID: PMC8064753 DOI: 10.7554/elife.65742] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 04/04/2021] [Indexed: 02/06/2023] Open
Abstract
Ribonucleoprotein (RNP) granules are dynamic condensates enriched in regulatory RNA binding proteins (RBPs) and RNAs under tight spatiotemporal control. Extensive recent work has investigated the molecular principles underlying RNP granule assembly, unraveling that they form through the self-association of RNP components into dynamic networks of interactions. How endogenous RNP granules respond to external stimuli to regulate RNA fate is still largely unknown. Here, we demonstrate through high-resolution imaging of intact Drosophila brains that Tyramine induces a reversible remodeling of somatic RNP granules characterized by the decondensation of granule-enriched RBPs (e.g. Imp/ZBP1/IGF2BP) and helicases (e.g. Me31B/DDX-6/Rck). Furthermore, our functional analysis reveals that Tyramine signals both through its receptor TyrR and through the calcium-activated kinase CamkII to trigger RNP component decondensation. Finally, we uncover that RNP granule remodeling is accompanied by the rapid and specific translational activation of associated mRNAs. Thus, this work sheds new light on the mechanisms controlling cue-induced rearrangement of physiological RNP condensates.
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Affiliation(s)
- Nadia Formicola
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Marjorie Heim
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Jérémy Dufourt
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, Montpellier, France
| | - Anne-Sophie Lancelot
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
| | - Akira Nakamura
- Department of Germline Development, Institute of Molecular Embryology and Genetics, and Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Mounia Lagha
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, Montpellier, France
| | - Florence Besse
- Université Côte d'Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France
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22
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Changes in Presynaptic Gene Expression during Homeostatic Compensation at a Central Synapse. J Neurosci 2021; 41:3054-3067. [PMID: 33608385 PMCID: PMC8026347 DOI: 10.1523/jneurosci.2979-20.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 12/02/2022] Open
Abstract
Homeostatic matching of pre- and postsynaptic function has been observed in many species and neural structures, but whether transcriptional changes contribute to this form of trans-synaptic coordination remains unknown. To identify genes whose expression is altered in presynaptic neurons as a result of perturbing postsynaptic excitability, we applied a transcriptomics-friendly, temperature-inducible Kir2.1-based activity clamp at the first synaptic relay of the Drosophila olfactory system, a central synapse known to exhibit trans-synaptic homeostatic matching. Twelve hours after adult-onset suppression of activity in postsynaptic antennal lobe projection neurons of males and females, we detected changes in the expression of many genes in the third antennal segment, which houses the somata of presynaptic olfactory receptor neurons. These changes affected genes with roles in synaptic vesicle release and synaptic remodeling, including several implicated in homeostatic plasticity at the neuromuscular junction. At 48 h and beyond, the transcriptional landscape tilted toward protein synthesis, folding, and degradation; energy metabolism; and cellular stress defenses, indicating that the system had been pushed to its homeostatic limits. Our analysis suggests that similar homeostatic machinery operates at peripheral and central synapses and identifies many of its components. The presynaptic transcriptional response to genetically targeted postsynaptic perturbations could be exploited for the construction of novel connectivity tracing tools. SIGNIFICANCE STATEMENT Homeostatic feedback mechanisms adjust intrinsic and synaptic properties of neurons to keep their average activity levels constant. We show that, at a central synapse in the fruit fly brain, these mechanisms include changes in presynaptic gene expression that are instructed by an abrupt loss of postsynaptic excitability. The trans-synaptically regulated genes have roles in synaptic vesicle release and synapse remodeling; protein synthesis, folding, and degradation; and energy metabolism. Our study establishes a role for transcriptional changes in homeostatic synaptic plasticity, points to mechanistic commonalities between peripheral and central synapses, and potentially opens new opportunities for the development of connectivity-based gene expression systems.
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23
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Daou A, Margoliash D. Intrinsic plasticity and birdsong learning. Neurobiol Learn Mem 2021; 180:107407. [PMID: 33631346 DOI: 10.1016/j.nlm.2021.107407] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 10/28/2020] [Accepted: 02/11/2021] [Indexed: 10/22/2022]
Abstract
Although information processing and storage in the brain is thought to be primarily orchestrated by synaptic plasticity, other neural mechanisms such as intrinsic plasticity are available. While a number of recent studies have described the plasticity of intrinsic excitability in several types of neurons, the significance of non-synaptic mechanisms in memory and learning remains elusive. After reviewing plasticity of intrinsic excitation in relation to learning and homeostatic mechanisms, we focus on the intrinsic properties of a class of basal-ganglia projecting song system neurons in zebra finch, how these related to each bird's unique learned song, how these properties change over development, and how they are maintained dynamically to rapidly change in response to auditory feedback perturbations. We place these results in the broader theme of learning and changes in intrinsic properties, emphasizing the computational implications of this form of plasticity, which are distinct from synaptic plasticity. The results suggest that exploring reciprocal interactions between intrinsic and network properties will be a fruitful avenue for understanding mechanisms of birdsong learning.
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Affiliation(s)
- Arij Daou
- University of Chicago, United States
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24
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Abstract
The integration of two or more distinct sensory cues can help animals make more informed decisions about potential food sources, but little is known about how feeding-related multimodal sensory integration happens at the cellular and molecular levels. Here, we show that multimodal sensory integration contributes to a stereotyped feeding behavior in the model organism Drosophila melanogaster Simultaneous olfactory and mechanosensory inputs significantly influence a taste-evoked feeding behavior called the proboscis extension reflex (PER). Olfactory and mechanical information are mediated by antennal Or35a neurons and leg hair plate mechanosensory neurons, respectively. We show that the controlled delivery of three different sensory cues can produce a supra-additive PER via the concurrent stimulation of olfactory, taste, and mechanosensory inputs. We suggest that the fruit fly is a versatile model system to study multisensory integration related to feeding, which also likely exists in vertebrates.
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25
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Perez-Catalan NA, Doe CQ, Ackerman SD. The role of astrocyte-mediated plasticity in neural circuit development and function. Neural Dev 2021; 16:1. [PMID: 33413602 PMCID: PMC7789420 DOI: 10.1186/s13064-020-00151-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 12/26/2020] [Indexed: 02/03/2023] Open
Abstract
Neuronal networks are capable of undergoing rapid structural and functional changes called plasticity, which are essential for shaping circuit function during nervous system development. These changes range from short-term modifications on the order of milliseconds, to long-term rearrangement of neural architecture that could last for the lifetime of the organism. Neural plasticity is most prominent during development, yet also plays a critical role during memory formation, behavior, and disease. Therefore, it is essential to define and characterize the mechanisms underlying the onset, duration, and form of plasticity. Astrocytes, the most numerous glial cell type in the human nervous system, are integral elements of synapses and are components of a glial network that can coordinate neural activity at a circuit-wide level. Moreover, their arrival to the CNS during late embryogenesis correlates to the onset of sensory-evoked activity, making them an interesting target for circuit plasticity studies. Technological advancements in the last decade have uncovered astrocytes as prominent regulators of circuit assembly and function. Here, we provide a brief historical perspective on our understanding of astrocytes in the nervous system, and review the latest advances on the role of astroglia in regulating circuit plasticity and function during nervous system development and homeostasis.
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Affiliation(s)
- Nelson A Perez-Catalan
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, USA
- Kennedy Center, Department of Pediatrics, The University of Chicago, Chicago, IL, USA
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, USA
| | - Sarah D Ackerman
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, USA.
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26
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Activity-Dependent Global Downscaling of Evoked Neurotransmitter Release across Glutamatergic Inputs in Drosophila. J Neurosci 2020; 40:8025-8041. [PMID: 32928887 DOI: 10.1523/jneurosci.0349-20.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 09/01/2020] [Accepted: 09/04/2020] [Indexed: 12/11/2022] Open
Abstract
Within mammalian brain circuits, activity-dependent synaptic adaptations, such as synaptic scaling, stabilize neuronal activity in the face of perturbations. Stability afforded through synaptic scaling involves uniform scaling of quantal amplitudes across all synaptic inputs formed on neurons, as well as on the postsynaptic side. It remains unclear whether activity-dependent uniform scaling also operates within peripheral circuits. We tested for such scaling in a Drosophila larval neuromuscular circuit, where the muscle receives synaptic inputs from different motoneurons. We used motoneuron-specific genetic manipulations to increase the activity of only one motoneuron and recordings of postsynaptic currents from inputs formed by the different motoneurons. We discovered an adaptation which caused uniform downscaling of evoked neurotransmitter release across all inputs through decreases in release probabilities. This "presynaptic downscaling" maintained the relative differences in neurotransmitter release across all inputs around a homeostatic set point, caused a compensatory decrease in synaptic drive to the muscle affording robust and stable muscle activity, and was induced within hours. Presynaptic downscaling was associated with an activity-dependent increase in Drosophila vesicular glutamate transporter expression. Activity-dependent uniform scaling can therefore manifest also on the presynaptic side to produce robust and stable circuit outputs. Within brain circuits, uniform downscaling on the postsynaptic side is implicated in sleep- and memory-related processes. Our results suggest that evaluation of such processes might be broadened to include uniform downscaling on the presynaptic side.SIGNIFICANCE STATEMENT To date, compensatory adaptations which stabilise target cell activity through activity-dependent global scaling have been observed only within central circuits, and on the postsynaptic side. Considering that maintenance of stable activity is imperative for the robust function of the nervous system as a whole, we tested whether activity-dependent global scaling could also manifest within peripheral circuits. We uncovered a compensatory adaptation which causes global scaling within a peripheral circuit and on the presynaptic side through uniform downscaling of evoked neurotransmitter release. Unlike in central circuits, uniform scaling maintains functionality over a wide, rather than a narrow, operational range, affording robust and stable activity. Activity-dependent global scaling therefore operates on both the presynaptic and postsynaptic sides to maintain target cell activity.
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27
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Experience-Dependent Development of Dendritic Arbors in Mouse Visual Cortex. J Neurosci 2020; 40:6536-6556. [PMID: 32669356 DOI: 10.1523/jneurosci.2910-19.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 06/26/2020] [Accepted: 06/30/2020] [Indexed: 12/27/2022] Open
Abstract
The dendritic arbor of neurons constrains the pool of available synaptic partners and influences the electrical integration of synaptic currents. Despite these critical functions, our knowledge of the dendritic structure of cortical neurons during early postnatal development and how these dendritic structures are modified by visual experience is incomplete. Here, we present a large-scale dataset of 849 3D reconstructions of the basal arbor of pyramidal neurons collected across early postnatal development in visual cortex of mice of either sex. We found that the basal arbor grew substantially between postnatal day 7 (P7) and P30, undergoing a 45% increase in total length. However, the gross number of primary neurites and dendritic segments was largely determined by P7. Growth from P7 to P30 occurred primarily through extension of dendritic segments. Surprisingly, comparisons of dark-reared and typically reared mice revealed that a net gain of only 15% arbor length could be attributed to visual experience; most growth was independent of experience. To examine molecular contributions, we characterized the role of the activity-regulated small GTPase Rem2 in both arbor development and the maintenance of established basal arbors. We showed that Rem2 is an experience-dependent negative regulator of dendritic segment number during the visual critical period. Acute deletion of Rem2 reduced directionality of dendritic arbors. The data presented here establish a highly detailed, quantitative analysis of basal arbor development that we believe has high utility both in understanding circuit development as well as providing a framework for computationalists wishing to generate anatomically accurate neuronal models.SIGNIFICANCE STATEMENT Dendrites are the sites of the synaptic connections among neurons. Despite their importance for neural circuit function, only a little is known about the postnatal development of dendritic arbors of cortical pyramidal neurons and the influence of experience. Here we show that the number of primary basal dendritic arbors is already established before eye opening, and that these arbors primarily grow through lengthening of dendritic segments and not through addition of dendritic segments. Surprisingly, visual experience has a modest net impact on overall arbor length (15%). Experiments in KO animals revealed that the gene Rem2 is positive regulator of dendritic length and a negative regulator of dendritic segments.
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Lnenicka GA. Crayfish and Drosophila NMJs. Neurosci Lett 2020; 732:135110. [PMID: 32497734 DOI: 10.1016/j.neulet.2020.135110] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/27/2020] [Accepted: 05/29/2020] [Indexed: 01/06/2023]
Abstract
Many synaptic studies have utilized the experimental advantages of the Arthropod NMJ and the most prominent preparations have been the crayfish and Drosophila larval NMJs. Early cellular studies in the crayfish established the framework for later molecular studies in Drosophila. The two neuromuscular systems are compared including the advantages presented by each preparation for cellular analysis. Beginning with the early work in the crayfish, research developments are followed in the areas of structure/function relationships, activity-dependent synaptic plasticity/development and synaptic homeostasis. A reoccurring theme in these studies is the regulation of active zone structure and function. Early studies in the crayfish focused on the role of active zone number/size and possible functional heterogeneity in regulating transmitter release. Recent studies in Drosophila have begun to characterize this heterogeneity using new approaches that combine imaging of transmitter release, Ca2+ influx and molecular composition for individual active zones.
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Affiliation(s)
- Gregory A Lnenicka
- Department of Biological Sciences, University at Albany, SUNY, Albany, NY 12222, United States.
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29
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Bartussek J, Lehmann FO. Sensory processing by motoneurons: a numerical model for low-level flight control in flies. J R Soc Interface 2019; 15:rsif.2018.0408. [PMID: 30158188 PMCID: PMC6127168 DOI: 10.1098/rsif.2018.0408] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 07/30/2018] [Indexed: 01/07/2023] Open
Abstract
Rhythmic locomotor behaviour in animals requires exact timing of muscle activation within the locomotor cycle. In rapidly oscillating motor systems, conventional control strategies may be affected by neural delays, making these strategies inappropriate for precise timing control. In flies, wing control thus requires sensory processing within the peripheral nervous system, circumventing the central brain. The underlying mechanism, with which flies integrate graded depolarization of visual interneurons and spiking proprioceptive feedback for precise muscle activation, is under debate. Based on physiological parameters, we developed a numerical model of spike initiation in flight muscles of a blowfly. The simulated Hodgkin–Huxley neuron reproduces multiple experimental findings and explains on the cellular level how vision might control wing kinematics. Sensory processing by single motoneurons appears to be sufficient for control of muscle power during flight in flies and potentially other flying insects, reducing computational load on the central brain during body posture reflexes and manoeuvring flight.
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Affiliation(s)
- Jan Bartussek
- Institute of Biological Sciences, Department of Animal Physiology, University of Rostock, 18059 Rostock, Germany
| | - Fritz-Olaf Lehmann
- Institute of Biological Sciences, Department of Animal Physiology, University of Rostock, 18059 Rostock, Germany
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30
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Guo H, Li Y, Shen L, Wang T, Jia X, Liu L, Xu T, Ou M, Hoekzema K, Wu H, Gillentine MA, Liu C, Ni H, Peng P, Zhao R, Zhang Y, Phornphutkul C, Stegmann APA, Prada CE, Hopkin RJ, Shieh JT, McWalter K, Monaghan KG, van Hasselt PM, van Gassen K, Bai T, Long M, Han L, Quan Y, Chen M, Zhang Y, Li K, Zhang Q, Tan J, Zhu T, Liu Y, Pang N, Peng J, Scott DA, Lalani SR, Azamian M, Mancini GMS, Adams DJ, Kvarnung M, Lindstrand A, Nordgren A, Pevsner J, Osei-Owusu IA, Romano C, Calabrese G, Galesi O, Gecz J, Haan E, Ranells J, Racobaldo M, Nordenskjold M, Madan-Khetarpal S, Sebastian J, Ball S, Zou X, Zhao J, Hu Z, Xia F, Liu P, Rosenfeld JA, de Vries BBA, Bernier RA, Xu ZQD, Li H, Xie W, Hufnagel RB, Eichler EE, Xia K. Disruptive variants of CSDE1 associate with autism and interfere with neuronal development and synaptic transmission. SCIENCE ADVANCES 2019; 5:eaax2166. [PMID: 31579823 PMCID: PMC6760934 DOI: 10.1126/sciadv.aax2166] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 08/27/2019] [Indexed: 05/30/2023]
Abstract
RNA binding proteins are key players in posttranscriptional regulation and have been implicated in neurodevelopmental and neuropsychiatric disorders. Here, we report a significant burden of heterozygous, likely gene-disrupting variants in CSDE1 (encoding a highly constrained RNA binding protein) among patients with autism and related neurodevelopmental disabilities. Analysis of 17 patients identifies common phenotypes including autism, intellectual disability, language and motor delay, seizures, macrocephaly, and variable ocular abnormalities. HITS-CLIP revealed that Csde1-binding targets are enriched in autism-associated gene sets, especially FMRP targets, and in neuronal development and synaptic plasticity-related pathways. Csde1 knockdown in primary mouse cortical neurons leads to an overgrowth of the neurites and abnormal dendritic spine morphology/synapse formation and impaired synaptic transmission, whereas mutant and knockdown experiments in Drosophila result in defects in synapse growth and synaptic transmission. Our study defines a new autism-related syndrome and highlights the functional role of CSDE1 in synapse development and synaptic transmission.
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Affiliation(s)
- Hui Guo
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA, USA
| | - Ying Li
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Lu Shen
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Tianyun Wang
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA, USA
| | - Xiangbin Jia
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Lijuan Liu
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
| | - Tao Xu
- Department of Neurobiology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Laboratory of Brain Disorders (Ministry of Science and Technology), Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Mengzhu Ou
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
| | - Kendra Hoekzema
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA, USA
| | - Huidan Wu
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Madelyn A. Gillentine
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA, USA
| | - Cenying Liu
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Hailun Ni
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Pengwei Peng
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Rongjuan Zhao
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yu Zhang
- Key Laboratory of Developmental Disorders in Children, Liuzhou Maternity and Child Healthcare Hospital, Liuzhou, Guangxi, China
| | - Chanika Phornphutkul
- Division of Human Genetics, Warren Alpert Medical School of Brown University, Hasbro Children's Hospital/Rhode Island Hospital, Providence, RI, USA
| | | | - Carlos E. Prada
- Department of Pediatrics, University of Cincinnati College of Medicine, Division of Human Genetics, Cincinnati Children’s Hospital, Cincinnati, OH, USA
| | - Robert J. Hopkin
- Department of Pediatrics, University of Cincinnati College of Medicine, Division of Human Genetics, Cincinnati Children’s Hospital, Cincinnati, OH, USA
| | - Joseph T. Shieh
- Institute for Human Genetics and Department of Pediatrics, University of California, San Francisco, San Francisco, CA, USA
| | | | | | | | | | - Ting Bai
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Min Long
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Lin Han
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yingting Quan
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Meilin Chen
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yaowen Zhang
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Kuokuo Li
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Qiumeng Zhang
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Jieqiong Tan
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Tengfei Zhu
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yaning Liu
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Nan Pang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
| | - Daryl A. Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Seema R. Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Mahshid Azamian
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Grazia M. S. Mancini
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam, Netherlands
| | - Darius J. Adams
- Goryeb Children’s Hospital, Atlantic Health System, Morristown, NJ, USA
| | - Malin Kvarnung
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Anna Lindstrand
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Ann Nordgren
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Jonathan Pevsner
- Department of Neurology, Kennedy Krieger Institute, Baltimore, MD, USA
- Program in Human Genetics, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Ikeoluwa A. Osei-Owusu
- Department of Neurology, Kennedy Krieger Institute, Baltimore, MD, USA
- Program in Human Genetics, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | | | | | | | - Jozef Gecz
- School of Medicine and the Robinson Research Institute, University of Adelaide at the Women’s and Children’s Hospital, Adelaide, South Australia, Australia
| | - Eric Haan
- Adult Genetics Unit, Royal Adelaide Hospital, and School of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Judith Ranells
- Department of Pediatrics, University of South Florida, Tampa, FL, USA
| | - Melissa Racobaldo
- Department of Pediatrics, University of South Florida, Tampa, FL, USA
| | - Magnus Nordenskjold
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Suneeta Madan-Khetarpal
- Division of Medical Genetics, Children’s Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA
| | - Jessica Sebastian
- Division of Medical Genetics, Children’s Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA
| | - Susie Ball
- Central Washington Genetics Program, Virginia Mason Memorial, Yakima, WA, USA
| | - Xiaobing Zou
- Children Development Behavior Center of the Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Jingping Zhao
- Mental Health Institute of the Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Zhengmao Hu
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Fan Xia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Baylor Genetics, Houston, TX, USA
| | - Pengfei Liu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Baylor Genetics, Houston, TX, USA
| | - Jill A. Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Bert B. A. de Vries
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, Netherlands
| | | | - Zhi-Qing David Xu
- Department of Neurobiology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Laboratory of Brain Disorders (Ministry of Science and Technology), Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Honghui Li
- Key Laboratory of Developmental Disorders in Children, Liuzhou Maternity and Child Healthcare Hospital, Liuzhou, Guangxi, China
| | - Wei Xie
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
| | - Robert B. Hufnagel
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, NIH, Bethesda, MD, USA
| | - Evan E. Eichler
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA
| | - Kun Xia
- Center for Medical Genetics and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
- Key Laboratory of Medical Information Research, Central South University, Changsha, Hunan, China
- CAS Center for Excellence in Brain Science and Intelligences Technology (CEBSIT), Chinese Academy of Sciences, Shanghai 200030, China
- Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, Hunan 410078, China
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James TD, Zwiefelhofer DJ, Frank CA. Maintenance of homeostatic plasticity at the Drosophila neuromuscular synapse requires continuous IP 3-directed signaling. eLife 2019; 8:39643. [PMID: 31180325 PMCID: PMC6557630 DOI: 10.7554/elife.39643] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 05/27/2019] [Indexed: 12/18/2022] Open
Abstract
Synapses and circuits rely on neuroplasticity to adjust output and meet physiological needs. Forms of homeostatic synaptic plasticity impart stability at synapses by countering destabilizing perturbations. The Drosophila melanogaster larval neuromuscular junction (NMJ) is a model synapse with robust expression of homeostatic plasticity. At the NMJ, a homeostatic system detects impaired postsynaptic sensitivity to neurotransmitter and activates a retrograde signal that restores synaptic function by adjusting neurotransmitter release. This process has been separated into temporally distinct phases, induction and maintenance. One prevailing hypothesis is that a shared mechanism governs both phases. Here, we show the two phases are separable. Combining genetics, pharmacology, and electrophysiology, we find that a signaling system consisting of PLCβ, inositol triphosphate (IP3), IP3 receptors, and Ryanodine receptors is required only for the maintenance of homeostatic plasticity. We also find that the NMJ is capable of inducing homeostatic signaling even when its sustained maintenance process is absent. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Thomas D James
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, United States.,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, United States
| | - Danielle J Zwiefelhofer
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, United States
| | - C Andrew Frank
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, United States.,Interdisciplinary Programs in Neuroscience, Genetics and Molecular Medicine, University of Iowa, Iowa City, United States
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32
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Goel P, Dufour Bergeron D, Böhme MA, Nunnelly L, Lehmann M, Buser C, Walter AM, Sigrist SJ, Dickman D. Homeostatic scaling of active zone scaffolds maintains global synaptic strength. J Cell Biol 2019; 218:1706-1724. [PMID: 30914419 PMCID: PMC6504899 DOI: 10.1083/jcb.201807165] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 12/14/2018] [Accepted: 03/06/2019] [Indexed: 12/23/2022] Open
Abstract
Synaptic terminals grow and retract throughout life, yet synaptic strength is maintained within stable physiological ranges. To study this process, we investigated Drosophila endophilin (endo) mutants. Although active zone (AZ) number is doubled in endo mutants, a compensatory reduction in their size homeostatically adjusts global neurotransmitter output to maintain synaptic strength. We find an inverse adaptation in rab3 mutants. Additional analyses using confocal, STED, and electron microscopy reveal a stoichiometric tuning of AZ scaffolds and nanoarchitecture. Axonal transport of synaptic cargo via the lysosomal kinesin adapter Arl8 regulates AZ abundance to modulate global synaptic output and sustain the homeostatic potentiation of neurotransmission. Finally, we find that this AZ scaling can interface with two independent homeostats, depression and potentiation, to remodel AZ structure and function, demonstrating a robust balancing of separate homeostatic adaptations. Thus, AZs are pliable substrates with elastic and modular nanostructures that can be dynamically sculpted to stabilize and tune both local and global synaptic strength.
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Affiliation(s)
- Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA
| | | | - Mathias A Böhme
- Neurocure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | - Luke Nunnelly
- Department of Neurobiology, University of Southern California, Los Angeles, CA
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | | | - Alexander M Walter
- Neurocure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | | | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA
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33
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Deveci D, Martin FA, Leopold P, Romero NM. AstA Signaling Functions as an Evolutionary Conserved Mechanism Timing Juvenile to Adult Transition. Curr Biol 2019; 29:813-822.e4. [PMID: 30799245 DOI: 10.1016/j.cub.2019.01.053] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 11/28/2018] [Accepted: 01/21/2019] [Indexed: 01/07/2023]
Abstract
The onset of sexual maturation is the result of a hormonal cascade peaking with the production of steroid hormones. In animals undergoing a program of determinate growth, sexual maturation also coincides with the attainment of adult size. The exact signals that time the onset of maturation and the mechanisms coupling growth and maturation remain elusive. Here, we show that the Drosophila neuropeptide AstA and its receptor AstAR1 act as a brain trigger for maturation and juvenile growth. We first identified AstAR1 in an RNAi-based genetic screen as a key regulator of sexual maturation. Its specific knockdown in prothoracicotropic hormone (PTTH)-producing neurons delays the onset of maturation by impairing PTTH secretion. In addition to its role in PTTH neurons, AstAR1 is required in the brain insulin-producing cells (IPCs) to promote insulin secretion and systemic growth. AstAR1 function is mediated by the AstA neuropeptide that is expressed in two bilateral neurons contacting the PTTH neurons and the IPCs. Silencing brain AstA expression delays the onset of maturation, therefore extending the growth period. However, no pupal overgrowth is observed, indicating that, in these conditions, the growth-promoting function of AstAR1 is also impaired. These data suggest that AstA/AstAR1 acts to coordinate juvenile growth with maturation. Interesting, AstA/AstAR1 is homologous to KISS/GPR54, a ligand-receptor signal required for human puberty, suggesting that an evolutionary conserved neural circuitry controls the onset of maturation.
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Affiliation(s)
- Derya Deveci
- University Côte d'Azur, CNRS, Inserm, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France
| | | | - Pierre Leopold
- Institut Curie, PSL Research University, CNRS UMR3215, Inserm U934, UPMC Paris-Sorbonne, 26 Rue d'Ulm, 75005 Paris, France.
| | - Nuria M Romero
- University Côte d'Azur, CNRS, Inserm, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France.
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34
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He T, Nitabach MN, Lnenicka GA. Parvalbumin expression affects synaptic development and physiology at the Drosophila larval NMJ. J Neurogenet 2018; 32:209-220. [PMID: 30175644 DOI: 10.1080/01677063.2018.1498496] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Presynaptic Ca2+ appears to play multiple roles in synaptic development and physiology. We examined the effect of buffering presynaptic Ca2+ by expressing parvalbumin (PV) in Drosophila neurons, which do not normally express PV. The studies were performed on the identified Ib terminal that innervates muscle fiber 5. The volume-averaged, residual Ca2+ resulting from single action potentials (APs) and AP trains was measured using the fluorescent Ca2+ indicator, OGB-1. PV reduced the amplitude and decay time constant (τ) for single-AP Ca2+ transients. For AP trains, there was a reduction in the rate of rise and decay of [Ca2+]i but the plateau [Ca2+]i was not affected. Electrophysiological recordings from muscle fiber 5 showed a reduction in paired-pulse facilitation, particularly the F1 component; this was likely due to the reduction in residual Ca2+. These synapses also showed reduced synaptic enhancement during AP trains, presumably due to less buildup of synaptic facilitation. The transmitter release for single APs was increased for the PV-expressing terminals and this may have been a homeostatic response to the decrease in facilitation. Confocal microscopy was used to examine the structure of the motor terminals and PV expression resulted in smaller motor terminals with fewer synaptic boutons and active zones. This result supports earlier proposals that increased AP activity promotes motor terminal growth through increases in presynaptic [Ca2+]i.
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Affiliation(s)
- Tao He
- a Division of Pulmonary and Critical Care Medicine , David Geffen School of Medicine at UCLA , Los Angeles , CA , USA
| | - Michael N Nitabach
- b Department of Cellular and Molecular Physiology , Yale School of Medicine , New Haven , CT , USA
| | - Gregory A Lnenicka
- c Department of Biological Sciences , University at Albany , Albany , NY , USA
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35
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Bronk P, Kuklin EA, Gorur-Shandilya S, Liu C, Wiggin TD, Reed ML, Marder E, Griffith LC. Regulation of Eag by Ca 2+/calmodulin controls presynaptic excitability in Drosophila. J Neurophysiol 2018; 119:1665-1680. [PMID: 29364071 PMCID: PMC6008097 DOI: 10.1152/jn.00820.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 01/15/2018] [Accepted: 01/16/2018] [Indexed: 11/22/2022] Open
Abstract
Drosophila ether-à-go-go ( eag) is the founding member of a large family of voltage-gated K+ channels, the KCNH family, which includes Kv10, 11, and 12. Concurrent binding of calcium/calmodulin (Ca2+/CaM) to NH2- and COOH-terminal sites inhibits mammalian EAG1 channels at submicromolar Ca2+ concentrations, likely by causing pore constriction. Although the Drosophila EAG channel was believed to be Ca2+-insensitive (Schönherr R, Löber K, Heinemann SH. EMBO J 19: 3263-3271, 2000.), both the NH2- and COOH-terminal sites are conserved. In this study we show that Drosophila EAG is inhibited by high Ca2+ concentrations that are only present at plasma membrane Ca2+ channel microdomains. To test the role of this regulation in vivo, we engineered mutations that block CaM-binding to the major COOH-terminal site of the endogenous eag locus, disrupting Ca2+-dependent inhibition. eag CaMBD mutants have reduced evoked release from larval motor neuron presynaptic terminals and show decreased Ca2+ influx in stimulated adult projection neuron presynaptic terminals, consistent with an increase in K+ conductance. These results are predicted by a conductance-based multicompartment model of the presynaptic terminal in which some fraction of EAG is localized to the Ca2+ channel microdomains that control neurotransmitter release. The reduction of release in the larval neuromuscular junction drives a compensatory increase in motor neuron somatic excitability. This misregulation of synaptic and somatic excitability has consequences for systems-level processes and leads to defects in associative memory formation in adults. NEW & NOTEWORTHY Regulation of excitability is critical to tuning the nervous system for complex behaviors. We demonstrate in this article that the EAG family of voltage-gated K+ channels exhibit conserved gating by Ca2+/CaM. Disruption of this inhibition in Drosophila results in decreased evoked neurotransmitter release due to truncated Ca2+ influx in presynaptic terminals. In adults, disrupted Ca2+ dynamics cripples memory formation. These data demonstrate that the biophysical details of channels have important implications for cell function and behavior.
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Affiliation(s)
- Peter Bronk
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Elena A Kuklin
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Srinivas Gorur-Shandilya
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Chang Liu
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Timothy D Wiggin
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Martha L Reed
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Eve Marder
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
| | - Leslie C Griffith
- Department of Biology, National Center for Behavioral Genomics and Volen Center for Complex Systems, Brandeis University , Waltham, Massachusetts
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Hur JH, Lee SH, Kim AY, Koh YH. Regulation of synaptic architecture and synaptic vesicle pools by Nervous wreck at Drosophila Type 1b glutamatergic synapses. Exp Mol Med 2018; 50:e462. [PMID: 29568072 PMCID: PMC5898900 DOI: 10.1038/emm.2017.303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Revised: 08/29/2017] [Accepted: 09/29/2017] [Indexed: 02/07/2023] Open
Abstract
Nervous wreck (Nwk), a protein that is present at Type 1 glutamatergic synapses that contains an SH3 domain and an FCH motif, is a Drosophila homolog of the human srGAP3/MEGAP protein, which is associated with mental retardation. Confocal microscopy revealed that circles in Nwk reticulum enclosed T-shaped active zones (T-AZs) and partially colocalized with synaptic vesicle (SV) markers and both exocytosis and endocytosis components. Results from an electron microscopic (EM) analysis showed that Nwk proteins localized at synaptic edges and in SV pools. Both the synaptic areas and the number of SVs in the readily releasable (RRPs) and reserve (RPs) SV pools in nwk2 were significantly reduced. Synergistic, morphological phenotypes observed from eag1;nwk2 neuromuscular junctions suggested that Nwk may regulate synaptic plasticity differently from activity-dependent Hebbian plasticity. Although the synaptic areas in eag1;nwk2 boutons were not significantly different from those of nwk2, the number of SVs in the RRPs was similar to those of Canton-S. In addition, three-dimensional, high-voltage EM tomographic analysis demonstrated that significantly fewer enlarged SVs were present in nwk2 RRPs. Furthermore, Nwk formed protein complexes with Drosophila Synapsin and Synaptotagmin 1 (DSypt1). Taken together, these findings suggest that Nwk is able to maintain synaptic architecture and both SV size and distribution at T-AZs by interacting with Synapsin and DSypt1.
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Affiliation(s)
- Joon Haeng Hur
- ILSONG Institute of Life Science, Hallym University, Anyang, Republic of Korea.,Department of Bio-Medical Gerontology, Hallym University Graduate School, Chuncheon, Republic of Korea
| | - Sang-Hee Lee
- BioMedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - A-Young Kim
- ILSONG Institute of Life Science, Hallym University, Anyang, Republic of Korea.,Department of Bio-Medical Gerontology, Hallym University Graduate School, Chuncheon, Republic of Korea
| | - Young Ho Koh
- ILSONG Institute of Life Science, Hallym University, Anyang, Republic of Korea.,Department of Bio-Medical Gerontology, Hallym University Graduate School, Chuncheon, Republic of Korea
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Kim H, Kim H, Kwon JY, Seo JT, Shin DM, Moon SJ. Drosophila Gr64e mediates fatty acid sensing via the phospholipase C pathway. PLoS Genet 2018; 14:e1007229. [PMID: 29420533 PMCID: PMC5821400 DOI: 10.1371/journal.pgen.1007229] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 02/21/2018] [Accepted: 01/29/2018] [Indexed: 12/02/2022] Open
Abstract
Animals use taste to sample and ingest essential nutrients for survival. Free fatty acids (FAs) are energy-rich nutrients that contribute to various cellular functions. Recent evidence suggests FAs are detected through the gustatory system to promote feeding. In Drosophila, phospholipase C (PLC) signaling in sweet-sensing cells is required for FA detection but other signaling molecules are unknown. Here, we show Gr64e is required for the behavioral and electrophysiological responses to FAs. GR64e and TRPA1 are interchangeable when they act downstream of PLC: TRPA1 can substitute for GR64e in FA but not glycerol sensing, and GR64e can substitute for TRPA1 in aristolochic acid but not N-methylmaleimide sensing. In contrast to its role in FA sensing, GR64e functions as a ligand-gated ion channel for glycerol detection. Our results identify a novel FA transduction molecule and reveal that Drosophila Grs can act via distinct molecular mechanisms depending on context. Fatty acids (FAs) are energy-rich nutrients that are detected through the gustatory system to promote feeding. Here, we show FA detection requires a Drosophila gustatory receptor, Gr64e. Although GR64e functions as a ligand-gated ion channel for glycerol detection, in FA sensing, it acts downstream of phospholipase C signaling. We identified a novel signaling molecule for FA sensing in Drosophila. Furthermore, our findings suggest Drosophila GRs have multiple modes of action depending on their cellular and molecular context.
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Affiliation(s)
- Hyeyon Kim
- Department of Oral Biology, BK21 PLUS, Yonsei University College of Dentistry, Yonsei-ro 50–1, Seodaemun-gu, Seoul, Korea
| | - Haein Kim
- Department of Biological Sciences, Sungkyunkwan University, Suwon, Gyeonggi-do, Korea
| | - Jae Young Kwon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, Gyeonggi-do, Korea
| | - Jeong Taeg Seo
- Department of Oral Biology, BK21 PLUS, Yonsei University College of Dentistry, Yonsei-ro 50–1, Seodaemun-gu, Seoul, Korea
| | - Dong Min Shin
- Department of Oral Biology, BK21 PLUS, Yonsei University College of Dentistry, Yonsei-ro 50–1, Seodaemun-gu, Seoul, Korea
| | - Seok Jun Moon
- Department of Oral Biology, BK21 PLUS, Yonsei University College of Dentistry, Yonsei-ro 50–1, Seodaemun-gu, Seoul, Korea
- * E-mail:
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38
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Abstract
Fluid clearance from the respiratory system during developmental transitions is critically important for achieving optimal gas exchange in animals. During insect development from embryo to adult, airway clearance occurs episodically each time the molt is completed by performance of the ecdysis sequence, coordinated by a peptide-signaling cascade initiated by ecdysis-triggering hormone (ETH). We find that the neuropeptide Kinin (also known as Drosokinin or Leukokinin) is required for normal respiratory fluid clearance or "tracheal air-filling" in Drosophila larvae. Disruption of Kinin signaling leads to defective air-filling during all larval stages. Such defects are observed upon ablation or electrical silencing of Kinin neurons, as well as RNA silencing of the Kinin gene or the ETH receptor in Kinin neurons, indicating that ETH targets Kinin neurons to promote tracheal air-filling. A Kinin receptor mutant fly line (Lkrf02594 ) also exhibits tracheal air-filling defects in all larval stages. Targeted Kinin receptor silencing in tracheal epithelial cells using breathless or pickpocket (ppk) drivers compromises tracheal air-filling. On the other hand, promotion of Kinin signaling in vivo through peptide injection or Kinin neuron activation through Drosophila TrpA1 (dTrpA1) expression induces premature tracheal collapse and air-filling. Moreover, direct exposure of tracheal epithelial cells in vitro to Kinin leads to calcium mobilization in tracheal epithelial cells. Our findings strongly implicate the neuropeptide Kinin as an important regulator of airway clearance via intracellular calcium mobilization in tracheal epithelial cells of Drosophila.
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Muscle Nicotinic Acetylcholine Receptors May Mediate Trans-Synaptic Signaling at the Mouse Neuromuscular Junction. J Neurosci 2018; 38:1725-1736. [PMID: 29326174 DOI: 10.1523/jneurosci.1789-17.2018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 01/02/2018] [Accepted: 01/08/2018] [Indexed: 11/21/2022] Open
Abstract
Block of neurotransmitter receptors at the neuromuscular junction (NMJ) has been shown to trigger upregulation of the number of synaptic vesicles released (quantal content, QC), a response termed homeostatic synaptic plasticity. The mechanism underlying this plasticity is not known. Here, we used selective toxins to demonstrate that block of α1-containing nicotinic acetylcholine receptors (nAChRs) at the NMJ of male and female mice triggers the upregulation of QC. Reduction of current flow through nAChRs, induced by drugs with antagonist activity, demonstrated that reduction in synaptic current per se does not trigger upregulation of QC. These data led to the remarkable conclusion that disruption of synaptic transmission is not sensed to trigger upregulation of QC. During studies of the effect of partial block of nAChRs on QC, we observed a small but reproducible increase in the decay kinetics of miniature synaptic currents. The change in kinetics was correlated with the increase in QC and raises the possibility that a change in postsynaptic nAChR conformation may be associated with the presynaptic increase in QC. We propose that, in addition to functioning in synaptic transmission, ionotropic muscle nicotonic nAChRs may serve as signaling molecules that participate in synaptic plasticity. Because nAChRs have been implicated in a number of disease states, the finding that nAChRs may be involved in triggering synaptic plasticity could have wide-reaching implications.SIGNIFICANCE STATEMENT The signals that initiate synaptic plasticity of the nervous system are still incompletely understood. Using the mouse neuromuscular junction as a model synapse, we studied how block of neurotransmitter receptors is sensed to trigger synaptic plasticity. Our studies led to the surprising conclusion that neither changes in synaptic current nor spiking of the presynaptic or postsynaptic cell are sensed to initiate synaptic plasticity. Instead, postsynaptic nicotinic acetylcholine receptors (nAChRs), in addition to functioning in synaptic transmission, may serve as signaling molecules that trigger synaptic plasticity. Because nAChRs have been implicated in a number of disease states, the finding that they may mediate synaptic plasticity has broad implications.
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40
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Ahn JE, Chen Y, Amrein H. Molecular basis of fatty acid taste in Drosophila. eLife 2017; 6:30115. [PMID: 29231818 PMCID: PMC5747521 DOI: 10.7554/elife.30115] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 12/08/2017] [Indexed: 01/01/2023] Open
Abstract
Behavioral studies have established that Drosophila appetitive taste responses towards fatty acids are mediated by sweet sensing Gustatory Receptor Neurons (GRNs). Here we show that sweet GRN activation requires the function of the Ionotropic Receptor genes IR25a, IR76b and IR56d. The former two IR genes are expressed in several neurons per sensillum, while IR56d expression is restricted to sweet GRNs. Importantly, loss of appetitive behavioral responses to fatty acids in IR25a and IR76b mutant flies can be completely rescued by expression of respective transgenes in sweet GRNs. Interestingly, appetitive behavioral responses of wild type flies to hexanoic acid reach a plateau at ~1%, but decrease with higher concentration, a property mediated through IR25a/IR76b independent activation of bitter GRNs. With our previous report on sour taste, our studies suggest that IR-based receptors mediate different taste qualities through cell-type specific IR subunits.
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Affiliation(s)
- Ji-Eun Ahn
- Department of Molecular and Cellular Medicine, Health Science Center, Texas A&M University, College Station, Texas, United States
| | - Yan Chen
- Department of Molecular and Cellular Medicine, Health Science Center, Texas A&M University, College Station, Texas, United States
| | - Hubert Amrein
- Department of Molecular and Cellular Medicine, Health Science Center, Texas A&M University, College Station, Texas, United States
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41
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Abstract
The study of behavior requires manipulation of the controlling neural circuits. The fruit fly, Drosophila melanogaster, is an ideal model for studying behavior because of its relatively small brain and the numerous sophisticated genetic tools that have been developed for this animal. Relatively recent technical advances allow the manipulation of a small subset of neurons with temporal resolution in flies while they are subject to behavior assays. This review briefly describes the most important genetic techniques, reagents, and approaches that are available to study and manipulate the neural circuits involved in Drosophila behavior. We also describe some examples of these genetic tools in the study of the olfactory receptor system.
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Affiliation(s)
- Fernando Martín
- a Department of Functional Biology (Genetics) , University of Oviedo , Oviedo , Spain
| | - Esther Alcorta
- a Department of Functional Biology (Genetics) , University of Oviedo , Oviedo , Spain
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42
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Shiozaki HM, Kazama H. Parallel encoding of recent visual experience and self-motion during navigation in Drosophila. Nat Neurosci 2017; 20:1395-1403. [PMID: 28869583 DOI: 10.1038/nn.4628] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Accepted: 07/26/2017] [Indexed: 12/16/2022]
Abstract
Animal navigation requires multiple types of information for decisions on directional heading. We identified neural processing channels that encode multiple cues during navigational decision-making in Drosophila melanogaster. In a flight simulator, we found that flies made directional choices on the basis of the location of a recently presented landmark. This experience-guided navigation was impaired by silencing neurons in the bulb (BU), a region in the central brain. Two-photon calcium imaging during flight revealed that the dorsal part of the BU encodes the location of a recent landmark, whereas the ventral part of the BU tracks self-motion reflecting turns. Photolabeling-based circuit tracing indicated that these functional compartments of the BU constitute adjacent, yet distinct, anatomical pathways that both enter the navigation center. Thus, the fly's navigation system organizes multiple types of information in parallel channels, which may compactly transmit signals without interference for decision-making during flight.
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Affiliation(s)
| | - Hokto Kazama
- RIKEN Brain Science Institute, Saitama, Japan.,Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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43
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Augmented quantal release of acetylcholine at the vertebrate neuromuscular junction following tdp-43 depletion. PLoS One 2017; 12:e0177005. [PMID: 28472174 PMCID: PMC5417676 DOI: 10.1371/journal.pone.0177005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/20/2017] [Indexed: 01/13/2023] Open
Abstract
TAR DNA binding protein (TDP-43) is a 43 kD, predominately nuclear, protein involved in RNA metabolism. Of clinical significance is that the majority of amyotrophic lateral sclerosis (ALS) patients display abnormal accumulation of misfolded TDP-43 in the cytoplasm, which is coincident with a loss of nuclear localization in the afflicted regions of the central nervous system. Little is known about defects that arise in loss-of-function models, in particular synaptic defects that arise at the neuromuscular junction (NMJ). In this report, we examined abnormalities arising at the NMJ following depletion of tdp-43 using a previously characterized mutant tardbp (encoding tdp-43) zebrafish line containing a premature stop codon (Y220X) that results in an unstable and degraded protein. Homozygous tardbpY220X/Y220X zebrafish do not produce tdp-43 but develop normally due to expression of an alternative splice variant of tardbpl (tardbp paralog). Using an antisense morpholino oligonucleotide to knockdown expression of the tardbpl in tardbpY220X/Y220X embryos, we examined locomotor defects, NMJ structural abnormalities and release of quantal synaptic vesicles at the NMJ. As in previous reports, larvae depleted of tdp-43 display reduced survival, gross morphological defects and severely impaired locomotor activity. These larvae also displayed an increased number of orphaned pre- and postsynaptic NMJ markers but surprisingly, we observed a significant increase (3.5 times) in the frequency of quantal acetylcholine release at the NMJ in larvae depleted of tdp-43. These results indicate that reduced TDP-43 levels alter quantal vesicle release at the NMJ during vertebrate development and may be relevant for understanding synaptic dysfunction in ALS.
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44
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Newman ZL, Hoagland A, Aghi K, Worden K, Levy SL, Son JH, Lee LP, Isacoff EY. Input-Specific Plasticity and Homeostasis at the Drosophila Larval Neuromuscular Junction. Neuron 2017; 93:1388-1404.e10. [PMID: 28285823 DOI: 10.1016/j.neuron.2017.02.028] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/18/2016] [Accepted: 02/15/2017] [Indexed: 11/28/2022]
Abstract
Synaptic connections undergo activity-dependent plasticity during development and learning, as well as homeostatic re-adjustment to ensure stability. Little is known about the relationship between these processes, particularly in vivo. We addressed this with novel quantal resolution imaging of transmission during locomotive behavior at glutamatergic synapses of the Drosophila larval neuromuscular junction. We find that two motor input types, Ib and Is, provide distinct forms of excitatory drive during crawling and differ in key transmission properties. Although both inputs vary in transmission probability, active Is synapses are more reliable. High-frequency firing "wakes up" silent Ib synapses and depresses Is synapses. Strikingly, homeostatic compensation in presynaptic strength only occurs at Ib synapses. This specialization is associated with distinct regulation of postsynaptic CaMKII. Thus, basal synaptic strength, short-term plasticity, and homeostasis are determined input-specifically, generating a functional diversity that sculpts excitatory transmission and behavioral function.
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Affiliation(s)
- Zachary L Newman
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Adam Hoagland
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Krishan Aghi
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Kurtresha Worden
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Sabrina L Levy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Jun Ho Son
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA; Berkeley Sensor and Actuator Center, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Luke P Lee
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA; Berkeley Sensor and Actuator Center, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA; Biomedical Institute for Global Health Research and Technology, National University of Singapore, 119077 Singapore, Singapore
| | - Ehud Y Isacoff
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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45
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Retzke T, Thoma M, Hansson BS, Knaden M. Potencies of effector genes in silencing odor-guided behavior in Drosophila melanogaster. ACTA ACUST UNITED AC 2017; 220:1812-1819. [PMID: 28235908 DOI: 10.1242/jeb.156232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 02/20/2017] [Indexed: 11/20/2022]
Abstract
The genetic toolbox in Drosophila melanogaster offers a multitude of different effector constructs to silence neurons and neuron populations. In this study, we investigated the potencies of several effector genes - when expressed in olfactory sensory neurons (OSNs) - to abolish odor-guided behavior in three different bioassays. We found that two of the tested effectors (tetanus toxin and Kir2.1) are capable of mimicking the Orco mutant phenotype in all of our behavioral paradigms. In both cases, the effectiveness depended on effector expression levels, as full suppression of odor-guided behavior was observed only in flies homozygous for both Gal4-driver and UAS-effector constructs. Interestingly, the impact of the effector genes differed between chemotactic assays (i.e. the fly has to follow an odor gradient to localize the odor source) and anemotactic assays (i.e. the fly has to walk upwind after detecting an attractive odorant). In conclusion, our results underline the importance of performing appropriate control experiments when exploiting the D. melanogaster genetic toolbox, and demonstrate that some odor-guided behaviors are more resistant to genetic perturbations than others.
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Affiliation(s)
- Tom Retzke
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Straße 8, Jena 07745, Germany
| | - Michael Thoma
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Straße 8, Jena 07745, Germany
| | - Bill S Hansson
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Straße 8, Jena 07745, Germany
| | - Markus Knaden
- Max Planck Institute for Chemical Ecology, Department of Evolutionary Neuroethology, Hans-Knoell-Straße 8, Jena 07745, Germany
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46
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Regulation of quantal currents determines synaptic strength at neuromuscular synapses in larval Drosophila. Pflugers Arch 2016; 468:2031-2040. [PMID: 27783155 DOI: 10.1007/s00424-016-1893-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 10/09/2016] [Accepted: 10/11/2016] [Indexed: 10/20/2022]
Abstract
Studies of synaptic homeostasis during muscle fiber (MF) growth in Drosophila larvae have focused on the regulation of the quantal content of transmitter release. However, early studies in crayfish and frog suggested that regulation of quantal current size may be an integral mechanism in synaptic homeostasis. To examine this further in Drosophila, we compared the electrical properties, miniature excitatory postsynaptic potentials (minEPSPs) and miniature excitatory postsynaptic currents (minEPSCs) in different-sized MFs in third-instar larvae and for a single MF during larval growth. The third-instar MFs showed differences in input resistance due to differences in size and specific membrane resistance. We found that electrical coupling between MFs did not contribute substantially to the electrical properties; however, the electrode leak conductance and a slower developing increase in membrane conductance can influence the electrical recordings from these MFs. Our results demonstrated that larger MFs had larger minEPSCs to compensate for changes in MF electrical properties. This was most clearly seen for MF4 during larval growth from the second to third instar. During a predicted 80 % decrease in MF input resistance, the minEPSCs showed a 35 % increase in amplitude and 165 % increase in duration. Simulations demonstrated that the increase in minEPSC size resulted in a 129 % increase in minEPSP amplitude for third-instar larvae; this was mainly due to the increase in minEPSC duration. We also found that MFs with common innervation had similar-sized minEPSCs suggesting that MF innervation influences minEPSC size. Overall, the results showed that increased quantal content and quantal current size contribute equally to synaptic homeostasis during MF growth.
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47
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Mechanosensory neurons control sweet sensing in Drosophila. Nat Commun 2016; 7:12872. [PMID: 27641708 PMCID: PMC5031804 DOI: 10.1038/ncomms12872] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 08/10/2016] [Indexed: 01/31/2023] Open
Abstract
Animals discriminate nutritious food from toxic substances using their sense of taste. Since taste perception requires taste receptor cells to come into contact with water-soluble chemicals, it is a form of contact chemosensation. Concurrent with that contact, mechanosensitive cells detect the texture of food and also contribute to the regulation of feeding. Little is known, however, about the extent to which chemosensitive and mechanosensitive circuits interact. Here, we show Drosophila prefers soft food at the expense of sweetness and that this preference requires labellar mechanosensory neurons (MNs) and the mechanosensory channel Nanchung. Activation of these labellar MNs causes GABAergic inhibition of sweet-sensing gustatory receptor neurons, reducing the perceived intensity of a sweet stimulus. These findings expand our understanding of the ways different sensory modalities cooperate to shape animal behaviour. How different sensory modalities interact to control feeding is poorly understood. Here, authors show that in Drosophila, activation of labellar mechanosensory neurons causes inhibition of sweet-sensing gustatory receptor neurons, as a result, Drosophila prefer soft food at the expense of sweetness.
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48
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Hussain A, Zhang M, Üçpunar HK, Svensson T, Quillery E, Gompel N, Ignell R, Grunwald Kadow IC. Ionotropic Chemosensory Receptors Mediate the Taste and Smell of Polyamines. PLoS Biol 2016; 14:e1002454. [PMID: 27145030 PMCID: PMC4856413 DOI: 10.1371/journal.pbio.1002454] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 04/07/2016] [Indexed: 11/29/2022] Open
Abstract
The ability to find and consume nutrient-rich diets for successful reproduction and survival is fundamental to animal life. Among the nutrients important for all animals are polyamines, a class of pungent smelling compounds required in numerous cellular and organismic processes. Polyamine deficiency or excess has detrimental effects on health, cognitive function, reproduction, and lifespan. Here, we show that a diet high in polyamine is beneficial and increases reproductive success of flies, and we unravel the sensory mechanisms that attract Drosophila to polyamine-rich food and egg-laying substrates. Using a combination of behavioral genetics and in vivo calcium imaging, we demonstrate that Drosophila uses multisensory detection to find and evaluate polyamines present in overripe and fermenting fruit, their favored feeding and egg-laying substrate. In the olfactory system, two coexpressed ionotropic receptors (IRs), IR76b and IR41a, mediate the long-range attraction to the odor. In the gustatory system, multimodal taste sensation by IR76b receptor and GR66a bitter receptor neurons is used to evaluate quality and valence of the polyamine providing a mechanism for the fly’s high attraction to polyamine-rich and sweet decaying fruit. Given their universal and highly conserved biological roles, we propose that the ability to evaluate food for polyamine content may impact health and reproductive success also of other animals including humans. Polyamines are beneficial nutrients for reproduction, cognition, and lifespan. This study reveals that insects are highly attracted to them and identify their sources through an ancient class of ionotropic receptors on their smell and taste organs. Animals, including humans, evaluate food by its smell and taste. Odors and tastes not only signal the presence of food, they also reveal details about the type and amount of nutrients contained in it. A preference for certain foods frequently reflects the specific metabolic needs of an animal. Among the important but less known compounds that animals consume with their diet are polyamines. These pungent smelling molecules are essential for reproduction, development, and cognition. Interestingly, they are also produced by the cell and body, but their levels decline with age. A diet high in polyamines can improve age-related memory deficits and loss of fertility. We have used the model fly Drosophila melanogaster to unravel if and how animals detect polyamines in their food and environment, and which role this detection plays in their food choice behavior. Polyamine levels are particularly high in the fly’s favorite food and egg-laying substrate, overripe and decaying fruit. We found that food supplemented with polyamines indeed improves the reproductive success of a fly couple. We show that Drosophila is highly attracted to polyamines and uses them to identify promising egg-laying and feeding sites. It detects them through an ancient clade of receptor proteins on its olfactory and taste organs. We speculate that other animals can also detect polyamines and use their smell and taste to identify sources of these beneficial nutrients.
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Affiliation(s)
- Ashiq Hussain
- Sensory Neurogenetics Research Group, Max-Planck Institute of Neurobiology, Munich, Germany
| | - Mo Zhang
- Sensory Neurogenetics Research Group, Max-Planck Institute of Neurobiology, Munich, Germany
| | - Habibe K. Üçpunar
- Sensory Neurogenetics Research Group, Max-Planck Institute of Neurobiology, Munich, Germany
| | - Thomas Svensson
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Elsa Quillery
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Nicolas Gompel
- Faculty of Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Rickard Ignell
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Ilona C. Grunwald Kadow
- Sensory Neurogenetics Research Group, Max-Planck Institute of Neurobiology, Munich, Germany
- * E-mail:
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49
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Ouanounou G, Baux G, Bal T. A novel synaptic plasticity rule explains homeostasis of neuromuscular transmission. eLife 2016; 5. [PMID: 27138195 PMCID: PMC4854514 DOI: 10.7554/elife.12190] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 04/07/2016] [Indexed: 11/13/2022] Open
Abstract
Excitability differs among muscle fibers and undergoes continuous changes during development and growth, yet the neuromuscular synapse maintains a remarkable fidelity of execution. Here we show in two evolutionarily distant vertebrates (Xenopus laevis cell culture and mouse nerve-muscle ex-vivo) that the skeletal muscle cell constantly senses, through two identified calcium signals, synaptic events and their efficacy in eliciting spikes. These sensors trigger retrograde signal(s) that control presynaptic neurotransmitter release, resulting in synaptic potentiation or depression. In the absence of spikes, synaptic events trigger potentiation. Once the synapse is sufficiently strong to initiate spiking, the occurrence of these spikes activates a negative retrograde feedback. These opposing signals dynamically balance the synapse in order to continuously adjust neurotransmitter release to a level matching current muscle cell excitability. DOI:http://dx.doi.org/10.7554/eLife.12190.001 Nerve cells communicate with each other, and with targets such as muscle cells, at junctions called synapses. The nerve cell before the synapses releases a chemical called a neurotransmitter, which binds to receptors on the cell after the synapses. However, the first cell cannot determine by itself whether it is releasing the correct amount of neurotransmitter to activate its partner. For this, it requires feedback from the second cell. This feedback is particularly important at synapses between nerve cells and muscle cells, which are known as neuromuscular junctions. The likelihood that a given amount of transmitter will activate a muscle cell can vary with age and after exercise. Muscle cells must therefore be able to instruct their nerve cell partners to increase or decrease neurotransmitter release to accommodate these changes. Ouanounou et al. have now identified the mechanism by which muscle cells determine whether nerve cells are releasing an appropriate amount of neurotransmitter. Experiments in two distantly related animals – mice and embryos from a frog called Xenopus – revealed that muscle cells use two calcium-based signals. The first is the flow of calcium ions into the muscle cell in response to binding of neurotransmitter to receptors at the synapses: this tells the muscle cell how active the nerve cell is. The second is the release of calcium ions from internal stores inside the muscle cell: this occurs whenever neurotransmitter release is sufficient to activate the muscle cell. In response to the first calcium signal, the muscle cell sends positive feedback to the neuron, telling it to increase neurotransmitter release further. In response to the second signal, the muscle cell sends negative feedback to reduce neurotransmitter release. Thus, when neurotransmitter release is not enough to activate the muscle, positive feedback dominates and neurotransmitter release increases. However, when the muscle is activated, the two types of feedback act in balance to maintain efficient communication across the synapse. The next steps are to identify the cell signaling cascades that are mobilized by the two calcium signals, including the specific molecule (or molecules) that regulate neurotransmitter release. DOI:http://dx.doi.org/10.7554/eLife.12190.002
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Affiliation(s)
- Gilles Ouanounou
- Unité de Neuroscience Information et Complexité, Centre National de la Recherche Scientifique, FRE 3693, Gif-sur-Yvette, France
| | - Gérard Baux
- Unité de Neuroscience Information et Complexité, Centre National de la Recherche Scientifique, FRE 3693, Gif-sur-Yvette, France
| | - Thierry Bal
- Unité de Neuroscience Information et Complexité, Centre National de la Recherche Scientifique, FRE 3693, Gif-sur-Yvette, France
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Cho RW, Buhl LK, Volfson D, Tran A, Li F, Akbergenova Y, Littleton JT. Phosphorylation of Complexin by PKA Regulates Activity-Dependent Spontaneous Neurotransmitter Release and Structural Synaptic Plasticity. Neuron 2016; 88:749-61. [PMID: 26590346 DOI: 10.1016/j.neuron.2015.10.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 08/20/2015] [Accepted: 09/29/2015] [Indexed: 10/22/2022]
Abstract
Synaptic plasticity is a fundamental feature of the nervous system that allows adaptation to changing behavioral environments. Most studies of synaptic plasticity have examined the regulated trafficking of postsynaptic glutamate receptors that generates alterations in synaptic transmission. Whether and how changes in the presynaptic release machinery contribute to neuronal plasticity is less clear. The SNARE complex mediates neurotransmitter release in response to presynaptic Ca(2+) entry. Here we show that the SNARE fusion clamp Complexin undergoes activity-dependent phosphorylation that alters the basic properties of neurotransmission in Drosophila. Retrograde signaling following stimulation activates PKA-dependent phosphorylation of the Complexin C terminus that selectively and transiently enhances spontaneous release. Enhanced spontaneous release is required for activity-dependent synaptic growth. These data indicate that SNARE-dependent fusion mechanisms can be regulated in an activity-dependent manner and highlight the key role of spontaneous neurotransmitter release as a mediator of functional and structural plasticity.
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Affiliation(s)
- Richard W Cho
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Lauren K Buhl
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Dina Volfson
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Adrienne Tran
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Feng Li
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, New Haven, CT 06520, USA
| | - Yulia Akbergenova
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J Troy Littleton
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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