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Sumathipala SH, Khan S, Kozol RA, Araki Y, Syed S, Huganir RL, Dallman JE. Context-dependent hyperactivity in syngap1a and syngap1b zebrafish models of SYNGAP1-related disorder. Front Mol Neurosci 2024; 17:1401746. [PMID: 39050824 PMCID: PMC11266194 DOI: 10.3389/fnmol.2024.1401746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 06/04/2024] [Indexed: 07/27/2024] Open
Abstract
Background and aims SYNGAP1-related disorder (SYNGAP1-RD) is a prevalent genetic form of Autism Spectrum Disorder and Intellectual Disability (ASD/ID) and is caused by de novo or inherited mutations in one copy of the SYNGAP1 gene. In addition to ASD/ID, SYNGAP1 disorder is associated with comorbid symptoms including treatment-resistant-epilepsy, sleep disturbances, and gastrointestinal distress. Mechanistic links between these diverse symptoms and SYNGAP1 variants remain obscure, therefore, our goal was to generate a zebrafish model in which this range of symptoms can be studied. Methods We used CRISPR/Cas9 to introduce frameshift mutations in the syngap1a and syngap1b zebrafish duplicates (syngap1ab) and validated these stable models for Syngap1 loss-of-function. Because SYNGAP1 is extensively spliced, we mapped splice variants to the two zebrafish syngap1a and b genes and identified mammalian-like isoforms. We then quantified locomotory behaviors in zebrafish syngap1ab larvae under three conditions that normally evoke different arousal states in wild-type larvae: aversive, high-arousal acoustic, medium-arousal dark, and low-arousal light stimuli. Results We show that CRISPR/Cas9 indels in zebrafish syngap1a and syngap1b produced loss-of-function alleles at RNA and protein levels. Our analyses of zebrafish Syngap1 isoforms showed that, as in mammals, zebrafish Syngap1 N- and C-termini are extensively spliced. We identified a zebrafish syngap1 α1-like variant that maps exclusively to the syngap1b gene. Quantifying locomotor behaviors showed that syngap1ab mutant larvae are hyperactive compared to wild-type but to differing degrees depending on the stimulus. Hyperactivity was most pronounced in low arousal settings, and hyperactivity was proportional to the number of mutant syngap1 alleles. Limitations Syngap1 loss-of-function mutations produce relatively subtle phenotypes in zebrafish compared to mammals. For example, while mouse Syngap1 homozygotes die at birth, zebrafish syngap1ab-/- survive to adulthood and are fertile, thus some aspects of symptoms in people with SYNGAP1-Related Disorder are not likely to be reflected in zebrafish. Conclusion Our data support mutations in zebrafish syngap1ab as causal for hyperactivity associated with elevated arousal that is especially pronounced in low-arousal environments.
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Affiliation(s)
- Sureni H. Sumathipala
- Department of Biology, University of Miami, Coral Gables, FL, United States
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, United States
| | - Suha Khan
- Department of Biology, University of Miami, Coral Gables, FL, United States
| | - Robert A. Kozol
- Department of Biology, University of Miami, Coral Gables, FL, United States
- Department of Biological Sciences, St. John’s University, Queens, NY, United States
| | - Yoichi Araki
- Department of Neuroscience and Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Sheyum Syed
- Department of Physics, University of Miami, Coral Gables, FL, United States
| | - Richard L. Huganir
- Department of Neuroscience and Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Julia E. Dallman
- Department of Biology, University of Miami, Coral Gables, FL, United States
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Kelly JJ, Wen H, Brehm P. Single-cell RNAseq analysis of spinal locomotor circuitry in larval zebrafish. eLife 2023; 12:RP89338. [PMID: 37975797 PMCID: PMC10656102 DOI: 10.7554/elife.89338] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023] Open
Abstract
Identification of the neuronal types that form the specialized circuits controlling distinct behaviors has benefited greatly from the simplicity offered by zebrafish. Electrophysiological studies have shown that in addition to connectivity, understanding of circuitry requires identification of functional specializations among individual circuit components, such as those that regulate levels of transmitter release and neuronal excitability. In this study, we use single-cell RNA sequencing (scRNAseq) to identify the molecular bases for functional distinctions between motoneuron types that are causal to their differential roles in swimming. The primary motoneuron, in particular, expresses high levels of a unique combination of voltage-dependent ion channel types and synaptic proteins termed functional 'cassettes.' The ion channel types are specialized for promoting high-frequency firing of action potentials and augmented transmitter release at the neuromuscular junction, both contributing to greater power generation. Our transcriptional profiling of spinal neurons further assigns expression of this cassette to specific interneuron types also involved in the central circuitry controlling high-speed swimming and escape behaviors. Our analysis highlights the utility of scRNAseq in functional characterization of neuronal circuitry, in addition to providing a gene expression resource for studying cell type diversity.
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Affiliation(s)
- Jimmy J Kelly
- Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
| | - Hua Wen
- Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
| | - Paul Brehm
- Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
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3
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Kelly JJ, Wen H, Brehm P. Single cell RNA-seq analysis of spinal locomotor circuitry in larval zebrafish. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.06.543939. [PMID: 37333232 PMCID: PMC10274715 DOI: 10.1101/2023.06.06.543939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Identification of the neuronal types that form the specialized circuits controlling distinct behaviors has benefited greatly from the simplicity offered by zebrafish. Electrophysiological studies have shown that additional to connectivity, understanding of circuitry requires identification of functional specializations among individual circuit components, such as those that regulate levels of transmitter release and neuronal excitability. In this study we use single cell RNA sequencing (scRNAseq) to identify the molecular bases for functional distinctions between motoneuron types that are causal to their differential roles in swimming. The primary motoneuron (PMn) in particular, expresses high levels of a unique combination of voltage-dependent ion channel types and synaptic proteins termed functional 'cassettes'. The ion channel types are specialized for promoting high frequency firing of action potentials and augmented transmitter release at the neuromuscular junction, both contributing to greater power generation. Our transcriptional profiling of spinal neurons further assigns expression of this cassette to specific interneuron types also involved in the central circuitry controlling high speed swimming and escape behaviors. Our analysis highlights the utility of scRNAseq in functional characterization of neuronal circuitry, in addition to providing a gene expression resource for studying cell type diversity.
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Affiliation(s)
- Jimmy J. Kelly
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Hua Wen
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Paul Brehm
- Vollum Institute, Oregon Health & Science University, Portland, OR, USA
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4
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Lescouzères L, Hassen-Khodja C, Baudot A, Bordignon B, Bomont P. A multilevel screening pipeline in zebrafish identifies therapeutic drugs for GAN. EMBO Mol Med 2023:e16267. [PMID: 37144692 DOI: 10.15252/emmm.202216267] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 03/30/2023] [Accepted: 04/05/2023] [Indexed: 05/06/2023] Open
Abstract
Giant axonal neuropathy (GAN) is a fatal neurodegenerative disorder for which there is currently no treatment. Affecting the nervous system, GAN starts in infancy with motor deficits that rapidly evolve toward total loss of ambulation. Using the gan zebrafish model that reproduces the loss of motility as seen in patients, we conducted the first pharmacological screening for the GAN pathology. Here, we established a multilevel pipeline to identify small molecules restoring both the physiological and the cellular deficits in GAN. We combined behavioral, in silico, and high-content imaging analyses to refine our Hits to five drugs restoring locomotion, axonal outgrowth, and stabilizing neuromuscular junctions in the gan zebrafish. The postsynaptic nature of the drug's cellular targets provides direct evidence for the pivotal role the neuromuscular junction holds in the restoration of motility. Our results identify the first drug candidates that can now be integrated in a repositioning approach to fasten therapy for the GAN disease. Moreover, we anticipate both our methodological development and the identified hits to be of benefit to other neuromuscular diseases.
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Affiliation(s)
- Léa Lescouzères
- ERC Team, NeuroMyoGene Insitute - Now PGNM, Inserm U1315, CNRS UMR5261, University of Lyon 1, Lyon, France
| | - Cédric Hassen-Khodja
- Montpellier Ressources Imagerie, BioCampus, University of Montpellier, CNRS, INSERM, Montpellier, France
| | - Anaïs Baudot
- Aix Marseille Univ, INSERM, MMG, Marseille Medical Genetics, CNRS, Marseille, France
| | - Benoît Bordignon
- Montpellier Ressources Imagerie, BioCampus, University of Montpellier, CNRS, INSERM, Montpellier, France
| | - Pascale Bomont
- ERC Team, NeuroMyoGene Insitute - Now PGNM, Inserm U1315, CNRS UMR5261, University of Lyon 1, Lyon, France
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Pugliese A, Holland SH, Rodolico C, Lochmüller H, Spendiff S. Presynaptic Congenital Myasthenic Syndromes: Understanding Clinical Phenotypes through In vivo Models. J Neuromuscul Dis 2023; 10:731-759. [PMID: 37212067 PMCID: PMC10578258 DOI: 10.3233/jnd-221646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2023] [Indexed: 05/23/2023]
Abstract
Presynaptic congenital myasthenic syndromes (CMS) are a group of genetic disorders affecting the presynaptic side of the neuromuscular junctions (NMJ). They can result from a dysfunction in acetylcholine (ACh) synthesis or recycling, in its packaging into synaptic vesicles, or its subsequent release into the synaptic cleft. Other proteins involved in presynaptic endplate development and maintenance can also be impaired.Presynaptic CMS usually presents during the prenatal or neonatal period, with a severe phenotype including congenital arthrogryposis, developmental delay, and apnoeic crisis. However, milder phenotypes with proximal muscle weakness and good response to treatment have been described. Finally, many presynaptic genes are expressed in the brain, justifying the presence of additional central nervous system symptoms.Several animal models have been developed to study CMS, providing the opportunity to identify disease mechanisms and test treatment options. In this review, we describe presynaptic CMS phenotypes with a focus on in vivo models, to better understand CMS pathophysiology and define new causative genes.
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Affiliation(s)
- Alessia Pugliese
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Stephen H. Holland
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Carmelo Rodolico
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Hanns Lochmüller
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Department of Medicine, Division of Neurology, The Ottawa Hospital, Ottawa, ON, Canada
- Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
- Department of Neuropediatrics and Muscle Disorders, Medical Center – University of Freiburg, Faculty of Medicine, Freiburg, Germany
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain
| | - Sally Spendiff
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
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Liu J, Gao S, Wei L, Xiong W, Lu Y, Song X, Zhang Y, Gao H, Li B. Choline acetyltransferase and vesicular acetylcholine transporter are required for metamorphosis, reproduction, and insecticide susceptibility in Tribolium castaneum. Gene 2022; 842:146794. [PMID: 35952841 DOI: 10.1016/j.gene.2022.146794] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 07/26/2022] [Accepted: 08/05/2022] [Indexed: 11/04/2022]
Abstract
Choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) are essential enzymes for synthesizing and transporting acetylcholine (ACh). But their functions in metamorphosis, reproduction, and the insecticide susceptibility were poorly understood in the insects. To address these issues, we identified the orthologues of chat and vacht in Tribolium castaneum. Spatiotemporal expression profiling showed Chat has the highest expression at the early adult stage, while vacht shows peak expression at the early larval stage. Both of them were highly expressed at the head of late adult. RNA interference (RNAi) of chat and vacht both led to a decrease in ACh content at the late larval stage. It is observed that chat knockdown severely affected larval development and pupal eclosion, but vacht RNAi only disrupted pupal eclosion. Further, parental RNAi of chat or vacht led to 35 % or 30 % reduction in fecundity, respectively, and knockdown of them completely inhibited egg hatchability. Further analysis has confirmed that both the reduction in fecundity and hatchability caused through the maternal specificity in T. castaneum. Moreover, the transcript levels of chat and vacht were elevated after carbofuran or dichlorvos treatment. Reduction of chat or vacht decreased the resistance to carbofuran and dichlorvos. This study provides the evidence for chat and vacht not only involved in development and reproduction of insects but also could as the potential targets of insecticides.
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Affiliation(s)
- Juanjuan Liu
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Shanshan Gao
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China; College of Biology and Food Engineering, Anyang Institute of Technology, Anyang 455000, China
| | - Luting Wei
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Wenfeng Xiong
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Yaoyao Lu
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Xiaowen Song
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Yonglei Zhang
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Han Gao
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Bin Li
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
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Sahyoun C, Krezel W, Mattei C, Sabatier JM, Legros C, Fajloun Z, Rima M. Neuro- and Cardiovascular Activities of Montivipera bornmuelleri Snake Venom. BIOLOGY 2022; 11:biology11060888. [PMID: 35741410 PMCID: PMC9219918 DOI: 10.3390/biology11060888] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/04/2022] [Accepted: 06/06/2022] [Indexed: 12/31/2022]
Abstract
Simple Summary Snake venoms are rich in molecules acting on different biological systems, and they are responsible for the complications following snake bite envenoming. These bioactive molecules are of interest in pharmaceutical industries as templates for drug design. Different biological activities of Montivipera bornmuelleri snake venom have been already studied; however, the venom’s activity on the nervous system has not yet been studied, and its effect on the cardiovascular system needs further investigation. Herein, we show that this venom induces toxicity on the nervous system and disrupts the cardiovascular system, highlighting a broad spectrum of biological activities. Abstract The complications following snake bite envenoming are due to the venom’s biological activities, which can act on different systems of the prey. These activities arise from the fact that snake venoms are rich in bioactive molecules, which are also of interest for designing drugs. The venom of Montivipera bornmuelleri, known as the Lebanon viper, has been shown to exert antibacterial, anticancer, and immunomodulatory effects. However, the venom’s activity on the nervous system has not yet been studied, and its effect on the cardiovascular system needs further investigation. Because zebrafish is a convenient model to study tissue alterations induced by toxic agents, we challenged it with the venom of Montivipera bornmuelleri. We show that this venom leads to developmental toxicity but not teratogenicity in zebrafish embryos. The venom also induces neurotoxic effects and disrupts the zebrafish cardiovascular system, leading to heartbeat rate reduction and hemorrhage. Our findings demonstrate the potential neurotoxicity and cardiotoxicity of M. bornmuelleri’s venom, suggesting a multitarget strategy during envenomation.
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Affiliation(s)
- Christina Sahyoun
- INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, University of Angers, 49000 Angers, France; (C.S.); (C.M.); (C.L.)
- Laboratory of Applied Biotechnology (LBA3B), Azm Center for Research in Biotechnology and Its Applications, EDST, Lebanese University, Tripoli 1300, Lebanon
| | - Wojciech Krezel
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM, CNRS, Université de Strasbourg, 67400 Illkirch, France;
| | - César Mattei
- INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, University of Angers, 49000 Angers, France; (C.S.); (C.M.); (C.L.)
| | - Jean-Marc Sabatier
- CNRS, INP, Institute of Neurophysiopathology, Aix-Marseille University, 13385 Marseille, France
- Correspondence: (J.-M.S.); (Z.F.); (M.R.)
| | - Christian Legros
- INSERM, CNRS, MITOVASC, Equipe CarMe, SFR ICAT, University of Angers, 49000 Angers, France; (C.S.); (C.M.); (C.L.)
| | - Ziad Fajloun
- Laboratory of Applied Biotechnology (LBA3B), Azm Center for Research in Biotechnology and Its Applications, EDST, Lebanese University, Tripoli 1300, Lebanon
- Department of Biology, Faculty of Sciences 3, Campus Michel Slayman, Lebanese University, Tripoli 1352, Lebanon
- Correspondence: (J.-M.S.); (Z.F.); (M.R.)
| | - Mohamad Rima
- Laboratory of Applied Biotechnology (LBA3B), Azm Center for Research in Biotechnology and Its Applications, EDST, Lebanese University, Tripoli 1300, Lebanon
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM, CNRS, Université de Strasbourg, 67400 Illkirch, France;
- Correspondence: (J.-M.S.); (Z.F.); (M.R.)
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Mullen P, Abbott JA, Wellman T, Aktar M, Fjeld C, Demeler B, Ebert AM, Francklyn CS. Neuropathy-associated histidyl-tRNA synthetase variants attenuate protein synthesis in vitro and disrupt axon outgrowth in developing zebrafish. FEBS J 2021; 288:142-159. [PMID: 32543048 PMCID: PMC7736457 DOI: 10.1111/febs.15449] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 05/11/2020] [Accepted: 06/09/2020] [Indexed: 12/13/2022]
Abstract
Charcot-Marie-Tooth disease (CMT) encompasses a set of genetically and clinically heterogeneous neuropathies characterized by length-dependent dysfunction of the peripheral nervous system. Mutations in over 80 diverse genes are associated with CMT, and aminoacyl-tRNA synthetases (ARS) constitute a large gene family implicated in the disease. Despite considerable efforts to elucidate the mechanistic link between ARS mutations and the CMT phenotype, the molecular basis of the pathology is unknown. In this work, we investigated the impact of three CMT-associated substitutions (V155G, Y330C, and R137Q) in the cytoplasmic histidyl-tRNA synthetase (HARS1) on neurite outgrowth and peripheral nervous system development. The model systems for this work included a nerve growth factor-stimulated neurite outgrowth model in rat pheochromocytoma cells (PC12), and a zebrafish line with GFP/red fluorescent protein reporters of sensory and motor neuron development. The expression of CMT-HARS1 mutations led to attenuation of protein synthesis and increased phosphorylation of eIF2α in PC12 cells and was accompanied by impaired neurite and axon outgrowth in both models. Notably, these effects were phenocopied by histidinol, a HARS1 inhibitor, and cycloheximide, a protein synthesis inhibitor. The mutant proteins also formed heterodimers with wild-type HARS1, raising the possibility that CMT-HARS1 mutations cause disease through a dominant-negative mechanism. Overall, these findings support the hypothesis that CMT-HARS1 alleles exert their toxic effect in a neuronal context, and lead to dysregulated protein synthesis. These studies demonstrate the value of zebrafish as a model for studying mutant alleles associated with CMT, and for characterizing the processes that lead to peripheral nervous system dysfunction.
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Affiliation(s)
- Patrick Mullen
- Department of Biochemistry, University of Vermont, Burlington, VT, USA
| | - Jamie A Abbott
- Department of Biochemistry, University of Vermont, Burlington, VT, USA
| | - Theresa Wellman
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | - Mahafuza Aktar
- Department of Biochemistry, University of Vermont, Burlington, VT, USA
| | - Christian Fjeld
- Department of Biochemistry, University of Vermont, Burlington, VT, USA
| | - Borries Demeler
- Department of Chemistry & Biochemistry, University of Lethbridge, Canada
| | - Alicia M Ebert
- Department of Biology, University of Vermont, Burlington, VT, USA
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Brehm P, Wen H. Zebrafish neuromuscular junction: The power of N. Neurosci Lett 2019; 713:134503. [PMID: 31557523 DOI: 10.1016/j.neulet.2019.134503] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 09/11/2019] [Accepted: 09/16/2019] [Indexed: 11/26/2022]
Abstract
In the early 1950s, Katz and his colleagues capitalized on the newly developed intracellular microelectrode recording technique to investigate synaptic transmission. For study they chose frog neuromuscular junction (NMJ), which was ideally suited due to the accessibility and large size of the muscle cells. Paradoxically, the large size precluded the use of next generation patch clamp technology. Consequently, electrophysiological study of synaptic function shifted to small central synapses made amenable by patch clamp. Recently, however, the unique features offered by zebrafish have rekindled interest in the NMJ as a model for electrophysiological study of synaptic transmission. The small muscle size and synaptic simplicity provide the singular opportunity to perform in vivo spinal motoneuron-target muscle patch clamp recordings. Additional incentive is provided by zebrafish lines harboring mutations in key synaptic proteins, many of which are embryonic lethal in mammals, but all of which are able to survive well past synapse maturation in zebrafish. This mini-review will highlight features that set zebrafish NMJs apart from traditional NMJs. We also draw into focus findings that offer the promise of identifying features that define release sites, which serve to set the upper limit of transmitter release. Since its conception several candidates representing release sites have been proposed, most of which are based on distinctions among vesicle pools in their state of readiness for release. However, models based on distinctions among vesicles have become enormously complicated and none adequately account for setting an upper limit for exocytosis in response to an action potential (AP). Specifically, findings from zebrafish NMJ point to an alternative model, positing that elements other than vesicles per se set the upper limits of release.
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Affiliation(s)
- Paul Brehm
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, USA.
| | - Hua Wen
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, USA
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10
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Mutation of a serine near the catalytic site of the choline acetyltransferase a gene almost completely abolishes motility of the zebrafish embryo. PLoS One 2018; 13:e0207747. [PMID: 30458023 PMCID: PMC6245786 DOI: 10.1371/journal.pone.0207747] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 11/06/2018] [Indexed: 12/29/2022] Open
Abstract
In zebrafish, the gene choline acetyltransferase a (chata) encodes one of the two ChAT orthologs responsible for the synthesis of acetylcholine. Acetylcholine (ACh) is essential for neuromuscular transmission and its impaired synthesis by ChAT can lead to neuromuscular junction disorders such as congenital myasthenic syndromes in humans. We have identified a novel mutation in the chata gene of zebrafish, chatatk64, in a collection of uncharacterised ENU-induced mutants. This mutant carries a missense mutation in the codon of a highly conserved serine changing it to an arginine (S102R). This serine is conserved among ChATs from zebrafish, rat, mice and chicken to humans. It resides within the catalytic domain and in the vicinity of the active site of the enzyme. However, it has not been reported so far to be required for enzymatic activity. Modelling of the S102R variant change in the ChAT protein crystal structure suggests that the change affects protein structure and has a direct impact on the catalytic domain of the protein which abolishes embryo motility almost completely.
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11
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Carlson BM, Klingler IB, Meyer BJ, Gross JB. Genetic analysis reveals candidate genes for activity QTL in the blind Mexican tetra, Astyanax mexicanus. PeerJ 2018; 6:e5189. [PMID: 30042884 PMCID: PMC6054784 DOI: 10.7717/peerj.5189] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 06/15/2018] [Indexed: 12/30/2022] Open
Abstract
Animal models provide useful tools for exploring the genetic basis of morphological, physiological and behavioral phenotypes. Cave-adapted species are particularly powerful models for a broad array of phenotypic changes with evolutionary, developmental and clinical relevance. Here, we explored the genetic underpinnings of previously characterized differences in locomotor activity patterns between the surface-dwelling and Pachón cave-dwelling populations of Astyanax mexicanus. We identified multiple novel QTL underlying patterns in overall levels of activity (velocity), as well as spatial tank use (time spent near the top or bottom of the tank). Further, we demonstrated that different regions of the genome mediate distinct patterns in velocity and tank usage. We interrogated eight genomic intervals underlying these activity QTL distributed across six linkage groups. In addition, we employed transcriptomic data and draft genomic resources to generate and evaluate a list of 36 potential candidate genes. Interestingly, our data support the candidacy of a number of genes, but do not suggest that differences in the patterns of behavior observed here are the result of alterations to certain candidate genes described in other species (e.g., teleost multiple tissue opsins, melanopsins or members of the core circadian clockwork). This study expands our knowledge of the genetic architecture underlying activity differences in surface and cavefish. Future studies will help define the role of specific genes in shaping complex behavioral phenotypes in Astyanax and other vertebrate taxa.
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Affiliation(s)
- Brian M Carlson
- Department of Biology, The College of Wooster, Wooster, OH, United States of America
| | - Ian B Klingler
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States of America
| | - Bradley J Meyer
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States of America
| | - Joshua B Gross
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, United States of America
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12
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Fatigue in Rapsyn-Deficient Zebrafish Reflects Defective Transmitter Release. J Neurosci 2017; 36:10870-10882. [PMID: 27798141 DOI: 10.1523/jneurosci.0505-16.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 09/03/2016] [Indexed: 12/29/2022] Open
Abstract
Rapsyn-deficient myasthenic syndrome is characterized by a weakness in voluntary muscle contraction, a direct consequence of greatly reduced synaptic responses that result from poorly clustered acetylcholine receptors. As with other myasthenic syndromes, the general muscle weakness is also accompanied by use-dependent fatigue. Here, we used paired motor neuron target muscle patch-clamp recordings from a rapsyn-deficient mutant line of zebrafish to explore for the first time the mechanisms causal to fatigue. We find that synaptic responses in mutant fish can follow faithfully low-frequency stimuli despite the reduced amplitude. This is in part helped by a compensatory increase in the number of presynaptic release sites in the mutant fish. In response to high-frequency stimulation, both wild-type and mutant neuromuscular junctions depress to steady-state response levels, but the latter shows exaggerated depression. Analysis of the steady-state transmission revealed that vesicle reloading and release at individual release sites is significantly slower in mutant fish during high-frequency activities. Therefore, reductions in postsynaptic receptor density and compromised presynaptic release collectively serve to reduce synaptic strength to levels that fall below the threshold for muscle action potential generation, thus accounting for use-dependent fatigue. Our findings raise the possibility that defects in motor neuron function may also be at play in other myasthenic syndromes that have been mapped to mutations in muscle-specific proteins. SIGNIFICANCE STATEMENT Use-dependent fatigue accompanies many neuromuscular myasthenic syndromes, including muscle rapsyn deficiency. Here, using a rapsyn-deficient line of zebrafish, we performed paired motor neuron target muscle patch-clamp recordings to investigate the mechanisms causal to this phenomenon. Our findings indicate that the reduced postsynaptic receptor density resulting from defective rapsyn contributes to weakness, but is not solely responsible for use-dependent fatigue. Instead, we find unexpected involvement of altered transmitter release from the motor neuron. Specifically, slowed reloading of vesicle release sites leads to augmented synaptic depression during repeated action potentials. Even at moderate stimulus frequencies, the depression levels for evoked synaptic responses fall below the threshold for the generation of muscle action potentials. The associated contraction failures are manifest as use-dependent fatigue.
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Ogino K, Hirata H. Defects of the Glycinergic Synapse in Zebrafish. Front Mol Neurosci 2016; 9:50. [PMID: 27445686 PMCID: PMC4925712 DOI: 10.3389/fnmol.2016.00050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/13/2016] [Indexed: 12/26/2022] Open
Abstract
Glycine mediates fast inhibitory synaptic transmission. Physiological importance of the glycinergic synapse is well established in the brainstem and the spinal cord. In humans, the loss of glycinergic function in the spinal cord and brainstem leads to hyperekplexia, which is characterized by an excess startle reflex to sudden acoustic or tactile stimulation. In addition, glycinergic synapses in this region are also involved in the regulation of respiration and locomotion, and in the nociceptive processing. The importance of the glycinergic synapse is conserved across vertebrate species. A teleost fish, the zebrafish, offers several advantages as a vertebrate model for research of glycinergic synapse. Mutagenesis screens in zebrafish have isolated two motor defective mutants that have pathogenic mutations in glycinergic synaptic transmission: bandoneon (beo) and shocked (sho). Beo mutants have a loss-of-function mutation of glycine receptor (GlyR) β-subunit b, alternatively, sho mutant is a glycinergic transporter 1 (GlyT1) defective mutant. These mutants are useful animal models for understanding of glycinergic synaptic transmission and for identification of novel therapeutic agents for human diseases arising from defect in glycinergic transmission, such as hyperekplexia or glycine encephalopathy. Recent advances in techniques for genome editing and for imaging and manipulating of a molecule or a physiological process make zebrafish more attractive model. In this review, we describe the glycinergic defective zebrafish mutants and the technical advances in both forward and reverse genetic approaches as well as in vivo visualization and manipulation approaches for the study of the glycinergic synapse in zebrafish.
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Affiliation(s)
- Kazutoyo Ogino
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
| | - Hiromi Hirata
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
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14
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Woehlbier U, Colombo A, Saaranen MJ, Pérez V, Ojeda J, Bustos FJ, Andreu CI, Torres M, Valenzuela V, Medinas DB, Rozas P, Vidal RL, Lopez-Gonzalez R, Salameh J, Fernandez-Collemann S, Muñoz N, Matus S, Armisen R, Sagredo A, Palma K, Irrazabal T, Almeida S, Gonzalez-Perez P, Campero M, Gao FB, Henny P, van Zundert B, Ruddock LW, Concha ML, Henriquez JP, Brown RH, Hetz C. ALS-linked protein disulfide isomerase variants cause motor dysfunction. EMBO J 2016; 35:845-65. [PMID: 26869642 PMCID: PMC4972141 DOI: 10.15252/embj.201592224] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2015] [Revised: 12/27/2015] [Accepted: 01/05/2016] [Indexed: 12/11/2022] Open
Abstract
Disturbance of endoplasmic reticulum (ER) proteostasis is a common feature of amyotrophic lateral sclerosis (ALS). Protein disulfide isomerases (PDIs) areERfoldases identified as possibleALSbiomarkers, as well as neuroprotective factors. However, no functional studies have addressed their impact on the disease process. Here, we functionally characterized fourALS-linked mutations recently identified in two majorPDIgenes,PDIA1 andPDIA3/ERp57. Phenotypic screening in zebrafish revealed that the expression of thesePDIvariants induce motor defects associated with a disruption of motoneuron connectivity. Similarly, the expression of mutantPDIs impaired dendritic outgrowth in motoneuron cell culture models. Cellular and biochemical studies identified distinct molecular defects underlying the pathogenicity of thesePDImutants. Finally, targetingERp57 in the nervous system led to severe motor dysfunction in mice associated with a loss of neuromuscular synapses. This study identifiesERproteostasis imbalance as a risk factor forALS, driving initial stages of the disease.
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Affiliation(s)
- Ute Woehlbier
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile Center for Genomics and Bioinformatics, Universidad Mayor, Santiago, Chile
| | - Alicia Colombo
- Program of Anatomy and Developmental Biology, Institute of Biomedical Sciences, University of Chile, Santiago, Chile Department of Pathological Anatomy, Hospital Clínico, University of Chile, Santiago, Chile
| | - Mirva J Saaranen
- Biocenter Oulu and Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Viviana Pérez
- Department of Cell Biology, Faculty of Biological Sciences, Millennium Nucleus of Regenerative Biology, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Concepción, Chile
| | - Jorge Ojeda
- Department of Cell Biology, Faculty of Biological Sciences, Millennium Nucleus of Regenerative Biology, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Concepción, Chile
| | - Fernando J Bustos
- Faculty of Biological Sciences and Faculty of Medicine, Center for Biomedical Research, Universidad Andres Bello, Santiago, Chile
| | - Catherine I Andreu
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Mauricio Torres
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Vicente Valenzuela
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
| | - Danilo B Medinas
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
| | - Pablo Rozas
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Rene L Vidal
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile Neurounion Biomedical Foundation, CENPAR, Santiago, Chile
| | | | - Johnny Salameh
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | | | - Natalia Muñoz
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile Neurounion Biomedical Foundation, CENPAR, Santiago, Chile
| | - Soledad Matus
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile Neurounion Biomedical Foundation, CENPAR, Santiago, Chile
| | - Ricardo Armisen
- Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Alfredo Sagredo
- Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Karina Palma
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Thergiory Irrazabal
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile
| | - Sandra Almeida
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Paloma Gonzalez-Perez
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Mario Campero
- Department of Neurology and Neurosurgery, Faculty of Medicine, University of Chile, Santiago, Chile Faculty of Medicine, Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Fen-Biao Gao
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Pablo Henny
- Department of Anatomy, Medical School, Universidad Católica de Chile, Santiago, Chile
| | - Brigitte van Zundert
- Faculty of Biological Sciences and Faculty of Medicine, Center for Biomedical Research, Universidad Andres Bello, Santiago, Chile
| | - Lloyd W Ruddock
- Biocenter Oulu and Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Miguel L Concha
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Anatomy and Developmental Biology, Institute of Biomedical Sciences, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile
| | - Juan P Henriquez
- Department of Cell Biology, Faculty of Biological Sciences, Millennium Nucleus of Regenerative Biology, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Concepción, Chile
| | - Robert H Brown
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Claudio Hetz
- Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile Program of Cellular and Molecular Biology, Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, University of Chile, Santiago, Chile Center for Geroscience, Brain Health and Metabolism, Santiago, Chile Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA, USA
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15
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Sun J, Pan C, Chew T, Liang F, Burmeister M, Low B. BNIP-H Recruits the Cholinergic Machinery to Neurite Terminals to Promote Acetylcholine Signaling and Neuritogenesis. Dev Cell 2015; 34:555-68. [DOI: 10.1016/j.devcel.2015.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 03/13/2015] [Accepted: 08/10/2015] [Indexed: 12/19/2022]
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16
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Helmprobst F, Frank M, Stigloher C. Presynaptic architecture of the larval zebrafish neuromuscular junction. J Comp Neurol 2015; 523:1984-97. [PMID: 25766140 DOI: 10.1002/cne.23775] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 02/13/2015] [Accepted: 03/04/2015] [Indexed: 12/13/2022]
Abstract
This article shows the ultrastructural architecture of larval zebrafish (Danio rerio) neuromuscular junctions in three dimensions. We compare classical electron microscopy fixation techniques with high-pressure freezing followed by freeze substitution (HPF/FS) in combination with electron tomography. Furthermore, we compare the structure of neuromuscular junctions in 4- and 8-dpf zebrafish larvae with HPF/FS because this allows for close-to-native ultrastructural preservation. We discovered that synaptic vesicles of 4-dpf zebrafish larvae are larger than those of 8-dpf larvae. Furthermore, we describe two types of dense-core vesicles and quantify a filamentous network of small filaments interconnecting synaptic vesicles as well as tethers connecting synaptic vesicles to the presynaptic cell membrane. In the center of active zones, we found elaborate electron-dense projections physically connecting vesicles of the synaptic vesicle pool to the presynaptic membrane. Overall this study establishes the basis for systematic comparisons of synaptic architecture at high resolution in three dimensions of an intact vertebrate in a close-to-native state. Furthermore, we provide quantitative information that builds the basis for diverse systems biology approaches in neuroscience, from comparative anatomy to cellular simulations.
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Affiliation(s)
- Frederik Helmprobst
- Division of Electron Microscopy, Biocenter, University of Würzburg, 97074, Würzburg, Germany
| | - Miriam Frank
- Division of Electron Microscopy, Biocenter, University of Würzburg, 97074, Würzburg, Germany
| | - Christian Stigloher
- Division of Electron Microscopy, Biocenter, University of Würzburg, 97074, Würzburg, Germany
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17
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Abstract
BACKGROUND Zebrafish is an amenable vertebrate model useful for the study of development and genetics. Small molecule screenings in zebrafish have successfully identified several drugs that affect developmental process. OBJECTIVE This review covers the basics of zebrafish muscle system such as muscle development and muscle defects. It also reviews the potential use of zebrafish for chemical screening with regards to muscle disorders. CONCLUSION During embryogenesis, zebrafish start to coil their body by contracting trunk muscles 17 h postfertilization, indicating that a motor circuit and skeletal muscle are functionally developed at early stages. Mutagenesis screens in zebrafish have identified many motility mutants that display morphological or functional defects in the CNS, clustering defects of acetylcholine receptors at the neuromuscular junctions or pathological defects of muscles. Most of the muscular mutants are useful as animal models of human muscle disease such as muscle dystrophy. As zebrafish live in water, pharmacological drugs are easily assayable during development, and thus zebrafish may be used to determine novel drugs that mitigate muscle disease.
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Affiliation(s)
- Hiromi Hirata
- Nagoya University, Graduate School of Science, Proof to Hiromi Hirata Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan +81 52 789 2980 ; +81 52 789 2979 ;
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18
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Wolman M, Granato M. Behavioral genetics in larval zebrafish: learning from the young. Dev Neurobiol 2012; 72:366-72. [PMID: 22328273 DOI: 10.1002/dneu.20872] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Deciphering the genetic code that determines how the vertebrate nervous system assembles into neural circuits that ultimately control behavior is a fascinating and challenging question in modern neurobiology. Because of the complexity of this problem, successful strategies require a simple yet focused experimental approach without limiting the scope of the discovery. Unbiased, large-scale forward genetic screens in invertebrate organisms have yielded great insight into the genetic regulation of neural circuit assembly and function. For many reasons, this highly successful approach has been difficult to recapitulate in the behavioral neuroscience field's classic vertebrate model organisms-rodents. Here, we discuss how larval zebrafish provide a promising model system to which we can apply the design of invertebrate behavior-based screens to reveal the genetic mechanisms critical for neural circuit assembly and function in vertebrates.
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Affiliation(s)
- Marc Wolman
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA
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19
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Friedrich T, Lambert AM, Masino MA, Downes GB. Mutation of zebrafish dihydrolipoamide branched-chain transacylase E2 results in motor dysfunction and models maple syrup urine disease. Dis Model Mech 2011; 5:248-58. [PMID: 22046030 PMCID: PMC3291646 DOI: 10.1242/dmm.008383] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Analysis of zebrafish mutants that demonstrate abnormal locomotive behavior can elucidate the molecular requirements for neural network function and provide new models of human disease. Here, we show that zebrafish quetschkommode (que) mutant larvae exhibit a progressive locomotor defect that culminates in unusual nose-to-tail compressions and an inability to swim. Correspondingly, extracellular peripheral nerve recordings show that que mutants demonstrate abnormal locomotor output to the axial muscles used for swimming. Using positional cloning and candidate gene analysis, we reveal that a point mutation disrupts the gene encoding dihydrolipoamide branched-chain transacylase E2 (Dbt), a component of a mitochondrial enzyme complex, to generate the que phenotype. In humans, mutation of the DBT gene causes maple syrup urine disease (MSUD), a disorder of branched-chain amino acid metabolism that can result in mental retardation, severe dystonia, profound neurological damage and death. que mutants harbor abnormal amino acid levels, similar to MSUD patients and consistent with an error in branched-chain amino acid metabolism. que mutants also contain markedly reduced levels of the neurotransmitter glutamate within the brain and spinal cord, which probably contributes to their abnormal spinal cord locomotor output and aberrant motility behavior, a trait that probably represents severe dystonia in larval zebrafish. Taken together, these data illustrate how defects in branched-chain amino acid metabolism can disrupt nervous system development and/or function, and establish zebrafish que mutants as a model to better understand MSUD.
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Affiliation(s)
- Timo Friedrich
- Molecular and Cellular Biology Graduate Program, Biology Department, University of Massachusetts, Amherst, MA 01003, USA
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20
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Mapping a sensory-motor network onto a structural and functional ground plan in the hindbrain. Proc Natl Acad Sci U S A 2011; 108:1170-5. [PMID: 21199937 DOI: 10.1073/pnas.1012189108] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hindbrain of larval zebrafish contains a relatively simple ground plan in which the neurons throughout it are arranged into stripes that represent broad neuronal classes that differ in transmitter identity, morphology, and transcription factor expression. Within the stripes, neurons are stacked continuously according to age as well as structural and functional properties, such as axonal extent, input resistance, and the speed at which they are recruited during movements. Here we address the question of how particular networks among the many different sensory-motor networks in hindbrain arise from such an orderly plan. We use a combination of transgenic lines and pairwise patch recording to identify excitatory and inhibitory interneurons in the hindbrain network for escape behaviors initiated by the Mauthner cell. We map this network onto the ground plan to show that an individual hindbrain network is built by drawing components in predictable ways from the underlying broad patterning of cell types stacked within stripes according to their age and structural and functional properties. Many different specialized hindbrain networks may arise similarly from a simple early patterning.
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21
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Wen H, Brehm P. Paired patch clamp recordings from motor-neuron and target skeletal muscle in zebrafish. J Vis Exp 2010:2351. [PMID: 21113124 PMCID: PMC3143584 DOI: 10.3791/2351] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target muscle. This is a direct consequence of the accessibility to both cell types and ability to visually distinguish the single segmental CaP motor-neuron on the basis of morphology and location. This video demonstrates the microscopic methods used to identify a CaP motor-neuron and target muscle cells as well as the methodologies for recording from each cell type. Identification of the CaP motor-neuron type is confirmed by either dye filling or by the biophysical features such as action potential waveform and cell input resistance. Motor-neuron recordings routinely last for one hour permitting long-term recordings from multiple different target muscle cells. Control over the motor-neuron firing pattern enables measurements of the frequency-dependence of synaptic transmission at the neuromuscular junction. Owing to a large quantal size and the low noise provided by whole cell voltage clamp, all of the unitary events can be resolved in muscle. This feature permits study of basic synaptic properties such as release properties, vesicle recycling, as well as synaptic depression and facilitation. The advantages offered by this in vivo preparation eclipse previous neuromuscular model systems studied wherein the motor-neurons are usually stimulated by extracellular electrodes and the muscles are too large for whole cell patch clamp. The zebrafish preparation is amenable to combining electrophysiological analysis with a wide range of approaches including transgenic lines, morpholino knockdown, pharmacological intervention and in vivo imaging. These approaches, coupled with the growing number of neuromuscular disease models provided by mutant lines of zebrafish, open the door for new understanding of human neuromuscular disorders.
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Affiliation(s)
- Hua Wen
- Vollum Institute, Oregon Health and Sciences University, USA
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22
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Abstract
Mutations in ubiquitously expressed metabolic genes often lead to CNS-specific effects, presumably because of the high metabolic demands of neurons. However, mutations in omnipresent metabolic pathways can conceivably also result in cell type-specific effects because of cell-specific requirements for intermediate products. One such example is the zebrafish noir mutant, which we found to be mutated in the pdhb gene, coding for the E1 beta subunit of the pyruvate dehydrogenase complex. This vision mutant is described as blind and was isolated because of its vision defect-related darker appearance. A detailed morphological, behavioral, and physiological analysis of the phenotype revealed an unexpected specific effect on the retina. Surprisingly, the cholinergic amacrine cells of the inner retina are affected earlier than the photoreceptors. This might be attributable to the inability of these cells to maintain production of their neurotransmitter acetylcholine. This is reflected in an earlier loss of motion vision, followed only later by a general loss of light perception. Since both characteristics of the phenotype are attributable to a loss of acetyl-CoA production by pyruvate dehydrogenase, we used a ketogenic diet to bypass this metabolic block and could indeed partially rescue vision and prolong survival of the larvae. The noir mutant provides a case for a systemic disease with ocular manifestation with a surprising specific effect on the retina given the ubiquitous requirement for the mutated gene.
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Olson BD, Sgourdou P, Downes GB. Analysis of a zebrafish behavioral mutant reveals a dominant mutation in atp2a1/SERCA1. Genesis 2010; 48:354-61. [PMID: 20533403 DOI: 10.1002/dvg.20631] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Zebrafish embryos demonstrate robust swimming behavior, which consists of smooth, alternating body bends. In contrast, several motility mutants have been identified that perform sustained, bilateral trunk muscle contractions which result in abnormal body shortening. Unlike most of these mutants, accordion (acc)(dta5) demonstrates a semidominant effect: Heterozygotes exhibit a distinct but less severe phenotype than homozygotes. Using molecular-genetic mapping and candidate gene analysis, we determined that acc(dta5) mutants harbor a novel mutation in atp2a1, which encodes SERCA1, a calcium pump important for muscle relaxation. Previous studies have shown that eight other acc alleles compromise SERCA1 function, but these alleles were all reported to be recessive. Quantitative behavioral assays, complementation testing, and analysis of molecular models all indicate that the acc(dta5) mutation diminishes SERCA1 function to a greater degree than other acc alleles through either haploinsufficient or dominant-negative molecular mechanisms. Since mutation of human ATP2A1 results in Brody disease, an exercise-induced impairment of muscle relaxation, acc(dta5) mutants may provide a particularly sensitive model of this disorder.
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Hirata H, Carta E, Yamanaka I, Harvey RJ, Kuwada JY. Defective glycinergic synaptic transmission in zebrafish motility mutants. Front Mol Neurosci 2010; 2:26. [PMID: 20161699 PMCID: PMC2813725 DOI: 10.3389/neuro.02.026.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 11/11/2009] [Indexed: 11/20/2022] Open
Abstract
Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem. Recently, in vivo analysis of glycinergic synaptic transmission has been pursued in zebrafish using molecular genetics. An ENU mutagenesis screen identified two behavioral mutants that are defective in glycinergic synaptic transmission. Zebrafish bandoneon (beo) mutants have a defect in glrbb, one of the duplicated glycine receptor (GlyR) beta subunit genes. These mutants exhibit a loss of glycinergic synaptic transmission due to a lack of synaptic aggregation of GlyRs. Due to the consequent loss of reciprocal inhibition of motor circuits between the two sides of the spinal cord, motor neurons activate simultaneously on both sides resulting in bilateral contraction of axial muscles of beo mutants, eliciting the so-called 'accordion' phenotype. Similar defects in GlyR subunit genes have been observed in several mammals and are the basis for human hyperekplexia/startle disease. By contrast, zebrafish shocked (sho) mutants have a defect in slc6a9, encoding GlyT1, a glycine transporter that is expressed by astroglial cells surrounding the glycinergic synapse in the hindbrain and spinal cord. GlyT1 mediates rapid uptake of glycine from the synaptic cleft, terminating synaptic transmission. In zebrafish sho mutants, there appears to be elevated extracellular glycine resulting in persistent inhibition of postsynaptic neurons and subsequent reduced motility, causing the 'twitch-once' phenotype. We review current knowledge regarding zebrafish 'accordion' and 'twitch-once' mutants, including beo and sho, and report the identification of a new alpha2 subunit that revises the phylogeny of zebrafish GlyRs.
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Affiliation(s)
- Hiromi Hirata
- Graduate School of Science, Nagoya UniversityNagoya, Japan
| | - Eloisa Carta
- Department of Pharmacology, The School of PharmacyLondon, UK
| | - Iori Yamanaka
- Graduate School of Science, Nagoya UniversityNagoya, Japan
| | | | - John Y. Kuwada
- Department of Molecular, Cellular and Developmental Biology, University of MichiganAnn Arbor, MI, USA
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