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de Jong-Bolm D, Sadeghi M, Bogaciu CA, Bao G, Klaehn G, Hoff M, Mittelmeier L, Basmanav FB, Opazo F, Noé F, Rizzoli SO. Protein nanobarcodes enable single-step multiplexed fluorescence imaging. PLoS Biol 2023; 21:e3002427. [PMID: 38079451 PMCID: PMC10735187 DOI: 10.1371/journal.pbio.3002427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 12/21/2023] [Accepted: 11/13/2023] [Indexed: 12/23/2023] Open
Abstract
Multiplexed cellular imaging typically relies on the sequential application of detection probes, as antibodies or DNA barcodes, which is complex and time-consuming. To address this, we developed here protein nanobarcodes, composed of combinations of epitopes recognized by specific sets of nanobodies. The nanobarcodes are read in a single imaging step, relying on nanobodies conjugated to distinct fluorophores, which enables a precise analysis of large numbers of protein combinations. Fluorescence images from nanobarcodes were used as input images for a deep neural network, which was able to identify proteins with high precision. We thus present an efficient and straightforward protein identification method, which is applicable to relatively complex biological assays. We demonstrate this by a multicell competition assay, in which we successfully used our nanobarcoded proteins together with neurexin and neuroligin isoforms, thereby testing the preferred binding combinations of multiple isoforms, in parallel.
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Affiliation(s)
- Daniëlle de Jong-Bolm
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
| | - Mohsen Sadeghi
- Department of Mathematics and Computer Science, Free University of Berlin, Berlin, Germany
| | - Cristian A. Bogaciu
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
| | - Guobin Bao
- Institute of Pharmacology and Toxicology, University Medical Center, Georg-August-University, Göttingen, Germany
| | - Gabriele Klaehn
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
| | - Merle Hoff
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
| | - Lucas Mittelmeier
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
| | - F. Buket Basmanav
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
- Campus Laboratory for Advanced Imaging, Microscopy and Spectroscopy, University of Göttingen, Göttingen, Germany
| | - Felipe Opazo
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University of Göttingen Medical Center, Göttingen, Germany
- NanoTag Biotechnologies GmbH, Göttingen, Germany
| | - Frank Noé
- Department of Mathematics and Computer Science, Free University of Berlin, Berlin, Germany
- Department of Physics, Free University of Technology, Berlin, Germany
- Department of Chemistry, Rice University, Houston, Texas, United States of America
- Microsoft Research AI4Science, Berlin, Germany
| | - Silvio O. Rizzoli
- Department of Neuro- and Sensory physiology, University of Göttingen Medical Center, Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), Göttingen, Germany
- NanoTag Biotechnologies GmbH, Göttingen, Germany
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2
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Liu X, Hua F, Yang D, Lin Y, Zhang L, Ying J, Sheng H, Wang X. Roles of neuroligins in central nervous system development: focus on glial neuroligins and neuron neuroligins. Lab Invest 2022; 20:418. [PMID: 36088343 PMCID: PMC9463862 DOI: 10.1186/s12967-022-03625-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 09/01/2022] [Indexed: 11/10/2022]
Abstract
Neuroligins are postsynaptic cell adhesion molecules that are relevant to many neurodevelopmental disorders. They are differentially enriched at the postsynapse and interact with their presynaptic ligands, neurexins, whose differential binding to neuroligins has been shown to regulate synaptogenesis, transmission, and other synaptic properties. The proper functioning of functional networks in the brain depends on the proper connection between neuronal synapses. Impaired synaptogenesis or synaptic transmission results in synaptic dysfunction, and these synaptic pathologies are the basis for many neurodevelopmental disorders. Deletions or mutations in the neuroligins genes have been found in patients with both autism and schizophrenia. It is because of the important role of neuroligins in synaptic connectivity and synaptic dysfunction that studies on neuroligins in the past have mainly focused on their expression in neurons. As studies on the expression of genes specific to various cells of the central nervous system deepened, neuroligins were found to be expressed in non-neuronal cells as well. In the central nervous system, glial cells are the most representative non-neuronal cells, which can also express neuroligins in large amounts, especially astrocytes and oligodendrocytes, and they are involved in the regulation of synaptic function, as are neuronal neuroligins. This review examines the mechanisms of neuron neuroligins and non-neuronal neuroligins in the central nervous system and also discusses the important role of neuroligins in the development of the central nervous system and neurodevelopmental disorders from the perspective of neuronal neuroligins and glial neuroligins.
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3
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Li H, Guo R, Guan Y, Li J, Wang Y. Modulation of Trans-Synaptic Neurexin-Neuroligin Interaction in Pathological Pain. Cells 2022; 11:cells11121940. [PMID: 35741069 PMCID: PMC9222181 DOI: 10.3390/cells11121940] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 06/13/2022] [Accepted: 06/15/2022] [Indexed: 11/16/2022] Open
Abstract
Synapses serve as the interface for the transmission of information between neurons in the central nervous system. The structural and functional characteristics of synapses are highly dynamic, exhibiting extensive plasticity that is shaped by neural activity and regulated primarily by trans-synaptic cell-adhesion molecules (CAMs). Prototypical trans-synaptic CAMs, such as neurexins (Nrxs) and neuroligins (Nlgs), directly regulate the assembly of presynaptic and postsynaptic molecules, including synaptic vesicles, active zone proteins, and receptors. Therefore, the trans-synaptic adhesion mechanisms mediated by Nrx-Nlg interaction can contribute to a range of synaptopathies in the context of pathological pain and other neurological disorders. The present review provides an overview of the current understanding of the roles of Nrx-Nlg interaction in the regulation of trans-synaptic connections, with a specific focus on Nrx and Nlg structures, the dynamic shaping of synaptic function, and the dysregulation of Nrx-Nlg in pathological pain. Additionally, we discuss a range of proteins capable of modulating Nrx-Nlg interactions at the synaptic cleft, with the objective of providing a foundation to guide the future development of novel therapeutic agents for managing pathological pain.
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Affiliation(s)
- Huili Li
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China;
| | - Ruijuan Guo
- Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing 100030, China;
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA;
| | - Junfa Li
- Department of Neurobiology, Capital Medical University, Beijing 100069, China;
| | - Yun Wang
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China;
- Correspondence: ; Tel.: +86-10-85231463
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4
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Maxeiner S, Benseler F, Brose N, Krasteva-Christ G. Of Humans and Gerbils— Independent Diversification of Neuroligin-4 Into X- and Y-Specific Genes in Primates and Rodents. Front Mol Neurosci 2022; 15:838262. [PMID: 35431802 PMCID: PMC9005811 DOI: 10.3389/fnmol.2022.838262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/03/2022] [Indexed: 11/13/2022] Open
Abstract
The neural cell adhesion protein neuroligin-4 has puzzled neuroscientists and geneticist alike for almost two decades. Its clinical association with autism spectrum disorders (ASD) is well established, however, its diversification into sex chromosome-specific copies, NLGN4X and NLGN4Y, remains uncharted territory. Just recently, the presence of substantial neuroligin-4 sequence differences between humans and laboratory mice, in which Nlgn4 is a pseudoautosomal gene, could be explained as a consequence of dramatic changes affecting the pseudoautosomal region on both sex chromosomes in a subset of rodents, the clade eumuroida. In this study, we describe the presence of sex chromosome-specific copies of neuroligin-4 genes in the Mongolian gerbil (Meriones unguiculatus) marking the first encounter of its kind in rodents. Gerbils are members of the family Muridae and are closely related to mice and rats. Our results have been incorporated into an extended evolutionary analysis covering primates, rodents, lagomorphs, treeshrews and culogos comprising together the mammalian superorder euarchontoglires. We gathered evidence that substantial changes in neuroligin-4 genes have also occurred outside eumuroida in other rodent species as well as in lagomorphs. These changes feature, e.g., a general reduction of its gene size, an increase in its average GC-content as well as in the third position (GC3) of synonymous codons, and the accumulation of repetitive sequences in line with previous observations. We further show conclusively that the diversification of neuroligin-4 in sex chromosome-specific copies has happened multiple times independently during mammal evolution proving that Y-chromosomal NLGN4Y genes do not originate from a single common NLGN4Y ancestor.
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Affiliation(s)
- Stephan Maxeiner
- Anatomy and Cell Biology, Saarland University, Homburg, Germany
- *Correspondence: Stephan Maxeiner,
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
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5
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Schöpf CL, Ablinger C, Geisler SM, Stanika RI, Campiglio M, Kaufmann WA, Nimmervoll B, Schlick B, Brockhaus J, Missler M, Shigemoto R, Obermair GJ. Presynaptic α 2δ subunits are key organizers of glutamatergic synapses. Proc Natl Acad Sci U S A 2021; 118:e1920827118. [PMID: 33782113 PMCID: PMC8040823 DOI: 10.1073/pnas.1920827118] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In nerve cells the genes encoding for α2δ subunits of voltage-gated calcium channels have been linked to synaptic functions and neurological disease. Here we show that α2δ subunits are essential for the formation and organization of glutamatergic synapses. Using a cellular α2δ subunit triple-knockout/knockdown model, we demonstrate a failure in presynaptic differentiation evidenced by defective presynaptic calcium channel clustering and calcium influx, smaller presynaptic active zones, and a strongly reduced accumulation of presynaptic vesicle-associated proteins (synapsin and vGLUT). The presynaptic defect is associated with the downscaling of postsynaptic AMPA receptors and the postsynaptic density. The role of α2δ isoforms as synaptic organizers is highly redundant, as each individual α2δ isoform can rescue presynaptic calcium channel trafficking and expression of synaptic proteins. Moreover, α2δ-2 and α2δ-3 with mutated metal ion-dependent adhesion sites can fully rescue presynaptic synapsin expression but only partially calcium channel trafficking, suggesting that the regulatory role of α2δ subunits is independent from its role as a calcium channel subunit. Our findings influence the current view on excitatory synapse formation. First, our study suggests that postsynaptic differentiation is secondary to presynaptic differentiation. Second, the dependence of presynaptic differentiation on α2δ implicates α2δ subunits as potential nucleation points for the organization of synapses. Finally, our results suggest that α2δ subunits act as transsynaptic organizers of glutamatergic synapses, thereby aligning the synaptic active zone with the postsynaptic density.
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Affiliation(s)
- Clemens L Schöpf
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Cornelia Ablinger
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Stefanie M Geisler
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
- Department of Pharmacology and Toxicology, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Ruslan I Stanika
- Division of Physiology, Karl Landsteiner University of Health Sciences, A-3500 Krems, Austria
| | - Marta Campiglio
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Walter A Kaufmann
- Institute of Science and Technology Austria, A-3400 Klosterneuburg, Austria
| | - Benedikt Nimmervoll
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Bettina Schlick
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Johannes Brockhaus
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms University, 48149 Münster, Germany
| | - Markus Missler
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms University, 48149 Münster, Germany
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria, A-3400 Klosterneuburg, Austria
| | - Gerald J Obermair
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria;
- Division of Physiology, Karl Landsteiner University of Health Sciences, A-3500 Krems, Austria
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6
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An Autism-Associated Mutation Impairs Neuroligin-4 Glycosylation and Enhances Excitatory Synaptic Transmission in Human Neurons. J Neurosci 2020; 41:392-407. [PMID: 33268543 DOI: 10.1523/jneurosci.0404-20.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 11/18/2020] [Accepted: 11/20/2020] [Indexed: 02/06/2023] Open
Abstract
Neuroligins (NLGNs) are a class of postsynaptic cell adhesion molecules that interact with presynaptic neurexins (NRXNs) and regulate synapse function. NLGN4 is a member of the NLGN family and consists of a unique amino acid sequence in humans that is not evolutionarily well conserved in rodents. The human-specific NLGN4 gene has been reported to be mutated in many patients with autism and other neurodevelopmental disorders. However, it remained unclear how these mutations might alter the molecular properties of NLGN4 and affect synaptic transmission in human neurons. Here, we describe a severely autistic male patient carrying a single amino acid substitution (R101Q) in the NLGN4 gene. When expressed in HEK293 cells, the R101Q mutation in NLGN4 did not affect its binding affinity for NRXNs or its capacity to form homodimers. This mutation, however, impaired the maturation of NLGN4 protein by inhibiting N-linked glycosylation at an adjacent residue (N102), which is conserved in all NLGNs. As a result, the R101Q substitution significantly decreased the surface trafficking of NLGN4 and increased its retention in the endoplasmic reticulum and Golgi apparatus. In human neurons derived from male stem cell lines, the R101Q mutation also similarly reduced the synaptic localization of NLGN4, resulting in a loss-of-function phenotype. This mutation-induced trafficking defect substantially diminished the ability of NLGN4 to form excitatory synapses and modulate their functional properties. Viewed together, our findings suggest that the R101Q mutation is pathogenic for NLGN4 and can lead to synaptic dysfunction in autism.
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7
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Qin L, Guo S, Han Y, Wang X, Zhang B. Functional mosaic organization of neuroligins in neuronal circuits. Cell Mol Life Sci 2020; 77:3117-3127. [PMID: 32077971 PMCID: PMC11104838 DOI: 10.1007/s00018-020-03478-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 02/06/2020] [Accepted: 02/07/2020] [Indexed: 11/30/2022]
Abstract
Complex brain circuitry with feedforward and feedback systems regulates neuronal activity, enabling neural networks to process and drive the entire spectrum of cognitive, behavioral, sensory, and motor functions. Simultaneous orchestration of distinct cells and interconnected neural circuits is underpinned by hundreds of synaptic adhesion molecules that span synaptic junctions. Dysfunction of a single molecule or molecular interaction at synapses can lead to disrupted circuit activity and brain disorders. Neuroligins, a family of cell adhesion molecules, were first identified as postsynaptic-binding partners of presynaptic neurexins and are essential for synapse specification and maturation. Here, we review recent advances in our understanding of how this family of adhesion molecules controls neuronal circuit assembly by acting in a synapse-specific manner.
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Affiliation(s)
- Liming Qin
- School of Chemical Biology and Biotechnology, Shenzhen Bay Laboratory, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
| | - Sile Guo
- School of Chemical Biology and Biotechnology, Shenzhen Bay Laboratory, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
| | - Ying Han
- School of Chemical Biology and Biotechnology, Shenzhen Bay Laboratory, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
| | - Xiankun Wang
- School of Chemical Biology and Biotechnology, Shenzhen Bay Laboratory, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
| | - Bo Zhang
- School of Chemical Biology and Biotechnology, Shenzhen Bay Laboratory, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
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8
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Selected Ionotropic Receptors and Voltage-Gated Ion Channels: More Functional Competence for Human Induced Pluripotent Stem Cell (iPSC)-Derived Nociceptors. Brain Sci 2020; 10:brainsci10060344. [PMID: 32503260 PMCID: PMC7348931 DOI: 10.3390/brainsci10060344] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 05/28/2020] [Accepted: 05/30/2020] [Indexed: 01/09/2023] Open
Abstract
Preclinical research using different rodent model systems has largely contributed to the scientific progress in the pain field, however, it suffers from interspecies differences, limited access to human models, and ethical concerns. Human induced pluripotent stem cells (iPSCs) offer major advantages over animal models, i.e., they retain the genome of the donor (patient), and thus allow donor-specific and cell-type specific research. Consequently, human iPSC-derived nociceptors (iDNs) offer intriguingly new possibilities for patient-specific, animal-free research. In the present study, we characterized iDNs based on the expression of well described nociceptive markers and ion channels, and we conducted a side-by-side comparison of iDNs with mouse sensory neurons. Specifically, immunofluorescence (IF) analyses with selected markers including early somatosensory transcription factors (BRN3A/ISL1/RUNX1), the low-affinity nerve growth factor receptor (p75), hyperpolarization-activated cyclic nucleotide-gated channels (HCN), as well as high voltage-gated calcium channels (VGCC) of the CaV2 type, calcium permeable TRPV1 channels, and ionotropic GABAA receptors, were used to address the characteristics of the iDN phenotype. We further combined IF analyses with microfluorimetric Ca2+ measurements to address the functionality of these ion channels in iDNs. Thus, we provide a detailed morphological and functional characterization of iDNs, thereby, underpinning their enormous potential as an animal-free alternative for human specific research in the pain field for unveiling pathophysiological mechanisms and for unbiased, disease-specific personalized drug development.
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9
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Constance WD, Mukherjee A, Fisher YE, Pop S, Blanc E, Toyama Y, Williams DW. Neurexin and Neuroligin-based adhesion complexes drive axonal arborisation growth independent of synaptic activity. eLife 2018; 7:31659. [PMID: 29504935 PMCID: PMC5869020 DOI: 10.7554/elife.31659] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 03/04/2018] [Indexed: 11/25/2022] Open
Abstract
Building arborisations of the right size and shape is fundamental for neural network function. Live imaging in vertebrate brains strongly suggests that nascent synapses are critical for branch growth during development. The molecular mechanisms underlying this are largely unknown. Here we present a novel system in Drosophila for studying the development of complex arborisations live, in vivo during metamorphosis. In growing arborisations we see branch dynamics and localisations of presynaptic proteins very similar to the ‘synaptotropic growth’ described in fish/frogs. These accumulations of presynaptic proteins do not appear to be presynaptic release sites and are not paired with neurotransmitter receptors. Knockdowns of either evoked or spontaneous neurotransmission do not impact arbor growth. Instead, we find that axonal branch growth is regulated by dynamic, focal localisations of Neurexin and Neuroligin. These adhesion complexes provide stability for filopodia by a ‘stick-and-grow’ based mechanism wholly independent of synaptic activity.
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Affiliation(s)
- William D Constance
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom.,King's-NUS Joint Studentship Program, King's College London, London, United Kingdom
| | - Amrita Mukherjee
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom
| | - Yvette E Fisher
- Department of Neurobiology, Stanford University, Stanford, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Sinziana Pop
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom
| | - Eric Blanc
- Berlin Institute of Health, Berlin, Germany
| | - Yusuke Toyama
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore.,Temasek Life Sciences Laboratory, Singapore, Singapore.,Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Darren W Williams
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom
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10
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Bush SJ, Chen L, Tovar-Corona JM, Urrutia AO. Alternative splicing and the evolution of phenotypic novelty. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2015.0474. [PMID: 27994117 DOI: 10.1098/rstb.2015.0474] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2016] [Indexed: 12/21/2022] Open
Abstract
Alternative splicing, a mechanism of post-transcriptional RNA processing whereby a single gene can encode multiple distinct transcripts, has been proposed to underlie morphological innovations in multicellular organisms. Genes with developmental functions are enriched for alternative splicing events, suggestive of a contribution of alternative splicing to developmental programmes. The role of alternative splicing as a source of transcript diversification has previously been compared to that of gene duplication, with the relationship between the two extensively explored. Alternative splicing is reduced following gene duplication with the retention of duplicate copies higher for genes which were alternatively spliced prior to duplication. Furthermore, and unlike the case for overall gene number, the proportion of alternatively spliced genes has also increased in line with the evolutionary diversification of cell types, suggesting alternative splicing may contribute to the complexity of developmental programmes. Together these observations suggest a prominent role for alternative splicing as a source of functional innovation. However, it is unknown whether the proliferation of alternative splicing events indeed reflects a functional expansion of the transcriptome or instead results from weaker selection acting on larger species, which tend to have a higher number of cell types and lower population sizes.This article is part of the themed issue 'Evo-devo in the genomics era, and the origins of morphological diversity'.
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Affiliation(s)
- Stephen J Bush
- The Roslin Institute, University of Edinburgh, Edinburgh EH25 9RG, UK
| | - Lu Chen
- West China Second University Hospital, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, People's Republic of China
| | | | - Araxi O Urrutia
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK .,Milner Centre for Evolution, University of Bath, Bath BA2 7AY, UK
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11
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Jeong J, Paskus JD, Roche KW. Posttranslational modifications of neuroligins regulate neuronal and glial signaling. Curr Opin Neurobiol 2017; 45:130-138. [PMID: 28577430 DOI: 10.1016/j.conb.2017.05.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/02/2017] [Accepted: 05/12/2017] [Indexed: 12/29/2022]
Abstract
This review covers the dynamic regulation of neuroligin isoforms, focusing on posttranslational events including phosphorylation, glycosylation and activity-dependent cleavage. There is a growing literature on how phosphorylation confers an isoform-specific level of modulation affecting a variety of protein interactions. In addition, recent studies describe activity-dependent proteolytic cleavage of neuroligins, revealing a broader role for neuroligins than just synaptic 'glue'. Interesting new research implicates the cleaved extracellular fragments of neuroligins in promoting glioma. These reports on cell signaling mediated by the cleavage products of neuroligins suggest novel and important roles for neuroligins in neuro-glial signaling.
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Affiliation(s)
- Jaehoon Jeong
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeremiah D Paskus
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA; Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Katherine W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA.
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12
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Singh SK, Stogsdill JA, Pulimood NS, Dingsdale H, Kim YH, Pilaz LJ, Kim IH, Manhaes AC, Rodrigues WS, Pamukcu A, Enustun E, Ertuz Z, Scheiffele P, Soderling SH, Silver DL, Ji RR, Medina AE, Eroglu C. Astrocytes Assemble Thalamocortical Synapses by Bridging NRX1α and NL1 via Hevin. Cell 2016; 164:183-196. [PMID: 26771491 DOI: 10.1016/j.cell.2015.11.034] [Citation(s) in RCA: 197] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 08/18/2015] [Accepted: 11/10/2015] [Indexed: 11/16/2022]
Abstract
Proper establishment of synapses is critical for constructing functional circuits. Interactions between presynaptic neurexins and postsynaptic neuroligins coordinate the formation of synaptic adhesions. An isoform code determines the direct interactions of neurexins and neuroligins across the synapse. However, whether extracellular linker proteins can expand such a code is unknown. Using a combination of in vitro and in vivo approaches, we found that hevin, an astrocyte-secreted synaptogenic protein, assembles glutamatergic synapses by bridging neurexin-1alpha and neuroligin-1B, two isoforms that do not interact with each other. Bridging of neurexin-1alpha and neuroligin-1B via hevin is critical for the formation and plasticity of thalamocortical connections in the developing visual cortex. These results show that astrocytes promote the formation of synapses by modulating neurexin/neuroligin adhesions through hevin secretion. Our findings also provide an important mechanistic insight into how mutations in these genes may lead to circuit dysfunction in diseases such as autism.
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Affiliation(s)
- Sandeep K Singh
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710.
| | - Jeff A Stogsdill
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Nisha S Pulimood
- Department of Pediatrics, University of Maryland, School of Medicine, Baltimore, MD 21201
| | - Hayley Dingsdale
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Yong Ho Kim
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710
| | - Louis-Jan Pilaz
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710
| | - Il Hwan Kim
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Alex C Manhaes
- Department of Pediatrics, University of Maryland, School of Medicine, Baltimore, MD 21201
| | - Wandilson S Rodrigues
- Department of Pediatrics, University of Maryland, School of Medicine, Baltimore, MD 21201
| | - Arin Pamukcu
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Eray Enustun
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Zeynep Ertuz
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | | | - Scott H Soderling
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710; Duke Institute for Brain Sciences (DIBS), Durham, NC 27710
| | - Debra L Silver
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710; Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710; Duke Institute for Brain Sciences (DIBS), Durham, NC 27710
| | - Ru-Rong Ji
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710
| | - Alexandre E Medina
- Department of Pediatrics, University of Maryland, School of Medicine, Baltimore, MD 21201
| | - Cagla Eroglu
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710; Duke Institute for Brain Sciences (DIBS), Durham, NC 27710.
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13
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Abstract
To create a presynaptic terminal, molecular signaling events must be orchestrated across a number of subcellular compartments. In the soma, presynaptic proteins need to be synthesized, packaged together, and attached to microtubule motors for shipment through the axon. Within the axon, transport of presynaptic packages is regulated to ensure that developing synapses receive an adequate supply of components. At individual axonal sites, extracellular interactions must be translated into intracellular signals that can incorporate mobile transport vesicles into the nascent presynaptic terminal. Even once the initial recruitment process is complete, the components and subsequent functionality of presynaptic terminals need to constantly be remodeled. Perhaps most remarkably, all of these processes need to be coordinated in space and time. In this review, we discuss how these dynamic cellular processes occur in neurons of the central nervous system in order to generate presynaptic terminals in the brain.
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Affiliation(s)
- Luke A D Bury
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Shasta L Sabo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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14
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Abstract
A fundamental physical interaction exists across the synapse. It is mediated by synaptic adhesion molecules, and is among the earliest and most indispensable of molecular events occurring during synaptogenesis. The regulation of adhesion molecules and their interactions with other synaptic proteins likely affect not only on synapse formation but also on ongoing synaptic function. We review research on one major family of postsynaptic adhesion molecules, neuroligins, which bind to their presynaptic partner neurexin across the synaptic cleft. We move from a structural overview to the broad cellular and synaptic context of neuroligins, intermolecular interactions, and molecular modifications that occur within a synapse. Finally, we examine evidence concerning the physiological functions of neuroligin in a cell and highlight areas requiring further investigation.
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Affiliation(s)
- Michael A Bemben
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA; Department of Biology, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA
| | - Seth L Shipman
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Roger A Nicoll
- Departments of Cellular and Molecular Pharmacology and Physiology, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - Katherine W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA.
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15
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Calahorro F, Holden-Dye L, O'Connor V. Analysis of splice variants for the C. elegans orthologue of human neuroligin reveals a developmentally regulated transcript. Gene Expr Patterns 2015; 17:69-78. [PMID: 25726726 DOI: 10.1016/j.gep.2015.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 02/17/2015] [Accepted: 02/19/2015] [Indexed: 11/20/2022]
Abstract
Neuroligins are synaptic adhesion molecules and important determinants of synaptic function. They are expressed at postsynaptic sites and involved in synaptic organization through key extracellular and intracellular protein interactions. They undergo trans-synaptic interaction with presynaptic neurexins. Distinct neuroligins use differences in their intracellular domains to selectively recruit synaptic scaffolds and this plays an important role in how they encode specialization of synaptic function. Several levels of regulation including gene expression, splicing, protein translation and processing regulate the expression of neuroligin function. We have used in silico and cDNA analyses to investigate the mRNA splicing of the Caenorhabditis elegans orthologue nlg-1. Transcript analysis highlights the potential for gene regulation with respect to both temporal expression and splicing. We found nlg-1 splice variants with all the predicted exons are a minor species relative to major splice variants lacking exons 13 and 14, or 14 alone. These major alternatively spliced variants change the intracellular domain of the gene product NLG-1. Interestingly, exon 14 encodes a cassette with two distinct potential functional domains. One is a polyproline SH3 binding domain and the other has homology to a region encoding the binding site for the scaffolding protein gephyrin in mammalian neuroligins. This suggests differential splicing impacts on NLG-1 competence to recruit intracellular binding partners. This may have developmental relevance as nlg-1 exon 14 containing transcripts are selectively expressed in L2-L3 larvae. These results highlight a developmental regulation of C. elegans nlg-1 that could play a key role in the assembly of synaptic protein complexes during the early stages of nervous system development.
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Affiliation(s)
- Fernando Calahorro
- Centre for Biological Sciences, Life Sciences Building 85, University of Southampton, Southampton SO17 1BJ, UK.
| | - Lindy Holden-Dye
- Centre for Biological Sciences, Life Sciences Building 85, University of Southampton, Southampton SO17 1BJ, UK
| | - Vincent O'Connor
- Centre for Biological Sciences, Life Sciences Building 85, University of Southampton, Southampton SO17 1BJ, UK
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16
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Abstract
The neurexin family of cell adhesion proteins consists of three members in
vertebrates and has homologs in several invertebrate species. In mammals, each
neurexin gene encodes an α-neurexin in which the extracellular portion is long,
and a β-neurexin in which the extracellular portion is short. As a result of
alternative splicing, both major isoforms can be transcribed in many variants,
contributing to distinct structural domains and variability. Neurexins act
predominantly at the presynaptic terminal in neurons and play essential roles in
neurotransmission and differentiation of synapses. Some of these functions require
the formation of trans-synaptic complexes with postsynaptic proteins such as
neuroligins, LRRTM proteins or cerebellin. In addition, rare mutations and
copy-number variations of human neurexin genes have been linked to autism and
schizophrenia, indicating that impairments of synaptic function sustained by
neurexins and their binding partners may be relevant to the pathomechanism of these
debilitating diseases.
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17
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Gill I, Droubi S, Giovedi S, Fedder KN, Bury LAD, Bosco F, Sceniak MP, Benfenati F, Sabo SL. Presynaptic NMDA receptors - dynamics and distribution in developing axons in vitro and in vivo. J Cell Sci 2014; 128:768-80. [PMID: 25526735 DOI: 10.1242/jcs.162362] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
During cortical development, N-methyl-D-aspartate (NMDA) receptors (NMDARs) facilitate presynaptic terminal formation, enhance neurotransmitter release and are required in presynaptic neurons for spike-timing-dependent long-term depression (tLTD). However, the extent to which NMDARs are found within cortical presynaptic terminals has remained controversial, and the sub-synaptic localization and dynamics of axonal NMDARs are unknown. Here, using live confocal imaging and biochemical purification of presynaptic membranes, we provide strong evidence that NMDARs localize to presynaptic terminals in vitro and in vivo in a developmentally regulated manner. The NR1 and NR2B subunits (also known as GRIN1 and GRIN2B, respectively) were found within the active zone membrane, where they could respond to synaptic glutamate release. Surprisingly, NR1 also appeared in glutamatergic and GABAergic synaptic vesicles. During synaptogenesis, NR1 was mobile throughout axons - including growth cones and filopodia, structures that are involved in synaptogenesis. Upon synaptogenic contact, NMDA receptors were quickly recruited to terminals by neuroligin-1 signaling. Unlike dendrites, the trafficking and distribution of axonal NR1 were insensitive to activity changes, including NMDA exposure, local glutamate uncaging or action potential blockade. These results support the idea that presynaptic NMDARs play an early role in presynaptic development.
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Affiliation(s)
- Ishwar Gill
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Sammy Droubi
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Silvia Giovedi
- Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
| | - Karlie N Fedder
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Luke A D Bury
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Federica Bosco
- Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
| | - Michael P Sceniak
- Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Fabio Benfenati
- Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, 16163 Genoa, Italy
| | - Shasta L Sabo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
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18
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Bury LA, Sabo SL. Dynamic mechanisms of neuroligin-dependent presynaptic terminal assembly in living cortical neurons. Neural Dev 2014; 9:13. [PMID: 24885664 PMCID: PMC4049477 DOI: 10.1186/1749-8104-9-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/12/2014] [Indexed: 12/23/2022] Open
Abstract
Background Synapse formation occurs when synaptogenic signals trigger coordinated development of pre and postsynaptic structures. One of the best-characterized synaptogenic signals is trans-synaptic adhesion. However, it remains unclear how synaptic proteins are recruited to sites of adhesion. In particular, it is unknown whether synaptogenic signals attract synaptic vesicle (SV) and active zone (AZ) proteins to nascent synapses or instead predominantly function to create sites that are capable of forming synapses. It is also unclear how labile synaptic proteins are at developing synapses after their initial recruitment. To address these issues, we used long-term, live confocal imaging of presynaptic terminal formation in cultured cortical neurons after contact with the synaptogenic postsynaptic adhesion proteins neuroligin-1 or SynCAM-1. Results Surprisingly, we find that trans-synaptic adhesion does not attract SV or AZ proteins nor alter their transport. In addition, although neurexin (the presynaptic partner of neuroligin) typically accumulates over the entire region of contact between axons and neuroligin-1-expressing cells, SV proteins selectively assemble at spots of enhanced neurexin clustering. The arrival and maintenance of SV proteins at these sites is highly variable over the course of minutes to hours, and this variability correlates with neurexin levels at individual synapses. Conclusions Together, our data support a model of synaptogenesis where presynaptic proteins are trapped at specific axonal sites, where they are stabilized by trans-synaptic adhesion signaling.
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Affiliation(s)
| | - Shasta L Sabo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
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19
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Grützmann K, Szafranski K, Pohl M, Voigt K, Petzold A, Schuster S. Fungal alternative splicing is associated with multicellular complexity and virulence: a genome-wide multi-species study. DNA Res 2013; 21:27-39. [PMID: 24122896 PMCID: PMC3925392 DOI: 10.1093/dnares/dst038] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Alternative splicing (AS) is a cellular process that increases a cell's coding capacity from a limited set of genes. Although AS is common in higher plants and animals, its prevalence in other eukaryotes is mostly unknown. In fungi the involvement of AS in gene expression and its effect on multi-cellularity and virulence is of great medical and economic interest. We present a genome-wide comparative study of AS in 23 informative fungi of different taxa, based on alignments of public transcript sequences. Random sampling of expressed sequence tags allows for robust and comparable estimations of AS rates. We find that a greater fraction of fungal genes than previously expected is associated with AS. We estimate that on average, 6.4% of the annotated genes are affected by AS, with Cryptococcus neoformans showing an extraordinary rate of 18%. The investigated Basidiomycota show higher average AS rates (8.6%) than the Ascomycota (6.0%), although not significant. We find that multi-cellular complexity and younger evolutionary age associate with higher AS rates. Furthermore, AS affects genes involved in pathogenic lifestyle, particularly in functions of stress response and dimorphic switching. Together, our analysis strongly supports the view that AS is a rather common phenomenon in fungi and associates with higher multi-cellular complexity.
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Affiliation(s)
- Konrad Grützmann
- 1Department of Bioinformatics, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, Jena D-07743, Germany
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20
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Kelemen O, Convertini P, Zhang Z, Wen Y, Shen M, Falaleeva M, Stamm S. Function of alternative splicing. Gene 2013; 514:1-30. [PMID: 22909801 PMCID: PMC5632952 DOI: 10.1016/j.gene.2012.07.083] [Citation(s) in RCA: 509] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/21/2012] [Accepted: 07/30/2012] [Indexed: 12/15/2022]
Abstract
Almost all polymerase II transcripts undergo alternative pre-mRNA splicing. Here, we review the functions of alternative splicing events that have been experimentally determined. The overall function of alternative splicing is to increase the diversity of mRNAs expressed from the genome. Alternative splicing changes proteins encoded by mRNAs, which has profound functional effects. Experimental analysis of these protein isoforms showed that alternative splicing regulates binding between proteins, between proteins and nucleic acids as well as between proteins and membranes. Alternative splicing regulates the localization of proteins, their enzymatic properties and their interaction with ligands. In most cases, changes caused by individual splicing isoforms are small. However, cells typically coordinate numerous changes in 'splicing programs', which can have strong effects on cell proliferation, cell survival and properties of the nervous system. Due to its widespread usage and molecular versatility, alternative splicing emerges as a central element in gene regulation that interferes with almost every biological function analyzed.
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Affiliation(s)
- Olga Kelemen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Paolo Convertini
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhaiyi Zhang
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Yuan Wen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Manli Shen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Marina Falaleeva
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Stefan Stamm
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
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21
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Shipman SL, Nicoll RA. A subtype-specific function for the extracellular domain of neuroligin 1 in hippocampal LTP. Neuron 2012; 76:309-16. [PMID: 23083734 DOI: 10.1016/j.neuron.2012.07.024] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/19/2012] [Indexed: 12/27/2022]
Abstract
At neuronal excitatory synapses, two major subtypes of the synaptic adhesion molecule neuroligin are present. These subtypes, neuroligin 1 and neuroligin 3, have roles in synaptogenesis and synaptic maintenance that appear largely overlapping. In this study, we combine electrophysiology with molecular deletion and replacement of these proteins to identify similarities and differences between these subtypes. In doing so, we identify a subtype-specific role in LTP for neuroligin 1 in young CA1, which persists into adulthood in the dentate gyrus. As neuroligin 3 showed no requirement for LTP, we constructed chimeric proteins of the two excitatory neuroligin subtypes to identify the molecular determinants particular to the unique function of neuroligin 1. Using in vivo molecular replacement experiments, we find that these unique functions depend on a region in its extracellular domain containing the B site splice insertion previously shown to determine specificity of neurexin binding.
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Affiliation(s)
- Seth L Shipman
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
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22
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Zeidan A, Ziv NE. Neuroligin-1 loss is associated with reduced tenacity of excitatory synapses. PLoS One 2012; 7:e42314. [PMID: 22860111 PMCID: PMC3409177 DOI: 10.1371/journal.pone.0042314] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 07/02/2012] [Indexed: 12/20/2022] Open
Abstract
Neuroligins (Nlgns) are postsynaptic, integral membrane cell adhesion molecules that play important roles in the formation, validation, and maturation of synapses in the mammalian central nervous system. Given their prominent roles in the life cycle of synapses, it might be expected that the loss of neuroligin family members would affect the stability of synaptic organization, and ultimately, affect the tenacity and persistence of individual synaptic junctions. Here we examined whether and to what extent the loss of Nlgn-1 affects the dynamics of several key synaptic molecules and the constancy of their contents at individual synapses over time. Fluorescently tagged versions of the postsynaptic scaffold molecule PSD-95, the AMPA-type glutamate receptor subunit GluA2 and the presynaptic vesicle molecule SV2A were expressed in primary cortical cultures from Nlgn-1 KO mice and wild-type (WT) littermates, and live imaging was used to follow the constancy of their contents at individual synapses over periods of 8-12 hours. We found that the loss of Nlgn-1 was associated with larger fluctuations in the synaptic contents of these molecules and a poorer preservation of their contents at individual synapses. Furthermore, rates of synaptic turnover were somewhat greater in neurons from Nlgn-1 knockout mice. Finally, the increased GluA2 redistribution rates observed in neurons from Nlgn-1 knockout mice were negated by suppressing spontaneous network activity. These findings suggest that the loss of Nlgn-1 is associated with some use-dependent destabilization of excitatory synapse organization, and indicate that in the absence of Nlgn-1, the tenacity of excitatory synapses might be somewhat impaired.
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Affiliation(s)
- Adel Zeidan
- Department of Physiology and Biophysics and Rappaport Institute, Technion Faculty of Medicine, and Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Haifa, Israel
| | - Noam E. Ziv
- Department of Physiology and Biophysics and Rappaport Institute, Technion Faculty of Medicine, and Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Haifa, Israel
- * E-mail:
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23
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Burton SD, Johnson JW, Zeringue HC, Meriney SD. Distinct roles of neuroligin-1 and SynCAM1 in synapse formation and function in primary hippocampal neuronal cultures. Neuroscience 2012; 215:1-16. [PMID: 22542674 DOI: 10.1016/j.neuroscience.2012.04.047] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 04/02/2012] [Accepted: 04/18/2012] [Indexed: 12/16/2022]
Abstract
Neuroligins are a family of cell adhesion molecules critical in establishing proper central nervous system connectivity; disruption of neuroligin signaling in vivo precipitates a broad range of cognitive deficits. Despite considerable recent progress, the specific synaptic function of neuroligin-1 (NL1) remains unclear. A current model proposes that NL1 acts exclusively to mature pre-existent synaptic connections in an activity-dependent manner. A second element of this activity-dependent maturation model is that an alternate molecule acts upstream of NL1 to initiate synaptic connections. SynCAM1 (SC1) is hypothesized to function in this capacity, though several uncertainties remain regarding SC1 function. Using overexpression and chronic pharmacological blockade of synaptic activity, we now demonstrate that NL1 is capable of robustly recruiting synapsin-positive terminals independent of synaptic maturation and activity in 2-week old primary hippocampal neuronal cultures. We further report that neither SC1 overexpression nor knockdown of endogenous SC1 impacts synapsin punctum densities, suggesting that SC1 is not a limiting factor of synapse initiation in maturing hippocampal neurons in vitro. Consistent with these findings, we observed profoundly greater recruitment of synapsin-positive presynaptic terminals by NL1 than SC1 in a mixed-culture assay of artificial synaptogenesis between primary neurons and heterologous cells. Collectively, our results contend multiple aspects of the proposed model of NL1 and SC1 function and motivate an alternative model whereby SC1 may mature synaptic connections forged by NL1. Supporting this model, we present evidence that combined NL1 and SC1 overexpression triggers excitotoxic neurodegeneration through SC1 signaling at synaptic connections initiated by NL1.
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Affiliation(s)
- S D Burton
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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24
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Elliott DA, Kim WS, Gorissen S, Halliday GM, Kwok JBJ. Leucine-rich repeat kinase 2 and alternative splicing in Parkinson's disease. Mov Disord 2012; 27:1004-11. [PMID: 22528366 DOI: 10.1002/mds.25005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 03/15/2012] [Accepted: 03/20/2012] [Indexed: 12/12/2022] Open
Abstract
Mutations of the leucine-rich repeat kinase 2 (LRRK2) gene are the most common genetic cause of Parkinson's disease (PD) and are associated with pleiomorphic neuropathology. We hypothesize that LRRK2 mediates its pathogenic effect through alternative splicing of neurodegeneration genes. Methods used in this study included western blotting analysis of subcellular protein fractions, exon-array analysis of RNA from cultured neuroblastoma cells transfected with LRRK2 expression vectors, and reverse-transcription polymerase chain reaction (RT-PCR) of RNA from cultured cells and postmortem tissue. Overexpression of the LRRK2 G2019S mutant resulted in a significant (2.6-fold; P = 0.020) decrease in nuclear transactive response DNA-binding protein 43 levels. Exon-array analyses revealed that wild-type LRRK2 had a significant effect on the expression of genes with nuclear (P < 10(-22) ) and cell-cycle functions (P < 10(-15) ). We replicated changes in gene expression in 30% of selected genes by quantitative RT-PCR. Overexpression of LRRK2 resulted in the altered splicing of two genes associated with PD, with an increased inclusion of exon 10 of microtubule-associated protein tau (1.7-fold; P = 0.001) and exon 5 of the alpha-synuclein (SNCA) gene (1.6-fold; P =0.005). Moreover, overexpression of LRRK2 (G2019S) and two mutant genes associated with neurodegeneration, TARDBP (M337V) and FUS (R521H), were associated with decreased inclusion out of the dystonin (DST) 1e precursor exons in SK-N-MC cells. Altered splicing of SNCA (1.9-fold; P < 0.001) and DST genes (log(2) 2.3-fold; P = 0.005) was observed in a cohort of PD, compared with neurologically healthy, brains. This suggests that aberrant RNA metabolism is an important contributor to idiopathic PD.
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Affiliation(s)
- David A Elliott
- Neuroscience Research Australia, Barker St., Randwick, Sydney, NSW 2031, Australia
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25
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The role of neurexins and neuroligins in the formation, maturation, and function of vertebrate synapses. Curr Opin Neurobiol 2012; 22:412-22. [PMID: 22424845 DOI: 10.1016/j.conb.2012.02.012] [Citation(s) in RCA: 174] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 02/23/2012] [Indexed: 11/20/2022]
Abstract
Neurexins (NXs) and neuroligins (NLs) are transsynaptically interacting cell adhesion proteins that play a key role in the formation, maturation, activity-dependent validation, and maintenance of synapses. As complex alternative splicing processes in nerve cells generate a large number of NX and NLs variants, it has been proposed that a combinatorial interaction code generated by these variants may determine synapse identity and network connectivity during brain development. The functional importance of NXs and NLs is exemplified by the fact that mutations in NX and NL genes are associated with several neuropsychiatric disorders, most notably with autism. Accordingly, major research efforts have focused on the molecular mechanisms by which NXs and NLs operate at synapses. In this review, we summarize recent progress in this field and discuss emerging topics, such as the role of alternative interaction partners of NXs and NLs in synapse formation and function, and their relevance for synaptic plasticity in the mature brain. The novel findings highlight the fundamental importance of NX-NL interactions in a wide range of synaptic functions.
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26
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Knight D, Xie W, Boulianne GL. Neurexins and neuroligins: recent insights from invertebrates. Mol Neurobiol 2011; 44:426-40. [PMID: 22037798 PMCID: PMC3229692 DOI: 10.1007/s12035-011-8213-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 10/17/2011] [Indexed: 11/28/2022]
Abstract
During brain development, each neuron must find and synapse with the correct pre- and postsynaptic partners. The complexity of these connections and the relatively large distances some neurons must send their axons to find the correct partners makes studying brain development one of the most challenging, and yet fascinating disciplines in biology. Furthermore, once the initial connections have been made, the neurons constantly remodel their dendritic and axonal arbours in response to changing demands. Neurexin and neuroligin are two cell adhesion molecules identified as important regulators of this process. The importance of these genes in the development and modulation of synaptic connectivity is emphasised by the observation that mutations in these genes in humans have been associated with cognitive disorders such as Autism spectrum disorders, Tourette syndrome and Schizophrenia. The present review will discuss recent advances in our understanding of the role of these genes in synaptic development and modulation, and in particular, we will focus on recent work in invertebrate models, and how these results relate to studies in mammals.
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Affiliation(s)
- David Knight
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
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27
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Bury LAD, Sabo SL. Coordinated trafficking of synaptic vesicle and active zone proteins prior to synapse formation. Neural Dev 2011; 6:24. [PMID: 21569270 PMCID: PMC3103415 DOI: 10.1186/1749-8104-6-24] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 05/10/2011] [Indexed: 11/10/2022] Open
Abstract
Background The proteins required for synaptic transmission are rapidly assembled at nascent synapses, but the mechanisms through which these proteins are delivered to developing presynaptic terminals are not understood. Prior to synapse formation, active zone proteins and synaptic vesicle proteins are transported along axons in distinct organelles referred to as piccolo-bassoon transport vesicles (PTVs) and synaptic vesicle protein transport vesicles (STVs), respectively. Although both PTVs and STVs are recruited to the same site in the axon, often within minutes of axo-dendritic contact, it is not known whether or how PTV and STV trafficking is coordinated before synapse formation. Results Here, using time-lapse confocal imaging of the dynamics of PTVs and STVs in the same axon, we show that vesicle trafficking is coordinated through at least two mechanisms. First, a significant proportion of STVs and PTVs are transported together before forming a stable terminal. Second, individual PTVs and STVs share pause sites within the axon. Importantly, for both STVs and PTVs, encountering the other type of vesicle increases their propensity to pause. To determine if PTV-STV interactions are important for pausing, PTV density was reduced in axons by expression of a dominant negative construct corresponding to the syntaxin binding domain of syntabulin, which links PTVs with their KIF5B motor. This reduction in PTVs had a minimal effect on STV pausing and movement, suggesting that an interaction between STVs and PTVs is not responsible for enhancing STV pausing. Conclusions Our results indicate that trafficking of STVs and PTVs is coordinated even prior to synapse development. This novel coordination of transport and pausing might provide mechanisms through which all of the components of a presynaptic terminal can be rapidly accumulated at sites of synapse formation.
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Affiliation(s)
- Luke A D Bury
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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Presenilin/γ-secretase regulates neurexin processing at synapses. PLoS One 2011; 6:e19430. [PMID: 21559374 PMCID: PMC3084856 DOI: 10.1371/journal.pone.0019430] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 04/04/2011] [Indexed: 12/21/2022] Open
Abstract
Neurexins are a large family of neuronal plasma membrane proteins, which function as trans-synaptic receptors during synaptic differentiation. The binding of presynaptic neurexins to postsynaptic partners, such as neuroligins, has been proposed to participate in a signaling pathway that regulates synapse formation/stabilization. The identification of mutations in neurexin genes associated with autism and mental retardation suggests that dysfunction of neurexins may underlie synaptic defects associated with brain disorders. However, the mechanisms that regulate neurexin function at synapses are still unclear. Here, we show that neurexins are proteolytically processed by presenilins (PS), the catalytic components of the γ-secretase complex that mediates the intramembraneous cleavage of several type I membrane proteins. Inhibition of PS/γ-secretase by using pharmacological and genetic approaches induces a drastic accumulation of neurexin C-terminal fragments (CTFs) in cultured rat hippocampal neurons and mouse brain. Neurexin-CTFs accumulate mainly at the presynaptic terminals of PS conditional double knockout (PS cDKO) mice lacking both PS genes in glutamatergic neurons of the forebrain. The fact that loss of PS function enhances neurexin accumulation at glutamatergic terminals mediated by neuroligin-1 suggests that PS regulate the processing of neurexins at glutamatergic synapses. Interestingly, presenilin 1 (PS1) is recruited to glutamatergic terminals mediated by neuroligin-1, thus concentrating PS1 at terminals containing β-neurexins. Furthermore, familial Alzheimer's disease (FAD)-linked PS1 mutations differentially affect β-neurexin-1 processing. Expression of PS1 M146L and PS1 H163R mutants in PS−/− cells rescues the processing of β-neurexin-1, whereas PS1 C410Y and PS1 ΔE9 fail to rescue the processing defect. These results suggest that PS regulate the synaptic function and processing of neurexins at glutamatergic synapses, and that impaired neurexin processing by PS may play a role in FAD.
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Abstract
AbstractThe olfactory system represents a perfect model to study the interactions between the central and peripheral nervous systems in order to establish a neural circuit during early embryonic development. In addition, another important feature of this system is the capability to integrate new cells generated in two neurogenic zones: the olfactory epithelium in the periphery and the wall of the lateral ventricles in the CNS, both during development and adulthood. In all these processes the combination and sequence of specific molecular signals plays a critical role in the wiring of the olfactory axons, as well as the precise location of the incoming cell populations to the olfactory bulb. The purpose of this review is to summarize recent insights into the cellular and molecular events that dictate cell settling position and axonal trajectories from their origin in the olfactory placode to the formation of synapses in the olfactory bulb to ensure rapid and reliable transmission of olfactory information from the nose to the brain.
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