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Kostka JK, Gretenkord S, Spehr M, Hanganu-Opatz IL. Bursting mitral cells time the oscillatory coupling between olfactory bulb and entorhinal networks in neonatal mice. J Physiol 2020; 598:5753-5769. [PMID: 32926437 DOI: 10.1113/jp280131] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 09/08/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS During early postnatal development, mitral cells show either irregular bursting or non-bursting firing patterns Bursting mitral cells preferentially fire during theta bursts in the neonatal olfactory bulb, being locked to the theta phase Bursting mitral cells preferentially fire during theta bursts in the neonatal lateral entorhinal cortex and are temporally related to both respiration rhythm- and theta phase Bursting mitral cells act as a cellular substrate of the olfactory drive that promotes the oscillatory entrainment of entorhinal networks ABSTRACT: Shortly after birth, the olfactory system provides not only the main source of environmental inputs to blind, deaf, non-whisking and motorically-limited rodents, but also the drive boosting the functional entrainment of limbic circuits. However, the cellular substrate of this early communication remains largely unknown. Here, we combine in vivo and in vitro patch-clamp and extracellular recordings to reveal the contribution of mitral cell (MC) firing to early patterns of network activity in both the neonatal olfactory bulb (OB) and the lateral entorhinal cortex (LEC), the gatekeeper of limbic circuits. We show that MCs predominantly fire either in an irregular bursting or non-bursting pattern during discontinuous theta events in the OB. However, the temporal spike-theta phase coupling is stronger for bursting than non-bursting MCs. In line with the direct OB-to-LEC projections, both bursting and non-bursting discharge augments during co-ordinated patterns of entorhinal activity, albeit with higher magnitude for bursting MCs. For these neurons, temporal coupling to the discontinuous theta events in the LEC is stronger. Thus, bursting MCs might drive the entrainment of the OB-LEC network during neonatal development.
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Affiliation(s)
- Johanna K Kostka
- Institute of Developmental Neurophysiology, Center for Molecular Neurobiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Sabine Gretenkord
- Institute of Developmental Neurophysiology, Center for Molecular Neurobiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marc Spehr
- Department of Chemosensation, Institute of Biology II, Rheinisch-Westfalische Technische Hochschule Aachen, Aachen, Germany
| | - Ileana L Hanganu-Opatz
- Institute of Developmental Neurophysiology, Center for Molecular Neurobiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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2
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Nazareth L, Chen M, Shelper T, Shah M, Tello Velasquez J, Walkden H, Beacham I, Batzloff M, Rayfield A, Todorovic M, Beagley KW, St John JA, Ekberg JAK. Novel insights into the glia limitans of the olfactory nervous system. J Comp Neurol 2019; 527:1228-1244. [PMID: 30592044 DOI: 10.1002/cne.24618] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 12/14/2018] [Accepted: 12/14/2018] [Indexed: 02/04/2023]
Abstract
Olfactory ensheathing cells (OECs) are often described as being present in both the peripheral and the central nervous systems (PNS and CNS). Furthermore, the olfactory nervous system glia limitans (the glial layer defining the PNS-CNS border) is considered unique as it consists of intermingling OECs and astrocytes. In contrast, the glia limitans of the rest of the nervous system consists solely of astrocytes which create a distinct barrier to Schwann cells (peripheral glia). The ability of OECs to interact with astrocytes is one reason why OECs are believed to be superior to Schwann cells for transplantation therapies to treat CNS injuries. We have used transgenic reporter mice in which glial cells express DsRed fluorescent protein to study the cellular constituents of the glia limitans. We found that the glia limitans layer of the olfactory nervous system is morphologically similar to elsewhere in the nervous system, with a similar low degree of intermingling between peripheral glia and astrocytes. We found that the astrocytic layer of the olfactory bulb is a distinct barrier to bacterial infection, suggesting that this layer constitutes the PNS-CNS immunological barrier. We also found that OECs interact with astrocytes in a similar fashion as Schwann cells in vitro. When cultured in three dimensions, however, there were subtle differences between OECs and Schwann cells in their interactions with astrocytes. We therefore suggest that glial fibrillary acidic protein-reactive astrocyte layer of the olfactory bulb constitutes the glia limitans of the olfactory nervous system and that OECs are primarily "PNS glia."
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Affiliation(s)
- Lynn Nazareth
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
| | - Mo Chen
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
| | - Todd Shelper
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
| | - Megha Shah
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
| | - Johana Tello Velasquez
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Heidi Walkden
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
| | - Ifor Beacham
- Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Michael Batzloff
- Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Andrew Rayfield
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
| | - Michael Todorovic
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia.,School of Nursing and Midwifery, Griffith University, Nathan, Queensland, Australia
| | - Kenneth W Beagley
- Institute for Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
| | - James A St John
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia.,Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Jenny A K Ekberg
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia.,Menzies Institute of Health Queensland, Griffith University, Southport, Queensland, Australia
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3
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Rich CA, Perera SN, Andratschke J, Stolt CC, Buehler DP, Southard-Smith EM, Wegner M, Britsch S, Baker CVH. Olfactory ensheathing cells abutting the embryonic olfactory bulb express Frzb, whose deletion disrupts olfactory axon targeting. Glia 2018; 66:2617-2631. [PMID: 30256452 PMCID: PMC6517278 DOI: 10.1002/glia.23515] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 07/19/2018] [Accepted: 07/30/2018] [Indexed: 12/11/2022]
Abstract
We and others previously showed that in mouse embryos lacking the transcription factor Sox10, olfactory ensheathing cell (OEC) differentiation is disrupted, resulting in defective olfactory axon targeting and fewer gonadotropin‐releasing hormone (GnRH) neurons entering the embryonic forebrain. The underlying mechanisms are unclear. Here, we report that OECs in the olfactory nerve layer express Frzb—encoding a secreted Wnt inhibitor with roles in axon targeting and basement membrane breakdown—from embryonic day (E)12.5, when GnRH neurons first enter the forebrain, until E16.5, the latest stage examined. The highest levels of Frzb expression are seen in OECs in the inner olfactory nerve layer, abutting the embryonic olfactory bulb. We find that Sox10 is required for Frzb expression in OECs, suggesting that loss of Frzb could explain the olfactory axon targeting and/or GnRH neuron migration defects seen in Sox10‐null mice. At E16.5, Frzb‐null embryos show significant reductions in both the volume of the olfactory nerve layer expressing the maturation marker Omp and the number of Omp‐positive olfactory receptor neurons in the olfactory epithelium. As Omp upregulation correlates with synapse formation, this suggests that Frzb deletion indeed disrupts olfactory axon targeting. In contrast, GnRH neuron entry into the forebrain is not significantly affected. Hence, loss of Frzb may contribute to the olfactory axon targeting phenotype, but not the GnRH neuron phenotype, of Sox10‐null mice. Overall, our results suggest that Frzb secreted from OECs in the olfactory nerve layer is important for olfactory axon targeting. Frzb is expressed by olfactory ensheathing cells abutting the embryonic mouse olfactory bulb. Frzb expression requires Sox10. Deletion of Frzb disrupts olfactory receptor neuron maturation, likely reflecting a defect in olfactory axon targeting.
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Affiliation(s)
- Constance A Rich
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Surangi N Perera
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | | | - C Claus Stolt
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Dennis P Buehler
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - E Michelle Southard-Smith
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Michael Wegner
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Stefan Britsch
- Institute of Molecular and Cellular Anatomy, Ulm University, Ulm, Germany
| | - Clare V H Baker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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4
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Schulz K, Rotermund N, Grzelka K, Benz J, Lohr C, Hirnet D. Adenosine A 1 Receptor-Mediated Attenuation of Reciprocal Dendro-Dendritic Inhibition in the Mouse Olfactory Bulb. Front Cell Neurosci 2018; 11:435. [PMID: 29379418 PMCID: PMC5775233 DOI: 10.3389/fncel.2017.00435] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 12/26/2017] [Indexed: 12/14/2022] Open
Abstract
It is well described that A1 adenosine receptors inhibit synaptic transmission at excitatory synapses in the brain, but the effect of adenosine on reciprocal synapses has not been studied so far. In the olfactory bulb, the majority of synapses are reciprocal dendro-dendritic synapses mediating recurrent inhibition. We studied the effect of A1 receptor activation on recurrent dendro-dendritic inhibition in mitral cells using whole-cell patch-clamp recordings. Adenosine reduced dendro-dendritic inhibition in wild-type, but not in A1 receptor knock-out mice. Both NMDA receptor-mediated and AMPA receptor-mediated dendro-dendritic inhibition were attenuated by adenosine, indicating that reciprocal synapses between mitral cells and granule cells as well as parvalbumin interneurons were targeted by A1 receptors. Adenosine reduced glutamatergic self-excitation and inhibited N-type and P/Q-type calcium currents, but not L-type calcium currents in mitral cells. Attenuated glutamate release, due to A1 receptor-mediated calcium channel inhibition, resulted in impaired dendro-dendritic inhibition. In behavioral tests we tested the ability of wild-type and A1 receptor knock-out mice to find a hidden piece of food. Knock-out mice were significantly faster in locating the food. Our results indicate that A1 adenosine receptors attenuates dendro-dendritic reciprocal inhibition and suggest that they affect odor information processing.
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Affiliation(s)
- Kristina Schulz
- Division of Neurophysiology, Institute of Zoology, University of Hamburg, Hamburg, Germany
| | - Natalie Rotermund
- Division of Neurophysiology, Institute of Zoology, University of Hamburg, Hamburg, Germany
| | - Katarzyna Grzelka
- Department of Physiology and Pathophysiology, Medical University of Warsaw, Warsaw, Poland
| | - Jan Benz
- Division of Neurophysiology, Institute of Zoology, University of Hamburg, Hamburg, Germany
| | - Christian Lohr
- Division of Neurophysiology, Institute of Zoology, University of Hamburg, Hamburg, Germany
| | - Daniela Hirnet
- Division of Neurophysiology, Institute of Zoology, University of Hamburg, Hamburg, Germany
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5
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Terni B, Pacciolla P, Masanas H, Gorostiza P, Llobet A. Tight temporal coupling between synaptic rewiring of olfactory glomeruli and the emergence of odor-guided behavior in Xenopus tadpoles. J Comp Neurol 2017; 525:3769-3783. [PMID: 28815589 DOI: 10.1002/cne.24303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 08/09/2017] [Accepted: 08/10/2017] [Indexed: 12/13/2022]
Abstract
Olfactory sensory neurons (OSNs) are chemoreceptors that establish excitatory synapses within glomeruli of the olfactory bulb. OSNs undergo continuous turnover throughout life, causing the constant replacement of their synaptic contacts. Using Xenopus tadpoles as an experimental system to investigate rewiring of glomerular connectivity, we show that novel OSN synapses can transfer information immediately after formation, mediating olfactory-guided behavior. Tadpoles recover the ability to detect amino acids 4 days after bilateral olfactory nerve transection. Restoration of olfactory-guided behavior depends on the efficient reinsertion of OSNs to the olfactory bulb. Presynaptic terminals of incipient synaptic contacts generate calcium transients in response to odors, triggering long lasting depolarization of olfactory glomeruli. The functionality of reconnected terminals relies on well-defined readily releasable and cytoplasmic vesicle pools. The continuous growth of non-compartmentalized axonal processes provides a vesicle reservoir to nascent release sites, which contrasts to the gradual development of cytoplasmic vesicle pools in conventional excitatory synapses. The immediate availability of fully functional synapses upon formation supports an age-independent contribution of OSNs to the generation of odor maps.
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Affiliation(s)
- Beatrice Terni
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona, Barcelona, Spain.,Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
| | - Paolo Pacciolla
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona, Barcelona, Spain.,Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
| | - Helena Masanas
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain.,Institut de Bioenginyeria de Catalunya (IBEC), Barcelona, Spain
| | - Pau Gorostiza
- Institut de Bioenginyeria de Catalunya (IBEC), Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.,Network Biomedic Research Center in Biophysics, Bioengineering and Nanomedicine (CIBER-bbn), Madrid, Spain
| | - Artur Llobet
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona, Barcelona, Spain.,Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain.,Institute of Neurosciences, University of Barcelona, Barcelona, Spain
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6
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Bartel DL, Rela L, Hsieh L, Greer CA. Dendrodendritic synapses in the mouse olfactory bulb external plexiform layer. J Comp Neurol 2015; 523:1145-61. [PMID: 25420934 DOI: 10.1002/cne.23714] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 11/18/2014] [Accepted: 11/20/2014] [Indexed: 12/31/2022]
Abstract
Odor information relayed by olfactory bulb projection neurons, mitral and tufted cells (M/T), is modulated by pairs of reciprocal dendrodendritic synaptic circuits in the external plexiform layer (EPL). Interneurons, which are accounted for largely by granule cells, receive depolarizing input from M/T dendrites and in turn inhibit current spread in M/T dendrites via hyperpolarizing reciprocal dendrodendritic synapses. Because the location of dendrodendritic synapses may significantly affect the cascade of odor information, we assessed synaptic properties and density within sublaminae of the EPL and along the length of M/T secondary dendrites. In electron micrographs the M/T to granule cell synapse appeared to predominate and was equivalent in both the outer and inner EPL. However, the dendrodendritic synapses from granule cell spines onto M/T dendrites were more prevalent in the outer EPL. In contrast, individual gephyrin-immunoreactive (IR) puncta, a postsynaptic scaffolding protein at inhibitory synapses used here as a proxy for the granule to M/T dendritic synapse was equally distributed throughout the EPL. Of significance to the organization of intrabulbar circuits, gephyrin-IR synapses are not uniformly distributed along M/T secondary dendrites. Synaptic density, expressed as a function of surface area, increases distal to the cell body. Furthermore, the distributions of gephyrin-IR puncta are heterogeneous and appear as clusters along the length of the M/T dendrites. Consistent with computational models, our data suggest that temporal coding in M/T cells is achieved by precisely located inhibitory input and that distance from the soma is compensated for by an increase in synaptic density.
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Affiliation(s)
- Dianna L Bartel
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut, 06520-8082
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7
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Mosca TJ, Luo L. Synaptic organization of the Drosophila antennal lobe and its regulation by the Teneurins. eLife 2014; 3:e03726. [PMID: 25310239 PMCID: PMC4194450 DOI: 10.7554/elife.03726] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 09/18/2014] [Indexed: 12/11/2022] Open
Abstract
Understanding information flow through neuronal circuits requires knowledge of their synaptic organization. In this study, we utilized fluorescent pre- and postsynaptic markers to map synaptic organization in the Drosophila antennal lobe, the first olfactory processing center. Olfactory receptor neurons (ORNs) produce a constant synaptic density across different glomeruli. Each ORN within a class contributes nearly identical active zone number. Active zones from ORNs, projection neurons (PNs), and local interneurons have distinct subglomerular and subcellular distributions. The correct number of ORN active zones and PN acetylcholine receptor clusters requires the Teneurins, conserved transmembrane proteins involved in neuromuscular synapse organization and synaptic partner matching. Ten-a acts in ORNs to organize presynaptic active zones via the spectrin cytoskeleton. Ten-m acts in PNs autonomously to regulate acetylcholine receptor cluster number and transsynaptically to regulate ORN active zone number. These studies advanced our ability to assess synaptic architecture in complex CNS circuits and their underlying molecular mechanisms.
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Affiliation(s)
- Timothy J Mosca
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Liqun Luo
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, United States
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8
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Holbrook EH, Iwema CL, Peluso CE, Schwob JE. The regeneration of P2 olfactory sensory neurons is selectively impaired following methyl bromide lesion. Chem Senses 2014; 39:601-16. [PMID: 25056730 DOI: 10.1093/chemse/bju033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The capacity of the peripheral olfactory system to recover after injury has not been thoroughly explored. P2-IRES-tauLacZ mice were exposed to methyl bromide, which causes epithelial damage and kills 90% of the P2 neurons. With subsequent neuronal regeneration, P2 neurons recover within their usual territory to equal control numbers by 1 month but then decline sharply to roughly 40% of control by 3 months. At this time, the P2 projection onto the olfactory bulb is erroneous in several respects. Instead of converging onto 1 or 2 glomeruli per surface, small collections of P2 axons innervate multiple glomeruli at roughly the same position in the bulb as in controls. Within these glomeruli, the P2 axons are aggregated near the edge, whereas the remainder of the glomerulus contains olfactory marker protein (+), non-P2 axons, violating the one receptor-one glomerulus rule normally observed. The aggregates are denser than found in control P2-innervated glomeruli, suggesting that the P2 axons may not be synaptically connected. Based on published literature and other data, we hypothesize that P2 neurons lose out in an activity-based competition for synaptic territory within the glomeruli and are not maintained at control numbers due to a lack of trophic support from the bulb.
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Affiliation(s)
- Eric H Holbrook
- Department of Otology and Laryngology, Harvard Medical School and Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA, Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Carrie L Iwema
- Department of Cell and Developmental Biology and Program in Neuroscience, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY 13210, USA and
| | - Carolyn E Peluso
- Program in Cell, Molecular, and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, 136 Harrison Avenue, Boston, MA 02111, USA
| | - James E Schwob
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA, Department of Cell and Developmental Biology and Program in Neuroscience, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY 13210, USA and
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9
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Gribaudo S, Bovetti S, Friard O, Denorme M, Oboti L, Fasolo A, De Marchis S. Transitory and activity-dependent expression of neurogranin in olfactory bulb tufted cells during mouse postnatal development. J Comp Neurol 2013; 520:3055-69. [PMID: 22592880 DOI: 10.1002/cne.23150] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Neurogranin (Ng) is a brain-specific postsynaptic calmodulin-binding protein involved in synaptic activity-dependent plasticity. In the adult olfactory bulb (OB), Ng is expressed by a large population of GABAergic interneurons in the granule cell layer. We show here that, during postnatal development, Ng is also expressed by OB neurons in the superficial external plexiform layer (sEPL) and glomerular layer (GL). These Ng-positive neurons display morphological and neurochemical features of superficial and external tufted cells. Ng expression in these cells is transient during OB development: few elements express Ng at postnatal day (P) 5, increasing in number and reaching a peak at P10, then progressively decreasing. At P30, Ng is rarely detectable in these neurons. Ng expression in developing tufted cells is also modulated at the cellular level: at earlier stages, Ng labeling is distributed throughout the cell body and dendritic arborization in the GL, but, at P20, when the glomerular circuits are fully matured, Ng becomes restricted to the soma and proximal portion of tufted cell apical dendrites. We show that olfactory deprivation at early postnatal stages induces a strong increase in Ng-positive tufted cells from P10 to P20, whereas no changes have been observed following olfactory deprivation in adult mice. These findings demonstrate that Ng expression in sEPL-GL is restricted to developmental stages and indicate its activity-dependent regulation in a time window critical for glomerular circuit development, suggesting a role for Ng in maturation and dendritic remodeling of tufted cells.
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Affiliation(s)
- S Gribaudo
- Department of Life Sciences and Systems Biology, University of Turin, 10123 Turin, Italy.
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10
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Dishevelled proteins are associated with olfactory sensory neuron presynaptic terminals. PLoS One 2013; 8:e56561. [PMID: 23437169 PMCID: PMC3577874 DOI: 10.1371/journal.pone.0056561] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 01/11/2013] [Indexed: 11/28/2022] Open
Abstract
Olfactory sensory neurons (OSNs) project their axons from the olfactory epithelium toward the olfactory bulb (OB) in a heterogeneous and unsorted arrangement. However, as the axons approach the glomerular layer of the OB, axons from OSNs expressing the same odorant receptor (OR) sort and converge to form molecularly homogeneous glomeruli. Axon guidance cues, cell adhesion molecules, and OR induced activity have been implicated in the final targeting of OSN axons to specific glomeruli. Less understood, and often controversial, are the mechanisms used by OSN axons to initially navigate from the OE toward the OB. We previously demonstrated a role for Wnt and Frizzled (Fz) molecules in OSN axon extension and organization within the olfactory nerve. Building on that we now turned our attention to the downstream signaling cascades from Wnt-Fz interactions. Dishevelled (Dvl) is a key molecule downstream of Fz receptors. Three isoforms of Dvl with specific as well as overlapping functions are found in mammals. Here, we show that Dvl-1 expression is restricted to OSNs in the dorsal recess of the nasal cavity, and labels a unique subpopulation of glomeruli. Dvl-2 and Dvl-3 have a widespread distribution in both the OE and OB. Both Dvl-1 and Dvl-2 are associated with intra-glomerular pre-synaptic OSN terminals, suggesting a role in synapse formation/stabilization. Moreover, because Dvl proteins were observed in all OSN axons, we hypothesize that they are important determinants of OSN cell differentiation and axon extension.
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11
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Hovis KR, Ramnath R, Dahlen JE, Romanova AL, LaRocca G, Bier ME, Urban NN. Activity regulates functional connectivity from the vomeronasal organ to the accessory olfactory bulb. J Neurosci 2012; 32:7907-16. [PMID: 22674266 PMCID: PMC3483887 DOI: 10.1523/jneurosci.2399-11.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 03/14/2012] [Accepted: 04/19/2012] [Indexed: 12/14/2022] Open
Abstract
The mammalian accessory olfactory system is specialized for the detection of chemicals that identify kin and conspecifics. Vomeronasal sensory neurons (VSNs) residing in the vomeronasal organ project axons to the accessory olfactory bulb (AOB), where they form synapses with principal neurons known as mitral cells. The organization of this projection is quite precise and is believed to be essential for appropriate function of this system. However, how this precise connectivity is established is unknown. We show here that in mice the vomeronasal duct is open at birth, allowing external chemical stimuli access to sensory neurons, and that these sensory neurons are capable of releasing neurotransmitter to downstream neurons as early as the first postnatal day (P). Using major histocompatibility complex class I peptides to activate a selective subset of VSNs during the first few postnatal days of development, we show that increased activity results in exuberant VSN axonal projections and a delay in axonal coalescence into well defined glomeruli in the AOB. Finally, we show that mitral cell dendritic refinement occurs just after the coalescence of presynaptic axons. Such a mechanism may allow the formation of precise connectivity with specific glomeruli that receive input from sensory neurons expressing the same receptor type.
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Affiliation(s)
- Kenneth R Hovis
- Department of Biological Sciences, Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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12
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Dendritic spines and development: towards a unifying model of spinogenesis--a present day review of Cajal's histological slides and drawings. Neural Plast 2011; 2010:769207. [PMID: 21584262 PMCID: PMC3091278 DOI: 10.1155/2010/769207] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 11/14/2010] [Indexed: 12/21/2022] Open
Abstract
Dendritic spines receive the majority of excitatory connections in the central nervous system, and, thus, they are key structures in the regulation of neural activity. Hence, the cellular and molecular mechanisms underlying their generation and plasticity, both during development and in adulthood, are a matter of fundamental and practical interest. Indeed, a better understanding of these mechanisms should provide clues to the development of novel clinical therapies. Here, we present original results obtained from high-quality images of Cajal's histological preparations, stored at the Cajal Museum (Instituto Cajal, CSIC), obtained using extended focus imaging, three-dimensional reconstruction, and rendering. Based on the data available in the literature regarding the formation of dendritic spines during development and our results, we propose a unifying model for dendritic spine development.
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13
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Katagiri H, Pallotto M, Nissant A, Murray K, Sassoè-Pognetto M, Lledo PM. Dynamic development of the first synapse impinging on adult-born neurons in the olfactory bulb circuit. NEURAL SYSTEMS & CIRCUITS 2011; 1:6. [PMID: 22330198 PMCID: PMC3278389 DOI: 10.1186/2042-1001-1-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 11/01/2010] [Indexed: 01/10/2023]
Abstract
The olfactory bulb (OB) receives and integrates newborn interneurons throughout life. This process is important for the proper functioning of the OB circuit and consequently, for the sense of smell. Although we know how these new interneurons are produced, the way in which they integrate into the pre-existing ongoing circuits remains poorly documented. Bearing in mind that glutamatergic inputs onto local OB interneurons are crucial for adjusting the level of bulbar inhibition, it is important to characterize when and how these inputs from excitatory synapses develop on newborn OB interneurons. We studied early synaptic events that lead to the formation and maturation of the first glutamatergic synapses on adult-born granule cells (GCs), the most abundant subtype of OB interneuron. Patch-clamp recordings and electron microscopy (EM) analysis were performed on adult-born interneurons shortly after their arrival in the adult OB circuits. We found that both the ratio of N-methyl-D-aspartate receptor (NMDAR) to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), and the number of functional release sites at proximal inputs reached a maximum during the critical period for the sensory-dependent survival of newborn cells, well before the completion of dendritic arborization. EM analysis showed an accompanying change in postsynaptic density shape during the same period of time. Interestingly, the latter morphological changes disappeared in more mature newly-formed neurons, when the NMDAR to AMPAR ratio had decreased and functional presynaptic terminals expressed only single release sites. Together, these findings show that the first glutamatergic inputs to adult-generated OB interneurons undergo a unique sequence of maturation stages.
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Affiliation(s)
- Hiroyuki Katagiri
- Laboratory for Perception and Memory, Institut Pasteur, Paris, France.
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14
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Miller AM, Maurer LR, Zou DJ, Firestein S, Greer CA. Axon fasciculation in the developing olfactory nerve. Neural Dev 2010; 5:20. [PMID: 20723208 PMCID: PMC2936880 DOI: 10.1186/1749-8104-5-20] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Accepted: 08/19/2010] [Indexed: 11/10/2022] Open
Abstract
Olfactory sensory neuron (OSN) axons exit the olfactory epithelium (OE) and extend toward the olfactory bulb (OB) where they coalesce into glomeruli. Each OSN expresses only 1 of approximately 1,200 odor receptors (ORs). OSNs expressing the same OR are distributed in restricted zones of the OE. However, within a zone, the OSNs expressing a specific OR are not contiguous - distribution appears stochastic. Upon reaching the OB the OSN axons expressing the same OR reproducibly coalesce into two to three glomeruli. While ORs appear necessary for appropriate convergence of axons, a variety of adhesion associated molecules and activity-dependent mechanisms are also implicated. Recent data suggest pre-target OSN axon sorting may influence glomerular convergence. Here, using regional and OR-specific markers, we addressed the spatio-temporal properties associated with the onset of homotypic fasciculation in embryonic mice and assessed the degree to which subpopulations of axons remain segregated as they extend toward the nascent OB. We show that immediately upon crossing the basal lamina, axons uniformly turn sharply, usually at an approximately 90° angle toward the OB. Molecularly defined subpopulations of axons show evidence of spatial segregation within the nascent nerve by embryonic day 12, within 48 hours of the first OSN axons crossing the basal lamina, but at least 72 hours before synapse formation in the developing OB. Homotypic fasciculation of OSN axons expressing the same OR appears to be a hierarchical process. While regional segregation occurs in the mesenchyme, the final convergence of OR-specific subpopulations does not occur until the axons reach the inner nerve layer of the OB.
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Affiliation(s)
- Alexandra M Miller
- Department of Neurosurgery, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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15
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Abstract
New olfactory bulb granule cells (GCs) are GABAergic interneurons continuously arising from neuronal progenitors and integrating into preexisting bulbar circuits. They receive both GABAergic and glutamatergic synaptic inputs from olfactory bulb intrinsic neurons and centrifugal afferents. Here, we investigated the spatiotemporal dynamic of newborn GC synaptogenesis in adult mouse olfactory bulb. First, we established that GABAergic synapses onto mature GC dendrites contain the GABA(A) receptor alpha2 subunit along with the postsynaptic scaffolding protein gephyrin. Next, we characterized morphologically and electrophysiologically the development of GABAergic and glutamatergic inputs onto newborn GCs labeled with eGFP (enhanced green fluorescent protein) using lentiviral vectors. Already when reaching the GC layer (GCL), at 3 d post-vector injection (dpi), newborn GCs exhibited tiny voltage-dependent sodium currents and received functional GABAergic and glutamatergic synapses, recognized immunohistochemically by apposition of specific presynaptic and postsynaptic markers. Thereafter, GABAergic and glutamatergic synaptic contacts increased differentially in the GCL, and at 7 dpi, PSD-95 clusters outnumbered gephyrin clusters. Thus, the weight of GABAergic input was predominant at early stages of GC maturation, but not later. Newborn GC dendrites first reached the external plexiform layer at 4 dpi, where they received functional GABAergic contacts at 5 dpi. Reciprocal synapses initially were formed on GC dendritic shafts, where they might contribute to spine formation. Their presence was confirmed ultrastructurally at 7 dpi. Together, our findings unravel rapid synaptic integration of newborn GCs in adult mouse olfactory bulb, with GABAergic and glutamatergic influences being established proximally before formation of output synapses by apical GC dendrites onto mitral/tufted cells.
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Bovolin P, Bovetti S, Fasolo A, Katarova Z, Szabo G, Shipley MT, Margolis FL, Puche AC. Developmental regulation of metabotropic glutamate receptor 1 splice variants in olfactory bulb mitral cells. J Neurosci Res 2009; 87:369-79. [PMID: 18816797 DOI: 10.1002/jnr.21864] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Alternative splicing of the metabotropic glutamate receptor 1 (mGluR1) receptor gene generates two major receptor isoforms, mGluR1a and mGluR1b, differing in intracellular function and distribution. However, little is known on the expression profiles of these variants during development. We examined the mRNA expression profile of mGluR1a/b in microdissected layers and acutely isolated mitral cells in the developing mouse olfactory bulb. This analysis showed that the two mGluR1 variants are differentially regulated within each bulb layer. During the first postnatal week, the mGluR1a isoform replaces GluR1b in the microdissected mitral cell layer (MCL) and in isolated identified mitral cells, coinciding with a developmental epoch of mitral cell dendritic reorganization. Although mGluR1a mRNA is expressed at high levels in both the adult external plexiform layer (EPL) and MCL, Western blotting analysis reveals a marked reduction of the mGluR1a protein in the MCL, where mitral cell bodies are located, and strong labeling in the EPL, which contains mitral cell dendrites. This suggests that there is increased dendritic trafficking efficiency of the receptor in adult. The temporal and spatial shift in mGluR1b/a expression suggests distinct roles of the mGluR1 isoforms, with mGluR1b potentially involved in the early mitral cell maturation and mGluR1a in dendritic and synapse function.
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Affiliation(s)
- P Bovolin
- Department of Animal and Human Biology, University of Turin, Turin, Italy
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17
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Tran H, Chen H, Walz A, Posthumus JC, Gong Q. Influence of olfactory epithelium on mitral/tufted cell dendritic outgrowth. PLoS One 2008; 3:e3816. [PMID: 19043569 PMCID: PMC2583930 DOI: 10.1371/journal.pone.0003816] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 11/07/2008] [Indexed: 12/14/2022] Open
Abstract
Stereotypical connections between olfactory sensory neuron axons and mitral cell dendrites in the olfactory bulb establish the first synaptic relay for olfactory perception. While mechanisms of olfactory sensory axon targeting are reported, molecular regulation of mitral cell dendritic growth and refinement are unclear. During embryonic development, mitral cell dendritic distribution overlaps with olfactory sensory axon terminals in the olfactory bulb. In this study, we investigate whether olfactory sensory neurons in the olfactory epithelium influence mitral cell dendritic outgrowth in vitro. We report a soluble trophic activity in the olfactory epithelium conditioned medium which promotes mitral/tufted cell neurite outgrowth. While the trophic activity is present in both embryonic and postnatal olfactory epithelia, only embryonic but not postnatal mitral/tufted cells respond to this activity. We show that BMP2, 5 and 7 promote mitral/tufted cells neurite outgrowth. However, the BMP antagonist, Noggin, fails to neutralize the olfactory epithelium derived neurite growth promoting activity. We provide evidence that olfactory epithelium derived activity is a protein factor with molecular weight between 50–100 kD. We also observed that Follistatin can effectively neutralize the olfactory epithelium derived activity, suggesting that TGF-beta family proteins are involved to promote mitral/tufted dendritic elaboration.
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Affiliation(s)
- Ha Tran
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Huaiyang Chen
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Andreas Walz
- The Rockefeller University, New York, New York, United States of America
| | - Jamie C. Posthumus
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Qizhi Gong
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California Davis, Davis, California, United States of America
- * E-mail:
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18
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Blanchart A, Romaguera M, García-Verdugo JM, de Carlos JA, López-Mascaraque L. Synaptogenesis in the mouse olfactory bulb during glomerulus development. Eur J Neurosci 2008; 27:2838-46. [PMID: 18588529 DOI: 10.1111/j.1460-9568.2008.06283.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synaptogenesis is essential for the development of neuronal networks in the brain. In the olfactory bulb (OB) glomeruli, numerous synapses must form between sensory olfactory neurons and the dendrites of mitral/tufted and periglomerular cells. Glomeruli develop from E13 to E16 in the mouse, coincident with an increment of the neuropil in the border between the external plexiform (EPL) and olfactory nerve layers (ONL), coupled to an extensive labelling of phalloidin and GAP-43 from the ONL to EPL. We have tracked synaptogenesis in the OB during this period by electron microscopy (EM) and immunolabelling of the transmembrane synaptic vesicle glycoprotein SV-2. No SV-2 labelling or synapses were detected at E13, although electrodense junctions lacking synaptic vesicles could be observed by EM. At E14, sparse SV-2 labelling appears in the most ventral and medial part of the incipient OB, which displays a ventro-dorsal gradient by E15 but covers the entire OB by E16. These data establish a spatio-temporal pattern of synaptogenesis, which perfectly matches with the glomeruli formation in developing OB.
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Affiliation(s)
- Albert Blanchart
- Department of Cellular, Molecular and Developmental Neurobiology, Instituto Cajal, CSIC, Madrid, Spain
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19
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McEwen DP, Jenkins PM, Martens JR. Olfactory cilia: our direct neuronal connection to the external world. Curr Top Dev Biol 2008; 85:333-70. [PMID: 19147011 DOI: 10.1016/s0070-2153(08)00812-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
An organism's awareness of its surroundings is dependent on sensory function. As antennas to our external environment, cilia are involved in fundamental biological processes such as olfaction, photoreception, and touch. The olfactory system has adapted this organelle for its unique sensory function and optimized it for detection of external stimuli. The elongated and tapering structure of olfactory cilia and their organization into an overlapping meshwork bathed by the nasal mucosa is optimized to enhance odor absorption and detection. As many as 15-30 nonmotile, sensory cilia on dendritic endings of single olfactory sensory neurons (OSNs) compartmentalize signaling molecules necessary for odor detection allowing for efficient and spatially confined responses to sensory stimuli. Although the loss of olfactory cilia or deletion of selected components of the olfactory signaling cascade leads to anosmia, the mechanisms of ciliogenesis and the selected enrichment of signaling molecules remain poorly understood. Much of our current knowledge is the result of elegant electron microscopy studies describing the structure and organization of the olfactory epithelium and cilia. New genetic and cell biological approaches, which compliment these early studies, show promise in elucidating the mechanisms of olfactory cilia assembly, maintenance, and compartmentalization. Importantly, emerging evidence suggests that olfactory dysfunction represents a previously unrecognized clinical manifestation of multiple ciliary disorders. Future work investigating the mechanisms of olfactory dysfunction combining both clinical studies with basic science research will provide us important new information regarding the pathogenesis of human sensory perception diseases.
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Affiliation(s)
- Dyke P McEwen
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109-5632, USA
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20
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Whitman MC, Greer CA. Synaptic integration of adult-generated olfactory bulb granule cells: basal axodendritic centrifugal input precedes apical dendrodendritic local circuits. J Neurosci 2007; 27:9951-61. [PMID: 17855609 PMCID: PMC6672649 DOI: 10.1523/jneurosci.1633-07.2007] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The adult mammalian olfactory bulb (OB) receives a continuing influx of new interneurons. Neuroblasts from the subventricular zone (SVZ) migrate into the OB and differentiate into granule cells and periglomerular cells that are presumed to integrate into the synaptic circuits of the OB. We have used retroviral infection into the SVZ of mice to label adult-generated granule cells and follow their differentiation and integration into OB circuitry. Using synaptic markers and electron microscopy, we show new granule cells integrating into the reciprocal circuitry of the external plexiform layer (EPL), beginning at 21 d postinfection (dpi). We further show that synapses are formed earlier, beginning at 10 dpi, on the somata and basal dendrites of new cells in the granule cell layer (GCL), before dendritic elaboration in the EPL. In the EPL, elaborate dendritic arbors with spines are first evident at 14 dpi. The density of spines increases from 14 to 28 dpi, and then decreases by 56 dpi. Despite the initial appearance of dendritic spines at 14 dpi in the EPL, no expression of presynaptic or postsynaptic markers is seen until 21 dpi. These data suggest that adult-generated granule cells are first innervated by centrifugal or mitral/tufted cell axon collaterals in the GCL and that these inputs may contribute to their differentiation, maturation, and synaptic integration into the dendrodendritic local circuits found in the EPL.
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Affiliation(s)
| | - Charles A. Greer
- Departments of Neurobiology and
- Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520-8082
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21
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Mack-Bucher JA, Li J, Friedrich RW. Early functional development of interneurons in the zebrafish olfactory bulb. Eur J Neurosci 2007; 25:460-70. [PMID: 17284187 DOI: 10.1111/j.1460-9568.2006.05290.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the adult olfactory bulb (OB) of vertebrates, local GABAergic interneurons (INs) mediate recurrent and lateral inhibition between the principal neurons of the OB, the mitral cells (MCs), and play pivotal roles in the processing of odor-evoked activity patterns. The properties and functions of INs in the developing OB are, however, not well understood. We studied the functional development of INs in the OB of living zebrafish larvae 3-6 days postfertilization using anatomical techniques and in-vivo two-photon Ca2+ imaging. We identified MCs and INs by cell-type-specific expression of transgenic fluorescent markers and found that the IN:MC ratio was lower than in the adult fish. Moreover, the fraction of INs responding with Ca2+ signals to a set of natural odors was substantially lower than in adults. Odors of different chemical classes evoked overlapping patterns of Ca2+ signals that were concentrated in the center of the IN layer. The GABA(A) receptor agonists GABA and muscimol strongly suppressed odor responses, whereas a GABA(A) receptor antagonist enhanced responses and altered the spatial distribution of odor-evoked activity. These results indicate that IN odor responses at early developmental stages are sparse and exhibit no obvious chemotopic organization. Nevertheless, GABAergic signaling is already inhibitory at early stages of OB development and strongly influences odor-evoked activity patterns. Hence, INs already participate in the processing of odor information at very early stages of OB development even though the majority of INs emerge only at later stages.
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Affiliation(s)
- Julia A Mack-Bucher
- Max-Planck-Institute for Medical Research, Department of Biomedical Optics, Heidelberg, Germany
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22
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El Meskini R, Crabtree KL, Cline LB, Mains RE, Eipper BA, Ronnett GV. ATP7A (Menkes protein) functions in axonal targeting and synaptogenesis. Mol Cell Neurosci 2007; 34:409-21. [PMID: 17215139 PMCID: PMC1876716 DOI: 10.1016/j.mcn.2006.11.018] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 11/11/2006] [Accepted: 11/20/2006] [Indexed: 12/19/2022] Open
Abstract
Menkes disease (MD) is a neurodegenerative disorder caused by mutations in the copper transporter, ATP7A, a P-type ATPase. We previously used the olfactory system to demonstrate that ATP7A expression is developmentally, not constitutive, regulated, peaking during synaptogenesis when it is highly expressed in extending axons in a copper-independent manner. Although not known to be associated with axonal functions, we explored the possibility that the inability of mutant ATP7A to support axon outgrowth contributes to the neurodegeneration seen in MD. In vivo analysis of the olfactory system in mottled brindled (Atp7aMobr) mice, a rodent model for MD, demonstrates that ATP7A deficiency affects olfactory sensory neuron (OSN) maturation. Disrupted OSN axonal projections and mitral/tufted cell dendritic growth lead to altered synapse integrity and glomerular disorganization in the olfactory bulbs of Atp7aMobr mice. Our data indicate that the neuronal abnormalities observed in MD are a result of specific age-dependent developmental defects. This study demonstrates a role for ATP7A and/or copper in axon outgrowth and synaptogenesis, and will further help identify the cause of the neuropathology that characterizes MD.
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Affiliation(s)
- Rajaâ El Meskini
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030, USA.
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23
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Dino MR, Harroch S, Hockfield S, Matthews RT. Monoclonal antibody Cat-315 detects a glycoform of receptor protein tyrosine phosphatase beta/phosphacan early in CNS development that localizes to extrasynaptic sites prior to synapse formation. Neuroscience 2006; 142:1055-69. [PMID: 16989954 DOI: 10.1016/j.neuroscience.2006.07.054] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 07/13/2006] [Accepted: 07/14/2006] [Indexed: 11/23/2022]
Abstract
Perineuronal nets (PNs) are lattice-like condensations of the extracellular matrix (ECM) that envelop synapses and decorate the surface of subsets of neurons in the CNS. Previous work has suggested that, despite the fact that PNs themselves are not visualized until later in development, some PN component molecules are expressed in the rodent CNS even before synaptogenesis. In the adult mammalian brain, monoclonal antibody Cat-315 recognizes a glycoform of aggrecan, a major component of PNs. In primary cortical cultures, a Cat-315-reactive chondroitin sulfate proteoglycan (CSPG) is also expressed on neuronal surfaces and is secreted into culture media as early as 24 h after plating. In this study, we show that in primary cortical cultures, the Cat-315 CSPG detected in early neural development is expressed in extrasynaptic sites prior to synapse formation. This suggests that ECM components in the CNS, as in the neuromuscular junction (NMJ), may prepattern neuronal surfaces prior to innervation. We further show that while the Cat-315-reactive carbohydrate decorates aggrecan in the adult, it decorates a different CSPG in the developing CNS. Using receptor protein tyrosine phosphatase beta (RPTPbeta/protein tyrosine phosphatase zeta) knock-out mice and immunoprecipitation techniques, we demonstrate here that in the developing rodent brain Cat-315 recognizes RPTPbeta isoforms. Our further examination of the Cat-315 epitope suggests that it is an O-mannose linked epitope in the HNK-1 family. The presence of the Cat-315 reactive carbohydrate on different PN components--RPTPbeta and aggrecan--at different stages of synapse development suggests a potential role for this neuron-specific carbohydrate motif in synaptogenesis.
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Affiliation(s)
- M R Dino
- Department of Neurobiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
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24
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Walz A, Omura M, Mombaerts P. Development and topography of the lateral olfactory tract in the mouse: imaging by genetically encoded and injected fluorescent markers. ACTA ACUST UNITED AC 2006; 66:835-46. [PMID: 16673392 DOI: 10.1002/neu.20266] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In mammals, conventional odorants are detected by OSNs located in the main olfactory epithelium of the nose. These neurons project their axons to glomeruli, which are specialized structures of neuropil in the olfactory bulb. Within glomeruli, axons synapse onto dendrites of projection neurons, the mitral and tufted (M/T) cells. Genetic approaches to visualize axons of OSNs expressing a given odorant receptor have proven very useful in elucidating the organization of these projections to the olfactory bulb. Much less is known about the development and connectivity of the lateral olfactory tract (LOT), which is formed by axons of M/T cells connecting the olfactory bulb to central neural regions. Here, we have extended our genetic approach to mark M/T cells of the main olfactory bulb and their axons in the mouse, by targeted insertion of IRES-tauGFP in the neurotensin locus. In NT-GFP mice, we find that M/T cells of the main olfactory bulb mature and project axons as early as embryonic day 11.5. Final innervation of central areas is accomplished before the end of the second postnatal week. M/T cell axons that originate from small defined areas within the main olfactory bulb, as visualized by localized injections of fluorescent tracers in wild-type mice at postnatal days 1 to 3, follow a dual trajectory: a branch of tightly packed axons along the dorsal aspect of the LOT, and a more diffuse branch along the ventral aspect. The dorsal, but not the ventral, subdivision of the LOT exhibits a topographical segregation of axons coming from the dorsal versus ventral main olfactory bulb. The NT-GFP mouse strain should prove useful in further studies of development and topography of the LOT, from E11.5 until 2 weeks after birth.
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Affiliation(s)
- Andreas Walz
- The Rockefeller University, New York, New York 10021, USA
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25
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Sivan E, Kopell N. Oscillations and slow patterning in the antennal lobe. J Comput Neurosci 2006; 20:85-96. [PMID: 16511657 DOI: 10.1007/s10827-006-4087-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 08/05/2005] [Accepted: 08/08/2005] [Indexed: 11/27/2022]
Abstract
Odor presentation generates both fast oscillations and slow patterning in the spiking activity of the projection neurons (PNs) in the antennal lobe (AL) of locusts, moths and bees. Experimental results indicate that the oscillations are the result of the interaction between the PNs and the inhibitory local neurons (LNs) in the AL; e.g., blocking inhibition by application of GABA-receptor antagonists abolishes these oscillations. The slow patterning, on the other hand, was shown to be somewhat resistant to such blockage. In a H-H model, we reproduce both the oscillations and the slow patterning. As previously suggested, the oscillations are the result of the interaction between the PNs and LNs. We suggest that calcium and calcium-dependent potassium channels (found in PNs of bees and moths) are sufficient to account for the slow patterning resistant to the application of GABA-receptor antagonists. The intrinsic bursting property of the PNs, resulting from these additional modeled currents, give rise to another network feature that was seen experimentally in locusts: A relatively small increase in the number of additional generated PN action potentials when LN input is blocked. Consequently, the major effect of network inhibition is to redistribute the action potentials of the PNs from bursting to one action potential per cycle of the oscillations.
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Affiliation(s)
- Ehud Sivan
- Center for Biodynamic, Boston University, 111 Cummington Street, MA, 02215, USA.
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26
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Matarazzo V, Cohen D, Palmer AM, Simpson PJ, Khokhar B, Pan SJ, Ronnett GV. The transcriptional repressor Mecp2 regulates terminal neuronal differentiation. Mol Cell Neurosci 2005; 27:44-58. [PMID: 15345242 DOI: 10.1016/j.mcn.2004.05.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2003] [Revised: 05/25/2004] [Accepted: 05/27/2004] [Indexed: 11/16/2022] Open
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder with features of autism that results from mutation of the gene encoding the transcriptional repressor methyl-CpG binding protein (MECP2). The consequences of loss of a transcription factor may be complex, affecting the expression of many proteins, thus limiting understanding of this class of diseases and impeding therapeutic strategies. This is true for RTT. Neither the cell biological mechanism(s) nor the developmental stage affected by MECP2 deficiency is known. In vivo analysis of the olfactory system demonstrates that Mecp2 deficiency leads to a transient delay in the terminal differentiation of olfactory neurons. This delay in maturation disrupts axonal targeting in the olfactory bulb, resulting in abnormal axonal projections, subglomerular disorganization, and a persistent reduction in glomerular size. These results indicate a critical cell biological function for Mecp2 in mediating the final stages of neuronal development.
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Affiliation(s)
- Valéry Matarazzo
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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27
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Vigers AJ, Böttger B, Baquet ZC, Finger TE, Jones KR. Neurotrophin-3 is expressed in a discrete subset of olfactory receptor neurons in the mouse. J Comp Neurol 2003; 463:221-35. [PMID: 12815759 DOI: 10.1002/cne.10752] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In transgenic neurotrophin-3 lacZ-neo (NT-3(lacZneo)) mice, in which the coding region for NT-3 is replaced by Eschericia coli lacZ, the expression of beta-galactosidase faithfully mimics the expression of NT-3 (Vigers AJ, Baquet ZC, Jones KR [2000], J Comp Neurol 416:398-416). During embryonic and early postnatal development, beta-galactosidase is detected in the olfactory system, beginning at embryonic day 11.5 in the nasal epithelium and at embryonic day 16.5 in the olfactory bulb. Levels of beta-galactosidase rise with age, reaching a peak during the second postnatal week, when beta-galactosidase reactivity is visible in up to 50% of the glomeruli. As the animal matures, the beta-galactosidase levels decline, but staining remains present in axons and cell bodies of a specific subset of olfactory receptor neurons (ORNs) projecting to a limited subset of glomeruli. The heavily labeled ORNs do not follow the typical OR expression zones in the epithelium but appear similar to the "patch" expression pattern of mOR37 receptors. The most heavily reactive glomeruli exhibit a striking reproducible pattern in the ventral olfactory bulb (OB). Some glomeruli of the OB contain calcitonin gene-related peptide (CGRP)-immunoreactive fibers of the trigeminal nerve. However, double-label immunocytochemistry for CGRP and beta-galactosidase rendered no correlation between trigeminal innervation and the degree of innervation by NT-3-expressing ORNs. Thus, the timing and presence of beta-galactosidase in a subset of ORNs suggests that NT-3 plays a role in synaptogenesis and/or synapse function in a specific subset of ORNs within the olfactory bulb.
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Affiliation(s)
- Alison J Vigers
- Rocky Mountain Taste and Smell Center, Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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28
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Cohen DRS, Matarazzo V, Palmer AM, Tu Y, Jeon OH, Pevsner J, Ronnett GV. Expression of MeCP2 in olfactory receptor neurons is developmentally regulated and occurs before synaptogenesis. Mol Cell Neurosci 2003; 22:417-29. [PMID: 12727440 DOI: 10.1016/s1044-7431(03)00026-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Rett syndrome, a neurodevelopmental disorder hypothesized to be due to defective neuronal maturation, is a result of mutations in the mecp2 gene encoding the transcriptional repressor methyl-CpG binding protein (MeCP2). We utilized the olfactory system, which displays postnatal neurogenesis, as a model to investigate MeCP2 expression during development and after injury. MeCP2 expression increased postnatally, localizing to mature olfactory receptor neurons (ORNs) and sustentacular supporting cells. The timing of MeCP2 expression was defined by using detergent ablation (to remove the ORNs) and unilateral olfactory bulbectomy (to remove the ORN target), both of which increase neurogenesis. MeCP2 expression in the ORNs reached prelesioning levels as cells matured after ablation, whereas expression was not completely restored after bulbectomy, in which functional synaptogenesis cannot occur. Thus, MeCP2 expression correlates with the maturational state of ORNs, and precedes synaptogenesis. Identifying the time window of MeCP2 expression should help further clarify the biological defects in Rett syndrome.
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Affiliation(s)
- Deborah R S Cohen
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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29
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Nyouist-Battie C, Gochee A. Alterations in the development of the main olfactory bulb of the mouse after ethanol exposure. Int J Dev Neurosci 2003; 3:211-22. [DOI: 10.1016/0736-5748(85)90026-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/1984] [Indexed: 11/29/2022] Open
Affiliation(s)
- Cynthia Nyouist-Battie
- Department of Biological Sciences; Northern Illinois University; DeKalb IL 60115-2854 U.S.A
| | - Angel Gochee
- Department of Biological Sciences; Northern Illinois University; DeKalb IL 60115-2854 U.S.A
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30
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Spoerri PE. Effects of gangliosides on the in vitro development of neuroblastoma cells: An ultrastructural study. Int J Dev Neurosci 2003; 1:383-91. [DOI: 10.1016/0736-5748(83)90020-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/1983] [Indexed: 10/27/2022] Open
Affiliation(s)
- P. E. Spoerri
- Department of Anatomy; University of Goettingen; Kreuzbergring 36 D-3400 Goettingen FRG
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31
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Guthrie KM, Gall C. Anatomic mapping of neuronal odor responses in the developing rat olfactory bulb. J Comp Neurol 2003; 455:56-71. [PMID: 12454996 DOI: 10.1002/cne.10452] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Behavioral evidence indicates that altricial mammals possess olfactory function at early developmental ages, before the olfactory bulb has matured anatomically. We monitored the early anatomic and functional development of the olfactory bulb in rat pups stimulated with odors using in situ localization of c-fos mRNA to identify responsive postsynaptic neurons. Odor-specific spatial patterns of neuronal activation in the glomerular layer were evident from birth, were sharply defined rather than diffuse, and remained relatively unchanged in terms of their bulbar distribution during the first 3 postnatal weeks. In neonates, focal postsynaptic responses in the glomerular layer occurred in the form of clusters of activated tufted neurons. Broad zones of activated mitral cells were located beneath these cell clusters, with scattered neurons in the underlying granule cell layer also expressing c-fos. The cellular composition of these functional neuronal groups shifted from predominantly output neurons at the earliest ages, to increasing incorporation of interneurons as they developed postnatally. The characteristic distribution of activated neurons in the mature glomerular layer, in which the boundaries of individual glomeruli are precisely defined by cells expressing c-fos, emerged near the end of the first week. Broad zones of cRNA hybridization in the mitral cell layer became increasingly restricted as the size of the activated granule cell population increased postnatally, correlating with the functional maturation of inhibitory circuitry. These results provide evidence that the types and distributions of neurons collectively activated by sensory input to glomeruli change as the rat olfactory bulb matures and that distinct, functional odor maps in the glomerular layer are established from birth.
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Affiliation(s)
- Kathleen M Guthrie
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA.
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32
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Marrs GS, Green SH, Dailey ME. Rapid formation and remodeling of postsynaptic densities in developing dendrites. Nat Neurosci 2001; 4:1006-13. [PMID: 11574832 DOI: 10.1038/nn717] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2001] [Accepted: 08/14/2001] [Indexed: 11/09/2022]
Abstract
The dynamics of postsynaptic density (PSD) formation and remodeling were investigated in live developing hippocampal tissue slices. Time lapse imaging of transfected neurons expressing GFP-tagged PSD95, a prominent PSD protein, revealed that up to 40% of PSDs in developing dendrites are structurally dynamic; they rapidly (<15 min) appear or disappear, but also grow, shrink and move within shafts and spines. New spines containing PSDs were formed by conversion of dynamic filopodia-like spine precursors in which PSDs appeared de novo, or by direct extension of spines or spine precursors carrying preformed PSDs from the shaft. PSDs are therefore highly dynamic structures that can undergo rapid structural alteration within dendrite shafts, spines and spine precursors, permitting rapid formation and remodeling of synaptic connections in developing CNS tissues.
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Affiliation(s)
- G S Marrs
- Department of Biological Sciences, 335 Biology Building, University of Iowa, Iowa City, Iowa 52242, USA
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33
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Abstract
To determine whether presynaptic input is necessary for postsynaptic differentiation, we isolated hippocampal neurons in microisland culture and thus deprived pyramidal cells of GABA input and GABAergic neurons of glutamate input. We find that glutamate input is necessary for clustering the AMPA-type glutamate receptor but not for clustering the NMDA receptor or the associated PSD-95 family scaffold in GABAergic cells; GABA input is not necessary for clustering the GABA(A) receptor or gephyrin in pyramidal cells. Isolated neurons showed a surprising mismatch of presynaptic and postsynaptic components. For example, in isolated pyramidal neurons, although GABA(A) receptor clusters covered <4% of the dendritic surface and presynaptic boutons covered <12%, a full two-thirds of the GABA(A) receptor clusters were localized inappropriately opposite the non-GABAergic, presumed glutamatergic, terminals. Furthermore, inhibitory and excitatory postsynaptic components were segregated into separate clusters in isolated cells and apposed to separate boutons of a single axon. Thus, GABA(A) receptors were clustered opposite some terminals, whereas NMDA receptors were clustered opposite other terminals of a single axon. These results suggest the involvement of a synaptogenic signal common to glutamate and GABA synapses that permits experimentally induced mismatching of presynaptic and postsynaptic components in isolated neurons, as well as a second specificity-conferring signal that mediates appropriate matching in mixed cultures.
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34
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35
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36
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Abstract
Neurestin is a putative transmembrane protein whose expression is developmentally regulated in neurons. Here we examined neurestin expression pattern in mitral/tufted cells in the developing rat olfactory bulb. In the main olfactory bulb, neurestin expression was segregated in the dorso-rostral area and in the ventro-caudal area, but not in between. In the accessory olfactory bulb, neurestin expression was found only in the far caudal area. This area did not completely correspond to a caudal half of the vomeronasal nerve and glomerular layers positive for a G-protein Go alpha. These spatio-temporal expression patterns suggest that neurestin functions as a target recognition molecule that specifies zonal projection patterns of olfactory and vomeronasal sensory neurons.
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Affiliation(s)
- J M Otaki
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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37
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Otaki JM, Firestein S. Neurestin: putative transmembrane molecule implicated in neuronal development. Dev Biol 1999; 212:165-81. [PMID: 10419693 DOI: 10.1006/dbio.1999.9310] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have cloned a novel cDNA encoding a putative transmembrane protein, neurestin, from the rat olfactory bulb. Neurestin was identified based on a sequence similar to that of the second extracellular loops of odorant receptors in the cysteine-rich CC box located immediately after EGF-like motifs. Neurestin shows homology to a neuregulin gene product, human gamma-heregulin, a Drosophila receptor-type pair-rule gene product, Odd Oz (Odz) / Ten(m), and Ten(a), suggesting a possible function in synapse formation and morphogenesis. Recently, a mouse neurestin homolog has independently been cloned as DOC4 from the NIH-3T3 cell line. Northern blot analysis showed that neurestin is highly expressed in the brain and also in other tissues at much lower levels. In situ hybridization studies showed that neurestin is expressed in many types of neurons, including pyramidal cells in the cerebral cortex and tufted cells in the olfactory bulb during development. In adults, neurestin is mainly expressed in olfactory and hippocampal granule cells, which are known to be generated throughout adulthood. Nonetheless, in adults the expression of neurestin was experimentally induced in external tufted cells during regeneration of olfactory sensory neurons. These results suggest a role for neurestin in neuronal development and regeneration in the central nervous system.
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Affiliation(s)
- J M Otaki
- Department of Biological Sciences, Columbia University, New York, New York, 10027, USA.
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38
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Bulfone A, Wang F, Hevner R, Anderson S, Cutforth T, Chen S, Meneses J, Pedersen R, Axel R, Rubenstein JL. An olfactory sensory map develops in the absence of normal projection neurons or GABAergic interneurons. Neuron 1998; 21:1273-82. [PMID: 9883721 DOI: 10.1016/s0896-6273(00)80647-9] [Citation(s) in RCA: 264] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Olfactory sensory neurons expressing a given odorant receptor project to two topographically fixed glomeruli in the olfactory bulb. We have examined the contribution of different cell types in the olfactory bulb to the establishment of this topographic map. Mice with a homozygous deficiency in Tbr-1 lack most projection neurons, whereas mice with a homozygous deficiency in Dlx-1 and Dlx-2 lack most GABAergic interneurons. Mice bearing a P2-IRES-tau-lacZ allele and deficient in either Tbr-1 or Dlx-1/Dlx-2 reveal the convergence of axons to one medial and one lateral site at positions analogous to those observed in wild-type mice. These observations suggest that the establishment of a topographic map is not dependent upon cues provided by, or synapse formation with, the major neuronal cell types in the olfactory bulb.
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Affiliation(s)
- A Bulfone
- Center for Neurobiology and Psychiatry, Department of Psychiatry, University of California, San Francisco 94143-0984, USA
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39
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Abstract
The number of synapses in the adult, female hippocampal CA1 region fluctuates naturally across the estrous cycle in an ovarian steroid-dependent manner. This phasic variation in synapse number occurs without identifiable degenerating synapses. Ultrastructural correlates of the dynamic aspect of this synapse loss and synapse formation thus remain undescribed. During early development, one hallmark of synaptogenesis is the presence of free postsynaptic densities (PSDs). Here we report that the incidence of free PSDs in CA1 fluctuates across the rat estrous cycle. The number of free PSDs is greatest on the afternoon of proestrus and is significantly decreased on the afternoon of estrus, 24 h later. We hypothesize that these free PSDs reflect synapse turnover in the adult CA1 region.
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Affiliation(s)
- N L Desmond
- Department of Neurological Surgery, University of Virginia, Health Sciences Center, Charlottesville 22908, USA
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40
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Abstract
The failure of regenerating axons to grow within the adult mammalian central nervous system (CNS) does not apply to the olfactory bulb (OB). In this structure, normal and transected olfactory axons are able to enter, regenerate, and reestablish lost synaptic contacts with their targets, throughout the lifetime of the organism. A remarkable difference between an axonal growth-permissive structure such as the OB and the remaining CNS resides in the presence of ensheathing glia in the former. These cells exhibit phenotypic and functional properties known to be involved in the process of axonal elongation that may explain the permissibility of the OB to axonal growth. In addition, transplants of ensheathing glia were successfully used to promote axonal regeneration within the injured adult CNS. The axonal growth-promoting properties of ensheathing glia make the study of this cell type interesting to provide an insight into the mechanisms underlying the process of axonal regeneration. Therefore, in this article we review the developmental, morphologic, immunocytochemical, and functional properties presented by this unique glial cell type, and correlate them with the axonal growth-promoting ability of ensheathing glia. In addition, we provide some evidence of the potentiality that ensheathing glia might have as a promoter of axonal regeneration within the injured nervous system.
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Affiliation(s)
- A Ramón-Cueto
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Facultad de Ciencias, Universidad Autónoma de Madrid, Spain.
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41
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Abstract
The formation of synaptic contacts is a crucial event during neural development and is thought to be achieved by complex interactions between incoming axons and the neurons in the target. We have focused on spine-like dendritic protrusions (SLDPs), which are transient pleomorphic protrusive structures seen in developing brains. Although the functional significance of SLDPs remains unknown, accumulating in vitro evidence suggests that the SLDP plays an important role in synaptogenetic interactions with axons. As a test of this idea, the present study was performed to examine whether the SLDPs are the preferential sites of synapse formation in vivo. The ultrastructure of biocytin-labeled corticorubral (CR) terminals was examined in serial thin sections during the period of synaptogenesis in newborn cats. We found that a major proportion (86%) of the CR synapses was formed on SLDPs. The presynaptic terminals were often invaginated by fine processes extending from the tips of SLDPs. Synaptic structures presumably of cortical origin were also found on SLDPs of HRP-labeled rubrospinal cells, suggesting that SLDPs postsynaptic to labeled CR terminals originate at least in part from rubrospinal cells. Taken together, these results indicate that SLDPs may represent preferred sites of synapse formation and support the notion that SLDPs play a role in synaptogenic interactions during brain development.
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42
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Mimmack ML, Saito H, Evans G, Bresler M, Keverne EB, Emson PC. A novel splice variant of the cell adhesion molecule BIG-2 is expressed in the olfactory and vomeronasal neuroepithelia. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1997; 47:345-50. [PMID: 9221934 DOI: 10.1016/s0169-328x(97)00104-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have cloned a mouse cDNA encoding a novel truncated form of the gene BIG-2 from the vomeronasal organ. The related proteins BIG-2 and BIG-1 possess a C-terminal glycosylphosphatidylinositol anchor, six immunoglobulin domains and four fibronectin type III repeats. They are related to certain axonal-associated cell adhesion molecules (AxCAMs) exhibiting most similarity to the TAG-1/F3 subgroup of neural cell adhesion molecules. The cDNA we have identified, termed BIG-2A, appears to represent a novel splice variant of BIG-2 possessing six Ig-like domains, a single fibronectin repeat and lacking the glycosylphosphatidylinositol-anchoring domain (GPI). To determine the expression of this gene, in situ hybridization analysis was performed in adult and developing mice using a riboprobe specific for BIG-2A. Maximum expression was observed in mature sensory cells of the vomeronasal neuroepithelium and a less intense signal was also evident in the olfactory neuroepithelium. These results suggest that alternative splicing of the BIG-2 gene transcript may play an important role in the organization of the vomeronasal and olfactory neuroepithelia.
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Affiliation(s)
- M L Mimmack
- Sub-Department of Animal Behaviour, University of Cambridge, Madingley, UK
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43
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Chotro MG, Kraebel KS, McKinzie DL, Molina JC, Spear N. Prenatal and postnatal ethanol exposure influences preweanling rats' behavioral and autonomic responding to ethanol odor. Alcohol 1996; 13:377-85. [PMID: 8836327 DOI: 10.1016/0741-8329(96)00027-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The specific question was how prenatal and/or postnatal experience with ethanol influences cardiac and behavioral responses to the odor of ethanol on postnatal day (PD) 16. In each of two experiments, pregnant rats were given ethanol or water on gestational days 17-20. Offspring were exposed on PD12 to one of three conditions: intragastric administration of 6% ethanol, indirect exposure to ethanol from littermates, or no treatment. Results of Experiment 1 indicated that, regardless of prenatal ethanol exposure, 16-day-olds exposed on PD12 either directly or indirectly to ethanol expressed a greater increase in HR in response to ethanol odor than pups not postnatally exposed to ethanol. In Experiment 2, in which a lower ethanol dose was used postnatally, an interaction between pre- and postnatal ethanol exposure was observed; that is, pups exposed pre- and postnatally to ethanol showed the greatest increases in HR and the smallest increases in motor activity in response to ethanol odor. In both experiments motor activity was dissociated from increases in HR. The results are discussed in terms of what is learned, prenatally and postnatally, in association with the chemosensory properties of ethanol.
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Affiliation(s)
- M G Chotro
- Center for Developmental Psychobiology, Binghamton University, NY 13902-6000, USA
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44
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Abstract
Using the fluorescent carbocyanine tracer DiI, we examined in detail the early development of the projections emanating from the rat olfactory bulb. The study commenced at embryonic day 13 when the first fibres can be detected and ended at embryonic day 20, when all major fibre systems have been established. The first axons arising from the prospective olfactory bulb area are seen at embryonic day 13. Labelled fibres are provided with elaborate axonal growth cones advancing through the ventrolateral part of the telencephalic vesicle. At embryonic day 14, while the main fibre tract has not developed much further, some isolated fibres are located quite distally from the prospective olfactory bulb. These early fibres apparently course within a narrow cell-free space that extends caudally along the ventrolateral part of the telencephalic vesicle. At embryonic day 15, a number of labelled fibres form a compact bundle, corresponding to the lateral olfactory tract, that ultimately reaches the prospective primary olfactory cortex. The fibres do not stop growing, but continue to extend caudally at embryonic day 17. The results of this study provide new information on the development of axonal tracts in the olfactory system. We show that the olfactory tract projection develops earlier than the morphological appearance of the olfactory bulbs. This suggests that the early development of olfactory projections might not depend on the arrival of the olfactory epithelium axons and thus, could be governed by factors intrinsic to the neurons and/or cues present in the target environment.
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45
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Sullivan SL, Bohm S, Ressler KJ, Horowitz LF, Buck LB. Target-independent pattern specification in the olfactory epithelium. Neuron 1995; 15:779-89. [PMID: 7576628 DOI: 10.1016/0896-6273(95)90170-1] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In mammals, odors are detected by approximately 1000 different types of odorant receptors (ORs), each expressed by a fraction of neurons in the olfactory epithelium. Neurons expressing a given OR are confined to one of four spatial zones but are distributed randomly throughout that zone. In the olfactory bulb, the axons of neurons expressing different ORs synapse at different sites, giving rise to a highly organized and stereotyped information map. An important issue is whether the epithelial and bulbar maps evolve independently or are linked, for example, by retrograde influences of the bulb on the epithelium. Here we examined the onset of expression and patterning of genes encoding ORs and sensory transduction molecules during mouse embryogenesis and in mice lacking olfactory bulbs. Our results argue for an independent development of epithelial and bulbar maps and an early functional development that may be pertinent to pattern development in the olfactory bulb.
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Affiliation(s)
- S L Sullivan
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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46
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Klintsova AY, Philpot BD, Brunjes PC. Fos protein immunoreactivity in the developing olfactory bulbs of normal and naris-occluded rats. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1995; 86:114-22. [PMID: 7656404 DOI: 10.1016/0165-3806(95)00015-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Immediate early genes such as c-fos may be a route through which extracellular events affect genomic expression. Expression of immediate early genes is important in the transcriptional regulation necessary for the normal development of the nervous system. Developmental patterns of Fos protein (the product of c-fos immediate early gene expression) were studied in the main olfactory bulb of the rat using immunocytochemistry. Embryonic Day 21 (E21, the last prenatal day), as well as Postnatal Day 0 (P0), P1, P5, P10, P15, P20 and P30 subjects were examined. Although staining was absent in the E21 bulb, there was a rapid onset of Fos synthesis within hours after birth. Distribution of Fos-immunoreactive (Fos-ir) nuclei corresponded to the sequence of bulb maturation: numerous mitral/tufted and granule cells were labeled on P0, followed by the appearance of Fos-ir in the nuclei of periglomerular cells and an increase in the number of stained granule cells with development. Surgical closure of an external naris on P1 resulted in a 70% reduction in the number of Fos-ir granule cell nuclei as early as 2 h after the manipulation. During the next 30 days, levels of Fos staining further diminished in experimental bulbs when compared to their contralateral controls. Nevertheless, electrical stimulation of the contralateral bulb in P20 pups resulted in a robust increase of Fos labeling in most main and accessory olfactory bulb mitral cells and in many granule and periglomerular neurons, suggesting that the experimental bulbs remain competent to express Fos protein.
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Affiliation(s)
- A Y Klintsova
- Department of Psychology, University of Virginia, Charlottesville 22903, USA
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47
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Salecker I, Boeckh J. Embryonic development of the antennal lobes of a hemimetabolous insect, the cockroach Periplaneta americana: light and electron microscopic observations. J Comp Neurol 1995; 352:33-54. [PMID: 7536222 DOI: 10.1002/cne.903520104] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In the hemimetabolous insect Periplaneta americana, the adult-like organization of the primary olfactory centers, the antennal lobes, is established during the approximately 31 days of embryogenesis. This report describes the temporal sequence of developmental events as viewed in the light and electron microscope by means of histological stains and by DiI labeling of antennal receptor axons with subsequent photoconversion. Glomeruli, characteristic differentiations of the antennal lobe neuropil, are first observed on day 19; their development, which is not synchronous in the various parts of the antennal lobe, lasts until about day 22. From day 10 on, glial cells begin to form a narrow boundary layer between the soma cortex and the central neuropil. They exhibit a lengthening of their processes in parallel with the formation of glomeruli. Marked proliferation or migration of these glial cells into the neuropil between glomeruli has not been observed. Antennal receptor axons could be labeled from stage 15 on. They terminate in an elongated growth cone with numerous filopodia. From day 18 on, some of these become bent or show an initial bifurcation. From day 22 on, the first afferent axons develop an adult-like arborization pattern. Synaptic contacts between receptor axons and unidentified neurons were observed as early as stages 16 and 19, in which the axons still have a growth cone-like form. In stage 27, in which the fibers have adult-like arborizations, many output contacts and few input contacts were found.
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Affiliation(s)
- I Salecker
- Institut für Zoologie, Universität Regensburg, Federal Republic of Germany
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48
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Fracek SP, Guo L, Schafer R. Morphological characteristics of cultured olfactory bulb cells. Exp Brain Res 1994; 100:421-36. [PMID: 7813680 DOI: 10.1007/bf02738402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cultured olfactory bulb cells from embryonic mice had ultrastructural characteristics similar to those of many cell types in the intact adult mouse olfactory bulb. Identified cultured cells included mitral/tufted cells, granule cells, short-axon cells, and fibrous and protoplasmic astrocytes. Cultured neurons were found as individual cells, clusters or aggregates. Clusters consisted of a loose array of neurons that appeared to be densely interconnected by neurites. However, few neurites or fascicles emanated from clusters to adjoining areas. Aggregates consisted of many small, usually rounded, neurons piled on top of one larger neuron, or on more than one, with typically many neurites and fascicles projecting to adjacent aggregates, clusters or individual neurons. Neurites of cultured olfactory bulb cells were well developed, and some were several millimeters long. Synapses were very prominent in these cultures, especially in aggregates, clusters, and fascicles. Electron-lucent, dense-core, and coated vesicles were present. Polarity, shape, and length of the long axis (size) of 815 cultured neurons, identified by positive anti-microtubule-associated protein 2 staining, were documented. Cultured neurons varied in size from 9 to 27 microns, with an average size of 16 microns. Elliptical bipolar (35%), triangular multipolar (21%), and round unipolar (15%) were the most common polarity/shape combinations found in culture. Multipolar, triangular, triangular multipolar, and elliptical bipolar cells increased in size with increasing age of culture. The relative proportions of triangular, multipolar, elliptical multipolar, and triangular multipolar cells decreased, whereas the relative proportions of round, unipolar, and round unipolar cells increased with increasing age of culture. These changes in population subtypes and cell size may indicate continued differentiation and maturation of cultured neurons.
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Affiliation(s)
- S P Fracek
- University of North Texas, Department of Biological Sciences, Denton 76203-5218
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49
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Fracek SP, Guo L, Schafer R. Morphological characteristics of cultured olfactory bulb cells. Exp Brain Res 1994. [DOI: 10.1007/bf00229182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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50
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Abstract
Cultured embryonic mouse olfactory bulb cells formed asymmetric, symmetric, axodendritic, and dendrodendritic synapses. These neurons contained electron lucent, dense core, and coated vesicles. Dense core and coated vesicles had an average diameter of 71 and 80 nm, respectively. Two statistically different populations of electron lucent vesicles were found, based on synaptic symmetry: electron lucent vesicles from asymmetric synapses had an average diameter of 46 nm with an estimated volume of 49,000 nm3, whereas those from symmetric synapses had an average diameter of 44 nm and an estimated volume of 42,000 nm3. Because these values are similar to those found for intact olfactory bulb, the synapses of these cultured cells have some of the same morphological characteristics as those in the intact olfactory bulb.
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Affiliation(s)
- S P Fracek
- University of North Texas, Department of Biological Sciences, Denton 76203-5218
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