501
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Embryonically expressed GABA and glutamate drive electrical activity regulating neurotransmitter specification. J Neurosci 2008; 28:4777-84. [PMID: 18448654 DOI: 10.1523/jneurosci.4873-07.2008] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurotransmitter signaling in the mature nervous system is well understood, but the functions of transmitters in the immature nervous system are less clear. Although transmitters released during embryogenesis regulate neuronal proliferation and migration, little is known about their role in regulating early neuronal differentiation. Here, we show that GABA and glutamate drive calcium-dependent embryonic electrical activity that regulates transmitter specification. The number of neurons expressing different transmitters changes when GABA or glutamate signaling is blocked chronically, either using morpholinos to knock down transmitter-synthetic enzymes or applying pharmacological receptor antagonists during a sensitive period of development. We find that calcium spikes are triggered by metabotropic GABA and glutamate receptors, which engage protein kinases A and C. The results reveal a novel role for embryonically expressed neurotransmitters.
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502
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Hewapathirane DS, Dunfield D, Yen W, Chen S, Haas K. In vivo imaging of seizure activity in a novel developmental seizure model. Exp Neurol 2008; 211:480-8. [DOI: 10.1016/j.expneurol.2008.02.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2007] [Revised: 02/06/2008] [Accepted: 02/16/2008] [Indexed: 10/22/2022]
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503
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Neuronal avalanches organize as nested theta- and beta/gamma-oscillations during development of cortical layer 2/3. Proc Natl Acad Sci U S A 2008; 105:7576-81. [PMID: 18499802 DOI: 10.1073/pnas.0800537105] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Maturation of the cerebral cortex involves the spontaneous emergence of distinct patterns of neuronal synchronization, which regulate neuronal differentiation, synapse formation, and serve as a substrate for information processing. The intrinsic activity patterns that characterize the maturation of cortical layer 2/3 are poorly understood. By using microelectrode array recordings in vivo and in vitro, we show that this development is marked by the emergence of nested - and beta/gamma-oscillations that require NMDA- and GABA(A)-mediated synaptic transmission. The oscillations organized as neuronal avalanches, i.e., they were synchronized across cortical sites forming diverse and millisecond-precise spatiotemporal patterns that distributed in sizes according to a power law with a slope of -1.5. The correspondence between nested oscillations and neuronal avalanches required activation of the dopamine D(1) receptor. We suggest that the repetitive formation of neuronal avalanches provides an intrinsic template for the selective linking of external inputs to developing superficial layers.
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504
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Peroxiredoxin 2 is Involved in the Neuroprotective Effects of PACAP in Cultured Cerebellar Granule Neurons. J Mol Neurosci 2008; 36:61-72. [DOI: 10.1007/s12031-008-9075-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 04/10/2008] [Indexed: 11/25/2022]
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505
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Abstract
The enteric nervous system (ENS) consists of many different types of enteric neurones forming complex reflex circuits that underlie or regulate many gut functions. Studies of humans with Hirschsprung's disease (distal aganglionosis), and of animal models of Hirschsprung's disease, have led to the identification of many of the genetic, molecular and cellular mechanisms responsible for the colonization of the gut by enteric neurone precursors. However, later events in the ENS development are still poorly understood, including the development of functioning ENS circuits. This article is a personal view of the current state of play in our understanding of the ENS development and of the future of the field.
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Affiliation(s)
- H M Young
- Department of Anatomy and Cell Biology, University of Melbourne, Melbourne, Victoria, Australia.
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506
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Prithviraj R, Kelly KM, Espinoza-Lewis R, Hexom T, Clark AB, Inglis FM. Differential regulation of dendrite complexity by AMPA receptor subunits GluR1 and GluR2 in motor neurons. Dev Neurobiol 2008; 68:247-64. [PMID: 18000827 DOI: 10.1002/dneu.20590] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Activity-dependent developmental mechanisms in many regions of the central nervous system are thought to be responsible for shaping dendritic architecture and connectivity, although the molecular mechanisms underlying these events remain obscure. Since AMPA glutamate receptors are developmentally regulated in spinal motor neurons, we have investigated the role of activation of AMPA receptors in dendritic outgrowth of spinal motor neurons by overexpression of two subunits, GluR1 and GluR2, and find that dendrite outgrowth is differentially controlled by expression of these subunits. Overexpression of GluR1 was associated with greater numbers of filopodia, and an increase in the length and complexity of dendritic arbor. In contrast, GluR2 expression did not alter dendritic complexity, but was associated with a moderate increase in length of arbor, and decreased numbers of filopodia. Neither GluR1 nor GluR2 had any effect on the motility of filopodia. In addition, GluR1 but not GluR2 expression increased the density of dendritic puncta incorporating a GFP-labeled PSD95, suggesting that GluR1 may mediate its effect in part by augmenting the number of excitatory synapses within motor neuron dendrites. Together these results suggest that in spinal motor neurons, AMPA receptors composed of GluR1 subunits may facilitate neurotrophic mechanisms in these neurons, permitting sustained dendrite outgrowth and synaptogenesis, whereas expression of AMPA receptors containing GluR2 acts to preserve existing dendritic arbor. Thus, the observed downregulation of GluR1 in motor neurons during postnatal development may limit the formation of new dendrite segments and synapses, promoting stabilized synaptic connectivity.
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Affiliation(s)
- Ranjini Prithviraj
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
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507
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Neurite outgrowth and in vivo sensory innervation mediated by a Ca(V)2.2-laminin beta 2 stop signal. J Neurosci 2008; 28:2366-74. [PMID: 18322083 DOI: 10.1523/jneurosci.3828-07.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Axons and dendrites of developing neurons establish distributed innervation patterns enabling precise discrimination in sensory systems. We describe the role of the extracellular matrix molecule, laminin beta2, interacting with the Ca(V)2.2 calcium channel in establishing appropriate sensory innervation. In vivo, Ca(V)2.2 is expressed on the growth cones of Xenopus laevis sensory neurites and laminin beta2 is expressed in the skin. Culturing neurons on a laminin beta2 substrate inhibits neurite outgrowth in a specific and calcium-dependent manner. Blocking signaling between laminin beta2 and Ca(V)2.2 leads to increased numbers of sensory terminals in vivo. These findings suggest that interactions between extracellular matrix molecules and calcium channels regulate connectivity in the developing nervous system.
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508
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509
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Smith DO, Rosenheimer JL, Kalil RE. Delayed rectifier and A-type potassium channels associated with Kv 2.1 and Kv 4.3 expression in embryonic rat neural progenitor cells. PLoS One 2008; 3:e1604. [PMID: 18270591 PMCID: PMC2225502 DOI: 10.1371/journal.pone.0001604] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Accepted: 01/21/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Because of the importance of voltage-activated K(+) channels during embryonic development and in cell proliferation, we present here the first description of these channels in E15 rat embryonic neural progenitor cells derived from the subventricular zone (SVZ). Activation, inactivation, and single-channel conductance properties of recorded progenitor cells were compared with those obtained by others when these Kv gene products were expressed in oocytes. METHODOLOGY/PRINCIPAL FINDINGS Neural progenitor cells derived from the subventricular zone of E15 embryonic rats were cultured under conditions that did not promote differentiation. Immunocytochemical and Western blot assays for nestin expression indicated that almost all of the cells available for recording expressed this intermediate filament protein, which is generally accepted as a marker for uncommitted embryonic neural progenitor cells. However, a very small numbers of the cells expressed GFAP, a marker for astrocytes, O4, a marker for immature oligodendrocytes, and betaIII-tubulin, a marker for neurons. Using immunocytochemistry and Western blots, we detected consistently the expression of Kv2.1, and 4.3. In whole-cell mode, we recorded two outward currents, a delayed rectifier and an A-type current. CONCLUSIONS/SIGNIFICANCE We conclude that Kv2.1, and 4.3 are expressed in E15 SVZ neural progenitor cells, and we propose that they may be associated with the delayed-rectifier and the A-type currents, respectively, that we recorded. These results demonstrate the early expression of delayed rectifier and A-type K(+) currents and channels in embryonic neural progenitor cells prior to the differentiation of these cells.
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Affiliation(s)
- Dean O Smith
- Stem Cell Research Laboratory, University of Hawaii at Manoa, Manoa, Hawaii, USA.
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510
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Reynolds A, Brustein E, Liao M, Mercado A, Babilonia E, Mount DB, Drapeau P. Neurogenic role of the depolarizing chloride gradient revealed by global overexpression of KCC2 from the onset of development. J Neurosci 2008; 28:1588-97. [PMID: 18272680 PMCID: PMC6671553 DOI: 10.1523/jneurosci.3791-07.2008] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 11/30/2007] [Accepted: 12/29/2007] [Indexed: 11/21/2022] Open
Abstract
GABA- and glycine-induced depolarization is thought to provide important developmental signals, but the role of the underlying chloride gradient has not been examined from the onset of development. We therefore overexpressed globally the potassium-chloride cotransporter 2 (KCC2) in newly fertilized zebrafish embryos to reverse the chloride gradient. This rendered glycine hyperpolarizing in all neurons, tested at the time that motor behaviors (but not native KCC2) first appear. KCC2 overexpression resulted in fewer mature spontaneously active spinal neurons, more immature silent neurons, and disrupted motor activity. We observed fewer motoneurons and interneurons, a reduction in the elaboration of axonal tracts, and smaller brains and spinal cords. However, we observed no increased apoptosis and a normal complement of sensory neurons, glia, and progenitors. These results suggest that chloride-mediated excitation plays a crucial role in promoting neurogenesis from the earliest stages of embryonic development.
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Affiliation(s)
- Annie Reynolds
- Department of Pathology and Cell Biology and Le Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada H3T 1J4
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada H3G 1A4
- Department of Biology, McGill University, Montréal, Québec, Canada H3A 1B1
| | - Edna Brustein
- Department of Pathology and Cell Biology and Le Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada H3T 1J4
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada H3G 1A4
| | - Meijiang Liao
- Department of Pathology and Cell Biology and Le Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada H3T 1J4
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada H3G 1A4
| | - Adriana Mercado
- Renal Division, Brigham and Women's Hospital, Harvard Institutes of Medicine, Boston, Massachusetts 02115, and
| | - Elisa Babilonia
- Renal Division, Brigham and Women's Hospital, Harvard Institutes of Medicine, Boston, Massachusetts 02115, and
| | - David B. Mount
- Renal Division, Brigham and Women's Hospital, Harvard Institutes of Medicine, Boston, Massachusetts 02115, and
- Division of General Internal Medicine, Veterans Affairs Boston Healthcare System, Harvard Medical School, West Roxbury, Massachusetts 02132
| | - Pierre Drapeau
- Department of Pathology and Cell Biology and Le Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada H3T 1J4
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada H3G 1A4
- Department of Biology, McGill University, Montréal, Québec, Canada H3A 1B1
- Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada H3A 2B4
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511
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Differential outgrowth of axons and their branches is regulated by localized calcium transients. J Neurosci 2008; 28:143-53. [PMID: 18171932 DOI: 10.1523/jneurosci.4548-07.2008] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
During development axon outgrowth and branching are independently regulated such that axons can stall or retract while their interstitial branches extend toward targets. Previous studies have shown that guidance cues and intracellular signaling components can promote branching of cortical axons without affecting axon outgrowth. However, the mechanisms that regulate differential outgrowth of axons and their branches are not well understood. Based on our previous work showing the importance of localized repetitive calcium transients in netrin-1-induced cortical axon branching, we sought to investigate the role of calcium signaling in regulating differential outgrowth of axons and their branches. Using fluorescence calcium imaging of dissociated developing cortical neurons, we show that localized spontaneous calcium transients of different frequencies occur in restricted regions of axons and their branches. Higher frequencies occur in more rapidly extending processes whereas lower frequencies occur in processes that stall or retract. Direct induction of localized calcium transients with photolysis of caged calcium induced rapid outgrowth of axonal processes. Surprisingly outgrowth of one axonal process was almost invariably accompanied by simultaneous retraction of another process belonging to the same axon, suggesting a competitive mechanism for differential process outgrowth. Conversely, reducing frequencies of calcium transients with nifedipine and TTX reduced the incidence of differential process outgrowth. Together these results suggest a novel activity-dependent mechanism whereby intrinsic localized calcium transients regulate the competitive growth of axons and their branches. These mechanisms may also be important for the development of cortical connectivity in vivo.
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512
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Distribution and phenotypes of unipolar brush cells in relation to the granule cell system of the rat cochlear nucleus. Neuroscience 2008; 154:29-50. [PMID: 18343594 DOI: 10.1016/j.neuroscience.2008.01.035] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 01/16/2008] [Indexed: 11/21/2022]
Abstract
In most mammals the cochlear nuclear complex (CN) contains a distributed system of granule cells (GCS), whose parallel fiber axons innervate the dorsal cochlear nucleus (DCN). Like their counterpart in cerebellum, CN granules are innervated by mossy fibers of various origins. The GCS is complemented by unipolar brush (UBCs) and Golgi cells, and by stellate and cartwheel cells of the DCN. This cerebellum-like microcircuit modulates the activity of the DCN's main projection neurons, the pyramidal, giant and tuberculoventral neurons, and is thought to improve auditory performance by integrating acoustic and proprioceptive information. In this paper, we focus on the rat UBCs, a chemically heterogeneous neuronal population, using antibodies to calretinin, metabotropic glutamate receptor 1alpha (mGluR1alpha), epidermal growth factor substrate 8 (Eps8) and the transcription factor T-box gene Tbr2 (Tbr2). Eps8 and Tbr2 labeled most of the CN's UBCs, if not the entire population, while calretinin and mGluR1alpha distinguished two largely separate subsets with overlapping distributions. By double labeling with antibodies to Tbr2 and the alpha6 GABA receptor A (GABAA) subunit, we found that UBCs populate all regions of the GCS and occur at remarkably high densities in the DCN and subpeduncular corner, but rarely in the lamina. Although GCS subregions likely share the same microcircuitry, their dissimilar UBC densities suggest they may be functionally distinct. UBCs and granules are also present in regions previously not included in the GCS, namely the rostrodorsal magnocellular portions of ventral cochlear nucleus, vestibular nerve root, trapezoid body, spinal tract and sensory and principal nuclei of the trigeminal nerve, and cerebellar peduncles. The UBC's dendritic brush receives AMPA- and NMDA-mediated input from an individual mossy fiber, favoring singularity of input, and its axon most likely forms several mossy fiber-like endings that target numerous granule cells and other UBCs, as in the cerebellum. The UBCs therefore, may amplify afferent signals temporally and spatially, synchronizing pools of target neurons.
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513
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Aller M, Wisden W. Changes in expression of some two-pore domain potassium channel genes (KCNK) in selected brain regions of developing mice. Neuroscience 2008; 151:1154-72. [DOI: 10.1016/j.neuroscience.2007.12.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2007] [Revised: 12/03/2007] [Accepted: 12/11/2007] [Indexed: 10/22/2022]
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514
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515
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Nishiyama H, Fukaya M, Watanabe M, Linden DJ. Axonal motility and its modulation by activity are branch-type specific in the intact adult cerebellum. Neuron 2008; 56:472-87. [PMID: 17988631 DOI: 10.1016/j.neuron.2007.09.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 08/13/2007] [Accepted: 09/09/2007] [Indexed: 11/16/2022]
Abstract
We performed two-photon in vivo imaging of cerebellar climbing fibers (CFs; the terminal arbor of olivocerebellar axons) in adult mice. CF ascending branches innervate Purkinje cells while CF transverse branches show a near complete failure to form conventional synapses. Time-lapse imaging over hours or days revealed that ascending branches were very stable. However, transverse branches were highly dynamic, exhibiting rapid elongation and retraction and varicosity turnover. Thus, different branches of the same axon, with different innervation patterns, display branch type-specific motility in the adult cerebellum. Furthermore, dynamic changes in transverse branch length were almost completely suppressed by pharmacological stimulation of olivary firing.
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Affiliation(s)
- Hiroshi Nishiyama
- Department of Neuroscience, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
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516
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Johansson PA, Dziegielewska KM, Liddelow SA, Saunders NR. The blood–CSF barrier explained: when development is not immaturity. Bioessays 2008; 30:237-48. [DOI: 10.1002/bies.20718] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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517
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Spontaneous coordinated activity in cultured networks: Analysis of multiple ignition sites, primary circuits, and burst phase delay distributions. J Comput Neurosci 2007; 24:346-57. [DOI: 10.1007/s10827-007-0059-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 10/03/2007] [Accepted: 10/17/2007] [Indexed: 10/22/2022]
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518
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Ben-Ari Y, Gaiarsa JL, Tyzio R, Khazipov R. GABA: a pioneer transmitter that excites immature neurons and generates primitive oscillations. Physiol Rev 2007; 87:1215-84. [PMID: 17928584 DOI: 10.1152/physrev.00017.2006] [Citation(s) in RCA: 892] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Developing networks follow common rules to shift from silent cells to coactive networks that operate via thousands of synapses. This review deals with some of these rules and in particular those concerning the crucial role of the neurotransmitter gamma-aminobuytric acid (GABA), which operates primarily via chloride-permeable GABA(A) receptor channels. In all developing animal species and brain structures investigated, neurons have a higher intracellular chloride concentration at an early stage leading to an efflux of chloride and excitatory actions of GABA in immature neurons. This triggers sodium spikes, activates voltage-gated calcium channels, and acts in synergy with NMDA channels by removing the voltage-dependent magnesium block. GABA signaling is also established before glutamatergic transmission, suggesting that GABA is the principal excitatory transmitter during early development. In fact, even before synapse formation, GABA signaling can modulate the cell cycle and migration. The consequence of these rules is that developing networks generate primitive patterns of network activity, notably the giant depolarizing potentials (GDPs), largely through the excitatory actions of GABA and its synergistic interactions with glutamate signaling. These early types of network activity are likely required for neurons to fire together and thus to "wire together" so that functional units within cortical networks are formed. In addition, depolarizing GABA has a strong impact on synaptic plasticity and pathological insults, notably seizures of the immature brain. In conclusion, it is suggested that an evolutionary preserved role for excitatory GABA in immature cells provides an important mechanism in the formation of synapses and activity in neuronal networks.
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Affiliation(s)
- Yehezkel Ben-Ari
- Insititut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale U. 29, Marseille, France.
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519
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Tárnok K, Czöndör K, Jelitai M, Czirók A, Schlett K. NMDA receptor NR2B subunit over-expression increases cerebellar granule cell migratory activity. J Neurochem 2007; 104:818-29. [PMID: 18005003 DOI: 10.1111/j.1471-4159.2007.05051.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Glutamate acting on NMDA receptors (NMDARs) is known to influence cerebellar granule cell migration. Subunit composition of NMDARs in granule cells changes characteristically during development: NR2B subunit containing receptors are abundant during migration towards the internal granule cell layer but are gradually replaced by NR2A and/or NR2C subunits once the final position is reached. Cerebellar granule cell migration was investigated using mutant mouse lines either with a deletion of the NR2C gene (NR2C(-/-) mice) or expressing NR2B instead of the NR2C subunit (NR2C-2B mice). BrdU-labeling revealed that over-expression of NR2B increased granule cell translocation in vivo, while the lack of NR2C subunit did not have any detectable effects on cell migration. Cellular composition of wild-type and mutant dissociated cerebellar granule cell cultures isolated from 10-day-old cerebella were similar, but NR2C-2B cultures had elevated level of NR2B subunits and intracellular Ca2+ imaging revealed higher sensitivity towards the addition of NR2B-selective antagonist in vitro. Time-lapse videomicroscopic observations revealed that average migratory velocity and the proportion of translocating cell bodies were significantly higher in NR2C-2B than in wild-type cultures. Our results provide evidence that NR2B-containing NMDARs can have specialized roles during granule cell migration and can increase migratory speed.
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Affiliation(s)
- Krisztián Tárnok
- Department of Physiology and Neurobiology, Eötvös Loránd University, Budapest, Hungary
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520
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Dellis O, Rossi AM, Dedos SG, Taylor CW. Counting functional inositol 1,4,5-trisphosphate receptors into the plasma membrane. J Biol Chem 2007; 283:751-5. [PMID: 17999955 DOI: 10.1074/jbc.m706960200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP(3)R) within the endoplasmic reticulum mediate release of Ca(2+) from intracellular stores. Different channels usually mediate Ca(2+) entry across the plasma membrane. In B lymphocytes and a cell line derived from them (DT40 cells), very few functional IP(3)R (approximately 2/cell) are invariably expressed in the plasma membrane, where they mediate about half the Ca(2+) entry evoked by activation of the B-cell receptor. We show that cells reliably count approximately 2 functional IP(3)R into the plasma membrane even when their conductance and ability to bind IP(3) are massively attenuated. We conclude that very small numbers of functional IP(3)R can be reliably counted into a specific membrane compartment in the absence of feedback signals from the active protein.
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Affiliation(s)
- Olivier Dellis
- Department of Pharmacology, Tennis Court Road, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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521
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Homeostasis of neuronal avalanches during postnatal cortex development in vitro. J Neurosci Methods 2007; 169:405-16. [PMID: 18082894 DOI: 10.1016/j.jneumeth.2007.10.021] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 10/24/2007] [Accepted: 10/28/2007] [Indexed: 11/23/2022]
Abstract
Cortical networks in vivo and in vitro are spontaneously active in the absence of inputs, generating highly variable bursts of neuronal activity separated by up to seconds of quiescence. Previous measurements in adult rat cortex revealed an intriguing underlying organization of these dynamics, termed neuronal avalanches, which is indicative of a critical network state. Here we demonstrate that neuronal avalanches persist throughout development in cortical slice cultures from newborn rats. More specifically, we find that in spite of large variations of average rate in activity, spontaneous bursts occur with power-law distributed sizes (exponent -1.5) and a critical branching parameter close to 1. Our findings suggest that cortical networks homeostatically regulate a critical state during postnatal maturation.
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522
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Allen MJ, Murphey RK. The chemical component of the mixed GF-TTMn synapse in Drosophila melanogaster uses acetylcholine as its neurotransmitter. Eur J Neurosci 2007; 26:439-45. [PMID: 17650116 PMCID: PMC1974813 DOI: 10.1111/j.1460-9568.2007.05686.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The largest central synapse in adult Drosophila is a mixed electro-chemical synapse whose gap junctions require the product of the shaking-B (shak-B) gene. Shak-B2 mutant flies lack gap junctions at this synapse, which is between the giant fibre (GF) and the tergotrochanteral motor neuron (TTMn), but it still exhibits a long latency response upon GF stimulation. We have targeted the expression of the light chain of tetanus toxin to the GF, to block chemical transmission, in shak-B2 flies. The long latency response in the tergotrochanteral muscle (TTM) was abolished indicating that the chemical component of the synapse mediates this response. Attenuation of GAL4-mediated labelling by a cha-GAL80 transgene, reveals the GF to be cholinergic. We have used a temperature-sensitive allele of the choline acetyltransferase gene (chats2) to block cholinergic synapses in adult flies and this also abolished the long latency response in shak-B2 flies. Taken together the data provide evidence that both components of this mixed synapse are functional and that the chemical neurotransmitter between the GF and the TTMn is acetylcholine. Our findings show that the two components of this synapse can be separated to allow further studies into the mechanisms by which mixed synapses are built and function.
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Affiliation(s)
- Marcus J Allen
- Department of Biosciences, University of Kent, Canterbury, Kent, UK.
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523
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Boyan GS, Williams JLD. Embryonic development of a peripheral nervous system: nerve tract associated cells and pioneer neurons in the antenna of the grasshopper Schistocerca gregaria. ARTHROPOD STRUCTURE & DEVELOPMENT 2007; 36:336-350. [PMID: 18089112 DOI: 10.1016/j.asd.2007.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2006] [Revised: 01/12/2007] [Accepted: 01/31/2007] [Indexed: 05/25/2023]
Abstract
The grasshopper antenna is an articulated appendage associated with the deutocerebral segment of the head. In the early embryo, the meristal annuli of the antenna represent segment borders and are also the site of differentiation of pioneer cells which found the dorsal and ventral peripheral nerve tracts to the brain. We report here on another set of cells which appear earlier than the pioneers during development and are later found arrayed along these tracts at the border of epithelium and lumen. These so-called nerve tract associated cells differ morphologically from pioneers in that they are bipolar, have shorter processes, and are not segmentally organized in the antenna. Nerve tract associated cells do not express horseradish peroxidase and so are not classical neurons. They do not express antigens such as repo and annulin which are associated with glia cells in the nervous system. Nerve tract associated cells do, however, express the mesodermal/mesectodermal cell surface marker Mes-3 and putatively derive from the antennal coelom and then migrate to the epithelium/lumen border. Intracellular recordings show that such nerve tract associated cells have resting potentials similar to those of pioneer cells and can be dye coupled to the pioneers. Similar cell types are present in the maxilla, a serially homologous appendage on the head. The nerve tract associated cells are organized into a cellular scaffold which we speculate may be relevant to the navigation of pioneer and sensory axons in the early embryonic antennal nervous system.
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Affiliation(s)
- G S Boyan
- Developmental Neurobiology Group, Department of Biology II, Section of Neurobiology, Biozentrum, Ludwig-Maximilians-Universität, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany.
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524
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Khorkova O, Golowasch J. Neuromodulators, not activity, control coordinated expression of ionic currents. J Neurosci 2007; 27:8709-18. [PMID: 17687048 PMCID: PMC3558984 DOI: 10.1523/jneurosci.1274-07.2007] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Electrical activity in identical neurons across individuals is often remarkably similar and stable over long periods. However, the ionic currents that determine the electrical activity of these neurons show wide animal-to-animal amplitude variability. This seemingly random variability of individual current amplitudes may obscure mechanisms that globally reduce variability and that contribute to the generation of similar neuronal output. One such mechanism could be the coordinated regulation of ionic current expression. Studying identified neurons of the Cancer borealis pyloric network, we discovered that the removal of neuromodulatory input to this network (decentralization) was accompanied by the loss of the coordinated regulation of ionic current levels. Additionally, decentralization induced large changes in the levels of several ionic currents. The loss of coregulation and the changes in current levels were prevented by continuous exogenous application of proctolin, an endogenous neuromodulatory peptide, to the pyloric network. This peptide does not exert fast regulatory actions on any of the currents affected by decentralization. We conclude that neuromodulatory inputs to the pyloric network have a novel role in the regulation of ionic current expression. They can control, over the long term, the coordinated expression of multiple voltage-gated ionic currents that they do not acutely modulate. Our results suggest that current coregulation places constraints on neuronal intrinsic plasticity and the ability of a network to respond to perturbations. The loss of conductance coregulation may be a mechanism to facilitate the recovery of function.
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Affiliation(s)
| | - Jorge Golowasch
- Federated Department of Biological Sciences and
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102
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525
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Jia M, Li MX, Fields RD, Nelson PG. Extracellular ATP in activity-dependent remodeling of the neuromuscular junction. Dev Neurobiol 2007; 67:924-32. [PMID: 17506503 DOI: 10.1002/dneu.20402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Electrical activity during early development affects the development and maintenance of synapses (Spitzer [2006]: Nature 4447:707-712), but the intercellular signals regulating maintenance of synapses are not well identified. At the neuromuscular junction, adenosine 5-triphosphate (ATP) is coreleased with acetylcholine at activated nerve terminals to modulate synaptic function. Here we use cocultured mouse motor neurons and muscle cells in a three-compartment cell culture chamber to test whether endogenously released ATP plays a role in activity-dependent maintenance of neuromuscular synapses. The results suggest that ATP release at the synapse counters the negative effect of electrical activity, thus stabilizing activated synapses. Confirming our previous work (Li et al. [2001]: Nat Neurosci 4:871-872), we found that in doubly innervated muscles, electrical stimulation induced heterosynaptic downregulation of the nonstimulated convergent input to the muscle fiber with no or little change of the stimulated inputs. However, in preparations that were stimulated in the presence of apyrase, an enzyme that degrades extracellular ATP, synapse downregulation of stimulated inputs was substantial and significant, and end plate potentials were reduced. Apyrase treatment for 20 h in the absence of stimulation did result in moderate diminution, but this was prevented by blocking spontaneous neural activity with tetrodotoxin. The P2 receptor blocker, suramin, also induced activity-dependent synapse diminution. The decrease in synaptic efficacy produced by prolonged stimulation in the presence of apyrase persisted for greater than 20 h, consistent with a developmental time-course and distinct from the rapid neuromodulatory actions of ATP that have been demonstrated by others. We conclude that extracellular ATP promotes stabilization of the neuromuscular junction and may play a role in activity-dependent synaptic modification during development.
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Affiliation(s)
- Min Jia
- National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892, USA.
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526
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Reimers S, Hartlage-Rübsamen M, Brückner G, Rossner S. Formation of perineuronal nets in organotypic mouse brain slice cultures is independent of neuronal glutamatergic activity. Eur J Neurosci 2007; 25:2640-8. [PMID: 17561838 DOI: 10.1111/j.1460-9568.2007.05514.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Perineuronal nets (PNs) are a specialized form of the extracellular matrix and cover specific sets of neurons in distinct brain areas. Animal experiments on sensory visual deprivation have demonstrated that the generation of PNs around neurons of the visual cortex is dependent on neuronal activity during the critical period of visual experience. The importance of the activity of specific neurotransmitter systems for PN formation has, however, not yet been demonstrated. Based on the predominantly glutamatergic innervation of the visual cortex we hypothesized that reduced glutamatergic activity impairs the development of PNs. To address this question, genetic mouse models with compromised glutamate release [Munc13-1-knockout (KO) and Munc13-1/2 double-KO (DKO)] and chronic pharmacological treatments interfering with specific steps of glutamatergic transmission were used. Under experimental conditions of glutamatergic hypofunction PN formation was studied in organotypic brain slice cultures with Wisteria floribunda lectin binding and with aggrecan immunohistochemistry. After cultivation for 21 days a regular PN formation was observed in brain slices (i) derived from Munc13-1-KO and Munc13-1/2-DKO mice, (ii) after blockade of metabotropic and ionotropic glutamate receptors with MCPG and kynurenate, and (iii) after suppression of glutamate release by blockade of presynaptic Ca++ channels with riluzole. Nonselective suppression of neuronal activity by blockade of voltage-gated sodium channels with tetrodotoxin clearly inhibited PN formation. These results indicate that neuronal activity is required but that the glutamatergic system is not essential for PN development.
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Affiliation(s)
- Sabrina Reimers
- Paul Flechsig Institute for Brain Research, Department of Neurochemistry, University of Leipzig, Jahnallee 59, 04109 Leipzig, Germany
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527
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Mazzoni A, Broccard FD, Garcia-Perez E, Bonifazi P, Ruaro ME, Torre V. On the dynamics of the spontaneous activity in neuronal networks. PLoS One 2007; 2:e439. [PMID: 17502919 PMCID: PMC1857824 DOI: 10.1371/journal.pone.0000439] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Accepted: 04/17/2007] [Indexed: 11/18/2022] Open
Abstract
Most neuronal networks, even in the absence of external stimuli, produce spontaneous bursts of spikes separated by periods of reduced activity. The origin and functional role of these neuronal events are still unclear. The present work shows that the spontaneous activity of two very different networks, intact leech ganglia and dissociated cultures of rat hippocampal neurons, share several features. Indeed, in both networks: i) the inter-spike intervals distribution of the spontaneous firing of single neurons is either regular or periodic or bursting, with the fraction of bursting neurons depending on the network activity; ii) bursts of spontaneous spikes have the same broad distributions of size and duration; iii) the degree of correlated activity increases with the bin width, and the power spectrum of the network firing rate has a 1/f behavior at low frequencies, indicating the existence of long-range temporal correlations; iv) the activity of excitatory synaptic pathways mediated by NMDA receptors is necessary for the onset of the long-range correlations and for the presence of large bursts; v) blockage of inhibitory synaptic pathways mediated by GABA(A) receptors causes instead an increase in the correlation among neurons and leads to a burst distribution composed only of very small and very large bursts. These results suggest that the spontaneous electrical activity in neuronal networks with different architectures and functions can have very similar properties and common dynamics.
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Affiliation(s)
| | | | | | - Paolo Bonifazi
- International School for Advanced Studies, Trieste, Italy
| | | | - Vincent Torre
- International School for Advanced Studies, Trieste, Italy
- * To whom correspondence should be addressed. E-mail:
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528
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Slusarski DC, Pelegri F. Calcium signaling in vertebrate embryonic patterning and morphogenesis. Dev Biol 2007; 307:1-13. [PMID: 17531967 PMCID: PMC2729314 DOI: 10.1016/j.ydbio.2007.04.043] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 04/25/2007] [Accepted: 04/29/2007] [Indexed: 10/23/2022]
Abstract
Signaling pathways that rely on the controlled release and/or accumulation of calcium ions are important in a variety of developmental events in the vertebrate embryo, affecting cell fate specification and morphogenesis. One such major developmentally important pathway is the Wnt/calcium signaling pathway, which, through its antagonism of Wnt/beta-catenin signaling, appears to regulate the formation of the early embryonic organizer. In addition, the Wnt/calcium pathway shares components with another non-canonical Wnt pathway involved in planar cell polarity, suggesting that these two pathways form a loose network involved in polarized cell migratory movements that fashion the vertebrate body plan. Furthermore, left-right axis determination, neural induction and somite formation also display dynamic calcium release, which may be critical in these patterning events. Finally, we summarize recent evidence that propose a role for calcium signaling in stem cell biology and human developmental disorders.
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Affiliation(s)
- Diane C. Slusarski
- Department of Biological Sciences, University of Iowa, Iowa City, IA 52242, Phone: 319.335.3229, FAX: 319.335.1069,
| | - Francisco Pelegri
- Laboratory of Genetics, University of Wisconsin – Madison, Madison, WI 53706, Phone: 608.265.9286, FAX: 608.262.2976,
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529
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Crandall SR, Adam M, Kinnischtzke AK, Nick TA. HVC neural sleep activity increases with development and parallels nightly changes in song behavior. J Neurophysiol 2007; 98:232-40. [PMID: 17428907 PMCID: PMC2268767 DOI: 10.1152/jn.00128.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sleep abnormalities are coexpressed with human communication disorders. Recent data from the birdsong system, the best model for human speech, indicate that sleep has a critical role in vocal learning. To understand the neural mechanisms that underlie behavioral changes during sleep, we recorded sleep activity in the song control area HVC longitudinally during song development in zebra finches. We focused on the sensorimotor phase of song learning, when the finch shapes his song behavior toward a learned tutor song model. Direct comparison of sleep activity in adults and juveniles revealed that the juvenile HVC has a lower spike rate and longer silent periods than the adult. Within individual finches, sleep silent periods decreased and spike rate increased with age. We next systematically compared neural sleep activity and song behavior. We now report that spike rate during sleep was significantly correlated with overnight changes in song behavior. Collectively, these data indicate that sleep activity in the vocal control area HVC increases with age and may affect song behavior.
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Affiliation(s)
- Shane R Crandall
- University of Minnesota, Department of Neuroscience and Center for Neurobehavioral Development, 6-145 Jackson Hall, Minneapolis, MN 55455, USA
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530
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Mizrahi A. Dendritic development and plasticity of adult-born neurons in the mouse olfactory bulb. Nat Neurosci 2007; 10:444-52. [PMID: 17369823 DOI: 10.1038/nn1875] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Accepted: 02/21/2007] [Indexed: 11/09/2022]
Abstract
The mammalian brain maintains few developmental niches where neurogenesis persists into adulthood. One niche is located in the olfactory system where the olfactory bulb continuously receives functional interneurons. In vivo two-photon microscopy of lentivirus-labeled newborn neurons was used to directly image their development and maintenance in the olfactory bulb. Time-lapse imaging of newborn neurons over several days showed that dendritic formation is highly dynamic with distinct differences between spiny neurons and non-spiny neurons. Once incorporated into the network, adult-born neurons maintain significant levels of structural dynamics. This structural plasticity is local, cumulative and sustained in neurons several months after their integration. Thus, I provide a new experimental system for directly studying the pool of regenerating neurons in the intact mammalian brain and suggest that regenerating neurons form a cellular substrate for continuous wiring plasticity in the olfactory bulb.
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Affiliation(s)
- Adi Mizrahi
- Department of Neurobiology, Institue for Life Sciences and the Interdisciplinary Center for Neural Computation, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
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531
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Valor LM, Charlesworth P, Humphreys L, Anderson CNG, Grant SGN. Network activity-independent coordinated gene expression program for synapse assembly. Proc Natl Acad Sci U S A 2007; 104:4658-63. [PMID: 17360580 PMCID: PMC1810326 DOI: 10.1073/pnas.0609071104] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Global biological datasets generated by genomics, transcriptomics, and proteomics provide new approaches to understanding the relationship between the genome and the synapse. Combined transcriptome analysis and multielectrode recordings of neuronal network activity were used in mouse embryonic primary neuronal cultures to examine synapse formation and activity-dependent gene regulation. Evidence for a coordinated gene expression program for assembly of synapses was observed in the expression of 642 genes encoding postsynaptic and plasticity proteins. This synaptogenesis gene expression program preceded protein expression of synapse markers and onset of spiking activity. Continued expression was followed by maturation of morphology and electrical neuronal networks, which was then followed by the expression of activity-dependent genes. Thus, two distinct sequentially active gene expression programs underlie the genomic programs of synapse function.
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Affiliation(s)
- Luis M. Valor
- Genes to Cognition Programme, The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom
| | - Paul Charlesworth
- Genes to Cognition Programme, The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom
| | - Lawrence Humphreys
- Genes to Cognition Programme, The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom
| | - Chris N. G. Anderson
- Genes to Cognition Programme, The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom
| | - Seth G. N. Grant
- Genes to Cognition Programme, The Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom
- *To whom correspondence should be addressed. E-mail:
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532
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Abstract
Neuronal motility is a fundamental feature that underlies the development, regeneration, and plasticity of the nervous system. Two major developmental events--directed migration of neuronal precursor cells to the proper positions and guided elongation of axons to their target cells--depend on large-scale neuronal motility. At a finer scale, motility is also manifested in many aspects of neuronal structures and functions, ranging from differentiation and refinement of axonal and dendritic morphology during development to synapse remodeling associated with learning and memory in the adult brain. As a primary second messenger that conveys the cytoplasmic actions of electrical activity and many neuroactive ligands, Ca(2+) plays a central role in the regulation of neuronal motility. Recent studies have revealed common Ca(2+)-dependent signaling pathways that are deployed for regulating cytoskeletal dynamics associated with neuronal migration, axon and dendrite development and regeneration, and synaptic plasticity.
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Affiliation(s)
- James Q Zheng
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
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