1
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So YH, Shin HS, Lee SH, Moon HJ, Jang HJ, Lee EH, Jung EM. Maternal exposure to polystyrene microplastics impairs social behavior in mouse offspring with a potential neurotoxicity. Neurotoxicology 2023; 99:206-216. [PMID: 37918694 DOI: 10.1016/j.neuro.2023.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 11/04/2023]
Abstract
As plastic production has been increasing steadily, environmental pollution resulting from microplastics (MPs) continues to draw considerable attention of the researchers. Several studies have reported that MPs are risk factors for various cellular and systemic dysfunctions. However, the effects of chronic MP exposure from the embryonic stage to adulthood on mouse brain remain unclear. Accordingly, determining the impacts of maternal exposure to MPs on mouse offspring was the main goal of this study. To this end, single cells of primary cortical neurons were isolated from mouse embryos. Subsequently, the cells were exposed to 2 µm polystyrene microplastics (PS-MPs), which resulted in a notable reduction in dendritic length, and PS-MPs cannot pass through the cellular membrane of neurons. Moreover, exposure to PS-MPs caused the proliferation increase and apoptosis in primary cortical neuronal cells. We then evaluated the neurotoxicity associated with chronic PS-MP exposure from the embryonic stage to adulthood in C57BL/6 J mouse offspring. PS-MPs were found to accumulate in the digestive and excretory organs of the offspring but not in the brain tissue. However, offspring exposed to PS-MPs exhibited no differences in the levels of expression of genes related to brain cell markers or synaptic organization. Nevertheless, PS-MP-exposed mice exhibited impaired social novelty preferences; however, no changes were observed in the emotional, compulsive, or cognitive behaviors. Taken together, these results demonstrate the potential neurotoxic effects of chronic exposure to PS-MPs in mouse offspring.
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Affiliation(s)
- Yun Hee So
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
| | - Hyun Seung Shin
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
| | - Seung Hyun Lee
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
| | - Ha Jung Moon
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
| | - Hyeon Jung Jang
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
| | - Eun-Hee Lee
- Department of Microbiology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
| | - Eui-Man Jung
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea.
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2
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Acutain MF, Baez MV. Reduced expression of GluN2A induces a delay in neuron maturation. J Neurochem 2023. [PMID: 38037434 DOI: 10.1111/jnc.16023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 11/13/2023] [Accepted: 11/15/2023] [Indexed: 12/02/2023]
Abstract
NMDA receptors (NMDARs) play an important role in synaptic plasticity both in physiological and pathological conditions. GluN2A and GluN2B are the most expressed NMDAR regulatory subunits, in the hippocampus and other cognitive-related brain structures. GluN2B is characteristic of immature structures and GluN2A of mature ones. Changes in GluN2A expression were associated with complex phenotypes that led to complex neurodevelopmental disorders, including the occurrence of seizures. However, little is known about the role of GluN2A in these phenotypes. In this work, we reduced GluN2A expression in mature neuronal cultures and observed an altered GluN2A/GluN2B ratio. Furthermore, those neurons exhibit an increase in immature dendritic spines and dendritic branching, as well as an increased response to glutamate stimulus. This phenotype (considering GluN2A/GluN2B ratio, index branching and glutamate response) resembles those observed at immature neuronal stages in vitro. We propose that this immature phenotype led to a higher response to glutamate stimulus which, in vivo, would be the basis of reduced threshold for seizure onset in GluN2A-pathological conditions.
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Affiliation(s)
- María Florencia Acutain
- Laboratorio de Sinapsis y Neurobiología Celular, Instituto de Biología Celular y Neurociencia (IBCN)-CONICET-UBA, Ciudad de Buenos Aires, Argentina
| | - María Verónica Baez
- Laboratorio de Sinapsis y Neurobiología Celular, Instituto de Biología Celular y Neurociencia (IBCN)-CONICET-UBA, Ciudad de Buenos Aires, Argentina
- 1UA de Histología, Embriología, Biología Celular y Genética, Facultad de Medicina, UBA, Ciudad de Buenos Aires, Argentina
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3
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Dutta SB, Linneweber GA, Andriatsilavo M, Hiesinger PR, Hassan BA. EGFR-dependent suppression of synaptic autophagy is required for neuronal circuit development. Curr Biol 2023; 33:517-532.e5. [PMID: 36640763 DOI: 10.1016/j.cub.2022.12.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 10/31/2022] [Accepted: 12/14/2022] [Indexed: 01/15/2023]
Abstract
The development of neuronal connectivity requires stabilization of dynamic axonal branches at sites of synapse formation. Models that explain how axonal branching is coupled to synaptogenesis postulate molecular regulators acting in a spatiotemporally restricted fashion to ensure branching toward future synaptic partners while also stabilizing the emerging synaptic contacts between such partners. We investigated this question using neuronal circuit development in the Drosophila brain as a model system. We report that epidermal growth factor receptor (EGFR) activity is required in presynaptic axonal branches during two distinct temporal intervals to regulate circuit wiring in the developing Drosophila visual system. EGFR is required early to regulate primary axonal branching. EGFR activity is then independently required at a later stage to prevent degradation of the synaptic active zone protein Bruchpilot (Brp). Inactivation of EGFR results in a local increase of autophagy in presynaptic branches and the translocation of active zone proteins into autophagic vesicles. The protection of synaptic material during this later interval of wiring ensures the stabilization of terminal branches, circuit connectivity, and appropriate visual behavior. Phenotypes of EGFR inactivation can be rescued by increasing Brp levels or downregulating autophagy. In summary, we identify a temporally restricted molecular mechanism required for coupling axonal branching and synaptic stabilization that contributes to the emergence of neuronal wiring specificity.
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Affiliation(s)
- Suchetana B Dutta
- Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié Salpêtrière, 75013 Paris, France; Division of Neurobiology, Free University of Berlin, 14195 Berlin, Germany; Einstein-BIH, Charité Universitätsmedizin, 10117 Berlin, Germany
| | | | - Maheva Andriatsilavo
- Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié Salpêtrière, 75013 Paris, France; Division of Neurobiology, Free University of Berlin, 14195 Berlin, Germany; Einstein-BIH, Charité Universitätsmedizin, 10117 Berlin, Germany
| | | | - Bassem A Hassan
- Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié Salpêtrière, 75013 Paris, France; Division of Neurobiology, Free University of Berlin, 14195 Berlin, Germany; Einstein-BIH, Charité Universitätsmedizin, 10117 Berlin, Germany.
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4
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Hsieh MY, Tuan LH, Chang HC, Wang YC, Chen CH, Shy HT, Lee LJ, Gau SSF. Altered synaptic protein expression, aberrant spine morphology, and impaired spatial memory in Dlgap2 mutant mice, a genetic model of autism spectrum disorder. Cereb Cortex 2022; 33:4779-4793. [PMID: 36169576 DOI: 10.1093/cercor/bhac379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 11/14/2022] Open
Abstract
A microdeletion of approximately 2.4 Mb at the 8p23 terminal region has been identified in a Taiwanese autistic boy. Among the products transcribed/translated from genes mapped in this region, the reduction of DLGAP2, a postsynaptic scaffold protein, might be involved in the pathogenesis of autism spectrum disorder (ASD). DLGAP2 protein was detected in the hippocampus yet abolished in homozygous Dlgap2 knockout (Dlgap2 KO) mice. In this study, we characterized the hippocampal phenotypes in Dlgap2 mutant mice. Dlgap2 KO mice exhibited impaired spatial memory, indicating poor hippocampal function in the absence of DLGAP2. Aberrant expressions of postsynaptic proteins, including PSD95, SHANK3, HOMER1, GluN2A, GluR2, mGluR1, mGluR5, βCAMKII, ERK1/2, ARC, BDNF, were noticed in Dlgap2 mutant mice. Further, the spine density was increased in Dlgap2 KO mice, while the ratio of mushroom-type spines was decreased. We also observed a thinner postsynaptic density thickness in Dlgap2 KO mice at the ultrastructural level. These structural changes found in the hippocampus of Dlgap2 KO mice might be linked to impaired hippocampus-related cognitive functions such as spatial memory. Mice with Dlgap2 deficiency, showing signs of intellectual disability, a common co-occurring condition in patients with ASD, could be a promising animal model which may advance our understanding of ASD.
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Affiliation(s)
- Ming-Yen Hsieh
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Li-Heng Tuan
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan.,School of Medicine, National Tsing Hua University, Hsinchu, Taiwan.,Institute of Systems Neuroscience, National Tsing Hua University, Hsinchu, Taiwan.,Department of Medical Science, National Tsing Hua University, Hsinchu, Taiwan
| | - Ho-Ching Chang
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Yu-Chun Wang
- Department of Otolaryngology, Head and Neck Surgery, Chi-Mei Medical Center, Tainan, Taiwan
| | - Chia-Hsiang Chen
- Department of Psychiatry, Chang Gung Memorial Hospital-Linkou, Taoyuan, Taiwan
| | - Horng-Tzer Shy
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Li-Jen Lee
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan.,Institute of Brain and Mind Sciences, National Taiwan University College of Medicine, Taipei, Taiwan.,Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
| | - Susan Shur-Fen Gau
- Institute of Brain and Mind Sciences, National Taiwan University College of Medicine, Taipei, Taiwan.,Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan.,Department of Psychiatry, National Taiwan University Hospital, Taipei, Taiwan
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5
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Bhandari A, Ward TW, Smith J, Van Hook MJ. Structural and functional plasticity in the dorsolateral geniculate nucleus of mice following bilateral enucleation. Neuroscience 2022; 488:44-59. [PMID: 35131394 PMCID: PMC8960354 DOI: 10.1016/j.neuroscience.2022.01.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Accepted: 01/31/2022] [Indexed: 02/08/2023]
Abstract
Within the nervous system, plasticity mechanisms attempt to stabilize network activity following disruption by injury, disease, or degeneration. Optic nerve injury and age-related diseases can induce homeostatic-like responses in adulthood. We tested this possibility in the thalamocortical (TC) neurons in the dorsolateral geniculate nucleus (dLGN) using patch-clamp electrophysiology, optogenetics, immunostaining, and single-cell dendritic analysis following loss of visual input via bilateral enucleation. We observed progressive loss of vGlut2-positive retinal terminals in the dLGN indicating degeneration post-enucleation that was coincident with changes in microglial morphology indicative of microglial activation. Consistent with the decline of vGlut2 puncta, we also observed loss of retinogeniculate (RG) synaptic function assessed using optogenetic activation of RG axons while performing whole-cell voltage clamp recordings from TC neurons in brain slices. Surprisingly, we did not detect any significant changes in the frequency of miniature post-synaptic currents (mEPSCs) or corticothalamic feedback synapses. Analysis of TC neuron dendritic structure from single-cell dye fills revealed a gradual loss of dendrites proximal to the soma, where TC neurons receive the bulk of RG inputs. Finally, analysis of action potential firing demonstrated that TC neurons have increased excitability following enucleation, firing more action potentials in response to depolarizing current injections. Our findings show that degeneration of the retinal axons/optic nerve and loss of RG synaptic inputs induces structural and functional changes in TC neurons, consistent with neuronal attempts at compensatory plasticity in the dLGN.
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6
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Durand J, Filipchuk A. Electrical and Morphological Properties of Developing Motoneurons in Postnatal Mice and Early Abnormalities in SOD1 Transgenic Mice. ADVANCES IN NEUROBIOLOGY 2022; 28:353-373. [PMID: 36066832 DOI: 10.1007/978-3-031-07167-6_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In this chapter, we review electrical and morphological properties of lumbar motoneurons during postnatal development in wild-type (WT) and transgenic superoxide dismutase 1 (SOD1) mice, models of amyotrophic lateral sclerosis. First we showed that sensorimotor reflexes do not develop normally in transgenic SOD1G85R pups. Fictive locomotor activity recorded in in vitro whole brainstem/spinal cord preparations was not induced in these transgenic SOD1G85R mice using NMDA and 5HT in contrast to WT mice. Further, abnormal electrical properties were detected as early as the second postnatal week in lumbar motoneurons of SOD1 mice while they develop clinical symptoms several months after birth. We compared two different strains of mice (G85R and G93A) at the same postnatal period using intracellular recordings and patch clamp recordings of WT and SOD1 motoneurons. We defined three types of motoneurons according to their discharge firing pattern (transient, sustained and delayed onset firing) when motor units are not yet mature. The delayed-onset firing motoneurons had the higher rheobase compared to the transient and sustained firing groups in the WT mice. We demonstrated hypoexcitability in the delayed onset-firing motoneurons of SOD1 mice. Intracellular staining of motoneurons revealed dendritic overbranching in SOD1 lumbar motoneurons that was more pronounced in the sustained firing motoneurons. We suggested that motoneuronal hypoexcitability is an early pathological sign affecting a subset of lumbar motoneurons in the spinal cord of SOD1 mice.
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Affiliation(s)
- Jacques Durand
- Institut de Neurosciences de la Timone (INT) P3M team, Aix Marseille Université, Marseille, cedex 05, France.
| | - Anton Filipchuk
- Department for Integrative and Computational Neuroscience (ICN), Paris-Saclay Institute of Neuroscience (NeuroPSI), Gif-sur-Yvette, France
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7
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Intrauterine hyperglycemia impairs memory across two generations. Transl Psychiatry 2021; 11:434. [PMID: 34417446 PMCID: PMC8379206 DOI: 10.1038/s41398-021-01565-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/27/2021] [Accepted: 08/10/2021] [Indexed: 12/22/2022] Open
Abstract
Studies on humans and animals suggest associations between gestational diabetes mellitus (GDM) with increased susceptibility to develop neurological disorders in offspring. However, the molecular mechanisms underpinning the intergenerational effects remain unclear. Using a mouse model of diabetes during pregnancy, we found that intrauterine hyperglycemia exposure resulted in memory impairment in both the first filial (F1) males and the second filial (F2) males from the F1 male offspring. Transcriptome profiling of F1 and F2 hippocampi revealed that differentially expressed genes (DEGs) were enriched in neurodevelopment and synaptic plasticity. The reduced representation bisulfite sequencing (RRBS) of sperm in F1 adult males showed that the intrauterine hyperglycemia exposure caused altered methylated modification of F1 sperm, which is a potential epigenetic mechanism for the intergenerational neurocognitive effects of GDM.
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8
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Koebis M, Urata S, Shinoda Y, Okabe S, Yamasoba T, Nakao K, Aiba A, Furuichi T. LAMP5 in presynaptic inhibitory terminals in the hindbrain and spinal cord: a role in startle response and auditory processing. Mol Brain 2019; 12:20. [PMID: 30867010 PMCID: PMC6416879 DOI: 10.1186/s13041-019-0437-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Accepted: 02/25/2019] [Indexed: 11/10/2022] Open
Abstract
Lysosome-associated membrane protein 5 (LAMP5) is a mammalian ortholog of the Caenorhabditis elegans protein, UNC-46, which functions as a sorting factor to localize the vesicular GABA transporter UNC-47 to synaptic vesicles. In the mouse forebrain, LAMP5 is expressed in a subpopulation of GABAergic neurons in the olfactory bulb and the striato-nigral system, where it is required for fine-tuning of GABAergic synaptic transmission. Here we focus on the prominent expression of LAMP5 in the brainstem and spinal cord and suggest a role for LAMP5 in these brain regions. LAMP5 was highly expressed in several brainstem nuclei involved with auditory processing including the cochlear nuclei, the superior olivary complex, nuclei of the lateral lemniscus and grey matter in the spinal cord. It was localized exclusively in inhibitory synaptic terminals, as has been reported in the forebrain. In the absence of LAMP5, localization of the vesicular inhibitory amino acid transporter (VIAAT) was unaltered in the lateral superior olive and the ventral cochlear nuclei, arguing against a conserved role for LAMP5 in trafficking VIAAT. Lamp5 knockout mice showed no overt behavioral abnormality but an increased startle response to auditory and tactile stimuli. In addition, LAMP5 deficiency led to a larger intensity-dependent increase of wave I, II and V peak amplitude of auditory brainstem response. Our results indicate that LAMP5 plays a pivotal role in sensorimotor processing in the brainstem and spinal cord.
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Affiliation(s)
- Michinori Koebis
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033 Japan
| | - Shinji Urata
- Department of Otolaryngology, Faculty of Medicine, The University of Tokyo, Tokyo, 113-8655 Japan
| | - Yo Shinoda
- Department of Environmental Health, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Tokyo, 192-0392 Japan
| | - Shigeo Okabe
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033 Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology, Faculty of Medicine, The University of Tokyo, Tokyo, 113-8655 Japan
| | - Kazuki Nakao
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033 Japan
| | - Atsu Aiba
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033 Japan
| | - Teiichi Furuichi
- Department of Applied Biological Sciences, Tokyo University of Science, Chiba, 278-8510 Japan
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9
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Lira M, Arancibia D, Orrego PR, Montenegro-Venegas C, Cruz Y, García J, Leal-Ortiz S, Godoy JA, Gundelfinger ED, Inestrosa NC, Garner CC, Zamorano P, Torres VI. The Exocyst Component Exo70 Modulates Dendrite Arbor Formation, Synapse Density, and Spine Maturation in Primary Hippocampal Neurons. Mol Neurobiol 2018; 56:4620-4638. [DOI: 10.1007/s12035-018-1378-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 10/01/2018] [Indexed: 02/07/2023]
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10
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Sheng C, Javed U, Gibbs M, Long C, Yin J, Qin B, Yuan Q. Experience-dependent structural plasticity targets dynamic filopodia in regulating dendrite maturation and synaptogenesis. Nat Commun 2018; 9:3362. [PMID: 30135566 PMCID: PMC6105721 DOI: 10.1038/s41467-018-05871-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 07/27/2018] [Indexed: 11/21/2022] Open
Abstract
Highly motile dendritic protrusions are hallmarks of developing neurons. These exploratory filopodia sample the environment and initiate contacts with potential synaptic partners. To understand the role for dynamic filopodia in dendrite morphogenesis and experience-dependent structural plasticity, we analyzed dendrite dynamics, synapse formation, and dendrite volume expansion in developing ventral lateral neurons (LNvs) of the Drosophila larval visual circuit. Our findings reveal the temporal coordination between heightened dendrite dynamics with synaptogenesis in LNvs and illustrate the strong influence imposed by sensory experience on the prevalence of dendritic filopodia, which regulate the formation of synapses and the expansion of dendritic arbors. Using genetic analyses, we further identified Amphiphysin (Amph), a BAR (Bin/Amphiphysin/Rvs) domain-containing protein as a required component for tuning the dynamic state of LNv dendrites and promoting dendrite maturation. Taken together, our study establishes dynamic filopodia as the key cellular target for experience-dependent regulation of dendrite development. During development, dendrites display structural plasticity, as reflected in the appearance of long, thin and highly motile dendritic filopodia. Here, the authors examine dendritic dynamics of ventral lateral neurons in the developing Drosophila larva, and identify Amphiphysin as an important regulator of this process.
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Affiliation(s)
- Chengyu Sheng
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Uzma Javed
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mary Gibbs
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Caixia Long
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jun Yin
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Bo Qin
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Quan Yuan
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA.
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11
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Inoue N, Nishizumi H, Naritsuka H, Kiyonari H, Sakano H. Sema7A/PlxnCl signaling triggers activity-dependent olfactory synapse formation. Nat Commun 2018; 9:1842. [PMID: 29743476 PMCID: PMC5943276 DOI: 10.1038/s41467-018-04239-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 04/13/2018] [Indexed: 11/17/2022] Open
Abstract
In mammals, neural circuits are formed based on a genetic program and further refined by neuronal activity during the neonatal period. We report that in the mouse olfactory system, the glomerular map is not merely refined but newly connected to second-order neurons by odorant-receptor-derived neuronal activity. Here, we analyzed a pair of molecules, Sema7A, expressed in olfactory sensory neurons (OSNs) in an activity-dependent manner, and PlxnC1, localized to dendrites of mitral/tufted (M/T) cells in the first week after birth. In Sema7A or PlxnC1 knockout (KO) mice, initiation of synapse formation and dendrite selection of M/T cells were perturbed. Reconstitution and rescue experiments demonstrated that Sema7A-PlxnC1 interaction is essential to form the post-synaptic assembly. Pharmacological blocking experiments indicated that synaptic transmission triggers primary dendrite selection by synaptic competition. We conclude that Sema7A signaling is key to inducing activity-dependent post-synapse events and dendrite selection in M/T-cells during the neonatal period.
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Affiliation(s)
- Nobuko Inoue
- Department of Brain Function, University of Fukui School of Medicine, 23-3 Shimo-aizuki, Matsuoka, Fukui, 910-1193, Japan
| | - Hirofumi Nishizumi
- Department of Brain Function, University of Fukui School of Medicine, 23-3 Shimo-aizuki, Matsuoka, Fukui, 910-1193, Japan
| | - Hiromi Naritsuka
- Department of Physiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hiroshi Kiyonari
- RIKEN Institute, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Hitoshi Sakano
- Department of Brain Function, University of Fukui School of Medicine, 23-3 Shimo-aizuki, Matsuoka, Fukui, 910-1193, Japan.
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12
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Constance WD, Mukherjee A, Fisher YE, Pop S, Blanc E, Toyama Y, Williams DW. Neurexin and Neuroligin-based adhesion complexes drive axonal arborisation growth independent of synaptic activity. eLife 2018; 7:31659. [PMID: 29504935 PMCID: PMC5869020 DOI: 10.7554/elife.31659] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 03/04/2018] [Indexed: 11/25/2022] Open
Abstract
Building arborisations of the right size and shape is fundamental for neural network function. Live imaging in vertebrate brains strongly suggests that nascent synapses are critical for branch growth during development. The molecular mechanisms underlying this are largely unknown. Here we present a novel system in Drosophila for studying the development of complex arborisations live, in vivo during metamorphosis. In growing arborisations we see branch dynamics and localisations of presynaptic proteins very similar to the ‘synaptotropic growth’ described in fish/frogs. These accumulations of presynaptic proteins do not appear to be presynaptic release sites and are not paired with neurotransmitter receptors. Knockdowns of either evoked or spontaneous neurotransmission do not impact arbor growth. Instead, we find that axonal branch growth is regulated by dynamic, focal localisations of Neurexin and Neuroligin. These adhesion complexes provide stability for filopodia by a ‘stick-and-grow’ based mechanism wholly independent of synaptic activity.
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Affiliation(s)
- William D Constance
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom.,King's-NUS Joint Studentship Program, King's College London, London, United Kingdom
| | - Amrita Mukherjee
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom
| | - Yvette E Fisher
- Department of Neurobiology, Stanford University, Stanford, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Sinziana Pop
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom
| | - Eric Blanc
- Berlin Institute of Health, Berlin, Germany
| | - Yusuke Toyama
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore.,Temasek Life Sciences Laboratory, Singapore, Singapore.,Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Darren W Williams
- Centre for Developmental Neurobiology, King's College London, London, United Kingdom
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13
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Kutsarova E, Munz M, Ruthazer ES. Rules for Shaping Neural Connections in the Developing Brain. Front Neural Circuits 2017; 10:111. [PMID: 28119574 PMCID: PMC5223306 DOI: 10.3389/fncir.2016.00111] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 12/16/2016] [Indexed: 11/13/2022] Open
Abstract
It is well established that spontaneous activity in the developing mammalian brain plays a fundamental role in setting up the precise connectivity found in mature sensory circuits. Experiments that produce abnormal activity or that systematically alter neural firing patterns during periods of circuit development strongly suggest that the specific patterns and the degree of correlation in firing may contribute in an instructive manner to circuit refinement. In fish and amphibians, unlike amniotic vertebrates, sensory input directly drives patterned activity during the period of initial projection outgrowth and innervation. Experiments combining sensory stimulation with live imaging, which can be performed non-invasively in these simple vertebrate models, have provided important insights into the mechanisms by which neurons read out and respond to activity patterns. This article reviews the classic and recent literature on spontaneous and evoked activity-dependent circuit refinement in sensory systems and formalizes a set of mechanistic rules for the transformation of patterned activity into accurate neuronal connectivity in the developing brain.
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Affiliation(s)
- Elena Kutsarova
- Montreal Neurological Institute, McGill University Montreal, QC, Canada
| | - Martin Munz
- Friedrich Miescher Institute, Neurobiology Group Basel, Switzerland
| | - Edward S Ruthazer
- Montreal Neurological Institute, McGill University Montreal, QC, Canada
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Impairments in dendrite morphogenesis as etiology for neurodevelopmental disorders and implications for therapeutic treatments. Neurosci Biobehav Rev 2016; 68:946-978. [PMID: 27143622 DOI: 10.1016/j.neubiorev.2016.04.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 04/13/2016] [Accepted: 04/13/2016] [Indexed: 02/08/2023]
Abstract
Dendrite morphology is pivotal for neural circuitry functioning. While the causative relationship between small-scale dendrite morphological abnormalities (shape, density of dendritic spines) and neurodevelopmental disorders is well established, such relationship remains elusive for larger-scale dendrite morphological impairments (size, shape, branching pattern of dendritic trees). Here, we summarize published data on dendrite morphological irregularities in human patients and animal models for neurodevelopmental disorders, with focus on autism and schizophrenia. We next discuss high-risk genes for these disorders and their role in dendrite morphogenesis. We finally overview recent developments in therapeutic attempts and we discuss how they relate to dendrite morphology. We find that both autism and schizophrenia are accompanied by dendritic arbor morphological irregularities, and that majority of their high-risk genes regulate dendrite morphogenesis. Thus, we present a compelling argument that, along with smaller-scale morphological impairments in dendrites (spines and synapse), irregularities in larger-scale dendrite morphology (arbor shape, size) may be an important part of neurodevelopmental disorders' etiology. We suggest that this should not be ignored when developing future therapeutic treatments.
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Emerging Roles of Filopodia and Dendritic Spines in Motoneuron Plasticity during Development and Disease. Neural Plast 2015; 2016:3423267. [PMID: 26843990 PMCID: PMC4710938 DOI: 10.1155/2016/3423267] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 09/10/2015] [Accepted: 09/21/2015] [Indexed: 01/16/2023] Open
Abstract
Motoneurons develop extensive dendritic trees for receiving excitatory and inhibitory synaptic inputs to perform a variety of complex motor tasks. At birth, the somatodendritic domains of mouse hypoglossal and lumbar motoneurons have dense filopodia and spines. Consistent with Vaughn's synaptotropic hypothesis, we propose a developmental unified-hybrid model implicating filopodia in motoneuron spinogenesis/synaptogenesis and dendritic growth and branching critical for circuit formation and synaptic plasticity at embryonic/prenatal/neonatal period. Filopodia density decreases and spine density initially increases until postnatal day 15 (P15) and then decreases by P30. Spine distribution shifts towards the distal dendrites, and spines become shorter (stubby), coinciding with decreases in frequency and increases in amplitude of excitatory postsynaptic currents with maturation. In transgenic mice, either overexpressing the mutated human Cu/Zn-superoxide dismutase (hSOD1G93A) gene or deficient in GABAergic/glycinergic synaptic transmission (gephyrin, GAD-67, or VGAT gene knockout), hypoglossal motoneurons develop excitatory glutamatergic synaptic hyperactivity. Functional synaptic hyperactivity is associated with increased dendritic growth, branching, and increased spine and filopodia density, involving actin-based cytoskeletal and structural remodelling. Energy-dependent ionic pumps that maintain intracellular sodium/calcium homeostasis are chronically challenged by activity and selectively overwhelmed by hyperactivity which eventually causes sustained membrane depolarization leading to excitotoxicity, activating microglia to phagocytose degenerating neurons under neuropathological conditions.
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El-Danaf RN, Krahe TE, Dilger EK, Bickford ME, Fox MA, Guido W. Developmental remodeling of relay cells in the dorsal lateral geniculate nucleus in the absence of retinal input. Neural Dev 2015; 10:19. [PMID: 26174426 PMCID: PMC4502538 DOI: 10.1186/s13064-015-0046-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 07/01/2015] [Indexed: 12/01/2022] Open
Abstract
Background The dorsal lateral geniculate nucleus (dLGN) of the mouse has been an important experimental model for understanding thalamic circuit development. The developmental remodeling of retinal projections has been the primary focus, however much less is known about the maturation of their synaptic targets, the relay cells of the dLGN. Here we examined the growth and maturation of relay cells during the first few weeks of life and addressed whether early retinal innervation affects their development. To accomplish this we utilized the math5 null (math5−/−) mouse, a mutant lacking retinal ganglion cells and central projections. Results The absence of retinogeniculate axon innervation led to an overall shrinkage of dLGN and disrupted the pattern of dendritic growth among developing relay cells. 3-D reconstructions of biocytin filled neurons from math5−/− mice showed that in the absence of retinal input relay cells undergo a period of exuberant dendritic growth and branching, followed by branch elimination and an overall attenuation in dendritic field size. However, math5−/− relay cells retained a sufficient degree of complexity and class specificity, as well as their basic membrane properties and spike firing characteristics. Conclusions Retinal innervation plays an important trophic role in dLGN development. Additional support perhaps arising from non-retinal innervation and signaling is likely to contribute to the stabilization of their dendritic form and function.
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Affiliation(s)
- Rana N El-Danaf
- Departments of Neuroscience, Neurobiology Section in the Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Thomas E Krahe
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Center, Richmond, VA, 23298, USA.
| | | | - Martha E Bickford
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, 40292, USA.
| | - Michael A Fox
- Virginia Tech Carilion Research Institute, Roanoke, VA, 24016, USA. .,Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA.
| | - William Guido
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, 40292, USA.
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Keeler AB, Molumby MJ, Weiner JA. Protocadherins branch out: Multiple roles in dendrite development. Cell Adh Migr 2015; 9:214-26. [PMID: 25869446 DOI: 10.1080/19336918.2014.1000069] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The proper formation of dendritic arbors is a critical step in neural circuit formation, and as such defects in arborization are associated with a variety of neurodevelopmental disorders. Among the best gene candidates are those encoding cell adhesion molecules, including members of the diverse cadherin superfamily characterized by distinctive, repeated adhesive domains in their extracellular regions. Protocadherins (Pcdhs) make up the largest group within this superfamily, encompassing over 80 genes, including the ∼60 genes of the α-, β-, and γ-Pcdh gene clusters and the non-clustered δ-Pcdh genes. An additional group includes the atypical cadherin genes encoding the giant Fat and Dachsous proteins and the 7-transmembrane cadherins. In this review we highlight the many roles that Pcdhs and atypical cadherins have been demonstrated to play in dendritogenesis, dendrite arborization, and dendritic spine regulation. Together, the published studies we discuss implicate these members of the cadherin superfamily as key regulators of dendrite development and function, and as potential therapeutic targets for future interventions in neurodevelopmental disorders.
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Key Words
- CNR, Cadherin related neuronal receptor
- CTCF, CCCTC-binding factor
- CaMKII, Ca2+/calmodulin-dependent protein kinase II.
- Celsr, Cadherin EGF LAG 7-pass G-type receptor 1
- DSCAM, Down syndrome cell adhesion molecule
- Dnmt3b, DNA (cytosine-5-)-methyltransferase 3 β
- Ds, Dachsous
- EC, extracellular cadherin
- EGF, Epidermal growth factor
- FAK, Focal adhesion kinase
- FMRP, Fragile X mental retardation protein
- Fj, Four jointed
- Fjx1, Four jointed box 1
- GPCR, G-protein-coupled receptor
- Gogo, Golden Goal
- LIM domain, Lin11, Isl-1 & Mec-3 domain
- MARCKS, Myristoylated alanine-rich C-kinase substrate
- MEF2, Myocyte enhancer factor 2
- MEK3, Mitogen-activated protein kinase kinase 3
- PCP, planar cell polarity
- PKC, Protein kinase C
- PSD, Post-synaptic density
- PYK2, Protein tyrosine kinase 2
- Pcdh
- Pcdh, Protocadherin
- RGC, Retinal ganglion cell
- RNAi, RNA interference
- Rac1, Ras-related C3 botulinum toxin substrate 1
- S2 cells, Schneider 2 cells
- SAC, starburst amacrine cell
- TAF1, Template-activating factor 1
- TAO2β, Thousand and one amino acid protein kinase 2 β
- TM, transmembrane
- arborization
- atypical cadherin
- branching
- cadherin superfamily
- cell adhesion
- da neuron, dendritic arborization neuron
- dendritic
- dendritic spine
- dendritogenesis
- fmi, Flamingo
- md neuron, multiple dendrite neuron
- neural circuit formation
- p38 MAPK, p38 mitogen-activated protein kinase
- self avoidance
- synaptogenesis
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Affiliation(s)
- Austin B Keeler
- a Department of Biology ; Neuroscience Graduate Program; University of Iowa ; Iowa City , IA USA
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Miller AC, Voelker LH, Shah AN, Moens CB. Neurobeachin is required postsynaptically for electrical and chemical synapse formation. Curr Biol 2014; 25:16-28. [PMID: 25484298 DOI: 10.1016/j.cub.2014.10.071] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 10/27/2014] [Accepted: 10/28/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND Neural networks and their function are defined by synapses, which are adhesions specialized for intercellular communication that can be either chemical or electrical. At chemical synapses, transmission between neurons is mediated by neurotransmitters, whereas at electrical synapses, direct ionic and metabolic coupling occur via gap junctions between neurons. The molecular pathways required for electrical synaptogenesis are not well understood, and whether they share mechanisms of formation with chemical synapses is not clear. RESULTS Here, using a forward genetic screen in zebrafish, we find that the autism-associated gene neurobeachin (nbea), which encodes a BEACH-domain-containing protein implicated in endomembrane trafficking, is required for both electrical and chemical synapse formation. Additionally, we find that nbea is dispensable for axonal formation and early dendritic outgrowth but is required to maintain dendritic complexity. These synaptic and morphological defects correlate with deficiencies in behavioral performance. Using chimeric animals in which individually identifiable neurons are either mutant or wild-type, we find that Nbea is necessary and sufficient autonomously in the postsynaptic neuron for both synapse formation and dendritic arborization. CONCLUSIONS Our data identify a surprising link between electrical and chemical synapse formation and show that Nbea acts as a critical regulator in the postsynaptic neuron for the coordination of dendritic morphology with synaptogenesis.
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Affiliation(s)
- Adam C Miller
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA.
| | - Lisa H Voelker
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA; Molecular and Cellular Biology, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Arish N Shah
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA
| | - Cecilia B Moens
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA
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19
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Optogenetic activation of cajal-retzius cells reveals their glutamatergic output and a novel feedforward circuit in the developing mouse hippocampus. J Neurosci 2014; 34:13018-32. [PMID: 25253849 DOI: 10.1523/jneurosci.1407-14.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cajal-Retzius cells orchestrate the development of cortical circuits by secreting the glycoprotein reelin. However, their computational functions are still unknown. In fact, the nature of their postsynaptic targets, major neurotransmitter released, as well as the class of postsynaptic receptors activated by their firing remain unclear. Here, we have addressed these questions by activating Cajal-Retzius cells optogenetically in mouse hippocampal slices. Light delivered to stratum lacunosum-moleculare triggered EPSCs both on local interneurons and on pyramidal cells. Responses recorded under voltage-clamp conditions had identical short latencies and similar amplitudes, but were kinetically different (i.e., faster in interneurons vs pyramidal cells). In both cases, responses were blocked by TTX, indicating that they were generated by action potential-dependent release. Responses in interneurons were rescued by the addition of 4-AP to TTX, and decreased when presynaptic firing in Cajal-Retzius cells was reduced by the chemokine CXCL12, indicating the existence of a direct Cajal-Retzius cell-interneuron monosynaptic connection. Although the combined application of 4-AP and TTX did not rescue responses in pyramidal cells, neither were they affected by the GABAA receptor blocker gabazine, which would be expected if they were polysynaptic. Both connections showed physiological and pharmacological properties indicating the involvement of AMPA- and NMDA-type glutamate receptors. The connectivity from presynaptic Cajal-Retzius cells to interneurons was strong enough to generate long-latency feedforward GABAergic input onto pyramidal cells. We propose that this newly defined Cajal-Retzius cell-dependent microcircuit may regulate synaptic plasticity and dendritic development in stratum lacunosum-moleculare, thus impacting the integrative properties of the developing hippocampus.
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20
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Casanova JR, Nishimura M, Swann JW. The effects of early-life seizures on hippocampal dendrite development and later-life learning and memory. Brain Res Bull 2013; 103:39-48. [PMID: 24140049 DOI: 10.1016/j.brainresbull.2013.10.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/04/2013] [Accepted: 10/07/2013] [Indexed: 01/08/2023]
Abstract
Severe childhood epilepsy is commonly associated with intellectual developmental disabilities. The reasons for these cognitive deficits are likely multifactorial and will vary between epilepsy syndromes and even among children with the same syndrome. However, one factor these children have in common is the recurring seizures they experience - sometimes on a daily basis. Supporting the idea that the seizures themselves can contribute to intellectual disabilities are laboratory results demonstrating spatial learning and memory deficits in normal mice and rats that have experienced recurrent seizures in infancy. Studies reviewed here have shown that seizures in vivo and electrographic seizure activity in vitro both suppress the growth of hippocampal pyramidal cell dendrites. A simplification of dendritic arborization and a resulting decrease in the number and/or properties of the excitatory synapses on them could help explain the observed cognitive disabilities. There are a wide variety of candidate mechanisms that could be involved in seizure-induced growth suppression. The challenge is designing experiments that will help focus research on a limited number of potential molecular events. Thus far, results suggest that growth suppression is NMDA receptor-dependent and associated with a decrease in activation of the transcription factor CREB. The latter result is intriguing since CREB is known to play an important role in dendrite growth. Seizure-induced dendrite growth suppression may not occur as a single process in which pyramidal cells dendrites simply stop growing or grow slower compared to normal neurons. Instead, recent results suggest that after only a few hours of synchronized epileptiform activity in vitro dendrites appear to partially retract. This acute response is also NMDA receptor dependent and appears to be mediated by the Ca(+2)/calmodulin-dependent phosphatase, calcineurin. An understanding of the staging of seizure-induced growth suppression and the underlying molecular mechanisms will likely prove crucial for developing therapeutic strategies aimed at ameliorating the intellectual developmental disabilities associated with intractable childhood epilepsy.
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Affiliation(s)
- J R Casanova
- The Department of Neuroscience, Baylor College of Medicine, USA; The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, USA
| | - Masataka Nishimura
- The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, USA; Department of Pediatrics, Baylor College of Medicine, USA
| | - John W Swann
- The Department of Neuroscience, Baylor College of Medicine, USA; The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, USA; Department of Pediatrics, Baylor College of Medicine, USA.
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21
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Hiester BG, Galati DF, Salinas PC, Jones KR. Neurotrophin and Wnt signaling cooperatively regulate dendritic spine formation. Mol Cell Neurosci 2013; 56:115-27. [PMID: 23639831 PMCID: PMC3793870 DOI: 10.1016/j.mcn.2013.04.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Revised: 04/20/2013] [Accepted: 04/23/2013] [Indexed: 01/13/2023] Open
Abstract
Dendritic spines are major sites of excitatory synaptic transmission and changes in their numbers and morphology have been associated with neurodevelopmental and neurodegenerative disorders. Brain-derived Neurotrophic Factor (BDNF) is a secreted growth factor that influences hippocampal, striatal and neocortical pyramidal neuron dendritic spine density. However, the mechanisms by which BDNF regulates dendritic spines and how BDNF interacts with other regulators of spines remain unclear. We propose that one mechanism by which BDNF promotes dendritic spine formation is through an interaction with Wnt signaling. Here, we show that Wnt signaling inhibition in cultured cortical neurons disrupts dendritic spine development, reduces dendritic arbor size and complexity, and blocks BDNF-induced dendritic spine formation and maturation. Additionally, we show that BDNF regulates expression of Wnt2, and that Wnt2 is sufficient to promote cortical dendrite growth and dendritic spine formation. Together, these data suggest that BDNF and Wnt signaling cooperatively regulate dendritic spine formation.
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Affiliation(s)
- Brian G Hiester
- Department of Molecular, Cellular and Developmental Biology, 347 UCB, University of Colorado, Boulder, CO 80309, United States
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22
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The molecular basis of experience-dependent motor system development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 782:23-38. [PMID: 23296479 DOI: 10.1007/978-1-4614-5465-6_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Neurons in the vertebrate nervous system acquire their mature features over an extended period in pre-natal and early post-natal life. The interaction of the organism with its environment (“experience”) has been shown to profoundly influence sensory neuron development. Over the past ~2 decades, it has become increasingly clear that motor system development is also experience-dependent. Glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype have been implicated in both sensory and motor system experience-dependent development. An additional molecular mechanism involves the GluA1 subunit of the 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid (AMPA) subtype glutamate receptors. GluA1-dependent development operates in an NMDA-R independent manner and uses a distinct set of signaling molecules. The synapse associated protein of 97 kDa molecular weight (SAP97) is key. A deeper understanding of how experiences guides motor system development may lead to new ways to improve function after central nervous system insult.
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23
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Diverse strategies engaged in establishing stereotypic wiring patterns among neurons sharing a common input at the visual system's first synapse. J Neurosci 2012; 32:10306-17. [PMID: 22836264 DOI: 10.1523/jneurosci.1581-12.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Sensory circuits use common strategies, such as convergence and divergence, typically at different synapses, to pool or distribute inputs. Inputs from different presynaptic cell types converge onto a common postsynaptic cell, acting together to shape neuronal output (Klausberger and Somogyi, 2008). Also, individual presynaptic cells contact several postsynaptic cell types, generating divergence of signals. Attaining such complex wiring patterns relies on the orchestration of many events across development, including axonal and dendritic growth and synapse formation and elimination (reviewed by Waites et al., 2005; Sanes and Yamagata, 2009). Recent work has focused on how distinct presynaptic cell types form stereotypic connections with an individual postsynaptic cell (Morgan et al., 2011; Williams et al., 2011), but how a single presynaptic cell type diverges to form distinct wiring patterns with multiple postsynaptic cell types during development remains unexplored. Here we take advantage of the compactness of the visual system's first synapse to observe development of such a circuit in mouse retina. By imaging three types of postsynaptic bipolar cells and their common photoreceptor targets across development, we found that distinct bipolar cell types engage in disparate dendritic growth behaviors, exhibit targeted or exploratory approaches to contact photoreceptors, and adhere differently to the synaptotropic model of establishing synaptic territories. Furthermore each type establishes its final connectivity patterns with the same afferents on separate time scales. We propose that such differences in strategy and timeline could facilitate the division of common inputs among multiple postsynaptic cell types to create parallel circuits with diverse function.
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Chu YF, Yen CT, Lee LJ. Neonatal whisker clipping alters behavior, neuronal structure and neural activity in adult rats. Behav Brain Res 2012; 238:124-33. [PMID: 23098795 DOI: 10.1016/j.bbr.2012.10.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 10/09/2012] [Accepted: 10/13/2012] [Indexed: 12/31/2022]
Abstract
Early experience plays critical roles during the development of sensory systems. For example, neonatal surgical manipulations of the whiskers in rodents lead to altered neural activity and behaviors later in life. However, while surgical procedures damage the sensory pathway; it is hard to examine the impact of whisker deprivation on adult animals. To address this issue, we performed a neonatal whisker clipping (WC0-3) paradigm, a non-invasive procedure, from the day of birth (P0) to postnatal day (P) 3, and examined behavioral performances in their adult age. With fully regrown whiskers, the WC0-3 rats exhibited shorter crossable distance than controls in a gap-crossing task, suggesting a defect in their whisker-specific tactile function. In their somatosensory cortex, the layer IV spiny stellate neurons had reduced dendritic complexity and spine density. After exploration in a novel environment, the expression of an activity-dependent immediate early gene, c-fos, increased dramatically in the somatosensory cortex. However, in WC0-3 rats, the number of c-Fos positive cells was less than those in control rats, indicating a fault in transducing sensory-related neural activity between cortical layers in WC0-3 rats. Together, our results demonstrate the roles of early tactile experience on the establishment of layer-specific excitatory connection in the barrel cortex. Early sensory insufficiency would leave long-lasting functional deficits in the sensory system.
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Affiliation(s)
- Yu-Fei Chu
- Graduate Institute of Zoology, National Taiwan University, Taipei, Taiwan
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25
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Zaccaria KJ, McCasland JS. Emergence of layer IV barrel cytoarchitecture is delayed in somatosensory cortex of GAP-43 deficient mice following delayed development of dendritic asymmetry. Somatosens Mot Res 2012; 29:77-88. [PMID: 22759196 DOI: 10.3109/08990220.2012.686936] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The emergence of barrel cytoarchitecture in mouse somatosensory cortex is extremely well defined. However, mechanisms underlying the development of this cellular organization are not completely understood. While it is generally accepted that hollows emerge via passive displacement of cortical cells by dense thalamocortical afferent clusters in barrel centers, it is not known what causes cellular segregation of barrel sides and septa. Here, we hypothesized that the emergence of sides and septa is related to the progressive asymmetry of dendrites from the cells of the barrel side toward the barrel hollow during development. We tested this hypothesis in the barrel cortex of growth-associated protein-43 heterozygous mice (GAP43 (+/-) mice) that display a 2-day delay in retraction of septally oriented dendrites compared to (+/+) littermates. We predicted that this delayed retraction would result in a subsequent 2-day delay in the emergence of barrel sides and septa. Using cresyl violet staining of barrel cortex, we found that initial emergence of hollows was not different between GAP43 (+/-) mice and (+/+) littermate controls. However, the emergence of sides and septa was delayed by 2 days, supporting our hypothesis that the emergence of barrel sides and septa is related to, and perhaps reliant upon, the developmental step of dendritic orientation toward barrel hollows. This process, which is mechanistically distinct from the emergence of barrel hollows, is likely due to both active and passive events resulting from asymmetric cell orientation.
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Affiliation(s)
- Kimberly J Zaccaria
- Department of Cell & Developmental Biology, SUNY Upstate Medical University, Syracuse, NY, USA.
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26
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Hossain S, Sesath Hewapathirane D, Haas K. Dynamic morphometrics reveals contributions of dendritic growth cones and filopodia to dendritogenesis in the intact and awake embryonic brain. Dev Neurobiol 2012; 72:615-27. [DOI: 10.1002/dneu.20959] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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N-cadherin-dependent neuron-neuron interaction is required for the maintenance of activity-induced dendrite growth. Proc Natl Acad Sci U S A 2010; 107:9873-8. [PMID: 20457910 DOI: 10.1073/pnas.1003480107] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Formation of neural circuits depends on stable contacts between neuronal processes, mediated by interaction of cell adhesion molecules, including N-cadherin. In the present study, we found that activity-dependent dendrite arborization specifically requires N-cadherin-mediated extracellular neuron-neuron interaction, because the enhancement did not occur for neurons cultured in isolation or plated on an astrocyte monolayer and was abolished by a recombinant soluble N-cadherin ectodomain. Furthermore, depolarization elevated the level of membrane-associated cadherin/catenin complexes and surface N-cadherin. Importantly, surface N-cadherin elevation is specifically required for the maintenance of nascent dendrite arbors. Through loss- and gain-of-function approaches, we showed that N-cadherin-mediated dendrite growth requires association of the cadherin/catenin complex with the actin cytoskeleton. In summary, these results identify a previously unexplored and specific function for activity-induced, N-cadherin-mediated neuron-neuron contacts in the maintenance of dendrite arbors.
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29
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Lenz KM, Graham MD, Parada M, Fleming AS, Sengelaub DR, Monks DA. Tactile stimulation during artificial rearing influences adult function and morphology in a sexually dimorphic neuromuscular system. Dev Neurobiol 2008; 68:542-57. [PMID: 18186491 DOI: 10.1002/dneu.20608] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Maternal licking of rat pups affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Maternal licking influences SNB motoneurons, with reductions in licking producing decreased SNB number, size, and dendritic length in adulthood. Reduced maternal licking also produces deficits in adult male copulatory behavior. In this experiment, we used an artificial rearing paradigm to assess the potential role of tactile stimulation in mediating the effects of maternal licking on the SNB neuromuscular system. During artificial rearing, pups were stroked with a paintbrush to mimic maternal licking, receiving low, medium, or high levels of daily stimulation. In adulthood, ex copula penile reflex behavior was tested and the morphology of SNB motoneurons assessed. SNB motoneurons were retrogradely labeled with cholera toxin-conjugated HRP and dendritic arbor was reconstructed in three dimensions. Animals that received low levels of stimulation showed deficits in penile reflexes relative to maternally reared controls, including a longer latency to erection, fewer cup erections, and fewer erection clusters. SNB dendritic morphology was also shaped by stimulation condition, with animals that received low or medium levels of stimulation showing an average 27% reduction in dendritic length. In addition, several reflex behaviors were significantly correlated with dendritic length, including latency to first erection, percent of cup erections, and number of erection clusters. These results suggest that tactile stimulation provided by maternal licking mediates some of the effects of maternal care on the development of male copulatory behavior.
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Affiliation(s)
- Kathryn M Lenz
- Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.
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30
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Mantilla CB, Sieck GC. Key aspects of phrenic motoneuron and diaphragm muscle development during the perinatal period. J Appl Physiol (1985) 2008; 104:1818-27. [PMID: 18403452 DOI: 10.1152/japplphysiol.01192.2007] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
At the time of birth, respiratory muscles must be activated to sustain ventilation. The perinatal development of respiratory motor units (comprising an individual motoneuron and the muscle fibers it innervates) shows remarkable features that enable mammals to transition from in utero conditions to the air environment in which the remainder of their life will occur. In addition, significant postnatal maturation is necessary to provide for the range of motor behaviors necessary during breathing, swallowing, and speech. As the main inspiratory muscle, the diaphragm muscle (and the phrenic motoneurons that innervate it) plays a key role in accomplishing these behaviors. Considerable diversity exists across diaphragm motor units, but the determinant factors for this diversity are unknown. In recent years, the mechanisms underlying the development of respiratory motor units have received great attention, and this knowledge may provide the opportunity to design appropriate interventions for the treatment of respiratory disease not only in the perinatal period but likely also in the adult.
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Cline H, Haas K. The regulation of dendritic arbor development and plasticity by glutamatergic synaptic input: a review of the synaptotrophic hypothesis. J Physiol 2008; 586:1509-17. [PMID: 18202093 PMCID: PMC2375708 DOI: 10.1113/jphysiol.2007.150029] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2007] [Accepted: 01/10/2008] [Indexed: 01/15/2023] Open
Abstract
The synaptotropic hypothesis, which states that synaptic inputs control the elaboration of dendritic (and axonal) arbors was articulated by Vaughn in 1989. Today the role of synaptic inputs in controlling neuronal structural development remains an area of intense research activity. Several recent studies have applied modern molecular genetic, imaging and electrophysiological methods to this question and now provide strong evidence that maturation of excitatory synaptic inputs is required for the development of neuronal structure in the intact brain. Here we critically review data concerning the hypothesis with the expectation that understanding the circumstances when the data do and do not support the hypothesis will be most valuable. The synaptotrophic hypothesis contributes at both conceptual and mechanistic levels to our understanding of how relatively minor changes in levels or function of synaptic proteins may have profound effects on circuit development and plasticity.
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Affiliation(s)
- Hollis Cline
- Cold Spring Harbour Laboratory, 1 Bungtown Road, Cold Spring Harbour, NY 11724, USA.
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Mumm JS, Williams PR, Godinho L, Koerber A, Pittman AJ, Roeser T, Chien CB, Baier H, Wong ROL. In vivo imaging reveals dendritic targeting of laminated afferents by zebrafish retinal ganglion cells. Neuron 2007; 52:609-21. [PMID: 17114046 PMCID: PMC1716713 DOI: 10.1016/j.neuron.2006.10.004] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 08/25/2006] [Accepted: 10/05/2006] [Indexed: 11/18/2022]
Abstract
Targeting of axons and dendrites to particular synaptic laminae is an important mechanism by which precise patterns of neuronal connectivity are established. Although axons target specific laminae during development, dendritic lamination has been thought to occur largely by pruning of inappropriately placed arbors. We discovered by in vivo time-lapse imaging that retinal ganglion cell (RGC) dendrites in zebrafish show growth patterns implicating dendritic targeting as a mechanism for contacting appropriate synaptic partners. Populations of RGCs labeled in transgenic animals establish distinct dendritic strata sequentially, predominantly from the inner to outer retina. Imaging individual cells over successive days confirmed that multistratified RGCs generate strata sequentially, each arbor elaborating within a specific lamina. Simultaneous imaging of RGCs and subpopulations of presynaptic amacrine interneurons revealed that RGC dendrites appear to target amacrine plexuses that had already laminated. Dendritic targeting of prepatterned afferents may thus be a novel mechanism for establishing proper synaptic connectivity.
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Affiliation(s)
- Jeff S Mumm
- Department of Anatomy & Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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33
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Lenz KM, Sengelaub DR. Maternal licking influences dendritic development of motoneurons in a sexually dimorphic neuromuscular system. Brain Res 2006; 1092:87-99. [PMID: 16674931 DOI: 10.1016/j.brainres.2006.03.070] [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] [Received: 02/24/2006] [Revised: 03/21/2006] [Accepted: 03/22/2006] [Indexed: 12/29/2022]
Abstract
Maternal licking of pups' perineal regions affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus in the lumbar spinal cord that controls penile reflexes involved with copulation. Maternal licking influences SNB motoneuron number, with reductions in licking resulting in fewer motoneurons. Reduced maternal licking also has functional consequences in adulthood, resulting in increased latency to ejaculation and postejaculatory intromission and longer interintromission intervals. In this experiment, we assessed the potential effect of maternal licking on the development of SNB dendritic morphology. To reduce maternal licking, dams were treated with intranasal application of zinc sulfate during the first two postnatal weeks, which interferes with their ability to detect the pup odors that drive the licking behavior. At either postnatal day (P) 28 (when SNB dendritic length is normally maximal) or P49 (when SNB dendritic morphology is normally mature), SNB motoneurons were retrogradely labeled with cholera toxin-conjugated HRP, and dendritic arbor was reconstructed in three dimensions. At P28, the dendritic arbor of reduced maternal licking pups was not different from controls; however at P49, reduced licking pups showed a 23% reduction in dendritic arbor in the SNB, an effect that was especially pronounced in the rostral end of the nucleus, where reductions reached 48%. These results suggest that reductions in perineal stimulation provided by maternal licking could affect adult male copulatory behavior via alterations in SNB motoneuron morphology, and thus support maternal licking as an important factor in normal neural and behavioral development.
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Affiliation(s)
- Kathryn M Lenz
- Department of Psychological and Brain Sciences and Program in Neuroscience, 1101 E. 10th Street, Indiana University, Bloomington, IN 47405, USA
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34
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Niell CM. Theoretical analysis of a synaptotropic dendrite growth mechanism. J Theor Biol 2006; 241:39-48. [PMID: 16387325 DOI: 10.1016/j.jtbi.2005.11.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 11/01/2005] [Accepted: 11/03/2005] [Indexed: 11/19/2022]
Abstract
It is generally believed that the genome cannot encode explicit instructions to form each synaptic connection in the nervous system, but may provide general neurite growth mechanisms which will result in proper connectivity. Recent in vivo imaging has provided evidence for a synaptotropic growth mechanism, wherein synapses could influence dendrite growth by selectively stabilizing filopodia upon which they form. We undertook a theoretical investigation into the consequences of such a growth process. Discrete stochastic simulations demonstrate that the synaptotropic mechanism can result in decreased dendritic wiring length, is capable of searching for regions of high density pre-synaptic partners, and can recapitulate specific patterns of dendrite growth and connectivity. A mean-field analysis shows that growth by selective stabilization of filopodia can be approximated as a reaction-diffusion system, with a spatially varying diffusion constant that depends on the probability of synapse formation. Thus, growth will occur faster in regions of appropriate synaptic connections, and the net growth can be shown to climb a gradient of synaptic partner density. Synaptotropic growth thus presents a mechanism for the emergent development of connectivity based on local properties of the circuit elements, rather than explicit dependence on global guidance molecules or innate predetermined branching programs.
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Affiliation(s)
- Cristopher M Niell
- Department of Molecular and Cell Physiology, Stanford University, Stanford, CA 94305, USA.
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35
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Li Y, Brewer D, Burke RE, Ascoli GA. Developmental changes in spinal motoneuron dendrites in neonatal mice. J Comp Neurol 2005; 483:304-17. [PMID: 15682391 DOI: 10.1002/cne.20438] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We examined the age-dependent morphological changes of lumbar spinal motoneurons (MNs) in neonatal Swiss-Webster mice during the first 2 weeks of postnatal life. Neurons labeled by intracellular injection of biocytin in hemisected lumbosacral spinal cords in vitro were reconstructed from serial sections. Digitized data were compared for young (P3; postnatal days 2-4; n = 9) and older animals (P11; postnatal days 10-13; n = 8). As expected, measures of dendritic size (e.g., stem branch diameter, total surface area, maximum distance to tips, and lateral tree spread) were all significantly greater for P11 than for P3 mice. In contrast, the number of dendrites per MN and parameters related to tree topology (e.g., terminations per tree and maximum branch order), although slightly greater for P11 animals, were not significantly different between the two ages. Dendrite growth appeared to be proportional throughout the tree because the ratios between average terminal and internal branch lengths were similar for the two groups. Furthermore, this elongation was proportional to enlargement of overall spinal cord dimensions. A variety of other morphometric measures showed no significant difference between age groups. The relative constancy of MN dendritic topology up to P13 was surprising, given the striking maturation in motor function during this time period.
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Affiliation(s)
- Yan Li
- Laboratory of Neural Control, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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36
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Shapiro LA, Korn MJ, Shan Z, Ribak CE. GFAP-expressing radial glia-like cell bodies are involved in a one-to-one relationship with doublecortin-immunolabeled newborn neurons in the adult dentate gyrus. Brain Res 2005; 1040:81-91. [PMID: 15804429 DOI: 10.1016/j.brainres.2005.01.098] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Revised: 01/20/2005] [Accepted: 01/21/2005] [Indexed: 02/08/2023]
Abstract
The present study examined the relationship between radial glial cells and newborn neurons in the adult dentate gyrus using three different methods. Single labeling immunocytochemistry for newly born neurons using doublecortin, as well as double labeling using an additional antibody to glial fibrillary acidic protein (GFAP) to label astrocytes were used at the light microscopic level. Furthermore, doublecortin immunoelectron microscopy was used to examine the ultrastructural relationship between newborn neurons and astrocytes in the adult dentate gyrus. These data showed an intimate one-to-one relationship between GFAP-expressing radial glia-like cell bodies and their non-radial processes that wrap around the basal and lateral sides of newborn neurons to cradle them in the subgranular zone. A similar relationship is observed for the newborn neurons at the base of the granule cell layer, but the cell body of the GFAP-expressing radial glia-like cells is not as intimately associated with the cell body of the newborn neurons at this site. Furthermore, newborn neurons with apical dendritic processes and growth cones in the granule cell layer extend them along radial glial processes. These newborn neurons do not receive axosomatic or axodendritic synapses indicating the absence of basket cell innervation. These data show that GFAP-expressing radial glia-like cells in the dentate gyrus cradle newborn neurons in the subgranular zone and that their radial processes provide a scaffold for neuronal process outgrowth.
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Affiliation(s)
- Lee A Shapiro
- Department of Anatomy and Neurobiology, College of Medicine, University of California, Irvine, CA 92697-1275, USA
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37
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Hua JY, Smith SJ. Neural activity and the dynamics of central nervous system development. Nat Neurosci 2004; 7:327-32. [PMID: 15048120 DOI: 10.1038/nn1218] [Citation(s) in RCA: 314] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2003] [Accepted: 01/21/2004] [Indexed: 11/09/2022]
Abstract
Recent imaging studies show that the formation of neural connections in the central nervous system is a highly dynamic process. The iterative formation and elimination of synapses and neuronal branches result in the formation of a much larger number of trial connections than is maintained in the mature brain. Neural activity modulates development through biasing this process of formation and elimination, promoting the formation and stabilization of appropriate synaptic connections on the basis of functional activity patterns.
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Affiliation(s)
- Jackie Yuanyuan Hua
- Department of Molecular and Cellular Physiology, Beckman Center B141, Stanford University, Stanford, California 94305, USA
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38
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Ribak CE, Korn MJ, Shan Z, Obenaus A. Dendritic growth cones and recurrent basal dendrites are typical features of newly generated dentate granule cells in the adult hippocampus. Brain Res 2004; 1000:195-9. [PMID: 15053968 DOI: 10.1016/j.brainres.2004.01.011] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2004] [Indexed: 10/26/2022]
Abstract
Granule cells in the hippocampal dentate gyrus are generated throughout adulthood of mammals, and recent studies indicate that they are incorporated into neural circuitry and mature into functional neurons. To determine whether newly generated granule cells form dendritic growth cones during this process of synaptogenesis, we used the immunocytochemical method to localize doublecortin, a protein associated with microtubules in newborn neurons. Here we show that both dendritic growth cones and recurrent basal dendrites are common features of newly generated granule cells. This study is the first to show dendritic growth cones in the dentate gyrus of the adult nervous system and suggests that dendrites in adult brains grow in a similar way as those found in immature brains.
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Affiliation(s)
- Charles E Ribak
- Department of Anatomy and Neurobiology, College of Medicine, University of California at Irvine, Irvine, CA 92697-1275, USA.
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39
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Niell CM, Meyer MP, Smith SJ. In vivo imaging of synapse formation on a growing dendritic arbor. Nat Neurosci 2004; 7:254-60. [PMID: 14758365 DOI: 10.1038/nn1191] [Citation(s) in RCA: 312] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Accepted: 01/14/2004] [Indexed: 11/08/2022]
Abstract
The form of a neuron's dendritic arbor determines the set of axons with which it may form synaptic contacts, thus establishing connectivity within neural circuits. However, the dynamic relationship between dendrite growth and synaptogenesis is not well understood. To observe both processes simultaneously, we performed long-term imaging of non-spiny dendritic arbors expressing a fluorescent postsynaptic marker protein as they arborized within the optic tectum of live zebrafish larvae. Our results indicate that almost all synapses form initially on newly extended dendritic filopodia. A fraction of these nascent synapses are maintained, which in turn stabilizes the subset of filopodia on which they form. Stabilized filopodia mature into dendritic branches, and successive iterations of this process result in growth and branching of the arbor. These findings support a 'synaptotropic model' in which synapse formation can direct dendrite arborization.
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Affiliation(s)
- Cristopher M Niell
- Neurosciences Program, Beckman Center, Stanford University, Stanford, California 94305, USA
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40
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Hebbeler SL, Sengelaub DR. Development of a sexually dimorphic neuromuscular system in male rats after spinal transection: morphologic changes and implications for estrogen sites of action. J Comp Neurol 2004; 467:80-96. [PMID: 14574681 DOI: 10.1002/cne.10911] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The lumbar spinal cord of rats contains the sexually dimorphic, steroid-sensitive spinal nucleus of the bulbocavernosus (SNB). In male rats, SNB motoneurons exhibit a biphasic pattern of dendritic growth, having an initial period of exuberant growth followed by a period of retraction to mature lengths by 7 weeks of age. This growth is steroid dependent: dendrites fail to grow after castration, but growth is supported in castrates treated with estradiol. In this experiment, we examined whether supraspinal afferent input by means of descending spinal tracts to the SNB was involved in the normal postnatal development of SNB motoneurons, and whether the effect of estradiol on SNB dendritic growth could be explained by an indirect action of estradiol on supraspinal afferents. Motoneuron morphology was assessed in normal males, early- or late-postnatally transected males, castrated males left untreated or treated with estradiol, and transected castrates treated with estradiol. SNB motoneurons were retrogradely labeled with cholera toxin-horseradish peroxidase during both the growth and retraction phases of dendritic development and reconstructed in three dimensions. The removal of supraspinal afferents resulted in extremely local effects within the developing SNB arbor, as well as transient alterations in somal growth. Furthermore, spinal transection did not block the trophic effect of estradiol on supporting SNB dendritic growth, indicating that estrogens do not act by means of supraspinal input to support SNB motoneuron development.
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Affiliation(s)
- Sara L Hebbeler
- Department of Psychology, Indiana University, Bloomington, Indiana 47405, USA
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41
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Abstract
The morphology of the mature motor neuron dendritic arbor is determined by activity-dependent processes occurring during a critical period in early postnatal life. The abundance of the AMPA receptor subunit GluR1 in motor neurons is very high during this period and subsequently falls to a negligible level. To test the role of GluR1 in dendrite morphogenesis, we reintroduced GluR1 into rat motor neurons at the end of the critical period and quantitatively studied the effects on dendrite architecture. Two versions of GluR1 were studied that differed by the amino acid in the "Q/R" editing site. The amino acid occupying this site determines single-channel conductance, ionic permeability, and other essential electrophysiologic properties of the resulting receptor channels. We found large-scale remodeling of dendritic architectures in a manner depending on the amino acid occupying the Q/R editing site. Alterations in the distribution of dendritic arbor were not prevented by blocking NMDA receptors. These observations suggest that the expression of GluR1 in motor neurons modulates a component of the molecular substrate of activity-dependent dendrite morphogenesis. The control of these events relies on subunit-specific properties of AMPA receptors.
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42
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Hebbeler SL, Verhovshek T, Sengelaub DR. N-methyl-D-aspartate receptor blockade inhibits estrogenic support of dendritic growth in a sexually dimorphic rat spinal nucleus. J Comp Neurol 2002; 451:142-52. [PMID: 12209833 DOI: 10.1002/cne.10347] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The lumbar spinal cord of rats contains the sexually dimorphic, steroid-sensitive spinal nucleus of the bulbocavernosus (SNB). Dendritic development of SNB motoneurons requires the action of both androgens and estrogens. Estrogenic effects are limited to the initial growth of SNB dendrites through 4 weeks of age. During this postnatal period, dendritic growth in other spinal motoneurons is regulated by N-methyl-D-aspartate (NMDA) receptor activation. In this study, we tested whether NMDA receptor activation was involved in SNB dendritic growth and whether the estrogenic support of SNB dendritic growth was dependent on the activation of NMDA receptors. Motoneuron morphology was assessed in normal males, intact males treated daily with the NMDA receptor antagonist MK-801, castrated males treated with estradiol benzoate (EB), and castrated males treated with both EB and MK-801. SNB motoneurons were retrogradely labeled with cholera toxin-horseradish peroxidase at 4 weeks of age (when dendritic length is normally maximal) and reconstructed in three dimensions. Somal area and dendritic length of SNB motoneurons in MK-801-treated, intact males were below those of normal males. Dendritic growth was partially supported in EB-treated castrates, but this growth was blocked by MK-801 treatment. These results suggest that, as in other motoneurons, dendritic development in the SNB involves NMDA receptors and, furthermore, that the estrogen-sensitive component of SNB dendritic development requires their activation.
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Hebbeler SL, Verhovshek T, Sengelaub DR. Ovariectomy attenuates dendritic growth in hormone-sensitive spinal motoneurons. JOURNAL OF NEUROBIOLOGY 2001; 48:301-14. [PMID: 11500843 DOI: 10.1002/neu.1059] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The lumbar spinal cord of rats contains the sexually dimorphic, steroid-sensitive spinal nucleus of the bulbocavernosus (SNB). Dendritic development of SNB motoneurons in male rats is biphasic, initially showing exuberant growth through 4 weeks of age followed by a retraction to mature lengths by 7 weeks of age. The initial growth is steroid dependent, attenuated by castration or aromatase inhibition, and supported by hormone replacement. Dendritic retraction is also steroid sensitive and can be prevented by testosterone treatment, but is unaffected by aromatase inhibition. Together, these results suggest a role for estrogens during the initial growth phase of SNB development. In this study, we tested whether ovarian hormones could support SNB somal and dendritic development. Motoneuron morphology was assessed in normal males and in females perinatally masculinized with dihydrotestosterone and then either ovariectomized or left intact. SNB motoneurons were retrogradely labeled with cholera toxin-HRP at 4 or 7 weeks of age and reconstructed in three dimensions. Initial growth of SNB dendrites was reduced after ovariectomy in masculinized females. However, no differences in dendritic length were seen at 7 weeks of age between intact and ovariectomized masculinized females, and lengths in both groups were significantly lower than those of normal males. Together with previous findings, these results suggest that estrogens are involved in the early growth of SNB dendrites, but not in their subsequent retraction.
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Affiliation(s)
- S L Hebbeler
- Department of Psychology, Indiana University, Bloomington 47405, USA
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44
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Gilmore SA, Sims TJ. Synaptophysin immunoreactivity in spinal white matter of young adult rats. Int J Dev Neurosci 2000; 18:557-64. [PMID: 10884600 DOI: 10.1016/s0736-5748(00)00019-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Patterns of synaptophysin immunoreactivity were examined in the ventral and lateral funiculi of rat lumbosacral spinal cords. In normal young adults, dendrites from neurons in the spinal gray matter extended into the ventral and lateral white matter as finger-like projections, immunopositive for synaptophysin. These projections appeared to diminish in size as they extended peripherally and, in general, did not reach the surface of the spinal cord, so that the outer one-third to one-fourth of the funiculi contained little or no immunoreactivity. The spinal cords of some of the animals studied were X-irradiated on the third postnatal day. When examined 6 weeks to 5 months later, the pattern of synaptophysin immunoreactivity was found to be markedly altered in these animals. In general, the synaptophysin immunoreactivity in the white matter was less organized than in the non-irradiated rat. As a result, the finger-like projections, particularly into the lateral funiculi, were not as distinct, and the immunoreactivity appeared to be more diffusely distributed in the white matter. Further, the immunoreactivity was present throughout the thickness of the white matter in the irradiated animals and subpial concentrations were evident, especially along the lateral aspect of the spinal cord. Ultrastructural evaluation of the synaptic profiles revealed no differences between irradiated and non-irradiated animals. The synapses occurred on both the shafts of the dendrites and on the spines. In general, both dendrites and axon terminals were covered by astrocyte processes except at synaptic sites, and the synaptic complexes were surrounded by astrocyte processes. Although the mechanisms underlying the altered pattern of synaptophysin immunoreactivity are not yet understood, they may be related to radiation-induced effects on the glial populations previously reported by the investigators and/or to radiation-induced alterations in reorganization or maturation of dendritic trees.
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Affiliation(s)
- S A Gilmore
- Department of Anatomy, University of Arkansas for Medical Science, 4301 West Markham Street, Little Rock, AR 72205, USA.
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45
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Abstract
Locomotor activity in many species undergoes pronounced alterations in early postnatal life, and environmental cues may be responsible for modifying this process. To determine how these events are reflected in the nervous system, we studied rats reared under two different conditions-the presence or absence of gravity-in which the performance of motor operations differed. We found a significant effect of rearing environment on the size and complexity of dendritic architecture of spinal motor neurons, particularly those that are likely to participate in postural control. These results provide evidence that neurons subserving motor function undergo activity-dependent maturation in early postnatal life in a manner analogous to sensory systems.
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Affiliation(s)
- F M Inglis
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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46
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Abstract
Nitric oxide (NO) has been implicated in the establishment of precise synaptic connectivity throughout the neuroaxis in several species. To determine the contribution of NO to NMDA receptor-dependent dendritic growth in motor neurons, we administered the NMDA antagonist MK-801 to wild-type mice and neuronal nitric oxide synthase (nNOS) knock-out mice between postnatal days 7 and 14. Compared to saline-treated wild-type animals the number of dendritic bifurcations was significantly reduced in nNOS knock-out animals and MK-801-treated wild-type animals. There was no significant difference in dendritic bifurcation between MK-801-treated wild-type, MK-801-treated nNOS knock-out, and saline-treated nNOS knock-out animals, suggesting that nNOS knock-out and NMDA receptor block had similar effects. The path of the longest dendrite and the number of primary dendrites was the same in all treatment groups, indicating an effect specific to bifurcation. Sholl analysis revealed that differences in bifurcation numbers occurred between 160 and 320 micrometers from the cell body, the distance at which second, third, and fourth order dendrites are most prevalent. Dendrite order analyses confirmed a significant reduction in numbers, but not lengths, of third and fourth order dendrites in nNOS knock-out and drug-treatment groups. Finally, immunohistochemical examination of the developing spinal cord indicated that NMDA receptors and nNOS are colocalized within interneurons surrounding the motor neuron pool. These results support the view that at least part of NMDA receptor-dependent arborization of motor neuron dendrites is mediated by the local production of NO within the developing spinal cord.
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47
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Burke KA, Kuwajima M, Sengelaub DR. Aromatase inhibition reduces dendritic growth in a sexually dimorphic rat spinal nucleus. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1097-4695(19990215)38:3<301::aid-neu1>3.0.co;2-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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48
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Abstract
We previously demonstrated that inhibitory synaptic transmission influences dendrite development in vivo. We now report an analogous finding in an organotypic culture of a glycinergic projection nucleus, the medial nucleus of the trapezoid body (MNTB), and its postsynaptic target, the lateral superior olive (LSO) of gerbils. Cultures were generated at 6-7 days postnatal and grown in serum containing medium with or without the glycine receptor antagonist, strychnine (SN), at 2 microM. LSO neurons were then labeled with biocytin, and the dendritic arbors were analyzed morphometrically. Compared to neurons form age-matched in vivo tissue, the neurons cultured in control media were somewhat atrophic, including decreases in dendritic branching and length. Incubation in strychnine led to a dramatic increase in dendritic branching and total dendritic length. Control neurons averaged 6.3 branches compared to 18 branches/neuron in SN-treated cultures. There was a similar increase in primary dendrites and total dendritic length. The physical elimination of MNTB cells did not mimic SN treatment, presumably because glycinergic LSO neurons generated intrinsic connections. In fact, the LSO soma area was significantly greater following MNTB removal, suggesting that these afferents provide a second signal to postsynaptic neurons. These results suggest that spontaneous glycinergic transmission regulates the growth of postsynaptic processes.
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Affiliation(s)
- D H Sanes
- Center for Neural Science, New York University, New York 10003, USA.
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49
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Hofmann H, Braun K. Slice cultures of the imprinting-relevant forebrain area MNH of the domestic chick: quantitative characterization of neuronal morphology. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1995; 86:283-96. [PMID: 7656421 DOI: 10.1016/0165-3806(95)00045-f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The persistence of morphological features of neurons in slice cultures of the imprinting-relevant forebrain area MNH (mediorostral neostriatum and hyperstriatum ventrale) of the domestic chick was analysed at 7, 14, 21 and 28 days in vitro. After having been explanted and kept in culture the neurons in vitro have larger soma areas, longer and more extensively branched dendritic trees and lower spine frequencies compared to the neurons in vivo. During the analyzed culturing period, the parameters soma area, total and mean dendritic length, number of dendrites, number of dendritic nodes per dendrite and per neuron as well as the spine densities in different dendritic segments showed no significant differences between early and late periods. Highly correlated in every age group were the total dendritic length and the number of dendritic nodes per neuron, indicating regular ramification during dendritic growth. Since these morphological parameters remain stable during the first 4 weeks in vitro, this culture system may provide a suitable model to investigate experimentally induced morphological changes.
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Affiliation(s)
- H Hofmann
- Federal Institute for Neurobiology, Magdeburg, Germany
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50
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Zec N, Tieman SB. Development of the dendritic fields of layer 3 pyramidal cells in the kitten's visual cortex. J Comp Neurol 1994; 339:288-300. [PMID: 8300909 DOI: 10.1002/cne.903390208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The cat's visual cortex is immature at birth and undergoes extensive postnatal development. For example, cells of layers 2 and 3 do not complete migration until about 3 weeks after birth. Despite the importance of dendritic growth for synaptic and functional development, there have been few studies of dendritic development in the cat's visual cortex to correlate with numerous studies of functional and synaptic development. Accordingly, we used the Golgi method to study the development of the dendrites of layer 3 pyramidal cells in the visual cortex of a series of cats ranging in age from 2 days to 3 years. Blocks of visual cortex were impregnated by the Golgi-Kopsch method and sectioned in the tangential plane. Layer 3 pyramidal cells were drawn with a camera lucida and analyzed by Sholl diagrams and vector addition. In kittens < 1 week old, these cells were very immature, with only an apical dendrite and no basal dendrites. Basal dendrites appeared during the second week. By 2 weeks, all of the basal dendrites had emerged from the soma, but they had few branches and were tipped with growth cones. By 4 weeks, they had finished branching but continued to grow in length until, by 5 weeks, they reached their adult size. Examination of the basal dendritic fields in the tangential plane revealed that their dendritic fields were more elongated at 2 weeks than at later ages, perhaps because of their smaller size. The distribution of dendritic field orientations was uniform at all ages except 3 and 4 weeks, when there was a preponderance of fields oriented in the rostrocaudal direction. Because dendritic growth and branching occurred very rapidly over a period that precedes and overlaps with the peak periods of synaptogenesis and of sensitivity to the effects of early visual experience, they may depend on afferent visual activity. The early emergence of primary dendrites, however, suggests that this process is independent of afferent activity. The coincident timing of dendritic branching with the presence of dendritic growth cones suggests that branching may occur at growth cones.
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Affiliation(s)
- N Zec
- Department of Biological Sciences, State University of New York, Albany 12222
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