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Bartkowska K, Koguc-Sobolewska P, Djavadian R, Turlejski K. Astrocytes of the Anterior Commissure Regulate the Axon Guidance Pathways of Newly Generated Neocortical Neurons in the Opossum Monodelphis domestica. Int J Mol Sci 2024; 25:1476. [PMID: 38338755 PMCID: PMC10855434 DOI: 10.3390/ijms25031476] [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: 12/15/2023] [Revised: 01/17/2024] [Accepted: 01/22/2024] [Indexed: 02/12/2024] Open
Abstract
In marsupials, upper-layer cortical neurons derived from the progenitors of the subventricular zone of the lateral ventricle (SVZ) mature morphologically and send their axons to form interhemispheric connections through the anterior commissure. In contrast, eutherians have evolved a new extra callosal pathway, the corpus callosum, that interconnects both hemispheres. In this study, we aimed to examine neurogenesis during the formation of cortical upper layers, including their morphological maturation in a marsupial species, namely the opossum (Monodelphis domestica). Furthermore, we studied how the axons of upper layers neurons pass through the anterior commissure of the opossum, which connects neocortical areas. We showed that upper-layer II/III neurons were generated within at least seven days in the opossum neocortex. Surprisingly, these neurons expressed special AT-rich sequence binding protein 2 (Satb2) and neuropilin 1 interacting protein (Nrp1), which are proteins known to be essential for the formation of the corpus callosum in eutherians. This indicates that extrinsic, but not intrinsic, cues could be key players in guiding the axons of newly generated cortical neurons in the opossum. Although oligodendrocyte precursor cells were present in the neocortex and anterior commissure, newly generated upper-layer neurons sent unmyelinated axons to the anterior commissure. We also found numerous GFAP-expressing progenitor cells in both brain structures, the neocortex and the anterior commissure. However, at P12-P17 in the opossums, a small population of astrocytes was observed only in the midline area of the anterior commissure. We postulate that in the opossum, midline astrocytes allow neocortical axons to be guided to cross the midline, as this structure resembles the glial wedge required by fibers to cross the midline area of the corpus callosum in the rodent.
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Affiliation(s)
- Katarzyna Bartkowska
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (K.B.); (P.K.-S.); (R.D.)
| | - Paulina Koguc-Sobolewska
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (K.B.); (P.K.-S.); (R.D.)
| | - Ruzanna Djavadian
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (K.B.); (P.K.-S.); (R.D.)
| | - Krzysztof Turlejski
- Faculty of Biology and Environmental Sciences, Cardinal Stefan Wyszynski University in Warsaw, 01-938 Warsaw, Poland
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2
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Park J, Chung WS. Astrocyte-dependent circuit remodeling by synapse phagocytosis. Curr Opin Neurobiol 2023; 81:102732. [PMID: 37247606 DOI: 10.1016/j.conb.2023.102732] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 04/30/2023] [Accepted: 05/03/2023] [Indexed: 05/31/2023]
Abstract
In the central nervous system, synaptic pruning, the removal of unnecessary synaptic contacts, is an essential process for proper circuit maturation in neurodevelopment as well as for synaptic homeostasis in the adult stage. Dysregulation of synaptic pruning can contribute to the initiation and progression of various mental disorders, such as schizophrenia and depression, as well as neurodegenerative diseases including Alzheimer's disease. In the past 15 years, pioneering works have demonstrated that different types of glial cells regulate the number of synapses by selectively eliminating them through phagocytic molecular machinery. Although a majority of findings have been focused on microglia, it is increasingly evident that astrocytes function as a critical player in activity-dependent synapse elimination in developing, adult, and diseased brains. In this review, we will discuss recent findings showing the mechanisms and physiological importance of astrocyte-mediated synapse elimination in controlling synapses and circuit homeostasis. We propose that astrocytes play dominant and non-redundant roles in eliminating synapses during the activity-dependent circuit remodeling processes that do not involve neuro-inflammation.
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Affiliation(s)
- Jungjoo Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
| | - Won-Suk Chung
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
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3
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Abstract
Neuroplasticity, i.e., the modifiability of the brain, is different in development and adulthood. The first includes changes in: (i) neurogenesis and control of neuron number; (ii) neuronal migration; (iii) differentiation of the somato-dendritic and axonal phenotypes; (iv) formation of connections; (v) cytoarchitectonic differentiation. These changes are often interrelated and can lead to: (vi) system-wide modifications of brain structure as well as to (vii) acquisition of specific functions such as ocular dominance or language. Myelination appears to be plastic both in development and adulthood, at least, in rodents. Adult neuroplasticity is limited, and is mainly expressed as changes in the strength of excitatory and inhibitory synapses while the attempts to regenerate connections have met with limited success. The outcomes of neuroplasticity are not necessarily adaptive, but can also be the cause of neurological and psychiatric pathologies.
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4
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Sharma K, Bisht K, Eyo UB. A Comparative Biology of Microglia Across Species. Front Cell Dev Biol 2021; 9:652748. [PMID: 33869210 PMCID: PMC8047420 DOI: 10.3389/fcell.2021.652748] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/10/2021] [Indexed: 12/26/2022] Open
Abstract
Microglia are unique brain-resident, myeloid cells. They have received growing interest for their implication in an increasing number of neurodevelopmental, acute injury, and neurodegenerative disorders of the central nervous system (CNS). Fate-mapping studies establish microglial ontogeny from the periphery during development, while recent transcriptomic studies highlight microglial identity as distinct from other CNS cells and peripheral myeloid cells. This evidence for a unique microglial ontogeny and identity raises questions regarding their identity and functions across species. This review will examine the available evidence for microglia in invertebrate and vertebrate species to clarify similarities and differences in microglial identity, ontogeny, and physiology across species. This discussion highlights conserved and divergent microglial properties through evolution. Finally, we suggest several interesting research directions from an evolutionary perspective to adequately understand the significance of microglia emergence. A proper appreciation of microglia from this perspective could inform the development of specific therapies geared at targeting microglia in various pathologies.
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Affiliation(s)
- Kaushik Sharma
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, United States.,Department of Neuroscience, University of Virginia, Charlottesville, VA, United States
| | - Kanchan Bisht
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, United States.,Department of Neuroscience, University of Virginia, Charlottesville, VA, United States
| | - Ukpong B Eyo
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, VA, United States.,Department of Neuroscience, University of Virginia, Charlottesville, VA, United States
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5
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Lynn JD, Anand C, Arshad M, Homayouni R, Rosenberg DR, Ofen N, Raz N, Stanley JA. Microstructure of Human Corpus Callosum across the Lifespan: Regional Variations in Axon Caliber, Density, and Myelin Content. Cereb Cortex 2021; 31:1032-1045. [PMID: 32995843 PMCID: PMC7906774 DOI: 10.1093/cercor/bhaa272] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 08/21/2020] [Accepted: 08/21/2020] [Indexed: 12/13/2022] Open
Abstract
The myeloarchitecture of the corpus callosum (CC) is characterized as a mosaic of distinct differences in fiber density of small- and large-diameter axons along the anterior-posterior axis; however, regional and age differences across the lifespan are not fully understood. Using multiecho T2 magnetic resonance imaging combined with multi-T2 fitting, the myelin water fraction (MWF) and geometric-mean of the intra-/extracellular water T2 (geomT2IEW) in 395 individuals (7-85 years; 41% males) were examined. The approach was validated where regional patterns along the CC closely resembled the histology; MWF matched mean axon diameter and geomT2IEW mirrored the density of large-caliber axons. Across the lifespan, MWF exhibited a quadratic association with age in all 10 CC regions with evidence of a positive linear MWF-age relationship among younger participants and minimal age differences in the remainder of the lifespan. Regarding geomT2IEW, a significant linear age × region interaction reflected positive linear age dependence mostly prominent in the regions with the highest density of small-caliber fibers-genu and splenium. In all, these two indicators characterize distinct attributes that are consistent with histology, which is a first. In addition, these results conform to rapid developmental progression of CC myelination leveling in middle age as well as age-related degradation of axon sheaths in older adults.
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Affiliation(s)
- Jonathan D Lynn
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit MI 48201, USA
- Institute of Gerontology, Wayne State University, Detroit MI 48202, USA
| | - Chaitali Anand
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit MI 48201, USA
- Institute of Gerontology, Wayne State University, Detroit MI 48202, USA
| | - Muzamil Arshad
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit MI 48201, USA
| | - Roya Homayouni
- Institute of Gerontology, Wayne State University, Detroit MI 48202, USA
- Department of Psychology, Wayne State University, Detroit MI 48201, USA
| | - David R Rosenberg
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit MI 48201, USA
| | - Noa Ofen
- Institute of Gerontology, Wayne State University, Detroit MI 48202, USA
- Department of Psychology, Wayne State University, Detroit MI 48201, USA
- Lifespan Cognitive Neuroscience, Merrill Palmer Skillman Institute, Wayne State University, Detroit MI 14195, USA
| | - Naftali Raz
- Institute of Gerontology, Wayne State University, Detroit MI 48202, USA
- Department of Psychology, Wayne State University, Detroit MI 48201, USA
- Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin 14195, Germany
| | - Jeffrey A Stanley
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit MI 48201, USA
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6
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Rombaut B, Kessels S, Schepers M, Tiane A, Paes D, Solomina Y, Piccart E, Hove DVD, Brône B, Prickaerts J, Vanmierlo T. PDE inhibition in distinct cell types to reclaim the balance of synaptic plasticity. Theranostics 2021; 11:2080-2097. [PMID: 33500712 PMCID: PMC7797685 DOI: 10.7150/thno.50701] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 11/17/2020] [Indexed: 02/06/2023] Open
Abstract
Synapses are the functional units of the brain. They form specific contact points that drive neuronal communication and are highly plastic in their strength, density, and shape. A carefully orchestrated balance between synaptogenesis and synaptic pruning, i.e., the elimination of weak or redundant synapses, ensures adequate synaptic density. An imbalance between these two processes lies at the basis of multiple neuropathologies. Recent evidence has highlighted the importance of glia-neuron interactions in the synaptic unit, emphasized by glial phagocytosis of synapses and local excretion of inflammatory mediators. These findings warrant a closer look into the molecular basis of cell-signaling pathways in the different brain cells that are related to synaptic plasticity. In neurons, intracellular second messengers, such as cyclic guanosine or adenosine monophosphate (cGMP and cAMP, respectively), are known mediators of synaptic homeostasis and plasticity. Increased levels of these second messengers in glial cells slow down inflammation and neurodegenerative processes. These multi-faceted effects provide the opportunity to counteract excessive synapse loss by targeting cGMP and cAMP pathways in multiple cell types. Phosphodiesterases (PDEs) are specialized degraders of these second messengers, rendering them attractive targets to combat the detrimental effects of neurological disorders. Cellular and subcellular compartmentalization of the specific isoforms of PDEs leads to divergent downstream effects for these enzymes in the various central nervous system resident cell types. This review provides a detailed overview on the role of PDEs and their inhibition in the context of glia-neuron interactions in different neuropathologies characterized by synapse loss. In doing so, it provides a framework to support future research towards finding combinational therapy for specific neuropathologies.
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7
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Villalón-Reina JE, Martínez K, Qu X, Ching CRK, Nir TM, Kothapalli D, Corbin C, Sun D, Lin A, Forsyth JK, Kushan L, Vajdi A, Jalbrzikowski M, Hansen L, Jonas RK, van Amelsvoort T, Bakker G, Kates WR, Antshel KM, Fremont W, Campbell LE, McCabe KL, Daly E, Gudbrandsen M, Murphy CM, Murphy D, Craig M, Emanuel B, McDonald-McGinn DM, Vorstman JA, Fiksinski AM, Koops S, Ruparel K, Roalf D, Gur RE, Eric Schmitt J, Simon TJ, Goodrich-Hunsaker NJ, Durdle CA, Doherty JL, Cunningham AC, van den Bree M, Linden DEJ, Owen M, Moss H, Kelly S, Donohoe G, Murphy KC, Arango C, Jahanshad N, Thompson PM, Bearden CE. Altered white matter microstructure in 22q11.2 deletion syndrome: a multisite diffusion tensor imaging study. Mol Psychiatry 2020; 25:2818-2831. [PMID: 31358905 PMCID: PMC6986984 DOI: 10.1038/s41380-019-0450-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 03/09/2019] [Accepted: 04/03/2019] [Indexed: 02/06/2023]
Abstract
22q11.2 deletion syndrome (22q11DS)-a neurodevelopmental condition caused by a hemizygous deletion on chromosome 22-is associated with an elevated risk of psychosis and other developmental brain disorders. Prior single-site diffusion magnetic resonance imaging (dMRI) studies have reported altered white matter (WM) microstructure in 22q11DS, but small samples and variable methods have led to contradictory results. Here we present the largest study ever conducted of dMRI-derived measures of WM microstructure in 22q11DS (334 22q11.2 deletion carriers and 260 healthy age- and sex-matched controls; age range 6-52 years). Using harmonization protocols developed by the ENIGMA-DTI working group, we identified widespread reductions in mean, axial and radial diffusivities in 22q11DS, most pronounced in regions with major cortico-cortical and cortico-thalamic fibers: the corona radiata, corpus callosum, superior longitudinal fasciculus, posterior thalamic radiations, and sagittal stratum (Cohen's d's ranging from -0.9 to -1.3). Only the posterior limb of the internal capsule (IC), comprised primarily of corticofugal fibers, showed higher axial diffusivity in 22q11DS. 22q11DS patients showed higher mean fractional anisotropy (FA) in callosal and projection fibers (IC and corona radiata) relative to controls, but lower FA than controls in regions with predominantly association fibers. Psychotic illness in 22q11DS was associated with more substantial diffusivity reductions in multiple regions. Overall, these findings indicate large effects of the 22q11.2 deletion on WM microstructure, especially in major cortico-cortical connections. Taken together with findings from animal models, this pattern of abnormalities may reflect disrupted neurogenesis of projection neurons in outer cortical layers.
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Affiliation(s)
- Julio E. Villalón-Reina
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA
| | - Kenia Martínez
- Department of Child and Adolescent Psychiatry, Hospital General Universitario Gregorio Marañón, Universidad Complutense, School of Medicine, IiSGM, Madrid, Spain ,grid.469673.90000 0004 5901 7501Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid, Spain ,grid.119375.80000000121738416Universidad Europea de Madrid, Madrid, Spain
| | - Xiaoping Qu
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA
| | - Christopher R. K. Ching
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA ,grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA
| | - Talia M. Nir
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA
| | - Deydeep Kothapalli
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA
| | - Conor Corbin
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA
| | - Daqiang Sun
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA ,grid.417119.b0000 0001 0384 5381Department of Mental Health, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA USA
| | - Amy Lin
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA
| | - Jennifer K. Forsyth
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA ,grid.19006.3e0000 0000 9632 6718Department of Psychology, University of California at Los Angeles, Los Angeles, CA USA
| | - Leila Kushan
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA
| | - Ariana Vajdi
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA
| | - Maria Jalbrzikowski
- grid.21925.3d0000 0004 1936 9000Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA USA
| | - Laura Hansen
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA
| | - Rachel K. Jonas
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA
| | - Therese van Amelsvoort
- grid.5012.60000 0001 0481 6099Department of Psychiatry & Neuropsychology, Maastricht University, Maastricht, Netherlands
| | - Geor Bakker
- grid.5012.60000 0001 0481 6099Department of Psychiatry & Neuropsychology, Maastricht University, Maastricht, Netherlands
| | - Wendy R. Kates
- grid.411023.50000 0000 9159 4457Department of Psychiatry and Behavioral Sciences, State University of New York, Upstate Medical University, Syracuse, NY USA
| | - Kevin M. Antshel
- grid.264484.80000 0001 2189 1568Department of Psychology, Syracuse University, Syracuse, NY USA
| | - Wanda Fremont
- grid.411023.50000 0000 9159 4457Department of Psychiatry and Behavioral Sciences, State University of New York, Upstate Medical University, Syracuse, NY USA
| | - Linda E. Campbell
- grid.266842.c0000 0000 8831 109XPriority Research Centre GrowUpWell, University of Newcastle, Newcastle, Australia ,grid.266842.c0000 0000 8831 109XSchool of Psychology, University of Newcastle, Newcastle, Australia
| | - Kathryn L. McCabe
- grid.266842.c0000 0000 8831 109XSchool of Psychology, University of Newcastle, Newcastle, Australia ,grid.27860.3b0000 0004 1936 9684UC Davis MIND Institute and Department of Psychiatry and Behavioral Sciences, Davis, CA USA
| | - Eileen Daly
- grid.13097.3c0000 0001 2322 6764Sackler Institute for Translational Neurodevelopment and Department of Forensic and Neurodevelopmental Sciences, King’s College London, Institute of Psychiatry, Psychology & Neuroscience, London, UK
| | - Maria Gudbrandsen
- grid.13097.3c0000 0001 2322 6764Sackler Institute for Translational Neurodevelopment and Department of Forensic and Neurodevelopmental Sciences, King’s College London, Institute of Psychiatry, Psychology & Neuroscience, London, UK
| | - Clodagh M. Murphy
- grid.13097.3c0000 0001 2322 6764Sackler Institute for Translational Neurodevelopment and Department of Forensic and Neurodevelopmental Sciences, King’s College London, Institute of Psychiatry, Psychology & Neuroscience, London, UK ,grid.451052.70000 0004 0581 2008Behavioural and Developmental Psychiatry Clinical Academic Group, Behavioural Genetics Clinic, National Adult Autism and ADHD Service, South London and Maudsley Foundation NHS Trust, London, UK
| | - Declan Murphy
- grid.13097.3c0000 0001 2322 6764Sackler Institute for Translational Neurodevelopment and Department of Forensic and Neurodevelopmental Sciences, King’s College London, Institute of Psychiatry, Psychology & Neuroscience, London, UK
| | - Michael Craig
- grid.13097.3c0000 0001 2322 6764Sackler Institute for Translational Neurodevelopment and Department of Forensic and Neurodevelopmental Sciences, King’s College London, Institute of Psychiatry, Psychology & Neuroscience, London, UK ,grid.415717.10000 0001 2324 5535National Autism Unit, Bethlem Royal Hospital, Bethlem, UK
| | - Beverly Emanuel
- grid.25879.310000 0004 1936 8972Division of Human Genetics, Children’s Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
| | - Donna M. McDonald-McGinn
- grid.25879.310000 0004 1936 8972Division of Human Genetics, Children’s Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
| | - Jacob A.S. Vorstman
- grid.7692.a0000000090126352Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands ,grid.42327.300000 0004 0473 9646Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON Canada ,grid.17063.330000 0001 2157 2938Department of Psychiatry, University of Toronto, Toronto, ON Canada
| | - Ania M. Fiksinski
- grid.7692.a0000000090126352Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands ,grid.155956.b0000 0000 8793 5925Clinical Genetics Research Program, Centre for Addiction and Mental Health, Toronto, ON Canada ,grid.231844.80000 0004 0474 0428The Dalglish Family 22q Clinic for 22q11.2 Deletion Syndrome, Toronto General Hospital, University Health Network, Toronto, ON Canada
| | - Sanne Koops
- grid.7692.a0000000090126352Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Kosha Ruparel
- grid.25879.310000 0004 1936 8972Department of Psychiatry, University of Pennsylvania, Philadelphia, PA USA
| | - David Roalf
- grid.25879.310000 0004 1936 8972Department of Psychiatry, University of Pennsylvania, Philadelphia, PA USA
| | - Raquel E. Gur
- grid.239552.a0000 0001 0680 8770Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania and Children’s Hospital of Philadelphia, Philadelphia, PA USA
| | - J. Eric Schmitt
- grid.25879.310000 0004 1936 8972Departments of Radiology and Psychiatry, University of Pennsylvania, Philadelphia, PA USA
| | - Tony J. Simon
- grid.27860.3b0000 0004 1936 9684UC Davis MIND Institute and Department of Psychiatry and Behavioral Sciences, Davis, CA USA
| | - Naomi J. Goodrich-Hunsaker
- grid.27860.3b0000 0004 1936 9684UC Davis MIND Institute and Department of Psychiatry and Behavioral Sciences, Davis, CA USA ,grid.253294.b0000 0004 1936 9115Brigham Young University, Provo, UT USA ,grid.223827.e0000 0001 2193 0096Department of Neurology, University of Utah, Salt Lake City, UT USA
| | - Courtney A. Durdle
- grid.27860.3b0000 0004 1936 9684UC Davis MIND Institute and Department of Psychiatry and Behavioral Sciences, Davis, CA USA
| | - Joanne L. Doherty
- grid.5600.30000 0001 0807 5670MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales UK ,grid.5600.30000 0001 0807 5670The Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff, Wales UK
| | - Adam C. Cunningham
- grid.5600.30000 0001 0807 5670MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales UK
| | - Marianne van den Bree
- grid.5600.30000 0001 0807 5670MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales UK
| | - David E. J. Linden
- grid.5600.30000 0001 0807 5670MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales UK ,grid.5600.30000 0001 0807 5670The Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff, Wales UK
| | - Michael Owen
- grid.5600.30000 0001 0807 5670MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales UK
| | - Hayley Moss
- grid.5600.30000 0001 0807 5670MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales UK
| | - Sinead Kelly
- grid.38142.3c000000041936754XDepartment of Psychiatry, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA USA
| | - Gary Donohoe
- grid.6142.10000 0004 0488 0789Centre for Neuroimaging and Cognitive Genomics (NICOG), Clinical Neuroimaging Laboratory, NCBES Galway Neuroscience Centre, National University of Ireland Galway, Galway, Ireland
| | - Kieran C. Murphy
- grid.4912.e0000 0004 0488 7120Department of Psychiatry, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Celso Arango
- Department of Child and Adolescent Psychiatry, Hospital General Universitario Gregorio Marañón, Universidad Complutense, School of Medicine, IiSGM, Madrid, Spain ,grid.469673.90000 0004 5901 7501Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid, Spain ,grid.119375.80000000121738416Universidad Europea de Madrid, Madrid, Spain
| | - Neda Jahanshad
- Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA, USA.
| | - Paul M. Thompson
- grid.42505.360000 0001 2156 6853Imaging Genetics Center, Mark and Mary Stevens Neuroimaging & Informatics Institute, Keck School of Medicine of the University of Southern California, Marina del Rey, CA USA ,grid.42505.360000 0001 2156 6853Departments of Neurology, Psychiatry, Radiology, Engineering, Pediatrics and Ophthalmology, University of Southern California, Los Angeles, CA USA
| | - Carrie E. Bearden
- grid.19006.3e0000 0000 9632 6718Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA USA ,grid.19006.3e0000 0000 9632 6718Department of Psychology, University of California at Los Angeles, Los Angeles, CA USA
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8
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Salas-Lucia F, Pacheco-Torres J, González-Granero S, García-Verdugo JM, Berbel P. Transient Hypothyroidism During Lactation Alters the Development of the Corpus Callosum in Rats. An in vivo Magnetic Resonance Image and Electron Microscopy Study. Front Neuroanat 2020; 14:33. [PMID: 32676012 PMCID: PMC7333461 DOI: 10.3389/fnana.2020.00033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 05/28/2020] [Indexed: 12/20/2022] Open
Abstract
Magnetic resonance imaging (MRI) data of children with late diagnosed congenital hypothyroidism and cognitive alterations such as abnormal verbal memory processing suggest altered telencephalic commissural connections. The corpus callosum (CC) is the major inter-hemispheric commissure that contra-laterally connects neocortical areas. However, in late diagnosed neonates with congenital hypothyroidism, the possible effect of early transient and chronic postnatal hypothyroidism still remains unknown. We have studied the development of the anterior, middle and posterior CC, using in vivo MRI and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated rats were studied. One group, as a model for early transient hypothyroidism, was MMI-treated from postnatal day (P) 0 to P21; some of these rats were also treated with L-thyroxine (T4) from P15 to 21. Another group modeling chronic hypothyroid, were treated with MMI from P0 to 150 and from embryonic day 10 to P170. The results obtained from these groups were compared with same age control rats. The normalized T2 signal obtained using MRI was higher in MMI-treated rats and correlated with a low number and percentage of myelinated axons. The number and density of myelinated axons decreased in transient and chronic hypothyroid rats at P150. The g-ratio (inner to outer diameter ratio) and the estimated conduction velocity of myelinated axons were similar between MMI-treated and controls, but the conduction delay decreased in the posterior CC of MMI-treated rats compared to controls. These data show that early postnatal transient and chronic hypothyroidism alters CC maturation in a way that may affect the callosal transfer of information. These alterations cannot be reversed after delayed T4-treatment. Our data support the findings of neurocognitive delay in late T4-treated children with congenital hypothyroidism.
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Affiliation(s)
- Federico Salas-Lucia
- Departamento de Histología y Anatomía, Facultad de Medicina, Universidad Miguel Hernández (UMH), Sant Joan d’Alacant, Spain
| | - Jesús Pacheco-Torres
- Instituto de Neurociencias de Alicante, UMH – Consejo Superior de Investigaciones Científicas, Sant Joan d’Alacant, Spain
| | - Susana González-Granero
- Laboratorio de Neurobiología Comparada, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universitat de València - Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Valencia, Spain
| | - José Manuel García-Verdugo
- Laboratorio de Neurobiología Comparada, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universitat de València - Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Valencia, Spain
| | - Pere Berbel
- Departamento de Histología y Anatomía, Facultad de Medicina, Universidad Miguel Hernández (UMH), Sant Joan d’Alacant, Spain
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9
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Bahia CP, Vianna-Barbosa RJ, Tovar-Moll F, Lent R. Terminal Arbors of Callosal Axons Undergo Plastic Changes in Early-Amputated Rats. Cereb Cortex 2020; 29:1460-1472. [PMID: 30873555 DOI: 10.1093/cercor/bhy043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 02/04/2018] [Accepted: 02/07/2018] [Indexed: 12/26/2022] Open
Abstract
Sensory information is processed in specific brain regions, and shared between the cerebral hemispheres by axons that cross the midline through the corpus callosum. However, sensory deprivation usually causes sensory losses and/or functional changes. This is the case of people who suffered limb amputation and show changes of body map organization within the somatosensory cortex (S1) of the deafferented cerebral hemisphere (contralateral to the amputated limb), as well as in the afferented hemisphere (ipsilateral to the amputated limb). Although several studies have approached these functional changes, the possible finer morphological alterations, such as those occurring in callosal axons, still remain unknown. The present work combined histochemistry, single-axon tracing and 3D microscopy to analyze the fine morphological changes that occur in callosal axons of the forepaw representation in early amputated rats. We showed that the forepaw representation in S1 was reduced in the deafferented hemisphere and expanded in the afferented side. Accordingly, after amputation, callosal axons originating from the deafferented cortex undergo an expansion of their terminal arbors with increased number of terminal boutons within the homotopic representation at the afferented cerebral hemisphere. Similar microscale structural changes may underpin the macroscale morphological and functional phenomena that characterize limb amputation in humans.
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Affiliation(s)
- Carlomagno Pacheco Bahia
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, CEP 21941-902 Rio de Janeiro (RJ), Brazil.,Institute of Health Sciences, Federal University of Pará, CEP 66075-110 Belém (PA), Brazil
| | - Rodrigo Jorge Vianna-Barbosa
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, CEP 21941-902 Rio de Janeiro (RJ), Brazil
| | - Fernanda Tovar-Moll
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, CEP 21941-902 Rio de Janeiro (RJ), Brazil.,D'Or Institute of Research and Education, CEP 22281-100 Rio de Janeiro (RJ), Brazil
| | - Roberto Lent
- Institute of Biomedical Sciences, Federal University of Rio de Janeiro, CEP 21941-902 Rio de Janeiro (RJ), Brazil
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10
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Eltokhi A, Janmaat IE, Genedi M, Haarman BCM, Sommer IEC. Dysregulation of synaptic pruning as a possible link between intestinal microbiota dysbiosis and neuropsychiatric disorders. J Neurosci Res 2020; 98:1335-1369. [PMID: 32239720 DOI: 10.1002/jnr.24616] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 02/16/2020] [Accepted: 02/26/2020] [Indexed: 02/06/2023]
Abstract
The prenatal and early postnatal stages represent a critical time window for human brain development. Interestingly, this window partly overlaps with the maturation of the intestinal flora (microbiota) that play a critical role in the bidirectional communication between the central and the enteric nervous systems (microbiota-gut-brain axis). The microbial composition has important influences on general health and the development of several organ systems, such as the gastrointestinal tract, the immune system, and also the brain. Clinical studies have shown that microbiota alterations are associated with a wide range of neuropsychiatric disorders including autism spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, and bipolar disorder. In this review, we dissect the link between these neuropsychiatric disorders and the intestinal microbiota by focusing on their effect on synaptic pruning, a vital process in the maturation and establishing efficient functioning of the brain. We discuss in detail how synaptic pruning is dysregulated differently in the aforementioned neuropsychiatric disorders and how it can be influenced by dysbiosis and/or changes in the intestinal microbiota composition. We also review that the improvement in the intestinal microbiota composition by a change in diet, probiotics, prebiotics, or fecal microbiota transplantation may play a role in improving neuropsychiatric functioning, which can be at least partly explained via the optimization of synaptic pruning and neuronal connections. Altogether, the demonstration of the microbiota's influence on brain function via microglial-induced synaptic pruning addresses the possibility that the manipulation of microbiota-immune crosstalk represents a promising strategy for treating neuropsychiatric disorders.
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Affiliation(s)
- Ahmed Eltokhi
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, Eberhard Karls University Tubingen, Tubingen, Germany
| | - Isabel E Janmaat
- Department of Biomedical Sciences, Cells & Systems, University Medical Centre Groningen, University of Groningen, Groningen, the Netherlands
| | - Mohamed Genedi
- Department of Biomedical Sciences, Cells & Systems, University Medical Centre Groningen, University of Groningen, Groningen, the Netherlands
| | - Bartholomeus C M Haarman
- Department of Psychiatry, University Medical Centre Groningen, University of Groningen, Groningen, the Netherlands
| | - Iris E C Sommer
- Department of Biomedical Sciences, Cells & Systems, University Medical Centre Groningen, University of Groningen, Groningen, the Netherlands
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11
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Charvet CJ, Das A, Song JW, Tindal-Burgess DJ, Kabaria P, Dai G, Kane T, Takahashi E. High Angular Resolution Diffusion MRI Reveals Conserved and Deviant Programs in the Paths that Guide Human Cortical Circuitry. Cereb Cortex 2020; 30:1447-1464. [PMID: 31667494 PMCID: PMC7132938 DOI: 10.1093/cercor/bhz178] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 06/13/2019] [Accepted: 07/10/2019] [Indexed: 02/07/2023] Open
Abstract
Diffusion magnetic resonance (MR) tractography represents a novel opportunity to investigate conserved and deviant developmental programs between humans and other species such as mice. To that end, we acquired high angular resolution diffusion MR scans of mice [embryonic day (E) 10.5 to postnatal week 4] and human brains [gestational week (GW) 17-30] at successive stages of fetal development to investigate potential evolutionary changes in radial organization and emerging pathways between humans and mice. We compare radial glial development as well as commissural development (e.g., corpus callosum), primarily because our findings can be integrated with previous work. We also compare corpus callosal growth trajectories across primates (i.e., humans and rhesus macaques) and rodents (i.e., mice). One major finding is that the developing cortex of humans is predominated by pathways likely associated with a radial glial organization at GW 17-20, which is not as evident in age-matched mice (E 16.5, 17.5). Another finding is that, early in development, the corpus callosum follows a similar developmental timetable in primates (i.e., macaques and humans) as in mice. However, the corpus callosum grows for an extended period of time in primates compared with rodents. Taken together, these findings highlight deviant developmental programs underlying the emergence of cortical pathways in the human brain.
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Affiliation(s)
| | - Avilash Das
- Medical Sciences in the College of Arts and Sciences, Boston University, Boston, MA 02215, USA
- Division of Newborn Medicine, Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02215, USA
- Fetal-Neonatal Brain Imaging and Developmental Science Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02215, USA
| | - Jae W Song
- Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, USA
| | | | - Priya Kabaria
- Department of Behavioral Neuroscience, Northeastern University, Boston, MA 02115, USA
| | - Guangping Dai
- Science Center, Wellesley College, Wellesley, MA 02481, USA
| | - Tara Kane
- Department of Behavioral Neuroscience, Northeastern University, Boston, MA 02115, USA
| | - Emi Takahashi
- Division of Newborn Medicine, Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02215, USA
- Fetal-Neonatal Brain Imaging and Developmental Science Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02215, USA
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
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12
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Innate Immunity: A Common Denominator between Neurodegenerative and Neuropsychiatric Diseases. Int J Mol Sci 2020; 21:ijms21031115. [PMID: 32046139 PMCID: PMC7036760 DOI: 10.3390/ijms21031115] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/05/2020] [Accepted: 02/05/2020] [Indexed: 02/06/2023] Open
Abstract
The intricate relationships between innate immunity and brain diseases raise increased interest across the wide spectrum of neurodegenerative and neuropsychiatric disorders. Barriers, such as the blood–brain barrier, and innate immunity cells such as microglia, astrocytes, macrophages, and mast cells are involved in triggering disease events in these groups, through the action of many different cytokines. Chronic inflammation can lead to dysfunctions in large-scale brain networks. Neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and frontotemporal dementia, are associated with a substrate of dysregulated immune responses that impair the central nervous system balance. Recent evidence suggests that similar phenomena are involved in psychiatric diseases, such as depression, schizophrenia, autism spectrum disorders, and post-traumatic stress disorder. The present review summarizes and discusses the main evidence linking the innate immunological response in neurodegenerative and psychiatric diseases, thus providing insights into how the responses of innate immunity represent a common denominator between diseases belonging to the neurological and psychiatric sphere. Improved knowledge of such immunological aspects could provide the framework for the future development of new diagnostic and therapeutic approaches.
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13
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Crespo-Castrillo A, Garcia-Segura LM, Arevalo MA. The synthetic steroid tibolone exerts sex-specific regulation of astrocyte phagocytosis under basal conditions and after an inflammatory challenge. J Neuroinflammation 2020; 17:37. [PMID: 31992325 PMCID: PMC6986022 DOI: 10.1186/s12974-020-1719-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 01/19/2020] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Tibolone is a synthetic steroid used in clinical practice for the treatment of climacteric symptoms and osteoporosis. Active metabolites of tibolone, generated in target tissues, have an affinity for estrogen and androgen receptors. Astrocytes are direct targets for estrogenic compounds and previous studies have shown that tibolone protects brain cortical neurons in association with a reduction in reactive astrogliosis in a mouse model of traumatic brain injury. Since phagocytosis is a crucial component of the neuroprotective function exerted by astrocytes, in the present study, we have assessed whether tibolone regulates phagocytosis in primary astrocytes incubated with brain-derived cellular debris. METHODS Male and female astrocyte cell cultures were obtained from newborn (P0-P2) female and male Wistar rats. Astrocytic phagocytosis was first characterized using carboxylate beads, Escherichia coli particles, or brain-derived cellular debris. Then, the effect of tibolone on the phagocytosis of Cy3-conjugated cellular debris was quantified by measuring the intensity of Cy3 dye-emitted fluorescence in a given GFAP immunoreactive area. Before the phagocytosis assays, astrocytes were incubated with tibolone in the presence or absence of estrogen or androgen receptor antagonists or an inhibitor of the enzyme that synthesizes estradiol. The effect of tibolone on phagocytosis was analyzed under basal conditions and after inflammatory stimulation with lipopolysaccharide. RESULTS Tibolone stimulated phagocytosis of brain-derived cellular debris by male and female astrocytes, with the effect being more pronounced in females. The effect of tibolone in female astrocytes was blocked by a selective estrogen receptor β antagonist and by an androgen receptor antagonist. None of these antagonists affected tibolone-induced phagocytosis in male astrocytes. In addition, the inhibition of estradiol synthesis in the cultures enhanced the stimulatory effect of tibolone on phagocytosis in male astrocytes but blocked the effect of the steroid in female cells under basal conditions. However, after inflammatory stimulation, the inhibition of estradiol synthesis highly potentiated the stimulation of phagocytosis by tibolone, particularly in female astrocytes. CONCLUSIONS Tibolone exerts sex-specific regulation of phagocytosis in astrocytes of both sexes, both under basal conditions and after inflammatory stimulation.
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Affiliation(s)
| | - Luis-Miguel Garcia-Segura
- Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.,Centro de Investigación Biomédica en Red Fragilidad y Envejecimiento Saludables (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - Maria-Angeles Arevalo
- Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain. .,Centro de Investigación Biomédica en Red Fragilidad y Envejecimiento Saludables (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain.
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14
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Innocenti GM. The Target of Exuberant Projections in Development. Cereb Cortex 2020; 30:3820-3826. [PMID: 31989156 DOI: 10.1093/cercor/bhz344] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 12/19/2019] [Indexed: 02/06/2023] Open
Abstract
In addition to neuronal death and elimination of synapses, the production of transient, exuberant axons, and axonal branches is a general phenomenon in development across species and systems. To understand what drives the decision of which axons are maintained and which are eliminated, it is important to monitor the interaction of juvenile axons at their target. As old and more recent work show, unlike what is claimed by Ribeiro Gomez et al. (2019), in the cerebral cortex, both classes of axons branch in the white matter near the target; axons destined to be maintained massively invade the gray matter where they develop terminal arbors and synapses. Axons destined to elimination remain in the white matter although a few transient, exploratory branches can enter the cortex. Axonal behavior and fate seem dictated by positional information probably conveyed by thalamic afferents and activity. Unlike what is suggested by Ribeiro Gomez et al. (2019), axonal selection should not be confused with synaptic reduction, which is a later event with minor or no impact on the topography of the connection.
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Affiliation(s)
- Giorgio M Innocenti
- Department of Neuroscience Karolinska Institutet, Stockholm, Sweden and Signal Processing Laboratory (LT55) Ecole Polytechnique Féderale de Lausanne (EPFL), Lausanne, Switzerland
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15
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Culjat M, Milošević NJ. Callosal septa express guidance cues and are paramedian guideposts for human corpus callosum development. J Anat 2019; 235:670-686. [PMID: 31070791 PMCID: PMC6704273 DOI: 10.1111/joa.13011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2019] [Indexed: 12/18/2022] Open
Abstract
The early development and growth of the corpus callosum are supported by several midline transient structures in mammals that include callosal septa (CS), which are present only in the second half of gestation in humans. Here we provide new data that support the guidance role of CS in corpus callosum development, derived from the analysis of 46 postmortem fetal brains, ranging in age from 16 to 40 post conception weeks (PCW). Using immunohistochemical methods, we show the expression pattern of guidance cues ephrinA4 and neogenin, extracellular protein fibronectin, as well as non-activated microglia in the CS. We found that the dynamic changes in expression of guidance cues, cellular and extracellular matrix constituents in the CS correlate well with the growth course of the corpus callosum at midsagittal level. The CS reach and maintain their developmental maximum between 20 and 26 PCW and can be visualized as hypointense structures in the ventral callosal portion with ex vivo (in vitro) T2-weighted 3T magnetic resonance imaging (MRI). The maximum of septal development overlaps with an increase in the callosal midsagittal area, whereas the slow, gradual resolution of CS coincides with a plateau of midsagittal callosal growth. The recognition of CS existence in human fetal brain and the ability to visualize them by ex vivoMRI attributes a potential diagnostic value to these transient structures, as advancement in imaging technologies will likely also enable in vivoMRI visualization of the CS in the near future.
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Affiliation(s)
- Marko Culjat
- MedStar Georgetown University HospitalWashingtonDCUSA
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16
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Tremblay ME, Cookson MR, Civiero L. Glial phagocytic clearance in Parkinson's disease. Mol Neurodegener 2019; 14:16. [PMID: 30953527 PMCID: PMC6451240 DOI: 10.1186/s13024-019-0314-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/15/2019] [Indexed: 12/21/2022] Open
Abstract
An emerging picture suggests that glial cells' loss of beneficial roles or gain of toxic functions can contribute to neurodegenerative conditions. Among glial cells, microglia and astrocytes have been shown to play phagocytic roles by engulfing synapses, apoptotic cells, cell debris, and released toxic proteins. As pathogenic protein accumulation is a key feature in Parkinson's disease (PD), compromised phagocytic clearance might participate in PD pathogenesis. In contrast, enhanced, uncontrolled and potentially toxic glial clearance capacity could contribute to synaptic degeneration. Here, we summarize the current knowledge of the molecular mechanisms underlying microglial and astrocytic phagocytosis, focusing on the possible implication of phagocytic dysfunction in neuronal degeneration. Several endo-lysosomal proteins displaying genetic variants in PD are highly expressed by microglia and astrocytes. We also present the evidence that lysosomal defects can affect phagocytic clearance and discuss the therapeutic relevance of restoring or enhancing lysosomal function in PD.
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Affiliation(s)
- Marie-Eve Tremblay
- Axe Neurosciences, Centre de Recherche du CHU de Québec, Université Laval, Quebec, QC Canada
- Département de Médecine Moléculaire, Faculté de Médecine, Université Laval, Quebec, QC Canada
| | - Mark R. Cookson
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD USA
| | - Laura Civiero
- Department of Biology, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy
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17
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Fischer TD, Dash PK, Liu J, Waxham MN. Morphology of mitochondria in spatially restricted axons revealed by cryo-electron tomography. PLoS Biol 2018; 16:e2006169. [PMID: 30222729 PMCID: PMC6160218 DOI: 10.1371/journal.pbio.2006169] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 09/27/2018] [Accepted: 09/05/2018] [Indexed: 11/25/2022] Open
Abstract
Neurons project axons to local and distal sites and can display heterogeneous morphologies with limited physical dimensions that may influence the structure of large organelles such as mitochondria. Using cryo-electron tomography (cryo-ET), we characterized native environments within axons and presynaptic varicosities to examine whether spatial restrictions within these compartments influence the morphology of mitochondria. Segmented tomographic reconstructions revealed distinctive morphological characteristics of mitochondria residing at the narrowed boundary between presynaptic varicosities and axons with limited physical dimensions (approximately 80 nm), compared to mitochondria in nonspatially restricted environments. Furthermore, segmentation of the tomograms revealed discrete organizations between the inner and outer membranes, suggesting possible independent remodeling of each membrane in mitochondria at spatially restricted axonal/varicosity boundaries. Thus, cryo-ET of mitochondria within axonal subcompartments reveals that spatial restrictions do not obstruct mitochondria from residing within them, but limited available space can influence their gross morphology and the organization of the inner and outer membranes. These findings offer new perspectives on the influence of physical and spatial characteristics of cellular environments on mitochondrial morphology and highlight the potential for remarkable structural plasticity of mitochondria to adapt to spatial restrictions within axons. Neurons are complex cells that communicate with each other via axons that can extend over distances of a meter or longer. Axons place enormous demands on neuronal energy production, and to maintain connections with local and distal targets, neurons have efficient systems that transport mitochondria to areas of high energy consumption. However, axons show variable dimensions, sometimes thinning to a diameter significantly smaller than the standard diameter of mitochondria, raising the question of how mitochondrial structures can adapt to the local spatial environment. In the present study, we employed electron tomography to investigate the physical and structural relationships between thin axons and the mitochondria that reside within them. We discovered that mitochondria exhibit a remarkable constriction of outer and inner membrane structure in regions of restricted physical dimensions of the axonal space. These findings highlight the remarkable structural plasticity of mitochondria and the potential influence of available space within cells on the structure of mitochondria. Given that maintaining a population of properly localized mitochondria is necessary to support synaptic function, the findings also suggest an adaptive role for mitochondrial structure in facilitating efficient axonal transport.
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Affiliation(s)
- Tara D. Fischer
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, United States America
| | - Pramod K. Dash
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- Vivian L. Smith Department of Neurosurgery, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Jun Liu
- Department of Pathology and Laboratory Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - M. Neal Waxham
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
- * E-mail:
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18
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Knabbe J, Nassal JP, Verhage M, Kuner T. Secretory vesicle trafficking in awake and anaesthetized mice: differential speeds in axons versus synapses. J Physiol 2018; 596:3759-3773. [PMID: 29873393 DOI: 10.1113/jp276022] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Accepted: 05/24/2018] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Despite their immense physiological and pathophysiological importance, we know very little about the biology of dense core vesicle (DCV) trafficking in the intact mammalian brain. DCVs are transported at similar average speeds in the anaesthetized and awake mouse brain compared to neurons in culture, yet maximal speed and pausing fraction of transport were higher. Microtubule plus (+)-end extension imaging visualized microtubular growth at 0.12 μm/s and revealed that DCVs were transported faster in the anterograde direction. DCV transport slowed down upon presynaptic bouton approach, possibly promoting synaptic localization and cargo release. Our work provides a basis to extrapolate DCV transport properties determined in cultured neurons to the intact mouse brain and reveals novel features such as slowing upon bouton approach and brain state-dependent trafficking directionality. ABSTRACT Neuronal dense core vesicles (DCVs) transport many cargo molecules like neuropeptides and neurotrophins to their release sites in dendrites or axons. The transport properties of DCVs in axons of the intact mammalian brain are unknown. We used viral expression of a DCV cargo reporter (NPY-Venus/Cherry) in the thalamus and two-photon in vivo imaging to visualize axonal DCV trafficking in thalamocortical projections of anaesthetized and awake mice. We found an average speed of 1 μm/s, maximal speeds of up to 5 μm/s and a pausing fraction of ∼11%. Directionality of transport differed between anaesthetized and awake mice. In vivo microtubule +-end extension imaging using MACF18-GFP revealed microtubular growth at 0.12 μm/s and provided positive identification of antero- and retrograde axonal transport. Consistent with previous reports, anterograde transport was faster (∼2.1 μm/s) than retrograde transport (∼1.4 μm/s). In summary, DCVs are transported with faster maximal speeds and lower pausing fraction in vivo compared to previous results obtained in vitro. Finally, we found that DCVs slowed down upon presynaptic bouton approach. We propose that this mechanism promotes synaptic localization and cargo release.
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Affiliation(s)
- Johannes Knabbe
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg University, Im Neuenheimer Feld 307, 69120, Heidelberg, Germany
| | - Joris Paul Nassal
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg University, Im Neuenheimer Feld 307, 69120, Heidelberg, Germany.,Departments of Functional Genomics and Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), VU University Amsterdam and VU University Medical Center, De Boelelaan, 1087, 1081 HV Amsterdam, The Netherlands
| | - Matthijs Verhage
- Departments of Functional Genomics and Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), VU University Amsterdam and VU University Medical Center, De Boelelaan, 1087, 1081 HV Amsterdam, The Netherlands
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg University, Im Neuenheimer Feld 307, 69120, Heidelberg, Germany
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19
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Khalil R, Contreras-Ramirez V, Levitt JB. Postnatal refinement of interareal feedforward projections in ferret visual cortex. Brain Struct Funct 2018; 223:2303-2322. [PMID: 29476239 DOI: 10.1007/s00429-018-1632-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 02/17/2018] [Indexed: 12/27/2022]
Abstract
We studied the postnatal refinement of feedforward (FF) projections from ferret V1 to multiple cortical targets during the period around eye opening. Our goal was to establish (a) whether the developmental refinement of FF projections parallels that of feedback (FB) cortical circuits, and (b) whether FF pathways from V1 to different target areas refine with a similar rate. We injected the tracer CTb into V1 of juvenile ferrets, and visualized the pattern of labeled axon terminals in extrastriate cortex. Bouton density of FF projections to target areas 18, 19, and 21 declined steadily from 4 to 8 weeks postnatal. However, in area Ssy this decline was delayed somewhat, not occurring until after 6 weeks. During this postnatal period, mean interbouton intervals along individual FF axons to all visual areas increased, and we observed a concomitant moderate decrease in axon density in areas 18, 21, and Ssy. These data suggest that FF circuits linking V1 to its main extrastriate targets remodel largely synchronously in the weeks following eye opening, that FF and FB cortical circuits share a broadly similar developmental timecourse, and that postnatal visual experience is critical for the refinement of both FF and FB cortical circuits.
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Affiliation(s)
- Reem Khalil
- Biology, Chemistry, and Environmental Sciences Department, American University of Sharjah, Sharjah, UAE.,Department of Biology MR526, City College of New York, 160 Convent Avenue, New York, NY, 10031, USA.,Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY, 10016, USA
| | | | - Jonathan B Levitt
- Department of Biology MR526, City College of New York, 160 Convent Avenue, New York, NY, 10031, USA. .,Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY, 10016, USA.
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20
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Errant gardeners: glial-cell-dependent synaptic pruning and neurodevelopmental disorders. Nat Rev Neurosci 2017; 18:658-670. [PMID: 28931944 DOI: 10.1038/nrn.2017.110] [Citation(s) in RCA: 185] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The final stage of brain development is associated with the generation and maturation of neuronal synapses. However, the same period is also associated with a peak in synapse elimination - a process known as synaptic pruning - that has been proposed to be crucial for the maturation of remaining synaptic connections. Recent studies have pointed to a key role for glial cells in synaptic pruning in various parts of the nervous system and have identified a set of critical signalling pathways between glia and neurons. At the same time, brain imaging and post-mortem anatomical studies suggest that insufficient or excessive synaptic pruning may underlie several neurodevelopmental disorders, including autism, schizophrenia and epilepsy. Here, we review current data on the cellular, physiological and molecular mechanisms of glial-cell-dependent synaptic pruning and outline their potential contribution to neurodevelopmental disorders.
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21
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Sleep Loss Promotes Astrocytic Phagocytosis and Microglial Activation in Mouse Cerebral Cortex. J Neurosci 2017; 37:5263-5273. [PMID: 28539349 DOI: 10.1523/jneurosci.3981-16.2017] [Citation(s) in RCA: 232] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 03/23/2017] [Accepted: 04/13/2017] [Indexed: 11/21/2022] Open
Abstract
We previously found that Mertk and its ligand Gas6, astrocytic genes involved in phagocytosis, are upregulated after acute sleep deprivation. These results suggested that astrocytes may engage in phagocytic activity during extended wake, but direct evidence was lacking. Studies in humans and rodents also found that sleep loss increases peripheral markers of inflammation, but whether these changes are associated with neuroinflammation and/or activation of microglia, the brain's resident innate immune cells, was unknown. Here we used serial block-face scanning electron microscopy to obtain 3D volume measurements of synapses and surrounding astrocytic processes in mouse frontal cortex after 6-8 h of sleep, spontaneous wake, or sleep deprivation (SD) and after chronic (∼5 d) sleep restriction (CSR). Astrocytic phagocytosis, mainly of presynaptic components of large synapses, increased after both acute and chronic sleep loss relative to sleep and wake. MERTK expression and lipid peroxidation in synaptoneurosomes also increased to a similar extent after short and long sleep loss, suggesting that astrocytic phagocytosis may represent the brain's response to the increase in synaptic activity associated with prolonged wake, clearing worn components of heavily used synapses. Using confocal microscopy, we then found that CSR but not SD mice show morphological signs of microglial activation and enhanced microglial phagocytosis of synaptic elements, without obvious signs of neuroinflammation in the CSF. Because low-level sustained microglia activation can lead to abnormal responses to a secondary insult, these results suggest that chronic sleep loss, through microglia priming, may predispose the brain to further damage.SIGNIFICANCE STATEMENT We find that astrocytic phagocytosis of synaptic elements, mostly of presynaptic origin and in large synapses, is upregulated already after a few hours of sleep deprivation and shows a further significant increase after prolonged and severe sleep loss, suggesting that it may promote the housekeeping of heavily used and strong synapses in response to the increased neuronal activity of extended wake. By contrast, chronic sleep restriction but not acute sleep loss activates microglia, promotes their phagocytic activity, and does so in the absence of overt signs of neuroinflammation, suggesting that like many other stressors, extended sleep disruption may lead to a state of sustained microglia activation, perhaps increasing the brain's susceptibility to other forms of damage.
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22
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Obst J, Simon E, Mancuso R, Gomez-Nicola D. The Role of Microglia in Prion Diseases: A Paradigm of Functional Diversity. Front Aging Neurosci 2017; 9:207. [PMID: 28690540 PMCID: PMC5481309 DOI: 10.3389/fnagi.2017.00207] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 06/09/2017] [Indexed: 12/26/2022] Open
Abstract
Inflammation is a major component of neurodegenerative diseases. Microglia are the innate immune cells in the central nervous system (CNS). In the healthy brain, microglia contribute to tissue homeostasis and regulation of synaptic plasticity. Under disease conditions, they play a key role in the development and maintenance of the neuroinflammatory response, by showing enhanced proliferation and activation. Prion diseases are progressive chronic neurodegenerative disorders associated with the accumulation of the scrapie prion protein PrPSc, a misfolded conformer of the cellular prion protein PrPC. This review article provides the current knowledge on the role of microglia in the pathogenesis of prion disease. A large body of evidence shows that microglia can trigger neurotoxic pathways contributing to progressive degeneration. Yet, microglia are also crucial for controlling inflammatory, repair and regenerative processes. This dual role of microglia is regulated by multiple pathways and evidences the ability of these cells to polarize into distinct phenotypes with characteristic functions. The awareness that the neuroinflammatory response is inextricably involved in producing tissue damage as well as repair in neurodegenerative disorders, opens new perspectives for the modulation of the immune system. A better understanding of this complex process will be essential for developing effective therapies for neurodegenerative diseases, in order to improve the quality of life of patients and mitigating the personal, economic and social consequences derived from these diseases.
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Affiliation(s)
- Juliane Obst
- Biological Sciences, University of Southampton, Southampton General HospitalSouthampton, United Kingdom
| | - Emilie Simon
- Biological Sciences, University of Southampton, Southampton General HospitalSouthampton, United Kingdom
| | - Renzo Mancuso
- Biological Sciences, University of Southampton, Southampton General HospitalSouthampton, United Kingdom
| | - Diego Gomez-Nicola
- Biological Sciences, University of Southampton, Southampton General HospitalSouthampton, United Kingdom
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23
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Son AI, Fu X, Suto F, Liu JS, Hashimoto-Torii K, Torii M. Proteome dynamics during postnatal mouse corpus callosum development. Sci Rep 2017; 7:45359. [PMID: 28349996 PMCID: PMC5368975 DOI: 10.1038/srep45359] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 02/27/2017] [Indexed: 02/08/2023] Open
Abstract
Formation of cortical connections requires the precise coordination of numerous discrete phases. This is particularly significant with regard to the corpus callosum, whose development undergoes several dynamic stages including the crossing of axon projections, elimination of exuberant projections, and myelination of established tracts. To comprehensively characterize the molecular events in this dynamic process, we set to determine the distinct temporal expression of proteins regulating the formation of the corpus callosum and their respective developmental functions. Mass spectrometry-based proteomic profiling was performed on early postnatal mouse corpus callosi, for which limited evidence has been obtained previously, using stable isotope of labeled amino acids in mammals (SILAM). The analyzed corpus callosi had distinct proteomic profiles depending on age, indicating rapid progression of specific molecular events during this period. The proteomic profiles were then segregated into five separate clusters, each with distinct trajectories relevant to their intended developmental functions. Our analysis both confirms many previously-identified proteins in aspects of corpus callosum development, and identifies new candidates in understudied areas of development including callosal axon refinement. We present a valuable resource for identifying new proteins integral to corpus callosum development that will provide new insights into the development and diseases afflicting this structure.
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Affiliation(s)
- Alexander I Son
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA
| | - Xiaoqin Fu
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA
| | - Fumikazu Suto
- Department of Ultrastructural Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan
| | - Judy S Liu
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA.,Department of Pediatrics, Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20052, USA
| | - Kazue Hashimoto-Torii
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA.,Department of Pediatrics, Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20052, USA.,Department of Neurobiology and Kavli Institute for Neuroscience, School of Medicine, Yale University, New Haven, CT 06510, USA
| | - Masaaki Torii
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA.,Department of Pediatrics, Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20052, USA.,Department of Neurobiology and Kavli Institute for Neuroscience, School of Medicine, Yale University, New Haven, CT 06510, USA
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24
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Reemst K, Noctor SC, Lucassen PJ, Hol EM. The Indispensable Roles of Microglia and Astrocytes during Brain Development. Front Hum Neurosci 2016; 10:566. [PMID: 27877121 PMCID: PMC5099170 DOI: 10.3389/fnhum.2016.00566] [Citation(s) in RCA: 344] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 10/25/2016] [Indexed: 01/17/2023] Open
Abstract
Glia are essential for brain functioning during development and in the adult brain. Here, we discuss the various roles of both microglia and astrocytes, and their interactions during brain development. Although both cells are fundamentally different in origin and function, they often affect the same developmental processes such as neuro-/gliogenesis, angiogenesis, axonal outgrowth, synaptogenesis and synaptic pruning. Due to their important instructive roles in these processes, dysfunction of microglia or astrocytes during brain development could contribute to neurodevelopmental disorders and potentially even late-onset neuropathology. A better understanding of the origin, differentiation process and developmental functions of microglia and astrocytes will help to fully appreciate their role both in the developing as well as in the adult brain, in health and disease.
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Affiliation(s)
- Kitty Reemst
- Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, Netherlands
| | - Stephen C. Noctor
- Department of Psychiatry and Behavioral Sciences, UC Davis MIND InstituteSacramento, CA, USA
| | - Paul J. Lucassen
- Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, Netherlands
| | - Elly M. Hol
- Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, Netherlands
- Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center UtrechtUtrecht, Netherlands
- Netherlands Institute for NeuroscienceAmsterdam, Netherlands
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25
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Axon diameter relates to synaptic bouton size: structural properties define computationally different types of cortical connections in primates. Brain Struct Funct 2016; 222:1169-1177. [DOI: 10.1007/s00429-016-1266-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 06/28/2016] [Indexed: 10/21/2022]
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26
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Butler BE, Chabot N, Lomber SG. Quantifying and comparing the pattern of thalamic and cortical projections to the posterior auditory field in hearing and deaf cats. J Comp Neurol 2016; 524:3042-63. [DOI: 10.1002/cne.24005] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/21/2016] [Accepted: 03/24/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Blake E. Butler
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute; University of Western Ontario; London Ontario Canada N6A 5B7
| | - Nicole Chabot
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute; University of Western Ontario; London Ontario Canada N6A 5B7
| | - Stephen G. Lomber
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Department of Psychology; University of Western Ontario; London Ontario Canada N6A 5C2
- Brain and Mind Institute; University of Western Ontario; London Ontario Canada N6A 5B7
- National Centre for Audiology; University of Western Ontario; London Ontario Canada N6G 1H1
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27
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Frost JL, Schafer DP. Microglia: Architects of the Developing Nervous System. Trends Cell Biol 2016; 26:587-597. [PMID: 27004698 DOI: 10.1016/j.tcb.2016.02.006] [Citation(s) in RCA: 244] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 02/16/2016] [Accepted: 02/19/2016] [Indexed: 11/18/2022]
Abstract
Microglia are resident macrophages of the central nervous system (CNS), representing 5-10% of total CNS cells. Recent findings reveal that microglia enter the embryonic brain, take up residence before the differentiation of other CNS cell types, and become critical regulators of CNS development. Here, we discuss exciting new work implicating microglia in a range of developmental processes, including regulation of cell number and spatial patterning of CNS cells, myelination, and formation and refinement of neural circuits. Furthermore, we review studies suggesting that these cellular functions result in the modulation of behavior, which has important implications for a variety of neurological disorders.
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Affiliation(s)
- Jeffrey L Frost
- Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Dorothy P Schafer
- Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
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28
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Perez-Pouchoulen M, VanRyzin JW, McCarthy MM. Morphological and Phagocytic Profile of Microglia in the Developing Rat Cerebellum. eNeuro 2015; 2:ENEURO.0036-15.2015. [PMID: 26464992 PMCID: PMC4596010 DOI: 10.1523/eneuro.0036-15.2015] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 08/08/2015] [Accepted: 08/12/2015] [Indexed: 01/28/2023] Open
Abstract
Microglia are being increasingly recognized as playing important roles in neurodevelopment. The cerebellum matures postnatally, undergoing major growth, but the role of microglia in the developing cerebellum is not well understood. Using the laboratory rat we quantified and morphologically categorized microglia throughout the vermis and across development using a design-based unbiased stereology method. We found that microglial morphology changed from amoeboid to ramified during the first 3 postnatal weeks in a region specific manner. These morphological changes were accompanied by the sudden appearance of phagocytic cups during the third postnatal week from P17 to P19, with an approximately fourfold increase compared with the first week, followed by a prompt decline at the end of the third week. The microglial phagocytic cups were significantly higher in the granular layer (∼69%) than in the molecular layer (ML; ∼31%) during a 3 d window, and present on ∼67% of microglia with thick processes and ∼33% of microglia with thin processes. Similar proportions of phagocytic cups associated to microglia with either thick or thin processes were found in the ML. We observed cell nuclei fragmentation and cleaved caspase-3 expression within some microglial phagocytic cups, presumably from dying granule neurons. At P17 males showed an approximately twofold increase in microglia with thin processes compared with females. Our findings indicate a continuous process of microglial maturation and a nonuniform distribution of microglia in the cerebellar cortex that implicates microglia as an important cellular component of the developing cerebellum.
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Affiliation(s)
- Miguel Perez-Pouchoulen
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Jonathan W. VanRyzin
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland 21201
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Margaret M. McCarthy
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland 21201
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland 21201
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29
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Chung WS, Allen NJ, Eroglu C. Astrocytes Control Synapse Formation, Function, and Elimination. Cold Spring Harb Perspect Biol 2015; 7:a020370. [PMID: 25663667 DOI: 10.1101/cshperspect.a020370] [Citation(s) in RCA: 502] [Impact Index Per Article: 55.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Astrocytes, through their close associations with synapses, can monitor and alter synaptic function, thus actively controlling synaptic transmission in the adult brain. Besides their important role at adult synapses, in the last three decades a number of critical findings have highlighted the importance of astrocytes in the establishment of synaptic connectivity in the developing brain. In this article, we will review the key findings on astrocytic control of synapse formation, function, and elimination. First, we will summarize our current structural and functional understanding of astrocytes at the synapse. Then, we will discuss the cellular and molecular mechanisms through which developing and mature astrocytes instruct the formation, maturation, and refinement of synapses. Our aim is to provide an overview of astrocytes as important players in the establishment of a functional nervous system.
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Affiliation(s)
- Won-Suk Chung
- Stanford University, School of Medicine, Department of Neurobiology, Stanford, California 94305
| | - Nicola J Allen
- Salk Institute for Biological Studies, Molecular Neurobiology Laboratory, La Jolla, California 92037
| | - Cagla Eroglu
- Duke University Medical Center, Cell Biology and Neurobiology Departments, Duke Institute for Brain Sciences, Durham, North Carolina 27710
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30
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Liewald D, Miller R, Logothetis N, Wagner HJ, Schüz A. Distribution of axon diameters in cortical white matter: an electron-microscopic study on three human brains and a macaque. BIOLOGICAL CYBERNETICS 2014; 108:541-57. [PMID: 25142940 PMCID: PMC4228120 DOI: 10.1007/s00422-014-0626-2] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 08/05/2014] [Indexed: 05/18/2023]
Abstract
The aim of this study was to obtain information on the axonal diameters of cortico-cortical fibres in the human brain, connecting distant regions of the same hemisphere via the white matter. Samples for electron microscopy were taken from the region of the superior longitudinal fascicle and from the transitional white matter between temporal and frontal lobe where the uncinate and inferior occipitofrontal fascicle merge. We measured the inner diameter of cross sections of myelinated axons. For comparison with data from the literature on the human corpus callosum, we also took samples from that region. For comparison with well-fixed material, we also included samples from corresponding regions of a monkey brain (Macaca mulatta). Fibre diameters in human brains ranged from 0.16 to 9 μm. Distributions of diameters were similar in the three systems of cortico-cortical fibres investigated, both in humans and the monkey, with most of the average values below 1 μm diameter and a small population of much thicker fibres. Within individual human brains, the averages were larger in the superior longitudinal fascicle than in the transitional zone between temporal and frontal lobe. An asymmetry between left and right could be found in one of the human brains, as well as in the monkey brain. A correlation was also found between the thickness of the myelin sheath and the inner axon diameter for axons whose calibre was greater than about 0.6 μm. The results are compared to white matter data in other mammals and are discussed with respect to conduction velocity, brain size, cognition, as well as diffusion weighted imaging studies.
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Affiliation(s)
- Daniel Liewald
- Max Planck Institute for Biological Cybernetics, Spemannstr. 38/41, 72076 Tübingen, Germany
| | - Robert Miller
- Department of Psychological Medicine, University of Otago, Wellington, New Zealand
| | - Nikos Logothetis
- Max Planck Institute for Biological Cybernetics, Spemannstr. 38/41, 72076 Tübingen, Germany
| | | | - Almut Schüz
- Max Planck Institute for Biological Cybernetics, Spemannstr. 38/41, 72076 Tübingen, Germany
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31
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Schuldiner O, Yaron A. Mechanisms of developmental neurite pruning. Cell Mol Life Sci 2014; 72:101-19. [PMID: 25213356 DOI: 10.1007/s00018-014-1729-6] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/02/2014] [Accepted: 09/04/2014] [Indexed: 12/19/2022]
Abstract
The precise wiring of the nervous system is a combined outcome of progressive and regressive events during development. Axon guidance and synapse formation intertwined with cell death and neurite pruning sculpt the mature circuitry. It is now well recognized that pruning of dendrites and axons as means to refine neuronal networks, is a wide spread phenomena required for the normal development of vertebrate and invertebrate nervous systems. Here we will review the arising principles of cellular and molecular mechanisms of neurite pruning. We will discuss these principles in light of studies in multiple neuronal systems, and speculate on potential explanations for the emergence of neurite pruning as a mechanism to sculpt the nervous system.
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Affiliation(s)
- Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, 7610001, Rehovot, Israel,
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32
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Berbel P, Navarro D, Román GC. An evo-devo approach to thyroid hormones in cerebral and cerebellar cortical development: etiological implications for autism. Front Endocrinol (Lausanne) 2014; 5:146. [PMID: 25250016 PMCID: PMC4158880 DOI: 10.3389/fendo.2014.00146] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 08/25/2014] [Indexed: 12/11/2022] Open
Abstract
The morphological alterations of cortical lamination observed in mouse models of developmental hypothyroidism prompted the recognition that these experimental changes resembled the brain lesions of children with autism; this led to recent studies showing that maternal thyroid hormone deficiency increases fourfold the risk of autism spectrum disorders (ASD), offering for the first time the possibility of prevention of some forms of ASD. For ethical reasons, the role of thyroid hormones on brain development is currently studied using animal models, usually mice and rats. Although mammals have in common many basic developmental principles regulating brain development, as well as fundamental basic mechanisms that are controlled by similar metabolic pathway activated genes, there are also important differences. For instance, the rodent cerebral cortex is basically a primary cortex, whereas the primary sensory areas in humans account for a very small surface in the cerebral cortex when compared to the associative and frontal areas that are more extensive. Associative and frontal areas in humans are involved in many neurological disorders, including ASD, attention deficit-hyperactive disorder, and dyslexia, among others. Therefore, an evo-devo approach to neocortical evolution among species is fundamental to understand not only the role of thyroid hormones and environmental thyroid disruptors on evolution, development, and organization of the cerebral cortex in mammals but also their role in neurological diseases associated to thyroid dysfunction.
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Affiliation(s)
- Pere Berbel
- Departamento de Histología y Anatomía, Facultad de Medicina, Universidad Miguel Hernández, Alicante, Spain
| | - Daniela Navarro
- Departamento de Histología y Anatomía, Facultad de Medicina, Universidad Miguel Hernández, Alicante, Spain
| | - Gustavo C. Román
- Department of Neurology, Weill Cornell Medical College, Cornell University, New York, NY, USA
- Methodist Neurological Institute, Houston, TX, USA
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33
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Szucs P, Luz LL, Pinho R, Aguiar P, Antal Z, Tiong SYX, Todd AJ, Safronov BV. Axon diversity of lamina I local-circuit neurons in the lumbar spinal cord. J Comp Neurol 2014; 521:2719-41. [PMID: 23386329 PMCID: PMC3738926 DOI: 10.1002/cne.23311] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/26/2012] [Accepted: 01/18/2012] [Indexed: 01/21/2023]
Abstract
Spinal lamina I is a key area for relaying and integrating information from nociceptive primary afferents with various other sources of inputs. Although lamina I projection neurons have been intensively studied, much less attention has been given to local-circuit neurons (LCNs), which form the majority of the lamina I neuronal population. In this work the infrared light-emitting diode oblique illumination technique was used to visualize and label LCNs, allowing reconstruction and analysis of their dendritic and extensive axonal trees. We show that the majority of lamina I neurons with locally branching axons fall into the multipolar (with ventrally protruding dendrites) and flattened (dendrites limited to lamina I) somatodendritic categories. Analysis of their axons revealed that the initial myelinated part gives rise to several unmyelinated small-diameter branches that have a high number of densely packed, large varicosities and an extensive rostrocaudal (two or three segments), mediolateral, and dorsoventral (reaching laminae III-IV) distribution. The extent of the axon and the occasional presence of long, solitary branches suggest that LCNs may also form short and long propriospinal connections. We also found that the distribution of axon varicosities and terminal field locations show substantial heterogeneity and that a substantial portion of LCNs is inhibitory. Our observations indicate that LCNs of lamina I form intersegmental as well as interlaminar connections and may govern large numbers of neurons, providing anatomical substrate for rostrocaudal "processing units" in the dorsal horn.
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Affiliation(s)
- Peter Szucs
- Spinal Neuronal Networks Group, Institute of Molecular and Cell Biology-IBMC, University of Porto, 4150-180 Porto, Portugal.
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34
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Schafer DP, Stevens B. Phagocytic glial cells: sculpting synaptic circuits in the developing nervous system. Curr Opin Neurobiol 2013; 23:1034-40. [PMID: 24157239 DOI: 10.1016/j.conb.2013.09.012] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 09/21/2013] [Accepted: 09/24/2013] [Indexed: 12/18/2022]
Abstract
In the developing nervous system, synaptic connections are formed in excess and must remodel to achieve the precise synaptic connectivity characteristic of the mature organism. Synaptic pruning is a developmental process in which subsets of synapses are eliminated while the remaining synapses are preserved and strengthened. Recent findings have demonstrated unexpected roles for glial cells in this developmental process. These data demonstrate that phagocytic glia engulf synaptic and/or axonal elements in the developing nervous system and disruptions in this process result in sustained deficits in synaptic connectivity. These new findings highlight the importance of glia for nervous system development and function and may shed new light on mechanisms underlying nervous system disease.
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Affiliation(s)
- Dorothy P Schafer
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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35
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Clarke LE, Barres BA. Emerging roles of astrocytes in neural circuit development. Nat Rev Neurosci 2013; 14:311-21. [PMID: 23595014 DOI: 10.1038/nrn3484] [Citation(s) in RCA: 665] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Astrocytes are now emerging as key participants in many aspects of brain development, function and disease. In particular, new evidence shows that astrocytes powerfully control the formation, maturation, function and elimination of synapses through various secreted and contact-mediated signals. Astrocytes are also increasingly being implicated in the pathophysiology of many psychiatric and neurological disorders that result from synaptic defects. A better understanding of how astrocytes regulate neural circuit development and function in the healthy and diseased brain might lead to the development of therapeutic agents to treat these diseases.
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Affiliation(s)
- Laura E Clarke
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California 94305, USA.
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36
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Innocenti GM, Vercelli A, Caminiti R. The diameter of cortical axons depends both on the area of origin and target. ACTA ACUST UNITED AC 2013; 24:2178-88. [PMID: 23529006 DOI: 10.1093/cercor/bht070] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In primates, different cortical areas send axons of different diameters into comparable tracts, notably the corpus callosum (Tomasi S, Caminiti R, Innocenti GM. 2012. Areal differences in diameter and length of corticofugal projections. Cereb Cortex. 22:1463-1472). We now explored if an area also sends axons of different diameters to different targets. We find that the parietal area PEc sends thicker axons to area 4 and 6, and thinner ones to the cingulate region (area 24). Areas 4 and 9, each sends axons of different diameters to the nucleus caudatus, to different levels of the internal capsule, and to the thalamus. The internal capsule receives the thickest axon, followed by thalamus and nucleus caudatus. The 2 areas (4 and 9) differ in the diameter and length of axons to corresponding targets. We calculated how diameter determines conduction velocity of the axons and together with pathway length determines transmission delays between different brain sites. We propose that projections from and within the cerebral cortex consist of a complex system of lines of communication with different geometrical and time computing properties.
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Affiliation(s)
| | - Alessandro Vercelli
- Neuroscience Institute Cavalieri Ottolenghi (NICO), Department of Neuroscience, University of Turin, Turin, Italy and
| | - Roberto Caminiti
- Department of Physiology and Pharmacology, University of Rome Sapienza, Rome, Italy
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The visual callosal connection: a connection like any other? Neural Plast 2013; 2013:397176. [PMID: 23634306 PMCID: PMC3619632 DOI: 10.1155/2013/397176] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 02/27/2013] [Indexed: 11/23/2022] Open
Abstract
Recent work about the role of visual callosal connections in ferrets and cats is reviewed, and morphological and functional homologies between the lateral intrinsic and callosal network in early visual areas are discussed. Both networks selectively link distributed neuronal groups with similar response properties, and the actions exerted by callosal input reflect the functional topography of those networks. This supports the notion that callosal connections perpetuate the function of the lateral intrahemispheric circuit onto the other hemisphere. Reversible deactivation studies indicate that the main action of visual callosal input is a multiplicative shift of responses rather than a changing response selectivity. Both the gain of that action and its excitatory-inhibitory balance seem to be dynamically adapted to the feedforward drive by the visual stimulus onto primary visual cortex. Taken together anatomical and functional evidence from corticocortical and lateral circuits further leads to the conclusion that visual callosal connections share more features with lateral intrahemispheric connections on the same hierarchical level and less with feedback connections. I propose that experimental results about the callosal circuit in early visual areas can be interpreted with respect to lateral connectivity in general.
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Jones RS, Minogue AM, Connor TJ, Lynch MA. Amyloid-β-induced astrocytic phagocytosis is mediated by CD36, CD47 and RAGE. J Neuroimmune Pharmacol 2012; 8:301-11. [PMID: 23238794 DOI: 10.1007/s11481-012-9427-3] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/02/2012] [Indexed: 11/26/2022]
Abstract
Astrocytes, the most numerous glial cell in the brain, have multiple functions and are key to maintenance of homeostasis in the central nervous system. Microglia are the resident immunocompetent cells in the brain and share several functions with macrophages, including their phagocytic ability. Indeed microglia are the resident phagocytes in the brain and express numerous cell surface proteins which act to enable receptor-mediated phagocytosis. However recent evidence suggests that astrocytes express some genes which permit phagocytosis of phosphatidylserine-decorated cells and this probably explains sporadic reports in the literature which suggest that astrocytes become phagocytic following brain trauma. Here we examined the potential of astrocytes to phagocytose fluorescently-labelled latex beads and amyloid-β (Aβ) and report that they competently engulf both in a manner that relies on actin polymerization since it was inhibited by cytochalasin D. The data indicate that incubation of cultured astrocytes or microglia with Aβ increased phagocytosis and markers of activation of both cell types. Aβ was found to markedly increase expression of the putative Aβ-binding receptors CD36 and CD47 in astrocytes, while it decreased expression of the receptor for advanced glycation endproducts (RAGE). It is demonstrated that blocking these receptors using a neutralizing antibody attenuated Aβ-induced phagocytosis of latex beads by astrocytes. Interestingly blocking these receptors also decreased uptake of beads even in the absence of Aβ. Here we demonstrate that astrocytes are competent phagocytes and are capable of engulfing Aβ.
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Affiliation(s)
- Raasay S Jones
- Trinity College Institute of Neuroscience, Department of Physiology, Lloyd Building, Trinity College, Dublin 2, Ireland
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Schafer DP, Lehrman EK, Stevens B. The "quad-partite" synapse: microglia-synapse interactions in the developing and mature CNS. Glia 2012; 61:24-36. [PMID: 22829357 DOI: 10.1002/glia.22389] [Citation(s) in RCA: 395] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 06/21/2012] [Indexed: 01/04/2023]
Abstract
Microglia are the resident immune cells and phagocytes of our central nervous system (CNS). While most work has focused on the rapid and robust responses of microglia during CNS disease and injury, emerging evidence suggests that these mysterious cells have important roles at CNS synapses in the healthy, intact CNS. Groundbreaking live imaging studies in the anesthetized, adult mouse demonstrated that microglia processes dynamically survey their environment and interact with other brain cells including neurons and astrocytes. More recent imaging studies have revealed that microglia dynamically interact with synapses where they appear to serve as "synaptic sensors," responding to changes in neural activity and neurotransmitter release. In the following review, we discuss the most recent work demonstrating that microglia play active roles at developing and mature synapses. We first discuss the important imaging studies that have led us to better understand the physical relationship between microglia and synapses in the healthy brain. Following this discussion, we review known molecular mechanisms and functional consequences of microglia-synapse interactions in the developing and mature CNS. Our current knowledge sheds new light on the critical functions of these mysterious cells in synapse development and function in the healthy CNS, but has also incited several new and interesting questions that remain to be explored. We discuss these open questions, and how the most recent findings in the healthy CNS may be related to pathologies associated with abnormal and/or loss of neural circuits.
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Affiliation(s)
- Dorothy P Schafer
- Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Hempel C, Hyttel P, Staalsø T, Nyengaard JR, Kurtzhals JAL. Erythropoietin treatment alleviates ultrastructural myelin changes induced by murine cerebral malaria. Malar J 2012; 11:216. [PMID: 22741599 PMCID: PMC3502138 DOI: 10.1186/1475-2875-11-216] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 04/03/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cerebral malaria (CM) is a severe complication of malaria with considerable mortality. In addition to acute encephalopathy, survivors frequently suffer from neurological sequelae. The pathogenesis is incompletely understood, hampering the development of an effective, adjunctive therapy, which is not available at present. Previously, erythropoietin (EPO) was reported to significantly improve the survival and outcome in a murine CM model. The study objectives were to assess myelin thickness and ultrastructural morphology in the corpus callosum in murine CM and to adress the effects of EPO treatment in this context. METHODS The study consisted of two groups of Plasmodium berghei-infected mice and two groups of uninfected controls that were either treated with EPO or placebo (n = 4 mice/group). In the terminal phase of murine CM the brains were removed and processed for electron microscopy. Myelin sheaths in the corpus callosum were analysed with transmission electron microscopy and stereology. RESULTS The infection caused clinical CM, which was counteracted by EPO. The total number of myelinated axons was identical in the four groups and mice with CM did not have reduced mean thickness of the myelin sheaths. Instead, CM mice had significantly increased numbers of abnormal myelin sheaths, whereas EPO-treated mice were indistinguishable from uninfected mice. Furthermore, mice with CM had frequent and severe axonal injury, pseudopodic endothelial cells, perivascular oedemas and intracerebral haemorrhages. CONCLUSIONS EPO treatment reduced clinical signs of CM and reduced cerebral pathology. Murine CM does not reduce the general thickness of myelin sheaths in the corpus callosum.
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Affiliation(s)
- Casper Hempel
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen University Hospital, Denmark.
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Bui Quoc E, Ribot J, Quenech’Du N, Doutremer S, Lebas N, Grantyn A, Aushana Y, Milleret C. Asymmetrical interhemispheric connections develop in cat visual cortex after early unilateral convergent strabismus: anatomy, physiology, and mechanisms. Front Neuroanat 2012; 5:68. [PMID: 22275883 PMCID: PMC3257851 DOI: 10.3389/fnana.2011.00068] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 12/19/2011] [Indexed: 11/13/2022] Open
Abstract
In the mammalian primary visual cortex, the corpus callosum contributes to the unification of the visual hemifields that project to the two hemispheres. Its development depends on visual experience. When this is abnormal, callosal connections must undergo dramatic anatomical and physiological changes. However, data concerning these changes are sparse and incomplete. Thus, little is known about the impact of abnormal postnatal visual experience on the development of callosal connections and their role in unifying representation of the two hemifields. Here, the effects of early unilateral convergent strabismus (a model of abnormal visual experience) were fully characterized with respect to the development of the callosal connections in cat visual cortex, an experimental model for humans. Electrophysiological responses and 3D reconstruction of single callosal axons show that abnormally asymmetrical callosal connections develop after unilateral convergent strabismus, resulting from an extension of axonal branches of specific orders in the hemisphere ipsilateral to the deviated eye and a decreased number of nodes and terminals in the other (ipsilateral to the non-deviated eye). Furthermore this asymmetrical organization prevents the establishment of a unifying representation of the two visual hemifields. As a general rule, we suggest that crossed and uncrossed retino-geniculo-cortical pathways contribute successively to the development of the callosal maps in visual cortex.
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Affiliation(s)
- Emmanuel Bui Quoc
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
- Service d’Ophtalmologie, Hôpital Robert DebréParis, France
| | - Jérôme Ribot
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
| | - Nicole Quenech’Du
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
| | - Suzette Doutremer
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
| | - Nicolas Lebas
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
| | - Alexej Grantyn
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
| | - Yonane Aushana
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
| | - Chantal Milleret
- Laboratoire de Physiologie de la Perception et de l’Action, Collège de FranceParis, France
- Laboratoire de Physiologie de la Perception et de l’Action, CNRS UMR 7152Paris, France
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Stolp H, Neuhaus A, Sundramoorthi R, Molnár Z. The Long and the Short of it: Gene and Environment Interactions During Early Cortical Development and Consequences for Long-Term Neurological Disease. Front Psychiatry 2012; 3:50. [PMID: 22701439 PMCID: PMC3372875 DOI: 10.3389/fpsyt.2012.00050] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 05/01/2012] [Indexed: 01/21/2023] Open
Abstract
Cortical development is a complex amalgamation of proliferation, migration, differentiation, and circuit formation. These processes follow defined timescales and are controlled by a combination of intrinsic and extrinsic factors. It is currently unclear how robust and flexible these processes are and whether the developing brain has the capacity to recover from disruptions. What is clear is that there are a number of cognitive disorders or conditions that are elicited as a result of disrupted cortical development, although it may take a long time for the full pathophysiology of the conditions to be realized clinically. The critical window for the manifestation of a neurodevelopmental disorder is prolonged, and there is the potential for a complex interplay between genes and environment. While there have been extended investigations into the genetic basis of a number of neurological and mental disorders, limited definitive associations have been discovered. Many environmental factors, including inflammation and stress, have been linked to neurodevelopmental disorders, and it may be that a better understanding of the interplay between genes and environment will speed progress in this field. In particular, the development of the brain needs to be considered in the context of the whole materno-fetal unit as the degree of the metabolic, endocrine, or inflammatory responses, for example, will greatly influence the environment in which the brain develops. This review will emphasize the importance of extending neurodevelopmental studies to the contribution of the placenta, vasculature, cerebrospinal fluid, and to maternal and fetal immune response. These combined investigations are more likely to reveal genetic and environmental factors that influence the different stages of neuronal development and potentially lead to the better understanding of the etiology of neurological and mental disorders such as autism, epilepsy, cerebral palsy, and schizophrenia.
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Affiliation(s)
- Helen Stolp
- Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK
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43
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Erblich B, Zhu L, Etgen AM, Dobrenis K, Pollard JW. Absence of colony stimulation factor-1 receptor results in loss of microglia, disrupted brain development and olfactory deficits. PLoS One 2011; 6:e26317. [PMID: 22046273 PMCID: PMC3203114 DOI: 10.1371/journal.pone.0026317] [Citation(s) in RCA: 421] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 09/23/2011] [Indexed: 01/01/2023] Open
Abstract
The brain contains numerous mononuclear phagocytes called microglia. These cells express the transmembrane tyrosine kinase receptor for the macrophage growth factor colony stimulating factor-1 (CSF-1R). Using a CSF-1R-GFP reporter mouse strain combined with lineage defining antibody staining we show in the postnatal mouse brain that CSF-1R is expressed only in microglia and not neurons, astrocytes or glial cells. To study CSF-1R function we used mice homozygous for a null mutation in the Csflr gene. In these mice microglia are >99% depleted at embryonic day 16 and day 1 post-partum brain. At three weeks of age this microglial depletion continues in most regions of the brain although some contain clusters of rounded microglia. Despite the loss of microglia, embryonic brain development appears normal but during the post-natal period the brain architecture becomes perturbed with enlarged ventricles and regionally compressed parenchyma, phenotypes most prominent in the olfactory bulb and cortex. In the cortex there is increased neuronal density, elevated numbers of astrocytes but reduced numbers of oligodendrocytes. Csf1r nulls rarely survive to adulthood and therefore to study the role of CSF-1R in olfaction we used the viable null mutants in the Csf1 (Csf1(op)) gene that encodes one of the two known CSF-1R ligands. Food-finding experiments indicate that olfactory capacity is significantly impaired in the absence of CSF-1. CSF-1R is therefore required for the development of microglia, for a fully functional olfactory system and the maintenance of normal brain structure.
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Affiliation(s)
- Bryna Erblich
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Liyin Zhu
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Anne M. Etgen
- Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, United States of America
- Center for the Study of Reproductive Biology and Women's Health, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Kostantin Dobrenis
- Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Jeffrey W. Pollard
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, United States of America
- Center for the Study of Reproductive Biology and Women's Health, Albert Einstein College of Medicine, New York, New York, United States of America
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Abstract
The production of genotypic and phenotypic diversity (differentiation) is the final outcome of both development and evolution, of nervous systems and of their components. Cortical axons, in particular, differentiate into a variety of phenotypes which are responsible for computational transformations of messages exchanged among neurons. One aspect of this differentiation concerns axon diameters whose diversity in development, but also within and across species, is enhanced by the addition of a relatively small proportion of thicker axons to some axonal pathways. This, combined with differences in the length of pathways and in brain volumes, has rescaled and expanded the temporal range of interneuronal communication. In both development and evolution, this and other aspects of axonal phenotypes, namely the structure and distribution of axonal arbors, differentiate by the combined action of cell intrinsic (genetic) variation, overproduction, and selection by the environment.
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Abstract
Axons are generally considered as reliable transmission cables in which stable propagation occurs once an action potential is generated. Axon dysfunction occupies a central position in many inherited and acquired neurological disorders that affect both peripheral and central neurons. Recent findings suggest that the functional and computational repertoire of the axon is much richer than traditionally thought. Beyond classical axonal propagation, intrinsic voltage-gated ionic currents together with the geometrical properties of the axon determine several complex operations that not only control signal processing in brain circuits but also neuronal timing and synaptic efficacy. Recent evidence for the implication of these forms of axonal computation in the short-term dynamics of neuronal communication is discussed. Finally, we review how neuronal activity regulates both axon morphology and axonal function on a long-term time scale during development and adulthood.
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Affiliation(s)
- Dominique Debanne
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Emilie Campanac
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Andrzej Bialowas
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Edmond Carlier
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
| | - Gisèle Alcaraz
- Institut National de la Santé et de la Recherche Médicale U.641 and Université de la Méditerranée, Faculté de Médecine Secteur Nord, Marseille, France
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Myelination transition zone astrocytes are constitutively phagocytic and have synuclein dependent reactivity in glaucoma. Proc Natl Acad Sci U S A 2011; 108:1176-81. [PMID: 21199938 DOI: 10.1073/pnas.1013965108] [Citation(s) in RCA: 167] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Optic nerve head (ONH) astrocytes have been proposed to play both protective and deleterious roles in glaucoma. We now show that, within the postlaminar ONH myelination transition zone (MTZ), there are astrocytes that normally express Mac-2 (also known as Lgals3 or galectin-3), a gene typically expressed only in phagocytic cells. Surprisingly, even in healthy mice, MTZ and other ONH astrocytes constitutive internalize large axonal evulsions that contain whole organelles. In mouse glaucoma models, MTZ astrocytes further up-regulate Mac-2 expression. During glaucomatous degeneration, there are dystrophic processes in the retina and optic nerve, including the MTZ, which contain protease resistant γ-synuclein. The increased Mac-2 expression by MTZ astrocytes during glaucoma likely depends on this γ-synuclein, as mice lacking γ-synuclein fail to up-regulate Mac-2 at the MTZ after elevation of intraocular pressure. These results suggest the possibility that a newly discovered normal degradative pathway for axons might contribute to glaucomatous neurodegeneration.
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Schmidt KE, Lomber SG, Innocenti GM. Specificity of neuronal responses in primary visual cortex is modulated by interhemispheric corticocortical input. ACTA ACUST UNITED AC 2010; 20:2776-86. [PMID: 20211943 PMCID: PMC2978237 DOI: 10.1093/cercor/bhq024] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Within the visual cortex, it has been proposed that interhemispheric interactions serve to re-establish the continuity of the visual field across its vertical meridian (VM) by mechanisms similar to those used by intrinsic connections within a hemisphere. However, other specific functions of transcallosal projections have also been proposed, including contributing to disparity tuning and depth perception. Here, we consider whether interhemispheric connections modulate specific response properties, orientation and direction selectivity, of neurons in areas 17 and 18 of the ferret by combining reversible thermal deactivation in one hemisphere with optical imaging of intrinsic signals and single-cell electrophysiology in the other hemisphere. We found interhemispheric influences on both the strength and specificity of the responses to stimulus orientation and direction of motion, predominantly at the VM. However, neurons and domains preferring cardinal contours, in particular vertical contours, seem to receive stronger interhemispheric input than others. This finding is compatible with interhemispheric connections being involved in horizontal disparity tuning. In conclusion, our results support the view that interhemispheric interactions mainly perform integrative functions similar to those of connections intrinsic to one hemisphere.
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Affiliation(s)
- Kerstin E Schmidt
- Max-Planck Research Group: Cortical Function and Dynamics, Max Planck Institute for Brain Research, Deutschordenstraße 46, Frankfurt/Main, Germany.
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Streit WJ, Xue QS. Life and death of microglia. J Neuroimmune Pharmacol 2009; 4:371-9. [PMID: 19680817 DOI: 10.1007/s11481-009-9163-5] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 06/30/2009] [Indexed: 01/05/2023]
Abstract
The importance of microglial cells in the maintenance of a well-functioning central nervous system (CNS) cannot be overstated. As descendants of the myelomonocytic lineage they are industrious housekeepers and watchful sentries that safeguard a homeostatic environment through a number of mechanisms designed to provide protection of fastidious neurons at all times. Microglia become particularly active after homeostasis has been perturbed by physical injury or other insults and they enter into a state of activation which is determined largely by the nature and severity of the lesion. Microglial activation is the main cellular event in acute neuroinflammation and essential for wound healing in the CNS. Recent studies from this laboratory have been focused on microglia in the aging brain and identified structural abnormalities, termed microglial dystrophy, that are consistent with cell senescence and progress to a form of accidental cell death that is marked by cytoplasmic degeneration and has been termed cytorrhexis. Cytorrhexis of microglia is infrequent in the normally aged human brain and non-detectable in aged rodents, but its occurrence increases dramatically during neurodegenerative conditions, including Alzheimer's disease (AD) in humans and motoneuron disease in transgenic rats. The identification of degenerating microglia has given rise to a novel theory of AD pathogenesis, the microglial dysfunction hypothesis, which views the loss of microglial neuroprotection as a central event in neurodegenerative disease development.
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Affiliation(s)
- Wolfgang J Streit
- Department of Neuroscience, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, FL 32610, USA.
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Hsu JYC, Stein SA, Xu XM. Abnormal growth of the corticospinal axons into the lumbar spinal cord of the hyt/hyt mouse with congenital hypothyroidism. J Neurosci Res 2009; 86:3126-39. [PMID: 18543337 DOI: 10.1002/jnr.21750] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Thyroid hormone deficiency may cause severe neurological disorders resulting from developmental deficits of the central nervous system. The mutant hyt/hyt mouse, characterized by fetal-onset, life-long hypothyroidism resulting from a point mutation of the thyroid-stimulating hormone receptor of the thyroid gland, displays a variety of abnormalities in motor behavior that are likely associated with dysfunctions of specific brain regions and a defective corticospinal tract (CST). To test the hypothesis that fetal and neonatal hypothyroidism cause abnormal CST development, the growth of the CST was investigated in hypothyroid hyt/hyt mice and their euthyroid progenitors, the BALB/cByJ mice. Anterograde labeling with biotinylated dextran amine demonstrated a decrease in the number of CST axons in the hyt/hyt mouse at the first lumbar level at postnatal day (P) 10. After retrograde tracing with fast blue (FB), fewer FB-labeled neurons were found in the motor cortex, the red nucleus, and the lateral vestibular nucleus of the hyt/hyt mouse. At the fourth lumbar level, the hyt/hyt mouse also showed smaller CST cross-sectional areas and significantly lower numbers of unmyelinated axons, myelinated axons, and growth cones within the CST during postnatal development. At P10, the hyt/hyt mouse demonstrated significantly lower immunoreactivity of embryonic neural cell adhesion molecule in the CST at the seventh cervical level, whereas the expression of growth-associated protein 43 remained unchanged. Our study demonstrated an abnormal development of the CST in the hyt/hyt mouse, manifested by reduced axon quantity and retarded growth pattern at the lumbar spinal cord.
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Affiliation(s)
- Jung-Yu C Hsu
- Department of Anatomy and Neurobiology, Saint Louis University School of Medicine, St Louis, MO, USA.
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Keogh MJ, Ridgway SH. Neuronal Fiber Composition of the Corpus Callosum Within Some Odontocetes. Anat Rec (Hoboken) 2008; 291:781-9. [DOI: 10.1002/ar.20701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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