101
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Microglia emerge as central players in brain disease. Nat Med 2017; 23:1018-1027. [PMID: 28886007 DOI: 10.1038/nm.4397] [Citation(s) in RCA: 1074] [Impact Index Per Article: 153.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 07/26/2017] [Indexed: 02/07/2023]
Abstract
There has been an explosion of new findings recently giving us insights into the involvement of microglia in central nervous system (CNS) disorders. A host of new molecular tools and mouse models of disease are increasingly implicating this enigmatic type of nervous system cell as a key player in conditions ranging from neurodevelopmental disorders such as autism to neurodegenerative disorders such as Alzheimer's disease and chronic pain. Contemporaneously, diverse roles are emerging for microglia in the healthy brain, from sculpting developing neuronal circuits to guiding learning-associated plasticity. Understanding the physiological functions of these cells is crucial to determining their roles in disease. Here we focus on recent developments in our rapidly expanding understanding of the function, as well as the dysfunction, of microglia in disorders of the CNS.
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102
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Roeper J. Closing gaps in brain disease-from overlapping genetic architecture to common motifs of synapse dysfunction. Curr Opin Neurobiol 2017; 48:45-51. [PMID: 28968515 DOI: 10.1016/j.conb.2017.09.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 09/11/2017] [Indexed: 10/18/2022]
Abstract
Recent progress in the synaptic pathophysiology of brain diseases is reviewed. To emphasize the emergence of common motifs in synapse dysfunctions across neurodevelopmental, psychiatric and neurological disorders, conventional clinical boundaries are disregarded and a decidedly trans-diagnostic, potentially unifying view of altered synapse function is promoted. Based on the overlapping genetic architecture of brain disorders, which often converges on genes related to synaptic functions, disease-related changes in basic pre-synaptic and post-synaptic communication, neuromodulation-gated changes in Hebbian plasticity, dynamic interactions between Hebbian and homeostatic plasticity, and changes in synaptic maintenance by autophagy and glial-mediated phagocytosis are highlighted.
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Affiliation(s)
- Jochen Roeper
- Institute of Neurophysiology, Goethe University, Frankfurt, Germany.
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103
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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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104
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Abstract
Microglial cells are the resident tissue macrophages of the CNS and are widely recognized for their immune surveillance of the healthy CNS. In addition to this well-accepted function, recent findings point to major roles for microglia in instructing and regulating the proper function of the neuronal networks in the adult CNS, but these cells are also involved in creating neuronal networks by orchestrating construction of the whole network during development. In this Review, we highlight recent findings about the steady-state functions of microglial cells, the factors that are important for physiological microglial function, and how microglia help to maintain tissue homeostasis in the CNS.
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Affiliation(s)
- Katrin Kierdorf
- Department of Life Sciences and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - Marco Prinz
- Institute of Neuropathology, Faculty of Medicine, University of Freiburg and BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
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105
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Mottahedin A, Ardalan M, Chumak T, Riebe I, Ek J, Mallard C. Effect of Neuroinflammation on Synaptic Organization and Function in the Developing Brain: Implications for Neurodevelopmental and Neurodegenerative Disorders. Front Cell Neurosci 2017; 11:190. [PMID: 28744200 PMCID: PMC5504097 DOI: 10.3389/fncel.2017.00190] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 06/20/2017] [Indexed: 12/27/2022] Open
Abstract
The brain is a plastic organ where both the intrinsic CNS milieu and extrinsic cues play important roles in shaping and wiring neural connections. The perinatal period constitutes a critical time in central nervous system development with extensive refinement of neural connections, which are highly sensitive to fetal and neonatal compromise, such as inflammatory challenges. Emerging evidence suggests that inflammatory cells in the brain such as microglia and astrocytes are pivotal in regulating synaptic structure and function. In this article, we will review the role of glia cells in synaptic physiology and pathophysiology, including microglia-mediated elimination of synapses. We propose that activation of the immune system dynamically affects synaptic organization and function in the developing brain. We will discuss the role of neuroinflammation in altered synaptic plasticity following perinatal inflammatory challenges and potential implications for neurodevelopmental and neurodegenerative disorders.
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Affiliation(s)
- Amin Mottahedin
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
| | - Maryam Ardalan
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
| | - Tetyana Chumak
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
| | - Ilse Riebe
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
| | - Joakim Ek
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
| | - Carina Mallard
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
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106
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Arcuri C, Mecca C, Bianchi R, Giambanco I, Donato R. The Pathophysiological Role of Microglia in Dynamic Surveillance, Phagocytosis and Structural Remodeling of the Developing CNS. Front Mol Neurosci 2017; 10:191. [PMID: 28674485 PMCID: PMC5474494 DOI: 10.3389/fnmol.2017.00191] [Citation(s) in RCA: 164] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 05/30/2017] [Indexed: 12/13/2022] Open
Abstract
In vertebrates, during an early wave of hematopoiesis in the yolk sac between embryonic day E7.0 and E9.0, cells of mesodermal leaflet addressed to macrophage lineage enter in developing central nervous system (CNS) and originate the developing native microglial cells. Depending on the species, microglial cells represent 5–20% of glial cells resident in adult brain. Here, we briefly discuss some canonical functions of the microglia, i.e., cytokine secretion and functional transition from M1 to M2 phenotype. In addition, we review studies on the non-canonical functions of microglia such as regulation of phagocytosis, synaptic pruning, and sculpting postnatal neural circuits. In this latter context the contribution of microglia to some neurodevelopmental disorders is now well established. Nasu-Hakola (NHD) disease is considered a primary microgliopathy with alterations of the DNAX activation protein 12 (DAP12)-Triggering receptor expressed on myeloid cells 2 (TREM-2) signaling and removal of macromolecules and apoptotic cells followed by secondary microglia activation. In Rett syndrome Mecp2-/- microglia shows a substantial impairment of phagocytic ability, although the role of microglia is not yet clear. In a mouse model of Tourette syndrome (TS), microglia abnormalities have also been described, and deficient microglia-mediated neuroprotection is obvious. Here we review the role of microglial cells in neurodevelopmental disorders without inflammation and on the complex role of microglia in developing CNS.
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Affiliation(s)
- Cataldo Arcuri
- Department of Experimental Medicine, Centro Universitario per la Ricerca sulla Genomica Funzionale, Perugia Medical School, University of PerugiaPerugia, Italy
| | - Carmen Mecca
- Department of Experimental Medicine, Centro Universitario per la Ricerca sulla Genomica Funzionale, Perugia Medical School, University of PerugiaPerugia, Italy
| | - Roberta Bianchi
- Department of Experimental Medicine, Centro Universitario per la Ricerca sulla Genomica Funzionale, Perugia Medical School, University of PerugiaPerugia, Italy
| | - Ileana Giambanco
- Department of Experimental Medicine, Centro Universitario per la Ricerca sulla Genomica Funzionale, Perugia Medical School, University of PerugiaPerugia, Italy
| | - Rosario Donato
- Department of Experimental Medicine, Centro Universitario per la Ricerca sulla Genomica Funzionale, Perugia Medical School, University of PerugiaPerugia, Italy
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107
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Wolf Y, Boura-Halfon S, Cortese N, Haimon Z, Sar Shalom H, Kuperman Y, Kalchenko V, Brandis A, David E, Segal-Hayoun Y, Chappell-Maor L, Yaron A, Jung S. Brown-adipose-tissue macrophages control tissue innervation and homeostatic energy expenditure. Nat Immunol 2017; 18:665-674. [PMID: 28459435 PMCID: PMC5438596 DOI: 10.1038/ni.3746] [Citation(s) in RCA: 188] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 04/11/2017] [Indexed: 12/12/2022]
Abstract
Tissue macrophages provide immunological defense and contribute to the establishment and maintenance of tissue homeostasis. Here we used constitutive and inducible mutagenesis to delete the nuclear transcription regulator Mecp2 in macrophages. Mice that lacked the gene encoding Mecp2, which is associated with Rett syndrome, in macrophages did not show signs of neurodevelopmental disorder but displayed spontaneous obesity, which was linked to impaired function of brown adipose tissue (BAT). Specifically, mutagenesis of a BAT-resident Cx3Cr1+ macrophage subpopulation compromised homeostatic thermogenesis but not acute, cold-induced thermogenesis. Mechanistically, malfunction of BAT in pre-obese mice with mutant macrophages was associated with diminished sympathetic innervation and local titers of norepinephrine, which resulted in lower expression of thermogenic factors by adipocytes. Mutant macrophages overexpressed the signaling receptor and ligand PlexinA4, which might contribute to the phenotype by repulsion of sympathetic axons expressing the transmembrane semaphorin Sema6A. Collectively, we report a previously unappreciated homeostatic role for macrophages in the control of tissue innervation. Disruption of this circuit in BAT resulted in metabolic imbalance.
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Affiliation(s)
- Yochai Wolf
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | | | - Nina Cortese
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
- Department of Immunology and Inflammation, Humanitas Clinical and Research Center, Rozzano, Italy
| | - Zhana Haimon
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Hadas Sar Shalom
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Yael Kuperman
- Department of Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel
| | - Vyacheslav Kalchenko
- Department of Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel
| | - Alexander Brandis
- Department of Biological Services, Weizmann Institute of Science, Rehovot, Israel
| | - Eyal David
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Yifat Segal-Hayoun
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | | | - Avraham Yaron
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Steffen Jung
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
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108
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Zhao D, Mokhtari R, Pedrosa E, Birnbaum R, Zheng D, Lachman HM. Transcriptome analysis of microglia in a mouse model of Rett syndrome: differential expression of genes associated with microglia/macrophage activation and cellular stress. Mol Autism 2017; 8:17. [PMID: 28367307 PMCID: PMC5372344 DOI: 10.1186/s13229-017-0134-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/17/2017] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Rett syndrome (RTT) is a severe, neurodevelopmental disorder primarily affecting girls, characterized by progressive loss of cognitive, social, and motor skills after a relatively brief period of typical development. It is usually due to de novo loss of function mutations in the X-linked gene, MeCP2, which codes for the gene expression and chromatin regulator, methyl-CpG binding protein 2. Although the behavioral phenotype appears to be primarily due to neuronal Mecp2 deficiency in mice, other cell types, including astrocytes and oligodendrocytes, also appear to contribute to some aspects of the RTT phenotype. In addition, microglia may also play a role. However, the effect of Mecp2 deficiency in microglia on RTT pathogenesis is controversial. METHODS In the current study, we applied whole transcriptome analysis using RNA-seq to gain insight into molecular pathways in microglia that might be dysregulated during the transition, in female mice heterozygous for an Mecp2-null allele (Mecp2+/-; Het), from the pre-phenotypic (5 weeks) to the phenotypic phases (24 weeks). RESULTS We found a significant overlap in differentially expressed genes (DEGs) with genes involved in regulating the extracellular matrix, and those that are activated or inhibited when macrophages and microglia are stimulated towards the M1 and M2 activation states. However, the M1- and M2-associated genes were different in the 5- and 24-week samples. In addition, a substantial decrease in the expression of nine members of the heat shock protein (HSP) family was found in the 5-week samples, but not at 24 weeks. CONCLUSIONS These findings suggest that microglia from pre-phenotypic and phenotypic female mice are activated in a manner different from controls and that pre-phenotypic female mice may have alterations in their capacity to response to heat stress and other stressors that function through the HSP pathway.
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Affiliation(s)
- Dejian Zhao
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA
| | - Ryan Mokhtari
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA
| | - Erika Pedrosa
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA
| | - Rayna Birnbaum
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA
| | - Deyou Zheng
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA.,Department of Neurology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA.,Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA
| | - Herbert M Lachman
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA.,Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA.,Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA.,Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY USA
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109
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Colonna M, Butovsky O. Microglia Function in the Central Nervous System During Health and Neurodegeneration. Annu Rev Immunol 2017; 35:441-468. [PMID: 28226226 DOI: 10.1146/annurev-immunol-051116-052358] [Citation(s) in RCA: 1398] [Impact Index Per Article: 199.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Microglia are resident cells of the brain that regulate brain development, maintenance of neuronal networks, and injury repair. Microglia serve as brain macrophages but are distinct from other tissue macrophages owing to their unique homeostatic phenotype and tight regulation by the central nervous system (CNS) microenvironment. They are responsible for the elimination of microbes, dead cells, redundant synapses, protein aggregates, and other particulate and soluble antigens that may endanger the CNS. Furthermore, as the primary source of proinflammatory cytokines, microglia are pivotal mediators of neuroinflammation and can induce or modulate a broad spectrum of cellular responses. Alterations in microglia functionality are implicated in brain development and aging, as well as in neurodegeneration. Recent observations about microglia ontogeny combined with extensive gene expression profiling and novel tools to study microglia biology have allowed us to characterize the spectrum of microglial phenotypes during development, homeostasis, and disease. In this article, we review recent advances in our understanding of the biology of microglia, their contribution to homeostasis, and their involvement in neurodegeneration. Moreover, we highlight the complexity of targeting microglia for therapeutic intervention in neurodegenerative diseases.
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Affiliation(s)
- Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110;
| | - Oleg Butovsky
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115;
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110
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Mosser CA, Baptista S, Arnoux I, Audinat E. Microglia in CNS development: Shaping the brain for the future. Prog Neurobiol 2017; 149-150:1-20. [DOI: 10.1016/j.pneurobio.2017.01.002] [Citation(s) in RCA: 158] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 01/24/2017] [Accepted: 01/24/2017] [Indexed: 12/22/2022]
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