501
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Zhou Y, Ulland TK, Colonna M. TREM2-Dependent Effects on Microglia in Alzheimer's Disease. Front Aging Neurosci 2018; 10:202. [PMID: 30038567 PMCID: PMC6046445 DOI: 10.3389/fnagi.2018.00202] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 06/13/2018] [Indexed: 12/31/2022] Open
Abstract
Alzheimer's disease (AD) is a late-onset dementia characterized by the deposition of amyloid plaques and formation of neurofibrillary tangles (NFTs) which lead to neuronal loss and cognitive deficits. Abnormal protein aggregates in the AD brain are also associated with reactive microglia and astrocytes. Whether this glial response is beneficial or detrimental in AD pathology is under debate. Microglia are the resident innate immune cells in the central nervous system (CNS) that survey the surrounding environment. Genome-wide association studies (GWAS) have identified the R47H variant of triggering receptor expressed on myeloid cell 2 (TREM2) as a risk factor for late-onset AD (LOAD) with an odds ratio of 4.5. TREM2 is an immunoreceptor primarily present on microglia in the CNS that binds to polyanionic molecules. The transmembrane domain of TREM2 signals through DAP12, an adaptor protein that contains an immunoreceptor tyrosine-based activation motif (ITAM), which mediates TREM2 signaling and promotes microglial activation and survival. In mouse models of AD, Trem2 haplodeficiency and deficiency lead to reduced microglial clustering around amyloid β (Aβ) plaques, suggesting TREM2 is required for plaque-associated microglial responses. Recently, TREM2 has been shown to enhance microglial metabolism through the mammalian target of rapamycin (mTOR) pathway. Although aberrant metabolism has long been associated with AD, not much was known regarding how metabolism in microglia might affect disease progression. In this review, we discuss the role of TREM2 and metabolism in AD pathology, highlighting how TREM2-mediated microglial metabolism modulates AD pathogenesis.
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Affiliation(s)
| | | | - Marco Colonna
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO, United States
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502
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Puntambekar SS, Saber M, Lamb BT, Kokiko-Cochran ON. Cellular players that shape evolving pathology and neurodegeneration following traumatic brain injury. Brain Behav Immun 2018; 71:9-17. [PMID: 29601944 DOI: 10.1016/j.bbi.2018.03.033] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 03/16/2018] [Accepted: 03/26/2018] [Indexed: 11/28/2022] Open
Abstract
Traumatic brain injury (TBI) is one of the leading causes of death and disability worldwide, and has emerged as a critical risk factor for multiple neurodegenerative diseases, particularly Alzheimer's disease (AD). How the inflammatory cascade resulting from mechanical stress, axonal shearing and the loss of neurons and glia following initial impact in TBI, contributes to the development of AD-like disease is unclear. Neuroinflammation, characterized by blood-brain barrier (BBB) dysfunction and activation of brain-resident microglia and astrocytes, resulting in secretion of inflammatory mediators and subsequent recruitment of peripheral immune cells has been the focus of extensive research in attempts to identify drug-targets towards improving functional outcomes post TBI. While knowledge of intricate cellular interactions that shape lesion pathophysiology is incomplete, a major limitation in the field is the lack of understanding of how distinct cell types differentially alter TBI pathology. The aim of this review is to highlight functional differences between populations of bone marrow derived, infiltrating monocytes/macrophages and brain-resident microglia based on differential expression of the chemokine receptors CCR2 and CX3CR1. This review will focus on how unique subsets of mononuclear phagocytes shape TBI pathophysiology, neurotoxicity and BBB function, in a disease-stage dependent manner. Additionally, this review summarizes the role of multiple microglia and macrophage receptors, namely CCR2, CX3CR1 and Triggering Receptor Expressed on Myeloid Cells-2 (TREM2) in pathological neuroinflammation and neurodegeneration vs. recovery following TBI. TREM2 has been implicated in mediating AD-related pathology, and variants in TREM2 are particularly important due to their correlation with exacerbated neurodegeneration. Finally, this review highlights behavioral outcomes associated with microglial vs. macrophage variances, the need for novel treatment strategies that target unique subpopulations of peripheral macrophages, and the importance of development of therapeutics to modulate inflammatory functions of brain-resident microglia at specific stages of TBI.
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Affiliation(s)
- Shweta S Puntambekar
- Stark Neuroscience Research Institute, Indiana University-Purdue University, Indianapolis, IN 46202, USA.
| | - Maha Saber
- Barrows Neurological Institute at Phoenix Children's Hospital, Phoenix, AZ 85016, USA.
| | - Bruce T Lamb
- Stark Neuroscience Research Institute, Indiana University-Purdue University, Indianapolis, IN 46202, USA.
| | - Olga N Kokiko-Cochran
- Department of Neuroscience, The Ohio State University, Institute for Behavioral Medicine Research, Columbus, OH, 43210, USA.
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503
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Deming Y, Li Z, Benitez BA, Cruchaga C. Triggering receptor expressed on myeloid cells 2 (TREM2): a potential therapeutic target for Alzheimer disease? Expert Opin Ther Targets 2018; 22:587-598. [PMID: 29889572 DOI: 10.1080/14728222.2018.1486823] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
INTRODUCTION There are currently no effective therapeutics for Alzheimer disease (AD). Clinical trials targeting amyloid beta thus far have shown very little benefit and only in the earliest stages of disease. These limitations have driven research to identify alternative therapeutic targets, one of the most promising is the triggering receptor expressed on myeloid cells 2 (TREM2). Areas covered: Here, we review the literature to-date and discuss the potentials and pitfalls for targeting TREM2 as a potential therapeutic for AD. We focus on research in animal and cell models for AD and central nervous system injury models which may help in understanding the role of TREM2 in disease. Expert opinion: Studies suggest TREM2 plays a key role in AD pathology; however, results have been conflicting about whether TREM2 is beneficial or harmful. More research is necessary before designing TREM2-targeting therapies. Successful therapeutics will most likely be administered early in disease.
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Affiliation(s)
- Yuetiva Deming
- a Department of Psychiatry , Washington University School of Medicine , St Louis , MO , USA
| | - Zeran Li
- a Department of Psychiatry , Washington University School of Medicine , St Louis , MO , USA
| | - Bruno A Benitez
- b Department of Medicine , Washington University School of Medicine , St Louis , MO , USA
| | - Carlos Cruchaga
- a Department of Psychiatry , Washington University School of Medicine , St Louis , MO , USA.,c Department of Developmental Biology , Washington University School of Medicine , St Louis , MO , USA.,d Knight Alzheimer's Disease Research Center , Washington University School of Medicine , St Louis , MO , USA.,e Hope Center for Neurological Disorders , Washington University School of Medicine , St Louis , MO , USA
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504
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Bedoui Y, Neal JW, Gasque P. The Neuro-Immune-Regulators (NIREGs) Promote Tissue Resilience; a Vital Component of the Host's Defense Strategy against Neuroinflammation. J Neuroimmune Pharmacol 2018; 13:309-329. [PMID: 29909495 DOI: 10.1007/s11481-018-9793-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 05/24/2018] [Indexed: 01/29/2023]
Abstract
An effective protective inflammatory response in the brain is crucial for the clearance of pathogens (e.g. microbes, amyloid fibrils, prionSC) and should be closely regulated. However, the CNS seems to have limited tissue resilience to withstand the detrimental effects of uncontrolled inflammation compromising functional recovery and tissue repair. Newly described neuro-immune-regulators (NIREGs) are functionally related proteins regulating the severity and duration of the host inflammatory response. NIREGs such as CD200, CD47 and CX3CL1 are vital for increasing tissue resilience and are constitutively expressed by neurons. The interaction with co-receptors (CD200R, CD172a, CX3CR1) will maintain microglia in the resting phenotype, directing aggressive microglia phenotype and limiting bystander injuries. Neurons can also express many of the complement NIREGs (CD55, CD46, CD59 and factor H). Neurons and glia also express suppressor of cytokine signaling proteins (SOCS) down regulating janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway and to lead to the polarization of microglia towards anti-inflammatory phenotype. Other NIREGs such as serine protease inhibitors (serpins) and thrombomodulin (CD141) inhibit neurotoxic systemic coagulation proteins such as thrombin. The unfolded protein response (UPR) detects misfolded proteins and other stressors to prevent irreversible cell injury. Microglial pattern recognition receptors (PRR) (TREM-2, CR3, FcγR) are important to clear apoptotic cells and cellular debris but in non-phlogystic manner through inhibitory signaling pathways. The TYRO3, Axl, Mer (TAM) tyrosine receptor kinases activated by Gas 6 and PROS1 regulate inflammation by inhibiting Toll like receptors (TLR) /JAK-STAT activation and contribute to NIREG's functions.
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Affiliation(s)
- Yosra Bedoui
- Université de la Réunion, CRNS 9192, INSERM U1187, IRD249, Unité Mixte Processus Infectieux en Milieu Insulaire Tropical (PIMIT), Plateforme Technologique CYROI, Saint -Clotilde, La Réunion, France
| | - Jim W Neal
- Infection and Immunity, Cardiff University, Henry Wellcome Building, Cardiff, CF14 4XN, UK.
| | - Philippe Gasque
- Laboratoire de biologie, secteur laboratoire d'immunologie Clinique et expérimentale ZOI, LICE-OI, CHU Felix Guyon Bellepierre, St Denis, La Réunion, France.
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505
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Cheng-Hathaway PJ, Reed-Geaghan EG, Jay TR, Casali BT, Bemiller SM, Puntambekar SS, von Saucken VE, Williams RY, Karlo JC, Moutinho M, Xu G, Ransohoff RM, Lamb BT, Landreth GE. The Trem2 R47H variant confers loss-of-function-like phenotypes in Alzheimer's disease. Mol Neurodegener 2018; 13:29. [PMID: 29859094 PMCID: PMC5984804 DOI: 10.1186/s13024-018-0262-8] [Citation(s) in RCA: 135] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 05/23/2018] [Indexed: 12/20/2022] Open
Abstract
Background The R47H variant of Triggering Receptor Expressed on Myeloid cells 2 (TREM2) confers greatly increased risk for Alzheimer’s disease (AD), reflective of a central role for myeloid cells in neurodegeneration. Understanding how this variant confers AD risk promises to provide important insights into how myeloid cells contribute to AD pathogenesis and progression. Methods In order to investigate this mechanism, CRISPR/Cas9 was used to generate a mouse model of AD harboring one copy of the single nucleotide polymorphism (SNP) encoding the R47H variant in murine Trem2. TREM2 expression, myeloid cell responses to amyloid deposition, plaque burden, and neuritic dystrophy were assessed at 4 months of age. Results AD mice heterozygous for the Trem2 R47H allele exhibited reduced total Trem2 mRNA expression, reduced TREM2 expression around plaques, and reduced association of myeloid cells with plaques. These results were comparable to AD mice lacking one copy of Trem2. AD mice heterozygous for the Trem2 R47H allele also showed reduced myeloid cell responses to amyloid deposition, including a reduction in proliferation and a reduction in CD45 expression around plaques. Expression of the Trem2 R47H variant also reduced dense core plaque number but increased plaque-associated neuritic dystrophy. Conclusions These data suggest that the AD-associated TREM2 R47H variant increases risk for AD by conferring a loss of TREM2 function and enhancing neuritic dystrophy around plaques. Electronic supplementary material The online version of this article (10.1186/s13024-018-0262-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Paul J Cheng-Hathaway
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA.,Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Erin G Reed-Geaghan
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Taylor R Jay
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Brad T Casali
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA.,Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Shane M Bemiller
- Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Department of Medical and Molecular Genetics, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Shweta S Puntambekar
- Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Department of Medical and Molecular Genetics, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Victoria E von Saucken
- Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Roxanne Y Williams
- Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - J Colleen Karlo
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Miguel Moutinho
- Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Guixiang Xu
- Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Department of Medical and Molecular Genetics, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA
| | - Richard M Ransohoff
- Cleveland Clinic Lerner Research Institute, Cleveland, OH, 44195, USA.,Third Rock Ventures, Boston, MA, 02116, USA
| | - Bruce T Lamb
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA.,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Department of Medical and Molecular Genetics, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.,Cleveland Clinic Lerner Research Institute, Cleveland, OH, 44195, USA
| | - Gary E Landreth
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA. .,Department of Anatomy and Cell Biology, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA. .,Paul and Carole Stark Neurosciences Research Institute, Indiana University, School of Medicine, Indianapolis, IN, 46202, USA.
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506
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Sudom A, Talreja S, Danao J, Bragg E, Kegel R, Min X, Richardson J, Zhang Z, Sharkov N, Marcora E, Thibault S, Bradley J, Wood S, Lim AC, Chen H, Wang S, Foltz IN, Sambashivan S, Wang Z. Molecular basis for the loss-of-function effects of the Alzheimer's disease-associated R47H variant of the immune receptor TREM2. J Biol Chem 2018; 293:12634-12646. [PMID: 29794134 DOI: 10.1074/jbc.ra118.002352] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 05/08/2018] [Indexed: 12/22/2022] Open
Abstract
Triggering receptor expressed on myeloid cells 2 (TREM2) is an immune receptor expressed on the surface of microglia, macrophages, dendritic cells, and osteoclasts. The R47H TREM2 variant is a significant risk factor for late-onset Alzheimer's disease (AD), and the molecular basis of R47H TREM2 loss of function is an emerging area of TREM2 biology. Here, we report three high-resolution structures of the extracellular ligand-binding domains (ECDs) of R47H TREM2, apo-WT, and phosphatidylserine (PS)-bound WT TREM2 at 1.8, 2.2, and 2.2 Å, respectively. The structures reveal that Arg47 plays a critical role in maintaining the structural features of the complementarity-determining region 2 (CDR2) loop and the putative positive ligand-interacting surface (PLIS), stabilizing conformations capable of ligand interaction. This is exemplified in the PS-bound structure, in which the CDR2 loop and PLIS drive critical interactions with PS via surfaces that are disrupted in the variant. Together with in vitro and in vivo characterization, our structural findings elucidate the molecular mechanism underlying loss of ligand binding, putative oligomerization, and functional activity of R47H TREM2. They also help unravel how decreased in vitro and in vivo stability of TREM2 contribute to loss of function in disease.
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Affiliation(s)
- Athena Sudom
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080,
| | - Santosh Talreja
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Jean Danao
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Eric Bragg
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Rob Kegel
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Xiaoshan Min
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Jason Richardson
- Amgen Discovery Research, Amgen Inc., Thousand Oaks, California 91320, and
| | - Zhongqi Zhang
- Amgen Discovery Research, Amgen Inc., Thousand Oaks, California 91320, and
| | - Nikolai Sharkov
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Edoardo Marcora
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Steve Thibault
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Jodi Bradley
- Amgen Discovery Research, Amgen Inc., Thousand Oaks, California 91320, and
| | - Steve Wood
- Amgen Discovery Research, Amgen Inc., Thousand Oaks, California 91320, and
| | - Ai-Ching Lim
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Hang Chen
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Songli Wang
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080
| | - Ian N Foltz
- Amgen Discovery Research, Amgen Inc., Burnaby, British Columbia V5A 1V7, Canada
| | - Shilpa Sambashivan
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080,
| | - Zhulun Wang
- From Amgen Discovery Research, Amgen Inc., San Francisco, California 94080,
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507
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Schlepckow K, Kleinberger G, Fukumori A, Feederle R, Lichtenthaler SF, Steiner H, Haass C. An Alzheimer-associated TREM2 variant occurs at the ADAM cleavage site and affects shedding and phagocytic function. EMBO Mol Med 2018; 9:1356-1365. [PMID: 28855300 PMCID: PMC5623859 DOI: 10.15252/emmm.201707672] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sequence variations occurring in the gene encoding the triggering receptor expressed on myeloid cells 2 (TREM2) support an essential function of microglia and innate immunity in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative disorders. TREM2 matures within the secretory pathway, and its ectodomain is shed on the plasma membrane. Missense mutations in the immunoglobulin (Ig)‐like domain such as p.T66M and p.Y38C retain TREM2 within the endoplasmic reticulum and reduce shedding as well as TREM2‐dependent phagocytosis. Using mass spectrometry, we have now determined the cleavage site of TREM2. TREM2 is shed by proteases of the ADAM (a disintegrin and metalloproteinase domain containing protein) family C‐terminal to histidine 157, a position where an AD‐associated coding variant has been discovered (p.H157Y) in the Han Chinese population. Opposite to the characterized mutations within the Ig‐like domain, such as p.T66M and p.Y38C, the p.H157Y variant within the stalk region leads to enhanced shedding of TREM2. Elevated ectodomain shedding reduces cell surface full‐length TREM2 and lowers TREM2‐dependent phagocytosis. Therefore, two seemingly opposite cellular effects of TREM2 variants, namely reduced versus enhanced shedding, result in similar phenotypic outcomes by reducing cell surface TREM2.
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Affiliation(s)
- Kai Schlepckow
- Biomedical Center (BMC), Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Gernot Kleinberger
- Biomedical Center (BMC), Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Akio Fukumori
- German Center for Neurodegenerative Diseases (DZNE) Munich, Munich, Germany
| | - Regina Feederle
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.,German Center for Neurodegenerative Diseases (DZNE) Munich, Munich, Germany.,Helmholtz Center Munich, German Research Center for Environmental Health, Institute for Diabetes and Obesity, Core Facility Monoclonal Antibody Development, Neuherberg, Germany
| | - Stefan F Lichtenthaler
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.,German Center for Neurodegenerative Diseases (DZNE) Munich, Munich, Germany.,Neuroproteomics, Klinikum Rechts der Isar, Technische Universität München, Munich, Germany.,Institute for Advanced Study, Technische Universität München, Garching, Germany
| | - Harald Steiner
- Biomedical Center (BMC), Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany.,German Center for Neurodegenerative Diseases (DZNE) Munich, Munich, Germany
| | - Christian Haass
- Biomedical Center (BMC), Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany .,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.,German Center for Neurodegenerative Diseases (DZNE) Munich, Munich, Germany
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508
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Navarro V, Sanchez-Mejias E, Jimenez S, Muñoz-Castro C, Sanchez-Varo R, Davila JC, Vizuete M, Gutierrez A, Vitorica J. Microglia in Alzheimer's Disease: Activated, Dysfunctional or Degenerative. Front Aging Neurosci 2018; 10:140. [PMID: 29867449 PMCID: PMC5958192 DOI: 10.3389/fnagi.2018.00140] [Citation(s) in RCA: 137] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 04/25/2018] [Indexed: 12/11/2022] Open
Abstract
Microglial activation has been considered a crucial player in the pathological process of multiple human neurodegenerative diseases. In some of these pathologies, such as Amyotrophic Lateral Sclerosis or Multiple Sclerosis, the immune system and microglial cells (as part of the cerebral immunity) play a central role. In other degenerative processes, such as Alzheimer’s disease (AD), the role of microglia is far to be elucidated. In this “mini-review” article, we briefly highlight our recent data comparing the microglial response between amyloidogenic transgenic models, such as APP/PS1 and AD patients. Since the AD pathology could display regional heterogeneity, we focus our work at the hippocampal formation. In APP based models a prominent microglial response is triggered around amyloid-beta (Aβ) plaques. These strongly activated microglial cells could drive the AD pathology and, in consequence, could be implicated in the neurodegenerative process observed in models. On the contrary, the microglial response in human samples is, at least, partial or attenuated. This patent difference could simply reflect the lower and probably slower Aβ production observed in human hippocampal samples, in comparison with models, or could reflect the consequence of a chronic long-standing microglial activation. Beside this differential response, we also observed microglial degeneration in Braak V–VI individuals that, indeed, could compromise their normal role of surveying the brain environment and respond to the damage. This microglial degeneration, particularly relevant at the dentate gyrus, might be mediated by the accumulation of toxic soluble phospho-tau species. The consequences of this probably deficient immunological protection, observed in AD patients, are unknown.
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Affiliation(s)
- Victoria Navarro
- Departamento Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain.,Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Elisabeth Sanchez-Mejias
- Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Instituto de Biomedicina de Malaga (IBIMA), Universidad de Málaga, Málaga, Spain
| | - Sebastian Jimenez
- Departamento Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain.,Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Clara Muñoz-Castro
- Departamento Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain.,Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Raquel Sanchez-Varo
- Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Instituto de Biomedicina de Malaga (IBIMA), Universidad de Málaga, Málaga, Spain
| | - Jose C Davila
- Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Instituto de Biomedicina de Malaga (IBIMA), Universidad de Málaga, Málaga, Spain
| | - Marisa Vizuete
- Departamento Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain.,Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Antonia Gutierrez
- Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Instituto de Biomedicina de Malaga (IBIMA), Universidad de Málaga, Málaga, Spain
| | - Javier Vitorica
- Departamento Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.,Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain.,Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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509
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Abstract
Microglia are a subset of tissue macrophages that constitute the major immune cell type of the central nervous system. These cells have long been known to change their morphology and functions in response to various neurological insults. Recently, a plethora of unbiased transcriptomics studies have revealed that across a broad spectrum of neurodegeneration-like disease models, microglia adopt a similar activation signature and perform similar functions. Despite these commonalities in response, the role of microglia has been described as both positive and negative in different murine disease models. In humans, genetic association studies have revealed strong connections between microglia genes and various neurodegenerative diseases, and mechanistic investigations of these mutations have added another layer of complexity. Here, we provide an overview of studies that have built a case for a common microglial response to neurodegeneration and discuss pathways that may be important to initiate and sustain this response; delineate the multifaceted functions of activated microglia spanning different diseases; and discuss insights from studying genes associated with disease in humans. We argue that strong evidence causally links activated microglia function to neurodegeneration and discuss what seems to be a conflict between mouse models and human genetics.
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Affiliation(s)
- Wilbur M Song
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States.
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510
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Filipello F, Morini R, Corradini I, Zerbi V, Canzi A, Michalski B, Erreni M, Markicevic M, Starvaggi-Cucuzza C, Otero K, Piccio L, Cignarella F, Perrucci F, Tamborini M, Genua M, Rajendran L, Menna E, Vetrano S, Fahnestock M, Paolicelli RC, Matteoli M. The Microglial Innate Immune Receptor TREM2 Is Required for Synapse Elimination and Normal Brain Connectivity. Immunity 2018; 48:979-991.e8. [PMID: 29752066 DOI: 10.1016/j.immuni.2018.04.016] [Citation(s) in RCA: 395] [Impact Index Per Article: 65.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 01/19/2018] [Accepted: 04/13/2018] [Indexed: 02/07/2023]
Abstract
The triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial innate immune receptor associated with a lethal form of early, progressive dementia, Nasu-Hakola disease, and with an increased risk of Alzheimer's disease. Microglial defects in phagocytosis of toxic aggregates or apoptotic membranes were proposed to be at the origin of the pathological processes in the presence of Trem2 inactivating mutations. Here, we show that TREM2 is essential for microglia-mediated synaptic refinement during the early stages of brain development. The absence of Trem2 resulted in impaired synapse elimination, accompanied by enhanced excitatory neurotransmission and reduced long-range functional connectivity. Trem2-/- mice displayed repetitive behavior and altered sociability. TREM2 protein levels were also negatively correlated with the severity of symptoms in humans affected by autism. These data unveil the role of TREM2 in neuronal circuit sculpting and provide the evidence for the receptor's involvement in neurodevelopmental diseases.
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Affiliation(s)
- Fabia Filipello
- Humanitas University, Department of Biomedical Sciences, Via Rita Levi Montalcini, 20090 Pieve Emanuele - Milan, Italy
| | - Raffaella Morini
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy
| | - Irene Corradini
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy; IN-CNR, 20129 Milano, Italy
| | - Valerio Zerbi
- Neural Control of Movement Lab, HEST, ETH Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Alice Canzi
- Humanitas University, Department of Biomedical Sciences, Via Rita Levi Montalcini, 20090 Pieve Emanuele - Milan, Italy
| | - Bernadeta Michalski
- Department of Psychiatry & Behavioural Neurosciences, HSC-4N80, McMaster University, Hamilton, ON, Canada
| | - Marco Erreni
- Department of Immunology and Inflammation, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy
| | - Marija Markicevic
- Neural Control of Movement Lab, HEST, ETH Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Chiara Starvaggi-Cucuzza
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy
| | - Karel Otero
- Department of Neuroimmunology, Acute Neurology and Pain, Biogen Inc., 115 Broadway, Cambridge, MA, USA
| | - Laura Piccio
- Department of Neurology, Washington University, St. Louis, MO, USA
| | | | - Fabio Perrucci
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy
| | - Matteo Tamborini
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy
| | - Marco Genua
- Department of Immunology and Inflammation, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy
| | - Lawrence Rajendran
- Systems and Cell Biology of Neurodegeneration, IREM, University of Zurich, Schlieren, Switzerland
| | - Elisabetta Menna
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy; IN-CNR, 20129 Milano, Italy
| | - Stefania Vetrano
- Humanitas University, Department of Biomedical Sciences, Via Rita Levi Montalcini, 20090 Pieve Emanuele - Milan, Italy
| | - Margaret Fahnestock
- Department of Psychiatry & Behavioural Neurosciences, HSC-4N80, McMaster University, Hamilton, ON, Canada
| | - Rosa Chiara Paolicelli
- Systems and Cell Biology of Neurodegeneration, IREM, University of Zurich, Schlieren, Switzerland
| | - Michela Matteoli
- Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano - Milan, Italy; IN-CNR, 20129 Milano, Italy.
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511
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Yanaizu M, Sakai K, Tosaki Y, Kino Y, Satoh JI. Small nuclear RNA-mediated modulation of splicing reveals a therapeutic strategy for a TREM2 mutation and its post-transcriptional regulation. Sci Rep 2018; 8:6937. [PMID: 29720600 PMCID: PMC5931963 DOI: 10.1038/s41598-018-25204-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 04/17/2018] [Indexed: 12/30/2022] Open
Abstract
Loss-of-function mutations in TREM2 cause Nasu-Hakola disease (NHD), a rare genetic disease characterized by early-onset dementia with leukoencephalopathy and bone cysts. An NHD-associated mutation, c.482 + 2 T > C, disrupts the splice donor site of intron 3 and causes aberrant skipping of exon 3, resulting in the loss of full-length TREM2 protein. Here, we examined the efficacy of artificial U1 and U7 small nuclear RNAs (snRNAs) designed to enhance exon 3 inclusion. Using mutant TREM2 minigenes, we found that some modified U1, but not U7, snRNAs enhanced exon 3 inclusion and restored TREM2 protein expression. Unexpectedly, we found that exon 3 of wild-type TREM2 is an alternative exon, whose skipping leads to reduced expression of the full-length protein. Indeed, TREM2 protein levels were modulated by modified snRNAs that either promoted or repressed exon 3 inclusion. The splice donor site flanking exon 3 was predicted to be weak, which may explain both the alternative splicing of exon 3 under normal conditions and complete exon skipping when the c.482 + 2 T > C mutation was present. Collectively, our snRNA-based approaches provide a potential therapeutic strategy for NHD-associated mis-splicing and novel insights into the post-transcriptional regulation of TREM2.
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Affiliation(s)
- Motoaki Yanaizu
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi, Tokyo, 204-8588, Japan
| | - Kenji Sakai
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi, Tokyo, 204-8588, Japan
| | - Youhei Tosaki
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi, Tokyo, 204-8588, Japan
| | - Yoshihiro Kino
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi, Tokyo, 204-8588, Japan.
| | - Jun-Ichi Satoh
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi, Tokyo, 204-8588, Japan
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512
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Disease-Associated Microglia: A Universal Immune Sensor of Neurodegeneration. Cell 2018; 173:1073-1081. [DOI: 10.1016/j.cell.2018.05.003] [Citation(s) in RCA: 717] [Impact Index Per Article: 119.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 04/17/2018] [Accepted: 04/29/2018] [Indexed: 11/18/2022]
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513
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Freudenberg-Hua Y, Li W, Davies P. The Role of Genetics in Advancing Precision Medicine for Alzheimer's Disease-A Narrative Review. Front Med (Lausanne) 2018; 5:108. [PMID: 29740579 PMCID: PMC5928202 DOI: 10.3389/fmed.2018.00108] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 04/03/2018] [Indexed: 12/12/2022] Open
Abstract
Alzheimer's disease (AD) is the most common type of dementia, which has a substantial genetic component. AD affects predominantly older people. Accordingly, the prevalence of dementia has been rising as the population ages. To date, there are no effective interventions that can cure or halt the progression of AD. The only available treatments are the management of certain symptoms and consequences of dementia. The current state-of-the-art medical care for AD comprises three simple principles: prevent the preventable, achieve early diagnosis, and manage the manageable symptoms. This review provides a summary of the current state of knowledge of risk factors for AD, biological diagnostic testing, and prospects for treatment. Special emphasis is given to recent advances in genetics of AD and the way genomic data may support prevention, early intervention, and development of effective pharmacological treatments. Mutations in the APP, PSEN1, and PSEN2 genes cause early onset Alzheimer's disease (EOAD) that follows a Mendelian inheritance pattern. For late onset Alzheimer's disease (LOAD), APOE4 was identified as a major risk allele more than two decades ago. Population-based genome-wide association studies of late onset AD have now additionally identified common variants at roughly 30 genetic loci. Furthermore, rare variants (allele frequency <1%) that influence the risk for LOAD have been identified in several genes. These genetic advances have broadened our insights into the biological underpinnings of AD. Moreover, the known genetic risk variants could be used to identify presymptomatic individuals at risk for AD and support diagnostic assessment of symptomatic subjects. Genetic knowledge may also facilitate precision medicine. The goal of precision medicine is to use biological knowledge and other health information to predict individual disease risk, understand disease etiology, identify disease subcategories, improve diagnosis, and provide personalized treatment strategies. We discuss the potential role of genetics in advancing precision medicine for AD along with its ethical challenges. We outline strategies to implement genomics into translational clinical research that will not only improve accuracy of dementia diagnosis, thus enabling more personalized treatment strategies, but may also speed up the discovery of novel drugs and interventions.
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Affiliation(s)
- Yun Freudenberg-Hua
- Litwin-Zucker Center for the study of Alzheimer’s Disease, The Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY, United States
- Division of Geriatric Psychiatry, Zucker Hillside Hospital, Northwell Health, Glen Oaks, NY, United States
| | - Wentian Li
- Robert S Boas Center for Genomics and Human Genetics, The Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY, United States
| | - Peter Davies
- Litwin-Zucker Center for the study of Alzheimer’s Disease, The Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY, United States
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514
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Effect of multiple neonatal sevoflurane exposures on hippocampal apolipoprotein E levels and learning and memory abilities. Pediatr Neonatol 2018; 59:154-160. [PMID: 28890046 DOI: 10.1016/j.pedneo.2017.08.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 04/21/2017] [Accepted: 08/22/2017] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Sevoflurane anesthesia is widely used in pediatric patients. In this study, we investigated whether early multiple exposures to sevoflurane induced cognitive dysfunction by altering the hippocampal expression of ApoE later in development. METHODS Sprague-Dawley rats were exposed to 2.6% sevoflurane at postnatal day 7 (P7), P14, and P21 for 2 h. The ability of learning and memory was assessed using the Morris water maze at P37 and P97. The hippocampal volume was measured by magnetic resonance imaging (MRI) at P37 and P97. The hippocampal expression of ApoE was assessed by immunohistochemical analyses and real-time polymerase chain reaction (PCR). RESULTS Behavioral testing revealed that the ability of learning and memory in the sevoflurane-exposed rats was decreased compared with the control animals; however, there was no significant difference (P > 0.05). The MRI results showed a significant decrease in the left hippocampal volume, left maximum hippocampal length, and right maximum hippocampal length in the sevoflurane young group compared with the control young group (P < 0.05). The brain volume, left maximum hippocampal length, right hippocampal volume, and maximum brain length were significantly lower in the sevoflurane adult group than in the control adult group (P < 0.05). In young animals, the ApoE expression in the hippocampal CA1 and CA3 regions and the ApoE mRNA level were significantly higher compared with the control group (P < 0.05), but not in the dentate gyrus region (P > 0.05). Among the adult animals, there was no significant difference between the groups in any parameter tested (P > 0.05). CONCLUSION Multiple exposures to sevoflurane during the neonatal period decreased the volume of the hippocampus and increased the hippocampal expression of ApoE. The differential expression level of ApoE in different hippocampal subdivisions suggested that the expression of ApoE was regionally specific and reversible.
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515
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Brownjohn PW, Smith J, Solanki R, Lohmann E, Houlden H, Hardy J, Dietmann S, Livesey FJ. Functional Studies of Missense TREM2 Mutations in Human Stem Cell-Derived Microglia. Stem Cell Reports 2018; 10:1294-1307. [PMID: 29606617 PMCID: PMC5998752 DOI: 10.1016/j.stemcr.2018.03.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 03/02/2018] [Accepted: 03/05/2018] [Indexed: 01/02/2023] Open
Abstract
The derivation of microglia from human stem cells provides systems for understanding microglial biology and enables functional studies of disease-causing mutations. We describe a robust method for the derivation of human microglia from stem cells, which are phenotypically and functionally comparable with primary microglia. We used stem cell-derived microglia to study the consequences of missense mutations in the microglial-expressed protein triggering receptor expressed on myeloid cells 2 (TREM2), which are causal for frontotemporal dementia-like syndrome and Nasu-Hakola disease. We find that mutant TREM2 accumulates in its immature form, does not undergo typical proteolysis, and is not trafficked to the plasma membrane. However, in the absence of plasma membrane TREM2, microglia differentiate normally, respond to stimulation with lipopolysaccharide, and are phagocytically competent. These data indicate that dementia-associated TREM2 mutations have subtle effects on microglia biology, consistent with the adult onset of disease in individuals with these mutations.
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Affiliation(s)
- Philip W Brownjohn
- The Gurdon Institute, ARUK Stem Cell Research Centre and Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK
| | - James Smith
- The Gurdon Institute, ARUK Stem Cell Research Centre and Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK
| | - Ravi Solanki
- The Gurdon Institute, ARUK Stem Cell Research Centre and Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK
| | - Ebba Lohmann
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen 72076, Germany; DZNE, German Center for Neurodegenerative Diseases, Tübingen 72076, Germany
| | - Henry Houlden
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - John Hardy
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Sabine Dietmann
- Wellcome Trust Medical Research Council Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Frederick J Livesey
- The Gurdon Institute, ARUK Stem Cell Research Centre and Department of Biochemistry, University of Cambridge, Cambridge CB2 1QN, UK.
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516
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Sekiya M, Wang M, Fujisaki N, Sakakibara Y, Quan X, Ehrlich ME, De Jager PL, Bennett DA, Schadt EE, Gandy S, Ando K, Zhang B, Iijima KM. Integrated biology approach reveals molecular and pathological interactions among Alzheimer's Aβ42, Tau, TREM2, and TYROBP in Drosophila models. Genome Med 2018; 10:26. [PMID: 29598827 PMCID: PMC5875009 DOI: 10.1186/s13073-018-0530-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 03/12/2018] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Cerebral amyloidosis, neuroinflammation, and tauopathy are key features of Alzheimer's disease (AD), but interactions among these features remain poorly understood. Our previous multiscale molecular network models of AD revealed TYROBP as a key driver of an immune- and microglia-specific network that was robustly associated with AD pathophysiology. Recent genetic studies of AD further identified pathogenic mutations in both TREM2 and TYROBP. METHODS In this study, we systematically examined molecular and pathological interactions among Aβ, tau, TREM2, and TYROBP by integrating signatures from transgenic Drosophila models of AD and transcriptome-wide gene co-expression networks from two human AD cohorts. RESULTS Glial expression of TREM2/TYROBP exacerbated tau-mediated neurodegeneration and synergistically affected pathways underlying late-onset AD pathology, while neuronal Aβ42 and glial TREM2/TYROBP synergistically altered expression of the genes in synaptic function and immune modules in AD. CONCLUSIONS The comprehensive pathological and molecular data generated through this study strongly validate the causal role of TREM2/TYROBP in driving molecular networks in AD and AD-related phenotypes in flies.
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Affiliation(s)
- Michiko Sekiya
- 0000 0004 1791 9005grid.419257.cDepartment of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511 Japan
| | - Minghui Wang
- 0000 0001 0670 2351grid.59734.3cDepartment of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, Room 8-111, Box 1498, New York, NY 10029 USA ,0000 0001 0670 2351grid.59734.3cIcahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY USA
| | - Naoki Fujisaki
- 0000 0004 1791 9005grid.419257.cDepartment of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511 Japan ,0000 0001 0728 1069grid.260433.0Department of Experimental Gerontology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Japan
| | - Yasufumi Sakakibara
- 0000 0004 1791 9005grid.419257.cDepartment of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511 Japan
| | - Xiuming Quan
- 0000 0004 1791 9005grid.419257.cDepartment of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511 Japan
| | - Michelle E. Ehrlich
- 0000 0001 0670 2351grid.59734.3cDepartment of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, Room 8-111, Box 1498, New York, NY 10029 USA ,0000 0001 0670 2351grid.59734.3cDepartment of Neurology, Alzheimer’s Disease Research Center, Icahn School of Medicine at Mount Sinai, New York, NY USA ,0000 0001 0670 2351grid.59734.3cDepartment of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Philip L. De Jager
- 0000 0001 2285 2675grid.239585.0Center for translational & Computational Neuroimmunology, Department of Neurology, The Neurological Institute of New York, Columbia University Medical Center, New York, NY USA ,grid.66859.34Broad Institute, Cambridge, MA USA
| | - David A. Bennett
- 0000 0001 0705 3621grid.240684.cRush Alzheimer’s Disease Research Center and Department of Neurology, Rush University Medical Center, 1750 W. Congress Parkway, Chicago, IL 60612 USA
| | - Eric E. Schadt
- 0000 0001 0670 2351grid.59734.3cDepartment of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, Room 8-111, Box 1498, New York, NY 10029 USA ,0000 0001 0670 2351grid.59734.3cIcahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY USA
| | - Sam Gandy
- 0000 0001 0670 2351grid.59734.3cDepartment of Neurology, Alzheimer’s Disease Research Center, Icahn School of Medicine at Mount Sinai, New York, NY USA ,0000 0001 0670 2351grid.59734.3cDepartment of Psychiatry and Alzheimer’s Disease Research Center, Icahn School of Medicine at Mount Sinai, New York, NY USA ,0000 0004 5907 0628grid.480949.8Center for NFL Neurological Care, Department of Neurology, New York, NY USA ,0000 0004 0420 1184grid.274295.fJames J. Peters VA Medical Center, 130 West Kingsbridge Road, New York, NY USA
| | - Kanae Ando
- 0000 0001 1090 2030grid.265074.2Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo, Japan
| | - Bin Zhang
- Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, Room 8-111, Box 1498, New York, NY, 10029, USA. .,Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA. .,Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, One Gustave L Levy Place, New York, NY, USA.
| | - Koichi M. Iijima
- 0000 0004 1791 9005grid.419257.cDepartment of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511 Japan ,0000 0001 0728 1069grid.260433.0Department of Experimental Gerontology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Japan
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517
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Cheng Q, Danao J, Talreja S, Wen P, Yin J, Sun N, Li CM, Chui D, Tran D, Koirala S, Chen H, Foltz IN, Wang S, Sambashivan S. TREM2-activating antibodies abrogate the negative pleiotropic effects of the Alzheimer's disease variant Trem2R47H on murine myeloid cell function. J Biol Chem 2018; 293:12620-12633. [PMID: 29599291 DOI: 10.1074/jbc.ra118.001848] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 03/23/2018] [Indexed: 12/28/2022] Open
Abstract
Triggering receptor expressed on myeloid cells 2 (TREM2) is an orphan immune receptor expressed on cells of myeloid lineage such as macrophages and microglia. The rare variant R47H TREM2 is associated with an increased risk for Alzheimer's disease, supporting the hypothesis that TREM2 loss of function may exacerbate disease progression. However, a complete knockout of the TREM2 gene in different genetic models of neurodegenerative diseases has been reported to result in both protective and deleterious effects on disease-related end points and myeloid cell function. Here, we describe a Trem2R47H transgenic mouse model and report that even in the absence of additional genetic perturbations, this variant clearly confers a loss of function on myeloid cells. The Trem2R47H variant-containing myeloid cells exhibited subtle defects in survival and migration and displayed an unexpected dysregulation of cytokine responses in a lipopolysaccharide challenge environment. These subtle phenotypic defects with a gradation in severity across genotypes were confirmed in whole-genome RNA-Seq analyses of WT, Trem2-/-, and Trem2R47H myeloid cells under challenge conditions. Of note, TREM2-activating antibodies that boost proximal signaling abrogated survival defects conferred by the variant and also modulated migration and cytokine responses in an antibody-, ligand-, and challenge-dependent manner. In some instances, these antibodies also boosted WT myeloid cell function. Our studies provide a first glimpse into the boost in myeloid cell function that can be achieved by pharmacological modulation of TREM2 activity that can potentially be ameliorative in neurodegenerative diseases such as Alzheimer's disease.
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Affiliation(s)
- Qingwen Cheng
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Jean Danao
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Santosh Talreja
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Paul Wen
- the Department of Discovery Research, Amgen, Thousand Oaks, California 91320, and
| | - Jun Yin
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Ning Sun
- the Department of Discovery Research, Amgen, Thousand Oaks, California 91320, and
| | - Chi-Ming Li
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Danny Chui
- the Department of Discovery Research, Amgen, Burnaby, British Columbia V5A IV7, Canada
| | - David Tran
- the Department of Discovery Research, Amgen, Thousand Oaks, California 91320, and
| | - Samir Koirala
- the Department of Discovery Research, Amgen, Thousand Oaks, California 91320, and
| | - Hang Chen
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Ian N Foltz
- the Department of Discovery Research, Amgen, Burnaby, British Columbia V5A IV7, Canada
| | - Songli Wang
- From the Department of Discovery Research, Amgen, San Francisco, California 94080
| | - Shilpa Sambashivan
- From the Department of Discovery Research, Amgen, San Francisco, California 94080,
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518
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Zhong L, Wang Z, Wang D, Wang Z, Martens YA, Wu L, Xu Y, Wang K, Li J, Huang R, Can D, Xu H, Bu G, Chen XF. Amyloid-beta modulates microglial responses by binding to the triggering receptor expressed on myeloid cells 2 (TREM2). Mol Neurodegener 2018; 13:15. [PMID: 29587871 PMCID: PMC5870375 DOI: 10.1186/s13024-018-0247-7] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 03/20/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND TREM2 is an innate immune receptor specifically expressed in microglia. Coding variations in TREM2 have been reported to increase the risk for Alzheimer's disease (AD) and other neurodegenerative diseases. While multiple studies support a role for TREM2 in microglial recruitment to amyloid plaques, the chemoattractant factor modulating TREM2-dependent microglial responses has not been defined. METHODS Potential binding of oligomeric amyloid-β 1-42 (oAβ1-42) to TREM2 was tested by complementary approaches including solid phase binding, surface plasmon resonance and immunoprecipitation assays. The ability of oAβ1-42 to activate TREM2 signaling pathways was examined by analyzing the phosphorylation of Syk and Akt in primary microglia as well as TREM2-mediated signaling in a reporter cell system. Lastly, the functional outcome of oAβ1-42-TREM2 interaction was tested by examining impacts on microglial migration in vitro and clustering around oAβ1-42-bearing brain areas in vivo. RESULTS We found that oAβ1-42 bound to TREM2 with high affinity and activated TREM2-dependent signaling pathway. Neither monomeric nor scrambled Aβ bound to TREM2 supporting a specific interaction between oAβ and TREM2. The disease-associated mutations of TREM2 reduced its binding affinity to oAβ1-42. Furthermore, we identified several positively charged amino acids within residues 31-91 of TREM2 that were crucial for its interaction with oAβ1-42. Importantly, oAβ1-42 promoted microglial migration in vitro and clustering in vivo in a TREM2-dependent manner. CONCLUSIONS Our data establish a critical link between oAβ1-42, a major pathological component of AD, and TREM2, a strong genetic risk factor for AD expressed in microglia, and suggest that such interaction contributes to the pathogenic events in AD by modulating microglial responses.
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Affiliation(s)
- Li Zhong
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Zongqi Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Daxin Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Zhe Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Yuka A Martens
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Linbei Wu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Ying Xu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Kai Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Jianguo Li
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Ruizhi Huang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Dan Can
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
| | - Huaxi Xu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, 92037, USA
| | - Guojun Bu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China.
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA.
| | - Xiao-Fen Chen
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen, 361102, China.
- Shenzhen Research Institute of Xiamen University, Shenzhen, 518063, China.
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519
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Murray CE, King A, Troakes C, Hodges A, Lashley T. APOE ε4 is also required in TREM2 R47H variant carriers for Alzheimer's disease to develop. Neuropathol Appl Neurobiol 2018; 45:183-186. [PMID: 29411406 DOI: 10.1111/nan.12474] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 01/23/2018] [Indexed: 01/04/2023]
Affiliation(s)
- C E Murray
- Queen Square Brain Bank for Neurological Disorders, Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - A King
- Department of Clinical Neuropathology, Kings College Hospital, London, UK.,London Neurodegenerative Diseases Brain Bank, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, UK
| | - C Troakes
- London Neurodegenerative Diseases Brain Bank, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, UK.,Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, Kings College London, London, UK
| | - A Hodges
- Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - T Lashley
- Queen Square Brain Bank for Neurological Disorders, Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
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520
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Ulrich JD, Ulland TK, Mahan TE, Nyström S, Nilsson KP, Song WM, Zhou Y, Reinartz M, Choi S, Jiang H, Stewart FR, Anderson E, Wang Y, Colonna M, Holtzman DM. ApoE facilitates the microglial response to amyloid plaque pathology. J Exp Med 2018; 215:1047-1058. [PMID: 29483128 PMCID: PMC5881464 DOI: 10.1084/jem.20171265] [Citation(s) in RCA: 176] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 12/28/2017] [Accepted: 02/07/2018] [Indexed: 01/22/2023] Open
Abstract
Increasing evidence suggests that apoE influences the innate immune response in neurodegeneration. Here, Ulrich et al. report that apoE influences amyloid plaque morphology and the microglial response to amyloid plaques, along with plaque-associated neuronal toxicity. One of the hallmarks of Alzheimer’s disease is the presence of extracellular diffuse and fibrillar plaques predominantly consisting of the amyloid-β (Aβ) peptide. Apolipoprotein E (ApoE) influences the deposition of amyloid pathology through affecting the clearance and aggregation of monomeric Aβ in the brain. In addition to influencing Aβ metabolism, increasing evidence suggests that apoE influences microglial function in neurodegenerative diseases. Here, we characterize the impact that apoE has on amyloid pathology and the innate immune response in APPPS1ΔE9 and APPPS1-21 transgenic mice. We report that Apoe deficiency reduced fibrillar plaque deposition, consistent with previous studies. However, fibrillar plaques in Apoe-deficient mice exhibited a striking reduction in plaque compaction. Hyperspectral fluorescent imaging using luminescent conjugated oligothiophenes identified distinct Aβ morphotypes in Apoe-deficient mice. We also observed a significant reduction in fibrillar plaque–associated microgliosis and activated microglial gene expression in Apoe-deficient mice, along with significant increases in dystrophic neurites around fibrillar plaques. Our results suggest that apoE is critical in stimulating the innate immune response to amyloid pathology.
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Affiliation(s)
- Jason D Ulrich
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
| | - Tyler K Ulland
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO
| | - Thomas E Mahan
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
| | - Sofie Nyström
- Department of Chemistry, IFM, Linköping University, Linköping, Sweden
| | - K Peter Nilsson
- Department of Chemistry, IFM, Linköping University, Linköping, Sweden
| | - Wilbur M Song
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO
| | - Yingyue Zhou
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO
| | - Mariska Reinartz
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Radboud University Nijmegen, Nijmegen, Netherlands
| | - Seulah Choi
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
| | - Hong Jiang
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
| | - Floy R Stewart
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
| | - Elise Anderson
- Department of Neurology, Washington University School of Medicine, St. Louis, MO.,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
| | - Yaming Wang
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO.,Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO
| | - David M Holtzman
- Department of Neurology, Washington University School of Medicine, St. Louis, MO .,Knight Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO.,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO
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521
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Condello C, Yuan P, Grutzendler J. Microglia-Mediated Neuroprotection, TREM2, and Alzheimer's Disease: Evidence From Optical Imaging. Biol Psychiatry 2018; 83:377-387. [PMID: 29169609 PMCID: PMC5767550 DOI: 10.1016/j.biopsych.2017.10.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/05/2017] [Accepted: 10/06/2017] [Indexed: 12/19/2022]
Abstract
Recent genetic studies have provided overwhelming evidence of the involvement of microglia-related molecular networks in the pathophysiology of Alzheimer's disease (AD). However, the precise mechanisms by which microglia alter the course of AD neuropathology remain poorly understood. Here we discuss current evidence of the neuroprotective functions of microglia with a focus on optical imaging studies that have revealed a role of these cells in the encapsulation of amyloid deposits ("microglia barrier"). This barrier modulates the degree of plaque compaction, amyloid fibril surface area, and insulation from adjacent axons thereby reducing neurotoxicity. We discuss findings implicating genetic variants of the microglia receptor, triggering receptor expressed on myeloid cells 2, in the increased risk of late onset AD. We provide evidence that increased AD risk may be at least partly mediated by deficient microglia polarization toward amyloid deposits, resulting in ineffective plaque encapsulation and reduced plaque compaction, which is associated with worsened axonal pathology. Finally, we propose possible avenues for therapeutic targeting of plaque-associated microglia with the goal of enhancing the microglia barrier and potentially reducing disease progression.
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Affiliation(s)
- Carlo Condello
- Institute for Neurodegenerative Diseases, Weill Institute for Neurosciences, University of California, San Francisco, CA 94158, USA,Department of Neurology, University of California, San Francisco, CA 94158, USA
| | - Peng Yuan
- Department of Biology, Stanford University, Palo Alto, CA 94305, USA
| | - Jaime Grutzendler
- Department of Neurology, Yale School of Medicine, New Haven, Connecticut; Department of Neuroscience, Yale School of Medicine, New Haven, Connecticut.
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522
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Pimenova AA, Raj T, Goate AM. Untangling Genetic Risk for Alzheimer's Disease. Biol Psychiatry 2018; 83:300-310. [PMID: 28666525 PMCID: PMC5699970 DOI: 10.1016/j.biopsych.2017.05.014] [Citation(s) in RCA: 136] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 05/15/2017] [Accepted: 05/15/2017] [Indexed: 01/01/2023]
Abstract
Alzheimer's disease (AD) is a genetically heterogeneous neurodegenerative disorder caused by fully penetrant single gene mutations in a minority of cases, while the majority of cases are sporadic or show modest familial clustering. These cases are of late onset and likely result from the interaction of many genes and the environment. More than 30 loci have been implicated in AD by a combination of linkage, genome-wide association, and whole genome/exome sequencing. We have learned from these studies that perturbations in endolysosomal, lipid metabolism, and immune response pathways substantially contribute to sporadic AD pathogenesis. We review here current knowledge about functions of AD susceptibility genes, highlighting cells of the myeloid lineage as drivers of at least part of the genetic component in late-onset AD. Although targeted resequencing utilized for the identification of causal variants has discovered coding mutations in some AD-associated genes, a lot of risk variants lie in noncoding regions. Here we discuss the use of functional genomics approaches that integrate transcriptomic, epigenetic, and endophenotype traits with systems biology to annotate genetic variants, and to facilitate discovery of AD risk genes. Further validation in cell culture and mouse models will be necessary to establish causality for these genes. This knowledge will allow mechanism-based design of novel therapeutic interventions in AD and promises coherent implementation of treatment in a personalized manner.
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Affiliation(s)
- Anna A Pimenova
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York; Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Towfique Raj
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York; Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Alison M Goate
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York; Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, New York, New York.
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523
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Abstract
With a rapidly aging global human population, finding a cure for late onset neurodegenerative diseases has become an urgent enterprise. However, these efforts are hindered by the lack of understanding of what constitutes the phenotype of aged human microglia-the cell type that has been strongly implicated by genetic studies in the pathogenesis of age-related neurodegenerative disease. Here, we establish the set of genes that is preferentially expressed by microglia in the aged human brain. This HuMi_Aged gene set captures a unique phenotype, which we confirm at the protein level. Furthermore, we find this gene set to be enriched in susceptibility genes for Alzheimer's disease and multiple sclerosis, to be increased with advancing age, and to be reduced by the protective APOEε2 haplotype. APOEε4 has no effect. These findings confirm the existence of an aging-related microglial phenotype in the aged human brain and its involvement in the pathological processes associated with brain aging.
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524
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Satoh JI, Kino Y, Yanaizu M, Saito Y. Alzheimer's disease pathology in Nasu-Hakola disease brains. Intractable Rare Dis Res 2018; 7:32-36. [PMID: 29552443 PMCID: PMC5849622 DOI: 10.5582/irdr.2017.01088] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Nasu-Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by progressive presenile dementia and formation of multifocal bone cysts, caused by genetic mutations of either triggering receptor expressed on myeloid cells 2 (TREM2) or TYRO protein tyrosine kinase binding protein (TYROBP), alternatively named DNAX-activation protein 12 (DAP12), both of which are expressed on microglia in the brain and form the receptor-adaptor complex that chiefly recognizes anionic lipids. TREM2 transmits the signals involved in microglial survival, proliferation, chemotaxis, and phagocytosis. A recent study indicated that a loss of TREM2 function causes greater amounts of amyloid-β (Aβ) deposition in the hippocampus of a mouse model of Alzheimer's disease (AD) owing to a dysfunctional response of microglia to amyloid plaques, suggesting that TREM2 facilitates Aβ clearance by microglia. TREM2/DAP12-mediated microglial response limits diffusion and toxicity of amyloid plaques by forming a protective barrier. However, the levels of Aβ deposition in postmortem brains of NHD, where the biological function of the TREM2/DAP12 signaling pathway is completely lost, remain to be investigated. By immunohistochemistry, we studied the expression of Aβ and phosphorylated tau (p-tau) in the frontal cortex and the hippocampus of five NHD cases. Although we identified several small Aβ-immunoreactive spheroids, amyloid plaques were almost undetectable in NHD brains. We found a small number of p-tau-immunoreactive neurofibrillary tangle (NFT)-bearing neurons in NHD brains. Because AD pathology is less evident in NHD than the full-brown AD, it does not play an active role in the development of NHD.
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Affiliation(s)
- Jun-ichi Satoh
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, Tokyo, Japan
- Address correspondence to: Dr. Jun-ichi Satoh, Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo, Japan. E-mail:
| | - Yoshihiro Kino
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, Tokyo, Japan
| | - Motoaki Yanaizu
- Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, Tokyo, Japan
| | - Yuko Saito
- Department of Laboratory Medicine, National Center Hospital, NCNP, Tokyo, Japan
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525
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Schetters STT, Gomez-Nicola D, Garcia-Vallejo JJ, Van Kooyk Y. Neuroinflammation: Microglia and T Cells Get Ready to Tango. Front Immunol 2018; 8:1905. [PMID: 29422891 PMCID: PMC5788906 DOI: 10.3389/fimmu.2017.01905] [Citation(s) in RCA: 231] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Accepted: 12/13/2017] [Indexed: 12/19/2022] Open
Abstract
In recent years, many paradigms concerning central nervous system (CNS) immunology have been challenged and shifted, including the discovery of CNS-draining lymphatic vessels, the origin and functional diversity of microglia, the impact of T cells on CNS immunological homeostasis and the role of neuroinflammation in neurodegenerative diseases. In parallel, antigen presentation outside the CNS has revealed the vital role of antigen-presenting cells in maintaining tolerance toward self-proteins, thwarting auto-immunity. Here, we review recent findings that unite these shifted paradigms of microglial functioning, antigen presentation, and CNS-directed T cell activation, focusing on common neurodegenerative diseases. It provides an important update on CNS adaptive immunity, novel targets, and a concept of the microglia T-cell equilibrium.
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Affiliation(s)
- Sjoerd T T Schetters
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, Netherlands
| | - Diego Gomez-Nicola
- Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom
| | - Juan J Garcia-Vallejo
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, Netherlands
| | - Yvette Van Kooyk
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, Netherlands
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526
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Mecca C, Giambanco I, Donato R, Arcuri C. Microglia and Aging: The Role of the TREM2-DAP12 and CX3CL1-CX3CR1 Axes. Int J Mol Sci 2018; 19:E318. [PMID: 29361745 PMCID: PMC5796261 DOI: 10.3390/ijms19010318] [Citation(s) in RCA: 155] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/17/2018] [Accepted: 01/18/2018] [Indexed: 12/21/2022] Open
Abstract
Depending on the species, microglial cells represent 5-20% of glial cells in the adult brain. As the innate immune effector of the brain, microglia are involved in several functions: regulation of inflammation, synaptic connectivity, programmed cell death, wiring and circuitry formation, phagocytosis of cell debris, and synaptic pruning and sculpting of postnatal neural circuits. Moreover, microglia contribute to some neurodevelopmental disorders such as Nasu-Hakola disease (NHD), and to aged-associated neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and others. There is evidence that human and rodent microglia may become senescent. This event determines alterations in the microglia activation status, associated with a chronic inflammation phenotype and with the loss of neuroprotective functions that lead to a greater susceptibility to the neurodegenerative diseases of aging. In the central nervous system (CNS), Triggering Receptor Expressed on Myeloid Cells 2-DNAX activation protein 12 (TREM2-DAP12) is a signaling complex expressed exclusively in microglia. As a microglial surface receptor, TREM2 interacts with DAP12 to initiate signal transduction pathways that promote microglial cell activation, phagocytosis, and microglial cell survival. Defective TREM2-DAP12 functions play a central role in the pathogenesis of several diseases. The CX3CL1 (fractalkine)-CX3CR1 signaling represents the most important communication channel between neurons and microglia. The expression of CX3CL1 in neurons and of its receptor CX3CR1 in microglia determines a specific interaction, playing fundamental roles in the regulation of the maturation and function of these cells. Here, we review the role of the TREM2-DAP12 and CX3CL1-CX3CR1 axes in aged microglia and the involvement of these pathways in physiological CNS aging and in age-associated neurodegenerative diseases.
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Affiliation(s)
- Carmen Mecca
- Department of Experimental Medicine, Perugia Medical School, University of Perugia, Piazza Lucio Severi 1, 06132 Perugia, Italy.
| | - Ileana Giambanco
- Department of Experimental Medicine, Perugia Medical School, University of Perugia, Piazza Lucio Severi 1, 06132 Perugia, Italy.
| | - Rosario Donato
- Department of Experimental Medicine, Perugia Medical School, University of Perugia, Piazza Lucio Severi 1, 06132 Perugia, Italy.
- Centro Universitario per la Ricerca sulla Genomica Funzionale, Perugia Medical School, University of Perugia, Piazza Lucio Severi 1, 06132 Perugia, Italy.
| | - Cataldo Arcuri
- Department of Experimental Medicine, Perugia Medical School, University of Perugia, Piazza Lucio Severi 1, 06132 Perugia, Italy.
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527
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Kang SS, Kurti A, Baker KE, Liu CC, Colonna M, Ulrich JD, Holtzman DM, Bu G, Fryer JD. Behavioral and transcriptomic analysis of Trem2-null mice: not all knockout mice are created equal. Hum Mol Genet 2018; 27:211-223. [PMID: 29040522 PMCID: PMC5886290 DOI: 10.1093/hmg/ddx366] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 08/31/2017] [Accepted: 09/21/2017] [Indexed: 01/08/2023] Open
Abstract
It is clear that innate immune system status is altered in numerous neurodegenerative diseases. Human genetic studies have demonstrated that triggering receptor expressed in myeloid cells 2 (TREM2) coding variants have a strong association with Alzheimer's disease (AD) and other neurodegenerative diseases. To more thoroughly understand the impact of TREM2 in vivo, we studied the behavioral and cognitive functions of wild-type (WT) and Trem2-/- (KO) mice during basal conditions and brain function in the context of innate immune stimulation with peripherally administered lipopolysaccharide (LPS). Early markers of neuroinflammation preceded Aif1 and Trem2 upregulation that occurred at later stages (24-48 h post-LPS). We performed a transcriptomic study of these cohorts and found numerous transcripts and pathways that were altered in Trem2-/- mice both at baseline and 48 h after LPS challenge. Importantly, our transcriptome analysis revealed that our Trem2-/- mouse line (Velocigene allele) results in exaggerated Treml1 upregulation. In contrast, aberrantly high Treml1 expression was absent in the Trem2 knockout line generated by the Colonna lab and the Jackson Labs CRISPR/Cas9 Trem2 knockout line. Notably, removal of the floxed neomycin selection cassette ameliorated aberrant Treml1 expression, validating the artifactual nature of Treml1 expression in the original Trem2-/- Velocigene line. Clearly further studies are needed to decipher whether the Treml1 transcriptional artifact is functionally meaningful, but our data indicate that caution is warranted when interpreting functional studies with this particular line. Additionally, our results indicate that other Velocigene alleles or targeting strategies with strong heterologous promoters need to carefully consider downstream genes.
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Affiliation(s)
- Silvia S Kang
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Aishe Kurti
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Kelsey E Baker
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Chia-Chen Liu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University, St. Louis, MO 63110, USA
| | - Jason D Ulrich
- Department of Neurology, Washington University, St. Louis, MO 63110, USA
| | - David M Holtzman
- Department of Neurology, Washington University, St. Louis, MO 63110, USA
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
- Neurobiology of Disease Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL 32224, USA
| | - John D Fryer
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
- Neurobiology of Disease Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, Jacksonville, FL 32224, USA
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528
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Song WM, Joshita S, Zhou Y, Ulland TK, Gilfillan S, Colonna M. Humanized TREM2 mice reveal microglia-intrinsic and -extrinsic effects of R47H polymorphism. J Exp Med 2018; 215:745-760. [PMID: 29321225 PMCID: PMC5839761 DOI: 10.1084/jem.20171529] [Citation(s) in RCA: 166] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 11/07/2017] [Accepted: 12/18/2017] [Indexed: 12/20/2022] Open
Abstract
The R47H variant of the microglia gene TREM2 has been linked to a significantly higher risk of Alzheimer’s disease. In this study, Song et al. generate human TREM2-expressing mice and demonstrate that R47H leads to a decreased microglia number and activation as well as a decreased presence of soluble TREM2 on neurons and plaques in a mouse model of Alzheimer’s disease. Alzheimer’s disease (AD) is a neurodegenerative disease that causes late-onset dementia. The R47H variant of the microglial receptor TREM2 triples AD risk in genome-wide association studies. In mouse AD models, TREM2-deficient microglia fail to proliferate and cluster around the amyloid-β plaques characteristic of AD. In vitro, the common variant (CV) of TREM2 binds anionic lipids, whereas R47H mutation impairs binding. However, in vivo, the identity of TREM2 ligands and effect of the R47H variant remain unknown. We generated transgenic mice expressing human CV or R47H TREM2 and lacking endogenous TREM2 in the 5XFAD AD model. Only the CV transgene restored amyloid-β–induced microgliosis and microglial activation, indicating that R47H impairs TREM2 function in vivo. Remarkably, soluble TREM2 was found on neurons and plaques in CV- but not R47H-expressing 5XFAD brains, although in vitro CV and R47H were shed similarly via Adam17 proteolytic activity. These results demonstrate that TREM2 interacts with neurons and plaques duing amyloid-β accumulation and R47H impairs this interaction.
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Affiliation(s)
- Wilbur M Song
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO
| | - Satoru Joshita
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO.,Department of Medicine, Division of Gastroenterology and Hepatology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Yingyue Zhou
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO
| | - Tyler K Ulland
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO
| | - Susan Gilfillan
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO
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529
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Smith AJ, Verkman AS. The "glymphatic" mechanism for solute clearance in Alzheimer's disease: game changer or unproven speculation? FASEB J 2018; 32:543-551. [PMID: 29101220 DOI: 10.1096/fj.201700999] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
How solutes and macromolecules are removed from brain tissue is of central importance in normal brain physiology and in how toxic protein aggregates are cleared in neurodegenerative conditions, including Alzheimer's disease (AD). Conventionally, solute transport in the narrow and tortuous extracellular space in brain parenchyma has been thought to be primarily diffusive and nondirectional. The recently proposed "glymphatic" (glial-lymphatic) hypothesis posits that solute clearance is convective and driven by active fluid transport from para-arterial to paravenous spaces though aquaporin-4 water channels in astrocyte endfeet. Glymphatic, convective solute clearance has received much attention because of its broad implications for AD and other brain pathologies and even the function of sleep. However, the theoretical plausibility of glymphatic transport has been questioned, and recent data have challenged its experimental underpinnings. A substantiated mechanism of solute clearance in the brain is of considerable importance because of its implications for pathogenic mechanisms of neurologic diseases and delivery of therapeutics.-Smith, A. J., Verkman, A. S. The "glymphatic" mechanism for solute clearance in Alzheimer's disease: game changer or unproven speculation?
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Affiliation(s)
- Alex J Smith
- Department of Medicine, University of California San Francisco, San Francisco, California, USA.,Department of Physiology, University of California San Francisco, San Francisco, California, USA
| | - Alan S Verkman
- Department of Medicine, University of California San Francisco, San Francisco, California, USA.,Department of Physiology, University of California San Francisco, San Francisco, California, USA
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530
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Evidence of microglial activation following exposure to serum from first-onset drug-naïve schizophrenia patients. Brain Behav Immun 2018; 67:364-373. [PMID: 28988033 DOI: 10.1016/j.bbi.2017.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 09/18/2017] [Accepted: 10/02/2017] [Indexed: 01/29/2023] Open
Abstract
Abnormal activation of brain microglial cells is widely implicated in the pathogenesis of schizophrenia. Previously the pathophysiology of microglial activation was considered to be intrinsic to the central nervous system. We hypothesised that due to their perivascular localization, microglia can also be activated by factors present in circulating blood. Through application of high-content functional screening, we show that peripheral blood serum from first-onset drug-naïve schizophrenia patients is sufficient to provoke microglial cell signalling network responses in vitro which are indicative of proinflammatory activation. We further explore the composition of the serum for the presence of analytes, with the potential to activate microglia, and the utility of the resultant microglial cellular phenotype for novel drug discovery.
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531
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532
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González-Reyes RE, Nava-Mesa MO, Vargas-Sánchez K, Ariza-Salamanca D, Mora-Muñoz L. Involvement of Astrocytes in Alzheimer's Disease from a Neuroinflammatory and Oxidative Stress Perspective. Front Mol Neurosci 2017; 10:427. [PMID: 29311817 PMCID: PMC5742194 DOI: 10.3389/fnmol.2017.00427] [Citation(s) in RCA: 329] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 12/06/2017] [Indexed: 12/19/2022] Open
Abstract
Alzheimer disease (AD) is a frequent and devastating neurodegenerative disease in humans, but still no curative treatment has been developed. Although many explicative theories have been proposed, precise pathophysiological mechanisms are unknown. Due to the importance of astrocytes in brain homeostasis they have become interesting targets for the study of AD. Changes in astrocyte function have been observed in brains from individuals with AD, as well as in AD in vitro and in vivo animal models. The presence of amyloid beta (Aβ) has been shown to disrupt gliotransmission, neurotransmitter uptake, and alter calcium signaling in astrocytes. Furthermore, astrocytes express apolipoprotein E and are involved in the production, degradation and removal of Aβ. As well, changes in astrocytes that precede other pathological characteristics observed in AD, point to an early contribution of astroglia in this disease. Astrocytes participate in the inflammatory/immune responses of the central nervous system. The presence of Aβ activates different cell receptors and intracellular signaling pathways, mainly the advanced glycation end products receptor/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, responsible for the transcription of pro-inflammatory cytokines and chemokines in astrocytes. The release of these pro-inflammatory agents may induce cellular damage or even stimulate the production of Aβ in astrocytes. Additionally, Aβ induces the appearance of oxidative stress (OS) and production of reactive oxygen species and reactive nitrogen species in astrocytes, affecting among others, intracellular calcium levels, NADPH oxidase (NOX), NF-κB signaling, glutamate uptake (increasing the risk of excitotoxicity) and mitochondrial function. Excessive neuroinflammation and OS are observed in AD, and astrocytes seem to be involved in both. The Aβ/NF-κB interaction in astrocytes may play a central role in these inflammatory and OS changes present in AD. In this paper, we also discuss therapeutic measures highlighting the importance of astrocytes in AD pathology. Several new therapeutic approaches involving phenols (curcumin), phytoestrogens (genistein), neuroesteroids and other natural phytochemicals have been explored in astrocytes, obtaining some promising results regarding cognitive improvements and attenuation of neuroinflammation. Novel strategies comprising astrocytes and aimed to reduce OS in AD have also been proposed. These include estrogen receptor agonists (pelargonidin), Bambusae concretio Salicea, Monascin, and various antioxidatives such as resveratrol, tocotrienol, anthocyanins, and epicatechin, showing beneficial effects in AD models.
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Affiliation(s)
- Rodrigo E González-Reyes
- Grupo de Investigación en Neurociencias (NeURos), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Mauricio O Nava-Mesa
- Grupo de Investigación en Neurociencias (NeURos), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Karina Vargas-Sánchez
- Biomedical Sciences Research Group, School of Medicine, Universidad Antonio Nariño, Bogotá, Colombia
| | - Daniel Ariza-Salamanca
- Grupo de Investigación en Neurociencias (NeURos), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Laura Mora-Muñoz
- Grupo de Investigación en Neurociencias (NeURos), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
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533
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Layé S, Nadjar A, Joffre C, Bazinet RP. Anti-Inflammatory Effects of Omega-3 Fatty Acids in the Brain: Physiological Mechanisms and Relevance to Pharmacology. Pharmacol Rev 2017; 70:12-38. [PMID: 29217656 DOI: 10.1124/pr.117.014092] [Citation(s) in RCA: 233] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 09/05/2017] [Indexed: 12/17/2022] Open
Abstract
Classically, polyunsaturated fatty acids (PUFA) were largely thought to be relatively inert structural components of brain, largely important for the formation of cellular membranes. Over the past 10 years, a host of bioactive lipid mediators that are enzymatically derived from arachidonic acid, the main n-6 PUFA, and docosahexaenoic acid, the main n-3 PUFA in the brain, known to regulate peripheral immune function, have been detected in the brain and shown to regulate microglia activation. Recent advances have focused on how PUFA regulate the molecular signaling of microglia, especially in the context of neuroinflammation and behavior. Several active drugs regulate brain lipid signaling and provide proof of concept for targeting the brain. Because brain lipid metabolism relies on a complex integration of diet, peripheral metabolism, including the liver and blood, which supply the brain with PUFAs that can be altered by genetics, sex, and aging, there are many pathways that can be disrupted, leading to altered brain lipid homeostasis. Brain lipid signaling pathways are altered in neurologic disorders and may be viable targets for the development of novel therapeutics. In this study, we discuss in particular how n-3 PUFAs and their metabolites regulate microglia phenotype and function to exert their anti-inflammatory and proresolving activities in the brain.
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Affiliation(s)
- Sophie Layé
- Institut National pour la Recherche Agronomique and Bordeaux University, Nutrition et Neurobiologie Intégrée, UMR 1286, Bordeaux, France (S.L., A.N., C.J.); and Department of Nutritional Sciences, University of Toronto, Ontario, Canada (R.P.B.)
| | - Agnès Nadjar
- Institut National pour la Recherche Agronomique and Bordeaux University, Nutrition et Neurobiologie Intégrée, UMR 1286, Bordeaux, France (S.L., A.N., C.J.); and Department of Nutritional Sciences, University of Toronto, Ontario, Canada (R.P.B.)
| | - Corinne Joffre
- Institut National pour la Recherche Agronomique and Bordeaux University, Nutrition et Neurobiologie Intégrée, UMR 1286, Bordeaux, France (S.L., A.N., C.J.); and Department of Nutritional Sciences, University of Toronto, Ontario, Canada (R.P.B.)
| | - Richard P Bazinet
- Institut National pour la Recherche Agronomique and Bordeaux University, Nutrition et Neurobiologie Intégrée, UMR 1286, Bordeaux, France (S.L., A.N., C.J.); and Department of Nutritional Sciences, University of Toronto, Ontario, Canada (R.P.B.)
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534
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Hansen DV, Hanson JE, Sheng M. Microglia in Alzheimer's disease. J Cell Biol 2017; 217:459-472. [PMID: 29196460 PMCID: PMC5800817 DOI: 10.1083/jcb.201709069] [Citation(s) in RCA: 1125] [Impact Index Per Article: 160.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 11/05/2017] [Accepted: 11/14/2017] [Indexed: 12/15/2022] Open
Abstract
Hansen et al. review the potential dual helpful and harmful roles of microglia in the development and progression of Alzheimer’s disease. Proliferation and activation of microglia in the brain, concentrated around amyloid plaques, is a prominent feature of Alzheimer’s disease (AD). Human genetics data point to a key role for microglia in the pathogenesis of AD. The majority of risk genes for AD are highly expressed (and many are selectively expressed) by microglia in the brain. There is mounting evidence that microglia protect against the incidence of AD, as impaired microglial activities and altered microglial responses to β-amyloid are associated with increased AD risk. On the other hand, there is also abundant evidence that activated microglia can be harmful to neurons. Microglia can mediate synapse loss by engulfment of synapses, likely via a complement-dependent mechanism; they can also exacerbate tau pathology and secrete inflammatory factors that can injure neurons directly or via activation of neurotoxic astrocytes. Gene expression profiles indicate multiple states of microglial activation in neurodegenerative disease settings, which might explain the disparate roles of microglia in the development and progression of AD pathology.
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Affiliation(s)
- David V Hansen
- Department of Neuroscience, Genentech, Inc., South San Francisco, CA
| | - Jesse E Hanson
- Department of Neuroscience, Genentech, Inc., South San Francisco, CA
| | - Morgan Sheng
- Department of Neuroscience, Genentech, Inc., South San Francisco, CA
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535
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Intracellular trafficking of TREM2 is regulated by presenilin 1. Exp Mol Med 2017; 49:e405. [PMID: 29611543 PMCID: PMC5750471 DOI: 10.1038/emm.2017.200] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 05/05/2017] [Accepted: 05/31/2017] [Indexed: 01/26/2023] Open
Abstract
Genetic mutations in triggering receptor expressed on myeloid cells 2 (TREM2) have been linked to a variety of neurodegenerative diseases including Alzheimer's disease, amyotrophic lateral sclerosis, frontotemporal dementia and Parkinson's disease. In the brain, TREM2 is highly expressed on the cell surface of microglia, where it can transduce signals to regulate microglial functions such as phagocytosis. To date, mechanisms underlying intracellular trafficking of TREM2 remain elusive. Mutations in the presenilin 1 (PS1) catalytic subunit of the γ-secretase complex have been associated with increased generation of the amyloidogenic Aβ (amyloid-β) 42 peptide through cleavage of the Aβ precursor amyloid precursor protein. Here we found that TREM2 interacts with PS1 in a manner independent of γ-secretase activity. Mutations in TREM2 alter its subcellular localization and affects its interaction with PS1. Upregulation of PS1 reduces, whereas downregulation of PS1 increases, steady-state levels of cell surface TREM2. Furthermore, PS1 overexpression results in attenuated phagocytic uptake of Aβ by microglia, which is reversed by TREM2 overexpression. Our data indicate a novel role for PS1 in regulating TREM2 intracellular trafficking and pathophysiological function.
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536
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Abstract
Microglia and non-parenchymal macrophages in the brain are mononuclear phagocytes that are increasingly recognized to be essential players in the development, homeostasis and diseases of the central nervous system. With the availability of new genetic, molecular and pharmacological tools, considerable advances have been made towards our understanding of the embryonic origins, developmental programmes and functions of these cells. These exciting discoveries, some of which are still controversial, also raise many new questions, which makes brain macrophage biology a fast-growing field at the intersection of neuroscience and immunology. Here, we review the current knowledge of how and where brain macrophages are generated, with a focus on parenchymal microglia. We also discuss their normal functions during development and homeostasis, the disturbance of which may lead to various neurodegenerative and neuropsychiatric diseases.
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537
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Assessing disease-modifying effects of norepinephrine in Down syndrome and Alzheimer's disease. Brain Res 2017; 1702:3-11. [PMID: 29102776 DOI: 10.1016/j.brainres.2017.09.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 09/18/2017] [Indexed: 11/23/2022]
Abstract
Building upon the knowledge that a number of important brain circuits undergo significant degeneration in Alzheimer's disease, numerous recent studies suggest that the norepinephrine-ergic system in the brainstem undergoes significant alterations early in the course of both Alzheimer's disease and Down syndrome. Massive projections from locus coeruleus neurons to almost the entire brain, extensive innervation of brain capillaries, and widespread distribution of noradrenergic receptors enable the norepinephrine-ergic system to play a crucial role in neural processes, including cognitive function. These anatomical and functional characteristics support the role of the norepinephrine-ergic system as an important target for developing new therapies for cognitive dysfunction. Careful neuropathological examinations using postmortem samples from individuals with Alzheimer's disease have implicated the role of the norepinephrine-ergic system in the etiopathogenesis of Alzheimer's disease. Furthermore, numerous studies have supported the existence of a strong interaction between norepinephrine-ergic and neuroimmune systems. We explore the interaction between the two systems that could play a role in the disease-modifying effects of norepinephrine in Alzheimer's disease and Down syndrome.
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538
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Fahrenhold M, Rakic S, Classey J, Brayne C, Ince PG, Nicoll JAR, Boche D. TREM2 expression in the human brain: a marker of monocyte recruitment? Brain Pathol 2017; 28:595-602. [PMID: 28987033 PMCID: PMC6221091 DOI: 10.1111/bpa.12564] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 10/02/2017] [Indexed: 01/04/2023] Open
Abstract
Mutation in the triggering receptor expressed on myeloid cells (TREM) 2 gene has been identified as a risk factor for several neurodegenerative diseases including Alzheimer's disease (AD). Experimental studies using animal models of AD have highlighted a number of functions associated with TREM2 and its expression by microglial cells. It has therefore been assumed that this is also the case in humans. However, there is very limited information concerning the cellular expression of TREM2 in the human brain. As part of investigations of microglia using post‐mortem resources provided by the Medical Research Council Cognitive Function and Ageing Studies (MRC‐CFAS), we immunostained the cerebral cortex of 299 participants for TREM2 using the Sigma antibody HPA010917 and compared with the macrophage/microglial markers Iba1 and CD68. As expected, Iba1 and CD68 labeled microglia and perivascular macrophages. However, in most cases (284/299), the TREM2 antibody labelled monocytes within vascular lumens, but not microglia or perivascular macrophages. In contrast, in 5 out of 6 cases with acute infarcts, TREM2 immunoreaction identified cells within the brain parenchyma interpreted as recruited monocytes. Six cases with old infarcts contained phagocytic foamy macrophages which were CD68‐positive but TREM2 negative. Our observations, using the HPA010917 anti‐TREM2 antibody, suggest that TREM2 is not expressed by microglia but instead seems to be a marker of recruited monocytes in the human brain. This finding has implications with regards to the role of TREM2 as a risk factor, emphasizing the importance of systemic immune responses in the development and progression of Alzheimer's disease.
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Affiliation(s)
- Marie Fahrenhold
- Clinical Neurosciences, Clinical and Experimental Sciences Academic Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
| | - Sonja Rakic
- Clinical Neurosciences, Clinical and Experimental Sciences Academic Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
| | - John Classey
- Clinical Neurosciences, Clinical and Experimental Sciences Academic Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
| | - Carol Brayne
- Cambridge Institute of Public Health, Department of Public Health and Primary Care, University of Cambridge, Cambridge, CB1 8RN, UK
| | - Paul G Ince
- Sheffield Institute for Translational Neuroscience, Sheffield University, Sheffield, S10 2HQ, UK
| | - James A R Nicoll
- Clinical Neurosciences, Clinical and Experimental Sciences Academic Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK.,Department of Cellular Pathology, University Hospital Southampton NHS Foundation Trust, Southampton, Southampton SO16 6YD, UK
| | - Delphine Boche
- Clinical Neurosciences, Clinical and Experimental Sciences Academic Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
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539
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Abstract
Microglial cell function is implicated in the etiology of Alzheimer's disease by human genetics. In this issue of Immunity, Krasemann et al. (2017) describe a gene expression signature associated with an APOE- and TREM2-dependent response of microglia to brain tissue damage that accumulates in aging and disease, defining an axis that might be amenable to therapeutic targeting.
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Affiliation(s)
- Anna A Pimenova
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Ronald M. Loeb Center for Alzheimer's disease, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Edoardo Marcora
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Ronald M. Loeb Center for Alzheimer's disease, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Alison M Goate
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Ronald M. Loeb Center for Alzheimer's disease, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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540
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TREM2 deficiency attenuates neuroinflammation and protects against neurodegeneration in a mouse model of tauopathy. Proc Natl Acad Sci U S A 2017; 114:11524-11529. [PMID: 29073081 PMCID: PMC5663386 DOI: 10.1073/pnas.1710311114] [Citation(s) in RCA: 306] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alzheimer’s disease (AD) is the most common cause of dementia and is a major public health problem for which there is currently no disease-modifying treatment. There is an urgent need for greater understanding of the molecular mechanisms underlying neurodegeneration in patients to create better therapeutic options. Recently, genetic studies uncovered novel AD risk variants in the microglial receptor, triggering receptor expressed on myeloid cells 2 (TREM2). Previous studies suggested that loss of TREM2 function worsens amyloid-β (Aβ) plaque-related toxicity. In contrast, we observe TREM2 deficiency mitigates neuroinflammation and protects against brain atrophy in the context of tau pathology. These findings indicate dual roles for TREM2 and microglia in the context of amyloid versus tau pathology, which are important to consider for potential treatments targeting TREM2. Variants in the gene encoding the triggering receptor expressed on myeloid cells 2 (TREM2) were recently found to increase the risk for developing Alzheimer’s disease (AD). In the brain, TREM2 is predominately expressed on microglia, and its association with AD adds to increasing evidence implicating a role for the innate immune system in AD initiation and progression. Thus far, studies have found TREM2 is protective in the response to amyloid pathology while variants leading to a loss of TREM2 function impair microglial signaling and are deleterious. However, the potential role of TREM2 in the context of tau pathology has not yet been characterized. In this study, we crossed Trem2+/+ (T2+/+) and Trem2−/− (T2−/−) mice to the PS19 human tau transgenic line (PS) to investigate whether loss of TREM2 function affected tau pathology, the microglial response to tau pathology, or neurodegeneration. Strikingly, by 9 mo of age, T2−/−PS mice exhibited significantly less brain atrophy as quantified by ventricular enlargement and preserved cortical volume in the entorhinal and piriform regions compared with T2+/+PS mice. However, no TREM2-dependent differences were observed for phosphorylated tau staining or insoluble tau levels. Rather, T2−/−PS mice exhibited significantly reduced microgliosis in the hippocampus and piriform cortex compared with T2+/+PS mice. Gene expression analyses and immunostaining revealed microglial activation was significantly attenuated in T2−/−PS mice, and there were lower levels of inflammatory cytokines and astrogliosis. These unexpected findings suggest that impairing microglial TREM2 signaling reduces neuroinflammation and is protective against neurodegeneration in the setting of pure tauopathy.
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541
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Miyahara H, Sawashita J, Ishikawa E, Yang M, Ding X, Liu Y, Hachiya N, Kametani F, Yazaki M, Mori M, Higuchi K. Comprehensive proteomic profiles of mouse AApoAII amyloid fibrils provide insights into the involvement of lipoproteins in the pathology of amyloidosis. J Proteomics 2017; 172:111-121. [PMID: 28988881 DOI: 10.1016/j.jprot.2017.10.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 08/17/2017] [Accepted: 10/05/2017] [Indexed: 02/06/2023]
Abstract
Amyloidosis is a disorder characterized by extracellular fibrillar deposits of misfolded proteins. The amyloid deposits commonly contain several non-fibrillar proteins as amyloid-associated proteins, but their roles in amyloidosis pathology are still unknown. In mouse senile amyloidosis, apolipoprotein A-II (ApoA-II) forms extracellular amyloid fibril (AApoAII) deposits with other proteins (AApoAII-associated proteins) in many organs. We previously reported that R1.P1-Apoa2c mice provide a reproducible model of AApoAII amyloidosis. In order to investigate the sequential alterations of AApoAII-associated protein, we performed a proteomic analysis of amyloid fibrils extracted from mouse liver tissues that contained different levels of AApoAII deposition. We identified 6 AApoAII-associated proteins that constituted 20 of the top-ranked proteins in mice with severe AApoAII deposition. Although the amount of AApoAII-associated proteins increased with the progression of amyloidosis, the relative abundance of AApoAII-associated proteins changed little throughout the progression of amyloidosis. On the other hand, plasma levels of these proteins showed dramatic changes during the progression of amyloidosis. In addition, we confirmed that AApoAII-associated proteins were significantly associated with lipid metabolism based on functional enrichment analysis, and lipids were co-deposited with AApoAII fibrils from early stages of development of amyloidosis. Thus, these results demonstrate that lipoproteins are involved in AApoAII amyloidosis pathology. SIGNIFICANCE This study presented proteomic profiles of AApoAII amyloidosis during disease progression and it revealed co-deposition of lipids with AApoAII deposits based on functional analyses. The relative abundance of AApoAII-associated proteins in the amyloid fibril fractions did not change over the course of development of AApoAII amyloidosis pathology. However, their concentrations in plasma changed dramatically with progression of the disease. Interestingly, several AApoAII-associated proteins have been found as constituents of lipid-rich lesions of other degenerative diseases, such as atherosclerosis and age-related macular degeneration. The common protein components among these diseases with lipid-rich deposits could be accounted for by a lipoprotein retention model.
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Affiliation(s)
- Hiroki Miyahara
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan
| | - Jinko Sawashita
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan; Department of Biological Sciences for Intractable Neurological Diseases, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 390-8621 Matsumoto, Japan
| | - Eri Ishikawa
- Division of Instrumental Research, Research Center for Supports to Advanced Science, Shinshu University, 390-8621 Matsumoto, Japan
| | - Mu Yang
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan
| | - Xin Ding
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan
| | - Yingye Liu
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan
| | - Naomi Hachiya
- Tokyo Metropolitan Industrial Technology Research Institute, Aomi, Koto-ku, 135-0064 Tokyo, Japan
| | - Fuyuki Kametani
- Department of Dementia and Higher Brain Function, Tokyo Metropolitan Institute of Medical Science, 156-8506 Tokyo, Japan
| | - Masahide Yazaki
- Department of Biological Sciences for Intractable Neurological Diseases, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 390-8621 Matsumoto, Japan
| | - Masayuki Mori
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan; Department of Advanced Medicine for Health Promotion, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 390-8621 Matsumoto, Japan
| | - Keiichi Higuchi
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 390-8621 Matsumoto, Japan; Department of Biological Sciences for Intractable Neurological Diseases, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 390-8621 Matsumoto, Japan.
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542
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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: 1069] [Impact Index Per Article: 152.7] [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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543
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The lipid-sensor TREM2 aggravates disease in a model of LCMV-induced hepatitis. Sci Rep 2017; 7:11289. [PMID: 28900132 PMCID: PMC5595927 DOI: 10.1038/s41598-017-10637-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 08/14/2017] [Indexed: 12/20/2022] Open
Abstract
Lipid metabolism is increasingly being appreciated to affect immunoregulation, inflammation and pathology. In this study we found that mice infected with lymphocytic choriomeningitis virus (LCMV) exhibit global perturbations of circulating serum lipids. Mice lacking the lipid-sensing surface receptor triggering receptor expressed on myeloid cells 2 (Trem2 -/-) were protected from LCMV-induced hepatitis and showed improved virus control despite comparable virus-specific T cell responses. Non-hematopoietic expression of TREM2 was found to be responsible for aggravated hepatitis, indicating a novel role for TREM2 in the non-myeloid compartment. These results suggest a link between virus-perturbed lipids and TREM2 that modulates liver pathogenesis upon viral infection. Targeted interventions of this immunoregulatory axis may ameliorate tissue pathology in hepatitis.
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544
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Genetics of Alzheimer's disease: From pathogenesis to clinical usage. J Clin Neurosci 2017; 45:1-8. [PMID: 28869135 DOI: 10.1016/j.jocn.2017.06.074] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/19/2017] [Indexed: 01/27/2023]
Abstract
Alzheimer's disease (AD) is the most common type of dementia and has caused a major global health concern. Understanding the etiology of AD can be beneficial for the diagnosis and intervention of this disease. Genetics plays a vital role in the pathogenesis of AD. Research methods in genetics such as the linkage analysis, study of candidate genes, genome-wide association study (GWAS), and next-generation sequencing (NGS) technology help us map the genetic information in AD, which can not only provide a new insight into the pathogenesis of AD but also be beneficial for early targeted intervention of AD. This review summarizes the pathogenesis as well as the diagnostic and therapeutic value of genetics in AD.
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545
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TREM2 Maintains Microglial Metabolic Fitness in Alzheimer's Disease. Cell 2017; 170:649-663.e13. [PMID: 28802038 DOI: 10.1016/j.cell.2017.07.023] [Citation(s) in RCA: 716] [Impact Index Per Article: 102.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 05/26/2017] [Accepted: 07/14/2017] [Indexed: 12/22/2022]
Abstract
Elevated risk of developing Alzheimer's disease (AD) is associated with hypomorphic variants of TREM2, a surface receptor required for microglial responses to neurodegeneration, including proliferation, survival, clustering, and phagocytosis. How TREM2 promotes such diverse responses is unknown. Here, we find that microglia in AD patients carrying TREM2 risk variants and TREM2-deficient mice with AD-like pathology have abundant autophagic vesicles, as do TREM2-deficient macrophages under growth-factor limitation or endoplasmic reticulum (ER) stress. Combined metabolomics and RNA sequencing (RNA-seq) linked this anomalous autophagy to defective mammalian target of rapamycin (mTOR) signaling, which affects ATP levels and biosynthetic pathways. Metabolic derailment and autophagy were offset in vitro through Dectin-1, a receptor that elicits TREM2-like intracellular signals, and cyclocreatine, a creatine analog that can supply ATP. Dietary cyclocreatine tempered autophagy, restored microglial clustering around plaques, and decreased plaque-adjacent neuronal dystrophy in TREM2-deficient mice with amyloid-β pathology. Thus, TREM2 enables microglial responses during AD by sustaining cellular energetic and biosynthetic metabolism.
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546
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Abud EM, Ramirez RN, Martinez ES, Healy LM, Nguyen CHH, Newman SA, Yeromin AV, Scarfone VM, Marsh SE, Fimbres C, Caraway CA, Fote GM, Madany AM, Agrawal A, Kayed R, Gylys KH, Cahalan MD, Cummings BJ, Antel JP, Mortazavi A, Carson MJ, Poon WW, Blurton-Jones M. iPSC-Derived Human Microglia-like Cells to Study Neurological Diseases. Neuron 2017; 94:278-293.e9. [PMID: 28426964 DOI: 10.1016/j.neuron.2017.03.042] [Citation(s) in RCA: 658] [Impact Index Per Article: 94.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 02/16/2017] [Accepted: 03/28/2017] [Indexed: 12/15/2022]
Abstract
Microglia play critical roles in brain development, homeostasis, and neurological disorders. Here, we report that human microglial-like cells (iMGLs) can be differentiated from iPSCs to study their function in neurological diseases, like Alzheimer's disease (AD). We find that iMGLs develop in vitro similarly to microglia in vivo, and whole-transcriptome analysis demonstrates that they are highly similar to cultured adult and fetal human microglia. Functional assessment of iMGLs reveals that they secrete cytokines in response to inflammatory stimuli, migrate and undergo calcium transients, and robustly phagocytose CNS substrates. iMGLs were used to examine the effects of Aβ fibrils and brain-derived tau oligomers on AD-related gene expression and to interrogate mechanisms involved in synaptic pruning. Furthermore, iMGLs transplanted into transgenic mice and human brain organoids resemble microglia in vivo. Together, these findings demonstrate that iMGLs can be used to study microglial function, providing important new insight into human neurological disease.
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Affiliation(s)
- Edsel M Abud
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Ricardo N Ramirez
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697, USA
| | - Eric S Martinez
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Luke M Healy
- Neuroimmunology Unit, Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC H3A 2B4, Canada
| | - Cecilia H H Nguyen
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Sean A Newman
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA
| | - Andriy V Yeromin
- Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697, USA
| | - Vanessa M Scarfone
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA
| | - Samuel E Marsh
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Cristhian Fimbres
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Chad A Caraway
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Gianna M Fote
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA
| | - Abdullah M Madany
- Division of Biomedical Sciences, Center for Glia-Neuronal Interactions, University of California, Riverside, Riverside, CA 92521, USA
| | - Anshu Agrawal
- Department of Medicine, School of Medicine, University of California Irvine, Irvine, CA 92697, USA
| | - Rakez Kayed
- Department of Neurology, George P. and Cynthia Woods Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Karen H Gylys
- UCLA School of Nursing, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Michael D Cahalan
- Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697, USA
| | - Brian J Cummings
- Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA; Anatomy and Neurobiology, University of California Irvine, Irvine, CA 92697, USA
| | - Jack P Antel
- Neuroimmunology Unit, Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC H3A 2B4, Canada
| | - Ali Mortazavi
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697, USA
| | - Monica J Carson
- Division of Biomedical Sciences, Center for Glia-Neuronal Interactions, University of California, Riverside, Riverside, CA 92521, USA
| | - Wayne W Poon
- Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA.
| | - Mathew Blurton-Jones
- Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California Irvine, Irvine, CA 92697, USA; Institute for Memory Impairments and Neurological Disorders, University of California Irvine, Irvine, CA 92697, USA.
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547
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Sirkis DW, Aparicio RE, Schekman R. Neurodegeneration-associated mutant TREM2 proteins abortively cycle between the ER and ER-Golgi intermediate compartment. Mol Biol Cell 2017; 28:2723-2733. [PMID: 28768830 PMCID: PMC5620379 DOI: 10.1091/mbc.e17-06-0423] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 07/28/2017] [Accepted: 07/28/2017] [Indexed: 11/21/2022] Open
Abstract
Mutations in the microglial cell surface receptor TREM2 are associated with multiple forms of neurodegeneration. Several of these mutant forms of TREM2 were thought to be retained in the endoplasmic reticulum (ER), but careful analysis reveals that they engage in an abortive cycling pathway between the ER and ER–Golgi intermediate compartment. Triggering receptor expressed on myeloid cells 2 (TREM2) is a transmembrane protein expressed on microglia within the brain. Several rare mutations in TREM2 cause an early-onset form of neurodegeneration when inherited homozygously. Here we investigate how these mutations affect the intracellular transport of TREM2. We find that most pathogenic TREM2 mutant proteins fail to undergo normal maturation in the Golgi complex and show markedly reduced cell-surface expression. Prior research has suggested that two such mutants are retained in the endoplasmic reticulum (ER), but we find, using a cell-free coat protein complex II (COPII) vesicle budding reaction, that mutant TREM2 is exported efficiently from the ER. In addition, mutant TREM2 becomes sensitive to cleavage by endoglycosidase D under conditions that inhibit recycling to the ER, indicating that it normally reaches a post-ER compartment. Maturation-defective TREM2 mutants are also efficiently bound by a lectin that recognizes O-glycans added in the ER–Golgi intermediate compartment (ERGIC) and cis-Golgi cisterna. Finally, mutant TREM2 accumulates in the ERGIC in cells depleted of COPI. These results indicate that efficient ER export is not sufficient to enable normal cell-surface expression of TREM2. Moreover, our findings suggest that the ERGIC may play an underappreciated role as a quality-control center for mutant and/or malformed membrane proteins.
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Affiliation(s)
- Daniel W Sirkis
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720
| | - Renan E Aparicio
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720
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548
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Jay TR, von Saucken VE, Landreth GE. TREM2 in Neurodegenerative Diseases. Mol Neurodegener 2017; 12:56. [PMID: 28768545 PMCID: PMC5541421 DOI: 10.1186/s13024-017-0197-5] [Citation(s) in RCA: 256] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022] Open
Abstract
TREM2 variants have been identified as risk factors for Alzheimer's disease (AD) and other neurodegenerative diseases (NDDs). Because TREM2 encodes a receptor exclusively expressed on immune cells, identification of these variants conclusively demonstrates that the immune response can play an active role in the pathogenesis of NDDs. These TREM2 variants also confer the highest risk for developing Alzheimer's disease of any risk factor identified in nearly two decades, suggesting that understanding more about TREM2 function could provide key insights into NDD pathology and provide avenues for novel immune-related NDD biomarkers and therapeutics. The expression, signaling and function of TREM2 in NDDs have been extensively investigated in an effort to understand the role of immune function in disease pathogenesis and progression. We provide a comprehensive review of our current understanding of TREM2 biology, including new insights into the regulation of TREM2 expression, and TREM2 signaling and function across NDDs. While many open questions remain, the current body of literature provides clarity on several issues. While it is still often cited that TREM2 expression is decreased by pro-inflammatory stimuli, it is now clear that this is true in vitro, but inflammatory stimuli in vivo almost universally increase TREM2 expression. Likewise, while TREM2 function is classically described as promoting an anti-inflammatory phenotype, more than half of published studies demonstrate a pro-inflammatory role for TREM2, suggesting that its role in inflammation is much more complex. Finally, these components of TREM2 biology are applied to a discussion of how TREM2 impacts NDD pathologies and the latest assessment of how these findings might be applied to immune-directed clinical biomarkers and therapeutics.
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Affiliation(s)
- Taylor R. Jay
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
| | - Victoria E. von Saucken
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
| | - Gary E. Landreth
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
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549
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Bohlen CJ, Bennett FC, Tucker AF, Collins HY, Mulinyawe SB, Barres BA. Diverse Requirements for Microglial Survival, Specification, and Function Revealed by Defined-Medium Cultures. Neuron 2017; 94:759-773.e8. [PMID: 28521131 DOI: 10.1016/j.neuron.2017.04.043] [Citation(s) in RCA: 402] [Impact Index Per Article: 57.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 03/31/2017] [Accepted: 04/28/2017] [Indexed: 12/14/2022]
Abstract
Microglia, the resident macrophages of the CNS, engage in various CNS-specific functions that are critical for development and health. To better study microglia and the properties that distinguish them from other tissue macrophage populations, we have optimized serum-free culture conditions to permit robust survival of highly ramified adult microglia under defined-medium conditions. We find that astrocyte-derived factors prevent microglial death ex vivo and that this activity results from three primary components, CSF-1/IL-34, TGF-β2, and cholesterol. Using microglial cultures that have never been exposed to serum, we demonstrate a dramatic and lasting change in phagocytic capacity after serum exposure. Finally, we find that mature microglia rapidly lose signature gene expression after isolation, and that this loss can be reversed by engrafting cells back into an intact CNS environment. These data indicate that the specialized gene expression profile of mature microglia requires continuous instructive signaling from the intact CNS.
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Affiliation(s)
- Christopher J Bohlen
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - F Chris Bennett
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Andrew F Tucker
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Hannah Y Collins
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sara B Mulinyawe
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Ben A Barres
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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550
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Bonanno L, Wyss-Coray T. OH MYeloid! Immune cells wreaking havoc on brain homeostasis. EMBO J 2017. [PMID: 28623242 DOI: 10.15252/embj.201797465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Liana Bonanno
- Stanford Neurosciences Graduate Training Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Tony Wyss-Coray
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA.,Center for Tissue Regeneration, Repair and Restoration, VA Palo Alto Healthcare System, Palo Alto, CA, USA.,Paul F. Glenn Center for the Biology of Aging, Stanford University School of Medicine, Stanford, CA, USA
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