The TREM2-APOE Pathway Drives the Transcriptional Phenotype of Dysfunctional Microglia in Neurodegenerative Diseases

Immunity. 2017 Sep 19;47(3):566-581.e9. doi: 10.1016/j.immuni.2017.08.008.

Abstract

Microglia play a pivotal role in the maintenance of brain homeostasis but lose homeostatic function during neurodegenerative disorders. We identified a specific apolipoprotein E (APOE)-dependent molecular signature in microglia from models of amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and Alzheimer's disease (AD) and in microglia surrounding neuritic β-amyloid (Aβ)-plaques in the brains of people with AD. The APOE pathway mediated a switch from a homeostatic to a neurodegenerative microglia phenotype after phagocytosis of apoptotic neurons. TREM2 (triggering receptor expressed on myeloid cells 2) induced APOE signaling, and targeting the TREM2-APOE pathway restored the homeostatic signature of microglia in ALS and AD mouse models and prevented neuronal loss in an acute model of neurodegeneration. APOE-mediated neurodegenerative microglia had lost their tolerogenic function. Our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target that could aid in the restoration of homeostatic microglia.

Keywords: APOE; Alzheimer’s disease; TREM2; amyotrophic lateral sclerosis; microglia; multiple sclerosis; neurodegeneration; transcriptional regulation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / genetics
  • Alzheimer Disease / metabolism
  • Alzheimer Disease / pathology
  • Amyloid beta-Peptides / metabolism
  • Amyloid beta-Protein Precursor / metabolism
  • Animals
  • Apolipoproteins E / deficiency
  • Apolipoproteins E / genetics
  • Apolipoproteins E / metabolism*
  • Apoptosis / genetics
  • Apoptosis / immunology
  • Cerebral Cortex / metabolism
  • Cerebral Cortex / pathology
  • Cluster Analysis
  • Disease Models, Animal
  • Encephalomyelitis, Autoimmune, Experimental
  • Female
  • Gene Expression Profiling
  • Gene Expression Regulation
  • Gene Targeting
  • Humans
  • Immune Tolerance
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Microglia / immunology
  • Microglia / metabolism*
  • Monocytes / immunology
  • Monocytes / metabolism
  • Neurodegenerative Diseases / genetics*
  • Neurodegenerative Diseases / immunology
  • Neurodegenerative Diseases / metabolism*
  • Neurons / metabolism
  • Phagocytosis / genetics
  • Phagocytosis / immunology
  • Phenotype
  • Plaque, Amyloid / metabolism
  • Plaque, Amyloid / pathology
  • Receptors, Immunologic / metabolism*
  • Signal Transduction*
  • Superoxide Dismutase-1 / genetics
  • Superoxide Dismutase-1 / metabolism
  • Transcriptome*
  • Transforming Growth Factor beta / metabolism

Substances

  • Amyloid beta-Peptides
  • Amyloid beta-Protein Precursor
  • Apolipoproteins E
  • Membrane Glycoproteins
  • Receptors, Immunologic
  • Transforming Growth Factor beta
  • Trem2 protein, mouse
  • Superoxide Dismutase-1