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TREM2→Microglial Dysfunction→Alzheimer's Disease Causal Chain

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TREM2→Microglial Dysfunction→Alzheimer's Disease Causal Chain

Overview

This causal chain traces the molecular pathway from TREM2 gene variants through microglial dysfunction to Alzheimer's disease pathology. TREM2 variants significantly increase AD risk by impairing microglial phagocytosis, lipid metabolism, and plaque clearance.[@lee2021]

Gene Summary: TREM2

| Property | Value |
|----------|-------|
| Gene Symbol | TREM2 (Triggering Receptor Expressed on Myeloid Cells 2) |
| Location | Chromosome 6p21.1 |
| Protein | TREM2 receptor (type I transmembrane protein) |
| Expression | Primarily on microglia in the brain [1] |
| Function | Pattern recognition receptor for lipid clearance, phagocytosis, inflammatory signaling [1] |

Key Variants and Risk

| Variant | Effect | Risk |
|---------|--------|------|
| R47H | Loss of function | 3-4x AD risk [2][@schulte2022] |
| R62H | Partial loss | ~1.5x AD risk [2] |
| D87N | Impaired ligand binding | 2-3x AD risk [2] |
| T96K | Altered signaling | ~2x AD risk [2] |

Protein Function: TREM2 Receptor

Structure

  • Extracellular domain: V-type immunoglobulin-like domain for ligand binding [3]
  • Transmembrane domain: Single pass with DAP12 (TYROBP) adaptor [3]
  • Intracellular tail: Contains ITAM motif for signaling [3]

Ligand Binding


TREM2 recognizes:
  • Lipids: Apolipoproteins (ApoE, ApoA1), oxidized phospholipids [4]
  • Lipidated proteins: Amyloid-beta, TDP-43 [4]
  • Bacterial components: LPS, lipoteichoic acid [4]

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📊 Evidence Profile Foundational
Evidence Balance
+0%
Certainty
100%
Debates
0
Incoming
322
Outgoing
362
0 supporting 0 contradicting 0 neutral
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