Disease-associated microglia (DAM) represent a critical innate immune response in the Alzheimer's disease brain. These specialized microglia adopt a distinct transcriptional and functional phenotype in response to neurodegeneration, amyloid pathology, and tau pathology. Understanding DAM biology is essential for developing microglia-targeting therapeutic strategies for AD.
| Property |
Value |
| Category |
Innate Immune Cells |
| Location |
Brain parenchyma, near amyloid plaques |
| Cell Type |
Activated microglia |
| Key Receptors |
TREM2, TLRs, CD33 |
| Discovery |
2019 (Keren-Shaul et al., Cell) |
| Taxonomy |
ID |
Name / Label |
| Cell Ontology (CL) |
CL:0000095 |
neuron associated cell |
- Morphology: neuron associated cell (source: Cell Ontology)
- Morphology can be inferred from Cell Ontology classification
| Database |
ID |
Name |
Confidence |
| Cell Ontology |
CL:0000095 |
neuron associated cell |
Medium |
| Cell Ontology |
CL:0000129 |
microglial cell |
Medium |
Disease-associated microglia develop through a staged progression from homeostatic microglia to a fully activated disease-associated phenotype:
| Feature |
Description |
| Trigger |
Microenvironmental signals (Aβ, neuronal injury) |
| Markers |
Downregulation of P2ry12, Cx3cr1 |
| Function |
Initial response, limited phagocytosis |
| TREM2 Status |
TREM2-independent |
| Feature |
Description |
| Trigger |
Accumulation of Aβ and cellular debris |
| Markers |
ApoE upregulation, lysosomal genes (Cst7, Cd68) |
| Function |
Enhanced phagocytosis |
| TREM2 Status |
TREM2-dependent activation |
| Feature |
Description |
| Trigger |
Chronic neurodegeneration |
| Markers |
Type II interferon signature, complement proteins |
| Function |
May become neurotoxic |
| TREM2 Status |
TREM2-dependent |
| Gene |
Function |
| APOE |
Lipid metabolism, Aβ binding/clearance |
| CST7 |
Lysosomal cysteine protease |
| CD68 |
Phagocytic marker |
| TYROBP |
TREM2 signaling adaptor |
| LPL |
Lipoprotein lipase |
| CTSB/C |
Cathepsins, lysosomal proteases |
| AXL |
Tyrosine kinase receptor (clearance) |
| Gene |
Function |
| P2RY12 |
Homeostatic microglial marker |
| CX3CR1 |
Fractalkine receptor |
| TMEM119 |
Microglial membrane protein |
| SLC2A5 |
Glucose transporter |
DAM play a complex role in amyloid pathophysiology:
- Protective function: Phagocytic clearance of Aβ plaques
- ApoE-mediated: ApoE4 allele impairs microglial Aβ clearance
- TREM2 variants: R47H (AD risk variant) impairs DAM activation
- Plaque association: DAM cluster around cored plaques
Microglia contribute to tau spreading:
- Inflammatory signaling: Cytokines may promote tau phosphorylation
- Neuronal uptake: May facilitate tau internalization
- Spread mechanism: Could transmit tau between neurons
- Neurofibrillary tangles: Associated with more DAM
DAM produce pro-inflammatory mediators:
| Cytokine/Factor |
Effect |
| IL-1β |
Pro-inflammatory, promotes tau pathology |
| IL-6 |
Acute phase response |
| TNF-α |
Cytotoxic, promotes neuron loss |
| C1q |
Complement-mediated synapse elimination |
| IL-10 |
Anti-inflammatory (also upregulated) |
TREM2 is critical for DAM activation:
Aβ/Lipids → TREM2 → TYROBP → SYK → Microglial Activation
| Variant |
Effect on DAM |
| R47H |
~3x AD risk, impaired Aβ phagocytosis |
| R62H |
Moderate risk, partial impairment |
| H157Y |
Impaired ligand binding |
| T96K |
Loss of function |
- TREM2 agonists: Small molecules activating TREM2
- TREM2 antibodies: Engineered to promote clustering
- Anti-Aβ antibodies: May enhance microglial clearance
- Gene therapy: TREM2 expression enhancement
DAM-like phenotypes appear in:
- Parkinson's Disease: α-Synuclein-triggered microglial activation
- ALS: SOD1-triggered neuroinflammation
- FTD: Tau and TDP-43 pathology
- MS: Chronic active lesions
- ** Huntington's Disease**: Mutant HTT-induced activation
| Strategy |
Approach |
Status |
| TREM2 activation |
AGO18, PY314 |
Clinical trials |
| CSF1R inhibition |
PLX5622 (in mice) |
Preclinical |
| Anti-inflammatory |
TNF inhibitors |
Various stages |
| Complement inhibition |
C1q, C3 blockers |
Preclinical |
- Balancing protective vs. harmful functions
- Timing of intervention (early vs. late)
- Peripheral vs. CNS effects
- Biomarker development for DAM activity
The study of Disease Associated Microglia In Alzheimer'S Disease has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.