This hypothesis proposes that TREM2 signaling in microglia directly regulates astrocytic calcium dynamics to control glymphatic tau clearance efficiency. The mechanism begins with TREM2/DAP12 signaling in perivascular microglia, where functional TREM2 receptors detect tau oligomers and activate the Syk-PI3K cascade. Critically, activated microglia release ATP and complement factors that bind to P2Y1 and C3aR receptors on adjacent astrocyte endfeet, triggering robust calcium oscillations through IP3-mediated calcium release from endoplasmic reticulum stores. These astrocytic calcium waves propagate along perivascular domains and activate calcium-dependent aquaporin-4 (AQP4) clustering and polarization at the blood-brain barrier interface. When TREM2 is dysfunctional due to variants like R47H or R62H, the microglial activation becomes insufficient to generate the necessary ATP/complement signaling. This results in dampened astrocytic calcium responses, leading to AQP4 depolarization and reduced water channel efficiency. The compromised AQP4 function disrupts the pressure gradients that drive cerebrospinal fluid influx and interstitial fluid efflux through the glymphatic system.
...Curated pathway from expert analysis
graph TD
A["MAPT gene<br/>expression"]
B["Tau protein<br/>production"]
C["Hyperphosphorylated<br/>tau accumulation"]
D["Locus coeruleus<br/>neurons"]
E["Microtubule<br/>destabilization"]
F["Axonal transport<br/>impairment"]
G["Norepinephrine<br/>release reduction"]
H["Hippocampal<br/>noradrenergic<br/>denervation"]
I["Synaptic plasticity<br/>dysfunction"]
J["Neuroinflammation<br/>activation"]
K["Cellular stress<br/>response failure"]
L["Hippocampal tau<br/>pathology spread"]
M["Memory and<br/>cognitive decline"]
N["Noradrenergic<br/>replacement therapy"]
O["Tau aggregation<br/>inhibitors"]
A -->|"transcription"| B
B -->|"pathological<br/>modification"| C
C -->|"selective<br/>vulnerability"| D
D -->|"tau toxicity"| E
E -->|"transport<br/>disruption"| F
F -->|"neurotransmitter<br/>depletion"| G
G -->|"circuit<br/>disconnection"| H
H -->|"loss of<br/>modulation"| I
H -->|"reduced<br/>anti-inflammatory"| J
H -->|"impaired<br/>neuroprotection"| K
I -->|"functional<br/>decline"| M
J -->|"tissue<br/>damage"| L
K -->|"vulnerability<br/>increase"| L
L -->|"progressive<br/>pathology"| M
N -->|"circuit<br/>restoration"| H
O -->|"tau<br/>reduction"| C
classDef normal fill:#4fc3f7,color:#0d0d1a
classDef therapeutic fill:#81c784,color:#0d0d1a
classDef pathology fill:#ef5350,color:#0d0d1a
classDef outcome fill:#ffd54f,color:#0d0d1a
classDef molecular fill:#ce93d8,color:#0d0d1a
class A,B,D,G molecular
class E,F,I,K normal
class C,H,J,L pathology
class M outcome
class N,O therapeuticMedian TPM across 13 brain regions for TREM2 from GTEx v10.
No curated ClinVar variants loaded for this hypothesis.
Run scripts/backfill_clinvar_variants.py to fetch P/LP/VUS variants.
No DepMap CRISPR Chronos data found for TREM2.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
No resource usage or linked notebooks recorded for this hypothesis yet.