APOE4 may bias microglia toward complement-mediated pruning that disproportionately strips vulnerable long-range cholinergic synapses, lowering acetylcholine tone and facilitating tau spread. The debate supports this as a strong modifier or subtype mechanism, but the claim of cholinergic selectivity remains underproven.
Curated pathway from expert analysis
flowchart TD
A["APOE4 Isoform<br/>Structural Instability"]
B["Impaired Lipid Loading<br/>Reduced Cholesterol Efflux"]
C["LRP1 Reduced Binding<br/>BBB Clearance Deficit"]
D["Amyloid-beta<br/>Accumulation"]
E["Synaptic Dysfunction<br/>Membrane Disruption"]
F["Neurodegeneration<br/>Cognitive Decline"]
G["APOE3 Comparison<br/>Normal Lipidation"]
A --> B
B --> C
C --> D
D --> E
E --> F
G -.->|"protective"| C
style A fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a
style F fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a
style G fill:#1b5e20,stroke:#81c784,color:#81c784No linked papers recorded for this hypothesis yet.
Median TPM across 13 brain regions for APOE, C1QA, C1QB, C1QC, C3, ITGAM from GTEx v10.
No clinical trials data linked to this hypothesis yet.
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 APOE, C1QA, C1QB, C1QC, C3, ITGAM.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| IF human APOE4 carriers undergo combined amyloid PET and cholinergic terminal PET imaging (e.g., acetylcholinesterase ligand) at baseline BEFORE amyloid positivity (Centiloid < 20), THEN reduced corti | CSF complement C3a and C1q concentrations will be significantly higher in APOE4 carriers (n≥40/group) and will explain >15% of variance in cholinergic terminal | — no observation — | pending | 0.65 |
| IF APOE4/4 iPSC-derived microglia are co-cultured with human cholinergic neurons (ESC-derived basal forebrain cholinergic neurons) and exposed to complement pathway activation (C1q+C3 opsonization) wi | APOE4 microglia will cause >50% reduction in cholinergic synaptic density (ChAT+ puncta colocalized with SYN+) compared to APOE3 microglia, and C3 blockade will | — no observation — | pending | 0.55 |