SASP-Secreted MMP-9 from Senescent Microglia Generates Pathological TDP-43 C-Terminal Fragments That Propagate ALS Pathology
🧪 Overview
The hypothesis proposes that MMP-9 (matrix metalloproteinase-9), secreted via the senescence-associated secretory phenotype (SASP) from senescent microglia, generates pathological C-terminal fragments of TARDBP (TDP-43) that propagate ALS pathology through cytoplasmic aggregation seeding. High-strength evidence from TDP-43 ALS mouse models demonstrates that reactive microglia expressing MMP-9 remodel perineuronal nets around motor neurons, suggesting a mechanistic link between MMP-9 expression and TDP-43 pathology. Additionally, genetic reduction of MMP-9 protects motor neurons from TDP-43-triggered degeneration in the rNLS8 ALS model, providing disease-model support for MMP-9 as a TDP-43 toxicity amplifier. Human ALS tissue contains disease-enriched C-terminal TDP-43 fragments measurable by targeted mass spectrometry, supporting the fragment endpoint in human disease, though the generating protease remains unidentified. Cell-model evidence further confirms that these C-terminal fragments aggregate readily and injure neurons, supporting their pathogenic relevance once generated.
...🧬 Mechanism
Curated pathway from expert analysis
flowchart TD
A["MMP9 Zymogen<br/>Proenzyme Activation"]
B["Pro-MMP9 Cleavage<br/>NGAL or Other Proteases"]
C["Basement Membrane Degradation<br/>Type IV Collagen Breakdown"]
D["Blood-Brain Barrier Disruption<br/>Endothelial Tight Junctions"]
E["Chemokine Release<br/>Proinflammatory Cascade"]
F["Microglial Activation<br/>CNS Immune Response"]
G["Neuronal Process Retraction<br/>Dendritic Spine Loss"]
H["Synaptic Dysfunction<br/>Memory Circuit Impairment"]
A --> B
B --> C
C --> D
D --> E
E --> F
F --> G
G --> H
style A fill:#7b1fa2,stroke:#ce93d8,color:#ce93d8
style H fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a⚖️ Evidence
No linked papers recorded for this hypothesis yet.
🏥 Translation
🧬 3D Protein Structure — MMP9
🧠 GTEx v10 Brain ExpressionJSON
Median TPM across 13 brain regions for MMP9 → TARDBP (C-terminal fragments) → cytoplasmic aggregation seeding from GTEx v10.
💉 Clinical Trials
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 MMP9 → TARDBP (C-terminal fragments) → cytoplasmic aggregation seeding.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
🏆 Tournament
🏆 Arenas / Elo
📊 Market Indicators
💾 Resource Usage
🔮 Predictions
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| IF senescent microglia are ablated using senolytics (ABT-263) in SOD1G93A mice at disease onset (day 90), THEN cytoplasmic TDP-43 aggregation in spinal motor neurons will be reduced by >40% at end-sta | >40% reduction in motor neuron cytoplasmic TDP-43 aggregates (quantified by immunohistochemistry and proteinase-K-resistant fraction on Western blot) | — no observation — | pending | 0.55 |
| IF MMP-9 activity is selectively inhibited in co-cultures of senescent microglia and motor neurons (via SB-3CT or MMP-9 siRNA), THEN the levels of TDP-43 C-terminal fragments (~25 kDa) will decrease b | >50% reduction in TDP-43 C-terminal fragment levels (Western blot densitometry, normalized to full-length TDP-43) | — no observation — | pending | 0.65 |
▸Metadatasource: v1_phase_c_backfill · origin_type: gap_debate
| source | v1_phase_c_backfill |
| origin_type | gap_debate |
| _schema_version | 1 |