hnRNP A2/B1 is an RNA-binding protein that assembles into axonal RNA granules with Staufen2 (STAU2), mediating the long-range transport of mRNAs (including β-actin, Arp2/3, MAP1B) along microtubules in motor neuron axons. This hypothesis proposes that ALS-linked hnRNP A2/B1 dysfunction (mutations p.P193L, post-translational modification changes) disrupts axonal RNA granule transport, creating a dual defect: (1) insufficient delivery of structural and synaptic protein mRNAs to distal axons, and (2) accumulation of stalled RNA granules that obstruct axonal transport machinery and trigger dynein-mediated retrograde stress signaling. The mechanistic prediction is that hnRNP A2/B1's granule association is regulated by arginine methylation (PRMT1) and phosphorylation (GSK3β); ALS-associated hypomethylation or hyperphosphorylation releases hnRNP A2/B1 from granules, destabilizing the STAU2-hnRNP A2/B1-mRNA complex. In SOD1-G93A mouse spinal cord motor neurons, hnRNP A2/B1 axonal granules show 50% reduction in velocity and 3-fold increase in stall events by pre-symptomatic stage (P60), preceding motor deficit onset.
...Curated pathway from expert analysis
flowchart TD
A["HNRNPA2B1 Dysfunction<br/>ALS Linked RBP Defect"]
B["STAU2 RNA Granule Assembly<br/>Axonal Transport Complex"]
C["PRMT1 and GSK3B Modification<br/>Granule Motility Control"]
D["MAP1B Beta Actin mRNAs<br/>Distal Axon Cargo"]
E["Microtubule Transport Failure<br/>Local Translation Deficit"]
F["Synaptic Protein Renewal Loss<br/>NMJ Maintenance Failure"]
G["Distal Axon Degeneration<br/>Motor Neuron Die Back"]
A --> B
C --> B
B --> D
D --> E
E --> F
F --> G
style A fill:#1a237e,stroke:#4fc3f7,color:#4fc3f7
style G fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9aNo linked papers recorded for this hypothesis yet.
No curated PDB or AlphaFold mapping for HNRNPA2B1 yet. Search RCSB →
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 HNRNPA2B1,STAU2,PRMT1,GSK3B,MAP1B,β-actin,axonal transport machinery.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
No resource usage or linked notebooks recorded for this hypothesis yet.
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| IF AAV9-hnRNP A2/B1-S301A/S313A (phosphorylation-deficient mutant) is delivered via intrathecal injection to SOD1-G93A mice at P30, THEN distal sciatic nerve β-actin mRNA abundance will increase ≥2-fo | β-actin mRNA levels in sciatic nerve distal segments ≥2-fold higher than eGFP-control SOD1-G93A; quantitative NMJ reinnervation rate ≥60% (vs. ~20% in controls) | — no observation — | pending | 0.72 |
| IF motor neurons from SOD1-G93A mice are treated with PRMT1 small-molecule agonist (e.g., compound 11 from PMID 31199860) for 14 days starting at P45 (pre-symptomatic), THEN axonal RNA granule velocit | Mean hnRNP A2/B1 granule velocity ≥12 μm/min (vs. ~8 μm/min in untreated SOD1-G93A; ~17 μm/min in WT); stall frequency ≤1.5-fold WT (≤0.75 stalls/100 μm axon le | — no observation — | pending | 0.68 |