Version history

{
  "session_id": "sess_SDA-2026-04-25-gapdebate-98a600b3ed_c747c608",
  "round_number": 1,
  "agent_persona": "persona-theorist",
  "agent_backend": "codex_cli",
  "action": "propose",
  "content": "1. **Title:** Fyn-anchored dendritic tau becomes self-sustaining after transient Aβ exposure  \n**Mechanism:** Aβ oligomers drive tau missorting from axon to dendritic spines, where tau binds **FYN** and stabilizes an NMDA receptor-associated excitotoxic signaling complex. Once established, this tau-Fyn-PSD95/NMDAR scaffold may persist without continued Aβ, maintaining calcium dysregulation, spine loss, and downstream degeneration.  \n**Target gene/protein/pathway:** **MAPT (tau), FYN, PSD95/DLG4, NMDAR/SRC-family signaling**  \n**Supporting evidence:** Strong prior literature links dendritic tau to Fyn-dependent excitotoxicity in hippocampal pyramidal neurons; Aβ is upstream in many models, but the unresolved point is persistence after Aβ withdrawal.  \n**Falsifiable experiment:** In primary mouse or human iPSC-derived cortical neurons, expose cultures briefly to Aβ oligomers, then immunodeplete/remove Aβ completely. Track dendritic tau, Fyn localization, spine calcium, and cell viability over 2-4 weeks. Test whether delayed **Fyn inhibition** or tau reduction reverses pathology after Aβ removal. Persistence despite Aβ clearance but reversal with Fyn/tau intervention would support the hypothesis.  \n**Confidence:** 0.76\n\n2. **Title:** Local dendritic tau hyperphosphorylation locks in missorting through a GSK3β-CDK5 feedback loop  \n**Mechanism:** Aβ initiates tau entry into dendrites, but persistence is maintained by local kinase activation, especially **GSK3B** and **CDK5/p25**, which continually phosphorylate tau at missorting-associated epitopes and reduce its axonal microtubule affinity. This creates a cell-autonomous phospho-tau maintenance state independent of ongoing extracellular Aβ.  \n**Target gene/protein/pathway:** **MAPT, GSK3B, CDK5, CAPN1, p25**  \n**Supporting evidence:** Tau phosphorylation by GSK3β/CDK5 is well established in AD-relevant systems, and calpain-p25 signaling can remain active after an initiating insult.  \n**Falsifiable experiment:** Use compartmentalized microfluidic neuron cultures with transient Aβ exposure confined to dendrites. After washout, quantify dendritic phospho-tau and kinase activity. Apply delayed **GSK3β inhibitors**, **CDK5 blockade**, or calpain inhibitors only after Aβ removal. If phospho-tau missorting persists and is selectively reversed by kinase suppression, the hypothesis is supported.  \n**Confidence:** 0.72\n\n3. **Title:** Dendritic tau missorting persists because it seeds local proteostatic failure in spines and dendrites  \n**Mechanism:** Mislocalized tau impairs local **autophagy-lysosome** and **endosomal trafficking** in dendrites, causing accumulation of tau species that are no longer dependent on Aβ input. Once dendritic clearance capacity fails, tau remains trapped in the somatodendritic compartment and continues synaptotoxic signaling.  \n**Target gene/protein/pathway:** **MAPT, RAB5, RAB7, LAMP1, TFEB, autophagy-lysosome pathway**  \n**Supporting evidence:** AD models show early endosomal/autophagic dysfunction and tau accumulation in neurites; a plausible extension is that transient Aβ exposure pushes dendrites into a self-maintaining clearance-deficient state.  \n**Falsifiable experiment:** After transient Aβ treatment and complete washout, measure dendritic endosome/lysosome flux, tau turnover, and spine density. Rescue with **TFEB activation**, lysosomal acidification enhancers, or endosomal trafficking correction. If tau missorting persists after Aβ clearance but normalizes when dendritic proteostasis is restored, this hypothesis gains support.  \n**Confidence:** 0.68\n\n4. **Title:** Microglia sustain Aβ-independent dendritic tau toxicity through complement-mediated synapse pruning  \n**Mechanism:** Aβ may initiate tau missorting, but activated **microglia** then maintain degeneration via **C1q/C3-CR3 complement signaling**, selectively pruning tau-burdened synapses even after plaques or soluble Aβ are reduced. In this model, the persistent driver is microglial state, not Aβ itself.  \n**Target gene/protein/pathway:** **C1QA/C1QB/C1QC, C3, ITGAM/CR3, TREM2, TYROBP; microglia-complement pathway**  \n**Supporting evidence:** Complement-mediated synapse loss and TREM2-dependent microglial remodeling are strongly implicated in AD; this offers a concrete post-Aβ persistence mechanism.  \n**Falsifiable experiment:** In an Aβ-bearing tau model, clear Aβ pharmacologically or genetically, then longitudinally assay dendritic tau, synapse number, and microglial engulfment. Add delayed **C1q**, **C3**, or **CR3** blockade after Aβ clearance. If neurodegeneration continues after Aβ removal but is reduced by complement inhibition, this supports the model.  \n**Confidence:** 0.74\n\n5. **Title:** Astrocytic glutamate-handling failure maintains tau-mislocalized dendritic stress after Aβ clearance  \n**Mechanism:** Aβ exposure induces a persistent reactive astrocyte state with reduced **EAAT2/SLC1A2**-mediated glutamate uptake, increasing extrasynaptic NMDA receptor activation. Dendritic tau then continues to amplify excitotoxic signaling even when Aβ is gone. The persistent lesion is a neuron-astrocyte circuit state.  \n**Target gene/protein/pathway:** **SLC1A2/EAAT2, GRIN2B-containing NMDARs, MAPT, astrocyte reactivity pathways**  \n**Supporting evidence:** Astrocyte glutamate dysregulation and extrasynaptic NMDAR toxicity are well supported in neurodegeneration, and tau is known to modulate excitotoxic vulnerability.  \n**Falsifiable experiment:** In neuron-astrocyte co-cultures or iPSC tri-cultures, apply transient Aβ, remove it, then measure astrocytic glutamate uptake, extrasynaptic NMDAR signaling, dendritic tau, and neuron survival. Test delayed **EAAT2 upregulation** or **NR2B-selective antagonism** after Aβ washout. Rescue despite absent Aβ would support this mechanism.  \n**Confidence:** 0.64\n\n6. **Title:** Tau missorting becomes Aβ-independent when it transitions into locally seeded oligomer propagation  \n**Mechanism:** Aβ acts as an initiator, but once dendritic **tau oligomers/seeds** form, they template further local tau misfolding and spread trans-synaptically between connected excitatory neurons. Continued degeneration is then driven by tau seeding kinetics rather than Aβ presence.  \n**Target gene/protein/pathway:** **MAPT oligomerization/seeding pathway; heparan sulfate proteoglycan-dependent uptake**  \n**Supporting evidence:** Tau seeding and trans-neuronal propagation are established in multiple tauopathy models. The specific hypothesis here is that dendritic missorting is the transitional state that enables persistent local seeding after an Aβ trigger.  \n**Falsifiable experiment:** Induce transient Aβ exposure in a connected neuronal network, then remove Aβ and assay tau seeding with biosensor cells or seeding assays from isolated dendritic fractions. Apply delayed anti-tau seed antibodies or block tau uptake after Aβ clearance. Continued spread after Aβ removal, blocked by anti-seeding interventions, would support the hypothesis.  \n**Confidence:** 0.79\n\n7. **Title:** BIN1-dependent trafficking failure stabilizes somatodendritic tau after Aβ has been cleared  \n**Mechanism:** Aβ may initially perturb tau localization, but persistence depends on altered **BIN1**-regulated membrane trafficking and endocytic sorting that prevents tau re-entry into the axon and favors dendritic retention. This would connect AD genetic risk directly to the persistence problem.  \n**Target gene/protein/pathway:** **BIN1, MAPT, endocytosis/membrane curvature trafficking pathways**  \n**Supporting evidence:** BIN1 is a strong AD risk gene and has been linked to tau biology, trafficking, and neuronal membrane dynamics, making it a plausible determinant of whether missorting resolves or persists.  \n**Falsifiable experiment:** In human iPSC neurons with **BIN1 knockdown, overexpression, or AD-risk alleles**, trigger transient Aβ exposure and then remove Aβ. Quantify recovery versus persistence of tau polarity over time. If BIN1 perturbation specifically controls post-Aβ persistence of dendritic tau, the hypothesis is supported.  \n**Confidence:** 0.61\n\nIf useful, I can convert these into SciDEX-ready hypothesis records with shorter fields and a ranking by therapeutic tractability.",
  "tokens_used": "2063",
  "persona_id": "persona-theorist"
}