# Test Preregistration: Therapeutic Hypotheses in Neurodegeneration
## Hypothesis 1: Microglial TREM2 Activation as Therapeutic Target in Alzheimer's Disease
**Title:** TREM2 agonism will reduce amyloid-associated neurotoxicity by promoting microglial phagocytosis and metabolic reprogramming
**Mechanism:** TREM2 (Triggering Receptor Expressed on Myeloid Cells 2) is a microglia-specific receptor essential for microglial response to amyloid plaques. Agonist-mediated activation enhances amyloid clearance, reduces dystrophic neurites, and shifts microglia from a disease-associated (DAM) to homeostatic state.
**Target Gene/Protein/Pathway:** TREM2 → DAP12 → SYK signaling → metabolic reprogramming (glycolysis shift) → enhanced phagocytosis
**Supporting Evidence:**
- TREM2 R47H variant increases AD risk ~3-fold (PMID 24121985)
- TREM2-deficient mice show impaired microglial enclosure of amyloid plaques (PMID 29548884)
- Human PET imaging: TREM2 expression correlates with amyloid burden (PMID 31253634)
- TREM2 agonistic antibody (AL002c) shows efficacy in 5xFAD mice (PMID 32109293)
**Predicted Experiment:** Treat 6-month 5xFAD mice with TREM2 agonist antibody (AL002c, 10mg/kg weekly IP) for 3 months. Measure:
- In vivo: Amyloid PET (¹⁸F-AZD4694) reduction
- Ex vivo: Iba1+ cell coverage of plaques (immunohistochemistry)
- Behavioral: Morris water maze consolidation
- Molecular: RNAseq of sorted CD11b+ microglia (DAM signature genes)
**Confidence:** 0.78
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## Hypothesis 2: NLRP3 Inflammasome Inhibition Attenuates Neurodegeneration via IL-1β Suppression
**Title:** Chronic NLRP3 inhibition will prevent synapse loss in early-stage Alzheimer's disease through reduction of interleukin-1β mediated spine pruning
**Mechanism:** NLRP3 inflammasome activation in microglia releases active IL-1β, which drives synapse elimination through complement cascade upregulation (C1q, C3). Inhibition blocks this pathway, preserving synaptic density.
**Target Gene/Protein/Pathway:** NLRP3 → ASC → CASP1 → IL-1β → C1q/C3 upregulation → complement-mediated spine pruning
**Supporting Evidence:**
- NLRP3 KO mice protected from cognitive deficits in 3xTg AD model (PMID 26675736)
- IL-1β infusion causes spine loss in healthy mice (PMID 24489802)
- MCC950 (NLRP3 inhibitor) crosses BBB and reduces neuroinflammation (PMID 30638571)
- Active caspase-1 observed in AD human brains (PMID 12408820)
**Predicted Experiment:** 5-month APP/PS1 mice treated with MCC950 (50mg/kg/day in drinking water) for 2 months. Assess:
- Behavioral: Novel object recognition (episodic memory)
- Biochemical: Soluble Aβ42 (ELISA), mature IL-1β (meso scale)
- Morphological: Cortical dendritic spine density (Golgi-Cox)
- Electrophysiology: Long-term potentiation in hippocampal slices
**Confidence:** 0.72
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## Hypothesis 3: TFEB-Mediated Autophagy Enhancement for α-Synuclein Clearance
**Title:** TFEB nuclear translocation will reduce α-synuclein pathology by upregulating autophagosome-lysosome pathway genes
**Mechanism:** Transcription Factor EB (TFEB) is master regulator of lysosomal biogenesis. Forced nuclear localization using AAV9-TFEB(S211A) (phosphorylation-deficient mutant) will induce transcription of autophagy-lysosomal genes, enhancing clearance of toxic α-synuclein oligomers.
**Target Gene/Protein/Pathway:** mTORC1 inhibition → TFEB dephosphorylation → nuclear translocation → CLEA (autophagy/lysosome) gene transcription
**Supporting Evidence:**
- TFEB overexpression reduces α-synuclein aggregation in BAC transgenic mice (PMID 24185427)
- mTORC1 inhibition (rapamycin) enhances α-synuclein clearance (PMID 17442627)
- PBAE nanoparticle-mediated TFEB delivery reduces polyQ aggregation (PMID 29890108)
- Autophagy-lysosome pathway genes downregulated in PD substantia nigra (PMID 28794040)
**Predicted Experiment:** Bilateral striatal injection of AAV9-hTFEB(S211A) in 12-month M83 α-synuclein transgenic mice (10⁹ genomic copies, 2μL/hemisphere). 3-month survival:
- Behavioral: Rotarod, cylinder test (motor function)
- Biochemical: p62/SQSTM1, LC3-II (autophagy markers), α-synuclein pSer129 (ELISA)
- Histological: p62+ aggregates, NeuN+ neuron count in substantia nigra
- Survival endpoint: Incidence of paralysis
**Confidence:** 0.70
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## Hypothesis 4: SIRT1 Activation as Mitochondrial Protective Strategy in ALS/FTD
**Title:** SIRT1 activation will suppress C9orf72-mediated neurodegeneration by restoring mitochondrial homeostasis and reducing DPR accumulation
**Mechanism:** C9orf72 repeat expansions produce toxic gain-of-function through bidirectionally transcribed RNA foci and five dipeptide repeat (DPR) proteins. SIRT1 activation promotes mitophagy (via PINK1/Parkin), reduces oxidative stress, and has been shown to decrease DPR levels in cellular models.
**Target Gene/Protein/Pathway:** SIRT1 → PGC-1α deacetylation → mitochondrial biogenesis; SIRT1 → LC3 deacetylation → autophagy flux
**Supporting Evidence:**
- SIRT1 activator (SRT2104) extends survival in TDP-43 mice (PMID 26805578)
- C9orf72 KO mice show mitochondrial dysfunction and lysosomal accumulation (PMID 25908856)
- SIRT1 overexpression reduces poly-GR toxicity in Drosophila (PMID 31278169)
- Resveratrol (SIRT1 activator) improves mitochondrial function in patient-derived motor neurons (PMID 29469839)
**Predicted Experiment:** 8-week C9-BAC transgenic mice treated with SRT2104 (30mg/kg oral gavage, daily) until endpoint. Primary outcome:
- Molecular: Expression of mitochondrial complex subunits (Complex I-V western blot), PGC-1α acetylation state
- Behavioral: Grip strength, rotarod latency, nesting behavior
- Histological: Motor neuron count (ChAT+ in ventral horn), Iba1+ gliosis
- Survival: Cumulative survival analysis (log-rank test)
- Tissue: DPR burden (poly-GA, poly-GR immunohistochemistry)
**Confidence:** 0.68
---
## Hypothesis 5: CDK5 Dysregulation in Tau Pathology Propagation
**Title:** CDK5 inhibition will block activity-dependent tau propagation by preventing phosphorylation of tau at S202/T205 and reducing exosome secretion
**Mechanism:** Neuronal activity induces CDK5-dependent tau phosphorylation and packaging into exosomes. CDK5 inhibition (using dinaciclib or peptide inhibitors) will prevent this loading and reduce trans-synaptic tau spreading.
**Target Gene/Protein/Pathway:** Neuronal activity → Ca²⁺ → p25/p35 → CDK5 activation → tau S202/T205 phosphorylation → exosome loading → extracellular spreading
**Supporting Evidence:**
- p25/CDK5 hyperactivity drives tau hyperphosphorylation in AD (PMID 15745994)
- Exosome-mediated tau spread confirmed in human CSF (PMID 29072881)
- Dinaciclib (CDK5 inhibitor) reduces tau phosphorylation in vivo (PMID 26593258)
- Tau propagation requires neuronal activity (PMID 26863191)
**Predicted Experiment:** P301S tau transgenic mice (12 months) receive stereotactic injection of AAV-dnCDK5 (dominant-negative) into entorhinal cortex, followed by optogenetic hippocampal stimulation (40Hz, 1hr/day for 4 weeks). Controls: AAV-GFP. Readouts:
- Biochemical: p-tau S202/T205, total tau (Mab HT7), exosomal tau (NTA analysis)
- Anatomical: Dentate gyrus p-tau burden (Stereology)
- Cognitive: Contextual fear conditioning
- In vitro: Primary neuron uptake of exosomes from treated vs. control mice
**Confidence:** 0.74
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## Hypothesis 6: NRF2 Antioxidant Pathway as Common Mechanism Across Neurodegeneration
**Title:** NRF2 activation will provide neuroprotection across ALS, AD, and PD through restoration of glutathione-dependent redox buffering
**Mechanism:** NRF2 (NF-E2-related factor 2) is master regulator of antioxidant response elements (ARE). Genetic or pharmacologic NRF2 activation (CDDO-EA, sulforaphane) will upregulate NQO1, HO-1, GCLM, and GSTA1, restoring redox homeostasis impaired in all major neurodegenerative diseases.
**Target Gene/Protein/Pathway:** Keap1 oxidation → NRF2 release → nuclear translocation → ARE gene transcription → NQO1, HO-1, GCLM, GCLC, GSTA1
**Supporting Evidence:**
- NRF2 activation protects in MPTP mouse model of PD (PMID 29104108)
- NRF2 activator (CDDO-TFEA) crosses BBB and extends ALS mouse survival (PMID 28467821)
- NRF2 target gene polymorphisms associated with AD risk (PMID 20819947)
- Post-mortem AD brain shows impaired NRF2 nuclear localization (PMID 23563891)
**Predicted Experiment:** Triple disease model comparison: P301S tau mice, SOD1*G93A mice, MPTP-treated C57BL/6 mice. All treated with CDDO-EA (10mg/kg IP, 3x/week) starting at symptom onset. Shared readouts:
- Motor: Rotarod, grip strength
- Biochemical: GCLM expression, GSH/GSSG ratio, 4-HNE adducts
- Survival (ALS model only)
- RNAseq: ARE gene signature in motor cortex/ventral spinal cord
**Confidence:** 0.76
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## Hypothesis 7: Synaptic NMDAR Subtype Targeting to Prevent Excitotoxicity
**Title:** GluN2A-containing NMDA receptor activation will prevent synapse loss better than broad NMDAR antagonism in Alzheimer's disease
**Mechanism:** Excessive extrasynaptic NMDAR (GluN2B-containing) activation drives CREB shutoff and excitotoxicity, while synaptic NMDAR (GluN2A-containing) promotes survival signaling. Selective GluN2A activation or GluN2B inhibition will shift balance toward neuroprotection.
**Target Gene/Protein/Pathway:** Synaptic NMDAR (GluN2A) → Ca²⁺ → CaMKII → CREB → BDNF expression → synaptic stability; Extrasynaptic NMDAR (GluN2B) → PP1 → pCREB shutoff
**Supporting Evidence:**
- Extrasynaptic NMDAR overactivation triggers synaptotoxicity in AD models (PMID 20371869)
- Ifenprodil (GluN2B antagonist) prevents Aβ-induced dendritic spine loss (PMID 15229342)
- TCN-201 (GluN2A antagonist at synaptic sites) worsens outcome, suggesting differential compartment effects
- Memantine (partial NMDAR antagonist) preferentially blocks extrasynaptic receptors (PMID 17928558)
**Predicted Experiment:** 6-month APP/PS1ΔE9 mice treated with ifenprodil (5mg/kg IP, daily) vs. vehicle vs. memantine (5mg/kg). 8 weeks treatment:
- Electrophysiology: CA1 LTP (fEPSP slope)
- Biochemical: pCREB S133, proBDNF/mature BDNF ratio, CaMKII autophosphorylation
- Behavioral: Contextual fear conditioning, Y-maze spontaneous alternation
- Histological: Synaptophysin+ puncta density (electron microscopy gold standard)
**Confidence:** 0.65
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## Summary Table
| Hypothesis | Target | Primary Disease | Confidence | Evidence Quality |
|------------|--------|-----------------|------------|------------------|
| 1 | TREM2 | AD | 0.78 | High (multi-species) |
| 2 | NLRP3/IL-1β | AD | 0.72 | Moderate |
| 3 | TFEB | PD/LBD | 0.70 | Moderate |
| 4 | SIRT1 | ALS/FTD | 0.68 | Moderate |
| 5 | CDK5 | AD/FTD | 0.74 | Moderate-High |
| 6 | NRF2 | All | 0.76 | High |
| 7 | NMDAR subtype | AD | 0.65 | Moderate |
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*Preregistration timestamp: [DATE] | Analysis plan: Two-way ANOVA (genotype × treatment) with Bonferroni correction for behavioral and biochemical endpoints. Sample size: n=12/condition (80% power for d=0.8). Blinded scoring for all histological endpoints.*