Tau Spreading Network Mapping via Spatial Transcriptomics in PSP

Tau Spreading Network Mapping via Spatial Transcriptomics in PSP

Background and Rationale

Progressive Supranuclear Palsy (PSP) is a devastating tauopathy characterized by selective vulnerability of brainstem and subcortical regions to 4-repeat (4R) tau aggregation. Current understanding of disease progression relies heavily on post-mortem analyses, limiting insights into dynamic spreading mechanisms. This study leverages cutting-edge spatial transcriptomics to map tau pathology spread in real-time within a PSP mouse model, testing the hypothesis that 4R-tau follows predictable anatomical connectivity patterns. We will utilize transgenic mice expressing human 4R-tau under the CaMKII promoter, combined with stereotaxic injection of pre-formed fibrils (PFFs) to initiate pathology at defined anatomical sites. The experimental design incorporates longitudinal sacrifice timepoints (1, 3, 6, and 12 months post-injection) with comprehensive spatial transcriptomic profiling using 10x Visium technology across entire brain hemispheres. Key measurements include tau gene expression gradients, microglial activation markers, synaptic integrity genes, and connectivity-associated transcripts.

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Tau Spreading Network Mapping via Spatial Transcriptomics in PSP

Background and Rationale

Progressive Supranuclear Palsy (PSP) is a devastating tauopathy characterized by selective vulnerability of brainstem and subcortical regions to 4-repeat (4R) tau aggregation. Current understanding of disease progression relies heavily on post-mortem analyses, limiting insights into dynamic spreading mechanisms. This study leverages cutting-edge spatial transcriptomics to map tau pathology spread in real-time within a PSP mouse model, testing the hypothesis that 4R-tau follows predictable anatomical connectivity patterns. We will utilize transgenic mice expressing human 4R-tau under the CaMKII promoter, combined with stereotaxic injection of pre-formed fibrils (PFFs) to initiate pathology at defined anatomical sites. The experimental design incorporates longitudinal sacrifice timepoints (1, 3, 6, and 12 months post-injection) with comprehensive spatial transcriptomic profiling using 10x Visium technology across entire brain hemispheres. Key measurements include tau gene expression gradients, microglial activation markers, synaptic integrity genes, and connectivity-associated transcripts. Advanced computational modeling will integrate transcriptomic data with established mouse connectome databases to identify vulnerability networks and predict spreading trajectories. Innovation lies in combining spatial resolution with transcriptomic depth to capture both pathological tau species and cellular responses simultaneously across anatomically-defined regions. This approach will validate whether tau spreading follows synaptic connectivity patterns, identify molecular signatures preceding overt pathology, and reveal potential intervention targets. The significance extends beyond PSP to other tauopathies, providing a generalizable framework for understanding protein aggregation spread in neurodegenerative diseases and informing therapeutic strategies targeting early disease stages.

This experiment directly tests predictions arising from the following hypotheses:

• Noradrenergic-Tau Propagation Blockade
• LRP1-Dependent Tau Uptake Disruption
• Synaptic Vesicle Tau Capture Inhibition
• HSP90-Tau Disaggregation Complex Enhancement
• Tau-Independent Microtubule Stabilization via MAP6 Enhancement

Experimental Protocol

Phase 1 (Months 1-2): Generate PSP mouse model using 3-month-old CaMKII-4R-tau transgenic mice (n=60). Perform stereotaxic injection of human 4R-tau PFFs (2μg in 2μL PBS) into substantia nigra and globus pallidus bilaterally under isoflurane anesthesia. Control groups receive PBS injection (n=24). Phase 2 (Months 3-14): Sacrifice cohorts at 1, 3, 6, and 12 months post-injection (n=15 per timepoint). Rapidly extract brains, embed in OCT, and prepare 10μm cryosections for spatial transcriptomics. Process sections using 10x Genomics Visium platform following manufacturer protocols, capturing 6-8 sections per brain spanning injection sites and connected regions. Phase 3 (Months 15-16): Perform immunohistochemistry on adjacent sections using AT8 (phospho-tau), Iba1 (microglia), and NeuN (neurons) antibodies. Quantify tau burden and cellular densities in regions-of-interest. Phase 4 (Months 17-20): Analyze spatial transcriptomic data using Space Ranger and Seurat pipelines. Identify differentially expressed genes in tau-positive regions, perform pathway enrichment analysis, and map expression gradients. Integrate data with Allen Mouse Brain Connectivity Atlas to model spreading patterns. Phase 5 (Months 21-24): Validate findings using quantitative PCR and Western blotting for key transcripts and tau species. Perform statistical modeling to predict vulnerability based on connectivity strength and gene expression signatures.

Expected Outcomes

• Spatial transcriptomics will reveal distinct gene expression signatures in tau-seeded regions within 1 month, with >500 differentially expressed genes (FDR<0.05) compared to control regions
• Tau pathology will spread to anatomically connected regions following a predictable temporal sequence, with 60-80% of connected regions showing molecular changes by 6 months
• Microglial activation markers (Iba1, Cd68, Trem2) will increase 2-4 fold in regions preceding detectable tau aggregation, serving as early predictive biomarkers
• Synaptic genes (Syn1, Dlg4, Homer1) will show progressive downregulation (30-50% reduction) correlating with connectivity strength to seeded regions
• Machine learning models incorporating connectivity and gene expression data will predict tau spreading with >85% accuracy for 12-month timepoints
• Differential vulnerability patterns will emerge, with monoaminergic nuclei showing 3-5x higher susceptibility scores compared to cortical regions

Success Criteria

• • Detection of statistically significant spatial gene expression gradients (p<0.001) extending from injection sites along anatomical pathways
• • Identification of at least 50 connectivity-associated genes showing distance-dependent expression changes from tau epicenters
• • Validation of predictive model accuracy >80% for tau spreading patterns using independent test cohorts
• • Demonstration of temporal precedence where transcriptomic changes precede histological tau pathology by ≥1 month in connected regions
• • Successful mapping of vulnerability networks with correlation coefficient >0.7 between predicted and observed tau burden
• • Generation of reproducible spatial transcriptomic atlas with <20% technical variation between biological replicates