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A shared microglial resolution-failure axis links brain injury to Alzheimer's disease

Mickey Pentecost, PhD — Built with Claude · Life Sciences Hackathon (Researcher Track)

📹 Watch the 3-minute explainer: https://www.youtube.com/watch?v=i6Fc2_6tdlU

A cross-modality, cross-species test of whether the same microglial inflammatory program that traumatic brain injury (TBI) installs is the one that Alzheimer's disease (AD) risk alleles predispose to — computed entirely from public data during the event.

One-sentence thesis. TBI installs environmentally what AD risk alleles predispose to genetically, and both converge on the same microglial accelerator axis (OPN/SPP1 · TREM2 · APOE · complement), while the pro-resolving brake arm (TSG-6/TNFAIP6 · CD44) stays disengaged — and both arms are read out at a single receptor, CD44.

This repository holds the complete analysis behind the submission: a coordinated microglial accelerator module tested across two species and four assay types (single-nucleus and bulk RNA, spatial transcriptomics, proteomics), anchored by common-variant and regulatory genetics, and integrated at CD44. Every result is computed here from public data — no prior analysis is reused — under an OSI-approved (MIT) license. The genetic-anchoring layer (variant enrichment, allelic chromatin effect, partitioned heritability) is documented in full below.


Start here: the submission and its five figures

The full plain-language write-up is SUBMISSION.md, and every panel is described in FIGURE_CAPTIONS.md. The five figures tell the story in order — each reads orient → data → interpret, with a shared color grammar (red = inflammatory accelerator, blue = brake/resolution, purple = astrocytes, slate = genetics, amber = conclusion):

Figure Question it answers
Fig 1 — the hook Is there one shared accelerator program, and does it hold up? (module recovery · up in both diseases · reproduces across species/methods · 31% of inherited AD risk)
Fig 2 — where & when Does the accelerator concentrate at the damage? (real tissue maps: at amyloid plaques in AD, at the lesion in injury; peaks ~7 days)
Fig 3 — trigger vs threshold Are inherited risk and injury-installed genes the same? (only APOE/TREM2 are inherited-risk; the effectors are not — trigger ≠ threshold)
Fig 4 — the regulatory switch Which master-control proteins turn the accelerator on and off? (NFκB activator · MEF2C repressor · SPI1/CEBPB identity proteins)
Fig 5 — the CD44 hub Where do the accelerator and brake meet, and how does the brake fail? (both signal through CD44; CD44 rises across four modalities while TSG-6 falls)

The design system these figures share is documented in figures/DESIGN_SYSTEM.md. Three Supplementary figures — the genetic anchor (variant enrichment, ChromBPNet allelic effect, S-LDSC heritability, colocalization), the resolution brake (HA machinery, oxidative-fragmentation routes, imbalance, reproducibility), and regulatory grammar plus cross-condition validation (motif ablation, trajectory, CTE cohort) — are captioned in FIGURE_CAPTIONS.md.


The result in one figure

Cross-arm synthesis

Accelerator genes sit high on both the environmental axis (installed by TBI and AD in single-nucleus data) and the genetic axis (carrying AD risk variants in microglial enhancers). The upstream microglial switches — TREM2, APOE, TNF — carry the genetic load (≥3 AD risk variants each); the effectors — SPP1/OPN, the C1q complement genes, C3, TLR2 — are installed environmentally (up in AD and/or TBI microglia, few common risk variants).


Are the gene modules real, or just a curated guess?

The accelerator/resolution axis is hypothesis-driven — defined a priori from the DAM/neuroinflammation literature and the pro-resolving TSG-6→CD44 mechanism, not derived from the datasets it is tested on. Two independent robustness checks confirm it holds up, and one honest limitation is stated plainly:

Module validation

The accelerator genes co-vary as a genuine module (beating 100% of detection-matched random sets) and re-emerge in unsupervised NMF; the module is organized around CD44, the receptor where the accelerator ligand SPP1/OPN and the brake ligand TSG-6 compete. The resolution arm is near-undetectable in single-nucleus RNA — its quantification requires bulk RNA-seq (results/refined_accelerator_geneset.csv).


Three independent genetic layers

Layer Question Result Figure
1 · Variant enrichment Do AD-associated variants concentrate in microglial accelerator-gene enhancers? OR = 1.56, MAF-matched permutation P = 0.0022 (1.59× over null); APOE-excluded P = 9.5×10⁻³; resolution arm OR = 0 figures/enrichment_results.png
2 · Allelic chromatin effect Do those variants change predicted microglial chromatin accessibility? AD-associated accelerator variants disrupt chromatin more than non-associated (ChromBPNet, Mann-Whitney P = 0.005); top hit rs3800342 in the TREM2 enhancer (AD P = 9.3×10⁻¹²) figures/chrombpnet_results.png
3 · Partitioned heritability What fraction of AD SNP-heritability sits in microglial regulatory DNA? Microglial peaks (1.5% of genome) carry 31% of AD h²21× enrichment, P = 1.1×10⁻⁵; conditional coefficient z = 3.62. Within axis enhancers the signal is accelerator-specific (z = +0.99) vs resolution (z = −1.04) figures/sldsc_heritability.png

Supporting GWAS locus map: figures/gwas_axis_loci.png.

Spatial and temporal arm — where the axis fires, and when the brake is available

Layer Question Result Figure
Spatial — AD plaque niche Does the accelerator concentrate around amyloid plaques? Subcellular Stereo-seq (18-mo App-NL-G-F, 142k bins at 50 µm): accelerator concentrates at plaques and survives a tissue-geometry control (partial ρ = −0.24 vs distance-to-centroid; near>far within every concentric band, Δ +0.16→+0.23); the resolution/HA brake is excluded (ρ = +0.38); astrocytes co-concentrate peri-plaque (the CD44 shell). WT_F5 negative control shows a general center-high tissue gradient (ρ=−0.44) accounting for ~half the marginal signal figures/spatial_stereoseq_AD.png
Spatial — TBI lesion niche Does the same axis concentrate at the TBI lesion? Visium (impact TBI 7 d, 6 TBI / 6 Sham): accelerator up TBI-vs-Sham (P = 4×10⁻²⁶) and tracks lesion proximity (ρ = +0.47, non-circular proxy). Same axis, two injury landmarks figures/spatial_convergence.png
Temporal — TBI time-course Is the resolution brake a level or a phase? CEREBRI (24 h → 7 d → 6 mo): the brake is highest acutely (24 h) and collapses by 7 d as the accelerator peaks (accel trend ρ = +0.44, brake ρ = −0.25). The chronic AD plaque niche resembles the 6-mo TBI state — accelerator without the acute brake figures/cerebri_timecourse.png

Supporting Visium genotype panel: figures/spatial_visium.png.


Why this matters

Epidemiology links moderate-to-severe TBI to elevated dementia risk, but the mechanism has been a black box. Here we show, from public data computed during the event, that TBI and AD engage the same microglial accelerator program: single-nucleus microglia from human AD (SEA-AD) and mouse TBI (CEREBRI) both up-regulate the accelerator genes, while the pro-resolving arm stays flat — and the genetic side supplies the causal direction: the human genetic architecture of AD is concentrated in exactly the microglial regulatory elements that control those accelerator genes. Two independent kinds of evidence — an environmental perturbation and inherited risk — point at the same molecular axis, which is what a shared, targetable mechanism should look like.


Repository layout

.
├── README.md                     # this file
├── LICENSE                       # MIT
├── DATA_PROVENANCE.md            # every external dataset, accession, URL, license
├── thesis.md                     # full causal argument + axis gene modules
├── corces_model_provenance.md    # ChromBPNet model source, cluster→cell-type map
├── requirements.txt              # Python environments (analysis + ChromBPNet + LDSC)
├── figures/                      # publication figures (PNG, 300 dpi)
├── results/                      # all result tables (CSV)
├── data/                         # axis targets + enhancer/annotation BEDs (GRCh38 + hg19)
├── code/                         # scoring + LD-score + munge scripts
└── notebooks/                    # reproducible analysis notebooks (see below)

Key result tables (results/)

  • axis_targets.csv — 38 human axis genes (accelerator 21 / resolution 9 / DAM-only 8), GRCh38 coordinates, ±100 kb cis-windows, arm assignment.
  • gwas_axis_gene_summary.csv — per-gene AD-GWAS signal (Bellenguez GCST90027158) in cis-windows.
  • ad_variants_in_microglia_enhancers.csv — 3,522 AD variants intersecting Corces C24 microglial enhancers, annotated by axis gene + arm.
  • enrichment_results.csv — Fisher + MAF-matched permutation enrichment, per arm.
  • chrombpnet_allelic_scores.csv — allelic effect (lfc, JSD) for 3,356 SNVs; chrombpnet_top_variants.csv — ranked chromatin-disruptors.
  • sldsc_results.csv — partitioned-heritability enrichment for 4 annotations (all-microglia, accelerator, DAM, resolution).
  • crossarm_convergence.csv — per-gene environmental (log₂FC) vs genetic (risk-variant load) scores.

Causal / perturbable arm

  • novelty_synthesis.md — the full causal narrative: convergence → causation/direction → perturbation/mechanism, plus the drug-target rationale.
  • caqtl_formal_coloc.csv / caqtl_enhancer_coloc.csv — primary-microglia (Kosoy/Raj, n=150) caQTL vs AD-GWAS; enhancer-level dissection (effectors vs inherited-risk loci) and formal shared-SNP coloc.
  • moloc_threeway.csv — pairwise colocalization across three molecular layers (caQTL, eQTL, AD GWAS): three independent shared-SNP Wakefield-ABF tests per gene (not a joint 3-trait model), both molecular QTLs from primary microglia. Columns: PP4_caQTL_eQTL, PP4_eQTL_GWAS, PP4_caQTL_GWAS.
  • caqtl_ep_ad_loops.csv — AD-locus variants in microglial enhancers physically looping (ABC/Hi-C) to axis genes.
  • coloc_mr_results.csv — cell-type-matched myeloid (macrophage/monocyte) eQTL vs AD-GWAS coloc.
  • full_circuit.csv — integrated per-gene circuit (AD-risk / caQTL / E-P loop / expression layers).
  • insilico_perturbation.csv / cebpb_perturbation.csv — ChromBPNet motif-ablation Δaccessibility for NFκB, MEF2, SPI1, CEBPB on the 754 axis enhancers.
  • pseudotime_drivers.csv — diffusion-pseudotime gene/TF trends across the homeostatic→accelerator transition.
  • adni_dod_sidequest.md — standalone prompt for the two-hit (TBI × APOE) clinical test, to run under separate data governance.

Reproducing the analysis

The pipeline runs on public data only. Three environments are used (requirements.txt documents exact versions):

  1. Analysis (Python 3.11 + pandas/scipy/pyliftover) — GWAS streaming, variant intersection, enrichment, figures.
  2. ChromBPNet inference (tf_infer: TensorFlow 2.19 + tf-keras) — allelic scoring. See code/chrombpnet_scoring.py; the Corces C24 microglial model is loaded via a bias-free inner-model reconstruction (documented in the script) to bypass a Python-3 Lambda-layer incompatibility. Validated against the authors' own scores (|LFC| Pearson r = 0.986).
  3. S-LDSC (ldsc: our Python-3 port of bulik/ldsc) — partitioned heritability. code/run_arm_ldscores.sh builds per-chromosome annotations and LD scores; code/_munge_stream.py streams and munges the Bellenguez sumstats.

Data you must fetch (all public, all scripted)

Data Source Size
AD GWAS (Bellenguez 2022) EBI GWAS Catalog GCST90027158, GRCh38-native 755 MB
Corces C24 microglial ChromBPNet model + peaks github.com/corceslab/variantapp ~90 MB
1000G EUR reference + baseline-LD v2.2 Zenodo 10515792 ~1.1 GB

See DATA_PROVENANCE.md for exact URLs, accessions, versions, and licenses.


Citation & provenance

  • AD GWAS: Bellenguez C, et al. Nat Genet 2022. GWAS Catalog GCST90027158 (PMID 35379992).
  • Microglial ChromBPNet models + scATAC peaks: Corces MR, et al. Nat Genet 2020 (PMID 33106633); model weights from corceslab/variantapp.
  • S-LDSC: Finucane HK, et al. Nat Genet 2015; Gazal S, et al. baseline-LD v2.2. Software: bulik/ldsc (GPL-3.0), Python-3 port included.
  • Environmental-arm single-nucleus data: SEA-AD MTG (Allen Institute) and CEREBRI mouse TBI (GEO GSE269748).

This work was produced for the Built with Claude — Life Sciences hackathon (Research Track). All analysis was performed during the event on public data.

License

MIT (see LICENSE). Third-party data and models retain their own licenses as documented in DATA_PROVENANCE.md.

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Injury meets inheritance

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