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Alzheimer's Association International Conference 2026

July 12-15, 2026 | London, United Kingdom, and Online

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Disentangling Brain-region Specific From Global Brain-wide Microglial Responses To Pathologies Of Alzheimer’s Disease

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Disentangling brain-region specific from global brain-wide microglial responses to pathologies of Alzheimer’s disease

Amy Watt1, David Fardo2, Suman Jayadev3, Katherine E. Prater3, Shubhabrata Mukherjee4, Kevin Z. Lin1

Motivation: 
  • Most transcriptomic studies of Alzheimer’s disease (AD) sample tissue from one brain region, and conclude cellular mechanisms of the entire brain.

  • However, these cellular mechanisms could strongly differ from region-to-region, for instance, due to how co-occurring neurodegenerative diseases spread throughout the brain.

  • Which cellular mechanism are region-specific vs. brain-wide?

  • We focus on microglia, the resident immune system of the brain.

  • After correcting for baseline snRNA-seq gene expression, correlation b/w brain regions is only modestly positive – this suggests possible region-specific mechanisms.

Fig. 1: A) Co-pathologies of AD are correlated with increased severity of AD (NACC data). B) Different pathologies spread along different routes, suggest the importance of distinguishing local-vs-global cellular mechanisms.

Fig. 2: Correlation of microglial transcriptomic profiles b/w brain regions (SEA-AD, 32 donors, spanning AD spectrum)


Goal and dataset:

Fig. 3: A) Goal – distinguish microglial brain-wide mechanisms those localized to the MTG. B) Stainings used to derive the HALO quantitative neuropathology (% area in gray matter), GFAP not shown.

Analysis workflow:

  • Step 1: Confirmatory factor analysis to derive MTG-specific burden

  • Step 2: Associate MTG-specific burden and global burden (Sinha, et al., 2023) to gene expression using NEBULA (He et al., 2021). 

Fig. 4: A) Schematic of association b/w MTG burden and gene expression, adjusting for covariates. B) Flowchart of how HALO neuropathology and snRNA-seq is used.
 
 

Latent MTG burden:

Fig. 5: Confirmatory factor analysis including 2 co-localization variables to improve model fit (CFI = 0.959, RMSEA = 0.058).

Fig. 6: A) SEA-AD cohort, showing last CASI score (Nested F-test p-value: 0.0581) or Braak. MTG is staged at Braak 4. The MTG-specific burden captures variability overlooked by the global BPS. B) Corroboration of the local-vs-global burden using ROS-MAP cohort. *Not exact replication is the quantified neuropathology is only amyloid and tau from the medial temporal cortex (MTC).


Associated genes:

  • Key genes (CHI3L1, apoptosis; SORL1, phagocytosis; CTSD, lysosome) implicated as responding locally in MTG burden.

Fig. 7: A) Schematic of how we compare genes associated w/ (global) BPS or (local) MTG. B) Comparison of the gene associations. Dashed line denotes the signed FDR multiple-testing thresholding.

Fig. 8: The microglial sig. genes associated with MTG are corroborated in the ROSMAP cohort


 

Microglial composition:

  • What shifts in microglial states (composition) are associated w/ MTG burden?

  • We transfer microglial state labels from Sun et al., 2023 (ROS-MAP) to SEA-AD.

Fig 9: A) Transferred microglial states in SEA-AD.. B) Compositional shifts along BPS (global) or MTG burden (local), w/ Pearson corr. shown.


 



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