Single nucleus RNA sequencing and spatial transcriptomics reveal unique functionalities of gray matter versus white matter oligodendrocytes in aging and Alzheimer's Disease
Oligodendrocyte (OL) dysfunction and white-matter (WM) vulnerability are increasingly recognized as important aspects of aging and Alzheimer's Disease (AD), yet human WM-focused, cellular-resolution transcriptomic data remain limited. Here, we profiled prefrontal WM from 48 brain donors spanning young adulthood and late-life with low versus high AD Neuropathologic Change (ADNC) using single-nucleus RNA sequencing followed by spatial transcriptomics (CosMx) in a subset of matched donors. We integrated aged WM OLs with a reference dorsolateral prefrontal cortex grey-matter (GM) OL dataset (SEA-AD) to define region- and pathology-associated OL programs. Across modalities, GM OLs exhibited a robust synapse/neurotransmitter-associated transcriptional signature relative to WM OLs, whereas this program was reduced with aging and attenuated in high ADNC GM. In contrast, WM OLs showed stronger immune-associated programs with aging and further enhancement in high ADNC, including cytokine/chemokine signaling and antigen presentation-related pathways. High ADNC WM OLs also displayed amplified proteostasis and stress-adaptation signatures, including selective upregulation of chaperone/heat shock genes and ferritin subunits, consistent with increased protein-folding demand and altered iron handling. To resolve OL state organization beyond static differential expression, we annotated OL sub-states using marker panels and inferred pseudotime-guided directional state-to-state flows within each tissue/condition stratum. This analysis identified a conserved newly formed differentiating (NFOL)/differentiating [->] lipid remodeling (APOE/ABCA1/LPL+) [->] Stress/ISR-reactive architecture, with a pronounced expansion of the Stress/ISR-reactive compartment and altered transition-associated pathway enrichment in high ADNC WM. Together, these data define WM-specific OL programs linked to aging and ADNC and nominate a stress/immune-enriched OL state landscape consistent with a putative senescence-like phenotype in diseased WM.