Region-specific transcriptional signatures of brain aging in the absence of neuropathology at the single-cell level.

As age is a significant risk factor for multiple neurodegenerative diseases, investigating normal brain aging may help identify molecular events contributing to increased disease risk over time. Single-nucleus RNA sequencing (snRNA-seq) enables analysis of gene expression changes within specific cell-types, offering insights into the molecular mechanisms underlying aging. However, most brain aging snRNA-seq datasets use age-matched controls from studies focused on pathology and sample cortical regions. Therefore, there is a need to investigate non-pathological aging within brain regions vulnerable to age-related diseases. We report a snRNA-seq study of 6 young (20-30 years) and 7 aged (60-85 years) individuals encompassing four different brain regions: the entorhinal cortex, middle temporal gyrus, subventricular zone, and putamen. We captured over 150,000 nuclei representing 10 broad cell-types. Region- and cell-type-specific differential expression analyses identified over 8000 age-associated genes. Notably, within a given cell-type, most of these associations were region-specific. Functional enrichment analyses of gene sets for each cell-type-region subgroup reflected multiple hallmarks of aging, including: proteostasis, interactions with cytokines, vesicular trafficking, metabolism, inflammation, metal ion homeostasis, and cellular senescence. Overall, our findings suggest that unique cell-types exhibit distinct transcriptional aging profiles both at the cell-type level and across different brain regions.