Integrative analysis of single-cell multi-omics reveals heterogeneity in piriform cortex principal neurons and their selective vulnerability in Alzheimer's disease.

BACKGROUND: The piriform cortex (PIR) is a key region of the olfactory system and is increasingly implicated in Alzheimer's disease (AD). However, the cellular heterogeneity of principal neurons (PN) in this region and their selective vulnerability in AD remain poorly understood. METHODS: Here, we integrated single-cell multi-omics datasets to systematically characterize PIR PN heterogeneity. We identified four transcriptionally and epigenetically distinct PN subtypes with different spatial distributions across the anterior and posterior PIR. RESULTS: In AD mouse models, the abundance of the Reln-positive superficial-layer (Reln+ SL) subtype was spatially associated with amyloid-β pathology, and its reduced proportion was confirmed by multiplex immunofluorescence. Cross-region comparison revealed that Reln+ SL neurons shared a Gpc5-high/Sort1-low molecular signature with vulnerable layer II excitatory neurons in the entorhinal cortex (EC). In human AD, this vulnerability-associated signature showed progressive enrichment in EC layer II neurons across Braak stages I-III. Furthermore, A Sort1-containing co-expression module captured regional differences between lateral and medial EC layer II populations and was enriched for proteostasis-related pathways. CONCLUSIONS: These findings reveal shared molecular features associated with selective vulnerability across PIR and EC layer II neurons and identify a proteostasis-related program linked to regional differences in neuronal vulnerability during AD. KEY POINTS: Single-cell multi-omics reveals molecular heterogeneity among piriform cortex principal neurons. Reln+ superficial-layer neurons show selective vulnerability in AD. Cross-region comparison identifies a shared Gpc5-high/Sort1-low signature in vulnerable layer II neurons of EC and PIR.