Abstract A091: Decoding the Etiology of Embolic Ischemic Stroke through Integrated Genomic, Proteomic and Single-cell Transcriptomic Analyses

Background: Understanding the molecular differences between embolic strokes caused by cardioembolism versus atheroembolism is key for identifying therapeutic targets and advancing precision medicine. We applied multiomics and integrative analyses to identify circulating proteins distinguishing atrial fibrillation (AF) from carotid atherosclerosis (CA) in large vessel occlusion strokes. Methods: We first analyzed the plasma proteome of UK Biobank ischemic stroke patients with AF (n=539) versus CA (n=127), comparing levels of 2,923 proteins (Olink platform; FDR<0.05). Second, in a Yale cohort, we examined differential expression of corresponding genes in thrombi from AF (n=7) and CA (n=7) patients, including cell-type–specific patterns. Third, we performed two-sample Mendelian Randomization (MR) using pQTLs to test causal links between proteins and stroke subtypes. Finally, pathway enrichment analyses identified biological processes associated with the proteins of interest. Results: Twelve proteins differed significantly between etiologies. AF was associated with higher NTproBNP, NPPB, and ACP5, and lower APCS, ANGPT2, PAMR1, PRCP, PROS1, LARP1, F7, F10, and LEO1 (all FDR<0.01, Figure 2). Single-cell analyses of embolic clots confirmed differential expression of ACP5, PRCP, LARP1, ANGPT2, and LEO1 (FDR<0.01) across multiple immune cell types (Figure 3). Pathway enrichment implicated coagulation and γ-carboxylation pathways in CA strokes, and natriuretic peptide signaling and riboflavin metabolism in AF strokes. MR supported causal roles for NTproBNP (OR 1.26, 95%CI 1.11–1.41), ANGPT2 (OR 1.17, 1.01–1.34), ACP5 (OR 1.06, 1.01–1.15), APCS (OR 1.14, 1.01–1.15), and PAMR1 (OR 1.11, 1.01–1.20), with no evidence of pleiotropy or reverse causation. Conclusion: This multimodal analysis reveals distinct proteomic signatures for AF- versus CA-related embolic strokes. Findings support established markers (NT-proBNP, F7) and highlight novel candidates with mechanistic plausibility. ACP5, a macrophage-derived enzyme linked to fibrosis, suggests a pathway for atrial cardiomyopathy in AF. The CA signature emphasizes local atherothrombosis, plaque inflammation (ANGPT2), and vascular dysregulation (PRCP). These proteins may improve etiologic classification and inform therapeutic development in ischemic stroke.