Cell-specific Associations Between Ferroptosis-related Genes and the Risk of Subarachnoid Hemorrhage: A Mendelian Randomization Study Based on sc-eQTLs from 14 Immune Cell Types

Abstract Background and Objectives Subarachnoid hemorrhage (SAH) involves multiple intertwined pathological processes, among which ferroptosis and immune-inflammatory responses are vital. However, the genetic causal effects of ferroptosis-related genes on SAH risk and their immunocellular type specificity remain unclear. This study aimed to investigate the association between ferroptosis-related genes and SAH and its immunocellular type specificity. Methods This study integrated expression quantitative trait loci (eQTL) data for ferroptosis-related genes, pooled genome-wide association study data for SAH, Gene Expression Omnibus (GEO) transcriptomic data, and single-cell (sc)-eQTL data. We used Mendelian randomization(MR) analysis to identify genes associated with SAH risk and validated these findings using independent eQTL datasets and GEO differential expression analysis. The inverse-variance-weighted method was used as the primary analytical approach, and sensitivity analyses assessed robustness. Sc-eQTL data were further used to explore immune cell-type-specific associations. Results Based on the initial screening using eQTLGen, the genetically predicted expression levels of 48 ferroptosis-related genes were significantly associated with SAH risk. Among them, the elevated CFL1 gene expression was associated with reduced SAH risk. This result was consistent across genotype-tissue expression whole-blood dataset. Combined with GEO differential expression results, CFL1 was identified as a key candidate gene. Finally, sc-eQTL analysis revealed that CFL1 gene expression in CD8NC cells was significantly associated with reduced SAH risk. Conclusion CFL1 may be a key ferroptosis gene associated with SAH; its elevated expression in CD8NC cells is associated with a significantly reduced SAH risk, providing new genetic evidence for exploring potential therapeutic targets for SAH.