Integration of Single-cell RNA Sequencing and Mendelian Randomization Analysis for Identifying Potential Immune Therapeutic Targets in Amyotrophic Lateral Sclerosis.

Adaptive immune responses play a critical role in the pathogenesis of amyotrophic lateral sclerosis (ALS). In this study, we investigated the functional mechanisms of T cell subtypes and assessed the causal links between CD4+ cytotoxic T cell-related genes and ALS risk. Single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) from patients with ALS and healthy controls (HC) was used to identify differentially expressed genes (DEGs) in CD4+ cytotoxic T cells. Comprehensive analyses of CD4+ cytotoxic T cells, including pseudotemporal trajectory, intercellular communication, and metabolic pathway analysis, were performed. Mendelian randomization (MR) analysis evaluated the causal effects of DEGs on ALS risk, with validation using independent genome-wide association study (GWAS) data. Expression patterns of the causal genes were further verified using scRNA-seq, bulk-seq, and clinical samples. CD4+ cytotoxic T cells were significantly expanded in patients with ALS. The upregulated genes S100A6, SERPINB6, SMAD7, and TPST2 were positively correlated with ALS susceptibility, whereas DIP2A showed a protective association. S100A6, SERPINB6, SMAD7, TPST2, and DIP2A were identified as causal genes and potential therapeutic targets in ALS, implicating CD4+ cytotoxic T cells in the disease mechanisms. Further studies targeting these genes and neuroinflammatory pathways are warranted.