CSF proteomic quantitative trait loci mapping reveals genetic insights into Alzheimer’s disease
Despite the identification of numerous genetic risk variants for Alzheimer's disease (AD), mechanisms through which these variants act remain unclear. Identifying specific proteins levels affected by genetic variation can provide valuable insights into the underlying biological pathways implicated in AD. To gain more insight into effects of genetic variation on AD-related processes, we conducted a genome-wide protein pQTL study using untargeted TMT mass spectrometry in cerebrospinal fluid (CSF) of 2,215 proteins across 487 individuals. Replication was assessed in the independent EMIF-AD MBD cohort of 242 individuals. We identified 399 independent CSF pQTL signals (PBonferroni < 2.26 × 10⁻11) associated with 222 proteins, 69% of which were novel. Findings included gene-protein links such as RPS23P10/HSPA6 with CSF FCGR2A, BIN2 with CSF GALNT6, APOE with CSF HS3ST1, and the HLA-region with CSF HLA-DPB1 and PLXDC2. We replicated 230 of 270 gene-protein associations. A proteome-wide association study identified genetically predicted CSF protein levels to be associated with AD, including SIRPA, PLXDC2, and GALNT6. Many AD pQTLs in CSF were enriched in neuroimmune activation, suggesting a genetic basis for neuroimmune dysregulation in AD. This study highlights how genetic variation shapes protein expression in the central nervous system, offering mechanistic insight into AD.