To match the significant SNPs to the genes for which they likely influence function, we conducted a series of positional and functional gene-mapping analyses. The positional mapping employed MBAT-combo19, while the functional mapping tested whether genetic variants associated with OCD were also associated with differential expression of nearby genes (within a 1-Mb window) using (1) TWAS20 using PsychENCODE data and included colocalization with COLOC27,28, and (2) SMR22 using whole-blood eQTL information and brain tissues from MetaBrain, alongside the HEIDI test, which tests for heterogeneity in GWAS signal and eQTL association. Furthermore, a PWAS was conducted. As a final step, genes within each locus were prioritized using PsyOPS26, which integrates both positional and functional information. The details of each method are described below.
