We tested for joint associations between fetal brain eQTL and GWAS signals using summary-statistics-based Mendelian randomization (SMR) [44]. We tested all eGenes/eTranscripts with eQTLs detected at FDR < 0.05, using linkage disequilibrium information from the samples used for our eQTL analysis. GWAS minor allele frequencies were obtained from the 1000 Genomes Project (European populations). SMR P values were Bonferroni corrected for the number of eGenes/eTranscripts tested. The HEIDI test was used to screen out joint associations that are likely to be driven by linkage using a nominal P value threshold of 0.05.
