For PAU in EUR, we performed TWAS using S-PrediXcan to integrate transcriptomic data from GTEx79. With prior knowledge that PAU is a brain-related disorder (evidenced by significant enrichment of gene expression in several brain tissues), 13 brain tissues were analyzed. The transcriptome prediction model database and the covariance matrices of the SNPs within each gene model were downloaded from the PredictDB repository (http://predictdb.org/). Significance of the gene–tissue association was determined following Bonferroni correction for the total number of gene–tissue pairs (P < 0.05/166,064 = 3.01 × 10−7). We also used S-MultiXcan to integrate evidence across the 13 brain tissues using multivariate regression to improve association detection. In total, 18,383 genes were tested in S-MultiXcan, leading to a significance P value threshold of 2.72 × 10−6.
