A detailed description of the GTEx methods (i.e., preprocessing, expression quantification, and association analysis) used is available at http://www.gtexportal.org/static/doc/analysis/Portal_Analysis_Methods_v6_08182016.pdf. Briefly, the association between genetic variant and gene expression was conducted using a linear regression analysis considering the covariates (i.e., top-3 ancestry principal components, genotyping array platform, PEER factors, and sex) applied to gene-cis-SNP pairs using Matrix eQTL30 and assuming an additive model.
