GTEx, CAGE, and eQTLGen were from previous analyses of standardized gene expression levels with mean 0 and variance 1, whereas expression levels in the other data sets (i.e., CMC, ROSMAP, and Braineac) were not standardized. To harmonize the units across data sets, we re-scaled the effect size and standard error (SE) of each eQTL in the CMC, ROSMAP, and Braineac based on the z-statistic, allele frequency and sample size using the method described in Zhu et al.21 so that the eQTL effects in all data sets can be interpreted in standard deviation (SD) units.
