Development of combined data sets. (A) PCA plots of 4,767 expression dataset. (B) PCA plots of multi-tissue expression dataset. These plots show the gene expression profiles of the samples plotted on the first two principal components. Each point represents a sample, and samples from the same data set have the same color. If there are batch effects, the samples from the same data set (the same color) will cluster together. If there are no batch effects, the colors should be mixed.