Despite high average levels of sharing of eQTLs among tissues, mash identified some eQTLs that are relatively “tissue-specific”. Indeed, the distribution of the number of tissues in which an eQTL is shared by magnitude has a mode at 1 (Fig. 5), representing a subset of eQTLs that have a much stronger effect in one tissue than in any other (henceforth, “tissue-specific” for brevity). Breaking down this group by tissue identified testis as the tissue with the most tissue-specific effects (Supplementary Fig. 7). Testis and whole blood stand out as having lower pairwise sharing of eQTLs with other tissues (Fig. 6). Other tissues showing larger than average tissue specificity (Fig. 5, Supplementary Fig. 7) include skeletal muscle, thyroid and transformed cell lines (fibroblasts and LCLs).
