Several recent studies have been published that examine the extent of genetic control in blood [20–22], brain [23], and adipose [21] gene expression via genetic association testing. In one of these studies [21], we performed the study on human blood and adipose tissues profiled on the same expression platform as the HLC, providing a straightforward way to compare the extent of cis eQTL overlap between blood, adipose, and liver tissues. In our characterization of blood and adipose tissue eQTL, there were 2,573 and 2,789 expression traits, respectively, represented on the microarray used to profile the HLC samples and that gave rise to cis eQTL. Of these, 752 blood and 881 adipose cis eQTL overlapped the set of 3,210 cis eQTL detected in the HLC. Therefore, in both adipose and blood, roughly 30% of the cis eQTL detected in these tissues were also detected in the HLC, confirming that there is significant, common genetic control between tissues. However, these overlaps also highlight that a majority of cis eQTL detected in one tissue may be specific to that tissue, potentially reflecting the genetic control of tissue-specific biological functions.
