We note that the availability of many other tissue types besides liver in GTEx offers the opportunity to assess for eQTLs in loci of interest. Even if the power of the GTEx liver cohort is limited, other GTEx tissue cohorts might reveal eQTLs of relevance in hepatocytes. This strategy would be more informative for eQTLs that are shared widely among tissues than for eQTLs that are specific to hepatocytes. Even so, non-liver-tissue eQTL findings should be interpreted with caution. For example, whereas there is a strong eQTL for VKORC1 in the GTEx liver cohort, there is also a strong eQTL for VKORC1 in the GTEx adrenal gland cohort—but with the opposite directionality (as assessed at the GTEx portal at the time of this writing, http://www.gtexportal.org/), suggesting different regulatory mechanisms in the two tissue types.
