The aim of the Genotype-Tissue Expression (GTEx) Project of the U.S. National Institutes of Health (NIH) Common Fund (https://commonfund.nih.gov/GTEx) is to determine how genetic variation affects normal gene expression in human tissues, and ultimately to assess how this relationship correlates with the development of disease. To achieve this goal, the project planned to collect multiple different human tissues from each of hundreds of donors, isolate nucleic acids from the tissues and perform genotyping, gene expression profiling, whole genome sequencing, and RNA sequencing, and analyze the data to identify expression quantitative trait loci (eQTL).1–3 The scientific goals of the project required that the donors and their biospecimens present with no evidence of disease (henceforth termed “normal tissues” or “normal biospecimens”).
