Because autolysis sets in immediately after death and may adversely affect the quality of RNA from postmortem tissues, well-planned measures were taken to reduce the postmortem interval (PMI) for GTEx biospecimens. PMI is defined as the interval between the time of death or the cessation of blood flow and the time that the tissue is placed in preservative. The average RIN value was 8.6 for tissues with a PMI less than 4 hours, and 6.7 for tissues with a PMI between 4 and 8 hours, while tissues with a PMI of >8 hours resulted in average RIN values below 6 (Fig. 6). An hourly correlation between PMI and RIN is presented in Supplementary Text S2. Based on these findings, the GTEx project made an effort to collect all tissues from each GTEx case within 8 hours from time of death or cessation of blood flow to maximize the number of tissues that will present with RIN values ≥6.
