The selection of endogenous genes in human postmortem tissues

Precisely determining the postmortem interval (PMI), which is crucial to criminal and forensic cases, is a research in which quantitative RT-PCR (also known as qRT-PCR or real-time RT-PCR) has been used to analyse gene expression levels and data normalisation should be required to eliminate the differences among the samples. Therefore, it is quite necessary to find stable molecular biological markers in PMI determination research. In this study, we compared nine commonly used endogenous markers (containing ACTB, GAPDH, B2M, U6, 18S rRNA, hsa-mir-1, hsa-mir-9, hsa-mir-194-1 and hsa-mir-203) in the 109 human tissue samples obtained from autopsy at the aim of finding stable markers in human tissues with consideration of the impact of parameters (PMI and cause of death). After RNA was extracted from four tissues (heart, brain, kidney, skin), the Ct values of nine endogenous markers were obtained by qRT-PCR and assessed by geNorm software. The results showed that U6, GAPDH and 18S rRNA were the suitable markers in our set of samples in various corpse conditions, that B2M and ACTB were reliable internal controls in heart tissue only, and that microRNAs had such high M values that they should not be chosen for endogenous control genes.