Abstract
RNA analysis of post-mortem tissues, or thanatotranscriptomics, has become a topic of interest in forensic science due to the essential information it can provide in forensic investigations. Several studies have previously investigated the effect of death on gene transcription, but it has never been conducted with samples of the same individual. For the first time, a longitudinal mRNA expression analysis study was performed with post-mortem human blood samples from individuals with a known time of death. The results reveal that, after death, two clearly differentiated groups of up- and down-regulated genes can be detected. Pathway analysis suggests active processes that promote cell survival and DNA damage repair, rather than passive degradation, are the source of early post-mortem changes of gene expression in blood. In addition, a generalized linear model with an elastic net restriction predicted post-mortem interval with a root mean square error of 4.75 h. In conclusion, we demonstrate that post-mortem gene expression data can be used as biomarkers to estimate the post-mortem interval though further validation using independent sample sets is required before use in forensic casework.
Highlights
RNA analysis of post-mortem tissues, or thanatotranscriptomics, has become a topic of interest in forensic science due to the essential information it can provide in forensic investigations
Zebrafish and human tissue samples from Genotype-Tissue Expression (GTEx) database suggest that some biological processes (BP) are still active up to 48 h after the death of an individual[12,13,14], either because of the activation of regulatory genes that allow the transcription of genes that were not active before[13] or because of gene regulation through induced changes in chromatin s tructure[12]
A total of 54 samples were collected from 7 individuals, 5 men and 2 women with ages ranging from 56 to 89 years old and post-mortem interval (PMI) ranging from 2 h 21 min to 37 h 50 min (Fig. 2)
Summary
RNA analysis of post-mortem tissues, or thanatotranscriptomics, has become a topic of interest in forensic science due to the essential information it can provide in forensic investigations. A longitudinal mRNA expression analysis study was performed with post-mortem human blood samples from individuals with a known time of death. Other studies involving human tissue samples have demonstrated a bi-modal wave in PM prostate tissues initiated by over-expressed anti-apoptotic genes followed by apoptosis inducing genes[15] or the simultaneous up-regulation of pro-apoptotic and down-regulation of anti-apoptotic genes in PM liver tissues[16]. Such studies have provided insight into PM gene regulation and have demonstrated the potential of the analysis of PM gene expression in forensic cases. On the other hand, showed that transcript expression of GUSB, COL1A1 and COLIII in the human heart was independent from PMI while NOS3 gene expression was found to be down-regulated with longer PMI (> 24 h)[25]
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