When a person dies, many of their genes vary in expression, as well as in a different way for each tissue.
An international team of scientists led by Roderic Guigó of the Center for Genomic Regulation of Barcelona (Spain) has revealed that changes in gene expression in different tissues triggered by death can be used to predict the exact moment of death of an individual.
In the study published in Nature Communications, the researchers suggest that when analyzing certain readily available tissues (for example, adipose or skin tissue), the post mortem interval (time elapsed since death) can be determined with considerable precision, which could have implications for forensic analysis to find out the exact moment of an individual's death.
It all started with the GTEx project, which aims to create a reference database and a tissue bank for scientists to study how genomic variants affect gene activity and susceptibility to disease.
GTEx was designed to apply sampling techniques to as many tissues as possible of a large number of individuals in order to understand the causal effects of genes and variants, and which tissues contribute to predisposition to disease.
"The GTEx data allow us to ask questions about genetic variation and its effects on gene expression in a tissue and in many tissues, since the samples we use come from deceased donors, we must find out if there were changes in gene expression related to death or the moment of death, so we could better model our predictions about tissue variation and disease, "explains Roderic Guigó, leader of the work.
To understand tissue-specific changes in gene expression after a person's death, Guigó and his colleagues studied RNA sequencing data from more than 7,000 samples from 36 different tissues obtained from 540 donors within the GTEx project.
Their results show that the time since death has an effect on gene expression and that this effect varies from one tissue to another. The authors developed models for post-mortem interval prediction based on these changes in tissue-specific gene expression using high-throughput sequencing of the cell.
"We found that many genes change their expression at relatively short post-mortem intervals, largely tissue-specific." This information helps us better understand the variation and also allows us to identify the transcription events that are triggered by death in a organism, "adds Pedro G. Ferreira, co-author of the study.
"We showed that RNA sequencing in some key tissues could become a powerful tool to help in forensic pathology," the researchers wrote.