A few hundred genes appear to actually increase in expression after death, New Scientist reports.
Researchers led by the University of Washington's Peter Anthony Noble report in a preprint available at bioRxiv that the transcriptional abundance of some 500 genes was significantly changed after death in healthy zebrafish and in healthy mice. While gene expression overall declined after death, the expression of some genes increased shortly after death and others increased 24 hours or 48 hours later. These genes, the researchers note, were commonly involved in stress, immunity, inflammation, apoptosis, and cancer.
Noble and his colleagues say that this post-mortem gene expression is likely due to residual energy in some cells and the decay of genes that would normally suppress other genes.
New Scientist adds that there are inklings that such a process may also occur in humans and could have implications for organ transplant recipients. People who receive liver donations, for instance, are at increased risk for developing cancer and Noble tells New Scientist that it's worth looking at whether these postmortem-activated genes have a role.
In addition, in a related paper, Noble and two colleagues suggest that this ebb and flow in gene activity after death can help predict time of death, a possible boon to forensic scientists.
The findings also have implications for our current definition of death, New Scientist says, asking "If genes can be active up to 48 hours after death, is the person technically still alive at that point?"