Hundreds of genes become active after death and can stay active for up to four days, according to a study.
The findings were posted on the pre-print server BioRxiv, which is not peer reviewed. If confirmed, this information could be useful in preserving organs for donation or in forensic investigations.
Researchers examined the expression of more than 1000 genes in the bodies of recently deceased mice and zebrafish, and found that 1063 genes became active within two days after death. Most genes became active after 30 minutes, but some didn't become active until 24 or even 48 hours after death.
Scientists have previously noted the post-mortem activity of a few genes, but this is the first evaluation of post-mortem gene expression on this scale, according to Science. Most of the genes activated were ones involved in counteracting stress to benefit the body in an emergency, but the function of some of the other genes was more surprising.
'What's jaw-dropping is that developmental genes are turned on after death,' lead researcher Dr Peter Noble of the University of Washington in Seattle told Science. Developmental genes are normally only active during embryonic development. One possible explanation for this is that the post-mortem cellular conditions resemble those of embryos, according to Science. Another possibility is tightly packed DNA loosens after death and frees genes that were previously suppressed.
The study also found that some cancer-promoting genes became active after death, and it was suggested that similar genes could become active in humans, according to GenomeWeb. This may explain why patients who receive donated organs from the recently deceased are at higher risk of developing cancer.
However, the results have been questioned by Professor Yoav Gilad of the department of human genetics at the University of Chicago, Illinois. In a discussion on BioRxiv, he suggests that there may be a different interpretation of the results and that the suggestion that gene activity ramps up after a couple of days may be incorrect.
In a related paper that was also posted to BioRxiv, Dr Noble and his team also stated that their gene-activity measurements could be used to estimate the time of death with greater accuracy.