Most research says that all brain activity stops as soon as a person is dead, but a new study reveals that some genes come to life soon after.
A team from the University of Illinois Chicago (UIC) found that these “zombie genes” were specific to a single type of cell — inflammatory cells called glial cells, which grow and sprout long arm-like appendages for several hours after death.
The researchers analyzed gene expression in fresh brain tissue collected during routine brain surgery to simulate the post-mortem interval and death, and found gene expression in some cells increased after a person dies.
Although seeing genes come alive after death may seem strange, experts say it is not a complete surprise because these cells are tasked with cleaning up things after a brain injury, like oxygen deprivation or a stroke.
“Most studies assume that everything in the brain stops when the heart stops beating, but this is not so, Our findings will be needed to interpret research on human brain tissues. We just haven’t quantified these changes until now. ” said Dr. Jeffrey Loeb, professor and head of neurology and rehabilitation at the UIC College of Medicine, who authored the study.
The study analyzed new brain tissue collected during a standard brain surgery for a person with a neurological disorder.
The team found that about 80% of the genes analyzed remained relatively stable for 24 hours – their expression did not change much.
The set of genes that were discovered were those that provide basic cellular functions and are commonly used in research studies to demonstrate tissue quality – also known as “housekeeping” genes.
Another set, known to be present in neurons, showed intricately involved in human brain activity such as memory, thinking and seizure activity, and rapidly deteriorated in the hours following death.
These genes are important for researchers studying disorders such as schizophrenia and Alzheimer’s disease, Loeb said.
A third set of genes – “zombie genes” – became active at the same time that neuronal genes were being turned back. The pattern of changes after death reached its peak in about 12 hours.
The results do not mean that we should get rid of human tissue research programs. Rather, they just mean that researchers need to take into account these genetic and cellular changes, and reduce the postmortem as much as possible to reduce the size of these changes.
“The good news from the results is that we now know which genes and cell types are stable, which degrade and increase over time so that the results of postmortem brain studies can be better understood,” said Loeb.
A previous study in 2016 found similar results in animals, which showed that more than 1,000 genes are activated after death, some of which only mill 24 hours after the event.
Researchers at the University of Washington turned to two laboratory animal models, mice and zebra fish, to look for signs of genetic activity.
By analyzing messenger RNA from mice and dead zebra fish, the team found evidence of activity in 1063 genes.
In a series of two studies published online in biorxiv in 2016, it was reported that the majority of genes start working half an hour after the animals die, but some appeared to intensify after 24 or even 48 hours.
For both animals, more than half of the active genes encoding proteins, while the other genes were regulatory genes – which show that significant energy is still used to keep the system orderly.