Death isn’t the end of the road for our brains, as new research reveals that certain genes become activated as soon as we check out of our mortal husk, causing some of our brain cells to increase their rate of growth. According to the study authors, this previously unseen flurry of post-mortem activity could have major implications for all future research into neurological disorders.
Researchers at the University of Illinois NeuroRepository analyzed the pattern of gene expression in brain tissue that had been removed from patients undergoing surgery for certain neurological conditions such as epilepsy. Straight away, they noticed that the transcriptomes of these fresh samples did not match those of any published post-mortem samples of human brain tissue.
This led them to believe that certain changes must occur in the brain in the hours after death, thereby generating discrepancies between fresh and post-mortem samples.
To investigate, the researchers ran a “simulated death experiment,” whereby recently extracted brain tissue samples were stored at room temperature for 24 hours, with genetic analyses conducted at numerous time points in order to observe how gene expression changes during the post-mortem period.
Writing in the journal Scientific Reports, the authors reveal that while about 80 percent of genes did not change their expression, those that are directly related to brain activity such as thinking and memory became significantly reduced within just a few hours. This is pretty unsurprising, given that death brings an end to these cognitive processes.
Strangely, however, a number of what the researchers call “zombie genes” actually became activated during the 24 hours after the brain tissue had been extracted. These genes were all related to inflammatory glial cells, which normally spring into action following a brain injury or stroke. As a consequence, glial cells within these samples were found to grow for many hours, even developing extra arm-like appendages.
"Most studies assume that everything in the brain stops when the heart stops beating, but this is not so," explained study author Jeffrey Loeb in a statement. This is important as most research into neurological disorders like dementia is performed on post-mortem human brain tissues, extracted from patients several hours or days after death.
Yet the results of this study suggest that such tissues are likely to have undergone significant changes in the intervening period, and may therefore differ greatly from the brain tissue of living patients.
Crucially, the authors noted that such changes occurred in the extracted brain tissues of healthy individuals, as well as those suffering from a range of disorders such as epilepsy, autism, schizophrenia, Parkinson’s and Huntington’s diseases.
Summing up the significance of this revelation, Loeb explained that "the good news from our findings is that we now know which genes and cell types are stable, which degrade, and which increase over time so that results from postmortem brain studies can be better understood."