We usually think about death as the end of life. As me, you would probably expect that after death the activity inside the cell stops… maybe not suddenly but at least it should slowly decrease.

This assumption might be quite wrong: recent evidence from the group of Peter Noble and Alex Pozhitkov at the University of Washington (Seattle) suggests that in two species (mice and the zebrafish) certain areas of DNA are still active post mortem or, even more, some genes become active specifically after death [1]. How did they prove that? They look for genes-activity after death, measuring the amount of mRNA – the intermediate stage between DNA and proteins, the functional products of genes. To their surprise, they found a rise in the quantities of mRNA for specific genes (548 in zebrafish and 515 in mouse ), not only minutes after death but even after a couple of days.
postmortem_genes_eng

While thus result doesn’t prove the existence of zombies, it still has important applications, for example in the field of organ transplantations. Some unexpected genes that were activated after death are related to cancer, which might explain the high propensity for transplanted organs to develop it. Other unexpected genes that turn on after death are involved in fetal development, suggesting certain similarities between the pre and post- life stages.

Noble and colleagues called this ensemble of genes thanato- transcriptome, from the Greek word Thanatos- (death) and transcriptome, the set of DNA->mRNA transformations, which is what it was actually analyzed.

While the thanato-transcriptome has been seen so far in mice and zebrafish, there are hints that it can extend to humans. Previous studies have shown that various genes, including those involved in contracting heart muscle and wound healing, were active more than 12 hours after death in humans [2].

Bibliography:

[1] Thanatotranscriptome: genes actively expressed after organismal death. Alexander E Pozhitkov, Rafik Neme, Tomislav DomazetLoso, Brian Leroux, Shivani Soni,Diethard Tautz, Peter Anthony Noble – bioRxiv 058305; doi: http://dx.doi.org/10.1101/058305

[2] Studies on RNA integrity and gene expression in human myocardial tissue, pericardial fluid and blood, and its postmortem stability. Lucas González-Herreraa, Aurora Valenzuelaa, Juan A. Marchalb, José A. Lorentea, Enrique Villanuevaa. Forensic Science International, doi.org/bj63