Zombie Genes: New Evidence Points to Genetic Life After Death

Image credit: “Internal anatomy of a fish (cutaway diagram)” by Alberto Rava is in the public domain. “A section of DNA” by Michael Ströck is licensed under CC Attribution-ShareAlike 3.0. Images modified by Malika Kumar.

What does it mean to die? The exact nature and definition of death has been a mysterious and often hotly debated topic since the times of the earliest human cultures. In a new study from the University of Washington in Seattle, a group of scientists has shown that the lives of our genes may far outlast our own lives [1].

After an animal dies, many of its cells can remain alive for many hours, or in some cases even days, calling into question what kind of processes continue to occur in these cells [2]. Alexander Pozhitkov and colleagues set out to determine whether an animal’s genes were turned off abruptly after death, or whether they slowly faded like a flashlight running out of battery. Pozhitkov’s team examined most of the genome to examine which genes were turned on and off in zebrafish and in the brains and livers of mice for up to 4 days after their death. What they found was surprising - the team discovered that expression of a large group of the genes they looked at was actually elevated even 48 hours after death.

Some of these upregulated groups of genes appeared to indicate cells “gasping” for life after the organism had died around them. These groups included genes involved in processes such as the cell’s stress response, cell death, and the cell’s response to oxygen deprivation. However, other groups of upregulated genes were more unexpected. These groups included genes involved in development of embryos and genes associated with cancer.

Pozhitkov and his colleagues stressed that rather than being part of a larger survival strategy for cells, the upregulation of many of these genes that occurred after the death of mice and zebrafish may simply be a product of the cell no longer having the ability to control its cellular processes. Regardless, the findings will potentially shed light on the processes by which a cell controls its genes, and may have profound implications for our ability to better understand health issues associated with organs transplanted from a recently deceased person into a living patient. Additionally, the finding that certain genes are turned on and off at different times after death may help forensic scientists more accurately determine when a victim died.

In short, be on the lookout: Pozhitkov’s findings may soon be coming to a TV near you on Grey’s Anatomy or CSI.
 

- Jeff Maloy (@JeffreyMaloy)
Staff Writer, Signal to Noise Magazine
PhD Candidate, Microbiology

 

References:
[1] Pozhitkov A.E., Neme R., Domazet-Loso T., Leroux B.G., Soni S., Tautz D., Noble P.A. Thanatotranscriptome: genes actively expressed after organismal death. Preprint in BioRxiv. (2016). DOI: 10.1126/science.aaf5802

[2] Singh M., Ma X., Amoah E., Kannan G. In vitro culture of fibroblast-like cells from postmortem skin of Katahdin sheep stored at 4 °C for different time intervals. In Vitro Cell Dev Biol Anim. (2011). DOI: 10.1007/s11626-011-9395-