Infographic: Gene Activity in the Cellular Afterlife

After an organism dies, most of its cells begin to extinguish activity and die shortly afterward. However, other cells exhibit a curious behavior. Instead of winding down their operations, certain gene activities resurrect.¹

	Low Oxygen Beginnings During the earliest stages of embryonic development, stem cells proliferate in a low oxygen environment. The genes that drive this stage are active for a short period of time. After the blastocyst implants into the uterus, eventually, oxygen levels increase and gene activity that was previously maintained by low oxygen levels silences.2,3
Survival Instinct Cellular life after death may seem paradoxical, but sudden changes in oxygen levels trigger protective responses in cells. Genes that are transcribed during the low oxygen phase of embryonic development are reactivated when oxygen levels plumet after organismal death. Many emergency-mode genes also activate to support cell survival, including those involved in inflammation, immunity, stress responses, and cancer. Scientists studied this in zebrafish and mice, as well as human blood, prostate, liver, and brain tissue samples.1,4,5,6,7
	Real-world Zombie Genes There are practical applications for understanding why and how genes are activated after death. For example, forensic scientists apply insights from postmortem gene transcription to estimate the time of death in criminal cases. Scientists also use information about cancer gene reactivation to improve organ transplant outcomes. Performing transplant surgery before these genes become active may help reduce the high incidence of cancer in organ transplant recipients.8

References

1. Pozhitkov AE, et al. Tracing the dynamics of gene transcripts after organismal death. Open Biol. 2017;7(1):160267.
2. Michiels C. Physiological and pathological responses to hypoxia. Am J Pathol. 2004;164(6):1875-1882.
3. Podkalicka P, et al. Hypoxia as a driving force of pluripotent stem cell reprogramming and differentiation to endothelial cells. Biomolecules. 2020;10(12):1614.
4. Antiga LG, et al. Cell survival and DNA damage repair are promoted in the human blood thanatotranscriptome shortly after death. Sci Rep. 2021;11(1):16585.
5. Dachet F, et al. Selective time-dependent changes in activity and cell-specific gene expression in human postmortem brain. Sci Rep. 2021;11(1):6078.
6. Javan GT, et al. The apoptotic thanatotranscriptome associated with the liver of cadavers. Forensic Sci Med Pathol. 2015;11(4):509-516.
7. Tolbert M, et al. The thanatotranscriptome: Gene expression of male reproductive organs after death. Gene. 2018;675:191-196.
8. Pozhitkov AE, Noble PA. Gene expression in the twilight of death: The increase of thousands of transcripts has implications to transplantation, cancer, and forensic research. Bioessays. 2017;39(9):10.1002/bies.201700066.

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