The genes remain activated days after the animals die, suggests microbiologist Peter Noble and colleagues at the University of Washington, Seattle.
The scientists wanted to test a new method they had developed to calibrate measurements of genetic activity.
Although scientists who analyzed blood and liver tissue from human corpses had previously noted the post-mortem activity of some genes, Noble and his colleagues systematically evaluated more than 1,000. The team measured which of these genes were functioning in tissues of mice and zebrafish recently deceased, tracking changes for 4 days in fish and 2 days in rodents.
That is, although most of these genes increased their activity in the first 24 hours after the animals expired and then decreased, in the fish some genes remained active 4 days after death. Many of these post mortem genes are beneficial in emergency situations; They perform tasks such as stimulating inflammation, activating the immune system and counteracting stress.
Other genes were more surprising. These genes normally help to sculpt the embryo, but they are not necessary after birth. One possible explanation for their post-mortem awakening, researchers say, is that the cellular conditions in newly dead bodies resemble those of embryos.
The team also discovered that several genes that promote cancer have become more active. That result could explain why people who receive transplants from the newly deceased have a higher risk of cancer.