An international team of scientists has shown that some genes become more active after death

    Abdulaziz Sobh

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    That's according to a scientific study published in Nature Communications.
    By analyzing post-mortem samples, an international team of scientists showed that some genes became more active after death.
    In addition to providing an important data set for other scientists, they also hope that this can become a forensic tool.
    Within the cells of our bodies, life develops under the powerful influence of our genes; its outputs controlled by a range of internal and external triggers.
    Understanding the activity of genes provides a perfect idea of what a cell, tissue or organ is doing in health and disease.
    The genes are enclosed in the DNA present in our cells and when they are turned on, a revealing molecule called RNA transcription is produced.
    Part of the RNA directly controls the processes that take place in the cell, but most of the RNA becomes the blueprint for proteins.
    They are the RNA transcripts that scientists often measure when they want to know what's happening in our cells, and we call this transcriptomic analysis.
    Inner workings
    But getting samples for the study is not easy.
    Blood is relatively easy to obtain, but cutting an arm or inserting a needle into the heart or liver of a living person is not a trivial task.
    Then, scientists rely on a relatively abundant source of samples: tissues and organs extracted after death.
    While studies of post-mortem samples can provide important information about the internal functioning of the body, it is not clear if these samples really represent what happens during life.
    The other confounding factor is that samples are rarely taken immediately after death, but a body is stored until a post-mortem examination is performed and a sample can be taken and its impact is not clear.
    And it is this confidence in the stored post-mortem samples that worries Prof. Roderic Guigó, a computational biologist based at the Institute of Science and Technology of Barcelona and his team.
    "One would expect that with the death of the individual, there would be a decrease in the activity of the genes," he explained.
    And this decrease could affect the correct interpretation of the transcriptomic data.
    The agony of death
    To see if this was the case, the team used next-generation mRNA sequencing in post-mortem samples collected within 24 hours of death and in a subset of blood samples collected from some of the patients before death and, as explained by Professor Guigó, discovered was surprising:
    "There is a reaction of the cells to the death of the individual, we see some pathways, some genes, that are activated and this means that at some point after death there is still some activity at the level of transcription," he said.
    Although the exact reason why the genes remained active was not clear, Professor Guigó has a possible explanation: "I guess one of the main changes is due to the cessation of blood flow, therefore, I would say probably the main change environmental is hypoxia, lack of oxygen, but I do not have proof for this. "
    What the study did provide was a set of predictions of changes in the level of RNA after death for a variety of commonly studied tissues against which future transcriptomic analyzes could be calibrated.
    And understanding changes in RNA levels that occur after death could also be critical in future criminal investigations.
    "We conclude that there is a signature or a fingerprint in the pattern of gene expression after death that could eventually be used in forensic science, but we do not pretend that we now have a method that can be used in the field," said Professor Guigó.
    Although the data were consistent across different cadavers, and precise predictions of time since death could be estimated from RNA levels, Professor Guigó explained that additional work would be necessary before its application in forensic medicine became reality:
    "It requires more research, longer postmortem intervals, not just 24 hours, the age of the individual, the cause of death, all this must be taken into account if we want to turn this into a useful tool."

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