crime scene forensic genetics

via Brandon Anderson

Cells continue to function even after an individual dies. That’s the latest discovery made by an international team of scientists who through analysing post-mortem samples found that some genes become more active after death. 

The results, published in Nature Communications have provided an important dataset for other scientists. The scientists are even hoping that this can be developed into a forensic tool. 

However, obtaining samples for the study wasn’t an easy process. Whilst studies of post-mortem samples can provide important insights into the body’s inner workings, it isn’t clear if these samples truly represent what goes on during life. Making matters more difficult, samples are rarely taken immediately after death, and instead, a body is stored until post-mortem examination and sampling can take place and its impact is unclear. 

As a result, scientists had to rely on a relatively abundant source of samples including tissues and organs, that was removed after death. These concerns were troubling Proffessor Roderic Guigo, a computational biologist based at the Barcelona Institute for Science and Technology. 

“You would expect that with the death of the individual, there would be a decay in the activity of the genes,” he said. This decay may well affect the proper interpretation of transcriptomics data. 

To see if this would be the case, the team used next-generation mRNA sequencing on post-mortem specimens collected within 24 hours of death, as well as on a subset of blood samples collected from some of the patients before death. 

Professor Guigo was left surprised, “There is a reaction by the cells to the death of the individual. We some pathways, come genes, that are activated and this means that sometime after death there is still some activity at the level of the transcription,” he explained. 

The reason why the genes remained active was unclear, but he suggested, “I would guess that one of the major changes is due to the cessation of flow of blood, therefore I would say probably the main environmental change is hypoxia, the lack of oxygen, but I don’t have the proof for this.”

Despite this, the study did provide a set of predictions of post-death RNA level changes for a variety of commonly studied tissues against which future transcriptomic analyses could be calibrated, something never done before. 

“We conclude 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 don’t pretend we have now a method that can be used in the field,” he added.

Extra work would, of course, be needed before its application in forensics could become a reality. He noted, “It requires further investigation, longer post-mortem intervals, not only 24 hours, the age of the individual, the cause of death – all of these will need to be taken into account if we are to convert this into a useful tool.”

 

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