RNA – short-term gene transcripts – from the "Tumat puppy" is an isolated wolf from the Pleistocene era and its sequence analyzed in a new study by Oliver Smith of the University of Copenhagen and his colleagues, published on July 30 in an open access journal PLOS Biology . The results establish the possibility of examining a number of transcripts of RNA from ancient organisms, a probability previously considered extremely unlikely due to the short life of RNA.
DNA, which encodes "hard copy" genes, has been known to survive for thousands of years under favorable conditions. But RNA – the short-lived working copy of a gene that transcribes from DNA into the cell and forms instructions for protein production – is rapidly degraded in living tissue by a set of recycling enzymes. This instability usually continues beyond death, and researchers therefore generally suggest that the probability of finding an intact ancient RNA cellular complex – its murals – was vanishingly small. But there are a few exceptions, most notably in plants, that prompted the authors to ask if there might be ancient animal transcriptomes well preserved to be sequenced.
They isolate and analyze RNA from liver tissue at 14,300 years of age. an old canid, probably a wolf or a partially domesticated wolf, which was preserved in the Siberian permafrost until its discovery, as well as a 19th and 20th century two wolf tissue for comparison. Using a variety of transcriptomic quality control techniques and measures, the team has shown that RNA sequenced by Pleistocene-era canid is truly representative of animal RNA, with very liver-specific transcripts that match more modern samples and wolves, and dogs.  The Siberian Canid transcript is the oldest RNA sequenced to date, surpassing the next oldest transcript of at least 13,000 years. The authors note that unlike paleo-genomics, paleo-transcriptomics is unlikely to become routine because even under the best conditions, RNA is not as well conserved as DNA.
However, there are probably a large number of other naturally occurring frozen specimens for which transcriptome decryption is possible, revealing to researchers not only the genes of ancient organisms but also the flow of cellular activity encoded by the transcript. because it is generally more unstable than DNA and more susceptible to enzymatic degradation, "says Dr. Smith." However, since our recent successes in sequencing plant-derived RNA, we have speculated that a well-preserved specimen of animals frozen in permafrost can just keep enough material for consistency. To our delight, we found that not only did we find RNA from different tissues, but in some cases the signal was so strong that we could distinguish the tissues in a way that made biological sense.
"Knowing that RNA acts as a mediator between DNA and proteins, both being more stable, it may be tempting to ask," and what? " But we believe that the future of ancient RNA has great potential. For example, many of the most clinically relevant viruses around today have the RNA genomes, and the RNA stage is often decisive for understanding the intricacies and complexities of gene regulation. This can have consequences when discussing the environmental pressures and stresses that drive evolution. "
Perfectly preserved glacial wolf head found in Siberia
Oliver Smith et al., Ancient RNA from Late Pleistocene Eternal Freezing and Historical Canids Shows Tissue-Specific Survival of Transcriptomes, PLOS Biology (2019). Doi: 10.1371 / journal.pbio.3000166
Public Library of Science
Genetic transcripts of the ancient wolf analyzed after 14,000 years in permafrost (2019, July 30)
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