The young woolly mammoth, now known as Yuka, lay frozen in Siberian permafrost for about 40,000 years before being discovered by local tusk hunters in 2010. Soon, the hunters handed him over to scientists, who were delighted to see his excellent state of preservation: with intact skin, muscle tissue and even reddish hair. Later studies showed that although complete cloning was impossible, Yuki's DNA was in such good condition that the nuclei of some cells could even begin to exhibit limited activity if placed in mouse eggs.
Now the team has successfully sequenced Yuki's RNA, a feat that many researchers once thought impossible. Researchers at Stockholm University carefully ground up pieces of muscle and other tissue from Yuka and nine other woolly mammoths, then used special chemical treatments to extract the remaining RNA fragments, which are generally considered too fragile to survive even hours after the organism's death. Scientists go to great lengths to extract RNA even from fresh samples, and most previous attempts with very old samples have either failed or been contaminated.
Another look
The team used RNA processing techniques adapted for ancient fragmented molecules. Their science session allowed them to study information that had never been available before, including which genes were active at the time of Yuki's death. In the creature's final moments of panic, its muscles tensed and its cells signaled distress, which is perhaps unsurprising since Yuka is believed to have died in a cave lion attack.
This is an extraordinary level of detail that scientists cannot obtain by simply analyzing DNA. “With RNA, you can access the actual biology of a cell or tissue happening in real time during the last moments of an organism's life,” said Emilio Marmol, the researcher who led the study. study. “Simply put, studying DNA alone can tell you a lot of information about the entire evolutionary history and origins of the organism being studied. “By obtaining this fragile and almost forgotten layer of cell biology in old tissues/samples, you can for the first time have a complete picture of the entire pipeline of life (from DNA to proteins, with RNA as an intermediate messenger).”
