A young woolly mammoth, now known as Yuka, was frozen in Siberian permafrost for around 40,000 years before being discovered by local tusk hunters in 2010. The hunters quickly handed it over to scientists, delighted to see its excellent level of preservation, with its skin, muscle tissue and even red hairs intact. Subsequent research showed that, although complete cloning was impossible, Yuka’s DNA was in such good condition that some cell nuclei could even begin limited activity when placed in mouse eggs.
Now, a team has successfully sequenced Yuka’s RNA, a feat 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 any remaining RNA fragments, which are normally considered far too fragile to survive even a few hours after an organism dies. Scientists go to great lengths to extract RNA even from fresh samples, and most previous attempts with very old samples have failed or been contaminated.
A different vision
The team used RNA manipulation methods suitable for ancient and fragmented molecules. Their science session allowed them to explore information that had never been accessible before, including which genes were active when Yuka died. In the creature’s final panicked moments, its muscles were tense and its cells signaled distress, perhaps unsurprising since Yuka is believed to have died following a cave lion attack.
This is an exquisite level of detail that scientists cannot obtain by simply analyzing DNA. “With RNA, you can access the actual biology of the cell or tissue that occurs in real time in the final moments of the organism’s life,” said Emilio Mármol, a researcher who led the study. “Simply put, studying DNA alone can give you a lot of information about the entire evolutionary history and ancestry of the organism being studied. By obtaining this fragile and largely forgotten layer of cell biology in old tissues/specimens, you can get for the first time a complete picture of the entire pipeline of life (from DNA to proteins, with RNA as the intermediate messenger).”
