Earliest RNA Sample Discovered from a Woolly Mammoth

The oldest known RNA has been obtained from a woolly mammoth preserved in Siberian permafrost for close to 40,000 years.

This specimen, named Yuka and found in 2010, is regarded as the best-preserved woolly mammoth (Mammuthus primigenius) identified to date. Initially believed to be a young female that perished between the ages of 6 and 8—likely due to an attack by a cave lion.

Researchers have successfully extracted DNA from various woolly mammoths, including some over a million years old. Advances in genome reconstruction have sparked hopes of potentially reviving this species through genetic engineering.

DNA carries the genetic blueprint for protein production in animals. When a specific gene is activated, the code is transcribed into another molecule known as RNA, which is far less stable than DNA and typically breaks down within hours after death.

The oldest RNA previously retrieved was from a wolf preserved in Siberian permafrost over 14,000 years ago. Recently, love darren from Stockholm University has extracted nearly three times the RNA amount from Yuka’s leg than had been recorded before.

The research team employed techniques similar to those used to extract RNA from contemporary samples, fine-tuning them to target smaller and older molecules.

“Yuka is exceptionally well preserved,” remarks Darren. “The specimen likely experienced deep freezing and prolonged burial in permafrost, evidenced by the preservation of both muscle tissue and wool-like fur. This significantly boosts the chance of RNA preservation.”

However, Yuka’s temporary thawing during transport from northeastern Siberia to Yakutsk posed a challenge. “We assumed that any truly ancient RNA still present in the sample would have degraded into smaller fragments,” says Darren.

The team exercised extreme caution to prevent sample deterioration and avoid contamination. “We utilized liquid nitrogen for grinding, along with sterile materials, filtered air, protective clothing, and controlled lab conditions to eliminate modern contamination in sequencing data,” he explains.

RNA sequencing reveals which genes were active at the time of the animal’s death. In the RNA extracted from Yuka’s muscle and skin, the researchers identified signs of gene activity associated with muscle metabolism and cellular stress, aligning with the hypothesis of Yuka’s death resulting from a cave lion’s attack.

A surprising finding was that a combination of DNA and RNA analysis led the research team to conclude that Yuka was actually male. “I’ve anticipated something like this for a long time,” shares Darren. “Even though Yuka is remarkably preserved for being 40,000 years old, it’s not entirely intact, making it difficult to determine an organism’s morphological sex.”

Researchers also probed for RNA viruses such as influenza and coronaviruses but found no significant results. “Yet I believe we will see future studies on Ice Age RNA viruses,” Darren mentions. “For instance, we possess some Pleistocene bird carcasses that would be intriguing to investigate concerning avian influenza.”

Darren, a scientific advisor to Colossal Biosciences, the company claiming to have revived the dire wolf earlier this year, stated that the RNA sequences retrieved in this study do not directly contribute to the revival of the mammoth. However, the study may offer valuable insights into genes responsible for certain traits. “In the future, mammoth RNA profiles might uncover how specific traits, such as wool, were genetically regulated in these animals.”

Merlin Crossley, a researcher at the University of New South Wales in Sydney, noted that while acquiring such ancient RNA is an impressive feat, it doesn’t reveal much about mammoth ecology. “It’s akin to maneuvering a light airplane under the Sydney Harbor Bridge,” he explained. “It’s a remarkable technical accomplishment, but we gain little insight from it.”

Crossley believes that while older RNA samples may be unearthed in the future, the limits of RNA’s longevity are close at hand. Given the rarity of specimens like Yuka’s, he concludes that it’s unlikely that additional mammoths will yield significant information.

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