Researchers have successfully sequenced ancient RNA from a juvenile mammoth named Yuka, who perished approximately 40,000 years ago in what is now Siberia. This groundbreaking discovery, detailed in the scientific journal Cell, marks the oldest RNA ever sequenced, offering new insights into the final moments of this extinct ice age creature.
The RNA was extracted from remarkably preserved mummified leg tissue found in permafrost, allowing scientists to examine the mammoth’s genetic activity at the time of its death. According to Love Dalén, a professor of evolutionary genomics at the Centre for Palaeogenetics in Stockholm, this research focuses on understanding how genes function in various cell types. “All the cells in an organism have the same DNA, but what makes these cells different is essentially the RNA,” Dalén explained.
The sequencing effort involved the analysis of ten frozen mammoth tissue samples, comprising muscle and skin, with only three yielding RNA fragments. Ultimately, detailed sequencing data was obtained from Yuka’s sample, revealing critical information about the mammoth’s biology just before it died. This includes insights into messenger RNA molecules, which code proteins, and microRNA, which regulates gene activity.
The findings suggest that Yuka was in a state close to death, as indicated by the metabolism of its muscle tissue. Emilio Mármol Sánchez, the study’s lead author and a postdoctoral researcher at the University of Copenhagen, noted that the data showed a predominance of slow-twitch muscle fibers, which could represent the tissue’s “final pulses.” Active proteins like titin, which is related to muscle elasticity, and nebulin, involved in skeletal muscle contraction, were also identified.
According to Marc Friedländer, a coauthor of the study, the discovery of muscle-specific microRNAs in Yuka’s tissue provides direct evidence of gene regulation occurring in ancient times. “It is the first time something like this has been achieved,” Friedländer stated, highlighting the significance of the findings.
The implications of this research extend beyond understanding mammoths. Erez Lieberman Aiden, a professor of biochemistry and molecular biology at the University of Texas Medical Branch, remarked that the ability to detect tissue-specific expression is quite impressive. He emphasized that it is logical for the mammoth’s muscle to be active at the time of death.
Dalén, who previously sequenced the world’s oldest mammoth DNA, expressed optimism about the potential of these techniques to further explore the past. While the three successful samples may seem limited, he believes that advancements in methods will enhance the recovery of RNA, which could help in studying ancient viruses and pathogens.
The applications of this research could also extend to efforts to revive extinct species. Dalén serves as a scientific adviser to Colossal Biosciences, a Texas-based biotech company aiming to “resurrect” animals like the mammoth through genome editing of their closest living relatives. He noted, “In principle, the methods used here could help narrow down what genes to edit.”
While Yuka’s RNA represents the oldest recovered to date, it is not the first instance of ancient RNA sequencing. Previous studies have sequenced RNA from a 130-year-old Tasmanian tiger and a 14,300-year-old wolf, among others. The ongoing research in this area indicates a promising future for understanding the genetic history of ancient organisms.
The recent study marks a significant advancement in the field, though the full impact of RNA research on our understanding of extinct species remains to be determined. As Aiden aptly put it, gauging the significance of this research is akin to predicting the happiness of a newlywed couple—it is a challenging endeavor.
