🧬 This woolly mammoth enabled sequencing of 40,000-year-old RNA, a record!

The discovery of a juvenile woolly mammoth named Yuka, found in Siberian permafrost with its skin and muscles intact, has already marked paleontological history. A team of scientists has just added an unprecedented dimension to this find by extracting 40,000-year-old RNA fragments from its tissues. These molecules, known for their extreme fragility, provide direct access to the animal's biological activity shortly before its death, revealing aspects of its physiology that DNA alone could not uncover.

This breakthrough relies on the study of ribonucleic acid, an essential molecule for cellular function. Unlike DNA, which constitutes the stable genetic blueprint of an organism, RNA plays a messenger and activator role. Its analysis allows determining which genes were functional in a specific tissue at a precise moment. Yuka's exceptional preservation in the Siberian ice enabled these molecules, which normally degrade within hours after death, to survive through millennia.

The technical feat and its biological revelations

The extraction of this ancient RNA represents a technical tour de force. Researchers had to develop specific methods to isolate and sequence these delicate molecules from muscle samples taken from Yuka's carcass. Their work, published in the journal Cell, demonstrates that RNA can persist much longer than previously thought under optimal preservation conditions. This discovery significantly expands the possibilities for studying extinct species.

The RNA analysis allowed reconstruction of the mammoth's "transcriptome," meaning the complete map of genes active in its muscles at the time of death. Scientists identified RNA coding for proteins involved in muscle contraction and energy metabolism regulation. Significantly, they also detected RNA associated with cellular stress response proteins. This particular molecular profile supports the hypothesis of an unnatural death, suggesting that the young mammoth suffered intense aggression, likely from cave lions, shortly before dying.

Among the most significant discoveries are microRNAs, small regulatory molecules that control gene expression. Their sequence showed rare mutations characteristic of mammoths, confirming the authenticity of these molecular remains. These microRNAs provide direct evidence of biological processes occurring at the moment of death, capturing cellular activity that was previously inaccessible to scientific investigation. They eternally preserve the animal's very last physiological processes.

Perspectives for paleogenetics and beyond

This success opens considerable perspectives for understanding extinct species. The possibility of studying ancient RNA now allows us to comprehend not only the genetic constitution of extinct animals but also the functioning of their organisms. This approach could be applied to other exceptionally well-preserved specimens, such as those from permafrost or ice caves, to explore various aspects of their biology.

One of the most promising applications concerns the study of ancient viruses. Many pathogens, such as influenza or coronaviruses, use RNA as their genetic material. The analysis of ancient tissues could enable detection of these viruses and trace their evolutionary history over millennia. This research path offers significant potential for understanding interactions between extinct animals and their pathogens.

Although this work has no direct application for de-extinction projects, it could nevertheless inform them indirectly. The detailed understanding of genes active in specific tissues, such as hair follicles responsible for mammoths' characteristic fur, could guide research aimed at recreating certain morphological traits in their modern elephantid cousins.

To go further: What is RNA and how does it differ from DNA?

RNA, or ribonucleic acid, is a fundamental molecule present in all living cells. Its chemical structure differs slightly from that of DNA, making it more flexible but also more susceptible to rapid degradation. While DNA stores genetic information stably, RNA performs essential dynamic functions.

One of RNA's main functions is to serve as an intermediary between DNA and protein production. It copies information contained in a gene and transports it to cellular factories where proteins are assembled. Without RNA, the instructions encoded in DNA could not be implemented by the cell.

Unlike DNA which forms a double helix, RNA typically consists of a single strand. This structure makes it more vulnerable to enzymes that naturally degrade it after completing its function. Its limited lifespan is precisely what makes its discovery in Yuka so remarkable.