Researchers from Stockholm University have achieved a remarkable feat of recovering RNA molecules from a 130-year-old Tasmanian tiger specimen. This is the first time that RNA has been retrieved from an extinct species, and it could have implications for resurrecting extinct animals and studying ancient viruses.
What is RNA and why is it important?
RNA, or ribonucleic acid, is a genetic material that is structurally similar to DNA, or deoxyribonucleic acid. DNA carries the genetic code and determines the traits of an organism, while RNA conveys the genetic information received from DNA and enables the synthesis of proteins and the regulation of cellular metabolism.
RNA is essential for understanding the biology and metabolism of extinct species, as it reveals how their genes are expressed and regulated. However, RNA is less stable than DNA and tends to degrade rapidly, especially under unfavorable conditions such as high temperature, humidity, or exposure to enzymes.
Therefore, recovering RNA from ancient specimens is a challenging task that requires advanced techniques and careful handling. Until now, the oldest RNA ever recovered was from a 14,000-year-old mammoth bone.
How did the researchers recover RNA from the Tasmanian tiger?
The Tasmanian tiger, also known as the thylacine, was a unique carnivorous marsupial native to Australia and Tasmania. It resembled a wolf with distinctive tiger-like stripes on its back. Due to human actions, such as hunting and habitat loss, the Tasmanian tiger was declared extinct in 1936. The last known individual died in captivity at the Hobart Zoo.
The researchers used a Tasmanian tiger specimen that was preserved in desiccation at room temperature in the Swedish Museum of Natural History in Stockholm. The specimen, which dates back to 1891, had its skin, muscles, and bones intact, but had lost its internal organs.
The researchers extracted RNA from the skin and muscle tissues and sequenced it using a method called RNA-seq, which allows the analysis of the entire transcriptome (the set of all RNA molecules) of a sample. They were able to reconstruct the gene expression patterns of the skin and skeletal muscle of the Tasmanian tiger for the first time.
They also compared the Tasmanian tiger’s transcriptome with that of other marsupials, such as the Tasmanian devil, the opossum, and the kangaroo, and found that they shared some common features, such as the expression of genes involved in skin development, hair growth, and muscle contraction.
What are the implications of this study?
The study, which was published in the journal Molecular Biology and Evolution, has several implications for both science and conservation.
First, it demonstrates that RNA can be recovered from ancient specimens that have been stored at room temperature for over a century, challenging the assumption that RNA degrades rapidly under such conditions. This opens new possibilities for studying the transcriptomes of other extinct species, such as the woolly mammoth, the dodo, or the passenger pigeon, and gaining insights into their biology and evolution.
Second, it suggests that RNA can be used as a source of genetic information for de-extinction projects, which aim to revive extinct species using biotechnology. By recovering RNA from extinct animals, scientists may be able to identify the genes that are responsible for their unique traits and introduce them into living relatives or surrogate hosts. For example, the Tasmanian tiger’s RNA could be used to modify the genome of a Tasmanian devil or a dog and create a hybrid animal that resembles the extinct predator.
Third, it indicates that RNA can be a valuable tool for investigating ancient viruses and their interactions with their hosts. RNA viruses, such as influenza, HIV, or coronavirus, are among the most diverse and rapidly evolving pathogens that can cause pandemics. By recovering RNA from ancient specimens, scientists may be able to trace the origin and evolution of these viruses and understand how they have affected human and animal health throughout history.
A real-life Jurassic Park?
The study has also sparked interest and curiosity among the public, as it evokes the idea of a real-life Jurassic Park, the fictional theme park where dinosaurs are brought back to life using DNA extracted from amber. However, the researchers caution that de-extinction is not a trivial task and will require a deep knowledge of both the genome and transcriptome regulation of extinct species, as well as ethical and ecological considerations.
“Resurrecting the Tasmanian tiger or the woolly mammoth is not a trivial task, and will require a deep knowledge of both the genome and transcriptome regulation of such renowned species, something that only now is starting to be revealed,” said Emilio Mármol, the lead author of the study, in a press release.
Moreover, the researchers point out that de-extinction should not distract from the urgent need to protect the existing biodiversity and prevent further extinctions. They argue that de-extinction should be seen as a complementary tool for conservation, not a replacement.
“De-extinction should not be seen as a way to bring back the past, but as a way to restore the present and the future,” said Mármol.