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| "Unlocking Genetic Secrets of Extinct Species: First-Ever Tasmanian Tiger RNA Sequencing Reveals Surprising Insights" |
For the first time in history, scientists have successfully sequenced RNA from an extinct animal species, specifically the Tasmanian tiger (Thylacinus cynocephalus). This groundbreaking achievement involved isolating millions of RNA sequences from muscle and skin samples obtained from a 132-year-old museum specimen. The RNA sequencing provides invaluable insights into the genes and proteins of this long-extinct creature, and the results, published in the journal Genome Research on September 19th, 2023, herald a promising avenue for unlocking the genetic secrets of other extinct species preserved in museums.
This remarkable breakthrough in analyzing RNA offers researchers a fresh perspective on understanding the genetic activity within organisms. Oliver Smith, a geneticist at Micropathology in Coventry, UK, emphasizes that this approach allows scientists not only to explore the genome's makeup but also to delve into its functional aspects.
The Tasmanian tiger, also known as the thylacine, was a carnivorous marsupial native to Tasmania in southeast Australia. The last known thylacine perished in captivity in 1936, leaving only a few preserved specimens in museums for future study.
The research focused on a well-preserved thylacine specimen housed at the Stockholm Natural History Museum since 1891. From this specimen, scientists meticulously gathered three muscle samples and three skin samples, each weighing approximately 80 milligrams.
Studying RNA from ancient samples posed unique challenges due to RNA's inherent instability compared to DNA, which has been successfully extracted from species that lived over a million years ago. RNA typically degrades rapidly once outside living cells, as Marc Friedländer, a geneticist at Stockholm University and a co-author of the study, explains.
To extract RNA from the preserved tissue samples, the research team developed a tailored protocol for ancient RNA, adapting conventional methods used for fresher samples. Surprisingly, they found authentic RNA sequences within this mummified Tasmanian tiger, defying the expectations of RNA's fragility.
The team managed to extract and purify 81.9 million RNA fragments from muscle tissue and 223.6 million RNA fragments from skin tissue. After eliminating duplicates and extremely short sequences, they identified 1.5 million RNA sequences from muscle tissue and 2.8 million RNA sequences from skin tissue.
Co-author Emilio Mármol-Sánchez, a computational biologist at Stockholm University, emphasizes that RNA sheds light on variations in gene expression within different tissues. In their analysis of the muscle samples, the researchers discovered sequences corresponding to 236 genes, including those responsible for actin and titin, crucial proteins governing muscle stretching and contraction. In the skin samples, they identified sequences related to 270 genes, including the gene responsible for producing the structural protein keratin.
Intriguingly, the scientists also detected a limited number of RNA molecules from viruses that either inhabited or infected the Tasmanian tiger. This discovery opens the door to the study of ancient viruses, a development of considerable interest to Hannes Schroeder, an ancient-DNA researcher at the University of Copenhagen.
While the field of ancient DNA sequencing is well-established, ancient RNA sequencing remains relatively underdeveloped. Oliver Smith notes that this study breathes new life into an underrepresented and underestimated field. He anticipates future studies that routinely combine both DNA and RNA sequencing to further our understanding of extinct species and the evolutionary history of life on Earth.
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