In a groundbreaking achievement, scientists have successfully recovered and decoded RNA from an extinct animal, the thylacine, also known as the Tasmanian tiger. This marsupial, resembling a wolf, met its demise in 1936 when the last known individual died in a Hobart, Tasmania zoo.
A specimen from a museum, estimated to be around 130 years old, has provided fragments of RNA, the delicate molecules responsible for translating genetic instructions from DNA into cellular functions.
This discovery, detailed in the August Genome Research, offers new insights into thylacine biology and could prove invaluable in future attempts to resurrect the species.
The thylacine was a remarkable creature, characterized by its tawny coat adorned with dark stripes and an impressive jaw capable of a wide 80-degree opening.
However, human expansion and sheep farming in 19th-century Tasmania led to the thylacine’s persecution due to its perceived threat to livestock. A bounty system for killing adult thylacines nearly drove them to extinction.
Prior genetic research had mapped the thylacine’s DNA and other extinct creatures like the woolly mammoth.
However, these studies exclusively focused on DNA, while RNA offers insight into how an organism’s cells function. Emilio Mármol-Sánchez, a geneticist, explains that RNA reveals “the real biology of the cell.”
In 2020, Mármol-Sánchez and a team stumbled upon a thylacine specimen at the Natural History Museum in Stockholm. They collected skin and muscle samples and processed them in the lab, isolating nucleotides RNA’s building blocks.
A computer algorithm was then employed to compare the RNA sequences with a vast database containing genomes from various organisms, including thylacine.
Approximately 70% of the RNA sequences were identified as reliable thylacine, though some contamination from human RNA occurred due to handling.
The analysis unveiled distinct protein-coding RNA molecules in skin and muscle samples, reflecting the different bodily roles these tissues play. Moreover, over 250 thylacine-specific microRNAs, which regulate cell functions, were identified.
These findings are remarkable, as RNA is less stable than DNA, and the specimen was stored at room temperature, unlike previous RNA extractions from samples preserved in alcohol or ice.
Andrew Pask, a developmental biologist at the University of Melbourne, underscores the transformative impact of studying museum and archive specimens.
In the near future, researchers hope to resurrect the thylacine by modifying the genes of its closest living relative, the fat-tailed dunnart.