For the first time, geneticists extracted and sequenced RNA molecules from a long-extinct organism.
The genetic material, which originated from a 130-year-old Tasmanian tiger, or thylacine, specimen in the Swedish Museum of Natural History in Stockholm, has helped scientists better understand how the animal’s genes worked. The researchers published their findings in the scientific journal Genome Research on Tuesday.
“RNA gives you the chance to go through the cell, the tissues, and find the real biology that has been preserved in time for that animal, the thylacine species, right before they died,” said lead study author Emilio Mármol Sánchez, a computational biologist at Sweden’s Centre for Palaeogenetics and SciLifeLab.
The thylacine was a marsupial predator about the size of a coyote. It vanished around 2,000 years ago almost everywhere except the Australian island state of Tasmania, where European settlers drove the population to extinction. Benjamin, the last thylacine in captivity, died of exposure in 1936 at the Beaumaris Zoo in Hobart, Tasmania.
Mármol Sánchez stated that, while de-extinction is not the objective of his team’s research, a deeper knowledge of the Tasmanian tiger’s genetic makeup may benefit recently initiated attempts to bring the species back in some way.
Resurrecting a lost species
Andrew Pask, who is leading an effort to restore the thylacine, called the report “groundbreaking.”
“We had previously thought that only DNA remained in old museum and ancient samples, but this paper shows that you can also get RNA from tissues,” said Pask, a professor at Australia’s University of Melbourne and the director of the Thylacine Integrated Genetic Restoration Research Lab.
“This will add significantly depth to our understanding of the biology of extinct animals and help us build much better extinct genomes,” he continued.
Under the appropriate circumstances, ancient DNA can endure for more than a million years, revolutionizing scientists’ understanding of the past.
RNA, a temporary replica of a piece of DNA, is more fragile and degrades faster than DNA and was not considered to last for long until recently.
A team sequenced RNA from the skin of a 14,300-year-old wolf frozen in permafrost in 2019, but this is the first time RNA has been extracted from an extinct species.
According to Mármol Sánchez, this discovery provides a proof of concept, and his team now aims to extract RNA from species that went out much earlier, such as the woolly mammoth.
The study team was able to sequence RNA from the specimen’s epidermis and skeletal muscle tissues and find thylacine-specific genes. This information is known as the animal’s transcriptome, just as the information contained in DNA is known as the animal’s genome.
DNA is sometimes characterized as an instruction manual for life that is found in every cell of the body. RNA, among other things, generates proteins by replicating a specific stretch of DNA in a process known as transcription.
Understanding RNA helps scientists to build a more comprehensive picture of an animal’s biology, according to Mármol Sánchez. He cites the example of a city where each restaurant is handed a single large cook book — the DNA. However, it is RNA that enables each restaurant to create unique recipes from that reference book.