Scientists have extracted RNA from a roughly 130-year-old specimen preserved in a museum: a Tasmanian tiger, also known as a thylacine. The feat marks the first time any RNA has been obtained from an extinct species, according to a new study published Tuesday in the journal Genome Research.
While DNA stores genetic information, RNA converts that information into a form that can build proteins. By looking at RNA, researchers can shed light on the biology of extinct animals, revealing how their cells worked.
It “opens up a whole new potential source of information,” Oliver Smith, a geneticist at the medical diagnostics company Micropathology in England who wasn’t involved in the research, tells Nature News’ Miryam Naddaf. “As opposed to looking at what a genome is, we can look at what the genome does.”
In recent years, researchers have extracted ancient DNA from specimens as much as two million years old. But scientists did not expect RNA, which is more fragile and breaks down easily, to stay intact for as long as DNA does, per New Scientist’s Jeanne Timmons. Previously, researchers had sequenced RNA from a dog preserved in permafrost dating to around 14,300 years ago, as well as historical wolf skins, per the paper.
RNA, a single-stranded nucleic acid found in all living cells, carries the instructions for making proteins needed for the structure, function and regulation of the body’s tissues and organs, according to the UMass Chan Medical School.
Being able to examine RNA can reveal “how the cell was metabolically working when it was alive, right before the cell died,” Emilio Mármol Sánchez, a co-author of the new study and bioinformatician at the Center for Paleogenetics in Sweden, tells Live Science’s Stephanie Pappas.
To attempt to extract this molecule from an extinct species, the researchers turned to the Tasmanian tiger. These large, striped marsupials once lived across Australia, but as of around 2,000 years ago, they had been confined to the island of Tasmania—perhaps due to competition with dingoes and hunting by humans. European colonizers eventually drove them to extinction, with the last known thylacine dying at a zoo in 1936.
The team took three skeletal muscle samples and three skin tissue samples, each weighing 80 milligrams, from a Tasmanian tiger specimen that had been preserved at room temperature at the Swedish Museum of Natural History. They successfully extracted millions of strands of RNA.
“It was surprising that we found these authentic RNA sequences in this mummified Tasmanian tiger,” Marc Friedländer, a co-author of the study and geneticist at Stockholm University, tells Nature News.
The researchers used the RNA to fill in gaps in the animal’s genome, and they discovered a microRNA sequence, which helps determine which genes are expressed in a cell, that had never been seen before, per Live Science. In the skin samples, they found RNA corresponding to genes that code for keratin, and in muscles, they identified RNA that helps make proteins involved in muscle stretching and contraction, writes Nature News.
The paper also identified traces of viral RNA. Viruses contain either RNA or DNA, but not both. Further research could use RNA extraction to learn more about viruses from both extinct and still-living species.
Despite being extinct, the Tasmanian tiger has been in the news in recent years, since some researchers are attempting to create a living proxy of the species, in part by editing the genes of one of its close living relatives.
This new advance “will add significant depth to our understanding of the biology of extinct animals and help us to build much better extinct genomes,” Andrew Pask, an epigeneticist at the University of Melbourne in Australia who is working on “bringing back” the Tasmanian tiger but did not contribute to the new study, tells CNN’s Katie Hunt.
Mármol Sánchez tells New Scientist that while these resurrection efforts are not the focus of his research, those involved with the “de-extinction” project will need RNA to understand how the Tasmanian tiger’s cells worked.