Tasmanian tiger RNA extracted — a first from extinct species

Written by Mrigakshi Dixit on September 26, 2023. Posted in Current News

The thylacine (Thylacinus cynocephalus) was a carnivorous marsupial native to Tasmania and Australia.

Except for the island state of Tasmania, this striped dog-sized animal vanished from its other native habitats some 2,000 years ago.

However, the creature met its tragic end with the arrival of Europeans.

The population was hunted down due to allegations that they killed sheep, valuable livestock for early European settlers in Tasmania. In 1888, a bounty of £1 to kill each adult individual of this species was introduced.

Tragically, it was declared extinct in the 20th century, with the last known member dying in captivity in 1936 at the Beaumaris Zoo in Hobart, Tasmania.

But scientists have not stopped learning about this top apex predator of that time. This remarkable breakthrough sheds light on the long-dead animal gene functioning, marking a significant milestone in biology.

Furthermore, these newfound insights may contribute to endeavors to resurrect the Tasmanian tiger.

“This is the first time that we have had a glimpse into the existence of thylacine-specific regulatory genes, such as microRNAs, that got extinct more than one century ago,” said Marc R. Friedländer, associate professor at the Department of Molecular Biosciences, The Wenner-Gren Institute at Stockholm University and SciLifeLab, in an official release.

The extraction of the RNA molecules

Scientists at Stockholm University successfully extracted RNA (Ribonucleic acid) molecules from a Tasmanian tiger specimen that had been desiccated and preserved at room temperature for 130 years in the Swedish Museum of Natural History in Stockholm.

They extracted, sequenced, and analyzed RNA from muscle and skin tissue samples to decode thylacine-specific genes.

The official release mentions that “this resulted in the reconstruction of skin and skeletal muscle transcriptomes from an extinct species for the first time.”

The term transcriptome refers to the entire set of RNA molecules generated within a cell or tissue.

Studying the transcriptome can help understand how genes are controlled in individual cells, identify changes in gene expression between normal and sick diseased cells, and gain insights into the cellular processes of any animal.

However, extracting and examining RNA samples dating back centuries poses significant challenges due to its rapid degradation into smaller fragments. Meanwhile, DNA remains stable and has been effectively extracted from species that lived over a million years ago.

Despite this obstacle, the research team managed to attain this remarkable milestone.

Ongoing resurrection efforts

In the last few years, the Tasmanian tiger has been the target of de-extinction efforts due to the relatively preserved natural habitat in Tasmania.

De-extinction requires a comprehensive understanding of the animal’s DNA and modern biotechnology and genetic engineering techniques to resurrect extinct species.

Colossal Biosciences, a de-extinction company, has taken a bold initiative to create a proxy species for thylacine.

However, recreating a functional, living Tasmanian tiger is an exceedingly intricate task fraught with numerous challenges.

“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 this study.

The goal of this study was not de-extinction but to gain insights into the top predator’s genetic makeup. Nevertheless, this significant breakthrough may assist in the ongoing endeavors to resurrect the Tasmanian tiger from extinction.

The breakthrough has paved the way for the recovery of RNA from long-dead animals. The researchers hope to isolate and analyze the RNA of other ancient animals, such as the woolly mammoth.

“In the future, we may be able to recover RNA not only from extinct animals, but also RNA virus genomes such as SARS-CoV2 and their evolutionary precursors from the skins of bats and other host organisms held in museum collections”, said Love Dalén.

The study results were reported in the journal Genome Research.

Study abstract:

Paleogenomics continues to yield valuable insights into the evolution, population dynamics, and ecology of our ancestors and other extinct species.

However, DNA sequencing cannot reveal tissue-specific gene expression, cellular identity, or gene regulation, which are only attainable at the transcriptional level.

Pioneering studies have shown that useful RNA can be extracted from ancient specimens preserved in permafrost and historical skins from extant canids, but no attempts have been made so far on extinct species.

We extract, sequence, and analyze historical RNA from muscle and skin tissue of a ∼130-year-old Tasmanian tiger (Thylacinus cynocephalus) preserved in desiccation at room temperature in a museum collection.

The transcriptional profiles closely resemble those of extant species, revealing specific anatomical features such as slow muscle fibers or blood infiltration.

Metatranscriptomic analysis, RNA damage, tissue-specific RNA profiles, and expression hotspots genome-wide further confirm the thylacine origin of the sequences.

See more here interestingengineering.com

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