Based on a specimen of a Tasmanian tiger head, experts have reconstructed an almost complete gene sequence, paving the way for the revival of this extinct species.
Scientists have created the most complete Tasmanian tiger genome to date from a head preserved in solution over a century ago, providing a nearly full DNA blueprint, Live Science reported on October 17. This is one of the breakthroughs aimed at reviving this extinct species by the American company Colossal Biosciences.
A 108-year-old Tasmanian tiger head still retains some skin (not the specimen in the new study by Colossal Biosciences). (Photo: Colossal Biosciences).
Tasmanian tiger, or Thylacine (Thylacinus cynocephalus), was a marsupial that went extinct in 1936 after decades of hunting by humans. It was a top predator in the food chain and played a vital role in the ecosystem of Tasmania, Australia.
In the new study, the team analyzed a 110-year-old Tasmanian tiger head that had been skinned and preserved in ethanol. The special preservation of the specimen allowed the researchers to assemble most of the DNA sequence, as well as RNA strands (molecules with a similar structure to DNA but consisting of a single strand) that indicate which genes were active in various tissues when the animal died.
“You can absolutely obtain a fantastic genome from old specimens. This genome provides a complete blueprint for reviving the Tasmanian tiger, so obtaining a complete and high-quality genome is a significant aid in that effort,” said Andrew Pask, a professor of genetics and developmental biology at the University of Melbourne, Australia.
The newly assembled genome is similar in size to the human genome, comprising 3 billion nucleotide base pairs—the molecules that form the rungs of the DNA ladder. There are still 45 gaps in the DNA sequence that the team hopes to fill in the coming months as they continue sequencing.
The last known Tasmanian tiger died at Beaumaris Zoo in Hobart, Tasmania, in 1936. (Photo: HUM Images/Universal Images Group).
The RNA fragments found in the preserved head will help the research team identify which genes were activated in various tissues while the Tasmanian tiger was alive, aiding in understanding what the animal could taste, smell, and see, as well as how its brain functioned. Compared to DNA, RNA is much less stable and prone to degradation over time, so the preservation of RNA may help humans understand the biological characteristics of the Tasmanian tiger in unprecedented ways, Pask noted.
Previously, Colossal Biosciences announced another breakthrough in the Tasmanian tiger revival project that could be applied to the conservation of living species: The research team studying Assisted Reproductive Technology (ART) has found a way to stimulate ovulation in Sminthopsis crassicaudata—a small, mouse-like marsupial and the closest living relative of the Tasmanian tiger. They can produce multiple eggs simultaneously for the research team to inject the Tasmanian tiger genome once it is completed. They will also have Sminthopsis crassicaudata act as a surrogate to develop Tasmanian tiger embryos.
Additionally, the research team is working with an artificial womb device to nurture marsupial embryos. This device can currently contain embryos from the beginning up to the mid-pregnancy stage.
