Ever since the film Jurassic Park, the idea of bringing extinct species back to life has been fascinating. A team specialized in paleogenetics sought to determine the method which would make it possible to resurrect a species of rat, the Rattus macleari.
Endemic to Christmas Island in the Indian Ocean, this species of rat disappeared regarding 120 years ago. The researchers didn’t go so far as to recreate a living specimen, but they say their study, published Wednesday in the journal Current Biology, shows how close scientists working on so-called ‘de-extinction’ projects might get.
“I don’t do de-extinction, but I think it’s an interesting idea and, technically, it’s very exciting,” the lead author of the work, Tom Gilbert, told AFP. University of Copenhagen.
Three techniques are explored to resuscitate extinct animals: crossing close species in order to find certain lost traits, cloning and, finally, genome editing. It is on the latter that Tom Gilbert and his colleagues looked.
Genetic manipulation
The idea is to take DNA from the extinct species and compare its genome to closely related modern species. Once the closest one has been selected, the CRISPR tool, nicknamed molecular scissors, is used to edit the modern genome, where it differs from the old one. The cells thus modified might then be used to create an embryo, to be implanted in a surrogate mother.
According to Tom Gilbert, ancient DNA is like a shredded book. The genome of a modern species is the reference book, intact, which can be used to decipher the damaged fragments of its ancestor.
The researchers used Norway rats, commonly present in laboratories, as a modern reference species. They determined that they might reconstruct 95% of the genome of the Christmas Island rat.
Although this proportion may sound like a great success, the 5% lost are part of regions of the genome controlling the sense of smell and the immune system: the resuscitated rat would thus certainly resemble the old one, but it would lack certain key functions.
These findings have important implications for ongoing ‘de-extinction’ projects, such as a US company’s resurrecting a mammoth. Mammoths, extinct around 4,000 years ago, are as distant from modern elephants as Rattus macleari is from brown rats.
In Australia, a team is trying to revive the Tasmanian tiger, the last specimen of which died in captivity in 1936.
/ ATS