Extinct 119 years ago, Maclear’s rat could return thanks to genetic modification CRISPR technology
Ever since man began to devise genetic engineering, he has fantasized about resurrecting extinct species. From dinosaurs to mammoths to saber teeth, some researchers have raised the possibility of recreating ancient DNA through new techniques. Researchers from the University of Copenhagen (Denmark) now propose a new extinct animal that could ‘come back to life: the Maclear’s rat ( Rattus clear ) or the Christmas Island Rat, which disappeared 119 years ago due to the action of the man.
In the work recently published in the journal ‘ Current Biology ‘, its authors describe how they sequenced the genome of R. macleari even with the stumbling block of facing degraded DNA, since after its extinction -due to the action of man and the diseases brought to the island on European ships – the preserved remains are not in very good condition for analysis.
Still, the researchers were lucky: Because it diverged relatively recently from other rat species, the Norwegian brown rat was found to share 95% of the genome.
“It was a pretty good test model,” says Tom Gilbert, an evolutionary geneticist and first author of the study. “It’s the perfect case because when you sequence the genome, you have to compare it to a really good modern reference.”
After sequencing the DNA as best as possible and comparing the genome to that of other living species, scientists would identify the mismatched parts and, in theory, use CRISPR technology – the genetic glue-cutter – to edit the DNA of the living species so that it coincides with that of the extinct. Here the same process described for the hypothetical recovery of the mammoth would be carried out: the necessary fragments would be changed to ‘convert’ the elephant calf into something more similar to extinct mammoths. “The brown rat to Christmas Island rat scenario is a particularly good test case because the evolutionary divergence is similar to that of the elephant and the mammoth,” the authors state.
Although the sequencing of the Christmas Island rat was fairly successful, some key genes were missing that were related to smell, meaning a resurrected Christmas Island rat probably wouldn’t be able to process odors the way it would. originally made. “With current technology, it may be completely impossible to recover the entire sequence, and therefore impossible to generate a perfect replica of the Christmas Island rat,” notes Gilbert. “It is very, very clear that we will never be able to get all the information to create a perfect recovered form of an extinct species. There will always be some kind of hybrid. In other words, if the ‘resurrection’ experiment were carried out, the remaining animal would be a kind of ‘Norwegian’ Christmas Island rat; as in the case of the mammoth, which would actually be something like a ‘woolly’ elephant capable of living in cold ecosystems. “Although a replica will never be perfect, the key is that scientists can edit the DNA that makes the extinct animal functionally different from the living one,” the authors note.
Gilbert plans to try doing actual gene editing in rats but would like to start with species that are still living. He intends to start by CRISPR-editing a black rat genome into a brown Norway rat before attempting to resurrect the Christmas Island rat. Although he is excited about his future research, the whole process carries some ethical implications: “I think it’s a fascinating idea in technology, but we have to ask ourselves if that’s the best use of money rather than keeping things alive that are still here?”.
