매머드를 잊어라 – 이 과학자들은 DNA를 편집하여 멸종된 크리스마스 섬 쥐를 되살리기 위해 노력하고 있습니다.

공룡은 6,500만 년 전에, 매머드는 4,000년 전에, 크리스마스 섬은 119년 전에 멸종했습니다. 1990년대 대중적인 개념이 된 이후 멸종 위기에 처한 전설적인 대형 동물에 대한 멸종 방지 노력이 집중되었지만 저널에 2022년 3월 9일 게재된 연구 논문에서 현재 생물학고생물학자 팀이 그에게 관심을 돌립니다. 라투스 맥클리어리그들의 발견은 모든 종에서 멸종을 제거하는 것의 한계에 대한 통찰력을 제공합니다.

소멸의 행위는 미지의 것에 의해 정의된다. 멸종된 종의 게놈을 시퀀싱할 때 과학자들은 감소하는 종의 연구에 어려움을 겪습니다.[{” attribute=””>DNA, which doesn’t yield all the genetic information required to reconstruct a full genome of the extinct animal. With the Christmas Island rat, which is believed to have gone extinct because of diseases brought over on European ships, evolutionary geneticist Tom Gilbert at University of Copenhagen and his colleagues lucked out.

Not only was the team able to obtain almost all of the rodent’s genome, but since it diverged from other Rattus species relatively recently, it shares about 95% of its genome with a living rat, the Norway brown rat. “It was a quite a nice test model,” says Gilbert. “It’s the perfect case because when you sequence the genome, you have to compare it to a really good modern reference.”

Maclear’s rat (Rattus macleari) is an extinct large rat endemic to Christmas Island in the Indian Ocean. Credit: Joseph Smit, Proceedings of the Zoological Society of London 1887

After the DNA has been sequenced as well as possible and the genome is matched up against the reference genome of the living species, the scientists identify the parts of the genomes that don’t match up and, in theory, would then use CRISPR technology to gene edit the DNA of the living species to match that of the extinct one. 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.

Though the sequencing of the Christmas Island rat was mostly successful, a few key genes were missing. These genes were related to olfaction, meaning that a resurrected Christmas Island Rat would likely be unable to process smells in the way as it would have originally. “With current technology, it may be completely impossible to ever recover the full sequence, and therefore it is impossible to ever generate a perfect replica of the Christmas Island rat,” says Gilbert.

“It is very, very clear that we are never going to be able to get all the information to create a perfect recovered form of an extinct species,” he says. “There will always be some kind of hybrid.” Though a replica will never be perfect, the key is that scientists are able to edit for the DNA that makes the extinct animal functionally different from the living one.

Gilbert says that in order to make an ecologically functional mammoth, for example, it might be enough to edit elephant DNA to make the animal hairy and able to live in the cold. “If you’re making a weird fuzzy elephant to live in a zoo, it probably doesn’t matter if it is missing some behavioral genes,” he says. “But that brings up a whole lot of ethical questions.”

Gilbert plans to try doing the actual gene editing on rats but would like to start with species that are still living. He intends to begin by doing CRISPR edits on a black rat genome to change it to a Norway brown rat before attempting to resurrect the Christmas Island rat. Though he is excited about his future research, the whole process still gives him pause. “I think it’s a fascinating idea in technology, but one has to wonder if that’s the best use of money as opposed to keeping the things alive that are still here,” he says.

Reference: “Probing the genomic limits of de-extinction in the Christmas Island rat” by Jianqing Lin, David Duchêne, Christian Carøe, Oliver Smith, Marta Maria Ciucani, Jonas Niemann, Douglas Richmond, Alex D. Greenwood, Ross MacPhee, Guojie Zhang, Shyam Gopalakrishnan and M. Thomas P. Gilbert, 9 March 2022, Current Biology.
DOI: 10.1016/j.cub.2022.02.027

This work was supported by the European Research Council and the Danish National Research Foundation.