May 15, 2022

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Forget mammoths, study shows how to revive Christmas Island mice

Forget mammoths, study shows how to revive Christmas Island mice

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Washington (AFP) – Since Jurassic Park, the idea of ​​bringing extinct animals back to life has captured the public’s imagination – but what might scientists turn their attention to first?

Instead of focusing on iconic species like the woolly mammoth or the Tasmanian tiger, a team of paleobiologists has studied how, using genetic editing, they could revive the humble Christmas Island mouse, which died about 120 years ago.

Although they did not follow up and create a live specimen, they say their paper, published in Current Biology on Wednesday, shows how close scientists working on de-extinction projects are to using current technology.

“I’m not arguing with extinction, but I think it’s a really interesting idea, and technically it’s really exciting,” senior author Tom Gilbert, an evolutionary geneticist at the University of Copenhagen, told AFP.

There are three pathways to bring back extinct animals: species related to backbreeding to achieve lost traits; cloning, which was used to create Dolly the sheep in 1996; and finally the gene editing that Gilbert and colleagues looked at.

The idea is to take surviving DNA from extinct species, compare it to the genomes of modern, closely related species, and then use techniques like CRISPR to modify the genomes of modern species in places where they differ.

The modified cells can then be used to create an embryo transplanted into an alternative host.

Ancient DNA is like a book that has been shredded, Gilbert said, while the genome of a modern species is like an intact “reference book” that can be used to piece together its degraded counterpart.

His interest in Christmas Island mice was sparked when a colleague studied their hides to look for evidence of the pathogens that caused their extinction around 1900.

The black rat brought on board European ships is believed to have decimated the native species, which was described in an 1887 entry in the Proceedings of the Zoological Society of London as a “wonderful new rat”, large in size with a long yellowish tail and small round. ears.

Major functions lost

The team used brown mice, commonly used in lab experiments, as a modern reference species, and found that they could reconstruct 95 percent of the genomes of mice on Christmas Island.

This might sound like a big success, but the five percent they couldn’t cure were from regions of the genome that control smell and immunity, meaning that the recovered rat might look the same but lack basic functions.

“Taking us home is, even if we basically had the perfect ancient DNA situation, we got a really good sample, we got it out of hell, and we still lacked five percent of it,” Gilbert said.

The two species diverged about 2.6 million years ago: close in evolutionary time, but not close enough to completely reconstruct the entire genome of a lost species.

This has important implications for extinction efforts, such as a project by the US biosciences company Colossal to revive the mammoth, which died about 4,000 years ago.

Mammoths have roughly the same evolutionary distance from modern elephants as brown rats and Christmas Island rats.

Meanwhile, teams in Australia are searching for the revival of the Tasmanian tiger, or Tasmanian tiger, whose last surviving member died in captivity in 1936.

Even if gene editing were to be perfected, the mock animals created with this technology would therefore have some critical shortcomings.

“Let’s say you bring back a giant only to find a hairy elephant in a zoo to raise money or for conservation awareness – it doesn’t really matter,” he said.

But if the goal was to return the animal exactly to its original form, “that would never happen,” he said.

Gilbert admitted that while the science was fascinating, he had mixed feelings about de-extinction projects.

“I am not convinced that this is the best use of anyone’s money,” he said. “If you had to choose between returning something or protecting what was left, I would put my money in protection.”