Forget mammoths: These researchers are exploring bringing back the
extinct Christmas Island rat

Date:
March 9, 2022
Source:
Cell Press
Summary:
Dinosaurs went extinct 65 million years ago, mammoths 4,000
years ago, and the Christmas Island Rat 119 years ago. Since
becoming a popular concept in the 1990s, de-extinction efforts have
focused on grand animals with mythical stature, but now a team of
paleogeneticists has turned their attention to Rattus macleari,
and their findings provide insights into the limitations of
de-extinction across all species.



FULL STORY ========================================================================== Dinosaurs went extinct 65 million years ago, mammoths 4,000 years ago,
and the Christmas Island Rat 119 years ago. Since becoming a popular
concept in the 1990s, de-extinction efforts have focused on grand animals
with mythical stature, but in a paper published March 9 in the journal
Current Biology, a team of paleogeneticists turn their attention to
Rattus macleari,and their findings provide insights into the limitations
of de-extinction across all species.


========================================================================== De-extinction work is defined by what is unknown. When sequencing the
genome of an extinct species, scientists face the challenge of working
with degraded 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 (@Evohologen) 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 Rattusspecies 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." 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.


========================================================================== Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Jianqing Lin, David Duche^ne, Christian Caro/e, Oliver Smith,
Marta Maria
Ciucani, Jonas Niemann, Douglas Richmond, Alex D. Greenwood, Ross
MacPhee, Guojie Zhang, Shyam Gopalakrishnan, M. Thomas P. Gilbert.

Probing the genomic limits of de-extinction in the Christmas
Island rat.

Current Biology, 2022; DOI: 10.1016/j.cub.2022.02.027 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220309111050.htm

--- up 1 week, 2 days, 10 hours, 51 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)