From climate change to overhunting by humans, there are many factors which contribute to the extinction of species in the animal kingdom. The Christmas Island rat, also known as Maclear’s rat, went extinct a century ago in what is believed to be the first and only case of extinction of a species due to disease. It has always been believed that once a species goes extinct, it is gone for good. That is until recently when scientists began experimenting with “de-extinction” efforts to bring back the Christmas Island rat.
As published March 9 in the science journal, Current Biology, a team of paleo geneticists from the University of Copenhagen recently conducted a study into gene sequencing the Christmas Island rat, in order to estimate the possibilities of future gene editing experiments which could bring the species “back to life”. The process of genetic editing for de-extinction efforts, as explained by the research team in their abstract, consists of first identifying the genome of the species and then editing the genes of similar species to make it more similar to that of that extinct one. The team used frozen somatic cells of the extinct rats, cells with a 2n number of chromosomes which are made during the process of mitosis. The team was able to sequence the rats’ genome, aside from some small portions which remain missing. They then had to identify the modern species which they could gene edit. Their findings established that the Christmas Island rat shares around 95% of DNA with the modern Norway brown rat. At this point, it
Now that the rat’s genome has been sequenced to the best of the team’s ability and a similar species has been identified, the gene editing possibilities are endless, especially with CRISPR technologies and techniques. “CRISPR” stands for Clustered Regularly Interspaced Short Palindromic Repeats in DNA sequencing. This system was discovered by a group of scientists, led by Dr. Emmanuelle Charpentier. CRISPR uses Cas9, an enzyme which cuts DNA at specified sections as guided by RNA. There are three different types of edits drone with CRISPR technology: disruption, deletion, or correction/insertion. Disruption editing is when the DNA is cut at one point and base pairs are either added or removed to inactivate a gene. Deletion editing is when the DNA is cut at two points and a larger sequence of pairs is removed. Correction/insertion editing is when a new gene is added into a sequence using homology directed repair.
Thomas Gilbert, the lead scientist on the team, says that he would like to conduct CRISPR gene editing experiments on living species of rats before attempting to replicate the DNA of an extinct species. For example, attempting to mutate the DNA of the Norway brown rat into that of the common black rat. Once this experiment is conducted, the possibilities of reviving the Christmas Island rat will be more clear. Until then, we can only hope! Do you think it’s possible to see the Christmas Island rat revived anytime soon?