In the 2006 animated comedy Distant, Roddy St. James, a spoiled pet mouse voiced by Hugh Jackman, is flushed down the toilet and into the sewer city of Ratropolis. In his attempt to return home, he uncovers a plot by animal mob boss The Toad to flood Ratropolis with a wave of feces during the FIFA World Cup half-time bathroom break. You see, the toad used to be Prince Charles’ pet, but then Charles got a rat and flushed it down the toilet, so now he hates rats and… that’s a whole thing.
Humans have also been known to make convoluted mousetraps throughout our history. Usually we are not motivated by a slight perception from all rodents everywhere, but mice and rats have posed a threat to health and resources over time, and in response we have come up with all kinds of ways to get rid of them. Now, thanks to scientists at the University of Adelaide, we might have the mousetrap to end all mousetraps. According to a recent article published in the Proceedings of the National Academy of Scienceswe bring the fight directly to their DNA.
For many of us rodents are little more than an occasional nuisance or even a beloved pet, but in some places they are invasive and harmful to both humans and other species. This is especially true in enclosed environments like islands, where particularly pernicious rodents can spread so quickly that they displace native species. With this problem in mind, the Adelaide researchers developed a modified version of CRISPR, which they call t-CRISPR, to push a mutation into a population.
This form of genetic engineering is often called gene drives and differs from conventional gene editing in one important way. Traditionally, gene editing changes a trait or set of traits in an individual, but these changes are not necessarily inherited by offspring. A gene drive increases the likelihood that a trait or set of traits will be passed on to the next generation. For this work, the scientists relied on a natural mutation in mice that makes them infertile. By targeting this mutation and increasing its probability of inheritance, you get a larger and larger population of infertile mice, and the total population goes down. At least, that’s what the models show.
The team used advanced computer modeling to simulate an environment with an invasive population of 200,000 mice. They then introduced just 250 mice modified with the desired fertility gene mutation, and they put the simulation on rotation. They discovered that their gene drive could push the inheritance of this mutation to excess and wipe out the entire population in just 20 years.
Of course, a simulation is only as good as its results in the real world, and that depended on being able to make transgenic mice capable of passing on the defective genes. To find out, the team engineered mice genetically modified using t-CRISPR and confirmed that they had biased inheritance – this increased inheritance – of the target mutation at levels that successfully wiped out the population. in simulation.
It should be mentioned that the genetic engineering of a population on this scale involves ethical and moral considerations that must be clarified before going all the way. These conversations are ongoing as similar efforts to use gene drives on insect populations are being developed. There is an argument to be made that this type of genetic population control is the human solution. It does not involve painful traps or chemicals of any kind. The mice that are born will live out their lives as they normally would, they will just have fewer and fewer offspring with each subsequent generation until they die out.
Instead of traps and poisons, we will turn their gene pool into a slowly tightening noose. It’s the kind of mousetrap you can’t escape from because you don’t even know you’re inside.
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