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CRISPR Gene Drives Could be Coming to a Squirrel Near You

New gene driving models could show up in ecosystems near you.

Today's gene drive technologies might be mixed to enable the control of the invasive gray squirrel population in the U.K. — with minimal risks posed to other populations, according to modeling newly published in the journal Scientific Reports.

CRISPR gene drives might be coming to a squirrel near you

Gene driving is the process of introducing altered genes into a population capable of inducing infertility in females — which lets scientists control population size. But this tactic faces technical difficulties like controlling the spread of altered genes while specific animals that are part of the gene drive population mate with uncontrolled populations — in addition to genetic resistance, which can reduce the effectiveness of gene drive efforts.

To overcome these issues, Nicky Faber and colleagues used computer modeling to evaluate the effectiveness of a combination of three distinct gene drive technologies — with the gray squirrel playing a leading role in a case study.

The study authors discovered that the combined gene drive, called "? HD-ClvR ?" successfully suppressed a target population of gray squirrels, with minimal risk to other populations. This was done via the combination of components with key advantages: Cleave-and-rescue, homing, and daisyfield.

Maintaining the balance of ecosystems

Cleave-and-rescue ensures offspring don't develop gene variants resistant to driving. Homing makes sure altered genes are passed down to future generations, while Daisyfield reduces and limits the number of altered genes one member of a species may pass to the next — which puts a boundary around the target population.

The new findings show that HD-ClvR can produce effective control of an invasive species without creating outsized risk to non-targeted native species.

However, the authors also emphasized the need for caution — since HDClvR has yet to be tested in live animals. Scientifically, we're not yet at a place to begin genetically engineering a new "animal kingdom," where only the species we want exist, and only at the population concentrations we want. An abrupt suppression of the gray squirrel population might have unforeseen impacts on the ecosystem — so all potential consequences must first be taken into account.

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However, significant steps like genetic driving could become a necessary tool for carving out a continued place in the world for humans, as the climate shifts.

Genetic driving may be necessary to maintain ecosystems

A 2020 study suggested that a large group of plants and animals might increase by 36% worldwide before 2050. The study suggested an average increase of 1,200 new anthropod and bird species, globally.

"Our study predicts that alien species will continue to be added to ecosystems at high rates through the next decades, which is concerning as this could contribute to harmful biodiversity change and extinction," said study co-author and Professor Tim Blackburn of the UCL Center for Biodiversity & Environment Research and the Institute of Zoology, in a UCL blog post.

With the substantial uptick in "alien" (or non-native) species globally, scientists and engineers will have to find new ways of adjusting the animal populations if we want to maintain current balances of biodiversity across species in specific regions. Naturally, reducing carbon emissions and embracing proven sustainable energy alternatives might slow the migration and introduction of new species into unprepared environments, but genetic driving could be a major tool in maintaining the delicate balance of animal populations.

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