In the opening sequence of “Jurassic Park: World,” the ferocious Indominus Rex (I-Rex) hatches from its incubated egg. I-Rex is the genetically modified hybrid of a T-Rex, Velociraptor, and several other modern animals. It’s also the park’s attempt to entertain an insatiable crowd of visitors with a creature that is bigger, faster, and stronger than its dinosaur ancestors. Predictably, the lab experiment backfires.
Genetic modification, long the stuff of science fiction books and movies, is no longer just for the big screen. In fact, it’s increasingly being applied to the world’s greatest global health challenges.
A controversial new genetic technology promises to wipe out a species of mosquito known as Aedes aegypti, the main vector of the Zika virus. Through a process called “gene driving,” man-made genetic mutations spread rapidly through wild populations of mosquitoes as they reproduce. Last year, the technology was successfully applied to fruit flies and one species of mosquito that transmits malaria.
“Gene drives” use a gene-editing technique called CRISPR-Cas9. CRISPR stands for “clustered regularly interspaced short palindromic repeats.” Cas9 refers to the enzyme that acts as molecular scissors. CRISPRs are repeat sequences of DNA that can be found in every species of creature, ranging from bacteria to people.
It is one of the simplest and cheapest methods of genetic mutation currently available to scientists. Journalist Laurie Garrett wrote of CRISPR-Cas9 in “CRISPR: Transformative and Troubling”:
… An elegant, amazingly accurate gene editing method that bacteria have used for billions of years, but humans have only understood and deployed for about thirty-six months.
The possibilities are seemingly endless. In March, researchers from Temple University in Philadelphia, reported using CRISPR-Cas9 in test tubes to excise latent HIV from inside human DNA, a landmark discovery bringing them potentially one step closer to curing HIV. A Duke group of researchers has also used the gene-editing technique in mice that shows promise to correct a rare genetic mutation in humans known as Duchenne’s muscular dystrophy. As start-ups emerge across the country, there’s talk of creating CRISPR-adapted mosquitos to eradicate malaria, lofty goals of bringing back from extinction mastadons and wooly mammoths, and efforts to render certain food allergies obsolete.
But all revolutionary ideas come with their share of consequences and cautions. Journalist Amy Maxmen wrote in “Easy DNA Editing Will Remake the World. Buckle Up”:
It could at last allow genetics researchers to conjure everything anyone has ever worried they would—designer babies, invasive mutants, species-specific bioweapons, and a dozen other apocalyptic sci-fi tropes. It brings with it all-new rules for the practice of research in the life sciences. But no one knows what the rules are—or who will be the first to break them.
CRISPR has provoked patent wars and ethical dilemmas around the limits of biology. Some scientists speculate that CRISPR-Cas9 could be a critical tool for permanently removing certain genetic traits, and as such, should be carefully regulated. Gene editing methods have also proven harder to control the more sophisticated the recipient.
In the case of Zika-carrying mosquitoes, scientists don’t well understand how the genetically modified insects will behave in the wild. No amount of lab testing can determine if modifications will end up altering mosquitoes’ behavior or host preferences. These methods turn Darwin’s Theory of Evolution on its head. The survival of the fittest may not apply if mankind can control its own evolution at a genetic level.
Editor’s note: And as this post was being finalized, the journal Nature reported that the US National Institutes of Health (NIH) had just approved a proposal to use CRISPR–Cas9 in clinical tests of cancer therapies using patients’ modified T cells.
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- Celina Kareiva is a project coordinator on both the Menstrual Health and Applied Behavioral Communication work teams at PATH.