What I’ve Learned:
“Gene drives: sometimes CRISPR is the best accessory.”
When you shop for a new outfit, you’re looking for a number of things. It has to fit. It has to look nice. The accessories should match. And ideally, it should be malaria-free.
Genetic scientists don’t shop for clothes much (lab coats never go out of style), but they do struggle with problems like that last one — reducing the impact of diseases around the world. Malaria and others are transmitted via mosquitoes, affecting hundreds of millions of people and killing more than one million worldwide every year. But what if there was a way to genetically alter the blood-sucking little bastards to prevent these infections? And what if it was as easy (relatively speaking, for the lab geek set) as picking out a cute hat to match that kicky new jacket?
Enter the gene drive, which could bring the concept of the extreme makeover to the chromosomes of bugs and pests and maybe even humans all over the world. It works using a system nicknamed CRISPR, which stands for a bunch of long sciency words that no one bothers to remember. The important thing is how it works, which comes below.
(Stick with me here. The beginning doesn’t seem to have much to do with malaria, but it gets better and then all comes together in the end. It’s like the anti-Matrix trilogy.)
Some bacteria have a very clever protein that helps them avoid virus infections. The bacterial cells keep snippets of viral genes around (the structure these are stored in is the thing actually called CRISPR), and this protein — called Cas9 — recognizes the viral sequence as a target, or “guide”. Whenever Cas9 sees this sequence, like when a virus barges in and starts throwing it around the joint, Cas9 cuts it right down the middle and ruins it. No viral genes, no virus, and the bacteria go on to lead long, happy, fulfilling tiny lives. Or not. They’re not really important to the rest of the story, so screw ’em.
The key is, this Cas9 protein doesn’t really care what guide sequence it’s given. So scientists can yank the Cas9 gene out of the bacteria and engineer it into other organisms. Like mosquitoes. They can also engineer in custom guide sequences matching that organism’s DNA — like one for mosquitoes’ immune response to malaria, for instance — and thus effectively delete or mutate just about any gene they like.
With a little extra fiddling — like a perfect scarf that ties the ensemble together — scientists can also use CRISPR and Cas9 to introduce new genes. Better still, those genes can be inserted in particular spots in the genome that have a genetic “competitive advantage”, meaning they get passed on to offspring more readily than most. That means these gene drives could spread through a population faster than the latest French runway fashion. And look damned good doing it.
Gene drives specifically in mosquitoes could be theoretically used in a number of ways. We could make the bugs resistant to malaria and other diseases. We could alter genes that allow insects to pass the disease on. Or we could go all snarky fashion critic on them and wipe them out completely — like skewing their offspring to be nearly all male.
See, “Raining Men” is one thing. But when it rains only men for a few generations, your species got a problem, yo.
The opportunities for gene drives are near-endless. Any species that reproduces sexually — which is most animals, up to and including (most) humans — could theoretically be CRISPR’ed, and convinced to “say yes to the gene”. There are one or two (or thousands) of ethical kinks to work out first, of course. But in terms of the science, we can rebuild those mosquitoes (and nearly everyone else). We have the technology. We can make them less malarial than they were before. Better. Stronger. CRISPRier.
