Jennifer Kahn is a science journalist whose articles cover the gene-editing abilities of CRISPR technology. Her TED talk, ‘Gene editing can now change an entire species – forever’ can be found on TED.com under the ‘Science’ section.
No one can deny the blight malaria has been on the world. UNICEF figures show over a million people still die from the disease each year, affecting large swathes of the globe including the continents of Africa, South America, and Southern Asia. Given the dire urgency with which a new solution to the malaria crisis is needed, it is perhaps unsurprising that after a decades long quest, new advances in gene editing technologies may provide the way for breakthrough.
This was has certainly been the case for Anthony James, a biologist who discovered that gene editing could be used to make mosquitoes resistant to the parasite that causes malaria, by making it impossible for the parasite to survive inside them. However, though James’ was able to succeed in making mosquitoes resistant, he still needed a way to allow these mosquitoes to breed and spread the malaria-resistant genes quickly into the wild, to counteract the breeding patterns of ordinary malaria-carriers.
Biologist Ethan Bier provided the answer by applying CRISPR technology, a tool that allows researchers to edit genes easily by cutting them with protein ‘scissors’ and making it possible to delete, input or edit genes. By editing the malaria-resistant mosquitoes genes further, Bier was able not only to edit out malaria, but also ensure these resistant mosquitoes would breed more successfully than those still susceptible. Indeed, as Kahn recounts, Bier was so successful in manipulating the gene pool that when he carried out an experiment with one mating malaria-resistant pair mixed with 30 ordinary mosquitoes, out of the 3,800 mosquitoes born, all ended up carrying the malaria resistant gene. But how was this feat possible?
‘this resulted not only in the gene being able to pass on, but indeed, to pass on so effectively that Bier’s experiment violated Mendelian genetics..’
As Kahn explains, it is possible to not only use CRISPR to insert genes, but also to input the ability of CRISPR itself to copy and paste genes into the genes itself, via a gene drive. Effectively, this means that by inserting the CRISPR gene into germline cells, the cells that possess genetic material to be passed down to offspring, they will automatically copy and paste the new gene into both the subjects chromosomes. This resulted not only in the gene being able to pass on, but indeed, to pass on so effectively that Bier’s experiment violated Mendelian genetics, the principle that a baby will inherit half of its DNA from each parent, male and female. By inserting the ability for the gene to copy and paste itself into the resistant mosquitoes chromosomes, Bier’s made it possible for all the mosquitoes to come out with the resistant gene, even if one of the parents was still susceptible to the malaria parasite.
Yet there is a dark side to this success story. While the achievement itself is impressive, it highlights the danger of the success of genetic mutations and the implications this could have on the outside world. To quote Kahn ‘normally when we mess around with an organism’s genes, we make that thing less evolutionary fit’, meaning that they ensure their genetically altered organism cannot survive and overtake those found naturally in the wild if it happened to escape.
These mosquitoes however present a use of gene editing technologies where the edited organisms are far superior to their natural counterparts in terms of reproducing. Though this is precisely what this particular experiment desired, it does raise alarm bells for future experiments where such a side affect could actively be a hindrance to the natural world, irrevocably altering an entire species for the worse rather than better.
Given the ability of many organisms to travel great distances, any accidental release could not be contained. More worrying than this, these edited genes have the ability to be interbred with other species, spreading the problem further. While this may not be such a problem for eliminating the ability of the malaria parasite to be transmitted to humans, this could be a very different story if a species has been edited to be eradicated altogether.
Before you are put off the idea completely however, Kahn implores you keep this in mind. While the mosquito experiment was a success, it is still difficult to engineer a trait that could be seen as destructive, even with CRISPR technology. Second, gene drives only work in sexually reproducing species, so we cannot engineer viruses or bacteria in this way to produce some kind of biological weapon. Third, even if an accident were to happen, and such edited organisms be released, it is ‘theoretically’ possible to overwrite the changes made in the first gene drive to eradicate the problematic edits.
‘nevertheless, the progression of our ability to play god still holds a worrying number of questions for the future’
Nevertheless, the progression of our ability to play god still holds a worrying number of questions for the future. Should we be allowed to use such technology, particularly with the potential negative side affects? How can we put safeguards in place to prevent the spread of an accidental release? While Kahn cannot answer these questions herself, she advocates talking honestly about the benefits and drawbacks of gene editing. Despite the drawbacks, she is confident that gene editing may lead the way to combat serious problems facing our society. As she notes, while gene drives have risks, gene editing has the possibility to eradicate malaria without the side affects that current prevention techniques such as spraying pesticides have on other species not causing harm.
While doubts and objections will remain around the use of gene editing, the potential benefits it may bring can outweigh the risks. I leave you with Kahn’s closing remark to ponder. ‘It can be frightening to act, but sometimes, not acting is worse.’ Perhaps , in the case of malaria eradication, this is something we need to remember.