Genetically modified organisms hold a lot of promise for creating hardier crops and faster growing fish, but even supporters are concerned about invasive organisms running wild. If a faster, better, stronger strain of bacteria escaped the lab, how would we stop it? Now, scientists have come up with a new solution: self-destructing DNA.
Published today in Nature Communications, the system would use cutting-edge gene-editing tools to erase DNA as soon as a given organism leaves its designated area, destroying both the cell and its genetic information. The result is a so-called "kill switch," eradicating any experimental or proprietary organisms before they can escape into the wild.
"When the system is turned on it will erase that [modified] DNA."
As GMOs become more ambitious and widespread, researchers have grown increasingly interested in containment techniques. In February, a group of Harvard scientists published a kill-switch system that used amino acids toward the same end. Under that system, synthetic organisms would die without regular access to a specific amino acid, found only in the containment area. As a result, no cells would be able to survive long in the wild, cutting down the risk of an accidental release, as well as the inherent danger of creating and experimenting with new self-replicating organisms.
The system published today goes even further, targeting the DNA itself. Not only will the cells die, but the genetic information used to create them will be obliterated without a trace. That's particularly useful for commercial GMOs, since companies treat their GMOs’ genes as trade secrets. The system is even precise enough to target specific portions of DNA, so a company could delete only the modified genes, leaving the others untouched.
"You can imagine, if you have an organism that has a bunch of modified organisms that are proprietary," says Christopher Voigt, an MIT bioengineer who worked on the study. "You just plug in all the systems you want erased, and when the system is turned on it will erase that DNA and largely leave the other DNA in place."
99 percent of the cells were dead within 15 minutes
The new system achieves that precision through CRISPR, a gene-editing system that's seen as one of the most exciting current developments in biotech. CRISPR is a collection of naturally occurring molecules that, when deployed right, can be used to cut out and replace sections of a cell's DNA. Researchers have already used the system to modify living genes and even edit the DNA of human embryos, generating significant controversy in bioethics circles.
The kill-switch system focuses on the DNA-removal part of CRISPR, deleting genes entirely rather than replacing them. Researchers tested out the system in a limited model, using E. coli bacteria and pre-established trigger mechanisms. If the test model came in contact with a specific sugar molecule called arabinose, it would trigger the CRISPR system to delete a specified portion of the E. coli DNA, resulting in the death of the cell. It took roughly two hours for the triggers to kick in after the arabinose was added, but after that, 99 percent of the cells were dead within 15 minutes.
The current version is only a proof of concept, and researchers expect more challenges as the system grows more complex. The arabinose trigger was chosen because it works well in the lab, but a field-ready version of the system would likely have a much more complex trigger that could have more trouble producing reliable results. Voigt said one possibility would be a system triggered by light, which would allow more aggressively modified organisms to be deployed in closed vats like fermenters. Still, ensuring that light triggers the kill-switch as reliably as arabinose will require a lot more research. "Putting it as part of a larger system is going to be key," Voigt says, "one that's able to respond to real environmental conditions."