Originally developed in the 1960s for pest control, gene drives are a technology in which organisms are engineered to keep desired genes propagating within their population. There is much interest in further developing gene drives to prevent the transmission of diseases such as malaria and dengue fever through mosquitoes or other vectors. However, scientists and ethicists have raised concerns over the potential unchecked spread of gene drives across an entire population. With rising fear over the ecological impact and unpredictable ramifications of altering or removing an entire species, scientists are trying to engineer gene drives that could keep this gene spread in check and retain the option of restoring the natural species if necessary.
To address this problem, researchers at UCSD have engineered a novel gene drive in fruit flies. Their technology uses the idea of speciation, which is the process by which a group within a population evolves away from the original population until they can no longer reproduce with each other. The new gene drive, called SPECIES (Synthetic Postzygotic barriers Exploiting CRISPR-based Incompatibilities for Engineering Species), uses CRISPR gene-editing technology to introduce and maintain a genetic mutation in flies. The gene drive was engineered such that any offspring who lose the new mutation will die, thus ensuring the propagation of the desired gene across generations. Just as speciation occurs in the wild, the engineered flies have multiple changes to their genome that prevent them from mating with the natural species. As a result, population replacement with the gene drive only occurs when the release of SPECIES individuals exceeds a given threshold frequency in the population.
Thus, this newly developed SPECIES gene drive provides a way to control populations in a safe and reversible manner by limiting their threshold population below 50 percent. Because of the universality of CRISPR gene-editing tools, this approach can be applied to any target gene in any sexually reproductive organism. For example, SPECIES mosquitoes could be engineered to contain a gene that prevents them from transmitting malaria. While there are logistical challenges for the high release requirements of threshold-dependent systems, the SPECIES system enables the beneficial use of gene drives to control pest and disease burdens without the risk of uncontrollable spread.
Dr. Omar Akbari is an Assistant Professor at the University of California San Diego in the Division of Biological Sciences. Anna Buchman was a former Research Data Analyst at UCSD. Isaiah Shriner was a former undergraduate Research Assistant at UCSD.
Managing Correspondent: Lauren Davancaze
Press Articles: “Synthetic SPECIES developed for use as a confinable gene drive,” Phys.org
Original Journal Article: “Engineered reproductively isolated species drive reversible population replacement,” Nature Communications
Image Credit: Michael Morgenstern, ScienceNews