Genes in sexually reproducing organisms typically have a 50 percent chance of being inherited. Some genes have naturally evolved methods of improving these odds; these are called “gene drives.” The genomes of almost every sexually reproducing species contain either active gene drives or remnants of drives. Ten years ago, Austin Burt of Imperial College London proposed designing drives to alter genes in natural populations of mosquitoes. But the difficulty of precisely editing genomes to create engineered drives stymied the realization of Burt’s vision. This is about to change.
The recent development of a powerful genome editing tool called CRISPR/Cas9 allows scientists to insert, replace, delete, and regulate genes. Since Cas9 can cut essentially any gene and works in most organisms, it could in principle be used to make gene drives in any sexually reproducing organism. CRISPR gene-drive laboratory experiments in yeast and mosquitoes are under way. Development of purpose-built gene drives in the next few years is very likely.
Unlike most applications of biological engineering, gene drives have the potential to propagate changes throughout populations of organisms with short reproduction cycles. And that creates the potential for powerful positive and negative effects. Gene drives could be used to make it harder for mosquitoes to carry malaria and dengue fever, or they could be used to suppress populations of invasive species such as Asian carp. But they could also be misused—for example, to increase the ability of insects to carry diseases, or to suppress populations of economically significant crops and livestock.
I’m less worried about those kinds of deliberate misuses than I am by the unintended environmental consequences. The truth is that we don’t fully understand the interactions between gene drives and the environment, or the mutations possible in drive-bearing organisms.
In July, along with other researchers from MIT, Harvard, and other institutions around the world, I published an article in Science that recommends 10 steps biological engineers, environmental scientists, and policy analysts need to take before releasing gene drives. These include research to improve our understanding of drives’ properties and side effects, measures to address identified risks, and hedges in case the initial assessments are wrong.
Gene drives don’t fit into any existing regulatory frames. There are no environmental regulations that would cover the use of gene drives consistently around the world. So the bottom line is that we need to move cautiously. Scientists need time to evaluate the risks and develop safeguards. Legislators need time to evaluate regulatory arrangements. And the public deserves time for an informed debate.
Kenneth Oye is an associate professor of political science and engineering systems at MIT.