Benefits and dangers in altering our evolutionary trajectory
The implications of revolutionary ‘gene-drive’ technology are both magnificent and worrisome, writes Stephen Fleischfresser.
The CRISPR gene-editing technology is once again flexing its muscle. Not only does it promise a way to rewrite the genome of living organisms and bring about the de-extinction of long dead species, including mammoths, but now might deliver profound breakthroughs in the areas of public health and conservation.
The Australian Academy of Science has released a discussion paper on the future of synthetic ‘gene drive’ technology in Australia. With domestic and international research proceeding at such a pace that widespread use of the technology is expected within three to five years, the academy says now is the time to start examining the implications.
Those implications are startling: magnificent and worrisome in equal measure.
Gene drives are technologies that distort the normal rules of Mendelian inheritance and evolution, ‘driving’ a particular gene to spread through a target population. It is a way to genetically manipulate an organism and force that change to spread down the generations.
Two copies of a gene are present in individuals of sexually reproducing species, one copy inherited from each parent, each having a 50% chance of being passed down to offspring. Gene drives alter this probability upwards; sometimes slightly over 50%, sometimes much higher.
The idea is an old one, but the technological capacity to make it a reality is very new.
Using what is called a ‘drive cassette’, containing the altered gene researchers want to insert into a organism, cellular natural repair mechanisms can be provoked to copy the cassette into the organism’s DNA. Two identical copies of the gene are thus incorporated into the genome, along with the cassette. Together these insertions vastly increase the chance of the gene being passed on in subsequent reproduction
In sexually reproducing organisms with short generation spans this could mean the inserted gene could spread through the population to become species-typical in a time stunningly short compared with the pace of natural selection.
The technology becomes truly staggering when one considers the applications. The academy’s discussion papers says it “could wipe out malaria-carrying mosquitoes, cane toads or other pests and plant diseases within years”.
Genes that reduce mosquitoes’ susceptibility to being infected by or transmitting diseases could be forced through the population: or a gene that alters sex ratio, reducing population growth, could be introduced. Such population suppression could be aimed at any pest organism researchers desire.
The paper’s lead author, Ary Hoffman of the University of Melbourne’s Bio21 Institute, says the technology “has enormous potential to control disease, increase agricultural productivity and to improve quality of life, particularly for those living in developing countries”.
It’s a powerful technology, with the capacity to alter the evolutionary trajectory of species and to warp the web of ecological relations in an unprecedented way.
With that power comes risk and uncertainty. As the report notes, “no synthetic gene drives have yet been released into wild populations,” so much remains untested.
The authors nonetheless express confidence the benefits outweigh the risks and have called for further research to be conducted in highly secure laboratories. Multiple containment, reversal and vaccination methods have been devised in the event of an uncontrolled release into wild populations.
Importantly, any future decisions on release of gene drives would be carried out on a case-by-case basis, taking into account environmental, ecological and evolutionary concerns.
The academy seems to be taking a cautious approach to getting it right.
As its president, Andrew Holmes, has said, “once gene drives are released into wild populations in other countries, they will inevitably reach Australia”.
One way or another, genes drives will be reality soon, and we best be prepared.