Gene Drives – Will Conqueror Biomolecular Bots Dictate a New Book of Life?
By Guest Blogger,
Tyler Kokjohn, Ph.D.
A new DNA engineering technique known by the strange name CRISPR-Cas9 allows scientists to edit the genomes of living cells with unprecedented ease and precision (1). The method has only been in wide use for a few years, so it is hard to envision all the breakthroughs it will foster. However, it is already clear the implications will extend far beyond the laboratory and clinic.
The CRISPR-Cas9 DNA editing system is versatile, but scientists have extended its capabilities by creating powerful new forms of this technology which function as gene drives (2). A gene drive disperses genetic alterations or DNA cargo rapidly through a population by overruling the normal patterns of inheritance. A recipient of a gene drive receives the complete genetic information needed to synthesize the enzymes and guide molecules required to edit pre-programmed DNA targets. This new genetic information is incorporated directly into the recipient genome and will be transmitted to all progeny during sexual reproduction. Because they will work automatically and are self-spreading after their release, gene drives may make it possible to edit the genetics of entire populations of wild animals to suit human specifications (3).
Gene drives may provide an effective means to control invasive species as well as a wide range of zoonotic diseases like malaria, dengue, Zika fever and Lyme disease (4). Despite the urgency, gene drives are wholly unproven control methods that must be tested to confirm their efficacy and safety. The problem with natural ecosystems is their innate complexity; everything literally is connected to everything else. That complexity can make it impossible to foresee adverse events and some issues only become apparent after the passage of considerable time. Even simple changes may create a chain reaction of ramifications. For example, the wide use of the nonsteroidal anti-inflammatory drug diclofenac in veterinary medicine was probably deemed to have few significant environmental impacts. However, while safe for many animals, vultures feeding on carcasses of diclofenac-treated animals developed lethal kidney failure due to deposition of uric acid (5). When vulture populations in India collapsed, feral dog populations expanded as this food source became available. An increased number of wild dogs seems to have been an important factor in a sudden surge of human rabies (5). That using diclofenac in veterinary medicine would result in a chain of events culminating in more human deaths from rabies would have been hard to predict before the fact.
Scientists involved with gene drive technology have undertaken proactive efforts to fully inform their colleagues and the general public about issues involved in its use (2). One general problem with released gene drives is that their impacts, good or bad, could become permanent. In fact, some propose creating ‘crash drives’ intentionally designed to change the species composition of ecosystems (6). Crash drives that interfere with reproduction might provide a precise means to eliminate undesired organisms like mosquitoes. Using and evaluating such potentially powerful technology will demand extraordinary care (2) because release of a crash drive might ultimately result in the deliberate extinction of an entire species. Assessing the benefits and risks of gene drives will be challenging because natural environments are complex, dynamic and sometimes just plain surprising.
Gene drives are immensely promising, potentially far-reaching tools. Their intended impacts on targeted species could range from tiny genetic tweaks to total annihilation. Predicting the full environmental consequences of their use is essentially impossible. Recently, concerns over whether fully autonomous weapons are a permissible military technology prompted serious discussion (7). The future use of gene drives warrants similar deliberation. Sovereign, self-spreading and as immortal as the species they will conquer, these invisible biomolecular bots could turn out to be more fearsome than killer robots. Unless we are careful or perhaps just plain lucky, freed or escaped gene drives could become DNA dictators empowered to rewrite the book of life.
(1) H. Ledford. 2016. CRISPR: Gene Editing is Just the Beginning. Nature, 7 March 2016. http://www.nature.com/news/crispr-gene-editing-is-just-the-beginning-1.19510
(2) K. M. Esvelt et al. 2014. Emerging Technology: Concerning RNA-guided gene drives for the alteration of wild populations. eLife 2014;3:e03401 https://elifesciences.org/content/3/e03401
(3) J. Lunshof. 2015. Regulate gene editing in wild animals. Nature 521:127 (14 May 2015) http://www.nature.com/news/regulate-gene-editing-in-wild-animals-1.17523
(4) R. Stein. NPR Morning Edition, 5 November 2015. http://www.npr.org/sections/health-shots/2015/11/05/451216596/powerful-gene-drive-can-quickly-change-an-entire-species
(5) C. Biondolillo. 2014. Scientists Call on Spain to Ban Vulture-killing Drug. Science, 28 March 2014. http://www.sciencemag.org/news/2014/03/scientists-call-spain-ban-vulture-killing-drug
(6) N. Wade. 2015. Gene Drives Offer New Hope Against Diseases and Crop Pests. New York Times, 21 December 2015. http://www.nytimes.com/2015/12/22/science/gene-drives-offer-new-hope-against-diseases-and-crop-pests.html?_r=0
(7) Author Anonymous. Killer Robots: The Case for Human Control. Human Rights Watch, 11 April 2016. https://www.hrw.org/print/288611
Also of interest on JayVay
https://jayvay.wordpress.com/2016/04/29/trust-them/ https://jayvay.wordpress.com/2016/04/19/titanic-opportunities/ https://jayvay.wordpress.com/2015/04/08/rewriting-all-the-rules-the-arrival-of-genomic-editing/