Caution Urged over Editing DNA in Wildlife
Caution Urged over Editing DNA in Wildlife
Rapid alteration of gene pools could fight disease—and
harm ecosystems
By Heidi Ledford and Nature magazine | August 4, 2015
“Crap!” That was the first word out of Kevin Esvelt’s
mouth as he scanned a paper published in Science last March. The work described
the use of a gene-editing technique to insert a mutation into fruit flies that
would be passed on to almost all of their offspring. Although intriguing, the
report made Esvelt feel uneasy: if engineered flies escaped from a lab, the
mutation could spread quickly through a wild population.
But that was exactly what exhilarated molecular biologist
Anthony James at the University of California, Irvine. “Holy mackerel!” he
wrote to the study’s authors. “Can we use it in mosquitoes?”
On July 30, the US National Academy of Sciences,
Engineering, and Medicine (NAS) held the first in a series of meetings meant to
find ways to balance the promise and perils of the technique, called ‘gene
drive’. The method can rapidly modify not just a single organism but a whole
population, by inserting a desired genetic modification into an organism along
with DNA that increases the rate at which the change is passed to the next
generation. The technique could be used to render mosquitoes unable to carry
malaria parasites or to wipe out harmful invasive species, but it could also
have unanticipated environmental costs and might be impossible to reverse.
“Once this is out there, you cannot call it back,” says Walter Tabachnick, a
population geneticist at the University of Florida in Vero Beach.
The idea of gene drive has been around for more than a
decade. But its practicality was given a huge boost around three years ago with
the arrival of CRISPR, a gene-editing technique that allows precise changes to
an organism’s DNA.
The Science paper, by developmental biologist Ethan Bier
and his student Valentino Gantz at the University of California, San Diego,
used CRISPR to insert a modification into genes on both chromosomes in a pair,
so that when the flies bred, they would pass the modification on to practically
all of their offspring.
The work came out of a desire to develop a system that
would make it easier to study genetic changes in organisms that are difficult
to breed in the laboratory. Because CRISPR has been shown to work in a wide
range of creatures, researchers hope one day to be able to engineer wild
populations in much the same way.
Call for concern
Mindful of both the potential and the risks, Esvelt, a
bioengineer at Harvard Medical School in Boston, Massachusetts, brought
together a group of scientists to write a Comment in Science, published last
week, laying out the need for multiple containment strategies for gene-drive
research that is done in the laboratory. Meanwhile, the NAS meeting marks the
start of a 15-month search for ways to minimize the risk in advance of field
releases. Because no one is known to have made CRISPR work in mosquitoes—the
mostly likely organism for the application of the technology—the committee has
some time to do its work.
But there is still urgency, noted Todd Kuiken, who
explores the interface of science and policy at the Wilson Center, a think tank
in Washington DC. CRISPR gene-drive technology is developing at a breakneck
pace, and has the potential to dramatically alter ecosystems in unexpected
ways. At the meeting, Kuiken used the invasion of Asian carp into some US lakes
as an example of how little is known about some wild ecosystems. “While this is
an invasive species, it’s also an established species,” he says. “I don’t think
we have a good understanding of how we evaluate what happens when we remove a
species from as large an ecosystem such as this.”
Meanwhile, Esvelt and his colleagues are studying the
CRISPR gene-drive system in the nematode Caenorhabditis elegans to learn more
about what happens to a population as engineered DNA is passed down through
generations, accumulating mutations as it goes. They are also testing ways to
make sure that a gene drive can be countermanded once it has been set loose.
These issues need immediate attention, says geneticist
Daniel Wattendorf at the US Defense Advanced Research Projects Agency (DARPA)
in Arlington, Virginia. Security concerns may mean that DARPA needs to start
working on the technology before guidelines are drawn up, he adds.
And Tabachnick remains concerned that these preparations
may not suffice. “How do you test such a system, and how do you do it safely?”
he asks. “I’m not convinced that any of this work could ever possibly provide
the assurance of safety that one might demand.”
This article is reproduced with permission and was first
published on August 4, 2015
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