With Gene-Altering Schemes, Be Careful What You Wish For


The short-tailed weasel, or stoat, decimated native bird populations after it was introduced to New Zealand. Altering the genes of invasive animals might save threatened species, scientists said, but could also have devastating consequences. Credit DeAgostini, via Getty Images

Two days ago we were intrigued by the notion; today, not so much. Is it a cat fight between two of the science writers most often linked to in these pages? Or perhaps it is an example of how scientific consensus is built:

‘Gene Drives’ Are Too Risky for Field Trials, Scientists Say

In 2013, scientists discovered a new way to precisely edit genes — technology called Crispr that raised all sorts of enticing possibilities. Scientists wondered if it might be used to fix hereditary diseases, for example, or to develop new crops.

One of the more intriguing ideas came from Kevin M. Esvelt and his colleagues at Harvard University: Crispr, they suggested, could be used to save endangered wildlife from extinction by implanting a fertility-reducing gene in invasive animals — a so-called gene drive.

When the genetically altered animals were released back into the wild, the fertility-reducing gene would spread through the population, eradicating the pests.

The idea appealed to conservation biologists who had spent decades fighting a losing battle against exotic species. Some labs began running preliminary experiments. But now, three years later, Dr. Esvelt wishes he hadn’t broached the idea.

“I feel like I’ve blown it,” Dr. Esvelt, now an assistant professor at M.I.T., said in an interview. Championing the notion was “an embarrassing mistake.”

His regret arises from a study that he and his colleagues published on Thursday on the preprint bioRxiv server.

They created a detailed mathematical model describing what happens following the release of Crispr-altered organisms. And they discovered an unacceptable risk: Altered genes might spread to places where the species isn’t invasive at all, but a well-established part of the ecosystem.

Dr. Esvelt, who also is a co-author of a commentary on the study’s implications in the journal PLOS Biology, and his colleagues still think it’s worth investigating gene drives to save threatened species. But researchers will have to invent safer forms of the technology first.

Dr. Esvelt and other researchers have also been investigating the possibility of using gene drives to eradicate diseases. The most advanced of these projects seeks to wipe out malaria-carrying mosquitoes. These projects are still viable but, Dr. Esvelt warned, scientists now must be mindful of just how powerful gene drives may become.

“It’s an important contribution,” said John M. Marshall, a mathematical biologist at the University of California, Berkeley, said of the new research. “A study like this is the beginning of a formal analysis we need.”

Crispr makes it possible to build molecules that can find a particular sequence of DNA inside a cell. The molecules then snip out the sequence, allowing it to be replaced by a different one.

The technique might make it possible to introduce not just a gene engineered to reduce fertility in, say, an invasive weasel, but also the genes for the Crispr molecules themselves. Then the weasel would gene-edit itself…

Read the whole story here.

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