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Powerful new way to edit DNA realized

By New York Times News Service
March 3, 2014 at 4:48 p.m.


In the late 1980s, scientists at Osaka University in Japan noticed unusual repeated DNA sequences next to a gene they were studying in a common bacterium. They mentioned them in the final paragraph of a paper: "The biological significance of these sequences is not known."

Now their significance is known, and it has set off a scientific frenzy.

The sequences, it turns out, are part of a sophisticated immune system that bacteria use to fight viruses. And that system, whose very existence was unknown until about seven years ago, may provide scientists with unprecedented power to rewrite the code of life.

In the past year or so, researchers have discovered that the bacterial system can be harnessed to make precise changes to the DNA of humans, as well as other animals and plants.

This means a genome can be edited, much as a writer might change words or fix spelling errors. It allows "customizing the genome of any cell or any species at will," said Charles Gersbach, an assistant professor of biomedical engineering at Duke University.

Already the molecular system, known as CRISPR, is being used to make genetically engineered laboratory animals more easily than could be done before, with changes in multiple genes. Scientists in China recently made monkeys with changes in two genes.

Scientists hope CRISPR might also be used for genomic surgery, as it were, to correct errant genes that cause disease. Working in a laboratory - not, as yet, in actual humans - researchers at the Hubrecht Institute in the Netherlands showed they could fix a mutation that causes cystic fibrosis.

But even as it is stirring excitement, CRISPR is raising profound questions. Like other technologies that once wowed scientists - like gene therapy, stem cells and RNA interference - it will undoubtedly encounter setbacks before it can be used to help patients.

It is known, for instance, that CRISPR can sometimes change genes other than the intended ones. That could lead to unwanted side effects.

The technique is also raising ethical issues. The ease of creating genetically altered monkeys and rodents could lead to more animal experimentation. And the technique of altering genes in their embryos could conceivably work with human embryos as well, raising the specter of "designer babies."

"It does make it easier to genetically engineer the human germ line," said Craig C. Mello, a Nobel laureate at the University of Massachusetts Medical School, referring to making genetic changes that could be passed to future generations.

Still, CRISPR is moving toward commercial use. Five academic experts recently raised $43 million to start Editas Medicine, a company in Cambridge, Mass., that aims to treat inherited disease. Other startups include Crispr Therapeutics, which is being formed in London, and Caribou Biosciences in Berkeley, Calif.

Agricultural companies might use CRISPR to change genes in crops to create new traits. That might sidestep the regulations and controversy surrounding genetically engineered crops, which generally have foreign DNA added.

It is likely to be a few years before CRISPR is tested in people. For now, there is a lot more to learn about it.

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