Crispr-Cas9

Easy DNA Editing Will Remake the World. Buckle Up.

A little bit of this and a little bit of that. A new and cheap way to implement genetic engineering, and a way to bypass the usual rules of population genetics.

The stakes, however, have changed. Everyone at the Napa meeting had access to a gene-editing technique called Crispr-Cas9. The first term is an acronym for “clustered regularly interspaced short palindromic repeats,” a description of the genetic basis of the method; Cas9 is the name of a protein that makes it work. Technical details aside, Crispr-Cas9 makes it easy, cheap, and fast to move genes around—any genes, in any living thing, from bacteria to people. “These are monumental moments in the history of biomedical research,” Baltimore says. “They don’t happen every day.”

ANY GENE TYPICALLY has just a 50–50 chance of getting passed on. Either the offspring gets a copy from Mom or a copy from Dad. But in 1957 biologists found exceptions to that rule, genes that literally manipulated cell division and forced themselves into a larger number of offspring than chance alone would have allowed.

A decade ago, an evolutionary geneticist named Austin Burt proposed a sneaky way to use these “selfish genes.” He suggested tethering one to a separate gene—one that you wanted to propagate through an entire population. If it worked, you’d be able to drive the gene into every individual in a given area. Your gene of interest graduates from public transit to a limousine in a motorcade, speeding through a population in flagrant disregard of heredity’s traffic laws. Burt suggested using this “gene drive” to alter mosquitoes that spread malaria, which kills around a million people every year. It’s a good idea. In fact, other researchers are already using other methods to modify mosquitoes to resist the Plasmodium parasite that causes malaria and to be less fertile, reducing their numbers in the wild. But engineered mosquitoes are expensive. If researchers don’t keep topping up the mutants, the normals soon recapture control of the ecosystem.

Push those modifications through with a gene drive and the normal mosquitoes wouldn’t stand a chance. The problem is, inserting the gene drive into the mosquitoes was impossible. Until Crispr-Cas9 came along.

Emmanuelle Charpentier did early work on Crispr.Today, behind a set of four locked and sealed doors in a lab at the Harvard School of Public Health, a special set of mosquito larvae of the African species Anopheles gambiae wriggle near the surface of shallow tubs of water. These aren’t normal Anopheles, though. The lab is working on using Crispr to insert malaria-resistant gene drives into their genomes. It hasn’t worked yet, but if it does … well, consider this from the mosquitoes’ point of view. This project isn’t about reengineering one of them. It’s about reengineering them all.

8 thoughts on “Crispr-Cas9

  1. That’s rather cool. I read Burt’s suggestion in his and Trivers’s excellent Genes in Conflict a few years back. Though I always worry about unintended consequences.

  2. Allan Miller: Though I always worry about unintended consequences.

    Yes. When Plasmodium adapts to the new mosquitoes will it be a much nastier organism?

  3. The lab is working on using Crispr to insert malaria-resistant gene drives into their genomes. It hasn’t worked yet, but if it does … well, consider this from the mosquitoes’ point of view.

    Um, they’d lose parasites. If anything, it might mean a good many more mosquitos, albeit ones that didn’t spread malaria.

    But if God is engineering P. falciparum like Behe says, how could we ever expect to win? Could be that’s why it hasn’t worked so far…

    Glen Davidson

  4. GlenDavidson: Um, they’d lose parasites. If anything, it might mean a good many more mosquitos, albeit ones that didn’t spread malaria.

    That would be a win win, except for all the itchy humans. Bats and birds that feed on mosquitos would be happy.

    Does anyone miss Smallpox?

  5. Raises an interesting ethical question. If you can use a HEG to drive resistance through mosquitoes, why not do the same in humans … ? (Apart from the painfully slow generation times, obviously. “Thanks to this new technology, malaria will be a thing of the past in 40,000 years”)

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