Gene editing made great strides this month when scientists reported success using a technique called CRISPR — Clustered Regularly Interspaced Short Palindromic Repeats — to correct a serious, disease-causing mutation in human embryos. Researchers fixed a mutation that leads to hypertrophic cardiomyopathy, a relatively common inherited disease of the heart muscle that affects about 1 in 500 people. The public response was wildly enthusiastic. But any new technology can spur confusion and hyperbole, and this one is no exception. Here are five myths about what CRISPR can and can’t do.
In February 2016, one CRISPR critic predicted in Mother Jones, “We are this close to ‘designer babies.’ ” This month, biologist Richard Dawkins mused that the genetically edited “designer babies ” on the horizon shouldn’t be any more worrisome than children who are pushed by their parents to hone their natural talents.
But CRISPR is not on the cusp of creating a super-race for one main reason: We don’t know how to do that. We don’t know how to build baby Einsteins or order up a finely chiseled and uber-flexible Simone Biles, because there is no single “smart gene” or “spunky, lithe gymnast gene.”
Much of what goes on inside our bodies and our brains is influenced by a combination of genes and environment, nature and nurture. Beauty, athleticism and musicality don’t hinge on a single sequence of base-pairs. Instead, these characteristics are considered “complex traits” that are shaped by the input of multiple genes, along with lifestyle and environmental factors. This is especially true of intelligence. Studies, many of which have tracked adopted children and twins, have indicated that just 50 percent of the variation in intelligence among people can be chalked up to genetics.
The Genetic Literacy Project, a group dedicated to increasing the public’s understanding of gene research, wrote this year that “parents worried about passing on genetic disorders to their children have hope: Gene editing.” Likewise, an Australian newspaper greeted this month’s CRISPR news with an ebullient headline: “Hope for parents as science deletes mutant killer gene.”
While it’s undeniable that the ability to home in on and fix a genetic error would enable some would-be parents to sidestep the possibility of transmitting a disease to their offspring, gene editing is not the only option in such cases. Preimplantation genetic diagnosis has been used for decades to help couples who go through IVF ensure that they select healthy embryos from among those fertilized in a clinic. The technology has allowed carriers of genetic disease to conceive unaffected children, starting in 1991, when it was first used to avoid cystic fibrosis.
In the event that not enough healthy embryos are created during the IVF process, CRISPR could one day lend a helping hand and repair defective embryos, giving a couple more choices. Still, an essay that accompanied this month’s research report, published in Nature, concluded that “embryo genetic testing during IVF remains the standard way to prevent the transmission of inherited diseases in human embryos.”
“I think it’s really likely that in the not-too-distant future it will cure genetic disease,” Jennifer Doudna, one of the scientists behind CRISPR, said at a recent conference . The Chicago Tribune’s editorial board shared the sentiment in April 2016, claiming that “for some people born with debilitating genetic diseases, scientists could give them relief from their symptoms — and maybe even cure them in the not-too-distant future.”
Not so fast. In the United States, a human-embryo research ban has been in place since 1996, prohibiting the use of federal money to support research in which embryos are created, destroyed or discarded. Recent embryo-editing studies were paid for by universities and foundations, but the lack of federal funding slows the science down.
Moreover, just because one experiment was successful doesn’t mean the next one will be. In fact, even though most embryos were successfully repaired in the recently reported study, more than a quarter weren’t. Another concern is that CRISPR may solve one problem while unintentionally creating another. A challenge is to avoid “off-target” edits or “mosaicism,” a condition that occurred in previous attempts, in which CRISPR successfully edited the specific mutation in some but not all cells. The technique needs much more practice before it’s ready for widespread public use.
“There is widespread interest in using CRISPR, which allows the targeted editing of specific genes, to potentially end genetic disease in humans,” Vice reported in December 2015 . A more recent headline from Wired cheered that “CRISPR may cure all genetic disease — one day.”
While that would certainly be nice, it’s impossible to edit out all genetic diseases, because not all genetic diseases are simply inherited. There are about 10,000 single-gene disorders that we’ve discovered — diseases caused by a specific, individual gene mutation. But there are thousands more that are caused by multiple genetic factors. Moreover, some genetic conditions are the result of new, spontaneous changes in DNA, called “de novo” mutations.
Cancer is a prime example. While some types of cancer can be inherited, many others don’t appear to have a primary genetic component, and often respond to a variety of environmental factors and other outside causes. Ending genetic disease is a worthy goal, but an extremely complicated one that will require more than eliminating heritable disease.
Recent advances in gene-editing technology have made the process cheaper , causing some commentators to predict a quick CRISPR proliferation on the horizon. “Gene Editing Is Now Cheap and Easy,” one 2015 headline claimed. A Wall Street Journal article concerned with amateurs imitating CRISPR’s technology likewise fretted that “DIY gene editing” is “fast, cheap — and worrisome.”
CRISPR may be cheaper than it once was, but it’s hard to foresee a future when all prospective parents who could benefit will be able to afford it. As a rule, genetic technologies are very expensive: Patients don’t pay just for the supplies used, but for doctors’ time, labor and equipment, often over a number of appointments. You don’t have to look any further than IVF to be reminded that using science to have babies costs a lot of money: The median cost of a single IVF cycle is $7,500. It is unclear whether insurance would cover CRISPR gene editing, but it’s highly unlikely considering that few pay for preimplantation genetic diagnosis — or IVF in the first place.
If CRISPR were to become a safe, accepted embryo-editing technique, it’s likely that only the well-to-do would be able to afford it, essentially making genetic diseases into diseases of poverty. It’s not too hard to imagine a wildly disparate economic playing field — a “dystopian vision,” in the words of StatNews writer Jim Kozubek, in which “these treatments will be available to only the wealthiest among us who can pay for them.”