When Chinese researchers reported using a technique called CRISPR/Cas9 to edit the genome of human embryos this past April, they sparked a worldwide debate over how this technology could (or should) be used. Scientists expressed legitimate fears: What are the side effects? Will this open the floodgates to designer humans?
The world’s foremost geneticists, biotechnologists, and bioethicists gathered in Washington, D.C., in December to address those questions and map the future of human-gene editing.
CRISPR isn’t the first genome-editing tool, but it is by far the best. Prior to its discovery in 2013, scientists relied on two methods—zinc finger nuclease (ZFN) and TALENS—to splice DNA at a specific location. With CRISPR, scientists can make precise changes much more rapidly, a capability that promises to halt certain diseases and revolutionize the treatment of others.
Sickle cell anemia, for example, is caused by a single mutation in the beta globin gene. Gang Bao, a bioengineer at Rice University, is among the researchers working with CRISPR to edit out this mutation. The gene will be modified in a somatic cell, which means that any change made to it affects only the individual and can’t be inherited. “Those modified stem cells have a finite life span,” Bao says, “and won’t be passed on to the patient’s children.”
What gives scientists pause are edits to germline cells (i.e., sperm and eggs). It’s one thing to pass down a cure for a disease; it’s another to propagate unintended side effects. CRISPR can accidentally edit genes that have a DNA sequence similar to its target, as happened with the Chinese team’s embryos. “If off-target effects accumulate in germline cells,” Bao says, “there might be permanent changes in the human genome.”
In order to better assess the risks, scientists at the December summit agreed that basic research should progress. But they essentially called for a moratorium on editing human embryos for pregnancies. George Daley, director of the stem cell transplantation program at Boston Children’s Hospital, says CRISPR is still too unpredictable for a baby to be brought to term. “But the science is essential for informing the debate,” he says.
Such conversations can’t just occur within the walls of a conference center. As CRISPR’s power comes into focus, public discussion should proceed in tandem. Without societal buy-in, Daley says, gene-editing research could be misunderstood or condemned—and that would undermine its many potentially life-changing benefits.
This article was originally published in the March/April 2016 issue of Popular Science.
