These genetic tools pose fraught biological and ethical questions—but how much call for them is there anyway?by Philip Ball / October 29, 2019 / Leave a comment
Gene editing of human embryos for reproductive purposes—a medical technology often said to promise (or threaten) “designer babies”—is more or less upon us already. It has arrived far sooner than many researchers imagined, and sooner than many wanted. And recent developments show that there may be more just around the corner.
To edit the genome of an embryo, biochemical tools snip out a section of its DNA (typically a gene or part thereof) before implantation, and an altered segment is inserted in its place. This was first done to human embryos in 2015, but not for reproductive purposes via IVF. Most scientists in the field had assumed the latter was still a long way off—until Chinese biologist He Jiankui announced in November last year that he had used a gene-editing technique called Crispr to modify the genes of twin baby girls born by IVF, in an attempt to give them resistance to infection by HIV.
Notwithstanding the shock and condemnation that greeted this announcement by most other researchers in the field, Russian biologist Denis Rebrikov now says he hopes soon to get approval to use Crispr to modify embryos for IVF, to change a gene mutation that would otherwise cause deafness.
Meanwhile, a new gene editing technique has just been unveiled by a team from the Broad Institute of Harvard and the Massachusetts Institute of Technology that seems to overcome much of the imprecision incurred by Crispr—a key reason why Crispr is widely considered still too risky for use in human reproduction. With better gene-editing tools potentially on hand, the safety objections to using it in this context might lose some of their force.
The main premise of gene editing for human embryos is that it could correct genetic mutations that cause disease. Rebrikov is planning to use Crispr to target one of these in a gene called GJB2, where the mutant form leads to severe hearing impairment. As with many impairment- or disease-linked genes, the defective form of GJB2 is recessive, meaning that only if a person has it in both copies of their genome (inherited from the biological mother and father) will they suffer the consequences—in this case, deafness that requires a cochlear implant or hearing aid. If at least one parent has a “healthy” copy of the gene, it is possible in principle to select an IVF embryo for implantation that also possesses it, an approach…