Scientists have been editing the genome of human embryos, a world first.
Chinese scientists have been editing the genome of human embryos, a world first which has set off an debate over genetic engineering.
A team led by Junjiu Huang, a gene-function researcher at Sun Yat-sen University in Guangzhou, published its results recently in an on-line journal, Protein & Cell. Their aim was to modify the gene for β-thalassaemia, a potentially lethal blood disorder, with a gene-editing technique known as CRISPR/Cas9. They used non-viable human embryos from IVF clinics. The idea was to eliminate the gene in a one-cell embryo so that it would develop into a child who would not suffer the disease.
From a technical point of view, the results were disappointing and Huang said that the technique is not currently suitable for medical use. The reseachers injected 86 embryos and examined them after 48 hours when they had grown to 8 cells. Of these, 71 survived, 54 were analysed. Only 28 had successfully spliced the target gene, but only a fraction of these contained the correct replacement gene. They also found that there were a number of “off-target” mutations somehow caused by CRISPR/Cas9.
“If you want to do it in normal embryos, you need to be close to 100%,” Huang told Nature News. “That’s why we stopped. We still think it’s too immature.”
What about the ethics of the technique? Since changes to the embryo genome are heritable, they will be passed on to the next generation. This opens the door to the controversial issues of designer babies and human enhancement.
Some observers were highly critical. “No researcher has the moral warrant to flout the globally widespread policy agreement against altering the human germline,” Marcy Darnovsky, executive director of the non-profit Centre for Genetics and Society in Berkeley, California.
In an editorial in Nature in March, when Huang’s research was only a rumour, several scientists published a call for a moratorium on experiments like theirs:
“In our view, genome editing in human embryos using current technologies could have unpredictable effects on future generations. This makes it dangerous and ethically unacceptable. Such research could be exploited for non-therapeutic modifications. We are concerned that a public outcry about such an ethical breach could hinder a promising area of therapeutic development, namely making genetic changes that cannot be inherited.
“At this early stage, scientists should agree not to modify the DNA of human reproductive cells. Should a truly compelling case ever arise for the therapeutic benefit of germline modification, we encourage an open discussion around the appropriate course of action.”
In Britain, it was hard to find scientists who were opposed, let alone alarmed, by the news. “It’s no worse than what happens in IVF all the time, which is that non-viable embryos are discarded,” says John Harris, a utilitarian bioethicist at the University of Manchester, UK. “I don’t see any justification for a moratorium on research.”
One of the UK’s leading stem cell researchers, Robin Lovell-Badge, was almost enthusiastic. “I disagree with a moratorium, which is in any case unlikely to work well,” he said. “Indeed I am fully supportive of research being carried out on early human embryos in vitro [in culture/in the lab], especially on embryos that are not required for reproduction and would otherwise be discarded.”
And Dr Anna Smajdor, a bioethicist at the University of East Anglia, said: “There is a whiff of hypocrisy about the moral outrage over reports that Chinese scientists have been modifying the DNA of embryos. Here in the UK we have given the go ahead to modifying the DNA of babies who will transmit these changes indefinitely to their offspring. The Chinese have tweaked DNA in embryos never destined to be born.”
In any case, it seems more than likely that this research will continue in China. CRISPRs have become a standard tool in laboratories around the world and the potential for interesting research is enormous. According to Nature, at least four groups are working on genetic engineering of human embryos in China.
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