A group of biologists, led by the co-discoverer of the technique Jennifer Doudna, say that safety and ethical concerns over the use of the technology in the human germline must be addressed first.
The need for these discussions has taken on a new urgency amid rumours that such experiments are already underway, leading to fears that the technique could be used clinically in countries that lack stringent regulations.
As any germline changes introduced by the technique can be inherited, the researchers say that this crosses an ethical boundary. 'You could exert control over human heredity with this technique, and that is why we are raising the issue,' Dr David Baltimore, former president of California Institute of Technology and one of the authors of the letter published in Science, told the New York Times.
The advent of the CRISPR/Cas9 system has revolutionised the field of genetic engineering (see BioNews 730) – enabling easy and precise alterations of the genetic code. Since its discovery in 2012 it has been used in organisms ranging from yeast and flies to monkeys. And, if reports are true, several papers will be published imminently on its use in human embryos.
'In humans, it holds the promise of curing genetic disease,' write the scientists. However, they caution that despite these rapid developments, we do not understand the risks this technology might pose if used in germ cells or embryos.
'We worry about people making changes without the knowledge of what those changes mean in terms of the overall genome,' said Dr Baltimore. 'I personally think we are just not smart enough - and won’t be for a very long time - to feel comfortable about the consequences of changing heredity, even in a single individual.'
A similar warning is sounded by authors of a second article, published in Nature. They argue that even though CRISPR/Cas9 is lauded for its precision, we do not know if it could cause unforeseen changes in a part of the genome other than the intended gene. Since such 'off-target effects' can be hard to detect, their consequences may only come to light after a baby is born.
Furthermore, they fear gene-editing in embryos could lead to non-therapeutic gene enhancement leading to the creation of so-called 'designer babies'.
Some, however, feel that given its potential, embryo gene-editing should get the go-ahead for research purposes until concerns over human use are worked out.
Nobel Prize-winning geneticist Dr Craig Mello of the University of Massachusetts told Nature: 'In the distant future, I could imagine that altered germ lines would protect humans against cancer, diabetes and other age-related problems.' In the nearer term, he said, 'there could be good reason to experiment with discarded embryos or embryonic stem cells for research purposes'.