Biologists in China have carried out the first experiment to alter the DNA of human embryos, igniting an outcry from scientists who warn against altering the human genome in a way that could last for generations.
The experiment used a controversial technique called CRISPR/Cas9, and represents a biological version of the “find and replace” function on a word processing program.
Scientists introduced enzymes that first bind to a mutated gene, such as one associated with disease, and then replace or repair it.
The study’s lead author Junjiu Huang, of Sun Yat-sen University in Guangzhou, and his team experimented on 86 one-cell human embryos, all from fertility clinics, that because of chromosomal defects were unable to develop into a baby.
Their target was a gene called HBB, which can cause the blood disease beta thalassemia.
About a dozen embryos did not even survive the genome-editing, the scientists reported, and of the surviving embryos, many showed “off-target” effects meaning genes other than HBB were altered.
Other embryos suffered “untoward mutations” and only a handful of embryos contained the healthy DNA meant to repair the defective HBB genes.
Mr Huang told Nature News that if this was done on normal embryos “you need to be close to 100 per cent” on target in terms of fixing only the target gene.
The study appeared last weekend in an obscure online journal called Protein & Cell, and an interview was published on Wednesday on the Nature journal website ,in which Mr Huang said both Nature and Science rejected the paper, partly for ethical reasons.
The controversy behind the research
At least half a dozen experiments have been planned or are underway using CRISPR on human eggs or embryos to correct genetic defects such as those causing cystic fibrosis or the BRCA1 breast cancer gene, the MIT magazine Technology Review recently reported.
However, a call for a global moratorium on such experiments was delivered last month by Chief executive of California-based Sangamo BioSciences Inc, Edward Lanphier, and part of a group of scientists.
Mr Lanphier said there have been “persistent rumours” of this kind of research taking place in China and this paper “takes it out of the hypothetical and into the real”.
Scientists warn that altering the DNA of human sperm, eggs, or embryos could produce unknown effects on future generations, since the changes are passed on to offspring.
They distinguish this type of so-called germ line engineering from that which alters the DNA of non-reproductive cells to repair diseased genes.
MIT biologist Rudolf Jaenisch, president of the International Society for Stem Cell Research, said it is too soon to apply these technologies to the human germ line in a clinical setting.
Future of human germ line engineering
Four or more groups in China are also doing similar experiments, Mr Huang told Nature News, which is why Mr Huang and his team have stopped.
Journals Science and Nature said their policies are not to comment on publication decisions.
Springer, which publishes Protein & Cell and is owned by European private equity firm BC Partners, did not immediately reply to questions about its decision to publish Huang’s paper.
According to a note in Protein & Cell, the paper was received on March 30 and accepted on April 1, which is a short amount of time for a complicated study to undergo peer review by journal editors and outside scientists.
Mr Lanphier fears that the call for a moratorium on editing the human germ line is being ignored.
“This is the first of what may be many papers” on human germ line engineering, he said.
Reuters