The professor, who was educated at Stanford University in the United States and works from a lab in the southern Chinese city of Shenzhen, said the girls' DNA was modified using Crispr, a technique that allows scientists to remove and replace a strand with pinpoint precision.
That said, He claims to have edited embryos' genomes for seven couples during fertility treatments, with one pregnancy resulting thus far. In one twin, all of her cells were edited so as to knock out the CCR5 gene; in the other, only some cells were. He said his goal was not to cure or prevent an inherited disease, but to try to bestow a trait that few people naturally have - an ability to resist possible future infection with HIV, the AIDS virus.
"I feel a strong responsibility that it's not just to make a first, but also make it an example, how to perform things like this, consider morality of the society and consider its impact to the public", He told the AP in an exclusive interview.
\While editing the DNA of a human embryo is not now allowed in the US, in 2017, an worldwide committee of the National Academy of Sciences called for loosening the moratorium and allowing trials of CRISPR in human embryos, under strict oversight, to treat rare genetic diseases that can't be addressed in any other way.
The controversial experiment, publicised through the media and videos posted online by He Jiankui of Southern University of Science and Technology of China, was criticised by many scientists worldwide as premature and called "rogue human experimentation".
Tests suggest that one twin had both copies of the intended gene altered and the other twin had just one altered, with no evidence of harm to other genes, He said.
The scientist announced the alleged feat in an interview with the AP and to organizers of a gene editing conference in Hong Kong.
Physics and bioengineering professor Michael Deem at Rice University in Houston, has claimed that he also worked on the project with He in China.
"So I think the biggest question mark is there", he said. "It's just nearly surreal", said Eric Topol, founder and director of the Scripps Research Translational Institute, who said he has seen some of the data behind the experiment. The gene modification was done with the help of CRISPR, a gene-editing tool that is cheap and easy to use. "No known diseases. Gene editing itself is experimental and is still associated with off-target mutations, capable of causing genetic problems early and later in life, including the development of cancer". The SUSTech Department of Biology Academic Committee believes that Dr. Jiankui HE's conduct in utilizing CRISPR/Cas9 to edit human embryos has seriously violated academic ethics and codes of conduct. 3.
The document, which was signed by committee members in June in 2017, said the research aimed to assess the safety of gene therapy in major genetic-related diseases and infertility. In China, human cloning is illegal, but gene editing isn't specifically against the law. However, this rational debate can only take place if all scientists play their part and ensure that all experiments are done in the public interest. This sort of gene editing is banned in the US, though Deem said he worked with He on the project in China.
"We don't know how much of this is true or verified".
Baylis said it was also ethically questionable that He chose to address an HIV gene, when there are other less risky ways to prevent HIV.
Jennifer Doudna, one of the pioneers of genome editing from the University of California, Berkeley, said that the experiment appeared to be a "clear break" from the cautious and transparent approach recommended by worldwide leaders.
"Gene surgery is and should remain a technology for healing", He added. "I was there for the informed consent of the parents". That may be true, to a point, but it's abundantly clear that many organizations within China maintain similar ethical standards to their counterparts overseas.
Feng Zhang, a leader in the field from the Broad Institute, called for a moratorium on implanting edited embryos until safety requirements have been set.
"The lack of transparency and disregard for risk are deeply concerning", Doudna said.
One pregnancy happened since his work started.
Doudna and other researchers noted that genetically editing for HIV didn't solve an unmet need.