"If we have the technology, we should make it available earlier. We can help earlier those people in need".
There is wide scientific agreement that rewriting DNA before birth - to prevent an inherited disease or to give a baby some "designer" trait - isn't yet safe to try outside laboratory experiments that do not lead to human births. "Yes, of course it's an HIV-infected father, a non-HIV infected mother, so certainly transmission to the baby is a concern, but there are other ways to do this".
There were 31 embryos created through in vitro fertilization, and 70 percent were successfully edited. "All medical advances, gene editing or otherwise and particularly those that impact vulnerable populations, should be cautiously and thoughtfully tested, discussed openly with patients, physicians, scientists, and other community members, and implemented in an equitable way". Such experiments would be illegal in many countries, including the United States.
The ethics of the procedure are also complicated by the fact that targeting specific segments of DNA may not be fully precise or could carry side effects that are hard to predict.
The gene-editing work had started three years ago, partly paid for by He, who had consulted, he said, with just a few colleagues about his plans.
But genome editing could also more controversially used for genetic enhancements, such as ensuring children have a particular desirable characteristic such as a certain eye colour.
He opened his appearance on Wednesday by apologizing for news about his work "leaking" before it passed peer review. In its statement, the university said it was unaware of He's project or its nature, and noted that the experiment was not conducted on its campus.
He did not name those people.
Today's medications have turned HIV from a death sentence into a manageable disease in much of the world, but He said he chose that gene because HIV remains a big problem in China.
However, he said he would suspend such procedures for now. He talked about visiting villages in China where 30 percent of children are HIV positive.
However, He maintained his research was valid, saying that he feels proud of what he had done with the girls' genes. "For this case, I feel proud". But he told his colleagues that he felt "proud.proudest" of his achievement. "When the baby was born, he sent a message at the first saying I will work hard for and take care of my two daughters for the second half of his life".
"The volunteers were informed of the risk posed by the existence of one potential off-target and they made a decision to implant", he said.
Born in China's Hunan Province, He graduated from the University of Science and Technology of China in 2006 and pursued a PhD at Rice and postdoctoral research at Stanford. The Chinese government has also since ordered an inquiry.
He's remarks come two days after The Associated Press reported on his experiment, which has since drawn both support and condemnation from the worldwide scientific community.
Research institutions have also distanced themselves from He's work.
In a planned presentation, He, an associate professor at Southern University of Science and Technology, in Shenzhen, described how he used Crispr-Cas9 to modify a gene called CCR5 in a number of embryos created through IVF for couples with HIV-positive fathers. Aside from the lack of verifiable evidence for this non-peer-reviewed claim, this research is premature, unsafe and irresponsible.
The hospital said it would lodge a police complaint against He.
A visual representation of CRISPR-Cas9 gene editing.
Daley, for his part, says he was surprised to hear that He knew about the brain research. But many other scientists seemed highly skeptical, with a conference organiser calling his actions irresponsible. "It's an appalling example of what not to do about a promising technology that has great potential to benefit society".
"I personally don't think that it was medically necessary".