He's unverified claim came on the eve of an global summit dedicated to discussing the emerging science and ethics around powerful tools that give scientists unprecedented potential to tweak traits and eliminate genetic diseases - but that have raised fears of "designer babies".
More than 100 scientists, most in China, said in an open letter on Tuesday the use of CRISPR-Cas9 technology to edit the genes of human embryos was unsafe and unjustified. Those babies were born earlier in November.
Why is everyone so upset, including the inventor of the CRISPR technology?
Some scientists in Hong Kong for the summit think it could induce serious problems for a person's immune system, while others think people should not be overly scared because it would not affect the core genome.
Chinese health and medical ethics authorities started an investigation on Monday into claims by a scientist who released videos on YouTube saying he had altered the genes of twins born earlier this month, creating the first gene edited babies.
The issue of editing human DNA is highly controversial, and only allowed in the USA in laboratory research - although U.S. scientists said past year that they had successfully edited the genetic code of piglets to remove dormant viral infections.
How has the babies' genome been modified?
There is no independent confirmation of the experiment's success, and it has not been published in any academic journal.
He said gene editing would help protect the girls from infection with HIV, the virus that causes AIDS. "The removal of CCR5 is not able to entirely prevent HIV infection due to the high variability of HIV".
The statement follows a move by the Chinese hospital named in He's ethical approval documents, Shenzhen Harmonicare Women's and Children's Hospital, to deny all involvement in the procedures.
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In his promotional video, He describes targeting the CCR5 gene, which helps the HIV virus enter healthy human cells. This led to one pregnancy and the birth of twin girls with pseudonyms Lulu and Nana.
Tests of the twins DNA suggest that editing worked on both copies of the gene of one twin and one copy was altered in the other twin.
We have little to no details on how this was performed and we must take these reports with a lot of caution.
The CRISPR tool is a recently developed tool for adding necessary genes or disabling harmful ones to treat diseases in adults, though the USA only allows it to be used in lab research. "We just don't know yet". There is an ongoing discussion as to how widespread "off target" and "on-targets" modifications are, and what the unintended consequences of these effects may be.
He lays out his ethical principles in one of the YouTube videos, including this statement: "No one has a right to determine a child's genetics except to prevent disease". "It's not known if those pregnancies were terminated, carried to term, or are ongoing". The tool has been used recently to treat deadly diseases in adults, but not in editing sperm, eggs, or embryos.
The reports fall in the grey area between attempts to cure diseases, and the dreaded "designer baby" scenario, where humans could be modified for benefits unrelated to health (potentially expanding to include intelligence, aesthetics and more). "So we try to provide the teeth to the ministry head, so they can bite people when people violate the regulations", he told reporters in English at a gene-editing conference in Hong Kong.
When the embryos were 3 to 5 days old, a few cells were removed and checked for editing.
CRISPR pioneers Jennifer Doudna and Emmanuelle Charpentier rightly noted the need for a rational public discourse on the use of the technology. Deem also holds what he called "a small stake" in - and is on the scientific advisory boards of - He's two companies. Currently, scientists were supposed to be restricted to editing somatic cells (the ones not involved in reproduction).
Based on the information now available, it is hard not to consider this latest experiment as anything but an attempt to win a "race" and grab attention.
"The University was deeply shocked by this event and has taken immediate action to reach [He] for clarification", the release said, adding that He's "previous affiliation, the Department of Biology (hereafter the Department) called an emergency meeting of the Department Academic Committee".