The Chinese scientists have been aggressive in using CRISPR, and one team made news earlier this year when it reported results from experiments on non-viable human embryos.
"The overriding question is when, if ever, we will want to use gene editing to change human inheritance," summit chair David Baltimore of Caltech said in his introductory remarks.
Another question, he said, is whether and when this technique should be used for "human enhancement".
Such genetic changes would potentially be for cosmetic or competitive advantages - not merely therapies for medical conditions.
"These are deep and disturbing questions that we hope will be illuminated by this meeting," Baltimore said.
The reason CRISPR is so controversial is that it works well on "germline" cells, such as sperm, eggs and embryonic cells, and the genetic editing results in heritable traits.
Many scientific organisations have called for a time-out on any experiments on human cells, fearing that this crosses into dicey ethical territory. Baltimore said he hopes that the final session tomorrow will include recommendations for a path forward.
In 1975, the Asilomar conference on the Monterey Peninsula was called after scientists realised they could splice DNA from one organism into another, raising the possibility of hybrid organisms and environmental risks.
They produced a set of protocols meant to lower those risks and allow the research to continue.
Now comes CRISPR. The technique borrows a move from bacteria. In a bacterium's DNA are segments of genetic information that bear the likeness of viral pathogens, kind of like the FBI's Most Wanted bulletins.
The bacterium has an enzyme, called Cas9, that can read that likeness, scout the environment for anything looking the same, and then, when finding a likely suspect, snip lengthwise the entwined double-helix DNA strands of the invader.
The CRISPR technique uses the Cas9 enzyme as a gene-snipper. If properly targeted it can precisely edit genes.
Getting to a high level of precision has been tricky to date, but the experimentalists have made great strides in just the few years since the idea of using the enzyme for gene editing emerged from laboratories in Massachusetts and California.
"Human intention is entering matter," the futurist Barbara Marx Hubbard told the Washington Post way back in 1998. "It means that instead of evolution working by natural and unconscious selection, evolution is beginning to happen through conscious choice."
Hubbard was not at all worried about this, because she envisioned the human species spreading through outer space, becoming galactic and ultimately a cosmic intelligence.
But in the meantime, we've got some decisions to make. There's nothing much at stake except human destiny.
- Bloomberg
