Bumping up the Stakes: Embryo Germline Editing Works Better in Viable Human Embryos

Back in March, we discussed a report from the National Academies for Science and Medicine saying germline editing could be acceptable for correcting certain genetic diseases (see my article here).  Germline editing means a kind of gene therapy that changes future generations. This includes changing DNA sequences of your gamete cells (eggs in women, sperm in men), the cells that give rise to future generation. It also includes changing DNA sequences in all the cells of an embryo, thereby affecting its future body parts and its descendants too. In March, we also discussed a Chinese study from a couple of years ago in which researchers attempted to modify human embryos to cure a genetic blood disease, beta thalassemia, with CRISPR gene editing. In that experiment, the genetic modification didn’t work very well. Only a fraction of the embryos were altered correctly, and in many cases there was mosaicism; some of the cells of an embryo got modified and others didn’t.

The Chinese researchers, and germline modification, got a lot of criticism, because it didn’t work well. Furthermore, there were various objections to human embryo research in some segments of society back when the study came out. Ethically speaking, though, the concerns were no more than a yellow alert for many people, because the researchers had used embryos that were left over from fertility clinics and were not viable; they had no chance of developing into human beings, so had they not been used in research prior to being discarded, they’d have been discarded anyway. But the ethical stakes have just been raised for editing of human embryos, because it now appears that embryo modification can work –if the research is done on healthy embryos.

A new study, also from China, found that the gene editing process that didn’t work so well in the dying human embryos works fairly well in healthy embryos. By ‘healthy’, I don’t mean embryos that are disease-free, but rather embryos that could develop through a normal pregnancy, leading to a living, full-term infant. This could include newborns with thalassemia, sickle cell disease, or pretty much any genetic condition that’s not lethal in the womb. The study was very small, involving only a few embryos, but other studies showing similar success of gene modification in viable embryos are on-deck for publication

What does this mean for society and the rules and regulations regarding embryos and biotechnology? It means that we can forget the scenario of researching germline modification mostly on embryos that could never become people. If we want to advance regenerative medicine, society will have to accept a slightly higher level of ethical baggage than would have been needed, if non-viable embryos could provide meaningful scientific results. Since they can’t, we’ll have to move into a zone that makes increasing numbers of people uncomfortable. If the technology lives up to expectations, however, more people also may give higher moral status to people who are sick and potentially curable than they give to embryos.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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