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Statements posted on this blog represent the views of individual authors and do not necessarily represent the views of the Center for Law Science & Innovation (which does not take positions on policy issues) or of the Sandra Day O'Connor College of Law or Arizona State University.

Weighing in on Human Germline Gene Modification

Much Ado About Foolhardiness

By Gary E. Marchant

The media and web are abuzz this week about the announcement that Chinese researchers modified human embryos using a powerful new gene editing technology known as the CRISPR system. The Chinese study is published in an obscure scientific journal called Protein and Cell after being rejected on ethical grounds by more prestigious scientific journals such as Science and Nature. This study is both irresponsible and foolhardy.

CRISPR is a relatively new technology that allows location-specific editing of a genome, a major improvement over past genetic modification techniques that relied primarily on random insertion of added genetic sequences into the genome. CRISPR is being used to modify new strains of microorganisms, plants and animals for many different beneficial uses. It also has tremendous potential for somatic cell gene therapy in humans, but has never been applied to human germline modification. Until now.

The Chinese scientists attempted to replace a defective copy of the beta-globin gene, which can cause the disease β-thalassaemia, in 86 non-viable human embryos using CRISPR. The experiment only succeeded in replacing the defective gene in a small number of embryos, and more importantly observed “off target mutations” in many of the embryos, which are unintended mutations elsewhere in the genome that could have had devastating effects on a future child if the embryos had been viable and implanted. Those unintended mutations would exist in many or most of the child’s tissues, and could be passed on to future generations.

Although the Chinese scientists had no intention of implanting the engineered embryos, and indeed, the embryos used had defects that ensured they were non-viable, the study was nevertheless an irresponsible and reckless step towards human germline gene modification. There has long been a formal or informal restriction on human germ line modifications in most parts of the world. There are two good reasons for this. First, there is no legitimate health reason for germline gene modification, at least at this time. If a couple who carry a serious disease gene wish to reproduce without risking creating a child with that genetic disease, they can use IVF and pre-implantation genetic diagnosis to identify and implant embryos that do not have the risky gene. Selecting out embryos with the gene is much easier, cheaper and effective than trying to replace the gene in those embryos.

Second, and more importantly, trying to engineer the genome of a human embryo is highly fraught with the risk of error at this point. Unlike somatic gene therapy that can only affect a small number of cells in the treated individual, germline gene modification errors would affect many or all cells in future generations of offspring. CRISPR studies in animals and plants, as well as the Chinese study on human embryos, all demonstrate this is a serious and unacceptable risk for humans.

For this reason, there is zero chance that an IRB or the FDA would approve such experiments on viable human embryos in the United States any time soon, and most European countries have expressly prohibited germline gene therapy. Any individual scientist who tries to do this on his own should and will be ostracized and discredited, just as the handful of scientists who claimed they were going to attempt human reproductive cloning over a decade ago. The same condemnation should apply to the scientists in China, which seems to becoming the “wild west” of genetic research.

So all the media hoopla about “fears arising” and “charging toward an era of genetically modified humans” is really more hype and sensationalism than a real and immediate concern. We have been trying to genetically alter the genes of somatic human cells for thirty years, with massive scientific investment and commitment and few if any ethical concerns, and yet have made only minimal progress. It is likely to be a similar timeline for human germline gene therapy to be scientifically and ethically viable, if ever. To be sure, the Chinese study is another warning bell to start thinking seriously about the social, ethical and legal implications of human genetic modification, but the reality is that existing and emerging technologies in cognitive-enhancing pharmaceuticals, brain-machine interfaces and maybe even 3D printing are going to be modifying humans long before geneticists get their turn.