How Did Scientists Edit the Genes of Human Embryos?

Scientists have successfully edited the genes of human embryos. What does this mean for the future of genetic engineering?

Sabrina Stierwalt, PhD,
August 8, 2017
Episode #249

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CRISPR-Cas9 was applied to sperm from a carrier of the disease as they were injected into eggs from non-carrier donors. The scientists then observed as the CRISPR-Cas9 scissors went to work removing the portion of the DNA with the mutation and replacing it with a healthy copy of the sequence from the maternal genes. Two key aspects of their study was first, the addition of the CRISPR-Cas9 to the egg at the same time as the sperm rather than hours later as had been done in previous studies, and second, the use of a short-lived version of CRISPR that would not hang around and cause potentially unwanted future edits.

In their paper titled ‘Correction of a pathogenic gene mutation in human embryos’, the authors note that the editing worked in 36 of their 54 regular human embryos. (Earlier work by Chinese scientists involved the successful editing of only immature embryos that were not capable of surviving until birth.)

What laws are there concerning the editing of the human genome?

The embryos used in the experiment at OHSU were not implanted in a woman’s uterus, and many more experiments must be run, using different mutations and different donors, for example, before that can be done. But for would-be parents who fear passing on a genetic disease, the possibilities the study suggests are a potential game changer. Those with access t o the gene editing tool could remove any doubt that they had passed on genetic predispositions toward sickle cell anemia, cystic fibrosis, or even breast cancer.

Doctors are already able to create embryos in vitro and then select only the ones that do not carry a specific genetic illness for implantation, a process called “preimplantation genetic diagnosis”. However, those embryos not chosen for implantation are often discarded.

While there is an obvious appeal to be able to control the disease-causing genetic mutations we pass on as parents, that level of control raises a wealth of concerns. Will gene editing eventually be used to create “designer babies” with more desirable traits? Who decides which qualities are desirable?

Currently, in the United States, research in genetic engineering is allowed but regulations prevent the US government from funding any research involved in the genetic engineering of human embryos, including studies like those at OHSU. Opponents of the federal government ban suggest it only moves the research into the realm of private industry while others believe it is an important limitation as the law tries to keep pace with scientific advancement.

While the answers to many of the questions surrounding the ethics of genetic engineering may be murky, one thing is clear. A fair and ethical path forward can only be found if scientists and law makers from diverse cultural backgrounds are included in the conversation.

Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.

Image courtesy of shutterstock.


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