They've been at it for a while, but scientists finally figured out how to delete disease-causing genetic code from single-celled human embryos—without any glitches—that were able to grow into disease-free multicellular embryos. Published yesterday in the journal Nature, the study has reignited the ethical conversation around "designer babies" and what a future without disease might look like for all of us.
How did they do it?
Scientists have used CRISPR, a method designed to precisely delete damaged DNA from human embryos. In this instance, leading scientist Shoukhrat Mitalipov, with help from researchers from the United States and South Korea, used CRISPR to delete a genetic mutation for "HCM," or hypertrophic cardiomyopathy, in the sperm of a man with the condition. HCM is a gradual thickening of the walls of the heart that can lead to sudden death in adults, making it an ideal gene to remove from the mix.
The timing of DNA deletion is paramount to the success of the procedure—previous embryo editing trials done in China in 2015 and 2016 attempted to delete mutated code after fertilization with wonky results. This time, Mitalipov deleted the mutation before fertilization so that the sperm is "fixed" before it combines with the egg. From there, the zygote is able to grow free of the mutation. Interestingly, though, this works if and only if one parent has the disease, not both, because the clipped DNA is copied from the healthy cell to the formerly mutated one.
This is important news for a number of reasons.
To eliminate inheritable disease between generations is a huge deal, especially for couples who have a high risk of passing along the disease because of their carrier status. It also means that women enduring IVF treatments may have more embryos to work with, resulting in fewer implantation attempts, according to what Mitalipov told the NYT.
Changes in legislation pave the way for germ-line editing experiments.
In a series of stop-and-go legislation over the past few years, North America finally lifted a ban on germ-line editing—a fancy term for editing inheritable genes, permanently altering the passage of DNA from generation to generation. There are a number of restrictions on exactly how a technique like CRISPR can be used, which include parameters like only using it to edit a genetically inherited disease. But critics say that opening the floodgates will eventually lead to "designer babies," altering genes that code for athletic ability, intelligence, and physical traits. Others maintain that we're decades away from this and that clinical applications will depend heavily on the evolving legislation around germ-line editing.
How will "designer babies" affect humanity?
Henry S. Greely said it's too early to tell. In an article he wrote for Scientific American, the director of the Center for Law and the Biosciences and professor (by courtesy) of genetics at the Stanford School of Medicine, has said that he does not think we are currently at risk for creating a possibility for genetically engineered "designer babies." Others maintain that we're inching toward a future of genetically modified humanity. In other words, there's no need to fear a brave-new-world reality...at least not yet.
Stay posted as the story unravels. In the same vein, one writer shares her journey through IVF and what she wishes other women knew.