New research has demonstrated a significant leap in the precision with which scientists can edit the DNA of human embryos, a development that could pave the way for future therapeutic applications but also intensifies long-standing ethical debates and highlights remaining safety concerns.
Sharpening Gene Editing Tools
While gene-editing technologies like CRISPR-Cas9 have revolutionized biological research and led to the first gene therapies for conditions such as sickle cell disease, they have historically been considered imprecise tools when applied to human embryos. Previous studies using CRISPR-Cas9 on embryos showed a risk of unintended and large-scale changes to the DNA, including the potential loss of entire chromosomes, raising concerns about unknown health effects. This imprecision was a key reason for the condemnation of Chinese researcher He Jiankui’s 2018 announcement of the birth of gene-edited babies.
A more refined gene-editing technique, known as base editing, which can alter a single DNA base at a time, has shown greater promise. Base editing has been used clinically to treat leukemia and a rare genetic disease in infants. Now, two new studies utilizing base editing on donated human embryos from IVF treatments have found it significantly reduces the likelihood of unintended chromosomal abnormalities compared to earlier methods.
One study, led by Kathy Niakan of the University of Cambridge, used base editing to investigate the function of the NANOG gene, crucial for early human embryo development. Niakan noted that base editing’s ability to precisely change a single nucleotide base pair out of billions represents an incredible feat with a far lower risk of causing unintended chromosome errors.
In a separate study, Dietrich Egli of Columbia University used base editing to introduce specific mutations into newly fertilized eggs, targeting genes known for their roles in cholesterol regulation (PCSK9) and fetal hemoglobin production (HBG). Egli indicated that his team’s findings have been conditionally accepted by a peer-reviewed journal.
Persistent Hurdles and Ethical Questions
Despite the enhanced precision, experts caution that significant obstacles remain before gene editing could be safely applied to human embryos for therapeutic purposes. Both studies identified two major challenges: mosaicism, where the intended edit does not occur in all cells of the embryo, and off-target effects, where unintended genes are altered. These issues are particularly concerning because any changes made to an embryo would be present in every cell of the resulting individual.
“This is a long stairway with many different steps and maybe some plateaus in between,” Egli stated. “We started at the very bottom and we’ve made a few steps in that direction, but I think we can look at the progress that has been made, and the discussion can be had about the pros and cons of going further.”
Amander Clark, director of the UCLA Center for Reproductive Science, Health and Education, who was not involved in the research, commented that this work “restores the possibility that gene editing for therapeutic purposes could be possible with IVF embryos in the future.” However, she noted that six years ago, she considered the use of gene editing in human embryos a “non-starter.”
Beyond technical safety, profound ethical questions persist. The scientific consensus and laws in 70 countries currently prohibit human germline editing, which manipulates DNA in embryos to prevent diseases from being passed to future generations. Concerns about the potential for creating “designer babies” with intentionally selected traits, rather than solely for therapeutic purposes, remain a significant ethical barrier.
Laurie Zoloth, a professor of religion and ethics at the University of Chicago, argued that research like this reignites the ethical debate, emphasizing that embryo editing, except for scientific research, should remain banned due to safety risks. She pointed out that existing methods like genetic screening and preimplantation testing can already help avoid genetic abnormalities. Zoloth also raised concerns about the potential for “slippage between treatment and enhancement,” leading to a society dictated by genetic perfection, a scenario depicted in the film “Gattaca.”
Helen O’Neill, an associate professor at University College London, highlighted the value of genome editing in human embryos for understanding early human development and aiding IVF success, suggesting it could eventually assist patients with serious inherited conditions for whom current testing is insufficient. She also stated that the debate is often narrowly framed around designer babies, overlooking the genuine scientific and clinical potential.
Mitchell Landsberg is the senior reporter for News Raise and focuses on Technology. Mitchell regularly writes about social media platforms and how influencers, industry and general people use them to communicate and make money.
