Researchers have recently reported using an advanced gene-editing technique to modify the DNA of human embryos for the second time this month.
This particular research utilized a method called base editing, aiming to gain insights into human development rather than finding ways to prevent diseases. Yet, the success of the experiment has intensified calls for discussions about the ethics surrounding embryo editing.
Published in Nature, the findings reveal that a crucial protein, NANOG, plays a significant role in embryo development, a discovery not previously observed in mouse studies. Janet Rossant, a developmental biologist in Toronto, emphasizes that understanding normal embryo development is vital for enhancing reproductive technologies.
This type of research often gets entangled in public debates over gene-editing human embryos, particularly regarding the prevention of genetic diseases or, more contentiously, modifying traits like intelligence. Progress on defining when such gene editing is acceptable has been minimal, which can be quite frustrating, according to sociologist Joy Zhang from the University of Kent.
Unexpected Findings
In the latest study, researchers led by Kathy Niakan at the University of Cambridge used base editing to disrupt the NANOG gene. They worked with donated sperm, eggs, and embryos, allowing the embryos to develop for about a week.
The embryos that underwent editing did not successfully form what is known as the ‘epiblast’, crucial for developing body tissues, although they managed to produce cells destined to create supporting structures like the placenta. This outcome is surprising since prior studies indicated that mice cannot form these structures without NANOG.
Previously, Niakan’s team employed the CRISPR–Cas9 technique to disable the production of another essential protein, OCT4, in human embryos. However, CRISPR–Cas9 can be less precise, possibly complicating result interpretations. It raises questions about whether embryos ceased developing due to the removal of OCT4 or unintended edits caused by the technique.
In contrast, base editing is considered to be less damaging to the genome. Researchers are optimistic that this precision will lead to a clearer understanding of NANOG’s role and potentially other proteins during human embryo development.
Alta Charo, a consultant in biotechnology ethics, suggests that base editing may eventually prove to be safer than CRISPR–Cas9 for editing genes in embryos. Yet, she cautions that this represents merely an initial step towards ensuring safety for embryos intended for implantation.
Safety Challenges
Charo notes that many safety improvements are still needed. One major issue is that base editing doesn’t always affect all cells in an embryo, resulting in a mosaic with both edited and unedited cells, which carries unknown risks for any resulting fetus.
These challenges have allowed researchers to defer tackling deeper ethical concerns regarding heritable gene editing. However, the latest advancements indicate that scientists cannot indefinitely avoid pressing questions about the appropriateness of editing embryos and the implications of making hereditary mutations.
