Could parents one day choose their baby’s traits? Scientists achieve major human embryo gene-editing milestone

Scientists at Columbia University have successfully edited the DNA of early human embryos with unprecedented precision, marking a significant breakthrough in genetic engineering that could one day allow doctors to correct inherited diseases before birth. The research, led by geneticist Dieter Egli, used a newer gene-editing technique known as base editing to make highly targeted changes to DNA without causing the extensive genetic damage often associated with traditional CRISPR technology.

The findings, which have been posted online and are currently under peer review, are already reigniting ethical concerns over the possibility of creating genetically enhanced or so-called "designer" babies. According to the researchers, base editing allows scientists to alter individual DNA letters rather than cutting out entire sections of genetic material. This approach significantly reduced the risk of major chromosomal damage that had plagued earlier embryo-editing experiments.

"We're not saying this is going to be used tomorrow in the clinics," Egli cautioned, stressing that important questions about safety and unintended consequences remain unanswered. The debate over editing human embryos has intensified since the development of CRISPR technology in 2012. While the technique opened the door to treating inherited diseases, it also raised fears that genetic engineering could eventually be used to select desirable traits, a prospect some ethicists have likened to modern-day eugenics.

The controversy reached a peak in 2018 when Chinese scientist He Jiankui announced that he had edited the genomes of human embryos to create babies resistant to HIV infection. His work was widely condemned by the scientific community, and he was later imprisoned by Chinese authorities.

'Absolutely catastrophic consequences’

Egli's team previously investigated the use of CRISPR in human embryos in 2020. In those experiments, researchers attempted to repair a mutation in the EYS gene linked to hereditary blindness. While some embryos were successfully corrected, many suffered severe genetic damage, including the loss of entire chromosomes.

"It had absolutely catastrophic consequences," Egli said of the earlier findings, according to the New York Times. The new study sought to avoid those problems by using base editing. Researchers targeted two genes, PCSK9, which is linked to cholesterol levels and heart disease risk, and HBG, a gene involved in foetal haemoglobin production.

The team introduced base-editing molecules into fertilised eggs and two-cell embryos donated by prospective parents. Unlike earlier CRISPR-based experiments, the researchers found no evidence of large-scale DNA damage and successfully altered both genes. In some cases, they edited both genes within the same embryo.

However, the technique was not flawless. Some embryos developed "mosaicism", a condition in which different cells carry different genetic versions because the edits did not occur uniformly throughout the embryo. Scientists warn that such genetic inconsistencies could potentially lead to health complications if edited embryos were carried to term.

Paula Amato, a fertility specialist at Oregon Health & Science University who was not involved in the study, described the approach as "promising" but said the scientific community would need to carefully examine the full data once the research undergoes peer review.

Bioethicist Ana Iltis of Wake Forest University also urged caution, warning that some harmful effects may not become apparent until after birth. Supporters argue that the technology could eventually benefit families undergoing in vitro fertilisation (IVF). Nathan Treff, chief clinical officer at Nucleus Genomics and a co-author of the study, said gene correction could allow parents to use embryos that might otherwise be discarded because of disease-causing mutations.

"There's still work to do before getting to that point, but this research gets us closer," Treff said.