Base Editing in Human Embryos Reveals Role of 'Master Gene' NANOG, Reignites Ethics Debate

Two independent teams — Kathy Niakan's lab at the University of Cambridge and Dietrich Egli's lab at Columbia University — published base-editing studies on donated human embryos in Nature. Niakan's team used base editing to disable NANOG, revealing its essential role in establishing the first cells that become the fetus and placenta. Egli's team introduced disease-linked mutations (targeting cholesterol regulation and hemoglobin genes) into fertilized eggs. Both teams reported that base editing carries a substantially lower risk of unintended chromosomal errors than conventional CRISPR-Cas9, but also found cases of mosaicism (edits not present in all cells) and off-target effects. The results reignited bioethical debate: bioethicist Laurie Zoloth (University of Chicago) warned the mosaicism problem 'is not resolved' and cautioned against a 'Gattaca problem' of societal obsession with genetic enhancement rather than therapy.