Study Shows NANOG Gene Starts Human Embryo Development but Edited Embryos Fail to Form Body Cells

Kathy Niakan at the University of Cambridge and colleagues used CRISPR base editing to disable the gene NANOG in fertilized human eggs donated by women undergoing IVF. None of the resulting cells developed into those that form the embryo itself, establishing that activation of NANOG starts the developmental program producing a human body.

The same intervention in mouse eggs blocked formation of yolk sac progenitors instead, showing that NANOG performs a different function in human development.

Embryos lacking NANOG still appeared normal when examined under a microscope. Niakan noted that embryo selection for IVF currently relies largely on shape. One out of two embryos judged viable by appearance nevertheless lacks the potential to implant, she said.

The study marks the first use of CRISPR base editing to examine gene function in human embryos. Earlier base-editing work on human embryos, including a 2017 effort and a May 2026 paper from Dieter Egli's group at Columbia University, focused on mutation correction rather than functional analysis.

Mary Herbert of Monash University, a member of the Niakan team, stated that the technology remains unsuitable for creating gene-edited children.

Egli observed that the findings confirm NANOG's distinct role in humans compared with mice. All three base-editing studies indicate the method produces fewer unintended chromosomal changes than earlier CRISPR techniques. Niakan's team injected the editing components into eggs together with sperm, yet half the eggs remained mosaic.

The paper appeared in Nature with DOI 10.1038/s41586-026-10792-1 and was amended on 26 June 2026 to clarify Egli's comments.