Overview
- Researchers led by Dieter Egli posted a preprint reporting the use of base editors to make precise A→G changes in early human embryos, marking a technical move beyond cutting‑based CRISPR.
- The team targeted PCSK9 and the fetal haemoglobin genes HBG1/HBG2 and showed that the PCSK9 edit effectively switched that gene off in some embryo cells.
- Edits were often mosaic, meaning some embryo cells carried the new base while others did not, and high doses of the editor’s mRNA caused cells to stop dividing, indicating dose‑dependent embryo harm.
- The work is an unpeer‑reviewed preprint and the authors say it is not ready for clinical use; Nucleus Genomics has agreed to support follow‑on experiments to reduce mosaicism and test editing at later, ~100‑cell embryo stages.
- The study revives ethical and regulatory questions about inheritable germline edits, highlights existing safer options such as IVF genetic screening, and raises concern about potential misuse for trait enhancement.