Writing in the journal Protein and Cell, the researchers show that the new procedure worked to some extent. Humans carry two copies, or alleles, of every gene and in many cases both versions have to be “healthy” to avoid disease. In the study, base editing sometimes repaired only one faulty gene rather than both, creating so-called mosaic embryos that had both normal and mutant cells. “This looks very promising, but all the embryos from which they were able to get information from more than one cell were clearly mosaic, with some cells still carrying both mutant alleles,” said Robin Lovell-Badge at the Francis Crick Institute in London.
While the development is exciting, experts in the field are urging caution:
While this is undoubtedly a highly significant advance, it is important not to get carried away about its widespread utility if put into clinical practice. An embryo would still need to be diagnosed as abnormal, then the base editor applied, then re-diagnosed to make sure that it had worked. This would be an involved procedure that would be very expensive. In the meantime, the ethical implications of gene manipulation in embryos need a thorough examination where safety is of paramount concern. -
Darren Griffin, geneticist at the University of Kent