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Chinese Researchers Correct Genetic Mutation In Embryos Using Base Editing (bbc.com)
dryriver writes: Chinese researchers have taken tissue from a beta-thallasemia patient, created cloned embryos from that patient's cells, and used a genetic editing technique known as Base Editing to correct the gene mutation that causes beta-thallasemia. The embryos were not implanted in a womb, so no actual babies were created during the procedure. The BBC reports: "Precise 'chemical surgery' has been performed on human embryos to remove disease in a world first, Chinese researchers have told the BBC. The team at Sun Yat-sen University used a technique called base editing to correct a single error out of the three billion 'letters' of our genetic code. They altered lab-made embryos to remove the disease beta-thalassemia. The embryos were not implanted. The team says the approach may one day treat a range of inherited diseases. Base editing alters the fundamental building blocks of DNA: the four bases adenine, cytosine, guanine and thymine. Base editing works on the DNA bases themselves to convert one into another. Prof David Liu, who pioneered base editing at Harvard University, describes the approach as 'chemical surgery.' He says the technique is more efficient and has fewer unwanted side-effects than Crispr. He told the BBC: 'About two-thirds of known human genetic variants associated with disease are point mutations. So base editing has the potential to directly correct, or reproduce for research purposes, many pathogenic [mutations].'"
Base Editing is a CRISPR variant where the DNA-cutting activity of Cas9 protein has been modified with a mutation that disables its DNA cutting ability and a fusion to another protein called Cytidine Deaminase which converts "C" bases to "U" bases (which are read as "T"). It is still guided to the precise chromosomal location by a "guide RNA" that is complementary to the region you want to edit.
The CRISPR field is very wild-west like at the moment and everyone is fighting for their share of the spotlight (and the potential wealth) with these minor variants. Whether it's truly safer than vanilla CRISPR will be better demonstrated over time and hopefully by labs without a direct financial interest in the success of one competing platform over another.