Chinese scientists report they have used genetic “base editing” to create mutations in cloned human embryos. Ethical questions, however, remain. Share on Pinterest Is it possible to eliminate disease-causing mutations from the human genome? In a study reported in the journal Protein & Cell, researchers from China have used genetic editing to correct disease-causing mutations in cloned human embryos. The investigators used a procedure known as base editing to repair mutations in the HBB gene that give rise to beta thalassemia. Beta thalassemia is an inheritable blood disorder. It causes potentially life-threatening anemia in people who carry two copies of the mutated HBB gene. “Our study demonstrated the feasibility of correcting pathogenic mutation by base editing in human cells and embryos,” Puping Liang, PhD, the first author of the study, told Healthline. While more research is needed on the efficiency, safety, and precision of base editing in human embryos, the investigators believe it holds promise for curing genetic diseases. “Germline gene therapy by base editor still needs to be investigated and discussed thoroughly,” Liang said. “But clinical applications of somatic cell gene therapy by base editors might be available in the near future.”

Base editing is precise and efficient This study is the first to use base editing to correct disease-causing mutations in human embryos. Base editing was pioneered by David Liu, PhD, professor of chemistry and chemical biology at Harvard University. Also known as “chemical surgery,” base editing uses an RNA-protein complex to catalyze conversions in the nucleotides that make up human genes. This process allows scientists to target and change specific nucleotides in mutated genes with more precision than CRISPR-Cas9, an older genetic editing technique. “For some applications, traditional CRISPR nuclease is a preferred approach,” Liu told Healthline. “But many human genetic diseases are caused by single point mutations that need to be precisely corrected, rather than disrupted, in order to treat or study the corresponding disease,” he continued. Beta thalassemia is one of those diseases. In earlier studies, Liang and other Chinese researchers tried to correct HBB mutations using CRISPR-Cas9 and another technique known as homology directed repair. Compared to those earlier efforts, base editing proved to be more precise. “The researchers observed quite efficient correction of the target mutation, by in vivo genome editing standards,” Liu said. Ongoing technical advancements might help further improve efficiency in base editing. For example, Liu’s team at Harvard has recently developed fourth-generation base editors. They show improved editing efficiency and product purity. “We are hopeful that base editing might advance the study and treatment of genetic diseases, and our laboratory is working hard toward this goal,” he said.