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Base Correction

Researchers in China have fixed a potentially lethal genetic mutation in cloned embryos, Nature News reports.

A team led by Sun Yat-sen University's Junjiu Huang used a version of the CRISPR/Cas9 gene-editing tool to repair a mutation in the HBB gene that leads to β-thalassemia, a recessive disease that causes severe anemia.

The researchers first generated embryos that were homozygous for the disease mutation using a nuclear transfer approach, as they describe in Protein & Cell. In particular, they collected lymphocyte cells from a β-thalassemia patient and fused them with mature oocytes lacking a nucleus.

By doing this, Nature News notes that the researchers avoided the issue of IVF clinics rarely having multiple embryos that are homozygous for the same β-thalassemia mutation.

The researchers then used a modification of the CRISPR/Cas9 gene-editing tool to fix the HBB gene mutation in these embryos. Rather than editing a stretch of DNA out, the researchers attempted to correct the A to G mutation present. Through this base editing, Huang and his colleagues had a gene correction efficiency of more than 23 percent, though they noted that some embryos were mosaic.

"The repair rate is pretty good, and certainly promising," Gaetan Burgio from the Australian National University tells Nature News.