Scientists remove harmful mutations from human embryos using “chemical surgery”

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A team of Chinese researchers at Sun Yat-sen University has performed the world’s first precise “chemical surgery” on human embryos to extract and eliminate diseases. The study was published in the journal Protein and Cell.

They used a technique called base editing to correct a single error out of the three billion “letters” of our genetic code by modifying lab-made embryos to remove the disease beta-thalassemia. This technique may potentially be used to cure a myriad of inherited diseases.

Base editing is used to change the building blocks of DNA: he four bases adenine, cytosine, guanine and thymine. Also known by respective letters, A, C, G and T. All the information and instructions for building and running the human body are encoded in combinations of those four bases.

A change to a single base in the genetic code – known as a point mutation – can lead to the life-threatening blood disorder beta-thalassemia. The team corrected the fault by scanning DNA for the error and converting a G to an A.

“We are the first to demonstrate the feasibility of curing genetic disease in human embryos by base editor system.” said Junjiu Huang, one of the researchers.

The new study opens new doors for treating patients and preventing babies being born with beta-thalassemia among numerous other inherited diseases. The experiments were performed in tissues taken from a patient with the blood disorder and in human embryos made through cloning.

A Revolution in Genetics

Base editing is an advance on a form of gene-editing known as CRISPR, that is already revolutionising science.

CRISPR breaks DNA. When the body tries to repair the break, it deactivates a set of instructions called a gene. It is also an opportunity to insert new genetic information. 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.

“So base editing has the potential to directly correct, or reproduce for research purposes, many pathogenic [mutations].”

This is the latest example of the rapidly growing ability of scientists to manipulate human DNA while provoking deep ethical and societal debate about what is and is not acceptable in efforts to prevent disease.

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