Scientists fix DNA error to give hope of curing inherited diseases

SCIENTISTS have coaxed the mutated DNA of human embryos back into healthy code in an experiment which could one day by used to cure a range of inherited diseases.

In a world’s first, researchers in China proved it was possible to correct a single error in three billion letters of genetic code to remove the disease beta-thalassemia, a debilitating blood disorder.

British scientists hailed the research as a ‘highly significant’ advance.

Prof Darren Griffin, professor of genetics, University of Kent, said: “For many years, we have been saying that direct gene editing in embryos is some way into the future. Now the future is here and there is much to consider.”

Although the embryos were not implanted, the team says the approach could be used to fix mutations which cause many inherited conditions.

Scientists have already proved it is possible to fix errors by replacing genetic code with donor DNA using a technique called Crispr, which acts as genetic scissors, but the new experiment is the first which alters the single building blocks of DNA, know as bases.

DNA is made up of four bases: adenine, cytosine, guanine and thymine, which are commonly known by their respective letters, A,C, G and T.

Different combinations of these bases are what provide the instructions for every function in the human body.

In beta-thalassemia, the disease is caused by a mistake in a single base in the genetic code – known as a point mutation. The Chinese team showed it was possible to find the point mutation and change a ‘G’ to an ‘A’, fixing the problem.

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

The technique was pioneered by Prof David Liu of Harvard University, who claims it has fewer side-effects than Crispr.

He told the BBC: “About twothirds of known human genetic variants associated with the disease are point mutations.

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

The research group at Sun Yat-sen University in Guangzhou was the first group in the world to use Crispr on human embryos, a breakthrough which shocked some scientists and led to claims that China was acting like ‘The Wild West’ of science.

Prof Robin Lovell-Badge, from the Francis Crick Institute in London, said: “There would need to be far more debate, covering the ethics, and how these approaches should be regulated.

“And in many countries, including China, there needs to be more robust mechanisms established for regulation, oversight, and long-term follow-up.

“It is a complex paper, with some interesting results that might indicate a route to avoiding certain genetic diseases – although it is far too early to even consider applying the methods clinically.”

Dr Helen Claire O’Neill, programme director of reproductive science and women’s health, University College London, said: “Base editing attempts to repair a mutation. It does this without the need for breaking the double-stranded DNA.

“More work is needed to assess the precision of this base editing technology.” (© Daily Telegraph London)

‘This complex paper might be a route to avoiding genetic diseases’