Scientists have successfully altered a piece of defective DNA in human embryos to prevent them from developing heart disease.
It’s the first time a mutation that causes a common inherited disease has been fixed using a gene-editing tool.
The trial’s success raises the prospect of gene editing being used to prevent thousands of inherited conditions from being passed down through generations in the future.
The procedure is highly controversial and there is no question of the technique being used to create babies with the genetic modification, as this would be illegal in both the US and the UK.
The research, published in the journal Nature, was carried out by scientists in the US at Oregon Health and Science University and the Salk Institute and at the Institute for Basic Science in South Korea.
Embryos used by the scientists were allowed to develop for five days before the experiment was stopped.
Had they been allowed to develop further, the babies and any future descendants would no longer have been at risk from the heart disease.
Dr Shoukhrat Mitalipov, from Oregon Health and Science University (OHSU) in Portland, said “Every generation on would carry this repair because we have removed the disease-causing gene variant from that family’s lineage.
“By using this technique, it’s possible to reduce the burden of this heritable disease on the family and eventually the human population.”
The scientists focused on editing the gene that causes hypertrophic cardiomyopathy, a common disorder that affects about one in 500 people and can cause the heart to suddenly stop beating.
The embryos were editing using a powerful gene-editing tool called Crispr-Cas9, which works by precisely snipping away the defective piece of DNA from embryos containing the mutation.
Once the gene was removed, the embryo’s own repair systems replaced them with the healthy version.
The procedure was successful in 42 out of 58 embryos that underwent gene editing.
Anybody carrying the gene ordinarily has a 50% chance of the disease being passed on to their offspring.
There are more than 10,000 heritable conditions that are caused by an error in a single gene which could be prevented by this treatment.
Not everybody is in favour of gene editing being used to prevent heritable conditions in the future.
Dr David King, director of the Human Genetics Alert, which opposes all tampering with the human genome, said: “If irresponsible scientists are not stopped, the world may soon be presented with a fait accompli of the first GM baby.
“We call on governments and international organisations to wake up and pass an immediate global ban on creating cloned or GM babies, before it is too late.”