Successful correction of genetic problems in mice before birth raises hopes of similar treatments for humans
Gene editing to correct faulty DNA in human embryos has taken a step closer to becoming a reality, with scientists showing it is possible to correct genetic problems in mice before they are born.
Researchers used a form of the gene-editing tool Crispr-Cas9 to introduce a mutation into a gene that would otherwise cause lethal liver failure in mice. While the approach has previously been shown to work in mice after birth, the latest study showed it was also possible to make the all-important tweak before they were born.
However the scientists stressed it will be some time before such an approach would be ready for use in humans.
“This is a very proof-of-concept study – it is the initial study, there are a lot more studies in mouse models as well as large animal models that need to be done before even considering doing this clinically,” said Dr William Peranteau, a paediatric and foetal surgeon at the Children’s Hospital of Philadelphia who co-led the study.
What is Crispr?
Crispr, or to give it its full name, Crispr-Cas9, allows scientists to precisely target and edit pieces of the genome. Crispr is a guide molecule made of RNA, that allows a specific site of interest on the DNA double helix to be targeted. The RNA molecule is attached to Cas9, a bacterial enzyme that works as a pair of “molecular scissors” to cut the DNA at the exact point required. This allows scientists to cut, paste and delete single letters of genetic code.
Even if the approach were eventually applied in humans, it would not be used for the majority of genetic disorders, Peranteau said. “The ideal disease to treat with this approach would be a disease that causes significant morbidity or mortality before or shortly after birth and for which there is currently not a very good treatment,” he said.
Writing in the journal Nature Medicine, a team of researchers in the US report how they conducted a series of experiments to explore the use of gene editing in mouse foetuses using a modified form of Crispr that can alter single “base pairs” – the molecules that couple up to form the rungs of the DNA double helix – but only cuts one strand of DNA when making a change. “In theory it is safer and avoids a lot of the concerns that have recently been published about standard Crispr,” said Peranteau.