Gene-editing technology partially restores vision

Researchers from the Salk Institute for Biological Studies in the US claim that for the first time, they have been able to insert DNA at a target location in the non-dividing cells that make up the majority of adult organs and tissues.“Until now, techniques that modify DNA – such as the CRISPR-Cas9 syst – have been most effective in dividing cells, such as those in skin or the gut, using the cells’ normal copying mechanisms,” a Salk Institute media statent explained.It was said the Salk technique was 10 times more efficient than other methods at incorporating new DNA into cultures of dividing cells.“But, more importantly, the Salk technique represents the first time scientists have managed to insert a new gene into a precise DNA location in adult cells that no longer divide, such as those of the eye, brain, pancreas or heart, offering new possibilities for therapeutic applications in these cells,” the statent continued.Salk researchers targeted a specific DNA-repair cellular pathway called ‘non-homologous end-joining’ (NHEJ), which repaired routine DNA breaks by rejoining the original strand ends. This process was paired with existing gene-editing technology to successfully place new DNA into a precise location in non-dividing cells.After optimising the NHEJ machinery for use within the CRISPR-Cas9 syst, the research team created a custom insertion package made up of a ‘nucleic acid cocktail’ called HITI (homology-independent targeted integration).After early success in using the HITI in non-dividing cells, the research team used the insertion package to deliver a functional copy of Mertk, one of the genes that is damaged in retinitis pigmentosa, to the eyes of three-week-old rats.By the time the rats were eight weeks old it was said they were able to respond to light. They also passed several tests that indicated healing in their retinal cells.Senior author Professor Juan Carlos Izpisua Belmonte said, “We now have a technology that allows us to modify the DNA of non-dividing cells, to fix broken genes in the brain, heart and liver. It allows us for the first time to be able to dream of curing diseases that we couldn’t before, which is exciting.”The team are now looking to improve the delivery efficiency of the HITI construct.