Salk scientists use new gene editing approach to restore sight in rats

A close image of a blue eye
Scientists at the Salk Institute are investigating a new gene-editing technique as a treatment for the blinding disease retinitis pigmentosa.

The gene-editing approach called CRISPR-Cas9 has been grabbing headlines for its potential to address diseases ranging from cancer to sickle cell disease—but scientists at the Salk Institute may have found a way to improve upon the technology. And they’ve shown their method could hold promise for restoring some sight in adults who are blind.

Salk announced that scientists there have developed a way to insert DNA in a specific location in cells that are no longer dividing. CRISPR-Cas9, by contrast, has been shown to work best in dividing cells, like those found in the skin and stomach, because the method piggybacks on those cells’ normal dividing processes. The ability to change the DNA of non-dividing cells could make gene editing more widely applicable, even to diseases of the brain and heart.

“So this is important because in adult organisms, the majority of our cells are non-dividing,” said Jun Wu, staff scientist and co-lead author of the study in a video from Salk.

The Salk team paired a DNA-repair pathway called non-homologous end-joining (NHEJ) with CRISPR-Cas9 technology, according to a release from the institution. Then they used an inert virus to deliver genetic instructions to neurons. It worked, so they decided to try the method on rat models of the disease retinitis pigmentosa, an inherited disorder that causes gradual blindness in people. 

The rats had functional copies of the gene Mertk, which has been implicated in retinitis pigmentosa. After the Salk team performed the gene-editing technique, the animals began responding to light, and they did well on several tests that showed their retinal cells were healing.

Retinitis pigmentosa is the most common genetic disease that damages the retina, which is the light-sensitive tissue at the back of the eye. Other techniques are being investigated to combat the disease, including gene therapy, which was shown in 2015 to preserve vision in dogs with a naturally occurring form of retinitis pigmentosa.

The next step for the Salk team is to prove their gene-editing technique will be safe to use in people, and to figure out whether they will need to make the modifications in just a few cells with the disease-causing genetic mutation or if they’ll have to fix several cells. Still, says Wu, the ability to modify neurons in the adult brain is significant because “we can specifically target a certain cell type, which other technologies had been incapable of doing up until now,” he said. “We are very optimistic that this technology can open doors for many newer, broader applications to either basic or translational medicine.”