CRISPR gene-editing technique reverses vision loss in mice

Summary: Using a very versatile form of CRISPR gene editing, researchers were able to restore vision in mice with retinitis pigmentosa.

Source: Rockefeller University Press

Researchers in China have succeeded in restoring vision to mice with retinitis pigmentosa, one of the leading causes of blindness in humans.

The study, which will be published on March 17 in the Journal of Experimental Medicineuses a new, highly versatile form of CRISPR-based genome editing with the potential to correct a wide variety of disease-causing genetic mutations.

Researchers have previously used genome editing to restore vision to mice with genetic diseases, such as Leber congenital amaurosis, which affect the retinal pigment epithelium, a layer of non-neuronal cells in the eye that supports light-sensitive rod and cone photoreceptor cells. . However, most inherited forms of blindness, including retinitis pigmentosa, are caused by genetic defects in the neural photoreceptors themselves.

“The ability to genome edit neural retinal cells, particularly diseased or dying photoreceptors, would provide much more compelling evidence for the potential applications of these genome editing tools in the treatment of diseases such as retinitis pigmentosa,” Kai says. Yao, a professor at Wuhan University of Science and Technology.

Retinitis pigmentosa can be caused by mutations in over 100 different genes and is estimated to impair the vision of 1 in 4,000 people. It begins with the dysfunction and death of rod cells sensitive to dim light, before spreading to the cone cells necessary for color vision, ultimately resulting in severe and irreversible vision loss.

Yao and his colleagues attempted to save the vision of mice with retinitis pigmentosa caused by a mutation in the gene coding for a critical enzyme called PDE6β. To do this, Yao’s team developed a new, more versatile CRISPR system called PE^Alertwhich can be programmed to correct many types of genetic mutations, regardless of their location in the genome.

When programmed to target the mutant PDE6β gene, PE^Alert was able to effectively correct the mutation and restore the activity of the enzyme in the mouse retina. This prevented the death of rod and cone photoreceptors and restored their normal electrical responses to light.

Yao and his colleagues performed a variety of behavioral tests to confirm that the genetically modified mice retained their vision even into old age. For example, the animals were able to exit a visually guided water maze nearly as well as normal, healthy mice and exhibited typical head movements in response to visual stimuli.

Yao warns that much more needs to be done to establish both safety and efficacy of PE^Alert system in man.

“However, our study provides substantial evidence for the in vivo applicability of this novel genome editing strategy and its potential in various research and therapeutic settings, particularly for inherited retinal diseases such as retinitis pigmentosa,” Yao said.

About this gene editing and visual neuroscience research news

Author: Press office
Source: Rockefeller University Press
Contact: Press Office – Rockefeller University Press
Picture: Image is credited to Qin et al/JEM

Original research: Free access.
“Rescue of vision via unconstrained in vivo master editing in degenerating neural retinas” by Huan Qin et al. Journal of Experimental Medicine

Abstract

Rescue of vision via unconstrained in vivo master editing in degenerating neural retinas

Retinitis pigmentosa (RP) is an inherited retinal dystrophy resulting in progressive and irreversible loss of retinal photoreceptors.

Here, we developed a genome editing tool characterized by versatility of major editors (PE) and unconstrained PAM requirement of an SpCas9 (SpRY) variant, termed PE^Alert.

The diseased retinas of Pde6b-the associated RP mouse model was transduced via a dual AAV PE packaging system^Alert for in vivo genome editing via non-NGG PAM (GTG).

The progressive cell loss was reversed once the mutation was corrected, leading to substantial rescue of photoreceptors and production of functional PDE6β. Treated mice showed significant responses on electroretinogram and performed well in passive and active avoidance tests.

Additionally, they exhibited apparent improvement in optomotor responses focused on visual stimuli and performed visually-guided water maze tasks effectively.

Together, our study provides compelling evidence for the prevention of vision loss caused by RP-associated genetic mutations via unconstrained in vivo primary editing in degenerating retinas.