A Wuhan University of Science and Technology-led team reporting in the Journal of Experimental Medicine shares findings from a study that used prime editing tools to treat a mouse model of a retinal degeneration disease called retinitis pigmentosa, an inherited condition marked by progressive retinal photoreceptor loss. Using prime editors, an unconstrained, protospacer adjacent motif-free version of the Cas9 enzyme known as SpRY, and corresponding guide RNAs, together with an adeno-associated virus delivery system, the researchers tackled a form of retinitis pigmentosa caused by alterations affecting the phosphodiesterase 6b-coding gene PDE6b, demonstrating that they could correct the mutation, halt the progressive loss of photoreceptors, and improve visual responses in the mouse model. "Together, our study provides convincing evidence for the prevention of vision loss caused by [retinitis pigmentosa]-associated gene mutations via unconstrained in vivo prime editing in the degenerating retinas," the authors write.