In vivo genome editing rescues photoreceptor degeneration via a Cas9/RecA-mediated homology-directed repair pathway

Abstract

Although Cas9-mediated genome editing has been widely used to engineer alleles in animal models of human inherited diseases, very few homology-directed repair (HDR)-based genetic editing systems have been established in postnatal mouse models for effective and lasting phenotypic rescue. Here, we developed an HDR-based Cas9/RecA system to precisely correct <i>Pde6b</i> mutation with increased HDR efficiency in postnatal <i>rodless</i> (<i>rd1</i>) mice, a retinitis pigmentosa (RP) mutant model characterized by photoreceptor degeneration and loss of vision. The Cas9/RecA system incorporated Cas9 endonuclease enzyme to generate double-strand breaks (DSBs) and bacterial recombinase A (RecA) to increase homologous recombination. Our data revealed that Cas9/RecA treatment significantly promoted the survival of both rod and cone photoreceptors, restored the expression of PDE6B in rod photoreceptors, and enhanced the visual functions of <i>rd1</i> mice. Thus, this study provides a precise therapeutic strategy for RP and other genetic diseases.