AAV-CRB2 protects against vision loss in an inducible CRB1 retinitis pigmentosa mouse model

Abstract Loss of CRB1 or CRB2 proteins in Muller cells or photoreceptors in the mouse retina results in a CRB-dose-dependent retinal phenotype. Here, we present a novel Muller cell-specific Crb1KOCrb2LowMGC retinitis pigmentosa mouse model (Complete loss of CRB1 and reduced levels of CRB2 specifically in Muller cells). The Crb double mutant mice showed deficits in electroretinography, optokinetic head tracking, and retinal morphology. Exposure of retinas to low levels of DL-α-aminoadipate acid induced gliosis and retinal disorganization in Crb1KOCrb2LowMGC but not in wild-type or Crb1-deficient retinas. Crb1KOCrb2LowMGC mice showed a substantial decrease in inner/outer photoreceptor segments length and optokinetic head-tracking response. Intravitreal application of rAAV vectors expressing human CRB2 in Muller cells of Crb1KOCrb2LowMGC mice subsequently exposed to low levels of DL-α-aminoadipate acid prevented loss of vision, whereas rAAV vectors expressing human CRB1 did not. Both rAAV-vectors partially protected the morphology of the retina. The results suggest that human CRB expression in Muller cells is vital for control of retinal cell adhesion at the outer limiting membrane, and that the rAAV-CMV-hCRB2 vector is more potent than the rAAV-CMVmin-hCRB1 in protection against loss of vision.