Modeling Cone/Cone-Rod Dystrophy Pathology by AAV-Mediated Overexpression of Mutant CRX Protein in the Mouse Retina

This study aims to evaluate the pathogenesis of cone/cone-rod dystrophy (CoD/CoRD) caused by a cone-rod homeobox (CRX) mutation, which was identified in a Chinese family, through adeno-associated virus (AAV)-mediated overexpression of mutant CRX protein in the mouse retina.

Comprehensive ophthalmologic examinations were performed for the pedigree members of a Chinese family with CoD/CoRD. Whole exome sequencing and Sanger sequencing were performed to determine the genetic cause of the disease. Furthermore, AAV vectors were used to construct AAV-CRX-mut-HA, which was transfected into mouse photoreceptor cells to clarify the pathogenesis of the mutant CRX.

Fundus photography and optical coherence tomography images displayed features that were consistent with CoD/CoRD, including macular atrophy and photoreceptor layer thinning. Electroretinogram analysis indicated an obvious decrease in photopic responses or both scotopic and photopic responses in affected individuals. A frameshift variant c.611delC (p.S204fs) in CRX was cosegregated with the disease in this family. AAV-CRX-mut-HA that subretinally injected into the C57BL/6 mice generally transfected the outer nuclear layer, leading to the loss of cone and rod photoreceptor cells, abnormal expression of CRX target genes, and a decrease in electroretinogram responses.

AAV-mediated overexpression of CRX[S204fs] in the mouse retina led to a CoRD-like phenotype and showed the possible pathogenesis of the antimorphic CRX mutation.

This study provides a modeling method to evaluate the pathogenesis of CoD/CoRD and other inherited retinal dystrophies caused by distinct gain-of-function mutations.