Identification of a Modifier Gene That Rescues Nr2e3Rd7/rd7 Associated Retina Defects

Abstract

Purpose: : The rd7 mouse, harboring a mutation in Nr2e3, is a model for the human retinal diseases Enhanced S Cone Syndrome and Retinitis Pigmentosa, and exhibits over-proliferation of blue opsin expressing cones and progressive retinal degeneration. Our previous studies identified several loci on two mouse strains (CAST/EiJ, AKR/J) that are able to suppress the rd7 retinal degenerative phenotype. The purpose of this study was to identify a genetic modifier gene in AKR/J strain (Mor7) that can ameliorate the retinal defects associated with Nr2e3 mutations.

Methods: : A combination of genetic fine mapping and candidate gene analysis was performed to identify the Mor7 gene. Sequence analysis was performed to identify polymorphisms in candidate genes that may confer resistance to Nr2e3^rd7/rd7 associated retinal degeneration. In vivo electroporation of candidate modifiers was performed in P0 Nr2e3^rd7/rd7 retinas. Electroporated eyes were examined at P14, P30, and P60 clinically, histologically, and functionally to determine if the modifier allele can ameliorate Nr2e3^rd7/rd7 associated retinal degeneration.

Results: : A sequence polymorphism was identified in the AKR/J allele of an Mor7 candidate modifier gene. Nr2e3^rd7/rd7 mice electroporated with the Mor7 candidate gene exhibited suppression of Nr2e3^rd7/rd7 associated retinal defects.

Conclusions: : We identified a genetic modifier gene, Mor7, in the AKR/J strain that is able to rescue Nr2e3^rd7/rd7 associated retinal degeneration. In the absence of Nr2e3, the Mor7^AKR/J allele is able to functionally compensate and restore normal photoreceptor development, and prevent retinal defects in Nr2e3^rd7/rd7 mice.

Keywords: gene modifiers • gene transfer/gene therapy • retinal development