Genetic modifiers of Cep290-mediated retinal degeneration
Mutations in CEP290 cause up to 30% of cases of Leber congenital amaurosis (LCA), a severe childhood blindness resulting from abnormalities in the photoreceptor connecting cilia that lead to rapid retinal degeneration. Like many genetic diseases, CEP290-LCA has considerable variable expressivity, indicating the presence of other factors that influence phenotypic outcome. Here, we have undertaken a phenotype-driven approach in mice to identify genetic modifiers of CEP290-mediated retinal degeneration through backcrosses and intercrosses between BXD24-Cep290rd16 mice and the genetically distinct inbred CAST strain to introduce genetic variation. Optical coherence tomography was used to quantitatively measure retinal thickness as a surrogate indication of photoreceptor degeneration in the resulting rd16-mutant mice. It was readily apparent that CEP290-mediated retinal degeneration in the resulting mice is sensitive to genetic background, with some mice exhibiting relatively thick laminated retinas and others having thin retinas with advanced disease. Quantitative trait locus (QTL) analysis identified multiple genomic loci capable of influencing the retinal degeneration phenotype in Cep290-mutant mice that together account for 71.7% of the phenotypic variation in retinal thickness observed in our population. Following the QTL analysis, two suppressor loci were studied in detail through a combination of physical and molecular approaches to narrow the critical region for each QTL and identify the probable causative genetic variations.