Purpose: We developed two strains of mouse with retinal dysfunction, named the ICR-derived retinal dysfunction (IRD)1 and IRD2, from one male ICR mouse with a retinal dysfunction but a normal fundus. The purpose of this study was to describe the features of retinal dysfunction in both mutant mice.
Methods: Scotopic and photopic electroretinograms (ERGs) were recorded from IRD1 and IRD2 mice at 1 month of age to evaluate retinal function, and then the structures of the retinas in both mutant mice were observed by light microscopy at 1 and 3 months of age. In a mating study, the inheritance pattern and the genetic relation of IRD1 and IRD2 mice were defined.
Results: At 1 month of age, IRD1 mice showed affected scotopic and photopic ERGs, and IRD2 mice exhibited normal photopic but affected scotopic ERGs. The retinal structures of both mutant mice remained normal even at 3 months of age. The IRD1, and IRD2 phenotypes showed an autosomal recessive pattern of inheritance and in the IRD1 backcross offspring some mice that had only cone dysfunction were seen in addition to normal, IRD1, and IRD2 phenotypes. All F1 (IRD1 x IRD2) offspring exhibited IRD2 phenotype, rod dysfunction.
Conclusions: IRD1 and IRD2 mice had affected rod systems caused by a homozygous mutation in the same rod function-related gene, and additionally IDR1 mice had affected cone systems caused by a homozygous mutation in the cone function-related gene, without apparent anatomical abnormalities in the retinas of either mutant mice even at 3 months of age. We believe that these mice could be new spontaneous animal models for the study of human inherited retinal disorders.