Characterization of Three Gene Targeted Mouse Models of RNA Splicing Factor Retinitis Pigmentosa

Abstract

Purpose: : Mutations in RNA splicing factor genes (PRPF3, PRPF8, PRPF31, RP9 and SNRNP200) are the second most common cause of autosomal dominant retinitis pigmentosa (RP). These factors are components of the spliceosome, a ubiquitous macromolecular complex required for splicing pre-mRNA in all cell types. It is not known, however, how mutations in these genes lead to retina-specific disease. To investigate the disease mechanism of splicing factor gene mutations, we generated and characterized three knockin mouse models.

Methods: : The Prpf3 mouse model was generated by introduction of a T494M missense mutation identified in RP18 patients. Prpf8 mice were generated by the introduction of a H2309P missense mutation found in RP13 patients. Prpf31 mice carry an A216P mutation identified in RP11 patients. Here we report the retina and retinal pigment epithelium (RPE) phenotype of these mice documented by electroretinography (ERG), light and electron microscopy, as well as phagocytosis assays.

Results: : The homozygous knockin Prpf3T494M/T494M mice experience late onset retinal dysfunction. At timepoints up to 18 months, no significant differences were found between the wild-type and knockin animals. However, at 24 months a significant difference was found in the maximal rod a-wave. Ultrastructural analyses revealed that the RPE cells of the Prpf3T494M/T494M mice exhibit vacuolization with loss of the basolateral infoldings and accumulation of amorphous deposits between the RPE and Bruch’s membrane. The photoreceptor cells in the homozygous knockin mice appear to be normal in histologic and ultrastructural analyses. At 24 months of age, the Prpf8H2309P/H2309P mice also exhibit evidence of degenerative changes in RPE cells; however no ERG alterations were detected. Similar RPE structural changes were observed in Prpf31+/A216P mice at 12 months of age. We also show effects of mutations in these splicing factor genes on the phagocytosis in the RPE.

Conclusions: : The three knockin mouse models of RNA splicing factor RP experience late onset retinal phenotype, characterized by degenerative changes in the RPE. The finding of similar RPE changes in all three mouse models suggests that the RPE is the primary tissue affected by RNA splicing factor RP.

Keywords: degenerations/dystrophies • genetics • retinal pigment epithelium