N-acetylcysteine suppresses retinal defects in Drosophila models of SNRNP200-associated retinitis pigmentosa.

Retinitis Pigmentosa (RP) is an inherited retinal degenerative disease that affects 1 in 4000 individuals worldwide and can lead to complete blindness. Early stages of RP involve death of rod photoreceptors via apoptosis, causing loss of peripheral and night vision, which is followed by death of cone photoreceptors, leading to loss of central and daytime vision. Mutations in over 300 genes cause RP. Many of these genes encode retina-specific proteins; however, some encode globally expressed proteins, such as pre-mRNA splicing factors. This study is focused on mutations in the SNRNP200 gene encoding a core pre-mRNA splicing factor. The pathological mechanisms of SNRNP200-associated RP are not well understood and treatments are limited. An approach to study pathogenic mechanisms is to utilize model organisms. Therefore, we developed Drosophila models in which RP-causing mutations were introduced into the Drosophila melanogaster orthologue Snrnp200. In addition, we used RNAi to knock-down Snrnp200 in the developing eye. Depletion of Snrnp200 caused an adult rough eye phenotype due to apoptosis of cells in the retina. When human RP-causing mutations were modeled in Drosophila Snrnp200, they resulted in abnormal retinal electrophysiology and defective patterning of photoreceptors. Further analysis of the photoreceptors revealed mitochondrial defects and altered expression of genes related to redox homeostasis. Consistent with these changes, treatment with the antioxidant N-acetylcysteine (NAC) partially suppressed the photoreceptor defects. Taken together, these findings established a new genetic model for studies of splicing-factor associated RP that recapitulates aspects of the human disease and suggests that antioxidants might serve as a treatment for individuals with SNRNP200-associated RP.