Mutations in the splicing regulator Prp31 lead to retinal degeneration in Drosophila

Abstract

Retinitis pigmentosa (RP) is a clinically heterogeneous disease affecting 1.6 million people worldwide. The second-largest group of genes causing autosomal dominant RP in human encodes regulators of the splicing machinery. Yet, how defects in splicing factor genes are linked to the aetiology of the disease remains largely elusive. To explore possible mechanisms underlying retinal degeneration caused by mutations in regulators of the splicing machinery, we induced mutations in Drosophila Prp31, the orthologue of human PRPF31, mutations in which are associated with RP11. Flies heterozygous mutant for Prp31 are viable and develop normal eyes and retina. However, photoreceptors degenerate under light stress, thus resembling the human disease phenotype. Degeneration is associated with increased accumulation of the visual pigment rhodopsin 1 and increased mRNA levels of twinfilin, a gene associated with rhodopsin trafficking. Reducing rhodopsin levels by raising animals in a carotenoid-free medium not only attenuates rhodopsin accumulation, but also retinal degeneration. Given a similar importance of proper rhodopsin trafficking for photoreceptor homeostasis in human, results obtained in flies presented here will also contribute to further unravel molecular mechanisms underlying the human disease.This paper has an associated First Person interview with the co-first authors of the article.

Modulating the Kynurenine pathway or sequestering toxic 3-hydroxykynurenine protects the retina from light induced damage in Drosophila

“…In all experiments, young flies (2-4 days) were used. We used w ndelT , a null allele previously designated as w* in (Hebbar, Lehmann et al, 2021). In contrast to wild-type eyes, or to eyes mutant for w ndelT exposed for the same time to less stringent light conditions, e.g.…”

“…Fig. S1A,B), or under light/dark conditions (Hebbar et al, 2021). Flies homozygous mutant for w and st (w;; st/st) have white eyes similar as w due to the absence of all screening pigments.…”

“…Histology and analyses of toluidine blue stained sections were carried out as previously described (Hebbar et al, 2021) and modified from (Bulgakova, Rentsch et al, 2010). To compare morphological aspects of degeneration across different conditions, two aspects of light-induced damage were quantified.…”

Untitled

“…Vesicular Rh1 signals reportedly appear in flies exposed to light, becoming even more prominent in mutants that have defects in Rh1 trafficking to the lysosome (24,25). We found that vesicular Rh1 patterns in fabp EY06747 -/-eyes were also light-dependent, as extra-rhabdomeric anti-Rh1 signals mostly disappeared in flies raised under constant darkness (Fig 6E).…”

“…Rh1 forms a stable complex with Arrestin and together undergo endocytosis [18][19][20][21]. The photoreceptors need to degrade those endocytosed Rh1, as excessive Rh1 accumulation in the endosome/lysosome can cause lightdependent retinal degeneration [18,19,[22][23][24][25][26]. These aspects appear to be conserved across phyla, as the human Rhodopsin mutants that exhibit high affinities for Arrestin display endosomal abnormalities and are associated with severe forms of ADRP [27,28].…”