Mutant Prpf31 causes pre-mRNA splicing defects and rod photoreceptor cell degeneration in a zebrafish model for Retinitis pigmentosa

Jun Yin,Jan Brocher,Christoph Winkler,Utz Fischer

doi:10.1186/1750-1326-6-56

Abstract

BackgroundRetinitis pigmentosa (RP) is an inherited eye disease characterized by the progressive degeneration of rod photoreceptor cells. Mutations in pre-mRNA splicing factors including PRPF31 have been identified as cause for RP, raising the question how mutations in general factors lead to tissue specific defects.ResultsWe have recently shown that the zebrafish serves as an excellent model allowing the recapitulation of key events of RP. Here we use this model to investigate two pathogenic mutations in PRPF31, SP117 and AD5, causing the autosomal dominant form of RP. We show that SP117 leads to an unstable protein that is mislocalized to the rod cytoplasm. Importantly, its overexpression does not result in photoreceptor degeneration suggesting haploinsufficiency as the underlying cause in human RP patients carrying SP117. In contrast, overexpression of AD5 results in embryonic lethality, which can be rescued by wild-type Prpf31. Transgenic retina-specific expression of AD5 reveals that stable AD5 protein is initially localized in the nucleus but later found in the cytoplasm concurrent with progressing rod outer segment degeneration and apoptosis. Importantly, we show for the first time in vivo that retinal transcripts are wrongly spliced in adult transgenic retinas expressing AD5 and exhibiting increased apoptosis in rod photoreceptors.ConclusionOur data suggest that distinct mutations in Prpf31 can lead to photoreceptor degeneration through different mechanisms, by haploinsufficiency or dominant-negative effects. Analyzing the AD5 effects in our animal model in vivo, our data imply that aberrant splicing of distinct retinal transcripts contributes to the observed retina defects.

Highlights

Retinitis pigmentosa (RP) is an inherited eye disease characterized by the progressive degeneration of rod photoreceptor cells
We have recently shown that zebrafish serves as an excellent in vivo model to study the consequences of prpf31 gene knock-down on retina function [15]
In RP11 families, a multitude of mutations including missense and nonsense substitutions, deletions as well as insertions have been reported in the PRPF31 gene

Summary

Introduction

Retinitis pigmentosa (RP) is an inherited eye disease characterized by the progressive degeneration of rod photoreceptor cells. Retinitis pigmentosa (RP), a general cause for blindness, is a clinically and genetically highly heterogeneous disorder affecting approximately 1.6 million people worldwide [1] This hereditary disease is characterized by the progressive degeneration of photoreceptor cells in the retina, firstly affects rods and later results in the loss of cones. These genes include PRPF3 [9], PRPF8 [10], PRPF31 [11], PAP1 [12,13] and SNRN200 [14] All these genes encode core components of the U4/U6.U5 tri-snRNP complex which constitutes a major building block of the pre-mRNA processing spliceosome [5,15]. PRPF31 interacts with U4 and is required during U4/U6.U5 tri-snRNP assembly and maintenance in spliceosomes [19,20]

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