Human iPSC-derived RPE and retinal organoids reveal impaired alternative splicing of genes involved in pre-mRNA splicing in PRPF31 autosomal dominant retinitis pigmentosa
Authors: Buskin Adriana , Zhu Lili , Chichagova Valeria , Basu Basudha , Mozaffari-Jovin Sina , Dolan David , Droop Alastair , Collin Joseph , Bronstein Revital , Mehrotra Sudeep , Farkas Michael , Hilgen Gerrit , White Kathryn , Hallam Dean , Bialas Katarzyna , Chung Git , Mellough Carla , Ding Yuchun , Krasnogor Natalio , Przyborski Stefan , Al-Aama Jumana , Alharthi Sameer , Xu Yaobo , Wheway Gabrielle , Szymanska Katarzyna , McKibbin Martin , Inglehearn Chris F , Elliott David J , Lindsay Susan , Ali Robin R , Steel David H , Armstrong Lyle , Sernagor Evelyne , Pierce Eric , Lüehrmann Reinhard , Grellscheid Sushma-Nagaraja , Johnson Colin A , Lako Majlinda 
Published: December 2017

Mutations in pre-mRNA processing factors (PRPFs) cause 40% of autosomal dominant retinitis pigmentosa (RP), but it is unclear why mutations in ubiquitously expressed PRPFs cause retinal disease. To understand the molecular basis of this phenotype, we have generated RP type 11 (PRPF31-mutated) patient-specific retinal organoids and retinal pigment epithelium (RPE) from induced pluripotent stem cells (iPSC). Impaired alternative splicing of genes encoding pre-mRNA splicing proteins occurred in patient-specific retinal cells and Prpf31+/− mouse retinae, but not fibroblasts and iPSCs, providing mechanistic insights into retinal-specific phenotypes of PRPFs. RPE was the most affected, characterised by loss of apical-basal polarity, reduced trans-epithelial resistance, phagocytic capacity, microvilli, and cilia length and incidence. Disrupted cilia morphology was observed in patient-derived-photoreceptors that displayed progressive features associated with degeneration and cell stress. In situ gene-editing of a pathogenic mutation rescued key structural and functional phenotypes in RPE and photoreceptors, providing proof-of-concept for future therapeutic strategies.

eTOC

PRPF31 is a ubiquitously expressed pre-mRNA processing factor that when mutated causes autosomal dominant RP. Using a patient-specific iPSC approach, Buskin and Zhu et al. show that retinal-specific defects result from altered splicing of genes involved in the splicing process itself, leading to impaired splicing, loss of RPE polarity and diminished phagocytic ability as well as reduced cilia incidence and length in both photoreceptors and RPE.

Highlights

Successful generation of iPSC-derived RPE and photoreceptors from four RP type 11 patients

RPE cells express the mutant PRPF31 protein and show the lowest expression of wildtype protein

PRPF31 mutations result in altered splicing of genes involved in pre-mRNA splicing in RPE and retinal organoids

Prpf31 haploinsufficiency results in altered splicing of genes involved in pre-mRNA splicing in mouse retina

RPE cells display loss of polarity, reduced barrier function and phagocytosis

Photoreceptors display shorter and fewer cilia and degenerative features

RPE cells display most abnormalities suggesting they might be the primary site of pathogenesis

In situ gene editing corrects the mutation and rescues key phenotypes