Mutant PRPF8 Causes Widespread Splicing Changes in Spliceosome Components in Retinitis Pigmentosa Patient iPSC-Derived RPE Cells

Abstract

Retinitis pigmentosa (RP) is a rare, progressive disease that affects photoreceptors and retinal pigment epithelial (RPE) cells with blindness as a final outcome. Despite high medical and social impact, there is currently no therapeutic options to slow down the progression of or cure the disease. The development of effective therapies was largely hindered by high genetic heterogeneity, inaccessible disease tissue, and unfaithful model organisms. The fact that components of ubiquitously expressed splicing factors lead to the retina-specific disease is an additional intriguing question. Herein, we sought to correlate the retinal cell-type-specific disease phenotype with the splicing profile shown by a patient with autosomal recessive RP, caused by a mutation in pre-mRNA splicing factor 8 (PRPF8). In order to get insight into the role of PRPF8 in homeostasis and disease, we capitalize on the ability to generate patient-specific RPE cells and reveal differentially expressed genes unique to RPE cells. We found that spliceosomal complex and ribosomal functions are crucial in determining cell-type specificity through differential expression and alternative splicing (AS) and that PRPF8 mutation causes global changes in splice site selection and exon inclusion that particularly affect genes involved in these cellular functions. This finding corroborates the hypothesis that retinal tissue identity is conferred by a specific splicing program and identifies retinal AS events as a framework toward the design of novel therapeutic opportunities.

Modeling PRPF31 retinitis pigmentosa using retinal pigment epithelium and organoids combined with gene augmentation rescue

“…The different PRPF31 -mutated iPSCs generated in our study expressed pluripotent markers and presented classical properties of human pluripotent stem cells, indicating that mutations in the ubiquitous PRPF31 gene did not affect the reprogramming of the pluripotent state per se. Furthermore, we were able to generate RPE cells and pseudo-laminated retinal organoids from several iPSC lines carrying different PRPF31 mutations, confirming that the differentiation process is not impaired, as recently reported for different PRPF8 and PRPF31 iPSCs 29 , 30 , 48 .…”

Aberrant Retinal Pigment Epithelial Cells Derived from Induced Pluripotent Stem Cells of a Retinitis Pigmentosa Patient with the PRPF6 Mutation

“…A heterozygous knock-in mouse model carrying the prpf31 p.A216P mutation displayed RPE pathological morphologies, including a drusen-like deposit, large lipofuscin accumulation and atrophy of basal infoldings [ 33 ]. However, intriguingly, it was reported that PRPF8 mutation caused widespread splicing changes but did not display distinctly abnormal behavior in patient iPSC-derived RPE cells [ 8 , 40 ]. Therefore, different member mutations from the PRPF family may lead to different effects on RPE.…”

“…Pre-mRNA processing factors (PRPFs) are essential for the U4/U6/U5 tri-snRNP complex, playing a critical role in the splicing process. Mutations in PRPF genes linked to adRP have been identified, including PRPF3 , PRPF4 , PRPF6 , PRPF8 , PRPF31 , SNRNP200 and RP9 [ 8 ].…”

Application of patient-derived induced pluripotent stem cells and organoids in inherited retinal diseases

“…Mutations in pre-mRNA processing factors (PRPFs) are the main cause of autosomal dominant RP related to the formation of the U4/U6.U5 tri-snRNP complex, a core spliceosome component [ 39 ]. For instance, RPE cells generated from iPSCs of an RP patient carrying the PRPF8 mutation showed widespread changes in alternative splicing events and dysregulated expression of genes involved in the splicing process and ribosome, indicating loss of spliceosome function [ 40 ]. In addition, ROs and RPE models from patient-specific iPSCs with the PRPF31 mutation showed impaired pre-mRNA splicing process as described by Baskin et al On the other hand, abnormal photoreceptor and RPE changes were also observed, including cell morphology, cilium structure, apical-basal polarity, and phagocytosis function of the photoreceptor outer segment (POS) [ 41 ].…”