Next-generation sequencing identifies unexpected genotype-phenotype correlations in patients with retinitis pigmentosa.

Johannes Birtel,Elisabeth Mangold,Frank G Holz,Hanno J Bolz,Steffen Lenzner,Tobias Eisenberger,Philipp L Müller,Peter Charbel Issa,Martin Gliem,Christian Betz,Christine Neuhaus,Diana Zahnleiter,Alfred S Lewin

doi:10.1371/journal.pone.0207958

Abstract

Retinitis pigmentosa (RP) is an inherited degenerative disease causing severe retinal dystrophy and visual impairment mainly with onset in infancy or adolescence. Targeted next-generation sequencing (NGS) has become an efficient tool to encounter the enormous genetic heterogeneity of diverse retinal dystrophies, including RP. To identify disease-causing mutations in unselected, consecutive RP patients, we conducted Sanger sequencing of genes commonly involved in the suspected genetic RP subtype, followed by targeted large-panel NGS if no mutation was identified, or NGS as primary analysis. A high (70%) detection rate of disease-causing mutations was achieved in a large cohort of 116 unrelated patients. About half (48%) of the solved RP cases were explained by mutations in four genes: RPGR, EYS, PRPF31 and USH2A. Overall, 110 different mutations distributed across 30 different genes were detected, and 46 of these mutations were novel. A molecular diagnosis was achieved in the majority (82–100%) of patients if the family history was suggestive for a particular mode of inheritance, but only in 60% in cases of sporadic RP. The diagnostic potential of extensive molecular analysis in a routine setting is also illustrated by the identification of unexpected genotype-phenotype correlations for RP patients with mutations in CRX, CEP290, RPGRIP1, MFSD8. Furthermore, we identified numerous mutations in autosomal dominant (PRPF31, PRPH2, CRX) and X-linked (RPGR) RP genes in patients with sporadic RP. Variants in RP2 and RPGR were also found in female RP patients with apparently sporadic or dominant disease. In summary, this study demonstrates that massively parallel sequencing of all known retinal dystrophy genes is a valuable diagnostic approach for RP patients.

Highlights

Retinitis pigmentosa (RP) is one of the most common forms of inherited retinal degenerations, affecting about 1:3.000 individuals.[1, 2] It is characterized by a primary rod photoreceptor degeneration and consecutive cone photoreceptor death, leading to night blindness and subsequent progressive vision loss
Disease-causing mutations were identified in 81 (70%) out of the 116 analyzed patients, a high diagnostic yield compared to previous reports using targeted nextgeneration sequencing (NGS) in RP patients (S2 and S3 Tables).[4,5,6,7,8, 10,11,12,13,14,15,16,17,18,19,20]
110 different mutations distributed across 30 different genes were detected in this study, and 46 of these mutations were novel at the time of molecular diagnosis (Fig 1, S2 and S4 Tables)

Summary

Introduction

Retinitis pigmentosa (RP) is one of the most common forms of inherited retinal degenerations, affecting about 1:3.000 individuals.[1, 2] It is characterized by a primary rod photoreceptor degeneration and consecutive cone photoreceptor death, leading to night blindness and subsequent progressive vision loss. Legal blindness at working age is common in RP patients, with devastating professional and social implications for the patients.[1, 2] typical characteristics of RP have been described, there is broad phenotypic variability, regarding both clinical presentation and age of onset. RP is genetically heterogeneous, with more than 60 diseasecausing RP genes reported so far (RetNet, https://sph.uth.edu/retnet/). With novel upcoming therapeutic options such as gene therapy, the identification of the disease-causing mutations has gained importance.[3]

Methods

Results

Conclusion