Long-term clinical course of 2 Japanese patients with PRPF31-related retinitis pigmentosa

Clinical and Genetic Findings in a Cohort of Patients with PRPF31-associated Retinal Dystrophy

PURPOSE

The purpose of our study was to assess the phenotypic and genotypic spectrum in a large cohort of patients with PRPF31-associated retinal dystrophy.

DESIGN

Retrospective cohort study METHODS: In this retrospective chart review study, we collected cross-sectional data on the phenotype and genotype of patients with PRPF31-associated retinal dystrophy from the clinics for inherited retinal dystrophies at the University of Tuebingen and the local RetDis database and biobank. Patients underwent thorough ophthalmological examinations and genetic testing.

RESULTS

Eighty-six patients from 61 families were available for clinical assessment, while genomic DNA was available for 111 individuals (index patients and family members). Fifty-three different disease-associated variants were observed in our cohort. Point mutations were the most common class. All but two patients exhibited features of a typical Retinitis pigmentosa (RP). One patient showed a cone-rod-dystrophy pattern. One mutation carrier revealed no signs of a retinal dystrophy. There was a statistically significant better visual acuity for patients with large deletions in the 20-39 age group. Cystoid macular edema was common in those with preserved central retina and showed an association with female sex.

CONCLUSION

Our study confirms high phenotypic variability in disease onset and age at which legal blindness is reached in PRPF31-linked RP. Non-penetrance is commonly documented in family history, although poorly represented in our study, possibly indicating that true asymptomatic mutation carriers are rare if followed-up over lifetime with thorough ophthalmologic workup.

Mutation spectrum of PRPF31, genotype-phenotype correlation in retinitis pigmentosa, and opportunities for therapy

Pathogenic variants in pre-messenger RNA (pre-mRNA) splicing factor 31, PRPF31, are the second most common genetic cause of autosomal dominant retinitis pigmentosa (adRP) in most populations. This remains a completely untreatable and incurable form of blindness, and it can be difficult to predict the clinical course of disease. In order to design appropriate targeted therapies, a thorough understanding of the genetics and molecular mechanism of this disease is required. Here, we present the structure of the PRPF31 gene and PRPF31 protein, current understanding of PRPF31 protein function and the full spectrum of all reported clinically relevant variants in PRPF31. We delineate the correlation between specific PRPF31 genotype and RP phenotype, suggesting that, except in cases of complete gene deletion or large-scale deletions, dominant negative effects contribute to phenotype as well as haploinsufficiency. This has important impacts on design of targeted therapies, particularly the feasibility of gene augmentation as a broad approach for treatment of PRPF31-associated RP. We discuss other opportunities for therapy, including antisense oligonucleotide therapy and gene-independent approaches and offer future perspectives on treatment of this form of RP.

•

PRPF31 is the second most common cause of autosomal dominant retinitis pigmentosa and a potential target for gene therapy.

•

We present all reported pathogenic variants in PRPF31 as a resource for clinicians, diagnostic genetics labs, and researchers.

•

Genotype-phenotype correlations suggest that, dominant negative effects contribute to disease in addition to haploinsufficiency.

•

This finding has important impacts on the suitability of gene augmentation approaches across all mutation types.

•

This finding may aid prognosis of disease in PRPF31-associated RP patients.

Direct comparison of retinal structure and function in retinitis pigmentosa by co-registering microperimetry and optical coherence tomography

PURPOSE

To evaluate the retinal structure-function relationships in the macula of retinitis pigmentosa (RP) patients by comparing microperimetry-3 (MP-3) images with co-registered optical coherence tomography (OCT) images.

METHODS

Thirty patients with typical RP were recruited from our hospital. The maculae of patients were examined with MP-3 and OCT. The retinal sensitivity was measured by MP-3 at 40 testing points arranged concentrically in a 16° diameter of the central retina, and we divided the 40 points into four zones according to degree from the fovea (2°, 4°, 6°, and 8°). We analyzed the correlation coefficients between the retinal sensitivity and the total retinal thickness (TRT), the length from the inner limiting membrane to the retinal pigment epithelium (RPE), and between the retinal sensitivity and the outer retinal thickness (ORT), the length from the outer plexiform layer to the RPE at each stimulus point.

RESULTS

TRT showed moderate correlations with the retinal sensitivity at 2° (median ρ = 0.59 interquartile range (IQR) [0.38-0.72]), 4° (ρ = 0.59 [0.55-0.68]) and 6° (ρ = 0.60 [0.54-0.63]), and TRT was weakly-to-moderately related to the retinal sensitivity at 8° (ρ = 0.27 [0.19-0.48]). ORT exhibited strong correlations at 2° (ρ = 0.72 [0.60-0.81]), 4° (ρ = 0.71 [0.75-0.67]) and 6° (ρ = 0.70 [0.54-0.74]), and a weak-to-moderate correlations at 8° (ρ = 0.34 [0.29-0.53]). ORT was more strongly correlated with the retinal sensitivity compared to TRT (p = 0.018).

CONCLUSION

ORT, rather than TRT, within 6° eccentricity was strongly correlated with the retinal sensitivity, suggesting that measuring ORT in those areas will help evaluate the macular status and progression in RP.