Retina Autosomal Dominant Retinitis Pigmentosa with Intrafamilial Variability and Incomplete Penetrance in Two Families Carrying Mutations in PRPF8 Ce´cilia G. Maubaret,1,2 Veronika Vaclavik,1,2,3,4,5 Rajarshi Mukhopadhyay,1,2,3 Naushin H. Waseem,1 Amanda Churchill,6 Graham E. Holder,1,3 Anthony T. Moore,1,3 Shomi S. Bhattacharya,1 and Andrew R. Webster1,3 PURPOSE. The aim of this study was to report detailed genotype/ mutation c.6930GϾC (p.R2310S) was found in the second phenotype correlation in two British autosomal dominant ret- family. initis pigmentosa (adRP) families with recently described mu- CONCLUSIONS. This is the first report of marked intrafamilial tations in PRPF8. variability associated with mutations in the PRPF8 gene, in- METHODS. Ten affected members from the two families (ex- cluding incomplete penetrance. PRPF8 mutations should be cluded for PRPF31 mutations) were assessed clinically. Seven suspected in patients with adRP and variable expressivity. (Invest subjects had fundus photography; some had electrophysiology, Ophthalmol Vis Sci. 2011;52:9304–9309) DOI:10.1167/iovs.11- autofluorescence imaging, and visual field testing. Linkage anal- 8372 ysis was performed from genomic DNA in one family. RNA was extracted from lymphocytes of the proband from both families, etinitis pigmentosa (RP) is term used to describe a group of reverse transcribed into cDNA and subsequently screened for Rinherited retinal disorders in which there is degeneration mutations in PRPF8. Segregation of mutations in each family of rod and cone photoreceptors. There is considerable genetic was tested by direct genomic sequencing of the specific exons and phenotypic heterogeneity. Typically the first symptom is carrying the mutation. night blindness reflecting early rod photoreceptor involvement RESULTS. All affected members complained of nyctalopia with and later there is peripheral field loss and ultimately visual loss variable age of onset. In the first family, there was marked due to involvement of cones in the central retina.1 RP is the variation in the clinical phenotype among affected individuals most frequent inherited form of blindness with a prevalence of ranging from severe rod-cone dystrophy to a 67-year-old pa- approximately 1 in 4000.2 The disorder may be inherited as an tient with a normal retinal appearance and mild rod dysfunc- autosomal dominant, autosomal recessive, or X-linked reces- tion on scotopic electroretinography (ERG). The second family sive trait; maternal, mitochondrial inheritance has also been demonstrated similar variability and a history of a nonpenetrant reported.3 RP may result from mutations in more than 45 individual. Linkage analysis in the first family showed strong genes.3 Dominant transmission occurs in approximately one evidence for linkage to markers on chromosome 17p implicat- third of cases and at least 17 genes have been implicated in ing PRPF8 as a candidate gene. A c.6353 CϾT change causing autosomal dominant RP (adRP).4 Three of these genes, PRPF3, a nonconservative missense mutation p.S2118F was found in PRPF8, and PRFP31 encode splicing factors which together exon 38 of PRPF8 by direct sequencing of the cDNA. The account for approximately 15% of families with adRP in the United Kingdom (RM, ARW, personal communication, 2011). There are few detailed descriptions of the clinical pheno- 5 1 type associated with PRPF8 mutation. The present report From the Institute of Ophthalmology, University College London, describes the detailed clinical phenotype in two British families London, United Kingdom; 3Moorfields Eye Hospital, London, United Kingdom; 4Ophthalmology Department, The University Hospitals of with adRP associated with mutations in PRPF8. Geneva (HUG), Geneva, Switzerland; 5Ophthalmology Hospital Jules Gonin, Lausanne, Switzerland; and 6Bristol Eye Hospital, Bristol, United Kingdom. PATIENTS AND METHODS 2These authors contributed equally to the work and should be considered equivalent first authors. The study adhered to the tenets of the Declaration of Helsinki and was Supported by grants from The Foundation Fighting Blindness, approved by the Local Research Ethics Committee. Fight for Sight European Union Grants EVI-GENORET LSHG-CT-2005– 512036 and RETNET MRTN-CT-2003–504003, a grant from Special Clinical Assessment Trustees of Moorfields Eye Hospital, RD Crusaders Foundation via Fight for Sight, National Institute for Health Research Biomedical Research Two families, a six-generation (family 1) and another three-generation Centre for Ophthalmology, Moorfields Eye Hospital, Foundation Fight- (family 2), were ascertained from the inherited eye disease clinic of the ing Blindness (USA), and the British Retinitis Pigmentosa Society. Moorfields Eye Hospital (Fig. 1). Eight members of family 1, seven Submitted for publication August 10, 2011; revised October 12, affected and one mildly symptomatic, underwent ophthalmic exami- 2011; accepted October 13, 2011. nation including best-corrected visual acuity, slit lamp examination and Disclosure: C.G. Maubaret, None; V. Vaclavik, None; R. fundoscopy. Full medical histories were obtained. Color fundus pho- Mukhopadhyay, None; N.H. Waseem, None; A. Churchill, None; tography was performed in five out of eight patients; three had auto- G.E. Holder, None; A.T. Moore, None; S.S. Bhattacharya, None; A.R. Webster, None fluorescence imaging (AF) and spectral-domain optical coherence to- Corresponding author: Rajarshi Mukhopadhyay, Institute of Oph- mography (SD-OCT) and four had Goldmann visual field examination thalmology, UCL, 11-43 Bath Street, EC1V 9EL London, UK; (VF). Four affected members of family 2 were examined and under- [email protected]. went color fundus photography and three had AF and SD-OCT. Investigative Ophthalmology & Visual Science, December 2011, Vol. 52, No. 13 9304 Copyright 2011 The Association for Research in Vision and Ophthalmology, Inc. Downloaded from iovs.arvojournals.org on 10/01/2021 IOVS, December 2011, Vol. 52, No. 13 Variability and Incomplete Penetrance in PRPF8 RP 9305 FIGURE 1. Pedigree and the electropherogram of family 1 showing mutation in exon 38 (c.6353 CϾT) (upper panel) and (lower panel) the pedigree and c.6930GϾC mutation in exon 42 of family 2. Full field electroretinography (ERG) was performed using the In- the families, genomic DNA was sequenced using primers e38F/e39R in ternational Society for Clinical Electrophysiology of Vision (ISCEV) family 1 and e42F/e42R in family 2. DNA from 130 healthy Caucasian standards6 in two of the milder affected members of family 1 (IV.8 and controls (Sigma-Aldrich, Dorset, UK) was sequenced for the two iden- V.12; Fig. 1) and a young (6-year-old) affected (III.2; Fig. 1) from family tified mutations from family 1 and family 2. 2 who underwent a modified pediatric ERG protocol.7 Molecular Genetic Analysis RESULTS After obtaining written consent, blood samples from affected and unaffected family members were collected for DNA and RNA extrac- Clinical Assessment tions. RNA was isolated from lymphocytes of one affected member Family 1. Seven clinically affected members aged between from each family (Trizol; Invitrogen, Paisley, UK), genomic DNA was 37 and 82 years and one mildly symptomatic, obligate carrier extracted using commercially-available kits (Nucleon DNA Isolation Kit (68 years) were assessed. Six affected subjects complained of for Mammalian Blood; Tepnel Life Sciences, Manchester, UK) accord- night blindness as the first symptom. The age of onset of the ing to the manufacturer’s instructions. Microsatellite markers flanking night blindness varied within family members from early child- known genes for adRP were selected from a linkage mapping set (ABI hood (patients V.10, V.11, V.12) to mid-thirties (IV.12). Visual Prism Linkage Mapping Set v 2.5; Applied Biosystems, Foster City, CA) field constriction was reported in late teens in patients III.2 and and additional FAM-labeled microsatellite markers were selected from V.11 and after the age of forty in patient IV.12. Patient IV.8, an 8 the Ensembl database. PCRs were done (Absolute QPCR; Thermo- obligate carrier, reported no problems driving at night or Fisher, Epsom, UK) according to manufacturer’s instructions. The looking at stars in the night sky although had confessed to mild resultant PCR products were loaded in a DNA sequencer (ABI model difficulty in different lighting conditions previously. He did not 3730; Applied Biosystems) and the genotyping calls and Mendelian complain of any visual field constriction. error checks were performed with commercial software (GeneMarker, Best corrected visual acuity (BCVA) in the better eye was version 1.70; Biogene, Cambridgeshire, UK) for linkage analysis. 6/12 or better in five out of seven symptomatic patients. In the 82-year-old female (III.2), BCVA was 6/18 in the right and 6/36 Mutation Screening in the left eye while in a 59-year-old male (IV.2), it was hand cDNA was synthesized from leukocyte RNA (patient IV.2 in family 1 movements right and 6/18 left eye. and II.2 in family 2) using reverse transcriptase (Superscript III Reverse Bilateral subcapsular cataract was observed in patients III.2 Transcriptase; Invitrogen) according to manufacturer’s instructions. at a young age, IV.2 (age 34 years), and V.11 (age 33 years). In Mutation analysis was performed by Sanger sequencing of the cDNA all patients fundoscopy revealed attenuated retinal vessels, pale using a terminator sequencing kit (BigDye ver 3.1; Life Technologies, optic nerve head and variable degrees of diffuse