Whole genome sequencing in patients with retinitis pigmentosa reveals pathogenic DNA structural changes and NEK2 as a new disease gene.

We performed whole genome sequencing in 16 unrelated patients with autosomal recessive retinitis pigmentosa (ARRP), a disease characterized by progressive retinal degeneration and caused by mutations in over 50 genes, in search of pathogenic DNA variants. Eight patients were from North America, whereas eight were Japanese, a population for which ARRP seems to have different genetic drivers. Using a specific workflow, we assessed both the coding and noncoding regions of the human genome, including the evaluation of highly polymorphic SNPs, structural and copy number variations, as well as 69 control genomes sequenced by the same procedures. We detected homozygous or compound heterozygous mutations in 7 genes associated with ARRP (USH2A, RDH12, CNGB1, EYS, PDE6B, DFNB31, and CERKL) in eight patients, three Japanese and five Americans. Fourteen of the 16 mutant alleles identified were previously unknown. Among these, there was a 2.3-kb deletion in USH2A and an inverted duplication of ~446 kb in EYS, which would have likely escaped conventional screening techniques or exome sequencing. Moreover, in another Japanese patient, we identified a homozygous frameshift (p.L206fs), absent in more than 2,500 chromosomes from ethnically matched controls, in the ciliary gene NEK2, encoding a serine/threonine-protein kinase. Inactivation of this gene in zebrafish induced retinal photoreceptor defects that were rescued by human NEK2 mRNA. In addition to identifying a previously undescribed ARRP gene, our study highlights the importance of rare structural DNA variations in Mendelian diseases and advocates the need for screening approaches that transcend the analysis of the coding sequences of the human genome.

The risk of pedestrian collisions with peripheral visual field loss.

Patients with peripheral field loss complain of colliding with other pedestrians in open-space environments such as shopping malls. Field expansion devices (e.g., prisms) can create artificial peripheral islands of vision. We investigated the visual angle at which these islands can be most effective for avoiding pedestrian collisions, by modeling the collision risk density as a function of bearing angle of pedestrians relative to the patient. Pedestrians at all possible locations were assumed to be moving in all directions with equal probability within a reasonable range of walking speeds. The risk density was found to be highly anisotropic. It peaked at ≈45° eccentricity. Increasing pedestrian speed range shifted the risk to higher eccentricities. The risk density is independent of time to collision. The model results were compared to the binocular residual peripheral island locations of 42 patients with forms of retinitis pigmentosa. The natural residual island prevalence also peaked nasally at about 45° but temporally at about 75°. This asymmetry resulted in a complementary coverage of the binocular field of view. Natural residual binocular island eccentricities seem well matched to the collision-risk density function, optimizing detection of other walking pedestrians (nasally) and of faster hazards (temporally). Field expansion prism devices will be most effective if they can create artificial peripheral islands at about 45° eccentricities. The collision risk and residual island findings raise interesting questions about normal visual development.

Two specific mutations are prevalent causes of recessive retinitis pigmentosa in North American patients of Jewish ancestry.

PURPOSE: Retinitis pigmentosa is a Mendelian disease with a very elevated genetic heterogeneity. Most mutations are responsible for less than 1% of cases, making molecular diagnosis a multigene screening procedure. In this study, we assessed whether direct testing of specific alleles could be a valuable screening approach in cases characterized by prevalent founder mutations. METHODS: We screened 275 North American patients with recessive/isolate retinitis pigmentosa for two mutations: an Alu insertion in the MAK gene and the p.Lys42Glu missense in the DHDDS gene. All patients were unrelated; 35 reported Jewish ancestry and the remainder reported mixed ethnicity. RESULTS: We identified the MAK and DHDDS mutations homozygously in only 2.1% and 0.8%, respectively, of patients of mixed ethnicity, but in 25.7% and 8.6%, respectively, of cases reporting Jewish ancestry. Haplotype analyses revealed that inheritance of the MAK mutation was attributable to a founder effect. CONCLUSION: In contrast to most mutations associated with retinitis pigmentosa-which are, in general, extremely rare-the two alleles investigated here cause disease in approximately one-third of North American patients reporting Jewish ancestry. Therefore, their screening constitutes an alternative procedure to large-scale tests for patients belonging to this ethnic group, especially in time-sensitive situations.

Visual Function in Carriers of X-Linked Retinitis Pigmentosa.

PURPOSE: To determine the frequency and severity of visual function loss in female carriers of X-linked retinitis pigmentosa (XLRP). DESIGN: Case series. PARTICIPANTS: Two hundred seventy-six XLRP carriers with cross-sectional data (n = 242) and longitudinal data (n = 34; median follow-up, 16 years; follow-up range, 3-37 years). Half of the carriers were from RPGR- or RP2-genotyped families. METHODS: Retrospective medical records review. MAIN OUTCOME MEASURES: Visual acuities, visual field areas, final dark adaptation thresholds, and full-field electroretinography (ERG) responses to 0.5-Hz and 30-Hz flashes. RESULTS: In genotyped families, 40% of carriers showed a baseline abnormality on at least 1 of 3 psychophysical tests. There was a wide range of function among carriers. For example, 3 of 121 (2%) genotyped carriers were legally blind because of poor visual acuity, some as young as 35 years. Visual fields were less affected than visual acuity. In all carriers, the average ERG amplitude to 30-Hz flashes was approximately 50% of normal, and the average exponential rate of amplitude loss over time was half that of XLRP males (3.7%/year vs. 7.4%/year, respectively). Among obligate carriers with affected fathers, sons, or both, 53 of 55 (96%) had abnormal baseline ERG results. Some carriers who initially had completely normal fundi in both eyes went on to experience moderately decreased vision, although not legal blindness. Among carriers with RPGR mutations, those with mutations in ORF15, compared with those in exons 1-14, had worse final dark adaptation thresholds and lower 0.5-Hz and 30-Hz ERG amplitudes. CONCLUSIONS: Most carriers of XLRP had mildly or moderately reduced visual function but rarely became legally blind. In most cases, obligate carriers could be identified by ERG testing. Carriers of RPGR ORF15 mutations tended to have worse visual function than carriers of RPGR exon 1 through 14 mutations. Because XLRP carrier ERG amplitudes and decay rates over time were on average half of those of affected men, these observations were consistent with the Lyon hypothesis of random X-inactivation.

A missense mutation in PRPF6 causes impairment of pre-mRNA splicing and autosomal-dominant retinitis pigmentosa.

Retinitis pigmentosa (RP) is an inherited form of retinal degeneration that leads to progressive visual-field constriction and blindness. Although the disease manifests only in the retina, mutations in ubiquitously expressed genes associated with the tri-snRNP complex of the spliceosome have been identified in patients with dominantly inherited RP. We screened for mutations in PRPF6 (NM_012469.3), a gene on chromosome 20q13.33 encoding an essential protein for tri-snRNP assembly and stability, in 188 unrelated patients with autosomal-dominant RP and identified a missense mutation, c.2185C>T (p.Arg729Trp). This change affected a residue that is conserved from humans to yeast and cosegregated with the disease in the family in which it was identified. Lymphoblasts derived from patients with this mutation showed abnormal localization of endogenous PRPF6 within the nucleus. Specifically, this protein accumulated in the Cajal bodies, indicating a possible impairment in the tri-snRNP assembly or recycling. Expression of GFP-tagged PRPF6 in HeLa cells showed that this phenomenon depended exclusively on the mutated form of the protein. Furthermore, analysis of endogenous transcripts in cells from patients revealed intron retention for pre-mRNA bearing specific splicing signals, according to the same pattern displayed by lymphoblasts with mutations in other PRPF genes. Our results identify PRPF6 as the sixth gene involved in pre-mRNA splicing and dominant RP, corroborating the hypothesis that deficiencies in the spliceosome play an important role in the molecular pathology of this disease.

Mutational screening of splicing factor genes in cases with autosomal dominant retinitis pigmentosa.

PURPOSE: Mutations in genes encoding proteins from the tri-snRNP complex of the spliceosome account for more than 12% of cases of autosomal dominant retinitis pigmentosa (adRP). Although the exact mechanism by which splicing factor defects trigger photoreceptor death is not completely clear, their role in retinitis pigmentosa has been demonstrated by several genetic and functional studies. To test for possible novel associations between splicing factors and adRP, we screened four tri-snRNP splicing factor genes (EFTUD2, PRPF4, NHP2L1, and AAR2) as candidate disease genes. METHODS: We screened up to 303 patients with adRP from Europe and North America who did not carry known RP mutations. Exon-PCR and Sanger methods were used to sequence the NHP2L1 and AAR2 genes, while the sequences of EFTUD2 and PRPF4 were obtained by using long-range PCRs spanning coding and non-coding regions followed by next-generation sequencing. RESULTS: We detected novel missense changes in individual patients in the sequence of the genes PRPF4 and EFTUD2, but the role of these changes in relationship to disease could not be verified. In one other patient we identified a novel nucleotide substitution in the 5' untranslated region (UTR) of NHP2L1, which did not segregate with the disease in the family. CONCLUSIONS: The absence of clearly pathogenic mutations in the candidate genes screened in our cohort suggests that EFTUD2, PRPF4, NHP2L1, and AAR2 are either not involved in adRP or are associated with the disease in rare instances, at least as observed in this study in patients of European and North American origin.

Screening of a large cohort of leber congenital amaurosis and retinitis pigmentosa patients identifies novel LCA5 mutations and new genotype-phenotype correlations.

This study was undertaken to investigate the prevalence of sequence variants in LCA5 in patients with Leber congenital amaurosis (LCA), early-onset retinal dystrophy (EORD), and autosomal recessive retinitis pigmentosa (arRP); to delineate the ocular phenotypes; and to provide an overview of all published LCA5 variants in an online database. Patients underwent standard ophthalmic evaluations after providing informed consent. In selected patients, optical coherence tomography (OCT) and fundus autofluorescence imaging were possible. DNA samples from 797 unrelated patients with LCA and 211 with the various types of retinitis pigmentosa (RP) were screened by Sanger sequence analysis of all LCA5 exons and intron/exon junctions. Some LCA patients were prescreened by APEX technology or selected based on homozygosity mapping. In silico analyses were performed to assess the pathogenicity of the variants. Segregation analysis was performed where possible. Published and novel LCA5 variants were collected, amended for their correct nomenclature, and listed in a Leiden Open Variation Database (LOVD). Sequence analysis identified 18 new probands with 19 different LCA5 variants. Seventeen of the 19 LCA5 variants were novel. Except for two missense variants and one splice site variant, all variants were protein-truncating mutations. Most patients expressed a severe phenotype, typical of LCA. However, some LCA subjects had better vision and intact inner segment/outer segment (IS/OS) junctions on OCT imaging. In two families with LCA5 variants, the phenotype was more compatible with EORD with affected individuals displaying preserved islands of retinal pigment epithelium. One of the families with a milder phenotype harbored a homozygous splice site mutation; a second family was found to have a combination of a stop mutation and a missense mutation. This is the largest LCA5 study to date. We sequenced 1,008 patients (797 with LCA, 211 with arRP) and identified 18 probands with LCA5 mutations. Mutations in LCA5 are a rare cause of childhood retinal dystrophy accounting for ∼2% of disease in this cohort, and the majority of LCA5 mutations are likely null. The LCA5 protein truncating mutations are predominantly associated with LCA. However, in two families with the milder EORD, the LCA5 gene analysis revealed a homozygous splice site mutation in one and a stop mutation in combination with a missense mutation in a second family, suggesting that this milder phenotype is due to residual function of lebercilin and expanding the currently known phenotypic spectrum to include the milder early onset RP. Some patients have remaining foveal cone structures (intact IS/OS junctions on OCT imaging) and remaining visual acuities, which may bode well for upcoming treatment trials.

PRPF mutations are associated with generalized defects in spliceosome formation and pre-mRNA splicing in patients with retinitis pigmentosa.

Proteins PRPF31, PRPF3 and PRPF8 (RP-PRPFs) are ubiquitously expressed components of the spliceosome, a macromolecular complex that processes nearly all pre-mRNAs. Although these spliceosomal proteins are conserved in eukaryotes and are essential for survival, heterozygous mutations in human RP-PRPF genes lead to retinitis pigmentosa, a hereditary disease restricted to the eye. Using cells from patients with 10 different mutations, we show that all clinically relevant RP-PRPF defects affect the stoichiometry of spliceosomal small nuclear RNAs (snRNAs), the protein composition of tri-small nuclear ribonucleoproteins and the kinetics of spliceosome assembly. These mutations cause inefficient splicing in vitro and affect constitutive splicing ex-vivo by impairing the removal of at least 9% of endogenously expressed introns. Alternative splicing choices are also affected when RP-PRPF defects are present. Furthermore, we show that the steady-state levels of snRNAs and processed pre-mRNAs are highest in the retina, indicating a particularly elevated splicing activity. Our results suggest a role for PRPFs defects in the etiology of PRPF-linked retinitis pigmentosa, which appears to be a truly systemic splicing disease. Although these mutations cause widespread and important splicing defects, they are likely tolerated by the majority of human tissues but are critical for retinal cell survival.

Spinocerebellar ataxia type 7: clinical course, phenotype-genotype correlations, and neuropathology.

Spinocerebellar ataxia type 7 is a neurodegenerative polyglutamine disease characterized by ataxia and retinal degeneration. The longitudinal course is unknown, and relationships between repeat expansion, clinical manifestations, and neuropathology remain uncertain. We followed 16 affected individuals of a 61-member kindred over 27 years with electroretinograms, neurological examinations including the Brief Ataxia Rating Scale, neuroimaging in five, and autopsy in four cases. We identified four stages of the illness: Stage 0, gene-positive but phenotypically silent; Stage 1, no symptoms, but hyperreflexia and/or abnormal electroretinograms; Stage 2, symptoms and signs progress modestly; and Stage 3, rapid clinical progression. CAG repeat length correlated inversely with age of onset of visual or motor signs (r = -0.74, p = 0.002). Stage 3 rate of progression did not differ between cases (p = 0.18). Electroretinograms correlated with Brief Ataxia Rating Scale score and were a biomarker of disease onset and progression. All symptomatic patients developed gait ataxia, extremity dysmetria, dysarthria, dysrhythmia, and oculomotor abnormalities. Funduscopy revealed pale optic discs and pigmentary disturbances. Visual acuity declined to blindness in those with longer CAG expansions. Hyperreflexia was present from Stage 1 onwards. Restless legs syndrome and sensory impairment were common. Neuropathological hallmarks were neuronal loss in cerebellar cortex, deep cerebellar nuclei, inferior olive, and anterior horns of the spinal cord, and axonal loss in spinocerebellar tracts, dorsal nerve roots, and posterior columns. Retinal pathology included photoreceptor degeneration and disruption of retinal pigment epithelium. Spinocerebellar ataxia type 7 evolves through four clinical stages; neuropathological findings underlie the clinical presentation; electroretinograms are a potential biomarker of disease progression.

Next generation sequencing of pooled samples reveals new SNRNP200 mutations associated with retinitis pigmentosa.

The gene SNRNP200 is composed of 45 exons and encodes a protein essential for pre-mRNA splicing, the 200 kDa helicase hBrr2. Two mutations in SNRNP200 have recently been associated with autosomal dominant retinitis pigmentosa (adRP), a retinal degenerative disease, in two families from China. In this work we analyzed the entire 35-Kb SNRNP200 genomic region in a cohort of 96 unrelated North American patients with adRP. To complete this large-scale sequencing project, we performed ultra high-throughput sequencing of pooled, untagged PCR products. We then validated the detected DNA changes by Sanger sequencing of individual samples from this cohort and from an additional one of 95 patients. One of the two previously known mutations (p.S1087L) was identified in 3 patients, while 4 new missense changes (p.R681C, p.R681H, p.V683L, p.Y689C) affecting highly conserved codons were identified in 6 unrelated individuals, indicating that the prevalence of SNRNP200-associated adRP is relatively high. We also took advantage of this research to evaluate the pool-and-sequence method, especially with respect to the generation of false positive and negative results. We conclude that, although this strategy can be adopted for rapid discovery of new disease-associated variants, it still requires extensive validation to be used in routine DNA screenings.

Premature termination codons in PRPF31 cause retinitis pigmentosa via haploinsufficiency due to nonsense-mediated mRNA decay.

Dominant mutations in the gene encoding the mRNA splicing factor PRPF31 cause retinitis pigmentosa, a hereditary form of retinal degeneration. Most of these mutations are characterized by DNA changes that lead to premature termination codons. We investigated 6 different PRPF31 mutations, represented by single-base substitutions or microdeletions, in cell lines derived from 9 patients with dominant retinitis pigmentosa. Five of these mutations lead to premature termination codons, and 1 leads to the skipping of exon 2. Allele-specific measurement of PRPF31 transcripts revealed a strong reduction in the expression of mutant alleles. As a consequence, total PRPF31 protein abundance was decreased, and no truncated proteins were detected. Subnuclear localization of the full-length PRPF31 that was present remained unaffected. Blocking nonsense-mediated mRNA decay significantly restored the amount of mutant PRPF31 mRNA but did not restore the synthesis of mutant proteins, even in conjunction with inhibitors of protein degradation pathways. Our results indicate that most PRPF31 mutations ultimately result in null alleles through the activation of surveillance mechanisms that inactivate mutant mRNA and, possibly, proteins. Furthermore, these data provide compelling evidence that the pathogenic effect of PRPF31 mutations is likely due to haploinsufficiency rather than to gain of function.

Novel mutations in the long isoform of the USH2A gene in patients with Usher syndrome type II or non-syndromic retinitis pigmentosa.

BACKGROUND: Usher syndrome type II (USH2) is an autosomal recessive disorder characterised by retinitis pigmentosa (RP) and mild to moderate sensorineural hearing loss. Mutations in the USH2A gene are the most common cause of USH2 and are also a cause of some forms of RP without hearing loss (ie, non-syndromic RP). The USH2A gene was initially identified as a transcript comprised of 21 exons but subsequently a longer isoform containing 72 exons was identified. METHODS: The 51 exons unique to the long isoform of USH2A were screened for mutations among a core set of 108 patients diagnosed with USH2 and 80 patients with non-syndromic RP who were all included in a previously reported screen of the short isoform of USH2A. For several exons, additional patients were screened. RESULTS: In total, 35 deleterious mutations were identified including 17 nonsense mutations, 9 frameshift mutations, 5 splice-site mutations, and 4 small in-frame deletions or insertions. Twenty-seven mutations were novel. In addition, 65 rare missense changes were identified. A method of classifying the deleterious effect of the missense changes was developed using the summed results of four different mutation assessment algorithms, SIFT, pMUT, PolyPhen, and AGVGD. This system classified 8 of the 65 changes as 'likely deleterious' and 9 as 'possibly deleterious'. CONCLUSION: At least one mutation was identified in 57-63% of USH2 cases and 19-23% of cases of non-syndromic recessive RP (calculated without and including probable/possible deleterious changes) thus supporting that USH2A is the most common known cause of RP in the USA.

Defects in RGS9 or its anchor protein R9AP in patients with slow photoreceptor deactivation.

The RGS proteins are GTPase activating proteins that accelerate the deactivation of G proteins in a variety of signalling pathways in eukaryotes. RGS9 deactivates the G proteins (transducins) in the rod and cone phototransduction cascades. It is anchored to photoreceptor membranes by the transmembrane protein R9AP (RGS9 anchor protein), which enhances RGS9 activity up to 70-fold. If RGS9 is absent or unable to interact with R9AP, there is a substantial delay in the recovery from light responses in mice. We identified five unrelated patients with recessive mutations in the genes encoding either RGS9 or R9AP who reported difficulty adapting to sudden changes in luminance levels mediated by cones. Standard visual acuity was normal to moderately subnormal, but the ability to see moving objects, especially with low-contrast, was severely reduced despite full visual fields; we have termed this condition bradyopsia. To our knowledge, these patients represent the first identified humans with a phenotype associated with reduced RGS activity in any organ.

Extended wearing trial of Trifield lens device for 'tunnel vision'.

Severe visual field constriction (tunnel vision) impairs the ability to navigate and walk safely. We evaluated Trifield glasses as a mobility rehabilitation device for tunnel vision in an extended wearing trial. Twelve patients with tunnel vision (5-22 degrees wide) due to retinitis pigmentosa or choroideremia participated in the 5-visit wearing trial. To expand the horizontal visual field, one spectacle lens was fitted with two apex-to-apex prisms that vertically bisected the pupil on primary gaze. This provides visual field expansion at the expense of visual confusion (two objects with the same visual direction). Patients were asked to wear these spectacles as much as possible for the duration of the wearing trial (median 8, range 6-60 weeks). Clinical success (continued wear, indicating perceived overall benefit), visual field expansion, perceived direction and perceived visual ability were measured. Of 12 patients, nine chose to continue wearing the Trifield glasses at the end of the wearing trial. Of those nine patients, at long-term follow-up (35-78 weeks), three reported still wearing the Trifield glasses. Visual field expansion (median 18, range 9-38 degrees) was demonstrated for all patients. No patient demonstrated adaptation to the change in visual direction produced by the Trifield glasses (prisms). For reported difficulty with obstacles, some differences between successful and non-successful wearers were found. Trifield glasses provided reported benefits in obstacle avoidance to 7 of the 12 patients completing the wearing trial. Crowded environments were particularly difficult for most wearers. Possible reasons for long-term discontinuation and lack of adaptation to perceived direction are discussed.

A single-base substitution within an intronic repetitive element causes dominant retinitis pigmentosa with reduced penetrance.

We report the study of a large American family displaying autosomal dominant retinitis pigmentosa with reduced penetrance, a form of hereditary retinal degeneration. Although the inheritance pattern and previous linkage mapping pointed to the involvement of the PRPF31 gene, extensive screening of all its exons and their boundaries failed in the past to reveal any mutation. In this work, we sequenced the entire PRPF31 genomic region by both the classical Sanger method and ultrahigh throughput (UHT) sequencing. Among the many variants identified, a single-base substitution (c.1374+654C>G) located deep within intron 13 and inside a repetitive DNA element was common to all patients and obligate asymptomatic carriers. This change created a new splice donor site leading to the synthesis of two mutant PRPF31 isoforms, degraded by nonsense-mediated mRNA decay. As a consequence, amounts of PRPF31 mRNA derived from the mutant allele were very reduced, with no evidence of mutant proteins being synthesized. Our results indicate that c.1374+654C>G causes retinitis pigmentosa via haploinsufficiency, similar to the vast majority of PRPF31 mutations described so far. We discuss the potential of UHT sequencing technologies in mutation screening and the continued identification of pathogenic splicing mutations buried deep within intronic regions.

Search for a correlation between telomere length and severity of retinitis pigmentosa due to the dominant rhodopsin Pro23His mutation.

PURPOSE: Great variation exists in the age of onset of symptoms and the severity of disease at a given age in patients with retinitis pigmentosa (RP). The final pathway for this disease may involve apoptotic photoreceptor cell death. Telomere length is associated with biologic aging, senescence, and apoptosis. We evaluated whether the length of telomeres in leukocytes correlated with the severity of RP in patients with the Pro23His rhodopsin mutation who have shown marked heterogeneity in disease severity. METHODS: We evaluated 122 patients with the Pro23His rhodopsin mutation. The patients' retinal function was stratified according to their 30-Hz cone electroretinogram (ERG). The length of telomeres in leukocytes was measured by the quantitative real time polymerase chain reaction (qRT-PCR) method in the 15 patients with the highest age-adjusted 30-Hz ERG amplitudes and in the 15 patients with the lowest amplitudes. RESULTS: Mean leukocyte telomere length was similar in the 15 patients with the highest cone ERG amplitudes (median: 0.40 units; interquartile range 0.36-0.56) and the 15 patients with the lowest cone amplitudes (median: 0.41 units; inter quartile range 0.34 -0.64; p=0.95). CONCLUSIONS: We found no evidence for an association between telomere length and the severity of RP as monitored by the cone ERG in patients with the Pro23His rhodopsin mutation.

Association of Vitamin A Supplementation With Disease Course in Children With Retinitis Pigmentosa.

Importance: While oral vitamin A supplementation is considered to potentially slow loss of retinal function in adults with retinitis pigmentosa and normal liver function, little data from children with this disease are available. Objective: To compare disease courses in children with retinitis pigmentosa taking or not taking vitamin A supplementation. Design, Setting, and Participants: Retrospective, nonrandomized comparison of vitamin A and control cohorts followed up for a mean of 4 to 5 years by the Electroretinography Service of the Massachusetts Eye and Ear Infirmary. The study included children with different genetic types of typical retinitis pigmentosa: 55 taking vitamin A and 25 not taking vitamin A. The dates for patient evaluations ranged from June 1976 to July 2016, and the data analysis occurred in October 2016. Interventions: Age-adjusted dose of oral vitamin A palmitate (≤15 000 IU/d). Main Outcomes and Measures: Mean exponential rates of change of full-field cone electroretinogram amplitude to 30-Hz flashes estimated by repeated-measures longitudinal regression without and with adjusting for potential confounders. Results: Of the 55 children in the vitamin A cohort, 38 (69%) were male; the mean [SD] age was 9.1 [1.9] years; and 48 (87%) were white , 6 (11%) were Asian, and 1 (2%) was black. Of the 25 members of the control cohort, 19 (76%) were male; the mean [SD] age was 9.2 [1.7] years; and 25 (100%) were white. The estimated mean rates of change with the unadjusted model were -0.0713 loge unit/y (-6.9% per year) for the vitamin A cohort and -0.1419 loge unit per year (-13.2% per year) for the control cohort (difference, 0.0706 loge unit per year; 95% CI for the difference, 0.0149-0.1263 loge unit per year; P = .01). The adjusted model confirmed a slower mean rate of decline in the vitamin A cohort (difference, 0.0771 loge-unit per year; 95% CI for the difference, 0.0191-0.1350 loge-unit per year; P = .009). With respect to ocular safety, the mean exponential rates of change of visual field area and visual acuity and the incidences of falling to a visual field diameter of 20° or less or a visual acuity of 20/200 or less in at least 1 eye did not differ by cohort. Conclusions and Relevance: A vitamin A palmitate supplement was associated with a slower loss of cone electroretinogram amplitude in children with retinitis pigmentosa. Although the relatively small-sample, retrospective, nonrandomized design does not allow a test of causation and is subject to possible biases, these findings support consideration of an age-adjusted dose of vitamin A in the management of most children with the common forms of retinitis pigmentosa.

Retinitis pigmentosa.

Hereditary degenerations of the human retina are genetically heterogeneous, with well over 100 genes implicated so far. This Seminar focuses on the subset of diseases called retinitis pigmentosa, in which patients typically lose night vision in adolescence, side vision in young adulthood, and central vision in later life because of progressive loss of rod and cone photoreceptor cells. Measures of retinal function, such as the electroretinogram, show that photoreceptor function is diminished generally many years before symptomic night blindness, visual-field scotomas, or decreased visual acuity arise. More than 45 genes for retinitis pigmentosa have been identified. These genes account for only about 60% of all patients; the remainder have defects in as yet unidentified genes. Findings of controlled trials indicate that nutritional interventions, including vitamin A palmitate and omega-3-rich fish, slow progression of disease in many patients. Imminent treatments for retinitis pigmentosa are greatly anticipated, especially for genetically defined subsets of patients, because of newly identified genes, growing knowledge of affected biochemical pathways, and development of animal models.

Disease course of patients with X-linked retinitis pigmentosa due to RPGR gene mutations.

PURPOSE: To measure the rates of visual acuity, visual field, and ERG loss in patients with X-linked retinitis pigmentosa due to RPGR mutations and to determine whether these rates differ from those of patients with dominant retinitis pigmentosa due to RHO mutations. METHODS: Snellen visual acuities, Goldmann visual field areas (V4e white test light), and 30 Hz (cone) full-field ERG amplitudes were recorded for an average of 9.8 years in 113 patients with RPGR mutations. After censoring data to eliminate ceiling and floor effects, we used longitudinal regression to estimate mean rates of change and to compare these rates with those of a previously studied cohort of 134 patients with dominant retinitis pigmentosa due to RHO mutations, who were followed for an average of 8.9 years. Survival analysis was used to compare the age distribution of legal blindness in these two groups. To explain group differences in visual acuity, optical coherence tomograms were recorded in some patients to visualize central retinal structure. RESULTS: Mean annual exponential rates of decline for the patients with RPGR mutations were 4.0% for visual acuity, 4.7% for visual field area, and 7.1% for ERG amplitude. Each of these rates was significantly different from zero (P < 0.001). The rates of visual acuity and visual field loss were significantly faster than the corresponding rates in the RHO patients (1.6%, P < 0.001 and 2.9%, P = 0.002, respectively), whereas the rate of ERG amplitude loss was comparable to that in the RHO patients (7.7%, P = 0.39). The median age of legal blindness was 32 years younger in the RPGR patients than in the RHO patients, due primarily to loss of visual acuity rather than to loss of visual field. Loss of acuity in RPGR patients appeared to be associated with foveal thinning. CONCLUSIONS: Patients with X-linked retinitis pigmentosa due to RPGR mutations lose visual acuity and visual field more rapidly than do patients with dominant retinitis pigmentosa due to RHO mutations.

Low prevalence of lecithin retinol acyltransferase mutations in patients with Leber congenital amaurosis and autosomal recessive retinitis pigmentosa.

PURPOSE: To determine the the prevalence of pathogenic mutations in the gene encoding lecithin retinol acyltransferase (LRAT) in patients from North America with either Leber congenital amaurosis (LCA) or autosomal recessive retinitis pigmentosa (ARRP). METHODS: Exon 1, exon 2, and the coding region of exon 3 of LRAT were PCR-amplified and directly sequenced from the leukocyte DNA of 82 unrelated patients with LCA and 190 unrelated patients with ARRP. RESULTS: One isocoding change was found in this screen of LRAT (Glu114 GAG>GAA; c.342), and 5 other sequence changes were found in intronic or untranslated regions of the gene. None of these changes were predicted to affect the encoded protein and were therefore deemed non-pathogenic. CONCLUSIONS: LRAT mutations are likely a rare cause of LCA among patients from North America.