Eliot L. Berson

A Randomized Trial of Vitamin A and Vitamin E Supplementation for Retinitis Pigmentosa

OBJECTIVEnTo determine whether supplements of vitamin A or vitamin E alone or in combination affect the course of retinitis pigmentosa.nnnDESIGNnRandomized, controlled, double-masked trial with 2 x 2 factorial design and duration of 4 to 6 years. Electroretinograms, visual field area, and visual acuity were measured annually.nnnSETTINGnClinical research facility.nnnPATIENTSn601 patients aged 18 through 49 years with retinitis pigmentosa meeting preset eligibility criteria. Ninety-five percent of the patients completed the study. There were no adverse reactions.nnnINTERVENTIONnPatients were assigned to one of four treatment groups receiving 15,000 IU/d of vitamin A, 15,000 IU/d of vitamin A plus 400 IU/d of vitamin E, trace amounts of both vitamins, or 400 IU/d of vitamin E.nnnMAIN OUTCOME MEASUREnCone electroretinogram amplitude.nnnRESULTSnThe two groups receiving 15,000 IU/d of vitamin A had on average a slower rate of decline of retinal function than the two groups not receiving this dosage (P = .01). Among 354 patients with higher initial amplitudes, the two groups receiving 15,000 IU/d of vitamin A were 32% less likely to have a decline in amplitude of 50% or more from baseline in a given year than those not receiving this dosage (P = .01), while the two groups receiving 400 IU/d of vitamin E were 42% more likely to have a decline in amplitude of 50% or more from baseline than those not receiving this dosage (P = .03). While not statistically significant, similar trends were observed for rates of decline of visual field area. Visual acuity declined about 1 letter per year in all groups.nnnCONCLUSIONSnThese results support a beneficial effect of 15,000 IU/d of vitamin A and suggest an adverse effect of 400 IU/d of vitamin E on the course of retinitis pigmentosa.

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.

NMNAT1 mutations cause Leber congenital amaurosis.

Leber congenital amaurosis (LCA) is an infantile-onset form of inherited retinal degeneration characterized by severe vision loss. Two-thirds of LCA cases are caused by mutations in 17 known disease-associated genes (Retinal Information Network (RetNet)). Using exome sequencing we identified a homozygous missense mutation (c.25G>A, p.Val9Met) in NMNAT1 that is likely to be disease causing in two siblings of a consanguineous Pakistani kindred affected by LCA. This mutation segregated with disease in the kindred, including in three other children with LCA. NMNAT1 resides in the previously identified LCA9 locus and encodes the nuclear isoform of nicotinamide mononucleotide adenylyltransferase, a rate-limiting enzyme in nicotinamide adenine dinucleotide (NAD+) biosynthesis. Functional studies showed that the p.Val9Met alteration decreased NMNAT1 enzyme activity. Sequencing NMNAT1 in 284 unrelated families with LCA identified 14 rare mutations in 13 additional affected individuals. These results are the first to link an NMNAT isoform to disease in humans and indicate that NMNAT1 mutations cause LCA.

Clinical trial of lutein in patients with retinitis pigmentosa receiving vitamin A.

OBJECTIVEnTo determine whether lutein supplementation will slow visual function decline in patients with retinitis pigmentosa receiving vitamin A.nnnDESIGNnRandomized, controlled, double-masked trial of 225 nonsmoking patients, aged 18 to 60 years, evaluated over a 4-year interval. Patients received 12 mg of lutein or a control tablet daily. All were given 15,000 IU/d of vitamin A palmitate. Randomization took into account genetic type and baseline serum lutein level.nnnMAIN OUTCOME MEASURESnThe primary outcome was the total point score for the Humphrey Field Analyzer (HFA) 30-2 program; prespecified secondary outcomes were the total point scores for the 60-4 program and for the 30-2 and 60-4 programs combined, 30-Hz electroretinogram amplitude, and Early Treatment Diabetic Retinopathy Study acuity.nnnRESULTSnNo significant difference in rate of decline was found between the lutein plus vitamin A and control plus vitamin A groups over a 4-year interval for the HFA 30-2 program. For the HFA 60-4 program, a decrease in mean rate of sensitivity loss was observed in the lutein plus vitamin A group (P = .05). Mean decline with the 60-4 program was slower among those with the highest serum lutein level or with the highest increase in macular pigment optical density at follow-up (P = .01 and P = .006, respectively). Those with the highest increase in macular pigment optical density also had the slowest decline in HFA 30-2 and 60-4 combined field sensitivity (P = .005). No significant toxic effects of lutein supplementation were observed.nnnCONCLUSIONnLutein supplementation of 12 mg/d slowed loss of midperipheral visual field on average among nonsmoking adults with retinitis pigmentosa taking vitamin A. Application to Clinical Practice Data are presented that support use of 12 mg/d of lutein to slow visual field loss among nonsmoking adults with retinitis pigmentosa taking vitamin A.nnnTRIAL REGISTRATIONnClinicalTrials.gov Identifier: NCT00346333.

Evidence That the Penetrance of Mutations at the RP11 Locus Causing Dominant Retinitis Pigmentosa Is Influenced by a Gene Linked to the Homologous RP11 Allele

A subset of families with autosomal dominant retinitis pigmentosa (RP) display reduced penetrance with some asymptomatic gene carriers showing no retinal abnormalities by ophthalmic examination or by electroretinography. Here we describe a study of three families with reduced-penetrance RP. In all three families the disease gene appears to be linked to chromosome 19q13.4, the region containing the RP11 locus, as defined by previously reported linkage studies based on five other reduced-penetrance families. Meiotic recombinants in one of the newly identified RP11 families and in two of the previously reported families serve to restrict the disease locus to a 6-cM region bounded by markers D19S572 and D19S926. We also compared the disease status of RP11 carriers with the segregation of microsatellite alleles within 19q13.4 from the noncarrier parents in the newly reported and the previously reported families. The results support the hypothesis that wild-type alleles at the RP11 locus or at a closely linked locus inherited from the noncarrier parents are a major factor influencing the penetrance of pathogenic alleles at this locus.

Electroretinographic Findings in Selected Pedigrees With Choroideremia

We recorded full-field electroretinograms from 47 males and 26 obligate carrier females with choroideremia. All males had responses that were subnormal with delayed cone b-wave implicit times or undetectable. Only four of 26 females had abnormal electroretinographic responses but 25 of 26 were identified by ophthalmoscopy.

Electroretinogram (ERG) sensitivity and phagosome frequency in the normal pigmented rat

Normal adult pigmented rats, born and raised in cyclic light for 25- to 27 days and then placed in darkness for up to 24 hr, showed an inverse relation between electroretinogram (ERG) sensitivity and phagosome frequency in the pigment epithelium over the course of a day. Linear regression revealed that a two-fold increase in the frequency of large phagosomes was associated with approximately a one-third decrease in ERG sensitivity. The observed 37-40% decline in ERG sensitivity 1.5 hr after expected light onset was significantly greater than what would be expected from the measured 11% shortening of rod outer segments at that time of day. Possible explanations for this disparity are considered.

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.

Diurnal rhythm in the electroretinogram of the royal college of surgeons (RCS) pigmented rat

RCS pigmented rats, born and raised in cyclic light for 22-23 days and then placed in darkness for up to 24 hr, showed a diurnal rhythm in the rod electroretinogram (ERG) that was comparable with that seen in normal pigmented rats. a-Wave and b-wave sensitivities were 21- and 34% lower, respectively, 1.5 hr after expected light onset compared with those at other times of day. In contrast to findings in normal rats, however, these sensitivity decreases in the RCS rats were not associated with an increase in the frequency of large phagosomes in the pigment epithelium; phagosome frequency was subnormal and relatively constant over the day. These findings suggest that depressed ERG sensitivities 1.5 hr after expected light onset in both normal and RCS pigmented rats reflect altered rod photoreceptor function associated with the process of outer-segment disc shedding and not with engulfment of shed discs into phagosomes by the pigment epithelium.

Two families from New England with usher syndrome type IC with distinct haplotypes

PURPOSEnTo search for patients with Usher syndrome type IC among those with Usher syndrome type I who reside in New England.nnnMETHODSnGenotype analysis of microsatellite markers closely linked to the USH1C locus was done using the polymerase chain reaction. We compared the haplotype of our patients who were homozygous in the USH1C region with the haplotypes found in previously reported USH1C Acadian families who reside in southwestern Louisiana and from a single family residing in Lebanon.nnnRESULTSnOf 46 unrelated cases of Usher syndrome type I residing in New England, two were homozygous at genetic markers in the USH1C region. Of these, one carried the Acadian USH1C haplotype and had Acadian ancestors (that is, from Nova Scotia) who did not participate in the 1755 migration of Acadians to Louisiana. The second family had a haplotype that proved to be the same as that of a family with USH1C residing in Lebanon. Each of the two families had haplotypes distinct from the other.nnnCONCLUSIONnThis is the first report that some patients residing in New England have Usher syndrome type IC. Patients with Usher syndrome type IC can have the Acadian haplotype or the Lebanese haplotype compatible with the idea that at least two independently arising pathogenic mutations have occurred in the yet-to-be identified USH1C gene.