Mutations in the TOPORS gene cause 1% of autosomal dominant retinitis pigmentosa.

PURPOSE: The purpose of this project was to determine if mutations, including large insertions or deletions, in the recently identified RP31 gene topoisomerase I-binding arginine-serine rich (RS) protein (TOPORS), cause an appreciable fraction of autosomal dominant retinitis pigmentosa (adRP). METHODS: An adRP cohort of 215 families was used to determine the frequency of TOPORS mutations. We looked for mutations in TOPORS by testing 89 probands from the cohort without mutations in other known adRP genes. Mutation detection was performed by fluorescent capillary sequencing and by multiplex ligation probe amplification. RESULTS: Two different TOPORS mutations, p.Glu808X and p.Arg857GlyfsX9, were each identified in one proband. Patients with these mutations exhibited clinical signs typical of advanced adRP. No large deletions or insertions of TOPORS were identified in our study. CONCLUSIONS: Point mutations and small insertions or deletions in TOPORS cause approximately 1% of adRP. Large deletions or insertions of TOPORS are not an appreciable cause of adRP. Contrary to previous reports, no distinct clinical phenotype was seen in these patients.

The Gly56Arg mutation in NR2E3 accounts for 1-2% of autosomal dominant retinitis pigmentosa.

PURPOSE: Mutations in the orphan nuclear receptor gene NR2E3 have been found to cause both recessive and dominant retinopathies. The purpose of this study was to determine the prevalence of the recently described Gly56Arg mutation in a well characterized cohort of families with autosomal dominant retinitis pigmentosa (adRP). METHODS: A cohort of 215 families with adRP which have already been screened for mutations in 13 of the other known adRP genes was used to determine the frequency of the Gly56Arg mutation. The 92 families without a disease-causing mutation in a known gene were tested for the presence of the Gly56Arg mutation using direct DNA sequencing. An additional set of 100 normal controls (200 chromosomes) was also screened by DNA sequencing. RESULTS: The Gly56Arg mutation was found in three of the 92 adRP families studied and was not found in unaffected control samples. CONCLUSIONS: The Gly56Arg mutation in NR2E3 accounts for approximately 1%-2% of adRP, making it one of the more common single mutations in adRP.

Spectrum and frequency of mutations in IMPDH1 associated with autosomal dominant retinitis pigmentosa and leber congenital amaurosis.

PURPOSE: The purpose of this study was to determine the frequency and spectrum of inosine monophosphate dehydrogenase type I (IMPDH1) mutations associated with autosomal dominant retinitis pigmentosa (RP), to determine whether mutations in IMPDH1 cause other forms of inherited retinal degeneration, and to analyze IMPDH1 mutations for alterations in enzyme activity and nucleic acid binding. METHODS: The coding sequence and flanking intron/exon junctions of IMPDH1 were analyzed in 203 patients with autosomal dominant RP (adRP), 55 patients with autosomal recessive RP (arRP), 7 patients with isolated RP, 17 patients with macular degeneration (MD), and 24 patients with Leber congenital amaurosis (LCA). DNA samples were tested for mutations by sequencing only or by a combination of single-stranded conformational analysis and by sequencing. Production of fluorescent reduced nicotinamide adenine dinucleotide (NADH) was used to measure enzymatic activity of mutant IMPDH1 proteins. The affinity and the specificity of mutant IMPDH1 proteins for single-stranded nucleic acids were determined by filter-binding assays. RESULTS: Five different IMPDH1 variants, Thr116Met, Asp226Asn, Val268Ile, Gly324Asp, and His 372Pro, were identified in eight autosomal dominant RP families. Two additional IMPDH1 variants, Arg105Trp and Asn198Lys, were found in two patients with isolated LCA. None of the novel IMPDH1 mutants identified in this study altered the enzymatic activity of the corresponding proteins. In contrast, the affinity and/or the specificity of single-stranded nucleic acid binding were altered for each IMPDH1 mutant except the Gly324Asp variant. CONCLUSIONS: Mutations in IMPDH1 account for approximately 2% of families with adRP, and de novo IMPDH1 mutations are also rare causes of isolated LCA. This analysis of the novel IMPDH1 mutants substantiates previous reports that IMPDH1 mutations do not alter enzyme activity and demonstrates that these mutants alter the recently identified single-stranded nucleic acid binding property of IMPDH. Studies are needed to further characterize the functional significance of IMPDH1 nucleic acid binding and its potential relationship to retinal degeneration.

Prevalence of disease-causing mutations in families with autosomal dominant retinitis pigmentosa: a screen of known genes in 200 families.

PURPOSE: To survey families with clinical evidence of autosomal dominant retinitis pigmentosa (adRP) for mutations in genes known to cause adRP. METHODS: Two hundred adRP families, drawn from a cohort of more than 400 potential families, were selected by analysis of pedigrees. Minimum criteria for inclusion in the adRP cohort included either evidence of at least three generations of affected individuals or two generations with evidence of male-to-male transmission. Probands from each family were screened for mutations in 13 genes known to cause adRP: CA4, CRX, FSCN2, IMPDH1, NRL, PRPF3 (RP18), PRPF8 (RP13), PRPF31 (RP11), RDS, RHO, ROM1, RP1, and RP9. Families without mutations in autosomal genes and in which an X-linked mode of inheritance could not be excluded were tested for mutations in ORF 15 of X-linked RPGR. Potentially pathogenic variants were evaluated based on a variety of genetic and computational criteria, to confirm or exclude pathogenicity. RESULTS: A total of 82 distinct, rare (nonpolymorphic) variants were detected among the genes tested. Of these, 57 are clearly pathogenic based on multiple criteria, 10 are probably pathogenic, and 15 are probably benign. In the cohort of 200 families, 94 (47%) have one of the clearly pathogenic variants and 10 (5%) have one of the probably pathogenic variants. One family (0.5%) has digenic RDS-ROM1 mutations. Two families (1%) have a pathogenic RPGR mutation, indicating that families with apparent autosomal transmission of RP may actually have X-linked genetic disease. Thus, 107 families (53.5%) have mutations in known genes, leaving 93 whose underlying cause is still unknown. CONCLUSIONS: Together, the known adRP genes account for retinal disease in approximately half of the families in this survey, mostly Americans of European origin. Among the adRP genes, IMPDH1, PRPF8, PRPF31, RDS, RHO, and RP1 each accounts for more than 2% of the total; CRX, PRPF3, and RPGR each accounts for roughly 1%. Disease-causing mutations were not found in CA4, FSCN2, NRL, or RP9. Because some mutations are frequent and some regions are more likely to harbor mutations than others, more than two thirds of the detected mutations can be found by screening less than 10% of the total gene sequences. Among the remaining families, mutations may lie in regions of known genes that were not tested, mutations may not be detectable by PCR-based sequencing, or other loci may be involved.

Frequent Dosing of Topical Cyclosporine A for Severe Ocular Surface Disease.

PURPOSE: To study the systemic safety and patient tolerability of frequent dosing of cyclosporine A (CsA) 0.05% eyedrops in the treatment of ocular surface disease. This is a retrospective case series. Patients with significant ocular surface diseases who were treated using topical CsA higher than the usual twice daily dosing (3-8 times daily and over a treatment period of 1-70 months). The main outcome measures are plasma levels of CsA and local tolerability. METHODS: Symptom assessment, corneal staining using fluorescein, conjunctival staining using lissamine green, tear film breakup time, and other signs according to the disease process were monitored. Discontinuation of treatment due to intolerability was recorded. CsA levels were measured in the plasma at a clinical laboratory. RESULTS: Plasma levels of CsA were below the level of detection (7 ng/mL) in all the 41 patients included. All patients tolerated the treatment well with none discontinuing due to any treatment-related local adverse effects. CONCLUSIONS: This study demonstrates that CsA 0.05% ophthalmic emulsion applied more frequently than the usual twice daily dosing was safe and well tolerated in patients with significant ocular surface diseases.

Phenotypic characterization of a large family with RP10 autosomal-dominant retinitis pigmentosa: an Asp226Asn mutation in the IMPDH1 gene.

PURPOSE: To evaluate the clinical features associated with the RP10 form of autosomal-dominant retinitis pigmentosa in 11 affected members of various ages from one family with a defined IMPDH1 mutation (Asp226Asn). DESIGN: Prospective, observational case series. METHODS: Visual function assessment included visual acuity, color vision, visual field, dark adaptometry, full-field electroretinography (ffERG), and multifocal electroretinography (mfERG). Ophthalmologic examinations, fundus photography, and optical coherence tomographic scans were also performed. Blood samples were obtained to screen for basic immune function. RESULTS: Visual acuity was slightly reduced in the teenage years and substantially reduced in association with cystoid macular edema (CME) at all ages. Color defects were observed in three patients (one teen, two adults). Dark-adapted thresholds were elevated. Visual fields were markedly constricted by age 40 (

The relationship between Graves' ophthalmopathy and dry eye syndrome.

BACKGROUND: A complex relationship between Graves' ophthalmopathy (GO) and dry eye syndrome exists. New research brings more insight into the association between these two diseases. METHODS: A review of the literature was conducted using the query terms "Graves' Ophthalmopathy", "Thyroid Eye Disease", and "Dry Eye" in MedLine (PubMed) and Scopus. A total of 55 papers were reviewed. Case reports were excluded. CONCLUSION: This review paper shows the close relationship between dry eye syndrome and GO. The underlying mechanisms behind their association suggest mechanical impairment of orbital muscles and immune-mediated lacrimal gland dysfunction as the causes of dry eye in GO patients. However, there are a variety of treatment options available for patients with GO with signs of dry eye, which help combat this issue.

In vitro effects of medium tonicity, nutrient concentration, and free chlorine content on Acanthamoeba.

BACKGROUND: The environment preferred by Acanthamoeba trophozoites and the mechanism by which the amebae enters the cornea are not yet fully understood. A better understanding of the pathogenesis of this disease may help with prevention and treatment. PURPOSE: To define the preferred environments for Acanthamoeba survival and proliferation in vitro by examining the effect of tonicity, nutrient concentration, and free chlorine content on Acanthamoeba. MATERIALS AND METHODS: Human corneal isolates of Acanthamoeba castellanii and Acanthamoeba polyphaga trophozoites were cultured at 22°C (room temperature) in PYG (peptone-yeast extract-glucose) medium. The effect of tonicity on amebae was determined by incubating trophozoites in sodium chloride solutions in concentrations ranging from 0% to 10% for 19 days. Two different sets of media were prepared-one with and the other without added nutrients. The tonicity varied from 50 to 3438 mOsm/L while the pH was maintained at 6.7-6.8. Aliquots were recovered to determine the number and morphologic type of the amebae. To test the effect of chlorine, Acanthamoeba trophozoites were incubated for 7 days in buffered solutions with free chlorine concentrations varying from 0 to 5 mg/L free chlorine at 22°C. The pH was maintained at 7.2 and the tonicity varied from 88 to 92 mOsm/L. Trophozoites were enumerated by hemocytometer. RESULTS: Low tonicity solutions (<300 mOsm/L) favored the trophozoite stage, but elevating tonicity encouraged encystment. Only 3.3-3.9% of the trophozoites remained in 10% NaCl, while 46-58% of the trophozoites were present in distilled water. Increasing osmolality yielded a smaller number of Acanthamoeba with a greater proportion of cysts. Nutrients improved the replication rate at lower concentrations, increased the number of trophozoites and reduced the percentage of cysts. Chlorine completely inhibited both species of Acanthamoeba at free chlorine levels of 5mg/L, while lesser concentrations were less inhibitory. CONCLUSIONS: Acanthamoeba prefer hypotonic environments. Nutrients merely slowed the conversion of trophozoites to cysts at higher tonicity levels. Chlorine concentrations less than 5 mg/L, ocular irritation level, did not effectively convert trophozoites into cysts. We conclude that contact lens patients should avoid hypotonic ocular exposures, especially tap water and stagnant media such as lake water, and water from poorly maintained swimming pools and hot-tubs.