Yuko Wada

Identifying Pathogenic Genetic Background of Simplex or Multiplex Retinitis Pigmentosa Patients: A Large-Scale Mutation Screening Study

Background and purpose: More than half of the retinitis pigmentosa (RP) cases are genetically simplex or multiplex. To date, 37 causative genes of RP have been identified; however, the elucidation of gene defects in simplex or multiplex RP patients/families remains problematic. The aim of our study was to identify the genetic causes of RP in patients with unknown or non-Mendelian inheritance. Methods and results: Since 2003, 52 simplex RP patients, 151 patients from 141 multiplex RP families, and six sporadic patients with retinal degeneration were studied. A total of 108 exons of 30 RP-causing genes that harboured the reported mutations were screened by an efficient denaturing high performance liquid chromatography (dHPLC) based assay. Aberrant fragments were subsequently analysed by automatic sequencing. Twenty-six mutations, including two frameshift mutations, one single amino acid deletion, and 23 missense mutations, were identified in 28 probands (14.07%). Eighteen mutations have not been reported to date. Three pairs of combined mutations in different genes were identified in two sporadic cases and one multiplex family, indicating the possibility of novel digenic patterns. Of the 23 missense mutations, 21 were predicted as deleterious mutations by computational methods using PolyPhen, SIFT, PANTHER, and PMut programs. Conclusion: We elucidated the mutation spectrum in Japanese RP patients and demonstrated the validity of the mutation detection system using dHPLC sequencing for genetic diagnosis in RP patients independent of familial incidence, which may provide a model strategy for identifying genetic causes in other diseases linked to a wide range of genes.

Macular dystrophy associated with monogenic Arg172Trp mutation of the peripherin/RDS gene in a Japanese family.

Objective Mutations of the peripherin/RDS gene have been reported in several kinds of retinal dystrophy, and they show variation of manifestation. In some pedigrees, the same mutation can produce different phenotypic features, a factor that makes it difficult to deduce certain rules for genotype-phenotype correlations in the peripherin/RDS gene. The authors report the phenotypic features of a Japanese family with a mutation in codon 172 of the peripherin/RDS gene and compare them to previously reported ocular findings in British pedigrees with the same mutation. Patients and Methods A 45-year-old man and his 15-year-old son were screened for mutations in the peripherin/RDS gene and the ROM1 gene. Clinical features were characterized by visual acuity and visual field testing, fundus examination, fluorescein angiography, and electroretinography. Results Both patients had the same mutation in codon 172 of the peripherin/RDS gene designated as Arg172Trp. No mutation was found in the ROM1 gene in either patient. Clinical features were summarized as autosomal dominant macular dystrophy. The father had sharply demarcated chorioretinal atrophy in the macula. The son showed mild granularity in the macular area in ophthalmoscopic appearances. Conclusions The Arg172Trp mutation was confirmed to produce autosomal dominant macular dystrophy. This particular phenotype was caused by the monogenic mutation in the peripherin/RDS gene.

Oguchi disease: phenotypic characteristics of patients with the frequent 1147delA mutation in the arrestin gene.

OBJECTIVE To characterize clinical features of patients with Oguchi disease associated with a homozygous deletion of adenine at nucleotide 1147 (1147delA) in codon 309 in the arrestin gene. METHODS Mutation screening by single-strand conformation polymorphism analysis was done, followed by sequencing. Ophthalmologic testing included evaluation of visual acuity and color vision, fundus examination, electroretinography, fluorescein angiography, evaluation of kinetic visual field, and dark adaptometry. Nine patients with Oguchi disease from seven unrelated families and family members who were unaffected by the disease were examined. RESULTS A homozygous 1147delA mutation in the arrestin gene was identified in eight patients from six families with Oguchi disease. All patients who were examined exhibited a golden-yellow retinal reflex associated with Mizuo-Nakamura phenomenon and impairment of rod function in dark adaptation tests, although fundus examination showed slight variation in these findings. Four patients with the mutation had slightly reduced visual acuity, and the electroretinograms of three patients showed slightly reduced amplitudes during 30-Hz flicker electroretinography. CONCLUSION Patients with Oguchi disease associated with the arrestin 1147delA mutation typically demonstrate retarded rod adaptation, whereas some patients have slightly impaired cone function.

Autosomal dominant cone-rod dystrophy associated with a Val200Glu mutation of the peripherin/RDS gene.

Objective: Mutations of the peripherin/RDS gene have been reported in several kinds of retinal dystrophy, and they show a variety of manifestations. The authors identified a novel Val200Glu mutation of the peripherin/RDS gene in a Japanese family with autosomal dominant cone-rod dystrophy (CRD). This report describes a genotype-phenotype correlation of the Val200Glu mutation. Patients and Methods: Fifteen members of one Japanese family with autosomal dominant CRD were screened for mutations in the peripherin/RDS and ROM 1 genes. Clinical features were identified by visual acuity, visual field testing, fundus examination, and electroretinography. Results: A Val200Glu mutation was found in all of the affected family members examined and was segregated with the disease. No patient had a mutation in the ROM 1 gene. Phenotypic characteristics of each affected member in this family showed intrafamilial similarity. Characteristic features included cone function more severely impaired than rod function and degenerative change in the macular region associated with peripheral retinal degeneration. Conclusion: The mutation at codon 200 of the peripherin/RDS gene causes both cone and rod degeneration. The Val200Glu mutation results in a type of autosomal dominant CRD.

Age at Onset Curves of Retinitis Pigmentosa

OBJECTIVE To calculate age at onset curves of retinitis pigmentosa (RP) to resolve the difficulty in calculating the recurrence risk in a family. Retinitis pigmentosa is a common hereditary retinal disease that leads to blindness. It is a slow-onset disease, and family members of patients sometimes develop RP later. METHODS We studied 370 patients with typical RP. The age at onset was defined as when the patients RP was diagnosed by an ophthalmologist. After confirmation that the age at onset came from normal distribution, we drew the age at onset curves. RESULTS The average age when patients were diagnosed with RP was 35.1 years, and the median age was 36.5. The onset ratio straightly increased with age until 65 years, so the onset ratio was relatively low at young ages. CONCLUSIONS The age at onset curves are quite simple and useful tools that facilitate counseling at an RP clinic. Without them, the recurrence risk would be misleading.

A novel (Pro79Thr) mutation in the FKHL7 gene in a Japanese family with Axenfeld–Rieger syndrome

PURPOSE To report the ocular and genetic findings of a Japanese family with Axenfeld-Rieger syndrome associated with a novel Pro79Thr mutation in the FKHL7 gene. METHODS Observational case series. Genomic DNA of patients from a family with Axenfeld-Rieger syndrome was extracted from leukocytes, and exons of the FKHL7 gene were amplified by polymerase chain reaction for direct sequencing. RESULTS Molecular genetic analysis disclosed that one Japanese family with Axenfeld-Rieger syndrome had a heterozygous C to A transversion in the first nucleotide at codon 79, designated Pro79Thr mutation in the FKHL7 gene. CONCLUSION Considering this novel Pro79Thr mutation together with previously reported findings, it is indicated that the clinical features of Axenfeld-Rieger syndrome may depend on the portion of the FKHL7 gene affected by the mutation, although more case reports are needed to clarify genotype-phenotype correlations of the FKHL7 gene.

Molecular Genetic Analysis of ABCR Gene in Japanese Dry Form Age-Related Macular Degeneration

PURPOSE To explore whether the mutation in the retina-specific ATP-binding cassette transporter (ABCR) gene, the Stargardts disease gene, contributes to the prevalence of the dry form of age-related macular degeneration (dry AMD) in Japanese unrelated patients. METHODS Twenty-five Japanese unrelated patients with dry AMD who were diagnosed by fluorescein angiography and indocyanine green angiography were chosen as the dry AMD group. None of these cases had apparent choroidal neovascularization. To detect the mutations in the ABCR gene, genomic DNA was extracted from leukocytes of peripheral blood, and 26 exons of the ABCR gene were amplified by polymerase chain reaction (PCR). All the PCR products were then directly sequenced. When a mutation was detected, the occurrence of a mutation was compared between these AMD patients and the control group. RESULTS After direct sequencing, a point mutation in exon 29 was found in one of the 25 dry AMD patients. In addition, a polymorphism in exon 45 was found in two other patients, and three sequence variations in exon 23 were detected in all patients. The incidence in AMD patients in whom a mutation in exon 29 (4%) was detected was less than that in controls (5%). Screening of the intron-exon boundaries also led to the identification of intronic mutation in intron 33. CONCLUSION In this study we found no relationship between allelic variation in the ABCR gene and the prevalence of dry AMD in Japanese unrelated patients.

Autosomal dominant cone-rod dystrophy with negative electroretinogram.

AIMS--The negative electroretinogram (ERG) is observed in many hereditary retinal disorders. However, no reports have described a negative ERG in a family with autosomal dominant cone-rod dystrophy. A Japanese family with autosomal dominant cone-rod dystrophy with negative ERG is described. METHOD--Members of a Japanese family with autosomal dominant cone-rod dystrophy were examined and evaluated with Goldmann and Humphrey perimetry, bright flash ERG with an intense white stimulus, rod, cone, and flicker ERGs, and fluorescein angiography. Molecular analysis of the rhodopsin and peripherin/RDS genes in the patients was also performed. RESULTS--A 45-year-old Japanese man (proband) presented with decreased visual acuity. His fundi revealed bulls eye maculopathy and his single flash bright ERG showed a negative configuration. Negative ERG responses also were found in his father, who had macular degeneration, and one of the probands three children who showed no fundus changes. No irregularities were found in their rhodopsin or peripherin/RDS genes. CONCLUSION--The condition of this family is believed to represent a previously undescribed autosomal dominant cone-rod dystrophy.

Clinical features of a Japanese family with autosomal dominant retinitis pigmentosa associated with a Thr494Met mutation in the HPRP3 gene

AbstractPurposeTo determine the clinical features of a Japanese family with autosomal dominant retinitis pigmentosa (ADRP) associated with a Thr494Met mutation in the HPRP3 gene.MethodsMutational screening by direct sequencing was performed on 96 unrelated patients with ADRP. The clinical features were determined by visual acuity, slit-lamp biomicroscopy, electroretinography, fluorescein angiography, and kinetic visual field testing.ResultsA Thr494Met mutation in the HPRP3 gene was found in one family and it cosegregated with ADRP in the three affected members. The ophthalmic findings were those of typical retinitis pigmentosa with rapid progression after 40-years-of-age. One patient also had retinoblastoma as a child.ConclusionWe conclude that the Thr494Met mutation in the HPRP3 gene causes ADRP in Japanese patients. This mutation was found in 1% of patients with ADRP in Japan.

Clinical features of Japanese families with a 402delT or a 555-556delAG mutation in choroideremia gene.

Purpose: To characterize the clinical features of two Japanese families with choroideremia associated with a 402delT and a 555–556delAG mutation in the choroideremia gene (CHM). Methods: Four affected members and one obligate carrier from two Japanese families with choroideremia were studied. To detect mutations of the CHM gene, the products of polymerase chain reaction were directly sequenced in both directions. The ophthalmologic examination included best-corrected visual acuity, slit-lamp examination, fundus examination, kinetic perimetry, electroretinography, and fluorescein angiography. Results: A 402delT and a 555–556delAG mutation were found in two Japanese families with choroideremia. All affected members had night-blindness, progressive constriction of the visual field, chorioretinal atrophy, and mottled appearance of the retinal pigment epithelium. The obligate carrier had mild patchy areas of retinal pigment epithelial atrophy with no visual symptoms. Conclusion: The authors found a 402delT and a 555–556delAG mutation in the CHM gene, one of which (402delT) is a novel mutation. They conclude that these mutations cause choroideremia in Japanese families.