ABSTRACT
Mutations in the RPE65 gene, associated with Leber congenital amaurosis, early-onset severe retinal dystrophy, and retinitis pigmentosa, gained growing attention since gene therapy for patients with RPE65-associated retinal dystrophy is available in clinical practice. RPE65 gene accounts for a very small proportion of patients with inherited retinal degeneration, especially Asian patients. Because RPE65-associated retinal dystrophy shares common clinical characteristics, such as early-onset severe nyctalopia, nystagmus, low vision, and progressive visual field constriction, with retinitis pigmentosa by other genetic mutations, appropriate genetic testing is essential to make a correct diagnosis. Also, fundus abnormalities can be minimal in early childhood, and the phenotype is highly variable depending on the type of mutations in RPE65-associated retinal dystrophy, which makes a diagnostic difficulty. The aim of this paper is to review the epidemiology of RPE65-associated retinal dystrophy, mutation spectrum, genetic diagnosis, clinical characteristics, and voretigene neparvovec, a gene therapy product for the treatment of RPE65-related retinal dystrophy.
ABSTRACT
Objectives@#. We, herein, report two novel USH2A variants from two unrelated Korean families and their clinical phenotypes, with attention to severe or more than severe sensorineural hearing loss (SNHL). @*Methods@#. Two postlingually deafened subjects (SB237-461, M/46 and SB354-692, F/34) with more than severe SNHL and also with suspicion of Usher syndrome type II (USH2) were enrolled. A comprehensive audiological and ophthalmological assessments were evaluated. We conducted the whole exome sequencing and subsequent pathogenicity prediction analysis. @*Results@#. We identified the following variants of USH2A from the two probands manifesting more than severe SNHL and retinitis pigmentosa (RP): compound heterozygosity for a nonsense (c.8176C>T: p.R2723X) and a missense variant (c.1823G>A: p.C608Y) in SB237, and compound heterozygosity for two frameshift variants (c.14835delT: p.S4945fs & c.13112_13115delAAAT: p.G4371fs) in SB354. Based on the American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines, two novel variants, c.1823G>A: p.C608Y and c.14835delT: p.Ser4945fs, can be classified as “uncertain significance” and “pathogenic,” respectively. The audiogram exhibited more than severe SNHL and a down-sloping configuration, necessitating cochlear implantation. The ophthalmic examinations revealed typical features of RP. Interestingly, one proband (SB 354-692) carrying two truncating compound heterozygous variants exhibited more severe hearing loss than the other proband (SB 237-461), carrying one truncation with one missense variant. @*Conclusion@#. Our results provide insight on the expansion of audiological spectrum encompassing more than severe SNHL in Korean subjects harboring USH2A variants, suggesting that USH2A should also be included in the candidate gene of cochlear implantation. A specific combination of USH2A variants causing truncating proteins in both alleles could demonstrate more severe audiological phenotype than that of USH2A variants carrying one truncating mutation and one missense mutation, suggesting a possible genotype-phenotype correlation. The understanding of audiological complexity associated with USH2A will be helpful for genetic counseling and treatment starategy.
ABSTRACT
The authors regret that there were errors in Table 2 and Supplementary Table.
ABSTRACT
BACKGROUND: Because of genetically and phenotypically heterogenous features, identification of causative genes for inherited retinal diseases (IRD) is essential for diagnosis and treatment in coming gene therapy era. To date, there are no large-scale data of the genes responsible for IRD in Korea. The aim of this study was to identify the distribution of genetic defects in IRD patients in Korea. METHODS: Medical records and DNA samples from 86 clinically diagnosed IRD patients were consecutively collected between July 2011 and May 2015. We applied the next-generation sequencing strategy (gene panel) for screening 204 known pathogenic genes associated with IRD. RESULTS: Molecular diagnoses were made in 38/86 (44.2%) IRD patients: 18/44 (40.9%) retinitis pigmentosa (RP), 8/22 (36.4%) cone dystrophy, 6/7 (85.7%) Stargardt disease, 1/1 (100%) Best disease, 1/1 (100%) Bardet-Biedl syndrome, 1/1 (100%) congenital stationary night blindness, 1/1 (100%) choroideremia, and 2/8 (25%) other macular dystrophies. ABCA4 was the most common causative gene associated with IRD and was responsible for causing Stargardt disease (n = 6), RP (n = 1), and cone dystrophy (n = 1). In particular, mutations in EYS were found in 4 of 14 autosomal recessive RP (29%). All cases of Stargardt disease had a mutation in the ABCA4 gene with an autosomal recessive trait. CONCLUSION: This study provided the distribution of genetic mutations responsible for causing IRD in the Korean patients. This data will serve as a reference for future genetic screening and treatment for Korean IRD patients.