RDH12 retinopathy: novel mutations and phenotypic description

PurposeTo identify patients with autosomal recessive retinal dystrophy caused by mutations in the gene, retinal dehydrogenase 12 (RDH12), and to report the associated phenotype.MethodsAfter giving informed consent, all patients underwent full clinical evaluation. Patients were selected for mutation analysis based upon positive results from the Asper Ophthalmics Leber congenital amaurosis arrayed primer extansion (APEX) microarray screening, linkage analysis, or their clinical phenotype. All coding exons of RDH12 were screened by direct Sanger sequencing. Potential variants were checked for segregation in the respective families and screened in controls, and their pathogenicity analyzed using in silico prediction programs.ResultsScreening of 389 probands by the APEX microarray and/or direct sequencing identified bi-allelic mutations in 29 families. Seventeen novel mutations were identified. The phenotype in these patients presented with a severe early-onset rod-cone dystrophy. Funduscopy showed severe generalized retinal pigment epithelial and retinal atrophy, which progressed to dense, widespread intraretinal pigment migration by adulthood. The macula showed severe atrophy, with pigmentation and yellowing, and corresponding loss of fundus autofluorescence. Optical coherence tomography revealed marked retinal thinning and excavation at the macula.ConclusionsRDH12 mutations account for approximately 7% of disease in our cohort of patients diagnosed with Leber congenital amaurosis and early-onset retinal dystrophy. The clinical features of this disorder are highly characteristic and facilitate candidate gene screening. The term RDH12 retinopathy is proposed as a more accurate description

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 genes (RetNet Retinal Information Network). Using exome sequencing, we identified a homozygous missense mutation (c.25G>A, p.Val9Met) in NMNAT1 as likely disease-causing in two siblings of a consanguineous Pakistani kindred affected by LCA. This mutation segregated with disease in their 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 the p.Val9Met mutation decreased NMNAT1 enzyme activity. Sequencing NMNAT1 in 284 unrelated LCA families identified 14 rare mutations in 13 additional affected individuals. These results are the first to link an NMNAT isoform to disease and indicate that NMNAT1 mutations cause LCA

Leber Congenital Amaurosis Associated with AIPL1: Challenges in Ascribing Disease Causation, Clinical Findings, and Implications for Gene Therapy

Leber Congenital Amaurosis (LCA) and Early Childhood Onset Severe Retinal Dystrophy are clinically and genetically heterogeneous retinal disorders characterised by visual impairment and nystagmus from birth or early infancy. We investigated the prevalence of sequence variants in AIPL1 in a large cohort of such patients (n = 392) and probed the likelihood of disease-causation of the identified variants, subsequently undertaking a detailed assessment of the phenotype of patients with disease-causing mutations. Genomic DNA samples were screened for known variants in the AIPL1 gene using a microarray LCA chip, with 153 of these cases then being directly sequenced. The assessment of disease-causation of identified AIPL1 variants included segregation testing, assessing evolutionary conservation and in silico predictions of pathogenicity. The chip identified AIPL1 variants in 12 patients. Sequencing of AIPL1 in 153 patients and 96 controls found a total of 46 variants, with 29 being novel. In silico analysis suggested that only 6 of these variants are likely to be disease-causing, indicating a previously unrecognized high degree of polymorphism. Seven patients were identified with biallelic changes in AIPL1 likely to be disease-causing. In the youngest subject, electroretinography revealed reduced cone photoreceptor function, but rod responses were within normal limits, with no measurable ERG in other patients. An increasing degree and extent of peripheral retinal pigmentation and degree of maculopathy was noted with increasing age in our series. AIPL1 is significantly polymorphic in both controls and patients, thereby complicating the establishment of disease-causation of identified variants. Despite the associated phenotype being characterised by early-onset severe visual loss in our patient series, there was some evidence of a degree of retinal structural and functional preservation, which was most marked in the youngest patient in our cohort. This data suggests that there are patients who have a reasonable window of opportunity for gene therapy in childhood

A Survey of DNA Variation of C2ORF71 in Probands with Progressive Autosomal Recessive Retinal Degeneration and Controls

PURPOSE. Mutations of C2ORF71 have recently been reported to be associated with autosomal recessive (AR) retinitis pigmentosa (RP) in humans and with visual defects in zebrafish. C2ORF71 is located on 2p23.2 and encodes a 1288-amino-acid protein of unknown function, predominately expressed in the photoreceptors. The study was conducted to determine the prevalence of mutations in C2ORF71 in a cohort of probands with AR retinal degeneration and to detect coding sequence variation in controls. METHODS. A combination of high-resolution DNA melting (HRM) analysis and automated DNA sequencing was used to screen for C2ORF71 in 286 affected unrelated individuals. Among them, 95 subjects had Leber congenital amaurosis, and 191 had AR RP. In a similar fashion, 151 European and 40 South Asian control DNAs were screened. RESULTS. Overall, 40 DNA sequence variants were detected, with 17 novel polymorphisms found in the control subjects (8 missense, 7 synonymous, and 2 other). Importantly, 11 novel sequence variants (6 missense and 5 synonymous) in 20 alleles were detected in the cohort of patients but not in the controls. Only one proband was a compound heterozygote but segregation analysis revealed her unaffected father to be homozygous for one of the putative mutations. CONCLUSIONS. C2ORF71 is a highly polymorphic gene (average heterozygosity of coding region in controls: 2.118 ϫ 10 Ϫ3 ) with many rare variants that confound mutation detection. Further analysis will determine the spectrum of retinal disease caused by mutations in C2ORF71 and distinguish true pathogenic alleles from the high background of polymorphism elucidating the role of this rare cause of RP in the visual process. (Invest Ophthalmol Vis Sci

Benign Yellow Dot Maculopathy A New Macular Phenotype

PurposeTo describe a novel macular phenotype that is associated with normal visual function.DesignRetrospective, observational case series.ParticipantsThirty-six affected individuals from 23 unrelated families.MethodsThis was a retrospective study of patients who had a characteristic macular phenotype. Subjects underwent a full ocular examination, electrophysiologic studies, spectral-domain optical coherence tomography (OCT), and fundus autofluorescence imaging. Genomic analyses were performed using haplotype sharing analysis and whole-exome sequencing.Main outcome measuresVisual acuity, retinal features, electroretinography, and whole-exome sequencing.ResultsTwenty-six of 36 subjects were female. The median age of subjects at presentation was 15 years (range, 5-59 years). The majority of subjects were asymptomatic and presented after a routine eye examination (22/36 subjects) or after screening because of a positive family history (13/36 subjects) or by another ophthalmologist (1/36 subjects). Of the 3 symptomatic subjects, 2 had reduced visual acuity secondary to nonorganic visual loss and bilateral ametropic amblyopia with strabismus. Visual acuity was 0.18 logarithm of the minimum angle of resolution (logMAR) or better in 30 of 33 subjects. Color vision was normal in all subjects tested, except for the subject with nonorganic visual loss. All subjects had bilateral symmetric multiple yellow dots at the macula. In the majority of subjects, these were evenly distributed throughout the fovea, but in 9 subjects they were concentrated in the nasal parafoveal area. The dots were hyperautofluorescent on fundus autofluorescence imaging. The OCT imaging was generally normal, but in 6 subjects subtle irregularities at the inner segment ellipsoid band were seen. Electrophysiologic studies identified normal macular function in 17 of 19 subjects and normal full-field retinal function in all subjects. Whole-exome analysis across 3 unrelated families found no pathogenic variants in known macular dystrophy genes. Haplotype sharing analysis in 1 family excluded linkage with the North Carolina macular dystrophy (MCDR1) locus.ConclusionsA new retinal phenotype is described, which is characterized by bilateral multiple early-onset yellow dots at the macula. Visual function is normal, and the condition is nonprogressive. In familial cases, the phenotype seems to be inherited in an autosomal dominant manner, but a causative gene is yet to be ascertained