Background/aims To investigate genotype-phenotype associations in patients with KCNV2 retinopathy.Methods Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants,... Show moreBackground/aims To investigate genotype-phenotype associations in patients with KCNV2 retinopathy.Methods Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants, electroretinography (ERG) and retinal imaging. Subjects were grouped according to the combination of KCNV2 variants-two loss-of-function (TLOF), two missense (TM) or one of each (MLOF)-and parameters were compared.Results Ninety-two patients were included. The mean age of onset (mean +/- SD) in TLOF (n=55), TM (n=23) and MLOF (n=14) groups was 3.51 +/- 0.58, 4.07 +/- 2.76 and 5.54 +/- 3.38 years, respectively. The mean LogMAR BCVA ( +/- SD) at baseline in TLOF, TM and MLOF groups was 0.89 +/- 0.25, 0.67 +/- 0.38 and 0.81 +/- 0.35 for right, and 0.88 +/- 0.26, 0.69 +/- 0.33 and 0.78 +/- 0.33 for left eyes, respectively. The difference in BCVA between groups at baseline was significant in right (p=0.03) and left eyes (p=0.035). Mean outer nuclear layer thickness ( +/- SD) at baseline in TLOF, MLOF and TM groups was 37.07 +/- 15.20 mu m, 40.67 +/- 12.53 and 40.38 +/- 18.67, respectively, which was not significantly different (p=0.85). The mean ellipsoid zone width (EZW) loss ( +/- SD) was 2051 mu m ( +/- 1318) for patients in the TLOF, and 1314 mu m ( +/- 965) for MLOF. Only one patient in the TM group had EZW loss at presentation. There was considerable overlap in ERG findings, although the largest DA 10 ERG b-waves were associated with TLOF and the smallest with TM variants.Conclusions Patients with missense alterations had better BCVA and greater structural integrity. This is important for patient prognostication and counselling, as well as stratification for future gene therapy trials. Show less
Georgiou, M.; Fujinami, K.; Vincent, A.; Nasser, F.; Khateb, S.; Vargas, M.E.; ... ; Michaelides, M. 2021
PURPOSE: To describe the detailed retinal phenotype of KCNV2-associated retinopathy.STUDY DESIGN: Multicenter international retrospective case series.METHODS: Review of retinal imaging including... Show morePURPOSE: To describe the detailed retinal phenotype of KCNV2-associated retinopathy.STUDY DESIGN: Multicenter international retrospective case series.METHODS: Review of retinal imaging including fundus autofluorescence (FAF) and optical coherence tomography (OCT), including qualitative and quantitative analyses.RESULTS: Three distinct macular FAF features were identified: (1) centrally increased signal (n = 35, 41.7%), (2) decreased autofluorescence (n = 27, 31.1%), and (3) ring of increased signal (n = 37, 44.0%). Five distinct FAF groups were identified based on combinations of those features, with 23.5% of patients changing the FAF group over a mean (range) follow-up of 5.9 years (1.9-13.1 years). Qualitative assessment was performed by grading OCT into 5 grades: (1) continuous ellipsoid zone (EZ) (20.5%); (2) EZ disruption (26.1%); (3) EZ absence, without optical gap and with preserved retinal pigment epithelium complex (21.6%); (4) loss of EZ and a hyporeflective zone at the foveola (6.8%); and (5) outer retina and retinal pigment epithelium complex loss (25.0%). Eighty-six patients had scans available from both eyes, with 83 (96.5%) having the same grade in both eyes, and 36.1% changed OCT grade over a mean follow-up of 5.5 years. The annual rate of outer nuclear layer thickness change was similar for right and left eyes.CONCLUSIONS: KCNV2-associated retinopathy is a slowly progressive disease with early retinal changes, which are predominantly symmetric between eyes. The identification of a single OCT or FAF measurement as an endpoint to determine progression that applies to all patients may be challenging, although outer nuclear layer thickness is a potential biomarker. Findings suggest a potential window for intervention until 40 years of age. (C) 2021 The Authors. Published by Elsevier Inc. Show less
Georgiou, M.; Robson, A.G.; Fujinami, K.; Leo, S.M.; Vincent, A.; Nasser, F.; ... ; Michaelides, M. 2021
center dot PURPOSE: To investigate genetics, electrophysiology, and clinical course of KCNV2-associated retinopathy in a cohort of children and adults. center dot STUDY DESIGN: This was a... Show morecenter dot PURPOSE: To investigate genetics, electrophysiology, and clinical course of KCNV2-associated retinopathy in a cohort of children and adults. center dot STUDY DESIGN: This was a multicenter international clinical cohort study. center dot METHODS: Review of clinical notes and molecular genetic testing. Full-field electroretinography (ERG) recordings, incorporating the international standards, were reviewed and quantified and compared with age and recordings from control subjects. center dot RESULTS: In total, 230 disease-associated alleles were identified from 117 patients, corresponding to 75 different KCNV2 variants, with 28 being novel. The mean age of onset was 3.9 years old. All patients were symptomatic before 12 years of age (range, 0-11 years). Decreased visual acuity was present in all patients, and 4 other symptoms were common: reduced color vision (78.6%), photophobia (53.5%), nyctalopia (43.6%), and nystagmus (38.6%). After a mean follow-up of 8.4 years, the mean best-corrected visual acuity (BCVA +/- SD) decreased from 0.81 +/- 0.27 to 0.90 +/- 0.31 logarithm of minimal angle of resolution. Full field ERGs showed pathognomonic waveform features. Quantitative assessment revealed a wide range of ERG amplitudes and peak times, with a mean rate of age-associated reduction indistinguishable from the control group. Mean amplitude reductions for the dark-adapted 0.01 ERG, dark-adapted 10 ERG a-wave, and LA 3.0 30 Hz and LA3 ERG b-waves were 55%, 21%, 48%, and 74%, respectively compared with control values. Peak times showed stability across 6 decades. center dot CONCLUSION: In KCNV2-associated retinopathy, full field ERGs are diagnostic and consistent with largely stable peripheral retinal dysfunction. Report 1 highlights the severity of the clinical phenotype and established a large cohort of patients, emphasizing the unmet need for trials of novel therapeutics. (Am J Ophthalmol 2021;225: 95-107. (c) 2020 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).) Show less
Khan, M.; Cornelis, S.S.; Pozo-Valero, M.D. del; Whelan, L.; Runhart, E.H.; Mishra, K.; ... ; Cremers, F.P.M. 2020
Purpose Missing heritability in human diseases represents a major challenge, and this is particularly true for ABCA4-associated Stargardt disease (STGD1). We aimed to elucidate the genomic and... Show morePurpose Missing heritability in human diseases represents a major challenge, and this is particularly true for ABCA4-associated Stargardt disease (STGD1). We aimed to elucidate the genomic and transcriptomic variation in 1054 unsolved STGD and STGD-like probands. Methods Sequencing of the complete 128-kb ABCA4 gene was performed using single-molecule molecular inversion probes (smMIPs), based on a semiautomated and cost-effective method. Structural variants (SVs) were identified using relative read coverage analyses and putative splice defects were studied using in vitro assays. Results In 448 biallelic probands 14 known and 13 novel deep-intronic variants were found, resulting in pseudoexon (PE) insertions or exon elongations in 105 alleles. Intriguingly, intron 13 variants c.1938-621G>A and c.1938-514G>A resulted in dual PE insertions consisting of the same upstream, but different downstream PEs. The intron 44 variant c.6148-84A>T resulted in two PE insertions and flanking exon deletions. Eleven distinct large deletions were found, two of which contained small inverted segments. Uniparental isodisomy of chromosome 1 was identified in one proband. Conclusion Deep sequencing of ABCA4 and midigene-based splice assays allowed the identification of SVs and causal deep-intronic variants in 25% of biallelic STGD1 cases, which represents a model study that can be applied to other inherited diseases. Show less
