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Mean sensitivity (MS) derived from a standard test grid using microperimetry is a sensitive outcome measure in clinical trials investigating new treatments for degenerative retinal diseases. This study hypothesizes that the functional decline is faster at the edge of the dense scotoma (eMS) than by using the overall MS.Multicenter, international, prospective cohort study: ProgStar Study.Stargardt disease type 1 patients (carrying at least 1 mutation in the ABCA4 gene) were followed over 12 months using microperimetry with a Humphrey 10-2 test grid. Customized software was developed to automatically define and selectively follow the test points directly adjacent to the dense scotoma points and to calculate their mean sensitivity (eMS).Among 361 eyes (185 patients), the mean age was 32.9 ± 15.1 years old. At baseline, MS was 10.4 ± 5.2 dB (n = 361), and the eMS was 9.3 ± 3.3 dB (n = 335). The yearly progression rate of MS (1.5 ± 2.1 dB/year) was significantly lower (β = -1.33; P.001) than that for eMS (2.9 ± 2.9 dB/year). There were no differences between progression rates using automated grading and those using manual grading (β = .09; P = .461).In Stargardt disease type 1, macular sensitivity declines significantly faster at the edge of the dense scotoma than in the overall test grid. An automated, time-efficient approach for extracting and grading eMS is possible and appears valid. Thus, eMS offers a valuable tool and sensitive outcome parameter with which to follow Stargardt patients in clinical trials, allowing clinical trial designs with shorter duration and/or smaller cohorts.

Choroideremia is an X-linked inherited retinal disorder (IRD) characterized by the degeneration of retinal pigment epithelium, photoreceptors, choriocapillaris and choroid affecting males with variable phenotypes in female carriers. Unlike other IRD, characterized by a large clinical and genetic heterogeneity, choroideremia shows a specific phenotype with causative mutations in only one gene, CHM. Ongoing gene replacement trials raise further interests in this disorder. We describe here the clinical and genetic data from a French cohort of 45 families, 25 of which carry novel variants, in the context of 822 previously reported choroideremia families. Most of the variants represent loss-of-function mutations with eleven families having large (i.e. ≥6 kb) genomic deletions, 18 small insertions, deletions or insertion deletions, six showing nonsense variants, eight splice site variants and two missense variants likely to affect splicing. Similarly, 822 previously published families carry mostly loss-of-function variants. Recurrent variants are observed worldwide, some of which linked to a common ancestor, others arisen independently in specific CHM regions prone to mutations. Since all exons of CHM may harbor variants, Sanger sequencing combined with quantitative polymerase chain reaction or multiplex ligation-dependent probe amplification experiments are efficient to achieve the molecular diagnosis in patients with typical choroideremia features.

Purpose To investigate the natural history of Stargardt disease (STGD1) using fixation location and fixation stability. Design Multicenter, international, prospective cohort study. Methods Fixation testing was performed using the Nidek MP-1 microperimeter as part of the prospective, multicenter, natural history study on the Prog ression of Star gardt disease (ProgStar). A total of 238 patients with ABCA4-related STGD1 were enrolled at baseline (bilateral enrollment in 86.6%) and underwent repeat testing at months 6 and 12. Results Outcome measures included the distance of the preferred retinal locus from the fovea (PRL) and the bivariate contour ellipse area (BCEA). After 12 months of follow-up, the change in the eccentricity of the PRL from the anatomic fovea was −0.0014 degrees (95% confidence interval [CI], −0.27 degrees, 0.27 degrees; P = .99). The deterioration in the stability of fixation as expressed by a larger BCEA encompassing 1 standard deviation of all fixation points was 1.21 degrees squared (deg2) (95% CI, −1.23 deg2, 3.65 deg2; P = .33). Eyes with increases and decreases in PRL eccentricity and/or BCEA values were observed. Conclusions Our observations point to the complexity of fixation parameters. The association of increasingly eccentric and unstable fixation with longer disease duration that is typically found in cross-sectional studies may be countered within individual patients by poorly understood processes like neuronal adaptation. Nevertheless, fixation parameters may serve as useful secondary outcome parameters in selected cases and for counseling patients to explain changes to their visual functionality.

Phenotypes observed in a large cohort of patients with cone and cone-rod dystrophies (COD/CORDs) are described based on multimodal retinal imaging features in order to help in analyzing massive next-generation sequencing data. Structural abnormalities of 58 subjects with molecular diagnosis of COD/CORDs were analyzed through specific retinal imaging including spectral-domain optical coherence tomography (SD-OCT) and fundus autofluorescence (BAF/IRAF). Findings were analyzed with the underlying genetic defects. A ring of increased autofluorescence was mainly observed in patients with CRX and GUCY2D mutations (33% and 22% of cases respectively). &ldquo, Speckled&rdquo, autofluorescence was observed with mutations in three different genes (ABCA4 64%, C2Orf71 and PRPH2, 18% each). Peripapillary sparing was only found in association with mutations in ABCA4, although only present in 40% of such genotypes. Regarding SD-OCT, specific outer retinal abnormalities were more commonly observed in particular genotypes: focal retrofoveal interruption and GUCY2D mutations (50%), foveal sparing and CRX mutations (50%), and outer retinal atrophy associated with hyperreflective dots and ABCA4 mutations (69%). This study outlines the phenotypic heterogeneity of COD/CORDs hampering statistical correlations. A larger study correlating retinal imaging with genetic results is necessary to identify specific clinical features that may help in selecting pathogenic variants generated by high-throughput sequencing.

We report a novel ARL2BP splice site mutation after whole-exome sequencing (WES) applied to a Moroccan family including two sisters affected with autosomal recessive rod-cone dystrophy (arRCD). Subsequent analysis of 844 index cases did not reveal further pathogenic chances in ARL2BP indicating that mutations in ARL2B are a rare cause of arRCD (about 0.1%) in a large cohort of French patients.

Genetic investigations were performed in three brothers from a consanguineous union, the two oldest diagnosed with rod-cone dystrophy (RCD), the youngest with early-onset cone-rod dystrophy and the two youngest with nephrotic-range proteinuria. Targeted next-generation sequencing did not identify homozygous pathogenic variant in the oldest brother. Whole exome sequencing (WES) applied to the family identified compound heterozygous variants in CC2D2A (c.2774G>C p.(Arg925Pro); c.4730_4731delinsTGTATA p.(Ala1577Valfs*5)) in the three brothers with a homozygous deletion in CNGA3 (c.1235_1236del p.(Glu412Valfs*6)) in the youngest correcting his diagnosis to achromatopsia plus RCD. None of the three subjects had cerebral abnormalities or learning disabilities inconsistent with Meckel-Gruber and Joubert syndromes, usually associated with CC2D2A mutations. Interestingly, an African woman with RCD shared the CC2D2A missense variant (c.2774G>C p.(Arg925Pro); with c.3182+355_3825del p.(?)). The two youngest also carried compound heterozygous variants in CUBN (c.7906C>T rs137998687 p.(Arg2636*); c.10344C>G p.(Cys3448Trp)) that may explain their nephrotic-range proteinuria. Our study identifies for the first time CC2D2A mutations in isolated RCD and underlines the power of WES to decipher complex phenotypes.

International audience; MER tyrosine kinase (MERTK) encodes a surface receptor localized at the apical membrane of the retinal pigment epithelium. It plays a critical role in photoreceptor outer segment internalization prior to phagocytosis. Mutations in MERTK have been associated with severe autosomal recessive retinal dystrophies in the RCS rat and in humans. We present here a comprehensive review of all reported MERTK disease causing variants with the associated phenotype. In addition, we provide further data and insights of a large cohort of 1,195 inherited retinal dystrophies (IRD) index cases applying state-of-the-art genotyping techniques and summarize current knowledge. A total of 79 variants have now been identified underlying rod-cone dystrophy and cone-rod dystrophy including 11 novel variants reported here. The mutation spectrum in MERTK includes 33 missense, 12 nonsense, 12 splice defects, 12 small deletions, two small insertion-deletions, three small duplications, and two exonic and three gross deletions. Altogether, mutations in MERTK account for ∼2% of IRD cases with a severe retinal phenotype. These data are important for current and future therapeutic trials including gene replacement therapy or cell-based therapy.

Rod-cone dystrophy (RCD), also known as retinitis pigmentosa, is a progressive inherited retinal disorder characterized by photoreceptor cell death and genetic heterogeneity. Mutations in many genes have been implicated in the pathophysiology of RCD, but several others remain to be identified. Herein, we applied whole-exome sequencing to a consanguineous family with one subject affected with RCD and identified a homozygous nonsense mutation, c.226CT (p.Arg76(∗)), in KIZ, which encodes centrosomal protein kizuna. Subsequent Sanger sequencing of 340 unrelated individuals with sporadic and autosomal-recessive RCD identified two other subjects carrying pathogenic variants in KIZ: one with the same homozygous nonsense mutation (c.226CT [p.Arg76(∗)]) and another with compound-heterozygous mutations c.119_122delAACT (p.Lys40Ilefs(∗)14) and c.52GT (p.Glu18(∗)). Transcriptomic analysis in mice detected mRNA levels of the mouse ortholog (Plk1s1) in rod photoreceptors, as well as its decreased expression when photoreceptors degenerated in rd1 mice. The presence of the human KIZ transcript was confirmed by quantitative RT-PCR in the retina, the retinal pigment epithelium, fibroblasts, and whole-blood cells (highest expression was in the retina). RNA in situ hybridization demonstrated the presence of Plk1s1 mRNA in the outer nuclear layer of the mouse retina. Immunohistology revealed KIZ localization at the basal body of the cilia in human fibroblasts, thus shedding light on another ciliary protein implicated in autosomal-recessive RCD.

International audience; GNAT1, encoding the transducin subunit Gα, is an important element of the phototransduc-tion cascade. Mutations in this gene have been associated with autosomal dominant and autosomal recessive congenital stationary night blindness. Recently, a homozygous trun-cating GNAT1 mutation was identified in a patient with late-onset rod-cone dystrophy. After exclusion of mutations in genes underlying progressive inherited retinal disorders, by targeted next generation sequencing, a 32 year-old male sporadic case with severe rod-cone dystrophy and his unaffected parents were investigated by whole exome sequencing. This led to the identification of a homozygous nonsense variant, c.963C>A p.(Cys321*) in GNAT1, which was confirmed by Sanger sequencing. The mother was heterozygous for this variant whereas the variant was absent in the father. c.963C>A p.(Cys321*) is predicted to produce a shorter protein that lacks critical sites for the phototransduction cascade. Our work confirms that the phenotype and the mode of inheritance associated with GNAT1 variants can vary from autosomal dominant, autosomal recessive congenital stationary night blindness to autosomal recessive rod-cone dystrophy.

Purpose To report the clinical and genetic findings of one family with autosomal recessive cone dystrophy (CD) and to identify the causative mutation. Methods An institutional study of three family members from two generations. The clinical examination included best-corrected Snellen visual acuity measurement, fundoscopy, the Farnsworth D-15 color vision test, a full-field electroretinogram (ERG) that incorporated the International Society for Clinical Electrophysiology of Vision standards and methodology, fundus autofluorescence (FAF) and infrared (IR), and spectral-domain optical coherence tomography (SD-OCT). Genetic findings were achieved with DNA analysis using whole exome sequencing (WES) and Sanger sequencing. Results The proband, a 9-year-old boy, presented with a condition that appeared to be congenital and stationary. The clinical presentation initially reflected incomplete congenital stationary night blindness (icCSNB) because of myopia, a decrease in visual acuity, abnormal oscillatory potentials, and reduced amplitudes on the 30 Hz flicker ERG but was atypical because there were no clear electronegative responses. However, no disease-causing mutations in the genes underlying icCSNB were identified. Following WES analysis of family members, a homozygous splice-site mutation in intron 3 of TTLL5 (c.182–3_182–1delinsAA) was found cosegregating within the phenotype in the family. Conclusions The distinction between icCSNB and CD phenotypes is not always straightforward in young patients. The patient was quite young, which most likely explains why the progression of the CD was not obvious. WES analysis provided prompt diagnosis for this family; thus, the use of this technique to refine the diagnosis is highlighted in this study.

To examine the association between characteristics of Stargardt disease and visual acuity (VA), to estimate the longitudinal rate of VA loss, and to identify risk factors for VA loss.Retrospective, multicenter cohort study.A total of 176 patients (332 eyes) with molecularly and clinically confirmed Stargardt disease enrolled from the United States and Europe.Standardized data report forms were used to collect retrospective data on participants' characteristics and best-corrected or presenting VA from medical charts. Linear models with generalized estimating equations were used to estimate the cross-sectional associations, and linear mixed effects models were used to estimate the longitudinal VA loss.Yearly change in VA.The median duration of observation was 3.6 years. At baseline, older age of symptom onset was associated with better VA, and a longer duration of symptoms was associated with worse VA. Longitudinal analysis estimated an average of 0.3 lines loss (P0.0001) per year overall, but the rate varied according to baseline VA: (1) eyes with baseline VA ≥20/25 (N = 53) declined at a rate of approximately 1.0 line per year; (2) eyes with VA between 20/25 and 20/70 (N = 65) declined at a rate of approximately 0.9 lines per year; (3) eyes with VA between 20/70 and 20/200 (N = 163) declined at a rate of 0.2 lines per year; and (4) eyes with VA worse than 20/200 (n = 49) improved at a rate of 0.5 lines per year. Older age of onset was associated with slower VA loss: Patients with onset age30 years showed 0.4 lines slower change of VA per year (P = 0.01) compared with patients with onset age ≤14 years.Given the overall slow rate of VA loss, VA is unlikely to be a sensitive outcome measure for treatment trials of Stargardt disease. However, given the faster decline in younger patients and those with no or mild visual impairment, VA may be a potential outcome measure for trials targeting such subgroups of patients. These observations will need to be assessed in a prospective study bearing in mind the inherent limitations of retrospective datasets.

Background Cone and cone-rod dystrophies are clinically and genetically heterogeneous inherited retinal disorders with predominant cone impairment. They should be distinguished from the more common group of rod-cone dystrophies (retinitis pigmentosa) due to their more severe visual prognosis with early central vision loss. The purpose of our study was to document mutation spectrum of a large French cohort of cone and cone-rod dystrophies. Methods We applied Next-Generation Sequencing targeting a panel of 123 genes implicated in retinal diseases to 96 patients. A systematic filtering approach was used to identify likely disease causing variants, subsequently confirmed by Sanger sequencing and co-segregation analysis when possible. Results Overall, the likely causative mutations were detected in 62.1 % of cases, revealing 33 known and 35 novel mutations. This rate was higher for autosomal dominant (100 %) than autosomal recessive cases (53.8 %). Mutations in ABCA4 and GUCY2D were responsible for 19.2 % and 29.4 % of resolved cases with recessive and dominant inheritance, respectively. Furthermore, unexpected genotype-phenotype correlations were identified, confirming the complexity of inherited retinal disorders with phenotypic overlap between cone-rod dystrophies and other retinal diseases. Conclusions In summary, this time-efficient approach allowed mutation detection in the most important cohort of cone-rod dystrophies investigated so far covering the largest number of genes. Association of known gene defects with novel phenotypes and mode of inheritance were established. Electronic supplementary material The online version of this article (doi:10.1186/s13023-015-0300-3) contains supplementary material, which is available to authorized users.