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Purpose: To assess the potential of next-generation sequencing (NGS) technologies to characterize cases diagnosed with autosomal recessive (ar) or sporadic (s) macular dystrophies (ar/sMD) and describe their mutational spectrum., Methods: A cohort of 1036 families was classified according to their suspected clinical diagnosis-Stargardt disease (STGD), cone and cone-rod dystrophy (CCRD) or other maculopathies (otherMD). Molecular studies included genotyping microarrays, Sanger sequencing, NGS, and sequencing of intronic regions of the ABCA4 gene. Clinical reclassification was done after the genetic study., Results: At the end of the study, 677 patients (65%) had a confirmed genetic diagnosis, representing 78%, 63%, and 38% of STGD, CCRD, and otherMD groups of patients, respectively. ABCA4 is the most mutated gene in all groups, and a second pathogenic variant was found in 76% of STGD patients with one previously identified mutated ABCA4 allele. Autosomal dominant or X-linked mutations were found in 5% of cases together with not-MD genes (CHM, EYS, RHO, RPGR, RLBP1, OPA1, and USH2A among others) leading to their reclassification. Novel variants in the very rare genes PLA2G5 and TTLL5 revealed additional phenotypic associations., Conclusions: This study provides for the first time a genetic landscape of 1036 ar/sMD families according to their suspected diagnosis. The analysis of >200 genes associated with retinal dystrophies and the entire locus of ABCA4 increase the rate of characterization, even regardless of available clinical and familiar data. The use of the suspected a priori diagnosis referred by the clinicians, especially in the past, could lead to clinical reclassifications to other inherited retinal dystrophies.

Introduction: Biallelic pathogenic RPE65 variants are related to a spectrum of clinically overlapping inherited retinal dystrophies (IRD). Most affected individuals progress to severe disease, with 50% of patients becoming legally blind by 20 years of age. Deeper knowledge of the mutational spectrum and the phenotype-genotype correlation in RPE65-related IRD is needed., Patients and Methods: Forty-five affected subjects from 27 unrelated families with a clinical diagnosis of RPE65-related IRD were included. Clinical evaluation consisted of self-reported ophthalmological history and objective ophthalmological examination. Patients' genotype was classified according to variant class (truncating or missense) or to variant location at different protein domains. The main phenotypic outcome measure was age at onset (AAO) of symptomatic disease and a Kaplan-Meier analysis of disease symptom event-free survival was performed., Results: Twenty-nine different RPE65 variants were identified in our cohort, 7 of them novel. Patients carrying two missense alleles showed a later disease onset than those with 1 or 2 truncating variants (log-rank test p <0.05). While 60% of patients carrying a missense/missense genotype presented symptoms before or during the first year of life, almost all patients with at least 1 truncating allele (91%) had an AAO ≤1 year (p <0.05)., Conclusion: Our findings suggest an association between the type of RPE65 variant carried and AAO. These findings provide useful data on RPE65-associated IRD phenotypes and may help improve clinical and therapeutic management of these patients., (Copyright © 2021. Published by Elsevier Ltd.)

Purpose: To provide a comprehensive overview of the molecular basis of autosomal dominant retinitis pigmentosa (adRP) in Spanish families. Thus, we established the molecular characterization rate, gene prevalence, and mutational spectrum in the largest European cohort reported to date., Methods: A total of 258 unrelated Spanish families with a clinical diagnosis of RP and suspected autosomal dominant inheritance were included. Clinical diagnosis was based on complete ophthalmologic examination and family history. Retrospective and prospective analysis of Spanish adRP families was carried out using a combined strategy consisting of classic genetic techniques and next-generation sequencing (NGS) for single-nucleotide variants and copy number variation (CNV) screening., Results: Overall, 60% of our families were genetically solved. Interestingly, 3.1% of the cohort carried pathogenic CNVs. Disease-causing variants were found in an autosomal dominant gene in 55% of the families; however, X-linked and autosomal recessive forms were also identified in 3% and 2%, respectively. Four genes (RHO, PRPF31, RP1, and PRPH2) explained up to 62% of the solved families. Missense changes were most frequently found in adRP-associated genes; however, CNVs represented a relevant disease cause in PRPF31- and CRX-associated forms., Conclusions: Implementation of NGS technologies in the adRP study clearly increased the diagnostic yield compared with classic approaches. Our study outcome expands the spectrum of disease-causing variants, provides accurate data on mutation gene prevalence, and highlights the implication of CNVs as important contributors to adRP etiology.

Objective: To determine the refractive error in patients with autosomal recessive retinitis pigmentosa (arRP) caused by RP1 mutations and to compare it with that of other genetic subtypes of RP., Methods: Twenty-six individuals had arRP with RP1 mutations, 25 had autosomal dominant RP (adRP) with RP1 mutation, 8 and 33 had X-linked RP (xlRP) with RP2 and RPGR mutations, respectively, 198 and 93 had Usher syndrome and arRP without RP1 mutations, respectively. The median of the spherical equivalent (SE) and the IQR (Q25-Q75) was determined and multiple comparisons were performed., Results: arRP patients with RP1 mutations had SE median at -4.0 dioptres (D) OD (Ocula Dextra); -3.88 D OS (Ocula Sinistra), whereas arRP patients without RP1 mutations (-0.50 D OD; -0.75 D OS) and Usher syndrome patients (-0.50 D OD; -0.38 D OS) were significantly less myopic (p<0.0001). Conversely, myopia of xlRP patients with either an RPGR mutation (-4.50 D OD; -5.25 D OS) or an RP2 mutation (-6.25 D OD; -6.88 D OS) was not significantly different from the arRP group with RP1 mutations. arRP without RP1 mutations, Usher syndrome and adRP with RP1 mutation had a narrow IQR (-9.06 to -1.13 D), whereas arRP with RP1 mutations and xlRP with RP2 or RPGR mutations had a larger range (-9.06; -1.13 D)., Conclusions: arRP patients with RP1 mutations have myopia not different from patients with xlRP with RP2 or RPGR mutations, while RP patients from other genetic subgroups were emmetropic or mildly myopic. We suggest that arRP patients with high myopic refractive error should be preferentially analysed for RP1 mutations., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Purpose: Next-generation sequencing (NGS) has been demonstrated to be an effective strategy for the detection of mutations in retinal dystrophies, a group of inherited diseases that are highly heterogeneous. Therefore, the aim of this study is the application of an NGS-based approach in a Spanish cohort of autosomal dominant retinitis pigmentosa (RP) patients to find out causative mutations., Methods: Index cases of 59 Spanish families with initial diagnosis of autosomal dominant RP and unsuccessfully studied for mutations in the most common RP causal genes, were selected for application of a NGS-based approach with a custom panel for 73 genes related to retinal dystrophies. Candidate variants were select based on frequency, pathogenicity, inherited model, and phenotype. Subsequently, confirmation by Sanger sequencing, cosegregation analysis, and population studies, was applied for determining the implication of those variants in the pathology., Results: Overall 31 candidate variants were selected. From them, 17 variants were considered as mutations causative of the disease, 64% (11/17) of them were novel and 36% (6/17) were known RP-related mutations. Therefore, applying this technology16 families were characterized rendering a mutation detection rate of 27% (16/59). Of them, 5% (3/59) of cases displayed mutations in recessive or X-linked genes (ABCA4, RPGR, and RP2) allowing a genetic and clinical reclassification of those families. Furthermore, seven novel variants with uncertain significance and seven novel variants probably not causative of disease were also found., Conclusions: This NGS strategy is a fast, effective, and reliable tool to detect known and novel mutations in autosomal dominant RP patients allowing genetic reclassification in some cases and increasing the knowledge of pathogenesis in retinal dystrophies.

Importance: A new statistical approach is needed to describe the clinical differences between type I and type II Usher syndrome and between the 2 most frequent mutations in the USH2A gene., Objectives: To describe the primary phenotypic characteristics and differences between type I and type II Usher syndrome and to establish a phenotype-genotype correlation for the 2 most frequent mutations in the USH2A gene., Design, Setting, and Participants: Cross-sectional study at a genetics department, in which clinical evaluations were performed for 433 patients (297 unrelated families) who were classified as having type I, II, III, atypical, or unclassified Usher syndrome according to their clinical history, pedigree data, results from ophthalmological studies, and audiological, neurophysiological, and vestibular test results. Molecular studies were performed for 304 patients (256 unrelated families). The Mann-Whitney U test or the χ2 test was used for calculating the differences between mean values for the analyzed parameters., Main Outcomes and Measures: Age at diagnosis; age at onset of night blindness, visual field loss, visual acuity loss, and cataracts; and severity and age at diagnosis of hearing loss., Results: The comparison between patients with type I Usher syndrome and those with type II Usher syndrome revealed P < .001 for most items analyzed. The most frequent mutations in the USH2A gene were the p.Glu767Serfs*21 and p.Cys759Phe mutations, with an allelic frequency of 23.2% (63 of 272 alleles) and 8.1% (22 of 272 alleles), respectively. The phenotypic analysis for patients carrying p.Cys759Phe showed P < .001 for most items analyzed when compared with patients carrying p.Glu767Serfs*21 and when compared with patients carrying other mutations in the USH2A gene. None of the p.Cys759Phe patients exhibited a severe hearing loss phenotype, and more than 60% had only mild hearing loss. Most patients carrying the p.Glu767Serfs*21 mutation (72.1%) were moderately deaf., Conclusions and Relevance: Our study presents the clinical differences between type I and type II Usher syndrome and between the 2 most frequent mutations in the USH2A gene. Detailed genotype-phenotype correlations, as presented in our study, allow for a better correlation of clinical signs with a known genotype and can improve the clinical management, genetic counseling, and risk assessment of patients with Usher syndrome because an estimated prognosis of their disease can be made.

Objective: To investigate the involvement of the Bardet-Biedl syndrome (BBS) gene BBS1 p.M390R variant in nonsyndromic autosomal recessive retinitis pigmentosa (RP)., Methods: Homozygosity mapping of a patient with isolated RP was followed by BBS1 sequence analysis. We performed restriction fragment length polymorphism analysis of the p.M390R allele in 2007 patients with isolated RP or autosomal recessive RP and in 1824 ethnically matched controls. Patients with 2 BBS1 variants underwent extensive clinical and ophthalmologic assessment., Results: In an RP proband who did not fulfill the clinical criteria for BBS, we identified a large homozygous region encompassing the BBS1 gene, which carried the p.M390R variant. In addition, this variant was detected homozygously in 10 RP patients and 1 control, compound heterozygously in 3 patients, and heterozygously in 5 patients and 6 controls. The 14 patients with 2 BBS1 variants showed the entire clinical spectrum, from nonsyndromic RP to full-blown BBS. In 8 of 14 patients, visual acuity was significantly reduced. In patients with electroretinographic responses, a rod-cone pattern of photoreceptor degeneration was observed., Conclusions: Variants in BBS1 are significantly associated with nonsyndromic autosomal recessive RP and relatively mild forms of BBS. As exemplified in this study by the identification of a homozygous p.M390R variant in a control individual and in unaffected parents of BBS patients in other studies, cis - or trans -acting modifiers may influence the disease phenotype., Clinical Relevance: It is important to monitor patients with an early diagnosis of mild BBS phenotypes for possible life-threatening conditions.