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Inherited retinal dystrophies comprise a broad group of genetic eye diseases without effective treatment. Among them, Stargardt disease is the second most prevalent pathology. This pathology triggers progressive retinal degeneration and vision loss in children and adults. In recent years, the evolution of several genome editing technologies, such as the CRISPR-Cas9 system, has revolutionized disease modeling and personalized medicine. Human induced pluripotent stem cells also provide a valuable tool for in vitro disease studies and therapeutic applications. Here, we show precise correction of two ABCA4 pathogenic variants in human induced pluripotent stem cells from two unrelated patients affected with Stargardt disease. Gene editing was achieved with no detectable off-target genomic alterations, demonstrating efficient ABCA4 gene correction without deleterious effects. These results will contribute to the development of emerging gene and cell therapies for inherited retinal dystrophies., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

Achromatopsia is an autosomal recessive disorder, in which cone photoreceptors undergo progressive degeneration, causing color blindness and poor visual acuity, among other significant eye affectations. It belongs to a group of inherited retinal dystrophies that currently have no treatment. Although functional improvements have been reported in several ongoing gene therapy studies, more efforts and research should be carried out to enhance their clinical application. In recent years, genome editing has arisen as one of the most promising tools for personalized medicine. In this study, we aimed to correct a homozygous PDE6C pathogenic variant in hiPSCs derived from a patient affected by achromatopsia through CRISPR/Cas9 and TALENs technologies. Here, we demonstrate high efficiency in gene editing by CRISPR/Cas9 but not with TALENs approximation. Despite a few of the edited clones displaying heterozygous on-target defects, the proportion of corrected clones with a potentially restored wild-type PDE6C protein was more than half of the total clones analyzed. In addition, none of them presented off-target aberrations. These results significantly contribute to advances in single-nucleotide gene editing and the development of future strategies for the treatment of achromatopsia.

Best Vitelliform Macular dystrophy (BVMD) is the most prevalent of the distinctive retinal dystrophies caused by mutations in the BEST1 gene. This gene, which encodes for a homopentameric calcium-activated ion channel, is crucial for the homeostasis and function of the retinal pigment epithelia (RPE), the cell type responsible for recycling the visual pigments generated by photoreceptor cells. In BVMD patients, mutations in this gene induce functional problems in the RPE cell layer with an accumulation of lipofucsin that evolves into cell death and loss of sight. In this work, we employ iPSC-RPE cells derived from a patient with the p.Pro77Ser dominant mutation to determine the correlation between this variant and the ocular phenotype. To this purpose, gene and protein expression and localization are evaluated in iPSC-RPE cells along with functional assays like phagocytosis and anion channel activity. Our cell model shows no differences in gene expression, protein expression/localization, or phagocytosis capacity, but presents an increased chloride entrance, indicating that the p.Pro77Ser variant might be a gain-of-function mutation. We hypothesize that this variant disturbs the neck region of the BEST1 channel, affecting channel function but maintaining cell homeostasis in the short term. This data shed new light on the different phenotypes of dominant mutations in BEST1 , and emphasize the importance of understanding its molecular mechanisms. Furthermore, the data widen the knowledge of this pathology and open the door for a better diagnosis and prognosis of the disease.

Background: The objective of this study was to carry out a cost-effectiveness analysis of dapagliflozin, as an add-on therapy to standard of care (SoC), for the treatment of type 2 diabetes mellitus (T2DM) in Spain, based on the results of the DECLARE-TIMI 58 trial., Methods: A discrete event simulation model (Cardiff T2DM) based on the data observed in the DECLARE-TIMI 58 trial was adapted to the Spanish setting to estimate the costs and health outcomes of treatment with dapagliflozin in patients with T2DM who had or were at risk of atherosclerotic cardiovascular disease. Macrovascular events (hospitalization for heart failure, myocardial infarction, stroke, and unstable angina), end-stage renal disease and cardiovascular and non-cardiovascular mortality were modeled according to the survival equations of the DECLARE-TIMI 58 study. Microvascular events (blindness and ulcers) were estimated based on the risk equations of the UK Prospective Diabetes Study. The analysis was conducted from the Spanish National Health System perspective and the time horizon was 30 years. The results were evaluated in terms of cost per quality-adjusted life year (QALY) gained. Only direct health costs were included, and a 3% discount rate was applied to costs and health outcomes. Univariate and probabilistic sensitivity analyses (PSA) were made to assess the robustness of the results., Results: In the main analysis, dapagliflozin was a dominant therapeutic option compared with placebo, with greater effectiveness (0.08 QALYs) and lower associated total costs per patient (€ -2,921). The univariate sensitivity analysis and the PSA confirmed the robustness of the results. The PSA showed the probability that dapagliflozin was a dominant alternative compared with placebo was 84.2% and that it was cost-effective of 92.1%, under a willingness-to-pay of € 20,000/QALY gained., Conclusions: The analysis of data from the DECLARE-TIMI 58 trial shows that dapagliflozin would be a cost-effective option in Spain for the treatment of adult patients with T2DM, as an add-on therapy to SoC, compared with placebo., (© 2022. The Author(s).)

Aims: Renin-angiotensin-aldosterone system inhibitors (RAASi) therapy is commonly used to reduce the risk of death and to slow down disease progression in patients with chronic kidney disease (CKD), heart failure (HF) and hypertension. However, the cardio-renal benefits of RAASi therapy are also associated with an increased risk of hyperkalemia (HK), which may lead to dose reduction or discontinuation of therapy. Patiromer has demonstrated to reduce the risk of HK, which enables to maintain optimal doses of RAASi therapy. This study aimed to assess the cost-effectiveness of patiromer for the management of HK in CKD patients with and without HF in Spain., Methods: A Markov model was developed to evaluate the costs and benefits of patiromer for the management of HK in patients with CKD stages 3-4 with and without HF treated with RAASi over a lifetime horizon. The main outcomes included total direct costs (€2021), quality-adjusted life-years (QALYs), life-years gained (LYG) and incremental cost-effectiveness ratio (ICER). Deterministic one-way and probabilistic sensitivity analyses were performed to assess the robustness of the results., Results: Patiromer was more effective compared to no patiromer (5.76 vs 5.57 QALYs; 7.73 vs 7.50 LYG), and resulted in an incremental cost of €3,574, yielding an ICER of €19,092/QALY gained and of €15,236/LYG. Sensitivity analyses suggested that the results were robust to changes in most input parameters., Conclusions: Patiromer is a cost-effective intervention in maintaining normokalemia and enabling optimal RAASi therapy in patients with CKD stages 3-4 with and without HF in Spain.

This study aims to genetically characterize a two-year-old patient suffering from multiple systemic abnormalities, including skeletal, nervous and developmental involvements and Leber congenital amaurosis (LCA). Genetic screening by next-generation sequencing identified two heterozygous pathogenic variants in nicotinamide mononucleotide adenylyltransferase 1 ( NMNAT1 ) as the molecular cause of the disease: c.439+5G>T and c.299+526_*968dup.This splice variant has never been reported to date, whereas pathogenic duplication has recently been associated with cases displaying an autosomal recessive disorder that includes a severe form of spondylo-epiphyseal dysplasia, sensorineural hearing loss, intellectual disability and LCA (SHILCA), as well as some brain anomalies. Our patient presented clinical manifestations which correlated strongly with this reported syndrome. To further study the possible transcriptional alterations resulting from these mutations, mRNA expression assays were performed in the patient and her father. The obtained results detected aberrant alternative transcripts and unbalanced levels of expression, consistent with severe systemic involvement. Moreover, these analyses also detected a novel NMNAT1 isoform, which is variably expressed in healthy human tissues. Altogether, these findings represent new evidence of the correlation of NMNAT1 and SHILCA syndrome, and provide additional insights into the healthy and pathogenic expression of this gene.

Best disease, also known as Best vitelliform macular dystrophy, is an autosomal dominant form of macular degeneration. Here, we have generated an induced pluripotent stem cell (iPSC) line derived from a Best disease patient carrying a new dominant mutation in the BEST1 gene. Skin fibroblasts were reprogrammed to iPSCs by the non-integrative Sendai-virus method. The iPSC line has been characterized preserving the BEST1 mutation, expressing the pluripotency markers and being capable to differentiate to endoderm, mesoderm and ectoderm in vitro., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Incomplete achromatopsia (ACHM) is a disorder in which there is function defect of cone photoreceptors in the retina and individuals with such disease retain residual color vision. Here, we have generated an induced pluripotent stem cell (iPSC) line carrying a homozygous mutation in the PDE6C gene, already related with this vision disorder. Skin fibroblasts from a patient with incomplete ACHM were reprogrammed to iPSCs by the non-integrative Sendai-virus method. Finally, the iPSC line has been characterized expressing the pluripotency markers and being capable to differentiate to endoderm, mesoderm and ectoderm in vitro., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Retinitis pigmentosa (RP) is an inherited retinal dystrophy characterized by the progressive degeneration of photoreceptors. In the present study, we have generated an induced pluripotent stem cell (iPSC) line derived from a RP patient with a dominant mutation in the RHO gene, responsible for the synthesis of rhodopsin. The reprogramming of these iPSCs was performed from skin fibroblasts by the Sendai-virus based approach. Characterization of the iPSC line showed a normal karyotype carrying the RHO mutation, expressed pluripotency markers and could be differentiated to endoderm, mesoderm and ectoderm in vitro., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Recessive Stargardt disease (STGD1) is an autosomal recessive retinal dystrophy, caused by mutations in the retina-specific ATP-binding cassette transporter (ABCA4) gene, which plays a role as a retinaldehyde flippase in the photoreceptor outer segments. In this work, two human induced pluripotent stem cell (iPSC) lines were generated from STGD1 patients carrying compound heterozygous mutations in ABCA4. Skin fibroblasts were reprogrammed with the Yamanaka factors using a non-integrating, Sendai virus-based approach. Both iPSC lines displayed typical embryonic stem cell morphology, had normal karyotype, expressed several pluripotency markers and were able to differentiate into all three germ layers. Resource table., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

A human induced pluripotent stem cell (iPSC) line was generated from a female patient affected by autosomal recessive retinitis pigmentosa with two mutations in the USH2A gene: c.2209C > T (p.Arg737Ter) and c.8693A > C (p.Tyr2898Ser). Skin fibroblasts were infected with Sendai virus containing the Yamanaka factors and the resulting cells were fully characterized to confirm successful reprogramming. The iPSC line expressed several pluripotency markers, could generate the three germ layers, had a normal karyotype, carried the two USH2A mutations and was free of Sendai virus. This cell line will serve as a model to unravel the pathogenic mechanisms underlying USH2A-associated retinal degeneration., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Retinitis pigmentosa (RP) refers to a clinical and genetic heterogeneous group of inherited retinal degenerations characterized by photoreceptor cell death. In this work, we have generated an induced pluripotent stem cell (iPSC) line derived from a RP patient with two heterozygous mutations in the cGMP-specific phosphodiesterase 6A alpha subunit (PDE6A) gene. Skin fibroblasts were generated and reprogrammed by using a Sendai virus-based approach. The iPSC line had a normal karyotype, carried the two PDE6A mutations, expressed pluripotency markers and could generate endoderm, mesoderm and ectoderm in vitro. Resource table., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Microphthalmia and anophthalmia (MA) are congenital eye abnormalities that show an extremely high clinical and genetic complexity. In this study, we evaluated the implementation of whole exome sequencing (WES) for the genetic analysis of MA patients. This approach was used to investigate three unrelated families in which previous single-gene analyses failed to identify the molecular cause., Methods: A total of 47 genes previously associated with nonsyndromic MA were included in our panel. WES was performed in one affected patient from each family using the AmpliSeq TM Exome technology and the Ion Proton TM platform., Results: A novel heterozygous OTX2 missense mutation was identified in a patient showing bilateral anophthalmia who inherited the variant from a parent who was a carrier, but showed no sign of the condition. We also describe a new PAX6 missense variant in an autosomal-dominant pedigree affected by mild bilateral microphthalmia showing high intrafamiliar variability, with germline mosaicism determined to be the most plausible molecular cause of the disease. Finally, a heterozygous missense mutation in RBP4 was found to be responsible in an isolated case of bilateral complex microphthalmia., Conclusion: This study highlights that panel-based WES is a reliable and effective strategy for the genetic diagnosis of MA. Furthermore, using this technique, the mutational spectrum of these diseases was broadened, with novel variants identified in each of the OTX2, PAX6, and RBP4 genes. Moreover, we report new cases of reduced penetrance, mosaicism, and variable phenotypic expressivity associated with MA, further demonstrating the heterogeneity of such disorders., (© 2017 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc.)

Inherited retinal dystrophies (IRD) comprise a wide group of clinically and genetically complex diseases that progressively affect the retina. Over recent years, the development of next-generation sequencing (NGS) methods has transformed our ability to diagnose heterogeneous diseases. In this work, we have evaluated the implementation of whole exome sequencing (WES) for the molecular diagnosis of IRD. Using Ion Proton TM system, we simultaneously analyzed 212 genes that are responsible for more than 25 syndromic and non-syndromic IRD. This approach was used to evaluate 59 unrelated families, with the pathogenic variant(s) successfully identified in 71.18% of cases. Interestingly, the mutation detection rate varied substantially depending on the IRD subtype. Overall, we found 63 different mutations (21 novel) in 29 distinct genes, and performed in vivo functional studies to determine the deleterious impact of variants identified in MERTK, CDH23, and RPGRIP1. In addition, we provide evidences that support CDHR1 as a gene responsible for autosomal recessive retinitis pigmentosa with early macular affectation, and present data regarding the disease mechanism of this gene. Altogether, these results demonstrate that targeted WES of all IRD genes is a reliable, hypothesis-free approach, and a cost- and time-effective strategy for the routine genetic diagnosis of retinal dystrophies., Competing Interests: The authors declare no competing financial interests.

Most diagnostic laboratories are confronted with the increasing demand for molecular diagnosis from patients and families and the ever-increasing genetic heterogeneity of visual disorders. Concerning Retinal Dystrophies (RD), almost 200 causative genes have been reported to date, and most families carry private mutations. We aimed to approach RD genetic diagnosis using all the available genetic information to prioritize candidates for mutational screening, and then restrict the number of cases to be analyzed by massive sequencing. We constructed and optimized a comprehensive cosegregation RD-chip based on SNP genotyping and haplotype analysis. The RD-chip allows to genotype 768 selected SNPs (closely linked to 100 RD causative genes) in a single cost-, time-effective step. Full diagnosis was attained in 17/36 Spanish pedigrees, yielding 12 new and 12 previously reported mutations in 9 RD genes. The most frequently mutated genes were USH2A and CRB1. Notably, RD3-up to now only associated to Leber Congenital Amaurosis- was identified as causative of Retinitis Pigmentosa. The main assets of the RD-chip are: i) the robustness of the genetic information that underscores the most probable candidates, ii) the invaluable clues in cases of shared haplotypes, which are indicative of a common founder effect, and iii) the detection of extended haplotypes over closely mapping genes, which substantiates cosegregation, although the assumptions in which the genetic analysis is based could exceptionally lead astray. The combination of the genetic approach with whole exome sequencing (WES) greatly increases the diagnosis efficiency, and revealed novel mutations in USH2A and GUCY2D. Overall, the RD-chip diagnosis efficiency ranges from 16% in dominant, to 80% in consanguineous recessive pedigrees, with an average of 47%, well within the upper range of massive sequencing approaches, highlighting the validity of this time- and cost-effective approach whilst high-throughput methodologies become amenable for routine diagnosis in medium sized labs.

Leber congenital amaurosis (LCA) is the earliest and most severe retinal degeneration (RD), and the most common cause of incurable blindness diagnosed in children. It is occasionally the presenting symptom of multisystemic ciliopathies which diagnosis will require a specific care of patients. Nineteen LCA genes are currently identified and three of them account for both non-syndromic and syndromic forms of the disease. RD3 (LCA12) was implicated as a LCA gene based on the identification of homozygous truncating mutations in two LCA families despite the screening of large cohorts of patients. Here we provide a comprehensive survey of RD3 mutations and of their clinical expression through the screening of a cohort of 852 patients originating worldwide affected with LCA or early-onset and severe RD. We identified three RD3 mutations in seven unrelated consanguineous LCA families - i.e., a 2 bp deletion and two nonsense mutations - predicted to cause complete loss of function. Five families originating from the Southern Shores of the Mediterranean segregated a similar mutation (c.112C>T, p.R38*) suggesting that this change may have resulted from an ancient founder effect. Considering the low frequency of RD3 carriers, the recurrence risk for LCA in non-consanguineous unions is negligible for both heterozygote and homozygote RD3 individuals. The LCA12 phenotype in our patients is highly similar to those of patients with mutant photoreceptor-specific guanylate cyclase (GUCY2D/LCA1). This observation is consistent with the report of the role of RD3 in trafficking of GUCYs and gives further support to a common mechanism of photoreceptor degeneration in LCA12 and LCA1, i.e., inability to increase cytoplasmic cGMP concentration in outer segments and thus to recover the dark-state. Similar to LCA1, LCA12 patients have no extraocular symptoms despite complete inactivation of both RD3 alleles, supporting the view that extraocular investigations in LCA infants with RD3 mutations should be avoided.