Publications by authors named "Frans P M Cremers"

250 Publications

Stargardt disease: monitoring incidence and diagnostic trends in the Netherlands using a nationwide disease registry.

Acta Ophthalmol 2021 Aug 25. Epub 2021 Aug 25.

Department of Ophthalmology, Radboud University Medical Centre, Nijmegen, the Netherlands.

Purpose: To assess the incidence of Stargardt disease (STGD1) and to evaluate demographics of incident cases.

Methods: For this retrospective cohort study, demographic, clinical and genetic data of patients with a clinical diagnosis of STGD1 were registered between September 2010 and January 2020 in a nationwide disease registry. Annual incidence (2014-2018) and point prevalence (2018) were assessed on the basis of this registry.

Results: A total of 800 patients were registered, 56% were female and 83% were of European ancestry. The incidence was 1.67-1.95:1,000,000 per year and the point prevalence in 2018 was approximately 1:22,000-1:19,000 (with and without 10% of potentially unregistered cases). Age at onset was associated with sex (p = 0.027, Fisher's exact); 1.9x more women than men were observed (140 versus 74) amongst patients with an age at onset between 10 and 19 years, while the sex ratio in other age-at-onset categories approximated one. Late-onset STGD1 (≥45 years) constituted 33% of the diagnoses in 2014-2018 compared to 19% in 2004-2008. Diagnostic delay (≥2 years between the first documentation of macular abnormalities and diagnosis) was associated with older age of onset (p = 0.001, Mann-Whitney). Misdiagnosis for age-related macular degeneration (22%) and incidental STGD1 findings (14%) was common in patients with late-onset STGD1.

Conclusion: The observed prevalence of STGD1 in real-world data was lower than expected on the basis of population ABCA4 allele frequencies. Late-onset STGD1 was more frequently diagnosed in recent years, likely due to higher awareness of its phenotype. In this pretherapeutic era, mis- and underdiagnosis of especially late-onset STGD1 and the role of sex in STGD1 should receive special attention.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/aos.14996DOI Listing
August 2021

PRPH2 mutation update: In silico assessment of 245 reported and 7 novel variants in patients with retinal disease.

Hum Mutat 2021 Aug 19. Epub 2021 Aug 19.

Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.

Mutations in PRPH2, encoding peripherin-2, are associated with the development of a wide variety of inherited retinal diseases (IRDs). To determine the causality of the many PRPH2 variants that have been discovered over the last decades, we surveyed all published PRPH2 variants up to July 2020, describing 720 index patients that in total carried 245 unique variants. In addition, we identified seven novel PRPH2 variants in eight additional index patients. The pathogenicity of all variants was determined using the ACMG guidelines. With this, 107 variants were classified as pathogenic, 92 as likely pathogenic, one as benign, and two as likely benign. The remaining 50 variants were classified as variants of uncertain significance. Interestingly, of the total 252 PRPH2 variants, more than half (n = 137) were missense variants. All variants were uploaded into the Leiden Open source Variation and ClinVar databases. Our study underscores the need for experimental assays for variants of unknown significance to improve pathogenicity classification, which would allow us to better understand genotype-phenotype correlations, and in the long-term, hopefully also support the development of therapeutic strategies for patients with PRPH2-associated IRD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/humu.24275DOI Listing
August 2021

Exploring the missing heritability in subjects with hearing loss, enlarged vestibular aqueducts, and a single or no pathogenic SLC26A4 variant.

Hum Genet 2021 Aug 19. Epub 2021 Aug 19.

Hearing and Genes, Department of Otorhinolaryngology, Radboud University Medical Center, Nijmegen, The Netherlands.

Pathogenic variants in SLC26A4 have been associated with autosomal recessive hearing loss (arHL) and a unilateral or bilateral enlarged vestibular aqueduct (EVA). SLC26A4 is the second most frequently mutated gene in arHL. Despite the strong genotype-phenotype correlation, a significant part of cases remains genetically unresolved. In this study, we investigated a cohort of 28 Dutch index cases diagnosed with HL in combination with an EVA but without (M0) or with a single (M1) pathogenic variant in SLC26A4. To explore the missing heritability, we first determined the presence of the previously described EVA-associated haplotype (Caucasian EVA (CEVA)), characterized by 12 single nucleotide variants located upstream of SLC26A4. We found this haplotype and a delimited V1-CEVA haplotype to be significantly enriched in our M1 patient cohort (10/16 cases). The CEVA haplotype was also present in two M0 cases (2/12). Short- and long-read whole genome sequencing and optical genome mapping could not prioritize any of the variants present within the CEVA haplotype as the likely pathogenic defect. Short-read whole-genome sequencing of the six M1 cases without this haplotype and the two M0/CEVA cases only revealed previously overlooked or misinterpreted splice-altering SLC26A4 variants in two cases, who are now genetically explained. No deep-intronic or structural variants were identified in any of the M1 subjects. With this study, we have provided important insights that will pave the way for elucidating the missing heritability in M0 and M1 SLC26A4 cases. For pinpointing the pathogenic effect of the CEVA haplotype, additional analyses are required addressing defect(s) at the RNA, protein, or epigenetic level.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00439-021-02336-6DOI Listing
August 2021

Non-syndromic inherited retinal diseases in Poland: Genes, mutations, and phenotypes.

Mol Vis 2021 16;27:457-465. Epub 2021 Jul 16.

Children's Memorial Health Institute, Warsaw, Poland.

Purpose: Inherited retinal diseases (IRDs), encompassing many clinical entities affecting the retina, are classified as rare disorders. Their extreme heterogeneity made molecular screening in the era before next-generation sequencing (NGS) expensive and time-consuming. Since then, many NGS studies of IRD molecular background have been conducted in Western populations; however, knowledge of the IRD mutational spectrum in Poland is still limited. Until now, there has been almost no comprehensive analysis of this particular population regarding the molecular basis and inheritance of IRDs. Therefore, the purpose of this study was to gain knowledge about the type and prevalence of causative variants in the Polish population.

Methods: We recruited 190 Polish families with non-syndromic IRDs, including Stargardt disease (STGD), retinitis pigmentosa (RP), cone- and cone-rod dystrophy (CD/CRD), achromatopsia, and congenital stationary night blindness. A pool of molecular inversion probes was used, which targeted 108 genes associated with non-syndromic IRDs known in 2013. We applied filtering for known variants occurring with an allele frequency >0.5% in public and in-house databases, with the exception of variants in , when the frequency filter was set to 3.0%. Hypomorphic p.(Asn1868Ile) was added manually. In the case of novel missense or splicing variants, we used in silico prediction software to assess mutation causality.

Results: We detected causative mutations in 115 of the 190 families with non-syndromic IRD (60.2%). Fifty-nine individuals with STGD, RP, and CD/CRD carried causal variants in . Novel single nucleotide variants were found in and . The complex allele c.[1622T>C;3113C>T], p.[Leu541Pro;Ala1038Val] was found in 33 individuals with -associated disorders, which makes it the most prevalent allele in the Polish population (17% of all solved cases). Diagnosis was reevaluated in 16 cases.

Conclusions: Previously, there were no comprehensive reports of IRDs in the Polish population. This study is the first to indicate that the most common IRDs in Poland are -associated diseases, regardless of the phenotype. In Polish patients with RP, the second most prevalent causal gene was and the third , while there were not as many mutations in as in Western populations. The number of initial erroneous diagnoses may be the result of limited access to diagnostics with advanced tools, such as electroretinography; however, it is necessary to raise awareness among Polish ophthalmologists of rare IRDs. Additionally, it must be emphasized that in some cases genetic analysis of the patient is necessary to achieve an accurate diagnosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8286799PMC
July 2021

CRB1-associated retinal dystrophies: a prospective natural history study in anticipation of future clinical trials.

Am J Ophthalmol 2021 Jul 25. Epub 2021 Jul 25.

Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands; Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, Amsterdam, the Netherlands. Electronic address:

Purpose: To describe the natural disease course of CRB1-associated retinal dystrophies, and to identify clinical endpoints for future clinical trials.

Design: Single center, prospective case series.

Methods: An investigator-initiated nationwide collaborative study that included 22 patients with CRB1-associated retinal dystrophies. Patients underwent ophthalmic assessment at baseline and 2 years after baseline. Clinical examination included best-corrected visual acuity (BCVA) using ETDRS charts, Goldmann kinetic perimetry (V4e isopter seeing retinal areas), microperimetry, full-field electroretinography (ERG), full-field stimulus threshold (FST), fundus photography, spectral-domain optical coherence tomography and fundus autofluorescence imaging.

Results: Based on genetic, clinical and electrophysiological data, patients were diagnosed with retinitis pigmentosa (n = 19; 86%), cone-rod dystrophy (n = 2; 9%) or isolated macular dystrophy (n = 1; 5%). Two-year analysis of the entire cohort showed no significant changes in BCVA (p = 0.069) or V4e isopter seeing retinal areas (p = 0.616), although signs of clinical progression were present in individual patients. Macular sensitivity measured on microperimetry revealed a significant reduction at 2-year follow-up (p < 0.001). FST responses were measurable in patients with non-recordable ERGs. On average, FST responses remained stable during follow-up.

Conclusion: In CRB1-associated retinal dystrophies, visual acuity and visual field measures remain relatively stable over the course of 2 years. Microperimetry showed a significant decrease in retinal sensitivity during follow-up, and may be a more sensitive progression marker. Retinal sensitivity on microperimetry may serve as a functional clinical endpoint in future human treatment trials for CRB1-associated retinal dystrophies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ajo.2021.07.021DOI Listing
July 2021

Molecular Inversion Probe-Based Sequencing of Exons and Splice Sites as a Cost-Effective Screening Tool in USH2 and arRP Cases.

Int J Mol Sci 2021 Jun 15;22(12). Epub 2021 Jun 15.

Department of Human Genetics, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 Nijmegen, The Netherlands.

A substantial proportion of subjects with autosomal recessive retinitis pigmentosa (arRP) or Usher syndrome type II (USH2) lacks a genetic diagnosis due to incomplete screening in the early days of genetic testing. These cases lack eligibility for optimal genetic counseling and future therapy. defects are the most frequent cause of USH2 and are also causative in individuals with arRP. Therefore, is an important target for genetic screening. The aim of this study was to assess unscreened or incompletely screened and unexplained USH2 and arRP cases for (likely) pathogenic variants. Molecular inversion probe (MIP)-based sequencing was performed for the exons and their flanking regions, as well as published deep-intronic variants. This was done to identify single nucleotide variants (SNVs) and copy number variants (CNVs) in 29 unscreened or partially pre-screened USH2 and 11 partially pre-screened arRP subjects. In 29 out of these 40 cases, two (likely) pathogenic variants were successfully identified. Four of the identified SNVs and one CNV were novel. One previously identified synonymous variant was demonstrated to affect pre-mRNA splicing. In conclusion, genetic diagnoses were obtained for a majority of cases, which confirms that MIP-based sequencing is an effective screening tool for . Seven unexplained cases were selected for future analysis with whole genome sequencing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms22126419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232728PMC
June 2021

Benchmarking deep learning splice prediction tools using functional splice assays.

Hum Mutat 2021 Jul 20;42(7):799-810. Epub 2021 May 20.

Centre for Molecular and Biomolecular Informatics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.

Hereditary disorders are frequently caused by genetic variants that affect pre-messenger RNA splicing. Though genetic variants in the canonical splice motifs are almost always disrupting splicing, the pathogenicity of variants in the noncanonical splice sites (NCSS) and deep intronic (DI) regions are difficult to predict. Multiple splice prediction tools have been developed for this purpose, with the latest tools employing deep learning algorithms. We benchmarked established and deep learning splice prediction tools on published gold standard sets of 71 NCSS and 81 DI variants in the ABCA4 gene and 61 NCSS variants in the MYBPC3 gene with functional assessment in midigene and minigene splice assays. The selection of splice prediction tools included CADD, DSSP, GeneSplicer, MaxEntScan, MMSplice, NNSPLICE, SPIDEX, SpliceAI, SpliceRover, and SpliceSiteFinder-like. The best-performing splice prediction tool for the different variants was SpliceRover for ABCA4 NCSS variants, SpliceAI for ABCA4 DI variants, and the Alamut 3/4 consensus approach (GeneSplicer, MaxEntScacn, NNSPLICE and SpliceSiteFinder-like) for NCSS variants in MYBPC3 based on the area under the receiver operator curve. Overall, the performance in a real-time clinical setting is much more modest than reported by the developers of the tools.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/humu.24212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8360004PMC
July 2021

Antisense Oligonucleotide-Based Rescue of Aberrant Splicing Defects Caused by 15 Pathogenic Variants in .

Int J Mol Sci 2021 Apr 28;22(9). Epub 2021 Apr 28.

Departments of Pediatrics and Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525GA Nijmegen, The Netherlands.

The discovery of novel intronic variants in the locus has contributed significantly to solving the missing heritability in Stargardt disease (STGD1). The increasing number of variants affecting pre-mRNA splicing makes a suitable candidate for antisense oligonucleotide (AON)-based splicing modulation therapies. In this study, AON-based splicing modulation was assessed for 15 recently described intronic variants (three near-exon and 12 deep-intronic variants). In total, 26 AONs were designed and tested in vitro using a midigene-based splice system. Overall, partial or complete splicing correction was observed for two variants causing exon elongation and all variants causing pseudoexon inclusion. Together, our results confirm the high potential of AONs for the development of future RNA therapies to correct splicing defects causing STGD1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms22094621DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8124656PMC
April 2021

branchpoint variant is associated with non-syndromic retinitis pigmentosa.

J Med Genet 2021 Apr 28. Epub 2021 Apr 28.

Department of Human Genetics, Radboudumc, Nijmegen, The Netherlands

Background: Inherited retinal diseases (IRDs) can be caused by variants in >270 genes. The Bardet-Biedl syndrome 1 () gene is one of these genes and may be associated with syndromic and non-syndromic autosomal recessive retinitis pigmentosa (RP). Here, we identified a branchpoint variant in and assessed its pathogenicity by in vitro functional analysis.

Methods: Whole genome sequencing was performed for three unrelated monoallelic cases with non-syndromic RP. A fourth case received MGCM 105 gene panel analysis. Functional analysis using a midigene splice assay was performed for the putative pathogenic branchpoint variant in . After confirmation of its pathogenicity, patients were clinically re-evaluated, including assessment of non-ocular features of Bardet-Biedl syndrome.

Results: Clinical assessments of probands showed that all individuals displayed non-syndromic RP with macular involvement. Through detailed variant analysis and prioritisation, two pathogenic variants in , the most common missense variant, c.1169T>G (p.(Met390Arg)), and a branchpoint variant, c.592-21A>T, were identified. Segregation analysis confirmed that in all families, probands were compound heterozygous for c.1169T>G and c.592-21A>T. Functional analysis of the branchpoint variant revealed a complex splicing defect including exon 8 and exon 7/8 skipping, and partial in-frame deletion of exon 8.

Conclusion: A putative severe branchpoint variant in , together with a mild missense variant, underlies non-syndromic RP in four unrelated individuals. To our knowledge, this is the first report of a pathogenic branchpoint variant in IRDs that results in a complex splice defect. In addition, this research highlights the importance of the analysis of non-coding regions in order to provide a conclusive molecular diagnosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/jmedgenet-2020-107626DOI Listing
April 2021

The Impact of Modern Technologies on Molecular Diagnostic Success Rates, with a Focus on Inherited Retinal Dystrophy and Hearing Loss.

Int J Mol Sci 2021 Mar 14;22(6). Epub 2021 Mar 14.

Department of Human Genetics, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands.

The identification of pathogenic variants in monogenic diseases has been of interest to researchers and clinicians for several decades. However, for inherited diseases with extremely high genetic heterogeneity, such as hearing loss and retinal dystrophies, establishing a molecular diagnosis requires an enormous effort. In this review, we use these two genetic conditions as examples to describe the initial molecular genetic identification approaches, as performed since the early 90s, and subsequent improvements and refinements introduced over the years. Next, the history of DNA sequencing from conventional Sanger sequencing to high-throughput massive parallel sequencing, a.k.a. next-generation sequencing, is outlined, including their advantages and limitations and their impact on identifying the remaining genetic defects. Moreover, the development of recent technologies, also coined "third-generation" sequencing, is reviewed, which holds the promise to overcome these limitations. Furthermore, we outline the importance and complexity of variant interpretation in clinical diagnostic settings concerning the massive number of different variants identified by these methods. Finally, we briefly mention the development of novel approaches such as optical mapping and multiomics, which can help to further identify genetic defects in the near future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms22062943DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998853PMC
March 2021

The need for widely available genomic testing in rare eye diseases: an ERN-EYE position statement.

Orphanet J Rare Dis 2021 03 20;16(1):142. Epub 2021 Mar 20.

ERN-EYE Coordination Center, Hopitaux Universitaires de Strasbourg, Strasbourg, France.

Background: Rare Eye Diseases (RED) are the leading cause of visual impairment and blindness for children and young adults in Europe. This heterogeneous group of conditions includes over 900 disorders ranging from relatively prevalent disorders such as retinitis pigmentosa to very rare entities such as developmental eye anomalies. A significant number of patients with RED have an underlying genetic etiology. One of the aims of the European Reference Network for Rare Eye Diseases (ERN-EYE) is to facilitate improvement in diagnosis of RED in European member states.

Main Body: Technological advances have allowed genetic and genomic testing for RED. The outcome of genetic testing allows better understanding of the condition and allows reproductive and therapeutic options. The increase of the number of clinical trials for RED has provided urgency for genetic testing in RED. A survey of countries participating in ERN-EYE demonstrated that the majority are able to access some forms of genomic testing. However, there is significant variability, particularly regarding testing as part of clinical service. Some countries have a well-delineated rare disease pathway and have a national plan for rare diseases combined or not with a national plan for genomics in medicine. In other countries, there is a well-established organization of genetic centres that offer reimbursed genomic testing of RED and other rare diseases. Clinicians often rely upon research-funded laboratories or private companies. Notably, some member states rely on cross-border testing by way of an academic research project. Consequently, many clinicians are either unable to access testing or are confronted with long turnaround times. Overall, while the cost of sequencing has dropped, the cumulative cost of a genomic testing service for populations remains considerable. Importantly, the majority of countries reported healthcare budgets that limit testing.

Short Conclusion: Despite technological advances, critical gaps in genomic testing remain in Europe, especially in smaller countries where no formal genomic testing pathways exist. Even within larger countries, the existing arrangements are insufficient to meet the demand and to ensure access. ERN-EYE promotes access to genetic testing in RED and emphasizes the clinical need and relevance of genetic testing in RED.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13023-021-01756-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7980559PMC
March 2021

Clinical Phenotype of -Associated Retinitis Pigmentosa.

Int J Mol Sci 2021 Feb 27;22(5). Epub 2021 Feb 27.

Molecular Genetics Laboratory, Institute for Ophthalmic Research, Centre for Ophthalmology, Eberhard Karls University Tübingen, 72076 Tübingen, Germany.

In this retrospective, longitudinal, observational cohort study, we investigated the phenotypic and genotypic features of retinitis pigmentosa associated with variants in the gene. Patients underwent clinical examination and genetic testing at a single tertiary referral center, including best-corrected visual acuity (BCVA), kinetic visual field (VF), full-field electroretinography, full-field stimulus threshold, spectral domain optical coherence tomography, and fundus autofluorescence imaging. The genetic testing comprised candidate gene sequencing, inherited retinal disease gene panel sequencing, whole-genome sequencing, and testing for familial variants by Sanger sequencing. Twenty-four patients with mutations in from 21 families were included in the study (mean age at the first visit: 32.1 ± 13.5 years). The majority of variants were putative splicing defects (8/23) and missense (7/23) mutations. Seventy-nine percent (38/48) of eyes had no visual acuity impairment at the first visit. Visual acuity impairment was mild in 4% (2/48), moderate in 13% (6/48), and severe in 4% (2/48). BCVA was symmetrical in the right and left eyes. The kinetic VF measurements were highly symmetrical in the right and left eyes, as was the horizontal ellipsoid zone (EZ) width. Regarding the genetic findings, 43% of the variants found in our patients were novel. Thus, this study contributed substantially to the mutation spectrum. The visual acuity impairment was mild in 83% of eyes, providing a window of opportunity for investigational new drugs. The EZ width was reduced in all patients and was highly symmetric between the eyes, making it a promising outcome measure. We expect these findings to have implications on the design of future -related retinitis pigmentosa (RP) clinical trials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms22052374DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7956818PMC
February 2021

Defining inclusion criteria and endpoints for clinical trials: a prospective cross-sectional study in CRB1-associated retinal dystrophies.

Acta Ophthalmol 2021 May 2;99(3):e402-e414. Epub 2021 Feb 2.

Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands.

Purpose: To investigate the retinal structure and function in patients with CRB1-associated retinal dystrophies (RD) and to explore potential clinical endpoints.

Methods: In this prospective cross-sectional study, 22 patients with genetically confirmed CRB1-RD (aged 6-74 years), and who had a decimal best-corrected visual acuity (BCVA) ≥ 0.05 at the last visit, were studied clinically with ETDRS BCVA, corneal topography, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence, Goldmann visual field (VF), microperimetry, full-field electroretinography (ERG) and full-field stimulus testing (FST). Ten patients were from a genetic isolate (GI).

Results: Patients had retinitis pigmentosa (n = 19; GI and non-GI), cone-rod dystrophy (n = 2; GI) or macular dystrophy (n = 1; non-GI). Median age at first symptom onset was 3 years (range 0.8-49). Median decimal BCVA in the better and worse-seeing eye was 0.18 (range 0.05-0.83) and 0.08 (range light perception-0.72), respectively. Spectral-domain optical coherence tomography (SD-OCT) showed cystoid maculopathy in 8 subjects; inner retinal thickening (n = 20), a well-preserved (para)foveal outer retina (n = 7) or severe (para)foveal outer retinal atrophy (n = 14). All retinal layers were discernible in 13/21 patients (62%), with mild to moderate laminar disorganization in the others. Nanophthalmos was observed in 8 patients (36%). Full-field stimulus testing (FST) provided a subjective outcome measure for retinal sensitivity in eyes with (nearly) extinguished ERG amplitudes.

Conclusions: Despite the generally severe course of CRB1-RDs, symptom onset and central visual function are variable, even at advanced ages. Phenotypes may vary within the same family. Imaging and functional studies in a prospective longitudinal setting should clarify which endpoints may be most appropriate in a clinical trial.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/aos.14597DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8248330PMC
May 2021

SENIOR-LØKEN SYNDROME: A Case Series and Review of the Renoretinal Phenotype and Advances of Molecular Diagnosis.

Retina 2021 Oct;41(10):2179-2187

Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel.

Purpose: To report genetic and clinical findings in a case series of 10 patients from eight unrelated families diagnosed with Senior-Løken syndrome.

Methods: A retrospective study of patients with Senior-Løken syndrome. Data collected included clinical findings electroretinography and ocular imaging. Genetic analysis was based on molecular inversion probes, whole-exome sequencing (WES), and Sanger sequencing.

Results: All patients who underwent electrophysiology (8/10) had widespread photoreceptor degeneration. Genetic analysis revealed two mutations in NPHP1, two mutations in NPHP4, and two mutations in IQCB1 (NPHP5). Five of the six mutations identified in the current study were found in a single family each in our cohort. The IQCB1-p.R461* mutation has been identified in 3 families. Patients harboring mutations in IQCB1 were diagnosed with Leber congenital amaurosis, while patients with NPHP4 and NPHP1 mutations showed early and sector retinitis pigmentosa, respectively. Full-field electroretinography was extinct for 6 of 10 patients, moderately decreased for two, and unavailable for another 2 subjects. Renal involvement was evident in 7/10 patients at the time of diagnosis. Kidney function was normal (based on serum creatinine) in patients younger than 10 years. Mutations in IQCB1 were associated with high hypermetropia, whereas mutations in NPHP4 were associated with high myopia.

Conclusion: Patients presenting with infantile inherited retinal degeneration are not universally screened for renal dysfunction. Modern genetic tests can provide molecular diagnosis at an early age and therefore facilitate early diagnosis of renal disease with recommended periodic screening beyond childhood and family planning.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/IAE.0000000000003138DOI Listing
October 2021

Structural Variants Create New Topological-Associated Domains and Ectopic Retinal Enhancer-Gene Contact in Dominant Retinitis Pigmentosa.

Am J Hum Genet 2020 11 5;107(5):802-814. Epub 2020 Oct 5.

University of Cape Town/MRC Genomic and Precision Medicine Research Unit, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, 7935, South Africa.

The cause of autosomal-dominant retinitis pigmentosa (adRP), which leads to loss of vision and blindness, was investigated in families lacking a molecular diagnosis. A refined locus for adRP on Chr17q22 (RP17) was delineated through genotyping and genome sequencing, leading to the identification of structural variants (SVs) that segregate with disease. Eight different complex SVs were characterized in 22 adRP-affected families with >300 affected individuals. All RP17 SVs had breakpoints within a genomic region spanning YPEL2 to LINC01476. To investigate the mechanism of disease, we reprogrammed fibroblasts from affected individuals and controls into induced pluripotent stem cells (iPSCs) and differentiated them into photoreceptor precursor cells (PPCs) or retinal organoids (ROs). Hi-C was performed on ROs, and differential expression of regional genes and a retinal enhancer RNA at this locus was assessed by qPCR. The epigenetic landscape of the region, and Hi-C RO data, showed that YPEL2 sits within its own topologically associating domain (TAD), rich in enhancers with binding sites for retinal transcription factors. The Hi-C map of RP17 ROs revealed creation of a neo-TAD with ectopic contacts between GDPD1 and retinal enhancers, and modeling of all RP17 SVs was consistent with neo-TADs leading to ectopic retinal-specific enhancer-GDPD1 accessibility. qPCR confirmed increased expression of GDPD1 and increased expression of the retinal enhancer that enters the neo-TAD. Altered TAD structure resulting in increased retinal expression of GDPD1 is the likely convergent mechanism of disease, consistent with a dominant gain of function. Our study highlights the importance of SVs as a genomic mechanism in unsolved Mendelian diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ajhg.2020.09.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7675008PMC
November 2020

Unique combination of clinical features in a large cohort of 100 patients with retinitis pigmentosa caused by FAM161A mutations.

Sci Rep 2020 09 16;10(1):15156. Epub 2020 Sep 16.

Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University Jerusalem, Jerusalem, Israel.

FAM161A mutations are the most common cause of autosomal recessive retinitis pigmentosa in the Israeli-Jewish population. We aimed to characterize the spectrum of FAM161A-associated phenotypes and identify characteristic clinical features. We identified 114 bi-allelic FAM161A patients and obtained clinical records of 100 of these patients. The most frequent initial symptom was night blindness. Best-corrected visual acuity was largely preserved through the first three decades of life and severely deteriorated during the 4th-5th decades. Most patients manifest moderate-high myopia. Visual fields were markedly constricted from early ages, but maintained for decades. Bone spicule-like pigmentary changes appeared relatively late, accompanied by nummular pigmentation. Full-field electroretinography responses were usually non-detectable at first testing. Fundus autofluorescence showed a hyper-autofluorescent ring around the fovea in all patients already at young ages. Macular ocular coherence tomography showed relative preservation of the outer nuclear layer and ellipsoid zone in the fovea, and frank cystoid macular changes were very rare. Interestingly, patients with a homozygous nonsense mutation manifest somewhat more severe disease. Our clinical analysis is one of the largest ever reported for RP caused by a single gene allowing identification of characteristic clinical features and may be relevant for future application of novel therapies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-72028-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7495424PMC
September 2020

Association of Sex With Frequent and Mild ABCA4 Alleles in Stargardt Disease.

JAMA Ophthalmol 2020 10;138(10):1035-1042

Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands.

Importance: The mechanisms behind the phenotypic variability and reduced penetrance in autosomal recessive Stargardt disease (STGD1), often a blinding disease, are poorly understood. Identification of the unknown disease modifiers can improve patient and family counseling and provide valuable information for disease management.

Objective: To assess the association of incompletely penetrant ABCA4 alleles with sex in STGD1.

Design, Setting, And Participants: Genetic data for this cross-sectional study were obtained from 2 multicenter genetic studies of 1162 patients with clinically suspected STGD1. Unrelated patients with genetically confirmed STGD1 were selected. The data were collected from June 2016 to June 2019, and post hoc analysis was performed between July 2019 and January 2020.

Main Outcomes And Measures: Penetrance of reported mild ABCA4 variants was calculated by comparing the allele frequencies in the general population (obtained from the Genome Aggregation Database) with the genotyping data in the patient population (obtained from the ABCA4 Leiden Open Variation Database). The sex ratio among patients with and patients without an ABCA4 allele with incomplete penetrance was assessed.

Results: A total of 550 patients were included in the study, among which the mean (SD) age was 45.7 (18.0) years and most patients were women (311 [57%]). Five of the 5 mild ABCA4 alleles, including c.5603A>T and c.5882G>A, were calculated to have incomplete penetrance. The women to men ratio in the subgroup carrying c.5603A>T was 1.7 to 1; the proportion of women in this group was higher compared with the subgroup not carrying a mild allele (difference, 13%; 95% CI, 3%-23%; P = .02). The women to men ratio in the c.5882G>A subgroup was 2.1 to 1, and the women were overrepresented compared with the group carrying no mild allele (difference, 18%; 95% CI, 6%-30%; P = .005).

Conclusions And Relevance: This study found an imbalance in observed sex ratio among patients harboring a mild ABCA4 allele, which concerns approximately 25% of all patients with STGD1, suggesting that STGD1 should be considered a polygenic or multifactorial disease rather than a disease caused by ABCA4 gene mutations alone. The findings suggest that sex should be considered as a potential disease-modifying variable in both basic research and clinical trials on STGD1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1001/jamaophthalmol.2020.2990DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7441467PMC
October 2020

The First Inherited Retinal Disease Registry in Iran: Research Protocol and Results of a Pilot Study.

Arch Iran Med 2020 07 1;23(7):445-454. Epub 2020 Jul 1.

Ophthalmic Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Background: To describe the protocol for developing a national inherited retinal disease (IRD) registry in Iran and present its initial report.

Methods: This community-based participatory research was approved by the Ministry of Health and Medical Education of Iran in 2016. To provide the minimum data set (MDS), several focus group meetings were held. The final MDS was handed over to an engineering team to develop a web-based software. In the pilot phase, the software was set up in two referral centers in Iran. Final IRD diagnosis was made based on clinical manifestations and genetic findings. Ultimately, patient registration was done based on all clinical and non-clinical manifestations.

Results: Initially, a total of 151 data elements were approved with Delphi technique. The registry software went live at www. IRDReg.org based on DHIS2 open source license agreement since February 2016. So far, a total of 1001 patients have been registered with a mean age of 32.41±15.60 years (range, 3 months to 74 years). The majority of the registered patients had retinitis pigmentosa (42%, 95% CI: 38.9% to 45%). Genetic testing was done for approximately 20% of the registered individuals.

Conclusion: Our study shows successful web-based software design and data collection as a proof of concept for the first IRD registry in Iran. Multicenter integration of the IRD registry in medical centers throughout the country is well underway as planned. These data will assist researchers to rapidly access information about the distribution and genetic patterns of this disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.34172/aim.2020.41DOI Listing
July 2020

Detailed Phenotyping and Therapeutic Strategies for Intronic ABCA4 Variants in Stargardt Disease.

Mol Ther Nucleic Acids 2020 Sep 12;21:412-427. Epub 2020 Jun 12.

Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands; Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, the Netherlands. Electronic address:

Stargardt disease is a progressive retinal disorder caused by bi-allelic mutations in the ABCA4 gene that encodes the ATP-binding cassette, subfamily A, member 4 transporter protein. Over the past few years, we and others have identified several pathogenic variants that reside within the introns of ABCA4, including a recurrent variant in intron 36 (c.5196+1137G>A) of which the pathogenicity so far remained controversial. Detailed clinical characterization of this variant confirmed its pathogenic nature, and classified it as an allele of intermediate severity. Moreover, we discovered several additional ABCA4 variants clustering in intron 36. Several of these variants resulted in aberrant splicing of ABCA4, i.e., the inclusion of pseudoexons, while the splicing defects caused by the recurrent c.5196+1137G>A variant strongly increased upon differentiation of patient-derived induced pluripotent stem cells into retina-like cells. Finally, all splicing defects could be rescued by the administration of antisense oligonucleotides that were designed to specifically block the pseudoexon insertion, including rescue in 3D retinal organoids harboring the c.5196+1137G>A variant. Our data illustrate the importance of intronic variants in ABCA4 and expand the therapeutic possibilities for overcoming splicing defects in Stargardt disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.omtn.2020.06.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7352060PMC
September 2020

A in-frame deletion is a frequent and highly penetrant cause of adult-onset hearing loss.

J Med Genet 2020 Jul 6. Epub 2020 Jul 6.

Department of Human Genetics, Radboudumc, Nijmegen, The Netherlands

Background: Hearing loss is one of the most prevalent disabilities worldwide, and has a significant impact on quality of life. The adult-onset type of the condition is highly heritable but the genetic causes are largely unknown, which is in contrast to childhood-onset hearing loss.

Methods: Family and cohort studies included exome sequencing and characterisation of the hearing phenotype. Ex vivo protein expression addressed the functional effect of a DNA variant.

Results: An in-frame deletion of 12 nucleotides in was identified as a highly penetrant cause of adult-onset progressive hearing loss that segregated as an autosomal dominant trait in 12 families from the Netherlands. Hearing loss associated with the deletion in 63 subjects displayed variable audiometric characteristics and an average (SD) age of onset of 30.6 (14.9) years (range 0-70 years). A functional effect of the variant was demonstrated by aberrant localisation of the mutant RIPOR2 in the stereocilia of cochlear hair cells and failure to rescue morphological defects in RIPOR2-deficient hair cells, in contrast to the wild-type protein. Strikingly, the variant is present in 18 of 22 952 individuals not selected for hearing loss in the Southeast Netherlands.

Conclusion: Collectively, the presented data demonstrate that an inherited form of adult-onset hearing loss is relatively common, with potentially thousands of individuals at risk in the Netherlands and beyond, which makes it an attractive target for developing a (genetic) therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/jmedgenet-2020-106863DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120656PMC
July 2020

Resolving the dark matter of ABCA4 for 1054 Stargardt disease probands through integrated genomics and transcriptomics.

Genet Med 2020 07 20;22(7):1235-1246. Epub 2020 Apr 20.

Bartiméus Diagnostic Center for Complex Visual Disorders, Zeist, The Netherlands.

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 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41436-020-0787-4DOI Listing
July 2020

Clinical spectrum, genetic complexity and therapeutic approaches for retinal disease caused by ABCA4 mutations.

Prog Retin Eye Res 2020 11 9;79:100861. Epub 2020 Apr 9.

Department of Ophthalmology, Columbia University, New York, NY, 10032, USA; Department of Pathology & Cell Biology, Columbia University, New York, NY, 10032, USA. Electronic address:

The ABCA4 protein (then called a "rim protein") was first identified in 1978 in the rims and incisures of rod photoreceptors. The corresponding gene, ABCA4, was cloned in 1997, and variants were identified as the cause of autosomal recessive Stargardt disease (STGD1). Over the next two decades, variation in ABCA4 has been attributed to phenotypes other than the classically defined STGD1 or fundus flavimaculatus, ranging from early onset and fast progressing cone-rod dystrophy and retinitis pigmentosa-like phenotypes to very late onset cases of mostly mild disease sometimes resembling, and confused with, age-related macular degeneration. Similarly, analysis of the ABCA4 locus uncovered a trove of genetic information, including >1200 disease-causing mutations of varying severity, and of all types - missense, nonsense, small deletions/insertions, and splicing affecting variants, of which many are located deep-intronic. Altogether, this has greatly expanded our understanding of complexity not only of the diseases caused by ABCA4 mutations, but of all Mendelian diseases in general. This review provides an in depth assessment of the cumulative knowledge of ABCA4-associated retinopathy - clinical manifestations, genetic complexity, pathophysiology as well as current and proposed therapeutic approaches.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.preteyeres.2020.100861DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7544654PMC
November 2020

In or Out? New Insights on Exon Recognition through Splice-Site Interdependency.

Int J Mol Sci 2020 03 26;21(7). Epub 2020 Mar 26.

Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands.

Noncanonical splice-site mutations are an important cause of inherited diseases. Based on in vitro and stem-cell-based studies, some splice-site variants show a stronger splice defect than expected based on their predicted effects, suggesting that other sequence motifs influence the outcome. We investigated whether splice defects due to human-inherited-disease-associated variants in noncanonical splice-site sequences in , , and could be rescued by strengthening the splice site on the other side of the exon. Noncanonical 5'- and 3'-splice-site variants were selected. Rescue variants were introduced based on an increase in predicted splice-site strength, and the effects of these variants were analyzed using in vitro splice assays in HEK293T cells. Exon skipping due to five variants in noncanonical splice sites of exons in , , and could be partially or completely rescued by increasing the predicted strengths of the other splice site of the same exon. We named this mechanism "splicing interdependency", and it is likely based on exon recognition by splicing machinery. Awareness of this interdependency is of importance in the classification of noncanonical splice-site variants associated with disease and may open new opportunities for treatments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21072300DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7177576PMC
March 2020

LONGITUDINAL STUDY OF RPE65-ASSOCIATED INHERITED RETINAL DEGENERATIONS.

Retina 2020 Sep;40(9):1812-1828

The Rotterdam Eye Hospital, Rotterdam, the Netherlands.

Purpose: To study the disease course of RPE65-associated inherited retinal degenerations (IRDs) as a function of the genotype, define a critical age for blindness, and identify potential modifiers.

Methods: Forty-five patients with IRD from 33 families with biallelic RPE65 mutations, 28 stemming from a genetic isolate. We collected retrospective data from medical charts. Coexisting variants in 108 IRD-associated genes were identified with Molecular Inversion Probe analysis.

Results: Most patients were diagnosed within the first years of life. Daytime visual function ranged from near-normal to blindness in the first four decades and met WHO criteria for blindness for visual acuity and visual field in the fifth decade. p.(Thr368His) was the most common variant (54%). Intrafamilial variability and interfamilial variability in disease severity and progression were observed. Molecular Inversion Probe analysis confirmed all RPE65 variants and identified one additional variant in LRAT and one in EYS in two separate patients.

Conclusion: All patients with RPE65-associated IRDs developed symptoms within the first year of life. Visual function in childhood and adolescence varied but deteriorated inevitably toward blindness after age 40. In this study, genotype was not predictive of clinical course. The variance in severity of disease could not be explained by double hits in other IRD genes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/IAE.0000000000002681DOI Listing
September 2020

ABCA4-Associated Stargardt Disease.

Klin Monbl Augenheilkd 2020 Mar 3;237(3):267-274. Epub 2020 Feb 3.

Department of Human Genetics, Radboudumc, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.

Autosomal recessive Stargardt disease (STGD1) is associated with variants in the gene. The phenotypes range from early-onset STGD1, that clinically resembles severe cone-rod dystrophy, to intermediate STGD1 and late-onset STGD1. These different phenotypes can be correlated with different combinations of variants which can be classified according to their degree of severity. A significant fraction of STGD1 cases, particularly late-onset STGD1 cases, were shown to carry only a single variant. A frequent coding variant (p.Asn1868Ile) was recently identified which - in combination with a severe variant - is generally associated with late-onset STGD1. In addition, an increasing number of rare deep-intronic variants have been found and some of these are also associated with late-onset STGD1. The effect of these and other variants on RNA was tested using assays in human kidney cells using specially designed midigenes. With stem cells and photoreceptor progenitor cells derived from patient skin or blood cells, retina-specific splice defects can be assessed. With expert clinical examination to distinguish STGD1 cases from other maculopathies, as well as in-depth genomics and transcriptomics data, it is now possible to identify both mutant alleles in > 95% of cases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1055/a-1057-9939DOI Listing
March 2020

Chromatic Full-Field Stimulus Threshold and Pupillography as Functional Markers for Late-Stage, Early-Onset Retinitis Pigmentosa Caused by Mutations.

Transl Vis Sci Technol 2019 Nov 20;8(6):45. Epub 2019 Dec 20.

Center for Ophthalmology, University of Tübingen, Tübingen, Germany.

Purpose: Mutations in the gene cause early-onset retinal degeneration (EORD). Clinical disease progression markers, such as visual fields or electrophysiology, are not reliably measurable in most patients to follow the retinal function in patients with -mutations.

Methods: Ten patients (five females, five males; age 22-56 years) with EORD caused by mutations were examined in a cross-sectional manner using best corrected visual acuity (BCVA), perimetry, full-field and multifocal electroretinography, full-field stimulus threshold (FST), and pupillography to red and blue light. Disease duration was defined as the difference between the age at the first symptoms to the age at examination in years.

Results: BCVA was quantifiable in six patients and ranged from light perception to 20/50. The visual field was measurable only in three patients who had the shortest disease duration. Full-field and multifocal electroretinography were not measurable in any patient. FST to blue and red light were measurable in all patients except the one with the longest disease duration; the thresholds ranged from -16.7 to 1.5 dB for red light and from -40.2 to 2.5 dB for blue light (0 dB = 0.01 cd.s/m) and showed correlations with disease duration ( = 0.87 for blue, = 0.65 for red, = 0.8 for blue-red difference). The maximal relative pupil constriction amplitude (MRA) showed low or no correlations with disease duration ( = -0.55 for blue, = -0.3 for red light); the blue-red difference in the post-illumination pupil responses (PIPR) showed no correlation with disease duration ( = -0.05). Compared to healthy eyes, the MRA to red and blue light was significantly decreased ( < 0.001) and the blue-red PIPR difference was significantly increased ( = 0.003).

Conclusions: FST features a valid clinical marker in late-stage early-onset retinitis pigmentosa caused by mutations correlating with disease duration. This indicates the potential as a progression marker of disease. The pupil responses to full-field chromatic stimuli show significant differences from the normal population: the remaining responses, although reduced, indicate a partially preserved inner retinal function despite severe photoreceptor dysfunction.

Translational Relevance: The functional measurements presented in this study present a valid clinical progression marker in late-stage early onset retinitis pigmentosa caused by biallelic mutations. Additionally, they can be used as outcome measures for safety and efficacy in clinical therapy trials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1167/tvst.8.6.45DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927735PMC
November 2019

Genetic Spectrum of -Associated Retinal Degeneration in Poland.

Genes (Basel) 2019 11 21;10(12). Epub 2019 Nov 21.

Children's Memorial Health Institute, 04-730 Warsaw, Poland.

Mutations in retina-specific ATP-binding cassette transporter 4 () are responsible for over 95% of cases of Stargardt disease (STGD), as well as a minor proportion of retinitis pigmentosa (RP) and cone-rod dystrophy cases (CRD). Since the knowledge of the genetic causes of inherited retinal diseases (IRDs) in Poland is still scarce, the purpose of this study was to identify pathogenic variants in a subgroup of Polish IRD patients. We recruited 67 families with IRDs as a part of a larger study. The patients were screened with next generation sequencing using a molecular inversion probes (MIPs)-based technique targeting 108 genes involved in the pathogenesis of IRDs. All identified mutations were validated and their familial segregation was tested using Sanger sequencing. In the case of the most frequent complex allele, consisting of two variants in exon 12 and 21, familial segregation was tested using restriction fragment length polymorphism (RFLP). The most prevalent variant, a complex change c.[1622T>C;3113C>T], p.[Leu541Pro;Ala1038Val], was found in this cohort in 54% of all solved -associated disorder cases, which is the highest frequency reported thus far. Additionally, we identified nine families displaying a pseudo-dominant mode of inheritance, indicating a high frequency of pathogenic variants within this population.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/genes10120959DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6947411PMC
November 2019

CEP290 Mutation Spectrum and Delineation of the Associated Phenotype in a Large German Cohort: A Monocentric Study.

Am J Ophthalmol 2020 03 14;211:142-150. Epub 2019 Nov 14.

Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany. Electronic address:

Purpose: Gene therapy for Leber congenital amaurosis (LCA) is becoming available, and therefore it is crucial to identify eligible candidates. We report the spectrum and associated phenotype of CEP290 mutations in the largest German cohort observed by a single clinical site.

Design: Prospective cohort study.

Methods: Twenty-three patients with mutations in CEP290 were included. Genomic DNA was analyzed by Sanger sequencing or high-throughput sequencing for all retinitis pigmentosa-associated genes in patients, and segregation analysis was done in family members. Patients underwent functional and morphologic examinations, including fundus autofluorescence and spectral-domain optical coherence tomography.

Results: The most frequent mutation was c.2991+1655A>G, found in 87% of patients (20/23). Thirty percent of patients (7/23) carried the mutation in an apparent homozygous state and 57% (13/23) in a likely compound heterozygous state. The most common clinical diagnosis was LCA and/or early onset severe retinal dystrophy in 82% (19/23), followed by retinitis pigmentosa in 14% (3/23) and cone-rod dystrophy (4%, 1/23). Best-corrected visual acuity was severely reduced to residual light perception and hand motion vision, with the exception of 3 patients with best-corrected visual acuity of 0.8 (Snellen). The visual field was severely decreased and electroretinogram was undetectable in most cases; however, retinal layers at the fovea appeared to be relatively well preserved. Systemic disorders were not noticed.

Conclusions: c.2991+1655A>G is by far the most important CEP290 mutation, contributing to 87% of patients with the CEP290 mutation in Germany. In our cohort, a homozygous c.2991+1655A>G genotype presented with a more severe phenotype. National studies and further detailed phenotype analysis seem to be important to assess the need for and promise of specific gene therapies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ajo.2019.11.012DOI Listing
March 2020

Late-Onset Stargardt Disease Due to Mild, Deep-Intronic ABCA4 Alleles.

Invest Ophthalmol Vis Sci 2019 10;60(13):4249-4256

Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands.

Purpose: To investigate the role of two deep-intronic ABCA4 variants, that showed a mild splice defect in vitro and can occur on the same allele as the low penetrant c.5603A>T, in Stargardt disease (STGD1).

Methods: Ophthalmic data were assessed of 18 STGD1 patients who harbored c.769-784C>T or c.4253+43G>A in combination with a severe ABCA4 variant. Subjects carrying c.[769-784C>T; 5603A>T] were clinically compared with a STGD1 cohort previously published carrying c.5603A>T noncomplex. We calculated the penetrances of the intronic variants using ABCA4 allele frequency data of the general population and investigated the effect of c.769-784C>T on splicing in photoreceptor progenitor cells (PPCs).

Results: Mostly, late-onset, foveal-sparing STGD1 was observed among subjects harboring c.769-784C>T or c.4253+43G>A (median age of onset, 54.5 and 52.0 years, respectively). However, ages of onset, phenotypes in fundo, and visual acuity courses varied widely. No significant clinical differences were observed between the c.[769-784C>T; 5603A>T] cohort and the c.4253+43G>A or the c.5603A>T cohort. The penetrances of c.769-784C>T (20.5%-39.6%) and c.4253+43G>A (35.8%-43.1%) were reduced, when not considering the effect of yet unidentified or known factors in cis, such as c.5603A>T (identified in 7/7 probands with c.769-784C>T; 1/8 probands with c.4253+43G>A). Variant c.769-784C>T resulted in a pseudo-exon insertion in 15% of the total mRNA (i.e., ∼30% of the c.769-784C>T allele alone).

Conclusions: Two mild intronic ABCA4 variants could further explain missing heritability in late-onset STGD1, distinguishing it from AMD. The observed clinical variability and calculated reduced penetrance urge research into modifiers within and outside of the ABCA4 gene.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1167/iovs.19-27524DOI Listing
October 2019

Highly Variable Disease Courses in Siblings with Stargardt Disease.

Ophthalmology 2019 12 16;126(12):1712-1721. Epub 2019 Jul 16.

Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands. Electronic address:

Purpose: To investigate intersibling phenotypic concordance in Stargardt disease (STGD1).

Design: Retrospective cohort study.

Participants: Siblings with genetically confirmed STGD1 and at least 1 available fundus autofluorescence (FAF) image of both eyes.

Methods: We compared age at onset within families. Disease duration was matched to investigate differences in best-corrected visual acuity (BCVA) and compared the survival time for reaching severe visual impairment (<20/200 Snellen or >1.0 logarithm of the minimum angle of resolution [logMAR]). Central retinal atrophy area was quantified independently by 2 experienced graders using semiautomated software and compared between siblings. Both graders performed qualitative assessment of FAF and spectral-domain (SD) OCT images to identify phenotypic differences.

Main Outcome Measures: Differences in age at onset, disease duration-matched BCVA, time to severe visual impairment development, FAF atrophy area, FAF patterns, and genotypes.

Results: Substantial differences in age at onset were present in 5 of 17 families, ranging from 13 to 39 years. Median BCVA at baseline was 0.60 logMAR (range, -0.20 to 2.30 logMAR; Snellen equivalent, 20/80 [range, 20/12-hand movements]) in the right eye and 0.50 logMAR (range, -0.20 to 2.30 logMAR; Snellen equivalent, 20/63 [range, 20/12-hand movements]) in the left eye. Disease duration-matched BCVA was investigated in 12 of 17 families, and the median difference was 0.41 logMAR (range, 0.00-1.10 logMAR) for the right eye and 0.41 logMAR (range, 0.00-1.08 logMAR) for the left eye. We observed notable differences in time to severe visual impairment development in 7 families, ranging from 1 to 29 years. Median central retinal atrophy area was 11.38 mm in the right eye (range, 1.98-44.78 mm) and 10.59 mm in the left eye (range, 1.61-40.59 mm) and highly comparable between siblings. Similarly, qualitative FAF and SD OCT phenotypes were highly comparable between siblings.

Conclusions: Phenotypic discordance between siblings with STGD1 carrying the same ABCA4 variants is a prevalent phenomenon. Although the FAF phenotypes are highly comparable between siblings, functional outcomes differ substantially. This complicates both sibling-based prognosis and genotype-phenotype correlations and has important implications for patient care and management.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ophtha.2019.07.010DOI Listing
December 2019
-->