BACKGROUND AND OBJECTIVES: Tandem repeats (TRs) are DNA regions of tandemly repeated nucleotide motifs. Their pathogenic expansions cause various, mainly neurologic, diseases. METHODS: We analyzed 65 TR loci using ExpansionHunter in individuals who underwent short-read whole-exome sequencing (WES) or whole-genome sequencing (WGS) for the diagnosis of a rare neurologic condition. RESULTS: Of 1,106 proband samples (1,053 WES, 53 WGS), we detected 232 TR expansions in the intermediate or pathogenic range in 18.7% (207/1,106). However, 51 TR expansions were revised as false positives (FPs) and 83 as nondisease-causing. Of the 98 disease-causing TR expansions, 5 were classified as causal hemizygous or heterozygous TR expansions associated with X-linked recessive (XLR) or autosomal dominant (AD) neurologic disorders in 5 probands (0.5%). The low incidence is due to the fact that individuals with typical clinical symptoms (spinocerebellar ataxia) were tested for TR expansion by conventional laboratory methods. Only 1 proband with clinical suspicion of spinal and bulbar muscular atrophy was fully explained by TR expansion in the AR gene, and in 4 others, we hypothesize the possible involvement of 2 different neurologic diseases. Another 82 causal hemizygous or heterozygous TR expansions associated with XLR or AD non-neurologic diseases (secondary findings) were identified in 81 probands (7.3%), of which 70 expansions in TCF4 were associated with Fuchs endothelial corneal dystrophy, a common eye disease in older patients. Finally, we detected 11 heterozygous TR expansions for XLR and autosomal recessive (AR) diseases in 11 probands who had no clinical symptoms of the associated TR disease. DISCUSSION: The unexpectedly high detection rate (18.7%) of TR expansions necessitates the filtration of FPs and nondisease-causing expansions, thereby underscoring the necessity of visual inspection of ExpansionHunter results. The study demonstrated that both WES and WGS diagnostics can benefit from TR expansion analysis. The secondary findings indicate that the previously published pathogenic ranges of TR expansions in RUNX2 and ZIC3 warrant further investigation.

• Publikační typ
• časopisecké články MeSH

IMPORTANCE: Understanding the pathogenic mechanisms of Fuchs endothelial corneal dystrophy (FECD) could contribute to developing gene-targeted therapies. OBJECTIVE: To investigate associations between demographic data and age at first keratoplasty in a genetically refined FECD cohort. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study recruited 894 individuals with FECD at Moorfields Eye Hospital (London) and General University Hospital (Prague) from September 2009 to July 2023. Ancestry was inferred from genome-wide single nucleotide polymorphism array data. CTG18.1 status was determined by short tandem repeat and/or triplet-primed polymerase chain reaction. One or more expanded alleles (≥50 repeats) were classified as expansion-positive (Exp+). Expansion-negative (Exp-) cases were exome sequenced. MAIN OUTCOMES AND MEASURES: Association between variants in FECD-associated genes, demographic data, and age at first keratoplasty. RESULTS: Within the total cohort (n = 894), 77.3% of patients were Exp+. Most European (668 of 829 [80.6%]) and South Asian (14 of 22 [63.6%]) patients were Exp+. The percentage of female patients was higher (151 [74.4%]) in the Exp- cohort compared to the Exp+ cohort (395 [57.2%]; difference, 17.2%; 95% CI, 10.1%-24.3%; P < .001). The median (IQR) age at first keratoplasty of the Exp + patients (68.2 years [63.2-73.6]) was older than the Exp- patients (61.3 years [52.6-70.4]; difference, 6.5 years; 95% CI, 3.4-9.7; P < .001). The CTG18.1 repeat length of the largest expanded allele within the Exp+ group was inversely correlated with the age at first keratoplasty (β, -0.087; 95% CI, -0.162 to -0.012; P = .02). The ratio of biallelic to monoallelic expanded alleles was higher in the FECD cohort (1:14) compared to an unaffected control group (1:94; P < .001), indicating that 2 Exp+ alleles were associated with increased disease penetrance compared with 1 expansion. Potentially pathogenic variants (minor allele frequency, <0.01; combined annotation dependent depletion, >15) were only identified in FECD-associated genes in 13 Exp- individuals (10.1%). CONCLUSIONS AND RELEVANCE: In this multicenter cohort study among individuals with FECD, CTG18.1 expansions were present in most European and South Asian patients, while CTG18.1 repeat length and zygosity status were associated with modifications in disease severity and penetrance. Known disease-associated genes accounted for only a minority of Exp- cases, with unknown risk factors associated with disease in the rest of this subgroup. These data may have implications for future FECD gene-targeted therapy development.

• MeSH
• celogenomová asociační studie MeSH
• dospělí MeSH
• Fuchsova endoteliální dystrofie * genetika   chirurgie   epidemiologie   diagnóza   MeSH
• genetická predispozice k nemoci * MeSH
• jednonukleotidový polymorfismus * MeSH
• lidé středního věku MeSH
• lidé MeSH
• retrospektivní studie MeSH
• rizikové faktory MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• stupeň závažnosti nemoci MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• multicentrická studie MeSH
• pozorovací studie MeSH

BACKGROUND: Fuchs endothelial corneal dystrophy (FECD) is the most common repeat-mediated disease in humans. It exclusively affects corneal endothelial cells (CECs), with ≤81% of cases associated with an intronic TCF4 triplet repeat (CTG18.1). Here, we utilise optical genome mapping (OGM) to investigate CTG18.1 tissue-specific instability to gain mechanistic insights. METHODS: We applied OGM to a diverse range of genomic DNAs (gDNAs) from patients with FECD and controls (n = 43); CECs, leukocytes and fibroblasts. A bioinformatics pipeline was developed to robustly interrogate CTG18.1-spanning DNA molecules. All results were compared with conventional polymerase chain reaction-based fragment analysis. FINDINGS: Analysis of bio-samples revealed that expanded CTG18.1 alleles behave dynamically, regardless of cell-type origin. However, clusters of CTG18.1 molecules, encompassing ∼1800-11,900 repeats, were exclusively detected in diseased CECs from expansion-positive cases. Additionally, both progenitor allele size and age were found to influence the level of leukocyte-specific CTG18.1 instability. INTERPRETATION: OGM is a powerful tool for analysing somatic instability of repeat loci and reveals here the extreme levels of CTG18.1 instability occurring within diseased CECs underpinning FECD pathophysiology, opening up new therapeutic avenues for FECD. Furthermore, these findings highlight the broader translational utility of FECD as a model for developing therapeutic strategies for rarer diseases similarly attributed to somatically unstable repeats. FUNDING: UK Research and Innovation, Moorfields Eye Charity, Fight for Sight, Medical Research Council, NIHR BRC at Moorfields Eye Hospital and UCL Institute of Ophthalmology, Grantová Agentura České Republiky, Univerzita Karlova v Praze, the National Brain Appeal's Innovation Fund and Rosetrees Trust.

• Klíčová slova
• Fuchs endothelial corneal dystrophy, Optical genome mapping, Somatic mosaicism, Tissue-specific repeat instability, Trinucleotide repeat expansion disease, Triplet repeat expansion-mediated disease,
• MeSH
• alely MeSH
• expanze trinukleotidových repetic MeSH
• Fuchsova endoteliální dystrofie * genetika   patologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mapování chromozomů MeSH
• nestabilita genomu MeSH
• orgánová specificita genetika   MeSH
• senioři MeSH
• transkripční faktor 4 * genetika   metabolismus   MeSH
• trinukleotidové repetice genetika   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• TCF4 protein, human MeSH Prohlížeč
• transkripční faktor 4 * MeSH

Fuchs endothelial corneal dystrophy (FECD) is an age-related cause of vision loss, and the most common repeat expansion-mediated disease in humans characterised to date. Up to 80% of European FECD cases have been attributed to expansion of a non-coding CTG repeat element (termed CTG18.1) located within the ubiquitously expressed transcription factor encoding gene, TCF4. The non-coding nature of the repeat and the transcriptomic complexity of TCF4 have made it extremely challenging to experimentally decipher the molecular mechanisms underlying this disease. Here we comprehensively describe CTG18.1 expansion-driven molecular components of disease within primary patient-derived corneal endothelial cells (CECs), generated from a large cohort of individuals with CTG18.1-expanded (Exp+) and CTG 18.1-independent (Exp-) FECD. We employ long-read, short-read, and spatial transcriptomic techniques to interrogate expansion-specific transcriptomic biomarkers. Interrogation of long-read sequencing and alternative splicing analysis of short-read transcriptomic data together reveals the global extent of altered splicing occurring within Exp+ FECD, and unique transcripts associated with CTG18.1-expansions. Similarly, differential gene expression analysis highlights the total transcriptomic consequences of Exp+ FECD within CECs. Furthermore, differential exon usage, pathway enrichment and spatial transcriptomics reveal TCF4 isoform ratio skewing solely in Exp+ FECD with potential downstream functional consequences. Lastly, exome data from 134 Exp- FECD cases identified rare (minor allele frequency <0.005) and potentially deleterious (CADD>15) TCF4 variants in 7/134 FECD Exp- cases, suggesting that TCF4 variants independent of CTG18.1 may increase FECD risk. In summary, our study supports the hypothesis that at least two distinct pathogenic mechanisms, RNA toxicity and TCF4 isoform-specific dysregulation, both underpin the pathophysiology of FECD. We anticipate these data will inform and guide the development of translational interventions for this common triplet-repeat mediated disease.

• MeSH
• alternativní sestřih genetika   MeSH
• endoteliální buňky metabolismus   MeSH
• expanze trinukleotidových repetic * genetika   MeSH
• Fuchsova endoteliální dystrofie * genetika   MeSH
• lidé MeSH
• rohovkový endotel metabolismus   patologie   MeSH
• transkripční faktor 4 * genetika   metabolismus   MeSH
• transkriptom genetika   MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• TCF4 protein, human MeSH Prohlížeč
• transkripční faktor 4 * MeSH

We report the phenotype of a 15-year-old female patient with anterior segment dysgenesis (ASD) caused by a novel heterozygous loss-of-function FOXC1 variant. The proband underwent an ophthalmic examination as well as a molecular genetic investigation comprising exome sequencing, a single nucleotide polymorphism array to access copy number and Sanger sequencing to exclude non-coding causal variants. There was bilateral mild iris hypoplasia with pupil deformation and iridocorneal adhesions. In addition to these features of ASD, the corneas were flat, with mean keratometry readings of 38.8 diopters in the right eye and 39.5 diopters in the left eye. There was a snail track lesion of the left cornea at the level of the Descemet membrane. The central corneal endothelial cell density was reduced bilaterally at 1964 and 1373 cells/mm2 in the right and left eyes, respectively. Molecular genetic analysis revealed that the proband was a carrier of a novel heterozygous frameshifting variant in FOXC1, c.605del p.(Pro202Argfs*113). Neither parent had this change, suggesting a de novo origin which was supported by paternity testing. We found no possibly pathogenic variants in the other genes associated with posterior corneal dystrophies or ASD. Further studies are warranted to verify whether there is a true association between snail track lesions, corneal flattening, and pathogenic variants in FOXC1.

• Klíčová slova
• FOXC1, anterior segment dysgenesis, corneal dystrophy, corneal endothelium, keratometry,
• Publikační typ
• časopisecké články MeSH

The aim of this study was to describe the ocular phenotype in a case with Kearns-Sayre syndrome (KSS) spectrum and to determine if corneal endothelial cell dysfunction could be attributed to other known distinct genetic causes. Herein, genomic DNA was extracted from blood and exome sequencing was performed. Non-coding gene regions implicated in corneal endothelial dystrophies were screened by Sanger sequencing. In addition, a repeat expansion situated within an intron of TCF4 (termed CTG18.1) was genotyped using the short tandem repeat assay. The diagnosis of KSS spectrum was based on the presence of ptosis, chronic progressive external ophthalmoplegia, pigmentary retinopathy, hearing loss, and muscle weakness, which were further supported by the detection of ~6.5 kb mtDNA deletion. At the age of 33 years, the proband's best corrected visual acuity was reduced to 0.04 in the right eye and 0.2 in the left eye. Rare ocular findings included marked corneal oedema with central corneal thickness of 824 and 844 µm in the right and left eye, respectively. No pathogenic variants in the genes, which are associated with corneal endothelial dystrophies, were identified. Furthermore, the CTG18.1 genotype was 12/33, which exceeds a previously determined critical threshold for toxic RNA foci appearance in corneal endothelial cells.

• Klíčová slova
• CTG18.1, Kearns-Sayre syndrome, TCF4, corneal dystrophy, corneal endothelium, endothelial failure, exome sequencing,
• MeSH
• dospělí MeSH
• fenotyp MeSH
• Fuchsova endoteliální dystrofie patologie   MeSH
• genotyp MeSH
• katarakta genetika   MeSH
• Kearnsův-Sayreův syndrom genetika   MeSH
• lidé MeSH
• mitochondriální DNA MeSH
• rohovkový endotel patologie   patofyziologie   MeSH
• sekvenční delece MeSH
• sekvenování exomu MeSH
• transkripční faktor 4 genetika   MeSH
• trinukleotidové repetice * MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• práce podpořená grantem MeSH
• Názvy látek
• mitochondriální DNA MeSH
• TCF4 protein, human MeSH Prohlížeč
• transkripční faktor 4 MeSH

PURPOSE: To demonstrate the utility of an amplification-free long-read sequencing method to characterize the Fuchs endothelial corneal dystrophy (FECD)-associated intronic TCF4 triplet repeat (CTG18.1). METHODS: We applied an amplification-free method, utilizing the CRISPR/Cas9 system, in combination with PacBio single-molecule real-time (SMRT) long-read sequencing, to study CTG18.1. FECD patient samples displaying a diverse range of CTG18.1 allele lengths and zygosity status (n = 11) were analyzed. A robust data analysis pipeline was developed to effectively filter, align, and interrogate CTG18.1-specific reads. All results were compared with conventional polymerase chain reaction (PCR)-based fragment analysis. RESULTS: CRISPR-guided SMRT sequencing of CTG18.1 provided accurate genotyping information for all samples and phasing was possible for 18/22 alleles sequenced. Repeat length instability was observed for all expanded (≥50 repeats) phased CTG18.1 alleles analyzed. Furthermore, higher levels of repeat instability were associated with increased CTG18.1 allele length (mode length ≥91 repeats) indicating that expanded alleles behave dynamically. CONCLUSION: CRISPR-guided SMRT sequencing of CTG18.1 has revealed novel insights into CTG18.1 length instability. Furthermore, this study provides a framework to improve the molecular diagnostic accuracy for CTG18.1-mediated FECD, which we anticipate will become increasingly important as gene-directed therapies are developed for this common age-related and sight threatening disease.

• Klíčová slova
• Fuchs endothelial corneal dystrophy, amplification-free sequencing, no-amp targeted sequencing, somatic mosaicism, triplet repeat-mediated disease,
• MeSH
• alely MeSH
• CRISPR-Cas systémy genetika   MeSH
• dospělí MeSH
• expanze trinukleotidových repetic genetika   MeSH
• Fuchsova endoteliální dystrofie genetika   patologie   MeSH
• genetická predispozice k nemoci * MeSH
• genotyp MeSH
• introny genetika   MeSH
• lidé středního věku MeSH
• lidé MeSH
• sekvenční analýza DNA MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• transkripční faktor 4 genetika   MeSH
• trinukleotidové repetice genetika   MeSH
• zobrazení jednotlivé molekuly MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• TCF4 protein, human MeSH Prohlížeč
• transkripční faktor 4 MeSH

PURPOSE: To report molecular genetic findings in six probands with congenital hereditary endothelial dystrophy (CHED) variably associated with hearing loss (also known as Harboyan syndrome). Furthermore, we developed a cellular model to determine if disease-associated variants induce aberrant SLC4A11 pre-mRNA splicing. METHODS: Direct sequencing of the entire SLC4A11 coding region was performed in five probands. In one individual, whole genome sequencing was undertaken. The effect of c.2240+5G>A on pre-mRNA splicing was evaluated in a corneal endothelial-like (CE-like) cell model expressing SLC4A11. CE-like cells were derived from autologous induced pluripotent stem cells (iPSCs) via neural crest cells exposed to B27, PDGF-BB, and DKK-2. Total RNA was extracted, and RT-PCR was performed followed by Sanger and a targeted next generation sequencing (NGS) approach to identify and quantify the relative abundance of alternatively spliced transcripts. RESULTS: In total, 11 different mutations in SLC4A11 evaluated as pathogenic were identified; of these, c.1237G>A, c.2003T>C, c.1216+1G>A, and c.2240+5G>A were novel. The c.2240+5G>A variant was demonstrated to result in aberrant pre-mRNA splicing. A targeted NGS approach confirmed that the variant introduces a leaky cryptic splice donor site leading to the production of a transcript containing an insertion of six base pairs with the subsequent introduction of a premature stop codon (p.Thr747*). Furthermore, a subset of transcripts comprising full retention of intron 16 also were observed, leading to the same functionally null allele. CONCLUSIONS: This proof-of-concept study highlights the potential of using CE-like cells to investigate the pathogenic consequences of SLC4A11 disease-associated variants.

• MeSH
• antiportéry biosyntéza   genetika   MeSH
• buněčná diferenciace MeSH
• dědičné dystrofie rohovky genetika   metabolismus   patologie   MeSH
• dítě MeSH
• dospělí MeSH
• indukované pluripotentní kmenové buňky cytologie   metabolismus   MeSH
• kultivované buňky MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• percepční nedoslýchavost genetika   metabolismus   patologie   MeSH
• předškolní dítě MeSH
• prekurzory RNA MeSH
• proteiny přenášející anionty biosyntéza   genetika   MeSH
• regulace genové exprese * MeSH
• RNA genetika   MeSH
• rodokmen MeSH
• rohovkový endotel metabolismus   patologie   MeSH
• senioři MeSH
• sestřih RNA MeSH
• Check Tag
• dítě MeSH
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• předškolní dítě MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antiportéry MeSH
• prekurzory RNA MeSH
• proteiny přenášející anionty MeSH
• RNA MeSH
• SLC4A11 protein, human MeSH Prohlížeč