Tissue-specific TCF4 triplet repeat instability revealed by optical genome mappingResearch in context
Christina Zarouchlioti,
Stephanie Efthymiou,
Stefano Facchini,
Natalia Dominik,
Nihar Bhattacharyya,
Siyin Liu,
Marcos Abreu Costa,
Anita Szabo,
Amanda N. Sadan,
Albert S. Jun,
Enrico Bugiardini,
Henry Houlden,
Andrea Cortese,
Pavlina Skalicka,
Lubica Dudakova,
Kirithika Muthusamy,
Michael E. Cheetham,
Alison J. Hardcastle,
Petra Liskova,
Stephen J. Tuft,
Alice E. Davidson
Affiliations
Christina Zarouchlioti
UCL Institute of Ophthalmology, London, UK
Stephanie Efthymiou
UCL Queen Square Institute of Neurology, Department of Neuromuscular Diseases, London, UK
Stefano Facchini
UCL Queen Square Institute of Neurology, Department of Neuromuscular Diseases, London, UK
Natalia Dominik
UCL Queen Square Institute of Neurology, Department of Neuromuscular Diseases, London, UK
Nihar Bhattacharyya
UCL Institute of Ophthalmology, London, UK
Siyin Liu
UCL Institute of Ophthalmology, London, UK; Moorfields Eye Hospital, London, UK
Marcos Abreu Costa
UCL Institute of Ophthalmology, London, UK
Anita Szabo
UCL Institute of Ophthalmology, London, UK
Amanda N. Sadan
UCL Institute of Ophthalmology, London, UK
Albert S. Jun
Cornea, Cataract, and External Disease Division, Wilmer Eye Institute, Johns Hopkins Medicine, Baltimore, USA
Enrico Bugiardini
UCL Queen Square Institute of Neurology, Department of Neuromuscular Diseases, London, UK
Henry Houlden
UCL Queen Square Institute of Neurology, Department of Neuromuscular Diseases, London, UK
Andrea Cortese
UCL Queen Square Institute of Neurology, Department of Neuromuscular Diseases, London, UK
Pavlina Skalicka
Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic; Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
Lubica Dudakova
Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
Kirithika Muthusamy
Moorfields Eye Hospital, London, UK
Michael E. Cheetham
UCL Institute of Ophthalmology, London, UK
Alison J. Hardcastle
UCL Institute of Ophthalmology, London, UK
Petra Liskova
Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic; Department of Paediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
Stephen J. Tuft
UCL Institute of Ophthalmology, London, UK; Moorfields Eye Hospital, London, UK
Alice E. Davidson
UCL Institute of Ophthalmology, London, UK; Moorfields Eye Hospital, London, UK; Corresponding author. UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK.
Summary: 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.
