Antisense Therapy for a Common Corneal Dystrophy Ameliorates TCF4 Repeat Expansion-Mediated Toxicity

Abstract

Fuchs endothelial corneal dystrophy (FECD) is a common disease for which corneal transplantation is the only treatment option in advanced stages, and alternative treatment strategies are urgently required. Expansion (≥50 copies) of a non-coding trinucleotide repeat in TCF4 confers >76-fold risk for FECD in our large cohort of affected individuals. An FECD subject-derived corneal endothelial cell (CEC) model was developed to probe disease mechanism and investigate therapeutic approaches. The CEC model demonstrated that the repeat expansion leads to nuclear RNA foci, with the sequestration of splicing factor proteins (MBNL1 and MBNL2) to the foci and altered mRNA processing. Antisense oligonucleotide (ASO) treatment led to a significant reduction in the incidence of nuclear foci, MBNL1 recruitment to the foci, and downstream aberrant splicing events, suggesting functional rescue. This proof-of-concept study highlights the potential of a targeted ASO therapy to treat the accessible and tractable corneal tissue affected by this repeat expansion-mediated disease.

CTG18.1 Expansion is the Best Classifier of Late-Onset Fuchs' Corneal Dystrophy Among 10 Biomarkers in a Cohort From the European Part of Russia

“…The development of antisense therapy against transcripts containing expanded CTG18.1 repeats may be helpful for this population. 24,26 The most distinct difference in the occurrence of FECD markers is for TCF4 variants between American/European populations and Indian, Chinese, and Japanese populations ( Table 7). Based on the results of our study, we can conclude that the occurrence of marker alleles in TCF4 gene variants in patients from the European part of Russia is very close to those of American and European FECD patients.…”

“…Marker alleles were not found in 21 FECD patients; thus, exome sequencing for those particular patients is warranted. 18,19,22,35 76.4-77.0 21,26 17.3-34.1 37,40 43.9 41 25.5 42 72…”

“…Transcripts from expanded CTG18.1 repeats may sequester the splicing regulators MBNL1 and MBNL2. [23][24][25][26] Mis-splicing of MBNL1 target transcripts has been detected in corneal endothelium of patients with expanded CTG18.1 repeats. 23,27 Thus, on the basis of its high specificity and sensitivity, the expansion of CTG18.1 trinucleotide repeats in the TCF4 gene intron is the most promising marker and potent driver of FECD so far.…”

Towards Clinical Trials in Fuchs Endothelial Corneal Dystrophy: Classification and Outcome Measures—The Bowman Club Lecture 2019

“…The discovery of the major genetic association of FECD in western populations in 2010,24 an intronic CTG-trinucleotide repeat expansion in the transcription factor 4 gene,25 has spurred new research to elucidate the downstream effects, which now appear to be mediated, at least in part, through RNA toxicity and mis-splicing events 26. This has led to the possibility of halting or slowing the progression of the disease by using targeted molecular therapies, such as to block RNA toxicity 27. The recognition of other downstream mechanisms in FECD, including repeat associated non-ATG translation,28 the unfolded protein response29 and oxidative stress,30 may similarly enable novel targeted therapies.…”

Expansion of trinucleotide CTG repeats in the TCF4 gene as a marker of fuchs’ endothelial corneal dystrophy

“…Однако пенетрантность и экспрессивность мутации могут значительно варьировать у разных больных. Носительство гетерозиготной или гомозиготной экспансии без объективных признаков ЭДР Фукса повышает риск развития заболевания в 76 раз [20].…”