Curation FECD3 TCF4

Targeted sequencing of TCF4 in leukocyte DNA from 68 FECD subjects and 16 unaffected controls found TGC expansion >50 repeats in 46/68 affected subjects and 1/16 controls; no single variant perfectly segregated with disease.

In 120 unrelated Caucasian FECD probands and 100 controls, expanded CTG18.1 (≥40 repeats) was significantly associated with FECD (OR 32.3, 95% CI 13.4–77.6).

Reduced penetrance was noted: TGC expansion >50 repeats occurred in one unaffected control in this cohort, and the authors discuss unaffected older expansion carriers.

Expanded CTG18.1 cosegregated with FECD in 15/29 families with complete penetrance and 3/29 with incomplete penetrance; one representative family had maximum LOD 0.90.

Russian case-control cohort of 100 FECD cases and 100 cataract controls found CTG18.1 expansion >40 repeats in 72% of cases versus 5% of controls; CTG18.1 was the best classifier among tested markers (AUC 0.84).

In 68 FECD cases and 16 controls, TGC expansion >50 repeats was observed in 46/68 cases versus 1/16 controls; repeat expansion was a better predictor than other TCF4-region variants but was not perfectly concordant with disease.

Australian cohort of 189 advanced late-onset FECD cases and 183 controls showed association of expanded TGC repeat ≥40 repeats with FECD (P=2.58×10−22; OR=15.66, 95% CI 7.79–31.49), with expanded genotype in 51% of cases versus 5% of controls.

In 574 FECD participants, expanded allele carriers had higher transplantation frequency (78/357, 21.8%) than non-carriers (28/217, 12.9%; P=0.007) and higher age-adjusted transplantation likelihood (HR 1.64, 95% CI 1.05–2.55).

Expanded TCF4 CUG-repeat RNA foci in FECD corneal endothelial cells co-localized with and sequestered MBNL1, consistent with RNA-mediated toxicity.

pmid:25593321 showed CTG18.1 expansion-positive FECD corneal endothelia have RNA foci and differential alternative splicing; pmid:29526280 showed expansion-positive CEC lines have altered MBNL1/MBNL2/NUMA1 splicing and ASO-responsive rescue.

FECD patient corneal endothelial tissue/cells with CTG18.1 expansion showed poly(CUG) RNA foci, MBNL1 co-localization/sequestration, and missplicing; expansion-negative FECD cells lacked these findings.

Control corneal endothelial cells and expansion-negative FECD cells were used as comparators; RNA foci and missplicing were not observed in non-expanded/control cells.

UVA-induced FECD mouse model showed corneal endothelial damage and downregulation of mtDNA repair genes Lig3, Neil2, and Top3a; model is not TCF4 CTG repeat-expansion specific.

In six expansion-positive FECD CEC lines, (CAG)7 ASO reduced CUG RNA foci; in four lines it reduced MBNL1-positive puncta, and in ten lines it shifted MBNL1/MBNL2/NUMA1 splicing toward control patterns.