Generation of a Mouse Model of Fuchs Endothelial Corneal Dystrophy by Knock-in of CTG Trinucleotide Repeat Expansion in the TCF4 Gene

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Purpose: Fuchs endothelial corneal dystrophy (FECD) is frequently associated with trinucleotide repeat (TNR) expansion in the TCF4 gene intron. The aim of this study was to establish a novel FECD mouse model with TNR expansion. Methods: We used CRISPR/Cas9-mediated genome editing to generate knock-in mice carrying 100 CTG repeats in the Tcf4 intron. Corneal endothelial phenotypes were evaluated using specular microscopy and transmission electron microscopy. Transcriptome analysis was performed using RNA sequencing of corneal endothelial tissue from Tcf4(CTG)100/(CTG)100 and wild-type mice. Results: Tcf4+/(CTG)100 and Tcf4(CTG)100/(CTG)100 mice developed characteristic FECD features, including progressive guttae formation and decreased corneal endothelial cell density. At 60 weeks, Tcf4+/(CTG)100 mice showed increased guttae percentage (0.314% ± 0.145%) versus wild-type (0.170% ± 0.089%), although not statistically significant. Tcf4(CTG)100/(CTG)100 mice exhibited significantly higher guttae formation (0.563% ± 0.293%) compared to controls. Similarly, endothelial cell density showed non-significant reduction in Tcf4+/(CTG)100 (1629 ± 71 cells/mm2) versus wild-type (1704 ± 68 cells/mm2), whereas Tcf4(CTG)100/(CTG)100 mice demonstrated significant decrease (1600 ± 76 cells/mm2). RNA sequencing identified 3221 differentially expressed genes (579 upregulated, 2,642 downregulated), with enrichment in pathways related to adaptive immune response, chemokine signaling, and cytokine-cytokine receptor interaction. Conclusions: Our study demonstrates that TNR expansion in the Tcf4 intron, on its own, is sufficient to induce FECD phenotypes in vivo. This mouse model provides a valuable tool for investigating FECD pathogenesis and developing targeted therapeutics.

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