TCF4 and Fuchs endothelial corneal dystrophy: We next wanted to explore if rare and potentially deleterious TCF4 variants could be contributing to disease in FECD cases without a CTG18.1 expansion, given that Exp+ CECs display alternative TCF4 exon usage and skewed ratios of TCF4 isoforms (Figs 3 and 4), with detectable downstream features of TCF4-driven dysregulation (Fig 2D).