STRs database » TCF4 locus
Overview of repeats
Fuchs endothelial corneal dystrophy type 3 (FECD3) is an eye disease associated with CTG repeat expansions in the TCF4 gene (Zarouchlioti et al. (2018)). The conservative approach has defined 50 or more CTG repeats as the conservative expansion threshold Zarouchlioti et al. (2018). In a study conducted by Wieben et al. (2012), it was reported that 79% of patients had more than 50 repeats (reaching to over 1000 repeats in 4 cases) and 20% of the cases had allele below 40 repeats. In the control group of 63 individuals, 95% of the subjects had below 40 repeats and 5% over 50 repeats (Wieben et al. (2012)). However, it was proposed that the length of at least 32 repeats should be considered as risk associated (Zarouchlioti et al. (2018)). Zhang et al. (2025) used at least 40 repeats to define expansion in a population study; median repeat lengths were approximately 17 in the Dallas Heart Study and 19 in the 1000 Genomes Project cohorts. Expanded alleles confer risk rather than inevitable disease. In a longitudinal study, Teo et al. (2026) found that blood alleles below 40 repeats remained unexpanded over approximately ten years.