Repeat Expansion and Somatic Instability in TCF4 in Patients With Fuchs Endothelial Corneal Dystrophy Identified by Small Pool PCR

The purpose of this study was to investigate trinucleotide repeat (TNR) expansion and somatic repeat instability in the TCF4 gene using small pool polymerase chain reaction (SP-PCR) in patients with Fuchs' endothelial corneal dystrophy (FECD). We selected 15 patients with FECD who had an abnormal CTG extension allele of 50 or more in the TCF4 gene via a short tandem repeat (STR) assay and triplet repeat primed PCR (TP-PCR). Expanded repeat number and variations in the number of repeat expansion within the leukocyte DNA of these 15 patients were examined via SP-PCR. DNA was collected from the corneal endothelium of a patient who underwent keratoplasty. Subsequently, SP-PCR was performed to compare the expanded alleles in the corneal endothelium and leukocytes. SP-PCR of the patients showed TNR expansion in TCF4, with an average maximum repeat number of 1602 ± 1258. The average expanded allele variation was 19 ± 15, indicating somatic repeat instability. Additionally, the maximum repeat number and somatic repeat instability varied significantly among patients, with a significant correlation between them (R = 0.84, P < 0.05). The maximum number of CTG repeats in the corneal endothelium was greater than that in leukocytes. Somatic repeat instability was observed in the leukocytes of the patients, demonstrating a correlation with the maximum number of repeats. Our results also indicated that TNR expansion of genomic DNA in the corneal endothelium was higher than that in the leukocytes of patients with FECD.