Abstract

ObjectiveAn intronic CTG triplet repeat expansion in the transcription factor 4 gene (TCF4) gene (CTG18.1) confers significant risk for the development of Fuchs’ endothelial corneal dystrophy (FECD). The objective of this study was to conduct an unbiased survey of the CTG18.1 repeat expansion allele frequencies in a multi-ethnic, population-based cohort from the United States and in global populations. DesignCross-sectional study SubjectsDallas Heart Study (DHS) cohort including 1,599 African Americans (AAs), 1,028 European Americans (EAs), and 458 Latinos; 2,500 individuals from the 1000 Genomes Project (1KGP) sampled from 26 populations across 5 continents. MethodsWe genotyped the CTG18.1 short tandem repeat in DHS using targeted polymerase chain reaction amplification followed by fragment analysis. We also inferred the CTG18.1 repeat genotype based on short-read whole-genome sequencing in 1KGP using the computational tool ExpansionHunter. Main Outcome MeasuresThe prevalence of an expanded CTG18.1 allele with ≥40 repeats was determined in U.S. and global populations. ResultsThe carrier rates of the expanded allele were 3.1%, 8.1%, and 3.3% in AAs, EAs, and Latinos, respectively, in the DHS, and 2.7%, 9.5%, 5.2%, 7.2%, and 5.2% in the African (AFR), European (EUR), East Asian (EAS), South Asian (SAS), and admixed American (AMR) continental populations, respectively, in the 1KGP. The distributions of the CTG18.1 repeat in DHS and in 1KGP are similar. The median repeat length was ∼17 with the interquartile range (IQR) between 12 and 23 in the DHS populations. The median repeat length was ∼19 in all the 1KGP populations with the IQR between 13 and 26. The highest prevalence of the expanded allele carriers ranging from 12.1% to 12.5% was observed in some EUR and AMR subpopulations. The frequency of expanded alleles carriers was absent or low (0 - 1.9%) in subpopulations of East Africa but was present at 6.2% in a Kenyan subpopulation in West Africa. ConclusionsThe TCF4 repeat expansion is most prevalent in people of European ancestry and least in African ancestry, which is consistent with FECD prevalence. The expanded TCF4 CTG18.1 allele is the most common disease-causing short tandem repeat in humans with worldwide implications for corneal disease.

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