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Ryosuke Hayashi, Naoki Okumura, Keisuke Ogata, Masakazu Nakano, Theofilos Tourtas, Ursula Schlotzer-Schrehardt, Friedrich E Kruse, Noriko Koizumi; Expression level of the TCF4 gene in the corneal endothelium of Fuchs endothelial corneal dystrophy patients. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1438.
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© ARVO (1962-2015); The Authors (2016-present)
The expansion of a CTG trinucleotide repeat in the third intron of transcription factor 4 (TCF4) has commonly been detected in FECD patients (Wieben E, et al). Though the importance of TCF4 in the pathogenesis in FECD has been theorized, the effect of CTG repeat expansion of TCF4 on TCF4 expression has yet to be elucidated. The purpose of this study was to determine the expansion level of TCF4 in FECD corneal endothelium and the relationship between repeat expansion and TCF4 level.
Genomic DNA was obtained from the blood of 493 German FECD patients using the DNeasy® Blood & Tissue Kit. The expansion of a CTG trinucleotide repeat was analyzed by polymerase chain reaction (PCR) and sequence analysis. Corneal endothelium tissues were obtained from the FECD patients at the time of corneal transplantation via Descemet’s membrane endothelial keratoplasty (DMEK). Total RNA was extracted from the corneal endothelium using the miRNeasy® Mini Kit. Expression of TCF4 was analyzed by real-time PCR.
Corneal endothelium RNA (RIN >5.2) was obtained from 309 of 493 patients, and then further analyzed. Of the 309 patients, 235 (76%) possessed CTG trinucleotide repeat lower than 50 repeats. On the other hand, 59 patients possessed CTG trinucleotide repeats higher than 50 repeats in a single allele (19%) and 15 patients possessed them in both alleles (5%). Real-time PCR demonstrated that the TCF4 transcript level of the 235 cases without CTG repeat expansion was 2.67±0.09 fold higher than that of control corneal endothelium (p<0.01). Likewise, the TCF4 transcript level of the patients who had CTG repeat expansion in a single allele was 2.68±0.15 fold higher, and that of the patients who had CTG repeat expansion in both alleles was 2.61±0.30 fold higher (p<0.01). No significant correlation was observed between the number of CTG repeat length and the expression level of the TCF4 gene.
Our findings revealed that 24% of FECD patients in Germany possess CTG repeat expansion longer than 50 repeats and that the expression level of TCF4 was significantly higher in the corneal endothelium of FECD patients than in the control subjects, regardless to CTG repeats. Further study regarding the role of TCF4 will be beneficial for elucidating the pathogenesis of FECD.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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