Abstract
The ends of eukaryotic chromosomes are composed of repetitive telomere sequences bound by the shelterin protein complex. Telomerase, a reverse transcriptase complex, is known to express in highly proliferative tissues and cells in humans to maintain a constant telomere length and to sustain their proliferative potential. Heterozygous missense mutations within one of the shelterin proteins, TIN2, have been identified in patients with Dyskeratosis Congenita (DC), a multiple stem-cell failure syndrome characterized by extremely short telomeres in affected patients. Our study aims to elucidate the mechanism by which TIN2 mutations shorten telomeres in human cells.
TIN2 is an essential protein that tethers the shelterin complex together. We generated HCT 116 colorectal cancer cell lines containing heterozygous TIN2 R282H mutation, one of the most common DC-related TIN2 mutations, by zinc-finger-nuclease facilitated gene editing. Clones with heterozygous TIN2 mutation showed progressive telomere shortening, while the wild-type (WT) clones showed no change in telomere length over extended cell proliferation. The progressive telomere shortening phenotype in TIN2 mutants can be rescued by exogenous expression of WT TIN2. However, TIN2 mutant clones do not contain elevated levels of deprotected telomeres, suggesting that the TIN2 mutation does not lead to overall telomere deprotection. We are currently investigating whether the DC-related TIN2 mutation induces telomere shortening by inhibiting telomerase or by accelerating telomere attrition through telomerase-independent mechanisms.
Citation Format: Duy C. Tran, Amanda K. Frank, Lifeng Xu. Investigation of telomere shortening caused by dyskeratosis congenita-associated heterozygous TIN2 mutations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 490. doi:10.1158/1538-7445.AM2014-490
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