Principles of stem cell biology and cancer: future applications and therapeutics. Edited by T. Regad, T. J. Sayers and R. C. Rees. John Wiley & Sons (2015)
Part II. Cancer stem cells
Telomerase (TERT) helps with the maintenance of the telomeric ends of chromosomes and has been shown to label long-term LRCs within small-intestinal crypts (De Mey and Freund, 2013). Adult stem cells may express high levels of TERT, and rare cells may express green fluorescent protein (GFP) under the mouse telomerase (mTERT) promoter in the unstressed mouse small intestine, which has been suggested to be distinct from Lgr5+ cells (Montgomery et al., 2011). These quiescent mTERT+ cells occur with a frequency of less than 1 in 150 small-intestinal crypt cells in the unstressed mouse small intestine but become actively cycling following radiation-induced damage. Lineage-tracing experiments suggest that these mTERT+ cells can differentiate into all epithelial intestinal cell types. Given the rarity of mTERT+ cells, it may seem unlikely that such a stem cell would contribute to epithelial homeostasis in the unstressed gut, or even under stressful conditions, considering the microstructure of the crypt. Furthermore, some evidence suggests that elevated mTERT activity is displayed in the cycling small-intestinal crypt, as compared to the standard reported frequency of mTERT+ cells (Schepers et al., 2011). Future experiments will characterize the relevance of TERT-expressing cells in controlling the homeostasis of the gut.
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