There is emerging evidence that distinct populations of actively cycling and quiescent intestinal stem cells (ISCs) co-exist within the small intestine epithelium and function cooperatively in tissue renewal. Previously, we have described Lgr5 as a marker of actively proliferating ISCs that contribute to homeostatic turnover of the intestinal epithelium, whereas Bmi1 is a marker of quiescent ISCs that contribute minimally to homeostatic tissue turnover but are robustly activated for epithelial repair following tissue injury. Recently, we have discovered through transcriptional profiling of active versus quiescent ISCs that crypt Bmi1 cells isolated from Bmi1-GFP reporter mice are actually mature enteroendocrine (EE) cells. Our preliminary data suggest that there is significant cellular heterogeneity amongst FACS isolated Bmi1-GFP+ cells. This proposal explores the hypothesis that only a rare and restricted subset of Bmi1 cells marked by expression of Bmi1-GFP are EE cells that are able to reconstitute the epithelium and that these cells are most functionally active under conditions of Lgr5+ ISC loss. Furthermore, we postulate that single-cell mRNA-seq can be employed to identify such populations in an unbiased manner. Our hypothesis is evaluated by two Specific Aims: (1) to characterize the heterogeneity of Bmi1-GFP+ subsets by single-cell transcriptional profiling and (2) to isolate and functionally characterize discrete Bmi1-GFP+ subsets. Achievement of these Aims should provide insight into exciting new areas of ISC biology in which cellular plasticity of differentiated epithelial cells enables tissue reconstitution in the setting of tissue injury.
Intestinal stem cells support the rapid and continuous turnover of the intestinal epithelium as well as aid in injury-induced tissue repair. Our proposal aims to understand how differentiated cells may serve as reserve intestinal stem cells following tissue injury. An improved understanding of this process may lead to new approaches to regeneration of intestine for therapy of intestinal diseases.
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|Yan, Kelley S; Gevaert, Olivier; Zheng, Grace X Y et al. (2017) Intestinal Enteroendocrine Lineage Cells Possess Homeostatic and Injury-Inducible Stem Cell Activity. Cell Stem Cell 21:78-90.e6|
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