Project description:The small intestinal epithelium is the most rapidly self-renewing tissue of mammals. Proliferative cells are confined to crypts, while differentiated cell types predominantly occupy the villi. We recently demonstrated the existence of a long-lived pool of cycling stem cells defined by Lgr5 expression and intermingled with post-mitotic Paneth cells at crypt bottoms. We have now determined a gene signature for these so called Crypt Base Columnar (CBC) cells. One of the genes within this stem cell signature is the Wnt target Ascl2. Transgenic expression of the Ascl2 transcription factor throughout the intestinal epithelium induces crypt hyperplasia and de novo crypt formation on villi. Induced deletion of the Ascl2 gene in adult small intestine leads to disappearance of the CBC stem cells within days. The combined results from these gain- and loss-of-function experiments imply that Ascl2 controls intestinal stem cell fate. Keywords: expression profiling
Project description:The small intestinal epithelium is the most rapidly self-renewing tissue of mammals. Proliferative cells are confined to crypts, while differentiated cell types predominantly occupy the villi. We recently demonstrated the existence of a long-lived pool of cycling stem cells defined by Lgr5 expression and intermingled with post-mitotic Paneth cells at crypt bottoms. We have now determined a gene signature for these so called Crypt Base Columnar (CBC) cells. One of the genes within this stem cell signature is the Wnt target Ascl2. Transgenic expression of the Ascl2 transcription factor throughout the intestinal epithelium induces crypt hyperplasia and de novo crypt formation on villi. Induced deletion of the Ascl2 gene in adult small intestine leads to disappearance of the CBC stem cells within days. The combined results from these gain- and loss-of-function experiments imply that Ascl2 controls intestinal stem cell fate. Experiment Overall Design: For the stem cell signature we used cell fractions of intestines from Lgr5-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Lgr5 promoter. RNA was isolated from two FACS sorted cell populations, one expressing GFP at high levels (GFPhi) and the other expressing GFP at low levels (GFPlo). For the analysis of Ascl2 target genes RNA was isolated from intestinal epithelial cells of Ah-Cre/Ascl2floxed/floxed animals and Ah-Cre/Ascl2floxed/wt control animals 3 and 5 days post induction. Differentially labelled cRNA from GFPhi and GFPlo cells from two different sorts (each combining three different mice) were hybridised on 4X44K Agilent Whole Mouse Genome dual colour Microarrays (G4122F) in two dye swap experiments, resulting in four individual arrays. For the Ascl2 target gene analysis we analyzed the 3 and 5 days PI experiments in two dye swap experiments, resulting in four individual arrays.
Project description:The currently accepted intestinal epithelial cell organization model equates crypt base columnar (CBC) cells, marked by high levels of Lgr5 expression, with the intestinal stem cell (ISC). However, recent intestinal regeneration studies have uncovered limitations of the ‘Lgr5-CBC’ model, leading to two major views: one favoring the presence of a quiescent reserve stem cell population, the other calling for differentiated cell plasticity. To test if an alternative model may help reconcile these perspectives, we studied the hierarchical organization of crypt epithelial cells in an unbiased fashion, by combining high-resolution, single-cell profiling and lineage tracing in multiple transgenic mouse models. These show that Lgr5 is not a specific ISC marker; rather, cells located in the crypt isthmus, which include Lgr5low cells, comprise the ISCs that sustain tissue homeostasis. Following irradiation or intestinal injury, surviving ISCs and progenitors, but not differentiated cells, participate in intestinal regeneration, suggesting that neither de-differentiation nor reserve stem cell populations are drivers of intestinal regeneration. Our results provide a novel viewpoint for the intestinal crypt epithelium, in which ISCs localize to the crypt isthmus, and ISC potential is restricted to stem and progenitor cells.
Project description:Intestinal epithelium are generated by intestinal stem cells, which are recognized morphologically as slender columnar cells at the base of the crypt. Stem cells produce transit-amplifying (TA) cells, which divide a number of times and the daughter cells differentiate into absorptive enterocytes as well as secretory-lineages. Intestinal stem cells highly express Lgr5 which is decreased in TA cells. Here, we show that the zinc transported SLC39A7/ZIP7 is essential for the proliferation of TA cells and maintenance of intestinal stem cells. Lgr5Med TA cells derived from Zip7-deficient mice upregulated the expression of unfold protein responses-related genes including pro-apoptotic genes, indicating of induction of ER stress in these cells. The same effect was seen in Lgr5Hi stem cells derived from Zip7-deficient mice. We conclude that ZIP7 is fundamental to the maintenance of crypt homeostasis by resolving ER stress. Small intestinal crypts were isolated form tamoxifen-treated control (Zip7flox/+, Villin-CreERT2, Lgr5-EGFP-ires-CreERT2) and tamoxifen-treated Zip7â??IEC (Zip7flox/flox, Villin-CreERT2, Lgr5-EGFP-ires-CreERT2) mice. We FACS purified intestinal crypt cells according to their Lgr5 expression levels. RNA was isolated from four FACS sorted cell populations: Lgr5Hi cells and Lgr5Med cells derived from control mice, Lgr5Hi cells and Lgr5Med cells derived from Zip7â??IEC mice. Isolated RNA was analyzed using the Affymetrix platform.
Project description:This study was performed to compare transcriptomic changes in the heterogeneous mouse skin epidermal stem cells and hair follicle stem cells (HFSC) populations during chronological aging. Slow-cycling stem cells (label retaining cells, LRCs), fast-cycling stem cells (non-label retaining cells, nLRCs) and hair follicle stem cells express unique gene signatures in young age (2 months old) and have independent stem cell identities. The changes in aging stem cells lineage identities have been a topic of discussion and here we examined if distinct stem cells cycling speed affects their aging process by comparing the transcriptomes of slow-and fast-cycling epidermal stem cells. Our data indicates the loss of unique stem cell identities in aging slow or fast-cycling epidermal stem cells or HFSC at 2 years of age with intermediary effects seen at 1.5 year old.
Project description:Tumor heterogeneity derives from diverse populations of cancer cells that contribute unique properties to the microenvironment and tumor progression. While multiple classification systems have been developed to define tumor subtypes in colorectal cancer (CRC), the lack of single cell resolution has prohibited a better understanding of how these distinct cancer cell subtypes influence the overall tumor phenotype. Here were report that two cancer stem cell subtypes that are oncogenic versions of the intestinal Crypt Base Columnar (CBC) and Regenerative Stem Cell (RSC) populations, are commonly co-present in human CRC. We develop subtype-specific xenograft models utilizing a heterogeneous patient cell line (SW480) that contains CBCs and RSCs, and we define their tumor microenvironments at high resolution via single cell RNA sequencing. RSCs create differentiated, inflammatory, slow growing tumors. CBCs create proliferative, immune-suppressive, invasive tumors. With this enhanced resolution, we unify current CRC patient classification schema with TME phenotypes and organization.
Project description:Tumor heterogeneity derives from diverse populations of cancer cells that contribute unique properties to the microenvironment and tumor progression. While multiple classification systems have been developed to define tumor subtypes in colorectal cancer (CRC), the lack of single cell resolution has prohibited a better understanding of how these distinct cancer cell subtypes influence the overall tumor phenotype. Here were report that two cancer stem cell subtypes that are oncogenic versions of the intestinal Crypt Base Columnar (CBC) and Regenerative Stem Cell (RSC) populations, are commonly co-present in human CRC. We develop subtype-specific xenograft models utilizing a heterogeneous patient cell line (SW480) that contains CBCs and RSCs, and we define their tumor microenvironments at high resolution via single cell RNA sequencing. RSCs create differentiated, inflammatory, slow growing tumors. CBCs create proliferative, immune-suppressive, invasive tumors. With this enhanced resolution, we unify current CRC patient classification schema with TME phenotypes and organization.
Project description:Conditional knockout of Snai1 in the mouse intestinal epithlium results in apoptotic loss of crypt base columnar cells and bias towards differentiation of secretory lineages. In vitro organoid cultures derived from Snail conditional knockout mice also undergo apoptosis when Snai1 is deleted. Snai1 is required for regulation of lineage choice and maintenance of CBC stem cells.
Project description:The intestinal epithelium has a remarkably high turnover in homeostasis. It remains unresolved how turnover is orchestrated at the cellular level and how the behaviour of stem and progenitor cells ensures tissue maintenance. To address this, we combined quantitative fate mapping in three complementary mouse models with mathematical modelling and single-cell RNA sequencing. Our integrated approach generated a spatially and temporally defined model of crypt maintenance that is based on two cycling populations: crypt-based columnar (CBC) and transit amplifying (TA) cells. Validation experiments substantiated the predictions from the model revealing TA cells as the major contributor to the absorptive lineage, while balanced CBC cell fate choices controlled the numbers of cells in the secretory lineage. By unravelling these mechanisms, we gain insights into the process of tissue turnover and provide direct evidence to support the notion of CBC cells as the major driver of the intestinal epithelium replenishment.
Project description:Lgr5+ crypt base columnar cells, the operational intestinal stem cells (ISCs), are thought to be dispensable for small intestinal (SI) homeostasis. Using a novel Lgr5-2A-DTR (Diphtheria Toxin Receptor) model which ablates Lgr5+ cells with near-complete efficiency and retains endogenous levels of Lgr5 expression, we show that persistent depletion of Lgr5+ ISCs in fact compromises SI epithelial integrity and reduces epithelial turnover in vivo. In vitro, Lgr5-2A-DTR SI organoids are unable to establish or survive when Lgr5+ ISCs are continuously eliminated when DT is in the media. However, transient exposure to DT at the start of culture allows organoids to form, and the rate of outgrowth reduces with increasing length of DT presence. Our results indicate that intestinal homeostasis requires a constant pool of Lgr5+ ISCs, which is supplied by rapidly reprogrammed non-Lgr5+ crypt populations when pre-existing Lgr5+ ISCs are ablated.