Project description:The identification of Lgr5 as an intestinal stem cell marker has made it possible to isolate and study primary stem cells from small intestine. Using the cell cycle specific expression og the mKi67 gene, we generated a novel Ki67-RFP knock-in allele which identifies dividing cells. Using Lgr5-GFP;Ki67-RFP mice, we isolated CBCs with distinct Wnt signaling levels and cell cycle features, and analyzed their global gene expression pattern using microarrays. We concluded that the cycling Lgr5hi stem cells exit the cell cycle in transition into the secretory lineage. Lgr5med Ki67low intermediate precursors reside in the zone of differentiation, resemble quiescent stem cells and generate the Dll1+ secretory precursors and the label retaining cells. Our findings support the cycling stem cell hypothesis and highlight the heterogeneity of early progenitors during lineage commitment. We used cell fractions of intestines from Lgr5-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Lgr5 promoter, and Ki67-TagRFP mice where the RFP is fused to the C-terminus of the endogenous Ki67 gene. RNA was isolated from several FACS sorted cell populations of combinations expressing different levels of GFP and RFP: GFP high RFP high (Lgr5hi Ki67hi), GFP high RFP low (Lgr5hi Ki67low), GFP medium RFP high (Lgr5med Ki67high) and GFP medium RFP low (Lgr5med Ki67low). Purified RNA was processed, hybridized, and scanned according to the manufacturerM-bM-^@M-^Ys protocol and were hybridized on Affymetrix Mouse Gene ST 1.1 arrays).
Project description:The identification of Lgr5 as an intestinal stem cell marker has made it possible to isolate and study primary stem cells from small intestine. Using the cell cycle specific expression og the mKi67 gene, we generated a novel Ki67-RFP knock-in allele which identifies dividing cells. Using Lgr5-GFP;Ki67-RFP mice, we isolated CBCs with distinct Wnt signaling levels and cell cycle features, and analyzed their global gene expression pattern using microarrays. We concluded that the cycling Lgr5hi stem cells exit the cell cycle in transition into the secretory lineage. Lgr5med Ki67low intermediate precursors reside in the zone of differentiation, resemble quiescent stem cells and generate the Dll1+ secretory precursors and the label retaining cells. Our findings support the cycling stem cell hypothesis and highlight the heterogeneity of early progenitors during lineage commitment.
Project description:Imbalance in intestinal stem cell (ISC) homeostasis leads to cancer and metabolic disease. Therefore intense efforts are underway to understand ISC hierarchy and the niche signals that control stem cell fate. Several ISC populations have been described according to their marker expression, cell-cycle behavior and lineage potential. Actively cycling Lgr5+ ISCs ensure homeostatic renewal. A less well-defined and minor population of quiescent and label-retaining cells (LRCs) is viewed as a reserve stem cell pool. However, the existence of quiescent stem cells distinct from the Lgr5+ ISCs is controversial. Indeed, recent findings identified quiescent intestinal cells as a subpopulation of Lgr5+ ISCs that are committed to the secretory fate, but the signals that maintain and activate quiescent cells/LRCs remain elusive.
Project description:Dynamic Reorganization of Chromatin Accessibility Signatures during Dedifferentiation of Secretory Precursors into Lgr5+ Intestinal Stem Cells
Project description:The epithelial lining of the small intestine is continuously renewed from a small number of stem cells including Lgr5 expressing crypt base cells that have been shown to be a rapidly cycling stem cell population in homeostasis. Alternative markers of intestinal stem cells have variously identified populations as rapidly cycling or quiescent with proposed roles for the latter as a parallel or reserve stem cell population. However, the exact nature of quiescent crypt cells remains unknown. Here by applying novel mouse models that permit their isolation and characterisation as label-retaining cells (LRCs), and for the first time performing lineage tracing from them, we show quiescent cells to be committed secretory precursors that are capable of recall to the stem cell state. We reveal LRCs to be a small subset of the rapidly cycling Lgr5 expressing population committed along the Paneth-enteroendocrine lineage. Significantly, after injury and subsequent regeneration they are clonogenic, as shown by both lineage tracing and organoid growth demonstrating that they can be recalled to the stem cell pool. These findings in establishing quiescent cells as an effective clonogenic reserve during injury provides a motivation for investigating their role in the maintenance of cancer growth following adjuvant treatment.
Project description:The introduction of GFP into the Dll1 locus has made it possible to isolate and study primary intestinal Dll1 positive cells, which constitute the secretory cell precursors of the intestine. Applying DNA array technology, we profiled the RNA changes of FACS-sorted Dll1_high/CD24_low, Dll1_high/CD24_medium and Dll1_high/CD24_high cells . We used cell fractions of intestines from Dll1-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Dll1 promoter. RNA was isolated from three FACS sorted cell populations: all are expressing Dll1-GFP at high levels, but are expressing different levels of Cd24 (low, medium and high). For this set two biological replicates were generated. One additional fraction was isolated from Lgr5-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Lgr5 promoter. This cell fraction contains intestinal stem cells. Differentially labelled cRNA from these cell fractions was hybridized against a reference (RNA isolated from whole intestine) on 4X44K Agilent Whole Mouse Genome dual colour Microarrays (G4122F).
Project description:A detailed understanding of intestinal stem cell (ISC) self-renewal and differentiation is required for better treatment options for a variety of chronic intestinal diseases, however, current models of ISC lineage hierarchy and segregation are still under debate. Here we report the identification of Lgr5+ ISCs that express Flattop (Fltp), a Wnt/planar cell polarity (PCP) reporter and effector gene. Functional analysis and lineage tracing revealed that Wnt/PCP-activated Fltp+ ISCs are primed towards either the enteroendocrine or Paneth cell lineage in vivo, while retaining self-renewal and multi-lineage capacity in vitro. Surprisingly, canonical Wnt/beta-catenin- and non-canonical Wnt/PCP-activated Lgr5+ ISCs are indistinguishable by the expression of stem-cell signature or secretory lineage-specifying genes, suggesting that lineage priming and cell-cycle exit is triggered at the post-transcriptional level by polarity cues and a switch of canonical to non-canonical Wnt signalling. Pseudotemporal ordering of targeted single-cell gene expression data allowed us to delineate the ISC differentiation path into enteroendocrine and Paneth cells. Strikingly, both lineages are directly recruited from ISCs via unipotent transition states, excluding the existence of formerly predicted bi- or multipotent secretory progenitors. Transitory cells that mature into Paneth cells are defined by label-retention and co-expression of stem cell and secretory lineage genes, indicating that these cells are the previously described Lgr5+ label-retaining cells (LRCs). Taken together, we identified the Wnt/PCP pathway as a new niche signal and polarity cue regulating stem cell fate. Active Wnt/PCP signalling represents one of the earliest events in ISC lineage priming towards the Paneth and enteroendocrine cell fate, preceding lateral inhibition and expression of secretory lineage-specifying genes. Thus, our findings provide a better understanding of the niche signals and redefine the mechanisms underlying ISC lineage hierarchy and segregation. Here we establish the Wnt/Planar cell polarity (PCP) gene Flattop (Fltp) as a unique marker for intestinal LRCs and their distinct secretory fate. We show that Fltp+ cells are characterized by a combined stem cell and secretory gene signature. A subset of Fltp+ cells is classified by label-retention and predominantly locates at position +4, indicative of quiescent stem cells. Strikingly, Fltp+ LRCs are specified by Wnt/PCP signaling in contrast to actively cycling stem cells that rely on the canonical Wnt/β-catenin pathway. In mice with disturbed Wnt/PCP signaling, the differentiation of enteroendocrine cells from LRCs is impaired. These findings establish Fltp as a novel marker for intestinal LRCs and implicate Wnt/PCP signaling in cell-cycle exit and commitment of ISCs to the secretory lineage. Taken together, we not only provide a marker to study LRCs in homeostatic and diseased conditions, but also identify the Wnt/PCP signaling pathway as a therapeutic target for colorectal cancer and metabolic disease.
Project description:The epithelial lining of the small intestine is continuously renewed from a small number of stem cells including Lgr5 expressing crypt base cells that have been shown to be a rapidly cycling stem cell population in homeostasis. Alternative markers of intestinal stem cells have variously identified populations as rapidly cycling or quiescent with proposed roles for the latter as a parallel or reserve stem cell population. However, the exact nature of quiescent crypt cells remains unknown. Here by applying novel mouse models that permit their isolation and characterisation as label-retaining cells (LRCs), and for the first time performing lineage tracing from them, we show quiescent cells to be committed secretory precursors that are capable of recall to the stem cell state. We reveal LRCs to be a small subset of the rapidly cycling Lgr5 expressing population committed along the Paneth-enteroendocrine lineage. Significantly, after injury and subsequent regeneration they are clonogenic, as shown by both lineage tracing and organoid growth demonstrating that they can be recalled to the stem cell pool. These findings in establishing quiescent cells as an effective clonogenic reserve during injury provides a motivation for investigating their role in the maintenance of cancer growth following adjuvant treatment. Six age and sex (female) matched Cyp1a1-H2B-YFP mice ten days post βNF induction were used comparing three cell populations from each. Following epithelial isolation, single cell preparation and staining with anti-CD24 anitbody and UEA-1 lectin, 30,000 cells were flow sorted for each population: Paneth cells (Paneth) were defined as CD24+/UEA+, YFP-LRCs (YFPpos) as CD24+/UEA-/YFP+ and LCCs (YFPneg) as CD24+/UEA-/YFP-. Microarray expression comparison was then performed to identify unique markers of each population. RNA amplification and hybridisation was performed at the Paterson Institute, Manchester, UK, Microarray Facility using Nugen Ovation Pico WTA System for amplification and then hybridisation to a Mouse Exon 1.0 ST Array. Arrays were scanned using an Affymetrix GeneChip scanner 3000 running GCOS software.
Project description:Perturbed intestinal epithelial homeostasis demonstrated as decreased Lgr5+ intestinal stem cells (Lgr5 ISCs) and increased secretory lineages were observed in our study where Lkb1 was specfically deleted in Lgr5 ISCs using Lgr5-EGFP-creERT2 (Tamoxifen) deletor. To gain mechanistic insight how Lkb1 maintains intestinal epithelial stem cell homeostasis, Lkb1 deficient ISCs (Lgr5-high cells) and progenitors (Lgr5-low cells) are isolated by flow cytometry and profiled by RNA sequencing to compare with controls (Lkb1 wild type ISCs and progenitors).