Project description:Lgr5+ stem cells reside at crypt bottoms of the small and large intestine. Small intestinal Paneth cells supply Wnt3, EGF and Notch signals to neighboring Lgr5+ stem cells. While the colon lacks Paneth cells, Deep Crypt Secretory (DCS) cells are intermingled with Lgr5+ stem cells at crypt bottoms. Here, we report Reg4 as a marker of DCS cells. To investigate a niche function, we eliminated DCS cells using the diphtheria-toxin receptor gene knocked into the murine Reg4 locus. Ablation of DCS cells results in loss of stem cells from colonic crypts and disrupts gut homeostasis and colon mini-gut formation. In agreement, sorted Reg4+ DCS cells promote organoid formation of single Lgr5+ colon stem cells. Stem cells are forced to generate DCS cells in vitro by combined Notch inhibition and Wnt activation. We conclude that Reg4+ DCS cells serve as Paneth cell equivalents in the colon crypt niche.
Project description:Homeostasis of self-renewing small intestinal crypts results from neutral competition between Lgr5 stem cells, small cycling cells located at crypt bottoms1, 2. Lgr5 stem cells are interspersed between terminally differentiated Paneth cells, that are known to produce bactericidal products such as lysozyme and cryptdins/defensins3. Single Lgr5-expressing stem cells can be cultured to form long-lived, self-organizing crypt-villus organoids in the absence of non-epithelial niche cells4. Here, we note a close physical association of Lgr5 stem cells with Paneth cells in vivo and in vitro. CD24+ Paneth cells express EGF, TGFα, Wnt3 and the Notch-ligand Dll4, all essential signals for stem cell maintenance in culture. Co-culturing of sorted stem cells with Paneth cells dramatically improves organoid formation. This Paneth cell requirement can be substituted by a pulse of exogenous Wnt. Genetic removal of Paneth cells in vivo results in the concomitant loss of Lgr5 stem cells. In colon crypts, CD24+ cells residing between Lgr5 stem cells may represent the Paneth cell equivalents. We conclude that Lgr5 stem cells compete for essential niche signals provided by a specialized daughter cell, the Paneth cell.
Project description:Homeostasis of self-renewing small intestinal crypts results from neutral competition between Lgr5 stem cells, small cycling cells located at crypt bottoms1, 2. Lgr5 stem cells are interspersed between terminally differentiated Paneth cells, that are known to produce bactericidal products such as lysozyme and cryptdins/defensins3. Single Lgr5-expressing stem cells can be cultured to form long-lived, self-organizing crypt-villus organoids in the absence of non-epithelial niche cells4. Here, we note a close physical association of Lgr5 stem cells with Paneth cells in vivo and in vitro. CD24+ Paneth cells express EGF, TGF?, Wnt3 and the Notch-ligand Dll4, all essential signals for stem cell maintenance in culture. Co-culturing of sorted stem cells with Paneth cells dramatically improves organoid formation. This Paneth cell requirement can be substituted by a pulse of exogenous Wnt. Genetic removal of Paneth cells in vivo results in the concomitant loss of Lgr5 stem cells. In colon crypts, CD24+ cells residing between Lgr5 stem cells may represent the Paneth cell equivalents. We conclude that Lgr5 stem cells compete for essential niche signals provided by a specialized daughter cell, the Paneth cell. We used intestinal cell fractions from Lgr5-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Lgr5 promoter. RNA was isolated from two FACS sorted cell populations: stem cells were sorted based on high level of GFP expression (GFPhi) and Paneth cells were sorted based on high level of CD24 expression (CD24hi) and high side-scatter (SSChi). Differentially labelled cRNA from GFPhi and CD24hi/SSChi cells from two different sorts (each combining ten individual mice) were hybridized on 4X44K Agilent Whole Mouse Genome dual colour Microarrays (G4122F) in two dye swap experiments, resulting in four individual arrays.
Project description:The gastrointestinal epithelial crypts are clonal units with a high cell turnover, driven by a small population of long-lived, Lgr5-expressing stem cells located in the crypt base. Despite this, depletion of Lgr5+ cells does not lead to severe pathology. Instead, other cell populations, such as secretory and enterocyte precursors are able to de-differentiate, replace Lgr5+ cells, and regenerate the crypt. However, the signals that regulate this epithelial plasticity are not well understood. Here we illuminate the hierarchical organization and regulation of stem cell plasticity in the colonic crypt. Using in vivo lineage tracing, we find that the classic Wnt target gene Axin2 is expressed in colonic Lgr5+ cells and adjacent Lgr5-negative cells that give rise to entire crypts upon Lgr5+ cell depletion. The identity of Lgr5+ cells is controlled by by R-spondin 3 (Rspo3) produced by myofibroblasts and the recovery of Lgr5+ cells upon depletion required functional Rspo3 signaling. In contrast, expression of Axin2 and the reserve stem cell function of Axin2+ cells is not dependent on Rspo3. Accordingly, upon knockout of Rspo3, Lgr5-negative Axin2+ cells are able to compensate the loss of the Lgr5+ cell compartment and maintain epithelial integrity. In contrast, Rspo3 is essential for maintaining epithelial integrity in the context of injury of the entire Axin2+ cell pool, as observed in the context of DSS colitis. We demonstrate that DSS induces a progressive loss of the Lgr5+ stem cells as well as Axin2+ Lgr5-negative reserve stem cell compartment. While Rspo3 deficient animals are unable to withstand this injury, in Rspo3 competent animals, crypt homeostasis and regeneration are fueled by the remaining Axin2-negative, differentiated cells. These cells can be reprogrammed by Rspo3 to proliferate and act as stem cells. Thus, we identity Rspo3 as a major regulator of the Lgr5 stem cell signature. While loss of this signature can be compensated by Rspo3-independent reserve stem cells under healthy conditions, it is essential for re-establishment of epithelial integrity upon crypt injury.
Project description:The intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. We have recently demonstrated the presence of approximately six cycling Lgr5+ stem cells at the bottoms of small intestinal crypts1. We have now established long-term culture conditions under which single crypts undergo multiple crypt fission events, whilst simultanously generating villus-like epithelial domains in which all differentiated cell types are present. Single sorted Lgr5+ stem cells can also initiate these crypt-villus organoids. Tracing experiments indicate that the Lgr5+ stem cell hierarchy is maintained in organoids. We conclude that intestinal crypt-villus units are self-organizing structures, which can be built from a single stem cell in the absence of a non-epithelial cellular niche. Keywords: expression profiling
Project description:At the base of the intestinal crypt, long-lived Lgr5+ stem cells are intercalated by Paneth cells that provide essential niche signals for stem-cell maintenance. This unique epithelial anatomy makes the intestinal crypt one of the most accessible models for the study of adult stem cell biology. The glycosylation patterns of this compartment are poorly characterized and the impact of glycans on stem cell differentiation remains largely unexplored. We found that Paneth cells, but not Lgr5+ stem cells, express abundant terminal N-acetyllactosamine (LacNAc). Employing an enzymatic method to edit glycans in cultured crypt organoids, we assessed the functional role of LacNAc in the intestinal crypt. We show that blocking access to LacNAc on Paneth cells leads to hyperproliferation of the neighbouring Lgr5+ stem cells, which is accompanied by the down-regulation of genes that are known as negative regulators of proliferation
Project description:The intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. We have recently demonstrated the presence of approximately six cycling Lgr5+ stem cells at the bottoms of small intestinal crypts1. We have now established long-term culture conditions under which single crypts undergo multiple crypt fission events, whilst simultanously generating villus-like epithelial domains in which all differentiated cell types are present. Single sorted Lgr5+ stem cells can also initiate these crypt-villus organoids. Tracing experiments indicate that the Lgr5+ stem cell hierarchy is maintained in organoids. We conclude that intestinal crypt-villus units are self-organizing structures, which can be built from a single stem cell in the absence of a non-epithelial cellular niche. Keywords: expression profiling Freshly isolated small intestinal crypts from two mice were divided into two parts. RNA was directly isolated from one part (RNeasy Mini Kit, Qiagen), the other part was cultured for one week according to the conditions described in the associated paper, followed by RNA isolation. We prepared labeled cRNA following the manufacturer’s instruction (Agilent Technologies). Differentially labelled cRNA from small intestinal crypts and organoids were hybridised separately for the two mice on a 4X44k Agilent Whole Mouse Genome dual colour Microarrays (G4122F) in two dye swap experiments, resulting in four individual arrays.
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).
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.