Nick Barker

The University of Edinburgh, Edinburgh, Scotland, United Kingdom

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Publications (81)1178.11 Total impact

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    ABSTRACT: The ovary surface epithelium (OSE) undergoes ovulatory tear and remodelling throughout life. Resident stem cells drive such tissue homeostasis in many adult epithelia, but their existence in the ovary has not been definitively proven. Lgr5 marks stem cells in multiple epithelia. Here we use reporter mice and single-molecule fluorescent in situ hybridization to document candidate Lgr5(+) stem cells in the mouse ovary and associated structures. Lgr5 is broadly expressed during ovary organogenesis, but becomes limited to the OSE in neonate life. In adults, Lgr5 expression is predominantly restricted to proliferative regions of the OSE and mesovarian-fimbria junctional epithelia. Using in vivo lineage tracing, we identify embryonic and neonate Lgr5(+) populations as stem/progenitor cells contributing to the development of the OSE cell lineage, as well as epithelia of the mesovarian ligament and oviduct/fimbria. Adult Lgr5(+) populations maintain OSE homeostasis and ovulatory regenerative repair in vivo. Thus, Lgr5 marks stem/progenitor cells of the ovary and tubal epithelia.
    Nature Cell Biology 07/2014; · 20.06 Impact Factor
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    ABSTRACT: Lgr5 is a marker for proliferating stem cells in adult intestine, stomach and hair follicle. However, Lgr5 is not expressed in adult hematopoietic stem and progenitor cells (HSPCs). Whether Lgr5 is expressed in the embryonic and fetal HSPCs that undergo rapid proliferation is unknown. Here we report the detection of Lgr5 expression in HSPCs in the aorta-gonad-mesonephros (AGM) and fetal liver. We also found that a portion of Lgr5(+) cells expressed Runx-1 genes that are critical for the ontogeny of HSPCs. A small portion of Lgr5(+) cells also expressed HSPC surface markers c-Kit and CD34 in AGM or CD41 in fetal liver. Furthermore, the majority of Lgr5(+) cells expressed Ki67, indicating their proliferating state. Transplantation of fetal liver-derived Lgr5-GFP(+) cells (E12.5) demonstrated that Lgr5-GFP(+) cells were able to reconstitute myeloid and lymphoid lineages in adult recipients, but the engraftment was short-term (4-8 weeks) and 20-fold lower compared to the Lgr5-GFP(-) control. Our data show that Lgr5-expressing cells mark short-term hematopoietic stem and progenitor cells, consistent with the role of Lgr5 in supporting HSPCs rapid proliferation during embryonic and fetal development.
    Journal of Biological Chemistry 06/2014; · 4.60 Impact Factor
  • Marc Leushacke, Nick Barker
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    ABSTRACT: Limited pools of resident adult stem cells are critical effectors of epithelial renewal in the intestine throughout life. Recently, significant progress has been made regarding the isolation and in vitro propagation of fetal and adult intestinal stem cells in mammals. It is now possible to generate ever-expanding, three-dimensional epithelial structures in culture that closely parallel the in vivo epithelium of the intestine. Growing such organotypic epithelium ex vivo facilitates a detailed description of endogenous niche factors or stem-cell characteristics, as they can be monitored in real time. Accordingly, this technology has already greatly contributed to our understanding of intestinal adult stem-cell renewal and differentiation. Transplanted organoids have also been proven to readily integrate into, and effect the long-term repair of, mouse colonic epithelia in vivo, establishing the organoid culture as a promising tool for adult stem cell/gene therapy. In another exciting development, novel genome-editing techniques have been successfully employed to functionally repair disease loci in cultured intestinal stem cells from human patients with a hereditary defect. It is anticipated that this technology will be instrumental in exploiting the regenerative medicine potential of human intestinal stem cells for treating human disorders in the intestinal tract and for creating near-physiological ex vivo models of human gastrointestinal disease.
    Gut 05/2014; · 13.32 Impact Factor
  • Shawna Tan, Nick Barker
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    ABSTRACT: The mammalian intestine is comprised of an epithelial layer that serves multiple functions in order to maintain digestive activity as well as intestinal homeostasis. This epithelial layer contains highly proliferative stem cells which facilitate its characteristic rapid regeneration. How these stem cells contribute to tissue repair and normal homeostasis are actively studied, and while we have a greater understanding of the molecular mechanisms and cellular locations that underlie stem cell regulation in this tissue, much still remains undiscovered. This review describes epithelial stem cells in both intestinal and non-intestinal tissues, as well as the strategies that have been used to further characterize the cells. Through a discussion of the current understanding of intestinal self-renewal and tissue regeneration in response to injury, we focus on how dysregulation of critical signaling pathways results in potentially oncogenic aberrations, and highlight issues that should be addressed in order for effective intestinal cancer therapies to be devised.
    Seminars in Cancer Biology 02/2014; · 9.14 Impact Factor
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    ABSTRACT: Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) is expressed in many organs, including female reproductive organs, and is a stem cell marker in the stomach and intestinal epithelium, hair follicles, and ovarian surface epithelium. Despite ongoing studies, the definitive physiological functions of Lgr5 remain unclear. We utilized mice with conditional deletion of Lgr5 (Lgr5(d/d)) in the female reproductive organs by progesterone receptor-Cre (Pgr(Cre)) to determine Lgr5's functions during pregnancy. Only 30% of plugged Lgr5(d/d) females delivered live pups, and their litter sizes were lower. We found that pregnancy failure in Lgr5(d/d) females was due to insufficient ovarian progesterone (P4) secretion that compromised decidualization, terminating pregnancy. The drop in P4 levels was reflected in elevated levels of P4-metabolizing enzyme 20α-hydroxysteroid dehydrogenase in corpora lutea (CL) inactivated of Lgr5. Of interest, P4 supplementation rescued decidualization failure and supported pregnancy to full term in Lgr5(d/d) females. These results provide strong evidence that Lgr5 is critical to normal CL function, unveiling a new role of LGR5 in the ovary.-Sun, X., Terakawa, J., Clevers, H., Barker, N., Daikoku, T., Dey, S. K. Ovarian LGR5 is critical for successful pregnancy.
    The FASEB Journal 01/2014; · 5.48 Impact Factor
  • David Wei-Min Tan, Nick Barker
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    ABSTRACT: The intestinal epithelium is a classic example of a rapidly self-renewing tissue fueled by dedicated resident stem cells. These stem cells reside at the crypt base, generating committed progeny that mature into the various functional epithelial lineages while following a rapid migratory path toward the villi. Two models of intestinal stem cell location were proposed half a century ago and data have been presented in support of both models, dividing the scientific community. Molecular markers have been identified and validated using new techniques such as in vivo lineage tracing and ex vivo organoid culture. The intestinal stem cell niche comprises both epithelial cells, in particular the Paneth cell, and the stromal compartment, where cell-associated ligands and soluble factors regulate stem cell behavior. This review highlights the recent advances in identifying and characterizing the intestinal stem cells and their defining niche.
    Current Topics in Developmental Biology 01/2014; 107C:77-107. · 4.21 Impact Factor
  • Nick Barker
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    ABSTRACT: Small populations of adult stem cells are responsible for the remarkable ability of the epithelial lining of the intestine to be efficiently renewed and repaired throughout life. The recent discovery of specific markers for these stem cells, together with the development of new technologies to track endogenous stem cell activity in vivo and to exploit their ability to generate new epithelia ex vivo, has greatly improved our understanding of stem cell-driven homeostasis, regeneration and cancer in the intestine. These exciting new insights into the biology of intestinal stem cells have the potential to accelerate the development of stem cell-based therapies and ameliorate cancer treatments.
    Nature Reviews Molecular Cell Biology 12/2013; · 37.16 Impact Factor
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    ABSTRACT: Like normal colorectal epithelium, colorectal carcinomas (CRC) are organized hierarchically and include populations of cells with stem-like properties. Leucine-rich-repeat-containing G-protein-coupled receptor 5 (LGR5) is associated with these stem cells in normal colorectal epithelium, however the precise function of LGR5 in CRC remains largely unknown. Here, we analyzed the functional and molecular consequences of short hairpin RNA-mediated silencing of LGR5 in CRC cell lines SW480 and HT-29. Additionally, we exposed Lgr5-EGFP-IRES-CreERT2 mice to azoxymethane/dextrane sodium sulfate (AOM/DSS) which induces inflammation-driven colon tumors. Tumors were then flow-sorted into fractions of epithelial cells that expressed high or low levels of Lgr5 and were molecularly characterized using gene expression profiling and array comparative genomic hybridization. Silencing of LGR5 in SW480 CRC cells resulted in a depletion of spheres but did not affect adherently growing cells. Spheres expressed higher levels of several stem cell-associated genes than adherent cells, including LGR5. Silencing of LGR5 reduced proliferation, migration and colony formation in vitro, and tumorigenicity in vivo. In accordance with these results, NOTCH signaling was down-regulated upon LGR5 silencing. In AOM/DSS-induced colon tumors Lgr5 high cells showed higher levels of several stem cell-associated genes and higher Wnt signaling than Lgr5 low tumor cells and Lgr5 high normal colon cells. Array comparative genomic hybridization revealed no genomic imbalances in either tumor cell fraction. Our data elucidate mechanisms that define the role of LGR5 as a marker for stem-like cells in CRC.
    Carcinogenesis 11/2013; · 5.27 Impact Factor
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    ABSTRACT: The pyloric epithelium continuously self-renews throughout life, driven by limited reservoirs of resident Lgr5(+) adult stem cells. Here, we characterize the population dynamics of these stem cells during epithelial homeostasis. Using a clonal fate-mapping strategy, we demonstrate that multiple Lgr5(+) cells routinely contribute to epithelial renewal in the pyloric gland and, similar to what was previously observed in the intestine, a balanced homeostasis of the glandular epithelium and stem cell pools is predominantly achieved via neutral competition between symmetrically dividing Lgr5(+) stem cells. Additionally, we document a lateral expansion of stem cell clones via gland fission under nondamage conditions. These findings represent a major advance in our basic understanding of tissue homeostasis in the stomach and form the foundation for identifying altered stem cell behavior during gastric disease.
    Cell Reports 10/2013; · 7.21 Impact Factor
  • Nick Barker, Shawna Tan, Hans Clevers
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    ABSTRACT: The ultimate success of global efforts to exploit adult stem cells for regenerative medicine will depend heavily on the availability of robust, highly selective stem cell surface markers that facilitate the isolation of stem cells from human tissues. Any subsequent expansion or manipulation of isolated stem cells will also require an intimate knowledge of the mechanisms that regulate these cells, to ensure maintenance of their regenerative capacities and to minimize the risk of introducing undesirable growth traits that could pose health risks for patients. A subclass of leucine-rich repeat-containing G-protein-coupled receptor (Lgr) proteins has recently gained prominence as adult stem cell markers with crucial roles in maintaining stem cell functions. Here, we discuss the major impact that their discovery has had on our understanding of adult stem cell biology in various self-renewing tissues and in accelerating progress towards the development of effective stem cell therapies.
    Development 06/2013; 140(12):2484-2494. · 6.27 Impact Factor
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    ABSTRACT: Cell-type plasticity within a tumor has recently been suggested to cause a bidirectional conversion between tumor-initiating stem cells and nonstem cells triggered by an inflammatory stroma. NF-κB represents a key transcription factor within the inflammatory tumor microenvironment. However, NF-κB's function in tumor-initiating cells has not been examined yet. Using a genetic model of intestinal epithelial cell (IEC)-restricted constitutive Wnt-activation, which comprises the most common event in the initiation of colon cancer, we demonstrate that NF-κB modulates Wnt signaling and show that IEC-specific ablation of RelA/p65 retards crypt stem cell expansion. In contrast, elevated NF-κB signaling enhances Wnt activation and induces dedifferentiation of nonstem cells that acquire tumor-initiating capacity. Thus, our data support the concept of bidirectional conversion and highlight the importance of inflammatory signaling for dedifferentiation and generation of tumor-initiating cells in vivo.
    Cell 12/2012; · 31.96 Impact Factor
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    ABSTRACT: Decades ago, two nonoverlapping crypt stem cell populations were proposed: Leblond's Crypt Base Columnar (CBC) cell and Potten's +4 cell. The identification of CBC markers including Lgr5 has confirmed Leblond's predictions that CBC cells are anatomically distinct, long-lived stem cells that permanently cycle. While Potten originally described +4 cells as proliferative and unusually radiation-sensitive, recent efforts to identify +4 stem cells have focused on the identification of cells that are quiescent and radiation-resistant. Here, we describe commonalities and discrepancies between the individual studies and discuss challenges of marker-based lineage tracing.
    Cell stem cell 10/2012; 11(4):452-60. · 23.56 Impact Factor
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    ABSTRACT: Multipotent stem cells and their lineage-restricted progeny drive nephron formation within the developing kidney. Here, we document expression of the adult stem cell marker Lgr5 in the developing kidney and assess the stem/progenitor identity of Lgr5(+ve) cells via in vivo lineage tracing. The appearance and localization of Lgr5(+ve) cells coincided with that of the S-shaped body around embryonic day 14. Lgr5 expression remained restricted to cell clusters within developing nephrons in the cortex until postnatal day 7, when expression was permanently silenced. In vivo lineage tracing identified Lgr5 as a marker of a stem/progenitor population within nascent nephrons dedicated to generating the thick ascending limb of Henle's loop and distal convoluted tubule. The Lgr5 surface marker and experimental models described here will be invaluable for deciphering the contribution of early nephron stem cells to developmental defects and for isolating human nephron progenitors as a prerequisite to evaluating their therapeutic potential.
    Cell Reports 09/2012; 2(2(3)-2012 Sep 27;2(3):540-52.):540-52. · 7.21 Impact Factor
  • Nick Barker
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    ABSTRACT: In their recent Science publication, Doupé et al. (2012) demonstrate that a single population of proliferating progenitor cells is solely responsible for homeostatic self-renewal and repair of injured esophageal epithelium. These findings argue against an obligate requirement for long-lived (reserve) stem cells in adult epithelia.
    Cell stem cell 09/2012; 11(3):284-6. · 23.56 Impact Factor
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    ABSTRACT: Lgr5(+) intestinal stem cells generate enterocytes and secretory cells. Secretory lineage commitment requires Notch silencing. The Notch ligand Dll1 is expressed by a subset of immediate stem cell daughters. Lineage tracing in Dll1(GFP-ires-CreERT2) knock-in mice reveals that single Dll1(high) cells generate small, short-lived clones containing all four secretory cell types. Lineage specification thus occurs in immediate stem cell daughters through Notch lateral inhibition. Cultured Dll1(high) cells form long-lived organoids (mini-guts) on brief Wnt3A exposure. When Dll1(high) cells are genetically marked before tissue damage, stem cell tracing events occur. Thus, secretory progenitors exhibit plasticity by regaining stemness on damage.
    Nature Cell Biology 09/2012; 14(10):1099. · 20.06 Impact Factor
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    ABSTRACT: The leucine-rich repeat-containing heterotrimeric guanine nucleotide-binding protein-coupled receptor 5 (LGR5) has been identified as a marker of cycling stem cells in several epithelial tissues, including small intestine, colon, stomach and hair follicle. To investigate whether LGR5 also marks mammary epithelial stem cells, we performed in situ lineage-tracing studies and mammary gland reconstitutions with LGR5-expressing mammary epithelial cells. Interestingly, the LGR5 progeny population in mammary epithelium switches from the luminal to the myoepithelial compartment during the first 12 days of postnatal development, likely reflecting local changes in Wnt signalling. Together, our findings point to a stage-specific contribution of LGR5-expressing cells to luminal and basal epithelial lineages during postnatal mammary gland development. Copyright © 2012 Pathological Society of Great Britain and Ireland.
    The Journal of Pathology 08/2012; 228(3):300-9. · 7.33 Impact Factor
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    ABSTRACT: Peyer's patches consist of domains of specialized intestinal epithelium overlying gut-associated lymphoid tissue (GALT). Luminal antigens reach the GALT by translocation through epithelial gatekeeper cells, the so-called M cells. We recently demonstrated that all epithelial cells required for the digestive functions of the intestine are generated from Lgr5-expressing stem cells. Here, we show that M cells also derive from these crypt-based Lgr5 stem cells. The Ets family transcription factor SpiB, known to control effector functions of bone marrow-derived immune cells, is specifically expressed in M cells. In SpiB(-/-) mice, M cells are entirely absent, which occurs in a cell-autonomous fashion. It has been shown that Tnfsf11 (RankL) can induce M cell development in vivo. We show that in intestinal organoid ("minigut") cultures, stimulation with RankL induces SpiB expression within 24 h and expression of other M cell markers subsequently. We conclude that RankL-induced expression of SpiB is essential for Lgr5 stem cell-derived epithelial precursors to develop into M cells.
    Molecular and Cellular Biology 07/2012; 32(18):3639-47. · 5.04 Impact Factor
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    ABSTRACT: Since aberrant wound healing and chronic inflammation can promote malignant transformation, we determined whether dietary bioactive fish oil (FO)-derived n-3 polyunsaturated fatty acids (n-3 PUFA) modulate stem cell kinetics in a colitis-wounding model. Lgr5-LacZ and Lgr5-EGFP-IRES-creER(T2) mice were fed diets enriched with n-3 PUFA vs n-6 PUFA (control) and exposed to dextran sodium sulfate (DSS) for 5days in order to induce crypt damage and colitis throughout the colon. Stem cell number, cell proliferation, apoptosis, expression of stem cell (Lgr5, Sox9, Bmi1, Hopx, mTert, Ascl2, and DCAMKL-1) and inflammation (STAT3) markers were quantified. DSS treatment resulted in the ablation of Lgr5(+) stem cells in the distal colon, concurrent with the loss of distal crypt structure and proliferating cells. Lgr5, Ascl2 and Hopx mRNA expression levels were decreased in damaged colonic mucosa. Lgr5(+) stem cells reappeared at day 5 of DSS recovery, with normal levels attained by day 6 of recovery. There was no effect of diet on the recovery of stem cells. FO fed animals exhibited higher levels of phospho-STAT3 at all time points, consistent with a higher wounding by DSS in FO feeding. n-3 PUFA-fed mice exhibited a reduction in stem cell associated factors, Ascl2, Axin2 and EphB3. These results indicate that rapidly cycling Lgr5(+) stem cells residing at position 1 in the colon epithelium are highly susceptible to DSS-induced damage and that dietary cues can impact stem cell regulatory networks.
    Biochimica et Biophysica Acta 06/2012; 1822(10):1600-7. · 4.66 Impact Factor

Publication Stats

13k Citations
1,178.11 Total Impact Points

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  • 2013–2014
    • The University of Edinburgh
      Edinburgh, Scotland, United Kingdom
  • 1997–2012
    • University Medical Center Utrecht
      • Department of Immunology
      Utrecht, Provincie Utrecht, Netherlands
  • 2011
    • Koninklijke Nederlandse Akademie van Wetenschappen
      Amsterdamo, North Holland, Netherlands
  • 2008–2011
    • Karolinska Institutet
      • Institutionen för biovetenskaper och näringslära
      Solna, Stockholm, Sweden
    • University of Melbourne
      • Biology Laboratory
      Melbourne, Victoria, Australia
  • 1998–2011
    • Hubrecht Institute
      Utrecht, Utrecht, Netherlands
  • 2003–2010
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands
  • 2002
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States