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Immunohistochemical distribution of Ki67 in epidermis of thick glabrous skin of human digits. Arch Dermatol Res 2017; 310:85-93. [PMID: 29119273 DOI: 10.1007/s00403-017-1793-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 10/23/2017] [Accepted: 11/01/2017] [Indexed: 11/27/2022]
Abstract
The glabrous skin on the flexor sides of hands and feet, compared to other integument regions, has thicker epidermis and more complex pattern of epidermal ridges, wherefore in microscopy is denominated as thick skin. The epidermis of this skin type has individually unique and permanent superficial patterns, called dermatoglyphics, which are maintained by regenerative potential of deep epidermal rete ridges, that interdigitate with adjacent dermis. Using light microscopy, we analyzed cadaveric big toes thick skin samples, described histology of deep epidermal ridges (intermediate, limiting, and transverse), and quantitatively evidenced their pattern of proliferation by immunohistochemical assessment of Ki67. Immunohistochemical distribution of Ki67 was confined to basal and suprabasal layers, with pattern of distribution specific for intermediate, limiting and transverse ridges that gradually transform within epidermal height. Deep epidermal ridges, interdigitating with dermal papillae, participate in construction of intricate epidermal base, whose possible role in epidermal regeneration was also discussed. Having a prominent morphology, this type of epidermis offers the best morphological insight in complexities of skin organization, and its understanding could challenge and improve currently accepted models of epidermal organization.
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2
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Transgenic mouse model expressing P53(R172H), luciferase, EGFP, and KRAS(G12D) in a single open reading frame for live imaging of tumor. Sci Rep 2015; 5:8053. [PMID: 25623590 PMCID: PMC4306974 DOI: 10.1038/srep08053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 01/02/2015] [Indexed: 01/21/2023] Open
Abstract
Genetically engineered mouse cancer models allow tumors to be imaged in vivo via co-expression of a reporter gene with a tumor-initiating gene. However, differential transcriptional and translational regulation between the tumor-initiating gene and the reporter gene can result in inconsistency between the actual tumor size and the size indicated by the imaging assay. To overcome this limitation, we developed a transgenic mouse in which two oncogenes, encoding P53R172H and KRASG12D, are expressed together with two reporter genes, encoding enhanced green fluorescent protein (EGFP) and firefly luciferase, in a single open reading frame following Cre-mediated DNA excision. Systemic administration of adenovirus encoding Cre to these mice induced specific transgene expression in the liver. Repeated bioluminescence imaging of the mice revealed a continuous increase in the bioluminescent signal over time. A strong correlation was found between the bioluminescent signal and actual tumor size. Interestingly, all liver tumors induced by P53R172H and KRASG12D in the model were hepatocellular adenomas. The mouse model was also used to trace cell proliferation in the epidermis via live fluorescence imaging. We anticipate that the transgenic mouse model will be useful for imaging tumor development in vivo and for investigating the oncogenic collaboration between P53R172H and KRASG12D.
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3
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Jones KB, Klein OD. Oral epithelial stem cells in tissue maintenance and disease: the first steps in a long journey. Int J Oral Sci 2013; 5:121-9. [PMID: 23887128 PMCID: PMC3967329 DOI: 10.1038/ijos.2013.46] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Accepted: 06/08/2013] [Indexed: 12/11/2022] Open
Abstract
The identification and characterization of stem cells is a major focus of developmental biology and regenerative medicine. The advent of genetic inducible fate mapping techniques has made it possible to precisely label specific cell populations and to follow their progeny over time. When combined with advanced mathematical and statistical methods, stem cell division dynamics can be studied in new and exciting ways. Despite advances in a number of tissues, relatively little attention has been paid to stem cells in the oral epithelium. This review will focus on current knowledge about adult oral epithelial stem cells, paradigms in other epithelial stem cell systems that could facilitate new discoveries in this area and the potential roles of epithelial stem cells in oral disease.
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Affiliation(s)
- Kyle B Jones
- Program in Craniofacial and Mesenchymal Biology, University of California, San Francisco, San Francisco, USA
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4
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Blanpain C, Simons BD. Unravelling stem cell dynamics by lineage tracing. Nat Rev Mol Cell Biol 2013; 14:489-502. [PMID: 23860235 DOI: 10.1038/nrm3625] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
During embryonic and postnatal development, the different cells types that form adult tissues must be generated and specified in a precise temporal manner. During adult life, most tissues undergo constant renewal to maintain homeostasis. Lineage-tracing and genetic labelling technologies are beginning to shed light on the mechanisms and dynamics of stem and progenitor cell fate determination during development, tissue maintenance and repair, as well as their dysregulation in tumour formation. Statistical approaches, based on proliferation assays and clonal fate analyses, provide quantitative insights into cell kinetics and fate behaviour. These are powerful techniques to address new questions and paradigms in transgenic mouse models and other model systems.
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Affiliation(s)
- Cédric Blanpain
- Université Libre de Bruxelles, Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Brussels, Belgium.
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5
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Sada A, Tumbar T. New insights into mechanisms of stem cell daughter fate determination in regenerative tissues. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 300:1-50. [PMID: 23273858 DOI: 10.1016/b978-0-12-405210-9.00001-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Stem cells can self-renew and differentiate over extended periods of time. Understanding how stem cells acquire their fates is a central question in stem cell biology. Early work in Drosophila germ line and neuroblast showed that fate choice is achieved by strict asymmetric divisions that can generate each time one stem and one differentiated cell. More recent work suggests that during homeostasis, some stem cells can divide symmetrically to generate two differentiated cells or two identical stem cells to compensate for stem cell loss that occurred by direct differentiation or apoptosis. The interplay of all these factors ensures constant tissue regeneration and the maintenance of stem cell pool size. This interplay can be modeled as a population-deterministic dynamics that, at least in some systems, may be described as stochastic behavior. Here, we overview recent progress made on the characterization of stem cell dynamics in regenerative tissues.
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Affiliation(s)
- Aiko Sada
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA
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6
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Mascré G, Dekoninck S, Drogat B, Youssef KK, Broheé S, Sotiropoulou PA, Simons BD, Blanpain C. Distinct contribution of stem and progenitor cells to epidermal maintenance. Nature 2012; 489:257-62. [PMID: 22940863 DOI: 10.1038/nature11393] [Citation(s) in RCA: 412] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/03/2012] [Indexed: 02/07/2023]
Abstract
The skin interfollicular epidermis (IFE) is the first barrier against the external environment and its maintenance is critical for survival. Two seemingly opposite theories have been proposed to explain IFE homeostasis. One posits that IFE is maintained by long-lived slow-cycling stem cells that give rise to transit-amplifying cell progeny, whereas the other suggests that homeostasis is achieved by a single committed progenitor population that balances stochastic fate. Here we probe the cellular heterogeneity within the IFE using two different inducible Cre recombinase–oestrogen receptor constructs targeting IFE progenitors in mice. Quantitative analysis of clonal fate data and proliferation dynamics demonstrate the existence of two distinct proliferative cell compartments arranged in a hierarchy involving slow-cycling stem cells and committed progenitor cells. After wounding, only stem cells contribute substantially to the repair and long-term regeneration of the tissue, whereas committed progenitor cells make a limited contribution.
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Affiliation(s)
- Guilhem Mascré
- Université Libre de Bruxelles, IRIBHM, Brussels B-1070, Belgium
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7
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Van Keymeulen A, Blanpain C. Tracing epithelial stem cells during development, homeostasis, and repair. ACTA ACUST UNITED AC 2012; 197:575-84. [PMID: 22641343 PMCID: PMC3365500 DOI: 10.1083/jcb.201201041] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Epithelia ensure many critical functions of the body, including protection against the external environment, nutrition, respiration, and reproduction. Stem cells (SCs) located in the various epithelia ensure the homeostasis and repair of these tissues throughout the lifetime of the animal. Genetic lineage tracing in mice has allowed the labeling of SCs and their progeny. This technique has been instrumental in characterizing the origin and heterogeneity of epithelial SCs, their tissue location, and their differentiation potential under physiological conditions and during tissue regeneration.
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Affiliation(s)
- Alexandra Van Keymeulen
- Université Libre de Bruxelles, Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, B-1070 Bruxelles, Belgium
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8
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Roshan A, Jones PH. Chronic low dose UV exposure and p53 mutation: tilting the odds in early epidermal preneoplasia? Int J Radiat Biol 2012; 88:682-7. [PMID: 22671441 DOI: 10.3109/09553002.2012.699697] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
PURPOSE This review addresses how mutation of the TP53 gene (p53) and ultraviolet light alter the behavior of normal progenitor cells in early epidermal preneoplasia. CONCLUSIONS Cancer is thought to evolve from single mutant cells, which expand into clones and ultimately into tumors. While the mutations in malignant lesions have been studied intensively, less is known about the earliest stages of preneoplasia, and how environmental factors may contribute to drive expansion of mutant cell clones. Here we review the evidence that ultraviolet radiation not only creates new mutations but drives the exponential growth of the numerous p53 mutant clones found in chronically exposed epidermis. Published data is reconciled with a new paradigm of epidermal homeostasis which gives insights into the behavior of mutant cells. We also consider the reasons why so few mutant cells progress into tumors and discuss the implications of these findings for cancer prevention.
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Affiliation(s)
- Amit Roshan
- Department of Plastic Surgery, Addenbrooke's Hospital, Cambridge, UK
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9
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Calcium-calmodulin signaling induced by epithelial cell differentiation upregulates BRAK/CXCL14 expression via the binding of SP1 to the BRAK promoter region. Biochem Biophys Res Commun 2012; 420:217-22. [PMID: 22382027 DOI: 10.1016/j.bbrc.2012.01.157] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 01/04/2012] [Indexed: 11/21/2022]
Abstract
The chemokine BRAK/CXCL14 (BRAK) is expressed in normal squamous epithelium, but is not expressed or is expressed at negligible levels in head and neck squamous cell carcinoma. Malignant cells are known to be dedifferentiated compared with normal epithelial cells, suggesting a role for differentiation cues in the expression of BRAK. Thus, we examined the relationship between BRAK expression and stages of differentiation level in epithelial cells. Immunohistochemical analysis showed that BRAK protein was expressed in cells above the spinous cell layer in normal epithelia. In HSC-3 cells in culture, expression of BRAK mRNA was significantly upregulated by cell contact in a cell density-dependent manner, and mRNA expression of cell differentiation markers such as involucrin, cystatin-A, TGM1, TGM3, and TGM5 was concomitantly augmented. Furthermore, the upregulation of BRAK induced by cell contact was suppressed by chlorpromazine, a specific inhibitor of calmodulin. We previously reported that GC boxes and a TATA-like sequence in the BRAK promoter region are associated with the expression of BRAK. Using a promoter assay and ChIP, we demonstrated that binding of the stimulating protein-1 (SP1) transcription factor to a GC box upstream of the BRAK transcription start site was necessary for cell density-dependent upregulation of BRAK. These results indicated that upregulation of BRAK was accompanied by differentiation of epithelial cells induced by calcium/calmodulin signaling, and that SP1 binding to the BRAK promoter region played an important role in this signaling.
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Croyle MJ, Lehman JM, O'Connor AK, Wong SY, Malarkey EB, Iribarne D, Dowdle WE, Schoeb TR, Verney ZM, Athar M, Michaud EJ, Reiter JF, Yoder BK. Role of epidermal primary cilia in the homeostasis of skin and hair follicles. Development 2011; 138:1675-85. [PMID: 21429982 DOI: 10.1242/dev.060210] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Skin and hair follicle morphogenesis and homeostasis require the integration of multiple signaling pathways, including Hedgehog (Hh) and Wingless (Wnt), and oriented cell divisions, all of which have been associated with primary cilia. Although studies have shown that disrupting dermal cilia causes follicular arrest and attenuated Hh signaling, little is known about the role of epidermal cilia. Here, epidermal cilia function was analyzed using conditional alleles of the ciliogenic genes Ift88 and Kif3a. At birth, epidermal cilia mutants appeared normal, but developed basaloid hyperplasia and ingrowths into the dermis of the ventrum with age. In addition, follicles in the tail were disorganized and had excess sebaceous gland lobules. Epidermal cilia mutants displayed fewer long-term label-retaining cells, suggesting altered stem cell homeostasis. Abnormal proliferation and differentiation were evident from lineage-tracing studies and showed an expansion of follicular cells into the interfollicular epidermis, as is seen during wound repair. These phenotypes were not associated with changes in canonical Wnt activity or oriented cell division. However, nuclear accumulation of the ΔNp63 transcription factor, which is involved in stratification, keratinocyte differentiation and wound repair, was increased, whereas the Hh pathway was repressed. Intriguingly, the phenotypes were not typical of those associated with loss of Hh signaling but exhibited similarities with those of mice in which ΔNp63 is overexpressed in the epidermis. Collectively, these data indicate that epidermal primary cilia may function in stress responses and epidermal homeostasis involving pathways other than those typically associated with primary cilia.
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Affiliation(s)
- Mandy J Croyle
- Department of Cell Biology, University of Alabama at Birmingham Medical School, Birmingham, AL 35294, USA
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11
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Doupé DP, Klein AM, Simons BD, Jones PH. The ordered architecture of murine ear epidermis is maintained by progenitor cells with random fate. Dev Cell 2010; 18:317-23. [PMID: 20159601 DOI: 10.1016/j.devcel.2009.12.016] [Citation(s) in RCA: 179] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 11/27/2009] [Accepted: 12/16/2009] [Indexed: 12/31/2022]
Abstract
Typical murine epidermis has a patterned structure, seen clearly in ear skin, with regular columns of differentiated cells overlying the proliferative basal layer. It has been proposed that each column is a clonal epidermal proliferative unit maintained by a central stem cell and its transit amplifying cell progeny. An alternative hypothesis is that proliferating basal cells have random fate, the probability of generating cycling or differentiated cells being balanced so homeostasis is achieved. The stochastic model seems irreconcilable with an ordered tissue. Here we use lineage tracing to reveal that basal cells generate clones with highly irregular shapes that contribute progeny to multiple columns. Basal cell fate and cell cycle time is random. Cell columns form due to the properties of postmitotic cells. We conclude that the ordered architecture of the epidermis is maintained by a stochastic progenitor cell population, providing a simple and robust mechanism of homeostasis.
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Affiliation(s)
- David P Doupé
- MRC Cancer Cell Unit, Hutchison-MRC Research Centre, Cambridge CB2 0XZ, UK
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12
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Youssef KK, Van Keymeulen A, Lapouge G, Beck B, Michaux C, Achouri Y, Sotiropoulou PA, Blanpain C. Identification of the cell lineage at the origin of basal cell carcinoma. Nat Cell Biol 2010; 12:299-305. [PMID: 20154679 DOI: 10.1038/ncb2031] [Citation(s) in RCA: 293] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 01/25/2010] [Indexed: 12/12/2022]
Abstract
For most types of cancers, the cell at the origin of tumour initiation is still unknown. Here, we used mouse genetics to identify cells at the origin of basal cell carcinoma (BCC), which is one of the most frequently occurring types of cancer in humans, and can result from the activation of the Hedgehog signalling pathway. Using mice conditionally expressing constitutively active Smoothened mutant (SmoM2), we activated Hedgehog signalling in different cellular compartments of the skin epidermis and determined in which compartments Hedgehog activation induces BCC formation. Activation of SmoM2 in hair follicle bulge stem cells and their transient amplifying progenies did not induce cancer formation, demonstrating that BCC does not originate from bulge stem cells, as previously thought. Using clonal analysis, we found that BCC arises from long-term resident progenitor cells of the interfollicular epidermis and the upper infundibulum. Our studies uncover the cells at the origin of BCC in mice and demonstrate that expression of differentiation markers in tumour cells is not necessarily predictive of the cancer initiating cells.
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13
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Blanpain C, Fuchs E. Epidermal homeostasis: a balancing act of stem cells in the skin. Nat Rev Mol Cell Biol 2009; 10:207-17. [PMID: 19209183 DOI: 10.1038/nrm2636] [Citation(s) in RCA: 878] [Impact Index Per Article: 58.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The skin epidermis and its array of appendages undergo ongoing renewal by a process called homeostasis. Stem cells in the epidermis have a crucial role in maintaining tissue homeostasis by providing new cells to replace those that are constantly lost during tissue turnover or following injury. Different resident skin stem cell pools contribute to the maintenance and repair of the various epidermal tissues of the skin, including interfollicular epidermis, hair follicles and sebaceous glands. Interestingly, the basic mechanisms and signalling pathways that orchestrate epithelial morphogenesis in the skin are reused during adult life to regulate skin homeostasis.
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Affiliation(s)
- Cédric Blanpain
- Université Libre de Bruxelles, Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, 808, route de Lennik, 1070 Bruxelles, Belgium
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Strachan LR, Ghadially R. Tiers of clonal organization in the epidermis: the epidermal proliferation unit revisited. ACTA ACUST UNITED AC 2008; 4:149-57. [PMID: 18574734 DOI: 10.1007/s12015-008-9020-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
As one of the most proliferative tissues in adult mammals, the epidermis is a good example of the precise regulation necessary between stem cell self-renewal and differentiation. The epidermis is derived from ectodermal progenitor cells and contains three distinct classes of cells: epidermal stem cells which are capable of infinite rounds of cell division; their immediate descendants, transient amplifying cells, which are capable of numerous but finite rounds of cell division; and finally, non-dividing, differentiating cells (Aberdam in Cell and Tissue Research 331:103-107, 2008). This proliferative hierarchy must be tightly regulated both temporally and spatially during epidermal development and homeostasis in order to prevent uncontrolled growth leading to hyperproliferative states and/or tumorigenesis. Historically, the most basic unit of epidermal proliferation has been described as the epidermal proliferation unit (EPU). The EPU, as originally characterized by Christophers, Potten and Mackenzie, is a proliferation unit consisting of approximately 10 basal cells with a clonogenic cell in the center and overlaid by the suprabasal and corneocyte progeny (reviewed in Potten, C. S. (1974). The epidermal proliferative unit: the possible role of the central basal cell. Cell and Tissue Kinetics, 7(1), 77-88). Numerous researchers have identified this classical EPU structure, consisting of approximately 20 cells, in a variety of mammalian skin sources. Recently however, lineage analyses have provided evidence for much larger clonal epidermal units consisting of hundreds to thousands of cells. Furthermore, cutaneous mosaicism as well as a variety of cutaneous pathologies indicate that clonal areas extend to whole patches of mammalian skin many centimeters across. In this review we revisit four decades of experimental evidence and put forward a model of clonal units derived from multiple classes of epidermal progenitors ranging from the largest and most primitive units, clonal ectodermal units, to epidermal stem cell units, and finally, to the most basic structural unit, the EPU.
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Affiliation(s)
- Lauren R Strachan
- Department of Dermatology, University of California San Francisco, San Francisco, CA 94143, USA
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15
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Jones P, Simons BD. Epidermal homeostasis: do committed progenitors work while stem cells sleep? Nat Rev Mol Cell Biol 2008; 9:82-8. [PMID: 17987044 DOI: 10.1038/nrm2292] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Tracking the fate of cells in murine epidermis in vivo has revealed that a committed progenitor cell population can maintain normal adult tissue in the long term without support from a long-lived, self-renewing population of stem cells. Here, we argue that these results challenge the dogma that stem-cell proliferation is required for the cellular homeostasis of the epidermis and other adult tissues, with important implications for tissue physiology and disease.
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Affiliation(s)
- Philip Jones
- Philip Jones is at the MRC Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, CB2 2XZ, UK.
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16
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Jones P, Simons BD. OPINION Epidermal homeostasis: do committed progenitors work while stem cells sleep? Nat Rev Mol Cell Biol 2008. [DOI: 10.1038/nrm2292x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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17
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Jones PH, Simons BD, Watt FM. Sic Transit Gloria: Farewell to the Epidermal Transit Amplifying Cell? Cell Stem Cell 2007; 1:371-81. [DOI: 10.1016/j.stem.2007.09.014] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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18
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Ro S, Rannala B. Inferring somatic mutation rates using the stop-enhanced green fluorescent protein mouse. Genetics 2007; 177:9-16. [PMID: 17603123 PMCID: PMC2013726 DOI: 10.1534/genetics.106.069310] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Accepted: 06/13/2007] [Indexed: 02/06/2023] Open
Abstract
A new method is developed for estimating rates of somatic mutation in vivo. The stop-enhanced green fluorescent protein (EGFP) transgenic mouse carries multiple copies of an EGFP gene with a premature stop codon. The gene can revert to a functional form via point mutations. Mice treated with a potent mutagen, N-ethyl-N-nitrosourea (ENU), and mice treated with a vehicle alone are assayed for mutations in liver cells. A stochastic model is developed to model the mutation and gene expression processes and maximum-likelihood estimators of the model parameters are derived. A likelihood-ratio test (LRT) is developed for detecting mutagenicity. Parametric bootstrap simulations are used to obtain confidence intervals of the parameter estimates and to estimate the significance of the LRT. The LRT is highly significant (alpha < 0.01) and the 95% confidence interval for the relative effect of the mutagen (the ratio of the rate of mutation during the interval of mutagen exposure to the rate of background mutation) ranges from a minimum 200-fold effect of the mutagen to a maximum 2000-fold effect.
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Affiliation(s)
- Simon Ro
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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19
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Klein AM, Doupé DP, Jones PH, Simons BD. Kinetics of cell division in epidermal maintenance. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:021910. [PMID: 17930068 DOI: 10.1103/physreve.76.021910] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 06/01/2007] [Indexed: 05/25/2023]
Abstract
The rules governing cell division and differentiation are central to understanding the mechanisms of development, aging, and cancer. By utilizing inducible genetic labeling, recent studies have shown that the clonal population in transgenic mouse epidermis can be tracked in vivo. Drawing on these results, we explain how clonal fate data may be used to infer the rules of cell division and differentiation underlying the maintenance of adult murine tail-skin. We show that the rates of cell division and differentiation may be evaluated by considering the long-time and short-time clone fate data, and that the data is consistent with cells dividing independently rather than synchronously. Motivated by these findings, we consider a mechanism for cancer onset based closely on the model for normal adult skin. By analyzing the expected changes to clonal fate in cancer emerging from a simple two-stage mutation, we propose that clonal fate data may provide a novel method for studying the earliest stages of the disease.
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Affiliation(s)
- Allon M Klein
- Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom
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20
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Clayton E, Doupé DP, Klein AM, Winton DJ, Simons BD, Jones PH. A single type of progenitor cell maintains normal epidermis. Nature 2007; 446:185-9. [PMID: 17330052 DOI: 10.1038/nature05574] [Citation(s) in RCA: 618] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Accepted: 11/24/2006] [Indexed: 11/09/2022]
Abstract
According to the current model of adult epidermal homeostasis, skin tissue is maintained by two discrete populations of progenitor cells: self-renewing stem cells; and their progeny, known as transit amplifying cells, which differentiate after several rounds of cell division. By making use of inducible genetic labelling, we have tracked the fate of a representative sample of progenitor cells in mouse tail epidermis at single-cell resolution in vivo at time intervals up to one year. Here we show that clone-size distributions are consistent with a new model of homeostasis involving only one type of progenitor cell. These cells are found to undergo both symmetric and asymmetric division at rates that ensure epidermal homeostasis. The results raise important questions about the potential role of stem cells on tissue maintenance in vivo.
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Affiliation(s)
- Elizabeth Clayton
- MRC Cancer Cell Unit, Hutchison-MRC Research Centre, Cambridge CB2 0XZ, UK
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