Notch1 maintains dormancy of olfactory horizontal basal cells, a reserve neural stem cell

The remarkable capacity of the adult olfactory epithelium (OE) to regenerate fully both neurosensory and nonneuronal cell types after severe epithelial injury depends on life-long persistence of two stem cell populations: the horizontal basal cells (HBCs), which are quiescent and held in reserve, and mitotically active globose basal cells. It has recently been demonstrated that down-regulation of the ΔN form of the transcription factor p63 is both necessary and sufficient to release HBCs from dormancy. However, the mechanisms by which p63 is down-regulated after acute OE injury remain unknown. To identify the cellular source of potential signaling mechanisms, we assessed HBC activation after neuron-only and sustentacular cell death. We found that ablation of sustentacular cells is sufficient for HBC activation to multipotency. By expression analysis, next-generation sequencing, and immunohistochemical examination, down-regulation of Notch pathway signaling is coincident with HBC activation. Therefore, using HBC-specific conditional knockout of Notch receptors and overexpression of N1ICD, we show that Notch signaling maintains p63 levels and HBC dormancy, in contrast to its suppression of p63 expression in other tissues. Additionally, Notch1, but not Notch2, is required to maintain HBC dormancy after selective neuronal degeneration. Taken together, our data indicate that the activation of HBCs observed after tissue injury or sustentacular cell ablation is caused by the reduction/elimination of Notch signaling on HBCs; elimination of Jagged1 expressed by sustentacular cells may be the ligand responsible.

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Transcription factor p63 controls the reserve status but not the stemness of horizontal basal cells in the olfactory epithelium

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1512272112 ◽

2015 ◽

Vol 112 (36) ◽

pp. E5068-E5077 ◽

Cited By ~ 37

Author(s):

Nikolai Schnittke ◽

Daniel B. Herrick ◽

Brian Lin ◽

Jesse Peterson ◽

Julie H. Coleman ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Olfactory Epithelium ◽

Tissue Injury ◽

Cell Types ◽

Stem Cell Population ◽

Basal Cells ◽

Loss Of Function ◽

Down Regulation ◽

Horizontal Basal Cells

Adult tissue stem cells can serve two broad functions: to participate actively in the maintenance and regeneration of a tissue or to wait in reserve and participate only when activated from a dormant state. The adult olfactory epithelium, a site for ongoing, life-long, robust neurogenesis, contains both of these functional stem cell types. Globose basal cells (GBCs) act as the active stem cell population and can give rise to all the differentiated cells found in the normal tissue. Horizontal basal cells (HBCs) act as reserve stem cells and remain dormant unless activated by tissue injury. Here we show that HBC activation following injury by the olfactotoxic gas methyl bromide is coincident with the down-regulation of protein 63 (p63) but anticipates HBC proliferation. Gain- and loss-of-function studies show that this down-regulation of p63 is necessary and sufficient for HBC activation. Moreover, activated HBCs give rise to GBCs that persist for months and continue to act as bona fide stem cells by participating in tissue maintenance and regeneration over the long term. Our analysis provides mechanistic insight into the dynamics between tissue stem cell subtypes and demonstrates that p63 regulates the reserve state but not the stem cell status of HBCs.

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Regulation of ERK basal and pulsatile activity control proliferation and exit from the stem cell compartment in mammalian epidermis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2006965117 ◽

2020 ◽

Vol 117 (30) ◽

pp. 17796-17807 ◽

Cited By ~ 4

Author(s):

Toru Hiratsuka ◽

Ignacio Bordeu ◽

Gunnar Pruessner ◽

Fiona M. Watt

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Basal Cells ◽

Mammalian Development ◽

Down Regulation ◽

Cell Dynamics ◽

Erk Mapk ◽

Differentiated Cells ◽

Erk Activity

Fluctuation in signal transduction pathways is frequently observed during mammalian development. However, its role in regulating stem cells has not been explored. Here we tracked spatiotemporal ERK MAPK dynamics in human epidermal stem cells. While stem cells and differentiated cells were distinguished by high and low stable basal ERK activity, respectively, we also found cells with pulsatile ERK activity. Transitions from Basalhi-Pulselo(stem) to Basalhi-Pulsehi, Basalmid-Pulsehi, and Basallo-Pulselo(differentiated) cells occurred in expanding keratinocyte colonies and in response to differentiation stimuli. Pharmacological inhibition of ERK induced differentiation only when cells were in the Basalmid-Pulsehistate. Basal ERK activity and pulses were differentially regulated by DUSP10 and DUSP6, leading us to speculate that DUSP6-mediated ERK pulse down-regulation promotes initiation of differentiation, whereas DUSP10-mediated down-regulation of mean ERK activity promotes and stabilizes postcommitment differentiation. Levels of MAPK1/MAPK3 transcripts correlated with DUSP6 and DUSP10 transcripts in individual cells, suggesting that ERK activity is negatively regulated by transcriptional and posttranslational mechanisms. When cells were cultured on a topography that mimics the epidermal−dermal interface, spatial segregation of mean ERK activity and pulses was observed. In vivo imaging of mouse epidermis revealed a patterned distribution of basal cells with pulsatile ERK activity, and down-regulation was linked to the onset of differentiation. Our findings demonstrate that ERK MAPK signal fluctuations link kinase activity to stem cell dynamics.

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Role of Jagged1-mediated Notch Signaling Activation in the Differentiation and Stratification of the Human Limbal Epithelium

Cells ◽

10.3390/cells9091945 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1945

Author(s):

Sheyla González ◽

Maximilian Halabi ◽

David Ju ◽

Matthew Tsai ◽

Sophie X. Deng

Keyword(s):

Notch Signaling ◽

Progenitor Cell ◽

Basal Layer ◽

Notch Signaling Pathway ◽

Basal Cells ◽

Proliferation Markers ◽

Limbal Epithelium ◽

Asymmetric Divisions ◽

Signaling Activation

The Notch signaling pathway plays a key role in proliferation and differentiation. We investigated the effect of Jagged 1 (Jag1)-mediated Notch signaling activation in the human limbal stem/progenitor cell (LSC) population and the stratification of the limbal epithelium in vitro. After Notch signaling activation, there was a reduction in the amount of the stem/progenitor cell population, epithelial stratification, and expression of proliferation markers. There was also an increase of the corneal epithelial differentiation. In the presence of Jag1, asymmetric divisions were decreased, and the expression pattern of the polarity protein Par3, normally present at the apical-lateral membrane of basal cells, was dispersed in the cells. We propose a mechanism in which Notch activation by Jag1 decreases p63 expression at the basal layer, which in turn reduces stratification by decreasing the number of asymmetric divisions and increases differentiation.

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Crosstalk between NOTCH and AKT signaling during murine megakaryocyte lineage specification

Blood ◽

10.1182/blood-2011-01-328567 ◽

2011 ◽

Vol 118 (5) ◽

pp. 1264-1273 ◽

Cited By ~ 47

Author(s):

Melanie G. Cornejo ◽

Vinciane Mabialah ◽

Stephen M. Sykes ◽

Tulasi Khandan ◽

Cristina Lo Celso ◽

...

Keyword(s):

Stem Cell ◽

Notch Signaling ◽

Signaling Pathway ◽

Hematopoietic Stem Cell ◽

Stem Cell Differentiation ◽

Notch Signaling Pathway ◽

Developmental Pathways ◽

Lineage Specification ◽

Hematopoietic Stem

Abstract The NOTCH signaling pathway is implicated in a broad range of developmental processes, including cell fate decisions. However, the molecular basis for its role at the different steps of stem cell lineage commitment is unclear. We recently identified the NOTCH signaling pathway as a positive regulator of megakaryocyte lineage specification during hematopoiesis, but the developmental pathways that allow hematopoietic stem cell differentiation into the erythro-megakaryocytic lineages remain controversial. Here, we investigated the role of downstream mediators of NOTCH during megakaryopoiesis and report crosstalk between the NOTCH and PI3K/AKT pathways. We demonstrate the inhibitory role of phosphatase with tensin homolog and Forkhead Box class O factors on megakaryopoiesis in vivo. Finally, our data annotate developmental mechanisms in the hematopoietic system that enable a decision to be made either at the hematopoietic stem cell or the committed progenitor level to commit to the megakaryocyte lineage, supporting the existence of 2 distinct developmental pathways.

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Notch Signaling Is Required to Maintain All Neural Stem Cell Populations – Irrespective of Spatial or Temporal Niche

Developmental Neuroscience ◽

10.1159/000090751 ◽

2006 ◽

Vol 28 (1-2) ◽

pp. 34-48 ◽

Cited By ~ 68

Author(s):

Tania O. Alexson ◽

Seiji Hitoshi ◽

Brenda L. Coles ◽

Alan Bernstein ◽

Derek van der Kooy

Keyword(s):

Stem Cell ◽

Notch Signaling ◽

Neural Stem Cell ◽

Cell Populations ◽

Temporal Niche ◽

Stem Cell Populations

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Ex vivo expansion of human hematopoietic stem and progenitor cells

Blood ◽

10.1182/blood-2011-01-283606 ◽

2011 ◽

Vol 117 (23) ◽

pp. 6083-6090 ◽

Cited By ~ 187

Author(s):

Ann Dahlberg ◽

Colleen Delaney ◽

Irwin D. Bernstein

Keyword(s):

Stem Cell ◽

Growth Factors ◽

Notch Signaling ◽

Progenitor Cells ◽

Ex Vivo ◽

Ex Vivo Expansion ◽

Hematopoietic Growth Factors ◽

Self Renewal ◽

Hematopoietic Stem ◽

Stem And Progenitor Cells

AbstractDespite progress in our understanding of the growth factors that support the progressive maturation of the various cell lineages of the hematopoietic system, less is known about factors that govern the self-renewal of hematopoietic stem and progenitor cells (HSPCs), and our ability to expand human HSPC numbers ex vivo remains limited. Interest in stem cell expansion has been heightened by the increasing importance of HSCs in the treatment of both malignant and nonmalignant diseases, as well as their use in gene therapy. To date, most attempts to ex vivo expand HSPCs have used hematopoietic growth factors but have not achieved clinically relevant effects. More recent approaches, including our studies in which activation of the Notch signaling pathway has enabled a clinically relevant ex vivo expansion of HSPCs, have led to renewed interest in this arena. Here we briefly review early attempts at ex vivo expansion by cytokine stimulation followed by an examination of our studies investigating the role of Notch signaling in HSPC self-renewal. We will also review other recently developed approaches for ex vivo expansion, primarily focused on the more extensively studied cord blood–derived stem cell. Finally, we discuss some of the challenges still facing this field.

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Hypoxia inhibits senescence and maintains mesenchymal stem cell properties through down-regulation of E2A-p21 by HIF-TWIST

Blood ◽

10.1182/blood-2010-05-287508 ◽

2011 ◽

Vol 117 (2) ◽

pp. 459-469 ◽

Cited By ~ 212

Author(s):

Chih-Chien Tsai ◽

Yann-Jang Chen ◽

Tu-Lai Yew ◽

Ling-Lan Chen ◽

Jir-You Wang ◽

...

Keyword(s):

Stem Cell ◽

Hypoxia Inducible Factor ◽

Human Mesenchymal Stem Cells ◽

Telomerase Activity ◽

Rapid Expansion ◽

Low Density ◽

Down Regulation ◽

Differentiation Potential ◽

Hypoxic Conditions ◽

Population Doublings

Abstract Although low-density culture provides an efficient method for rapid expansion of human mesenchymal stem cells (MSCs), MSCs enriched by this method undergo senescence and lose their stem cell properties, which could be preserved by combining low-density and hypoxic culture. The mechanism was mediated through direct down-regulation of E2A-p21 by the hypoxia-inducible factor–1α (HIF-1α)–TWIST axis. Expansion under normoxia induced E2A and p21 expression, which were abrogated by overexpression of TWIST, whereas siRNA against TWIST up-regulated E2A and p21 in hypoxic cells. Furthermore, siRNA against p21 in normoxic cells enhanced proliferation and increased differentiation potential, whereas overexpression of p21 in hypoxic cells induced a decrease in proliferation and a loss of differentiation capacity. More importantly, MSCs expanded under hypoxic conditions by up to 100 population doublings, exhibited telomerase activity with maintained telomere length, normal karyotyping, and intact genetic integrity, and did not form tumors. These results support low-density hypoxic culture as a method for efficiently expanding MSCs without losing stem cell properties or increasing tumorigenicity.

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Repression of differentiation genes by Hes transcription factors fuels neural tumour growth in Drosophila

The International Journal of Developmental Biology ◽

10.1387/ijdb.210187cd ◽

2021 ◽

Author(s):

Chrysanthi Voutyraki ◽

Alexandros Choromidis ◽

Vasiliki Theodorou ◽

Christina Efraimoglou ◽

Gerasimos Anagnostopoulos ◽

...

Keyword(s):

Stem Cell ◽

Transcription Factors ◽

Notch Signaling ◽

Tumour Growth ◽

Metabolic Reprogramming ◽

Cell Physiology ◽

Malignant Tumours ◽

Rna Profiling ◽

A Cell

Background: Neural stem cells (NSC) in divide asymmetrically to generate a cell that retains stem cell identity and another that is routed to differentiation. Prolonged mitotic activity of the NSCs gives rise to the plethora of neurons and glial cells that wire the brain and nerve cord. Genetic insults, such as excess of Notch signaling, perturb the normal NSC proliferation programs and trigger the formation of NSC hyperplasias, that can later progress to malignancies. Hes proteins are crucial mediators of Notch signaling and in the NSC context they act by repressing a cohort of early pro-differentiation transcription factors. Downregulation of these pro-differentiation factors makes NSC progeny cells susceptible to adopting an aberrant stem cell program. We have recently shown that Hes overexpression in Drosophila leads to NSC hyperplasias that progress to malignant tumours after allografting to adult hosts. Methods: We have combined genetic analysis, tissue allografting and transcriptomic approaches to address the role of Hes genes in NSC malignant transformation. Results: We show that the E(spl) genes are important mediators in the progression of Notch hyperplasias to malignancy, since allografts lacking the E(spl) genes grow much slower. We further present RNA profiling of Hes-induced tumours at two different stages after allografting. We find that the same cohort of differentiation-promoting transcription factors that are repressed in the primary hyperplasias continue to be downregulated after transplantation. This is accompanied by an upregulation of stress-response genes and metabolic reprogramming. Conclusions: The combination of dedifferentiation and cell physiology changes most likely drive tumour growth.

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