201
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Faubert A, Lessard J, Sauvageau G. Are genetic determinants of asymmetric stem cell division active in hematopoietic stem cells? Oncogene 2004; 23:7247-55. [PMID: 15378084 DOI: 10.1038/sj.onc.1207944] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Stem cells have acquired a golden glow in the past few years as they represent possible tools for reversing the damage wreak on organs. These cells are found not only in major regenerative tissues, such as the epithelia, blood and testes, but also in 'static tissues', such as the nervous system and liver, where they play a central role in tissue growth and maintenance. The mechanism by which stem cells maintain populations of highly differentiated, short-lived cells seems to involve a critical balance between alternate fates: daughter cells either maintain stem cell identity or initiate differentiation. Recent studies in lower organisms have unveiled the regulatory mechanisms of asymmetric stem cell divisions. In these models, the surrounding environment likely provides key instructive signals for the cells to choose one fate over another. Our understanding now extends to the intrinsic mechanisms of cell polarity that influence asymmetrical stem cell divisions. This article focuses on the genetic determinants of asymmetric stem cell divisions in lower organisms as a model for studying the process of self-renewal of mammalian hematopoietic stem cells.
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Affiliation(s)
- Amélie Faubert
- Laboratory of Molecular Genetics of Hematopoietic Stem Cells, Institute of Research in Immunology and Cancer, University of Montreal, Quebec, Canada
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202
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Wang W, Struhl G. Drosophila Epsin mediates a select endocytic pathway that DSL ligands must enter to activate Notch. Development 2004; 131:5367-80. [PMID: 15469974 DOI: 10.1242/dev.01413] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent findings suggest that Delta/Serrate/Lag2 (DSL) signals activate Notch by an unprecedented mechanism that requires the ligands to be endocytosed in signal-sending cells to activate the receptor in signal-receiving cells. Here, we show that cells devoid of Epsin, a conserved adaptor protein for Clathrin-mediated endocytosis, behave normally except that they cannot send DSL signals. Surprisingly, we find that Epsin is not required for bulk endocytosis of DSL proteins. Instead, Epsin appears to be essential for targeting DSL proteins to a special endocytic pathway that they must enter to acquire signaling activity. We present evidence that DSL proteins must be mono-ubiquitinated to be targeted by Epsin to this pathway. Furthermore, we show that the requirements for both Epsin and mono-ubiquitination can be bypassed by introducing the internalization signal that mediates endocytosis and recycling of the Low Density Lipoprotein (LDL) receptor. We propose that Epsin is essential for DSL signaling because it targets mono-ubiquitinated DSL proteins to an endocytic recycling compartment that they must enter to be converted into active ligands. Alternatively Epsin may be required to target mono-ubiquitinated DSL proteins to a particular subclass of coated pits that have special properties essential for Notch activation.
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Affiliation(s)
- Weidong Wang
- Howard Hughes Medical Institute, Department of Genetics and Development, Columbia University College of Physicians and Surgeons, 701 West 168th Street, New York, NY 10032, USA
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203
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Abstract
Notch signaling is required for normal T cell development. However, Notch expression must be precisely regulated as constitutive Notch signaling leads to T cell lymphomas. Recent evidence has provided insights into potential mechanisms of Notch-mediated lymphomagenesis and its relationship to T cell development. The evidence suggests that Notch likely interacts with several important cellular pathways and can cooperate with other oncogenes during lymphomagenesis. In particular, Notch appears to modulate pre-TCR signaling, inhibit the E2A pathway, and in murine leukemia models, frequently cooperates with Myc, E2A-PBX and dominant negative Ikaros dysregulation. This review will present current knowledge in these areas and explore theories on Notch-mediated T cell lymphomagenesis.
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204
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Szymkiewicz I, Shupliakov O, Dikic I. Cargo- and compartment-selective endocytic scaffold proteins. Biochem J 2004; 383:1-11. [PMID: 15219178 PMCID: PMC1134037 DOI: 10.1042/bj20040913] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Accepted: 06/24/2004] [Indexed: 01/05/2023]
Abstract
The endocytosis of membrane receptors is a complex and tightly controlled process that is essential for maintaining cellular homoeostasis. The removal of receptors from the cell surface can be constitutive or ligand-induced, and occurs in a clathrin-dependent or -independent manner. The recruitment of receptors into specialized membrane domains, the formation of vesicles and the trafficking of receptors together with their ligands within endocytic compartments are regulated by reversible protein modifications, and multiple protein-protein and protein-lipid interactions. Recent reports describe a variety of multidomain molecules that facilitate receptor endocytosis and function as platforms for the assembly of protein complexes. These scaffold proteins typically act in a cargo-specific manner, recognizing one or more receptor types, or function at the level of endocytic cellular microcompartments by controlling the movement of cargo molecules and linking endocytic machineries to signalling pathways. In the present review we summarize present knowledge on endocytic scaffold molecules and discuss their functions.
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Key Words
- cargo
- endocytosis
- microcompartment
- scaffold
- alix, alg-2 (apoptosis-linked gene 2)-interacting protein x
- anth domain, ap180 n-terminal homology domain
- ap-2, adaptor protein-2
- arh, autosomal recessive hypercholesterolaemia
- bar domain, bin/amphiphysin/rvs domain
- cd2ap, cd2-associated protein
- cin85, cbl-interacting protein of 85 kda
- dab2, disabled-2
- eea1, early endosome antigen 1
- egfr, epidermal growth factor receptor
- eh domain, eps15 homology domain
- enth domain, epsin n-terminal homology domain
- escrt, endosomal sorting complexes required for transport
- fyve, fab1p, yotb, vac1p and eea1
- gap, gtpase-activating protein
- gpcr, g-protein-coupled receptor
- hrs, hepatocyte growth factor-regulated tyrosine kinase substrate
- lbpa, lysobiphosphatidic acid
- ldl, low-density lipoprotein
- lnx, ligand of numb protein x
- mvb, multivesicular body
- nak, numb-associated kinase
- nsf, n-ethylmaleimide-sensitive fusion protein
- pon, partner of numb
- ptb domain, phosphotyrosine-binding domain
- rtk, receptor tyrosine kinase
- sh3, src homology 3
- snare, soluble nsf attachment protein receptor
- stam, signal-transducing adaptor molecule
- tcr, t-cell receptor
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Affiliation(s)
- Iwona Szymkiewicz
- *Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
| | - Oleg Shupliakov
- †Department of Neuroscience, CEDB, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Ivan Dikic
- *Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
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205
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Kiaris H, Politi K, Grimm LM, Szabolcs M, Fisher P, Efstratiadis A, Artavanis-Tsakonas S. Modulation of notch signaling elicits signature tumors and inhibits hras1-induced oncogenesis in the mouse mammary epithelium. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:695-705. [PMID: 15277242 PMCID: PMC1618582 DOI: 10.1016/s0002-9440(10)63333-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Deregulation of Notch signaling, which normally affects a broad spectrum of cell fates, has been implicated in various neoplastic conditions. Here we describe a transgenic mouse model, which demonstrates that expression of a constitutively active form of the Notch1 receptor in the mammary epithelium induces the rapid development of pregnancy/lactation-dependent neoplasms that consistently exhibit a characteristic histopathological pattern. These signature tumors retain the ability to respond to apoptotic stimuli and regress on initiation of mammary gland involution, but eventually appear to progress in subsequent pregnancies to nonregressing malignant adenocarcinomas. Additionally, we present evidence indicating that cyclin D1 is an in vivo target of Notch signals in the mammary glands and demonstrate that we can effectively inhibit Hras1-driven, cyclin D1-dependent mammary oncogenesis by transgenic expression of the Notch antagonist Deltex.
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MESH Headings
- Adenocarcinoma/pathology
- Animals
- Apoptosis
- Carrier Proteins/metabolism
- Cell Transformation, Neoplastic/genetics
- Cyclin D1
- Female
- Gene Expression Regulation, Neoplastic
- Genes, ras
- Humans
- Lactation
- Male
- Mammary Glands, Animal/embryology
- Mammary Glands, Animal/growth & development
- Mammary Neoplasms, Animal/genetics
- Mammary Neoplasms, Animal/pathology
- Mammary Tumor Virus, Mouse/genetics
- Mammary Tumor Virus, Mouse/physiology
- Membrane Proteins/metabolism
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Transgenic
- Pregnancy
- Receptors, Notch
- Signal Transduction/physiology
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Affiliation(s)
- Hippokratis Kiaris
- Department of Cell Biology, Massachusetts General Hospital Center for Cancer Research, Department of Cell Biology, Harvard Medical School, 13th St., Bldg. 149, Charlestown, MA 02129, USA
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206
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Kovall RA, Hendrickson WA. Crystal structure of the nuclear effector of Notch signaling, CSL, bound to DNA. EMBO J 2004; 23:3441-51. [PMID: 15297877 PMCID: PMC516623 DOI: 10.1038/sj.emboj.7600349] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 07/08/2004] [Indexed: 11/08/2022] Open
Abstract
Notch signaling is a conserved pathway of communication between neighboring cells that results in cell fate specification, and CSL is the universal transcriptional effector of Notch signaling. The Notch intracellular domain translocates to the nucleus after proteolytic release upon Notch extracellular engagement, and there it displaces corepressors from DNA-bound CSL and recruits activators of Notch target genes. Here we report the 2.85 A crystal structure of CSL with a target DNA. CSL comprises three structurally integrated domains: its amino (NTD)- and carboxy (CTD)-terminal domains are strikingly similar to those of Rel transcription factors, but a surprising beta-trefoil domain (BTD) is inserted between them. CSL-bound DNA is recognized specifically by conserved residues from NTD and BTD. A hydrophobic pocket on BTD is identified as the likely site of Notch interaction with CSL, which has functional implications for the mechanism of Notch signaling.
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Affiliation(s)
- Rhett A Kovall
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY, USA
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA. Tel.: +1 212 305 3456; Fax: +1 212 305 7379; E-mail:
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207
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Shawber CJ, Kitajewski J. Notch function in the vasculature: insights from zebrafish, mouse and man. Bioessays 2004; 26:225-34. [PMID: 14988924 DOI: 10.1002/bies.20004] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Vascular development entails multiple cell-fate decisions to specify a diverse array of vascular structures. Notch proteins are signaling receptors that regulate cell-fate determination in a variety of cell types. The finding that Notch genes are robustly expressed in the vasculature suggests roles for Notch in guiding endothelial and associated mural cells through the myriad of cell-fate decisions needed to form the vasculature. In fact, mice with defects in genes encoding Notch, Notch ligands, and components of the Notch signaling cascade invariably display vascular defects. Human Notch genes are linked to Alagille's Syndrome, a developmental disorder with vascular defects, and CADASIL, a cerebral arteriopathy. Studies in zebrafish, mice and humans indicate that Notch works in conjunction with other angiogenic pathways to pattern and stabilize the vasculature. Here, we will focus on established functions for Notch in vascular remodeling and arterial/venous specification and more speculative roles in vascular homeostasis and organ-specific angiogenesis.
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208
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Jang MS, Miao H, Carlesso N, Shelly L, Zlobin A, Darack N, Qin JZ, Nickoloff BJ, Miele L. Notch-1 regulates cell death independently of differentiation in murine erythroleukemia cells through multiple apoptosis and cell cycle pathways. J Cell Physiol 2004; 199:418-33. [PMID: 15095289 DOI: 10.1002/jcp.10467] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Notch signaling is a potential therapeutic target for various solid and hematopoietic malignancies. We have recently shown that downregulation of Notch-1 expression has significant anti-neoplastic activity in pre-clinical models. However, the mechanisms through which Notch modulation may affect cell fate in cancer remain poorly understood. We had previously shown that Notch-1 prevents apoptosis and is necessary for pharmacologically induced differentiation in murine erythroleukemia (MEL) cells. We investigated the mechanisms of these effects using three experimental strategies: (1) MEL cells stably transfected with antisense Notch-1 or constitutively active Notch-1, (2) activation of Notch-1 by a cell-associated ligand, and (d3) activation of Notch-1 by a soluble peptide ligand. We show that: (1) downregulation of Notch-1 sensitizes MEL cells to apoptosis induced by a Ca(2+) influx or anti-neoplastic drugs; (2) Notch-1 downregulation induces phosphorylation of c-Jun N-terminal kinase (JNK) while constitutive activation of Notch-1 or prolonged exposure to a soluble Notch ligand abolishes it; (3) Notch-1 has dose- and time-dependent effects on the levels of apoptotic inhibitor Bcl-x(L) and cell cycle regulators p21(cip1/waf1), p27(kip1), and Rb; and (4) Notch-1 activation by a cell-associated ligand is accompanied by rapid and transient induction of NF-kappaB DNA-binding activity. The relative effects of Notch-1 signaling on these pathways depend on the levels of Notch-1 expression, the mechanism of activation, and the timing of activation. The relevance of these findings to the role of Notch signaling in differentiation and cancer are discussed.
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Affiliation(s)
- Mei-Shiang Jang
- Cardinal Bernardin Cancer Center, Loyola University Chicago, Maywood, Illinois, USA
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209
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Lai EC, Orgogozo V. A hidden program in Drosophila peripheral neurogenesis revealed: fundamental principles underlying sensory organ diversity. Dev Biol 2004; 269:1-17. [PMID: 15081353 DOI: 10.1016/j.ydbio.2004.01.032] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Revised: 01/22/2004] [Accepted: 01/26/2004] [Indexed: 11/19/2022]
Abstract
How is cell fate diversity reliably achieved during development? Insect sensory organs have been a favorable model system for investigating this question for over 100 years. They are constructed using defined cell lineages that generate a maximum of cell diversity with a minimum number of cell divisions, and display tremendous variety in their morphologies, constituent cell types, and functions. An unexpected realization of the past 5 years is that very diverse sensory organs in Drosophila are produced by astonishingly similar cell lineages, and that their diversity can be largely attributed to only a small repertoire of developmental processes. These include changes in terminal cell differentiation, cell death, cell proliferation, cell recruitment, cell-cell interactions, and asymmetric segregation of cell fate determinants during mitosis. We propose that most Drosophila sensory organs are built from an archetypal lineage, and we speculate about how this stereotyped pattern of cell divisions may have been built during evolution.
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Affiliation(s)
- Eric C Lai
- Howard Hughes Medical Institute, 545 Life Sciences Addition, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
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210
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Yang X, Klein R, Tian X, Cheng HT, Kopan R, Shen J. Notch activation induces apoptosis in neural progenitor cells through a p53-dependent pathway. Dev Biol 2004; 269:81-94. [PMID: 15081359 DOI: 10.1016/j.ydbio.2004.01.014] [Citation(s) in RCA: 237] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2003] [Revised: 01/13/2004] [Accepted: 01/14/2004] [Indexed: 10/26/2022]
Abstract
Notch signaling is involved in a variety of cell-fate decisions during development. Here we investigate the role of Notch signaling in apoptotic cell death of neural progenitors through the generation and analysis of cell type-specific conditional transgenic and knockout mice. We show that conditional expression of a constitutively active form of Notch1 in early neural progenitor cells, but not postmitotic neurons, selectively induces extensive apoptosis, resulting in a markedly reduced progenitor population. Conversely, attenuation of Notch signaling in Notch1 conditional knockout or Presenilin-1-/- mice results in reduced apoptosis of early neural progenitor cells. Furthermore, Notch activation in neural progenitor cells leads to elevated levels of nuclear p53 and transcriptional upregulation of the target genes Bax and Noxa, and the promotion of apoptotic cell death by Notch activation is completely suppressed by p53 deficiency. Together, these complementary gain-of-function and loss-of-function studies reveal a previously unappreciated role of Notch signaling in the regulation of apoptotic cell death during early mammalian neural development.
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Affiliation(s)
- Xudong Yang
- Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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211
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Abstract
Notch is a transmembrane receptor that mediates local cell-cell communication and coordinates a signaling cascade present in all animal species studied to date. Notch signaling is used widely to determine cell fates and to regulate pattern formation; its dysfunction results in a tremendous variety of developmental defects and adult pathologies. This primer describes the mechanism of Notch signal transduction and how it is used to control the formation of biological patterns.
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Affiliation(s)
- Eric C Lai
- Howard Hughes Medical Institute, 545 Life Sciences Addition, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA.
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212
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Li Y, Baker NE. The roles of cis-inactivation by Notch ligands and of neuralized during eye and bristle patterning in Drosophila. BMC DEVELOPMENTAL BIOLOGY 2004; 4:5. [PMID: 15113404 PMCID: PMC420236 DOI: 10.1186/1471-213x-4-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Accepted: 04/27/2004] [Indexed: 11/17/2022]
Abstract
Background The receptor protein Notch and its ligand Delta are expressed throughout proneural regions yet non-neural precursor cells are defined by Notch activity and neural precursor cells by Notch inactivity. Not even Delta overexpression activates Notch in neural precursor cells. It is possible that future neural cells are protected by cis-inactivation, in which ligands block activation of Notch within the same cell. The Delta-ubiquitin ligase Neuralized has been proposed to antagonize cis-inactivation, favoring Notch activation. Cis-inactivation and role of Neuralized have not yet been studied in tissues where neural precursor cells are resistant to nearby Delta, however, such as the R8 cells of the eye or the bristle precursor cells of the epidermis. Results Overexpressed ligands could block Notch signal transduction cell-autonomously in non-neural cells of the epidermis and retina, but did not activate Notch nonautonomously in neural cells. High ligand expression levels were required for cis-inactivation, and Serrate was more effective than Delta, although Delta is the ligand normally regulating neural specification. Differences between Serrate and Delta depended on the extracellular domains of the respective proteins. Neuralized was found to act cell nonautonomously in signal-sending cells during eye development, inconsistent with the view that Neuralized antagonizes cis-inactivation in non-neural cells. Conclusions Delta and Neuralized contribute cell nonautonomously to Notch signaling in neurogenesis, and the model that Neuralized antagonizes cis-inactivation to permit Notch activity and specification of non-neural cells is refuted. The molecular mechanism rendering Notch insensitive to paracrine activation in neural precursor cells remains uncertain.
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Affiliation(s)
- Yanxia Li
- Department of Molecular Genetics Albert Einstein College of Medicine 1300 Morris Park Avenue Bronx NY 10261 USA
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10261, USA
| | - Nicholas E Baker
- Department of Molecular Genetics Albert Einstein College of Medicine 1300 Morris Park Avenue Bronx NY 10261 USA
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213
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Fuss B, Josten F, Feix M, Hoch M. Cell movements controlled by the Notch signalling cascade during foregut development inDrosophila. Development 2004; 131:1587-95. [PMID: 14998929 DOI: 10.1242/dev.01057] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Notch signalling is an evolutionarily conserved cell interaction mechanism,the role of which in controlling cell fate choices has been studied extensively. Recent studies in both vertebrates and invertebrates revealed additional functions of Notch in proliferation and apoptotic events. We provide evidence for an essential role of the Notch signalling pathway during morphogenetic cell movements required for the formation of the foregut-associated proventriculus organ in the Drosophila embryo. We demonstrate that the activation of the Notch receptor occurs in two rows of boundary cells in the proventriculus primordium. The boundary cells delimit a population of foregut epithelial cells that invaginate into the endodermal midgut layer during proventriculus morphogenesis. Notch receptor activation requires the expression of its ligand Delta in the invaginating cells and apical Notch receptor localisation in the boundary cells. We further show that the movement of the proventricular cells is dependent on the short stop gene that encodes the Drosophila plectin homolog of vertebrates and is a cytoskeletal linker protein of the spectraplakin superfamily. short stop is transcriptionally activated in response to the Notch signalling pathway in boundary cells and we demonstrate that the localisation of the Notch receptor and Notch signalling activity depend on short stop activity. Our results provide a novel link between the Notch signalling pathway and cytoskeletal reorganisation controlling cell movement during the development of foregut-associated organs.
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Affiliation(s)
- Bernhard Fuss
- Universität Bonn, Institut für Molekulare Physiologie und Entwicklungsbiologie, Abteilung für Molekulare Entwicklungsbiologie, Poppelsdorfer Schloss, D-53115 Bonn, Germany
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214
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Radtke F, Wilson A, Mancini SJC, MacDonald HR. Notch regulation of lymphocyte development and function. Nat Immunol 2004; 5:247-53. [PMID: 14985712 DOI: 10.1038/ni1045] [Citation(s) in RCA: 399] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Notch proteins regulate a broad spectrum of cell fate decisions and differentiation processes during fetal and postnatal development. Mammals have four Notch receptors that bind five different ligands. The function of Notch signaling during lymphopoiesis and T cell neoplasia, based on gain-of-function and conditional loss-of-function approaches for the Notch1 receptor, indicates Notch1 is essential in T cell lineage commitment. Recent studies have addressed the involvement of other Notch receptors and ligands as well as their downstream targets, demonstrating additional functions of Notch signaling in embryonic hematopoiesis, intrathymic T cell development, B cell development and peripheral T cell function.
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Affiliation(s)
- Freddy Radtke
- The Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Chemin des Boveresses 155, 1066 Epalinges, Switzerland.
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215
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Abstract
The Drosophila eye is a highly ordered epithelial tissue composed of approximately 750 subunits called ommatidia arranged in a reiterated hexagonal pattern. At higher resolution, observation of the constituent photoreceptors, cone cells, and pigment cells of the eye reveals a highly ordered mosaic of amazing regularity. This relatively simple organization belies the repeated requirement for spatially and temporally coordinated inputs from the Hedgehog (Hh), Wingless (Wg), Decapentaplegic (Dpp), JAK-STAT, Notch, and receptor tyrosine kinase (RTK) signaling pathways. This review will discuss how signaling inputs from the Notch and RTK pathways, superimposed on the developmental history of a cell, facilitate context-specific and appropriate cell fate specification decisions in the developing fly eye. Lessons learned from investigating the combinatorial signal integration strategies underlying Drosophila eye development will likely reveal cell-cell communication paradigms relevant to many aspects of invertebrate and mammalian development. Developmental Dynamics 229:162-175, 2004.
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Affiliation(s)
- Matthew G Voas
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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216
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Ahmed A, Chandra S, Magarinos M, Vaessin H. Echinoid mutants exhibit neurogenic phenotypes and show synergistic interactions with the Notch signaling pathway. Development 2004; 130:6295-304. [PMID: 14623819 DOI: 10.1242/dev.00796] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During neurogenesis in Drosophila, groups of ectodermal cells are endowed with the capacity to become neuronal precursors. The Notch signaling pathway is required to limit the neuronal potential to a single cell within each group. Loss of genes of the Notch signaling pathway results in a neurogenic phenotype: hyperplasia of the nervous system accompanied by a parallel loss of epidermis. Echinoid (Ed), a cell membrane associated Immunoglobulin C2-type protein, has previously been shown to be a negative regulator of the EGFR pathway during eye and wing vein development. Using in situ hybridization and antibody staining of whole-mount embryos, we show that Ed has a dynamic expression pattern during embryogenesis. Embryonic lethal alleles of ed reveal a role of Ed in restricting neurogenic potential during embryonic neurogenesis, and result in a phenotype similar to that of loss-of-function mutations of Notch signaling pathway genes. In this process Ed interacts closely with the Notch signaling pathway. Loss of ed suppresses the loss of neuronal elements caused by ectopic activation of the Notch signaling pathway. Using a temperature-sensitive allele of ed we show, furthermore, that Ed is required to suppress sensory bristles and for proper wing vein specification during adult development. In these processes also, ed acts in close concert with genes of the Notch signaling pathway. Thus the extra wing vein phenotype of ed is enhanced upon reduction of Delta (Dl) or Enhancer of split [E(spl)] proteins. Overexpression of the membrane-tethered extracellular region of Ed results in a dominant-negative phenotype. This phenotype is suppressed by overexpression of E(spl)m7 and enhanced by overexpression of Dl. Our work establishes a role of Ed during embryonic nervous system development, as well as adult sensory bristle specification and shows that Ed interacts synergistically with the Notch signaling pathway.
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Affiliation(s)
- Amina Ahmed
- Molecular, Cellular and Developmental Biology Program, Center for Molecular Neurobiology, Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA
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217
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Karp X, Greenwald I. Post-transcriptional regulation of the E/Daughterless ortholog HLH-2, negative feedback, and birth order bias during the AC/VU decision in C. elegans. Genes Dev 2004; 17:3100-11. [PMID: 14701877 PMCID: PMC305261 DOI: 10.1101/gad.1160803] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The anchor cell/ventral uterine precursor cell (AC/VU) decision in Caenorhabditis elegans is a canonical example of lin-12/Notch-mediated lateral specification. Two initially equivalent cells interact via the receptor LIN-12 and its ligand LAG-2, so that one becomes the AC and the other a VU. During this interaction, feedback loops amplify a small difference in lin-12 activity, limiting lin-12 transcription to the presumptive VU and lag-2 transcription to the presumptive AC. Here, we find that hlh-2 appears to be required for the VU fate and directly activates lag-2 transcription in the presumptive AC. HLH-2 appears to accumulate selectively in the presumptive AC prior to differential transcription of lin-12 or lag-2, and is therefore the earliest detectable difference between the two cells undergoing the AC/VU decision. The restricted accumulation of HLH-2 to the presumptive AC reflects post-transcriptional down-regulation of HLH-2 in the presumptive VU. Our observations suggest that hlh-2 is regulated as part of the negative feedback that down-regulates lag-2 transcription in the presumptive VU. Finally, we show that the AC/VU decision in an individual hermaphrodite is biased by the relative birth order of the two cells, so that the first-born cell is more likely to become the VU. We propose models to suggest how birth order, HLH-2 accumulation, and transcription of lag-2 may be linked during the AC/VU decision.
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Affiliation(s)
- Xantha Karp
- Department of Genetics and Development, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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218
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Wong GT, Manfra D, Poulet FM, Zhang Q, Josien H, Bara T, Engstrom L, Pinzon-Ortiz M, Fine JS, Lee HJJ, Zhang L, Higgins GA, Parker EM. Chronic treatment with the gamma-secretase inhibitor LY-411,575 inhibits beta-amyloid peptide production and alters lymphopoiesis and intestinal cell differentiation. J Biol Chem 2004; 279:12876-82. [PMID: 14709552 DOI: 10.1074/jbc.m311652200] [Citation(s) in RCA: 561] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inhibition of gamma-secretase, one of the enzymes responsible for the cleavage of the amyloid precursor protein (APP) to produce the pathogenic beta-amyloid (Abeta) peptides, is an attractive approach to the treatment of Alzheimer disease. In addition to APP, however, several other gamma-secretase substrates have been identified (e.g. Notch), and altered processing of these substrates by gamma-secretase inhibitors could lead to unintended biological consequences. To study the in vivo consequences of gamma-secretase inhibition, the gamma-secretase inhibitor LY-411,575 was administered to C57BL/6 and TgCRND8 APP transgenic mice for 15 days. Although most tissues were unaffected, doses of LY-411,575 that inhibited Abeta production had marked effects on lymphocyte development and on the intestine. LY-411,575 decreased overall thymic cellularity and impaired intrathymic differentiation at the CD4(-)CD8(-)CD44(+)CD25(+) precursor stage. No effects on peripheral T cell populations were noted following LY-411,575 treatment, but evidence for the altered maturation of peripheral B cells was observed. In the intestine, LY-411,575 treatment increased goblet cell number and drastically altered tissue morphology. These effects of LY-411,575 were not seen in mice that were administered LY-D, a diastereoisomer of LY-411,575, which is a very weak gamma-secretase inhibitor. These studies show that inhibition of gamma-secretase has the expected benefit of reducing Abeta in a murine model of Alzheimer disease but has potentially undesirable biological effects as well, most likely because of the inhibition of Notch processing.
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Affiliation(s)
- Gwendolyn T Wong
- Department of Central Nervous System Research, Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
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219
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Abstract
Animals sense their chemical environment using multiple chemosensory neuron types, each of which exhibits characteristic response properties. The chemosensory neurons of the nematode Caenorhabditis elegans provide an excellent system in which to explore the developmental mechanisms giving rise to this functional diversity. In this review, we discuss the principles underlying the patterning, generation, differentiation, and diversification of chemosensory neuron subtypes in C. elegans. Current knowledge of the molecular mechanisms underlying each of these individual steps is derived from work in different model organisms. It is essential to describe the complete developmental pathways in each organism to determine whether functional diversification in chemosensory systems is achieved via conserved or novel mechanisms. Such a complete description may be possible in C. elegans.
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Affiliation(s)
- Tali Melkman
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
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220
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Rawlins EL, Lovegrove B, Jarman AP. Echinoid facilitates Notch pathway signalling during Drosophila neurogenesis through functional interaction with Delta. Development 2003; 130:6475-84. [PMID: 14627723 DOI: 10.1242/dev.00882] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The Notch intercellular signalling pathway is important throughout development, and its components are modulated by a variety of cellular and molecular mechanisms. Ligand and receptor trafficking are tightly controlled, although context-specific regulation of this is incompletely understood. We show that during sense organ precursor specification in Drosophila, the cell adhesion molecule Echinoid colocalises extensively with the Notch ligand, Delta, at the cell membrane and in early endosomes. Echinoid facilitates efficient Notch pathway signalling. Cultured cell experiments suggest that Echinoid is associated with the cis-endocytosis of Delta, and is therefore linked to the signalling events that have been shown to require such Delta trafficking. Consistent with this, overexpression of Echinoid protein causes a reduction in Delta level at the membrane and in endosomes. In vivo and cell culture studies suggest that homophilic interaction of Echinoid on adjacent cells is necessary for its function.
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Affiliation(s)
- Emma L Rawlins
- The Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JR, UK
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221
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Abstract
Notch receptors and ligands were first identified in flies and worms, where they were shown to regulate cell proliferation, cell differentiation, and, in particular, binary cell fate decisions in a variety of developmental contexts. The first mammalian Notch homolog was discovered to be a partner in a chromosomal translocation in a subset of human T-cell leukemias. Subsequent studies in mice and humans have shown that Notch signaling plays essential roles at multiple stages of hematopoiesis, and also regulates the development or homeostasis of cells in many tissues and organs. Thus, it is not surprising that mutations which disrupt Notch signaling cause a wide range of cancers and developmental disorders. Perhaps because it is so widely used, Notch signaling is subject to many unusual forms of regulation. In this review, we will first outline key aspects of Notch signaling and its regulation by endocytosis, glycosylation, and ubiquitination. We will then overview recent literature elucidating how Notch regulates cell-lineage decisions in a variety of developmental contexts. Finally, we will describe the roles of dysregulated Notch signaling in causing several types of cancer and other pathologies.
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Affiliation(s)
- J A Harper
- Program in Developmental Biology, Hospital for Sick Children Research Institute, Department of Immunology, University of Toronto, Rm 8104, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8
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222
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Nickoloff BJ, Osborne BA, Miele L. Notch signaling as a therapeutic target in cancer: a new approach to the development of cell fate modifying agents. Oncogene 2003; 22:6598-608. [PMID: 14528285 DOI: 10.1038/sj.onc.1206758] [Citation(s) in RCA: 238] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Notch signaling controls cell fate decisions including during development and stem cell renewal and differentiation in many postnatal tissues. Increasing evidence suggests that the Notch signaling network is frequently deregulated in human malignancies and that genetic or pharmacological manipulation of Notch signaling is a novel potential strategy for the treatment of human neoplasms. This review article summarizes the most recent preclinical and clinical evidence linking Notch signaling to cancer, delineates questions that remain unanswered and explores potential biopharmacological strategies to manipulate Notch signaling in vivo.
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223
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Cinar HN, Richards KL, Oommen KS, Newman AP. The EGL-13 SOX Domain Transcription Factor Affects the Uterine Cell Lineages in Caenorhabditis elegans. Genetics 2003; 165:1623-8. [PMID: 14668410 PMCID: PMC1462816 DOI: 10.1093/genetics/165.3.1623] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
We isolated egl-13 mutants in which the cells of the Caenorhabditis elegans uterus initially appeared to develop normally but then underwent an extra round of cell division. The data suggest that egl-13 is required for maintenance of the cell fate.
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Affiliation(s)
- Hediye Nese Cinar
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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224
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Cattaneo M, Orlandini S, Beghelli S, Moore PS, Sorio C, Bonora A, Bassi C, Talamini G, Zamboni G, Orlandi R, Ménard S, Bernardi LR, Biunno I, Scarpa A. SEL1L expression in pancreatic adenocarcinoma parallels SMAD4 expression and delays tumor growth in vitro and in vivo. Oncogene 2003; 22:6359-68. [PMID: 14508516 DOI: 10.1038/sj.onc.1206665] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recent data suggest that SEL1L may play an important role in pancreatic carcinoma, similar to breast cancer, where the expression of SEL1L has been associated with a reduction in both proliferative activity in vitro and clinical tumor aggressiveness. To investigate this possibility, we examined the expression of Sel1L in a series of primary pancreatic carcinomas by immunohistochemistry and characterized the effects of Sel1L overexpression both in vitro and in vivo. In 74 pancreatic cancers analysed, 36% lacked Sel1L expression, although there was no significant correlation between the expression of Sel1L and any clinicopathologic parameter, including survival. However, immunohistochemical reactivity for Sel1L and Dpc4/Smad4 was concordant in 69% of cases (chi(2) test P&<0.004). Overexpression of SEL1L in stably transfected pancreatic cancer cells caused both a decrease in clonogenicity and anchorage-independent growth as well as a significant increase in the levels of activin A and SMAD4. When implanted in nude mice, Suit-2-SEL1L-overexpressing clones displayed a considerably reduced rate of tumor growth. Thus, it can be hypothesized that Sel1L plays an important function in the growth and aggressiveness of pancreatic carcinoma. Moreover, our data provide evidence that SEL1L has an impact on the expression of genes involved in regulation of cellular growth, possibly through the TGF-beta signaling pathway.
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Affiliation(s)
- Monica Cattaneo
- 1Institute for Biomedical Technologies (National Research Council), Milano, Italy
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225
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Abstract
Notch signaling plays a preeminent role during development in not only regulating cell fate decisions, but it can also influence growth and survival of progenitor cells. In the immune system, Notch is required for the maintenance of hematopoietic stem cells and in directing T- versus B-lineage commitment. In this review, I will summarize some of the recent findings relating to the function of Notch in the immune system during lymphocyte development and in the generation and function of mature cells.
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Affiliation(s)
- Gerard F Hoyne
- ACRF Genetics Laboratory and Medical Genome Centre, John Curtin School of Medical Research, Australian National University, Mills Road, P.O. Box 334, Canberra, ACT, Australia 2601.
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226
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Sasamura T, Sasaki N, Miyashita F, Nakao S, Ishikawa HO, Ito M, Kitagawa M, Harigaya K, Spana E, Bilder D, Perrimon N, Matsuno K. neurotic, a novel maternal neurogenic gene, encodes an O-fucosyltransferase that is essential for Notch-Delta interactions. Development 2003; 130:4785-95. [PMID: 12917292 DOI: 10.1242/dev.00679] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Notch signalling, which is highly conserved from nematodes to mammals, plays crucial roles in many developmental processes. In the Drosophila embryo, deficiency in Notch signalling results in neural hyperplasia, commonly referred to as the neurogenic phenotype. We identify a novel maternal neurogenic gene, neurotic, and show that it is essential for Notch signalling. neurotic encodes a Drosophila homolog of mammalian GDP-fucose protein O-fucosyltransferase, which adds fucose sugar to epidermal growth factor-like repeats and is known to play a crucial role in Notch signalling. neurotic functions in a cell-autonomous manner, and genetic epistasis tests reveal that Neurotic is required for the activity of the full-length but not an activated form of Notch. Further, we show that neurotic is required for Fringe activity, which encodes a fucose-specific beta1, 3 N-acetylglucosaminyltransferase, previously shown to modulate Notch receptor activity. Finally, Neurotic is essential for the physical interaction of Notch with its ligand Delta, and for the ability of Fringe to modulate this interaction in Drosophila cultured cells. We present an unprecedented example of an absolute requirement of a protein glycosylation event for a ligand-receptor interaction. Our results suggest that O-fucosylation catalysed by Neurotic is also involved in the Fringe-independent activities of Notch and may provide a novel on-off mechanism that regulates ligand-receptor interactions.
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Affiliation(s)
- Takeshi Sasamura
- PRESTO, Japan Science and Technology Corporation, Noda, Chiba, Japan
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227
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García-Peydró M, de Yébenes VG, Toribio ML. Sustained Notch1 signaling instructs the earliest human intrathymic precursors to adopt a gammadelta T-cell fate in fetal thymus organ culture. Blood 2003; 102:2444-51. [PMID: 12829602 DOI: 10.1182/blood-2002-10-3261] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Notch1 activity is essential for the specification of T-lineage fate in hematopoietic progenitors. Once the T-cell lineage is specified, T-cell precursors in the thymus must choose between alphabeta and gammadelta lineages. However, the impact of Notch1 signaling on intrathymic pro-T cells has not been addressed directly. To approach this issue, we used retroviral vectors to express constitutively active Notch1 in human thymocyte progenitors positioned at successive developmental stages, and we followed their differentiation in fetal thymus organ culture (FTOC). Here we show that sustained Notch1 signaling impairs progression to the double-positive (DP) stage and efficiently diverts the earliest thymic progenitors from the main alphabeta T-cell pathway toward development of gammadelta T cells. The impact of Notch1 signaling on skewed gammadelta production decreases progressively along intrathymic maturation and is restricted to precursor stages upstream of the pre-T-cell receptor checkpoint. Close to and beyond that point, Notch1 is not further able to instruct gammadelta cell fate, but promotes an abnormal expansion of alphabeta-committed thymocytes. These results stress the stage-specific impact of Notch1 signaling in intrathymic differentiation and suggest that regulation of Notch1 activity at defined developmental windows is essential to control alphabeta versus gammadelta T-cell development and to avoid deregulated expansion of alphabeta-lineage cells.
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MESH Headings
- Animals
- Antigens, CD34/analysis
- Cell Differentiation/immunology
- Cell Lineage/immunology
- Child, Preschool
- Fetus
- Flow Cytometry
- Gene Expression Regulation, Developmental/immunology
- Humans
- Infant
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice
- Organ Culture Techniques
- Receptor, Notch1
- Receptors, Antigen, T-Cell, alpha-beta/analysis
- Receptors, Antigen, T-Cell, alpha-beta/physiology
- Receptors, Antigen, T-Cell, gamma-delta/analysis
- Receptors, Antigen, T-Cell, gamma-delta/physiology
- Receptors, Cell Surface
- Signal Transduction/immunology
- Stem Cells/chemistry
- Stem Cells/cytology
- Stem Cells/immunology
- Thymus Gland/cytology
- Thymus Gland/embryology
- Transcription Factors
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Affiliation(s)
- Marina García-Peydró
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Madrid, Spain
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228
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O'Connor-Giles KM, Skeath JB. Numb inhibits membrane localization of Sanpodo, a four-pass transmembrane protein, to promote asymmetric divisions in Drosophila. Dev Cell 2003; 5:231-43. [PMID: 12919675 DOI: 10.1016/s1534-5807(03)00226-0] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cellular diversity is a fundamental characteristic of complex organisms, and the Drosophila CNS has proved an informative paradigm for understanding the mechanisms that create cellular diversity. One such mechanism is the asymmetric localization of Numb to ensure that sibling cells respond differently to the extrinsic Notch signal and, thus, adopt distinct fates (A and B). Here we focus on the only genes known to function specifically to regulate Notch-dependent asymmetric divisions: sanpodo and numb. We demonstrate that sanpodo, which specifies the Notch-dependent fate (A), encodes a four-pass transmembrane protein that localizes to the cell membrane in the A cell and physically interacts with the Notch receptor. We also show that Numb, which inhibits Notch signaling to specify the default fate (B), physically associates with Sanpodo and inhibits Sanpodo membrane localization in the B cell. Our findings suggest a model in which Numb inhibits Notch signaling through the regulation of Sanpodo membrane localization.
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Affiliation(s)
- Kate M O'Connor-Giles
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA
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229
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Abstract
The polarisation of the embryonic anteroposterior (AP) axis requires the establishment of positional cues with spatial information, and often involves complex intercellular communications, cell adhesion and cell movement. Recent work on several fronts has begun to shed light on how the initial asymmetries are established and maintained. In this review, I discuss the polarisation of the AP axis during Drosophila oogenesis, focusing on the function of the Notch signalling pathway and its relationship to the activation of the epidermal growth factor receptor. I make special reference to some aspects of Notch activity regulation during oogenesis that appear to depart from the canonical pathway. Finally, I hypothesise on possible similarities between these activities of Notch signalling during Drosophila oogenesis and vertebrate somitogenesis.
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Affiliation(s)
- Hernán López-Schier
- Howard Hughes Medical Institute, The Rockefeller University (Box 314) 1230 York Ave., New York, NY 10021, USA.
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230
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Takeyama K, Aguiar RCT, Gu L, He C, Freeman GJ, Kutok JL, Aster JC, Shipp MA. The BAL-binding protein BBAP and related Deltex family members exhibit ubiquitin-protein isopeptide ligase activity. J Biol Chem 2003; 278:21930-7. [PMID: 12670957 DOI: 10.1074/jbc.m301157200] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the DTX (Deltex) family act as Notch signaling modifiers and may also regulate transcription through interactions with specific transcription factors. DTX proteins have a basic N terminus; a central proline-rich region; and a C-terminal RING finger domain, a motif often found in ubiquitin-protein isopeptide ligases (E3). Recently, we identified and characterized a unique diffuse large B-cell lymphoma risk-related gene named BAL (B aggressive lymphoma). Using a yeast two-hybrid screen for BAL-binding partners, we have now identified a novel protein termed BBAP (B-lymphoma- and BAL-associated protein). Although BBAP has a unique N terminus, the C-terminal region is highly homologous to that of DTX family members. Herein, we report that BBAP and the human family of DTX proteins (DTX1, DTX2, and DTX3) function as E3 ligases based on their capacity for self-ubiquitination. DTX family members homodimerize and heterodimerize in vivo, suggesting that physical interactions between various DTX family members modify E3 activity and/or substrate availability. Consistent with this idea, BBAP and DTX1 associate via their unique N termini, resulting in enhanced self-ubiquitination.
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Affiliation(s)
- Kunihiko Takeyama
- Department of Medical Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA
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231
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Cui M, Han M. Cis regulatory requirements for vulval cell-specific expression of the Caenorhabditis elegans fibroblast growth factor gene egl-17. Dev Biol 2003; 257:104-16. [PMID: 12710960 DOI: 10.1016/s0012-1606(03)00033-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Caenorhabditis elegans EGL-17/FGF protein is involved in the gonadal signaling that guides the migrations of sex myoblasts (SMs). egl-17::GFP reporter constructs are expressed dynamically in vulval cell lineages. Expression in the primary vulval cells is correlated with the precise positioning of SMs. We have investigated the cis-regulatory requirements for cell- and stage-specific expression of egl-17. Three enhancer elements that specify the expression of the egl-17::GFP reporter gene in primary or secondary vulval cells at certain stages were identified. Sequence analysis has suggested a number of potential transcription factor binding sites within the enhancer elements. egl-17 is most likely a direct target of the LIN-39 Hox protein because mutations either in the lin-39/hox gene or at the consensus HOX/PBC binding site within the distal enhancer of the egl-17 gene eliminated distal enhancer-activated egl-17 expression. Since expression of egl-17::GFP driven by the distal enhancer can no longer be turned off at late stages in lin-1 and lin-31 mutants, egl-17 may also be regulated by Ras signaling through repression of LIN-1 and LIN-31 activities. Interspecies transformation experiments showed that egl-17 cis-regulatory elements are structurally and functionally conserved between C. elegans and C. briggsae.
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Affiliation(s)
- Mingxue Cui
- Howard Hughes Medical Institute, and Department of Molecular, Cellular, and Developmental Biology, University of Colorado, 80309-0347, Boulder, CO, USA
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232
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Abstract
The Notch family of cell-surface receptors has been proposed to regulate cell-fate decisions by modulating the ability of each cell to respond to environmental cues. In vertebrates, gain-of-function and loss-of-function studies have demonstrated a requirement for Notch signaling for proper patterning of the vasculature during embryogenesis. To examine the molecular mechanisms by which Notch regulates vascular development, we analyzed changes in gene expression in response to Notch signaling. Notch signal transduction and function were assessed in primary human endothelial cells isolated from the dermal microvasculature of neonates, HMVECd. We demonstrate that HMVECd cells express a heterodimeric form of endogenous Notch4 on their cell surface. Using an in vitro coculture assay, we found that Delta4 can function as a ligand for Notch4 in HMVECd cells. Moreover, ectopic expression of an activated allele of Notch4 upregulated the expression of Delta4, suggesting that there may be a regulatory loop between Notch4 and its ligand, Delta4. Notch4 activation also induced the expression of the transcriptional repressors, HES1, HERP1, and HERP2, as well as ephrinB2, an angiogenic factor proposed to be involved in arterial/venous endothelial cell specification.
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Affiliation(s)
- Carrie J Shawber
- Department of Pathology and OB/GYN, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA
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233
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Abstract
Recent studies have shown that disruption of Notch1 signaling in lymphocyte progenitors (LP) inhibits T cell development and promotes B cell development in the thymus. Conversely, inappropriate activation of Notch1 in LP inhibits B cell development and causes ectopic T cell development in the bone marrow. These observations imply that Notch1 activation must be spatially regulated to ensure that LP generate B cells in the bone marrow and T cells in the thymus. However, Notch ligands are expressed in both tissues. Studies in flies and worms have revealed that Notch activation is extremely sensitive to small changes in the amount of receptor or ligand expressed, and defined multiple mechanisms that limit Notch activation to discrete cells at specific times during development. Here, we describe how some of these mechanisms might regulate Notch activity in LP during the T/B lineage decision.
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Affiliation(s)
- Ute Koch
- Program in Developmental Biology, Department of Immunology, University of Toronto, Hospital for Sick Children Research Institute, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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234
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Abstract
Notch signaling is an extremely conserved and widely used mechanism regulating cell fate in metazoans. Interaction of Notch receptors (Notch) with their ligands (Delta-like or Jagged) leads to cleavage of the Notch intracellular domain (NICD) that migrates into the nucleus. In the nucleus, NICD associates with a transcription factor, RBP-Jk. The NICD-RBP-Jk complex, in turn, upregulates expression of primary target genes of Notch signaling, such as hairy and enhancer of split (HES) and HES-related repressor protein (HERP) transcriptional repressors. Recent evidence has demonstrated that the Notch pathway is involved in multiple aspects of vascular development, including proliferation, migration, smooth muscle differentiation, angiogenic processes, and arterial-venous differentiation. In this brief review, we focus on ligands, receptors, and target genes of Notch signaling in the vascular system and discuss (1) tissue distribution; (2) gain- and loss-of-function studies; and (3) the role of Notch components in human diseases involving the vascular system.
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Affiliation(s)
- Tatsuya Iso
- Second Department of Internal Medicine, Gunma University School of Medicine, Gunma 371-8511, Japan
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235
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Iso T, Kedes L, Hamamori Y. HES and HERP families: multiple effectors of the Notch signaling pathway. J Cell Physiol 2003; 194:237-55. [PMID: 12548545 DOI: 10.1002/jcp.10208] [Citation(s) in RCA: 946] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Notch signaling dictates cell fate and critically influences cell proliferation, differentiation, and apoptosis in metazoans. Multiple factors at each step-ligands, receptors, signal transducers and effectors-play critical roles in executing the pleiotropic effects of Notch signaling. Ligand-binding results in proteolytic cleavage of Notch receptors to release the signal-transducing Notch intracellular domain (NICD). NICD migrates into the nucleus and associates with the nuclear proteins of the RBP-Jkappa family (also known as CSL or CBF1/Su(H)/Lag-1). RBP-Jkappa, when complexed with NICD, acts as a transcriptional activator, and the RBP-Jkappa-NICD complex activates expression of primary target genes of Notch signaling such as the HES and enhancer of split [E(spl)] families. HES/E(spl) is a basic helix-loop-helix (bHLH) type of transcriptional repressor, and suppresses expression of downstream target genes such as tissue-specific transcriptional activators. Thus, HES/E(spl) directly affects cell fate decisions as a primary Notch effector. HES/E(spl) had been the only known effector of Notch signaling until a recent discovery of a related but distinct bHLH protein family, termed HERP (HES-related repressor protein, also called Hey/Hesr/HRT/CHF/gridlock). In this review, we summarize the recent data supporting the idea of HERP being a new Notch effector, and provide an overview of the similarities and differences between HES and HERP in their biochemical properties as well as their tissue distribution. One key observation derived from identification of HERP is that HES and HERP form a heterodimer and cooperate for transcriptional repression. The identification of the HERP family as a Notch effector that cooperates with HES/E(spl) family has opened a new avenue to our understanding of the Notch signaling pathway.
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Affiliation(s)
- Tatsuya Iso
- Institute for Genetic Medicine, Department of Biochemistry and Molecular Biology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90089, USA
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236
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Taichman DB, Loomes KM, Schachtner SK, Guttentag S, Vu C, Williams P, Oakey RJ, Baldwin HS. Notch1 and Jagged1 expression by the developing pulmonary vasculature. Dev Dyn 2003; 225:166-75. [PMID: 12242716 DOI: 10.1002/dvdy.10146] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The molecular mechanisms of pulmonary vascular development are poorly understood. Cell-specific developmental pathways are influenced by cell-cell signaling. Notch signaling molecules are highly conserved receptors active in many cell-fate determination systems. Recent observations of Notch molecules and a Notch ligand, Jagged1, suggest their importance in vascular morphogenesis, and particularly pulmonary vascular development. We performed a systematic evaluation of Notch1/Jagged1 gene and protein expression in the developing mouse lung from embryonic day 11 until adulthood by using quantitative PCR, immunofluorescence, and electron microscopic analysis. mRNA transcripts for Notch1-4 and Jagged1 increased progressively from early to later lung development, accompanied by a simultaneous rise in endothelial cell-specific gene expression, a pattern not seen in other organs. Notch1 mRNA was identified on both epithelial and mesenchymal structures of the embryonic lung. Immunofluorescence staining revealed the progressive acquisition of Notch1 and Jagged1 proteins by the emerging endothelium. Notch1 and Jagged1 were seen initially on well-formed, larger vessels within the embryonic lung bud and progressively on finer vascular networks. Each was also expressed on surrounding nonvascular structures. The localization of Notch1 and Jagged1 on endothelial cell surface membranes within the alveolar microvasculature was confirmed by immuno-electron microscopy. These temporal and spatial patterns in Notch1/Jagged1 gene and protein expression suggest multiple potential paths of cell-cell signaling during lung development and vascular morphogenesis.
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Affiliation(s)
- Darren B Taichman
- Pulmonary, Allergy and Critical Care Division, University of Pennsylvania Medical Center, Children's Hospital of Philadelphia and the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
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237
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Pepper ASR, Killian DJ, Hubbard EJA. Genetic analysis of Caenorhabditis elegans glp-1 mutants suggests receptor interaction or competition. Genetics 2003; 163:115-32. [PMID: 12586701 PMCID: PMC1462416 DOI: 10.1093/genetics/163.1.115] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
glp-1 encodes a member of the highly conserved LIN-12/Notch family of receptors that mediates the mitosis/meiosis decision in the C. elegans germline. We have characterized three mutations that represent a new genetic and phenotypic class of glp-1 mutants, glp-1(Pro). The glp-1(Pro) mutants display gain-of-function germline pattern defects, most notably a proximal proliferation (Pro) phenotype. Each of three glp-1(Pro) alleles encodes a single amino acid change in the extracellular part of the receptor: two in the LIN-12/Notch repeats (LNRs) and one between the LNRs and the transmembrane domain. Unlike other previously described gain-of-function mutations that affect this region of LIN-12/Notch family receptors, the genetic behavior of glp-1(Pro) alleles is not consistent with simple hypermorphic activity. Instead, the mutant phenotype is suppressed by wild-type doses of glp-1. Moreover, a trans-heterozygous combination of two highly penetrant glp-1(Pro) mutations is mutually suppressing. These results lend support to a model for a higher-order receptor complex and/or competition among receptor proteins for limiting factors that are required for proper regulation of receptor activity. Double-mutant analysis with suppressors and enhancers of lin-12 and glp-1 further suggests that the functional defect in glp-1(Pro) mutants occurs prior to or at the level of ligand interaction.
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Affiliation(s)
- Anita S-R Pepper
- Department of Biology, New York University, New York, New York 10003, USA
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238
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Bulik DA, Robbins PW. The Caenorhabditis elegans sqv genes and functions of proteoglycans in development. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1573:247-57. [PMID: 12417407 DOI: 10.1016/s0304-4165(02)00391-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In the nematode Caenorhabditis elegans, the vulva is a simple tubular structure linking the gonads with the external cuticle. In this review we summarize knowledge of inter- and intracellular signaling during vulval development and of the genes required for vulval invagination. Mutants of one set of these genes, the sqv genes, have a normal number of vulval precursor cells (VPCs) with an unperturbed cell lineage but the invagination space, normally a tube, is either collapsed or absent. We review evidence that the sqv genes are involved in glycosaminoglycan synthesis and speculate on ways in which defective glycosaminoglycan formation might lead to collapse of the vulval structure.
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Affiliation(s)
- Dorota A Bulik
- Department of Molecular and Cell Biology, School of Dental Medicine, Boston University, MA 02118, USA.
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239
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Dansereau DA, Lunke MD, Finkielsztein A, Russell MA, Brook WJ. Hephaestus encodes a polypyrimidine tract binding protein that regulates Notch signalling during wing development in Drosophila melanogaster. Development 2002; 129:5553-66. [PMID: 12421697 DOI: 10.1242/dev.00153] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We describe the role of the Drosophila melanogaster hephaestus gene in wing development. We have identified several hephaestus mutations that map to a gene encoding a predicted RNA-binding protein highly related to human polypyrimidine tract binding protein and Xenopus laevis 60 kDa Vg1 mRNA-binding protein. Polypyrimidine tract binding proteins play diverse roles in RNA processing including the subcellular localization of mRNAs, translational control, internal ribosome entry site use, and the regulation of alternate exon selection. The analysis of gene expression in imaginal discs and adult cuticle of genetic mosaic animals supports a role for hephaestus in Notch signalling. Somatic clones lacking hephaestus express the Notch target genes wingless and cut, induce ectopic wing margin in adjacent wild-type tissue, inhibit wing-vein formation and have increased levels of Notch intracellular domain immunoreactivity. Clones mutant for both Delta and hephaestus have the characteristic loss-of-function thick vein phenotype of DELTA: These results lead to the hypothesis that hephaestus is required to attenuate Notch activity following its activation by Delta. This is the first genetic analysis of polypyrimidine tract binding protein function in any organism and the first evidence that such proteins may be involved in the Notch signalling pathway.
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Affiliation(s)
- David A Dansereau
- Genes and Development Research Group, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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240
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Abstract
T cell lineage commitment as the double-positive (DP) thymocyte matures into the single-positive (SP) T cell requires the irreversible repression or maintenance of CD4 gene expression. Signals transmitted from the T cell antigen receptor (TCR) during thymic selection are believed to be linked to the transcriptional regulation of the CD4 gene; thus, a study of the factors that control CD4 gene expression may lead to further insight into the molecular mechanisms that drive T cell development. This review discusses the work conducted to date to identify and characterize the transcriptional control elements in the CD4 locus and the factors that mediate their function. From these studies, it is clear that the molecular mechanisms controlling CD4 gene expression are very complex and are controlled by many different signals as the thymocyte develops.
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Affiliation(s)
- Gerald Siu
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA.
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241
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Holley SA, Takeda H. Catching a wave: the oscillator and wavefront that create the zebrafish somite. Semin Cell Dev Biol 2002; 13:481-8. [PMID: 12468251 DOI: 10.1016/s1084952102001015] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Segmentation of the paraxial mesoderm is governed by an oscillator mechanism that creates a dynamic prepattern within the caudal presomitic mesoderm. The oscillator is comprised of genetic circuit involving the Notch signaling pathway and its target genes her1 and her7. The stabilization of the oscillating prepattern is antagonized by a gradient of Fgf signaling which is highest in the caudal presomitic mesoderm. Once the level of Fgf signaling declines in the rostral presomitic mesoderm, a wavefront mediated by the transcription factor fss/tbx24, stabilizes the prepattern and leads to the segmental expression of a number of genes which then establish segment polarity and initiate morphological somite formation.
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Affiliation(s)
- Scott A Holley
- Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA.
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242
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Firulli AB, Thattaliyath BD. Transcription factors in cardiogenesis: the combinations that unlock the mysteries of the heart. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 214:1-62. [PMID: 11893163 DOI: 10.1016/s0074-7696(02)14002-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Heart formation is one of the first signs of organogenesis within the developing embryo and this process is conserved from flies to man. Completing the genetic roadmap of the molecular mechanisms that control the cell specification and differentiation of cells that form the developing heart has been an exciting and fast-moving area of research in the fields of molecular and developmental biology. At the core of these studies is an interest in the transcription factors that are responsible for initiation of a pluripotent cell to become programmed to the cardiac lineage and the subsequent transcription factors that implement the instructions set up by the cells commitment decision. To gain a better understanding of these pathways, cardiac-expressed transcription factors have been identified, cloned, overexpressed, and mutated to try to determine function. Although results vary depending on the gene in question, it is clear that there is a striking evolutionary conservation of the cardiogenic program among species. As we move up the evolutionary ladder toward man, we encounter cases of functional redundancy and combinatorial interactions that reflect the complex networks of gene expression that orchestrate heart development. This review focuses on what is known about the transcription factors implicated in heart formation and the role they play in this intricate genetic program.
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Affiliation(s)
- Anthony B Firulli
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio 78229, USA
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243
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Eimer S, Donhauser R, Baumeister R. The Caenorhabditis elegans presenilin sel-12 is required for mesodermal patterning and muscle function. Dev Biol 2002; 251:178-92. [PMID: 12413907 DOI: 10.1006/dbio.2002.0782] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in presenilin genes impair Notch signalling and, in humans, have been implicated in the development of familial Alzheimer's disease. We show here that a reduction of the activity of the Caenorhabditis elegans presenilin sel-12 results in a late defect during sex muscle development. The morphological abnormalities and functional deficits in the sex muscles contribute to the egg-laying defects seen in sel-12 hermaphrodites and to the severely reduced mating efficiency of sel-12 males. Both defects can be rescued by expressing sel-12 from the hlh-8 promoter that is active during the development of the sex muscle-specific M lineage, but not by expressing sel-12 from late muscle-specific promoters. Both weak and strong sel-12 mutations cause defects in the sex muscles that resemble the defects we found in lin-12 hypomorphic alleles, suggesting a previously uncharacterised LIN-12 signalling event late in postembryonic mesoderm development. Together with a previous study indicating a role of lin-12 and sel-12 during the specification of the pi cell lineage required for proper vulva-uterine connection, our data suggest that the failure of sel-12 animals to lay eggs properly is caused by defects in at least two independent signalling events in different tissues during development.
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Affiliation(s)
- Stefan Eimer
- ABI, Department of Biochemistry, Laboratory of Molecular Neurogenetics, Ludwig-Maximilians-Universitaet Munich, Schillerstrasse 44, Munich D-80336, Germany
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244
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Eimer S, Lakowski B, Donhauser R, Baumeister R. Loss of spr-5 bypasses the requirement for the C.elegans presenilin sel-12 by derepressing hop-1. EMBO J 2002; 21:5787-96. [PMID: 12411496 PMCID: PMC131058 DOI: 10.1093/emboj/cdf561] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2002] [Revised: 08/19/2002] [Accepted: 09/02/2002] [Indexed: 11/12/2022] Open
Abstract
Presenilins are part of a protease complex that is responsible for the intramembraneous cleavage of the amyloid precursor protein involved in Alzheimer's disease and of Notch receptors. In Caenorhabditis elegans, mutations in the presenilin sel-12 result in a highly penetrant egg-laying defect. spr-5 was identified as an extragenic suppressor of the sel-12 mutant phenotype. The SPR-5 protein has similarity to the human polyamine oxidase-like protein encoded by KIAA0601 that is part of the HDAC-CoREST co-repressor complex. Suppression of sel-12 by spr-5 requires the activity of HOP-1, the second somatic presenilin in C.elegans. spr-5 mutants derepress hop-1 expression 20- to 30-fold in the early larval stages when hop-1 normally is almost undetectable. SPR-1, a C.elegans homologue of CoREST, physically interacts with SPR-5. Moreover, down-regulation of SPR-1 by mutation or RNA interference also bypasses the need for sel-12. These data strongly suggest that SPR-5 and SPR-1 are part of a CoREST-like co-repressor complex in C.elegans. This complex might be recruited to the hop-1 locus controlling its expression during development.
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Affiliation(s)
| | - B. Lakowski
- ABI, Department of Biochemistry, Laboratory of Molecular Neurogenetics, Ludwig-Maximilians-Universität Munich, Schillerstraße 44, D-80336 Munich, Germany
Present address: Department of Neuroscience, Pasteur Institute, Paris, France Corresponding author e-mail:
| | | | - R. Baumeister
- ABI, Department of Biochemistry, Laboratory of Molecular Neurogenetics, Ludwig-Maximilians-Universität Munich, Schillerstraße 44, D-80336 Munich, Germany
Present address: Department of Neuroscience, Pasteur Institute, Paris, France Corresponding author e-mail:
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245
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Mishra-Gorur K, Rand MD, Perez-Villamil B, Artavanis-Tsakonas S. Down-regulation of Delta by proteolytic processing. J Cell Biol 2002; 159:313-24. [PMID: 12403816 PMCID: PMC2173041 DOI: 10.1083/jcb.200203117] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Notch signaling regulates cell fate decisions during development through local cell interactions. Signaling is triggered by the interaction of the Notch receptor with its transmembrane ligands expressed on adjacent cells. Recent studies suggest that Delta is cleaved to release an extracellular fragment, DlEC, by a mechanism that involves the activity of the metalloprotease Kuzbanian; however, the functional significance of that cleavage remains controversial. Using independent functional assays in vitro and in vivo, we examined the biological activity of purified soluble Delta forms and conclude that Delta cleavage is an important down-regulating event in Notch signaling. The data support a model whereby Delta inactivation is essential for providing the critical ligand/receptor expression differential between neighboring cells in order to distinguish the signaling versus the receiving partner.
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Affiliation(s)
- Ketu Mishra-Gorur
- Department of Cell Biology, Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
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246
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Chan SK, Struhl G. Evidence that Armadillo transduces wingless by mediating nuclear export or cytosolic activation of Pangolin. Cell 2002; 111:265-80. [PMID: 12408870 DOI: 10.1016/s0092-8674(02)01037-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Secreted proteins of the Wnt family have profound organizing roles during animal development and are transduced via the activities of the Frizzled (Fz) class of transmembrane receptors and the TCF/LEF/Pangolin class of transcription factors. beta-catenins, including Drosophila Armadillo (Arm), link activation of Fz at the cell surface to transcriptional regulation by TCF in the nucleus. The consensus view is that Wnt signaling induces beta-catenin to enter the nucleus and combine with TCF to form a transcription factor complex in which TCF binds DNA and the C-terminal domain of beta-catenin activates transcription. Here, we present findings, which challenge this view and suggest instead that beta-catenin may transduce Wnt signals by exporting TCF from the nucleus or activating it in the cytoplasm.
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Affiliation(s)
- Siu-Kwong Chan
- Department of Genetics, Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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247
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Jarriault S, Greenwald I. Suppressors of the egg-laying defective phenotype of sel-12 presenilin mutants implicate the CoREST corepressor complex in LIN-12/Notch signaling in C. elegans. Genes Dev 2002; 16:2713-28. [PMID: 12381669 PMCID: PMC187465 DOI: 10.1101/gad.1022402] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Presenilin is an essential component of the LIN-12/Notch signaling pathway and also plays a critical role in the genesis of Alzheimer's disease. Previously, a screen for suppressors of the egg-laying defective phenotype caused by partial loss of presenilin activity in Caenorhabditis elegans identified a number of new spr genes that are potentially involved in the regulation of LIN-12/Notch signaling or presenilin activity. Here we report the molecular identity of two spr genes, spr-1 and spr-5. Our genetic analysis indicates that loss of spr-1 elevates lin-12/Notch gene activity in many different cell fate decisions, suggesting that spr-1 is a negative regulator of LIN-12/Notch signaling. Sequence analysis revealed that spr-1 is an ortholog of human CoREST, a known corepressor. SPR-1 is localized to the nucleus and acts in a cell-autonomous manner; furthermore, human CoREST can substitute for SPR-1 in C. elegans. We also show that spr-5 encodes a homolog of p110b, another known member of the CoREST corepressor complex. Our results suggest that the CoREST corepressor complex might be functionally conserved in worms, and we discuss the potential role of SPR-1 and SPR-5 in the repression of transcription of genes involved in, or downstream of, LIN-12/Notch signal transduction.
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Affiliation(s)
- Sophie Jarriault
- Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
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248
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Abstract
Notch signals regulate multiple cell fate decisions during metazoan development. During hematopoiesis, Notch affects both hematopoietic stem cells and committed progenitors. In hematopoietic stem cells, Notch signaling has the propensity to expand the stem cells, promote their self-renewal, and influence their survival. In committed progenitors, Notch signaling plays a key role in determining lymphoid cell fates. This review focuses on recent developments to understand the role of Notch signaling in early events in hematopoiesis.
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Affiliation(s)
- David Allman
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA 19104-6160, USA
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249
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Fortini ME. Gamma-secretase-mediated proteolysis in cell-surface-receptor signalling. Nat Rev Mol Cell Biol 2002; 3:673-84. [PMID: 12209127 DOI: 10.1038/nrm910] [Citation(s) in RCA: 500] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Many cell-surface receptors transmit signals to the nucleus through complex protein cascades. By contrast, the Notch signalling pathway uses a relatively direct mechanism, in which the intracellular domain of the receptor is liberated by intramembrane cleavage and translocates to the nucleus. This critical cleavage is mediated by the gamma-secretase complex, and new findings reveal that this mechanism is used by various receptors, although many questions remain about the biochemical details.
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Affiliation(s)
- Mark E Fortini
- Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Building 560, Room 22-12, Fort Detrick, Frederick, Maryland 21702, USA.
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250
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Yan B, Raben N, Plotz P. The human acid alpha-glucosidase gene is a novel target of the Notch-1/Hes-1 signaling pathway. J Biol Chem 2002; 277:29760-4. [PMID: 12065598 DOI: 10.1074/jbc.m204721200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acid alpha-glucosidase (GAA) is a lysosomal enzyme that degrades glycogen. A deficiency of GAA is responsible for a recessively inherited myopathy and cardiomyopathy, glycogenosis type II. Previously, we identified an intronic repressor element in the GAA gene and demonstrated that Hes-1, a basic helix-loop-helix factor, binds to a C class E box within the element and functions as a transcriptional repressor in HepG2 cells. Hes-1 is a well studied downstream target gene in the Notch signaling pathway. In this study, over-expression and depletion of Notch-1 intracellular domain (NICD) strategies were used to investigate whether expression of the GAA gene is under the control of Notch-1/Hes-1 signaling. In co-transfection experiments, Hes-1, up-regulated by over-expressed NICD, enhanced the repressive effect of the DNA element with wild type Hes-1 binding sites but not with mutant Hes-1 binding sites. Conversely, depletion of Notch-1 with phosphorothioated antisense oligonucleotides, corresponding to the fourth ankyrin repeat within NICD, led to reduced Hes-1. Constitutively over-expressed Hes-1 and Notch-1 repressed GAA gene expression. Therefore, our data establish that the human GAA gene, encoding a lysosomal enzyme, is a downstream target of the Notch-1/Hes-1 signaling pathway.
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Affiliation(s)
- Bo Yan
- Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892-1820, USA
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