351
|
Monocytes express high amounts of Notch and undergo cytokine specific apoptosis following interaction with the Notch ligand, Delta-1. Blood 2000. [DOI: 10.1182/blood.v95.9.2847.009k19_2847_2854] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Notch signaling has been shown to play a key role in cell fate decisions in numerous developmental systems. Using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we reported the expression of human Notch-1 in CD34+ progenitors. In this study, we evaluated the expression of human Notch-1 and Notch-2 protein by hematopoietic cells. In immunofluoresence study, we detected low amounts of Notch-1 and Notch-2 protein in both CD34+ and CD34+Lin− cells, high amounts in CD14+ monocytes as well as B and T cells, but no expression in CD15+ granulocytes. We further found that an immobilized truncated form of the Notch ligand, Delta-1, induced apoptosis in monocytes in the presence of macrophage colony-stimulating factor (M-CSF), but not granulocyte-macrophage colony-stimulating factor (GM-CSF). The widespread expressions of Notch proteins suggest multiple functions for this receptor during hematopoiesis. These studies further indicate a novel role for Notch in regulating monocyte survival.
Collapse
|
352
|
Singh N, Phillips RA, Iscove NN, Egan SE. Expression of notch receptors, notch ligands, and fringe genes in hematopoiesis. Exp Hematol 2000; 28:527-34. [PMID: 10812242 DOI: 10.1016/s0301-472x(00)00146-6] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE Hematopoiesis is the process by which mature blood cell types are generated from a small population of pluripotent hematopoietic stem cells. How these cells undergo fate selection, however, is not fully understood. The Notch signaling system is known to mediate cell fate decisions of multipotent precursors in a wide range of complex animals throughout development. As Notch signaling involves cell-cell interactions, we sought to determine the expression of Notch receptors, ligands, and regulators in individual cell populations along the hematopoietic differentiation pathway. MATERIALS Described here is a single cell RT-PCR analysis of Notch1, Notch3, Notch4, Notch ligands (Dll1 and Jagged1), and Fringe gene expression in cells of the blood system. As previously described, single cell globally amplified cDNA was generated by RT-PCR from various hematopoietic precursor cells whose potential was known from sibling analysis. A precursor hierarchy slot blot was created containing these cDNAs as well as samples from maturing blood cell populations and two fibroblast cell lines. The precursor slot blot was screened with probes for each of the candidate genes. RESULTS Macrophage precursors expressed high levels of Notch1 transcript, while maturing macrophages expressed high levels of both Notch1 and Notch4. The Jagged 1 ligand transcript was highly expressed in terminally maturing cells including mast cells and megakaryocytes. In contrast, the Manic Fringe gene was highly expressed in uncommitted bi- and tri-potential precursors as well as in committed neutrophil and macrophage precursors. CONCLUSIONS Distinct expression patterns of Jagged1 and Manic Fringe suggest that their corresponding proteins could regulate cell fate choices during hematopoiesis and may be responsible for regulating communication between lineage compartments during hematopoietic development.
Collapse
Affiliation(s)
- N Singh
- Program in Cancer & Blood Research and, Toronto, Ontario, Canada
| | | | | | | |
Collapse
|
353
|
Abstract
Sexual reproduction of multicellular organisms depends critically on the coordinate development of the germ line and somatic gonad, a process known as gonadogenesis. Together these tissues ensure the formation of functional gametes and, in the female of many species, create a context for production and further development of the zygote. Since the future of the species hangs in the balance, it is not surprising that gonadogenesis is a complex process involving conserved and multi-faceted developmental mechanisms. Genetic, anatomical, cell biological, and molecular experiments have established the nematode Caenorhabditis elegans as a paradigm for studying gonadogenesis. Furthermore, these studies demonstrate the utility of C. elegans gonadogenesis for exploring broad issues in cell and developmental biology, such as cell fate specification, morphogenesis, cell signaling, cell cycle control, and programmed cell death. The synergy of molecular genetics and cell biology conducted at single-cell resolution in real time permits an extraordinary depth of analysis in this organism. In this review, we first describe the embryonic and post-embryonic development and morphology of the C. elegans gonad. Next we recount seminal experiments that established the field, highlight recent results that provide insight into conserved developmental mechanisms, and present future prospects for the field.
Collapse
Affiliation(s)
- E J Hubbard
- Department of Biology, New York University, New York, USA
| | | |
Collapse
|
354
|
Parks AL, Klueg KM, Stout JR, Muskavitch MA. Ligand endocytosis drives receptor dissociation and activation in the Notch pathway. Development 2000; 127:1373-85. [PMID: 10704384 DOI: 10.1242/dev.127.7.1373] [Citation(s) in RCA: 343] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Endocytosis of the ligand delta; is required for activation of the receptor Notch during Drosophila development. The Notch extracellular domain (NotchECD) dissociates from the Notch intracellular domain (NotchICD) and is trans-endocytosed into delta;-expressing cells in wild-type imaginal discs. Reduction of dynamin-mediated endocytosis in developing eye and wing imaginal discs reduces Notch dissociation and Notch signalling. Furthermore, dynamin-mediated delta endocytosis is required for Notch trans-endocytosis in Drosophila cultured cell lines. Endocytosis-defective delta proteins fail to mediate trans-endocytosis of Notch in cultured cells, and exhibit aberrant subcellular trafficking and reduced signalling capacity in Drosophila. We suggest that endocytosis into delta-expressing cells of NotchECD bound to delta plays a critical role during activation of the Notch receptor and is required to achieve processing and dissociation of the Notch protein.
Collapse
Affiliation(s)
- A L Parks
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | | | | | | |
Collapse
|
355
|
Zhou S, Fujimuro M, Hsieh JJ, Chen L, Miyamoto A, Weinmaster G, Hayward SD. SKIP, a CBF1-associated protein, interacts with the ankyrin repeat domain of NotchIC To facilitate NotchIC function. Mol Cell Biol 2000; 20:2400-10. [PMID: 10713164 PMCID: PMC85419 DOI: 10.1128/mcb.20.7.2400-2410.2000] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Notch proteins are transmembrane receptors that mediate intercell communication and direct individual cell fate decisions. The activated intracellular form of Notch, NotchIC, translocates to the nucleus, where it targets the DNA binding protein CBF1. CBF1 mediates transcriptional repression through the recruitment of an SMRT-histone deacetylase-containing corepressor complex. We have examined the mechanism whereby NotchIC overcomes CBF1-mediated transcriptional repression. We identified SKIP (Ski-interacting protein) as a CBF1 binding protein in a yeast two-hybrid screen. Both CBF1 and SKIP are highly conserved evolutionarily, and the SKIP-CBF1 interaction is also conserved in assays using the Caenorhabditis elegans and Drosophila melanogaster SKIP homologs. Protein-protein interaction assays demonstrated interaction between SKIP and the corepressor SMRT. More surprisingly, SKIP also interacted with NotchIC. The SMRT and NotchIC interactions were mutually exclusive. In competition binding experiments SMRT displaced NotchIC from CBF1 and from SKIP. Contact with SKIP is required for biological activity of NotchIC. A mutation in the fourth ankyrin repeat that abolished Notch signal transduction did not affect interaction with CBF1 but abolished interaction with SKIP. Further, NotchIC was unable to block muscle cell differentiation in myoblasts expressing antisense SKIP. The results suggest a model in which NotchIC activates responsive promoters by competing with the SMRT-corepressor complex for contacts on both CBF1 and SKIP.
Collapse
Affiliation(s)
- S Zhou
- Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | | | | | | | |
Collapse
|
356
|
Abstract
After many years of research, somitogenesis is still one of the major unresolved problems in developmental biology. Recent experimental findings show a novel type of pattern formation in which a signal sweeps along the presomitic mesoderm and narrows simultaneously as a new somite is formed. The signal then residues in the posterior half of the new somite, and another wave begins to sweep up from the caudal end. This behaviour is not easily explained by the existing theoretical models. We present a new model for somitogenesis that can account for this behaviour and is consistent with previous experimental observations.
Collapse
Affiliation(s)
- S Schnell
- Centre for Mathematical Biology, Mathematical Institute, Oxford, United Kingdom.
| | | |
Collapse
|
357
|
Rand MD, Grimm LM, Artavanis-Tsakonas S, Patriub V, Blacklow SC, Sklar J, Aster JC. Calcium depletion dissociates and activates heterodimeric notch receptors. Mol Cell Biol 2000; 20:1825-35. [PMID: 10669757 PMCID: PMC85363 DOI: 10.1128/mcb.20.5.1825-1835.2000] [Citation(s) in RCA: 317] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Notch receptors participate in a highly conserved signaling pathway that regulates morphogenesis in multicellular animals. Maturation of Notch receptors requires the proteolytic cleavage of a single precursor polypeptide to produce a heterodimer composed of a ligand-binding extracellular domain (N(EC)) and a single-pass transmembrane signaling domain (N(TM)). Notch signaling has been correlated with additional ligand-induced proteolytic cleavages, as well as with nuclear translocation of the intracellular portion of N(TM) (N(ICD)). In the current work, we show that the N(EC) and N(TM) subunits of Drosophila Notch and human Notch1 (hN1) interact noncovalently. N(EC)-N(TM) interaction was disrupted by 0.1% sodium dodecyl sulfate or divalent cation chelators such as EDTA, and stabilized by millimolar Ca(2+). Deletion of the Ca(2+)-binding Lin12-Notch (LN) repeats from the N(EC) subunit resulted in spontaneous shedding of N(EC) into conditioned medium, implying that the LN repeats are important in maintaining the interaction of N(EC) and N(TM). The functional consequences of EDTA-induced N(EC) dissociation were studied by using hN1-expressing NIH 3T3 cells. Treatment of these cells for 10 to 15 min with 0.5 to 10 mM EDTA resulted in the rapid shedding of N(EC), the transient appearance of a polypeptide of the expected size of N(ICD), increased intranuclear anti-Notch1 staining, and the transient activation of an Notch-sensitive reporter gene. EDTA treatment of HeLa cells expressing endogenous Notch1 also stimulated reporter gene activity to a degree equivalent to that resulting from exposure of the cells to the ligand Delta1. These findings indicate that receptor activation can occur as a consequence of N(EC) dissociation, which relieves inhibition of the intrinsically active N(TM) subunit.
Collapse
Affiliation(s)
- M D Rand
- Massachusetts General Hospital Cancer Center, Department of Cell Biology, Harvard Medical School, Charlestown, Massachusetts 02129, USA
| | | | | | | | | | | | | |
Collapse
|
358
|
Abstract
Notch has been known for many years as a receptor for inhibitory signals that shapes the pattern of the nervous system during its development. Genes in the Notch pathway function to prevent neural determination so that only a subset of the available ectodermal cells become neural precursors. The localization of Notch signaling is crucial for determining where neural precursor cells arise on a cell-by-cell basis. The unresolved problem is that studies of the expression of Notch protein and its ligands are inconsistent with the pattern of neurogenesis. During neural cell fate specification, distributions of Notch protein and of its ligand Delta appear uniform. Under the reigning paradigm, such widespread expression should lead to N signal transduction in all cells and thereby prevent any neural specification. Yet, contrary to this expectation, neural elements still form, in characteristic patterns, hence, Notch signal transduction must have been inactive in the precursor cells. The mechanism preventing Notch signaling in certain cells must be posttranslational but it has not yet been identified. This review will outline the experimental evidence supporting this view of Notch signaling, and briefly evaluate some of the possible mechanisms that have been suggested.
Collapse
Affiliation(s)
- N E Baker
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| |
Collapse
|
359
|
Zaffran S, Frasch M. Barbu: an E(spl) m4/m(alpha)-related gene that antagonizes Notch signaling and is required for the establishment of ommatidial polarity. Development 2000; 127:1115-30. [PMID: 10662650 DOI: 10.1242/dev.127.5.1115] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Notch signaling pathway is required, in concert with cell-type-specific transcriptional regulators and other signaling processes, for multiple cell fate decisions during mesodermal and ectodermal tissue development. In many instances, Notch signaling occurs initially in a bidirectional manner and then becomes unidirectional upon amplification of small inherent differences in signaling activity between neighboring cells. In addition to ligands and extracellular modulators of the Notch receptor, several intracellular proteins have been identified that can positively or negatively influence the activity of the Notch pathway during these dynamic processes. Here, we describe a new gene, Barbu, whose product can antagonize Notch signaling activity during Drosophila development. Barbu encodes a small and largely cytoplasmic protein with sequence similarity to the proteins encoded by the transcription units m4 and m(alpha) of the E(spl) complex. Ectopic expression studies with Barbu provide evidence that Barbu can antagonize Notch during lateral inhibition processes in the embryonic mesoderm, sensory organ specification in imaginal discs and cell type specification in developing ommatidia. Barbu loss-of-function mutations cause lethality and disrupt the establishment of planar polarity and photoreceptor specification in eye imaginal discs, which may also be a consequence of altered Notch signaling activities. Furthermore, in the embryonic neuroectoderm, Barbu expression is inducible by activated Notch. Taken together, we propose that Barbu functions in a negative feed-back loop, which may be important for the accurate adjustment of Notch signaling activity and the extinction of Notch activity between successive rounds of signaling events.
Collapse
Affiliation(s)
- S Zaffran
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
| | | |
Collapse
|
360
|
Mizutani K, Matsubayashi T, Iwase S, Doi TS, Kasai K, Yazaki M, Wada Y, Takahashi T, Obata Y. Murine Delta homologue, mDelta1, expressed on feeder cells controls cellular differentiation. Cell Struct Funct 2000; 25:21-31. [PMID: 10791891 DOI: 10.1247/csf.25.21] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Delta/Serrate-Notch pathway is involved in intercellular signaling that controls cell fate during the development of invertebrates and vertebrates. Delta is a prototype of Notch ligands and has been studied extensively in Drosophila. In higher vertebrates, four Delta/Serrate homologues and four Notch homologues have been identified. Recent studies showed that the murine Delta homologue, mDelta1, is essential in early embryogenesis. The biological activity of mammalian Delta and its roles in cellular differentiation, however, have remained unclear. In this study, we first surveyed expression of mDelta1 in the adult mouse and found it to be present in a wide range of tissues. For testing biological activity of mDelta1, we expressed a mDelta1 full-length cDNA in L cells using a eukaryotic expression vector. Effects of mDelta1 on cellular differentiation were examined in two independent systems, featuring C2C12 myogenic differentiation and multipotent murine bone marrow cell differentiation. Inhibition of the former was observed with mDelta1 expression on L cells, associated with suppression of myogenin, a myogenic transcription factor. Expression of mDelta1 in conjunction with GM-CSF promoted differentiation of bone marrow cells to myeloid dendritic cells at the expense of other lineages. Although the effects of mDelta1 on two differentiation systems appeared opposing, as inhibition occurring in one and induction in the other, this can be understood by the unifying concept of generation of diverse cell types from equivalent progenitors. Thus, the present study provided evidence that mammalian Delta participates in intercellular signaling, determining the cell fate in a wide variety of tissues.
Collapse
Affiliation(s)
- K Mizutani
- Laboratory of Immunology, Aichi Cancer Center Research Institute, Chikusaku, Nagoya
| | | | | | | | | | | | | | | | | |
Collapse
|
361
|
Mumm JS, Schroeter EH, Saxena MT, Griesemer A, Tian X, Pan DJ, Ray WJ, Kopan R. A ligand-induced extracellular cleavage regulates gamma-secretase-like proteolytic activation of Notch1. Mol Cell 2000; 5:197-206. [PMID: 10882062 DOI: 10.1016/s1097-2765(00)80416-5] [Citation(s) in RCA: 636] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Gamma-secretase-like proteolysis at site 3 (S3), within the transmembrane domain, releases the Notch intracellular domain (NICD) and activates CSL-mediated Notch signaling. S3 processing occurs only in response to ligand binding; however, the molecular basis of this regulation is unknown. Here we demonstrate that ligand binding facilitates cleavage at a novel site (S2), within the extracellular juxtamembrane region, which serves to release ectodomain repression of NICD production. Cleavage at S2 generates a transient intermediate peptide termed NEXT (Notch extracellular truncation). NEXT accumulates when NICD production is blocked by point mutations or gamma-secretase inhibitors or by loss of presenilin 1, and inhibition of NEXT eliminates NICD production. Our data demonstrate that S2 cleavage is a ligand-regulated step in the proteolytic cascade leading to Notch activation.
Collapse
Affiliation(s)
- J S Mumm
- Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | | | | | | | |
Collapse
|
362
|
Hoyne GF, Le Roux I, Corsin-Jimenez M, Tan K, Dunne J, Forsyth LM, Dallman MJ, Owen MJ, Ish-Horowicz D, Lamb JR. Serrate1-induced notch signalling regulates the decision between immunity and tolerance made by peripheral CD4(+) T cells. Int Immunol 2000; 12:177-85. [PMID: 10653853 DOI: 10.1093/intimm/12.2.177] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Signals derived from antigen-presenting cells (APC) influence the functional differentiation of CD4(+) T cells. We report here that Serrate1 (Jagged1), a ligand for the Notch1 receptor, may contribute to the differentiation of peripheral CD4(+) T cells into either helper or regulatory cells. Our findings demonstrate that antigen presented by murine APC overexpressing human Serrate1 induces naive peripheral CD4(+) T cells to become regulatory cells. These cells can inhibit primary and secondary immune responses, and transfer antigen-specific tolerance to recipient mice. Our results show that Notch signalling may help explain 'linked' suppression in peripheral tolerance, whereby tolerance induced to one epitope encompasses all epitopes on that antigen during the course of an immune response.
Collapse
Affiliation(s)
- G F Hoyne
- Respiratory Medicine Unit, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
363
|
Rebay I, Chen F, Hsiao F, Kolodziej PA, Kuang BH, Laverty T, Suh C, Voas M, Williams A, Rubin GM. A genetic screen for novel components of the Ras/Mitogen-activated protein kinase signaling pathway that interact with the yan gene of Drosophila identifies split ends, a new RNA recognition motif-containing protein. Genetics 2000; 154:695-712. [PMID: 10655223 PMCID: PMC1460949 DOI: 10.1093/genetics/154.2.695] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The receptor tyrosine kinase (RTK) signaling pathway is used reiteratively during the development of all multicellular organisms. While the core RTK/Ras/MAPK signaling cassette has been studied extensively, little is known about the nature of the downstream targets of the pathway or how these effectors regulate the specificity of cellular responses. Drosophila yan is one of a few downstream components identified to date, functioning as an antagonist of the RTK/Ras/MAPK pathway. Previously, we have shown that ectopic expression of a constitutively active protein (yan(ACT)) inhibits the differentiation of multiple cell types. In an effort to identify new genes functioning downstream in the Ras/MAPK/yan pathway, we have performed a genetic screen to isolate dominant modifiers of the rough eye phenotype associated with eye-specific expression of yan(ACT). Approximately 190,000 mutagenized flies were screened, and 260 enhancers and 90 suppressors were obtained. Among the previously known genes we recovered are four RTK pathway components, rolled (MAPK), son-of-sevenless, Star, and pointed, and two genes, eyes absent and string, that have not been implicated previously in RTK signaling events. We also isolated mutations in five previously uncharacterized genes, one of which, split ends, we have characterized molecularly and have shown to encode a member of the RRM family of RNA-binding proteins.
Collapse
Affiliation(s)
- I Rebay
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
364
|
Selkoe DJ. Notch and presenilins in vertebrates and invertebrates: implications for neuronal development and degeneration. Curr Opin Neurobiol 2000; 10:50-7. [PMID: 10679435 DOI: 10.1016/s0959-4388(99)00054-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Recent progress in elucidating the biology of Notch and presenilin has revealed a close functional relationship between these two proteins during cell fate determination in worms, flies and humans. Presenilins are required for the putatively intramembranous proteolysis of Notch to release its intracellular domain to the nucleus. This finding establishes a specific biochemical role for presenilins in Notch signaling and interfaces with emerging evidence about how frizzled, disheveled and numerous other genes regulate the highly complex Notch pathway. Advances in understanding Notch and presenilin functions in the differentiation of neurons and non-neural cells have important implications not only for development but also for late-life degenerative disorders such as Alzheimer's disease.
Collapse
Affiliation(s)
- D J Selkoe
- Center for Neurologic Diseases, Harvard Medical School, Brigham and Women's Hospital, HIM 730, MA 02115, USA.
| |
Collapse
|
365
|
Lai EC, Bodner R, Kavaler J, Freschi G, Posakony JW. Antagonism of notch signaling activity by members of a novel protein family encoded by the bearded and enhancer of split gene complexes. Development 2000; 127:291-306. [PMID: 10603347 DOI: 10.1242/dev.127.2.291] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cell-cell signaling through the Notch receptor is a principal mechanism underlying cell fate specification in a variety of developmental processes in metazoans, such as neurogenesis. In this report we describe our investigation of seven members of a novel gene family in Drosophila with important connections to Notch signaling. These genes all encode small proteins containing predicted basic amphipathic (α)-helical domains in their amino-terminal regions, as described originally for Bearded; accordingly, we refer to them as Bearded family genes. Five members of the Bearded family are located in a newly discovered gene complex, the Bearded Complex; two others reside in the previously identified Enhancer of split Complex. All members of this family contain, in their proximal upstream regions, at least one high-affinity binding site for the Notch-activated transcription factor Suppressor of Hairless, suggesting that all are directly regulated by the Notch pathway. Consistent with this, we show that Bearded family genes are expressed in a variety of territories in imaginal tissue that correspond to sites of active Notch signaling. We demonstrate that overexpression of any family member antagonizes the activity of the Notch pathway in multiple cell fate decisions during adult sensory organ development. These results suggest that Bearded family genes encode a novel class of effectors or modulators of Notch signaling.
Collapse
Affiliation(s)
- E C Lai
- Department of Biology, Center for Molecular Genetics, University of California San Diego, La Jolla, CA, USA
| | | | | | | | | |
Collapse
|
366
|
Redmond L, Oh SR, Hicks C, Weinmaster G, Ghosh A. Nuclear Notch1 signaling and the regulation of dendritic development. Nat Neurosci 2000; 3:30-40. [PMID: 10607392 DOI: 10.1038/71104] [Citation(s) in RCA: 263] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To understand the function of Notch in the mammalian brain, we examined Notch1 signaling and its cellular consequences in developing cortical neurons. We found that the cytoplasmic domain of endogenous Notch1 translocated to the nucleus during neuronal differentiation. Notch1 cytoplasmic-domain constructs transfected into cortical neurons were present in multiple phosphorylated forms, localized to the nucleus and could induce CBF1-mediated transactivation. Molecular perturbation experiments suggested that Notch1 signaling in cortical neurons promoted dendritic branching and inhibited dendritic growth. These observations show that Notch1 signaling to the nucleus exerts an important regulatory influence on the specification of dendritic morphology in neurons.
Collapse
Affiliation(s)
- L Redmond
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | | | |
Collapse
|
367
|
Berechid BE, Thinakaran G, Wong PC, Sisodia SS, Nye JS. Lack of requirement for presenilin1 in Notch1 signaling. Curr Biol 1999; 9:1493-6. [PMID: 10607593 DOI: 10.1016/s0960-9822(00)80121-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Studies in invertebrates have indicated a functional requirement for presenilin (PS) genes in the Notch pathway [1-5]. One model of Notch signal transduction suggests that proteolysis releases an activated Notch fragment that migrates to the nucleus and regulates gene transcription in concert with CBF1/Su(H)/lag1 (CSL) proteins [6-9]. Recent studies suggest that PS genes control the proteolysis and nuclear access of the Notch intracellular domain [3,4,10,11], offering a basis for the functional interaction of PS and Notch genes [12]. Here, we report that Notch1 signaling elicited by the ligand Delta1 was quantitatively unchanged in PS1-deficient primary embryonic fibroblasts (PEFs). Notch1 signals were measured by both the activation of the hairy/enhancer of split (HES1) promoter and by the antagonism of MyoD-induced muscle creatine kinase (MCK) promoter activity. A membrane-tethered ligand-independent Notch1 construct also showed full efficacy in both assays, despite its presumed requirement for cleavage. Although signaling through Notch1 persisted in PS1-deficient cells, we found a marked reduction in the appearance of a complex of a cleaved, intracellular Notch fragment (NICD) and a CSL protein, as previously reported [6] [10]. These studies reveal that PS1 is not required for ligand-dependent Notch signaling, and that PS1 and PS2 may be redundant. Our data also suggest that the identified NICD fragment may not be necessary for Notch signal transduction [9].
Collapse
Affiliation(s)
- B E Berechid
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago 60611, USA
| | | | | | | | | |
Collapse
|
368
|
Tomlinson A, Struhl G. Decoding vectorial information from a gradient: sequential roles of the receptors Frizzled and Notch in establishing planar polarity in the Drosophila eye. Development 1999; 126:5725-38. [PMID: 10572048 DOI: 10.1242/dev.126.24.5725] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Drosophila eye is composed of several hundred ommatidia that can exist in either of two chiral forms, depending on position: ommatidia in the dorsal half of the eye adopt one chiral form, whereas ommatidia in the ventral half adopt the other. Chirality appears to be specified by a polarizing signal with a high activity at the interface between the two halves (the ‘equator’), which declines in opposite directions towards the dorsal and ventral poles. Here, using genetic mosaics, we show that this polarizing signal is decoded by the sequential use of two receptor systems. The first depends on the seven-transmembrane receptor Frizzled (Fz) and distinguishes between the two members of the R3/R4 pair of presumptive photoreceptor cells, predisposing the cell that is located closer to the equator and having higher Fz activity towards the R3 photoreceptor fate and the cell further away towards the R4 fate. This bias is then amplified by subsequent interactions between the two cells mediated by the receptor Notch (N) and its ligand Delta (Dl), ensuring that the equatorial cell becomes the R3 photoreceptor while the polar cell becomes the R4 photoreceptor. As a consequence of this reciprocal cell fate decision, the R4 cell moves asymmetrically relative to the R3 cell, initiating the appropriate chiral pattern of the remaining cells of the ommatidium.
Collapse
Affiliation(s)
- A Tomlinson
- Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
| | | |
Collapse
|
369
|
Craig KL, Tyers M. The F-box: a new motif for ubiquitin dependent proteolysis in cell cycle regulation and signal transduction. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1999; 72:299-328. [PMID: 10581972 DOI: 10.1016/s0079-6107(99)00010-3] [Citation(s) in RCA: 198] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The ubiquitin system of intracellular protein degradation controls the abundance of many critical regulatory proteins. Specificity in the ubiquitin system is determined largely at the level of substrate recognition, a step that is mediated by E3 ubiquitin ligases. Analysis of the mechanisms of phosphorylation directed proteolysis in cell cycle regulation has uncovered a new class of E3 ubiquitin ligases called SCF complexes, which are composed of the subunits Skp1, Rbx1, Cdc53 and any one of a large number of different F-box proteins. The substrate specificity of SCF complexes is determined by the interchangeable F-box protein subunit, which recruits a specific set of substrates for ubiquitination to the core complex composed of Skp1, Rbx1, Cdc53 and the E2 enzyme Cdc34. F-box proteins have a bipartite structure--the shared F-box motif links F-box proteins to Skp1 and the core complex, whereas divergent protein-protein interaction motifs selectively bind their cognate substrates. To date all known SCF substrates are recognised in a strictly phosphorylation dependent manner, thus linking intracellular signalling networks to the ubiquitin system. The plethora of different F-box proteins in databases suggests that many pathways will be governed by SCF-dependent proteolysis. Indeed, genetic analysis has uncovered roles for F-box proteins in a variety of signalling pathways, ranging from nutrient sensing in yeast to conserved developmental pathways in plants and animals. Moreover, structural analysis has revealed ancestral relationships between SCF complexes and two other E3 ubiquitin ligases, suggesting that the combinatorial use of substrate specific adaptor proteins has evolved to allow the regulation of many cellular processes. Here, we review the known signalling pathways that are regulated by SCF complexes and highlight current issues in phosphorylation dependent protein degradation.
Collapse
Affiliation(s)
- K L Craig
- Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada
| | | |
Collapse
|
370
|
|
371
|
Affiliation(s)
- B Osborne
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst 01003, USA.
| | | |
Collapse
|
372
|
Fares H, Greenwald I. SEL-5, a serine/threonine kinase that facilitates lin-12 activity in Caenorhabditis elegans. Genetics 1999; 153:1641-54. [PMID: 10581273 PMCID: PMC1460874 DOI: 10.1093/genetics/153.4.1641] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ligands present on neighboring cells activate receptors of the LIN-12/Notch family by inducing a proteolytic cleavage event that releases the intracellular domain. Mutations that appear to eliminate sel-5 activity are able to suppress constitutive activity of lin-12(d) mutations that are point mutations in the extracellular domain of LIN-12, but cannot suppress lin-12(intra), the untethered intracellular domain. These results suggest that sel-5 acts prior to or during ligand-dependent release of the intracellular domain. In addition, sel-5 suppression of lin-12(d) mutations is tissue specific: loss of sel-5 activity can suppress defects in the anchor cell/ventral uterine precursor cell fate decision and a sex myoblast/coelomocyte decision, but cannot suppress defects in two different ventral hypodermal cell fate decisions in hermaphrodites and males. sel-5 encodes at least two proteins, from alternatively spliced mRNAs, that share an amino-terminal region and differ in the carboxy-terminal region. The amino-terminal region contains the hallmarks of a serine/threonine kinase domain, which is most similar to mammalian GAK1 and yeast Pak1p.
Collapse
Affiliation(s)
- H Fares
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
| | | |
Collapse
|
373
|
Abstract
Notch-ligand interactions are a highly conserved mechanism that regulates cell fate decisions. Over the past few years, numerous observations have shown that this mechanism operates to regulate cell differentiation in an enormous variety of developmental and cell maturation processes. Recent studies indicate that in addition to cell differentiation, Notch signaling has direct effects on proliferation and programmed cell death. The picture emerging from these findings suggests that, depending on cellular and developmental context, Notch signaling may function as a general "arbiter" of cell fate, regulating differentiation potential, rate of proliferation, and apoptotic cell death. In this review, we briefly summarize the current knowledge of the structure and function of Notch receptors and discuss the recent evidence that Notch signaling regulates apoptotic cell death. The possible mechanisms of this effect and its potential implications for developmental biology, immunobiology, neuropathology, and tumor biology are discussed.
Collapse
Affiliation(s)
- L Miele
- Cardinal Bernardin Cancer Center, Loyola University Medical Center, Maywood, Illinois 60153, USA.
| | | |
Collapse
|
374
|
Nakagawa O, Nakagawa M, Richardson JA, Olson EN, Srivastava D. HRT1, HRT2, and HRT3: a new subclass of bHLH transcription factors marking specific cardiac, somitic, and pharyngeal arch segments. Dev Biol 1999; 216:72-84. [PMID: 10588864 DOI: 10.1006/dbio.1999.9454] [Citation(s) in RCA: 227] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Members of the Hairy/Enhancer of Split family of basic helix-loop-helix (bHLH) transcription factors are regulated by the Notch signaling pathway in vertebrate and Drosophila embryos and control cell fates and establishment of sharp boundaries of gene expression. Here, we describe a new subclass of bHLH proteins, HRT1 (Hairy-related transcription factor 1), HRT2, and HRT3, that share high homology with the Hairy family of proteins yet have characteristics that are distinct from those of Hairy and other bHLH proteins. Each HRT gene was expressed in distinct cell types within numerous organs, particularly in those patterned along the anterior-posterior axis. HRT1 and HRT2 were expressed in atrial and ventricular precursors, respectively, and were also expressed in the cardiac outflow tract and aortic arch arteries. HRT1 and HRT2 transcripts were also detected in precursors of the pharyngeal arches and subsequently in the pharyngeal clefts. Within somitic precursors, HRT1 and HRT3 exhibited dynamic expression in the presomitic mesoderm, mirroring the expression of other components of Notch-Delta signaling pathways. The HRT genes were expressed in other sites of epithelial-mesenchymal interactions, including the developing kidneys, brain, limb buds, and vasculature. The unique and complementary expression patterns of this novel subfamily of bHLH proteins suggest a previously unrecognized role for Hairy-related pathways in segmental patterning of the heart and pharyngeal arches, among other organs.
Collapse
Affiliation(s)
- O Nakagawa
- Department of Molecular Biology, The University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Boulevard, Dallas, Texas, 75235-9148, USA
| | | | | | | | | |
Collapse
|
375
|
Abstract
The EH domain is an evolutionary conserved protein-protein interaction domain present in a growing number of proteins from yeast to mammals. Even though the domain was discovered just 5 years ago, a great deal has been learned regarding its three-dimensional structure and binding specificities. Moreover, a number of cellular ligands of the domain have been identified and demonstrated to define a complex network of protein-protein interactions in the eukaryotic cell. Interestingly, many of the EH-containing and EH-binding proteins display characteristics of endocytic "accessory" proteins, suggesting that the principal function of the EH network is to regulate various steps in endocytosis. In addition, recent evidence suggests that the EH network might work as an "integrator" of signals controlling cellular pathways as diverse as endocytosis, nucleocytosolic export, and ultimately cell proliferation.
Collapse
Affiliation(s)
- E Santolini
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy
| | | | | | | | | |
Collapse
|
376
|
Rusconi JC, Corbin V. A widespread and early requirement for a novel Notch function during Drosophila embryogenesis. Dev Biol 1999; 215:388-98. [PMID: 10545245 DOI: 10.1006/dbio.1999.9483] [Citation(s) in RCA: 13] [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
The Notch pathway plays a key role in the formation of many tissues and cell types in Metazoans. We recently showed that Notch acts in two pathways to determine muscle precursor fates. The first is the "standard" Notch pathway, in which Delta activates the Notch receptor, which then translocates into the nucleus in conjunction with Su(H) to reprogram transcription patterns and bring about changes in cell fates. The second pathway is poorly defined, but known to be independent of the ligands and downstream effectors of the standard pathway. The standard pathway is required in many different developmental contexts and we wondered if there was also a general requirement for the novel pathway. Here we show that the novel Notch pathway is required for the development of each of five examined cell types. These results indicate that the novel pathway is a widespread and fundamental component of Notch function. We further show that both Notch pathways operate in the differentiation of the same cell types. In such cases, the novel pathway acts first and appears to set up or limit the size of equivalence groups. The standard pathway then acts within the equivalence groups to limit individual cell fates.
Collapse
Affiliation(s)
- J C Rusconi
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
| | | |
Collapse
|
377
|
Troemel ER, Sagasti A, Bargmann CI. Lateral signaling mediated by axon contact and calcium entry regulates asymmetric odorant receptor expression in C. elegans. Cell 1999; 99:387-98. [PMID: 10571181 DOI: 10.1016/s0092-8674(00)81525-1] [Citation(s) in RCA: 210] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
C. elegans detects several odorants with the bilaterally symmetric pair of AWC olfactory neurons. A stochastic, coordinated decision ensures that the candidate odorant receptor gene str-2 is expressed in only one AWC neuron in each animal--either the left or the right neuron, but never both. An interaction between the two AWC neurons generates asymmetric str-2 expression in a process that requires normal axon guidance and probably AWC axon contact. This interaction induces str-2 expression by reducing calcium signaling through a voltage-dependent Ca2+ channel and the CaM kinase II UNC-43. CaMKII activity acts as a switch in the initial decision to express str-2; thus, calcium signals can define distinct cell types during neuronal development. A cGMP signaling pathway that is used in olfaction maintains str-2 expression after the initial decision has been made.
Collapse
Affiliation(s)
- E R Troemel
- Howard Hughes Medical Institute, Department of Anatomy, The University of California, San Francisco 94143-0452, USA
| | | | | |
Collapse
|
378
|
Schlöndorff J, Blobel CP. Metalloprotease-disintegrins: modular proteins capable of promoting cell-cell interactions and triggering signals by protein-ectodomain shedding. J Cell Sci 1999; 112 ( Pt 21):3603-17. [PMID: 10523497 DOI: 10.1242/jcs.112.21.3603] [Citation(s) in RCA: 408] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Metalloprotease-disintegrins (ADAMs) have captured our attention as key players in fertilization and in the processing of the ectodomains of proteins such as tumor necrosis factor (α) (TNF(α)), and because of their roles in Notch-mediated signaling, neurogenesis and muscle fusion. ADAMs are integral membrane glycoproteins that contain a disintegrin domain, which is related to snake-venom integrin ligands, and a metalloprotease domain (which can contain or lack a catalytic site). Here, we review and critically discuss current topics in the ADAMs field, including the central role of fertilin in fertilization, the role of the TNF(α) convertase in protein ectodomain processing, the role of Kuzbanian in Notch signaling, and links between ADAMs and processing of the amyloid-precursor protein.
Collapse
Affiliation(s)
- J Schlöndorff
- Cellular Biochemistry and Biophysics Program, Memorial Sloan Kettering Cancer Center, Box 368, Tri-Institutional (Cornell/ Rockefeller University/Sloan-Kettering Institute) MD/PhD Program, New York, NY 10021, USA
| | | |
Collapse
|
379
|
Sestan N, Artavanis-Tsakonas S, Rakic P. Contact-dependent inhibition of cortical neurite growth mediated by notch signaling. Science 1999; 286:741-6. [PMID: 10531053 DOI: 10.1126/science.286.5440.741] [Citation(s) in RCA: 462] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The exuberant growth of neurites during development becomes markedly reduced as cortical neurons mature. In vitro studies of neurons from mouse cerebral cortex revealed that contact-mediated Notch signaling regulates the capacity of neurons to extend and elaborate neurites. Up-regulation of Notch activity was concomitant with an increase in the number of interneuronal contacts and cessation of neurite growth. In neurons with low Notch activity, which readily extend neurites, up-regulation of Notch activity either inhibited extension or caused retraction of neurites. Conversely, in more mature neurons that had ceased their growth after establishing numerous connections and displayed high Notch activity, inhibition of Notch signaling promoted neurite extension. Thus, the formation of neuronal contacts results in activation of Notch receptors, leading to restriction of neuronal growth and a subsequent arrest in maturity.
Collapse
Affiliation(s)
- N Sestan
- Section of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, USA
| | | | | |
Collapse
|
380
|
Ikeya T, Hayashi S. Interplay of Notch and FGF signaling restricts cell fate and MAPK activation in the Drosophila trachea. Development 1999; 126:4455-63. [PMID: 10498681 DOI: 10.1242/dev.126.20.4455] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The patterned branching in the Drosophila tracheal system is triggered by the FGF-like ligand Branchless that activates a receptor tyrosine kinase Breathless and the MAP kinase pathway. A single fusion cell at the tip of each fusion branch expresses the zinc-finger gene escargot, leads branch migration in a stereotypical pattern and contacts with another fusion cell to mediate fusion of the branches. A high level of MAP kinase activation is also limited to the tip of the branches. Restriction of such cell specialization events to the tip is essential for tracheal tubulogenesis. Here we show that Notch signaling plays crucial roles in the singling out process of the fusion cell. We found that Notch is activated in tracheal cells by Branchless signaling through stimulation of Δ expression at the tip of tracheal branches and that activated Notch represses the fate of the fusion cell. In addition, Notch is required to restrict activation of MAP kinase to the tip of the branches, in part through the negative regulation of Branchless expression. Notch-mediated lateral inhibition in sending and receiving cells is thus essential to restrict the inductive influence of Branchless on the tracheal tubulogenesis.
Collapse
Affiliation(s)
- T Ikeya
- Genetic Strains Research Center and The Graduate University for Advanced Studies, National Institute of Genetics, Mishima 411-8540, Japan.
| | | |
Collapse
|
381
|
Abstract
The Notch pathway mediates cell-cell interaction in many developmental processes. Multiple proteins regulate the Notch pathway, among these are the products of the fringe genes. The first fringe gene was identified in Drosophila, where it is involved in the formation of the dorsal/ventral border of the wing disc. It has now been found to be crucial for determining the dorsal/ventral border of the Drosophila eye. In vertebrates, fringe genes play roles in the formation of the apical ectodermal ridge, the dorsal/ventral border in the limb bud, and in the development of somitic borders. The roles of fringe in the neural tube or the eyes of vertebrate embryos are not clear, although it is unlikely that these roles are evolutionarily related to those in the same tissues in Drosophila. Genetic evidences suggest that Fringe protein functions by modulating the Notch signaling pathway, perhaps through differential regulation of Notch activation by different ligands; however, the mechanism underlying Fringe function remains to be investigated.
Collapse
Affiliation(s)
- J Y Wu
- Departments of Pediatrics, and Molecular Biology and Pharmacology Box 8116 Washington University School of Medicine, St Louis, Missouri, 63110, USA.
| | | |
Collapse
|
382
|
Bazzoni G, Dejana E, Lampugnani MG. Endothelial adhesion molecules in the development of the vascular tree: the garden of forking paths. Curr Opin Cell Biol 1999; 11:573-81. [PMID: 10508655 DOI: 10.1016/s0955-0674(99)00023-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In the past, year targeted null mutation studies have further supported the concept that endothelial cell-matrix and cell-cell adhesion is involved in the formation and maintenance of the network of branched tubes within the vascular tree. In addition, recent results derived from the closely related experimental system of branching tubulogenesis in epithelial cells may provide an appealing model for endothelial biology.
Collapse
Affiliation(s)
- G Bazzoni
- Laboratory of Vascular Biology Istituto di Ricerche Farmacologiche Mario Negri via Eritrea 62, 20157, Milano, Italy
| | | | | |
Collapse
|
383
|
Annaert W, De Strooper B. Presenilins: molecular switches between proteolysis and signal transduction. Trends Neurosci 1999; 22:439-43. [PMID: 10481190 DOI: 10.1016/s0166-2236(99)01455-1] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mis-sense mutations of presenilin 1 increase the release of amyloidogenic peptide from amyloid precursor protein (APP) and are a major cause of familial Alzheimer's Disease. Loss-of-function mutations of presenilins in the mouse, Caenorhabditis elegans and Drosophila result in severe developmental defects caused by disturbed Notch signalling. Recent studies suggest that the diverse biological roles of presenilin 1 can be explained at the molecular level by its role in the proteolytic cleavage of the integral membrane domains of Notch and APP. This cleavage is a central switch in Notch signalling, while, for APP, its physiological role remains elusive. Evidence that presenilin 1 itself has catalytic properties could explain many of the biological and biochemical alterations caused by presenilin-1 deficiency or clinical mutations in presenilin 1. However, as presenilins reside in the endoplasmic reticulum and the cleavage of Notch and APP is believed to occur close to the cell membrane, the scientific field now faces a 'spatial paradox'.
Collapse
Affiliation(s)
- W Annaert
- Neuronal Cell Biology and Gene Transfer Laboratory, Centre for Human Genetics, Flanders Interuniversitary, Institute for Biotechnology (VIB4), Gasthuisberg, KULeuven, B-3000 Leuven, Belgium
| | | |
Collapse
|
384
|
Abstract
Reports from the past year have demonstrated that neural basic helix-loop-helix genes and LIM homeobox genes contribute to neuronal subtype specification in vertebrates and invertebrates, that Notch signaling specifies cell fates in the developing vertebrate inner ear, and that the organization of the central nervous system into three columns is shared by vertebrates and invertebrates. These findings pave the way for future work that will help to establish the extent to which these similarities represent evolutionary conservation.
Collapse
Affiliation(s)
- Y M Chan
- Howard Hughes Medical Institute Departments of Physiology and Biochemistry University of California, San Francisco 94143-0725, USA.
| | | |
Collapse
|
385
|
Rauskolb C, Correia T, Irvine KD. Fringe-dependent separation of dorsal and ventral cells in the Drosophila wing. Nature 1999; 401:476-80. [PMID: 10519550 DOI: 10.1038/46786] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The separation of cells into populations that do not intermix, termed compartments, is a fundamental organizing principle during development. Dorsal-ventral compartmentalization of the Drosophila wing is regulated downstream of the apterous (ap) gene, which encodes a transcription factor that specifies dorsal wing fate. fringe (fng) is normally expressed by dorsal cells downstream of ap; here we show that fng plays a key role in dorsal-ventral compartmentalization. Loss of fng function causes dorsal cells to violate the compartment boundary, and ectopic expression of the Fng protein causes ventral cells to violate thecompartment boundary. Fng modulates signalling through the Notch receptor. Notch and its ligands are essential for formation of the dorsal-ventral compartment border, and repositioning the stripe of Notch activation that is normally established there appears to reposition the compartment border. However, activation of Notch does not itself confer either dorsal or ventral cell location, and fng can influence compartmentalization even within regions of ubiquitous Notch activation. Our results indicate that the primary mechanism by which fng establishes a compartment border is by positioning a stripe of Notch activation, but also that fng may exert additional influences on compartmentalization.
Collapse
Affiliation(s)
- C Rauskolb
- Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers, The State University, Piscataway, New Jersey 08854, USA
| | | | | |
Collapse
|
386
|
Nellesen DT, Lai EC, Posakony JW. Discrete enhancer elements mediate selective responsiveness of enhancer of split complex genes to common transcriptional activators. Dev Biol 1999; 213:33-53. [PMID: 10452845 DOI: 10.1006/dbio.1999.9324] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In Drosophila, genes of the Enhancer of split Complex [E(spl)-C] are important components of the Notch (N) cell-cell signaling pathway, which is utilized in imaginal discs to effect a series of cell fate decisions during adult peripheral nervous system development. Seven genes in the complex encode basic helix-loop-helix (bHLH) transcriptional repressors, while 4 others encode members of the Bearded family of small proteins. A striking diversity is observed in the imaginal disc expression patterns of the various E(spl)-C genes, suggestive of a diversity of function, but the mechanistic basis of this variety has not been elucidated. Here we present strong evidence from promoter-reporter transgene experiments that regulation at the transcriptional level is primarily responsible. Certain E(spl)-C genes were known previously to be direct targets of transcriptional activation both by the N-signal-dependent activator Suppressor of Hairless [Su(H)] and by the proneural bHLH proteins achaete and scute. Our extensive sequence analysis of the promoter-proximal upstream regions of 12 transcription units in the E(spl)-C reveals that such dual transcriptional activation is likely to be the rule for at least 10 of the 12 genes. We next show that the very different wing imaginal disc expression patterns of E(spl)m4 and E(spl)mgamma are a property of small (200-300 bp), evolutionarily conserved transcriptional enhancer elements, which can confer these distinct patterns on a heterologous promoter despite their considerable structural similarity [each having three Su(H) and two proneural protein binding sites]. We also demonstrate that the characteristic inactivity of the E(spl)mgamma enhancer in the notum and margin territories of the wing disc can be overcome by elevated activity of the N receptor. We conclude that the distinctive expression patterns of E(spl)-C genes in imaginal tissues depend to a significant degree on the capacity of their transcriptional cis-regulatory apparatus to respond selectively to direct proneural- and Su(H)-mediated activation, often in only a subset of the territories and cells in which these modes of regulation are operative.
Collapse
Affiliation(s)
- D T Nellesen
- Department of Biology and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0349, USA
| | | | | |
Collapse
|
387
|
Pui JC, Allman D, Xu L, DeRocco S, Karnell FG, Bakkour S, Lee JY, Kadesch T, Hardy RR, Aster JC, Pear WS. Notch1 expression in early lymphopoiesis influences B versus T lineage determination. Immunity 1999; 11:299-308. [PMID: 10514008 DOI: 10.1016/s1074-7613(00)80105-3] [Citation(s) in RCA: 727] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Notch receptors regulate fate decisions in many cells. One outcome of Notch signaling is differentiation of bipotential precursors into one cell type versus another. To investigate consequences of Notch1 expression in hematolymphoid progenitors, mice were reconstituted with bone marrow (BM) transduced with retroviruses encoding a constitutively active form of Notch1. Although neither granulocyte or monocyte differentiation were appreciably affected, lymphopoiesis was dramatically altered. As early as 3 weeks following transplantation, mice receiving activated Notch1-transduced BM contained immature CD4+ CD8+ T cells in the BM and exhibited a simultaneous block in early B cell lymphopoiesis. These results suggest that Notch1 provides a key regulatory signal in determining T lymphoid versus B lymphoid lineage decisions, possibly by influencing lineage commitment from a common lymphoid progenitor cell.
Collapse
Affiliation(s)
- J C Pui
- Department of Pathology and Laboratory Medicine and Institute of Medicine and Engineering, University of Pennsylvania Medical Center, Philadelphia 19104, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
388
|
zur Lage P, Jarman AP. Antagonism of EGFR and notch signalling in the reiterative recruitment of Drosophila adult chordotonal sense organ precursors. Development 1999; 126:3149-57. [PMID: 10375505 DOI: 10.1242/dev.126.14.3149] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The selection of Drosophila melanogaster sense organ precursors (SOPs) for sensory bristles is a progressive process: each neural equivalence group is transiently defined by the expression of proneural genes (proneural cluster), and neural fate is refined to single cells by Notch-Delta lateral inhibitory signalling between the cells. Unlike sensory bristles, SOPs of chordotonal (stretch receptor) sense organs are tightly clustered. Here we show that for one large adult chordotonal SOP array, clustering results from the progressive accumulation of a large number of SOPs from a persistent proneural cluster. This is achieved by a novel interplay of inductive epidermal growth factor-receptor (EGFR) and competitive Notch signals. EGFR acts in opposition to Notch signalling in two ways: it promotes continuous SOP recruitment despite lateral inhibition, and it attenuates the effect of lateral inhibition on the proneural cluster equivalence group, thus maintaining the persistent proneural cluster. SOP recruitment is reiterative because the inductive signal comes from previously recruited SOPs.
Collapse
Affiliation(s)
- P zur Lage
- Institute of Cell and Molecular Biology, University of Edinburgh, King's Buildings, Edinburgh, EH9 3JR, UK
| | | |
Collapse
|
389
|
Kokubo H, Lun Y, Johnson RL. Identification and expression of a novel family of bHLH cDNAs related to Drosophila hairy and enhancer of split. Biochem Biophys Res Commun 1999; 260:459-65. [PMID: 10403790 DOI: 10.1006/bbrc.1999.0880] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In this report we describe the initial characterization of murine, human, and Drosophila hesr-1 (for hairy and enhancer of split related-1) a novel evolutionary conserved family of hairy/enhancer of split homologs. Hesr-1 cDNAs display features typical of hairy and enhancer of split-type bHLH proteins including a N-terminal bHLH domain a conserved orange domain immediately C-terminal to the bHLH region. Despite their similarity to known hairy/enhancer of split homologs, hesr-1 cDNAs are divergent members of the hairy and enhancer of split bHLH family since the degree of sequence identity within the bHLH and their nearest homologs are relatively low. Moreover, the tetrapeptide motif, WRPW, which is found in all hairy and enhancer of split family members, is not present in hesr-1. Rather, a variant of this motif, YRPW, is found. Analysis of embryonic murine hesr-1 expression by in situ hybridization reveals strong expression in the somitic mesoderm, the central nervous system, the kidney, the heart, nasal epithelium, and limbs indicating a role for hesr-1 in the development of these tissues. Like the enhancer of split cDNAs in Drosophila, we show that hesr-1 expression depends critically on signaling through the notch pathway in murine embryos, suggesting that aspects of hesr-1 regulation and function might also be evolutionary conserved.
Collapse
Affiliation(s)
- H Kokubo
- Department of Biochemistry and Molecular Biology, University of Texas, MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas, 77030, USA
| | | | | |
Collapse
|
390
|
Abstract
Intercellular signaling through the Notch receptor and its ligands leads to the spatial differentiation of cell fate in vertebrates and invertebrates. In Myxococcus xanthus, fruiting-body development requires the transmission of a cell-bound intercellular signal by the protein called C-factor, which is functionally equivalent to the eukaryotic Notch ligands. Functional parallels between these two signaling systems include strong positive and negative feedback, and a consequent role in spatial differentiation. Consideration of these parallels enables us to make testable experimental predictions about Notch and C-signaling.
Collapse
Affiliation(s)
- D Kaiser
- Departments of Biochemistry and Developmental Biology, Beckman Center, B300, Stanford University School of Medicine, Stanford, CA 94305-5329, USA.
| |
Collapse
|
391
|
Jennings BH, Tyler DM, Bray SJ. Target specificities of Drosophila enhancer of split basic helix-loop-helix proteins. Mol Cell Biol 1999; 19:4600-10. [PMID: 10373509 PMCID: PMC84258 DOI: 10.1128/mcb.19.7.4600] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Seven Enhancer of split genes in Drosophila melanogaster encode basic-helix-loop-helix transcription factors which are components of the Notch signalling pathway. They are expressed in response to Notch activation and mediate some effects of the pathway by regulating the expression of target genes. Here we have determined that the optimal DNA binding site for the Enhancer of split proteins is a palindromic 12-bp sequence, 5'-TGGCACGTG(C/T)(C/T)A-3', which contains an E-box core (CACGTG). This site is recognized by all of the individual Enhancer of split basic helix-loop-helix proteins, consistent with their ability to regulate similar target genes in vivo. We demonstrate that the 3 bp flanking the E-box core are intrinsic to DNA recognition by these proteins and that the Enhancer of split and proneural proteins can compete for binding on specific DNA sequences. Furthermore, the regulation conferred on a reporter gene in Drosophila by three closely related sequences demonstrates that even subtle sequence changes within an E box or flanking bases have dramatic consequences on the overall repertoire of proteins that can bind in vivo.
Collapse
Affiliation(s)
- B H Jennings
- Department of Anatomy, University of Cambridge, Cambridge CB2 3DY, United Kingdom
| | | | | |
Collapse
|
392
|
Abstract
The possession of segmented appendages is a defining characteristic of the arthropods. By analyzing both loss-of-function and ectopic expression experiments, we show that the Notch signaling pathway plays a fundamental role in the segmentation and growth of the Drosophila leg. Local activation of Notch is necessary and sufficient to promote the formation of joints between segments. This segmentation process requires the participation of the Notch ligands, Serrate and Delta, as well as Fringe. These three proteins are each expressed in the developing leg and antennal imaginal discs in a segmentally repeated pattern that is regulated downstream of the action of Wingless and Decapentaplegic. Our studies further show that Notch activation is both necessary and sufficient to promote leg growth. We also identify target genes regulated both positively and negatively downstream of Notch signaling that are required for normal leg development. Together, these observations outline a regulatory hierarchy for the segmentation and growth of the leg. The Notch pathway is also deployed for segmentation during vertebrate somitogenesis, which raises the possibility of a common origin for the segmentation of these distinct tissues.
Collapse
Affiliation(s)
- C Rauskolb
- Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers, The State University, Piscataway, New Jersey, 08854, USA
| | | |
Collapse
|
393
|
Wen C, Greenwald I. p24 proteins and quality control of LIN-12 and GLP-1 trafficking in Caenorhabditis elegans. J Biophys Biochem Cytol 1999; 145:1165-75. [PMID: 10366590 PMCID: PMC2133156 DOI: 10.1083/jcb.145.6.1165] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Mutations in the Caenorhabditis elegans sel-9 gene elevate the activity of lin-12 and glp-1, which encode members of the LIN-12/NOTCH family of receptors. Sequence analysis indicates SEL-9 is one of several C. elegans p24 proteins. Allele-specific genetic interactions suggest that reducing sel-9 activity increases the activity of mutations altering the extracellular domains of LIN-12 or GLP-1. Reducing sel-9 activity restores the trafficking to the plasma membrane of a mutant GLP-1 protein that would otherwise accumulate within the cell. Our results suggest a role for SEL-9 and other p24 proteins in the negative regulation of transport of LIN-12 and GLP-1 to the cell surface, and favor a role for p24 proteins in a quality control mechanism for endoplasmic reticulum-Golgi transport.
Collapse
Affiliation(s)
- C Wen
- Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA
| | | |
Collapse
|
394
|
Ellmeier W, Sawada S, Littman DR. The regulation of CD4 and CD8 coreceptor gene expression during T cell development. Annu Rev Immunol 1999; 17:523-54. [PMID: 10358767 DOI: 10.1146/annurev.immunol.17.1.523] [Citation(s) in RCA: 208] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The two major subsets of T lymphocytes in the peripheral immune system, the helper and cytotoxic T cells, are defined by their expression of either the CD4 or the CD8 glycoproteins, respectively. Expression of these molecules, which serve as coreceptors by interacting specifically with either MHC class II or class I molecules, also defines discrete stages of T cell development within the thymus. Thus, CD4+ and CD8+ single-positive (SP) thymocytes arise from common progenitor double positive (DP) cells that express both CD4 and CD8, during a process known as positive selection. The molecular mechanisms underlying the developmental choice toward the helper or cytotoxic lineage remain poorly understood. Because regulation of coreceptor gene expression appears to be coupled to the phenotypic choice of the differentiating T cell, it is likely that shared signaling pathways direct CD4 and CD8 transcription and the development of an uncommited DP thymocyte toward either the helper or cytotoxic lineage. Therefore, an understanding of how CD4 and CD8 expression is regulated will not only provide insights into transcriptional control mechanisms in T cells, but may also result in the identification of molecular factors that are involved in lineage choices during T cell development. In this review, we summarize recent progress that has been made toward an understanding of how CD4 and CD8 gene expression is regulated.
Collapse
Affiliation(s)
- W Ellmeier
- Molecular Pathogenesis Program, Skirball Institute of Biomolecular Medicine, New York, NY 10016, USA
| | | | | |
Collapse
|
395
|
Song W, Nadeau P, Yuan M, Yang X, Shen J, Yankner BA. Proteolytic release and nuclear translocation of Notch-1 are induced by presenilin-1 and impaired by pathogenic presenilin-1 mutations. Proc Natl Acad Sci U S A 1999; 96:6959-63. [PMID: 10359821 PMCID: PMC22024 DOI: 10.1073/pnas.96.12.6959] [Citation(s) in RCA: 287] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Notch family of proteins consists of transmembrane receptors that play a critical role in the determination of cell fate. Genetic studies in Caenorhabditis elegans suggest that the presenilin proteins, which are associated with familial Alzheimer's disease, regulate Notch signaling. Here we show that proteolytic release of the Notch-1 intracellular domain (NICD), an essential step in the activation of Notch signaling, is markedly reduced in presenilin-1 (PS1)-deficient cells and is restored by PS1 expression. Nuclear translocation of the NICD is also markedly reduced in PS1-deficient cells, resulting in reduced transcriptional activation. Mutations in PS1 that are associated with familial Alzheimer's disease impair the ability of PS1 to induce proteolytic release of the NICD and nuclear translocation of the cleaved protein. These results suggest that PS1 plays a central role in the proteolytic activation of the Notch-1-signaling pathway and that this function is impaired by pathogenic PS1 mutations. Thus, dysregulation of proteolytic function may underlie the mechanism by which presenilin mutations cause Alzheimer's disease.
Collapse
Affiliation(s)
- W Song
- Department of Neurology, Harvard Medical School and Division of Neuroscience, The Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA
| | | | | | | | | | | |
Collapse
|
396
|
Llimargas M. The Notch pathway helps to pattern the tips of the Drosophila tracheal branches by selecting cell fates. Development 1999; 126:2355-64. [PMID: 10225995 DOI: 10.1242/dev.126.11.2355] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The Drosophila tracheal system consists of a stereotyped network of epithelial tubes formed by several tracheal cell types. By the end of embryogenesis, when the general branching pattern is established, some specialised tracheal cells then mediate branch fusion while others extend fine terminal branches. Here evidence is presented that the Notch signalling pathway acts directly in the tracheal cells to distinguish individual fates within groups of equivalent cells. Notch helps to single out those tracheal cells that mediate branch fusion by blocking their neighbours from adopting the same fate. This function of Notch would require the restricted activation of the pathway in specific cells. In addition, and probably later, Notch also acts in the selection of those tracheal cells that extend the terminal branches. Both the localised expression and the mutant phenotypes of Delta, a known ligand for Notch, suggest that Delta may activate Notch to specify cell fates at the tips of the developing tracheal branches.
Collapse
Affiliation(s)
- M Llimargas
- Medical Research Council, Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK.
| |
Collapse
|
397
|
Affiliation(s)
- Y M Chan
- Howard Hughes Medical Institute, Department of Physiology, University of California, San Francisco, 94143-0725, USA
| | | |
Collapse
|
398
|
Kavaler J, Fu W, Duan H, Noll M, Posakony JW. An essential role for the Drosophila Pax2 homolog in the differentiation of adult sensory organs. Development 1999; 126:2261-72. [PMID: 10207150 DOI: 10.1242/dev.126.10.2261] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The adult peripheral nervous system of Drosophila includes a complex array of mechanosensory organs (bristles) that cover much of the body surface of the fly. The four cells (shaft, socket, sheath, and neuron) which compose each of these organs adopt distinct fates as a result of cell-cell signaling via the Notch (N) pathway. However, the specific mechanisms by which these cells execute their conferred fates are not well understood. Here we show that D-Pax2, the Drosophila homolog of the vertebrate Pax2 gene, has an essential role in the differentiation of the shaft cell. In flies bearing strong loss-of-function mutations in the shaven function of D-Pax2, shaft structures specifically fail to develop. Consistent with this, we find that D-Pax2 protein is expressed in all cells of the bristle lineage during the mitotic (cell fate specification) phase of bristle development, but becomes sharply restricted to the shaft and sheath cells in the post-mitotic (differentiative) phase. Two lines of evidence described here indicate that D-Pax2 expression and function is at least in part downstream of cell fate specification mechanisms such as N signaling. First, we find that the lack of late D-Pax2 expression in the socket cell (the sister of the shaft cell) is controlled by N pathway activity; second, we find that loss of D-Pax2 function is epistatic to the socket-to-shaft cell fate transformation caused by reduced N signaling. Finally, we show that misexpression of D-Pax2 is sufficient to induce the production of ectopic shaft structures. From these results, we propose that D-Pax2 is a high-level transcriptional regulator of the shaft cell differentiation program, and acts downstream of the N signaling pathway as a specific link between cell fate determination and cell differentiation in the bristle lineage.
Collapse
Affiliation(s)
- J Kavaler
- Department of Biology, University of California San Diego, La Jolla, CA 92093-0349, USA
| | | | | | | | | |
Collapse
|
399
|
Barrantes IB, Elia AJ, Wünsch K, Hrabe de Angelis MH, Mak TW, Rossant J, Conlon RA, Gossler A, de la Pompa JL. Interaction between Notch signalling and Lunatic fringe during somite boundary formation in the mouse. Curr Biol 1999; 9:470-80. [PMID: 10330372 DOI: 10.1016/s0960-9822(99)80212-7] [Citation(s) in RCA: 197] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND The process of somitogenesis can be divided into three major events: the prepatterning of the mesoderm; the formation of boundaries between the prospective somites; and the cellular differentiation of the somites. Expression and functional studies have demonstrated the involvement of the murine Notch pathway in somitogenesis, although its precise role in this process is not yet well understood. We examined the effect of mutations in the Notch pathway elements Delta like 1 (Dll1), Notch1 and RBPJkappa on genes expressed in the presomitic mesoderm (PSM) and have defined the spatial relationships of Notch pathway gene expression in this region. RESULTS We have shown that expression of Notch pathway genes in the PSM overlaps in the region where the boundary between the posterior and anterior halves of two consecutive somites will form. The Dll1, Notch1 and RBPJkappa mutations disrupt the expression of Lunatic fringe (L-fng), Jagged1, Mesp1, Mesp2 and Hes5 in the PSM. Furthermore, expression of EphA4, mCer 1 and uncx4.1, markers for the anterior-posterior subdivisions of the somites, is down-regulated to different extents in Notch pathway mutants, indicating a global alteration of pattern in the PSM. CONCLUSIONS We propose a model for the mechanism of somite border formation in which the activity of Notch in the PSM is restricted by L-fng to a boundary-forming territory in the posterior half of the prospective somite. In this region, Notch function activates a set of genes that are involved in boundary formation and anterior-posterior somite identity.
Collapse
Affiliation(s)
- I B Barrantes
- Amgen Institute, Ontario Cancer Institute, Departments of Medical Biophysics and Immunology University of Toronto 620 University Avenue, Toronto, Ontario, M5G 2C1, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
400
|
Domen J, Weissman IL. Self-renewal, differentiation or death: regulation and manipulation of hematopoietic stem cell fate. MOLECULAR MEDICINE TODAY 1999; 5:201-8. [PMID: 10322312 DOI: 10.1016/s1357-4310(99)01464-1] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Hematopoietic stem cells (HSCs) are the rare cells from which all hematopoietic cells are derived. The absence of HSCs is not compatible with life because many essential cells, such as myeloid and erythroid cells, are short lived. The hematopoietic system is the first essential organ system that fails following cytotoxic treatments. It is the vulnerability of HSCs that prevents regeneration following treatment and thus long-term survival. Because HSCs have the capacity to regenerate a functional hematopoietic system, the manipulation of these cells in vitro holds many promises for gene-therapeutic and other applications; however, these are severely curtailed by current difficulties in maintaining and expanding HSCs in culture. This review focuses on recent approaches towards understanding how the HSC compartment is regulated in vivo and discusses how this knowledge might be applied to manipulating HSC numbers.
Collapse
Affiliation(s)
- J Domen
- Dept of Pathology and Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305-5428, USA.
| | | |
Collapse
|