201
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Reugels AM, Boggetti B, Scheer N, Campos-Ortega JA. Asymmetric localization of Numb:EGFP in dividing neuroepithelial cells during neurulation inDanio rerio. Dev Dyn 2006; 235:934-48. [PMID: 16493689 DOI: 10.1002/dvdy.20699] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In the neural plate and tube of the zebrafish embryo, cells divide with their mitotic spindles oriented parallel to the plane of the neuroepithelium, whilst in the neural keel and rod, the spindle is oriented perpendicular to it. This change is achieved by a 90 degrees rotation of the mitotic spindle. We cloned zebrafish homologues of the gene for the Drosophila cell fate determinant Numb, and analyzed the localization of EGFP fusion proteins in vivo in dividing neuroepithelial cells during neurulation. Whereas Numb isoform 3 and the related protein Numblike are localized in the cytoplasm, Numb isoform 1 is localized to the cell membrane. Time-lapse analyses showed that Numb 1 is distributed uniformly around the cell cortex in dividing cells during plate and keel stages, but becomes localized at the basolateral membrane of some dividing cells during the transition from neural rod to tube. Using in vitro mutagenesis and Numb:EGFP deletion constructs, we showed that the first 196 amino acids of Numb are sufficient for this localization. Furthermore, we found that an 11-amino acid insertion in the PTB domain is essential for localization to the cortex, whereas amino acids 2-12 mediate the basolateral localization in the neural tube stage.
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Affiliation(s)
- Alexander M Reugels
- Institut für Entwicklungsbiologie, Universität zu Köln, 50923 Köln, Germany.
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202
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Hutterer A, Knoblich JA. Numb and alpha-Adaptin regulate Sanpodo endocytosis to specify cell fate in Drosophila external sensory organs. EMBO Rep 2006; 6:836-42. [PMID: 16113648 PMCID: PMC1369167 DOI: 10.1038/sj.embor.7400500] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 05/30/2005] [Accepted: 07/01/2005] [Indexed: 11/08/2022] Open
Abstract
During asymmetric cell division in Drosophila sensory organ precursors (SOPs), the Numb protein segregates into one of the two daughter cells, in which it inhibits Notch signalling to specify pIIb cell fate. We show here that Numb acts in SOP cells by inducing the endocytosis of Sanpodo, a four-pass transmembrane protein that has previously been shown to regulate Notch signalling in the central nervous system. In sanpodo mutants, SOP cells divide symmetrically into two pIIb cells. We show that Sanpodo is cortical in pIIa, but colocalizes with Notch and Delta in Rab5- and Rab7-positive endocytic vesicles in pIIb. Sanpodo endocytosis requires alpha-Adaptin, a Numb-binding partner involved in clathrin-mediated endocytosis. In numb or alpha-adaptin mutants, Sanpodo is not endocytosed. Surprisingly, this defect is observed already before and during mitosis, which suggests that Numb not only acts in pIIb, but also regulates endocytosis throughout the cell cycle. Numb binds to Sanpodo by means of its phosphotyrosine-binding domain, a region that is essential for Numb function. Our results establish numb- and alpha-adaptin-dependent endocytosis of Sanpodo as the mechanism by which Notch is regulated during external sensory organ development.
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Affiliation(s)
- Andrea Hutterer
- Institute of Molecular Biotechnology (IMBA), Dr Bohr Gasse 3-5, 1030 Vienna, Austria
| | - Juergen A Knoblich
- Institute of Molecular Biotechnology (IMBA), Dr Bohr Gasse 3-5, 1030 Vienna, Austria
- Tel: +43 1 79730 451; Fax: +43 1 79730 459; E-mail:
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203
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Le Borgne R. Regulation of Notch signalling by endocytosis and endosomal sorting. Curr Opin Cell Biol 2006; 18:213-22. [PMID: 16488590 DOI: 10.1016/j.ceb.2006.02.011] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Accepted: 02/08/2006] [Indexed: 01/31/2023]
Abstract
Cell-cell signalling is an essential process in the formation of multicellular organisms. Notch is the receptor of an evolutionarily conserved signalling pathway regulating numerous developmental decisions. Indeed, its misregulation is linked to multiple developmental and physiological disorders. Notch and its ligands are distributed widely throughout development, yet Notch activity is highly controlled and restricted in time and space. Recent advances have highlighted that endocytosis followed by endosomal sorting of both the Notch receptor and its ligands is an essential mechanism by which Notch-mediated signalling is developmentally controlled.
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Affiliation(s)
- Roland Le Borgne
- CNRS UMR 6061, Faculté de Médecine, 2 avenue du Professeur Léon Bernard, CS 34317, 35043 Rennes Cedex, France.
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204
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Yang SR, Kim SJ, Byun KH, Hutchinson B, Lee BH, Michikawa M, Lee YS, Kang KS. NPC1 Gene Deficiency Leads to Lack of Neural Stem Cell Self-Renewal and Abnormal Differentiation Through Activation of p38 Mitogen-Activated Protein Kinase Signaling. Stem Cells 2006; 24:292-8. [PMID: 16099992 DOI: 10.1634/stemcells.2005-0221] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Neural stem cells (NSCs) are capable of giving rise to neurons, glia, and astrocytes. Although self-renewal and differentiation in NSCs are regulated by many genes, such as Notch and Numb, little is known about the role of defective genes on the self-renewal and differentiation of NSCs from developing brain. The Niemann-Pick type C1 (NPC1) disease is a neurodegenerative disease caused by a mutation of the NPC1 gene that affects the function of the NPC1 protein. The ability of NSC self-renewal and differentiation was investigated using a model of NPC1 disease. The NPC1 disorder significantly affected the self-renewal ability of NSCs, as well as the differentiation. NSCs from NPC1-/- mice showed impaired self-renewal ability compared with the NPC1+/+ mice. These alterations were accompanied by the enhanced activity of p38 mitogen-activated protein kinases (MAPKs). Further, the specific p38 MAPK inhibitor SB202190 improved the self-renewal ability of NSCs from NPC-/- mice. This indicated that the NPC1 deficiency can lead to lack of self-renewal and altered differentiation of NSCs mediated by the activation of p38 MAPK, impairing the generation of neurospheres from NPC1-/- Thus, the NPC1 gene may play a crucial role in NSC self-renewal associated with p38 MAPK.
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Affiliation(s)
- Se-Ran Yang
- Laboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, Seoul National University, SAN 56-1, Sillim-Dong, Kwanak-gu, Seoul 151-742, Korea
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205
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Tosoni D, Puri C, Confalonieri S, Salcini AE, De Camilli P, Tacchetti C, Di Fiore PP. TTP specifically regulates the internalization of the transferrin receptor. Cell 2006; 123:875-88. [PMID: 16325581 DOI: 10.1016/j.cell.2005.10.021] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2005] [Revised: 08/10/2005] [Accepted: 10/13/2005] [Indexed: 10/25/2022]
Abstract
Different plasma membrane receptors are internalized through saturable/noncompetitive pathways, suggesting cargo-specific regulation. Here, we report that TTP (SH3BP4), a SH3-containing protein, specifically regulates the internalization of the transferrin receptor (TfR). TTP interacts with endocytic proteins, including clathrin, dynamin, and the TfR, and localizes selectively to TfR-containing coated-pits (CCP) and -vesicles (CCV). Overexpression of TTP specifically inhibits TfR internalization, and causes the formation of morphologically aberrant CCP, which are probably fission impaired. This effect is mediated by the SH3 of TTP, which can bind to dynamin, and it is rescued by overexpression of dynamin. Functional ablation of TTP causes a reduction in TfR internalization, and reduced cargo loading and size of TfR-CCV. Tyrosine phosphorylation of either TTP or dynamin prevents their interaction, pointing to a possible mechanism of exclusion of TTP from some CCP. Thus, TTP might represent one of the long sought for molecules that allow cargo-specific control of clathrin endocytosis.
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Affiliation(s)
- Daniela Tosoni
- IFOM, Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy
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206
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Ohtsuka T, Imayoshi I, Shimojo H, Nishi E, Kageyama R, McConnell SK. Visualization of embryonic neural stem cells using Hes promoters in transgenic mice. Mol Cell Neurosci 2006; 31:109-22. [PMID: 16214363 DOI: 10.1016/j.mcn.2005.09.006] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Revised: 08/18/2005] [Accepted: 09/07/2005] [Indexed: 10/25/2022] Open
Abstract
In the central nervous system, neural stem cells proliferate in the ventricular zone (VZ) and sequentially give rise to both neurons and glial cells in a temporally and spatially regulated manner, suggesting that stem cells may differ from one another in different brain regions and at different developmental stages. For the purpose of marking and purifying neural stem cells to ascertain whether such differences exist, we generated transgenic mice using promoters from Hes genes (pHes1 or pHes5) to drive expression of destabilized enhanced green fluorescent protein. In the developing brains of these transgenic mice, GFP expression was restricted to undifferentiated cells in the VZ, which could asymmetrically produce a Numb-positive neuronal daughter and a GFP-positive progenitor cell in clonal culture, indicating that they retain the capacity to self-renew. Our results suggest that pHes-EGFP transgenic mice can be used to explore similarities and differences among neural stem cells during development.
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Affiliation(s)
- Toshiyuki Ohtsuka
- Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA.
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207
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Baker C, Nielsen HM, Minthon L, Wright HT, Chappell S, Okyere J, May S, Morgan K, Kalsheker N, Janciauskiene SM. Effects of Alzheimer's peptide and alpha1-antichymotrypsin on astrocyte gene expression. Neurobiol Aging 2005; 28:51-61. [PMID: 16364502 DOI: 10.1016/j.neurobiolaging.2005.10.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Revised: 10/20/2005] [Accepted: 10/21/2005] [Indexed: 01/08/2023]
Abstract
We employed gene array technology to investigate the effects of alpha1-antichymotrypsin (ACT), soluble or fibrillar Alzheimer's peptide (Abeta(1-42)) alone and the combination of ACT/Abeta(1-42) on human astrocytes. Using a 1.2-fold change as significance threshold, 398 astrocyte genes showed altered expression in response to these treatments compared to controls. Of the 276 genes affected by the ACT/soluble Abeta(1-42) combination, 195 (70.6%) were suppressed. The ACT/fibrillar Abeta(1-42) combination affected expression of 64 genes of which 58 (90.5%) were up-regulated. The most prominent gene expression changes in response to the ACT/soluble Abeta(1-42), were the down-regulation of at least 60 genes involved in transcription, signal transduction, apoptosis and neurogenesis. The ACT/fibril Abeta(1-42) increased the expression of genes involved in transcription regulation and signal transduction. Surprisingly, gene expression of astrocytes exposed to soluble or fibrillar Abeta(1-42) alone was largely unaffected. Thus, the molecular forms generated by the combination of ACT/Abeta(1-42) alter expression of astrocyte genes more profoundly in breadth and magnitude than soluble or fibrillar Abeta(1-42) alone, suggesting that pathogenic effects of Abeta(1-42) may occur as a consequence of its association with other proteins.
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Affiliation(s)
- Crystal Baker
- Institute of Genetics, School of Molecular Medical Sciences, University of Nottingham, Nottingham NG7 2UH, UK.
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208
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Jafar-Nejad H, Andrews HK, Acar M, Bayat V, Wirtz-Peitz F, Mehta SQ, Knoblich JA, Bellen HJ. Sec15, a component of the exocyst, promotes notch signaling during the asymmetric division of Drosophila sensory organ precursors. Dev Cell 2005; 9:351-63. [PMID: 16137928 DOI: 10.1016/j.devcel.2005.06.010] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2005] [Revised: 06/13/2005] [Accepted: 06/30/2005] [Indexed: 01/05/2023]
Abstract
Asymmetric division of sensory organ precursors (SOPs) in Drosophila generates different cell types of the mature sensory organ. In a genetic screen designed to identify novel players in this process, we have isolated a mutation in Drosophila sec15, which encodes a component of the exocyst, an evolutionarily conserved complex implicated in intracellular vesicle transport. sec15(-) sensory organs contain extra neurons at the expense of support cells, a phenotype consistent with loss of Notch signaling. A vesicular compartment containing Notch, Sanpodo, and endocytosed Delta accumulates in basal areas of mutant SOPs. Based on the dynamic traffic of Sec15, its colocalization with the recycling endosomal marker Rab11, and the aberrant distribution of Rab11 in sec15 clones, we propose that a defect in Delta recycling causes cell fate transformation in sec15(-) sensory lineages. Our data indicate that Sec15 mediates a specific vesicle trafficking event to ensure proper neuronal fate specification in Drosophila.
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Affiliation(s)
- Hamed Jafar-Nejad
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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209
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Emery G, Hutterer A, Berdnik D, Mayer B, Wirtz-Peitz F, Gaitan MG, Knoblich JA. Asymmetric Rab 11 endosomes regulate delta recycling and specify cell fate in the Drosophila nervous system. Cell 2005; 122:763-73. [PMID: 16137758 DOI: 10.1016/j.cell.2005.08.017] [Citation(s) in RCA: 251] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Revised: 06/22/2005] [Accepted: 08/16/2005] [Indexed: 01/15/2023]
Abstract
Drosophila sensory organ precursor (SOP) cells are a well-studied model system for asymmetric cell division. During SOP division, the determinants Numb and Neuralized segregate into the pIIb daughter cell and establish a distinct cell fate by regulating Notch/Delta signaling. Here, we describe a Numb- and Neuralized-independent mechanism that acts redundantly in cell-fate specification. We show that trafficking of the Notch ligand Delta is different in the two daughter cells. In pIIb, Delta passes through the recycling endosome which is marked by Rab 11. In pIIa, however, the recycling endosome does not form because the centrosome fails to recruit Nuclear fallout, a Rab 11 binding partner that is essential for recycling endosome formation. Using a mammalian cell culture system, we demonstrate that recycling endosomes are essential for Delta activity. Our results suggest that cells can regulate signaling pathways and influence their developmental fate by inhibiting the formation of individual endocytic compartments.
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Affiliation(s)
- Gregory Emery
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr Gasse 3-5, 1030 Vienna, Austria
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210
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Abstract
This review discusses current understanding of the role that endogenous and exogenous progenitor cells may have in the treatment of the diseased heart. In the last several years, a major effort has been made in an attempt to identify immature cells capable of differentiating into cell lineages different from the organ of origin to be employed for the regeneration of the damaged heart. Embryonic stem cells (ESCs) and bone marrow-derived cells (BMCs) have been extensively studied and characterized, and dramatic advances have been made in the clinical application of BMCs in heart failure of ischemic and nonischemic origin. However, a controversy exists concerning the ability of BMCs to acquire cardiac cell lineages and reconstitute the myocardium lost after infarction. The recognition that the adult heart possesses a stem cell compartment that can regenerate myocytes and coronary vessels has raised the unique possibility to rebuild dead myocardium after infarction, to repopulate the hypertrophic decompensated heart with new better functioning myocytes and vascular structures, and, perhaps, to reverse ventricular dilation and wall thinning. Cardiac stem cells may become the most important cell for cardiac repair.
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Affiliation(s)
- Annarosa Leri
- Cardiovascular Research Institute, Department of Medicine, New York Medical College, Valhalla, NY10595, USA
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211
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Bhalerao S, Berdnik D, Török T, Knoblich JA. Localization-Dependent and -Independent Roles of Numb Contribute to Cell-Fate Specification in Drosophila. Curr Biol 2005; 15:1583-90. [PMID: 16139215 DOI: 10.1016/j.cub.2005.07.061] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 07/11/2005] [Accepted: 07/14/2005] [Indexed: 11/23/2022]
Abstract
During asymmetric cell division, protein determinants are segregated into one of the two daughter cells. The Numb protein acts as a segregating determinant during both mouse and Drosophila development. In flies, Numb localizes asymmetrically and is required for cell-fate specification in the central and peripheral nervous systems, as well as during muscle and heart development. Whether its asymmetric segregation is important to the performance of these functions is not firmly established. Here, we demonstrate that Numb acts both in a localization-dependent and in a localization-independent manner. We have generated numb mutants that affect only the asymmetric localization of the protein during mitosis. We demonstrate that asymmetric segregation of Numb into one of the two daughter cells is absolutely essential for cell-fate specification in the Drosophila peripheral nervous system. Numb localization is also essential in MP2 neuroblasts in the central nervous system and during muscle development. Surprisingly, in dividing ganglion mother cells or during heart development, Numb function is independent of its ability to segregate asymmetrically in mitosis. Our results suggest that two classes of asymmetric cell division exist, each with different requirements for asymmetric inheritance of cell-fate determinants.
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Affiliation(s)
- Sheetal Bhalerao
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Dr. Bohr Gasse 3-5, 1030 Vienna, Austria
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212
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Montesinos ML, Castellano-Muñoz M, García-Junco-Clemente P, Fernández-Chacón R. Recycling and EH domain proteins at the synapse. ACTA ACUST UNITED AC 2005; 49:416-28. [PMID: 16054223 DOI: 10.1016/j.brainresrev.2005.06.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 06/13/2005] [Accepted: 06/14/2005] [Indexed: 11/29/2022]
Abstract
In neurons, a network of endocytic proteins accomplishes highly regulated processes such as synaptic vesicle cycling and the timely internalization of intracellular signaling molecules. In this review, we discuss recent advances on molecular networks created through interactions between proteins bearing the Eps15 homology (EH) domain and partner proteins containing the Asn-Pro-Phe (NPF) motif, which participate in important aspects of neuronal function as the synaptic vesicle cycle, the internalization of nerve growth factor (NGF), the determination of neuronal cell fate, the development of synapses and the trafficking of postsynaptic receptors. We discuss novel functional findings on the role of intersectin and synaptojanin and then we focus on the features of an emerging family of EH domain proteins termed EHDs (EH domain proteins), which are important for endocytic recycling of membrane proteins.
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Affiliation(s)
- María Luz Montesinos
- Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Avda. Sánchez-Pizjuán 4, E-41009 Sevilla, Spain.
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213
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Yoon K, Gaiano N. Notch signaling in the mammalian central nervous system: insights from mouse mutants. Nat Neurosci 2005; 8:709-15. [PMID: 15917835 DOI: 10.1038/nn1475] [Citation(s) in RCA: 444] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The Notch pathway, although originally identified in fruit flies, is now among the most heavily studied in mammalian biology. In mice, loss-of-function and gain-of-function work has demonstrated that Notch signaling is essential both during development and in the adult in a multitude of tissues. Prominent among these is the CNS, where Notch has been implicated in processes ranging from neural stem cell regulation to learning and memory. Here we review the role of Notch in the mammalian CNS by focusing specifically on mutations generated in mice. These mutations have provided critical insight into Notch function in the CNS and have led to the identification of promising new directions that are likely to generate important discoveries in the future.
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Affiliation(s)
- Keejung Yoon
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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214
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Traub LM. Common principles in clathrin-mediated sorting at the Golgi and the plasma membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:415-37. [PMID: 15922462 DOI: 10.1016/j.bbamcr.2005.04.005] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 04/17/2005] [Accepted: 04/19/2005] [Indexed: 12/12/2022]
Abstract
Clathrin-mediated vesicular trafficking events underpin the vectorial transfer of macromolecules between several eukaryotic membrane-bound compartments. Classical models for coat operation, focused principally on interactions between clathrin, the heterotetrameric adaptor complexes, and cargo molecules, fail to account for the full complexity of the coat assembly and sorting process. New data reveal that targeting of clathrin adaptor complexes is generally supported by phosphoinositides, that cargo recognition by heterotetrameric adaptors depends on phosphorylation-driven conformational alterations, and that dedicated clathrin-associated sorting proteins (CLASPs) exist to promote the selective trafficking of specific categories of cargo. A host of accessory factors also participate in coat polymerization events, and the independently folded appendage domains that project off the heterotetrameric adaptor core function as recruitment platforms that appear to oversee assembly operations. It is also now clear that focal polymerization of branched actin microfilaments contributes to clathrin-coated vesicle assembly and movement at both plasma membrane and Golgi sites. This improved appreciation of the complex mechanisms governing clathrin-dependent sorting events reveals several common principles of clathrin operation at the Golgi and the plasma membrane.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology and Physiology University of Pittsburgh School of Medicine 3500 Terrace Street, S325BST Pittsburgh, PA 15206, USA.
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215
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Maillard I, Fang T, Pear WS. Regulation of lymphoid development, differentiation, and function by the Notch pathway. Annu Rev Immunol 2005; 23:945-74. [PMID: 15771590 DOI: 10.1146/annurev.immunol.23.021704.115747] [Citation(s) in RCA: 341] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The Notch pathway is gaining increasing recognition as a key regulator of developmental choices, differentiation, and function throughout the hematolymphoid system. Notch controls the generation of hematopoietic stem cells during embryonic development and may affect their subsequent homeostasis. Commitment to the T cell lineage and subsequent stages of early thymopoiesis is critically regulated by Notch. Recent data indicate that Notch can also direct the differentiation and activity of peripheral T and B cells. Thus, the full spectrum of Notch effects is just beginning to be understood. In this review, we discuss this explosion of knowledge as well as current controversies and challenges in the field.
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Affiliation(s)
- Ivan Maillard
- Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA.
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216
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Sun Y, Goderie SK, Temple S. Asymmetric distribution of EGFR receptor during mitosis generates diverse CNS progenitor cells. Neuron 2005; 45:873-86. [PMID: 15797549 DOI: 10.1016/j.neuron.2005.01.045] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Revised: 12/23/2004] [Accepted: 01/27/2005] [Indexed: 11/25/2022]
Abstract
It has been debated whether asymmetric distribution of cell surface receptors during mitosis could generate asymmetric cell divisions by yielding daughters with different environmental responsiveness and, thus, different fates. We have found that in mouse embryonic forebrain ventricular and subventricular zones, the EGFR can distribute asymmetrically during mitosis in vivo and in vitro. This occurs during divisions yielding two Nestin+ progenitor cells, via an actin-dependent mechanism. The resulting sibling progenitor cells respond differently to EGFR ligand in terms of migration and proliferation. Moreover, they express different phenotypic markers: the EGFRhigh daughter usually has radial glial/astrocytic markers, while its EGFRlow sister lacks them, indicating fate divergence. Lineage trees of cultured cortical glioblasts reveal repeated EGFR asymmetric distribution, and asymmetric divisions underlie formation of oligodendrocytes and astrocytes in clones. These data suggest that asymmetric EGFR distribution contributes to forebrain development by creating progenitors with different proliferative, migratory, and differentiation responses to ligand.
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Affiliation(s)
- Yu Sun
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA
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217
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Roegiers F, Jan LY, Jan YN. Regulation of membrane localization of Sanpodo by lethal giant larvae and neuralized in asymmetrically dividing cells of Drosophila sensory organs. Mol Biol Cell 2005; 16:3480-7. [PMID: 15901829 DOI: 10.1091/mbc.e05-03-0177] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In Drosophila, asymmetric division occurs during proliferation of neural precursors of the central and peripheral nervous system (PNS), where a membrane-associated protein, Numb, is asymmetrically localized during cell division and is segregated to one of the two daughter cells (the pIIb cell) after mitosis. numb has been shown genetically to function as an antagonist of Notch signaling and also as a negative regulator of the membrane localization of Sanpodo, a four-pass transmembrane protein required for Notch signaling during asymmetric cell division in the CNS. Previously, we identified lethal giant larvae (lgl) as a gene required for numb-mediated inhibition of Notch in the adult PNS. In this study we show that Sanpodo is expressed in asymmetrically dividing precursor cells of the PNS and that Sanpodo internalization in the pIIb cell is dependent cytoskeletally associated Lgl. Lgl specifically regulates internalization of Sanpodo, likely through endocytosis, but is not required for the endocytosis Delta, which is a required step in the Notch-mediated cell fate decision during asymmetric cell division. Conversely, the E3 ubiquitin ligase neuralized is required for both Delta endocytosis and the internalization of Sanpodo. This study identifies a hitherto unreported role for Lgl as a regulator of Sanpodo during asymmetric cell division in the adult PNS.
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Affiliation(s)
- Fabrice Roegiers
- Howard Hughes Medical Institute and Department of Physiology and Biochemistry, University of California-San Francisco, San Francisco, CA 94143-0725, USA.
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218
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Abstract
The transport of tubulin and microtubules in a growing axon is essential for axonal growth and maintenance. However, the molecular mechanism underlying the linkage of tubulin and microtubules to motor proteins is not yet clear. Collapsin response mediator protein-2 (CRMP-2) is enriched at the distal part of growing axons in primary hippocampal neurons and plays a critical role in axon differentiation through its interaction with tubulin dimer and Numb. In this study, we show that CRMP-2 regulates tubulin transport by linking tubulin and Kinesin-1. The C-terminal region of CRMP-2 directly binds to the tetratricopeptide repeat domain of kinesin light chain 1 (KLC1). Soluble tubulin binds to the middle of CRMP-2 and forms a trimeric complex with CRMP-2/KLC1. Furthermore, the movement of GFP-tubulin in the photobleached area is weakened by knockdown of KLCs or CRMP-2. These results indicate that the CRMP-2/Kinesin-1 complex regulates soluble tubulin transport to the distal part of the growing axon.
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Affiliation(s)
- Toshihide Kimura
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Showa-ku, Nagoya, Aichi, Japan
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219
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Langevin J, Le Borgne R, Rosenfeld F, Gho M, Schweisguth F, Bellaïche Y. Lethal Giant Larvae Controls the Localization of Notch-Signaling Regulators Numb, Neuralized, and Sanpodo in Drosophila Sensory-Organ Precursor Cells. Curr Biol 2005; 15:955-62. [PMID: 15916953 DOI: 10.1016/j.cub.2005.04.054] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Revised: 04/18/2005] [Accepted: 04/18/2005] [Indexed: 11/21/2022]
Abstract
Asymmetric distribution of fate determinants is a fundamental mechanism underlying the acquisition of distinct cell fates during asymmetric division. In Drosophila neuroblasts, the apical DmPar6/DaPKC complex inhibits Lethal giant larvae (Lgl) to promote the basal localization of fate determinants. In contrast, in the sensory precursor (pI) cells that divide asymmetrically with a planar polarity, Lgl inhibits Notch signaling in the anterior pI daughter cell, pIIb, by a yet-unknown mechanism. We show here that Lgl promotes the cortical recruitment of Partner of Numb (Pon) and regulates the asymmetric distribution of the fate determinants Numb and Neuralized during the pI cell division. Analysis of Pon-GFP and Histone2B-mRFP distribution in two-color movies confirmed that Lgl regulates Pon localization. Moreover, posterior DaPKC restricts Lgl function to the anterior cortex at mitosis. Thus, Lgl functions similarly in neuroblasts and in pI cells. We also show that Lgl promotes the acquisition of the pIIb cell fate by inhibiting the plasma membrane localization of Sanpodo and thereby preventing the activation of Notch signaling in the anterior pI daughter cell. Thus, Lgl regulates cell fate by controlling Pon cortical localization, asymmetric localization of Numb and Neuralized, and plasma-membrane localization of Sandopo.
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Affiliation(s)
- Johanna Langevin
- Institut Curie, Unité mixte de recherche 144, 26 rue d'Ulm, 75248 Paris cedex 05, France
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220
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Zhou Y, Zhang J, King ML. Polarized distribution of mRNAs encoding a putative LDL receptor adaptor protein, xARH (autosomal recessive hypercholesterolemia) in Xenopus oocytes. Mech Dev 2005; 121:1249-58. [PMID: 15327785 DOI: 10.1016/j.mod.2004.05.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Revised: 04/30/2004] [Accepted: 05/14/2004] [Indexed: 10/26/2022]
Abstract
The Xenopus homologue of hARH (human autosomal recessive hypercholesterolemia) was identified in a screen for vegetally localized RNAs. xARH contains a N-terminal phosphotyrosine binding (PTB) domain that is 91% identical to that of the human gene, a domain previously shown to bind the LDL receptor family members. Maternal xARH, unlike hARH, is present as two transcripts that differ in their 3' UTRs. The large transcript, xARH-alpha, primarily localizes to the oocyte vegetal cortex. The small transcript, xARH-beta, is not localized. During embryogenesis, xARH RNA is found redistributed in a perinuclear pattern. Similar to hARH, xARH is found in the adult liver, but at low levels compared to oocytes. Downstream of the PTB domain is a conserved clathrin box and a C terminal region 50% identical to that of hARH. Previous in vitro studies from this lab have shown xARH can bind the LDLR as well as the vitellogenin (VTG) receptor. We find that injection of the C terminal region missing the PTB domain significantly reduces the internalization of VTG in early stage oocytes, an event that requires the VTG receptor. The data strongly suggest that xARH encodes an adaptor protein that functions in the essential receptor-mediated endocytosis of nutrients during oogenesis. Because xARH protein is found uniformly distributed along the animal/vegetal axis in oocytes, we propose that the localization of xARH-alpha to the vegetal cortex while xARH-beta remains unlocalized, facilitates the uniform distribution of the protein in this extraordinarily large cell.
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Affiliation(s)
- Yi Zhou
- Department of Cell Biology and Anatomy, University of Miami School of Medicine, 1011 NW 15th St., Miami, FL 33136, USA
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221
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Le Borgne R, Bardin A, Schweisguth F. The roles of receptor and ligand endocytosis in regulating Notch signaling. Development 2005; 132:1751-62. [PMID: 15790962 DOI: 10.1242/dev.01789] [Citation(s) in RCA: 262] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cell-cell signaling is a central process in the formation of multicellular organisms. Notch (N) is the receptor of a conserved signaling pathway that regulates numerous developmental decisions, and the misregulation of N has been linked to various physiological and developmental disorders. The endocytosis of N and its ligands is a key mechanism by which N-mediated cell-cell signaling is developmentally regulated. We review here the recent findings that have highlighted the importance and complexity of this regulation.
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Affiliation(s)
- Roland Le Borgne
- CNRS UMR 8542, Ecole Normale Supérieure, 46, rue d'Ulm 75230 Paris cedex, France
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222
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Tang H, Rompani SB, Atkins JB, Zhou Y, Osterwalder T, Zhong W. Numb proteins specify asymmetric cell fates via an endocytosis- and proteasome-independent pathway. Mol Cell Biol 2005; 25:2899-909. [PMID: 15798180 PMCID: PMC1069617 DOI: 10.1128/mcb.25.8.2899-2909.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2004] [Revised: 12/20/2004] [Accepted: 01/10/2005] [Indexed: 12/25/2022] Open
Abstract
Numb proteins are evolutionarily conserved signaling molecules that make the daughter cells different after asymmetric divisions by segregating to only one daughter. They contain distinct binding motifs for alpha-adaptin (alpha-Ada) and proteins with Eps15 homology (EH) domains, which regulate endocytosis, and for E3 ubiquitin ligases, which target proteins for proteasome-mediated degradation. In Drosophila melanogaster, Numb acts by inhibiting Notch activity to cause a bias in Notch-mediated cell-cell communication. These findings have led to the hypothesis that Numb modulates Notch signaling by using endocytosis and proteasomes to directly reduce Notch protein levels at the cell surface. Here we show that two Drosophila EH proteins, Eps15 homologue 1 (EH1) and the dynamin-associated 160-kDa protein (Dap160), negatively regulate Notch signaling. However, neither elimination of the binding motifs for endocytic proteins nor simultaneous reduction of proteasome activity affects the activity of Numb proteins. Our findings indicate that an endocytosis- and proteasome-independent pathway may mediate Numb signaling in asymmetric cell fate specification.
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Affiliation(s)
- Haiyan Tang
- Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520, USA
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223
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Okano H, Kawahara H, Toriya M, Nakao K, Shibata S, Imai T. Function of RNA-binding protein Musashi-1 in stem cells. Exp Cell Res 2005; 306:349-56. [PMID: 15925591 DOI: 10.1016/j.yexcr.2005.02.021] [Citation(s) in RCA: 253] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 02/21/2005] [Accepted: 02/23/2005] [Indexed: 01/05/2023]
Abstract
Musashi is an evolutionarily conserved family of RNA-binding proteins that is preferentially expressed in the nervous system. The first member of the Musashi family was identified in Drosophila. This protein plays an essential role in regulating the asymmetric cell division of ectodermal precursor cells known as sensory organ precursor cells through the translational regulation of target mRNA. In the CNS of Drosophila larvae, however, Musashi is expressed in proliferating neuroblasts and likely has a different function. Its probable mammalian homologue, Musashi-1, is a neural RNA-binding protein that is strongly expressed in fetal and adult neural stem cells (NSCs). Mammalian Musashi-1 augments Notch signaling through the translational repression of its target mRNA, m-Numb, thereby contributing to the self-renewal of NSCs. In addition to its functions in NSCs, the role of mammalian Musashi-1 protein in epithelial stem cells, including intestinal and mammary gland stem cells, is attracting increasing interest.
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Affiliation(s)
- Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
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224
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Abstract
Cells in multicellular organisms need to decipher extracellular cues into appropriate responses including correct differentiation choices. A considerable portion of this information is relayed through a surprisingly small number of signaling pathways, which are highly evolutionarily conserved and used in many different cell types. This "ivy league" of signaling mechanisms comprises the Wnt/wingless, BMP/TGF-beta, Sonic Hedgehog, receptor tyrosine kinases, nuclear receptors, JAK/STAT and, the subject of this review, the Notch signaling pathway. The aim of this article is to provide an overview of the Notch signaling pathway. The role of Notch in various types of cancers is discussed in the accompanying articles in this issue of SCBI.
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Affiliation(s)
- Emil M Hansson
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm SE-171 77, Sweden
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225
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Anderson AC, Kitchens EA, Chan SW, St Hill C, Jan YN, Zhong W, Robey EA. The Notch regulator Numb links the Notch and TCR signaling pathways. THE JOURNAL OF IMMUNOLOGY 2005; 174:890-7. [PMID: 15634911 DOI: 10.4049/jimmunol.174.2.890] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Both the Notch and TCR signaling pathways play an important role in T cell development, but the links between these signaling pathways are largely unexplored. The adapter protein Numb is a well-characterized inhibitor of Notch and also contains a phosphotyrosine binding domain, suggesting that Numb could provide a link between these pathways. We explored this possibility by investigating the physical interactions among Notch, Numb, and the TCR signaling apparatus and by examining the consequences of a Numb mutation on T cell development. We found that Notch and Numb cocluster with the TCR at the APC contact during Ag-driven T cell-APC interactions in both immature and mature T cells. Furthermore, Numb coimmunoprecipitates with components of the TCR signaling apparatus. Despite this association, T cell development and T cell activation occur normally in the absence of Numb, perhaps due to the expression of the related protein, Numblike. Together our data suggest that Notch and TCR signals may be integrated at the cell membrane, and that Numb may be an important adapter in this process.
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MESH Headings
- Animals
- Antigen-Presenting Cells/immunology
- Antigen-Presenting Cells/metabolism
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Cells, Cultured
- Gene Deletion
- Intracellular Signaling Peptides and Proteins
- Membrane Proteins/deficiency
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Mice
- Mice, Transgenic
- Nerve Tissue Proteins/biosynthesis
- Nerve Tissue Proteins/deficiency
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Receptor, Notch1
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/physiology
- Receptors, Cell Surface/metabolism
- Receptors, Cell Surface/physiology
- Signal Transduction/genetics
- Signal Transduction/immunology
- T-Lymphocytes/cytology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- Thymus Gland/cytology
- Thymus Gland/metabolism
- Transcription Factors/metabolism
- Transcription Factors/physiology
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Affiliation(s)
- Ana C Anderson
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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226
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Abstract
Heterotrimeric G-proteins are intracellular partners of G-protein-coupled receptors (GPCRs). GPCRs act on inactive Galpha.GDP/Gbetagamma heterotrimers to promote GDP release and GTP binding, resulting in liberation of Galpha from Gbetagamma. Galpha.GTP and Gbetagamma target effectors including adenylyl cyclases, phospholipases and ion channels. Signaling is terminated by intrinsic GTPase activity of Galpha and heterotrimer reformation - a cycle accelerated by 'regulators of G-protein signaling' (RGS proteins). Recent studies have identified several unconventional G-protein signaling pathways that diverge from this standard model. Whereas phospholipase C (PLC) beta is activated by Galpha(q) and Gbetagamma, novel PLC isoforms are regulated by both heterotrimeric and Ras-superfamily G-proteins. An Arabidopsis protein has been discovered containing both GPCR and RGS domains within the same protein. Most surprisingly, a receptor-independent Galpha nucleotide cycle that regulates cell division has been delineated in both Caenorhabditis elegans and Drosophila melanogaster. Here, we revisit classical heterotrimeric G-protein signaling and explore these new, non-canonical G-protein signaling pathways.
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Affiliation(s)
- C R McCudden
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, and UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-7365, USA.
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227
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Abstract
Notch signaling can be viewed as an elegantly simple pathway that begins when the Notch receptor binds ligand, and ends when the Notch intracellular domain enters the nucleus and activates transcription. However, it is becoming increasingly clear that this core pathway is subject to a wide array of regulatory influences, from those that affect ligand-receptor interactions to those that govern the choice of Notch target genes. Even Notch ligands are now being scrutinized with respect to the possibility that they, too, function in the nucleus. A complete understanding of Notch signaling therefore requires us to look well beyond the core pathway.
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Affiliation(s)
- Tom Kadesch
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6145, USA.
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228
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Abstract
Clathrin-coated vesicles (CCVs) are responsible for the transport of proteins between various compartments of the secretory and endocytic systems. Clathrin forms a scaffold around these vesicles that is linked to membranes by clathrin adaptors. The adaptors simultaneously bind to clathrin and to transmembrane proteins and/or phospholipids and can also interact with each other and with other components of the CCV formation machinery. The result is a collection of proteins that can make multiple, moderate strength (microM Kd) interactions and thereby establish the dynamic regulatable networks to drive vesicle genesis at the correct time and place in the cell. This review focuses on the structure of clathrin adaptors and how these structures provide functional information on the mechanism of CCV formation.
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Affiliation(s)
- David J Owen
- Cambridge Institute for Medical Research, Department of Clinical Biochemistry, University of Cambridge, Cambridge CB2 2XY, UK.
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229
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Uhlik MT, Temple B, Bencharit S, Kimple AJ, Siderovski DP, Johnson GL. Structural and evolutionary division of phosphotyrosine binding (PTB) domains. J Mol Biol 2005; 345:1-20. [PMID: 15567406 DOI: 10.1016/j.jmb.2004.10.038] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Revised: 10/13/2004] [Accepted: 10/13/2004] [Indexed: 11/21/2022]
Abstract
Proteins encoding phosphotyrosine binding (PTB) domains function as adaptors or scaffolds to organize the signaling complexes involved in wide-ranging physiological processes including neural development, immunity, tissue homeostasis and cell growth. There are more than 200 proteins in eukaryotes and nearly 60 human proteins having PTB domains. Six PTB domain encoded proteins have been found to have mutations that contribute to inherited human diseases including familial stroke, hypercholesteremia, coronary artery disease, Alzheimer's disease and diabetes, demonstrating the importance of PTB scaffold proteins in organizing critical signaling complexes. PTB domains bind both peptides and headgroups of phosphatidylinositides, utilizing two distinct binding motifs to mediate spatial organization and localization within cells. The structure of PTB domains confers specificity for binding peptides having a NPXY motif with differing requirements for phosphorylation of the tyrosine within this recognition sequence. In this review, we use structural, evolutionary and functional analysis to divide PTB domains into three groups represented by phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like and phosphotyrosine-independent Dab-like PTBs, with the Dab-like PTB domains representing nearly 75% of proteins encoding PTB domains. In addition, we further define the binding characteristics of the cognate ligands for each group of PTB domains. The signaling complexes organized by PTB domain encoded proteins are largely unknown and represents an important challenge in systems biology for the future.
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Affiliation(s)
- Mark T Uhlik
- Department of Pharmacology and University of North Carolina School of Medicine, 1108 Mary Ellen Jones Building, Campus Box 7365, Chapel Hill, NC 27599-7365, USA
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230
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Dudu V, Pantazis P, González-Gaitán M. Membrane traffic during embryonic development: epithelial formation, cell fate decisions and differentiation. Curr Opin Cell Biol 2005; 16:407-14. [PMID: 15261673 DOI: 10.1016/j.ceb.2004.06.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The analysis of membrane trafficking has in the past mainly dealt with single cells in culture. Recent studies of membrane trafficking in Drosophila focus on how cells are organized in tissues and form epithelia during embryogenesis. During these processes, the specific involvement of distinct biosynthetic and endocytic routes is starting to be understood. Once organized in epithelia, cells communicate with each other to make cell fate decisions through morphogen gradients and lateral inhibition. Endocytosis seems to play unexpected roles in shaping morphogen gradients and in biasing lateral inhibition events. Once committed to a developmental program, cells differentiate. In the case of neurons, trafficking through the biosynthetic and endocytic pathways may give the necessary speed of response and versatility to axons that navigate through a changing environment during pathfinding.
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Affiliation(s)
- Veronica Dudu
- Max-Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstr. 108. D-01307 Dresden, Germany
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231
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Kerr ML, Small DH. Cytoplasmic domain of the ?-amyloid protein precursor of Alzheimer's disease: Function, regulation of proteolysis, and implications for drug development. J Neurosci Res 2005; 80:151-9. [PMID: 15672415 DOI: 10.1002/jnr.20408] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The beta-amyloid protein precursor (APP) has been extensively studied for its role in amyloid production and the pathogenesis of Alzheimer's disease (AD). However, little is known about the normal function of APP and its biological interactions. In this Mini-Review, the role of the cytoplasmic domain of APP in APP trafficking and proteolysis is described. These studies suggest that proteins that bind to the cytoplasmic domain may be important targets for drug development in AD.
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Affiliation(s)
- Megan L Kerr
- Laboratory of Molecular Neurobiology, Department of Biochemistry and Molecular Biology, and Monash University Centre for Brain and Behaviour, Monash University, Victoria, Australia
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232
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Huang EJ, Li H, Tang AA, Wiggins AK, Neve RL, Zhong W, Jan LY, Jan YN. Targeted deletion of numb and numblike in sensory neurons reveals their essential functions in axon arborization. Genes Dev 2004; 19:138-51. [PMID: 15598981 PMCID: PMC540232 DOI: 10.1101/gad.1246005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mouse Numb homologs antagonize Notch1 signaling pathways through largely unknown mechanisms. Here we demonstrate that conditional mouse mutants with deletion of numb and numblike in developing sensory ganglia show a severe reduction in axonal arborization in afferent fibers, but no deficit in neurogenesis. Consistent with these results, expression of Cre recombinase in sensory neurons from numb conditional mutants results in reduced endocytosis, a significant increase in nuclear Notch1, and severe reductions in axon branch points and total axon length. Conversely, overexpression of Numb, but not mutant Numb lacking alpha-adaptin-interacting domain, leads to accumulation of Notch1 in markedly enlarged endocytic-lysosomal vesicles, reduced nuclear Notch1, and dramatic increases in axonal length and branch points. Taken together, our data provide evidence for previously unidentified functions of Numb and Numblike in sensory axon arborization by regulating Notch1 via the endocytic-lysosomal pathways.
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Affiliation(s)
- Eric J Huang
- Department of Pathology, University of California San Francisco, San Francisco, California 94143, USA.
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233
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Sapir A, Assa-Kunik E, Tsruya R, Schejter E, Shilo BZ. Unidirectional Notch signaling depends on continuous cleavage of Delta. Development 2004; 132:123-32. [PMID: 15576412 DOI: 10.1242/dev.01546] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Unidirectional signaling from cells expressing Delta (Dl) to cells expressing Notch is a key feature of many developmental processes. We demonstrate that the Drosophila ADAM metalloprotease Kuzbanian-like (Kul) plays a key role in promoting this asymmetry. Kul cleaves Dl efficiently both in cell culture and in flies, and has previously been shown not to be necessary for Notch processing during signaling. In the absence of Kul in the developing wing, the level of Dl in cells that normally receive the signal is elevated, and subsequent alterations in the directionality of Notch signaling lead to prominent phenotypic defects. Proteolytic cleavage of Dl by Kul represents a general mechanism for refining and maintaining the asymmetric distribution of Dl, in cases where transcriptional repression of Dl expression does not suffice to eliminate Dl protein.
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Affiliation(s)
- Amir Sapir
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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234
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Betschinger J, Knoblich JA. Dare to be different: asymmetric cell division in Drosophila, C. elegans and vertebrates. Curr Biol 2004; 14:R674-85. [PMID: 15324689 DOI: 10.1016/j.cub.2004.08.017] [Citation(s) in RCA: 322] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
One widespread mechanism for the generation of diverse cell types is the unequal inheritance of cell fate determinants. Several such determinants have been identified in the fruitfly Drosophila melanogaster and the worm Caenorhabditis elegans and the molecular machinery responsible for their asymmetric segregation is beginning to be unraveled. To divide asymmetrically, cells establish an axis of polarity, orient the mitotic spindle along this axis and localize cell fate determinants to one side of the cell. During cytokinesis, determinants are then segregated into one of the two daughter cells where they direct cell fate. Here, we outline the steps and factors that are involved in this process in Drosophila and C. elegans and discuss their potential conservation in vertebrates.
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Affiliation(s)
- Jörg Betschinger
- Research Institute of Molecular Pathology, Dr. Bohr Gasse 7, 1030 Vienna, Austria.
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235
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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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236
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Overstreet E, Fitch E, Fischer JA. Fat facets and Liquid facets promote Delta endocytosis and Delta signaling in the signaling cells. Development 2004; 131:5355-66. [PMID: 15469967 DOI: 10.1242/dev.01434] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Endocytosis modulates the Notch signaling pathway in both the signaling and receiving cells. One recent hypothesis is that endocytosis of the ligand Delta by the signaling cells is essential for Notch activation in the receiving cells. Here, we present evidence in strong support of this model. We show that in the developing Drosophila eye Fat facets (Faf), a deubiquitinating enzyme, and its substrate Liquid facets (Lqf), an endocytic epsin, promote Delta internalization and Delta signaling in the signaling cells. We demonstrate that while Lqf is necessary for three different Notch/Delta signaling events at the morphogenetic furrow, Faf is essential only for one: Delta signaling by photoreceptor precluster cells, which prevents recruitment of ectopic neurons. In addition, we show that the ubiquitin-ligase Neuralized (Neur), which ubiquitinates Delta, functions in the signaling cells with Faf and Lqf. The results presented bolster one model for Neur function in which Neur enhances Delta signaling by stimulating Delta internalization in the signaling cells. We propose that Faf plays a role similar to that of Neur in the Delta signaling cells. By deubiquitinating Lqf, which enhances the efficiency of Delta internalization, Faf stimulates Delta signaling.
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Affiliation(s)
- Erin Overstreet
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Moffett Molecular Biology Building, 2500 Speedway, Austin, TX 78712, USA
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237
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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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238
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Merdes G, Soba P, Loewer A, Bilic MV, Beyreuther K, Paro R. Interference of human and Drosophila APP and APP-like proteins with PNS development in Drosophila. EMBO J 2004; 23:4082-95. [PMID: 15385958 PMCID: PMC524346 DOI: 10.1038/sj.emboj.7600413] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Accepted: 08/23/2004] [Indexed: 11/09/2022] Open
Abstract
The view that only the production and deposition of Abeta plays a decisive role in Alzheimer's disease has been challenged by recent evidence from different model systems, which attribute numerous functions to the amyloid precursor protein (APP). To investigate the potential cellular functions of APP and its paralogs, we use transgenic Drosophila as a model. Upon overexpression of the APP-family members, transformations of cell fates during the development of the peripheral nervous system were observed. Genetic analysis showed that APP, APLP1 and APLP2 induce Notch gain-of-function phenotypes, identified Numb as a potential target and provided evidence for a direct involvement of Disabled and Neurotactin in the induction of the phenotypes. The severity of the induced phenotypes not only depended on the dosage and the particular APP-family member but also on particular domains of the molecules. Studies with Drosophila APPL confirmed the results obtained with human proteins and the analysis of flies mutant for the appl gene further supports an involvement of APP-family members in neuronal development and a crosstalk between the APP family and Notch.
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Affiliation(s)
- Gunter Merdes
- ZMBH, University of Heidelberg, Heidelberg, Germany.
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239
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Somogyi K, Rørth P. Cortactin modulates cell migration and ring canal morphogenesis during Drosophila oogenesis. Mech Dev 2004; 121:57-64. [PMID: 14706700 DOI: 10.1016/j.mod.2003.10.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Cortactin is a Src substrate that interacts with F-actin and can stimulate actin polymerization by direct interaction with the Arp2/3 complex. We have isolated complete loss-of-function mutants of the single Drosophila cortactin gene. Mutants are viable and fertile, showing that cortactin is not an essential gene. However, cortactin mutants show distinct defects during oogenesis. During oogenesis, Cortactin protein is enriched at the F-actin rich ring canals in the germ line, and in migrating border cells. In cortactin mutants, the ring canals are smaller than normal. A similar phenotype has been observed in Src64 mutants and in mutants for genes encoding Arp2/3 complex components, supporting that these protein products act together to control specific processes in vivo. Cortactin mutants also show impaired border cell migration. This invasive cell migration is guided by Drosophila EGFR and PDGF/VEGF receptor (PVR). We find that accumulation of Cortactin protein is positively regulated by PVR. Also, overexpression of Cortactin can by itself induce F-actin accumulation and ectopic filopodia formation in epithelial cells. We present evidence that Cortactin is one of the factors acting downstream of PVR and Src to stimulate F-actin accumulation. Cortactin is a minor contributor in this regulation, consistent with the cortactin gene not being essential for development.
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Affiliation(s)
- Kálmán Somogyi
- European Molecular Biology Laboratory, Developmental Biology Programme, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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240
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Yoshida T, Tokunaga A, Nakao K, Okano H. Distinct expression patterns of splicing isoforms of mNumb in the endocrine lineage of developing pancreas. Differentiation 2004; 71:486-95. [PMID: 14641329 DOI: 10.1046/j.1432-0436.2003.7108006.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The pancreas is composed of three tissues: endocrine, exocrine, and duct. The endocrine/exocrine lineages diverge from the ductal lineage before E12.5 in mice, and then further separate into endocrine and exocrine precursors. These processes are regulated by differential activation of Notch1-mediated signaling, which is required to repress the expression of the pro-endocrine gene neurogenin3 (ngn3) in the exocrine lineage. Mammalian Numb (mNumb) is an ortholog of Drosophila Numb (dNumb), which is likely to be an intracellular inhibitor of Notch signaling, and has four splicing isoforms: PTBS-PRRS, PTBL-PRRS, PTBS-PRRL, and PTBL-PRRL. Here we developed an anti-PRRL antibody, which recognizes only the PRRL forms of mNumb. We then performed immunohistochemical analyses using anti-PRRL together with anti-pan Numb, which recognizes all the isoforms of mNumb, antibodies that determine the spatio-temporal expression pattern of mNumb in the mouse fetal pancreas. mNumb PRRS and PRRL were first expressed in identical cells in the early stage of pancreatic development (i.e., E10.5), but gradually became biased. At the stage of endocrine and exocrine divergence, mNumb PRRS continued to be expressed in endocrine lineage cells, whereas PRRL was down-regulated during endocrine differentiation. Even after the endocrine/exocrine divergence, notch1 expression was sustained in endocrine lineage, where ngn3 was expressed. These results agree with the notion that mNumb PRRS has an inhibitory effect on Notch signaling, indicating its potential roles in the differentiation of pancreatic endocrine lineage. In addition, islet cells, which are produced from ductal tissue, were immunostained by the anti-panNb antibody. Our present results will contribute to the understanding of the mechanisms of islet development from ductal tissue.
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Affiliation(s)
- Tetsu Yoshida
- Department of Physiology Keio University School of Medicine 35 Shinanomachi, Shinjuku-ku Tokyo 160-8582, Japan
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241
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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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242
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Smith CA, Dho SE, Donaldson J, Tepass U, McGlade CJ. The cell fate determinant numb interacts with EHD/Rme-1 family proteins and has a role in endocytic recycling. Mol Biol Cell 2004; 15:3698-708. [PMID: 15155807 PMCID: PMC491829 DOI: 10.1091/mbc.e04-01-0026] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The adaptor protein Numb is necessary for the cell fate specification of progenitor cells in the Drosophila nervous system. Numb is evolutionarily conserved and previous studies have provided evidence for a similar functional role during mammalian development. The Numb protein has multiple protein-protein interaction regions including a phosphotyrosine binding (PTB) domain and a carboxy-terminal domain that contains conserved interaction motifs including an EH (Eps15 Homology) domain binding motif and alpha-adaptin binding site. In this study we identify the EHD/Rme-1/Pincher family of endocytic proteins as Numb interacting partners in mammals and Drosophila. The EHD/Rme-1 proteins function in recycling of plasma membrane receptors internalized by both clathrin-mediated endocytosis and a clathrin-independent pathway regulated by ADP ribosylation factor 6 (Arf6). Here we report that Numb colocalizes with endogenous EHD4/Pincher and Arf6 and that Arf6 mutants alter Numb subcellular localization. In addition, we present evidence that Numb has a novel function in endosomal recycling and intracellular trafficking of receptors.
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Affiliation(s)
- Christian A Smith
- Arthur and Sonia Labatt Brain Tumour Research Centre, Hospital for Sick Children, Toronto, Ontario, Canada, M5G 1X8
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243
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Le Gall M, Giniger E. Identification of two binding regions for the suppressor of hairless protein within the intracellular domain of Drosophila notch. J Biol Chem 2004; 279:29418-26. [PMID: 15123610 DOI: 10.1074/jbc.m404589200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Notch is a phylogenetically conserved transmembrane receptor that is required for many aspects of animal development. Upon ligand stimulation, a fragment of Notch is released proteolytically and enters the nucleus to form a complex with the DNA-binding protein CSL (CBF1/Suppressor of Hairless/Lag1) and activate transcription of Notch-CSL target genes. The physical structure of the Notch-CSL complex remains unclear, however, clouding the interpretation of previous efforts to correlate Notch structure and function. We have, therefore, characterized the binding of Drosophila CSL (called Suppressor of Hairless, or Su(H)) to the intracellular domain of Drosophila Notch both in vitro and in vivo. We report the identification of two Su(H) binding regions in Notch. The first is in the juxtamembrane region (the "RAM" domain). The second is just C-terminal to the Notch ankyrin repeats, overlapping or identical to two previously proposed nuclear localization sequences, in a domain we term PPD (potential phosphorylated domain). The ankyrin repeats themselves do not bind to Su(H); however, they substantially enhance binding of Su(H) to the more C-terminal region. Consistent with this picture, removal of either the Ram or PPD binding sites, separately, modestly reduces Notch activity in vivo, whereas removal of both renders Notch severely defective. These results clarify the relationship between Notch and CSL, help to explain the importance of the ankyrin repeats in Notch signaling, and reconcile many apparently contradictory results from previous Notch structure/function studies. Moreover, they suggest a second function for the Notch nuclear localization sequence elements.
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Affiliation(s)
- Maude Le Gall
- Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA
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244
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Bardin AJ, Le Borgne R, Schweisguth F. Asymmetric localization and function of cell-fate determinants: a fly's view. Curr Opin Neurobiol 2004; 14:6-14. [PMID: 15018932 DOI: 10.1016/j.conb.2003.12.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One mechanism to generate daughter cells with distinct fates is the asymmetric inheritance of regulatory proteins, leading to differential gene regulation in the daughter cells. This mode of cell division is termed 'asymmetric cell division.' The nervous system of the fly employs asymmetric cell division, both in the central nervous system, to generate neural precursors, neurons and glial cells; and in the peripheral nervous system, to create sensory organs that are composed of multiple cell types. These cell lineages are excellent models to examine the gene expression program that leads to fate acquisition, the cell-fate determinants that control these programs and how these determinants, in turn, are distributed through cell polarity machinery.
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Affiliation(s)
- Allison J Bardin
- Ecole Normale Supérieure, CNRS UMR 8542, 46, rue d'Ulm, 75230 Paris Cedex 05, France
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245
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Abstract
Adaptors select cargo for inclusion into coated vesicles in the late secretory and endocytic pathways. Although originally there were thought to be just two adaptors, AP-1 and AP-2, it is now clear that there are many more: two additional adaptor complexes, AP-3 and AP-4, which might function independently of clathrin; a family of monomeric adaptors, the GGAs; and an ever-growing number of cargo-specific adaptors. The adaptors are targeted to the appropriate membrane at least in part by interacting with phosphoinositides, and, once on the membrane, they form interconnected networks to get different types of cargo into the same vesicle. Adaptors participate in trafficking pathways shared by all cells, and they are also used to generate specialized organelles and to influence cell fate during development.
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Affiliation(s)
- Margaret S Robinson
- University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge, UK CB2 2XY.
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246
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Abstract
Asymmetric cell division is a conserved mechanism for partitioning information during mitosis. Over the past several years, significant progress has been made in our understanding of how cells establish polarity during asymmetric cell division and how determinants, in the form of localized proteins and mRNAs, are segregated. In particular, genetic studies in Drosophila and Caenorhabditis elegans have linked cell polarity, G protein signaling and regulation of the cytoskeleton to coordination of mitotic spindle orientation and localization of determinants. Also, several new studies have furthered our understanding of how asymmetrically localized cell fate determinants, such as the Numb, a negative regulator Notch signaling, functions in biasing cell fates in the developing nervous system in Drosophila. In vertebrates, analysis of dividing neural progenitor cells by in vivo imaging has raised questions about the role of asymmetric cell divisions during neurogenesis.
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Affiliation(s)
- Fabrice Roegiers
- Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California, San Francisco, 533 Parnassus Ave, San Francisco, California, 94122, USA
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247
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Wang QT, Piotrowska K, Ciemerych MA, Milenkovic L, Scott MP, Davis RW, Zernicka-Goetz M. A genome-wide study of gene activity reveals developmental signaling pathways in the preimplantation mouse embryo. Dev Cell 2004; 6:133-44. [PMID: 14723853 DOI: 10.1016/s1534-5807(03)00404-0] [Citation(s) in RCA: 406] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The preimplantation development of the mammalian embryo encompasses a series of critical events: the transition from oocyte to embryo, the first cell divisions, the establishment of cellular contacts, the first lineage differentiation-all the first subtle steps toward a future body plan. Here, we use microarrays to explore gene activity during preimplantation development. We reveal robust and dynamic patterns of stage-specific gene activity that fall into two major phases, one up to the 2-cell stage (oocyte-to-embryo transition) and one after the 4-cell stage (cellular differentiation). The mouse oocyte and early embryo express components of multiple signaling pathways including those downstream of Wnt, BMP, and Notch, indicating that conserved regulators of cell fate and pattern formation are likely to function at the earliest embryonic stages. Overall, these data provide a detailed temporal profile of gene expression that reveals the richness of signaling processes in early mammalian development.
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Affiliation(s)
- Q Tian Wang
- Department of Biochemistry and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.
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248
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249
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Duan Z, Li FQ, Wechsler J, Meade-White K, Williams K, Benson KF, Horwitz M. A novel notch protein, N2N, targeted by neutrophil elastase and implicated in hereditary neutropenia. Mol Cell Biol 2004; 24:58-70. [PMID: 14673143 PMCID: PMC303357 DOI: 10.1128/mcb.24.1.58-70.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Mutations in ELA2, encoding the human serine protease neutrophil elastase, cause cyclic and severe congenital neutropenia, and recent evidence indicates that the mutations alter the membrane trafficking of neutrophil elastase. These disorders feature impaired bone marrow production of neutrophils along with excess monocytes-terminally differentiated lineages corresponding to the two alternative fates of myeloid progenitor cells. We utilized a modified yeast two-hybrid system and identified a new, widely expressed gene, N2N, whose product is homologous to Notch2, that interacts with neutrophil elastase. N2N is a 36-kDa protein distributed throughout the cell and secreted. Its amino-terminal sequence consists of several EGF repeats identical to those of the extracellular region of Notch2, and its carboxyl terminus contains a unique 24-residue domain required for interaction with neutrophil elastase. Neutrophil elastase cleaves N2N within EGF repeats in vitro and in living cells, but the C-terminal domain retards proteolysis. In vitro, N2N represses transcriptional activities of Notch proteins. Disease-causing mutations of neutrophil elastase disrupt the interaction with N2N, impair proteolysis of N2N and Notch2, and interfere with Notch2 signaling, suggesting defective proteolysis of an inhibitory form of Notch as an explanation for the alternate switching of cell fates characteristic of hereditary neutropenia.
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Affiliation(s)
- Zhijun Duan
- Division of Medical Genetics, Department of Medicine, University of Washington School of Medicine, Seattle, Washington 98195, USA
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250
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Abstract
The ability to internalize macromolecules by endocytosis is a property of all eukaryotic cells. Frontline research on endocytosis has been presented in a successful series of biannual meetings in Europe. This year's meeting on "Membrane Dynamics in Endocytosis" was held September 13-18 in Acquafredda di Maratea, on the coast of southern Italy. Four key questions were addressed: What are the molecular mechanisms of endocytic membrane trafficking? How does endocytosis modulate receptor signaling and vice versa? What is the importance of endocytosis during development? How do endocytic organelles contribute to immunity or susceptibility to pathogens?
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Affiliation(s)
- Marcos González-Gaitán
- Max-Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307 Dresden, Germany.
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