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At least 19 recordsLinked to original sources

Notch1 and Notch2 receptors influence progressive hair graying in a dose-dependent manner.

The Notch signaling pathway is involved in diverse biological processes such as cell fate decisions or stem cell maintenance. In this study, we assessed the role of this pathway for melanocyte development and hair pigmentation using RBP-Jkappa, Notch1, and Notch2 conditional knockout mice. Disruption of the Notch pathway by inactivating RBP-Jkappa in the melanocyte lineage using Tyr::Cre mice led to a severe coat color dilution. Similarly, hair graying was observed when Notch1 and/or Notch2 receptors were ablated in melanocytes. This phenotype was proportional to the number of floxed Notch alleles, with the most pronounced effect seen in Tyr::Cre/degrees; Notch1(flox/flox); Notch2(flox/flox) mice. Deletion of Notch1 and/or Notch2 in melanoblasts did not induce a congenital defect. The number of Dct-expressing cells at embryonic stages was not affected, but melanocytes located within the hair matrix progressively disappeared during the first regeneration of the hair follicle. In contrast, non-follicular melanocytes and pigmentation in the dermis and in the choroid were not affected. We suggest that both Notch1 and Notch2 receptors contribute to the maintenance of melanoblasts and melanocyte stem cells, and are essential for proper hair pigmentation.

Alleles↗

NOTCH2 mutations cause Alagille syndrome, a heterogeneous disorder of the notch signaling pathway.

Alagille syndrome (AGS) is caused by mutations in the gene for the Notch signaling pathway ligand Jagged1 (JAG1), which are found in 94% of patients. To identify the cause of disease in patients without JAG1 mutations, we screened 11 JAG1 mutation-negative probands with AGS for alterations in the gene for the Notch2 receptor (NOTCH2). We found NOTCH2 mutations segregating in two families and identified five affected individuals. Renal manifestations, a minor feature in AGS, were present in all the affected individuals. This demonstrates that AGS is a heterogeneous disorder and implicates NOTCH2 mutations in human disease.

Alagille Syndrome↗

The notch receptor and its ligands are selectively expressed during hematopoietic development in the mouse.

Members of the Notch family of transmembrane receptors are found on primitive hematopoietic precursors, and Notch ligand expression has been demonstrated on the surface of stromal cells, suggesting a role for Notch signaling in mammalian blood cell development. The current report examines the expression of Notch receptors and their ligands in murine hematopoietic tissues to determine: A) which blood cell lineages in the adult are influenced by Notch activity, and B) whether fetal hematopoiesis in the embryo involves the Notch pathway. In the adult mouse, a combination of flow cytometry, immunohistochemistry and Northern analysis was used to examine Notch receptor or ligand expression in bone marrow and spleen. In the embryo, Northern analysis and in situ hybridization were used to characterize Notch receptor and ligand expression in fetal liver on embryonic day 12 (E12) through E17, an active period encompassing both erythropoiesis and granulopoeisis. Flow cytometry demonstrated the presence of Notch1 and Notch2 receptors on bone marrow-derived myeloid cells but not on erythroid cells positive for the marker, Ter-119. In situ hybridization of E12 through E17 fetal liver demonstrated widespread expression of Jagged1 and Delta1 in a pattern similar to but less abundant than that of the erythropoietin receptor. Taken together with earlier functional results, the current expression data suggest a role for Notch activity in establishing definitive hematopoiesis in fetal liver, as well as a selective use of Notch signaling in adult erythropoiesis and granulopoiesis. Notch receptors in the adult are most likely utilized by early erythroid precursors and intermediate-stage granulocytes, but not by terminally differentiating cells of either subset.

Animals↗

Localization of ADAM10 and Notch receptors in bone.

In Drosophila melanogaster, the role of the metallodisintegrin, Kuzbanian (kuz), is thought to involve activation of the Drosophila Notch receptor that plays a role in cell-fate determination during neurogenesis and myoblast differentiation. To understand the possible function(s) of a-disintegrin and metalloproteinase (ADAM10), the mammalian ortholog of kuz, in the skeleton, we studied its expression as well as the messenger RNA (mRNA) encoding one candidate substrate, the mammalian Notch2 receptor in bone, bone cells, and cartilage. In sections of neonatal rat tibiae, ADAM10 is expressed in specific regions of articular cartilage and metaphyseal bone. Expression of ADAM10 in articular cartilage occurs predominantly in superficial chondrocytes and becomes more sporadic with increasing distance from the articular surface. In bone, ADAM10 is expressed by periosteal cells, osteoblasts, and osteocytes at locations of active bone formation. Osteoclasts did not express ADAM10. Notch2 mRNA expression was not detectable in superficial chondrocytes. However it colocalized at all sites of ADAM10 expression in bone cells. In vitro, both primary human osteoblasts and osteoblast cell lines expressed a single 4.5 kb and 7.5 kb transcript of ADAM10 and the Notch2 receptor homolog, respectively. Subcellular localization of the ADAM10 protein in MG-63 cells was determined using immunofluorescent techniques. These observations showed clearly that the ADAM10 protein was expressed in the trans-Golgi network and on the plasma membrane. Western blot analysis of fractionated cells showed that, in the plasma membrane fraction, the previously characterized 58 kDa and 56 kDa isoforms were present, whereas, in the trans-Golgi network, the ADAM10 protein was present in several additional bands, possibly indicative of further interdomain processing of the ADAM10 protein. The metallodisintegrins (ADAMs) have several putative functions, including modulation of cell adhesion, membrane-associated proteolysis, and cell-cell signaling. These observations suggest that, in bone but not cartilage, ADAM10 has catalytic activity within the transGolgi network and may play a role in the activation of Notch receptor homologs. This implicates ADAM10 in cell-fate determination of osteoblast progenitor cells, possibly during skeletal development and normal bone remodeling. Plasma-membrane-associated ADAM10 may confer alternative functions.

Amino Acid Sequence↗

Chondroitin synthase 1 is a key molecule in myeloma cell-osteoclast interactions.

There is a symbiotic relationship between continued growth and proliferation of myeloma cells and the bone destructive process. It has been shown in animal models that blocking bone destruction can result in decreased myeloma tumor burden. Osteoclasts are bone destroying cells found in the bone marrow, and their significance in myeloma is supported by recent findings that osteoclasts alone can support sustained survival and proliferation of purified primary myeloma cells in ex vivo co-cultures. However, molecular mechanisms associated with interactions between myeloma cells and osteoclasts remain unclear. Here, we show that when myeloma plasma cells are co-cultured with osteoclasts, chondroitin synthase 1 (CHSY1) is the most significantly altered soluble, secreted protein present in the conditioned medium. RNA interference experiments with CHSY1 small interfering RNA (siRNA) reduced the amount of CHSY1 in the co-culture conditioned medium, and this was associated with a 6.25-fold increase in apoptotic myeloma cells over control co-cultures. CHSY1 contains a Fringe domain, and Fringe is well known for its regulation of Notch signaling via its DDD motif. And interestingly, Fringe domain in CHSY1 has this DDD motif. Shortly after co-culture with osteoclasts, we found that the Notch2 receptor was activated in myeloma cells but Notch1 was not. Activation of Notch2 was down-regulated by CHSY1 siRNA treatment. Modulating Notch signaling by CHSY1 via its DDD motif provides new insight into mechanisms of the interactions between myeloma cells and their bone marrow microenvironment. Targeting this interaction could shed light on treatment of myeloma, which is currently incurable.

Cell Communication↗

Notch signaling in kidney development.

PURPOSE OF REVIEW: Notch signaling is a highly conserved mechanism used by multicellular animals to specify cell fate decisions during the formation of complex structures such as the kidney. A number of studies have recently identified requirements for Notch signaling during kidney organogenesis and tissue repair. This review will summarize these studies and compare Notch signaling in the mammalian kidney with Notch signaling in other organ systems. RECENT FINDINGS: A targeted mutation in the mouse Notch2 receptor resulted in kidneys that are devoid of glomerular endothelial and mesangial cells. The mutant epithelial cells of the developing glomerulus have reduced amounts of vascular endothelial growth factor expression, which may be responsible for the lack of vascularization observed in these glomeruli. Notch2 is expressed in the epithelial cells of the developing glomerulus, and a potential ligand, Jagged1 is expressed in the endothelial cells of the glomerulus. Mice simultaneously heterozygous for mutations in both Notch2 and Jagged1 phenocopy the kidney defects seen in mice homozygous for the Notch2 mutation. These doubly heterozygous mice also display liver and heart developmental abnormalities reminiscent of Alagille's syndrome. SUMMARY: Notch signaling is required for kidney development, and the expression of Notch genes is increased in response to kidney damage. Further studies of Notch signaling will be important in order to understand kidney development and tissue repair.

Animals↗

The Tat protein of the caprine arthritis encephalitis virus interacts with the Notch2 EGF-like repeats and the epithelin/granulin precursor.

Using the yeast two-hybrid system, we screened a human placenta cDNA library and identified two proteins that interacted with the Tat protein of the caprine arthritis encephalitis virus (CAEV): the EGF-like repeats 1-6 of the extracellular domain of the human Notch2 receptor and the epithelin/granulin growth factor precursor. This interaction was also confirmed in mammalian cells. Using in vitro mutagenesis assays, we showed that each one of the three cysteine residues located within the cysteine-rich domain of the CAEV Tat protein is essential for the binding of Tat to both the Notch2 and the epithelin/granulin protein. It is thus suggested that the cysteine-rich domain of Tat plays a role in the interaction between the Tat and either Notch2 or the epithelin/granulin domains, both of which exhibit EGF-like-repeat-imposed spatial conformation. It is assumed that such interactions might modulate the physiological functions of Notch2 and epithelin/granulin, thereby affecting various pathologies associated with CAEV.

Animals↗

Functional diversity among Notch1, Notch2, and Notch3 receptors.

To clarify functional diversities among the Notch receptors, we generated truncated forms of Notch1, Notch2, and Notch3 comprising the intracellular domain (aN1, aN2, and aN3) and investigated their transcriptional activities for HES1 and HES5 promoters driving the luciferase reporter gene (HES1-Luc and HES5-Luc). The reporter assays demonstrated that the transcriptional activities of aNs were markedly different from each other and dependent on the promoters examined. Furthermore, relative activities between some aN and another for each promoter were altered by the expression level of RBP-J kappa. We also found that the activities of aN1 and aN3 were reduced by coexpression of aN2. These observations suggest that each Notch receptor has a diverse role in the downstream gene expression and that the levels of HES1 and HES5 gene expression are complexly determined by various factors, such as the type and combination of the Notch receptors which confer the downstream signals and the expression level of RBP-J kappa.

Animals↗

The role of Notch receptor expression in bile duct development and disease.

Mutations in the Jagged1 gene, a ligand for the Notch signalling pathway, have been implicated in the pathogenesis of Alagille syndrome (AGS), resulting in bile duct paucity. Recently, a mouse model for AGS suggested that abnormalities of the Notch2 receptor, as well as of Jagged1, may be present. Expression patterns of Notch receptors have not been described in the developing human liver or in paediatric liver. The expression of Notch receptors and ligands was examined in fetal, paediatric normal, and diseased human liver by RT-PCR and immunohistochemistry. RT-PCR showed Notch1-4 mRNA expression to be present. In fetal liver, Notch3 protein was expressed on mesenchymal cells, closely adjacent to ductal plate cells that expressed Jagged1. In paediatric normal liver, Notch1 and Notch2 were present on mature bile duct cells. Notch expression was altered in disease, with distinct differences in AGS from extrahepatic biliary atresia (EHBA) and alpha1-anti-trypsin deficiency (alpha1AT). In AGS, where extensive ductular reaction was present, Jagged1 was expressed on ductular reactive cells (DRCs), along with marked Notch2 and Notch3 staining. Where there was ductular paucity, Notch2 and Notch3 were not expressed on remaining biliary epithelial cells. In EHBA and alpha1AT, Notch receptor expression was not seen on DRCs. Instead, Notch2 and Notch3 were expressed by stromal cells. In all diseases, Notch3 was expressed on neovessels in portal tracts and cirrhotic fibrous septa. In conclusion, Notch3 is expressed in close proximity to Jagged1 at the time of ductal plate formation, suggesting that Notch3 is important for bile duct development. The expression of both Notch2 and Notch3 in AGS on DRCs confirms that these receptors may be important in the pathogenesis of this disease. Further studies are required to investigate the presence of Notch2 and Notch3 at other periods in liver development and to clarify the role of Notch signalling in paediatric cholestases.

Adolescent↗

Developmental restriction of Mash-2 expression in trophoblast correlates with potential activation of the notch-2 pathway.

Mash-2 expression begins during preimplantation development, but is restricted to trophoblasts after the blastocyst stage. Within the trophoblast lineage, Mash-2 transcripts are first expressed in the ectoplacental cone and chorion, but not in terminally differentiated trophoblast giant cells. After day 8.5 of gestation, Mash-2 expression becomes further restricted to focal sites within the spongiotrophoblast and labyrinth. Downregulation is probably important for normal development since overexpression of Mash-2 reduces giant cell formation. We have investigated the role that the Notch signaling pathway may play in trophoblast development. Mash-2 is a homologue of Drosophila achaete/scute complex genes. In Drosophila, activation of the Notch receptor induces transcriptional repressors encoded by the hairy/Enhancer of split (HES) genes, which interact with the Groucho protein to shut off achaete-scute transcription. In the developing mouse placenta, we found that all elements of the Notch pathway were expressed. In particular, the Notch-2, HES-2, and HES-3 genes were coexpressed in trophoblast giant cells and in foci within the spongiotrophoblast at day 10.5 when Mash-2 transcription becomes restricted. Two members of the mammalian Groucho family were expressed in trophoblasts; TLE3 was expressed broadly in the giant cell, spongiotrophoblast, and labyrinthine regions, whereas TLE2 was limited to giant cells and focal regions of the spongiotrophoblast. These data suggest that Notch signaling through activation of HES transcriptional repressors may play a role in murine placental development.

Animals↗

Notch 2 and Notch 1/3 segregate to neuronal and glial lineages of the developing olfactory epithelium.

The murine olfactory epithelium (OE) generates olfactory receptor neurons (ORNs) throughout development and into adulthood, but only a few of the factors regulating olfactory neuro- and glio-genesis have been delineated. Notch receptors maintain CNS neuronal progenitors and drive glial differentiation, and the Notch effectors Hes 1 and 5 are expressed in the OE, but the Notch receptors that stimulate Hes gene activation in defined lineages during OE development have not been determined. Here, we first use RT-PCR to reveal which Notch receptors and ligands are expressed in the developing and adult OE. This is followed by immunofluorescent detection, combined with lineage-specific markers to define the stage-specific developmental expression of different Notch family members. We show that throughout development, Notch 1 and 3 are expressed in cells retained within the lamina propria, where Notch 3 is expressed in olfactory ensheathing cells (OECs). In contrast, Notch 2 is expressed in apical embryonic and early postnatal OE neuronal progenitors. In postnatal and adult OE, Notch 1 is expressed predominantly in Bowman's glands, and Notch 2 in sustentacular cells. Notch 2 and Notch 1/3 may, therefore, have different roles in the commitment and differentiation of neuronal and glial lineages of the OE during development, and the maintenance of non-neuronal phenotypes postnatally.

Animals↗

High delta-like 1 expression in a subset of neuroblastoma cell lines corresponds to a differentiated chromaffin cell type.

The childhood tumour neuroblastoma originates from neural crest-derived progenitors of the sympathetic nervous system. By Serial Analysis of Gene Expression (SAGE), we previously identified the Drosophila Delta homologue Dlk1 as one of the genes most highly expressed in the neuroblastoma cell line SK-N-FI. The Delta-Notch pathway controls many differentiation steps in Drosophila and man. We analysed expression of 21 genes of this pathway in 21 neuroblastoma cell lines. Dlk1 expression was very high in 5 cell lines, while another subset expressed Notch3. The imprinting of Dlk1 was faithfully preserved in neuroblastomas. The single paternal allele can therefore produce over 0.5% of all cellular mRNAs. Dlk1 maps to 14q32, a region that exhibited LOH in 31/170 (18%) tumours. The random parental origin of the deleted alleles excluded Dlk1 as target of the LOH. In addition, Dlk1 was not amplified, rearranged or mutated in neuroblastoma cell lines and tumours. We therefore analysed whether high Dlk1 expression marks a specific differentiation stage of the sympatho-adrenal lineage. Many neuroblastomas arise in the adrenal medulla, which predominantly consists of chromaffin cells. Normal adrenal medulla exhibited equally high Dlk1 levels as the SK-N-FI cell line. Chromaffin cells in young children are marked by noradrenalin production, which is mediated by dopamine-beta-hydroxylase (DBH). DBH expression in the neuroblastoma cell lines almost perfectly corresponded to Dlk1 expression. Neuroblastoma cell lines with high Dlk1 expression are therefore arrested in a relatively late stage of chromaffin lineage differentiation, while Notch3 expression might correspond to earlier precursor stages or to an alternative developmental fate.

Adrenal Medulla↗

Expression of Notch pathway components in spermatogonia and Sertoli cells of neonatal mice.

Members of the Notch gene family have been shown to play an important role in the control of cell fate in many developmental systems. We hypothesized that the fate of the male germ line stem cells may also be mediated through the Notch signaling pathway. We therefore sought to determine whether the components of the Notch pathway are expressed in the mouse testis. Western blot analysis revealed the expression of three Notch receptors (Notch 1, Notch 2, and Notch 3), Notch ligands (Jagged 1, Jagged 2, and Delta 1), and presenilin 1 (PS1) in neonatal mouse testis. We then examined their cellular localization by immunohistochemical analysis of cocultures of spermatogonia and Sertoli cells. The 3 Notch receptors were found to be expressed in spermatogonia. Sertoli cells expressed only Notch 2 receptor. Among the Notch ligands, Delta 1 and Jagged 1 were localized exclusively in spermatogonia and Sertoli cells, respectively. PS1 was apparent in both spermatogonia and Sertoli cells. The presence of Notch receptors and Notch ligands in spermatogonia and Sertoli cells indicates that these cells are capable of responding to and eliciting Notch signaling during the process of spermatogenesis. Key words: Cell fate, delta, jagged, presenilin, spermatogenesis.

Animals↗

Cortisol regulates the expression of Notch in osteoblasts.

Glucocorticoids have important effects on osteoblastic replication, differentiation, and function, and the Notch family of receptors is considered to play a role in osteoblastic cell differentiation. We postulated that cortisol could regulate Notch and Notch ligand expression in osteoblastic cells, providing an additional mechanism by which glucocorticoids could regulate osteoblastic differentiation. We examined the expression and regulation of Notch1, 2, 3, and 4 and their ligands Jagged 1 and 2 and Delta 1 and 3 by cortisol in cultures of osteoblastic MC3T3-E1 cells. Cortisol caused a time-dependent increase in Notch1 and 2 mRNA levels in MC3T3 cells. Notch3 and 4 were not detected in the presence or absence of cortisol. MC3T3 cells expressed Delta 1 and Jagged 1 but not Jagged 2 or Delta 3 mRNAs, and cortisol did not have a substantial effect on the expression of any of these ligands. Cortisol increased the rate of Notch1 and 2 transcription and, in transcriptionally arrested cells, did not modify the decay of the transcripts, indicating a transcriptional level of control. In conclusion, cortisol stimulates Notch1 and 2 transcription in osteoblasts. Since Notch signaling appears to play a negative role in osteoblastic differentiation, its increased expression could be relevant to the actions of cortisol in bone.

Animals↗

Downregulation of rheumatoid arthritis-related antigen RA-A47 (HSP47/colligin-2) in chondrocytic cell lines induces apoptosis and cell-surface expression of RA-A47 in association with CD9.

Previously, we showed that gene expression of the rheumatoid arthritis-related antigen RA-A47, which is identical to human heat shock protein (HSP)47, was downregulated in chondrocytes by inflammatory cytokines such as TNFalpha. Associated with this phenomenon, RA-A47 appeared on the cell surface concomitant with upregulation of metabolic factors related to cartilage destruction. The upregulation of the metabolic factors could be achieved by downregulation of RA-A47 expression with ra-a47-specific anti-sense oligonucleotide. Here, we show that the enhanced surface expression of RA-A47 on a chondrocytic cell line, HCS-2/8 was also a direct result of RA-A47 downregulation by ra-a47 anti-sense oligonucleotide, independent of the cytokine effects. Moreover, cell-surface expression of CD9, a beta1 integrin-associated transmembrane protein that is involved in cell adhesion and cell motility events, was enhanced in the ra-a47 anti-sense oligonucleotide-treated cells. The CD9 was colocalized with RA-A47 on the cell surface, where it may have affected integrin signaling. Furthermore, Annexin-V binding to the cell surface and the level of a number of apoptosis-related genes including caspase-9 were increased after ra-a47 anti-sense oligonucleotide treatment, suggesting that enhanced surface expression of RA-A47 and CD9 may be initiating apoptosis. Differential screening using a cDNA gene array showed induction of metallothionein-III and chemokine receptor CXCR4 and of factors of the Notch signaling pathway by the anti-sense treatment, but not by TNFalpha. Thus, here we show for the first time an alternative mechanism of inducing apoptosis by downregulating molecular chaperones, independent of the action of TNFalpha. The surface-exposed RA-A47 may induce autoantibodies and inflammatory reactions in autoimmune disease situations such as rheumatoid arthritis.

Annexin A5↗

Physical interaction of Delta1, Jagged1, and Jagged2 with Notch1 and Notch3 receptors.

The Delta/Serrate/LAG-2 (DSL) domain-containing proteins, Delta1, Jagged1, and Jagged2, are considered to be ligands for Notch receptors. However, the physical interaction between the three DSL proteins and respective Notch receptors remained largely unknown. In this study, we investigated this issue through the targeting of Notch1 and Notch3 in two experimental systems using fusion proteins comprising their extracellular portions. Cell-binding assays showed that soluble forms of Notch1 and Notch3 proteins physically bound to the three DSL proteins on the cell surface. In solid-phase binding assays using immobilized soluble Notch1 and Notch3 proteins, it was revealed that each DSL protein directly bound to the soluble Notch proteins with different affinities. All interactions between the DSL proteins and soluble Notch proteins were dependent on Ca(2+). Taken together, these results suggest that Delta1, Jagged1, and Jagged2 are ligands for Notch1 and Notch3 receptors.

Animals↗

DBI-1, a novel gene related to the notch family, modulates mitogenic response to insulin-like growth factor 1.

The insulin-like growth factor 1 (IGF-1) receptor has been found to transform fibroblast cells when overexpressed. The removal of 108 aa from the C-terminus of the IGF-1 receptor abolishes the transforming ability of the receptor without affecting its ability to induce cell growth. The availability of this mutant receptor provides a means to examine the changes in gene expression which take place during transformation, solely in response to an increased number of IGF-1 receptors. Using differential display, we have examined differences in gene expression between cells expressing a wild-type, transforming IGF-1 receptor and cells expressing a C-terminally truncated, nontransforming IGF-1 receptor. We have cloned a novel 6. 3-kb cDNA transcript (DBI-1) which is expressed at much lower levels in cells containing the wild-type IGF-1 receptor. The predicted protein sequence of DBI-1 contains seven EGF-like repeats, which bear >90% sequence identity to the rat Notch 2 protein. The cDNA also contains a potential DEAD box in the C-terminal region. The DBI-1 message is detected at relatively high levels in cardiac tissue and at lower levels in lung, liver, and kidney. Antibodies generated to a unique region of the DBI-1 protein recognize a protein of 88 kDa, which is localized in the nucleus. Overexpression of DBI-1 in cells which contain the wild-type IGF-1 receptor diminishes the mitogenic response to IGF-1.

3T3 Cells↗

Isolation and characterization of the notch ligand delta4.

Notch signaling plays a critical role in a variety of developmental programs. In vertebrates, the complexity of the process is underscored by the existence of multiple Notch receptors and multiple ligands, each of which displays a distinct expression profile. Furthermore, the ligands can be subdivided into two families, the Serrate/Jagged family and the Delta family. Here we present the isolation of a novel Notch ligand, Delta4. Expression analyses indicate that mouse Delta4 is highly expressed in the eye and lung during embryogenesis and in the heart, lung, liver, and kidney of the adult. Functionally, Delta4 is indistinguishable from Jagged1 in its abilities to inhibit myogenesis and to stimulate transcription through Notch1 and the DNA binding protein CSL.

3T3 Cells↗