• Development and Reproduction
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• v.7 no.2
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• pp.69-80
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• 2003

The zebrafish(Danio rerio) is a pre-eminent vertebrate model system for clarification of the roles of specific genes and signaling pathways in development. We show examples of positional cloning in two developmental mutants in zebrafish. headless: The severe head defects in headless(hdl) mutants are due to a mutation in T-cell factor-3(Tcf3). Loss of Tcf3 function in the hdl mutant reveals that Hdl represses Wnt target genes. The results provide genetic evidence that a component of the Wnt signaling pathway is essential in vertebrate head formation and patterning. mind bomb: Reduced lateral inhibition in mind bomb(mib) mutants permits too many neural precursors to differentiate as neurons. Positional cloning of mib revealed that it is a gene in the Notch pathway that encodes a ubiquitin E3 ligase. Mib interacts with the intracellular domain of Delta to promote its internalization. The results suggest a model for Notch activation where the Delta-Notch interaction is followed by endocytosis of Delta and transendocytosis of the Notch extracellular domain by the signaling cell.

• Journal of Korean Neurosurgical Society
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• v.64 no.5
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• pp.716-725
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• 2021

Objective : The anti-tumor effect of the beta-adrenergic receptor antagonist propranolol in breast cancer is well known; however, its activity in glioblastoma is not well-evaluated. The Notch-Hes pathway is known to regulate cell differentiation, proliferation, and apoptosis. We investigated the effect of propranolol to human glioblastoma cell lines, and the role of Notch and Hes signaling in this process. Methods : We performed immunohistochemical staining on 31 surgically resected primary human glioblastoma tissues. We also used glioblastoma cell lines of U87-MG, LN229, and neuroblastoma cell line of SH-SY5Y in this study. The effect of propranolol and isoproterenol on cell proliferation was evaluated using the MTT assay (absorbance 570 nm). The impact of propranolol on gene expression (Notch and Hes) was evaluated using real-time polymerase chain reaction (RT-PCR, whereas protein levels of Notch1 and Hes1 were measured using Western blotting (WB), simultaneously. Small interfering RNA (siRNA) was used to suppress the Notch gene to investigate its role in the proliferation of glioblastoma. Results : Propranolol and isoproterenol caused a dose-dependent decrease in cell proliferation (MTT assay). RT-PCR showed an increase in Notch1 and Hes1 expression by propranolol, whereas WB demonstrated increase in Notch1 protein, but a decrease in Hes1 by propranolol. The proliferation of U87-MG and LN229 was not significantly suppressed after transfection with Notch siRNA. Conclusion : These results demonstrated that propranolol suppressed the proliferation of glioblastoma cell lines and neuroblastoma cell line, and Hes1 was more closely involved than Notch1 was in glioblastoma proliferation.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.3
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• pp.343-348
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• 2013

This experiment was conducted to evaluate the development of T cells in intrauterine growth retarded (IUGR) piglets at different gestational stages, and tentatively explore the relationship between T cells development and the Notch signaling pathway. A total of 18 crossbred (Landrace${\times}$Large white) primiparous sows were mated at similar weights and estruses and euthanized at d 60, 90 and 110 of gestation with six replicates for each time point. One IUGR and one normal fetus were picked from each litter. The T-cell subsets, mRNA expression of Delta-like1, Delta-like4, Jagged1, and Notch2 genes in the thymus were investigated. Compared to normal piglets, $CD3^+CD4^-CD8^+$ cells in IUGR fetuses at d 90 was 0.13% lower (p<0.05). At d 110 of gestation $CD8^+$ T cells in IUGR fetuses was 0.19% lower (p<0.05). The percentage of $CD8^+$ T cells was 3.14% lower (p<0.05) of the total T cells in IUGR pigs at d 60. The abundance of Notch2 and Delta-like4 mRNA at d 110 was 20.93% higher and 0.77% (p<0.05) lower, and Delta-like1 mRNA at d 90 was 0.19% (p<0.05) higher compared to normal pigs. These results suggested that normal fetuses had a greater proportion of T-cell subsets at earlier gestation periods, and the Notch signaling pathway was likely partially responsible for these differences to some degree.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.11
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• pp.5345-5351
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• 2012

Radiotherapy is an important part of modern cancer management for many malignancies, and enhancing the radiosensitivity of tumor cells is critical for effective cancer therapies. The Notch signaling pathway plays a key role in regulation of numerous fundamental cellular processes. Further, there is accumulating evidence that dysregulated Notch activity is involved in the genesis of many human cancers. As such, Notch inhibitors are attractive therapeutic agents, although as for other anticancer agents, they exhibit significant and potential side effects. Thus, Notch inhibitors may be best used in combination with other agents or therapy. Herein, we describe evidence supporting the use of Notch inhibitors as novel and potent radiosensitizers in cancer therapy.

• Reproductive and Developmental Biology
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• v.30 no.2
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• pp.143-156
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• 2006

Major characteristics of embryonic stem cells (ESCs) are sustaining of sternness and pluripotency by self-renewal. In this report, transcriptional profiles of the molecules in the developmentally important signaling pathways including Wnt, BMP4, $TGF-\beta$, RTK, Hh, Notch, and JAK/STAT signaling pathways were investigated to understand the self-renewal of mouse ESCs (mESCs), J1 line, and compared with the NIH3T3 cell line and mouse embryonic fibroblast (MEF) cells as controls. In the Wnt signaling pathway, the expression of Wnt3 was seen widely in mESCs, suggesting that the ligand may be an important regulator for self-renewal in mESCs. In the Hh signaling pathway, the expression of Gli and N-myc were observed extensively in mESCs, whereas the expression levels of in a Shh was low, suggesting that intracellular molecules may be essential for the self-renewal of mESCs. IGF-I, IGF-II, IGF-IR and IGF-IIR of RTK signaling showed a lower expression in mESCs, these molecules related to embryo development may be restrained in mESCs. The expression levels of the Delta and HESS in Notch signaling were enriched in mESCs. The expression of the molecules related to BMP and JAK-STAT signaling pathways were similar or at a slightly lower level in mESCs compared to those in MEF and NIH3T3 cells. It is suggested that the observed differences in gene expression profiles among the signaling pathways may contribute to the self-renewal and differentiation of mESCs in a signaling-specific manner.

• Journal of Microbiology
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• v.44 no.2
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• pp.217-225
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• 2006

Kaposi's sarcoma-associated herpesvirus (KSHV) RTA transcription factor is recruited to its responsive elements through interaction with RBP-Jk that is a downstream transcription factor of the Notch signaling pathway that is important in development and cell fate determination. This suggests that KSHV RTA mimics cellular Notch signal transduction to activate viral lytic gene expression. Here, I demonstrated that unlike other B lymphoma cells, KSHV -infected primary effusion lymphoma BCBL1 cells displayed the constitutive activation of ligand-mediated Notch signal transduction, evidenced by the Jagged ligand expression and the complete proteolytic process of Notch receptor I. In order to investigate the effect of Notch signal transduction on KSHV gene expression, human Notch intracellular (hNIC) domain that constitutively activates RBP-Jk transcription factor activity was expressed in BCBL1 cells, TRExBCBL1-hNIC, in a tetracycline inducible manner. Gene expression profiling showed that like RTA, hNIC robustly induced expression of a number of viral genes including KS immune modulatory gene resulting in downregulation of MHC I and CD54 surface expression. Finally, the genetic analysis of KSHV genome demonstrated that the hNIC-mediated expression of KS during viral latency consequently conferred the downregulation of MHC I and CD54 surface expression. These results indicate that cellular. Notch signal transduction provides a novel expression profiling of KSHV immune deregulatory gene that consequently confers the escape of host immune surveillance during viral latency.

• Proceedings of the Zoological Society Korea Conference
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• 1999.04a
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• pp.36-36
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• 1999

No Abstract, See Full Text

• Biomolecules & Therapeutics
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• v.22 no.5
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• pp.371-383
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• 2014

The nematode Caenorhabditis elegans (C. elegans) offers a unique opportunity for biological and basic medical researches due to its genetic tractability and well-defined developmental lineage. It also provides an exceptional model for genetic, molecular, and cellular analysis of human disease-related genes. Recently, C. elegans has been used as an ideal model for the identification and functional analysis of drugs (or small-molecules) in vivo. In this review, we describe conserved oncogenic signaling pathways (Wnt, Notch, and Ras) and their potential roles in the development of cancer stem cells. During C. elegans germline development, these signaling pathways regulate multiple cellular processes such as germline stem cell niche specification, germline stem cell maintenance, and germ cell fate specification. Therefore, the aberrant regulations of these signaling pathways can cause either loss of germline stem cells or overproliferation of a specific cell type, resulting in sterility. This sterility phenotype allows us to identify drugs that can modulate the oncogenic signaling pathways directly or indirectly through a high-throughput screening. Current in vivo or in vitro screening methods are largely focused on the specific core signaling components. However, this phenotype-based screening will identify drugs that possibly target upstream or downstream of core signaling pathways as well as exclude toxic effects. Although phenotype-based drug screening is ideal, the identification of drug targets is a major challenge. We here introduce a new technique, called Drug Affinity Responsive Target Stability (DARTS). This innovative method is able to identify the target of the identified drug. Importantly, signaling pathways and their regulators in C. elegans are highly conserved in most vertebrates, including humans. Therefore, C. elegans will provide a great opportunity to identify therapeutic drugs and their targets, as well as to understand mechanisms underlying the formation of cancer.

• Molecules and Cells
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• v.27 no.1
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• pp.15-19
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• 2009

Notch signaling is controlled at multiple levels. In particular, stabilized Notch receptor activation directly affects the transcriptional activations of Notch target genes. Although some progress has been made in terms of defining the regulatory mechanism that alters Notch stability, it has not been determined whether Notch1/NICD stability is regulated by $GSK-3{\alpha}$. Here, we show that Notch1/NICD levels are significantly regulated by $GSK-3{\beta}$ and by $GSK-3{\alpha}$. Treatment with LiCl (a specific GSK-3 inhibitor) or the overexpression of the kinase-inactive forms of $GSK-3{\alpha}/{\beta}$ significantly increased Notch1/NICD levels. Endogenous NICD levels were also increased by either $GSK-3{\alpha}/{\beta}$- or $GSK-3{\alpha}$-specific siRNA. Furthermore, it was found that $GSK-3{\alpha}$ binds to Notch1. Deletion analysis showed that at least three Thr residues in Notch1 (Thr-1851, 2123, and 2125) are critical for its response to LiCl, which increased not only the transcriptional activity of endogenous NICD but also Hes1 mRNA levels. Taken together, our results indicate that $GSK-3{\alpha}$ is a negative regulator of Notch1/NICD.

• Molecules and Cells
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• v.27 no.5
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• pp.497-502
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• 2009

In mouse embryos, somite formation occurs every two hours, and this periodic event is regulated by a biological clock called the segmentation clock, which involves cyclic expression of the basic helix-loop-helix gene Hes7. Hes7 expression oscillates by negative feedback and is cooperatively regulated by Fgf and Notch signaling. Both loss of expression and sustained expression of Hes7 result in severe somite fusion, suggesting that Hes7 oscillation is required for proper somite segmentation. Expression of a related gene, Hes1, also oscillates by negative feedback with a period of about two hours in many cell types such as neural progenitor cells. Hes1 is required for maintenance of neural progenitor cells, but persistent Hes1 expression inhibits proliferation and differentiation of these cells, suggesting that Hes1 oscillation is required for their proper activities. Hes1 oscillation regulates cyclic expression of the proneural gene Neurogenin2 (Ngn2) and the Notch ligand Delta1, which in turn lead to maintenance of neural progenitor cells by mutual activation of Notch signaling. Taken together, these results suggest that oscillatory expression with short periods (ultradian oscillation) plays an important role in many biological events.