Ling, Yick Hin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 72-77). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Cheung, Hei Nga. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 63-72). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Notch signaling plays an important role in developmental and pathological angiogenesis. Notch ligands, Dll4 and Jag1, have been implicated in tumor angiogenesis. Inhibition of Dll4-mediated Notch signaling results in hypersprouting of non-functional vasculature in tumors. We have constructed and analyzed pan-Notch ligand inhibitors, Notch1 decoys 1-24 and 1-36, which are based on the extracellular EGF-like repeats of Notch1. Both Notch1 decoys block angiogenesis in in vitro endothelial cell-based assays and in the mouse retina. We also show that they similarly inhibit Dll4- and Jag1-induced Notch signaling in vitro and result in a significant decrease in tumor growth and tumor vasculature in mouse and human tumor xenograft models. Interestingly, truncated Notch1 decoy variants, Notch1 decoys 1-13 and 10-24, act as ligand-specific Notch inhibitors. Notch1 decoy 1-13 is Dll4-specific whereas Notch1 decoy 10-24 is Jag1-specific. Ligand-specific Notch1 decoys effectively reduce tumor growth in tumor xenograft models in the mouse, including Mm5MT-FGF4, KP1-VEGF, LLC, and B16-F10. Notch1 decoy 1-13 has been demonstrated to increase tumor vasculature by increasing endothelial sprouting and number of tip cells. However, similar to the previously reported effects of Dll4 blockade, the tumor vessels are poorly perfused and hardly functional. On the other hand, Jag1-specific Notch1 decoy 10-24 significantly reduces tumor vessel density and disrupting endothelial-pericyte interactions, causing the impaired vascular structure and attenuated vascular perfusion. In addition, Notch1 decoys 1-13, 10-24, and 1-24 show an anti-metastatic potential in causing a delay of lung metastasis in the B16-F10 tumor model. Unlike gamma-secretase inhibitors and Dll4-blocking agents, Notch1 decoys do not cause GI-associated toxicity or vascular neoplasms. Therefore, our Notch1 decoys may represent a novel alternative and may hold future promise for Notch-targeted cancer therapy.

Cellular differentiation is the cornerstone of metazoan development. Cell-cell signaling mechanisms are responsible for the specification of many cell fates. The response of a particular cell to a given signal is highly context dependent allowing signaling mechanisms to be reused to produce a variety of different outcomes. The EGFR and LIN-12/Notch signaling pathways are well-conserved across metazoan species and govern many fate-specification events. The specification of C. elegans Vulval Precursor Cells (VPCs) offers a powerful system to investigate how these signaling mechanisms specify cell-fates, and previous studies of VPC fate patterning have identified several forms of crosstalk between these two critical signaling mechanisms. In this thesis, I investigate how input from both the EGFR and LIN-12/Notch signaling pathways is integrated by the VPCs. I provide evidence that VPCs respond to the relative levels of LIN-12/Notch and EGFR signaling. I show that LIN-1/Elk1 is critical for VPCs to adopt discrete cell fates. In addition, I show that the Mediator components SUR-2/Med23 and the CDK-8 kinase module (CKM), in cooperation with LIN-1/Elk1, are required for an EGFR-mediated resistance to LIN-12/Notch activity. I also used CRISPR/Cas9 techniques to generate endogenous, fluorescently-tagged LAG-1 proteins. Characterization of tagged LAG-1 accumulation in the VPCs and in the somatic gonad show that LAG-1 is present in all VPCs at low levels in a lin-12/Notch independent manner. Activation of LIN-12/Notch is correlated with higher levels of LAG-1 accumulation compared to cells that do not have activated LIN-12/Notch. These findings suggest a potential autoregulation mechanism for lag-1 in certain contexts. They also suggest that endogenously tagged LAG-1 may be a useful molecular marker of LIN-12/Notch activation.

Notch signaling controls normal and pathological angiogenesis through transcriptional regulation of a wide network of target genes. Despite intensive studies of the endothelial Notch function, a comprehensive list of Notch-regulated genes, especially direct transcriptional targets, has not been assembled in endothelial cells (ECs). Here we uncovered novel EC Notch targets that are rapidly regulated by Notch signaling using several unbiased in vivo and in vitro screening approaches that captured genes regulated within 6 hours or less of Notch signal activation. We used a gamma-secretase inhibitor in neonates to profile Notch targets in the brain endothelium using the RiboTag technique, allowing for isolation of endothelial specific mRNA from a complex tissue without disrupting cell-cell contact. We used two types of primary cultured endothelial cells to define ligand-specific Notch targets by tethered-ligand stimulation. The identified Notch targets were validated by determining their regulation within one to two hours of EGTA-mediated Notch activation. By comparing significantly regulated genes in each of the screens, we assembled a comprehensive database of potential Notch targets in endothelial cells. Of particular interest, we uncovered G protein pathway related genes as potential novel Notch targets. We focused on a novel candidate target passing selection criteria after all screens, a small GTPase RND1. RND1(Rho GTPase1) regulates cytoskeleton arrangement through Rho and Ras signaling. RND1 was validated as an endothelial Notch target in multiple endothelial cell types. In Human Umbilical Vein Endothelial Cells (HUVECs) we established angiogenic activity for RND1 that included regulation of cell migration towards VEGF and function in sprouting angiogenesis. We established that Notch and RND1 suppressed Ras activation but had no effects on Rho activation in HUVECs. These results demonstrate that RND1 expression is regulated by Notch signaling in endothelium and suggest that RND1 functions downstream of Notch in sprouting angiogenesis, revealing an unexplored role of endothelial Notch in regulating G protein pathways.

The Major Histocompatibility Complex class II B (MHC II B) gene encodes a protein that is part of the adaptive immune system and critical for the non-self recognition ability of immune cells. This gene has been characterized in the Bald Eagle, ten unique alleles were found in two subpopulations at the geographic extremes of the range margins. Geographic genetic variation is suggested by the presence of population specific alleles. The results showed considerable divergence of groups of Bald Eagle alleles when compared to alleles from other birds of prey. Particular codons within the exon II show signs of balancing selection driving the evolution of the MHC II B. Transcription data showed statistically significant differential expression of alleles. This can be interpreted as meaning a particular locus is being preferentially expressed in blood. The analysis of the polymorphism of this adaptive marker may aid managers of wildlife during this age of global climate change and the biodiversity crisis. / by Andrew Smith. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

In this thesis, we propose to discover co-regulated genes using microarray expression data, as well as providing visualization functionalities for domain experts to study relationships among discovered co-regulated genes. To discover co-regulated genes, we first use existing gene selection methods to select a small portion of genes which are relevant to the target diseases, on which we build an ordered similarity matrix by using nearest neighbor based similarity assessment criteria. We then apply a threshold based clustering algorithm named Spectral Clustering to the matrix to obtain a number of clusters. The genes which are clustered together in one cluster represent a group of co-regulated genes and to visualize them, we use Java Swings as the tool and develop a visualization platform which provides functionalities for domain experts to study relationships between different groups of co-regulated genes; study internal structures within each group of genes, and investigate details of each individual gene and of course for gene function prediction. Results are analyzed based on microarray expression datasets collected from brain tumor, lung cancers and leukemia samples. / by Vaibhan Lad. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Biotic stress is one of the most serious constraints on rice productivity. Strategy adopting regulators in signal transduction of systemic acquired resistance for conferring long-lasting disease resistance against broad spectrum of pathogens become highly favorable. To achieve this, signal transduction of disease resistance should be well characterized. / OsGPBP1 is a putative G-protein binding protein and interacts with a member of the YchF G-protein subfamily that has not been thoroughly studied in plants, while OsRHC1 is a novel RING zinc finger protein harboring multiple transmembrane domains at the N-half and a unique RING-HC domain at the C terminus. Both of them were induced in the bacterial blight resistant near isogenic rice line upon wounding. Gain-of-function tests in transgenic Arabidopsis thaliana showed that their ectopic expressions are able to trigger the expression of both defense marker genes mediated either by SA- or JA/ET-pathways and led to increased resistance toward the pathogen Pseudomonas syringae pv. tomato DC3000 and both of the two clones seemed to rely on NPR1 (disease resistance key regulator) for function. Furthermore, over-expressions of the two clones in its native system are also able to activate rice defense marker genes. / Suppression subtractive hybridization experiment, using RNA samples from a pair of near-isogenic rice lines either containing the R gene Xa14 (CBB14) or its susceptible recurrent parent (SN1033), were previously performed in our laboratory. Two gene candidates ( OsGPBP1 and OsRHC1) probably encoding two novel types of signal transduction components related to disease resistance are chosen for further analysis. / Cheung, Ming Yan. / "September 2007." / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4555. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 148-168). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

The Hippo pathway is a master regulator of cell proliferation and organ size, namely through regulation of transcriptional co-activators YAP and TAZ which bind TEAD1-4 transcription factors. The Hippo effector YAP is dysregulated in many human solid tumours including rhabdomyosarcoma and oesophageal cancer. Additionally, persistent hyperactivity of YAP in activated but not quiescent satellite cells can give rise to embryonal rhabdomyosarcoma. However, the question of exactly how YAP acts as an oncogene and actively gives rise to tumour progression in these cancers remains unknown. In this thesis I characterised the mechanisms which determine the functional role of YAP in driving instability in the genome. Secondly, lentiviral mediated knockdown of YAP is performed to determine and investigate its effect on tumorigenesis. Thirdly, gene sets from constitutive YAP S127A induced mouse ERMS tumours subjected to array-CGH were further analysed. Finally, I cloned chicken Yap1, Tead1 and Fstl5 to identify its role during chick embryonic development, by the retroviral mediated loss of function approach. The results demonstrated that constitutive YAP S127A expression in-vitro as well as in-vivo induces chromosomal instability by increasing the rate of mitotic chromosome segregation errors and copy number alterations of oncogenes and other cancer related genes. Recurrent copy number gains of the p53 inhibitor Mdm2 were observed in YAP S127A-driven ERMS tumours. Moreover, lentiviral mediated YAP knockdown showed significant reduction in proliferation, migration and invasion as well as transformation potential in human cultured cancer cells. Moreover, retroviral YAP S127A expression during early stages of chick embryo development did not lead to an overt phenotype and showed poor survival. Additionally, I have cloned RCAS-RNAi vectors to study the loss of function effect on Hippo targets and Fstl5 during chicken embryo development. Collectively, my data provides insight into the mechanisms with which YAP could drive tumorigenesis and that YAP knockdown can be considered a potential therapeutic target to reduce cancer progression.

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