Tsang, Chi Keung. / "November 2011." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 103-116). / Abstracts in English and Chinese. / Abstract --- p.I / 摘要 --- p.III / Acknowledgement --- p.IV / Table of content --- p.V / List of Figures --- p.VIII / List of Tables --- p.XI / Abbreviations --- p.XII / Chapter Chapter 1: --- INTRODUCTION --- p.1 / Chapter 1.1. --- Hepatocellular carcinoma --- p.2 / Chapter 1.1.1. --- Etiological factors --- p.11 / Chapter 1.1.1.1. --- Chronic Hepatitis and Liver Cirrhosis --- p.13 / Chapter 1.1.1.2. --- HBV --- p.13 / Chapter 1.1.1.3. --- HCV --- p.17 / Chapter 1.1.1.4. --- Male gender --- p.20 / Chapter 1.1.1.5. --- Aflatoxin B1 exposure --- p.21 / Chapter 1.2. --- Genomic abnormalities in HCC --- p.23 / Chapter 1.3. --- GEF-H1 --- p.24 / Chapter 1.4. --- RhoA --- p.26 / Chapter 1.5. --- Epithelial-Mesenchymal Transition (EMT) --- p.29 / Chapter 1.6. --- Aims of Thesis --- p.31 / Chapter Chapter 2: --- MATERIALS AND METHODS --- p.32 / Chapter 2.1. --- Materials --- p.33 / Chapter 2.1.1. --- Chemicals and Reagents --- p.33 / Chapter 2.1.2. --- Buffers --- p.35 / Chapter 2.1.3. --- Cell Culture --- p.37 / Chapter 2.1.4. --- Nucleic Acids --- p.38 / Chapter 2.1.5. --- Enzymes --- p.39 / Chapter 2.1.6. --- Equipments --- p.40 / Chapter 2.1.7. --- Kits --- p.41 / Chapter 2.1.8. --- Antibodies --- p.42 / Chapter 2.1.9. --- Software and Web Resources --- p.43 / Chapter 2.2. --- Fluorescence In Situ Hybridization (FISH) --- p.44 / Chapter 2.2.1. --- Probe Preparation --- p.44 / Chapter 2.2.1.1. --- Human Bacterial Artificial Chromosome (BAC) probe preparation --- p.44 / Chapter 2.2.1.2. --- Nick translation --- p.44 / Chapter 2.2.2. --- Hybridization --- p.45 / Chapter 2.3. --- Genomic DNA extraction --- p.47 / Chapter 2.4. --- Copy number analysis --- p.48 / Chapter 2.5. --- Exon Sequencing analysis --- p.49 / Chapter 2.5.1. --- PCR amplification of GEF-H1 exons --- p.49 / Chapter 2.5.2. --- Cycle sequencing --- p.49 / Chapter 2.6. --- Ectopic expression of GEF-H1 in immortalized hepatocyte cell line --- p.52 / Chapter 2.6.1. --- Construction of GEF-H1 expressing vector --- p.52 / Chapter 2.6.2. --- Sub-cloning --- p.52 / Chapter 2.6.3. --- Transfection and clonal selection --- p.53 / Chapter 2.7. --- Gene Expression Analysis by Quantitative RT-PCR --- p.55 / Chapter 2.7.1. --- Total RNA extraction --- p.55 / Chapter 2.7.2. --- qRT-PCR analysis for gene expression --- p.55 / Chapter 2.8. --- Western blot --- p.58 / Chapter 2.9. --- Functional Analysis --- p.60 / Chapter 2.9.1. --- Cell viability (MTT) assay --- p.60 / Chapter 2.9.2. --- Cell proliferation assays (BrdU-incorporation) --- p.60 / Chapter 2.9.3. --- Mitomycin C treatment --- p.61 / Chapter 2.9.4. --- Migration and Invasion assays --- p.63 / Chapter 2.9.5. --- Wound healing assay --- p.65 / Chapter 2.9.6. --- Transient knock-down of RhoA --- p.65 / Chapter 2. --- 10. Immuno-fluorescent imaging --- p.66 / Chapter 2. --- 11. In vivo tumorigenic study of GEF-H1 by subcutaneous injection --- p.68 / Chapter 2. --- 12. Statistical analysis --- p.69 / Chapter Chapter 3: --- RESULTS --- p.70 / Chapter 3.1. --- Verifying copy number gain of GEF-H1 in high GEF-H1 expressing HCC --- p.71 / Chapter 3.2. --- Verifying if there is any GEF-H1 exon point mutation in HCC --- p.75 / Chapter 3.3. --- Functional roles of GEF-H1 in HCC --- p.77 / Chapter 3.4. --- GEF-Hl-induced functions were RhoA independent --- p.83 / Chapter 3.5. --- GEF-H1 Induction of Epithelial-mesenchymal transition in HCC --- p.88 / Chapter 3.6. --- GEF-H1 induced tumorigenicity of MIHA cells --- p.95 / Chapter Chapter 4: --- DISCUSSIONS --- p.96 / Chapter 4.1. --- GEF-H1 in HCC and other cancers --- p.97 / Chapter 4.2. --- GEF-H1 promotes cell motility --- p.98 / Chapter 4.3. --- GEF-H1 induced tumorigenicity --- p.100 / Chapter Chapter 5: --- CONCLUSIONS AND PROPOSED FUTURE INVESTIGATIONS --- p.101 / Chapter Chapter 6: --- REFERENCES --- p.103

Les acteurs neuroendocriniens régulant la physiologie des Lophotrochozoaires, groupe frère des Ecdysozoaires parmi les Protostomiens, demeurent peu connus. Grâce à l’émergence récente de ressources génomiques, transcriptomiques et peptidomiques chez l’huître creuse Crassostrea gigas, l’étude des couples ligand(s)/récepteur(s) régulant les fonctions physiologiques est désormais facilitée. Ainsi, par une approche d’endocrinologie inverse consistant à éprouver l’activité d’un panel de ligands potentiels, plusieurs récepteurs couplés aux protéines G (RCPGs), jusqu’alors orphelins ont pu être caractérisés sur le plan fonctionnel. Trois voies de signalisation ont été étudiées : la voie de type cholécystokinine/sulfakinine (CCK/SK) la voie de type calcitonine (CT) et la voie de type dopamine (DA). Grâce à des tests fonctionnels, deux neuropeptides et deux récepteurs de type CCK/SK ont pu être caractérisés. Des tests d’activité biologique in vitro et des expériences de conditionnement alimentaire ont montré la potentielle implication de ces couples dans la régulation de la digestion et de la satiété chez l’huître. Par ailleurs, deux couples neuropeptide/récepteur de type CT ont été caractérisés montrant, à l’image de leurs homologues chez les vertébrés, leur possible rôle dans la régulation hydrique ou ionique. D’autre part, un récepteur activé de manière spécifique par la dopamine et la tyramine a été caractérisé. Ce système de signalisation semble être impliqué dans la médiation du stress et intervenir dans les processus régulateurs de la reproduction au niveau de la gonade. Ainsi, les différents résultats obtenus au cours de ces travaux ont permis d’identifier des couples ligands/récepteurs d’huître homologues de systèmes de signalisation présents chez les Ecdysozoaires et les vertébrés confirmant l’origine de ces systèmes neuroendocriniens depuis l’ancêtre commun des Bilatériens. Les résultats obtenus ont également permis de mieux comprendre comment l’huître intègre les paramètres du milieu et donc s’acclimate aux différentes contraintes environnementales. / The neuroendocrine regulators of the physiology of Lophotrochozoa, the sister clade of Ecdysozoa among Protostoma, remain poorly understood. Thanks to the recent emergence of genomic, transcriptomic and peptidomic resources in the Pacific oyster Crassostrea gigas, the functional characterization of ligand/receptor pairs regulating a diversity of physiological functions has been facilitated. Using a reverse endocrinology approach, a number of orphan G Protein-Coupled Receptors (GPCRs) have been functionally characterized. Three signalling systems have been studied in the oyster: The cholecystokinin/sulfakinin (CCK/SK), the calcitonin (CT) and the dopamine (DA) signalling systems. Two CCK/SK receptors and ligands have been characterized. In vitro bioassays and feeding conditions suggested the potential involvement of this signalling system in the regulation of digestion and satiety. Besides, two couples of CT-type peptides and receptors have been characterized showing, as for their vertebrate counterparts, their possible role in the regulation of water and ion balance. A receptor specifically activated by dopamine and by tyramine has also been characterized. This signalling system appeared to be implicated in the mediation of stress and to play a role in the regulatory processes of reproduction in the gonads. This study allowed the characterization in the oyster of ligand receptor pairs homolog to known signalling systems present in Ecdysozoa and vertebrates, thus confirming the origin of these neuroendocrine systems in the common ancestor of Bilateria. The results of this study also contributed to understand how the oyster integrates external parameters and adapts to various environmental constrains.

G protein-coupled receptors (GPCRs) are known to exist as oligomers, but there is much uncertainty over the oligomeric size, the number of interacting G proteins and the stability of that interaction. The present approach to these questions has been threefold. Monomers of the M2 muscarinic receptor were purified from Spodoptera frugiperda (Sf9) cells and reconstituted in phospholipid vesicles, where they spontaneously formed tetramers. The size of the reconstituted complex was determined from its electrophoretic mobility after cross-linking and inferred from a quantitative, model-based assessment of cooperative effects in the binding of two muscarinic antagonists: N-methylscopolamine and quinuclidinylbenzilate. Binding of the agonist oxotremorine-M to receptor reconstituted with purified G proteins revealed at least three classes of sites that interconverted from higher to lower affinity upon the addition of guanylylimidotriphosphate (GMP-PNP). The binding properties resemble those of muscarinic receptors in myocardial preparations, thereby implying the existence of tetramers in native tissues. G proteins that copurify with the M2 receptor from cardiac membranes also were found to exist as oligomers, some of which contain both alpha(o) and alpha(i2), and the purified complexes contained receptor and G protein in near-equal amounts. A tetrameric receptor implies a tetramer of G proteins, a conclusion that is supported by the distribution of sites between different states identified in the binding of [35S]GTPgammaS to the purified complex. Covalent adducts of a GPCR fused to a Galpha-subunit provide a model system in which the relationship between receptor and G protein complex is defined with respect to stability and composition. Such a fusion of the M2 receptor and Galpha(i1) underwent a cleavage near the amino terminus of the alpha-subunit, however, flagging the likelihood of similar effects in other such adducts. Truncation of the amino terminus prior to fusion generated a stable product that revealed GMP-PNP-sensitive, biphasic binding of oxotremorine-M and noncompetitive interactions between N-methylscopolamine and quinuclidinylbenzilate. A covalent RG complex therefore exhibits the functional properties of M2 receptors in native systems. These observations are consistent with the notion that signaling through the M2 receptor occurs via cooperative interactions within a stable complex that comprises four receptors and four G proteins.

<p>Fungi have a genetically controlled sex determination system, which is governed by a small, sex-specific region in the genome called the mating-type locus (MAT). In the basidiomycetous yeast Cryptococcus neoformans, the pathogen that causes cryptococcal meningitis and cryptococcosis, sex has been associated with virulence. To further understand how sex is genetically regulated in C. neoformans, we focused our studies on the evolution of the MAT locus and molecular dissection of the pheromone signaling pathway that controls sexual development. Two MAT-linked meiotic recombination hotspots that likely drove the assembly and rearrangement of MAT were identified. Fine mapping through the integration of genetic markers established that two hotspots, one on each side of the MAT locus, are located in an ~10 kb and ~5 kb region. Plotting the G + C content along MAT and the flanking regions revealed a strong association between the location of these two hotspots and a high G + C content. By deletion and insertion of the G + C rich region, we demonstrated that the high G + C rich region is required but not sufficient to induce recombination. On the other hand, to provide direct experimental evidence to support the previously proposed model for the evolution of MAT, we sought to recapitulate the ancestral tetrapolar, and the intermediate tripolar mating systems of C. neoformans by manipulating the MAT structure to model a tetrapolar system. In the two modified "a" and "α" strains, the sex-determining genes SXI1α or SXI2a residing at the MAT locus were disrupted and the wild-type allele of these two genes was then reintroduced at another genomic location (URA5) that is unlinked to MAT. Our results show that C. neoformans can complete the sexual cycle with a tetrapolar mating configuration and the transitional tripolar state might be under strong negative selection pressure, which could have facilitated the transition from a tripolar state to the final bipolar mating system. </p><p>The MAT locus is the major determinant of the sexual identity of a cell, but several signaling pathways, including the pheromone signaling pathway, are required to regulate mating and sexual development. Many components of the pheromone signaling pathway have been identified; however, it is less clear what lies upstream of the MAPK cascade. To address this question, we studied the role of two Gα subunits (Gpa2, Gpa3) in mating and concluded that they share both redundant and divergent roles in mating. gpa2 gpa3 double mutants, but neither gpa2 nor gpa3 single mutants, are sterile in bilateral crosses. In their GTP-bound form, they signal in opposition: Gpa2 promotes mating whereas Gpa3 inhibits. Furthermore, we also studied the functions of a novel upstream component Cpr2, a pheromone receptor-like gene, in pheromone signaling and sexual development. All lines of evidence suggest that Cpr2 is a constitutive ligand-independent receptor that, when expressed, engages the same G-proteins and activates the same pheromone signaling pathway as the canonical ligand-activated pheromone receptors. Expression of Cpr2 is induced post cell fusion during mating, and likely introduces a positive feedback loop to allow a self-perpetuating signaling state to enable efficient mating. Cells lacking this receptor are fertile, but produce abnormal filamentous structures. Overexpression of CPR2 in a or α cells strongly enhances fruiting, an alternative same-sex mating process in C. neoformans. Therefore, Cpr2 establishes a new paradigm for a naturally occurring constitutively active GPCR that governs cell fate in fungi. </p><p>Finally, we described a sex-induced silencing (SIS) phenomenon in C. neoformans. Using genetic approaches, we showed that SIS is triggered by a tandem insertion of a transgene during the sexual cycle. Interestingly, only a proportion of progeny carrying the transgene are silenced. Gene deletion, RIP, or DNA methylation do not contribute to SIS but the RNAi machinery is required. In conclusion, these studies provide further understanding of sex in C. neoformans from different perspectives, which invites comparisons to other fungal and even more broadly, eukaryotic pathogens to address the role of sex in evolution.</p> / Dissertation

Signal transduction pathways mediated by G protein-coupled receptors (GPCRs) and their intracellular coupling partners, the heterotrimeric G proteins, are crucial for several physiological functions in eukaryotes, including humans. This thesis describes a broad genomic survey and extensive comparative phylogenetic analysis of GPCR and G protein families from a wide selection of eukaryotes. A robust mining of GPCR families in fungal genomes (Paper I) provides the first evidence that homologs of the mammalian families of GPCRs, including Rhodopsin, Adhesion, Glutamate and Frizzled are present in Fungi. These findings further support the hypothesis that all main GPCR families share a common origin. Moreover, we clarified the evolutionary hierarchy by showing for the first time that Rhodopsin family members are found outside metazoan lineages. We also characterized the GPCR superfamily in two important model organisms (Amphimedon queenslandica and Saccoglossus kowalevskii) that belong to different metazoan phyla and which differ greatly in morphological characteristics. Curation of the GPCR superfamily (Paper II) in Amphimedon queenslandica (an important model to understand evolution of animal multicellularity) reveals the presence of four of the five GRAFS families and several other GPCR gene families. However, we find that the sponge GPCR subset is divergent from GPCRs in other studied bilaterian and eumetazoan lineages. Mapping of the GPCR superfamily (Paper III) in a hemichordate Saccoglossus kowalevskii (an essential model to understand the evolution of the chordate body plan) revealed the presence of all major GPCR GRAFS families. We find that S. kowalevskii encodes local expansions of peptide and somatostatin- like GPCRs. Furthermore, we delineate the overall evolutionary hierarchy of vertebrate-like G protein families (Paper IV) and provide a comparative perspective with GPCR repertoires. The study also maps the individual gene gain/loss events of G proteins across holozoans with more expanded invertebrate taxon sampling than earlier reports. In addition, Paper V describes a broad survey of nematode chemosensory GPCR families and provides insights into the evolutionary events that shaped the GPCR mediated chemosensory system in protostomes. Overall, our findings further illustrate the evolutionary hierarchy and the diversity of the major components of the G protein-coupled receptor signaling system in eukaryotes.

G protein-coupled receptors (GPCRs) are known to exist as oligomers, but there is much uncertainty over the oligomeric size, the number of interacting G proteins and the stability of that interaction. The present approach to these questions has been threefold. Monomers of the M2 muscarinic receptor were purified from Spodoptera frugiperda (Sf9) cells and reconstituted in phospholipid vesicles, where they spontaneously formed tetramers. The size of the reconstituted complex was determined from its electrophoretic mobility after cross-linking and inferred from a quantitative, model-based assessment of cooperative effects in the binding of two muscarinic antagonists: N-methylscopolamine and quinuclidinylbenzilate. Binding of the agonist oxotremorine-M to receptor reconstituted with purified G proteins revealed at least three classes of sites that interconverted from higher to lower affinity upon the addition of guanylylimidotriphosphate (GMP-PNP). The binding properties resemble those of muscarinic receptors in myocardial preparations, thereby implying the existence of tetramers in native tissues. G proteins that copurify with the M2 receptor from cardiac membranes also were found to exist as oligomers, some of which contain both alpha(o) and alpha(i2), and the purified complexes contained receptor and G protein in near-equal amounts. A tetrameric receptor implies a tetramer of G proteins, a conclusion that is supported by the distribution of sites between different states identified in the binding of [35S]GTPgammaS to the purified complex. Covalent adducts of a GPCR fused to a Galpha-subunit provide a model system in which the relationship between receptor and G protein complex is defined with respect to stability and composition. Such a fusion of the M2 receptor and Galpha(i1) underwent a cleavage near the amino terminus of the alpha-subunit, however, flagging the likelihood of similar effects in other such adducts. Truncation of the amino terminus prior to fusion generated a stable product that revealed GMP-PNP-sensitive, biphasic binding of oxotremorine-M and noncompetitive interactions between N-methylscopolamine and quinuclidinylbenzilate. A covalent RG complex therefore exhibits the functional properties of M2 receptors in native systems. These observations are consistent with the notion that signaling through the M2 receptor occurs via cooperative interactions within a stable complex that comprises four receptors and four G proteins.

Thesis (Ph. D.)--Duke University, 2007. / Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains vi, 96 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 143-152). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Washington, 1997. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.