O meduloblastoma (MB) é o tumor cerebral maligno mais comum na infância. A formação/progressão desta neoplasia foi associada a alterações moleculares, que inclui a desregulação da via de sinalização Wingless (Wnt), responsável pelo desenvolvimento embrionário. Além disso, as proteínas da família Aurora-quinases (A, B e C) têm sido amplamente estudadas, uma vez que a Aurora A e B foram encontrados hiperexpressas em diversas neoplasias, como o MB. Estudos recentes mostraram que existe uma associação entre a Via Wnt e as Aurora-quinases. No entanto, poucos trabalhos foram realizados para confirmar essa associação. Ademais, não existem trabalhos que relatem os efeitos do AMG900, um pan-inibidor de aurora-quinases, em MB, dando enfoque na regulação da via Wnt. Assim, o objetivo deste trabalho foi avaliar a modulação da via Wnt pelo inibidor AMG900 nas linhagens celulares de meduloblastoma pediátrico. Foram realizados os ensaios de PCR convencional, sequenciamento, qRT-PCR, transfecção transiente, ensaio clonogênico, Western Blot e ciclo celular. As linhagens celulares UW402, UW473 e ONS-76 não apresentaram mutações no éxon 3 do gene CTNNB1 (?-catenina) e no éxon 15 do gene APC. Não foi observada uma expressão significativa de CTNNB1, confirmando que as linhagens não possuíam a via Wnt ativa. Com isso foi necessário a transfecção transiente com a ?- catenina. Após este ensaio, houve um aumento da expressão de CTNNB1, Ciclina D1 e CMyc nas três linhagens, o que não ocorreu com as Auroras A e B. No ensaio clonogênico foi observado uma redução do número de colônias nas linhagens UW473 e ONS-76. Observou-se um aumento da expressão proteica da ?-catenina, da Aurora A e B na UW473, o que ocorreu somente com a ?-catenina na linhagem ONS-76. Após o tratamento com o AMG900 ocorreu uma diminuição da expressão proteica de ?-catenina, da Aurora A e B em ambas as linhagens. A transfecção não alterou o percentil celular em G2/M na UW402 e UW473. Já na ONS-76 houve um aumento significativo em G2/M, e o AMG900 potencializou esse bloqueio apenas nessa linhagem. Os resultados sugerem que pode haver alguma relação entre a inibição das proteínas Aurora-quinases e a expressão de proteínas da via Wnt. / Medulloblastoma (MB) is the most common malignant brain tumor in childhood. Tumor formation/progression has been associated to molecular alterations that include dysregulation of signaling pathway Wingless (Wnt), responsible for embryonic development. In addition, cell cycle proteins Aurora-kinase (A, B and C) have been widely studied since Aurora A and B were found overexpressed in many cancers such as MB. Recent studies show that there is an association between Wnt pathway and Aurora kinase proteins. However, few studies have been conducted to confirm this association. Moreover, there are no studies reporting the effects of AMG900 in MB, by focusing on the regulation of the Wnt pathway. The aim of this study is to evaluate Wnt pathway modulation by Aurora kinases inhibitor AMG900 in pediatric medulloblastoma cell lines. Conventional PCR, sequencing, qRT-PCR, transient transfection, clonogenic assay, Western Blot and cell cycle assays were performed. UW402, UW473 and ONS-76 cell lines did not present mutations in exon 3 of CTNNB1 gene and exon 15 of APC gene. There was no significant expression of CTNNB1 and their target genes in these cell lines, confirming that they did not have Wnt pathway activated. Considering this, transient transfection was necessary. After this trial, there was an increase in expression of CTNNB1 gene and its target genes Cyclin D1 and C-Myc in the three cell lines, which was not observed in Aurora kinases. Furthermore, in the clonogenic assay, a reduction in the number of colonies in UW473 and ONS-76 cell lines was observed. It was also observed an increase in ?-catenin protein, Aurora A and B in UW473 cell line, but not in ONS-76 cell line. However, after treatment there was a decrease in protein expression of ?-catenin, Aurora A and B in both cells. Transfection did not change the cellular percentile in G2 / M in UW402 and UW473. In ONS-76 there was a significant increase in G2 / M, and the treatment with AMG900 potentiated this block only in this cell line. Results suggest that there may be some relation between the inhibition of Aurora kinase protein and protein expression in Wnt pathway.

<p>Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpesvirus which chronically infects >95% of the global population, and can give rise to a number of malignancies in B cells and epithelial cells. In EBV latently infected epithelial cells, such as nasopharyngeal carcinoma (NPC) and gastric carcinoma (GaCa) cells, viral protein expression is low. In contrast, a cluster of viral microRNAs (miRNAs) called miR-BARTs is highly expressed. MiRNAs are small non-coding RNAs which regulate gene expression by binding to complementary sequences in mRNAs. It is likely that miR-BARTs play a crucial role in EBV-infected epithelial cells, however a comprehensive understanding of miR-BARTs is currently lacking. Here, I present two studies utilizing the phenotypic and the target approaches, respectively, to demonstrate that miR-BARTs can inhibit apoptosis and activate the Wnt signaling pathway. To discover miR-BARTs that can inhibit apoptosis, I individually expressed miR-BARTs in the EBV- GaCa cell line AGS, and identified five miR-BARTs that conferred this phenotype. To identify pro-apoptotic genes targeted by the five anti-apoptotic miRNAs, I validated one previously published target and identified nine novel targets by performing photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) in the EBV+ NPC cell line C666. Next, I thoroughly demonstrated that the 10 candidate target genes were substantially suppressed by expression of the relevant miR-BARTs, as measured by 3’UTR-containing firefly luciferase (FLuc) expression, mRNA and protein levels, and knockdown of seven of the 10 candidate genes could suppress apoptosis, mimicking the effects of relevant miR-BARTs. On the other hand, in order to identify miR-BARTs that can activate the Wnt signaling pathway, I analyzed the PAR-CLIP data set of C666 cells and discovered nine anti-Wnt signaling targets of miR-BARTs, including seven novel genes and two pro-apoptotic genes identified above. Using FLuc 3’UTR indicator assays, I proved that the 3’UTRs of all seven newly identified anti-Wnt signaling genes were indeed targeted by the relevant miR-BARTs identified by PAR-CLIP. Utilizing a Wnt signaling FLuc reporter TOPflash which measures the Wnt signaling activation, I confirmed that expression of many miR-BARTs that target Wnt signaling inhibitors can indeed upregulate the Wnt signaling pathway. Together, my results identified and validated a substantial number of novel targets of miR-BARTs involved in apoptosis and the Wnt signaling pathway, indicating that EBV may employ miR-BARTs to heavily target these two pathways to facilitate chronic infection.</p> / Dissertation

Mathematical modeling has been important in the study of biology. Two main challenges with modeling biological problems are the lack of quantitative data and the complexity of biological problems. With the invention of new techniques, like single molecule transcript counting, very quantitative gene expression measurements at the level of single transcript in individual cells can now be obtained. Biological systems are very complex, involving many reactions and players with unknown reaction rates. To reduce the complexity, scientists have often proposed simplified phenomenological models that are tractable and capture the main essence of the biological systems. These simplified models allow scientists to describe the behavior of biological systems with a few meaningful parameters. In this thesis, by integrating quantitative single-cell measurements with phenomenological modeling, we study the (1) roles of Wnt ligands and receptors in sensing and amplification in Caenorhabditis elegans’ P cells and (2) regulation of rDNA transcription in Saccharomyces cerevisiae. The initiation of cell polarity consists of two sequential processes: an external gradient is first sensed and then the resulting signal is amplified by intracellular signaling. It is challenging to determine the role of proteins towards sensing and amplification as these two processes are intertwined. We integrated quantitative single-cell measurements with phenomenological modeling to determine the roles of Wnt ligands and receptors in sensing and amplification in the P cells of Caenorhabditis elegans. By systematically exploring how P cell polarity is altered in Wnt ligand and receptor mutants, we inferred that ligands predominantly affect sensing, whereas receptors are needed for both sensing and amplification. Most eukaryotes contain many tandem repeats of ribosomal RNA genes of which only a subset is transcribed at any given time. Current biochemical methods allow for the determination of the fraction of transcribing repeats (ON) versus nontranscribing repeats (OFF) but do not provide any dynamical information. By using the single molecule transcript counting technique complemented with theoretical modeling, we determine the rate of switching from OFF to ON (activation rate) and the average number of RNA molecules produced during each transcriptional burst (burst size). We explore how these two variables change in mutants and different growth conditions.

Prostate and breast cancer are among the most commonly diagnosed cancers and leading causes of cancer-related deaths in men and women worldwide. It is therefore evident that enhanced understanding of tumorigenesis is required to improve diagnostic tools, improve prognostics and identify novel therapeutic targets. The goal of this dissertation was to elucidate the role of primary cilia in prostate and breast cancer. Little is known about the role primary cilia may play in these cancers. Primary cilia are microtubule-based organelles which aid in sensing the extracellular environment and participate in signal transduction. Important developmental signaling pathways, such as Hedgehog (Hh) and Wnt signaling pathways, involve cilia. These pathways have also been implicated in prostate and breast cancer. In this work, we demonstrate that cilia are lost through prostate cancer progression. The few remaining cilia on prostate cancers appeared to be dysfunctional, as assessed by quantifying cilia lengths, an indirect measure of functionality. We also investigated a link between the observed cilia loss and canonical Wnt signaling in prostate cancers. Primary cilia have been determined to have a suppressive role in Wnt signaling, therefore we predicted loss of cilia to correlate with increased Wnt signaling. A link between cilia loss or shortened cilia and activated Wnt signaling was suggested in a subset of prostate cancers. Our lab has established that cilia are similarly lost in breast cancer. These data suggested the hypothesis that cilia may act as tumor suppressor organelles in the prostate and breast. To test this hypothesis, we knocked down cilia in an oncogenic mammary mouse model and assessed changes in tumor growth and characteristics. We observed enhanced tumor growth with cilia loss. The data supports the hypothesis that primary cilia may be playing a tumor suppressor role in the prostate and breast, and provides promising avenues for identifying novel therapeutic approaches for cancer patients.

No description available.

The increase in the prevalence of obesity and obesity-related diseases has caused greater attention to be placed on the molecular mechanisms controlling adipogenesis. In this study, we studied the role of 5-aza-2'-deoxycytidine (5-Aza-dC), an inhibitor of DNA methylation, on adipocyte differentiation. We found that inhibiting DNA methylation by 5-Aza-dC significantly inhibited adipocyte differentiation whereas promoting osteoblastogenesis. Wnt10a was up-regulated by 5-Aza-dC treatment and it was suggested that Wnt10a might play a vital role in suppressing adipogenesis and promoting osteoblastogenesis by inhibiting DNA methylation. In 3T3-L1 cells, Wnt signaling inhibitor IWP-2 was found to reverse the inhibitory effect of 5-Aza-dC on Adipocyte differentiation, whereas in mesenchymal stem cell line, ST2 cells, IWP-2 treatment reversed the effect of 5-Aza-dC on promoting osteoblastogenesis. These studies will provide a better understanding to the cause and treatment of obesity and bone-related diseases.

We sought to determine whether activation of the Wnt signaling pathway altered the function of hNSCs in vitro. We took three approaches to activate Wnt signaling: Wnt3a, constitutively stabilized β-catenin (ΔN90), and the GSK3 inhibitor BIO. While Wnt3a and ΔN90 had no effect on proliferation in both stem cell (+EGF/FGF) and differentiating (-EGF/FGF) conditions, BIO reduced proliferation in both. All methods of Wnt signaling activation promoted neuronal lineage commitment during hNSC differentiation. Furthermore, BIO was able to induce mild neuronal differentiation in stem cell conditions, suggesting that GSK3-inhibition interferes with several pathways to regulate hNSC fate decisions. We also probed BTSC function using BIO-mediated GSK3 inhibition. We found that in stem cell conditions, BIO was able to induce neuronal differentiation, decrease proliferation, and induce cell cycle arrest. Together this data suggests that GSK3-inhibition, possibly through activation of Wnt signaling, may offer a novel mechanism for the differentiation treatment of glioblastomas.

We sought to determine whether activation of the Wnt signaling pathway altered the function of hNSCs in vitro. We took three approaches to activate Wnt signaling: Wnt3a, constitutively stabilized β-catenin (ΔN90), and the GSK3 inhibitor BIO. While Wnt3a and ΔN90 had no effect on proliferation in both stem cell (+EGF/FGF) and differentiating (-EGF/FGF) conditions, BIO reduced proliferation in both. All methods of Wnt signaling activation promoted neuronal lineage commitment during hNSC differentiation. Furthermore, BIO was able to induce mild neuronal differentiation in stem cell conditions, suggesting that GSK3-inhibition interferes with several pathways to regulate hNSC fate decisions. We also probed BTSC function using BIO-mediated GSK3 inhibition. We found that in stem cell conditions, BIO was able to induce neuronal differentiation, decrease proliferation, and induce cell cycle arrest. Together this data suggests that GSK3-inhibition, possibly through activation of Wnt signaling, may offer a novel mechanism for the differentiation treatment of glioblastomas.

Wolbachia are widely spread, maternally transmitted insect endosymbiotic intracellular bacteria. They have been implicated in the control of several insect transmitted diseases, including dengue, yellow fever, Zika and malaria. Effective pathogen suppression in the insect host is shown to be proportional to the intracellular levels of bacteria. Therefore, understanding the molecular mechanisms underlying Wolbachia accumulation within organisms is extremely important for future epidemic control and research. Using Drosophila as a model insect, our lab has previously observed Wolbachia tropism to stem cell niches. Current work has identified polar cells as an additional site of Wolbachia tropism and demonstrated that Wg/Wnt signaling is important for Wolbachia intracellular accumulation in these somatic cells. In this thesis, we first observed that the Wg/Wnt pathway protein Armadillo also controls Wolbachia levels in the germline cells, indicating the possibility of having a conserved molecular mechanism controlling Wolbachia. Using RNAi and small molecule inhibitors of Shaggy, another component of the canonical Wg/Wnt pathway, we demonstrate that the canonical Wg/Wnt signaling is essential for Wolbachia intracellular accumulation. Our investigation provides fundamental insights into the mechanisms of Wolbachia intracellular accumulation. Furthermore, it offers novel strategies to modulate Wolbachia in non-model insect species, including various disease transmitting Anopheles, Culex, and Aedes. These findings potentially will increase the effectiveness of a Wolbachia-based vector transmitted disease suppression. / 2017-02-28

xi, 62 p. : ill. (some col.) / This dissertation describes research into microbial influences on host signaling in the zebrafish intestine. Vertebrate organisms are consistently exposed to microbes, especially on epithelial tissues that are exposed to the environment, such as the skin and the gastrointestinal tract. The close association between these tissues and microbes over time has resulted in a symbiotic state, whereby microorganisms have gained the ability to utilize vertebrate epithelia as a niche for replication and the acquisition of nutrients. These associations run the gamut from beneficial to exceedingly pathogenic and often involve complex bidirectional signaling between microbe and host. Microbial signals can interact with host cell pathways involved in a wide range of cellular processes. Here, we describe our investigations into one such pathway, the Wnt signaling pathway, and how microbial activation of Wnt signaling can translate into alterations in cell proliferation and homeostasis in the intestinal epithelium of the teleost fish Danio rerio. We report that epithelial cell proliferation in the developing zebrafish intestine is stimulated both by the presence of the resident microbiota and by activation of Wnt signaling and demonstrate that resident intestinal bacteria enhance the stability of β-catenin in intestinal epithelial cells, promoting cell proliferation in the developing vertebrate intestine. We also describe how transgenic expression of the bacterial effector protein CagA from the human gastric pathogen Helicobacter pylori is capable of causing significant overproliferation of the intestinal epithelium and adult intestinal hyperplasia, as well as significant upregulation of the Wnt target genes cyclinD1 and the zebrafish c-myc ortholog myca. We show that co-expression of CagA with a mutant allele of the β-catenin destruction complex protein Axin1 resulted in a further increase in intestinal proliferation, while co-expression of CagA with a null allele of the essential β-catenin transcriptional cofactor Tcf4 restored intestinal proliferation to wild-type levels. These results suggest that CagA activates canonical Wnt signaling downstream of the β-catenin destruction complex and upstream of Tcf4. Our studies provide in vivo evidence of Wnt pathway activation by CagA and implicate this activation in CagA-induced epithelial overproliferation, an early step in gastrointestinal cancer development. This dissertation contains both my previously published and unpublished co-authored material. / Committee in charge: Dr. Judith Eisen, Chairperson; Dr. Karen Guillemin, Advisor; Dr. Tory Herman, Member; Dr. Hui Zong, Member; Dr. Kenneth Prehoda, Outside Member