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dc.contributor.advisorMisra, Vikramen_US
dc.creatorBodnarchuk, Timothyen_US
dc.date.accessioned2011-06-22T14:59:25Zen_US
dc.date.accessioned2013-01-04T04:40:01Z
dc.date.available2012-07-11T08:00:00Zen_US
dc.date.available2013-01-04T04:40:01Z
dc.date.created2011-04en_US
dc.date.issued2011-04en_US
dc.date.submittedApril 2011en_US
dc.identifier.urihttp://hdl.handle.net/10388/etd-06222011-145925en_US
dc.description.abstractMedulloblastoma cells do not contain detectable amounts of the bZIP protein Zhangfei. However, previous work has shown that expression of this protein in cells of the ONS-76 line, derived from a human medulloblastoma, causes the cells to stop growing and develop processes that resemble neuritis (a characteristic of differentiated neurons). Zhangfei-expressing cells eventually die. My objective was to determine the molecular mechanisms by which Zhangfei influences ONS-76 cells. My strategy was to infect ONS-76 cells with adenovirus vectors expressing either Zhangfei or the control E. coli protein â-galactosidase (LacZ) and then to compare the following parameters in Zhangfei and LacZ-expressing cells: a) markers of apoptosis, autophagy and macropinocytosis (the three main pathways of cell death); b) transcripts for genes involved in neurogenesis and apoptosis; c) phosphorylation of peptide targets of selected cellular protein kinases; and d) active transcription factors. Zhangfei-expressing cells appeared to succumb to apoptosis as determined by the expression of phosphatidylserine on the cell surface and intensity of nuclear staining with the DNA dye Hoechst. Increased staining for autophagic vesicles and upregulated expression of autophagy response genes in these cells indicated that they were undergoing autophagy, possibly associated with apoptosis. My analysis of steady-state transcripts for genes involved in apoptosis and neurogenesis and functional protein kinases in Zhangfei-expressing cells indicated that the mitogen-activated protein kinase (MAPK) pathway was active in these cells. In addition, I found that the transcription factor Brn3a as well as factors implicated in differentiation were also active. These observations led me to hypothesize that Zhangfei enhances the expression of Brn3a, a known inducer of TrkA, the high-affinity receptor for nerve growth factor (NGF). TrkA then binds in an autocrine manner to NGF, triggering the MAPK pathway and leading to differentiation of ONS-76 cells into neuron and glia-like cells, eventually bringing about cell death by apoptosis and autophagy. I tested this hypothesis by showing that Zhangfei could enhance transcription from the isolated Brn3a promoter, that ONS-76 cells produce NGF as detected in a bioassay, and that antibodies against NGF and inhibitors of TrkA and selected components of the MAPK pathway could partially restore the growth of Zhangfei-expressing ONS-76 cells. My work supports previous work highlighting the importance of NGF-TrkA signaling in the outcome of medulloblastomas and shows how Zhangfei is able to trigger this pathway.en_US
dc.language.isoen_USen_US
dc.subjectZhangfeien_US
dc.subjectautophagyen_US
dc.subjectapoptosisen_US
dc.subjectBrn3aen_US
dc.subjectmedulloblastomaen_US
dc.subjectMapKen_US
dc.subjectTrkAen_US
dc.subjectmacropinocytosisen_US
dc.titleZhangfei suppresses the growth of Medulloblastoma cells and commits them to programmed cell deathen_US
thesis.degree.departmentVeterinary Microbiologyen_US
thesis.degree.disciplineVeterinary Microbiologyen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M.Sc.)en_US
dc.type.materialtexten_US
dc.type.genreThesisen_US
dc.contributor.committeeMemberMousseau, Darrellen_US
dc.contributor.committeeMemberNapper, Scotten_US
dc.contributor.committeeMemberBonham, Keithen_US
dc.contributor.committeeMemberHill, Janeten_US


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