Thesis (M.S.) --Marshall University, 2008. / Title from document title page. Includes abstract. Document formatted into pages: contains 51 pages. Includes bibliographical references (p. 37-38).

Thesis (M.S.) --Marshall University, 2008. / Title from document title page. Includes abstract. Document formatted into pages: contains 51 pages. Includes bibliographical references (p. 37-38).

No description available.

Thesis advisor: David R. Burgess / Polarity established by the first cleavages in sea urchin embryos was investigated in this thesis revealing precocious embryonic polarity. Studies of embryonic polarity have focused on protostomes such as <italics>C. elegans</italics>, and those on deuterostomes have focused on later developmental stages. I find asymmetries in the sea urchin membrane cell cortex as early as the first division after fertilization as a result of new membrane addition in the cleavage furrow. Membrane domains and the polarity determinants Par6, aPKC, and Cdc42 are polarized to the apical, or free, cell surface, while the cell-cell contact site remains distinct. Using immunofluorescence, fluorescence recovery after photobleaching (FRAP), and specific inhibitor treatments, myosin filaments were identified as the major regulator of membrane cortex polarity. However, membrane domains and cortical polarity determinants are differentially regulated with respect to blastomere dissociation. These asymmetries are required for proper spindle alignment and cleavage plane determination and are responsible for polarized fluid phase endocytosis. The work in this thesis and future studies addressing the connection between the membrane cortex and myosin filaments has and will lead to a greater understanding of the maintenance of embryonic polarity in cleavage stage sea urchin embryos. / Thesis (PhD) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Dictyostelium DdINCENP is a chromosomal passenger protein associated with centromeres, the spindle midzone and poles during mitosis and the cleavage furrow during cytokinesis. Disruption of the single DdINCENP gene revealed important roles for this protein in mitosis and cytokinesis. DdINCENP null cells lack a robust spindle midzone and are hypersensitive to microtubule depolymerizing drugs suggesting that their spindles may not be stable. Furthermore DdCP224, a protein homologous to the microtubule-stabilizing protein TOGp/XMAP215, was absent from the spindle midzone of DdINCENP null cells. Overexpression of DdCP224 rescued the weak spindle midzone defect of DdINCENP null cells. While not required for the localization of the myosin II contractile ring and subsequent formation of a cleavage furrow, DdINCENP is important for the abscission of daughter cells at the end of cytokinesis. The localization of DdINCENP at the cleavage furrow is modulated by myosin II. Loss of myosin II restricted the localization of DdINCENP to a narrow zone at the cleavage furrow. Kif12, a homolog of mitotic kinesin like protein (MKLP), was essential for relocalization of DdINCENP from the central spindle to the cleavage furrow. Furthermore, Kif12 was also localized at the cortex of the cleavage furrow and its localization during cytokinesis closely resembled that of DdINCENP, suggesting a possible interaction between them. The correct localization of DdINCENP during cytokinesis also required its N-terminal sequence. DdINCENP1-500 was found at the cleavage furrow and interacted with the actin cytoskeleton. Domain analysis of DdINCENP also revealed that its DdINCENP1-500 was sufficient to rescue the weak spindle defect of DdINCENP null cells. / text

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<p>Primary cilia are evolutionarily conserved, acetylated microtubule-based organelles that transduce mechanical and chemical signals. Primary cilium assembly is tightly controlled and its deregulation causes a spectrum of human diseases. Formation of primary cilium is a collaborative effort of multiple cellular machineries, including microtubule, actin network and membrane trafficking. How cells coordinate these components to construct the primary cilia remains unclear. In this dissertation research, we utilized a combination of cell biology, biochemistry and light microscopy technologies to tackle the enigma of primary cilia formation, with particular focus on isoform-specific roles of non-muscle myosin II family members. We found that myosin IIB (Myh10) is required for cilium formation. In contrast, myosin IIA (Myh9) suppresses cilium formation. In Myh10 deficient cells, Myh9 inactivation significantly restores cilia formation. Myh10 antagonizes Myh9 and increases actin dynamics, permitting pericentrosomal preciliary complex formation required for cilium assembly. Importantly, Myh10 is upregulated upon serum starvation-induced ciliogenesis and this induction requires Atat1/Mec-17, the microtubule acetyltransferase. Our findings suggest that Atat1/Mec17-mediated microtubule acetylation is coupled to Myh10 induction, whose accumulation overcomes the Myh9-dependent actin cytoskeleton, thereby activating cilium formation. Thus, Atat1/Mec17 and myosin II coordinate microtubules and the actin cytoskeleton to control primary cilium biogenesis.</p> / Dissertation

<p>The ability of cells to migrate is of fundamental importance to a diverse array of biological processes, both physiological and pathological, such as development, the immune response and cancer cell metastasis, to name a few. The process of cell movement is a complicated cycle of coordinated steps involving dynamic and precise rearrangement of the actin-myosin cytoskeleton. As a critical component of the migration machinery, the molecular motor protein nonmuscle myosin II (myosin II) has long been a subject of scientific inquiry. It is now generally accepted that the contractile forces generated by myosin II contribute directly or indirectly to every step in migration. Interestingly, three isoforms of myosin II (myosin IIA, IIB and IIC) have been identified, and although each isoform performs the same basic molecular functions, recent findings suggest that the different myosin II isoforms make unique contributions to the motile process. In this dissertation work I used RNA interference technology to specifically deplete cells of myosin IIA and IIB in order to characterize the distinct migration phenotypes associated with loss-of-function of each individual isoform. Surprisingly, I found that the two myosin II isoforms perform not only distinct but opposing functions in cell migration, with myosin IIA and IIB normally inhibiting and facilitating proper cell movement, respectively. Furthermore, using pharmacological and microscopy techniques, I investigated the cellular mechanisms allowing for isoform-specific function. My results provide evidence for at least two isoform-specific regulatory mechanisms, namely selectivity in signaling pathways and subcellular distribution. A particularly significant finding is the identification of the different assembly properties of myosin IIA and IIB as the key element responsible for directing isoform-distinct distribution. Together the data presented herein represent a considerable advance in our understanding of the distinct functions and regulation of myosin II in cell motility.</p> / Dissertation

O carcinoma espinocelular (CEC) de cabeça e pescoço é uma neoplasia maligna de prognóstico desfavorável e baixa taxa de sobrevida. Entender os processos biológicos envolvidos na carcinogênese poderá ser de extrema importância para o desenvolvimento de novas tecnologias de tratamento e melhora do prognóstico em pacientes acometidos pela doença. A maior causa de insucessos clínicos em termos de terapia e prognóstico em pacientes com câncer é a invasão tecidual e o desenvolvimento de potencial metastático. A migração celular é indispensável para a progressão tumoral e as células apresentam motores moleculares desempenhados especialmente pela família da Miosina II não muscular (MNMII). Codificadas por diferentes genes, existem três isoformas conhecidas em células de mamíferos (MNMIIA, MNMIIB, MNMIIC). As MNMIIs estão envolvidas em funções celulares como migração, adesão e citocinese. Sendo o entendimento da migração, adesão celular e citocinese fatores chave na progressão tumoral, e que o a invasão tecidual e o desenvolvimento de potencial metastático são essenciais na definição do prognóstico dos pacientes, o objetivo deste estudo foi descrever o perfil e exposição à fatores de risco como álcool e fumo dos pacientes diagnosticados com CEC de cabeça e pescoço, graduação histológica, parâmetros clínicos tumorais (TNM), padrão de expressão das isoformas de MNMII (MNMIIA, MNMIIB, MNMIIC) no centro do tumor, zona de invasão e tecido epitelial não neoplásico adjacente ao tumor, relacionando a expressão e localização dessas proteínas com os dados descritos bem como evolução dos pacientes após 5 anos de acompanhamento. De acordo com os resultados sugere-se que a MNMIIB expressa no EA possa indicar o potencial de metástase regional do CEC e a MNMIIC presente na zona de invasão tumoral (ZI) seja um fator predictor de prognóstico ruim da doença. Sendo assim, é possível propor que a avaliação de imunorreatividade da MNMIIB no EA e MNMIIC na ZI seja utilizada na análise das peças operatórias, como complemento à análise morfológica de rotina. / Squamous cell carcinoma (SCC) of the head and neck is a malignant neoplasm of poor prognosis and low survival rate. Understand the biological processes involved in carcinogenesis can be extremely important for the development of new treatment technologies and improved prognosis in patients affected by the disease. The major cause of clinical failure in terms of therapy and prognosis in cancer patients is the development of tissue invasion and metastatic potential. Cell migration is essential for tumor progression and the cells have molecular motors especially formed from non-muscular myosin II family (NMMII). Encoded by different genes, there are three known isoforms in mammalian cells (NMMIIA, NMMIIB, NMMIIC). The NMMIIs are involved in cellular functions such as migration, adhesion, and cytokinesis. As the understanding of migration, cell adhesion and cytokinesis key factors in tumor progression, and that the tissue invasion and metastatic potential for development are essential in defining the prognosis of patients, the objective of this study was to describe the profile and exposure to risk factors such as alcohol and tobacco of patients diagnosed with head and neck SCC, histological grading, tumor clinical parameters (TNM), pattern of expression of isoforms NMMII (NMMIIA, NMMIIB, NMMIIC) in the center of the tumor (CT), tumor invasion zone area and not neoplastic adjacent to the tumor (AE), relating the expression and localization of these proteins with the data described and outcome of patients after 5 years of follow-up. According to the results it is suggested that the NMMIIB expressed in AE may indicate the potential regional metastasis of SCC and NMMIIC present in the tumor invasion zone (IZ) is a predictor factor of poor prognosis of the disease. Therefore, it is possible to propose that immunoreactivity assessment of NMMIIB in EA and NMMIIC in IZ could be used in the analysis of operative parts, as a complement to routine morphological analysis.

xii, 107 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Non-muscle myosin II generates contractile forces for processes such as cytokinesis, motility, and polarity. Contractility requires assembly of myosin molecules into bipolar mini-filaments through electrostatic interactions between coiled-coil tail domains of the heavy chains. Analyses of myosin II from various organisms have revealed "assembly domains" within the C-terminal portion of the tail domain that mediate filament formation. However, it has been unclear precisely how assembly domains interact with one another, or otherwise contribute to tail-tail interactions, to form the bipolar mini-filament structure. To understand tail domain interactions, we first identified a 90-residue region (1849-1940) of the Drosophila non-muscle myosin II tail domain that was necessary and sufficient for filament formation, using salt-dependent solubility and a novel fluorescence energy transfer assay. We identified residues within this "assembly domain" that were critical for filament assembly by analyzing the effect of point mutations. We found that single point mutations in specific positively charged regions completely disrupt filament assembly. Surprisingly, none of the negatively charged regions within the assembly domain are required for assembly. Most of the mutations in positively charged residues that disrupted filament assembly clustered within a 15-residue segment (1880-1894) that appears to form a critical interaction surface. Using this information, along with known geometrical constraints and electrostatic calculations, we constructed a structural model of the bipolar mini-filament. This model features one favored anti-parallel tail overlap and multiple slightly less stable alternative overlaps. The ability of the positive segment to interact with multiple negative regions explains the lack of required negatively charged residues in the assembly domain. To our knowledge, this structural model of the non- muscle myosin II bipolar filament is consistent with all physical observations and provides a framework for understanding the detailed mechanism by which this fundamental cellular structure is generated. This dissertation contains previously published and unpublished co-authored material. / Committee in charge: Tom Stevens, Chairperson, Chemistry; Kenneth Prehoda, Advisor, Chemistry; J. Andrew Berglund, Member, Chemistry; Christopher Doe, Member, Biology; Karen Guillemin, Outside Member, Biology