No description available.

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

<p> Innate immune protein C1q plays a dual role in atherosclerosis. In early stages, C1q plays a protective role, but the mechanism is not fully understood. Autophagy is a catabolic pathway that has shown to play a role in cellular survival and is an important process in many phagocytic cells, such as macrophages. We hypothesize that complement C1q increases autophagy in macrophages during clearance of modified lipoprotein and acts in an atheroprotective manner to increase macrophage survival. We examined the influence of C1q on macrophage autophagy markers Atg5, Beclin 1, LC3B-II, and p62 during clearance of oxidized LDL. Levels of initiation and elongation protein, Beclin 1 and Atg5, are not modulated by C1q, but levels of autophagosome proteins, LC3B-II and p62, were increased in immunoblot. Quantitative PCR revealed that the increase in p62 protein levels was not due to an increase in transcription. Immunofluorescence microscopy verified that the increase in LC3B and p62 by C1q resulted in an increase in autophagosome formation during oxLDL and acLDL clearance. TEM verified the formation of double membrane vesicles. By inhibiting autolysosome maturation with chloroquine during modified LDL clearance, C1q modulation of autophagy was found to not have an effect on macrophage survival. These findings further our knowledge of C1q protective mechanisms, and the goal of developing future atherosclerosis therapies.</p>

<p>Heart disease is the leading cause of death in the developed world. Adult mammals cannot replace lost cardiac tissue after injury, leading to reduced quality of life and increased instances of future cardiac issues. Zebrafish possess the ability to regenerate lost cardiac muscle after injury. Upon injury, the zebrafish heart responds in a coordinated fashion resulting in activation of the epicardium and endocardium, cardiomyocyte proliferation, and subsequent vascularization and innervation of the newly formed muscle. Thus zebrafish represent an ideal genetic model to dissect the mechanisms of heart regeneration. Previously, it was discovered that regulatory sequences of the cardiac transcription factor, gata4, become active in the ventricular wall following injury and that these gata4+ cardiomyocytes proliferate and contribute the majority of new muscle to the regenerate. We uncovered that gata4 function is required for cardiomyocyte proliferation and regeneration after injury. Cardiomyocyte proliferation is required to achieve proper regeneration and lack of cardiomyocyte proliferation is a hallmark of failed regeneration in the mammalian system. Therefore, understanding the signals that induce mature cardiomyocyte division is of great scientific and clinical relevance. Utilizing transgenic approaches, we have found that gata4 function and Nrg1 signaling are critical regulators of cardiomyocyte proliferation. We found that Nrg1 was expressed following injury in the zebrafish heart and that inhibition of nrg1-erbb signaling blunted cardiomyocyte proliferation. Using transgenic over-expression of Nrg1, we found that Nrg1 was capable of increasing injury-induced cardiomyocyte proliferation. Furthermore we found that activation of Nrg1 in the uninjured adult heart induces cardiomyocyte proliferation and hallmarks of the regenerative program. Long-term nrg1 expression leads to patterned hyperplastic expansion of the zebrafish ventricle. To our knowledge, this is the first description of a single factor that is sufficient to induce such a dramatic hyperplastic response in an adult heart.</p> / Dissertation

High-risk human papillomaviruses (HPVs) are causative agents of most cervical cancers and a significant portion of other anogenital tract and oral carcinomas. The major oncogenic activities of HPV16 E6 and E7 oncoproteins are associated with the degradation of the p53 and retinoblastoma tumor suppressors, respectively. E6 also causes increased expression of the catalytic subunit of telomerase, hTERT. In addition, E6 and E7 contribute to carcinogenesis through induction of genomic instability. Accurate chromosome segregation during mitosis is essential for preservation of genomic stability and HPV16 E7 perturbs mitosis in several ways. HPV16 E7 induces the synthesis of supernumerary centrosomes and increases the incidence of multipolar mitoses, which can lead to chromosome missegregation. Moreover, HPV16 E7 expression causes a prometaphase delay, which usually reflects an activation of the mitotic spindle assembly checkpoint (SAC), yet some studies suggested that the SAC is abrogated in HPV16 E7-expressing cells.

Fascin is an actin bundling protein whose overexpression has in recent years been systematically linked to increased metastasis and poor outcome in cancer patients. It is well established that fascin expression correlates with enhanced cell migration; however, the underlying mechanisms are poorly understood. We combined various methods of high-resolution live cell imaging and computational analysis to investigate the role of fascin in increasing cell motility. We found that fascin promotes collective migration in normal epithelial cells and that this behavior is in agreement with protrusive activities at the single cell level. Traction force measurements indicated that fascin expression level is negatively correlated with traction stress levels and that a cell expressing high levels of fascin protrudes over longer distances than cells with lower levels. Together this led to the hypothesis that fascin distributes cell traction more efficiently, which lowers the load on individual adhesions and actin filaments growing against increasing membrane tension during one protrusion cycle. Measurements of adhesion formation and maturation indicate that fascin expression indeed promotes nascent adhesion formation over a wide area behind the leading edge. In metastatic cells with high fascin expression, we observed decreased invasion upon fascin knock down. These observations demonstrate a role for fascin in promoting cell motility in normal and neoplastic cells, in part by templating nascent adhesions at the leading edge.

<p> Baker&rsquo;s yeast serves as an ideal model to study endomembrane system due to high conservation of its regulation and trafficking between yeast and human. <i>ENV9</i> is a novel gene involved in vesicular trafficking in <i>Saccharomyces cerevisiae.</i> Previous characterization by our laboratory established that <i>ENV9</i> deletion leads to lysosomal defects and that Env9 is localized to lipid droplets (LDs). Our bioinformatics studies show that <i>ENV9</i> is conserved among eukaryotes and is an orthologue of human Retinol Dehydrogenase 12 (<i> RDH12</i>). </p><p> In this study, we show that Env9 is involved in LD biogenesis by positively regulating LD fusion and glycerol-induced LD proliferation. We establish Env9 to be an oxidoreductase <i>in vitro</i> that displays specific oxidoreductase activity towards RDH12 toxic aldehyde substrate. We also show that Env9 oxidoreductase activity requires its conserved functional domains. Furthermore, we show that oxidoreductase activity is essential for the observed cellular function of Env9 and that interactions with <i>ENV10</i> may be required for <i> ENV9</i>-dependent promotion of LD fusion.</p>

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy