Cell polarity is fundamental to numerous cellular processes including migration, molecular transport, and cell division. The establishment and organization of polarity is crucial to the maintenance of cellular homeostasis in mammalian systems. Deregulation of cell polarity is observed in disease states, including cancer. Numb is an adaptor protein that functions in regulating endocytic trafficking events. Numb was originally identified in Drosophila as an asymmetrically localized cell fate determinant, and was subsequently found to be conserved in vertebrates. In mammalian polarized epithelial cells, Numb is distributed asymmetrically along the basolateral membrane domain. The work herein describes phosphorylation of Numb by the Par complex protein, atypical Protein Kinase C (aPKC), as a means of regulating membrane localization and asymmetric distribution of Numb. A mutant of Numb that cannot be phosphorylated by aPKC accumulates on the plasma membrane and localizes to both apical and basolateral membranes. In aPKC-depleted cells, endogenous Numb is unable to achieve polarized distribution and localizes around the entire cell cortex. We demonstrate that this mechanism is conserved in Drosophila as mutation of the corresponding phosphorylation sites disrupts Numb asymmetric localization in dividing sensory organ precursor cells. In polarized epithelial cells, one function of Numb is to promote epithelial morphology when cells are challenged with external stimuli that disrupt cell-cell adhesion. For example, depletion of Numb results in enhanced sensitivity of cells to lose cell-cell contacts when treated with calcium chelating agents. Loss of Numb potentiates hepatocyte growth factor (HGF)-induced lamellipodia formation and cell dispersal – early steps in epithelial-mesenchymal transition (EMT). In Numb-depleted cells, Rac1-GTP loading is enhanced, which corresponds with increased rate in loss of cell-cell adhesion and increased lamellipodia formation, following depletion of extracellular calcium and HGF stimulation, respectively. Together, this work identifies a mechanism that regulates polarized distribution of Numb and provides insight into its function in polarized epithelial cells.

Cell polarity is fundamental to numerous cellular processes including migration, molecular transport, and cell division. The establishment and organization of polarity is crucial to the maintenance of cellular homeostasis in mammalian systems. Deregulation of cell polarity is observed in disease states, including cancer. Numb is an adaptor protein that functions in regulating endocytic trafficking events. Numb was originally identified in Drosophila as an asymmetrically localized cell fate determinant, and was subsequently found to be conserved in vertebrates. In mammalian polarized epithelial cells, Numb is distributed asymmetrically along the basolateral membrane domain. The work herein describes phosphorylation of Numb by the Par complex protein, atypical Protein Kinase C (aPKC), as a means of regulating membrane localization and asymmetric distribution of Numb. A mutant of Numb that cannot be phosphorylated by aPKC accumulates on the plasma membrane and localizes to both apical and basolateral membranes. In aPKC-depleted cells, endogenous Numb is unable to achieve polarized distribution and localizes around the entire cell cortex. We demonstrate that this mechanism is conserved in Drosophila as mutation of the corresponding phosphorylation sites disrupts Numb asymmetric localization in dividing sensory organ precursor cells. In polarized epithelial cells, one function of Numb is to promote epithelial morphology when cells are challenged with external stimuli that disrupt cell-cell adhesion. For example, depletion of Numb results in enhanced sensitivity of cells to lose cell-cell contacts when treated with calcium chelating agents. Loss of Numb potentiates hepatocyte growth factor (HGF)-induced lamellipodia formation and cell dispersal – early steps in epithelial-mesenchymal transition (EMT). In Numb-depleted cells, Rac1-GTP loading is enhanced, which corresponds with increased rate in loss of cell-cell adhesion and increased lamellipodia formation, following depletion of extracellular calcium and HGF stimulation, respectively. Together, this work identifies a mechanism that regulates polarized distribution of Numb and provides insight into its function in polarized epithelial cells.

Endothelial cells (ECs) respond to flow but the exact mechanism producing alignment is not completely understood. We characterized EC alignment in microfluidic channels, 4 mm wide by 350 um high, to generate shear of 20 dynes / cm2 across the cell surface. In microchannels, ECs aligned perpendicular under flow. Analytical tools were developed to quantify nuclear alignment at 67% for human umbilical vein endothelial cells (HUVECs); cell elongation under shear flow shifted aspect ratio from 2.41 to 2.86. We next sought to probe the mechanism through which ECs communicate during realignment. The planar cell polarity (PCP) signaling pathway is involved in cell organization and coordination during development. A number of genes are known to affect the formation and organization of cellular structures through PCP signaling in human ECs. Higher expression of Vangl1 and Dvl1 proteins did not alter cell reorganization; knockdown of Vangl1 expression decreased EC alignment.

Endothelial cells (ECs) respond to flow but the exact mechanism producing alignment is not completely understood. We characterized EC alignment in microfluidic channels, 4 mm wide by 350 um high, to generate shear of 20 dynes / cm2 across the cell surface. In microchannels, ECs aligned perpendicular under flow. Analytical tools were developed to quantify nuclear alignment at 67% for human umbilical vein endothelial cells (HUVECs); cell elongation under shear flow shifted aspect ratio from 2.41 to 2.86. We next sought to probe the mechanism through which ECs communicate during realignment. The planar cell polarity (PCP) signaling pathway is involved in cell organization and coordination during development. A number of genes are known to affect the formation and organization of cellular structures through PCP signaling in human ECs. Higher expression of Vangl1 and Dvl1 proteins did not alter cell reorganization; knockdown of Vangl1 expression decreased EC alignment.

This paper will clarify the debate surrounding contemporary American foreign policy, and it seeks to bring awareness to the vast field surrounding the topic. This essay is a case study, and it focuses mainly on the Obama doctrine, it does also shed light to the former foreign policy of the Bush administration. The research questions seek to investigate what theory of polarity characterises the Obama doctrine. It does also investigate how the United States foreign policy has changed under the Obama administration, by applying the methodology of a text analysis, the three theories of polarity: “Balance of power, hegemonic theory, and multipolarity” are in turn applied on three challenging areas for contemporary American foreign policy. The results show that the foreign policy led by the Obama administration, is heavily influenced by the theory of multipolarity. / <p>Jag har inte publicerat min uppsats, blev klar med den juni 2013.</p><p></p><p>Tack</p>

A genetic screen for dominant, temperature-sensitive, maternal-effect embryonic lethal mutations identified mel-43(sb41), a gene required for early embryonic viability (Mitenko et al., 1997). Linkage mapping placed mel-43 within a small region on chromosome IV. Genetic analyses suggested that mel-43(sb41) was a neomorphic mutation. While refining the genetic position of the mel-43 gene, data suggested that the genetic position of mel-43 was inconsistent with the published location. In light of this new location, previous conclusions regarding the genetic behaviour of mel-43(sb41) were re-examined. Deficiency analysis suggests that mel-43(sb41) is a haploinsufficient loss-of-function mutation. mel-43(sb41) embryos are significantly delayed in meiosis II independent of cyclin B1 degradation. Consequently, embryos fail to produce meiosis II polar bodies and do not establish proper polarity. Although the function of mel-43 remains unknown, the persistent meiotic spindle suggests that mel-43 acts upstream of the microtubule rearrangements necessary to promote the metaphase II to anaphase II transition. / Molecular Biology and Genetics

No description available.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 3 uppsatser.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 45-48). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Thesis (Ph. D.)--University of California, San Diego, 1998. / Vita. Includes bibliographical references (leaves 275-288).