Abstract All neurons and macroglial cells of vertebrates derive from the neuroepithelium. Neuroepithelial (NE) cells first proliferate and, after closure of the neural tube, some cells start generating neurons. It is still unclear what triggers differentiation but apparently there is interplay between extrinsic (secreted or transmembrane signals) and intrinsic factors. Diriving from the embryonic ectoderm, the NE cells inherit epithelial characteristics. It has been shown in other developmental systems that epithelial determinants, such as cell-cell contacts and contact to basal laminar components can guide differentiation. The key epithelial features include cell polarity, and tight junctions. We studied these in the NE at two developmental stages, the neural plate, a proliferative stage and the neural tube, a differentiative stage. The polarity of membrane proteins in NE cells was studied with polarly budding viruses. Mouse embryos were infected with Fowl plague- and vesicular stomatitis viruses and cultured in a whole embryo culture system. Viral envelope proteins (HA and G-protein) were localized by indirect immunofluorescence and immunoelectron microscopy. HA was polarized in the plate stage neuroepithelial cells, whereas in the tube it was not polarized anymore. It is also shown by penetrance of apically injected horseradish peroxidase that in the neural plate, NE cells have functional tight junctions. At this stage, they also express occludin, a transmembrane protein of tight junctions, as shown by indirect immunofluorescence. In the neural tube, the paracellular barrier is lost and there is no occludin expression. In contrast, expression of ZO-1, a cytoplasmic protein binding to occiudin, is upregulated. The downregulation of these epithelial features occurs in all NE cells, irrespective of their mode of division and before any neurons are generated in the NE. The change is initiated already at the plate stage and coincides with the switch from E- to N-cadherin. Later, with birth of neurons, the proliferative cell layer also looses contact to basal lamina. This is probably an important step in the regulation of neurogenesis. Furthermore, lack of apico-basolateral polarity of non-anchored membrane proteins may contribute to the mechanism of rapid neuron generation. Until now, it has been impossible to distinguish a neuroepithelial cell preparing for neuron generation from the surrounding cells that give rise to two precursor cells. In this study, the immediate neuron precursors are shown to express the antiproliferative gene TIS2 1. Using this new marker and ISH in serial sections, we show that the switch to differentiation is initiated in single NE cells.

Through his work in ludics and Geometry of Interaction, Jean-Yves Girard invites us to a change of paradigm in the study of logic: the quest for a transcendental syntax, some kind of idealized language that emerges from the rules of logic. Amongst these rules, "testing" plays a leading role in defining a duality for the interpretation of negation. The present work focuses on a notion of polarity which is a central technique used throughout Girard's work to express linear negation. We describe some properties and illustrate them with examples with the purpose of getting acquainted with the technique. We also highlight how the classical connectives (conjunction and disjunction) arise from an interpretation based on testing. In a sense, this work is intended to provide an alternative introduction to Girard's ideas and we hope it can have some pedagogical value.

A key part of a fruit fly's development is the formation of segmentsin its body. These structures are built by the protein forms of so-called segment polarity (SP) genes. It is the asymmetric expression of SP genes which creates the fruit-fly's segmental structure. The SP genes and their products (e.g. proteins) can be said to form a system which is self-regulating, i.e. genes are used to make proteins and, in turn, proteins are used to turn genes on or off. How this system achieves stable asymmetry of this kind is mathematically interesting as it can be thought of in a different way - multiple symmetries in the same system. This is unusual and we attempt to explain how it is possible using a mathematical model constructed by von Dassow et al. When trying to understand a biological system of this kind, there are two main approaches - reductionist and holistic. We try to show that they are not mutually exclusive - we look at the whole system but reduce what is meant by the whole. For example, von Dassow's model is large scale and, using it as a template, we show that a similar (but smaller) model inherits its properties. Smaller models can be made by short-handing the translation process (through which RNA is used to make protein) wherever an SP gene has a unique protein form. Our data indicates that the simultaneous wild-type expression of key SP genes (engrailed and wingless) takes place only when cumulative regulation of the wingless gene by two SP proteins is weak. The absence of this regulation would explain coexistence of multiple mathematical symmetries in one system (representative of genetic asymmetry) as it acts like a division between them. In this way, the system itself can be thought to divide into two independent sub-systems which can be treated separately.

Indiana University-Purdue University Indianapolis (IUPUI) / Our ability to hear relies on sensory cells found in the inner ear that transduce sound into biological signals. Microvilli-like protrusions called stereocilia are bundled on the apical surfaces of these cells and allow them to respond to sound-evoked vibrations. The architecture of the stereocilia bundle is highly patterned to ensure normal hearing. Filaments of polymerized actin proteins are bundled in parallel into large cylindrical structures that define the dimensions of stereocilia. This network is then anchored to the cell by inserting into another actin-based structure called the cuticular plate, which forms a gel-like structure and facilitates the mechanical properties of the bundle. The shape of the bundle is determined through tissue-level and intrinsic polarization signaling pathways. Auditory brainstem-evoked response testing, immunofluorescence imaging, scanning electron microscopy, and biochemical labeling techniques were used to study how the ADF/cofilin family of actin filament severing and depolymerizing proteins contributes to the development of the stereocilia bundle. Loss of these proteins disrupts the normal bundle patterning process, changes the lengths and widths of stereocilia, and alters the regulation of filament ends near the ion channel at stereocilia tips that is responsible for mechanotransduction. The activity of this channel regulates ADF/cofilins and the actin at stereocilia tips. Aberrant actin growth in actin networks beneath the stereocilia bundle influences the bundle patterning process, causes dysmorphic bundles to form. This work identifies that ADF/cofilins are necessary during auditory sensory cell development to facilitate normal bundle patterning and establishes this protein family as a molecular link between mechanotransduction and stereocilia bundle maturation.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21262号 / 医博第4380号 / 新制||医||1029(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 平井 豊博, 教授 伊達 洋至, 教授 渡邊 直樹 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The US-led war to oust the regime of Saddam Hussein elicited a wide range of responses among liberal states, from active diplomatic opposition in the prelude to war to actual combat support once hostilities commenced. These divergent responses, in part, reflected different perceptions of the legitimacy of force and international law. Furthermore, I contend that these perceptions are rooted in the unique regional security environment in which each state is situated, with states located in relatively insecure regional environments being more favorably disposed to view US military preponderance and use of force as a legitimate public good. Consequently, I hypothesize that the more insecure a state's regional security environment, the more likely it was to support, either diplomatically or militarily, the "major combat" phase of Operation Iraqi Freedom. To this end, I develop a measure of regional security based on concepts of power and polarity adapted from John Mearsheimer's The Tragedy of Great Power Politics. I then test this measure using a logistic regression analysis for 85 states located in 10 regions. The results indicate support for the hypothesis, but also illuminate the need for more research on the implications of power distributions within regional settings for international conflict in the post-Cold War era. / Master of Arts

Little is known about the molecular components and interactions of the planar cell polarity pathway that regulate neuronal polarity. This study uses a prkl-1 induced backwards locomotion defect as an array to perform a prkl-1 suppressor screen in C. elegans looking for new components of the planar cell polarity pathway involved in the neuronal polarization of VC4 and VC5. The screen discovered twelve new alleles of vang-1, one new allele of fntb-1 and five new mutations in unknown polarity genes. fntb-1 encodes for the worm ortholog of Farnesyltransferase β-subunit and is important for neuronal polarization. Acting cell and non-cell autonomously, fntb-1 regulates the function and localization of prkl-1 through the recognition of a CAAX motif. Therefore, fntb-1 modifies prkl-1 to regulate the neuronal polarity of VC4 and VC5.

The establishment and maintenance of cell polarity during development is an active process that requires specific protein sorting and targeting to apical and basolateral regions of the cell. Our lab has identified an apical early endosomal marker, endotubin, in developing rat intestine, which we have used to label specialized apical endosomal tubules, and to probe for components of the apical sorting machinery. Studies with endotubin have implicated the small GTPase Rab14 as part of the sorting machinery for apical targeting. The current work pursues further study of the interaction between Rab14 and endotubin, as well as the role for Rab14 in the establishment of cell asymmetry. Interestingly, even nonpolarized cells may utilize polarized trafficking components for proper sorting and dynamics of endotubin.

Little is known about the molecular components and interactions of the planar cell polarity pathway that regulate neuronal polarity. This study uses a prkl-1 induced backwards locomotion defect as an array to perform a prkl-1 suppressor screen in C. elegans looking for new components of the planar cell polarity pathway involved in the neuronal polarization of VC4 and VC5. The screen discovered twelve new alleles of vang-1, one new allele of fntb-1 and five new mutations in unknown polarity genes. fntb-1 encodes for the worm ortholog of Farnesyltransferase β-subunit and is important for neuronal polarization. Acting cell and non-cell autonomously, fntb-1 regulates the function and localization of prkl-1 through the recognition of a CAAX motif. Therefore, fntb-1 modifies prkl-1 to regulate the neuronal polarity of VC4 and VC5.

xiii, 92 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. / Cellular polarity is a biological mechanism that is conserved across metazoa and is used in many different biological processes, one of which is stem cell self-renewal and differentiation. Stem cells generate cellular diversity during development by polarizing molecular determinants responsible for directing one daughter cell to maintain stem cell-like qualities and the other daughter cell to initiate a specific cell fate. The stem cell self-renewal versus differentiation choice is critical to avoid overproliferation of stem cells and tumor formation or underdevelopment of tissues and early animal death. Drosophila neural stem cells (neuroblasts) undergo asymmetric cell division (ACD) to populate the fly central nervous system and provide an excellent model system to study processes involving cellular polarity, ACD, stem cell self-renewal, and differentiation. Neuroblasts divide unequally to produce a large, apical self-renewing neuroblast and a small, basal ganglion mother cell that goes on to divide and form two neurons or glia. In this way, a small population of neuroblasts can give rise to thousands of neurons and glia to generate a functional central nervous system. Atypical Protein Kinase C (aPKC) is critical to establish and maintain neuroblast polarity, ACD, stem cell self-renewal, and differentiation. aPKC is part of the evolutionarily conserved Par complex, whose other members include Bazooka and Par-6, and they localize to the neuroblast apical cortex and function to restrict cell-fate determinants into one daughter cell. How aPKC is asymmetrically localized and how its activity translates into cell-fate specification are of incredible importance as apkc mutants where localization is disrupted no longer segregate cell-fate determinants. This work will show that Cdc42 recruits the Par-6/aPKC complex to the neuroblast apical cortex independent of Bazooka. Once there, aPKC phosphorylates the cell-fate determinant Miranda to exclude it from the apical cortex and restrict it basally. Par-6 and Cdc42 regulate aPKC kinase activity though inter- and intramolecular interactions that allow high aPKC kinase activity at the apical cortex and suppressed activity elsewhere. Cdc42 also functions to keep aPKC asymmetrically localized by recruiting the PAK kinase Mushroom bodies tiny to regulate cortical actin and provide binding sites for cortical polarity determinants. This dissertation includes previously published co-authored material. / Adviser: Kenneth Prehoda