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

No description available.

Growing evidence from animal and clinical studies suggests that cardiac cell therapy can restore perfusion and improve function in the ischemic/infarcted myocardium. However, cell therapy is hindered by insufficient cell numbers, inefficient cell homing and engraftment, and inadequate cellular interactions. Furthermore, the biological mechanisms and local effects of transplanted cells have not been well-elucidated. The research presented herein attempts to address some of these issues. In manuscript #1, a new subpopulation of circulating progenitor cells (CPCs), termed derived CD133+ cells, was generated from the CD133- fraction of human peripheral blood. The derived CD133+ progenitors appeared to have superior vasculogenic potential in vitro, which may prove to be beneficial in inducing vasculogenesis in ischemic tissues. Positron emission tomography (PET) with direct cell labeling and reporter gene techniques were employed to assess the fate of transplanted human CPCs in vivo at different subjects of investigation, and different stages of cell transplantation. In manuscript #2, PET imaging with 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) direct cell labeling was used to demonstrate that collagen-based matrices improve the early homing and retention of delivered CPCs in a rat ischemic hindlimb model. This mechanism conferred by the matrix may have implications on cell therapy at the early stages after transplantation. In manuscript #3, a more efficient, stable and accurate labeling method, hexadecyl-4-[18F]fluorobenzoate (18F-HFB) direct cell labeling, was developed to quantify cell distribution of transplanted CPCs in a rat myocardial infarction model. PET imaging of 18F-HFB-CPCs revealed significant cell washout from the myocardium immediately after intramyocardial injection, with only a small proportion of transplanted CPCs remaining in the target area in the first 4 hours after delivery. In manuscript #4, human CPCs transduced with lentiviral vectors showed stable expression of PET reporter genes. This reporter gene based-cell labeling technique can be developed for noninvasive tracking cells within a bioengineered matrix by PET, while preserving cell phenotype, viability and function. These studies contribute important insights into the biology and physiology of transplanted stem cells and the ability of delivery matrices to improve transplanted cell engraftment, survival, and function. I believe with further refinement, cell expansion, tissue engineering and PET imaging could facilitate the clinical applications of cell therapies in years to come.

The cell division cycles of differentiating cells are coordinated so as to generate sufficient numbers of mature cells. The cell cycle may also regulate the process of differentiation, in ways that are not well understood. We previously discovered that during erythropoiesis, the cell cycle is synchronized with a specific developmental switch, where erythroid progenitors known as colony-forming-unit-erythroid (CFU-e) transition from a self-renewal state to a state of erythroid terminal differentiation (ETD). This switch takes place during a single cell cycle S phase and is dependent on S-phase progression. My work shows that this S phase is unusual, in that it is shorter than S phase in preceding cycles, as a result of a global increase in replication fork speed. I found that the CDK inhibitor, p57KIP2, negatively regulates replication fork speed in self-renewing CFU-e, and its down-regulation at the switch to ETD results in S-phase shortening. p57KIP2-mediated inhibition of CDK2 is essential for CFU-e self-renewal. It exerts this effect by reducing replication stress and also reducing the probability of transition from CFU-e to ETD, promoting CFU-e self-renewal instead. CDK2 inhibiting drugs that mimic the action of p57KIP2 stimulate erythropoiesis both in vitro and in vivo, through expansion of the CFU-e pool. In addition to p57KIP2, E2f4 also regulates S-phase shortening and the efficiency of the CFU-e to ETD transition. Overall, my work shows that S-phase speed regulates a key erythroid cell fate decision, and suggests a possible translational application of CDK2 inhibiting drugs in the stimulation of erythropoiesis.

No description available.

Pluripotent stem cells are a special population of stem cell with indefinitely self-renewal and unlimited differentiation capability, which makes them an attractive avenue for regenerative medicine and disease modeling. Therefore, it is important to understanding the fundamental mechanisms that govern and maintain their pluripotent state. A phenomenon termed mitotic bookmarking has recently been suggested as a potential mechanism involved in the stable propagation of cellular identity through the cell cycles. Candidate-based studies have identified mitotic bookmarking factors that are retained on the mitotic chromatin and preserve the transcriptional memory of the cell. Nevertheless, there is a poor understanding of which proteins can serve as mitotic bookmarks, as well as the chromatin dynamics of bookmarked sites during mitosis and the start of the G1 phase. We have previously identified a list of putative mitotic bookmarking factors in pluripotent stem cells, from which we tested the role of PARP1, HDGF, and PSIP1 as potential bookmarks for the propagation of the pluripotent state through mitosis. Here we showed that the absence of PARP1 at the M-G1 transition impairs self-renewal capability of pluripotent stem cells without affecting the proliferation and cell cycle progression. Conclusive evidence that establishes a role for HDGF or PSIP1 in mitotic bookmarking of pluripotent stem cells has yet to emerge. However, our work provides a new avenue for exploring the functional importance of mitotic bookmarks in pluripotent maintenance. / Thesis / Master of Science (MSc)

The immune defense is geared to protect against a tremendous array of invaders. The ultimate goal of the immune system is to induce effective and balanced inflammatory responses that enable the efficient elimination of possible threats while avoiding both immunodeficiency and autoimmunity. The skewness towards inflammatory responses causing excessive collateral damage could lead to diverse autoimmune conditions. These conditions could be organ-specific or result from systemic immune dysregulations called systemic autoimmunity. The multifaceted nature and the intricate clinical heterogeneity of systemic autoimmune conditions indicate a strong influence of environmental factors on their immunopathogenesis, where environmental factors could either hinder or contribute to autoimmune development. We focused our research on deciphering the complex effects of environmental factors on the immunopathogenesis of systemic immune dysregulation, taking systemic lupus erythematosus (SLE or Lupus) as a model of systemic autoimmunity. SLE is one of the most mysterious autoimmune disorders with no known cure. In SLE, breaching of tolerance to self-antigens and the subsequent persistent inflammation and collateral tissue damage in multiple organs lead to very diverse clinical manifestations. These manifestations are a result from the interplay between multiple genetic susceptibilities and diverse environmental factors. To date, management plans for SLE are based on non-selective immunosuppressants that could impose significant side effects including increased risks of infection and infection-related mortalities. In parallel, environmental factors and the quality of life could significantly impact SLE management strategies. Therefore, delineating the immunomodulatory capacities of environmental factors would likely unravel more effective management strategies for SLE patients. The current research aims to investigate the central hypothesis that dietary and hygienic components modulate the immune dysregulations of SLE in a tissue- and disease stage-specific manner. We have focused on uncovering the complex effects of Vitamin A (VA) as an essential micronutrient with very diverse immunomodulatory capacities, and quaternary ammonium compound (QAC)-based disinfectants as ubiquitously used disinfectants that have been linked to immunotoxicity, on the immunopathogenesis of SLE. Due to the strong female bias of SLE where women especially of childbearing age are more prone to lupus, we have focused our research on delineating how these diverse factors shape the immunopathogenesis of SLE in female mice only. The first project dissected the immunomodulatory effects of VA, a potent immunomodulatory dietary component. Notably, VA exerts its function through a predominant metabolite known as all-trans-retinoic acid (tRA) that, as we have previously shown, has paradoxical and tissue-specific implications on lupus inflammation. Here, we utilized a pristane-induced model of lupus to investigate the disease stage-dependent effects of tRA. Oral supplementation of tRA was given either before pristane induction of lupus from weaning (3 weeks) to 3 months of age or after pristane induction of lupus from 3 to 9 months of age. We found that tRA treatment mediated disease stage-dependent effects and differentially affected the lupus-associated kidney inflammation (lupus nephritis) when given at the initiation vs. continuation phase of lupus. Unlike tRA treatment during active disease, pre-pristane treatment with tRA aggravated glomerulonephritis through potentiating leukocyte activation and trafficking to the kidney and augmenting renal pro-fibrotic signals. Post-pristane tRA treatment, on the other hand, exerted immunosuppressive functions of decreasing circulatory and renal deposition of autoantibodies as well as suppressing the renal expression of proinflammatory cytokines and chemokines. Interestingly, both pre- and post-pristane treatments with tRA reversed the pristane-induced leaky gut and similarly modulated the gut microbiota, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus. As tRA could be protective against lupus nephritis especially during the active disease stage, and previous reports had shown hypovitaminosis A (reduced serum retinol levels) proceeding SLE, we expanded our investigation to decipher whether VA deficiency (VAD) was a contributing factor for severe SLE and to delineate how VAD affected the initiation and/or the progression of lupus nephritis in genetically-prone conditions. For that purpose, we utilized the classical murine lupus-prone model, MRL/lpr, and initiated VAD either during the gestation or after weaning to reveal potential time-dependent effects. VAD exacerbated lupus nephritis by provoking severe neutrophilic tubulointerstitial nephritis, and accelerated renal failure. This was concomitant with significantly higher mortality in all VAD mice. Mechanistically, VAD enhanced early activation of plasma cells and augmented their autoantibodies production. In addition, VAD led to an enhanced expansion of pathogenic T lymphocytes. In parallel, VAD increased renal infiltration of conventional and plasmacytoid dendritic cells. Our findings establish VAD as a driving factor for lupus nephritis progression in genetically predisposed conditions. These findings emphasize the importance of monitoring VA levels in SLE patients and urge for VA supplementations for patients at higher risk for hypovitaminosis A, especially during the maternal-neonatal interface. Additionally, this project warrants further investigations to delineate the molecular targets through which VA modulates cellular functions as well as immunopathogenesis of lupus nephritis. The information obtained from these studies may also benefit women with other autoimmune conditions and will pave the way for VA supplementations to be tested in clinical trials. The second project investigated the effects of ambient exposure to QAC-based disinfectants on the progression of murine SLE in genetically prone mice. We compared the disease progression in MRL/Lpr mice that have been exposed to QACs vs. those kept under a complete QAC-free condition. QAC-based disinfectants CP-64 or Labsan 256 were used under QAC-exposed conditions, while ethanol was used in the QAC-free environment. We found that compared to QAC-free mice, ambient exposure of lupus-prone mice to QACs led to smaller spleens with no change in circulating autoantibodies or the severity of glomerulonephritis. This suggests that QACs may have immunosuppressive effects on lupus. Using a microfluidic device, we showed that ambient exposure to QACs reduced directional migration of bone marrow-derived neutrophils toward an inflammatory chemoattractant ex vivo. Consistent with this, we found decreased infiltration of neutrophils into the spleen. While bone marrow-derived neutrophils appeared to exhibit a pro-inflammatory profile, upregulated expression of PD-L1 was observed on neutrophils that infiltrated the spleen, which in turn interacted with PD-1 on T cells and modulated their fate. Specifically, QAC exposure hindered activation of splenic T cells and increased apoptosis of effector T-cell populations. Collectively, these results suggest that ambient QAC exposure decreases lupus-associated splenomegaly likely through neutrophil-mediated toning of T-cell activation and/or apoptosis. However, our findings also indicate that even ambient exposure could alter immune cell phenotypes, functions, and their fate. Further investigations on how QACs affect immunity under steady-state conditions are warranted. Collectively, the findings of this doctoral research suggest temporal and spatial effects of diet and hygiene on systemic autoimmunity and emphasize the strong influence of environmental factors toning cellular immune responses and subsequently shaping autoimmune outcomes. Our findings could pave the way for more personalized healthcare plans for autoimmune patients that take into consideration tissue involvement, disease stages, and the patient's lifestyle. / Doctor of Philosophy / The immune system is efficiently toned to discriminate between friends and foes. It effectively protects against a wide array of pathogens while at the same time avoiding attacking self-tissues. The inability of immune defenses to achieve this optimal discrimination could lead to the breakdown of tolerance to self in a wide range of autoimmune conditions. Diverse genetic susceptibilities are implicated in the development of autoimmunity. In parallel, during the recent decades, the tremendous increase in the prevalence of autoimmune conditions coincides with evolving dietary and hygiene styles in Westernized societies. This suggests a strong influence of environmental factors such as dietary and hygienic components on the way that the immune system works. Therefore, the current research investigates whether diet and hygiene modulate the immune dysregulations of lupus disease as a model for systemic autoimmunity; and if so, whether such effects are tissue- and/or disease stage-specific. We utilized different mouse models to delineate the mechanisms by which essential nutrients such as vitamin A (VA) and widely used disinfectant compounds known as quaternary ammonium disinfectants (QACs) modulate the systemic autoimmunity in lupus disease. We found that these modulators influence various aspects of the cellular immune responses including (1) leukocyte activation and subsequent expansion of pathogenic (disease contributing) lymphocytes, production of antibodies directed against self-tissue molecules (i.e., autoantibodies), and production of inflammatory mediators (i.e., cytokines and chemokines); (2) cell trafficking and their infiltration into the tissues; (3) signal transduction pathways that modulate cell fate (e.g., PD-1: PD-L1 signaling). Importantly, environmental modulation of autoimmunity during different stages of autoimmune development could significantly impact the disease outcome. VA treatment, for example, differentially modulates the progression of kidney inflammation when given during the initiation vs. progressive disease stages. Similarly, VA deficiency has the most prominent effects on worsening kidney inflammation under genetically prone conditions when the deficiency is initiated early and at the prenatal stage. In parallel, the effects of environmental factors are also tissue-specific. For example, ambient exposure to QAC-based disinfectants exerted immunosuppressive effects on lupus-associated inflammation of lymphoid tissues with no change in circulating autoantibodies or the severity of kidney inflammation. Collectively, the findings of this doctoral research delineated the cellular mechanisms through which environmental factors could shape autoimmune responses. Further studies will dig into the underlying molecular pathways. Ultimately, our research emphasizes the strong influence of exogenous factors on immunity and will pave the way for more effective healthcare management plans and benefit vulnerable populations affected by autoimmune conditions such as lupus.

Stem and progenitor cell fate (self-renewal, proliferation, survival, differentiation) is tightly controlled by niche factors and the interplay of these factors is particularly important to comprehend for the development of stem cell therapies. During erythropoiesis, erythroid progenitors at the colony forming unit-erythroid (CFU-E) stage are responsive to both stem cell factor (SCF) and erythropoietin (EPO); however, the joint action of SCF and EPO in these cells and the underlying mechanisms remain to be defined. In this study, quantitative data on the activation of signaling pathways and gene expression profiles provided definitive evidence for two parallel but complementary mechanisms that resulted in enhanced generation of red blood cells from mouse bone marrow-derived CFU-E culture in the presence of SCF and EPO. First, SCF and EPO signaling intersected within the extracellular signal-regulated kinase (ERK) pathway and the sustained ERK activation was required for the maximal changes in the expression levels of genes that are involved in the proliferation and survival of CFU-Es. Second, the apparent competition between SCF and EPO in regulating c-Kit expression was found to have a dramatic impact on the terminal differentiation of CFU-Es. The latter mechanism was, for the first time, reported in a primary cell system. In addition, a fetal liver-derived conditioned medium further enhanced the survival and proliferation of bone marrow CFU-Es in the presence of SCF and EPO by not only increasing the ERK signaling duration but also, the amplitude. The agents present in the conditioned media possess significant clinical potential to stimulate erythropoiesis both in vivo and in vitro. In conclusion, our study has provided novel insights into the mechanisms by which combinations of niche factors control the fate of erythroid progenitors at a unique transitional stage and highlighted the important role of the ERK signaling dynamics in adult erythropoiesis.

Members of the Six4/5 family of homeobox transcription factors have been implicated in multiple human disorders, including type I mytonic dystrophy, branchio-oto-renal syndrome, and holoprosencephaly, suggesting a role for these factors in the nervous system development. Using a forward genetics approach, we identified unc-39, a C. elegans homologue of the human SIX5 gene, as a novel regulator of the development of a specific neuron, called RID. Our data support the role of unc-39 early in C. elegans development and suggest a possibility of complete absence of RID neuron in unc-39 mutants. unc-39 mutant has a similar locomotion phenotype to the RID-ablated animals, which provides further support to the hypothesis that the absence of RID contributes to the locomotion phenotype observed in the mutant. We show that unc-39 functions at multiple points in the lineage that gives rise to the RID neuron, and that its function is context-dependent.

Stem and progenitor cell fate (self-renewal, proliferation, survival, differentiation) is tightly controlled by niche factors and the interplay of these factors is particularly important to comprehend for the development of stem cell therapies. During erythropoiesis, erythroid progenitors at the colony forming unit-erythroid (CFU-E) stage are responsive to both stem cell factor (SCF) and erythropoietin (EPO); however, the joint action of SCF and EPO in these cells and the underlying mechanisms remain to be defined. In this study, quantitative data on the activation of signaling pathways and gene expression profiles provided definitive evidence for two parallel but complementary mechanisms that resulted in enhanced generation of red blood cells from mouse bone marrow-derived CFU-E culture in the presence of SCF and EPO. First, SCF and EPO signaling intersected within the extracellular signal-regulated kinase (ERK) pathway and the sustained ERK activation was required for the maximal changes in the expression levels of genes that are involved in the proliferation and survival of CFU-Es. Second, the apparent competition between SCF and EPO in regulating c-Kit expression was found to have a dramatic impact on the terminal differentiation of CFU-Es. The latter mechanism was, for the first time, reported in a primary cell system. In addition, a fetal liver-derived conditioned medium further enhanced the survival and proliferation of bone marrow CFU-Es in the presence of SCF and EPO by not only increasing the ERK signaling duration but also, the amplitude. The agents present in the conditioned media possess significant clinical potential to stimulate erythropoiesis both in vivo and in vitro. In conclusion, our study has provided novel insights into the mechanisms by which combinations of niche factors control the fate of erythroid progenitors at a unique transitional stage and highlighted the important role of the ERK signaling dynamics in adult erythropoiesis.