1,721,046 research outputs found
Pharmacologic regulation of Wnt/β-Catenin Signaling in Stem and Progenitor Cells
No full textThesis (Ph.D.)--University of Washington, 2014The Wnt/Ã -Catenin signaling pathway is a key regulator of proliferation, differentiation, and programmed cell death in stem and progenitor cells. Misregulated or aberrant signaling events in the pathway contributes to the pathology of diseases such as cancer and neurodegeneration. It stands to reason that if we can monitor and influence Wnt/Ã -Catenin signaling in stem and progenitor cells with sufficient resolution, it will be possible to design rationally targeted therapies. The body of work presented in this thesis contributes to the realization of this goal through discovery of molecular agents for controlling Wnt/Ã -catenin signaling, examination of the biological mechanisms linking this pathway to disease, and identification of cases where the pharmacological perturbation of Wnt/Ã -Catenin signaling may have therapeutic utility
Characterization of novel, context-dependent modulators of WNT signaling in cancer
No full textThesis (Ph.D.)--University of Washington, 2012WNTs comprise a family of secreted proteins that play critical roles in both embryogenesis and in the etiology of human diseases such as cancer. Even after more than three decades of research, our understanding of the complex roles of various WNT signaling pathways in cancer is rudimentary at best. Just as either activating or inactivating different WNT signaling pathways results in unique consequences at different stages of animal development and in different tissues types during embryogenesis, so too do WNTs contribute to cancer progression in a context-dependent manner. The work presented in this dissertation identifies and characterizes novel modulators of WNT signaling in cancer and explores possible mechanisms of action for these signaling effectors including crosstalk with other signal transduction pathways. First, I describe a novel role for AGGF1 in colorectal cancer as a chromatin-associated enhancer of beta-catenin-dependent transcription. Second, I find that the planar cell polarity protein SCRIB does not universally act as a tumor suppressor as presumed by many researchers, but rather that SCRIB can either promote or inhibit tumorigenesis in a context-dependent manner. My working hypothesis is that this switch from pro- to anti-tumorigenic function likely involves changes in the proteins associated with SCRIB such as NOS1AP, ARHGEF7 and VANGL. Finally, I characterize a novel role for a WNT5A/FZD7/RYK/AKT pathway in promoting the growth and viability of both naïve melanoma cells and melanoma cells that have acquired resistance to BRAF/MAPK pathway inhibition. With the exception of the work on AGGF1, these studies highlight context-dependent, functional roles for beta-catenin-independent WNT signaling in modulating numerous cancer cell behaviors ranging from the regulation of cell motility to the acquirement of drug resistance
WTX is a novel regulator of ubiquitination in the Wnt/beta-catenin and KEAP1/NRF2 pathways
No full textThesis (Ph.D.)--University of Washington, 2012Ubiquitination of proteins and subsequent proteosome-mediated degradation is one mechanism cells use to regulate protein steady-state levels. This essential process permits cells to rapidly respond to extracellular cues or cytotoxic insult, through selective modulation of intracellular signaling cascades. For example, the Wnt/beta-catenin pathway is controlled by ubuitination. In the absence of a WNT ligand, the transcription factor beta-catenin is directed to the SCFBTRC E3 ubiquitin ligase complex where it is poly-ubiqutinated. Poly-ubiquitinated beta-catenin is then recognized and rapidly degraded by the proteosome. WNT ligand binding to its cognate receptor prevents beta-catenin ubiquitination, allowing it to circumvent proteasome degradation, accumulate in the nucleus and drive transcription of genes required for proliferation and differentiation. My research investigated the functional roles of a novel regulator of the Wnt/beta-catenin pathway, Wilms Tumor gene on the X-chromosome (WTX). My study revealed that WTX interacts with two E3 ubiquitin ligase adaptors, BTRC and KEAP1. The WTX/BTRC complex promoted -catenin ubiquitination, while the WTX/KEAP1 complex inhibited ubiquitination of the stress response transcription factor NRF2). Mutations in WTX have been proposed to the cause of Wilms tumor, the most common form of pediatric kidney cancer. Therefore, the results of my thesis provide a mechanism explaining how mutations in WTX cause disease, and provide potential solutions to treating this disorder
Resolving mechanisms of apoptosis in response to WNT3A in Melanoma
No full textThesis (Ph.D.)--University of Washington, 2012Wnt/β-catenin and ERK/MAPK signaling regulate the balance of differentiation and proliferation in melanoma. Aberrant activation of ERK/MAPK signaling results from the BRAFV600E or NRASQ61X mutations in greater than 70% of primary melanoma samples. Previous data have shown that BRAF inhibition in combination with Wnt/β-catenin activation promotes robust melanoma apoptosis in a subset of melanomas. This finding raised the question of what factors predict sensitivity to apoptosis in response to WNT3A and how Wnt/β-catenin signaling is regulated in melanoma. My thesis research addresses this question by testing if Wnt/β-catenin signaling can promote apoptosis in BRAF and NRAS-mutant backgrounds, and it addresses how Wnt/β-catenin signaling is regulated in melanoma using combinatorial screening techniques. Here, I present evidence that combined ERK/MAPK pathway inhibition and Wnt/β-catenin activation leads to apoptosis in NRAS-mutant melanomas. Additional experiments demonstrate that the stability AXIN1 protein, a negative regulator of Wnt/β-catenin signaling, is required for resistance to apoptosis. Finally, I use high throughput screening to discover FAM129B as a novel positive regulator of Wnt/β-catenin signal transduction and the apoptotic response to WNT3A in melanoma. Collectively, these data expand the genetic contexts melanomas undergo apoptosis following WNT3A treatment and MEK inhibition, and further resolves Wnt/β-catenin pathway regulation in melanoma. The findings presented here highlight the importance of AXIN1 depletion across multiple mutational backgrounds, and identify numerous putative regulators of Wnt/β-catenin signaling which may ultimately regulate apoptosis in melanoma
The Role of RNA-Binding Protein, Muscleblind-Like 1, in Cardiac Wound Healing and Remodeling
No full textThesis (Ph.D.)--University of Washington, 2018Myocardial infarction (MI) triggers cardiomyocyte necrosis and a reparative response that involves deposition of a collagenous, fibrotic scar. Persistent scar formation leads to adverse remodeling of the heart structure and progression to heart failure, which is the leading cause of death worldwide. Although advancements in treatments have allowed patients to live longer, the underlying fibrotic scar is not remedied. The primary effector of cardiac fibrosis is the myofibroblast, which is a specialized, heterogeneous cell type that secretes extracellular matrix (ECM) and functionally contracts to help maintain ventricular wall integrity and prevent heart rupture after acute MI. Our lab previously identified the RNA-binding protein, Muscleblind-Like 1 (MBNL1), to be robustly upregulated during myofibroblast transformation. MBNL1 (a) stabilizes mRNA transcripts, (b) activates nodal signaling axes that transition fibroblasts into a myofibroblast cell fate and (c) augments fibrosis in the heart after MI. However, there are still several unanswered questions: (1) Which cardiac cell type contributes to MBNL1-mediated fibrotic remodeling after MI? (2) Could genetically dosing MBNL1 in the heart improve cardiac function post-infarct? (3) What other protein complexes associate with MBNL1 to regulate mRNA maturation and cell differentiation? In order to answer these questions, we either genetically knocked out or overexpressed Mbnl1 selectively in two different cells within the heart, fibroblasts and cardiomyocytes, to determine if Mbnl1 is a global mediator in the fibrotic response. We hypothesized fibroblasts were the main contributor to MBNL1-dependent fibrosis after MI. Indeed, we demonstrated that genetic deletion of Mbnl1 in resident cardiac fibroblasts diminishes the formation of a fibrotic scar and protects the heart from cardiac dysfunction post-MI. Mbnl1 depletion in resident cardiac fibroblasts inhibits TGFβ-mediated myofibroblast differentiation, which can be rescued by reintroduction of functional pro-fibrogenic transcripts serum response factor (Srf) and calcineurin (CnA) that are bound and regulated by MBNL1. A decrease in fibrosis post-MI was also observed in mice with cardiomyocyte-specific Mbnl1 loss of function, suggesting Mbnl1 function in cardiomyocytes also contributes to post-infarction wound healing and fibrotic remodeling after MI. Mechanistically, we show for the first time that MBNL1 binds with RNA processing machinery in fibroblasts to promote myofibroblast differentiation. When Mbnl1 is overexpressed in cardiac fibroblasts and cardiomyocytes, we observed diastolic dysfunction phenotypes in the absence of injury, highlighting MBNL1’s regulatory role in maintaining homeostasis in the cell. Collectively, this dissertation addresses the cell-specific role of MBNL1 in cardiac remodeling after MI by genetically manipulating Mbnl1 levels in both resident cardiac fibroblasts and cardiomyocytes. This work is significant because it will build upon a basic scientific understanding of transcriptome changes during cardiac wound healing and may provide new approaches to functionally repair and heal the myocardium post-MI
Wnt/β-catenin Signaling Regulates Regeneration in Diverse Tissues of the Zebrafish
No full textThesis (Ph.D.)--University of Washington, 2016-06The ability to regenerate tissue after injury is limited by species, tissue type, and age of the organism. Understanding the mechanisms of endogenous regeneration provides greater insight into this remarkable biological process while also offering up potential therapeutic targets for promoting regeneration in humans. The Wnt/β-catenin signaling pathway has been implicated in zebrafish regeneration, including the fin and nervous system. The body of work presented here expands upon the role of Wnt/β-catenin signaling in regeneration, characterizing roles for Wnt/β-catenin signaling in multiple tissues. We show that cholinergic signaling is required for blastema formation and Wnt/β-catenin signaling initiation in the caudal fin, and that overexpression of Wnt/β-catenin ligand is sufficient to rescue blastema formation in fins lacking cholinergic activity. Next, we characterized the glial response to Wnt/β-catenin signaling after spinal cord injury, demonstrating that Wnt/β-catenin signaling is necessary for recovery of motor function and the formation of bipolar glia after spinal cord injury. Lastly, we defined a role for Wnt/β-catenin signaling in heart regeneration, showing that cardiomyocyte proliferation is regulated by Wnt/β-catenin signaling. These data demonstrate a conserved role for Wnt/β-catenin signaling in promoting regeneration across multiple tissue types in the zebrafish, and further show conservation of some of these functions in human tissue
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
