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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Deciphering the Role of MEF2D Splice Forms During Skeletal Muscle Differentiation

Rakopoulos, Patricia 26 May 2011 (has links)
Members of the Mef2 transcription factor family are extensively studied within the muscle field for their ability to cooperate with the myogenic regulatory factors MyoD and myogenin during muscle differentiation. Although it is known that Mef2 pre-mRNAs undergo alternative splicing, the different splice forms have not been functionally annotated. In this thesis, my studies aimed to characterize three Mef2D splice forms: MEF2Dα'β, MEF2Dαβ, MEF2Dαø. Our results show that MEF2D splice forms can be differentially phosphorylated by p38 MAPK and PKA in vitro. Gene expression analysis using cell lines over-expressing each Mef2D splice form suggests that they can differentially activate desmin, myosin heavy chain and myogenin expression. Mass spectrometry analyses from our pull-down assays reveal known and novel MEF2D binding partners. Our work suggests that Mef2D splice forms have overlapping but distinct roles and provides new insight into the importance of Mef2D alternative splicing during skeletal myogenesis.
272

H3K36me3 in Muscle Differentiation: Regulation of Tissue-specific Gene Expression by H3K36-specific Histonemethyltransferases

Dhaliwal, Tarunpreet January 2012 (has links)
The dynamic changes in chromatin play a significant role in lineage commitment and differentiation. These epigenetic modifications control gene expression through recruitment of transcription factors. While the active mark H3K4me3 is present around the transcription start site on the gene, the function of the H3K36me3 mark is unknown. A number of H3K36-specific histone methyltransferases (HMTs) have been identified, however the focus of this study is the HMT Hypb. To elucidate the role of H3K36me3 in mediating expression of developmentally-regulated loci, native chromatin immunoprecipitation (N-ChIP) was performed at a subset of genes. Upon differentiation, we observe that H3K36me3 becomes enriched at the 3’ end of several muscle-specific genes. To further investigate the role of H3K36me3 in myogenesis, a lentiviral-mediated knockdown of the H3K36 HMT Hypb was performed in muscle myoblasts using shRNA. Upon Hypb knockdown, we were surprised to observe enhanced myogenesis. N-ChIP was also performed on differentiated Hypb knockdown cell lines in order to look at H3K36me3 enrichment on genes involved in muscle differentiation. N-ChIP data show a drop in H3K36me3 enrichment levels on myogenin and Ckm genes. The possible occupancy of Hypb on the coding regions of muscle-specific genes was experimentally observed by cross-linked chromatin immunoprecipitation (X-ChIP) on differentiated C2C12 cells and subsequently confirmed by X-ChIP on knockdown lines where the occupancy was lost. A model is proposed that links the observed phenotype with H3K36me3.
273

The Role of Effector Caspases in DNA Damage Response and Chromatin Remodeling During Myogenic Differentiation

Al-Khalaf, Mohammad January 2017 (has links)
Effector caspase activation is a critical regulatory step in apoptosis, as well as an essential inductive cut in numerous non-death related processes that occur within complex cell systems. Here we report two novel studies detailing mechanisms by which effector caspase activation advances muscle cell differentiation. In the first study, we demonstrate that caspase 3 triggered DNA damage leads to rapid formation of XRCC1 repair foci within differentiating myonuclei, which dissipates as the maturation program proceeds. Skeletal myoblast deletion of XRCC1 does not impact cell growth, yet leads to perinatal lethality, with sustained DNA damage and impaired myofiber development. These observations demonstrate that the temporal deployment of the XRCC1-related DNA repair mechanisms are effector caspase mediated, and essential for muscle cell differentiation. In the second study, we sought to investigate whether effector caspase enzymes altered chromatin structure to promote the early differentiation of muscle progenitor cells. Past research has shown that Matrix Attachment region proteins known as Special AT-rich binding proteins are expressed abundantly in stem and progenitor cells, showing rapid decrease in expression as the cell advances into its mature phenotype. Here we demonstrate that effector caspase-7 is responsible for cleavage of Satb2, rather than caspase 3. Satb2 degradation alters the expressed genetic profile leading to acceleration of the muscle differentiation program. Our cumulative work adds novel roles in which effector caspases are vital in the development of cells.
274

Investigating the role of Integrin Linked Kinase in mammary epithelial cell differentiation

Rooney, Nicholas January 2014 (has links)
Epithelial cell adhesion to the surrounding extracellular matrix (ECM) is necessary for their proper behaviour and function. During pregnancy and lactation mammary epithelial cells (MECs) require signals imparted by specific β1 integrin-laminin interactions for their functional differentiation in response to Prolactin (Prl) and for the correct formation of polarised secretory acini. Downstream of β1 integrin (β1Itg), the scaffold protein Integrin Linked Kinase (ILK) has been identified as the key signal transducer that is required for both Prl driven lactational differentiation and the establishment of apico-basal polarity in MECs. ILK is a multifunctional adaptor protein that links integrins to the actin cytoskeleton and Rho GTPases such as Rac1. ILK forms a ternary IPP (ILK-PINCH-Parvin) complex with PINCH and Parvins, which are central to its adaptor functions. However, it is not known which of ILKs interacting partners are important for controlling tissue-specific gene expression, or what acts downstream of the IPP complex. In this thesis I have now established that inducible ILK deletion in MECs from ILKfl/flCreER mice, prevents phosphorylation of Stat5 leading to a failure of Prl induced milk expression. In addition I have established a 3-dimensional culture model using the EpH4 mammary epithelial cell line, which respond to Prl treatment and form polarised acini similar to primary cells. In these cells knocking down β1Itg and ILK by lentiviral shRNA delivery was confirmed to have a profound effect on β-Casein production. Expression of ILK mutants that disrupt its protein-protein interactions, showed that mutation of K220 and E359 in the kinase domain also reduced milk production. This means that ILKs kinase domain is important for MEC differentiation, and suggests that Parvin binding (which is disrupted by these mutations) is key in mediating ILKs differentiation functions. Using a complimentary shRNA approach, knockdown of the βParvin binding Rac guanine nucleotide exchange factor αPix also prevented MEC differentiation. This identified for the first time that αPix is required for differentiation and suggests a route by which ILK, via it’s interaction with Parvin, can link integrins to αPix and Rac activity. Interestingly, αPix depletion did not disrupt the IPP complex or polarity, suggesting that αPix represents a differentiation specific bifurcation point in β1Itg-ILK adhesive signalling. Together, this work has helped to establish how ILK is involved in MEC differentiation and has identified a new role for the downstream Rac GEF αPix. In addition, this work contributes to our understanding of the molecular mechanisms by which cell adhesion regulates fundamental cell biological behaviours.
275

A new role for Filamin A as a regulator of Runx2 function

Lopez Camacho, Cesar January 2011 (has links)
Filamin A is a well-characterised cytoskeletal protein which regulates cell shape and migration by cross-linking with actin. Filamin A mutations cause a number of human developmental disorders, many of which exhibit skeletal dysplasia. However, the molecular mechanisms by which Filamin A affects skeletal development are unknown. The transcription factor Runx2 is a master regulator of osteoblast and chondrocyte differentiation. Data presented in this thesis show that Filamin A forms a complex with Runx2 in osteoblastic cell lines. Moreover, it is demonstrated that Filamin A is present in the nucleus in several cell lines, including those of osteoblastic origin. The data presented show that the Filamin A/Runx2 complex suppresses the expression of the gene encoding the matrix-degrading enzyme, matrix metalloproteinase-13 (MMP-13), which is an important osteoblastic differentiation marker. ChIP assays were employed to demonstrate that endogenously expressed Filamin A associates with the promoter of the MMP-13 gene. In addition, Filamin A is not only located in the nucleus but also in the nucleolus, an important nuclear compartment involved in ribosomal RNA (rRNA) transcription. Ribosomal DNA promoter-driven reporter assays, Filamin A-knockdown experiments and exogenous Filamin A transfections demonstrated that Filamin A and Runx2 can repress ribosomal gene expression activity. Importantly, Filamin A is recruited to the human ribosomal DNA promoter, suggesting its direct involvement in the regulation of rRNA transcription. These findings reveal a novel role of Filamin A in the direct regulation of ribosomal gene expression. Finally, by using microarray technology, changes in gene expression were identified when Filamin A was downregulated. Some of the differentially expressed genes were known orchestrators of bone development. The data presented in this thesis strengthen the link between Filamin A and bone development and provide a molecular rationale for how Filamin A, acting as a regulator of gene expression, might influence osteoblastic differentiation.
276

Detection and possible significance of a common leukemia-associated antigen, CAMAL, in human myeloid leukemia

Logan, Patricia Marie January 1987 (has links)
Human acute nonlymphoblastic or myelogenous leukemia (ANLL or AML) is a malignant disease of the bone marrow involving hemopoietic (blood-forming) cells of the myeloid lineage. ANLL is a complex neoplastic disease, whose fundamental nature is only partially understood despite intensive research. The disease is complicated by its apparent heterogeneity in terms of the degree of differentiation of hemopoietic stem cell involvement in different patients and the cellular expression of immunologically defined surface markers. The presence of a common antigen in myelogenous leukemia (CAMAL) has been previously identified. This thesis examines the expression of the CAMAL marker in or on bone marrow (BM) and peripheral blood (PB) cells using a monoclonal antibody-based indirect immunoperoxidase slide test. Increased numbers of CAMAL-positive cells were found in or on BM and PB of myeloid leukemia patients (with acute or chronic forms of the disease) compared with those found in normals or most lymphoid malignancies. Results presented herein have demonstrated that fluctuations in CAMAL BM values (% positive cells) correlated with survival time prior to relapse. In a blind study, ANLL patients Whose CAMAL BM values decreased post-chemotherapy had significantly (p < 0.025) longer first remission times (x = 19.2 months) than patients with increasing or static CAMAL BM values (x = 6.8 months). CAMAL BM values were often observed to increase during remission, prior to relapse, suggesting the presence of residual subclinical disease. Addition of excess purified leukemia-derived CAMAL to an in vitro myeloid progenitor cell assay caused profound inhibition of normal CFU-c growth but had no inhibitory effect on CFU-c growth from myeloid leukemia patients in active disease states. Depletion of CAHAL from normal plasma and conditioned media (sources of numerous hemopoietic growth regulatory factors) caused significant inhibition of normal, but not myeloid leukemic, CFU-c growth. These results indicated that myeloid leukemic cells possessed apparent differences in responsiveness to CAMAL-mediated hemopoietic regulation compared to normal cells. Lack of responsiveness to inhibition by leukemia-derived CAMAL may facilitate dominance of the malignant clone over normal cells. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate
277

Genetic regulation of pulmonary progenitor cell differentiation

Stupnikov, Maria Rose January 2019 (has links)
The respiratory system represents a major interface between the body and the external environment. Its design includes a tree-like network of conducting tubules (airways) that carries air to millions of alveoli, where gas exchange occurs. The conducting airways are characterized by their great diversity in epithelial cell types with multiple populations of secretory, multiciliated, and neuroendocrine cells. How these different cell types arise and how these populations are balanced are questions still not well understood. Aberrant patterns of airway epithelial differentiation have been described in various human pulmonary diseases, chronic bronchitis, asthma, neuroendocrine hyperplasia of infancy, and others. The goal of this thesis is to investigate mechanisms of regulation of airway epithelial cell fate in the developing lung epithelium. More specifically, these studies focus on Notch signaling and address a long unresolved issue whether the different Notch ligands (Jagged and Delta) have distinct roles in the epithelial differentiation program of the extrapulmonary and intrapulmonary airways. Moreover, these studies investigate the ontogeny of the bHLH transcription factor Ascl1 and identify its targets in the developing airways as potential regulators of neuroepithelial body (NEB) size and maturation. My studies provide evidence that the Notch ligand families Jag and Dll are required for the specification and formation of different cell lineages in the developing airway epithelia. Jag ligands regulate multiciliated versus secretory (club) cell fates but also controls abundance of basal cell progenitors in extrapulmonary airways. Dll ligands regulate pulmonary neuroendocrine versus club cell fates in intrapulmonary airways. Analysis of mouse mutants showed that loss of Jag ligands has minimal impact on the size or abundance of NEBs and their associated secretory cells while loss of Dll ligands results in an expansion of NEB size and associated cells. To gain additional insights into the potential mechanisms of how neuroendocrine cells develop and undergo aberrant hyperplasia, I characterized the global transcriptional profile of embryonic lungs from mice deficient in Ascl1, which lack NEBs and neuroendocrine cells and identified a number of genes associated with neuroendocrine cell development, maturation, and the NEB microenvironment. Among these genes, components of the catecholamine biosynthesis pathway, such as tyrosine hydroxylase (Th), a key enzyme for catecholamine production, were downregulated in Ascl1 null lungs. Subsequent functional analysis using a pharmacological inhibitor of this pathway in lung organ cultures showed expansion of pulmonary neuroendocrine cells and NEB size, an observation of potential relevance in human diseases in which neuroendocrine cells are aberrantly expanded. Together these studies highlight the distinct role of Notch ligands and further implicate Ascl1 targets, as illustrated by catecholamine pathway components, in regulating epithelial cell fate. Further examination of these pathways may provide insights into the pathogenesis and ultimately therapeutic approaches for airway diseases.
278

Alternative cell fate in response to DNA damage regulated by differential p53 pathway dynamics

Chen, Xi 01 January 2012 (has links)
No description available.
279

Evaluating the regulation of signaling pathways downstream of CD44 antibody treatment in AML

Alghuneim, Arwa 08 1900 (has links)
Acute myeloid leukemia (AML) is a subset of leukemia that is characterized by the clonal expansion of cytogenetically and molecularly abnormal myeloid blasts. These blasts are highly proliferative accumulating in bone marrow and blood which leads to severe infections, anemia, and bone marrow failure. The poor prognosis of AML patients caused by the low tolerance to intensive chemotherapy has encouraged the pursuit of alternative therapeutic approaches. Differentiation therapy which involves the use of agents that can release the differentiation block in these leukemic blasts has emerged as a promising therapeutic approach. The use of All-trans retinoic acid (ATRA) represents a successful example of such an approach, nonetheless its efficacy is restricted to one subtype of AML. Efforts have been focused on finding differentiation agents which are effective for the other more common AML subtypes. Anti-CD44 targeted antibodies that activate the CD44 cell surface antigen are a promising candidate. Previous studies have shown that anti-CD44 treatment has been able to release the differentiation block in AML1 through AML5 subtypes. The exact mechanism by which anti-CD44 treatment is able to induce its effects has not been fully elucidated. Recent studies highlight the role that epigenetic mechanisms play during haematopoiesis and leukemogenesis and therefore, in this work we investigated the epigenetic mechanisms associated with anti-CD44 induced differentiation. Using AML cell lines from different subtypes, we demonstrated that anti-CD44-induced differentiation results in an extensive change of histone modification levels. We found that inhibiting enzymes responsible for the H3K9ac, H3K4me, H3K9me, and H3K27me modifications, attenuated the anti-proliferative and differentiation promoting effects of antic-CD44 treatment. Taken together, these data highlight the promising potential of using anti-CD44 as a therapeutic agent across multiple subtypes in AML
280

Genetically Matched Human iPS Cells Reveal that Propensity for Cartilage and Bone Differentiation Differs with Clones, not Cell Type of Origin / 同一ドナー由来のiPS細胞の軟骨・骨分化傾向は、由来細胞よりもクローンにより左右される

Nasu, Akira 23 July 2014 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18504号 / 医博第3924号 / 新制||医||1005(附属図書館) / 31390 / 京都大学大学院医学研究科医学専攻 / (主査)教授 妻木 範行, 教授 開 祐司, 教授 中辻 憲夫 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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