|
|
Pathophysiologic aspects of myelodysplastics syndromes in relation to the effect of targeted imunomodulation and demetylation therapy
Jonášová, Anna ; Stopka, Tomáš (advisor) ; Maisnar, Vladimír (referee) ; Faber, Edgar (referee)
Myelodysplastic syndromes (MDS) represent a group of clonal stem cell disorders characterized by ineffective hematopoiesis, peripheral cytopenia, morphological dysplasia and the risk of transformation to acute myeloid leukemia (AML). MDS belongs to one of the most common hematological diseases in patients over 60 years old. MDS incidence is still increasing. Appropriate therapy of MDS remains challenging. There is no curative approach besides peripheral stem cells transplantation, which is regretfully appropriate only for a small group of patients due to a higher median age of the MDS population. This is why the search for therapeutic alternatives remains paramount. MDS treatment was rather frustrating until the recent introduction of two new therapeutic approaches: immunomodulation therapy with lenalidomide and epigenetic or demethylating therapy with 5-azacytidine. Both new drugs have significantly higher effect than standard therapy. However, the precise mechanism of this effect remains unknown. As a result, we decided to initiate several research projects while introducing this promising treatment to our patients. Our aim is to investigate the mechanism of both agents in relation to disease pathogenesis by examining changes of certain occurrences and factors prior to and during the course of...
|
|
|
Epigenetic Aspects of normal and malignant hematopoiesis: role of chromatin remodeling ISWIATPase.
Zikmund, Tomáš ; Stopka, Tomáš (advisor) ; Dráber, Peter (referee) ; Otáhal, Pavel (referee)
Chromatin remodeling protein Smarca5 participates on many cellular processes, which are important for tissue development and tumorigenesis. Among these processes utilizing ATPase activity of Smarca5 belong also transcription, replication and DNA repair. We hypothesized that Smarca5 represents essential molecule for chromatin modulation primarily at early developmental stages at the level of fast-dividing progenitors of many origins, in whose the ATPase is highly expressed. To such tissues may belong also hematopoiesis, in which the Smarca5 has highest expression. The subject of my doctoral thesis is therefore analysis of the effect Smarca5 depletion on proliferation and differentiation of hematopoietic progenitors in vivo and a search for mechanisms behind the resulted developmental defects. We utilized conditionally knockout allele of Smarca5 in blood precursors to study in a mouse model how depletion of the ISWI ATPase causes accumulation of earliest progenitors inhibited from further maturation to erythroid and other myeloid lines. The proerythroblasts became dysplastic and the majority of basophilic erythroblasts ceased cycling around the G2/M stage. An expected mechanism for observed changes appeared the activation of stress pathway of protein p53 that is often associated with unrepaired DNA...
|
|
|
Differentiation plasticity of hematopoietic cells
Polgárová, Kamila ; Stopka, Tomáš (advisor) ; Otáhal, Pavel (referee) ; Šálek, Cyril (referee)
Hematopoiesis has been for many years seen as a straightforward process based on sequential restriction of cell fate potential leading to production of mature blood cells. In the last decade, however, several works documented an unexpected plasticity of hematopoietic cells with expanded potential of myeloid development from lymphoid progenitors and vice versa. Under physiologic conditions hematopoiesis is tightly controlled and the definite cell fate is denominated by multiple factors that all lead to changes in regulatory networks that include transcription factors, epigenetic changes and post-transcriptional modulations. Any disruption of this strict regulation, caused by mutations or other events, affects the proliferation and lineage fidelity of hematopoietic precursors. This may lead to clonal growth of variable significance or leukemogenesis and may possibly affect the treatment sensitivity of the hematological malignancies. For better understanding of hematopoietic regulation we described gene expression changes during physiological development of lymphoid and myeloid lineages and in leukemic specimens using our own simplified real-time PCR based platform. We investigated expression of 95 genes connected with lymphoid and myeloid differentiation or with leukemogenesis in sorted hematopoietic...
|
|
|
Regulatory mechanisms in normal and malignant granulopoiesis
Kardošová, Miroslava ; Alberich Jorda, Meritxell (advisor) ; Stopka, Tomáš (referee) ; Balounová, Jana (referee)
Neutrophils, known primarily as key players in defense against invading pathogens, represent an essential component of both the innate and adaptive immunity. Continuous production of large quantities of neutrophils is ensured by a complex process termed granulopoiesis. In order to maintain a stable neutrophilic population, granulopoiesis requires to be tightly regulated. Moreover, impaired granulopoiesis may lead to aberrant bone marrow function and, ultimately, give rise to acute myeloid leukemia (AML). Despite decades of research, the mechanisms regulating granulopoiesis are still unclear. In particular, the CCAAT/enhancer binding protein (C/EBP) family of transcription factors plays a critical role in this process. C/EBPα acts as a master regulator of granulopoiesis mainly by orchestrating expression of its target genes, which will mediate granulocytic differentiation. Thus, characterization of novel C/EBPα target genes is critical for a better understanding of the molecular mechanisms that regulate granulopoiesis. Previously, we showed that another C/EBP member, CEBPG, is a direct target of C/EBPα. In the first part of the present work, we addressed the unknown role of C/EBPγ in granulopoiesis. We observed that Cebpg conditional knockout (KO) mice, which have the Cebpg gene ablated specifically...
|
|
|
Production and analysis of cellular conditional inactivation models of the ISWI ATPase Smarca5
Tauchmanová, Petra ; Stopka, Tomáš (advisor) ; Burda, Pavel (referee)
The eukaryotic nuclear processes such as replication, DNA damage repair (DDR) and transcription are highly dependent on the regulation of chromatin structure. The dynamic changes in chromatin accessibility are controlled by a class of chromatin-remodeling factors which form multimeric complexes and use ATP as the source of their helicase activity. In this study we have established a mouse embryonic fibroblast in vitro model with conditional inactivation of chromatin remodeling ATPase Smarca5 and used this powerful tool to test the regulation of cell cycle, proliferation and DDR signaling in conditions with low Smarca5 activity. Our results show that decreased dosages lead to decreased proliferation apparent already within few days post induction of Smarca5 deletion that is accompanied with decrease of cells in S and M phases of cell cycle, increasing cell ploidy and accelerated cell senescence. Additionally, the Smarca5 depleted cells upregulated many protein markers associated with DNA damage and cellular stress. Our results thus indicate that Smarca5 has indispensable roles during cell proliferation including in the maintenance of genome integrity during S phase of cell cycle.
|
|
|
Epigenetic factors CTCF a SMARCA5 control expression of hematopoietic transcription factor SPI1 in cells of acute myeloid leukemia and myelodysplastic syndrome.
Dluhošová, Martina ; Stopka, Tomáš (advisor) ; Machová Poláková, Kateřina (referee) ; Kozák, Tomáš (referee)
CCCTC-binding factor (CTCF) can both activate as well as inhibit transcription by forming chromatin loops between regulatory regions and promoters. In this regard, Ctcf binding on the non-methylated DNA and its interaction with the Cohesin complex results in differential regulation of the H19/Igf2 locus. Similarly, a role for CTCF has been established in normal hematopoietic development; however its involvement, despite mutations in CTCF and Cohesin complex were identified in leukemia, remains elusive. CTCF regulates transcription dependently on DNA methylation status and can if bound block interactions of enhancers and promoters. Here, we show that in hematopietic cells CTCF binds to the imprinting control region of H19/Igf2 and found that chromatin remodeller Smarca5, which also associates with the Cohesin complex, facilitates Ctcf binding and regulatory effects. Furthermore, Smarca5 supports CTCF functionally and is needed for enhancer-blocking effect at imprinting control region. We identified new CTCF-recognized locus near hematopoietic regulator SPI1 (PU.1) in normally differentiating myeloid cells together with members of the Cohesin complex. Due to DNA methylation, CTCF binding to the SPI1 gene is reduced in AML blasts and this effect was reversible by DNA methylation inhibitor 5-azacitidine.
|
|
|
Investigating critical mechanisms of oncogenesis using cell model systems
Hušková, Hana ; Stopka, Tomáš (advisor) ; Macůrek, Libor (referee) ; Vojtěšek, Bořivoj (referee)
(EN) Humans and cells in their bodies are exposed to various mutagens in their lifetime that cause DNA damage and mutations, which affect the biology and physiology of the target cell, and can lead to the expansion of an immortalized cell clone. Genome-wide massively parallel sequencing allows the identification of DNA mutations in the coding sequences (whole exome sequencing, WES), or even the entire genome of a tumour. Mutational signatures of individual mutagenic processes can be extracted from these data, as well as mutations in genes potentially important for cancer development ('cancer drivers', as opposed to 'passengers', which do not confer a comparative growth advantage to a cell clone). Many known mutational signatures do not yet have an attributed cause; and many known mutagens do not have an attributed signature. Similarly, it is estimated that many cancer driver genes remain to be identified. This Thesis proposes a system based on immortalization of mouse embryonic fibroblasts (MEF) upon mutagen treatment for modelling of mutational signatures and identification and testing of cancer driver genes and mutations. The signatures extracted from WES data of 25 immortalized MEF cell lines, which arose upon treatment with a variety of mutagens, showed that the assay recapitulates the...
|
|
|
Anaemia disease models
Vondráková, Zuzana ; Bartůněk, Petr (advisor) ; Stopka, Tomáš (referee)
Hematopoiesis is a process by which blood cells are generated. All vertebrates have two phases of hematopoiesis - primitive and definitive. The main purpose of primitive hematopoiesis is the production of red blood cells, which provide oxygenation to the developing embryo. Other blood cell lineages are established by definitive hematopoiesis. The main function of erythrocytes is oxygen transport to all tissues. When erythrocyte production is decreased or they are damaged due to the membrane, enzyme or hemoglobin impairment, the condition called anemia arises. Sickle cell disease and β-thalassemia are called hemoglobinopathies as they are caused by the damaged hemoglobin. Fanconi anemia is caused by mutations in one of 21 genes of Fanconi anemia pathway, which plays an essential role in DNA repair. Diamond Blackfan anemia is caused by mutations gene for ribosomal proteins. Human cells, Mus musculus, Gallus gallus, Xenopus laevis and Danio rerio seem to be good models for study of this diseases and they are also useful for achieving therapeutical goals.
|
|
|
Identification and functional characterization of C/EBPalpha targets in normal and malignant hematopoiesis
Zjablovskaja, Polina ; Alberich Jorda, Meritxell (advisor) ; Stopka, Tomáš (referee) ; Fuchs, Ota (referee)
Thehematopoieticsystemisahighlyorganizedstructure, whichhastobetightly regulatedinordertofunctionproperly.Abnormalitiesinhematopoieticdevelopmentmaylead tohematologicaldisorders,suchasacutemyeloidleukemia(AML).Thefunctionalityofthe hematopoieticsystemlargelyreliesontranscriptionfactors.C/EBPtranscriptionfactoris knownasoneofthe majorhematopoieticregulators,requiredforthefunctionalityof hematopoieticstemcellsaswellasformyeloidlineagedevelopment.Importantly,C/EBP expressionisalteredinalargeproportionofAMLcases.C/EBPregulateshematopoiesis mainlythroughorchestratingexpressionofitstargetgenes.ManyoftheC/EBPtargetshave previouslybeenshowntoplayaroleinthehematopoieticsystemandtobeinvolvedin leukemictransformation. That makesidentificationofnovel C/EBP targetsandtheir functionalcharacterizationanexcitingsubjectofresearch.Hereweidentifiedalistofgenes whoseexpressiondependsontheactivityofC/EBPthesocalledC/EBPsignature. We demonstratedthattreatment withhistonedeacetylase(HDAC)inhibitorsreactivatesthe expressionofthesegenesincellswithnon-functionalC/EBP.Inaddition,wedemonstrated thattreatmentwiththeHDACinhibitorspromotesmyeloiddifferentiationinAMLsamples carryingbi-allelicCEBPA mutationsandcharacterizedbythereducedexpressionofthe...
|
|
|
Role of Smarca5 (Snf2h) chromation remodeling ATPase in hematopoitic development and erythropoiesis
Kokavec, Juraj ; Stopka, Tomáš (advisor) ; Divoký, Vladimír (referee) ; Kořínek, Vladimír (referee)
The Imitation Switch (ISWI) nuclear ATPase Smarca5 (Snf2h) is one of the most conserved chromatin remodeling factors. It exists in a variety of oligosubunit complexes that move DNA with respect to the histone octamer to generate regularly spaced nucleosomal arrays. Smarca5 interacts with different accessory proteins and represents a molecular motor for DNA replication, repair and transcription. We deleted Smarca5 at the onset of definitive hematopoiesis (Vav1-iCre) and observed that animals die during late fetal development due to anemia. Hematopoietic stem and progenitor cells (HSPCs) accumulated but their maturation towards erythroid and myeloid lineages was inhibited. Proerythroblasts were dysplastic while basophilic erythroblasts were blocked in G2/M and depleted. Smarca5 deficiency led to increased p53 levels, its activation at two residues, one associated with DNA damage (S-18) second with CBP/p300 (K376Ac), and finally activation of the p53 targets. We also deleted Smarca5 in committed erythroid cells (Epor-iCre) and observed that animals were anemic postnatally. Furthermore, 4- OHT-mediated deletion of Smarca5 in the ex vivo cultures confirmed its requirement for erythroid cell proliferation. Thus, Smarca5 plays indispensable roles during early hematopoiesis and erythropoiesis.
|
guest ::
