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Role of intestinal circadian clock in epithelial transport, proliferation, and tumourigenesis
Soták, Matúš
AABBSSTTRRAACCTT The molecular circadian clock enables anticipation of environmental changes. In mammals, clocks are ubiquitously present in almost all tissues and they are comprised of transcriptional-translational feedback loops of the so-called clock genes. The central clock represents the intrinsic pacemaker which is located in suprachiasmatic nuclei (SCN) of hypothalamus and synchronizes peripheral clocks. Clockwork system in alimentary tract and its regulatory link to intestinal functions are poorly understood. Therefore the objective of the thesis was to characterize molecular clock in particular parts of the rat intestine and to elucidate its link to the intestinal transport, regulation of cell cycle and neoplastic transformation in colonic tissue. We used quantitative RT-PCR (qPCR) to determine circadian profiles of mRNA expression of clock genes in the epithelium of duodenum, jejunum, ileum, and colon of rat. Furthermore, we analysed the expression of genes coding sodium chloride transporters and channels as well as cell cycle regulators in colon. To focus more precisely on different structures of intestinal epithelia we used laser capture microdissection. In addition, we performed Ussing chamber measurements to determine the colonic electrogenic transport. To study the contribution of circadian...
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CIrcadian regulation of miRNA and clock-controlled genes in tumorigenesis
Balounová, Kateřina ; Pácha, Jiří (advisor) ; Bendová, Zdeňka (referee)
The circadian clock generates circadian rhythms, which participate on regulation of a number of signalling pathways. Disruption of the circadian regulatory mechanism is linked to a development and a progression of certain types of cancer including colorectal tumorigenesis. Progression of tumorigenesis depends on the cell cycle machinery related to cell proliferation and apoptosis. MiRNAs play a role in initiation and progression of tumorigenesis because they interfere in regulatory pathways associated with tumorigenesis. The aim of the thesis was to determinate existence of circadian rhytms in clock controlled genes (Tef, Dbp), miRNAs (miR-1-3p, miR-16-5p, miR-34a-5p, miR-155-5p, miR-192-3p) and genes of the cell cycle machinery (Ccnd1, Ccne1, Ccna1, Ccnb1) and apoptosis (Casp3, Bcl2, Bad). Further, to compare detected circadian rhythms during aging and neoplastic transformation of colon by quantitative RT-PCR. We have observed circadian expression of Tef, Dbp, Ccne1, Ccna1, Ccnb1, Casp3 and Bcl2 in young mice colon, Tef, Dbp, miR-1-3p, Ccne1, Ccna1 in old mice colon and Tef and Dbp in colorectal tumors. In summary, circadian expression of clock controlled genes varied but was maintained in mice colorectal tumors. In aging we demonstrated weakening of circadian rhythms of the genes of the cell...
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Circadian clocks in the brain and their function
Miklasová, Veronika ; Sumová, Alena (advisor) ; Kubová, Hana (referee)
In the brain, there is a center regulating circadian rhythms, which is located in the SCN. Outside these nuclei, there are other structures, which contribute significantly to coordination of circadian rhythms. Most of those nuclei are located in the hypothalamus and are connected with the SCN. These areas are involved in the management of basic physiological functions such as thermoregulation, food intake, sleep/wake cycles, hormonal secretion and control of locomotor activity. Outside the hypothalamus, there are other clocks, which work according to their location, e.g., clock in the limbic system participates in the control of cognitive functions. The olfactory lobe and retina harbor autonomous clocks that operate independently of the SCN. This work is focused on summary of the information about the selected extra- SCN oscillators in the brain their regulation of physiological functions. Key words: clock genes, circadian clocks, brain
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Role of intestinal circadian clock in epithelial transport, proliferation, and tumourigenesis
Soták, Matúš ; Pácha, Jiří (advisor) ; Bendová, Zdeňka (referee) ; Herichová, Iveta (referee)
AABBSSTTRRAACCTT The molecular circadian clock enables anticipation of environmental changes. In mammals, clocks are ubiquitously present in almost all tissues and they are comprised of transcriptional-translational feedback loops of the so-called clock genes. The central clock represents the intrinsic pacemaker which is located in suprachiasmatic nuclei (SCN) of hypothalamus and synchronizes peripheral clocks. Clockwork system in alimentary tract and its regulatory link to intestinal functions are poorly understood. Therefore the objective of the thesis was to characterize molecular clock in particular parts of the rat intestine and to elucidate its link to the intestinal transport, regulation of cell cycle and neoplastic transformation in colonic tissue. We used quantitative RT-PCR (qPCR) to determine circadian profiles of mRNA expression of clock genes in the epithelium of duodenum, jejunum, ileum, and colon of rat. Furthermore, we analysed the expression of genes coding sodium chloride transporters and channels as well as cell cycle regulators in colon. To focus more precisely on different structures of intestinal epithelia we used laser capture microdissection. In addition, we performed Ussing chamber measurements to determine the colonic electrogenic transport. To study the contribution of circadian...
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Role of microRNA in regulations of circadian rhythms and tumorigenesis
Balounová, Kateřina ; Pácha, Jiří (advisor) ; Červená, Kateřina (referee)
MicroRNAs (miRNAs) are ~22nt long single-strand RNA found in all groups of organisms, where they affect biochemical, physiological and behavioral pathways by regulation of protein expression. Regulation of protein expression is mediated by silencing mRNA of target genes in one of two processes, translation repression or degradation of mRNA. Changed expression of miRNA can lead to aberrant regulatory pathways resulting in various pathophysiological conditions like cardiovascular diseases, cancer or neurological disorders. MiRNA can play a role in cancer both as an oncogen or as a tumor suppressor, and it is tissue and cancer-type specific. In colorectal cancer miRNAs downregulate or upregulate signaling pathways including key processes involved in cancer development, like proliferation, cell cycle, apoptosis and metastasis formation. Circadian clock in mammals synchronizes cellular and physiological processes by transcriptional-translational feedback loops. Not only miRNAs regulate the levels of key clock genes and clock controlled genes, but also a number of miRNAs exhibit circadian expression. Therefore aberrant circadian rhythms increase risk of colorectal cancer also by altered expression of miRNAs. The main aim of the thesis was to identify miRNAs, which regulate both tumorigenesis and circadian...
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Circadian regulation of glucocorticoid secretion
Tejkal, Karel ; Sumová, Alena (advisor) ; Soták, Matúš (referee)
Glucocorticoids belong to a family of steroid hormones synthesized in the adrenal gland. They fulfill a variety of functions related to metabolism, immune response and ontogenesis. Glucocorticoids function as the end-effector of hypothalamic-pituitary-adrenal (HPA) axis and as such, their levels in blood are elevated after exposure to stressors. The basal levels of glucocorticoid also show a pronounced diurnal rhythm, suggesting involvement of the circadian clock in the regulation of HPA axis. Studies have shown that other regulatory mechanisms apart from the HPA axis are involved in regulation of diurnal glucocortioid secretion. The disturbances of the regulatory mechanisms may lead to serious pathological conditions. This thesis describes the rhythmic nature of glucocorticoid release and mechanisms by which the circadian clock exerts its influence over the rhythm. Thereafter, the feedback of glucocorticoids onto the clock system is briefly explained. Finally, some examples of a role of abnormal glucocorticoid secretion in selected pathologies are provided.
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Molecular and environmental factors connected to diapause and aging in insect
ZDECHOVANOVÁ, Lenka
Current models state that insect peripheral oscillators are directly responsive to light, while mammalian peripheral clock genes are coordinated by a master clock in the brain via intermediate factors, possibly hormonal. We show that the expression levels of two circadian clock genes, period (per) and Par Domain Protein 1 (Pdp1) in the peripheral tisue of an insect model species are inversely affected by contrasting photoperiods. The effect of photoperiod on per and Pdp1 mRNA levels was found to be mediated by the juvenile hormone. Our results provide the first experimental evidence for hormonal regulation of circadian clock gene expression in insects.
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