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Role of glucocorticoids in synchronization of fetal suprachiasmatic nuclei
Janáčová, Klára ; Sumová, Alena (advisor) ; Lužná, Vendula (referee)
The development and entrainment of fetal suprachiasmatic nuclei (SCN) are controlled by maternal cues, including hormones that cross through the placenta in a circadian rhythm. A recent study highlighted the effect of glucocorticoids (GC) on fetal SCN both in vitro and in vivo, where the application of the synthetic glucocorticoid, dexamethasone (DEX) in vivo regulated the c-Fos gene expression (Čečmanová et al., 2019). Using organotypic SCN explants from embryonic day 17 (E17) of a transgenic mPer2Luc mouse model, this research built on the initial study to further elucidate the action of GC upon in vitro application. Real-time recording of PER2-bioluminescence in E17 SCN explants confirmed that DEX increases the amplitude of E17 SCN explants, and DEX application at CT 15-18 leads to a phase advance of the rhythm. The specificity of the DEX effect was confirmed by application of the glucocorticoid receptor antagonist, mifepristone. Inhibition of the protein kinase A and C signalling pathways, which regulate c-Fos gene expression had no effect on DEX action in vitro in E17 SCN explants. No effect of DEX on PER2 protein turnover was observed. Using a newly optimized RNA isolation method followed by RT-qPCR, an increased level of c-Fos was detected in E17 SCN explants 1h after DEX application at CT...
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The role of posttranslational modifications in the molecular mechanism of the circadian clock
Janáčová, Klára ; Sumová, Alena (advisor) ; Sládek, Martin (referee)
The timing of the biological processes of organism is controlled by an endogenous circadian clock. The molecular clock is present in almost every cell and is synchronized with the external environment. The main mechanism of the clock is a transcription-translation feedback loop. The 24-hour circadian rhythm period is provided by reversible posttranslational modifications (PTMs) of the clock proteins and another regulators of the circadian clock. PTMs are further important for clock entrainment, their regulation by metabolic state in the cell, and reciprocal regulation of the circadian clock end cell cycle. Phosphorylation, histones PTMs, acetylation, SUMOylation, ubiquitination, O-linked N-acetylglucosamination and polyADP-ribosylation play a crucial role. The molecular mechanism of the biological clock is an evolutionarily conserved mechanism found in most organisms. This bachelor thesis summarizes the knowledge about the role of PTMs in the molecular mechanism of the mammalian and human circadian clocks. Key words: circadian clock, clock genes, clock proteins, posttranslational modifications
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