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Methods for the visualization of circadian rhythms: From molecules to organisms
Published in Raquel Seruca, Jasjit S. Suri, João M. Sanches, Fluorescence Imaging and Biological Quantification, 2017
Rukeia El-Athman, Jeannine Mazuch, Luise Fuhr, Mónica Abreu, Nikolai Genov, Angela Relógio
To elucidate whether clocks in other brain regions are operating independently from the SCN clock, bioluminescence imaging of the olfactory bulb in SCN intact and lesioned Per1:luc rats was performed in a daytime-dependent manner. By placing a sterile port and a glass window into the skull of the rat, imaging can be done at different time points around circadian cycles following the injection of D-luciferin via the port. Signals from reporter rats can be imaged with an ultrasensitive CCD camera device using In Vivo Imaging Systems (IVIS, Alameda, CA) and provided software (Living Image, Xenogen; Igor, WaveMetrics, Portland, OR) [81]. Commonly used for studying in vivo rhythms is the PER2::LUCIFERASE knock-in mouse that expresses a PER2::LUC fusion protein [83]. Injection of D-luciferin into anesthetized PER2::LUC reporter mice enables the imaging of circadian rhythms in peripheral tissues [84–86]. Bioluminescence is recorded by IVIS and analyzed by Living Image software (IVIS Kinetics; Caliper Life Sciences, Perkin Elmer), as illustrated in Figure 13.5.
The Biological Basis of Non-Image-Forming Vision
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
Activation of the retinohypothalamic tract stimulates SCN neurons, and increases their spike rate and intracellular calcium levels. The light-evoked increase in the intracellular calcium level seems to play a role in shifting molecular oscillations [Diekman et al. 2013]. The resistance of the clock gene induction (per1, per2) and the clock to the phase-shift during the subjective day (the low effect of light on the increase of the neuron spike rate in the SCN) may be due to the fact that intracellular calcium levels are stabilized at a high level during the day.
The potential interaction of environmental pollutants and circadian rhythm regulations that may cause leukemia
Published in Critical Reviews in Environmental Science and Technology, 2022
Francisco Alejandro Lagunas-Rangel, Błażej Kudłak, Wen Liu, Michael J. Williams, Helgi B. Schiöth
CML patients showed a significant reduction in the expression of CLOCK, BMAL1, PER2, and CRY1 compared to the expression levels in healthy controls (Table 1) (Rahman et al., 2017). In CML KCL22 cells, it was observed that the overexpression of the PER2 gene prevented its proliferation by modifying the number of cells in each phase of the cell cycle, increasing cells in G1 and decreasing in S/G2 (N. Wang et al., 2020). Meanwhile, in CML K562 cells, the overexpression of PER2 caused an arrest in the G2 phase of the cell cycle that later led to apoptosis as p53 levels increased and MYC and Cyclin B1 decreased. Thus, the tumors caused by these cells were smaller and with less infiltration in murine models (Sun et al., 2010). The PER2 promoter contains several potential binding sites for the CCAAT/enhancer-binding protein (C/EBP) transcription factors, and at least C/EBP alpha (C/EBPA) and C/EBP epsilon (C/EBPE) are known to bind directly at these sites and stimulate their expression, and where C/EBPA was notably the strongest transcriptional modulator. Likewise, the expression of C/EBP proteins could be regulated by circadian genes, which would represent a feedback loop that could be involved in the development of myeloid leukemias by inhibition of the granulocytic differentiation (Gery et al., 2005). Although BMAL1 oscillations are lost in CML cells, inhibition of SIRT1 has been shown to restore them, which also tells us that this protein plays an important role in "fine-tuning" the circadian clock (Rahman et al., 2017).
Zearalenone perturbs the circadian clock and inhibits testosterone synthesis in mouse Leydig cells
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Lijia Zhao, Yaoyao Xiao, Cuimei Li, Jing Zhang, Yaojia Zhang, Meina Wu, Tiantian Ma, Luda Yang, Xiaoyu Wang, Haizhen Jiang, Qian Li, Hongcong Zhao, Yiqun Wang, Aihua Wang, Yaping Jin, Huatao Chen
It was postulated that ZEA might inhibit testosterone synthesis by perturbing the circadian clock in mouse LCs. We examined the effects of ZEA on PER2::LUC oscillations in mouse primary LCs isolated from PER2::LUCIFERASE reporter gene knock in mice. In addition the influence of ZEA was assessed on the expression profiles of several canonical clock genes and steroidogenic genes, as well as testosterone synthesis in TM3 cells and primary LCs. Further, the in vivo consequences of ZEA exposure on the expression of core clock and steroidogenic genes in testes of mice as well as serum testosterone levels were determined.