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Clock Genes in Glia Cells

View Article: PubMed Central - PubMed

ABSTRACT

Circadian rhythms are periodic patterns in biological processes that allow the organisms to anticipate changes in the environment. These rhythms are driven by the suprachiasmatic nucleus (SCN), the master circadian clock in vertebrates. At a molecular level, circadian rhythms are regulated by the so-called clock genes, which oscillate in a periodic manner. The protein products of clock genes are transcription factors that control their own and other genes’ transcription, collectively known as “clock-controlled genes.” Several brain regions other than the SCN express circadian rhythms of clock genes, including the amygdala, the olfactory bulb, the retina, and the cerebellum. Glia cells in these structures are expected to participate in rhythmicity. However, only certain types of glia cells may be called “glial clocks,” since they express PER-based circadian oscillators, which depend of the SCN for their synchronization. This contribution summarizes the current information about clock genes in glia cells, their plausible role as oscillators and their medical implications.

No MeSH data available.


Related in: MedlinePlus

Molecular mechanisms of the clock. The mammalian circadian oscillator is composed of an autoregulatory transcriptional network with two interlocked feedback loops: core and auxiliary. The CLOCK/BMAL1 heterodimer, the integral component of the core loop, induces E-box mediated transcription of the negative regulators Periods (PERs) and Cryptochromes (CRYs). Accumulated PER and CRY proteins intensively repress E-box mediated transcription until their levels have sufficiently decreased. Additionally, another regulatory loop is induced by CLOCK:BMAL1 activating transcription of the nuclear receptors RORa and Rev-erba, which modulate Bmal1 mRNA levels by competitive actions on the RRE element residing in the Bmal1 promoter. Collectively, the cycling of the clock components also determines the levels of the clock-controlled genes (CCGs) by transcription via the E-box or RRE to achieve their oscillating patterns and thus to generate rhythmic physiological output.
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fig1-1759091416670766: Molecular mechanisms of the clock. The mammalian circadian oscillator is composed of an autoregulatory transcriptional network with two interlocked feedback loops: core and auxiliary. The CLOCK/BMAL1 heterodimer, the integral component of the core loop, induces E-box mediated transcription of the negative regulators Periods (PERs) and Cryptochromes (CRYs). Accumulated PER and CRY proteins intensively repress E-box mediated transcription until their levels have sufficiently decreased. Additionally, another regulatory loop is induced by CLOCK:BMAL1 activating transcription of the nuclear receptors RORa and Rev-erba, which modulate Bmal1 mRNA levels by competitive actions on the RRE element residing in the Bmal1 promoter. Collectively, the cycling of the clock components also determines the levels of the clock-controlled genes (CCGs) by transcription via the E-box or RRE to achieve their oscillating patterns and thus to generate rhythmic physiological output.

Mentions: Another regulatory loop is mediated by the orphan nuclear receptors, the Retinoic Acid Receptor-Related Orphan Receptor α/β/γ (ROR α/β/γ) and the Reverse Erb α/β (Rev-erb α/β), that are responsible to activate and inhibit, respectively, transcription of Bmal1 through the retinoic acid Receptor Response Element (RRE) in its promoter, leading it to oscillate in a circadian manner (Figure 1; Preitner et al., 2002; Sato et al., 2004; Akashi and Takumi, 2005; Guillaumond et al., 2005).Figure 1.


Clock Genes in Glia Cells
Molecular mechanisms of the clock. The mammalian circadian oscillator is composed of an autoregulatory transcriptional network with two interlocked feedback loops: core and auxiliary. The CLOCK/BMAL1 heterodimer, the integral component of the core loop, induces E-box mediated transcription of the negative regulators Periods (PERs) and Cryptochromes (CRYs). Accumulated PER and CRY proteins intensively repress E-box mediated transcription until their levels have sufficiently decreased. Additionally, another regulatory loop is induced by CLOCK:BMAL1 activating transcription of the nuclear receptors RORa and Rev-erba, which modulate Bmal1 mRNA levels by competitive actions on the RRE element residing in the Bmal1 promoter. Collectively, the cycling of the clock components also determines the levels of the clock-controlled genes (CCGs) by transcription via the E-box or RRE to achieve their oscillating patterns and thus to generate rhythmic physiological output.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2 - License 3
Show All Figures
getmorefigures.php?uid=PMC5037500&req=5

fig1-1759091416670766: Molecular mechanisms of the clock. The mammalian circadian oscillator is composed of an autoregulatory transcriptional network with two interlocked feedback loops: core and auxiliary. The CLOCK/BMAL1 heterodimer, the integral component of the core loop, induces E-box mediated transcription of the negative regulators Periods (PERs) and Cryptochromes (CRYs). Accumulated PER and CRY proteins intensively repress E-box mediated transcription until their levels have sufficiently decreased. Additionally, another regulatory loop is induced by CLOCK:BMAL1 activating transcription of the nuclear receptors RORa and Rev-erba, which modulate Bmal1 mRNA levels by competitive actions on the RRE element residing in the Bmal1 promoter. Collectively, the cycling of the clock components also determines the levels of the clock-controlled genes (CCGs) by transcription via the E-box or RRE to achieve their oscillating patterns and thus to generate rhythmic physiological output.
Mentions: Another regulatory loop is mediated by the orphan nuclear receptors, the Retinoic Acid Receptor-Related Orphan Receptor α/β/γ (ROR α/β/γ) and the Reverse Erb α/β (Rev-erb α/β), that are responsible to activate and inhibit, respectively, transcription of Bmal1 through the retinoic acid Receptor Response Element (RRE) in its promoter, leading it to oscillate in a circadian manner (Figure 1; Preitner et al., 2002; Sato et al., 2004; Akashi and Takumi, 2005; Guillaumond et al., 2005).Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Circadian rhythms are periodic patterns in biological processes that allow the organisms to anticipate changes in the environment. These rhythms are driven by the suprachiasmatic nucleus (SCN), the master circadian clock in vertebrates. At a molecular level, circadian rhythms are regulated by the so-called clock genes, which oscillate in a periodic manner. The protein products of clock genes are transcription factors that control their own and other genes’ transcription, collectively known as “clock-controlled genes.” Several brain regions other than the SCN express circadian rhythms of clock genes, including the amygdala, the olfactory bulb, the retina, and the cerebellum. Glia cells in these structures are expected to participate in rhythmicity. However, only certain types of glia cells may be called “glial clocks,” since they express PER-based circadian oscillators, which depend of the SCN for their synchronization. This contribution summarizes the current information about clock genes in glia cells, their plausible role as oscillators and their medical implications.

No MeSH data available.


Related in: MedlinePlus