Circadian Rhythm of Dna Synthesis and Mitotic Activity in Tongue Keratinocytes

García, Marcela Nilda; Barbeito, CG; Andrini, L.A.; Badrán, Amado F.

doi:10.1006/cbir.2000.0585

Cited by 23 publications

(24 citation statements)

References 27 publications

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“…Previous studies have shown that cell mitosis occurs at a specific time of day in animal tissues in vivo (2)(3)(4)(47)(48)(49), suggesting that the timing of cell mitosis is gated by the circadian cycle. Therefore, we hypothesized that there would be a consistent phase relationship between the circadian and cellcycle rhythms in cultured cells.…”

Section: Resultsmentioning

confidence: 99%

“…These data suggest that it may be possible for the cell-cycle rhythm to be entrained to 24-h fluctuations in temperature in a rhythmic host environment. Discussion DNA synthesis, mitosis, and the expression of cell-cycle proteins in mammalian tissues (e.g., skin, bone marrow, gut, tongue, and oral mucosa) occur with a 24-h cycle in vivo (3)(4)(5)(49)(50)(51)(52)(53)(54)(55) and circadian periodicity of cell mitosis persists in rodents in constant darkness (2,5). Daily rhythms of cell-cycle protein expression (Cyclins E, A, and B1) were also observed in human oral epithelium sampled by biopsy at 4-h intervals for 24 h from healthy human subjects (3).…”

Section: Resultsmentioning

confidence: 99%

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Circadian-independent cell mitosis in immortalized fibroblasts

Yeom

Pendergast

Ohmiya

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Two prominent timekeeping systems, the cell cycle, which controls cell division, and the circadian system, which controls 24-h rhythms of physiology and behavior, are found in nearly all living organisms. A distinct feature of circadian rhythms is that they are temperaturecompensated such that the period of the rhythm remains constant (∼24 h) at different ambient temperatures. Even though the speed of cell division, or growth rate, is highly temperature-dependent, the cell-mitosis rhythm is temperature-compensated. Twenty-fourhour fluctuations in cell division have also been observed in numerous species, suggesting that the circadian system is regulating the timing of cell division. We tested whether the cell-cycle rhythm was coupled to the circadian system in immortalized rat-1 fibroblasts by monitoring cell-cycle gene promoter-driven luciferase activity. We found that there was no consistent phase relationship between the circadian and cell cycles, and that the cell-cycle rhythm was not temperature-compensated in rat-1 fibroblasts. These data suggest that the circadian system does not regulate the cell-mitosis rhythm in rat-1 fibroblasts. These findings are inconsistent with numerous studies that suggest that cell mitosis is regulated by the circadian system in mammalian tissues in vivo. To account for this discrepancy, we propose two possibilities: (i) There is no direct coupling between the circadian rhythm and cell cycle but the timing of cell mitosis is synchronized with the rhythmic host environment, or (ii) coupling between the circadian rhythm and cell cycle exists in normal cells but it is disconnected in immortalized cells.O rganization of physiology and behavior into specific time domains is a fundamental property of nearly all living organisms. Anticipation of periodic changes in the environment presumably increased survival and reinforced the development of endogenous circadian oscillators (1). Because cell division is critical to the survival of unicellular organisms and the integrity of DNA is susceptible to UV irradiation, the progression of the cell cycle was probably also strongly affected by daily changes in the environment. Indeed, multiple studies have measured diurnal fluctuations in cell division such that mitosis occurs at a specific time of day in numerous species ranging from unicellular organisms (2) to humans (3-5). These data suggest that the circadian and cell cycles may be coupled in vivo.Circadian rhythms are self-sustained oscillations in physiology and behavior with endogenous periods of ≈24 h that can be synchronized, or entrained, to environmental cues such as the light/dark cycle or temperature (6). In mammals, the master circadian clock is located in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. Genes that are important for circadian timekeeping are expressed not only in the SCN but also in many peripheral tissues, including fibroblasts (7-11). Immortalized embryonic fibroblasts exhibit circadian rhythms of gene expression (12) and, using singlecell imaging...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Circadian-independent cell mitosis in immortalized fibroblasts

Yeom

Pendergast

Ohmiya

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…In higher eukaryotes, however, a similar link between the two cellular clocks has not been widely reported, although there are some examples in the literature. Diurnal cycles of cell division have been observed in mammalian tongue and oral epithelia (24,63,153), gastrointestinal cells (24,29,125), epidermis (28), liver (79), bone marrow (185), and cornea (176). The molecular mechanisms by which the circadian clock may exert control over division in these various cell types have not been elucidated.…”

Section: Emerging Relationships Between the Circadian System And Cellmentioning

confidence: 99%

MAMMALIAN CIRCADIAN BIOLOGY: Elucidating Genome-Wide Levels of Temporal Organization

Lowrey

Takahashi

2004

Annu. Rev. Genom. Hum. Genet.

868

727

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During the past decade, the molecular mechanisms underlying the mammalian circadian clock have been defined. A core set of circadian clock genes common to most cells throughout the body code for proteins that feed back to regulate not only their own expression, but also that of clock output genes and pathways throughout the genome. The circadian system represents a complex multioscillatory temporal network in which an ensemble of coupled neurons comprising the principal circadian pacemaker in the suprachiasmatic nucleus of the hypothalamus is entrained to the daily light/dark cycle and subsequently transmits synchronizing signals to local circadian oscillators in peripheral tissues. Only recently has the importance of this system to the regulation of such fundamental biological processes as the cell cycle and metabolism become apparent. A convergence of data from microarray studies, quantitative trait locus analysis, and mutagenesis screens demonstrates the pervasiveness of circadian regulation in biological systems. The importance of maintaining the internal temporal homeostasis conferred by the circadian system is revealed by animal models in which mutations in genes coding for core components of the clock result in disease, including cancer and disturbances to the sleep/wake cycle.

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“…There are substantial evidences that progression through the cell cycle occurs at specific times of the day/night cycle, suggesting that a function of the circadian clock system is to control this fundamental process. 42,[48][49][50] Indeed, microarray analyses revealed that key elements of the cell cycle machinery including cyclin D1, cyclin B1, cyclin E, cyclin A, P53, Wee1, c-myc, Mdm2 and Gadd45 exhibit circadian-dependent expression (Table 2). 51 …”

Section: Clock-related Genes Regulate the Transcription Of Cell Cyclementioning

confidence: 99%

Cell “circadian” cycle: New role for mammalian core clock genes

Borgs¹,

Beukelaers²,

Vandenbosch³

et al. 2009

Cell Cycle

109

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In mammals, 24 hours rhythms are organized as a biochemical network of molecular clocks that are operative in all tissues, with the master clock residing in the hypothalamic suprachiasmatic nucleus (SCN). The core pacemakers of these clocks consist of auto-regulatory transcriptional/post-transcriptional feedback loops. Several lines of evidence suggest the existence of a crosstalk between molecules that are responsible for the generation of circadian rhythms and molecules that control the cell cycle progression. In addition, highly specialized cell cycle checkpoints involved in DNA repair after damage seem also, at least in part, mediated by clock proteins. Recent studies have also highlighted a putative connection between clock protein dysfunction and cancer progression. This review discusses the intimate relation that exists between cell cycle progression and components of the circadian machinery.

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Circadian Rhythm of Dna Synthesis and Mitotic Activity in Tongue Keratinocytes

Cited by 23 publications

References 27 publications

Circadian-independent cell mitosis in immortalized fibroblasts

Circadian-independent cell mitosis in immortalized fibroblasts

MAMMALIAN CIRCADIAN BIOLOGY: Elucidating Genome-Wide Levels of Temporal Organization

Cell “circadian” cycle: New role for mammalian core clock genes

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