NCBI Summary:
This gene is a member of the Period family of genes and is expressed in a circadian pattern in the suprachiasmatic nucleus, the primary circadian pacemaker in the mammalian brain. Genes in this family encode components of the circadian rhythms of locomotor activity, metabolism, and behavior. This gene is upregulated by CLOCK/ARNTL heterodimers but then represses this upregulation in a feedback loop using PER/CRY heterodimers to interact with CLOCK/ARNTL. Polymorphisms in this gene may increase the risk of getting certain cancers and have been linked to sleep disorders. [provided by RefSeq, Jan 2014]
General function
Nucleic acid binding, DNA binding, Transcription factor
Comment
Cellular localization
Nuclear
Comment
Ovarian function
Steroid metabolism
Comment
Integration of the nuclear receptor REV-ERBα linked with circadian oscillators in the expressions of Alas1, Ppargc1a, and Il6 genes in rat granulosa cells. Chen H et al. (2015) The nuclear receptor REV-ERBα links circadian rhythms and numerous physiological processes, but its physiological role in ovaries remains largely unknown. The aim of this study was to determine the potential role of REV-ERBα in the regulation of the transcription of its putative target genes in granulosa cells (GCs) prepared from Per2-destablized luciferase (dLuc) reporter gene transgenic rats. Alas1, Ppargc1a, and Il6 were chosen as representatives for genes analysis. A real-time monitoring system of Per2 promoter activity was performed to detect Per2-dLuc circadian oscillations. Two agonists (GSK4112, heme) and an antagonist (SR8278) of REV-ERBα as well as Rev-erbα siRNA knockdown were used to identify its target genes. Clear Per2-dLuc circadian oscillations were generated in matured GCs after synchronization with GSK4112 or SR8278. GSK4112 treatment lengthened and SR8278 treatment shortened the period of circadian oscillations in matured GCs stimulated with or without luteinizing hormone (LH). GSK4112 showed an inhibitory effect on the amplitude of circadian oscillations and caused an arrhythmic expression of canonical clock genes. SR8278 also had a subtle effect on their daily expression profiles, but the treatment resulted only in the arrhythmic expression of Rev-erbα. These findings indicate the functional biological activity of REV-ERBα in response to its ligands. Its natural ligand heme further elongated the period of circadian oscillations and alleviated their amplitudes in GCs cultured with LH. Heme treatment also repressed the expressions of clock genes, Alas1, Il6, and Ppargc1a. Rev-erbα knockdown up-regulated these transcript levels. Collectively, these data extend the recent finding to rat GCs and demonstrate that REV-ERBα represses the expressions of Alas1, Ppargc1a, and Il6, providing novel insights into the physiological significance of REV-ERBα in ovarian circadian oscillators.//////////////////
Circadian clock gene regulation of steroidogenic acute regulatory protein gene expression in pre-ovulatory ovarian follicles. Nakao N et al. It is now known that circadian clocks are localized not only in the central pacemaker but also in peripheral organs. An example of a clock-dependent peripheral organ is the ovary of domestic poultry where ovulation is induced by the positive feed-back action of ovarian progesterone on the neuroendocrine system to generate a pre-ovulatory release of LH during a daily 6-10 hr 'open period' of the ovulatory cycle. It has previously been assumed that the timing of ovulation in poultry is controlled solely by a clock-dependent mechanism within neuroendocrine system. Here, we question this assumption by demonstrating the expression of the clock genes, Per2 and 3, Clock and Bmal1 in pre-ovulatory follicles in laying quail. Diurnal changes in Per2 and 3 expression were seen in the largest pre-ovulatory follicle (F1), but not in smaller follicles. We next sought to identify clock-driven genes in pre-ovulatory follicles focusing on those involved in the synthesis of progesterone. One such gene was identified, encoding steroidogenic acute regulatory protein (StAR), which showed 24 hr changes in expression in the F1 follicle coinciding with those of Per2. Evidence that StAR gene expression is clock-driven was obtained by showing that its 5' flanking region contains E-box enhancers, which bind to CLOCK/BMAL1 heterodimers to activate gene transcription. We also showed that LH administration increased the promoter activity of chicken StAR. We therefore suggest that the timing of ovulation in poultry involves a LH- responsive F1 follicular clock that is involved in the timing of the pre-ovulatory release of progesterone.
Circadian Clock genes Per2 and clock regulate steroid production, cell proliferation, and luteinizing hormone receptor transcription in ovarian granulosa cells. Shimizu T et al. Circadian Clock genes are associated with the estrous cycle in female animals. Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression in follicle-stimulating hormone FSH-treated granulosa cells. Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom, whereas Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. Similarly, expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. Our data provide a new insight that Per2 and Clock have different action on ovarian granulosa cell functions.
Expression regulated by
FSH, LH, Steroids, T3, androgen
Comment
Effect of lipopolysaccharide on circadian clock genes Per2 and Bmal1 in mouse ovary. Shimizu T et al. (2017) In mammals, circadian rhythms are associated with multiple physiological events. The aim of the present study was to examine the effect of lipopolysaccharide (LPS) on circadian systems in the ovary. Immature female mice were received an intra-peritoneal injection of equine chorionic gonadotropin (eCG) and LPS. Total RNA was collected from the ovary at 6-h intervals throughout a 48 h of experimental period. The expression of the circadian genes period 2 (Per2) and brain and muscle ARNT-like 1 (Bmal1) such as circadian genes was measured by quantitative PCR. Although expression of Per2 and Bmal1 in the ovary did not display clear diurnal oscillation, LPS suppressed the amplitude of Per2 expression. Additionally, LPS inhibited the expression of cytochrome P450 aromatase (CYP19) and luteinizing hormone receptor (LHr) genes in the ovary of eCG-treated mice. Our data suggest that Per2 may be associated with the inhibition of CYP19 and LHr expression by LPS in the ovaries of immature mice.//////////////////
Expression pattern of circadian genes and steroidogenesis-related genes after testosterone stimulation in the human ovary. Chen M et al. (2016) Previous studies have shown that circadian genes might be involved in the development of polycystic ovarian syndrome (PCOS). Hyperandrogenism is a hallmark feature of PCOS. However, the effect of hyperandrogenism on circadian gene expression in human granulosa cells is unknown, and the general expression pattern of circadian genes in the human ovary is unclear. Expression of the circadian proteins CLOCK and PER2 in human ovaries was observed by immunohistochemistry. The mRNA expression patterns of the circadian genes CLOCK, PER2, and BMAL1, and the steroidogenesis-related genes STAR, CYP11A1, HSD3B2, and CYP19A1 in cultured human luteinized granulosa cells were analyzed over the course of 48 h after testosterone treatment by quantitative polymerase chain reaction. Immunostaining of CLOCK and PER2 protein was detected in the granulosa cells of dominant antral follicles but was absent in the primordial, primary, or preantral follicles of human ovaries. After testosterone stimulation, expression of PER2 showed an oscillating pattern, with two peaks occurring at the 24th and 44th hours; expression of CLOCK increased significantly to the peak at the 24th hour, whereas expression of BMAL1 did not change significantly over time in human luteinized granulosa cells. Among the four steroidogenesis-related genes evaluated, only STAR displayed an oscillating expression pattern with two peaks occurring at the 24th and 40th hours after testosterone stimulation. Circadian genes are expressed in the dominant antral follicles of the human ovary. Oscillating expression of the circadian gene PER2 can be induced by testosterone in human granulosa cells in vitro. Expression of STAR also displayed an oscillating pattern after testosterone stimulation. Our results indicate a potential relationship between the circadian clock and steroidogenesis in the human ovary, and demonstrate the effect of testosterone on circadian gene expression in granulosa cells.//////////////////
FSH induces the development of circadian clockwork in rat granulosa cells via a gap junction protein Cx43-dependent pathway. Chen H et al. The present study was designed to assess the relationship between gap junctions and the maturation of a clock system in rat granulosa cells stimulated by FSH. Immature and mature granulosa cells were prepared by puncturing the ovaries of diethylstilbestrol- and equine chorionic gonadotropin (eCG)-treated mouse Period2 (Per2)-dLuc reporter gene transgenic rats, respectively. Mature granulosa cells exposed to dexamethasone (DXM) synchronization displayed several Per2-dLuc oscillations and a rhythmic expression of clock genes. Intriguingly, we observed clear evidence that the FSH stimulation significantly increased the amplitude of Per2 oscillations in the granulosa cells, which was confirmed by the elevation of the Per2 and Rev-erba (Nr1d1) mRNA levels. FSH also induced a major phase-advance shift of Per2 oscillations. The mature granulosa cells cultured for 2 d with FSH expressed higher mRNA level of Per2, Rev-erba, Bmal1 (Arnt1), Lhcgr, and Cx43 (Gja1) compared to the immature granulosa cells. Consistently, our immunofluorescence results revealed abundant Cx43 protein in antral follicles stimulated with eCG, and weak or no fluorescence signal of Cx43 in primary and preantral follicles. Similar results were confirmed by western blotting analysis. Two gap junction blockers, lindane and carbenoxolone (CBX), significantly decreased the amplitude of Per2 oscillations, which further adhered significant decreases in Per2 and Rev-erba transcript levels. In addition, both lindane and CBX induced a clear phase-delay shift of Per2 oscillations. These findings suggest that FSH induces the development of the clock system by increasing the expression of Cx43.
Contribution of FSH and triiodothyronine to the development of circadian clocks during granulosa cell maturation. Chu G et al. The involvement of FSH and triiodothyronine (T3) in the circadian clocks was investigated using immature granulosa cells of ovaries during the progress of cell maturation. The granulosa cells were prepared from preantral follicles of mouse Period2 (Per2)-dLuc reporter gene transgenic rats injected subcutaneously with a synthetic nonsteroidal estrogen diethylstilbestrol. The analysis of the cellular clock of the immature granulose cells was performed partly using a serum-free culture system. Several bioluminescence oscillations of Per2-dLuc promoter activity were generated in the presence of FSH + fetal bovine serum, but not in the presence of either FSH or serum. As revealed by bioluminescence recording and analysis of clock gene expression, the granulosa cells lack the functional cellular clock at the immature stage, although Lhr was greatly expressed during the period of cell maturation. The granulosa cells gained a strong circadian rhythm of bioluminescence during stimulation with FSH, whereas LH reset the cellular clock of matured granulosa cells. During strong circadian rhythms of clock genes, the Star gene showed a significant expression in matured granulosa cells. In contrast, T3 showed an inhibitory effect on the development of the functional cellular clock during the period of cell maturation. These results indicate that FSH provides a cue for the development of the functional cellular clock of the immature granulosa cells, and T3 blocks the development of the cellular clock.
Influence of the Estrous Cycle on Clock Gene Expression in Reproductive Tissues: Effects of Fluctuating Ovarian Steroid Hormone Levels. Nakamura TJ et al. Circadian rhythms in physiology and behavior are known to be influenced by the estrous cycle in female rodents. The clock genes responsible for the generation of circadian oscillations are widely expressed both within the central nervous system and peripheral tissues, including those that comprise the reproductive system. To address whether the estrous cycle affects rhythms of clock gene expression in peripheral tissues, we first examined rhythms of clock gene expression (Per1, Per2, Bmal1) in reproductive (uterus, ovary) and non-reproductive (liver) tissues of cycling rats using quantitative real-time PCR (in vivo) and luminescent recording methods to measure circadian rhythms of PER2 expression in tissue explant cultures from cycling PER2::LUCIFERASE (PER2::LUC) knockin mice (ex vivo). We found significant estrous variations of clock gene expression in all three tissues in vivo, and in the uterus ex vivo. We also found that exogenous application of estrogen and progesterone altered rhythms of PER2::LUC expression in the uterus. In addition, we measured the effects of ovarian steroids on clock gene expression in a human breast cancer cell line (MCF-7 cells) as a model for endocrine cells that contain both the steroid hormone receptors and clock genes. We found that progesterone, but not estrogen, acutely up-regulated Per1, Per2, and Bmal1 expression in MCF-7 cells. Together, our findings demonstrate that the timing of the circadian clock in reproductive tissues is influenced by the estrous cycle and suggest that fluctuating steroid hormone levels may be responsible, in part, through direct effects on the timing of clock gene expression.
The Luteinizing Hormone Surge Regulates Circadian Clock Gene Expression in the Chicken Ovary. Tischkau SA et al. The molecular circadian clock mechanism is highly conserved between mammalian and avian species. Avian circadian timing is regulated at multiple oscillatory sites, including the retina, pineal, and hypothalamic suprachiasmatic nucleus (SCN). Based on the authors' previous studies on the rat ovary, it was hypothesized that ovarian clock timing is regulated by the luteinizing hormone (LH) surge. The authors used the chicken as a model to test this hypothesis, because the timing of the endogenous LH surge is accurately predicted from the time of oviposition. Therefore, tissues can be removed before and after the LH surge, allowing one to determine the effect of LH on specific clock genes. The authors first examined the 24-h expression patterns of the avian circadian clock genes of Bmal1, Cry1, and Per2 in primary oscillatory tissues (hypothalamus and pineal) as well as peripheral tissues (liver and ovary). Second, the authors determined changes in clock gene expression after the endogenous LH surge. Clock genes were rhythmically expressed in each tissue, but LH influenced expression of these clock genes only in the ovary. The data suggest that expression of ovarian circadian clock genes may be influenced by the LH surge in vivo and directly by LH in cultured granulosa cells. LH induced rhythmic expression of Per1 and Bmal1 in arrhythmic, cultured granulosa cells. Furthermore, LH altered the phase and amplitude of clock gene rhythms in serum-shocked granulosa cells. Thus, the LH surge may be a mechanistic link for communicating circadian timing information from the central pacemaker to the ovary. (Author correspondence: stischkau@siumed.edu).
Ovarian localization
Granulosa, Luteal cells
Comment
Alterations of Circadian Clockworks During Differentiation and Apoptosis of Rat Ovarian Cells. Chu G et al. Ovarian development is related to cell proliferation, differentiation, and apoptosis of granulosa cells and luteal cells under the control of various modulators, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), and growth factors. In the present study, the expression of clock genes and the related regulation mechanism were analyzed in different ovarian cell types during differentiation and apoptosis. The authors focused on the circadian expression of Per2 as a core clock gene for the maintenance of circadian rhythms. By using a real-time monitoring system of the Per2 promoter activity, the circadian oscillation was analyzed in the granulosa and luteal cells from preantral follicles, antral follicles, and corpora lutea of immature Per2 promoter-destabilized luciferase transgenic rats that were primed with diethylstilbestrol, equine chorionic gonadotropin (eCG), and/or human CG. In addition, transcript levels of Per2, Bmal1, Clock, and Nampt were quantified by quantitative polymerase chain reaction (qPCR). Immunohistochemical studies revealed strong circadian rhythmicity of PER2 protein in the luteal cells, but apparently little rhythmicity in granulosa cells of both preantral and antral follicles. In vitro monitoring of promoter activity showed generation of several oscillations in luteal cells after exposure to dexamethasone (DXM), whereas oscillatory amplitudes of immature and mature granulosa cells were rapidly attenuating. The circadian rhythm of the Bmal1 transcript levels, but not the Per2 transcript, was very weak in the granulosa cells, as compared with that in luteal cells. Granulosa cells gained a strong circadian rhythm ability of the Per2 promoter activity after stimulation with FSH for 3 days. In contrast, LH had little effect on the circadian rhythm before stimulation of granulosa cells with FSH, probably owing to lack of LH receptor. In luteal cells, induction of apoptosis by inhibiting progesterone synthesis resulted in deregulation of Per2 circadian oscillation. Transcript levels of Bmal1 and Clock, but not Per2 and Nampt, were significantly decreased in apoptotic luteal cells. The Bmal1 transcript level was particularly reduced. Consequently, these results strongly suggest the circadian clockwork alters in ovarian cells during follicular development, luteinization, and apoptosis, and expression of Bmal1 may be related to the switch-on and switch-off of the circadian oscillation. (Author correspondence: mhattori@agr.kyushu-u.ac.jp ).
Circadian Clock Gene Expression in the Ovary: Effects of Luteinizing Hormone. Karman BN et al. A molecular device that measures time on a daily, or circadian, scale is a nearly ubiquitous feature of eukaryotic organisms. A core group of clock genes, whose coordinated function is required for this timekeeping, is expressed both in the central clock and within numerous peripheral organs. We examined expression of clock genes in the rat ovary. Transcripts for core oscillator elements (Arntl, Clock, Per1, Per2, Cry1) were present in the ovary as indicated by quantitative real-time RT-PCR. Rhythmic expression patterns of Arntl and Per2 transcripts and protein products were out-of-phase with respect to the central oscillator and in complete anti-phase to each other. Expression of Arntl was significantly elevated after the LH surge on the day of proestrus. Finally, human chorionic gonadotropin (hCG) treatment induced cyclic expression of both Arntl and Per2 gene products in hypophysectomized, immature rats primed with pregnant mares serum gonadotropin (eCG). Collectively, these data suggest that the core underpinnings of the transcriptional/translational feedback loop that drives circadian rhythmicity is present in the rat ovary. Furthermore, the study identifies luteinizing hormone (LH) as a potential regulator of circadian clock gene rhythms in the ovary.
Follicle stages
Preovulatory, Corpus luteum
Comment
The disruption of circadian clockwork in differentiating cells from rat reproductive tissues as identified by in vitro real-time monitoring system. He PJ et al. The circadian clock, regulating hormonal secretion and metabolisms in accordance with the environmental light-dark cycle, resides in almost all peripheral tissues as well as in the superchiasmatic nucleus. Clock gene expression has been found to be noncyclic during spermatogenesis and the differentiation of thymocytes. However, currently little is known about how cell differentiation could affect circadian clockwork. We performed this study using the in vitro real-time oscillation monitoring system to examine the clockwork in several types of differentiating cells originated from reproductive tissues of transgenic rats (constructed with Period gene 2 (Per2) promoter-destabilized luciferase reporter gene). After treatment with dexamethasone (DXM), persistent oscillation of Per2 expression was observed in both gonadotropin-induced and pregnant ovarian luteal cells, proliferative uterine stromal cells (USCs), and nondifferentiating testicular interstitial cells, with a cyclic period of ~24 h. In contrast to these cell types, only one cycle of oscillation was sustained in granulosa cells undergoing differentiation. Additionally, Per2 oscillation was irregular in USCs undergoing decidualization induced by medroxyprogesterone acetate plus N6, 2-O-dibutyryl adenosine 3':5'-cyclic monophosphate. Furthermore, no oscillation of Per2 expression was evoked by DXM in Leydig cells and thymocytes. In conclusion, the present study characterized the oscillation of Per2 gene expression in several types of ovarian, uterine, and testicular cells, and it is strongly suggested that circadian clockwork is affected during cellular differentiation.
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: type: None fertility: fertile Comment: Developmental Programming by Androgen Affects the Circadian Timing System in Female Mice. Mereness AL et al. (2015) Circadian clocks play essential roles in the timing of events in the mammalian hypothalamo-pituitary-ovarian (HPO) axis. The molecular oscillator driving these rhythms has been localized to tissues of the HPO axis. It has been suggested that synchrony among these oscillators is a feature of normal reproductive function. The impact of fertility disorders on clock function and the role of the clock in the etiology of endocrine pathology remain unknown. Polycystic ovary syndrome (PCOS) is a particularly devastating fertility disorder, affecting 5-10% of women at childbearing age with features including a polycystic ovary, anovulation and elevated serum androgen. Approximately 40% of these women have metabolic syndrome, marked by hyperinsulinemia, dyslipidemia and insulin resistance. It has been suggested that developmental exposure to excess androgen contributes to the etiology of fertility disorders including PCOS. In an effort to better define the role of the timing system in these disorders we have determined the effects of androgen-dependent developmental programming on clock gene expression in tissues of the metabolic and HPO axes. Female PERIOD2:luciferase (PER2::LUC) mice were exposed to androgen [dihydrotestosterone; DHT] in utero (days 16-18 of gestation) or for 9-10 weeks (DHT pellet) beginning at weaning (pubertal androgen excess; PAE). As expected, both groups of androgen-treated mice had disrupted estrous cycles. Analysis of PER2::LUC expression in tissue explants reveals that excess androgen produced circadian misalignment via tissue-dependent effects on phase distribution. In vitro treatment with DHT differentially affected the period of PER2::LUC expression in tissue explants and granulosa cells, indicating that androgen has direct and tissue specific effects on clock gene expression that may account for the effects of developmental programming on the timing system.//////////////////