NCBI Summary:
The protein encoded by this gene is a basic helix-loop-helix protein that forms a heterodimer with CLOCK. This heterodimer binds E-box enhancer elements upstream of Period (PER1, PER2, PER3) and Cryptochrome (CRY1, CRY2) genes and activates transcription of these genes. PER and CRY proteins heterodimerize and repress their own transcription by interacting in a feedback loop with CLOCK/ARNTL complexes. Defects in this gene have been linked to infertility, problems with gluconeogenesis and lipogenesis, and altered sleep patterns. Several transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2014]
General function
Nucleic acid binding, DNA binding, Transcription factor
Comment
Rev-erba regulates circadian rhythms and StAR expression in rat granulosa cells as identified by the agonist GSK4112. Chen H et al. The Rev-erba gene is regarded as a circadian clock gene and clock-regulated gene which regulates the circadian transcriptional/translational loop in a subtle way. Here, we first detected the circadian oscillation in mature granulosa cells from antral follicles using a real-time monitoring system of Per2 promoter activity with the addition of FSH. Then we used GSK4112, an agonist ligand of Rev-erba, to investigate the function of Rev-erba. GSK4112 treatment significantly reduced the Per2-dLuc amplitude and induced the Per2 oscillation phase advance shift. GSK4112 significantly inhibited Bmal1 mRNA expression, whereas it did clearly stimulate expression of StAR mRNA in a dose-dependent manner. Our data are the first to show the Rev-erba function in the steroid biosynthesis of rat granulosa cells, and to suggest that Rev-erba may coordinate circadian rhythm and metabolism in rat ovaries.
Cellular localization
Nuclear
Comment
Ovarian function
Follicle atresia, Steroid metabolism
Comment
Core clock gene Bmal1 deprivation impairs steroidogenesis in mice luteinized follicle cells. Wang Y et al. (2020) Luteinization is the event of corpus luteum formation, a way of follicle cells transformation and a process of steroidogenesis alteration. As the core clock gene, Bmal1 was involved in regulation of ovulation process and luteal function afterwards. Till now, the underlying roles of luteinization played by Bmal1 remain unknown. To explore the unique role of Bmal1 in luteal steroidogenesis and its underlying pathway, we investigated luteal hormone synthesis profile in Bmal1 knockout female mice. We found that luteal hormone synthesis was notably impaired, and phosphorylation of PI3K/NfκB pathway was significantly activated. Then, the results were verified in in vitro cultured cells, including isolated Bmal1 interference granulosa cells (GCs) and theca cells (TCs) respectively. Hormones levels of supernatant culture media and mRNA expressions of steroidogenesis-associated genes (star, Hsd3β2, cyp19a1 in GCs, Lhcgr, star, Hsd3β2, cyp17a1 in TCs) were mutually decreased, while the phosphorylation of PI3K/NfκB was promoted during in vitro luteinization. After PI3K specific-inhibitor LY294002 intervention, mRNA expressions of Lhcgr and Hsd32 were partially-rescued in Bmal1 interference TCs, together with significantly increased androstenedione and T synthesis. Further exploration in TCs demonstrated BMAL1 interacted directly but negatively with NfκB p65 (RelA), a subunit which was supposed as a mediator in Bmal1-governed PI3K signaling regulation. Taken together, we verified the novel role of Bmal1 in luteal steroidogenesis, achieving by negative interplay with RelA mediated PI3K/NfκB pathway.//////////////////
Bmal1 interference impairs hormone synthesis and promotes apoptosis in porcine granulosa cells. Wang W et al. (2017) In mammals, granulosa cell proliferation, differentiation, luteinization, apoptosis, and hormone synthesis are tightly related to oocyte maturation, follicular development and ovarian function. In current study, we investigated the role of the key circadian clock gene, brain and muscle arnt-like protein-1 (Bmal1), on porcine granulosa cell hormone secretion and apoptosis. The transcription levels of circadian clock genes, including Bmal1 and period circadian clock 2 (Per2), were detected by RT-qPCR. We found that the circadian clock genes exhibited rhythmic change and were further enhanced by dexamethasone synchronization in granulosa cells. Bmal1 knockdown reduced transcriptional levels of hormone receptor genes, including follicle stimulating hormone receptor (Fshr), luteinizing hormone/choriogonadotropin receptor (Lhcgr) and estrogen receptor 2 (Esr2), and decreased the mRNA and protein levels of cytochrome P450 family 11 subfamily A member 1 (Cyp11a1), cytochrome P450 family 19 subfamily A member 1 (Cyp19a1) and steroidogenic acute regulatory protein (Star), which are the key enzymes involved in hormone synthesis. Synthesis of progesterone and estradiol were also inhibited by Bmal1 siRNA treatment in granulosa cells. Moreover, flow cytometry analysis demonstrated suppressing Bmal1 promoted granulosa cells apoptosis. Western blot analysis showed that Bmal1 interference inactivated the PI3K/Akt/mTOR signaling pathway. In conclusion, Bmal1 plays a critical role in secretion of hormone and apoptosis of porcine granulosa cells via the PI3K/Akt/mTOR signaling pathway.//////////////////
Down-regulation of core clock gene Bmal1 attenuates expression of progesterone and prostaglandin biosynthesis-related genes in rat luteinizing granulosa cells. Chen H et al. Ovarian circadian oscillators have been implicated in the reproductive processes of mammals. However, there are few reports regarding the detection of ovarian clock-controlled genes (CCGs). The present study was designed to unravel the mechanisms through which CCGs ovarian circadian oscillators regulate fertility, primarily using quantitative RT-PCR and RNA interference against Bmal1 in rat granulosa cells. Mature granulosa cells were prepared from mouse Per2-destabilized luciferase (dLuc) reporter gene transgenic rats. A real-time monitoring system of Per2 promoter activity was employed to detect Per2-dLuc oscillations. The cells exposed to LH displayed clear Per2-dLuc oscillations and a rhythmic expression of clock genes (Bmal1, Per1, Per2, Rev-erba, and Dbp). Meanwhile, the examined ovarian genes (Star, Cyp19a1, Cyp11a1, Ptgs2, Lhcgr, and p53) showed rhythmic transcript profiles except for Hsd3b2, indicating that these rhythmic expression genes may be CCGs. Notably, Bmal1 siRNA treatment significantly decreased both the amplitude of Per2-dLuc oscillations and Bmal1 mRNA levels compared to non-silencing RNA treatment in luteinizing granulosa cells. Depletion of Bmal1 by siRNA decreased the transcript levels of clock genes (Per1, Per2, Rev-erba, and Dbp) and examined ovarian genes (Star, Cyp19a1, Cyp11a1, Ptgs2, Hsd3b2, and Lhcgr). Accordingly, knockdown of Bmal1 also inhibited the synthesis of progesterone and prostaglandin E2, which are associated with crucial reproductive processes. Collectively, these data suggest that ovarian circadian oscillators regulate the synthesis of steroid hormones and prostaglandins through ovarian-specific CCGs in response to LH stimuli. The present study provides new insights into the physiologic significance of Bmal1 related to fertility 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.
Expression regulated by
FSH, LH
Comment
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.
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
Theca
Comment
Found in an ovualtion array.
Expression of the clock genes Per1 and Bmal1 during follicle development in the rat ovary. Effects of gonadotropin stimulation and hypophysectomy. Gr?S et al. Daily oscillations of clock genes have recently been demonstrated in the ovaries of several species. Clock gene knockout or mutant mice demonstrate a variety of reproductive defects. Accumulating evidence suggests that these rhythms act to synchronise the expression of specific ovarian genes to hypothalamo-pituitary signals and that they are regulated by one or both of the gonadotropins. The aim of this study has been to examine the spatio-temporal expression of the clock genes Per1 and Bmal1 during gonadotropin-independent and gonadotropin-dependent follicle development in the rat ovary. We have examined the ovaries of prepubertal rats, of prepubertal rats stimulated with equine chorionic gonadotropin (eCG)/human chorionic gonadotropin (hCG) and of hypophysectomised adult animals. Using quantitative reverse transcription with the polymerase chain reaction, in situ hybridisation histochemistry and immunohistochemistry, we have demonstrated that the expression of the two clock genes is low and arrhythmic in ovarian cells during early gonadotropin-independent follicle development in prepubertal animals and in hypophysectomised animals. We have also demonstrated that the expression of the clock genes becomes rhythmic following eCG stimulation in the theca interna cells and the secondary interstitial cells and that, following additional hCG stimulation, the expression of the clock genes also becomes rhythmic in the granulosa cells of preovulatory follicles. These findings link the initiation of clock gene rhythms in the rat ovary to the luteinising hormone receptor and suggest a functional link to androgen and progesterone production. In hypophysectomised animals, rhythmic clock gene expression is also observed in the corpora lutea and in secondary interstitial cells demonstrating that, in these compartments, entrainment of clock gene rhythms is gonadotropin-independent.
Follicle stages
Comment
Phenotypes
Mutations
3 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: subfertile Comment: Reproductive biology of female Bmal1 null mice. Boden M et al. The light/dark cycle and suprachiasmatic nucleus rhythmicity are known to have important influences on reproductive function of rodents. We studied reproductive function in female heterozygous and homozygous Bmal1 null mice, which lack central and peripheral cellular rhythms. Heterozygous Bmal1 mice developed normally and were fertile, with apparent normal pregnancy progression and litter size, although postnatal mortality up to weaning was high (1.1 - 1.3/litter). The genotype distribution was skewed with both heterozygous and null genotypes underrepresented (1.0:1.7:0.7; P < 0.05), suggesting loss of a single Bmal1 allele may impact on post natal survival. Homozygous Bmal1 null mice were 30% lighter at weaning and while they grew at a similar rate to the wild type mice, they never achieved a comparable body weight. They had delayed vaginal opening (4 days), disrupted estrus cyclicity and reduced ovarian weight (30%). Bmal1 null mice had a 40% reduction in ductal length and a 43% reduction in ductal branches in the mammary gland. Surprisingly the Bmal1 mice ovulated, but progesterone synthesis was reduced in conjunction with altered corpora lutea formation. Pregnancy failed prior to implantation presumably due to poor embryo development. While Bmal1 null ovaries responded to PMSG/HCG stimulation, ovulation rate was reduced, the fertilised oocytes progressed poorly to blastocysts and failed to implant. The loss of Bmal1 gene expression resulted in a loss of rhythmicity of many genes in the ovary and downregulation of Steroidogenic acute regulatory protein (Star). In conclusion, it is clear that the profound infertility of Bmal1 null mice is multifactorial.
Species: mouse
Mutation name: None
type: null mutation fertility: subfertile Comment: Loss of BMAL1 in ovarian steroidogenic cells results in implantation failure in female mice. Liu Y 2014 et al.
The circadian clock plays a significant role in many aspects of female reproductive biology, including estrous cycling, ovulation, embryonic implantation, onset of puberty, and parturition. In an effort to link cell-specific circadian clocks to their specific roles in female reproduction, we used the promoter that controls expression of Steroidogenic Factor-1 (SF1) to drive Cre-recombinase-mediated deletion of the brain muscle arnt-like 1 (Bmal1) gene, known to encode an essential component of the circadian clock (SF1-Bmal1(-/-)). The resultant SF1-Bmal1(-/-) females display embryonic implantation failure, which is rescued by progesterone supplementation, or bilateral or unilateral transplantation of wild-type ovaries into SF1-Bmal1(-/-) dams. The observation that the central clock, and many other peripheral clocks, are fully functional in this model allows the assignment of the implantation phenotype to the clock in ovarian steroidogenic cells and distinguishes it from more general circadian related systemic pathology (e.g., early onset arthropathy, premature aging, ovulation, late onset of puberty, and abnormal estrous cycle). Our ovarian transcriptome analysis reveals that deletion of ovarian Bmal1 disrupts expression of transcripts associated with the circadian machinery and also genes critical for regulation of progesterone production, such as steroidogenic acute regulatory factor (Star). Overall, these data provide a powerful model to probe the interlocking and synergistic network of the circadian clock and reproductive systems.
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Species: mouse
Mutation name: type: null mutation fertility: subfertile Comment: Conditional deletion of Bmal1 in ovarian theca cells disrupts ovulation in female mice. Mereness AL et al. (2015) Rhythmic events in female reproductive physiology, including ovulation, are tightly controlled by the circadian timing system. The molecular clock, a feedback loop oscillator of clock gene transcription factors, dictates rhythms of gene expression in the hypothalamo-pituitary-ovarian axis (HPO). Circadian disruption due to environmental factors (e.g shift work) or genetic manipulation of the clock has negative impacts on fertility. Though the central pacemaker in the suprachiasmatic nucleus classically regulates the timing of ovulation, we have shown that this rhythm also depends on phasic sensitivity to luteinizing hormone (LH). We hypothesized that this rhythm depends on clock function in a specific cellular compartment of the ovarian follicle. To test this hypothesis we generated mice with deletion of the Bmal1 locus in ovarian granulosa cells (GCs; GCKO) or theca cells (TCs; TCKO). Reproductive cycles, pre-ovulatory LH secretion, ovarian morphology and behavior were not grossly altered in GCKO or TCKO mice. We detected phasic sensitivity to LH in wild-type littermate control (LC) and GCKO mice, but not TCKO mice. This decline in sensitivity to LH is coincident with impaired fertility and altered patterns of LH receptor (LHR; Lhcgr) mRNA abundance in the ovary of TCKO mice. These data suggest that the theca cell is a pacemaker that contributes to the timing and amplitude of ovulation by modulating phasic sensitivity to LH. The TC clock may play a critical role in circadian disruption-mediated reproductive pathology and could be a target for chronobiotic management of infertility due to environmental circadian disruption and/or hormone-dependent reprogramming in women.//////////////////