Fos-related antigen 2 (Fra-2) memorizes photoperiod in the rat pineal gland

The Drosophila circadian phase response curve to light: Conservation across seasonally relevant photoperiods and anchorage to sunset

Photic history, including the relative duration of day versus night in a 24-hour cycle, is known to influence subsequent circadian responses to light in mammals. Whether such modulation is present in Drosophila is currently unknown. To date, all photic phase-response curves (PRCs) generated from Drosophila have done so with animals housed under seasonally agnostic equatorial photoperiods with alternating 12-hour segments of light and darkness. However, the genus contains thousands of species, some of which populate high and low-latitude habitats (20-50° north or south of the Equator) where seasonal variations in the light-dark schedule are pronounced. Here, we address this disconnect by constructing the first high-resolution Drosophila seasonal atlas for light-induced circadian phase-resetting. Testing the light responses of over 4,000 Drosophila at 120 timepoints across 5 seasonally-relevant rectangular photoperiods (i.e., LD 8:16, 10:14, 12:12, 14:10, and 16:8; 24 hourly intervals surveyed in each), we determined that many aspects of the fly circadian PRC waveform are conserved with increasing daylength. Surprisingly though, irrespective of LD schedule, the start of the PRCs always remained anchored to the timing of subjective sunset, creating a differential overlap of the advance zone with the morning hours after subjective sunrise that was maximized under summer photoperiods and minimized under winter photoperiods. These data suggest that there may be differences in flies versus mammals as to how the photoperiod modulates the waveform and amplitude of the circadian PRC to light. On the other hand, they support the possibility that the lights-off transition determines the phase-positioning of photic PRCs across seasons and across species. More work is necessary to test this claim and whether it might factor into the timing of seasonal light responses in humans.

Fra-2 overexpression upregulates pro-metastatic cell-adhesion molecules, promotes pulmonary metastasis, and reduces survival in a spontaneous xenograft model of human breast cancer

Purpose

The transcription factor Fra-2 affects the invasive potential of breast cancer cells by dysregulating adhesion molecules in vitro. Previous results suggested that it upregulates the expression of E- and P-selectin ligands. Such selectin ligands are important members of the leukocyte adhesion cascade, which govern the adhesion and transmigration of cancer cells into the stroma of the host organ of metastasis. As so far, no in vivo data are available, this study was designed to elucidate the role of Fra-2 expression in a spontaneous breast cancer metastasis xenograft model.

Methods

The effect of Fra-2 overexpression in two stable Fra-2 overexpressing clones of the human breast cancer cell line MDA MB231 on survival and metastatic load was studied after subcutaneous injection into scid and E- and P-selectin-deficient scid mice.

Results

Fra-2 overexpression leads to a significantly shorter overall survival and a higher amount of spontaneous lung metastases not only in scid mice, but also in E- and P-deficient mice, indicating that it regulates not only selectin ligands, but also selectin-independent adhesion processes.

Conclusion

Thus, Fra-2 expression influences the metastatic potential of breast cancer cells by changing the expression of adhesion molecules, resulting in increased adherence to endothelial cells in a breast cancer xenograft model.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03812-2.

Role of linc00174/miR-138-5p (miR-150-5p)/FOSL2 Feedback Loop on Regulating the Blood-Tumor Barrier Permeability

The blood-tumor barrier (BTB) limits the transport of chemotherapeutic drugs to brain tumor tissues and impacts the treatment of glioma. Long non-coding RNAs play critical roles in various biological processes of tumors; however, the function of these in BTB permeability is still unclear. In this study, we have identified that long intergenic non-protein coding RNA 174 (linc00174) was upregulated in glioma endothelial cells (GECs) from glioma tissues. Additionally, linc00174 was also upregulated in GECs from the BTB model in vitro. Knock down of linc00174 increased BTB permeability and reduced the expression of the tight junction-related proteins ZO-1, occludin, and claudin-5. Both bioinformatics data and results of luciferase reporter assays demonstrated that linc00174 regulated BTB permeability by binding to miR-138-5p and miR-150-5p. Furthermore, knock down of linc00174 inhibited FOSL2 expression via upregulating miR-138-5p and miR-150-5p. FOSL2 interacted with the promoter regions and upregulated the promoter activity of ZO-1, occludin, claudin-5, and linc00174 in GECs. In conclusion, the present study demonstrated that the linc00174/miR-138-5p (miR-150-5p)/FOSL2 feedback loop played an essential role in regulating BTB permeability.

Endothelial Regeneration of Large Vessels Is a Biphasic Process Driven by Local Cells with Distinct Proliferative Capacities

The cellular and mechanistic bases underlying endothelial regeneration of adult large vessels have proven challenging to study. Using a reproducible in vivo aortic endothelial injury model, we characterized cellular dynamics underlying the regenerative process through a combination of multi-color lineage tracing, parabiosis, and single-cell transcriptomics. We found that regeneration is a biphasic process driven by distinct populations arising from differentiated endothelial cells. The majority of cells immediately adjacent to the injury site re-enter the cell cycle during the initial damage response, with a second phase driven by a highly proliferative subpopulation. Endothelial regeneration requires activation of stress response genes including Atf3, and aged aortas compromised in their reparative capacity express less Atf3. Deletion of Atf3 reduced endothelial proliferation and compromised the regeneration. These findings provide important insights into cellular dynamics and mechanisms that drive responses to large vessel injury.

MicroRNA (miR)-597-5p Inhibits Colon Cancer Cell Migration and Invasion by Targeting FOS-Like Antigen 2 (FOSL2)

Our previous work had shown that FOS-like antigen 2 (FOSL2) is regulated by miR-143-5p in colorectal cancer (CRC). Given that it has been shown by others that FOSL2 is also a target of miR-597-5p in breast adenocarcinoma, the objective of the current work was to determine whether FOSL2 is regulated by miR-597-5p in CRC and the role of miR-597-5p in CRC. MiR-597-5p expression was determined in RNA obtained from 30 paired samples of colon cancer and tumor adjacent normal tissue, as well as in the LoVo (CRC cell line) and FHC (normal colonic epithelial cells) by quantitative real time polymerase chain reaction (qRT-PCR). MiR-597-5p expression was significantly downregulated in both CRC tissue and LoVo cells. Reporter assays using wild-type and miR-597-5p seed mutant FOSL2 confirmed that FOSL2 is a bona fide target of miR-597-5p. Modulating miR-597-5p expression levels in FHC and LoVo cells using antagomir and mimic, respectively, impacted expression of epithelial and mesenchymal cell markers as well as in vitro migration and invasion, without any effect on cell proliferation, showing that miR-597-5p functions as a suppressor of epithelial to mesenchymal transition. Restoration of FOSL2 expression rescued pro-metastatic functional properties of LoVo cells conforming that effect of miR-597-5p was being mediated by targeting FOSL2. Xenograft assays in athymic nude mice showed that miR-597-5p mimic did not reduce tumor incidence or growth in LoVo cells. However, using a hepatic metastasis model showed that miR-597-5p mimic can significantly prevent hepatic metastatic nodule formation as well as FOSL2 expression in these metastatic nodules. Importantly, FOSL2 mRNA and miR-597-5p expression was found to be inversely correlated in an independent cohort of 21 CRC patients Cumulatively our results show that miR-597-5p functions as a suppressor of metastatic progression in CRC by targeting FOSL2. Replenishment of miR-597-5p can be a potential therapeutic target where its expression along with FOSL2 can serve as potential diagnostic markers in CRC.

Fos-like antigen 2 (FOSL2) promotes metastasis in colon cancer

Among different cancers, incidence and mortality of colorectal cancer (CRC) is one of the highest. KRAS mutation is one of the underlying features in the pathogenesis of CRC with CRC tumors harboring mutant KRAS exhibiting a more aggressive behavior compared to CRC tumors with wild type KRAS. We had earlier shown that the microRNA-143 (miR-143) replenishment not only chemosensitizers CRC cell line with mutant KRAS instead of wild-type KRAS gene, to paclitaxel-mediated cytotoxicity, but also inhibits cell migration and invasion ability. Hence, the study aimed to determine how miR-143 replenishment is inhibiting pre-metastatic behavior in CRC cells with mutant KRAS. Top ten mRNA targets of miR-143 as predicted by TargetScan were evaluated by qRT-PCR in LoVo cells which were performed mock transfection or miR-143 mimic transfection. Evaluation of the changes in cognate mRNA target(s) was done in 30 paired CRC tissue and tumor adjacent normal tissue specimens and in LoVo cells by western blot. Effect of the mRNA target on pro-metastatic behavior was assayed by gain- and loss-of-function studies using a combination of western blotting and in vitro cell proliferation and transwell migration/invasion assay in LoVo cells and in the normal colonic epithelium cell line FHC. In vivo effect of the cognate mRNA target on CRC metastasis was assayed by xenograft assay. Of the 10 predicted mRNA targets, FOSL2 (P < 0.05) and IGFBP5 (P > 0.05) was down regulated in LoVo cells transfected with the miR-143 mimic. FOSL2 mRNA levels were significantly downregulated in CRC tissue specimens compared with adjacent normal tissue (P < 0.05). Immunoblot analysis showed that FOSL2, but not IGFBP5, protein expression is down regulated in LoVo cells after the miR-143 mimic transfection. FOSL2 overexpression in the normal colonic epithelial cell line FHC or siRNA-mediated silencing in LoVo cells induced and repressed, respectively, pro-mesenchymal cell features. Whereas manipulation of FOSL2 expression did not have any effect on cell proliferation rates, silencing its expression inhibited cell migration and invasion ability in vitro. In addition, silencing of FOSL2 expression in the LoVo cells can significantly inhibited invasion of hepatic, while no effect was found for tumorigenic potential. Our results suggest that FOSL2 is a critical regulator of CRC metastasis and might be an important marker for prognostic in CRC patients.

miR-597 inhibits breast cancer cell proliferation, migration and invasion through FOSL2

Many reports suggest that the discovery of microRNAs (miRNAs) might provide a novel therapeutical target for many diseases, even of human cancers; however, there are no reports on the role of miR-597 in human cancers. In the present study, by detecting mRNA expression with qRT-PCR, compared with the adjacent normal tissues we found that miR-597 was significantly downregulated in breast cancer tissues. By using the MTT assay, the cell wound-healing assay and the cell invasion assay, we demonstrated that miR-597 mimics were able to suppress breast cancer cell proliferation, migration and invasion. Additionally, with flow cytometry, we found that miR-597 influenced the growth of breast cancer cells through regulating the G1-S phase transition. Furthermore, we identified one binding site for miR-597 at the 3′UTR of the FOSL2 gene, using bioinformatics methods and the luciferase reporter assay, it was confirmed that FOSL2 was a direct target of miR-597. Moreover, overexpression of FOSL2 in MDA-MB-231 and SK-BR-3 cells can block the vast majority of the miR-597 roles, suggesting that miR-597 acts as a tumor suppressor in breast cancer cells by the downregulation of FOSL2. Additionally, we also found a negative correlation between the expression of FOSL2 and miR-597 in the tumor samples. This new regulatory mechanism in breast cancer may provide another method for diagnosis and therapy.

FOSL2 positively regulates TGF-β1 signalling in non-small cell lung cancer

Fos-related antigen 2 (FRA-2/FOSL2) belongs to the AP-1 transcription factor family. Although FOSL2 has been shown to be involved in diverse physiological and pathological processes, very little is known about the signalling pathways that regulate FOSL2 expression and the mechanisms of FOSL2 function. Here, we show that FOSL2 expression is regulated by TGF-β1 and that FOSL2 is required for TGF-β1-induced migration. We demonstrate that FOSL2 interacts with Smad3 in vitro and in vivo and thus up-regulates TGF-β1-induced signalling responses. Mechanistically, FOSL2 promotes P300 binding to Smad3 and the acetylation of Smad3 by P300. Furthermore, we show that the expression of FOSL2 correlates with activated Smad3 expression in clinical non-small cell lung cancer (NSCLC) samples. In summary, the present study indicates that FOSL2 facilitates TGF-β1-induced migration by interaction with Smad3 in NSCLC and suggests FOSL2 as a potential therapeutic target for NSCLC.

Selective genomic targeting by FRA-2/FOSL2 transcription factor: regulation of the Rgs4 gene is mediated by a variant activator protein 1 (AP-1) promoter sequence/CREB-binding protein (CBP) mechanism

FRA-2/FOSL2 is a basic region-leucine zipper motif transcription factor that is widely expressed in mammalian tissues. The functional repertoire of this factor is unclear, partly due to a lack of knowledge of genomic sequences that are targeted. Here, we identified novel, functional FRA-2 targets across the genome through expression profile analysis in a knockdown transgenic rat. In this model, a nocturnal rhythm of pineal gland FRA-2 is suppressed by a genetically encoded, dominant negative mutant protein. Bioinformatic analysis of validated sets of FRA-2-regulated and -nonregulated genes revealed that the FRA-2 regulon is limited by genomic target selection rules that, in general, transcend core cis-sequence identity. However, one variant AP-1-related (AP-1R) sequence was common to a subset of regulated genes. The functional activity and protein binding partners of a candidate AP-1R sequence were determined for a novel FRA-2-repressed gene, Rgs4. FRA-2 protein preferentially associated with a proximal Rgs4 AP-1R sequence as demonstrated by ex vivo ChIP and in vitro EMSA analysis; moreover, transcriptional repression was blocked by mutation of the AP-1R sequence, whereas mutation of an upstream consensus AP-1 family sequence did not affect Rgs4 expression. Nocturnal changes in protein complexes at the Rgs4 AP-1R sequence are associated with FRA-2-dependent dismissal of the co-activator, CBP; this provides a mechanistic basis for Rgs4 gene repression. These studies have also provided functional insight into selective genomic targeting by FRA-2, highlighting discordance between predicted and actual targets. Future studies should address FRA-2-Rgs4 interactions in other systems, including the brain, where FRA-2 function is poorly understood.

Phosphodiesterase 10A in the rat pineal gland: localization, daily and seasonal regulation of expression and influence on signal transduction

The cyclic nucleotide phosphodiesterase 10A (PDE10A) is highly expressed in striatal spiny projection neurons and represents a therapeutic target for the treatment of psychotic symptoms. As reported previously [J Biol Chem 2009; 284:7606-7622], in this study PDE10A was seen to be additionally expressed in the pineal gland where the levels of PDE10A transcript display daily changes. As with the transcript, the amount of PDE10A protein was found to be under daily and seasonal regulation. The observed cyclicity in the amount of PDE10A mRNA persists under constant darkness, is blocked by constant light and is modulated by the lighting regime. It therefore appears to be driven by the master clock in the suprachiasmatic nucleus (SCN). Since adrenergic agonists and dibutyryl-cAMP induce PDE10A mRNA, the in vitro clock-dependent control of Pde10a appears to be mediated via a norepinephrine → β-adrenoceptor → cAMP/protein kinase A signaling pathway. With regard to the physiological role of PDE10A in the pineal gland, the specific PDE10A inhibitor papaverine was seen to enhance the adrenergic stimulation of the second messenger cAMP and cGMP. This indicates that PDE10A downregulates adrenergic cAMP and cGMP signaling by decreasing the half-life of both nucleotides. Consistent with its effect on cAMP, PDE10A inhibition also amplifies adrenergic induction of the cAMP-inducible gene arylalkylamine N-acetyltransferase (Aanat) which codes the rate-limiting enzyme in pineal melatonin formation. The findings of this study suggest that Pde10a expression is under circadian and seasonal regulation and plays a modulatory role in pineal signal transduction and gene expression.

Restraint-induced fra-2 and c-fos expression in the rat forebrain: relationship to stress duration

The protein product of the fra-2 gene (Fra-2), a fos-family member, can compete with Fos protein for participation in activating protein-1 (AP-1) transcription factor complexes and each protein can contribute different transactivational consequences to an AP-1 complex. To date, there is limited characterization of fra-2 mRNA expression in the rat forebrain. We examined basal and restraint-induced mRNA expression (in situ hybridization) of fra-2 in the rat forebrain and compared its temporal-spatial pattern to c-fos. In contrast to the very low basal expression of c-fos, fra-2 basal expression was moderately high throughout cortex and some subcortical structures, including prominent basal expression in the hypothalamic paraventricular nucleus (PVN). Restraint-induced fra-2 expression was quantified in the prefrontal cortex (PFC), lateral septum (LS) and PVN. Maximal fra-2 gene induction in the PFC and LS was delayed (60 min) after restraint onset with respect to c-fos (15 min), whereas in the PVN, fra-2 mRNA increased within 15 min of restraint. Additionally we compared c-fos and fra-2 gene expression in rats given shorter or longer restraint durations, but equal total time from stress onset to sample collection, to determine the extent to which the kinetics of gene induction matched that of a hypothalamic-pituitary-adrenal axis hormone response. Rats given 45 min recovery after 15 min restraint showed less c-fos expression in the PVN, less fra-2 expression in the prelimbic and infralimbic PFC, and no difference in the LS compared with rats restrained for 60 min. Thus, the expression of both genes was sensitive to stressor duration, but this sensitivity varied with brain region. Differential basal and stress-induced expression patterns of the fra-2 and c-fos genes are likely to have important functional consequences for AP-1 transcription factor dependent regulation of neural plasticity.

The role of repressor proteins in the adrenergic induction of type II iodothyronine deiodinase in rat pinealocytes

In this study, we investigated the transcriptional regulation of the adrenergic induction of type II iodothyronine deiodinase (Dio2) in rat pinealocytes. Treatment of pinealocytes with norepinephrine (NE) caused an increase in the mRNA level of Dio2 that peaked around 2 h and declined over the next 5 h. Both beta- and alpha1-adrenergic receptors contributed to the NE induction of Dio2 expression through a cAMP/protein kinase A mechanism. In pinealocytes that had been stimulated by NE, inhibition of transcription by actinomycin had no discernible effect on Dio2 expression. In contrast, inhibition of protein synthesis by cycloheximide enhanced the NE induction of Dio2 expression, suggesting the involvement of a repressor protein. Transient transfection of pinealocytes with adenovirus expressing small interfering RNA against Fos-related antigen 2 (Fra2) enhanced the NE induction of Dio2 expression, whereas the effect of overexpression of the full-length transcript of Fra2 was inhibitory. Time-course study indicated that preventing the NE induction of Fra2 enhanced the NE induction of Dio2 after 3 h, and the enhancement persisted beyond 6 h after NE stimulation. In comparison, transient transfection of pinealocytes with small interfering RNA against inducible cAMP early repressor (Icer) had no effect on the NE induction of Dio2 expression, whereas overexpression of the full-length transcript of Icer caused a small reduction of the NE-stimulated Dio2 expression. Together, our results support Fra-2 as an important transcriptional repressor that helps shape the time profile of the adrenergic induction of Dio2 expression in the rat pineal gland.

Cyclic AMP-inducible genes respond uniformly to seasonal lighting conditions in the rat pineal gland

The encoding of photoperiodic information ensues in terms of the daily profile in the expression of cyclic AMP (cAMP)-inducible genes such as the arylalkylamine N-acetyltransferase (AA-NAT) gene that encodes the rate-limiting enzyme in melatonin formation. In the present study, we compared the influence of the photoperiodic history on the cAMP-inducible genes AA-NAT, inducible cyclic AMP early repressor (ICER), fos-related antigen-2 (FRA-2), mitogen-activated protein kinase phosphatase-1 (MKP-1), nerve growth factor inducible gene-A (NGFI-A) and nerve growth factor inducible gene-B (NGFI-B) in the pineal gland of rats. For this purpose, we monitored the daily profiles of each gene in the same pineal gland under a long (light/dark 16:8) and a short (light/dark 8:16) photoperiod by measuring the respective mRNA amounts by real-time polymerase chain reaction analysis. We found that, for all genes under investigation, the duration of increased nocturnal expression is lengthened and, in relation to light onset, the nocturnal rise is earlier under the long photoperiod (light/dark 16:8). Furthermore, with the exception of ICER, all other cAMP-inducible genes tend to display higher maximum expression under light/dark 8:16 than under light/dark 16:8. Photoperiod-dependent changes persist for all of the cAMP-inducible genes when the rats are kept for two cycles under constant darkness. Therefore, all cAMP-inducible genes are also influenced by the photoperiod of prior entrained cycles. Our study indicates that, despite differences regarding the expressional control and the temporal phasing of the daily profile, cAMP-inducible genes are uniformly influenced by photoperiodic history in the rat pineal gland.

The interplay between the pineal complex and the habenular nuclei in lower vertebrates in the context of the evolution of cerebral asymmetry

This paper presents an overview on the epithalamus of vertebrates, with particular reference to the pineal and to the asymmetrical organization of the habenular nuclei in lower vertebrates. The relationship between the pineal and the habenulae in the course of phylogenesis is here emphasized, taking data in the frog as example. Altogether the data support the hypothesis, put forward also in earlier studies, of a correlation of habenular asymmetry in lower vertebrates with phylogenetic modification of the pineal complex. The present re-visitation was also stimulated by recent data on the asymmetrical expression of Nodal genes, which involves the pineal and habenular structures in zebrafish. The comparative analysis of data, from cyclostomes to mammals, suggests that transformation of epithalamic structures may play an important role in brain evolution. In addition, in mammals, including rodents, a remarkable complexity has evolved in the organization of the habenulae and their functional interactions with the pineal gland. The evolution of these two epithalamic structures seems to open also new perspectives of knowledge on their implication in the regulation of biological rhythms.