The Fos protein complex is associated with DNA in isolated nuclei and binds to DNA cellulose

Neuronal circuits and the magnetic sense: central questions

Magnetoreception is the ability to sense the Earth's magnetic field, which is used for orientation and navigation. Behavioural experiments have shown that it is employed by many species across all vertebrate classes; however, our understanding of how magnetic information is processed and integrated within the central nervous system is limited. In this Commentary, we review the progress in birds and rodents, highlighting the role of the vestibular and trigeminal systems as well as that of the hippocampus. We reflect on the strengths and weaknesses of the methodologies currently at our disposal, the utility of emerging technologies and identify questions that we feel are critical for the advancement of the field. We expect that magnetic circuits are likely to share anatomical motifs with other senses, which culminates in the formation of spatial maps in telencephalic areas of the brain. Specifically, we predict the existence of spatial cells that encode defined components of the Earth's magnetic field.

Scutellarin protects against lipopolysaccharide-induced acute lung injury via inhibition of NF-kappaB activation in mice

This paper investigates the effect of natural scutellarin on acute lung injury (ALI) induced by Escherichia coli endotoxin lipopolysaccharide (LPS) in mice and its mechanism of action. Mouse ALI was induced by the injection of LPS (15 mg/kg) via the tail vein, and mice were intraperitoneally injected with 50 and 25 mg/kg of scutellarin before the LPS injection. The lung index, serum NO2(-)/NO3(-), and tumor necrosis factor-alpha (TNF-alpha) levels were determined using kits. The lung lesions were examined by light microscope. The mRNA levels of TNF-alpha, inducible nitric oxide synthase (iNOS), and FasL in pulmonary tissues were detected by RT-PCR. c-Fos, c-Jun, IkappaB, and iNOS proteins were detected by the western blotting method. Pretreatment with 25 and 50 mg/kg of scutellarin significantly reduced lung injury induced by LPS, which expressed in the decrease in lung morphological lesions, serum NO2(-)/NO3(-), TNF-alpha levels, lactate dehydrogenase release, and total protein in the lavage fluid of bronchoalveolar of the lung. The mRNA level of TNF-alpha, iNOS, the protein content of c-Fos, iNOS, and the activation of NF-kappaB in pulmonary tissues were all inhibited, while the lung glutathione level increased. In conclusion, scutellarin has protective action against LPS-induced lung damage in mice, and its underlying mechanism might be the inhibition of IkappaB alpha degradation and the expression of TNF-alpha mRNA.

The function of activity-regulated genes in the nervous system

The mammalian brain is plastic in the sense that it shows a remarkable capacity for change throughout life. The contribution of neuronal activity to brain plasticity was first recognized in relation to critical periods of development, when manipulating the sensory environment was found to profoundly affect neuronal morphology and receptive field properties. Since then, a growing body of evidence has established that brain plasticity extends beyond development and is an inherent feature of adult brain function, spanning multiple domains, from learning and memory to adaptability of primary sensory maps. Here we discuss evolution of the current view that plasticity of the adult brain derives from dynamic tuning of transcriptional control mechanisms at the neuronal level, in response to external and internal stimuli. We then review the identification of "plasticity genes" regulated by changes in the levels of electrical activity, and how elucidating their cellular functions has revealed the intimate role transcriptional regulation plays in fundamental aspects of synaptic transmission and circuit plasticity that occur in the brain on an every day basis.

Autocrine motility factor stimulates the invasiveness of malignant cells as well as up-regulation of matrix metalloproteinase-3 expression via a MAPK pathway

The autocrine motility factor (AMF) is a multifunctional protein that is involved in tumor progression including enhanced invasiveness via induction of matrix metalloproteinase-3 (MMP3). The increase in MMP3 was found in an AMF-high production tumor cell line, and c-Jun, c-Fos and mitogen-activated protein kinases (MAPKs) were also highly phosphorylated compared with the parent line. AMF stimulation induced the rapid phosphorylation of the cellular MAPK cascade and MMP3 secretion, which was blocked using a specific MAPK inhibitor. Results of this study suggest that AMF stimulation stimulates MMP3 expression via a MAPK signaling pathway.

Calcitonin gene-related peptide partially mediates nociception in acute experimental pancreatitis

BACKGROUND

The mechanism by which pancreatitis causes pain is unknown. The neuropeptide calcitonin gene-related peptide (CGRP) is released after sensory nerve activation and promotes nociceptive signaling in models of visceral pain. We hypothesized that acute pancreatitis leads to the activation of pancreatic sensory neurons that release CGRP in the dorsal horn of the spinal cord. This signal is ultimately transmitted to the brain, and pain is sensed.

METHODS

To induce pancreatitis, rats were injected with l-arginine (500 mg/kg) intraperitoneally or saline (control). Pancreatitis was confirmed by measuring serum amylase and evaluating pancreatic histology. Activation of nociceptive pathways was evaluated by counting Fos-like immunoreactive nuclei (FLI) in the dorsal horn of the spinal cord at T3-L1. Some animals received the CGRP antagonist CGRP(8-37) (50 microg intrathecally) 2 hours before perfusion. Animals were compared using a 2-tailed t test.

RESULTS

l-Arginine treatment induced acute necrotizing pancreatitis in the rat at 24 hours. l-Arginine (24 hours) increased FLI in the dorsal horn of the spinal cord, with a peak effect at L1. Intrathecal administration of CGRP(8-37) significantly decreased the number of FLI nuclei in the dorsal horn of the spinal cord in T11-L1.

CONCLUSIONS

Nociception in the l-arginine model of acute pancreatitis is partially mediated by the release of CGRP in the dorsal horn of the spinal cord. Antagonism of CGRP or its receptors may be useful in treating pain from acute pancreatitis.

Co-induction of activity-dependent genes in songbirds

Song behavior in songbirds induces the expression of activity-dependent genes in brain areas involved in perceptual processing, production and learning of song. This genomic response is thought to represent a link between neuronal activation and long-term changes in song-processing circuits of the songbird brain. Here we demonstrate that Arc, an activity-regulated gene whose product has dendritic localization and is associated with synaptic plasticity, is rapidly induced by song in the brain of zebra finches. We show that, in the context of song auditory stimulation, Arc expression is induced in several telencephalic auditory areas, most prominently the caudomedial nidopallium and mesopallium, whereas in the context of singing, Arc is also induced in song control areas, namely nucleus HVC, used as a proper name, the robust nucleus of the arcopallium and the interface nucleus of the nidopallium. We also show that song-induced Arc expression co-localizes at the cellular level with those of the transcriptional regulators zenk and c-fos, and that the song induction of these three genes is dependent on activation of the mitogen-activated protein kinase signaling pathway. These findings provide evidence for an involvement of Arc in the brain's response to birdsong. They also demonstrate that genes representing distinct genomic and cellular regulatory programs, namely early effectors and transcription factors, are co-activated in the same neuronal cells by a naturally learned stimulus.

Immunochemical analysis of protein expression in breast epithelial cells transformed by estrogens and high linear energy transfer (LET) radiation

Breast cancer is a complex disease involving numerous genetic aberrations. Immunochemical analysis of protein expression is presented in a human breast epithelial cell line neoplastically transformed by high linear energy transfer (LET) alpha particle radiation in the presence of 17beta estradiol (E) and in the parental human breast epithelial cell line (MCF-10F) which served as a non-tumorigenic control. The aim of this work was to determine the levels of mRNA and protein expression in control and transformed cells at various stages of the neoplastic process. The levels of mRNA and protein expression of PCNA, c-fos, JNK2 and Fra-1 were increased in the transformed cell line compared to the levels in non-tumorigenic control cells. The transforming factor Rho A was significantly increased only in the tumor cell line. Furthermore, the levels of mRNA and protein expression of ErbB2 were significantly increased in the transformed cell line and in tumor cells derived from the transformed cells after injecting them into nude mice. A decrease in RbA/p48 protein expression and mRNA levels was observed in cells treated with double doses of alpha particle radiation in the presence of estrogen, regardless of tumorigenicity. Such expression was lower than that in the control untreated MCF-10F cells. In summary, these studies show that estrogen and high LET-radiation induce changes in oncoprotein expression and mRNA levels of human breast cell lines. These changes are indicative of a cascade of events that characterize the process of cell transformation in breast cancer. These results provide evidence that multiple steps with consecutive changes are involved when normal cells become tumorigenic cells as a result of alpha particle irradiation and estrogen treatments.

Basic Fibroblast Growth Factor Activates ERK and Induces c-Fos in Human Embryonic Stem Cell Line MizhES1

Human embryonic stem (hES) cells can be maintained in a proliferative undifferentiated state in vitro by growing them on feeder layers of mouse embryonic fibroblast (MEF) cells along with basic fibroblast growth factor (bFGF/FGF-2). To understand the molecular mechanisms involved in the requirement of bFGF in human ES cells, we investigated expression of FGF receptors and intracellular signaling events in response to bFGF in human ES cell line MizhES1. On the basis of the results of RT-PCR, clear expression of FGF receptors FGFR1, FGR2, and FGFR3 was noticed. Because MAPK, PI3K, and PKC pathways are well-known pathways triggered by bFGF in other cells, these pathways were investigated after stimulation with bFGF. bFGF did not induce activation of PI3K or PKC, but induced activation of ERK (extracellular signal-regulated kinase). To monitor the consequences of ERK activation, we examined expression of the immediate early gene c-fos, one downstream target of the MEK1/ERK pathway. mRNA and protein levels of the c-fos gene were increased by bFGF. Induction of c-Fos was dependent on MEKl. Therefore, it is likely that bFGF contributes to maintenance of human ES cells, at least in part, through the MEK1/ERK pathway.

Enhancement of cell survival by stromal cell-derived factor-1/CXCL12 involves activation of CREB and induction of Mcl-1 and c-Fos in factor-dependent human cell line MO7e

Stromal cell-derived factor-1 (SDF-1/CXCL12) enhances the survival of hematopoietic stem and progenitor cells in synergy with other cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), steel factor, and thrombopoietin (TPO), and both the PI3K/Akt and MAPK pathways have been linked to this survival. To further evaluate intracellular signaling involved in SDF-1/CXCL12 survival effects, we investigated modulation of downstream signaling molecules. The synergistic survival enhancement of SDF-1/CXCL12 plus other cytokines were directly linked to enhanced phosphorylation of p70/85S6K and cAMP responsive element binding protein (CREB), as well as enhanced induction of the Bcl-2 family member Mcl-1. Most prominently, c-Fos, a component of AP1 transcription factor, was synergistically induced by SDF-1/CXCL12 plus other cytokines. These results suggest that SDF-1/CXCL12 enhanced cell survival in synergy with other cytokines involves activation of CREB and induction of Mcl-1 and c-Fos.

Activation of nociceptive neurons in T9 and T10 in cerulein pancreatitis

Mechanisms of pain transduction in acute pancreatitis are poorly understood. Increased Fos expression in the spinal cord is a marker of activation of nociceptive neurons. We hypothesized that cerulein pancreatitis leads to increased Fos expression at T9 and T10, which receive sensory input from the pancreas. Rats were injected with cerulein (100 microg/kg, s.c.) or saline carrier (NS). Endpoints at 4, 6, and 10 h were serum amylase, myeloperoxidase activity (MPO), and spinal cord Fos expression (number of immunoreactive nuclei/section dorsal gray matter). Fos-like immunoreactivity (FLI) at T9-T10 was compared to internal controls (T6, T12). An average of 20 spinal cord histologic sections were evaluated per rat. Some animals were injected with the mu-opioid receptor agonist, buprenorphine (90 microg/kg, s.c.), 3 h after cerulein, and their endpoints were measured at 6 h. Analysis of variance and t tests were used for statistical analysis. Results are means +/- SEM. As expected, cerulein induced edematous pancreatitis, with a 4-fold increase in serum amylase at 6 h [cer (n = 8): 14,000 +/- 1,300 U/ml versus NS (n = 10): 3,700 +/- 300, P < 0.005)] and a 2-fold increase in MPO activity (0.25 +/- 0.05) activity units/dry wt versus 0.13 +/- 0.02, P < 0.05). Cerulein induced nearly a 2-fold increase in FLI at T9 and T10 [n = 10 (cer) and n = 13 (NS): T9, 14 +/- 1.5 versus 7.8 +/- 0.88; T10, 15 +/- 1.7 versus 8.3 +/- 0.70; P < 0.05]. Peak effects of cerulein on FLI occurred at 6 h and were greatest at T9/T10 with relative sparing of T6/T12. T6/T12 expression was similar in experimental and control groups. Buprenorphine significantly reduced both serum amylase and FLI and T9/T10. Cerulein-induced acute pancreatitis in rat increases visceral nociceptive signaling at spinal cord levels T9 and T10, with a peak at 6 h. Blockade of this effect by the mu-opioid receptor agonist buprenorphine could occur either by direct activation of central opioid receptors and/or an anti-inflammatory mechanism. FLI is a useful tool for studying the pathophysiology of pain in experimental acute pancreatitis.

Molecular cloning and differential expression of the cat immediate early gene c-fos

Recently, the effect of binocular central retinal lesions on the expression of immediate early genes in the visual system of adult cats was demonstrated using in situ hybridization and immunocytochemistry. The present study was undertaken to quantify cat c-fos mRNA expression differences in the cat primary visual cortex after sensory deafferentation. Prior to quantification, DNA fragments obtained using reverse transcription-polymerase chain reaction (RT-PCR) in combination with rapid amplification of complementary DNA ends (RACE) were cloned and sequenced. This provided us with the necessary sequence(1) information to prepare cat-specific c-fos primers for the development of a new quantitative RT-PCR assay. We optimized a reverse transcription-competitive polymerase chain reaction (RT-cPCR) method with a heterologous DNA fragment (competitor) as external standard to quantify relative amounts of cat c-fos mRNA expression levels. Internal standardization was accomplished by quantifying, in a parallel RT-cPCR, a well-characterized housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). This cat-specific RT-cPCR assay allowed us to measure c-fos mRNA expression levels in central and peripheral regions of primary visual cortex in normal and retinal lesion cats.

Decreased CSF pH at ventral brain stem induces widespread c-Fos immunoreactivity in rat brain neurons

Physiological evidence has indicated that central respiratory chemosensitivity may be ascribed to neurons located at the ventral medullary surface (VMS); however, in recent years, multiple sites have been proposed. Because c-Fos immunoreactivity is presumed to identify primary cells as well as second- and third-order cells that are activated by a particular stimulus, we hypothesized that activation of VMS cells using a known adequate respiratory stimulus, H(+), would induce production of c-Fos in cells that participate in the central pH-sensitive respiratory chemoreflex loop. In this study, stimulation of rostral and caudal VMS respiratory chemosensitive sites in chloralose-urethane-anesthetized rats with acidic (pH 7.2) mock cerebrospinal fluid induced c-Fos protein immunoreactivity in widespread brain sites, such as VMS, ventral pontine surface, retrotrapezoid, medial and lateral parabrachial, lateral reticular nuclei, cranial nerves VII and X nuclei, A(1) and C(1) areas, area postrema, locus coeruleus, and paragigantocellular nuclei. At the hypothalamus, the c-Fos reaction product was seen in the dorsomedial, lateral hypothalamic, supraoptic, and periventricular nuclei. These results suggest that 1) multiple c-Fos-positive brain stem and hypothalamic structures may represent part of a neuronal network responsive to cerebrospinal fluid pH changes at the VMS, and 2) VMS pH-sensitive neurons project to widespread regions in the brain stem and hypothalamus that include respiratory and cardiovascular control sites.

Free leucine dissociates homo- and heterodimers formed between proteins containing leucine heptad repeats

A highly specific method for the dissociation of protein dimers has been developed. The method involves exposure of the dimers to free leucine at a concentration ranging between 3 and 10 mM. Using this method it has been possible to dissociate goat uterine oestrogen receptor homodimers, heterodimers formed between the non-activated oestrogen receptor (naER) and the oestrogen receptor activation factor (E-RAF) of the goat uterus, c-jun homodimers derived from bovine bone marrow and also glucocorticoid receptor homodimers isolated from rat liver cytosol. The pattern of dimer dissociation by leucine clearly differentiates two classes of proteins. The first is represented by steroid hormone receptors where dimerization is apparently contributed by both coiled-coil dimerization interfaces and the conserved heptad repeats of leucine. The second is represented by oncoproteins like c-fos and c-jun which dimerize through the exclusive involvement of leucine zippers. The patterns of dissociation of these two groups of proteins from the concerned affinity columns are distinctly different. This indicates a possibility that the elution pattern may be used as a yardstick to determine whether two proteins dimerize through the exclusive involvement of leucine zippers or whether coiled-coil interfaces are also involved in the dimerization process.

A new cat Fos antibody to localize the immediate early gene c-fos in mammalian visual cortex after sensory stimulation

We developed a novel antibody against cat Fos by immunizing rabbits with a 26-amino-acid peptide. Immunocytochemistry on visual cortex of cats undergoing different visual manipulations was applied to test the reliability and the efficacy of this antiserum. One hour of light stimulation after an overnight dark adaptation resulted in strongly induced Fos expression in supra- and infragranular layers of cat primary visual cortex. Short-term monocular deprivation changed the Fos expression profile into a columnar immunostaining related to ocular dominance columns. Fos expression has also been analyzed in cats in which visual input was confined to the right hemisphere by sectioning the left optic tract and the corpus callosum. In the right hemisphere, visual stimulation elicited Fos induction, whereas in the contralateral hemisphere a very low Fos signal was observed. The specificity of this newly synthesized antibody was confirmed by Western blotting. To further establish the applicability of this Fos antiserum, we performed immunostaining on monkey and rat visual cortex. This new cat Fos antibody appears to be excellent for study of Fos expression as a marker for mapping neuronal activity in mammalian brain.

Genetic dissection of the signals that induce synaptic reorganization

Synaptic reorganization of mossy fibers following kainic acid (KA) administration has been reported to contribute to the formation of recurrent excitatory circuits, resulting in an epileptogenic state. It is unclear, however, whether KA-induced mossy fiber sprouting results from neuronal cell loss or the seizure activity that KA induces. We have recently demonstrated that certain strains of mice are resistant to excitotoxic cell death, yet exhibit seizure activity similar to what has been observed in rodents susceptible to KA. The present study takes advantage of these strain differences to explore the roles of seizure activity vs cell loss in triggering mossy fiber sprouting. In order to understand the relationships between gene induction, cell death, and the sprouting response, we assessed the regulation of two molecules associated with the sprouting response, c-fos and GAP-43, in mice resistant (C57BL/6) and susceptible (FVB/N) to KA-induced cell death. Following administration of KA, increases in c-fos immunoreactivity were observed in both strains, although prolonged induction of c-fos was present only in the hippocampal neurons of FVB/N mice. Mossy fiber sprouting following KA administration was also only observed in FVB/N mice, while induction of GAP-43, a marker associated with mossy fiber sprouting, was not observed in either strain. These results indicate that: (i) KA-induced seizure activity alone is insufficient to induce mossy fiber sprouting; (ii) mossy fiber sprouting may be due to the loss of hilar neurons following kainate administration; and (iii) induction of GAP-43 is not a necessary component of the sprouting response that occurs following KA in mice.

Validation of a new antiserum directed towards the synthetic c-terminus of the FOS protein in avian species: immunological, physiological and behavioral evidence

In the past 10 years, the study of the expression of immediate early genes, such as c-fos, in the brain has become a common method for the identification of brain areas involved in the regulation of specific physiological and behavioral functions. The use of this method in avian species has been limited by the paucity of suitable antibodies that cross-react with the FOS protein in birds. We describe in this paper the preparation of an antibody directed against a synthetic fragment of the protein product of the c-fos gene in chickens (Gallus domesticus). We demonstrate that this new antibody can be used in several avian species to study FOS expression induced by a variety of pharmacological, physiological and behavioral stimuli. Western blot studies indicated that this antibody recognizes a protein of the expected size (47 kDa) but also cross reacts to some extent with proteins of lower molecular weight that share sequence homology with FOS (Fos-related antigens). FOS immunocytochemistry was performed with this antibody in four species of birds in three different laboratories utilizing diverse variants of the immunocytochemical procedure. In all cases the antibody provided a reliable identification of the FOS antigen. The new antibody described here appears to be suitable for the study of FOS expression in several different avian species and situations. It is available in substantial amounts and will therefore make it possible to use FOS expression as a tool to map brain activity in birds as has now been done for several years in mammalian species.

Inducible and constitutive transcription factors in the mammalian nervous system: control of gene expression by Jun, Fos and Krox, and CREB/ATF proteins

This article reviews findings up to the end of 1997 about the inducible transcription factors (ITFs) c-Jun, JunB, JunD, c-Fos, FosB, Fra-1, Fra-2, Krox-20 (Egr-2) and Krox-24 (NGFI-A, Egr-1, Zif268); and the constitutive transcription factors (CTFs) CREB, CREM, ATF-2 and SRF as they pertain to gene expression in the mammalian nervous system. In the first part we consider basic facts about the expression and activity of these transcription factors: the organization of the encoding genes and their promoters, the second messenger cascades converging on their regulatory promoter sites, the control of their transcription, the binding to dimeric partners and to specific DNA sequences, their trans-activation potential, and their posttranslational modifications. In the second part we describe the expression and possible roles of these transcription factors in neural tissue: in the quiescent brain, during pre- and postnatal development, following sensory stimulation, nerve transection (axotomy), neurodegeneration and apoptosis, hypoxia-ischemia, generalized and limbic seizures, long-term potentiation and learning, drug dependence and withdrawal, and following stimulation by neurotransmitters, hormones and neurotrophins. We also describe their expression and possible roles in glial cells. Finally, we discuss the relevance of their expression for nervous system functioning under normal and patho-physiological conditions.

Ultrastructure of Fos-labeled neurons relating to nociceptive primary afferent and substance P terminals in rat spinal superficial laminae

The presence of Fos-labeled neurons at ultrastructural level was confirmed in the spinal superficial laminae following an injection of formalin into rat hindpaw in the present study. The Fos-like immunoreactive products were found exclusively in regions associated with the euchromatin in the nuclei of Fos-labeled neurons. By the methods used-of anterograde transport of horseradish peroxidase conjugated to wheat-germ agglutinin and immunocytochemistry-it was observed that some Fos-labeled neuronal bodies received synaptic contacts from, or were apposed directly to, small diameter primary afferent terminals in the spinal superficial laminae. By means of double-labeled immunocytochemistry, a direct apposition was often observed and a synaptic relationship was occasionally found between Fos-labeled neuronal bodies and substance P-like immunoreactive terminals.

The comparative effects of haloperidol, (-)-sulpiride, and SCH23390 on c-fos and c-jun mRNA expressions, and AP-1 DNA binding activity

The c-fos and c-jun mRNA expressions were measured by the RNase protection assay method following intraperitoneal injection of haloperidol, (D1 and D2 receptor antagonists), (-)-sulpiride, (D2 receptor antagonist), and SCH23390, (D1 receptor antagonist). Haloperidol and (-)-sulpiride increased their mRNA expressions in a dose-dependent manner, peaking at 30 min after injection followed by a gradual decline. The SCH23390 did not induce expression of either c-fos or c-jun mRNA. A significant decrease of c-fos as well as c-jun mRNA expression was found due to pretreatment with SCH23390 (1 mg/kg i.p.) followed by injection of (-)-sulpiride (20 mg/kg i.p.). The results suggest that the expression of these mRNAs is closely related to the dopamine D2-like antagonism. Administration of haloperidol or (-)-sulpiride increased AP-1 DNA binding activity with similar manner of dose-dependence, whereas their activities were reduced by Fos and Jun antibodies, implying that AP-1 components, transcriptional factors, forming due to Fos and Jun were actually activated by either haloperidol or (-)-sulpiride.

Characterization of the signalling pathways involved in ATP and basic fibroblast growth factor-induced astrogliosis

1. A brief challenge of rat astrocytes with either alpha, beta-methyleneATP (alpha, beta-meATP) or basic fibroblast growth factor (bFGF) resulted, three days later, in morphological differentiation of cells, as shown by marked elongation of astrocytic processes. The P2 receptor antagonist suramin prevented alpha, beta-meATP- but not bFGF-induced astrocytic elongation. Similar effects on astrocytic elongation were also observed with ATP and other P2 receptor agonists (beta, gamma meATP, ADP beta S, 2meSATP and, to a lesser extent, UTP). 2. Pertussis toxin completely abolished alpha, beta-meATP- but not bFGF-induced effects. No effects were exerted by alpha, beta-meATP on cyclic AMP production; similarly, neomycin had no effects on elogation of processes induced by the purine analogue, suggesting that adenylyl cyclase and phospholipase C are probably not involved in alpha, beta-meATP-induced effects (see also the accompanying paper by Centemeri et al., 1997). The tyrosine-kinase inhibitor genistein greatly reduced bFGF- but not alpha, beta-meATP-induced astrocytic elongation. 3. Challenge of cultures with alpha, beta-meATP rapidly and concentration-dependently increased [3H]-arachidonic acid (AA) release from cells, suggesting that activation of phospholipase A2 (PLA2) may be involved in the long-term functional effects evoked by purine analogues. Consistently, exogenously added AA markedly elongated astrocytic processes. Moreover, various PLA2 inhibitors (e.g. mepacrine and dexamethasone) prevented both the early alpha, beta-meATP-induced [3H]-AA release and/or the associated long-term morphological changes, without affecting the astrocytic elongation induced by bFGF. Finally, the protein kinase C (PKC) inhibitor H7 fully abolished alpha, beta-meATP- but not bFGF-induced effects. 4. Both alpha, beta-meATP and bFGF rapidly and transiently induced the nuclear accumulation of Fos and Jun. Both c-fos and c-jun induction by the purine analogue could be fully prevented by pretreatment with suramin. In contrast, the effects of bFGF were unaffected by this P2 receptor antagonist. 5. It was concluded that alpha, beta-meATP- and bFGF-morphological differentiation of astrocytes occurs via independent transductional pathways. For the purine analogue, signalling involves a Gi/G(o) protein-coupled P2Y-receptor which may be linked to activation of PLA2 (involvement of an arachidonate-sensitive PKC is speculated); for bFGF, a tyrosine kinase receptor is involved. Both pathways merge on some common intracellular target, as suggested by induction of primary response genes, which in turn may regulate late response genes mediating long-term phenotypic changes of astroglial cells. 6. These findings implicate P2 receptors as novel targets for the pharmacological regulation of reactive astrogliosis, which has intriguing implications in nervous system diseases characterized by degenerative events.

Suppression of c-fos induction in rat brain impairs retention of a brightness discrimination reaction

Recently, the induction of transcription factor-encoding immediate-early genes such as c-fos was observed in distinct brain regions of rats trained to acquire a footshock-motivated brightness discrimination in a Y-maze. The functional relevance of inducible transcription factors for learning and memory formation is, however, not clear. To address this question in the present study, we have used a synthetic antisense phosphorothioate oligodeoxynucleotide to suppress in vivo the expression of c-fos in rat brain. Intrahippocampal application of the oligodeoxynucleotide 10 hr and 2 hr before starting a brightness discrimination training drastically reduced the induction of c-Fos immunoreactivity normally observed in limbic and cortical areas after the training session. Acquisition of the discrimination reaction was not affected by this treatment. In a relearning test 24 hr after the first training, retention of the discrimination reaction was specifically impaired compared with rats pretreated with control oligodeoxynucleotide or saline. Our findings are consistent with the hypothesis that the inducible transcription factor c-Fos is involved in processes underlying the formation of long-term memory.

Characterization of a leucine zipper-containing protein identified by retroviral insertion in avian neuroretina cells

We reported previously that post-mitotic chicken embryonic neuroretina (NR) cells are induced to proliferate following in vitro infection with RAV-1, a retrovirus that does not carry an oncogene. NR cell multiplication results from the frequent activation and subsequent retroviral transduction of two related serine/threonine protein kinases, the c-mil/c-raf or c-Rmil/B-raf genes. We also showed that a very early event in the activation of these proto-oncogenes is the synthesis of chimeric mRNAs containing viral and cellular sequences joined by a splicing mechanism. In the current study, we have examined the ability of RAV-1 to induce proliferation of quail NR cells. By using the reverse transcription-polymerase chain reaction technique, we identified, in several proliferating quail NR cultures infected with RAV-1, a chimeric mRNA containing cellular sequences joined to the RAV-1 splice donor site. These cellular sequences are derived from a gene designated R10, which is expressed through a 1.9-kilobase (kb) mRNA detected in several embryonic tissues. A second transcript of 2.3 kb is specifically expressed in the NR, where both transcripts are developmentally regulated. The R10 cDNA encodes a 251-amino acid polypeptide that contains a leucine zipper motif. It exhibits significant similarity with the putative D52/N8L protein, encoded by an mRNA reported previously to be overexpressed in human breast and lung carcinomas. By using polyclonal antibodies specific for its amino-terminal and leucine zipper-containing regions, we identified the R10 gene product as a cytoplasmic protein of 23 kDa in cultured avian fibroblasts. A second protein of 30 kDa is detected in post-mitotic NR cells that express the 2.3-kb transcript. We also show, by in vitro transcription/translation and immunoprecipitation, that the R10 protein can readily form homodimers, presumably through its leucine zipper motif.

Subnuclear localization of FOS-like immunoreactivity in the rat parabrachial nucleus after nociceptive stimulation

The effect of noxious stimulation on the expression of FOS-like immunoreactivity (FOS-LI) in neurons of the parabrachial nucleus (PB) was studied in awake, freely moving rats. In one series of experiments, the rats were subjected to noxious mechanical stimulation (pinch) of either the nape of the neck or the base of the tail for 20 seconds every 5 minutes for 90 minutes, and then they were killed by transcardial perfusion after 45-210 minutes. Control animals received innocuous mechanical stimulation (brush) of the tail. Noxious stimuli resulted in FOS-LI in neurons in the dorsal part of the lateral PB, with heavy labeling in the superior lateral (PBsl) and the dorsal lateral (PBdl) subnuclei. FOS-LI was also elicited in the central lateral subnucleus (PBcl) and, although much more sparsely, in the external lateral subnucleus and the Kölliker-Fuse nucleus. Tail and neck stimulation resulted in similar labeling patterns, but more neurons, particularly in PBsl, expressed FOS-LI after pinch of the tail than of the neck. In another series of experiments, rats received injection of 5% formalin into one hindpaw. After 75-90 minutes, FOS-LI was seen in the same parts of PB as after noxious mechanical stimulation. The heaviest labeling was seen on the side contralateral to the injection side, with statistically significant (P < 0.05) side differences present in PBsl and PBdl. In a third series of experiments, rats were hemisected at low cervical-upper thoracic segments, allowed 2 weeks to recover, and then given formalin injections in both hindpaws. Significantly more neurons were FOS-labeled in PBdl, PBsl, and PBcl on the side contralateral to the hemisection than on the ipsilateral side. These observations are discussed in relation to the organization of the spinal afferent input and the efferent connections of PB. It is concluded that the FOS-LI expression in PBdl and PBsl and probably also in PBcl, to a large extent, is evoked by the ascending spinal nociceptive input to PB. Because these subnuclei project to several hypothalamic regions, it is suggested that neurons in PB that express FOS after noxious mechanical and chemical stimulation primarily are involved in autonomic and homeostatic responses to behavioral situations that involve tissue-damaging stimuli.

Identification of an osteocalcin gene promoter sequence that binds AP1

Osteoblasts are differentiated cells that produce bone matrix components including the bone-specific protein osteocalcin. The osteocalcin gene promoter has become a model for understanding how genes are regulated, specifically in osteoblasts. One model for cell-specific regulation suggests that osteoblast-expressed genes are regulated through common promoter sequences which bind osteoblast-specific transcriptional activators. The phenotype suppression model suggests osteoblast-specific promoters are switched off through the action of the common transcriptional activator AP1. We previously demonstrated that a short sequence element (OSCARE-2) in the osteocalcin promoter was homologous to a repressive element in the collagen type 1 (alpha 1) promoters. In this paper we use electrophoretic mobility shift (EMS) assays to examine DNA-protein interactions in the OSCARE-2 sequence. In EMS assays, OSCARE-2 binds a complex of proteins, including AP1. This supports the role of AP1 sites in contributing to the regulation of the osteocalcin promoter. Exogenous c-JUN protein bound to OSCARE-2 and increasing c-JUN incubated with nuclear extract amounts caused a progressive increase in a higher-molecular-weight complex, consistent with c-JUN involvement in protein-protein as well as DNA-protein interactions. Anti-c-FOS antibody was capable of supershifting OSCARE-2 DNA-protein complexes produced using osteoblast-like cell nuclear extracts. In addition, EMS assays of nuclear proteins from osteoblast-like cells indicated that 1,25 (OH)2D3-inducible proteins are bound to OSCARE-2. Osteocalcin promoter constructs showed that OSCARE-2 contributed to the 1,25 (OH)2D3 response, albeit in a minor way. These data support the role of AP1 protein as a regulator of osteoblast-specific gene expression during osteoblast development.

-Fos expression in female hamster brain following sexual and aggressive behaviors

The goal of these experiments was to use c-Fos immunocytochemistry to determine areas of the female hamster brain that are active during lordosis and aggression. Ovariectomized hamsters were given (i) estradiol and progesterone, plus a lordosis test, (ii) estradiol and progesterone, but no lordosis test, (iii) oil, plus an aggressive behavior test, or (iv) oil, but no behavior test. Results showed that following lordosis, there was increased c-Fos expression in the medial bed nucleus of the stria terminalis, medial accumbens, medial preoptic nucleus, paraventricular nucleus and medial amygdala. Following a single aggression test, c-Fos was significantly increased only within the medial amygdala. There was no effect of lordosis or aggression on c-Fos expression within the lateral or central ventromedial hypothalamus, suprachiasmatic nucleus or dorsal midbrain central gray. In a second experiment, ovariectomized female hamsters were given (i) repeated aggressive experience, (ii) a single aggression test or (iii) no aggression test. Because some females were not aggressive towards males, they became a separate group post hoc. The number of cells expressing c-Fos was higher in the medial preoptic nucleus and medial amygdala of females given a single aggressive test and in non-aggressive females vs control females. Females given prior aggressive experience showed higher c-Fos expression only in the medial preoptic nucleus. These results demonstrate that increased neural activation in several forebrain nuclei is seen after sexual or aggressive behaviors in female hamsters. However, because the pattern of c-Fos staining in the non-aggressive females was similar to the pattern in aggressive females, this questions previous conclusions regarding the behavioral specificity of these effects and suggests instead that such activation is common to social interactions in general.

Thermal sensitivity in NIH 3T3 fibroblasts transformed by the v-fos oncogene. Correlation with reduced accumulation of 68-kDa and 25-kDa stress proteins after heat shock

The effect of v-fos transformation on the cellular response to heat shock has been investigated. NIH 3T3 fibroblasts were transfected with the FBR p75gag-fos gene fusion under the control of the long terminal repeat (LTR) promoter of Finkel-Biskin-Reilly (FBR) murine sarcoma virus and with the gene encoding hygromycin resistance. Several hygromycin-resistant clone isolates, that expressed various levels of p75gag-fos oncoprotein, were analyzed as they displayed properties of transformed cells, such as altered morphology, shorter doubling time, serum-independent growth and foci formation in soft agar. The thermal response of these clones was compared to that of the control cells expressing the hygromycin-resistance gene only. Here, we report that the v-fos-transformed clones displayed an enhanced thermosensitivity which resulted in a reduced tolerance to thermal stress. Heat-treated v-fos-transformed cells displayed a decreased expression and accumulation of the major stress proteins Hsp68 (68-kDa heat-shock protein) and Hsp25 which probably resulted of a reduced accumulation of the corresponding mRNAs. This effect was particularly intense at the level of Hsp25. These alterations in cell survival and stress-protein expression appeared correlated to the level of p75gag-fos. At least for Hsp68, the transcription of this gene was not found altered by v-fos expression suggesting that this oncogene increases the turn-over of Hsp68 mRNA. After the heat-shock treatment, v-fos transformation also reduced the time period during which the constitutively expressed stress protein Hsc70 redistributes inside the nucleus. Since Hsp68 and Hsp25 are molecular chaperones that in vivo protect cells against the deleterious effects of heat shock, it is conceivable that their reduced accumulation and altered cellular distribution following heat shock may contribute, at least in part, to the thermosensitivity of v-fos-transformed NIH 3T3 fibroblasts.

Effects of Ca2+ channel blockers on cortical hypoperfusion and expression of c-Fos-like immunoreactivity after cortical spreading depression in rats

1. We examined the effects of two Ca2+ channel blockers, lomerizine (KB-2796) and flunarizine, on the cortical hypoperfusion (measured by hydrogen clearance and laser Doppler flowmetry methods) and cortical c-Fos-like immunoreactivity that follow KCl-induced cortical spreading depression in anaesthetized rats. Cortical spreading depression was induced by application of 1 M KCl for 30 s to the cortical surface, 3.0 mm posterior to the area of cerebral blood flow measurement. 2. In control rats, KB-2796 (0.3 and 1 mg kg-1, i.v.) dose-dependently increased cerebral blood flow significantly at 30 min and 15 min, respectively, after its administration. Flunarizine (1 mg kg-1, i.v.) significantly increased cerebral blood flow 15 min after its administration. In contrast, dimetotiazine (3 mg kg-1, i.v.), a 5-HT2 and histamine H1 antagonist, failed to affect cerebral blood flow significantly. 3. After KCl application to the cortex, cerebral blood flow monitored by the laser Doppler flowmetry method increased transiently, for a few minutes, then fell and remained approximately 20 to 30% below control for at least 60 min. Cerebral blood flow monitored by the hydrogen clearance method was also approximately 20 to 30% below baseline for at least 60 min after KCl application. KB-2796 (0.3 and 1 mg kg-1, i.v.) and flunarizine (1 and 3 mg kg-1, i.v.) administered 5 min before KCl application inhibited the cortical hypoperfusion that followed KCl application, but dimetotiazine (1 and 3 mg kg-1, i.v.) did not. 4. An indicator of neuronal activation, c-Fos-like immunoreactivity, was detected in the ipsilateral, but not in the contralateral frontoparietal cortex 2 h after KCl application. No c-Fos-like immunoreactivity was seen on either side of the brain in the hippocampus, thalamus, striatum or cerebellum. 5. KB-2796 (1 mg kg-1, i.v.) and flunarizine (3 mg kg-1, i.v.), but not dimetotiazine (3 mg kg-1, i.v.), significantly attenuated the expression of c-Fos-like immunoreactivity in the ipsilateral frontoparietal cortex. 6. These findings suggest that the inhibitory effects of KB-2796 and flunarizine on the cortical hypoperfusion and expression of c-Fos-like immunoreactivity induced by spreading depression are mediated via the effects of Ca(2+)-entry blockade, which may include an increase in cerebral blood flow and the prevention of excessive Ca2+ influx into brain cells. KB-2796 and flunarizine may prove useful as inhibitors of cortical spreading depression in migraine.

Follicle-stimulating hormone transiently induces expression of protooncogene c-myc in primary Sertoli cell cultures of early pubertal and prepubertal rat

The protooncogene c-myc plays an important role in the regulation of cellular proliferation and differentiation. To evaluate the possibility that the protooncogene c-myc plays some roles in follicle-stimulating hormone (FSH)-dependent gene regulation of Sertoli cells, the effects of FSH on the expression of c-myc has been investigated in primary Sertoli cell cultures. FSH was no change to the c-myc mRNA level before 18 h, but transiently increased c-myc mRNA levels, with maximal stimulation reached in 18 h. The induction of c-myc was dependent on the concentration of FSH. Th c-myc mRNA was also increased after treatment with dibutyryl c-AMP and forskolin in primary Sertoli cell cultures. FSH-dependent c-myc mRNA levels were superinduced in cells treated for 3 h with cycloheximide but it was reduced by actinomycin-D pretreatment. Even in the absence of FSH in culture medium c-myc mRNA was clearly detectable in Sertoli cells from 8-day-old rats but hardly detectable in cells from 14 and 28 days of age. FSH stimulated c-myc mRNA expression in the primary Sertoli cells derived from only 8- and 14-day-old rats but had almost no effect in the 28-day-old rats. These results suggest that FSH induces c-myc mRNA levels in the primary Sertoli cells from prepubertal and early pubertal rats, and then transient expression of c-myc may be responsible for some roles in the regulation of FSH-dependent genes in Sertoli cells.

Biphasic induction of immediate early gene expression accompanies activity-dependent angiogenesis and myofiber remodeling of rabbit skeletal muscle

Sustained contractile activity of skeletal muscle promotes angiogenesis, as well as transformation of contractile protein isoforms and mitochondrial proliferation within myofibers. Since the products of immediate early genes such as c-fos, c-jun, and egr-1 function in many signaling pathways governing cellular responses to external stimuli, we sought to determine whether sustained contractile activity induces their expression in skeletal muscle. Low voltage electrical stimulation was applied to the motor nerve innervating rabbit tibialis anterior muscles for periods ranging from 45 min to 21 d. Northern and Western analysis demonstrated marked but transient inductions of c-fos, c-jun, and egr-1 mRNA and protein within the first 24 h. Longer durations of stimulation were associated with a secondary and sustained rise in the abundance of c-fos, c-jun, and p88egr-1 protein that, surprisingly, was not accompanied by detectable changes in mRNA. Immunohistochemistry demonstrated c-fos immunoreactivity within myofiber and vascular cell nuclei during both early and late phases of this response. These findings reveal a complex pattern of c-fos, c-jun, and egr-1 expression in response to nerve stimulation and suggest that these proteins could function in regulatory pathways that modify muscle phenotype.

Expression of c-fos-like protein in the rat brain after injection of interleukin-1-beta into the gingiva

Expression of the c-fos proto-oncogene in the rat brain was examined by immunostaining for fos, the nuclear protein product of the c-fos gene, after injection of interleukin-1-beta (IL-1 beta) into the gingiva of an incisor. The distribution pattern of labelled cells was compared with that induced by tooth pulp stimulation. Neurons that express fos-immunoreactivity (fos-IR) appeared in several regions in the neuraxis 1.5 h after IL-1 beta injection, peaked at 2 h, and then declined. Labelled cells were found bilaterally in regions that contribute to pain-relay and pain-inhibition. The distribution of labelled cells almost matched the pattern induced by noxious tooth pulp stimulation. In indomethacin-pretreated animals, no neurons expressing fos-IR were found in nuclei associated with relay of nociception nor in nuclei contributing to inhibition of nociception. The results suggest that a small amount of IL-1 beta at the site of periodontal disease can induce fos-IR in brain neurons through increased prostaglandin production.

Expression of Fos in rat central nervous system elicited by afferent stimulation of the femoral nerve

To investigate the distribution of Fos-like immunoreactivity (FLI) in the central nervous system of urethane anesthesized rats after activation of a somatosympathetic reflex pathway, the cut central end of the right femoral nerve of 17 male Wistar rats was stimulated electrically for 1 h at parameters such that increases in heart rate and arterial pressure were elicited. Sections of brain and spinal cord were incubated in anti-Fos antibody and the presence of FLI was detected using the ABC immunoperoxidase method. In the spinal cord FLI was present in the ipsilateral lumbar spinal cord (laminae 1 and 2, 4-6 and 10) and contralateral intermediolateral nucleus in the thoracic spinal cord. In the hindbrain, FLI was present in the contralateral rostral ventrolateral medulla and bilaterally in the cochlear nucleus, external cuneate nucleus, locus coeruleus and lateral parabrachial nucleus. In the midbrain, label appeared in the Edinger-Westphal nucleus and peripeduncular nucleus on both sides. In the forebrain, FLI appeared bilaterally in the central nucleus of the amygdala, para- and periventricular hypothalamus, supraoptic nucleus, paraventricular thalamus, reuniens nucleus, subfornical organ and bed nucleus of the stria terminalis. These results define the central nervous system pathways of somatosympathetic reflexes and demonstrate that areas in the forebrain not previously known to be activated by somatosympathetic reflexes, but previously implicated in mediating the defense reaction, are activated by these reflexes.

Differential roles for Fos and Jun in DNA-binding: redox-dependent and independent functions

The Fos and Jun family of transcription factors contain an invariant sequence motif lysine-cysteine-arginine (KCR) in the highly conserved DNA-binding region. Reduction of the cysteine residue is necessary to facilitate DNA-binding. Here, we examined the potential dual roles of the flanking lysine and arginine residues in influencing the redox reactivity of the cysteine and the DNA-binding activity of Fos and Jun. Two sets of Fos and Jun mutants were generated: the KCR and KSR series representing proteins capable of redox-dependent and redox-independent DNA-binding activity, respectively. Mutation of the lysine in Fos-Jun heterodimers had no obvious effect on the redox reactivity of the cysteine, suggesting that lysine is not essential in this respect. However, mutation of the arginine but not lysine, in both the KCR and the KSR series abolished DNA-binding activity. Thus, the arginine but not the lysine residue in the KCR motif is critical for both redox-dependent and redox-independent functions in DNA-binding. Surprisingly, the triple substitution, ISI, exhibited high levels of DNA-binding activity. This demonstrates that the effects of amino acid substitutions can be highly dependent on context and that non-basic amino acids can function efficiently in DNA-binding. Analysis of combinations of wild-type and mutant Fos and Jun proteins indicated that Fos was dominant in dictating the DNA-binding ability of Fos-Jun heterodimers. This suggests that the lysine and arginine residues in the KCR region of Fos are not equivalent to those in Jun and that they interact with DNA differently.

Nuclear Fos domains in transcriptionally activated supraoptic nucleus neurons

This study has analysed by light and electron microscopy immunolocalization the nuclear pattern of distribution of Fos-related proteins in supraotic neurons. Two experimental models of transcriptional activation have been used: sustained, global transcriptional activation, at relatively near physiological conditions, by six days of chronic intermittent salt loading; and superinduction of c-fos gene by this salt loading regime plus cycloheximide treatment for 4 h. In the first condition, the ultrastructural analysis showed a distribution of Fos-like immunoreactivity on the reticular network of dispersed chromatin that extends between the nucleolar surface and the nuclear envelope, whereas the Fos-negative adjacent interchromatin spaces appeared rich in interchromatin granules by using a cytochemical staining for ribonucleoproteins. The nucleolus associated heterochromatin, fibrillar centers of the nucleolus and coiled bodies were free of immunoreactivity. This immunoelectron pattern seems to indicate that active genes containing activator protein-1 and cyclic AMP response element recognition sites are extensively distributed in euchromatin regions and suggests that the Fos-positive nuclear domains correspond to the actively transcribing chromatin regions, at least in supraoptic neurons. It also suggests that these Fos-positive transcription domains are complementary to adjacent ribonucleoprotein-rich interchromatin spaces which are involved in the processing and splicing of pre-messenger RNA. Moreover, the absence of immunoreactivity on the fibrillar centers, the sites of pre-ribosomal RNA synthesis, suggests that the Fos protein complexes are not involved in regulating the expression of ribosomal RNA genes. Following superinduction of c-fos gene by osmotic stimulation plus cycloheximide treatment, a conspicuous Fos-like immunoreactivity was detected in dispersed chromatin regions, whereas the heterochromatin masses, nucleoli and coiled bodies showed no immunoreaction. Moreover, this treatment induced the formation of nuclear "dense bodies" of a fibrillar nature which were free of immunolabelling. Since Fos proteins are known to be short-lived, the expression of these nuclear constituents, under conditions of protein synthesis inhibition induced by the cycloheximide, suggests the stabilization of chromatin-bound Fos complexes or, alternatively, a preferential synthesis of Fos proteins.

c-Fos expression by dorsal horn neurons chronically deafferented by peripheral nerve section in response to spared, somatotopically inappropriate nociceptive primary input

Subcutaneous formalin injection into the hindpaw of rats induces c-Fos expression in neurons in the ipsilateral spinal cord dorsal horn. In laminae I and II of the dorsal horn at the junction of 4th and 5th segments of the lumbar spinal cord, neurons exhibiting c-Fos protein-like immunoreactivity (Fos-LI) are concentrated in the medial 3/4 that correspond to the terminal field of primary neurons innervating the sciatic nerve. Subacute tibial nerve section 24 h before formalin stimulation caused almost complete elimination of neurons with the formalin-induced Fos-LI in the medial 1/2 (tibial territory) of the above sciatic territory of the dorsal horn. Following a longer survival period (chronic tibial nerve section of 21 days standing), neurons with the formalin-induced Fos-LI re-appeared in the tibial territory. In addition, the number of neurons with the formalin-induced Fos-LI increased in the medial part of the peroneal territory (the lateral 1/2 of the sciatic territory). The results indicate that the activation of c-Fos expression in that part of dorsal horn that has been chronically deafferented by the tibial nerve section is taken over by the spared, but somatotopically inappropriate primary nociceptors. Furthermore, dorsal horn neurons outside but near the deafferented tibial nerve's territory exhibit hypersensitivity to c-Fos expression evoked by intact, somatotopically appropriate primary nociceptive input.

Profile of Fos-like immunoreactivity induction by light stimuli in the intergeniculate leaflet is different from that of the suprachiasmatic nucleus

Light stimuli induce Fos-like immunoreactivity (FLI) in suprachiasmatic nucleus (SCN) and intergeniculate leaflet (IGL). Short pulses of light stimuli that synchronize the circadian rhythms induce FLI in SCN. The characteristics of light induction of FLI in the IGL were studied using immunohistochemistry. In the IGL, at least 2 h of sustained light stimuli were necessary to show an increase of FLI. This FLI persisted while the light was turned on. FLI induction in the IGL by light stimuli was not circadian time specific response. These findings imply that the functional significance of Fos activation on circadian rhythms and mechanism of FLI induction in IGL would be different from that in SCN.

Electroacupuncture accelerated the expression of c-fos protooncogene in serotonergic neurons of nucleus raphe dorsalis

It has been proposed that the FOS protein encoded by c-fos protooncogene functions as a nuclear "third messenger" molecule that couples short-term extracellular signals to long-term alterations in cell function, by regulating the expression of specific target genes. In the present study, immunocytochemical double staining technique was used to investigate the effects of electroacupuncture on the expression of c-fos oncogene in the serotonergic neurons in the nucleus raphe dorsalis (NRD) that has been known to play an important role in the endogenous analgesic system of the brain. The number of FOS positive serotonergic cells in the NRD increased significantly after the electroacupuncture stimulation. These results indicate that electroacupuncture can activate central serotonergic neurons at gene expression level.

Fos-like expression and nuclear size in osmotically stimulated supraoptic nucleus neurons

This study has analysed by immunocytochemistry the pattern of expression of Fos-related proteins, as well as variations in nuclear size, after the osmotically induced activation of supraoptic nucleus neurons of the rat. In control rats most supraoptic nucleus neurons were Fos-like negative. After acute and chronic dehydration by salt-loading, the number of Fos-like positive neurons increased dramatically. The level of Fos-like immunoreactivity was higher in chronically stimulated rats, and also the neurons of the ventral region of the supraoptic nucleus were more intensely stained than those of the dorsal region. The karyometric analysis was made on electron micrographs. The mean nuclear profile area showed a significant increase in dehydrated rats with respect to the controls (73 +/- 16 microns 2 in those dehydrated for six days vs 54 +/- 13 in controls, mean +/- S.D.). However, no significant differences in this parameter were found when one-day and six-day dehydrated groups were compared. The invagination factor of the nuclear membrane, a nuclear shape indicator, decreased significantly in dehydrated rats, indicating a tendency towards spherical nuclei. It is noteworthy that the nuclear profile perimeter was constant, about 32 microns, in control and osmotically simulated rats. The higher nuclear accumulation of Fos-related antigens after six days of dehydration suggests that in chronically stimulated supraoptic nucleus neurons there is a sustained induction of cell-specific genes. Moreover, the transcription rate of the target genes containing the consensus DNA sequence TGAC/GTCA or c-AMP responsive elements recognition sites may depend upon the nuclear concentration of Fos-related antigens in supraoptic nucleus neurons. Our results also suggest that the initial Fos-related antigen expression and nuclear size increase are triggered concomitantly in supraoptic nucleus neurons after a short period of osmotic stimulation. On the other hand, we propose that nuclear envelope invaginations represent a reservoir of nuclear membrane which allows dynamic changes in nuclear size and shape depending on the metabolic status of the supraoptic nucleus neurons.

Changes in chromatin proteins during optic nerve regeneration in the goldfish

Regeneration of the goldfish optic nerve involves massive changes in the structure and pattern of macro-molecular synthesis in the retinal ganglion cells. To explore the mechanisms that underlie these events, we investigated the changes in chromatin proteins during the course of regeneration. Three major retinal chromatin proteins, two with apparent molecular weights of 58 kDa (C1 and C2) and one at 51 kDa (C3), all having isoelectric points around 5.5, showed a fourfold increase in their synthesis and/or accumulation by 14 days of regeneration. Synthesis of C1 and C3 decreased by day 32, the time at which the axons have grown back to the optic tectum and have formed many of their synapses; synthesis of C2 remained high through day 32. All three proteins bound to DNA-cellulose and required high salt concentrations (0.2-0.5 M KCl) to be eluted. C1 and C2 had similar proteolytic digestion patterns and reacted with monoclonal antibodies that recognize the goldfish intermediate filament proteins of the ON complex. The proteins identified here could be involved in structural alterations in the chromatin, or might serve as transcription factors to regulate gene expression during nerve regeneration.

NeuN, a neuronal specific nuclear protein in vertebrates

A battery of monoclonal antibodies (mAbs) against brain cell nuclei has been generated by repeated immunizations. One of these, mAb A60, recognizes a vertebrate nervous system- and neuron-specific nuclear protein that we have named NeuN (Neuronal Nuclei). The expression of NeuN is observed in most neuronal cell types throughout the nervous system of adult mice. However, some major cell types appear devoid of immunoreactivity including cerebellar Purkinje cells, olfactory bulb mitral cells, and retinal photoreceptor cells. NeuN can also be detected in neurons in primary cerebellar cultures and in retinoic acid-stimulated P19 embryonal carcinoma cells. Immunohistochemically detectable NeuN protein first appears at developmental timepoints which correspond with the withdrawal of the neuron from the cell cycle and/or with the initiation of terminal differentiation of the neuron. NeuN is a soluble nuclear protein, appears as 3 bands (46-48 × 10(3) M(r)) on immunoblots, and binds to DNA in vitro. The mAb crossreacts immunohistochemically with nervous tissue from rats, chicks, humans, and salamanders. This mAb and the protein recognized by it serve as an excellent marker for neurons in the central and peripheral nervous systems in both the embryo and adult, and the protein may be important in the determination of neuronal phenotype.

Modulation of mRNA levels during human keratinocyte differentiation

Cultures of human keratinocytes provide an excellent model system in which to study differentiation. Using the phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA) and calcium, two agents known to induce keratinocyte differentiation in vitro, we examined the expression of the genes encoding c-fos, c-myc, and c-jun; involucrin, a protein precursor of the keratinocyte cornified envelope; and L-7, a ribosomal protein. Overall, at the doses studied, TPA induced a more rapid and profound differentiation than did calcium, as evaluated by culture morphology and northern blot analysis. Our studies showed a constant low level of c-fos and c-jun expression in unstimulated cells with no significant change after addition of either TPA or calcium except when transcript breakdown was inhibited by cycloheximide. The c-myc proto-oncogene, known to have a high constitutive expression in actively proliferating cells, was strongly downregulated by TPA, but calcium had no effect over a 32 hour period, consistent with the greater growth inhibition of TPA in this system. Involucrin was induced about ninefold by both TPA and calcium as early as 8 hours after stimulation, suggesting transcriptional regulation of this gene during differentiation. L-7, recently demonstrated to be downregulated in late passage human fibroblasts in an in vitro model of senescence, was also strongly downregulated by either TPA or calcium, consistent with an interrelationship between the basic cellular processes of aging and differentiation. These finding expand our knowledge of the differentiation process in human keratinocytes.

Expression of c-fos-like immunoreactivity in brainstem after meningeal irritation by blood in the subarachnoid space

The expression of c-fos protein was examined by immunohistochemistry in serial sections of brainstem following the instillation of either autologous arterial blood (0.3 ml) or mock cerebrospinal fluid (0.3 ml) through a catheter placed in the cisterna magna, or following catheter placement alone in pentobarbital-anesthetized Sprague-Dawley rats. After injection, blood was distributed within the subarachnoid space surrounding the brainstem and in the region of the circle of Willis. c-fos protein-like immunoreactivity was present at 1 h, peaked at 2 h and decreased by 8 h. At 2 h, immunoreactivity was strongly expressed within trigeminal nucleus caudalis (lamina I, IIo), as well as within nucleus of the solitary tract, area postrema, ependyma, pia mater and arachnoid in every animal. Moderate labeling was found in parabrachial nucleus, medullary lateral reticular nucleus and central gray. Sparse labeling was present in trigeminal nucleus caudalis (lamina III-V) and trigeminal nucleus interpolaris; few or no labeled cells were detected in other parts of the trigeminal nuclear complex, thalamus, cerebral cortex, cerebellar cortex or trigeminal ganglion. The number of positive cells was not related to the volume of injectate but was related to the amount of injected blood. The density of cell labeling evoked by injecting mock cerebrospinal fluid or after catheter placement was markedly lower than after blood in all brainstem areas. The number of labeled cells was greatly reduced within trigeminal nuclear complex, parabrachial nucleus and medullary lateral reticular nucleus, but not within the nucleus of the solitary tract, area postrema or ependyma when blood was injected into adult animals in which unmyelinated C-fibers were destroyed by neonatal capsaicin treatment. Similar results were obtained after blood was instilled into the cisterna magna of rats in which meningeal afferents were chronically sectioned at the ethmoidal foramen bilaterally. We conclude that blood in the subarachnoid space is an effective stimulus for activating c-fos expression within subpopulations of brainstem neurons. Activation within trigeminal nucleus caudalis is mediated in large part by excitation of small-caliber meningeal afferents (trigeminovascular fibers), whereas c-fos expression within nucleus of the solitary tract and area postrema may reflect direct stimulation of blood or blood products, or possibly the response to autonomic activation from noxious stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)