Regulation of expression of the neuronal POU protein Oct-2 by nerve growth factor

Oct-2 transcription factor binding activity and expression up-regulation in rat cerebral ischaemia is associated with a diminution of neuronal damage in vitro

Brain plasticity provides a mechanism to compensate for lesions produced as a result of stroke. The present study aims to identify new transcription factors (TFs) following focal cerebral ischaemia in rat as potential therapeutic targets. A transient focal cerebral ischaemia model was used for TF-binding activity and TF-TF interaction profile analysis. A permanent focal cerebral ischaemia model was used for the transcript gene analysis and for the protein study. The identification of TF variants, mRNA analysis, and protein study was performed using conventional polymerase chain reaction (PCR), qPCR, and Western blot and immunofluorescence, respectively. Rat cortical neurons were transfected with small interfering RNA against the TF in order to study its role. The TF-binding analysis revealed a differential binding activity of the octamer family in ischaemic brain in comparison with the control brain samples both in acute and late phases. In this study, we focused on Oct-2 TF. Five of the six putative Oct-2 transcript variants are expressed in both control and ischaemic rat brain, showing a significant increase in the late phase of ischaemia. Oct-2 protein showed neuronal localisation both in control and ischaemic rat brain cortical slices. Functional studies revealed that Oct-2 interacts with TFs involved in important brain processes (neuronal and vascular development) and basic cellular functions and that Oct-2 knockdown promotes neuronal injury. The present study shows that Oct-2 expression and binding activity increase in the late phase of cerebral ischaemia and finds Oct-2 to be involved in reducing ischaemic-mediated neuronal injury.

Negative regulation of Yap during neuronal differentiation

Regulated proliferation and cell cycle exit are essential aspects of neurogenesis. The Yap transcriptional coactivator controls proliferation in a variety of tissues during development, and this activity is negatively regulated by kinases in the Hippo signaling pathway. We find that Yap is expressed in mitotic mouse retinal progenitors and it is downregulated during neuronal differentiation. Forced expression of Yap prolongs proliferation in the postnatal mouse retina, whereas inhibition of Yap by RNA interference (RNAi) decreases proliferation and increases differentiation. We show Yap is subject to post-translational inhibition in the retina, and also downregulated at the level of mRNA expression. Using a cell culture model, we find that expression of the proneural basic helix-loop-helix (bHLH) transcription factors Neurog2 or Ascl1 downregulates Yap mRNA levels, and simultaneously inhibits Yap protein via activation of the Lats1 and/or Lats2 kinases. Conversely, overexpression of Yap prevents proneural bHLH proteins from initiating cell cycle exit. We propose that mutual inhibition between proneural bHLH proteins and Yap is an important regulator of proliferation and cell cycle exit during mammalian neurogenesis.

A high throughput embryonic stem cell screen identifies Oct-2 as a bifunctional regulator of neuronal differentiation

Neuronal differentiation is a complex process that involves a plethora of regulatory steps. To identify transcription factors that influence neuronal differentiation we developed a high throughput screen using embryonic stem (ES) cells. Seven-hundred human transcription factor clones were stably introduced into mouse ES (mES) cells and screened for their ability to induce neuronal differentiation of mES cells. Twenty-four factors that are capable of inducing neuronal differentiation were identified, including four known effectors of neuronal differentiation, 11 factors with limited evidence of involvement in regulating neuronal differentiation, and nine novel factors. One transcription factor, Oct-2, was studied in detail and found to be a bifunctional regulator: It can either repress or induce neuronal differentiation, depending on the particular isoform. Ectopic expression experiments demonstrate that isoform Oct-2.4 represses neuronal differentiation, whereas Oct-2.2 activates neuron formation. Consistent with a role in neuronal differentiation, Oct-2.2 expression is induced during differentiation, and cells depleted of Oct-2 and its homolog Oct-1 have a reduced capacity to differentiate into neurons. Our results reveal a number of transcription factors potentially important for mammalian neuronal differentiation, and indicate that Oct-2 may serve as a binary switch to repress differentiation in precursor cells and induce neuronal differentiation later during neuronal development.

Stress and reactivation of latent herpes simplex virus: a fusion of behavioral medicine and molecular biology

Since 1978, the study of health and behavior has become a major focus of scientists in psychology, psychiatry, nursing, neuroscience, and in traditional medical science disciplines. Investigation of psychological or behavioral influences on biological systems has established that biobehavioral processes such as stress play an important role in disease processes. An excellent example of the interactions between stress and health outcomes is the reactivation of latent herpes simplex virus (HSV) leading to recurrent lesions. This article describes what is currently known about HSV latency and reactivation and considers some mechanisms by which stress-induced changes in the host's immune and nervous systems might allow for either the establishment or reactivation of latent viral infections.

Brn-3a suppresses pseudorabies virus-induced cell death in sensory neurons

Sensory neurons of the trigeminal ganglion (TG) are of crucial importance in the pathogenesis of many alphaherpesviruses, constituting major target cells for latency and reactivation events. We showed earlier that a subpopulation of porcine TG neurons, in contrast to other porcine cell types, is highly resistant to cell death induced by infection with the porcine alphaherpesvirus pseudorabies virus (PRV). Here, we report that expression of Brn-3a, a neuron-specific transcription factor implicated in cell survival of sensory neurons, correlates with the increased resistance of TG neurons towards PRV-induced cell death. In addition, overexpression of Brn-3a in the sensory neuronal cell line ND7 markedly increased resistance of these cells to PRV-induced cell death. Hence, Brn-3a may play a hitherto uncharacterized role in protection of sensory neurons from alphaherpesvirus-induced cell death, which may have implications for different aspects of the alphaherpesvirus life cycle, including latency/reactivation events.

Neurotrophin-induced preprotachykinin-A gene promoter modulation in organotypic rat spinal cord culture

To study regulation of the preprotachykinin-A gene promoter, we utilised a biolistic gene transfer protocol to deliver a DNA construct that incorporates a portion of the preprotachykinin-A gene promoter and an enhanced green fluorescent protein reporter gene into neonatal rat spinal cord organotypic slices. The ability of the neurokinin-1 receptor agonist [Sar9,Met(O2)11]-substance P, nerve growth factor and brain derived neurotrophic factor to modulate positively preprotachykinin-A gene promoter construct activity, as indicated by de novo enhanced green fluorescent protein expression, was determined. Treatment of organotypic slices with [Sar9, Met(O2)11]-substance P (10 microm, P < 0.05), nerve growth factor (200 ng/mL, P < 0.001) or brain derived neurotrophic factor (200 ng/mL, P < 0.02) significantly increased the proportion of cytomegaloviral promoter-DsRed transfected cells (used to visualise total transfected cells) that co-expressed enhanced green fluorescent protein. The distribution of enhanced green fluorescent protein/DsRed-positive neurones across spinal laminae was broadly in line with the known distribution of spinal Trk and neurokinin-1 receptors. These data suggest a modulated activity of the preprotachykinin-A gene promoter in spinal neurones in vitro by substance P and/or neurotrophins. The functional consequences of such transcriptional changes within central peptidergic circuitry and their relevance to chronic pain are considered.

A proximal E-box modulates NGF effects on rat PPT-A promoter activity in cultured dorsal root ganglia neurones

The rat preprotachykinin A (rtPPTA) promoter fragment spanning -865+92, relative to the major transcriptional start, has previously been demonstrated to be nerve growth factor (NGF) responsive in primary cultures of rat dorsal root ganglion (DRG) neurones [Harrison, P.T., Dalziel, R.G., Ditchfield, N.A., Quinn, J.P., 1999. Neuronal-specific and nerve growth factor-inducible expression directed by the preprotachykinin-A promoter delivered by an adeno-associated virus vector. Neuroscience 94, 997-1003]. In this communication, we demonstrate that an E box element at -60, in part, regulates the activity of this rtPPT-A promoter fragment in DRG neurones in response to NGF. Differential regulation of the promoter is observed in the presence or absence of NGF when the E Box site is present. Under basal conditions binding of proteins to this -60 element may antagonise promoter activity. Hence, in the absence of NGF, mutation of the -60 E box increased reporter gene expression. Further, comparison of levels of reporter gene expression supported by both WT and mutated promoter indicate that in the presence of NGF the -60 E box element also plays a role as an activator domain. This represents a novel mechanism for NGF regulation of rtPPT-A. Similarly, an important role for this signalling pathway was observed in neonate rat DRG neuronal cultures, which require NGF for their survival, namely mutation of the -60 element resulted in higher levels of reporter gene expression.

Brn-3a transcription factor blocks p53-mediated activation of proapoptotic target genes Noxa and Bax in vitro and in vivo to determine cell fate

The Brn-3a POU transcription factor is associated with survival and the differentiation of sensory neuronal cells during development. Brn-3a mediates its effects either by the direct regulation of target genes or indirectly upon interaction with proteins such as p53. Brn-3a differentially regulates p53-mediated gene expression and modifies its effect on cell fate. Here we show that, like Bax, Brn-3a antagonizes p53-mediated transcription of another proapoptotic target, Noxa, significantly reducing transactivation of the Noxa promoter by p53. This effect requires the p53 binding site, and electrophoretic mobility shift assay studies suggest that Brn-3a is associated with p53 when it is bound to its site in the Noxa promoter. The wild type but not the mutant promoter can be immunoprecipitated with Brn-3a in chromatin immunoprecipitation assays. Thus, Brn-3a may act by preventing the recruitment of cofactors required for p53 to transactivate this promoter. The co-expression of Brn-3a and p53 results in decreased endogenous Noxa protein in the neuronal cell line, ND7, suggesting a direct functional effect of this interaction. Moreover, there is a significant elevation of both proapoptotic Bax and Noxa proteins in sensory neuronal tissue taken from Brn-3a-/- embryos during development, compared with wild type controls. Striking changes occurred at embryonic day 14.5, a time that precedes a significant loss of specific neurons in the mutant embryos, but not at embryonic day 16.5 when Brn-3a-expressing cells are already lost by apoptosis. Therefore, the lack of antagonism by Brn-3a on activation of proapoptotic p53 target genes may contribute to the increased apoptosis seen in the Brn-3a-/- embryos. These results support a crucial role for Brn-3a in determining the pathway taken by p53 when co-expressed during development and thus in controlling the fate of these cells.

Nerve growth factor induces the expression of the LIM homeodomain transcription factor Isl-1 with the kinetics of an immediate early gene in adult rat dorsal root ganglion

LIM-homeodomain genes encode a major class of transcription factors which play a critical role in regulating tissue specific gene expression. In this report, we have shown that three members of the LIM-homeodomain gene family - Isl-1, Rlim and Lim-3 are expressed in adult rat sensory neurons. Furthermore, we show that the addition of nerve growth factor (NGF) to cultures of primary dorsal root ganglion neurons leads to the induction of Isl-1, Rlim and Lim-3 mRNA expression. The increase in Isl-1 mRNA levels upon NGF addition was rapid and occurred even in the presence of cycloheximide. These findings place Isl-1 as a novel member of the immediate early class of genes. In contrast, Rlim and Lim-3mRNA induction by NGF required protein synthesis. The role of LIM-homeodomain genes in mediating responses to NGF in adult sensory neurons is discussed.

Factors controlling lineage specification in the neural crest

The neural crest is a transitory tissue of the vertebrate embryo that originates in the neural folds, populates the embryo, and gives rise to many different cell types and tissues of the adult organism. When neural crest cells initiate their migration, a large fraction of them are still pluripotent, that is, capable of generating progeny that consists of two or more distinct phenotypes. To elucidate the cellular and molecular mechanisms by which neural crest cells become committed to a particular lineage is therefore crucial to the understanding of neural crest development and represents a major challenge in current neural crest research. This chapter discusses selected aspects of neural crest cell differentiation into components of the peripheral nervous system. Topics include sympathetic neurons, the adrenal medulla, primary sensory neurons of the spinal ganglia, some of their mechanoreceptive and proprioceptive end organs, and the enteric nervous system.

Immunohistochemical analysis of primary sensory neurons latently infected with herpes simplex virus type 1

We characterized the populations of primary sensory neurons that become latently infected with herpes simplex virus (HSV) following peripheral inoculation. Twenty-one days after ocular inoculation with HSV strain KOS, 81% of latency-associated transcript (LAT)-positive trigeminal ganglion (TG) neurons coexpressed SSEA3, 71% coexpressed Trk(A) (the high-affinity nerve growth factor receptor), and 68% coexpressed antigen recognized by monoclonal antibody (MAb) A5; less than 5% coexpressed antigen recognized by MAb KH10. The distribution of LAT-positive, latently infected TG neurons contrasted sharply with (i) the overall distribution of neuronal phenotypes in latently infected TG and (ii) the neuronal distribution of viral antigen in productively infected TG. Similar results were obtained following ocular and footpad inoculation with KOS/62, a LAT deletion mutant in which the LAT promoter is used to drive expression of the Escherichia coli lacZ gene. Thus, although all neuronal populations within primary sensory ganglia appear to be capable of supporting a productive infection with HSV, some neuronal phenotypes are more permissive for establishment of a latent infection with LAT expression than others. Furthermore, expression of HSV LAT does not appear to play a role in this process. These findings indicate that there are marked differences in the outcome of HSV infection among the different neuronal populations in the TG and highlight the key role that the host neuron may play in regulating the repertoire of viral gene expression during the establishment of HSV latent infection.

Herpes simplex virus type 1 vector-mediated expression of nerve growth factor protects dorsal root ganglion neurons from peroxide toxicity

Nerve growth factor beta subunit (beta-NGF) transgene delivery and expression by herpes simplex virus type 1 (HSV-1) vectors was examined in a cell culture model of neuroprotection from hydrogen peroxide toxicity. Replication-competent (tk- K mutant background) and replication-defective (ICP4(-);tk- S mutant background) vectors were engineered to contain the murine beta-NGF cDNA under transcriptional control of either the human cytomegalovirus immediate-early gene promoter (HCMV IEp) (e.g., KHN and SHN) or the latency-active promoter 2 (LAP2) (e.g., KLN and SLN) within the viral thymidine kinase (tk) locus. Infection of rat B103 and mouse N2A neuronal cell lines, 9L rat glioma cells, and Vero cells with the KHN or SHN vectors resulted in the production of beta-NGF-specific transcripts and beta-NGF protein reaching a maximum at 3 days postinfection (p.i.). NGF protein was released into the culture media in amounts ranging from 10.83 to 352.86 ng/ml, with the highest levels being achieved in B103 cells, and was capable of inducing neurite sprouting of PC-12 cells. The same vectors produced high levels of NGF in primary dorsal root ganglion (DRG) cultures at 3 days. In contrast to HCMV IEp-mediated expression, the LAP2-NGF vectors showed robust expression in primary DRG neurons at 14 days. The neuroprotective effect of vector produced NGF was assessed by its ability to inhibit hydrogen peroxide-induced neuron toxicity in primary DRG cultures. Consistent with the kinetics of vector-mediated NGF expression, HCMV-NGF vectors were effective in abrogating the toxic effects of peroxide at 3 but not 14 days p.i. whereas LAP2-NGF vector transduction inhibited apoptosis in DRG neurons at 14 days p.i. but was ineffective at 3 days p.i. Similar kinetics of NGF expression were observed with the KHN and KLN vectors in latently infected mouse trigeminal ganglia, where high levels of beta-NGF protein expression were detected at 4 wks p.i. only from the LAP2; HCMV-NGF-driven expression peaked at 3 days but could not be detected during HSV latency at 4 weeks. Together, these results indicate that (i) NGF vector-infected cells produce and secrete mature, biologically active beta-NGF; (ii) vector-synthesized NGF was capable of blocking peroxide-induced apoptosis in primary DRG cultures; and (iii) the HCMV-IEp functioned to produce high levels of NGF for several days; but (iv) only the native LAP2 was capable of long-term expression of a therapeutic gene product in latently infected neurons in vivo.

Developments in quantitative PCR

In recent years the growing interest in quantitative applications of the polymerase chain reaction (PCR) has favoured the development of a large number of assay procedures suitable for this purpose. In this paper we review some basic principles of quantitative PCR and in particular the role of reference materials and calibrators and the different strategies adopted for nucleic acid quantification. We focus on two methodological approaches for quantitative PCR in this review: competitive PCR and real-time quantitative PCR based on the use of fluorogenic probes. The first is one of the most common methods of quantitative PCR and we discuss the structure of the competitors and the various assay procedures. The second section is dedicated to a recent promising technology for quantitative PCR in which the use of fluorogenic probes and dedicated instrumentation allows the development of homogeneous methods. Assay performance of these methods in terms of practicability and reliability indicates that these kinds of technologies will have a widespread use in the clinical laboratory in the near future.

A role for the octamer-binding protein in preprotachykinin-A gene expression

A rat Preprotachykinin-A promoter fragment has been previously identified which supports reporter gene activity in primary cultures of adult dorsal root ganglion neurons. That study demonstrated that two promoter domains which exhibit enhancer activity in these neurons are bound by the same classes of transcription factors. Further, the two domains exhibit similarities with respect to the relationship of bound transcription factors within each domain. This suggests that these domains may function in an identical manner or may act synergistically to regulate gene expression. These domains contain recognition motifs for at least three classes of transcription factors: octamer-binding proteins, Sp1-related proteins and an as yet unidentified but distinct factor. The definition of an octamer-binding protein site within these domains is of interest, as this class of factor has recently been suggested as mediating the effect of nerve growth factor in sensory neurons. Nerve growth factor is a well-characterized regulator of preprotachykinin-A gene expression. Definition of these sites within the promoter allows for the design of rational experiments to address the mechanism of transcriptional regulation of the rat preprotachykinin-A gene.

Identification of a chicken homologue in the Brn-3 subfamily of POU-transcription factors

Among the many transcription factors thus far identified several are found to be expressed almost exclusively in the nervous system. The Brn-3 subfamily of POU-transcription factors constitutes a highly conserved group of such factors showing expression predominantly in sensory neurons. We now describe the nucleotide sequence and proposed amino acid sequence of a chicken homologue to the murine and human Brn-3 genes. Furthermore we characterise the early embryonic expression pattern of this chicken Brn-3 gene and show it to be expressed in peripheral sensory ganglia as well as in retinal ganglion cells. Based on these findings we conclude that the chicken homologue to the murine and human Brn-3a genes has been cloned. We have begun to examine possible regulatory pathways of Brn-3a by stimulating chick embryonic peripheral ganglia with trophic factors and assaying resulting levels of Brn-3a with a quantitative PCR approach. Trigeminal and dorsal root ganglia stimulated in culture by NGF and NT-3 embryonic day 9 (E9) produce neurites without raising the Brn-3a mRNA levels.

The molecular biology of preprotachykinin-A gene expression

The expression of neuropeptides is largely tissue-specific and under strictly regulated and complex control. In view of the diversity of neuronal phenotypes, with concomitant plasticity of gene expression within any phenotype, it is obvious that there is coordinated activation and repression of genes. One of the central observations from these studies is that neuropeptide gene expression is dependent upon the combinatorial interaction of multiple transcription factors with the regulatory elements which determine mRNA synthesis. These factors mediate both tissue specific and stimulus inducible gene expression. We will illustrate some of the mechanisms that regulate neuropeptide gene expression utilizing our own studies on the rat preprotachykinin-A gene (rPPT) and, where appropriate, expand on the generality of these findings to other neuropeptide genes.

Vanilloid receptors: new insights enhance potential as a therapeutic target

Compounds related to capsaicin and its ultrapotent analog, resiniferatoxin (RTX), collectively referred to as vanilloids, interact at a specific membrane recognition site (vanilloid receptor), expressed almost exclusively by primary sensory neurons involved in nociception and neurogenic inflammation. Desensitization to vanilloids is a promising therapeutic approach to mitigate neuropathic pain and pathological conditions (e.g. vasomotor rhinitis) in which neuropeptides released from primary sensory neurons play a major role. Capsaicin-containing preparations are already commercially available for these purposes. The use of capsaicin, however, is severely limited by its irritancy, and the synthesis of novel vanilloids with an improved pungency/desensitization ratio is an on-going objective. This review highlights the emerging evidence that the vanilloid receptor is not a single receptor but a family of receptors, and that these receptors recognize not simply RTX and capsaicin structural analogs but are broader in their ligand-binding selectivity. We further focus on ligand-induced messenger plasticity, a recently discovered mechanism underlying the analgesic actions of vanilloids. Lastly, we give a brief overview of the current clinical uses of vanilloids and their future therapeutic potential. The possibility is raised that vanilloid receptor subtype-specific drugs may be synthesized, devoid of the undesirable side-effects of capsaicin.

Herpes simplex: evolving concepts

A large body of molecular biologic research has begun to clarify some basic aspects of viral latency and reactivation. The clinical definition of herpes simplex virus infection is expanding, with the recognition that the disease is largely asymptomatic and that most transmission occurs during periods of asymptomatic viral shedding. With this awareness, serologic diagnosis has become increasingly important. New treatment modalities are now available, and other promising treatments are in development.

Activation of the gene encoding decay accelerating factor following nerve growth factor treatment of sensory neurons is mediated by promoter sequences within 206 bases of the transcriptional start site

Using two independent differential screening procedures designed to identify novel mRNAs induced by nerve growth factor (NGF) treatment of adult dorsal root ganglion (DRG) neurons, we have isolated cDNA clones derived from the gene encoding decay accelerating factor (DAF). Hybridization analysis and semi-quantitative polymerase chain reaction confirmed that the DAF mRNA was indeed induced in NGF-treated adult DRG neurons. Moreover, the DAF gene promoter is NGF inducible (approximately two- to threefold) when transfected into DRG neurons, and this effect is primarily dependent on sequences between -206 and -77 relative to the transcriptional start site. Hence, the DAF gene constitutes a novel NGF-inducible gene whose mRNA is elevated in response to NGF treatment of DRG neurons. The potential significance of this effect is discussed in terms of the role of NGF in modulating the transcriptional activity and function of adult DRG neurons.

Specific up-regulation of the POU domain transcription factor Oct-2 following axotomy

Peripheral nerve damage causes a dramatic alteration to the gene expression in primary sensory neurons, changes within the neuronal cell body giving rise to an altered phenotype, adapted for axonal regeneration. Such changes suggest an alteration in activity, or levels, of cellular transcription factors. The POU family transcription factor Oct-2 is known to be induced in sensory neurons by nerve growth factor (NGF) and might therefore be affected by the removal of target-derived NGF following axotomy. Paradoxically, however, the expression of Oct-2 showed a transient increase of two- to three-fold 24 h after axotomy. In contrast, axotomy had no effect on the levels of the Brn-3 sub-family of POU proteins, indicating that this effect was specific for Oct-2.

Induction of the Oct-2 transcription factor in primary sensory neurons during inflammation is nerve growth factor-dependent

The mRNA encoding the POU family transcription factor Oct-2 is induced in cultured adult sensory neurons following treatment with nerve growth factor (NGF) but not with a variety of other growth factors. We show here that the Oct-2 mRNA is also upregulated in vivo in sensory neurons innervating inflamed tissue following intraplantar injection of complete Freund's adjuvant. This rise is abolished by systemic administration of anti-NGF neutralizing antibodies indicating that it is an NGF-dependent effect. Hence a very specific aspect of the NGF response occurs in sensory neurons innervating inflamed tissue in vivo. In turn, the induction of Oct-2 may play a role in the other changes observed in such neurons both in gene expression and in their ability to respond to painful stimuli.

Nerve growth factor-regulated properties of sensory neurones in Oct-2 null mutant mice

The POU-domain transcription factor Oct-2 is expressed in both B lymphocytes and sensory neurones, where its expression is regulated by nerve growth factor (NGF). In order to define a possible role for Oct-2 in neurotrophin signalling, we examined the expression of an NGF-regulated channel (capsaicin-evoked ion fluxes), neuropeptides (substance P, calcitonin gene-related peptide), structural proteins (neurofilaments and peripherin) and receptors (trks) in dorsal root ganglion neurones derived from perinatal transgenic mice containing a defective Oct-2 structural gene. Northern blots show that central nervous tissue contains a larger than normal (> 10 kb) mRNA transcript corresponding in size to an Oct-2 transcript encoding a defective protein. PCR analysis shows the absence of normal Oct-2 transcripts in dorsal root ganglia. In null mutants, capsaicin sensitivity, and neuropeptide and cytoskeletal protein expression were unaffected by the loss of Oct-2 expression. The number of sensory neurones and the gross morphology of CNS tissues that normally express high levels of Oct-2 were also examined and found to be normal in the null mutant. Heterozygous animals show normal thresholds of sensitivity to noxious heat and normal inflammatory responses. Oct-2 does not therefore play an essential role in the NGF responsiveness of sensory neurones in these animals.

Direct evidence that the POU family transcription factor Oct-2 represses the cellular tyrosine hydroxylase gene in neuronal cells

The POU family transcription factor Oct-2 was originally identified in B lymphocytes but has been shown to be expressed in neuronal cells, although it is absent in most other cell types. Cotransfection of Oct-2 expression vectors into nonneuronal cells with a tyrosine hydroxylase promoter/reporter plasmid suggests that Oct-2 can repress this promoter in this artificial situation. Here we report that reduction of endogenous Oct-2 levels in a neuronal cell line by an antisense approach results in an increase in endogenous tyrosine hydroxylase levels. In contrast, the level of the neuronal marker protein PGP9.5 remains unchanged in the antisense lines whereas that of the neuronal nitric oxide synthase decreases. Hence, the tyrosine hydroxylase gene is a natural target for repression by Oct-2 in neuronal cells. The significance of this effect is discussed in terms of the processes that regulate tyrosine hydroxylase gene expression and the role of Oct-2 in neuronal cells.

Multiple protein complexes, including AP2 and Sp1, interact with a specific site within the rat preprotachykinin-A promoter

We demonstrate that there is a unique AP2 binding site in the rat preprotachykinin-A promoter (rPPT) spanning -865 to -47. AP2 is a transcription factor whose expression in sensory neurons has been correlated with rPPT expression in these cells. This binding site is adjacent to an element we previously identified as binding a single stranded DNA binding protein which was also present in sensory neurons. These two complexes encompass a region which we had proposed might form a stem-loop structure, allowing binding of the single stranded DNA binding protein to the DNA. Here using electrophoretic mobility shift analysis we demonstrate that the DNA region corresponding to the putative stem-loop structure is bound by a variety of transcription factors, including in addition to AP2 the ubiquitous Sp1. DNase 1 footprint analysis demonstrates that binding to this domain by the proteins recognising the double-stranded form of the cis acting element is mutually exclusive. A promoter fragment containing this domain demonstrated a DNase 1 footprint over the 5' region of the stem-loop structure. Competition of the binding for this element by an oligonucleotide corresponding to the stem-loop structure removed the 5' footprint and exposed a new footprint over the 3' region of the stem-loop structure and extending for several base pairs. This change in protection observed with DNase 1 digestion also correlated with changes of the DNase 1 pattern at specific locations 3' of the proposed stem-loop structure. These changes correlated with two DNA sequences which were homologous to one another and to a region within the proposed stem-loop structure. Our results indicate that AP2 could regulate rPPT gene expression by a variety of mechanisms.

Regulation of NF-kappa B activity in rat dorsal root ganglia and PC12 cells by tumour necrosis factor and nerve growth factor

Members of the nuclear factor kappa-B (NF-kappa B) family of transcription factors are activated by tissue damaging stimuli that cause oxidative stress. The regulation of NF-kappa B activity in rat dorsal root ganglia (DRG) and the neural-crest derived pheochromocytoma cell line PC12 was examined. Electrophoretic mobility shift assays show that specific kappa B binding activities are present in DRG extracts and PC12 cells. These activities can be supershifted with antisera directed against p50, p52 and p65. South-western blots show the presence of a single NF-kappa B binding protein with picomolar affinity, co-migrating with NF-kappa B2 (p49/p52) immunoreactive material in dorsal root ganglia. Intraplantar injection of tumour necrosis factor but not nerve growth factor (NGF) induces NF-kappa B activity in the DRG of adult rats 6 h later. NGF has no effect on NF-kappa B activity in PC12 cells after 6 h, but elevates NF-kappa B activity more than 5-fold after 24 h treatment. These data suggest a role for NF-kappa B in delayed rather than immediate-early responses of the peripheral nervous system and related cell lines to inflammatory cytokines.

Nerve growth factor induces the Oct-2 transcription factor in sensory neurons with the kinetics of an immediate-early gene

The Oct-2 transcription factor has a predominantly inhibitory effect on gene expression in neuronal cell lines. This factor and its corresponding mRNA have previously been shown to be elevated in adult rat dorsal root ganglion (DRG) neurons chronically exposed to nerve growth factor (NGF). Here we show that the Oct-2 mRNA is rapidly induced in DRG cells exposed to NGF and that such induction still occurs to a lesser extent in the presence of the protein synthesis inhibitor cycloheximide. These findings characterize Oct-2 as a novel member of the immediate-early class of NGF-induced transcription factors whose previously defined members have a predominantly stimulatory effect on the expression of other genes. Induction of the Oct-2 mRNA was also observed in DRG neurons treated with acidic fibroblast growth factor or epidermal growth factor but not with a range of other growth factors and neurotrophins. The role of the Oct-2 transcription factor in mediating the response of DRG neurons to NGF is discussed.

Characterisation of potential regulatory elements within the rat preprotachykinin-A promoter

The rat preprotachykinin-A (rPPT-A) gene encodes the precursor of several tachykinin neuropeptides including substance P. Previous studies have demonstrated the presence of multiple DNA sequences important for directing expression of the rPPT-A gene in dorsal root ganglion neurons within a region of the promoter spanning nucleotides -865 and -47. In order to identify potential cis acting elements, we have carried out DNase 1 footprinting analysis using a series of constructs containing fragments from this region of the promoter. This study has defined three potential AP-1 complex interactions, two E box binding protein interactions and two dG rich elements, which are potentially bound by complexes related to AP-2 or Sp1 in this region of the promoter.

Regulated splicing of the Oct-2 transcription factor RNA in neuronal cells

The primary RNA transcript derived from the gene encoding the Oct-2 transcription factor is alternatively spliced to yield a number of different mRNAs which encode different isoforms of this protein. The mRNAs encoding two such isoforms Oct-2c and mini Oct-2 were originally detected in neuronal cells. We show here that the mRNAs encoding these forms also occur in other tissues with the proportion of the mini Oct-2 mRNA being much higher in the spleen than in the brain. However, the levels of the mini Oct-2 mRNA increase in neuronal cell lines in response to differentiation-inducing stimuli and decrease upon exposure to growth factors. Hence the splicing of the Oct-2 transcript can be regulated in both a tissue specific manner and in neuronal cells in response to specific stimuli. The significance of this effect is discussed in terms of the differing ability of different forms of Oct-2 to activate or inhibit gene expression.

Down regulation of the octamer binding protein Oct-1 during growth arrest and differentiation of a neuronal cell line

The octamer binding transcription/DNA replication factor Oct-1 is present in virtually all cell types including proliferating cell lines of neuronal origin but is not detectable in mature non-dividing neurons. Cell cycle arrest in G0/G1 and morphological differentiation of a neuronal cell line is accompanied by a decline in the level of Oct-1 DNA binding, although the level of DNA binding by another octamer binding protein, Oct-2 is unaltered. This effect is paralled by a decline in the level of the Oct-1 mRNA in the non-dividing cells. The decrease in Oct-1 levels occurs only with the production of a mature, non-dividing neuronal phenotype and not when the cells are arrested in late G1 and do not undergo morphological differentiation. The potential role of Oct-1 and other octamer binding proteins in gene regulation in neuronal cells and in their differentiation is discussed.

Nerve growth factor induces expression of immediate-early genes NGFI-A (Egr-1) and NGFI-B (nur 77) in adult rat dorsal root ganglion neurons

We have used primary cultures of adult rat dorsal root ganglia (DRG), enriched in sensory neurons, to investigate the induction of immediate-early genes by NGF and a variety of other growth factors. Using the polymerase chain reaction we have quantitatively amplified specific mRNA transcripts induced by NGF, in the presence and absence of the protein synthesis inhibitor cycloheximide. NGFIA (Egr-1) and NGFIB (nur 77) mRNAs were elevated in level within 60 min of NGF treatment and independently of de novo protein synthesis. This was consistent with the behaviour of immediate-early genes. These kinetics were seen at a range of NGF concentrations. NGFIA and NGFIB mRNAs were also found to be induced in DRG cultures by a variety of other growth factors. Different patterns of induction of NGFIA and NGFIB mRNA observed in DRG cultures suggested that transcript-specific pathways of signal transduction were operating within neurons, dependent upon the particular growth factor stimulus. Comparison of data reported from growth factor treatment of other cell types with data from DRG cultures also revealed patterns of NGFIA and NGFIB mRNA induction specific to DRG neurons.

Pharmacology of chronic pain

Chronic pain, which is associated with prolonged tissue damage or injuries to the peripheral or central nervous system, results from a number of complex changes in nociceptive pathways. These include alterations of cell phenotype and changes in the expression of proteins such as receptors, transmitters and ion channels, as well as modifications of neural structure, for example, cell loss, nerve regeneration and synaptic reorganizations. The resultant increase in neural excitability can be reduced with receptor-selective drugs that block peripheral or central chemical mediators or that control ectopic activity or cellular phenotype changes. In this article, Andy Dray, Laszlo Urban and Anthony Dickenson focus on some current mechanistic aspects of chronic pain imposed by inflammation and peripheral neuropathy, and review in particular the molecular changes involving the pharmacology of nociceptive pathways since these have important implications for the management of pain.

The sequence of 5' flanking DNA from the rat preprotachykinin gene; analysis of putative transcription factor binding sites

The rat preprotachykinin A (rPPT-A) gene is expressed in restricted populations of neurons and endocrine cells, including a subset of dorsal root ganglion (DRG) neurons. As part of a study to investigate the DNA sequences responsible for tissue-specific expression of the gene, we have determined the sequence of the 5' flanking DNA to 3350 bp upstream of the transcription start site. The sequenced region encodes a number of putative transcription factor binding sites which may play important roles in the regulation of rPPT-A gene transcription.