Nucleotide sequence and evolution of a mammalian alpha-tubulin messenger RNA

Interaction of Recombinant Gallus gallus SEPT5 and Brain Proteins of H5N1-Avian Influenza Virus-Infected Chickens

Septin forms a conserved family of cytoskeletal guanosine triphosphate (GTP) binding proteins that have diverse roles in protein scaffolding, vesicle trafficking, and cytokinesis. The involvement of septins in infectious viral disease pathogenesis has been demonstrated by the upregulation of SEPT5 protein and its mRNA in brain tissues of H5N1-infected chickens, thus, providing evidence for the potential importance of this protein in the pathogenesis of neurovirulence caused by the avian influenza virus. In this study, cloning, expression, and purification of Gallus gallus SEPT5 protein was performed in Escherichia coli. The SEPT5 gene was inserted into the pRSETB expression vector, transformed in the E. coli BL21 (DE3) strain and the expression of SEPT5 protein was induced by IPTG. The SEPT5 protein was shown to be authentic as it was able to be pulled down by a commercial anti-SEPT5 antibody in a co-immunoprecipitation assay. In vivo aggregation of the recombinant protein was limited by cultivation at a reduced temperature of 16 °C. Using co-immunoprecipitation techniques, the purified recombinant SEPT5 protein was used to pull down host’s interacting or binding proteins, i.e., proteins of brains of chickens infected with the H5N1 influenza virus. Interacting proteins, such as CRMP2, tubulin proteins, heat-shock proteins and other classes of septins were identified using LCMS/MS. Results from this study suggest that the codon-optimized SEPT5 gene can be efficiently expressed in the E. coli bacterial system producing authentic SEPT5 protein, thus, enabling multiple host’s proteins to interact with the SEPT5 protein.

Endogenous BDNF regulates induction of intrinsic neuronal growth programs in injured sensory neurons

Identification of the molecule(s) that globally induce a robust regenerative state in sensory neurons following peripheral nerve injury remains elusive. A potential candidate is brain-derived neurotrophic factor (BDNF), the sole neurotrophin upregulated in sensory neurons after peripheral nerve injury. Here we tested the hypothesis that BDNF plays a critical role in the regenerative response of mature rat sensory neurons following peripheral nerve lesion. Neutralization of endogenous BDNF was performed by infusing BDNF antibodies intrathecally via a mini-osmotic pump for 3 days at the level of the fifth lumbar dorsal root ganglion, immediately following unilateral spinal nerve injury. This resulted in decreased expression of the injury/regeneration-associated genes growth-associated protein-43 and Talpha1 tubulin in the injured sensory neurons as compared to injury plus control IgG infused or injury alone animals. Similar results were observed following inhibition of BDNF expression by intrathecal delivery of small interfering RNAs (siRNA) targeting BDNF starting 3 days prior to injury. The reduced injury/regeneration-associated gene expression correlated with a significantly reduced intrinsic capacity of these neurons to extend neurites when assayed in vitro. In contrast, delayed infusion of BDNF antibody for 3 days beginning 1 week post-lesion had no discernible influence on the elevated expression of these regeneration-associated markers. These results support an important role for endogenous BDNF in induction of the cell body response in injured sensory neurons and their intrinsic ability to extend neurites, but BDNF does not appear to be necessary for maintaining the response once it is induced.

A crucial role for primary cilia in cortical morphogenesis

Primary cilia are important sites of signal transduction involved in a wide range of developmental and postnatal functions. Proteolytic processing of the transcription factor Gli3, for example, occurs in primary cilia, and defects in intraflagellar transport (IFT), which is crucial for the maintenance of primary cilia, can lead to severe developmental defects and diseases. Here we report an essential role of primary cilia in forebrain development. Uncovered by N-ethyl-N-nitrosourea-mutagenesis, cobblestone is a hypomorphic allele of the IFT gene Ift88, in which Ift88 mRNA and protein levels are reduced by 70-80%. cobblestone mutants are distinguished by subpial heterotopias in the forebrain. Mutants show both severe defects in the formation of dorsomedial telencephalic structures, such as the choroid plexus, cortical hem and hippocampus, and also a relaxation of both dorsal-ventral and rostral-caudal compartmental boundaries. These defects phenocopy many of the abnormalities seen in the Gli3 mutant forebrain, and we show that Gli3 proteolytic processing is reduced, leading to an accumulation of the full-length activator isoform. In addition, we observe an upregulation of canonical Wnt signaling in the neocortex and in the caudal forebrain. Interestingly, the ultrastructure and morphology of ventricular cilia in the cobblestone mutants remains intact. Together, these results indicate a critical role for ciliary function in the developing forebrain.

Dual effect of butyrate on IL-1beta--mediated intestinal epithelial cell inflammatory response

Butyrate (NaBu), a product of intestinal microbial metabolism, has been proposed as an anti-inflammatory agent for treating inflammatory bowel diseases. However, the molecular mechanisms implicated in the modulation of intestinal epithelial cell inflammatory response to NaBu remain unknown. Here, microarray analysis performed on nontransformed human crypt intestinal epithelial cells (HIEC) shows that NaBu regulated specifically the short-term IL-1beta -dependent induction of different inflammatory genes. While NaBu significantly increased the IL-1beta -induction of genes like SAA2, C3, and IL-1alpha , other inflammatory genes like CXCL5, CXCL11, and IL-1beta were decreased. Induction of various genes such as CXCL8, CCL20, and IL-6 was unaffected by NaBu. We show that, compared to genes that are upregulated or downregulated by NaBu, genes that are unaffected by NaBu were induced more rapidly after IL-1beta treatment and contained a higher concentration of transcription factor binding sites in their promoter region. In addition, transient treatment with IL-1beta was sufficient for subsequent induction of NaBu-upregulated and NaBu-unaffected classes of genes, while a continuous presence of IL-1beta was required for NaBu-downregulated gene expression. In conclusion, our results suggest that fundamental differences predispose inflammatory genes to specific regulation by NaBu in intestinal epithelial cells, thereby allowing precise control of inflammation.

Dendritic BC1 RNA in translational control mechanisms

Translational control at the synapse is thought to be a key determinant of neuronal plasticity. How is such control implemented? We report that small untranslated BC1 RNA is a specific effector of translational control both in vitro and in vivo. BC1 RNA, expressed in neurons and germ cells, inhibits a rate-limiting step in the assembly of translation initiation complexes. A translational repression element is contained within the unique 3' domain of BC1 RNA. Interactions of this domain with eukaryotic initiation factor 4A and poly(A) binding protein mediate repression, indicating that the 3' BC1 domain targets a functional interaction between these factors. In contrast, interactions of BC1 RNA with the fragile X mental retardation protein could not be documented. Thus, BC1 RNA modulates translation-dependent processes in neurons and germs cells by directly interacting with translation initiation factors.

Synergy between deacetylase inhibitors and IL-1beta in activation of the serum amyloid A2 gene promoter

Butyrate (NaBu) regulates intestinal inflammatory gene expression in part through inhibition of deacetylase activity, but the exact mechanisms involved remain to be determined. In this study, we showed by Northern blot a synergistic induction of the acute phase protein gene SAA2 with a combination of deacetylase inhibitors (Trichostatin A or NaBu) and IL-1beta in the colon carcinoma cell line Caco-2. While the NF-kappa B DNA-binding site was essential for SAA2 regulation by IL-1beta and deacetylase inhibitors, the C/EBP DNA-binding site modulated SAA2 expression levels, as assessed by transient transfection assays and mutagenesis studies. NaBu was sufficient to induce SAA2 expression after transient treatment with IL-1beta and, conversely, IL-1beta induced SAA2 after transient treatment with NaBu. These data suggest that pretreatment with either NaBu or IL-1beta predisposes the SAA2 promoter to further stimulation. Indeed, both NaBu and IL-1beta led to increased recruitment of NF-kappa B p65, C/EBPbeta, and C/EBP delta, and decreased NF-kappa B p50 and C/EBP alpha DNA-binding to the proximal SAA2 promoter, as assessed by chromatin immunoprecipitation assays. Interestingly, while IL-1beta, in contrast to NaBu, induced histone H4 acetylation, addition of IL-1beta and NaBu increased histone H4 acetylation and both C/EBPbeta and NF-kappa B p65 DNA-binding. Therefore, these results suggest that NaBu and IL- 1beta mediate SAA2 synergistic induction by establishing and maintaining similar and complementary chromatin modifications and transcription factor recruitment as well. In addition to global effects, NaBu specifically regulate gene expression, as exemplified by SAA2.

IL-1 beta-dependent regulation of C/EBP delta transcriptional activity

We have previously shown that the transcription factor C/EBP delta is involved in the intestinal inflammatory response. C/EBP delta regulates several inflammatory response genes, such as haptoglobin, in the rat intestinal epithelial cell line IEC-6 in response to IL-1. However, the different C/EBP delta domains involved in IL-1 beta-mediated transcriptional activation and the kinases implicated have not been properly defined. To address this, we determined the role of the p38 MAP kinase in the regulation of C/EBP delta transcriptional activity. The IL-1-dependent induction of the acute phase protein gene haptoglobin in IEC-6 cells was decreased in response to the p38 MAP kinase inhibitor SB203580, as determined by Northern blot. Transcriptional activity of C/EBP delta was repressed by the specific inhibitor of the p38 MAP kinase, as assessed by transient transfection assays. Mutagenesis studies and transient transfection assays revealed an important domain for transcriptional activation between amino acids 70 and 108. This domain overlapped with a docking site for the p38 MAP kinase, between amino acids 75 and 85, necessary to insure C/EBP delta phosphorylation. Deletion of this domain led to a decrease in basal transcriptional activity of C/EBP delta and in p300-dependent transactivation, as assessed by transient transfection assays, and in IL-1-dependent haptoglobin induction. This unusual arrangement of a kinase docking site within a transactivation domain may functionally be important for the regulation of C/EBP delta transcriptional activity.

Tubulin and actin mRNAs in the young-adult and the aged rat brain: effects of repeated administration with bifemelane hydrochloride

In an attempt to identify the age-dependent changes in the potential synthesis of cytoskeletal proteins, we investigated changes in messenger RNA (mRNA) of alpha-tubulin and beta-actin in the young-adult and the aged rat brain using Northern blot analysis. alpha-Tubulin mRNA levels in the frontal cortex and hippocampus, and beta-actin mRNA levels in the hippocampus were significantly decreased in the aged rat brain. Age-dependent decreases in these mRNAs may be related to the neuronal dysfunction associated with aging, in addition to the reduction of several kinds of receptors previously reported. Repeated administration of bifemelane hydrochloride (4-(2-benzylphenoxy)-N-methylbutylamine hydrochloride) for 14 days increased the levels of beta-actin mRNA in the frontal cortex and the striatum of both young-adult and aged rats, although the effect of bifemelane treatment was smaller and not significant in the aged group. These results suggest that bifemelane treatment may enhance the synthesis of cytoskeletal protein and promote neural plasticity by inducing neurite growth or synapse formation.

Cdk2-dependent phosphorylation of homeobox transcription factor CDX2 regulates its nuclear translocation and proteasome-mediated degradation in human intestinal epithelial cells

By having demonstrated previously that p27(Kip1), a potent inhibitor of G(1) cyclin-cyclin-dependent kinases complexes, increases markedly during intestinal epithelial cell differentiation, we examined the effect of p27(Kip1) on the activity of the transcription factor CDX2. The present results revealed the following. 1) p27(Kip1) interacts with the CDX2 transcription factor. 2) In contrast to CDX2 mRNA levels, CDX2 protein expression levels significantly increased as soon as Caco-2/15 cells reached confluence, slowed their proliferation, and began their differentiation. The mechanism of CDX2 regulation is primarily related to protein stability, because inhibition of proteasome activity increased CDX2 levels. The half-life of CDX2 protein was significantly enhanced in differentiated versus undifferentiated proliferative intestinal epithelial cells. 3) Cdk2 interacted with CDX2 and phosphorylated CDX2, as determined by pull-down glutathione S-transferase and immunoprecipitation experiments with proliferating undifferentiated Caco-2/15 cell extracts. 4) Treatment of Caco-2/15 cells with MG132 (a proteasome inhibitor) and (R)-roscovitine (a specific Cdk2 inhibitor) induced an increase in CDX2 protein levels. 5) Conversely, ectopic expression of Cdk2 resulted in decreased expression of CDX2 protein. 6) Of note, treatment of proliferative Caco-2/15 cells with (R)-roscovitine or leptomycin (an inhibitor of nuclear export through CRM1) led to an accumulation of CDX2 into the nucleus. These data suggest that CDX2 undergoes CRM1-dependent nuclear export and cytoplasmic degradation in cells in which Cdk2 is activated, such as in proliferative intestinal epithelial cells. The targeted degradation of CDX2 following its phosphorylation by Cdk2 identifies a new mechanism through which CDX2 activity can be regulated in coordination with the cell cycle machinery.

Proteolytic stress causes heat shock protein induction, tau ubiquitination, and the recruitment of ubiquitin to tau-positive aggregates in oligodendrocytes in culture

Molecular chaperones and the ubiquitin-proteasome system are participants in the defense against unfolded proteins and provide an effective protein quality control system that is essential for cellular functions and survival. Ubiquitinated tau-positive inclusion bodies containing the small heat shock protein alphaB-crystallin in oligodendrocytes are consistent features of a variety of neurodegenerative diseases, and defects in the proteasome system might contribute to the aggregation process. Oligodendrocytes, the myelin-forming cells of the CNS, are specifically sensitive to stress situations. Here we can show that in cultured rat brain oligodendrocytes proteasomal inhibition by MG-132 or lactacystin caused apoptotic cell death and the induction of heat shock proteins in a time- and concentration-dependent manner. Specifically, alphaB-crystallin was upregulated, and ubiquitinated proteins accumulated. After incubation with MG-132 the tau was dephosphorylated, which enhanced its microtubule-binding capacity. Proteasomal inhibition led to ubiquitination of tau and its association with alphaB-crystallin and to the occurrence of thioflavine S-positive aggregates in the oligodendroglial cytoplasm. These aggregates were positive for tau and also contained ubiquitin and alphaB-crystallin; hence they resembled the glial cytoplasmic inclusions observed in white matter disease and frontotemporal dementias with parkinsonism linked to chromosome 17 (FTDP-17). In summary, the data underscore the specific sensitivity of oligodendrocytes to stress situations and point to a causal relationship of proteasomal impairment and inclusion body formation.

Role of specific CCAAT/enhancer-binding protein isoforms in intestinal epithelial cells

Intestinal epithelial cells participate in the acute phase response in response to inflammation. We have shown that acute phase protein genes are induced during intestinal acute phase response, and that the CCAAT/enhancer binding protein family of transcription factors are involved. To address the role of specific C/EBP isoforms, we generated IEC-6 rat intestinal epithelial cell lines expressing different C/EBP isoforms, by retroviral infection. Overexpression of C/EBPalpha p30 and C/EBPdelta led to increases in C/EBPbeta LAP and C/EBPbeta LIP endogenous protein levels, as determined by electrophoretic mobility shift assays and Western blot. Inhibition of C/EBP activity with dominant negative C/EBPs (C/EBPbeta LIP, 3hF, 4hF) decreased glucocorticoid-, cAMP- and IL-1 responsiveness of the endogenous haptoglobin gene, while overexpression of each C/EBP isoform increased the responsiveness to these regulators. In contrast, dominant negative C/EBPs or C/EBP isoforms did not alter the expression of alpha-acid glycoprotein in response to dexamethasone and of C/EBPbeta and C/EBPdelta in response to various regulators as assessed by Northern blot. These data show that the three C/EBP isoforms are involved in the regulation of haptoglobin and that C/EBPbeta, C/EBPdelta, and alpha-acid glycoprotein expression are not induced by C/EBP isoforms in contrast to other cell types. C/EBPbeta LAP-expressing cells showed an inhibition of cell growth characterized by a delay in p27(Kip1) decrease in response to serum and a decrease in cyclin D isoforms and cyclin E protein levels. Finally, C/EBP isoforms interact with the E2F4 transcription factor. Thus, specific C/EBP isoforms are involved in the differential expression of acute phase protein genes in response to hormones and cytokines. Furthermore, C/EBP isoforms may play a role in the control of cell cycle progression.

Altered hippocampal gene expression prior to the onset of spontaneous seizures in the rat post-status epilepticus model

Neuronal loss, gliosis and axonal sprouting in the hippocampal formation are characteristics of the syndrome of mesial temporal sclerosis (MTS). In the post-status epilepticus (SE) rat model of spontaneous seizures these features of the MTS syndrome can be reproduced. To get a global view of the changes in gene expression in the hippocampus we applied serial analysis of gene expression (SAGE) during the early phase of epileptogenesis (latent period), prior to the onset of the first spontaneous seizure. A total of 10 000 SAGE tags were analyzed per experimental group, resulting in 5053 (SE) and 5918 (control group) unique tags (genes), each representing a specific mRNA transcript. Of these, 92 genes were differentially expressed in the hippocampus of post-SE rats in comparison to controls. These genes appeared to be mainly associated with ribosomal proteins, protein processing, axonal growth and glial proliferation proteins. Verification of two of the differentially expressed genes by in situ hybridization confirmed the changes found by SAGE. Histological analysis of hippocampal sections obtained 8 days after SE showed extensive cell loss, mossy fibre sprouting and gliosis in hippocampal sub regions. This study identifies new high-abundant genes that may play an important role in post-SE epileptogenesis.

Estrogen effects on neurite outgrowth and cytoskeletal gene expression in ERalpha-transfected PC12 cell lines

The potential of gonadal steroids like estrogen (E) to promote neurite sprouting is of interest in development and aging, as well as after neural trauma. The specific roles of the two main estrogen receptors, ERalpha and ERbeta, in neuronal sprouting are not yet well understood. We examined the hypothesis that E can enhance nerve growth factor (NGF)-stimulated neurite sprouting in an ERalpha-dependent manner. PC12 cells that were stably transfected with the full-length rat ERalpha gene (PCER) and a control line of cells transfected with vector DNA alone (PCCON) were compared. Both cell lines vigorously differentiate neurites when treated with NGF. We determined that both lines show basal expression of ERbeta mRNA, but only the PCER cells express ERalpha mRNA. Estrogen treatment markedly enhanced NGF-stimulated neurite outgrowth from PCER but not from PCCON cells. Significantly larger proportions of PCER cells (34 and 53% at 24 and 48 h, respectively) had neurites than did the PCCON cells (17 and 26% at 24 and 48 h) after E plus NGF treatment. We also examined the effects of E and NGF treatment of PCER and PCCON cells on peripherin, alpha-tubulin, and tau mRNA expression. In undifferentiated PCER cells, E treatment increased peripherin, reduced alpha-tubulin, and did not alter tau mRNA levels. No changes in these mRNAs were observed in the controls (undifferentiated PCCON cells) after E treatment. NGF treatment markedly stimulated expression of peripherin, alpha-tubulin, and tau mRNAs in both PCER and PCCON cells. From these observations we conclude that E synergizes with NGF and stimulates neurite sprouting and also modulates expression of several cytoskeletal mRNAs through ERalpha.

Intestinal epithelial cell differentiation involves activation of p38 mitogen-activated protein kinase that regulates the homeobox transcription factor CDX2

The intracellular signaling pathways responsible for cell cycle arrest and differentiation along the crypt-villus axis of the human small intestine remain largely unknown. p38 mitogen-activated protein kinases (MAPKs) have recently emerged as key modulators of various vertebrate cell differentiation processes. In order to elucidate further the mechanism(s) responsible for the loss of proliferative potential once committed intestinal cells begin to differentiate, the role and regulation of p38 MAPK with regard to differentiation were analyzed in both intact epithelium as well as in well established intestinal cell models recapitulating the crypt-villus axis in vitro. Results show that phosphorylated and active forms of p38 were detected primarily in the nuclei of differentiated villus cells. Inhibition of p38 MAPK signaling by 2-20 microm SB203580 did not affect E2F-dependent transcriptional activity in subconfluent Caco-2/15 or HIEC cells. p38 MAPK activity dramatically increased as soon as Caco-2/15 cells reached confluence, whereas addition of SB203580 during differentiation of Caco-2/15 cells strongly attenuated sucrase-isomaltase gene and protein expression as well as protein expression of villin and alkaline phosphatase. The binding of CDX2 to the sucrase-isomaltase promoter and its transcriptional activity were significantly reduced by SB203580. Pull-down glutathione S-transferase and immunoprecipitation experiments demonstrated a direct interaction of CDX3 with p38. Finally, p38-dependent phosphorylation of CDX3 was observed in differentiating Caco-2/15 cells. Taken together, our results indicate that p38 MAPK may be involved in the regulation of CDX2/3 function and intestinal cell differentiation.

Glial cell line-derived neurotrophic factor (GDNF) gene delivery protects dopaminergic terminals from degeneration

Previously, we observed that injection of an adenoviral (Ad) vector expressing glial cell line-derived neurotrophic factor (GDNF) into the striatum, but not the substantia nigra (SN), prior to a partial 6-OHDA lesion protects dopaminergic (DA) neuronal function and prevents the development of behavioral impairment in the aged rat. This suggests that striatal injection of AdGDNF maintains nigrostriatal function either by protecting DA terminals or by stimulating axonal sprouting to the denervated striatum. To distinguish between these possible mechanisms, the present study examines the effect of GDNF gene delivery on molecular markers of DA terminals and neuronal sprouting in the aged (20 month) rat brain. AdGDNF or a control vector coding for beta-galactosidase (AdLacZ) was injected unilaterally into either the striatum or the SN. One week later, rats received a unilateral intrastriatal injection of 6-OHDA on the side of vector injection. Two weeks postlesion, rats injected with AdGDNF into either the striatum or the SN exhibited a reduction in the area of striatal denervation and increased binding of the DA transporter ligand [(125)I]IPCIT in the lesioned striatum compared to control animals. Furthermore, injections of AdGDNF into the striatum, but not the SN, increased levels of tyrosine hydroxylase mRNA in lesioned DA neurons in the SN and prevented the development of amphetamine-induced rotational asymmetry. In contrast, the level of T1 alpha-tubulin mRNA, a marker of neuronal sprouting, was not increased in lesioned DA neurons in the SN following injection of AdGDNF either into the striatum or into the SN. These results suggest that GDNF gene delivery prior to a partial lesion ameliorates damage caused by 6-OHDA in aged rats by inhibiting the degeneration of DA terminals rather than by inducing sprouting of nigrostriatal axons.

Inhibition by deacetylase inhibitors of IL-1-dependent induction of haptoglobin involves CCAAT/Enhancer-binding protein isoforms in intestinal epithelial cells

Intestinal epithelial cells participate in an acute phase response (APR) by responding to cytokines and by expressing acute phase protein genes. We hypothesized that butyrate, a fermentation product of the bacterial intestinal flora with deacetylase activity, affects the APR in intestinal epithelial cells. Sodium butyrate (NaBu) and Trichostatin A (TSA) induced alkaline phosphatase activity and histone H4 acetylation in IEC-6 rat intestinal epithelial cells treated with or without interleukin-1beta (IL-1). In contrast, both NaBu and TSA attenuated the IL-1-dependent induction of the acute phase protein gene haptoglobin, as well as C/EBPbeta and C/EBPdelta transcription factors mRNAs. Gel shift and supershift assays showed a strong decrease in the IL-1-induced C/EBPbeta and C/EBPdelta containing complexes binding to the HaptoA C/EBP DNA-binding site of the haptoglobin promoter, by NaBu and TSA. Furthermore, site-specific mutation of the HaptoA site abolished the NaBu- and TSA-dependent inhibition of haptoglobin, as determined by transient transfection assays. These results suggest that deacetylase inhibitors may regulate the IL-1 dependent induction of haptoglobin by down-regulating C/EBP isoforms, and that C/EBPs represent a target for the action of butyrate in the control of the APR of intestinal epithelial cells.

Spontaneous retinoic acid receptor beta 2 expression during mesoderm differentiation of P19 murine embryonal carcinoma cells

Exposure of aggregated murine P19 embryonal carcinoma cells to dimethylsulfoxide (DMSO) induces mesoderm and both embryonic cardiac and skeletal muscle differentiation, while retinoic acid (RA) is an inducer of neuroectodermal differentiation. P19 cells constitutively express the retinoic acid receptor alpha (RAR alpha) and RAR gamma mRNAs while RAR beta expression is induced by RA through a consensus RA-response element in the RAR beta promoter. In the present study we show that the RAR beta transcript is strongly expressed in both P19 cells and in a RA-nonresponsive derivative of P19 cells, called RAC65, during DMSO-induced mesoderm and muscle differentiation. Reverse transcriptase-polymerase chain reaction analysis indicated that RAR beta 2 is the predominant isoform expressed in DMSO-differentiated cells, providing the first evidence for RA-independent regulation of RAR beta 2 transcript levels. Immunoblot analysis showed a 3-fold increase in the RAR beta protein expression over basal levels in differentiated cells, and immunohistochemistry indicated that all cells in the culture including muscle reacted positively for the RAR beta protein. RAR beta 2 transcript expression was differentiation-dependent and occurred without transactivation of a transfected RARE beta 2 reporter gene. Little transcription of the RAR beta gene was detected in nuclear run-off assays of undifferentiated P19 cells and only a small increase in transcription was observed in nuclei from DMSO-treated cells. RA treatment of P19 cells stably transfected with the RA-responsive element from the RAR beta gene showed that RAR beta 2 mRNA expression during DMSO differentiation was associated with increased sensitivity to RA. Together these data show that RAR beta 2 is expressed spontaneously in an apparently RA-independent manner in differentiating mesoderm and mesoderm derivatives, resulting in increased sensitivity to RA in these cells.

Attenuation of haptoglobin gene expression by TGFbeta requires the MAP kinase pathway

In addition to important roles in the regulation of cell growth and cell restitution, both pro- and anti-inflammatory effects have been ascribed to TGFbeta in intestinal epithelial cells. However, the mechanisms involved in TGFbeta-dependent anti-inflammatory activities remain to be determined. In the rat intestinal epithelial cell line IEC-6, TGFbeta attenuated the glucocorticoid-dependent increases in mRNA levels of the acute phase protein gene haptoglobin, and of C/EBP isoforms beta and delta. Supershift assays demonstrated a TGFbeta-mediated decrease in the binding of C/EBP isoforms beta and delta to the haptoA and haptoC C/EBP DNA-binding sites from the haptoglobin promoter. Mutations of both HaptoA and HaptoC sites abolished the glucocorticoid-dependent activation and the TGFbeta-mediated attenuation of the haptoglobin promoter, as assessed by transient transfection assays. TGFbeta induced p42/p44 MAP kinase activities. Treatment with the MEK 1/2 inhibitor PD 98059 abolished TGFbeta attenuation. These results suggest that C/EBP isoforms are involved both in the glucocorticoid-dependent induction and in the TGFbeta-mediated attenuation of haptoglobin expression. Furthermore, p42/p44 MAP kinases may function in a TGFbeta-dependent signaling pathway leading to attenuation of haptoglobin expression.

Developmental regulation of alternatively spliced isoforms of mRNA encoding MAP2 and tau in rat brain oligodendrocytes during culture maturation

Oligodendrocytes are responsible for the formation and maintenance of the myelin sheaths in the central nervous system (CNS), and microtubules essentially participate in the elaboration and stabilization of myelin-containing cellular processes. We have shown before that the two major groups of neuronal microtubule-associated proteins (MAPs), MAP2 and tau, are expressed in the myelin forming cells of the CNS (Mueller et al. [1997] Cell Tissue Res. 288:239-249). Here we demonstrate for the first time that during culture maturation, changes in mRNA splicing and a shift from immature to mature MAP2 and tau mRNAs occur in oligodendrocytes. Similarly to neurons, a developmental shift from MAP2 isoforms with 3 microtubule (MT)-binding domains (3R) to the isoforms with 4 MT-binding domains (4R) is observable. MAP2c constitutes the major MAP2 isoform in oligodendrocytes. They contain tau mRNA splice products with both 3 and 4 MT-binding repeats (3R, 4R) with no amino terminal insert or with exon 2, and do not express isoforms containing exon 3. The shortest form tau 1 (3R; no inserts) representing the immature tau isoform is most prominently expressed in early progenitor cells and gradually decreases during culture maturation, while tau 5 (4R; with exon 2) appears later during in vitro differentiation. The product corresponding to tau 2 (3R; with exon 2) and tau 4 (4R; no inserts) remains approximately at the same level. Hence, the occurrence of MAPs in oligodendrocytes is developmentally regulated. While in progenitor cells, 3R- and 4R-MAP2c are expressed at approximately the same level, in mature oligodendrocytes after 12 days in vitro, the ratio of 4R- to 3R-MAP2c is nearly 2. In contrast, the ratio of 4R- to 3R-tau in progenitor cells is 1:3 and shifts to 1:1 after 12 days in culture.

Negative regulation of glucocorticoid-dependent induction of c-fos by ras in intestinal epithelial cells

In order to investigate the regulatory mechanisms involved in the expression of fos and jun family members by glucocorticoids, and the effect of ras transformation in intestinal epithelial cells, we used the rat cell line IEC-6. Dexamethasone treatment induced transiently c-jun mRNAs, in contrast to the sustained expression of c-fos, whereas its effect on junB expression resulted in a later increase. Dexamethasone-dependent stimulation of c-fos and c-jun was modulated predominantly at the level of transcription. Sustained levels of induced c-fos and c-jun proteins were observed after dexamethasone treatment. AP-1 DNA-binding capacity of c-fos, and to a smaller extent c-jun, was increased by glucocorticoids later than after serum treatment. To analyse the effect of ras on the glucocorticoid response of AP-1 components, we studied several IEC-6 cell clones transformed by the Ha-ras oncogene. In comparison to normal cells, these transformants displayed increased AP-1 DNA-binding activity with higher levels of junB and variable levels of c-jun in the AP-1 complex. Ras transformation repressed the growth-inhibitory properties of glucocorticoids. Furthermore, ras inhibited the glucocorticoid-dependent induction of c-fos protein and mRNA, leading to changes in AP-1 composition as compared to normal cells. As assessed by transient transfection luciferase assays, glucocorticoids induced significantly a minimal promoter containing 3 copies of an AP-1 DNA-binding site as well as the murine c-fos -276 to +112 promoter in non-transformed cells. In contrast, glucocorticoid addition did not induce these constructs in two ras transformed cell lines. These results suggest that ras negatively modulates specific responses of intestinal epithelial cells to glucocorticoids.

Activation of haptoglobin gene expression by cAMP involves CCAAT/enhancer-binding protein isoforms in intestinal epithelial cells

CCAAT/enhancer-binding protein (C/EBP) isoforms are expressed in rodent intestine and in the rat intestinal epithelial cell line IEC-6 but their role remains to be determined. Treatment of IEC-6 cells with the adenylate cyclase activator forskolin led to coordinate induction of C/EBP isoforms alpha, beta and delta at the mRNA and protein levels. Transient transfection assays showed that their expression is controlled at the transcriptional level. Forskolin treatment induced haptoglobin mRNA levels. Electrophoretic mobility shift and supershift assays demonstrated an increase in DNA-binding activities of the three C/EBP isoforms to the haptoA and haptoC C/EBP DNA-binding sites of the proximal haptoglobin promoter. Site-specific mutations of both sites led to a decrease in transcriptional induction by forskolin, suggesting that C/EBP isoforms are involved in the cAMP-dependent regulation of the acute-phase protein gene haptoglobin in intestinal epithelial cells.

Identification in the rat prolactin gene of sequences homologous to the distal promoter of the human prolactin gene

The goal of the present study was to test the hypothesis that a second, more distal, promoter exists upstream from the rat prolactin (PRL) gene (rPrl) that is homologous to that identified upstream from the human prolactin gene (hPrl). The nucleotide sequence of the rat genome extending from 7.4 to 2.5 kb upstream from the proximal rPrl promoter was determined, revealing significant sequence homology to the hPrl distal promoter and its 5'-flanking domain. Using reverse transcription-polymerase chain reaction, novel rPrl transcripts that originate upstream from the proximal rPrl promoter were detected in rat uterus, spleen, pons medulla, anterior pituitary and the GH4C1 pituitary tumor cell line. Further characterization of these novel 5'-extended rPrl transcripts from GH4C1 cells indicated that they were full length, polyadenylated and properly spliced. However, data from primer extension (5'-RACE) experiments strongly suggested that the 5'-extended rPrl transcripts originate, not at the distal promoter-like motif, but at scattered sites located 60-153 bp upstream from the proximal promoter. Therefore, it appears improbable that the rat sequences homologous to the hPrl distal promoter comprise a functional promoter.

The Dazh gene is expressed in male and female embryonic gonads before germ cell sex differentiation

The autosomal homologs of the human Y-chromosomal DAZ gene (DAZH and Dazh in human and mouse, respectively) are strong candidate for Azoospermia factor and encode a testis specific RNA-binding proteins. We studied the expression pattern of the mouse Dazh during embryonic development by using Northern-blotting of developing gonads. In the mouse, we have detected 3.5 kb and 4.5 kb transcripts in male and female embryonic gonads at 12.5 dpc (days post coitum). During this period, the only germ cells present in the gonad are primordial germ cells. Dazh transcripts were not detected in embryonic gonads of mice that lack germ cells because of mutation in W gene, suggesting that expression is limited to germ-cells. In females, oogonia enter meiosis at 13.5-14.5 dpc: at this time Dazh transcription levels are similar to those of the male (when prospermatogonia are in the male gonad). Transcription levels decrease steadily after birth as the number of oocytes is depleted and is hardly detectable by puberty. A human DAZH transcript was also detected by Northern-blotting in the human ovary in levels which are of about 100 fold lower than those observed in the human testis. The expression of the Dazh in male and female gonad before germ cell sex differentiation suggests that these genes may act at the first phase of male and female gametogenesis.

Isolation and characterization of a gene encoding alpha-tubulin from Candida albicans

A gene encoding the alpha-tubulin of Candida albicans has been cloned and characterized. Nucleotide sequence analysis reveals the presence of an intron within the structural gene and predicts the synthesis of a polypeptide of 448 amino acid residues. Comparison of nucleotide and amino acid sequences with the Saccharomyces cerevisiae alpha-tubulin encoding genes shows a 75% homology and about 92% similarity respectively. In contrast to S. cerevisiae, C. albicans appears to possess only one gene for alpha-tubulin which is able to functionally complement a S. cerevisiae cold-sensitive tub1 mutant.

Effect of gonadotropin-releasing hormone (GnRH) pulse frequency on serum and pituitary concentrations of luteinizing hormone and follicle-stimulating hormone, GnRH receptors, and messenger ribonucleic acid for gonadotropin subunits in cows

Thirty-two nutritionally anestrous cows were used to determine the effect of the frequency of exogenous GnRH pulses on ovarian follicular growth, serum concentrations of LH and FSH, and concentrations of LH, FSH, GnRH receptors (GnRH-R), messenger RNA (mRNA) for GnRH-R, and mRNA for gonadotropin subunits in the pituitary. Cows were randomly assigned to one of four treatments: 2 micrograms GnRH infused (i.v.) continuously during 1 h, 2 micrograms GnRH infused during 5 min once every hour, 2 micrograms GnRH infused during 5 min once every fourth hour, or saline (control) for 13 days. Infusion of GnRH every hour increased LH concentrations in serum (P < 0.05), but FSH concentrations were not affected by GnRH infusion. Luteal activity (LA) was assessed by the presence of corpora lutea and/or serum progesterone greater than 1 ng/ml. Six of eight cows infused with GnRH every hour had LA by day 13, whereas only 25% of cows infused either continuously or with a pulse every fourth hour had LA by day 13. None of the control cows had LA during the experiment (P < 0.01). Concentrations of LH and FSH in the pituitary were significantly reduced when GnRH was infused hourly or continuously. Concentrations of common alpha and FSH beta mRNA were not influenced by treatment. However, continuous infusion of GnRH decreased (P < 0.05) LH beta mRNA subunit. Concentrations of GnRH-R (P < 0.1) and GnRH-R mRNA (P < 0.05) were reduced when GnRH was infused continuously. We concluded that pulsatile secretion of LH is necessary for follicular growth and LA in beef cattle, and GnRH treatment differentially regulates LH and FSH gene transcription and serum concentrations of LH and FSH in cattle.

Comparison of the expression of a T alpha 1:nlacZ transgene and T alpha 1 alpha-tubulin mRNA in the mature central nervous system

We have previously demonstrated that one member of the alpha-tubulin multigene family, termed T alpha 1 in rats, is a panneuronal gene that is regulated as a function of neuronal growth and regeneration. Moreover, 1.1 kb of the 5' upstream region from this gene is sufficient to direct expression of a marker gene to growing neurons in transgenic mice. In this report, we have characterized the distribution of the T alpha 1:nlacZ transgene in the mature central nervous system in two lines of transgenic mice and have compared its expression to that of the endogenous T alpha 1 alpha-tubulin mRNA. These results demonstrate that the pattern of expression of the T alpha 1:nlacZ transgene is similar to that of T alpha 1 mRNA, with a few notable differences. Furthermore, expression of the transgene and the mRNA within the mature brain is panneuronal and, in many cases, is highest in those populations of neurons that show some capacity for morphological growth. These results, together with our previous studies on mature regenerating neurons (Gloster et al. [1994] J. Neurosci. 14:7319-7330; Wu et al. [1994] Soc. Neurosci. Abstr. 20:542) suggest that the T alpha 1:nlacZ transgene will provide a useful marker of growth-associated gene expression in the mature nervous system.

Germ-line passage is required for establishment of methylation and expression patterns of imprinted but not of nonimprinted genes

Embryonic stem (ES) cells homozygous for a disruption of the DNA (cytosine-5)-methyltransferase gene (Dnmt) proliferate normally with their DNA highly demethylated but die upon differentiation. Expression of the wild-type Dnmt cDNA in mutant male ES cells caused an increase in methylation of bulk DNA and of the Xist and Igf2 genes to normal levels, but did not restore the methylation of the imprinted genes H19 and Igf2r. These cells differentiated normally in vitro and contributed substantially to adult chimeras. While the Xist gene was not expressed in the remethylated male ES cells, no restoration of the normal expression profile was seen for H19, Igf2r, or Igf2. This indicates that ES cells can faithfully reestablish normal methylation and expression patterns of nonimprinted genes but lack the ability to restore those of imprinted genes. Full restoration of monoallelic methylation and expression was imposed on H19, Igf2, and Igf2r upon germ-line transmission. These results are consistent with the presence of distinct de novo DNA methyltransferase activities during oogenesis and spermatogenesis, which specifically recognize imprinted genes but are absent in the postimplantation embryo and in ES cells.

Selective upregulation of T alpha 1 alpha-tubulin and neuropeptide Y mRNAs after intermittent excitatory stimulation in adult rat hippocampus in vivo

Adult central neurons exhibit significant structural and molecular changes in epilepsy. We have examined changes in two markers of morphological and physiological plasticity, T alpha 1 alpha-tubulin (T alpha 1) and neuropeptide Y (NPY) mRNAs, in response to intermittent (20 Hz, 10 seconds, 1 minute-1) stimulation of the rat perforant path in vivo. Stimulus trains elicited brief (0.5-3 seconds) afterdischarges in the ipsilateral dentate gyrus (DG). Four hours of stimulation caused no significant loss of inhibition in the DG 40-48 hours after stimulation ceased. However, it did lead to an increase in NPY mRNA in neurons of the ipsilateral and, to a lesser extent, contralateral DGs and Ammon's Horn. Many of these were presumably interneurons that normally express NPY. However, dentate granule cells (DGCs), which do not normally express this peptide, also expressed robust levels of NPY mRNA bilaterally. NPY mRNA levels peaked at 4-24 hours and returned to baseline by 48 hours poststimulation. Although 24 hours of stimulation induced a similar increase in interneurons, DGCs showed no detectable NPY mRNA. Afterdischarges were necessary to elevate NPY mRNA expression. Four hours of stimulation elevated T alpha 1 mRNA expression in both ipsilateral and, to a lesser extent, contralateral DGCs; this elevation peaked at 24 hours poststimulation and declined to baseline by 72 hours. Stimulation for 24 hours caused broader changes in T alpha 1 mRNA expression, with increases in DGCs and in CA3 pyramidal cells bilaterally. Acute denervation of the DG did not affect T alpha 1 mRNA level in the hippocampal formation. Elevated synaptic input resulting in afterdischarges, but not necessarily in excitability changes in the DG, led to alterations in the expression of molecular markers of plasticity. These changes may reflect adaptive responses to physiological activation.

Developmental regulation of two distinct neuronal phenotypes in rat dorsal root ganglia

In a previous study we described two distinct neuronal phenotypes in rat dorsal root ganglia based on immunocytochemical assays for the neuronal intermediate filament proteins, peripherin and low-molecular-weight neurofilaments [Goldstein M. E. et al. (1991) J. Neurosci. Res. 30, 92-104]. In this paper we have extended this classification by using in situ hybridization to localize and evaluate the levels of various cytoskeletal and neuropeptide messenger RNAs within the peripherin-immunoreactive and peripherin-immunoreactive-negative neurons found in embryonic day 15 and 20, postnatal day 2 and adult dorsal root ganglia. We found in postnatal and adult dorsal root ganglia in vivo that the large, peripherin-immunoreactive-negative neurons, which are intensely stained by low-molecular-weight neurofilament antibodies, also contain high levels of low, medium and high-molecular-weight neurofilament messenger RNAs, whereas the smaller peripherin-immunoreactive neurons do not. On the other hand, both cell types contained comparable levels of peripherin and alpha-tubulin messenger RNA. The presence of peripherin messenger RNA but no peripherin immunoreactivity in the large cells suggested either a translational or post-translational regulation of this polypeptide, or rapid clearance of this protein from the perikaryon into the axon. In adult dorsal root ganglia, more than 50% of the peripherin-immunoreactive neurons also contained high levels of substance P and/or calcitonin gene-related peptide messenger RNAs, while less than 20% of the large peripherin-immunoreactive-negative neurons did. The attainment of these phenotypic characteristics during development in vivo was studied by northern blot and in situ hybridization histochemistry. In early embryonic stages (embryonic days 15-16), virtually all neurons were peripherin-immunoreactive and were positive for peripherin, alpha-tubulin and low-molecular-weight neuro-filament messenger RNAs, suggesting a homogeneous population. By embryonic day 20, the two adult phenotypes became clearly evident, and were fully established by postnatal day 2. In cultures of embryonic day 15 dorsal root ganglion neurons grown in the presence of nerve growth factor, peripherin and low-molecular-weight neurofilament messenger RNAs were expressed in all neurons, even after nine days in vitro, similar to embryonic dorsal root ganglia in vivo. Nerve growth factor supplemented by skeletal and heart muscle extracts did up-regulate neurofilament gene expression, but not to the extent characteristic of the peripherin-immunoreactive-negative adult phenotype. These results suggest that development of the mature phenotype of dorsal root ganglion neurons occurs by postnatal day 2 in vivo and is dependent upon target contact and/or target-derived factors.

Developmental regulation of alpha-tubulin mRNAs during the differentiation of cultured cerebellar granule cells

T alpha 1 and T26 alpha-tubulin mRNA expression was examined during the differentiation of rat cerebellar granule cells in vitro and in situ. High levels of T alpha 1 transcript correlated with neurons extending processes and hence may implicate T alpha 1 with neuritogenesis. In comparison, T26 labeling was much less prominent, appeared more constitutive and was possibly associated with cell proliferation. Such profiles indicate that the different isotypes play different roles in the assembly and function of microtubules during neuronal differentiation.

Constitutive expression of calreticulin in osteoblasts inhibits mineralization

Recent studies have shown that the multifunctional protein calreticulin can localize to the cell nucleus and regulate gene transcription via its ability to bind a protein motif in the DNA-binding domain of nuclear hormone receptors. A number of known modulators of bone cell function, including vitamin D, act through this receptor family, suggesting that calreticulin may regulate their action in bone cells. We have used a gain-of-function strategy to examine this putative role of calreticulin in MC3T3-E1 osteoblastic cells. Purified calreticulin inhibited the binding of the vitamin D receptor to characterized vitamin D response elements in gel retardation assays. This inhibition was due to direct protein-protein interactions between the vitamin D receptor and calreticulin. Expression of calreticulin transcripts declined during MC3T3-E1 osteoblastic differentiation. MC3T3-E1 cells were transfected with calreticulin expression vectors; stably transfected cell lines overexpressing recombinant calreticulin were established and assayed for vitamin D-induced gene expression and the capacity to mineralize. Constitutive calreticulin expression inhibited basal and vitamin D-induced expression of the osteocalcin gene, whereas osteopontin gene expression was unaffected. This pattern mimicked the gene expression pattern observed in parental cells before down-regulation of endogenous calreticulin expression. In long-term cultures of parental or vector-transfected cells, 1 alpha,25-dihydroxyvitamin D3 (1,25[OH]2D3) induced a two- to threefold stimulation of 45Ca accumulation into the matrix layer. Constitutive expression of calreticulin inhibited the 1,25(OH)2D3-induced 45Ca accumulation. This result correlated with the complete absence of mineralization nodules in long-term cultures of calreticulin-transfected cells. These data suggest that calreticulin can regulate bone cell function by interacting with specific nuclear hormone receptor-mediated pathways.

N-methyl-D-aspartate acutely increases proenkephalin mRNA in the rat striatum

Studies in which glutamate (GLU) neurotransmission has been reduced at striatal synapses have shown that GLU influences the biosynthesis of certain peptide cotransmitters by striatal neurons. The present experiment was designed to test the effects of direct activation of the NMDA or AMPA types of GLU receptor on the levels of two mRNAs that encode the peptide cotransmitters met5-enkephalin (ME) and substance P (SP). In situ hybridization histochemistry of forebrain tissue sections from rats 8 h after a single intracerebroventricular infusion of NMDA or AMPA revealed a significant and dose-dependent elevation (to a maximum of almost 50%) of striatal ME mRNA when compared to vehicle-injected controls. SP mRNA was not significantly affected. NMDA was more effective than AMPA over the dose range used. Pretreatment with a potent and highly specific AMPA antagonist (NBQX) predictably blocked the AMPA-mediated elevation, and was only slightly effective against the NMDA-induced response. In striking contrast, pretreatment with a potent and highly selective NMDA antagonist (CGP37849) fully opposed both the NMDA- and the AMPA-mediated elevation of ME mRNA. These data further implicate the NMDA receptor in the regulation of peptide cotransmitter gene transcription. They suggest also that the AMPA receptor may play an indirect, synergistic role in the genetic responses of striatal neurons to GLU transmission.

Differentially expressed genes after peripheral nerve injury

In an attempt to identify genes associated with Wallerian degeneration and peripheral nerve regeneration we have performed differential hybridization screening of a cDNA library from crushed rat sciatic nerve (7 days postlesion) using radioactively labeled cDNA prepared from poly(A)+ RNA of normal vs. crushed nerve. Screening of 5,000 randomly selected colonies yielded 24 distinct clones that were regulated following nerve injury. Fifteen of the differentially expressed sequences could be classified as induced, whereas 9 sequences appeared to be repressed at 1 week postcrush. Sequencing and computer-assisted sequence comparison revealed 3 classes of regulated cDNA clones representing 1) novel gene sequences (8 clones) including 3 transcripts containing a repetitive "brain identifier" (ID) element; 2) identified genes (7 clones) with previously undetected expression in the peripheral nervous system (PNS), such as apolipoprotein D, peripheral myelin protein 22kD (PMP22), SPARC (secreted protein, acidic and rich in cysteine), sulfated glycoprotein SGP-1, apoferritin, decorin, and X16/SRp20; and 3) identified genes (9 clones) with known expression in the PNS including, e.g., the myelin protein P0, gamma-actin, vimentin, alpha-tubulin, chargerin II, and cytochrome c-oxidase subunit I. Northern blot and polymerase chain reaction analyses with RNA from crushed and transected nerve demonstrated that sequences with related function, like the group of myelin genes, cytoskeleton genes, genes involved in RNA processing and translation, in lipid transport or energy metabolism showed closely related temporal patterns of expression during nerve degeneration and regeneration. Finally, we compared the differentially expressed genes identified at 7 days after crush injury (this investigation) with the regulated sequences isolated previously by De Leon et al. (J Neurosci Res 29:437-488, 1991) from a 3 day postcrush sciatic nerve cDNA library.

Effect of fasting and growth hormone (GH) administration on GH receptor (GHR) messenger ribonucleic acid (mRNA) and GH-binding protein (GHBP) mRNA levels in male rats

To elucidate whether GHR and GHBP are coordinately regulated or not, we studied the effect of fasting with or without GH administration on the GHR and GHBP mRNAs in the liver as well as in extrahepatic tissues in rats. Tissues were collected from 7-week-old male rats by decapitation 1,3, and 7 days after the start of fasting. Liver GHR mRNA levels were not affected 1 day after the start of fasting but progressively decreased for the subsequent 3 and 7 days of fasting as compared with those in control rats fed ad libitum. In contrast, liver GHBP mRNA levels significantly rose after 1 day fasting, returned to the control level after 3 days and further reduced after 7 days of fasting. Changes in GHBP mRNA level after fasting were different among the tissues. A transient increase in GHBP mRNA levels was observed in muscle and heart as well as liver, while the GHBP mRNA levels in fat tissues did not change throughout 7 days of fasting. Next, bovine GH(bGH) was administered ip to the fasted rats and control fed rats for either 1 day(100 micrograms [corrected], tid) or 5 days(150 micrograms [corrected], daily). In fed rats, liver GHR mRNA level was significantly increased by 1 day bGH treatment, but after 5 days treatment with bGH it was not different from the level in saline-injected control. Accordingly, net increment of plasma IGF-I was 296.0 ng/ml with 1 day bGH treatment and 234.2 ng/ml with bGH administration for 5 days. In fasted rats, liver GHR mRNA level did not changed after 1 day treatment with bGH, but markedly decreased 5 days after bGH administration. Net increment of plasma IGF-I was slightly reduced to 284 ng/ml with 1 day treatment with bGH, and markedly decreased to 37.0 with bGH administration for 5 days. The effect of GH administration on liver GHBP mRNA level was virtually absent in either fasting or fed state. These findings suggest that GHR and GHBP mRNAs in the liver are expressed in different ways and that expression of GHBP mRNA is differently regulated among tissues.

Thy-1-mediated activation of rat basophilic leukemia cells does not require co-expression of the high-affinity IgE receptor

The glycosylphosphatidylinositol (GPI)-anchored protein Thy-1 is one of the most abundant molecules expressed on the surface of rat mast cells and rat basophilic leukemia cells, RBL-2H3. Antibody-mediated aggregation of Thy-1 induces in these cells release of secretory components; so does aggregation of the receptor with high affinity for IgE (Fc epsilon RI). To examine whether there is any relationship between Thy-1- and Fc epsilon RI-mediated activation, we have isolated from mutagenized RBL-2H3 cells a variant cell line deficient in the expression of surface Fc epsilon RI, and analyzed its ability to be activated by an antibody to Thy-1. Northern and immuno-blot analyses revealed that the variant cells were deficient in the expression of a structural or a regulatory gene for Fc epsilon RI gamma subunit. The cells did not respond by release of secretagogues and protein-tyrosine phosphorylation to IgE and antigen and anti-Fc epsilon RI monoclonal antibody (mAb) but their response to anti-Thy-1.1 mAb and calcium ionophore A23187 was retained. Transfection of the cloned Fc epsilon RI gamma subunit into the variant cells restored the surface expression of Fc epsilon RI and responsiveness to both the antigen and anti-Fc epsilon RI mAb but had no effect on responsiveness to anti-Thy-1 mAb. The combined data indicate that aggregation of surface Thy-1 glycoproteins activates a metabolic pathway which is independent of the presence of Fc epsilon RI gamma subunit and surface expression of Fc epsilon RI.

Inhibition of transcription factor GATA-4 expression blocks in vitro cardiac muscle differentiation

Commitment of mesodermal cells to the cardiac lineage is a very early event that occurs during gastrulation, and differentiation of cardiac muscle cells begins in the presomite stage prior to formation of the beating heart tube. However, the molecular events, including gene products that are required for differentiation of cardiac muscle cells, remain essentially unknown. GATA-4 is a recently characterized cardiac muscle-restricted transcription factor whose properties suggest an important regulatory role in heart development. We tested the role of GATA-4 in cardiac differentiation, using the pluripotent P19 embryonal carcinoma cells, which can be differentiated into beating cardiac muscle cells. In this system, GATA-4 transcripts and protein are restricted to cells committed to the cardiac lineage, and induction of GATA-4 precedes expression of cardiac marker genes and appearance of beating cells. Inhibition of GATA-4 expression by antisense transcripts blocks development of beating cardiac muscle cells and interferes with expression of cardiac muscle markers. These data indicate that GATA-4 is necessary for development of cardiac muscle cells and identify for the first time a tissue-specific transcription factor that may be crucial for early steps of mammalian cardiogenesis.

Cloning characterization and expression of the cDNA encoding a neuron-specific alpha-tubulin isoform highly represented in the electric lobe of Torpedo marmorata

A cDNA (alpha T6) encoding an alpha-tubulin from Torpedo marmorata (Tm) was isolated and sequenced. The deduced 451-amino-acid (aa) sequence codes for an alpha-tubulin of 50,161 Da. The aa sequence of alpha T6 of Tm showed a 70-99.6% identity to the other alpha-tubulins previously described. Moreover, the alpha T6 aa sequence was 95-99.6% identical to neural-specific tubulins of mouse, rat, human and siberian salmon. The corresponding mRNA is highly represented in the giant motoneurons of the electric lobe. All neuronal populations of the Tm brain exhibit variable levels of alpha T6 expression, with the highest levels in the long-axon-projecting neurons. These results suggest that this alpha-tubulin isoform may play an important role in the maintenance and/or remodeling of the neuronal cytoskeleton.

Expression of beta-actin and alpha-tubulin mRNA in gerbil brain following transient ischemia and reperfusion up to 1 month

The time course of mRNA expressions of two cytoskeletal proteins, beta-actin and alpha-tubulin, was studied by Northern blot analysis and in situ hybridization in the same gerbil brains at various periods of recirculation following 10 min of forebrain ischemia. On Northern blot analysis, beta-actin mRNA in the forebrain showed increase after 6 h and 24 h recirculation. There was wide variation in its expression 3 days postischemia (PI), and by 7 days PI it had returned to control. The alpha-tubulin mRNA in the forebrain was shown to be reduced 6 h PI in our previous study. In the present analysis of Northern blots of delayed postischemic periods, there was no significant change in its expression even though there were variations. In situ hybridization revealed a decline in the mRNA expressions of both alpha-tubulin and beta-actin in the CA1 region as early as 6-24 h PI with the reductions being prominent at 3 days PI. By 7 days PI, beta-actin was only faintly visible while alpha-tubulin was completely absent in the CA1 region. Neither RNA was detectable in CA1 1 month PI. The heat shock-70 protein was expressed by 1 h PI, and it continued to be expressed up to 24 h, returning to control by 3 days PI. These results indicate that ischemia inhibits mRNA expressions of cytoskeletal protein in the selectively vulnerable region of the brain, i.e. CA1. The time course of the reduction of the two mRNAs coincides with delayed neuronal death suggesting that the cytoskeletal proteins may play important roles in selective postischemic neuronal injury.

Selective expression of the tba-1 alpha tubulin gene in a set of mechanosensory and motor neurons during the development of Caenorhabditis elegans

In the nematode Caenorhabditis elegans, a monoclonal antibody 3A5 raised against Drosophila alpha tubulins selectively stains the nervous system immuno-cytochemically. Direct screening of a C. elegans cDNA expression library with 3A5 has allowed cloning of the tba-1 (tubulin alpha-1) gene from C. elegans. The corresponding genomic DNA encodes a protein of 449 amino acid residues that has a high homology with the vertebrate alpha tubulins but a lower homology with yeast alpha tubulins. Interestingly, the carboxyl-terminus sequence EEEGEEY (Glu-Glu-Glu-Gly-Glu-Glu-Tyr) of the nematode tba-1 encoded isotype is identical to these residues in human, mouse, rat, pig and chicken alpha-1 tubulin isotypes that are expressed in the brain. Temporal and spatial expression studies of the tba-1 gene using Northern blot analysis and tba-1::lacZ fusion gene expression analysis during embryonic and the postembryonic development of C. elegans reveal that the tba-1 tubulin is preferentially expressed in the nematode nervous system, especially in a set of mechanosensory neurons and a set of ventral cord motor neurons (DA, DB, VA, and VB) during embryonic and postembryonic development. Our results indicate an inter-species conservation of the alpha tubulin carboxyl-terminal domain in functionally related brain specific isotypes from metazoans as divergent as mammals and nematodes. These results also suggest specificity of the individual alpha tubulin isotypes during neural development.

In situ hybridization detection of short viral amplicon sequences within cultured cells and body fluids after the in situ polymerase chain reaction

Using single primer pairs, intracellular gene sequences of cytomegalovirus (CMV-Towne's strain) and alpha-tubulin were amplified (in situ PCR) from cells in human body fluids and in suspensions. Visualization of CMV amplificants was carried out by in situ hybridization (ISH), using both a biotinylated double-stranded DNA probe and a radiolabelled oligonucleotide probe. Visualization of alpha-tubulin amplificants was achieved using both radiolabelled single-stranded cRNA and oligonucleotide probes. Liberated amplificants were also identified by bands of expected size by gel electrophoresis. The specificity of the PCR products was confirmed by Southern blot analysis. Intracellular amplification was identified both in unfixed cells and, optimally, after brief alcohol fixation, whilst maintaining relative isotonicity in all working solutions. For CMV, enhanced signal was observed in cells (cultured fibroblasts or urine sediment) undergoing in situ PCR using either biotinylated or radiolabelled probes compared with controls undergoing ISH alone. For alpha-tubulin, radiolabelled riboprobes and oligoprobes only produced signals within cells (human peripheral lymphocytes, ascitic fluid and bladder washings from routine cytological specimens) after in situ PCR, but not after ISH alone. Morphological evaluation was superior with biotinylated probes, and minimal back-diffusion effect was found compared with radiolabelled probes. Up to 80% of cells survived thermal cycling. In situ PCR detected short sequence (100 bp) foreign DNA and low copy number genomic DNA, and was superior to ISH alone. In contrast to radiolabelled probes, very small CMV amplificants could be detected without a significant 'back-diffusion' effect when using the large biotinylated probe in this model system.

HIT cells secrete β-cell mitogenic factors

We studied the growth characteristics of the insulin-producing HIT cells. Although successful in many cell lines such as βTC1, growth arrest could not be obtained with HIT cells left for 3 days without serum. Cytofluorometric analysis showed that about 24% of the cells continuously exposed to serum peaked in the S phase. A similar proportion was found for cells cultured for 1 or 2 days in serum-free medium. A treatment with suramin, disrupting the binding of ligands from their receptors, was associated with a rapid and transient increase in c-fos and c-jun gene expression after suramin removal, in the absence of serum. In addition, HIT cells secrete mitogenic factors, different from IGF-I or IGF-II, acting on insulin-secreting βTC1 cells and on BP-A31 fibroblasts. Chromatography of the medium conditioned by the HIT cells on gel filtration gave two major mitogenic fractions, of hydrodynamic characteristics 33 000 and 3000-10 000. The activity was heat stable and bound to heparin. Comparative studies of the self-regulatory HIT cells, with the βTC1 cells requiring external growth factors, should contribute significantly to our understanding of the regulation of β cell growth.

Inhibition of cell cycle progression by sodium butyrate in normal rat kidney fibroblasts is altered by expression of the adenovirus 5 early 1A gene

The effect of sodium butyrate (NaBut) on cell growth was studied in normal rat kidney (NRK) fibroblasts, and in NRK cells stably transfected with either the adenoviral gene E1A (wild-type), or mutated E1A (E1Amut; with a deletion in the CR1 domain), or with the transforming Ha-ras (EJ) gene. The growth of all these cell lines was inhibited by milimolar concentrations of sodium butyrate (NaBut). However, whereas the NRK cells as well as the NRK-E1Amut and NRK-ras cells were arrested in the G1 phase of the cell cycle, the NRK-E1A cells progressively accumulated in the G2 phase, suggesting that the E1A gene expression caused a "leaky" inhibition of G1 phase progression. The expression of late cell cycle-related genes cdc2 and PCNA (proliferating cell nuclear antigen) was not affected by NaBut in the NRK-E1A cells while it was totally suppressed in the other NRK-derived cell lines.

Correlation between reactive sprouting and microtubule protein expression in epileptic hippocampus

Temporal lobe epilepsy in both human and rats is associated with a collateral sprouting of hippocampal mossy fibers (i.e. the axons of granule cells). This sprouting generates abnormal recurrent synaptic connections. We previously showed that in the experimental model of temporal lobe epilepsy induced by an intra-amygdaloid injection of kainate, the synaptic remodeling of mossy fibers was preceded by a transient increased expression of alpha-tubulin in granule cells. This suggests that an overproduction of tubulin polymers may be responsible, at least in part, for the elongation and side-branching of mossy fibers, which occurs 12-30 days after seizures. In the present study we show that this increased expression of alpha-tubulin is accompanied by an increased expression of the microtubule-associated proteins MAP2 and TAU. Thus, using in situ hybridization, we observe that MAP2 messenger RNA levels increased in granule cell bodies and dendrites from day 3 to two weeks after kainate treatment. This rise is associated with a concomitant transient increase of MAP2 immunoreactivity in the granule cell dendrites. TAU messenger RNA also increases in granule cell bodies, while TAU immunoreactivity increases in their axons, the mossy fibers. The time course of these changes parallels that of alpha-tubulin, and develops before and during the axonal mossy fiber sprouting. Since MAP2 and TAU are important for the initiation, elongation and stabilization of neurites, we suggest that the overexpression of these proteins via the formation of microtubules may play an important role in the sprouting of mossy fibers in epileptic rats.

Induction of c-fos gene expression is not responsible for increased proenkephalin mRNA levels in the hippocampal dentate gyrus following NMDA stimulation

The increased levels of proenkephalin mRNA in the dentate gyrus following hippocampal stimulation have been assumed to be a consequence of the transient induction of c-fos. Injection of 50 microM NMDA in vivo onto the dendrites of a small number of granule cells causes a pronounced but highly localised elevation in proenkephalin mRNA levels 24 h later, whereas vehicle has no effect. In contrast, there is a widespread induction of c-fos mRNA throughout the dentate gyrus, 45 min after injection of either vehicle or NMDA, suggesting that induction of c-fos expression is unrelated to the subsequent, anatomically discrete, increase in proenkephalin mRNA levels.

An amino-terminal tetrapeptide specifies cotranslational degradation of beta-tubulin but not alpha-tubulin mRNAs

The steady-state level of alpha- and beta-tubulin synthesis is autoregulated by a posttranscriptional mechanism that selectively alters alpha- and beta-tubulin mRNA levels in response to changes in the unassembled tubulin subunit concentration. For beta-tubulin mRNAs, previous efforts have shown that this is the result of a selective mRNA degradation mechanism which involves cotranslational recognition of the nascent amino-terminal beta-tubulin tetrapeptide as it emerges from the ribosome. Site-directed mutagenesis is now used to determine that the minimal sequence requirement for conferring the full range of beta-tubulin autoregulation is the amino-terminal tetrapeptide MR(E/D)I. Although tubulin-dependent changes in alpha-tubulin mRNA levels are shown to result from changes in cytoplasmic mRNA stability, transfection of wild-type and mutated alpha-tubulin genes reveals that alpha- and beta-tubulin mRNA degradation is not mediated through a common pathway. Not only does the amino-terminal alpha-tubulin tetrapeptide MREC fail to confer regulated mRNA degradation, neither wild-type alpha-tubulin transgenes nor an alpha-tubulin gene mutated to encode an amino-terminal MREI yields mRNAs that are autoregulated. Further, although slowing ribosome transit accelerates the autoregulated degradation of endogenous alpha- and beta-tubulin mRNAs, degradation of alpha-tubulin transgene mRNAs is not enhanced, and in one case, the mRNA is actually stabilized. We conclude that, despite similarities, alpha- and beta-tubulin mRNA destabilization pathways utilize divergent determinants to link RNA instability to tubulin subunit concentrations.

An amino-terminal tetrapeptide specifies cotranslational degradation of beta-tubulin but not alpha-tubulin mRNAs

The steady-state level of alpha- and beta-tubulin synthesis is autoregulated by a posttranscriptional mechanism that selectively alters alpha- and beta-tubulin mRNA levels in response to changes in the unassembled tubulin subunit concentration. For beta-tubulin mRNAs, previous efforts have shown that this is the result of a selective mRNA degradation mechanism which involves cotranslational recognition of the nascent amino-terminal beta-tubulin tetrapeptide as it emerges from the ribosome. Site-directed mutagenesis is now used to determine that the minimal sequence requirement for conferring the full range of beta-tubulin autoregulation is the amino-terminal tetrapeptide MR(E/D)I. Although tubulin-dependent changes in alpha-tubulin mRNA levels are shown to result from changes in cytoplasmic mRNA stability, transfection of wild-type and mutated alpha-tubulin genes reveals that alpha- and beta-tubulin mRNA degradation is not mediated through a common pathway. Not only does the amino-terminal alpha-tubulin tetrapeptide MREC fail to confer regulated mRNA degradation, neither wild-type alpha-tubulin transgenes nor an alpha-tubulin gene mutated to encode an amino-terminal MREI yields mRNAs that are autoregulated. Further, although slowing ribosome transit accelerates the autoregulated degradation of endogenous alpha- and beta-tubulin mRNAs, degradation of alpha-tubulin transgene mRNAs is not enhanced, and in one case, the mRNA is actually stabilized. We conclude that, despite similarities, alpha- and beta-tubulin mRNA destabilization pathways utilize divergent determinants to link RNA instability to tubulin subunit concentrations.

Coexpression of interleukin-1 beta and interleukin-6 in human brain tumors

Deregulation of the expression of cytokine genes appears to play a role in the development of gliomas. Interleukin-1 beta has been shown to be synthesized in small amounts by astrocytes and can induce the expression of interleukin-6. Interleukin-6 is not expressed by unstimulated astrocytes, but the deregulation of its expression has been implicated in the progression of several tumor types. In this study, tumor specimens from 16 brain tumors and 22 glioma cell lines were studied for the gene expression of both interleukin-1 beta and interleukin-6, and the coexpression of these two cytokines was found in a significant number of these specimens. The expression of these two growth factor genes may play an important role in the growth and development of human gliomas.