Transdiagnostic Role of Glutamate and White Matter Damage in Neuropsychiatric Disorders: A Systematic Review

Introduction

Neuropsychiatric disorders including Generalized Anxiety Disorder (GAD), Obsessive-Compulsive Disorder (OCD), Major Depressive Disorder (MDD), Bipolar Disorder (BD), and Schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology.

Objectives

We aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities from a transdiagnostic perspective.

Methods

The PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 399 studies were included.

Results

The findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus was found to be affected in all the reviewed disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients.

Conclusions

The results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.

Disclosure

No significant relationships.

Significant population genetic structuring but a lack of phylogeographic structuring in the endemic Tasmanian tree frog (Litoria burrowsae)

Conservation of frogs is of global concern, owing to declines resulting from habitat destruction, global climate change, and disease. Knowledge of genetic variation in frog species is therefore desirable for the identification of management units. Here we surveyed mitochondrial DNA sequence variation in the Tasmanian endemic hylid frog Litoria burrowsae, which is infected by chytrid fungus, Batrachochytrium dendrobatidis, and may be declining. Neither phylogeographic structure nor deep phylogenetic divergence was detected in the species, although its populations were highly differentiated with respect to haplotype frequencies. The low-haplotype diversity in L. burrowsae suggests a recent bottleneck in the species, and population genetic structuring may reflect isolation by distance as well as founder effects associated with range expansion. Three putative management units were identified that require verification based on nuclear DNA variation and adaptation to local environments.

Nitric oxide levels following perfusion differ in donation after circulatory death and donation after brain death transplants

Affiliated to the Association of Surgeons in Training and the British Transplantation Society, the Carrel Club is the transplant trainee surgical society. The Carrel Club held a joint meeting with the Chapter of Transplant Surgeons, a subsidiary organisation of the British Transplantation Society, at the Manchester Hilton Hotel on 31 January and 1 February 2013. As part of the meeting, ten abstracts were presented. A selection is printed below. The winner of the Best Presentation award was Mr Mownah.

Isolation of Aspergillus species from the airway of lung transplant recipients is associated with excess mortality

BACKGROUND

Aspergillus spp. are the leading cause of invasive fungal infection in lung transplant recipients. We investigated the relationship between the isolation of Aspergillus spp. from the respiratory tract of lung transplant recipients and their risk of mortality.

METHODS

A retrospective, observational cohort study of all patients who received lung allografts between January 1999 and May 2011 at a single UK centre was performed. The time from transplantation to death was analysed using Cox regression models. Isolation of Aspergillus spp. from the respiratory tract was included as a covariate in the Cox regression model.

RESULTS

Two hundred-thirteen patients were included. The median follow-up time was 5 years during which 102 patients (47.9%) died. Aspergillus was isolated from 74 (34.7%) patients. Twenty patients (27%) had Aspergillus isolated in the first 60 days post-transplant. Forty-one patients (55.4%) in the Aspergillus group and 61 patients (43.9%) in the non-Aspergillus group died during follow-up. A hazard ratio of 2.2 (95% CI 1.5-3.3; P < 0.001) for death following a positive Aspergillus sample was observed.

CONCLUSION

Isolation of Aspergillus spp. from patients following lung transplantation is associated with a significant increase in mortality. Novel preventative strategies are required to minimise the impact of Aspergillus in lung transplant recipients.

The caspase family in urochordates: distinct evolutionary fates in ascidians and larvaceans

BACKGROUND INFORMATION

Caspases are cysteine proteases that mediate apoptosis (programmed cell death) initiation and execution. Apoptosis is a conserved mechanism shared by all metazoans, although its physiological function and complexity show considerable taxon-dependent variations. To gain insight into the caspase repertoire of putative ancestors to vertebrates, we performed exhaustive genomic searches in urochordates, a sister taxon to vertebrates in which ascidians and appendicularians display chordate characters at early stages of their development.

RESULTS

We identified the complete caspase families of two ascidians (Ciona intestinalis and C. savignyi) and one larvacean (Oikopleura dioica). We found in ascidian species an extremely high number of caspase genes (17 for C. intestinalis and 22 for C. savignyi), deriving from five founder gene orthologues to human pro-inflammatory, initiator and executioner caspases. Although considered to be sibling species, C. intestinalis and C. savignyi only share 11 orthologues, most of the additional genes resulting from recent mass duplications. A sharply contrasted picture was found in O. dioica, which displayed only three caspase genes deriving from a single founder gene distantly related to caspase 3/7. The difference between ascidian and larvacean caspase repertoires is discussed in the light of their developmental patterns and life cycles.

CONCLUSIONS

The identification of caspase members in two ascidian species delineates five founder genes that bridge the gap between vertebrates and Ecdysozoa (arthropods and nematodes). Given the amazing diversity among urochordates, determination and comparison of the caspase repertoires in species from orders additional to Enterogona (ascidians) and Oikopleuridae might be highly informative on the evolution of caspase-dependent physiological processes.

TC10 controls human myofibril organization and is activated by the sarcomeric RhoGEF obscurin

The contractile activity of striated muscle depends on myofibrils that are highly ordered macromolecular complexes. The protein components of myofibrils are well characterized, but it remains largely unclear how signaling at the molecular level within the sarcomere and the control of assembly are coordinated. We show that the Rho GTPase TC10 appears during differentiation of human primary skeletal myoblasts and it is active in differentiated myotubes. We identify obscurin, a sarcomere-associated protein, as a specific activator of TC10. Indeed, TC10 binds directly to obscurin via its predicted RhoGEF motif. Importantly, we demonstrate that obscurin is a specific activator of TC10 but not the Rho GTPases Rac and Cdc42. Finally, we show that inhibition of TC10 activity by expression of a dominant-negative mutant or its knockdown by expression of specific shRNA block myofibril assembly. Our findings reveal a novel signaling pathway in human skeletal muscle that involves obscurin and the Rho GTPase TC10 and implicate this pathway in new sarcomere formation.

CT colonography: interpretative performance in a non-academic environment

AIM

To investigate interpretative accuracy and reporting time for radiologists performing computed tomography (CT) colonography in day-to-day non-academic clinical practice.

MATERIALS AND METHODS

Thirteen radiologists from seven centres, who were reporting CT colonography in non-academic daily clinical practice, interpreted a dataset of 15 colonoscopically validated cases in a controlled environment. Ten cases had either a cancer or polyp >10mm; one case had a medium polyp and four were normal. Correct case categorization and interpretation times were compared using analysis of variance to aggregated results obtained from both experienced observers and observers recently trained using 50 cases, working in an academic environment. The effect of experience was determined using Spearman's rank correlation.

RESULTS

Individual accuracy was highly variable, range 53% (95% CI 27-79%) to 93% (95% CI 68-100%). Mean accuracy overall was significantly inferior to experienced radiologists (mean 75 versus 88%, p=0.04) but not significantly different from recently trained radiologists (p=0.48). Interpretation time was not significantly different to experienced readers (mean 12.4 min versus 11.7, p=0.74), but shorter than recently trained radiologists (p=0.05). There was a significant, positive, linear correlation between prior experience and accuracy (p<0.001) with no plateau.

CONCLUSION

Accuracy for sub-specialist radiologists working in a non-academic environment is, on average, equivalent to radiologists trained using 50 cases. However, there is wide variability in individual performance, which generally falls short of the average performance suggested by meta-analysis of published data. Experience improves accuracy, but alone is insufficient to determine competence.

Identification of Rho GTPases implicated in terminal differentiation of muscle cells in ascidia

BACKGROUND INFORMATION

Members of the Rho GTPase family mediate changes in the actin cytoskeleton and are also implicated in developmental processes, including myogenesis. Nevertheless, a comprehensive analysis of these proteins during myofibrillogenesis has never been performed in any organism.

RESULTS

Using the ascidian model to identify the role of Rho GTPases on myofibrillogenesis, we show that transcripts for all Rho GTPases are detected in muscle cells of the embryo. We find that activation of RhoA, TC10 and Cdc42 (cell division cycle 42) disturbs the polarity of muscle cells, whereas that of other Rho GTPases induced cell positioning defects. Moreover, dominant negative version of five Rho GTPases, RhoA, Rac2, RCL2 (Rac- and Cdc42-like 2), TC10 and WRCH (Wnt-1 responsive Cdc42 homologue), impaired the formation of mature myofibrils.

CONCLUSIONS

Taken together, our results show that several Rho GTPase-dependent pathways are required to control the spatial localization of muscle cells in the embryo and to coordinate myofibril assembly. This stresses the importance of analysing the entire Rho family when studying a new biological process.

Brain tissue fragments in jugular vein blood of cattle stunned by use of penetrating or nonpenetrating captive bolt guns

Although the incidence of bovine spongiform encephalopathy in cattle continues to decline in the United Kingdom, it remains important to maintain vigilance of all potential routes of transmission of infection to humans. Initial studies have demonstrated a potential risk of carcass contamination with brain tissue following the use of captive bolt gun stunning in cattle. The objective of this study was to further explore these initial findings particularly in regard to captive bolt guns currently in use in the United Kingdom. Brain tissue fragments or elevated levels of a marker protein for brain tissue were detected in venous blood samples from 4% (95% confidence interval, 1.6 to 9.8%) of cattle stunned by penetrating captive bolt gun and from 2% (95% confidence interval, 0.6 to 7%) of those stunned by nonpenetrating captive bolt gun.

Cyclin A repression in quiescent cells is associated with chromatin remodeling of its promoter and requires Brahma/SNF2alpha

Cell cycle-dependent expression of cyclin A is controlled by transcriptional repression in early phase of the cell cycle. In this study, we directly examine the chromatin structure of the mouse cyclin A promoter through in vivo micrococcal nuclease footprinting. We describe here that cyclin A repression is associated with two positioned nucleosomes and that histones progressively lose DNA contact synchronously with gene activation. This particular nucleosomal organization is disrupted by mutations of the cyclin A bipartite repressor sequence. Moreover, the same sequence recruits the chromatin remodeling factor Brahma/SNF2alpha (Brm) onto the cyclin A promoter. Accordingly, cyclin A proximal promoter is not wrapped around nucleosomes and not repressed in quiescent cells lacking Brm. These results provide molecular explanations for the transcriptional repression state of cyclin A, as well as insights into the action of Brm chromatin remodeling factor as cell cycle regulator.

Activation of cyclin D1 expression by the ERK5 cascade

Transcriptional activation of the cyclin D1 gene is a key step in cell proliferation. Accordingly, cyclin D1 overexpression is frequently an early step in neoplastic transformation, particularly in mammary epithelium. Numerous studies have linked elevated cyclin D1 promoter activity to a sustained activation of the ERK1/2 cascade. Here we show that the ERK5 cascade, a distinct mitogen-induced MAPK pathway, can also drive cyclin D1 expression. In CCL39 cells, serum induces a strong, prolonged peak of ERK1/2 and ERK5 phosphorylation, and subsequently elevates cyclin D1 mRNA and protein levels. Overexpression of constitutively active MEK5 and wt ERK5 induces a cyclin D1 reporter gene (D1 -973-luciferase) at least as well as constitutively active MEK1. Activation is blocked by kinase-dead mutants of ERK5 and ERK2, respectively. Mutation of the CRE at -50 in the cyclin D1 promoter decreases activation by the ERK5 but not the ERK1/2 cascade. Importantly, expression of kinase-dead ERK5 diminishes endogenous cyclin D1 protein induction by serum in CCL39 cells and the breast cancer cell lines MCF-7 and HS579. These data identify the cyclin D1 gene as a novel target of the ERK5 cascade, an observation with important implications in cancers involving cyclin D1 deregulation.

Ascidians as a vertebrate-like model organism for physiological studies of Rho GTPase signaling

GTPases of the Rho family are evolutionarily conserved proteins that control cell shape dynamics during physiological processes as diverse as cell migration and polarity, axon outgrowth and guidance, apoptosis and phagocytosis. In mammals, 18 Rho proteins are distributed in 7 subfamilies. Rho, Rac and Cdc42 are the best-characterized ones, benefiting from the use of worm and drosophila, which only express these 3 subfamilies. An additional model would therefore help understand the physiological role of other mammalian subfamilies. We identified in genome databases the complete Rho family of two ascidians, Ciona intestinalis and Ciona savignyi, and showed that these families contain single ancestors of most mammalian Rho subfamilies. In Ciona intestinalis, all Rho genes are expressed and display specific developmental variations of mRNA expression during tadpole formation. Although C. intestinalis expresses five additional Rac compared to the closely related Ciona savignyi, only two appeared fully active in functional assays. Last, we identified in Ciona intestinalis database more than 50 Rho regulators (RhoGEFs and RhoGAPs) and 20 effector targets, whose analysis further supports the notion that Rho signaling components are of comparable complexity in mammals and ascidians. Since the tadpole of ascidians combines vertebrate-like developmental features with reduced cell number, particularly adapted to evolutionary and developmental biology studies, our data advocate this model for physiological studies of Rho signaling pathways.

Oct-1 potentiates CREB-driven cyclin D1 promoter activation via a phospho-CREB- and CREB binding protein-independent mechanism

Cyclin D1, the regulatory subunit for mid-G(1) cyclin-dependent kinases, controls the expression of numerous cell cycle genes. A cyclic AMP-responsive element (CRE), located upstream of the cyclin D1 mRNA start site, integrates mitogenic signals that target the CRE-binding factor CREB, which can recruit the transcriptional coactivator CREB-binding protein (CBP). We describe an alternative mechanism for CREB-driven cyclin D1 induction that involves the ubiquitous POU domain protein Oct-1. In the breast cancer cell line MCF-7, overexpression of Oct-1 or its POU domain strongly increases transcriptional activation of cyclin D1 and GAL4 reporter genes that is specifically dependent upon CREB but independent of Oct-1 DNA binding. Gel retardation and chromatin immunoprecipitation assays confirm that POU forms a complex with CREB bound to the cyclin D1 CRE. In solution, CREB interaction with POU requires the CREB Q2 domain and, notably, occurs with CREB that is not phosphorylated on Ser 133. Accordingly, Oct-1 also potently enhances transcriptional activation mediated by a Ser133Ala CREB mutant. Oct-1/CREB synergy is not diminished by the adenovirus E1A 12S protein, a repressor of CBP coactivator function. In contrast, E1A strongly represses CBP-enhanced transactivation by CREB phosphorylated on Ser 133. Our observation that Oct-1 potentiates CREB-dependent cyclin D1 transcriptional activity independently of Ser 133 phosphorylation and E1A-sensitive coactivator function offers a new paradigm for the regulation of cyclin D1 induction by proliferative signals.

Jugular venous emboli of brain tissue induced in sheep by the use of captive bolt guns

Emboli of central nervous tissue were detected in the jugular venous blood of two of 15 sheep stunned with a conventional cartridge-operated captive bolt gun and in two of 15 sheep stunned with a pneumatically activated gun. No emboli were detected in arterial blood from these sheep or in venous blood from sheep stunned electrically. Emboli from an animal with BSE could transmit the disease to people.

Three-dimensionally ordered array of air bubbles in a polymer film

We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.

Method for procuring specific populations of viable human prostate cells for research

SUMMARY

A wider range of research can be conducted on viable tissue samples than on fixed or frozen samples. A major obstacle to studying viable prostate tissue samples is the inability to accurately identify cancer on direct examination of unembedded tissue. We used a dissecting microscope to identify cancer in unfixed prostate tissue samples stained on the cut surface with 0.5% aqueous toluidine blue. We measured the diagnostic accuracy of this technique in 25 consecutive prostatectomies, determined the viability of procured samples, and estimated the effect on final pathologic assessment. Both surfaces of a 3- to 5-mm thick cross-section taken midway between base and apex of the prostate were examined. A 4-mm punch biopsy was directed to one benign and one malignant area when clearly present. The dissecting microscope allowed clearcut recognition of carcinoma in 17 of the 25 cross-sections, and carcinoma was confirmed in all 17 (100%). In 8 of 25 cases, no procurement was attempted because no carcinoma was evident in the one cross-section studied. Twenty of 25 cross-sections were adequate for benign tissue procurement; five of the cross-sections were not suitable for procurement because of the presence of extensive carcinoma or atrophy. Seventeen of the 20 were accurately diagnosed as benign (85%); one showed pseudohyperplastic adenocarcinoma, one showed focal high-grade prostatic intraepithelial neoplasia, and one showed urothelial carcinoma in situ. Prostatic epithelium obtained with the technique remains viable and can be separated from stroma. The dissecting microscope technique appears to facilitate rather than interfere with accurate pathologic assessment: extraprostatic extension or positive margins were correctly identified during tissue procurement in three cases. The procedure takes only about 30 minutes.

Hepatoblastoma presenting with lung metastases: treatment results of the first cooperative, prospective study of the International Society of Paediatric Oncology on childhood liver tumors

BACKGROUND

The prognosis of children who are affected by hepatoblastoma (HB) that presents with lung metastases has always been considered very poor. In light of the overall improvement in the survival of HB patients since the introduction of cisplatin (CDDP) in the therapeutic armament of this tumor, the question has been raised whether patients with metastatic HB also would benefit from this drug. The purpose of the current study was to address this issue by analyzing the treatment outcome of those patients presenting with metastases who entered into the first HB study on childhood liver tumors conducted by the International Society of Paediatric Oncology (SIOPEL 1).

METHODS

SIOPEL 1 was a prospective, international, multicentric, single-arm study based on preoperative chemotherapy that was open to patient registration from January 1990 to February 1994. After undergoing a biopsy, patients received four courses of CDDP (80 mg/m(2) in a 24-hour, continuous infusion) on Day 1 followed by doxorubicin (60 mg/m(2) in a 48-hour, continuous infusion) on Days 2 and 3 (PLADO). Surgery was performed after four courses of PLADO and was followed by two more courses. Untreated children age < 16 years with biopsy-proven HB were eligible for the study. Metastatic spread was assessed by chest X-ray and, where available, lung computed tomography scan.

RESULTS

Thirty-one of 154 children that entered into the trial presented with metastases. Eight children presently are alive with no evidence of disease (NED) after being treated with protocol therapy only (median follow-up, 60 months); nine children are alive with NED after having failed PLADO and having been rescued with alternative therapies (median follow-up, 80 months). The 5-year overall and event free survival rates for these children were 57% (95% confidence interval, 39-75%) and 28% (95% confidence interval, 12-44%), respectively. Persistent lung disease was the main reason for PLADO failure (17 of 23 patients; 74%).

CONCLUSIONS

The SIOPEL 1 therapeutic strategy seems to cure 25% of the HB patients who present with metastases. However, further chemotherapy and the use of thoracotomies still can save significant numbers of these children.

Extinction of rac1 and Cdc42Hs signalling defines a novel p53-dependent apoptotic pathway

Apoptosis is a normal physiological process which eliminates cells that do not receive adequate extracellular signals. One of the pathways signalling apoptosis is controlled by the small GTPases of the Rho family, also involved in cell proliferation, differentiation and motility. Another major apoptosis signalling pathway involves the p53 tumour suppressor which is activated by a variety of stress and mediates growth arrest or apoptosis in normal cells. We show here that upon detachment from the extracellular matrix, fibroblasts undergo rapid apoptosis that can be rescued by constitutive activation of Rac1 and Cdc42Hs GTPases. Conversely, inhibition of Rac1 and Cdc42Hs efficiently triggers apoptosis in adherent cells. Interestingly, apoptosis is not observed in p53-/- cells either cultured in suspension or inhibited for Rac1 and Cdc42Hs activity. Moreover, Rac1 and Cdc42Hs extinction in normal cells activates endogenous p53. Using specific inhibitors of MAPK pathways, we demonstrate that, in our experimental system, p38 signals survival, while ERK activity is required for apoptosis. Our data constitute the first demonstration that Rac1 and Cdc42Hs control pathways that require simultaneous signalling through MAPK ERK and p53 to induce apoptosis.

A CDE/CHR-like element mediates repression of transcription of the mouse RB2 (p130) gene

The bipartite repressor elements, termed cell cycle-dependent element (CDE)/cell cycle regulatory element (CCRE)-cell cycle homology region (CHR) control the growth-dependent transcription of the cyclin A, cdc25C, cdc2 genes. Here, we have identified a functional element displaying the signature of the CDE-CHR in the promoter of the mouse RB2 (p130) gene, encoding the retinoblastoma protein family (pRB)-related protein p130. This element locates close to the major transcription start site where it makes major groove contacts with proteins that can be detected in a cellular context using in vivo genomic footprinting techniques. Inactivation of either the CDE or CHR sequence strongly up-regulates the p130 promoter activity in exponentially growing cells, a situation where endogenous p130 gene expression is almost undetectable. Electrophoretic mobility shift assays suggest that two different protein complexes bind independently to the p130 CDE and CHR elements, and that the protein(s) bound to the CDE might be related to those bound on cyclin A and cdc2 promoters.

Differential effect of Rac and Cdc42 on p38 kinase activity and cell cycle progression of nonadherent primary mouse fibroblasts

The Rho GTPases play an important role in transducing signals linking plasma membrane receptors to the organization of the cytoskeleton and also regulate gene transcription. Here, we show that expression of constitutively active Ras or Cdc42, but not RhoA, RhoG, and Rac1, is sufficient to cause anchorage-independent cell cycle progression of mouse embryonic fibroblasts. However, in anchorage free conditions, whereas activation of either Cdc42 or Ras results in cyclin A transcription and cell cycle progression, Cdc42 is not required for Ras-mediated cyclin A induction, and the two proteins act in a synergistic manner in this process. Surprisingly, the ability of Cdc42 to induce p38 MAPK activity in suspended mouse embryonic fibroblast was impaired. Moreover, inhibition of p38 activity allowed Rac1 to induce anchorage-independent cyclin A transcription, indicating that p38 MAPK has an inhibitory function on cell cycle progression of primary fibroblasts. Finally, a Rac mutant, which is unable to induce lamellipodia and focal complex formation, promoted cyclin A transcription in the presence of SB203580, suggesting that the organization of the cytoskeleton is not required for anchorage-independent proliferation. This demonstrates a novel function for Cdc42, distinct from that of Rac1, in the control of cell proliferation.

CHF: a novel factor binding to cyclin A CHR corepressor element

Cell cycle modulation of cyclin A expression is due to the periodic relief of a transcriptional repression mediated by a bipartite negative DNA regulatory region. The 5' element (Cell Cycle Responsive Element: CCRE; cell Cycle Dependent Element: CDE) is clearly occupied in a cyclic manner in vivo, whereas the 3' element, whose sequence is shared by B-myb, cdc25C and cdc2 genes (cell Cycle gene Homology Region: CHR), is involved in more subtle interactions. Mutation of either element results in complete deregulation of cyclin A promoter activity. Whereas some reports claim that E2F/DP can bind to the CCRE/CDE, the nature of the protein(s) interacting with the CHR is unknown. In the present work we have characterized an activity present in quiescent cells and absent in cells blocked in S phase, which binds specifically to cyclin A CHR, but not to B-myb, or to cdc25C, or to cdc2 CHRs. A 90 kD protein, named CHF (cyclin A CHR binding factor), has been identified through preparative electrophoresis and UV crosslinking experiments. In order to address in more functional terms the binding of CHF to cyclin A CHR, we developed in vitro and in vivo oligonucleotide competition assays. Both in vitro transcription and in vivo microinjection experiments demonstrate that a functional difference exists between the composite CCRE/CDE-CHR repressor regions of cell cycle regulated genes such as cyclin A and cdc25C.

Heterodimerization between members of the Nur subfamily of orphan nuclear receptors as a novel mechanism for gene activation

We have recently shown that the orphan nuclear receptor Nur77 (NGFI-B) is most active in transcription when it is interacting with a cognate DNA sequence as a homodimer. Further, we have shown that the target for Nur77 dimers, the Nur response element (NurRE), is responsive to physiological stimuli in both endocrine and lymphoid cells, whereas other DNA targets of Nur77 action are not. The Nur77 subfamily also includes two related receptors, Nur-related factor 1 (Nurr1) and neuron-derived orphan receptor 1 (NOR-1). Often, more than one member of this subfamily is induced in response to extracellular signals. We now show that Nur77 and Nurr1 form heterodimers in vitro in the presence or absence of NurRE, and we have documented interactions between these proteins in vivo by using a two-hybrid system in mammalian cells. These heterodimers synergistically enhance transcription from NurRE reporters in comparison to that seen with homodimers. The naturally occurring NurRE from the pro-opiomelanocortin gene preferentially binds and activates transcription in the presence of Nur77 homo- or heterodimers, while a consensus NurRE sequence does not show this preference. Taken together, the data indicate that members of the Nur77 subfamily are most potent as heterodimers and that different dimers exhibit target sequence preference. Thus, we propose that a combinatorial code relying on specific NurRE sequences might be responsible for the activation of subsets of target genes by one of the members of the Nur77 subfamily of transcription factors.

Timing of cyclin E gene expression depends on the regulated association of a bipartite repressor element with a novel E2F complex

Transient induction of the cyclin E gene in late G1 gates progression into S. We show that this event is controlled via a cyclin E repressor module (CERM), a novel bipartite repressor element located near the cyclin E transcription start site. CERM consists of a variant E2F-binding site and a contiguous upstream AT-rich sequence which cooperate during G0/G1 to delay cyclin E expression until late G1. CERM binds the protein complex CERC, which disappears upon progression through G0-G1 and reappears upon entry into the following G1. CERC disappearance correlates kinetically with the liberation of the CERM module in vivo and cyclin E transcriptional induction. CERC contains E2F4/DP1 and a pocket protein, and sediments faster than classical E2F complexes in a glycerol gradient, suggesting the presence of additional components in a novel high molecular weight complex. Affinity purified CERC binds to CERM but not to canonical E2F sites, thus displaying behavior different from known E2F complexes. In cells nullizygous for members of the Rb family, CERC is still detectable and CERM-dependent repression is functional. Thus p130, p107 and pRb function interchangeably in CERC. Notably, the CERC-CERM complex dissociates prematurely in pRb-/- cells in correspondence with the premature expression of cyclin E. Thus, we identify a new regulatory module that controls repression of G1-specific genes in G0/G1.

Anchorage-dependent expression of cyclin A in primary cells requires a negative DNA regulatory element and a functional Rb

Many cells, when cultured in suspension, fail to express cyclin A, a regulatory component of cell cycle kinases cdc2 and cdk2 and as a consequence, do not enter S phase. However, many cell type-specific differences are disclosed between not only normal and transformed cells, but also between cell lines whose proliferation is strictly anchorage-dependent. These apparent discrepancies are seen in established cell lines most probably because of adaptative events that have occurred during cell culture. We have therefore used primary cells to understand how cyclin A transcription is controlled by cell anchorage properties. To this aim, we have used embryonic fibroblasts from either wild type, Rb(-/-) or p107(-/-)/p130(-/-) mice and tested the effect of an ectopic expression of Rb mutants. In the experiments reported here, we show that anchorage-dependent expression of cyclin A (i) is reflected by the in vivo occupancy of a negative DNA regulatory element previously shown to be instrumental in the down regulation of cyclin A transcription in quiescent cells (Cell Cycle Responsive Element: CCRE) (ii) requires a functional Rb but neither p107 nor p130 (iii) mutation of the CCRE abolishes both adhesion-dependent regulation and response to Rb.

[Cyclin A: a good markers for the study of cell cycle control and tumor progression?]

Cyclin A is a positive regulatory component of kinases required for the progression through S phase and for the transition between the G2 and M phases of the cell division cycle. Previous studies conducted in established cell lines and in primary human T lymphocytes, have demonstrated that the promoter of its gene is under negative transcriptional control in quiescent cells. The DNA sequences mediating this repression have been delineated through in vitro mutagenesis as well as in vivo genomic footprinting experiments. Indirect observations suggest the involvement of proteins related to the retinoblastoma tumor suppressor protein (pRb). Using primary fibroblasts from either pRb(-/-), p107(-/-), p130(-/-) or p107(-/-)/p130(-/-) mice, we show in this work that mutation of the pRb gene has the more profound effect on cyclin A transcription. Finally, normal fibroblasts cultured in suspension fail to express cyclin A and can no longer enter S phase and proliferate, revealing thus a dependence of cyclin A expression on cell anchorage. Our work suggests the existence of at least two sets of regulators controlling cell cycle progression. On the one hand, proteins like cyclin D1, whose expression is a direct consequence of the activation of the ras signalling pathway and on the other hand, proteins like cyclin A which are secondary response effectors. As a result, growth factor stimulation leads to a transcriptional activation of the former set, while the transcription of the latter set is under the control of a repressor whose effect is alleviated after triggering the ras cascade. The status of pRb thus dictates whether cells continue their progression through the cell cycle when ras is mutated, probably by allowing the uncontrolled expression of critical genes like cyclin A.

FRA-1 expression level modulates regulation of activator protein-1 activity by estradiol in breast cancer cells

We compared the effect of estradiol on activator protein-1 (AP-1) activity in estrogen receptor positive (ER alpha+) and estrogen receptor negative (ER alpha-) human breast cancer cell lines transiently transfected with the AP-1-responsive reporter plasmid AP-1-TK-CAT and an ER alpha expression vector. While estradiol increased AP-1 activity in the ER alpha+ cell lines MCF7, ZR75.1, and T47D, it decreased (MDA-MB231 and BT20 cells) or had no significant effect (MDA-MB435 cells) on AP-1-mediated transcription in ER alpha- cells. Estradiol also inhibited AP-1 activity in ER alpha-MDA-MB231 cells stably transfected with ER alpha and in which ER alpha levels are close to those found in MCF7. Use of ER alpha mutant expression vectors demonstrated that the DNA-binding domain of ER alpha was needed for stimulation or inhibition of AP-1 activity by estradiol but suggested that ER alpha binding to estrogen-responsive elements was not required for these effects. Changes in regulation paralleled quantitative and qualitative changes in protein binding to AP-1 sites, as demonstrated by gel shift assay: protein binding was greater and DNA/protein complexes migrated faster for ER alpha--than for ER alpha+ cells. In fact, by Northern blot, a high level of Fra-1 mRNA was found in BT20 and MDA-MB231 cells as compared with ER alpha+ cells, and MDA-MB435 cells showed an intermediary level of expression. The differential expression of Fra-1 in MCF7 and MDA-MB231 cells was confirmed at the protein level by supershift experiments. In addition, overexpression of Fra-1 in MCF7 cells decreased the positive effect of estradiol while inhibition of Fra-1 expression in MDA-MB231 cells, by transient transfection of the Fra-1 antisense expression vector, abolished the negative effect of the hormone. In conclusion, we demonstrated that ER alpha- breast cancer cell lines differ from ER+ cells by a high level of AP-1 DNA-binding activity due, at least in part, to high Fra-1 constitutive expression. High Fra-1 concentration is crucial for the negative regulation of AP-1 activity by estradiol and thus may take part in estradiol-induced inhibition of cell proliferation in ER alpha- breast cancer cells transfected with ER alpha expression construct.

Novel mechanism of action for Nur77 and antagonism by glucocorticoids: a convergent mechanism for CRH activation and glucocorticoid repression of POMC gene transcription

Whereas orphan nuclear receptors of the Nur77 (NGFI-B) subfamily were previously known to act on transcription as monomers or as heterodimers with RXR, we have recently shown that Nur77 homodimers potently activate transcription upon interaction with a novel palindromic response element, the NurRE. In fact, reporter plasmids containing the NurRE respond to physiological stimuli in conditions where the NBRE, a binding site for Nur77 monomers, does not. Nur77 and its related receptors were shown to be important mediators for control of apoptosis induced by the T-cell receptor, and they also mediate the effect of the hypothalamic hormone CRH on transcription of the pituitary pro-opiomelanocotin (POMC) gene. In both systems, glucocorticoids antagonize the stimulatory effects of Nur77 on transcription by a mechanism that involves protein:protein interactions. Thus, the Nur77 signalling pathway appears to be a point of convergence for stimulatory signals and glucocorticoid repression in both endocrine and lymphoid systems.

The retinoblastoma protein is essential for cyclin A repression in quiescent cells

Cyclin A is a positive regulatory component of kinases required for the progression through S phase and for the transition between the G2 and M phases of the cell division cycle. Previous studies have demonstrated that the promoter of its gene is under transcriptional repression in quiescent cells. Whereas the DNA sequences mediating this effect have been clearly delineated, the nature of the proteins acting in trans is still debated. Indirect observations suggest the involvement of proteins related to the retinoblastoma tumor suppressor protein (pRb). However, the precise role of these proteins has been difficult to assess, since most experiments designed to analyse their function have been carried out in transformed cell lines. Nevertheless, a current model has emerged whereby the role of the p130 protein would be restricted to resting and early G1 cells and p107, absent in quiescent cells, would be involved later in the control of the G1/S transition, whilst pRb would be effective throughout the cell cycle. We show here that cyclin A transcriptional inhibition is relieved in primary fibroblasts from pRb(-/-) embryos and not in fibroblasts from p13O(-/-), p107(-/-) or even p130(-/-)/p107(-/-) double mutant embryos. This suggests a unique role for pRb in controlling the extinction of specific genes in G0, providing thus the first example of non-overlapping functions achieved by the different pocket proteins.

Novel dimeric Nur77 signaling mechanism in endocrine and lymphoid cells

Within the nuclear receptor family, Nur77 (also known as NGFI-B) distinguishes itself by its ability to bind a target sequence (the NBRE) as a monomer and by its role in T-cell receptor (TCR)-induced apoptosis in T cells. We now report on a novel mechanism of Nur77 action that is mediated by homodimers. These dimers bind a Nur77 response element (NurRE), which has been identified as a target of CRH-induced Nur77 in the pro-opiomelanocortin (POMC) gene promoter. Both halves of the palindromic NurRE are required for responsiveness to physiological signals, like CRH in pituitary-derived AtT-20 cells. Similarly, in T-cell hybridomas, TCR activation induced NurRE but not NBRE reporters. The in vivo signaling function of Nur77 thus appears to be mediated by dimers acting on a palindromic response element of unusual spacing between its half-sites. This mechanism may represent the biologically relevant paradigm of action for this subfamily of orphan nuclear receptors.

Antagonism between Nur77 and glucocorticoid receptor for control of transcription

Two important functions of glucocorticoids (Gc), namely, suppression of immune system function and feedback repression of the hypothalamo-pituitary-adrenal (HPA) axis, are mediated through repression of gene transcription. Previous studies have indicated that this repression is exerted in part through antagonism between the glucocorticoid receptors (GR) and the AP-1 family of transcription factors. However, this mechanism could not account for repression of the pro-opiomelanocortin (POMC) gene, an important regulator of the HPA axis. Our recent identification of the orphan nuclear receptor Nur77 as a mediator of CRH induction of POMC transcription led us, in the present work, to show that Gc antagonize this positive signal at two levels. First, Gc partly blunt the CRH induction of Nur77 mRNA, and second, they antagonize Nur77-dependent transcription. GR repression is exerted by antagonism of Nur77 action on the NurRE element of the POMC gene. Gc antagonism of NurRE activity was observed in response to physiological stimuli in both endocrine (CRH induction of POMC) and lymphoid (T-cell receptor activation) cells. In transfection experiments, transcriptional activation by Nur77 and the repressor activity of liganded GR titrated each other on their cognate DNA target. In vitro binding experiments as well as mutation analysis of GR suggest that the mechanism of GR antagonism of Nur77 is very similar to that of the antagonism between GR and AP-1. The convergence of positive signals mediated by Nur77 (and also probably by related family members) and negative signals exerted by GR appears to be a general mechanism for control of transcription, since it is active in both endocrine and lymphoid cells.

Relief of cyclin A gene transcriptional inhibition during activation of human primary T lymphocytes via CD2 and CD28 adhesion molecules

Cyclin A transcription is cell cycle regulated and induced by cell proliferative signals. To understand the mechanisms underlined in this regulation in normal human cells, we have analysed in vivo protein-DNA interactions at the Cyclin A locus in primary T lymphocytes. Stimulation of purified T lymphocytes by a combination of monoclonal antibodies directed at CD2 and CD28 adhesion molecules gives rise to a long lasting proliferation in the absence of accessory cells. Cyclin A was observed after 4 days of costimulation with anti CD2 + CD28 whereas stimulation by anti CD2 or anti CD28 alone was not effective. In vivo genomic DMS footprinting revealed upstream of the major transcription initiation sites, the presence of at least three protein binding sites, two of which were constitutively occupied. They bind in vitro respectively ATF-1 and NF-Y proteins. The third site was occupied in quiescent cells or in cells stimulated by anti CD2 or anti CD28 alone. The mitogenic combination of anti CD2 + anti CD28 released the footprint as cells were committed to proliferation. Consistent with theses results, nuclear extracts prepared from quiescent cells formed a specific complex with this element, whereas extracts prepared from cells treated with anti CD2 + anti CD28 failed to do so after cells entered a proliferative state.

Comparison of the efficacy, safety and acceptability of cefixime and amoxicillin/clavulanate in acute otitis media

BACKGROUND

Use of a beta-lactamase stable antibiotic is called for in cases of acute otitis media (AOM) likely to be caused by beta-lactamase-producing Haemophilus influenzae or Moraxella catarrhalis. Two beta-lactamase-stable agents commonly used for empirical treatment of AOM are amoxicillin/clavulanate and cefixime.

METHODS

A multicenter, randomized clinical trial compared cefixime (CFX; 8 mg/kg once daily) with amoxicillin/clavulanate (A/C; 40 mg/kg/day in three divided doses) for the treatment of children with AOM. Three hundred thirteen children were randomly assigned to a 10-day course of either CFX (n = 158) or A/C (n = 155). Based on history, physical examinations and otoscopic and tympanometric assessments, clinical responses were evaluated as cure, improvement, failure, relapse or nonevaluable. Compliance and patient/parent acceptability were also analyzed.

RESULTS

Overall favorable clinical responses (cure plus improvement) were comparable post-therapy for the two treatments (CFX = 76%; A/C = 77%). Significant differences in response rates for both treatments were noted among different geographic regions, with the highest response rates observed in the Northeast and South. Acceptability of CFX was significantly better than that of A/C (P = 0.0001), and the adverse experience rate was lower (P = 0.001). The most frequently reported adverse experiences were diarrhea (CFX 15.2%, A/C 29.7%) and vomiting (CFX 3.2%, A/C 10.32%). Relapse rates were 26% for CFX and 29% for A/C.

CONCLUSION

This study demonstrated that CFX has comparable clinical efficacy and a better adverse events profile than A/C when used to treat AOM of childhood.

Extra low frequency electric and magnetic fields in the bedplace of children diagnosed with leukaemia: a case-control study

This retrospective case-control study of 56 cases and 56 controls measured extra low frequency (ELF) electric and magnetic fields between 2000 h and 0800 h in the bedplaces of children with leukaemia. Mean ELF electric field (E-field) levels found in case homes of 13.9 Vm-1 (SD: 13.6) were significantly higher (P < 0.01) compared with only 7.3 Vm-1 (SD: 12.9) in controls matched for age and sex. Moreover, applying conditional logistic regression, a dose-response relationship emerged between E-field exposure and incidence: above 20 Vm-1 the relative risk was 4.69 (95% CI: 1.17-27.78; P = 0.025), whereas at levels of 10-19 Vm-1 it was 2.40 (95% CI: 0.79-8.09) and at levels of 5-9 Vm-1 it was only 1.46 (95% CI: 0.47-5.10). By contrast, similar readings of the rms ELF magnetic field found no significant case-control differences: mean levels in cases' homes of 0.070 microT (SD: 0.070) compared with 0.057 microT (SD: 0.038) in controls. Although there were imperfections in the study design, it is concluded that the importance of the E-field may have been overlooked in epidemiological studies to date.

Genomic cross-talk between the estrogen receptor and growth factor regulatory pathways in estrogen target tissues

Cell proliferation and differentiation are modulated by both estrogens and growth factors. Even though these two kinds of effectors interact with receptors localized in different compartments of the cell, their nuclear end points are often on the same genes. We review here the first evidence for transcriptional interference between these two regulatory pathways which might be essential in understanding the control of cell proliferation and invasion in human estrogen-responsive cancers.

Synthetic antiestrogens modulate induction of pS2 and cathepsin-D messenger ribonucleic acid by growth factors and adenosine 3',5'-monophosphate in MCF7 cells

In MCF7 human breast cancer cells, the antiestrogens 4-hydroxy-tamoxifen and ICI 164,384 inhibit the mitogenic activity of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I). These growth factors also stimulate the expression of cathepsin-D and pS2 genes. Therefore, we studied the effects of antiestrogens on growth factor induction of pS2 and cathepsin-D mRNA. The two antiestrogens strongly inhibited the transcriptional induction of pS2 by growth factors. On the contrary, estradiol and IGF-I or EGF had an additive effect on pS2 mRNA accumulation. Growth factor induction of cathepsin-D was also inhibited by ICI 164,384. By contrast, 4-hydroxytamoxifen had an agonist effect on cathepsin-D and an additive effect on IGF-I-induced mRNA. When 12-O-tetradecanoylphorbol-13-acetate or 8-bromo-cAMP (8-Br-cAMP) was used instead of growth factors, similar effects of 4-hydroxytamoxifen and ICI 164,384 were obtained on pS2 (12-O-tetradecanoylphorbol-13-acetate and 8-Br-cAMP) and cathepsin-D (8-Br-cAMP) induction. A mechanism based on the classical competitive inhibition by antiestrogens of estrogen binding and action on the estrogen receptor was very unlikely, as 1) no antigrowth factor activity was obtained with R5020, which was a potent inhibitor of estrogen induction of pS2 and cathepsin-D mRNA; 2) in the Ishikawa endometrial cancer cell line, the cathepsin-D gene is unresponsive to estrogen, but was inhibited by antiestrogen after its induction by EGF or 8-Br-cAMP; and 3) the residual estrogen concentration in cells was too low to induce the expression of estrogen-specific genes. However, antiestrogens did not inhibit the expression of all genes induced by growth factors, as they were without effect on IGF-I induction of glyceraldehyde-3-phosphate dehydrogenase mRNA. These results demonstrate that antiestrogens can modulate the transcription of some growth factor-induced genes and strongly suggest that this effect is not due to interference with residual estrogens.

Estradiol increases and anti-estrogens antagonize the growth factor-induced activator protein-1 activity in MCF7 breast cancer cells without affecting c-fos and c-jun synthesis

In estrogen receptor positive human breast cancer cells, anti-estrogens inhibit the mitogenic effect of growth factors in the absence of estrogens. As activator protein-1 (AP-1) activity is one of the first nuclear events following growth factor receptor activation, we studied the effects of estrogens and anti-estrogens on growth factor-induced AP-1 activity using transient transfection of the AP-1-responsive gene (AP-1)4-TK-CAT into MCF7 cells. The growth factor-induced AP-1 response was increased by estradiol and inhibited by anti-estrogens in conditions where growth factor-induced c-fos and c-jun mRNA levels were unchanged by hormone and anti-hormone treatments. The same regulations were obtained when the AP-1 response was directly induced by co-transfection of c-fos and c-jun expression vectors. Co-transfection of the wild-type estrogen receptor HEGO amplified both effects. Inhibition of AP-1 activity by anti-estrogens was unlikely to be explained by the presence of residual estrogens in MCF7 cells. (i) anti-estrogens inhibited AP-1 activity in conditions where they had no effect on basal ERE-mediated activity levels, whereas estradiol was as efficient in stimulating both activities. (ii) The relative efficacy of the two anti-estrogens, OH-tamoxifen and ICI 164,384 in inhibiting these two activities was different; OH-tamoxifen was more efficient in inhibiting ERE-mediated activity, whereas ICI 164,384 was more efficient in trans-repressing AP-1-mediated activity. We conclude that in conditions where c-fos and c-jun syntheses were not affected, the estrogen receptor cooperated with growth factors to stimulate the AP-1 response when activated by estrogens but inhibited AP-1-mediated transcription when occupied by anti-estrogens.