IF du Neurocentre

31 publications

* equal contribution
Les IF indiqués ont été collectés par le Web of Sciences en Juin 2021

28/01/2021 | Mol Psychiatry   IF 16
PAI-1 protein is a key molecular effector in the transition from normal to PTSD-like fear memory.
Bouarab C*, Lacarriere V*, Vallee M, Leroux A, Guette C, Mennesson M, Marighetto A, Desmedt A*, Piazza PV*, Revest JM*

Moderate stress increases memory and facilitates adaptation. In contrast, intense stress can induce pathological memories as observed in post-traumatic stress disorders (PTSD). A shift in the balance between the expression of tPA and PAI-1 proteins is responsible for this transition. In conditions of moderate stress, glucocorticoid hormones increase the expression of the tPA protein in the hippocampal brain region which by triggering the Erk1/2(MAPK) signaling cascade strengthens memory. When stress is particularly intense, very high levels of glucocorticoid hormones then increase the production of PAI-1 protein, which by blocking the activity of tPA induces PTSD-like memories. PAI-1 levels after trauma could be a predictive biomarker of the subsequent appearance of PTSD and pharmacological inhibition of PAI-1 activity a new therapeutic approach to this debilitating condition.

Serotonin2B receptor (5-HT2BR) antagonists inhibit cocaine-induced hyperlocomotion independently of changes of accumbal dopamine (DA) release. Given the tight relationship between accumbal DA activity and locomotion, and the inhibitory role of medial prefrontal cortex (mPFC) DA on subcortical DA neurotransmission and DA-dependent behaviors, it has been suggested that the suppressive effect of 5-HT2BR antagonists on cocaine-induced hyperlocomotion may result from an activation of mPFC DA outflow which would subsequently inhibit accumbal DA neurotransmission. Here, we tested this hypothesis by means of the two selective 5-HT2BR antagonists, RS 127445 and LY 266097, using a combination of neurochemical, behavioral and cellular approaches in male rats. The intraperitoneal (i.p.) administration of RS 127445 (0.16 mg/kg) or LY 266097 (0.63 mg/kg) potentiated cocaine (10 mg/kg, i.p.)-induced mPFC DA outflow. The suppressant effect of RS 127445 on cocaine-induced hyperlocomotion was no longer observed in rats with local 6-OHDA lesions in the mPFC. Also, RS 127445 blocked cocaine-induced changes of accumbal glycogen synthase kinase (GSK) 3beta phosphorylation, a postsynaptic cellular marker of DA neurotransmission. Finally, in keeping with the location of 5-HT2BRs on GABAergic interneurons in the dorsal raphe nucleus (DRN), the intra-DRN perfusion of the GABAAR antagonist bicuculline (100 muM) prevented the effect of the systemic or local (1 muM, intra-DRN) administration of RS 127445 on cocaine-induced mPFC DA outflow. Likewise, intra-DRN bicuculline injection (0.1 mug/0.2 mul) prevented the effect of the systemic RS 127445 administration on cocaine-induced hyperlocomotion and GSK3beta phosphorylation. These results show that DRN 5-HT2BR blockade suppresses cocaine-induced hyperlocomotion by potentiation of cocaine-induced DA outflow in the mPFC and the subsequent inhibition of accumbal DA neurotransmission.

09/12/2019 | J Neurosci Methods   IF 2.8
Alpha technology: A powerful tool to detect mouse brain intracellular signaling events.
Zanese M*, Tomaselli G*, Roullot-Lacarriere V, Moreau M, Bellocchio L, Grel A, Marsicano G, Sans N, Vallee M, Revest JM

BACKGROUND: Phosphorylation by protein kinases is a fundamental molecular process involved in the regulation of signaling activities in living organisms. Understanding this complex network of phosphorylation, especially phosphoproteins, is a necessary step for grasping the basis of cellular pathophysiology. Studying brain intracellular signaling is a particularly complex task due to the heterogeneous complex nature of the brain tissue, which consists of many embedded structures. NEW METHOD: Overcoming this degree of complexity requires a technology with a high throughput and economical in the amount of biological material used, so that a large number of signaling pathways may be analyzed in a large number of samples. We have turned to Alpha (Amplified Luminescent Proximity Homogeneous Assay) technology. COMPARISON WITH EXISTING METHOD: Western blot is certainly the most commonly used method to measure the phosphorylation state of proteins. Even though Western blot is an accurate and reliable method for analyzing modifications of proteins, it is a time-consuming and large amounts of samples are required. Those two parameters are critical when the goal of the research is to comprehend multi-signaling proteic events so as to analyze several targets from small brain areas. RESULT: Here we demonstrate that Alpha technology is particularly suitable for studying brain signaling pathways by allowing rapid, sensitive, reproducible and semi-quantitative detection of phosphoproteins from individual mouse brain tissue homogenates and from cell fractionation and synaptosomal preparations of mouse hippocampus. CONCLUSION: Alpha technology represents a major experimental step forward in unraveling the brain phosphoprotein-related molecular mechanisms involved in brain-related disorders.

24/01/2019 | Neurobiol Dis   IF 5.2
Cannabinoid type-1 receptor blockade restores neurological phenotypes in two models for Down syndrome.
Navarro-Romero A, Vazquez-Oliver A, Gomis-Gonzalez M, Garzon-Montesinos C, Falcon-Moya R, Pastor A, Martin-Garcia E, Pizarro N, Busquets-Garcia A, Revest JM, Piazza PV, Bosch F, Dierssen M, de la Torre R, Rodriguez-Moreno A, Maldonado R, Ozaita A

Intellectual disability is the most limiting hallmark of Down syndrome, for which there is no gold-standard clinical treatment yet. The endocannabinoid system is a widespread neuromodulatory system involved in multiple functions including learning and memory processes. Alterations of this system contribute to the pathogenesis of several neurological and neurodevelopmental disorders. However, the involvement of the endocannabinoid system in the pathogenesis of Down syndrome has not been explored before. We used the best-characterized preclinical model of Down syndrome, the segmentally trisomic Ts65Dn model. In male Ts65Dn mice, cannabinoid type-1 receptor (CB1R) expression was enhanced and its function increased in hippocampal excitatory terminals. Knockdown of CB1R in the hippocampus of male Ts65Dn mice restored hippocampal-dependent memory. Concomitant with this result, pharmacological inhibition of CB1R restored memory deficits, hippocampal synaptic plasticity and adult neurogenesis in the subgranular zone of the dentate gyrus. Notably, the blockade of CB1R also normalized hippocampal-dependent memory in female Ts65Dn mice. To further investigate the mechanisms involved, we used a second transgenic mouse model overexpressing a single gene candidate for Down syndrome cognitive phenotypes, the dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A). CB1R pharmacological blockade similarly improved cognitive performance, synaptic plasticity and neurogenesis in transgenic male Dyrk1A mice. Our results identify CB1R as a novel druggable target potentially relevant for the improvement of cognitive deficits associated with Down syndrome.

23/09/2018 | Exp Neurol   IF 4.5
Serotonin2B receptors in the rat dorsal raphe nucleus exert a GABA-mediated tonic inhibitory control on serotonin neurons.
Cathala A, Devroye C, Drutel G, Revest JM, Artigas F, Spampinato U

The central serotonin2B receptor (5-HT2BR) is a well-established modulator of dopamine (DA) neuron activity in the rodent brain. Recent studies in rats have shown that the effect of 5-HT2BR antagonists on accumbal and medial prefrontal cortex (mPFC) DA outflow results from a primary action in the dorsal raphe nucleus (DRN), where they activate 5-HT neurons innervating the mPFC. Although the mechanisms underlying this interaction remain largely unknown, data in the literature suggest the involvement of DRN GABAergic interneurons in the control of 5-HT activity. The present study examined this hypothesis using in vivo (intracerebral microdialysis) and in vitro (immunohistochemistry coupled to reverse transcription-polymerase chain reaction) experimental approaches in rats. Intraperitoneal (0.16mg/kg) or intra-DRN (1muM) administration of the selective 5-HT2BR antagonist RS 127445 increased 5-HT outflow in both the DRN and the mPFC, these effects being prevented by the intra-DRN perfusion of the GABAA antagonist bicuculline (100muM), as well as by the subcutaneous (0.16mg/kg) or the intra-DRN (0.1muM) administration of the selective 5-HT1AR antagonist WAY 100635. The increase in DRN 5-HT outflow induced by the intra-DRN administration of the selective 5-HT reuptake inhibitor citalopram (0.1muM) was potentiated by the intra-DRN administration (0.5muM) of RS 127445 only in the absence of bicuculline perfusion. Finally, in vitro experiments revealed the presence of the 5-HT2BR mRNA on DRN GABAergic interneurons. Altogether, these results show that, in the rat DRN, 5-HT2BRs are located on GABAergic interneurons, and exert a tonic inhibitory control on 5-HT neurons innervating the mPFC.

05/03/2018 | Mol Psychiatry   IF 11.6
Depleting adult dentate gyrus neurogenesis increases cocaine-seeking behavior.
Deroche-Gamonet V, Revest JM, Fiancette JF, Balado E, Koehl M, Grosjean N, Abrous DN, Piazza PV

The hippocampus is the main locus for adult dentate gyrus (DG) neurogenesis. A number of studies have shown that aberrant DG neurogenesis correlates with many neuropsychiatric disorders, including drug addiction. Although clear causal relationships have been established between DG neurogenesis and memory dysfunction or mood-related disorders, evidence of the causal role of DG neurogenesis in drug-seeking behaviors has not been established. Here we assessed the role of new DG neurons in cocaine self-administration using an inducible transgenic approach that selectively depletes adult DG neurogenesis. Our results show that transgenic mice with decreased adult DG neurogenesis exhibit increased motivation to self-administer cocaine and a higher seeking response to cocaine-related cues. These results identify adult hippocampal neurogenesis as a key factor in vulnerability to cocaine addiction.

01/11/2014 | Neuropharmacology   IF 4.8
Serotonin receptor stimulation inhibits cocaine-induced Fos expression and DARPP-32 phosphorylation in the rat striatum independently of dopamine outflow.
Devroye C, Cathala A, Maitre M, Piazza PV, Abrous DN, Revest JM, Spampinato U

The serotonin2C receptor (5-HT2CR) is known to control dopamine (DA) neuron function by modulating DA neuronal firing and DA exocytosis at terminals. Recent studies assessing the influence of 5-HT2CRs on cocaine-induced neurochemical and behavioral responses have shown that 5-HT2CRs can also modulate mesoaccumbens DA pathway activity at post-synaptic level, by controlling DA transmission in the nucleus accumbens (NAc), independently of DA release itself. A similar mechanism has been proposed to occur at the level of the nigrostriatal DA system. Here, using in vivo microdialysis in freely moving rats and molecular approaches, we assessed this hypothesis by studying the influence of the 5-HT2CR agonist Ro 60-0175 on cocaine-induced responses in the striatum. The intraperitoneal (i.p.) administration of 1 mg/kg Ro 60-0175 had no effect on the increase in striatal DA outflow induced by cocaine (15 mg/kg, i.p.). Conversely, Ro 60-0175 inhibited cocaine-induced Fos immunoreactivity and phosphorylation of the DA and c-AMP regulated phosphoprotein of Mr 32 kDa (DARPP-32) at threonine 75 residue in the striatum. Finally, the suppressant effect of Ro 60-0175 on cocaine-induced DARPP-32 phosphorylation was reversed by the selective 5-HT2CR antagonist SB 242084 (0.5 mg/kg, i.p.). In keeping with the key role of DARPP-32 in DA neurotransmission, our results demonstrate that 5-HT2CRs are capable of modulating nigrostriatal DA pathway activity at post-synaptic level, by specifically controlling DA signaling in the striatum.

09/2014 | Mol Psychiatry   IF 15.1
BDNF-TrkB signaling through Erk1/2 MAPK phosphorylation mediates the enhancement of fear memory induced by glucocorticoids.
Revest JM, Le Roux A, Roullot-Lacarriere V, Kaouane N, Vallee M, Kasanetz F, Rouge-Pont F, Tronche F, Desmedt A, Piazza PV

Activation of glucocorticoid receptors (GR) by glucocorticoid hormones (GC) enhances contextual fear memories through the activation of the Erk1/2(MAPK) signaling pathway. However, the molecular mechanism mediating this effect of GC remains unknown. Here we used complementary molecular and behavioral approaches in mice and rats and in genetically modified mice in which the GR was conditionally deleted (GR(NesCre)). We identified the tPA-BDNF-TrkB signaling pathway as the upstream molecular effectors of GR-mediated phosphorylation of Erk1/2(MAPK) responsible for the enhancement of contextual fear memory. These findings complete our knowledge of the molecular cascade through which GC enhance contextual fear memory and highlight the role of tPA-BDNF-TrkB-Erk1/2(MAPK) signaling pathways as one of the core effectors of stress-related effects of GC.

In keeping with its ability to control the mesoaccumbens dopamine (DA) pathway, the serotonin2C receptor (5-HT2C R) plays a key role in mediating the behavioral and neurochemical effects of drugs of abuse. Studies assessing the influence of 5-HT2C R agonists on cocaine-induced responses have suggested that 5-HT2C Rs can modulate mesoaccumbens DA pathway activity independently of accumbal DA release, thereby controlling DA transmission in the nucleus accumbens (NAc). In the present study, we assessed this hypothesis by studying the influence of the 5-HT2C R agonist Ro 60-0175 on cocaine-induced behavioral, neurochemical and molecular responses. The i.p. administration of 1 mg/kg Ro 60-0175 inhibited hyperlocomotion induced by cocaine (15 mg/kg, i.p.), had no effect on cocaine-induced DA outflow in the shell, and increased it in the core subregion of the NAc. Furthermore, Ro 60-0175 inhibited the late-onset locomotion induced by the subcutaneous administration of the DA-D2 R agonist quinpirole (0.5 mg/kg), as well as cocaine-induced increase in c-Fos immunoreactivity in NAc subregions. Finally, Ro 60-0175 inhibited cocaine-induced phosphorylation of the DA and c-AMP regulated phosphoprotein of Mr 32 kDa (DARPP-32) at threonine residues in the NAc core, this effect being reversed by the selective 5-HT2C R antagonist SB 242084 (0.5 mg/kg, i.p.). Altogether, these findings demonstrate that 5-HT2C Rs are capable of modulating mesoaccumbens DA pathway activity at post-synaptic level by specifically controlling DA signaling in the NAc core subregion. In keeping with the tight relationship between locomotor activity and NAc DA function, this interaction could participate in the inhibitory control of cocaine-induced locomotor activity.

03/01/2014 | Science   IF 31.5
Pregnenolone can protect the brain from cannabis intoxication.
Vallee M, Vitiello S, Bellocchio L, Hebert-Chatelain E, Monlezun S, Martin-Garcia E, Kasanetz F, Baillie GL, Panin F, Cathala A, Roullot-Lacarriere V, Fabre S, Hurst DP, Lynch DL, Shore DM, Deroche-Gamonet V, Spampinato U, Revest JM, Maldonado R, Reggio PH, Ross RA, Marsicano G, Piazza PV

Pregnenolone is considered the inactive precursor of all steroid hormones, and its potential functional effects have been largely uninvestigated. The administration of the main active principle of Cannabis sativa (marijuana), Delta(9)-tetrahydrocannabinol (THC), substantially increases the synthesis of pregnenolone in the brain via activation of the type-1 cannabinoid (CB1) receptor. Pregnenolone then, acting as a signaling-specific inhibitor of the CB1 receptor, reduces several effects of THC. This negative feedback mediated by pregnenolone reveals a previously unknown paracrine/autocrine loop protecting the brain from CB1 receptor overactivation that could open an unforeseen approach for the treatment of cannabis intoxication and addiction.

15/05/2012 | Mol Psychiatry   IF 14.9
Prefrontal synaptic markers of cocaine addiction-like behavior in rats.
Kasanetz F*, Lafourcade M*, Deroche-Gamonet V*, Revest JM, Berson N, Balado E, Fiancette JF, Renault P, Piazza PV*, Manzoni OJ*

Defining the drug-induced neuroadaptations specifically associated with the behavioral manifestation of addiction is a daunting task. To address this issue, we used a behavioral model that differentiates rats controlling their drug use (Non-Addict-like) from rats undergoing transition to addiction (Addict-like). Dysfunctions in prefrontal cortex (PFC) synaptic circuits are thought to be responsible for the loss of control over drug taking that characterizes addicted individuals. Here, we studied the synaptic alterations in prelimbic PFC (pPFC) circuits associated with transition to addiction. We discovered that some of the changes induced by cocaine self-administration (SA), such as the impairment of the endocannabinoid-mediated long-term synaptic depression (eCB-LTD) was similarly abolished in Non-Addict- and Addict-like rats and thus unrelated to transition to addiction. In contrast, metabotropic glutamate receptor 2/3-mediated LTD (mGluR2/3-LTD) was specifically suppressed in Addict-like rats, which also show a concomitant postsynaptic plasticity expressed as a change in the relative contribution of AMPAR and NMDAR to basal glutamate-mediated synaptic transmission. Addiction-associated synaptic alterations in the pPFC were not fully developed at early stages of cocaine SA, when addiction-like behaviors are still absent, suggesting that pathological behaviors appear once the pPFC is compromised. These data identify specific synaptic impairments in the pPFC associated with addiction and support the idea that alterations of synaptic plasticity are core markers of drug dependence.Molecular Psychiatry advance online publication, 15 May 2012; doi:10.1038/mp.2012.59.

02/2012 | Hippocampus   IF 5.5
Adult-born neurons are necessary for extended contextual discrimination.
Tronel S, Belnoue L, Grosjean N, Revest JM, Piazza PV, Koehl M, Abrous DN

New neurons are continuously produced in the adult dentate gyrus of the hippocampus. It has been shown that one of the functions of adult neurogenesis is to support spatial pattern separation, a process that transforms similar memories into nonoverlapping representations. This prompted us to investigate whether adult-born neurons are required for discriminating two contexts, i.e., for identifying a familiar environment and detect any changes introduced in it. We show that depleting adult-born neurons impairs the animal's ability to disambiguate two contexts after extensive training. These data suggest that the continuous production of new dentate neurons plays a crucial role in extracting and separating efficiently contextual representation in order to discriminate features within events.

15/06/2011 | J Neurosci Methods
Western blot detection of brain phosphoproteins after performing Laser Microdissection and Pressure Catapulting (LMPC).
Maitre M, Roullot-Lacarriere V, Piazza PV, Revest JM

The Central Nervous System (CNS) is constituted of complex and specific anatomical regions that cluster together and interact with each other with the ultimate objective of receiving and delivering information. This information is characterized by selective biochemical changes that happen within specific brain sub-regions. Most of these changes involve a dynamic balance between kinase and phosphatase activities. The fine-tuning of this kinase/phosphatase balance is thus critical for neuronal adaptation, transition to long-term responses and higher brain functions including specific behaviors. Data emerging from several biological systems may suggest that disruption of this dynamic cell signaling balance within specific brain sub-regions leads to behavioral impairments. Therefore, accurate and powerful techniques are required to study global changes in protein expression levels and protein activities in specific groups of cells. Laser-based systems for tissue microdissection represent a method of choice enabling more accurate proteomic profiling. The goal of this study was to develop a methodological approach using Laser Microdissection and Pressure Catapulting (LMPC) technology combined with an immunoblotting technique in order to specifically detect the expression of phosphoproteins in particular small brain areas.

19/04/2011 | Proc Natl Acad Sci U S A
Conditional reduction of adult neurogenesis impairs bidirectional hippocampal synaptic plasticity.
Massa F, Koehl M, Wiesner T, Grosjean N, Revest JM, Piazza PV, Abrous DN, Oliet SH

Adult neurogenesis is a process by which the brain produces new neurons once development has ceased. Adult hippocampal neurogenesis has been linked to the relational processing of spatial information, a role attributed to the contribution of newborn neurons to long-term potentiation (LTP). However, whether newborn neurons also influence long-term depression (LTD), and how synaptic transmission and plasticity are affected as they incorporate their network, remain to be determined. To address these issues, we took advantage of a genetic model in which a majority of adult-born neurons can be selectively ablated in the dentate gyrus (DG) and, most importantly, in which neurogenesis can be restored on demand. Using electrophysiological recordings, we show that selective reduction of adult-born neurons impairs synaptic transmission at medial perforant pathway synapses onto DG granule cells. Furthermore, LTP and LTD are largely compromised at these synapses, probably as a result of an increased induction threshold. Whereas the deficits in synaptic transmission and plasticity are completely rescued by restoring neurogenesis, these synapses regain their ability to express LTP much faster than their ability to express LTD. These results demonstrate that both LTP and LTD are influenced by adult neurogenesis. They also indicate that as newborn neurons integrate their network, the ability to express bidirectional synaptic plasticity is largely improved at these synapses. These findings establish that adult neurogenesis is an important process for synaptic transmission and bidirectional plasticity in the DG, accounting for its role in efficiently integrating novel incoming information and in forming new memories.

12/2010 | Mol Psychiatry   IF 10.9
The enhancement of stress-related memory by glucocorticoids depends on
Revest JM, Kaouane N, Mondin M, Le Roux A, Rouge-Pont F, Vallee M, Barik J, Tronche F, Desmedt A, Piazza PV

The activation of glucocorticoid receptors (GR) by glucocorticoids increases

10/2009 | Mol Psychiatry
Adult hippocampal neurogenesis is involved in anxiety-related behaviors.
Revest JM, Dupret D, Koehl M, Funk-Reiter C, Grosjean N, Piazza PV, Abrous DN

Adult hippocampal neurogenesis is a unique example of structural plasticity, the functional role of which has been a matter of intense debate. New transgenic models have recently shown that neurogenesis participates in hippocampus-mediated learning. Here, we show that transgenic animals, in which adult hippocampal neurogenesis has been specifically impaired, exhibit a striking increase in anxiety-related behaviors. Our results indicate that neurogenesis plays an important role in the regulation of affective states and could be the target of new treatments for anxiety disorders.

2009 | PLoS ONE
Transcriptional effects of glucocorticoid receptors in the dentate gyrus increase anxiety-related behaviors.
Sarrazin N*, Di Blasi F*, Roullot-Lacarriere V, Rouge-Pont F, Leroux A, Costet P, Revest JM*, Piazza PV*

2008 | PLoS ONE
Spatial relational memory requires hippocampal adult neurogenesis.
Dupret D, Revest JM, Koehl M, Ichas F, De Giorgi F, Costet P, Abrous DN, Piazza PV

The dentate gyrus of the hippocampus is one of the few regions of the mammalian brain where new neurons are generated throughout adulthood. This adult neurogenesis has been proposed as a novel mechanism that mediates spatial memory. However, data showing a causal relationship between neurogenesis and spatial memory are controversial. Here, we developed an inducible transgenic strategy allowing specific ablation of adult-born hippocampal neurons. This resulted in an impairment of spatial relational memory, which supports a capacity for flexible, inferential memory expression. In contrast, less complex forms of spatial knowledge were unaltered. These findings demonstrate that adult-born neurons are necessary for complex forms of hippocampus-mediated learning.

05/2005 | Nat Neurosci
The MAPK pathway and Egr-1 mediate stress-related behavioral effects of glucocorticoids
Revest J M, Di Blasi F, Kitchener P, Rouge-Pont F, Desmedt A, Turiault M, Tronche F, Piazza P V

Many of the behavioral consequences of stress are mediated by the activation of the glucocorticoid receptor by stress-induced high levels of glucocorticoid hormones. To explore the molecular mechanisms of these effects, we combined in vivo and in vitro approaches. We analyzed mice carrying a brain-specific mutation (GR(NesCre)) in the glucocorticoid receptor gene (GR, also called Nr3c1) and cell lines that either express endogenous glucocorticoid receptor or carry a constitutively active form of the receptor (DeltaGR) that can be transiently induced. In the hippocampus of the wild-type [corrected] mice after stress, as well as in the cell lines, activation of glucocorticoid receptors greatly increased the expression and enzymatic activity of proteins in the MAPK signaling pathway and led to an increase in the levels of both Egr-1 mRNA and protein. In parallel, inhibition of the MAPK pathway within the hippocampus abolished the increase in contextual fear conditioning induced by glucocorticoids. The present results provide a molecular mechanism for the stress-related effects of glucocorticoids on fear memories.

11/2003 | Development
A crucial role for Fgfr2-IIIb signalling in epidermal development and hair follicle patterning.
Petiot A, Conti FJ, Grose R, Revest JM, Hodivala-Dilke KM, Dickson C

To understand the role Fgf signalling in skin and hair follicle development, we analysed the phenotype of mice deficient for Fgfr2-IIIb and its main ligand Fgf10. These studies showed that the severe epidermal hypoplasia found in mice null for Fgfr2-IIIb is caused by a lack of the basal cell proliferation that normally results in a stratified epidermis. Although at term the epidermis of Fgfr2-IIIb null mice is only two to three cells thick, it expresses the classical markers of epidermal differentiation and establishes a functional barrier. Mice deficient for Fgf10 display a similar but less severe epidermal hypoplasia. By contrast, Fgfr2-IIIb-/-, but not Fgf10-/-, mice produced significantly fewer hair follicles, and their follicles were developmentally retarded. Following transplantation onto nude mice, grafts of Fgfr2-IIIb-/- skin showed impaired hair formation, with a decrease in hair density and the production of abnormal pelage hairs. Expression of Lef1, Shh and Bmp4 in the developing hair follicles of Fgfr2-IIIb-/- mice was similar to wild type. These results suggest that Fgf signalling positively regulates the number of keratinocytes needed to form a normal stratified epidermis and to initiate hair placode formation. In addition, Fgf signals are required for the growth and patterning of pelage hairs.

15/08/2001 | J Immunol
Development of the thymus requires signaling through the fibroblast growth factor receptor R2-IIIb.
Revest JM, Suniara RK, Kerr K, Owen JJ, Dickson C

Mice deficient for fibroblast growth factor (Fgf)R2-IIIb show a block in thymic growth after embryonic day 12.5, a stage that just precedes its detection in thymic epithelial cells. Fgf7 and Fgf10, the main ligands for FgfR2-IIIb, are expressed in the mesenchyme surrounding the thymic epithelial primordium, and Fgf10-deficient mice also exhibit impaired thymic growth. Hence, Fgf signaling is essential for thymic epithelial proliferation. In addition to the proliferative block, most thymic epithelial cells fail to progress from an immature cytokeratin 5-positive to a cytokeratin 5-negative phenotype. Nevertheless, sufficient epithelial cell differentiation occurs in the severely hypoplastic thymus to allow the development of CD4/CD8-double-positive thymocytes and a very small number of single-positive thymocytes expressing TCRs.

15/08/2001 | Nucleic Acids Res
SOX6 binds CtBP2 to repress transcription from the Fgf-3 promoter.
Murakami A, Ishida S, Thurlow J, Revest JM, Dickson C

Fgf-3 is expressed in a complex pattern during mouse development. Previously, an essential regulatory element PS4A was identified in the promoter region, and shown to bind at least three factors. To identify the transcription factor(s), we used a yeast one-hybrid screen and obtained a novel Sox6 cDNA (SOX6D). When introduced into cells it strongly repressed activity from both an Fgf-3 reporter gene as well as an artificial promoter containing three PS4A elements. In situ hybridisation analysis showed that Sox6 and Fgf-3 are co-expressed in the otic vesicle of E9.5 mouse embryos in a mutually exclusive pattern, consistent with a repression of Fgf-3 transcription by SOX6. To characterise additional factor(s) involved in Fgf-3 gene repression, a yeast two-hybrid screen was used with the N-terminal portion of SOX6D. Mouse CtBP2 cDNA clones were isolated and shown to bind SOX6 in yeast and mammalian cells. Furthermore, mutational analysis of SOX6 showed that binding to CtBP2, and its responsiveness to this co-repressor, were dependent on a short amino acid sequence motif PLNLSS. Co-expression studies in NIH3T3 cells showed that SOX6 and CtBP2 co-operate to repress activity from the Fgf-3 promoter through the enhancer element PS4A. These results show that SOX6 can recruit CtBP2 to repress transcription from the Fgf-3 promoter.

Mice deficient for FgfR2-IIIb were generated by placing translational stop codons and an IRES-LacZ cassette into exon IIIb of FgfR2. Expression of the alternatively spliced receptor isoform, FgfR2-IIIc, was not affected in mice deficient for the IIIb isoform. FgfR2-IIIb(-/-) (lac)(Z) mice survive to term but show dysgenesis of the kidneys, salivary glands, adrenal glands, thymus, pancreas, skin, otic vesicles, glandular stomach, and hair follicles, and agenesis of the lungs, anterior pituitary, thyroid, teeth, and limbs. Detailed analysis of limb development revealed an essential role for FgfR2-IIIb in maintaining the AER. Its absence did not prevent expression of Fgf8, Fgf10, Bmp4, and Msx1, but did prevent induction of Shh and Fgf4, indicating that they are downstream targets of FgfR2-IIIb activation. In the absence of FgfR2-IIIb, extensive apoptosis of the limb bud ectoderm and mesenchyme occurs between E10 and E10.5, providing evidence that Fgfs act primarily as survival factors. We propose that FgfR2-IIIb is not required for limb bud initiation, but is essential for its maintenance and growth.

Fibroblast growth factors (FGFs) transmit their signals through four transmembrane receptors that are designated FGFR1-4. Alternative splicing in the extracellular region of FGFR1-3 generates receptor variants with different ligand binding affinities. Thus two types of transmembrane receptors (IIIb and IIIc isoforms) have been identified for FGFR2 and FGFR3, and the existence of analogous variants has been postulated for FGFR1 based on its genomic structure. However, only a single full-length transmembrane FGFR1 variant (FGFR1-IIIc) has been identified so far. Here we describe the cloning of a full-length cDNA encoding FGFR1-IIIb from a mouse skin wound cDNA library. This receptor isoform was expressed at the highest levels in a subset of sebaceous glands of the skin and in neurons of the hippocampus and the cerebellum. FGFR1-IIIb was expressed in L6 rat skeletal muscle myoblasts and used in cross-linking and receptor binding studies. FGF-1 was found to bind the receptor with high affinity, whereas FGF-2, -10, and -7 bound with significantly lower affinities. Despite their apparently similar but low affinities, FGF-10 but not FGF-7 induced the activation of p44/42 mitogen-activated protein kinase in FGFR1-IIIb-expressing L6 myoblasts and stimulated mitogenesis in these cells, demonstrating that this new receptor variant is a functional transmembrane receptor for FGF-10.

Fibroblast growth factors are a family of intercellular signaling molecules with multiple and varied roles in animal development. Most are exported from cells by means of a classical amino-terminal signal sequence that is cleaved from the mature protein during its passage through the secretory pathway. Fibroblast growth factor-9 (Fgf-9) does not contain a recognizable signal sequence, although it is efficiently secreted. In this study, we show that Fgf-9 enters the endoplasmic reticulum and traverses the Golgi complex in a similar manner to other constitutively secreted proteins. Deletion and point mutation analysis has revealed an atypical non-cleaved signal sequence within the amino-terminal region of Fgf-9. Moreover, the first 28 amino acids of Fgf-9 can function as an efficient non-cleaved signal peptide when appended to the amino terminus of green fluorescent protein.

02/2000 | Development
An important role for the IIIb isoform of fibroblast growth factor receptor 2 (FGFR2) in mesenchymal-epithelial signalling during mouse organogenesis.
De Moerlooze L, Spencer-Dene B, Revest JM, Hajihosseini M, Rosewell I, Dickson C

The fibroblast growth factor receptor 2 gene is differentially spliced to encode two transmembrane tyrosine kinase receptor proteins that have different ligand-binding specificities and exclusive tissue distributions. We have used Cre-mediated excision to generate mice lacking the IIIb form of fibroblast growth factor receptor 2 whilst retaining expression of the IIIc form. Fibroblast growth factor receptor 2(IIIb) null mice are viable until birth, but have severe defects of the limbs, lung and anterior pituitary gland. The development of these structures appears to initiate, but then fails with the tissues undergoing extensive apoptosis. There are also developmental abnormalities of the salivary glands, inner ear, teeth and skin, as well as minor defects in skull formation. Our findings point to a key role for fibroblast growth factor receptor 2(IIIb) in mesenchymal-epithelial signalling during early organogenesis.

F3, a mouse glycosyl-phosphatidylinositol anchored molecule of the immunoglobulin superfamily, is known to influence axonal growth and fasciculation via multiple interactions of its modular immunoglobulin-like domains. We prepared an Fc chimeric molecule (F3IgFc) to identify molecules interacting with these domains and characterize the functional impact of the interactions. We affinity-isolated tenascin-C and isoforms of the proteoglycan-type protein tyrosine phosphatases zeta/beta (PTPzeta/RPTPbeta) from extracts of developing mouse brain. We showed that both PTPzeta/RPTPbeta and tenascin-C can bind directly to F3, possibly in an exclusive manner, with the highest affinity for the F3-PTPzeta/RPTPbeta interaction. We observed a strong binding of F3IgFc-coated fluorospheres to astrocytes in neural primary cultures and to C6 astrocytoma cells, and demonstrated, in antibody perturbation experiments, that F3-Ig binding on astrocytes depends on its interaction with PTPzeta/RPTPbeta. We also found by confocal analysis that tenascin-C and PTPzeta/RPTPbeta were colocalized on astrocytes which suggests a complex interplay of interactions between PTPzeta/RPTPbeta, tenascin-C and F3. We showed that the interaction between PTPzeta/RPTPbeta and F3-Ig-like domains can trigger bidirectional signalling. C6 glia-expressed PTPzeta/RPTPbeta stimulated neurite outgrowth by cortical and cerebellar neurons, whereas preclustered F3IgFc specifically modified the distribution of phosphotyrosine labelling in these glial cells. Both effects could be prevented and/or mimicked by anti-F3 and anti-6B4PG antibodies. These results identify F3 and PTPzeta/RPTPbeta as potential mediators of a reciprocal exchange of information between glia and neurons.

1999 | Adv Exp Med Biol
Bidirectional signaling between neurons and glial cells via the F3 neuronal adhesion molecule.
Revest JM, Faivre-Sarrailh C, Schachner M, Rougon G

F3, a glycosyl-phosphatidylinositol anchored molecule of the immunoglobulin superfamily, is known to influence axonal growth and fasciculation via multiple interactions of its modular immunoglobulin-like domains. We prepared a Fc chimeric molecule (F3IgFc) to identify a) the phenotype of cells bearing F3Ig receptors, b) the glial-expressed molecules interacting with these domains and, c) to characterize in in vitro models the functional impact of the interactions. We observed a strong binding of F3IgFc coated fluorospheres to astrocytes in neural primary cultures and to C6 astrocytoma cells. In agreement, in extracts of developing mouse brain F3IgFc is able to bind tenascin-R, tenascin-C, and isoforms of the proteoglycan-type protein tyrosine phosphatases z/beta. All these molecules are synthetized by glial cells as an indication that F3 participates in neuron-glia interactions. We showed that C6 glia-expressed PTPz/RPTP beta stimulated neurite outgrowth by cortical and cerebellar neurons whereas preclustered F3IgFc specifically modified the distribution and intensity of phosphotyrosine labeling in these glial cells. We also showed that inhibition of tenascin-R interaction with F3 prevented defasciculation of cerebellar explants which normally display a defasciculated outgrowth of neurites on a growth permissive substrate. These results identify F3, RTPz/RPTP beta, and tenascin-R as potential mediators of a reciprocal exchange of information between glia and neurons.

01/09/1998 | J Neurosci
A functional interaction between the neuronal adhesion molecules TAG-1 and F3 modulates neurite outgrowth and fasciculation of cerebellar granule cells.
Buttiglione M, Revest JM, Pavlou O, Karagogeos D, Furley A, Rougon G, Faivre-Sarrailh C

F3 and TAG-1 are two closely related adhesion glycoproteins of the Ig superfamily that are both expressed by the axons of cerebellar granule cells. In an in vitro system in which cerebellar granule cells were cultured on monolayers of transfected Chinese hamster ovary (CHO) cells, we show that F3 and TAG-1 interact functionally. F3 transfectants have been shown to inhibit outgrowth and induce fasciculation of granule cell neurites. By contrast TAG-1 transfectants have no effect on these events. However, when TAG-1 is coexpressed with F3, the inhibitory effect of F3 is blocked. Two possible mechanisms may account for this functional interaction: (1) either TAG-1 and F3 compete for the same neuronal receptor, and in favor of this we observed that binding sites for microspheres conjugated with F3 and TAG-1 are colocalized on the granule cell growth cones, (2) or alternatively, F3 and TAG-1 associate in a multimolecular complex after their binding to independent receptors. Extensive co-clustering of F3 with TAG-1 can in fact be achieved by anti-TAG-1 antibody-mediated cross-linking in double-transfected CHO cells. Moreover, F3 coimmunoprecipitates with TAG-1 in Triton X-100-insoluble microdomains purified from newborn brain. These data strongly suggest that F3 and TAG-1 may associate under physiological conditions to modulate neurite outgrowth and fasciculation of the cerebellar granule cells.

15/05/1998 | J Neurosci Res
Defasciculation of neurites is mediated by tenascin-R and its neuronal receptor F3/11.
Xiao ZC, Revest JM, Laeng P, Rougon G, Schachner M, Montag D

Fasciculation and defasciculation of axons are major morphogenetic events in the formation of neuronal pathways during development. We have identified the extracellular matrix glycoprotein tenascin-R (TN-R) and its neuronal receptor, the immunoglobulin superfamily recognition molecule F3, as promoters of neurite defasciculation in cerebellar explant cultures. Perturbation of the interaction between these two molecules using both antibodies and an antisense oligonucleotide resulted in increased neurite fasciculation. The domains involved in defasciculation were identified as the N-terminal region of TN-R containing the cysteine-rich stretch and the 4.5 epidermal growth factor-like repeats and the immunoglobulin-like domains of F3. Fasciculation induced by antibodies and the antisense oligonucleotide could be reverted by a phorbol ester activator of protein kinase C, whereas the protein kinase inhibitor staurosporine increased fasciculation. Our observations indicate that defasciculated neurite outgrowth does not only depend on the reduction of the expression of fasciculation enhancing adhesion molecules, such as L1 and the neural cell adhesion molecule (NCAM), but also on recognition molecules that actively induce defasciculation by triggering second messenger systems.

F3 is a glycane phosphatidylinositol-anchored neuronal adhesion glycoprotein which consists of immunoglobulin (Ig) domains and fibronectin type III repeats. Here we showed that total F3 or F3-Ig domains when presented as membrane components of CHO transfected cells influenced growth cone morphology, strongly inhibited outgrowth, and induced fasciculation of cerebellar granule cell axons. An F3-Ig-Fc chimera induced neurite fasciculation from cerebellar neuron aggregates when used as a coated substrate but not in the soluble form. The F3 effect on neurite elongation is highly specific for neuronal cell types since under the same experimental conditions it did not modify neurite outgrowth of hippocampal neurons and was shown to stimulate elongation of neurites from sensory neurons in both membrane-anchored and soluble form. Our results provide evidence to extend the proposed role of F3 and strongly suggest that axonal-growth-controlling molecules may quite generally exert dual actions which are likely to depend on the receptor repertoire of the responding neuron.