Biology subjects

Girault, J.-A.

Publications and source records attributed to Girault, J.-A..

11 recordsLinked to original sources

bioRxiv2025

Molecular Basis and Cellular Effects of Janus-Class-Driven Cytoplasmic PYK2 Coacervates

Kinase activity is increasingly associated with biomolecular phase separation. Focal adhesion kinase (FAK) forms membrane-associated condensates with paxillin to promote adhesion. Here we show that its paralogue, proline-rich tyrosine kinase 2 (PYK2), undergoes phase separation via a distinct mechanism. PYK2 forms cytoplasmic condensates primarily driven by its kinase- FAT linker (KFL) region. Overexpression of PYK2 induces condensates enriched in its autophosphorylated form, which sequester paxillin from focal adhesions and impair cell adhesion. We uncover an autoregulatory mechanism involving the KFL, linking self-association, autophosphorylation, and condensation. Uncommon among known phase separation drivers, KFL condensation is phosphorylation-independent and its sequence belongs to the "Janus" class. Using a transformer-based protein language model, we identified non-homologous sequences with similar features, many from adhesion and cytoskeletal regulators. We validated the phase-separating potential of several of these sequences in cells. These findings reveal a novel mechanism linking phase separation with kinase activation, and demonstrate distinct condensation behavior in close homologues. Our results also highlight how protein concentration modulates condensate function, with implications for disease, and expand the landscape of phase separation drivers.

cell biology↗

bioRxiv2024

PYK2 in the dorsal striatum of Huntington disease R6/2 mouse model

Huntingtons disease (HD) is a devastating disease due to autosomal dominant mutation in the HTT gene. Its pathophysiology involves multiple molecular alterations including transcriptional defects. We previously showed that in HD patients and mouse model, the protein levels of the non-receptor tyrosine kinase PYK2 were decreased in the hippocampus and that viral expression of PYK2 improved the hippocampal phenotype. Here, we investigated the possible contribution of PYK2 in the striatum, a major brain region altered in HD. PYK2 mRNA levels were decreased in the striatum and hippocampus of R6/2 mice, a severe HD model. PYK2 protein levels were also decreased in the dorsal striatum of R6/2 mice and in the putamen of human patients. PYK2 knockout by itself did not result in motor symptoms observed in HD mouse models. Yet, we examined whether PYK2 deficiency participated in the R6/2 mice phenotype by expressing PYK2 in the dorsal striatum using AAV vectors. With an AAV1/Camk2a promoter, we did not observe significant improvement of body weight, clasping, motor activity and coordination (rotarod) alterations observed in R6/2 mice. With an AAV9/SYN1 promoter we found an improvement of body weight loss and a tendency to better rotarod performance. DARPP-32 immunofluorescence was increased following AAV9/SYN1-PYK2 injection compared to AAV9/SYN1-GFP, suggesting a possible partial beneficial effect on striatal projection neurons. We conclude that PYK2 mRNA and protein levels are decreased in the striatum as in hippocampus of HD patients and mouse models. However, in contrast to hippocampus, striatal viral expression of PYK2 has only a slight effect on the R6/2 model striatal motor phenotype. HighlightsO_LIHuntingtons disease is a lethal genetic disease altering striatum, cortex, and hippocampus C_LIO_LIRestoring PYK2 levels in hippocampus improved hippocampal phenotype of a Huntington mouse model C_LIO_LIWe show that PYK2 levels are decreased in the striatum of R6/2 mice and human patients C_LIO_LIViral expression of PYK2 in the striatum has only a small effect on R6/2 mouse model motor phenotype but improves weight loss C_LI

neuroscience↗

bioRxiv2023

Operant training for highly palatable food alters translating mRNA in nucleus accumbens D2 neurons and reveals a modulatory role of Neurochondrin

BACKGROUNDHighly palatable food triggers behavioral alterations reminiscent of those induced by addictive drugs. These effects involve the reward system and dopamine neurons, which modulate neurons in the nucleus accumbens (NAc). The molecular mechanisms underlying the effects of highly palatable food on feeding behavior are poorly understood. METHODSWe studied the effects of 2-week operant conditioning of mice with standard or isocaloric highly palatable food. We investigated the behavioral effects and dendritic spine modifications in the NAc. We compared the translating mRNA in NAc neurons identified by the type of dopamine receptors they express, depending on the type of food and training. We tested the consequences of invalidation of an abundant downregulated gene, Ncdn (Neurochondrin). RESULTSOperant conditioning for highly palatable food increases motivation for food even in well-fed mice. In control mice, free access to regular or highly palatable food results in increased weight as compared to regular food only. Highly palatable food increases spine density in the NAc. In animals trained for highly palatable food, translating mRNAs are modified in NAc dopamine D2-receptor-expressing neurons, mostly corresponding to striatal projection neurons, but not in those expressing D1-receptors. Knock-out of Ncdn, an abundant down-regulated gene, opposes the conditioning-induced changes in satiety-sensitive feeding behavior and apparent motivation for highly palatable food, suggesting down-regulation may be a compensatory mechanism. CONCLUSIONSOur results emphasize the importance of mRNA alterations D2 striatal projection neurons in the NAc in the behavioral consequences of highly palatable food conditioning and suggest a modulatory contribution of Ncdn downregulation.

neuroscience↗

bioRxiv2021

Cell type- and region-specific modulation of cocaine seeking by micro-RNA-1 in striatal projection neurons

The persistent and experience-dependent nature of drug addiction may result in part from epigenetic alterations, including non-coding micro-RNAs (miRNAs), which are both critical for neuronal function and modulated by cocaine in the striatum. Two major striatal cell populations, the striato-nigral and striato-pallidal projection neurons, express respectively the D1 (D1-SPNs) and D2 (D2-SPNs) dopamine receptor, and display distinct but complementary functions in drug-evoked responses. However, a cell-type-specific role for miRNAs action has yet to be clarified. Here, we evaluated the expression of a subset of miRNAs proposed to modulate cocaine effects in the nucleus accumbens (NAc) and dorsal striatum (DS) upon sustained cocaine exposure in mice and showed that these selected miRNAs were preferentially up-regulated in the NAc. We then focused on miR-1 considering the important role of some of its predicted mRNA targets, such as fosb and npas4, in the effects of cocaine. We validated these targets in vitro and in vivo and further showed that overexpression of miR-1 in D1-SPNs of the DS reduced cocaine-induced CPP reinstatement, whereas it increased cue-induced reinstatement of cocaine-SA, without affecting other cocaine-mediated adaptive behavior. In addition, miR-1 overexpression in D2-SPNs of the DS reduced the motivation to self-administer cocaine but did not modify other measured behaviors. Together, our results highlight a precise cell-type- and region-specific control of relapse to cocaine-seeking behaviors by miR-1, and illustrate the importance of cell-specific investigations.

neuroscience↗

bioRxiv2021

Pyk2 in dorsal hippocampus plays a selective role in spatial memory and synaptic plasticity

Pyk2 is a Ca2+-activated non-receptor tyrosine kinase enriched in the forebrain, especially in pyramidal neurons of the hippocampus. Previous reports suggested its role in hippocampal synaptic plasticity and spatial memory but with contradictory findings possibly due to experimental conditions. Here we address this issue and show that novel object location, a simple test of spatial memory induced by a single training session, is altered in Pyk2 KO mice and that re-expression of Pyk2 in the dorsal hippocampus corrects this deficit. Bilateral targeted deletion of Pyk2 in dorsal hippocampus CA1 region also alters novel object location. Long term potentiation (LTP) in CA1 is impaired in Pyk2 KO mice using a high frequency stimulation induction protocol nut not with a theta burst protocol, explaining differences between previous reports. The same selective LTP alteration is observed in mice with Pyk2 deletion in dorsal hippocampus CA1 region. Thus, our results establish the role of Pyk2 in specific aspects of spatial memory and synaptic plasticity and show the dependence of the phenotype on the type of experiments used to reveal it. In combination with other studies they provide evidence for a selective role of non-receptor tyrosine kinases in specific aspects of hippocampal neurons synaptic plasticity.

neuroscience↗

bioRxiv2020

Dopamine D1 receptor-expressing neurons activity is essential for locomotor and sensitizing effects of a single injection of cocaine

D1 dopamine receptors play an important role in the effects of cocaine. Here we investigated the role of neurons which express these receptors (D1-neurons) in the acute locomotor effects of cocaine and the locomotor sensitization observed after a second injection of this drug. We inhibited D1-neurons using double transgenic mice conditionally expressing the inhibitory Gi-coupled designer receptor exclusively activated by designer drugs (Gi-DREADD) in D1-neurons. Chemogenetic inhibition of D1-neurons by a low dose of clozapine (0.1 mg/kg) decreased the induction of Fos in striatal neurons. It diminished the basal locomotor activity and acute hyper-locomotion induced by cocaine (20 mg/kg). Clozapine 0.1 mg/kg had no effect by itself and did not alter cocaine effects in non-transgenic mice. Inhibition of D1-neurons during the first cocaine administration reduced the sensitization of the locomotor response in response to a second cocaine administration ten days later. At day 11, inhibition of D1-neurons by clozapine stimulation of Gi-DREADD, prevented the expression of the sensitized locomotor response, whereas at day 12, in the absence of clozapine and D1-neurons inhibition, all mice displayed a sensitized response to cocaine. These results show that chemogenetic inhibition of D1-neurons decreases spontaneous and cocaine-induced locomotor activity. It blunts the induction and prevents the expression of sensitization in a two-injection protocol of sensitization but does not alter established sensitization. Our study further supports the central role of D1-neurons in mediating the acute locomotor effects of cocaine and its sensitization.

neuroscience↗

bioRxiv2020

Hippocampal Egr1-dependent neuronal ensemblesnegatively regulate motor learning

Motor skills learning is classically associated with brain regions including cerebral and cerebellar cortices and basal ganglia. Less is known about the role of the hippocampus in the acquisition and storage of motor skills. Here we show that mice receiving a long-term training in the accelerating rotarod display marked transcriptional changes in the striatum and hippocampus when compared with short-term trained mice. We identify Egr1 as a modulator of gene expression in the hippocampus during motor learning. Using mice in which neural ensembles are permanently labeled in an Egr1 activity-dependent fashion we identify ensembles of Egr1-expressing pyramidal neurons in CA1 activated in short- and long-term trained mice in the rotarod task. When Egr1 is downregulated or these neuronal ensembles are depleted, motor learning is improved whereas their chemogenetic stimulation impairs motor learning performance. Thus, Egr1 organizes specific CA1 neuronal ensembles during the accelerating rotarod task that limit motor learning.

neuroscience↗

bioRxiv2020

Long-lasting tagging of neurons activated by seizures or cocaine administration in Egr1-CreERT2 transgenic mice

Permanent tagging of neuronal ensembles activated in specific experimental situations is an important objective to study their properties and adaptations. In the context of learning and memory these neurons are referred to as engram neurons. Here we describe and characterize a novel mouse line, Egr1-CreERT2, which carries a transgene in which the promoter of the immediate early gene Egr1 drives the expression of the CreERT2 recombinase that is only active in the presence of tamoxifen metabolite, 4-hydroxy-tamoxifen (4-OHT). Egr1-CreERT2 mice were crossed with various reporter mice, Cre-dependently expressing a fluorescent protein. Without tamoxifen or 4-OHT, no or few tagged neurons were observed. Epileptic seizures induced by pilocarpine or pentylenetetrazol in the presence of tamoxifen or 4-OHT, induced the persistent tagging of many neurons and some astrocytes in the dentate gyrus of hippocampus, where Egr1 is transiently induced by seizures. One week after cocaine and 4-OHT administration, these mice displayed a higher number of tagged neurons in the dorsal striatum than saline/4-OHT controls, with differences between reporter lines. Cocaine-induced tagging required ERK activation and tagged neurons were more likely than others to exhibit ERK phosphorylation or Fos induction after a second injection. Interestingly neurons tagged in saline-treated mice also had an increased propensity to express Fos, suggesting the existence of highly responsive striatal neurons susceptible to be re-activated by cocaine repeated administration, which may contribute to the behavioral adaptations. Our report validates a novel transgenic mouse model for permanently tagging activated neurons and studying long term alterations of Egr1-expressing cells.

neuroscience↗

bioRxiv2020

Translational profiling of mouse dopaminoceptive neurons reveals a role of PGE2 in dorsal striatum

Forebrain dopaminoceptive neurons play a key role in movement, action selection, motivation, and working memory. Their activity is dysregulated in addiction, Parkinsons disease and other conditions. To characterize the diverse dopamine target neuronal populations, we compare translating mRNAs in neurons of dorsal striatum and nucleus accumbens expressing D1 or D2 dopamine receptor and prefrontal cortex expressing D1 receptor. We identify D1/D2 and striatal dorso-ventral differences in the translational and splicing landscapes, which establish the characteristics of dopaminoceptive neurons. Expression differences and network analyses identify novel transcription factors with presumptive roles in these differences. Prostaglandin E2 appears as a candidate upstream regulator in the dorsal striatum, a hypothesis supported by converging functional evidence indicating its role in enhancing D2 dopamine receptor action. Our study provides powerful resources for characterizing dopamine target neurons, new information about striatal gene expression patterns, and reveals the unforeseen role of prostaglandin E2 in the dorsal striatum.

neuroscience↗

bioRxiv2019

fMRI detects bilateral brain network activation following unilateral chemogenetic activation of direct striatal projection neurons

Although abnormal structural and functional connectivity in the striatum during neurological disorders has been reported using functional magnetic resonance imaging (fMRI), the effects of cell-type specific neuronal stimulation on fMRI and related behavioral alterations are not well understood. In this study, we successfully combined DREADD-technology with fMRI (chemo-fMRI) to investigate the alterations of spontaneous neuronal activity induced by the unilateral activation of dopamine D1 receptor-expressing neurons (D1-neurons) in the mouse dorsal striatum (DS). We compared the effects of two different DREADD ligands, clozapine (CLZ) and clozapine-N-oxide (CNO), on behavior and fMRI. We found that the effects of CLZ on behavior were more rapid than those of CNO. In fMRI, both systemic CLZ and CNO administrations, which evoked unilateral activations of D1-neurons in DS, increased the fractional amplitude of low frequency fluctuations (fALFF) in the thalamus and bilateral cortex. In addition, we found the increased gamma-band of local field potentials in DS and bilateral cortex after CLZ-evoked unilateral activation of D1-neuron in the striatum. These results provide bases for better interpretation of cell type-specific activity changes in fMRI.

neuroscience↗

bioRxiv2019

Pyk2 in D1 receptor-expressing neurons of the nucleus accumbens modulates the acute locomotor effects of cocaine

The striatum is a critical brain region for locomotor response to cocaine. Although the D1 receptor-expressing neurons are centrally involved in mediating the locomotor effects of cocaine, the molecular pathways controlling this response are not fully understood. Here we studied the role of Pyk2, a non-receptor calcium-dependent protein-tyrosine kinase, in striatum-related functions. We discovered that cocaine injection increases Pyk2 phosphorylation in the striatum of mice in vivo. Pyk2-deficient mice displayed an altered locomotor response to acute cocaine injection. In contrast, they developed normal locomotor sensitization and cocaine-conditioned place preference. Accordingly, a cocaine-activated signaling pathway essential for these late responses, ERK phosphorylation, was not altered. Specific deletion of Pyk2 in the nucleus accumbens or in D1 neurons reproduced this phenotype, whereas deletion of Pyk2 in the dorsal striatum or in A2A receptor-expressing neurons did not. Mice lacking Pyk2 in D1-neurons also displayed lower locomotor response to the D1 receptor agonist SKF-81297 but not to an anticholinergic drug. Our results identify Pyk2 as a regulator of acute locomotor responses to psychostimulants and suggest that changes in Pyk2 expression or activation may alter specific responses to drugs of abuse, or possibly other behavioral responses linked to dopamine action.

neuroscience↗