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International audience; The establishment of neuronal connectivity relies on the microtubule (MT) cytoskeleton, which provides mechanical support, roads for axonal transport and mediates signalling events. Fine-tuned spatiotemporal regulation of MT functions by tubulin post-translational modifications and MT-associated proteins is critical for the coarse wiring and subsequent refinement of neuronal connectivity. The defective regulation of these processes causes a wide range of neurodevelopmental disorders associated with connectivity defects. This review focuses on recent studies unravelling how MT composition, post-translational modifications and associated proteins influence MT functions in axon guidance and/or pruning to build functional neuronal circuits. We here summarise experimental evidence supporting the key role of this network as a driving force for growth cone steering and branch-specific axon elimination. We further provide a global overview of the MT-interactors that tune developing axon behaviours, with a special emphasis on their emerging versatility in the regulation of MT dynamics/structure. Recent studies establishing the key and highly selective role of the tubulin code in the regulation of MT functions in axon pathfinding are also reported. Finally, our review highlights the emerging molecular links between these MT regulation processes and guidance signals that wire the nervous system.

International audience; In several forms of dementia, such as Alzheimer's disease, the cytoskeleton-associated protein tau undergoes proteolysis, giving rise to fragments that have a toxic impact on neuronal homeostasis. How these fragments interact with cellular structures, in particular with the cytoskeleton, is currently incompletely understood. Here, we developed a method, derived from a Tobacco Etch Virus (TEV) protease system, to induce controlled cleavage of tau at specific sites. Five tau proteins containing specific TEV recognition sites corresponding to pathological proteolytic sites were engineered, and tagged with GFP at one end and mCherry at the other. After a controlled cleavage to produce GFP-N-terminal and C-terminal-mCherry fragments, we followed the fate of tau fragments in cells. Our results showed that whole engineered tau proteins associate with the cytoskeleton similarly to the non-modified tau, whereas tau fragments adopted different localizations with respect to the actin and microtubule cytoskeletons. These distinct localizations were confirmed by expressing each separate fragment in cells. Some cleavages-in particular cleavages at amino-acid positions 124 or 256-displayed a certain level of cellular toxicity, with an unusual relocalization of the N-terminal fragments to the nucleus. Based on the data presented here, inducible cleavage of tau by the TEV protease appears to be a valuable tool to reproduce tau fragmentation in cells and study the resulting consequences on cell physiology.

International audience; Frontotemporal dementia and amyotrophic lateral sclerosis are rare neurodegenerative diseases with no effective treatment. The development of biomarkers allowing an accurate assessment of disease progression is crucial for evaluating new therapies. Concretely, neuroimaging and transcriptomic (microRNA) data have been shown useful in tracking their progression. However, no single biomarker can accurately measure progression in these complex diseases. Additionally, large samples are not available for such rare disorders. It is thus essential to develop methods that can model disease progression by combining multiple biomarkers from small samples. In this paper, we propose a new framework for computing a disease progression score (DPS) from cross-sectional multimodal data. Specifically, we introduce a supervised multimodal variational autoencoder that can infer a meaningful latent space, where latent representations are placed along a disease trajectory. A score is computed by orthogonal projections onto this path. We evaluate our framework with multiple synthetic datasets and with a real dataset containing 14 patients, 40 presymptomatic genetic mutation carriers and 37 controls from the PREV-DEMALS study. There is no ground truth for the DPS in real-world scenarios, therefore we use the area under the ROC curve (AUC) as a proxy metric. Results with the synthetic datasets support this choice, since the higher the AUC, the more accurate the predicted simulated DPS. Experiments with the real dataset demonstrate better performance in comparison with stateof-the-art approaches. The proposed framework thus leverages cross-sectional multimodal datasets with small sample sizes to objectively measure disease progression, with potential application in clinical trials.

International audience; We present the phenotypes of seven previously unreported patients with Marbach-Schaaf neurodevelopmental syndrome, all carrying the same recurrent heterozygous missense variant c.1003C>T (p.Arg335Trp) in PRKAR1B. Clinical features of this cohort include global developmental delay and reduced sensitivity to pain, as well as behavioral anomalies. Only one of the seven patients reported here was formally diagnosed with autism spectrum disorder (ASD), while ASD-like features were described in others, overall indicating a lower prevalence of ASD in Marbach-Schaaf neurodevelopmental syndrome than previously assumed. The clinical spectrum of the current cohort is similar to that reported in the initial publication, delineating a complex developmental disorder with behavioral and neurologic features. PRKAR1B encodes the regulatory subunit R1beta of the protein kinase A complex (PKA), and is expressed in the adult and embryonal central nervous system in humans. PKA is crucial to a plethora of cellular signaling pathways, and its composition of different regulatory and catalytic subunits is cell-type specific. We discuss potential molecular disease mechanisms underlying the patients' phenotypes with respect to the different known functions of PKA in neurons, and the phenotypes of existing R1beta-deficient animal models.

The melanocortin system plays a critical role in the central regulation of food intake and energy balance. This system consists of neurons producing pro-opiomelanocortin (POMC), melanocortin receptors (MC4Rs), and the endogenous antagonist agouti-related peptide (AgRP). Pomc and Mc4r deficiency in rodents and humans causes early onset of obesity, whereas a loss of Agrp function is associated with leanness. Accumulating evidence shows that many chronic diseases, including obesity, might originate during early life. The melanocortin system develops during a relatively long period beginning during embryonic life with the birth of POMC and AgRP neurons and continuing postnatally with the assembly of their neuronal circuitry. The development of the melanocortin system requires the tight temporal regulation of molecular factors, such as transcription factors and axon guidance molecules, and cellular mechanisms, such as autophagy. It also involves a complex interplay of endocrine and nutritional factors. The disruption of one or more of these developmental factors can lead to abnormal maturation and function of the melanocortin system and has profound metabolic consequences later in life.

Purpose: Alzheimer’s Disease (AD) is a heterogeneous disease that disproportionately affects women and people with the APOE-ε4 susceptibility gene. We aim to describe the not-well-understood influence of both risk factors on the dynamics of brain atrophy in AD and healthy aging.Approach: Regional cortical thinning and brain atrophy were modeled over time using non-linear mixed-effect models and the FreeSurfer software. Covariance analysis was used to disentangle the effect of sex and APOE genotype on the regional onset age and pace of atrophy, while correcting for educational level. A map of the regions most affected by neurodegeneration is provided. Results were confirmed on gray matter density data from the SPM software.Results: Women experience faster atrophic rates in the temporal, frontal, parietal lobes and limbic system and earlier onset in the amygdalas, but slightly later onset in the postcentral and cingulate gyri as well as all regions of the basal ganglia and thalamus. APOE-ε4 genotypes leads to earlier and faster atrophy in the temporal, frontal, parietal lobes and limbic system in AD patients, but not in healthy patients. Higher education was found to slightly delay atrophy in healthy patients, but not for AD patients. A cohort of amyloid positive patients with MCI showed a similar impact of sex as in the healthy cohort, while APOE-ε4 showed similar associations as in the AD cohort.Conclusion: Female sex is as strong a risk factor for AD as APOE−ε4 genotype regarding neurodegeneration, women experience a sharper atrophy in the later stages of the disease although not a significantly earlier onset. These findings may have important implications for the development of targeted intervention.

Besides the consequences of retrotransposition, long interspersed element 1 (L1) retrotransposons can affect the host genome through their antisense promoter. In addition to the sense promoter, the evolutionarily recent L1 retrotransposons, which are present in several thousand copies, also possess an anti-sense promoter that can produce L1 chimeric transcripts (LCT) composed of the L1 5′ UTR followed by the adjacent genomic sequence. The full extent to which LCT expression occurs in a given tissue and whether disruption of the defense mechanisms that normally control L1 retrotransposons affects their expression and function in cancer cells, remain to be established. By using CLIFinder, a dedicated bioinformatics tool, we found that LCT expression was widespread in normal brain and aggressive glioma samples, and that approximately 17% of recent L1 retrotransposons, from the L1PA1 to L1PA7 subfamilies, were involved in their production. Importantly, the transcriptional activities of the L1 antisense promoters and of their host loci were coupled. Accordingly, we detected LCT-producing L1 retrotransposons mainly in transcriptionally active genes and genomic loci. Moreover, changes in the host genomic locus expression level in glioma were associated with a similar change in LCT expression level, regardless of the L1 promoter methylation status. Our findings support a model in which the host genomic locus transcriptional activity is the main driving force of LCT expression. We hypothesize that this model is more applicable when host gene and LCT are transcribed from the same strand.

International audience; Bipolar disorder is a severe and chronic psychiatric disease resulting from a combination of genetic and environmental risk factors. Here, we identified a significant higher mutation rate in a gene encoding the calcium-dependent activator protein for secretion (CADPS) in 132 individuals with bipolar disorder, when compared to 184 unaffected controls or to 21,070 non-psychiatric and non-Finnish European subjects from the Exome Aggregation Consortium. We found that most of these variants resulted either in a lower abundance or a partial impairment in one of the basic functions of CADPS in regulating neuronal exocytosis, synaptic plasticity and vesicular transporter-dependent uptake of catecholamines. Heterozygous mutant mice for Cadps+/- revealed that a decreased level of CADPS leads to manic-like behaviours, changes in BDNF level and a hypersensitivity to stress. This was consistent with more childhood trauma reported in families with mutation in CADPS, and more specifically in mutated individuals. Furthermore, hyperactivity observed in mutant animals was rescued by the mood-stabilizing drug lithium. Overall, our results suggest that dysfunction in calcium-dependent vesicular exocytosis may increase the sensitivity to environmental stressors enhancing the risk of developing bipolar disorder.

International audience; Extracellular adenosine plays prominent roles in the brain in both physiological and pathological conditions. Adenosine can be generated following the degradation of extracellular nucleotides by various types of ectonucleotidases. Several ectonucleotidases are present in the brain parenchyma: ecto-nucleotide triphosphate diphosphohydrolases 1 and 3 (NTPDase 1 and 3), ecto-nucleotide pyrophosphatase/ phosphodiesterase 1 (NPP 1), ecto-5’-nucleotidase (eN), and tissue non-specific alkaline phosphatase (TNAP, whose function in the brain has received little attention). Here we examined, in a living brain preparation, the role of these ectonucleotidases in generating extracellular adenosine. We recorded local field potentials evoked by electrical stimulation of the lateral olfactory tract in the mouse piriform cortex in vitro. Variations in adenosine level were evaluated by measuring changes in presynaptic inhibition generated by adenosine A1 receptors (A1Rs) activation. A1R-mediated presynaptic inhibition was present endogenously and was enhanced by bath-applied AMP and ATP. We hypothesized that inhibiting ectonucleotidases would reduce extracellular adenosine concentration, which would result in a weakening of presynaptic inhibition. However, inhibiting TNAP had no effect in controlling endogenous adenosine action and no effect on presynaptic inhibition induced by bath-applied AMP. Furthermore, contrary to our expectation, inhibiting TNAP reinforced, rather than reduced, presynaptic inhibition induced by bath-applied ATP. Similarly, inhibition of NTPDase 1 and 3, NPP1, and eN induced stronger, rather than weaker presynaptic inhibition, both in endogenous condition and with bath-applied ATP and AMP. Consequently, attempts to suppress the functions of extracellular adenosine by blocking its extracellular synthesis in living brain tissue could have functional impacts opposite to those anticipated.

The aim of this Phase 1/2, 2-part, multicenter trial was to report clinical safety and efficacy of long-term golodirsen treatment among ambulatory patients with exon 53 skip-amenable Duchenne muscular dystrophy (DMD). Part 1 was a 12-week, randomized, double-blind, placebo-controlled, dose-titration study followed by 9-week safety review. Part 2 was a 168-week, open-label evaluation of golodirsen 30 mg/kg. Part 1 primary endpoint was safety. Part 2 primary endpoints were dystrophin protein expression and 6-minute walk test (6MWT); secondary endpoints were percent predicted forced vital capacity (FVC%p) and safety. Post hoc ambulation analyses used mutation-matched external natural history controls. All patients from Part 1 (golodirsen, n = 8; placebo, n = 4) plus 13 additional patients entered Part 2; 23 completed the study. Adverse events were generally mild, nonserious, and unrelated to golodirsen, with no safety-related discontinuations or deaths. Golodirsen increased dystrophin protein (16.0-fold; P

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It has long been known that orofacial movements for feeding can be triggered, coordinated, and often rhythmically organized at the level of the brainstem, without input from higher centers. We uncover two nuclei that can organize the movements for ingesting fluids in mice. These neuronal groups, IRtPhox2b and Peri5Atoh1, are marked by expression of the pan-autonomic homeobox gene Phox2b and are located, respectively, in the intermediate reticular formation of the medulla and around the motor nucleus of the trigeminal nerve. They are premotor to all jaw-opening and tongue muscles. Stimulation of either, in awake animals, opens the jaw, while IRtPhox2b alone also protracts the tongue. Moreover, stationary stimulation of IRtPhox2b entrains a rhythmic alternation of tongue protraction and retraction, synchronized with jaw opening and closing, that mimics lapping. Finally, fiber photometric recordings show that IRtPhox2b is active during volitional lapping. Our study identifies one of the subcortical nuclei underpinning a stereotyped feeding behavior., Orofacial movements for feeding can be triggered, coordinated and rhythmically organised at the level of the brainstem. Here, the authors show two nuclei can organise the stereotyped movements for ingesting fluids in mammals, these neuronal groups are marked by expression of Phox2b and are located in the intermediate reticular formation of the medulla and around the motor nucleus of the trigeminal nerve.

Gephyrin (GPHN) regulates the clustering of postsynaptic components at inhibitory synapses and is involved in pathophysiology of neuropsychiatric disorders. Here, we uncover an extensive diversity of GPHN transcripts that are tightly controlled by splicing during mouse and human brain development. Proteomic analysis reveals at least a hundred isoforms of GPHN incorporated at inhibitory Glycine and gamma-aminobutyric acid A receptors containing synapses. They exhibit different localization and postsynaptic clustering properties, and altering the expression level of one isoform is sufficient to affect the number, size, and density of inhibitory synapses in cerebellar Purkinje cells. Furthermore, we discovered that splicing defects reported in neuropsychiatric disorders are carried by multiple alternative GPHN transcripts, demonstrating the need for a thorough analysis of the GPHN transcriptome in patients. Overall, we show that alternative splicing of GPHN is an important genetic variation to consider in neurological diseases and a determinant of the diversity of postsynaptic inhibitory synapses.

International audience; TCF4 haploinsufficiency by deletions, truncating variants or loss-of-function missense variants within the DNA-binding and protein interacting bHLH domain causes Pitt-Hopkins syndrome (PTHS). This neurodevelopmental disorder (NDD) is characterized by severe intellectual disability (ID), epilepsy, hyperbreathing and a typical facial gestalt. Only few aberrations of the N-terminus of TCF4 were associated with milder or atypical phenotypes. By personal communication and searching databases we assembled six cases with the novel, recurrent, de novo missense variant c.1165C > T, p.(Arg389Cys) in TCF4. This variant was identified by diagnostic exome or panel sequencing and is located upstream of the bHLH domain. All six individuals presented with moderate to severe ID with language impairment. Microcephaly occurred in two individuals, epilepsy only in one, and no breathing anomalies or myopia were reported. Facial gestalt showed some aspects of PTHS but was rather non-specific in most individuals. Interestingly, the variant is located within the AD2 activation domain next to a highly conserved coactivator-recruitment motif and might alter interaction with coactivator proteins independently from the bHLH domain. Our findings of a recurrent missense variant outside the bHLH domain in six individuals with an ID phenotype overlapping with but not typical for PTHS delineate a novel genotype-phenotype correlation for TCF4-related NDDs.

International audience; The serotonin 5-HT6 receptor (5-HT6R) is a promising target to improve cognitive symptoms of psychiatric diseases of neurodevelopmental origin, such as autism spectrum disorders and schizophrenia. However, its expression and localization at different stages of brain development remain largely unknown, due to the lack of specific antibodies to detect endogenous 5-HT6R. Here, we used transgenic mice expressing a GFP-tagged 5-HT6R under the control of its endogenous promoter (Knock-in) as well as embryonic stem cells expressing the GFP-tagged receptor to extensively characterize its expression at cellular and subcellular levels during development. We show that the receptor is already expressed at E13.5 in the cortex, the striatum, the ventricular zone, and to a lesser extent the subventricular zone. In adulthood, it is preferentially found in projection neurons of the hippocampus and cerebral cortex, in striatal medium-sized spiny neurons, as well as in a large proportion of astrocytes, while it is expressed in a minor population of interneurons. Whereas the receptor is almost exclusively detected in the primary cilia of neurons at embryonic and adult stages and in differentiated stem cells, it is located in the somatodendritic compartment of neurons from some brain regions at the neonatal stage and in the soma of undifferentiated stem cells. Finally, knocking-out the receptor induces a shortening of the primary cilium, suggesting that it plays a role in its function. This study provides the first global picture of 5-HT6R expression pattern in the mouse brain at different developmental stages. It reveals dynamic changes in receptor localization in neurons at the neonatal stage, which might underlie its key role in neuronal differentiation and psychiatric disorders of neurodevelopmental origin.

International audience; Hippocampal adult neurogenesis is involved in many memory processes from learning, to remembering and forgetting. However, whether or not the stimulation of adult neurogenesis is a sufficient condition to improve memory performance remains unclear. Here, we developed and validated, using ex-vivo electrophysiology, a chemogenetic approach that combines selective tagging and activation of discrete adult-born neuron populations. Then we demonstrated that, in rats, this activation can improve accuracy and strength of remote memory. These results show that stimulation of adult-born neuron activity can counteract the natural fading of memory traces that occurs with the passage of time. This opens up new avenues for treating memory problems that may arise over time.

N-methyl-D-aspartate receptors (NMDARs) populate GABAergic interneurons, where they play a critical role in shaping circuit motifs and memory. However, we are largely ignoring whether and how NMDARs at GABAergic interneurons are gated by signals released in their surrounding microenvironment. Here we explore the dynamics of the co-agonist site occupancy by D-serine and glycine at glutamatergic synapses onto parvalbumin positive GABAergic interneurons in the adolescent prefrontal cortex, an area central to complex cognitive operation. We discovered that D-serine but not glycine is required for maintaining the activity of NMDAR at the GABAergic interneurons and that the identity of the co-agonist is not determined by the synaptic regime. Our study extends the physiological implications of D-serine in brain physiopathology by uncovering its control of inhibitory synaptic networks through NMDARs.

From the development of a neuron through morphogenesis and migration to mature stages with plasticity events, all stages of a neuron’s life requires the neuronal cytoskeleton. Actin filaments and microtubules (MT) are the main elements of the cytoskeleton. They are dynamic polymers regulated by associated proteins that helps them assemble, disassemble or stabilize and organize them in specific structures. The Microtubule Associated Protein 6 (MAP6) is known for its unique ability to stabilize neuronal MTs. MAP6 also regulate the actin cytoskeleton in dendritic spines during neuronal plasticity events. MAP6 regulation of the MT and actin cytoskeletons is required for normal neuronal development and function and affects mice behavior and cognitive abilities. As such, MAP6 knock-out mouse is a model of schizophrenia. A precise understanding of how MAP6 interacts and modulates the cytoskeleton was lacking at the molecular level. By using in vitro reconstitution systems, we showed that MAP6 is a MT stabilizer that induces MT coiling. By demonstrating that MT coiling is due to MAP6 localization in the MT lumen, we identified the first neuronal Microtubule Inner Protein (MIP). This discovery paves the way to decipher the physiological role of neuronal MIPs. It is now clear that several proteins involved in either MT or actin regulation are in fact able to regulate both cytoskeletons. By analyzing MT and actin assembly in the presence of MAP6 both in separated and simultaneous systems, we identify MAP6 as the first protein able to promote both MT and actin filament nucleation. Moreover, MT nucleation and MAP6 MIP activities are linked. MAP6 is also structuring the cytoskeleton by forming actin bundles and crosslinking actin filaments with microtubules. Finally, we show that MAP6 isoforms differentially regulate the cytoskeleton through phase separation mechanisms. Overall, the use of minimal reconstitution systems allowed us to demonstrate that MAP6 is a multifunctional regulator of the cytoskeleton., Du développement d'un neurone, en passant par la morphogenèse et la migration, jusqu'aux stades de maturité avec des événements de plasticité, toutes les étapes de la vie d'un neurone nécessitent le cytosquelette neuronal. Les filaments d'actine et les microtubules (MT) sont les principaux éléments du cytosquelette. Ce sont des polymères dynamiques régulés par des protéines associées qui les aident à s'assembler, à se désassembler ou à se stabiliser et à s'organiser en structures spécifiques. La protéine associée aux microtubules 6 (MAP6) est connue pour sa capacité unique à stabiliser les MTs neuronaux. MAP6 régule également le cytosquelette d'actine dans les épines dendritiques pendant les événements de plasticité neuronale. La régulation par MAP6 des cytosquelettes de MTs et d'actine est nécessaire au développement et au fonctionnement normal des neurones et affecte le comportement et les capacités cognitives des souris. À ce titre, la souris knock-out MAP6 est un modèle de schizophrénie. Une compréhension précise de la manière dont MAP6 interagit et module le cytosquelette faisait défaut au niveau moléculaire. En utilisant des systèmes de reconstitution in vitro, nous avons montré que MAP6 est un stabilisateur des MTs qui induit la formation de MTs hélicoïdaux. En démontrant que la formation de MTs en hélices est due à la localisation de MAP6 dans la lumière des MTs, nous avons identifié la première protéine interne des microtubules (MIP) neuronale. Cette découverte ouvre la voie au décryptage du rôle physiologique des MIPs neuronales. Il est maintenant clair que certaines protéines impliquées dans la régulation des MTs ou de l'actine sont en fait capables de réguler les deux cytosquelettes. En analysant l'assemblage des MTs et de l'actine en présence de MAP6 dans des systèmes séparés et simultanés, nous identifions MAP6 comme la première protéine capable de promouvoir la nucléation des MTs et des filaments d'actine. De plus, la nucléation des MT et les activités MIP de MAP6 sont liées. MAP6 structure également le cytosquelette en formant des faisceaux d'actine et en réticulant les filaments d'actine avec les microtubules. Enfin, nous montrons que les isoformes de MAP6 régulent de manière différentielle le cytosquelette par des mécanismes de séparation de phase. Globalement, l'utilisation de systèmes de reconstitution in vitro nous a permis de démontrer que MAP6 est un régulateur multifonctionnel du cytosquelette.

International audience; Purpose: The aim of this study was to define the role of dystrophin Dp71 in corneal angiogenesis.Methods: Inflammation-induced corneal neovascularization experiments were performed in Dp71-null mice and C57BL/6J wild-type mice.Results: The corneal neovascular area covered by neovascularization was larger in the injured corneas of the Dp71-null mice compared to the corneas of the wild-type mice: 40.72% versus 26.33%, respectively (p

Feedback connections play a major role in many theories of brain function. Previous studies of feedback connections to early visual areas have mainly concentrated on the representation of central visual fields. Here, injections of tracers at different eccentricities in areas V1 and V2 revealed retinotopically organized feedback. Peripheral injections revealed projections from 15 areas that are not labeled by central injections. Connection strengths for the majority of projections vary significantly with eccentricity in a systematic fashion with respect to distance and origin; whereas projections to central and upper visual fields are significantly stronger from ventral stream areas, peripheral and lower field projections are stronger from the dorsal stream. Non-invasive functional connectivity suggests a similar anatomical organization in humans. These features are discussed with respect to the cognitive and perceptual roles of these feedback pathways.

International audience; Interleukin-33 (IL-33) is an immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. IL-33 is abundant within the brain and spinal cord tissues where it acts as a key cytokine to coordinate the exchange between the immune and central nervous system (CNS). In this review, we report the recent advances to our knowledge regarding the role of IL-33 and of its receptor ST2 in cerebral malaria, and in particular, we highlight the pivotal role that IL-33/ST2 signaling pathway could play in brain and cerebrospinal barriers permeability. IL-33 serum levels are significantly higher in children with severe Plasmodium falciparum malaria than children without complications or noninfected children. IL-33 levels are correlated with parasite load and strongly decrease with parasite clearance. We postulate that sequestration of infected erythrocytes or merozoites liberation from schizonts could amplify IL-33 production in endothelial cells, contributing either to malaria pathogenesis or recovery.

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International audience; Introduction: The anatomical substrate of motor disability in MS patients is not fully understood. Studyingthe distribution of corticospinal tracts (CST) lesions per side, from the brain to the end of the thoracic spinal cord (SC) couldprovide a better association with patient motor deficits evaluated per limb.Objectives: i) To describe lesion preferential location along the CST; ii) To investigate the association between CST lesionsand motor functional consequences, as measured using the EDSS, and the ASIA motor scores and electrophysiology (Centralmotor conduction time (CMCT)) per limb.Methods: 21 relapsing remitting MS (median EDSS=2.5) and 9 progressive MS patients (median EDSS=5.2) with clinicalpyramidal symptoms were scanned on a 3T Siemens MRI scanner. White matter lesions were segmented on 3D FLAIR for thebrain, on T2* for cervical SC and T2 for thoracic SC. For each patient, registration to an atlas was computed using Anima andSCT toolboxes. Lesion volume fraction along the CST (defined as "lesion volume along the CST"/"overall CST volume") wascalculated separately for the both sides on 3 regions: brain including brainstem, C1 to C7 (C1C7) and T1 to T10 (T1T10).Finally, the relationships between lesion volume fraction and the associated lateralized disability scores were assessed usingmultiple linear models, adjusting for age and disease duration.Results: In MS patients, lesion volume fraction was higher in the C1C7 portion compared to the brain and T1T10 portion (allp’s.6; all p’s

International audience; Homeostatic synaptic plasticity is a process by which neurons adjust their synaptic strength to compensate for perturbations in neuronal activity. Whether the highly diverse synapses on a neuron respond uniformly to the same perturbation remains unclear. Moreover, the molecular determinants that underlie synapse-specific homeostatic synaptic plasticity are unknown. Here, we report a synaptic tagging mechanism in which the ability of individual synapses to increase their strength in response to activity deprivation depends on the local expression of the spine-apparatus protein synaptopodin under the regulation of miR-124. Using genetic manipulations to alter synaptopodin expression or regulation by miR-124, we show that synaptopodin behaves as a "postsynaptic tag" whose translation is derepressed in a subpopulation of synapses and allows for nonuniform homeostatic strengthening and synaptic AMPA receptor stabilization. By genetically silencing individual connections in pairs of neurons, we demonstrate that this process operates in an input-specific manner. Overall, our study shifts the current view that homeostatic synaptic plasticity affects all synapses uniformly to a more complex paradigm where the ability of individual synapses to undergo homeostatic changes depends on their own functional and biochemical state.

Action potential (AP) shape is a critical electrophysiological parameter, in particular because it strongly modulates neurotransmitter release. AP shape is also used to distinguish neuronal populations, as it greatly varies between neuronal types. For instance, AP duration ranges from hundreds of microseconds in cerebellar granule cells to 2-3 milliseconds in substantia nigra pars compacta (SNc) dopaminergic (DA) neurons. While most of this variation seems to arise from differences in the subtypes of voltage- and calcium-gated ion channels expressed, a few studies suggested that dendritic morphology may also affect AP shape. However, AP duration also displays significant variability in a same neuronal type, while the determinants of these variations are poorly known. Using electrophysiological recordings, morphological reconstructions and realistic Hodgkin-Huxley modeling, we investigated the relationships between dendritic morphology and AP shape in SNc DA neurons. In this neuronal type where the axon arises from an axon-bearing dendrite (ABD), the duration of the somatic AP could be predicted from a linear combination of the complexities of the ABD and the non-ABDs. Dendrotomy simulation and experiments showed that these correlations arise from the causal influence of dendritic topology on AP duration, due in particular to a high density of sodium channels in the somato-dendritic compartment. In addition, dendritic morphology also modulated AP back-propagation efficiency in response to barrages of EPSCs in the ABD. In line with previous findings, these results demonstrate that dendritic morphology plays a major role in defining the electrophysiological properties of SNc DA neurons and their cell-to-cell variations.SIGNIFICANCE STATEMENTAction potential (AP) shape is a critical electrophysiological parameter, in particular because it strongly modulates neurotransmitter release. AP shape (e.g. duration) greatly varies between neuronal types but also within a same neuronal type. While differences in ion channel expression seem to explain most of AP shape variation across cell types, the determinants of cell-to-cell variations in a same neuronal type are mostly unknown. We used electrophysiological recordings, neuronal reconstruction and modeling to show that, due to the presence of sodium channels in the somato-dendritic compartment, a large part of cell-to-cell variations in somatic AP duration in substantia nigra pars compacta dopaminergic neurons is explained by variations in dendritic topology.

Background Perineuronal nets (PNNs) are specialized extracellular matrix structures mainly found around fast-spiking parvalbumin (FS-PV) interneurons. In the adult, their degradation alters FS-PV-driven functions, such as brain plasticity and memory, and altered PNN structures have been found in neurodevelopmental and central nervous system disorders such as Alzheimer’s disease, leading to interest in identifying targets able to modify or participate in PNN metabolism. The serine protease tissue-type plasminogen activator (tPA) plays multifaceted roles in brain pathophysiology. However, its cellular expression profile in the brain remains unclear and a possible role in matrix plasticity through PNN remodeling has never been investigated. Result By combining a GFP reporter approach, immunohistology, electrophysiology, and single-cell RT-PCR, we discovered that cortical FS-PV interneurons are a source of tPA in vivo. We found that mice specifically lacking tPA in FS-PV interneurons display denser PNNs in the somatosensory cortex, suggesting a role for tPA from FS-PV interneurons in PNN remodeling. In vitro analyses in primary cultures of mouse interneurons also showed that tPA converts plasminogen into active plasmin, which in turn, directly degrades aggrecan, a major structural chondroitin sulfate proteoglycan (CSPG) in PNNs. Conclusions We demonstrate that tPA released from FS-PV interneurons in the central nervous system reduces PNN density through CSPG degradation. The discovery of this tPA-dependent PNN remodeling opens interesting insights into the control of brain plasticity.

Neural activity in the sensory cortex combines stimulus responses and ongoing activity, but it remains unclear whether these reflect the same underlying dynamics or separate processes. In the present study, we show in mice that, during wakefulness, the neuronal assemblies evoked by sounds in the auditory cortex and thalamus are specific to the stimulus and distinct from the assemblies observed in ongoing activity. By contrast, under three different anesthetics, evoked assemblies are indistinguishable from ongoing assemblies in the cortex. However, they remain distinct in the thalamus. A strong remapping of sensory responses accompanies this dynamic state change produced by anesthesia. Together, these results show that the awake cortex engages dedicated neuronal assemblies in response to sensory inputs, which we suggest is a network correlate of sensory perception.

International audience; The large number of ion channels found in all nervous systems poses fundamental questions concerning how the characteristic intrinsic properties of single neurons are determined by the specific subsets of channels they express. All neurons display many different ion channels with overlapping voltage- and time-dependent properties. We speculate that these overlapping properties promote resilience in neuronal function. Individual neurons of the same cell type show variability in ion channel conductance densities even though they can generate reliable and similar behavior. This complicates a simple assignment of function to any conductance and is associated with variable responses of neurons of the same cell type to perturbations, deletions, and pharmacological manipulation. Ion channel genes often show strong positively correlated expression, which may result from the molecular and developmental rules that determine which ion channels are expressed in a given cell type.

Background Myogenesis is a highly regulated process ending with the formation of myotubes, the precursors of skeletal muscle fibers. Differentiation of myoblasts into myotubes is controlled by myogenic regulatory factors (MRFs) that act as terminal effectors of signaling cascades involved in the temporal and spatial regulation of muscle development. Such signaling cascades converge and are controlled at the level of intracellular trafficking, but the mechanisms by which myogenesis is regulated by the endosomal machinery and trafficking is largely unexplored. The Endosomal Sorting Complex Required for Transport (ESCRT) machinery composed of four complexes ESCRT-0 to ESCRT-III regulates the biogenesis and trafficking of endosomes as well as the associated signaling and degradation pathways. Here, we investigate its role in regulating myogenesis. Results We uncovered a new function of the ESCRT-0 hepatocyte growth factor-regulated tyrosine kinase substrate Hrs/Hgs component in the regulation of myogenesis. Hrs depletion strongly impairs the differentiation of murine and human myoblasts. In the C2C12 murine myogenic cell line, inhibition of differentiation was attributed to impaired MRF in the early steps of differentiation. This alteration is associated with an upregulation of the MEK/ERK signaling pathway and a downregulation of the Akt2 signaling both leading to the inhibition of differentiation. The myogenic repressors FOXO1 as well as GSK3β were also found to be both activated when Hrs was absent. Inhibition of the MEK/ERK pathway or of GSK3β by the U0126 or azakenpaullone compounds respectively significantly restores the impaired differentiation observed in Hrs-depleted cells. In addition, functional autophagy that is required for myogenesis was also found to be strongly inhibited. Conclusions We show for the first time that Hrs/Hgs is a master regulator that modulates myogenesis at different levels through the control of trafficking, signaling, and degradation pathways.

In the central nervous system, astrocytes are glial cells displaying crucial roles in the brain physiology by regulating synaptic transmission, ion homeostasis, the blood brain barrier integrity or the cerebral blood flow. These functions are sustained by morphological and molecular polarities of astrocytes with specific interfaces contacting synapses, the perisynaptic processes (PAP), and blood vessels, the perivascular processes (PvAP). Recently, my laboratory and others demonstrated the presence of mRNAs, ribosomes and local protein synthesis in PAPs and PvAPs and proposed local translation as a mechanism for setting astrocytic polarity. However, little is known about the mechanisms of translation in astrocytes. My PhD project aimed at deciphering how translation is regulated in astrocytes and their interfaces and the role of these mechanisms in brain physiology. First, to characterize the distribution of mRNAs in astrocytes, I developed AstroDot, a specific in-situ approach to quantify the density and distribution of mRNAs in astrocytes. I determined that in hippocampal astrocytes, the distribution and density of mRNAs encoding α and δ isoforms of the glial fibrillary acidic protein (GFAP) are altered and vary with the presence of amyloid plaques in APP/PS1dE9 mice, a mouse model of Alzheimer’s disease. I also demonstrated for the first time the presence of mRNAs in microglia processes, a resident glial cell involved in particular in brain immunity. Following this study, I aimed at identifying mechanisms setting translation in astrocytes and focused on proteins associated with polysomes in astrocytes. I developed a method combining translating ribosome affinity purification in astrocytes with mass spectrometry. Among immunoprecipitated proteins, I focused on RACK1, a scaffold protein known to associate with the small subunit of ribosomes. Our previous analysis of the translatome in PAPs identified Gnb2l1 encoding RACK1 as one of the most enriched translated mRNAs in PAPs, suggesting its possible role in the regulation of translation at this interface. RACK1 acts as a ribosome formation mediator, a translation regulator and takes part in RNA quality control. Its role in astrocytes was unknown. Using a restricted panel of astrocytic enriched or specific mRNAs, I showed that RACK1 preferentially associates with Kncj10 coding for the potassium channel KIR4.1, one of the main regulator of K+ homeostasis in PAPs and PvAPs, and Slc1a2 coding for a glutamate transporter GLT1 which allows glutamate recycling in PAPs. To further address the role of RACK1 in astrocytes, I developed a mouse model in which RACK1 is specifically inactivated in astrocytes (RACK1 cKO). In this model, I found the level of KIR4.1 upregulated in the brain and in PAPs, whereas GLT1 was unchanged. RACK1 can act on the ribosome and on the RNA levels to regulate translation. In vitro investigations on RACK1 KO HEK cells transfected with luciferase reporters showed that KIR4.1 upregulation does not involve ribosome stalling on the Kncj10 coding sequence but relies on a part of the 5’UTR of Kcnj10 (Collaboration with Clément Chapat, Polytechnique). We finally addressed the physiological consequences of these regulations. Performing electrophysiological recordings (Collaboration with Nathalie Rouach, CIRB), we determined that KIR4.1 increase in absence of RACK1 leads to changes in the electrophysiological properties of the hippocampal neurons with an overall protection against high synaptic activity, certainly due to a higher capacity of PAPs to uptake K+. In summary, I developed during my thesis a new method to characterize mRNA distribution in astrocytes. I identified a pool of proteins associated to polysomes in astrocytes. Finally, I focused on RACK1 and identified it as an important regulator of KIR4.1 translation and astrocytic perisynaptic K+ homeostasis., Dans le système nerveux central, les astrocytes, cellules gliales, jouent des rôles cruciaux dans la physiologie du cerveau en régulant la transmission synaptique, l’homéostasie ionique, l’intégrité de la barrière sang-cerveau et le flux sanguin cérébral. Ces fonctions sont soutenues par des polarités morphologique et moléculaire des astrocytes avec des interfaces contactant les synapses, avec les prolongements périsynaptiques (PAP), et les vaisseaux sanguins, avec les prolongements périvasculaires (PvAP). Nous et d’autres avons démontré la présence d’ARNm, de ribosomes et de synthèse protéique locale dans les PAPs et PvAPs et proposé que la traduction locale soit un mécanisme pour la mise en place de la polarité astrocytaire. Cependant, on connaît peu les mécanismes de traduction dans les astrocytes. Mon projet de thèse a eu pour but de décrypter comment la traduction dans les astrocytes est régulée et le quels sont les rôles de ces mécanismes dans la physiologie du cerveau. Nous avons d’abord caractérisé la distribution des ARNm dans les astrocytes en développant AstroDot, une approche in situ pour quantifier la densité et la distribution des ARNm. Nous avons déterminé dans les astrocytes de l’hippocampe que la distribution et la densité d’ARNm codant pour les isoformes alpha et delta de la GFAP étaient altérées et variaient avec la présence de plaques amyloïdes dans un modèle murin de la maladie d’Alzheimer. Nous avons aussi montré pour la 1ère fois la présence d’ARNm dans les prolongements de microglies, une cellule gliale impliquée dans l’immunité cérébrale. Après, j’ai voulu identifier les mécanismes de mise en place de la traduction dans les astrocytes et je me suis concentré sur les protéines associées aux polysomes de cette cellule. J’ai développé une méthode combinant le TRAP avec la spectrométrie de masse. Parmi les protéines immunoprécipitées, je me suis concentré sur RACK1, une protéine d’échafaudage connue pour s’associer avec la petite sous unité des ribosomes. Notre analyse précédente du translatome des PAPs a identifié Gnb2l1, codant pour RACK1, comme l’un des ARNm traduit les plus enrichis dans les PAPs suggérant son rôle dans la régulation de la traduction à cette interface. RACK1 agit comme un régulateur de la formation des ribosomes, de la traduction et prend part au contrôle qualité des ARNm. Son rôle dans les astrocytes était inconnu. En utilisant un panel restreint d’ARN astrocytaires spécifiques, j’ai montré que RACK1 était préférentiellement associé à Kcnj10 codant pour le canal potassique KIR4.1 et Slc1a2 codant pour le transporteur au glutamate GLT1. Pour adresser le rôle de RACK1 dans les astrocytes, j’ai développé un modèle de souris dans laquelle RACK1 est inactivé dans les astrocytes. Dans ce modèle, le niveau de KIR4.1 était augmenté dans le cerveau et dans les PAPs alors que GLT1 était inchangé. RACK1 peut agir aux niveaux du ribosome et de l’ARN pour réguler la traduction. Des expériences in vitro sur des cellules HEK RACK1 KO transfectées avec des rapporteurs luciférase ont montré que l’augmentation de KIR4.1 n’impliquait pas le blocage des ribosomes sur la séquence codante de son ARNm kcnj10 mais était lié à sa partie 5’ non codante. Nous avons adressé les conséquences physiologiques de ces régulations. Par enregistrements électrophysiologiques, nous avons déterminé que l’augmentation de KIR4.1 en l’absence de RACK1 menait à un changement dans les propriétés électriques des neurones de l’hippocampe avec une protection globale contre des activités synaptiques élevées certainement due à une plus grande capacité des PAPs à capturer le potassium. En résumé, j’ai développé une nouvelle méthode pour caractériser la distribution des ARNm dans les astrocytes. J’ai identifié un pool de protéines associées aux polyribosomes astrocytaires. Enfin, Je me suis concentré sur RACK1 et je l’ai identifié comme un régulateur de la traduction de KIR4.1 et de l’homéostasie du potassium périsynaptique.

Ethical approval: The research related to human use complies with all the relevant national regulations, institutional policies and was performed in accordance with the tenets of the Helsinki Declaration and has been approved by the authors’ institutional review board or equivalent committee.; International audience; Deep brain stimulation is widely used to alleviate symptoms of movement disorders. During intraoperative stimulation the influence of active or passive movements on the neuronal activity is often evaluated but the evaluation remains mostly subjective. The objective of this paper is to investigate the potential of a previously developed Weightedfrequency Fourier Linear combiner and Kalman filter-based algorithm to identify tremor types and to isolate the tremorous part. The method is applied to ten intraoperatively acquired accelerometer recordings from eight patients from which 186 phases were manually annotated into: rest, postural and kinetic phase without tremor, and rest, postural and kinetic phase with tremor. The overall accuracy for tremorous phases only is 89.1% and 76.3% when also non-tremorous phases are considered. Two main misclassification cases are identified and further discussed. The results demonstrate the potential of the developed algorithm for the use as an online tremorous movement classifier based on the acquired digital biomarkers.

International audience; β1 integrins are important in blood vessel formation and function, finely tuning the adhesion of endothelial cells to each other and to the extracellular matrix. The role of integrins in the vascular disease, cerebral cavernous malformation (CCM) has yet to be explored in vivo. Endothelial loss of the gene KRIT1 leads to brain microvascular defects, resulting in debilitating and often fatal consequences. We tested administration of a monoclonal antibody that enforces the active β1 integrin conformation, (clone 9EG7), on a murine neonatal CCM mouse model, Krit1 flox/flox ;Pdgfb-iCreERT2 (Krit1 ECKO), and on KRIT1-silenced human umbilical vein endothelial cells (HUVECs). In addition, endothelial deletion of the master regulator of integrin activation, Talin 1 (Tln1), in Krit1 ECKO mice was performed to assess the effect of completely blocking endothelial integrin activation on CCM. Treatment with 9EG7 reduced lesion burden in the Krit1 ECKO model and was accompanied by a strong reduction in the phosphorylation of the ROCK substrate, myosin light chain (pMLC), in both retina and brain endothelial cells. Treatment of KRIT1-silenced HUVECs with 9EG7 in vitro stabilized cell-cell junctions. Overnight treatment of HUVECs with 9EG7 resulted in significantly reduced total surface expression of β1 integrin, which was associated with reduced pMLC levels, supporting our in vivo findings. Genetic blockade of integrin activation by Tln1 ECKO enhanced bleeding and did not reduce CCM lesion burden in Krit1 ECKO mice. In sum, targeting β1 integrin with an activated-specific antibody reduces acute murine CCM lesion development, which we found to be associated with suppression of endothelial ROCK activity.

International audience; Recent evidence has shown that even mild mutations in the Huntingtin gene that are associated with late-onset Huntington’s disease (HD) disrupt various aspects of human neurodevelopment. To determine whether these seemingly subtle early defects affect adult neural function, we investigated neural circuit physiology in newborn HD mice. During the first postnatal week, HD mice have less cortical layer 2/3 excitatory synaptic activity than wild-type mice, express fewer glutamatergic receptors, and show sensorimotor deficits. The circuit self-normalizes in the second postnatal week but the mice nonetheless develop HD. Pharmacologically enhancing glutamatergic transmission during the neonatal period, however, rescues these deficits and preserves sensorimotor function, cognition, and spine and synapse density as well as brain region volume in HD adult mice.

Nucleic-acid aptamers are of strong interest for diagnosis and therapy. Compared with antibodies, they are smaller, stable upon variations in temperature, easy to modify, and have higher tissue-penetration abilities. However, they have been little described as detection probes in histology studies of human tissue sections. In this study, we performed fluorescence imaging with two aptamers targeting cell-surface receptors EGFR and integrin α5β1, both involved in the aggressiveness of glioblastoma. The aptamers’ cell-binding specificities were confirmed using confocal imaging. The affinities of aptamers for glioblastoma cells expressing these receptors were in the 100–300 nM range. The two aptamers were then used to detect EGFR and integrin α5β1 in human glioblastoma tissues and compared with antibody labeling. Our aptafluorescence assays proved to be able to very easily reveal, in a one-step process, not only inter-tumoral glioblastoma heterogeneity (differences observed at the population level) but also intra-tumoral heterogeneity (differences among cells within individual tumors) when aptamers with different specificities were used simultaneously in multiplexing labeling experiments. The discussion also addresses the strengths and limitations of nucleic-acid aptamers for biomarker detection in histology.

Recent understanding of Autism Spectrum Disorder (ASD) showed that peripheral primary mechanosensitive neurons involved in touch sensation and central neurons affected in ASD share transcriptional regulators. Mutant mice for ASD-associated transcription factors exhibit impaired primary tactile perception, and restoring those genes specifically in primary sensory neurons rescue some of the anxiety-like behavior and social interaction defects.Interestingly, peripheral mechanosensitive sensory neurons also project to internal organs including the cardio-vascular system, and an imbalance of the cardio-vascular sympatho-vagal regulation is evidenced in ASD and intellectual disability. ASD patients have decreased vagal tone, suggesting dysfunction of sensory neurons involved in cardio-vascular sensing.In light of our previous finding that the ASD-associated Meis2 gene is necessary for normal touch neurons development and function, we investigated here if its inactivation in mouse peripheral sensory neurons also affects cardio-vascular sympatho-vagal regulation and baroreflex. Combining echocardiography, pharmacological challenge, blood pressure monitoring and heart rate variability analysis, we found that Meis2 mutant mice exhibited a blunted vagal response independently of any apparent cardiac malformation. These results suggest that defects in primary sensory neurons with mechanosensitive identity could participate in the imbalanced cardio-vascular sympatho-vagal tone found in ASD patients, reinforcing current hypotheses on the role of primary sensory neurons in the etiology of ASD.

International audience; Psychostimulant drugs, such as cocaine, d-amphetamine and methylphenidate, alter a wide range of behaviors including locomotor activity and somatosensory perception. These altered behaviors are accompanied by the activation of specific neuronal populations within reward-, emotion- and locomotion-related circuits. However, whether such regulation occurs at the level of the spinal cord, a key node for neural circuits integrating and coordinating sensory and motor functions has never been addressed. By evaluating the temporal and spatial expression pattern of the phosphorylated form of the immediate early gene cFos at Ser32 (pS32-cFos), used as a proxy of neuronal activation, we demonstrate that, in adult male mice, d-amphetamine increases pS32-cFos expression in both inhibitory and excitatory neurons in dorsal and ventral horns at the lumbar spinal cord level. Interestingly, a fraction of neurons activated by a first exposure to d-amphetamine can be re-activated following d-amphetamine re-exposure. Similar expression patterns were observed in response to cocaine and methylphenidate, but not following morphine and dozilcipine administration. Finally, the blockade of dopamine reuptake was sufficient to recapitulate the increase in pS32-cFos expression induced by psychostimulant drugs. Our work provides evidence that cFos expression can be activated in lumbar spinal cord in response to acute psychostimulants administration. Running title: Psychostimulant-evoked neuronal ensembles in spinal cord.

International audience; The hypothalamus is a large brain region made of nuclei and areas involved in the control of behaviors and physiological regulations. Among them, the arcuate nucleus (ARH) and the lateral hypothalamic area (LHA) contain key neuronal populations expressing the pro-opiomelanocortin (POMC), the agouti-related peptide (AgRP), and the melanin-concentrating hormone (MCH), respectively, that are involved in goal-oriented behaviors (such as feeding behavior) and glucose homeostasis. These neuronal populations are generated from distinct parts of the germinative neuroepithelium during embryonic life, and acquire their cell fate under the influence of morphogen proteins, specific transcription factors, and epigenetic modulators. POMC and MCH neuronal development continues by sending long descending axonal projections before birth under the control of axon guidance molecules such as Netrin1 and Slit2. Later, during the postnatal period, POMC and AgRP neurons develop intra-hypothalamic projections notably to the paraventricular nucleus of the hypothalamus through the influence of other axon guidance cues such as the class3 Semaphorins. Other cellular processes, such as autophagy and primary cilia function, and hormonal cues also appear critical for the proper development of POMC neurons.

Authorized uncorrected proof; International audience; Myotonic dystrophy type 1 (DM1) exhibits highly heterogeneous clinical manifestations caused by an unstable CTG repeat expansion reaching up to 4000 CTG. The clinical variability depends on CTG repeat number, CNG repeat interruptions, and somatic mosaicism. Currently, none of these factors are simultaneously and accurately determined due to the limitations of gold standard methods used in clinical and research laboratories. An amplicon method for targeting the DMPK locus using singlemolecule real-time sequencing was recently developed to accurately analyze expanded alleles. However, amplicon-based sequencing still depends on PCR, and the inherent bias toward preferential amplification of smaller repeats can be problematic in DM1. Thus, an amplification-free long-read sequencing method was developed by using CRISPR/Cas9 technology in DM1. This method was used to sequence the DMPK locus in patients with CTG repeat expansion ranging from 130 to >1000 CTG. We showed that elimination of PCR amplification improves the accuracy of measurement of inherited repeat number and somatic repeat variations, two key factors in DM1 severity and age at onset. For the first time, an expansion composed of >85% CCG repeats was identified by using this innovative method in aDM1 family with an atypical clinical profile. No-amplification targeted sequencing represents a promising method that can overcome research and diagnosis shortcomings, with translational implications for clinical and genetic counseling in DM1

International audience; Slowness of movement initiation is a cardinal motor feature of Parkinson’s disease (PD) and is not fully reverted by current dopaminergic treatments. This trouble could be due to the dysfunction of executive processes and, in particular, of inhibitory control of response initiation, a function possibly associated with the noradrenergic (NA) system. The implication of NA in the network supporting proactive inhibition remains to be elucidated using pharmacological protocols. For that purpose, we administered 150 μg of clonidine to 15 healthy subjects and 12 parkinsonian patients in a double-blind, randomized, placebo-controlled design. Proactive inhibition was assessed by means of a Go/noGo task, while pre-stimulus brain activity was measured by event-related functional MRI. Acute reduction in noradrenergic transmission induced by clonidine enhanced difficulties initiating movements reflected by an increase in omission errors and modulated the activity of the anterior node of the proactive inhibitory network (dorsomedial prefrontal and anterior cingulate cortices) in PD patients. We conclude that NA contributes to movement initiation by acting on proactive inhibitory control via the α2-adrenoceptor. We suggest that targeting noradrenergic dysfunction may represent a new treatment approach in some of the movement initiation disorders seen in Parkinson’s disease

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International audience; Somatostatin receptor (SSTR)-targeted peptide receptor radionuclide therapy (PRRT) represents a promising approach for treatment-refractory meningiomas progressing after surgery and radiotherapy. The aim of this study was to provide outcomes of patients harboring refractory meningiomas treated by 177Lu-DOTATATE and an overall analysis of progression-free survival at 6 months (PFS-6) of the same relevant studies in the literature. Eight patients with recurrent and progressive WHO grade II meningiomas were treated after multimodal pretreatment with 177Lu-DOTATATE between 2019 and 2022. Primary and secondarily endpoints were progression-free survival at 6-months (PFS-6) and toxicity, respectively. PFS-6 analysis of our case series was compared with other similar relevant studies that included 86 patients treated with either 177Lu-DOTATATE or 90Y-DOTATOC. Our retrospective study showed a PFS-6 of 85.7% for WHO grade II progressive refractory meningiomas. Treatment was clinically and biologically well tolerated. The overall analysis of the previous relevant studies showed a PFS-6 of 89.7% for WHO grade I meningiomas (n = 29); 57.1% for WHO grade II (n = 21); and 0 % for WHO grade III (n = 12). For all grades (n = 86), including unknown grades, PFS-6 was 58.1%. SSTR-targeted PRRT allowed us to achieve prolonged PFS-6 in patients with WHO grade I and II progressive refractory meningiomas, except the most aggressive WHO grade II tumors. Large scale randomized trials are warranted for the better integration of PRRT in the treatment of refractory meningioma into clinical practice guidelines.

Prader-Willi syndrome (PWS) is a rare genetic neurodevelopmental disorder involving nutritional, endocrine /metabolic, emotional and behavior dimensions. There is evidence for impaired hypothalamic development and function in PWS, involving oxytocin and ghrelin, which can account for the typical PWS phenotype. Hyperphagia with addiction-like behavior is one of the common features of PWS and is a consequence of the hypothalamic dysfunction. In this study, we hypothesized that brain regions associated with compulsive eating behavior would be abnormally activated by food-related odors in PWS, as these can stimulate the appetite and induce hunger-related behavior.MethodsWe used a classic olfactory discrimination test to verify that olfaction was normal in patients with PWS. In an fMRI scanner, we presented two odors, a tulip and a caramel odor, which have a different hedonic valence and a different capacity to arouse hunger-related behavior.ResultsThere was a five-fold higher activation in the right amygdala for the caramel odor compared with the tulip odor in patients with PWS (n=14). No such hyperactivation was found in age-matched controls (n=11). Cluster analysis of clinical hyperphagia scores in patients with PWS revealed a link with the right amygdala hyperactivation.ConclusionsOur study provides evidence for functional alteration of the right amygdala in PWS, which is part of the brain reward network involved in food addiction. This finding may relate to dysfunction of the ghrelin and oxytocin systems in PWS, as these are involved in addictive behavior, appetite, and olfactory bulb regulation.

International audience; Recurrent or high-grade meningiomas are an unmet medical need. Recently, we demonstrated that targeting mTOR by everolimus was relevant both in vitro and in humans. However, everolimus induces an AKT activation that may impact the anti-proliferative effect of the drug. Moreover, the MAP kinase pathway was shown to be involved in meningioma tumorigenesis. We therefore targeted both the Pi3k-AKT-mTOR and MAP kinase pathways by using combinations of the Pi3k inhibitor alpelisib and the MEK inhibitor trametinib. Our study was performed in vitro on the human meningioma cell lines and on a large series of primary cultures providing from 63 freshly operated meningiomas including 35 WHO grade 1, 23 grade 2, and five grade 3, half of which presented a NF2 genomic alteration. Alpelisib induced a higher inhibitory effect on cell viability and proliferation than everolimus in all cell lines and 32 randomly selected tumors no matter the genomic status, the histological subtype or grade. Trametinib also strongly inhibited cell proliferation and induced AKT activation. Combined treatment with alpelisib plus trametinib reversed the AKT activation induced by trametinib and induced an additive inhibitory effect irrespective of the cell lines or tumor features. Co-targeting pathways seems promising and may be considered particularly for aggressive meningioma

International audience; One aim of comparative neuroanatomy is to better understand brain function among species. It is tempting to try and explain brain differences throughout the animal kingdom by differences in adaptive behaviors as well as ecological factors. Based on this idea, we explored, with MRI, the brain morphology of three species with different sociality and predator avoidance (Bongo, Java deer mouse and Maki Catta). Brains were collected after death of natural causes and MR-imaged. Brain and body weights were collected, and volumes of brain were estimated after MRI segmentation. The brain-to-body weight ratio was close to 1 for the Java deer mouse (1.04%) and the maki catta (1.05%) but only 0.26% for the bongo. Encephalization quotients (EQ) were calculated using formulas defined for human (hEQ, constants 0.12 and 2/3; Cairó 2011, doi:10.3389/fnhum.2011.00108) and for dog (dEQ, constants 0.14 and 0.528; Saganuwan 2021, doi:10.1186/s13104-021-05638-0). Whatever the method, the Java deer mouse EQs were the smallest (hEQ=0.98; dEQ=0.88). The maki catta had a higher hEQ (1.23) than the bongo (1.14) whereas the order was reversed for the dEQ (maki catta dEQ=1.21; bongodEQ=1.96). These values are coherent with the idea that EQ is higher in prey species using active predator avoidance (bongo) and in social species (bongo and maki catta)

International audience; • Stimulation a dissected retina with a sequence of periodic dark flashes • Extracellular spike recordings. 2. Identification of necessary components via pharmacological inhibition of synaptic transmission onto : • ON bipolar cells via mGluR6 receptor antagonist LAP-4. • OFF bipolar cells via AMPA receptor antagonist ACET. Results ON BC inhibition cancels the OSR.

SummaryOrienting in space requires the processing and encoding of visual spatial cues. The dominant hypothesis about the brain structures mediating the coding of spatial cues stipulates the existence of a hippocampal-dependent system for the representation of geometry and a striatal-dependent system for the representation of landmarks. However, this dual-system hypothesis is based on paradigms that presented spatial cues conveying either conflicting or ambiguous spatial information and that amalgamated the concept of landmark into both discrete 3D objects and wall features. These confounded designs introduce difficulties in interpreting the spatial learning process. Here, we test the hypothesis of a complex interaction between the hippocampus and the striatum during landmark and geometry visual coding in humans. We also postulate that object-based and feature-based navigation are not equivalent instances of landmark-based navigation as currently considered in human spatial cognition. We examined the neural networks associated with geometry-, object-, and feature-based spatial navigation in an unbiased, two-choice behavioral paradigm using fMRI. We showed evidence of a synergistic interaction between hippocampal and striatal coding underlying flexible navigation behavior. The hippocampus was involved in all three types of cue-based navigation, whereas the striatum was more strongly recruited in the presence of geometric cues than object or feature cues. We also found that unique, specific neural signatures were associated with each spatial cue. Critically, object-based navigation elicited a widespread pattern of activity in temporal and occipital regions relative to feature-based navigation. These findings challenge and extend the current view of a dual, juxtaposed hippocampal-striatal system for visual spatial coding in humans. They also provide novel insights into the neural networks mediating object vs. feature spatial coding, suggesting a need to distinguish these two types of landmarks in the context of human navigation.HighlightsComplex hippocampal-striatal interaction during visual spatial coding for flexible human navigation behavior.Distinct neural signatures associated with object-, feature-, and geometry-based navigation.Object- and feature-based navigation are not equivalent instances of landmark-based navigation.

Background Glioblastomas stem-like cells (GSCs) by invading the brain parenchyma, remains after resection and radiotherapy and the tumoral microenvironment become stiffer. GSC invasion is reported as stiffness sensitive and associated with altered N-glycosylation pattern. Glycocalyx thickness modulates integrins mechanosensing, but details remain elusive and glycosylation enzymes involved are unknown. Here, we studied the association between matrix stiffness modulation, GSC migration and MGAT5 induced N-glycosylation in fibrillar 3D context. Method To mimic the extracellular matrix fibrillar microenvironments, we designed 3D-ex-polyacrylonitrile nanofibers scaffolds (NFS) with adjustable stiffnesses by loading multiwall carbon nanotubes (MWCNT). GSCs neurosphere were plated on NFSs, allowing GSCs migration and MGAT5 was deleted using CRISPR-Cas9. Results We found that migration of GSCs was maximum at 166 kPa. Migration rate was correlated with cell shape, expression and maturation of focal adhesion (FA), Epithelial to Mesenchymal Transition (EMT) proteins and (β1,6) branched N-glycan binding, galectin-3. Mutation of MGAT5 in GSC inhibited N-glycans (β1–6) branching, suppressed the stiffness dependence of migration on 166 kPa NFS as well as the associated FA and EMT protein expression. Conclusion MGAT5 catalysing multibranched N-glycans is a critical regulators of stiffness induced invasion and GSCs mechanotransduction, underpinning MGAT5 as a serious target to treat cancer.

International audience; Resting-state functional magnetic resonance imaging (fMRI) is a common translational method to evaluate brain functional connectivity (FC) in preclinical neurologic applications. However, unlike human studies, preclinical fMRI studies are usually performed under anesthetic condition. The confounding effect of the anesthesia on fMRI measurements is not clear. Indeed, a controversy exists between those who claim that anesthesia change FC (Paasonen et al., 2018) and other who maintain that FC is preserved (Becq et al., 2020). Our hypothesis is that physiological changes induced by anesthesia could explain this discrepancy. While in human studies, fMRI analysis generally includes cleaning of physiological-noise (Glover et al., 2000; Kassinopoulos & Mitsis, 2019), preclinical study processing is rather often limited to a low-pass temporal filtering. We aimed first to demonstrate that the global MRI signal of animal brain includes, like in human, a physiological component. Second, that a normalization of this component based on global signal can reduce variability of FC assessment.

International audience; Cerebral fMRI is a useful imaging tool that allows to visualize neuronal activity based on blood oxygen levels. However, except the neuronal component of interest, fMRI signal contains “noise” components due to physiological processes (heartbeat, respiration...). Litterature contains attempts to estimate this part of the signal, but not to measure it. This study aims to measure the respective impact of cardiac pulse and respiratory cycle on MRI signal in human brain and its regions with short TR.

International audience; The microglial response to a pathological microenvironment is hallmarked by a change in cellular morphology. Following a pathological stimulus, microglia become reactive and simultaneously divide to create daughter cells. Although a wide array of microglial morphologies has been observed, the exact functions of these distinct morphologies are unknown, as are the morphology and reactivity status of dividing microglia. In this study, we used kainic acid to trigger microglial activation and cell division. Following a cortical kainic acid injection, microglial morphology and proliferation were examined at 3 days post-injection using immunohistochemistry for ionized calcium binding adapter molecule 1 (Iba1) to stain for microglia, and KI67 as a marker of cell division. Individual microglial cells were isolated from photomicrographs and skeletal and fractal analyses were used to examine cell size and spatial complexity. We examined the morphology of microglia in both wildtype and microglia-specific tumor necrosis factor (TNF)-α knockout mice. Data were analyzed using generalized linear mixed models or a two-way ANOVA. We found that dividing microglia had a more reactive morphology (larger cell body area, longer cell perimeter, and less ramification) compared to microglia that were not dividing, regardless of microglial release of TNF-α. However, we also observed dividing microglia with a complex, more ramified morphology. Changes in microglial morphology and division were greatest near the kainic acid injection site. This study uses robust and quantitative techniques to better understand microglial cell division, morphology, and population dynamics, which are essential for the development of novel therapeutics that target microglia.