Cav2.1 C‐terminal fragments produced in Xenopus laevis oocytes do not modify the channel expression and functional properties

International audienceThe sequence and genomic organization of the CACNA1A gene that encodes the Cav2.1 subunit of both P and Q type Ca2+ channels are well conserved in mammals. In human, rat and mouse CACNA1A, the use of an alternative acceptor site at the exon 46‐47 boundary results in the expression of a long Cav2.1 splice variant. In transfected cells, the long isoform of human Cav2.1 produces a C‐terminal fragment, but it is not known whether this fragment affects Cav2.1 expression or functional properties. Here, we cloned the long isoform of rat Cav2.1 (Cav2.1(e47)) and identified a novel variant with a shorter C‐terminus (Cav2.1(e47s)) that differs from those previously described in the rat and mouse. When expressed in Xenopus laevis oocytes, Cav2.1(e47) and Cav2.1(e47s) displayed similar functional properties as the short isoform (Cav2.1). We show that Cav2.1 isoforms produced short (CT1) and long (CT1(e47)) C‐terminal fragments that interacted in vivo with the auxiliary Cavβ4a subunit. Overexpression of the C‐terminal fragments did not affect Cav2.1 expression and functional properties. Furthermore, the functional properties of a Cav2.1 mutant without the C‐terminal Cavβ4 binding domain (Cav2.1ΔCT2) were similar to those of Cav2.1, and were not influenced by the co‐expression of the missing fragments (CT2 or CT2(e47)). Our results exclude a functional role of the C‐terminal fragments in Cav2.1 biophysical properties in an expression system widely used to study this channel

La transformation de Fisz pour l'estimation d'images d'intensité Poissonnienne dans le domaine des ondelettes

Nous présentons un nouvel estimateur d'images d'intensité Poissonnienne dans le domaine des ondelettes. Cette méthode est basée sur la normalité asymptotique d'une fonction non-linéaire des coefficients de détail et d'échelle de la transformée de Haar, appelée la transformée de Fisz. Nous exposons quelques résultats asymptotiques, tels que la normalité et la décorrélation des pixels de l'image transformée. Fort de ces résultats, l'image originale bruitée par un processus de Poisson, peut être considérée après transformation de Fisz comme étant contaminée par un bruit Gaussien additif blanc. Ainsi, les débruiteurs classiques s'appliquent directement. Plus exactement, nous appliquons dans le cadre de ce papier un estimateur Bayesien que nous avons récemment développé, utilisant comme a priori une nouvelle classe de distributions, les formes K de Bessel (FKB). Les simulations menées montrent que la transformation de Fisz offre des performances au moins aussi bonnes que les transformations stabilisatrices pour des images d'intensité régulière ou constante par morceaux. Elle dépasse clairement ces approches lorsque le taux de comptage faible. Combiner la transfortmation de Fisz avec le débruiteur Bayesien FKB offre les meilleurs résultats

Combining Microfluidics, Optogenetics and Calcium Imaging to Study Neuronal Communication In Vitro

International audienceIn this paper we report the combination of microfluidics, optogenetics and calcium imaging as a cheap and convenient platform to study synaptic communication between neuronal populations in vitro. We first show that Calcium Orange indicator is compatible in vitro with a commonly used Channelrhodopsine-2 (ChR2) variant, as standard calcium imaging conditions did not alter significantly the activity of transduced cultures of rodent primary neurons. A fast, robust and scalable process for micro-chip fabrication was developed in parallel to build micro-compartmented cultures. Coupling optical fibers to each micro-compartment allowed for the independent control of ChR2 activation in the different populations without crosstalk. By analyzing the post-stimuli activity across the different populations, we finally show how this platform can be used to evaluate quantitatively the effective connectivity between connected neuronal populations

Synapto-protective drugs evaluation in reconstructed neuronal network

Chronic neurodegenerative syndromes such as Alzheimer’s and Parkinson’s diseases, or acute syndromes such as ischemic stroke or traumatic brain injuries are characterized by early synaptic collapse which precedes axonal and neuronal cell body degeneration and promotes early cognitive impairment in patients. Until now, neuroprotective strategies have failed to impede the progression of neurodegenerative syndromes. Drugs preventing the loss of cell body do not prevent the cognitive decline, probably because they lack synapto-protective effects. The absence of physiologically realistic neuronal network models which can be easily handled has hindered the development of synapto-protective drugs suitable for therapies. Here we describe a new microfluidic platform which makes it possible to study the consequences of axonal trauma of reconstructed oriented mouse neuronal networks. Each neuronal population and sub-compartment can be chemically addressed individually. The somatic, mid axon, presynaptic and postsynaptic effects of local pathological stresses or putative protective molecules can thus be evaluated with the help of this versatile “brain on chip” platform. We show that presynaptic loss is the earliest event observed following axotomy of cortical fibers, before any sign of axonal fragmentation or post-synaptic spine alteration. This platform can be used to screen and evaluate the synapto-protective potential of several drugs. For instance, NAD+ and the Rho-kinase inhibitor Y27632 can efficiently prevent synaptic disconnection, whereas the broad-spectrum caspase inhibitor zVAD-fmk and the stilbenoid resveratrol do not prevent presynaptic degeneration. Hence, this platform is a promising tool for fundamental research in the field of developmental and neurodegenerative neurosciences, and also offers the opportunity to set up pharmacological screening of axon-protective and synapto-protective drugs

Long-lasting impairment of mGluR5-activated intracellular pathways in the striatum after withdrawal of cocaine self-administration

Background: Cocaine addiction continues to be a major heath concern, and despite public health intervention there is a lack of efficient pharmacological treatment options. A newly identified potential target are the group I metabotropic glutamate receptors (mGluR1/5), with allosteric modulators showing particular promise. Methods: We evaluated the capacity of mGluR1/5 receptors to induce functional responses in ex vivo striatal slices from rats with 1) acute cocaine self-administration (CSA), 2) chronic CSA and 3) 60 days CSA withdrawal by westernblot and extracellular recordings of synaptic transmission. Results: We found that striatal mGluR5 are the principal mediator of the mGluR1/5 agonist DHPG-induced CREB phosphorylation. Both acute and chronic CSA blunted mGluR1/5 effects on CREB phosphorylation in the striatum, which correlated with the capacity to induce long-term depression, an effect which was maintained 60 days after chronic CSA withdrawal. In the nucleus accumbens, the principal brain region mediating the rewarding effects of drugs, chronic CSA blunted mGluR1/5 stimulation of ERK1/2 and CREB. Interestingly, the mGluR5 antagonist/inverse-agonist, MPEP, lead to a specific increase in CREB phosphorylation after chronic CSA specifically in the nucleus accumbens, but not in the striatum. Conclusions: Prolonged CSA, through withdrawal, leads to a blunting of mGluR1/5 responses in the striatum. In addition, specifically in the accumbens, mGluR5 signaling to CREB shifts from an agonist-induced to an antagonist-induced CREB phosphorylation

Cellular distribution of the histamine H3 receptor in the basal ganglia : functional modulation of dopamine and glutamate neurotransmission

This is the author's version of a work that was accepted for publication in Basal ganglia. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Vol. 3 Núm. 2 (Jul. 2013)Altres ajuts: Red_de_Trastornos_Adictivos/RD06/0001/0015Histamine H3 receptors (H3R) are widely expressed in the brain where they participate in sleep-wake cycle and cognition among other functions. Despite their high expression in some regions of the basal ganglia, their functional role in this forebrain neural network remains unclear. The present findings provide in situ hybridization and immunohistochemical evidence for H3R expression in several neuronal populations of the rat basal ganglia but not in astrocytes (glial fibrillary acidic protein immunoreactive cells). We demonstrate the presence of H3R mRNA and protein in dopaminergic neurons (tyrosine hydroxylase positive) of the ventral tegmental area and substantia nigra. In the dorsal and ventral (nucleus accumbens) striatal complex we show H3R immunoreactivity in cholinergic (choline acetyltransferase immunoreactive) and GABAergic neurons (substance P, proenkephalin or dopamine D1 receptor positive) as well as in corticostriatal terminals (VGLUT1-immunoreactive). Double-labelling experiments in the medial prefrontal cortex show that H3R is expressed in D1R-positive interneurons and VGLUT1-positive corticostriatal output neurons. Our functional experiments confirm that H3R ligands modulate dopamine synthesis and the probability of glutamate release in the striatum from cortico-striatal afferents. The presence of H3R in such different neuronal populations and its involvement in the control of striatal dopaminergic and glutamatergic transmission ascribes a complex role to H3R in the function of the basal ganglia neural network

ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations

The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we manage to collect observations for half of the post-discovery years (median), with data that have a median uncertainty less than one minute. In comparison with literature, the ephemerides generated by the project are more precise and less biased. More than 40\% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95\%), and also the identification of missing data. The dedicated ExoClock network effectively supports this task by contributing additional observations when a gap in the data is identified. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (TTVs - Transit Timing Variations) for a sample of 19 planets. All products, data, and codes used in this work are open and accessible to the wider scientific community.Comment: Recommended for publication to ApJS (reviewer's comments implemented). Main body: 13 pages, total: 77 pages, 7 figures, 7 tables. Data available at http://doi.org/10.17605/OSF.IO/P298

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion