Développement des circuits neuronaux

Publications de l’équipe

Année de publication : 2011

Claire Wyart, Filippo Del Bene (2011 May 28)

Let there be light: zebrafish neurobiology and the optogenetic revolution.

Reviews in the neurosciences : 121-30 : DOI : 10.1515/RNS.2011.013 En savoir plus
Résumé

Optogenetics has revolutionized the toolbox arsenal that neuroscientists now possess to investigate neuronal circuit function in intact and living animals. With a combination of light emitting ‘sensors’ and light activated ‘actuators’, we can monitor and control neuronal activity with minimal perturbation and unprecedented spatiotemporal resolution. Zebrafish neuronal circuits represent an ideal system to apply an optogenetic based analysis owing to its transparency, relatively small size and amenability to genetic manipulation. In this review, we describe some of the most recent advances in the development and applications of optogenetic sensors (i.e., genetically encoded calcium indicators and voltage sensors) and actuators (i.e., light activated ion channels and ion pumps). We focus mostly on the tools that have already been successfully applied in zebrafish and on those that show the greatest potential for the future. We also describe crucial technical aspects to implement optogenetics in zebrafish including strategies to drive a high level of transgene expression in defined neuronal populations, and recent optical advances that allow the precise spatiotemporal control of sample illumination.

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Filippo Del Bene, Claire Wyart (2011 May 14)

Optogenetics: a new enlightenment age for zebrafish neurobiology.

Developmental neurobiology : 404-14 : DOI : 10.1002/dneu.20914 En savoir plus
Résumé

Zebrafish became a model of choice for neurobiology because of the transparency of its brain and because of its amenability to genetic manipulation. In particular, at early stages of development the intact larva is an ideal system to apply optical techniques for deep imaging in the nervous system, as well as genetically encoded tools for targeting subsets of neurons and monitoring and manipulating their activity. For these applications,new genetically encoded optical tools, fluorescent sensors, and light-gated channels have been generated,creating the field of « optogenetics. » It is now possible to monitor and control neuronal activity with minimal perturbation and unprecedented spatio-temporal resolution.We describe here the main achievements that have occurred in the last decade in imaging and manipulating neuronal activity in intact zebrafish larvae. We provide also examples of functional dissection of neuronal circuits achieved with the applications of these techniques in the visual and locomotor systems.

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Année de publication : 2010

Filippo Del Bene, Claire Wyart, Estuardo Robles, Amanda Tran, Loren Looger, Ethan K Scott, Ehud Y Isacoff, Herwig Baier (2010 Oct 30)

Filtering of visual information in the tectum by an identified neural circuit.

Science (New York, N.Y.) : 669-73 : DOI : 10.1126/science.1192949 En savoir plus
Résumé

The optic tectum of zebrafish is involved in behavioral responses that require the detection of small objects. The superficial layers of the tectal neuropil receive input from retinal axons, while its deeper layers convey the processed information to premotor areas. Imaging with a genetically encoded calcium indicator revealed that the deep layers, as well as the dendrites of single tectal neurons, are preferentially activated by small visual stimuli. This spatial filtering relies on GABAergic interneurons (using the neurotransmitter γ-aminobutyric acid) that are located in the superficial input layer and respond only to large visual stimuli. Photo-ablation of these cells with KillerRed, or silencing of their synaptic transmission, eliminates the size tuning of deeper layers and impairs the capture of prey.

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Année de publication : 2009

Aristides B Arrenberg, Filippo Del Bene, Herwig Baier (2009 Oct 7)

Optical control of zebrafish behavior with halorhodopsin.

Proceedings of the National Academy of Sciences of the United States of America : 17968-73 : DOI : 10.1073/pnas.0906252106 En savoir plus
Résumé

Expression of halorhodopsin (NpHR), a light-driven microbial chloride pump, enables optical control of membrane potential and reversible silencing of targeted neurons. We generated transgenic zebrafish expressing enhanced NpHR under control of the Gal4/UAS system. Electrophysiological recordings showed that eNpHR stimulation effectively suppressed spiking of single neurons in vivo. Applying light through thin optic fibers positioned above the head of a semi-restrained zebrafish larva enabled us to target groups of neurons and to simultaneously test the effect of their silencing on behavior. The photostimulated volume of the zebrafish brain could be marked by subsequent photoconversion of co-expressed Kaede or Dendra. These techniques were used to localize swim command circuitry to a small hindbrain region, just rostral to the commissura infima Halleri. The kinetics of the hindbrain-generated swim command was investigated by combined and separate photo-activation of NpHR and Channelrhodopsin-2 (ChR2), a light-gated cation channel, in the same neurons. Together this « optogenetic toolkit » allows loss-of-function and gain-of-function analyses of neural circuitry at high spatial and temporal resolution in a behaving vertebrate.

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Claire Wyart, Filippo Del Bene, Erica Warp, Ethan K Scott, Dirk Trauner, Herwig Baier, Ehud Y Isacoff (2009 Sep 18)

Optogenetic dissection of a behavioural module in the vertebrate spinal cord.

Nature : 407-10 : DOI : 10.1038/nature08323 En savoir plus
Résumé

Locomotion relies on neural networks called central pattern generators (CPGs) that generate periodic motor commands for rhythmic movements. In vertebrates, the excitatory synaptic drive for inducing the spinal CPG can originate from either supraspinal glutamatergic inputs or from within the spinal cord. Here we identify a spinal input to the CPG that drives spontaneous locomotion using a combination of intersectional gene expression and optogenetics in zebrafish larvae. The photo-stimulation of one specific cell type was sufficient to induce a symmetrical tail beating sequence that mimics spontaneous slow forward swimming. This neuron is the Kolmer-Agduhr cell, which extends cilia into the central cerebrospinal-fluid-containing canal of the spinal cord and has an ipsilateral ascending axon that terminates in a series of consecutive segments. Genetically silencing Kolmer-Agduhr cells reduced the frequency of spontaneous free swimming, indicating that activity of Kolmer-Agduhr cells provides necessary tone for spontaneous forward swimming. Kolmer-Agduhr cells have been known for over 75 years, but their function has been mysterious. Our results reveal that during early development in zebrafish these cells provide a positive drive to the spinal CPG for spontaneous locomotion.

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Année de publication : 2008

Filippo Del Bene, Ann M Wehman, Brian A Link, Herwig Baier (2008 Sep 23)

Regulation of neurogenesis by interkinetic nuclear migration through an apical-basal notch gradient.

Cell : 1055-65 : DOI : 10.1016/j.cell.2008.07.017 En savoir plus
Résumé

The different cell types in the central nervous system develop from a common pool of progenitor cells. The nuclei of progenitors move between the apical and basal surfaces of the neuroepithelium in phase with their cell cycle, a process termed interkinetic nuclear migration (INM). In the retina of zebrafish mikre oko (mok) mutants, in which the motor protein Dynactin-1 is disrupted, interkinetic nuclei migrate more rapidly and deeply to the basal side and more slowly to the apical side. We found that Notch signaling is predominantly activated on the apical side in both mutants and wild-type. Mutant progenitors are, thus, less exposed to Notch and exit the cell cycle prematurely. This leads to an overproduction of early-born retinal ganglion cells (RGCs) at the expense of later-born interneurons and glia. Our data indicate that the function of INM is to balance the exposure of progenitor nuclei to neurogenic versus proliferative signals.

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