Talks by Filippo Del Bene, Nathalie Jurisch-Yaksi and Emre Yaksi on 7 July at IEM HAS

Dear Colleagues,

On 7 July (Friday), we will host three excellent colleagues working on the zebrafish model system.

10:00-11:00 – Filippo Del Bene: Deciphering anatomy and function of an inter-hemispheric neural circuit in the zebrafish optic tectum
15:00-15:45 – Nathalie Jurisch-Yaksi: The role of motile cilia-generated flow in olfaction
15:45-16:30 – Emre Yaksi: Studying the function and connectivity of habenular networks in zebrafish brain

The abstracts of the talks:

1. Deciphering anatomy and function of an inter-hemispheric neural circuit in the zebrafish optic tectum
1 Institut Curie, Unité de Génétique et Biologie du Développement, 26, rue d’Ulm, 75248 PARIS France
2 Department of Neuroscience, Physiology & Pharmacology, UCL, UK

The optic tectum is the main retino-recipient brain structure in zebrafish and as such receives direct input exclusively from the contralateral retina. Based on observations of the behaviour of zebrafish larvae during capturing of prey like e.g. paramecia, it is likely that visual signals coming from both eyes of the animal have to be integrated e.g. for efficient hunting (Bianco et al. 2011, Bianco et al. 2015) but the neural substrate for such a mechanism is as of yet unknown.
We recently identified a zebrafish line that specifically expresses the trans-activator Gal4 in a novel, previously undescribed neuron population in the visual system of the zebrafish. Using transient UAS:GFP-expression for single-cell labeling in this zebrafish line, we find these neurons to be distributed in two bilateral-symmetric nuclei adjacent to the ventral tectum. Furthermore, they send their axons and form arbors in both tectal halves and were thus termed intertectal neurons (ITNs). ITNs are therefore good candidates for the potential transfer and/or the integration of visual signals coming from both eyes.
First, we described the anatomy and temporal development of the ITN neurons and their connections, i.e. their axon trajectories, potential up- and downstream neurons, the development and distribution of the ITN synapses and also their neurotransmitter type.
Second, using 2-photon Calcium-imaging, we established that ITNs respond to a range of visual stimuli including looming stimuli and direction selective bars. Furthermore, after unilateral eye-ablation at 2dpf, we observed Calcium transients in the tectal hemisphere not receiving any retinal input at 5-6dpf that were time-locked to the presented visual stimuli and co-localized with the trajectories of the arbors originating from the contralateral ITNs.

2. The role of motile cilia-generated flow in olfaction
Nathalie Jurisch-Yaksi

Motile cilia are cellular appendages that cover a range of epithelia across the body including the lungs, the brain ventricles, the spinal cord and the nasal cavity. Motile cilia-generated flow plays a central role in the nervous system as human patients or animal models with ciliary defects develop neurological features including hydrocephalus. Still, very little is known about how the nervous system generates and regulates specific flow patterns and how flow controls neural activity and animal behavior. In my talk, I will discuss the interactions between cilia-mediated flow and neuronal function using zebrafish olfactory epithelium as model system. Specifically, I will describe the mechanisms used by motile cilia to generate specific flow pattern and the function of the flow in olfactory processing. Our long-term goal is to understand the role of this increasingly popular organelle in the brain, which has recently attracted much attention from diverse disciplines of neuroscience.

3. Studying the function and connectivity of habenular networks in zebrafish brain
Authors: Ewelina Bartoszek, Suresh Kumar Jetti, Stephanie Fore, Maximillian Hoffmann, Emre Yaksi,
Affiliation: Kavli Institute for Systems Neuroscience, NTNU, Trondheim, Norway

The habenula (Hb) is a brain region with increasing popularity due to its strong link to addiction, mood disorders and experience dependent fear. We demonstrated that Hb neurons respond to odors and light asymmetrically. Moreover, we showed that Hb neurons exhibit structured spontaneous activity that is spatially and temporally organized. This spontaneous activity resembles neural attractors, which can switch the preferred state of the Hb and regulate the transmission of sensory information to downstream monoaminergic brainstem nuclei. In order to explore the source of Hb spontaneous activity, we investigate the local connectivity within Hb and the global functional inputs to Hb. Our results showed that recurrent excitatory connections within Hb is important for maintaining spatio-temporal organization of Hb activity. Moreover, we observed that functional inputs form zebrafish homologue of hippocampus & amygdala (Dl&Dm) and sensory inputs from visual and olfactory systems are the major drivers of spontaneous Hb activity. Our results suggested that these limbic and sensory inputs are integrated in Hb in a non-linear fashion and can regulate sensory representations in Hb. We propose that Hb lies in the heart of a brain wide network and act as “a hub” or “a switchboard”, which can regulate or gate the communication of sensory systems and limbic forebrain areas with the monoaminergic brainstem nuclei that control animal behaviors.

Some recent papers of the presenters:

Neural Circuits Underlying Visually Evoked Escapes in Larval Zebrafish.
Dunn TW, Gebhardt C, Naumann EA, Riegler C, Ahrens MB, Engert F, Del Bene F.
Neuron. 2016 Feb 3;89(3):613-28. doi: 10.1016/j.neuron.2015.12.021. Epub 2016 Jan 21.

Deletion of a kinesin I motor unmasks a mechanism of homeostatic branching control by neurotrophin-3.
Auer TO, Xiao T, Bercier V, Gebhardt C, Duroure K, Concordet JP, Wyart C, Suster M, Kawakami K, Wittbrodt J, Baier H, Del Bene F.
Elife. 2015 Jun 15;4. doi: 10.7554/eLife.05061.

Motile-Cilia-Mediated Flow Improves Sensitivity and Temporal Resolution of Olfactory Computations.
Reiten I, Uslu FE, Fore S, Pelgrims R, Ringers C, Diaz Verdugo C, Hoffman M, Lal P, Kawakami K, Pekkan K, Yaksi E, Jurisch-Yaksi N.
Curr Biol. 2017 Jan 23;27(2):166-174. doi: 10.1016/j.cub.2016.11.036. Epub 2016 Dec 29.

Spontaneous activity governs olfactory representations in spatially organized habenular microcircuits.
Jetti SK, Vendrell-Llopis N, Yaksi E.
Curr Biol. 2014 Feb 17;24(4):434-9. doi: 10.1016/j.cub.2014.01.015. Epub 2014 Feb 6.

All are welcome.