Functional Imaging in the Zebrafish Visual System

Lead Research Organisation: King's College London
Department Name: MRC Ctr for Developmental Neurobiology

Abstract

The brain controls everything that sustains us in our every day life. But because of its complexity we have very little idea of how the brain works or how it is wired up during development.
We are using zebrafish to understand how the brain performs one of its many tasks, namely the processing of visual information. Even at early stages of development zebrafish use vision to hunt small prey and avoid predators.
We have generated zebrafish that express fluorescent indicators of neural activity in nerve cells within the visual system. Active neurons fluoresce brightly while silent neurons are dimly fluorescent. Thus, the neurons themselves can tell us when they are active and when they are not. Because young zebrafish are translucent we can see these fluorescent signals inside the brains of living intact larvae. We are using these fluorescent fish to see how nerve cells within the brain respond to different visual stimuli and how these responses change as the larval brain develops.
Investigating how the normal brain develops will give us insight into the causes and consequences of disorders of the brain, many of which (schizophrenia, epilepsy and Alzheimer?s for example) place a major burden on society.

Technical Summary

Understanding how the brain processes sensory information is a major challenge in neuroscience. The aim of this proposal is to use the optic tectum of larval zebrafish as a system to investigate how a defined visual stimulus is processed at defined stages in the visual pathway. Specifically we will characterize the circuit components that underlie the perception of motion. A major focus of the application is to also investigate how such circuitry develops. Firstly we will characterise direction-selective retinal ganglion cells (DSGCs). We have established a system to provide precisely controlled visual stimuli to zebrafish while performing in vivo imaging in the tectum. In order to visualise neural activity in RGCs specifically we have fused the genetically encoded calcium sensor, GCaMP3 to the presynaptic vesicle protein, synaptophysin to generate SyGCaMP3. We have generated a transgenic line of zebrafish that expresses SyGCaMP3 specifically in RGCs, thus allowing us to visualise motion-induced activity at the presynaptic terminals of RGCs in the tectum. Using this approach we will characterise the functional development of DSGCs and also map the laminar location of different types of DSGC axon in the tectum. This functional map will then be used as a point of reference to ask how information from DSGCs is processed and integrated in the postsynaptic tectal neurons. This will be achieved using bulk loading of the fluorescent calcium indicator, Oregon Green BAPAT 488 AM into tectal cells. We will determine how tectal neurons are tuned to motion in different directions and the location of each characterised cell within the tectum will also be mapped. We will also examine how the tuning properties and functional organisation of tectal cells develops. We will also characterise the functional properties of morphologically identified tectal neurons. This will be achieved through expression of a membrane targeted version of GCaMP3 which will allow morphological and functional characterisation of neurons. By describing each of the circuit components in this way we can begin to understand how the tectum as a whole processes visual stimuli. As part of this last aim we hope to isolate genomic regulatory regions that will permit expression of transgenes in subsets of tectal neuron. With these molecular tools in hand we can selectively manipulate different cell types and in the long-term ask how they contribute to the perception of motion and the generation of behaviours.

Publications

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Antinucci P (2016) Orientation Selectivity in the Retina: ON Cell Types and Mechanisms. in The Journal of neuroscience : the official journal of the Society for Neuroscience

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Hunter PR (2013) Emergent properties of the optic tectum revealed by population analysis of direction and orientation selectivity. in The Journal of neuroscience : the official journal of the Society for Neuroscience

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Lowe AS (2013) A systems-based dissection of retinal inputs to the zebrafish tectum reveals different rules for different functional classes during development. in The Journal of neuroscience : the official journal of the Society for Neuroscience

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Walker AS (2013) Functional imaging in the zebrafish retinotectal system using RGECO. in Frontiers in neural circuits

 
Description King's Health Partners Research Development Fund
Amount £80,000 (GBP)
Organisation King's College London 
Sector Academic/University
Country United Kingdom
Start 11/2013 
End 10/2014
 
Description Research grant
Amount £536,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 01/2014 
End 12/2017
 
Description Investigating the role of ODZ proteins during visual circuit development 
Organisation King's College London
Department MRC Centre for Developmental Neurobiology
Country United Kingdom 
Sector Academic/University 
PI Contribution We provided expertise and reagents
Collaborator Contribution They provided expertise in ODZ function
Impact We have recently had a paper accepted for publication in Cell Reports
Start Year 2012
 
Description Gave talk at Judd Grammar School, Tonbridge, Kent 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Local
Primary Audience Schools
Results and Impact I gave a talk to Judd school science club which consists of approximately 20 A-level students

The talk will now be a yearly event and there is now a regular arrangement between Judd and our centre for hosting summer lab placements for some students
Year(s) Of Engagement Activity 2013
 
Description Gave talk at conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Gave talk on our labs progress to 50 scientists and students

None yet
Year(s) Of Engagement Activity 2012