Through comprehensive identification and examination of neural circuits that control innate behaviors in larval zebrafish, the Engert laboratory focuses on building a complete, multi-level picture of simple neural circuits. Such knowledge will advance our understanding of human brain functions and the neuronal activities that control complex behaviors.

• Correlate specific neural activity to particular changes in the behavior of an organism.
• Determine how a visual input signal relates to a motor action output.
• Investigate how neurons and synapses within a neural circuit translate visual information into motor commands.
• Perform these studies in an in vivo vertebrate system to obtain a holistic understanding of neural circuits.

• Calcium indicators
• Two-photon microscopy
• Bioluminescence
• Transgenic zebrafish with genetically encoded neurons
• Ca2+-GFP-Aequorin

The Engert laboratory has been at the forefront of understanding how vertebrate neural circuits relate to behaviors. Zebrafish larvae, with their transparency, small size, and readily available genetic tools, are an ideal system for integrating cell biology, anatomy, and physiology studies of the nervous system. The Engert group has developed a series of assays to analyze the correlation between the input stimulus, the resulting neuronal activity and the behavioral output, which enables the identification of the underlying brain circuitry involved and provides insights into the processing steps that the brain undertakes.

The group has previously used calcium indicator dyes to label neurons, which enables them to monitor their activity by two-photon microscopy. More recently, they have developed a non-invasive assay that uses bioluminescence in transgenic zebrafish to monitor specific neurons in freely swimming larvae. The laboratory has the ability to examine very small subsets of neurons in vivo with high temporal and spatial resolution. This technique holds great potential for application to other neuroscience models such as Drosophila melanogaster larvae or Caenorhabditis elegans.

The Engert group has also utilized Xenopus tadpoles to study neural connections. Through calcium labeling similar to that of the zebrafish, they directly showed that different regions of a dendrite could respond separately to stimuli in different locations, creating a spatial map of sensory processing. The laboratory has also studied activation of single neurons in the zebrafish and the corresponding impact on their motor reflexes. They are currently able to track freely swimming fish larvae by their swim pattern or body position. By controlling the input stimuli, they can therefore study the connection between the firing of neural circuits and the behavioral response in the fish.

The hypocretin/orexin neurons in the hypothalamus were marked in larval zebrafish by GFP, as shown above in Figure A (Figure B is a higher magnification of the red rectangle marked in Figure A). By monitoring these neurons with the GFP luminescence during the zebrafish’s circadian rhythms, the Engert group confirmed that these neurons are specifically active during periods of motor activity and inhibit rest when they are active. For more information, see Naumann, et al., 2010. Nature Neuroscience. 13(4):513-20.

Biological Mechanisms and Pathways

• Aging •
• Channelrhodopsin-2 •
• Hypothalamus •
• Neuron
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Central Nervous System

• Action potential •
• Binocular function •
• Hypothalamus •
• Neural connections •
• Neurodegenerative disease •
• Optomotor response •
• Reticular spinal formation •
• Retinotectal pathway •
• Sensory processing •
• Subcellular dendritic topography •
• Visual stimuli
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Disease Mechanisms

• Behavioral disorders •
• Neurodegenerative disease •
• Retinal disorders
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Metabolism; Metabolic Disease and Aging

• Aging
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Research Tools and Instrumentation

• Bioluminescence •
• Ca2+-GFP-Aequorin •
• Ca2+-GFP-Aequorin •
• Calcium indicators •
• Cellular ablation •
• Escape behavior •
• Transgenic zebrafish •
• Two-photon microscopy •
• Xenopus tadpoles •
• Zebrafish larvae
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