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Circadian rhythmicity and light sensitivity of the zebrafish brain

Moore, HA; Whitmore, D; (2014) Circadian rhythmicity and light sensitivity of the zebrafish brain. PLoS One , 9 (1) , Article e86176. 10.1371/journal.pone.0086176. Green open access

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Abstract

Traditionally, circadian clocks have been thought of as a neurobiological phenomenon. This view changed somewhat over recent years with the discovery of peripheral tissue circadian oscillators. In mammals, however, the suprachiasmatic nucleus (SCN) in the hypothalamus still retains the critical role of a central synchronizer of biological timing. Zebrafish, in contrast, have always reflected a more highly decentralized level of clock organization, as individual cells and tissues contain directly light responsive circadian pacemakers. As a consequence, clock function in the zebrafish brain has remained largely unexplored, and the precise organization of rhythmic and light-sensitive neurons within the brain is unknown. To address this issue, we used the period3 (per3)-luciferase transgenic zebrafish to confirm that multiple brain regions contain endogenous circadian oscillators that are directly light responsive. In addition, in situ hybridization revealed localised neural expression of several rhythmic and light responsive clock genes, including per3, cryptochrome1a (cry1a) and per2. Adult brain nuclei showing significant clock gene expression include the teleost equivalent of the SCN, as well as numerous hypothalamic nuclei, the periventricular grey zone (PGZ) of the optic tectum, and granular cells of the rhombencephalon. To further investigate the light sensitive properties of neurons, expression of c-fos, a marker for neuronal activity, was examined. c-fos mRNA was upregulated in response to changing light conditions in different nuclei within the zebrafish brain. Furthermore, under constant dark (DD) conditions, c-fos shows a significant circadian oscillation. Taken together, these results show that there are numerous areas of the zebrafish central nervous system, which contain deep brain photoreceptors and directly light-entrainable circadian pacemakers. However, there are also multiple brain nuclei, which possess neither, demonstrating a degree of pacemaker complexity that was not previously appreciated.

Type: Article
Title: Circadian rhythmicity and light sensitivity of the zebrafish brain
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1371/journal.pone.0086176
Publisher version: http://dx.doi.org/10.1371/journal.pone.0086176
Language: English
Additional information: © 2014 Moore, Whitmore. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: Animals, Biological Clocks, Brain, Circadian Rhythm, Cryptochromes, Eye Proteins, Gene Expression, Gene Expression Regulation, Light, Period Circadian Proteins, Proto-Oncogene Proteins c-fos, Zebrafish, Zebrafish Proteins
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Cell and Developmental Biology
URI: https://discovery.ucl.ac.uk/id/eprint/1470848
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