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Melanopsin elevates locomotor activity during the wake state of the diurnal zebrafish

ABSTRACT: Mammalian and fish pineals play a key role in adapting behaviour to the ambient light conditions through the release of melatonin. In mice, light inhibits nocturnal locomotor activity via the nonvisual photoreceptor Melanopsin. In contrast to the extensively studied function of Melanopsin in the indirect regulation of the rodent pineal, its role in the intrinsically photosensitive zebrafish pineal has not been elucidated. Therefore, it is not evident if the light signalling mechanism is conserved between distant vertebrates, and how Melanopsin could affect diurnal behaviour. A double knockout of melanopsins (opn4.1-opn4xb) was generated in the diurnal zebrafish, which manifests attenuated locomotor activity during the wake state. Transcriptome sequencing gave insight into pathways downstream of Melanopsin, implying that sustained repression of the melatonin pathway is required to elevate locomotor activity during the diurnal wake state. Moreover, we show that light induces locomotor activity during the diurnal wake state in an intensity-dependent manner. These observations suggest a common Melanopsin-driven mechanism between zebrafish and mammals, while the diurnal and nocturnal chronotypes are inversely regulated downstream of melatonin.

ORGANISM(S): Danio rerio

PROVIDER: GSE189906 | GEO | 2021/12/06

REPOSITORIES: GEO

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Project description:The zebrafish pineal gland (epiphysis) is an autonomous clock organ. In addition to being a site of melatonin production, it contains photoreceptor cells and functions as a circadian clock pace maker, making zebrafish a useful model system to study the developmental control of expression of genes associated with melatonin synthesis and photodetection, and the circadian clock. Here we have used DNA microarray technology to study the zebrafish pineal transcriptome. Analysis of gene expression at five different developmental stages (three embryonic and two adult) has revealed a highly dynamic transcriptional profile, revealing many genes that are highly expressed in the pineal gland. Statistical analysis of the data based on Gene Ontology (GO) annotation indicates that many transcription factors and cell cycle genes are highly expressed during embryonic stages, whereas genes dedicated to visual system signal transduction are preferentially expressed in the adult. Furthermore, several genes were identified that exhibit day/night differences in expression. Our data provide a rich source of candidate genes for distinct functions at different stages of pineal gland development. Experiment Overall Design: Adults and embryos were kept under a 14-hr-light/10-hr-dark cycle. Pineal glands were isolated manually, guided by GFP fluorescence, from embryonic (3d, 5d, and 10d) and adult (3 month and 1-2 yr) transgenic zebrafish in which expression of the GFP gene is driven by the pineal-specific aanat2 promoter. For comparison, brain tissue from which the pineal gland and eyes had been removed was also collected (referred to as “brain”). Altogether, we collected 20 types of samples: five time points (3d, 5d, 10d, 3 mo, and 1-2 yr), two organs (pineal gland and brain), and two sampling times (day and night). For each type of sample, tissue was obtained and processed three to five times. Total RNA was prepared from each sample using the RNeasy Lipid Tissue Mini Kit (Qiagen) and biotin-labeled cDNA was generated using the Ovation Biotin system kit (NeuGen). The Affymetrix GeneChip® Zebrafish Genome Array was hybridized and processed using the standard Affymetrix protocol.

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Melanopsin elevates locomotor activity during the wake state of the diurnal zebrafish

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