Starting the Zebrafish Pineal Circadian Clock with a Single Photic Transition

Vuilleumier, Robin; Besseau, Laurence; Bœuf, Gilles; Piparelli, Aurélien; Gothilf, Yoav; Gehring, Walter; Klein, David C.; Falcón, Jack

doi:10.1210/en.2005-1565

Cited by 57 publications

(57 citation statements)

References 26 publications

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“…The pineal opsin protein Exorh is expressed in pineal photoreceptors from early embryogenesis to adulthood and is thus an excellent candidate to be mediating these light responses [5,38,60]. Consistent with this, the action spectrum of acute melatonin suppression in isolated adult pineal organs suggests that Exorh is one of several opsins involved in this process [65].…”

Section: Introductionmentioning

confidence: 70%

“…Vuilleumier and colleagues recently reported that exorh is expressed with a daily rhythm, with higher expression during the dark phase of the circadian cycle [60]. However, they found that the day/night differences in expression were not statistically significant [60].…”

Section: Results Exorh Transcription Is Rhythmicmentioning

confidence: 98%

“…The exorh gene is expressed in pineal photoreceptors from approximately 18 hours post fertilization (hpf) to adulthood [5,19,38,60]. Vuilleumier and colleagues recently reported that exorh is expressed with a daily rhythm, with higher expression during the dark phase of the circadian cycle [60].…”

Section: Results Exorh Transcription Is Rhythmicmentioning

confidence: 99%

“…The normal onset of rhythmic exorh transcription requires exposure of embryos to a light/dark or dark/light transition [60]. Since Exorh protein is likely involved in pineal photoreception, this raises the possibility that Exorh could regulate the expression of its own gene.…”

Section: Loss Of Exorh Protein Reduces Transcription From the Exorh Pmentioning

confidence: 99%

“…In zebrafish, pineal photoreceptors have been implicated in several responses to light, including entrainment of the circadian clock, triggering the onset of pineal rhythms during development, and mediating acute suppression of melatonin by a light pulse during the dark period [11,60,[63][64][65]. The pineal opsin protein Exorh is expressed in pineal photoreceptors from early embryogenesis to adulthood and is thus an excellent candidate to be mediating these light responses [5,38,60].…”

Section: Introductionmentioning

confidence: 99%

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Novel functions for Period 3 and Exo-rhodopsin in rhythmic transcription and melatonin biosynthesis within the zebrafish pineal organ

et al. 2008

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Entrainment of circadian clocks to environmental cues such as photoperiod ensures that daily biological rhythms stay in synchronization with the Earth's rotation. The vertebrate pineal organ has a conserved role in circadian regulation as the primary source of the nocturnal hormone melatonin. In lower vertebrates, the pineal has an endogenous circadian clock as well as photoreceptive cells that regulate this clock. The zebrafish opsin protein Exo-rhodopsin (Exorh) is expressed in pineal photoreceptors and is a candidate to mediate the effects of environmental light on pineal rhythms and melatonin synthesis. We demonstrate that Exorh has an important role in regulating gene transcription within the pineal. In developing embryos that lack Exorh, expression of the exorh gene itself and of the melatonin synthesis gene serotonin N-acetyl transferase 2 (aanat2) are significantly reduced. This suggests that Exorh protein at the cell membrane is part of a signaling pathway that positively regulates transcription of these genes, and ultimately melatonin production, in the pineal. Like many other opsin genes, exorh is expressed with a daily rhythm: mRNA levels are higher at night than during the day. We find that the transcription factor Orthodenticle homeobox 5 (Otx5) activates exorh transcription, while the putative circadian clock component Period 3 (Per3) represses expression during the day, thereby contributing to the rhythm of transcription. This work identifies novel roles for Exorh and Per3, and gives insight into potential interactions between the sensory and circadian systems within the pineal.

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Section: Introductionmentioning

confidence: 70%

Section: Results Exorh Transcription Is Rhythmicmentioning

confidence: 98%

Section: Results Exorh Transcription Is Rhythmicmentioning

confidence: 99%

Section: Loss Of Exorh Protein Reduces Transcription From the Exorh Pmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Novel functions for Period 3 and Exo-rhodopsin in rhythmic transcription and melatonin biosynthesis within the zebrafish pineal organ

et al. 2008

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Transcriptome Dynamics

Carter¹,

Coon²,

Gothilf³

et al. 2016

Molecular Neuroendocrinology

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Waste Nitrogen Metabolism and Excretion in Zebrafish Embryos: Effects of Light, Ammonia, and Nicotinamide

2013

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Bony fish primarily excrete ammonia as adults however the persistence of urea cycle genes may reflect a beneficial role for urea production during embryonic stages in protecting the embryo from toxic effects of ammonia produced from a highly nitrogenous yolk. This study aimed to examine the dynamic scope for changes in rates of urea synthesis and excretion in one such species (zebrafish, Danio rerio) by manipulating the intrinsic developmental rate (by alteration of light:dark cycles), as well as by direct chemical manipulation via ammonia injection (to potentially activate urea production) and nicotinamide exposure (to potentially inhibit urea production). Continuous dark exposure delayed development in embryos as evidenced by delayed appearance of hallmark anatomical features (heartbeat, eye pigmentation, body pigmentation, lateral line, fin buds) at 30 and 48 hr post-fertilization, as well by a lower hatching rate compared to embryos reared in continuous light. Both ammonia and urea excretion were similarly effected and were generally higher in embryos continuously exposed to light. Ammonia injection resulted in significant increases (up to fourfold) of urea N excretion and no changes to ammonia excretion rates along with modest increases in yolk ammonia content during 2-6 hr post-injection. Nicotinamide (an inhibitor of urea synthesis in mammals) reduced the ammonia-induced increase in urea excretion and led to retention of ammonia in the yolk and body of the embryo. Our results indicate that there is a relatively rapid and large scope for increases in urea production/excretion rates in developing embryos. Potential mechanisms for these increases are discussed.

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Starting the Zebrafish Pineal Circadian Clock with a Single Photic Transition

Cited by 57 publications

References 26 publications

Novel functions for Period 3 and Exo-rhodopsin in rhythmic transcription and melatonin biosynthesis within the zebrafish pineal organ

Novel functions for Period 3 and Exo-rhodopsin in rhythmic transcription and melatonin biosynthesis within the zebrafish pineal organ

Transcriptome Dynamics

Waste Nitrogen Metabolism and Excretion in Zebrafish Embryos: Effects of Light, Ammonia, and Nicotinamide

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