Exo-rhodopsin: a novel rhodopsin expressed in the zebrafish pineal gland

Mano, Hiroaki; Kojima, Daisuke; Fukada, Yoshitaka

doi:10.1016/s0169-328x(99)00242-9

Cited by 127 publications

(139 citation statements)

References 39 publications

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“…Exorh protein shares a 70% sequence identity with the photoreceptive retinal opsin protein Rhodopsin, and is predicted to have seven transmembrane domains typical of G-protein coupled receptors [38]. These observations, together with the early pineal-specific expression of exorh, are consistent with Exorh functioning as a major light-sensing molecule in the developing zebrafish pineal.…”

Section: Discussion Exorh Protein Is Important For Gene Transcriptionmentioning

confidence: 60%

“…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%

“…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%

“…Embryos injected with exorh MO had severely reduced levels of exorh mRNA compared to embryos injected with a control MO ( Figure 4A, B). Embryos were analyzed using a probe that binds to the 3' end of the exorh open reading frame and recognizes both correctly and incorrectly spliced transcripts [38]. Thus, the reduced expression suggests that exorh transcripts were being degraded due to improper splicing, and that the exorh MO effectively knocks-down Exorh protein.…”

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

confidence: 99%

“…Samples were stored in 100% methanol at −20°C unless processed by in situ hybridization immediately. Transcripts of exorh [38], opn1lw1 [46], otx5 [20], per3 [18] and aanat2 [22] were detected by WISH as previously described [36]. Stained embryos were visualized using a Zeiss Axioplan2 imaging microscope.…”

Section: Wishmentioning

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: Discussion Exorh Protein Is Important For Gene Transcriptionmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 70%

Section: Results Exorh Transcription Is Rhythmicmentioning

confidence: 99%

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

confidence: 99%

Section: Wishmentioning

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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Exorhodopsin and melanopsin systems in the pineal complex and brain at early developmental stages of Atlantic halibut (Hippoglossus hippoglossus)

Eilertsen

Drivenes

Edvardsen

et al. 2014

J of Comparative Neurology

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The complexity of the nonvisual photoreception systems in teleosts has just started to be appreciated, with colocalization of multiple photoreceptor types with unresolved functions. Here we describe an intricate expression pattern of melanopsins in early life stages of the marine flat fish Atlantic halibut (Hippoglossus hippoglossus), a period when the unpigmented brain is directly exposed to environmental photons. We show a refined and extensive expression of melanopsins in the halibut brain already at the time of hatching, long before the eyes are functional. We detect melanopsin in the habenula, suprachiasmatic nucleus, dorsal thalamus, and lateral tubular nucleus of first feeding larvae, suggesting conserved functions of the melanopsins in marine teleosts. The complex expression of melanopsins already at larval stages indicates the importance of nonvisual photoreception early in development. Most strikingly, we detect expression of both exorhodopsin and melanopsin in the pineal complex of halibut larvae. Double-fluorescence labeling showed that two clusters of melanopsin-positive cells are located lateral to the central rosette of exorhodopsin-positive cells. The localization of different photopigments in the pineal complex suggests that two parallel photoreceptor systems may be active. Furthermore, the dispersed melanopsin-positive cells in the spinal cord of halibut larvae at the time of hatching may be primary sensory cells or interneurons representing the first example of dispersed high-order photoreceptor cells. The appearance of nonvisual opsins early in the development of halibut provides an alternative model for studying the evolution and functional significance of nonvisual opsins.

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Start the clock! Circadian rhythms and development

Vallone

Lahiri

Dickmeis

et al. 2006

Developmental Dynamics

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The contribution of timing cues from the environment to the coordination of early developmental processes is poorly understood. The day-night cycle represents one of the most important, regular environmental changes that animals are exposed to. A key adaptation that allows animals to anticipate daily environmental changes is the circadian clock. In this review, we aim to address when a light-regulated circadian clock first emerges during development and what its functions are at this early stage. In particular, do circadian clocks regulate early developmental processes? We will focus on results obtained with Drosophila and vertebrates, where both circadian clock and developmental control mechanisms have been intensively studied. Developmental Dynamics 236:142-155, 2007.

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Exo-rhodopsin: a novel rhodopsin expressed in the zebrafish pineal gland

Cited by 127 publications

References 39 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

Exorhodopsin and melanopsin systems in the pineal complex and brain at early developmental stages of Atlantic halibut (Hippoglossus hippoglossus)

Start the clock! Circadian rhythms and development

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