Cellular circadian clocks in the pineal

Falcón, Jack

doi:10.1016/s0301-0082(98)00078-1

Cited by 259 publications

(253 citation statements)

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“…It is synthesised in a rhythmic fashion, with increased synthesis in darkness and inhibited synthesis during the light phase of the light/dark cycle (Falcon, 1999). The production of melatonin is stim ulated by increasing plasma Ca2+ levels (Begay et al, 1994) and inhibited following hypocalcemia (Meissl et al, 1996).…”

Section: Melatoninmentioning

confidence: 99%

Parathyroid hormone-related protein in teleost fish

Abbink

Flik

2007

General and Comparative Endocrinology

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A brief description is given of the discovery of PTHrP and the roles of the peptide in mammalian physiology. Next, the occurrence of PTHrP in the earliest vertebrates, sharks, skates and fishes, is reviewed and the calciotropic functions of PTHrP are addressed more spe cifically in fishes. Parathyroid hormone-related protein (PTHrP) is a hypercalcemic hormone in teleostean fishes, but also has para-and autocrine functions. After the isolation and identification of fish PTHrP and PTHrP receptors and the subsequent development of recom binant protein and a real-time quantitative PCR, a calciotropic role of PTHrP in fish physiology could be assessed. PTHrP influences calcium physiology via regulation of calcium mobilisation from internal sources (bone and scales) and via calcium uptake from the envi ronment (water and diet). Continuous variations in the need for calcium and in the availability of environmental calcium require fast calciotropes to guarantee calcium balance, in which PTHrP is pivotal for the fish. PTHrP is essential in fish bone physiology, e.g. in min eralisation and calcium reabsorption from the scales. Moreover, PTHrP plays a role in vitellogenesis, cortisol production, regulation of renal Mrp2 activity and melatonin synthesis. The plethora of functions of PTHrP in fish concern endocrine, paracrine and autocrine (and possibly intracrine) functions; calciotropic actions of PTHrP at the organismal and cellular level are prominent in fish. The strong con servation of the pthrp gene in the vertebrate lineage and the N-terminal similarity of the coded proteins relates to the important role of PTHrP in calcium physiology that is of paramount importance to all physiological processes. Recent and ongoing studies will contribute to our rapidly expanding knowledge of the original physiological functions of PTHrP in teleost fish.

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Section: Melatoninmentioning

confidence: 99%

Parathyroid hormone-related protein in teleost fish

Abbink

Flik

2007

General and Comparative Endocrinology

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“…It has been found in Gram-positive bacteria, protists, fungi, some lower plants, algae, and cephalochordates. The broad detoxification role of NV-AANAT contrasts with the dedicated role that VT-AANAT plays in melatonin synthesis, which was seen in teleosts and tetrapods (6,18).Melatonin is recognized as the vertebrate hormone of the night, because circulating levels are markedly elevated at night. In bony fish and tetrapods, VT-AANAT is highly expressed in the pineal gland, the primary source of circulating melatonin (6, 18).…”

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confidence: 99%

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confidence: 99%

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Drastic neofunctionalization associated with evolution of the timezyme AANAT 500 Mya

Falcón

Coon

Besseau

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Melatonin (N-acetyl-5-methoxytrypamine) is the vertebrate hormone of the night: circulating levels at night are markedly higher than day levels. This increase is driven by precisely regulated increases in acetylation of serotonin in the pineal gland by arylalkylamine N-acetyltransferase (AANAT), the penultimate enzyme in the synthesis of melatonin. This unique essential role of AANAT in vertebrate timekeeping is recognized by the moniker the timezyme. AANAT is also found in the retina, where melatonin is thought to play a paracrine role. Here, we focused on the evolution of AANAT in early vertebrates. AANATs from Agnathans (lamprey) and Chondrichthyes (catshark and elephant shark) were cloned, and it was found that pineal glands and retinas from these groups express a form of AANAT that is compositionally, biochemically, and kinetically similar to AANATs found in bony vertebrates (VT-AANAT). Examination of the available genomes indicates that VT-AANAT is absent from other forms of life, including the Cephalochordate amphioxus. Phylogenetic analysis and evolutionary rate estimation indicate that VT-AANAT evolved from the nonvertebrate form of AANAT after the Cephalochordate-Vertebrate split over one-half billion years ago. The emergence of VT-AANAT apparently involved a dramatic acceleration of evolution that accompanied neofunctionalization after a duplication of the nonvertebrate AANAT gene. This scenario is consistent with the hypotheses that the advent of VT-AANAT contributed to the evolution of the pineal gland and lateral eyes from a common ancestral photodetector and that it was not a posthoc recruitment.E yes have evolved in all animals to facilitate interactions with the photic environment (1, 2). However, among animals, vertebrates are unique in that they also possess a photoneuroendocrine structure, the pineal gland (3). It converts the 24-h rhythm in environmental lighting into a 24-h rhythm in circulating melatonin, thereby providing a unique and valuable signal of the photic environment. The details of pineal evolution are not clear (4, 5). However, it has been posited that an essential element was arylalkylamine N-acetyltransferase (AANAT; E.C. 2.3.1.87), the penultimate enzyme in the melatonin biosynthesis pathway (6-8); this scenario is referred to as the AANAT hypothesis of pineal evolution (7,8).AANAT catalyzes the N-acetylation of arylalkylamines using acetyl CoA (AcCoA) as the acetyl group donor. The AANAT family, which belongs to the GCN5 superfamily (9, 10), is composed of two subfamilies termed vertebrate (VT) AANAT and nonvertebrate (NV) AANAT. † This nomenclature reflects the phylogenetic distribution of the family members (13-17). The most striking differences between VT-and NV-AANAT are found in regulatory and catalytic regions of the encoded proteins (Fig. 1), consistent with different metabolic roles (7,8).The NV-AANAT is thought to perform a detoxification function through acetylation of a broad range of endogenous and exogenous arylalkylamines and polyamines (13-16). It has been fo...

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“…It is a photoreceptive organ and contains an intrinsic circadian oscillator that drives rhythms of melatonin production (10,11). Consequently, circadian rhythmicity of melatonin production and photic entrainment of the oscillator can be observed when zebrafish pineal glands are placed in culture (12).…”

mentioning

confidence: 99%

Circadian time-keeping during early stages of development

Ziv¹,

Gothilf

2006

Proc. Natl. Acad. Sci. U.S.A.

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The zebrafish pineal gland is a photoreceptive organ containing an intrinsic central circadian oscillator, which drives daily rhythms of gene expression and the melatonin hormonal signal. Here we investigated the effect of light, given at early developmental stages before pineal gland formation, on the pineal circadian oscillator. Embryos that were exposed to light at 0 -6, 10 -13, or 10 -16 h after fertilization exhibited clock-controlled rhythms of arylalkylamine-N-acetyltransferase (zfaanat2) mRNA in the pineal gland during the third and fourth day of development. This rhythm was absent in embryos that were placed in continuous dark within 2 h after fertilization (before blastula stage). Differences in the phases of these rhythms indicate that they are determined by the time of illumination. Light treatments at these stages also caused a transient increase in period2 mRNA levels, and the development of zfaanat2 mRNA rhythm was abolished by PERIOD2 knock-down. These results indicate that light exposure at early developmental stages, and light-induced expression of period2, are both required for setting the phase of the circadian clock. The 24-h rhythm is then maintained throughout rapid proliferation and, remarkably, differentiation.AANAT ͉ light ͉ period2 ͉ pineal ͉ zebrafish

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Cellular circadian clocks in the pineal

Cited by 259 publications

References 304 publications

Parathyroid hormone-related protein in teleost fish

Parathyroid hormone-related protein in teleost fish

Drastic neofunctionalization associated with evolution of the timezyme AANAT 500 Mya

Circadian time-keeping during early stages of development

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