Functional absence of extraocular photoreception in hamster circadian rhythm entrainment

Meijer, Johanna H.; Thio, Bing; Albus, Henk; Schaap, Jeroen; Ruijs, Aleid

doi:10.1016/s0006-8993(99)01509-7

Cited by 30 publications

(18 citation statements)

References 13 publications

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“…In non-mammalian vertebrates, melatonin does not play a significant role in seasonal photoperiodic responses. The eye in mammals is the only photoreceptive organ and its removal also abolishes photoperiodic responses (Reiter 1980, Nelson & Zucker 1981, Meijer et al . 1999).…”

Section: Light Input Mechanisms and The Rhythmic Melatonin Signalmentioning

confidence: 99%

Clocks for all seasons: unwinding the roles and mechanisms of circadian and interval timers in the hypothalamus and pituitary

Wood

Loudon

2014

Journal of Endocrinology

157

129

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Adaptation to the environment is essential for survival, in all wild animal species seasonal variation in temperature and food availability needs to be anticipated. This has led to the evolution of deep-rooted physiological cycles, driven by internal clocks, which can track seasonal time with remarkable precision. Evidence has now accumulated that a seasonal change in thyroid hormone (TH) availability within the brain is a crucial element. This is mediated by local control of TH-metabolising enzymes within specialised ependymal cells lining the third ventricle of the hypothalamus. Within these cells, deiodinase type 2 enzyme is activated in response to summer day lengths, converting metabolically inactive thyroxine (T4) to tri-iodothyronine (T3). The availability of TH in the hypothalamus appears to be an important factor in driving the physiological changes that occur with season. Remarkably, in both birds and mammals, the pars tuberalis (PT) of the pituitary gland plays an essential role. A specialised endocrine thyrotroph cell (TSH-expressing) is regulated by the changing day-length signal, leading to activation of TSH by long days. This acts on adjacent TSH-receptors expressed in the hypothalamic ependymal cells, causing local regulation of deiodinase enzymes and conversion of TH to the metabolically active T3. In mammals, the PT is regulated by the nocturnal melatonin signal. Summer-like melatonin signals activate a PT-expressed clock-regulated transcription regulator (EYA3), which in turn drives the expression of the TSHβ sub-unit, leading to a sustained increase in TSH expression. In this manner, a local pituitary timer, driven by melatonin, initiates a cascade of molecular events, led by EYA3, which translates to seasonal changes of neuroendocrine activity in the hypothalamus. There are remarkable parallels between this PT circuit and the photoperiodic timing system used in plants, and while plants use different molecular signals (constans vs EYA3) it appears that widely divergent organisms probably obey a common set of design principles.

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Section: Light Input Mechanisms and The Rhythmic Melatonin Signalmentioning

confidence: 99%

Clocks for all seasons: unwinding the roles and mechanisms of circadian and interval timers in the hypothalamus and pituitary

Wood

Loudon

2014

Journal of Endocrinology

157

129

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“…A recent report on circadian photoreception through the skin in humans (113) awaits confirmation. In blind hamsters exposure of shaved skin to light does not elicit a circadian response (114).…”

Section: Anatomy Of the Mammalian Circadian Systemmentioning

confidence: 99%

Cryptochrome: The Second Photoactive Pigment in the Eye and Its Role in Circadian Photoreception

Sancar

2000

Annu. Rev. Biochem.

243

201

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Key Words blue-light photoreceptor, flavoprotein, retina, suprachiasmatic nucleus, circadian blind mice, seasonal affective disorder s Abstract Circadian rhythms are oscillations in the biochemical, physiological, and behavioral functions of organisms that occur with a periodicity of approximately 24 h. They are generated by a molecular clock that is synchronized with the solar day by environmental photic input. The cryptochromes are the mammalian circadian photoreceptors. They absorb light and transmit the electromagnetic signal to the molecular clock using a pterin and flavin adenine dinucleotide (FAD) as chromophore/cofactors, and are evolutionarily conserved and structurally related to the DNA repair enzyme photolyase. Humans and mice have two cryptochrome genes, CRY1 and CRY2, that are differentially expressed in the retina relative to the opsin-based visual photoreceptors. CRY1 is highly expressed with circadian periodicity in the mammalian circadian pacemaker, the suprachiasmatic nucleus (SCN). Mutant mice lacking either Cry1 or Cry2 have impaired light induction of the clock gene mPer1 and have abnormally short or long intrinsic periods, respectively. The double mutant has normal vision but is defective in mPer1 induction by light and lacks molecular and behavioral rhythmicity in constant darkness. Thus, cryptochromes are photoreceptors and central components of the molecular clock. Genetic evidence also shows that cryptochromes are circadian photoreceptors in Drosophila and Arabidopsis, raising the possibility that they may be universal circadian photoreceptors. Research on cryptochromes may provide new understanding of human diseases such as seasonal affective disorder and delayed sleep phase syndrome. CONTENTS

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“…Although in many animals there is more than one organ for circadian photoreception (4), it is commonly believed that the eyes are the sole photosensory organs for vision, circadian entrainment, and masking in mammals (5,6). Remarkably, both light entrainment of the circadian clock (7)(8)(9)(10)(11) and light masking of behavior (12)(13)(14)(15)(16) are largely preserved in retinal degenerate (rd͞rd) mice. The murine rd mutation causes total loss of rods and massive loss of cones, rendering the animals visually and electrophysiologically blind by 3 months of age (12,13).…”

mentioning

confidence: 99%

Functional redundancy of cryptochromes and classical photoreceptors for nonvisual ocular photoreception in mice

Selby

Thompson²,

Schmitz

et al. 2000

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

158

121

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The daily light-dark (LD) cycle exerts a powerful influence on the temporal organization of behavior and physiology. Much of this influence is preserved in behaviorally blind retinally degenerate mice; the photoreceptors underlying this nonvisual phototransduction are unknown. The mammalian eye contains at least two classes of photoactive pigments, the vitamin A-based opsins and the vitamin B2-based cryptochromes. To genetically define the roles of these pigments in light modulation of behavior, we generated rd͞rd;mCry1 ؊ ͞mCry1 ؊ ;mCry2 ؊ ͞mCry2 ؊ mutant mice lacking rods and most cones as well as both cryptochrome proteins. The response of the mutant mouse to photic input was analyzed at both behavioral and molecular levels. Behaviorally, mice lacking either classical photoreceptors or cryptochromes exhibited strongly rhythmic locomotor responses to 10 and 100 lux daily LD 12 h͞12-h cycles; however, triple mutant mice carrying both cryptochrome and retinal degenerate mutations were nearly arrhythmic under both LD cycles and in constant darkness. At the molecular level, the light induction of c-fos transcription in the suprachiasmatic nucleus was markedly reduced in the triple mutant mouse compared with either rd͞rd or cryptochrome mutant mice. These data indicate that classical opsins and cryptochromes serve functionally redundant roles in the transduction of light information to behavioral modulation and suggest a pleomorphic role for cryptochromes in both photoreception and central clock mechanism.circadian photoreceptor ͉ c-fos ͉ suprachiasmatic nucleus L ight exerts a powerful influence on the organization of behavior in most eukaryotes. The precise effect of light's influence on behavior is genetically determined, rendering some species diurnal and others nocturnal. Two mechanisms exist in mammals that produce light-dependent behavioral modification. When kept in total darkness, mammals maintain circadian rhythms of behavior that are nearly, but not exactly, 24 h long. The circadian oscillator is located in the suprachiasmatic nuclei (SCN) of the ventral hypothalamus. Light received by the eyes synchronizes the oscillator through the retinohypothalamic tract and hence synchronizes the behavior of the organism with the daily 24-h light-dark (LD) cycle. In addition to light entrainment of circadian rhythms, light also directly suppresses the activity of nocturnal animals, a phenomenon called masking (1). Light masking of behavior does not depend on the circadian clock, as it is preserved in SCN-lesioned animals (2, 3). Although in many animals there is more than one organ for circadian photoreception (4), it is commonly believed that the eyes are the sole photosensory organs for vision, circadian entrainment, and masking in mammals (5, 6). Remarkably, both light entrainment of the circadian clock (7-11) and light masking of behavior (12-16) are largely preserved in retinal degenerate (rd͞rd) mice. The murine rd mutation causes total loss of rods and massive loss of cones, rendering the animals visually and ...

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Functional absence of extraocular photoreception in hamster circadian rhythm entrainment

Cited by 30 publications

References 13 publications

Clocks for all seasons: unwinding the roles and mechanisms of circadian and interval timers in the hypothalamus and pituitary

Clocks for all seasons: unwinding the roles and mechanisms of circadian and interval timers in the hypothalamus and pituitary

Cryptochrome: The Second Photoactive Pigment in the Eye and Its Role in Circadian Photoreception

Functional redundancy of cryptochromes and classical photoreceptors for nonvisual ocular photoreception in mice

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