Light acts directly on organs and cells in culture to set the vertebrate circadian clock
Article Abstract:
New evidence has been produced to show that the circadian system in vertebrates exists as a decentralized collection of peripheral clocks. It was established that the peripheral organ clocks of zebrafish are set by light-dark cycles in culture. It appears that PAC-2, one zebrafish embryonic cell line, contains the photopigments and functional signal transduction cascades required for the light signal to reach the clock mechanism. Action spectra and functional experiments will be needed to establish whether cryptochrome pigments are used or whether novel opsins are the vital phototransducing molecules.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 2000
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Adaptive inducibility of CREM as transcriptional memory of circadian rhythms
Article Abstract:
Transcriptional response of the CREM gene is regulated by the length of the night and the memory of previous photoperiods. CREM encodes the transcriptional repressor ICER which is expressed in the pineal gland. ICER's expression is maximum at night and is regulated by light via the suprachiasmatic nucleus (SCN). During darkness, transcription occurs by SCN adrenergic input to the pineal gland, which activates the ICER promoter with cyclic AMP and the transcriptional activator CREB.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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Cryptic clues to clock function
Article Abstract:
The mouse counterparts of plant photopigments known as cryptochromes are needed for normal operation of the mouse circadian clock. Mice lacking functional genes for the cryptochromes Cry1 and Cry2 behaved in the same way as normal mice when maintained on a 24-hour cycle of 12 hours of light and 12 hours of darkness. However, when placed in constant darkness, they ran randomly at all times of the day. It appears that cryptochromes are vital for normal clock function, and may also be involved in the central clock mechanism.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1999
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