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Functional Development of the Zebrafish Pineal Gland: Light‐Induced Expression of Period2 is Required for Onset of the Circadian Clock
Author(s) -
Ziv L.,
Levkovitz S.,
Toyama R.,
Falcon J.,
Gothilf Y.
Publication year - 2005
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.2005.01315.x
Subject(s) - circadian rhythm , zebrafish , pineal gland , biology , clock , endocrinology , medicine , light effects on circadian rhythm , cryptochrome , circadian clock , microbiology and biotechnology , rhythm , gene expression , gene , genetics
In zebrafish, the pineal gland is a photoreceptive organ that contains an intrinsic circadian oscillator and exhibits rhythmic arylalkylamine‐ N ‐acetyltransferase ( zfaanat2 ) mRNA expression. In the present study, we investigated the role of light and of a clock gene, zperiod2 ( zper2 ), in the development of this rhythm. Analysis of zfaanat2 mRNA expression in the pineal gland of 3‐day‐old zebrafish embryos after exposure to different photoperiodic regimes indicated that light is required for proper development of the circadian clock‐controlled rhythmic expression of zfaanat2 , and that a 1‐h light pulse is sufficient to initiate this rhythm. Analysis of zper2 mRNA expression in zebrafish embryos exposed to different photoperiodic regimes indicated that zper2 expression is transiently up‐regulated by light but is not regulated by the circadian oscillator. To establish the association between light‐induced zper2 expression and light‐induced clock‐controlled zfaanat2 rhythm, zPer2 knock‐down experiments were performed. The zfaanat2 mRNA rhythm, induced by a 1‐h light pulse, was abolished in zPer2 knock‐down embryos. These experiments indicated that light‐induced zper2 expression is crucial for establishment of the clock‐controlled zfaanat2 rhythm in the zebrafish pineal gland.