Functional development of the zebrafish pineal gland: light-induced expression of period2 is required for onset of the circadian clock.
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.
Ziv
L
L
Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
Levkovitz
S
S
Toyama
R
R
Falcon
J
J
Gothilf
Y
Y
D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D015415:Biomarkers / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018507:Gene Expression Regulation, Developmental / Q000528:radiation effects*; D008027:Light; D008297:Male; D056950:Period Circadian Proteins; D010870:Pineal Gland / Q000196:embryology / Q000201:enzymology* / Q000528:radiation effects; D012333:RNA, Messenger / Q000032:analysis; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins
D015415:Biomarkers; D005136:Eye Proteins; D029941:Fish Proteins; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D029961:Zebrafish Proteins; C498846:per2 protein, zebrafish; D047068:Arylalkylamine N-Acetyltransferase