Starting the zebrafish pineal circadian clock with a single photic transition.
The issue of what starts the circadian clock ticking was addressed by studying the developmental appearance of the daily rhythm in the expression of two genes in the zebrafish pineal gland that are part of the circadian clock system. One encodes the photopigment exorhodopsin and the other the melatonin synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT2). Significant daily rhythms in AANAT2 mRNA abundance were detectable for several days after fertilization in animals maintained in a normal or reversed lighting cycle providing 12 h of light and 12 h of dark. In contrast, these rhythms do not develop if animals are maintained in constant lighting or constant darkness from fertilization. In contrast to exorhodopsin, rhythmicity of AANAT2 can be initiated by a pulse of light against a background of constant darkness, by a pulse of darkness against a background of constant lighting, or by single light-to-dark or dark-to-light transitions. Accordingly, these studies indicate that circadian clock function in the zebrafish pineal gland can be initiated by minimal photic cues, and that single photic transitions can be used as an experimental tool to dissect the mechanism that starts the circadian clock in the pineal gland.
Laboratoire Aragó, Observatoire Océanologique de Banyuls, Centre National de la Recherche Scientifique Unité Mixte de Recherche 7628, Université de Paris VI, Banyuls/Mer, France.
Robin
R
Vuilleumier
Laurence
L
Besseau
Gilles
G
Boeuf
Aurélien
A
Piparelli
Yoav
Y
Gothilf
Walter G
WG
Gehring
David C
DC
Klein
Jack
J
Falcón
D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000235:genetics / Q000502:physiology*; D002940:Circadian Rhythm; D003624:Darkness; D005306:Fertilization; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008027:Light; D008854:Microscopy, Electron; D017440:Photoperiod; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism; D010870:Pineal Gland / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D012160:Retina / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000378:metabolism
D012333:RNA, Messenger; D029961:Zebrafish Proteins; D047068:Arylalkylamine N-Acetyltransferase