Localization of a circadian clock in mammalian photoreceptors

• Published in: The FASEB journal Vol. 21; no. 14; pp. 3866 - 3871
• Main Authors: Tosini, Gianluca, Davidson, Alec J, Fukuhara, Chiaki, Kasamatsu, Manami, Castanon-Cervantes, Oscar
• Format: Journal Article
• Language: English
• Published: United States The Federation of American Societies for Experimental Biology 01.12.2007
• Subjects: Animals; Animals, Genetically Modified; Cell Cycle Proteins - biosynthesis; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Cycle Proteins - physiology; Circadian Rhythm - genetics; Circadian Rhythm - physiology; CLOCK Proteins; Eye Proteins - biosynthesis; Eye Proteins - genetics; Eye Proteins - metabolism; Eye Proteins - physiology; Gene Expression Regulation - physiology; Luciferases - genetics; Melatonin - biosynthesis; Melatonin - physiology; Organ Culture Techniques; Period Circadian Proteins; Photoreceptor Cells, Vertebrate - metabolism; Photoreceptor Cells, Vertebrate - physiology; Rats; Rats, Wistar; Trans-Activators - biosynthesis; Trans-Activators - genetics; Trans-Activators - metabolism
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.07-8371com

Several studies have demonstrated that the mammalian retina contains an autonomous circadian clock. Dopaminergic and other inner retinal neurons express many of the clock genes, whereas some of these genes seem to be absent from the photoreceptors. This observation has led to the suggestion that in mammalian retina the circadian pacemaker driving retinal rhythms is located in the inner nuclear layer. However, other evidence points to the photoreceptor layer as the site of the mammalian retinal clock. The goal of the present study was to demonstrate the presence of a functional circadian clock in photoreceptors. First, using laser capture microdissection and reverse transcriptase-polymerase chain reaction, we investigated which of the clock genes are expressed in rat photoreceptors. We then prepared photoreceptor layer cultures from the retina to test whether these isolated cultures were viable and could drive circadian rhythms. Our data indicated that Per1, Per3, Cry1, Cry2, Clock, Bmal1, Rev-erbα, and Rora RNAs were present in the photoreceptors, whereas we were unable to amplify mRNA for Per2 and Npas2. Photoreceptor layers obtained from Period1-luciferase rats expressed a robust circadian rhythm in bioluminescence and melatonin synthesis. These results demonstrate that mammalian photoreceptors contain the circadian pacemaker driving rhythmic melatonin synthesis.--Tosini, G., Davidson, A. J., Fukuhara, C., Kasamatsu, M., Castanon-Cervantes, O. Localization of a circadian clock in mammalian photoreceptors.