Ontogeny of circadian clock gene expression in the pineal and the suprachiasmatic nucleus of chick embryo

• Published in: Brain research Vol. 990; no. 1; pp. 231 - 234
• Main Authors: Okabayashi, Naritoshi, Yasuo, Shinobu, Watanabe, Miwa, Namikawa, Takao, Ebihara, Shizufumi, Yoshimura, Takashi
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 14.11.2003; Amsterdam Elsevier; New York, NY
• Subjects: Animals; Biological and medical sciences; Chick Embryo; Chronobiology; Circadian rhythm; Circadian Rhythm - genetics; Clock gene; Darkness; Eye Proteins - biosynthesis; Eye Proteins - genetics; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - physiology; Melatonin - biosynthesis; Melatonin - genetics; Ontogeny; Pineal; Pineal Gland - embryology; Pineal Gland - physiology; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Suprachiasmatic nucleus; Suprachiasmatic Nucleus - embryology; Suprachiasmatic Nucleus - physiology; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Suprachiasmatic nucleus; Pineal; Chick embryo; Ontogeny; Circadian rhythm; Clock gene; Neural basis of behavior; Embryonic development; Embryo; Endocrine gland; Central nervous system; Pineal body; Biological rhythm; Hypothalamus; Gene expression; Encephalon; Vertebrata; Chicken; Aves
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(03)03531-5

Avian circadian rhythms are regulated by a multiple oscillatory system consisting of the pineal, the suprachiasmatic nucleus (SCN) and the eye. In the present study, ontogeny of circadian clock in the pineal and the SCN of chick embryo was examined using Per2 expression as a marker. A daily rhythmicity of Per2 expression was first detectable at embryonic day (ED) 18 in the pineal and at ED 16 in the SCN under light–dark (LD) cycles. The amplitude of the rhythmicity increased during the development. In contrast, little expression was observed during the development in constant darkness. These results suggest that although circadian clock matures by the end of the embryonic life in chicken, LD cycles are required for the expression of the Per2.