CLONING OF AVIAN CLOCK GENES AND ANALYSIS OF CIRCADIAN CLOCK AND PHOTOTERIODIC TIME MEASUREMENT

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Circadian rhythms, observed in a wide variety of physiological and behavioral parameters, are important for adaptation to natural environment in organisms living on the earth. Recently we have succeeded in cloning avian clock genes (qPer2, qPer3, qClock) which constitute the core of the circadian clock in Japanese quail. In this project, we have analyzed avian circadian clock and photoperiodic time measurement with these clock genes. The results are summarized as follows. (1) Analysis of clock gene expression : Clock genes are expressed in the pineal gland, the retina and many peripheral tissues. In particular, qPer2 and qPer3 show distinct circadian rhythms (Mol Brain Res, 2000). (2) Identification of the avian SCN : The avian SCN, the site of which had not been determined for more than 20 years, was identified with the expression of clock genes (Am J Physiol, 2001). (3) Effects of melatonin on the expression of clock gene in the avian SCN : Because melatonin is involved in the regula … More tion of avian circadian rhythms, effects of melatonin administration on the clock gene expression in the SCN were examined. The results indicate that melatonin does not affect the transcription of clock genes, but rather melatonin seems to affect the coupling among the SCN cells (Europ J Neurosci, 2002), (4) Clock genes and photoperiodic response : To examine how clock genes are involved in photoperiodic time measurement, the expression patterns of clock genes in the pineal, the SCN and the infundibular nucleus of quail under long and short days were examined. The results indicate that the patterns alter in the SCN and the pineal, but not in the infundibular nucleus which is the center for the photoperiodic response. (5) The function of clock genes in the ovary : Clock gene expression was examined in the ovary, and the results suggest that the clock in the ovary regulates the ovulation. (6) Ontogeny of clock genes : Using chicken embryo, ontogeny of clock gene expression was studied. The results indicate that light-dark cycles are required for the expression of clock gene because under constant darkness no expression was observed. (7) Novel gene controlling photoperiodic response : Weisolated a novel gene regulating photoperiodic response in Japanese quail. Less