Research Area Basic Biology Keyword Biological clock, circadian rhythm, signal transduction, neuroscience, photobiology Purpose and Background of the Research Most living organisms show a variety of rhythms by virtue of having an intrinsic time-measuring system, called circadian clock, which can be entrained to daily variation of the environmental conditions such as light-dark cycle. In mammals...

BACKGROUND Circadian clocks are synchronized to the solar day via visual and specialized photoreceptors. In Drosophila, CRYPTOCHROME (CRY) is a major photoreceptor that mediates resetting of the circadian clock via light-dependent degradation of the clock protein TIMELESS (TIM). However, in the absence of CRY, this TIM-mediated resetting still occurs in some pacemaker neurons, resulting in sync...

Recent studies of several species have reported a latitudinal cline in the circadian clock gene, Clock, which influences rhythms in both physiology and behavior. Latitudinal variation in this gene may hence reflect local adaptation to seasonal variation. In some bird populations, there is also an among-individual association between Clock poly-Q genotype and clutch initiation date and incubatio...

OBJECTIVE Circadian Clock gene mutant mice show dampened 24-h feeding rhythms and an increased sensitivity to high-fat diet (HFD) feeding. Restricting HFD access to the dark phase counteracts its obesogenic effect in wild-type mice. The extent to which altered feeding rhythms are causative for the obesogenic phenotype of Clock mutant mice, however, remains unknown. METHODS Metabolic parameter...

Circadian rhythms are responsive to external and internal cues, light and metabolism being among the most important. In mammals, the light signal is sensed by the retina and transmitted to the suprachiasmatic nucleus (SCN) master clock [1], where it is integrated into the molecular oscillator via regulation of clock gene transcription. The SCN synchronizes peripheral oscillators, an effect that...

The mammalian clock system is composed of a master clock and peripheral clocks. At the molecular level, the rhythm-generating mechanism is controlled by a molecular clock composed of positive and negative feedback loops. However, the underlying mechanisms for molecular clock regulation that affect circadian clock function remain unclear. Here, we show that Egr1 (early growth response 1), an ear...

Circadian locomotor output cycles kaput (CLOCK) is a nuclear transcription factor that is a component of the central autoregulatory feedback loop that governs the generation of biological rhythms. Homozygous Clock mutant mice contain a truncated CLOCK(Δ19) protein within somatic cells, subsequently causing an impaired ability to rhythmically transactivate circadian genes. The present study soug...