| 1. |
Akira Matsumoto, Maki Ukai-Tadenuma, Rikuhiro G. Yamada, Jerry Houl, Kenichiro D. Uno, Takeya Kasukawa, Brigitte Dauwalder, Taichi Q. Itoh, Kuniaki Takahashi, Ryu Ueda, Paul E. Hardin, Teiichi Tanimura, Hiroki R. Ueda, A functional genomics strategy reveals clockwork orange as a transcriptional regulator in the Drosophila circadian clock, Genes and Development, 10.1101/gad.1552207, 21, 13, 1687-1700, 2007.07, The Drosophila circadian clock consists of integrated autoregulatory feedback loops, making the clock difficult to elucidate without comprehensively identifying the network components in vivo. Previous studies have adopted genome-wide screening for clock-controlled genes using high-density oligonucleotide arrays that identified hundreds of clock-controlled genes. In an attempt to identify the core clock genes among these candidates, we applied genome-wide functional screening using an RNA interference (RNAi) system in vivo. Here we report the identification of novel clock gene candidates including clockwork orange (cwo), a transcriptional repressor belonging to the basic helix-loop-helix ORANGE family. cwo is rhythmically expressed and directly regulated by CLK-CYC through canonical E-box sequences. A genome-wide search for its target genes using the Drosophila genome tiling array revealed that cwo forms its own negative feedback loop and directly suppresses the expression of other clock genes through the E-box sequence. Furthermore, this negative transcriptional feedback loop contributes to sustaining a high-amplitude circadian oscillation in vivo. Based on these results, we propose that the competition between cyclic CLK-CYC activity and the adjustable threshold imposed by CWO keeps E-box-mediated transcription within the controllable range of its activity, thereby rendering a Drosophila circadian clock capable of generating high-amplitude oscillation.. |
| 2. |
Shun Uchizono, Yumi Tabuki, Natsumi Kawaguchi, Teiichi Tanimura, Taichi Q. Itoh, Mated Drosophila melanogaster females consume more amino acids during the dark phase, PloS one, 10.1371/journal.pone.0172886, 12, 2, 2017.02, To maintain homeostasis, animals must ingest appropriate quantities, determined by their internal nutritional state, of suitable nutrients. In the fruit fly Drosophila melanogaster, an amino acid deficit induces a specific appetite for amino acids and thus results in their increased consumption. Although multiple processes of physiology, metabolism, and behavior are under circadian control in many organisms, it is unclear whether the circadian clock also modulates such motivated behavior driven by an internal need. Differences in levels of amino acid consumption by flies between the light and dark phases of the day:night cycle were examined using a capillary feeder assay following amino acid deprivation. Female flies exhibited increased consumption of amino acids during the dark phase compared with the light phase. Investigation of mutants lacking a functional period gene (per0 ), a well-characterized clock gene in Drosophila, found no difference between the light and dark phases in amino acid consumption by per0 flies. Furthermore, increased consumption of amino acids during the dark phase was observed in mated but not in virgin females, which strongly suggested that mating is involved in the rhythmic modulation of amino acid intake. Egg production, which is induced by mating, did not affect the rhythmic change in amino acid consumption, although egg-laying behavior showed a per0 -dependent change in rhythm. Elevated consumption of amino acids during the dark phase was partly induced by the action of a seminal protein, sex peptide (SP), on the sex peptide receptor (SPR) in females. Moreover, we showed that the increased consumption of amino acids during the dark phase is induced in mated females independently of their internal level of amino acids. These results suggest that a post-mating SP/SPR signal elevates amino acid consumption during the dark phase via the circadian clock.. |
| 3. |
Hiroyuki J. Kanaya, Yoshitaka Kobayakawa, Taichi Q. Itoh, Hydra vulgaris exhibits day-night variation in behavior and gene expression levels, Zoological Letters, 10.1186/s40851-019-0127-1, 5, 1, 2019.03. |
| 4. |
Hiroyuki J Kanaya, Sungeon Park, Ji-Hyung Kim, Junko Kusumi, Sofian Krenenou, Etsuko Sawatari, Aya Sato, Jongbin Lee, Hyunwoo Bang, Yoshitaka Kobayakawa, Chunghun Lim, Taichi Q Itoh, A sleep-like state in Hydra unravels conserved sleep mechanisms during the evolutionary development of the central nervous system, Science Advances, 10.1126/sciadv.abb9415, 6, 41, 2020.10, Sleep behaviors are observed even in nematodes and arthropods, yet little is known about how sleep-regulatory mechanisms have emerged during evolution. Here, we report a sleep-like state in the cnidarian Hydra vulgaris with a primitive nervous organization. Hydra sleep was shaped by homeostasis and necessary for cell proliferation, but it lacked free-running circadian rhythms. Instead, we detected 4-hour rhythms that might be generated by ultradian oscillators underlying Hydra sleep. Microarray analysis in sleep-deprived Hydra revealed sleep-dependent expression of 212 genes, including cGMP-dependent protein kinase 1 (PRKG1) and ornithine aminotransferase. Sleep-promoting effects of melatonin, GABA, and PRKG1 were conserved in Hydra However, arousing dopamine unexpectedly induced Hydra sleep. Opposing effects of ornithine metabolism on sleep were also evident between Hydra and Drosophila, suggesting the evolutionary switch of their sleep-regulatory functions. Thus, sleep-relevant physiology and sleep-regulatory components may have already been acquired at molecular levels in a brain-less metazoan phylum and reprogrammed accordingly.. |
