title: Helix-loop-helix protein Id2 stabilizes mammalian circadian oscillation under constant light conditions.
abstract: The mammalian circadian oscillator is composed of interacting positive and negative transcription events. The clock proteins PER1 and PER2 play essential roles in a negative limb of the feedback loop that generates the circadian rhythm in mammals. In addition, the proteins CLOCK and BMAL1 (also known as ARNTL) form a heterodimer that drives the Per genes via the E-box consensus sequences within their promoter regions. In the present study, we demonstrate that Id2 is involved in stabilization of the amplitudes of the circadian oscillations by suppressing transcriptional activation of clock genes Clock and Bmal1. Id2 shows dynamic oscillation in the SCN, with a peak in the late subjective night. Under constant dark conditions (DD), Id2(-/-) mice showed no apparent difference in locomotor activity, however, under constant light conditions (LL), Id2(-/-) mice exhibit aberrant locomotor activity, with lower circadian oscillation amplitudes, although the free running periods in Id2(-/-) mice show no differences from those in either wild type or heterozygous mice. Id2(-/-) animals also exhibit upregulation of Per1 in constant light, during both the subjective night and day. In wild type mice, Id2 is upregulated by constant light exposure during the subjective night. We propose that Id2 expression in the SCN contributes to maintenance of dynamic circadian oscillations.
authors: 1 Department of Anatomy and Neurobiology, Kinki University School of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511, Japan.
authors: Akihito A
authors: AA
authors: Adachi
authors: Atsuko
authors: A
authors: Fujioka
authors: Mamoru
authors: M
authors: Nagano
authors: Koh-hei
authors: KH
authors: Masumoto
authors: Toru
authors: T
authors: Takumi
authors: Takashi
authors: T
authors: Yoshimura
authors: Shizufumi
authors: S
authors: Ebihara
authors: Kentaro
authors: K
authors: Mori
authors: Yoshifumi
authors: Y
authors: Yokota
authors: Yasufumi
authors: Y
authors: Shigeyoshi
mesh_terms: D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D051797:Inhibitor of Differentiation Protein 2 / Q000235:genetics / Q000378:metabolism*; D008027:Light; D051379:Mice; D009043:Motor Activity
chemical_list: C497452:Idb2 protein, mouse; D051797:Inhibitor of Differentiation Protein 2; D056926:CLOCK Proteins