Chen et al. Mol Cell, 36:417-430, 2009

Rhythmic PER Abundance Defines a Critical Nodal Point for Negative Feedback within the Circadian Clock Mechanism

Circadian rhythms in mammals are generated by a transcriptional negative feedback loop that is driven primarily by oscillations of PER and CRY, which inhibit their own transcriptional activators, CLOCK and BMAL1. Current models posit that CRY is the dominant repressor, while PER may play an accessory role. In this study, however, constitutive expression of PER, and not CRY1, severely disrupted the clock in fibroblasts and liver. Furthermore, constitutive expression of PER2 in the brain and SCN of transgenic mice caused a complete loss of behavioral circadian rhythms in a conditional and reversible manner. These results demonstrate that rhythmic levels of PER2, rather than CRY1, are critical for circadian oscillations in cells and in the intact organism. Our biochemical evidence supports an elegant mechanism for the disparity: PER2 directly and rhythmically binds to CLOCK:BMAL1, while CRY only interacts indirectly; PER2 bridges CRY and CLOCK:BMAL1 to drive the circadian negative feedback loop.

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Circadianのocillationには、CRYではなくPERのoscillationが必須、という内容。

●Per2Lucノックインマウスに、CMV-AdenoでPER1またはPER2を戻すと、リズムが完全に失われる（Fig1）。BMAL1プロモーターでPER2を過剰発現してもリズムが失われる（Fig6）。

●PERの過剰発現により、CRY1の発現量増加（Fig2）、PERとClockのリズムの喪失（Fig2）、Clock：BMAL1ダイマーの増加（Fig4）が観察される。

●Fig5でPERを”Scaffoliding Molecule”と表記、PERとCRYのinteractionがリズムに必須（Fig5）であることを示す。

●Scg2プロモーター（brain specificと記載※）-ｔTA　x　tetO-Per2のダブルTgマウスでは、Per2のドライブ依存的にリズムが失われる（reversible）（Fig7）。

※Fig7Bで、SCNに強発現、ほかの部位にもそれなりに発現していることをin situで示す。

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Fig7のマウスが利用できるかを検討。

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時計、少し勉強しないとなー。