Cycling vrille Expression Is Required for a Functional Drosophila Clock

A novel regulatory loop within Drosophila's circadian clock was identified, with vri being essential for its function.

• The transcription factor vri is critical for embryonic development and is expressed in circadian pacemaker cells.
• vri RNA levels exhibit oscillation in line with a circadian rhythm.
• The oscillation of vri is directly controlled by the transcription factors dCLOCK and CYCLE.
• Disruption of the normal vri cycle leads to suppressed expression of period and timeless genes, resulting in long-period rhythms and arrhythmia.
• dCLOCK and vri independently regulate levels of the neuropeptide pigment dispersing factor, which is associated with behavioral regulation.

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